Alleviating the Potential Hysteresis of Na _3.5 MnCr _0.5 Ti _0.5 (PO _{4 Hongwei Zhang, Shan Wang, Ziqi Wen, Jingping Wang, Youlong Xu}

ABSTRACT

Na _3.5 MnCr _0.5 Ti _0.5 (PO ₄ ) ₃ (NMCrTP) demonstrates significant development potential as a cathode material for sodium‐ion batteries owing to its low cost and high discharge plateau. However, the severe potential hysteresis phenomenon caused by Mn·Na anti‐site defects (Mn·Na‐ASD) of Mn ²⁺ residing in Na vacancies is hindering its performance release. Here, a strategy is proposed to alleviate the anti‐site defects in NMCrTP through doping Mo at the Ti sites using the sol–gel method. Rietveld refinement results confirm that the content of Mn·Na‐ASD decreases from 6.30% in NMCrTP/C to 0.98% in NMCrTP/C‐0.05Mo. Meanwhile, Hall effect measurements verify that the Mo donor induces the carrier‐type transformation from p‐type to n‐type, enhancing electronic conductivity from 3.07 × 10 ⁻³ to 3.61 × 10 ⁻³ S cm ⁻¹ . Moreover, the ion diffusion coefficient measured by GITT increases from 3.96 × 10 ⁻¹² to 1.34 × 10 ⁻¹¹ cm ² /s. In result, the mean discharge potential of the NMCrTP/C‐0.05Mo cathode increases from 2.62 V (vs. Na ⁺ /Na) to 3.47 V, and the electrochemical polarization decreases from ΔV = 0.20 to 0.09 V. As expected, the NMCrTP/C‐0.05Mo cathode delivers an excellent rate performance of 88.4 mAh g ⁻¹ at a high rate of 10 C. This work presents an effective strategy to alleviate the potential hysteresis of the NMCrTP cathode for high‐rate SIBs.