Long-Term Charge/Discharge Cycling Stability of MnO2 Aqueous Supercapacitor under Positive Polarization

Ataherian, Fatemeh; Wu, Nae‐Lih

doi:10.1149/1.3555469

Cited by 35 publications

(29 citation statements)

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“…Because the potential will be pinned at the valence band and conduction band edges, the formation energies are not plotted beyond the band gap. The accuracy of the predicted charge-switching model is corroborated by multiple experimental observations; a) We predict that protons will occupy Mn vacancies, creating Ruetschi-type defects as observed experimentally; 34 b) Our results show Mn vacancies become favorable at Φ < 0.1, and O vacancies become favorable at Φ > 0.8, resulting in a predicted stable potential window similar to the experimental potential window of 0 < Φ < 1.0 V vs. a Ag/AgCl reference electrode 29,30 ; and c) We show that interstitial protons ( 1×1 H and 2×2 H) and protonated Mn vacancies (H Mn ) undergo charge-switching at potentials within the SPW of the electrolyte, indicating that these defects lead to proton mediated charge storage in α-MnO 2 . [16][17][18] The calculated density of states (DOS), band gap and the SPW allowed by the aqueous electrolyte are also displayed for reference for α-MnO 2 in Figure 3b.…”

Section: Cation Induced Electronic Charge-switching Statessupporting

confidence: 86%

Charge Storage in Cation Incorporated α-MnO₂

et al. 2015

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Electrochemical supercapacitors utilizing α-MnO 2 offer the possibility of both high power density and high energy density. Unfortunately, the mechanism of electrochemical charge storage in α-MnO 2 and the effect of operating conditions on the charge storage mechanism are generally not well understood. Here, we present the first detailed charge storage mechanism of α-MnO 2 and explain the capacity differences between α-and β-MnO 2 using a combined theoretical electrochemical and band structure analysis. We identify the importance of the band gap, work function, the point of zero charge, and the tunnel sizes of the electrode material, as well as the pH and stability window of the electrolyte in determining the viability of a given electrode material. The high capacity of α-MnO 2 results from cation induced charge-switching states in the band gap that overlap with the scanned potential allowed by the electrolyte. The charge-switching states originate from interstitial and substitutional cations (H + , Li + , Na + , and K + ) incorporated into the material. Interstitial cations are found to induce chargeswitching states by stabilizing Mn-O antibonding orbitals from the conduction band. Substitutional cations interact with O[2p] dangling bonds that are destabilized from the valence band by Mn vacancies to induce charge-switching states. We calculate the equilibrium electrochemical potentials at which these states are reduced and predict the effect of the electrochemical operating conditions on their contribution to charge storage. The mechanism and theoretical approach we report is general and can be used to computationally screen new materials for improved charge storage via ion incorporation.

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Section: Cation Induced Electronic Charge-switching Statessupporting

confidence: 86%

Charge Storage in Cation Incorporated α-MnO₂

et al. 2015

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“…11 Previous studies on MnO 2 -based supercapacitors have mainly focused on achieving high specific capacitance; only a few studies [12][13][14] have focused on understanding the mechanisms that underlie the cycling stability.…”

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confidence: 99%

Investigating Mechanisms Underlying Elevated-Temperature-Induced Capacity Fading of Aqueous MnO₂Polymorph Supercapacitors: Cryptomelane and Birnessite

