Supporting Information

Effects of Microstructure and Electrochemical Properties of Ti/IrO2-

SnO2-Ta2O5 as anodes on Binder-Free Asymmetric Supercapacitors

with Ti/RuO2-NiO as cathodes

Yanbin Zhang1,Qiongqiong Ma1, Keke Feng1, Jie Guo1, Xinli Wei1, Yanqun Shao1,2*,

Jianhuang ZHUANG3, Tianshun Lin,3

1. College of Materials Science and Engineering, Fuzhou University, Fuzhou, Fujian

350108, China

2. Zhicheng College, Fuzhou University, Fuzhou, Fujian 350002, China

3. Putian power supply co., Ltd.，Putian, Fujian 351100,China)

* Corresponding authors.

Tel.: +86 18950477698

E-mail address: yqshao1989@163.com (Y. Shao)

ContentsFig. S1. EDX spectra of Ti/IrO2-SnO2-Ta2O5 electrode annealed under different temperature: (a) 310 °C; (b) 350 °C; (c) 370 °C; (d) 450 °C.Tab. S1. Atomic percentage of elements on the surface of Ti/IrO2-SnO2-Ta2O5 electrode annealed under different temperature.

Fig. S2. Nitrogen absorption and desorption curve and pore size distribution plot of Ti/IrO2-SnO2-Ta2O5 electrode annealed at different temperature: (a) 310°C; (b) 330°C; (c) 350°C; (d) 370 °C; (e) 390°C; (f) 450°C.Fig. S3. XPS spectra of Ti/IrO2-SnO2-Ta2O5 electrode annealed under different temperature: (a) Ir 4f, (b) Ta5f, (c) Sn3d, (d) O 1s, (e) Cl 2p. Fig. S4. The XRD patterns of Ti/IrO2-SnO2-Ta2O5 electrodes prepared at 450,500 and 550°C.Fig. S5. (a) CV curves, (b) surface charge density, (c) GCD curves, (d) specific capacitance curves of the Ti/IrO2, Ti/IrO2-SnO2, Ti/ IrO2-Ta2O5 and Ti/IrO2-SnO2-Ta2O5 coating prepared at 370°C.Fig. S6. Ti/RuO2-NiO electrodes prepared at 500°C: (a) XRD spectra; (b) SEM spectra; (c-e) EDX spectra.Fig. S7. Ti/RuO2-NiO electrodes prepared at 500°C: (a) CV curves; (b) Nuquist plots with a frequency range from 0.05 to 105 Hz; (c) the equivalent circuit fitted with impedance spectra; (d) enlarged view of the high frequency range.

(a)

(b)

(c)

(d)

Fig. S1. SEM of Ti/IrO2-SnO2-Ta2O5 electrodes annealed at different temperatures: (a) 310°C, (b)

350°C, (c) 370°C, (d) 450°C.

Fig. S1 showed the EDX element distribution diagram of Ti/IrO2-SnO2-Ta2O5

electrodes prepared at different temperatures, which intuitively characterizes the

elemental composition of the coating. It could be seen from the figure that the Ir, Sn,

Ta, O and Cl elements are uniformly distributed in the coating, which indicates that

there were also chlorides in the structure that had not been converted into oxides, the

structure coexists with amorphous and crystalline states. Tab. S1 shows that as the

temperature increased, the Cl content in the coating gradually decreased and the

oxygen content increased. It showed that the amount of chloride conversion was

increasing and the content of active oxides was increasing. The annealing temperature

was increased from 310 °C to 450 °C, and the chloride content of the coating was

reduced by 8.89%. At the same time, the results show that the atomic ratio of Ir: Sn:

Ta was about 4: 3: 3, which was the same as that in the precursor solution.

Tab. S1. Atomic percentage of elements on the surface of Ti/IrO2-SnO2-Ta2O5 electrode annealed

under different temperature

Temperature Ir(%) Sn(%) Ta(%) O(%) Cl(%)

310 °C 12.11 8.92 9.07 55.12 14.78

350°C 12.47 9.07 9.26 57.26 11.94

370°C 12.72 9.21 9.34 58.6 10.13

450°C 12.97 9.32 9.44 62.38 5.89

Fig. S2. Nitrogen absorption and desorption curve and pore size distribution plot of Ti/IrO2-SnO2-

Ta2O5 electrode annealed at different temperature: (a) 310°C; (b) 330°C; (c) 350°C; (d) 370 °C; (e)

390°C; (f) 450°C.

