In-situ polymerized electrolyte modified with oligomeric cyclotetrasiloxane for all-solid-state lithium metal batteries

Abstract

High energy density and high-safety is expected for the ongoing revolution of lithium-ion batteries (LIBs). All-solid-state lithium metal batteries (ASSLMBs) are promising to break through the bottleneck of traditional liquid LIBs. However, the huge interfacial resistance between solid electrolytes and cathode is a hinder to the develop ASSLMBs. Herein, we report an in-situ polymerized solid-state electrolytes (SPE) based on oligomeric cyclotetrasiloxane (CTS) and polyethylene glycol diglycidyl ether (PEGDE) to solve this problem. CTS can provide a three-dimensional skeleton for the cross-linked SPE, which can effectively improve the properties of SPE. When the CTS content is 10 wt%, SPE exhibits a high ionic conductivity at 28 °C (0.37 mS cm−1) and a wide electrochemical stable window of 5.02 V (vs Li/Li+). Benefiting from the in-situ polymerization properties, ionic transportation at the cathode/electrolyte interface can be enhanced. Especially, the in-situ SPE exhibits outstanding compatibility against lithium metal over 600 h at a current density of 0.2 mA cm−2, the Li/SPE/LiCoO2 can deliver a capacity of 120.5 mAh g−1 at 0.05 C after 100 cycles. Our study, therefore, provides a new type of SPE to meet both interfacial and bulk conductivity requirements for ASSLMBs.