Dual-Temperature Composite Phase Change Material Adapted for Wide-Temperature-Range Applications in Battery Thermal Management.

To address the challenge of efficient thermal management for lithium-ion batteries across a wide temperature range, we developed a novel dual-temperature composite phase change material (CPCM). The CPCM, constructed with an expanded graphite matrix incorporating paraffin (∼45 °C) and potassium alum (∼90 °C), achieves two distinct phase change platforms and a high total latent heat of 211.4 J/g. Its thermal conductivity was significantly enhanced to 2.53 W/(m·K). In practical battery tests, the CPCM demonstrated superior performance: it reduced the maximum temperature by ∼10 °C across 0.2 to 1C discharge rates and maintained excellent temperature uniformity (Δ < 2.2 °C). Crucially, under thermal runaway conditions, it lowered the peak temperature of adjacent cells by ∼134 °C, effectively delaying hazardous heat propagation. This work provides a material solution that synergistically combines efficient cooling at normal operating temperatures with robust thermal barrier functionality under extreme conditions.