Electrolytes for hybrid carbon–MnO2 electrochemical capacitors

Mosqueda, Hugo A.; Crosnier, Olivier; Athouël, Laurence; Dandeville, Y.; Scudeller, Y.; Guillemet, Philippe; Schleich, D. M.; Brousse, Thierry

doi:10.1016/j.electacta.2010.01.022

Cited by 53 publications

(32 citation statements)

References 21 publications

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“…16,54,55 Since manganese oxides have poor ionic and electronic conductivity, it is therefore of common practice to combine them with conductive carbons to form composite to improve their electrochemical performances. 4,7,9,17,56 In a previous work, we have reported that the physical mixing of MnO 2 with a carbon black such as Black Pearls (BP) cannot contribute to increase the specific capacitance of the composite electrode despite the high specific surface area of BP relative to a conventional carbon black. 21 In fact, the large pool of ionic species present with BP did not significantly improve the utilization of MnO 2 which remained relatively low.…”

Section: Resultsmentioning

confidence: 99%

Chemical Mapping and Electrochemical Performance of Manganese Dioxide/Activated Carbon Based Composite Electrode for Asymmetric Electrochemical Capacitor

Gambou-Bosca

Bélanger

2015

J. Electrochem. Soc.

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A MnO 2 @BP nanocomposite was synthesized by simultaneously reduction of KMnO 4 with Mn(CH 3 COO) 2 .4H 2 O and highly porous Black Pearls 2000 at room temperature. The specific surface area, porosity, crystalline form and conductivity of MnO 2 @BP nanocomposite were characterized by nitrogen gas adsorption measurements, scanning electron microscopy, X-ray diffraction and 4-point probe measurements, respectively. The content of MnO 2 and BP in the composite was determined by thermogravimetric analysis. Chemical mapping using Raman spectroscopy was performed to investigate the distribution of MnO 2 and BP in a composite electrode film prepared with polytetrafluoroethylene (PTFE) as binder. This composite electrode exhibits more homogeneously distributed MnO 2 particles when compared to an electrode made by physical mixing of MnO 2 , BP and PTFE (MnO 2 /BP-PTFE). Also, Raman spectroscopy data of both composite electrodes indicates a loss of electrical conductivity of BP in the case of MnO 2 @BP-PTFE. The electrochemical properties were characterized by cyclic voltammetry in aqueous 0.65 M K 2 SO 4 . The specific capacitance of MnO 2 @BP-PTFE composite electrode was 122 ± 5 F/g, which is statistically equivalent to the capacitance of MnO 2 /BP-PTFE composite electrode (129 ± 6 F/g Owing to its large theoretical capacitance, low cost, environmental friendliness and high density, manganese dioxide (MnO 2 ) is an ideal candidate for positive electrode in asymmetric electrochemical capacitor.1-4 However the performance of MnO 2 -based electrodes is limited by the low electrical and ionic conductivities of MnO 2 . Approaches to increase the low specific capacitance of MnO 2 -based electrode include the addition of a conductive additive such as carbons [5][6][7][8][9] or conductive polymers 10-14 to MnO 2 for the fabrication of a composite electrode. On the other hand, the deposition of a thin MnO 2 layer on carbon with various (nano)architectures 7,15-24 yielded high capacitance (∼700 F/g) when only the mass of MnO 2 was taking into account. 1,8,9,16 Such composite electrodes show typical specific capacitance in the range of 150-250 F/g. Thus, the reported specific capacitance per mass of manganese dioxide is more dependent on the quantity of MnO 2 than the nature of the conductive carbon. 5,8,9,16,[21][22][23][25][26][27][28][29][30][31][32][33] Obtaining good electrochemical performance for MnO 2 -based composite electrodes requires that the electrical contact between MnO 2 and the carbon to be as intimate as possible. 21,34 An attractive approach to achieve it, involves the deposition of MnO 2 onto carbon. 15,22,31,[34][35][36][37][38] By this mean, the effective interfacial area between manganese oxide and the solution is greatly increased. Moreover the contact between MnO 2 and carbon will lead to a high electronic conductivity. MnO 2 has been deposited onto a carbon support by various methods such as sol-gel route, thermal decomposition, electrodeposition, sonochemical synthesis, and redox reaction. 18,31,[34][35]...

