Nanophase separated, grafted alternate copolymer styrene-maleic anhydride as an efficient room temperature solid state lithium ion conductor

Abstract

All solid-state lithium metal batteries (ASSLMBs) based on polymer solid electrolyte and lithium metal anode have attracted much attention due to their high energy density and intrinsic safety. However, the low ionic conductivity at room temperature and poor mechanical properties of the solid polymer electrolyte result in increased polarization and poor cycling stability of the Li metal batteries. In order to improve the ionic conductivity at room temperature while maintaining mechanical strength, we combine the conductivity of short chain polyethylene oxide (PEO) and strength of styrene-maleic anhydride copolymer (SMA) to obtain a grafted block copolymer with nanophase separation structure, which has room temperature ionic conductivity up to 1.14 × 10−4 S/cm and tensile strength up to 1.4 MPa. Li||Li symmetric cell can work stably for more than 1500 h under the condition of 0.1 mA/cm2. Li||LiFePO4 full cells can deliver a high capacity of 151.4 mAh/g at 25°C and 0.2 C/0.2 C charge/discharge conditions, showing 85.6% capacity retention after 400 cycles. Importantly, the all solid state Li||LiFePO4 pouch cell shows excellent safety performance under different abuse conditions. These results demonstrate that the nanophase separated, grafted alternate copolymer electrolyte has huge potential for application in Li metal batteries.