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

Abstract

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.