Review

Graphene: Chemistry and Applications for Lithium‐Ion
Batteries
Roshny Joy 1, Neethu T. M. Balakrishnan 1, Akhila Das 1, Shimna Shafeek 2, Vijay Kumar Thakur 3, Karim Zaghib 4,
Jabeen Fatima Manamkeri Jaffarali 1,*, Mogalahalli Venkatesh Venkatashamy Reddy 5,* and Prasanth Raghavan 1,6,*
Material Science and Nano Engineering (MSNE) Lab, Department of Polymer Science and Rubber
Technology (PSRT), Cochin University of Science and Technology (CUSAT), Cochin 682022, India;
roshnijoy@cusat.ac.in (R.J.); neethu@cusat.ac.in (N.T.M.B.); akhila@cusat.ac.in (A.D.)
2 Mechanical Engineering, RAK Campus, Bolton University, Al Khaimah P.O.Box 16038, United Arab Emirates;s.shafeek@bolton.ac.uk
3 Biorefining and Advanced Materials Research Centre, Scotland’s Rural College Barony Campus,
Dumfries DG1 3NE, UK; vijay.thakur@sruc.ac.uk
4 Department of Chemical and Materials Engineering, Concordia University, 1455 Boulevard deMaisonneuve O, Montréal, QC H3G 1M8, Canada; karim.zaghib@mcgill.ca
5 Nouveau Monde Graphite (NMG), Saint‐Michel‐des‐Saints, QC J0K 3B0, Canada
6 Department of Materials Engineering and Convergence Technology, Gyeongsang National University,
Jinju 52828, Korea* Correspondence: jabeen@cusat.ac.in (J.F.M.J.); reddymvvr@gmail.com (M.V.V.R.);
prasanth@cusat.ac.in (P.R.); Tel.: +91‐(0)‐984‐6306468 (J.F.M.J.); +1‐514‐2269‐9783 (M.V.V.R.);+91‐(0)‐790‐7533273 (P.R.)
1

Citation: Joy, R.; Balakrishnan, N.T.M.;
Das, A.; Shafeek, S.; Thakur, V.K.;
Zaghib, K.; Jaffarali, J.F.M.; Reddy,
M.V.V.; Raghavan, P. Graphene:
Chemistry and Applications for Lith‐ium‐Ion Batteries. Electrochem 2022, 3,
143–183. https://doi.org/10.3390/
electrochem3010010
Academic Editor: Masato Sone
Received: 30 December 2021

Abstract: In the present era, different allotropes of carbon have been discovered, and graphene isthe one among them that has contributed to many breakthroughs in research. It has been considered
a promising candidate in the research and academic fields, as well as in industries, over the last
decade. It has many properties to be explored, such as an enhanced specific surface area and bene‐
ficial thermal and electrical conductivities. Graphene is arranged as a 2D structure by organizing
sp2 hybridized C with alternative single and double bonds, providing an extended conjugation com‐bining hexagonal ring structures to form a honeycomb structure. The precious structure and out‐
standing characteristics are the major reason that modern industry relies heavily on graphene, and
it is predominantly applied in electronic devices. Nowadays, lithium‐ion batteries (LIBs) foremostly
utilize graphene as an anode or a cathode, and are combined with polymers to use them as polymer
electrolytes. After three decades of commercialization of the lithium‐ion battery, it still leads in con‐sumer electronic society due to its higher energy density, wider operating voltages, low self‐dis‐charge, noble high‐temperature performance, and fewer maintenance requirements. In this review,
we aim to give a brief review of the domination of graphene and its applications in LIBs.

Accepted: 15 February 2022
Published: 25 February 2022

Keywords: lithium‐ion battery; graphene; anode; cathode; electrolyte

Publisher’s Note: MDPI stays neu‐
tral with regard to jurisdictional
claims in published maps and institu‐

1. Introduction

tional affiliations.

Copyright: © 2022 by the authors.
Licensee MDPI, Basel, Switzerland.
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distributed under the terms andconditions of the Creative Commons
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license(http://creativecommons.org/licenses/by/4.0/).

Modern society is built up by materials, and carbon‐based materials are widely held
and have a vital role in human civilization. Carbon allotropes are promising candidates
for wide applications. Life is impossible without carbon. Carbon is famous for forming
many allotropes; graphite, carbon nanotubes, fullerenes, graphene, and diamond aresome of the well‐known forms of carbon. The structure of some carbon allotropes has
been depicted in Figure 1. Compounds based on carbon have been widely used in appli‐
cations such as environmental, biomedical, energy, photochemical, etc. Carbon is a signif‐
icant component used in electrochemical applications, such as batteries, supercapacitors,
photoelectrochemical water splitting, solar cells, fuel cells, sensors, etc. The advanced

Electrochem 2022, 3, 143–183. https://doi.org/10.3390/electrochem3010010

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large‐scale energy storage devices, redox flow cells, are also reliant on carbon‐based elec‐
trodes [1,2]. Initially, lithium‐ion battery research was focused on positive and negativeelectrodes, wherein the negative electrodes commonly investigated were based on Li
metal and lithium alloys [3–5]. However, safety concerns are the prime problem, so thefocus has mainly been placed on safer anode dendrites, which led to the synthesis of LiC6
in 1965 [6]. In 1967, Besenhard and Eichinger made a discovery that led to the creation of
the reversible intercalation of lithium ions from a graphite electrode to form LiC6 [7,8]. At
that time, in the absence of appropriate electrolytes to avoid the co‐intercalation, graphite
was not cast off as a cathode material. In 1978, [9] used polymer electrolytes to overcome
the concerns about safety issues, and successfully recognized graphite as an intercalated
anode. The important applications of carbon in energy storage devices is authenticated as
the commercialized battery is equipped with a graphite anode, which was introduced by
Rachid Yazami, for which he was awarded the prestigious Draper Prize in Engineering.
Applications for carbon anode materials have been discovered in metal creation, energy
stockpiling gadgets like batteries, and supercapacitors. Specifically, graphite and gra‐
phene have found successes as anodes, which is not surprising owing to their outstanding
electrical properties [10]. Nowadays, the research field is growing very vast, and more
contributions have been added to the carbon allotropes by exposing 3D Buckminster full‐erene, 2D graphene, and 1D carbon nanotubes (CNTs).

Figure 1. Structure of various carbon allotropes: (a) carbon chains; (b) polycyclic aromatic hydro‐
carbon; (c) graphene; (d) carbon nanotube (CNT); (e) C60; (f) C70; (g) graphite; (h) amorphous car‐bon; and (i) diamond.

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In the present day, a wide variety of carbon allotropes has been discovered and stud‐ied, among which graphite leads a fantastic role in both the industry and research fields[10]. Since 2004, the discovery of graphene, awarded to Konstantin Novoselov and Andre
Geim [11] (with the prestigious Nobel Prize in Physics, 2010) paved a new trend in the
research world; this led to an explosion of advancement in energy storage devices, elec‐
tronic devices, optoelectronic devices, catalysis, and sensors, as well as in the biomedical
field [11]. The discovery of graphene is considered the most delightful victory in the dis‐
cipline of material science, engineering, and technology. The material has many unambig‐
uous physiognomies, such as excellent electronic conductivity, significant specific surface
areas, mechanical properties, and elevated thermal stability [12]. Among carbon allo‐
tropes, graphene is one of the significant crystalline allotropes; it has a hexagonal, single
layer of graphite and the simplest form, with bond distances of 0.142 nm among carbon–
carbon single bonds. It has sp2‐hybridized carbon atoms, with alternative single and dou‐
ble bonds developing a hexagonal ring structure to form a planar 2D nanosheet structure[13]. Graphene itself occurs in numerous forms, such as nanosheets, nanoribbons, 3D
structures, and nanoplates.
Graphene is the most popular carbon allotrope wherein the carbon atoms are bonded
to form a unique electronic cloud, which is highly stable and has a size of less than 20 nm.
It has been known to exhibit the quantum hall phenomenon. Based on its exceptional
characteristics, graphene and its derivatives are gaining a gigantic reputation in every as‐pect [14]. Graphene can be modified into different forms such as 0D fullerene, 1D CNTs,
and 3D graphite, as depicted in Figure 2. In the applied research field, graphene has
mostly been used in batteries and sensors. In graphene, all the carbon atoms are sp2 hy‐
bridized, leading to an extended π electron cloud all over the structure, which results insuper ballistic electronic conductivity [15]. High electronic conductivity can be tuned ac‐
cording to applications by synthesis methods, which aids graphene in a wide variety of
applications. The enhanced electronic conductivity makes the allotrope an attractive com‐ponent in lithium‐ion batteries (LIBs).

Figure 2. 2D Graphene nanosheets as the basic building units of various carbon allotropes (a) 0D,(b) 1D, and (c) 3D.

Electrochem 2022, 3, 143–183

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Rechargeable LIBs were commercialized in 1991. To date (2021), LIBs are the mostreliable and dependent energy storage device, and they have a leading role in the market
as well as in research, thanks to the rigorous efforts and hard work of researchers. The
first commercialized LIBs relied on the graphite anode and the replacement of the anode,with more conductive graphene is under research. The amazing electron mobility, as wellas enhanced surface area, imparted the material to be developed as an inevitable compo‐
nent in energy devices. The premium properties of graphene have paved the way for the
researchers all around the world for multipurpose use of the material including its appli‐
cation as components for rechargeable batteries [16]. In the future, the electrochemicalenactments of rechargeable batteries will have relied on the advancement in the electrodedesign as well as its synergistic properties, hence graphene is expected to lead a giganticrole[17,18]. The roadmap of the development of graphene, the timeline of its evolution, issummarized in Figure 3.

Figure 3. Roadmap representing the development and future of graphene reproduced from Ref.
[19].

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2. Graphene; Properties and Synthesis
Graphene comprises sp2 bonded carbon atoms in a single‐atom‐thick planar sheet toform a hexagonal framework. The astonishing properties of graphene dominate the re‐search world due to the potential applications since its discovery in 2004. The versatile
applications including electrochemical performances were tested by various scientists
worldwide who concluded that graphene is a promising candidate as an electrode as wellas electrolyte for rechargeable batteries. Recently, the major challenge that the future ofenergy storage devices is focusing on is the commercial‐scale synthesis of graphene
through ambient methods. In conclusion, future electronic gadgets will be powered bygraphene as an electrode as well as electrolyte. Here, the present review provides a precise
and brief on the synthesis, properties, application, and the major challenges faced by gra‐
phene as active components in LiBs [20].
2.1. Chemical and Physicall Properties of Graphene
Graphene is quite an interesting material for the scientific and industrial community
because it is non‐toxic, chemically and thermally stable, electrically conductive, and me‐
chanically robust. It is the lightest known material as well as considered to be the building
block for the development of other allotropes of carbon, such as one‐dimensional carbon
nanotubes (CNTs) by rolling up 2D graphene into a tubular form; it also can be wrapped
into spherical zero‐dimensional bucky balls as well as stacked together to form a three‐dimensional (3D) structure of graphite. A virtual demonstration of the evolution of 0D,
1D, and 3D allotropic carbon forms has been demonstrated in Figure 2. On the groundsof the extraordinary electronic properties of graphene, it has been known to be a pseudo‐
conductor with zero electrical bandgap and hence has also been designated as a quasi‐
metal compound. The charge mobility and carrier concentration in graphene was exten‐
sively studied and explained on the basis of Dirac equation. It has a perfect crystalline
structure; hence, the energy reduced quasi‐particles showed an angular frequency pro‐portional to the wavenumber explained by linear dispersion relation. It is also known formany unusual electronic properties such as ballistic transport electron flow. The grapheneis also known to have a pseudospin chirality which was based on the ‘‘Berry phase’’. The
material also possess an ambient half‐integer quantum Hall effect, as well as a remarkableelectronic conductivity in the deficiency of charge carriers. The electronic properties of thegraphene inevitably proves its capability as a potential component for upcoming elec‐
tronic materials, and with a sense of humor, it predicted that the silicon is changed tocarbon. Graphene possess the fastest known electronic mobility rate of 15,000 cm2 V−1cm−1.
The material also displayed about 200 times enhancement in the mobility of temperature‐
independent charge carriers (200,000 cm2 V−1S−1) than that of silicon. It also delivered a
Fermi velocity of 106 m s−1 in the ambient condition. The graphene also imparts stupen‐
dous optical, mechanical, electrochemical, and thermal properties, loftier than other car‐bonaceous materials. The important properties of graphene in comparison with other al‐
lotropes of carbon are enumerated in Table 1. Monolayer graphene is known to possess
an excellent mechanical property delivering a Young’s modulus of 1.0 TPa. The stiffnessof graphene is obtained to be in the range of 130 Gpa. The monolayer material also dis‐played an optical transmittance of 97.7% which makes it applicable for transparent elec‐
tronic gadgets. It also displayed superior thermal conductivity of about 100 times com‐pared with Cu (5000 W m−1K−1). The enhanced theoretical specific surface area (2620 m2g−1) makes the material exploitable in the area of catalysis and energy storage applications.
The inimitable properties of graphene upgraded the material for wide variety of applica‐tion which is known to out‐perform various other carbon allotropes such as CNTs andgraphite, as well as metals such as Cu, Pt, etc. in various applications. The tunability inbandgap of the graphene by introduction of dopants and defect states makes it a compet‐
itive replacer of several semiconductors for various electronic applications [21].

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Table 1. Physical and electronic properties of different allotropes of carbon. Adapted and repro‐
duced from ref. [20].

Graphene

Fullerene (C60)

Three
sp2
2.09–2.23
Hexagonal

Carbon Nanotube
(CNT)
One
Mainly sp2>1
Icosahedral

two
sp2
>1
Hexagonal

Zero
Mainly sp2
1.72
Tetragonal

~0–10

~1300

~2300

80–90

Carbon Allotropes

Diamond

Graphite

DimensionHybridized form
Density (g cm−3)
Crystal system
Experimental specificsurface area (m2 g−1)

Three
sp3
3.50–3.53
Octahedral
20–160Insulator, semi‐ Electrical con‐ Metallic and semi‐ Semimetal, zero‐
Insulator
conductor
ductorconducting
gap semiconductor
Thermal Conductivity
1500–2000 a, 5–900–2320
3500
4840–5300
0.4−1−1(W m K )10 c
Flexible non‐Tenacity‐
Flexible elastic
Flexible elastic
Elastic
elastic
Highest (single
High
Hardness
UltrahighHighHighlayer)
Structural depend‐ 97.7% of optical Non‐linear optical
Optical properties
Isotropic
Uniaxial
ent properties
transmittance
response
Electrical conductivity
Anisotropic Structure depend‐
2000
10−10
‐
(S cm−1)ent
2–3 × 104 a, 6 b
Electronic Propertiesaa–direction, b b–direction, c c–direction.

2.2. Various Synthesis Methods Exploited for Preparation of Graphene
Two major modes of synthesis of graphene have been explored to date. The known
methods of synthesis can be categorized as the bottom‐up and the top‐down methods.
The bottom‐up procedure predominantly incorporates the strategies for the developmentof graphene epitaxially as well as chemical vapor deposition (CVD). Building the material
from atomic‐scale can be achieved by CVD, and the epitaxial growth technique can leadto the formation of imperfection‐free graphene nanosheets [22]. Thermal reduction, chem‐
ical reduction, epitaxial growth, and micromechanical cleavage of graphene oxide (GO)are the main methods used to prepare graphene nanosheets in the top‐down method.
Among the reported modes of synthesis, the chemical reduction of GO is the most vowing
method for the commercialization of graphene. Chemical exfoliation of graphite to gra‐
phene oxide can be achieved by several methods such as the Brodie method, Hummer’s
method, and Staudenmaier method. GO has a similar layered structure to graphene andin its basal planes has epoxide and hydroxyl groups along with carbonyl and carboxylgroups [23]. These oxidative functional groups are also available at the edges of the GO
sheets. The different methods followed from 2004 to now are discussed below, and theprocess involved in the synthesis is listed in a flow chart and displayed in Figure 4 [24].

