Hye-Ran Jung

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.

Porous Nickel-Tin Nano-Dendritic Electrode for Rechargeable Lithium Battery

A porous nickel-tin nano-dendritic electrode, for use as the anode in a rechargeable lithium battery, has been prepared by using an electrochemical deposition process. The adjustment of the complexing agent content in the deposition bath enabled the nickel-tin alloys to have specific stoichiometries while the amount of acid, as a dynamic template for micro-porous structure, was limited to a certain amount to prevent its undesirable side reaction with the complexing agent. The ratios of nickel to tin in the electro-deposits were nearly identical to the ratios of nickel ion to tin ion in the deposition bath; the particle changed from spherical to dendritic shape according to the tin content in the deposits. The nickel to tin ratio and the dendritic structure were quite uniform throughout the thickness of the deposits. The resulting nickel-tin alloy was reversibly lithiated and delithiated as an anode in rechargeable lithium battery. Furthermore, the resulting anode showed much more stable cycling performance up to 50 cycles, as compared to that resulting from dense electro-deposit with the same atomic composition and from tin electrodeposit with a similar porous structure. From the results, it is expected that highly-porous nickel-tin alloys presented in this work could provide a promising option for the high performance anode materials for rechargeable lithium batteries.