Fabrication of TiO2 coated porous CoMn2O4 submicrospheres for advanced lithium-ion anodes

Abstract

Herein, a facile and general way for the synthesis of TiO₂ coated cobalt manganese oxide CoMn₂O₄ (CMO) has been developed. In this contribution, uniform Co_0.33Mn_0.67CO₃ spheres are firstly fabricated via a solvothermal method. Porous CMO with a diameter of about 800 nm is obtained by a subsequent annealing procedure. Finally, a thin layer of TiO₂ is coated on the surface of the CMO through a hydrolysis and subsequent condensation process. When evaluated as anode materials for lithium ion batteries (LIBs), after 500 cycles at a current density of 1000 mA g⁻¹, the CMO@TiO₂ spheres possessed high reversible capacities of 940 mA h g⁻¹ with a suitable discharge plateau of ∼0.6 V, much higher than the pristine CMO. In addition, the CMO@TiO₂ shows better rate performance than CMO, as high as 196 mA h g⁻¹ at a very fast discharge current of 5 A g⁻¹. The high electrochemical performance of CMO@TiO₂ should be attributed to its special structure of nanometer scale spheres with high porosity and the thin layer coating of TiO₂ as a zero-strain shell, which can effectively reduce the diffusion length of electrolyte, Li⁺ and electrons, buffer volume expansion during the Li⁺ insertion/extraction processes and thus reduce the materials' pulverization.