Showing posts with label supercapacitors. Show all posts
Showing posts with label supercapacitors. Show all posts

Wednesday, November 18, 2015

Graphene - ALD bendable Supercaps by Nanyang Technological University and Partners

Nanowerk had an interesting post today on how Nanyang Technological University and Partners in Singapore and China are using graphene and ALD Metal Nitrides to fabricate bendable solid-state asymmetric super capacitors. Check out the processing to achieve the metal nitrides below - not the usual way but via the oxides and solution based chemistry! I assume that graphene is a tricky material to grow metal nitrides on


Illustration of the asymmetric supercapacitor, consisting of vertically aligned graphene nanosheets coated with iron nitride and titanium nitride as the anode and cathode, respectively. (as published in Nanowerk, ©WILEY-VCH Verlag)


"To get the maximum benefit from the graphene surface, the team used a precise method for creating thin-films, a process known as atomic layer deposition, to grow two different materials on vertically aligned graphene nanosheets: titanium nitride for their supercapacitor’s cathode and iron nitride for the anode." 



Tracking back to the original publication in Advanced Materials "All Metal Nitrides Solid-State Asymmetric Supercapacitors" DOI: 10.1002/adma.201501838 there are some more details available in the free to download supporting information from the authors where it is reviled that a BENEQ TFS 200 ALD reactor was used for the cathode and anode. Here´s the link and some details are given below:

A BENEQ TFS 200 that come in many sorts and flavours (www.beneq.com)

Electrode Material Synthesis

Preparation of TiN@GNS Cathode: All chemicals were bought from Sigma Aldrich and used without further purification. Graphene nanosheets (467 m2 g-1) were provided by INCUBATION ALLIANCE, INC. The cathode fabrication process is mainly composed of two steps: TiO2 deposition by atomic layer deposition (ALD) and transferring to nitride through annealing in ammonia (NH3) atmosphere. Before ALD, the GNS substrates were treated with oxygen plasma at 200 W for 10 minutes with an O2 gas flow of 100 sccm, 70 mTorr. In a typical ALD (Beneq TFS 200) process, 120 °C was applied to the GNS substrate with TiCl4 and water as the titanium and oxygen source, respectively. 166 cycles (~ 1.2 Å per cycle) deposition was conducted to obtain 20 nm TiO2 coating during which the reaction chamber was maintained with a steady N2 steam at 300 sccm (cubic centimeter per minute) at 1.0 mbar. The sample of TiO2@GNS was then annealed in NH3 atmosphere at 800 °C for 1 h with a gas flow of 50 sccm and heating rate of 20 °C per minute. The control sample of TiO2@GNS was synthesized with the same ALD process. 

Preparation of Fe2N@GNS Anode: 20 nm ZnO was deposited on GNS (oxygen plasma pretreated) with ALD at 200 °C. The ZnO@GNS sample was then immersed in 0.5 M Fe(NO3)3 solution for 2 h to have a thorough transformation from ZnO to FeOOH as reported by the previous work[1]. The FeOOH@GNS sample was then annealed with the same NH3 atmosphere situation at a lower temperature of 600 °C. The control sample of FeOOH@GNS was fabricated by the same method just without the afterward annealing.

Also Available in the supporting information linked above is a quite impressive results from a bending test odf a charged super capacitor (see figure below)


Capacitance retention of the full device at different bending conditions. "All Metal Nitrides Solid-State Asymmetric Supercapacitors" DOI: 10.1002/adma.201501838 (©WILEY-VCH Verlag).

Wednesday, September 16, 2015

ALD of Co9S8 and Its Application for Supercapacitors

Vapor-Phase Atomic Layer Deposition of Co9S8 and Its Application for Supercapacitors

Hao Li, Yuanhong Gao, Youdong Shao, Yantao Su, and Xinwei Wang
School of Advanced Materials, Shenzhen Graduate School, Peking University, Shenzhen 518055, China
Nano Lett., Article ASAP
Publication Date (Web): August 27, 2015



