Anion-Trap Engineering toward Remarkable Crystallographic Reorientation and Efficient Cation Migration of Zn Ion Batteries

Abstract

Zn batteries are considered as potential candidates in future power sources, however suffer problems of rampant dendrite/by-product on Zn anodes, torpid Zn²⁺ transfer/diffusion and poor energy density. Inspired by the host-guest interaction chemistry, an anion-trap agent β-cyclodextrin (β-CD) is introduced into the Zn(ClO₄)₂ electrolyte to induce dominant Zn (002) deposition and improve Zn²⁺ migration behaviors. The anion ClO₄⁻ is revealed to be trapped inside the cavity of β-CD, impairing barriers for Zn²⁺ migration and significantly elevating the Zn²⁺ transference number to 0.878. Meanwhile, the β-CD@ClO₄⁻ complex shows the function in preferential growth of the Zn (002), blocking the approach of dendrite growth. Above combined functions lead to substantial enhancement in long-term stability and cell capacity, as proved by 10 times longer life of Zn||Zn symmetric cells and 57 % capacity increasement of Zn-MnO₂ full cells (at 0.1 A g⁻¹) compared with that of pure Zn(ClO₄)₂ electrolyte.