Stress relief and crystal face transition process contribute to the stability of zinc anodes

Abstract

Zn electrodes are suffering the dendrite growth owing to the enrichment of local space charge, distinct exposed face and residual stress. In this work, we investigated the crystal face properties and stress state of Zn foil through static energy calculations, dynamic crystal growth analysis and finite element simulation of stress states. Then thermal driven is deployed to modify the exposure face and residual stress of Zn foil, aiming for a dendrite-free electrode. The calculation of surface energies and simulation of crystal growth models for different crystal faces indicate that the (001) face can maintain stability during deposition. Inspired by this mechanism, the (101) exposed commercial Zn foil is modified by thermal processing. Firstly, the exposure level of the (001) face increases, though only the peak corresponding to the (002) crystal face is observed, due to the extinction effect of the densely packed plane (001) face. Further, the surface morphology becomes smooth and the stress is released with the progresses time. These stress relief and crystal face transition process strengthen the uniformity of ion distribution, and increase the interface stability during the crystal growth, which reduce the defect sites in the deposition. As a result, the Zn electrode exhibits tiny voltage hysteresis and outstanding cycle stability, which reveals improved electrochemical performance. Additionally, Li and Na can also be improved in exposed crystal faces and release strain energy through similar methods to enhance cycling stability.