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Section: Resultsmentioning

confidence: 99%

Chemical Mapping and Electrochemical Performance of Manganese Dioxide/Activated Carbon Based Composite Electrode for Asymmetric Electrochemical Capacitor

Gambou-Bosca

Bélanger

2015

J. Electrochem. Soc.

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“…Another study of supercapacitors using similar electrodes and electrolyte showed an energy loss of 15 % at −40°C, compared to that at +25°C (a power density of 500 W kg −1 ) [14]. A highly concentrated electrolyte, 5 M LiNO 3 , seems to be a good candidate to improve lowtemperature performance and long-term cycling ability of aqueous electrolyte-based carbon//MnO 2 asymmetric supercapacitors [16]. The capacitance decay and ESR increase of supercapacitors based on 5 M LiNO 3 is much less than that of 0.5 M K 2 SO 4 electrolytes at −8°C, compared to those at 20°C.…”

Section: Aqueous Electrolytesmentioning

confidence: 97%

Influence of Temperature on Supercapacitor Performance

Xiong

Kundu

Fisher

2015

Thermal Effects in Supercapacitors

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Because of the negligible faradic reactions in double-layer capacitors, heat generated during charge/discharge processes derives mostly from Joule heating, which is determined by internal resistance (or equivalent series resistance, ESR). However, heat generated in pseudo-capacitors derives from both Joule heating and exothermic/ endothermic Faradic reactions. Thus, understanding how temperature affects capacitance and ESR is essential to predict supercapacitor performance under different operating conditions. The general techniques (e.g., CV, constant current-charge/ discharge and EIS) to evaluate capacitance and ESR have been discussed in Sect. 2.4.Many factors contribute to ESR in a supercapacitor: (i) interfacial resistance (contact resistance) between the electrode and the current collectors; (ii) electronic resistance of the electrode material; (iii) resistance of ions migrating through the electrode pores; (v) electrolyte resistance, and (vi) resistance of ions migrating through the separator [2,3]. Consequently, ESR depends on the active area and porosity of electrodes, ionic conductivity of the electrolyte, and physical properties of the separator (e.g., porosity, thickness and tortuosity). Notably, electrolyte resistance is only part of ESR. ESR depends on many factors (e.g., electrode structure, materials, electrolytes, fabrication and temperature). ESR is suggested to be inversely proportional to σ within certain ranges [4], but this relation can be violated. For instance, ESR is more dominated by the carbon electrode resistance and the interface resistance at the current collector than electrolyte resistance, as indicated by a much smaller activation energy of ACN-based supercapacitors than that of the electrolyte [5]. Capacitance is a function of surface area and volume of the electrodes, and ionic conductivity of electrolytes, which strongly depends on temperature variations.The operating temperature strongly influences the properties of electrolytes (e.g., viscosity, solubility of the salt in solvents, ionic conductivity, and thermal stability), leading to dramatic changes of capacitance and ESR, particularly at extreme temperatures (ultra-low and ultra-high temperatures). Consequently, the influence of

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“…Indeed, transportation applications required operating temperatures as low as −30 • C, which are difficult to achieve with neutral aqueous electrolytes. Highly concentrated nitrate solutions help fulfill this requirement, as recently reported [68,69].…”

Section: Activated Carbon/mno 2 Devicesmentioning

confidence: 71%

Asymmetric and Hybrid Devices in Aqueous Electrolytes

Brousse¹,

Bélanger²,

Guay³

2013

Supercapacitors

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IntroductionCarbon-based symmetrical electrochemical double-layer capacitors (EDLCs) demonstrate higher energy density and power capability in organic-based electrolytes compared to aqueous-based electrolytes owing to their high operating voltage (2.5-2.7 V). Indeed, despite a lower capacitance of carbon-based electrodes in organic electrolytes (C), the maximum energy density (E max ) is expressed asand is proportional to the square of the maximum operating voltage (U max ), which is limited to the water electrochemical stability window that cannot theoretically exceed 1.23 V. Thus, even if the capacitance of a symmetrical carbon-based device in an aqueous electrolyte is twice that of an EDLC in an organic electrolyte (C aq = 2C org ), the maximum operating voltage of an organic-based device is more than twice that of an aqueous-based capacitor (U org = 2U aq ) resulting in:Obviously, this simple calculation does not take into account additional factors such as electrolyte concentration, ionic conductivity, packaging, and so on, but some more detailed theoretical calculation [1] points out the superiority of symmetrical carbon-based EDLC in an organic electrolyte (5.7 vs 1.7 Wh kg −1 for symmetrical carbon-based devices in aqueous electrolytes). Practically, the superiority of organicbased carbon/carbon devices has been demonstrated and most commercial-based devices use organic electrolytes. However, aqueous-based devices possess a number of advantages that can be emphasized in a commercial system, such as their high ionic conductivity, which can be useful to achieve high power density [2,3]. In addition, the electrothermal safety of aqueous-based devices will be greater in all cases than for organic-based electrolytes [4], which is one of the major points now addressed by electrochemical capacitor (EC) manufacturers as high currents and fast cycling rates are usually required, thus possibly leading to thermal rather than chemical runaway of the

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Electrolytes for hybrid carbon–MnO2 electrochemical capacitors

Cited by 53 publications

References 21 publications

Chemical Mapping and Electrochemical Performance of Manganese Dioxide/Activated Carbon Based Composite Electrode for Asymmetric Electrochemical Capacitor

Chemical Mapping and Electrochemical Performance of Manganese Dioxide/Activated Carbon Based Composite Electrode for Asymmetric Electrochemical Capacitor

Influence of Temperature on Supercapacitor Performance

Asymmetric and Hybrid Devices in Aqueous Electrolytes

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