Category: Battery News

A Japanese research group developed a rechargeable battery based on a new principle in cooperation with Nippon Shokubai Co Ltd.

The group is led by Noritaka Mizuno, professor at the School of Engineering, the University of Tokyo. The new battery uses the oxidation-reduction reaction between oxide ions and peroxide ions at the positive electrode. The group proved that peroxides are generated and dispersed due to charge and discharge reactions by using a material made by adding cobalt (Co) to the crystal structure of lithium oxide (Li2O) for the positive electrode, verifying a battery system based on a new principle.

The new technology can realize an energy density seven times higher than that of existing lithium (Li)-ion rechargeable batteries, increase capacity, lower price and enhance safety. It is expected to be used for batteries for electric vehicles (EVs) and next-generation stationary batteries.

The oxidation-reduction reaction between Li2O and Li2O2 (lithium peroxide) and oxidation-reduction reaction of metal Li are used at the positive and negative electrodes, respectively, of the new battery. The battery has a theoretical capacity of 897mAh per 1g of the positive/negative electrode active material, voltage of 2.87V and theoretical energy density of 2,570Wh/kg.

At that time, the energy density is 370Wh per 1kg of the positive/negative electrode active material, which is about seven times higher than that of existing Li-ion rechargeable batteries using LiCoO2 positive electrodes and graphite negative electrodes. The theoretical energy density of the new battery is lower than that of lithium-air batteries (3,460Wh/kg). But it has a sealed structure like conventional Li-ion batteries, realizing a high reliability and safety.

This time, as the positive electrode material, the research group used a material made by using a planetary ball mill to add Co to the crystal structure of LiO2. And the group proved that it is possible to realize a battery system in which the oxidation-reduction reaction between oxides and peroxides reversibly proceeds. And it proved that (1) peroxides are generated in the positive electrode for charge, (2) the peroxides are dispersed for discharge and (3) those reactions are repeated, by quantitatively analyzing the peroxides.

The group also proved that neither O2 nor CO2 is generated in the range where it is possible to reversibly charge/discharge the battery.

The positive electrode used in the demonstration test enables to repeatedly charge/discharge the battery with a capacity of 200mAh/g and to quickly charge/discharge the battery with a large current. The positive electrode has a smaller mass ratio of Co than LiCoO2, which is used for existing Li-ion batteries, and possibly lowers costs.

South Korean supplier LG Chem plans to supply batteries for electric vehicles that can travel more than 200 miles, or 321 kilometers, per charge in 2016, its CFO said on Friday.

The CFO, Cho Suk-jeh, did not elaborate on which automakers will use the so-called second-generation batteries.

LG Chem currently supplies batteries for General Motors, Renault SA and other automakers.

GM's former CEO, Dan Akerson, said last year the U.S. automaker, which currently sells the Chevrolet Volt and Cadillac ELR hybrids, was working on new electric vehicles, including one with a 200-mile driving range.

Researchers have tested a unique combination of hybrid supercapacitor-battery materials that combines fast electrochemical charge times with the high energy density of a li-ion battery.

Li-ion batteries with high specific energy, high power density, long cycle life and low cost are critical for widespread adoption of electric vehicles. A key bottleneck in achieving this goal is the limited fast charging ability of Li-ion Batteries. Rapid charging causes accelerated degradation of the battery as well as a potential fire hazard due to local over-potential build-up and increased heat generation. Li-ion Batteries have the highest energy density but typically suffer from low power density.

On the other extreme, electrochemical double-layer supercapacitors, which store energy through accumulation of ions on the electrode surface, have low energy storage capacity but very high power density.

A special category of electrochemical capacitors is provided by redox capacitors. Here, charge is stored through surface or bulk (pseudocapacitive) redox reactions, similar to Li-ion Batteries, yet, with a very fast charge transfer response, similar to electrochemical double-layer capacitors. Although excellent capacity retention for extended cycling can be obtained even at high charge - discharge rates, specific capacity of redox capacitors is typically lower than for Li-ion batteries.

The most intuitive approach to combine high energy and high power density within a single device is to combine the different types of energy storage sources. So far, mainly hybridization between electrochemical double-layer capacitors and Li-ion batteries has been explored. The primary drawback of this approach is that power and energy performances are decoupled. At high current densities, the response is dominated by the electrochemical double-layer capacitor component, considerably diminishing the energy density of the hybrid device.

