Journal of Power Sources Advances最新文献

Three-dimensional measuring method of the material distribution of an all-solid-state lithium-ion battery (ASSLiB) cathode, by synchrotron radiation high-resolution X-ray computational tomography (nanotomography, nano-CT) and deep learning is proposed in this study. The cathode of the ASSLiB comprised materials with high X-ray absorption coefficients, such as LiCoO₂ and LiNi_0.5Co_0.2Mn_0.3O₂. Such high absorption coefficients imparted difficulties in obtaining a high-resolution, high-contrast image and in identifying materials with conventional CT value method. The method proposed in this study was effective in acquiring a high-resolution image with fewer artifacts and measured the heavy materials at a high signal-to-noise ratio. We used deep learning with a customized U-net, enabling high accuracy and ultra-high-speed material identification. Using this method, constituent materials were successfully identified in three dimensions. This material identification technique showed great potential for application to other techniques such as focused ion beam–scanning electron microscopy.

In many lithium-ion battery (LIB) applications, e.g. hybrid vehicles and load-levelling storage systems, only part of the state-of-charge (SOC) range needs to be utilised. This offers the possibility to use an optimal SOC window to avoid LIB ageing. Here, a large test matrix is designed to study LIB ageing in a commercial 26 Ah pouch cell, in order to map the ageing behaviour at different SOC levels with respect to temperature and current. A quantification of the degradation modes, loss of lithium inventory (LLI), loss of active positive (LAM_PE) and negative (LAM_NE) electrode materials is made by analysing the change in the open circuit voltage (OCV). A key result is that lower SOC intervals significantly improved battery ageing. Even during harsh test conditions, such as high C-rates and temperatures, the cells deliver more than three times the expected number of full cycle equivalents. High SOC combined with high C-rate increase ageing where the dominating ageing mechanisms are LLI, followed by LAM_PE.

This work aims at assessment of TiO₂ as the main layer component for self-cleaning layers in photovoltaic panels. TiO₂ (derived from titanium (IV) butoxide or titanium (IV) isopropoxide) without and with silver was examined to find titania suitable microstructure and optical properties. For this purpose silver amounts ranging from 0.1 to 1% were used for 3 separate chemical methods of modification. Microstructure of powders was characterized by means of scanning electron microscopy (SEM) and transmission electron microscopy (TEM) with X-ray energy dispersion spectroscopy. Three techniques: spin-coating, doctor blade, and spray-coating were used to deposit TiO₂ and TiO₂–Ag layers on glass and silicon solar cells. The photocatalytic activity of TiO₂ and TiO₂–Ag were investigated in the presence of methylene blue. Concentration of dye, amount of silver, type of TiO₂ with Ag modification and stability over time were analysed towards the best photocatalytic properties. Finally, TiO₂ layers which were used to coat a new type of photovoltaic modules had marginal influence on photovoltaic parameters.

The construction of Solid Electrolyte Interface (SEI) film in Li-ion batteries with functional electrolyte additives is able to passivate the active material surface and inhibit the decomposition of the electrolyte continuously. In addition, safety issue is also an important factor restricting the large scale application of present lithium-ion batteries. Therefore, the additives for film-forming and safety enhancement are a class of cost-effective components that promote the application and development of batteries. Fluorine is a kind of “bipolar” element, which has strong electronegativity and weak polarity. Fluorine-containing electrolyte additives have excellent kinetic reactivity, which can preferentially generate stable SEI films and uniform Cathode-Electrolyte Interface (CEI) films to effectively improve the electrochemical performance of the batteries. Meanwhile, fluorine-containing electrolyte additives can also be used as flame-retardants to improve safety performance. In this review, we summarize the research status of fluorine-containing additives in recent years and elaborate its reaction mechanisms of improving battery performance. Finally, a personal perspective on the future of the development of fluorine-containing additives is presented.

