composites of graphene and encapsulated silicon for ... · nano res 1 nano research doi...

Nano Res

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Nano Research DOI 10.1007/s12274‐014‐0463‐6

Composites of Graphene and Encapsulated Silicon for Practically Viable High-Performance Lithium-Ion Batteries

Xin Zhao*, Minjie Li, Kuo-Hsin Chang, Yu-Ming Lin*

Nano Res., Just Accepted Manuscript • DOI: 10.1007/s12274-014-0463-6 http://www.thenanoresearch.com on April 1, 2014 © Tsinghua University Press 2014

Just Accepted This is a “Just Accepted” manuscript, which has been examined by the peer‐review process and has been accepted for publication. A “Just Accepted” manuscript is published online shortly after its acceptance, which is prior to technical editing and formatting and author proofing. Tsinghua University Press (TUP) provides “Just Accepted” as an optional and free service which allows authors to make their results available to the research community as soon as possible after acceptance. After a manuscript has been technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Please note that technical editing may introduce minor changes to the manuscript text and/or graphics which may affect the content, and all legal disclaimers that apply to the journal pertain. In no event shall TUP be held responsible for errors or consequences arising from the use of any information contained in these “Just Accepted” manuscripts. To cite this manuscript please use its Digital Object Identifier (DOI®), which is identical for all formats of publication.

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Graphical Table of Contents

By encapsulating silicon particles via in-situ polymerization and carbonization of

phloroglucinol-formaldehyde gel, followed by incorporation of graphene sheets, a high-

performance Si composite anode was demonstrated in half cell and full cell configurations,

yielding remarkably enhanced capacity and stability for advanced lithium-ion batteries.

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Composites of Graphene and Encapsulated Silicon for Practically

Viable High-Performance Lithium-Ion Batteries


Bluestone Global Tech, 169 Myers Corners Road, Wappingers Falls, NY 12590, USA.

E-mail: [email protected], [email protected]

Abstract

A facile and scalable approach to synthesize silicon composite anode was developed by

encapsulating Si particles via in-situ polymerization and carbonization of phloroglucinol-

formaldehyde gel, followed by incorporation of graphene nanoplatelets. Attributed to the

improved structural integrity, a high packing density and an intimate electrical contact

consolidated by the conductive networks, the composite anode yielded remarkably enhanced

electrochemical performance in terms of charge storage capability, cycling life and coulombic

efficiency. A half cell achieved reversible capacities of 1600 mAh g-1 and 1000 mAh g-1 at 0.5 A

g-1 and 2.1 A g-1, respectively, while retaining more than 70% of the initial capacities over 1000

cycles. Complete lithium-ion pouch cells coupling such anode with lithium metal oxide cathode

demonstrated superior cycling performance and energy output, representing significant advance

in developing Si-based electrode practically applicable to high-performance lithium-ion batteries.

Keywords: Silicon nanoparticles, graphene nanoplatelets, phloroglucinol-formaldehyde gel,

lithium-ion batteries


mailto:[email protected],

mailto:[email protected]



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1 Introduction

The pressing need for advanced battery technologies has accelerated innovation of electrode

formulations to replace conventional intercalation compounds and graphitic materials used in

cathode and anode, respectively, in lithium-ion batteries. Among any known anode materials,

silicon demonstrates the highest gravimetric capacity of 3579 mAh g-1, attributed to the

formation of an alloy composition of Li15Si4 via electrochemical lithiation of Si at room

temperature [1-4]. However, the practical implementation of Si-based anode is notoriously

impeded by its massive volumetric expansion/contraction and subsequent structural pulverization,

as well as the overall swelling in a practical cell format. Besides, electrolyte decomposition at the

freshly formed Si/electrolyte interface along with continual formation of side-reaction products

gradually depletes the available Li ions and isolates the electrode fragments, which severely

hinders the rate capability, deep cycling ability and lifespan of Si-based anode [5-8].

In order to overcome mechanical cracking or fracture during cycling, it is usually necessary to

reduce the particle size of Si, while the potential of nano-sized Si to be fully adopted in

commercial entities is largely sacrificed consequential of reduced tap density and low areal mass

loading [9-11]. Incorporating carbonaceous species into Si offers an alternative solution to

suppress the detrimental effects of volumetric variation and improve the electrical continuity.

