Polymer Encapsulation Strategy toward 3D Printable, Sustainable, and Reliable Form-Stable Phase Change Materials for Advanced Thermal Energy Storage

Confined Crystallization Polyether-Based Flexible Phase Change Film for Thermal Management

Phase change materials (PCMs) possess the potential to regulate temperature by utilizing their thermal properties to absorb and release heat. Nevertheless, the application of PCMs in thermal management is constrained by issues such as liquid leakage and limited flexibility. In this study, we propose a novel approach to address these challenges by incorporating a pore structure within nanofibers to confine the crystallization of phase change molecules, thereby enhancing the flexibility of the composite material. Additionally, inspired by the adaptive mechanisms observed in plants, we have developed a form stable PCM based on polyether, which effectively mitigates the issue of liquid leakage at higher temperatures. Despite being a solid-liquid PCM at its core, this material exhibits molecular-scale flow and macroscopic shape stability as a result of intermolecular forces. The composite film material possesses remarkable flexibility, efficient thermal management capabilities, adjustable phase transition temperature, and the ability to undergo repeated processing and utilization. Consequently, it holds promising potential for applications in personal thermal energy management.

Bottlebrush Networks: A Primer for Advanced Architectures

Bottlebrush networks (BBNs) are an exciting new class of materials with interesting physical properties derived from their unique architecture. While great strides have been made in our fundamental understanding of bottlebrush polymers and networks, an interdisciplinary approach is necessary for the field to accelerate advancements. This review aims to act as a primer to BBN chemistry and physics for both new and current members of the community. In addition to providing an overview of contemporary BBN synthetic methods, we developed a workflow and desktop application (LengthScale), enabling bottlebrush physics to be more approachable. We conclude by addressing several topical issues and asking a series of pointed questions to stimulate conversation within the community.

A Uniform Self-Reinforced Organic/Inorganic Hybrid SEI Chelation Strategy on Microscale Silicon Surfaces for Stable-Cycling Anodes in Lithium-Ion Batteries

A promising anode material for Li-ion batteries, silicon (Si) suffers from volume expansion-induced pulverization and solid electrolyte interface (SEI) instability. Microscale Si with high tap density and high initial Coulombic efficiency (ICE) has become a more anticipated choice, but it will exacerbate the above issues. In this work, the polymer polyhedral oligomeric silsesquioxane-lithium bis (allylmalonato) borate (PSLB) is constructed by in situ chelation on microscale Si surfaces via click chemistry. This polymerized nanolayer has an "organic/inorganic hybrid flexible cross-linking" structure that can accommodate the volume change of Si. Under the stable framework formed by PSLB, a large number of oxide anions on the chain segment preferentially adsorb LiPF6 and further induce the integration of inorganic-rich, dense SEI, which improves the mechanical stability of SEI and provides accelerated kinetics for Li+ transfer. Therefore, the Si4@PSLB anode exhibits significantly enhanced long-cycle performance. After 300 cycles at 1 A g-1 , it can still provide a specific capacity of 1083 mAh g-1 . Cathode-coupled with LiNi0.9 Co0.05 Mn0.05 O2 (NCM90) in the full cell retains 80.8% of its capacity after 150 cycles at 0.5 C.

Printing Composites with Salt Hydrate Phase Change Materials for Thermal Energy Storage

Salt hydrate phase change materials are important in advancing thermal energy storage technologies for the development of renewable energies. At present, their widespread use is limited by undesired undercooling and phase separation, as well as their tendency to corrode container materials. Herein, we report a direct ink writing (DIW) additive manufacturing technique to print noncorrosive salt hydrate composites with thoroughly integrated nucleating agents and thermally conductive additives. First, salt hydrate particles are prepared from nonaqueous Pickering emulsions and then employed as rheological modifiers to formulate thixotropic inks with polymer dispersions in toluene serving as the matrix. These inks are successfully printed at room temperature and cured by solvent evaporation under ambient conditions. The resulting printed and cured composites, containing up to 70 wt % of the salt hydrate, exhibit reliable thermal cyclability for 10 cycles and suppressed undercooling compared to the bulk salt hydrate. Remarkably, the composites consistently maintain their structural integrity and thermal performance throughout the entirety of both the melting and solidification processes. We demonstrate the versatility of this approach by utilizing two salt hydrates, magnesium nitrate hexahydrate (MNH, Tm = 89 °C) and zinc nitrate hexahydrate (ZNH, Tm = 36 °C), to achieve desired thermal characteristics across a wide range of temperatures. Further, we establish that the incorporation of carbon black in these inks enhances the thermal conductivity by at least 33%. This approach consolidates the strengths of additive manufacturing and salt hydrate phase change materials to harness customizable thermal properties, well suited for targeted thermal energy management applications.

