Asymmetric Aqueous Supercapacitor Based on p- and n-Type

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Letter

An asymmetric aqueous supercapacitor based on p- and n-type conducting polymers Anton V. Volkov, Hengda Sun, Renee Kroon, Tero-Petri Ruoko, Canyan Che, Jesper Edberg, Christian Müller, Simone Fabiano, and Xavier Crispin ACS Appl. Energy Mater., Just Accepted Manuscript • DOI: 10.1021/acsaem.9b00853 • Publication Date (Web): 26 Jul 2019 Downloaded from pubs.acs.org on July 27, 2019

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ACS Applied Energy Materials

An asymmetric aqueous supercapacitor based on pand n-type conducting polymers Anton V. Volkov,†,‡ Hengda Sun,†,‡ Renee Kroon,§ Tero-Petri Ruoko,† Canyan Che,† Jesper Edberg,# Christian Müller,§ Simone Fabiano,†,* and Xavier Crispin,†,* †

Laboratory of Organic Electronics, Department of Science and Technology, Linköping

University, SE-601 74 Norrköping, Sweden. §

Department of Chemistry and Chemical Engineering, Chalmers University of Technology, SE-

412 96 Göteborg, Sweden. #

RISE Acreo, Printed Electronics, SE-601 74 Norrköping, Sweden.

KEYWORDS: asymmetric supercapacitor, aqueous electrolyte, conducting polymers, energy storage

ACS Paragon Plus Environment

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ABSTRACT: We demonstrated an asymmetric aqueous supercapacitor made of p- and n-type conducting polymer electrodes. We used the high electron affinity (EA) n-type polymer poly(benzimidazobenzophenanthroline) (BBL) as the anode conducting material, and the low ionization potential (IP) p-type polar polythiophene p(g42T-T) as the cathode material. EABBL matches IPp(g4 2T-T) , enabling the fabrication of all-organic asymmetric p/n-supercapacitors that function in aqueous electrolytes. The devices operate in a voltage window up to 1 V, yielding areal capacitances of 90 mF cm–2 and specific capacitances of 33 F g–1 as well as excellent cycling stability with almost 100% capacitance retention over 10,000 cycles.


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The research on energy production and storage underwent a significant growth in the last decades. Because of their high power density, rapid charging/discharging and good cycling stability, supercapacitors represent one of the most promising class of energy storage devices.1-3 Nowadays supercapacitors are attracting more attention as potential large scale devices to dampen fluctuations that arise from the intermittent electrical power generated by green-energy sources (i.e. wind, waves and sun) and provide a constant power to the grid. Hence, the use of electrode materials made of abundant elements is a prerequisite for the development of supercapacitors. Moreover, because of health (toxicity/volatility) and safety (fire/explosion) risks commonly associated with the use of organic solvents, aqueous electrolytes are more and more being considered as alternatives to avoid expensive safety regulations around the energy storage devices. Various materials have been used as electrodes in supercapacitors including carbon based materials,4 transition metal oxides,5 2D metal carbides and nitrides,6 and conducting polymers.7-9 Conducting polymer electrodes are especially attractive for supercapacitor applications because they combine a series of compelling properties: (i) they are typically composed of abundant elements such as carbon, oxygen, nitrogen, sulfur; (ii) their surface is oxygen-free and does not promote undesirable side reactions; (iii) they are stable in aqueous electrolytes; (iv) they transport efficiently ions and electrons, enabling charge-storage not just at the electrode-electrolyte interface but throughout the bulk; (v) they are processable from solution at room temperature, which is a prerequisite for low cost, large-area manufacturing, resulting in a short energy payback time of the technology. This feature is unique compared to nanostructured inorganic (semi-)conductors that generally require a high temperature annealing step to sinter the nanoparticles into conducting thin films. (vi) Finally, their versatile chemical synthesis allows for a fine tuning of the polymer electronic properties.


