Multifunctional flexible phase change materials: From material design to thermal energy storage in renewable scenarios

Flexible phase change materials (FPCMs) have been widely recognized for latent heat storage and mechanical adaptability in advanced thermal energy storage applications. Nevertheless, the practical implementation of FPCMs continues to face substantial limitations arising from thermal leakage, and insufficient mechanical resilience under operational conditions. In this review, recent progress in the structural design and synthetic engineering of FPCMs is systematically examined, with particular emphasis placed on the development of advanced fabrication strategies including porous adsorption, spinning, encapsulation, molecular engineering, and 3D printing. The effectiveness of these approaches in improving thermal conductivity, mechanical integrity, and phase transition stability is comparatively analyzed. Moreover, the potential of FPCMs for multifunctional integration is discussed, focusing on application domains such as temperature regulation, healthcare, energy conversion, shape memory, and stealth technologies, highlighting opportunities for cross-disciplinary deployment. In the context of growing demand for flexible and distributed energy solutions, the ability to buffer transient thermal fluctuations and enable localized thermal management is further emphasized. By identifying unresolved technical bottlenecks and analyzing future research priorities from both material-oriented and application-driven perspectives, this review is intended to offer a forward-looking framework for the advancement of multifunctional thermal energy storage technologies based on flexible phase change systems.