Portable Electronic Systems Research Articles

Coaxial direct writing of ultra-strong supercapacitors with braided continuous carbon fiber based electrodes

Supercapacitors produced based on 3D printing technology greatly expand the range of materials and geometric complexity. However, the production of fiber-based supercapacitors typicallyrequires subsequent steps. For the first time, we report a coaxial direct writing technique that enables the one-step fabrication of braided flexible solid-state supercapacitors. Continuous carbon fiber is used as a flexible substrate. α-manganese dioxide nanowires and activated carbon are used as active materials. The entire electrode assembly is coated with solid-state electrolyte and then braided. Through coaxial direct writing technology, the braided electrodes and sealings can be extruded by a coaxial nozzle to continuously print free-form ultra-strong supercapacitors with a tensile strength of the braided electrodes up to 636 MPa. Electrochemical measurement results show that the printed capacitor exhibits an excellent specific capacitance, and it still maintains a capacitance retention of 90.1% after 1000 cycles. The supercapacitor exhibits nearly identical electrochemical capacitive characteristics at various bent angles. This work paves the way for integrating enhanced durability and adaptability into next-generation wearable and portable electronic systems.

Synergistic Layered Design of Aerogel Nanocomposite of Graphene Nanoribbon/MXene with Tunable Absorption Dominated Electromagnetic Interference Shielding.

Electromagnetic pollution presents growing challenges due to the rapid expansion of portable electronic and communication systems, necessitating lightweight materials with superior shielding capabilities. While prior studies focused on enhancing electromagnetic interference (EMI) shielding effectiveness (SE), less attention is given to absorption-dominant shielding mechanisms, which mitigate secondary pollution. By leveraging material science and engineering design, a layered structure is developed comprising rGOnR/MXene-PDMS nanocomposite and a MXene film, demonstrating exceptional EMI shielding and ultra-high electromagnetic wave absorption. The 3D interconnected network of the nanocomposite, with lower conductivity (10-3-10-2 S/cm), facilitates a tuned impedance matching layer with effective dielectric permittivity, and high attenuation capability through conduction loss, polarization loss at heterogeneous interfaces, and multiple scattering and reflections. Additionally, the higher conductivity MXene layer exhibits superior SE, reflecting passed electromagnetic waves back to the nanocomposite for further attenuation due to a π/2 phase shift between incident and back-surface reflected electromagnetic waves. The synergistic effect of the layered structures markedly enhances total SE to 54.1 dB over the Ku-band at a 2.5 mm thickness. Furthermore, the study investigates the impact of hybridized layered structure on reducing the minimum required thickness to achieve a peak absorption (A) power of 0.88 at a 2.5 mm thickness.

Resistive switching behavior and thermal stability in the flexible BEFO/ZnO/LSMO heterostructure for flexible/wearable electronics

With the advent of the internet era, wearable electronic devices and flexible electronic technology are rapidly emerging, and new resistive random access memory (RRAM) based on flexible substrates have thus gained extensive attention. Here, the flexible Bi0·95Er0·05FeO3/ZnO/La0·66Sr0·34MnO3 (BEFO/ZnO/LSMO) heterostructure is prepared on Mica substrate using the sol-gel method. The high resistance state (HRS) to low resistance state (LRS) ratio consistently surpasses 102 under the flat and the 15 mm bending radius state. There is no significant change in the resistive switching (RS) behavior after 30 I–V curve cycles and 103 write/erase operations on the BEFO/ZnO/LSMO heterostructure, which reflects excellent stability. In addition, the device still works properly at 175 °C for dynamic conversion between HRS and LRS. The observed RS behavior in the BEFO/ZnO/LSMO heterostructure is attributed to ion migration and alterations in the potential barrier height at the interfaces. These results suggest that the BEFO/ZnO/LSMO heterostructure based on a flexible Mica substrate plays a crucial role in the development of next-generation portable and flexible electronic systems due to its excellent flexibility and thermal stability.

