Achieving Fully Reversible Conversion in MoO₃ for Lithium Ion Batteries by Rational Introduction of CoMoO₄

Electrode materials based on conversion reactions with lithium ions generally show much higher energy density. One of the main challenges in the design of these electrode materials is to improve initial Coulombic efficiency and alleviate the volume changes during the lithiation-delithiation processes. Here, we achieve fully reversible conversion in MoO₃ as an anode for lithium ion batteries by the hybridization of CoMoO₄. The porous MoO₃-CoMoO₄ microspheres are constructed by homogeneously dispersed MoO₃ and CoMoO₄ subunits and their lithiation/delithiation processes were studied by ex situ TEM to reveal the mechanism of the reversible conversion reaction. Co nanoparticles are in situ formed from CoMoO₄ during the lithiation process, which then act as the catalyst to guarantee the reversible decomposition of Li₂O, thus effectively improving the reversible specific capacity and initial Coulombic efficiency. Moreover, the pores in MoO₃-CoMoO₄ microspheres also greatly enhance their mechanical strength and provide enough cavity to alleviate volume changes during repeated cycling. Such a design concept makes MoO₃ to be a potential promising anode in practical applications. The full cell (LiFePO₄ cathode/MoO₃-CoMoO₄ anode) displays a high capacity up to 155.7 mAh g^-1 at 0.1 C and an initial Coulombic efficiency as high as 97.35%. This work provides impetus for further development in electrochemical charge storage devices.