Intrinsically flame retardant composite phase change materials with epoxy resin melamine phosphate derivative skeleton for battery thermal safety

One-pot synthesis has coupled epoxy curing, phase matrix and intrinsic flame retardancy. • Phosphoric acid is benefit for curing, framework crosslinking and flame retardancy. • Melamine is crosslinked P N synergistic flame-retardant skeleton among composite. • Flame-retardant skeleton and expandable graphite form continuous conductive heat pathways. • This composite enables cooling and prevent localized thermal-abuse in battery module. Organic phase-change materials (PCMs) are pivotal for passive battery thermal management, but their deployment is hindered by intrinsic flammability, molten leakage, and low thermal conductivity. The conventional flame-retardant CPCMs typically suffer from a functionally segregated architecture, while the PCM, support matrix, flame retardants, and fillers are physically blended. This often leads to compromised interfacial compatibility and trade-offs among thermal storage, mechanical stability, and fire safety. Herein, we have proposed a novel intrinsically flame-retardant CPCM via a one-pot, structurally integrated designation. Phosphoric acid serves a multifunctional role, replacing the conventional curing agent to initiate epoxy ring-opening, facilitating the covalent tethering of PEG2000, and constructing phosphorus-rich networks. Subsequent incorporation of Epoxy A, phosphate and melamine (APM) occurs fireproof framework, enabling P N synergistic flame retardancy. Expandable graphite is integrated to establish efficient thermal highways. This design ensures that the APM framework concurrently addresses PEG immobilization, structural reinforcement and flame-retardant properties. The optimized composite of PAPM3 with 12.34% MA exhibits exceptional durability, retaining 99.54% of its mass after aging at 150 °C for 5 h. Its thermal conductivity reaches to 1.153 W·m −1 ·K −1 , representing a 33.3% enhancement over controls. Benefiting from the condensed-phase charring and gas-phase dilution effects, PAPM3 achieves a UL94 V-0 rating and an LOI of 26.10%, with a 37.18% reduction in PHRR compared to PABM. In battery module tests, PAPM3 maintains the peak temperature below 48.08 °C and the maximum temperature difference within 7.77 °C under 3C discharge. Especially, under simulated localized thermal abusing condition, PAPM3 mitigates localized heat accumulation and delays thermal propagation. This research provides an efficient strategy to harmonize high temperature stability and fire proof safety for advanced battery thermal management systems.