INDIDO: A novel low-power approach for domino logic circuits

Power dissipation in Nanoelectronic circuits at advanced technology nodes is dominated by leakage power dissipation. This is due to an increase in short channel effects in the scaled transistors.The VLSI industry is seeking alternative options to enhance the performance of portable electronic systems by ensuring higher speed and reduced power dissipation. In the ultra-deep submicron (DSM) regime, a new device called the fin-shaped field effect transistor (FinFET) was developed to replace CMOS technology. FinFET, a multi-gate device, significantly reduces power dissipation compared to planer MOS (Metal Oxide Semiconductor ) transistor, but it doesn’t entirely resolve the issue. To further reduce power dissipation in the ultra DSM regime, low power approaches are required. Domino logic, a widely-used dynamic logic, is commonly utilized in high-speed VLSI architectures. In this research work, a novel INput Dependent Inverter DOmino (INDIDO) logic approach for low-power domino logic circuits using FinFET devices is proposed. A comparative analysis between the proposed INDIDO method and the existing approaches is performed for domino logic circuits for various performance metrics at the 16 nm technology node. In this research, various circuits like domino buffer, domino OR, domino AND, domino XOR and domino half adder are designed using the proposed INDIDO approach.The proposed INDIDO FinFET buffer circuit offers significant improvement in energy efficiency and FOM (Figure of Merit) by 53.18% and 82% respectively as compared to conventional FinFET footed domino buffer circuit. Beside this, proposed circuits like INDIDO OR, INDIDO AND, INDIDO XOR and INDIDO Half adder circuit follow the same trend as INDIDO buffer circuit and show better performance parametres in comparison to the existing low power domino approaches as well. In addition to this, the proposed INDIDO buffer circuits are also analyzed for PVT(process voltage and temperature) variability.This whole analysis makes us to conclude that proposed INDIDO approach reduces power dissipation and delay penalty, have high noise tolerance capacity, more immunity against PVT variations and high energy efficiency in comparison to the already existing techniques.

Tailoring the multifunctional properties of hydrothermally synthesized reduced graphene oxide/tungsten oxide supported nanorods to enhance the electrochemical and water-splitting activities

Herein, we employ the synergistic effect and better conductivity of graphene oxide (GO) and reduced graphene oxide (rGO) to boost the energy storage capacity and electrical conductivity of tungsten oxide (WO3) nanomaterials. The structural analysis of the WO3 and its composites revealed the presence of a monoclinic phase with a periodic arrangement. However, the field emission scanning electron microscopy revealed the nanorod-shaped morphology for WO3 and the nonuniform interconnected nanorod nanosheet-like morphology for composites. The identification of functional groups and stretching–bending vibrations of W–O, CO WO, and C–C bonds are revealed by FT-IR and Raman spectroscopy. Additionally, the transmission electron microscopy and X-ray photoelectron spectroscopy confirmed the morphological, structural, and electronic states of hybrid rGO/WO3 nanostructures. The supercapacitive properties and electrocatalytic activity of WO3, GO/WO3, and rGO/WO3–nickel foam (NF) electrodes were investigated using a 2 M KOH via an three-electrode system in the desired potential window. As a result, the rGO/WO3 electrode exhibited promising electrochemical performance with a large specific capacity, 135 mAh/g (972 F/g) with high energy (ED), and power density (PD) of 33 Wh/kg and 1100 W/kg at 5 mA/cm2, and excellent retention of 92 % after 5000 CV cycles. However, the hybrid device is fabricated using rGO/WO3//rGO-NF as electrodes and exhibited a high specific capacity (78 mAh/g and 177 F/g at 5 mV/s), decent cycling stability (85 % after 5000 cycles), and high ED/PD (33 Wh/kg /1166 W/kg) respectively. Moreover, the electrocatalytic activity of WO3, GO/WO3, and rGO/WO3 electrodes was studied using 2 M KOH respectively. The superior electrochemical activities such as overpotential, Tafel slope, and the good electrochemical surface area (ESCA) of 328 mV, 95.5 mV/dec, and 38.2 cm2 with good stability were observed for rGO/WO3 electrode. The proposed asymmetric design provides promising material for developing next-generation energy storage devices for various portable electronic systems and water-splitting activity.

