Arranging cation mixing and charge compensation of TiNb ₂ O ₇ with W ⁶⁺ doping for high lithium storage performance

Abstract

Abstract TiNb 2 O 7 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, TiNb 2 O 7 with W 6+ doping was synthesized by a convenient solid‐state method. The doping of W 6+ 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 0.06 Ti 0.91 Nb 2 O 7 is increased by 9.96 times greater than that of TiNb 2 O 7 . Besides, as the calculation proves, due to the partial reduction of the Nb 5+ and Ti 4+ caused by charge compensation, W 6+ doping results in low charge transfer resistance and excellent electronic conductivity. Moreover, W 6+ doping accounts for a high pseudocapacitive contribution. At the scan rate of 1 mV·s −1 , the pseudocapacitive contribution for TiNb 2 O 7 is 78%, while that for W 0.06 Ti 0.91 Nb 2 O 7 increases to 83%. The reversible specific capacity of W 0.06 Ti 0.91 Nb 2 O 7 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 TiNb 2 O 7 (97.49 mAh·g −1 ). Our present study provides ideas for the development of electrode materials for lithium‐ion batteries.