Constructing flame retardant microspheres for safe and stable poly (ethylene oxide) based All-Solid-State batteries at high voltage

Abstract

The development of all-solid-state polymer electrolytes (ASSPE) based on poly (ethylene oxide) (PEO) is facing a series of challenges, such as poor ionic conductivity, low Li+ transference number, flammability, and the limited electrochemical windows of 4 V. Herein, we report our recent effort to meet these challenges by introducing flame retardant microspheres (TH) into PEO-based ASSPE to form stable solid cathode electrolyte interface (CEI) films and enhance safety performance. TH is constructed by reacting tetrabromobisphenol A (TBBA) with hexachlorocyclotriphosphazene (HCCP). With the presence of only 5 wt% TH, the LiNi0.8Mn0.1Co0.1O2 (NCM811)//Li cell achieves a high capacity retention rate of 77.61 % after 100 cycles at the cutoff voltage of 4.3 V and 0.5C, and achieves a capacity retention of 75.7 % at the voltage range of 3–4.5 V after 50 cycles at 0.5C. In addition, the PEO-based ASSPE with TH (TH-PEO/PE) shows excellent flame retardancy, which endows the NCM811//Li pouch cell with good resistance to fire and mechanical abuse. This simple process is compatible with the existing production lines in the battery industry, which exhibits enormous promise in manufacturing commercialized all-solid-state lithium metal batteries (ASSLMBs) with high energy density and safety capabilities.