Application of amidoxime-modified polymer of intrinsic microporosity to achieve highly stable poly(ethylene oxide)-based solid electrolytes

Poly (ethylene oxide) (PEO)-based solid polymer electrolytes (SPEs) have attracted intensive attention in recent years due to the high salt solubility and flexibility in lithium-ion batteries (LIBs). However, the application of such solid electrolytes is severely limited owing to low ionic conductivity and poor mechanical strength. The integration of the amidoxime modified polymer of intrinsic microporosity (AOPIM-1) with PEO electrolyte is designed to attain a novel composite solid electrolyte (CPE). At an optimal doping amount of 1.5%, the effects of AOPIM-1 on the physicochemical and electrochemical properties of CPE are investigated and discussed. Because of the electrostatic action between Li+ and polar amidoxime groups, more rapid Li+ transport could promote the electrochemical performances of CPE. The liquid-free CPE-1.5% AOPIM-1 could show a satisfactory ionic conductivity (1.18 × 10−3 S cm−1 at 60°C). The rigid skeleton of AOPIM-1 endows the high mechanical strength of CPE to inhibit the growth of lithium dendrites for favorable interfacial stability with lithium metal. The LiFePO4 batteries combined with CPE-1.5% AOPIM-1 can supply 78.4 % capacity retention after 750 cycles at 0.5 C and 88.7% capacity retention after 200 cycles at 1.0 C (60°C). The use of AOPIM-1 would raise the oxidation potential of CPE, exhibiting a superior cycling stability (77.8 % capacity retention after 200 cycles at 0.5 C) in high-voltage LiNi0.5Co0.2 Mn0.3O2 (NCM523)/Li cells. This research can provide novel insights to achieve the much enhanced performance of composite electrolytes.