Dual-Function Design of Anisotropic Nanocellulose Sponge for Thermal Management and PCM Encapsulation

This study demonstrates a strategy for fabricating anisotropic cellulose nanofibril (CNF) sponges with precisely tailored microstructures via directional freezing. By decoupling the effects of solid content and freezing temperature, we reveal their distinct and synergistic roles in governing the final microstructure: solid content primarily dictates the framework density and porosity, while freezing temperature strongly governs the pore dimensions. This mechanistic understanding enables the rational and orthogonal optimization of multifunctional performance, achieving both high thermal insulation (axial: 46.1 mW m–1 K–1, radial: 42.4 mW m–1 K–1) and superior phase change material encapsulation (98.49% loading efficiency, 1.96% leakage rate). The resulting phase change composite material exhibits a high enthalpy of 186.2 J g–1, demonstrating excellent thermal energy storage capacity. This work provides a design blueprint for developing sustainable, high-performance thermal management materials from renewable nanocellulose.