EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Nowadays there is an increasing interest on the development of energy storage systems for electric mobility that could provide enough energy and reduce mass from vehicles. Structural supercapacitors based on composite materials are a potential alternative to satisfy both requirements. Transferring part of the energy storage responsibility towards structural elements will reduce weight from batteries currently used in electric vehicles.

Composite laminates are common structural elements due to their excellent mechanical properties and low weight. Electrical conductivity of carbon fiber also makes it a suitable material for energy storage applications. Supercapacitors storage capacitance rely heavily on the specific surface area of electrodes, which is the main weak point of the fibers.

Different structures with high specific surface have been studied to modify carbon fiber surface and increase their energy storage capacitance. Carbon nanoparticles, such as GNP, MWCNT and carbon black, with specific surface areas from 65 to 750 m2/g and excellent electrical conductivity have been deposited on the surface of carbon fibers. Synthesis of structures that can exceed 2000 m2/g of specific surface area, such as carbon aerogels and metal-organic frameworks, have also been studied.

Influence of particles and deposition technique on the multifunctional behavior of modified electrodes have been studied. Electrochemical characterization through cyclic voltammetry shows important improvements on the capacitance of the fibers. Modified carbon fibers mechanical properties have been evaluated with single filament tensile tests. Deposition of carbon nanoparticles show capacitance values up to 2 F/g keeping tensile strength close to 4000 MPa.

Structural supercapacitors were built with the modified carbon fibers and solid electrolyte developed. Both electrochemical and mechanical characterization were performed to evaluate their suitability for structural applications and study the effect of electrode-electrolyte interphase. These multifunctional composites store three times more energy than pristine carbon fiber with good mechanical properties.