Thermally triggered tunable-thermal-conductivity phase-change composites for lithium-ion battery thermal management and runaway mitigation

As high-energy-density power sources for electric vehicles and grid storage, lithium-ion batteries demand stringent thermal safety standards. However, thermal accumulation during fast charging and propagating thermal runaway (TR) cascades remain critical bottlenecks, where conventional phase change materials (PCMs) are difficult to balance the contradiction between heat dissipation and emergency thermal blocking. To address thermal accumulation and prevent TR propagation in lithium-ion battery modules, a tunable-thermal-conductivity phase change material (MF@MXene/PA) was synthesized. The MF@MXene/PA integrates paraffin (PA) within an MXene-reinforced melamine-formaldehyde resin (MF) porous matrix synthesized via hydrogen bond-directed in-situ self-assembly. Structural analyses confirmed that the incorporation of MXene could regulate the porous microstructure, and the optimal latent heat (157.01 J/g) and thermal conductivity (0.3754 W/m·K) were obtained at 2 mg/mL MXene. The porous structure in the MXene-MF framework provides strong capillary forces to adsorb PA. Meanwhile, under the synergistic effect of high temperature and air, the thermal conductivity of self-extinguishing MF@MXene reduced by 66.1 %, showed the thermal-triggered tunable thermal conductivity. In thermal management tests, the composite lowered peak temperatures by 11.2–23.1 % during 1C/2C cycling and maintained thermal homogeneity (<3 °C variation) by enhancing thermal conductivity. During the TR propagation, the composites delayed adjacent batteries ignition by 857 s and extended propagation intervals by 205–304 %, attributable to heat absorption of phase change and synergistic insulation from MXene-derived TiO₂. The dual functionality (heat dissipation and TR suppression), combined with self-extinguishing behavior, makes MF@MXene/PA a promising candidate for a safer battery thermal management system.