Effect of vacuum assistance on the morphology and electrochemical properties of LiMn0.2Fe0.8PO4/C composites prepared by solid-phase method

The vacuum-assisted solid-phase method is used to synthesize the LiMn0.2Fe0.8PO4/C composite that was then characterized by XRD, XPS, Raman, FESEM, EDS, HRTEM and galvanostatic charge-discharge testing. X-ray diffraction (XRD) patterns show that the composite was found in the olivine structure crystal phase. Unlike the typical spherical morphology, the LiMn0.2Fe0.8PO4/C prepared under vacuum (LiMn0.2Fe0.8PO4/C-V) consisted of unique layered stacked antler-like particles with many dispersed connected holes as observed from the FESEM images. The electrochemical performance tests show that LiMn0.2Fe0.8PO4/C-V has a higher initial discharge specific capacity and superior specific discharge capacity at various rates and cycles. At the same time, cyclic voltammetry tests showed that this material displays a higher degree of reversibility and lower polarization during the redox reaction. The improvement in electrochemical performance characteristics is attributed to the unique morphology that provides connected holes for the conduction of ions and electrons. This work shows that the vacuum-assisted solid-phase method is an effective approach for improving the electrochemical performance of olivine-type lithium phosphate battery cathode materials.