How Reliable is Coin Cell-Based Ranking of Li Anode Coulombic Efficiency?

Lithium (Li) metal Coulombic efficiency (CE) benchmarking has historically been conducted in coin cells. Recently, journals have required detailed reporting of factors like cycling conditions and electrolyte composition, which influence CE. However, variability in cell assembly is often overlooked. This study investigates how representative parameters (crimping load, spacer count, spring type) impact internal cell mechanics, CE accuracy, and comparisons across electrolytes. Internal pressure, both during and after crimping, varied (~100–170 kPa steady-state) depending on construction, producing a range in measured CE especially when CE is low. When comparing different but self-consistent cell construction methods applied to a set of electrolytes with diverse CE, absolute CE values exhibited notable variation, but CE rankings were generally robust. Literature CE benchmarks are best reproduced when allowing cell construction methods to vary between electrolytes, highlighting a major potential source of variance in reported data. Implications for best reporting practices are discussed.