1

Supporting Information

Suppressed Polysulfide Crossover in Li-S

Batteries Through a High-Flux Graphene Oxide

Membrane Supported on Sulfur Cathode

Mahdokht Shaibani,†, ‡ Abozar Akbari,

† Phillip Sheath,

† Christopher D. Easton,

‡ Parama

Chakraborty Banerjee,† Kristina Konstas,

‡ Armaghan Fakhfouri,

† Marzieh Barghamadi,

‡, §

Mustafa M. Musameh,‡ Adam S. Best,

‡ Thomas Rüther,

‡ Peter J. Mahon,

§ Matthew R. Hill,

*,‡,

^ Anthony F. Hollenkamp,

*,‡ and Mainak Majumder

*,†

† Nanoscale Science and Engineering Laboratory (NSEL), Department of Mechanical and

Aerospace Engineering, Monash University, Clayton, VIC 3168, Australia ‡

CSIRO, Clayton, VIC 3168, Australia § Department of Chemistry and Biotechnology, Swinburne University of Technology, VIC

3122, Australia

^ Department of Chemical Engineering, Monash University, Clayton, VIC 3168, Australia

Table of contents

Section SI. Materials

Section SII. Supporting Figures

Figure S1 SEM images of uniformly coated sulfur cathode and poorly coated sulfur cathode

Figure S2 Characterization of the porous structure of the microporous carbon

Figure S3 High resolution C 1s XPS spectrum of carbon coated separator

Figure S4 Cyclic voltammogram of GO coating alone

Figure S5 Cyclic voltammogram of GO coated cathode

Figure S6 FTIR spectrum of GO coated cathode

Figure S7 High resolution C 1s XPS spectrum of GO coated cathode

Figure S8 Effect of giving a resting time before cycling

Figure S9 Capacity Contribution of the GO coating

2

Figure S10 Capacity retention of GO coated electrode after 400 cycles at different lower rates

Figure S11 Influence of the structural order of GO membrane on the performance of Li-S cell

Figure S12 Proposed electrical equivalent circuit (EEC)

Figure S13 Comparison of the experimental and the simulated EIS data

Figure S14 Effect of GO coating thickness on cyclability

Figure S15 Effect of the conductive interlayer thickness on cyclability

Figure S16 Cycling performance in a liNO3-free electrolyte

Section SIII. Supporting Tables

Table S1 Calculated resistances of the different interfaces of cells with different separators

Table S2 Survey data measured by XPS

Table S3 Component fitting of high resolution S 2p spectra measured by XPS

Table S4 Comparison of the performances of advanced Li-S cells

Table S5 Comparison of the performances of Li-S cells with GO in their configuration.

Section SI. Materials

Graphite powder (SP-1 grade 325 mesh) was purchased from Bay Carbon Inc. Microporous

carbon (Black Pearls 2000) was purchased from CABOT Co. Potassium persulfate,

Phosphorus pentoxide, Potassium permanganate, Ammonium persulfate, N-methyl-2-

pyrrolidinone, Bis(trifluoromethane)sulfonimide lithium salt and Lithium nitrate were

purchased from Sigma-Aldrich and directly used without any further purification.

Battery grade etched Al foil (30 µm thickness) was purchased from Japan Capacitor

Industrial Co. Solupor 7P03A separator was purchased from Lydall, Inc., UK and Glass fiber

BG03013 separator (0.203 mm, max pore size= 15.5 µm) was purchased from, Hollingsworth

& Vose (H&V), USA. Cross-linked polyacrylate copolymer based hydrogel beads were

purchased from Demi Co, Ltd, China. Cross-linked polyacrylate copolymer based hydrogel

beads were purchased from Demi Co, Ltd, China.

3

Section SII. Supporting Figures

Figure S1. Effect of the gap size of the doctor blade -which demonstrates the thickness of the

GO membrane - on the coverage of the GO coating on the cathode: (a) SEM image of a GO

coated cathode with a large enough gap size of the doctor blade showing uniform coverage of

the cathode surface. (b) SEM image of a GO coated cathode with a not large enough gap size

of the doctor blade revealing electrode areas which are not covered with the GO membrane.

Decreasing the thickness of the coated GO membrane is limited only by the surface

roughness of the cathode.

1 µm 1 µm

a b

S cathode

GO coting

4

Figure S2. Characterization of the porous structure of the microporous carbon used in this

work for fabricating carbon coated separators: (a) N2 adsorption isotherm at 77K, (b) Pore-

size distribution.

Figure S3. High resolution C 1s XPS spectrum of carbon coated separator.

a b

5

Figure S4. Control experiment on the GO coating on Al foil, without the sulfur cathode:

Cyclic voltammetry at 0.1 mV s-1

in a potential window from 1.8 to 2.8 V vs Li+/Li

0.

Figure S5. Cyclic voltammetry of GO coated electrode at 0.1 mV s-1

in a potential window

from 1.8 to 2.8 V vs Li+/Li

0.

