层状LiNi1/3Mn1/3Co1/3O2正极材料的合成

用碳酸盐同沉淀法合成了LiNi_1/3Mn_1/3Co_1/3O₂正极材料,采用XRD(X7-Ray Diffraction)、SEM (Scanning Electron Microscope)、差分计时电位法和充放电循环等对材料的物理化学性质及电化学性能进行了测试分析。XRD分析表明在合成温度为800℃或更高时,所合成的产物均为α-NaFeO₂型的层状结构,SEM分析表明在合成温 度为800或850℃时,产物为微小晶粒团聚成的球形颗粒,合成温度为900℃以上时,产物颗粒发生破碎,形状不规则。950℃合成的LiNi_1/3Mn_1/3Co_1/3O₂材料在2.5～4.4V电位区间内, 首次放电容量为162 mAh·g^-1, 并具有良好的循环性能。随着充放电电压的升高,首次不可逆放电容量增大, 循环稳定性减弱。在低温(800, 850℃)下合成的LiNi_1/3Mn_1/3Co_1/3O₂材料与高温下(900, 950℃)得到的材料性能有很大差别,这是由于在高温和低温下得到材料的结构差别所造成的。

Synthesis and Electrochemical Properties of Layered LiNi1/3Mn1/3Co1/3O2 Cathode Material

LiNi_1/3Mn_1/3Co_1/3O₂ cathode material was synthesized by carbonate simultaneous precipitation method. The material was characterized by XRD (X-Ray Diffraction), SEM (Scanning Electron Microscope), differential chronopotentiometry and galvanostatic cycling. XRD results show that all the products synthesized above 800℃ have typical α-NaFeO₂ layered structure. SEM results show that the powders synthesized at 800℃ have a spherical structure composed of small aggregates, whereas the products synthesized above 900℃ have an irregular structure and are fractured. In the voltage range of 2.5~4.4V, the LiNi_1/3Mn_1/3Co_1/3O₂ cathode material synthesized at 950℃ has an initial specific discharge capacity of 162mAh·g^-1 with effective cycling performance. With the increase of the charge-discharge voltage, electrochemical stability was reduced and irreversible capacity loss occurred during the first cycle. The samples synthesized at lower temperatures (800, 850℃) exhibited higher specific capacities and slower capacity fading upon cycling than the samples synthesized at higher temperatures (900, 950℃), which was due to the structural difference.