Conductive Layered Cellulose-Based Aerogel Films for Supercapacitor Electrodes and Flexible Sensors

Sophisticated structural designs play a pivotal role in enabling wearable energy storage devices and flexible sensors to achieve optimal performance. In this study, a simple yet effective approach integrating directed freezing, freeze-drying, and hot pressing was adopted for the fabrication of aerogel films. These films consist of cellulose nanofibrils (CNF), carbon nanotubes (CNT), activated carbon (AC), and manganese dioxide (MnO2). Within this composite system, CNT act as efficient electron transport channels, while AC/MnO2 contributes to the energy storage performance based on pseudocapacitance. CNF, on the other hand, forms the main backbone, thereby endowing the films with excellent mechanical properties and a lamellar structure and promoting the uniform dispersion of CNT, AC, and MnO2 via synergistic hydrogen bonding, electrostatic repulsion, and steric hindrance. The AC/MnO2 particles interact with the conductive layered 3D porous network structure formed by the entangled CNF and CNT, which results in strong interfacial bonding. Benefiting from this conductive layered structure, the CNF/CNT-AC/MnO2 (CCAM) aerogel films exhibit promising electrochemical performance when they are used as supercapacitor (SC) electrode materials. Specifically, at a current density of 1 mA cm–2, the mass-specific capacitance and area-specific capacitance achieve 342.8 F g–1 and 1.35 F cm–2, respectively. The as-fabricated asymmetric flexible supercapacitors (FSCs) also exhibit impressive electrochemical performance with an energy density of 31.3 Wh kg–1 and a power density of 446.5 W kg–1. Moreover, they exhibit ultralong cycling stability, which retains 80.5% of their capacity after 10,000 cycles. In addition to their application in energy storage, these aerogel films also perform well as flexible sensors, thereby exhibiting excellent sensitivity. Such a characteristic endows them with great potential for detecting body surface information and monitoring human motion.