Electrode Polarization in Glassy Electrolytes: Large Interfacial Capacitance Values and Indication for Pseudocapacitive Charge Storage

TL;DR

This study investigates electrode polarization in glassy electrolytes, revealing large interfacial capacitance values and pseudocapacitive charge storage mechanisms that could enhance solid-state supercapacitors.

Contribution

It provides new insights into pseudocapacitive processes in solid electrolytes, highlighting their potential for improved energy storage applications.

Findings

Interfacial capacitance exceeds double layer theory predictions.

Capacitance peaks around 1 V bias voltage.

Evidence of pseudocapacitive Na+ ion adsorption and charge transfer.

Abstract

We study the electrode polarization behaviour of different Na-Ca-phosphosilicate glasses by measuring the differential capacitance between blocking Pt electrodes. At low applied dc bias voltages, we detect a linear capacitance regime with interfacial capacitance values considerably larger than expected from double layer theories and also considerably larger than found for ionic liquids with similar ion concentrations. With increasing bias voltages, the differential capacitance of interfacial layer exhibits a maximum around 1 V and a strong drop at higher voltages. We suggest that these features are caused by pseudocapacitive processes, namely by the adsorption of mobile Na+ ions at the electrodes followed by electronic charge transfer. While pseudocapacitive processes are well known in liquid electrochemistry, more detailed studies on solid electrolytes should offer perspectives for improved energy storage in solid-state supercapacitors