A promising next‐generation high‐energy cathode material, LiNiO2 (LNO) has failed to realize commercialization due to severe capacity degradation during cycling. The dual mechanisms of surface oxygen evolution due to anion redox and anisotropic volume change upon delithiation synergistically pulverize and degrade the material. Detailed Density Functional Theory (DFT) modeling and analysis of the anisotropic structural changes associated with crack formation in LiNiO2 (LNO) reveals the link of mechanical behavior to charge transfer and oxygen redox activity upon deep charge cycling (>4.2 V vs Li/Li+). In the two‐phase region and H2–H3 transition from 66% to 100% delithiation, oxygen of [NiO6] octahedra is discovered to undergo redox in growing the Li‐deficient regions, causing c‐lattice mechanical weakening and collapse as the Li‐slab becomes depleted. Li‐site dopants are investigated to locally compensate against anion redox, resulting in enhanced coulombic repulsion and supporting the interslab layer thickness even at 100% depth of charge. Ionic size and oxidation state of M in Lix‐yMyNiO2 are found to fundamentally impact stabilization capability, moderating the anisotropic strain and volume expansion asynchronously. Optimization of mixed doping composition may then enable “zero strain” high‐Ni Li(Ni,Co,Mn)O2 (NCM) or LNO.

中文翻译：

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阴离子氧化还原在 LiNiO2 中的机械降解通过支柱抵消


作为一种前景广阔的下一代高能正极材料，LiNiO2 （LNO） 由于循环过程中容量严重退化而未能实现商业化。由于阴离子氧化还原引起的表面析氧和脱锂时各向异性体积变化的双重机制协同粉碎和降解材料。详细的密度泛函理论 （DFT） 建模和与 LiNiO2 （LNO） 中裂纹形成相关的各向异性结构变化的分析揭示了机械行为与深度电荷循环（>4.2 V vs Li/Li+）中电荷转移和氧氧化还原活性的联系。在两相区域和 H2-H3 从 66% 到 100% 脱锂的转变中，发现 [NiO6] 八面体的氧在生长缺锂区域发生氧化还原，导致 c 晶格机械减弱和塌陷随着锂板的耗尽。研究锂基掺杂剂以局部补偿阴离子氧化还原，从而增强库仑排斥力并支持板间层厚度，即使在 100% 的电荷深度下也是如此。发现 Lix‐yMyNiO2 中 M 的离子大小和氧化态从根本上影响稳定能力，异步调节各向异性应变和体积膨胀。然后，混合掺杂成分的优化可以实现“零应变”高 Ni Li（Ni，Co，Mn）O2 （NCM） 或 LNO。