Hexaazatriphenylene-doped MXene films for the high-performance micro-supercapacitors and wearable pressure sensor system

Two-dimensional MXene nanosheets have found extensive applications in portable electronic devices and flexible energy storage systems. However, the self-stacking effect caused by van der Waals forces severely restricts the rapid transport of electrolyte ions, thereby impacting the electrochemical performance. Here, nitrogen-doped MXene nanosheets (MXene-H) were obtained via surface modification of MXene with hexaazidotriphenylene (HAT) derivatives. The nitrogen atoms introduced between the layers act as pillars, widening the layer spacing and exposing more electrochemically active sites. By optimizing the doping ratio, the MXene-H micro-supercapacitor (MXene-H-MSC) exhibits outstanding electrochemical performance, with an area capacitance of 210.1 mF/cm2 and an energy density of 29.18 mWh/cm2, significantly surpassing that of previously reported MXene-based micro-supercapacitors. Moreover, the MXene-H-MSC demonstrates excellent cycling stability and flexibility, retaining 95% capacitance after 10,000 cycles, with no significant capacitance degradation observed in the CV curves tested at different angles. Furthermore, a micro-integrated system composed of the MXene-H-MSC and an MXene hydrogel pressure sensor in series can effectively respond to small changes in body movements, including speaking and finger flexing. This work provides potential guidance for research into the next generation of microelectronics.

Development and Scaling up of the Purification and Regeneration Integrated Materials Engineering (“PRIME”) Process for Cathodes Direct Recycling and Upcycling

Lithium-ion batteries (LIBs) are the primary power source for portable electronic devices, electric vehicles (EVs), and energy storage systems (ESS) due to their high energy and power densities. However, with an average lifespan of mostly 5-10 years, million tons of end-of-life (EoL) LIBs will be produced by 2030. Recycling spent LIBs will bring new opportunities in reducing constraints imposed by material scarcity, enhancing environmental sustainability, and providing a safer and more resilient circular supply chain. The current commercialized recycling methods, including pyrometallurgy and hydrometallurgy, require extreme conditions, such as high temperatures and strong acids, to destroy the chemical bonds. The subsequent extraction process is lengthy, with high energy consumption and cost. A new direct recycling pathway has been brought to the field, defined as recycling valuable components without breaking down the chemical structure. Direct recycling can be efficient, cost and energy effective, but the currently developed methods can only be demonstrated at a lab scale due to the lack of robustness and tedious pre-treatments. Recently, we have identified that the direct recycling method combining hydrothermal relithiation and subsequent short annealing can successfully restore the composition, structural defects, and electrochemical performance of different spent cathode materials to the same level as the pristine material. More importantly, the method is extended to recover spent cathode materials with various impurities, such as conductive agents, binders, residual salts, and aluminum shreds. Such purification has been integrated into the regeneration process, which enables a practical pathway for cathode direct recycling. The related technology is named “Purification and Regeneration Integrated Materials Engineering (“PRIME”) and has been granted by the Department of Energy (DOE) under Bipartisan Infrastructure Law (“BIL”). The PRIME process merges the advantages of direct cathode recycling techniques with the novel purification strategy to improve the quality of recovered cathode materials with significantly reduced unit operation steps, which can be scaled up to an industrial level. Meanwhile, the PRIME process can recover the cathode with high consistency and yield. This new direct recycling process will provide a solid technical foundation for mass production of the next generation of LIBs recycling.

