Li[Mn_(1/3-x/3)Ni_(1/3-x/3)Co_(1/3-x/3)Cr_x]O_2系列正极材料的合成及性能研究

Synthesis and Electrochemical Properties of Li[Mn_(1/3-x/3)Ni_(1/3-x/3)Co_(1/3-x/3)Cr_x]O_2 as Cathode Materials for Lithium-ion Secondary Batteries

采用改进的固相法一步反应成功制备了掺杂Cr的系列正极材料L i[Mn1/3-x/3N i1/3-x/3Co1/3-x/3Crx]O2(x=0,0.015,0.025,0.050,0.100),用XRD,SEM和充放电测试等考察了它们的物理性质和电化学性能。结果表明,所合成的正极材料具有O2层状结构,规则的形貌和均匀的粒径尺寸分布,其嵌锂脱锂均为一步机理。加入适量的Cr可提高该系列正极材料的电化学性能和循环稳定性。x=0.015时的正极材料电化学性能最佳,室温下其首次放电比容量为138.60 mAh.g-1,并且循环性能最好。

The layered Li[Mn 1/3-x/3 Ni 1/3-x/3 Co 1/3-x/3 Crx]O2（x =0, 0. 015, 0. 025, 0. 050, 0. 100） materials were prepared by means of an improved solid-state reaction, and their physical and electro- chemical properties were investigated by XRD, SEM and electrochemical testing techniques. When x = 0 and 0. 015, the mean size of samples is about 800 nm and the samples have uniform morphology and normal grain-size distribution. The materials showed only one plateau between 2.5 V -4.5 V. A significant structure transformation to the spinel-type phase was not found in the charge-discharge cycling. The layered structure was stabilized and the discharge capacity was also increased by doping appropriate amount of Cr^3＋. The 1.5 mol% chromium-doped active materials exhibited the best cycle performance. It delivered an initial discharge capacity of 138.60 mAh · g^-1 in a cut-off range between 2.5 V and 4.5 V at room temperature, but the capacity and retention were found to decrease when the concentration of Cr^3＋ was over 1.5 mol%.