Ni-rich layered oxides are considered to be a promising cathode material with high capacity, and their surface structure should be extensively explored to understand the complex associated phenomena. We investigated the surface stability and morphology of LiNiO₂ as a representative of these materials by using density functional theory calculations. The results reveal that the Li-exposed surfaces have lower energies than the oxygen surfaces, irrespective of the facets, and the Ni-exposed ones are the least stable. The equilibrium morphology can vary from truncated trigonal bipyramid to truncated egg shape, according to the chemical potential, whose range is confined by the phase diagram. Moreover, the electrochemical window of stable facets is found to strongly depend on the surface elements rather than the facet directions. Contrary to the stable Li surfaces, oxygen exposure on the surface considerably lowers the Fermi level to the level of electrolyte, thereby accelerating oxidative decomposition of the electrolyte on the cathode surface.

中文翻译：

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锂离子电池LiNiO ₂阴极表面稳定性和形貌的理论预测

富镍层状氧化物被认为是一种有前途的高容量阴极材料，应广泛探索其表面结构以了解复杂的相关现象。我们研究了LiNiO ₂的表面稳定性和形态通过使用密度泛函理论计算来代表这些材料。结果表明，与小面无关，暴露于Li的表面的能量都比发生氧的表面低，而暴露于Ni的表面的稳定性最差。根据化学势，平衡形态可以从截断的三角锥状双锥体转变为截短的卵形，其范围受相图限制。此外，发现稳定刻面的电化学窗口在很大程度上取决于表面元素而不是刻面方向。与稳定的锂表面相反，暴露在表面上的氧气将费米能级大大降低到电解质的能级，从而加速了阴极表面上电解质的氧化分解。