Investigation On Solid Polymer Electrolyte And Anode Material Of Lithium Ion Batteries

The work principle and the development of lithium ion batteries have been described in this dissertation.The drawbacks and some modification methods of Poly(ethyleneoxide)(PEO)-based polymer electrolytes have been introduced with emphasis.Mesoporous silica SBA- 15 was surface-modified byγ-glycidoxypropyltrimethoxy silane(GPTMS),and novel poly(ethylene oxide) (PEO)-based composite polymer electrolytes(CPE) using the silane-modified SBA-15(SBA-15-GPTMS) as filler were prepared.The CPEs were characterized by scanning electron microscopy(SEM),Fourier-transform infrared(FT-IR) and X-ray diffraction(XRD).The ionic conductivity of CPE was determined by electrochemical impedance spectroscopy(EIS),and the electrochemical stability window of the CPEs was determined by linear sweep voltammetry(LSV).In addition,the tin electrodes for lithium ion batteries were prepared by the electrodeposition.The structure and the performance of tin electrodes were investigated by SEM and charge-discharge test.The results of the low-angle XRD patterns and FT-IR spectroscopy indicated that GPTMS has been successfully attached to the surface of SBA-15 with a high degree of mesoscopic hexagonal pore structure.The incorporation of SBA-15-GPTMS in the PEO- LiCIO4 matrix effectively reduced the PEO crystallinity and obviously improved the conductivity and electrochemical stability of the CPEs.The CPE with 10 wt.%SBA-15-GPTMS provided the highest conductivity among all the tested CPEs,about 2 - 3 orders of magnitude higher than that of the PEO- LiCIO4 matrix below the melting temperature of PEO.The decomposition potential of the CPEs with relatively high SBA-15-GPTMS content (≥10 wt.%) exceeds 5.0 V.This improves the electrochemical stability of the CPEs.The results of SEM showed that the crystal grains of the tin electrodes prepared by the electrodeposition in the bath with an organic additive(P123) were comparatively homogeneous,presenting much decreased grain sizes and better adhesion on the copper substrate.The as-prepared tin film electrodes showed larger reversible capacities and obviously improved cycle performance.