Room-Temperature Liquid Metal Confined in MXene Paper as a Flexible, Freestanding, and Binder-Free Anode for Next-Generation Lithium-Ion Batteries

Oxhide gelatin-regulated aramid nanofiber/liquid metal films with sandwiched structure for electromagnetic interference shielding

Liquid metal (LM) based electromagnetic interference (EMI) shielding materials with high conductivity and continuous deformation capacity are important needs for meeting modern advanced electronic equipment. However, an independent free-standing film with LM is difficult to achieve due to its unique fluidity properties. Here, a simple alternating filtration film-forming method was utilized to orderly construct a sandwiched EMI shielding film with LM stabilized by bio-based oxhide gelatin (gel) as the intermediate conductive layer, and two films of aramid nanofibers/oxhide gel (ANF/gel) as the external insulating protective layers. This design not only prevents LM from being exposed to environmental conditions, but also reduces the risk of chemical corrosion in practical applications. Under optimal LM addition conditions, the sandwiched film (0.3-3 L) exhibited better EMI shielding performance of 50.4 dB in the X-band than the blended film (0.7 dB), as well as excellent mechanical properties (tensile strength of 65.8 MPa, strain 8.6 %). More importantly, the sandwiched film still maintained reliable EMI shielding performance after being experienced largely physical deformation. This study provides a new solution for preparing LM-based EMI shielding composites, and is expected to arouse pursuit of high EMI shielding effects of bio-based gel while also paying attention to their safety.

Microconfined Assembly of High-Resolution and Mechanically Robust EGaIn Liquid Metal Stretchable Electrodes for Wearable Electronic Systems

Stretchable electrodes based on liquid metals (LM) are widely used in human-machine interfacing, wearable bioelectronics, and other emerging technologies. However, realizing the high-precision patterning and mechanical stability remains challenging due to the poor wettability of LM. Herein, a method is reported to fabricate LM-based multilayer solid-liquid electrodes (m-SLE) utilizing electrohydrodynamic (EHD) printed confinement template. In these electrodes, LM self-assembled onto these high-resolution templates, assisted by selective wetting on the electrodeposited Cu layer. This study shows that a m-SLE composed of PDMS/Ag/Cu/EGaIn exhibits line width of ≈20 µm, stretchability of ≈100%, mechanical stability ≈10 000 times (stretch/relaxation cycles), and recyclability. The multi-layer structure of m-SLE enables the adjustability of strain sensing, in which the strain-sensitive Ag part can be used for non-distributed detection in human health monitoring and the strain-insensitive EGaIn part can be used as interconnects. In addition, this study demonstrates that near field communication (NFC) devices and multilayer displays integrated by m-SLEs exhibit stable wireless signal transmission capability and stretchability, suggesting its applicability in creating highly-integrated, large-scale commercial, and recyclable wearable electronics.

Stabilizing Solid Electrolyte Interphase on Liquid Metal Via Dynamic Hydrogel-Derived Carbon Framework Encapsulation

Eutectic gallium-indium liquid metal (EGaIn-LM), with a considerable capacity and unique self-healing properties derived from its intrinsic liquid nature, gains tremendous attention for lithium-ion batteries (LIBs) anode. However, the fluidity of the LM can trigger continuous consumption of the electrolyte, and its liquid-solid transition during the lithiation/de-lithiation process may result in the rupture of the solid electrolyte interface (SEI). Herein, LM is employed as an initiator to in situ assemble the 3D hydrogel for dynamically encapsulating itself; the LM nanoparticles can be homogeneously confined within the hydrogel-derived carbon framework (HDC) after calcination. Such design effectively alleviates the volume expansion of LM and facilitates electron transportation, resulting in a superior rate capability and long-term cyclability. Further, the "dual-layer" SEI structure and its key components, including the robust LiF outer layer and corrosion-resistant and ionic conductive LiGaOx inner layer are revealed, confirming the involvement of LM in the formation of SEI, as well as the important role of carbon framework in reducing interfacial side reactions and SEI decomposition. This work provides a distinct perspective for the formation, structural evolution, and composition of SEI at the liquid/solid interface, and demonstrates an effective strategy to construct a reliable matrix for stabilizing the SEI.

