A dendrite-free Li–S battery with a cerium-doped sulfide glass–ceramic composite electrolyte

Abstract

The development of composite polymer electrolytes (CPEs) that simultaneously achieve high ionic conductivity, mechanical flexibility, and interfacial compatibility is crucial for advancing solid-state lithium–sulfur (Li–S) batteries. Herein, we report a dual-phase electrolyte system based on a poly(vinylidene fluoride) (PVDF) matrix embedded with a cerium-doped sulfide glass–ceramic filler, Li₇P_2.9Ce_0.1S₁₁. Cerium incorporation facilitates lithium-ion transport by inducing lattice distortion and increasing vacancy concentrations, while strong interfacial bonding with PVDF ensures uniform filler dispersion and mechanical robustness. The resulting CPE exhibits a high ionic conductivity of 9.00 × 10⁻⁴ S cm⁻¹ at 25 °C and a lithium-ion transference number of 0.623, with an apparent oxidative stability limit of 4.56 V vs. Li⁺/Li as determined by linear sweep voltammetry. The galvanostatic intermittent titration technique (GITT) confirms a lithium diffusion coefficient of 4.8 × 10⁻⁷ cm² s⁻¹, highlighting fast transport kinetics. When applied in a Li–S cell with high sulfur loading (5 mg cm⁻²) and lean electrolyte (5 μL mg⁻¹), the CPE enables a stable discharge capacity of 642 mAh g⁻¹ over 1000 cycles at 1C with 39% capacity retention. A symmetric Li|CPE|Li cell further demonstrates dendrite-free cycling over 330 hours at 1 mA cm⁻². This work demonstrates that Ce-doped Li₇P₃S₁₁-based CPEs offer a viable pathway toward stable, high-performance, solid-state Li–S batteries operating under practical conditions.