6

Figure S6. FTIR spectrum of graphene oxide coated electrode shows hydroxyls (broad peak

at 3000-3800 cm-1

), carboxyls (1650-1750 cm-1

) and ethers and/or –C-O- (1000-1280 cm-1

).

Figure S7. High resolution C 1s XPS spectrum of graphene oxide coated electrode. Various

carbon-oxygen functional groups, including hydroxyl, epoxy, and carboxylic acid, are likely

present in the GO membrane as represented by the signal intensity at binding energies

greater than ~ 286 eV, and supported by the FTIR results.

7

Figure S8. Effect of resting time before cycling: Putting a cell on rest for 24 h before cycling

at a high 1 C rate allows for the electrolyte to diffuse through the GO layer and wet the sulfur

cathode. Accordingly the cell starts at its highest capacity compared to a cell which was

cycled immediately after assembly and requires some activation cycle to reach its maximum

capacity.

Figure S9. Capacity Contribution of the GO coating: (a) Charge discharge V-t profiles of GO

coating at the same current density as a typical Li-S cell in this work in a potential window

from 1.8 to 2.8 V vs Li+/Li

0. (b) Cycling performance comparison of GO coating at the same

current density as a typical Li-S c ell in this work shows negligible capacity contribution

from the GO coating.

a b

8

Figure S10. Capacity retention of GO coated cathode after 400 cycles at different lower rates:

After 400 cycles the cells can still maintain specific capacities of 1100 mAh g-1

at 0.1 C, 985

mAh g-1

at 0.2 C and 885 mAh g-1

at 0.5 C rates providing one of the best performances

demonstrated so far for a Li-S cell.

9

Figure S11. Influence of the structural order of the GO membrane on the

electrochemical response and performance fading of the Li-s battery: (a) Configuration

of a cell assembled with a bare separator, (b) configuration of a cell assembled with a shear-

aligned GO coated separator made by blade coating, (c) configuration of a cell assembled

with a disordered GO coated separator made by vacuum filtration technique. (d) Comparing

the 1st cycle of cells a, b and c; (e) comparing the 5

th cycles of cells a, b and c.

Predicted organization of

graphene sheets in the

Vacuum filtered GO film

on the separator 1, 2

Li

Separator

Sulfur cathode

Predicted organization of

graphene sheets in the

Shear aligned GO film

on the separator

a b c

d e

Go coated Separator Go coated Separator

Sulfur cathode Sulfur cathode

Li Li

10

Figure S12 Proposed electrical equivalent circuit (EEC) to analyse the impedance data of the

cells containing a bare separator, an ordered and a disordered GO coated separators. In this

study, complex nonlinear least square method was used to analyse the data. The fitting

procedure, weighing modulus and circuit description codes are explained elsewhere.3

Figure S13 Comparison

of the experimental and the simulated (a) Nyquist, (b) Bode |Z| and (c) Bode phase angle

plots of a cell assembled with a sheer aligned GO coated separator made by blade coating. A

good agreement between the simulated and experimental data confirms the validity of the

proposed EEC. (d) Error plot of the same cell shows less than 5 % error in |Z|, and the error

in angle simulation was less 4 degree.

11

Figure S14. Effect of GO coating thickness on cyclability (1C rate): A thicker coating

clearly interferes with both ion movement and mass transport.

≈ 0.80 µm thick GO film on the

cathode ≈ 1.60 µm thick GO film on the cathode

12

Figure S15. (a) Cross section SEM image of a relatively heavy carbon coated separator (≈ 15

µm and ≈ 0.7 mg cm-2

), (b) SEM image of a lightweight carbon coated separator (≈ 6.5 µm

and ≈ 0.24 mg cm-2

), (c) Effect of the mass of the conductive interlayer on the cycling

performance of GO coated cathodes. If we only consider the sulfur utilization (mAh g-1

S) the

specific capacity of the cell configured with a heavy conductive interlayer is slightly higher.

However if we take into account the mass of the whole cathodic system (Cathode (sulfur+

conductive agent+ binder) + Additional layers (GO on the cathode and carbon on the separator)), the total gravimetric

capacity of the cell with a lightweight coating is ≈ 280 mAh g-1

which is significantly higher

than that of the cell with a heavy coating: ≈ 216 mAh g-1

.

a b

c

13

Figure S16. Cycling performance in a liNO3-free electrolyte.

Section SIII. Supporting Tables

Table S1 Calculated resistances of the different interfaces of the cells containing bare

separator, sheer aligned GO coated separator and disordered GO coated separator before and

Sample Re (Ω) Rint (Ω) Rct (Ω)

Before after Before after Before after

Bare separator 5 7 108 200 31 194

Sheer aligned GO

coated separator

8 6 83 107 132 148

Disordered GO coated

separator

9 12 99 181 106 236

14

after 5 cycles of CV

15

Table S2. Survey data measured by XPS (atomic percentage, %). Listed are the mean values

(± deviation) based on +2 analyses points.

