Constriction and contact impedance of ceramic solid electrolytes

TL;DR

This paper investigates how contact area and pressure affect impedance at ceramic solid electrolyte interfaces in solid-state batteries, revealing key factors influencing interfacial resistance and proposing mitigation insights.

Contribution

It systematically analyzes the roles of recoverable and unrecoverable contact areas in impedance rise, combining experiments and simulations to quantify their impacts.

Findings

Interfacial resistance scales with recoverable contact area and pressure.

Distributed contacts lead to lower impedance and more uniform potential.

Simulations agree with experimental measurements of interfacial resistance.

Abstract

The development of solid-state batteries (SSBs) is hindered by degradation at solid-solid interfaces due to void formation and contact loss, resulting in increased impedance. Here, we systematically investigate the roles of real and unrecoverable interfacial contact areas at the electrode/Li$_6$PS$_5$Cl interface in driving the impedance rise. By controlling contact geometries and applied pressures, we identify their distinct contributions to the impedance spectra and quantify their influence on the interfacial resistance and transport. Experiments reveal that interfacial resistance varies strongly with recoverable contact area and applied pressure following power law scaling, with exponents of -1 and -0.5, respectively. Moreover, distributed contacts result in lower impedance due to smaller potential gradients and a more uniform potential distribution. Continuum simulations of the contact geometries predict interfacial resistances in agreement with experiments. Our work highlights the influence of unrecoverable and recoverable contact losses on SSB impedance while quantifying the effectiveness of mitigation strategies.