Engineers design tiny batteries for powering cell-sized robots

A tiny battery designed by MIT engineers could enable the deployment of cell-sized, autonomous robots for drug delivery within in the human body, as well as other applications such as locating leaks in gas pipelines.

The new battery, which is 0.1 millimeters long and 0.002 millimeters thick -- roughly the thickness of a human hair -- can capture oxygen from air and use it to oxidize zinc, creating a current of up to 1 volt. That is enough to power a small circuit, sensor, or actuator, the researchers showed.

"We think this is going to be very enabling for robotics," says Michael Strano, the Carbon P. Dubbs Professor of Chemical Engineering at MIT and the senior author of the study. "We're building robotic functions onto the battery and starting to put these components together into devices."

Ge Zhang PhD '22 and Sungyun Yang, an MIT graduate student, are the lead author of the paper, which appears in Science Robotics.

Powered by batteries

For several years, Strano's lab has been working on tiny robots that can sense and respond to stimuli in their environment. One of the major challenges in developing such tiny robots is making sure that they have enough power.

Other researchers have shown that they can power microscale devices using solar power, but the limitation to that approach is that the robots must have a laser or another light source pointed at them at all times. Such devices are known as "marionettes" because they are controlled by an external power source. Putting a power source such as a battery inside these tiny devices could free them to roam much farther.

"The marionette systems don't really need a battery because they're getting all the energy they need from outside," Strano says. "But if you want a small robot to be able to get into spaces that you couldn't access otherwise, it needs to have a greater level of autonomy. A battery is essential for something that's not going to be tethered to the outside world."

To create robots that could become more autonomous, Strano's lab decided to use a type of battery known as a zinc-air battery. These batteries, which have a longer lifespan than many other types of batteries due to their high energy density, are often used in hearing aids.

The battery that they designed consists of a zinc electrode connected to a platinum electrode, embedded into a strip of a polymer called SU-8, which is commonly used for microelectronics. When these electrodes interact with oxygen molecules from the air, the zinc becomes oxidized and releases electrons that flow to the platinum electrode, creating a current.

In this study, the researchers showed that this battery could provide enough energy to power an actuator -- in this case, a robotic arm that can be raised and lowered. The battery could also power a memristor, an electrical component that can store memories of events by changing its electrical resistance, and a clock circuit, which allows robotic devices to keep track of time.

The battery also provides enough power to run two different types of sensors that change their electrical resistance when they encounter chemicals in the environment. One of the sensors is made from atomically thin molybdenum disulfide and the other from carbon nanotubes.

"We're making the basic building blocks in order to build up functions at the cellular level," Strano says.

Robotic swarms

In this study, the researchers used a wire to connect their battery to an external device, but in future work they plan to build robots in which the battery is incorporated into a device.

"This is going to form the core of a lot of our robotic efforts," Strano says. "You can build a robot around an energy source, sort of like you can build an electric car around the battery."

One of those efforts revolves around designing tiny robots that could be injected into the human body, where they could seek out a target site and then release a drug such as insulin. For use in the human body, the researchers envision that the devices would be made of biocompatible materials that would break apart once they were no longer needed.

The researchers are also working on increasing the voltage of the battery, which may enable additional applications.

Read more at Science Daily

Discovery of new Li ion conductor unlocks new direction for sustainable batteries

One of the grand challenges for materials science is the design and discovery of new materials that address global priorities such as Net Zero.

In a paper published in the journal Science, researchers at the University of Liverpool have discovered a solid material that rapidly conducts lithium ions.

Such lithium electrolytes are essential components in the rechargeable batteries that power electric vehicles and many electronic devices.

Consisting of non-toxic earth-abundant elements, the new material has high enough Li ion conductivity to replace the liquid electrolytes in current Li ion battery technology, improving safety and energy capacity.

Using a transformative scientific approach to design the material, the interdisciplinary research team from the University synthesised the material in the laboratory, determined its structure (the arrangement of the atoms in space) and demonstrated it in a battery cell.

The new material is one of a very small number of solid materials that achieve Li ion conductivity high enough to replace liquid electrolytes, and operates in a new way because of its structure.

Its discovery was achieved through a collaborative computational and experimental workflow that used AI and physics-based calculations to support decisions made by chemistry experts at the University.

The new material provides a platform for the optimisation of chemistry to further enhance the properties of the material itself, and to identify other materials based on the new understanding provided by the study.

Professor Matt Rosseinsky, from the University of Liverpool's Department of Chemistry, said: "This research demonstrates the design and discovery of a material that is both new and functional. The structure of this material changes previous understanding of what a high-performance solid-state electrolyte looks like.

"Specifically, solids with many different environments for the mobile ions can perform very well, not just the small number of solids where there is a very narrow range of ionic environments. This dramatically opens up the chemical space available for further discoveries.

Recent reports and media coverage herald the use of AI tools to find potentially new materials.

In these cases, the AI tools are working independently and thus are likely to recreate what they were trained on in various ways, generating materials that may be very similar to known ones.

"This discovery research paper shows that AI and computers marshalled by experts can tackle the complex problem of real-world materials discovery, where we seek meaningful differences in composition and structure whose impact on properties is assessed based on understanding."

"Our disruptive design approach offers a new route to discovery of these and other high-performance materials that rely on the fast motion of ions in solids."

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Next-generation batteries could go organic, cobalt-free for long-lasting power

In the switch to "greener" energy sources, the demand for rechargeable lithium-ion batteries is surging. However, their cathodes typically contain cobalt -- a metal whose extraction has high environmental and societal costs. Now, researchers in ACS Central Science report evaluating an earth-abundant, carbon-based cathode material that could replace cobalt and other scarce and toxic metals without sacrificing lithium-ion battery performance.

Today, lithium-ion batteries power everything from cell phones to laptops to electric vehicles.

One of the limiting factors for realizing a global shift to energy produced by renewable sources -- particularly for the transition from gasoline-powered cars to electric vehicles -- is the scarcity and mining difficulty of the metals, such as cobalt, nickel and magnesium, used in rechargeable battery cathode manufacturing.

Previous researchers have developed cathodes from more abundant and lower cost carbon-containing materials, including organosulfur and carbonyl compounds, but those prototypes couldn't match the energy output and stability of traditional lithium-ion batteries.

So, Mircea Dincǎ and his colleagues wanted to see if other carbon-based cathode materials could be more successful.

They may have found a worthy candidate in bis-tetraaminobenzoquinone (TAQ). TAQ molecules form layered solid-state structures than can potentially compete with traditional cobalt-based cathode performance.

Building on their prior work that showed TAQ's effectiveness as a supercapacitor material, Dincǎ's team tested the compound in a cathode for lithium-ion batteries. To improve cycling stability and to increase TAQ adhesion to the cathode's stainless-steel current collector, they added cellulose- and rubber-containing materials to the TAQ cathode. In the researchers' proof-of-concept demonstration, the new composite cathode cycled safely more than 2,000 times, delivered an energy density higher than most cobalt-based cathodes and charged-discharged in as little as six minutes. The TAQ-based cathodes need additional testing before they appear on the market, but the researchers are optimistic that they could enable the high-energy, long-lasting and fast-charging batteries needed to help speed a global transition to a renewable energy future that's cobalt- and nickel-free.

Read more at Science Daily

New designs for solid-state electrolytes may soon revolutionize the battery industry

Researchers led by Professor KANG Kisuk of the Center for Nanoparticle Research within the Institute for Basic Science (IBS), have announced a major breakthrough in the field of next-generation solid-state batteries. It is believed that their new findings will enable the creation of batteries based on a novel chloride-based solid electrolyte that exhibits exceptional ionic conductivity.

