Charge–Discharge Performance of Copper Metal Positive Electrodes in Fluorohydrogenate Ionic Liquids for Fluoride-Shuttle Batteries

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Figures

(a)

Current density / A (g-Cu) -1

(b)

-2

1st

2nd

3rd

-4

-6

-0.5

0.5

1.0

Potential / V vs. CuF22/Cu

CuF2/Cu

vs. CuF

V vs.

Potential // V

/Cu

Potential

1.0

0.5

-0.5

200

400

600

Capacity / mAh (g-Cu) -1

Fig. 1 (a) Cyclic voltammograms and (b) initial charge–discharge curves of the copper metal

electrode in the [C2C1im][(FH)2.3F] electrolyte at 298 K. Scan rate in (a): 10 mV s−1. Charge–

discharge rate in (b): 0.05C.

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▼ Cu (01-085-1326)

Pt

/ cps

Intensity

Intensity

(a)

2×104 cps

Pt

Pt

2×104 cps

(b)

Pt

Pt

2×104 cps

Pt

(c)

20

25

30

35 40 45 50

2 / deg. (Cu-K)

55

60

Fig. 2 X-ray diffraction patterns of the copper metal electrodes (a) before charging (pristine

state), (b) after charging to 0.7 V vs. CuF2/Cu, and (c) after 1 cycle to −0.3 V vs. CuF2/Cu in

the [C2C1im][(FH)2.3F] electrolyte at 298 K. The diffraction peaks of Pt metal arise from the Pt

current collector.

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Cu 2p3/2

Cu 2p1/2

CuF2

satellite

CuF2

Cu0

CuF2

satellite

CuO

CuF2

Cu0

CuO

/ a.u.

Intensity

Intensity

(a)

(b)

(c)

970

960

950

940

930

Binding energy / eV

Fig. 3 Cu 2p XPS profiles of the copper metal electrodes (a) before charging (pristine state),

(b) after charging to 0.7 V vs. CuF2/Cu, and (c) after 1 cycle to −0.3 V vs. CuF2/Cu. in the

[C2C1im][(FH)2.3F] electrolyte at 298 K.

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(a)

CuF2/Cu

vs. CuF2/Cu

V vs.

Potential // V

Potential

1.0

20th 10th

1st 2nd

0.5

-0.5

200

400

600

Capacity / mAh (g-Cu)-1

(g-Cu)−1

−1

Capacity

mAh

(g-Cu)

Specific capacity / mAh (g-Cu)-1

(b)

600

Charge

Discharge

400

200

10

15

Cycle number

20

Fig. 4 (a) Charge–discharge curves and (b) cycling characteristics of the copper metal electrode

in the [C2C1im][(FH)2.3F] electrolyte at 298 K. Charge–discharge rate: 0.05C.

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(a)

CuF2/Cu

Potential / V vs. CuF2/Cu

1.0

20th 10th 1st 2nd

0.5

(b)

capacity // mAh

Discharge capacity

mAh (g-Cu)-1

(g-Cu)−1

Discharge

Discharge capacity / mAh (g-Cu)-1

-0.5

100 200 300 400 500

[C2C1im][(FH)2.3F]

Capacity

/ mAh (g-Cu)-1

(g-Cu)−1

[C2C1pyrr][(FH)2.3F]

600

[C

[C2C1im][(FH)2.3F]

2C1im][(FH)2.3F]

[C

[C2C1pyrr][(FH)2.3F]

2C1pyrr][(FH)2.3F]

400

600

200

400

200

10

15

Cycle number

20

Fig. 5 (a) Charge–discharge curves of the copper metal electrode in [C2C1pyrr][(FH)2.3F]

electrolyte at 298 K. (b) A comparison of discharge capacities of the copper metal electrode

in the [C2C1im][(FH)2.3F] and [C2C1pyrr][(FH)2.3F] electrolytes at 298 K. Charge–discharge

rate: 0.05C.

10

15

Cycle number

20

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Cu

(a) Pristine

10 μm

Cu

(b) After 20 cycles

([C2C1im][(FH)2.3F])

10 μm

Cu

(c) After 20 cycles

([C2C1pyrr][(FH)2.3F])

10 μm

Fig. 6 SEM images and corresponding EDX mapping of the copper metal electrodes surfaces

(a) before charging (pristine state), (b) after 20 cycles in the [C2C1im][(FH)2.3F], and (c) after

20 cycles in the [C2C1pyrr][(FH)2.3F] at 298 K.

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Figure captions

Fig. 1 (a) Cyclic voltammograms and (b) initial charge–discharge curves of the copper metal

electrode in the [C2C1im][(FH)2.3F] electrolyte at 298 K. Scan rate in (a): 10 mV s−1. Charge–

discharge rate in (b): 0.05C.

Fig. 2 X-ray diffraction patterns of the copper metal electrodes (a) before charging (pristine

state), (b) after charging to 0.7 V vs. CuF2/Cu, and (c) after 1 cycle to −0.3 V vs. CuF2/Cu in

the [C2C1im][(FH)2.3F] electrolyte at 298 K. The diffraction peaks of Pt metal arise from the Pt

current collector.

Fig. 3 Cu 2p XPS profiles of the copper metal electrodes (a) before charging (pristine state),

(b) after charging to 0.7 V vs. CuF2/Cu, and (c) after 1 cycle to −0.3 V vs. CuF2/Cu. in the

[C2C1im][(FH)2.3F] electrolyte at 298 K.

Fig. 4 (a) Charge–discharge curves and (b) cycling characteristics of the copper metal electrode

in the [C2C1im][(FH)2.3F] electrolyte at 298 K. Charge–discharge rate: 0.05C.

Fig. 5 (a) Charge–discharge curves of the copper metal electrode in [C2C1pyrr][(FH)2.3F]

electrolyte at 298 K. (b) A comparison of discharge capacities of the copper metal electrode

in the [C2C1im][(FH)2.3F] and [C2C1pyrr][(FH)2.3F] electrolytes at 298 K. Charge–discharge

rate: 0.05C.

Fig. 6 SEM images and corresponding EDX mapping of the copper metal electrodes surfaces

(a) before charging (pristine state), (b) after 20 cycles in the [C2C1im][(FH)2.3F], and (c) after

20 cycles in the [C2C1pyrr][(FH)2.3F] at 298 K.

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