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Figure 4. Flow chart representing the synthesis procedure of graphene.

The top‐down method mainly takes into account the exfoliation of graphite. The ex‐foliation of the graphite results in the breakage of Van der Waals’ force of attraction thatheld the graphite layer together by physical or chemical methods. Significant difficulties
in this region incorporate successfully isolating the layers without harming the sheets andforestalling re‐agglomeration of the sheets once the layers have been shed. Top‐down ap‐
proaches experience the effects of low yields. Graphite can be created artificially underhigh‐temperature conditions but not mostly appropriate for graphene synthesis due tohelpless degrees of graphitization and sporadic morphologies. For bottom‐up schemes,
undeniable degrees of graphitization should be elevated to create great quality material,so these techniques for the most part require high temperatures. The cycles included are
generally basic, albeit the material created can contain more elevated levels of deformities
than noticed for hierarchical techniques. In expansion to shaping graphene nanosheets,
bottom‐up techniques can likewise be utilized to shape enormous region graphene films
utilizing development on certain substrates [25]. A schematic illustration of the top‐downin addition to bottom‐up synthesis technique has been depicted in Figure 5.

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Figure 5. Pictorial representation of the synthesis method of graphene, categorized by the top‐downalong with bottom‐up techniques. Adapted and reproduced from Ref.[23]. Copyright 2015 Royal
Society of Chemistry.

2.2.1. Top‐Down Method
The very first method used to isolate monolayer graphene was micromechanicalcleavage. In this method, the graphite was exfoliated to separate the layer using adhesive
tape. Hence, this method is widely known as the Scotch tape or the Peel‐off method [25].
It is the principal technique used for the synthesis of graphene, offering better electronic
conductivity compared with other synthesis methods. This strategy permits solid andsimple preparation however experiences a low yield [21,26].
Chemical exfoliation is referred to as the finest method. In this method, graphene isproduced from bulk graphite and graphite intercalation compounds. Graphene oxides
were produced in 1860 by Brodie, Hummers, and Staudenmaier methods. Mainly, two
steps are involved in this process, the formation of intercalation compounds and the ex‐foliation by sonification. GO is commonly synthesized by the Hummers method, the mostpopular chemical exfoliation method. The exfoliation of GO can be achieved by an oxida‐
tive technique of graphite separating the interlayers using strongest oxidizing agents suchas NaNO3 in H2SO4/H3PO4 and KMnO4 followed by ultrasonication in a dimethyl forma‐mide (DMF) water mixture (typically 9:1 v/v) mixture to produce single‐layer graphene
oxide. Thermal exfoliation and reduction of graphite oxide similarly produce good‐qual‐
ity graphene [25,27].

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2.2.2. Bottom‐Up Method
On account of the epitaxial development method, at elevated temperatures, graphene
is grown on silicon carbide (SiC) as well as metals substrates such as ruthenium, platinum,etc., under ultrahigh vacuum. The proposed method is capable of developing graphenewith reduced defect states. However, the high‐vacuum conditions enhance the expense of
manufacture and yield a lower amount of product compared with other methods [25].
The development of graphene on SiC also favored the sublimation of silicon along withthe formation of graphite with excess number of carbon atoms at elevated temperatures
exceeding 1000 °C and ultra‐high vacuum (UHV) conditions. Growth of graphene in theargon atmosphere or the presence of minor amounts of di‐silane has been exposed to de‐crease the rate of silicon sublimation, leading to higher temperatures to be castoff andwhich produce higher‐quality graphene. Preferential Si sublimation can be prompted bypulsed electron irradiation [25,28].
Chemical vapor deposition (CVD): In this method, graphene was formed by the dis‐
integration of hydrocarbons followed by deposition of graphene from atomic‐scale at el‐evated temperatures on metal oxide such as alumina (Al2O3) and magnesia (MgO) as wellas metal substrates such as nickel, platinum, and copper. The CVD method mainly de‐pends on the substrates and produces high‐quality graphene; however, there is a signifi‐
cant expense and moderately low yield. On the other hand, this methodology has an ex‐
traordinary potential that can be added for additional improvement. Mainly, the peelingof graphitic materials is the key procedure and includes oxidation, intercalation, sheddingof graphene subordinates, such as graphite, CNTs, expandable graphite, graphite oxide,
graphite intercalation compounds, and graphite fluoride. The reduction of graphite oxidewith a minimum about of expense could yield a huge amount of rGO with high processa‐
bility. The major growth parameters taken into account while using the CVD method are
the substrate quality, C/H ratio, pressure, temperature, and oxygen on the substrate sur‐face influences the graphene synthesis [25,28].
3. Lithium‐Ion Battery: A Brief Overview
In comparison to the battery chemistries, LIBs are still ruling the portable gadget
market attributable to their specific characteristics such as prodigious energy density, bor‐
der operating voltage, good temperature performances, low self‐discharging capacity,
long cycling life, sustainability, and minimal maintenance requirement. Sony Japan com‐
mercialized LIBs for the first time in 1991, and the application levels are extended to moredifferent fields including defense, aerospace, and automobile industries, and renewableenergy integration. The performance of these rechargeable batteries greatly relies on thephysiochemical properties of both anodes as well as cathodes. Additionally, it is affectedby the electrode structure and synthesis routes. Schematic illustration of a typical LIB havebeen demonstrated in Figure 6. The commercial LIBs consist of carbon (graphite) based
active material as anode and lithium metal oxide‐based active material in cathode alongwith a carbonate‐based organic electrolyte along with inorganic lithium salts for lithium
ions to move back and forth easily [27].

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Figure 6. Schematic demonstration of typical LIB comprising of graphite as anode, lithium iron
phosphate as cathode, and lithium salt‐based electrolyte.

4. Graphene as Components in LIBs
In the current scenario, the LIBs industry has been mainly ruled by graphite. Graph‐
ite is commercially used as the anode in rechargeable LIBs due to the low cost, low volume
change, great Coulombic efficiency, stable cycling performance, and conductivity as well
as availability. However, graphite possesses a theoretical specific capacity of 372 mAh g−1,
comparatively much lower; it also shows a poor rate of performance. The graphite anodebecomes confined to meet the current practical sense of LIBs requirement due to the lim‐
ited lithium storage sites. To overcome the issues of graphite, graphene becomes the most
relevant component [29,30]. As described earlier, the LIBs comprise three major parts, an‐ode, cathode, and electrolytes. The major advantage of graphene is the ability of the ma‐
terial to augment the performance of all these components, thereby boosting the overall
performance of the battery.
4.1. Pristine Graphene and Graphene Composites as Anodes in LIBs
LIBs are widely utilized in versatile hardware, for example in phones, laptops, tab‐lets, computerized cameras, and so forth, and are accepted to be promising decisions asenergy‐successful and climate well‐disposed gadgets. For the most part, LIBs are madeout of anodes, electrolytes, and cathodes. During the charging of LIBs, the de‐lithiationfrom the positive electrode traverse along the electrolyte and embed into the negativeelectrode. Further re‐energizing, finished with the Li‐particle inclusion/extraction meas‐
ure in the cathodes, the idea of the two‐terminal materials is pivotal to the performance of
LIBs. The present terminal materials utilized in LIBs exist Li intercalation mixtures suchas graphite as negative electrode and lithium cobalt oxide (LiCoO2 and LCO) as positiveElectrochem 2022, 3, 143–183

153

electrode material, as they displayed effective reversible charging/releasing under inter‐calation possibilities. Even if graphite electrode displayed better Coulombic efficiency, it
fell behind in higher Li stockpiling limit (hypothetical worth: 372 mAh g−1) as a viable
negative electrode material in the upgraded power stockpiling gadgets. Consequently, amuch higher accused stockpiling limit of promising cyclability and rate capability of neg‐
ative electrodes in LIB research has gained serious consideration. The presence of gra‐
phene‐based negative electrode with its nano structural advancement is to be utilized as
an anode in r‐LIBs. A current commercial negative electrode, graphite can be replaced bygraphene, which is considered to enhance the performance of the device without incorpo‐
ration of harmful chemicals such as lithium. The graphene‐based anodes may consist ofpristine graphene nanosheets, graphene nanosheets composite with carbon nanomaterials(CNT, fullerene, etc.), metals, chalcogenides, and doped graphene nanosheets.
4.1.1. Pristine Graphene as Anode for LIBs
Graphene is also specified as graphene nanosheets (GNS) and is widely explored as
the negative electrodes for energy storage devices. The theoretical specific capacity of gra‐
phene is reported to be 744 mAh g−1 which is twofold than that of the 3D graphite (372mAh g−1) [31]. Initial reports on graphene nanosheets based anode for LIBs were reportedby Honma et al. [32] in 2008, wherein they compared the performance of graphite withgraphene nanosheets, graphene nanosheets composites with CNT, and fullerene. The in‐vestigation of the reversible capacity of various anodes at 0.05 A g−1 revealed that graphite
anode delivered a capacitance of 340 mAh g−1 whereas GNS, GNS/C60, and GNS/CNT
anodes delivered a reversible capacity of 540, 784, and 730 mAh g−1, respectively, which
confirms that graphene nanosheets offer almost double intercalation of lithium ions thangraphite anodes [32]. The charge–discharge profiles and cycling stability have been de‐picted in Figure 7.

Figure 7. Charge–discharge profiles and cycle stability of the graphite, graphene (GNS), GNS + car‐bon nanotube (CNT), and GNS + Fullerene (C60); (a) charge/discharge curves at 0.05 A g‐1, (b) com‐
parison of cycling performance. Adapted and reproduced with permission from [32]. Copyright2008 American Chemical Society.

A modification in the result was introduced by Song et al. [33] (2009) wherein gra‐
phene nanosheets were prepared by Staudenmaier’s method. The anode was fabricatedwith GNSs/acetylene black/poly (vinylidene difluoride) (PVdF) 80:10:10 wt.% and the cellstudies of the anode were investigated in the electrolytic medium of 1 M LiPF6 in EC: DMC(1:1 v/v). The anodes retained an electrochemical stability voltage ranging from 0 to 3.5 V.
The initial cycling performance of the cell revealed a charge/discharge capacity of 1233
and 672 mAh g−1, respectively, at a current density of 0.2 mA cm2. After prolonged cycling
exceeding to 30 cycles, it displayed a reversible capacity of 502 mAh g−1 [33] comparable
to the previous report [33]. A reasonable advancement in the performance of GNS anodeElectrochem 2022, 3, 143–183

154

was reported in 2013 by Hassoun et al. [34]. In the study, GNS was fabricated by the ex‐foliation of graphite by the wet chemical method followed by the fabrication of the fullcell with GNS/PVdF/carbon super P in the ratio 80:15:5 coated on the copper foil as anodeand cathode as LiNi0.5Mn1.5O4 coated on aluminum foil. The electrolytic medium was thesame as that of the previous report [33]. The cell displayed a stabilized capacity of 600
mAh g−1 dropped from an initial performance of 2000 mAh g−1 [34] (Figure 8a) as well asa working voltage of ~0.9 V, which was substantially higher than the previously reported
performances. The comparison of charge–discharge voltage profiles of the first two cyclesof GNS/LNMO cell depicted in Figure 8b shows the drop in performance due to lithiationof the electrode [34].

Figure 8. Cycling performance of GNS as anode; (a) charge–discharge profiles of GNS at 149 mA
g−1, (b) charge/discharge profiles of the GNS resulting by the pre‐cycling process at 74 mAh g‐1 inlithium and LNMO half cells. Adapted and reproduced with permission from [34]. Copyright 2013
Royal Society of Chemistry.

In 2013, Sun et al. [35] reported structurally modified GNS as a negative electrode for
LIBs. The report revealed the structures have an evident task in the enhancement of stor‐
age competence of the negative electrode. In relevance to the explanation, three different
types of GNSs were fabricated with variable morphologies. For the synthesis of two of themorphologies, modified Hummer’s method was adopted by varying the stirring time, andanother sample was prepared by autoclaving the second GNS fabricated by modified
Hummer’s method using urea and was labeled as GNS I, II, and III, respectively [35]. The
morphologies of corresponding samples have been depicted in Figure 9 [35]. These GNSs
synthesized via modified Hummer’s method resulted in the formation of thin translucent
nanosheets with more extent of exfoliation was evident for GNS II where additional stir‐ring was provided during the synthesis. The morphology of the hydrothermally treated
GNS samples showed much reduction in the size which can be associated with the en‐hancement in the extent of exfoliation as evident from Figure 9c,d [35].

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Figure 9. Morphological analysis of graphene nanosheets (GNS) synthesized in varying conditions;
SEM images of (a) GNS‐I, (b) GNS‐II, and I GNS‐III; TEM images of (c) GNS‐I, (d) GNS‐II,(e) SEM
image of GNS‐III; TEM image of GNS‐II and (f) GNS‐III. Adapted and reproduced with permission
from ref [35]. Copyright 2013 Royal Society of Chemistry.

The cell studies of the structurally modified GNS samples were conducted in a coincell with copper foil as current collector on which the active material (GNS) was coatedwith PVdF binder in the ratio of 90:10. The electrolyte employed was 1 M LiPF6 in
EC/DEC/EMC in equi‐volume ratio. The initial charge capacities of GNS‐I, GNS‐II, and
GNS‐III were obtained at 1275, 861, and 1233 mAh g−1, and the discharge capacity was
obtained at 925, 418, and 2561 mAh g−1, respectively [35]. On prolonged cycling, the ca‐
pacity decreases, which is ascribed to the formation of the SEI layer. After 99 cycles, GNS
I, II, and III exhibited a discharge capacity of ~270, 400, and 690 mAh g−1, respectively [35]as depicted in Figure 10a. The Coulombic efficiency of the samples has been displayed in
Figure 10b, which indicates that the GNS I and II showed variation in the efficiency
whereas GNS III maintained the performance almost equivalent to 100%. Overall, the per‐formance of the GNS anode has relied on the extent of exfoliation, the more the extent of
exfoliation efficiency will be the anode [35]. In 2020, Mu et al. [36] further added verticalgraphene sheets support (not exclusively) the lithium‐ion transport rate due to its inherent
high electrical conductivity, however likewise can altogether diminish convolution of lith‐ium‐particle transport due to its exceptionally particular lithium‐particle inclusion ways.
Into equal parts cells, the vertical graphene sheets/graphite can persevere through 3000
cycles in 3 min of charge time per cycle. All the more strikingly, a full cell with verticalgraphene sheets/graphite anode and LiFePO4 cathode shows an elevated energy densityof around 312 Wh kg−1 in 10 min of charge time per cycle at 4 C, showing that the verticalgraphene sheets/graphite anode has the capacity of outrageously quick charging while atthe same time keeping up high energy density.

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Figure 10. Cycling stability of graphene nanosheets synthesized by varying the conditions as anodes
tested in the half cell; (a) Coulombic efficiency against cycle numbers of various GNSs, (b) cyclingstability of various GNSs at 100 mA g−1. Adapted and reproduced with permission from ref [35].
Copyright 2013 Royal Society of Chemistry.

