The Sustainable Potential of Single-Ion Conducting Polymers

Abstract

Energy storage technologies are critical for sustainable development, with electrolyte materials playing a decisive role in performance and safety. Single-ion conducting polymers (SICPs) represent a distinct materials class characterized by selective ion transport through immobilized ionic groups. While their potential for battery applications is recognized, an analysis of their sustainability implications and pathways to practical implementation has been lacking. This work demonstrates how strategic design of SICPs can contribute to sustainable energy storage through both materials' development and device integration. Recent advances in lithium borate-based systems and CO₂-derived polycarbonate architectures have achieved ionic conductivities exceeding 10^-4 S cm^-1 at room temperature through scalable synthesis routes. In lithium-metal batteries, their high transference numbers and viscoelastic properties enable stable cycling with industrial-relevant cathode loadings, while as electrode binders, they enable aqueous processing and enhanced interfacial stability. Their versatility extends to sustainable chemistries, including sodium and zinc systems. Analysis reveals that while SICPs can enhance energy storage sustainability through improved performance, processability, and potential recyclability, opportunities remain in investigating end-of-life management. This work highlights frameworks for advancing SICP sustainability while maintaining the performance requirements for practical implementation in next-generation energy storage.

Keywords: batteries; energy storage; ionic monomers; polycarbonates; single‐ion conducting polymers.

Figure 1

a) Schematic representation of SICP architectures showing anionic groups (blue) in pendant (more common) and backbone‐integrated positions (e.g., ref. [69]). This fundamental design enables sustainable materials development opportunities evaluated in this work. b,c) Current state‐of‐knowledge for enhanced SICP Li‐ion conductivity (σ), compiled from recent reviews[ ⁹ , ⁷⁰ ] and developments in delocalized anions,^{[ 13} , ^{37 ]} backbone chemistry,^{[ 16} , ^{17 ]} nanostructured block copolymers,^{[ 18 ]} side‐chain engineering, ^[19b] additives^{[ 20 ]} and composites.^{[ 28 ]}

Figure 2

a) Scalable vinyl monomers commercially available for C—C backbone SICP synthesis. b) Alternative approach to potentially sustainable polycarbonate backbones utilizing CO₂/epoxide ROCOP and cyclic carbonate ROP, followed by postpolymerization ionic functionalization, alongside polycondensation of salt‐modified diols with dimethyl carbonate.[ ³⁴ , ³⁷ ] c) Effective salt introduction strategies: thiol‐ene postpolymerization functionalization,^{[ 39 ]} ionic crosslinking^{[ 41 ]} and direct polymerization of salt‐based monomers.[ ³⁷ , ⁴⁴ ]

Figure 3

Reprocessing and recycling of SICPs utilizing reversible dynamic covalent chemistry, which has been validated for furan‐maleimide Diels–Alder/retro‐Diels–Alder equilibrium.^{[ 46 ]}

Figure 4

a) Processability of SICPs into thin films, highlighting their potential for scalable manufacturing. b) Key roles in battery energy storage, including the formation of SEIs. c) Enhanced mechanical properties of SICPs compared to dual‐ion conductors, with relative toughness values derived from stress–strain curves.[ ¹⁸ , ⁶¹ ] d) Adhesive performance of SICPs, demonstrated through nanoindentation^{[ 60 ]} and peel tests^{[ 62 ]} (relative values given). These properties contribute to the sustainability of SICPs by improving battery performance and enabling solvent‐free/aqueous electrode processing and recycling practices.