Chloride-Reinforced Solid Polymer Electrolyte for High-Performance Lithium Metal Batteries

Flexible solid-state polymer electrolytes (SPEs) enable intimate contact with the electrode and reduce the interfacial impedance for all-solid-state lithium batteries (ASSLBs). However, the low ionic conductivity and poor mechanical strength restrict the development of SPEs. In this work, the chloride superionic conductor Li₂ZrCl₆ (LZC) is innovatively introduced into the poly(ethylene oxide) (PEO)-based SPE to address these issues since LZC is crucial for improving the ionic conductivity and enhancing the mechanical strength. The as-prepared electrolyte provides a high ionic conductivity of 5.98 × 10^-4 S cm^-1 at 60 °C and a high Li-ion transference number of 0.44. More importantly, the interaction between LZC and PEO is investigated using FT-IR and Raman spectroscopy, which is conducive to inhibiting the decomposition of PEO and beneficial to the uniform deposition of Li ions. Therefore, a minor polarization voltage of 30 mV is exhibited for the Li||Li cell after cycling for 1000 h. The LiFePO₄||Li ASSLB with 1% LZC-added composite electrolyte (CPE-1% LZC) demonstrates excellent cycling performance with a capacity of 145.4 mA h g^-1 after 400 cycles at 0.5 C. This work combines the advantages of chloride and polymer electrolytes, exhibiting great potential in the next generation of all-solid-state lithium metal batteries.