Effect of directional arrangement one-dimensional Fe3O4-coated sepiolite structure on the Li+ conduction of PEO-based polymer electrolyte

Abstract

The low Li+ conductivity and high cost of polyethylene oxide (PEO)-based polymer electrolytes still restrict their application. Herein, a natural one-dimensional sepiolite (SEP) material is coated with Fe3O4 (FSEP) to construct a FSEP-PEO composite polymer electrolyte (CPE) with a directional arrangement structure, which significantly improved the Li+ conductivity. Results show that the Li+ conductivity of CPE (9.1 ×10−5 S cm−1) based on vertical arrangement FSEP is 43 times higher than that of PEO (2.1 ×10−6 S cm−1), and 9.1 times and 3.1 times higher than that of parallel (1.0 ×10−5 S cm−1) and disordered arrangement (2.9 ×10−5 S cm−1), respectively. The arrangement direction of FSEP has no obvious effect on the crystallinity of PEO and the dissociation degree of LiTFSI, while it has a great influence on the Li+ migration number (tLi+). The tLi+ of CPE with vertical arrangement (0.333) increased by 99.4% compared with that of the parallel arrangement (0.167), suggesting a short and fast migration path. Through multi-physical field simulation, the high current density in CPE is mainly distributed at the FSEP/PEO interface, indicating that the FSEP/PEO interface plays a dominant role in Li+ conduction. In addition, lithium symmetric batteries and LiFePO4 batteries based on vertically arranged CPE have excellent cycle and rate performance.