Tailoring Zn²⁺ Flux by an Ion Acceleration Layer Modified Separator for High-Rate Long-Lasting Zn Metal Anodes

A large concentration gradient originating from sluggish ion transport on the surface of Zn metal anodes will result in uneven Zn²⁺ flux, giving rise to severe dendrite growth, especially at high current density. Herein, an ion acceleration layer is introduced by a facile separator engineering strategy to realize modulated Zn²⁺ flux and dendrite-free deposition. Zinc hexacyanoferrate as the modifying agent featuring strong zincophilicity and rapid diffusion tunnel can enable fast trap for Zn²⁺ near the electrode surface and immediate transport onto deposition sites, respectively. The ion acceleration effect is substantiated by improved ion conductivity, decreased activated energy, and promoted Zn²⁺ transference number, which can moderate concentration gradient to guide homogenous Zn²⁺ flux distribution. As a result, the separator engineering guarantees Zn||Zn symmetrical cells with long-term stability of 2700 h at 2 mA cm^-2, and 1770 h at a large current density of 10 mA cm^-2. Moreover, cycling stability and rate capability for full cells with different cathodes can be substantially promoted by the modified separator, validating its superior practical feasibility. This study supplies a new scalable approach to tailoring ion flux near the electrode surface to enable robust Zn metal anodes at a high current density.