Fiber-based structures are highly desirable for wearable electronics that are expected to be light-weight, long-lasting, flexible, and conformable Many fibrous structures have been manufactured by well-established lost-effective textile processing technologies, normally at ambient conditions The advancement of nanotechnology has made it feasible to build electronic devices directly on the surface or inside of single fibers, which have typical thickness of several to tens microns However, imparting electronic functions to porous, highly deformable and three-dimensional fiber assemblies and maintaining them during wear represent great challenges from both views of fundamental understanding and practical implementation This article attempts to critically review the current state-of-arts with respect to materials, fabrication techniques, and structural design of devices as well as applications of the fiber-based wearable electronic products In addition, this review elaborates the performance requirements of the fiber-based wearable electronic products, especially regarding the correlation among materials, fiber/textile structures and electronic as well as mechanical functionalities of fiber-based electronic devices Finally, discussions will be presented regarding to limitations of current materials, fabrication techniques, devices concerning manufacturability and performance as well as scientific understanding that must be improved prior to their wide adoption

Fiber‐Based Wearable Electronics: A Review of Materials, Fabrication, Devices, and Applications

Owing to high specific energy, low cost, and environmental friendliness, lithium–sulfur (Li–S) batteries hold great promise to meet the increasing demand for advanced energy storage beyond portable electronics, and to mitigate environmental problems. However, the application of Li–S batteries is challenged by several obstacles, including their short life and low sulfur utilization, which become more serious when sulfur loading is increased to the practically accepted level above 3–5 mg cm−2. More and more efforts have been made recently to overcome the barriers toward commercially viable Li–S batteries with a high sulfur loading. This review highlights the recent progress in high-sulfur-loading Li–S batteries enabled by hierarchical design principles at multiscale. Particularly, basic insights into the interfacial reactions, strategies for mesoscale assembly, unique architectures, and configurational innovation in the cathode, anode, and separator are under specific concerns. Hierarchy in the multiscale design is proposed to guide the future development of high-sulfur-loading Li–S batteries.

Review on High-Loading and High-Energy Lithium–Sulfur Batteries

With the advent of flexible electronics, flexible lithium-ion batteries have attracted great attention as a promising power source in the emerging field of flexible and wearable electronic devices such as roll-up displays, touch screens, conformable active radio-frequency identification tags, wearable sensors and implantable medical devices. In this review, we summarize the recent research progress of flexible lithium-ion batteries, with special emphasis on electrode material selectivity and battery structural design. We begin with a brief introduction of flexible lithium-ion batteries and the current development of flexible solid-state electrolytes for applications in this field. This is followed by a detailed overview of the recent progress on flexible electrode materials based on carbon nanotubes, graphene, carbon cloth, conductive paper (cellulose), textiles and some other low-dimensional nanostructured materials. Then recently proposed prototypes of flexible cable/wire type, transparent and stretchable lithium-ion batteries are highlighted. The latest advances in the exploration of other flexible battery systems such as lithium–sulfur, Zn–C (MnO2) and sodium-ion batteries, as well as related electrode materials are included. Finally, the prospects and challenges toward the practical uses of flexible lithium-ion batteries in electronic devices are discussed.

Progress in flexible lithium batteries and future prospects

Flexible solid-state supercapacitors (FSSCs) are frontrunners in energy storage device technology and have attracted extensive attention owing to recent significant breakthroughs in modern wearable electronics In this study, we review the state-of-the-art advancements in FSSCs to provide new insights on mechanisms, emerging electrode materials, flexible gel electrolytes and novel cell designs The review begins with a brief introduction on the fundamental understanding of charge storage mechanisms based on the structural properties of electrode materials The next sections briefly summarise the latest progress in flexible electrodes (ie, freestanding and substrate-supported, including textile, paper, metal foil/wire and polymer-based substrates) and flexible gel electrolytes (ie, aqueous, organic, ionic liquids and redox-active gels) Subsequently, a comprehensive summary of FSSC cell designs introduces some emerging electrode materials, including MXenes, metal nitrides, metal–organic frameworks (MOFs), polyoxometalates (POMs) and black phosphorus Some potential practical applications, such as the development of piezoelectric, photo-, shape-memory, self-healing, electrochromic and integrated sensor-supercapacitors are also discussed The final section highlights current challenges and future perspectives on research in this thriving field

Towards flexible solid-state supercapacitors for smart and wearable electronics

Miniaturized energy storage is essential for the continuous development and further miniaturization of electronic devices. Electrochemical capacitors (ECs), also called supercapacitors, are energy storage devices with a high power density, fast charge and discharge rates, and long service life. Small-scale supercapacitors, or micro-supercapacitors, can be integrated with microelectronic devices to work as stand-alone power sources or as efficient energy storage units complementing batteries and energy harvesters, leading to wider use of these devices in many industries. In recent years, the research in this field has rapidly advanced and micro-supercapacitors with improved storage capacity and power density have been developed. The important factors affecting the performance of micro-supercapacitors are the intrinsic properties of electrode materials and electrolyte, architectural design of the device and the fabrication methods. This paper reviews the recent advances in fabrication of materials and devices and provides a critical analysis of reported performances of micro-supercapacitors.

