Nickel-rich cobalt-low layered oxides have attracted much attention as positive electrode materials for high-energy lithium-ion batteries due to their high capacity and low cost, but their inherent stress accumulation and severe cationic mixed reactions will deteriorate the cycling performance. Herein, the nickel-rich single-crystalline LiNi_0.90Co_0.06Mn_0.04O₂ cathode material doped with W and Mg (NCM-WM) has been fabricated to overcome its structure degradation issues. It can be found that the Li/Ni cation mixture can be suppressed by the introduction of Mg²⁺ into Li⁺ situs and the replacement of transition metal ions by W⁶⁺. Meanwhile, the co-doing strategy synergistically depresses the irreversible H2-H3 phase transition to weaken the internal stress, and employs the heteroatoms as the pillar ions to prevent layer structure collapse. In addition, the reduced particle size induced by the W⁶⁺ and increased free electron resulted by Mg²⁺ can cooperatively improve the migration kinetics of ions and electrons in the process of cycling. As expected, the above advanced effects result in the prominent cycling properties (capacity retention of 86.7 %, 150 cycles, 2C) of the designed Ni-rich electrode materials. These results demonstrate that the co-doped design is a greatly effective strategy to reinforce the cycling performance of Ni-rich single-crystalline materials.

中文翻译：

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协同掺杂化学使锂离子电池用单晶富镍阴极的循环性能成为可能


富镍钴低层氧化物因其容量大、成本低而作为高能锂离子电池的正极材料备受关注，但其固有的应力积累和严重的阳离子混合反应会恶化其循环性能。在此，制备了掺杂 W 和 Mg 的富镍单晶 LiNi _0.90Co_0.06Mn_0.04O 2 正极材料 （NCM-WM），以克服其结构降解问题。可以发现，通过将 Mg²⁺ 引入 Li⁺ 位置并用 W⁶⁺ 取代过渡金属离子，可以抑制 Li/Ni 阳离子混合物。同时，协同作用策略协同抑制不可逆的 H2-H3 相变以减弱内应力，并采用杂原子作为支柱离子以防止层结构崩溃。此外，W⁶⁺ 诱导的粒径减小和 Mg²⁺ 导致的自由电子增加可以协同改善离子和电子在循环过程中的迁移动力学。正如预期的那样，上述先进效果导致所设计的富镍电极材料具有突出的循环性能（容量保持率 86.7 %，150 次循环，2C）。这些结果表明，共掺杂设计是增强富镍单晶材料循环性能的一种非常有效的策略。