Environmental protection and renewable sources for energy conversion and storage remain an important
topic nowadays. Major challenges of the 21st century that mankind has to face are certainly energy
supply, its storage and conversion in a way that essentially protect the environment. In this scenario the
nanocellulose has come up as a sustainable and promising nanomaterial with its unique structure and
remarkable properties, such as high specific modulus, excellent stability in most solvents, low toxicity
and natural abundance. Its ecofriendly nature, low cost, easy availability and simple synthesis techniques
render the nanocellulose as a promising candidate for the fabrication of green renewable energy storage
devices. Herein, we present a comprehensive review of the current research activities that focus on the
development of nanocellulose materials for energy storage applications, particularly on supercapacitors.
To begin with, we give a brief introduction on the necessity of ecofriendly approaches towards the
development of supercapacitors that make use of nanocellulose. We then focus on various investigations
that have been carried out to fabricate supercapacitors based on nanocellulose or its composites. Finally,
we describe our outlook on several issues that warrant further investigations in this topic with immense
potentials.
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an
8912
, Ind
, Ind
30 April 2019
Accepted 3 June 2019
Available online 12 June 2019
Keywords:
Nanocellulose
Supercapacitor
topic nowadays. Major challenges of the 21 century that mankind has to face are certainly energy
In recent time we have seen considerable improvements in the
environmental concerns due to the generation of electronic and
plastic wastes [1]. The extraordinary growth in portable electronic
batteries, super capacitors, or fuel cells [2,3]. Super capacitors, also
itors, have a high
interesting prop-
g the gap between
rrently, polymeric
ained wide atten-
y, lightweight, and
tive polymers due
tter and safer re-
des [6]. Since the
able there must be extraordinary and viable efforts for the devel-
opment of low-cost, lightweight, environment-friendly, high-
performance super capacitors and batteries [7]. Among bio-
polymers, natural polysaccharides are being developed as sub-
stitutes to synthetic materials for electrochemical devices [4].
Nanocellulose, is a structural polysaccharide that has gained much
attentions nowadays due to its renewability, inherent biocompati-
bility and biodegradability, cost-effectiveness, natural abundance
* Corresponding author.
E-mail addresses: jasminejose764@gmail.com (J. Jose), vinoythoma@gmail.com
(V. Thomas), vrindavinod.kk@gmail.com (V. Vinod), raniabraham@gmail.com
(R. Abraham), susanmi@gmail.com (S. Abraham).
Contents lists availab
Journal of Science: Advance
journal homepage: www.el
Journal of Science: Advanced Materials and Devices 4 (2019) 333e340Peer review under responsibility of Vietnam National University, Hanoi.tionary changes to our society and along with this arises serious future generation electronics industry needs to be highly sustain-living standard which doubtlessly could be attributed to the inno-
vation and development of more viable products through more
efficient processes. To keep this process moving we need to make
use of resources that are renewable and sustainable. Moreover, the
technologies have reached a new era of information technology and
material innovation is experiencing an unpredictable pace of pro-
gressing. Numerous types of sensors, electronic devices and so on
are built everyday using advanced ceramics, metals, and plastics.
The huge advancement of today's technology is bringing revolu-
termed as electrochemical double-layer capac
capacity with a fast charge/discharge rate. These
erties havemade super capacitors capable of fillin
batteries and conventional capacitors [4]. Cu
materials for super capacitor applications have g
tions because of their properties, such as flexibilit
stable cycling performance [5]. Further, redox ac
to their recyclability and sustainability are be
placements for heavy metals in battery electroresearchers in developing versatile energy storage devices, such as
1. Introductionhttps://doi.org/10.1016/j.jsamd.2019.06.003
2468-2179/© 2019 The Authors. Publishing services b
( has come up as a sustainable and promising nanomaterial with its unique structure and
remarkable properties, such as high specific modulus, excellent stability in most solvents, low toxicity
and natural abundance. Its ecofriendly nature, low cost, easy availability and simple synthesis techniques
render the nanocellulose as a promising candidate for the fabrication of green renewable energy storage
devices. Herein, we present a comprehensive review of the current research activities that focus on the
development of nanocellulose materials for energy storage applications, particularly on supercapacitors.
To begin with, we give a brief introduction on the necessity of ecofriendly approaches towards the
development of supercapacitors that make use of nanocellulose. We then focus on various investigations
that have been carried out to fabricate supercapacitors based on nanocellulose or its composites. Finally,
we describe our outlook on several issues that warrant further investigations in this topic with immense
potentials.
© 2019 The Authors. Publishing services by Elsevier B.V. on behalf of Vietnam National University, Hanoi.
