High Latent‐Heat, Soft yet Robust Crystalline Salogels via Dual‐Network Design and Solvent Engineering

Solid-liquid phase change materials (PCMs) hold great promise for addressing challenges in thermal energy storage and temperature management. Yet, they suffer from severe issues of melting leakage and crystalline rigidity in practical applications. Here, an approach is proposed to achieve flexible, high-latent heat PCMs with intrinsic softness and toughness in the crystalline state through the combination of dual polymer networks and inorganic salt hydrates. This strategy constructs salogels via in situ polymerization, leveraging strong polymer-ion-water interactions and introducing excess water to form a solvated polymer network embedded within crystalline salt hydrates. The prepared crystalline salogels demonstrated high energy density (∆H_m, 179-209 J g^-1) with ultra-soft (E, 0.05-5 MPa) yet strong (σ_b, 1-3 MPa) and tough (Γ, 2-6 MJ m^-3) mechanical performance, along with low contact thermal resistance (R_c = 0.03 cm² K W^-1). The fabricated thermal management devices present both phase-change-driven heat absorption and hygroscopicity-driven moisture absorption, enabling highly efficient thermal regulation, with a 10 °C reduction observed in a lab suit fitted with a 25 × 15 × 0.5 cm³ salogel patch over 1 h compared to one without the patch. This work provides guidelines for designing crystalline-flexible yet robust salogels from cost-effective salt hydrates for advanced thermal management applications.