Ref.: MCoMeim32-001
Apresentador: Daniel Vieira Silva
Autores (Instituição): Silva, D.V.(Instituto de Pesquisas Energéticas e Nucleares); Garcia, R.H.(Instituto de Pesquisas Energéticas e Nucleares); Lazar, D.R.(Instituto de Pesquisas Energéticas e Nucleares); Faria, R.N.(Instituto de Pesquisas Energéticas e Nucleares);
Resumo:
Lithium salts have been employed in aqueous and non-aqueous electrolytes of
supercapacitors. In non-aqueous electrolytes, lithium salts are commonly dissolved in
carbon-based solvents such as ethylene carbonate and dimethyl carbonate. Ethylene
carbonate is an important component for the manufacture of electrolytes for rechargeable
lithium-ion batteries. Due to the high conductivity, well known common electrolytes for
carbon-based electrochemical supercapacitors are the tetraethylammonium tetrafluoroborate
salt (NEt 4 BF 4 ) dissolved in ethylene carbonate (EC) or acetonitrile (ACN). These organic
solvents have the disadvantage of requiring a controlled atmosfere chamber for handling of
the liquid due to their susceptibility to moisture and intrinsic toxicity. In addition, organic
electrolytes also evaporate easily, and commercial supercapacitors are limited to operating
near room temperature (<70ºC). In this study, ethylene carbonate was replaced by ethylene
glycol (C 2 H 6 O 2 ) which is a cheap and easy-to-use material, famous for its use as an antifreeze.
Ethylene glycol was also employed in other applications such as catalysts, support electrolyte
and stabilizer. Ethylene glycol is a synthetic, colorless, and odorless liquid with low vapor
pressure (0.092 mmHg at 25ºC) and is relatively safe for the environment, decomposing in the
air in approximately 10 days and in the soil and water in a few weeks. Solid state
electrochemical supercapacitors were produced using activated carbon electrodes with
electrolytes based on ethylene glycol and lithium perchlorate in different molar ratios. These
devices were electrochemically characterized by cyclic voltammetry varying the scan rate
from 1mV.s -1 to 300 mV.s -1 , by galvanostatic cycle with current densities of 10 to 30 mA.g -1
and by electrochemical impedance in the range of 1mHz to 100 KHz varying the voltage from
0V to 1V. The cyclic voltammograms at room temperature resulted in a specific capacitance
of 47 Fg -1 for the ethylene glycol and lithium perchlorate ratio 1:1.