However, conformal carbon coatings on Si would rapture readily upon swelling and re-expose it

to side-product deposition [12-14]. Conductive polymers and carbon nanostructures, in particular

carbon nanotubes and their derivatives, provide flexible backbones to better accommodate the Li

ion insertion/extraction stress when introduced into Si anode [15-19]. Nevertheless, the

inherently high surface energy of Si nanoparticles is conducive to electrochemical sintering,

leaving the long-term cycling stability and inferior coulombic efficiency unresolved [20, 21]; the




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high surface carbonaceous materials further compromises the coulombic efficiency due to the

formation and propagation of solid electrolyte interphase (SEI), and prevents the high-capacity

anode from being viable when paired with cathodes in full cell formats [9, 22]. As the material

loading increases, the primary Si particles located near the center of large aggregates become

separated from the conductive components, leading to fatal deterioration of overall performance.

Thus until now, there is still a lack of transformative Si anode development and full cell designs

that are compatible with commercial configurations and high-throughput manufacturing

protocols.

Here we report a high-performance Si composite anode constructed from carbon gel sheathed Si

particles and graphene building blocks by a facile and scalable synthetic approach. The Si

particles were encapsulated by a uniform carbonized phloroglucinol- formaldehyde (PF) gel and

enveloped in a graphene platelet matrix (Fig. 1a), which confers a combination of advantageous

features: (1) an intimate electrical contact assured by the carbonaceous networks; (2) a restrained

structural damage and irreversible capacity loss warranted by the SiOx/carbon coating and

graphene sheets in contrast to rigid carbon shells and conventional carbon additives [12, 13, 23];

and (3) a high packing density and sustained structural integrity enabled by the compact graphitic

domains [24, 25]. These synergetic functions afforded superior rate capability, cycling life and

improved volumetric capacity. Proceeded by tape casting and coupling with a formulated lithium

metal oxide cathode, the Si composite anode displayed enhanced performance at practically

viable high mass loading in full cell formats.

2 Experimental




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2.1 Synthesis of PF gel encapsulated Si particles

Si powders (~100 nm, Alfa Aesar) were removed from argon environment and exposed to air

overnight. In a typical run, 0.25 g phloroglucinol (Sigma-Aldrich) was dispersed in 5 mL DDI

water under vigorous stirring, followed by dropwise addition of 0.02 g concentrated hydrochloric

acid. 0.73 g Si particles were poured into the suspension, and after stirring at room temperature

for 30 min, 0.26 g 37% formaldehyde aqueous solution (Sigma-Aldrich) was added in. The

mixture was kept at room temperature under stirring until a viscous gel-like structure was

formed. The mixture was vacuum-dried at 70 ºC for overnight, and then calcined at 800 ºC for

2.5 h under a flow of Ar (100 mL min-1).

2.2 Characterization

Sample morphology was investigated using JEOL JSM-7001 scanning electron microscopy and

JEOL JEM-2100F transmission electron microscopy. X-ray diffraction patterns were collected

by a Bruker AXS Gmbh diffractometer with CuK radiation (=1.5418 Å) at 30 kV/10 mA, a

scan rate of 4o min-1. Raman spectra were recorded on a WiTec alpha500 automated confocal

Raman microscope at 532 nm laser excitation. Thermogravimetric analysis was performed by

heating the samples to 800ºC at the rate of 10ºC min-1 in flowing air. The weight loss, after

correcting for oxidation of Si, was used to calculate the carbon fraction. Surface area was

determined from N2 adsorption/desorption isotherm at 77K, collected using Micromeritics ASAP

2000 and analyzed using Brunauer-Emmett-Teller (BET) method.

2.3 Electrochemical measurement

The anode film was fabricated by pasting a slurry containing PF-Si particles, graphene

nanoplatelets (XG Sciences), and poly(acrylic acid) (Sigma-Aldrich) with a weight ratio of 6:3:1




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onto a copper foil. The typical mass loading was of the order of 1-4 mg cm-2. The electrode was

dried at 90 ºC under vacuum for overnight, and compressed at 10 MPa before being assembled

into a cell.

Charge/discharge tests versus lithium were carried out using a CR2032-type coin cell. The cells

were assembled in an argon-filled glove box, using a metallic lithium disc as the counter

electrode and a Whatman GF/F microporous borosilicate glass-fiber membrane as the separator.

