Chen Cheng, Han Zhen, Chen Shuangqiang, Qi Shuo, Lan Xinyue, Zhang Chunchen, Chen Lin, Wang Peng, Wei Weifeng
State Key Laboratory of Powder Metallurgy , Central South University , Changsha , Hunan 410083 , People's Republic of China.
National Laboratory of Solid State Microstructures, College of Engineering and Applied Sciences, and Collaborative Innovation Center of Advanced Microstructures , Nanjing University , Nanjing , Jiangsu 210093 , People's Republic of China.
ACS Appl Mater Interfaces. 2020 Feb 12;12(6):7144-7152. doi: 10.1021/acsami.9b19260. Epub 2020 Jan 28.
Sodium layered oxides are considered to be cathode candidates with the most potential for large-scale energy storage because of their high reversible capacity and wide availability of sodium resources. A significant hurdle to wide application of these layered oxides lies in simultaneously satisfying high-energy density and long cycle life because of the intrinsic problems associated with their structural irreversibility. Herein, a O3/O'3-P2 core-shell composite that integrates a high specific capacity from O-type Ni-based core and good structural stability from P2-type Mn-rich shell is presented. Multiscale electron microscopy and affiliated spectroscopy analyses reveal that, in addition to the microscale O3/O'3-P2 core-shell structure, a nanoscale coherent P2/O3 intergrown structure can also be identified in the composite. Such well-tailored structures not only constrain the structural damages (microscale cracks) induced by repeated volumetric changes upon desodiation and resodiation but also facilitate fast Na ions diffusion through the exterior P2-type layered structure. This work may provide new clues into the design of high-performance cathode materials for sodium-ion batteries.
钠层状氧化物因其高可逆容量和钠资源的广泛可得性，被认为是最具大规模储能潜力的正极材料候选者。由于其结构不可逆性所带来的固有问题，这些层状氧化物广泛应用的一个重大障碍在于要同时满足高能量密度和长循环寿命。在此，我们展示了一种O3/O'3-P2核壳复合材料，它整合了来自O型镍基核的高比容量和来自P2型富锰壳的良好结构稳定性。多尺度电子显微镜及相关光谱分析表明，除了微观尺度的O3/O'3-P2核壳结构外，在该复合材料中还能识别出纳米尺度的相干P2/O3共生结构。这种精心设计的结构不仅能抑制脱钠和再嵌钠过程中反复体积变化所导致的结构损伤（微观裂纹），还能促进钠离子通过外部P2型层状结构的快速扩散。这项工作可能为钠离子电池高性能正极材料的设计提供新的线索。
