The Modification Of LiV₃O₈and Its Electrochemical Properties As Anode Material For Aqueous Rechargeable Lithium Batteries

Lithium vanadate oxides（LiV₃O₈） are promising materials for lithium ion batteriesbecause of their high capacity. Their initial discharge capacities can reach above300mAh g^-1. It can use in nonaqueous lithiumion as the cathode material batteries and inaqueous lithiumion batteries as anode material, However, bare LiV₃O₈exhibit largecapacity fade during cycling and also show poor rate capability, which hinder theirpractical applications.In this work, we attempted to incorporate polypyrrole and nano-NiO into LiV₃O₈and tried to improve the electrochemical characteristics of the composite.Polypyrrole-LiV₃O₈（PPy-LiV₃O₈） composite has been chemically synthesized withsol-gel synthesized LiV₃O₈by an oxidative polymerization. The influences of thecoating on the structure, morphology, and electrochemical properties of LiV₃O₈havebeen characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM）,cyclic voltammetry（CV）, electrochemical impedance spectroscopy（EIS）, andgalvanostatic charge/discharge experiments.The PPy-LiV₃O₈composite electrodeexhibited better cycling behavior and superior rate capability as compared with thebare LiV₃O₈electrode. Besides, the NiO coated LiV₃O₈was prepared byNi（NO₃）2·6H₂O and solution with sol-gel synthesized LiV₃O₈in distilled water, NiOcoated were coated on the surfaces of LiV₃O₈powders. The surface morphology wascharacterized by SEM. The structural changes of the cathode materials before andafter coating were revealed by XRD. The coating has been found to improve theelectrochemical performance of LiV₃O₈significantly. Especially,5.0wt.%NiOcoated LiV₃O₈shows much better electrochemical performance than uncoatedLiV₃O₈.Aqueous electrolytes have the advantages of good safety performance and low cost.In this work, we investigated the electrochemical properties of LiV₃O₈in aqueousLi₂SO₄solutions and LiNO₃solutions with different concentrations to provide betterunderstanding for ARLBs systems. The electrochemical properties of the LiV₃O₈electrodes in1mol L^-1Li₂SO₄,2mol L^-1Li₂SO₄, and saturated Li₂SO₄aqueouselectrolytes have been studied using CV、EIS and galvanostatic charge/dischargeexperiments in this work. The results show that LiV₃O₈electrode in saturated Li₂SO₄electrolyte exhibits the best electrochemical properties. The electrochemicalperformance of the LiV₃O₈electrodes in1mol L^-1LiNO₃,5mol L^-1LiNO₃and saturated LiNO₃aqueous electrolytes has been studied using cyclic voltammetry, acimpedance and charge/discharge tests in this work. The results show that LiV₃O₈electrode in saturated LiNO₃electrolyte exhibits good electrochemical performance interms of specific capacity and charge/discharge cycle ability.it better than in saturatedLi₂SO₄electrolyte. Although LiV₃O₈electrode shows relative good electrochemicalproperties in saturated LiNO₃solution, further researchis needed to improve itselectrochemical properties, such as capacity, coulombic efficiency, and rate capability,especially for cycling performance.So,in this paper,The electrochemical performance of aqueous rechargeable lithiumbattery （ARLB） with NiO-LiV₃O₈as the anode and LiMn₂O₄as the cathode insaturated LiNO₃electrolyte is studied. The electrochemical properties have beenstudied using CV、EIS and galvanostatic charge/discharge experiments. Cycling testsreveal that the stability of the ARLB with NiO coated anode has been greatlyimproved. Moreover, the rate capability of the ARLB with coated anode is alsoenhanced compared with the ARLB with bare anode. The improvement ofelectrochemical properties for ARLB with coated anode can be attributed to NiOcoating improves the stability of LiV₃O₈in the aqueous electrolyte effectively.