A Low‐Concentration All‐Phosphate Electrolyte for High‐Voltage and High‐Safety Lithium‐Ion Batteries

Abstract

ABSTRACT The majority of safety incidents associated with lithium‐ion batteries (LIBs) arise from the utilization of highly volatile and flammable carbonate electrolytes. The adoption of non‐flammable all‐phosphate‐solvent electrolytes could significantly enhance the safety of LIBs. Nevertheless, all‐phosphate‐solvent electrolytes at low‐concentrations (≈1  m ) are not compatible with commercial graphite anodes. Herein, we design and synthesize a new six‐membered cyclic phosphate (HTP) with intrinsic graphite passivation ability as electrolyte solvent. Conventional tris(2,2,2‐trifluoroethyl) phosphate (FTEP) is introduced as co‐solvent to regulate the electrolyte solvation structure through solvent–solvent interactions between HTP and FTEP, which facilitates Li + de‐solvation and contributes to the formation of a highly robust inorganic‐polymeric CEI/SEI. The resulting low‐concentration electrolyte with all‐phosphate‐solvent not only exhibits wide potential window, unmeasurably high flash point, excellent non‐flammability and thermal stability, but also promises the 4.5 V graphite||LiNi 0.8 Mn 0.1 Co 0.1 O 2 full‐cells to operate stably at extreme temperatures up to 100°C and pass various rigorous safety tests. This work provides new insights into the design of non‐flammable electrolytes for high‐voltage and high‐safety LIBs and are broadly applicable to other batteries.