Wang Yang-Yang, Gao Ming-Yue, Liu Sheng, Li Guo-Ran, Gao Xue-Ping
Institute of New Energy Material Chemistry, School of Materials Science and Engineering, Nankai University, Tianjin 300350, China.
ACS Appl Mater Interfaces. 2021 Feb 17;13(6):7343-7354. doi: 10.1021/acsami.0c21990. Epub 2021 Feb 8.
The high-nickel layered oxides are potential candidate cathode materials of next-generation high energy lithium-ion batteries, in which higher nickel/lower cobalt strategy is effective for increasing specific capacity and reducing cost of cathode. Unfortunately, the fast decay of capacity/potential, and serious thermal concern are critical obstacles for the commercialization of high-nickel oxides due to structural instability. Herein, in order to improve the structure and thermal stability of high-nickel layered oxides, we demonstrate a feasible and simple strategy of the surface gradient doping with yttrium, without forming the hard interface between coating layer and bulk. As expected, after introducing yttrium, the surface gradient doping layer is formed tightly based on the oxidation induced segregation, leading to improved structure and thermal stability. Correspondingly, the good capacity retention and potential stability are obtained for the yttrium-doped sample, together with the superior thermal behavior. The excellent electrochemical performance of the yttrium-doped sample is primarily attributed to the strong yttrium-oxygen bonding and stable oxygen framework on the surface layer. Therefore, the surface manipulating strategy with the surface gradient doping is feasible and effective for improving the structure and thermal stability, as well as the capacity/potential stability during cycling for the high-Ni layered oxides.
高镍层状氧化物是下一代高能量锂离子电池潜在的正极材料候选物，其中高镍/低钴策略对于提高比容量和降低正极成本是有效的。不幸的是，由于结构不稳定，容量/电位的快速衰减以及严重的热问题是高镍氧化物商业化的关键障碍。在此，为了改善高镍层状氧化物的结构和热稳定性，我们展示了一种可行且简单的表面用钇进行梯度掺杂的策略，而不会在涂层与主体之间形成硬界面。正如预期的那样，引入钇后，基于氧化诱导偏析紧密形成了表面梯度掺杂层，从而改善了结构和热稳定性。相应地，钇掺杂样品具有良好的容量保持率和电位稳定性，以及优异的热性能。钇掺杂样品优异的电化学性能主要归因于表面层上强的钇 - 氧键和稳定的氧骨架。因此，表面梯度掺杂的表面调控策略对于改善高镍层状氧化物的结构和热稳定性以及循环过程中的容量/电位稳定性是可行且有效的。
