On the molecular origin of supercapacitance in nanoporous carbon electrodes

Merlet, Céline; Rotenberg, Benjamin; Madden, Paul A.; Taberna, Pierre‐Louis; Simon, Patrice; Gogotsi, Yury; Salanne, Mathieu

doi:10.1038/nmat3260

Cited by 900 publications

(958 citation statements)

References 30 publications

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“…We anticipate that materials could also be developed in which anions shift valence-band states into the band gap by a similar mechanism. For instance, the anion induced chargeswitching states created by O 2-intercalation may be responsible for the observed charge storage in LaMnO 3 . 42 If these charge-switching states overlap with the SPW allowed by the electrolyte, those materials will store charge by an analogous mechanism to the one proposed here for α-MnO 2 .…”

Section: Conclusion Insights For Materials and Electrolyte Selectionmentioning

confidence: 99%

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: Conclusion Insights For Materials and Electrolyte Selectionmentioning

confidence: 99%

Charge Storage in Cation Incorporated α-MnO₂

et al. 2015

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“…In particular, the overscreening effect 4 was shown to be the origin of the low capacitance of planar electrodes. Nanoporous carbons are excellent materials for supercapacitor electrodes [5][6][7][8] , with enhanced capacitances: owing to confinement effects, the overscreening is quenched, leading to a more efficient charge storage characterized by much higher capacitances 9 and a large electronic screening by the pore walls of like-like ions repulsive Coulombic interactions occurs, allowing for a denser packing of the ions inside the pores 10,11 .…”

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confidence: 99%

Highly confined ions store charge more efficiently in supercapacitors

et al. 2013

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Liquids exhibit specific properties when they are adsorbed in nanoporous structures. This is particularly true in the context of supercapacitors, for which an anomalous increase in performance has been observed for nanoporous electrodes. This enhancement has been traditionally attributed in experimental studies to the effect of confinement of the ions from the electrolyte inside sub-nanometre pores, which is accompanied by their partial desolvation. Here we perform molecular dynamics simulations of realistic supercapacitors and show that this picture is correct at the microscopic scale. We provide a detailed analysis of the various environments experienced by the ions. We pick out four different adsorption types, and we, respectively, label them as edge, planar, hollow and pocket sites upon increase of the coordination of the molecular species by carbon atoms from the electrode. We show that both the desolvation and the local charge stored on the electrode increase with the degree of confinement.

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“…IC-QM/MM is potentially a valuable tool to study these interfaces with large-scale MD and to allow implications on electrochemical properties of metal electrodes. Successful application of the classical equivalent of the IC approach in electrochemistry [18][19][20] also suggests that the method holds promise especially for electrochemical systems.…”

Section: Resultsmentioning

confidence: 99%

“…The Gaussian charge method developed by Siepmann and Sprik 15 treats the image charges as dynamical variables and realizes the mutual modification of induced and adsorbate charges. The Siepmann-Sprik scheme has been successfully applied to water/platinum interfaces [15][16][17] as well as ionic liquids at platinum 18 and graphene 19,20 electrodes within a purely classical frame.…”

Section: Introductionmentioning

confidence: 99%

Simulation of Adsorption Processes at Metallic Interfaces: An Image Charge Augmented QM/MM Approach

Golze

Iannuzzi

Nguyen

et al. 2013

J. Chem. Theory Comput.

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A novel method for including polarization effects within hybrid quantum mechanics/molecular mechanics (QM/MM) simulations of adsorbate-metal systems is presented. The interactions between adsorbate (QM) and metallic substrate (MM) are described at the MM level of theory. Induction effects are additionally accounted for by applying the image charge formulation. The charge distribution induced within the metallic substrate is modeled by a set of Gaussian charges (image charges) centered at the metal atoms. The image charges and the electrostatic response of the QM potential are determined self-consistently by imposing the constant-potential condition within the metal. The implementation is embedded in a highly efficient Gaussian and plane wave framework and is naturally suited for periodic systems. Even though the electronic properties of the metallic substrate are not taken into account explicitly, the augmented QM/MM scheme can reproduce characteristic polarization effects of the adsorbate. The method is assessed through the investigation of structural and electronic properties of benzene, nitrobenzene, thymine, and guanine on Au(111). The study of small water clusters adsorbed on Pt(111) is also reported in order to demonstrate that the approach provides a sizable correction of the MM-based interactions between adsorbate and substrate. Large-scale molecular dynamics (MD) simulations of a water film in contact with a Pt(111) surface show that the method is suitable for simulations of liquid/metal interfaces at reduced computational cost.

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On the molecular origin of supercapacitance in nanoporous carbon electrodes

Cited by 900 publications

References 30 publications

Charge Storage in Cation Incorporated α-MnO₂

Charge Storage in Cation Incorporated α-MnO₂

Highly confined ions store charge more efficiently in supercapacitors

Simulation of Adsorption Processes at Metallic Interfaces: An Image Charge Augmented QM/MM Approach

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On the molecular origin of supercapacitance in nanoporous carbon electrodes

Cited by 900 publications

References 30 publications

Charge Storage in Cation Incorporated α-MnO2

Charge Storage in Cation Incorporated α-MnO2

Highly confined ions store charge more efficiently in supercapacitors

Simulation of Adsorption Processes at Metallic Interfaces: An Image Charge Augmented QM/MM Approach

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Product

Resources

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Charge Storage in Cation Incorporated α-MnO₂

Charge Storage in Cation Incorporated α-MnO₂