School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing , No. 30 College Road, Haidian District, Beijing 100083, China.
China Electric Power Research Institute , Haidian District, Beijing 100192, China.
ACS Appl Mater Interfaces. 2017 Aug 23;9(33):27936-27945. doi: 10.1021/acsami.7b07221. Epub 2017 Aug 10.
Lithium-rich layered oxides (LLOs) have been attractive cathode materials for lithium-ion batteries because of their high reversible capacity. However, they suffer from low initial Coulombic efficiency and capacity/voltage decay upon cycling. Herein, facile surface modification of LiMnNiCoO cathode material is designed to overcome these defects by the protective effect of a surface heterostructure composed of an induced spinel layer and a PrPO modification layer. As anticipated, a sample modified with 3 wt % PrPO (PrP3) shows an enhanced initial Coulombic efficiency of 90% compared to 81.8% for the pristine one, more excellent cycling stability with a capacity retention of 89.3% after 100 cycles compared to only 71.7% for the pristine one, and less average discharge voltage fading from 0.6353 to 0.2881 V. These results can be attributed to the fact that the modification nanolayers have moved amounts of oxygen and lithium from the lattice in the bulk crystal structure, leading to a chemical activation of the LiMnO component previously and forming a spinel interphase with a 3D fast Li diffusion channel and stable structure. Moreover, the elaborate surface heterostructure on a lithium-rich cathode material can effectively curb the undesired side reactions with the electrolyte and may also extend to other layered oxides to improve their cycling stability at high voltage.
富锂层状氧化物 (LLOs) 因其具有高可逆容量而成为锂离子电池有吸引力的阴极材料。然而，它们在循环过程中存在初始库仑效率低和容量/电压衰减的问题。在此，通过诱导尖晶石层和 PrPO 修饰层组成的表面异质结构的保护作用，设计了简便的 LiMnNiCoO 阴极材料表面改性，以克服这些缺陷。正如预期的那样，与原始样品相比，修饰 3wt% PrPO（PrP3）的样品具有更高的初始库仑效率 90%，100 次循环后具有更好的循环稳定性，容量保持率为 89.3%，而原始样品仅为 71.7%，平均放电电压从 0.6353V 降至 0.2881V。这些结果可以归因于这样一个事实，即修饰纳米层已经将大量的氧和锂从体相晶体结构中的晶格中移动出来，从而对 LiMnO 成分进行了化学激活，并形成了具有 3D 快速 Li 扩散通道和稳定结构的尖晶石界面相。此外，富锂阴极材料上的精细表面异质结构可以有效地抑制与电解质的不良副反应，并且也可能扩展到其他层状氧化物，以提高其在高压下的循环稳定性。
