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Stable high-voltage aqueous pseudocapacitive energy storage device with slow self-discharge

Hemesh Avireddy1, Bryan W. Byles3,4, David Pinto3,4, Jose Miguel Delgado Galindo1, Jordi Jacas Biendicho1, Xuehang Wang3,4, Cristina Flox1, Olivier Crosnier5,6, Thierry Brousse5,6, Ekaterina Pomerantseva3,4, Joan Ramon Morante1,2, Yury Gogotsi3,4

1IREC, Catalonia Institute for Energy Research. Jardins de les Dones de Negre 1, 08930. Sant Adrià de Besòs, Spain.2Faculty of Physics, University of Barcelona, Barcelona, Spain3Department of Materials Science & Engineering, Drexel University, Philadelphia, PA 19104, USA4A.J. Drexel Nanomaterials Institute, Drexel University, Philadelphia, PA 19104, USA5Institut des Matériaux Jean Rouxel (IMN), CNRS UMR 6502-Université de Nantes, 2 rue de la Houssinière BP32229, 44322, Nantes Cedex 3, France6Réseau sur le Stockage Electrochimique de l’Energie, FR CNRS 3459, 80039 Amiens Cedex, France

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10 20 30 40 50 60 70

0010008006004

002

103110

109107

105

004 101

104

Inte

nsity

(a.u

)

2

Ti3C2

Ti3AlC2

002

Fig. S1. XRD pattern of titanium aluminum carbide (Ti3AlC2) MAX and titanium carbide (Ti3C2) MXene.

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7 μm

60 μm

a

b

10 μm

c

Coun

ts (a

.u)

Coun

ts (a

.u)

Coun

ts (a

.u)

Energy (keV)

Energy (keV)

Energy (keV)

Fig. S2. SEM image and corresponding EDS spectra of (a) titanium aluminum carbide (Ti3AlC2)

MAX, (b) titanium carbide (Ti3C2) MXene and (c) α-MnO2

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-1.6 -1.4 -1.2 -1.0 -0.8 -0.6 -0.4 -0.2 0.0-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

E 1 m = E+ - E- = -0.1 V - (- 1.1 V) = 1.0 V

C.E. % = 93 %C.E. % = 94 %

21.9 mAh g-1 (79 Fg-1)

I (A

g-1)

Ewe vs SCE

1 m Potassium acetate 21 m Potassium acetate

Scan rate: 5 mV s-1

32 mAh g-1

(77 Fg-1)

E 21 m = E+ - E- = -0.1 V - (- 1.6 V) = 1.5 V

1 m potassium acetate 21 m potassium acetate

-1.8 -1.7 -1.6 -1.5 -1.4 -1.3 -1.2-1.0x10-1

-8.0x10-2

-6.0x10-2

-4.0x10-2

-2.0x10-2

0.0

I (m

A)

Ewe vs. SCE (V)

a

b

Fig. S3. (a) Cyclic voltammogram of the Ti3C2 Mxene in 1 m (red curve) and 21 m of potassium

acetate electrolyte solution (scan rate: 5 mVs-1). (b) Cyclic voltammogram of a glassy carbon

electrode in 1 m (red curve) and 21 m of potassium acetate electrolyte solution (scan rate 2 mVs-

1).

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21 m at -0.35 vs SCE 30 m at -0.5 vs SCE

0.4 0.8 1.2 1.6 2.0-1.6

-1.2

-0.8

-0.4

0.0

0.79

log

I (m

A)

log (mV s-1)

0.91

-1.4 -1.2 -1.0 -0.8 -0.6 -0.4 -0.2-8

-6

-4

-2

0

2

4

6

8

I (A

g-1)

Ewe vs SCE

2 mVs-1

5 mVs-1

10 mVs-1

20 mVs-1

50 mVs-1

100 mVs-1

21 m

-1.4 -1.2 -1.0 -0.8 -0.6 -0.4 -0.2-8

-6

-4

-2

0

2

4

6

8

I (A

g-1)

Ewe vs SCE

2 mVs-1

5 mVs-1

10 mVs-1

20 mVs-1

50 mVs-1

100 mVs-1

30 m

a

b

c

Fig. S4. Cyclic voltammogram in various scan rates for the Ti3C2 Mxene in (a) 21 m and (b) 30

m of potassium acetate electrolyte solution (scan rates : 2, 5, 10, 20, 50 and 100 mVs-1). (b) Log

plot of current versus scan rate of cyclic voltammograms measured from the Fig. S4a and b.

