Ion gels consisting of room-temperature ionic liquids and polymer gelators are considered attractive solid-state electrolyte platforms for functional electrochemical applications due to their tunable electrochemical/mechanical properties, nonvolatility even in a vacuum, and compatibility with various solution processes.

In principle, the design of block copolymers for ion gels should include both IL-compatible and IL-incompatible blocks. For example, representative ABA triblock copolymers, such as polystyrene-block-poly(ethylene oxide)- block-polystyrene (PS-b-PEO-b-PS, SOS) and PS-block-poly(methyl methacrylate)- block-PS (PS-b-PMMA-b-PS, SMS), are composed of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMI] [TFSI])-insoluble short PS end blocks and [EMI][TFSI]-soluble midblock of PEO or PMMA. When properly selected triblock copolymers and ILs are blended, IL-insoluble parts such as PS agglomerate into spheres with minimal surface areas in order to decrease the enthalpic penalty. This process improves the mechanical resilience of the gel. On the other hand, IL-soluble midblocks swollen with ILs provide ionic conductive channels for electrochemical reactions. Conventional physically crosslinked ion gels exhibited moderate mechanical robustness (elastic modulus of a few kPa) with good ionic conductivity (1–10 mS cm−1 ) at room temperature. One important requirement for achieving these values is that the IL-insoluble spheres should be directly connected by the midblocks, to form a network structure with a small portion of block copolymers (10–20 wt%). In this context, ABC triblock copolymers with IL-insoluble A and C blocks are also suitable, but AB diblock copolymers cannot serve as an efficient polymer host. Without sacrificing ionic conductivity, the mechanical modulus can be enhanced by selective chemical crosslinking of IL-insoluble blocks, but this complicates copolymer synthesis.

In this regard, the random copolymer strategy that form random geometry of soluble/insoluble parts is a simple but effective approach to obtain versatile gel electrolytes for electrochemical applications.