Li Jie, Li Wenting, Zhang Chao, Han Ce, Chen Xinping, Zhao He, Xu Hanying, Jia Guixiao, Li Zelin, Li Jinxing, Zhang Yujuan, Guo Xin, Gao Fei, Liu Jing, Qiu Xinping
Key Laboratory of Organic Optoelectronics and Molecular Engineering, Department of Chemistry, Tsinghua University, Beijing 100084, People's Republic of China.
School of Materials and Metallurgy, Inner Mongolia University of Science and Technology, Baotou 014010, People's Republic of China.
ACS Nano. 2023 Sep 12;17(17):16827-16839. doi: 10.1021/acsnano.3c03666. Epub 2023 Aug 15.
Severe capacity/voltage fading still poses substantial obstacles in the commercial applications of Li-rich layered oxides, which stems from the aggregation of LiMnO-like domains and unstable surface structure. Here, we report highly stabilized Co-free LiNiMnO with uniformly dispersed LiMnO-like domains and a protective rock-salt structure shell by reducing the oxygen partial pressure during high-temperature calcination. Experimental characterizations and DFT calculations reveal that the uniformly dispersed and small-sized LiMnO-like domains suppress the peroxidation of lattice oxygen, enabling highly reversible oxygen redox and excellent structural stability. Moreover, the induced rock-salt structure shell significantly restrains lattice oxygen release, TM dissolution, and interfacial side reactions, thereby improving the interfacial stability and facilitating Li diffusion. Consequently, the obtained LiNiMnO which was calcinated under an oxygen partial pressure of 0.1% (LNMO-0.1) delivers a high reversible capacity of 276.5 mAh g at 0.1 C with superior cycling performance (a capacity retention rate of 85.4% after 300 cycles with a small voltage fading rate of 0.76 mV cycle) and excellent thermal stability. This work links the synthesis conditions with the domain structure and electrochemical performance of Li-rich cathode materials, providing some insights for designing high-performance Li-rich cathodes.
严重的容量/电压衰减仍然是富锂层状氧化物商业应用中的重大障碍，这源于类LiMnO域的聚集和不稳定的表面结构。在此，我们报道了通过在高温煅烧过程中降低氧分压，制备出具有均匀分散的类LiMnO域和保护性岩盐结构壳层的高度稳定的无钴LiNiMnO。实验表征和DFT计算表明，均匀分散且尺寸较小的类LiMnO域抑制了晶格氧的过氧化，实现了高度可逆的氧氧化还原和优异的结构稳定性。此外，诱导形成的岩盐结构壳层显著抑制了晶格氧释放、过渡金属溶解和界面副反应，从而提高了界面稳定性并促进了锂扩散。因此，在0.1%氧分压下煅烧得到的LiNiMnO（LNMO-0.1）在0.1 C下具有276.5 mAh g的高可逆容量，具有优异的循环性能（300次循环后容量保持率为85.4%，电压衰减率小，为0.76 mV/循环）和出色的热稳定性。这项工作将合成条件与富锂正极材料的域结构和电化学性能联系起来，为设计高性能富锂正极提供了一些见解。
