A novel strategy to improve the electrochemical properties of in-situ polymerized 1,3-dioxolane electrolyte in lithium metal batteries.

The application of solid-state electrolytes (SSEs) is anticipated to enhance the safety performance of lithium metal batteries (LMBs). However, the progress of SSEs has been hindered by the unstable electrode-electrolyte interfaces (EEIs). In this study, in-situ polymerization of 1,3-dioxolane (DOL) is employed for the preparation of SSEs, with the addition of tributyl borate (TBB) to establish stable EEIs, particularly under high-voltage conditions. On one hand, the addition of TBB promotes the dissociation of lithium salts and increases the concentration of free Li⁺, resulting in an increase in room temperature ionic conductivity to 1.13 × 10^-4 S cm^-1 and an improvement in the Li⁺ transference number to 0.69 for the prepared poly-DOL electrolytes (PDE-TBB). Benefiting from the enhanced Li⁺ transport, the Li/PDE-TBB/Li symmetric cell exhibits a cycle life exceeding 1,000 h with a low polarization voltage as low as 12 mV, and the Li/PDE-TBB/LiFePO₄ cell demonstrates exceptional cyclic stability over 800 cycles at 1C, with a coulombic efficiency exceeding 99.8 % and a capacity retention of 89.6 %. On the other hand, PDE-TBB exhibits improved stability under high-voltage conditions and the capacity to establish robust boron-rich cathode electrolyte interphase (CEI) on the LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811) surface, thereby enhancing the structural stability of cathode materials and ensuring exceptional cycling performance of Li/PDE-TBB/NCM811cell. This work presents a promising strategy for developing novel ether-based SSEs suitable for high-voltage lithium metal batteries.