4.1.2. Doped‐Graphene as Anode for LIBs
Conductivity and electrochemical performance of 2D graphene sheets were pro‐foundly enhanced by doping with nitrogen, boron, phosphorous, etc. The method is quite
similar to N‐doping and P‐doping in semiconductors. N‐doped graphene was developedby CVD [37] technique as well as arc discharge technique [38]. The first principle studies
revealed that the conductivity of graphene was substantially enhanced with the introduc‐tion of nitrogen or boron atom to the lattice [38]. The bond length of the N‐C bond was
almost the same, whereas the B‐C bond length was slightly more than that of the carbon–
carbon single bond length in pristine graphene. An analogues’ property was also observedin the case of interlayer spacing; N doped GNS showed slight enhancement in the spacing,whereas B doped GNS with considerable enhancement in the spacing [38]. Theoreticalstudies of doped graphene as anode material in LIBs were conducted by Zhou et al. in2011 [37]. The first principle studies revealed that the Li desorption and adsorption un‐dergoes faster in N and B‐doped GNS. The activation barrier of the delithiation process of
N‐doped graphene is relatively inferior to that of graphene. Successively, the authentica‐
tion in the theoretical results was investigated by Sun et al. [39] developing an investiga‐
tional proof. The N‐doped graphene was synthesized by chemical exfoliation using mod‐ified Hummer’s method forming graphite oxide followed by annealing at 1050 °C undera nitrogen atmosphere. Thus, received samples were further annealed in the occurrenceof ammonia gas (NH3) leading to the materialization of N‐doped GNS. The morphologicalanalysis of the GNS and N‐doped GNS has been depicted in Figure 11 [39]. The reversible
discharge capacity after 100 cycles of the GNS and N‐doped GNS resulted in 269 and 452
mAh g−1, respectively. Discharge capacity of N‐doped GNS was found to increase up to
500 cycles and remained almost constant in the range of 684 mAh g−1 [39].

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Figure 11. Electron micrographs of GNS and N‐GNS; SEM images (a) GNS and (b) N‐GNS; TEM (c)GNS and (d) N‐GNS. Adapted and reproduced with permission from ref [39]. Copyright 2011 Else‐vier.

Properties of N‐doped GNS were enhanced by the addition of additives such as Fe3C
[40], SiO2 [41], Li3VO4 [42], MoS2 [43], etc. Fe–Fe3C/N‐doped GNS binary composite wassynthesized by pyrolysis process of MIL‐100 (Fe) (porous metal‐organic framework)
which delivered a discharge performance of 607 mAh g−1 at 1000 mA g−1 extending thecycle stability to 100 cycles [40]. SiO2/GNS composite was fabricated by the hydrothermal
method [41]. The sample with 1:0.5 of GNS: SiO2 showed a considerable enhancement in
the performance, and the analysis at current densities ranging from 100, 200, 500, 1000,
2000, to 5000 mA g−1 resulted in discharge capacity of 1052, 866, 670, 536, 415, and 272 mAh
g−1 [41], respectively. The results revealed superior properties for SiO2/GNS composite as
anode material in LIBs. Li3VO4/GNS composite was synthesized by the hydrothermal
method which displayed an initial charge–discharge capacities of 429 and 550 mAh g−1,
respectively, at a current density of 0.15 A g−1 [42]. On prolonged cycling, the performance
was increased and was sustained after 100 cycles at 476 and 478 mAh g−1, respectively [42].
The MoS2/GNS nanocomposite was prepared by hydrothermal method followed by ther‐
mal treatment. The samples dispensed enhanced performance with a reversible capacityof 1151 mAh g− 1 at 0.1 A g−1. The cycle stability was retained up to 92.6% even after 600
cycles [43].
Recently, N‐GNS with MoS2 (N‐GRs/MoS2) have been reported by Xiao et al. [43].
The graphene oxide was prepared by spray drying technique from graphene oxide
nanosheets (GONs), which were sonographically dispersed in deionized water. To thedispersed solution, L‐cysteine along with sodium molybdate mixture in deionized waterElectrochem 2022, 3, 143–183

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was added dropwise followed by stirring [43]. The solution mixture was then subjectedto hydrothermal treatment for 12 h. The resultant product was repeatedly washed with
deionized water followed by freeze‐drying. The final product was obtained after anneal‐ing the dry samples at 800 °C for 2 h in an Ar atmosphere (denoted as N‐GRs/MoS2). For
comparison, pristine MoS2, N‐doped graphene ribbons (N‐GRs), and N‐doped graphenenanosheets/MoS2 (N‐GNs/MoS2) were also synthesized. A schematic illustration of thesynthesis of N‐GRs/MoS2 and N‐GNs/MoS2 has been demonstrated in Figure 12 [43]. The
performance of the material as the anode in LIBs was tested using Li half‐cell and N‐
GRs/MoS2//LiFePO4 full cell configurations. The anode was coated on aluminum foil bymixing sample/conductive material (Super P)/polyvinylidene difluoride binder (PVdF) in
the ratio of 8:1:1 [43]. The electrolyte used for the study was the 1 M solution of LiPF6 incarbonate mixtures of ethylene carbonate (EC)/dimethyl carbonate (DMC)/ethyl methylcarbonate (EMC) in the ratio of 1:1:1. The performance of the cell with varying current
densities is displayed in Figure 12b, evidently showing the enhanced discharge capacityof the anode of about 499 mAh g−1 even at an elevated current density (8.0 A g−1) [43].
Moreover, samples also displayed better cycling as shown in Figure 12c. The cycling was
extended up to 200 cycles at 0.5 A g−1, where N‐GRs/MoS2, N‐GNs/MoS2, and pristine
MoS2 anodes delivered a discharge performance of 925, 389, and 311 mAh g−1, respec‐tively, wherein N‐GRs/MoS2 displayed a capacity retention of 102%, which is 2.38 and2.98% greater than that of N‐GNs/MoS2 and pristine MoS2, respectively [43]. The results
reveal the enhanced and sustained performance of N‐GRs/MoS2 anodes‐based LIBs.

Figure 12. Nitrogen‐doped graphene nanoribbons and nanosheets composite with MoS2; (a) sche‐matic illustration on the preparation of N‐doped graphene ribbons/molybdenum sulfide (N‐GRs/MoS2) and N‐doped graphene nanosheets/molybdenum sulfide (N‐GNs/MoS2) composites, (b)cycle stability of N‐GRs/MoS2 from 0.1 to 8.0 A g−1 and (c) cycling performance comparison of N‐
GRs/MoS2, N‐GNs/MoS2, and pure MoS2 at the current density of 0.5 A g−1. Adapted and reproducedwith permission from ref [43]. Copyright 2021 Elsevier.

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4.1.3. Nanocomposites Based on Graphene as Anode for LIBs
Nanocomposites based on graphene are polyphase materials where the graphenestays as a network stage. The majority of the composite materials grown at any point
formed by the incorporation of metal oxide, sulfide, and metal nanoparticles into gra‐
phene. Wu et al. [20] demonstrated the prevalence (as far as electrochemical highlights) ofgraphene/metal oxides composites, for example, moored, wrapped, typified, layered,sandwiched, and blended models, (Figure 13) compared with that of pristine compound[44]. Graphene‐based inorganic composites of several metal chalcogenides were widely
explored. Co3O4 [45], silicon [46,47], sulfur [48], Fe3O4 [48], SnO2 [49], CuO [50], TiO2 [51],
MoS2 [52], MoO2 [53], MgO [54], Fe2Mo3O8 [55], Co2Mo3O8 [56], Sb2S3 [57], Fe2O3 [58,59],
ZnMo3O8 [60], and graphene eggshells in‐graphene foam [61] were also reported ascomposite anode for LIBs. The possibility of graphene composites as components in LIB
is an alluring one due to their fantastic electrochemical exhibitions. Herein, the sum up ofgraphene based composites has been investigated at this point just to stamp theirsuperlative electrochemical highlights came about due to creative designing.

Figure 13. Schematic representation of metal oxide/graphene composite models: (a) surface
anchored model, (b) wrapped model, (c) encapsulated model, (d) sandwich model, (e) layered
model, and (f) mixed model. In the structures, red balls represent metal oxide particles and the blue
sheets represent 2D graphene sheets. Adapted and reproduced with permission from ref [20].
Copyright 2012 Elsevier.

Fe2O3/Graphene Based Composite as Anode for LIBs
Iron oxide (Fe2O3) is widely explored as an anode material owing to the ease ofintercalation/deintercalation of the lithium ions in the lattice of the metal oxide. The low
cost, reduced toxicity, and ease of fabrication make the anode a widely accepted metaloxide for application [62–66]. The Fe2O3 based anodes are known to intercalate six lithium
ions in the lattice‐based on Equation (1) [58].
Fe2O3 + 6 Li+ + 6 e‐  2 Fe + 3 Li2O

(1)

Wang et al. [67] investigated the graphene/Fe2O3 nanocomposite prepared by
reduction of the graphite oxide by hydrogen reduction method at 500 °C which wasincorporated in the Fe2O3 synthesized by in situ hydrothermal treatment. The
electrochemical performance of the nanocomposites was compared with the pristine Fe2O3
micro particles prepared by the same technique. The electrochemical performance ofcomposites was analyzed by fabricating electrode CR2430 coin cell assembled withcomposite material as anode vs. Li+/Li reference electrode. The charge–dischargeElectrochem 2022, 3, 143–183

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performance of the cell was analyzed 0.005 V to 3.0 V vs. Li+/Li reference electrode.
Graphene/Fe2O3 cells delivered an initial discharge capacity of 1800 mAh g−1 at 160 mA g−1
and a charge capacity of 1420 mAh g−1 at the same condition. Comparing the performanceof Graphene/Fe2O3 with pristine graphene and Fe2O3 electrodes at the same current
density after 100 cycles displayed a 660 mAh g−1, which was much higher than that of thepristine cells (Graphene electrode‐550 mAh g−1 and Fe2O3 450 mAh g−1. A similar study
conducted by Li et al. [68] Graphene/Fe2O3 composites were prepared by solution mixing
of Fe2O3 nanoparticles with graphene oxide synthesized by modified Hummer’s method
by ultra‐sonication followed by freeze‐drying technique. The electrochemical studies ofcoin cells fabricated with composite as anode vs. lithium metal revealed an initial charge–
discharge capacity of 2550 and 1551 mAh g−1 , respectively, at 0.1 C cycled between 0.01 to
2.5 V. Zhu et al. [58] reported a simple two‐step reaction for the synthesis of rGO/Fe2O3
nanocomposite by homogeneous precipitation of FeCl3 in a suspension of graphene oxide
platelets with urea, with subsequent decrease in the graphene oxide with hydrazine bymicrowave technique to yield rGO platelets decorated with Fe2O3 nanoparticles [58]. The
scattered Fe2O3 nanoparticles on rGO nanoplatelets offered an enhanced electricalconductivity. The charge and discharge capacities of rGO/Fe2O3 composite revealed theenhanced performance of 1227 and 1693 mAh g−1. The specific capacity of rGO/Fe2O3 hasenhanced considerably than the pristine RG‐O and Fe2O3 confirming the synergistic effectof rGO and Fe2O3 on the improvement of electrochemical performance.
Copper Oxide/Graphene Composites as Anode for LIBs
Copper oxide is one of the widely explored anode materials for LIBs. The eco‐friendly
nature of the metal oxide, along with superior theoretical capacitance (674 mAh g−1) as
well as the availability of the material makes it a highly attractive candidate as the anodein rechargeable batteries. Several reports on exploring CuO as the anode in LIBs have beenreported so far [69–71]. The lithium insertion in the CuO anode causes volume expansion
leading to a decrease in the cyclability of the batteries is considered to be a major drawbackof these anodes. Hence, to enhance the cycling stability of CuO, carbon allotropes areadded as a composite material. Among carbon allotropes, graphene is the mostprominent. Lithiation and de‐lithiation of the CuO anode, analyzed by transmission
electron microscopy, revealed the formation of Li2O in the CuO matrix by Equation (2)[72]. The schematic illustration of in situ analysis of TEM of LIB is depicted in Figure 14a.
Figure 14b reveals the TEM image of the composite CuO/graphene electrode. Based on
the morphological variation, an ion‐conducting pathway has been proposed in Figure 14b.
The size of the CuO nanoparticles anchored on graphene resulted in a volumetric
expansion of during the lithiation and delithiation process of the anode. Figure 14h
displays a focused image of the lithiated CuO nanoparticles, evidently displaying that thesurfaces, as well as the edges of the composite electrodes, were coated with thin shells of
Li2O which was further confirmed by Figure 14i. The variation in size of the CuOcomposite during lithiation and delithiation process is demonstrated in Figure 14j [72].
CuO + 2 Li+ + 2e− → Cu + Li2O

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Figure 14. Morphological images of the changes occurring in pristine CuO/graphene electrode on
charge–discharge cycling in a nano‐LIB; (a) Illustration of the electrochemical setup for in situ TEM
imaging, (b) schematic representation of the reaction front in a single CuO particle and the transport
pathway for Li+ ions and electrons; TEM image of (c) the pristine CuO nanoparticle, (d) the firstlithiation product, (e) delithiated CuO nanoparticle, (f) the second lithiated CuO, (g) delithiatedCuO nanoparticle (h) HRTEM image recorded from a lithiated CuO nanoparticle, (i) lithiated CuOnanoparticles, (red circles indicate the formation of Cu grains and the inset represents highresolution images, and (j) the schematic illustration of the variation in size of the CuO onlithiation/delithiation process. Adapted and reproduced with permission from ref [72]. Copyright2015 American Chemical Society.

Liu et al. [73] reported the fabrication of free‐standing and flexible CuO nanosheets(NSs)/reduced graphene oxide (r‐GO) hybrid lamellar paper via simple vacuum filtration
method followed by hydrothermal reduction of the products. The surface charge of GO
being the negative the positively charged copper oxide are decorated on the GO surface
as depicted in Figure 15. The morphological analysis of the composite membrane confirms
the decorated structure (Figure 15). The electrochemical performance of the composite

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was analyzed in three different mass ratios of CuO NSs to r‐GO (2:1, 1:1, 1:2) which was
directly employed as the working electrode, and Li metal foil was used as the referenceelectrode. The working electrode was used in pristine form without the binder andconductive carbon. The studies revealed that CuO NSs/rGO (1:1) delivered an enhanced
discharge specific capacity of 736.8 mA h g−1 at a current density of 67 mA g−1 [73].

Figure 15. (a) Schematic representation of the synthesis of flexible free‐standing CuO nanosheets(NSs) with graphene oxide (GO)/reduced graphene oxide (r‐GO) hybrid lamellar paper via simple
vacuum filtration method followed by hydrothermal reduction (CuO NSs/GO and CuO NSs/r‐GO
paper); Morphological analysis of the sample, top‐view SEM images (b) CuO NSs/GO and (c) CuO
NSs/r‐GO paper, the inset in c is a digital photograph of CuO NSs/rGO paper with a diameter of ca.
19 mm; Cross‐section SEM images of (d,e) CuO NSs/r‐GO paper, the inset in e is a digital
photograph shows good flexibility (the inset in e), (f,g) TEM images of the CuO NSs/r‐GO paper,
inset of (g) is electron diffraction pattern. Adapted and reproduced with permission from ref [73].
Copyright 2013 American Chemical Society.