The impact of physicochemical features of carbon electrodes on the capacitive performance of supercapacitors: a machine learning approach

Hybrid electric vehicles and portable electronic systems use supercapacitors for energy storage owing to their fast charging/discharging rates, long life cycle, and low maintenance. Specific capacitance is regarded as one of the most important performance-related characteristics of a supercapacitor’s electrode. In the current study, Machine Learning (ML) algorithms were used to determine the impact of various physicochemical properties of carbon-based materials on the capacitive performance of electric double-layer capacitors. Published experimental datasets from 147 references (4899 data entries) were extracted and then used to train and test the ML models, to determine the relative importance of electrode material features on specific capacitance. These features include current density, pore volume, pore size, presence of defects, potential window, specific surface area, oxygen, and nitrogen content of the carbon-based electrode material. Additionally, categorical variables as the testing method, electrolyte, and carbon structure of the electrodes are considered as well. Among five applied regression models, an extreme gradient boosting model was found to best correlate those features with the capacitive performance, highlighting that the specific surface area, the presence of nitrogen doping, and the potential window are the most significant descriptors for the specific capacitance. These findings are summarized in a modular and open-source application for estimating the capacitance of supercapacitors given, as only inputs, the features of their carbon-based electrodes, the electrolyte and testing method. In perspective, this work introduces a new wide dataset of carbon electrodes for supercapacitors extracted from the experimental literature, also giving an instance of how electrochemical technology can benefit from ML models.

Single-pixel reconstructive mid-infrared micro-spectrometer.

Miniaturized spectrometers in the mid-infrared (MIR) are critical in developing next-generation portable electronics for advanced sensing and analysis. The bulky gratings or detector/filter arrays in conventional micro-spectrometers set a physical limitation to their miniaturization. In this work, we demonstrate a single-pixel MIR micro-spectrometer that reconstructs the sample transmission spectrum by a spectrally dispersed light source instead of spatially grated light beams. The spectrally tunable MIR light source is realized based on the thermal emissivity engineered via the metal-insulator phase transition of vanadium dioxide (VO2). We validate the performance by showing that the transmission spectrum of a magnesium fluoride (MgF2) sample can be computationally reconstructed from sensor responses at varied light source temperatures. With potentially minimum footprint due to the array-free design, our work opens the possibility where compact MIR spectrometers are integrated into portable electronic systems for versatile applications.

Experiments on thermal performance of heat pipes using nanoparticle layer as the wick

To enhance the usability of heat pipes and vapor chambers as the cooling device for portable electronic systems, necessity of thin wick is rapidly increasing. In the present work, the layer of silica nanoparticles of about 10 μm in thickness was formed on the copper tube inner wall to explore experimentally if it works as the thin wick. It was demonstrated that in comparison with the ordinary heat pipe using a wire mesh as the wick, the thermal resistance was even improved (0.62 to 0.23 K/W) and the deterioration of the maximum heat transfer rate was not significant (120 to 78 W). This indicated that the present nanoparticle layer can be used as a very thin wick of the heat pipes and vapor chambers. If the mass of nanoparticles deposited on the heat pipe inner wall was sufficient, the thermal performance was not deteriorated even after the maximum heat transfer rate condition was experienced. It was also demonstrated that the maximum heat transfer rate can be enhanced up to 100 W when the nanoparticles were suspended in the working fluid enclosed in the container.

Edge device for movement pattern classification using neural network algorithms

Portable electronic systems allow the analysis and monitoring of continuous time signals, such as human activity, integrating deep learning techniques with cloud computing, causing network traffic and high energy consumption. In addition, the use of algorithms based on neural networks are a very widespread solution in these applications, but they have a high computational cost, not suitable for edge devices. In this context, solutions are created that bring data analysis closer to the edge of the network, so in this paper models adapted to an edge device for the recognition of human activity are evaluated, considering characteristics such as inference time, memory, and precision. Two categories of models based on deep and convolutional neural networks are developed by implementing them in C language and comparing with the TensorFlow Lite platform. The results show that the implementations with libraries have a better accuracy result of 76% using principal component analysis inputs, obtaining an execution time of 9ms. Therefore, when evaluating the models, we must not only consider their accuracy but also the execution time and memory on the device.

