| With the in-depth research of lithium ion battery cathode material, Ni-rich anode materials LiNi1-x-yCoxMnyO2 and LiNi1-x-yCoxAlyO2 are considered to be the most potential power battery electrode materials which are applied in hybrid electric vehicles （HEV） and electric vehicles （BEV）. Compared to the traditional lithium-ion battery cathode materials like LiCoO2, LiMn2O4 and LiFePO4, LiNi1-x-yCoxMnyO2 has high capacity, high discharge voltage platform and low cost; LiNi1-x-yCoxAlyO2 has high power and superior performance rate. But in the actual application, the poor cycle performance and lower initial coulomb efficiency is adverse to its application.This paper first discusses LiNi0.8Co0.1Mn0.1O2 precursor material synthesized via co-precipitation. We optimized the preparation technology from the complexing agent concentration, reaction temperature and pH these three aspects to. A novel method, named one-step electrolysis, for synthesizing Ni0.8Co0.1Mn0.1（OH）2 precursor material was proposed, and we studied the process parameters systematically. Then we preliminary discussed the process conditions of LiNi0.8Co0.15Al0.05O2 cathode material precursor from the Al<sup>3+feeding mode, complexing concentration and pH. By means of SEM, XRD, the electrochemical workstation, charge and discharge measurement, we studied the morphology, lattice parameter and electrochemical properties of the material. The results are as follows:（1）In the process of synthesizing Ni0.8Co0.1Mn0.1（OH）2 precursor material, the structure and properties of materials are closely related to the precursor material synthesis process conditions. The test results show that the optimum process conditions of Ni0.8Co0.1Mn0.1（OH）2 precursor are metal ions and complexing agent concentration ratio of 1:2, pH=11.0, t=57 ℃. Under the condition of the optimal synthesis of precursor material present a kind of spherical morphology, a good layered a-NaFeO2 structure, c/a=4.9476, I003/I104=1.1464. At the discharge current of 0.1C, the specific discharge capacity reaches 172.3 mAh·g-1（2）For synthesizing Ni0.8Co0.1Mn0.1（OH）2 precursor material via one-step electrolysis under single cathode, the optimum process conditions are t=50 ℃, c（NH3）=6 mol·L-1, pH=12.0. Under these conditions, the precursor particle is evenly distuibuted, and the particle size is about 5 μm, which present the best electrochemical performance. At the discharge current of 0.1 C, the specific discharge capacity reaches 166.5 mAh-g"1, after 30 cycles, about 80.3% of the capacity is maintained. At the discharge current of 1C, the specific discharge capacity also has 103 mAh·g-1（3）For synthesizing Ni0.8Co0.1Mn0.1（OH）2 precursor material via one-step electrolysis under triple cathode and the optimum process conditions which are t=50 ℃, c（NH3）=6 mol·L-1, pH=12.0. At the discharge current of 0.1C, after 30 cycles, about 87.1% of the capacity is maintained synthesized by adding the auxiliary electrolyte of KNO3. The material synthesized by adding the auxiliary electrolyte of Co（NO3）2 has high discharge voltage platform（3.85V）. At the discharge current of 0.1C, after 30 cycles, about 89.2% of the capacity is maintained synthesized by adding the auxiliary electrolyte of NiCl2. Other conditions unchanged, when the pH=11.5, and adding a small amount of NiCl2 and Co（NO3）2,the lattice parameters of synthetic material is c/a=4.9251,I003/I104=1.4349. The material has a typical layered a-NaFeO2 structure, and compared with the materials synthesized via co-precipitation, it has a lower degree of cation mixing, which present a good electrochemical performance. At the discharge current of 0.1 C, the specific discharge capacity reaches 152.4 mAh-g"1, after 30 cycles, about 89.6% of the capacity is maintained. At the discharge current of 1C, the specific discharge capacity also has 116.8 mAh-g"1（4）In preparation of LiNi0.8Co0.15Al0.05O2 cathode material via hydroxide co-precipitation, the Al3+ and NH3 directly react to Al（OH）3, so we firstly optimize the process route of feeding mode of Al3+. The results show that:Dissolving the Al3+ in a certain concentration of NaOH and NH3 H2O, make it involved in the reaction in the form of AlO2-. Finally, the optimum process conditions of precursor is c（NH3）=1.5 mol·L-1, pH=11.5. After high temperature calcination, the cathode material shows good crystal structure which is c/a=4.9626, I003/I104=1.5178. At the discharge current of 0.1C, the specific discharge capacity reaches 175.0 mAh-g"1, after 30 cycles, about 86.7% of the capacity is maintained. At the discharge current of 1C, the specific discharge capacity also has 123.7 mAh-g"1 which shows a good electrochemical performance. |
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