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Effective water management is crucial for the optimal operation of low‐temperature polymer electrolyte membrane fuel cells (PEMFCs). Excessive liquid water production can cause flooding in the gas diffusion electrodes and flow channels, limiting mass transfer and reducing PEMFC performance. To tackle this issue, a nature‐inspired chemical engineering (NICE) approach has been adopted that takes cues from the integument structure of desert‐dwelling lizards for passive water transport. By incorporating engraved, capillary microchannels into conventional flow fields, PEMFC performance improves significantly, including a 15% increase in maximum power density for a 25 cm2 cell and 13% for a 100 cm2 cell. Electro‐thermal maps of the lizard‐inspired flow field demonstrate a more uniform spatial distribution of current density and temperature than the conventional design. Neutron radiography provides evidence that capillary microchannels in the lizard‐inspired flow field facilitate the efficient transport and removal of generated liquid water, thereby preventing blockages in the reactant channels. These findings present a universally applicable and highly efficient water management strategy for PEMFCs, with the potential for widespread practical implementation for other electrochemical devices. [ABSTRACT FROM AUTHOR]

Zn‐based hybrid supercapacitors (ZHSCs) have received increasing attention in recent research, due to their high electrochemical performance and low cost. Herein, a composite cathode is developed based on polyaniline (PANI) and cobalt hexacyanoferrate (CoHCF), exhibiting excellent electrochemical performance. The results showed that PANI is coated on CoHCF, thereby enhancing the electrical conductivity and Zn2+ transport kinetics. As a result, the as‐prepared materials demonstrate remarkable specific capacitance (741.7 F g−1 at 5 mV s−1), good cycling durability (86.15% capacitance retention over 5000 cycles at 10 A g−1), high peak energy density (312 Wh kg−1 at 500 W kg−1), and superior power density (75 294 W kg−1 at 25 Wh kg−1). The excellent electrochemical performance confirms that PANI–CoHCF composites are promising cathode candidates for ZHSCs in practical applications. [ABSTRACT FROM AUTHOR]

Although proton exchange membranes (PEMs) are widely deployed in an array of commercial applications, limitations linked to their proton conductivity, water retention, and gas permeability still limit ultimate device performance. While ex situ studies have shown additives can enhance membrane stability and mass transport, to date few have demonstrated that these performance enhancements are maintained when tested in commercially relevant electrochemical technologies, such as fuel cells or electrolyzers. Herein, a new multifunctional additive, 2D poly(triazine imide) (PTI), is demonstrated for composite PEMs, which is shown to boost proton conductivity by 37% under optimal high relative humidity (RH) conditions and 67% at low RHs. PTI also enables major improvements (over 55%) in both current and power densities in industrially relevant PEM fuel cells (PEMFCs). Most importantly, in situ and ex situ characterization suggests that the enhanced performance is due to polymer aggregate‐PTI clusters that form with increasing 2D character and improved long‐range connectivity, while acid‐base interactions with pyridinic nitrogen facilitate the critical proton hopping mechanism at all RHs. Hence, this work offers both a new membrane concept with proven benefits for important electrochemical technologies, as well as design principles for future optimization of proton transport and water management within PEMs. [ABSTRACT FROM AUTHOR]

For zinc‐ion batteries (ZIBs), the non‐uniform Zn plating/stripping results in a high polarization and low Coulombic efficiency (CE), hindering the large‐scale application of ZIBs. Here, inspired by biomass seaweed plants, an anionic polyelectrolyte alginate acid (SA) was used to initiate the in situ formation of the high‐performance solid electrolyte interphase (SEI) layer on the Zn anode. Attribute to the anionic groups of −COO−, the affinity of Zn2+ ions to alginate acid induces a well‐aligned accelerating channel for uniform plating. This SEI regulates the desolvation structure of Zn2+ and facilitates the formation of compact Zn (002) crystal planes. Even under high depth of discharge conditions (DOD), the SA‐coated Zn anode still maintains a stable Zn stripping/plating behavior with a low potential difference (0.114 V). According to the classical nucleation theory, the nucleation energy for SA‐coated Zn is 97 % less than that of bare Zn, resulting in a faster nucleation rate. The Zn||Cu cell assembled with the SA‐coated electrode exhibits an outstanding average CE of 99.8 % over 1,400 cycles. The design is successfully demonstrated in pouch cells, where the SA‐coated Zn exhibits capacity retention of 96.9 % compared to 59.1 % for bare Zn anode, even under the high cathode mass loading (>10 mg/cm2). [ABSTRACT FROM AUTHOR]

The development of low‐cost, robust and efficient non‐noble metal electrocatalysts is still a pursuit for the hydrogen evolution reaction (HER). Herein, a self‐standing electrocatalyst, Ni2P/CoP nanosheet, was fabricated directly on three‐dimensional Ni foams by two facile steps, which illustrated both high activity and stability for HER in different electrolytes. Benefiting from the porous structures of nanosheets with large specific surface area and the hybrid Ni2P/CoP, the as‐prepared electrocatalyst presented remarkable HER with overpotentials of 65.2 and 87.8 mV to reach a current density of −10 mA cm−2 in neutral and alkaline media, respectively. Density function theory calculations revealed a lower activation energy of water dissociation and efficient HER steps of hybrid Ni2P/CoP nanosheets compared with mono CoP. The self‐standing electrocatalyst maintained excellent chemical stability. Additionally, the HER process in domestic wastewater was realized with more impressive performance by using Ni2P/CoP nanosheets compared with commercial Pt/C. Hydrogen was continuously generated for 20 h in mildly alkaline dishwashing wastewater. This work provides a feasible way to fabricate non‐noble metal and self‐standing hybrid bimetallic phosphides for HER in neutral and alkaline media, showing great potential for efficient hydrogen production by re‐utilizing wastewater resources. [ABSTRACT FROM AUTHOR]

