Arranging cation mixing and charge compensation of TiNb₂O₇ with W⁶⁺ doping for high lithium storage performance

TiNb₂O₇ is an advanced anode material for high-energy density lithium-ion batteries (LIBs) due to its considerable specific capacity and satisfactory safety. However, its rate capability is limited by its poor ionic conductivity and electronic conductivity. To solve this problem, TiNb₂O₇ with W⁶⁺ doping was synthesized by a convenient solid-state method. The doping of W⁶⁺ will lead to arranging cation mixing and charge compensation. The cation rearrangement creates a new Li-conductive environment for lithiation, resulting in a low-energy barrier and the fast Li⁺ storage/diffusion. The results show that the Li⁺ diffusion coefficient of W_0.06Ti_0.91Nb₂O₇ is increased by 9.96 times greater than that of TiNb₂O₇. Besides, as the calculation proves, due to the partial reduction of the Nb⁵⁺ and Ti⁴⁺ caused by charge compensation, W⁶⁺ doping results in low charge transfer resistance and excellent electronic conductivity. Moreover, W⁶⁺ doping accounts for a high pseudocapacitive contribution. At the scan rate of 1 mV·s⁻¹, the pseudocapacitive contribution for TiNb₂O₇ is 78%, while that for W_0.06Ti_0.91Nb₂O₇ increases to 83%. The reversible specific capacity of W_0.06Ti_0.91Nb₂O₇ after 600 cycles is maintained at 148.90 mAh·g⁻¹ with a loss of only 16.37% at 10.0C. Also, it delivers a commendable capacity of 161.99 mAh·g⁻¹ at 20.0C. Even at 30.0C, it still retains a satisfactory capacity of 147.22 mAh·g⁻¹, much higher than TiNb₂O₇ (97.49 mAh·g⁻¹). Our present study provides ideas for the development of electrode materials for lithium-ion batteries.