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Molybdenum Chalcogenide/Graphene Composites as Anodes for LIBs
Molybdenum composites are one of the most widely explored two‐dimensional
materials due to their properties similar to that of graphene. Hence, molybdenum‐based
chalcogenides such as molybdenum oxide, molybdenum sulfide, etc., are widely
investigated as anodes composited with graphene for enhancing the anodic properties in
LIBs lithium‐ion batteries. Chang et al. [52] investigated layered MoS2/graphene
composites revealed the most elevated explicit limit of 1571 mAh g−1 at a current densityof 100 mA g−1 estimated from MoS2/G (1:2) on account of its round 3D morphology (Figure16a). The intercalation of the Li+ ions was eased which was evident from the cyclic stability
and rate capability delivered by the cell studies as depicted in Figure 16c,d. In 2014, Choiet al. [74] arranged folded graphene/MoO3 composite by shower pyrolysis, ensuingtempering at 300 °C [74]. They closed its performance as improved explicit limit (1490mAh g−1), higher Coulombic efficiency, better cyclic security, and expanded rate ability incorrelation with uncovered MoO3 powders (Figure 16). Petnikota et al. [53] found theintercalation of Li‐ion and explained the synthesis of exfoliated graphene oxide/MoO2
composites as anode materials through a modest solid‐state graphenothermal reduction
method. The results revealed intercalation mechanism is best for steady‐state capacity
during the cycling for the reason of superfluous graphene and stability window even in
the operating voltage of 0.005−3.0 V and MoO2 undergoes conversion below 0.8 V.
Almodavar et al. [75] studied hexagonal molybdenum trioxide (h‐MoO3) micro rods andtheir composites with graphite, graphene, and graphene oxide. The h‐MoO3/GO terminals
convey a striking explicit limit of 789 mAh g−1 after 100 cycles at a high current density of1000 mA g−1, while h‐MoO3‐graphene cathodes show a great steadiness at extremely highcurrent densities, with a specific capacity limit exceeding 665 and 490 mAh g−1 at 2000 and3000 mA g−1, respectively. EIS estimations and SEM‐EDX of the cycled terminals uncoverthat the consistently scattered graphene and GO layers increase the structural stability of
the composites and make a conductive organization that guarantees compellingambipolar dispersion of electrons and Li+ particles, bringing about a huge electrochemical
limit and rate execution at raised current densities. These outcomes grow the possible usesof h‐MoO3 and their composites towards LIBs, making them ready for future upgrades.

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Figure 16. Morphology and electrochemical properties of layered MoS2/graphene composites(MoS2/G) synthesized in variable ratios; Morphology of layered MoS2/graphene composites(MoS2/G) synthesized in 1:2 ratio (a) SEM image, (b) TEM image; electrochemical properties of lay‐ered MoS2/graphene composites (MoS2/G) synthesized in variable ratios, (c) cycling behavior of
MoS2, MoS2/G (1:1), MoS2/G (1:2), and MoS2/G (1:3) after annealing in H2/N2 at 800 °C for 2 h at acurrent density of 100 mA g−1; (d) Rate capability of MoS2/G samples at different current densities(inset provided the SEM image, SAED pattern and HRTEM images of MoS2/G composites). Adapted
and reproduced with permission from ref [52]. Copyright 2011 American Chemical Society.

Titanium Oxide/Graphene Composites as Anode for LIBs
Titanium oxide, otherwise known as titania, is a wide bandgap semiconductor mate‐rial. The optical band gap of titania is reported to be 3.1 eV. Titania crystalizes in threeforms, namely anatase, rutile, and brookite, out of which rutile form is stable in room
temperature conditions and is widely formed when titania is synthesized in the bulk form,
whereas anatase and brookite are metastable forms stabilized in lower size regimes. Tita‐
nia has been widely explored as anode material in LIBs [76–80]. However, the perfor‐
mance of the anode can be enhanced by incorporating various nanomaterials in the metaloxide as a composite. Graphene is one of the major composites added to titania to improve
the performance of the anode in LIBs. The TiO2/graphene, as well as TiO2/reduced gra‐
phene oxide (rGO) composites, are widely explored in this area. These composites aremostly synthesized by reacting graphene oxide (GO) and TiO2 nanoparticles through hy‐
drothermal reaction [74], UV photocatalytic reduction of GO in the presence of TiO2 [81],and even synthesized by dispersing graphene as sol‐gel along with titania precursor [82]A schematic illustration on the formation of TiO2/graphene composite with titanium hy‐
droxide precursor is depicted in Figure 17.

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Figure 17. Schematic representation of the mechanism of the formation of the TiO2/graphene nano‐composite, wherein Ti(OH)4 reacts with functional groups of GO sheets leading to the reaction ofoxygen atoms with titanium precursor to form graphene/TiO2 nanocomposites. Adapted and repro‐
duced with permission from ref [83]. Copyright 2014 Elsevier.

Qiu et al. [83] reported mesoporous TiO2/graphene composite was synthesized bytitania oxysulfate (TiOSO4) as TiO2 precursor which was hydrothermally composited withgraphene oxide (GO) by a one‐step hydrothermal route. The electrochemical studies of
the composite were analyzed by fabricating working electrodes with TiO2/G, acetylene
black, and binder (polytetrafluoroethylene, PTFE) at a weight ratio of 70:20:10 and lithium
metal as reference electrode, with electrolyte medium of 1 M LiPF6 in ethylene car‐bonate/dimethyl carbonate (EC/DMC, v/v 1:1) mixture. The alteration in discharge capac‐
ity at variable current densities (500 to 5000 mA g−1) investigated revealed a discharge
capacity of 206.7 mAh g−1 at 500 mA g−1 after the 10th cycle which was further diminished
to 190.9, 179.1, 169.5, 160.8, and 141.7 mAh g−1 at the current densities of 1000, 2000, 3000,
4000, and 5000 mA g−1, respectively. The same group also reported the synthesis of TiO2/graphene composites by the photocatalytic method [81]. For the same, GO was synthe‐
sized by modified Hummer’s method and titania (anatase) was synthesized by hydrother‐mal method from titanium butoxide precursor. TiO2/graphene composite was preparedby homogeneously mixing GO (0.04 g in ethanol) with TiO2 (25 mL) solution (2% w/v) inan ultrasonic bath followed by UV irradiation under 1000‐W xenon lamp with prolonged
stirring (2−5 h). The resultant solution was then filtered and rinsed with deionized water,
and the resultant composite obtained was dried in a vacuum oven at 60 °C for 12 h. Thus,
the obtained TiO2/graphene composite was used for electrochemical analysis as an anodein LIBs. The reversible discharge capacity of TiO2‐rGO, TiO2‐GO, and TiO2 was 310, 220,
and 150 mAh g−1, respectively, which was much higher than the previous report [81]. The
transport properties of TiO2/graphene composites were reported by Lam et al. [84]. The
TiO2 with tiny subunits enclosed in highly conductive graphene oxide nanosheets, which
possess a highly porous network structure facile the diffusion of the electrolyte facilitating
the lithium–ion intercalation and enhancing the electronic conductivity to the external cir‐
cuit, as depicted in Figure 18.

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Figure 18. Schematic representation of the transport path of lithium ions and electrons in thetheTiO2/graphene hybrids where TiO2 with tiny subunits enclosed in highly conductive graphene
oxide nanosheet (TGR) hybrids. Adapted and reproduced with permission from ref [84]. Copyright2015 Nature.

Graphene/Silicon Composites as Anode for LIBs
Si nanoparticles have been widely investigated as anode in LIBs for their most ele‐
vated known hypothetical charge limit (4200 mAh g−1) and poor release potential (~0.5 V
versus Li/Li+) [85] [86]. Similarly, its powerful application in LIB cannot be executed inlight of its gigantic volumetric extension (~270%) from electrochemical responses [87].
Subsequently, hardly any more works have been investigated to reveal graphene fuse asframework stage along with the nanoparticles based on Si to beat these inadequacies[87,88]. For instance, Lee et al. [47] reported the synthesis of Si nanoparticles incorporated
graphene sheet (Si/GS) by sandwiching the 3D graphite network with well‐dispersed Si
nanoparticles inside the graphene layers. The fabricated anode material is capable of ex‐
hibiting a greater capacity limit of ~2200 mAh g−1 after 50 cycles with a capacity retentionof ~1500 mAh g−1 even after 200 cycles. The cross‐section of the electrode before and after
200 cycles has been given in Figure 19. The expansion of the electrode is visible from thegiven images. Modification of Si/GS structure was reported by Kim et al. They have used
the strategy of covering the gel by ex situ carbon and carbonization to form thermallydecreased 2D planer Si/GS structure and settled three‐dimensional Si/graphene sheet/car‐bon (Si/GS/C) nanocomposite having enough inner void space [86]. The gathering dis‐closed a prevalent explicit limit ~1350 mAh g−1 and good cyclic security (~600 mAh g−1
after 200 cycles) as compared with Si/GS in the premise of extended cycle exhibitions.

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Figure 19. Morphological analysis of a cross‐section of Si/graphene sheet/carbon (Si/GS/C)‐S@Gr
before and after cycling; (a) before and (b) after cycling for 200 cycles. Adapted and reproducedwith permission from ref [86]. Copyright 2016 authors.

In 2017, Yi et al. [89] displayed a compelling plan and blend of SiC/G nanocomposite
where nanoparticles of SiC are homogeneously implanted in GNS. They proposed a sim‐pler SiC/graphene anode combination with improved electrochemistry through Li+ ion
dispersion. The report estimated a reversible limit of 1044 mAh g−1 at a current density of
100 mA g−1 and an extraordinary electrochemical stability of 230 mAh g−1 even after 1000
cycles at 1 Ag−1 (Figure 20). Another recent work was proposed by Shi et al. [90]. They
have explored CVD method to synthesize vertical graphene‐epitomized SiO microparti‐
cles (d‐SiO@vG) (Figure 20). The interconnected vertical graphene–SiO anodes showed
good cycle stability of 1600 mAh g−1 with about 93% of retention in capacity even after 100
cycles. Nanostructure correction of Si/graphene nanocomposite by surficial carbon cover‐ing additionally gained a lot of consideration from researchers. Li et al. [91] revealed in2013 a carbon‐covered Si nanoparticle/ graphene composite (Si@C/G) thermal annealingof the freeze‐dried mixture of Si nanoparticles, sucrose, and GO. Here, the carbon‐covered
Si nanoparticles disperse simultaneously with GO, which delivers cycling stability of 1410
mAh g−1 at a current density of 500 mA g−1 after 100 cycles. Ma et al. [92] revealed in 2017an upgrade which resulted in carbon nanofibers interlaced graphene/silicon (G/Si@CFs)
structure. Graphene oxide (GO) was synthesized by Hummer’s method followed by spraydrying. GO powder was then calcined at a high temperature of 1000 °C under nitrogen
atmosphere protection to form micron‐sized spherical particles with curved and loose‐packed graphene sheets (GS). Si nanoparticles were then deposited onto the surface of GS
to form a G/Si composite by a chemical vapor deposition (CVD) at 550 °C [92]. Silane wasused as Si precursor and hydrogen was used as the carrying gas. Synthesized G/Si parti‐
cles were followed by mechanical mixing in DMF solution of polyacrylonitrile (PAN), theresultant medium was subjected to electrospinning process, PAN compounded G/Si par‐ticles and PAN nanofibers composite film was prepared. The annealing at 800 °C in Ar
gas caused the carbonization of PAN to form a composite film of a high conductive carbon
nanofibers network and the carbon‐coated G/Si particles. A schematic illustration of thesame has been depicted in Figure 20A [92]. In this investigation, at first, pre‐arranged
Si/graphene composite was covered by exceptionally conductive carbon nanofibers net‐
works is evident from the SEM and transmission electron microscopic (TEM) images asgiven in Figure 20 [87]. The resulting electrochemical highlights of this structure are a
beginning release limit of 1792.1 mAh g−1, 86.5% limit maintenance after 200 cycles, andhigh rate execution esteemed 543 mAh g−1 limit at the pace of 1000 mA g−1. Subsequently,
successful Si/graphene‐based nanocomposite configuration may be those constructionsElectrochem 2022, 3, 143–183

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where graphene stays as a non‐stop conductive organization to convey familiar sectionsof Li‐ions to dynamic materials and support the volume change of Si‐based materials.
Thus, Si‐based nanoparticles disseminated homogeneously with high surface regions
ought to be filled in as host destinations of lithiation and delithiation. It has been, as of thetime of writing, accepted that the nanosized metallic oxides, sulfides, and carbides are
better than their mass partners [93].

Figure 20. (A) Schematic illustration on the synthesis of process of the G/Si@CFs composites (a) SEM image of G/Si parti‐cles, (b,c) HRTEM image of G/Si particles, (d) low magnification SEM image of G/Si@CFs, and (e) high magnification SEM
image of G/Si@CFs. Adapted and reproduced with permission from ref [92]. Copyright 2017 Nature.

4.2. Graphene as Cathodes for LIBs
Different types of graphene‐based composites have been reported as cathodes in
LIBs. Due to its 2D versatility, graphene can easily connect dynamically to metal oxidesurfaces. Pristine graphene, doped graphene, graphene composites such asElectrochem 2022, 3, 143–183

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graphene/metal phosphates, graphene/metal silicates, graphene/metal chalcogenides,
etc., are some of the most commonly reported graphene composite cathodes for LIBs.
Among them, olivine phosphate (Li2MPO4) and silicate (Li2MSiO4) (M = Fe, Mn, and Co)
have the benefits of minimal expense, good electrochemical performance, high stability,
and so forth, explored widely as cathode materials in LIBs [94,95].
4.2.1. Pristine Graphene as Cathodes for LIBs
Graphene as an anode was widely explored in LIBs, but the same as a potential can‐didate for cathode was less investigated. The carbon‐based electrodes are capable of theformation of oxocarbon salt (Li2C6O6) reversibly enabling the development of new gener‐
ation sustainable as well as eco‐friendly energy storage devices [96–98]. In 2013, Sung etal. [99] reported the development of reduced graphene oxide which serves as free‐stand‐ing cathodes for LIBs. The GO synthesized by modified Hummer’s method was subse‐
quently thermally reduced to rGO under Ar/H2 atmosphere. Thus, prepared rGO wasthen mixed with CTAB (cetyltrimethylammonium bromide) by stirring and sonication
technique. The mixture was centrifuged to collect the supernatant liquid followed by fil‐tration in the AAO membrane to prepare free‐standing rGO films [99]. The electrochemi‐
cal studies of the membrane were conducted by assembling coin cells with rGO, lithium
metal and Celgard 2600 as the working electrode, counter electrode, and separator, re‐spectively. The electrolyte medium employed was the 1 M solution of LiPF6 in ethylene
carbonate/dimethyl carbonate (EC/DMC (1:1) v/v). rGO 15 (the sample with carbon to ox‐ygen ratio 15) reveals an initial discharge capacity of ∼125 mAh g−1, and within five cycles,
it is stabilized at 110−115 mAh g−1 (Figure 21). Xiong et al. [100] reported enhancement in
the electrochemical properties of the rGO on an increase in oxygen‐containing functionalgroups. The rGO was synthesized from GO by thermal reduction procedure at different
annealing temperatures and times. The cell studies were conducted by fabricating theelectrode in the active material, conductive carbon, and PVdF (binder) in NMP in the ratioof 80:10:10 and coin cells were fabricated similar to that of the previous procedure. The
sample, annealed for 1 min at 950 °C, revealed an initial discharge capacity of 163 mAh
g−1, enhanced up to 220 mAh g−1 at 50 mA g−1 [100].

Figure 21. The performances of rGO15 films at 0.137 A g−1 for 30 cycles; (a) charge–discharge curves,(b) cyclability of rGO15, and (c) schematic illustration of the synthesis of rGO electrode. Adapted
and reproduced with permission from ref [99]. Copyright 2013 American Chemical Society.

