Study On Nickel - Cobalt Aluminum Cathode Materials For Lithium Ion Batteries

Because of global warming and the exhaustion of fossil fuels, considerable attention has been paid to lithium-ion batteries(LIBs) In recently years, LiNi0.8Co0.15Al0.05(NCA) composite with high capacity for cathode materials has applied in electric vehicles(EVs) and hybrid electric vehicles(HEVs). Based on, we wish to explore a simple and practical method to prepare NCA cathode materials.Firstly, the precursor for NCA cathode material with homogeneous spherical morphology, distribute of elements and controlled particle size have been prepared by spray drying method. Then the NCA cathode material has been prepared by sintering. In this thesis, the morphology and electrochemical performance for NCA composite has been tested, and the influence of the following factors: way of lithium coordination, the ratio of lithium, the presintering temperature, the calcination tmperature and time. Finally, we found the optimal conditions to prepare NCA cathode material were determined.The optimum method is:The precursors containing the lithium source were first pre-sintered at the temperature of 450℃ and then sintered at 800℃ for 10 h. The optimal ratio of Li/(Ni+Co+Al) is 1.03:1. The structure of NCA composite was characterized by X-ray diffraction(XRD), scanning electron microscopy(SEM). We found that NCA composite has good electrochemical performance: the NCA electrode delivers a discharge specific capacity of 190mAh/g at 0.1C in the first cycle, and remains 90% capacity after 50 cycles.When the NCA cathode material was coated with LPAN, the electrochemical performance has been improved. After coated modification, the direct contact between the material and the electrolyte is effectively voided, which can prevent the electrolyte from being broken down. Coating NCA composite with LPAN can not only improve the stabilization of material, but also improve the electrochemical performance. The results indicated that the best LPAN coating amount was about 20% of NCA cathode material.Under this condition, the capacity retention increased to more than 95% after 50 cycles at a high current density.