Preparation Of Transition Metal Oxides/porous Carbon Composites And Their Co-storage Mechanism For Lithium Storage Mechanism

With the use of graphene,carbon nanotubes and other materials in electrochemical energy storage,carbon-based materials have received a lot of attention.Pyrolytic carbon as a new electrode material has attracted much attention.In this study,the polymer absorbent resin was used as carbon source to explore its electrochemical performance after pyrolysis,but it has a lower capacity as a lithium-ion battery.In addition,transition metal oxides such as iron oxide and zinc oxide have high theoretical specific capacity,but they are easy to produce volume changes and other defects in the charging and discharging process when they are used as anode materials alone,so they are often combined with carbon materials to improve their performance.In this paper,transition metal oxide/N doped carbon anode material was prepared and its electrochemical performance in lithium-ion batteries was investigated.Firstly,iron oxide carbon composites were successfully prepared by high temperature pyrolysis.The effect of iron oxide on the structure and morphology of SAP carbon material at different temperatures was investigated.The composite of ferrous oxide and carbon material with large particles was prepared by treating with hydrochloric acid of a certain concentration,to optimize the structure of the material and improve its electrochemical performance.It was found that the interconnected SAP carbon matrix could not only provide efficient ion diffusion and rapid electron migration,but also prevent the iron oxide nanoparticles from being exposed to the electrolyte,thus giving the material good electrode dynamics and excellent structural stability.Through various characterization methods,it is found that the pore size of the composite surface at 500℃and 600℃is widely distributed and the density is high,mainly because of the advantage of honeycomb wall structure,which provides a high-speed smooth channel for Li⁺diffusion and accelerates the charge transfer.When the temperature is higher,the nanohole on the surface of the composite material shrinks to different degrees under the action of thermal stress.And as the negative electrode of LIBs,the reversible capacity of the composite obtained from 600℃pyrolysis at 0.1A g^-1 current density for 100 cycles is as high as 618.8 m Ah g^-1.Secondly,due to the different physical properties of different transition metals,the degree of disorder of carbon composite materials is greatly different.In this paper,the optimal pyrolysis conditions（600℃）and acid optimization were used to prepare carbon matrix composite electrode materials loaded with different transition metal oxide nanoparticles.Through scanning electron microscopy,Raman,nitrogen adsorption desorption,pore size distribution and other testing methods,it is found that the prepared material is porous carbon material,and it shows dual-function energy storage behavior.The anchoring of different metal ions makes the structure of the carbon matrix show diversity.However,the ion migration rate of the three composite electrodes is fast,ranging from 10^-8 to 10^-12cm² s^-1.The electrode impedance is small in the charging and discharging process,and it has a high reversible capacity and good rate performance depending on the advantage of collaborative energy storage.Finally,due to the unstable cycling performance of the composite materials prepared by carbon materials and single metal oxides at high current density,the N-doped Zn Fe₂O₄ carbon composite was prepared by template method in this paper to study its performance as the negative electrode of lithium-ion batteries.SAP pyrolytic carbon was used as the template,and then some metal particles were removed by etching to expand the channel.The morphology of Zn Fe₂O₄nanoparticles showed uniform loading through high temperature carbonization of polymer and crystallization of inorganic elements.After the addition of nitrogen,the composite modified by nanoparticles showed higher lithium activity.Assists in charge transfer of nitrogen-doped porous carbon.Further,self-growth is carried out in an oxygen-enriched high-temperature environment.After removing the template,the composite material has a large specific surface area.This clear structure and morphology promote the transport of Li⁺,enhance the effective contact area with the electrolyte,and provide a rich range of active sites,ensuring sufficient conversion reactions between Zn Fe₂O₄ and Li⁺during the lithification process,mitigating volume expansion,and prevents crushing/aggregation during long cycles at high current density.