A green, robust, and versatile BN nanosheet unidirectional aerogel encapsulated phase change material for effective thermal management of electronics and solar-thermoelectric conversion

Abstract

Thermal harvesting and storage using phase change materials (PCMs) plays a critical role in thermal management and solar energy utilization. However, the intrinsically low thermal conductivity, solid–liquid leakage, and poor solar-thermoelectric conversion capacity are significant challenges for applications of PCMs in these fields. Herein, we report a green, robust, and versatile carboxymethyl cellulose/boron nitride nanosheet unidirectional aerogel (CBNA) with extraordinary mechanical properties to encapsulate lauric acid (LA). The obtained LA@CBNA composite PCM (CPCM) exhibits an ultrahigh latent heat of 190.4 J g⁻¹, which is up to 98.1% that of LA. Compared with LA, the thermal conductivity of LA@CBNA is significantly increased from 0.2011 to 1.1425 W m⁻¹ K⁻¹. The preeminent thermophysical properties endow this CPCM with an extraordinary thermal management performance in electronic devices. The thermal management tests show that the temperature of a working chip can be reduced by 36.1 °C at 2.5 W. The addition of a small trace of graphene (10% of boron nitride nanosheets) can endow the CPCM with an excellent solar-thermal conversion efficiency of 88.89%, while the thermal conductivity is further improved to 1.2856 W m⁻¹ K⁻¹. Meanwhile, a solar-thermal energy conversion and storage system integrated with a thermoelectric generator can achieve 54.56% solar-thermoelectric conversion efficiency.