Abstract
Al2O3-coated spinel LiMn2O4 cathode materials, presintered LiMn2O4 (P-LMO), and calcined LiMn2O4 (C-LMO) were synthesized by chemical deposition and thermal treating method using presintered and calcined LiMn2O4 as precursors. The crystal structure, morphology, the thickness of the coating layer, and particle size of prepared samples were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), and Malvern instruments. The average particle size of P-LMO with like-spheres (0.3 μm) is much smaller than that of C-LMO (0.5 μm). The Al2O3 layer of P-LMO can effectively reduce the charge transfer resistance and inhibit the Mn dissolution. The electrochemical performance of P-LMO is better than that of C-LMO. It is found that the LiMn2O4 cathode materials have excellent electrochemical cyclability by coated 2 mol% Al2O3 at the surface of presintered material. The initial discharge capacity of the material with 2 mol% Al2O3-coated is 114.0 mAh·g−1 at 0.1C rate and 55 °C, and the capacity retention is 87.3 % at 0.5C rate.
Highlights
Spinel LiMn2O4, owing to its easy preparation, economic, and environmental advantages, is considered to be a promising material for the positive electrode of secondary lithium batteries [1,2,3]
After separating the cathode material power via filtering through filter paper, the dissolved Mn2? in the electrolyte was extracted into water phase using 10 ml HCl (0.1 molÁL-1) acid, and the Mn contents were quantitatively determined by atomic absorption spectroscopy (AAS)
For the same amount of Al2O3 surface-modified spinel LiMn2O4, the (440) diffraction peaks of calcined LiMn2O4 (C-LMO) have a further leftward than those of presintered LiMn2O4 (P-LMO), which indicates that P-LMO has smaller lattice parameter
Summary
Spinel LiMn2O4, owing to its easy preparation, economic, and environmental advantages, is considered to be a promising material for the positive electrode of secondary lithium batteries [1,2,3]. Morphology, surface chemistry, surface species of the cathodes and the interface between cathodes and electrolyte are of great importance to the electrochemical performance of lithium-ion batteries Oxides such as MgO, TiO2, CeO2, ZnO, ZrO2, and Al2O3 [13,14,15,16,17], were studied to suppress capacity fading, indicating that the effectiveness of surface modification on spinel LiMn2O4. Al2O3 was improved to be one of the surface coating materials for lithium-ion batteries because of its various advantages such as low cost, excellent chemical stability, and high electronic conductivity possessed by amphoteric oxides [18]. The layer can effectively isolate the LiMn2O4 and electrolyte, reduce the contact area and diffusion of Mn in the electrolyte, and further improve the electrochemical performance of spinel LiMn2O4 cathode materials. In this work, presintered LiMn2O4(P-LMO) and calcined LiMn2O4(C-LMO) coated with different amounts of Al2O3 were prepared, and the effects of Al2O3 coating on the electrochemical cycling performances of LiMn2O4 were systematically studied
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