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Polymer-based supercapacitors generally consist of two polymer electrodes separated by an electrolyte.7-8 Today, hole-transporting (p-type) conducting polymers are typically used as both anode and cathode electrodes in such devices. Organic symmetric p/p-supercapacitors, comprising two identical p-type polymer electrodes, typically lead to low energy density and low power density as the negative electrode becomes depleted of charge carriers while the positive electrode is fully doped. The depletion of charge carrier (de-doping) at the negative electrode is accompanied by a decrease of its electrical conductivity and thus a rise in the device internal resistance limiting the power output.10 The fact that the same polymer is used at both electrodes limits the potential range. In order to increase the potential range, an organic asymmetric p/p-supercapacitor has been proposed with two different p-type polymer electrodes having different ionization potentials (IPs).7, 11 In such a device, the positive electrode is conducting in a wide potential window at positive voltages, while the negative electrode has low potential window and remains doped under negative biases. As an alternative, another commonly used strategy to enhance the operational voltage window of a supercapacitor is to utilize metal oxides or metal nitrides as the negative electrode and polymer-based composite as the positive electrode.12 However, one of the major drawbacks of using supercapacitors with the aforementioned architectures is that such devices cannot release all of the stored energy during the discharge process because both electrodes are still significantly doped under zero biases.7 A further development is represented by the case of an organic symmetric n/p-supercapacitor where the same undoped semiconducting polymer (e.g., polydithienothiophene) is used at both electrodes, in a way that the polymer becomes n-doped at the cathode and p-doped at the anode upon biasing the device with 3 V.13 However, this strategy is challenging for the development of aqueous based organic supercapacitors since it would require the use of semiconducting polymers with very small band gap (< 1.2 eV).13-15 Recently, energy


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storage devices with asymmetric n/p-type semiconducting polymers as the electrode materials have been reported.16 These devices, however, do not perform as regular supercapacitors, exhibiting non-linear galvanostatic charge-discharge curves. Moreover, they suffer from low cycling stability, with about 20% capacity loss after only 1,000 cycles, as well as high selfdischarge rate.16 Here, we report an organic asymmetric p/n-supercapacitor comprising different p- and ntype conducting polymer electrodes that have an electronic structure which is appropriate for operation in aqueous electrolyte.7 Figure 1a shows a schematic of the proposed asymmetric supercapacitor. The negative electrode comprises the high electron affinity (EA ≈ 4-4.4 eV17) ladder-type n-type semiconducting polymer poly(benzimidazobenzophenanthroline) (BBL, Figure 1b), which reveals capacitive behavior under negative potentials (vs. Ag/AgCl, Figure 1d). Importantly, beside its high stability even in aqueous medium,18 BBL possesses one of the highest electrical conductivity upon n-doping reported to date (2 S cm–1),19 ensuring low contribution to the device internal resistance and a high delivered power. The positive electrode comprises instead the low ionization potential (IP ≈ 4.4 eV) p-type semiconducting polythiophene functionalized with tetraethylene glycol side chains (p(g42T-T), Figures 1c and S1),20 which shows capacitive charging for positive voltages as reported in Figure 1d. It is important to choose a p-type semiconducting polymer with an IP that matches the EA of the n-type polymer in order to have the two electrodes in their conducting states even when the device is close to discharge at low voltage. The application of a positive bias to the asymmetric BBL/p(g42T-T) supercapacitor leads to the simultaneous injection of electrons into BBL and holes into p(g42T-T), compensated by the injection of cations and anions, respectively. The result is that both electrodes are in the highly


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conductive state during charging and discharging, while at zero bias during discharge both electrodes release most of the stored charges, allowing for large energy storage.

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Figure 1. (a) Schematic of aqueous supercapacitor with n- and p-type conducting polymer electrodes. Chemical structure of (b) n-type BBL and (c) p-type p(g42T-T). (d) Cyclic voltammograms of BBL and p(g42T-T) electrodes prepared by spraying 8 ml polymer suspension in three-electrode system with 0.4 M Na2SO4 aqueous media at 50 mV s–1.

