Optimizing the performance of the lithium metal anode is required to enable the next generation of high energy density batteries. Anode-free lithium metal cells are particularly attractive as they facilitate the highest energy density cell architecture. In this work, we investigate the performance of anode-free cells cycled under different protocols. We demonstrate the impact of charge and discharge current density with three different cycling conditions: a symmetric charge-discharge, an asymmetric faster charge and an asymmetric slower charge. We show that the relative rate of charge vs discharge is more important than the absolute current densities, and that cycling with an asymmetric slower charge protocol is optimal in agreement with previous studies on cells with lithium metal anodes. We also examine the effect of depth of discharge and demonstrate how the lower voltage cut-off can be chosen to form a lithium reservoir in situ. We show that the capacity of the lithium reservoir significantly benefits lifetime for cells cycled with a limited depth of discharge. Finally, we develop a specialized intermittent high depth of discharge cycling protocol optimized for anode-free lithium metal cells.
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The Electrochemical Society was founded in 1902 to advance the theory and practice at the forefront of electrochemical and solid state science and technology, and allied subjects.
JES is the flagship journal of The Electrochemical Society. Published continuously from 1902 to the present, JES remains one of the most highly-cited journals in electrochemistry and solid-state science and technology.
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A. J. Louli et al 2021 J. Electrochem. Soc. 168 020515
Yuliya Preger et al 2020 J. Electrochem. Soc. 167 120532
Energy storage systems with Li-ion batteries are increasingly deployed to maintain a robust and resilient grid and facilitate the integration of renewable energy resources. However, appropriate selection of cells for different applications is difficult due to limited public data comparing the most commonly used off-the-shelf Li-ion chemistries under the same operating conditions. This article details a multi-year cycling study of commercial LiFePO 4 (LFP), LiNi xCo yAl 1−x−yO 2 (NCA), and LiNi xMn yCo 1−x−yO 2 (NMC) cells, varying the discharge rate, depth of discharge (DOD), and environment temperature. The capacity and discharge energy retention, as well as the round-trip efficiency, were compared. Even when operated within manufacturer specifications, the range of cycling conditions had a profound effect on cell degradation, with time to reach 80% capacity varying by thousands of hours and cycle counts among cells of each chemistry. The degradation of cells in this study was compared to that of similar cells in previous studies to identify universal trends and to provide a standard deviation for performance. All cycling files have been made publicly available at batteryarchive.org, a recently developed repository for visualization and comparison of battery data, to facilitate future experimental and modeling efforts.
Rainer Küngas 2020 J. Electrochem. Soc. 167 044508
Recently, the field of CO 2 electrolysis has experienced rapid scientific and technological progress. This review focuses specifically on the electrochemical conversion of CO 2 into carbon monoxide (CO), an important “building block” for the chemicals industry. CO 2 electrolysis technologies offer potentially carbon-neutral routes for the production of specialty and commodity chemicals. Many different technologies are actively being pursued. Electrochemical CO 2 reduction from aqueous solutions stems from the success of alkaline and polymer electrolyte membrane electrolyzers for water electrolysis and uses performance metrics established within the field of aqueous electrochemistry. High-temperature CO 2 electrolysis systems rely heavily on experience gained from developing molten carbonate and solid oxide fuel cells, where device performance is evaluated using very different parameters, commonly employed in solid-state electrochemistry. In this review, state-of-the-art low-temperature, molten carbonate, and solid oxide electrolyzers for the production of CO are reviewed, followed by a direct comparison of the three technologies using some of the most common figures of merit from each field. Based on the comparison, high-temperature electrolysis of CO 2 in solid oxide electrolysis cells seems to be a particularly attractive method for electrochemical CO production, owing to its high efficiency and proven durability, even at commercially relevant current densities.
Srikanth Namuduri et al 2020 J. Electrochem. Soc. 167 037552
The downtime of industrial machines, engines, or heavy equipment can lead to a direct loss of revenue. Accurate prediction of such failures using sensor data can prevent or reduce the downtime. With the availability of Internet of Things (IoT) technologies, it is possible to acquire the sensor data in real-time. Machine Learning and Deep Learning (DL) algorithms can then be used to predict the part and equipment failures, given enough historical data. DL algorithms have shown significant advances in problems where progress has eluded the practitioners and researchers for several decades. This paper reviews the DL algorithms used for predictive maintenance and presents a case study of engine failure prediction. We also discuss the current use of sensors in the industry and future opportunities for electrochemical sensors in predictive maintenance.
Eli M. Espinoza et al 2019 J. Electrochem. Soc. 166 H3175
What is the best approach for estimating standard electrochemical potentials, E (0), from voltammograms that exhibit chemical irreversibility? The lifetimes of the oxidized or reduced forms of the majority of known redox species are considerably shorter than the voltammetry acquisition times, resulting in irreversibility and making the answer to this question of outmost importance. Half-wave potentials, E (1/2), provide the best experimentally obtainable representation of E (0). Due to irreversible oxidation or reduction, however, the lack of cathodic or anodic peaks in cyclic voltammograms renders E (1/2) unattainable. Therefore, we evaluate how closely alternative potentials, readily obtainable from irreversible voltammograms, estimate E (0). Our analysis reveals that, when E (1/2) is not available, inflection-point potentials provide the best characterization of redox couples. While peak potentials are the most extensively used descriptor for irreversible systems, they deviate significantly from E (0), especially at high scan rates. Even for partially irreversible systems, when the cathodic peak is not as pronounced as the anodic one, the half-wave potentials still provide the best estimates for E (0). The importance of these findings extends beyond the realm of electrochemistry and impacts fields, such as materials engineering, photonics, cell biology, solar energy engineering and neuroscience, where cyclic voltammetry is a key tool.
