Phase Change Systems Research Articles

Hierarchical microencapsulation of phase change material with carbon-nanotubes/polydopamine/silica shell for synergistic enhancement of solar photothermal conversion and storage

Aiming at improving the utilization efficiency of solar photothermal energy, this study focuses on a novel phase-change microcapsule system based on an n-docosane core and a carbon-nanotubes (CNTs)/polydopamine (PDA)/silica hierarchical shell. The system was fabricated by encapsulating n-docosane in a silica shell and then depositing a PDA layer on the shell surface, followed by conglutinating CNTs onto the PDA layer. The resultant microcapsule system shows a regular spherical morphology together with desired core-shell hierarchical microstructure and chemical compositions. The presence of CNTs/PDA coating layer can impart an efficient solar light-to-heat energy conversion capability to the microcapsule system through photon capture and sunlight absorption. The microcapsule system not only shows a good latent heat-storage capability with satisfactory phase-change enthalpies of over 130 J/g but also exhibits an optimal photothermal conversion efficiency of 90.1%. The microcapsule system also exhibits good leakage-prevention performance, high thermal cycle stability, excellent thermal impact resistance, and good shape/form stability to deal with a wide range of solar photothermal energy applications. Through integrating CNTs and PDA into a phase-change microcapsule system, this work provides a promising approach for the development of PCMs-based functional materials with enhanced solar light-to-heat energy conversion and storage performance for efficient utilization of solar energy.

New insight and evaluation of secondary Amine/N-butanol biphasic solutions for CO2 Capture: Equilibrium Solubility, phase separation Behavior, absorption Rate, desorption Rate, energy consumption and ion species

• MAE + n-butanol + H 2 O system for CO 2 capture was first proposed. • The phase change mechanism and energy consumption of the system were investigated. • The influence of temperature on absorption capacity was explored. • The developed biphasic absorbent has excellent energy saving advantages. Effective phase-change solvent system, n-methyl-2-hydroxyethylamine (MAE) + water-insoluble alcohol + H 2 O, was developed for CO 2 capture. First, a preliminary screening of several alcohols was carried out and showed that the MAE/n-butanol/water system had the potential to become an excellent phase change absorbent. Then, through phase change experiment, absorption experiment, desorption experiment, and theoretical energy consumption analysis, the MAE:n-butanol:water ratio of 3:4:3 possessed the most impressive CO 2 capture performance. Theoretical calculation of CO 2 desorption energy consumption showed that in comparison with 30 wt% monoethanolamine (MEA), 50% of reboiler heat duty can be reduced in case of the 3:4:3 system. In addition, equilibrium phase diagram of the three components showed that concentration of n-butanol significantly affected the phase separation. The two-phase species distribution after phase separation was determined using Nuclear magnetic resonance spectroscopy (NMR). This work also shows that temperature has influence on absorption and desorption performance. Finally, the absorbent stability test during absorption–desorption process confirmed that MAE/n-butanol/water absorbent had a great potential for capturing CO 2 .

Experimental study of the mass transfer behavior of carbon dioxide absorption into ternary phase change solution in a packed tower

Phase change absorbents for CO 2 are of great interest because they are expected to greatly reduce the heat energy consumption during the regeneration process. Compared with other phase change absorbents, monoethanolamine (MEA)-sulfolane-water is inexpensive and has a fast absorption rate. It is one of the most promising solvents for large-scale industrial applications. Therefore, this study investigates the mass transfer performance of this phase change system in the process of CO 2 absorption in a packed tower. By comparing the phase change absorbent and the ordinary absorbent, it is concluded that the use of MEA/sulfolane phase change absorbent has significantly improved mass transfer efficiency compared to a single MEA absorbent at the same concentration. In the 4 mol⋅L −1 MEA/5 mol⋅L −1 sulfolane system, the CO 2 loading of the upper liquid phase after phase separation is almost zero, while the volume of the lower liquid phase sent to the desorption operation is about half of the total volume of the absorbent, which greatly reduces the energy consumption. This study also investigates the influence of operating parameters such as lean CO 2 loading, gas and liquid flow rates, CO 2 partial pressure, and temperature on the volumetric mass transfer coefficient ( K G a V ). The research shows that K G a V increases with increasing liquid flow rate and decreases with the increase of lean CO 2 loading and CO 2 partial pressure, while the inert gas flow rate and temperature have little effect on K G a V . In addition, based on the principle of phase change absorption, a predictive equation for the K G a V of MEA-sulfolane in the packed tower was established. The K G a V obtained from the experiment is consistent with the model prediction, and the absolute average deviation (AAD) is 7.8%.

