Supplementary Information

A new strategy for synthesis of hierarchical MnO2-Mn3O4 nanocomposite via

reduction-induced exfoliation of MnO2 nanowires and its application in high-

performance asymmetric supercapacitor

Ling Kang a, Chun Huang a, Jian Zhang a, b, Mengyao Zhang a, Nan Zhang a, Yaqin He a, Chen Luo

a, Chaolun Wang a, Xiaofeng Zhou a, Xing Wu a

a Shanghai Key Laboratory of Multidimensional Information Processing, East China Normal

University, 500 Dongchuan Road, 200241 Shanghai, China.

b Shanghai Institute of Intelligent Electronics Systems, Fudan University, Shanghai 200433, China.

* Corresponding authors

E-mail addresses: Jzhang@ee.ecnu.edu.cn

Fig. S1. HRTEM images of α -MnO2

Fig. S2. Nitrogen adsorption-desorption isotherms of the samples.

Fig. S3. O 1s XPS spectra of α -MnO2, MnOx-1, MnOx-2, MnOx-3, MnOx-4 and MnOx-5.

Fig. S3 shows the binding energy spectra of O 1s for all samples. The binding energy

values for O1s show a continuous shift to high energy direction from MnO2 to MnOx-

5, indicating the decrease of the bulk oxygen in MnO2. This result is in agreement

with the published results [S1, S2]. This phenomenon further verifies that the Mn

valence state decreases along with the increase of NaBH4 concentration.

Fig. S4. The contribution of the surface-controlled process (the white area) and diffusion-

controlled process (the red area) at a scan rate of 10 mV s-1 of (a) α -MnO2, (b) MnOx-1, (c) MnOx-

2, (d) MnOx-3, (e) MnOx-4, and (f) MnOx-5 electrodes for the charge storage.

Fig. S5. CV curves of (a) α-MnO2, (b) MnOx-1, (c) MnOx-2, (d) MnOx-4, and (e) MnOx-5

electrodes obtained at various scan rates.

Fig. S6. GCD curves of (a) α-MnO2, (b) MnOx-1, (c) MnOx-2, (d) MnOx-4, and (e) MnOx-5

electrodes collected at different current densities.

Fig. S7. (a) XRD diffraction peaks and (b) SEM image of pure Mn3O4. (c) CV curves obtained at

different scan rates and (d) GCD profiles recorded at various current densities of Mn 3O4 electrode.

(e) CV curves obtained at different scan rates and (f) GCD profiles recorded at various current

densities of MnO2/Mn3O4 mixture electrode.

Fig. S7a shows the SEM image for the as-received Mn3O4. The contour of Mn3O4 is in

accordance with the MnOx nanoparticles. And no nanowire is found. All these results

indicate that the α -MnO2 is fully reduced by NaBH4. XRD analysis (shown in Fig.

S7b) confirms this since no α-MnO2 characteristic peaks can be found. For the CV

testing (Fig. S7c) of Mn3O4 electrode, the current densities recorded at various scan

rates are rather high, suggesting its excellent charge-storage capability. This merit is

also found from the corresponding GCD profiles (Fig. S7d). Its specific capacitance

can reach up to 439.5 F g-1 at a current density of 1 A g-1, which is slightly higher than

MnOx-3 electrode (406.2 F g-1) and α -MnO2/Mn3O4 electrode (302.3 F g-1). However,

at higher scan rates, an obvious variation of CV curves for Mn3O4 electrodes is

observed, which results from the low electrical conductivity and the sluggish kinetics.

And for the α -MnO2/Mn3O4 electrode, the similar phenomenon was also observed

(Fig. S7e) which is attributed to the loose contact between α -MnO2 nanowires and

Mn3O4 nanoparticles.

Fig. S8. Specific capacitances of MnOx-3, Mn3O4, MnO2/Mn3O4 electrodes as function of current

density.

Fig. S9. Nyquist plots of MnOx-1, MnOx-2, MnOx-4 and MnOx-5 electrodes.

Fig. S10. Cycling stability of MnOx-1, MnOx-2, MnOx-4 and MnOx-5 electrodes at a current

density of 10 A g-1.

Fig. S11. TEM image of MnOx-3 after 5000 GCD cycles.

References

[S1] J. Zhao, J. Nan, Z. Zhao, N. Li, J. Liu, F. Cui. Energy-efficient fabrication of a novel

multivalence Mn3O4-MnO2 heterojunction for dye degradation under visible light irradiation.

Appl. Catal., B 2017;202:509-517.

[S2] X. Gu, J. Yue, L. Li, H. Xue, J. Yang, X. Zhao. General Synthesis of MnOx (MnO2, Mn2O3,

Mn3O4, MnO) Hierarchical Microspheres as Lithium-ion Battery Anodes. Electrochim. Acta

2015;184:250-256.