Supercapacitors formed from porous carbon and graphene‐oxide (GO) materials are usually dominated by either electric double‐layer capacitance, pseudo‐capacitance, or both. Due to these combined features, reduced GO materials have been shown to offer superior capacitance over typical nanoporous carbon materials; however, there is a significant variation in reported values, ranging between 25 and 350 F g−1. This undermines the structure (e.g., oxygen functionality and/or surface area)‐performance relationships for optimization of cost and scalable factors. This work demonstrates important structure‐controlled charge storage relationships. For this, a series of exfoliated graphene (EG) derivatives are produced via thermal‐shock exfoliation of GO precursors and following controlled graphitization of EG (GEG) generates materials with varied amounts of porosity, redox‐active oxygen groups and graphitic components. Experimental results show significantly varied capacitance values between 30 and 250 F g−1 at 1.0 A g−1 in GEG structures; this suggests that for a given specific surface area the redox‐active and hydrophilic oxygen content can boost the capacitance to 250–300% higher compared to typical mesoporous carbon materials. GEGs with identical oxygen functionality show a surface area governed capacitance. This allows to establish direct structure‐performance relationships between 1) redox‐active oxygen functional concentration and capacitance and 2) surface area and capacitance. [ABSTRACT FROM AUTHOR]

Demand for low carbon energy storage has highlighted the importance of imaging techniques for the characterization of electrode microstructures to determine key parameters associated with battery manufacture, operation, degradation, and failure both for next generation lithium and other novel battery systems. Here, recent progress and literature highlights from magnetic resonance, neutron, X‐ray, focused ion beam, scanning and transmission electron microscopy are summarized. Two major trends are identified: First, the use of multi‐modal microscopy in a correlative fashion, providing contrast modes spanning length‐ and time‐scales, and second, the application of machine learning to guide data collection and analysis, recognizing the role of these tools in evaluating large data streams from increasingly sophisticated imaging experiments. [ABSTRACT FROM AUTHOR]

Reduced graphene‐oxide (RGO)‐based electrodes in supercapacitors deliver high energy/power capacities compared to typical nanoporous carbon materials. However, extensive critical analysis of literature reveals enormous discrepancies (up to 250 F g−1) in the reported capacitance (variation of 100–350 F g−1) of RGO materials synthesized under seemingly similar methods, inhibiting an understanding of capacitance variation. Here, the key factors that control the capacitance performance of RGO electrodes are demonstrated by analyzing and optimizing various types of commonly applied electrode fabrication methods. Beyond usual data acquisition parameters and oxidation/reduction properties of RGO, a substantial difference of more than 100% in capacitance values (with change from 190 ± 20 to 340 ± 10 F g−1) is found depending on the electrode preparation method. For this demonstration, ≈40 RGO‐based electrodes are fabricated from numerous distinctly different RGO materials via typically applied methods of solution (aqueous and organic) casting and compressed powders. The influence of data acquisition conditions and capacitance estimation practices are also discussed. Furthermore, by optimizing electrode processing method, a direct surface area governed capacitance relationship for RGO structures is revealed. [ABSTRACT FROM AUTHOR]

The electrochemical synthesis of hydrogen peroxide (H2O2) via a two‐electron (2 e−) oxygen reduction reaction (ORR) process provides a promising alternative to replace the energy‐intensive anthraquinone process. Herein, we develop a facile template‐protected strategy to synthesize a highly active quinone‐rich porous carbon catalyst for H2O2 electrochemical production. The optimized PCC900 material exhibits remarkable activity and selectivity, of which the onset potential reaches 0.83 V vs. reversible hydrogen electrode in 0.1 M KOH and the H2O2 selectivity is over 95 % in a wide potential range. Comprehensive synchrotron‐based near‐edge X‐ray absorption fine structure (NEXAFS) spectroscopy combined with electrocatalytic characterizations reveals the positive correlation between quinone content and 2 e− ORR performance. The effectiveness of chair‐form quinone groups as the most efficient active sites is highlighted by the molecule‐mimic strategy and theoretical analysis. [ABSTRACT FROM AUTHOR]

Electrocatalytic oxygen reduction reaction (ORR) has been intensively studied for environmentally benign applications. However, insufficient understanding of ORR 2 e−‐pathway mechanism at the atomic level inhibits rational design of catalysts with both high activity and selectivity, causing concerns including catalyst degradation due to Fenton reaction or poor efficiency of H2O2 electrosynthesis. Herein we show that the generally accepted ORR electrocatalyst design based on a Sabatier volcano plot argument optimises activity but is unable to account for the 2 e−‐pathway selectivity. Through electrochemical and operando spectroscopic studies on a series of CoNx/carbon nanotube hybrids, a construction‐driven approach based on an extended "dynamic active site saturation" model that aims to create the maximum number of 2 e− ORR sites by directing the secondary ORR electron transfer towards the 2 e− intermediate is proven to be attainable by manipulating O2 hydrogenation kinetics. [ABSTRACT FROM AUTHOR]

Routine electrolyte additives are not effective enough for uniform zinc (Zn) deposition, because they are hard to proactively guide atomic‐level Zn deposition. Here, based on underpotential deposition (UPD), we propose an "escort effect" of electrolyte additives for uniform Zn deposition at the atomic level. With nickel ion (Ni2+) additives, we found that metallic Ni deposits preferentially and triggers the UPD of Zn on Ni. This facilitates firm nucleation and uniform growth of Zn while suppressing side reactions. Besides, Ni dissolves back into the electrolyte after Zn stripping with no influence on interfacial charge transfer resistance. Consequently, the optimized cell operates for over 900 h at 1 mA cm−2 (more than 4 times longer than the blank one). Moreover, the universality of "escort effect" is identified by using Cr3+ and Co2+ additives. This work would inspire a wide range of atomic‐level principles by controlling interfacial electrochemistry for various metal batteries. [ABSTRACT FROM AUTHOR]