Development of photoluminescence phase-change microcapsules for comfort thermal regulation and fluorescent recognition applications in advanced textiles

To expand the application range of microencapsulated phase change materials into advanced textiles, we designed and developed a type of photoluminescence phase-change microcapsule system based on an n-eicosane core and a Eu3+-doped CaCO3/Fe3O4 composite shell. This type of functionalized phase-change microcapsules was fabricated by encapsulating n-eicosane in the CaCO3/Fe3O4 composite shell through in-situ precipitation in a Pickering emulsion-templating system, followed by doping Eu3+ on the surface of the CaCO3/Fe3O4 composite shell. The resultant microcapsules show a well-defined core–shell microstructure and regular spherical morphology with a rough surface due to the presence of Eu3+. Introducing Fe3O4 nanoparticles as a light absorber into the CaCO3 shell enhanced the utilization efficiency of solar photothermal energy for the phase-change microcapsules. The fabricated microcapsules not only exhibited a satisfactory thermal regulation capability under a latent heat capacity of over 125 J/g, but also achieved a high photothermal conversion efficiency of 67.6%. Doping Eu3+ into the CaCO3/Fe3O4 composite shell imparted a photoluminescence function to the phase-change microcapsules, resulting in a fluorescence emission at an excitation wavelength of 394 nm. An application investigation of the phase-change microcapsules in advanced textiles was carried out to confirm their contributions to the thermal comfort of human body together with high recognition under the extreme conditions. With excellent solar photothermal conversion, latent heat storage, and photoluminescence performance, the phase-change microcapsules developed by this study exhibit great potential for bifunctional applications of comfort thermal regulation and fluorescent recognition in advanced textiles.

Theoretical performance characteristics of a travelling-wave phase-change thermoacoustic heat pump

Thermoacoustic technology is a promising approach for environmentally-benign, low-cost heat pumping. Herein, we present a theoretical investigation on phase-change thermoacoustic heat pumping employing both an ideal model (a short heat pump in a pure travelling-wave field), as well as a full-size, looped-tube thermoacoustic heat pump. In the analysis of the short heat pump, we identified and assessed the main factors and their influence on the performance of an ideal phase-change travelling-wave heat pump. The results show that, ideally, the cooling power can be significantly increased by up to one order of magnitude, and the COP (coefficient of performance) can also be improved by the incorporation of phase change into the thermoacoustic cycle. Meanwhile, the analysis of the full system provides a more practical view of the enhancement due to phase change. A significant increase of cooling power is observed in the phase-change system with a high concentration of the reactive component, but increased of the COP only occurs under small temperature differences (below 10 K). The main reason for the gap in observed performance between the ideal model and the full system is the deviation, under a large temperature difference, of the acoustic field from the requirements for effective enhancement, as revealed in the ideal model. Our results demonstrate the potential of the phase-change travelling-wave thermoacoustic heat pump for efficient and low-cost heat pumping, especially for small temperature difference applications.

