Phase Change Materials for Life Science Applications

Phase change materials (PCMs) are a class of thermo-responsive materials that can be utilized to trigger a phase transition which gives them thermal energy storage capacity. Any material with a high heat of fusion is referred to as a PCM that is able to provide cutting-edge thermal storage. PCMs are commercially used in many applications like textile industry, coating, and cold storage typically for heat control. These intriguing substances have recently been rediscovered and employed in a broad range of life science applications, including biological, human body, biomedical, pharmaceutical, food, and agricultural applications. Benefiting from the changes in physicochemical properties during the phase transition makes PCMs also functional for barcoding, detection, and storage. Paraffin wax and polyethylene glycol are the most commonly studied PCMs due to their low toxicity, biocompatibility, high thermal stability, high latent enthalpy, relatively wide transition temperature range, and ease of chemical modification. Current challenges in employing PCMs for life science applications include biosafety and/or engineering difficulties. The focus of this review article is on the life science applications, evaluation, and safety aspects of PCMs. Herein, the advances and the potential of employing PCMs as a versatile platform for various types of life science applications are highlighted.     

Single‐Walled Carbon Nanotube/Phase Change Material Composites: Sunlight‐Driven,Reversible, Form‐Stable Phase Transitions for Solar Thermal Energy Storage

The development of solar energy conversion materials is critical to the growth of a sustainable energy infrastructure in the coming years. A novel hybrid material based on single‐walled carbon nanotubes (SWNTs) and form‐stable polymer phase change materials (PCMs) is reported. The obtained materials have UV‐vis sunlight harvesting, light‐thermal conversion, thermal energy storage, and form‐stable effects. Judicious application of this efficient photothermal conversion to SWNTs has opened up a rich field of energy materials based on novel SWNT/PCM composits with enhanced performance in energy conversion and storage.     

太阳能热利用储热材料的研究与应用

储热材料在太阳能热利用过程中发挥着重要作用,本文综述了各类储热材料的研究与应用。从显热储热和相变储热两个方面分别介绍了低温和中高温储热材料的研究进展,分析了各类储热材料的特点,并展望了今后太阳能热利用储热材料的应用前景及研究方向。     

Optically Triggered Synchronous Heat Release of Phase-Change Enthalpy and Photo-Thermal Energy in Phase-Change Materials at Low Temperatures

Phase-change materials (PCMs) are used in several energy recycling utilization systems due to their latent-heat-storage and -release ability. However, the inability of PCMs to release heat at temperatures below their freezing point limits their application in distributed energy utilization systems. This paper reports optically-triggered low-temperature heat release in PCMs based on a solid–liquid phase change (PC) controlled by the trans–cis (E–Z) photo-isomerization of azobenzene. To achieve this, a photo-responsive alkyl-grafted Azo is incorporated into tetradecane (Ted) to create a photo-sensitive energy barrier for the PC. The Azo/Ted composite exhibits controllable supercooling (4.04–8.80 °C) for heat storage and achieves synchronous heat release of PC enthalpy and photo-thermal energy. In addition, the Azo reduces the crystallization of Ted by intercalating into its molecular alignment. Furthermore, under light illumination, the Azo/Ted composite releases considerable heat (207.5 J g⁻¹) at relatively low temperatures (−1.96 to −6.71 °C). The temperature of the annular device fabricated for energy utilization increases by 4 °C in a low-temperature environment (−5 °C). This study will pave the way for the design of advanced distributed energy systems that operate by controlling the energy storage/release of PCMs over a wide range of temperatures.     

The Performance of Small‐Pore Microporous Aluminophosphates in Low‐Temperature Solar Energy Storage: The Structure–Property Relationship

The utilization of the reversible chemical and physical sorption of water on solids provides a new thermal energy storage concept with a great potential for lossless long‐term storage. The performance of microporous aluminophosphates in heat storage applications is highlighted by a comparative thermogravimetric and calorimetric study of three known materials (SAPO‐34, AlPO₄‐18, APO‐Tric) and is correlated with their structural features. The maximum water sorption capacity is similar for all three samples and results in a stored energy density of 240 kWh m^?3 in the 40–140 °C range. The elemental composition influences the gradual (silicoaluminophosphate SAPO‐34) or sudden (aluminophosphates AlPO₄‐18, APO‐Tric) water uptake, with the latter being favourable in storage systems. The driving force for the determined sorption process is the formation of highly ordered water clusters in the pores, which is enabled by rapid and reversible changes in the Al coordination and optimal pore diameters. The ease with which changes in the Al coordination can occur in APO‐Tric is related to the use of the fluoride route in the synthesis. The understanding of these fundamental structure/sorption relationships forms an excellent basis for predicting the storage potential of numerous known or new microporous aluminophosphates and other porous materials from their crystal structures.     

