Modulation of lithium-ion transport kinetics in polymer-based electrolytes by defect engineering for ultralong-cycling solid-state lithium metal batteries

Abstract

Solid-state lithium metal batteries (SSLMBs) have emerged with great promise in the field of next-generation battery technology, owing to the inherent safety and energy density benefits. However, there is an urgent need to address the core bottlenecks of slow ion migration and the unstable electrode/electrolyte interface in polymer electrolytes for their development. Herein, a composite polymer electrolyte (PHMS) is constructed by introducing sulfur vacancy-enriched 2D MoS_x nanosheets into a poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) matrix through a defect engineering strategy, which is employed to simultaneously optimise lithium ion transport kinetics and construct a stable interface. Theoretical calculations and experiments have confirmed that MoS_x significantly promotes the dissociation of lithium salts and induces the conversion of polymers to the high-dielectric β-phase to form high-speed ion channels. Furthermore, synchronous triggering of the in situ reaction with lithium metal can generate a heterogeneous solid electrolyte interface (SEI) layer containing LiF/lithium–molybdenum compounds, which enhances the long-term operational stability of the battery. Consequently, a stable cycling capacity of 8500 cycles at 8C multiplicity can be obtained for the LFP|PHMS|Li cell, with a single-cycle decay rate of a mere 0.002%, and the pouch cell also exhibits considerable practical potential. This study proposes a novel approach for designing a polymer electrolyte for the development of long-life and high-safety solid-state batteries.