Design Optimization of Phase-Change Material Thermal Management Systems for Fast-Charging of Electric Vehicle Battery Modules with Cylindrical Lithium-Ion Cells

Design Optimization of Phase-Change Material Thermal Management Systems for Fast-Charging of Electric Vehicle Battery Modules with Cylindrical Lithium-Ion Cells

Cascade phase change based on hydrate salt/carbon hybrid aerogel for intelligent battery thermal management

Working performance of Li-ion battery in electric vehicle will degrade under cold environment. Excess heat of battery can be stored via melting of calcium chloride hexahydrate (CCH) and then released to warm battery when environment temperature drops. Formation of composite can improve thermal conductivity and stability of pristine CCH but reduce loading content. Meanwhile, energy stored in phase change material (PCM) is utilized in low efficiency as homogeneously filled PCM releasing heat uncontrollably. Therefore, there is an urgent need to achieve efficient heat storage and controllable heat release by designing an intelligent phase change system. In this research, MOF-derived carbon (MOF-C)/graphene oxide (GO) hybrid aerogel was proposed to load CCH. PCM loading content could be enhanced by the synergistic effect between MOF-C and GO, while thermal conductivity of PCM composite could be improved due to the formation of hybrid aerogel three-dimensional network. Furthermore, CCH@MOF-C/GO structures with gradient freezing point (FP) were designed to build a cascade phase change system to release heat efficiently, in which CCH with high FP triggering heat release of adjacent PCM with low FP. Comparing with the homogeneously filled PCM, warming time was prolonged and discharge capacity of battery was enhanced successfully under cold environment by utilizing the cascade PCM.

Magnetic field-assisted acceleration of energy storage based on microencapsulation of phase change material with CaCO3/Fe3O4 composite shell

Energy conversion and storage are crucial for overcoming energy-shortage problems. Herein, we designed and synthesized a type of magnetic phase-change microcapsule system for enhancing solar light-to-heat conversion efficiency through the synergetic conversion of photothermal and magnetocaloric energy. This microcapsule system was based on an n-eicosane core and a Fe3O4/CaCO3 composite shell and fabricated by means of a Pickering emulsion-templated in-situ precipitation technique. The composite microcapsules so obtained exhibit a regular spherical morphology and a well-defined core–shell microstructure, together with the desired chemical compositions and magnetic characteristics. The introduction of Fe3O4 nanoparticles enhanced the stability of the emulsion-templating system, resulting in an improvement in the phase-change enthalpies of the resultant composite microcapsules. Moreover, the presence of Fe3O4 nanoparticles endowed the microcapsule system with magnetic characteristics to realize a photothermal and magnetocaloric synergetic conversion. The composite microcapsules achieved a satisfactory latent-heat capacity of over 110 J/g and high photothermal conversion efficiency of 86.4%. More importantly, the composite microcapsules developed in this work presented a remarkable accelerated period of energy storage by 47.5% under an alternating magnetic field compared to those without an applied magnetic field. This study provides a promising approach for the design and development of phase-change microcapsules with a magnetism-accelerated energy conversion capability for efficient utilization of solar energy.

Experimental Study on Thermal Performance of Pre-formed Thin Heating Floor Filled with Shaped PCM

A shape-stabilized phase change material (PCM) with high-density polyethylene was prepared as the supporting material to be added to a pre-fabricated light and dry-type heating floor. A system for underfloor heating experiments was set up in the laboratory to test the effects of average supply and return water temperatures and different temperature differences on the thermal performance of two floor heating systems under 10 different operating conditions, respectively. The results show that the surface heat-flux density of a phase change floor (PCF) is higher than that of an ordinary one at the stable stage. The proportion of heat transfer to the heating room is about 13% higher in the phase change system compared to the normal system, and the heat loss is reduced by more than 10%. At the cooling stage, the surface temperature of PCF decreases slowly, compared to the rapid decrease of the ordinary one.