George E. Blomgren 2017 J. Electrochem. Soc. 164 A5019
This year, the battery industry celebrates the 25 th anniversary of the introduction of the lithium ion rechargeable battery by Sony Corporation. The discovery of the system dates back to earlier work by Asahi Kasei in Japan, which used a combination of lower temperature carbons for the negative electrode to prevent solvent degradation and lithium cobalt dioxide modified somewhat from Goodenough's earlier work. The development by Sony was carried out within a few years by bringing together technology in film coating from their magnetic tape division and electrochemical technology from their battery division. The past 25 years has shown rapid growth in the sales and in the benefits of lithium ion in comparison to all the earlier rechargeable battery systems. Recent work on new materials shows that there is a good likelihood that the lithium ion battery will continue to improve in cost, energy, safety and power capability and will be a formidable competitor for some years to come.
Jason B. Quinn et al 2018 J. Electrochem. Soc. 165 A3284
The standard format for cylindrical Li-ion cells is about to change from 18650-type cells (18mm diameter, 65mm height) to 21700-type cells (21mm diameter, 70mm height). We investigated the properties of five 18650 cells, three of the first commercially available 21700, and three types of the similar 20700 cells in detail. In particular, the (i) specific energy/energy density and electrode thickness, (ii) electrode area and cell resistance, (iii) specific energy as a function of discharge C-rate, as well as (iv) heating behavior due to current flow are analyzed. Finally, the production effort for cells and packs are roughly estimated for 21700 cells compared to 18650 cells.
Zhanlai Ding et al 2020 J. Electrochem. Soc. 167 070541
All solid-state lithium batteries (ASSLBs) employing inorganic solid electrolytes or solid polymer electrolytes are attracting increasing interests for electrochemical energy storage devices due to their advantages of high energy density, high safety, wide operating temperature range and long cycle life. However, the large interfacial resistance originated from the insufficient solid-solid contact at electrolyte/electrode interface hinders the development of ASSLBs. In addition, the interfacial stability and compatibility also greatly affect the electrochemical performance of batteries. To realize the ASSLB’s application requires significant research in solid electrolyte materials and solid electrolyte/electrode interfaces. This review summarizes the research and development in solid electrolyte materials and the interfaces of solid electrolyte/electrode, paying special attention to the challenges and progress for the studies of interface issues in ASSLBs. Based on the overview, we attempt to propose approaches to the issue by interface engineering and prospective developments of ASSLBs.
Laura Bravo Diaz et al 2020 J. Electrochem. Soc. 167 090559
The Lithium-ion battery (LIB) is an important technology for the present and future of energy storage, transport, and consumer electronics. However, many LIB types display a tendency to ignite or release gases. Although statistically rare, LIB fires pose hazards which are significantly different to other fire hazards in terms of initiation route, rate of spread, duration, toxicity, and suppression. For the first time, this paper collects and analyses the safety challenges faced by LIB industries across sectors, and compares them to the research contributions found in all the review papers in the field. The comparison identifies knowledge gaps and opportunities going forward. Industry and research efforts agree on the importance of understanding thermal runaway at the component and cell scales, and on the importance of developing prevention technologies. But much less research attention has been given to safety at the module and pack scales, or to other fire protection layers, such as compartmentation, detection or suppression. In order to close the gaps found and accelerate the arrival of new LIB safety solutions, we recommend closer collaborations between the battery and fire safety communities, which, supported by the major industries, could drive improvements, integration and harmonization of LIB safety across sectors.
Umamaheswari Janakiraman et al 2020 J. Electrochem. Soc. 167 160552
Lithium-ion batteries (LiB) offer a low-cost, long cycle-life and high energy density solution to the automotive industry. There is a growing need of fast charging batteries for commercial application. However, under certain conditions of high currents and/or low temperatures, the chance for Li plating increases. If the anode surface potential falls below 0 V vs Li/Li +, the formation of metallic Li is thermodynamically feasible. Therefore, determination of accurate Li plating curve is crucial in estimating the boundary conditions for battery operation without compromising life and safety. There are various electrochemical and analytical methods that are employed in deducing the Li plating boundary of the Li-ion batteries. The present paper reviews the common test methods and analysis that are currently utilized in Li plating determination. Knowledge gaps are identified, and recommendations are made for the future development in the determination and verification of Li plating curve in terms of modeling and analysis.
Most cited
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Rainer Küngas 2020 J. Electrochem. Soc. 167 044508
Recently, the field of CO 2 electrolysis has experienced rapid scientific and technological progress. This review focuses specifically on the electrochemical conversion of CO 2 into carbon monoxide (CO), an important “building block” for the chemicals industry. CO 2 electrolysis technologies offer potentially carbon-neutral routes for the production of specialty and commodity chemicals. Many different technologies are actively being pursued. Electrochemical CO 2 reduction from aqueous solutions stems from the success of alkaline and polymer electrolyte membrane electrolyzers for water electrolysis and uses performance metrics established within the field of aqueous electrochemistry. High-temperature CO 2 electrolysis systems rely heavily on experience gained from developing molten carbonate and solid oxide fuel cells, where device performance is evaluated using very different parameters, commonly employed in solid-state electrochemistry. In this review, state-of-the-art low-temperature, molten carbonate, and solid oxide electrolyzers for the production of CO are reviewed, followed by a direct comparison of the three technologies using some of the most common figures of merit from each field. Based on the comparison, high-temperature electrolysis of CO 2 in solid oxide electrolysis cells seems to be a particularly attractive method for electrochemical CO production, owing to its high efficiency and proven durability, even at commercially relevant current densities.
