Journal of Power Sources Advances最新文献

The performance and stability of polymer electrolyte membrane fuel cells (PEMFCs) are directly affected by the distribution of water molecules inside the membrane. In this study, coherent anti-Stokes Raman scattering (CARS) spectroscopy was used to measure the distribution of water in a Nafion® membrane under transient conditions after increasing the current density. At the cathodic surface of the membrane, an overshoot in amount of water was observed as a result of the increase in the rate of water production and electro-osmosis, while at the other locations in the membrane was observed a gradual increase of water as a result of water transport. The calculation of the water diffusion coefficient during power generation was subsequently carried out, which was consistent with the results of the previous values obtained statically.

Dual-graphite batteries (DGBs), which are based on anion intercalation into graphite positive electrodes, exhibit great potential for stationary energy storage due to use of more sustainable and low-cost electrode materials and processing routes. Binary-mixed highly concentrated electrolytes (HCEs) appeal highly suitable for the high operating voltages of DGBs, although the lack of sufficient insights into the formation of graphite intercalation compounds (GICs) limits the cell performance in terms of specific capacity and lifetime so far. Herein, anion intercalation from single-salt HCEs (LiPF₆ and LiBF₄) and an equimolar binary mixture of LiPF₆/LiBF₄ are studied in graphite || Li metal cells, revealing an improved performance in terms of specific capacity and Coulombic efficiency in the order LiPF₆ > LiPF₆/LiBF₄ > LiBF₄. LiBF₄-based cells exhibit an increased onset potential for anion intercalation and higher area specific impedance, suggesting an ineffective interphase formation at graphite. X-ray diffraction reveals GIC formation, while a lower stage number is achieved for the LiBF₄-based HCE. ¹⁹F MAS NMR spectroscopy analysis at various states-of-charge confirms no significant charge transfer between the intercalated anions and the graphite host and suggest preferred intercalation of PF₆^- compared to BF₄^- as well as a high translational and/or rotational mobility of the intercalated anions.

The vanadium redox flow battery (VRFB) as one of the most promising electrochemical storage systems for stationary applications still needs further cost reductions. Tubular cell designs might reduce production costs by extrusion production of cell components and small sealing lengths. Based on a first study of the authors [1], this work demonstrates the feasibility of extruded tubular VRFB cells with high power density in the flow-by electrode configuration. Extruded cell components are the perfluorosulfonic acid cation exchange membrane with a diameter of 5.0 mm and carbon composite current collectors. The cell performance is experimentally characterized by polarization curve, ohmic resistance and galvanostatic cycling measurements. A maximum volumetric power density of 407 kW/m³ and a maximum current density of 500 mA/cm² can be achieved. A non linear E_cell/i-model is used to evaluate exchange and limiting current densities while in-situ half cell SoC monitoring is applied to evaluate the extruded membrane.

In a high performance all-solid-state lithium-ion battery (ASSLiB), lithium-ion should be smoothly transported to minimize overpotential. Nanoscale pores in the ASSLiB can inhibit ionic transportation; therefore, the pore structure should be measured and nanoscale pores should be prevented for high performance batteries. In this study, laboratory-scale ultra-small-angle X-ray scattering (USAXS) measurements are proposed to evaluate the nanoscale pores in ASSLiBs. The results measured with the USAXS are validated by comparing them with synchrotron radiation (SR) X-ray nanotomography data. The pore volumetric density distributions from the USAXS measurements are very close to those from SR X-ray nanotomography; this demonstrates that the nanoscale pores in ASSLiBs can be measured by USAXS. USAXS measurements of pore structures of solid electrolytes prepared from micron-scale and submicron-scale particles solid electrolyte (SE) reveal that the pore structure is not simply dependent on the SE particle size.

This study investigated unpressed and pressed electrodes with the synchrotron radiation X-ray computed laminography (CL) technique to clarify the relationship between the packing structure formation of an electrode processed with a roll press and the performance of all-solid-state batteries. Additionally, we evaluated the length and thickness of percolation paths constructed by the electrode particles using the 3-dimensional structure obtained by the X-ray CL measurement. The smallest packing fraction was in the cathode layers in both the pressed and unpressed electrodes. The cathode packing fraction had a non-uniform distribution shape as a function of the layer thickness. A similar distribution shape was maintained after pressing, except near the surface in contact with the pressing roller. Pressing caused the packing fraction of the cathode layer to become much larger than the unpressed one, especially near the surface where it significantly increased. The thickness of the percolation paths in the cathode layer also increased after pressing. Furthermore, we discovered that the cathode local path thickness, measured by using regions segmented by packing fraction values, had a linear relationship with the packing fraction. Consequently, the performance bottle neck is caused by the local layer that has the smallest packing fraction.

