Constructing interfacial gradient layers and enhancing lithium salt dissolution kinetics for high-rate solid-state batteries

The stability of the interfacial layers depends mainly on the composition and distribution of the decomposition products from solid-state electrolytes (SSEs) in lithium metal batteries. Therefore, the design of SSEs becomes an attractive way to construct a homogeneous stable interfacial layer. Herein, pentafluorostyrene (PFS) as a block is used to generate robust interfacial layers for solid-state batteries. Meanwhile, PFS facilitates the dissociation of lithium salts to produce more free Li-ions which can enhance the ionic conductivity from the results of 7Li solid-state NMR spectra, density functional theory, and molecular dynamics calculations. Subsequently, XPS depth etching and TOF-SIMS characterizations together show that the gradient interfacial layer is composed of a rich C-F bond surface layer and a rich–LiF&Li3N bottom layer, enabling rapid transport and uniform deposition of lithium ions. As a result, the Li/Li symmetric cell can achieve a stable ultra-long cycle time of more than 3000 h at 0.2 mA cm−2 and a critical current density of 2.4 mA cm−2. The as-prepared SSE exhibits a high ionic conductivity of 4.3 × 10−4 S cm−1 at 25 °C and remarkable cycling stability at 0 °C and − 20 °C. Moreover, the lithium metal batteries based on as-prepared SSEs deliver high-rate (2 C) capability and high-voltage (NCM811) stability at room temperatures.