Bridging the Gap Between Pouch and Coin Cell Electrochemical Performance in Lithium Metal Batteries

Abstract

In lithium metal battery research, coin cells (CC) are the most widely used laboratory instrument in academic settings. However, results thus obtained often don’t translate into pouch cell (PC) performance, which is regarded as a more reliable indicator for commercial relevance. Using both experimental and computational results, we show here that the root cause lies in the pressure distribution in these two cell formats. CCs suffer from a severe pressure inhomogeneity due to the geometry of the wave spring used to apply pressure to the cell stack. Replacing the wave spring with an elastic rubber disc applies a laterally uniform force to the cell stack, resulting in a homogeneous pressure distribution. Li||Cu half cells and Cu||LiNi0.5Mn0.3Co0.2O2 anode-free full cells using the updated structure show performance metrics on par with chemically identical PCs while traditional CCs underperform. Our solution to this common problem retains the quick, easy fabrication of CCs while producing results comparable to the PC-level.