Coordination-Constrained Zinc Ions Transport in Solid-State Electrolytes: Mechanisms and Design Principles.

Zinc-ion batteries (ZIBs) are regarded as potential candidates for next-generation energy storage systems due to their intrinsic safety, low cost, and environmental sustainability. Solid-state electrolytes hold potential for effectively addressing issues in aqueous electrolytes. However, the development of solid-state ZIBs is fundamentally limited by the physicochemical characteristics of Zn2+. Due to the multivalent nature of Zn2+, they are subject to stronger coordination constraints, and Zn2+ migration is dominated by desolvation processes and coordination restructuring, contributing to slow ion transport in solid-state environments. Here, we establish a mechanism-oriented framework for understanding Zn2+ transport in solid-state electrolytes, including inorganic solid-state electrolytes, solid-state polymer electrolytes, and quasi-solid-state electrolytes. Specifically, we summarize the vacancy transport mechanism and gap transport mechanism for Zn2+ transport in inorganic solid-state electrolytes, the chain segment motion-assisted transport mechanism in solid-state polymer electrolytes, and the liquid-solid synergistic mechanism in quasi-solid-state electrolytes. On this basis, we propose general design principles for overcoming coordination constraints in each type of solid-state electrolyte. Importantly, the concepts presented here extend beyond zinc-ion systems and offer a unified perspective on multivalent-ion transport in solid-state electrolytes. This work will provide actionable insights for the rational design of next-generation solid-state batteries.