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Fig. S5. Cyclic voltammogram of a glassy carbon electrode (CHI instruments) in 21 m potassium acetate electrolyte at a scan rate of 2 mV s-1

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0 20

25

50

75

2.4 V

0 20

25

50

75

2.3 V

0 20

25

50

75

1.5 V

0 20

25

50

75

2.5 V

0 20

25

50

75

1.6 V

0 20

25

50

75

1.7 V

0 20

25

50

75

1.8 V

0 20

25

50

75

1.9 V

0 20

25

50

75

2.0 V

0 20

25

50

75

2.1 V

0 20

25

50

75

2.2 V

Curr

ent d

ensit

y (m

A g-1

)

Time (h)

Fig. S6. Voltage-hold tests in asymmetric Ti3C2 // α-MnO2 cell. Voltage-hold tests indicate a slight evolution of parasitic current at 2.3 V. Beyond that, leakage current start to decrease, which implies the breakdown of the cell.

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-1.6 -1.2 -0.8 -0.4 0.0 0.4 0.8 1.2-200

-100

0

100

200

Cur

rent

den

sity

(mA

g-1)

Ewe vs SCE (V)

Ti3C2 MXene MnO2

0.0 0.5 1.0 1.5 2.0

-100

0

100

200

Cur

rent

den

sity

(m

A g

-1)

Ecell (V)

before hold test after hold tests

After 2.5 V hold tests

-1.6 -1.2 -0.8 -0.4 0.0 0.4 0.8 1.2-200

-100

0

100

200

Cur

rent

den

sity

(mA

g-1)

Ewe vs SCE (V)

Ti3C2 MXene MnO2

a

b

c

Fig. S7. Cyclic voltammogram of (a) Ti3C2 // α-MnO2 cell before and after hold tests at 2.5 V for 2 h. Cyclic voltammogram of both individual electrodes at 5 mV s-1 (b) before and (c) after hold tests. Extension of the cell voltage to 2.5 V widens the MnO2 electrochemical potential window.

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0.0 0.5 1.0 1.5 2.0

0.8

1.0

E v

s S

CE

(V)

Time (h)

at 2.2 V hold test at 2.5 V hold test

0.0 0.5 1.0 1.5 2.0-1.6

-1.5

-1.4

E v

s S

CE

(V)

Time (h)

at 2.2 V hold test at 2.5 V hold test

alpha-MnO2

Ti3C2

a

b

Fig. S8. Evolution of potential during hold tests for (a) α-MnO2 and (b) Ti3C2 electrode.

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0 20 40 60 80 100 120 140 160 1800.0

0.5

1.0

1.5

2.0

E c

ell (

V)

t (s)

0.25 Ag-1

0.5 Ag-1

0.75 Ag-1

1 Ag-1

2 Ag-1

Fig. S9. Charge and discharge curve of Ti3C2 // α-MnO2 asymmetric supercapacitor in 21 m

potassium acetate at different current densities (weight of both electrodes).

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R1 CPE1

R2 W1

Element Freedom Value Error Error %R1 Free(±) 9.836 0.23387 2.3777CPE1-T Free(±) 4.3668E-06 1.7072E-06 39.095CPE1-P Free(±) 0.84903 0.034084 4.0145R2 Free(±) 15.56 0.90682 5.8279W1-R Free(±) 1670 49.217 2.9471W1-T Free(±) 9.599 0.39952 4.1621W1-P Free(±) 0.46661 0.003206 0.68708

Chi-Squared: 0.0020853Weighted Sum of Squares: 0.16891

Data File: c:\users\jjacas\desktop\coses pendents\hemesh\respond to reviewers\transform\total_1.z

Circuit Model File: C:\Users\JJacas\Desktop\coses pendents\hemesh\respond to reviewers\transform\MODEL.mdl

Mode: Run Fitting / Selected Points (0 - 43)Maximum Iterations: 100Optimization Iterations: 0Type of Fitting: ComplexType of Weighting: Calc-Modulus

a b

c

1.4 V 1.5 V 1.6 V 1.7 V 1.8 V 1.9 V 2.0 V 2.1 V 2.2 V

0 1000 2000 3000 40000

1000

2000

3000

4000

Ti3C2Tx // MnO2

-Img.