A pressing concern with current commercial batteries their reliance on liquid electrolytes, which leads to flammability and explosion risks. Therefore, the development of non-combustible solid electrolytes is of paramount importance for advancing solid-state battery technology. As the world gears up to regulate internal combustion engine vehicles and expand the use of electric vehicles in the ongoing global shift toward sustainable transportation, research into the core components of secondary batteries, particularly solid-state batteries, has gained significant momentum.

To make solid-state batteries practical for everyday use, it is crucial to develop materials with high ionic conductivity, robust chemical and electrochemical stability, and mechanical flexibility. While previous research successfully led to sulfide and oxide-based solid electrolytes with high ionic conductivity, none of these materials fully met all these essential requirements.

In the past, scientists have also explored chloride-based solid electrolytes, known for their superior ionic conductivity, mechanical flexibility, and stability at high voltages. These properties led some to speculate that chloride-based batteries are the most likely candidates for solid-state batteries. However, these hopes quickly died out, as the chloride batteries were considered impractical due to their heavy reliance on expensive rare earth metals, including yttrium, scandium, and lanthanide elements, as secondary components.

To address these concerns, the IBS research team looked at the distribution of metal ions in chloride electrolytes. They believed the reason trigonal chloride electrolytes can achieve low ionic conductivity is based on the variation of metal ion arrangements within the structure.

They first tested this theory on lithium yttrium chloride, a common lithium metal chloride compound. When the metal ions were positioned near the pathway of lithium ions, electrostatic forces caused obstruction in their movement. Conversely, if the metal ion occupancy was too low, the path for lithium ions became too narrow, impeding their mobility.

Building on these insights, the research team introduced strategies to design electrolytes in a way that mitigates these conflicting factors, ultimately leading to the successful development of a solid electrolyte with high ionic conductivity. The group went further to successfully demonstrate this strategy by creating a lithium-metal-chloride solid-state battery based on zirconium, which is far cheaper than the variants that employ rare earth metals. This was the first instance where the significance of the metal ions arrangement on a material's ionic conductivity was demonstrated.

This research brings to light the often-overlooked role of metal ion distribution in the ionic conductivity of chloride-based solid electrolytes. It is expected that the IBS Center's research will pave the way for the development of various chloride-based solid electrolytes and further drive the commercialization of solid-state batteries, promising improved affordability and safety in energy storage.

Read more at Science Daily

Cobalt-free battery for cleaner, greener power

High-capacity and reliable rechargeable batteries are a critical component of many devices and even modes of transport. They play a key role in the shift to a greener world. A wide variety of elements are used in their production, including cobalt, the production of which contributes to some environmental, economic, and social issues. For the first time, a team including researchers from the University of Tokyo presents a viable alternative to cobalt which in some ways can outperform state-of-the-art battery chemistry. It also survives a large number of recharge cycles, and the underlying theory can be applied to other problems.

The chances are, you are reading this article on a laptop or smartphone, and if not, you probably own at least one of those. Inside either device, and many others, you will find a lithium-ion battery (LIB). For decades now, LIBs have been the standard way of powering portable or mobile electronic devices and machines. As the world transitions from fossil fuels, they are seen as an important step for use in electric cars and home batteries for those with solar panels. But just as batteries have a positive end and a negative end, LIBs have negative points set against their positive ones.

For one thing, although they are some of the most power-dense portable power sources available, many people wish that LIBs could yield a larger energy density to make them either last longer or power even more demanding machines. Also, they can survive a large number of recharge cycles, but they also degrade with time; it would be better for everyone if batteries could survive more recharge cycles and maintain their capacities for longer. But perhaps the most alarming problem with current LIBs lies in one of the elements used for their construction.

Cobalt is widely used for a key part of LIBs, the electrodes. All batteries work in a similar way: Two electrodes, one positive and one negative, promote the flow of lithium ions between them in what's called the electrolyte when connected to an external circuit. Cobalt, however, is a rare element; so rare in fact that there is only one main source of it at present: a series of mines located in the Democratic Republic of Congo. Many issues have been reported over the years about the environmental consequences of these mines, as well as the labor conditions there, including the use of child labor. From a supply perspective also, the source of cobalt is an issue due to political and economic instability in the region.

"There are many reasons we want to transition away from using cobalt in order to improve lithium-ion batteries," said Professor Atsuo Yamada from the Department of Chemical System Engineering. "For us the challenge is a technical one, but its impact could be environmental, economic, social and technological. We are pleased to report a new alternative to cobalt by using a novel combination of elements in the electrodes, including lithium, nickel, manganese, silicon and oxygen -- all far more common and less problematic elements to produce and work with."

The new electrodes and electrolyte Yamada and his team created are not only devoid of cobalt, but they actually improve upon current battery chemistry in some ways. The new LIBs' energy density is about 60% higher, which could equate to longer life, and it can deliver 4.4 volts, as opposed to about 3.2-3.7 volts of typical LIBs. But one of the most surprising technological achievements was to improve upon the recharge characteristics. Test batteries with the new chemistry were able to fully charge and discharge over 1,000 cycles (simulating three years of full use and charging), whilst only losing about 20% of their storage capacity.

"We are delighted with the results so far, but getting here was not without its challenges. It was a struggle trying to suppress various undesirable reactions that were taking place in early versions of our new battery chemistries which could have drastically reduced the longevity of the batteries," said Yamada. "And we still have some way to go, as there are lingering minor reactions to mitigate in order to improve the safety and longevity even further. At present, we are confident that this research will lead to improved batteries for many applications, but some, where extreme durability and lifespan are required, might not be satisfied just yet."

Read more at Science Daily

Scientists invent micrometers-thin battery charged by saline solution that could power smart contact lenses

Scientists from Nanyang Technological University, Singapore (NTU Singapore) have developed a flexible battery as thin as a human cornea, which stores electricity when it is immersed in saline solution, and which could one day power smart contact lenses.

Smart contact lenses are high-tech contact lenses capable of displaying visible information on our corneas and can be used to access augmented reality. Current uses include helping to correct vision, monitoring wearers' health, and flagging and treating diseases for people with chronic health conditions such as diabetes and glaucoma. In the future, smart contact lenses could be developed to record and transmit everything a wearer sees and hears to cloud-based data storage.

However, to reach this future potential a safe and suitable battery needs to be developed to power them. Existing rechargeable batteries rely on wires or induction coils that contain metal and are unsuitable for use in the human eye, as they are uncomfortable and present risks to the user.

The NTU-developed battery is made of biocompatible materials and does not contain wires or toxic heavy metals, such as those in lithium-ion batteries or wireless charging systems. It has a glucose-based coating that reacts with the sodium and chloride ions in the saline solution surrounding it, while the water the battery contains serves as the 'wire' or 'circuitry' for electricity to be generated.

The battery could also be powered by human tears as they contain sodium and potassium ions, at a lower concentration. Testing the current battery with a simulated tear solution, the researchers showed that the battery's life would be extended an additional hour for every twelve-hour wearing cycle it is used. The battery can also be charged conventionally by an external power supply.

Associate Professor Lee Seok Woo, from NTU's School of Electrical and Electronic Engineering (EEE), who led the study, said: "This research began with a simple question: could contact lens batteries be recharged with our tears? There were similar examples for self-charging batteries, such as those for wearable technology that are powered by human perspiration.

