Beyond thermal delay: Enthalpy-matched molten-salt architectures for chemistry-specific suppression of battery thermal runaway

Thermal runaway propagation (TRP) remains a critical safety challenge in high energy density lithium-ion battery modules, where conventional insulation materials limit heat transfer but provide minimal heat absorption. Here, we present an architectured molten-salt phase change material (PCM) heat shield that mitigates TRP via enthalpy buffering and structural design. Differential scanning calorimetry identified an optimal LiNO 3 –KCl composition (LK90: 90 wt% LiNO 3 , 10 wt% KCl) with a latent heat of ∼290 J g −1 and phase transition within the critical 130–190 °C safety window. Component-level tests show that thermal buffering depends on both PCM enthalpy and architecture. A sandwich PCM (SPCM) design reduced rear-side temperature by 46 °C compared to a monolithic plate of equal thickness and achieved delay performance comparable to silica aerogel. System-level cell-to-cell TRP experiments reveal strong chemistry dependence: no propagation to the adjacent cell was observed in high-reactivity NCA88 cells with a 6 mm SPCM and passive cooling, whereas a 3 mm SPCM was sufficient for LFP cells without auxiliary cooling. These results demonstrate that effective TRP mitigation requires matching enthalpy capacity and heat shield architecture to cell chemistry, establishing a co-design strategy for compact, multifunctional battery safety systems.