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Study On Performance Of AC/Li4Ti5O12 Electrochemical Hybrid Capacitor

Posted on:2008-08-17Degree:MasterType:Thesis
Country:ChinaCandidate:X F GuoFull Text:PDF
GTID:2132360245491048Subject:Chemical processes
Abstract/Summary:PDF Full Text Request
The electrochemical hybrid capacitors(EHC) is a novel storage device between supercapacitor and battery, with more specific capacitance and energy density compared with supercapacitor and more power density compared with battery, it's one of the optimum choices for hybrid electrochemical vehicles and power sources. The focus is the electrode materials and the system construction. AC/Li4Ti5O12 electrochemical hybrid capacitor was assembled using an activated carbon cathode and an intercalation compound Li4Ti5O12 anode, and it was investigated by means of constant charge/discharge, cyclic voltammetry and electrochemical impedance spectroscopy measurements.The spinal phase Li4Ti5O12 was prepared with high-temperature solid-state method and molten salt method, and the XRD and SEM measurements showed that the both productions exhibited high phase purity and good crystallite. The Li4Ti5O12 synthesize by high-temperature solid-state method has wide charge/discharge plateau and stable cyclic performance, with a specific capacitance of 128.8mAh·g-1 at 30mA·g-1 current, and the cycle efficiency reached to 98.2%.The AC/Li4Ti5O12 hybrid capacitor, consisted of a high specific surfance area AC cathode and a Li4Ti5O12 anode synthesize by high-temperature solid-state method in 1M LiClO4/PC, exhibits a good electrochemical performance. The capacitor (mAC/mLi4Ti5O12=3:1) delivers a specific capacitance of 29.2mAh·g-1(based on the total weight of the electrod materials) at 50mA·g-1 current, and the cycle efficiency reached to 98.6%. The capacitor also has a sloping profile from 2.8 to 1.5V, and it exhibits a good cycling profile and desirable high rate capability. The hybrid capacitor delivers a specific energy of 67.5Wh·kg-1 based on the total active materials, the working volage is 2.25V. The CV curves showed that simultaneous with nonfaradic reaction in AC cathode, a faradic reaction occurred on Li4Ti5O12 anode. AC impedance spectra of the capacitor at charge/discharge potentials shows that electrochemical impedance was possibly infltenced by the corresponding conductivity at Li+ insertion extend.The hybrid capacitor using AC as cathode and MCMB as anode was developed, and the electrochemical performace was studied primarily. The AC/MCMB capacitor delivers a specific capacitance of 30.4mAh·g-1 at 50mA·g-1 current, and the cycle efficiency is 91.6%.
Keywords/Search Tags:Hybrid capacitor, Li4Ti5O12, activated carbon, asymmetric
PDF Full Text Request
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