"However, previous techniques for lens batteries were not perfect as one side of the battery electrode was charged and the other was not. Our approach can charge both electrodes of a battery through a unique combination of enzymatic reaction and self-reduction reaction. Besides the charging mechanism, it relies on just glucose and water to generate electricity, both of which are safe to humans and would be less harmful to the environment when disposed, compared to conventional batteries."

Co-first author Dr Yun Jeonghun, a research fellow from NTU's EEE said: "The most common battery charging system for smart contact lenses requires metal electrodes in the lens, which are harmful if they are exposed to the naked human eye. Meanwhile, another mode of powering lenses, induction charging, requires a coil to be in the lens to transmit power, much like wireless charging pad for a smartphone. Our tear-based battery eliminates the two potential concerns that these two methods pose, while also freeing up space for further innovation in the development smart contact lenses."

Highlighting the significance of the work done by the research team, NTU School of Mechanical & Aerospace Engineering Associate Professor Murukeshan Vadakke Matham, who specialises in biomedical and nanoscale optics and was not involved in the study, said: "As this battery is based on glucose oxidase, which occurs naturally in humans and powered by chloride and sodium ions, such as those in our tears, they should be compatible and suitable for human usage. Besides that, the smart contact lenses industry has been looking for a thin, biocompatible battery that does not contain heavy metals, and this invention could help further their development to meet some unmet needs of the industry."

The research team has filed for a patent through NTUitive, NTU's innovation and enterprise company. They are also working towards commercialising their invention.

The findings were published in the scientific journal Nano Energy in June.

Cry me a current

The team demonstrated their invention using a simulated human eye. The battery, which is about 0.5 millimetres-thin generates electrical power by reacting with the basal tears -- the constant tears that create a thin film over our eyeballs -- for the devices embedded within the lenses to function.

The flexible and flat battery discharges electricity through a process called reduction when its glucose oxidase coating reacts with the sodium and chloride ions in the tears, generating power and current within the contact lenses.

The team demonstrated that the battery could produce a current of 45 microamperes and a maximum power of 201 microwatts, which would be sufficient to power a smart contact lens.

Laboratory tests showed that the battery could be charged and discharged up to 200 times. Typical lithium-ion batteries have a lifespan of 300 to 500 charging cycles.

The team recommends that the battery should be placed for at least eight hours in a suitable solution that contains a high quantity of glucose, sodium and potassium ions, to be charged while the user is asleep.

Co-first author Miss Li Zongkang, a PhD student from NTU's EEE said: "Although wireless power transmission and supercapacitors supply high power, their integration presents a significant challenge due to the limited amount of space in the lens. By combining the battery and biofuel cell into a single component, the battery can charge itself without the need for additional space for wired or wireless components. Furthermore, the electrodes placed at the outer side of the contact lens ensures that the vision of the eye cannot be obstructed."

Read more at Science Daily

New platform could boost development of carbon-capturing batteries

Efficient and cheap batteries that can also capture harmful emissions could be right around the corner, thanks to a new system that speeds up the development of catalysts for lithium-CO2 (Li-CO2) batteries.

The technology has been developed by the University of Surrey, Imperial College London, and Peking University to address the slow and inefficient methods currently used to produce catalysts for Li-CO2 batteries.

In the study, researchers used their tool to test and screen materials like platinum, gold, silver, copper, iron and nickel to easily investigate whether they would be suitable candidates for developing high-performing Li-CO2 batteries.

Dr Kai Yang, corresponding author of this work, project co-leader and Lecturer from the Advanced Technology Institute at the University of Surrey, explained:

"We have created a cutting-edge lab-on-a-chip electrochemical testing platform that can do multiple things at the same time. It helps evaluate electrocatalysts, optimise operation conditions, and study CO2 conversion in high-performance lithium-CO2 batteries. This new method is more cost-effective, efficient, and controllable than traditional ways of making these materials."

Li-CO2 batteries are a promising new type of battery that work by combining lithium and carbon dioxide; they not only store energy effectively but also offer a way to capture CO2, potentially making a dual-contribution to the fight against climate change.

Dr Yunlong Zhao, the lead corresponding author of this study and a Senior Lecturer at Imperial College London, the National Physical Laboratory, and visiting academic from the University of Surrey, said:

"It is crucial that we develop new negative emissions technologies. Our lab-on-a-chip platform will play a crucial role in advancing this goal. It will not only enhance our understanding of novel batteries, but it can also be applied to other systems like metal-air batteries, fuel cells, and photoelectrochemical cells.

Read more at Science Daily

Generating power with blood sugar

In type 1 diabetes, the body does not produce insulin. This means that patients have to obtain the hormone externally to regulate their blood sugar levels. Nowadays, this is mostly done via insulin pumps that are attached directly to the body. These devices, as well as other medical applications such as pacemakers, require a reliable energy supply, which at present is met primarily by power from either single-use or rechargeable batteries.

Now, a team of researchers led by Martin Fussenegger from the Department of Biosystems Science and Engineering at ETH Zurich in Basel have put a seemingly futuristic idea into practice. They have developed an implantable fuel cell that uses excess blood sugar (glucose) from tissue to generate electrical energy. The researchers have combined the fuel cell with artificial beta cells developed by their group several years ago. These produce insulin at the touch of a button and effectively lower blood glucose levels much like their natural role models in the pancreas.

"Many people, especially in the Western industrialised nations, consume more carbohydrates than they need in everyday life," Fussenegger explains. This, he adds, leads to obesity, diabetes and cardiovascular disease. "This gave us the idea of using this excess metabolic energy to produce electricity to power biomedical devices," he says.

Fuel cell in tea bag format

At the heart of the fuel cell is an anode (electrode) made of copper-based nanoparticles, which Fussenegger's team created specifically for this application. It consists of copper-based nanoparticles and splits glucose into gluconic acid and a proton to generate electricity, which sets an electric circuit in motion.

Wrapped in a nonwoven fabric and coated with alginate, an algae product approved for medical use, the fuel cell resembles a small tea bag that can be implanted under the skin. The alginate soaks up body fluid and allows glucose to pass from the tissue into the fuel cell within.

A diabetes network with its own power supply

In a second step, the researchers coupled the fuel cell with a capsule containing artificial beta cells. These can be stimulated to produce and secrete insulin using electric current or blue LED light. Fussenegger and his colleagues already tested such designer cells some time ago (see ETH News, 8 December 2016).

The system combines sustained power generation and controlled insulin delivery. As soon as the fuel cell registers excess glucose, it starts to generate power. This electrical energy is then used to stimulate the cells to produce and release insulin into the blood. As a result, blood sugar dips to a normal level. Once it falls below a certain threshold value, the production of electricity and insulin stops.

The electrical energy provided by the fuel cell is sufficient not only to stimulate the designer cells but also to enable the implanted system to communicate with external devices such as a smartphone. This allows potential users to adjust the system via a corresponding app. A doctor could also access it remotely and make adjustments. "The new system autonomously regulates insulin and blood glucose levels and could be used to treat diabetes in the future," Fussenegger says.

Read more at Science Daily

Recyclable mobile phone batteries a step closer with rust-busting invention

Mobile phone batteries with a lifetime up to three times longer than today's technology could be a reality thanks to an innovation led by engineers at RMIT University.

Rather than disposing of batteries after two or three years, we could have recyclable batteries that last for up to nine years, the team says, by using high-frequency sound waves to remove rust that inhibits battery performance.

Only 10% of used handheld batteries, including for mobile phones, are collected for recycling in Australia, which is low by international standards. The remaining 90% of batteries go to landfill or are disposed of incorrectly, which causes considerable damage to the environment.