Ravinder Kour et al 2020 J. Electrochem. Soc. 167 037555
In the last three decades, a lot of scientific research has been carried out in the field of Carbon nanomaterials all over the world due to their significant electronic, optical, mechanical, chemical and thermal properties. The zero, one, two and three dimensional Carbon nanomaterials (i.e. fullerenes, Carbon nanotubes, Graphene, Carbon quantum dots, Carbon Nanohorns, Nanodiamonds, Carbon Nanofibres and Carbon black) have exhibited such inherent features that can be easily exploited in the development of advanced technology for sensing applications. The employment of nanomaterials within sensors has paved new way and opportunities for the detection of analytes or target molecules. Carbon nanomaterials based electrochemical biosensors have reported biocompatibility, better sensitivity, better selectivity and lower limits of detection to detect a wide range of chemical to biological molecules. In this paper, a comprehensive review has been made to cover recent developments in the field of Carbon based nanomaterials as electrochemical biosensors. The characteristic features of a variety of nanomaterials like fullerenes, Carbon nanotubes, Graphene, Carbon quantum dots, Carbon Nanohorns, Carbon Nanodiamonds, Carbon Nanofibres, Carbon black etc. have been discussed along with their synthesis methods. The recent application of all these nanomaterials as electrochemical biosensors for the detection of various biomolecules have been highlighted; the future prospects and possibilities in this field have been outlined.
Nicola Boaretto et al 2020 J. Electrochem. Soc. 167 070524
Rechargeable batteries are becoming increasingly important for our daily life due to their strong capability of efficiently storing electric energy under chemical form. The replacement of conventional liquid electrolytes with polymer electrolytes (PEs) has been deemed as one of the most viable solutions towards safer and higher energy density electrochemical energy storage systems which are coveted for e-mobility applications (e.g., electric vehicles, EVs). In recent years, the introduction of inorganic materials into PEs has captured escalating interest, aiming at harmonizing advantages from both organic and inorganic phases. In this review, we present the progress and recent advances in PEs containing nano-sized inorganic materials, with due attention paid to the role of inorganic phases on the physical and chemical properties of the electrolytes. The paradigm shift from composite polymer electrolytes (CPEs, obtained by physical blending) to hybrid polymer electrolytes (HPEs, obtained by chemical grafting) is highlighted and the possible improvement and future directions in CPEs and HPEs are discussed.
Feiyun Cui et al 2020 J. Electrochem. Soc. 167 037525
Cancer is a dreadful disease with a high mortality rate, and it has become more and more prevalent worldwide. Early diagnosis, prognosis and treatment monitoring with robust and non-invasive tools will potentially be the future focus. Electrochemical biosensor can be a strong candidate for cancer theranostics owing to their advantage of ultra-sensitivity, high selectivity, low cost, quick readout, and simplicity. Furthermore, electrochemical biosensors are easier to be miniaturized and mass fabricated, which grant them a better fit for point-of-care applications. In this review, various electrochemical measurement methods, bioreceptor surface, signal generation and amplification, integration of electrochemical sensors in microfluidic chips were summarized. Especially, multiplexed and ratiometric electrochemical biosensor were emphasized in cancer biomarkers detection. Then, measurement and analysis of cancers based on electrochemical biosensors in molecular level (DNA, RNA, and protein), organelle level (exosomes), cell level (cell counting, phenotypic and metabolism analysis, drug sensitivity monitoring) were comprehensively discussed. As a new research trend, the integration of electrochemical biosensors in cancer-on-a-chip has been highlighted. In brief, we present an overall review of current advances in cancers measurement and analysis using electrochemical biosensors. Finally, the current challenges and future directions were discussed.
Tugba Ozer et al 2020 J. Electrochem. Soc. 167 037523
Infectious diseases commonly occur in contaminated water, food, and bodily fluids and spread rapidly, resulting in death of humans and animals worldwide. Among infectious agents, viruses pose a serious threat to public health and global economy because they are often difficult to detect and their infections are hard to treat. Since it is crucial to develop rapid, accurate, cost-effective, and in-situ methods for early detection viruses, a variety of sensors have been reported so far. This review provides an overview of the recent developments in electrochemical sensors and biosensors for detecting viruses and use of these sensors on environmental, clinical and food monitoring. Electrochemical biosensors for determining viruses are divided into four main groups including nucleic acid-based, antibody-based, aptamer-based and antigen-based electrochemical biosensors. Finally, the drawbacks and advantages of each type of sensors are identified and discussed.
Latest articles
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Zhihao Lu et al 2021 J. Electrochem. Soc. 168 036508
Innovative electrochemical processing was proposed in this paper to remove residual copper from carbon saturated iron melt. A direct current electric field was applied to treat the copper-bearing molten iron with molten sulfide flux between a cathode immersed in the sulfide flux and an anode immersed in the molten iron, and a better decopperization effect was achieved with the action of the electric field. Including the copper removal ratio increased to 94%, the distribution ratio of copper between the sulfide and iron increased by about four times, and the sulfur content in the iron melt was decreased by about 50%. Electrochemical tests were carried out to study the reasons for those effects. The results indicated that the electrodeposition of Cu+ on the cathode promotes the mass transfer of Cu from iron melt to molten sulfide, and the excess S2− in the iron melt was oxidized to volatile sulfur on the anode. The molten sulfide has been widely concerned in pyrometallurgy for its potential to remove copper from iron-based melts, and this study verified that molten sulfide could also be used as an electrolyte for electrorefining of iron-based melts.
