Supercapacitors are promising energy storage devices for flexible electronics and micro-energy systems, but their performance is often limited by electrode materials. Graphene is an attractive electrode material for supercapacitors, but its tendency to restack during fabrication often limits ion transport and reduces energy storage efficiency.
In this study, the researchers introduce a capillary slit-induced self-assembly strategy that uses narrow glass slits to guide the arrangement of graphene sheets driven by evaporation. During drying, capillary forces and microscale flows within the slit guide sulfuric acid-treated graphene oxide and commercial graphene flakes to stack into a highly oriented laminated structure. This ordered laminated structure provides effective paths for ion movement and electron transport.
In addition to structural alignment, the researchers applied a mild sulfuric acid treatment to activate oxygen-containing functional groups on graphene oxide. This treatment converts inactive epoxy groups into more electrochemically active hydroxyl groups, enhancing pseudocapacitive reactions without compromising structural stability. After thermal reduction, the freestanding graphene films achieve a favorable balance between electrical conductivity and pseudocapacitance.
As a result, the slit-assembled graphene films exhibit an ultrahigh areal capacitance of 1,589.78 mF cm^-2 and maintain 99.80% of their initial capacitance after 20,000 charge-discharge cycles. Compared with films prepared by conventional drop-casting methods, the capillary slit-assembled electrodes show significantly improved energy density, power density, and cycling stability.
This work provides a simple and scalable approach to fabricating graphene electrodes with enhanced structural integrity and electrochemical performance. The approach provides new opportunities for designing compact, flexible, and durable energy storage systems for future electronics and smart devices. The work entitled “Capillary slit induced graphene laminate films towards enhanced areal capacitive energy storage” was published on Energy Materials (published on Jan. 19, 2026).
DOI: 10.20517/energymater.2025.133