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The study of degradation behavior of electrocatalysts in an industrial context calls for rapid and efficient analysis methods. Optical methods like Raman spectroscopy fulfil these requirements and are thus predestined for this purpose. However, the iridium utilized in proton exchange membrane electrolysis (PEMEL) is Raman inactive in its metallic state. This work demonstrates the high oxidation sensitivity of iridium and its utilization in analysis of catalyst materials. Laser induced oxidation Raman spectroscopy (LIORS) is established as a novel method for qualitative, chemical and structural analysis of iridium catalysts. Differences in particle sizes of iridium powders drastically change oxidation sensitivity. Oxidation of the iridium powders to IrO 2 occurred at a laser power density of 0.47 ± 0.06 mW μm -2 for the 850 μm powder and at 0.12 ± 0.06 mW μm -2 and 0.019 ± 0.015 mW μm -2 for the 50 μm and 0.7-0.9 μm powders respectively. LIORS was utilized to assess possible deterioration of an iridium electrocatalyst due to operation under electrolysis. The operating electrocatalyst exhibited higher oxidation sensitivity, suggesting smaller iridium particle size due to catalyst dissolution. Peak shifts of the IrO 2 signal were utilized to assess differences in transformation temperatures. The operated electrocatalyst transformed to IrO 2 at lower temperature (8 cm -1 redshift) relative to the pristine catalyst (10 cm -1 redshift), demonstrating that pre-oxidation of the iridium to amorphous IrO x during electrolysis diminishes the energy barrier needed for IrO 2 formation. Thus, LIORS can be utilized as a straightforward screening method for the analysis of iridium electrocatalysts in the industrial application of PEMEL.

A series of four new thorium tungstates, A 4 Th(WO 4 ) 4 (A=Li, K, Rb, Cs), were synthesized using high-temperature solid-state method. Structural studies of the materials reveal distinct structural changes with underlying similarities influenced by the nature of A-site cations. Li 4 Th(WO 4 ) 4 exhibits a two-dimensional corrugated sheet structure stabilized by Li + cations, crystallizing in P 1 ‾ ${\bar{1}\ }$ space group. K 4 Th(WO 4 ) 4 crystallizes in I4 1 /a space group and exhibits a three-dimensional framework consisting of ThO 8 antiprisms and WO 4 tetrahedra. Rb 4 Th(WO 4 ) 4 forms in C2/c space group, showcasing a framework with two-dimensional sheet structure. Cs 4 Th(WO 4 ) 4 is isostructural to Rb 4 Th(WO 4 ) 4 but displays increased interlayer spacing due to the larger ionic radius of Cs. Raman spectroscopy confirms the structural data, revealing distinct vibrational modes that correlate with tungsten coordination changes from WO 6 in Li 4 Th(WO 4 ) 4 to WO 4 in the Cs 4 Th(WO 4 ) 4 . This study demonstrates how variation of alkali metals affects the structural properties of thorium tungstates series, showing a morphotropic evolution as a factor of the ionic radii of the alkali metals., (© 2024 The Author(s). Chemistry - A European Journal published by Wiley-VCH GmbH.)

Anode free concepts are gaining traction in battery research. To improve cyclability, a better understanding of the deposition processes and morphologies is necessary. Correlative experiments enable a link between a variety of properties obtained, such as chemical, mechanical or electrochemical data. Here, electron paramagnetic resonance imaging (EPRI) is correlated with atomic force microscopy (AFM) to gain a deeper understanding of the microscopic topography and local stiffness at different intensities of the lithium selective EPRI map. Experiments were carried out on a sample of lithium deposited on copper foil from standard battery electrolyte. The correlation of both methods reveals that EPRI has a high sensitivity towards small lithium structures, while bulk lithium was not detected. The results demonstrate that EPRI can be used for prescreening to identify regions with different properties, which can then be analysed individually by AFM., (© 2025 The Authors. ChemPhysChem published by Wiley-VCH GmbH.)