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4.2.2. Doped Graphene as Cathodes for LIBs
The performance of graphene‐based cathodes in LIBs can be enriched by the additionof atoms. Even though sulfur, nitrogen, and boron have been reported as a dopant in gra‐
phene‐based anodes, in the case of cathodes, nitrogen was chosen to be the most appro‐
priate electron donor which facilitates the insertion of lithium ions. Nitrogen‐doped GNS
was synthesized by the hydrothermal method, mixing the GO with urea in the ratio 1:0,
1:20, and 1:300 at 180 °C for 2 h labeled as GNS, NGNS I, and NGNS II [101]. The
electrochemical performance of nitrogen‐doped GNS was compared with the HGNS
electrode as depicted in Figure 22. The cyclic voltammetry studies conducted in the rangeof 1.5–4.5 V vs. Li/Li+ at 0.1 mV s−1 revealed similar behavior with a slight change in thecurrent displayed by HNGNS II attributed to the enhanced surface defects. The charge–
discharge profiles depicted in Figure 22b in the same voltage range at 50 mA g−1 displayed
an enhancement in the reversible performance of NGNS‐II having a capacity of 330 mAhg−1, whereas undoped samples showed lower capacity (195 mAh g−1). The cycle
performances of the GNS, NGNS‐I, and NGNS‐II at the same condition are depicted in
Figure 22c, where NGNS II samples showed the highest reversible capacity of 345 mAh
g−1 even at 200 cycles. The rate capabilities of GNS, NGNS‐I, and NGNS‐II displayed in
Figure 22d at different C rates also displayed enhanced performance of NGNS‐II electrodewhich exhibits an average capacity of 315, 327, 290, and 254 mAh g−1 at 0.05, 0.1, 0.2, and
0.4 A g−1, respectively. The electrochemical performance of NGNS II is attributed toincreased N doping and an increase in urea concentration during the synthesis [101].

Figure 22. (a) Cyclic voltammogram of GNS, NGNS‐I, and NGNS‐II electrodes in the second cycle
at a scan rate of 0.1 mV s−1; (b) Galvanostatic charge–discharge profiles, and (c) cycle performanceof GNS, NGNS‐I, and NGNS‐II electrodes at a current density of 0.05 A g−1; (d) Rate performance of
GNS, NGNS‐I, and NGNS‐II electrodes at various current densities in the range of 0.05–0.4 A g−1;
and (e) Cycle performance of NGNS‐I and NGNS‐II electrodes (up to 1000 cycles) and the
Coulombic efficiency of NGNS‐II at a high current density of 1 A g−1. All experiments were in a

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voltage range of 1.5–4.5 V vs. Li/Li+. Adapted and reproduced with permission from ref [101]. Cop‐yright 2017 American Chemical Society.

4.2.3. Graphene/Metal Chalcogenide Composites as Cathodes for LIBs
Conventional LIBs are confined with graphite and lithium metal oxide as anode andcathode, respectively. The safety issues and reduced cycling stability have paved a way
for researchers to explore newer materials as components for lithium‐ion batteries.
Among chalcogenides, sulfur compounds have a potential role as a cathode that possesses
an elevated energy density of 2600 Wh kg−1. The property of sulfide compounds to form
polysulfide compounds with lithium has been investigated in lithium‐sulfur batteries[102]. The lack of cyclability of such cells has diminished the performance of such batteries[103]. Recently, Chang et al. [103] reported the molybdenum sulfide composited rGO as
cathode for lithium‐ion batteries. The electrode fabrication is being conducted by electro‐
chemical pulverization of MoS3 from bulk. The presence of an oxygenated functionalgroup on the rGO surface adheres to the nano MoS3 particles on its surface, ensuring thesynergistic effect of both components. The electrochemical analysis of half‐cell deliveredvoltage stability in the range of 0.5–3 V vs. Li/Li+ and full cell study with lithiated Si/C
anode displayed an initial discharge performance of 2062 mAh g−1 at 0.5 A g−1 that are
reduced spontaneously to 431 mAh g−1 on prolonged cycling up to 24 cycles (Figure 23a).
Gradually the capacity was raised to 1126 mAh g−1 on cycling above 110 cycles which
retained the performance up to 400 cycles. The cycling stability of the cell conducted at 5C
displayed lower capacity initially (700 mAh g−1) which increased to 1200 mAh g−1 on cy‐
cling above 1000 cycles followed by a diminishing performance to ~900 mAh g−1 above
1500 cycles, which retained the capacity up to 2500 cycles (Figure 23c) [103].

Figure 23. Cycling performance of a MoS3/r‐GO half‐cell with electrolyte additive (FEC); (a) the half‐cell test for the MoS3/r‐GO for the cathode with electrolyte additive (FEC) is carried out between
0.05 and 3.0 V at 25 °C. (b) The cyclability and CE of the full‐cell measured at 0.25 A g−1 for 150
cycles. (c) The half‐cell test for the MoS3/r‐GO for the cathode with FEC is carried out between 0.05
and 3.0 V, respectively, at 25 °C. The cyclability and Coulombic efficiency (CE) of the MoS3/r‐GO
half‐cell is measured at 5.0 A g−1 (5C based on average reversible capacity (∼1000 mAh g−1) over 2500

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cycles. The specific capacity is calculated based on the MoS3/r‐GO cathode. Adapted and repro‐
duced with permission from ref [103]. Copyright 2019 American Chemical Society.

4.2.4. Graphene/Silicate Composites as Cathodes for LIBs
Graphene silicate composites are one of the rarely explored composites as cathodefor LIBs. Among graphene silicate composites, the most widely are is Li2FeSiO4 [95,104],
Li2MnSiO4 [105], and Li2VSi2O6 [106], etc. Li2FeSiO4 is also abbreviated as LFS and is widely
explored among silicate cathodes owing to its theoretical capacity of 332 mAh g−1 whichaccommodates two lithium ions in the lattice [95]. Even though the LFS possess better
theoretical capacity, the performance is less due to the reduced electrical conductivity,
hence to enhance the performance of cathode LFS is composited with rGO. Zhang et al.
[95] reported rGO modified LFS/C composite cathode synthesized by citrate‐nitrate gel
combustion (sol‐gel) method with citric acid as a chelating agent. A control sample with‐out rGO was also synthesized to compare the electrochemical performance of the material.
The electrochemical studies revealed LFS/(C + rGO) electrode displayed an enhanced ini‐tial discharge capacity of 188.7 mAh g−1 compared with LFS/C which delivered an initialdischarge capacity of 162.1 mAh g−1 at 0.1 C. The electronic conductivity of the LFS/(C +rGO) cathode showed considerable enhancement of 1.5 × 10−3 S cm−1 due to incorporationof rGO compared with that of the LFS/C cathode which displayed an electronic conduc‐tivity of 7.1 × 10−4 S cm−1. Similarly, Zhu et al. [105] reported Li2MnSiO4 C/graphene cath‐ode for LIBs. The electrochemical studies revealed that LMS/C/G composite displayed in‐itial charge/discharge capacities of 336.5 and 270.7mAh g−1, respectively, gradually de‐creasing the discharge capacity to 252.7mAh g−1 in the 5th cycle. The author, Reddy, re‐ported the synthesis and electrochemical performance of Li2VSi2O6/G cathode for LIBs
synthesized by single‐step solid‐state reaction at 900 °C in Ar atmosphere. The half cell
test displayed a discharge capacity of 108 mAh g−1 at a current density of 20 mA g−1 (0.15C)over a potential window of 1.5–4.5 V Li/Li+ at room temperature [106].
4.2.5. Graphene/Phosphate Composites as Cathodes for Lithium‐Ion Batteries
Phosphate‐based cathodes belong to the most accepted cathode material owing toenhanced safety, cycling stability, and low cost of the material. Among phosphates, lith‐ium iron phosphate is the most widely explored cathode in LIBs. Lithium Ferro phos‐
phate, otherwise known as lithium iron phosphate and abbreviated as LFP, is one of themost widely investigated cathode materials for LIBs. Even though the energy density andvoltage stability window of LFP is lower than that of LCO, considering the risk factors
associated with LCO makes LFP a prominent alternative cathode material. The energy
density of LFP is around 90–160 Wh kg−1 with a nominal cell voltage of 3.2 V, whereas in
LCO the energy density ranges from 150 to 200 Wh kg−1 with a nominal cell voltage of 3.6
V. In 2014, Zhu et al. [107] reported LFP/rGO composite cathode with high performance.
GO was synthesized by modified Hummer’s method followed by composition by in situ
synthesis of LFP from Fe(NO3)3, NH4H2PO4, and urea, followed by refluxing at 90 °C for
1.5 h. The resultant product was then annealed at inert atmosphere for about 8 h to ensurecomplete conversion to obtain phase pure composite. The rGO/LFP composite with 15
wt.% of rGO delivered an initial charge/discharge capacity of 160.2 and 172 mAh g−1. On
prolonged cycling up to 50 cycles, the hybrid cell displayed a specific capacity of 168 mAh
g−1 with a capacity retention of 97.5%.
Zhou et al. [108] reported graphene‐modified LiFePO4 cathode for LIBs. Contradic‐
tory to the previous method, herein LFP and GO were synthesized separately followed bymixing both the systems LFP/GO (10:1 v/v) by ultra‐sonication followed by spray drying
the composite. The resultant composite of LFP/GO was then annealed at 600 °C for 5 h at
Ar atmosphere for converting GO to rGO. A schematic representation of the same has
been depicted in Figure 24. The morphological analysis of the composites have been dis‐played in Figure 25a reveals that the LFP/G forms secondary quasi‐spherical particles in
the micrometer regime (2–5 μm). On increased magnification (Figure 25b) the aggregation

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of the LFP nanoparticles entrapped in graphene sheets is displayed. The elemental map‐ping of LFP nanoparticles (red) and graphene (green) supports the inference of the SEM
analysis (Figure 25c,d). Figure 25e and f further confirm the entrapment of LFP in gra‐
phene sheets. On comparison of the electrochemical performance of the samples, LFP/G
displayed better performance with an initial discharge capacity of 148 mAh g−1 whereas
LFP/C/G displayed performance of ~150 mAh g−1 at 0.1C. The studies revealed that the
LFP/C/G is a more efficient cathode than LFP/G owing to the incorporation of activatedcarbon. Kim et al. [109] reported catalyst assistant self‐assembly of graphene on LFP. The
electrochemical study of the samples was compared with carbon‐coated LFP samples re‐vealing that both the cathodes discharge capacities of ∼150 mAh g−1 at 1 C. After 100 cy‐
cles, the G/LFP delivered a discharge capacity of 135 mAh g−1 with retention of 95.0% of
its initial discharge capacity, C/LFP displayed a discharge capacity of 121 mAh g−1 with acapacity retention of 86.7%.

Figure 24. Schematic illustration of the synthesis of rGO modified LiFePO4. Adapted and repro‐
duced with permission from ref [108]. Copyright 2011 Royal Society of Chemistry.

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Figure 25. Illustration of the preparation process and the microscale structure of LFP/graphene com‐posite. (a,b) SEM images show an overview of the LFP/G particles, (c) TEM image of the LFP/G
particles, (d) corresponding elemental map using EELS of the same area showing graphene‐sheets
wrapping on LFP nanoparticles, where red represents the LFP nanoparticles, obtained from the P
L‐edge, and the green represents graphene sheets, obtained from C K‐edge, (e) TEM image on theedge of individual microspheres. The inset is a high‐resolution TEM image illustrating the 3–5 mon‐olayer thickness of the graphene sheets on the surface of an individual LFP nanoparticle, and (f)TEM image showing a 3D graphene network obtained by removing LFP nanoparticles with an HCl
solution. Adapted and reproduced with permission from ref. [108]. Copyright 2011 Royal Society ofChemistry.

Yang et al. [110] reported a 3D porous hybrid graphene/LFP cathode. The synthesisof the composite electrode was achieved by template free sol‐gel method. GNS was syn‐thesized from graphite oxide followed by mixing with lithium dihydrogen phosphate andiron (III) citrate to form a gel which was combusted at 700 °C for 10 h at Ar atmosphere.
A control sample was prepared by omitting the GNS to form porous LFP structures. A
schematic illustration of the synthesis of porous graphene LFP composite (p‐G/LFP) andporous LFP (p‐LFP) has been depicted in Figure 26. The electrochemical analysis of the P‐
LFP and p‐G/LFP showed a considerable difference of ~100 and ~130 mAh g−1 at a current
density of 17 mA g−1 [110].

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Figure 26. Schematic representation of the formation of 3D porous networks (a) LFP/graphene and(b) LFP. Adapted and reproduced with permission from ref. [110]. Copyright 2012 Elsevier.

4.2.6. Graphene Polymer Composites as Cathodes for Lithium‐Ion Batteries
Several polymers are explored as a composite material with graphene as cathode for
LIBs. Polyimides are the most prominent polymer in this category [111,112]. Unless, likeinorganic cathodes, organic cathodes are more flexible and stable, which is capable to en‐
hance the cycle stability of the batteries. The diminished conductivity of organic electro‐
lyte retards its efficiency; hence, to elevate the conductivity of these materials, graphene
compounds are incorporated as composites. In 2016, Ahmad et al. [112] reported graphene
polyimide cathodes for LIBs. In the proposed synthesis, exfoliated graphene was mixed
with pyromellitic dianhydride (PMDA) monomer and ethylenediamine (EDA) (1:1 ratio)in N‐methyl pyrrolidone (NMP) solvent followed by refluxation at 150 °C under inert at‐mosphere for 9 h. The synthesized composite was washed in ethanol followed by drying
at an inert atmosphere (300 °C for 7 h). The resultant product was dissolved in acetone
and extracted with the Soxhlet apparatus. The electrochemical performance of the mate‐rial was investigated in a half cell with an electrode fabricated with active material/ con‐ductive carbon and PTFE binder in the ratio 65:30:5. The role of the polymer was analyzed
by varying the concentration of the monomer PMDA from 0.01 to 0.15 mmol mL−1. At alower concentration the electrode delivers the capacity of 177 mAh g−1 at 0.1 C, on increasein concentration to 0.05 mmol mL−1, the capacity declined to 167 mAh g−1. On further in‐crease in the concentration of PDMS to 0.15 mmol mL−1, the discharge capacity further
decreased to 90 mAh g−1 [112]. On the other hand, Huang et al. [111] reported a 3D polyi‐
mide graphene composite synthesized by the one‐pot method by mixing 1,4,5,8‐naphtha‐lene tetracarboxylic dianhydride (NTCDA) in GO and 1‐methyl‐2‐pyrrolidinone (NMP)
mixture, which is ultrasonicated by adding ethylenediamine followed by solvothermal
treatment to obtain 3D GNS/PI composite (Figure 27). Electrochemical study of the com‐posite delivered a discharge capacity of 240 mAh g−1 at 40 mA g−1 compared with that ofcarbon/PI composite which delivered 153 mAh g−1 at the same current density [111].

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Figure 27. (a) Low‐ and (b) high‐magnification SEM images and (c) TEM image of GF–PI; (d) low‐and (e) high‐magnification SEM images of pure PI; (f–i) elemental mapping images of GF–PI (bySEM): carbon (g), N (h), and O (i) distribution in the selected area. Adapted and reproduced withpermission from ref. [111]. Copyright 2017 Royal Society of Chemistry.