Both BBL and p(g42T-T) polymer electrodes were manufactured by spray coating (Figure S2). This technique allows for different volumes of the deposited material by simply varying the amount of sprayed solution.21 This is important to fabricate scalable devices. As BBL is not soluble in common organic solvents, we used a re-precipitation method22 to prepare a dispersion of BBL nanoparticles in isopropanol. In the case of p(g42T-T), a dispersion in acetone was used for spray


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coating. Scanning electron microscopy (SEM) images of the spray-coated BBL and p(g42T-T) films reveal a flaky morphology on surfaces and a layered structure in the cross-section for both electrode materials (Figure S3). The electrochemical properties of spray-coated BBL and p(g42T-T) electrodes were investigated with an aqueous electrolyte (0.4 M Na2SO4) by using a three-electrode system. Cyclic voltammetry (CV) measurements of BBL films show quasi-square-shaped voltammograms (Figure 2a) under negative biases (-0.5 to 0 V vs. Ag/AgCl). Galvanostatic charge/discharge (GCD) measurements reveal a triangular shape (Figure 2b) and good cycling life (Figure S4). Both CV and GCD curves indicate typical capacitive storage mechanism in BBL electrodes. In order to confirm volumetric charge storage in BBL electrodes, we tested several devices having BBL films with different thickness, as prepared by spray-coating different volumes of the BBL polymer suspension on 1 cm2 gold current collectors. Figures 2c-d show the effect of sprayed volume on CV and GCD curves. The increase in the amount of sprayed BBL suspension volume leads to a corresponding increase of the areal capacitance (Figure 2e). The areal capacitance calculated from GCD curves at 1 mA cm–2 was 175 mF cm–2 for electrode prepared by spraying 32 ml of the polymer suspension. The specific capacitance reported in Figure 2f was determined from the GCD curves (Figure S5) to be as high as 226 F g–1 at 1 A g–1 (electrode surface area of 6.76 cm2 and sprayed volume of 32 ml). We attribute the slight decrease in the capacitance with increasing the current density to a limited diffusion of ions into the BBL film. From the onset reduction potential in the forward scan of the CV (Figure S6a), we estimated an electron affinity for BBL of ~4.4 eV, which is in agreement with previous reports.17, 23 Spectroelectrochemistry measurements reveal accumulation of charges throughout the bulk of BBL films (Figure S6b).


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Figure 2. Evaluation of the electrochemical performance of spray-coated BBL electrodes. (a) Cyclic voltammograms and (b) galvanostatic charge/discharge curves of BBL electrode prepared by spraying 8 ml polymer suspension. (c) Cyclic voltammograms at 50 mV s–1 and (d) galvanostatic charge/discharge curves of BBL electrodes prepared by spraying different volumes of polymer suspension (e) Areal capacitance at different current densities for BBL electrodes prepared by spraying different volumes of polymer suspension. (f) Specific capacitance of BBL electrode prepared by spraying 32 ml of polymer suspension. Results for (a)-(e) obtained by spraying polymer suspension on 1 cm2 gold current collectors. Results for (f) obtained by spraying polymer suspension on current collectors with area 6.76 cm2. Similar electrochemical tests were performed on p(g42T-T) electrodes. The CV curves of p(g42T-T) films show a typical quasi-rectangular shape (Figure 3a) under positive biases (0 to 0.5 V vs. Ag/AgCl). The GCD curves show a linear dependence of the applied potential with time, which is indicative of a capacitive behavior (Figure 3b). Stability test indicates also a good cycle life for p(g42T-T) electrodes (Figure S7). Varying the volume of sprayed polymer suspension leads to a proportional current level change in the CV curves (Figure 3c), charge/discharge time in the GCD curves (Figure 3d) and a corresponding change in film capacitance (Figure 3e). Overall, these observations are indicative of a volumetric charge storage mechanism in p(g42T-T) electrodes, as also confirmed by spectroelectrochemistry measurements (Figure S8a). The areal


