Chapter Two - Wearable energy storage

Last developments in polymers for wearable energy storage devices

Techno-economic analysis of long-duration energy storage and flexible power generation technologies to support high-variable renewable energy grids

PREDICTION OF IN-HOSPITAL MORTALITY AND LENGTH OF STAY IN ACUTE CORONARY SYNDROME PATIENTS USING MACHINE-LEARNING METHODS

The development of wearable energy sto rage and harvesting devices is pivotal for advancing next-generation healthcare technologies, facilitating continuous and real-time health monitoring. Traditional wearable devices have been constricted by bulky and rigid batteries, limiting their practicality and comfort. However, recent advancements in materials science have enabled the creation of flexible, stretchable, and lightweight energy storage and harvesting solutions. The integration of energy storage and harvesting technologies is essential for developing self-sustaining systems that minimize reliance on external power sources and enhance device longevity. These integrated systems ensure the continuous operation of sensors and processors vital for real-time health monitoring. This review examines recent significant progress in wearable energy storage and harvesting, focusing on the latest advancements in wearable devices, solar cells, biofuel cells, triboelectric nanogenerators, magnetoelastic gene rators, supercapacitors, lithium-ion batteries, and zinc-ion batteries. It also discusses key parameters crucial for their wearable applications, such as energy density, power density, and durability. Finally, the review addresses future challenges and prospects in this rapidly evolving field, underscoring the potential for developing innovative, self-powered wearable systems for healthcare applications.Graphical

The continuous evolution of wearable and flexible devices has driven the need for resilient energy storage systems that can uphold their power and energy density amidst varying mechanical deformations. Among the diverse energy storage mediums, fiber-type solid-state supercapacitors (FSSCs) have been spotlighted for their potential in wearable energy storage, thanks to their inherent capability to blend into diverse structural forms, mirroring the versatility of traditional fibers [1]. In this context, Carbon nanotube fibers (CNTFs) produced through a wet-spinning process based on the liquid crystalline (LC) phase emerge as an ideal electrode material, given their remarkable electrical conductivity, mechanical robustness, and unmatched flexibility [2].While the excellent physical properties of CNTFs is undeniably compelling, their electrochemical inactivity has been a persistent hurdle in realizing their full potential in FSSC applications. Most prior studies have aimed to circumvent this by modifying the fiber’s surface with active materials, such as metal oxides [3] and conductive polymers [4], to serve as energy storage sites. Despite its successes, this approach has been plagued by issues like active material detachment during long-term usage and, more importantly, increasing processing costs due to the need for additional materials and process.In this study, we have pioneered a new approach to enhance the electrochemical activity of LC spun CNTFs without the need for additional post-processing or active materials, addressing the challenge of the sp2 carbon surface's limitations. Through strategic surface functionalization and subsequent LC phase development of CNTs, an unprecedented high-concentration dope (i.e., 160 mg/mL) for wet-spinning was realized. Leveraging high-concentration dope, the as-spun functionalized CNTF (F-CNTF) exhibits more aligned and densely packed structures compared to raw CNTF, resulting in significantly improved mechanical and electrical properties. While the raw CNTF exhibited a specific capacitance of 4.2 F/g at 0.5 A/g, the electrochemically activated F-CNTF, bearing enhanced physicochemical properties, demonstrated a high specific capacitance of 139.4 F/g at the same charge-discharge rate, all without any active materials or post-processing. For practical application, we integrated symmetric FSSCs using F-CNTFs into a textile and used it as a power source for a 1.5 V digital clock, which was operating effectively for over 15 minutes. Additionally, wrist straps integrated with F-CNTF FSSCs could function effectively as a power source even when folded, rolled, or worn on the wrist. This study not only highlights the potential for efficient, mass-produced fiber-type energy storage electrodes but also marks a significant departure from the conventional, non-economical sheath-core strategy, paving the way for more sustainable and efficient energy storage solutions in wearable technology.[1] A. Fakharuddin, H. Li, F. Di Giacomo, T. Zhang, N. Gasparini, A. Y. Elezzabi, A. Mohanty, A. Ramadoss, J. Ling, A. Soultati, M. Tountas, L. Schmidt-Mende, P. Argitis, R. Jose, M. K. Nazeeruddin, A. R. B. Mohd Yusoff, M. Vasilopoulou, Fiber-Shaped Electronic Devices, Advanced Energy Materials (2021) 11, 2101443[2] N. Behabtu, C. C. Young, D. E. Tsentalovich, O. Kleinerman, X. Wang, A. W. K. Ma, E. A. Bengio, R. F. Ter Waarbeek, J. J. De Jong, R. E. Hoogerwerf, S. B. Fairchild, J. B. Ferguson, B. Maruyama, J. Kono, Y. Talmon, Y. Cohen, M. J. Otto, M. Pasquali, Strong, Light, MultifunctionalFibers of Carbon Nanotubes with Ultrahigh Conductivity, Science (2013) 339, 182[3] J.-G. Kim, D.-M. Lee, J. Y. Jung, M. J. Kim, M.-S. Khil, H. S. Jeong, N. D. Kim, Hybrid polyaniline/Liquid Crystalline CNT Fiber Composite for Ultimate Flexible Supercapacitors, ACS Applied Energy Materials (2021) 4, 1130[4] J.-G. Kim, H. Yu, J. Y. Jung, M. J. Kim, D.-Y. Jeon, H. S. Jeong, N. D. Kim, 3D Architecturing Strategy on the Utmost Carbon Nanotube Fiber for Ultra-High Performance Fiber-Shaped Supercapacitor, Advanced Functional Materials (2022) 32, 2113057

