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

Efficient thermal energy harvesting using phase-change materials (PCMs) has great potential for cost-effective thermal management and energy storage applications. However, the low thermal conductivity of PCMs (KPCM ) is a long-standing bottleneck for high-power-density energy harvesting. Although PCM-based nanocomposites with an enhanced thermal conductivity can address this issue, achieving a higher K (>10 W m-1 K-1 ) at filler loadings below 50 wt% remains challenging. A strategy for synthesizing highly thermally conductive phase-change composites (PCCs) by compression-induced construction of large aligned graphite sheets inside PCCs is demonstrated. The millimeter-sized graphite sheet consists of lateral van-der-Waals-bonded and oriented graphite nanoplatelets at the micro/nanoscale, which together with a thin PCM layer between the sheets synergistically enhance KPCM in the range of 4.4-35.0 W m-1 K-1 at graphite loadings below 40.0 wt%. The resulting PCCs also demonstrate homogeneity, no leakage, and superior phase change behavior, which can be easily engineered into devices for efficient thermal energy harvesting by coordinating the sheet orientation with the thermal transport direction. This method offers a promising route to high-power-density and low-cost applications of PCMs in large-scale thermal energy storage, thermal management of electronics, etc.

High‐Performance Thermally Conductive Phase Change Composites by Large‐Size Oriented Graphite Sheets for Scalable Thermal Energy Harvesting

Nanocomposites, multiphase solid materials with at least one nanoscaled component, have been attracting ever-increasing attention because of their unique properties. Graphene is an ideal filler for high-performance multifunctional nanocomposites in light of its superior mechanical, electrical, thermal, and optical properties. However, the 2D nature of graphene usually gives rise to highly anisotropic features, which brings new opportunities to tailor nanocomposites by making full use of its excellent in-plane properties. Here, recent progress on graphene/polymer nanocomposites is summarized with emphasis on strengthening/toughening, electrical conduction, thermal transportation, and photothermal energy conversion. The influence of the graphene configuration, including layer number, defects, and lateral size, on its intrinsic properties and the properties of graphene/polymer nanocomposites is systematically analyzed. Meanwhile, the role of the interfacial interaction between graphene and polymer in affecting the properties of nanocomposites is also explored. The correlation between the graphene distribution in the matrix and the properties of the nanocomposite is discussed in detail. The key challenges and possible solutions are also addressed. This review may provide a constructive guidance for preparing high-performance graphene/polymer nanocomposite in the future.

Recent Progress in Graphene/Polymer Nanocomposites.

Phase change materials (PCMs) have been widely used for passive thermal management and energy storage due to the high latent heat capacity near phase transition points. However, the low thermal conductivity and leakage issue are two long-standing bottlenecks in PCM-based heat-related applications. Although the state of the art can address one or both of these issues by synthesizing phase change composites (PCCs), it remains challenging to achieve high-performance PCCs with simultaneously superior thermal and mechanical properties and phase change behaviors. In this work, a new method is reported to prepare highly thermally conductive, flexible and leakage-proof PCCs by constructing dual polymer and graphite nanoplatelet networks as the functional matrix of PCMs. In the composites, paraffin wax serves as the PCM, the macromolecular olefin block copolymer (OBC) forms a cross-linked polymer network to enclose the molten PCM and endow the composite film with flexibility, and expanded graphite (EG) with a long-chain structure forms an aligned and interconnected graphite nanoplatelet percolation network to enable the high thermal conductivity of PCCs. The radial thermal conductivities reach 4.2–32.8 W m−1 K−1 at EG loadings of 5–40 wt%. The resultant flexible composite film shows efficient and reliable thermal management performance by lowering the working temperature of a commercial lithium-ion battery by more than 12 °C at high discharge rates. Our work provides an efficient and cost-effective route to synthesizing high-performance PCCs for various heat-related applications including the thermal harvesting of renewable energy, building energy management, thermal management of electronics, etc.

Highly thermally conductive and flexible phase change composites enabled by polymer/graphite nanoplatelet-based dual networks for efficient thermal management

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.

Yanxia Du

Papers

Latent Heat Thermal Energy Storage Systems with Solid–Liquid Phase Change Materials: A Review

A Novel Solid–Solid Phase Change Material: Pentaglycerine/Expanded Graphite Composite PCMs