Influence of the Drying Temperature on the Performance and Binder Distribution of Sulfurized Poly(acrylonitrile) Cathodes

Abstract

The drying of electrodes during the manufacturing process strongly affects both the cell performance and production costs of lithium-sulfur (Li-S) batteries. Herein, we present a detailed study on the effect of temperature during the drying process on the performance and binder distribution of sulfurized poly(acrylonitrile) (SPAN) based electrodes using poly(vinylidene fluoride) (PVdF) or poly(acrylic acid) (PAA) as the binder. The electrochemical performance of the PVdF- and PAA-based cathode coatings, which were dried at three different temperatures (30 °C, 60 °C and 90 °C), is analyzed by cycling against lithium metal and utilizing reference-assisted impedance spectroscopy. Time-of-flight secondary ion mass spectrometry (ToF SIMS) is applied on both the surface and the cross-section of the electrodes to determine the binder distribution. Contrary to the PAA-based cathodes, PVdF-based electrodes exhibit binder migration to the electrode surface at elevated coating drying temperatures. The enrichment of PVdF on the surface leads to an increase in the charge transfer resistance and thereby reduces the rate capability.