In response to the growing global energy needs, the dependency on fossil fuels can lead to the harsh effects on the environment. Thus, it is crucial to recognize continuously growing energy demand by expanding the energy conversion and storage technologies, which exploit clean and renewable energy resources. In this concern, the progress of new energy conversion and storage devices are detected as one of the most important topics in clean energy applications. To efficiently use the produced energy in automobiles, portable applications, it must be stored absolutely so that it can be reproduced when required. Supercapacitors are new class of energy storage devices, in which carbon nanomaterials with controlled porous structure and unique physicochemical properties are among the crucial components. Supercapacitors have the benefit of rapid recharge ability, greater stability, and long cycle life. However, further enhancement of the electrochemical performance, particularly improving the energy density, is a quite challenging. To deal this difficulty, several approaches such as the utilization of carbon materials with high active surface area and studies in various non-aqueous electrolytes also have been attempted. Further, electrochemically energetic materials such as conducting polymers have been developed to enhance the specific capacitance. But they found limited practical applications due to the deterioration of the rate capability and cycle stability. Hetero-atom doping is another productive approach to modify the properties of the carbon nanomaterials and their electrochemical performance. Conductive polymers specifically, polypyrrole is ideal precursor for preparation of hetero-atom doped carbon nanomaterials. However, there is a demand to develop highly conductive porous carbon nanomaterials with high active surface area and hetero-atom doping using a simple method. Here, we present a simple yet productive method for synthesizing hetero-atom doped highly conductive porous carbon with high specific surface area and unique hierarchical pore structure. We prepared the large-scale synthesis of nitrogen-doped porous carbon wrapped reduced graphene oxide-partially exfoliated carbon nanotubes (NP-(rGO-PECNT)) with interconnected hierarchical porous structure. Here, the polypyrrole conductive polymer acts as both nitrogen and carbon source, thereby contributing to pseudocapacitance while, rGO-PECNT conductive matrix provides a high specific surface area for ion and charge transportation. The derived porous (NP-(rGO-PECNT)) displays 7 at % nitrogen content with a specific surface area 2400 m2 g-1, and pore volume 1.81 cm3 g-1. The fabricated supercapacitor using (NP-(rGO-PECNT)) as an electrode material exhibits excellent specific capacitance of 800 F g-1 at 2 A g-1, with high cycling stability of 96 % over 10000 cycles.

