A V-doped W3Nb14O44 anode in a Wadsley–Roth structure for ultra-fast lithium-ion half/full batteries

Niobium-based oxides are considered to be promising anode materials for lithium-ion batteries (LIBs) due to their high capacity, excellent cycling performance and desirable safety. However, the poor intrinsic conductivity and relatively sluggish reaction kinetics limit its broad applications. Herein, V5+ was in situ doped into W3Nb14O44 using a solution combustion method. It was found that V5+ doping did not destroy the intrinsic Wadsley–Roth crystal structure of W3Nb14O44. Instead, it led to a reduction in both the cell volume and material size, which was convenient for the contact between the electrode material and the electrolyte, increased the number of reaction sites and shortened the Li+ transport path. Meanwhile, the EIS and CV results demonstrate that the doping of V5+ is beneficial to improve the electronic conductivity and Li+ diffusion coefficient of the materials. Consequently, microsized W3V0.28Nb13.72O44 exhibits superior electrochemical properties, including an outstanding rate capability of 144.17 mA h g−1 at 100 C and excellent cyclic stability with a capacity retention of 80.29% after 500 cycles at 5 C. In addition, the LiFePO4//W3V0.28Nb13.72O44 full cell also exhibits good cycling stability over 800 cycles at 10 C with tiny capacity loss of only 0.02% per cycle. This work provides a general approach for the design and development of low-conductivity electrode materials for fast Li+ storage.