Study On Lithium Vanadium Oxide Based Compounds As Anode Material Of Aqueous Lithium-ion Battery

LiV₃O₈ as a anode material for aqueous lithium-ion battery has high capacity, low cost, environmental friendly, etc., and has great development potential. However, when LiV₃O₈ is used as the anode material of the aqueous lithium-ion battery during charge and discharge, and the cycling performance is not ideal enough, the commercial application and development are affected. The electrochemical performance of LiV₃O₈ will be improved by doping modification with Mg and Fe as the doping elements respectively. LiV₃O₈ and Li_1-2xMg_xV₃O₈?x=0.5%, 1%, 2%, 3%?, LiMg_xV₃O₈?x=0.5%, 1%, 3%, 5%?, Li_1+2xV_3-xFe_xO₈?x=5%, 10%, 15%? as the anode materials, were prepared by sol-gel method, their structure, morphology and electrochemical performance were tested by XRD, SEM, CV, EIS, constant current charging-discharging technology.The prepared LiV₃O₈ and Li_1-2xMg_xV₃O₈ materials are bar structures, the average particle lengths are about 450 nm, and the widths are about 170 nm. When x=2%, the cyclic reversibility of the material is the best, its initial discharge specific capacity is 73.1 m Ah·g^-1, the discharge capacity and the capacity retention rate are 63.2 m Ah·g^-1 and 86.4% respectively after 50 cycles, and the impedance increased by only 0.83 ?, the capacity fading has been relieved significantly, and the cycling performance has been improved obviously.The structures of the prepared LiMg_xV₃O₈ materials are similar to LiV₃O₈. When x=5%, the cyclic reversibility of the material is the best, its initial discharge specific capacity is 64.7 m Ah·g^-1, the discharge capacity can reach 73.1 m Ah·g^-1 after 50 cycles, and the least increase of the impedance is only 0.02 ?, the doping of the excessive Mg increases the unit cell volume, which is beneficial to the diffusion of Li+, which can improve the stability of the cycle.The structures of the prepared Li_1+2xV_3-xFe_xO₈ materials are similar to LiV₃O₈. When x=5%, the main phase of the material is LiV₃O₈, containing a small amount of Li_0.3V₂O₅, and the capacity is significantly higher than the non-doped LiV₃O₈, its first discharge capacity and coulombic efficiency are the highest, respectively, are 107.3 m Ah·g^-1 and 80.6%. The discharge specific capacity and capacity retention rate are also the highest, respectively, are 75.8 m Ah·g^-1 and 70.6% after 50 cycles, and the impedance increased by 2.25 ?, the cycling performance has been significantly improved.