Researchers have now shown that enhanced battery-capacitor hybrids can be constructed by careful choice of the super-capacitor and battery components. They combined a lithium iron phosphate (LiFePO4) battery material with poly (PTMA) redox capacitor. The PTMA and LiFePO4 hybrid ultra-battery gives best-of-both-worlds performance characteristics: high energy and power capacity as well as fast and stable recharge for more than 1,500 cycles.

In addition to improved cycling and rate performances, the hybrid electrode features a unique fast charge storage mechanism. When a charge current is applied on the hybrid electrode, the polarization of PTMA and LiFePO4 overlap above the equilibrium values and both components are charged (or, oxidized). However, the faster redox kinetics of PTMA results in excess charging of the PTMA component.

When the current supply is stopped, the potential of both components in the electrode tends to reach their equilibrium open circuit potential. However, the electrochemical potential of the PTMA is higher than that of LiFePO4. According to the first law of thermodynamics the overall state-of-charge (SOC) of the electrode will remain unchanged, mainly the PTMA/LiFePO4 charged species ratio will change.

The hybridization of the two separate components yields a remarkable set of properties. The appropriate redox couples, flat-potential profile and elevated specific capacity yet, different redox kinetics for PTMA and LiFePO4, offer a hybrid battery electrode where the fast electrochemical response of PTMA delays the voltage rise during the charge process. This implies significant improvements for the rate performance, cycle lifetime and safety of lithium-ion batteries during rapid recharge.

This novel approach paves the way to new design rules for Li-ion battery electrodes and may prove pivotal in pushing the performance envelope of Li-ion batteries towards the goal of increasing adoption of electric vehicles.

Source: Nature

Researchers at the University of California, Riverside’s Bourns College of Engineering have created a lithium ion battery that outperforms the current industry standard by three times. The key material: sand.

“This is the holy grail – a low cost, non-toxic, environmentally friendly way to produce high performance lithium ion battery anodes,” said Zachary Favors, a graduate student working with Cengiz and Mihri Ozkan, both engineering professors at UC Riverside.

The idea came to Favors six months ago. He was relaxing on the beach after surfing in San Clemente, Calif. when he picked up some sand, took a close look at it and saw it was made up primarily of quartz, or silicon dioxide.

His research is centered on building better lithium ion batteries, primarily for personal electronics and electric vehicles. He is focused on the anode, or negative side of the battery. Graphite is the current standard material for the anode, but as electronics have become more powerful graphite’s ability to be improved has been virtually tapped out.

Researchers are now focused on using silicon at the nanoscale, or billionths of a meter, level as a replacement for graphite. The problem with nanoscale silicon is that it degrades quickly and is hard to produce in large quantities.

Favors set out to solve both these problems. He researched sand to find a spot in the United States where it is found with a high percentage of quartz. That took him to the Cedar Creek Reservoir, east of Dallas, where he grew up.

Sand in hand, he came back to the lab at UC Riverside and milled it down to the nanometer scale, followed by a series of purification steps changing its color from brown to bright white, similar in color and texture to powdered sugar.

After that, he ground salt and magnesium, both very common elements found dissolved in sea water into the purified quartz. The resulting powder was then heated. With the salt acting as a heat absorber, the magnesium worked to remove the oxygen from the quartz, resulting in pure silicon.

The Ozkan team was pleased with how the process went. And they also encountered an added positive surprise. The pure nano-silicon formed in a very porous 3-D silicon sponge like consistency. That porosity has proved to be the key to improving the performance of the batteries built with the nano-silicon.

The improved performance could mean increasing the expected lifespan of silicon based electric vehicle batteries up to three times or more, which would be significant for consumers, considering replacement batteries cost thousands of dollars. The energy density is more than three times higher than that of traditional graphite based anodes, which means cell phones and tablets could last three times longer between charges.

With support from the National Science Foundation, researchers at George Washington University, led by Stuart Licht, think they have developed a novel solution, and they're calling it the "molten air battery."

These new rechargeable batteries, which use molten electrolytes, oxygen from air, and special "multiple electron" storage electrodes, have the highest intrinsic electric energy storage capacities of any other batteries to date. Their energy density, durability and cost effectiveness give them the potential to replace conventional electric car batteries, said Licht, a professor in GWU's Columbian College of Arts and Sciences' Department of Chemistry.