The increasing adoption of additive manufacturing (AM), also known as 3D printing, is revolutionizing the production of wearable electronics and energy storage devices (ESD) such as batteries, supercapacitors, and fuel cells. This surge can be attributed to its outstanding process versatility, precise control over geometrical aspects, and potential to reduce costs and material waste. In this comprehensive review, major AM processes like inkjet printing, direct ink writing, fused deposition modeling, and selective laser sintering/melting along with possible configurations and architectures, are elaborately discussed for each bespoke ESD. The application of 3D‐printed energy storage devices in wearable electronics, Internet of Things (IoT)‐based devices, and electric vehicles are also mentioned in the review. The role of AM in facilitating the production of solid‐state batteries has also revolutionized the electric vehicle (EV) industry. Recent progress in the field of AM of energy systems with solid electrolytes and potential future directions such as 4D printing to incorporate stimuli‐responsive behavior in 3D‐printed materials, biomimetic design optimization, and additive manufacturing of ESD in a micro‐gravity environment have also been highlighted. Extensive research and continuous progress in this field are expected to enhance the longetivity, industrial scalability, and electrochemical performance of 3D‐printed energy storage devices in future.

Driving innovation in energy and telecommunications involves leveraging next-generation energy storage and 5G technology to enhance connectivity and energy solutions. This review explores the intersection of these two domains, highlighting the importance of advancements in energy storage and 5G technology for a sustainable and connected future. Energy storage is crucial for balancing the supply and demand of electricity in modern power systems. Traditional energy storage methods, such as batteries and pumped hydro, have limitations in terms of scalability, efficiency, and cost-effectiveness. Next-generation energy storage technologies, including advanced batteries, hydrogen storage, and thermal storage, offer promising solutions to overcome these limitations. These technologies enable efficient energy storage at scale, facilitating the integration of renewable energy sources like solar and wind into the grid. By storing excess energy generated during periods of low demand, next-generation energy storage systems ensure a reliable and stable power supply, reducing the reliance on fossil fuels and lowering greenhouse gas emissions. In parallel, the evolution of telecommunications technology, particularly the advent of 5G networks, is revolutionizing connectivity and communication. 5G technology offers significantly higher data transfer speeds, lower latency, and increased network capacity compared to its predecessors. These capabilities are essential for supporting emerging technologies such as the Internet of Things (IoT), autonomous vehicles, and smart grids. With 5G-enabled IoT devices, utilities can monitor energy consumption in real-time, optimize grid operations, and detect and respond to faults more efficiently. Moreover, 5G connectivity enhances the efficiency and reliability of energy storage systems by enabling seamless communication between distributed energy resources and grid operators. The convergence of next-generation energy storage and 5G technology presents numerous opportunities for driving innovation in both energy and telecommunications sectors. One of the key areas of innovation is the development of smart energy storage systems equipped with 5G connectivity. These systems can autonomously adjust their operation based on grid conditions, weather forecasts, and energy demand patterns, optimizing energy storage and distribution in real-time. Furthermore, advanced energy management algorithms leveraging artificial intelligence (AI) and machine learning (ML) algorithms can optimize energy usage and storage, further improving the efficiency and reliability of the grid. Another area of innovation lies in the integration of renewable energy resources with 5G-enabled microgrids. Microgrids are localized energy systems that can operate independently or in conjunction with the main grid. By combining renewable energy sources with energy storage and 5G-enabled communication, microgrids can provide reliable, clean, and resilient power to remote or urban areas. These microgrids can also facilitate peer-to-peer energy trading, allowing consumers to buy and sell excess energy within their communities, fostering energy independence and sustainability. Furthermore, advancements in battery technology, such as solid-state batteries and flow batteries, are enhancing the performance and reliability of energy storage systems. Solid-state batteries offer higher energy density, faster charging rates, and improved safety compared to conventional lithium-ion batteries. Flow batteries, on the other hand, provide scalability and long-duration storage capabilities, making them suitable for grid-scale applications. Integrating these advanced battery technologies with 5G-enabled monitoring and control systems enhances the overall resilience and flexibility of the energy infrastructure. In addition to technological advancements, driving innovation in energy and telecommunications requires collaboration among various stakeholders, including policymakers, regulators, industry players, and research institutions. Policies and regulations should incentivize the deployment of next-generation energy storage and 5G infrastructure, promote interoperability standards, and ensure data privacy and security. Public-private partnerships can facilitate the investment and deployment of innovative solutions, while research and development initiatives can spur further technological advancements. Driving innovation in energy and telecommunications through next-generation energy storage and 5G technology is essential for building a sustainable, connected, and resilient future. By leveraging advanced energy storage systems, smart grids, and 5G-enabled communication networks, we can optimize energy usage, reduce carbon emissions, and enhance the reliability and efficiency of our energy infrastructure. Collaboration and investment across various sectors are key to unlocking the full potential of these transformative technologies and achieving a brighter, more sustainable future for generations to come. Keywords: Innovation, Energy, Telecommunications, Next-Generation, 5G technology, Enhanced connectivity.

