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.

The effect of electrode design parameters on battery performance and optimization of electrode thickness based on the electrochemical–thermal coupling model

Abstract: Electrodes are the most important components in the lithium-ion battery, and their design, which ultimately determines the quantity and speed of lithium storage, directly affects the capacity, power density, and energy density of the battery. Herein, an electrochemical–thermal coupling model was established for an 18.5 A h lithium-ion battery, and the model was validated by experiment at four discharge rates. Based on this model, the effects of the electrode design parameters (electrode thickness, volume fraction of active material and particle size) on the battery performance (electrochemical characteristics, thermal behavior, energy density and power density) were initially investigated. It was found that as the electrode thickness and volume fraction of the active material increased, the polarization, heat generation rate and energy density increased, while the power density degraded. In addition, as the particle size decreased, both the energy density and power density improved, which can provide guidance for the design of electrodes. Subsequently, a multi-parameter (thickness of the positive and negative electrodes) and multi-objective (energy density and power density) optimization procedure was performed via two optimization methods, and the positive electrode thickness of 55.335 μm and negative electrode thickness of 63.188 μm were determined to be the optimized parameters.

Particle Size Polydispersity in Li-Ion Batteries

Abstract: Starting from three-dimensional X-ray tomography data of a commercial LiMn2O4 battery electrode, the effect of microstructure on the electrochemical and chemo-mechanical response of lithium-ion batteries is analyzed. Simulations show that particle size polydispersity impact the local chemical and electrical behavior of a porous electrode, while particle-particle mechanical interactions favor intercalation induced stress accumulation, resulting in a mechanically unreliable electrode microstructure. Simulations based on computer-generated electrode microstructures demonstrate that broad particle size distributions deliver up to two times higher energy density than monodisperse-sized particles based electrodes for low C-rates. However, monodisperse particle size distribution electrodes deliver the highest energy and power density for high discharge rates due to a higher surface area of reactive material per unit volume. Calculations show that the surface roughness in experimentally determined electrodes is 2.5 times higher than the one delivered by perfectly smooth spherical particles in computer generated electrodes, and provide high instantaneous power performance, but accelerate side reactions that impact negatively on power performance. The combined experimental and modeling approach demonstrates that porous electrodes with spatially uniform microstructural features improve electrochemical performance and mechanical reliability, especially for high power density applications. © 2014 The Electrochemical Society. All rights reserved.

Hierarchically porous carbon foams for electric double layer capacitors

Abstract: The growing demand for portable electronic devices means that lightweight power sources are increasingly sought after. Electric double layer capacitors (EDLCs) are promising candidates for use in lightweight power sources due to their high power densities and outstanding charge/discharge cycling stabilities. Three-dimensional (3D) self-supporting carbon-based materials have been extensively studied for use in lightweight EDLCs. Yet, a major challenge for 3D carbon electrodes is the limited ion diffusion rate in their internal spaces. To address this limitation, hierarchically porous 3D structures that provide additional channels for internal ion diffusion have been proposed. Herein, we report a new chemical method for the synthesis of an ultralight (9.92 mg/cm3) 3D porous carbon foam (PCF) involving carbonization of a glutaraldehydecross-linked chitosan aerogel in the presence of potassium carbonate. Electron microscopy images reveal that the carbon foam is an interconnected network of carbon sheets containing uniformly dispersed macropores. In addition, Brunauer–Emmett–Teller measurements confirm the hierarchically porous structure. Electrochemical data show that the PCF electrode can achieve an outstanding gravimetric capacitance of 246.5 F/g at a current density of 0.5 A/g, and a remarkable capacity retention of 67.5% was observed when the current density was increased from 0.5 to 100 A/g. A quasi-solid-state symmetric supercapacitor was fabricated via assembly of two pieces of the new PCF and was found to deliver an ultra-high power density of 25 kW/kg at an energy density of 2.8 Wh/kg. This study demonstrates the synthesis of an ultralight and hierarchically porous carbon foam with high capacitive performance.

Energy efficiency of NO removal by pulsed corona discharges

Abstract: Pulsed positive corona discharges are used to remove NO from the flue gas of a methane burner. At low power input this leads to an increase in NO2, which shows that the process is oxidative. Removal efficiency is greatest when discharges are produced with high-voltage pulses, which are shorter in duration than the time required by the primary streamers to cross the discharge gap, in combination with a dc bias. Other important parameters are input power density and residence time. The best result obtained so far is an energy consumption of 20 eV per NO molecule removed, at 50% deNOx i.e., a removal of 150 ppm NOx, using a residence time of 15 s and an input power density, of 3.5 Wh/Nm3. [Wh/Nm3 stands for watt-hour per normal cubic meter, i.e., at normal conditions (273 K and 1 bar). This implies that 1 Nm3 contains 2.505 1025 molecules.] There appears to be room for improvement by the addition of gaseous and particulate chemicals or the use of multiple corona treatment. It is argued front comparison between results from models and experiments that the direct production of OH by the discharge is only the initiation of the cleaning process.

Vehicular power supply apparatus and engine-drive-regulation supporting apparatus

Abstract: A power feed portion includes a power storage portion and a power generating portion. The power storage portion includes a storage battery. The power feed portion feeds electric power to a plurality of on-vehicle loads. In cases where the sum of feedable electric power is smaller than the sum of required electric power or in cases where an electric quantity related to the sum of feedable electric power is smaller than an electric quantity related to the sum of required electric power, a control portion increases the sum of feedable electric power or decreases the sum of required electric power. The sum of feedable electric power is equal to electric power which can be fed from the power feed portion to the on-vehicle loads, and which contains electric power generated by the power generating portion and electric power feedable from the storage battery.