Rechargeable aqueous zinc‐iodine batteries (ZIBs) are considered a promising newly‐developing energy‐storage system, but the corrosion and dendritic growth occurring on the anode seriously hinder their future application. Here, the corrosion mechanism of polyiodide is revealed in detail, showing that it can spontaneously react with zinc and cause rapid battery failure. To address this issue, a sulfonate‐rich ion‐exchange layer (SC‐PSS) is purposely constructed to modulate the transport and reaction chemistry of polyiodide and Zn2+ at the zinc/electrolyte interface. The resulting ZIBs can work properly over 6000 cycles with high‐capacity retention (90.2%) and reversibility (99.89%). Theoretical calculations and experimental characterization reveal that the SC‐PPS layer blocks polyiodide permeation through electrostatic repulsion, while facilitating desolvation of Zn(H2O)62+ and restricting undesirable 2D diffusion of Zn2+ by chemisorption. [ABSTRACT FROM AUTHOR]

A stable cathode–electrolyte interface (CEI) is crucial for aqueous zinc‐ion batteries (AZIBs), but it is less investigated. Commercial binder poly(vinylidene fluoride) (PVDF) is widely used without scrutinizing its suitability and cathode‐electrolyte interface (CEI) in AZIBs. A water‐soluble binder is developed that facilitated the in situ formation of a CEI protecting layer tuning the interfacial morphology. By combining a polysaccharide sodium alginate (SA) with a hydrophobic polytetrafluoroethylene (PTFE), the surface morphology, and charge storage kinetics can be confined from diffusion‐dominated to capacitance‐controlled processes. The underpinning mechanism investigates experimentally in both kinetic and thermodynamic perspectives demonstrate that the COO− from SA acts as an anionic polyelectrolyte facilitating the adsorption of Zn2+; meanwhile fluoride atoms on PTFE backbone provide hydrophobicity to break desolvation penalty. The hybrid binder is beneficial in providing a higher areal flux of Zn2+ at the CEI, where the Zn‐Birnessite MnO2 battery with the hybrid binder exhibits an average specific capacity 45.6% higher than that with conventional PVDF binders; moreover, a reduced interface activation energy attained fosters a superior rate capability and a capacity retention of 99.1% in 1000 cycles. The hybrid binder also reduces the cost compared to the PVDF/NMP, which is a universal strategy to modify interface morphology. [ABSTRACT FROM AUTHOR]

Layered manganese oxides adopting pre‐accommodated cations have drawn tremendous interest for the application as cathodes in aqueous zinc‐ion batteries (AZIBs) owing to their open 2D channels for fast ion‐diffusion and mild phase transition upon topochemical (de)intercalation processes. However, it is inevitable to see these "pillar" cations leaching from the hosts owing to the loose interaction with negatively charged Helmholtz planes within the hosts and shearing/bulking effects in 2D structures upon guest species (de)intercalation, which implies a limited modulation to prevent them from rapid performance decay. Herein, a new class of layered manganese oxides, Mg0.9Mn3O7·2.7H2O, is proposed for the first time, aims to achieve a robust cathode for high‐performance AZIBs. The cathode can deliver a high capacity of 312 mAh g−1 at 0.2 A g−1 and exceptional cycling stability with 92% capacity retention after 5 000 cycles at 5 A g−1. The comprehensive characterizations elucidate its peculiar motif of pined Mg‐□Mn‐Mg dumbbell configuration along with interstratified hydrogen bond responsible for less Mn migration/dissolution and quasi‐zero‐strain characters. The revealed new structure‐function insights can open up an avenue toward the rational design of superstructural cathodes for reversible AZIBs. [ABSTRACT FROM AUTHOR]

In this study, cycle life performance of a prototype lithium‐sulfur (Li−S) pouch cell is investigated using system identification and X‐ray tomography methods. Li−S cells are subjected to characterization and ageing tests while kept inside a controlled‐temperature chamber. After completing the experimental tests, two analytical approaches are used: i) The parameter variations of an equivalent‐circuit model due to ageing are determined using a system identification technique. ii) Physical changes of the aged Li−S cells are analyzed using X‐ray tomography. The results demonstrate that Li−S cell's degradation is significantly affected by temperature. Comparing to 10 °C, Li−S cell capacity fade happens 1.4 times faster at 20 °C whereas this number increases to 3.3 at 30 °C. In addition, X‐ray results show a significant swelling when temperature rises from 10 to 20 °C, correspondingly the gas volume increases from 13 to 62 mm3. [ABSTRACT FROM AUTHOR]

Sodium super‐ionic conductor (NASICON)‐structured phosphates are emerging as rising stars as cathodes for sodium‐ion batteries. However, they usually suffer from a relatively low capacity due to the limited activated redox couples and low intrinsic electronic conductivity. Herein, a reduced graphene oxide supported NASICON Na3Cr0.5V1.5(PO4)3 cathode (VC/C‐G) is designed, which displays ultrafast (up to 50 C) and ultrastable (1 000 cycles at 20 C) Na+ storage properties. The VC/C‐G can reach a high energy density of ≈470 W h kg−1 at 0.2 C with a specific capacity of 176 mAh g−1 (equivalent to the theoretical value); this corresponds to a three‐electron transfer reaction based on fully activated V5+/V4+, V4+/V3+, V3+/V2+ couples. In situ X‐ray diffraction (XRD) results disclose a combination of solid‐solution reaction and biphasic reaction mechanisms upon cycling. Density functional theory calculations reveal a narrow forbidden‐band gap of 1.41 eV and a low Na+ diffusion energy barrier of 0.194 eV. Furthermore, VC/C‐G shows excellent fast‐charging performance by only taking ≈11 min to reach 80% state of charge. The work provides a widely applicable strategy for realizing multi‐electron cathode design for high‐performance SIBs. [ABSTRACT FROM AUTHOR]

