Bifunctional Liquid Metals Allow Electrical Insulating Phase Change Materials to Dual-Mode Thermal Manage the Li-Ion Batteries

A Janus Smart Window for Temperature-Adaptive Radiative Cooling and Adjustable Solar Transmittance

The advancement of sophisticated smart windows exhibiting superior thermoregulation capabilities in both solar spectrum and long-wave infrared range maintains a prominent objective for researchers in this field. In this study, a Janus window is proposed and prepared based on polymer-stabilized liquid-crystal films/thermochromic materials. It can achieve switchable front long-wave infrared emissivity (εFront) and solar modulation ability (ΔTsol) through dynamic flipping, making it suitable for different seasonal energy-saving requirements. Outdoor experiments show that under daytime illumination, the indoor temperature decreases by 8 °C, and the nighttime temperature drops by 5 °C. MATLAB simulation calculations indicate that the daytime cooling power is 93 W m-2, while the nighttime cooling power reaches 142 W m-2. Interestingly, by modifying the conductive layer, it can effectively shield electromagnetic radiation (within the X-band frequency range (8.2-12.4) GHz). Energy simulation reveals the substantial superiority of this device in energy savings compared with single-layer polymer-stabilized liquid crystal, poly(N-isopropyl acrylamide), and normal glass when applied in different climate zones. This research presents a compelling opportunity for the development of sophisticated smart windows characterized by exceptional thermoregulation capabilities.

Interfacial Engineering of Liquid Metals in Thermal Science and Technology

Liquid metals (LMs), with their unique metallic and fluidic properties at room temperature, show promising potential in advanced thermal-related applications. Nevertheless, challenges, such as high surface tension, limited wettability, phase separation, leakage, and corrosion, limit their integration into broader applications. In this Perspective, we overview the interfacial engineering approaches in enhancing the compatibility and stability of LMs in complex application environments. Additionally, applications of LMs in thermal energy conduction, storage, conversion, and infrared modulation and control are discussed. This Perspective highlights the critical role of interfacial engineering in LM-based systems and the pathways for developing next-generation LM-enabled thermal technologies.

Boron Nitride-Polymer Composites with High Thermal Conductivity: Preparation, Functionalization Strategy and Innovative Structural Regulation

The escalating thermal challenges posed by increasing power densities in electronic devices emerge as a critical barrier to maintain their sustained and reliable operation. Addressing this issue requires the strategic development of materials with superior thermal conductivity properties to facilitate progress in high-power electronics development. Thermal conductive polymer composites by incorporating ceramic material renowned for their exceptional thermal conductivity adjustability, insulating properties, and moldability, are emerging as a promising solution to this urgent challenge. Hexagonal boron nitride (h-BN) nanomaterials emerge as highly promising candidates for thermal management applications, owing to their exceptional mechanical properties, superior thermal stability, remarkable thermal conductivity coefficients, minimal thermal expansion characteristics, and outstanding chemical inertness. In this work, the progress of ≈10 years on high thermal conductive boron nitride-filled polymer composites is thoroughly summarized. Moreover, strategies for h-BN and other boron nitride nanomaterials-filled polymer composites at synthesis, functionalization, and innovative structural design are discussed in detail. The main challenges and future development of boron nitride-polymer composites in thermal management are also proposed, which will provide meaningful guidance for the design and practical applications of thermal management materials.

Double-Network Aerogel-Based Composite Phase Change Material Inspired by Beaver Damming for All-Weather Thermal Management of Lithium Batteries