4.3. Graphene as Filler in Electrolyte for Lithium‐Ion Battery
Electrolytes are an important part of battery technology. Recent research works give
more attention to electrolytes, which mainly focuses to satisfy the increasing demand for
portable electronic devices and electronic vehicles, with the aim of better energy densities
and a long shelf life with a satisfying level of safety at a reasonable price [113]. For the lastfew decades, the main focus of battery research has been dedicated to electrolytes. Even
though liquid electrolytes belong to the primary electrolytes, which have huge benefits
such as high ionic conductivity with a good wetting ability which enables wetting of elec‐
trode surfaces. The most prominent disadvantages of liquid electrolytes include negligible
vapor pressure, low thermal and electrochemical stability, poor ion selectivity, and safetyissues [113,114]. The replacement of liquid electrolytes with more stable ionic liquids is
one of the alternatives for liquid electrolytes. Ionic liquids are molten salts that exist as aliquid under 100 °C [114]. The first generation LIBs were commercialized by Sony in 1990
with polycarbonate electrolytes [115]. However, the concentration of the electrolyte dis‐
rupted the graphitic anodes. The mostly employed lithium salts for electrolytes are LiPF6,
LiClO4, LiBF4, LiAsF6, etc. Among these salts, LiPF6 are thermally unstable and LiClO4 ishighly explosive when it comes to contact with organics; LiBF4 possess better stability asElectrochem 2022, 3, 143–183

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compared with the above stated, but it interferes at the anode; LiAsF6 is lethal; solutionsof LiSO3CF3 possess low conductivities; and LiN(SO2CF3)2 and LiC(SO2CF3)3 corrode of theelectrode. LiPF3(C2F5)3 (LiFAP), LiN(SO2CF3)2, (LiTFSI), and LiBC4O8 (LiBOB) are the othersalts used in lithium‐ion batteries [116]. These drawbacks lead to the development of non‐flammable, low‐cost electrolytes for LIBs. Polymer electrolytes and solid‐state electrolytes
are the common categories of electrolytes under study. Solid‐state electrolytes for LIBs aremainly categorized into three types, inorganic solid electrolytes, solid polymer electro‐
lytes, and hybrid solid polymer electrolytes. The first class contains solid electrolytes ofoxides (garnet, perovskite, anti‐perovskite, and LiPON13) and sulfides. The polymer elec‐
trolytes are poly(ethylene oxide) (PEO) based systems, polycarbonate‐based systems, andpolysiloxane‐based systems are the main systems [117]. Polymer electrolyte membranes
mainly act as a separator in LIBs, and they should need some specifications such as chem‐
ical stability, high proton conductivity, low fuel crossover, low electronic conductivity,
high permselectivity, low cost, and appropriate thickness with high thermal and mechan‐ical stability [118,119]
Yuan et.al [120] developed a solid polyethylene oxide/lithium salt electrolyte withhigh surface area and good mechanical strength by adding 1 wt.% GO nanosheet. The
tensile strength was enhanced up to 260% compared with that of pristine PEO. The ionic
conductivity of the composite polymer electrolyte was 5.6×10−8 S cm−1 ensuring the appli‐
cation of the same in LIBs. Later, Shim et.al, [121] modified the electrolytic system by in‐corporating poly(ethylene glycol)‐grafted graphene oxide (PGO) as filler in an organic/in‐organic hybrid copolymer electrolyte. The organic/inorganic hybrid copolymer electrolyte
employed was branched‐graft copolymer (BCP) based on poly(ethylene glycol) methyl
ether methacrylate (PEGMA) and 3‐(3,5,7,9,11,13,15‐hepta isobutyl pentacyclo‐[9.5.1.13,9.15,15.17,13]octasiloxane‐1‐yl)propyl methacrylate (MA‐POSS) was used as pol‐ymer matrix. The addition of 0.2 wt.% PGO showed considerable enhancement in the ionic
conductivity of 2.1 × 10−4 S cm−1 whereas pristine co‐polymer delivered an ionic conduc‐tivity of 1.1 × 10−5 S cm−1. The linear sweep voltammetry of the samples revealed a stability
window extending up to 5.3 V at 60°C. The cell performance of the cells was analyzed in
Li/SPE/V2O5 cells. The composite BCP/PGO electrolyte delivered an initial discharge ca‐
pacity of 287 mAh g−1 at 0.1 C rate (60°C) which was considerably higher than that of pris‐tine BCP (~185 mAh g−1 at 0.1 C rate).
Recently, sulfide‐based electrolytes are widely used due to their unique properties
such as high ionic conductivity and wide electrochemical windows. However, in a lith‐
ium‐ion battery, it might be due to severe issues such as obstructing the lithium‐ion flow
during the cycling process and increased interfacial resistance. To control these problems,
Li et al. [122] produced GO‐coated solid electrolyte Li7P3S11 (LPS) through the solution
synthesis method. This electrolyte particularly addresses the concerns of interfacial stabil‐
ity between the sulfide solid electrolyte and shows improved performance and excellent
cycling stability with the 1% GO/LPS. The other solid electrolyte was reported by Wen etal. [117]. In that report, (GO) is employed to improve the electrochemical performance,
thermal stability, and mechanical strength of the poly (ethylene oxide) (PEO) based elec‐
trolyte. They represent the electrolyte as LiFePO4//GO‐PEO//Li, showing the discharge ca‐
pacity of 142 mAh g−1 at 0.5 C, and 91% capacity retention after 100 cycles are the high‐lights. It can also complete a stable cycle charging and discharging process.
5. Conclusions
The present review summarizes the use of graphene and its composites as compo‐
nents in lithium‐ion batteries. Exploring the relevant as well as new studies, it has beenshown how graphene enhances the rate capability and performances, and how it reduces
the shutter effects in lithium‐ion batteries. From the information available, one could con‐clude that without graphene, the energy storage devices could not produce better perfor‐
mances. The structure and the specific characteristics are the highlights of graphene. Op‐
timistically, the day is not far away when the effective application of graphene‐based

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anode in rechargeable batteries will be treated as an innovation in battery performance.
For practical applications of bare graphene, further reduction in discharge and charge
voltages is needed.
Author Contributions: Conceptualization, M.V.V.R. and P.R.; writing—original draft preparation,
R.J.; N.T.M B.; A.D.; S.S.; writing—review and editing, V.K.T.; K.Z.; supervision, writing—review
and editing, J.F.M.J.; M.V.V.R.; P.R. All authors have read and agreed to the published version of
the manuscript.
Funding: This research received no external funding.
Institutional Review Board Statement: Not applicable.
Informed Consent Statement: Not applicable.
Acknowledgments: Authors Jabeen Fatima M.J. and Prasanth Raghavan would like to acknowledge
the Kerala State Council for Science, Technology, and Environment (KSCSTE) and Kerala State
Higher Education Council, Government of Kerala for financial assistance.
Conflicts of Interest: The authors declare no conflicts of interest. The funders had no role in thedesign of the study; in the collection, analyses, or interpretation of data; in the writing of the manu‐
script, or in the decision to publish the results.

References
1.

2.
3.
4.
5.
6.
7.
8.
9.
10.
11.

12.
13.

14.
15.

16.
17.

Zhang, H.; Chen, N.; Sun, C.; Luo, X. Investigations on physicochemical properties and electrochemical performance ofgraphite felt and carbon felt for iron‐chromium redox flow battery. Int. J. Energy Res. 2020, 44, 3839–3853.
https://doi.org/10.1002/er.5179.
Chen, N.; Zhang, H.; Luo, X.‐D.; Sun, C.‐Y. SiO2‐decorated graphite felt electrode by silicic acid etching for iron‐chromium
redox flow battery. Electrochim. Acta 2020, 336, 135646. https://doi.org/10.1016/j.electacta.2020.135646.
Akridge, J.; Vourlis, H. Solid state batteries using vitreous solid electrolytes. Solid State Ion. 1986, 18–19, 1082–1087.
https://doi.org/10.1016/0167‐2738(86)90313‐9.
Akridge, J.; Vourlis, H. Performance of Li/TiS2 solid state batteries using phosphorous chalcogenide network former glasses
as solid electrolyte. Solid State Ion. 1988, 28–30, 841–846. https://doi.org/10.1016/s0167‐2738(88)80156‐5.
Anderman, M.; Lundquist, J.; Johnson, S.; Giovannoni, R. Rechargeable lithium‐titanium disulphide cells of spirally‐wounddesign. J. Power Sources 1989, 26, 309–312. https://doi.org/10.1016/0378‐7753(89)80139‐9.
Guerard, D.; Herold, A. Intercalation of lithium into graphite and other carbons. Carbon 1975, 13, 337–345.
https://doi.org/10.1016/0008‐6223(75)90040‐8.
Eichinger, G.; Besenhard, J. High energy density lithium cells: Part II. Cathodes and complete cells. J. Electroanal. Chem.
Interfacial Electrochem. 1976, 72, 1–31. https://doi.org/10.1016/s0022‐0728(76)80072‐1.
Besenhard, J.; Eichinger, G. High energy density lithium cells: Part I. Electrolytes and anodes. J. Electroanal. Chem. Interfacial
Electrochem. 1976, 68, 1–18. https://doi.org/10.1016/s0022‐0728(76)80298‐7.
Reddy, M.V.; Mauger, A.; Julien, C.M.; Paolella, A.; Zaghib, K. Brief History of Early Lithium‐Battery Development. Mate‐rials 2020, 13, 1884.
Yu, P.; Lowe, S.E.; Simon, G.; Zhong, Y.L. Electrochemical exfoliation of graphite and production of functional graphene.
Curr. Opin. Colloid Interface Sci. 2015, 20, 329–338. https://doi.org/10.1016/j.cocis.2015.10.007.
Media, N. (2014) Nobel Prize in Physics. In: Nobelprize.org. Nobel Media AB. Available online: https://www.no‐
belprize.org/prizes/physics/2010/geim/facts/%0Ahttps://www.nobelprize.org/nobel_prizes/physics/laureates/2010/geim‐
facts.html (accessed 24 December 2021).
Geng, C.‐Y.; Yu, J.; Shi, F.‐N. Few‐layers of graphene modified TiO2/graphene composites with excellent electrochemical
properties for lithium‐ion battery. Ionics 2019, 25, 3059–3068.
Ouyang, D.‐D.; Hu, L.‐B.; Wang, G.; Dai, B.; Yu, F.; Zhang, L.‐L. A review of biomass‐derived graphene and graphene‐likecarbons for electrochemical energy storage and conversion. New Carbon Mater. 2021, 36, 350–372.
https://doi.org/10.1016/s1872‐5805(21)60024‐0.
Tiwari, S.K.; Sahoo, S.; Wang, N.; Huczko, A. Graphene research and their outputs: Status and prospect. J. Sci. Adv. Mater.
Devices 2020, 5, 10–29. https://doi.org/10.1016/j.jsamd.2020.01.006.
Kumar, R.K.; Bandurin, D.A.; Pellegrino, F.M.D.; Cao, Y.; Principi, A.; Guo, H.; Auton, G.H.; Ben Shalom, M.; Ponomarenko,
L.A.; Falkovich, G.; et al. Superballistic flow of viscous electron fluid through graphene constrictions. Nat. Phys. 2017, 13,1182–1185. https://doi.org/10.1038/nphys4240.
Peter, F.S.; Raghavan, P.; Figerez, S.P.; Prasanth, R. Graphene and Carbon Nanotubes for Advanced Lithium Ion Batteries, 1st ed.;CRC Press: Boca Raton, FL, USA, 2018. https://doi.org/10.1201/9780429434389.
Cao, Y.‐C.; Xu, C.; Wu, X.; Wang, X.; Xing, L.; Scott, K. A poly (ethylene oxide)/graphene oxide electrolyte membrane forlow temperature polymer fuel cells. J. Power Sources 2011, 196, 8377–8382. https://doi.org/10.1016/j.jpowsour.2011.06.074.

Electrochem 2022, 3, 143–183

179

18. Alshamsi, H.A.; Jaber, N.A.A.‐B.; Altaa, S.H.A. Facile Green Synthesis of Reduced Graphene Oxide in L‐cysteine Solution
and its Structural, Morphological, Optical and Thermal Characteristics. J. Physics: Conf. Ser. 2021, 1999, 012016.
https://doi.org/10.1088/1742‐6596/1999/1/012016.
19. Madurani, K.A.; Suprapto, S.; Machrita, N.I.; Bahar, S.L.; Illiya, W.; Kurniawan, F. Progress in Graphene Synthesis and its
Application: History, Challenge and the Future Outlook for Research and Industry. ECS J. Solid State Sci. Technol. 2020, 9,093013. https://doi.org/10.1149/2162‐8777/abbb6f
20. Wu, Z.‐S.; Zhou, G.; Yin, L.‐C.; Ren, W.; Li, F.; Cheng, H.‐M. Graphene/metal oxide composite electrode materials for energy
storage. Nano Energy 2012, 1,107–131. https://doi.org/10.1016/j.nanoen.2011.11.001
21. Geim AK, Novoselov KS (2007) The rise of graphene. Nat Mater 6:183–191. https://doi.org/10.1038/nmat1849
22. Krishnamoorthy, K.; Kim, G.‐S.; Kim, S.J. Graphene nanosheets: Ultrasound assisted synthesis and characterization. Ultra‐
son. Sonochemistry 2013, 20, 644–649. https://doi.org/10.1016/j.ultsonch.2012.09.007.
23. Khan, M.; Tahir, M.N.; Adil, S.F.; Khan, H.U.; Siddiqui, M.R.H.; Al‐Warthan, A.A.; Tremel, W. Graphene based metal andmetal oxide nanocomposites: Synthesis, properties and their applications. J. Mater. Chem. A 2015, 3, 18753–18808.
https://doi.org/10.1039/c5ta02240a.
24. Edwards, R.S.; Coleman, K.S. Graphene synthesis: Relationship to applications. Nanoscale 2012, 5, 38–51.
https://doi.org/10.1039/c2nr32629a.
25. Choi, W.; Lahiri, I.; Seelaboyina, R.; Kang, Y.S. Synthesis of Graphene and Its Applications: A Review. Crit. Rev. Solid State
Mater. Sci. 2010, 35, 52–71. https://doi.org/10.1080/10408430903505036.
26. Botas, C.; Álvarez, P.; Blanco, P.; Granda, M.; Blanco, C.; Santamaria, R.; Romasanta, L.J.; Verdejo, R.; López‐Manchado,
M.A.; Menéndez, R. Graphene materials with different structures prepared from the same graphite by the Hummers andBrodie methods. Carbon 2013, 65, 156–164. https://doi.org/10.1016/j.carbon.2013.08.009.
27. Sehrawat, P.; Shabir, A.; Abid; Julien, C.; Islam, S. Recent trends in silicon/graphene nanocomposite anodes for lithium‐ion
batteries. J. Power Sources 2021, 501, 229709. https://doi.org/10.1016/j.jpowsour.2021.229709.
28. Liang, M.; Zhi, L. Graphene‐based electrode materials for rechargeable lithium batteries. J. Mater. Chem. 2009, 19, 5871–5878.
https://doi.org/10.1039/b901551e.
29. Geng, C.‐Y.; Yu, J.; Shi, F.‐N. Electrochemical study on different layers of graphene based TiO2/graphene composites as an
anode for lithium‐ion batteries. Res. Chem. Intermed. 2019, 45, 3409–3424. https://doi.org/10.1007/s11164‐019‐03799‐z.
30. Guo, B.; Ananth, K.P.; Zhang, J.; Ji, X.; Bai, J. Investigation of wet‐milled graphene nanosheets with sulfur doping for lithium‐
ion battery. Ionics 2020, 26, 3267–3274.
31. Sui, D.; Si, L.; Li, C.; Yang, Y.; Zhang, Y.; Yan, W. A Comprehensive Review of Graphene‐Based Anode Materials for Lith‐ium‐ion Capacitors. Chemistry 2021, 3, 1215–1246. https://doi.org/10.3390/chemistry3040089.
32. Yoo, E.; Kim, J.; Hosono, E.; Zhou, H.‐S.; Kudo, T.; Honma, I. Large Reversible Li Storage of Graphene Nanosheet Families
for Use in Rechargeable Lithium Ion Batteries. Nano Lett. 2008, 8, 2277–2282. https://doi.org/10.1021/nl800957b.
33. Guo, P.; Song, H.; Chen, X. Electrochemical performance of graphene nanosheets as anode material for lithium‐ion batteries.
Electrochem. Commun. 2009, 11, 1320–1324. https://doi.org/10.1016/j.elecom.2009.04.036.
34. Vargas, O.; Caballero, A.; Morales, J.; Elia, G.A.; Scrosati, B.; Hassoun, J. Electrochemical performance of a graphenenanosheets anode in a high voltage lithium‐ion cell. Phys. Chem. Chem. Phys. 2013, 15, 20444–20446.
https://doi.org/10.1039/c3cp53718h.
35. Li, X.; Hu, Y.; Liu, J.; Lushington, A.; Li, R.; Sun, X. Structurally tailored graphene nanosheets as lithium ion battery anodes:
An insight to yield exceptionally high lithium storage performance. Nanoscale 2013, 5, 12607–12615.
https://doi.org/10.1039/c3nr04823c.
36. Mu, Y.; Han, M.; Li, J.; Liang, J.; Yu, J. Growing vertical graphene sheets on natural graphite for fast charging lithium‐ion
batteries. Carbon 2020, 173, 477–484. https://doi.org/10.1016/j.carbon.2020.11.027.
37. Wu, D.H.; Li, Y.F.; Zhou, Z. First‐principles studies on doped graphene as anode materials in lithium‐ion batteries. Theor.
Chim. Acc. 2011, 130, 209–213. https://doi.org/10.1007/s00214‐011‐0961‐5.
38. Panchakarla, L.S.; Subrahmanyam, K.S.; Saha, S.K.; Govindaraj, A.; Krishnamurthy, H.R.; Waghmare, U.V.; Rao, C.N.R.
Synthesis, Structure, and Properties of Boron‐ and Nitrogen‐Doped Graphene. Adv. Mater. 2009, 21, 4726–4730.
https://doi.org/10.1002/adma.200901285.
39. Li, X.; Geng, D.; Zhang, Y.; Meng, X.; Li, R.; Sun, X. Superior cycle stability of nitrogen‐doped graphene nanosheets as anodes
for lithium ion batteries. Electrochem. Commun. 2011, 13, 822–825. https://doi.org/10.1016/j.elecom.2011.05.012.
40. Tan, Y.; Zhu, K.; Li, D.; Bai, F.; Wei, Y.; Zhang, P. N‐doped graphene/Fe–Fe3C nano‐composite synthesized by a Fe‐based
metal organic framework and its anode performance in lithium ion batteries. Chem. Eng. J. 2014, 258, 93–100.
https://doi.org/10.1016/j.cej.2014.07.066.
41. Dong, X.; Zheng, X.; Deng, Y.; Wang, L.; Hong, H.; Ju, Z. SiO2/N‐doped graphene aerogel composite anode for lithium‐ion
batteries. J. Mater. Sci. 2020, 55, 13023–13035. https://doi.org/10.1007/s10853‐020‐04905‐y.
42. Ni, S.; Zhang, J.; Ma, J.; Yang, X.; Zhang, L. Li3VO4/N‐doped graphene with high capacity and excellent cycle stability as
anode for lithium ion batteries. J. Power Sources 2015, 296, 377–382. https://doi.org/10.1016/j.jpowsour.2015.07.053.
43. Xiao, Z.; Sheng, L.; Jiang, L.; Zhao, Y.; Jiang, M.; Zhang, X.; Zhang, M.; Shi, J.; Lin, Y.; Fan, Z. Nitrogen‐doped grapheneribbons/MoS2 with ultrafast electron and ion transport for high‐rate Li‐ion batteries. Chem. Eng. J. 2020, 408, 127269.
https://doi.org/10.1016/j.cej.2020.127269.