A. Rajora and J. W. Haverkort 2021 J. Electrochem. Soc. 168 034506
The diffusion layer is a crucial part of most fuel cells and electrolyzers. We analytically solve a simplified set of visco-capillary equations for the gas and liquid saturation profiles inside such layers. Contrary to existing numerical simulations, this approach allows us to obtain general scaling relations. We derive simple explicit equations for the limiting current density associated with reactant starvation, flooding, and membrane dehydration, including the effect of fluid properties, contact angle, tortuosity, and the pore size distribution. This is the first explicit, extensive and thorough analytical modeling framework for the two-phase transport in an electrochemical cell that provides useful insights into the performance characteristics of the diffusion layer. A more even pore size distribution generally allows higher currents. Explicit expressions for the minimum pore size and maximum layer thickness show that modern diffusion layers are typically well-designed.
Yike Xiong et al 2021 J. Electrochem. Soc. 168 030510
Ni-rich cathode materials in the field of Li-ion batteries have been facing problems, such as poor cycle life and unstable crystal structure, which continue to baffle researchers. Herein, because of the extraordinary electric and magnetic properties of Gd, the dual Gd-modified Ni-rich cathode material LiNi0.88Co0.09Al0.03O2 (NCA) was successfully prepared in a high temperature solid-state method. As a result, the synergistic modification facilitates the migration of Li+ and protects the structure of electrode material. The dual Gd-modified NCA material exhibits capacity of 176 mAh
g−1 with retention reaching 89.3% at 1 C over 3.0–4.3 V at 25 °C after 100 cycles, whereas the pristine NCA material only delivers 151 mAh
g−1 with the retention of 77.0%. Otherwise, the capacity retention at 8 C as well as 55 °C improved sharply to over 80%. The significant improvement of rate and high temperature performance are attributed to the dual modification of Gd. This study will provide a new idea for the modification of Ni-rich layered cathode materials.
Dževad K. Kozlica et al 2021 J. Electrochem. Soc. 168 031504
Unambiguous evidence is presented that the chloride ions play a dual role in the formation of a micrometre thick film of polymerized [Cu-Cl-MBI]n. This occurs when the copper is exposed to 3 wt.% NaCl solution containing 1 mM of mixture of inhibitors 2-mercaptobenzimidazole, MBI, and octylphosphonic acid, OPA, in the molar ratio MBI:OPA of 9:1. The chloride ions act simultaneously as a promoter of polymerized [Cu–MBI]n/[Cu–Cl–MBI]n film formation and a reactant that is incorporated in the film, as confirmed by time-of-flight secondary ion mass spectrometry. Also, formation of a Cu2O film under the Cu-inhibitor film was proven by focused ion beam microscopy, with chemical analysis being employed at the cross-section of the thick polymerized film. The Cu(I) oxide underlayer, together with the porous straw-like morphology of the [Cu–Cl–MBI]n overlayer, is believed to be responsible for the excellent corrosion protection of copper, even in a chloride environment without the reservoir of MBI+OPA. We also report a new insight into the mechanism of degradation of the Cu–MBI/Cu–Cl–MBI film that results in the formation of (MBI)2 dimers. The inhibitor layer, formed in NaCl solution and containing the synergistic combination of MBI and OPA, showed outstanding resistance to degradation.
Manar M. Elhassan et al 2021 J. Electrochem. Soc. 168 036507
Ipragliflozin, a highly potent and selective sodium glucose cotransporter II inhibitor, is an effective blood glucose lowering drug in patients with type 2 diabetes mellitus by promoting urinary glucose excretion. The present work represents the first electrochemical determination of ipragliflozin that depends on the oxidation of sulfur atom present in its structure. Cyclic wave and differential pulse voltammetry were applied by scanning potential over range of 0 to 2.8 V vs the reference electrode Ag/Ag+ in non-aqueous medium. The method was developed and validated in accordance with the guidelines of the International Council for Harmonisation (ICH). With a detection limit of 1.98 × 10–6 M, the method was considered to be linear in the range of 7.5 × 10–6–1 × 10–3 M. The method was then efficiently applied for the determination of ipragliflozin in spiked human plasma. The method proved to be an excellent green analysis according to analytical eco-scale for greenness assessment.
Review articles
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Angela Mihaela Baracu and Livia Alexandra Dinu Gugoasa 2021 J. Electrochem. Soc. 168 037503
Over the past decade, the development of amperometric sensors and biosensors using microfabrication techniques has gained considerable attention. This interdisciplinary approach aims at bringing together scientific fields such as: chemistry, physics, engineering and biology to achieve devices’ miniaturization, integration and automatization. Among the technologies that have been reviewed for the fabrication of the microelectrodes, the most common are: soft lithography and microfabrication techniques, such as physical vapor deposition of different metals, photolithography, chemical wet etching method and anodic bonding process. The required parameters in the design of a microfabricated electrode array, such as inter-electrode distance, the three-electrode system, and the role of each electrode have been intensively discussed. This review provides an overview about the state-of-the-art microfabrication devices and their applications, as well as the recent advances in the fabrication of microelectrodes as transducers for amperometric sensors, immunosensors and biosensors with various applications in environmental, biomedical and pharmaceutical fields.
Hans-Henning Strehblow 2021 J. Electrochem. Soc. 168 021510
Among several surface analytical methods Ion Scattering is a possibility to study the composition and depth profile of passive layers. Examples are presented for Rutherford Backscattering Spectroscopy (RBS) for the investigation of thick oxide layers up to more than 100 nm on Al containing additions of other metals like Cu and low Energy Ion Scattering Spectroscopy (ISS or LEIS) for thin passive layers of a few nm thickness of binary alloys. The chemical structure of thin passive layers with a high depth resolution is obtained by ISS depth profiles, which supports the results for these films obtained by X-ray Photoelectron Spectroscopy (XPS). A reliable specimen preparation in an electrochemical cell attached to the UHV spectrometer, i.e. in a closed system is described, which helps to exclude changes and artifacts by unwanted environmental factors, which might affect the results of fundamental investigations.
