Design,Preparation And Capacitive Performance Of High Density Polyaniline/Graphene Composite

Chemically converted graphene can be self-assembled into electrode materials with three dimensional porous structure,which are suitable used as carbon matrix materials for graphene-based composite materials with high volumetric capacitance.In this paper,we prepared a metal-free composite material with high volumetric capacitance by using graphene hydrogel as the carbon matrix and further composited with polyaniline(PANI).In addition,we clarified the proton bulk transport mechanism of PANI in the porosity-free composite materials,and studied the pseudo-capacitive characteristics of the PANI/graphene composite materials in different electrolyte solutions.What's more,we also revealed the synergistic energy storage mechanism of PANI and carbon nanomaterials in the composites.Here,we proposed the design principle for high volumetric capacitance composite electrodes and densifying preparation method,and obtained a high-density PANI/graphene composite by using static adsorption,chemical in-situ polymerization and capillary evaporation induced drying methods.The PANI/graphene composites exhibited a high gravimetric capacitance and a record high volumetric capacitance of691 F/g and 1036 F/cm~3.The electrode can still deliver 400 F/cm~3 with electrode thickness of 200?m.The high-density PANI/graphene composite was shrinking to the most compact structure and almost porosity-free,which enabled maximized space utilization of the electrode volume.The proton bulk transport mechanism of PANI in the PANI/graphene composite materials was studied,which indicated that the proton could percolate into the inner of the dense micro-particles from the electrode/electrolyte interface along the PANI polymer chain.The bipolaron and polaron play the role of carriers in the proton bulk transport processes.Besides,we also demonstrated the effect of proton bulk transport distance and proton concentrations in the electrolyte on the proton transport processes.The electrochemical performance of the PANI/graphene composites in different electrolytes solution with different pH values was studied.We also revealed the pseudo-capacitive energy storage behavior and the structure conversion which formed during the redox protonation/deprotonation reactions in different electrolyte solutions.The electron transfer and ions transport processes of the PANI/graphene composites in different electrolyte solutions were also discussed to reveal the synergistic energy storage mechanism between PANI and carbon materials.This work inspires new insight into better design and constructing of the novel composite electrodes for energy storage devices to meet the requirements of the practical applications.