Non-flammable long chain phosphate ester based electrolyte via competitive solventized structures for high-performance lithium metal batteries

Safety remains a persistent challenge for high-energy-density lithium metal batteries（LMBs）.The development of safe and non-flammable electrolytes is especially important in harsh conditions such as high temperatures.Herein,a flame-retardant,low-cost and thermally stable long chain phosphate ester based（tributyl phosphate,TBP） electrolyte is reported,which can effectively enhance the cycling stability of highly loaded high-nickel LMBs with high safety through co-solvation strategy.The interfacial compatibility between TBP and electrode is effectively improved using a short-chain ether（glycol dimethyl ether,DME）,and a specially competitive solvation structure is further constructed using lithium borate difluorooxalate（LiDFOB） to form the stable and inorganic-rich electrode interphases.Benefiting from the presence of the cathode electrolyte interphase（CEI） and solid electrolyte interphase（SEI） enriched with LiF and LixPOyFz,the electrolyte demonstrates excellent cycling stability assembled using a 50 μm lithium foil anode in combination with a high loading NMC811(15.4 mg cm-2) cathode,with 88% capacity retention after 120 cycles.Furthermore,the electrolyte exhibits excellent high-temperature characteristics when used in a 1-Ah pouch cell（N/P=0.26）,and higher thermal runaway temperature（238℃） in the ARC（accelerating rate calorimeter） demonstrating high safety.This novel electrolyte adopts long-chain phosphate as the main solvent for the first time,and would provide a new idea for the development of extremely high safety and high-temperature electrolytes.