Phase change materials (PCMs) have shown significant potential in enhancing the thermal regulation of lithium-ion (Li-ion) batteries. However, existing organic solid-liquid PCMs encounter several issues, including leakage, limited energy density, and an inability to fulfill the demands of comprehensive thermal management across various environmental conditions. This study takes inspiration from beavers, which construct dams to regulate the temperature of their habitats in different climates, and introduces a dual-network aerogel-based composite PCM (CPCM) designed for the all-weather thermal control of Li-ion batteries. The developed CPCM incorporates tetradecanol (TD) as the core phase change material, a poly(vinyl alcohol)/carboxylated cellulose nanocrystal (PVA/CNC-C) aerogel as the potting material, borax for cross-linking, and graphene nanoplatelets (GNPs) to facilitate photothermal conversion. This CPCM demonstrates a high energy density of 199.1 J/g and remarkable cyclic durability. Furthermore, it features excellent shape retention, superior mechanical strength, and an impressive photothermal conversion efficiency of 94.5%. In addition, the CPCM effectively regulates the thermal behavior of Li-ion batteries: at elevated temperatures, it ensures that the battery's maximum operating temperature remains below 55 °C, while at lower temperatures, it maintains the battery above 10 °C for 30-40 min. Moreover, it possesses the capability to preheat batteries, enhancing their functionality in cold environments. This research presents an innovative approach to designing materials that address the comprehensive thermal management needs of Li-ion batteries under varying climatic conditions.

Enhancing Thermal Protection in Lithium Batteries with Power Bank-Inspired Multi-Network Aerogel and Thermally Induced Flexible Composite Phase Change Material

Thermal runaway (TR) is considered a significant safety hazard for lithium batteries, and thermal protection materials are crucial in mitigating this risk. However, current thermal protection materials generally suffer from poor mechanical properties, flammability, leakage, and rigid crystallization, and they struggle to continuously block excess heat transfer and propagation once thermal saturation occurs. This study proposes a novel type of thermal protection material: an aerogel coupled composite phase change material (CPCM). The composite material consists of gelatin/sodium alginate (Ge/SA) composite biomass aerogel as an insulating component and a thermally induced flexible CPCM made from thermoplastic polyester elastomer as a heat-absorbing component. Inspired by power bank, we coupled the aerogel with CPCM through the binder, so that CPCM can continue to 'charge and store energy' for the aerogel, effectively absorbing heat, delaying the heat saturation phenomenon, and maximizing the duration of thermal insulation. The results demonstrate that the Ge/SA aerogel exhibits excellent thermal insulation (with a temperature difference of approximately 120 °C across a 1 cm thickness) and flame retardancy (achieving a V-0 flame retardant rating). The CPCM exhibits high heat storage density (811.9 J g-1), good thermally induced flexibility (bendable above 40 °C), and thermal stability. Furthermore, the Ge/SA-CPCM coupled composite material shows even more outstanding thermal insulation performance, with the top surface temperature remaining at 89 °C after 100 min of exposure to a high temperature of 230 °C. This study provides a new direction for the development of TR protection materials for lithium batteries.

Composite Gel Polymer Electrolyte for High-Performance Flexible Zinc-Air Batteries

Enhancing ionic conductivity and electrolyte uptake is of significance for gel polymer electrolytes (GPEs) for flexible zinc-air batteries (FZABs). Herein, a composite mesoporous silica/polyacrylamide (5 wt.% mPAM) GPE is constructed with comparable ionic conductivity to aqueous electrolytes, where the ionic conductivity is up to 337 mS cm-1, and the weight loss after exposing in air 72 h is less than 18%, owing to the excellent electrolyte uptake and continuous ion migration network provided by the mesoporous silica fillers. When used as a quasi-solid-electrolyte, the rechargeable FZAB exhibited high electrochemical performance and structural stability, where the peak power density is up to 162.8 mW cm-2, and the initial charge-discharge potential gap is as low as 0.62 V, resulting in a long lifespan exceeding 110 h, showcasing the combination of high durability, cost-effectiveness and easy production for practical applications.

van der Waals-bonded graphene clusters enhance thermal conductivity of phase-change materials for advanced thermal energy management

