To improve supercapacitor performance, mechanisms of operation should be understood. Here the authors identify parameters controlling ion charge storage mechanisms and show that charging initially implies a non-equilibrium ion configuration followed by charge-neutral equilibration

C. Koczwara

C. Prehal

H. Amenitsch

O. Paris

V. Presser

Nature Communications

A fundamental understanding of ion charge storage in nanoporous electrodes is essential to improve the performance of supercapacitors or devices for capacitive desalination. Here, we employ in situ X-ray transmission measurements on activated carbon supercapacitors to study ion concentration changes during electrochemical operation. Whereas counter-ion adsorption was found to dominate at small electrolyte salt concentrations and slow cycling speed, ion replacement prevails for high molar concentrations and/or fast cycling. Chronoamperometry measurements reveal two distinct time regimes of ion concentration changes. In the first regime the supercapacitor is charged, and counter- and co-ion concentration changes align with ion replacement and partially co-ion expulsion. In the second regime, the electrode charge remains constant, but the total ion concentration increases. We conclude that the initial fast charge neutralization in nanoporous supercapacitor electrodes leads to a non-equilibrium ion configuration. The subsequent, charge-neutral equilibration slowly increases the total ion concentration towards counter-ion adsorption

Prehal, C.

Koczwara, C.

Amenitsch, H.

Presser, V.

Paris, O.

Repositorium für Naturwissenschaften und Technik  (TIB Hannover)

English

Salt concentration and charging velocity determine ion charge storage mechanism in nanoporous supercapacitors

Salt concentration and charging velocity determine ion charge storage mechanism in nanoporous supercapacitors

Abstract

Similar works

Full text

Available Versions

Repositorium für Naturwissenschaften und Technik (TIB Hannover)

INMdok (Leibniz Institute for New Materials)