Preparation Of Nanosheets-based Self-assemblies And Their Energy-storage Performance In Secondary Batteries

Rechargeable batteries were widely used in our daily life,in which some new-typed batteries developed in recent years aroused great interest.Lithium-sulfur batteries（LSBs）,whose high-energy density make it impossible to be utilized as a traction-battery in long-term vehicles.While the insulation and great volume-change of elemental sulfur、shuttle effect resulted from polysulfides excessively hinder the development of LSBs.Besides,rechargeable aqueous zinc-ion batteries（AZIBs）are promising to be used in wearable devices owing to the low-cost and eco-friendly.However,the problems of low potential range、unsatisfactory electrode materials and instability when applied in flexible wearable devices are seriously unsolved.Herein,sheet-structured nanomaterials self-assemblies and their applications in secondary batteries are profoundly studied to bring the properties of buffering volume-change and fastening ion and electron transport,which deliver stable high-performance properties.The contents and innovations in our studies are as followed:（1）Three-dimensionally sheet-assembled porous CuS/S composite was prepared by using novel sheet-structured metal organic frameworks（MOFs）.The unique structure benefit for the embedment of sulfur particles,and expose more active sites to adsorb polysulfides in electrolyte.Adsorption energy between the frame and polysulfides were further calculated by density functional theory.When cycled at 0.1 C,the CuS/S cathode showed a stable capacity of 750 m Ah g^-1.The rate-performance after three rounds still delivered a good reversibility.（2）A template-sacrificing method as employed to obtain a uniqueμ-cube-S composite（CuS/S/Co₃O₄）,which composed of sheet-assembled Co₃O₄ shell and CuS core.Sulfur was loading in the space between two phases.It is beneficial to accommodate volume-change of elemental sulfur and prevent from polysulfide dissolution.Theμ-cube-S cathode showed a high capacity of 1480 m Ah g^-1 at the current density of 0.1 C,while the Coulombic Efficiency over 99%.When cycled at 0.2 C for 400 times,the capacity was still over 500m Ah g^-1,with the CE over 99.83%.It showed a high capacity over 490 m Ah g^-1 at 0.5 C,with the CE over 96%.The low-temperature tolerance test at?5°C showed an extraordinary performance,it delivered a capacity over 700 m Ah g^-1 at 0.2 C after 200 cycles.（3）VS₂ nanosheets and Zn nanowires were hydrothermally and electrodeposited grown on the substrate of carbon cloth,respectively.Polyvinyl alcohol-zinc acetate-manganese acetate hydrogel（PVA-Zn/Mn）was employed as solid electrolyte.After bending 60°,90°and 180°,the flexible self-healing battery showed a capacity of 110,121 and 106 m Ah g^-1,respectively,when cycled at 50 m A g^-1.Even being cut and healed for several times,the battery showed an excellent self-healing performance.In summary,nanosheet-assembled materials applying in secondary batteries efficiently enhance the electrochemical performance.The stable structure,which possesses a large specific area provides more active sites,and buffers the volume-change during ion insertion/desertion.Depending on the improvement of preparation technologies and the investigation of more emerging materials,it is expected that the nanosheet-structured materials would be applied in many fields to significantly promote the development of novel batteries.