Organic phase-change materials possess immense application potential, but their low thermal conductivity (≤0.5 W m-1 K-1) severely limits the thermal energy charge/discharge rate, impeding their practical implementation in the field of advanced energy. While incorporating thermally conductive fillers into the phase-change matrix can address this issue, achieving a thermal conductivity exceeding 10 W m-1 K-1 at a filler content below 30 vol% remains challenging, attributed to the absence of a well-designed filler interface and structure. Herein, a strategy for developing planar graphene clusters and subsequently integrating them with phase-change microcapsules to fabricate composites using compression molding was demonstrated. The proposed graphene clusters are formed by closely aligned and overlapping graphene sheets that bond together through van der Waals forces, resulting in a significant decrease in junction thermal resistance within the composites. Combining this interface design with compression-induced construction of a highly oriented structure, the composites achieved a remarkable thermal conductivity of 103 W m-1 K-1 with ≈29 vol% filler addition, enhancing the thermal energy charge/discharge rate by over two orders of magnitude. Furthermore, we demonstrated that the composites possess the essential enthalpy values, competent strength, and ease of shaping, making them applicable across various domains of thermal energy management.

2D Materials-Based Thermal Interface Materials: Structure, Properties, and Applications

The challenges associated with heat dissipation in high-power electronic devices used in communication, new energy, and aerospace equipment have spurred an urgent need for high-performance thermal interface materials (TIMs) to establish efficient heat transfer pathways from the heater (chip) to heat sinks. Recently, emerging 2D materials, such as graphene and boron nitride, renowned for their ultrahigh basal-plane thermal conductivity and the capacity to facilitate cross-scale, multi-morphic structural design, have found widespread use as thermal fillers in the production of high-performance TIMs. To deepen the understanding of 2D material-based TIMs, this review focuses primarily on graphene and boron nitride-based TIMs, exploring their structures, properties, and applications. Building on this foundation, the developmental history of these TIMs is emphasized and a detailed analysis of critical challenges and potential solutions is provided. Additionally, the preparation and application of some other novel 2D materials-based TIMs are briefly introduced, aiming to offer constructive guidance for the future development of high-performance TIMs.

Thermal shock protection with scalable heat-absorbing aerogels

Improving thermal insulation is vital for addressing thermal protection and energy efficiency challenges. Though silica aerogel has a record-low thermal conductivity at ambient pressure, its high production cost, due to its nanoscale porous structure, has hindered its widespread use. In this study, we introduce a cost-effective and mild method that enhances insulation by incorporating phase change materials (PCMs) into a micron-porous framework. With a thermal conductivity at 0.041 W m-1K-1 on par with conventional insulation materials, this PCMs aerogel presents additional advantages for thermal protection from transient high-temperature loads by effectively delaying heat propagation through heat absorption. Moreover, the PCMs aerogel remains stable under cyclic deformation and heating up to 300 °C and is self-extinguishing in the presence of fire. Our approach offers a promising alternative for affordable insulation materials with potential wide applications in thermal protection and energy conservation areas.

Gallium-Based Liquid Metals in Rechargeable Batteries: From Properties to Applications

Gallium-based (Ga-based) liquid metals have attracted considerable interest due to their low melting points, enabling them to feature both liquid properties and metallic properties at room temperature. In light of this, Ga-based liquid metals also possess excellent deformability, high electrical and thermal conductivity, superior metal affinity, and unique self-limited surface oxide, making them popular functional materials in energy storage. This provides a possibility to construct high-performance rechargeable batteries that are deformable, free of dendrite growth, and so on. This review primarily starts with the property of Ga-based liquid metal, and then focuses on the potential applications in rechargeable batteries by exploiting these advantages, aiming to construct the correlation between properties and structures. The glorious applications contain interface protection, self-healing electrode construction, thermal management, and flexible batteries. Finally, the opportunities and obstacles for the applications of liquid metal in batteries are presented.