The Promising Potential of Gallium Based Liquid Metals for Energy Storage

Energy storage devices play a crucial role in various applications, such as powering electronics, power backup for homes and businesses, and support for the integration of renewable energy sources into electrical grid applications. Electrode materials for energy storage devices are preferred to have a flexible nature, conductive, better capacity, and low-toxicity. Using Gallium based liquid metal alloys, such as Eutectic Gallium-Indium (EGaIn), Eutectic Gallium-Tin (EGaSn), and Eutectic Gallium-Indium-Tin (EGaInSn), as electrode materials play very important role in energy storage devices. These liquid metals have some interesting properties with a self-healing nature, high mechanical stability, compatibility with various materials, fluidity, low young's modulus, high electrical and thermal conductivity. Those properties have made it suitable to be used in various energy storage devices. In this mini review, we have concisely described the advantages and challenges of using liquid metal as electrode materials for various energy storage devices.

Multifunctional Liquid Metal-Bridged Graphite Nanoplatelets/Aramid Nanofiber Film for Thermal Management

Miniaturization of modern micro-electronic devices urges the development of multi-functional thermal management materials. Traditional polymer composite-based thermal management materials are promising candidates, but they suffer from single functionality, high cost, and low fire-resistance. Herein, a multifunctional liquid metal (LM)-bridged graphite nanoplatelets (GNPs)/ aramid nanofibers (ANFs) film is fabricated via a facile vacuum-assisted self-assembly approach followed by compression. ANFs serve as interfacial binders to link LM and GNPs together via hydrogen bondings and π-π interactions, while LM bridges the adjacent layer of GNPs to endow a fast thermal transport by phonons and electrons. The resultant composite films exhibit a high bidirectional thermal conductivity (In-plane: 29.5 W m-1K-1 and through-plane: 5.3 W m-1K-1), offering a reliable and effective cooling. Moreover, the as-fabricated composite films exhibit superior flame-retardance (peak of heat release rate of 4000J g-1), outstanding Joule heating performance (200 °C at supplied voltage of 3.5 V), and excellent electromagnetic interference shielding effectiveness (EMI SE of 62 dB). This work provides an efficient avenue to fabricate multifuntional thermal management materials for micro-electronic devices, battery thermal management, and artificial intelligence.

A Room-Temperature Self-Healing Liquid Metal-Infilled Microcapsule Driven by Coaxial Flow Focusing for High-Performance Lithium-Ion Battery Anode

Liquid metals have attracted a lot of attention as self-healing materials in many fields. However, their applications in secondary batteries are challenged by electrode failure and side reactions due to the drastic volume changes during the "liquid-solid-liquid" transition. Herein, a simple encapsulated, mass-producible method is developed to prepare room-temperature liquid metal-infilled microcapsules (LMMs) with highly conductive carbon shells as anodes for lithium-ion batteries. Due to the reasonably designed voids in the microcapsule, the liquid metal particles (LMPs) can expand freely without damaging the electrode structure. The LMMs-based anodes exhibit superior capacity of rete-performance and ultra-long cycling stability remaining 413 mAh g-1 after 5000 cycles at 5.0 A g-1. Ex situ X-ray powder diffraction (XRD) patterns and electrochemical impedance spectroscopy (EIS) reveal that the LMMs anode displays a stable alloying/de-alloying mechanism. DFT calculations validate the electronic structure and stability of the room-temperature LMMs system. These findings will bring some new opportunities to develop high-performance battery systems.

MXene as Promising Anode Material for High-Performance Lithium-Ion Batteries: A Comprehensive Review

Broad adoption has already been started of MXene materials in various energy storage technologies, such as super-capacitors and batteries, due to the increasing versatility of the preparation methods, as well as the ongoing discovery of new members. The essential requirements for an excellent anode material for lithium-ion batteries (LIBs) are high safety, minimal volume expansion during the lithiation/de-lithiation process, high cyclic stability, and high Li+ storage capability. However, most of the anode materials for LIBs, such as graphite, SnO2, Si, Al, and Li4Ti5O12, have at least one issue. Hence, creating novel anode materials continues to be difficult. To date, a few MXenes have been investigated experimentally as anodes of LIBs due to their distinct active voltage windows, large power capabilities, and longer cyclic life. The objective of this review paper is to provide an overview of the synthesis and characterization characteristics of the MXenes as anode materials of LIBs, including their discharge/charge capacity, rate performance, and cycle ability. In addition, a summary of the potential outlook for developments of these materials as anodes is provided.