Energy storage technology helps make possible many of the freedoms and personal mobility enjoyed by today's society. In consumer electronics for example, devices such as cell phones and laptops have experienced a great surge in popularity in large-part thanks to advances in battery energy density. In addition to providing convenience, energy storage technology is also a critical enabler on the pathway to the low carbon lifestyle required for future sustainable societies. For these reasons, worldwide interest in energy storage research continues to grow. In conventional vehicle applications, lead acid batteries remain the preferred low-cost solution, providing good cranking power capability to start internal combustion engines at low temperatures. But for electric traction applications, more energy and power-dense chemistries are required. The nickel-metal hydride chemistry, with roughly double the power and energy of the lead acid chemistry, has functioned for some years as the battery of choice for mild and medium hybrid electric vehicles. But to effectively transition our vehicles to run on electricity rather than fossil-based fuels requires substantial further advancement in energy dense, long life, low cost energy storage. The lithium ion chemistry is presently poised to enter transportation markets. Lithium ion battery safety remains a concern, however, given the energetic nature of the chemistry. Another compelling technology for power and cycling-intensive transportation applications are electrochemical ultracapacitors that function based on a double layer charge separation, rather than faradic mechanism. Given the intermittency of sun and wind availability, widespread penetration of renewable energy also requires some means to store it, often for many hours. Today's lithium ion chemistries are too expensive for such large-scale applications. Less-expensive traditional technologies such as lead acid suffer from short life. In certain geographic locations, compressed air and pumped hydraulic power may have a role in renewable energy storage. Novel electrochemical technologies, such as the vanadium redox flow battery, readily scalable and with promising life, may also have a role. Battery science and engineering spans diverse subject areas ranging from electrochemistry to materials science, mechanical and electrical engineering. Battery research, by definition, is a multidisciplinary endeavor. Taking lithium ion safety as an example, safety improvements are sought on multiple fronts. Good design and selection of stable materials, careful quality control during manufacture, proper thermal and electrical design of battery packs under normal and abusive conditions, and sound design of monitoring electronics, algorithms and controls are all needed to produce a safe, high-energy battery. For all storage chemistries, breakthrough advances will no doubt come from research groups that merge the boundaries of several of these traditional science and engineering disciplines. In the theme of multidisciplinary energy storage research, this special issue of International Journal of Energy Research compiles overview and research articles from a broad array of leading researchers in industry, government laboratories and academia. We trust that the findings compiled herein will motivate further investigation in the rapidly evolving field of energy storage.

Harnessing Interfacial Electron Transfer in Redox Flow Batteries

Energy conversion, consumption, and storage technologies are essential for a sustainable energy ecosystem. Energy storage technologies like batteries, supercapacitors, and fuel cells bridge the gap between energy conversion and consumption, ensuring a reliable energy supply. From ancient methods to modern advancements, research has focused on improving energy storage devices. Challenges remain, including performance, environmental impact and cost, but ongoing research aims to overcome these limitations. A special issue titled "Recent Advances in Electrochemical Energy Storage" presents cutting-edge progress and inspiring further development in energy storage technologies.

