Study On Gel Polymer Electrolyte Power Battery Based On Ternary Cathode Materials

Lithium ion battery has become one of most important the electric energy storage devices.With the continuous development of electric energy application field,it is singnificant to develop lithium ion batteries with high safety,high energy density and long cycle life.There are many factors that affect the performance of commercial lithium ion batteries,including the selection of electrode materials,electrolyte materials and the matching of those components.Among them,the selection of cathode materials for lithium ion batteries is particularly significant.There is an urgent need of the market for developing promising cathode materials,such as nickel manganese cobalt or nickel cobalt aluminum ternary cathode materials.However,as the most promising cathode material to replace LiCoO₂,there is lots of work to do to improve the cycle stability,the rate performance and safety performance for the ternary cathode materials.In this work,on one hand,the effect was studied of different reaction condition by co-precipitation on the final ternary cathode materials LiNi_1/3Co_1/3Mn_1/3O₂?NCM?.On the other hand,the ternary cathode materials LiNi_0.8Co_0.15Al_0.05O₂?NCA?was matched with different anode materials and electrolyte to assemble power batteries,respectively,then the electrochemical performance and safety performance of those power batteries were studied.The study results provide significant guidance for the large-scale industrialization of the ternary cathode materials and batteries.In this paper,a series of NCM ternary materials were prepared by co-precipitation method.Firstly,the effects of type of precipitating agent,the addition amount of chelating agent and the amount of surfactant on the morphology and dispersion of precursor were investigated.Secondly,the effects of precursor morphology,pretreatment for precursors,sintering conditions on the morphology and electrochemical properties of NCM ternary materials were investigated.Then,a series of power batteries were assembled with the NCA as cathode,matching with graphite and graphite-Si/C as anode,respectively,in which common liquid electrolyte?LE?and gel polymer electrolyte?GPE?were adopted.The GPE was synthesized via radical polymerization of pentaerythritol tetraacrylate?PETEA?monomers using azodiisobutyronitrile?AIBN?as the initiator in the presence of liquid electrolyte.Tests show that,batteries based on GPE shows obvious advantages in cycle stability performance,rate performance,safety performance compared with batteries based on LE.Finally,in order to further explore the protection mechanism of the GPE compared with the ordinary liquid electrolyte in improving the comprehensive electrochemical performance and safety performance of the battery,cell opening and post-mortem investigations were carried.The anode and cathode material were analyzed by XRD,SEM and XPS besides electrochemical test.The results show that the GPE-based batteries form a layer of"protective film"on the surface of the electrode.On the one hand,the surface film can effectively restrain the decomposition of electrolyte and the electrochemical side and heat reaction.On the other hand,it can maintain the structural integrity of both electrodes and reduce the consumption of reversible lithium ion and the loss of active materials,especially the loss of NCA.The work of this paper provides a good theoretical basis and practical basis for improving the electrochemical performance and safety performance of commercial lithium-ion power battery based on NCM and NCA ternary cathode materials.