The researchers started with iron, carbon or vanadium boride for their ability to transfer multiple electrons. Molten air batteries made with iron, carbon or vanadium boride can store three, four and 11 electrons per molecule respectively, giving them 20 to 50 times the storage capacity of a lithium-ion battery, which is only able to store one electron per molecule of lithium. "Molten air introduces an entirely new class of batteries," Licht said.

Other multiple-electron-per-molecule batteries the Licht group has introduced, such as the super-iron or coated vanadium boride air battery, also have high storage capacities. But they had one serious drawback: They were not rechargeable. Rechargeable molten batteries (without air), such as a molten sulfur battery, have been previously investigated, but are limited by a low storage capacity.

The new molten air batteries, by contrast, offer the best of both worlds: a combination of high storage capacity and reversibility. As the name implies, air acts as one of the battery electrodes, while simple nickel or iron electrodes can serve as the other. "Molten" refers to the electrolyte, which is mixed with reactants for iron, carbon or vanadium boride, then heated until the mixture becomes liquid. The liquid electrolyte covers the metal electrode and is also exposed to the air electrode.

The batteries are able to recharge by electrochemically reinserting a large number of electrons. The rechargeable battery uses oxygen directly from the air, not stored, to yield high battery capacity. The high activity of molten electrolytes is what allows this charging to occur, according to Licht.

The electrolytes are all melted to a liquid by temperatures between 700 and 800 degrees Celsius. This high-temperature requirement is challenging to operate inside a vehicle, but such temperatures are also reached in conventional internal combustion engines.

The researchers continue to work on their model to make the batteries viable candidates for extending electric cars' driving range. In the Licht group's latest study, the molten air battery operating temperature has been lowered to 600 degrees Celsius or less. The new class of molten-air batteries could also be used for large-scale energy storage for electric grids. "A high-temperature battery is unusual for a vehicle, but we know it has feasibility," Licht said. "It presents an interesting engineering question."

Researchers at Florida University have turned copper wires into batteries for much simpler power storage.

The breakthrough could mean smaller consumer electronics, or could be embedded in to hybrid and electric cars or even clothing to help recharge gadgets like phones.

Nanotechnology scientist Jayan Thomas was reported in the media as saying "he believes he has discovered a way to store energy in a thin sheath around an ordinary lightweight copper electrical wire so that wires sending energy can also store it. "We can just convert those wires into batteries so there is no need of a separate battery," Thomas told Reuters. "It has applications everywhere."

The discovery has created a lot excitement in both the mainstream and scientific media. It's both the cover story in the latest Advanced Materials Journal and an article in the current edition of science magazine Nature.

One of the co-authors of the study, Thomas's Ph.D. student Zenan Yu, told Reuters the process is relatively simple.

"First", he said, "he heated the copper wire to create what he described as fuzzy "nano-whiskers," which are naturally insulated by copper oxide, vastly expanding the wire's surface area that can store energy."

"A second plastic-covered layer of nano-whiskers creates a second electrode, similar to the positive and negative sides of a standard battery," Thomas told Reuters.

"The technique could be used to lighten airplanes and spacecraft, to store excess energy from solar panels, and to further miniaturize small electronics," he said.

"The technique could also replace high energy-density supercapacitors, sometimes mistaken by hybrid car owners as a second battery, which provide the quick shot of energy that cars and heavy machinery need to start."

"You open your trunk and you see a lot of space is taken by your batteries. If you can just use some of the cables along the length of your car, you don't need any of that space for batteries," Thomas said.

He plans further research to apply the same technique to fibers woven into clothing along with a flexible solar cell, creating a wearable battery pack.

Battery weight has long vexed engineers designing electric cars for the mass market. Bigger batteries are needed to power a car for longer distances, but their weight in turn requires the car to expend more energy. But what if the body of the car itself was a battery?

Researchers at KTH Royal Institute of Technology have found a promising solution with carbon fibre. Eric Jacques, a researcher in vehicle and aerospace engineering at KTH, says carbon fibre can fill two functions in an electric car: as a lightweight composite reinforcement material for the car’s body, and as an active electrode in lithium ion batteries.

