Flexible films with three-dimensional ion transport channels: Carbon nanotubes@MnO2 as interlayer spacers in porous graphene electrodes for high-performance supercapacitors

Abstract

Flexible supercapacitors have a high potential for application in wearable electronics and microdevices, but their commercial appeal is limited because of low energy density. To overcoming this challenge, this paper proposes a strategy to fabricate dense films with high specific capacitance. A composite film with rapid ion diffusion channels and a high density of 0.86 g cm–3 was synthesized by combining porous graphene nanosheets (PGNs), carbon nanotubes (CNTs), and MnO2 nanosheets. The incorporation of CNTs@MnO2 between graphene layers effectively mitigated aggregation and enhanced electrolyte ion diffusion within the dense graphene structure. PGNs and CNTs synergistically established a three-dimensional pathway for efficient ion transport while optimizing electron dynamics. In 1 mol L–1 Na2SO4 electrolyte, the material exhibited a gravimetric capacitance of up to 320 F g–1 at 1 A g–1 and a volumetric capacitance reached 275 F cm–3. Furthermore, the assembled asymmetric supercapacitors, PGNs-CNTs@MnO2//PGNs-CNTs, exhibited a gravimetric energy density of up to 26.4 Wh kg–1 and a volumetric energy density of up to 22.7 Wh L–1. These findings offer insights into advancing flexible supercapacitor technology for diverse applications.