Sample: Un-coated cycled cathode

GO-coated cycled cathode

Atomic% Mean Std Mean Std

Na 1s 0.08 0.03 0.00 0.00

F 1s 20.13 1.47 23.20 1.62

O 1s 25.88 0.65 29.82 0.55

N 1s 4.27 0.10 3.67 0.13

C 1s 25.03 1.16 21.18 0.33

S 2p 11.14 0.37 8.29 0.23

Li 1s 13.45 1.18 13.85 1.34

Si 2p 0.03 0.05 0.00 0.00

Table S3. Component fitting of high resolution S 2p spectra measured by XPS (atomic

percentage, %). Listed are the mean values (± deviation) based on 3 analyses points.

Sample

Un-coated cycled cathode

GO-coated cycled cathode

Atomic% Mean Std Mean Std

S 1 4.79 0.32 2.85 1.00

S 2 27.96 2.78 6.08 2.79

S 3 6.97 0.27 2.22 1.23

S 4 2.25 0.75 2.19 0.45

S 5 12.74 0.58 4.82 1.39

S 6 19.57 1.05 34.88 0.80

S 7 25.72 2.55 46.97 4.63

S 2p components:

S 1: Li2S; S*-SO3 (thiosulphate)

S 2: Li2S2; polysulfide (Sterminal)

S 3: polysulfide (Sbridge)

S 4: S8

S 5: Range of oxidised and S+ groups

S 6: Sulfite (RSO3); RS(O)OR

S 7: Sulfate (RSO4); ROSO2OR, RSO2F

16

Table S4. Performance of the state of the art Li-S batteries.

a Values were extracted from the main texts. b Values were estimated from the relevant

figures.

Sulfur

Fraction

(%)

Sulfur

Loading

(mg cm-2

)

Interlyer

weight

(mg cm-2

)

Rate /

cycle

Discharge capacity at nth

cycle per mass

of

(mAh g-1

)

sulfur composite

cathode

composite

cathode

+interlayer

GO/Amylopectin

host 4a

52 4 N/A 0.5 C (100) 430 223 N/A

Hollow core-shell

interlinked carbon

spheres host 5a

52.5 1 N/A 0.5 C (200) 960 504 N/A

Mesoporous

Carbon Nanotube

host 6a

60 1.87 N/A 0.1 C (100) 866 520 N/A

polar, high surface

area metallic oxide

host 7a

48

56 0.75-0.9 N/A

0.5 C (100)

0.5 C (100)

870

850 417

476 N/A

g-C3N4

polar host 8a

56 1.5 N/A 1 C (200) 730 408 N/A

PEDOT:PSS-

coated CMK-

3/sulfur composite 9a

43 1 N/A 0.2 C (150) 600 258 N/A

Phenyl sulfonated

graphene/sulfur10

63 1.15-1.77 N/A

0.2 C (50)

0.2 C (400)

717

460 452

290

GO on the

separator 11b

63 1-1.5 0.12 0.1 C (100) ~700 ~ 441 ~ 376

GO/O-CNT on the

separator 12b

65 1.2-1.4 0.3 1 C (100) ~ 750 ~ 487 ~ 300

CNF interlayer 13a

60 1.4 4.2 0.2 C (100) 1161 696 73

Polypropylene/

Graphene

Oxide/Nafion

separator 14b

54 1.2 0.0532 0.1 C (100) ~850 ~ 459 ~ 408

SWCNT

Modulated

Separator 15b

75 1.5 0.13 0.5 C (100)

0.5 C (300)

~800

501

~ 600

375 ~ 484

302

Graphene current

collector + vacuum

filtered graphene

separator 16b

70 3-4 1.3 0.75 A g

-1

(100)

~950

~665

~527

This work

35

70

80

1-1.2

1-1.2

1.3-1.4

0.29 0.5 C (100)

1003

1190

1040

350

834

835

278

572

577

17

18

Table S5. Comparison of the performances of Li-S cells with GO in their configuration.

a Values were extracted from the main texts.

b Values were estimated from the relevant

figures.

Electrolyte Rate 1st

discharge

capacity, mAh g-1

Discharge

capacity at nth

cycle, mAh g-1

Coulombic

efficiency, %

GO/S cathode 17a

Organic

IL

0.1 C

0.1 C

1014

1014

736 (16)

954 (50)

96.7

GO/S/CTAB cathode 18b

Organic

IL

1.0 C

1.0 C

~860

~860

~640 (100)

~680 (400)

96.7

96.3

GO/S/Amylopectin

cathode 4a

Organic

0.5 C 596 430 (100) 98

GO coated separator 11b

Organic 0.1 C ~1000 ~700 (100) 95-98

This work Organic

Organic

Organic

1.0 C

1.0 C

0.2 C

1170

1170

1616

950 (100)

750 (400)

1200 (100)

~100

99.75

99.55

19

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