Concrete Soft‐Gel Electrodes with a Unified Instability Criterion for Sustainable Aqueous Batteries

Electrochemical energy storage has long been constrained by the structural instability of solid electrodes and the costly design of liquid-based systems. Here, we report a transformative concrete soft-gel electrode that reconciles mechanical robustness with interfacial fluidity, enabling improved stability in aqueous full batteries. Critically, we uncover the fundamental origin of electrode detachment and propose the Ji-Ran instability criterion, which unifies osmotic pressure, electrokinetic shear, and elastic-adhesive balance into a single quantitative framework. Inspired by structural concrete, the incorporation of BaTiO₃ particles reinforces the soft-gel network, raising elastic modulus, adhesion energy, and interfacial integrity. The resulting full batteries deliver high Coulombic efficiency, mitigated capacity decay, and facile recyclability via water-assisted disassembly. This work establishes a generalizable paradigm for concrete soft-gel electrodes and opens a pathway to sustainable, long-lasting aqueous batteries.