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.

Hierarchical three-dimensional microbattery electrodes combining bottom-up self-assembly and top-down micromachining.

Abstract: The realization of next-generation portable electronics and integrated microsystems is directly linked with the development of robust batteries with high energy and power density. Three-dimensional micro- and nanostructured electrodes enhance energy and power through higher surface area and thinner active materials, respectively. Here, we present a novel approach for the fabrication of hierarchical electrodes that combine benefits of both length scales. The electrodes consist of self-assembled, virus-templated nanostructures conformally coating three-dimensional micropillars. Active battery material (V2O5) is deposited using atomic layer deposition on the hierarchical micro/nanonetwork. Electrochemical characterization of these electrodes indicates a 3-fold increase in energy density compared to nanostructures alone, in agreement with the surface area increase, while maintaining the high power characteristics of nanomaterials. Investigation of capacity scaling for varying active material thickness reveals...

Graphene-Oxide-Coated LiNi0.5Mn1.5O4 As High Voltage Cathode for Lithium Ion Batteries With High Energy Density and Long Cycle Life

Abstract: Lithium ion batteries are receiving enormous attention as power sources and energy storage devices in the renewable energy field. With the ever increasing demand for higher energy and power density, high voltage cathodes have emerged as an important option for new generation batteries. Here, we report graphene-oxide-coated LiNi0.5Mn1.5O4 as a high voltage cathode and demonstrate that the batteries showed superior cycling performance for up to 1000 cycles. Mildly oxidized graphene oxide coating was found to improve the battery performance by enhancing the conductivity and protecting the cathode surface from undesired reactions with the electrolyte. As a result, the graphene-oxide-coated high voltage cathode LiNi0.5Mn1.5O4 showed 61% capacity retention after 1000 cycles in the cycling test, which converts to only 0.039% capacity decay per cycle. At large current rates of 5 C, 7 C and 10 C, the batteries were able to deliver 77%, 66% and 56% of the 1 C capacity, respectively (1 C = 140 mA g−1). In contrast, the LiNi0.5Mn1.5O4 cathode without graphene oxide coating showed 88.7% capacity retention after only 100 cycles. The promising results demonstrated the potential of developing high energy density batteries with the high voltage cathode LiNi0.5Mn1.5O4 and improving the battery performance by surface modification with mildly oxidized graphene oxide.

A thermally synergistic photo-electrochemical hydrogen generator operating under concentrated solar irradiation

Abstract: Achieving high current densities while maintaining high energy conversion efficiency is one of the main challenges for enhancing the competitiveness of photo-electrochemical devices. We describe a concept that allows this challenge to be overcome by operating under concentrated solar irradiation (up to 474 kW m−2), using thermal integration, mass transport optimization and a close electronic integration between the photoabsorber and electrocatalyst. We quantify the increase in the theoretical maximum efficiencies resulting from thermal integration, and experimentally validate the concept using a III–V-based photoabsorber and IrRuOx–Pt-based electrocatalysts. We reach current densities higher than 0.88 A cm−2 at calculated solar-to-hydrogen conversion efficiencies above 15%. Device performance, dynamic response and stability are investigated, demonstrating the ability to produce hydrogen stably under varying conditions for more than two hours. The current density and output power (27 W) achieved provide a pathway for device scalability aimed towards the large-scale deployment of photo-electrochemical hydrogen production. For photo-electrochemical hydrogen production to become viable on a large scale, not only efficiency but also power density must be optimized. Here, the authors explore the impact of thermal integration on photo-electrochemical devices driven by concentrated solar irradiation and design one that operates with high efficiency and power density output.

A novel cobalt-free cathode with triple-conduction for proton-conducting solid oxide fuel cells with unprecedented performance

Abstract: Bi and Sn co-doped perovskite BaFe0.8−XSn0.2BiXO3−δ materials have been designed and characterized as a series of new cathodes for proton-conducting solid oxide fuel cells (SOFCs), providing a new life for the traditional BaFeO3-based cathodes. Proton uptake of the cathode increases significantly with bismuth-doping, favoring the application of Bi and Sn co-doped perovskite BaFe0.8−XSn0.2BiXO3−δ materials in proton-conducting SOFCs. The density functional theory (DFT) calculation also suggests that the bismuth-doping leads to a dramatic increase of hydration energy and acceleration of proton migration for the BFS material. The XPS results show that the oxygen reduction reaction (ORR) activity of the cathode is enhanced after bismuth is added, which is consistent with the experimental results of the power density of the single cell. The maximum power density of the single cells with the structure of NiO-BaZr0.1Ce0.7Y0.2O3−δ|BaZr0.1Ce0.7Y0.2O3−δ| BaFe0.5Sn0.2Bi0.3O3−δ (BFSBi0.3) reached 1277 mW cm−2 at 700 °C, which is a record-high performance for proton-conducting SOFCs using cobalt-free cathodes, compared with previous reports. The outstanding fuel cell performance and good long term stability indicate that bismuth-doping is an effective way of promoting proton-conduction in traditional cathodes. This study opens a new door to the design of high performance cathodes for proton-conducting SOFCs.

Review of GaN totem-pole bridgeless PFC

Abstract: Switching-mode AC/DC converters are widely used in modern power supplies for computers, data centers and telecommunication equipment. Achieving Power Factor Correction (PFC) and high efficiency are the two most important requirements. In many cases, high power density is also of tremendous interest. Both power efficiency and power density are greatly influenced by the power devices, the topology and the control used. Compared with conventional Si power MOSFET and Si super-junction MOSFET, the newly introduced 600 V GaN devices not only eliminate the reverser recovery, but also have much lower switching and driving losses. These excellent properties enable the emergence of the totem-pole bridgeless AC/DC converter as the next generation preferred solution for PFC instead of the state-of-the art Si-based boost PFC. In this paper, the key technologies and designs for both hard-switching and soft-switching GaN totem-pole PFC are reviewed and the key performance metrics are compared. A soft switching, 3.2 kW totem-pole PFC prototype with 99% efficiency and 130 W/inch3 power density has been achieved in the author's group as a proof of the concept. Based on the power density comparison, the high frequency soft-switching GaN totem-pole PFC is the preferred choice to achieve both high efficiency and high power density at the same time.