Atomic layer deposition (ALD) of cobalt sulfide (Co9S8) is reported. The deposition process uses bis(N,N′-diisopropylacetamidinato)cobalt(II) and H2S as the reactants and is able to produce high-quality Co9S8 films with an ideal layer-by-layer ALD growth behavior. The Co9S8films can also be conformally deposited into deep narrow trenches with aspect ratio of 10:1, which demonstrates the high promise of this ALD process for conformally coating Co9S8 on high-aspect-ratio 3D nanostructures. As Co9S8 is a highly promising electrochemical active material for energy devices, we further explore its electrochemical performance by depositing Co9S8 on porous nickel foams for supercapacitor electrodes. Benefited from the merits of ALD for making high-quality uniform thin films, the ALD-prepared electrodes exhibit remarkable electrochemical performance, with high specific capacitance, great rate performance, and long-term cyclibility, which highlights the broad and promising applications of this ALD process for energy-related electrochemical devices, as well as for fabricating complex 3D nanodevices in general.

Wednesday, July 8, 2015

MIT develops Supercapacitors from Niobium Nanowire Yarns for wearable electronics

As reported by MIT News : Wearable electronic devices for health and fitness monitoring are a rapidly growing area of consumer electronics; one of their biggest limitations is the capacity of their tiny batteries to deliver enough power to transmit data. Now, researchers at MIT and in Canada have found a promising new approach to delivering the short but intense bursts of power needed by such small devices.

The key is a new approach to making supercapacitors — devices that can store and release electrical power in such bursts, which are needed for brief transmissions of data from wearable devices such as heart-rate monitors, computers, or smartphones, the researchers say. They may also be useful for other applications where high power is needed in small volumes, such as autonomous microrobots.

The new approach uses yarns, made from nanowires of the element niobium, as the electrodes in tiny supercapacitors (which are essentially pairs of electrically conducting fibers with an insulator between). The concept is described in a paper in the journal ACS Applied Materials and Interfaces by MIT professor of mechanical engineering Ian W. Hunter, doctoral student Seyed M. Mirvakili, and three others at the University of British Columbia.

Here below is the abstract for the publication or you can continue reading the story from MIT News.

High-Performance Supercapacitors from Niobium Nanowire Yarns

Seyed M. Mirvakili, Mehr Negar Mirvakili, Peter Englezos, John D. W. Madden, and Ian W. Hunter

ACS Appl. Mater. Interfaces, 2015, 7 (25), pp 13882–13888
DOI: 10.1021/acsami.5b02327





The large-ion-accessible surface area of carbon nanotubes (CNTs) and graphene sheets formed as yarns, forests, and films enables miniature high-performance supercapacitors with power densities exceeding those of electrolytics while achieving energy densities equaling those of batteries.1−7 Capacitance and energy density can be enhanced by depositing highly pseudocapacitive materials such as conductive polymers on them.3,8−15 Yarns formed from carbon nanotubes are proposed for use in wearable supercapacitors.3,16 In this work, we show that high power, energy density, and capacitance in yarn form are not unique to carbon materials, and we introduce niobium nanowires as an alternative. These yarns show higher capacitance and energy per volume and are stronger and 100 times more conductive than similarly spun carbon multiwalled nanotube (MWNT) and graphene yarns.6,17−22 The long niobium nanowires, formed by repeated extrusion and drawing,17 achieve device volumetric peak power and energy densities of 55 MW·m–3 (55 W·cm–3) and 25 MJ·m–3 (7 mWh·cm–3), 2 and 5 times higher than that for state-of-the-art CNT yarns, respectively.3 The capacitance per volume of Nb nanowire yarn is lower than the 158 MF·m–3 (158 F·cm–3) reported for carbon-based materials such as reduced graphene oxide (RGO) and CNT wet-spun yarns,5 but the peak power and energy densities are 200 and 2 times higher, respectively.5 Achieving high power in long yarns is made possible by the high conductivity of the metal, and achievement of high energy density is possible thanks to the high internal surface area. No additional metal backing is needed, unlike for CNT yarns and supercapacitors in general, saving substantial space. As the yarn is infiltrated with pseudocapacitive materials such as poly(3,4-ethylenedioxythiophene) (PEDOT), the energy density is further increased to 10 MJ·m–3 (2.8 mWh·cm–3). Similar to CNT yarns, niobium nanowire yarns are highly flexible and show potential for weaving into textiles and use in wearable devices.