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Low-cost flexible supercapacitors with high-energy density based on nanostructured MnO2 and Fe2O3 thin films directly fabricated onto stainless steel.

Gund GS, Dubal DP, Chodankar NR, Cho JY, Gomez-Romero P, Park C, Lokhande CD - Sci Rep (2015)

Bottom Line: The results verify that the fabricated symmetric and asymmetric FSS-SCs present excellent reversibility (within the voltage window of 0-1 V and 0-2 V, respectively) and good cycling stability (83 and 91%, respectively for 3000 of CV cycles).Additionally, the asymmetric SC shows maximum specific capacitance of 92 Fg(-1), about 2-fold of higher energy density (41.8 Wh kg(-1)) than symmetric SC and excellent mechanical flexibility.Furthermore, the "real-life" demonstration of fabricated SCs to the panel of SUK confirms that asymmetric SC has 2-fold higher energy density compare to symmetric SC.

View Article: PubMed Central - PubMed

Affiliation: 1] Thin Film Physics Laboratory, Department of Physics, Shivaji University, Kolhapur, - 416004 (M.S), India [2] Department of Materials Science and Engineering, Seoul National University, Seoul 151-744, South Korea [3] Catalan Institute of Nanoscience and Nanotechnology, CIN2, ICN2 (CSIC-ICN), Campus UAB, E-08193 Bellaterra (Barcelona), Spain.

ABSTRACT
The facile and economical electrochemical and successive ionic layer adsorption and reaction (SILAR) methods have been employed in order to prepare manganese oxide (MnO2) and iron oxide (Fe2O3) thin films, respectively with the fine optimized nanostructures on highly flexible stainless steel sheet. The symmetric and asymmetric flexible-solid-state supercapacitors (FSS-SCs) of nanostructured (nanosheets for MnO2 and nanoparticles for Fe2O3) electrodes with Na2SO4/Carboxymethyl cellulose (CMC) gel as a separator and electrolyte were assembled. MnO2 as positive and negative electrodes were used to fabricate symmetric SC, while the asymmetric SC was assembled by employing MnO2 as positive and Fe2O3 as negative electrode. Furthermore, the electrochemical features of symmetric and asymmetric SCs are systematically investigated. The results verify that the fabricated symmetric and asymmetric FSS-SCs present excellent reversibility (within the voltage window of 0-1 V and 0-2 V, respectively) and good cycling stability (83 and 91%, respectively for 3000 of CV cycles). Additionally, the asymmetric SC shows maximum specific capacitance of 92 Fg(-1), about 2-fold of higher energy density (41.8 Wh kg(-1)) than symmetric SC and excellent mechanical flexibility. Furthermore, the "real-life" demonstration of fabricated SCs to the panel of SUK confirms that asymmetric SC has 2-fold higher energy density compare to symmetric SC.

No MeSH data available.


Cyclic voltammograms of(a) MnO2 and (b) Fe2O3 electrodes at different scan rates, (c) plots of specific capacitance versus potential scan rate. (d) Nyquist plots of MnO2 and Fe2O3 electrodes.
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f3: Cyclic voltammograms of(a) MnO2 and (b) Fe2O3 electrodes at different scan rates, (c) plots of specific capacitance versus potential scan rate. (d) Nyquist plots of MnO2 and Fe2O3 electrodes.

