1
Supporting Information
For
Photo-rechargeable Zinc-ion Batteries
Buddha Deka Boruah1,*, Angus Mathieson1,2, Bo Wen1,2, Sascha Feldmann3, Wesley M.
Dose1,4, Michael De Volder1,*
1 Institute for Manufacturing, Department of Engineering, University of Cambridge, Cambridge CB3 0FS, United Kingdom
2 Cambridge Graphene Centre, University of Cambridge, Cambridge CB3 0FA, United Kingdom
3 Cavendish Laboratory, University of Cambridge, JJ Thomson Ave, Cambridge CB3 0HE, United Kingdom
4 Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, United Kingdom
* Corresponding authors. E-mail: [email protected]
E-mail: [email protected]
Electronic Supplementary Material (ESI) for Energy & Environmental Science.This journal is © The Royal Society of Chemistry 2020
2
0.0 0.2 0.4 0.6 0.8 1.00
40
80
120
160
Vol
ume
adso
rbed
(c
m3 g-1
, STP
)Relative pressure (P/Po)
Adsorption curve Desorption curve
Fig. S1 BET N2 adsorption/desorption isotherms of V2O5 nanofibers.
1 µm
Fig. S2 SEM image of photo-cathode.
Fig. S3 Schematic illustration of the photo-ZIB configuration.
3
400 500 600 700 800
1
2
3
4 Pristine V2O5
V2O5+rGO V2O5+P3HT V2O5+rGO+P3HT
PL in
tens
ity (a
.u.
105 )
Wavelength (nm)
a
b c
Fig. S4 (a) Steady state PL spectra of V2O5 photo-electrodes at various stages of composition
of pristine V2O5, V2O5+rGO (V2O5 and rGO in a 98:2 ratio), V2O5+P3HT (V2O5 and P3HT in
a 98:2 ratio) and V2O5+rGO+P3HT (V2O5, rGO and P3HT in a 98:1:1 ratio). (b) TA spectra
at various pump-probe delay times. (c) TA kinetics, spectrally integrated over the ground state
bleach centered around 500 nm (grey shaded area in (b)) and the secondary transition of the
oxygen deficiency state at ~720 nm in blue and orange, respectively.
4
0.0 0.4 0.8 1.2 1.6-1
0
1
Curre
nt d
ensit
y (A
g-1)
Voltage (V vs. Zn/Zn2+)
Dark Illuminated
0.0 0.4 0.8 1.2 1.6
-1
0
1
2
3
Cur
rent
den
sity
(A g
-1)
Voltage (V vs. Zn/Zn2+)
12 mW cm-2
5 mW cm-2
0.0 0.4 0.8 1.2 1.6-1.0
-0.5
0.0
0.5
1.0
1.5
Cur
rent
den
sity
(Ag-1
)
Voltage (V vs. Zn/Zn2+)
1st
2nd
3rd
4th
5th
ba
c d
0.0 0.4 0.8 1.2 1.6-2-1012345
Cur
rent
den
sity
(Ag-1
)
Voltage (V vs. Zn/Zn2+)
Dark 420 nm 455 nm 470 nm 528 nm White light
1.02 1.04 1.06 1.08 1.10
3
Cur
rent
den
sity
(Ag-1
)
Voltage (V vs. Zn/Zn2+)
Dark 420 nm 455 nm 470 nm 528 nm White light
Fig. S5 (a) CV curves of the initial five cycles at scan of 0.5 mV s-1 in the voltage range of 0.2
V to 1.6 V. (b) CVs of the photo-ZIC at scan rate of 0.5 mV s-1 in dark and illuminated (λ ~ 455
nm, intensity ~ 12 mW cm-2) conditions. (c) CVs at different illumination intensities of 12 mW
cm-2 and 5 mW cm-2 under λ ~ 455 nm illumination. (d) CV profiles at dark and different light
illuminations at scan rate of 1 mV s-1.