Physics based transmission line models (TLMs) are a convenient tool for the analysis of the impedance response of electrochemical systems – the most prominent examples being double-layer capacitors, solar cells, and batteries. TLMs can provide a good quali- and quantitative evaluation of the main transport-reaction steps occurring in a given system - at a moderate mathematical effort. This mini review focuses on the theoretical development and application of TLM schemes in porous battery electrodes and other porous battery components. After a short historical overview of the main achievements in the field, we discuss in some detail the conventional TLM based on the de Levie's original proposal. Afterwards we present a couple of upgrades that address the deficiencies of the conventional model at low frequencies in which diffusion in electrolyte phases (in porous electrode and in separator) is supposed to be observed. We compare systematically the impedance responses of several TLMs and comment on their ability to simulate the measured impedance spectra. Simplifications and limitations of the discussed models are also considered. Finally, a comparison between the proposed TLMs and the output of the well-known Newman's porous electrode model is shown.

Electrochemical impedance spectroscopy (EIS) is a well-established method to analyze a polymer electrolyte membrane fuel cell (PEMFC). However, without further data processing, the impedance spectrum yields only qualitative insight into the mechanism and individual contribution of transport, kinetics, and ohmic losses to the overall fuel cell limitations. The distribution of relaxation times (DRT) method allows quantifying each of these polarization losses and evaluates their contribution to a given electrocatalyst's depreciated performances. We coupled this method with a detailed morphology study to investigate the impact of the 3D-structure on the processes occurring inside a high-temperature polymer electrolyte membrane fuel cell (HT-PEMFC). We tested a platinum catalyst (Pt/C), a platinum-cobalt alloy catalyst (Pt₃Co/C), and a platinum group metal-free iron-nitrogen-carbon (Fe–N–C) catalyst. We found that the hampered mass transport in the latter is mainly responsible for its low performance in the MEA (along with its decreased intrinsic performances for the ORR reaction). The better performance of the alloy catalyst can be explained by both improved mass transport and a lower ORR resistance. Furthermore, single-cell tests show that the catalyst layer morphology influences the distribution of phosphoric acid during conditioning.

A two-layer rechargeable oxide battery using a stack initially developed for solid oxide cells was operated for 2100 h with more than 1000 charging/discharging cycles. The operation temperature was 800 °C and the applied current density (on the solid oxide cell) was 150 mA cm⁻². During operation, no electrochemical indications for degradation were measured. The voltages achieved during redox cycling were in good agreement with the equilibrium voltages of the envisaged corresponding phases. For the first time, a storage material based on the calcium–iron oxide with the richest iron content was used. Storage utilization was 86%, thereby reaching a capacity of 20.6 Ah per layer. Post-test analysis of the storage revealed mostly expected storage phases and sufficient remaining storage porosity.

Electrochemical cleaning, a recently proposed mitigation strategy for chromium poisoning in solid oxide fuel cell (SOFC) cathodes, involves rapid in-situ removal of Cr₂O₃ deposits from LSM-YSZ cathodes accompanied by a recovery of a large fraction of the cell performance originally lost due to Cr poisoning. By operating the cell briefly as a solid oxide electrolyzer cell (SOEC), the cleaning method effectively reverses the Cr deposition reactions, reforming Cr-containing vapor species, thereby freeing up electrochemically active sites and restoring cell performance. In practice, this method can be periodically applied to the system after a specified amount of degradation due to chromium poisoning has occurred. The current study investigates the efficacy of this method by cycling a single cell through a stage of accelerated poisoning followed by electrochemical cleaning for a total of three times. Current-voltage measurements demonstrate repeated loss in performance due to Cr poisoning and recovery in performance due to electrochemical cleaning, reinforcing the utility of this cleaning method over the lifetime of the cell operation.

Under alkaline conditions, hydroxide ions can deplete at the anode of a water electrolyser for hydrogen production, resulting in a limiting current density. We found experimentally that in a micro-porous separator, an electro-osmotic flow from anode to cathode lowers this limiting current density. Using the Nernst-Planck equation, a useful expression for the potential drop in the presence of diffusion, migration, and advection is derived. A quasi-stationary, one-dimensional model is used to successfully describe the transient dynamics. Electro-osmotic flow-driven cross-over of dissolved oxygen is argued to impact the hydrogen purity.