Lithium–sulfur batteries (LSBs) with high theoretical capacity are regarded as the most promising candidates for next‐generation energy storage systems. However, the low conductivity, high volume change, and shuttle effect need to be addressed before the commercialization of LSBs. Organosulfur with covalent CS bonds can solve these problems when applied as different components of LSBs. Recent advances of application of organosulfur as cathodes, electrolytes, interlayers, and binders in LSBs are reviewed. Finally, the prospects for organosulfur are proposed from both the perspectives of mechanism understanding and practical applications. [ABSTRACT FROM AUTHOR]

Electrochemical clean energy conversion and the production of sustainable chemicals are critical in the journey to realizing a truly sustainable society. To progress electrochemical storage and conversion devices to commercialization, improving the electrocatalyst performance and cost are of utmost importance. Research into dual‐metal atom catalysts (DACs) is rising in prominence due to the advantages of these sites over single‐metal atom catalysts (SACs), such as breaking scaling relationships for the adsorption energy of reaction intermediates and synergistic effects. This review provides an examination of the fundamental theoretical principles and experimental electrochemical performance of DACs in idealized half cells, as well as fuel cells, before proceeding to analyze the methods used for producing and identifying DACs. Current challenges and potential future research directions of DACs are also discussed. [ABSTRACT FROM AUTHOR]

Lithium‐ion battery manufacturing chain is extremely complex with many controllable parameters especially for the drying process. These processes affect the porous structure and properties of these electrode films and influence the final cell performance properties. However, there is limited available drying information and the dynamics are poorly understood due to the limitation of the existing metrology. There is an emerging need to develop new methodologies to understand the drying dynamics to achieve improved quality control of the electrode coatings. A comprehensive summary of the parameters and variables relevant to the wet electrode film drying process is presented, and its consequences/effects on the finished electrode/final cell properties are mapped. The development of the drying mechanism is critically discussed according to existing modeling studies. Then, the existing and potential metrology techniques, either in situ or ex situ in the drying process are reviewed. This work is intended to develop new perspectives on the application of advanced techniques to enable a more predictive approach to identify optimum lithium‐ion battery manufacturing conditions, with a focus upon the critical drying process. [ABSTRACT FROM AUTHOR]

Atomically dispersed transition metal‐nitrogen‐carbon catalysts are emerging as low‐cost electrocatalysts for the oxygen reduction reaction in fuel cells. However, a cost‐effective and scalable synthesis strategy for these catalysts is still required, as well as a greater understanding of their mechanisms. Herein, iron, nitrogen co‐doped carbon spheres (Fe@NCS) have been prepared via hydrothermal carbonization and high‐temperature post carbonization. It is determined that FeN4 is the main form of iron existing in the obtained Fe@NCS. Two different precursors containing Fe2+ and Fe3+ are compared. Both chemical and structural differences have been observed in catalysts starting from Fe2+ and Fe3+ precursors. Fe2+@NCS‐A (starting with Fe2+ precursor) shows better catalytic activity for the oxygen reduction reaction. This catalyst is studied in an anion exchange membrane fuel cell. The high open‐circuit voltage demonstrates the potential approach for developing high‐performance, low‐cost fuel cell catalysts. [ABSTRACT FROM AUTHOR]

Durable and efficient hydrogen evolution reaction (HER) electrocatalysts that can satisfy industrial requirements need to be developed. Platinum (Pt)‐based catalysts represent the benchmark performance but are less studied for HER under high current densities in neutral electrolytes due to their high cost, poor stability, and extra water dissociation step. Here a facile and low‐temperature synthesis for constructing "blackberry‐shaped" Pt nanocrystals on copper (Cu) foams with low loading as self‐standing electrodes for HER in neutral media is proposed. Optimized hydrogen adsorption free energy and robust interaction induced by charge density exchange between Pt and Cu ensure the efficient and robust HER, especially under high current densities, which are demonstrated from both experimental and theoretical approaches. The electrode exhibits small overpotentials of 35 and 438 mV to reach current densities of ‐10 and ‐1000 mA cm−2, respectively. Meanwhile the electrode illustrates outstanding stability during chronoamperometry measurement under high current densities (‐100 to ‐400 mA cm−2) and 1000 cycles linear sweep voltammetry tests reaching ‐1000 mA cm−2. This study provides new design strategies for self‐standing electrocatalysts by fabricating robust metal–metal interactions between active materials and current collectors, thus facilitating the stable function of electrodes for HER under technologically relevant high current densities. [ABSTRACT FROM AUTHOR]

Although lithium, and other alkali ion, batteries are widely utilized and studied, many of the chemical and mechanical processes that underpin the materials within, and drive their degradation/failure, are not fully understood. Hence, to enhance the understanding of these processes various ex situ, in situ and operando characterization methods are being explored. Recently, electrochemical atomic force microscopy (EC‐AFM), and related techniques, have emerged as crucial platforms for the versatile characterization of battery material surfaces. They have revealed insights into the morphological, mechanical, chemical, and physical properties of battery materials when they evolve under electrochemical control. This critical review will appraise the progress made in the understanding batteries using EC‐AFM, covering both traditional and new electrode–electrolyte material junctions. This progress will be juxtaposed against the ability, or inability, of the system adopted to embody a truly representative battery environment. By contrasting key EC‐AFM literature with conclusions drawn from alternative characterization tools, the unique power of EC‐AFM to elucidate processes at battery interfaces is highlighted. Simultaneously opportunities for complementing EC‐AFM data with a range of spectroscopic, microscopic, and diffraction techniques to overcome its limitations are described, thus facilitating improved battery performance. [ABSTRACT FROM AUTHOR]

