(Digital Presentation) Impact of the Sulfur Loading Method on the Morphological and Electrochemical Properties of Additive-Free Cathodes for Li-S Batteries Prepared By Composite Electroforming
Authors: El Mofid Wassima , Soergel Timo 
Published: November 2022

In order to produce conductive agent and binder free electrodes for batteries with a synergistic optimization of the mechanical and electrical bonding of the active material, „composite electroforming“ synthesis method has been developed in Aalen University as a novel approach for additives-free battery electrodes production [1-6]. The aim throughout this method is to achieve high-performance accumulators with a focus on a high gravimetric and volumetric power and energy density. The aspects of energy efficiency, cycleability and safety are also considered, especially that the composite electroforming process allows environmentally friendly and resource-saving production of electrodes.

The novel electrodes for Li-S batteries proposed in the present work are composed of Ni matrix which also acts as current collector, and sulfur loaded on etched Al alloy carrier particles AlSi10Mg.

The sulfur loading which is a key step of our cathodes manufacturing was conducted using two different ways; by spin coating in melted sulfur at 160°C or by electrochemical loading using potasium sulfide based aqueous electrolyte (K2S)aq and applying a current density of 0,5 A/dm² at room temperature.

SEM and elemental mapping measurements of the sulfur spin coated cathode and that with electrochemically loaded sulfur showed a big difference in terms of the sulfur distribution and the surface morphology between the two cathodes.

Electrochemical characterization of the sulfur cathodes was then conducted, mainly galvanostatic cycling (GC), by imposing a fixed current to the cell between the two potential limits 1.7 and 2.8 V vs. Li+/Li. The rate, namely the current density applied to the electrode during cycling, was calculated based on the loaded sulfur mass in the tested electrode and the theoretical capacity of sulfur (1673 mAh g-1). By calculating the ratio of the active to the total loaded sulfur, the sulfur accessibilty for the electrochemically loaded cathode was five times higher than the spin coated cathode regardless of holding almost the same sulfur loading (3.9 mg/cm² and 3.96 mg/cm² respectivelly). GC at C/10 rate proved that the two cathodes delivered different values of specific capacity, capacity retention with cycling and coulombic efficiency that are significantly improved for the electrochemically loaded cathode than the spin coated one. Finally, In order to characterize the response of the sulfur electrochemically loaded cathode to different C rates, rate capability test was carried out and illustrated that the tested cathode was able to regain almost its entire initial capacity when back to the initial C rate after applying high C rates.

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