Carbon nanofibers confined polyoxometalate derivatives as flexible self-supporting electrodes for robust sodium storage

Flexible self-supporting film electrodes, which eliminate the need for additional adhesive, conductive agents, or current collectors, offer significant advantages in terms of mechanical properties, specific capacity, and energy density for energy storage applications. In this study, we successfully developed a flexible film electrode by incorporating derivatives of Mo and Fe-based polyoxometalates (POMs-D) into carbon nanofibers (CNFs). The integration of CNFs significantly enhanced the structural stability of POMs-D, while the internally formed electrical field facilitated efficient electron transfer, resulting in good performance in sodium storage. The film electrode demonstrated a high capacitive contribution of 90.0 % for sodium uptake/release at a scan rate of 1.0 mV s-1. It maintained a capacity of approximately 170 mA h g-1 even after 8000 cycles at a current density of 3.0 A g-1. Moreover, the film electrode exhibited a decent capacity with a 40.0-fold increase in current density, along with high power capability and energy density in sodium-ion hybrid supercapacitors, showcasing the versatility. These findings unveil the structure-functionality relationship and offer an advanced approach for developing high-performance film electrode materials, opening new possibilities in the fields of material science and energy storage.

Amorphous TiO2 shells: an Essential Elastic Buffer Layer for High-Performance Self-Healing Eutectic GaSn Nano-Droplet Room-Temperature Liquid Metal Battery

Gallium-based alloy liquid metal batteries currently face limitations such as volume expansion, unstable solid electrolyte interface (SEI) film and substantial capacity decay. In this study, amorphous titanium dioxide is used to coat eutectic GaSn nanodroplets (eGaSn NDs) to construct the core-shell structure of eGaSn@TiO2 nanodroplets (eGaSn@TiO2 NDs). The amorphous TiO2 shell (~6.5 nm) formed a stable SEI film, alleviated the volume expansion, and provided electron/ion transport channels to achieve excellent cycling performance and high specific capacity. The resulting eGaSn@TiO2 NDs exhibited high capacities of 580, 540, 515, 485, 456 and 426 mAh g-1 at 0.1, 0.2, 0.5, 1, 2 and 5 C, respectively. No significant decay was observed after more than 500 cycles with a capacity of 455 mAh g-1 at 1 C. In situ X-ray diffraction (in situ XRD) was used to explore the lithiation mechanism of the eGaSn negative electrode during discharge. This study elucidates the design of advanced liquid alloy-based negative electrode materials for high-performance liquid metal batteries (LMBs).

A liquid metal-fluoropolymer artificial protective film enables robust lithium metal batteries at sub-zero temperatures

Batteries that are both high-energy-density and durable at sub-zero temperatures are highly desirable for deep space and subsea exploration and military defense applications. Our design incorporates a casting membrane technology to prepare a gallium indium liquid metal (LM)/fluoropolymer hybrid protective film on a lithium metal anode. The LM not only spontaneously forms a passivation alloy layer with lithium but also reduces the nucleation potential barrier and homogenizes the Li+ flux on the surface of the lithium anode. The fluoropolymer's polar functional groups (-C-F-) effectively induce targeted dispersion of gallium indium seeds, and the unique pit structure on the surface provides oriented sites for lithium plating. By implementing these strategies optimally, the protected lithium metal anode remains in operation at a current density of 20 mA cm-2 with an over-potential of about 50.4 mV after 500 h, and the full cells have a high capacity retention rate of up to 98.5% at a current density of 0.5 C after 100 cycles. Furthermore, the battery shows improved low temperature performance at -30 °C, validating the potential of the protective film to enable battery operation at sub-zero temperatures.

