p‐Phenylenediamine‐Bridged Binder‐Electrolyte‐Unified Supramolecules for Versatile Lithium Secondary Batteries

Abstract The binder is an essential component in determining the structural integrity and ionic conductivity of Li‐ion battery electrodes. However, conventional binders are not sufficiently conductive and durable to be used with solid‐state electrolytes. In this study, a novel system is proposed for a Li secondary battery that combines the electrolyte and binder into a unified structure, which is achieved by employing para‐phenylenediamine (pPD) moiety to create supramolecular bridges between the parent binders. Due to a partial crosslinking effect and charge‐transferring structure of pPD, the proposed strategy improves both the ionic conductivity and mechanical properties by a factor of 6.4 (achieving a conductivity of 3.73 × 10⁻⁴ S cm⁻¹ for poly(ethylene oxide)‐pPD) and 4.4 (reaching a mechanical strength of 151.4 kPa for poly(acrylic acid)‐pPD) compared to those of conventional parent binders. As a result, when the supramolecules of pPD are used as a binder in a pouch cell with a lean electrolyte loading of 2 µL mAh⁻¹, a capacity retention of 80.2% is achieved even after 300 cycles. Furthermore, when it is utilized as a solid‐state electrolyte, an average Coulombic efficiency of 99.7% and capacity retention of 98.7% are attained under operations at 50 °C without external pressure or a pre‐aging process.