Large-scale and template-free synthesis of hierarchically porous MnCo2O4.5 as anode material for lithium-ion batteries with enhanced electrochemical performance

We report a simple and large-scale synthetic method of hierarchically porous manganese cobalt oxides without using any template that exhibit enhanced electrochemical performance compared with the nanoparticles counterpart. The hierarchically porous structures consist of close-packed large grains within wormlike hierarchical pores resulting from the piling of the nanoparticles wall. The calcination container conditions are of key importance to affect the morphology and structure of the manganese cobalt oxides. In order to check the fundamental significance of hierarchically porous structure, pristine manganese cobalt oxides without coating any conducting agent are tested as the lithium-ion battery anodes. The cycling stability and rate performance of the hierarchically porous electrode are much better than that of the nanoparticles counterpart with specific capacity as high as 413 mAh g−1 after 100 cycles at a current density of 300 mA g−1. For the purpose of explaining the improved electrochemical performance of the hierarchically porous materials, both electrodes were analyzed with cyclic voltammetry, electrochemical impedance spectroscopy, and transmission electron microscopy measurement. We found that the close-packed morphology and the hierarchically porous structure are responsible for the volume change accommodation and electron-contact maintenance leading to the high specific capacity, cycling stability, and rate performance.