Study On Synthesis And Electrochemical Characteristics Of CuV₂O₆ Cathode Material For Lithium Batteries

Recently,rapid progresses have been made in the research of lithium batteries due to their excellent properties.The lithium batteries,such as Li/MnO₂,Li/I₂,Li/Ag₂V₄O₁₁,Li/SO₂, Li/SOCl₂,Li/FeS₂,Li/（CF）_n,Li/CuO etc.,were invented successively.Among all these primary batteries,Li/Ag₂V₄O₁₁ battery was widely used as the power source of the iatrical devices because of its high volumetric and gravimetric specific capacity,and also its excellent rate capability.However,the Ag₂V₄O₁₁ material was very expensive,and,because of the micromation development of the implantable medical devices such as the implantable cardiac pacemaker,new request in the aspect of energy density was brought forward.Compared to Ag₂V₄O₁₁,CuV₂O₆,as a novel metal vanadate cathode material for lithium batteries, possesses lots of merits:low cost,higher discharge capacity,ease of synthesis and stability in air.Thus,it was a promising cathode material to replace the Ag₂V₄O₁₁ used as the power of medical devices.In addition,the CuV₂O₆ material could be used as a cathode material for lithium secondary batteries.In this paper,the CuV₂O₆ materials were synthesized by high temperature solid-state method,co-precipitation method and sol-gel method.The optimum condition to synthesize CuV₂O₆ via different method and the performances of the products synthesized in different conditions were discussed as well.A modified conventional high temperature solid-state synthesis procedure without pre-heat treatment of the raw materials of V₂O₅ and CuO was used to prepare CuV₂O₆ by mixing the raw materials through wet-mill and then calcination of the mixture.The results showed that the optimal calcination of temperature and time were 620℃and 2h,respectively.The CuV₂O₆ synthesized under such a condition had better electrochemical performance than that of the product prepared by conventional high temperature solid-state reaction.A co-precipitation method with V₂O₅ and Cu（NO₃）₂ as main raw materials was used to prepare CuV₂O₆ by dissolution of V₂O₅ with NH_3.H₂O,adjustment of solution pH with NH_3.H₂O and hydrochloric acid,and then heat-treatment of the precipitation of CuV₂O₆ precursor.An investigation of the influence of synthesized conditions on the electrochemical performance of CuV₂O₆ indicated that the optimal temperature of heat-treatment was 600℃and the discharge capacity of CuV₂O₆ synthesized under this optimal condition was higher than that of product synthesized by solid-state reaction.Based on the co-precipitation method,a sol-gel method using NH₄VO₃ and alkaline copper carbonate as raw materials was proposed to prepare the precursor of CuV₂O₆.The CuV₂O₆ was obtained after heat-treatment of the precursor at different temperatures and the investigation of the influence of heat-treatment temperature on the structure,morphology and electrochemical performance of CuV₂O₆ was carried out.The results showed that the CuV₂O₆ heat-treated at 550℃had excellent properties,its initial discharge capacity reaching to 357mAh·g^-1.The investigations of electrochemical performance of Cu_1-xM_xV₂O₆（M=Mn,Ni,Li₂） synthesized by sol-gel method,copper-coated CuV₂O₆ and CuV₂O₆ coated by acetylene black were carried out.The results showed that the Ni doping into the Cu position of CuV₂O₆ crystal could improve its cycle performance,the copper coating on the surface of CuV₂O₆ could enhance its discharge capacity,furthermore,the acetylene black coating on the surface of CuV₂O₆ could improve not only its discharge capacity,but also its cycle performance.