The electrolyte solution was 1 M LiPF6 in ethylene carbonate/dimethyl carbonate (EC/DMC 1:1

by volume, BASF) plus 10 vol% fluoroethylene carbonate additive. Galvanostatic

charge/discharge measurements were conducted with a Maccor Series 4000 automated test

system at various current densities in the voltage range of 0.02-1.5 V vs. Li/Li+. Electrochemical

impedance spectroscopy (EIS) measurements were conducted using an Ametak VersaSTAT3

potentiostat/galvanostat by applying an AC voltage of 10 mV amplitude and DC open circuit

voltage (OCV) in the frequency range of 1 MHz-0.01 Hz at room temperature. Theoretical

capacity of composite anode is calculated as 3500 mAh g-1 × 60% (Si wt-%) = 2100 mAh g-1

(1C=2.1 A g-1).

For full cell assembly, a lithium nickel cobalt manganese oxide (NMC) cathode was fabricated

by pasting a mixture of LiNi0.5Co0.2Mn0.3O2 powders (Toda America), carbon black (Super C45,

Timcal) and poly(vinylidene fluoride) (Arkema) with a weight ratio of 86:6:8 onto an aluminum

foil. The cathode mass loading was 8.5-20 mg cm-2 and the anode mass loading was 1-3.6 mg

cm-2 on single side. The pair of electrodes was isolated by a Celgard 2325 trilayer separator and

sealed inside an aluminum laminated pouch. The pouch cell was cycled at a constant rate of 0.5C

in the voltage range of 3-4.1 V.




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3 Results and discussion

Carbon encapsulated Si particles were fabricated by carbonizing 100 nm-sized Si powders

bonded to phloroglucinol-formaldehyde (PF) gel. The mixture of phloroglucinol and

formaldehyde monomers was selected as an inexpensive carbonaceous precursor, as it undergoes

polymerization under less stringent processing conditions relative to other phenolic resin

monomers [26]. Specifically, Si particles were exposed to air to ensure formation of a stable

hydrophilic oxide layer. The particles were dispersed directly in an aqueous suspension of

phloroglucinol by sonication, and polymerization was completed within three hours at room

temperature, converting the mixture to a gel after addition of formaldehyde in the presence of

hydrochloric acid. The oxide passivation layer was expected to facilitate the dispersing of Si

particles and anchoring of the hydroxyl groups of phloroglucinol to the surface of Si (Fig. 1b) via

a hydrogen-bonding interaction, creating homogeneous tethering to the Si particles and

preventing their sintering into bulk agglomerates.

The PF gel was carbonized in an inert atmosphere at 800 ºC, and tuning of the Si content was

achieved by varying the weight ratio of Si and PF polymer precursors. PF-Si composites with

three different Si contents were prepared, denoted as PF-Si-1, PF-Si-2, and PF-Si-3, with the Si

content of 78%, 83%, and 86%, respectively, as determined by weight losses upon combustion of

the carbon layer in thermogravimetric analysis (Fig. S1 in the ESM). Transmission electron

microscopy (TEM) images confirmed the encapsulation of Si particles with an amorphous and

continuous layer that was ca. 10 nm thick (Fig. 2a and b). The presence of native SiOx was

observed in pristine Si particles [24] and verified by the energy dispersive X-ray (EDX) spectra




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taken from the carbonized Si surface (Fig. 2c). An individual Si particle analyzed by elemental

mapping with regard to the distribution of Si, O and C suggested an atomic concentration

gradient across the conformal coating (Fi. 2d). The accumulation of oxygen on the surface of Si

correlated to the native SiOx layer. However, there was no distinct boundary between the carbon

and SiOx coating, probably because of the atom fluxes across the interface during calcination. X-

ray diffraction (XRD) patterns of carbonized Si particles displayed the characteristic peaks of

crystalline Si only, whereas the graphite diffraction peaks were absent (Fig. 3a). Raman

spectroscopy performed at a wavelength of 532 nm depicted a broad peak located at 520 cm-1 in

the carbonized Si particles, which was indicative of crystalline Si and remained unchanged after

calcination (Fig. 3b).