Direct Regeneration of Spent Lithium-Ion Battery Cathodes: From Theoretical Study to Production Practice

Direct regeneration method has been widely concerned by researchers in the field of battery recycling because of its advantages of in situ regeneration, short process and less pollutant emission. In this review, we firstly analyze the primary causes for the failure of three representative battery cathodes (lithium iron phosphate, layered lithium transition metal oxide and lithium cobalt oxide), targeting at illustrating their underlying regeneration mechanism and applicability. Efficient stripping of material from the collector to obtain pure cathode material has become a first challenge in recycling, for which we report several pretreatment methods currently available for subsequent regeneration processes. We review and discuss emphatically the research progress of five direct regeneration methods, including solid-state sintering, hydrothermal, eutectic molten salt, electrochemical and chemical lithiation methods. Finally, the application of direct regeneration technology in production practice is introduced, the problems exposed at the early stage of the industrialization of direct regeneration technology are revealed, and the prospect of future large-scale commercial production is proposed. It is hoped that this review will give readers a comprehensive and basic understanding of direct regeneration methods for used lithium-ion batteries and promote the industrial application of direct regeneration technology.

Recent progress in multifunctional, reconfigurable, integrated liquid metal-based stretchable sensors and standalone systems

Possessing a unique combination of properties that are traditionally contradictory in other natural or synthetical materials, Ga-based liquid metals (LMs) exhibit low mechanical stiffness and flowability like a liquid, with good electrical and thermal conductivity like metal, as well as good biocompatibility and room-temperature phase transformation. These remarkable properties have paved the way for the development of novel reconfigurable or stretchable electronics and devices. Despite these outstanding properties, the easy oxidation, high surface tension, and low rheological viscosity of LMs have presented formidable challenges in high-resolution patterning. To address this challenge, various surface modifications or additives have been employed to tailor the oxidation state, viscosity, and patterning capability of LMs. One effective approach for LM patterning is breaking down LMs into microparticles known as liquid metal particles (LMPs). This facilitates LM patterning using conventional techniques such as stencil, screening, or inkjet printing. Judiciously formulated photo-curable LMP inks or the introduction of an adhesive seed layer combined with a modified lift-off process further provide the micrometer-level LM patterns. Incorporating porous and adhesive substrates in LM-based electronics allows direct interfacing with the skin for robust and long-term monitoring of physiological signals. Combined with self-healing polymers in the form of substrates or composites, LM-based electronics can provide mechanical-robust devices to heal after damage for working in harsh environments. This review provides the latest advances in LM-based composites, fabrication methods, and their novel and unique applications in stretchable or reconfigurable sensors and resulting integrated systems. It is believed that the advancements in LM-based material preparation and high-resolution techniques have opened up opportunities for customized designs of LM-based stretchable sensors, as well as multifunctional, reconfigurable, highly integrated, and even standalone systems.

Dressing Paraffin Wax/Boron Nitride Phase Change Composite with a Polyethylene "Underwear" for the Reliable Battery Safety Management

Phase change material (PCM) can provide a battery system with a buffer platform to respond to thermal failure problems. However, current PCMs through compositing inorganics still suffer from insufficient thermal-transport behavior and safety reliability against external force. Herein, a best-of-both-worlds method is reported to allow the PCM out of this predicament. It is conducted by combining a traditional PCM (i.e., paraffin wax/boron nitride) with a spirally weaved polyethylene fiber fabric, just like the traditional PCM is wearing functional underwear. On the one hand, the spirally continuous thermal pathways of polyethylene fibers in the fabric collaborate with the boron nitride network in the PCM, enhancing the through-plane and in-plane thermal conductivity to 10.05 and 7.92 W m-1 K, respectively. On the other, strong polyethylene fibers allow the PCM to withstand a high puncture strength of 47.13 N and tensile strength of 18.45 MPa although above the phase transition temperature. After this typical PCM packs a triple Li-ion battery system, the battery can be promised reliable safety management against both thermal and mechanical abuse. An obvious temperature drop of >10 °C is observed in the battery electrode during the cycling charging and discharging process.

