Construction of LiMn2O4 microcubes and spheres via the control of the (104) crystal planes of MnCO3 for high rate Li-ions batteries

摘要

We have studied a synthetic route to control the morphology of MnCO3 precursors. Taking the (104) crystal planes in the structure of MnCO3 as the research point, the hydrothermal method was used to synthesize MnCO3 cubes with highly exposed (104) crystal planes and densely crystallized MnCO3 spheres by changing the water-ethanol reaction system. The MnCO3 cubes and spheres were used as self templates to prepare spinel LiMn2O4 by thermal decomposition and topological crystallization. The formation mechanism of MnCO3 and LiMn2O4 was analyzed using characterization methods such as X-ray diffraction, scanning electron microscopy and high-resolution transmission electron microscopy. Electrochemical tests evidenced that the electrochemical performance of the as-made cubic and spherical LiMn2O4 significantly improved compared with that of pristine LiMn2O4. The results manifested that the LiMn2O4 cubes and spheres have superior discharge capacity, delivering first discharge capacities of 130 and 115.1 mA h g(-1) at 0.5C, and 96.4 and 88.3 mA h g(-1) even at a high rate of 20C, respectively. After calculating the Li+ diffusion coefficients of the samples, the results elicited that the diffusion ability of the Li+ in the cubic and spherical LiMn2O4 was significantly improved.