磷酸铜表面修饰富锂层状正极材料的制备及电化学性质

Preparation and Electrochemical Properties of Cu3(PO4)2 Modified Li-Rich Layered Cathode Material

用溶胶-凝胶法制备富锂锰基层状正极材料Li1.18Ni0.15Co0.15Mn0.52O2,并对其进行Cu3(PO4)2表面修饰。用X射线衍射、扫描电子显微镜和红外光谱测试样品的表面形貌,并对样品进行恒电流充放电测试及电化学阻抗谱测试。结果表明:Cu3(PO4)2均匀包覆在材料表面,以非晶态存在,修饰后Li+在过渡金属层中的有序排列被破坏;表面修饰后富锂材料的首圈库仑效率由77%提高至94%;表面修饰前后材料的初始放电比容量均为244mA·h/g,100圈循环后经Cu3(PO4)2表面修饰的富锂材料的放电比容量为203mA·h/g,容量保持率为83%;表面修饰后的材料在3.0,2.7V出现了一对氧化还原峰,相对应在充放电曲线出现新平台;Cu3(PO4)2修饰后富锂层状正极材料的阻抗明显减小。

Lithium-rich layered cathode material Li1.18Ni0.15Co0.15Mn0.52O2 was synthesized by the sol-gel method,then surface coated using Cu3(PO4)2.The surface morphology of the samples was measured by X-ray diffraction(XRD),scanning electron microscopy(SEM)and infrared spectroscopy,and the samples were tested by constant current charge-discharge and electrochemical impedance spectroscopy.The results show that Cu3(PO4)2 distributes uniformly on the surface of the material.Cu3(PO4)2 exists in amorphous form and the ordered arrangement of Li+in transition metal layer is destroyed after modification.The initial Coulomb efficiency of the material is increased from 77% to 94% after surface modification.The initial discharge capacity of the all materials is244 mA·h/g,the specific discharge capacity of the Cu3(PO4)2 modified material is 203 mA·h/g after 100 cycles,and the capacity retention is 83%.A pair of redox peaks appear at 3.0,2.7 Vwhile the charge/discharge curve appear a new platform after surface modification.The impedance of surface modified lithium-rich layered cathode material is obviously reduced.