Three-dimensionally multiple protected silicon anode toward ultrahigh areal capacity and stability

Silicon (Si) is considered as one of the most promising candidates for next-generation lithium-ion battery (LIB) anode due to its high theoretical capacity. However, the drastic volume change of Si anodes during lithiation/delithiation processes leads to rapid capacity fade. Herein, a three-dimensional Si anode with multiple protection strategy is proposed, including citric acid-modification of Si particles (CA@Si), GaInSn ternary liquid metal (LM) addition, and porous copper foam (CF) based electrode. The CA modified supports strong adhesive attraction of Si particles with binder and LM penetration maintains good electrical contact of the composite. The CF substrate constructs a stable hierarchical conductive framework, which could accommodate the volume expansion to retain integrity of the electrode during cycling. As a result, the obtained Si composite anode (CF-LM-CA@Si) demonstrates a discharge capacity of 3.14 mAh cm^-2 after 100 cycles at 0.4 A g^-1, corresponding to 76.1% capacity retention rate based on the initial discharge capacity and delivers comparable performance in full cells. The present study provides an applicable prototype of high-energy density electrodes for LIBs.

Flexible stretchable low-energy X-ray (30-80 keV) radiation shielding material: Low-melting-point Ga1In1Sn7Bi1 alloy/thermoplastic polyurethane composite

A highly flexible stretchable thermoplastic polyurethane (TPU) composite loaded with a low-melting-point Ga₁In₁Sn₇Bi₁ multiprincipal element alloy (LMPEA) was prepared, and its radiation shielding performance was evaluated. The fluid characteristic of LMPEA and the flexibility of TPU enable good interface compatibility. Ga₁In₁Sn₇Bi₁ LMPEA consists of two eutectic structures, and the liquid gallium-rich phases are distributed at the boundary of the InBi intermetallic compound and Sn solid solution. In the low-photon energy range of 30-80 keV, LMPEA has a theoretical specific lead equivalent of 0.803 mmPb/mm and a theoretical weight reduction of 17.27% compared with lead. To evaluate the photon attenuation capability for the LMPEA/TPU composites, the Phy-X procedure and Monte Carlo simulations were used to determine the shielding parameters, such as the mass attenuation coefficient, linear attenuation coefficient, half-value layer, tenth-value layer, mean free path, effective atomic number, and fast neutron removal cross section. The attenuation performance test of X-ray protective materials measured the actual lead equivalent. At the same thickness, the LMPEA/TPU composite (66.667, 50.000 wt% LMPEA loading) has a higher measured lead equivalent than the in-service medical shielding materials, which meets the lead equivalent requirements of X-ray protective clothing. LMPEA/TPU composites are nontoxic, lightweight, and have excellent low-energy X-ray shielding ability, offering great potential for application in medical wearable materials.

Conductive Iodine-Doped Red Phosphorus Enabled Dendrite-Free Lithium Deposition on MXene Matrix

The highest theoretical capacity and lowest redox potential of lithium metal make lithium-based batteries the "holy grail" of the next-generation batteries. However, the uncontrollable dendrite growth and infinite volume change of lithium seriously hinder the real-world implementation of lithium-based batteries. Herein, a flexible MXene@iodine-doped red phosphorus (MXene@RP) paper with iodine-doped red phosphorous particles evenly distributed on the surface and interlayer of MXene matrix is designed by a simple vapor condensation reduction approach. The MXene@RP paper can be used as an efficient matrix to enable dendrite-free lithium deposition. On the one hand, the iodine doping alleviates the low conductivity shortcoming of red phosphorus, making it facilitate homogeneous lithium nucleation, thus promoting uniform lithium deposition and suppressing dendrite growth. On the other hand, the unique layered structure of conductive MXene paper provides ion transport channels and free spaces for lithium loading, alleviating the volume change induced structural damage. As a result, the MXene@RP paper with preloaded lithium exhibits long-term cycling stability. Particularly, a full cell based on Li-MXene@RP anode can maintain 81.4% of the initial capacity after 600 cycles at 4 C. The MXene@RP-based anode increases the potential applications of MXene and provides a guide for the design of dendrite-free lithium hosts.

