Homovalent doping: An efficient strategy of the enhanced TiNb₂O₇ anode for lithium-ion batteries

The low energy density, unsatisfied cycling performance, potential safety issue and slow charging kinetics of the commercial lithium-ion batteries restrained their further application in the fields of fast charging and long-haul electric vehicles. Monoclinic TiNb₂O₇ (TNO) with the theoretical capacity of 387 mAh g^-1 has been proposed as a high-capacity anode materials to replace Li₄Ti₅O₁₂. In this work, homovalent doping strategy was used to enhance the electrochemical performance of TiNb₂O₇ (TNO) by employing Zr to partial substitute Ti through solvothermal method. The doping of Zr⁴⁺ ions can enlarge the lattice structure without changing the chemical valence of the original elements, refine and homogenize the grains, improve the electrical conductivity, and accelerate the ion diffusion kinetics, and finally enhance the cycle and rate performance. Specifically, Z_0.05-TNO shows initial discharge capacity of as high as 312.2 mAh g^-1 at 1 C and 244.8 mAh g^-1 at 10 C, and still maintains a high specific capacity of 171.3 mAh g^-1 after 800 cycles at 10 C. This study provides a new strategy for high-performance fast-charging energy storage electrodes.