This is an open access article under the CC BY license (
systems during the past few decades have gained the attention ofReceived 8 January 2019
Received in revised form supply, its storage and conversion in a way that essentially protect the environment. In this scenario theArticle history: Environmental protection and renewable sources for energy conversion and storage remain an important
stReview Article
Nanocellulose based functional materia
applications
Jasmine Jose a, Vinoy Thomas a, *, Vrinda Vinod a, R
a Centre for Functional Materials, Christian College, Chengannur University of Kerala, 6
b Department of Chemistry, Christian College, Chengannur University of Kerala, 689122
c Department of Economics, Christian College, Chengannur University of Kerala, 689122
a r t i c l e i n f o a b s t r a c ty Elsevier B.V. on behalf of Vietnamfor supercapacitor
i Abraham b, Susan Abraham c
2, India
ia
ia
le at ScienceDirect
d Materials and Devices
sevier .com/locate/ jsamdNational University, Hanoi. This is an open access article under the CC BY license
and eco-friendly nature [8]. Cellulose is an odourless, biodegrad-
able, hydrophilic, water insoluble material which can be obtained
from plants, animals, or bacteria, and the term ‘nanocellulose’
usually refers to the cellulosic extracts or processed materials,
having nano-scale structural dimensions. Nanocellulose can be
classified into three types: (i) cellulose nanocrystals (CNCs)/nano-
crystalline cellulose (NCC) and cellulose nanowhiskers (CNWs), (ii)
cellulose offers a unique combination of properties including flex-
films, can be synthesized by combining with nanocelluloses [25].
This type of porous structures reveal a great potential as substrates
g1] Young's Modulus [GPa] Average size
Diameter length
20e60 10 mm >10 mm
50e160 10e80 nm <10 mm
J. Jose et al. / Journal of Science: Advanced Materials and Devices 4 (2019) 333e340334ible surface chemistry, transparency, low thermal expansion, high
elasticity, anisotropy and the ability to bind to other conductive
materials, enabling extensive application in flexible energy-storage
devices [11,12].
Extraction of nanocelluloses can be done through chemical
treatment, mechanical processing, and enzymatic treatments. The
different methods of preparation are shown schematically in Fig. 2.
Integrating nanocelluloses into energy-related devices would
definitely inspirate research in the area of eco-friendly materials
and we find it very promising to address the important environ-
mental concerns. In addition, a cellulose expresses itself as a low
cost material with large-scale promises [17]. With the cellulose-
related materials gaining more and more popularity, a number of
good review articles have appeared in the area of the synthesis of
nanocelluloses and their properties. Several reviews published in
the past few years have also focused on the application of cellulose-
based energy related devices, such as batteries, sensors, and other
electronic systems [18]. Current focus, however, seems to be in the
field associated with cellulose-based sustainable supercapacitors
which is fast growing with a very high progress rate. Although the
interest for designing cellulose based devices for energy storage
applications grew fast in the recent past according to Nyholm et al.
[19] it is quite interesting to note (Fig. 3) that investigations in the
field have hardly increased since 2012.
In this review, we essentially focus on the potential applications
of nanocelluloses in energy-related areas, and particularly, in the
field of supercapacitors. Our investigations in the area were
concentrated in the synthesis of nanocelluloses and the experi-
mental evaluation of their thermo-optic properties using the
thermal lensing technique. We were able to develop an UV pro-
tection system using nanocellulose/PVA composites. With the
current experimental background and information we plan to
expand our area of research and focus on the possible applications
of nanocelluloses in the field of energy-related devices, especially
in the development of supercapacitors.
2. Cellulose-based functional materials
Cellulose is one of the most abundant natural organic polymers
on the Earth and is usually extracted from plants, agricultural by-
products, woods etc. [4]. The properties of a cellulose and cellulose
derived materials can be enhanced by functionalizing it with
Table 1
Primary characteristics of cellulose types [13e15].
Material Crystallinity Surface area [m2
Cellulose micro fibres (CMF) <60% <1
Cellulose nano fibres (CNF) 50% z 90% z100cellulose nanofibrils (CNFs), also referred to as nano-fibrillated
cellulose (NFC), and (iii) bacterial cellulose (BC) (Table 1) [9].
