Achieving a high loading of cathode in PVDF-based solid-state battery

Abstract

The lack of fundamental understanding of ion transport in the cathode of polyvinylidene fluoride (PVDF)-based solid-state lithium metal batteries restricts their rate performance and cycle stability, especially under high cathode mass loadings. Herein, we reveal that the lithium ion (Li⁺) solvated with N,N-dimethylformamide ([Li(DMF)_x]⁺) in PVDF electrolyte spontaneously diffuses into the cathode, but its diffusion depth is limited, and a continuous Li⁺ transport network can only be built in cathodes with low loadings. We further find that carbon-coated Li_1.4Al_0.4Ti_1.6(PO₄)₃ nanowires (C@LATP NW) as a cathode filler not only conduct Li⁺, but also exhibit strong adsorption of the [Li(DMF)_x]⁺ complex, which promotes the uniform diffusion of [Li(DMF)_x]⁺ in a thick cathode to construct a highly efficient Li⁺ transport network and achieve full reaction of the thick cathode. The carbon layer on C@LATP NW greatly suppresses the side decomposition reactions of DMF and LiFSI to improve the stability of the conductive network and structure of the cathode materials. The cathode with 3 wt% C@LATP NW enables excellent rate performance and cycle stability of solid-state batteries with high mass loadings of up to 15 mg cm⁻², which opens a way for practical cathode design of solid-state batteries.