Frank C. Walsh et al 2021 J. Electrochem. Soc. 168 023503
The concept of a trickle tower, using ordered bipolar electrode elements stacked in (10 to 80) similar layers of porous, 3D electrodes separated by insulating separator meshes is described and key features of electrochemical reactors based on the bipolar trickle tower reactor (BTTR) geometry are reviewed. Fluid flow, mass transfer, active area and bypass current are considered in detail, since they affect the reaction environment. Modified reactor designs have resulted from the process of electrode selection and tower construction. The performance of BTTRs is illustrated by examples from laboratory and industry, including electrosynthesis and environmental treatment. Experimental data are used to rationalise reaction environment and simulate performance. Operational factors such as electrolyte flow, mass transfer rates and volumetric electrode area are highlighted as important factors in achieving high efficiency; minimisation of internal bypass currents is critical. Developments have enabled improvements in reactor construction and a wider choice of electrode material. Future R & D needs are highlighted.
Xiaoli Zan and Hongwei Bai 2021 J. Electrochem. Soc. 168 027504
Recently, flexible electrochemical biosensors have been attracting more and more attentions throughout the world both in academia and industry, because of its leading role in the development of efficient, miniaturized, rapid and user-friendly device towards health monitoring, environmental microsense systems and defense systems. Herein, we shine a light on the advances in flexible electrochemical biosensors by tracking the developments of novel carbon nanomaterials based smart device design and versatile applications. Particularly, the flexible electrochemical biosensors either with supported substrates or free-standing are summarized. We start from retrospection on the outlook of the field and highlight the direction of flexible electrochemical biosensors in the areas of healthcare, security and environmental monitoring. And then we review the recently developed fabrication approaches with discussing the state-of-art findings for each category. It is believed that the flexible electrochemical biosensors will play a more and more pivotal role in the emergent body sensor networks arena with the fast development of carbon nanomaterials and smart devices design.
Asha Sharma et al 2021 J. Electrochem. Soc. 168 027505
Electrochemical, chemiresistive and wearable sensors based on tin oxide (SnO 2) were investigated for chemical sensing applications. There is an increased usage of SnO 2 as modifier electrode materials because of its astonishing features of thermal stability, biocompatibility, excellent bandgap, cost effective and abundant availability. The surface of working electrode is modified by nanomaterials of SnO 2 in combination with various metals, semiconductors and carbon derivatives for improved sensing performance. Various voltammetric and amperometric techniques were involved in studying the electrochemical properties and behaviour of the anlaytes at the surface of modified electrodes. This review focused on some recent works that provides an overview of the applications of SnO 2 nanomaterials for the development of chemiresistive, electrochemical, and wearable sensors.
Editor's Choice
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Alexander Oleinick et al 2020 J. Electrochem. Soc. 167 013530
This review presents the main principles underlying the theoretical description of the behavior of regular and random arrays of nanometric active sites. It is further shown how they can be applied for establishing a useful semi-analytical approximation of the arrays responses under diffusion limited conditions when they involve the common situation of active sites with identical sizes. This approximation is general and, as exemplified for different type of arrays, can be employed for describing the behavior of any array involving arbitrary distributions of their active sites onto the substrate surface. Furthermore, this efficient approach allows statistical characterization of active sites distributions of any array based on chronoamperometric data.
R. C. P. Oliveira et al 2019 J. Electrochem. Soc. 166 E547
The present study focuses on the electrolysis of kraft black liquor (BL) for energy and lignin recovery. The concept has economic and environmental advantages, as it simultaneously generates a clean fuel gas (hydrogen) at the cathode and a solid with economic value (lignin) at the anode. Platinum (Pt), nickel (Ni), and AISI 304 stainless steel (SS) are assessed as potential anodes and cathodes for the BL electrolysis. Voltammetric methods are used to study the lignin oxidation in the BL, allowing the calculation of the charge transfer coefficient and the number of exchanged electrons. The hydrogen evolution reaction (HER) in BL is also evaluated in the same electrodes, with the Tafel slopes, charge transfer coefficients and exchange current densities being determined. Pt leads to the best results for both HER and lignin oxidation, followed by Ni, whereas AISI 304 SS is not appropriate. A small-scale laboratory BL electrolyzer using Ni plate electrodes is assembled and tested. The lignin electrodeposited at the anode is characterized by Fourier Transform Mid Infrared Spectroscopy and compared with lyophilized lignin and Klason lignin. The higher purity of the lignin obtained by BL electrolysis suggests further work on the development of this new technology.
Daniel Pritzl et al 2019 J. Electrochem. Soc. 166 A4056
Washing is a commonly used method to remove surface impurities of cathode materials for lithium-ion batteries. However, a clear mechanistic understanding of the washing process is missing in the literature. In this study, we will investigate the effect of washing and subsequent drying of nickel-rich NCM cathodes (85% nickel) with respect to gassing and impedance of the washed cathodes. By on-line electrochemical mass spectrometry (OEMS), we will show a drastic reduction of the O 2 release above 80% SOC for the NCM washed with deionized water, suggesting the formation of an oxygen-depleted surface layer on the NCM particle surface. The modification of the surface can be confirmed by a strong impedance buildup of cathodes composed of washed NCM (using a micro-reference electrode in a full-cell), revealing that the impedance increases strongly with increasing drying temperature after washing. Last, we will propose a comprehensive mechanism on the processes occurring during the washing/drying process of nickel-rich NCM materials and identify the drying temperature after washing as the dominant factor influencing the surface properties.