High energy density electrochemical systems such as metal batteries suffer from uncontrollable dendrite growth on cycling, which can severely compromise battery safety and longevity. This originates from the thermodynamic preference of metal nucleation on electrode surfaces, where obtaining the crucial information on metal deposits in terms of crystal orientation, plated volume, and growth rate is very challenging. In situ liquid phase transmission electron microscopy (LPTEM) is a promising technique to visualize and understand electrodeposition processes, however a detailed quantification of which presents significant difficulties. Here by performing Zn electroplating and analyzing the data via basic image processing, this work not only sheds new light on the dendrite growth mechanism but also demonstrates a workflow showcasing how dendritic deposition can be visualized with volumetric and growth rate information. These results along with additionally corroborated 4D STEM analysis take steps to access information on the crystallographic orientation of the grown Zn nucleates and toward live quantification of in situ electrodeposition processes., (© 2024 The Authors. Small Methods published by Wiley‐VCH GmbH.)

Ga-doped Li 7 La 3 Zr 2 O 12 garnet solid electrolytes exhibit the highest Li-ion conductivities among the oxide-type garnet-structured solid electrolytes, but instabilities toward Li metal hamper their practical application. The instabilities have been assigned to direct chemical reactions between LiGaO 2 coexisting phases and Li metal by several groups previously. Yet, the understanding of the role of LiGaO 2 in the electrochemical cell and its electrochemical properties is still lacking. Here, we are investigating the electrochemical properties of LiGaO 2 through electrochemical tests in galvanostatic cells versus Li metal and complementary ex situ studies via confocal Raman microscopy, quantitative phase analysis based on powder X-ray diffraction, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and electron energy loss spectroscopy. The results demonstrate considerable and surprising electrochemical activity, with high reversibility. A three-stage reaction mechanism is derived, including reversible electrochemical reactions that lead to the formation of highly electronically conducting products. The results have considerable implications for the use of Ga-doped Li 7 La 3 Zr 2 O 12 electrolytes in all-solid-state Li-metal battery applications and raise the need for advanced materials engineering to realize Ga-doped Li 7 La 3 Zr 2 O 12 for practical use.

The solvation of dissolved transition metal ions in lithium-ion battery electrolytes is not well-characterised experimentally, although it is important for battery degradation mechanisms governed by metal dissolution, deposition, and reactivity in solution. This work identifies the coordinating species in the Mn 2+ and Ni 2+ solvation spheres in LiPF 6 /LiTFSI-carbonate electrolyte solutions by examining the electron-nuclear spin interactions, which are probed by pulsed EPR and paramagnetic NMR spectroscopy. These techniques investigate solvation in frozen electrolytes and in the liquid state at ambient temperature, respectively, also probing the bound states and dynamics of the complexes involving the ions. Mn 2+ and Ni 2+ are shown to primarily coordinate to ethylene carbonate (EC) in the first coordination sphere, while PF 6 - is found primarily in the second coordination sphere, although a degree of contact ion pairing does appear to occur, particularly in electrolytes with low EC concentrations. NMR results suggest that Mn 2+ coordinates more strongly to PF 6 - than to TFSI - , while the opposite is true for Ni 2+ . This work provides a framework to experimentally determine the coordination spheres of paramagnetic metals in battery electrolyte solutions.

Pentavalent uranium compounds are key components of uranium's redox chemistry and play important roles in environmental transport. Despite this, well-characterized U(V) compounds are scarce primarily because of their instability with respect to disproportionation to U(IV) and U(VI). In this work, we provide an alternate route to incorporation of U(V) into a crystalline lattice where different oxidation states of uranium can be stabilized through the incorporation of secondary cations with different sizes and charges. We show that iriginite-based crystalline layers allow for systematically replacing U(VI) with U(V) through aliovalent substitution of 2+ alkaline-earth or 3+ rare-earth cations as dopant ions under high-temperature conditions, specifically Ca(U VI O 2 )W 4 O 14 and Ln(U V O 2 )W 4 O 14 (Ln=Nd, Sm, Eu, Gd, Yb). Evidence for the existence of U(V) and U(VI) is supported by single-crystal X-ray diffraction, high energy resolution X-ray absorption near edge structure, X-ray photoelectron spectroscopy, and optical absorption spectroscopy. In contrast with other reported U(V) materials, the U(V) single crystals obtained using this route are relatively large (several centimeters) and easily reproducible, and thus provide a substantial improvement in the facile synthesis and stabilization of U(V)., (© 2024 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

