Zhang Chunxiao, Wei Bo, Jiang Wenjun, Wang Meiyu, Hu Wang, Liang Chaoping, Wang Tianshuo, Chen Libao, Zhang Ruifeng, Wang Peng, Wei Weifeng
State Key Laboratory of Powder Metallurgy, Central South University, Changsha, Hunan 410083, P. R. China.
School of Materials Science and Engineering, Beihang University, Beijing 100191, P. R. China.
ACS Appl Mater Interfaces. 2021 Sep 29;13(38):45619-45629. doi: 10.1021/acsami.1c13908. Epub 2021 Sep 17.
Lithium-rich manganese-based layered oxides (LLOs) are considered to be the most promising cathode materials for next-generation lithium-ion batteries (LIBs) for their higher reversible capacity, higher operating voltage, and lower cost compared with those of other commercially available cathode materials. However, irreversible lattice oxygen release and associated severe structural degradation that exacerbate under high temperature and deep delithiation hinder the large-scale application of LLOs. Herein, we propose a strategy to stabilize the layered lattice framework and improve the thermal stability of cobalt-free LiMnNiO by doping with 4d transition metal niobium (Nb). Detailed atomic-scale imaging, characterization, and DFT simulations confirm that the induced strong Nb-O bonds stabilize the oxygen lattice framework and restrains the fracture of TM-O bonds, thereby inhibiting the release of lattice oxygen and the continuous migration of TM ions to the lithium layer during the cycle. Furthermore, Nb doping also promotes the surface rearrangement to form a Ni-enrichment layered/rocksalt heterogeneous interface to enhance surface structural stability. As a result, the Nb-doped material delivers a capacity of 181.7 mAh g with retention of 85.5% after 200 cycles at 1C, extraordinary thermal stability with a capacity retention of 80.7% after 200 cycles at 50 °C, and superior rate capability.
富锂锰基层状氧化物（LLOs）因其与其他商用正极材料相比具有更高的可逆容量、更高的工作电压和更低的成本，被认为是下一代锂离子电池（LIBs）最有前景的正极材料。然而，不可逆的晶格氧释放以及在高温和深度脱锂条件下加剧的严重结构退化阻碍了LLOs的大规模应用。在此，我们提出一种策略，通过掺杂4d过渡金属铌（Nb）来稳定层状晶格框架并提高无钴LiMnNiO的热稳定性。详细的原子尺度成像表征和DFT模拟证实，诱导产生的强Nb-O键稳定了氧晶格框架并抑制了TM-O键的断裂，从而在循环过程中抑制了晶格氧的释放和TM离子向锂层的持续迁移。此外，Nb掺杂还促进了表面重排，形成富Ni的层状/岩盐异质界面，以增强表面结构稳定性。结果，Nb掺杂材料在1C下200次循环后容量为181.7 mAh g，容量保持率为85.5%；在50℃下200次循环后具有非凡的热稳定性，容量保持率为80.7%，并且具有优异的倍率性能。
