Electrochemical Performance Optimization And Mechanism Analysis Of Sponge-NiMn Oxide/hydroxide Flexible Electrode

With the rapid development of portable devices and wearable electronic devices,the preparation of flexible energy storage devices has become an emerging field.Flexible supercapacitors with various microstructures and macro characteristics have been extensively studied.The research on flexible electrodes has promoted the development of flexible energy storage technology and wearable electronic devices.Among them,the flexible three-dimensional porous electrode has good flexibility,and a large amount of electrochemically active materials can be supported on the flexible substrate material,making it possible to prepare electrodes with high energy density.The purpose of this paper is to study the flexible electrode with excellent performance.The melamine sponge is used as the flexible substrate.The loading and performance optimization of nickel-manganese oxide/hydroxide is the main research content.Nickel-manganese oxidation is performed by means of water bath,ice bath,and calcination.Nano-materials including Ni Mn oxides/hydroxides,PPy,graphene was analyzed to understand mechanism of performance optimization.The main experimental content and conclusions are as follows:(1)Commercially available melamine sponges were used as flexible substrates.Ni Mn LDH nanosheets were modified on the surface of the sponge by hydrothermal reaction.With a one-step calcination process,Ni Mn LDHs were converted into nickel-manganese oxide.By adjusting the proportion of nickel and manganese,the effects of composition on morphology and electrochemical performance were studied.The results showed that calcination can effectively transform sponges into cross-linked porous carbon and oxidize Ni Mn hydroxides.The porous carbon-Ni Mn oxides has good interface bonding stability,and the three-dimensional network structure composite material can efficiently conduct electrons.When Ni:Mn is 3:1,it has the best specific capacitance.At a current density of 0.5 A g^-1,the specific capacitance is 870 F g^-1.Also,the material has good cycle stability.After 5000 times repeakted charge and discharge,the capacitance retained 89.9%.(2)Based on the research of the previous chapter,flexible electrodes were further optimized.Polypyrrole nanoparticles were grown on the surface of the sponge-Ni Mn LDH electrode,and the sponge-Ni Mn LDH-PPy composites with different polypyrrole loadings were obtained by adjusting the polymerization time.Studies have shown that the specific capacitance and cyclic stability of flexible electrodes can be improved by depositing PPy nanoparticles,but too dense PPy nanoparticles prevent the inner layer of Ni Mn LDH nanosheets from participating in the reaction,leading to degradation of electrochemical performance.Sponge-Ni Mn LDH-PPy has the best electrochemical performance(1103.1 F g^-1).After 5000 cycles of charge and discharge,the specific capacitance retained 92.8%of the initial capacitance.(3)Graphene is a two-dimensional layered material with good structural stability and electrical conductivity.Wrapping graphene on the three-dimensional fibers of the sponge can further enhance the flexibility and stability of the flexible electrode.Graphene was evenly covered on the surface of the sponge,providing a large amount of specific surface area for the growth of Ni Mn LDH.The staggered growth of Ni Mn LDH nanosheets can not only provide rapid electrolyte transport,but also alleviate volume changes during charge and discharge.At the current density of 1 A g^-1,the specific capacitance of sponge-graphene-Ni Mn LDH reaches 1260.1 F g^-1,and 91.5%of the initial capacitance is retained after 5000 cycles of charge and discharge.