Electrochemical Performance Of Si Anode Materials And Manufacturing Technology For Lithium Ion Batteries

As the member of anode materials for lithium ion battery, silicon is considered to be one of the most appealing candidates due to its high theoretical capacity of4200mAh g-1, relatively low working potential, abundant resources and environmentally benignity. However, the poor cycle performance during charge-discharge process hinders its practical application. To combine the advantages of nanostructure and composite, the Co/Si nanostructured films were synthesized. Furthermore, we took part in the design of composite cathode materails and adjusted the manufacturing parameters of batteries. We also attempted to improve the electrochemical performances of the batteries at low temperature to meet the market demand. The main research contents are shown as follows.(1) After the cobalt nanomountain arrays (NMAs) are electrodeposited on the copper foil, the silicon is sputtered on it to synthesize Co/Si nanostructured film. And we compare the electrochemical performances of Co/Si nanostructured films with different thickness of Si. The nanostructured Si film with a thickness of200nm shows impressive electrochemical performances with a high discharge capacity of1917.8mAh g-1at0.1C rate over100cycles. As the rates increase first from0.1C (0.4A g-1) to0.5C (2A g-1), and then to3C (12Ag-1), the specific capacities of the Si/Co electrode decrease first from2329.9mAh g-1to1953.3mAh g-1, and then to1166.1mAh g-1, indicating its execlent rate capability. When the thickness of Si film increases to400-600nm, the discharge capacity declines to around2200mAh g-1at0.1C,1400mAh g-1at0.5C and650mAh g-1at2C, respectively.(2) After participating in the technics designs for lithium ion batteries, we studied the influence of different electrode materials, such as LiFePO4and LiMn1/3Co1/3Ni1/3O2, on the key parameters of the manufacture of lithium-ion batteries. Meanwhile, the effect of process parameters on high-energy and high-power batteries using LiMn1/3Co1/3Ni1/3O2was the object of this work. Lithium bis(trifluoromethanesulphonyl)imide is added to the commercial electrolyte to improve the electrochemical performance of the lithium-ion batteries at low temperature. Comparing with the other three composition of electrolyte, the electrode working in LiTFSI-0.1exhibites the best electrochemical performance at0℃with a discharge capacity of161mAh g-1at0.1C, about86%of capacity at25℃, and100.0mAh g-1at0.5C, about75%of the capacity at25℃. In addtion, an increment of18mAh g-1is obtained for the electrode working in LiTFSI-0.1comparing to that working in commercial electrolyte at0℃...