Franziska Friedrich et al 2019 J. Electrochem. Soc. 166 A3760
Ni-rich layered oxides, like NCM-811, are promising lithium-ion battery cathode materials for applications such as electric vehicles. However, pronounced capacity fading, especially at high voltages, still lead to a limited cycle life, whereby the underlying degradation mechanisms, e.g. whether they are detrimental reactions in the bulk or at the surface, are still controversially discussed. Here, we investigate the capacity fading of NCM-811/graphite full-cells over 1000 cycles by a combination of in situ synchrotron X-ray powder diffraction, impedance spectroscopy, and X-ray photoelectron spectroscopy. In order to focus on the NCM-811 material, we excluded Li loss at the anode by pre-lithiating the graphite. We were able to find a quantitative correlation between NCM-811 lattice parameters and capacity fading. Our results prove that there are no considerable changes in the bulk structure, which could be responsible for the observed ≈20% capacity loss over the 1000 cycles. However, we identified the formation of a resistive surface layer, which is responsible for (i) an irreversible loss of capacity due to the material lost for its formation, and (ii) for a considerable impedance growth. Further evidence is provided that the surface layer is gradually formed around the primary NCM-811 particles.
A. N. Colli and J. M. Bisang 2020 J. Electrochem. Soc. 167 013513
A mathematical model to calculate tertiary current distributions in electrochemical reactors is presented taking into account the potential and concentration fields together with the hydrodynamics under laminar or turbulent conditions. Multiple reactions with different kinetic controls are considered at both electrodes. The computational algorithm solving the model was implemented in OpenFOAM. It allows the calculations for a given local potential at the working electrode, potentiostatic control, or for a fixed cell potential difference and also for a current flowing through the cell, galvanostatic operation. The model was validated by using the reduction of ferricyanide and the oxidation of ferrocyanide from dilute solutions as main test reactions and hydrogen and oxygen evolution as secondary ones, in a modified hydrocyclone. A close agreement between experimental and predicted current distributions was obtained. The hydrocyclone presents a promising electrochemical performance being the mass-transfer conditions in its cylindrical part better than in the conical region. The computational tool developed in this paper can be employed to optimize both cells stack design and system operation conditions. Likewise, the algorithm can also be used to check, when limiting current studies are needed, whether the desired reaction is under mass-transfer or charge-transfer control for a given geometric configuration.
Accepted manuscripts
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Buckley et al
Using our standard methodology, we examined the thermal stability of vanadium flow battery catholytes over a range of temperature from 30 to 70°C with stable lifetimes from 11 minutes to 87 days. At higher temperatures (45–70°C) measurements showed excellent reproducibility but at lower temperatures (30–45°C) showed some scatter. Measurements at higher temperatures are in good agreement with our (single-slope) model which is based on earlier data but there is some divergence from the model at lower temperatures. Arrhenius plots of the data show two linear regimes: one in the range 45–70°C and another in the range 30–45°C, the latter having a higher Arrhenius slope. Based on linear least-squares best fits in these two regimes, we have formulated an improved stability model (two-slope model). We use our models to derive expressions for accelerated testing of thermal stability using increased temperature, increased vanadium concentration and decreased sulphate concentration and estimate values for the acceleration factors over a range of test and use temperatures and concentrations. We analyse the effect of changing concentration to counteract the decrease in electrolyte stability at higher temperatures and derive expressions to calculate the necessary concentrations.
Mohseninia et al
This work describes the effects of catalyst layers (CLs) consisting of hydrophobic PTFE on the performance and water management of PEM fuel cells. Catalyst inks with various PTFE contents were coated on Nafion membranes and characterized using contact angle measurements, SEX-EDX, and mercury porosimetry. Fuel cell tests and electrochemical impedance spectroscopy (EIS) were conducted under varying operating conditions for the prepared materials. At dry conditions, CLs with 5 wt.% PTFE were advantageous for cell performance due to improved membrane hydration, whereas under humid conditions and high air flow rates CLs with 10 wt.% PTFE improved the performance in high current density region. Higher PTFE contents (≥20 wt.%) increased the mass transport resistance due to reduced porosity of the CLs structure. Operando neutron radiography was utilized to study the effects of hydrophobicity gradients within CLs and cathode microporous layer (MPLC) on liquid water distribution. More hydrophobic CLs increased the water content in adjacent layers and improved performance, especially at dry conditions. MPLC with higher PTFE contents increased the overall liquid water within the CLs and GDLs and escalated the water transfer to the anode side. Furthermore, the role of back-diffusion transport mechanism on water distribution was identified for the investigated cells.
Sheikh et al
Battery failures are obvious after being subject to abuse conditions however predicting these failures in advance is crucial when using test and validation techniques to understand battery potential. Lithium-ion battery cells are widely used due to their high energy and power densities. When abusive conditions like the three point bend loading are applied to lithium-ion batteries, what occurs to the mechanical behaviours and components is still mostly unknown. To further this understanding, this paper investigates the mechanical behaviour of the separator in the LiCoO2/Graphite cylindrical 18650 cells. Internal short circuit (ISC) behaviour, strain rate dependency and electrochemical status of the cells (i.e. SOC dependency) are studied to understand failure pattern. Furthermore, simple and effective constitutive model for the separator layer is formed, facilitating further mechanical analysis and numerical simulation of lithium-ion battery study. Occurrence of ISC is investigated by jellyroll deformation where casing is removed, and quasi-static load is applied. Numerical simulation model is developed to further investigate sequential structural failures and temperature changes. Simulation results showed good accuracy with experimental results and are useful to predict structural failure of cells. Number of failures including electrolyte leakage, change in shape, sudden voltage drop/temperature rise, and gas venting are observed.
Aykol et al
Forecasting the health of a battery is a modeling effort that is critical to driving improvements in and adoption of electric vehicles. Purely physics-based models and purely data-driven models have advantages and limitations of their own. Considering the nature of battery data and end-user applications, we outline several architectures for integrating physics-based and machine learning models that can improve our ability to forecast battery lifetime. We discuss the ease of implementation, advantages, limitations and short versus long-term viability of each architecture, given the state of the art in the battery and machine learning fields.
