Multi-shelled MgCo2O4 hollow microspheres as anodes for lithium ion batteries

Multi-shelled MgCo2O4 hollow microspheres (MCOs) with a spinel structure as an anode material for lithium ion batteries are prepared through a solvothermal process using colloidal carbon spheres as a template, followed by a calcination process in air. The multi-shelled MgCo2O4 hollow microspheres are synthesized via heterogeneous contraction by non-equilibrium heat balance owing to the temperature gradient. With the change in the calcination temperature, different MCO structures are formed indicating the variations of the electrochemical performance and stability. MCO-400 calcined at 400 °C outstandingly delivers a 100th discharge capacity of 1360 mA h g−1 at a current density of 500 mA g−1 without any obvious decay, while MCO-300 and MCO-500 deliver only 865 and 898 mA h g−1 showing a big difference of around 460 mA h g−1 under the same conditions. The presence of mesoporous interstitial space and meso-/macroporous void space in the quadruple-shelled MgCo2O4 hollow microspheres provides excellent rate capability and electrochemical stability caused by the formation of nanoparticles in the outer and inner shells leading to a remarkable capability for lithium storage and structural integrity, facile mass transfer by the numerous interstitial spaces of the interfacial region between the electrode and the electrolyte, and the void space in the multiple-shelled hollow microspheres preventing volume expansion along the radial direction occurring during Li+ insertion and extraction.