Study On Solid Electrolyte Interface Film(SEI Film) And Relative Properties Of Anode Materials For Lithium Ion Batteries

The electrode materials and electrolytes for lithium ion batters have an important influence on each performance of lithium ion batteries. Therefore, people have paid a lot of attention to study and exploit novelty electrode materials and electrolyte. Solid electrolyte interphase (SEI) film formed on anode materials affects power capacity, safety, cycles and self-discharge of lithium ion batteries, and so on. So, it is important aspect for us to study it. The SEI film, Si-based materials and the properties between SnO and electrolyte were studied in this thesis. 1. Surface Enhanced Raman spectroscopic study on SEI film formed on silver electrode Noble metals and carbon material at low potentials and same electrolyte have similar surface film (SEI film). High quality surface Enhanced Raman spectrum of the SEI film was perfectly observed by Surface Enhanced Raman Scattering (SERS) for the first time in the world. Careful study on silver electrode at discharging to OV was carried out. The result indicates that LiCO3 exists by amorphous structure and the other characteristic peak of the SEI film attributes to LiOH.H20 and LiF , et al.. We study the SERS of Li-Ag alloy for the first time in order to know further information of the SEI film. The results indicate that the reaction of Li-Ag alloy occurred between Li ion and Ag with Li ion inserting into silver electrode. This leads to roughness of silver electrode and SERS of Li-Ag alloy at last. Concentration and roughness of alloy have an influence on SERS of Li-Ag alloy. SER spectra of the SET film attribute to SERS of Li-Ag alloy, besides, SERS of R6G comes from the long-range electromagnetic effect. Further study on the SET film at different discharge states indicates the its component is varied, but, the main component (LiCO3) is invariable. The other characteristic peak attributes to lithium alkylcarbonates (ROCO2Li). iii The results also show that water have an important influence on the component of the SET film when trace water exist. Meanwhile, the formed mechanism of SET film was discussed. 2. The elementary study on SET film formed on Au electrode by SERS For further study on SET film formed on other electrode, we have successfully obtained SER spectrum of SEI film at discharging to O.1V. The results indicate that LiCQ3 in the SEI film also exists by amorphous structure and the characteristic peak of other decomposition species of electrolyte( for example ROCO2Li, LiOH.H20 and LiOH, and so on) also appears in the SER spectrum. The formed mechanism of SEI film on Au electrode is similar to silver electrode. The study on the SEI film formed on Au electrode also provides a viable approach for study on the SET film: it is viable approach to investigate the SEI film on noble metal by SERS. 3. Spectroscopic study on Si-based anode materials Nano-Si has shown high and reversible electrochemical capacity at room temperature, which attracts people great interest. For further study on the influence of crystal lattice and energy band of silicon inserted by lithium ion, we have investigated the structure and property of nano-Si , monocrystalline silicon and porous silicon by in-situ PL spectra and Raman spectra. The results of in situ Raman spectra indicated that the crystalline structure of Si (nano-Si, monocrystalline silicon and porous silicon) was destroyed gradually with the incre...