The high cost of recycling lithium and other materials from batteries is a major barrier to these items being reused, but the team's innovation could help to address this challenge.

The team are working with a nanomaterial called MXene, a class of materials that they say promises to be an exciting alternative to lithium for batteries in the future.

Leslie Yeo, Distinguished Professor of Chemical Engineering and lead senior researcher, said MXene was similar to graphene with high electrical conductivity.

"Unlike graphene, MXenes are highly tailorable and open up a whole range of possible technological applications in the future," said Yeo from RMIT's School of Engineering.

The big challenge with using MXene was that it rusted easily, thereby inhibiting electrical conductivity and rendering it unusable, he said.

"To overcome this challenge, we discovered that sound waves at a certain frequency remove rust from MXene, restoring it to close to its original state," Yeo said.

The team's innovation could one day help to revitalise MXene batteries every few years, extending their lifetime up to three times, he said.

"The ability to prolong the shelf life of MXene is critical to ensuring its potential to be used for commercially viable electronic parts," Yeo said.

The research is published in Nature Communications.

How the innovation works

Co-lead author Mr Hossein Alijani, a PhD candidate, said the greatest challenge with using MXene was the rust that forms on its surface in a humid environment or when suspended in watery solutions.

"Surface oxide, which is rust, is difficult to remove especially on this material, which is much, much thinner than a human hair," said Alijani from RMIT's School of Engineering.

"Current methods used to reduce oxidation rely on the chemical coating of the material, which limits the use of the MXene in its native form.

"In this work, we show that exposing an oxidised MXene film to high-frequency vibrations for just a minute removes the rust on the film. This simple procedure allows its electrical and electrochemical performance to be recovered."

The potential applications of the team's work

The team says their work to remove rust from Mxene opens the door for the nanomaterial to be used in a wide range of applications in energy storage, sensors, wireless transmission and environmental remediation.

Associate Professor Amgad Rezk, one of the lead senior researchers, said the ability to quickly restore oxidised materials to an almost pristine state represented a gamechanger in terms of the circular economy.

"Materials used in electronics, including batteries, generally suffer deterioration after two or three years of use due to rust forming," said Rezk from RMIT's School of Engineering.

"With our method, we can potentially extend the lifetime of battery components by up to three times."

Read more at Science Daily

Scientists convert waste paper into battery parts for smartphones and electric vehicles

Scientists from Nanyang Technological University, Singapore (NTU Singapore) have developed a technique to convert waste paper, from single-use packaging and bags, and cardboard boxes, into a crucial component of lithium-ion batteries.

Through a process called carbonisation which converts paper into pure carbon, the NTU researchers turned the paper's fibres into electrodes, which can be made into rechargeable batteries that power mobile phones, medical equipment, and electric vehicles.

To carbonise the paper, the team exposed the paper to high temperatures, which reduces it to pure carbon, water vapour and oils that can be used for biofuel. As carbonisation takes place in the absence of oxygen, this emits negligible amounts of carbon dioxide, and the process is a greener alternative to disposing of kraft paper through incineration, producing large amounts of greenhouse gasses.

The carbon anodes produced by the research team also demonstrated superior durability, flexibility, and electrochemical properties. Laboratory tests showed that the anodes could be charged and discharged up to 1,200 times, which is at least twice as durable as anodes in current phone batteries. The batteries that use the NTU-made anodes could also withstand more physical stress than their counterparts, absorbing crushing energy up to five times better.

The NTU-developed method also uses less energy-intensive processes and heavy metals compared to current industrial methods of manufacturing battery anodes. As the anode is worth 10 per cent to 15 per cent of the total cost of a lithium-ion battery, this latest method, which uses a low-cost waste material, is expected to also bring down the cost of manufacturing them.

The findings were published in the scientific peer-reviewed journal Additive Manufacturing in October.

Using waste paper as the raw material to produce battery anodes would also ease our reliance on conventional sources for carbon, such as carbonaceous fillers and carbon-yielding binders, which are mined and later processed with harsh chemicals and machinery.

Paper waste, which comprises disposed paper bags cardboard, newspaper, and other paper packaging, accounted for nearly a fifth of the waste generated in Singapore in 2020.

Kraft paper bags, which make up the bulk of Singapore's paper waste, were also found to have large environmental footprints compared to their counterparts made of cotton and plastic, due to their greater contribution to global warming when incinerated and the eco-toxicity potential in producing them, a separate 2020 NTU study found.

The current innovation which presents an opportunity to upcycle waste products and reduce our dependence on fossil fuels, accelerating our transition towards a circular economy, green materials, and clean energy, reflects NTU's commitment to mitigate our impact on the environment, which is one of four humanity's grand challenges that the University seeks to address through its NTU 2025 strategic plan.

Assistant Professor Lai Changquan, from NTU's School of Mechanical & Aerospace Engineering, who led the project, said: "Paper is used in many facets in our daily lives, from gift wrapping and arts and crafts, to a myriad of industrial uses, such as heavy-duty packaging, protective wrapping, and the filling of voids in construction. However, little is done to manage it when it is disposed of, besides incineration, which generates high levels of carbon emissions due to their composition. Our method to give kraft paper another lease of life, funnelling it into the growing need for devices such as electric vehicles and smartphones, would not only help cut down on carbon emissions but would also ease the reliance on mining and heavy industrial methods."

The research team has filed for a patent with NTUitive, NTU's innovation and enterprise company. They are also working towards commercialising their invention.

The recipe for greener battery parts

To produce the carbon anodes, the NTU researchers joined and laser cut several thin sheets of kraft paper to form different lattice geometries, some resembling a spikey piñata. The paper was then heated to 1200°C in a furnace without the presence of oxygen, to convert it into carbon, forming the anodes.

The NTU team attributes the anode's superior durability, flexibility, and electrochemical properties to the arrangement of the paper fibres. They said the combination of strength and mechanical toughness shown by the NTU-made anodes would allow batteries of phones, laptops and automobiles to better withstand shocks from falls and crashes.

Current lithium battery technology relies on internal carbon electrodes that gradually crack and crumble after physical shocks from being dropped, which is one of the main reasons why battery life gets shorter with time.

The researchers say that their anodes, which are hardier than current electrodes used in batteries, would help address this problem and extend the life of batteries in a wide array of uses, from electronics to electric vehicles.

Co-author of the study Mr Lim Guo Yao, a research engineer from NTU's School of Mechanical & Aerospace Engineering, said: "Our anodes displayed a combination of strengths, such as durability, shock absorption, electrical conductivity, which are not found in current materials. These structural and functional properties demonstrate that our kraft paper-based anodes are a sustainable and scalable alternative to current carbon materials, and would find economic value in demanding, high-end, multifunctional applications, such as the nascent field of structural batteries."

Asst Prof Lai added: "Our method converts a common and ubiquitous material -- paper -- into another that is extremely durable and in high demand. We hope that our anodes will serve the world's quickly growing need for a sustainable and greener material for batteries, whose manufacturing and improper waste management have shown to have a negative impact on our environment."

Highlighting the significance of the work done by the NTU research team, Professor Juan Hinestroza from the Department of Human Centered Design of Cornell University, US, who was not involved in the research, said: "As kraft paper is produced in very large quantities and disposed likewise all over the world, I believe that the creative approach pioneered by the researchers at NTU Singapore has a great potential for impact at a global scale. Any discovery that will allow the use of waste as a raw material for high-value products like electrodes and foams is indeed a great contribution. I think that this work may open a new avenue and motivate other researchers to find pathways for the transformation of other cellulose-based substrates, such as textiles and packaging materials, which are being discarded in large quantities all over the globe."