Polymer electrolyte fuel cells (PEFCs) are a promising replacement for the fossil fuel–dependent automotive and energy sectors. They have become increasingly commercialized in the last decade; however, significant limitations on durability and performance limit their commercial uptake. Catalyst layer (CL) design is commonly reported to impact device power density and durability; although, a consensus is rarely reached due to differences in testing conditions, experimental design, and types of data reported. This is further exacerbated by aspects of CL design such as catalyst support, proton conduction, catalyst, fabrication, and morphology, being significantly interdependent; hence, a wider appreciation is required in order to optimize performance, improve durability, and reduce costs. Here, the cutting‐edge research within the field of PEFCs is reviewed, investigating the effect of different manufacturing techniques, electrolyte distribution, support materials, surface chemistries, and total porosity on power density and durability. These are critically appraised from an applied perspective to inform the most relevant and promising pathways to make and test commercially viable cells. This holistic view of the competing aspects of CL design and preparation will facilitate the development of optimized CLs, especially the incorporation of novel catalyst support materials. [ABSTRACT FROM AUTHOR]

Supercapacitors are increasingly used in short‐distance electric transportation due to their long lifetime (≈15 years) and fast charging capability (>10 A g−1). To improve their market penetration, while minimizing onboard weight and maximizing space‐efficiency, materials costs must be reduced (<10 $ kg−1) and the volumetric energy‐density increased (>8 Wh L−1). Carbon nanofibers display good gravimetric capacitance, yet their marketability is hindered by their low density (0.05–0.1 g cm−3). Here, the authors increase the packing density of low‐cost, free‐standing carbon nanofiber mats (from 0.1 to 0.6 g cm−3) through uniaxial compression. X‐ray computed tomography reveals that densification occurs by reducing the inter‐fiber pore size (from 1–5 µm to 0.2–0.5 µm), which are not involved in double‐layer capacitance. The improved packing density is directly proportional to the volumetric performances of the device, which reaches a volumetric capacitance of 130 F cm−3 and energy density of 6 Wh L−1 at 0.1 A g−1 using a loading of 3 mg cm−2. The results outperform most commercial and lab‐scale porous carbons synthesized from bioresources (50–100 F cm−3, 1–3 Wh L−1 using 10 mg cm−2) and contribute to the scalable design of sustainable electrodes with minimal 'dead volume' for efficient supercapacitors. [ABSTRACT FROM AUTHOR]

Since the 1970s, electrochemical dilatometry (ECD) has been used to investigate the dilation of layered host materials due to the intercalation of guest ions, atoms or molecules, and has recently gained traction in application to various electrochemical devices, such as lithium‐ion batteries (LiBs), which have electrodes that undergo volume changes during cycling, resulting in particle cracking and electrode degradation. With resolution capabilities spanning tens of microns down to a few nanometres, dilatometry is a valuable tool in understanding how commonly used electrodes dilate and degrade and can therefore be of critical value in improving their performance. In recent years, there has been a plethora of studies using dilatometry as a monitoring tool for understanding operating performance in various electrochemical devices; however, to our knowledge, there has been no in‐depth review of this body of research to date. This paper seeks to address this by reviewing how dilatometry works and how it has been used for the characterisation of electrochemical energy storage devices. [ABSTRACT FROM AUTHOR]

It remains a challenge to develop efficient electrocatalysts in neutral media for hydrogen evolution reaction (HER) due to the sluggish kinetics and switch of the rate determining step. Although metal phosphides are widely used HER catalysts, their structural stability is an issue due to oxidization, and the HER performance in neutral media requires improvement. Herein, a new material, i.e., grapevine‐shaped N‐doped iron phosphide on carbon nanotubes, as an efficient HER catalyst in neutral media is developed. The optimized catalyst shows an overpotential of 256 mV at a large current density of 65 mA cm−2, which is even 10 mV lower than that of the commercial 20% Pt/C catalyst. The excellent performance of the catalyst is further studied by combined computational and experimental techniques, which proves that the interaction between nitrogen and iron phosphides can provide more efficient active structures and stabilize the metal phosphide electrocatalysts for HER. [ABSTRACT FROM AUTHOR]

Electrochemical impedance spectroscopy (EIS) is widely used to probe the physical and chemical processes in lithium (Li)‐ion batteries (LiBs). The key parameters include state‐of‐charge, rate capacity or power fade, degradation and temperature dependence, which are needed to inform battery management systems as well as for quality assurance and monitoring. All‐solid‐state batteries using a solid‐state electrolyte (SE), promise greater energy densities via a Li metal anode as well as enhanced safety, but their development is in its nascent stages and the EIS measurement, cell set‐up and modelling approach can be vastly different for various SE chemistries and cell configurations. This review aims to condense the current knowledge of EIS in the context of state‐of‐the‐art solid‐state electrolytes and batteries, with a view to advancing their scale‐up from the laboratory to commercial deployment. Experimental and modelling best practices are highlighted, as well as emerging impedance methods for conventional LiBs as a guide for opportunities in the solid‐state. [ABSTRACT FROM AUTHOR]

Herein, individual cell currents in parallel connected battery strings are measured using micro‐Hall‐effect sensors. Cells are routinely connected in electrical series and parallel to meet the power and energy requirements of automotive and consumer electronics applications. Cells connected in series have been extensively studied; however, cells in parallel are often assumed to be a "black box" in battery management systems. Poor pack design can result in positive feedback between current and temperature differentials along the parallel string, driving greater levels of heterogeneous behavior and uneven degradation. Herein, a noninvasive multisensor array board using Hall‐effect sensors is used to individually record the current passing through eight parallel connected cells in two different electrical configurations, showing highly heterogeneous current distribution. Characteristic "waves" of current and temperature are found to propagate along the parallel battery string and cell rebalancing is found to occur over hundreds of seconds with individual cell currents of up to 1 C rate. [ABSTRACT FROM AUTHOR]

