Design And Synthesis Of Flexible Self-supporting Materials For Lithium/Sodium/Potassium Ion Batteries

Electrochemical energy storage has attracted wide attention due to its high energy density,good safty,low cost and eco-friendly.However,with the continuous development of the economic society,people have put forward higher requirements of lithium-ion batteries.In order to solving the low energy density,short cycle life,poor rate performances and poor flexibility of the electrode materials in the current lithium/sodium/potassiumion batteries.In this paper,three types of free-standing electrode include graphenebased self-supporting materials,carbon cloth-based self-supporting materials and electrospinning nanofiber membrane were prepared.The main work are as follows:1.Fabrication of graphene-based flexible self-supporting electrodes by a composite method.First,Ag-Fe2O3 hollow nanospheres were fabricated by a templatefree method and the formation mechanism of hollow structure were explored.The decoration of Ag nanoparticles can enhance the electronic conductivity of the composites and the hollow structure can buffer the volume expansion during the cycling,thereby improving the electrochemical performances of composites.Then,Ag-Fe2O3 nanospheres were filtered with graphene in a certain proportion,the obtained selfsupporting electrode exhibited excellent flexibility and mechanical strength.When displayed as free-standing electrode,Ag-Fe2O3-rGO composite maintained a capacity of 539 mAh g-1 at a current density of 100 mA g-1 after 400 cycles.2.Fabrication of carbon cloth-based flexible self-supporting electrodes by a load method.Metal 1T phase MoS2 nanosheets with good conductivity were grown on the carbon cloth.Ultra-small SnS2 nanoparticles were dispersed in the surface of MoS2 nanosheets uniformly which could improve the structure stability and accelerate the transport of electron.The prepared electrode displayed a good flexibility and mechanical strength.When applied as a binder-free,flexible Li-ion battery anode,it exhibited admirable cycling stability and excellent rate performance.A highly flexible battery based on SnS2/MoS2/carbon fiber cloth and LiCoO2 was fabricated,demonstrating excellent mechanical flexibility and cycling stability.The flexible full cell which could use as energy supply equipment for the commercial LED light.3.Fabrication of nanofiber-based flexible self-supporting electrodes by one-step electrospinning method.PMMA used as a pore former to fabricate hollow structure of Sb@N-C nanotubes.One-dimensional hollow structure of Sb@N-C nanotubes can accommodate the volume expansion of Sb nanoparticles.Sb nanoparticles embedded in the hollow N-doped carbon shell can prevent agglomeration of the electrode so that can improve the cycling performance of Sb@N-C electrode.Benefiting from the advantages above,the anode of Sb@N-C nanotubes demonstrated remarkable electrochemical properties in LIBs,SIBs and PIBs compare to pure carbon,Sb@N-C nanofibers.Furthermore,Sb@N-C nanotubes exhibited high flexibility and mechanical strength which could be used as free-standing electrode directly,so that can increase the energy density of the full cell.4.Fabrication of nanofiber-based flexible self-supporting electrodes by two-step electrospinning method.We synthesized hollow CoSn nanoboxes encaplasulated in the N-doped carbon nanotubes by the coprecipitation and electrospinning.Hollow structure of nanotubes and the interior present in the hollow CoSn nanoboxes can provide extra space to tolerate volume expansion,so that improve the cycling performance.The prepared nanofiber membranes exhibited high flexibility and mechanical strength,when applied as free-standing electrode,the CoSn@N-C nanotubes exhibited excellent electrochemical properties.What's more,the prepared electrode of CoSn@N-C nanotubes can maintain a reversible capacity of 178 mAh g-1 at a current density of 500 mA g-1 after 2000 cycles in PIBs,which demonstrating an excellent structural stability.