High performance sodium-ion hybrid capacitor based on
Na
2
Ti
2
O
4
(OH)
2
nanostructures
Binson Babu, M.M. Shaijumon
*
School of Physics, Indian Institute of Science Education and Research Thiruvananthapuram, CET Campus, Sreekaryam, Thiruvananthapuram, Kerala, 695
016, India
highlights graphical abstract
Hybrid Na-ion capacitor is fabricated
with Na
2
Ti
2
O
4
(OH)
2
as anode.
Na
2
Ti
2
O
4
(OH)
2
electrode exhibits
~57.2% capacitive nature at
1.0 mV s
1
.
The hybrid ion capacitor exhibits
excellent energy and power densities.
Good cyclability with more than 93%
capacitive retention after 3000
cycles.
article info
Article history:
Received 20 January 2017
Received in revised form
8 March 2017
Accepted 30 March 2017
Keywords:
Energy storage
Sodium-ion battery anode
Pseudo capacitor
Sodium titanium oxide hydroxide
Hybrid device
abstract
Hybrid Na-ion capacitors bridge the performance gap between Na-ion batteries and supercapacitors and
offer excellent energy and power characteristics. However, designing efficient anode and cathode ma-
terials with improved kinetics and long cycle life is essential for practical implementation of this tech-
nology. Herein, layered sodium titanium oxide hydroxide, Na
2
Ti
2
O
4
(OH)
2
, synthesized through
hydrothermal technique, is studied as efficient anode material for hybrid Na-ion capacitor. Half-cell
electrochemical studies vs. Na/Na
þ
showed excellent performance for Na
2
Ti
2
O
4
(OH)
2
electrode, with
~57.2% of the total capacity (323.3 C g
1
at 1.0 mV s
1
) dominated by capacitive behavior and the
remaining due to Na-intercalation. The obtained values are in good agreement with Trasatti plots
indicating the potential of this material as efficient anode for hybrid Na-ion capacitor. Further, a full cell
Na-ion capacitor is fabricated with Na
2
Ti
2
O
4
(OH)
2
as anode and chemically activated Rice Husk Derived
Porous Carbon (RHDPC-KOH) as cathode by using organic electrolyte. The hybrid device, operated at a
maximum cell voltage of 4 V, exhibits stable electrochemical performance with a maximum energy
density of ~65 Wh kg
1
(at 500 W kg
1
, 0.20 A g
1
) and with more than ~ 93% capacitive retention after
3000 cycles.
© 2017 Elsevier B.V. All rights reserved.
1. Introduction
Electrochemical energy storage devices are becoming increas-
ingly recognized for their widespread use in portable electronics,
electric vehicles and smart grids and hence there is great need to
explore newer mechanisms and directions for energy storage,
* Corresponding author.
E-mail address: shaiju@iisertvm.ac.in (M.M. Shaijumon).
Contents lists available at ScienceDirect
Journal of Power Sources
journal homepage: www.elsevier.com/locate/jpowsour
http://dx.doi.org/10.1016/j.jpowsour.2017.03.143
0378-7753/© 2017 Elsevier B.V. All rights reserved.
Journal of Power Sources 353 (2017) 85e94