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capacitance, as calculated from the GCD curves, was 239 mF cm–2 (at 1 mA cm–2) for electrodes prepared by spraying 32 ml of polymer suspension on 1 cm2 current collector. The electrode with larger surface area (6.76 cm2) was used to estimate the specific capacitance from the GCD curves (Figure S9), yielding a value of 113 F g–1 at 1 A g–1 for the 32-ml-sprayed suspension volume (Figure 3f). The ionization potential IP ≈ 4.4 eV for p(g42T-T) was estimated by using the onset oxidation potential in the forward scan of the CV (Figure S8b). The IP of p(g42T-T) closely matches the IPs of similar bithiophene-thienothiophene polymer functionalized with tetraethylene glycol side chains.24 As the IP of p(g42T-T) approaches the EA of BBL, it allows for asymmetric supercapacitors having two electrodes that are always in their conducting state even when the device is close to discharge at low voltage.

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To demonstrate the possibility of storing charges in an asymmetric supercapacitor with pand n-type conducting polymer electrodes, we assembled a two-electrode device comprising BBL and p(g42T-T) polymer electrodes operating in aqueous electrolyte (0.4M Na2SO4). In order to maintain an almost balanced total capacitance for both electrodes, thus achieving optimal device performance, we fabricated several devices with asymmetric n-type BBL and p-type p(g42T-T) electrodes by spraying identical volumes (2, 8, or 32 ml) of the two polymer suspensions. As the CV and GCD curves for all devices reveals similar shapes (Figure S10), here we focused our discussion on the device assembled by spraying 8 ml of the corresponding polymer suspension on each electrode (the area of each current collector was 1 cm2). Figure 4a shows the CV curves of the asymmetric BBL/p(g42T-T) supercapacitor under positive biases, revealing a quasi-rectangular shape. It should be noted that applying negative potential to the device leads to depletion of charge carriers in the polymer electrodes, as indicated by the low current level in the CV curves (Figure 4b). Thus, the fabricated device can effectively operate as a polar capacitor. The GCD curves reveal a typical triangular shape originated from the capacitive charging mechanism of each electrode in the system (Figure 4c). Stability tests show that 99% of the capacitance can be retained (areal capacitance ≈ 20.4 mF cm–2), with equivalent series resistance ESR ≈ 10 Ω, and coulombic efficiency around 100% over 10,000 cycles (Figures 4d-e), at current density of 2 mA cm–2. It should be noted that all of the devices investigated here are stable at operational voltages of up to 1 V in aqueous electrolyte, which is just below the potential required for water splitting (~1.23 V). Figures 4f-g indicate good scaling of the capacitive properties of BBL/p(g42T-T) supercapacitors with varying the sprayed volume of the polymer suspension. The asymmetric BBL/p(g42T-T) supercapacitor, prepared by spraying 32 ml of the corresponding polymer suspensions on 1 cm2 gold current collectors, delivers an areal energy density of 12.4 µWh cm–2


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at 0.25 mW cm–2 with areal capacitance ≈ 90 mF cm–2 (current density = 0.5 mA cm–2), which is the highest value among all of the fabricated devices (Figure 4f). The obtained areal capacitances outperform previously reported PEDOT (3 mF cm–2)25 and PEDOT:PSS (6.4 mF cm–2) devices.26

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Figure 4. Electrochemical performance of an asymmetric aqueous supercapacitor with spraycoated BBL and p(g42T-T) electrodes. (a) and (b) Cyclic voltammograms, (c) galvanostatic charge/discharge curves, (d) areal capacitance, equivalent series resistance (ESR), and (e) coulombic efficiency of BBL/p(g42T-T) supercapacitor (electrodes were prepared by spraying 8 ml of corresponding polymer suspension on 1 cm2 gold current collectors). (f) Areal capacitance at different current densities and (g) Ragone plot for devices prepared by spraying 2 ml (device 1), 8 ml (device 2) and 32ml (device 3) of corresponding polymer suspension on 1 cm2 gold current collectors. (h) Specific capacitance and (i) Ragone plot for device where electrodes were prepared by spraying 32 ml of corresponding polymer suspension on current collectors with area 6.76 cm2.


