Of Lifepo <sub> 4 </ Sub> Study Of The Electrochemical Properties In Aqueous Solution

Aqueous lithium battery is a new type of rechargeable lithium batteries with aqueous electrolyte instead of flammable organic electrolyte, which will eliminate burning, explosive crisis resulted from organic electrolyte. It has competitive potential compared with lead-acid, nickel-cadmium and some other low voltage batteries.LiFePO₄ is a new type of cathode materials for lithium battery, which shows excellent reversibility in lithium insertion and extration. Its structure stability, appropriate working voltage (0.4V vs. NHE) just in the H₂O stability region, low cost, environment friendly, good cycle performance and some other advantages make it a good candidate as cathode for aqueous lithium battery. Present investigation has been focused on its synthesis technique and its charge and discharge behaviors, but report on the research of its characteristics as the cathode for aqueous lithium battery is seldom. In this paper, Cyclic Voltammogram (CV), Charge and discharge test, and X-ray Diffraction (XRD) were used to investigate the variation of structure, surface and electrochemical characteristics of LiFePO₄ in aqueous electrolyte. An aqueous lithium battery consisting of a combination of LiFePO₄ as cathode material, TiO₂ as anode material and saturated LiNO₃ solution as electrolyte was proposed. Electrochemical Impedance Spectroscopy (EIS) was applied to investigate lithium insertion and extraction processes under different testing conditions. Scanning Electron Microscope (SEM) was applied to analyze the electrode before and after dipping. The results obtained from charge and discharge test were used simultaneously to analyze its related electrochemical behavior in different frequency regions. New equivalent circuit was presented to fit the experimental data. Kinetics of electrode processes of LiFePO₄ in saturated LiNO₃ solution was investigated by using the fitting results from Zview2.Lithium diffusion coefficient in active material is very important parameter in lithium insertion and extration, which has significant influence on electrode polarization and its charge and discharge performance. Basic research on aqueous lithium battery at present is very few, and its electrode kinetics investigation is fewer. Potentiostatic Intermittent Titration Technique (PITT), CV and EIS were used to investigate the electrochemical lithium insertion and extration behavior of LiFePO₄, and the corresponding kinetics and lithium diffusion coefficient were proposed.