烧结温度对0.5Li_2MnO_3·0.5Li[Mn_(1/3)Ni_(1/3)Co_(1/3)]O_2结构、形貌及电化学性能的影响

Effect of Sintering Temperature on the Structure,Morphology and Electrochemical Properties of 0.5Li_2MnO_3·0.5Li[Mn_(1/3)Ni_(1/3)Co_(1/3)]O_2

以乙酸锂、乙酸锰、乙酸镍和乙酸钴为原料,去离子水为溶剂,乙醇酸作为配位剂,采用溶胶凝胶法分别在800℃、850℃、900℃和950℃烧结制备了0.5Li2MnO3· 0.5Li[Mn1/3Ni1/3Co1/3]O2富锂锰基固溶体粉末.采用X射线衍射（XRD）和扫描电子显微镜（SEM）表征了不同烧结温度制备的粉末的结构和形貌;并将制备的粉末材料经过涂布,冲压等工艺,在真空手套箱中组装成扣式电池.采用电池充放电测试系统以及阻抗分析仪测试了样品的循环稳定性和电化学性能.实验结果表明：在850℃烧结的粉末样品具有最佳的电化学性能.在2～4.8 V电压范围内,以0.1C大小的电流对850℃烧结的样品进行充放电测试,其首次放电容量可达240.3 mAhg^-1,首次库仑效率约为70％,50次循环后其可逆容量为148 mAhg^-1.该样品在0.2C、0.5C和1C的不同倍率下测试,得到相对应的放电容量分别为181.25 mAhg^-1、142mAhg^-1和130.7 mAg^-1.

Lithium acetate,manganese acetate,nickel and cobalt acetate were used as raw materials,with deionized water as solvent,and glycollic acid as chelating agents,0.5Li2 MnO3 · 0.5 Li[Mn1/3 Ni1/3 Co1/3]O2 powders were synthesized at 800 ℃,850 ℃,900 ℃ and 950 ℃ by sol-gel method,respectively,which is a typical Li-rich solid solution cathode material.The structure and morphology of the prepared powders were characterized by X-ray diffraction （XRD） and scanning electron microscope （SEM）.After the powders were processed with coating and punching,then were assembled into button cell in a glove box.The electrochemical properties of different samples were investigated by battery test system.The results demonstrated that the powder sintered at 850 ℃ exhibits the best electrochemical performance,the first discharge capacity reaching 240.3 mAhg^-1,while coulomb efficiency is about 70% and reversible capacity retaining 148 mAhg^-1 after 50 cycles at 0.1 C in the voltage range of 2.0～4.8 V.The corresponding discharge capacities of the different samples at 0.2 C,0.5 C,1 C are 181.25 mAhg^-1,142 mAhg^-1 and 130.7 mAhg^-1,respectively.