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Gravimetric measurements were performed for the device comprising electrodes with larger current collector area (6.76 cm2). Figures 4h-i show the capacitance as a function of current density and the Ragone plot for the device with 32 ml of sprayed volume on each electrode, respectively (calculated from the GCD curves reported in Figure S11a). Specific capacitance of 33 F g–1 with corresponding energy density of 4.4 Wh kg–1 and power density of 550 W kg–1 were observed at current density of 1 A g–1. Our devices reveal higher specific capacitance compared to previously reported capacitors comprising p-type and n-type electrodes (∼20 F g–1), although a somewhat lower energy density is achieved compared to previous works (∼10 Wh kg–1).14-15 We attributed this to the use of aqueous electrolyte in our devices which limits the potential window to 1 V. The obtained results for our p/n-supercapacitors are comparable to PEDOT-based capacitors in terms of energy density (1-4 Wh kg–1)25 and power density (35-2500 W kg–1)25 and in the same range of carbon-based supercapacitors (energy density 1-31 Wh kg–1).4, 27-30 Larger energy densities could be obtained by using electrolytes with wider operating windows, and/or using p- and n-type polymer electrodes with high and well-matched gravimetric capacitances. In conclusion, we have shown an asymmetric aqueous supercapacitor based on p- and ntype conducting polymers with matching IP and EA. The p- and n-organic (semi-)conductor polymers are chosen to fit the voltage window of water and to ensure that they stay in their conducting state even at low discharge voltage. This strategy results in a low internal resistance independent of voltage and no electrochemical stress (over-oxidation of the p-doped polymer or over-reduction of the n-doped polymer). This leads to a remarkable stability of the p/nsupercapacitors with 100% faradaic efficiency in charge-discharge (0-1 V) even after 10,000 cycles in an aqueous electrolyte. This strategy hold promises for the development of stable organic supercapacitors.


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ASSOCIATED CONTENT Supporting Information The Supporting Information is available free of charge on the ACS Publications website at DOI: Experimental details of the preparation and characterization of the supercapacitors, as well as supplementary figures (PDF) AUTHOR INFORMATION Corresponding Authors *E-mail [email protected] (S.F.), [email protected] (X.C.). Author Contributions ‡A.V.V. and H.S. contributed equally to this work. The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript. Notes The authors declare no competing financial interest. ACKNOWLEDGMENT Authors thanks Kosala Wijeratne, Anna Hofmann and Ujwala Ail for useful comments on the work. The authors acknowledge financial support from the Swedish Research Council, the Swedish Foundation for Strategic Research, the Knut and Alice Wallenberg Foundation, ÅForsk, VINNOVA and the Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linköping University (Faculty Grant SFO-Mat-LiU No 2009 00971). REFERENCES