Read more at Science Daily

Affordable and sustainable alternative to lithium-ion batteries proposed

Concerns regarding scarcity, high prices, and safety regarding the long-term use of lithium-ion batteries has prompted a team of researchers from Rensselaer Polytechnic Institute to propose a greener, more efficient, and less expensive energy storage alternative.

In research published recently in Proceedings of the National Academy of Sciences (PNAS), corresponding author Nikhil Koratkar, the John A. Clark and Edward T. Crossan Professor of Engineering at Rensselaer, and his team, assert that calcium ions could be used as an alternative to lithium-ions in batteries because of its abundance and low cost.

"The vast majority of rechargeable battery products are based on lithium-ion technology, which is the gold standard in terms of performance," said Dr. Koratkar. "However, the Achilles' heel for lithium-ion technology is cost. Lithium is a limited resource on the planet, and its price has increased drastically in recent years. We are working on an inexpensive, abundant, safe, and sustainable battery chemistry that uses calcium ions in an aqueous, water-based electrolyte."

While the larger size and higher charge density of calcium ions relative to lithium impairs diffusion kinetics and cyclic stability, Dr. Koratkar and his team offer oxide structures containing big open spaces (heptagonal and hexagonal channels) as a prospective solution. In their work, an aqueous calcium-ion battery is demonstrated using orthorhombic and trigonal polymorphs of molybdenum vanadium oxide (MoVO) as a host for calcium ions.

"The calcium ion is divalent, and hence one ion insertion will deliver two electrons per ion during battery operation," explains Dr. Koratkar. "This allows for a highly efficient battery with reduced mass and volume of calcium ions. However, the higher ionic charge and the larger size of calcium ions relative to lithium makes it very challenging to insert calcium ions into the battery electrodes. We overcome this problem by developing a special class of materials called molybdenum vanadium oxides that contain large hexagonal and heptagonal shaped channels or tunnels that run through the material."

The team demonstrated that calcium ions can be rapidly inserted and extracted from the material, with these tunnels acting as "conduits" for reversible and fast ion transport and the findings indicate that MoVO provides one of the best performances reported to date for the storage of calcium ions.

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Longer lasting sodium-ion batteries on the horizon

Cheap and abundant, sodium is a prime promising candidate for new battery technology. But limited performance of sodium-ion batteries has hindered their large-scale applications.

Now, a research team from the Department of Energy's Pacific Northwest National Laboratory has developed a sodium-ion battery with greatly extended longevity in laboratory tests. An ingenious shift in the ingredients that make up the liquid core of the battery prevents the performance issues that have bedeviled sodium-based batteries. The findings, described in the journal Nature Energy, provide a promising recipe for a battery that may one day power electric vehicles and store energy from the sun.

"Here, we have shown in principle that sodium-ion batteries have the potential to be a long lasting and environmentally friendly battery technology," said PNNL lead author Jiguang (Jason) Zhang, a pioneer of battery technologies with more than 23 patented inventions in energy storage technology.

The right salt

In batteries, electrolyte is the circulating "blood" that keeps the energy flowing. The electrolyte forms by dissolving salts in solvents, resulting in charged ions that flow between the positive and negative electrodes. Over time, the electrochemical reactions that keep the energy flowing get sluggish, and the battery can no longer recharge. In current sodium-ion battery technologies, this process happens much faster than in similar lithium-ion batteries.

The PNNL team, led by scientists Yan Jin and Phung Le, attacked that problem by switching out the liquid solution and the type of salt flowing through it to create a wholly new electrolyte recipe. In laboratory tests, the new design proved durable, holding 90 percent of its cell capacity after 300 cycles at 4.2 V, which is higher than most sodium-ion batteries previously reported.

The current electrolyte recipe for sodium-ion batteries results in the protective film on the negative end (the anode) dissolving over time. This film is critical because it allows sodium ions to pass through while preserving battery life. The PNNL-designed technology works by stabilizing this protective film. The new electrolyte also generates an ultra-thin protective layer on the positive pole (the cathode) that contributes to additional stability of the entire unit.

Non-flammable technology

The new PNNL-developed sodium-ion technology uses a naturally fire-extinguishing solution that is also impervious to temperature changes and can operate at high voltages. One key to this feature is the ultra-thin protective layer that forms on the anode. This ultra-thin layer remains stable once formed, providing the long cycle life reported in the research article.

"We also measured the production of gas vapor at the cathode," said Phung Le, a PNNL battery chemist and one of the lead authors of the study. "We found very minimal gas production. This provides new insights to develop stable electrolyte for sodium-ion batteries that may operate at elevated temperatures."

For now, the sodium-ion technology still lags behind lithium in energy density. But it has its own advantages, such as imperviousness to temperature changes, stability and long cycle life, which are valuable for applications of certain light-duty electric vehicles and even grid energy storage in the future.

The research team continues to refine their design. Le noted that the team is experimenting with other designs in an effort to reduce -- and eventually eliminate -- the need to include cobalt, which is toxic and expensive if not recovered or recycled.

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Banning the sale of fossil-fuel cars benefits the climate when replaced by electric cars

If a ban were introduced on the sale of new petrol and diesel cars, and they were replaced by electric cars, the result would be a great reduction in carbon dioxide emissions. That is the finding of new research from Chalmers University of Technology, Sweden, looking at emissions from the entire life cycle -- from manufacture of electric cars and batteries, to electricity used for operation. However, the total effect of a phasing out of fossil-fuelled cars will not be felt until the middle of the century -- and how the batteries are manufactured will affect the extent of the benefit.

A rapid and mandatory phasing in of electric cars could cause emissions from Swedish passenger cars' exhausts to approach zero by 2045. The Swedish government has proposed an outright ban on the sale of new fossil fuel cars from the year 2030 -- but that alone will not be enough to achieve Sweden's climate targets on schedule.

"The lifespan of the cars currently on the roads and those which would be sold before the introduction of such a restriction mean that it would take some time -- around 20 years -- before the full effect becomes visible," says Johannes Morfeldt, researcher in Physical Resource Theory at Chalmers University of Technology and lead author of the recently published scientific study.

To have the desired effect, a ban would either need to be introduced earlier, by the year 2025, or, if the ban is not brought in until 2030, then the use of biofuels in petrol and diesel cars needs to increase significantly before then -- in accordance with the revised Swedish "reduction obligation." The combination of these two measures would have the effect of achieving zero emissions from passenger vehicles and keeping to Sweden's climate targets.

"The results from our study show that rapid electrification of the Swedish car fleet would reduce life cycle emissions, from 14 million tonnes of carbon dioxide in 2020 to between 3 and 5 million tonnes by the year 2045. The end result in 2045 will depend mainly on the extent to which possible emission reductions in the manufacturing industry are realised," says Johannes Morfeldt.

A transition from petrol and diesel cars to electric cars will mean an increased demand for batteries. Batteries for electric cars are often criticised, not least for the fact that they result in high levels of greenhouse gas emissions during manufacture.

"There are relatively good opportunities to reduce emissions from global battery manufacturing. Our review of the literature on this shows that average emissions from global battery manufacturing could decrease by about two thirds per kilowatt hour of battery capacity by the year 2045. However, most battery manufacturing takes place overseas, so Swedish decision-makers have more limited opportunities to influence this question," says Johannes Morfeldt.

