There’s hidden resistance in solid state batteries in a form that scientists call space charge layers. These layers occur at the points where solid electrolytes interface with electrodes, and can impede the flow of ions.
A smooth ion flow between electrodes through electrolytes, is a critical success factor for optimum battery performance.
How Space Charge Layers Cause Hidden Resistance
Space charge layers form during charging and discharging cycles, as ions travel between electrodes through solid electrolytes. Their accumulation at this point repels some other ions approaching. This is the cause of the hidden resistance we referred to earlier.
Scientists from Max Plank Institute for Polymer Research, noticed that space charge layers form mainly at positive electrodes. This obstruction may be as thin as the thinnest layer of a soap bubble. But that’s enough to create hidden resistance in solid state batteries.
The Max Plank researchers discovered something even more interesting when they investigated further. The extent of the space charge layer – and its ion-resistance – varies depending on the state of charge. In extreme cases, it could be as much as 7% of total solid-state battery resistance.
This is the first time we have seen clear proof of the extent of state-of-charge’s ability to interrupt the flow of ions. The researchers built an experimental battery to determine where and how this hidden resistance in solid state batteries forms.
How They Studied Solid State Battery Resistance
The researchers constructed a special ultra-thin all-solid-state battery, and scanned a cross-section to obtain the information. This data included the influence of voltage, and how lithium-ions accumulate at the positive electrode interface point.
Max Plank and their associates plan to investigate modifying the special battery structure, to reduce resistance and improve solid-state battery performance.
This ground-breaking work could influence future solid state battery design, thanks to these fresh insights into hidden resistance in solid state battery cells.
More Information
Internal Resistance in Batteries
Battery Internal Resistance in Practice
Preview Image: Probing Space Charge Layers
