Unravelling the Structure and Electrochemical Performance of Li-Cr-Mn-O Cathodes: From Spinel to Layered.

To explore a new series of cathode materials with high electrochemical performance, the spinel-layered (1 - x)[LiCrMnO4 ]· x[Li2 MnO3 ·LiCrO2 ] ( x = 0, 0.25, 0.5, 0.75, and 1) composites are synthesized with the sol-gel method. X-ray diffraction, high-resolution transmission electron microscopy, selected area electron diffraction, and Raman spectra reveal that the structure of the (1 - x)[LiCrMnO4 ]· x[Li2 MnO3 ·LiCrO2 ] cathode materials evolves from spinel to hybrid spinel-layered and layered structures with the increase of the Li concentration. Test results reveal that the structure and electrochemical performance of (1 - x)[LiCrMnO4 ]· x[Li2 MnO3 ·LiCrO2 ] ( x = 0.25, 0.5 and 0.75) composites have the characteristics of both spinel ( x = 0) and Li-rich layered phases ( x = 1). In particular, x = 0.5 and 0.75 electrodes exhibit relatively high capacity retention and rate capability, which is mainly ascribed to the synergistic effect of the spinel and Li-rich layered phases, the 3D Li-ion diffusion channels of the spinel phase, and the low charge-transfer resistance ( Rct ) and Warburg diffusion impedance ( Wo ).