Solution-Processed Graphene/MnO₂ Nanostructured Textiles for High-Performance Electrochemical Capacitors

TLDR

Large‑scale energy storage systems require low‑cost, high‑power, long‑life devices, yet achieving grid‑scale performance demands environmentally friendly, low‑temperature, scalable materials. This study demonstrates that solution‑exfoliated graphene nanosheets can be conformably coated onto three‑dimensional porous textiles, enabling high loading of active materials and efficient electrolyte access. By electrodepositing pseudocapacitive MnO₂ nanomaterials onto the graphene textile and assembling asymmetric capacitors with a SWNT textile negative electrode in aqueous Na₂SO₄, the hybrid achieves a specific capacitance of 315 F g⁻¹. The resulting devices deliver a maximum power density of 110 kW kg⁻¹, an energy density of 12.5 Wh kg⁻¹, retain ~95 % capacitance after 5,000 cycles, and illustrate the promise of low‑cost, high‑performance energy textiles for large‑scale storage.

Abstract

Large scale energy storage system with low cost, high power, and long cycle life is crucial for addressing the energy problem when connected with renewable energy production. To realize grid-scale applications of the energy storage devices, there remain several key issues including the development of low-cost, high-performance materials that are environmentally friendly and compatible with low-temperature and large-scale processing. In this report, we demonstrate that solution-exfoliated graphene nanosheets (∼5 nm thickness) can be conformably coated from solution on three-dimensional, porous textiles support structures for high loading of active electrode materials and to facilitate the access of electrolytes to those materials. With further controlled electrodeposition of pseudocapacitive MnO2 nanomaterials, the hybrid graphene/MnO2-based textile yields high-capacitance performance with specific capacitance up to 315 F/g achieved. Moreover, we have successfully fabricated asymmetric electrochemical capacitors with graphene/MnO2-textile as the positive electrode and single-walled carbon nanotubes (SWNTs)-textile as the negative electrode in an aqueous Na2SO4 electrolyte solution. These devices exhibit promising characteristics with a maximum power density of 110 kW/kg, an energy density of 12.5 Wh/kg, and excellent cycling performance of ∼95% capacitance retention over 5000 cycles. Such low-cost, high-performance energy textiles based on solution-processed graphene/MnO2 hierarchical nanostructures offer great promise in large-scale energy storage device applications.