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1. González, A.; Goikolea, E.; Barrena, J. A.; Mysyk, R., Review on supercapacitors: Technologies and materials. Renew. Sust. Energ. Rev. 2016, 58, 1189-1206. 2. Wang, G.; Zhang, L.; Zhang, J., A review of electrode materials for electrochemical supercapacitors. Chem. Soc. Rev. 2012, 41 (2), 797-828. 3. Jost, K.; Dion, G.; Gogotsi, Y., Textile energy storage in perspective. J. Mater. Chem. A 2014, 2 (28), 10776-10787. 4. Zhang, L. L.; Zhao, X. S., Carbon-based materials as supercapacitor electrodes. Chem. Soc. Rev. 2009, 38 (9), 2520-2531. 5. Shi, F.; Li, L.; Wang, X.-l.; Gu, C.-d.; Tu, J.-p., Metal oxide/hydroxide-based materials for supercapacitors. RSC Adv. 2014, 4 (79), 41910-41921. 6. Anasori, B.; Lukatskaya, M. R.; Gogotsi, Y., 2D metal carbides and nitrides (MXenes) for energy storage. Nat. Rev. Mater. 2017, 2, 16098. 7. Bryan, A. M.; Santino, L. M.; Lu, Y.; Acharya, S.; D’Arcy, J. M., Conducting Polymers for Pseudocapacitive Energy Storage. Chem. Mater. 2016, 28 (17), 5989-5998. 8. Zhiheng, Z.; Georgia, F. R.; Qingshi, M.; Shenmin, Z.; Hsu-Chiang, K.; Jun, M., PEDOT-based composites as electrode materials for supercapacitors. Nanotechnology 2016, 27 (4), 042001. 9. Snook, G. A.; Kao, P.; Best, A. S., Conducting-polymer-based supercapacitor devices and electrodes. J. Power Sources 2011, 196 (1), 1-12. 10. Jiao, F.; Edberg, J.; Zhao, D.; Puzinas, S.; Khan, Z. U.; Mäkie, P.; Naderi, A.; Lindström, T.; Odén, M.; Engquist, I.; Berggren, M.; Crispin, X., Nanofibrillated Cellulose-Based Electrolyte and Electrode for Paper-Based Supercapacitors. Advanced Sustainable Systems 2018, 2 (1), 1700121. 11. Kurra, N.; Wang, R.; Alshareef, H. N., All conducting polymer electrodes for asymmetric solid-state supercapacitors. J. Mater. Chem. A 2015, 3 (14), 7368-7374. 12. Choudhary, N.; Li, C.; Moore, J.; Nagaiah, N.; Zhai, L.; Jung, Y.; Thomas, J., Asymmetric Supercapacitor Electrodes and Devices. Adv. Mater. 2017, 29 (21), 1605336-n/a. 13. Arbizzani, C.; Catellani, M.; Mastragostino, M.; Mingazzini, C., N- and P-doped Polydithieno[3,4-B:3′,4′-D] thiophene: A narrow band gap polymer for redox supercapacitors. Electrochim. Acta 1995, 40 (12), 1871-1876. 14. Kinlen, P. J.; Mbugua, J.; Kim, Y.-G.; Jung, J.-H.; Viswanathan, S., Supercapacitors using n and p-Type Conductive Polymers Exhibiting Metallic Conductivity. ECS Trans. 2010, 25 (35), 157-162. 15. Arbizzani, C.; Mastragostino, M.; Meneghello, L., Polymer-based redox supercapacitors: A comparative study. Electrochim. Acta 1996, 41 (1), 21-26. 16. Moia, D.; Giovannitti, A.; Szumska, A. A.; Maria, I. P.; Rezasoltani, E.; Sachs, M.; Schnurr, M.; Barnes, P. R. F.; McCulloch, I.; Nelson, J., Design and evaluation of conjugated polymers with polar side chains as electrode materials for electrochemical energy storage in aqueous electrolytes. Energy Environ. Sci. 2019, 12 (4), 1349-1357. 17. Alam, M. M.; Jenekhe, S. A., Conducting Ladder Polymers: Insulator-to-Metal Transition and Evolution of Electronic Structure upon Protonation by Poly(styrenesulfonic Acid). J. Phys. Chem. B 2002, 106 (43), 11172-11177. 18. Sun, H.; Vagin, M.; Wang, S.; Crispin, X.; Forchheimer, R.; Berggren, M.; Fabiano, S., Complementary Logic Circuits Based on High-Performance n-Type Organic Electrochemical Transistors. Adv. Mater. 2018, 30 (9), 1704916.