Chemically, a cellulose consists of linear chains of repeating b-D-
glucopyranose units, covalently connected through b-1, 4 glycosidic
bonds (Fig.1) [10]. A large number of hydrogen bonds exist intra and
inter molecularly and yield different cellulosic structures. Nano-Cellulose nano crystals (CNC) z90% z200suitable materials [20] or through structural modifications for
specific applications. Cellulose nanofibres (CNF) (<100 nm width)
were synthesized very recently in our laboratory using raw cotton
as the source material through green techniques (Fig. 4). In-depth
investigations were carried out to evaluate their thermo-optical
properties and ultraviolet blocking capabilities. Ultra-sensitive dual
beam mode matched thermal lensing technique was used for the
measurement of thermo- optical properties (Fig. 5). The low ther-
mal diffusivity (2.61 10 8 m2/s) and thermal conductivity
(0.108 W/mK) value of the system indicated its thermal insulation
behavior. Further, highly transparent plasmon-enhanced ultravio-
let radiation blocking CNF-PVA films (Fig. 6) for environmental
applications were developed and we found that the UV blocking
capability of the synthesized films is almost the same as that of
commercial films available in the market. With our current interest
on the development of functionalized nanocellulose based systems
for energy storage applications, the development of functionalized
nanocellulose based aerogels for supercapacitor applications is
underway in our lab. This review therefore has been carried out to
bring a fresh picture of nanocellulose based supercapacitors, which
we believe, is highly significant in the present scenario.
3. Cellulose based supercapacitors
Supercapacitors, also called ultracapacitors or electrochemical
capacitors, offer a promising approach to meet the growing power
demands owing to their high power density, superior rate capa-
bility, quick charging/discharging rate, long cycle life, simple prin-
ciples, fast dynamics of charge propagation and low maintenance
cost [21]. These supercapacitors are classified into electrical double
layer capacitors, which store energy through electrostatically
accumulated charges at the electrode/electrolyte interface and
pseudo capacitors based on fast redox reactions at the electrodes
for huge pseudo capacitance [22]. There are also hybrid super-
capacitors comprising of both types of electrodes thereby
combining both double layer capacitive and pseudocapacitive
charging and discharging schemes. Such supercapacitors have high
energy density, high power density and high cycling stability. With
these developments the supercapacitors are proficient to bridge the
gap between the batteries/fuel cells (with high energy density) and
the conventional capacitors (with high power density) [23,24]. For
electro-chemical double layer supercapacitors a large specific sur-
face area is favorable as it delivers more space for the adsorption of
the electrolyte ions. Highly porous materials that possess high
mechanical strength and large surface area, such as aerogels and
Fig. 1. Structure of celluloses.50e140 5e30 nm z100 nm
Fig. 2. Various preparation methods of nanocelluloses [adapted from reference [16]].
Fig. 3. Scopus database on the research output in form of research articles using
celluloses and supercapacitors as keywords. Fig. 4. HR-TEM image of CNF prepared from cotton.
J. Jose et al. / Journal of Science: Advanced Materials and Devices 4 (2019) 333e340 335
ed MFig. 5. Thermal lensing plot of CNF.
J. Jose et al. / Journal of Science: Advanc336for flexible supercapacitors [29] and their efficiencies modified by
doping with carbon conductive materials like CNTs [26,27] and
graphene oxides (GO) [28].
Though cellulose-based materials are environmental friendly
the chemical processes involved in its preparation indicates a threat
to the ecology. Therefore, while designing the green energy storage
devices, one has to focus more on reducing the effect of chemical
treatments. Koga and co-workers successfully converted recycled
waste pulp-fibres and single-layer GO sheets into a cellulose paper/
Reduced Graphene oxide (RGO) composite using a blend of
papermaking process and flash reduction techniques (Fig. 7). The
room temperature, additive free, and millisecond time scale
reduction of GO was achieved in the composite by irradiating with
high intensity pulsed light. This cellulose paper/RGO composite
electrode gave a high specific capacitance of 177 F/g. It was suc-
cessfully applied for an all-paper based flexible supercapacitor that
provided a capacitance of 212 F/g [30].
The extraction of cellulose fibres from waste paper, and subse-
quent application in supercapacitor electrodes is proposed as a cost
effective route for developing energy storage devices with
improved performance [32]. Habio Su et al. demonstrated an all
solid state symmetric flexible supercapacitor based on the office
waste paper fibers/reduced graphene oxide/manganese dioxide
(PF/RGO/MnO2) which acts as both the positive and negative
electrodes. Flexible PF/RGO/MnO2 electrodes with a good physical
flexibility and excellent mechanical strength were fabricated via a
simple solution phase assembly and vacuum filtration method
without using any binding agents. Moreover, owing to the advan-
tages of large surface area and microfibers present in paper fiber,
the PF based hybrid flexible electrodes show a high specific
capacitance of 410 F,g 1 at 0.8 A,g 1 and retain 93% of the
Fig. 6. UV/Visible spectrum showing transparency of the PVA/CNF/AgNP film.capacitance over 5000 cycles, and display an outstanding electro-
chemical performance. In addition, the assembled solid-state
symmetric supercapacitors exhibit a high energy density
(19.6 Whkg 1 at 400 Wkg 1) and an excellent cycling stability of
85.3% retention even after 2000 folding and bending cycles. These
investigations, thus, demonstrate a renewable method of turning
waste into wealth and deliver a new method to fabricate the sus-
tainable and self-supporting paper-based supercapacitor for the
application in flexible energy storage devices [33].
