Electrospinning-Assisted Assemblies Of MOF-based Derivative Materials In Li-ion Batteries

In this paper,different kinds of metal organic frameworks?MOFs?particles are assembled into one-dimensional nanofibers by electrospinning technology,and then MOF-based composite carbon materials containing transition metal oxides is obtained by using post-processing.In this process,different materials are prepared by adjusting the conditions for preparing MOFs,spinning conditions,calcination conditions,etc.,which are used as anode materials for lithium ion batteries.When the prepared materials are used as a lithium battery performance study,it can be found that different components and structures of the material have a huge impact on its lithium battery performance,so a more excellent MOF-based composite carbon material is prepared.The main content and results of this paper are as follows:1. Prepared ultra-small SnO₂/N doped core-shell structure carbon-based composite nanofibers?PCNF@SnO₂@CN?.First,the prepared ZIF-8 particles were assembled into polyacrylonitrile?PAN?electrospun fibers by using electrospinning technology,and further converted into N-doped porous carbon nanofibers?called PCNFs?by subsequent high-temperature calcination.Then,by the hydrothermal method,using Sn Cl₂·2H₂O as a precursor,ultra-small SnO₂crystals?3-5 nm?were successfully embedded into PCNFs?PCNF@SnO₂?.Finally,by in situ polymerizing dopamine hydrochloridea?PDA?on the surface of the fiber and calcined further,a coaxial porous carbon nanofiber?called PCNF@SnO₂@CN?with ultra-small SnO₂ nanocrystals embedded in the interface was prepared.The prepared one-dimensional fiber has a porous core-shell structure,which reserves space for the material to expand during charging and discharging,which can effectively relieve the pressure caused by the volume change,to ensure that the structure of the material was more stable,and high specific surface area facilitates full contact between active material and electrolyte,ultra-small SnO₂nanocrystals can effectively shorten the ion diffusion path,thereby enhancing the reaction kinetics,especially the outer layer of nitrogen-doped carbon can further improve the conductivity and capacitance while forming a stable solid electrolyte interface?SEI?layer and maintain its mechanical integrity.Thanks to the above advantages of the structure and materials,the lithium battery performance test results show that PCNF@SnO₂@CN has much higher lithium battery performance than other comparative samples,it exhibits a high capacity of 1101 m Ah g^-1after 100 cycles at 0.5 Ag^-1,and at 1 Ag^-1,it exhibits a high capacity of 994 m Ah g^-1after 200 cycles.2. Co₃O₄/N-doped carbon nanofibers?ES-CNCo₃O₄@rGO?with graded pore structure were prepared.First,coat the surface of the ZIF-67 cube with high crystallinity with a layer of GO to obtain the ZIF-67@GO nanocube;then assemble it into one-dimensional composite nanofibers by electrospinning;finally,after high-temperature reduction and inert atmosphere,ES-CNCo₃O₄@rGO was prepared by two-step heat treatment at low temperature in air.The prepared material has the following advantages:first,the specific surface area and porosity of the material were improved by increasing the crystallinity of ZIF-67,so that the material has better stability.Second,the GO nanosheets were coated on the surface of the ZIF-67 nanocube.Since GO was reduced to rGO during the calcination process,the conductivity and capacity of the composite nanofibers can be effectively improved,while improving the stability of the particles.In particular,the carbon layer derived from the electrospun polymer can prevent the rGO layer from falling off,thereby further improving the cycle stability of the anode material.Lithium battery performance test results show that ES-CNCo₃O₄@rGO has higher specific capacity and rate performance and cycle stability compared to non-spun samples,and can maintain 1315 m Ah g^-1after 100 cycles of 0.1 Ag^-1.The capacity can maintain a high reversible capacity of 1234 m Ah g^-1after 500 cycles under 1 Ag^-1.