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19. Wang, S.; Sun, H.; Ail, U.; Vagin, M.; Persson, P. O. Å.; Andreasen, J. W.; Thiel, W.; Berggren, M.; Crispin, X.; Fazzi, D.; Fabiano, S., Thermoelectric Properties of SolutionProcessed n-Doped Ladder-Type Conducting Polymers. Adv. Mater. 2016, 28 (48), 1076410771. 20. Kroon, R.; Kiefer, D.; Stegerer, D.; Yu, L.; Sommer, M.; Müller, C., Polar Side Chains Enhance Processability, Electrical Conductivity, and Thermal Stability of a Molecularly p-Doped Polythiophene. Adv. Mater. 2017, 29 (24), 1700930. 21. Wolz, A.; Zils, S.; Michel, M.; Roth, C., Structured multilayered electrodes of proton/electron conducting polymer for polymer electrolyte membrane fuel cells assembled by spray coating. J. Power Sources 2010, 195 (24), 8162-8167. 22. Janietz, S.; Sainova, D., Significant Improvement of the Processability of Ladder‐Type Polymers by Using Aqueous Colloidal Dispersions. Macromol. Rapid Commun. 2006, 27 (12), 943-947. 23. Alam, M. M.; Jenekhe, S. A., Efficient Solar Cells from Layered Nanostructures of Donor and Acceptor Conjugated Polymers. Chem. Mater. 2004, 16 (23), 4647-4656. 24. Kiefer, D.; Kroon, R.; Hofmann, A. I.; Sun, H.; Liu, X.; Giovannitti, A.; Stegerer, D.; Cano, A.; Hynynen, J.; Yu, L.; Zhang, Y.; Nai, D.; Harrelson, T. F.; Sommer, M.; Moulé, A. J.; Kemerink, M.; Marder, S. R.; McCulloch, I.; Fahlman, M.; Fabiano, S.; Müller, C., Double doping of conjugated polymers with monomer molecular dopants. Nature Materials 2019, 18 (2), 149-155. 25. Carlberg, J. C.; Inganäs, O., Poly(3,4‐ethylenedioxythiophene) as Electrode Material in Electrochemical Capacitors. J. Electrochem. Soc. 1997, 144 (4), L61-L64. 26. Fan, L.; Zhang, N.; Sun, K., Flexible patterned micro-electrochemical capacitors based on PEDOT. Chem. Commun. 2014, 50 (51), 6789-6792. 27. Li, W.; Chen, D.; Li, Z.; Shi, Y.; Wan, Y.; Wang, G.; Jiang, Z.; Zhao, D., Nitrogencontaining carbon spheres with very large uniform mesopores: The superior electrode materials for EDLC in organic electrolyte. Carbon 2007, 45 (9), 1757-1763. 28. Bordjiba, T.; Mohamedi, M.; Dao, L. H., New Class of Carbon-Nanotube Aerogel Electrodes for Electrochemical Power Sources. Adv. Mater. 2008, 20 (4), 815-819. 29. Portet, C.; Yushin, G.; Gogotsi, Y., Electrochemical performance of carbon onions, nanodiamonds, carbon black and multiwalled nanotubes in electrical double layer capacitors. Carbon 2007, 45 (13), 2511-2518. 30. Barbieri, O.; Hahn, M.; Herzog, A.; Kötz, R., Capacitance limits of high surface area activated carbons for double layer capacitors. Carbon 2005, 43 (6), 1303-1310.


15


TOC GRAPHICS

Current Density (mA/cm2)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 16 of 21

2

O

O

N

N

N

N

p(g42T-T) (p-type) n

0 −2

BBL (n-type)

O

4

O 4

O

S SO O O O S S

O

4

n 4

S

n

S



16

A

ACS Applied– Energy B MaterialsO Au electrode e

O

Page 17 of 21 1 2 3 45+ 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29

BBL (n-type)

N N

+

Aqueous electrolyte

C

anion

–

D

S O

O

Au electrode

S O

4O

O S O

4

S

S

p(g42T-T) S

4O

2

BBL

p(g42T-T)