Mentions: We performed cyclic voltammetry (CV) and electrochemical impedance measurements for MnO2 and Fe2O3 electrodes, in order to investigate their capacitive behavior, electrochemical stability and mechanistic ion transport properties, before employing these electrodes for device fabrication. The CV studies of interconnected NSs (MnO2: positive electrode) and NPs (Fe2O3: negative electrode) were carried out in 1 M Na2SO4 electrolyte within 0 to +1 and −1 to 0 V/SCE operational windows, respectively at different scan rates (5 to 100 mV s−1) using a three-electrode cell configuration, see Fig. 3(a,b). The cell consists of interconnected NSs and NPs electrodes as a working electrode (1 cm2), platinum as a counter electrode and saturated calomel electrode (SCE) as reference electrode. The enhancement of current density with increasing scan rate, for both NSs containing MnO2 and NPs covered Fe2O3 electrodes, indicates excellent supercapacitive behavior for both electrodes. The non-rectangular shape of the CV profile is associated with the faradic reactions i.e. reduction (Mx to Mx−1) and oxidation (Mx−1 to Mx) on the electrodes39. The estimated specific capacitances and potential dependent charge storage (i.e. capacitive retention relating to scan rate) of the positive and negative electrodes through CV analysis are portrayed in Fig. 3(c). The estimated values of specific capacitance for positive and negative electrodes are 333 and 283 F g−1, respectively at 5 mV s−1 scan rate. The depletion of charge storage capacity (from 333 to174 F g−1 for positive and 283 to 144 F g−1 for negative electrode) with the potential is clearly displayed from Fig. 3(c) (the capacitive retention with respect to scan rate exhibited in supporting information 5(a)), which is associated to ion exchange mechanism. Particularly, highly porous nanostructures of MO electrodes need enough time for intercalation-deintercalation process during charging-discharging, so most of the electrode material remains unused at high potential due to fast rate of intercalation and deintercalation processes40. A good electrochemical stability of the electrodes is a must for their practical application in SC fabrication. Accordingly, CV measurements of positive and negative electrodes were repeated for 3,000 cycles at the scan rate of 100 mV s−1 and the calculated capacitive retention as a function of cycles for both electrodes displayed in supporting information 5(b). The capacitive remnants for positive and negative electrodes after 3,000 CV cycles were determined to be 91 and 75%, respectively. The better capacitive retention of positive electrode as compare to negative electrode may be consequence of good adhesion and less dissolution of MnO2 NSs as compare to Fe2O3 interconnected NPs in electrolyte during the cycling. Furthermore, the ion transport features of the prepared electrodes were examined through electrochemical impedance spectroscopy (EIS) analysis with AC amplitude of 10 mV and in a frequency range of 100 mHz −100 kHz. The obtained Nyquist plot (Z” vs Z’) comprises a high frequency semicircle and low frequency straight line, as illustrated in Fig. 3(d). The intercept of high frequency semicircle on real axis is associated with the equivalent series resistance (Rs) (combination of ionic resistance of electrolyte, intrinsic resistance of electrode material and interfacial resistances), while the radius of the semicircle offers information on the charge transfer resistance (Rct) (consequence of Faradaic and non-Faradaic reactions on the electrode surface)4142. The slope of the straight line in the low frequency region indicates the capacitive behavior of the electrode: reflection of excellent capacitive behavior associated to inclination from 45° to 90° with the fall of frequency. The observed values of Rs and Rct indicate excellent ion conductivity of positive (1.4 and 1.2 Ω cm−2, respectively) and negative (14.8 and 28.6 Ω cm−2, respectively) electrodes on SS sheets; see Fig. 3(d). The slightly better performance of positive electrode (i.e. charge storage capacity, electrochemical stability and conductivity) is associated to the highly porous nanostructure and different mass loading on electrodes. In any event, the excellent electrochemical properties of the chemically prepared MnO2 and Fe2O3 electrodes point to their efficient utilization for device fabrication.


Low-cost flexible supercapacitors with high-energy density based on nanostructured MnO2 and Fe2O3 thin films directly fabricated onto stainless steel.

Gund GS, Dubal DP, Chodankar NR, Cho JY, Gomez-Romero P, Park C, Lokhande CD - Sci Rep (2015)

Cyclic voltammograms of(a) MnO2 and (b) Fe2O3 electrodes at different scan rates, (c) plots of specific capacitance versus potential scan rate. (d) Nyquist plots of MnO2 and Fe2O3 electrodes.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4513645&req=5

