Study on the Interfacial Mechanism of Bisalt Polyether Electrolyte for Lithium Metal Batteries

Abstract Solid‐state batteries are considered a new avenue for storing high‐energy and safe electrochemical energy in both traditional and niche applications. However, the inferior tolerance under high voltage as well as poor interfacial contact has become the bottleneck for its application in high‐energy‐density Li metal batteries (LMBs). Herein, a bisalt polyether electrolyte (BSPE) is designed via in situ polymerization process for quasi‐solid LMBs. In particular, the BSPE exhibited a wide electrochemical stability window (4.4 V versus Li + /Li), and in situ Fourier transform infrared spectrocopy combined with X‐ray photoelectron spectroscopy technology revealed the oxidation mechanism of BSPE at high voltage. Benefiting from this design, the Li|Li symmetric cells with BSPE are stable over 1200 h with low overpotential. Additionally, Li|LiFePO 4 (LFP), Li|Li 4 Ti 5 O 12 (LTO), and Li|LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) LMBs delivered excellent cycling performance at ambient temperature. Therefore, it is believed that the BSPE can be a promising gel polymer electrolyte candidate for high‐energy‐density LMBs.