With rising energy concerns, efficient energy conversion and storage devices are urgently required to provide a sustainable, green energy supply. Electrochemical energy storage devices, such as supercapacitors and batteries, have been proven to be the most effective energy conversion and storage technologies for practical application. Currently, carbon materials hold the key for the development of high-performance electrochemical energy storage devices. However, the widely used carbon materials, such as graphite and activated carbon are often derived from non-renewable resources under relatively harsh environments, which hinders the sustainable development of electrochemical energy storage systems. In this context, biomass demonstrates many desired properties to derive renewable carbon materials for both electrochemical energy storage applications, because of its natural abundance and unlimited availability. Here, natural biomass, such as cotton textile, wheat flour, and corncobs, have been explored to produce renewable carbon materials via a low-cost and high throughput manufacturing process for energy storage systems design. Excitingly, the biomass-derived renewable activated carbon scaffolds not only demonstrated hierarchically porous structures but also excellent flexibility, making them ideal backbones for next-generation energy storage design. Specifically, activated cotton textile (ACT) with excellent flexibility and conductivity has been successfully derived from cotton textile for flexible energy storage systems design, such as flexible supercapacitors, flexible lithium-ion batteries, and flexible lithium-sulfur batteries. Besides flexible ACT, carbon nanotubes (CNTs) have also successfully derived from the natural yeast-fermented wheat dough without using any extra-catalysts or additional carbon sources. Yeast-derived carbon nanotubes from the fermented wheat dough not only provide an ideal sulfur host for lithium-sulfur batteries with a record lifespan of 1500 cycles but also expand our current understanding of the synthesis of carbon nanotubes. Biowastes-corncob, have also been explored to derive onion-like carbon materials for energy storage application. These research activities not only brought new insights on the deriving renewable carbon materials from natural abundant biomass resources but also boosted the design and fabrication of next-generation flexible energy-storage devices, which hold great promise for future wearable/flexible electronics.

Over the past couple of years there has been a tremendous interest in flexible sensors for the purpose of activity tracking and health monitoring purposes. With the helps of novel designs, these devices can conform to the curvature of the human body, which helps improve the signal to noise ratio, and the comfort of the user. To power such devices, the battery should be flexible, and retain its capacity after multiple flexing cycling. Batteries based on lithium ion chemistry are an ideal choice for flexible batteries due to its high energy density and stable electrochemical performance. Flexible battery consists of an anode and cathode, which are separated by a thin polymeric separator. Repeated bending can lead to swelling and delamination of the active layers. Currently, there are no standard protocols to test the mechanical strength of battery electrodes. To prevent sudden failures in flexible batteries, the thickness of the electrodes are limited to 20-40 micron to reduce the maximum stresses the electrode would experience during flexing. Reducing the electrode thickness decrease the energy density of the battery. In flexible lithium ion batteries, the relation between the electrode composition and its mechanical flexibility is poorly understood. Factors such as shape and size of the particles, and choice of binder plays an important role in defining the mechanical characteristics of the electrodes. By understanding the link between different variables in the ink composition to the mechanical property of the electrodes, mechanically resilient electrodes can be designed. In this talk, I will present two mechanical testing methodologies to quantify the strength of battery electrodes. The first method is based on combining conventional tape test with an INSTRON. Based on the force required to peel the active layers, and the resulting failure mode, the mechanical strength of electrodes with different compositions can be compared and the mode of failure during flexing can be predicted. The second testing procedure is based on dragging a micro-tip through the active layers. By measuring the force required to remove the active layer and the mode of cracking, the mechanical strength of electrodes can be compared. We study the effect of tip size, drag speed and tip height on the force required to drag a tip through the electrode. We study the effects of conductive additives, particle size and binder choice using the tape and drag test. The mechanical strength of cathode increases by a factor of two using a combination of graphite and anode as the conductive additive. The larger size of graphite particles improves the mechanical strength of the electrode and the carbon particle occupies the void spaces between the graphite particles, which improve the electronic conductivity of the electrode. The electrodes with small size particles have poor cohesion strength due to larger exposed surface area, which reduces the effective thickness of the binder on the particles. The adhesion between the graphite anode and the foil increase when the PVDF binder is replaced with PSBR binder. Based on the result of the mechanical testing we were able to modify the ink composition and fabricate flexible lithium ion battery with improved electro-mechanical performance.