Morphology-controlled fabrication of magnetic phase-change microcapsules for synchronous efficient recovery of wastewater and waste heat

Contamination and waste heat are major issues in water pollution. Aiming at efficient synchronous recovery wastewater and waste heat, we designed a novel CaCO3-based phase-change microcapsule system with an n-docosane core and a CaCO3/Fe3O4 composite shell. The system was fabricated through an emulsion-templated in situ precipitation approach in a structure-directing mode, resulting in a controllable morphology for the resultant microcapsules, varying from a peanut hull through ellipsoid to dumbbell shapes. The system has a significantly enlarged specific surface area of approximately 55 m2·g−1 with the CaCO3 phase transition from vaterite to calcite. As a result, the microcapsule system exhibits improved adsorption capacities of 497.6 and 79.1 mg/g for Pb2+ and Rhodamine B removal, respectively, from wastewater. Moreover, increase in the specific surface area of the microcapsule system with a sufficient latent heat capacity of approximately 130 J·g−1 also resulted in an enhanced heat energy-storage capability and thermal conductance for waste-heat recovery. The microcapsule system also exhibits a good leakage-prevention capability and good multicycle reusability owing to the tight magnetic CaCO3/Fe3O4 composite shell. This study provides a promising approach for developing CaCO3-based phase-change microcapsules with enhanced thermal energy storage and adsorption capabilities for efficient synchronous recovery of wastewater and waste heat.

Thermal self-regulatory smart biosensor based on horseradish peroxidase-immobilized phase-change microcapsules for enhancing detection of hazardous substances

Conventional enzyme-based biosensors are highly sensitive to operation temperature due to a strong temperature dependency of biocatalytic activity. Aiming to enhance the biosensing detection of hazardous substances at high ambient temperatures, we focused on the design and construction of a thermal self-regulatory smart biosensor through an innovative combination of phase change material (PCM) and bioelectrocatalytic material. A bioelectrocatalytic phase-change microcapsule system was first fabricated by microencapsulating n-eicosane as a PCM core in the TiO2 shell and then depositing polypyrrole (PPy) as an electroactive coating layer on the surface of TiO2 shell, followed by immobilizing horseradish peroxidase on the surface of PPy coating layer through physical adsorption. The resultant microcapsules exhibit a regular spherical morphology and layer-by-layer core–shell microstructure with the desired chemical compositions. The microcapsules not only exhibit a good thermal management ability to perform effective temperature regulation under a latent-heat capacity of approximately 115 J/g, but also reveal high thermal impact resistance and good thermal cycle stability for the long-term thermal management application in biosensors. A working electrode was modified with the microcapsules obtained above and then used to construct an electrochemical biosensing system imparted with a thermal self-regulation capability. With a high sensitivity of 5.571 µA·L·µmol−1·cm−2 and a low detection limit of 5.384 µmol/L at 55 °C, the resultant smart biosensor exhibits a better determination ability to detect catechol as a model hazardous substance at high operation temperatures than conventional biosensors thanks to the in-situ thermal management derived from its n-eicosane core. This study provides a new approach for development of thermal self-regulatory smart biosensors with an enhanced identification capability to detect hazardous substances over a wide range of temperatures.

System-Level Simulation for Integrated Phase-Change Photonics

Conventional computing systems are limited in performance by the well-known von Neumann bottleneck, arising from the physical separation of processor and memory units. The use of electrical signals in such systems also limits computing speeds and introduces significant energy losses. There is thus a pressing need for unconventional computing approaches, ones that can exploit the high bandwidths/speeds and low losses intrinsic to photonics. A promising platform for such a purpose is that offered by integrated phase-change photonics. Here, chalcogenide phase-change materials are incorporated into standard integrated photonics devices to deliver wide-ranging computational functionality, including non-volatile memory and fast, low-energy arithmetic and neuromorphic processing. We report the development of a compact behavioral model for integrated phase-change photonic devices, one which is fast enough to allow system level simulations to be run in a reasonable timescale with basic computing resources, while also being accurate enough to capture the key operating characteristics of real devices. Moreover, our model is readily incorporated with commercially available simulation software for photonic integrated circuits, thereby enabling the design, simulation and optimization of large-scale phase-change photonics systems. We demonstrate such capabilities by exploring the optimization and simulation of the operating characteristics of two important phase-change photonic systems recently reported, namely a spiking neural network system and a matrix-vector photonic crossbar array (photonic tensor core). Results show that use of our behavioral model can significantly facilitate the design and optimization at the system level, as well as expediting exploration of the capabilities of novel phase-change computing architectures.