Formulation of PF-Si with graphene was accomplished by mechanical agitation of PF-Si

particles with exfoliated graphene nanoplatelets, in which PF-Si comprised 67% of the total

mass. The graphene nanoplatelets were 5-10 nm thick stacks consisting of graphene sheets, with

an interlayer d-spacing of ca. 3.4 Å (Fig. 3a) and lateral dimension of 10-30 m (Fig. S2 in the

ESM). The graphene nanoplatelets were fabricated by heat exfoliation and mechanical

pulverization, which were employed here in light of a high electrical conductivity and moderate

specific surface area of 120 m2 g-1. The observation of both D (1350 cm-1) and G-band (1610 cm-

1) in the graphene sheets attested to the existence of disordered and ordered carbon features,

respectively. The intensity ratios of the D/G bands corresponded to an approximately 400 nm-

sized ordered graphitic domain fitted to the empirical Tuinstra-Koenig relation [27]. The surface

topology of PF-Si/graphene composites was shown in the scanning electron microscopy (SEM)

images in Fig. 2d. The PF-Si particles were uniformly supported on exfoliated graphene sheets,

leading to a surface area of 41 m2 g-1 for the composite powders. The tap density of the




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composite was as high as 1.1 g cm-3, which is very close to that of conventional graphite and

outperforms many other Si/carbon systems, such as recently reported hierarchical (0.49 g cm-3)

[28] or micron-sized (0.78 g cm-3) [10] Si/carbon granules.

The electrochemical performance of pristine Si particles and PF-Si/graphene composites was

evaluated using deep charge/discharge galvanostatic cycling between 1.5-0.02 V (vs. Li/Li+) in a

half-cell setup with Li metal foils as the counter electrode. The first charge/discharge voltage

profile of PF-Si/graphene composites exhibited an extended plateau at ca. 0.1 V, corresponding

to the phase transformation from crystalline Si to lithium silicide (Fig. S3 in the ESM) [29]. A

coulombic efficiency of 70% was obtained for the first cycle. The irreversible capacity loss was

attributed to initial solid electrolyte interphase (SEI) formation, and reactions of Li ions with the

SiOx layer and residual functional groups on the carbon surfaces [30]. The relatively low surface

area of graphene nanoplatelets was beneficial in depressing the SEI growth and thus preserving

electrical contact over cycling, compared to chemical exfoliated and graphene oxide (GO)-

derived graphene [31-34]. It has been suggested that the SiOx reacts with Li ions, forming

irreversible Li4SiO4 or reversible Li2Si2O5 phases, which further assisted the formation of stable

SEI layer [35-37]. Afterwards, the charge/discharge showed sloping profiles characteristic of

lithiation/delithiation of amorphous Si in two different voltage regions (Fig. 4a and S3 in the

ESM). The coulombic efficiency rapidly increased and stabilized at around 99% after 10 cycles,

which was higher than that of previously studied Si/graphene composite anode [24, 38-41].

When cycled at a constant current density of 0.5 A g-1 (0.25C based on the theoretical capacity),

the composite anode PF-Si-2 with 50 wt% Si loading attained the highest reversible capacity of

approximately 1600 mAh g-1 based on the mass of PF-Si particles (Fig. 4b). The rising of

capacity in the beginning few cycles was ascribed to the inward diffusion of electrolyte




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throughout the compact network and increasing of accessible surface area of “pushed out” Si

particles [42]. After 300 full charge/discharge cycles, a coulombic efficiency of 99.5% and the

initial capacity was very well retained without any discernible decline. This was equivalent to a

capacity of 1000 mAh g-1 based on the entire laminate weight when taking the mass of graphene

and binder into account. Attributed to a high packing density, the volumetric capacity of the

entire anode reached 1100 mAh cm-3, almost doubling that of conventional graphitic anode (620

mAh cm-3) [43, 44], and is among the best results for engineered Si anode to date [16, 19, 45-

48]. In comparison, the as-received Si nanoparticles supported on graphene exhibited a first

cycle coulombic efficiency of 30% and lost over 50% of the initial value after only 50 cycles,

while all the encapsulated samples showed drastically improved capacity and stability. The

existence of optimum Si loading can be attributed to a combination of balanced factors such as

electrical and ionic conduction throughout the carbonaceous networks, as well as stress

dissipation and structural integrity.

