SUPPORTING INFORMATION Flexible Asymmetrical Solid-state Supercapacitors Based on Laboratory Filter Paper Leicong Zhang,,,# Pengli Zhu,,,#, * Fengrui Zhou, Wenjin Zeng, Haibo Su, Gang Li, Jihua Gao, Rong Sun,, * Ching-ping Wong ǁ,, * Shenzhen Institutes of Advanced Technology, Chinese Academy of Science, Shenzhen 51855, China Shenzhen Key Laboratory of Special Functional Materials, College of Materials, Shenzhen University, Shenzhen 5186, China School of Materials Science and Engineering, Nanjing University of Posts and Telecommunications, Nanjing, China ǁ School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, USA Department of Electronics Engineering, The Chinese University of Hong Kong, Hong Kong, China *Corresponding author, email: pl.zhu@siat.ac.cn, rong.sun@siat.ac.cn, cpwong@cuhk.edu.hk
Figure S1. SEM image of cross section of Ni(II)-FP.
(a) (e) - - - -..2.4.6.8 5 mv/s 1 mv/s 2 mv/s mv/s mv/s..2.4.6.8 5 mv/s 1 mv/s 2 mv/s mv/s mv/s (b) (f) Areal specific capacitance (mf/cm 2 ) 1 - - -1 2 18 1 12 9 6 3..2.4.6.8 5 mv/s 1 mv/s 2 mv/s mv/s mv/s 4 min 8 min 1 min 12 min 15 min 2 4 6 8 Scan rate (mv/s) (c) (g) Areal specific capacitance (mf/cm 2 ) 1 - - -1 2 18 16 14 12..2.4.6.8 4 6 8 1 12 14 16 Deposition time (min) 5 mv/s 1 mv/s 2 mv/s mv/s mv/s (d) (h) -Z" (ohm) 1 - - 4 3 2 1..2.4.6.8 -Z" (ohm) 4 2 5 mv/s 1 mv/s 2 mv/s mv/s mv/s 2 4 6 Z' (ohm) 1 2 3 4 6 Z' (ohm) Figure S2. CV curves of a) Ni/MnO 2 (4)-FP electrode; b) Ni/MnO 2 (8)-FP electrode; c) Ni/MnO 2 (1)-FP electrode; d) Ni/MnO 2 (12)-FP electrode and Ni/MnO 2 (15)-FP electrode at scan rates of 5- mv/s; (f) Areal specific capacitance of different Ni/MnO 2 -FP electrodes calculated from CV curves at different scan rates; (g) Areal specific capacitance of different Ni/MnO 2 -FP electrodes calculated from CV curves at 5mV/s; (h) Nyquist plot of the EIS for Ni/MnO 2 (1)-FP electrode and the magnification of the high-frequency region is provided in the inset.
(a) 6 (b) 6 4 4 2-2 -4-6 -8 Ni(II)-FP Ni/AC-FP -1. -.8 -.6 -.4 -.2. 2-2 -4-6 -8 1 mv/s 2 mv/s mv/s mv/s 1 mv/s 2 mv/s -1. -.8 -.6 -.4 -.2. (c) 32 Areal specific capacitance (mf/cm 2 ) (e) Areal specific capacitance (mf/cm 2 ) 24 16 8 4 3 2 1 2 Scan rate (mv/s) 1 15 2 25 3 (d) (f) -Z" (ohm). -.2 -.4 -.6 -.8-1. 3 2 2 1 2 4 6 8 -Z" (ohm) 2 1 Time (s) 1 ma/cm 2 15 ma/cm 2 2 ma/cm 2 3 ma/cm 2 1 2 3 4 5 Z' (ohm) 2 3 Z' (ohm) Figure S3. a) CV curves of Ni/AC-FP electrode and porous Ni(II)-FP at scan rate of 2 mv/s; b) CV curves of
Ni/AC-FP electrode at scan rate of 1-2 mv/s; c) Areal specific capacitance of Ni/AC-FP electrode calculated from CV curves as function of scan rate; d) GCD curves of Ni/AC-FP electrode at current densities of 1-3 ma/cm 2 ; e) Areal specific capacitance of Ni/AC-FP electrode calculated from GCD curves as function of current density; f) Nyquist plots of the EIS for Ni/AC-FP electrode with a magnification of the high-frequency region is provided in the inset. Cyclic voltammetry (CV), galvanostatic charging/discharging (GCD) and electrochemical impedance spectroscopy (EIS) test of the as-prepared Ni/AC-FP electrode as negative electrode were also investigated by a three-electrode configuration in 1 M Na 2 SO 4 aqueous electrolyte solution. And Ni/AC-FP, platinum plate and saturated calomel electrode were used as working, counter and reference electrodes, respectively. The applied potential window of CV and GCD was -1- V. And the frequency varied from khz to 1 mhz with an amplitude of 5 mv at an open-circuit voltage for EIS was conducted. As shown in Figure S3a, the rectangle-like shape of CV curve clearly reveals the electric double layer capacitor (EDLC) characteristics derived from the high specific surface area of activated carbon, which can store so much electricity. The CV curve of Ni/AC-FP electrode shows much larger integral area than the Ni(II)-FP, indicating that the major source of electrochemical capacitance is from AC. Figure S3b gives the representative CV curves of the Ni/AC-FP electrode at various scan rates ranging from 5 to mv/s. Clearly, the shape of these CV curves does not significantly changes with the increase of scan rate, even at high scan rate of 2 mv/s, the observation of which suggests a relatively low resistance of electrode and fast diffusion rate of ion and transfer rate of electron due to the good adhesion between AC and
