Raman and XRD studies on the influence of nano silicon surface modification on Li+ dynamics processes of LiFePO4

• LiFePO4@C/Si possesses faster charged and discharged velocity than LiFePO4@C.
• Si surface modification promotes Li+ ion transfer rate.
• Si surface modification suppresses the Fe dissolution and enhances the stability of LiFePO4 and cycle performance.

In this letter, Li+ ion kinetic processes of LiFePO4@C and LiFePO4@C modified by nano silicon (LiFePO4@C/Si) have been systematically investigated by X-ray diffraction, Raman spectra and Electrochemical impedance spectroscopy (EIS), respectively. The experimental results indicate that, (1) LiFePO4@C/Si possesses faster charged and discharged velocity than LiFePO4@C; (2) the nano silicon surface modification induces the larger diffusion coefficient and less activation energy of Li ions, which promotes Li+ ion transfer rate; (3) it suppresses effectively the Fe dissolution and enhances the stability of LiFePO4 phase and cycle performance; (4) there exists the best silicon surface modification content (Si content = 2.46 at.%) in enhancing the electrochemical performances of LiFePO4. Additionally, it is suggested that constant-voltage charge is with some time indispensable for a fully delithiation of the LiFePO4 material.

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