Multiple H-Bonding Cross-Linked Supramolecular Solid-Solid Phase Change Materials for Thermal Energy Storage and Management

Solid-solid phase change materials (SSPCMs) are considered among the most promising candidates for thermal energy storage and management. However, the application of SSPCMs is consistently hindered by the canonical trade-off between high TES capacity and mechanical robustness. In addition, they suffer from poor recyclability due to chemical cross-linking. Herein, a straightforward but effective strategy for fabricating supramolecular SSPCMs with high latent heat and mechanical strength is proposed. The supramolecular polymer employs multiple H-bonding interactions as robust physical cross-links. This enables SSPCM with a high enthalpy of phase transition (142.5 J g-1 ), strong mechanical strength (36.9 MPa), and sound shape stability (maintaining shape integrity at 120 °C) even with a high content of phase change component (97 wt%). When SSPCM is utilized to regulate the operating temperature of lithium-ion batteries, it significantly diminishes the battery working temperature by 23 °C at a discharge rate of 3 C. The robust thermal management capability enabled through solid-solid phase change provides practical opportunities for applications in fast discharging and high-power batteries. Overall, this study presents a feasible strategy for designing linear SSPCMs with high latent heat and exceptional mechanical strength for thermal management.

Flexible and Robust Functionalized Boron Nitride/Poly(p-Phenylene Benzobisoxazole) Nanocomposite Paper with High Thermal Conductivity and Outstanding Electrical Insulation

With the rapid development of 5G information technology, thermal conductivity/dissipation problems of highly integrated electronic devices and electrical equipment are becoming prominent. In this work, "high-temperature solid-phase & diazonium salt decomposition" method is carried out to prepare benzidine-functionalized boron nitride (m-BN). Subsequently, m-BN/poly(p-phenylene benzobisoxazole) nanofiber (PNF) nanocomposite paper with nacre-mimetic layered structures is prepared via sol-gel film transformation approach. The obtained m-BN/PNF nanocomposite paper with 50 wt% m-BN presents excellent thermal conductivity, incredible electrical insulation, outstanding mechanical properties and thermal stability, due to the construction of extensive hydrogen bonds and π-π interactions between m-BN and PNF, and stable nacre-mimetic layered structures. Its λ∥ and λ⊥ are 9.68 and 0.84 W m-1 K-1, and the volume resistivity and breakdown strength are as high as 2.3 × 1015 Ω cm and 324.2 kV mm-1, respectively. Besides, it also presents extremely high tensile strength of 193.6 MPa and thermal decomposition temperature of 640 °C, showing a broad application prospect in high-end thermal management fields such as electronic devices and electrical equipment.

Dry-Contact Thermal Interface Material with the Desired Bond Line Thickness and Ultralow Applied Thermal Resistance

Efforts to directly utilize thixotropic polymer composites for out-of-plane thermal transport applications, known as thermal interface materials (TIMs), have been impeded by their mediocre applied thermal resistance (Reff) in a sandwiched structure. Different from traditional attempts at enhancing thermal conductivity, this study proposes a low-bond line thickness (BLT) path for mitigating the sandwiched thermal impedance. Taking the most common TIM, polydimethylsiloxane/aluminum oxide/zinc oxide (PDMS/Al2O3/ZnO), as an example, liquid metal is designed to on-demand localize at the Al2O3-polymer and Al2O3-filler interface regions, breaking rheological challenges for lowering the BLT. Specifically, during the sandwiched compression process, interfacial LM is just like the lubricant, dexterously promoting the relaxation of immobilized PDMS chains and helping fillers to flow through mitigating the internal friction between Al2O3 and adjacent filler. As a result, this TIM first time exhibits a boundary BLT (4.28 μm) that almost approaches the diameter of the maximum filler and performs an ultralow dry-contact Reff of 4.05 mm2 K/W at 40 psi, outperforming most reported and commercial dry-contact TIMs. This study of the low-BLT direction is believed to point to a new path for future research on high-performance TIMs.