f3: Cyclic voltammograms of(a) MnO2 and (b) Fe2O3 electrodes at different scan rates, (c) plots of specific capacitance versus potential scan rate. (d) Nyquist plots of MnO2 and Fe2O3 electrodes.
Mentions: We performed cyclic voltammetry (CV) and electrochemical impedance measurements for MnO2 and Fe2O3 electrodes, in order to investigate their capacitive behavior, electrochemical stability and mechanistic ion transport properties, before employing these electrodes for device fabrication. The CV studies of interconnected NSs (MnO2: positive electrode) and NPs (Fe2O3: negative electrode) were carried out in 1 M Na2SO4 electrolyte within 0 to +1 and −1 to 0 V/SCE operational windows, respectively at different scan rates (5 to 100 mV s−1) using a three-electrode cell configuration, see Fig. 3(a,b). The cell consists of interconnected NSs and NPs electrodes as a working electrode (1 cm2), platinum as a counter electrode and saturated calomel electrode (SCE) as reference electrode. The enhancement of current density with increasing scan rate, for both NSs containing MnO2 and NPs covered Fe2O3 electrodes, indicates excellent supercapacitive behavior for both electrodes. The non-rectangular shape of the CV profile is associated with the faradic reactions i.e. reduction (Mx to Mx−1) and oxidation (Mx−1 to Mx) on the electrodes39. The estimated specific capacitances and potential dependent charge storage (i.e. capacitive retention relating to scan rate) of the positive and negative electrodes through CV analysis are portrayed in Fig. 3(c). The estimated values of specific capacitance for positive and negative electrodes are 333 and 283 F g−1, respectively at 5 mV s−1 scan rate. The depletion of charge storage capacity (from 333 to174 F g−1 for positive and 283 to 144 F g−1 for negative electrode) with the potential is clearly displayed from Fig. 3(c) (the capacitive retention with respect to scan rate exhibited in supporting information 5(a)), which is associated to ion exchange mechanism. Particularly, highly porous nanostructures of MO electrodes need enough time for intercalation-deintercalation process during charging-discharging, so most of the electrode material remains unused at high potential due to fast rate of intercalation and deintercalation processes40. A good electrochemical stability of the electrodes is a must for their practical application in SC fabrication. Accordingly, CV measurements of positive and negative electrodes were repeated for 3,000 cycles at the scan rate of 100 mV s−1 and the calculated capacitive retention as a function of cycles for both electrodes displayed in supporting information 5(b). The capacitive remnants for positive and negative electrodes after 3,000 CV cycles were determined to be 91 and 75%, respectively. The better capacitive retention of positive electrode as compare to negative electrode may be consequence of good adhesion and less dissolution of MnO2 NSs as compare to Fe2O3 interconnected NPs in electrolyte during the cycling. Furthermore, the ion transport features of the prepared electrodes were examined through electrochemical impedance spectroscopy (EIS) analysis with AC amplitude of 10 mV and in a frequency range of 100 mHz −100 kHz. The obtained Nyquist plot (Z” vs Z’) comprises a high frequency semicircle and low frequency straight line, as illustrated in Fig. 3(d). The intercept of high frequency semicircle on real axis is associated with the equivalent series resistance (Rs) (combination of ionic resistance of electrolyte, intrinsic resistance of electrode material and interfacial resistances), while the radius of the semicircle offers information on the charge transfer resistance (Rct) (consequence of Faradaic and non-Faradaic reactions on the electrode surface)4142. The slope of the straight line in the low frequency region indicates the capacitive behavior of the electrode: reflection of excellent capacitive behavior associated to inclination from 45° to 90° with the fall of frequency. The observed values of Rs and Rct indicate excellent ion conductivity of positive (1.4 and 1.2 Ω cm−2, respectively) and negative (14.8 and 28.6 Ω cm−2, respectively) electrodes on SS sheets; see Fig. 3(d). The slightly better performance of positive electrode (i.e. charge storage capacity, electrochemical stability and conductivity) is associated to the highly porous nanostructure and different mass loading on electrodes. In any event, the excellent electrochemical properties of the chemically prepared MnO2 and Fe2O3 electrodes point to their efficient utilization for device fabrication.

Bottom Line: The results verify that the fabricated symmetric and asymmetric FSS-SCs present excellent reversibility (within the voltage window of 0-1 V and 0-2 V, respectively) and good cycling stability (83 and 91%, respectively for 3000 of CV cycles).Additionally, the asymmetric SC shows maximum specific capacitance of 92 Fg(-1), about 2-fold of higher energy density (41.8 Wh kg(-1)) than symmetric SC and excellent mechanical flexibility.Furthermore, the "real-life" demonstration of fabricated SCs to the panel of SUK confirms that asymmetric SC has 2-fold higher energy density compare to symmetric SC.

View Article: PubMed Central - PubMed

Affiliation: 1] Thin Film Physics Laboratory, Department of Physics, Shivaji University, Kolhapur, - 416004 (M.S), India [2] Department of Materials Science and Engineering, Seoul National University, Seoul 151-744, South Korea [3] Catalan Institute of Nanoscience and Nanotechnology, CIN2, ICN2 (CSIC-ICN), Campus UAB, E-08193 Bellaterra (Barcelona), Spain.

ABSTRACT
The facile and economical electrochemical and successive ionic layer adsorption and reaction (SILAR) methods have been employed in order to prepare manganese oxide (MnO2) and iron oxide (Fe2O3) thin films, respectively with the fine optimized nanostructures on highly flexible stainless steel sheet. The symmetric and asymmetric flexible-solid-state supercapacitors (FSS-SCs) of nanostructured (nanosheets for MnO2 and nanoparticles for Fe2O3) electrodes with Na2SO4/Carboxymethyl cellulose (CMC) gel as a separator and electrolyte were assembled. MnO2 as positive and negative electrodes were used to fabricate symmetric SC, while the asymmetric SC was assembled by employing MnO2 as positive and Fe2O3 as negative electrode. Furthermore, the electrochemical features of symmetric and asymmetric SCs are systematically investigated. The results verify that the fabricated symmetric and asymmetric FSS-SCs present excellent reversibility (within the voltage window of 0-1 V and 0-2 V, respectively) and good cycling stability (83 and 91%, respectively for 3000 of CV cycles). Additionally, the asymmetric SC shows maximum specific capacitance of 92 Fg(-1), about 2-fold of higher energy density (41.8 Wh kg(-1)) than symmetric SC and excellent mechanical flexibility. Furthermore, the "real-life" demonstration of fabricated SCs to the panel of SUK confirms that asymmetric SC has 2-fold higher energy density compare to symmetric SC.

No MeSH data available.