Synthesis And Properties Of Lithium-rich Manganese Based Material Li[Li_0.2Mn_0.54Ni_0.13Co_0.13]O₂as Cathode Material Of Lithium-ion Battery

Since its high specific capacity, high cost efficient and high safe stabilityperformance, lithium-rich manganese-based cathode materials xLi2MnO3(1-x)LiMO2(M=Ni, Co, Mn…) have drawn a great deal of attention, and this materialexpected to be a new generation material used as lithium ion battery to replaceLiCoO2. However, due to its low first cycle coulomb efficiency, phase and structurechanges during the cycles, and the poor rate performance, the development of thiskind of materials have been limited seriously.In this paper, Li[Li0.2Mn0.54Ni0.13Co0.13]O2was studied and the powders weresynthesized by sol-gel method. In order to modified the properties, theLa2O3/Li[Li0.2Mn0.54Ni0.13Co0.13]O2and the TiO2/Li[Li0.2Mn0.54Ni0.13Co0.13]O2composite powders were synthesized respectively. The sample’s structure andmorphology were studied by X–ray diffraction (XRD), scanning electron microscopy(SEM) and transmission electron microscope (TEM), later on the synthesizedmaterials were assembled into button cell. The electrochemical properties of thesamples were investigated by charge-discharge battery test system andelectrochemical workstation. The results are as follows:The Li[Li0.2Mn0.54Ni0.13Co0.13]O2powders were synthesized by sol-gel method,in this process, the transition metal acetate and lithium acetate were used as the rawmaterials, acrylic acid was used as coupling agent. The effect of different secondarysintering temperature, sintering time and dopping content of Li to electrochemicalproperties, structure, and morphology of lithium-rich manganese-based cathodematerials were studied. The optimum synthesis conditions were like this: annealed at850oC for15hours and the dopping content should be3%. The electrochemicalproperties test results of the sample synthesized on the optimum conditions at0.1C,2~4.8V were as follows: the first discharge specific capacity was240.3mAhg-1, thecoulomb efficiency was67%, the reversible capacity was148mAhg–1after50cycles,the discharge capacity was130mAh/g under1C current density.Based on the modified process, the La2O3/Li[Li0.2Mn0.54Ni0.13Co0.13]O2and theTiO2/Li[Li0.2Mn0.54Ni0.13Co0.13]O2composite powders were synthesized respectively.Because the proportion is too little, the X–ray diffraction (XRD) results showed thatthe diffraction peak of La2O3and TiO2were not be found in the modified lithium-richmaterial, the scanning electron microscopy (SEM) and transmission electron microscope (TEM) results showed that the surface uniformity of the composite andcoated samples were not uniform. The electrochemical test results showed that thefirst discharge capacity of La2O3/Li[Li0.2Mn0.54Ni0.13Co0.13]O2composite under0.1Cwas193.779mAh/g, the coulomb efficiency was57%, the reversible specific capacitywas182.1mAh/g after30cycles, the discharge specific capacity were156.5mAh/gand125.8mAh/g under1C and2C current density respectively. However, the firstspecific capacity of that TiO2/Li[Li0.2Mn0.54Ni0.13Co0.13]O2was255.7mAh/g, thecoulomb efficiency was70%, the reversible capacity was231.1mAh/g after20cyclesand the discharge specific capacity were182.3mAh/g and104.7mAh/g under1Cand2C current density respectively. The cycling stability of the composite sampleswere improved, however, the rate capability still need to be improved. The first cyclecoulomb efficiency of the La2O3composite sample also need to be improved.