Preparation of coconut oil/aluminum nitride/expanded graphite composite phase change materials with high thermal conductivity and stable shape for thermal energy storage

• The novel SSPCM achieved a thermal conductivity of 2.985 W·m⁻¹·K⁻¹, a 1765% increase over pure coconut oil, significantly enhancing heat transfer rates. • The latent heat of the composite reached 83.67 J·g⁻¹, retaining 99% of the theoretical value, indicating high energy storage capacity. • The SSPCM exhibited excellent thermal stability and reliability over repeated thermal cycles, making it suitable for long-term thermal energy storage applications. • The use of renewable coconut oil and a simple vacuum impregnation method offers a cost-effective and scalable approach for advanced PCM composites.