Pan

Ghodbane

Weng

et al. 2015

J. Electrochem. Soc.

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The effects of elevated operating temperature on the charge-storage capacity fading of two MnO 2 polymorph pseudocapacitive electrodes, namely cryptomelane and birnessite, in an aqueous K 2 SO 4 electrolyte were investigated. These two polymorphs have been shown to exhibit markedly different volume expansion and contraction behaviors during cycling. An increase in the cycling temperature from 25 to 50 • C dramatically increased the fading rate for both the electrodes, but the underlying mechanisms were different. For the cryptomelane electrode, in which the MnO 2 structure exhibits negligible volume variations during cycling, an increase in the operating temperature increased the irreversible structural distortion that originated from the Jahn-Teller distortion of MnO 6 octahedra. The structural distortion hindered the redox reactions involving K + intercalation into the MnO 2 lattice and led to a significant increase in charge-transfer resistance at the solid-electrolyte interface, thus accelerating capacity fading. For the birnessite electrode, cycling produced a marked increase in the electrical resistivity of active layer. This resistivity increase is attributable to the large cyclic volume variations in the birnessite structure, which cause debonding of binder with the constituent particles of the electrode. Accelerated capacity fading resulting from an increased operating temperature is attributed to deteriorating mechanical strength of the binder with increasing temperature. Pseudocapacitive supercapacitors that make use of fast redox reactions of electrochemically active metal oxide materials are attractive energy storage cells. They can deliver substantially higher power densities than rechargeable batteries, while offering significantly greater specific charge-storage capacity than symmetric electric double-layer capacitors.6-8 The practical application of supercapacitors relies heavily on their cycling stability. Commercial supercapacitors are expected to operate over relatively wide temperature ranges (e.g., from −20 to 60• C for advanced commercial carbon-based supercapacitors) in specific environments. The behaviors of pseudocapacitive supercapacitors at extreme temperatures, either well above or below room temperature, are relatively unknown, and related reports are scarce.Since first reported by Goodenough et al., 9,10 MnO 2 has attracted considerable attention as a promising pseudocapacitive supercapacitor electrode material because of its high theoretical specific capacitance (1370 F g −1 for one-electron transfer over a potential range of 1 V), low cost, natural abundance, and environmental friendliness. In addition, the use of aqueous neutral electrolytes in MnO 2 -based supercapacitors provides greater device safety compared with strong acidic electrolytes (e.g., those used in RuO 2 -based supercpactors).11 Previous studies on MnO 2 -based supercapacitors have mainly focused on achieving high specific capacitance; only a few studies [12][13][14] have focused on understanding the mechanisms t...

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“…The active material need also to form a good contact with the electrode surface, so it wouldn't peel off at high charge-discharge rates [18]. This is because at the high charge-discharge rate the undesirable processes, such as gas evolution due to electrolyte decomposition, are more pronounced at high charge-discharge rates [27]. This can lead to reduced contact surface between the material and current collector due to material peeling off, resulting in a decrease of the overall capacity of the electrode.…”

Section: Literature Review and Problem Statementmentioning

confidence: 99%

The properties investigation of the faradaic supercapacitor electrode formed on foamed nickel substrate with polyvinyl alcohol using

Kotok

Кovalenko

2017

EEJET

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Long-Term Charge/Discharge Cycling Stability of MnO2 Aqueous Supercapacitor under Positive Polarization

Cited by 35 publications

References 31 publications

Charge Storage in Cation Incorporated α-MnO₂

Charge Storage in Cation Incorporated α-MnO₂

Investigating Mechanisms Underlying Elevated-Temperature-Induced Capacity Fading of Aqueous MnO₂Polymorph Supercapacitors: Cryptomelane and Birnessite

The properties investigation of the faradaic supercapacitor electrode formed on foamed nickel substrate with polyvinyl alcohol using

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Long-Term Charge/Discharge Cycling Stability of MnO2 Aqueous Supercapacitor under Positive Polarization

Cited by 35 publications

References 31 publications

Charge Storage in Cation Incorporated α-MnO2

Charge Storage in Cation Incorporated α-MnO2

Investigating Mechanisms Underlying Elevated-Temperature-Induced Capacity Fading of Aqueous MnO2Polymorph Supercapacitors: Cryptomelane and Birnessite

The properties investigation of the faradaic supercapacitor electrode formed on foamed nickel substrate with polyvinyl alcohol using

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Product

Resources

About

Charge Storage in Cation Incorporated α-MnO₂

Charge Storage in Cation Incorporated α-MnO₂

Investigating Mechanisms Underlying Elevated-Temperature-Induced Capacity Fading of Aqueous MnO₂Polymorph Supercapacitors: Cryptomelane and Birnessite