Tan Zhouliang, Li Yunjiao, Lei Changlong, Li Yue, Xi Xiaoming, Jiang Shijie, Wu Feixiang, He Zhenjiang
School of Metallurgy and Environment, Central South University, Changsha, 410083, P. R. China.
Engineering Research Center of the Ministry of Education for Advanced Battery Materials, Central South University, Changsha, 410083, China.
Small. 2024 Feb;20(5):e2305618. doi: 10.1002/smll.202305618. Epub 2023 Sep 27.
Planar gliding along with anisotropic lattice strain of single-crystalline nickel-rich cathodes (SCNRC) at highly delithiated states will induce severe delamination cracking that seriously deteriorates LIBs' cyclability. To address these issues, a novel lattice-matched MgTiO (MTO) layer, which exhibits same lattice structure as Ni-rich cathodes, is rationally constructed on single-crystalline LiNi Co Mn O (SC90) for ultrastable mechanical integrity. Intensive in/ex situ characterizations combined with theoretical calculations and finite element analysis suggest that the uniform MTO coating layer prevents direct contact between SC90 and organic electrolytes and enables rapid Li-ion diffusion with depressed Li-deficiency, thereby stabilizing the interfacial structure and accommodating the mechanical stress of SC90. More importantly, a superstructure is simultaneously formed in SC90, which can effectively alleviate the anisotropic lattice changes and decrease cation mobility during successive high-voltage de/intercalation processes. Therefore, the as-acquired MTO-modified SC90 cathode displays desirable capacity retention and high-voltage stability. When paired with commercial graphite anodes, the pouch-type cells with the MTO-modified SC90 can deliver a high capacity of 175.2 mAh g with 89.8% capacity retention after 500 cycles. This lattice-matching coating strategy demonstrate a highly effective pathway to maintain the structural and interfacial stability in electrode materials, which can be a pioneering breakthrough in commercialization of Ni-rich cathodes.
在高度脱锂状态下，单晶富镍阴极（SCNRC）的平面滑动以及各向异性晶格应变会引发严重的分层开裂，这会严重降低锂离子电池的循环性能。为了解决这些问题，一种与富镍阴极具有相同晶格结构的新型晶格匹配MgTiO（MTO）层被合理地构建在单晶LiNi Co Mn O（SC90）上，以实现超稳定的机械完整性。大量的原位/非原位表征结合理论计算和有限元分析表明，均匀的MTO涂层可防止SC90与有机电解质直接接触，并能在锂缺乏程度降低的情况下实现快速锂离子扩散，从而稳定界面结构并承受SC90的机械应力。更重要的是，SC90中同时形成了一种超结构，它可以有效缓解连续高压脱嵌过程中的各向异性晶格变化并降低阳离子迁移率。因此，所制备的MTO改性SC90阴极表现出理想的容量保持率和高压稳定性。当与商用石墨阳极配对时，采用MTO改性SC90的软包电池在500次循环后可提供175.2 mAh g的高容量，容量保持率为89.8%。这种晶格匹配涂层策略展示了一种在电极材料中维持结构和界面稳定性的高效途径，这可能是富镍阴极商业化的一项开创性突破。
