Layered nickel-rich cathodes generally suffer from their unstable surface because of lithium impurities. Thus, building an interface with both high electrochemical stability and electroactivity is essential for the development of cathodes. In this work, a Li_0.73Co_1–xAl_xO₂ thin layer was successfully coated on pristine LiNi_0.8Co_0.15Al_0.05O₂ (NCA) spheres by the reaction of the surface residual lithium with cobalt oxalate nanomaterials. Then, the surface chemical states of NCA were effectively modulated by Li_0.73Co_1–xAl_xO₂ coating, including less surface lithium impurities, lower resistance, enhanced ion conductivity, and cycling stability. As a potential cathode material with a higher oxidation potential than that of NCA, Li_0.73Co_1–xAl_xO₂ coating plays both roles of an isolation layer and active layer. The advances of Li_0.73Co_1–xAl_xO₂ coating may be related to the enhanced covalence property of the Co–O bond and the coexistence of Co⁴⁺ and Al³⁺, which can help to form a stable cathode–electrolyte interface and boost the ion diffusion of the coated NCA cathode. This Li_0.73Co_1–xAl_xO₂-modified NCA cathode exhibits a highly competitive performance, such as a capacity of 215.2 mA h g^–1 at the initial cycle (0.1 C) and a retention rate of 62.7% after 200 cycles at 5 C. This surface chemical state modulation strategy provides a new possibility of surface engineering with nickel-rich cathodes for high-energy Li-ion batteries.

中文翻译：

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NCA阴极界面活化和稳定的见解：铝介电的Li _0.73 CoO ₂涂层的表面化学状态调节

由于锂杂质，层状富镍阴极通常遭受其不稳定的表面的困扰。因此，建立具有高电化学稳定性和电活性的界面对于开发阴极至关重要。在这项工作中，通过表面残留的锂与草酸钴纳米材料的反应，在原始的LiNi _0.8 Co _0.15 Al _0.05 O ₂（NCA）球上成功地涂覆了Li _0.73 Co _{1– x} Al _x O ₂薄层。然后，Li _0.73 Co _{1– x} Al _x O有效地调节了NCA的表面化学态。₂涂层，包括较少的表面锂杂质，较低的电阻，增强的离子电导率和循环稳定性。Li _0.73 Co _{1– x} Al _x O ₂涂层作为具有比NCA更高的氧化电位的潜在阴极材料，同时起到隔离层和有源层的作用。Li _0.73 Co _{1– x} Al _x O ₂涂层的发展可能与Co–O键的共价性增强以及Co ⁴⁺和Al ³⁺的共存有关。，这可以帮助形成稳定的阴极-电解质界面，并促进涂覆的NCA阴极的离子扩散。Li _0.73 Co _{1– x} Al _x O ₂改性的NCA阴极展现出极具竞争力的性能，例如在初始循环（0.1 C）下的容量为215.2 mA hg ^–1，在200循环下的保持率为62.7％。 5 C.这种表面化学状态调节策略为高能锂离子电池的富镍阴极提供了一种表面工程化的新可能性。