Li Guangxin, You Longzhen, Wen Ya, Zhang Congcong, Huang Ben, Chu BinBin, Wu Jian-Hua, Huang Tao, Yu Aishui
Laboratory of Advanced Materials, Institute of New Energy, Fudan University, 2205, Songhu Road, Shanghai 200438, China.
Department of Chemistry, Collaborative Innovation Center of Chemistry for Energy Materials, Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials, Fudan University, 2205, Songhu Road, Shanghai 200438, China.
ACS Appl Mater Interfaces. 2021 Mar 10;13(9):10952-10963. doi: 10.1021/acsami.0c22356. Epub 2021 Feb 23.
Single-crystal LiNiCoMnO cathode materials can effectively suppress intergranular cracks that usually is seen in commercial polycrystal LiNiCoMnO cathode materials. However, the surface structure degradation for single-crystal LiNiCoMnO cathode materials is still aggravated at a higher cutoff voltage (over 4.5 V). In this work, we prepare single-crystal LiNiCoMnO cathode materials via a solid-state method and then coat an ultrathin Li-Si-O layer on their surface by a wet coating method. The results show that the single-crystal LiNiCoMnO cathode materials with a Li-Si-O coating layer deliver excellent cycling performance even at a higher cutoff voltage of 4.5 V. The optimized Li-Si-O-modified sample displays a capacity retention of 90.6% after 100 cycles, whereas only 68.0% for unmodified single-crystal LiNiCoMnO. Further analysis of the cycled electrodes reveals that the surface structure degradation is the main reason for the decrease of electrochemical performance of single-crystal LiNiCoMnO at a high voltage (4.5 V). In contrast, with Li-Si-O coating, this phenomenon can be suppressed effectively to maintain interfacial stability and prolong the cycling life.
单晶LiNiCoMnO正极材料能够有效抑制通常在商用多晶LiNiCoMnO正极材料中出现的晶间裂纹。然而，单晶LiNiCoMnO正极材料的表面结构退化在较高截止电压（超过4.5 V）下仍会加剧。在这项工作中，我们通过固态法制备了单晶LiNiCoMnO正极材料，然后通过湿涂法在其表面包覆一层超薄的Li-Si-O层。结果表明，具有Li-Si-O包覆层的单晶LiNiCoMnO正极材料即使在4.5 V的较高截止电压下也具有优异的循环性能。优化后的Li-Si-O改性样品在100次循环后容量保持率为90.6%，而未改性的单晶LiNiCoMnO仅为68.0%。对循环后的电极进行进一步分析表明，表面结构退化是单晶LiNiCoMnO在高电压（4.5 V）下电化学性能下降的主要原因。相比之下，通过Li-Si-O包覆，可以有效抑制这种现象，以保持界面稳定性并延长循环寿命。
