Construction of cobalt oxyhydroxide nanosheets with rich oxygen vacancies as high-performance lithium-ion battery anodes

Abstract

Cobalt oxyhydroxide (CoOOH) is a promising anode material for lithium-ion batteries (LIBs) due to its high electronic conductivity (5 S cm⁻¹) and theoretical specific capacity (1457 mA h g⁻¹). Herein, CoOOH nanosheets are successfully obtained using a facile one-pot method, and a hierarchical nanoporous structure is formed by oxidizing cobalt hydroxide (Co(OH)₂) in NaOH and (NH₄)₂S₂O₈ solution. The CoOOH anode shows better electrochemical performance compared to Co(OH)₂ and Co₃O₄ electrodes when applied to LIBs. The hierarchical nanoporous structure and high electronic conductivity of the CoOOH anode contribute to its outstanding initial discharge capacity (1478 mA h g⁻¹ at 0.2 A g⁻¹), high initial coulombic efficiency (ICE, 90%), and excellent cyclability (1588 mA h g⁻¹ after 300 cycles). Experiments and density functional theory (DFT) calculations confirmed that the high ICE and prominent rate capability (574 mA h g⁻¹ at 5 A g⁻¹) of the nanosheets could be ascribed to the rapid and complete conversion reaction of CoOOH upon lithiation/delithiation facilitated by hydroxyl groups and oxygen vacancies. This study provides new insights into the structure–property relationship of transition-metal oxyhydroxide anode materials for LIBs.