The up-to-date lifespan of zero-excess lithium (Li) metal batteries is limited to a few dozen cycles due to irreversible Li-ion loss caused by interfacial reactions during cycling. Herein, a chemical prelithiated composite interlayer, made of lithiophilic silver (Ag) and lithiophobic copper (Cu) in a 3D porous carbon fiber matrix, is applied on a planar Cu current collector to regulate Li plating and stripping and prevent undesired reactions. The Li-rich surface coating of lithium oxide (Li 2 O), lithium carboxylate (RCO 2 Li), lithium carbonates (ROCO 2 Li), and lithium hydride (LiH) is formed by soaking and directly heating the interlayer in n -butyllithium hexane solution. Although only a thin coating of ∼10 nm is created, it effectively regulates the ionic and electronic conductivity of the interlayer via these surface compounds and reduces defect sites by reactions of n -butyllithium with heteroatoms in the carbon fibers during formation. The spontaneously formed lithiophilic-lithiophobic gradient across individual carbon fiber provides homogeneous Li-ion deposition, preventing concentrated Li deposition. The porous structure of the composite interlayer eliminates the built-in stress upon Li deposition, and the anisotropically distributed carbon fibers enable uniform charge compensation. These features synergistically minimize the side reactions and compensate for Li-ion loss while cycling. The prepared zero-excess Li metal batteries could be cycled 300 times at 1.17 C with negligible capacity fading.

Solid-state polymer electrolytes (SPEs), such as poly(ethylene oxide) (PEO), have good flexibility when compared to ceramic-type solid electrolytes. Therefore, it could be an ideal solid electrolyte for zero-excess all-solid-state Li metal battery (ZESSLB), also known as anode-free all-solid-state Li battery, development by offering better contact to the Cu current collector. However, the low Coulombic efficiencies observed from polymer type solid-state Li batteries (SSLBs) raise the concern that PEO may consume the limited amount of Li in ZESSLB to fail the system. Here, we designed ZESSLBs by using all-ceramic half-cells and an extra PEO electrolyte interlayer to study the reactivity between PEO and freshly deposited Li under a real battery operating conduction. By shuttling active Li back from the anode to the cathode, the PEO SPEs can be separated from the ZESSLBs for experimental studies without the influence from cathode materials or possible contamination from the usage of Li foil as the anode. Electrochemical cycling of ZESSLBs shows that the capacities of ZESSLBs with solvent-free and solvent-casted PEO SPEs significantly degraded compared to the ones with Li metal as the anode for the all-solid-state Li batteries. The fast capacity degradation of ZESSLBs using different types of PEO SPEs is evidenced to be associated with Li reacting with PEO, residual solvent, and water in PEO and dead Li formation upon the presence or absence of residual solvent. The results suggest that avoiding direct contact between the PEO electrolyte and deposited lithium is necessary when there is only a limited amount of Li available in ZESSLBs.

Varying the electrode potential rearranges the charges in the double layer (DL) of an electrochemical interface by a resistive-capacitive current response. The capacitances of such charge relocations are frequently used in the research community to estimate electrochemical active surface areas (ECSAs), yet the reliability of this methodology is insufficiently examined. Here, the relation of capacitances and ECSAs is critically assessed with electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) data on polished (Au, Ti, Ru, Pt, Ni, glassy carbon, graphite plate) and porous (carbon fleeces) electrodes. By investigating this variety of electrodes, the frequency-dependencies observed in the measured capacitances are shown to arise from the inherent resistive-capacitive DL response, charge transfer reactions, and resistively damped capacitive currents in microstructures (such as pores, pinholes, or cracks). These frequency-dependencies are typically overlooked when capacitances are related to ECSAs. The capacitance at the specimen-characteristic relaxation frequency of the resistive-capacitive DL response is proposed as a standardized capacitance-metric to estimate ECSAs. In 1 M perchloric acid, the polished gold electrode and the high-surface area carbon fleeces show ratios of capacitance-metric over surface-area of around 3.7 μF cm -2 . Resistively damped currents in microstructures and low-conducting oxide layers are shown to complicate trustworthy capacitance-based estimations of ECSAs. In the second part of this study, advanced equivalent circuits models to describe the measured EIS and CV responses are presented.