Fig. S2 (a1) ~ (e1) showed the nitrogen adsorption and desorption curves of the

Ti/IrO2-SnO2-Ta2O5 coating prepared at different temperatures, and Fig. S2 (a)~

(e)showed pore size distribution plot of the coating at each temperature. From Fig.

S2(a1)~ (e1), we could see from the N2 adsorption and desorption curve that the

coating prepared at high temperature had a higher adsorption capacity for nitrogen

than the coating prepared at low temperature. It was a hysteresis loop in the coatings

prepared at different temperatures between 0.4~1.0. The classification of adsorption

and desorption isotherms by IUPAC could determine that the isothermal adsorption

curves of Ti/IrO2-SnO2-Ta2O5 composite coatings prepared at different temperatures

belong to type IV curves, it indicated that the coated electrode materials prepared at

different temperatures belong to the mesoporous structure. Combined with IUPAC's

classification of hysteresis loops, the hysteresis loops exhibited by the coating

structure at 310 ~ 370 °C should belong to H3 type. The hysteresis of samples

prepared at 390 °C and 450 °C is divided into H2 type, H2 mesoporous type was

tubular, close-packed structure and some spherical particle interstitial pores.

According to the desorption branch, the BJH model evaluated the pore size

distribution under high pressure and obtained the pore size distribution in right figure.

The electrode material had a wider pore size distribution and a larger average pore

size, this may be due to the process of nucleation and growth of grains with increasing

temperature.

Fig. S3. XPS spectra of Ti/IrO2-SnO2-Ta2O5 electrode annealed under different

temperature: (a) Ir 4f, (b) Ta5f, (c) Sn3d, (d) O 1s, (e) Cl 2p.

Fig. S3 (a)~ (e) showed the peak intensity comparison spectra of electrode

coatings prepared at different annealing temperatures. The electrodes prepared at

390℃ exhibited higher Ir 4f, Ta 4f, Sn 3d and O 1s peak intensity but a relatively

lower Cl 2p one, which suggested more precursor solution was oxidized along with

the rise of annealing temperatures.

Fig. S4. The XRD patterns of Ti/IrO2-SnO2-Ta2O5 electrodes prepared at 450,500

and 550°C.

As Fig. S4 showed that as the temperature rose to 500 °C, the intensity of the

diffraction peaks that characterize the rutile phase in the spectra became higher and

sharper showed that the coating had a high degree of crystallization. The peaks at 2θ

of 27.7°and 34.4° may be corresponded to (Ir,Sn,Ta)Ox solid solution The diffraction

peaks (28.27°) corresponded to standard diffraction peaks of Ta2O5 (1110) profile

(PDF 43-1027), which proved that Ta2O5 was present in the Ti/IrO2-SnO2-Ta2O5

electrode.

Fig. S5. (a) CV curves, (b) surface charge density, (c) GCD curves, (d) specific

capacitance curves of the Ti/IrO2, Ti/IrO2-SnO2, Ti/IrO2-Ta2O5 and Ti/IrO2-SnO2-Ta2O5

coating prepared at 370°C.

The amount of Ir in all electrode coatings were 0.5 mg/cm2. and the mole ratio of

Ir and Sn was 4:3 for Ti/IrO2-SnO2 coating. the mole ratio of Ir and Ta was also 4:3 for

Ti/IrO2-Ta2O5 coating. Fig. S5 (a) showed the CV curves (10 mV s-1) of all electrode

coatings prepared at 370°C. We could see that CV curves of Ti/IrO2-SnO2, Ti/IrO2-