Z (O

hm)

Real Z (Ohm)

0 500 10000

500

1000

d

datafit

datafit

Fig. S10. (a) Impedance data show a high frequency semicircle with an inclined spike

of ~45° at intermediate frequencies, (b) Open circuit or capacitive behavior at even

lower frequencies, (c) Equivalent circuit used for the fitting and (d) Nyquist plot at different

voltages for the Ti3C2 // α-MnO2 cell. Inset shows the impedance behavior at the knee frequency.

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Fig. S11. Capacitance over scan rate performance of YP-50 // YP-50 and Ti3C2 // α-MnO2 cell in

21 m potassium acetate electrolyte.

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Figure 8: Different tunnels structures used in the present study

0.0 0.5 1.0 1.5 2.0-100

-50

0

50

100C

urre

nt d

ensi

ty (m

A g

-1)

Ecell (V)

Before hold tests

After 25 hr hold test

Scan rate: 5 mVs-1

0 5 10 15 20 250

5

10

Cur

rent

den

sity

(mA

g-1)

Time (hr)

0 5 10 15 20 250.80

0.75

Ew

e (

MnO

2) v

s S

CE

Time (hr)

0 5 10 15 20 25-1.45

-1.40

Ece

(Ti 3C

2Tx)

vs S

CE

Time (hr)

a b c

dFig. S12. Cyclic voltammogram of the Ti3C2 // α-MnO2, before and after 25 h hold tests at 2.2 V

in 21 m potassium acetate electrolyte. Current is normalised to the mass of both the electrodes.

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0 5 10 15 20 250.80

0.79

0.78

0.77

0.76

0.75

Ew

e (

MnO

2) vs

SC

E (V

)

Time (h)

0 5 10 15 20 25-1.45

-1.44

-1.43

-1.42

-1.41

-1.40

Ece

(Ti 3C

2) vs

SC

E (V

)

Time (h)

a

b

Fig. S13. Evolution of potential during long term hold tests for (a) α-MnO2 and (b) Ti3C2

electrode at 2.2 V for 25 h in 21 m water-in-salt potassium acetate electrolyte.

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10 100 1000

1

10E

nerg

y (m

Wh

cm-3)

Power (Wh cm-3)

AC // MnO2 in 21 m LiTFSI AC // AC in 31 m LiTFSI AC // AC in 7 m LiTFSI AC // AC in 21 m KoAC Ti3C2 // MnO2 in 21 m KoAC

Fig. S.14. Ragone plot showing the correlation between the volummetric energy and power

density between the asymmetric cell of Ti3C2 // α-MnO2 and YP-50 // YP-50. The observed

volumetric energy density of Ti3C2 // α-MnO2 cell (16.80 mWh cm-3 at 137 mW cm-3) is higher

than the existing supercapacitors based on water-in-salt electrolytes, such as and AC // MnO2 in

21 m Li-TFSI [1] (10 mWh cm-3 at 44 mW cm-3 mWh cm-3), AC // AC in 7 m Li-TFSI [2] (6

mWh cm-3 at 49 mW cm-3) and AC // AC cell in 31 m Li-TFSI (8 mWh cm-3 at 57 mW cm-3

mWh cm-3 at 137 mW cm-3).AC : Activated carbon; LiTFSI: lithium bis(trifluromethane)-

sulfonimide; KoAc: potassium acetate

References:

[1] A. Gambou-Bosca, D. Bélanger, Electrochemical characterization of MnO2-based composite in the presence of salt-in-water and water-in-salt electrolytes as electrode for electrochemical capacitors, J. Power Sources. 326 (2016) 595–603. doi:10.1016/j.jpowsour.2016.04.088.

[2] P. Lannelongue, R. Bouchal, E. Mourad, C. Bodin, M. Olarte, S. le Vot, F. Favier, O.

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Fontaine, “Water-in-Salt” for Supercapacitors: A Compromise between Voltage, Power Density, Energy Density and Stability, J. Electrochem. Soc. 165 (2018) A657–A663. doi:10.1149/2.0951803jes.

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