Binder-conductive additive design for practical sulfurized polyacrylonitrile lithium–sulfur batteries

Kurzfassung

Lithium–sulfur batteries are widely regarded as promising next-generation energy storage owing to their high theoretical energy density and the abundance of sulfur. Sulfurized polyacrylonitrile (SPAN) has emerged as a compelling active material, retaining the advantages of sulfur while mitigating several of its challenges. However, due to SPANs low active material content, optimizing electrode density becomes essential to minimize electrolyte content and maximize energy density at cell level. Calendering SPAN electrodes triggers a pronounced spring-back effect that compromises conductive additive percolation and electrochemical performance. This study evaluates the mechanical and electrochemical properties of SPAN electrodes with various binders and conductive additives, focusing on their performance before and after calendering. Rheological investigations and tensile tests revealed comparable behaviors between the acrylonitrile multi-copolymer binder LA133 and carboxymethyl cellulose (CMC)/styrene butadiene rubber (SBR). Resistivity measurements demonstrated superior conductivity with multi-walled carbon nanotubes (MWCNT), especially in calendered state. Electrochemical impedance spectroscopy of symmetrical cells highlighted the material morphology impact, showing enhanced stability in systems employing LA133 and MWCNT across calendering degrees. Furthermore, the optimized formulation enabled rate capabilities up to 3 C with approximately 75% capacity retention in calendered state and long-term cycling over 700 cycles in coin cells. Multi-layered pouch cells exhibited 90% capacity retention after 100 cycles, underscoring the practical viability of SPAN-based cell design with advanced electrode formulations.