Ta2O5 and Ti/IrO2-SnO2-Ta2O5 coating exhibited both obvious redox peaks and

strengthened current response. The CV area of Ti/IrO2-SnO2-Ta2O5 coating had the

max value. As shown in Fig. S5 (b), the Ti/IrO2-SnO2-Ta2O5 coating also exhibited the

largest surface charge density by 0.50 C cm-2, indicating stronger charge storage

ability. Fig. S5 (c) showed the GCD curves of all coatings with the current density of

1mA cm-2, all curves exhibited highly symmetrical charging and discharging results,

which indicated they had a great reversibility performance. And Fig. S5(d) indicated

the specific capacitance of Ti/IrO2-SnO2-Ta2O5 coating also had the max value of 383

Fg-1, which was more than twelve times that of the pure IrO2 electrode. It proved that

the addition of SnO2 and Ta2O5 could improve the specific capacitance of Ir-based

electrode electrode material.

Fig. S6. Ti/RuO2-NiO electrodes prepared at 500°C: (a) XRD spectra; (b) SEM spectra; (c-e) EDX

spectra

Fig. S6 (a) showed the XRD spectra of the Ti/RuO2-NiO oxide coating annealed

at 500 °C. It appeared diffraction peaks that characterize crystalline rutile RuO2 and

NiO. The 2θ values of the diffraction peaks were 28.05°, 35.1°, 54.35°and 62.85°.

Compared with the standard PDF card (PDF-88-0288), it was found that the

diffraction peaks at this place correspond to the (110), (201), (211) and (220) crystal

planes of rutile, it indicated that both RuO2 and NiO could crystallize at the

temperature and the oxide coating was composed of a mixture of RuO2 and NiO. As

Fig. S6 (b) showed, the surface of the electrode coating prepared at 500°C showed a

"cracked" morphology, elements of Ni, Ru and Cl were uniformly distributed on the

dense coating surface, indicated that the coating structure was most likely a composite

(a)

(b)

(c) (d) (e)

(a)

oxide structure of iridium oxide and nickel oxide. At the same time, the presence of Cl

at this position indicated that there were still chlorides in the coating that had not been

converted into oxides.

Fig. S7. Ti/RuO2-NiO electrodes prepared at 500°C: (a) CV curves; (b) Nuquist plots with a

frequency range from 0.05 to 105 Hz; (c) the equivalent circuit fitted with impedance spectra; (d)

enlarged view of the high frequency range.

According to the CV curve in Fig. S7 (a), as the scan rate increased, the current

response increased. The cyclic voltammetry curve of the Ti/RuO2-NiO electrode

tested at different scan rates in the potential range of -0.4-0V was tapered, which

deviate significantly ideal rectangular shape. Combined with the XRD results, it was

known that the coating was basically crystal-based, and the internal structure of the

crystal is high, rigid, and internal gap defects are small, it was difficult for ions in the

electrolyte to reach the interior of the coating through diffusion to participate in the

reaction. It was also the reason why the area of the cyclic voltammetry curve of the

electrode prepared at high temperature was small

Fig. S7 (b) and (d) showed the enlarged view of the low-frequency region and

(a)

high-frequency region of Ti/RuO2-NiO electrode annealed at 500 °C, respectively, and

Fig. S7 (c) was the equivalent circuit diagram of the electrode. The real axis (z’ axis)

was usually used to describe the impedance properties of the electrodes, while the

imaginary axis Zim reflected the capacitive reactance properties of the electrodes

during the reaction. The high-frequency region of the prepared electrode had a

semicircular shape, and the radius of the semicircle was generally used to represent

the charge conduction resistance( Rct). The intersection of the left end of the

semicircle and Zre was the equivalent series resistance (Rs), which represented the

resistance of the solution, Q represented the constant phase angle elements, Cdl

reflected the charge amount saved due to the double-layer. The values of Cdl

determined the line length in the low frequency region of the electrode's AC

impedance. Zw referred to the semi-infinite diffusion, which corresponded to the

liquid-phase mass transfer process and determined the deviation of the curve from the

ideal capacitance. The low-frequency region of Ti/RuO2-NiO electrode was

approximately parallel to the imaginary axis, which indicates that the energy storage

reaction mechanism of the electrode had not changed abruptly.