Highly uniform Co-Cu bimetallic sulfides for rechargeable alkaline aqueous zinc batteries

Abstract

Rechargeable alkaline aqueous zinc batteries (RAZBs) have attracted increasing attention. However, most RAZBs are hindered by the limited availability of cathode materials. The practical electrochemical performance of most cathode materials is lower than the theoretical value due to their poor electrical conductivity and low utilization capacity. In this work, we develop a facile hydrothermal procedure to prepare highly uniform bimetallic sulfides as novel cathode materials for RAZBs. Copper-cobalt binary metallic oxides materials possess higher conductivity and larger capacity compared with their mono-metal oxides compounds due to bimetallic synergistic effects and multiple oxidation states. Furthermore, bimetallic sulfide compounds have smaller bond energy and longer bond length than their oxides, leading to less structural damage, faster kinetics of electrochemical reactions, and better stability. The as-prepared Co-Cu bimetallic sulfides show enhanced electrochemical performance due to various valences of Co and Cu as well as the existence of S. As a result, aqueous Zn/CuCo2S4 battery shows a high specific capacity of 117.4 mAh/g at 4 A/g and a good cycle life of over 8000 cycles. Based on PANa hydrogel electrolytes, a flexible Zn/CuCo2S4 battery demonstrates excellent cycling stability. This battery can also meet the requirements of electronic devices with different shapes and performs well in extreme environments, such as freezing, drilling, and hammering. This work opens new avenues to obtain high-rate and long-life cathode materials for RAZBs by utilizing the synergistic effects of bimetallic sulfides and provides a new platform for flexible energy storage devices.