采用高温固相法制备LiNi_（1/3）Co_（1/3）Mn_（1/3）O_2正极材料,并用三氧化二铝（Al_2O_3）进行表面包覆改性。通过XRD、SEM对材料晶体结构、形貌进行分析,用恒流充放电和循环伏安等对材料进行测试。Al_2O_3包覆的LiNi_（1/3）Co_（1/3）Mn_（1/3）O_2正极材料具有典型的空间群,为R-3m的六方层状α-Na Fe O2结构。以0.2 C在2.5-4.3 V循环,Al_2O_3包覆量为1%的材料电化学性能最好,首次放电比容量可达145.7 m Ah/g,第30次循环的容量保持率为94.0%,比未包覆Al_2O_3材料在相同条件下的放电比容量提高了6.3%。
The well-distribution spindle Li Fe PO4(LFP)nanoparticles as cathode of lithium secondary batteries were synthesized by a solvothermal reaction route at low temperature(180 °C) in which the ascorbic acid was used as reducing agent. In order to guarantee that the p H values of thermal systems were not affected too much and the reducibility of the system was enhanced at the same time,glucose was chosen as an auxiliary reductant in this reaction. The obtained powders were characterized by X-ray diffraction(XRD), scanning electron microscopy(SEM),and laser particle analyzer. The results show that the carbon-coated uniform spindle olivine Li Fe PO4/C-glucose particles(glucose as auxiliary reductant, LFP/C-G) are prepared with the size 500–600 nm and without any impurity phases. Their electrochemical properties were evaluated by electrochemical impedance spectroscopy,cyclic voltammetry, and galvanostatic charge/discharge tests. LFP/C-G has a higher conductivity and better reversible capability than carbon-coated LFP(LFP/C). The highest discharge capacity of LFP/C-G is 161.3 mAh·g-1at0.1C and 108.6 mAh·g-1at 5.0C, respectively. The results imply that the neat crystal nanostructure of LFP/C-G has excellent capacity retention and cycling stability.The adding of glucose is the key factor for the welldistribution and neat crystal structure of nanoparticles,thus the electrochemical performances of materials are improved.
