Lithiophilic Li-Si alloy-solid electrolyte interface enabled by high-concentration dual salt-reinforced quasi-solid-state electrolyte

Solid polymer electrolytes (SPEs) are urgently required to achieve practical solid-state lithium metal batteries (LMBs) and lithium-ion batteries (LIBs). Herein, we proposed a mechanism for modulating interfacial conduction and anode interfaces in high-concentration SPEs by LiDFBOP. Optimized electrolyte exhibits superior ionic conductivity and remarkable interface compatibility with salt-rich clusters: (1) polymer-plastic crystal electrolyte (P-PCE, TPU-SN matrix) dissociates ion pairs to facilitate Li⁺ transport in the electrolyte and regulates Li⁺ diffusion in the SEI. The crosslinking structure of the matrix compensates for the loss of mechanical strength at high-salt concentrations; (2) dual-anion TFSI^–_n-DFBOP^–_m in the Li⁺ solvation sheath facilitates facile Li⁺ desolvation and formation of salt-rich clusters and is conducive to the formation of Li conductive segments of TPU-SN matrix; (3) theoretical calculations indicate that the decomposition products of LiDFBOP form SEI with lower binding energy with LiF in the SN system, thereby enhancing the interfacial electrochemical redox kinetics of SPE and creating a solid interface SEI layer rich in LiF. As a result, the optimized electrolyte exhibits an excellent ionic conductivity of 9.31 × 10⁻⁴ S cm⁻¹ at 30 °C and a broadened electrochemical stability up to 4.73 V. The designed electrolyte effectively prevents the formation of Li dendrites in Li symmetric cells for over 6500 h at 0.1 mA cm⁻². The specific Li-Si alloy-solid state half-cell capacity shows 711.6 mAh g⁻¹ after 60 cycles at 0.3 A g⁻¹. Excellent rate performance and cycling stability are achieved for these solid-state batteries with Li-Si alloy anodes and NCM 811 cathodes. NCM 811|| Prelithiated silicon-based anode solid-state cell delivers a discharge capacity of 195.55 mAh g⁻¹ and a capacity retention of 97.8% after 120 cycles. NCM 811||Li solid-state cell also delivers capacity retention of 84.2% after 450 cycles.