From a climate perspective, it does not matter where the emissions take place, and the risk with decisions taken at a national level for lowering passenger-vehicle emissions is that they could lead to increased emissions elsewhere -- a phenomenon sometimes termed 'carbon leakage'. In this case, the increase in emissions would result from greater demand for batteries, and the risk is thus greater the higher the emissions from battery production.

In that case, the Swedish decision would not have as great an effect on reducing the climate impact as desired. The life-cycle emissions would end up in the upper range -- around 5 million tonnes of carbon dioxide instead of around 3 million tonnes. Due to this, there may be reason to regulate emissions in both vehicle and battery production, from a life cycle perspective.

"Within the EU, for example, there is a discussion about setting a common standard for the manufacture of batteries and vehicles -- in a similar way as there is a standard that regulates what may be emitted from exhausts," says Johannes Morfeldt.

But, given Sweden's low emissions from electricity production, a ban on sales of new fossil-fuel cars would indeed result in a sharp reduction of the total climate impact, regardless of how the manufacturing industry develops.

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An anode-free zinc battery that could someday store renewable energy

 Renewable energy sources, such as wind and solar power, could help decrease the world's reliance on fossil fuels. But first, power companies need a safe, cost-effective way to store the energy for later use. Massive lithium-ion batteries can do the job, but they suffer from safety issues and limited lithium availability. Now, researchers reporting in ACS' Nano Letters have made a prototype of an anode-free, zinc-based battery that uses low-cost, naturally abundant materials.

Aqueous zinc-based batteries have been previously explored for grid-scale energy storage because of their safety and high energy density. In addition, the materials used to make them are naturally abundant. However, the rechargeable zinc batteries developed so far have required thick zinc metal anodes, which contain a large excess of zinc that increases cost. Also, the anodes are prone to forming dendrites -- crystalline projections of zinc metal that deposit on the anode during charging -- that can short-circuit the battery. Yunpei Zhu, Yi Cui and Husam Alshareef wondered whether a zinc anode was truly needed. Drawing inspiration from previous explorations of "anode-free" lithium and sodium-metal batteries, the researchers decided to make a battery in which a zinc-rich cathode is the sole source for zinc plating onto a copper current collector.

In their battery, the researchers used a manganese dioxide cathode that they pre-intercalated with zinc ions, an aqueous zinc trifluoromethanesulfonate electrolyte solution and a copper foil current collector. During charging, zinc metal gets plated onto the copper foil, and during discharging the metal is stripped off, releasing electrons that power the battery. To prevent dendrites from forming, the researchers coated the copper current collector with a layer of carbon nanodiscs. This layer promoted uniform zinc plating, thereby preventing dendrites, and increased the efficiency of zinc plating and stripping. The battery showed high efficiency, energy density and stability, retaining 62.8% of its storage capacity after 80 charging and discharging cycles. The anode-free battery design opens new directions for using aqueous zinc-based batteries in energy storage systems, the researchers say.

From Science Daily

Inexpensive battery charges rapidly for electric vehicles, reduces range anxiety

 Range anxiety, the fear of running out of power before being able to recharge an electric vehicle, may be a thing of the past, according to a team of Penn State engineers who are looking at lithium iron phosphate batteries that have a range of 250 miles with the ability to charge in 10 minutes.

"We developed a pretty clever battery for mass-market electric vehicles with cost parity with combustion engine vehicles," said Chao-Yang Wang, William E. Diefenderfer Chair of mechanical engineering, professor of chemical engineering and professor of materials science and engineering, and director of the Electrochemical Engine Center at Penn State. "There is no more range anxiety and this battery is affordable."

The researchers also say that the battery should be good for 2 million miles in its lifetime.

They report today (Jan. 18) in Nature Energy that the key to long-life and rapid recharging is the battery's ability to quickly heat up to 140 degrees Fahrenheit, for charge and discharge, and then cool down when the battery is not working.

"The very fast charge allows us to downsize the battery without incurring range anxiety," said Wang.

The battery uses a self-heating approach previously developed in Wang's center. The self-heating battery uses a thin nickel foil with one end attached to the negative terminal and the other extending outside the cell to create a third terminal. Once electrons flow it rapidly heats up the nickel foil through resistance heating and warm the inside of the battery. Once the battery's internal temperature is 140 degrees F, the switch opens and the battery is ready for rapid charge or discharge.

Wang's team modeled this battery using existing technologies and innovative approaches. They suggest that using this self-heating method, they can use low-cost materials for the battery's cathode and anode and a safe, low-voltage electrolyte. The cathode is thermally stable, lithium iron phosphate, which does not contain any of the expensive and critical materials like cobalt. The anode is made of very large particle graphite, a safe, light and inexpensive material.

Because of the self-heating, the researchers said they do not have to worry about uneven deposition of lithium on the anode, which can cause lithium spikes that are dangerous.

"This battery has reduced weight, volume and cost," said Wang. "I am very happy that we finally found a battery that will benefit the mainstream consumer mass market."

According to Wang, these smaller batteries can produce a large amount of power upon heating -- 40 kilowatt hours and 300 kilowatts of power. An electric vehicle with this battery could go from zero to 60 miles per hour in 3 seconds and would drive like a Porsche, he said.

"This is how we are going to change the environment and not contribute to just the luxury cars," said Wang. "Let everyone afford electric vehicles."

Other Penn State researchers working on this project were Xiao-Guang Yang, assistant research professor of mechanical engineering, and Teng Liu, doctoral student in mechanical engineering.

Read more at Science Daily

Supercapacitors challenge batteries

 A team working with Roland Fischer, Professor of Inorganic and Metal-Organic Chemistry at the Technical University Munich (TUM) has developed a highly efficient supercapacitor. The basis of the energy storage device is a novel, powerful and also sustainable graphene hybrid material that has comparable performance data to currently utilized batteries.

Usually, energy storage is associated with batteries and accumulators that provide energy for electronic devices. However, in laptops, cameras, cellphones or vehicles, so-called supercapacitors are increasingly installed these days.

Unlike batteries they can quickly store large amounts of energy and put it out just as fast. If, for instance, a train brakes when entering the station, supercapacitors are storing the energy and provide it again when the train needs a lot of energy very quickly while starting up.

However, one problem with supercapacitors to date was their lack of energy density. While lithium accumulators reach an energy density of up to 265 Kilowatt hours (KW/h), supercapacitors thus far have only been delivering a tenth thereof.

Sustainable material provides high performance

The team working with TUM chemist Roland Fischer has now developed a novel, powerful as well as sustainable graphene hybrid material for supercapacitors. It serves as the positive electrode in the energy storage device. The researchers are combining it with a proven negative electrode based on titan and carbon.

The new energy storage device does not only attain an energy density of up to 73 Wh/kg, which is roughly equivalent to the energy density of an nickel metal hydride battery, but also performs much better than most other supercapacitors at a power density of 16 kW/kg. The secret of the new supercapacitor is the combination of different materials -- hence, chemists refer to the supercapacitor as "asymmetrical."

Hybrid materials: Nature is the role model

The researchers are betting on a new strategy to overcome the performance limits of standard materials -- they utilize hybrid materials. "Nature is full of highly complex, evolutionarily optimized hybrid materials -- bones and teeth are examples. Their mechanical properties, such as hardness and elasticity were optimized through the combination of various materials by nature," says Roland Fischer.

The abstract idea of combining basic materials was transferred to supercapacitors by the research team. As a basis, they used the novel positive electrode of the storage unit with chemically modified graphene and combined it with a nano-structured metal organic framework, a so-called MOF.

