A High-Energy Four-Electron Zinc Battery Enabled by Evoking Full Electrochemical Activity in Copper Sulfide Electrode
Shizhen Li, Zhiquan Wei, Jinlong Yang, Guangming Chen, Chunyi Zhi, Hongfei Li, Zhuoxin Liu
Abstract
The growing global demand for sustainable and cost-effective energy storage solutions has driven the rapid development of zinc batteries. Despite significant progress in recent years, enhancing the energy density of zinc batteries remains a crucial research focus. One prevalent strategy involves the development of high-capacity and/or high-voltage cathode materials. CuS, a commonly used electrode material, exhibits a two-electron transfer mechanism; however, the reduced sulfion lacks electrochemical activity and thereby limits its discharge capacity and redox potential. In this study, we activate a CuS cathode to form a high-valence Cu 2+ &S compound using a deep-eutectic-solvent (DES)-based electrolyte. The presence of Cl – in the DES-based electrolyte is crucial to the reversibility of the redox chemistry, and the liquid-phase-involved electrochemical process facilitates redox kinetics. A four-electron transfer pathway involving five reaction steps is identified for the CuS electrode, which unleashes the full electrochemical activity of the S element. Consequently, the full cell delivers a large discharge capacity of ∼800 mAh g –1 at 0.2 A g –1 and yields a high discharge plateau starting at 1.58 V, contributing to energy densities of up to 650 Wh kg –1 (based on CuS). This work offers a promising approach to developing high-energy zinc batteries.