High-Performance Graphene Biocomposite Enabled by Fe3+ Coordination for Thermal Management

Emerging biocomposites with excellent heat dissipation capabilities and inherent sustainability are urgently needed to address the cooling issues of modern electronics and growing environmental concerns. However, the moisture stability, mechanical performance, thermal conductivity, and even flame retardancy of biomass-based materials are generally insufficient for practical thermal management applications. Herein, we present a high-performance graphene biocomposite consisting of carboxylated cellulose nanofibers and graphene nanosheets through an evaporation-induced self-assembly and subsequent Fe3+ cross-linking strategy. The Fe3+ coordination plays a critical role in stabilizing the material structure, thereby improving the mechanical strength and water stability of the biocomposite films, and its effect is revealed by density functional theory calculations. The hierarchical structure of the biocomposite films also leads to a high in-plane thermal conductivity of 42.5 W m-1 K-1, enabling a superior heat transfer performance. Furthermore, the resultant biocomposite films exhibit outstanding Joule heating performance with a fast thermal response and long-term stability, improved thermal stability, and flame retardancy. Therefore, such a general strategy and the desired overall properties of the biocomposite films offer wide application prospects for functional and safe thermal management.

Functional Materials and Innovative Strategies for Wearable Thermal Management Applications

Highlights

This article systematically reviews the thermal management wearables with a specific emphasis on materials and strategies to regulate the human body temperature. Thermal management wearables are subdivided into the active and passive thermal managing methods. The strength and weakness of each thermal regulatory wearables are discussed in details from the view point of practical usage in real-life.

Abstract

Thermal management is essential in our body as it affects various bodily functions, ranging from thermal discomfort to serious organ failures, as an example of the worst-case scenario. There have been extensive studies about wearable materials and devices that augment thermoregulatory functionalities in our body, employing diverse materials and systematic approaches to attaining thermal homeostasis. This paper reviews the recent progress of functional materials and devices that contribute to thermoregulatory wearables, particularly emphasizing the strategic methodology to regulate body temperature. There exist several methods to promote personal thermal management in a wearable form. For instance, we can impede heat transfer using a thermally insulating material with extremely low thermal conductivity or directly cool and heat the skin surface. Thus, we classify many studies into two branches, passive and active thermal management modes, which are further subdivided into specific strategies. Apart from discussing the strategies and their mechanisms, we also identify the weaknesses of each strategy and scrutinize its potential direction that studies should follow to make substantial contributions to future thermal regulatory wearable industries.

Tetris-Style Stacking Process to Tailor the Orientation of Carbon Fiber Scaffolds for Efficient Heat Dissipation

As the miniaturization of electronic devices and complication of electronic packaging, there are growing demands for thermal interfacial materials with enhanced thermal conductivity and the capability to direct the heat toward heat sink for highly efficient heat dissipation. Pitch-based carbon fiber (CF) with ultrahigh axial thermal conductivity and aspect ratios exhibits great potential for developing thermally conductive composites as TIMs. However, it is still hard to fabricate composites with aligned carbon fiber in a general approach to fully utilize its excellent axial thermal conductivity in specific direction. Here, three types of CF scaffolds with different oriented structure were developed via magnetic field-assisted Tetris-style stacking and carbonization process. By regulating the magnetic field direction and initial stacking density, the self-supporting CF scaffolds with horizontally aligned (HCS), diagonally aligned and vertically aligned (VCS) fibers were constructed. After embedding the polydimethylsiloxane (PDMS), the three composites exhibited unique heat transfer properties, and the HCS/PDMS and VCS/PDMS composites presented a high thermal conductivity of 42.18 and 45.01 W m-1 K-1 in fiber alignment direction, respectively, which were about 209 and 224 times higher than that of PDMS. The excellent thermal conductivity is mainly ascribed that the oriented CF scaffolds construct effective phonon transport pathway in the matrix. In addition, fishbone-shaped CF scaffold was also produced by multiple stacking and carbonization process, and the prepared composites exhibited a controlled heat transfer path, which can allow more versatility in the design of thermal management system.

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.