Concentrated electrolytes have been attracting increasing attention due to their unique properties. However, despite the concern about their thermal stability, few research has been done on their exothermic behaviors, especially with the coexistence of electrodes. Herein, we report the results of detailed investigation into the thermal properties of LiBF₄, LiPF₆, LiTFSI, and LiFSI/carbonate concentrated solutions and their thermal behaviors with the coexistence of fully lithiated graphite. Concentrated LiBF₄ solutions showed no practical application possibilities because they were unstable on C₆Li. Increasing the salt concentration decreased the thermal stability of LiPF₆/PC solutions with the coexistence of C₆Li. The organic salt dominated the thermal behavior of the solution when mixed with C₆Li. A drastic exothermic reaction happened at 210–220 °C when C₆Li was mixed with LiFSI solutions, indicating a very high thermal risk of LiFSI carbonate solutions as LIB electrolytes. In contrast, LiTFSI solutions showed much milder reactions with C₆Li. On the other hand, because of the different LiF content in SEI, the exothermic onset temperature of the C₆Li mixture with the concentrated solution increased in the order of LiFSI > LiTFSI > LiPF₆. Comprehensively, concentrated LiTFSI electrolytes should be a good choice for LIB from the standpoint of battery safety.

Thea article presents the latest research on reticulated carbon collectors in lead-acid batteries. A comparison of the performance characteristics of lead-acid cells and batteries based on two porous conductive carbon materials is presented: commercially available reticulated vitreous carbon (RVC), used in earlier studies, and porous conductive carbon (CPC) developed at the Faculty of Chemistry, University of Warsaw. Lead layers electrodeposited on CPC had better properties and more uniform thickness. Carbon-based negative and positive plates were tested regarding their capacity using different current rates and cycle life. Experiments on complete 2 and 12 V batteries are presented as well. CPC is proven to be as good material as RVC for use as current collectors in lead-acid cells. Obtained results show that there are reticulated carbon materials different from RVC with properties that allow them to be successfully employed in construction of both negative and positive plates in lead-acid batteries.

Electrolytes are an integral part of any electrochemical energy storage systems, including batteries. Among the many properties which determine the applicability of a Li-ion battery electrolyte, electrochemical stability – and for high voltage electrodes, in particular anodic stability – is a key parameter to consider. Despite being simple and straightforward to employ, the conventional linear sweep voltammetry (LSV) technique often leads to an over-estimation of the oxidative stability. In this study, an alternative approach termed Synthetic Charge-discharge Profile Voltammetry (SCPV) is explored to investigate the oxidative electrolyte stability. We have found this to be a convenient method of quantifying the anodic stability of the electrolyte in a more practically representative manner, in which passivation kinetics and electrode potential changes at the electrode-electrolyte interface are more appropriately reproduced. The viability of this technique is explored with liquid electrolytes based on ether, carbonate, sulfone and carbonate-sulfone mixtures, all with lithium hexafluorophosphate (LiPF₆) salt, tested for a potential profile equivalent to LiNi_0.5Mn_1.5O₄ electrodes. The credibility of this technique is validated by correlations to the coulombic efficiencies of corresponding half-cells.

Thin protonic ceramic electrolyte contributes to lower ohmic resistance and enhances electrochemical performance of protonic ceramic electrochemical cells. However, manufacturing of large-scale thin electrolyte remains a challenge. Wet powder spraying is an attractive technique to deposit <10 μm thin electrolyte when advanced atomizing techniques and optimized spraying process are integrated. Here ultrasonic atomization is integrated in the wet powder spray technique to reduce the thickness of electrolyte. Moreover, a parametric study is conducted to optimize the wet powder spray process to deposit uniform and crack-free electrolyte film. It is illustrated that tuning of solid loading rates and spray passes can affect the morphology of the as-sprayed electrolyte film, enabling the structural compactness of the sintered electrolyte layer. To maintain chemical stability of the electrolyte layer during sintering, effect of sintering temperature is further investigated to produce a physically thin, structurally dense, and chemically homogeneous electrolyte layer. The protonic ceramic electrochemical cells fabricated with optimized spraying and sintering parameters demonstrate excellent performance under both fuel cell and electrolysis modes. In addition, the cells exhibit remarkable structural integrity during redox and long-term stability tests.

Anion-exchange membrane fuel cells (AEMFCs) show substantially enhanced (initial) performance and efficiency with the increase of operational temperature (where typical values are below 80 °C). This is directly due to the increase in reaction and mass transfer rates with temperature. Common sense suggests however that the increase of ionomeric material chemical degradation kinetics with temperature is likely to offset the above mentioned gain in performance and efficiency. In this computational study we investigate the combined effect of a high operating temperature, up to 120 °C, on the performance and stability of AEMFCs. Our modeling results demonstrate the expected positive impact of operating temperature on AEMFC performance. More interestingly, under certain conditions, AEMFC performance stability is surprisingly enhanced as temperature increases. While increasing cell temperature enhances degradation kinetics, it simultaneously improves water diffusivity through the membrane, resulting in higher hydration levels at the cathode. This, in turn, encourages a decrease in ionomer chemical degradation which depends on the hydration as well as on temperature, leading to a significant increase in AEMFC performance stability and, therefore, in its lifetime. These findings predict the possible advantage (and importance), in terms of performance and durability, of developing high-temperature AEMFCs for automotive and other applications.