Synergistic anion receptor-polymer regulate electrolyte solvation structure for high-rate solid-state lithium metal batteries

The advancement of solid-state lithium metal batteries (SSLMBs) with high rate capability possess challenges due to the relatively slow kinetics of ion transport properties and the lack of compatibility between the phases derived from solid-state electrolytes. Here, the tris(pentafluorophenyl) boron (TPFPB) is incorporated as an highly effective additive into a poly(ionic liquid)-based solid-state composite polymer electrolyte (CPE) to realize SSLMBs with enhanced high rate performance. The theoretical calculation and experimental analysis demonstrated that the TPFPB serves as an anion receptor agent and a modifier of the electrode/electrolyte interphase. In a notable advancement, the ionic conductivity, lithium transport kinetics, and electrochemical stability of CPE have been significantly enhanced. Additionally, TPFPB has demonstrated an impressive capacity to suppress undesirable side reactions with both the cathode and lithium anode. The presence of Li₂O, Li₂CO₃ and an adequate amount of LiF derived from TPFPB in the interphase between the CPE and Li metal anode results in enhanced high-rate performance. The reasonable design enables the achievement of a considerable ion conductivity of 5.28 × 10⁻⁴ S cm⁻¹ (25 °C) and a lithium-ion transference number of 0.48 for CPE. The solid-state LiFePO₄/CPE/Li batteries delivers excellent rate performance and cycle stability, with a high discharge specific capacity of 94.4 mAh g⁻¹ at 10C (1 mA cm⁻²) and a remarkable capacity retention of 76.5 % after 700 cycles at 8C. Moreover, the TPFPB functionalized CPE is capable of operating in conjunction with the high-voltage LiNi_0.85Co_0.15Al_0.05O₂ cathode. The excellent performance of the as-prepared SSLMBs at a wide temperature range of −15 °C and 60 °C also verified that the effectiveness of TPFPB as additives into solid-state electrolytes.