High safety and cycling stability of ultrahigh energy lithium ion batteries

High-nickel layered oxide Li-ion batteries (LIBs) dominate the electric vehicle market, but their potentially poor safety and thermal stability remain a public concern. Here, we show that an ultrahigh-energy LIB (292 Wh kg(-1)) becomes intrinsically safer when a small amount of triallyl phosphate (TAP) is added to standard electrolytes. TAP passivates the electrode-electrolyte interfaces and limits the maximum cell temperature during nail penetration to 55 degrees C versus complete cell destruction (>950 degrees C) without TAP. The downside of this reliable safety solution is higher interfacial impedance and hence lower battery power; however, thermal modulation for battery operation around 60 degrees C can restore power completely. When cycled at 60 degrees C, the cell stabilized with TAP achieved 2,413 cycles at 76% capacity retention. Such an unconventional combination of interface-passivating electrolyte additive with cell thermal modulation renders the most energy-dense LIBs even safer than LiFePO4 chemistry, while enjoying high power and cycling stability concurrently.

Automated summary

By adding triallyl phosphate (TAP) to standard electrolytes, high-energy LIBs can become safer with controlled temperatures, reducing the risk of fire at high temperatures. However, this may result in lower battery power, which can be restored through thermal modulation, and the cells stabilized with TAP exhibit good cycling stability at 60 degrees Celsius.