Yo Han Kwon

Cable‐Type Flexible Lithium Ion Battery Based on Hollow Multi‐Helix Electrodes

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 ]

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

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.

UV-curable semi-interpenetrating polymer network-integrated, highly bendable plastic crystal composite electrolytes for shape-conformable all-solid-state lithium ion batteries

A facile approach to fabricate a highly bendable plastic crystal composite electrolyte (PCCE) for use in shape conformable all-solid-state lithium-ion batteries is demonstrated. This strategy is based on integration of a semi-interpenetrating polymer network (semi-IPN) matrix with a plastic crystal electrolyte (PCE, 1 M lithium bis-trifluoromethanesulfonimide in succinonitrile). In comparison to conventional carbonate-based electrolytes, salient benefits of the PCE are the thermal stability and nonflammability, which show promising potential as a safer electrolyte. The semi-IPN matrix in the PCCE is composed of a UV (ultraviolet)-crosslinked ethoxylated trimethylolpropane triacrylate polymer network and polyvinylidene fluoride-co-hexafluoropropylene (as a linear polymer). Solid electrolyte properties of the PCCE are investigated in terms of plastic crystal behavior, mechanical bendability, and ionic transport. Owing to the presence of the anomalous semi-IPN matrix, the PCCE exhibits unprecedented improvement in bendability, along with affording high ionic conductivity. Based on this understanding of the PCCE characteristics, feasibility of applying the PCCE to solid electrolytes for lithium-ion batteries is explored. The facile ionic transport of the PCCE, in conjunction with suppressed growth of cell impedance during cycling, plays a crucial role in providing excellence in cell performance. These advantageous features of the PCCE are further discussed with an in-depth consideration of the semi-IPN matrix architecture and its specific interaction with the PCE.