Single-Phase Ternary Compounds with a Disordered Lattice and Liquid Metal Phase for High-Performance Li-Ion Battery Anodes

Si is considered as the promising anode materials for lithium-ion batteries (LIBs) owing to their high capacities of 4200 mAh g-1 and natural abundancy. However, severe electrode pulverization and poor electronic and Li-ionic conductivities hinder their practical applications. To resolve the afore-mentioned problems, we first demonstrate a cation-mixed disordered lattice and unique Li storage mechanism of single-phase ternary GaSiP2 compound, where the liquid metallic Ga and highly reactive P are incorporated into Si through a ball milling method. As confirmed by experimental and theoretical analyses, the introduced Ga and P enables to achieve the stronger resistance against volume variation and metallic conductivity, respectively, while the cation-mixed lattice provides the faster Li-ionic diffusion capability than those of the parent GaP and Si phases. The resulting GaSiP2 electrodes delivered the high specific capacity of 1615 mAh g-1 and high initial Coulombic efficiency of 91%, while the graphite-modified GaSiP2 (GaSiP2@C) achieved 83% of capacity retention after 900 cycles and high-rate capacity of 800 at 10,000 mA g-1. Furthermore, the LiNi0.8Co0.1Mn0.1O2//GaSiP2@C full cells achieved the high specific capacity of 1049 mAh g-1 after 100 cycles, paving a way for the rational design of high-performance LIB anode materials.

Flexible, Highly Thermally Conductive and Electrically Insulating Phase Change Materials for Advanced Thermal Management of 5G Base Stations and Thermoelectric Generators

Thermal management has become a crucial problem for high-power-density equipment and devices. Phase change materials (PCMs) have great prospects in thermal management applications because of their large capacity of heat storage and isothermal behavior during phase transition. However, low intrinsic thermal conductivity, ease of leakage, and lack of flexibility severely limit their applications. Solving one of these problems often comes at the expense of other performance of the PCMs. In this work, we report core-sheath structured phase change nanocomposites (PCNs) with an aligned and interconnected boron nitride nanosheet network by combining coaxial electrospinning, electrostatic spraying, and hot-pressing. The advanced PCN films exhibit an ultrahigh thermal conductivity of 28.3 W m-1 K-1 at a low BNNS loading (i.e., 32 wt%), which thereby endows the PCNs with high enthalpy (> 101 J g-1), outstanding ductility (> 40%) and improved fire retardancy. Therefore, our core-sheath strategies successfully balance the trade-off between thermal conductivity, flexibility, and phase change enthalpy of PCMs. Further, the PCNs provide powerful cooling solutions on 5G base station chips and thermoelectric generators, displaying promising thermal management applications on high-power-density equipment and thermoelectric conversion devices.

Liquid Metal-Assisted High-Efficiency Exfoliation of Boron Nitride for Electrically Insulating Heat-Spreader Film

Boron nitride nanosheets (BNNSs) are regarded as promising two-dimensional materials in thermally conductive yet electrically insulating applications. Attributed to the strong interlayer "lip-lip" interactions in bulk hexagonal boron nitride (h-BN), high-efficiency exfoliation and scalable fabrication of BNNSs via the top-down strategies remain formidable challenges. Herein, an interesting observation is manifested that gallium-based liquid metal (LM) forming robust coordination interactions with h-BN helps reduce the lip-lip interlayer interactions and thus facilitates successful exfoliation under intense shearing force. For example, employing the ball-milling technique, the BNNS yield can increase to 41.21% with the assistance of LM at only 2 h milling time. Its exfoliation efficiency (yield/time) reaches as high as 26.72%/h, more than 2-fold that of other previously reported methods, including sonication and other ball-milling methods. Moreover, the exfoliated BNNSs are still found to be highly electrically insulating with a band gap of 4.65 eV, showing prospective potential in thermally conductive yet electrical insulating applications. As a proof of concept, a microwave-transparent heat spreader (cellulose nanofiber/BNNSs) is fabricated and verified for applications in high-frequency thermal-management fields.