Crystal facet correlated Zn growth on Cu for aqueous Zn metal batteries

Abstract

Aqueous Zn metal batteries are one of the most attractive systems for large-scale energy storage applications. Planar Cu substrates are widely utilized as current collectors for Zn anodes. Although different approaches have been applied to improve performance of Zn anodes, the nature of native Cu current collector for Zn growth has not been fully understood. In this work, we explore native planar Cu foils and find that the Zn anode exhibits distinct electrochemical properties on the Cu current collectors with different dominant crystal facets. Specifically, in asymmetric Cu-Zn cell tests, the Zn anodes using Cu foils with Cu-100 or Cu-110 dominant crystal planes exhibit the first-cycle CE of 95% with plate-like deposition morphology and long cycle life of 1000 h, which is a significant improvement compared to that with Cu-111 dominant crystal facet. In addition, activated carbon-Zn/Cu hybrid capacitors based on Cu-100 or Cu-110 for Zn anodes exhibit higher specific capacity and longer cycle life than that of Cu-111. Further, DFT calculations show that the adsorption energies of Cu-100 and Cu-110 crystal facets during Zn deposition are much higher than that of the Cu-111 crystal facet, validating the significant crystal facet selectivity on the Zn anode chemistry. This work reveals the crystal facet correlation with the Zn anode electrochemical performance, providing opportunities for the future development of high-energy and long-life Zn metal batteries.