Chiang et al
This work mainly focuses on the effects of two additives, thiourea (TU) and allyl thioura (ATU), on the electrodeposition behavior and microstructure development of copper deposits plated from the methane-sulfonic acid (MSA) bath. Three variables, including additive types, additive concentration, and current density, have been investigated in order to observe the variation in the crystallographic texture of Cu deposits. From the polarization behavior through the rotating ring disk electrode (RRDE) voltammograms and chronopotentiometric (CP) steady state electrode potential analyses, TU and ATU show the suppression ability of Cu deposition and the interaction strength between Cu2+ and ATU is weaker than that between Cu2+ and TU. The operating current density range of the preferential (111) Cu deposition becomes wider with the introduction of TU and ATU additives in the plating bath. The influences of TU and ATU on the nucleation and growth of Cu grains are significantly different, leading to the very different surface morphologies and surface roughness of resultant Cu films although both additives are of the similar molecular structures and show a suppression ability on Cu deposition.
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Andrei Kulikovsky 2021 J. Electrochem. Soc. 168 034501
Placing a catalyst layer between two membranes in a PEM fuel cell one gets a membrane–electrode assembly with inactive catalyst layer (ICL). A model for ICL impedance is developed taking into account finite electron conductivity of the layer. Analytical expression for the ICL impedance is derived. Analysis of characteristic features of the ICL Nyquist spectrum leads to simple analytical expressions for the high–frequency and polarization resistivity, for the summit frequency and for the straight high–frequency part of the spectrum. The results allow to estimate the ICL proton and electron conductivities and double layer capacitance without complicated curve fitting.
Chunmei Wang et al 2021 J. Electrochem. Soc. 168 034503
Three protocols of accelerated startup and shutdown (SU/SD) test were investigated: startup and shutdown with air supply and soak to both anode and cathode (air-SU/SD), hydrogen protected startup and shutdown (H 2-SU/SD), and hydrogen protected startup and shutdown with a load (H 2-SU/SD with a load). The performance losses, electrochemical surface area (ECSA) reduction, and catalyst layer degradation were characterized and compared for these SU/SD protocols. Air-SU/SD protocol showed much more severe performance loss and catalyst layer degradation than hydrogen protected ones, which confirmed the benefits of hydrogen protection. The temperature effect on air-SU/SD was significant in a broad range from 20 °C to 70 °C, with low temperature greatly reducing the degradation. The mechanism of H 2 protection and load drawn in alleviating carbon corrosion was explained based on reactions and charge conservation during SU/SD. This paper provides comprehensive test data and failure analysis to quantify the benefits of H 2 protection and load drawn and to facilitate future enhancement of system strategies on SU/SD durability.
Annika Carlson et al 2021 J. Electrochem. Soc. 168 034505
The hydrogen electrode in the anion-exchange membrane fuel cell needs further attention to understand the overall cell limitations. In this study, electrochemical impedance spectroscopy and galvanodynamic measurements in combination with a physics-based model are used to determine the kinetic parameters of the hydrogen oxidation reaction and hydrogen evolution reaction on Pt/C porous gas-diffusion electrodes in an AEMFC. Two semicircles are observed in the Nyquist plot of a symmetrical AEM hydrogen cell, indicating a two‑step reaction pathway. The fit of the model shows that the Tafel-Volmer pathway describes the kinetics better than the Heyrovsky-Volmer pathway. The reaction rates of the adsorption and charge transfer steps are similar in magnitude implying that both need consideration during modeling and evaluation of the hydrogen electrode. Furthermore, the performance is limited also by the ionic conductivity in the electrode. Comparison of the impedance of the HOR and a hydrogen/oxygen AEMFC indicates that the low-frequency semicircle is mainly associated with the oxygen reduction reaction and the cathode, while the high-frequency semicircle is likely related to a combination of the anode and the cathode. Based on this work, a platform for further studies of losses and total impedance of operating AEMFC has been created.
A. Rajora and J. W. Haverkort 2021 J. Electrochem. Soc. 168 034506
The diffusion layer is a crucial part of most fuel cells and electrolyzers. We analytically solve a simplified set of visco-capillary equations for the gas and liquid saturation profiles inside such layers. Contrary to existing numerical simulations, this approach allows us to obtain general scaling relations. We derive simple explicit equations for the limiting current density associated with reactant starvation, flooding, and membrane dehydration, including the effect of fluid properties, contact angle, tortuosity, and the pore size distribution. This is the first explicit, extensive and thorough analytical modeling framework for the two-phase transport in an electrochemical cell that provides useful insights into the performance characteristics of the diffusion layer. A more even pore size distribution generally allows higher currents. Explicit expressions for the minimum pore size and maximum layer thickness show that modern diffusion layers are typically well-designed.
Michael K. G. Bauer and J. R. Dahn 2021 J. Electrochem. Soc. 168 020501
If the positive electrode of a lithium-ion cell faces a surface with no opposing negative electrode, Li + ions can plate on the nearest edge of the negative electrode current collector. This poses considerable danger to the battery, and so modern Li-ion cells have a negative electrode that is both wider and longer than the positive electrode. In this work, we present evidence using Li-ion cell differential thermal analysis that this overhang causes the formation of long lived electrolyte concentration gradients after discharge or charge due to the long times needed for the lithium content in the overhang region of the negative electrode to equilibrate with the lithium content in the bulk of the negative electrode. Several cases are shown, as well as a comparison to a commercial cell, and an estimation of the type and magnitude of the electrolyte concentration gradient is given. Finally, it is shown that this phenomenon can be applied to easily distinguish between graphite electrodes with high and low tortuosity using differential thermal analysis.
