PNNL

Abstract

Lithium (Li) metal batteries (LMBs) are revitalized in recent years in response to the increasing demand for high energy density batteries. However, the instability of Li metal anode (LMA) in electrolytes is still a critical barrier limiting the application of these batteries. This work optimized tris(2,2,2-trifluoroethyl) orthoformate (TFEO) based electrolytes and revealed the fundamental mechanism behind their stability towards both LMA and high voltage cathode. The optimized electrolytes demonstrated superior electrochemical properties when used in high voltage LMBs with nickel-rich layered cathode LiNi0.8Mn0.1Co0.1O2 (NMC811) under very challenging conditions required for practical application of high energy density LMBs. These TFEO based localized high-concentration electrolytes led to highly effective solid electrolyte interphase and cathode electrolyte interphase, preventing continuous electrode/electrolyte side reactions and significantly prolonging the cycle life of Li||NMC811 batteries. The design principles discovered in this work for highly stable electrolytes under practical conditions provide guidance for further development of novel electrolytes for the stable operation of practical high energy density LMBs.