Controllable Synthesis of Co³⁺-Enriched Anisotropy Co₃O₄ Hexagonal Prisms toward Enhanced Lithium Storage

Lithium ion batteries are the most feasible energy storage technology for modern society. However, the electrochemical performance of commercial products is not satisfactory, which severely limits the development of electrode materials. An urgent call to balance the demands of high surface area, rich site activity, enhanced electrical conductivity, and controlled electrochemical stability becomes even more desired. In this work, we report a Co₃O₄ hexagonal prism (CHP) with a unique anisotropy structure as the anode material for lithium ion storage. Specifically, the CHP has a solid microframework on the six sidewalls and porous nanotunnels on the top and bottom surfaces, which not only enhances lithium ion storage and transmission but also provides sufficient electrochemical stability (i.e., minimize volume expansion). Additionally, it has much higher Co³⁺ contents and oxygen vacancies on all the surfaces which contribute to rich site activity and enhanced electrical conductivity. Based on these, the anisotropy CHPs show a remarkably higher initial capacity, excellent rate capability, and unique cycling stability than those of Co₃O₄ nanowires and commercial Co₃O₄ microparticles. The resulting CHP electrodes demonstrate an excellent reversible capacity of 800 mA h g^-1 after 800 cycles at 1 A g^-1. A further mechanistic study reveals the relationship between the material properties and the electrochemical performances, which can be mainly attributed to the synergistic effect of the anisotropy architecture, the surface pseudocapacitance, and the enriched Co³⁺ on the material surface. This synthetic strategy provides insights for the development of high-performance anodes. Copyright © 2020 American Chemical Society.