Scientists at UC San Diego have discovered that a ‘disordered rocksalt’ anode enables lithium-ion batteries to be safely fast-recharged for thousands of cycles.
The new anode is made up of lithium, vanadium and oxygen atoms arranged in a similar way as ordinary kitchen table salt, but ‘randomly’.
Fast charging graphite, the most common anode material, can result in lithium metal plating. The safer alternative, lithium titanate, can be recharged rapidly but has a decreased energy density.
The disordered rocksalt anode— Li3V2O5— sits in an important middle ground: it is safer to use than graphite, and offers more energy than lithium titanate.
The study, jointly led by nanoengineers in the laboratories of professors Ping Liu and Shyue Ping Ong, was published in Nature.
In the study, the team found a disordered rocksalt anode could reversibly cycle two lithium ions at an average voltage of 0.6 V— higher than the 0.1 V of graphite. This eliminates lithium metal plating at a high charge rate, which makes the battery safer, but lower than the 1.5 V at which lithium-titanate intercalates lithium, and therefore store more energy.
Haodong Liu, a postdoctoral scholar in professor Liu’s lab and first author of the paper, said: “The capacity and energy will be a little bit lower than graphite, but it’s faster, safer and has a longer life. It has a much lower voltage and therefore much improved energy density over current commercialised fast charging lithium-titanate anodes.
“So with this material we can make fast-charging, safe batteries with a long life, without sacrificing too much energy density.”
The researchers also showed the Li3V2O5 anode could be cycled for more than 6,000 cycles with negligible capacity decay, and could deliver more than 40% of its capacity in 20 seconds.
The researchers have formed a company called Tyfast in order to commercialise the discovery.
The start-up will target electric bus and power tool applications.
Professor Liu said: “For a long time, the battery community has been looking for an anode material operating at a potential just above graphite to enable safe, fast-charging lithium-ion batteries.
“This material fills an important knowledge and application gap. We are excited for its commercial potential since the material can be a drop-in solution for today’s lithium-ion battery manufacturing process.”
Image: Researchers Haodong Liu and Ping Liu hold batteries made with the disordered rocksalt anode material they discovered, standing in front of a device used to fabricate battery pouch cells