High-rate lithium storage performance of TiNb2O7 anode due to single-crystal structure coupling with Cr3+-doping

TiNb2O7 (TNO) is regarded as a promising anode candidate for lithium-ion batteries due to its high capacity and suitable lithiation potential to avoid Li plating issue, but it suffers from the poor rate capability. Herein, an effective strategy combining single-crystal structure and ion doping is proposed to boost the high-rate performance. The single-crystal structure with few grain boundaries could significantly reduce the resistance of Li+ transport and the side reactions. The Cr-doping increases the electronic conductivity and promotes fast Li+ diffusion. Benefited from the single-crystal structure coupling with Cr-doping, high electrochemical lithium storage performance of TNO material is achieved. The single-crystal TNO with 2 at % Cr-doping delivers a reversible capacity of 285.4 mA h g(-1) at 0.1 C and 103.2 mA h g(-1) at an extremely high current rate of 50 C, which also displays 97% of the initial capacity is still retained at 50 C after 500 cycles. It is noteworthy that the high-performance TNO material has micron-scale particle size, which is suitable for industrial production and applications. This work suggests that the combination of single-crystal structure and ion doping is a promising strategy to develop the high-rate anode material, providing a new way for fast-charging lithium-ion batteries.