Graphene/temperature-responsive microsphere/polyurea composite coatings with high thermal conductivity and ultrahigh thermal switching ratio for intelligent thermal management

As high-power electronics and battery systems trend toward higher integration, thermal management now requires both efficient heat dissipation and thermal isolation during runaway. Conventional materials, with fixed thermal conductivity, fail to balance these contradictory demands. Herein, a graphene/temperature-responsive microsphere/polyurea composite film was fabricated via blade coating, integrating high thermal conductivity, an ultrahigh thermal switching ratio, and robust coating performance. Systematic investigations revealed that the G10-PU composite (10 wt% graphene) achieved optimal filler dispersion and network integrity. It exhibited an initial thermal conductivity of 5.812 W/(m·K), which plummeted to 0.309 W/(m·K) at 160–180 °C, yielding an ultrahigh thermal switching ratio of 18.8. The G10-PU coating also demonstrated excellent adhesion (5.41 MPa), exceptional wear resistance (0.0121 g mass loss after 1050 Taber cycles), and strong salt spray resistance. Practical validation showed that the heating rate of a coated iron box decreased from 51.3 °C/min to 7.2 °C/min post-expansion, with the temperature difference versus an uncoated box widening from 13.5 °C to 32.7 °C. This work presents a novel material solution for the intelligent thermal management of high-power devices, synergizing efficient heat dissipation, active thermal protection, and long-term durability.