Stable Solid‐State Zinc–Iodine Batteries Enabled by an Inorganic ZnPS3 Solid Electrolyte with Interconnected Zn2+ Migration Channels

Abstract Aqueous zinc–iodine (Zn–I 2 ) batteries, with their outstanding merits in safety, cost, and environmental friendliness, have received extensive attention. However, the unstable electrochemistry at the electrode–electrolyte interface originating from free water results in zinc dendrite growth, hydrogen evolution reaction (HER), and polyiodide ions shuttle, hindering their practical applications. Herein, solid‐state Zn–I 2 batteries based on an inorganic ZnPS 3 (ZPS) electrolyte are developed to overcome inherent interfacial issues associated with aqueous electrolytes. The inorganic ZnPS 3 electrolyte, with a low Zn 2+ diffusion energy barrier of ≈0.3 eV, demonstrates an exceptional ion conductivity of 2.0 × 10 −3 S cm −1 (30 °C), which also satisfies high chemical/electrochemical stability and mechanical strength. The solid Zn 2+ conduction mechanism, facilitated by bounded water only on grains, effectively suppresses HER and polyiodide ions shuttling. During cycling, a ZnS functional layer is spontaneously formed on the anode/electrolyte interphase, promoting dendrite‐free Zn deposition behavior with a more stable (002) crystal orientation. Consequently, the solid‐state configuration of Zn–I 2 battery enables an impressive reversible capacity of 154.2 mAh g −1 after 400 cycles at 0.1 A g −1 . Importantly, the compatibility of the solid‐state ZnPS 3 electrolyte is also confirmed in the Zn||CuS cell, indicating its potential as a versatile platform for developing inorganic solid‐state zinc‐ion batteries (ZIBs).