Ion‐Conductive,Viscosity‐Tunable Hexagonal Boron Nitride Nanosheet Inks

Liquid‐phase exfoliation of layered solids holds promise for the scalable production of 2D nanosheets. When combined with suitable solvents and stabilizing polymers, the rheology of the resulting nanosheet dispersions can be tuned for a variety of additive manufacturing methods. While significant progress is made in the development of electrically conductive nanosheet inks, minimal effort is applied to ion‐conductive nanosheet inks despite their central role in energy storage applications. Here, the formulation of viscosity‐tunable hexagonal boron nitride (hBN) inks compatible with a wide range of printing methods that span the spectrum from low‐viscosity inkjet printing to high‐viscosity blade coating is demonstrated. The inks are prepared by liquid‐phase exfoliation with ethyl cellulose as the polymer dispersant and stabilizer. Thermal annealing of the printed structures volatilizes the polymer, resulting in a porous microstructure and the formation of a nanoscale carbonaceous coating on the hBN nanosheets, which promotes high wettability to battery electrolytes. The final result is a printed hBN nanosheet film that possesses high ionic conductivity, chemical and thermal stability, and electrically insulating character, which are ideal characteristics for printable battery components such as separators. Indeed, lithium‐ion battery cells based on printed hBN separators reveal enhanced electrochemical performance that exceeds commercial polymer separators.     

Advanced Antiscaling Interfacial Materials toward Highly Efficient Heat Energy Transfer

The energy problem has been a matter of some concern worldwide over the past 20 years. On the opposite side of energy production, energy loss is another crucial problem of current energy due to the low efficiency of heat transfer from scale deposition. However, less attention has been paid on the further development of advanced antiscaling interfacial materials, which may provide promising ways to save energy by reducing scale fouling. Herein, the development of antiscaling strategies is summarized from the basic theories and fabrication methods to antiscaling interfacial materials with potential applications. First, the mechanism of scale formation and the corresponding effect on thermal conductivity are introduced. Second, the typical fabrication approaches of antiscaling interfacial materials are briefly described. Finally, the performance, potential applications, future challenges, and opportunities of the advanced antiscaling interfacial materials are comprehensively discussed.     

Wood‐Derived Materials for Advanced Electrochemical Energy Storage Devices

Over the past decade, wood‐derived materials have attracted enormous interest for both fundamental research and practical applications in various functional devices. In addition to being renewable, environmentally benign, naturally abundant, and biodegradable, wood‐derived materials have several unique advantages, including hierarchically porous structures, excellent mechanical flexibility and integrity, and tunable multifunctionality, making them ideally suited for efficient energy storage and conversion. In this article, the latest advances in the development of wood‐derived materials are discussed for electrochemical energy storage systems and devices (e.g., supercapacitors and rechargeable batteries), highlighting their micro/nanostructures, strategies for tailoring the structures and morphologies, as well as their impact on electrochemical performance (energy and power density and long‐term durability). Furthermore, the scientific and technical challenges, together with new directions of future research in this exciting field, are also outlined for electrochemical energy storage applications.     

Recent Progress in Advanced Organic Electrode Materials for Sodium‐Ion Batteries: Synthesis,Mechanisms, Challenges and Perspectives

Rechargeable sodium‐ion batteries (SIBs) are considered attractive alternatives to lithium‐ion batteries for next‐generation sustainable and large‐scale electrochemical energy storage. Organic sodium‐ion batteries (OSIBs) using environmentally benign organic materials as electrodes, which demonstrate high energy/power density and good structural designability, have recently attracted great attention. Nevertheless, the practical applications and popularization of OSIBs are generally restricted by the intrinsic disadvantages related to organic electrodes, such as their low conductivity, poor stability, and high solubility in electrolytes. Here, the latest research progress with regard to electrode materials of OSIBs, ranging from small molecules to organic polymers, is systematically reviewed, with the main focus on the molecular structure design/modification, the electrochemical behavior, and the corresponding charge‐storage mechanism. Particularly, the challenges faced by OSIBs and the effective design strategies are comprehensively summarized from three aspects: function‐oriented molecular design, micromorphology regulation, and construction of organic–inorganic composites. Finally, the perspectives and opportunities in the research of organic electrode materials are discussed.     