Lightweight All Graphene‐Based Two‐Phase Heat Transport Devices

AbstractGraphene‐based composites show great potential in the development of lightweight functional devices and systems, and polymers are usually used as binders to enhance the mechanical properties of these composites. Due to the low thermal conductivity of the polymer and the high inherent interfacial thermal resistance between polymer and graphene, however, the developed devices and systems generally possess low thermal conductivity, which seriously limits their further thermal‐related applications. Here, a lightweight two‐phase heat transport device (TPHTD) based on a vapor‐liquid phase transition‐based heat transfer by using a graphene‐based composite material as the casing is generated. The graphene‐based TPHTD has high thermal conductivity of up to 1408 W (mK)−1 and realizes ultra‐high specific thermal conductivity of ≈5600 W (mKg)−1. This graphene‐based device with lightweight and high heat transfer capacity offers new opportunities for efficient thermal management of compact, portable, or wearable electronic and power systems.

Thermal monitoring of lithium-ion batteries based on machine learning and fibre Bragg grating sensors

Lithium-ion batteries (LiBs) are well-known power sources due to their higher power and energy densities, longer cycle life and lower self-discharge rate features. Hence, these batteries have been widely used in various portable electronic devices, electric vehicles and energy storage systems. The primary challenge in applying a Lithium-ion battery (LiB) system is to guarantee its operation safety under both normal and abnormal operating conditions. To achieve this, temperature management of batteries should be placed as a priority for the purpose of achieving better lifetime performance and preventing thermal failures. In this paper, fibre Bragg Grating (FBG) sensor technology coupling with machine learning (ML) has been explored for battery temperature monitoring. The results based on linear and nonlinear models have confirmed that the novel methods can estimate temperature variations reliably and accurately.

Evaluation of nanostructured electrode materials for high-performance supercapacitors using multiple-criteria decision-making approach

<abstract> <p>The enhancement of electrode materials' properties for improving mercantile supercapacitors' performances is a remarkable research area. Throughout recent years, a significant amount of research has been devoted to improving the electrochemical performance of supercapacitors via the improvement of novel electrode materials. The nanocomposite structure provides a greater specific surface area (SSA) and lower ion/electron diffusion tracks, consequently enhancing supercapacitors' energy density and specific capacitance. These significant properties offer a wide range of potential for the electrode materials to be applied in diverse applications. For instance, their applications are in portable electronic systems such as all-solid-state supercapacitors, flexible/transparent supercapacitors and hybrid supercapacitors. The authors of this paper introduced a multi-criteria model to assess the priority of nanostructured electrode materials (NEMs) for high-performance supercapacitors (HPSCs). This work combines Analytic Hierarchy Process (AHP) with the Evaluation Based on Distance from Average Solution (EDAS) and Grey Relational Analysis (GRA) methods. Herein, the rough concept addresses the uncertainties resulting from the group decision-making process and the vague values of the properties of the NEMs. The modified R-AHP method was employed to find the criteria weights based on the multi-experts' opinions. The results reveal that specific capacitance (SC) and energy density (ED) are the most important criteria. R-AHP was integrated with R-EDAS and R-GRA models to evaluate the fourteen NEMs. The results of the R-EDAS method were compared with those provided by the R-GRA method. The results of the proposed integrated approach confirmed that it results in reliable and reputable ranks that will provide a framework for further applications and help physicists find optimal materials by evaluating various alternatives.</p> </abstract>

Understanding effect of distortions and vacancies in wurtzite AlScN ferroelectric memory materials: Vacancy-induced multiple defect state types and relaxation dependence in transition energy levels

