Preparation And Lithium Ion Batteries Performance Of Co And V-based Oxide Anode Materials

Lithium-ion batteries（LIBs）are one of the most important energy storage devices in today’s society,and they are widely used in portable electronic devices,electric vehicles,aerospace and energy storage systems.The electrochemical performance of LIBs is heavily determined by the properties of electrode materials.Comparing with traditional commercial anode materials,transition metal oxides（TMOs）have the advantages of high energy density,simple preparation method and low cost,which makes them be the ideal electrod materials for LIBs.However,the intrinsic shortages of volume expansion,poor conductivity and easy agglomeration greatly limit the application of TMOs in the field of LIBs.In this paper,Co and V-based oxides were modified from the perspectives of improving the stability of electrode materials,enhancing their conductivity and constructing special structures,and CoO@N-C,Co-V₂O₃-24 and Co₃V₂O₈@Ni Co LDH were successfully synthesized.We not only investigated the morphologies,structure,chemical composition and synthesis principle of electrode materials,but also systematically studied the effects of the introduction of carbon,the doping of metal element and the construction of composite materials on the electrochemical performance of TMOs.The main contents of this paper are as follows:1.Co-MOFs precursors were firstly prepared by precipitation at room temperature.After being annealed in the air,Co-MOFs precursors were turned into porous Co₃O₄.Then,dopamine hydrochloride（DA）was used to synthesize Co₃O₄@PDA.Finally,CoO@N-C cubes were obtained after the heat treatment of Co₃O₄@PDA under the protection of argon.The results of material characterization showed that CoO@N-C cubes were piled up by CoO which were coated with N-C layers.The electrochemical results indicated that CoO@N-C delivered the specific capacity of 931 m Ah/g at 0.5A/g and 649.8 m Ah/g at 1 A/g after 1000 cycles.The introduction of N-C layers decreased the agglomeration and volume expansion,while the conductivity of the anode materials was increased during the charging/discharging process.CoO@N-C cubes can exhibite excellent cycling properties and high reversible specific capacity.2.Co（NO₃）₂·6H₂O and VO（acac）₂ were used to prepare Co-V-IPA precursors through solvothermal method.Followed by heat treatment under the protection of argon,Co-V₂O₃-24 was obtained under the optimized reaction conditions by adjusting the time of solvothermal procedure,the amount of metal salts and the species of metal salts.SEM and TEM showed that Co-V₂O₃-24 were spheres with yolk-shell structure.The shell of Co-V₂O₃-24 spheres was assembled with thin nanosheets,while the inner yolk had porous structure.The results of material characterization indicated that Co was uniformly doped and evenly distributed in V₂O₃ spheres.Electrochemical testing demonstrated that Co-V₂O₃-24 exhibited reversible specific capacity of 986.2 m Ah/g at 0.5 A/g and 457.6 m Ah/g at 5 A/g after 2200 cycles.The excellent lithium storage performance mainly benefited from the novel 3D hierarchical structure and Co doping.3.Co₃V₂O₈ was prepared by solvothermal process and heat treatment.By using PVP-Co₃V₂O₈as templates,3D hierarchical composite Co₃V₂O₈@Ni Co LDH was synthesized after refluxing procedure.The morphologies and structure testing results displayed that only with the assistance of PVP,Ni Co LDH can grow on the surface and in the internal space of Co₃V₂O₈ successfully and uniformly.Electrochemical investigation results showed that Co₃V₂O₈@Ni Co LDH exhibited 1329.4 m Ah/g at 1A/g and 893.1 m Ah/g at 5 A/g after 950 cycles.The composite materials can achieve excellent lithium storage performance,which may be attributed to high conductivity,great stability and the synergistic effect of hybrid materials.