锂离子电池正极梯度材料的制备及电性能研究

Electrochemistry synthesis and characterization of cathode gradient material for lithium-ion batteries

采用金属离子混合硫酸盐溶液分次共沉淀法制备前躯体,混锂后通过高温固相反应得到具有镍、钴和锰浓度梯度的层状LiNi0.56Co0.22Mn0.22O2锂离子电池正极材料。通过x射线衍射(XRD)、扫描电子显微镜(SEM)及恒电流充放电测试对合成的材料进行了表征。结果表明,750～900℃焙烧15h下合成的产物均具有典型的α-NaFeO2型层状结构特征,晶型结构完整,粒度均匀。800℃合成的正极材料具有较好的电化学性能。在充放电倍率0.4C、2.75-4.2V电压范围内,材料的首次充放电比容量分别为170.0mAh/g和131.8mAh/g,放电效率为77.5%;第51次循环的充放电比容量分别为131.3mAh/g和130.5mAh/g,放电效率为99.4%,容量保持率达到99.0%。

Layered gradient cathode material of lithium ion battery,LiNi0.56Co0.22Mn0.22O2,which had concentration grads of Ni,Co,Mn,was synthesized by mixing precursor with excess LiOH·H2O followed by heat treatment.The precursor was prepared via multiple co-precipitation of sulphate solutions with different compositions of Ni,Co,Mn.The cathode material was characterized using X-ray diffraction（XRD）,scanning electron microscope（SEM）,galvanostatic chargedischarge test.The results showed that all the samples prepared at 750~900℃ for 15 hours were layered materials with typical α-NaFeO2 structure.The crystal structure was orbicular and the particle size was well-proportioned.The sample prepared at 800℃delivered the higher discharge capacity and better cycling performance.At the current density of 5C and in the voltage range 2.75~4.2V,this powder had the initial charge capacity of 170.0mAh/g and discharge capacity of 131.8mAh/g,the initial discharge efficiency was 77.5%.After 51 cycles,it still had the charge capacity of 131.3mAh/g and discharge capacity of 130.5mAh/g,and the capacity retention was 99.0%.