Ultrathin and Stretchable Rechargeable Devices with Organic Polymer Nanosheets Conformable to Skin Surface

Abstract

are too thick (>1 mm) to attach skin surface intimately. [18][19][20] Emerging micro norder printing techniques of electrode active materials enabled the fabrication of submillimeterthick batteries. [21] However, the intrinsic brittleness of the conventional inorganic electrodeactive materials and "harsh" electrolytes (e.g., flammable and toxic organic solvents for LIBs and alka line for Nihydrogen, zinc-air, and NiCd batteries) should be problematic for safety. The sealing must also be sufficiently thick and strict to prevent the flammable and toxic materials from exposure. Another major drawback of the conventional inorganic electrodeactive materials is the rather low rate performance. In the case of conventional electrodeactive materials in LIBs, only small current density around 1 µA cm −2 is obtained with a submicron thick electrode according to the limited current rate of ≈70 mA g −1 (assuming the condition of 100 nm thickness, 0.5 C, 140 mAh g −1 , and a tap density of 2.6 g cm −3 , where x C rate corresponds to the full charge/discharge in 1/x h). [22] The output is not enough for powerconsuming applications such as electromagnetic wave emission and biomonitoring display.Design of stretchable batteries is also required for the con formable attaching to skin. Applying zigzag, helix, buckled, mesh, and porous electrodes in geometry are typical approaches to provide stretchability with the inorganic electrodeactive Ultrathin flexible electronic devices have been attracting substantial attention for biomonitoring, display, wireless communication, and many other ubiquitous applications. In this article, organic robust redox-active polymer/carbon nanotube hybrid nanosheets with thickness of just 100 nm are reported as power sources for ultrathin devices conformable to skin. Regardless of the extreme thinness of the electrodes, a moderately large current density of 0.4 mA cm −2 is achieved due to the high output of the polymers (>10 A g −1 ). For the first time, the use of mechanically robust yet intrinsically soft electrodes and polymer nanosheet sealing leads to the fabrication of rechargeable devices with only 1-µm thickness and even with stretchable properties.

A Highly Flexible Yet >300 mAh cm−3 Energy Density Lithium‐Ion Battery Assembled with the Cathode of a Redox‐Active Polyether Binder

“…The porosity was significantly lower than those of the previously reported flexible electrodes with a porosity of >80% . The very low porosity yet flexible PTVE/LiCoO 2 /SWNT1 hybrid could be attributed to the highly adhesive and elastic properties of the radical polymer PTVE binder …”

Metal‐Free, Solid‐State, Paperlike Rechargeable Batteries Consisting of Redox‐Active Polyethers

“…Because the polyethers were not mechanically tough enough to be used as self‐standing films, singe‐walled carbon nanotubes (SWNTs) or cellulose nanofibers (CNFs) were composited with the polymers as reinforcements (Figure S2 in the Supporting Information). We have reported hybrid nanosheets composed of a radical polymer and SWNTs as ultrathin electrodes (100 nm) . In the nanosheets, the polymers facilely filled the empty spaces of the SWNT networks, which were mechanically strong and electrically conducting .…”

“…We have reported hybrid nanosheets composed of a radical polymer and SWNTs as ultrathin electrodes (100 nm) . In the nanosheets, the polymers facilely filled the empty spaces of the SWNT networks, which were mechanically strong and electrically conducting . An only 1 μm‐thick rechargeable device was made from the nanosheet electrodes and brine as electrolyte solution .…”

“…Instead of just replacing ceramics as the electrode active materials, developing organic batteries with new functions is an option to spread the new technology. For instance, biodegradable, electrochromic, high‐elastic‐modulus, flexible, and stretchable properties are facilely achievable with organic electrodes. In particular, the unique mechanical properties of plastics or rubbers (mechanically robust, flexible, and even stretchable) can be attractive for new‐type batteries; for example, it would be interesting to replace conventional plastic housings for electronic devices with rechargeable polymer batteries.…”

Super‐ and Ultrathin Organic Field‐Effect Transistors: from Flexibility to Super‐ and Ultraflexibility

“…While many groups concentrate on developing ultrathin and flexible skin‐laminatable devices, the issue of ultrathin power sources has attracted significantly less attention. To this end, Nishide et al from Waseda University in Tokyo, Japan, have demonstrated such ultrathin and stretchable redox‐active polymer/carbon nanotube rechargeable batteries . With SBS (poly(styrene–butadiene–styrene)) used as top and bottom encapsulation layers, the device structure of PTAm (poly(TEMPO‐substituted acrylamide); cathode)/PLA (poly(d,l‐lactic acid); separator)/PAQE (poly(anthraquinone substituted ethyleneimine); anode) devices with a total thickness of approximately 1 µm were shown undergoing physical stretching.…”