5
-2 -1 0 1 2-8
-4
0
4
8
Cur
rent
(A
)
Voltage (V)
Dark 455 nm
ba
0 100 200 300 400 500 6000.0
0.3
0.6
0.9
1.2
Res
pons
e cu
rren
t (A
)
Time (s)
c
0 100 200 300 400 500 600
0.0
0.1
0.2
0.3
0.4
Res
pons
e cu
rren
t (A
)
Time (s)
d
0 100 200 300 400 500 6000.0
0.3
0.6
0.9
1.2
1.5
Res
pons
e cu
rren
t (A
)
Time (s)
e
Light
Dark
Fig. S6 (a) Schematic representation of Au-V2O5-Au (metal-semiconductor-metal) based
photodetector and right bottom inset shows the digital. (b) IV responses of the photodetector
in dark and illuminated (λ ~ 455 nm) conditions. (c) Cyclic response current (Ilight – Idark; where
Ilight and Idark are currents in dark and light illuminated conditions) plots with different light
illuminations of (c) λ ~ 455 nm, (d) λ ~ 528 nm and (e) white light at same bias voltage of 2 V.
6
We confirm the light sensitivity of the V2O5 nanofibers by measuring the electrical response
of the V2O5 nanofibers in dark and illuminated conditions. We fabricated a photodetector based
on V2O5 nanofibers active materials, which is drop casted on Gold (Au) Inter Digitated
Electrodes (IDEs) as shown in Fig. S6a (device schematic and optical photograph). The
increase in the current under illumination (λ ~ 455 nm) as compared to dark confirm photo-
sensitivity of V2O5 nanofibers (Fig S6b, current – voltage curves). Moreover, the current-time
responses at applied bias voltage of 2 V (Fig S6c-e) under different light illuminations (λ ~ 455
nm, λ ~ 528 nm and white light) show increase in response currents under illuminations. The
relatively lower response current of the photodetector under illumination of green light (λ ~
528 nm) as compared to blue (λ ~ 455) nm and white illuminations is mainly because of lower
intensity and hence limited photo-excitations.
0.0 0.4 0.8 1.2 1.6
-2-101234
Cur
rent
den
sity
(Ag-1
)
Voltage (V vs. Zn/Zn2+)
Dark Illuminated
Fig. S7 CV responses of V2O5 - rGO (V2O5, rGO and PVDF in a 93:2:5 ratio) photo-cathode
without P3HT in dark and illuminated (λ ~ 455 nm, intensity ~ 12 mW cm-2) conditions at scan
rate of 1.0 mV s-1.
7
0 50 100 150 200 250 3000.4
0.8
1.2
1.6
Vol
tage
(V v
s. Zn
/Zn2+
)
Capacity (mAh g-1)
Dark Illuminated
at 100 mA g-1
a
0 50 100 150 200 2500.4
0.8
1.2
1.6
Vol
tage
(V v
s. Zn
/Zn2+
)
Capacity (mAh g-1)
Dark Illuminated
at 200 mA g-1
b
0 50 100 150 2000.4
0.8
1.2
1.6
Vol
tage
(V v
s. Zn
/Zn2+
)
Capacity (mAh g-1)
Dark Illuminated
at 500 mA g-1
c
Fig. S8 GCDs of the photo-ZIB at (a) 100 mA g-1, (b) 200 mA g-1 and (c) 500 mA g-1 in dark
and light.
0
100
200
0.4 0.8 1.2 1.60
100
200
Cap
acity
(mA
hg-1
)
Voltage (V vs. Zn/Zn2+)
ab
c
d e
fg
a
16 18 20 22
Nor
mal
ised
inte
nsity
(a.u
.)
2 (degree)
a
b
c
d
ef
g
Pristine electrode
b
200 400 600 800 1000
Nor
mal
ised
inte
nsity
(a.u
.)
Raman shift (cm-1)
a
b
c
d
ef
g
Pristine electrode
c
Fig. S9 (b,c) XRD and Raman studies of the photo-electrodes at different charge and discharge
states (Fig. S9a). The corresponding positions of the XRD patterns and Raman spectra are
labeled with respect to the colors and letters in GCD curve.
