High performance hybrid supercapacitors by using
para-Benzoquinone ionic liquid redox electrolyte
Paula Navalpotro
a
, Jesús Palma
a
, Marc Anderson
a, b
, Rebeca Marcilla
a, *
a
Electrochemical Processes Unit, IMDEA Energy Institute, Avda. Ram on de la Sagra 3, Parque Tecnol ogico de M ostoles, 28935 M ostoles, Spain
b
Environmental Chemistry and Technology Program, University of WisconsineMadison, 53706, WI, USA
highlights
Redox electrolyte based on quinone species dissolved in ionic liquid was developed.
Hybrid Supercapacitors with 3 times higher values of Cam were achieved.
Hybrid Supercapacitors with 3 times higher values of Ereal were achieved.
The nature of carbon electrode has strong influence in electrochemical performance.
Faradaric contribution is more relevant in non-microporous carbon.
article info
Article history:
Received 25 August 2015
Received in revised form
4 December 2015
Accepted 19 December 2015
Available online xxx
Keywords:
Redox electrolyte
Hybrid Supercapacitor
Energy storage
Ionic liquid
Quinone
Redox flow battery
abstract
A solution of 0.4M para-Benzoquinone (p-BQ) in the ionic liquid N-butyl-N-methylpyrrolidinium bis(-
trifluoromethanesulfonyl) imide (PYR
14
TFSI) was used as a redox electrolyte in hybrid supercapacitors.
Two carbons with very different textural properties, Pica carbon and Vulcan carbon, were used as
electrode material. Electrochemical performance of these energy storage systems was investigated by
cyclic voltammetry (CV) and galvanostatic charge-discharge (CD). Unlike SCs with pure IL electrolyte,
new battery-like features appeared in the CV curves and CD profiles. This electrochemical performance,
associated with the faradaic contribution of the redox electrolyte, results in a significant improvement of
the electrochemical performance of the hybrid system. For Vulcan carbon with low specific surface area
(S
BET
¼ 240 m
2
g
-1
), specific capacitance (C
s
) and specific real energy (E
real
) values as high as 70 Fg
-1
and
10.3 WhKg
1
were obtained at 5 mAcm
2
with hybrid SC operating at 3 V. This represents an increment
of 300% in C
s
and E
real
with respect to the SC based on pure PYR
14
TFSI. For high surface area carbon such
as Pica (S
BET
¼ 2410 m
2
g
-1
), the addition of the redox quinone molecule resulted in a moderate
enhancement reaching values of 156 Fg
-1
and 30 WhKg
1
under the same experimental conditions (36%
and 10% increment, respectively).
© 2015 Elsevier B.V. All rights reserved.
1. Introduction
Electrical power generation is changing and growing rapidly
over last years. The power network faces great challenges, for
example, to meet demand with the daily and seasonal variations
in the production from wind and solar renewable energies. The
development of energy storage technologies capable of storing
energy excess and convert it to electrical energy when it is
needed has become a key element on the massive entrance of
renewable energies into the energy mix. In this sense the elec-
trochemical energy storage devices such as batteries and super-
capacitors are bound to be useful technologies due to its
flexibility, modularity and good fitting in the renewable energies
systems [1].
Supercapacitors (SCs), are electrochemical energy storage de-
vices characterized by having high power density, good cyclability
but low energy density [2,3]. Activated carbons with capacitances
in the range of 80e150 Fg
-1
are widely employed as active ma-
terial for SC electrodes [4,5] due to their high specific surface area
(1000e2000 m
2
g
-1
), high electric conductivity and low cost. In
order to boost energy density, different strategies are pursued
* Corresponding author.
E-mail address: rebeca.marcilla@imdea.org (R. Marcilla).
Contents lists available at ScienceDirect
Journal of Power Sources
journal homepage: www.elsevier.com/locate/jpowsour
http://dx.doi.org/10.1016/j.jpowsour.2015.12.103
0378-7753/© 2015 Elsevier B.V. All rights reserved.
Journal of Power Sources 306 (2016) 711e717