The effect of the blending procedure on the C−S suspension and therefore, on the Li−S battery performance is investigated. By comparing a common laboratory blender with a high shear mixing device, the higher shear forces result in a lower porosity and improved homogeneity of the electrode leading to enhanced cycle life, especially in multi-layered pouch cells under lean electrolyte conditions.

Abstract

The lithium sulfur (Li−S) cell chemistry is promising due to the high specific capacity of its active materials resulting in high specific energy cells. In the past years, the number of publications on practical prototype cells have increased, already reporting high specific energies over 400 Wh kg⁻¹ with low electrolyte-to-sulfur (E : S) ratios. To enable the complex conversion chemistry at low E : S ratios, the cathode porosity adaption is crucial and depends for example on the suspension blending procedure. There are several methods and devices to prepare suspensions for battery electrodes, e. g. dissolver and planetary mixers. In this study, a standard laboratory blender with low shear forces (EL1) is compared with a high shear mixer (HSM) for preparing porous carbon-sulfur suspensions in a relevant scale. In this study, the influence of the slurry preparation on the final performance is investigated by coating via slot die on a roll-to-roll device to produce carbon-sulfur-cathodes. The electrodes are characterized via optical and mechanical measurements. Electrochemical analysis is conducted using coin cells for pre-evaluation as well as multi-layered pouch cells with reduced electrolyte volume (3.0 μl mg(S)⁻¹). It could be shown that the HSM enables increased binder dispersion and enhanced density leading to improved cycle life.