Preparation And Electrochemical Properties Of Cobalt Oxide/carbon Composite As Electrode Materials

The rapid development of electric vehicles and large-scale energy storage systems has accelerated the update of new-generation batteries which simultaneously possess high energy density and low cost.Lithium-sulfur batteries have attracted widespread attention from researchers due to the high energy density(2600 Wh kg^-1).However,in the practical application of lithium-sulfur batteries,some inherent disadvantages of sulfur electrodes have severely limited their development.The disadvantages include the extremely poor conductivity of sulfur at room temperature,the shuttle effect of lithium polysulfides(intermediate products during the charge and discharge reactions),and the different density of the products during the charge and discharge reactions.Cobalt oxide(CoO),as a polar additive,has the advantages of low cost,simple preparation,and strong adsorption capacity.It is a very promising sulfur host material,but its practical application is still limited by insufficient conductivity and easy agglomeration.In order to solve the problems of insufficient conductivity and easy agglomeration of CoO in the application process,this paper uses carbon nanotubes(CNTs)and reduced graphene oxides(r GO)to load CoO nanoparticles as sulfur carriers for lithium-sulfur batteries.Subsequently,S-CoO/CNTs and S-CoO/Hr GO were prepared by compounding them with elemental sulfur.The micro-morphology,physical properties,electrochemical performances and the charge-discharge reaction mechanism of S-CoO/CNTs and S-CoO/Hr GO composites were explored in detail,which provided theoretical and experimental basis for the subsequent research and application of lithium-sulfur batteries.(1)CoO/CNTs three-dimensional porous material was prepared by spray-drying method and subsequent calcination treatment,and then it was compounded with sulfur by the melt diffusion method to obtain S-CoO/CNTs composite.The effects of CoO content on micro-morphology,physical properties and electrochemical properties of S-CoO/CNTs composite were discussed.The results show that,as the content of CoO increases,the electrochemical performance increases first and then decreases.The electrochemical performance of the prepared S-CoO/CNTs-M cathode was the best when the molar concentration of Co²⁺in the precursor solution was 3×10^-3 m M.It exhibited a high initial discharge specific capacity of 1345 m Ah g^-1 under 0.2 C.After100 cycles,a discharge specific capacity of 1119 m Ah g^-1 can still be maintained.(2)CoO/Hr GO porous reduced graphene oxide microspheres with three-dimensional hollow structure and CoO/r GO microspheres without hollow structure were prepared by spray drying and high-temperature calcination.Subsequently,S-CoO/Hr GO and S-CoO/r GO were prepared by compounding them with elemental sulfur.The differences between S-CoO/Hr GO and S-CoO/r GO in micromorphology,physical properties,and electrochemical performance were explored.The results show that the hollow CoO/Hr GO exhibited better electrochemical performance than non-hollow S-CoO/r GO.S-CoO/Hr GO cathode show a specific discharge capacity of 1435 m Ah g^-1 in the first cycle under the test condition of 0.2 C.After 150 cycles,a reversible discharge specific capacity of 1010m Ah g^-1 can still be maintained.