Trends of the electrocatalytic activities for the hydrogen evolution reaction (HER) across transition metals are typically explained by d-band properties such as center or upper edge positions in relation to Fermi levels. Here, the universality of this relation is questioned for alloys, exemplified for the AuPt system which is examined with electrocatalytic measurements and density functional theory (DFT) calculations. At small overpotentials, linear combinations of the pure-metals' Tafel kinetics normalized to the alloy compositions are found to precisely resemble the measured HER activities. DFT calculations show almost neighbor-independent adsorption energies on Au and Pt surface-sites, respectively, as the adsorbed hydrogen influences the electron density mostly locally at the adsorption site itself. In contrast, the density of states of the d-band describe the delocalized conduction electrons in the alloys, which are unable to portray the local electronic environments at adsorption sites and related bonding strengths. The adsorption energies at element-specific surface sites are related to overpotential-dependent reaction mechanisms in a multidimensional reinterpretation of the volcano plot for alloys, which bridges the found inconsistencies between activity and bonding strength descriptors of the common electrocatalytic theory for alloys.

Methods for electronic structure computations, such as density functional theory (DFT), are routinely used for the calculation of spectroscopic parameters to establish and validate structure-parameter correlations. DFT calculations, however, are computationally expensive for large systems such as polymers. This work explores the machine learning (ML) of isotropic g values, g iso , obtained from electron paramagnetic resonance (EPR) experiments of an organic radical polymer. An ML model based on regression trees is trained on DFT-calculated g values of poly(2,2,6,6-tetramethylpiperidinyloxy-4-yl methacrylate) (PTMA) polymer structures extracted from different time frames of a molecular dynamics trajectory. The DFT-derived g values, g iso calc , for different radical densities of PTMA, are compared against experimentally derived g values obtained from in operando EPR measurements of a PTMA-based organic radical battery. The ML-predicted g iso values, g iso pred , were compared with g iso calc to evaluate the performance of the model. Mean deviations of g iso pred from g iso calc were found to be on the order of 0.0001. Furthermore, a performance evaluation on test structures from a separate MD trajectory indicated that the model is sensitive to the radical density and efficiently learns to predict g iso values even for radical densities that were not part of the training data set. Since our trained model can reproduce the changes in g iso along the MD trajectory and is sensitive to the extent of equilibration of the polymer structure, it is a promising alternative to computationally more expensive DFT methods, particularly for large systems that cannot be easily represented by a smaller model system.

A key task in today's inorganic synthetic chemistry is to develop effective reactions, routes, and associated techniques aiming to create new functional materials with specifically desired multilevel structures and properties. Herein, we report an ultrathin two-dimensional layered composite of graphene ribbon and silicate via a simple and scalable one-pot reaction, which leads to the creation of a novel carbon-metal-silicate hybrid family: carbosilicate. The graphene ribbon is in situ formed by unzipping carbon nanotubes, while the ultrathin silicate is in situ obtained from bulk silica or commercial glass; transition metals (Fe or Ni) oxidized by water act as bridging agent, covalently bonding the two structures. The unprecedented structure combines the superior properties of the silicate and the nanocarbon, which triggers some specific novel properties. All processes during synthesis are complementary to each other. The associated synergistic chemistry could stimulate the discovery of a large class of more interesting, functionalized structures and materials., (© 2023 Wiley-VCH GmbH.)

The effect of two atmospheric post-treatment conditions directly after the KOH activation of polyacrylonitrile-based nanofibres is studied in this work. As post-treatment different N 2  : O 2 flow conditions, namely high O 2 -flow and low O 2 -flow, are applied and their impact on occurring reactions and carbon nanofibres' properties is studied by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), Raman spectroscopy, elemental analysis and CO 2 and Ar gas adsorption. At high O 2 -flow conditions a pyrophoric effect was observed on the KOH-activated carbon nanofibers. Based on the obtained results from the TGA and DSC the pyrophoric effect is attributed to the oxidation reactions of metallic potassium formed during the KOH activation process and a consequent carbon combustion reaction. Suppression of this pyrophoric effect is achieved using the low O 2 -flow conditions due to a lower heat formation of the potassium oxidation and the absence of carbon combustion. Compared to the high O 2 -flow samples no partial destruction of the carbon nanofibers is observed in the SEM images. The determination of the adsorption isotherms, the surface area, the pore size distribution and the isosteric enthalpies of adsorption show the superior properties under low O 2 -flow conditions. The present micropore volume is increased from 0.424 cm 3 g -1 at high O 2 -flow to 0.806 cm 3 g -1 for low O 2 -flow samples, resulting in an increase of CO 2 adsorption capacity of 38% up to 6.6 mmol g -1 at 1 bar. This significant improvement clearly points out the importance of considering highly exothermic potassium oxidation reactions and possible post-treatment strategies when applying KOH activation to electrospun carbon nanofiber materials., Competing Interests: The authors have no competing interest to declare., (This journal is © The Royal Society of Chemistry.)

