基于不同共溶剂体系对于高电压正极材料LiCoPO4的形貌控制

水分别与乙醇、乙二醇、二乙二醇混合为共溶剂, 通过溶剂热法制备高电压锂离子电池正极材料LiCoPO₄, 研究不同醇类溶剂对于样品的微观形貌和颗粒尺寸的影响。借助X射线衍射、扫描电子显微镜和比表面积测试对样品的成分、晶型、微观形貌和颗粒尺寸进行分析。研究表明, 制备得到的LiCoPO₄颗粒平均尺寸大小与醇类溶剂对于前驱体的溶解度差异相一致, 而与溶剂粘度没有明显联系。通过乙二醇/水制备得到的LiCoPO₄颗粒呈六边形片状, 平均尺寸最小, 而通过乙醇/水和二乙二醇/水制备得到的LiCoPO₄颗粒呈菱形片状形态。此外, 前者结晶度较高且循环性能较好, 0.05C下首圈放电容量为130 mAh/g, 20圈后容量保留率为88%。

Morphology Controlling of the High-voltage Cathode Materials with Different Co-solvents

Cathode material LiCoPO₄ was synthesized by solvothermal method with a variety of water/alcohol solvent mixtures, including ethanol (ET), ethylene glycol (EG), and diethylene glycol (DEG). Focus of this work was set on the effect of the different alcohol solvent on morphology and particle size of material. Composition, crystal structure, morphology and particle size of the as-prepared samples were characterized by X-ray-diffraction, scanning electron microscopy and specific surface area test. The results show that relationship of the average particle size of the LiCoPO₄ samples synthesized with different alcohols solvents is in agreement with solubility of solvent for the precursor, but is inconsistent with the viscosity of solvent. Furthermore, LiCoPO₄ sample synthesized with EG/H₂O possesses the smallest particle size, great crystallinity and excellent cycle performance. Its initial discharge specific capacities reaches to 130 mAh/g at 0.05C, and it shows a capacity retention of the initial value of 88% in 20th cycle. A variety of shapes are obtained from various co-solvents: hexagonal platelets for LiCoPO₄ obtained from EG, whereas, square platelets for LiCoPO₄ from ET/H₂O and DEG/H₂O.