PNNL

Abstract

Rechargeable lithium metal batteries (LMBs) are regarded as the “holy grail” of energy storage systems, but their practical applications have long been hindered by poor cyclability and severe safety concerns. In this work, we report a nonflammable localized high concentration electrolyte consisting of 1.2 M lithium bis(fluorosulfonyl)imide in a mixture of flame-retarded triethyl phosphate/bis(2,2,2-trifluoroethyl) ether (1:3 by mol) for 4-V class LMBs. This electrolyte enables dendrite-free and stable cycling of lithium metal anode with high CE of up to 99.2%. Moreover, it exhibits excellent anodic stability even at >4.5 V and greatly enhances the cycle performance of LMBs. For example, with this electrolyte, a Li||NMC622 battery shows >97% capacity retention after 600 cycles at 1 C, corresponding to negligible capacity decay of