The effect of lithium sources and thermal treatment on the structure and electrochemistry of Li 1.2 Ti 0.4 Mn 0.4 O 2 and Li 1.3 Nb 0.3 Mn 0.4 O 2 cathodes

Li-excess cathode materials with a disordered rock-salt structure (DRX) Li 1.2 Ti 0.4 Mn 0.4 O 2 and Li 1.3 Nb 0.3 Mn 0.4 O 2 were prepared by mechanochemically assisted solid-state synthesis at various synthesis conditions using different lithium sources (Li 2 O and LiOH). As-prepared samples were characterized by X-ray powder diffraction (XRD), thermal analysis in combination with mass spectrometry (DSC/TG/MS), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), electron paramagnetic resonance spectroscopy (EPR), in situ time-resolved synchrotron powder X-ray diffraction (SPXRD) and galvanostatic cycling. The effects of different lithium sources and synthesis temperature on the crystal and local structure and the impact of additional thermal treatment (re-heating) on electrochemical performance of the DRX oxides were investigated. The results obtained show that the optimal synthesis temperature is 950 °C and the use of LiOH as a lithium source leads to the synthesis of the DRX oxides with a fully disordered structure, which is stable when re-heated at a temperature of 600 °C. In addition, re-heating leads to further optimization of the properties of the DRX oxides; this results in a significant improvement of their electrochemical properties. Graphical abstract