Surface decoration of mesocarbon microbeads with multifunctional TiNbO_4−x@C coating layer as high rate and stable anode of Li-ion batteries

Surface modification of graphite anode with electroactive matters has been proven of a more practical strategy in enhancing the performance of Li-ion batteries than exploring alternative novel anode materials. Herein, rutile TiNbO_4−x nanoparticles with a tunnel structure are employed as multifunctional decoration substances in combination with a carbon coating layer to improve the rate and cycle properties of mesocarbon microbeads (MCMBs). As compared to pristine MCMB, the Li⁺ diffusion coefficients of the composite anodes are enhanced due to the synergistic effect of TiNbO_4−x@C. Meanwhile, the overcharge and voltage polarization of the composite anodes at high rate are obviously minimized due to the current sharing effect of the high-potential TiNbO_4−x. Moreover, the amorphous Li_yTiNbO_4−x converted from TiNbO_4−x in the initial lithiation process can deliver pseudocapacitive capacity to the composite anodes from the second cycle. All of these functions of TiNbO_4−x@C coating layer have directly contributed to the improved rate and cycle performance of the MCMB/TiNbO_4−x@C composite anodes. The one containing 12.0 wt% TiNbO_4−x exhibits a high reversible specific capacity of 118 mAh·g⁻¹ at 10C (1C = 372 mA·g⁻¹), together with a high capacity retention of 90.9% after 300 cycles at 3C, which are all much superior to those of pristine MCMB.