Utilizing heterogeneity of lignin to diminish supercooling of phase change material nano-capsules with high latent heat.

Fatty acids, in particular, are valued as phase change materials (PCMs) for their non-toxic, biodegradable nature and thermal stability. However, the leakage and supercooling issues during phase transitions limit their application. Microencapsulation of PCMs, while improving thermal response, often leads to supercooling, complicating temperature regulation and increasing energy consumption. Lignin, a renewable biomass resource, offers potential as a shell material for PCM encapsulation. To address compatibility issues between lignin and fatty acids, we modified lignin via acetylation and prepared hybrid acetylated lignin-stearic acid capsules (hyb-ACLSCs) using an anti-solvent method. Density functional theory (DFT) revealed that acetylated lignin exhibits stronger interactions with fatty acids, leading to higher particle yields (40.8 %), enhanced fatty acid loading (57.2 %) with a high phase-transition temperature of about 70 ℃, and improved phase transition behavior with a stable latent heat of about 250 J/g after 50 heating-cooling cycles. The heterogeneity of lignin facilitated multi-hierarchical self-assembly, preventing supercooling and enabling the formation of nano-sized phase change materials. The resulting hybrid capsules demonstrated high latent heat, negligible supercooling, and are highly promising for energy storage applications.