Currently, two materials are used as anodes in most commercially available lithium-ion batteries that power items like cellphones, laptops, and electric vehicles. The most common, a graphite anode, is extremely energy dense — a lithium-ion battery with a graphite anode can power a car for hundreds of miles without needing to be recharged; however, recharging a graphite anode too quickly can result in fire and explosions due to a process called lithium metal plating. A safer alternative, the lithium titanate anode, can be recharged rapidly but results in a significant decrease in energy density, which means the battery needs to be recharged more frequently.
Researchers have developed a new anode material that enables lithium-ion batteries to be safely recharged within minutes for thousands of cycles. Known as a disordered rocksalt, the new anode is made up of earth-abundant lithium, vanadium, and oxygen atoms arranged in a similar way as ordinary kitchen table salt, but randomly. It is promising for commercial applications where both high energy density and high power are desired such as electric cars, vacuum cleaners, or drills.
This new disordered rocksalt anode — Li3V2O5 — sits in an important middle ground: it is safer to use than graphite yet offers a battery with at least 71 percent more energy than lithium titanate. It has a much lower voltage, and therefore, much improved energy density over current commercialized fast-charging lithium-titanate anodes.
The 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 — eliminating lithium metal plating at a high charge rate makes the battery safer but lower than the 1.5 V at which lithium-titanate intercalates lithium, and therefore, storing much more energy. The researchers showed that the Li3V2O 5 anode can be cycled for more than 6,000 cycles with negligible capacity decay and can charge and discharge energy rapidly, delivering more than 40 percent of its capacity in 20 seconds. The low voltage and high rate of energy transfer are due to a unique redistributive lithium intercalation mechanism with low energy barriers.
The lithium-vanadium oxide anode material will be further developed while researchers also optimize other battery components to develop a commercially viable full cell. The material can be a drop-in solution for today's lithium-ion battery manufacturing process.