Poly(2‐ethyl‐2‐oxazoline) as a Gel Additive to Improve the Performance of Sulfur Cathodes in Lithium‐Sulfur Batteries

Arginine as a Multifunctional Additive for High Performance S-Cathode

Advancement of sulfur (S) cathode of lithium-sulfur (Li-S) batteries is hindered by issues such as insulating nature of sulfur, sluggish redox kinetics, polysulfide dissolution and shuttling. To address these issues, we initiate a study on applying an important amino acid of protein, arginine (Arg), as a functional additive into S cathode. Based on our simulation study, the positively charged Arg facilitates strong interactions with polysulfides. The experimental results indicate that the interaction enable capability of trapping polysulfides within the S cathode, responsible for reducing shuttle effects. Furthermore, the positively charged Arg also promotes efficient ion diffusion and polysulfides conversion. The new findings include that, with addition of only 1 wt % Arg, the resultant cathode demonstrates effectively enhanced electrolyte wettability, polysulfide adsorption and redox kinetics, leading to enhanced rate performance and long-term cycling stability. This study highlights the great potential of amino acids being able to act as effective functional bio-additives in S cathode, paving a new way to high-performance and sustainable energy storage solutions.

Poly(Ethylene Glycol-block-2-Ethyl-2-Oxazoline) as Cathode Binder in Lithium-Sulfur Batteries

Functional binders constitute a strategy to overcome several challenges that lithium-sulfur (Li-S) batteries are facing due to soluble reaction intermediates in the positive electrode. Poly (ethylene oxide) (PEO) and poly (vinylpyrrolidone) (PVP) are in this context a previously well-explored binder mixture. Their ether and amide groups possess affinity to the dissolved sulfur species, which enhances the sulfur utilization and mitigates the parasitic redox shuttle. However, the immiscibility of PEO and PVP is a concern for electrode stability. Copolymers comprising ether and amide groups are thus promising candidates to improve the stability the system. Here, a series of poly (ethylene glycol-block-2-ethyl-2-oxazoline) with various block lengths is synthesized and explored as binders in S/C composite electrodes in Li-S cells. While the electrochemical analyses show that although the sulfur utilization and capacity retention of the tested electrodes are similar, the integrity of the as-cast electrodes can play a key role for power capability.