0

−2

−4


−0.8


n

4

2


O

p(g42T-T) (p-type)

4

N

BBL

cation

h+

N

0.8

n

5 0 −5 −10 −15 −0.5


2

−0.1 −0.2 −0.3 0.5 mA/cm2 1 mA/cm2 2 mA/cm2 4 mA/cm2

−0.4 −0.5

0

0

E

0 −0.1 −0.2 −0.3 −0.4

2 ml 8 ml 32 ml

−0.5 0

20 40 60 80 100 120 140 160 180 Time (s)



10

C


0

10

20

30

40 50 Time (s)

60

70

150 2 ml 8 ml 32 ml

50

0


0


10 5 0 −5

2 ml 8 ml 32 ml

−10 −0.5

F

200

100

Page 18 of 21

80



D

15

B

200 mV/s 400 mV/s

2

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33

10 mV/s 50 mV/s 100 mV/s


2


A


0


8

250 200 150 100 50 0

0

10 5 0 −5 −10 −15 −20

0


0.4 0.3 0.2 0.1 0


0.4

2

2 ml 8 ml 32 ml

0.3 0.2 0.1 0

0

50

100 150 Time (s)

200

250

F 250 200 2 ml 8 ml 32 ml

150 100 50 0


0


15 10 5 0 −5 2 ml 8 ml 32 ml

−10 −15

10 20 30 40 50 60 70 80 90 100 Time (s)

E 0.5

C 2


0.5

0

0.5

D Potential (V vs. Ag/AgCl)



15

B

200 mV/s 400 mV/s


2


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33

10 mV/s 50 mV/s 100 mV/s


A

Page 1920 of 21

0


0.5

200

150

100

50

0

0


4

3 0 −3 −6 −9

20

10 10 5 0

2k


10k

0

H Specific Capacitance (F/g)

2

1

0

10

–2

0.8 0.6 0.4 0.2

−6

10

device 1 (2 ml) device 2 (8 ml) device 3 (32 ml) –1

0

10 2 Power Density (mW/cm )

−0.5

0 0.5 Potential (V)

10

1

0

1.0

F 100 80 60 40 20 0

2

Energy Density (µWh/cm )

15

10

−3

E

40

20

–1

0

−1.0

30

10

3

1.0

0

2k


0

10 20 30 40 50 60 70 80 90 Time (s)

100

30

20

10 ACS Paragon Plus Environment


4

device 1 (2 ml) device 2 (8 ml) device 3 (32 ml)

60 40 20 0

I

0

80

10k

40

0

0.5 mA/cm2 1 mA/cm2 2 mA/cm2 4 mA/cm2 8 mA/cm2

2

0.8

25

10

6


0.4 0.6 Potential (V)

30

10

9

Page 20 of 21

1.0

Energy Density (Wh/kg)

0.2

ESR (Ω)

G

10 mV/s 50 mV/s 100 mV/s 200 mV/s 400 mV/s

−9 0

0

C


12

Potential (V)

6

2


D

9

Coulombic Efficiency (%)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51

B

200 mV/s 400 mV/s

2

10 mV/s 50 mV/s 100 mV/s


12

2


A

10

0

2 4 6 2 Current Density (mA/cm )

8

3

Combustion engine

Fuel cells

10

2

10

1

10

0

Batteries

36 s

0.36 s

10

–1

10

–2

Sup erca paci tors

3.6 ms

Capacitors

10

0

10

1

2

3

4

5

10 10 10 10 10 Power Density (W/kg)

6

10

7

Current Density (mA/cm2)

Page 21 of 21 1 2 3 4 5 6 7 8 9 10 11 12 13 14

2

ACS Applied Energy Materials O

O

N

N

N

N

p(g42T-T) (p-type) n

0 −2

BBL (n-type)

O

4

O 4

O

S SO O O O S S

O


4

n 4

S

n

S


Asymmetric Aqueous Supercapacitor Based on p- and n-Type

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