Electrochem 2022, 3, 143–183

180

44. Pant, H.; Petnikota, S.; Vadali, V.S.S.S. Review—Brief Review of the Solid‐State Graphenothermal Reduction for Processing
Metal Oxide‐Reduced Graphene Oxide Nanocomposites for Energy Applications. ECS J. Solid State Sci. Technol. 2021, 10,031002. https://doi.org/10.1149/2162‐8777/abe8b4.
45. Wu, Z.‐S.; Ren, W.; Wen, L.; Gao, L.; Zhao, J.; Chen, Z.; Zhou, G.; Li, F.; Cheng, H.‐M. Graphene Anchored with Co3O4
Nanoparticles as Anode of Lithium Ion Batteries with Enhanced Reversible Capacity and Cyclic Performance. ACS Nano
2010, 4, 3187–3194.
46. Zhao, X.; Hayner, C.M.; Kung, M.C.; Kung, H.H. In‐Plane Vacancy‐Enabled High‐Power Si‐Graphene Composite Electrodefor Lithium‐Ion Batteries. Adv. Energy Mater. 2011, 1, 1079–1084. https://doi.org/10.1002/aenm.201100426.
47. Lee, J.K.; Smith, K.B.; Hayner, C.M.; Kung, H.H. Silicon nanoparticles–graphene paper composites for Li ion battery anodes.
Chem. Commun. 2010, 46, 2025–2027. https://doi.org/10.1039/b919738a.
48. Zhou, G.; Wang, D.‐W.; Li, F.; Zhang, L.; Li, N.; Wu, Z.‐S.; Wen, L.; Lu, G.Q.; Cheng, H.‐M. Graphene‐Wrapped Fe3O4 AnodeMaterial with Improved Reversible Capacity and Cyclic Stability for Lithium Ion Batteries. Chem. Mater. 2010, 22, 5306–5313.
https://doi.org/10.1021/cm101532x.
49. Zhang, L.‐S.; Jiang, L.‐Y.; Yan, H.‐J.; Wang, W.D.; Song, W.‐G.; Guo, Y.‐G.; Wan, L.‐J. Mono dispersed SnO2 nanoparticles
on both sides of single layer graphene sheets as anode materials in Li‐ion batteries. J. Mater. Chem. 2010, 20, 5462–5467.
https://doi.org/10.1039/c0jm00672f.
50. Mai, Y.; Wang, X.; Xiang, J.; Qiao, Y.; Zhang, D.; Gu, C.; Tu, J. CuO/graphene composite as anode materials for lithium‐ion
batteries. Electrochim. Acta 2011, 56, 2306–2311. https://doi.org/10.1016/j.electacta.2010.11.036.
51. Choi, D.; Wang, D.; Viswanathan, V.V.; Bae, I.‐T.; Wang, W.; Nie, Z.; Zhang, J.‐G.; Graff, G.L.; Liu, J.; Yang, Z.; et al. Li‐ion
batteries from LiFePO4 cathode and anatase/graphene composite anode for stationary energy storage. Electrochem. Commun.
2010, 12, 378–381. https://doi.org/10.1016/j.elecom.2009.12.039.
52. Chang, K.; Chen, W. L‐Cysteine‐Assisted Synthesis of Layered MoS2/Graphene Composites with Excellent Electrochemical
Performances for Lithium Ion Batteries. ACS Nano 2011, 5, 4720–4728.
53. Petnikota, S.; Teo, K.W.; Chen, L.; Sim, A.; Marka, S.K.; Reddy, M.V.; Srikanth, V.V.S.S.; Adams, S.; Chowdari, B. ExfoliatedGraphene Oxide/MoO2 Composites as Anode Materials in Lithium‐Ion Batteries: An Insight into Intercalation of Li andConversion Mechanism of MoO2. ACS Appl. Mater. Interfaces 2016, 8, 10884–10896. https://doi.org/10.1021/acsami.6b02049.
54. Petnikota, S.; Rotte, N.K.; Reddy, M.V.; Srikanth, V.V.S.S.; Chowdari, B.V.R. MgO‐Decorated Few‐Layered Graphene as an
Anode for Li‐Ion Batteries. ACS Appl. Mater. Interfaces 2015, 7, 2301–2309. https://doi.org/10.1021/am5064712.
55. Maseed, H.; Petnikota, S.; Srikanth, V.V.S.S.; Srinivasan, M.; R., C.B.V.; Reddy, M.V.; Adams, S. Fe2Mo3O8/exfoliated gra‐
phene oxide: Solid‐state synthesis, characterization and anodic application in Li‐ion batteries. New J. Chem. 2018, 42, 12817–
12823. https://doi.org/10.1039/c8nj01847b.
56. Marka, S.K.; Petnikota, S.; Srikanth, V.V.S.S.; Reddy, M.V.; Adams, S.; Chowdari, B.V.R. Co2Mo3O8/reduced graphene oxide
composite: Synthesis, characterization, and its role as a prospective anode material in lithium ion batteries. RSC Adv. 2016,
6, 55167–55175. https://doi.org/10.1039/c6ra10192e.
57. Hameed, A.S.; Reddy, M.V.; Chen, J.L.T.; Chowdari, B.V.R.; Vittal, J.J. RGO/Stibnite Nanocomposite as a Dual Anode for
Chem.
Eng.
2016,
4,
2479–2486.
Lithium
andSodiumIon
Batteries.
ACS
Sustain.
https://doi.org/10.1021/acssuschemeng.5b01211.
58. Zhu, X.; Zhu, Y.; Murali, S.; Stoller, M.D.; Ruoff, R.S. Nanostructured Reduced Graphene Oxide/Fe2O3 Composite As a High‐
Performance Anode Material for Lithium Ion Batteries. ACS Nano 2011, 5, 3333–3338. https://doi.org/10.1021/nn200493r.
59. Petnikota, S.; Marka, S.K.; Banerjee, A.; Reddy, M.; Srikanth, V.; Chowdari, B. Graphenothermal reduction synthesis of ‘ex‐foliated graphene oxide/iron (II) oxide’ composite for anode application in lithium ion batteries. J. Power Sources 2015, 293,
253–263. https://doi.org/10.1016/j.jpowsour.2015.05.075.
60. Petnikota, S.; Marka, S.K.; Srikanth, V.V.; Reddy, M.V.; Chowdari, B.V. Elucidation of few layered graphene‐complex metaloxide (A2Mo3O8, A = Co, Mn and Zn) composites as robust anode materials in Li ion batteries. Electrochim. Acta 2015, 178,
699–708. https://doi.org/10.1016/j.electacta.2015.08.066.
61. Goh, B.‐M.; Wang, Y.; Reddy, M.V.; Ding, Y.L.; Lu, L.; Bunker, C.; Loh, K.P.; V., R.M. Filling the Voids of Graphene Foam
with Graphene “Eggshell” for Improved Lithium‐Ion Storage. ACS Appl. Mater. Interfaces 2014, 6, 9835–9841.
https://doi.org/10.1021/am5022655.
62. Han, F.; Li, D.; Li, W.‐C.; Lei, C.; Sun, Q.; Lu, A.‐H. Nanoengineered Polypyrrole‐Coated Fe2O3@C Multifunctional Compo‐
sites with an Improved Cycle Stability as Lithium‐Ion Anodes. Adv. Funct. Mater. 2012, 23, 1692–1700.
https://doi.org/10.1002/adfm.201202254.
63. Yan, Y.; Tang, H.; Wu, F.; Xie, Z.; Xu, S.; Qu, D.; Wang, R.; Wu, F.; Pan, M.; Qu, D. Facile synthesis of Fe2O3@graphite
nanoparticle composite as the anode for Lithium ion batteries with high cyclic stability. Electrochim. Acta 2017, 253, 104–113.
https://doi.org/10.1016/j.electacta.2017.09.061.
64. Sun, M.; Sun, M.; Yang, H.; Song, W.; Nie, Y.; Sun, S. Porous Fe2O3 nanotubes as advanced anode for high performancelithium ion batteries. Ceram. Int. 2016, 43, 363–367. https://doi.org/10.1016/j.ceramint.2016.09.166.
65. Lv, X.; Deng, J.; Wang, B.; Zhong, J.; Sham, T.‐K.; Sun, X.; Sun, X. γ‐Fe2O3@CNTs Anode Materials for Lithium Ion Batteries
Investigated by Electron Energy Loss Spectroscopy. Chem. Mater. 2017, 29, 3499–3506. https://doi.org/10.1021/acs.chem‐mater.6b05356.

