Effect of Cl-Doping on K₃PS₄ as a Superionic Solid Electrolyte for K-Ion Batteries

Solid-state K-ion batteries (KIBs) have emerged as a promising alternative to lithium-ion batteries, yet the low ionic conductivity of solid-state electrolytes (SSEs) and poor moisture stability of sulfide-based SSEs severely impede their practical application. K₃PS₄ is a potential sulfide SSE owing to the high abundance and low cost of phosphorus, but its ionic conductivity and resistance to hydrolysis require further optimization. In this work, we comprehensively investigated the effects of Cl-doping on K-ion diffusion behavior via DeepMD. Cl-doping induces potassium vacancies, which significantly facilitate long-range K⁺ transport and cooperative hopping. Specifically, the cubic K_2.9375PS_3.9375Cl_0.0625 exhibits a low activation energy of 0.22 eV, with an ionic conductivity of 1.11 × 10^-4 S cm^-1 at 300 K. Metadynamics simulations show that Cl-doping increases the initial water-dissociation barrier on the surface of the electrolyte, and may suppress subsequent degradation to some extent. Moreover, Cl-doping barely alters the band gap (2.76 eV) of K₃PS₄, retaining its excellent electronic blocking capability. This study offers a feasible strategy and theoretical case for the development of a sulfide solid electrolyte for KIBs.