Hierarchically Structured Porous Materials for Energy Conversion and Storage

Materials with hierarchical porosity and structures have been heavily involved in newly developed energy storage and conversion systems. Because of meticulous design and ingenious hierarchical structuration of porosities through the mimicking of natural systems, hierarchically structured porous materials can provide large surface areas for reaction, interfacial transport, or dispersion of active sites at different length scales of pores and shorten diffusion paths or reduce diffusion effect. By the incorporation of macroporosity in materials, light harvesting can be enhanced, showing the importance of macrochannels in light related systems such as photocatalysis and photovoltaics. A state‐of‐the‐art review of the applications of hierarchically structured porous materials in energy conversion and storage is presented. Their involvement in energy conversion such as in photosynthesis, photocatalytic H₂ production, photocatalysis, or in dye sensitized solar cells (DSSCs) and fuel cells (FCs) is discussed. Energy storage technologies such as Li‐ions batteries, supercapacitors, hydrogen storage, and solar thermal storage developed based on hierarchically porous materials are then discussed. The links between the hierarchically porous structures and their performances in energy conversion and storage presented can promote the design of the novel structures with advanced properties.     

Thermal Conductivity of Amorphous Materials

Thermal conductivity is one of the most fundamental properties of solid materials. The thermal conductivity of ideal crystal materials has been widely studied over the past hundreds years. On the contrary, for amorphous materials that have valuable applications in flexible electronics, wearable electrics, artificial intelligence chips, thermal protection, advanced detectors, thermoelectrics, and other fields, their thermal properties are relatively rarely reported. Moreover, recent research indicates that the thermal conductivity of amorphous materials is quite different from that of ideal crystal materials. In this article, the authors systematically review the fundamental physical aspects of thermal conductivity in amorphous materials. They discuss the method to distinguish the different heat carriers (propagons, diffusons, and locons) and the relative contribution from them to thermal conductivity. In addition, various influencing factors, such as size, temperature, and interfaces, are addressed, and a series of interesting anomalies are presented. Finally, the authors discuss a number of open problems on thermal conductivity of amorphous materials and a brief summary is provided.     

Microsphere Structure Composite Phase Change Material with Anti-Leakage,Self-Sensing,and Photothermal Conversion Properties for Thermal Energy Harvesting and Multi-Functional Sensor

The low thermal conductivity and liquid melt leakage of phase change materials are long-standing bottlenecks for efficient and safe thermal energy harvesting. Although high thermal conductivity materials combined with phase change materials can address the thermal conductivity problem, ensuring no leakage and no reduction in latent heat in the meantime remains challenging. Here, a strategy to synthesize microsphere-structured phase change composites by encapsulating phase change materials in graphene via emulsion polymerization (no additional emulsifier) and chemical reduction is proposed. Multiple graphene sheets are connected to construct an efficient thermally conductive (increase 58.5 times in thermal conductivity) and electrically conductive network. The composite microspheres exhibit no leakage (<0.5%) and superior phase transition behavior after 1500 heating-cooling cycles, and sense external environments such as temperature changes and water drops falling, allowing them to be engineered into devices for temperature monitoring. In addition, it converts electrical energy into thermal energy to achieve rapid temperature increases. The incorporation of polydopamine improves the photothermal efficiency of the phase change microspheres and senses light irradiation, offering a promising route to extend the single source of thermal energy. This method provides new insight into the photothermal integration and intelligent sensing of phase-change materials.     