Energy-efficient compact alternatives to fully digital computing strategies could be achieved by implementations of artificial neural networks (ANNs) that borrow analog techniques. In-memory computing based on crossbar device architectures with memristive materials systems that execute, in an analog way, multiply-and-accumulate operations prevalent in ANN is a notable example. Ferroelectric (FE) materials are promising candidates for achieving ANN thanks to their excellent down-scalability, improved electrical control, and high energy efficiency. However, it remains challenging to develop a crossbar device architecture using FE materials. The difficulty stems from decreasing the leakage current of FE hardware and, simultaneously, reducing the film thickness for achieving compact systems. Here, we have performed density-functional-theory calculations to investigate the electronic, energy-based, and structural signatures of wurtzite FE material Al0.75Sc0.25N with a nitrogen vacancy (VN) in different charge states. We find that VN can introduce two defect states, viz., the singlet state above the valence band maximum (VBM) and a triplet state below the conduction band minimum in wurtzite AlScN models. The calculations reveal that the group of transition levels E3+/2+/E2+/1+ with small formation energies occur at ∼0.78/1.03 eV above the VBM in the wurtzite AlScN with a relaxed configuration, which may shift by a large degree to lower energy levels if atoms surrounding the defect are not fully relaxed. Theoretical studies elucidate the vacancy-enhanced increase in the leakage current utilizing large AlScN supercells. These findings render atomistic insights that can provide a path forward for the design of next-generation portable low-power electronic systems.

Probing the energy conversion and storage process in two dimensional layered bismuthene-hexagonal boron nitride nanocomposite electrode and PVA-KOH-BaTiO3 piezoelectrolyte nanogenerators

The design and fabrication of effective piezoelectric self charging hybrid supercapacitor that efficiently harvest, convert, and store energies in a sustainable and cost-effective way is a cutting edge in the fields of advanced research. However, the output power generated from self charging power devices is insufficient to drive the portable and smart electronic systems. Herein, we fabricated a novel Polyvinyl Alcohol - Potassium hydroxide - Barium Titanate (PVA-KOH-BTO) multifunctional piezoelectrolyte based nanogenerators that potentially convert the mechanical energy to electrical energy. The all-in-one self charging hybrid supercapacitor (SCHSC) was fabricated using two dimensional Bismuthene-hexagonal Boron Nitride nanocomposite (Biene-h-BN NC) as cathode, activated carbon (AC) as anode and the PVA-KOH-BTO as piezoelectrolyte, delivering the specific capacity of 280 C/g at 1 A/g. Moreover, the SCHSC provides the high energy density of 87.5 Wh/kg and the high power density of 11250 W/kg. Remarkably, the self charging performance of SCHSC was investigated by externally applying compressive forces, delivering the maximum self charging potential of 146 mV at the compressive force of 50 N. This research generates a new idea towards the understanding of self charging performance by piezoelectrochemical effect and can be utilized as a potential candidate for the fabrication of futuristic smart electronic devices.

Lithiation and Delithiation Behaviors of the Li-Cu Porous Anode in Li-Metal Battery System

The demand for High-energy-density batteries is rapidly increasing due to fast evolution of portable electronic devices, electric cars and energy storage systems. Lithium ion battery system based on graphite anode has made a lot of progress, however, it has almost reached its limit with the low theoretical capacity. Lithium metal anode has the advantages of high theoretical specific capacity (3860mAhg-1) and lowest electrochemical potential voltage (-3.04V vs standard hydrogen electrode). However, the commercialization of lithium metal is still hindered by several inherent challenges such as inhomogeneous lithium dendrites and huge volume expansion during deposition and dissolution. In this study, a use of the pore between Li and Cu powder for stable Li deposition without volume changes from commercially available cathode materials like NCM is investigated. In this system, binder-free anode is facilely and simply fabricated by pressing the well-mixed two powders of similar size. The effect of pore space created by adjusting the pressure on battery performance is verified. A utilization of Li powder induces controllable and uniform dendrite growth because the current density per unit area is lowered by increasing the specific surface area. Inert Cu powder not only leads to localize Lithium deposition, but also maintains a robust skeleton without volume changes. The lithiation and delithiation behavior of Li-Cu porous anode are thoroughly studied by material characterizations and electrochemical properties

