High electrochemical stability of a 3D cross-linked network PEO@nano-SiO2 composite polymer electrolyte for lithium metal batteries

Abstract

Polymer electrolytes have attracted great attention due to their promising abilities, however, only on further improving their safety and electrochemical performance can they be used as next generation electrolytes. Here, a novel composite polymer electrolyte (CPE) with nano-SiO₂ acting as a cross-linking agent to form a 3D cross-linked network was synthesized to improve the electrochemical stability and mechanical ability. The novel CPE exhibited some excellent properties such as high ionic conductivity (4.65 × 10⁻³ S cm⁻¹ at room temperature) with a broad electrochemical stability window (∼5.4 V vs. Li/Li⁺), high ionic transfer number (0.45), high mechanical robustness and flexibility (Young’s module ∼8.9 MPa, breaking strain 181%), and excellent interface stability. The lithium metal battery LiFePO₄/CPE/Li was assembled and delivered a specific capacity of 160 mA h g⁻¹ with a capacity retention of above 90% after 500 cycles at 1C. Furthermore, to cooperate with high voltage cathode materials LiNi_0.8Co_0.1Mn_0.1O₂ and LiNi_0.5Mn_1.5O₄, the novel CPE still delivered superior cycling performance compared to traditional electrolytes.