MXene-Reinforced Liquid Metal/Polymer Fibers via Interface Engineering for Wearable Multifunctional Textiles

Stretchable conductive fibers are an important component of wearable electronic textiles, but often suffer from a decrease in conductivity upon stretching. The use of liquid metal (LM) droplets as conductive fillers in elastic fibers is a promising solution. However, there is an urgent need to develop effective strategies to achieve high adhesion of LM droplets to substrates and establish efficient electron transport paths between droplets. Here, we use large-sized MXene two-dimensional conductive materials to modify magnetic LM droplets and prepare MXene/magnetic LM/poly(styrene-butadiene-styrene) composite fibers (MLMS fibers). The MXene sheets decorated on the surface of magnetic LM droplets not only enhance the droplet adhesion to substrate but also bridge adjacent droplets to establish efficient conductive paths. MLMS fibers show several-fold improvements in tensile strength and elongation and a 30-fold increase in conductivity compared with pure LM-filled fibers. These conductive fibers can be easily woven into multifunctional textiles, which exhibit strong electromagnetic interference shielding and stable Joule heating performances even under large tensile deformation. In addition, other advantages of MLMS textiles, such as high gas/liquid permeability, strong chemical resistance (acid and alkaline conditions), high/low-temperature tolerance (-40-150 °C) and water washability, make them particularly suitable for wearable applications.

Dynamic Liquid Metal Catalysts for Boosted Lithium Polysulfides Redox Reaction

Designing efficient electrocatalysts with high electroconductivity, strong chemisorption, and superior catalytical efficiency to realize rapid kinetics of the lithium polysulfides (LiPSs) conversion process is crucial for practical lithium-sulfur (Li-S) battery applications. Unfortunately, most current electrocatalysts cannot maintain long-term stability due to the possible failure of catalytic sites. Herein, a novel dynamic electrocatalytic strategy with the liquid metal (i.e., gallium-tin, EGaSn) to facilitate LiPSs redox reaction is reported. The combined theoretical simulations and microstructure experiment analysis reveal that Sn atoms dynamically distributed in the liquid Ga matrix act as the main active catalytic center. Meanwhile, Ga provides a uniquely dynamic environment to maintain the long-term integrity of the catalytic system. With the participation of EGaSn, a tailor-made 2 Ah Li-S pouch cell with a specific energy density of 307.7 Wh kg^-1 is realized. This work opens up new opportunities for liquid-phase binary alloys as electrocatalysts for high-specific-energy Li-S batteries.

Radical Covalent Organic Frameworks Associated with Liquid Na-K toward Dendrite-Free Alkali Metal Anodes

Liquid sodium-potassium (Na-K) alloy has the characteristics of high abundance, low redox potential, high capacity, and no dendrites, which has become an ideal alternative material for potassium/sodium metal anodes. However, the high surface tension of liquid sodium potassium alloy at room temperature makes it inconvenient in practical use. Here, the Na-K as reducing agent treats with hydrazone linkages of covalent organic frameworks (COFs) and obtain the carbon-oxygen radical COFs (COR-Tf-DHzDM-COFs). The preparation method solves the problems that the preparation process of the traditional Na-K composite anode is complex and has high cost. The structures of the COR-Tf-DHzDM-COFs are characterized by X-ray diffraction （XRD), fourier transform infrared (FT-IR), electron paramagnetic resonance (EPR), and solid-state NMR measurements. It is the first time that carbon-oxygen radical COFs from bulk COFs are constructed by one-step method and the operation is flexible, convenient, and high rate of quality, which is suitable for big production and widely used. The cycle stability of the composite Na-K anode is improved, which provides a new idea for the design of high-performance liquid metal anode.

MXene chemistry, electrochemistry and energy storage applications

The diverse and tunable surface and bulk chemistry of MXenes affords valuable and distinctive properties, which can be useful across many components of energy storage devices. MXenes offer diverse functions in batteries and supercapacitors, including double-layer and redox-type ion storage, ion transfer regulation, steric hindrance, ion redistribution, electrocatalysts, electrodeposition substrates and so on. They have been utilized to enhance the stability and performance of electrodes, electrolytes and separators. In this Review, we present a discussion on the roles of MXene bulk and surface chemistries across various energy storage devices and clarify the correlations between their chemical properties and the required functions. We also provide guidelines for the utilization of MXene surface terminations to control the properties and improve the performance of batteries and supercapacitors. Finally, we conclude with a perspective on the challenges and opportunities of MXene-based energy storage components towards future practical applications.

