Power density

About: Power density is a research topic. Over the lifetime, 9534 publications have been published within this topic receiving 197264 citations. The topic is also known as: volumic power & volume power density.

Bendable polymer electrolyte fuel cell using highly flexible Ag nanowire percolation network current collectors

Abstract: This study reports a polymer electrolyte fuel cell based on polydimethylsiloxane coated with a flexible current-collecting layer of Ag nanowire percolation networks The reactive area of the bendable fuel cell was 9 cm2 and showed the maximum absolute power of 639 mW (the power density was 71 mW cm−2) under various bending conditions Impedance spectra of the operating cell revealed that ohmic and Faradaic resistances decreased under the bent condition Overall, the degree of bending improves the cell performances The structural modeling result showed that decrease of the resistance and corresponding performance enhancement were due to the increased compressive force normal to the membrane electrode assembly, which was investigated through finite element simulation of the stress within the bendable fuel cell

Hybrid solid state supercapacitors (HSSC’s) for high energy & power density: an overview

Abstract: A hybrid supercapacitor (HSC) is a supercapacitor (SC) based on two different electrode materials. One electrode is based on battery type faradic reactions (also known as extrinsic pseudocapacitor), and the other is based on the electric double-layer capacitor (non-faradic, known as intrinsic pseudocapacitor). In HSC, generally negative electrode material includes carbonbased materials (such as activated carbon, carbon nanotubes (CNT’s) and graphene), metal oxides (such as V2O5 and MoO3), and their composites, while positive electrode materials are Ni, Co-based, mixed metal oxide, binary metal-based, layered double hydroxide (LDH) based materials etc. The synergy between high conductivity, specific surface area of negative electrode and architectures, heterostructures of positive electrodes is used to improve the overall electrochemical performances of the HSC’s device. In this review, the basic charge storing mechanisms, a method for determination of capacitive and diffusion-controlled contribution, are explained. This review highlights the importance of hybrid solid-state supercapacitors (HSSC’s) as energy storage devices. Finally, recent advancement in the HSSC fields is discussed and will guide future work in the HSSC field.

Scalable High-Power Redox Capacitors with Aligned Nanoforests of Crystalline MnO2 Nanorods by High Voltage Electrophoretic Deposition

Abstract: It is commonly perceived that reduction–oxidation (redox) capacitors have to sacrifice power density to achieve higher energy density than carbon-based electric double layer capacitors. In this work, we report the synergetic advantages of combining the high crystallinity of hydrothermally synthesized α-MnO2 nanorods with alignment for high performance redox capacitors. Such an approach is enabled by high voltage electrophoretic deposition (HVEPD) technology which can obtain vertically aligned nanoforests with great process versatility. The scalable nanomanufacturing process is demonstrated by roll-printing an aligned forest of α-MnO2 nanorods on a large flexible substrate (1 inch by 1 foot). The electrodes show very high power density (340 kW/kg at an energy density of 4.7 Wh/kg) and excellent cyclability (over 92% capacitance retention over 2000 cycles). Pretreatment of the substrate and use of a conductive holding layer have also been shown to significantly reduce the contact resistance between the alig...

A method and apparatus for magnetically enhanced sputtering

Abstract: In magnetically enhanced sputtering, pulses are applied having a very high instantaneous power, of the order of at least 0.1 kW-1 MW. In such sputtering regions (23) exist in which electrons are trapped by the magnetic field generated by magnets (17) cooperating with the electric field between the anode being part of the wall (5) enclosing the chamber in which sputtering is performed and the cathode which at the same time is the target (9), from which material is to be sputtered. An ionization of the gas in the chamber will then for lower applied power occur preferably in those regions (23) causing a non-uniform erosion of the target (9). For very high power in the pulses or power density in the pulses the gas in said regions and in regions adjacent thereto will enter another state of fully ionization, which considered in energy terms is located above the unwanted state of an electric arc which is formed for a lower supplied power. The region (27) in which this another state exists will be more homogeneous and have a wider extension than the ionized regions (23) produced for a lower supplied power. This results in a more uniform erosion of the target (9) and a more uniform coating of the substrate (13). The high power pulses can also be used in sputtering ion pumps, allowing them to start pumping from moderately low pressures, e.g. in the range of 10-1-10-2 torr.

Biowaste-Derived Hierarchical Porous Carbon Nanosheets for Ultrahigh Power Density Supercapacitors.

Abstract: Low-cost activated carbons with high capacitive properties remain desirable for supercapacitor applications. Herein, a three-dimensional scaffolding framework of porous carbon nanosheets (PCNSs) has been produced from a typical biowaste, namely, ground cherry calyces, the specific composition and natural structures of which have contributed to the PCNSs having a very large specific surface area of 1612 m2 g-1 , a hierarchical pore size distribution, a turbostratic carbon structure with a high degree graphitization, and about 10 % oxygen and nitrogen heteroatoms. A high specific capacitance of 350 F g-1 at 0.1 A g-1 has been achieved in a two-electrode system with 6 m KOH; this value is among the highest specific capacitance of biomass-derived carbon materials. More inspiringly, a high energy density of 22.8 Wh kg-1 at a power density of 198.8 W kg-1 can be obtained with 1 m aqueous solution of Li2 SO4 , and an ultrahigh energy density of 81.4 Wh kg-1 at a power density of 446.3 W kg-1 is realized with 1-ethyl-3-methylimidazolium tetrafluoroborate electrolyte.