8
To understand the charge storage reversibility of the photo-electrodes, we examine ex-situ
XRD and Raman measurements at different states of charge and discharge in dark conditions
(Fig. S9a). Fig. S9b shows the XRD evolution of the photo-electrodes during the second GCD
scan. While discharging (Zn intercalation) the photo-cathodes from upper voltage of 1.6 V to
0.4 V the XRD pattern changes from the expected patterns for the pristine electrode to one that
demonstrates various changes to the crystallographic structure. At 0.6 V and 0.2 V (deep
discharge state), the diffraction peak intensities at 2θ ~ 15.4o (200) and 2θ ~ 21.8o (101) are
decreased, and the peak at 2θ ~ 20.3o (001) broadens. These characteristic behaviors are due to
intercalation of Zn2+ ions into the layered V2O5 nanofibers structure, where the strong
electrostatic interaction between the intercalated Zn2+ and V2O5 layers influences the lattice
parameters1. An inverse trend can be observed in subsequent charge states (deintercalation),
where the XRD pattern of the photo-electrodes return to resemble the respective pattern
obtained during the discharge cycle. This implies a strong reversibility of the Zn2+ intercalation
and deintercalation reactions in the photo-electrodes. The additional diffraction peak (not
observed in the pristine electrode) observed at 2θ ~ 21o corresponds to the
precipitation/dissolution of electrolyte cluster out of the aqueous medium2,3. Similarly,
evidence for structural reversibility is observed in the Raman spectra (Fig. S9c) in
discharging/charging states. Raman peaks intensities associated with the V2O5 decrease while
discharging the electrode from 1.6 V (upper voltage) to 0.2 V (deep discharge state). The modes
associated with the V=O stretching vibration of the vanadyl bond (~ 982 cm-1), V-O3-V
symmetric stretching (~ 480 cm-1) and angle-bending of V-O3-V (~ 405 cm-1) are absent at
deep discharge states (e.g. 0.6 V and 0.2 V)4. The characteristic peaks of stretching of V-O-V
bonds (~ 699 cm-1), V3-Oc triply coordinated oxygen (~ 527 cm-1), bending vibrational mode
of V-Oc (~ 304 cm-1) and bending vibrations of Oc-V-Ob bonds (~ 284 cm-1), respectively
become broad and shift toward lower Raman shift4. A splitting of the peak at 144 cm-1,
9
corresponding to the vibration mode of V-OV chains is also observed, and a new Raman peak
is observed at 118 cm-1 when the photo-electrodes are discharged to 0.6 V and 0.2 V (deep
discharge). These characteristics are due to the insertion of Zn2+ into V2O5 layers influencing
the bonding energies. Similarly to the XRD pattern, a reverse trend is observed during the
subsequent charge cycle back to 1.6V where identical Raman spectra at the respective
discharge/charge states are observed - confirming the reversibility of the photo-electrode
material during potential cycling.
0.0 0.2 0.4 0.6 0.8 1.00.2
0.4
0.6
0.8
1.0
Vol
tage
(V v
s. Zn
/Zn2+
)
Areal capacity (mAh cm-2)
20 mA m-2
100 mA m-2
160 mA m-2
Fig. S10 Photo-charged capacities in the dark discharge condition at different current
densities of 20 mA m-2, 100 mA m-2 and 160 mA m-2.
10
2 µm
500 nm
b
c d e
10 µm
a
15 20 25 30 35 40 45 50 55
(220
)(112
)
(401
)(2
11)
Inte
nsity
(a.u
.)
2 (degree)
VO
(200
)
(001
)(1
01)
(201
)(1
10)
(301
)(0
11)
(310
)(111
)
(002
)(1
02)
(411
)(6
00) (
302)
(012
)(0
20) (6
01)
f
200 400 600 800 1000
987
694
521
474
398
29927
8
192
142
Inte
nsity
(a.u
.)
