Surface engineering Co-B nanoflakes on Mn0.33Co0.67CO3 microspheres as multifunctional bridges towards facilitating Li+ storing performance

In virtue of high capacity and low manufacturing expense, transition metal carbonates (TMCs) have recently arisen enormous research interests as the anode materials for rechargeable lithium ion batteries (LIBs). However, the low electrical conductivity and unstable cycle performance impeded their further development. In this work, Co-B compounds are surface-engineered for the first time onto the mixed single-phase Mn0.33Co0.67CO3 microspheres to accelerate the reaction kinetics and suppress the volume fluctuation of the electrodes during Li+ insertion/extraction. Specifically, Co-B nanoflakes not only function as the robust mechanical bridges between Mn0.33Co0.67CO3 primary nanoparticles, but also provide extra pathways for electron/charge transport, both of which facilitate the improvement of electrochemical behaviors. Morever, the synergetic effect between Mn0.33Co0.67CO3 and Co-B nanoflakes allow a high flux of Li+ across the interface to provide signifcantly boosted Li+ diffusivity. Impressively, the Mn0.33Co0.67CO3@Co-B electrode delivers a high reversible capacity of 806 mA h g(-1) over 500 cycles at a high rate of 1.0 A g(-1), demonstrating its superior cycling stability. Therefore, surface engineering of borides may be an effective and promising way to improve the electrochemical behaviors of conversion type anodes like TMCs.