中南大学的袁明亮研究小组探索了Mo⁶⁺掺杂对尖晶石型LiMn₂O₄正极材料结构和电化学性能的影响。相关论文于2024年8月6日发表于国际顶尖学术期刊《颗粒学报》杂志上。

姜-泰勒效应和Mn的溶解是导致尖晶石LiMn₂O₄正极材料，在充放电过程中容量下降的重要因素。该研究采用简单固相烧结法，制备了掺杂Mo⁶⁺的多晶八面体Li_1.05Mn_2-xMo_xO₄ (x= 0,0.005, 0.01, 0.015)的正极材料，并对其晶体结构、微观形貌和元素组成进行了表征和分析。结果表明，Mo⁶⁺的掺杂促进了(111)晶面的生长，提高了Mn³⁺/Mn⁴⁺的比值。

研究人员还对材料的电化学性能进行了测试，发现Mo⁶⁺的掺杂显著提高了材料的初始充放电比容量和循环稳定性。改性后的样品(LMO-0.01Mo)在300次循环后的可逆容量为114.83 mAh/g，容量保留率为97.29%。此外，Mo⁶⁺的掺杂形成了更薄、更光滑的SEI膜，有效地抑制了Mn的溶解。

团队利用密度泛函理论(DFT)计算分析掺杂机理，发现掺杂缩短了晶格内Mn-O键的长度，增加了Li-O键的长度。这意味着Li⁺的扩散通道被加宽，从而增加了Li⁺的扩散速率。此外，改性减小了能带隙，从而提高了电子导电性能。

附：英文原文

Title: Effect of Mo6+ doping on the structure and electrochemical properties of spinel-type LiMn2O4 cathode materials

Author: Mingliang Yuan

Issue&Volume: 2024/08/06

Abstract: The Jahn-Teller effect and the dissolution of Mn are significant factors contributing to the capacity degradation of spinel LiMn2O4 cathode materials during charging and discharging. In this study, Mo6+-doped polycrystalline octahedral Li1.05Mn2-xMoxO4 (x=0, 0.005, 0.01, 0.015) cathode materials were prepared by simple solid-phase sintering, and their crystal structures, microscopic morphologies, and elemental compositions were characterized and analyzed. The results showed that the doping of Mo6+ promoted the growth of (111) crystalline facets and increased the ratio of Mn3+/Mn4+. The electrochemical performance of the materials was also tested, revealing that the doping of Mo6+ significantly improved the initial charge/discharge specific capacity and cycling stability. The modified sample (LMO-0.01Mo) retained a reversible capacity of 114.83 mAh/g with a capacity retention of 97.29% after 300 cycles. Additionally, the doping of Mo6+ formed a thinner, smoother SEI film and effectively inhibited the dissolution of Mn. Using density-functional theory (DFT) calculations to analyze the doping mechanism, it was found that doping shortens the Mn-O bond length inside the lattice and increases the Li-O bond length. This implies that the Li+ diffusion channel is widened, thereby increasing the Li+ diffusion rate. Additionally, the modification reduces the energy band gap, resulting in higher electronic conductivity.

DOI: 10.1016/j.partic.2024.07.020

Source: https://www.sciencedirect.com/science/article/abs/pii/S1674200124001470