Influence of annealing temperature on microstructure and lithium storage performance of self-templated CuxCo3−xO4 hollow microspheres

Abstract

Spinel Cu_xCo_3−xO₄ (x ≤ 0.30) hollow microspheres have been readily prepared via a self-templated solvothermal reaction followed by a thermal annealing step. Scanning electron microscopy and transmission electron microscopy images show that the as-prepared hollow microspheres possess an average diameter of ∼450 nm and a compact, thin, polycrystalline shell with an average thickness of ∼50 nm. When used as an anode material for lithium ion batteries, Cu_xCo_3−xO₄ hollow microspheres exhibit a high lithium storage capacity, which is strongly dependent on the annealing temperature of the Cu_xCo_3−xO₄ intermediate. As a result, Cu_xCo_3−xO₄ hollow microspheres annealed at 400 °C deliver a reversible discharge specific capacity as high as 1187 mA h g⁻¹ at a current density of 100 mA g⁻¹ after 50 cycles. Such superior lithium storage performance is derived from the particular microstructure of the shell, which is composed of highly close-connected fine nanoparticles, as well as the resultant better electronic conductivity.