The superior rate capability facilitated by the continuous conducting network and amorphous

carbon coating was evident when charging/discharging the PF-Si/graphene composite anode at

high rates (Fig. 4c). The reversible capacity of PF-Si-2 composite stabilized at 1100 mAh g-1,

maintaining 68% of the original capacity with increasing the rate from 0.25 A g-1 (C/8) to 2.1 A

g-1 (1C). When switching back to the initial rate, the original capacity was fully recovered. At a

constant rate of 2.1 A g-1, a single charge/discharge cycle took only 15 minutes, while the

capacity fade was as low as < 0.04% per cycle up to 1000 cycles on average (Fig. 4d). The

volumetric capacity remained a quite high value of 730 mAh g-1 after 500 cycles. Despite higher

gravimetric capacities > 2000 mAh g-1 given by various Si nanostructures e.g. Si nanowires [5,

18, 49], nanotubes [13] and hollow spheres or monolithics [7, 14], our composite anode achieved




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an unprecedented balance across capacity and retention at high rates and long-term cycling,

which is more competitive than previously reported nanostructured Si-based anode [16-20, 37-

41, 45-48, 50]. Notably, even at a high mass loading of 4 mg cm-2, there was almost no

degradation in the capacity (Fig. S5 in the ESM). Electrochemical impedance spectroscopy (EIS)

further confirmed the improved charge-transfer and Li ion diffusion kinetics of PF-Si particles

compared to pristine Si (Fig. 4e). Both the Ohmic resistance Rs (real impedance at 100 kHz, ~3

) and the charge-transfer resistance Rct (estimated diameter of the semicircle, ~65 ) of the PF-

Si-2/graphene anode were smaller that of the pristine Si/graphene anode (Rs~14 Rct~125

when fitted to the equivalent circuit in the inset of Fig. 4e [51], accompanied with a less

inclined Warburg region for the PF-Si-2/graphene anode contrasting the pristine Si/graphene

anode.

To validate the anode performance in a full cell, the PF-Si-2/graphene anode was coupled with a

NMC cathode and sealed in a laminated pouch with tab leads extending out (Fig. 5). The NMC

was selected via a cathode screening, because of its satisfactory capacity and lifetime, a relative

flat voltage plateau and reasonably high operating potential (Fig. S4 in the ESM). The

insufficient initial coulombic efficiency of the anode film can be tackled by prelithiation prior to

incorporation into the pouch cell battery [52]. The balancing mass ratio of anode (1.2 mg cm-2)

and cathode materials (8.5 mg cm-2) was set as 1:7 by using the total capacity of 1000 mAh g-1

and 140 mAh g-1 for anode and cathode, respectively. When cycled between 3 and 4.1 V at a

constant rate of 0.5C, the cell reversibly charged and discharged with stable capacity retention

close to its designed cell capacity of 1.2 mAh cm-2, showing a potential plateau at around 3.5 V

(Fig. 5d). After 100 cycles, the cell maintained 85% of its initial capacity (Fig. 5e), while

delivering a high gravimetric energy density of 420 Wh kg-1 based upon the total mass of




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electrode materials. The corresponding anode capacity was ca. 930 mAh g-1 at maximum, closed

to 90% depth-of-discharge (DOD). The pouch cell with a single pair of electrodes was flexible

and could suffer medium strain without malfunction. The variation in the discharge

characteristics and cycling stability was quite negligible between the bending and non-bending

states. The anode coating remained integral after cycling (Fig. S6 in the ESM), while the

capacity retention of pouch cells after 50 cycles could be hurdled by gas evolution and cell

swelling resulted from electrolyte decomposition and side reactions induced by residual

moisture.

By applying slightly excess anode materials, a stacked pouch cell consisting of two pairs of

double-sided cathode/anode couple was fabricated, with a designed anode capacity of the order

of 800 mAh g-1 (3.6 mg cm-2 one side). The cell exhibited a total capacity of 240 mAh with only

4% of capacity decay after 60 cycles, while the areal capacity of a single pair of electrode

attained 5.6 mAh cm-2, which already exceeds that offered by commercial Li-ion batteries for

smart phones and tablets. Further extension of cycling life can be envisaged by designing stable

SEI layers, optimizing the cut-off voltage window and switching to moisture controlled or

automatic cell production environment.

4 Conclusions

In conclusion, carbon encapsulation of Si particles enabled by in-situ polymerization and

carbonization of phloroglucinol-formaldehyde gel was successfully demonstrated as an effective

and high-throughput strategy for high-performance Si anode. Enveloping the carbon/SiOx

sheathed Si particles in graphene sheets further eliminated pulverization and electrical isolation




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of active materials, resulting in a composite with excellent gravimetric and volumetric capacity,

rate capability and cyclability. Very significantly, the preparation method employed can be easily

adapted and scaled up to existing high-throughput protocols for electrode and cell manufacture.

As-assembled pouch cell batteries incorporating the composite anode rendered stable energy

outputs and storage capabilities when subjected to long cycling, allowing a promising boost for

the realization of high-performance energy storage devices.

