上海科技大学知识管理系统

Lithium- and manganese-rich (LMR) oxides cathode materials, due to their anomalous capacity, are now among the most attractive candidates for next-generation energy storage materials. However, the severe Mn dissolution that occurs during long-term cycling, leading to capacity loss, inhibits their application prospects. Here, nano AlPO4 coated Li1.2Ni0.13Co0.13Mn0.54O2 (LMR@APO) with significantly enhanced electrochemical performance was successfully synthesized to mitigate the Mn dissolution and suppress local structural distortion at high voltage, using a simple and effective sol-gel method. Due to the complex evolution of the structure and oxidation state of LMR materials during electrochemical cycling, which is difficult to observe and analyze through traditional single characterization methods, therefore we combine various synchrotron-based characterization techniques to conduct a detailed analysis of the electronic and coordination structures of the cathode material from the surface to the bulk. Synchrotron-based hard and soft X-ray spectroscopy were integrated to investigate the differences of O and Mn evolution between surfaces and bulk of cathode. Meanwhile, advanced synchrotron-based transmission X-ray microscopy combined with X-ray near-edge absorption spectrum (TXM-XANES) technology was utilized for the visualization of the two-dimensional nanometer-scale reactivity of LMR cathode. The AlPO4 coating layer can stabilize surface structure of LMR material, effectively alleviating the irreversible oxygen release on the surface and prevents the dissolution of Mn2+ at the interface caused by side reactions after long-time cycle. Therefore, the spatial reaction uniformity of Mn is enhanced by AlPO4 coating layer and rapid capacity decay caused by Mn deactivation is prevented. The AlPO4 coating method provides an available and facile modifying strategy for high performance LMR materials.