All-carbon composite paper as a flexible conducting substrate for the direct growth of polyaniline particles and its applications in supercapacitors

Polyaniline (PANI) has been recognized as an ideal candidate for electrode materials in supercapacitors. However, its relatively low electrical conductivity and poor cyclic stability greatly limit its potential applications in supercapacitors. In this study, nano-sized PANI particles have been immobilized onto a conducting paper-like substrate which utilizes graphene (G) sheets and pristine carbon nanotubes (CNTs) as building blocks, thus obtaining flexible G-CNT-PANI ternary hybrid papers with hierarchical nanostructures. The ternary hybrid paper exhibits a reversible capacity of up to 432 F g(-1) at a discharge rate of 0.5 A g(-1), which is much larger than that of bare G-CNT composite paper (172.4 F g(-1)); and, its cyclic performance is dramatically enhanced sustaining greater than 96% of its original capacitance after 600 charge-discharge cycles. The dimensional confinement of PANI particles on the surface of the all-carbon planar substrate prohibits volume expansion and shrinkage upon electrolyte soakage, and meanwhile, the immobilized PANI particles can endow the all-carbon composite paper with pseudocapacitive behavior and an improved electrode-electrolyte interfacial structure. Besides, the good electrical conductivity of the G-CNT composite paper provides improved conductive pathways for charge transfer at the electrodes thus resulting in superior capacitance during charge-discharge processes. Therefore, the method reported here provides a simple and efficient approach to fabricating G-CNT-PANI ternary hybrid papers with designed hierarchical nanostructures, and may be easily extended to the design of next generation high performance flexible supercapacitors.