Enhancing Cycle Life of Lithium Metal Batteries By Regulating Solid-Electrolyte Interphase Using Gel Polymer Electrolyte

Abstract

Lithium metal with high theoretical capacity and low redox potential is one of the promising anode materials for high energy density batteries. However, the lithium metal has safety problems and poor cycling performance, due to the growth of Li dendrite and side reactions between Li and electrolytes. One of the most effective strategies to stabilize Li metal is forming robust solid-electrolyte interphase (SEI). Recently, anion-derived and inorganic-rich SEI is known to be stable and ionic conductive, leading to good cycling stability. One of the most popular strategies to form durable SEI is to use the localized high-concentration electrolytes (LHCE) which construct an anion-derived SEI layer on Li metal. In this work, we synthesized LHCE-based gel polymer electrolytes to form a stable SEI layer and enhance cycling stability. Small amount of cross-linking agent was added into dimethoxyethane (DME)-based LHCE when synthesizing gel polymer electrolyte. The functional groups in cross-linking agents increase Li+ and anion interaction in the gel polymer electrolytes, resulting in formation of the stable SEI layer. The solvation structure and chemical composition of the SEI layer were investigated by density functional theory (DFT) calculation and spectroscopic analyses such as FT-IR, Raman, and XPS. The Li/NCM811 cells with LHCE-based gel polymer electrolyte were assembled for the cycling test, and they exhibited superior cycling performance than liquid electrolyte-based cells.