Epoxy Phase-Change Materials Based on Paraffin Wax Stabilized by Asphaltenes

The usual problem of meltable phase-change agents is the instability in their form upon heating, which can be solved by placing them into a continuous polymer matrix. Epoxy resin is a suitable medium for dispersing molten agents, but it is necessary to make the obtained droplets stable during the curing of the formed phase-change material. This work shows that molten paraffin wax forms a Pickering emulsion in an epoxy medium and in the presence of asphaltenes extracted from heavy crude oil. Theoretical calculations revealed the complex equilibrium in the epoxy/wax/asphaltene triple system due to their low mutual solubility. Rheological studies showed the viscoplastic behavior of the obtained dispersions at 25 °C, which disappears upon the heating and melting of the paraffin phase. Wax and asphaltenes increased the viscosity of the epoxy medium during its curing but did not inhibit cross-linking or reduce the glass transition temperature of the cured polymer. As a result of curing, it is possible to obtain phase-change materials containing up to 45% paraffin wax that forms a dispersed phase with a size of 0.2-6.5 μm. The small size of dispersed wax can decrease its degree of crystallinity to 13-29% of its original value, reducing the efficiency of the phase-change material.

Phase Change Thermal Storage Materials for Interdisciplinary Applications

Functional phase change materials (PCMs) capable of reversibly storing and releasing tremendous thermal energy during the isothermal phase change process have recently received tremendous attention in interdisciplinary applications. The smart integration of PCMs with functional supporting materials enables multiple cutting-edge interdisciplinary applications, including optical, electrical, magnetic, acoustic, medical, mechanical, and catalytic disciplines etc. Herein, we systematically discuss thermal storage mechanism, thermal transfer mechanism, and energy conversion mechanism, and summarize the state-of-the-art advances in interdisciplinary applications of PCMs. In particular, the applications of PCMs in acoustic, mechanical, and catalytic disciplines are still in their infancy. Simultaneously, in-depth insights into the correlations between microscopic structures and thermophysical properties of composite PCMs are revealed. Finally, current challenges and future prospects are also highlighted according to the up-to-date interdisciplinary applications of PCMs. This review aims to arouse broad research interest in the interdisciplinary community and provide constructive references for exploring next generation advanced multifunctional PCMs for interdisciplinary applications, thereby facilitating their major breakthroughs in both fundamental researches and commercial applications.

Phase Change Energy Storage Material with Photocuring, Photothermal Conversion, and Self-Cleaning Performance via a Two-Layer Structure

Compared with the thermal curing process, the photocuring process has advantages such as high efficiency and less energy consumption. However, the preparation of photocurable phase change materials (PCMs) with photothermal conversion and self-cleaning properties is challenging due to the conflict between the transparency required by the photocurable resin system and the opacity deduced by the large number of fillers required by photothermal conversion and the negative effect of filler steric hindrance on the reaction rate and crystallinity. In this work, a "thiol-ene" click chemical reaction induced using UV was used to prepare photocurable PCMs, followed by spraying a carboxylated multiwalled carbon nanotube (CCNT) suspension (with ethyl acetate) onto the surface to achieve an effective two-layer composite of the PCM and CCNTs, by which the rough surface of the PCM and the interaction offered by the hydrogen bonds on the interface of the PCM and the CCNTs provide sufficient adhesion for the two phases. The "thiol-ene" cross-linked polymer network provided shape stability as a support material. 1-Octadectanethiol (ODT) and beeswax (BW) were encapsulated in the cross-linked polymer network as phase change components, providing phase change latent heat. The CCNT layer provided excellent photothermal conversion and self-cleaning properties. The experimental results show that the latent heat of the PCM can reach 124.2 J/g, the water contact angle is 144°, the photothermal conversion efficiency reaches 75%, and it has significant self-cleaning performance. To the best of our knowledge, this is the first report on a photocurable PCM with photothermal conversion and self-cleaning properties.