<br>钼掺杂无钴正极通过增强共价键实现电化学稳定性,Small

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钼掺杂无钴正极通过增强共价键实现电化学稳定性
Small ( IF 13.0 ) Pub Date : 2024-06-21 , DOI: 10.1002/smll.202403828
Jiayi Wang ₁ , Xincheng Lei ₂ , Shengnan Guo ₂ , Xiaomin Zhang ₁ , Yaping Deng _{3,

4} , Qianyi Ma ₄ , Mingliang Jin ₅ , Lingzhi Zhao ₅ , Xin Wang _{1,

5} , Zhongwei Chen ₃ , Dong Su ₂

Affiliation

该掺杂策略有效提高了无钴富镍正极的容量和循环稳定性。了解掺杂剂的内在贡献对于优化阴极的性能非常重要。本研究研究了 Mo 掺杂 LiNi0.8Mn0.2O2 (NM82) 阴极的结构修饰与其性能之间的相关性。掺杂Mo价态的作用已被证明在晶格结构修饰和电子态调整方面都有作用。虽然阴极表面Mo的高价态不可避免地会降低Ni的价态以达到电子中性，从而导致离子混合，但原始Mo的价态会影响其扩散深度。结构分析表明，Mo 掺杂会在表面形成混合层，其中高价 Mo 形成细长的阳离子混合层，从而增强结构稳定性和锂离子传输。此外，研究发现Mo6+离子的高价掺杂剂部分占据了未填充的4d轨道，这可能通过增加共价键来强化Mo─O键，从而降低氧迁移率。这使得具有高 Mo 价态的 Mo-NM82 阴极具有令人印象深刻的容量保持率（200 次循环后为 90.0%）。这些发现强调了掺杂对层状氧化物阴极性能的价态效应，为下一代阴极的开发提供了指导。

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Molybdenum‐Doped Cobalt‐Free Cathode Realizing the Electrochemical Stability by Enhanced Covalent Bonding

The doping strategy effectively enhances the capacity and cycling stability of cobalt‐free nickel‐rich cathodes. Understanding the intrinsic contributions of dopants is of great importance to optimize the performances of cathodes. This study investigates the correlation between the structure modification and their performances of Mo‐doped LiNi0.8Mn0.2O2 (NM82) cathode. The role of doped Mo's valence state has been proved functional in both lattice structural modification and electronic state adjustment. Although the high‐valence of Mo at the cathode surface inevitably reduces Ni valence for electronic neutrality and thus causes ion mixing, the original Mo valence will influence its diffusion depth. Structural analyses reveal Mo doping leads to a mixed layer on the surface, where high‐valence Mo forms a slender cation mixing layer, enhancing structural stability and Li‐ion transport. In addition, it is found that the high‐valence dopant of Mo6+ ions partially occupies the unfilled 4d orbitals, which may strengthen the Mo─O bond through increased covalency and therefore reduce the oxygen mobility. This results in an impressive capacity retention (90.0% after 200 cycles) for Mo‐NM82 cathodes with a high Mo valence state. These findings underscore the valence effect of doping on layered oxide cathode performance, offering guidance for next‐generation cathode development.

更新日期：2024-06-21

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