There has been an emerging interest in stretchable power sources compatible with flexible/wearable electronics. Such power sources must be able to withstand large mechanical strains and still maintain function. Here we report a highly stretchable H3PO4-poly(vinyl alcohol) (PVA) polymer electrolyte obtained by optimizing the polymer molecular weight and its weight ratio to H3PO4 in terms of conductivity and mechanical properties. The electrolyte demonstrates a high conductivity of 3.4 x 10-3 S cm-1, and a high fracture strain at 410% elongation. It is mechanically robust with a tensile strength of 2 MPa and a Young's modulus of 1 MPa, and displays a small plastic deformation (5%) after 1000 stretching cycles at 100% strain. A stretchable supercapacitor device has been developed based on buckled polypyrrole electrodes and the polymer electrolyte. The device shows only a small capacitance loss of 5.6% at 30% strain, and can retain 81% of the initial capacitance after 1000 cycles of such stretching. ABSTRACT: There has been an emerging interest in stretchable power sources compatible with flexible/wearable electronics. Such power sources must be able to withstand large mechanical strains and still maintain function. Here we report a highly stretchable H 3 PO 4 -poly(vinyl alcohol) (PVA) polymer electrolyte obtained by optimizing the polymer molecular weight and its weight ratio to H 3 PO 4 in terms of conductivity and mechanical properties. The electrolyte demonstrates a high conductivity of 3.4×10 -3 S cm -1 , and a high fracture strain at 410% elongation. It is mechanically robust with a tensile strength of 2 MPa and a Young's modulus of 1 MPa, and displays a small plastic deformation (5%) after 1000 stretching cycles at 100% strain. A stretchable supercapacitor device has been developed based on buckled polypyrrole electrodes and the polymer electrolyte. The device shows only a small capacitance loss of 5.6% at 30%strain, and can retain 81% of the initial capacitance after 1000 cycles of such stretching.2

Common fabrication techniques typically require multiple and complex MEMS processing steps to create 3D electrode architectures. Here we report on the use of Additive Fabrication metal printing based on Selective Laser Melting (SLM) technology to produce 3D titanium interdigitated electrodes. This was used as a platform to deposit polypyrrole and the resultant structure was evaluated for use as a capacitive electrode. We also demonstrate a solid-state interdigitated supercapacitor using a poly(vinyl alcohol) (PVA)-H3PO4 polymer electrolyte.

Flexible freestanding electrodes are highly desired to realize wearable/flexible batteries as required for the design and production of flexible electronic devices. Here, the excellent electrochemical performance and inherent flexibility of atomically thin 2D MoS 2 along with the self-assembly properties of liquid crystalline graphene oxide (LCGO) dispersion are exploited to fabricate a porous anode for high-performance lithium ion batteries. Flexible, free-standing MoS 2 -reduced graphene oxide (MG) film with a 3D porous structure is fabricated via a facile spontaneous self-assembly process and subsequent freeze-drying. This is the first report of a one-pot self-assembly, gelation, and subsequent reduction of MoS 2 /LCGO composite to form a flexible, high performance electrode for charge storage. The gelation process occurs directly in the mixed dispersion of MoS 2 and LCGO nanosheets at a low temperature (70 °C) and normal atmosphere (1 atm). The MG film with 75 wt% of MoS 2 exhibits a high reversible capacity of 800 mAh g −1 at a current density of 100 mA g −1 . It also demonstrates excellent rate capability, and excellent cycling stability with no capacity drop over 500 charge/discharge cycles at a current density of 400 mA g −1 .

. (2016). A cytocompatible robust hybrid conducting polymer hydrogel for use in a magnesium battery. Advanced Materials, 28 (42), 9349-9355.

A novel nitrogen-doped porous graphene material (NPGM) was prepared by freeze-drying a graphene/melamine-formaldehyde hydrogel and subsequent thermal treatment. The use of melamine-formaldehyde resin as a cross-linking agent and nitrogen source enhances the nitrogen content. NPGM possesses a hierarchical porous structure, a large Brunauer-Emmett-Teller surface area (up to 1170 m 2 g -1 ), and a considerable nitrogen content (5.8 at%). NPGM displays a discharge capacity of 672 mA h g -1 at a current density of 100 mA g -1 when used as an anode material for lithium ion batteries, much higher than that observed for a nitrogen-free graphene porous material (450 mA h g -1 ). The NPGM electrode also possesses superior cycle stability.No capacity loss was observed even after 200 charge/discharge cycles at a current density of 400 mA g -1 . The enhanced electrochemical performance is attributed to nitrogen doping, high specific surface area, and the three-dimensional porous network structure.Melamine-formaldehyde resin (MF) was synthesized by adding formaldehyde (1.01 g, 37 wt%) and 0.63 g melamine into ultrapure water (7.86 g), followed by the addition of aqueous sodium hydroxide solution (0.5 mL, 0.1 M). This mixture was heated at 80 °C for 15 min till it turned clear. The resultant soluble MF (1.0 g) was 13 of graphene material. In addition, a great amount of crumpled sheets can be observed in the TEM images of NPGM and PGM, and these sheets are entangled with each other (Figs. 4c and d). Both NPGM and PGM possess a 3D interconnected network structure as expected, which may deliver superior electrochemical properties. Fig. 4 SEM images of NPGM (a) and PGM (b), TEM images of NPGM (c) and PGM (d).A nitrogen adsorption-desorption measurement was applied to further investigate porous properties. Both NPGM and PGM exhibit type IV isotherms, and their nitrogen adsorption-desorption isotherms show high uptake at a low relative pressure of 0-0.1, suggesting the microporous nature. Compared with PGM, NPGM displays a larger hysteresis at the relative pressure range of 0.45-1.0 (Fig. 5a), indicating the presence of 21 graphene sheets, which is helpful to the adsorption and infiltration of lithium ions into electrode. 23 The reduced charge-transfer resistance is beneficial to the electron transfer and lithium ion transport between the electrode and electrolyte. Fig. 9 (a) Electrochemical impedance spectra of NPGM and PGM electrodes (Inset is the corresponding simulation results for NGPM and PGM electrodes), (b) the simulated Randles equivalent circuit for NPGM and PGM electrodes. (CPE and R stand for the constant phase element and resistance, respectively.) ConclusionsIn this work, we prepared a graphene-based hydrogel by using melamine-formaldehyde resin as a cross-linking agent. NPGM was fabricated through freeze-drying of GMF hydrogel and subsequent thermal treatment. The as-prepared NPGM possessed a hierarchical porous structure, large specific surface area, and