The electrolytic reduction of CO 2 in aqueous media promises a pathway for the utilization of the green house gas by converting it to base chemicals or building blocks thereof. However, the technology is currently not economically feasible, where one reason lies in insufficient reaction rates and selectivities. Current research of CO 2 electrolysis is becoming aware of the importance of the local environment and reactions at the electrodes and their proximity, which can be only assessed under true catalytic conditions, i.e. by in operando techniques. In this work, multinuclear in operando NMR techniques were applied in order to investigate the evolution of the electrolyte chemistry during CO 2 electrolysis. The CO 2 electroreduction was performed in aqueous NaHCO 3 or KHCO 3 electrolytes at silver electrodes. Based on 13 C and 23 Na NMR studies at different magnetic fields, it was found that the dynamic equilibrium of the electrolyte salt in solution, existing as ion pairs and free ions, decelerates with increasingly negative potential. In turn, this equilibrium affects the resupply rate of CO 2 to the electrolysis reaction from the electrolyte. Substantiated by relaxation measurements, a mechanism was proposed where stable ion pairs in solution catalyze the bicarbonate dehydration reaction, which may provide a new pathway for improving educt resupply during CO 2 electrolysis., (© 2023. The Author(s).)

Liquid-phase transmission electron microscopy (LPTEM) technique has been used to perform a wide range of in situ and operando studies. While most studies are based on the sample contrast change in the liquid, acquiring high qualitative results in the native liquid environment still poses a challenge. Herein, we present a novel and facile method to perform high-resolution and analytical electron microscopy studies in a liquid flow cell. This technique is based on removing the liquid from the observation area by a flow of gas. It is expected that the proposed approach can find broad applications in LPTEM studies., (© The Author(s) 2023. Published by Oxford University Press on behalf of The Japanese Society of Microscopy. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Reducing non-radiative recombination energy loss (ΔE 3 ) is one key to boosting the efficiency of organic solar cells. Although the recent studies have indicated that the Y-series asymmetric acceptors-based devices featured relatively low ΔE 3 , the understanding of the energy loss mechanism derived from molecular structure change is still lagging behind. Herein, two asymmetric acceptors named BTP-Cl and BTP-2Cl with different terminals were synthesized to make a clear comparative study with the symmetric acceptor BTP-0Cl. Our results suggest that asymmetric acceptors exhibit a larger difference of electrostatic potential (ESP) in terminals and semi-molecular dipole moment, which contributes to form a stronger π-π interaction. Besides, the experimental and theoretical studies reveal that a lower ESP-induced intermolecular interaction can reduce the distribution of PM6 near the interface to enhance the built-in potential and decrease the charge transfer state ratio for asymmetric acceptors. Therefore, the devices achieve a higher exciton dissociation efficiency and lower ΔE 3 . This work establishes a structure-performance relationship and provides a new perspective to understand the state-of-the-art asymmetric acceptors., (© 2023 Wiley-VCH GmbH.)

An exact understanding of the conductivity of individual fibers and their networks is crucial to tailor the overall macroscopic properties of polyacrylonitrile (PAN)-based carbon nanofibers (CNFs). Therefore, microelectrical properties of CNF networks and nanoelectrical properties of individual CNFs, carbonized at temperatures from 600 to 1000 °C, are studied by means of conductive atomic force microscopy (C-AFM). At the microscale, the CNF networks show good electrical interconnections enabling a homogeneously distributed current flow. The network's homogeneity is underlined by the strong correlation of macroscopic conductivities, determined by the four-point-method, and microscopic results. Both, microscopic and macroscopic electrical properties, solely depend on the carbonization temperature and the exact resulting fiber structure. Strikingly, nanoscale high-resolution current maps of individual CNFs reveal a large highly resistive surface fraction, representing a clear limitation. Highly resistive surface domains are either attributed to disordered highly resistive carbon structures at the surface or the absence of electron percolation paths in the bulk volume. With increased carbonization temperature, the conductive surface domains grow in size resulting in a higher conductivity. This work contributes to existing microstructural models of CNFs by extending them by electrical properties, especially electron percolation paths., (© 2023 The Authors. Advanced Materials published by Wiley-VCH GmbH.)