Gas Diffusion,Energy Transport,and Thermal Accommodation in Single‐Walled Carbon Nanotube Aerogels

The thermal conductivity of gas‐permeated single‐walled carbon nanotube (SWCNT) aerogel (8 kg m^?3 density, 0.0061 volume fraction) is measured experimentally and modeled using mesoscale and atomistic simulations. Despite the high thermal conductivity of isolated SWCNTs, the thermal conductivity of the evacuated aerogel is 0.025 ± 0.010 W m^?1 K^?1 at a temperature of 300 K. This very low value is a result of the high porosity and the low interface thermal conductance at the tube–tube junctions (estimated as 12 pW K^?1). Thermal conductivity measurements and analysis of the gas‐permeated aerogel (H₂, He, Ne, N₂, and Ar) show that gas molecules transport energy over length scales hundreds of times larger than the diameters of the pores in the aerogel. It is hypothesized that inefficient energy exchange between gas molecules and SWCNTs gives the permeating molecules a memory of their prior collisions. Low gas‐SWCNT accommodation coefficients predicted by molecular dynamics simulations support this hypothesis. Amplified energy transport length scales resulting from low gas accommodation are a general feature of CNT‐based nanoporous materials.     

Recent Developments of Planar Micro‐Supercapacitors: Fabrication,Properties, and Applications

The increasing development of wearable, portable, implantable, and highly integrated electronic devices has led to an increasing demand for miniaturization of energy storage devices. In recent years, supercapacitors, as an energy storage device, have received enormous attention owing to their excellent properties of quick charge and discharge, high power density, and long life cycle with minimal maintenance. Micro‐supercapacitors (MSCs) as a promising candidate for miniaturized energy storage components have undergone considerable theoretical and experimental investigations. Particularly, planar MSCs with a 2D architecture design have more attractive application prospects due to their flexible design and excellent electrochemical performance. However, the major drawbacks of MSCs are their intrinsically low energy density. For this reason, researchers have conducted much investigation to improve their energy density in order to promote their practical application. Herein, the recent development and progress of planar MSCs from the scope of the substrates, electrode materials, fabrication methods, electrochemical properties, and applications are discussed. Finally, the currently existing challenges and developments associated with planar MSCs are also discussed. All in all, planar MSCs have great application potential in various fields of electrochemical energy storage, self‐powered wireless sensors, and stimuli‐responsive and photoresponsive, alternating current line filtering.     

Porous Carbons Derived from Collagen‐Enriched Biomass: Tailored Design,Synthesis, and Application in Electrochemical Energy Storage and Conversion

As byproducts of the meat‐processing industry, nearly 100 million tons of bones, skin, and scales are generated from livestock, poultry, and fish every year and are generally discarded as waste. However, these widespread and low‐cost biomass materials are rich in collagen that is primarily composed of the elements C, N, O, and S. By controlled pyrolysis, these collagen‐enriched biomass materials can be transformed into biomass‐derived porous carbons (BPCs). The ordered biotic structures and specific elemental compositions of the natural precursors endow BPCs with unique nanostructures and heteroatom doping, leading to promising applications in electrochemical energy storage and conversion. In particular, BPCs derived from animal bones and fish scales show novel porosities and morphologies due to their abundance of hydroxyapatite crystals, which act as naturally occurring nanostructured templates. Here, the first review focusing on the design and synthesis of collagen‐derived porous carbons (CPCs) is given. The specific applications of different CPCs in electrochemical energy storage and conversion are also summarized. Finally, the challenges and prospects for the controllable synthesis and large‐scale applications of CPCs are assessed.     

Graphene‐Based Devices for Thermal Energy Conversion and Utilization

Thermal energy conversion and utilization of integrated circuits is a very important research topic. Graphene is a new 2D material with superior electrical, mechanical, thermal, and optical properties, which is expected to continue Moore's law and make breakthroughs in the direction of “More than Moore.” Graphene‐based functionalized devices are applied in various aspects, including breakthroughs in thermal devices, due to their high thermal conductivity and thermal rectification. According to the coupling of different physical quantities, graphene‐based thermal devices can be divided into four categories: uncoupled thermal devices, thermoacoustic coupling devices, thermoelectric coupling devices, and thermo‐optical coupling devices. The structure, working mechanism, and performance of these devices are discussed, as well as the coupling methods of physical quantities. Moreover, scale‐up production of graphene and prospect for future graphene‐based thermal devices are summarized. In‐depth study of the development tendency of these graphene‐based thermal devices is expected to contribute to the development of new high‐performance thermal nanoelectronic devices in the future.     

