Preparation And Electrochemical Properties Of CNT/PANI Based Paper Aerogel Composite Electrode Materials

Polyaniline（PANI）has the advantages of simple synthesis,high conductivity and high theoretical capacity.However,due to its own structural defects,PANI is easy to expand in the process of repeated charging and discharging,resulting in structural damage or mass loss.In practical application,the cycle stability is low,and the rate stability is low due to the relatively poor conductivity,Carbon nanotubes（CNTs）are used as electrode materials with high conductivity,stable structure and low capacity.When CNT and PANI are combined to form CNT/PANI electrode,the CNT framework will limit the volume expansion of PANI particles,and it will also act as an effective conductive path to promote the electron transfer of the electrode as a whole.The formed porous electrode will also shorten the diffusion path of electrolyte ions to obtain high-performance CNT/conductive polymer electrode.In this project,CNT/PANI buckypaper-based electrode was prepared by directional pressure filtration technology using CNT,PANI and polyvinyl alcohol（PVA）as raw materials.On the basis of this,the vacuum aeration pressure impregnation technology was used to impregnate the PANI and PVA mixed solution of CNT/PANI buckypaper,and then the CNT/PANI aerogel electrode was obtained after several times freezing thawing cycles and freeze-drying.On the basis of this,we explored the preparation of CNT/PANI aerogel electrode by using vacuum directional pressure impregnation technology for CNT/PANI buckypaper impregnation aniline（ANi）and PVA mixed solution and ammonium persulfate（APS）solution,and then through in-situ polymerization,freezing thawing cycle and freeze drying.The thickness of CNT/PANI buckypaper is 10-30μm,the diameter is 100-140mm,the bulk density is 0.3-0.4 g/cm³,the porosity is 70-75%,and the pore area is65-70 m²/g.The paper electrode can be tightly wound around the glass rod with the diameter of 4 mm without damage.In the CNT/PANI buckypaper,PANI nano to submicron particles are firmly embedded in the CNT conductive network,and the highest PANI loading is 2.7 mg/cm².PANI has the best comprehensive performance when the load is 2.2 mg/cm².Under the test condition of 4 m A/cm^2,the capacity is 1.88F/cm²,the capacity retention rate is 125.78%when the charge discharge cycle is 1200,and the capacity retention rate is 78.43%after 180°bending for 500 times.Under the current density of 5 m A/cm²,the specific capacitance is 0.48 F/cm²,the capacity retention rate is 94.3%,the energy density and power density are 213.75 m Wh cm³and2163.22 m W/cm³,respectively.On the basis of CNT/PANI buckypaper,after directional pressure impregnation of mixed solution of PANI and PVA,a self supporting CNT/PANI aerogel flexible electrode was obtained after freezing,thawing cycle and freeze-drying.The thickness of the porous electrode is 10-30μm,the diameter is 100-140 mm,the bulk density is0.6-0.9 g/cm³,the porosity is 40-45%,the pore area is 25-30 m²/g and the maximum frequency aperture is 100 nm.The electrode can be bent to any shape and the surface does not break.At the same time,when CNT encapsulated PANI particles,PVA aerogels give the CNT network higher strength and flexibility.The maximum load of PANI is 3mg/cm².Under the 4 m A/cm²test condition,the capacity is 2.03 F/cm²,and the capacity retention rate is 36.1%when charging and discharging 5000 cycles,but after 5000cycles,the surface capacitance is still higher to 420 m F/cm².Even if the 180°fold（with sharp creases）is 2000 times,the capacity retention rate is 93%,and the Z-shaped 180°fold（with sharp creases）is 100 times,the capacity retention rate is 81.13%.Such a self supporting CNT/PANI aerogel flexible electrode has excellent electrochemical properties and excellent mechanical properties,and has wide application in the field of wearable electrodes.Based on the direct impregnation of PANI and PVA mixed solution,PANI nanowires,nanorods and nanoparticles were obtained by sequential impregnation of ANi,PVA mixed solution and APS solution.The effect of morphology on the electrochemical properties of CNT/PANI composites was investigated.However,the hard shell of PANI and PVA particles formed on the electrode surface due to the crystallization of PVA during the impregnation process,which reduced the flexibility of the material and caused the plugging effect.At the current density of 4 m A/cm²,the capacitance is 2.16 F/cm².After 500 cycles,the capacitance is 1.29 F/cm²and the capacity retention rate is 51.62%.