Applications of liquid metals in nanotechnology

Post-transition liquid metals (LMs) offer new opportunities for accessing exciting dynamics for nanomaterials. As entities with free electrons and ions as well as fluidity, LM-based nanomaterials are fundamentally different from their solid counterparts. The low melting points of most post-transition metals (less than 330 °C) allow for the formation of nanodroplets from bulk metal melts under mild mechanical and chemical conditions. At the nanoscale, these liquid state nanodroplets simultaneously offer high electrical and thermal conductivities, tunable reactivities and useful physicochemical properties. They also offer specific alloying and dealloying conditions for the formation of multi-elemental liquid based nanoalloys or the synthesis of engineered solid nanomaterials. To date, while only a few nanosized LM materials have been investigated, extraordinary properties have been observed for such systems. Multi-elemental nanoalloys have shown controllable homogeneous or heterogeneous core and surface compositions with interfacial ordering at the nanoscale. The interactions and synergies of nanosized LMs with polymeric, inorganic and bio-materials have also resulted in new compounds. This review highlights recent progress and future directions for the synthesis and applications of post-transition LMs and their alloys. The review presents the unique properties of these LM nanodroplets for developing functional materials for electronics, sensors, catalysts, energy systems, and nanomedicine and biomedical applications, as well as other functional systems engineered at the nanoscale.

MXene/Organics Heterostructures Enable Ultrastable and High-Rate Lithium/Sodium Batteries

Organic electrode materials have shown potential for rechargeable batteries because they are environmentally friendly, earth-abundant sources, recyclable, high sustainable, designable, flexible, and lightweight. However, low electrical conductivity and dissolution in organic liquid electrolytes hinder their further development. Herein, MXene/organics heterostructures are designed to address the problems of organic electrodes via a scalable and simple electrostatic self-assembly strategy. Under the effect of the electrostatic interaction, organic cathode material, 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA), is tightly attached to MXene nanosheets. Owing to the high electronic conductivity and special two-dimensional (2D) structure of MXene nanosheets, the issues of PTCDA cathode are effectively relieved. When applied in lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs), the MXene@PTCDA heterostructure exhibits significantly enhanced rate capability and cycling performance than bare PTCDA. The heterostructures proposed here can be applied to other (K, Zn, Al, Mg, Ca, etc.) battery systems. In addition to energy storage and conversion, the heterostructures can be also extended to many fields such as catalysis, sensors, electronics, optics, membranes, semiconductors, biomedicines, etc.

Covalent Organic Frameworks and Their Derivatives for Better Metal Anodes in Rechargeable Batteries

Metal anodes based on a plating/stripping electrochemistry such as metallic Li, Na, K, Zn, Ca, Mg, Fe, and Al are recognized as promising anode materials for constructing next-generation high-energy-density rechargeable metal batteries owing to their low electrochemical potential, high theoretical specific capacity, superior electronic conductivity, etc. However, inherent issues such as high chemical reactivity, severe growth of dendrites, huge volume changes, and unstable interface largely impede their practical application. Covalent organic frameworks (COFs) and their derivatives as emerging multifunctional materials have already well addressed the inherent issues of metal anodes in the past several years due to their abundant metallophilic functional groups, special inner channels, and controllable structures. COFs and their derivatives can solve the issues of metal anodes by interfacial modification, homogenizing ion flux, acting as nucleation seeds, reducing the corrosion of metal anodes, and so on. Nevertheless, related reviews are still absent. Here we present a detailed review of multifunctional COFs and their derivatives in metal anodes for rechargeable metal batteries. Meanwhile, some outlooks and opinions are put forward. We believe the review can catch the eyes of relevant researchers and supply some inspiration for future research.

Design Principles and Applications of Next-Generation High-Energy-Density Batteries Based on Liquid Metals

Increasing need for the renewable energy supply accelerated the thriving studies of Li-ion batteries, whereas if the high-energy-density Li as well as alkali metals should be adopted as battery electrodes is still under fierce debate for safety concerns. Recently, a group of low-melting temperature metals and alloys that are in liquid phase at or near room-temperature are being reported for battery applications, by which the battery energy could be improved without significant dendrite issue. Besides the dendrite-free feature, liquid metals can also promise various high-energy-density battery designs on the basis of unique materials properties. In this review, the design principles for liquid metals-based batteries from mechanical, electrochemical, and thermodynamical aspects are provided. With the understanding of the theoretical basis, currently reported relevant designs are summarized and analyzed focusing on the working mechanism, effectiveness evaluation, and novel application. An overview of the state-of-the-art liquid metal battery developments and future prospects is also provided in the end as a reference for further research explorations.

