Mathematical statistical analysis between crystal structure and “fast-charging” behavior of niobium tungsten oxides anodes for lithium-ion batteries

Niobium tungsten oxide materials (NbWOs) have safe operating voltage and stable structure in lithium-ion batteries, which is beneficial for fast-charging performance. The phase structure could be controlled by adjusting atomic ratios. Clarifying the mathematical relationship between phase structure parameters and Li⁺ storage behavior is an important prerequisite for guiding the design of “fast-charging” niobium-based oxides. Therefore, Pearson’s correlation coefficient method is for the first time employed to analyze the relationship between the crystal structure parameters and Li⁺ storage behaviors of NbWOs. According which, the lithium-ion storage mechanism of TTB phase (Nb₂W₃O₁₄ and Nb₂WO₈) with excellent rate performance is dominated by pseudocapacitive behavior, while for Wadsley-Roth phase (Nb₁₂WO₃₃ and Nb₁₄W₃O₄₄) is jointly by pseudocapacitive and battery behaviors, and the ion diffusion channels perpendicular to the main diffusion axis provide a “shunt-buffer zone” for Li⁺ at a high current density enabling them with outstanding cycling stability. The core of modification for “fast-charging” of NbWOs lies in balancing the ionic diffusion channel proportion of the tetragonal and pentagonal while minimizing the triangular, which can be achieved by adjusting the feeding molar ratio of Nb/W.