Vanadium Oxide/Pitch-Based Cabon Composites And Their Lithium Storage Properties

LIBs have the advantages of high operating voltage,large energy density,long cycle life,safety and environmental protection,etc.,and are widely used in mobile electronic devices such as mobile phones and notebook computers.The performance of the secondary battery places higher requirements.Vanadium oxide has attracted the attention of researchers due to its high theoretical capacity and abundant reserves.However,its low conductivity when used alone as an electrode material for lithium ion batteries and its large volume expansion during charging have limited its wide application.Carbon packages as a modification method,bituminous carbon is used as a carbon source.The introduction of bituminous carbon can improve the conductivity of composite materials on the one hand,and can also effectively suppress the volume expansion during the charging process.Vanadium oxide/pitch composite was prepared in this paper and then used as a positive and negative electrode material for lithium ion batteries for a series of electrochemical characterizations.The main research contents are as follows:?1?Using vanadium pentoxide and coal tar medium-temperature pitch as raw materials,V₂O₅/pitch spherical composite precursor was prepared by a suspension method,and the V₂O₃/pitch-based spherical composite was successfully prepared through non-melting and carbonization treatment.The results show that the V₂O₃/pitch-based spherical composite material still has a reversible specific capacity of 245.2 m Ah/g after 100 cycles under the test conditions of current density of 0.1 A/g and voltage range of 0.05-3V.?2?In order to achieve uniform coating of V₂O₃ by coal tar medium temperature pitch,the experiment uses coal tar medium temperature pitch as raw material,and water-soluble pitch is prepared by mixed acid method;then vanadium pentoxide,oxalic acid,and water-soluble pitch are used as raw materials.V₂O₃/pitch nanocomposite precursor was prepared by a hydrothermal method using a mixed solution of diol and water as a solvent.The precursor was calcined at 550°C in a mixed atmosphere?N₂/H₂?for 3 hours,and the V₂O₃/pitch nanocomposite was successfully prepared.The results show that the V₂O₃/pitch nanocomposite still has a reversible specific capacity of 580 m Ah/g after 100 cycles under the test conditions of current density of 0.1 A/g and voltage range of 0.05-3V.?3?In the experiment,a V₂O₅ precursor was prepared by an inorganic sol-gel method,and the V₂O₅ nanorod was calcined in an air atmosphere at 500°C for 2 hours.In order to investigate the effect of different morphologies of V₂O₅ on its electrochemical performance,a homemade solution of V₂O₅ nanorods and oxalic acid was used as the raw material,and a mixed solution of ethylene glycol and water was used as a solvent.Different surfactants were added to prepare the hydrothermal method.V₂O₅ microspheres with different morphologies;V₂O₅ microspheres were surface-modified and compounded with acidified pitch carbon to prepare V₂O₅/pitch carbon composites.The results show that: using cetyltrimethylammonium bromide as a surfactant,the prepared V₂O₅ is composed of ultra-thin nanosheets,and the presence of nanosheets can still be observed after carbon coating.V₂O₅/pitch carbon composite material has the best cycle stability and rate performance.Under the test conditions of current density of 0.1 A/g and voltage range of 2.0-4.0V,234 m Ah/g is still reversible after 50 cycles Specific capacity.