Capacitive energy storage in micro-scale devices: recent advances in design and fabrication of micro-supercapacitors

An important focus in product design is the creation of practical and aesthetic devices. In portable electronics, in particular, the limiting factor is often the shape of the battery; indeed, removal of this battery restriction would constitute a disruptive technology that could open up a path for design innovation. [ 1 ] However, despite the development of smaller, thinner, and lighter batteries, the existing battery technology is still far from realizing such design fl exibility, mainly owing to the fi xed shapes, i.e., cylindrical, prismatic, or pouch shape. [ 2 ] Hence, there is increasing recognition of the need for a new concept that would permit various product designs previously impossible with traditional technologies. To this end, fl exible batteries are considered a promising solution, owing to their potential to adapt to mechanical stress and accordingly change shape. Furthermore, the progress made in fl exible electronics such as roll-up displays and wearable electronics would receive a strong stimulus with the development of bendable/twistable batteries. [ 3 ] Several recent studies of energy conversion devices have focused on the development of fl exible batteries or supercapacitors [ 4–7 ] using soft materials such as poly mer electrolytes, [ 8 ] nanometer-sized active materials, [ 9–14 ]

/pdf/cable-type-flexible-lithium-ion-battery-based-on-hollow-3abdufe5z6.pdf

Cable-type flexible lithium ion battery based on hollow multi-helix electrodes.

The unending demand for portable, flexible, and even wearable electronic devices that have an aesthetic appeal and unique functionality stimulates the development of advanced power sources that have excellent electrochemical performance and, more importantly, shape versatility. The challenges in the fabrication of next-generation flexible power sources mainly arise from their limited form factors, which prevent their facile integration into differently shaped electronic devices, and from the lack of reliable electrochemical materials that exhibit optimized attributes and suitable processability. This review describes the technological innovations and challenges associated with flexible energy storage and conversion systems such as lithium-ion batteries and supercapacitors, along with an overview of the progress in flexible proton exchange membrane fuel cells (PEMFCs) and solar cells. In particular, recently highlighted cable-type flexible batteries with extreme omni-directional flexibility are comprehensively discussed.

Progress in flexible energy storage and conversion systems, with a focus on cable-type lithium-ion batteries

Disclosed herein is a porous silicon-based electrode active material, comprising a silicon phase, a SiO x (0<x<2) phase and a silicon dioxide phase and having a porosity of 7-71%

Porous silicon-based electrode active material and secondary battery comprising the same

Provided are an anode active material including a porous silicon oxide-carbon material composite which includes a porous silicon oxide including pores and a line-type carbon material coated on a surface, in the pores, or on the surface and in the pores of the porous silicon oxide, and a method of preparing the anode active material. Since the silicon oxide of the anode active material according to an embodiment of the present invention may include the plurality of pores, resistance to the mechanical stress due to a volume change may be improved. Also, since the line-type carbon material is bonded to the inside of the pores, conductivity may not be decreased even in the case in which internal cracks occur in the porous silicon oxide and lifetime characteristics may be improved.

Anode active material including porous silicon oxide-carbon material composite and method of preparing the same

Provided is a cable-type secondary battery having a predetermined-shaped horizontal cross section and extending in a longitudinal direction, which includes a hollow core portion having a gel polymer electrolyte injected thereinto, an inner electrode which includes an inner current collector surrounding an outer surface of the hollow core portion and an inner electrode active material layer formed on a surface of the inner current collector, a separation layer surrounding an outer surface of the inner electrode, an outer electrode which includes an outer electrode active material layer surrounding an outer surface of the separation layer and an outer current collector surrounding an outer surface of the outer electrode active material layer, and a protective coating layer.

Hye Ran Jung

Papers

Cable-type flexible lithium ion battery based on hollow multi-helix electrodes.

Progress in flexible energy storage and conversion systems, with a focus on cable-type lithium-ion batteries

Porous silicon-based electrode active material and secondary battery comprising the same

Anode active material including porous silicon oxide-carbon material composite and method of preparing the same

Cable-type secondary battery and method of preparing the same