With the rapid growth in energy consumption, renewable energy is a promising solution. However, renewable energy (e.g., wind, solar, and tidal) is discontinuous and irregular by nature, which poses new challenges to the new generation of large‐scale energy storage devices. Rechargeable batteries using aqueous electrolyte and multivalent ion charge are considered more suitable candidates compared to lithium‐ion and lead‐acid batteries, owing to their low cost, ease of manufacture, good safety, and environmentally benign characteristics. However, some substantial challenges hinder the development of aqueous rechargeable multivalent ion batteries (AMVIBs), including the narrow stable electrochemical window of water (≈1.23 V), sluggish ion diffusion kinetics, and stability issues of electrode materials. To address these challenges, a range of encouraging strategies has been developed in recent years, in the aspects of electrolyte optimization, material structure engineering and theoretical investigations. To inspire new research directions, this review focuses on the latest advances in cathode materials for aqueous batteries based on the multivalent ions (Zn2+, Mg2+, Ca2+, Al3+), their common challenges, and promising strategies for improvement. In addition, further suggestions for development directions and a comparison of the different AMVIBs are covered. [ABSTRACT FROM AUTHOR]

Solid‐state lithium batteries will revolutionize the lithium‐ion battery and energy storage applications if certain key challenges can be resolved. The formation of lithium‐protrusions (dendrites) that can cause catastrophic short‐circuiting is one of the main obstacles, and progresses by a mechanism that is not yet fully understood. By utilizing X‐ray computed tomography with nanoscale resolution, the 3D morphology of lithium protrusions inside short‐circuited solid electrolytes has been obtained for the first time. Distinguishable from adjacent voids, lithium protrusions partially filled cracks that tended to propagate intergranularly through the solid electrolyte, forming a large waved plane in the shape of the grain boundaries. Occasionally, the lithium protrusions bifurcate into flat planes in a transgranular mode. Within the cracks themselves, lithium protrusions are preferentially located in regions of relatively low curvature. The crack volume filled with lithium in two samples is 82.0% and 83.1%, even though they have distinctly different relative densities. Pre‐existing pores in the solid electrolyte, as a consequence of fabrication, can also be part‐filled with lithium, but do not have a significant influence on the crack path. The crack/lithium‐protrusion behavior qualitatively supports a model of propagation combining electrochemical and mechanical effects. [ABSTRACT FROM AUTHOR]

The next generation of automotive lithium‐ion batteries may employ NMC811 materials; however, defective particles are of significant interest due to their links to performance loss. Here, it is demonstrated that even before operation, on average, one‐third of NMC811 particles experience some form of defect, increasing in severity near the separator interface. It is determined that defective particles can be detected and quantified using low resolution imaging, presenting a significant improvement for material statistics. Fluorescence and diffraction data reveal that the variation of Mn content within the NMC particles may correlate to crystallographic disordering, indicating that the mobility and dissolution of Mn may be a key aspect of degradation during initial cycling. This, however, does not appear to correlate with the severity of particle cracking, which when analyzed at high spatial resolutions, reveals cracking structures similar to lower Ni content NMC, suggesting that the disconnection and separation of neighboring primary particles may be due to electrochemical expansion/contraction, exacerbated by other factors such as grain orientation that are inherent in such polycrystalline materials. These findings can guide research directions toward mitigating degradation at each respective length‐scale: electrode sheets, secondary and primary particles, and individual crystals, ultimately leading to improved automotive ranges and lifetimes. [ABSTRACT FROM AUTHOR]

The development of non‐Pt hydrogen oxidation reaction catalysts for hydrogen‐fuelled polymer electrolyte fuel cells allows for an overall reduction in electrode Pt content and therefore helps reduce the cost of devices, one of the biggest commercial challenges. Herein, a novel ternary alloy catalyst supported on carbon, PdIrAu/C, has been synthesised, characterised and compared to the binary PdIr/C to show how the addition of Au improves the stability of the catalyst. Transmission electron microscopy was utilised to analyse electrode structure as a function of the synthesis method, showing the optimum annealing temperature, of those tested, to be 400 °C, while inductively‐coupled plasma mass spectrometry provided analysis of the degradation of the two catalysts, confirming the PdIrAu/C catalyst is more stable at potentials similar to those at a fuel cell anode than PdIr/C. [ABSTRACT FROM AUTHOR]

Vast quantities of powder leave production lines each day, often with strict control measures. For quality checks to provide the most value, they must be capable of screening individual particles in 3D and at high throughput. Conceptually, X‐ray computed tomography (CT) is capable of this; however, achieving lab‐based reconstructions of individual particles has, until now, relied upon scan‐times on the order of tens of hours, or even days, and although synchrotron facilities are potentially capable of faster scanning times, availability is limited, making in‐line product analysis impractical. This work describes a preparation method and high‐throughput scanning procedure for the 3D characterization of powder samples in minutes using nano‐CT by full‐filed transmission X‐ray microscopy with zone‐plate focusing optics. This is demonstrated on various particle morphologies from two next‐generation lithium‐ion battery cathodes: LiNi0.8Mn0.1Co0.1O2 and LiNi0.6Mn0.2Co0.2O2; namely, NMC811 and NMC622. Internal voids are detected which limit energy density and promote degradation, potentially impacting commercial application such as the drivable range of an electric vehicle. [ABSTRACT FROM AUTHOR]

The hydrogen evolution reaction (HER) is a critical process in the electrolysis of water. Recently, much effort has been dedicated to developing low‐cost, highly efficient, and stable electrocatalysts. Transition metal phosphides are investigated intensively due to their high electronic conductivity and optimized absorption energy of intermediates in acid electrolytes. However, the low stability of metal phosphide materials in air and during electrocatalytic processes causes a decay of performance and hinders the discovery of specific active sites. The HER in alkaline media is more intricate, which requires further delicate design due to the Volmer steps. In this work, phosphorus‐modified monoclinic β‐CoMoO4 is developed as a low‐cost, efficient, and stable HER electrocatalyst for the electrolysis of water in alkaline media. The optimized catalyst shows a small overpotential of 94 mV to reach a current density of 10 mA cm−2 for the HER with high stability in KOH electrolyte, and an overpotential of 197 mV to reach a current density of 100 mA cm−2. Combined computational and in situ spectroscopic techniques show P is present as a surface phosphate ion; that electron holes localize on the surface ions and both (PO1−) and Co3+OH− are prospective surface active sites for the HER. [ABSTRACT FROM AUTHOR]

