Topic
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.
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TL;DR: A revolutionary advance in a conversion-reaction cathode is reported by developing a core-shell FeOF@PEDOT nanorods, in which partial substitution of fluorine with oxygen in FeF3 substantially enhance the reaction kinetics and reduce the potential hysteresis, while conformal nanolayer PEDOT coating provides a roubst fast electronic connection and prevents the side reactions.
Abstract: Conversion-reaction cathodes can potentially double the energy density of current Li-ion batteries. However, the poor cycling stability, low energy efficiency, and low power density of conversion-reaction cathodes limit their applications for Li-ion batteries. Herein, we report a revolutionary advance in a conversion-reaction cathode by developing a core–shell FeOF@PEDOT nanorods, in which partial substitution of fluorine with oxygen in FeF3 substantially enhance the reaction kinetics and reduce the potential hysteresis, while conformal nanolayer PEDOT coating provides a roubst fast electronic connection and prevents the side reactions. The FeOF@PEDOT nanorods deliver a capacity of 560 mA h g–1 at 10 mA g–1 with an energy density of >1100 W h kg–1, which is more than two times higher than the theoretical energy density of LiCoO2. The FeOF@PEDOT nanorods can maintain a capacity of ∼430 mA h g–1 at 50 mA g–1 (840 W h kg–1) for over 150 cycles with capacity decay rate of only 0.04% per cycle, which is 2 orde...
89 citations
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TL;DR: In this article, a series of Co-N-C catalysts with different CoN4 densities are differentiated in the study, showing the crucial role of the high active site density to the high power density.
Abstract: Improvement of proton exchange membrane fuel cell (PEMFC) performance of Co-N-C electrocatalyst requires an in-depth understanding of performance enhancement mechanism. Herein, we synthesize a series of Co-N-C catalysts with different CoN4 densities. CoN4 active sites (electrochemical accessible ones) and CoN4 species are differentiated in the study. The power density shows a slow linear increase in the low concentration region and an accelerated increase in the high concentration region of CoN4 active sites, showing the crucial role of the high active site density to the high power density of Co-N-C. The optimized Co-N-C achieves a high power density of 826 mW cm−2. Meanwhile, CoN4 ORR turnover frequency (TOF) is calculated to be 0.01 s−1 at 0.8 V vs. RHE in acid media. The results allow us to predict that many non-precious metal catalysts with only moderate activity may have considerable PEMFC performance as long as possessing sufficiently dense active sites.
89 citations
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TL;DR: In this article, a unipolar pulse electrodeposition method was employed to controllably synthesize nanosheet type NiCo LDH and the effect of concentration rate on crystalline structure, morphology and supercapacitive performance was investigated systematically.
Abstract: A unipolar pulse electrodeposition method was employed to controllably synthesize nanosheet type NiCo LDH. The effect of concentration rate of Ni(NO3)2/Co(NO3)2 preparation solution on crystalline structure, morphology and supercapacitive performance was investigated systematically. Experimental found that the morphology and composition of NiCo LDH was highly depend on the Ni2+/Co2+ molar ratios of preparation solution; and the obtained Ni0.76Co0.24 LDH materials showed small nanosheet size and uniform distribution on carbon fiber electrode. Ni0.76Co0.24 LDH electrode was evaluated for supercapacitor application, which revealed a high specific capacitances of 2189.8 and 1908.8 F g−1 at the current density of 1 and 30 A g−1 respectively and a good cycle stability, retaining 70.3 % of the initial capacitance after 20000 charge and discharge cycles at 50 A g−1. Moreover, the Ni0.76Co0.24 LDH electrode exhibits a high energy density of 76 Wh Kg−1 at a power density of 250 W Kg−1 and a high power density of 7500 W Kg−1 at energy density of 66 Wh Kg−1. The as-prepared Ni0.76Co0.24 LDH as positive electrode for asymmetric supercapacitor exhibits excellent energy density of 4.1 Wh Kg-1 at a power density of 4000 W Kg-1
88 citations
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29 Jan 2008TL;DR: In this paper, a review of recent results on high-power, high-efficiency two-dimensional vertical-cavity surface-emitting laser (VCSEL) arrays emitting around 980nm is presented.
Abstract: We review recent results on high-power, high-efficiency two-dimensional vertical-cavity surface-emitting laser
(VCSEL) arrays emitting around 980nm. Selectively oxidized, bottom-emitting single VCSEL emitters with 51% power
conversion efficiency were developed as the basic building block of these arrays. More than 230W of continuous-wave
(CW) power is demonstrated from a ~5mm x 5mm array chip. In quasi-CW mode, smaller array chips exhibit 100W
output power, corresponding to more than 3.5kW/cm2 of power density. High-brightness arrays have also been
developed for pumping fiber lasers, delivering a fiber output power of 40W. We show that many of the advantages of
low-power single VCSEL devices such as reliability, wavelength stability, low-divergence circular beam, and low-cost
manufacturing are preserved for these high-power arrays. VCSELs thus offer an attractive alternative to the dominant
edge-emitter technology for many applications requiring compact high-power laser sources.
88 citations