Lithium Metal Solid-State Pouch Cell: Pressure Dependence of Rate Performance

Too much pressure, or not enough?

Pouch cells can be very sensitive to how much pressure is put on them during cycling. Often the performance will improve with pressure, ensuring good contact between all layers etc. Sometimes though, it’s possible to have too much of a good thing. Very high pressure can e.g. restrict the ion diffusion pathways, increasing the internal resistance.

Especially when using lithium metal anodes, pressure control becomes extremely important. Many studies have shown the huge impact that pressure can have on the quality of lithium stripping and plating, and in effect cell performance and life.

In collaboration with Battery LabFactory Braunschweig

I recently had the chance to test the performance of a solid-state pouch cell with Li anode, LFP cathode, and a PEO based electrolyte, under various pressures and with precise pressure monitoring using the CompreFrame with CompreCell Pouch.

Increasing the pressure gave higher capacity, especially at higher rates, but eventually this behavior was reversed. The optimal performance was achieved at 300 kPa for this pouch cell. The link between pressure and cycling was also apparent in that the charge/discharge induced large (~20 kPa) pressure swings.

A big thanks to Laura Helmers at Battery LabFactory Braunschweig/TU Braunschweig for the collaboration on this project!