“The objective of our research was to develop a structural battery consisting of multifunctional lightweight materials that simultaneously manage mechanical loads, and store electrical energy,” says Eric Jacques, a researcher in Aeronautical and Vehicle Engineering at KTH.

“This can result in a weight reduction for electric vehicles,” Jacques says.

He says carbon fibre offers a viable alternative to graphite. Lithium can be inserted into the carbon fibre microstructure and the carbon fibre acts as a good conductor. The carbon fibre which the KTH researchers have worked with is very light and has a continuous structure and excellent mechanical properties, Jacques says

“The research project has demonstrated very good results, but we have some work to do before we can display finished batteries.”

The project is run as a partnership between three professors at KTH: Göran Lindbergh, Chemical Engineering; Mats Johansson, Fibre and Polymer Technology; and Dan Zenkert, Aeronautical and Vehicle Engineering. The research is done in cooperation with Swerea SICOMP and Luleå Insitute of Technology.

Johansson says the work is about improving the mechanical properties of batteries – so that it not only stores energy but is part of the design.

“For example, the hood of the car could be part of the battery,” Johansson says, adding that similar consolidation of battery and structural material could be used in mobile phones and other battery-operated devices.

Graphene – the world’s thinnest material – could make batteries light, durable and suitable for high capacity energy storage from renewable generation.

Graphene promises a revolution in electrical and chemical engineering. It is a potent conductor, extremely lightweight, chemically inert and flexible with a large surface area. It could be the perfect candidate for high capacity energy storage.

Soon after graphene’s isolation, early research already showed that lithium batteries with graphene in their electrodes had a greater capacity and lifespan than standard designs.

A new project ‘Electrochemical Energy Storage with Graphene-Enabled Materials’ is exploring different ways to reduce the size and weight of batteries and extend their lifespan by adding graphene as a component material.

“But before we build the batteries we need to know how graphene will interact with the chemical components – specifically electrolytes,” comments Professor Andrew Forsyth from the School of Electronics and Electrical Engineering.

His colleague Professor Robert Dryfe from the School of Chemistry performs experiments to analyse the chemical interactions between graphene and lithium ions. Professor Dryfe is also exploring how quickly electrons are transferred across graphene and the magnitude of capacitance – the amount of electrical energy that can be stored on graphene surfaces.

The academics are working with a number of commercial partners, including Rolls-Royce, Sharp and Morgan Advanced Materials. Commercial partnership is crucial for developing the future applications of graphene. Graphene@Manchester is currently working with more than 30 companies from around the world on research projects and applications.

Another focus of the project is graphene-based supercapacitors, which tend to have high power capability and longer cycle life than batteries, but lower energy storage capacity. Nevertheless, they hold much promise to complement batteries as part of an integrated storage solution.

According to Professor Forsyth a combination of graphene batteries and supercapacitors could give electric car sales some serious thrust. Today these green vehicles run on batteries that weigh 200kg – as much as three passengers. By reducing the weight of the batteries graphene should boost vehicle efficiency and increase the driving range of electric cars to beyond 100km – a limitation that currently prevents their widespread uptake.

“If we can extend the distances that cars can travel between charge points we will instantly make them more popular,” Professor Forsyth states. “But how will the batteries cope with the real-life strains of driving? Electric cars – like all other vehicles – are not driven smoothly. Dramatic peaks in power demand as drivers accelerate will stress the battery and potentially limit its lifespan.”

To test whether prototype graphene batteries and supercapacitors are up to the job, Professor Forsyth will expose them to real world stresses that mimic different driving profiles. “We can even test the technology for driving in extreme weather conditions,” he added. “Many batteries struggle to perform in cold conditions, but our weather chamber will reveal any weaknesses.”

Of course, graphene-based storage is not limited to transport. It could play a major role in the future of the National Grid as Britain becomes ever more dependent upon renewable energy. “If we rely on solar and wind power to produce energy, what will happen when clouds block the sun and the wind is just a breeze?” asks Professor Forsyth. “If we can develop high capacity electrical storage, operators will be able to store electricity for times of low generation.”

A grid-scale battery and converter system is being installed on Manchester’s campus to test large scale electrical storage. Researchers will use the battery system to develop methods to control the flow of electricity and reconcile differences between power generation and local demand.