Ultrahigh Energy‐Storage Density in NaNbO3‐Based Lead‐Free Relaxor Antiferroelectric Ceramics with Nanoscale Domains

Dielectric energy‐storage capacitors have received increasing attention in recent years due to the advantages of high voltage, high power density, and fast charge/discharge rates. Here, a new environment‐friendly 0.76NaNbO₃–0.24(Bi_0.5Na_0.5)TiO₃ relaxor antiferroelectric (AFE) bulk ceramic is studied, where local orthorhombic Pnma symmetry (R phase) and nanodomains are observed based on high‐resolution transmission electron microscopy, selected area electron diffraction, and in/ex situ synchrotron X‐ray diffraction. The orthorhombic AFE R phase and relaxor characteristics synergistically contribute to the record‐high energy‐storage density W_rec of ≈12.2 J cm^?3 and acceptable energy efficiency η ≈ 69% at 68 kV mm^?1, showing great advantages over currently reported bulk dielectric ceramics. In comparison with normal AFEs, the existence of large random fields in the relaxor AFE matrix and intrinsically high breakdown strength of NaNbO₃‐based compositions are thought to be responsible for the observed energy‐storage performances. Together with the good thermal stability of W_rec (>7.4 J cm^?3) and η (>73%) values at 45 kV mm^?1 up to temperature of 200 °C, it is demonstrated that NaNbO₃‐based relaxor AFE ceramics will be potential lead‐free dielectric materials for next‐generation pulsed power capacitor applications.     

Advanced Exfoliation Strategies for Layered Double Hydroxides and Applications in Energy Conversion and Storage

Along with the increasing aggravation of energy and environmental problems, the demand and utilization of renewable energy have increased. The rational design of advanced functional materials serves as a critical point for the improvement of performance and the practical application in renewable energy devices. Layered double hydroxides (LDHs) with 2D layered structures are promising energy materials for their unique physical and chemical properties. Nevertheless, the applications are limited by the structure of stacking with irrational electronic structure, sluggish mass transfer, and low activity. The exfoliation of LDHs into single‐ or few‐layered nanosheets appears to be a promising approach to overcome the above disadvantages. Herein, the recent progress on the development of exfoliation strategies for LDHs including liquid phase exfoliation, plasma‐induced exfoliation, and other advanced exfoliation strategies is highlighted and the applications in energy conversion and storage are systematically introduced.     

Thermal Transport in Conductive Polymer–Based Materials

The demand for flexible conductive materials has motivated many recent studies on conductive polymer–based materials. However, the thermal conductivity of conductive polymers is relatively low, which may lead to serious heat dissipation problems for device applications. This review provides a summary of the fundamental principles for thermal transport in conductive polymers and their composites, and recent advancements in regulating their thermal conductivity. The thermal transport mechanisms in conductive polymer–based materials and up‐to‐date experimental approaches for measuring thermal conductivity are first summarized. Effective approaches for the regulation of thermal conductivity are then discussed. Finally, thermal‐related applications and future perspectives are given for conductive polymers and their composites.     

Advances on Emerging Materials for Flexible Supercapacitors: Current Trends and Beyond

The progressive size reduction of electronic components is experiencing bottlenecks in shrinking charge storage devices like batteries and supercapacitors, limiting their development into wearable and flexible zero‐pollution technologies. The inherent long cycle life, rapid charge–discharge patterns, and power density of supercapacitors rank them superior over other energy storage devices. In the modern market of zero‐pollution energy devices, currently the lightweight formula and shape adaptability are trending to meet the current requirement of wearables. Carbon nanomaterials have the potential to meet this demand, as they are the core of active electrode materials for supercapacitors and texturally tailored to demonstrate flexible and stretchable properties. With this perspective, the latest progress in novel materials from conventional carbons to recently developed and emerging nanomaterials toward lightweight stretchable active compounds for flexi‐wearable supercapacitors is presented. In addition, the limitations and challenges in realizing wearable energy storage systems and integrating the future of nanomaterials for efficient wearable technology are provided. Moreover, future perspectives on economically viable materials for wearables are also discussed, which could motivate researchers to pursue fabrication of cheap and efficient flexible nanomaterials for energy storage and pave the way for enabling a wide‐range of material‐based applications.