Researches On The Preparation And Modification Of Lithium-ion Battery Cathode Material LiNi_1/3Co_1/3Mn_1/3O₂

On the basis of systematically reviewing the developments of the lithium ion battery cathode materials in this paper, a new type of cathode material LiNi_1/3Co_1/3Mn_1/3O₂ and its doping was synthesized with co-precipitation method and hydrothermal method. The specific work was shown as follows:(1) In this paper, solid materials NiSO₄·6H₂O, CoSO₄·7H₂O, MnSO₄·H₂O were prepared 0.3M solution in accordance with the 1:1:1 (molar ratio), Ni₍1/3_Co_1/3Mn_1/3(OH)₂ was synthesized with 0.3M of NaOH solution by coprecipitation. And then precursor and LiOH·H₂O were treated in 480℃, LiNi_1/3Co_1/3Mn_1/3O₂ was synthesized by the second high-temperature.Through X-ray diffraction (XRD), scanning electron microscopy (SEM), electrochemical testing of samples was characterized. The optimum process of synthesizing LiNi_1/3Co_1/3Mn_1/3O₂ was listed as follows: the molar ratio of n(Li):n(Ni+Co+Mn) was 1.05:1, then the mixture was calcined in 900℃for 10 hours. In the range of 2.8-4.3V with 18mA/g current density for charging and discharging, the first discharge capacity of 159.6mAh/g, the discharging capacity retained 151mAh/g after 30 cycles.(2) In this paper, we tried to use a certain concentration of the LiOH solution mixed with precursor with hydrothermal method of synthesis of LiNi_1/3Co_1/3Mn_1/3O₂ by improving synthetic method. The concentration of alkali and secondary high temperature were contact with the sample of structure, morphology and electrochemical properties. The result was shown: better sample was synthesized with 3.5M LiOH solution; and hydrothermal sample was treated in 900℃high temperature, its charge-discharge was 136.9/122.3mAh/g, electrochemical performance had been greatly up graded.(3) In addition, in order to improve the electrochemical properties of the sample, we doped Mg and Ti in the sample. Electrochemical tests was shown: LiNi_1/3Co_1/3Mn_1/4 Mg_1/12O₂ sample was tested in range of 2.8-4.3V with 18mA/g current density for charging and discharging, after 50 cycles the discharge capacity retention rate was still 86.7%, the sample had a good cycling performance.