| Li-ion batteries have a promising future in many energy storage devices.The design of the material structure,the preparation of electrode plates and the assembling process of the battery have great influence on the performance of the lithium battery.Binder,an important part of Li-ion battery electrodes,can conduct carbon black,the electrode material and electrode effectively,ensure uniform coating on the collection,and reduce the effect of the volume change in the charging and discharging process.Consequently,binder is crucial to the electrochemical performance of Li-ion batteries.Moreover,the structure design of electrode materials is another key factor to effect electrochemical performance.For example,the setup of heterostructure improves the stability of the composite materials by buffering volume change of electrode materials,lithium storage performance via providing more lithium ion storage sites,and the electrochemical performance by the synergy work of all the components.Study on coating with conductive polymer layer is drawn more and more consideration for the benefit on solving the problems of the nanoparticles agglomeration,increasing the electrical conductivity and stability of the electrode material.In this paper,alpha-ferric oxide and tin dioxide were adopted as materials for unique nanostructure and high theoretical capacity,respectively.A novel snowflake alpha-ferric oxide/tin dioxide heterostructure nanocomposites was synthesized via two steps hydrothermal synthesis methods.Moreover,nanocomposites and conductive carbon materials were also made as to improve its electrochemical performance.The specific research contents are as follows:1.Battery binder plays an important role in the battery performance of reversible capacity,life cycle,and internal resistance.In this study,water-soluble binder CMC and oil soluble PVDF were employed for study on the electrochemical performance impact of alpha-ferric oxide.The results showed that the alpha-ferric oxide with CMC binder had a better cycling performance and rate performance.It exhibited a high discharge capacity of 1372.6 mA h·g-1 in its initial cycle at a current density of 100 mA·g-1.It also showed very fast capacity fading with a very low reversible capacity of 402 mA h·g-1 after 50 cycles.And the coulomb efficiency reached nearly 98%.Whereas using PVDF,the reversible capacity of composite only reached 177 mA h·g-1 after 50 cycles.Moreover,the cycle stability of ferric oxide as a single component material is not ideal for lithum battery anode electrode.2.A novel snowflake alpha-ferric oxide/tin dioxide nanomaterials with heterostructure was synthesize by two-steps hydrothermal methods.Compared with the alpha-ferric oxide with a single component,the electrochemical performance was improved.Under the current density of 100 mA·g-1,the reversible capacity of composite reached high than 650 mA h·g-1 after 200 cycles.And the coulomb efficiency reached nearly 99.5%.The good synergy work between these two components can attributed to increase the contact area and efficiency between the electrolyte and material,resulting in reducing the diffusion and transport path of lithium ions and electrons.This work has important value and reference significance for the design of the structure of lithium ion batteries materials and the mechanism research in energy storage materials.3.Based on the structure design,electrochemical performance,and electrical conductivity of alpha-ferric oxide and tin oxide composite materials,alpha-ferric oxide/tin dioxide nanocomposite material coated by conductive polymer layer of polypyrrole was synthesized.The results of electrochemical performance test showed that the modified materials had a better stable cycling performance,Under the current density of 100 mA·g-1,the reversible capacity of composite reached high than 521.4 mA h·g-1 after 120 cycles.And the coulomb efficiency reached nearly 99.2%.This work also revealed that the method of coating with conductive polymer is a good route to improve the electrical conductivity of the composite material and lithium storage ability of battery cathode. |
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