Submicrometer porous Li_3V_2(PO_4)_3/C composites with high rate electrochemical performance prepared by sol-gel combustion method

摘要

Submicrometer porous Li_3V_2(PO_4)_3/C composite (LVP/C-1) is synthesized by sol-gel combustion method with NH_4NO_3 as additive and it exhibits a superior electrochemical performance. The other Li_3V_2(PO_4)_3/C (LVP/C-2) is obtained by the conventional sol-gel method without the addition of NH_4NO_3 for the comparison. The physical and electrochemical properties of the Li_3V_2(PO_4)_3/C are examined by many characterizations including TG-DTG-DSC, XRD, SEM, TEM, BET, XPS, EIS and galvanostatic charge-discharge cycling. A carbon layer uniformly coated on the surface of particles can be seen from TEM images. XPS spectra demonstrate that V is trivalent for the composite. The sample LVP/C-1 with the addition of NH_4NO_3 illuminates a more excellent high rate performance with capacity fading rate of only 9% after 20 C in the voltage of 3.0-4.5 V. And LVP/C-1 still can show a discharge capacity of 75.0 mAh g~(-1) even at high rate of 80 C. The EIS tests show that the lithium-ion diffusion coefficient of LVP/C-1 is 2 orders of magnitude higher than LVP/C-2, indicating that LVP/C-1 has a good mass transport performance.