Co-free Li-rich Mn-based cathode materials (Co-free LRMOs) have become one of the most promising cathode materials in lithium-ion batteries for the next generation due to their low cost, high capacity, and environmental friendliness. Under high voltage, redox reactions involving anions can easily lead to various issues, including oxygen release, dissolution of transition metal elements (TMs), and structural collapse in these materials. The absence of the Co element further exacerbates this issue. Here, a simple one-step solid-phase reaction strategy is proposed to achieve nanoscale dual modification of the Co-free LRMOs with F and Tb doping. The dual modification has a relatively small impact on the cell parameters and Li⁺ diffusion ability of the LRMOs, leading to no significant improvement in its rate performance. The modified LRMOs only exhibited discharge capacities of 220.7, 200.1, 140.0, 115.5, and 90.9 mAh·g^–1 at 0.1, 0.2, 1.0, 2.0, and 5.0 C, respectively. However, the modified Co-free LRMOs exhibit extremely strong structural stability and retain 95.1% of the initial capacity after 300 cycles, so far, the highest capacity retention rates among all Ni/Mn-based Li-rich materials. Mechanism studies have shown that the enhancement in structural stability of the Co-free LRMOs is attributed to the increased concentration of oxygen vacancies and Ni³⁺ ions through F doping. Furthermore, Tb doping not only hinders the release of O₂ but also enhances the Li⁺ migration and electronic conductivity coefficient of the LRMOs.

中文翻译：

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通过 TbF3 处理实现超稳定的无钴富锂氧化物


无钴富锂锰基正极材料（无钴LRMO）因其低成本、高容量和环境友好而成为下一代锂离子电池中最有前途的正极材料之一。在高电压下，涉及阴离子的氧化还原反应很容易导致各种问题，包括氧气释放、过渡金属元素（TM）溶解以及这些材料的结构崩溃。 Co元素的缺失进一步加剧了这个问题。在此，提出了一种简单的一步固相反应策略，以实现 F 和 Tb 掺杂的无 Co LRMO 的纳米级双重修饰。双重修饰对LRMOs的电池参数和Li ⁺ 扩散能力影响相对较小，导致其倍率性能没有显着改善。改性LRMO在0.1、0.2、1.0、2.0和5.0 C下的放电容量分别为220.7、200.1、140.0、115.5和90.9 mAh·g ^–1 。然而，改性后的无钴LRMO表现出极强的结构稳定性，在300次循环后仍保留了95.1%的初始容量，是迄今为止所有镍/锰基富锂材料中容量保留率最高的。机理研究表明，无Co LRMOs结构稳定性的增强归因于F掺杂增加了氧空位和Ni ³⁺ 离子的浓度。此外，Tb掺杂不仅阻碍了O ₂ 的释放，而且增强了LRMOs的Li ⁺ 迁移和电子电导系数。