In a pioneering work, Weng and his co-workers [34] reported a
simple and scalable method to fabricate graphene-cellulose paper
(GCP) membranes that act as freestanding and binder-free elec-
trodes for flexible supercapacitors. The electrical conductivity of
the GCP membrane shows great stability with a reduction of only
6% after being bent 1000 times. This flexible GCP electrode has a
high capacitance per geometric area of 81 mFcm 2, which is
equivalent to a gravimetric capacitance of 120 Fg 1 of graphene,
and retains >99% of the capacitance over 5000 cycles. Under highly
flexible conditions, the supercapacitors exhibit a high capacitance
per geometric area of 46mFcm 2 for the complete device. All these
results indicate that polymer supercapacitors made using GCP
membranes are versatile.
The fabrication of supercapacitors and lithium ion batteries
using commercial paper sheets that were coated with aqueous
Carbon Nanotube (CNT) ink using sodium dodecyl benzene sulfo-
nate (SDBS) as surfactant was introduced by Cui and team [35]. The
process was based on a simple Meyer rod coating process in line
with the main principles of green chemistry. The method implied
ways to reduce the consumption of organic solvents, usage of low
energy intake processes avoiding high temperature or high pres-
sure since paper absorbs water easily and binds to CNTs. The
resulting conductive paper exhibited flexibility and good mechan-
ical strength as well. Supercapacitors based on CNT conductive
paper also displayed a specific capacitance of 200 Fg1 and the
stable cycling life over 40000 cycles. Later, the same team coated
single-walled CNTs (SWCNTs) onto cotton fibres and attained a
highly electrically conductive interconnecting network [36].
Supercapacitors made with such electrodes had excellent cycling
performance (good capacity retention after 35000 cycles) and a
specific capacitance of 70e80 Fg1. Due to these properties, the
combination of the cotton/SWCNT electrodes into the wearable
electronics was proposed widely. Kang et al. developed a solid state
flexible supercapacitor by coating CNT onto office papers using the
drop-dry method using gel electrolytes with ionic liquid (i.e. fumed
silica nanopowders were mixed with ionic liquid, 1-ethyl-3-
methylimidazolium). Even though the supercapacitor exhibited
excellent stability, flexibility and a specific capacitance of about
135 Fg1, the approach was a pull out from green chemistry prin-
ciples as the use of ionic liquids is debatable due to their unsafe
synthesis [37]. Later, a simple route to obtain three dimensional,
lightweight, hybrid aerogels possessing excellent capacitance
retention at charge/discharge rates required for a flexible energy
storage device was proposed by Xuan Yang et al. in their work. They
demonstrated the use of CNC aerogels as universal substrates by
incorporating polypyrrole nanofibers (PPy-NF), polypyrrole-coated
carbon nanotubes (PPy-CNT), and spherical manganese dioxide
nanoparticles (MnO2-NP), during the aerogel assembly [38].
Lee et al. demonstrated a new green method of cellulose acti-
vation using coffee. In their work they soaked a piece of paper in the
espresso coffee which acted as a natural activating agent followed
by a pyrolysis to give paper derived carbons (EKACs). Potassium
ions being the core ingredients in the espresso coffee play an
important role in augmenting the pyrolysis kinetics and achieving a
porous structure and a specific capacitance of 131 Fg1 at a scan
aterials and Devices 4 (2019) 333e340rate of 1.0 mVs1 was obtained. All the flexible paper super-
lose
ed Materials and Devices 4 (2019) 333e340 337capacitors were fabricated by assembling the EKAC/CNT mixture
embedded paper towel as the electrode, the PVA/KOH mixture
paper towel as the electrolyte and polydimethylsiloxane infiltrated
paper towel as the packing substance. This coffee mediated acti-
Fig. 7. Preparation of the composite derived from single layer GO and recycled cellu
reference [31].
J. Jose et al. / Journal of Science: Advancvation of cellulose and the resultant super-capacitor provide a new
material and an environmental friendly power source [39].
Conductive polymers are usually the polymers with highly p-
conjugated polymeric chains and among these polymers the most
widely used ones include polypyrrole (PPy, 0.3e100 Scm1), poly-
aniline (PANI, 0.01e5 Scm1), polyacetylene (PA, 3e1000 Scm1),
polythiophene (PTh, 2e150 Scm1), poly (phenylenevinylene) (PPV,
103- 100 Scm1) and their derivatives [40]. These conductive
polymers have been widely studied for use in sensors, electro-
chemical capacitors, fuel cell electrodes, batteries, memory devices,
and field emission devices [41]. In recent years, significant research
efforts