Synthesis And Electrochemical Performance Of Amblygonite-type Cathode Material For Lithium-ion Batteries

Recently, a family of materials, which is isostructural with amblygonite (LiAlPO4Fx(OH)1-x) or tavorite (LiFePO4(OH)), has interested researchers. The structure of this type of materials is similar to the NASICON (Na+super ion conductor), which owns three-dimensional framework for ion-diffusion and structural stability, with wide developing prospect. This paper has studied the synthesis and electrochemical properties of LiFePO4F and LiVPO4F.A ceramic process is used to synthesize LiFePO4F. A series of samples are obtained through changing the calcination temperature. XRD, SEM are used for phase analysis and morphology analysis. Galvanostatic method and EIS method are used for electrochemical characterization. The results indicate that the sample obtained under550℃is single phase with the best electrochemical performance.A sol-gel process is used to synthesize LiFePQ4F. A series of samples are obtained through changing the calcination temperature of the precursor. XRD, SEM are used for phase analysis and morphology analysis. Galvanostatic method and EIS method are used for electrochemical characterization. The results indicate that the sample obtained under550℃is single phase with the best electrochemical performance. Comparative study of the LiFePO4F samples synthesized by the two methods is implemented. The experiments reveal that the particles sizes obtained by sol-gel process are200-300nm, whereas the ones obtained by ceramic method are1000nm. The initial discharge capacities (0.1C) of the samples synthesized by sol-gel process and ceramic method are145mAh/g and134mA/g respectively, meanwhile the Li+diffusion coefficients of the two samples are5.89×10-13cm2/s and9.09×10-13cm2/s respectively.This paper demonstrates that the Li+diffusion coefficient of LiFePO4F without modification is higher than that of raw LiFePO4F by three orders of magnitude.A sol-gel process is used to synthesize LiVPO4F. A series of samples are obtained through changing the calcination temperature of the precursor. XRD, SEM are used for phase analysis and morphology analysis. Galvanostatic method and EIS method are used for electrochemical characterization. The results indicate that the sample obtained under700℃is single phase, and its initial discharge capacity at0.1C is142mA/g.