Supporting Information. Rationally Designed Self-Healing Hydrogel Electrolyte towards a Smart and. Sustainable Supercapacitor

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1 Supporting Information Rationally Designed Self-Healing Hydrogel Electrolyte towards a Smart and Sustainable Supercapacitor Jingchen Wang, Fatang Liu, Feng Tao, Qinmin Pan* (State Key Laboratory of Robotics and Systems, School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin 151, P. R. China) Corresponding author: Qinmin Pan panqm@hit.edu.cn S-1

2 1385 Figure S1. Optical images showing the electrical contact of the nickel foam after self-healing. As the current collector of capacitor, the Ni foams were cut into halves with the capacitor together. Once the cut halves were brought into contact, they coalesce into a single one through the self-healing of the hydrogel electrolyte. The self-healing induced effective contact of nickel foams attached to the electrolyte, as shown in Figure S9. Therefore, although the Ni foam collector is not intrinsically self-healable, it was able to maintain good electrical contact after self-healing. Figure S2. Optical image of the as-prepared P(VI-co-HPA)/NaNO 3 hydrogel electrolyte Transmittance / % Wavenumber / cm -1 Figure S3. FT-IR spectrum of the P(VI-co-HPA)/NaNO 3 hydrogel electrolyte. The content of NaNO 3 and P(VI-co-HPA) is 1. mol L 1 and 29.1 wt%, respectively. S-2

3 Figure S3 is the FT-IR spectrum of the hydrogel electrolyte. The characteristic peaks of imidazole are located at 16 cm 1 (C=N stretching), 122 cm 1 (ring vibration), 18 cm 1 (in-plane C H bending), 918 cm 1 (out-of-plane C H bending) and 663 cm 1 (torsion stretching). 1 The feature vibrations of hydroxypropyl acrylate can be found at ~34 cm 1 ( OH stretching) and 1728 cm 1 (O=C O stretching). 2 The strong absorbance at 1385 cm 1 is ascribed to NO 3. 3 Figure S4. Optical images of the P(VI-co-HPA)/NaNO 3 prepared in the absence of MBAA. (a) 6 (b) Z'' (ohm) mol L mol L mol L Z'' (ohm) wt% 35. wt% 43.7 wt% wt% 87.4 wt% Z' (ohm) Z' (ohm) NaNO 3 = 3. mol L Concentration of NaNO 3 / mol L -1 Content of P(VI-co-HPA) / wt% Figure S5. Effect of the content of (a) NaNO 3 and (b) P(VI-co-HPA) on the room-temperature ionic conductivity of the hydrogel electrolytes. Insets are the corresponding EIS spectra recorded for the electrolytes. S-3

4 (a) Z'' (ohm) M 2 2. M 3. M Z' (ohm) Temperature = -15 o C (b) NaNO 3 = 3. mol L -1 Temperature = -15 o C Concentration of NaNO 3 / mol L Content of P(VI-co-HPA) / wt% Figure S6. Effect of the content of (a) NaNO 3 and (b) P(VI-co-HPA) on the ionic conductivity of the hydrogel electrolyte at -15 o C. Insets are the corresponding EIS spectra recorded for the electrolytes. Figure S5 and S6 show that increasing the concentration of NaNO 3 results in a higher ionic conductivity at both room and subzero temperatures, while high content of P(VI-co-HPA) is detrimental to the ionic conduction. 6 5 Original pieces Urea treated pieces Tensile stress / kpa Strain / % Figure S7. Stress-strain curves of the original and urea treated P(VI-co-HPA)/NaNO 3 electrolyte pieces after contact for 1 min at 25 o C. The electrolyte pieces contained 1. mol L 1 NaNO 3 and 29.1 wt% P(VI-co-HPA). To investigate the self-healing mechanism of the P(VI-co-HPA)/NaNO 3 electrolyte, we treated the cut electrolyte pieces with urea before healing. After they were brought into contact for 1 min at 25 o C, tensile experiments were conducted on the resulting electrolytes. Figure S7 records the stress-strain curves of the original and urea-treated electrolyte pieces. Compared with its original counterpart, the urea-treated electrolyte dramatically reduces the tensile strength to.18 kpa. The value is only 3.3% of that measured for the original S-4

5 electrolyte. Since urea can effectively damage hydrogen interactions, 4,5 the dramatic decrease of the tensile strength demonstrates that intermolecular hydrogen bonding is a main driving force for the self-healing of the P(VI-co-HPA)/NaNO 3 electrolyte. Figure S8. Electrochemical performance of capacitor at the temperature of 45 o C. (a) CV curves at 1 mv s 1, (b) GCD profiles at 1. A g 1, (c) cycling characteristics Z'' / ohm 1 5 o C -5 o C -1 o C -15 o C Z' / ohm Figure S9. EIS spectra of the capacitor recorded at subzero temperatures ranging from to -15 o C. Inset is the fitting results of the EIS spectra. Table S1. Fitting results of the EIS spectra recorded for the capacitor after self-healing at 25 o C for different S-5

6 cycles. Healing cycle R s (Ω) R ct (Ω) Original st nd th th Table S2. Fitting results of the EIS spectra recorded for the capacitor after self-healing at -15 o C for different cycles. Healing cycle R s (Ω) R ct (Ω) Original st nd th th Table S3. Fitting results of the EIS spectra recorded for the capacitor after regeneration for different cycles. Regeneration cycle R s (Ω) R ct (Ω) 1 st nd rd th th S-6

7 References (1) Yu, C.; Wang, C. F.; Chen, S. Robust Self-Healing Host Guest Gels from Magnetocaloric Radical Polymerization. Adv. Funct. Mater. 214, 24, (2) Deng, K. L.; Tian, H.; Zhang, P. F.; Zhong, H. B.; Ren, X. B.; Wang, H. J. ph Temperature Responsive Poly(HPA-Co-AMHS) Hydrogel as A Potential Drug-Release Carrier. J. Appl. Polym. Sci. 29, 114, (3) Vijay Kumar, T.; Sadananda CharyA, A.; Awasthi, A. M.; Bhardwaj, S.; Narender Reddy, S. Effect of nano SiO 2 on properties of structural, thermal and ionic conductivity of 85.32[NaNO 3 ] 14.68[Sr(NO 3 ) 2 ] mixed system. Ionics 215, 21, (4) Levy, M.; Magoulas, J. P. Effect of Urea on Hydrogen Bonding in Some Dicarboxylic Acids. J. Am. Chem. Soc. 1962, 84, (5) Wang, Z. K.; Tao, F.; Pan, Q. M. A Self-healable Polyvinyl Alcohol-Based Hydrogel Electrolyte for Smart Electrochemical Capacitors. J. Mater. Chem. A. 216, 4, S-7