Exergy Analysis of Phase-Change Heat-Storage Coupled Solar Heat Pump Heating System.

With the rapid development of industrialization, the excessive use of fossil fuels has caused problems such as increased greenhouse gas emissions and energy shortages. The development and use of renewable energy has attracted increased attention. In recent years, solar heat pump heating technology that uses clean solar energy combined with high-efficiency heat pump units is the development direction of clean heating in winter in northern regions. However, the use of solar energy is intermittent and unstable. The low-valley electricity policy is a night-time electricity price policy. Heat pump heating has problems such as frosting and low efficiencies in cold northern regions. To solve these problems, an exergy analysis model of each component of a phase-change heat-storage coupled solar heat pump heating system was established. Exergy analysis was performed on each component of the system to determine the direction of optimization and improvement of the phase-change heat-storage coupled solar heat pump heating system. The results showed that optimizing the heating-end heat exchanger of the system can reduce the exergy loss of the system. When the phase-change heat-storage tank meets the heating demand, its volume should be reduced to lower the exergy loss of the tank heat dissipation. Air-type solar collectors can increase the income exergies of solar collectors.

Optimum design of industrial post-combustion CO2 capture processes using phase-change solvents

Phase-change solvents (PCSs) is a class of chemicals that promises significant cost reductions in post-combustion CO2 capture. However, their use in the design of efficient absorption/desorption processes is challenged by their non-ideal behavior. A generic and flexible model is proposed for the design of phase-change CO2 capture process systems, that enables the effective identification of highly performing flowsheet configurations and recycle stream redistribution policies. The validation of the model using experimental data for the PCS mixture of MAPA/DEEA (3-(Methylamino)-Propylamine/2-(Diethylamino)-Ethanol) indicates only 4% and 0.5% differences in the reboiler duty and in the absorption and desorption temperatures. The novel PCS mixture of S1N/DMCA (N-Cyclohexyl-1,3-Propanediamine/N,N-Dimethylcyclohexylamine) and the PCS MCA (N-methylcyclohexylamine) are used in the optimum design of CO2 capture process units in two industrial cases; a quicklime production plant and a gas-fired power plant. The reboiler duty of S1N/DMCA reaches 2.1 GJ/ton CO2 and the solvent exhibits up to 47% lower operating costs than the conventional MEA (Monoethanolamine), with only 1.7% higher capital costs. The loading of S1N/DMCA reaches up to 1.35 mol CO2/mol of solvent at the exit stream of the phase-separator, whereas this solvent exhibits up to 181% higher CO2 release efficiency than MEA in the desorber. S1N/DMCA is an excellent option for plants with flue gas CO2 concentration as low as 3.5 mol%.

Thermal self-regulatory intelligent biosensor based on carbon-nanotubes-decorated phase-change microcapsules for enhancement of glucose detection

Enzyme-based biosensors are sensitive to temperature due to their strong temperature dependency of catalytic activity. Aiming at enhancing biosensing detection for glucose assay over a wide range of applicable temperatures, we designed a thermal self-regulatory intelligent biosensor through an innovative integration of phase change material (PCM) and bioelectrocatalytic substances. An electroactive phase-change microcapsule system was firstly fabricated by microencapsulating n-docosane as a PCM core in the SiO2 shell, followed by depositing polydopamine along with carbon nanotubes as an electroactive layer on the surface of SiO2 shell. The resultant microcapsules showed a regularly spherical morphology and well-defined core-shell microstructure. They also exhibited a satisfactory latent heat capacity of around 137 J/g for implementing temperature regulation with a good working stability. An electrochemical biosensing system was constructed with the resultant electroactive microcapsules together with glucose oxidase as a redox enzyme, achieving a thermal self-regulation capability to enhance the biosensing detection of glucose under in-situ thermal management at higher temperatures. With a high sensitivity of 5.95 μA⋅mM−1⋅cm−2 and a lower detection limit of 13.11 μM at 60 °C, the intelligent biosensor developed by this study demonstrated a superior determination capability and better detection performance toward glucose than conventional biosensors in a high temperature region thanks to effective regulation of microenvironment temperature in the electrode system. This study provides a promising strategy for the development of thermal self-regulatory smart biosensors with an enhanced identification ability to detect various chemical substances over a wide range of applicable temperatures.

