Abstract
The commercial application of LiMnxFe1-xPO4 materials has always been a great challenge because of their unsatisfactory structure stability during cycling and the safety issue. Herein, single-particle (SP) electrodes, where aggregated LiMnxFe1-xPO4 is dispersed into SPs so they can distribute homogeneously in the carbon-nanotube networks, have been prepared and characterized to probe the degradation mechanism of LiMnxFe1-xPO4 for the first time. Compared with a conventionally prepared cathode, the SP LiMnxFe1-xPO4 cathode shows prominent capacity-fading with cycle numbers, which can be attributed to the formation of the MnF2 nanocrystals on the surface of LiMnxFe1-xPO4 because of the reaction between F- and dissolved Mn2+ at the interface between the electrolyte and LiMnxFe1-xPO4 . The different electrochemical behaviors can be ascribed to LiMnxFe1-xPO4 SPs surface reconstruction with MnF2 nucleation and growth by the interfacial reactions. In addition, by applying a thin protecting layer of Al2O3 on the surface of LiMnxFe1-xPO4 , the interfacial side reactions can be suppressed. This work demonstrates that the SP method is a powerful tool to extract the information of interfacial reactions, which sometimes appear to be negligible compared with bulk reactions.