The latent heat storage of PCMs has gained increasing attention in the solar energy application field due to their high thermal energy storage density. However, the lack of energy conversion ability of the organic PCMs results in the low utilization efficiency of solar energy. Herein, we report a novel PEG/Ti₃C₂T_x layered composite PCM with superior photothermal storage capability, which consists of stacked Ti₃C₂T_x nanosheets and PEG filled within the spaces between the flakes. The resulting composites exhibited a strong absorption capacity for electromagnetic waves at the UV-Vis-NIR region. Notably, there are two enhanced absorption bands at the visible and near-infrared regions due to the localized surface plasmon resonance (LSPR) effect of the Ti₃C₂T_x nanosheets, which endows the composite PCM with excellent photo-to-thermal storage efficiencies (up to 94.5%) under actual solar light irradiation. In addition, the composite PCM also possesses a high energy storage density and form-stable property before and after the phase transition. These results indicate that the synthesized composite presents superior comprehensive properties suitable for solar energy storage applications.

In addition to their lower thermal conductivity, leakage during the melting phase and poor energy conversion ability, the fragility of phase change materials is an issue that is worth addressing to widen their application scope. Herein, we propose a low-cost and facile method to develop a flexible electro-driven phase change composite with unidirectional shape memory effects and motion detection properties. The phase change composite is composed of carbonized cotton cloth as a conductive supporting structure, paraffin wax as a latent heat storage material and thermoplastic polyurethane as a protective layer. The woven framework of carbonized cloth endowed the paraffin wax with the ability to generate Joule heating at a lower voltage due to its high electrical conductivity (374 S m⁻¹). The multifunctional layer of thermoplastic polyurethane wrapped the carbon cloth/paraffin and greatly improved the form-stability, flexibility and mechanical strength of the composite. Shape fixity and shape recovery properties of the composite were achieved by the synergic effect of the phase transition in paraffin and the elasticity of thermoplastic polyurethane. Moreover, the presence of conductive carbon cloth enabled the composite to achieve good electrothermal conversion efficiency and motion sensing properties. The fabricated flexible phase change composite may serve as a smart material for versatile thermal management applications.

The development of thermal energy storage materials is essential to enhance the energy utilization. In particular, form-stable composite phase change materials (CPCMs) have attracted considerable interest because of their outstanding thermal properties and shape stability. However, their energy storage capacity decreases due to the fact that the filling of organic phase change components is limited by the pore diameter and void ratio of inorganic aerogels while following the common impregnation method. Herein, we present a simple and effective approach for fabricating form-stable CPCMs with in situ polyethylene glycol (PEG) filling in the 3D graphene oxide network side-to-side cross-linked by Ca²⁺. The filler content of PEG is maximized to 99.5 wt% because the side-to-side cross-linking mode greatly widens the void ratio of the 3D network. The prepared CPCMs exhibit high energy storage density as their melting enthalpy reaches 218.9 J g⁻¹, which is close to that of pure PEG6000; their thermal conductivity is enhanced by 63.0–87.7% compared to that of pure PEG. Meanwhile, the prepared materials have excellent thermal stability and shape stability.

This review presents the latest advances in energy conversion phase change materials and their electron-triggered mechanism of energy conversion.