| As a new type of battery with high specific energy,lithium-oxygen battery has attracted wide attention due to its high theoretical energy density(3,500 Wh Kg-1).However,many unsolved major scientific problems such as the slow reaction kinetics of three-phase interface,electrolyte decomposition,lithium dendrite,still hinder its practical development.Although noble metal catalyst has high catalytic activity,aside from the high cost,the electrolyte decomposition can hardly be avoided.The introduction of sulfide with high electron conductivity can improve the reaction kinetics,but it is vulnerable to be attacked by oxygen to be deactivated.Compared with traditional metal materials,the new high entropy materials have the advantages of high entropy effect,lattice distortion effect,slow diffusion effect and cocktail effect and display broad application prospects in the field of battery energy storage.By combining the properties of high entropy material and sulfide,it is expected to achieve the construction of stable,highly efficient cathode catalysts and their application in rechargeable batteries.According to the abovementioned aspects as follows:(1)Firstly,the acicular high entropy sulfide(Co Ni Fe Cr Cu)3S4 was in situ grown on carbon cloth by hydrothermal method.Specifically,the nitrate of Co,Ni,Fe,Cr,Cu was dissolved in water,and the sodium sulfide and ammonia were added.After the hydrothermal reaction,the high entropy sulfide in the shape of array needle was generated.The structure and morphology of the high entropy material were characterized by SEM,XRD and XPS,and the high electron conductivity of the high entropy sulfide(0.02 S cm-1)was proved by the impedance test.Taking advantage of the high stability originated from the high entropy effect and the advantage of high electron conductivity of sulfide,the discharge capacity,rate performance and cycle performance of lithium-oxygen battery based on(Co Ni Fe Cr Cu)3S4 cathode have been greatly improved.The discharge capacity of lithium-oxygen battery is up to 17500 m Ah g-1 at a current density of 1000 m A g-1.And the charging potential remains about 3.6V after 100 cycles at a current density of 500 m A g-1.(2)Large,spherical,high entropy sulfide(Co Ni Fe Mn Cr)S2 and its composite with carbon nanotubes(Co Ni Fe Mn Cr)S2/CNT are synthesized by solvothermal method.The results demonstrate that the combination of(Co Ni Fe Mn Cr)S2 and carbon nanotubes effectively reduces the size of high entropy sulfide and improves the mass transfer kinetics of the material.The catalytic activity of oxygen reduction/oxygen evolution reaction of the lithium-oxygen battery based on the(Co Ni Fe Mn Cr)S2/CNT cathode is effectively improved,and the discharge voltage is increased to 2.8 V,while the charging voltage is maintained at 3.3 V.Further,(Co Ni Fe Mn Cr)S2/CNT can also effectively regulate the generation of discharge products,and the generated spherical discharge products are prone to be decomposed,contributing to sueprior cycle performance.Under the current density of 200 m A g-1 and the limited capacity of 500 m Ah g-1,the charging voltage of the(Co Ni Fe Mn Cr)S2/CNT-based lithium-oxygen battery is maintained at 3.3 V aftera charge-discharge cycle of 375 h.The results show that the high entropy sulfide composite carbon material can effectively reduce the overpotential of charge and discharge while maintaining the stability of high entropy material.A new strategy for constructing high entropy sulfide catalyst is proposed in this paper to improve the catalytic activity and stability of cathode materials.According to a series of characterization technologies,the reaction kinetics and thedeposition and decomposition behavior of the discharge product for lithium-oxygen battery were studied,providing a new idea for the development of cathode catalysts in lithium-oxygen battery,and also providing a theoretical and experimental foundation for the application of high entropy materials in secondary energy storage system. |
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