Bifunctional sandwich structure of vertically-oriented graphenes and boron nitride nanosheets for thermal management of LEDs and Li-ion battery

Highlights: • Bifunctional sandwich structure is proposed for efficient thermal management. • Vertically-oriented graphenes build thermal expressways for heat transfer. • Thermal and electrical property can be regulated by manipulating the morphology. • Heating rate of sandwich structure is ∼4 times higher than that of pure polymer. • Practical thermal management of Li-ion battery and LEDs is demonstrated. -- Abstract: Efficient thermal management is a critical issue in the microelectronics. This work proposes a bifunctional sandwich structure composing of vertically-oriented graphenes (VGs) and boron nitride nanosheets (BNNSs) for thermal management of LEDs and lithium-ion (Li-ion) battery. VGs exploit the ultrahigh in-plane thermal conductivity of graphene for heat dissipation, meanwhile BNNSs suppress electron transfer for electrical insulation. Thermal and electrical property can be regulated by manipulating the morphology, which is further interpreted by Maxwell-Garnett's effective medium approximation and finite element simulation. Especially, sandwich structure achieves superior thermal conductivity (∼4.03 W m⁻¹ K⁻¹, ∼19 times higher than that of polymer) and good electrical insulation (>10⁷ Ω cm). Moreover, it exhibits a good thermal stability (up to 100 °C), extending the glass transition temperature to 119.7 °C. Infrared thermal imaging technology suggests that heating-up rate of composite is over ∼4 times higher than that of polymer. During the practical thermal management, sandwich structure can effectively decrease the operating temperature of LEDs and Li-ion battery by ∼16.6 °C and ∼10 °C, respectively. As such, capacity retention of battery is remarkably improved by ∼22.2% during the charging/discharging process. This strategy may open a new avenue of designing sandwich structure for efficient thermal management.