Porous LiMn₂O₄ Microspheres With Different Pore Size: Preparation and Application as Cathode Materials for Lithium Ion Batteries

Three types of LiMn₂O₄ (LMO) microspheres with different pore size are prepared by a facile method, using porous MnCO₃–MnO₂ and Mn₂O₃ microspheres as the self-supporting template, for lithium ion batteries (LIBs) cathode material. Briefly, Mn₂O₃ and MnO₂ microspheres are heated in air at 600 °C for 10 h to synthesize porous Mn₂O₃ spheres. Then the mixture of as-prepared spherical Mn₂O₃ and LiNO₃ is calcined to obtain the LMOs. The morphology and structure of LMOs are characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and nitrogen adsorption/desorption analyses. The result shows that the maximum pore diameters of LMOs are 17 nm, 19 nm, and 11 nm, respectively. All LMOs microspheres are composed of similar sized nanoparticles; however, the surface of these microspheres is strewed with dense tinier pores or sparse larger pores. Generally, the nanoparticles will reduce the path of Li⁺ ion diffusion and increases the reaction sites for lithium insertion/extraction. Moreover, the pores can provide buffer spaces for the volume changes during charge–discharge process. The electrochemical performances of LMOs are investigated and LMO2 exhibits extremely good electrochemical behavior, especially the rate capability. The as-prepared LMO2 delivers a discharge capacity of 124.3 mAh g⁻¹ at 0.5 C, retaining 79.6 mAh g⁻¹ even at 5 C. The LMO2 sample also shows good capacity retention of 96.9% after 100 cycles at 0.5 C.