Interest in new energy storage technologies, especially to support transportation and renewable energy generation, is increasing at a rapid rate. New technologies face many challenges, such as material abundance, efficiency, charge storage capacity and long term cycle-ability. Emerging devices, like supercapacitors, have the potential to provide high energy storage capacity and fast charge-discharge rates to bridge the gap between traditional batteries and high-power capacitors.In a supercapacitor, many types of electrode material can be used, ranging from high surface area, inert carbon nanomaterials to Faradaic metal oxides and conducting polymers. Porous carbon nanomaterials rely upon electrical double layer capacitance, in which charged are stored physically at the electrode interfaces rather than through charge transfer with the electrode (Faradaic). While EDLC devices can discharge at high rates (high power), they are limited by low energy densities. Electroactive conductive polymers (ECPs) are promising materials, since they are conductive, possess moderate to high energy storage capacity, and can be synthesized using low cost and large scale methods.In this work, we investigate a simple approach to preparing large quantities of conducting polymer microtubes without the need for a solution or substrate based template. Due to its fairly high specific power and energy, polypyrrole is studied as the electrode material for microtube-based devices. However, since the mechanism for electrochemical synthesis is similar for various monomers, we expect this approach can be applied to other materials relative ease. In this presentation, we will discuss how to control the polymer assembly and microtube synthesis by changing the substrate geometry. Figure 1. Polypyrrole microtubes on 200x200 stainless steel mesh. Deposition at 10mA/s for 30C.Electrodes prepared using our template-free synthesis with polypyrrole to achieve microtube structures is shown in Figure 1. Polypyrrole was electrochemically polymerized on various stainless steel mesh substrates (40x40, 200x200, 400x400, among others) with various mass, current density and monomer concentration. Electrodes were studied to understand the growth mechanism and microtube formation, and how the electrode structure affects the charge storage properties.Variations in the substrate surface structure resulted in an easy tool to manipulate the microtube size (100μm up to 1 mm), shape (cone-like or tube-like structure) and density of microtubes along the electrode. The finer meshes (200x200 and 400x400) gave the highest density (about 350 microtubes/cm2) and the best electrochemical performance (200 F/g) measured by cyclic voltammetry, electrochemical impedance spectroscopy and galvanodynamic cycling.The microtube’s formation and growth mechanism was studied using scanning electron microscopy (SEM) on samples prepared through different stages of growth (1C up to 30C). Figure 2 shows how the tube structures evolve from an initial nucleus, which forms at the intersection of two metal wires in the mesh, to the final tube. Figure 2. Microtubes growth mechanism.Polypyrrole microtubes exhibit similar electrochemical properties compared to thin films. Electrodes prepared on 200x200 and 400x400 mesh displayed a high density of microtubes and good electrochemical properties, as shown in Figure 3. It should be noted that some microtubes exhibited poor electrochemical performance due to the high potentials required during synthesis (e.g. large mesh sizes, 40x40). Figure 3. Cyclic voltammetry of 8.26mg polypyrrole microtube electrodes.These results led us to understand the influence of the substrate, current density and concentration in the template-free assembly and electrochemical performance of polypyrrole, as well as new ways to manipulate the physical structure of redox materials for supercapacitor electrodes. Importantly, this approach has been used to synthesis tens of milligrams of material per square centimeter, and is amenable for scale to large systems.

Graphene/cotton fibers show significant promise in wearable energy storage due to their low cost, porous structure, and exceptional integration ability into wearable systems. However, the eco-unfriendly reductants and standalone electric double-layer capacitor hindered their application. Herein, a green and rapid hydrothermal-electrodeposition method was proposed to fabricate polyaniline (PANI) decorated reduced graphene oxide (rGO)/cotton yarns without using any chemical reductants and oxidants. The PANI/rGO/cotton (PRC) yarn exhibited porous conductive network, structural controllability, and mechanical flexibility. Additionally, the PRC yarn electrode delivers a fast electron transport and ion migration, synergistic energy storage contribution, and a controllable capacitance (up to 81.2 mF cm−1 at 0.2 mA cm−1). The assembled yarn supercapacitor shows a good capacitance (19.8 mF cm−1 at 0.08 mA cm−1), excellent energy-power density (2.7 μWh cm−1 at 40 μW cm−1), and great capacitance retention. This green fabrication of PRC yarns brings new insights into the development of wearable energy storage.