Scientists from Austria’s Graz University of Technology (TU Graz) are investigating a hybrid system that combines a lithium-ion battery with a supercapacitor.
The team aims to find an alternative electrochemical energy storage system for use in e-mobility and storing renewable sources
Research centered around a variant of a hybrid supercapacitor that uses a carbon and aqueous sodium iodide (NaI) electrolyte, with a positive battery electrode and a negative supercapacitor electrode.
Researchers investigated how the electrochemical energy storage in this supercapacitor works and what happens in the nanometer-sized pores of the carbon electrode.
The goal is to develop a system that can cycle as quickly as a capacitor and store almost as much energy as conventional batteries.
TU Graz researchers presented their research results in Nature Communications.
Christian Prehal, the first author of the study who moved from TU Graz to ETH Zurich, said: “The system we are looking at in detail consists of nanoporous carbon electrodes and an aqueous sodium iodide electrolyte, in other words salt water. This makes this system particularly environmentally friendly, cost-effective, incombustible and easy to recycle.”
With the aid of small-angle X-ray scattering and Raman spectroscopy, the researchers proved for the first time that solid iodine nanoparticles are formed in the carbon nanopores of the battery electrode during charging, which dissolve again during discharge.
This corrects the previously suspected reaction mechanism and has far-reaching consequences.
Prehal said: “The degree of filling of the nanopores with solid iodine determines how much energy can be stored in the electrode. This enables the energy storage capacity of the iodine carbon electrodes to reach unexpectedly high values by storing all chemical energy in the solid iodine particles.”
Such hybrid capacitors have been very successfully investigated and further developed for several years by Qamar Abbas, currently a Lise Meitner FWF scholarship holder at the Institute of Chemistry and Technology of Materials and another main author of the study.
Image: Harald Fitzek, Christian Prehal and Qamar Abbas (from left) at the SAXS facility SAXSpoint 2.0 (Anton Paar GmbH): With their work at Graz University of Technology, the researchers are providing new insights into hybrid supercapacitors. © Lunghammer – TU Graz