碳包覆LiFePO_4的一步固相法制备及高温电化学性能

One-step Solid-state Synthesis and High-temperature Electrochemical Performance of Carbon Coated LiFePO_4 Cathode

Carbon coated LiFePO4 cathode material was synthesized by one-step solid-state reaction and characterized by X-ray diffraction (XRD), field-emission-scanning electron microscope (FESEM). Electrochemical performances of the material as cathode in lithium-ion battery were investigated at medium and elevated temperature (30 and 55 ℃) by galvanostatic charge-discharge and A.C. impedance tests. The results show that carbon coated LiFePO4 powder exhibits a well-crystallized olivine structure and spherical morphology with an average particle size of about 500 nm. Galvanostatic charge-discharge tests show that the reversible discharge capacity at 1 C and 1.5 C rates was improved from 121 and 105 mAh·g-1 at 30 ℃ to 136 and 123 mAh·g-1 at 55℃, respectively, while the enhancement of high temperature on electrochemical performance is less obvious at a rate lower than 0.5 C. Impedance spectra analyses indicate that the cathode material has a remarkably higher lithium-ion diffusivity at 55 ℃ than that at 30 ℃, which improves the electrochemical performance at high temperature.

Carbon coated LiFePO4, cathode material was synthesized by one-step solid-state reaction and characterized by X-ray diffraction (XRD), field-emission-scanning electron microscope (FESEM). Electrochemical performances of the material as cathode in lithimn-ion battery were investigated at medium and elevated temperature (30 and 55 degrees C) by galvanostatic charge-discharge and A.C. impedance tests. The results show that carbon coated LiFePO4, powder exhibits a well-crystallized olivine structure and spherical morphology with an average particle size of about 500 nm. Galvanostatic charge-discharge tests show that the reversible discharge capacity at 1 C and 1.5 C rates was improved from 121 and 105 mAh - g(-1) at 30 degrees C to 136 and 123 mAh - g(-1) at 55 degrees C, respectively, while the enhancement of high temperature on electrochemical performance is less obvious at a rate lower than 0.5 C. Impedance spectra analyses indicate that the cathode material has a remarkably higher lithium-Ion diffusivity at 55 degrees C than that at 30 degrees C, which improves the electrochemical performance at high temperature.