Recently there is strong interest in lightweight, flexible, and wearable electronics to meet the technological demands of modern society. Integrated energy storage devices of this type are a key area that is still significantly underdeveloped. Here, we describe wearable power devices using everyday textiles as the platform. With an extremely simple "dipping and drying" process using single-walled carbon nanotube (SWNT) ink, we produced highly conductive textiles with conductivity of 125 S cm(-1) and sheet resistance less than 1 Omega/sq. Such conductive textiles show outstanding flexibility and stretchability and demonstrate strong adhesion between the SWNTs and the textiles of interest. Supercapacitors made from these conductive textiles show high areal capacitance, up to 0.48F/cm(2), and high specific energy. We demonstrate the loading of pseudocapacitor materials into these conductive textiles that leads to a 24-fold increase of the areal capacitance of the device. These highly conductive textiles can provide new design opportunities for wearable electronics and energy storage applications.

We developed two-step solution-phase reactions to form hybrid materials of Mn(3)O(4) nanoparticles on reduced graphene oxide (RGO) sheets for lithium ion battery applications. Selective growth of Mn(3)O(4) nanoparticles on RGO sheets, in contrast to free particle growth in solution, allowed for the electrically insulating Mn(3)O(4) nanoparticles to be wired up to a current collector through the underlying conducting graphene network. The Mn(3)O(4) nanoparticles formed on RGO show a high specific capacity up to ∼900 mAh/g, near their theoretical capacity, with good rate capability and cycling stability, owing to the intimate interactions between the graphene substrates and the Mn(3)O(4) nanoparticles grown atop. The Mn(3)O(4)/RGO hybrid could be a promising candidate material for a high-capacity, low-cost, and environmentally friendly anode for lithium ion batteries. Our growth-on-graphene approach should offer a new technique for the design and synthesis of battery electrodes based on highly insulating materials.

Paper, invented more than 2,000 years ago and widely used today in our everyday lives, is explored in this study as a platform for energy-storage devices by integration with 1D nanomaterials. Here, we show that commercially available paper can be made highly conductive with a sheet resistance as low as 1 ohm per square (⍀/sq) by using simple solution processes to achieve conformal coating of single-walled carbon nanotube (CNT) and silver nanowire films. Compared with plastics, paper substrates can dramatically improve film adhesion, greatly simplify the coating process, and significantly lower the cost. Supercapacitors based on CNT-conductive paper show excellent performance. When only CNT mass is considered, a specific capacitance of 200 F/g, a specific energy of 30 -47 Watt-hour/kilogram (Wh/kg), a specific power of 200,000 W/kg, and a stable cycling life over 40,000 cycles are achieved. These values are much better than those of devices on other flat substrates, such as plastics. Even in a case in which the weight of all of the dead components is considered, a specific energy of 7.5 Wh/kg is achieved. In addition, this conductive paper can be used as an excellent lightweight current collector in lithiumion batteries to replace the existing metallic counterparts. This work suggests that our conductive paper can be a highly scalable and low-cost solution for high-performance energy storage devices.conformal coating ͉ carbon nanotubes ͉ nanomaterial ͉ solution process P rintable solution processing has been exploited to deposit various nanomaterials, such as fullerene, carbon nanotubes (CNTs), nanocrystals, and nanowires for large-scale applications, including thin-film transistors (1-3), solar cells (4, 5), and energy-storage devices (6, 7), because the process is low-cost while maintaining the unique properties of the nanomaterials. In these processes, flat substrates, such as glass, metallic films, Si wafers, and plastics, have been used to hold nanostructure films. Nanostructured materials are usually first capped with surfactant molecules so that they can be well-dispersed as separated particles in a solvent to form ''ink.'' The ink is then deposited onto the flat substrates, followed by surfactant removal and solvent evaporation. To produce high-quality films, significant efforts have been spent on ink formulation and rheology adjustment. Moreover, because the surfactants are normally insulating, and thus limit the charge transfer between the nanomaterials, their removal is particularly critical. However, this step involves extensive washing and chemical displacement, which often cause mechanical detachment of the film from the flat substrate. Polymer binders or adhesives have been used to improve the binding of nanomaterials to substrates, but these can also cause an undesirable decrease in the film conductivity. These additional procedures increase the complexity of solution processing and result in high cost and low throughput. Here, we exploit paper substrates used in daily life to solve these issues a...

We introduce a novel design of carbon-silicon core-shell nanowires for high power and long life lithium battery electrodes. Amorphous silicon was coated onto carbon nanofibers to form a core-shell structure and the resulted core-shell nanowires showed great performance as anode material. Since carbon has a much smaller capacity compared to silicon, the carbon core experiences less structural stress or damage during lithium cycling and can function as a mechanical support and an efficient electron conducting pathway. These nanowires have a high charge storage capacity of approximately 2000 mAh/g and good cycling life. They also have a high Coulmbic efficiency of 90% for the first cycle and 98-99.6% for the following cycles. A full cell composed of LiCoO(2) cathode and carbon-silicon core-shell nanowire anode is also demonstrated. Significantly, using these core-shell nanowires we have obtained high mass loading and an area capacity of approximately 4 mAh/cm(2), which is comparable to commercial battery values.

These authors contributed equally to this work. Because of their high energy and power density, lithium ion batteries that were mainly used for portable electronics are now extending to large applications such as power tools and vehicle electrification. Extensive research has been carried out to find new electrode materials and new electrode structure designs to improve energy densities for both anode and cathode. Silicon as an anode material has attracted extensive research because it has the highest known capacity, more than 10 times the value of the current commercial graphite anode. However, the intrinsic volume expansion and contraction of Si during Li cycling cause rapid capacity fading and limit its wide application. Various approaches have been carried out to overcome this issue, including the use of nanosized active materials, 1Ϫ6 active/inactive composite materials, 7Ϫ9 and siliconϪcarbon composites.9Ϫ14 These studies have resulted in improvements of the electrochemical performance of Si-based anodes, but only to a limited extent. Recently we found silicon nanowires directly grown on a current collector can greatly improve the performance of the Si anode due to the excellent electrical connection between Si nanowires and the current collector and the nature of one-dimensionality to effectively release the strain. 15,16 Cho and coworkers also demonstrated great anode performance using carbon-coated, very small (Յ10 nm) silicon nanoparticles (SiNPs) or silicon nanotubes. 17,18 However, in these nanosilicon electrodes, the heavy current collector is larger in weight than Si active material. In a commercial lithium ion cell, the anode material is usually coated on a copper foil current collector to form an anode electrode in thin sheet form. The metal current collector on the anode side is usually a 10 m thick copper sheet with an areal density ϳ10 mg/cm 2 . This copper sheet is a relatively heavy component in a lithium ion cell, which is comparable in weight to the anode active material and accounts for ϳ10% of the total weight of the cell. 19Random networks of carbon nanotube (CNT) have been explored as transparent electrodes in various devices including solar cells, organic light emitting diodes, and smart windows, where CNT networks show optical transmittances of ϳ80% and sheet resistances of 100Ϫ1000 Ohm/sq. 20Ϫ25 Recently, we reported the replacement of the conventional metal current collector with lightweight, CNT-enabled conductive paper, which can significantly reduce the weight of Li-ion batteries.19,26 Inks of CNT