Acknowledgements

The authors acknowledge Dr. Thanasis Georgiou for his assistance on TGA measurement.

Electronic Supplementary Material: Supplementary material is available in the online version of

this article at:

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Figure 1 Electrode structure and fabrication. (a) Schematic drawing of carbon gel sheathed Si

particles that are embedded between flexible graphene sheets, enabling continuous conducting

pathways between Si particles, (b) schematics of carbon encapsulated Si particles. Si particles

are conformally coated with phloroglucinol layers through interactions between surface hydroxyl

groups and the phloroglucinol molecules, which enables uniform carbon coating through post

carbonization of PF gel, and (c) fabrication of large-area PF-Si/graphene composite anode

coatings through formulation of PF-Si powders with graphene sheets, dispersing in a binder

solution by high shear mixing, and coating onto a copper foil over large area uniformly (from left

to right).




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Figure 2 (a) Low-magnification TEM images of carbonized PF-Si particles, (b) high-

magnification TEM image of the highlighted region in (a) showing approximately 10 nm thick

amorphous carbon and SiOx shell, and the lattice fringe of the Si (111) plane. Inset: selected

electron diffraction (SAED) taken from the crystalline Si core, (c) EDX spectrum of the surface




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of carbonized PF-Si particles, (d) elemental mapping of Si (blue), oxygen (green) and carbon

(red) further confirming encapsulation of Si, (e) SEM image of PF-Si/graphene composites, and

(f) high-magnification view of PF-Si particles distributed on graphene sheets uniformly.




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Figure 3 (a) X-ray diffraction patterns of PF-Si particles carbonized at 800 ºC and graphene

nanoplatelets, and (b) Raman spectra of untreated PF-Si particles, carbonized PF-Si particles and

graphene nanoplatelets.




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Figure 4 Electrochemical testing of PF-Si/graphene composite anodes. (a) Galvanostatic

charge/discharge profiles of PF-Si-2/graphene composite anode between 0.02-1.5 V at various

current densities ranging from 0.25 to 2.1 A g-1, (b) specific delithiation capacity and coulombic

efficiency of PF-Si/graphene composite anodes in comparison of pristine Si/graphene anode at a

constant current density of 0.5 A g-1, (c) specific delithiation capacity and coulombic efficiency




26

of PF-Si/graphene composite anodes at various current densities ranging from 0.25 to 2.1 A g-1,

(d) long-term cycling test of PF-Si-2/graphene composite anode at a constant current density of

0.5 A g-1 and 2.1 A g-1, and (e) Nyquist plots of PF-Si-2/graphene composite anode and pristine

Si/graphene composite anode after 100 charge/discharge cycles at 0.5 A g-1. Both plots displayed

a broad depressed semicircle at high frequencies (>10 Hz) for the charge-transfer kinetic-

controlled region and a straight line at low frequencies for the mass-transfer kinetic-controlled

Warburg region, which can be presented by the equivalent circuit (inset). Rs is equivalent circuit

resistance, Rct is charge-transfer resistance, CPE is constant phase element referring to an electric

double-layer capacitance of non-homogeneous systems, and Ws is Warburg element referring to

an one-dimensional diffusion resistance.




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Figure 5 Electrochemical testing of pouch cell prototypes comprising NMC cathode and PF-Si-

2/graphene composite anode. Photograph of a pouch cell lightening a LED (a) under non-

bending, (b) under bending, and (c) a cell before sealing in an Al laminated pouch. (d) 10th and

50th-cycle galvanostatic charge/discharge profiles of the pouch cell at a constant rate of 0.5C

between 3-4.1 V. The 3.8×5.9 cm single electrode pair attained a cell capacity of 26 mAh. (e)




28

capacity retention and corresponding anode capacity during galvanostatic cycling under non-

bending and bending conditions as shown in (a) and (b). (f) Photograph of a stacked pouch cell

with two pairs of double-sided electrodes and a total cell capacity of 240 mAh, and (g) capacity

retention and corresponding anode capacity during galvanostatic cycling at a constant rate of

0.5C between 3-4.1 V.




1

Graphical Table of Contents

By encapsulating silicon particles via in-situ polymerization and carbonization of

phloroglucinol-formaldehyde gel, followed by incorporation of graphene sheets, a high-

performance Si composite anode was demonstrated in half cell and full cell configurations,

yielding remarkably enhanced capacity and stability for advanced lithium-ion batteries.


