球形LiMn1.5Ni0.5O4材料的嵌脱动力学

为明晰Li Mn1.5Ni0.5O4正极材料的动力学性能,采用水热辅助共沉淀法合成了尖晶石Li Mn1.5Ni0.5O4正极材料,并采用扫描电镜(SEM)、X射线粉末衍射(XRD)和电化学阻抗(EIS)研究了材料的结构和锂离子嵌脱动力学.实验结果表明:共沉淀法制备的Li Ni0.5Mn1.5O4材料颗粒呈均匀球形,且平均粒径较小,粒度分布较窄.在循环过程中,Li Ni0.5Mn1.5O4的电荷转移电阻增大,锂离子扩散系数减小,进而电子电导率和离子电导率下降.温度升高后,Li Ni0.5Mn1.5O4材料的溶液电阻变化不大,但是电荷转移电阻逐渐增大,锂离子扩散系数逐渐减小;此外,随着温度的升高,Li Ni0.5Mn1.5O4材料的溶解速度加快,从而导致SEI膜的厚度增大.Li Ni0.5Mn1.5O4材料的嵌脱锂动力学与温度和循环次数有密切关系.

Insertion-extraction kinetic of spherical LiMn1.5Ni0.5O4 material

To figure out kinetic performance of LiMn_1.5Ni_0.5O₄ positive-electrode material, spinel LiMn_1.5Ni_0.5O₄ positive-electrode materials were prepared by a hydrothermal-assisted coprecipitation method. The structure and lithium ion insertion-extraction kinetic of the material were investigated by X-ray diffractometry (XRD), scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). The results showed that LiMn_1.5Ni_0.5O₄ material powders prepared by coprecipitation method had a spherical morphology, a small particle size and narrow particle size distribution. During cycling of LiNi_0.5Mn_1.5O₄, the transfer resistance increased the diffusion coefficient of lithium-ion decreased, and then the electronic conductivity and ionic conductivity reduced. After the temperature rose, the solution resistance for LiNi_0.5Mn_1.5O₄ material changed a little, but the transfer resistance gradually increased and the diffusion coefficient of lithium-ion gradually decreased. In addition, the dissolution rate of LiNi_0.5Mn_1.5O₄ material was accelerated, and the thickness of solid electrolyte interphase (SEI) layer extended. The insertion-extraction kinetic of LiMn_1.5Ni_0.5O₄ material had a close relationship with temperature and cycle times.