Cost‐effective and environment‐friendly aqueous zinc‐ion batteries (AZIBs) exhibit tremendous potential for application in grid‐scale energy storage systems but are limited by suitable cathode materials. Hydrated vanadium bronzes have gained significant attention for AZIBs and can be produced with a range of different pre‐intercalated ions, allowing their properties to be optimized. However, gaining a detailed understanding of the energy storage mechanisms within these cathode materials remains a great challenge due to their complex crystallographic frameworks, limiting rational design from the perspective of enhanced Zn2+ diffusion over multiple length scales. Herein, a new class of hydrated porous δ‐Ni0.25V2O5.nH2O nanoribbons for use as an AZIB cathode is reported. The cathode delivers reversibility showing 402 mAh g−1 at 0.2 A g−1 and a capacity retention of 98% over 1200 cycles at 5 A g−1. A detailed investigation using experimental and computational approaches reveal that the host "δ" vanadate lattice has favorable Zn2+ diffusion properties, arising from the atomic‐level structure of the well‐defined lattice channels. Furthermore, the microstructure of the as‐prepared cathodes is examined using multi‐length scale X‐ray computed tomography for the first time in AZIBs and the effective diffusion coefficient is obtained by image‐based modeling, illustrating favorable porosity and satisfactory tortuosity. [ABSTRACT FROM AUTHOR]

Nanoporous carbons (NPCs) with engineered specific pore sizes and sufficiently high porosities (both specific surface area and pore volume) are necessary for storing energy in the form of electric charges and molecules. Herein, NPCs, derived from biomass pine‐cones, coffee‐grounds, graphene‐oxide and metal‐organic frameworks, with systematically increased pore width (<1.0 nm to a few nm), micropore volume (0.2–0.9 cm3 g−1) and specific surface area (800–2800 m2 g−1) are presented. Superior CO2, H2, and H2O uptakes of 35.0 wt% (≈7.9 mmol g−1 at 273 K), 3.0 wt% (at 77 K) and 85.0 wt% (at 298 K), respectively at 1 bar, are achieved. At controlled microporosity, supercapacitors deliver impressive performance with a capacity of 320 and 230 F g−1 at 500 mA g−1, in aqueous and organic electrolytes, respectively. Excellent areal capacitance and energy density (>50 Wh kg−1 at high power density, 1000 W kg−1) are achieved to form the highest reported values among the range of carbons in the literature. The noteworthy energy storage performance of the NPCs for all five cases (CO2, H2, H2O, and capacitance in aqueous and organic electrolytes) is highlighted by direct comparison to numerous existing porous solids. A further analysis on the specific pore type governed physisorption capacities is presented. [ABSTRACT FROM AUTHOR]

Current "state‐of‐the‐art" monitoring and control techniques for lithium‐ion cells rely on full‐cell potential measurement and occasional surface temperature measurements. However, Li‐ion cells are complex multi‐layer devices and as such these techniques have poor resolution, limiting applicability. In this work we develop hybrid thermo‐electrochemical sensing arrays placed within the cell. The arrays are integrated into A5 pouch cells during manufacture and are used to create thermal maps in parallel with anode and cathode electrochemical data. The sensor array can be adapted to a range of cell formats and chemistries and installed into commercial or other industrially relevant cells, incorporating enhanced thermal and electrochemical diagnostic capability into a standard cell build. [ABSTRACT FROM AUTHOR]

Herein, a nanometric CuO anode for lithium‐ion batteries was investigated by combining electrochemical measurements and ex situ X‐ray computed tomography (CT) at the nanoscale. The electrode reacted by conversion at about 1.2 and 2.4 V versus Li+/Li during discharge and charge, respectively, to deliver a capacity ranging from 500 mAh g−1 to over 600 mAh g−1. Three‐dimensional nano‐CT imaging revealed substantial reorganization of the CuO particles and precipitation of a Li+‐conducting film suitable for a possible application in the battery. A lithium‐ion cell, exploiting the high capacity of the conversion process, was assembled by using a high‐performance LiNi0.33Co0.33Mn0.33O2 cathode reacting at 3.9 V versus Li+/Li. The cell was proposed as an energy‐storage system with an average working voltage of about 2.5 V, specific capacity of 170 mAh gcathode−1, and efficiency exceeding 99 % with a very stable cycling. [ABSTRACT FROM AUTHOR]

The development of alternative electrocatalysts exhibiting high activity in the oxygen reduction reaction (ORR) is vital for the deployment of large‐scale clean energy devices, such as fuel cells and zinc–air batteries. N‐doped carbon materials offer a promising platform for the design and synthesis of electrocatalysts due to their high ORR activity, high surface area, and tunable porosity. In this study, materials in which MnO nanoparticles are entrapped in N‐doped mesoporous carbon (MnO/NC) were developed as electrocatalysts for the ORR, and their performances were evaluated in zinc–air batteries. The obtained carbon materials had large surface area and high electrocatalytic activity toward the ORR. The carbon compounds were fabricated by using NaCl as template in a one‐pot process, which significantly simplifies the procedure for preparing mesoporous carbon materials and in turn reduces the total cost. A primary zinc–air battery based on this material exhibits an open‐circuit voltage of 1.49 V, which is higher than that of conventional zinc–air batteries with Pt/C (Pt/C cell) as ORR catalyst (1.41 V). The assembled zinc–air battery delivered a peak power density of 168 mW cm−2 at a current density of about 200 mA cm−2, which is higher than that of an equivalent Pt/C cell (151 mW cm−2 at a current density of ca. 200 mA cm−2). The electrocatalytic data revealed that MnO/NC is a promising nonprecious‐metal ORR catalyst for practical applications in metal–air batteries. Composite electrocatalysts: Materials in which MnO nanoparticles are entrapped in N‐doped mesoporous carbon (MnO/NC) were developed as electrocatalysts for the oxygen evolution reaction, and their performance was evaluated in a zinc–air battery (see figure), which delivered a peak power density of 168 mW cm−2 at a current density of about 200 mA cm−2, which is higher than that of an equivalent Pt/C cell (151 mW cm−2 at a current density of ca. 200 mA cm−2). [ABSTRACT FROM AUTHOR]

