Study On The LiODFB-based Electrolyte And Its Compatibility With LiFePO₄-AC/AG-AC Super-capacitor Battery Electrode Materials

Super-capacitor battery is a new kind of energy storage device possessing high energy density of lithium ion battery as well as high power density of super-capacitor.It has great application aspects in fields of transportation,mobile communication and information technology,etc. The success of its technological breakthroughs will raise a new revolution in the field of energy storage devices.As one of the core material of super-capacitor battery,electrolyte has an extremely impact on capacity, resistance,and temperature properties,etc.In this paper,the compatibility between LiODFB-based electrolytes with the electrode materials of LiFePO₄-AC/AG-AC battery was studied.LiBF₄ and H₂C₂O₄ was dissolved in solvent as the precursor,SiCl₄ was added to the solution as the catalyzer,combined with solventing-out crystallization,LiODFB was synthesized in one step.The test results of the product rate,the qualities of impurity and the water content were 80%, 0.0371%,and 1.01 PPm,respectively.These targets satisfied the request of lithium ion batteries.The result of FTIR and NMP show that the synthetic product LiODFB shows high qualities.The TG-DTA curves show the onset of the endothermic dissociation of LiODFB is at about 278.9℃.That is to say LiODFB has high temperature stability than the most widely used LiPF₆ obviously.Study on the solvent optimize of LiODFB salt for LiFePO₄-AC/AG-AC battery electrode materials.Five kinds of solvent system with excellent physical and chemical properties were employed and mixed into nine different electrolyte systems.The optimal concentration of LiODFB salt was determined by conductivity tests.The compatibility between different solvent electrolyte systems and LiFePO₄, AG,AC electrodes was studied through constant current charge-discharge, CV,EIS,etc.The result shows that the EC-PC-DMC system takes fine compatibility with LiFePO₄-AC/AG-AC electrodes.This system is proved to be the best solvent. After the solvent system was determined as EC-PC-DMC,the optimization of LiODFB-LiX blend salt electrolyte was studied in this system.Four different electrolytes were prepared with changing the proportion of LiODFB and LiX.The compatibility with LiFePO₄-AC/AG-AC electrodes was studied using the same methods as solvent optimize.The characteristics of LiFePO₄/AG battery as well as AC/AC super-capacitor performances were improved by adding some LiX to LiODFB based electrolytes.When the concentrations of LiODFB and LiX were respectively 0.8 M and 0.2 M,electrolyte plays the optimal compatibility with LiFePO₄-AC/AG-AC super-capacitor battery.In the same solvent system,ammonium salt which is the excellent electrolyte salt of super capacitor was added into LiODFB based electrolytes to optimize blend salt electrolytes.The electrochemical performances of different electrode-materials were considered generally, and the results indicate that capacitance characteristics were improved significantly by adding ammonium salt to 1.0 M LiODFB based electrolyte.However,high concentrations of ammonium salt A affect the properties of SEI film in AG electrode,that go against to improve the charge-discharge performances of LiFePO₄/AG cell.To sum up,we point out that the most applicable electrolyte to LiFePO₄-AC/AG-AC super-lithium capacitor is LiODFB-LiX/ EC-PC-DMC,and the concentration of lithium salt is 1 mol/L.