| As a new kind of secondary battery, the rechargable lithium-ion battery has the best overall performance at present. Further requirements such as higher electrochemical capacity and better reversibility are advanced to lithium ion battery with the development of our society. In the first cycle of lithium ion battery, solvent decomposition reaction on the surface of electrode will lead to the formation of a passivating layer, commonly named solid electrolyte interface film (SEI film). It is only several nanometers thick but has great impact on the electrochemical capacity, security, self-discharge and has become a focus in the study of lithium ion battery.The SEI film has been extensively investigated by FT-IR, HRTEM, SEM, XPS and AFM, which are the methods of surface analysis with very high sensitivity. However,those methods cannot differentiate all species in the SEI film. But Raman spectrum is a ideal test method to study the SEI film,which can provide the informations of the component and variety of the film.At present the mainly research of the SEI film has been concentrated on the cathode material and the investigation of the SEI film on the positive electrodes has been a rarity. For the SEI film on the positive electrode is very thin and it's electrochemistry performance is too feeble to be observed. During the last several years our group has been concentrated on the cathode material for Lithium Ion Batteries. But the active silver substrate of SERS used in the study of the cathode material cannot be used in positive electrodes. In the lithium ion battery the working voltage of positive electrode may reach and exceed 4.0V, however the silver will be oxidated at 3.6V (vs Li/Li+), and in the first charge process, the nanometer silver can be dissolved into the electrolyte and no longer has SERS active. But the gold may withstand the high oxidized voltage as high as 5.02V (vs Li/Li+) and the nanometer gold also is a good SERS substrate.
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