A Systematic Study of the Impact of Charge Capacity and Current Density on the Reported Coulombic Efficiency of Lithium-Copper Batteries

Coulombic Efficiency is a characterization used by researchers to assess cyclability and practicality of new and/or improved batteries. Mathematically, coulombic efficiency is the ratio of the total charge extracted from the battery to the total charge input into the battery over a full cycle. This characterization thus describes the charge efficiency by which electrons are transferred in batteries and can thus be used to effectively indicate battery performance.

However, different researchers use different charge capacities and current densities in their battery cycling systems to assess coulombic efficiency. Consequently, it is important to investigate whether or not the parameters chosen to cycle batteries will influence their reported coulombic efficiency.

This poster will present the findings from a systematic study where lithium-copper coin cells of identical compositions are cycled under varying charge capacities and current densities and their coulombic efficiencies assessed. The coin-cells used for this study are assembled using commercial grade celgard battery separators, with the aim that this study could be used to improve the assessment of practical commercial batteries which incorporate these types of separator. Additionally, both carbonate and ether electrolytes were incorporated in the assembly of the coin-cells used in the study, so that the findings may be applied to a larger range of battery compositions.

The findings of this study indicates that the choice of current density and charging capacity in the cycling of batteries of the same composition does in fact affect reported coulombic efficiency. Consequently, a standard charge capacity and current density should be used by researchers to assess reported coulombic efficiency, so that findings from different studies may be fairly compared without results being skewed based on individual choices of current density and charge capacity.