Powerful and stable

Decisive for the performance of graphene hybrids are on the one hand a large specific surface and controllable pore sizes and on the other hand a high electrical conductivity. "The high performance capabilities of the material is based on the combination of the microporous MOFs with the conductive graphene acid," explains first author Jayaramulu Kolleboyina, a former guest scientist working with Roland Fischer.

A large surface is important for good supercapacitors. It allows for the collection of a respectively large number of charge carriers within the material -- this is the basic principle for the storage of electrical energy.

Through skillful material design, the researchers achieved the feat of linking the graphene acid with the MOFs. The resulting hybrid MOFs have a very large inner surface of up to 900 square meters per gram and are highly performant as positive electrodes in a supercapacitor.

Long stability

However, that is not the only advantage of the new material. To achieve a chemically stable hybrid, one needs strong chemical bonds between the components. The bonds are apparently the same as those between amino acids in proteins, according to Fischer: "In fact, we have connected the graphene acid with a MOF-amino acid, which creates a type of peptide bond."

The stable connection between the nano-structured components has huge advantages in terms of long term stability: The more stable the bonds, the more charging and discharging cycles are possible without significant performance impairment.

For comparison: A classic lithium accumulator has a useful life of around 5,000 cycles. The new cell developed by the TUM researchers retains close to 90 percent capacity even after 10,000 cycles.

International network of experts

Fischer emphasizes how important the unfettered international cooperation the researchers controlled themselves was when it came to the development of the new supercapacitor. Accordingly, Jayaramulu Kolleboyina built the team. He was a guest scientist from India invited by the Alexander von Humboldt Foundation and who by now is the head of the chemistry department at the newly established Indian Institute of Technology in Jammu.

"Our team also networked with electro-chemistry and battery research experts in Barcelona as well as graphene derivate experts from the Czech Republic," reports Fischer. "Furthermore, we have integrated partners from the USA and Australia. This wonderful, international co-operation promises much for the future."

Read more at Science Daily

Charging electric cars up to 90% in 6 minutes

 With Telsa in the lead, the electric vehicle market is growing around the world. Unlike conventional cars that use internal combustion engines, electric cars are solely powered by lithium ion batteries, so the battery performance defines the car's overall performance. However, slow charging times and weak power are still barriers to be overcome. In light of this, a POSTECH research team has recently developed a faster charging and longer lasting battery material for electric cars.

The research teams of Professor Byoungwoo Kang and Dr. Minkyung Kim of the Department of Materials Science and Engineering at POSTECH and Professor Won-Sub Yoon in the Department of Energy Science at Sungkyunkwan University have together proved for the first time that when charging and discharging Li-ion battery electrode materials, high power can be produced by significantly reducing the charging and discharging time without reducing the particle size. These research findings were published in the recent issue of Energy & Environmental Science, a leading international journal in the energy materials field.

For fast charging and discharging of Li-ion batteries, methods that reduce the particle size of electrode materials were used so far. However, reducing the particle size has a disadvantage of decreasing the volumetric energy density of the batteries.

To this, the research team confirmed that if an intermediate phase in the phase transition is formed during the charging and discharging, high power can be generated without losing high energy density or reducing the particle size through rapid charging and discharging, enabling the development of long-lasting Li-ion batteries.

In the case of phase separating materials that undergo the process of creating and growing new phases while charging and discharging, two phases with different volumes exist within a single particle, resulting in many structural defects in the interface of the two phases. These defects inhibit the rapid growth of a new phase within the particle, hindering quick charging and discharging.

Using the synthesis method developed by the research team, one can induce an intermediate phase that acts as a structural buffer that can dramatically reduce the change in volume between the two phases in a particle.

In addition, it has been confirmed that this buffering intermediate phase can help create and grow a new phase within the particle, improving the speed of insertion and removal of lithium in the particle. This in turn proved that the intermediate phase formation can dramatically increase the charging and discharging speed of the cell by creating a homogenous electrochemical reaction in the electrode where numerous particles is composed of. As a result, the Li-ion battery electrodes synthesized by the research team charge up to 90% in six minutes and discharge 54% in 18 seconds, a promising sign for developing high-power Li-ion batteries.

"The conventional approach has always been a trade-off between its low energy density and the rapid charge and discharge speed due to the reduction in the particle size," remarked Professor Byoungwoo Kang, the corresponding author of the paper. He elaborated, "This research has laid the foundation for developing Li-ion batteries that can achieve quick charging and discharging speed, high energy density, and prolonged performance."

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'Spillway' for electrons could keep lithium metal batteries from catching fire

Nanoengineers at the University of California San Diego developed a safety feature that prevents lithium metal batteries from rapidly heating up and catching fire in case of an internal short circuit.

The team made a clever tweak to the part of the battery called the separator, which serves as a barrier between the anode and cathode, so that it slows down the flow of energy (and thus heat) that builds up inside the battery when it short circuits.

The researchers, led by UC San Diego nanoengineering professor Ping Liu and his Ph.D. student Matthew Gonzalez, detail their work in a paper published in Advanced Materials.

"We're not trying to stop battery failure from happening. We're making it much safer so that when it does fail, the battery doesn't catastrophically catch on fire or explode," said Gonzalez, who is the paper's first author.

Lithium metal batteries fail because of the growth of needle-like structures called dendrites on the anode after repeated charging. Over time, dendrites grow long enough to pierce through the separator and create a bridge between the anode and cathode, causing an internal short circuit. When that happens, the flow of electrons between the two electrodes gets out of control, causing the battery to instantly overheat and stop working.

The separator that the UC San Diego team developed essentially softens this blow. One side is covered by a thin, partially conductive web of carbon nanotubes that intercepts any dendrites that form. When a dendrite punctures the separator and hits this web, electrons now have a pathway through which they can slowly drain out rather than rush straight towards the cathode all at once.

Gonzalez compared the new battery separator to a spillway at a dam.

"When a dam starts to fail, a spillway is opened up to let some of the water trickle out in a controlled fashion so that when the dam does break and spill out, there's not a lot of water left to cause a flood," he said. "That's the idea with our separator. We are draining out the charge much, much slower and prevent a 'flood' of electrons to the cathode. When a dendrite gets intercepted by the separator's conductive layer, the battery can begin to self-discharge so that when the battery does short, there's not enough energy left to be dangerous."

Other battery research efforts focus on building separators out of materials that are strong enough to block dendrites from breaking through. But a problem with this approach is that it just prolongs the inevitable, Gonzalez said. These separators still need to have pores that let ions flow through in order for the battery to work. As a consequence, when the dendrites eventually make it through, the short circuit will be even worse.

Rather than block dendrites, the UC San Diego team sought to mitigate their effects.

In tests, lithium metal batteries equipped with the new separator showed signs of gradual failure over 20 to 30 cycles. Meanwhile, batteries with a normal (and slightly thicker) separator experienced abrupt failure in a single cycle.

"In a real use case scenario, you wouldn't have any advance warning that the battery is going to fail. It could be fine one second, then catch on fire or short out completely the next. It's unpredictable," Gonzalez said. "But with our separator, you would get advance warning that the battery is getting a little bit worse, a little bit worse, a little bit worse, each time you charge it."

Read more at Science Daily

Will the future's super batteries be made of seawater?

We all know the rechargeable and efficient lithium ion (Li-ion) batteries sitting in our smartphones, laptops and also in electric cars.

Unfortunately, lithium is a limited resource, so it will be a challenge to satisfy the worlds' growing demand for relatively cheap batteries. Therefore, researchers are now looking for alternatives to the Li-ion battery.

