Surface Modified Nanocellulose Fibers Yield Conducting Polymer-Based Flexible Supercapacitors with Enhanced Capacitances

Abstract

We demonstrate that surface modified nanocellulose fibers (NCFs) can be used as substrates to synthesize supercapacitor electrodes with the highest full electrode-normalized gravimetric (127 F g(-1)) and volumetric (122 F cm(-3)) capacitances at high current densities (300 mA cm(-2) ≈ 33 A g(-1)) until date reported for conducting polymer-based electrodes with active mass loadings as high as 9 mg cm(-2). By introducing quaternary amine groups on the surface of NCFs prior to polypyrrole (PPy) polymerization, the macropore volume of the formed PPy-NCF composites can be minimized while maintaining the volume of the micro- and mesopores at the same level as when unmodified or carboxylate groups functionalized NCFs are employed as polymerization substrates. Symmetric, aqueous electrolyte-based, devices comprising these porosity-optimized electrodes exhibit device-specific volumetric energy and power densities of 3.1 mWh cm(-3) and 3 W cm(-3) respectively; which are among the highest values reported for conducting polymer electrodes in aqueous electrolytes. The functionality of the devices is verified by powering a red light-emitting diode with the device in different mechanically challenging states.

Flexible all-solid-state micro-supercapacitor based on Ni fiber electrode coated with MnO2 and reduced graphene oxide via electrochemical deposition

“…As one of the key energy storage devices, conventional supercapacitors are still too heavy, thick, rigid and bulky to fully meet the practical requirements for portable devices due to the presence of inactive components such as metal substrates, binders and conductive additives [26]. In order to meet the growing demands of modern society, some reformations were brought into SCs to make them small, thin, lightweight, flexible and even wearable.…”

Assembly of flexible CoMoO4@NiMoO4·xH2O and Fe2O3 electrodes for solid-state asymmetric supercapacitors

“…However, meeting the increasing demand of future emerging markets are lightweight, solid state, and flexible energy devices4567. Among them, supercapacitors (SCs) are considered as promising candidates that can offer long cycle life, high power density, fast charge/discharge rates and safety89101112131415. Unfortunately, the energy densities of supercapacitors are still unsatisfactory, which seriously limit their practical applications.…”

Carbonized cellulose beads for efficient capacitive energy storage

“…Two-electrode symmetric supercapacitor devices hermetically heat-sealed in laminated aluminum foil were made as previously described (Wang et al 2014(Wang et al , 2015. A piece of filter paper, pre-soaked with 1.0 M H 2 SO 4 solution and used as the separator, was sandwiched between two carbon electrodes.…”

“…Supercapacitors can be divided into two categories according to their charge storage mechanisms: pseudocapacitors and electrical double layer capacitors (EDLCs) (Wang et al 2012;Winter and Brodd 2004). Pseudocapacitors store electrical energy by fast, reversible faradaic reactions (redox reactions, electrosorption or intercalation) occurring on the electrode materials, typically of metal oxides (Jeong et al 2016;Wang et al 2013a) or conducting polymers (Wang et al 2014(Wang et al , 2015Zhao et al 2017). EDLCs are associated with an electrodepotential-dependent accumulation of electrostatic charge at the interface between the electrolyte and the electrode, typically of carbon (Ghosh and Lee 2012).…”