Probing Li-ion diffusion in Li1.17Ti0.33TM0.25Mo0.25O2 (TM= Mo, Cr, Fe, Ni) with a disordered rocksalt-type structure using μ+SR

Cation-disordered rocksalt (DRS) Li-rich oxides are promising cathode materials for Li-ion batteries due to their high capacities (ca. 300 mAh/g), compositional versatility, and structural stability. However, their intrinsic Li-ion diffusion properties remain poorly understood. Conventional techniques such as NMR and impedance spectroscopy are limited by magnetic interactions and microstructural effects, complicating accurate determination of diffusion coefficients (DLi) and activation energies (Ea). We propose to investigate Li-ion transport in four cobalt-free DRS oxides containing transition metals such as Mo, Cr, Fe, and Ni. Our electrochemical data show distinct voltage profiles and cycling stability among these materials. Preliminary operando pair distribution function (PDF) and ex situ X-ray absorption spectroscopy (XAS) analyses reveal variations in short-range order (SRO) and differing degrees of reversible metal migration. We hypothesise that these structural differences influence Li-ion mobility. By combining μ⁺SR measurements with our structural data, we aim to directly determine DLi and Ea as a function of transition metal chemistry and local structure. This will allow us to correlate Li-ion transport with SRO and guide the rational design of next-generation cathodes with improved performance.

阳离子无序岩盐（Cation-disordered rocksalt, DRS）富锂氧化物是极具应用前景的锂离子电池正极材料，因其兼具高比容量（约300 mAh/g）、组成多样性与结构稳定性。然而，该类材料的本征锂离子扩散特性仍未得到充分阐释。
传统表征技术如核磁共振波谱法（Nuclear Magnetic Resonance, NMR）与阻抗光谱法受限于磁相互作用与微观结构效应，难以精准测定锂离子扩散系数（DLi）与活化能（Ea）。
本研究拟针对四种含钼、铬、铁及镍等过渡金属的无钴DRS氧化物开展锂离子输运特性研究。我们的电化学测试数据显示，上述材料展现出迥异的电压曲线与循环稳定性。
初步的原位对分布函数（Pair Distribution Function, PDF）与非原位X射线吸收光谱（X-ray Absorption Spectroscopy, XAS）分析表明，其短程有序（short-range order, SRO）结构存在差异，且可逆金属迁移程度各不相同。
我们提出假设：上述结构差异会对锂离子迁移率产生影响。
通过将μ⁺SR测量结果与结构表征数据相结合，本研究旨在直接获取基于过渡金属化学组成与局域结构的DLi与Ea参数。
该工作将有助于建立锂离子输运与短程有序结构之间的构效关联，并为设计性能更优异的下一代锂离子电池正极材料提供理性指导思路。