Tuning the space charge polarization of PVDF based ternary composite for piezo-tribo hybrid energy harvesting

Enhancement in the output performance of triboelectric nanogenerators by using different suitable techniques is of tremendous interest among researchers. Here, we propose an easy and cost-effective technique to improve the output performance of the rarely explored poly(vinylidene fluoride) (PVDF) based piezo-tribo hybrid nanogenerators. The space charge polarization of the PVDF based composites has been tuned here by forming a PVDF/0.5(Ba0.7Ca0.3)TiO3–0.5Ba(Ti0.8Zr0.2)O3 (BCZT)/Multi-Walled Carbon Nanotube (MWCNT) based ternary composite. Along with the improved piezoelectricity of PVDF–BCZT based binary composites, the addition of a third MWCNT phase has helped in significantly improving the space charge polarization. The ac conductivity is increased to 5.29 × 10−12 and 1.23 × 10−11 Ω−1 cm−1 for the binary and ternary composites, respectively, from a value of 7.64 × 10−13 Ω−1 cm−1 (at 1 kHz) for neat PVDF. This improved conducting pathway formed by the increased space charge polarization has supported the easy transportation of mobile charge carriers within the composite film and film to the electrode, which has augmented the overall output piezo-tribo hybrid energy harvesting performance of the device. An ultrahigh output power density of ∼150 μW/cm2 has been achieved for the said ternary system, which suppresses the value of output power density of the other similar kind of devices fabricated via a similar technique. The applicability of this device has been further demonstrated by using it in powering up small electronic devices and in different sensing and energy harvesting applications. Thus, the device, after further tuning of its dimension, may be applied as a power source in various low-power-consuming portable electronic systems and self-powered sensing devices.

Tug-of-War in the Selection of Materials for Battery Technologies

Batteries are the heart and the bottleneck of portable electronic systems. They power electronics and determine the system run time, with the size and volume determining factors in their design and implementation. Understanding the material properties of the battery components—anode, cathode, electrolyte, and separator—and their interaction is necessary to establish selection criteria based on their correlations with the battery metrics: capacity, current density, and cycle life. This review studies material used in the four battery components from the perspective and the impact of seven ions (Li+, Na+, K+, Zn2+, Ca2+, Mg2+, and Al3+), employed in commercial and research batteries. In addition, critical factors of sustainability of the supply chains—geographical raw materials origins vs. battery manufacturing companies and material properties (Young’s modulus vs. electric conductivity)—are mapped. These are key aspects toward identifying the supply chain vulnerabilities and gaps for batteries. In addition, two battery applications, smartphones and electric vehicles, in light of challenges in the current research, commercial fronts, and technical prospects, are discussed. Bringing the next generation of batteries necessitates a transition from advances in material to addressing the technical challenges, which the review has powered.

Water Droplet‐Based Nanogenerators

AbstractWater is one of the most sustainable resources in the world, offering an abundance of hydro energy. Getting a large amount of electricity through conventional water energy harvesting is expensive, with complex mechanisms and bulky installation systems. In the case of the small amount of energy for some portable electronic devices and sensor systems, water droplet harvesting as a sustainable energy resource has become a forward‐looking step to meet the future demand for green energy. The ultimate demand for green energy in the future requires all the possible sustainable energy sources surrounding human society. The emerging potential of water droplet‐driven energy‐harvesting nanogenerators can meet a significant portion of the green energy demand. In this review, the recent developments in droplets‐driven nanogenerators for effective energy scavenging is summarized. It also includes an extensive discussion about the device structures from the material selection and output performance aspects. This review also gives a brief discussion on the applications of droplet‐based nanogenerators and outlines the future possibilities via the current improvement in designs and fabrication strategies that have been introduced by the field.