Integrated Mg-Cl hydrogen production process and CaO/CaCO3-CaCl2 thermochemical energy storage phase change system using solar tower system

Hydrogen has been considered as a clean and sustainable fuel to meet heat requirements. The Mg-Cl hydrogen production cycle has been introduced as a promising thermochemical low-temperature cycle. In this paper, a solar system is integrated with a Mg-Cl cycle and a phase change CaO/CaCO3-CaCl2 thermochemical energy storage system (TCES). The heat generated by the solar tower is stored by the TCES in the charge mode. In the cases of low solar radiation, the TCES cycle stands in discharge mode and, if necessary, an auxiliary heat exchanger is utilized to provide the heat for the Mg-Cl cycle. The solar system is modeled by EES software and the other two cycles are simulated by Aspen Plus. Sensitivity and exergy analyses were performed for the system and reported along with the annual results of the whole system. The amount of 11.01 MW heat is stored in the charge mode and 9.536 MW is released in the discharge mode and 35.6 mol/s of hydrogen is acquired by the Mg-Cl cycle. The total exergy efficiencies of the TCES system and Mg-Cl cycle are 62.2% and 84.3%. The Mg-Cl cycle efficiency is enhanced due to the heat recovery of the internal streams and the TCES cycle efficiency is elevated due to the phase change process. The most exergy destroyer components of the TCES and Mg-Cl units belong to Carbonation and Electrolysis1 reactors with the value of 663.7 kW and 3747.4 kW, respectively. According to annual analysis, the most exergy destructions are related to the Electrolysis1 reactor, followed by solar system, which comprise 29.73% and 23.4% of total annual exergy destruction, respectively. Moreover, the annual system efficiency, exergy efficiency and solar fraction are 63.74%, 54.76, and 83.59%, respectively.

Numerical study on the thermal performance analysis of packed-bed latent heat thermal storage system with biomimetic vein hierarchical structure

ABSTRACT The vein hierarchical structure has high efficiency of component transportation capacity, it has been widely used in energy storage, solar thermochemical reactions, and photocatalysis. In this paper, the idea of packed-bed latent heat thermal heat storage system (LHTESS) with biomimetic vein hierarchical structure is proposed to improve the heat transfer rate and heat storage efficiency of the packed-bed LHTESS. The size of heat storage unit changes along the axial and radial direction under the same porosity as the conventional uniform structure. The effects of inlet velocity on the completion rate, temperature distribution, pressure drop, and liquid fraction of the conventional structure and biomimetic structure are analyzed. The numerical results indicate that the biomimetic vein hierarchical structure can ameliorate the temperature inhomogeneity, increase the heat transfer area, and improve the thermal response of the packed-bed compared with the conventional uniform structure. The maximum increase of liquid fraction is 25% under different inlet velocities, and the average completion rate of phase change material and system in charge process is increased by 12% and 6%, respectively.

