Three-dimensional hierarchical urchin-like TiNbO microspheres encapsulated in N-doped carbon for high-rate lithium storage.

Wadsley-Roth phase TiNbO has been known as a potential anode material in high-power lithium-ion batteries (LIBs) owing to its enhanced safety, reliable cycling performance, and substantial theoretical capacity. However, its commercial application is restricted by poor electronic conductivity and slow Li-ion migration kinetics. Herein, we have developed urchin-structured TiNbO microspheres with an ultrathin N-doped carbon coating through a two-step hydrothermal and polydopamine carbonization process. When used as LIBs anode, the TiNbO@N-C composite demonstrates a remarkable rate capability of 216 mAh g at 30 C and a durable lifespan with a capacity retention of 89 % after 500 cycles (10 C). In addition, by pairing with LiNiMnO cathode, the full cell also reveals outstanding electrochemical performance even at high rates. The enhanced lithium storage capabilities of TiNbO@N-C can be credited to the integrated superiorities of the multilevel urchin-like architecture and the external conductive layer, which shortens the Li/electron transfer paths, buffer the volume fluctuations of active substance, and improves the overall conductivity of the composite electrode.