Many electrochemical energy storage and conversion devices employ porous media as electrodes, gas diffusion layers or separators. Recently, electrospinning has received significant attention as a way to generate nano‐fibers of polymers with controlled morphology and properties that, once carbonised, can act as conductive and porous media for electrochemical energy devices. The recent advances in X‐ray computed tomography have led the technique to be widely used in the characterisation of energy technologies and porous media as it offers a uniquely non‐destructive insight into the 3D microstructure of materials. Here we present electrospun fibrous mats with uncontrolled, controlled and aligned morphology for use as redox flow battery electrodes and, for the first time, obtain ultra‐high resolution nano‐tomographic X‐ray imaging of the materials using a lab source. The virtual 3D volumes enable extraction of parameters that would not be possible via other characterisation routes. Electrospun Fibres: Electrodes for redox flow batteries are synthesised using electrospinning on a rotating drum, allowing for good control of fibre size and a degree of alignment in the mats. Nano‐scale x‐ray computed tomography is used in both absorption and phase contrast modes to obtain high resolution and quality 3D images of the microstructure that are used for various computational models to assess the effect of alignment in the performance of the electrodes. The permeability and tortuosity of the pore phase is highly dependent on local heterogeneities in the structure and the alignment of the fibres. [ABSTRACT FROM AUTHOR]

Abstract: As the energy density of lithium‐ion cells and batteries increases, controlling the outcomes of thermal runaway becomes more challenging. If the high rate of gas generation during thermal runaway is not adequately vented, commercial cell designs can rupture and explode, presenting serious safety concerns. Here, ultra‐high‐speed synchrotron X‐ray imaging is used at >20 000 frames per second to characterize the venting processes of six different 18650 cell designs undergoing thermal runaway. For the first time, the mechanisms that lead to the most catastrophic type of cell failure, rupture, and explosion are identified and elucidated in detail. The practical application of the technique is highlighted by evaluating a novel 18650 cell design with a second vent at the base, which is shown to avoid the critical stages that lead to rupture. The insights yielded in this study shed new light on battery failure and are expected to guide the development of safer commercial cell designs. [ABSTRACT FROM AUTHOR]

Tracking the dynamic morphology of active materials during operation of lithium batteries is essential for identifying causes of performance loss. Digital volume correlation (DVC) is applied to high‐speed operando synchrotron X‐ray computed tomography of a commercial Li/MnO2 primary battery during discharge. Real‐time electrode material displacement is captured in 3D allowing degradation mechanisms such as delamination of the electrode from the current collector and electrode crack formation to be identified. Continuum DVC of consecutive images during discharge is used to quantify local displacements and strains in 3D throughout discharge, facilitating tracking of the progression of swelling due to lithiation within the electrode material in a commercial, spiral‐wound battery during normal operation. Displacement of the rigid current collector and cell materials contribute to severe electrode detachment and crack formation during discharge, which is monitored by a separate DVC approach. Use of time‐lapse X‐ray computed tomography coupled with DVC is thus demonstrated as an effective diagnostic technique to identify causes of performance loss within commercial lithium batteries; this novel approach is expected to guide the development of more effective commercial cell designs. [ABSTRACT FROM AUTHOR]

The redox properties of gadolinium doped ceria (CGO) and nickel oxide (NiO) composite cermets underpin the operation of solid oxide electrochemical cells. Although these systems have been widely studied, a full comprehension of the reaction dynamics at the interface of these materials is lacking. Here, in situ Raman spectroscopic monitoring of the redox cycle is used to investigate the interplay between the dynamic and competing processes of hydrogen spillover and water dissociation on the doped ceria surface. In order to elucidate these mechanisms, the redox process in pure CGO and NiO is studied when exposed to wet and dry hydrogen and is compared to the cermet behavior. In dry hydrogen, CGO reduces relatively rapidly via a series of intermediate phases, while NiO reduces via a single‐step process. In wet reducing atmospheres, however, the oxidation state of pure CGO is initially stabilized due to the dissociation of water by reduced Ce(III) and subsequent incorporation of oxygen into the structure. In the reduction process involving the composite cermet, the close proximity of the NiO improves the efficiency and speed of the composite reduction process. Although NiO is already incorporated into working cells, these observations suggest direct routes to further improve cell performance. [ABSTRACT FROM AUTHOR]

Cover Feature: Investigation of the Effect of Temperature on Lithium-Sulfur Cell Cycle Life Performance Using System Identification and X-Ray Tomography (Batteries & Supercaps 8/2022) Egradation modelling, electrochemistry, energy Conversion, lithium-sulfur battery, temperature, 3D gas thickness, X-ray tomography Keywords: egradation modelling; electrochemistry; energy Conversion; lithium-sulfur battery; temperature; 3D gas thickness; X-ray tomography EN egradation modelling electrochemistry energy Conversion lithium-sulfur battery temperature 3D gas thickness X-ray tomography 1 1 1 08/09/22 20220801 NES 220801 B The Cover Feature b illustrates a discharge profile of a 19 Ah lithium-sulfur (Li-S) pouch cell subject to the required power on the Millbrook London Transport Bus (MLTB) driving cycle. [Extracted from the article]

This review discusses the range of diagnostic techniques reported in the literature for spatially resolved studies of operating fuel cells. In situ diagnostic techniques continue to reveal more about the working of fuel cells and in so doing allow for improved cell hardware design, materials selection, and choice of operating conditions to realize advanced electrochemical performance and longevity. These techniques also allow us to scrutinize the validity of conventional bulk electrical measurements and develop detailed models of fuel cell operation. [ABSTRACT FROM AUTHOR]