A promising alternative is to replace lithium with the metal sodium -- to make Na-ion batteries. Sodium is found in large quantities in seawater and can be easily extracted from it.

"The Na-ion battery is still under development, and researchers are working on increasing its service life, lowering its charging time and making batteries that can deliver many watts," says research leader Dorthe Bomholdt Ravnsbæk of the Department of Physics, Chemistry and Pharmacy at University of Southern Denmark.

She and her team are preoccupied with developing new and better rechargeable batteries that can replace todays' widely used Li-ion batteries.

For the Na-ion batteries to become an alternative, better electrode materials must be developed -- something she and colleagues from the University of Technology and the Massachusetts Institute of Technology, USA, have looked at in a new study published in the journal ACS Applied Energy Materials.

But before looking at the details of this study, let's take a look at why the Na-ion battery has the potential to become the next big battery success.

"An obvious advantage is that sodium is a very readily available resource, which is found in very large quantities in seawater. Lithium, on the other hand, is a limited resource that is mined only in a few places in the world," explains Dorthe Bomholdt Ravnsbæk.

Another advantage is that Na-ion batteries do not need cobalt, which is still needed in Li-ion batteries. The majority of the cobalt used today to make Li-ion batteries, is mined in the Democratic Republic of Congo, where rebellion, disorganized mining and child labor create uncertainty and moral qualms regarding the country's cobalt trade.

It also counts on the plus side that Na-ion batteries can be produced at the same factories that make Li-ion batteries today.

In their new study, Dorthe Bomholdt Ravnsbæk and her colleagues have investigated a new electrode material based on iron, manganese and phosphorus.

The new thing about the material is the addition of the element manganese, which not only gives the battery a higher voltage (volts), but also increases the capacity of the battery and is likely to deliver more watts. This is because the transformations that occur at the atomic level during the discharge and charge are significantly changed by the presence of manganese.

"Similar effects have been seen in Li-ion batteries, but it is very surprising that the effect is retained in a Na-ion battery, since the interaction between the electrode and Na-ions is very different from that of Li-ions," says Dorthe Bomholdt Ravnsbæk.

She will not try and predict when we can expect to find seawater-based Na-ion batteries in our phones and electric cars, because there are still some challenges to be solved.

One challenge is that it can be difficult to make small Na-ion batteries. But large batteries also have value -- for example, when it comes to storing wind or solar energy.

Read more at Science Daily

Go with the flow: Scientists design new grid batteries for renewable energy

High-voltage tower

How do you store renewable energy so it's there when you need it, even when the sun isn't shining or the wind isn't blowing? Giant batteries designed for the electrical grid -- called flow batteries, which store electricity in tanks of liquid electrolyte -- could be the answer, but so far utilities have yet to find a cost-effective battery that can reliably power thousands of homes throughout a lifecycle of 10 to 20 years.

Now, a battery membrane technology developed by researchers at the U.S. Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) may point to a solution.

As reported in the journal of Joule, the researchers developed a versatile yet affordable battery membrane -- from a class of polymers known as AquaPIMs. This class of polymers makes long-lasting and low-cost grid batteries possible based solely on readily available materials such as zinc, iron, and water. The team also developed a simple model showing how different battery membranes impact the lifetime of the battery, which is expected to accelerate early stage R&D for flow-battery technologies, particularly in the search for a suitable membrane for different battery chemistries.

"Our AquaPIM membrane technology is well-positioned to accelerate the path to market for flow batteries that use scalable, low-cost, water-based chemistries," said Brett Helms, a principal investigator in the Joint Center for Energy Storage Research (JCESR) and staff scientist at Berkeley Lab's Molecular Foundry who led the study. "By using our technology and accompanying empirical models for battery performance and lifetime, other researchers will be able to quickly evaluate the readiness of each component that goes into the battery, from the membrane to the charge-storing materials. This should save time and resources for researchers and product developers alike."

Most grid battery chemistries have highly alkaline (or basic) electrodes -- a positively charged cathode on one side, and a negatively charged anode on the other side. But current state-of-the-art membranes are designed for acidic chemistries, such as the fluorinated membranes found in fuel cells, but not for alkaline flow batteries. (In chemistry, pH is a measure of the hydrogen ion concentration of a solution. Pure water has a pH of 7 and is considered neutral. Acidic solutions have a high concentration of hydrogen ions, and are described as having a low pH, or a pH below 7. On the other hand, alkaline solutions have low concentrations of hydrogen ions and therefore have a high pH, or a pH above 7. In alkaline batteries, the pH can be as high as 14 or 15.)

Fluorinated polymer membranes are also expensive. According to Helms, they can make up 15% to 20% of the battery's cost, which can run in the range of $300/kWh.

One way to drive down the cost of flow batteries is to eliminate the fluorinated polymer membranes altogether and come up with a high-performing yet cheaper alternative such as AquaPIMs, said Miranda Baran, a graduate student researcher in Helms' research group and the study's lead author. Baran is also a Ph.D. student in the Department of Chemistry at UC Berkeley.

Getting back to basics

Helms and co-authors discovered the AquaPIM technology -- which stands for "aqueous-compatible polymers of intrinsic microporosity" -- while developing polymer membranes for aqueous alkaline (or basic) systems as part of a collaboration with co-author Yet-Ming Chiang, a principal investigator in JCESR and Kyocera Professor of Materials Science and Engineering at the Massachusetts Institute of Technology (MIT).

Through these early experiments, the researchers learned that membranes modified with an exotic chemical called an "amidoxime" allowed ions to quickly travel between the anode and cathode.

Later, while evaluating AquaPIM membrane performance and compatibility with different grid battery chemistries -- for example, one experimental setup used zinc as the anode and an iron-based compound as the cathode -- the researchers discovered that AquaPIM membranes lead to remarkably stable alkaline cells.

In addition, they found that the AquaPIM prototypes retained the integrity of the charge-storing materials in the cathode as well as in the anode. When the researchers characterized the membranes at Berkeley Lab's Advanced Light Source (ALS), the researchers found that these characteristics were universal across AquaPIM variants.

Baran and her collaborators then tested how an AquaPIM membrane would perform with an aqueous alkaline electrolyte. In this experiment, they discovered that under alkaline conditions, polymer-bound amidoximes are stable -- a surprising result considering that organic materials are not typically stable at high pH.

Such stability prevented the AquaPIM membrane pores from collapsing, thus allowing them to stay conductive without any loss in performance over time, whereas the pores of a commercial fluoro-polymer membrane collapsed as expected, to the detriment of its ion transport properties, Helms explained.

This behavior was further corroborated with theoretical studies by Artem Baskin, a postdoctoral researcher working with David Prendergast, who is the acting director of Berkeley Lab's Molecular Foundry and a principal investigator in JCESR along with Chiang and Helms.

Baskin simulated structures of AquaPIM membranes using computational resources at Berkeley Lab's National Energy Research Scientific Computing Center (NERSC) and found that the structure of the polymers making up the membrane were significantly resistant to pore collapse under highly basic conditions in alkaline electrolytes.

A screen test for better batteries

While evaluating AquaPIM membrane performance and compatibility with different grid battery chemistries, the researchers developed a model that tied the performance of the battery to the performance of various membranes. This model could predict the lifetime and efficiency of a flow battery without having to build an entire device. They also showed that similar models could be applied to other battery chemistries and their membranes.

"Typically, you'd have to wait weeks if not months to figure out how long a battery will last after assembling the entire cell. By using a simple and quick membrane screen, you could cut that down to a few hours or days," Helms said.

Read more at Science Daily