. (2015). Reduced graphene oxide and polypyrrole/reduced graphene oxide composite coated stretchable fabric electrodes for supercapacitor application. Electrochimica Acta, Reduced graphene oxide and polypyrrole/reduced graphene oxide composite coated stretchable fabric electrodes for supercapacitor application AbstractThe advent of self-powered functional garments has given rise to a demand for stretchable energy storage devices that are amendable to integration into textile structures. The electromaterials (anode, cathode and separator) are expected to sustain a deformation of 3% to 55% associated with body movement. Here, we report a stretchable fabric supercapacitor electrode using commonly available nylon lycra fabric as the substrate and graphene oxide (GO) as a dyestuff. It was prepared via a facile dyeing approach followed by a mild chemical reduction. This reduced graphene oxide (rGO) coated fabric electrode retains conductivity at an applied strain of up to 200%. It delivers a specific capacitance of 12.3 F g −1 at a scan rate of 5 mV s −1 in 1.0 M lithium sulfate aqueous solution. The capacitance is significantly increased to 114 F g −1 with the addition of a chemically synthesized polypyrrole (PPy) coating. This PPy-rGO-fabric electrode demonstrates an improved cycling stability and a higher capacitance at 50% strain when compared to the performance observed with no strain.Keywords supercapacitor, electrodes, fabric, stretchable, graphene, coated, application, composite, reduced, polypyrrole, oxide Disciplines Engineering | Physical Sciences and Mathematics Publication DetailsZhao, C., Shu, K., Wang, C., Gambhir, S. & Wallace, G. G. (2015 AbstractThe advent of self-powered functional garments has given rise to a demand for stretchable energy storage devices that are amendable to integration into textile structures. The electromaterials (anode, cathode and separator) are expected to sustain a deformation of 3% to 55% associated with body movement. Here, we report a stretchable fabric supercapacitor electrode using commonly available nylon lycra fabric as the substrate and graphene oxide (GO) as a dyestuff. It was prepared via a PPy-rGO-fabric electrode demonstrates an improved cycling stability and a higher capacitance at 50% strain when compared to the performance observed with no strain.

The significance of developing implantable, biocompatible, miniature power sources operated in a low current range has become manifest in recent years to meet the demands of the fast-growing market for biomedical microdevices. In this work, we focus on developing high-performance cathode material for biocompatible zinc/polymer batteries utilizing biofluids as electrolyte. Conductive polymers and graphene are generally considered to be biocompatible and suitable for bioengineering applications. To harness the high electrical conductivity of graphene and the redox capability of polypyrrole (PPy), a polypyrrole fiber/graphene composite has been synthesized via a simple one-step route. This composite is highly conductive (141 S cm -1 ) and has a large specific surface area (561 m 2 g -1 ). It performs more effectively as the cathode material than pure polypyrrole fibers. The battery constructed with PPy fiber/reduced graphene oxide cathode and Zn anode delivered an energy density of 264 mWh g -1 in 0.1 M phosphate-buffer saline. ABSTRACTThe significance of developing implantable, bio-compatible, miniature power sources operated in a low current range has become manifest in recent years to meet the demands of the fast growing market for biomedical microdevices. In this work, we focus on developing high performance cathode material for biocompatible zinc/polymer batteries utilizing biofluids as electrolyte.Conductive polymers and graphene are generally considered to be biocompatible and suitable for bioengineering applications. To harness the high electrical conductivity of graphene and the redox capability of polypyrrole (PPy), a polypyrrole fibre/graphene composite has been synthesized via a simple one-step route. This composite is highly conductive (141 S cm -1 ) and has a large specific surface area (561 m 2 g -1 ). It performs more effectively as the cathode material than the pure polypyrrole fibres. The battery constructed with PPy fibre/reduced graphene oxide (RGO) cathode and Zn anode delivered an energy density of 264 mWh g -1 in 0.1 M phosphate buffer saline.

An overview of recent advances on conducting polymer composites for unconventional solid-state supercapacitors is presented.