Electrochem 2022, 3, 143–183

181

66. Peng, P.; Zhao, Q.; Zhu, P.; Liu, W.; Yuan, Y.; Ding, R.; Gao, P.; Sun, X.; Liu, E. Amorphous Fe2O3 film‐coated mesoporous
Fe2O3 core‐shell nanosphere prepared by quenching as a high‐performance anode material for lithium‐ion batteries. J. Elec‐troanal. Chem. 2021, 898, 115633. https://doi.org/10.1016/j.jelechem.2021.115633.
67. Wang, G.; Liu, T.; Luo, Y.; Zhao, Y.; Ren, Z.; Bai, J.; Wang, H. Preparation of Fe2O3/graphene composite and its electrochem‐
ical performance as an anode material for lithium ion batteries. J. Alloys. Compd. 2011, 509, L216–L220.
https://doi.org/10.1016/j.jallcom.2011.03.151
68. Li, H.; Zhu, X.; Sitinamaluwa, H.; Wasalathilake, K.; Xu, L.; Zhang, S.; Yan, C. Graphene oxide wrapped Fe2O3 as a durable
anode material for high‐performance lithium‐ion batteries. J. Alloy. Compd. 2017, 714, 425–432. https://doi.org/10.1016/j.jall‐com.2017.04.260.
69. Wang, P.; Gou, X.‐X.; Xin, S.; Cao, F.‐F. Facile synthesis of CuO nanochains as high‐rate anode materials for lithium‐ion
batteries. New J. Chem. 2019, 43, 6535–6539. https://doi.org/10.1039/c9nj01015g.
70. Liu, Y.; Qiao, Y.; Zhang, W.; Hu, P.; Chen, C.; Li, Z.; Yuan, L.; Hu, X.; Huang, Y. Facile fabrication of CuO nanosheets on Cu
substrate as anode materials for electrochemical energy storage. J. Alloy. Compd. 2014, 586, 208–215.
https://doi.org/10.1016/j.jallcom.2013.10.024.
71. Jia, S.; Wang, Y.; Liu, X.; Zhao, S.; Zhao, W.; Huang, Y.; Li, Z.; Lin, Z. Hierarchically porous CuO nano‐labyrinths as binder‐
free anodes for long‐life and high‐rate lithium ion batteries. Nano Energy 2019, 59, 229–236.
https://doi.org/10.1016/j.nanoen.2019.01.081.
72. Su, Q.; Yao, L.; Zhang, J.; Du, G.; Xu, B. In Situ Transmission Electron Microscopy Observation of the Lithiation‐Delithiation
Conversion Behavior of CuO/Graphene Anode. ACS Appl. Mater. Interfaces. 2015, 7, 23062–23068.
https://doi.org/10.1021/acsami.5b06548
73. Liu, Y.; Wang, W.; Gu, L.; Wang, Y.; Ying, Y.; Mao, Y.; Sun, L.; Peng, X. Flexible CuO Nanosheets/Reduced‐Graphene Oxide
Composite Paper: Binder‐Free Anode for High‐Performance Lithium‐Ion Batteries. ACS Appl. Mater. Interfaces 2013, 5, 9850–
9855. https://doi.org/10.1021/am403136e.
74. Choi, S.H.; Kang, Y.C. Crumpled Graphene‐Molybdenum Oxide Composite Powders: Preparation and Application in Lith‐ium‐Ion Batteries. ChemSusChem 2013, 7, 523–528. https://doi.org/10.1002/cssc.201300838.
75. Almodóvar, P.; López, M.L.; Ramírez‐Castellanos, J.; Nappini, S.; Magnano, E.; González‐Calbet, J.M.; Díaz‐Guerra, C. Syn‐thesis, characterization and electrochemical assessment of hexagonal molybdenum trioxide (h‐MoO3) micro‐composites
with graphite, graphene and graphene oxide for lithium ion batteries. Electrochim. Acta 2020, 365, 137355.
https://doi.org/10.1016/j.electacta.2020.137355.
76. Vazquez‐Santos, M.B.; Tartaj, P.; Morales, E.; Amarilla, J.M. TiO2 Nanostructures as Anode Materials for Li/Na‐Ion Batteries.
Chem. Rec. 2018, 18, 1178–1191. https://doi.org/10.1002/tcr.201700103.
77. Xin, X.; Zhou, X.; Wu, J.; Yao, X.; Liu, Z. Scalable Synthesis of TiO2/Graphene Nanostructured Composite with High‐Rate
Performance for Lithium Ion Batteries. ACS Nano 2012, 6, 11035–11043. https://doi.org/10.1021/nn304725m.
78. Zhang, C.; Liu, S.; Qi, Y.; Cui, F.; Yang, X. Conformal carbon coated TiO2 aerogel as superior anode for lithium‐ion batteries.
Chem. Eng. J. 2018, 351, 825–831. https://doi.org/10.1016/j.cej.2018.06.125.
79. Choi, S.I.; Jung, E.‐J.; Park, M.; Shin, H.‐S.; Huh, S.; Won, Y.S. Phase‐dependent performance of lotus‐root shaped TiO2 anodefor lithium‐ion batteries (LIBs). Appl. Surf. Sci. 2020, 508, 145237. https://doi.org/10.1016/j.apsusc.2019.145237.
80. Zhang, Y.; Tang, Y.; Li, W.; Chen, X. Nanostructured TiO2‐Based Anode Materials for High‐Performance Rechargeable Lith‐ium‐Ion Batteries. ChemNanoMat 2016, 2, 764–775. https://doi.org/10.1002/cnma.201600093.
81. Qiu, J.; Zhang, P.; Ling, M.; Li, S.; Liu, P.; Zhao, H.; Zhang, S. Photocatalytic Synthesis of TiO2 and Reduced Graphene Oxide
Nanocomposite for Lithium Ion Battery. ACS Appl. Mater. Interfaces 2012, 4, 3636–3642. https://doi.org/10.1021/am300722d.
82. Li, W.; Wang, F.; Feng, S.; Wang, J.; Sun, Z.; Li, B.; Li, Y.; Yang, J.; Elzatahry, A.; Xia, Y.; et al. Sol–Gel Design Strategy for
Ultradispersed TiO2 Nanoparticles on Graphene for High‐Performance Lithium Ion Batteries. J. Am. Chem. Soc. 2013, 135,
18300–18303. https://doi.org/10.1021/ja4100723.
83. Qiu, J.; Lai, C.; Wang, Y.; Li, S.; Zhang, S. Resilient mesoporous TiO2/graphene nanocomposite for high rate performancelithium‐ion batteries. Chem. Eng. J. 2014, 256, 247–254. https://doi.org/10.1016/j.cej.2014.06.116.
84. Lan, T.; Qiu, H.; Xie, F.; Yang, J.; Wei, M. Rutile TiO2 Mesocrystals/Reduced Graphene Oxide with High‐Rate and Long‐
Term Performance for Lithium‐Ion Batteries. Sci. Rep. 2015, 5, 8498. https://doi.org/10.1038/srep08498.
85. Chan, C.K.; Peng, H.; Liu, G.; McIlwrath, K.; Zhang, X.F.; Huggins, R.A.; Cui, Y. High‐performance lithium battery anodes
using silicon nanowires. Nat. Nanotechnol. 2007, 3, 31–35. https://doi.org/10.1038/nnano.2007.411.
86. Kim, N.; Oh, C.; Kim, J.; Kim, J.‐S.; Jeong, E.D.; Bae, J.‐S.; Hong, T.E.; Lee, J.K. High‐Performance Li‐Ion Battery Anodes
Based on Silicon‐Graphene Self‐Assemblies. J. Electrochem. Soc. 2016, 164, A6075–A6083. https://doi.org/10.1149/2.0101701jes.
87. Beattie, S.D.; Larcher, D.; Morcrette, M.; Simon, B.; Tarascon, J.‐M. Si Electrodes for Li‐Ion Batteries—A New Way to Lookat an Old Problem. J. Electrochem. Soc. 2008, 155, A158–A163. https://doi.org/10.1149/1.2817828.
88. Chou, S.‐L.; Wang, J.‐Z.; Choucair, M.; Liu, H.‐K.; Stride, J.A.; Dou, S.‐X. Enhanced reversible lithium storage in a nanosize
silicon/graphene composite. Electrochem. Commun. 2010, 12, 303–306. https://doi.org/10.1016/j.elecom.2009.12.024.
89. Yi, X.; Zhang, Y.; He, W.; Zhang, X.; Yang, G.; Wang, Z.; Wang, Y.; Cheng, Q. Low‐Temperature Synthesis of Graphene/SiC
Nanocomposite
AnodeswithSuper‐Long
Cycling
Stability.
ChemElectroChem
2017,
4,1320–1326.
https://doi.org/10.1002/celc.201700028.

Electrochem 2022, 3, 143–183

182

90. Shi, L.; Pang, C.; Chen, S.; Wang, M.; Wang, K.; Tan, Z.; Gao, P.; Ren, J.; Huang, Y.; Peng, H.; et al. Vertical Graphene Growthon SiO Microparticles for Stable Lithium Ion Battery Anodes. Nano Lett. 2017, 17, 3681–3687.
https://doi.org/10.1021/acs.nanolett.7b00906.
91. Li, H.; Lu, C.; Zhang, B. A straightforward approach towards Si@C/graphene nanocomposite and its superior lithium stor‐
age performance. Electrochim. Acta 2014, 120, 96–101. https://doi.org/10.1016/j.electacta.2013.12.048.
92. Ma, X.; Hou, G.; Ai, Q.; Zhang, L.; Si, P.; Feng, J.; Ci, L. A heart‐coronary arteries structure of carbon nanofibers/graphene/sil‐
icon composite anode for high performance lithium ion batteries. Sci. Rep. 2017, 7, 9642. https://doi.org/10.1038/s41598‐017‐
09658‐4.
93. Al Hassan, M.; Sen, A.; Zaman, T.; Mostari, M. Emergence of graphene as a promising anode material for rechargeable
batteries: A review. Mater. Today Chem. 2018, 11, 225–243. https://doi.org/10.1016/j.mtchem.2018.11.006.
94. Chen, X.; Tian, Y. Review of Graphene in Cathode Materials for Lithium‐Ion Batteries. Energy Fuels 2021, 35, 3572–3580.
https://doi.org/10.1021/acs.energyfuels.0c04191.
95. Zhang, L.‐L.; Duan, S.; Yang, X.‐L.; Peng, G.; Liang, G.; Huang, Y.‐H.; Jiang, Y.; Ni, S.‐B.; Li, M. Reduced Graphene Oxide
Modified Li2FeSiO4/C Composite with Enhanced Electrochemical Performance as Cathode Material for Lithium Ion Batter‐ies. ACS Appl. Mater. Interfaces 2013, 5, 12304–12309. https://doi.org/10.1021/am402434n.
96. Lee, S.W.; Yabuuchi, N.; Gallant, B.M.; Chen, S.; Kim, B.‐S.; Hammond, P.T.; Shao‐Horn, Y. High‐power lithium batteries
from functionalized carbon‐nanotube electrodes. Nat. Nanotechnol. 2010, 5, 531–537. https://doi.org/10.1038/nnano.2010.116.
97. Chen, H.; Armand, M.; Demailly, G.; Dolhem, F.; Poizot, P.; Tarascon, J.‐M. From Biomass to a Renewable LiXC6O6 Organic
Electrode for Sustainable Li‐Ion Batteries. ChemSusChem 2008, 1, 348–355. https://doi.org/10.1002/cssc.200700161.
98. Maseed, H.; Petnikota, S.; Srikanth, V.V.; Rotte, N.K.; Srinivasan, M.; Bonaccorso, F.; Pellegrini, V.; Reddy, M.V. A new
insight into Li‐staging, in‐situ electrochemical exfoliation, and superior Li storage characteristics of highly crystalline few‐
layered graphene. J. Energy Storage 2021, 41, 102908. https://doi.org/10.1016/j.est.2021.102908.
99. Ha, S.H.; Jeong, Y.S.; Lee, Y.J. Free Standing Reduced Graphene Oxide Film Cathodes for Lithium Ion Batteries. ACS Appl.
Mater. Interfaces 2013, 5, 12295–12303. https://doi.org/10.1021/am4044147.
100. Xiong, D.; Li, X.; Shan, H.; Zhao, Y.; Dong, L.; Xu, H.; Zhang, X.; Li, D.; Sun, X. Oxygen‐containing Functional Groups
Enhancing Electrochemical Performance of Porous Reduced Graphene Oxide Cathode in Lithium Ion Batteries. Electrochim.
Acta 2015, 174, 762–769. https://doi.org/10.1016/j.electacta.2015.06.041.
101. Xiong, D.; Li, X.; Bai, Z.; Shan, H.; Fan, L.; Wu, C.; Li, D.; Lu, S. Superior Cathode Performance of Nitrogen‐Doped Graphene
Frameworksfor
Lithium
Ion
Batteries.
ACS
Appl.
Mater.
Interfaces
2017,9,10643–10651.
https://doi.org/10.1021/acsami.6b15872.
102. Zhao, Y.; Zhang, Y.; Gosselink, D.; Doan, T.N.L.; Sadhu, M.; Cheang, H.‐J.; Chen, P. Polymer Electrolytes for Lithium/Sulfur
Batteries. Membranes 2012, 2, 553–564. https://doi.org/10.3390/membranes2030553.
103. Chang, U.; Lee, J.T.; Yun, J.‐M.; Lee, B.; Lee, S.W.; Joh, H.‐I.; Eom, K.; Fuller, T.F.; Lee, B. In Situ Self‐Formed Nanosheet
MoS3/Reduced Graphene Oxide Material Showing Superior Performance as a Lithium‐Ion Battery Cathode. ACS Nano 2019,13, 1490–1498. https://doi.org/10.1021/acsnano.8b07191.
104. Wang, K.; Ren, W.; Yang, J.; Tan, R.; Liu, Y.; Pan, F. Depolarization effects of Li2FeSiO4 nanocrystals wrapped in different
conductive carbon networks as cathodes for high performance lithium‐ion batteries. RSC Adv. 2016, 6, 47723–47729.
https://doi.org/10.1039/C6RA07755B.
105. Zhu, H.; He, H.; Xin, X.; Ma, X.; Zan, L.; Zhang, Y. Facile synthesis of Li2MnSiO4/C/graphene composite with superior high‐rate performances as cathode materials for Li‐ion batteries. Electrochim. Acta 2015, 155, 116–124.
https://doi.org/10.1016/j.electacta.2014.12.147.
106. Hameed, A.S.; Reddy, M.V.; AlQaradawi, S.; Adams, S. Synthesis, structural and lithium storage studies of graphene‐
LiVSi2O6 composites. Ionics 2018, 25, 1559–1566. https://doi.org/10.1007/s11581‐018‐2760‐7.
107. Zhu, X.; Hu, J.; Wu, W.; Zeng, W.; Dai, H.; Du, Y.; Liu, Z.; Li, L.; Ji, H.; Zhu, Y. LiFePO4/reduced graphene oxide hybrid
cathode for lithium ion battery with outstanding rate performance. J. Mater. Chem. A 2014, 2, 7812–7818.
https://doi.org/10.1039/c4ta00580e.
108. Zhou, X.; Wang, F.; Zhu, Y.; Liu, Z. Graphene modified LiFePO4 cathode materials for high power lithium ion batteries. J.
Mater. Chem. 2011, 21, 3353–3358. https://doi.org/10.1039/c0jm03287e.
109. Kim, W.; Ryu, W.‐H.; Han, D.; Lim, S.; Eom, J.; Kwon, H. Fabrication of Graphene Embedded LiFePO4 Using a Catalyst
Assisted Self Assembly Method as a Cathode Material for High Power Lithium‐Ion Batteries. ACS Appl. Mater. Interfaces
2014, 6, 4731–4736. https://doi.org/10.1021/am405335k.
110. Yang, J.; Wang, J.; Wang, D.; Li, X.; Geng, D.; Liang, G.; Gauthier, M.; Li, R.; Sun, X. 3D porous LiFePO4/graphene hybrid
cathodes with enhanced performance for Li‐ion batteries. J. Power Sources 2012, 208, 340–344. https://doi.org/10.1016/j.jpow‐
sour.2012.02.032.
111. Huang, Y.; Li, K.; Liu, J.; Zhong, X.; Duan, X.; Shakir, I.; Xu, Y. Three‐dimensional graphene/polyimide composite‐derived
flexible high‐performance organic cathode for rechargeable lithium and sodium batteries. J. Mater. Chem. A 2017, 5, 2710–
2716. https://doi.org/10.1039/c6ta09754e.
112. Ahmad, A.; Wu, H.; Guo, Y.; Meng, Q.; Meng, Y.; Lu, K.; Liu, L.; Wei, Z. A graphene supported polyimide nanocomposite
as a high performance organic cathode material for lithium ion batteries. RSC Adv. 2016, 6, 33287–33294.
https://doi.org/10.1039/c5ra27471k.

Electrochem 2022, 3, 143–183

183

113. Manthiram, A.; Yu, X.; Wang, S. Lithium battery chemistries enabled by solid‐state electrolytes. Nat. Rev. Mater. 2017, 2,
16103. https://doi.org/10.1038/natrevmats.2016.103.
114. Osada, I.; De Vries, H.; Scrosati, B.; Passerini, S. Ionic‐Liquid‐Based Polymer Electrolytes for Battery Applications. Angew.
Chem. Int. Ed. 2015, 55, 500–513. https://doi.org/10.1002/anie.201504971.
115. Xu, K. Li‐ion battery electrolytes. Nat. Energy 2021, 6, 763–763. https://doi.org/10.1038/s41560‐021‐00841‐6.
116. Balakrishnan, P.; Ramesh, R.; Kumar, P. Safety mechanisms in lithium‐ion batteries. J. Power Sources 2006, 155, 401–414.
https://doi.org/10.1016/j.jpowsour.2005.12.002.
117. Wen, J.; Zhao, Q.; Jiang, X.; Ji, G.; Wang, R.; Lu, G.; Long, J.; Hu, N.; Xu, C. Graphene Oxide Enabled Flexible PEO‐Based
Solid Polymer Electrolyte for All‐Solid‐State Lithium Metal Battery. ACS Appl. Energy Mater. 2021, 4, 3660–3669.
https://doi.org/10.1021/acsaem.1c00090.
118. Gahlot, S.; Kulshrestha, V. Graphene based polymer electrolyte membranes for electro‐chemical energy applications. Int. J.
Hydrogen Energy 2019, 45, 17029–17056. https://doi.org/10.1016/j.ijhydene.2019.06.047.
119. Roth, E.P.; Orendorff, C.J. How Electrolytes Influence Battery Safety. Electrochem. Soc. Interface 2012, 21, 45.
120. Yuan, M.; Erdman, J.; Tang, C.; Ardebili, H. High performance solid polymer electrolyte with graphene oxide nanosheets.
RSC Adv. 2014, 4, 59637–59642. https://doi.org/10.1039/c4ra07919a.
121. Shim, J.; Kim, D.‐G.; Kim, H.J.; Lee, J.H.; Baik, J.‐H.; Lee, J.‐C. Novel composite polymer electrolytes containing poly (eth‐ylene glycol)‐grafted graphene oxide for all‐solid‐state lithium‐ion battery applications. J. Mater. Chem. A. 2014, 2:13873–
13883. https://doi.org/10.1039/c4ta02667e
122. Li, J.; Li, Y.; Cheng, J.; Sun, Q.; Dai, L.; Nie, X.; Chen, L.; Han, G.; Ci, L. A graphene oxide coated sulfide‐based solid electro‐
lyte for dendrite‐free lithium metal batteries. Carbon 2021, 177, 52–59. https://doi.org/10.1016/j.carbon.2021.01.159.