High Performance Ternary Cathode Material For Lithium-Ion Baterry Research

The high nickel ternary cathode material has the advantages of large discharge capacity,better cycling performance and low cost,and it is considered to be one of the promising cathode materials for replacing LiNiO₂,LiCoO₂ and LiMnO₂.Through the synergistic action of Ni-Co-Mn?or Ni-Co-Al?ternary material combines the advantages of three materials:high specific capacity of LiNiO₂,better cycling performance of LiCoO₂,high security and low cost of LiMnO₂.In order to further improve the electrochemical performance of high nickel cathode materials.The development of new precursor synthesis methods and the exploration of surface modification methods of cathode materials were investigated.The effects of synthesis process and doping modification strategy on the electrochemical properties of cathode materials were investigated.It mainly includes the following three aspects.?1?Study on the effect of precipitant in the process of synthesizing precursor by rapid mixing and hydrothermal treatment.The spherical[Ni_0.6Co_0.2Mn_0.2]CO₃ precursor was prepared by rapid mixing and hydrothermal treatment with nickel sulfate,cobalt sulfate and manganese sulfate as the raw materials and?NH₄?₂CO₃ as precipitant.The results show that the initial discharge capacity is 197.7 mA h g^-1 at 0.1 C and 176.9 mA h g^-1 at 2 C.Furthermore,the discharge capacity still remains 116.1 mA h g^-1 at a high rate of 20 C.It has been found that the coupling of the complexing agent and the precipitating agent plays a very important role in the performance of the electrochemical performance.?2?Effect of different manganese sources on electrochemical performance of cathode materials:[Ni_0.8Co_0.15]?OH?_1.9.9 was synthesized according to the molar ratio of nickel to cobalt of 80:15,then nickel sulfate and cobalt sulfate are mixed into a certain concentration solution when using?NH₄?₂CO₃ and NaOH as complexing agent and precipitating agent respectively.The results show that the optimal doping level of Al is 0.025,and relevant sintering temperature is 750? when using manganese acetate as Mn source.The prepared materials deliver a discharge capacity of 200.3 mA h g^-1 at 0.1 C,and 120 mA h g^-1 at 20 C.The synthesized cathode materials sintered at 850? show good performance with0.0375 Al when utilizing MnCO₃ as Mn source.The discharge capacity reaches216.4 mA h g^-1 at 0.1 C,and 156.8 mA h g^-1 at 5 C.It is found that the decomposition and diffusion mode of the manganese source has a very important influence on the performance of the electrochemical performance.?3?Surface modification of W-doped cathode materials:To futrher improved performance of[Ni_0.8Co_0.15]?OH?_1.9 perepared at above sections,we doped Al and W into the crystal structure.The XRD results indicate that doping of W leads to seperation of ?006?/?102?and?108?/?110? diffraction peaks,meaning excellent layered structure have been achieved.The electrochemical data shows that the Li(Ni_0.8Co_0.15Al_0.05)O₂ prepared at 850? can diliver 169.6 mA h g^-1 in the first cycle at current density of 0.2 C,while Li(Ni_0.8Co_0.15Al_0.049W_0.001)O₂ exhibits 193.3mAhg^-1.Additionally,theinitialdischargespecificcapacityof Li(Ni_0.8Co_0.15Al_0.049W_0.001)O₂ can reach 177.9 mA h g^-1 at 2 C,and 84.32% discharge capacity(193.3 mA h g^-1)is matained after 300 cycles.However the Li(Ni_0.8Co_0.15Al_0.05)O₂ dilever 169.4 mA h g^-1 at first cycle with 2 C,and 82.56% specific capacity(193.3 mA h g^-1)is kept.Based on these results,we can draw the conclution that multi-valent metal ion W doping has positive significance for improving the electron conduction and hole generation of Li(Ni_0.8Co_0.15Al_0.05)O₂...