highly conductive Ni(II)-FP substrate. The areal specific capacitance of the Ni/AC-FP calculated from CV curves are shown in Figure S3c, apparently, the Ni(II)-FP substrate supported AC electrode exhibits large capacitance of 325, 31, 259, 219, 183 and 175 mf/cm 2 at scan rate of 1, 2,,, 1 and 2 mv/s, respectively. To further evaluate the capacitance value of the Ni/AC-FP, GCD measurement was carried out at different constant current densities of 1-3 ma/cm 2, as shown in Figure S3d. It can be observed that the symmetrical triangle-like curves represent a typical feature of EDLC. The duration time of electrode reaches 82 s at a high current density of 1 ma/cm 2. Encouragingly, the Ni/AC-FP electrode shows excellent capacitance of 43, 375, 36 and 3 mf/cm 2 at current density of 1, 15, 2 and 3 ma/cm 2, respectively, indicating that about 81% retention of capacitance is still achieved when the charge-discharge current density is increased from 1 to 3 ma/cm 2 (Figure S3e). These superior electrochemical capacitances prove that both the fast transfer rate of electron and diffusion rate of ion are realized, which the EIS was conducted to demonstrate again. As shown in Figure S3f, a semicircle at high frequency region followed by an straight-line at low frequency region is plotted. The result shows that the equivalent series resistance R s value of 3.87 Ω for Ni/AC-FP electrode is lower than 4.6 Ω for Ni/MnO 2 -FP because of the conductive AC. The low R s and the high slope of straight-line corporately ensure the well electrochemical performance of Ni/AC-FP electrode.
(a) Areal specific capacitance (mf/cm 2 ) 2 2 1 2.5 1. 1.5 2. 2.5 3. Potential window (V) 8 6 4 Volume specific capacitance (mf/cm 3 ) (b) Areal specific capacitance (F/cm 2 ).8.6.4.2 2 4 6 8 Scan rate (mv/s) 2. 1.6 1.2.8.4. Volume specific capacitance (F/cm 3 ) Figure S4. (a) Areal and volume specific capacitance of FAAS under different potential windows calculated from CV curves at mv/s; (b) Areal and volume specific capacitance of FAAS calculated from CV curves at different scan rates. Figure S5. The digital photograph of the mold used for bending test.
Figure S6. The digital photograph of a 3-Volt LED indicator lighted by two bended FAAS devices. Figure S7. The screenshots from Movie S1: the FAAS device was bended at a) one side; b) the normal state; c) the other side. Capacitance retention (%) 8 6 4 2 At current density of 25 ma/cm 3 2 3 4 Bending number Figure S8. Dependence of capacitance retention on the bending number.
The stability of the device has been proved by mechanical bending cycles, which was quantitatively studied by tracing the capacitance in the bending process. In detail, the test was conducted through repeatedly bending FAAS device to 18 o several times with hands and then tested its capacitance by GCD at a current density of 25 ma/cm 3. As shown in Figure S8, the initial capacitance was measured before bending distortion, and then after ten times bending distortion, the capacitance of FAAS device was tested and recorded, after another 9 times bending number, the test was conducted again. Then, the device was continuously tested after bending cycles and further, 2 and 3 bending cycles. Finally, the bending cycles reached to a total of times and the FAAS device shows 96.3% retention according to the initial capacitance, indicating well cycling stability and flexibility.
Table S1. Comparison of electrochemical properties of flexible supercapacitor devices. Positive Electrode Negative Electrochemical performance (device) Maximum Energy density/ mwh/cm 3 Volume capacitance/ F/cm 3 Maximum Power density/ mw/cm 3 Reference Ni/MnO 2 -FP Ni/AC-FP 1.76 at 1 mv/s.78 Our work MnO 2 /NCAs AC/Al foil ------------ 2.7 3. 1 Ni(OH) 2 /NGP Mn 3 O 4 /NGP 3. at 1 mv/s.35 32.5 2 MnO 2 /ZnO HI-rGO.52 at 1 mv/s.234 133 3 MVNN/CNTs MVNN/CNTs 7.9 at 25 ma/cm 3.54 43 4 MnO 2 N-Fe 2 O 3 1.2 at 1 mv/s.41 5 Graphite/Ni/ Graphite/Ni/ Co 2 NiO 4 -CP AC-CP 7.6 at 5 mv/s 2.48 79 6 TiN TiN.33 at 2.5 ma/cm 3.5 3 7 ZnO@ZnO-doped ZnO@ZnO-doped MnO 2 MnO 2.325 at.5 ma/cm 2.4 2.44 8 TiO 2 @C TiO 2 @C ------------.11 32 9 Graphite/PANI Graphite/PANI 3.55 at 4.57 ma/cm 3.32 54 1
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