EDCLs nowadays are considered one of the most important energy storage devices.
They are characterized by high power densities, long life cycle and superior efficiencies against lithium-ion batteries.
EDCLs (Electrostatic Double-Layer Capacitors) are rechargeable batteries, typically they store 10 up to 100 times more energy per unit volume or mass than electrolytic capacitors. These supercapacitors are suitable for cars, buses, trains, cranes, elevators. Other minor units are empolyed for SRAM (static random-access memory).
The Institute for Technical and Environmental Chemistry of the Jena University (Germany) conducted an interesting study, reaching a better understanding of the influence of ions and the solvent on the formation of the electrochemical double layers, the self-discharge mechanism and temperature dependence of EDCLs.
A TGA coupled with IR spectroscopy and a GCMS (TG-IR-GCMS Balanced Flow Transfer Lines) has been used to investigate the voltage windows and capacitance of different kind of batteries.
Moreover, by coupling these three instruments together for the analysis of the Evolved Gases also the decomposition temperature stability has been assessed.
The study deals with the behaviour of EDLCs containing 4 different types of electrolytes based on PC (Propylene Carbonate), BC (Butylene Carbonate) and other salts1.
First of all, the chemical physical properties of these electrolytes and their impact of the operative voltage have been considered. Afterwards, the self-discharge of high voltage and then finally, the thermal behavior with a preliminary investigation about the influence of the electrolyte composition on the degradation processes occurring in high voltage EDLCs have been carried out.
TG-IR-GCMS transfer lines heated up to 280°C to transfer evolved gases from the TGA to the FTIR and then GCMS. The combination of these instruments allows a better understand of the decomposition of the electrolytes by recording constantly during the time of the thermal experiment.
The GCMS inlet valves filled at the time when the main weight losses observed on the thermogram allow to easy separate solvent and salt fragments on the column and detect them in the MS.
Constant high sensitivity carried with TG-IR-GCMS with long samplings programs and long operational activities led to easy understanding also of complex compounds. Using alternative electrolytes disclosed the realization of EDLCs more reliable, highly operative and with good performance.
Future intentions are to uncover dynamics of the decomposition processes, as this is a very new industry which needs more attentions on developing parts. Supercapacitors and also Ultracapacitors are part of our future, an alternative to fossil fuels.
Discover more on this application here: “The impact of carbonate solvents on the self-discharge, thermal stability and performance retention of high voltage electrochemical double layer capacitors”
1 N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)-imide (Pyr14TFSI) and tetraethylammonium bis(trifluoromethanesulfonyl)imide (Et4NTFSI)