The Manipulation of Ring-Open Polymerization Process to Boost the Electrochemical Performance for Solid-State Lithium Metal Batteries.

Abstract

Solid-state polyether electrolytes formed by in-situ ring-opening polymerization (ROP) of 1,3-dioxolane (DOL) have attracted great attention due to their high lithium-ion conductivity, and good interface compatibility. However, DOL ring-opening polymerization is difficult to control, resulting in the formation of poly(1,3-dioxolane) (PDOL) with high molecular weight and high crystallinity, which hinder Li⁺ diffusion and deteriorate the interfacial contact. Herein, trimethylsilyl isocyanate (IPTS) was introduced into DOL ring-opening system as a moisture eliminating agent to weaken the Li salt-based initiating system and regulate the polymerization process. Based on this, the resultant PDOL electrolytes with 3 wt.% IPTS exhibit ionic conductivity of 2.8×10^-4 S cm^-1, a high Li⁺ transference number (0.68) and excellent stability with Li anode. The Li|PDOL-3 %IPTS|Li battery exhibits a stable cycling performance for more than 1100 h under 0.5 mA cm^-2 and 0.5 mAh cm^-2. Furthermore, the LiFePO₄|PDOL-3 %IPTS|Li cell shows a capacity retention rate of 89.2 % after 200 cycles (25 °C, 1 °C) and 94.5 % (60 °C, 1 °C) after 500 cycles, which is much higher than that of PDOL (6.6 %) after 70 cycles (25 °C, 1 °C). This work provides guidance for the manipulation of ROP process further to enhance the performance of solid-state lithium metal batteries.