Closely Compacted TiNb₂O₇-C Assembly for Fast-Charging Battery Anodes

The fast-charging capability of lithium-ion batteries (LIBs) is becoming more important than before to meet the increasing requirements in practical applications. Because of safe working potential (above 1 V) and moderately high specific capacity, titanium niobium oxide (TiNb2O7, TNO) shows great potential as a fast-charging anode. Herein, a TNO-C assembly consisting of active initial TNO nanoparticles with conformal carbon coating is fabricated. The small size of TNO nanoparticles provides a short diffusion distance for lithium ions, and surficial carbon layers enable good electronic conductivity within the entire assembly. Moreover, the compact structure within the TNO assembly and efficient space packing of spheroidal secondary particles are beneficial for close packing, leading to an overall short distance for electron transport and ion diffusion. As expected, the as-designed TNO-C electrode delivers a high capacity of 194 mAh g–1 under 10C, and 71% of capacity was achieved under 0.2C. Moreover, the TNO-C electrode shows stable cycling performance with capacity retention of 92.2% after 100 cycles under 2C. In addition, by pairing with a lithium nickel–cobalt manganate (LiNi0.6Co0.2Mn0.2O2, NCM) cathode, the full cell exhibits a high capacity of 140 mAh g–1 under 3C and a high capacity retention of 97.4% after 100 cycles. The rational design of a TNO-C assembly makes it an excellent anode candidate for fast-charging LIBs.