Novel strategies and supporting materials applied to shape-stabilize organic phase change materials for thermal energy storage–A review

Phase change materials (PCMs) have been extensively characterized as constant temperature latent heat thermal energy storage (TES) materials. Nevertheless, the widespread utilization of PCMs is limited due to the flow of liquid PCMs during melting, phase separation, supercooling and low heat transfer rate. In order to overcome these inherent problems and to improve thermo-physical properties, the confinement of PCMs at the nanoscale has been identified as a versatile strategy, which ensures the encapsulation of PCMs in much smaller nano-containers. Such strategies including core–shell, longitudinal, interfacial and porous confinement have been widely presented in recent years to efficiently encapsulate PCMs in nanospaces and are presenting attractive ways to enhance thermal performance. This review summarizes the recent advancement and critical issues of nanoconfinement technologies of PCMs from the point of view of material design. In addition, the potential applications of nanoconfined PCMs in diverse fields, including energy conversion and storage, thermal rectification and temperature controlled drug delivery systems, are presented in detail. Finally, the major drawbacks associated with nanoconfined PCMs and their prospective solutions are also provided.

Nanoconfined phase change materials for thermal energy applications

Macroscopically three-dimensional (3D) structural materials with tailorable properties are ideal alternatives for the fabrication of composites. High-performance composite phase change materials (PCMs), as advanced energy storage materials, have been significantly developed in recent years owing to the progress in multifunctional 3D structural materials, including metallic foams, carbon foams, graphene aerogels and porous scaffolds. This review focuses on the role of 3D structural materials in organic solid–liquid composite PCMs and the relationships between their architectures and properties (shape stability and thermal conductivity). In addition, recent progress in energy conversion using composite PCMs is included, which provides an insight into potential applications in advanced energy conversion devices and systems. Finally, future directions and challenges in the development of high-performance organic composite PCMs are presented.

High-performance composite phase change materials for energy conversion based on macroscopically three-dimensional structural materials

Thermal energy harvesting technologies based on composite phase change materials (PCMs) are capable of harvesting tremendous amounts of thermal energy via isothermal phase transitions, thus showing enormous potential in the design of state-of-the-art renewable energy infrastructure. Great progress has been recently made in terms of enhancing the thermal energy storage capability, transfer rate, conversion efficiency and utilization of composite PCMs. Although there are some recent reviews on composite PCMs, they are mainly concentrated on the thermal transfer enhancement and conventional utilization of PCMs. There are few systematic reviews concerning optimization strategies of PCM for thermal energy conversion. In particular, advanced multifunctional utilization of PCMs is still in its infancy. Herein, we systematically summarize the optimization strategies and mechanisms of recently reported composite PCMs for thermal energy storage, thermal transfer, energy conversion (solar-to-thermal, electro-to-thermal and magnetic-to-thermal conversion) and advanced utilization (fluorescence emission, infrared stealth technologies, drug release systems, thermotherapy and thermal protection), including some novel supporting materials (BN nanosheets and metal organic frameworks (MOFs)). Simultaneously, we provide in-depth and constructive insights into the correlations between the structural optimization strategies and thermal performances of composite PCMs. Finally, future research trends, alternative strategies and prospects are also highlighted according to up-to-date optimization strategies.

Optimization strategies of composite phase change materials for thermal energy storage, transfer, conversion and utilization

Phase change materials (PCMs) can alleviate concerns over energy to some extent by reversibly storing a tremendous amount of renewable and sustainable thermal energy. However, the low thermal conductivity, low electrical conductivity, and weak photoabsorption of pure PCMs hinder their wider applicability and development. To overcome these deficiencies and improve the utilization efficiency of thermal energy, versatile carbon materials have been increasingly considered as supporting materials to construct shape-stabilized composite PCMs. Despite some carbon-based composite PCMs reviews regarding thermal conductivity enhancement, a comprehensive review of carbon-based composite PCMs does not exist. Herein, a systematic overview of recent carbon-based composite PCMs for thermal storage, transfer, conversion (solar-to-thermal, electro-to-thermal and magnetic-to-thermal), and advanced multifunctional applications, including novel metal organic framework (MOF)-derived carbon materials are provided. The current challenges and future opportunities are also highlighted. The authors hope this review can provide in-depth insights and serve as a useful guide for the targeted design of high-performance carbon-based composite PCMs.

Carbon-Based Composite Phase Change Materials for Thermal Energy Storage, Transfer, and Conversion.

Functionalized carbon nanotubes as phase change materials with enhanced thermal, electrical conductivity, light-to-thermal, and electro-to-thermal performances

Fabrication and characterization of novel shape-stabilized synergistic phase change materials based on PHDA/GO composites

Fabrication and properties of graphene oxide-grafted-poly(hexadecyl acrylate) as a solid-solid phase change material

A phase change material (PCM) essentially making up hexadecyl acrylate-grafted graphene (HDA- g-GN) was fabricated via a solvent-free Diels-Alder (DA) reaction. The novel material exhibits multiresponsive, enhanced thermal and electrical conductivities and valid thermal enthalpy. In addition, the optimum DA reaction conditions were explored. A variety of characterization techniques were used to study the thermal, crystalline, and structural properties of HDA- g-GN. The melting and crystallizing enthalpies of HDA- g-GN were as high as 57 and 55 J/g, respectively. Furthermore, the melting and freezing points of HDA- g-GN were 29.5 and 32.7 °C, respectively. The thermal conductivity of HDA- g-GN reached 3.957 W/(m K), which is well above that of HDA itself and the previously reported PCMs. HDA- g-GN exhibited an excellent electric conductivity of 219 S/m. Compared to HDA, the crystalline activation energy of HDA- g-GN decreased from 397 to 278 kJ/mol (Kissinger model) and 373 to 259 kJ/mol (Ozawa model). Moreover, HDA- g-GN exhibited excellent thermal stability, shape stability, and thermal reliability. More importantly, HDA- g-GN can be employed to realize high-performance light-to-thermal and electron-to-thermal energy conversion and storage, which provides wide application prospects in energy-saving buildings, battery thermal management system, bioimaging, biomedical devices, as well as real-time and time-resolved applications.

Ruirui Cao

Papers

Functionalized carbon nanotubes as phase change materials with enhanced thermal, electrical conductivity, light-to-thermal, and electro-to-thermal performances

Fabrication and characterization of novel shape-stabilized synergistic phase change materials based on PHDA/GO composites

Fabrication and properties of graphene oxide-grafted-poly(hexadecyl acrylate) as a solid-solid phase change material

Multiresponsive Shape-Stabilized Hexadecyl Acrylate-Grafted Graphene as a Phase Change Material with Enhanced Thermal and Electrical Conductivities.

Mechanical stimuli-induced multiple photophysical responsive AIEgens with high contrast properties.