Binder-Centered Design of Sustainable Liquid Metal Composites for Adaptive Soft Energy Storage Systems: A...

Gallium (Ga)-based liquid metal (LM) composites, particularly those based on eutectic gallium-indium (EGaIn) and related alloys, have emerged as a promising materials platform for soft and deformable energy storage owing to their unique combination of metallic conductivity, fluidic deformability, and adaptive interfaces. Despite rapid advances in LM-enabled devices, binders remain insufficiently understood and are still commonly regarded as passive structural components. Here, we present a comprehensive binder-centered perspective for LM composites, establishing the binder as a key regulator of electro-chemo-mechanical coupling, interfacial stability, transport behavior, and processability in soft energy systems. We show that tailored binder chemistries in Ga-based LM systems-including stretchable batteries, printable conductors, and soft electrochemical devices-govern LM droplet dispersion, suppress coalescence and leakage, and preserve conductive percolation under large deformation, while enabling room-temperature fabrication and printability through rheological regulation and interfacial wetting. Beyond mechanical confinement, emerging binder functionalities-including dynamic bonding, supramolecular interactions, ionically conductive networks, and reversible polymer architectures-enable self-healing interfaces, adaptive transport pathways, and robust adhesion in deformable devices. By integrating recent advances in stretchable batteries, flexible supercapacitors, printable electronics, and multifunctional soft energy systems, we establish a unified multiscale framework linking binder molecular design to device-level electrochemical and mechanical performance. We further discuss sustainability and manufacturing considerations, including recyclable polymer networks, low-temperature fabrication, and scalable processing strategies. Finally, we outline current challenges and future opportunities toward programmable binder systems with tunable viscoelasticity, interfacial reactivity, and adaptive functionality. This Review establishes binder-centered engineering as a key pathway for transforming LM composites from proof-of-concept materials into resilient, manufacturable, and multifunctional soft energy technologies for wearable, stretchable, and biointegrated electronics.