Paul Gasper et al 2021 J. Electrochem. Soc. 168 020502
Various modeling techniques are used to predict the capacity fade of Li-ion batteries. Algebraic reduced-order models, which are inherently interpretable and computationally fast, are ideal for use in battery controllers, technoeconomic models, and multi-objective optimizations. For Li-ion batteries with graphite anodes, solid-electrolyte-interphase (SEI) growth on the graphite surface dominates fade. This fade is often modeled using physically informed equations, such as square-root of time for predicting solvent-diffusion limited SEI growth, and Arrhenius and Tafel-like equations predicting the temperature and state-of-charge rate dependencies. In some cases, completely empirical relationships are proposed. However, statistical validation is rarely conducted to evaluate model optimality, and only a handful of possible models are usually investigated. This article demonstrates a novel procedure for automatically identifying reduced-order degradation models from millions of algorithmically generated equations via bi-level optimization and symbolic regression. Identified models are statistically validated using cross-validation, sensitivity analysis, and uncertainty quantification via bootstrapping. On a LiFePO 4/Graphite cell calendar aging data set, automatically identified models utilizing square-root, power law, stretched exponential, and sigmoidal functions result in greater accuracy and lower uncertainty than models identified by human experts, and demonstrate that previously known physical relationships can be empirically “rediscovered” using machine learning.
Rownak J. Mou and Koffi P.C. Yao 2021 J. Electrochem. Soc. 168 020503
Core–shell and core-gradient hybrid cathode materials for lithium-ion batteries display enhanced rate capability over their homogeneous counterparts. The apparent enhancement of transport is explained herein as resulting from advective flow of Li + from the higher free-energy core towards the lower free-energy shell compositions. First-principles analysis of a planar model of these hybrid structures concludes that the inbuilt free-energy gradient enhances the Li + de-intercalation process by reducing the average overpotential during extreme fast-charging. Analysis of representative LiNi 0.8Co 0.1Mn 0.1O 2∣∣LiNi 0.4Co 0.2Mn 0.4O 2 core/shell reveals: (i) an optimal components ratio exists that maximizes storage capacity during fast-charging and (ii) components should be selected with appreciably large chemical potential difference between the core and shell to further exploit the free-energy gradient effects provided volume ratios are optimized against the potential gradient. In the case of NCM811∣∣NCM424 studied herein, a balanced (ca. 40/60 vol.%) structure appears optimal. This finding indicates that the shell must not necessarily be confined to a thin chemically-protective coating; higher relative volumes of the lower free-energy shell may provide performance benefits at high-rates. The presented insights will serve towards optimizing and developing high capacity, more rate capable core–shell particles for extreme fast charging batteries.
Congxiao Wei and M. N. Obrovac 2021 J. Electrochem. Soc. 168 020505
The inorganic compounds, lithium polysilicate (Li 2Si 5O 11), sodium polyphosphate ((NaPO 3) n), and lithium phosphate monobasic (H 2LiPO 4) were investigated as the sole binders in Si-alloy and graphite electrodes for Li cells. Surprisingly, the coating quality and cycling performance of Si-alloy anodes with these inorganic binders is similar to those electrodes using the state of the art lithium polyacrylate (LiPAA) organic binder. Graphite electrodes with inorganic binders show good cycling despite having poor coating quality. Graphite electrodes with lithium polysilicate binder have three times the binder volume than expected, indicating that this binder has an open framework microstructure.
Marius Flügel et al 2021 J. Electrochem. Soc. 168 020506
Cu dissolution in Li-ion cells during over-discharge to 0 V was investigated by Post-Mortem analysis. Commercial 18650 type cells with graphite anode and NMC/LMO cathodes as well as pilot-scale pouch full cells with graphite/NMC chemistry with reference electrode were investigated. The effects of discharge time at 0 V in the range of 100 h to 1000 h for fresh cells as well as the effect of cells cycled under Li deposition conditions were considered. For comparison, electrodes from cells discharged to the end-of-discharge voltage (2.0 V) were examined. By extensive Post-mortem analysis using inductively coupled plasma (ICP-OES), scanning electron microscopy (SEM) with BSE and SE detectors, energy dispersive X-ray analysis (EDX), and glow discharge optical emission spectroscopy (GD-OES), we show that Cu compounds are present on the anode surface and on the cathode from cells, which were over-discharged. Cross-sections show that the Cu originates from pitting corrosion of the negative current collector. Combined electrochemical/ICP-OES measurements in commercial cells as well as reference electrode measurements in 3-electrode pouch full cells suggest that Cu is dissolved as Cu + ions.
Yang Wang et al 2021 J. Electrochem. Soc. 168 020507
Two-dimensional nanosheets show promise as electrode materials for high electrochemical performance lithium-ion batteries owing to their unique properties. However, individual nanosheets cannot meet all the required properties for batteries in one material to achieve optimal performance. Here, we demonstrate a new type of two-dimensional heterostructure cathode material for lithium-ion batteries by inkjet printing a composite ink based on high capacity V 2O 5 nanosheets and high electronic conductivity Ti 3C 2T x nanosheets. The excellent electronic conductivity of Ti 3C 2T x nanosheets and layer-by-layer heterostructure design enable fast electron transport and minimization of detrimental volume changes during the electrochemical process, respectively. The printed cathodes exhibit a high capacity of 321 mAh g −1 at 1C, high-rate capability of 112 mAh g −1 at 10.5C and good cycling stability after 680 cycles with 91.8% capacity retention, indicating high electrochemical performance of the printed heterostructure cathode. This work opens new opportunities of two-dimensional heterostructures for high performance energy storage applications.