A MOF-based single-ion Zn2+ solid electrolyte leading to dendrite-free rechargeable Zn batteries

Rechargeable Zn ion battery is a promising alternative for the current portable and mobile energy storage technologies because of its good safety, low cost, and material abundance. Poor deposition reversibility with dendrite formation of Zn metal anode in aqueous electrolytes, which brings the risk of short-circuit and capacity loss (dead Zn), is one of the critical issues that plague its practical applications. To improve the performances of Zn ion batteries, a crystalline single-ion Zn2+ solid-state electrolyte (SSE) is designed based on a post-synthetic modified metal–organic framework. The SSE possesses many advantages such as high ionic conductivity of 2.1 × 10−4 S cm−1 at 30 °C, minor activation energy of 0.12 eV, high Zn2+ transference number of 0.93, along with the good mechanical and electrochemical stability. Due to the restricted and guided Zn deposition through the nanowetted Zn/SSE interface at which Zn(H2O)62+ ions are confined, excellent compatibility between Zn metal anode and the SSE is revealed, which is confirmed firmly by the stable Zn plating/stripping performance, giving rise to a homogeneous, compact, and smooth Zn deposition layer. The good properties of the SSE are further verified in VS2/Zn batteries, which deliver a reversible capacity of 125 mAh g−1 over 250 cycles at 0.2 A g−1 and a reasonable rate capability with ~40% capacity retention (vs. 0.1 A g−1) at 2 A g−1.