Research On The Synthesis And Electrochemical Performence Of Nano Silicon Based Material

Silicon based anode materials as lithium ion battery materials is a very promising anode material as its high specific capacity,low price and other advantages.Compared with silicon,the discharge potential of SiO₂ almost equal to the low discharge potential of Si,and its theoretical capacity is high,furthermore,non active Li2 O and Li4SiO4 could be produced in the intercalation process,these two substances could alleviate the volume expansion to a certain extent.Therefore,the cycle stability of silica?SiO₂?anode material is better than Si.However,SiO₂ anode material for commercial use is limited mainly due to its low intrinsic conductivity and volume effect,while the carbon material has good conductivity and long recycling life,which can improve the defects of SiO₂ anode materials to a certain extent.The low cost soft template method was applied to synthesizing mesoporous SiO₂ nanoparticles under different conditions.And different carbon source mixed SiO₂ were proplyzed to gain SiO₂/C composite.The main contents of this thesis as follows:?1?Mesoporous SiO₂ nanoparticles were synthetized through soft template method,and the different synthesis conditions?solution concentration,TEOS dropping rate,temperature?affect the morphology of mesoporous SiO₂ nanoparticles.The results showed that the best synthesis condition was 0.1*10-3mol/L F127 and 0.005mol/L CTAB,2 hours for adding TEOS?average adding speed was 12.25ul/min?,and the temperature was 70?.The cyclic voltammetry and rotating disk?RDE?were applied to test the electrochemical activity of mesoporous SiO₂ material synthesized under the optimum conditions.The results showed that the mesoporous SiO₂ material has electrochemical activity.And then the charge and discharge test of the mesoporous SiO₂ nanoparticles as anode materials for lithium ion battery showed that the first discharge capacity of the material was 116mAh/g.?2?The morphology and electrochemical performance of SiO₂/C material derived from three different hard carbon materials?sucrose,PVDF,a resol resin?were studied.Electrochemical performance test?cyclic voltammetry,RDE,charge and discharge tests?for sucrose as carbon source showed that 66.8% SiO₂ in SiO₂/C had the strongest electrochemical activity,the initial discharge capacity was 425 mAh/g.When PVDF as carbon source,the electrochemical activity of SiO₂/C derived from SiO₂:PVDF=19:4 was the strongest,the first discharge capacity of the material was 350mAh/g;The electrolic test of SiO₂/C derived from the pyrolysis of A resol resin mixed nano SiO₂ showed that 71.6% SiO₂ of the material had better activity,and its initial discharge capacity was 250 m Ah/g.Compared to pure mesoporous SiO₂ material,the electrochemical performance of SiO₂/C composite was better than SiO₂ material,which indicated that the addition of carbon could enhance the electrochemical performance of silicon based materials.In addition,the electrochemical test results showed that 66.8% SiO₂ in SiO₂/C material,which derived from sucrose as carbon source mixed nano SiO₂ particles,had the best electrochemical performance among all the three carbon source.