Production of Uniformly Sized Gallium-Based Liquid Alloy Nanodroplets via Ultrasonic Method and Their Li-Ion Storage

Gallium-based liquid alloys are attractive due to their unique properties, and they can potentially be applied in the field of flexible electronics as coolant materials for nuclear and liquid batteries, due to the high thermal conductivity and excellent fluid properties of liquid metals. However, it is still challenging to fabricate gallium-based liquid alloy nanodroplets with uniform and small size. Here, we performed a systematical study on the influence of various factors affecting the size of nanodroplets. Liquid metal nanodroplets with an average size of 74 nm and narrow size distribution were successfully fabricated. Li-ion half-cells were assembled with eutectic GaIn (eGaIn) nanodroplets as anode active materials, which showed higher specific capacity than the bulk eGaIn alloy under the same testing conditions.

Liquid metal-based nanocomposite materials: fabrication technology and applications

Research on liquid metals has been steadily garnering more interest in recent times, especially in flexible electronics applications because of their properties like possessing high conductivity and being liquid state at room temperature. The unique properties afforded by such materials at low temperatures can compensate for the limitations of stretchable electronic devices, particularly robustness and their fluidic property, which can enhance the flexibility and deformation of these devices. Therefore, interest in liquid-metal nanoparticles and liquid metals with nanocomposites has enabled research into their fabrication technologies as well as utilisation in fields such as chemistry, polymer engineering, computational modelling, and nanotechnology. In particular, in flexible and stretchable electronic device applications, the research attention is focused on the fabrication methodologies of liquid-metal nanoparticles and liquid metals containing nanocomposites. This review attempts to summarise the available stretchable and flexible electronics applications that use liquid-metal nanoparticles as well as liquid metals with nanomaterial additives.

Electrochemical Insights, Developing Strategies, and Perspectives toward Advanced Potassium-Sulfur Batteries

The boosting demand for high-capacity energy storage systems requires innovative battery technologies with low-cost and sustainability. The advancement of potassium-sulfur (K-S) batteries have been triggered recently due to abundant resource and cost effectiveness. However, the functional performance of K-S batteries is fundamentally restricted by the vague understanding of K-S electrochemistry and the imperfect cell components or architectures, facing the issues of low cathode conductivity, intermediate shuttle loss, poor anode stability, electrode volume fluctuation, etc. Inspired by considerable research efforts on rechargeable metal-sulfur batteries, the holistic K-S system can be stabilized and promoted through various strategies on rational physical regulation and chemical engineering. In this review, first an attempt is made to address the electrochemical kinetic concept of K-S system on the basis of the emerging studies. Then, the classification of performance-improving strategies is thoroughly discussed in terms of specific battery component and prospective outlooks in materials optimization, structure innovations, as well as relevant electrochemistry are provided. Finally, the critical perspectives and challenges are discussed to demonstrate the forward-looking developmental directions of K-S batteries. This review not only endeavors to provide a deep understanding of the electrochemistry mechanism and rational designs for high-energy K-S batteries, but also encourages more efforts in their large-scale practical realization.

A Wearable Supercapacitor Based on Conductive PEDOT:PSS-Coated Cloth and a Sweat Electrolyte

A sweat-based flexible supercapacitor (SC) for self-powered smart textiles and wearable systems is presented. The developed SC uses sweat as the electrolyte and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) as the active electrode. With PEDOT:PSS coated onto cellulose/polyester cloth, the SC shows specific capacitance of 8.94 F g^-1 (10 mF cm^-2 ) at 1 mV s^-1 . With artificial sweat, the energy and power densities of the SC are 1.36 Wh kg^-1 and 329.70 W kg^-1 , respectively for 1.31 V and its specific capacitance is 5.65 F g^-1 . With real human sweat the observed energy and power densities are 0.25 Wh kg^-1 , and 30.62 W kg^-1 , respectively. The SC performance is evaluated with different volumes of sweat (20, 50, and 100 µL), bending radii (10, 15, 20 mm), charging/discharging stability (4000 cycles), and washability. With successful on-body testing, the first demonstration of the suitability of a sweat-based SC for self-powered cloth-based sensors to monitor sweat salinity is presented. With attractive performance and the use of body fluids, the presented approach is a safe and sustainable route to meet the power requirements in wearable systems.