Microencapsulating n-docosane phase change material into CaCO3/Fe3O4 composites for high-efficient utilization of solar photothermal energy

Microencapsulating phase-change materials (PCMs) into CaCO3 shell is considered as an effective way to resolve the leakage problem of the microcapsule system and enhance its heat transfer. Herein, we designed and fabricated a type of phase-change microcapsule system based on an n-docosane core and CaCO3/Fe3O4 composite shell using a nonaqueous emulsion-templated self-assembly technology for enhancing solar photothermal energy absorption, conversion and storage performance. The type and addition amount of templating agent and the mass ratio of PCM core to wall material play key roles in the formation of microcapsules with a controllable spherical or rhombohedral morphology and a perfect core-shell microstructure. The resultant phase-change microcapsules show a satisfactory latent heat-storage capacity of around 140 J/g, high encapsulation ratio of over 59%, high thermal conductivity of 0.795 W m−1 K−1, excellent leakage prevention capability and good thermal cycle stability when synthesized under the optimum synthetic condition. More importantly, the phase-change microcapsules exhibit a significant enhancement in solar photothermal conversion and storage performance due to the presence of Fe3O4 nanoparticles in their shell, and their photothermal conversion efficiency was improved by 47.9% compared to the corresponding microcapsules without Fe3O4. In conclusion, the phase-change microcapsules developed in this work show considerable potential in high-efficient solar energy utilization.

Surface construction of Ni(OH)2 nanoflowers on phase-change microcapsules for enhancement of heat transfer and thermal response

A phase-change microcapsule system based on an n-docosane core and SiO2/nanostructural Ni(OH)2 layer-by-layer shell was designed with the aim to enhance the heat transfer and thermal response capability of phase-change microcapsules. This system was fabricated through emulsion-templated interfacial polycondensation to form a SiO2/n-docosane microcapsule system, followed by anchoring Ni(OH)2 nanoflowers on the surface of the SiO2 shell via structure-directed interfacial precipitation. The resultant microcapsule system achieved a satisfactory latent heat-storage capacity of around 130 J/g with high energy-storage efficiency over 99%. Compared to conventional SiO2/n-docosane phase-change microcapsules, this microcapsule system not only presents high thermal conductivity, rapid heat transfer rate, good leakage prevention capability, high heat charging-discharging stability, but also exhibits a good phase-change reversibility and resilience ability to perform repetitious solid-liquid phase transformations. The combination of traditional phase-change microcapsules with a nanostructural Ni(OH)2 outer layer results in a significant enhancement in heat transfer, which makes the system a fast thermal response ability to satisfy a variety of applications where fast and stable thermal energy storage/release is required. Through constructing the Ni(OH)2 nanoflowers on the surface of conventional phase-change microcapsules, this study offers a promising strategy for the design and fabrication of high-performance phase-change microcapsules with fast thermal response.

Nanoflaky nickel-hydroxide-decorated phase-change microcapsules as smart electrode materials with thermal self-regulation function for supercapacitor application

A nanoflaky nickel-hydroxide-decorated phase-change microcapsule system [designated as Ni(OH)2-SiO2-MEPCM] was designed as a smart electrode material for supercapacitor application. This system was constructed through microencapsulating n-docosane core into a silica shell via emulsion-templated interfacial polycondensation, followed by fabricating a nanoflaky Ni(OH)2 layer on the surface of silica shell through structure-directed interfacial precipitation. Such a combination of phase-change microcapsules and electrochemically active material makes the Ni(OH)2-SiO2-MEPCM synchronously implement thermal self-regulation and electrochemical energy storage. The Ni(OH)2-SiO2-MEPCM shows a perfect core-shell structured morphology and well-defined nanoflaky surface microstructure. The Ni(OH)2-SiO2-MEPCM not only possesses a good temperature regulation capability with a latent-heat capacity of around 140 J/g but also exhibits an excellent thermal cycle stability and good high-temperature shape stability. Most importantly, compared to traditional electrode materials, the Ni(OH)2-SiO2-MEPCM can perform effective thermal self-regulation to regulate the micro-ambient temperature by its n-docosane core when used as an electrode material for supercapacitors, leading to improved electrochemical performance and good long-term cycle stability with capacitance retention of 86.2% after 3000 charge-discharge cycles at a high ambient temperature of 50 °C. All of these features indicate that the Ni(OH)2-SiO2-MEPCM developed by this work has great potential as a smart electrode material for electrochemical energy-storage applications.