Porous LiMn2O4 Nano-Microspheres as Durable High Power Cathode Materials for Lithium Ion Batteries

Resumo

Porous LiMn₂O₄ spheres was easily fabricated with MnCO₃ spheres and MnO₂ as precursors and characterized in terms of structure and performance as the cathode of a lithium ion battery. The presence of pores with the average size of about 50 nm throughout the whole LiMn₂O₄ microspheres was confirmed by scanning electron microscope (SEM) and N₂ adsorption-desorption measurements. The electrochemical tests show that the synthesized product has smaller electrochemical polarization, faster Li-ion intercalation kinetics and higher electrochemical stability. It exhibits excellent rate capability and cyclic stability: delivering a reversible discharge capacity of 71 mA h g⁻¹ at a 5 C rate and yielding a capacity retention of over 92% at a rate of 0.5 C after 100 cycles. The superior performance of the synthesized product is attributed to its special structure: porous secondary spheres particles consisting of primary single-crystalline nanoparticles. The nanoparticle reduces the path of Li-ion diffusion and increases the reaction sites for lithium insertion/extraction, the pores provide room to buffer the volume changes during charge-discharge and the single crystalline nanoparticle endows the spinel with the best stability. Taking the excellent electrochemical performance and facile synthesis into consideration, the presented porous LiMn₂O₄ spheres could be a competitive candidate cathode material for high-performance lithium-ion batteries.