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.