Oak Ridge National Laboratory researchers are taking fast charging for electric vehicles, or EVs, to new extremes.
A team of battery scientists recently developed a lithium-ion battery material that not only recharges 80% of its capacity in 10 minutes but keeps that ability for 1,500 charging cycles.
When a battery operates or recharges, ions move between electrodes through a medium called the electrolyte. ORNL’s Zhijia Du led a team who developed new formulations of lithium salts with carbonate solvents to form an electrolyte that maintains better ion flow over time and performs well when high current heats up the battery during extreme fast charging. Project partners tested battery pouch cells made at ORNL’s Battery Manufacturing Facility to prove the battery’s safety and cycling characteristics.
“We found this new electrolyte formulation basically triples the Department of Energy’s target for the lifespan of an extreme-fast-charging battery,” Du said.
Efficient and mild: Recycling of used lithium-ion batteries
Lithium-ion batteries (LIBs) provide our portable devices like tablets and mobiles — and increasingly also vehicles — with power. As the share of volatile renewable energy needing electricity storage increases, more and more LIBs are needed, lithium prices rise, resources dwindle, and the amount of depleted batteries that contain toxic substances increases. In the journal Angewandte Chemie, researchers introduce a novel approach for the recovery of lithium from used LIBs.
The recycling of LIBs is a difficult undertaking. The recovery of lithium of a quality high enough to be used again is complicated and expensive. Most recycling processes are targeted at extracting the lithium from cathodes (where most of the lithium in discharged batteries is located). However, it then precipitates out together with other metals contained in the cathode and must be painstakingly separated. Extraction from the anodes, which consist primarily of graphite, is significantly more efficient and can be carried out without discharging the battery beforehand. Because of their high reactivity, however, the risk of fires and explosions is high if the anodes are leached out with aqueous solutions, as is usual. These reactions release large amounts of energy and may produce hydrogen.
A team led by Yu-Guo Guo and Qinghai Meng at the Institute of Chemistry of the Chinese Academy of Sciences (ICCAS) and the University of Chinese Academy of Sciences (UCAS) has now developed an alternative method that avoids these problems. Instead of water, they use aprotic organic solutions to recover lithium from anodes. Aprotic substances cannot release any hydrogen ions, so no hydrogen gas can form.
The solutions consist of a polycyclic aromatic hydrocarbon (PAH) and an ether as the solvent. Certain PAHs can take up a positively charged lithium ion from the graphite anode together with one electron. Under mild conditions, this redox reaction is controlled and very efficient. With the PAH pyrene in tetraethylene glycol dimethyl ether, it was possible to dissolve the active lithium from the anodes almost completely.
An additional advantage is that the resulting lithium-PAH solutions can be used directly as reagents, for example, in adding lithium to new anodes in preprocessing or in regenerating spent cathodes. The PAH/solvent system can be varied to optimize it for the material being treated.
This recovery process is efficient and inexpensive, reduces safety risks, avoids waste, and opens new prospects for the sustainable recycling of lithium-ion batteries.
New study finds ways to suppress lithium plating in automotive batteries for faster charging electric vehicles
A new study led by Dr. Xuekun Lu from Queen Mary University of London in collaboration with an international team of researchers from the UK and USA has found a way to prevent lithium plating in electric vehicle batteries, which could lead to faster charging times. The paper was published in the journal Nature Communications.
Lithium plating is a phenomenon that can occur in lithium-ion batteries during fast charging. It occurs when lithium ions build up on the surface of the battery’s negative electrode instead of intercalating into it, forming a layer of metallic lithium that continues growing. This can damage the battery, shorten its lifespan, and cause short-circuits that can lead to fire and explosion.
Dr. Xuekun Lu explains that lithium plating can be significantly mitigated by optimizing the microstructure of the graphite negative electrode. The graphite negative electrode is made up of randomly distributed tiny particles, and fine-tuning the particle and electrode morphology for a homogeneous reaction activity and reduced local lithium saturation is the key to suppress lithium plating and improve the battery’s performance.
“Our research has revealed that the lithiation mechanisms of graphite particles vary under distinct conditions, depending on their surface morphology, size, shape and orientation. It largely affects the lithium distribution and the propensity of lithium plating,” said Dr. Lu. “Assisted by a pioneering 3D battery model, we can capture when and where lithium plating initiates and how fast it grows. This is a significant breakthrough that could have a major impact on the future of electric vehicles.”
The study provides new insights into developing advanced fast charging protocols by improving the understanding of the physical processes of lithium redistribution within graphite particles during fast charging. This knowledge could lead to an efficient charging process while minimising the risk of lithium plating.
In addition to faster charging times, the study also found that refining the microstructure of the graphite electrode can improve the battery’s energy density. This means that electric cars could travel further on a single charge.
These findings are a major breakthrough in the development of electric vehicle batteries. They could lead to faster-charging, longer-lasting, and safer electric cars, which would make them a more attractive option for consumers.