Raman shift (cm-1)
VOg
Fig. S11 (a,b) SEM images at low and high-magnifications of V2O5 power used for the
synthesis of V2O5 nanofibers. (c) EDS mapping of the V2O5 powder: (d) V and (e) O elements.
(f,g) XRD pattern and Raman spectrum of V2O5 powder.
11
a b
c
Fig. S12 (a) TEM image of V2O5 nanofibers and the respective EDS mapping of (b) V and (c)
O elements.
200 400 600 800 1000
995
699
527
480
405
304
284
197
Inte
nsity
(a.u
.)
Raman shift (cm-1)
144
Fig. S13 Raman spectrum of V2O5 nanofibers.
12
Calculation:
For the calculation of the light enhance diffusion constant of the photo-ZIB, we used the current
peak position (strong reduction/oxidation peaks at ~ 0.85/~ 1.1 V) of CV at different scan rates.
The relationship between peak current ( ) and diffusion constant ( ) can be expressed as5,𝑖𝑝 𝐷
𝑖𝑝 = 0.4463𝐹( 𝐹𝑅𝑇)1
2 𝐶 ∗ 𝜗1
2𝐴𝐷1
2
; where 𝑖𝑝 = 𝐾𝜗1
2𝐷1
2 𝐾 = 0.4463𝐹( 𝐹𝑅𝑇)1
2 𝐶 ∗ 𝐴
𝑖𝑝𝐾 = 𝐷
12𝜗
12
Here, , , and represent Faraday constant, initial concentration in mol cm-3, scan rate 𝐹 𝐶 ∗ 𝜗 𝐴
in V s-1 and electrode area in cm2, respectively. The value of K is same for both dark and
illuminated conditions. Below Fig. S14 shows the vs both in dark and illuminated 𝑖𝑝
𝐾 𝜗1
2
conditions. Table S1 shows the calculation of diffusion enhancement under illumination,
where slopes obtained from the Fig. S14.
0.000 0.005 0.010 0.015 0.020 0.025 0.030 0.035-2
-1
0
1
2
3
4
Dark Illuminated
i p/K
Root square of scan rate (V/s)1/2
EquationWeightResidual Sum of SquaresPearson's rAdj. R-Square
-Ip illuminated-Ip illuminatedIp light (1)Ip light (1)Ip light (2)Ip light (2)
13
Fig. S14 Graph of the vs both in dark and illuminated (λ ~ 455 nm, intensity ~ 12 𝑖𝑝
𝐾 𝜗1
2
mW cm-2) conditions.
Table S1. Calculation of diffusion enhancement under illumination (slopes taken from Fig.
S14)
Peak position at potential Slope ( ) in dark𝐷
12
Slope ( ) in 𝐷1
2
illuminated
Diffusion (i.e. slope) enhancement under
illumination~ 1.1 V 77.35 101.94 ~ 32%
~ 0.85 V -32.92 -47.16 ~ 43%
References
1. C. Xia, J. Guo, Y. Lei, H. Liang, C. Zhao and H.N. Alshareef, Adv. Mater., 2018, 30,
1705580.
2. Z. Li, D. Chen, Y. An, C. Chen, L. Wu, Z. Chen, Y. Sun and X. Zhang, Energy Storage
Mater., 2020, 28, 307-314.
3. L. Dong, X. Ma, Y. Li, L. Zhao, W. Liu, J. Cheng, C. Xu, B. Li, Q.-H. Yang and F. Kang,
Energy Storage Mater., 2018, 13, 96-102.
4. T. Zhai, H. Liu, H. Li, X. Fang, M. Liao, L. Li, H. Zhou, Y. Koide, Y. Bando and D. Golberg,
Adv. Mater., 2010, 22, 2547-2552.
5. Y.W. Denis, C. Fietzek, W. Weydanz, K. Donoue, T. Inoue, H. Kurokawa and S. Fujitani,
J. Electrochem. Soc., 2007, 154, A253-A257.
