| Lithium-ion batteries bring the great convenience to society,at the same time,its own defects led people to constant pursuit the lower cost,better performance lithium-ion batteries.Cathode materials play the indispensable part of the Lithium-ion batteries,and the nickel-rich ternary cathode material LiNi0.8Co0.1Mn0.1O2 contains the advantages of LiCoO2,LiNiO2,LiMnO2,LiNi0.8Co0.1Mn0.1O2,it has been considered as the most promising cathode material.But because the LiNi0.8Co0.1Mn0.1O2 material is prone to absorb the water which may depredates material performance.;because of its high Ni content,resulting in the material prone to cationic mixing,In this paper,the synthesis processes of LiNi0.8Co0.1Mn0.1O2 were studied,and the synthesis parameters were optimized.and then LiNi0.8Co0.1Mn0.1O2 was coated by LiAlO2.In recent years,there have been many battery burning events and explosion accidents because of the thermal abuse of batteries.The thermals and electrochemical properties of LiNi0.8Co0.1Mn0.1O2 were studied by electrochemical-calorimetric methods in this paper.The thermoelectric properties of LiNi0.8Co0.1Mn0.1O2 material was evaluated compared with several different cathode materials.Finally,the properties of LiNi0.8Co0.1Mn0.1O2 material coated by LiAlO2 were calculated by first principle.1.Ni-rich ternary cathode material LiNi0,8Co0.1Mn0.1O2 for lithium-ion battery was synthesized by a high-temperature solid-state reaction method,and its process conditions were optimized.The structural and morphological features of as prepared LiNi0.8Co0.1Mn0.1O2 cathode material were investigated with X-ray diffraction and scanning electron microscopy.Its electrochemical properties also were analyzed.The results show that under the oxygen atmosphere,the ratio of lithium to metal elements was 1.05:1,the sintering time was 15 h and the sintering temperature was 750 ℃,the optimal synthesis conditions were obtained.The initial discharge capacity of the sample was 174.9 mAh·g-1 at 1.0 C,the specific capacity was 158.5 mAh ·g-1 after 50 cycles,and the capacity retention rate was 90.62%,which showed good cycle stability.The results of XRD and SEM showed that the sample sintered in oxygen atmosphere had a good layered structure with a small degree of cationic mixing and a good spherical shape.The particles were uniformly distributed in the range of 10-20 μm.The results of cyclic voltammetry(CV)and electrochemical impedance spectroscopy(EIS)show that the electrochemical performance of the cathode materials was improved by optimization conditions.2.The surface of LiNi0.8Co0.1Mn0.1O2 particles was modified by LiAlO2 by hydrolysis-hydrothermal method.The effects of different coating amount(bare,0.5%,1%,2%,5%)on the structure,morphology and electrochemical properties of LiNi0.8Co0.1Mn0.1O2 were studied by The XRD,SEM and electrochemical performance tests,the results show that when the coating amount was 1%,the cathode material LiNi0.8Co0.1Mn0.1O2 has the smallest degree of cationic mixing,with a good layered structure,the size of material particles is very uniform,and the particles still maintain a spherical appearance,the discharge capacity of material was 173.7 mA h ·g-i after 50 cycles at 1.0 C,and the capacity retention rate was 96.9%,Based on the above datas,the coating amount of 1%was the best.3.The thermo-electrochemical properties of uncoated and coated LiNi0.8Co0.1Mn0.1O2 cathode materials at different temperatures were studied by electrochemical-calorimetry.It was found that the specific capacity of the uncoated and coated cathode electrode material decreased with the increase of the rate at the same ambient temperature;The specific capacity of uncoated and coated cathode materials reduced with the increased of ambient temperaturea at same rate;when the temperature rised from 30 ℃ to 50 ℃,the first discharge specific capacity of the uncoated cathode material decreased by 19.1 mAh· g-1,19.6 mAh·g-1 and 20.2 mAh·g-1;and the first discharge capacity of the coated cathode material decreased by 17.2 mAh· g-1,17,5 mAh· g-1 and 18.2 mAh·g-1.These datas showed that the discharge specific capacity of uncoated material was lower than coated material,which proved the existence of the coating on the material played a very good protective effect.4.Through the comprehensive analysis of LiMnO2,LiFePO4,LiNi0.5Co0.2Mn0.3O2,LiNi0.8Co0.1Mn0.1O2 and other cathode materials thermodynamic parameters at 50 ℃,the results showed that the discharge capacity of LiNi0.8Co0.1Mn0.1O2 was the highest under the same conditions,also showed that thermal stability of LiNi0.8Co0.1Mn0.1O2 is better,and the heat generated of coated material was slightly lower than uncoated,its heat production less than other several cathode materials,So LiNi0.8Co0.1Mn0.1O2 is very suitable used in large electric vehicles.Even so,the modification of materials was still the focus of the current research,in oeder to solve the battery safety problems and to meet the demand for most electric vehivles.5.The first-principles calculation of LiAlO2-coated LiNi0.8Co0.1Mn0.1O2 was carried out by using PW91 method in generalized gradient approximation(GGA)based on density functional theory(DFT).The energy band structure and State density of coated material were analysed.It was found that the LiAlO2 coating reduced the energy gap between the conduction band and the valence band,which was helpful to improve the electrochemical performance of the material. |
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