Battery safety is increasingly important due to the widespread use of various portable electronics, electric vehicles, and energy storage systems. Simultaneously, lithium-ion batteries with higher energy densities are in demand. One strategy for accomplishing both of these goals is replacing traditional flammable liquid electrolytes with non-flammable alternatives and enabling the batteries to operate at high voltages. This could help to achieve an increase in energy density without compromising safety.

Seung-Wan Song, Chungnam National University, Daejeon, Republic of Korea, and colleagues have developed a new non-flammable liquid electrolyte for lithium-ion batteries. The team used a formulation of 1 M LiPF₆ in a solvent mixture of propylene carbonate (PC), fluorinated ethyl methyl carbonate (FEMC), and bis(2,2,2-trifluoroethyl) sulfate (FES) in a ratio of 30:55:15 vol %, with 2 wt% vinylene carbonate (VC) as an additive.

The researchers showed that the non-flammable electrolyte can be used under harsh conditions, i.e., at a high charge voltage of 4.4 V and at a high temperature of 45 °C. The electrolyte was used in combination with graphite anodes and nickel-rich cathodes. It formed robust solid-electrolyte interphase (SEI) layers at the electrodes, which improve the cycle life. The team used the new non-flammable electrolyte in a lithium-ion pouch battery and demonstrated its high performance and overcharge- and thermal abuse tolerance.

• Design of Non‐Incendive High‐Voltage Liquid Electrolyte Formulation for Safe Lithium‐Ion Batteries,
  Sehyun Kwak, Kihun An, Yen Hai Thi Tran, Seung‐Wan Song,
  ChemSusChem 2021.
  https://doi.org/10.1002/cssc.202102546