Li 10 GeP 2 S 12 is a phosphosulfide solid electrolyte that exhibits exceptionally high Li-ion conductivity, reaching a conductivity above 10 -3 S cm -1 at room temperature, rivaling that of liquid electrolytes. Herein, a method to produce glassy-ceramic Li 10 GeP 2 S 12 via a single-step utilizing high-energy ball milling was developed and systematically studied. During the high energy milling process, the precursors experience three different stages, namely, the 'Vitrification zone' where the precursors undergo homogenization and amorphization, 'Intermediary zone' where Li 3 PS 4 and Li 4 GeS 4 are formed, and the 'Product stage' where the desired glassy-ceramic Li 10 GeP 2 S 12 is formed after 520 min of milling. At room temperature, the as-milled sample achieved a high ionic conductivity of 1.07 × 10 -3 S cm -1 . It was determined via quantitative phase analyses (QPA) of transmission X-ray diffraction results that the as-milled Li 10 GeP 2 S 12 possessed a high degree of amorphization (44.4 wt %). To further improve the crystallinity and ionic conductivity of the Li 10 GeP 2 S 12 , heat treatment of the as-milled sample was carried out. The optimal heat-treated Li 10 GeP 2 S 12 is almost fully crystalline and possesses a room temperature ionic conductivity of 3.27 × 10 -3 S cm -1 , an over 200% increase compared to the glassy-ceramic Li 10 GeP 2 S 12 . These findings help provide previously lacking insights into the controllable preparation of Li 10 GeP 2 S 12 material.

Organic radical batteries (ORBs) represent a viable pathway to a more sustainable energy storage technology compared to conventional Li-ion batteries. For further materials and cell development towards competitive energy and power densities, a deeper understanding of electron transport and conductivity in organic radical polymer cathodes is required. Such electron transport is characterised by electron hopping processes, which depend on the presence of closely spaced hopping sites. Using a combination of electrochemical, electron paramagnetic resonance (EPR) spectroscopic, and theoretical molecular dynamics as well as density functional theory modelling techniques, we explored how compositional characteristics of cross-linked poly(2,2,6,6-tetramethyl-1-piperidinyloxy-4-yl methacrylate) (PTMA) polymers govern electron hopping and rationalise their impact on ORB performance. Electrochemistry and EPR spectroscopy not only show a correlation between capacity and the total number of radicals in an ORB using a PTMA cathode, but also indicates that the state-of-health degrades about twice as fast if the amount of radical is reduced by 15%. The presence of up to 3% free monomer radicals did not improve fast charging capabilities. Pulsed EPR indicated that these radicals readily dissolve into the electrolyte but a direct effect on battery degradation could not be shown. However, a qualitative impact cannot be excluded either. The work further illustrates that nitroxide units have a high affinity to the carbon black conductive additive, indicating the possibility of its participation in electron hopping. At the same time, the polymers attempt to adopt a compact conformation to increase radical-radical contact. Hence, a kinetic competition exists, which might gradually be altered towards a thermodynamically more stable configuration by repeated cycling, yet further investigations are required for its characterisation., (© 2023. The Author(s).)

The structural and morphological changes of the Lithium superionic conductor Li 10 GeP 2 S 12 , prepared via a widely used ball milling-heating method over a comprehensive heat treatment range (50 - 700 °C), are investigated. Based on the phase composition, the formation process can be distinctly separated into four zones: Educt, Intermediary, Formation, and Decomposition zone. It is found that instead of Li 4 GeS 4 -Li 3 PS 4 binary crystallization process, diversified intermediate phases, including GeS 2 in different space groups, multiphasic lithium phosphosulfides (Li x P y S z ), and cubic Li 7 Ge 3 PS 12 phase, are involved additionally during the formation and decomposition of Li 10 GeP 2 S 12 . Furthermore, the phase composition at temperatures around the transition temperatures of different formation zones shows a significant deviation. At 600 °C, Li 10 GeP 2 S 12 is fully crystalline, while the sample decomposed to complex phases at 650 °C with 30 wt.% impurities, including 20 wt.% amorphous phases. These findings over such a wide temperature range are first reported and may help provide previously lacking insights into the formation and crystallinity control of Li 10 GeP 2 S 12 ., (© 2023 The Authors. Small published by Wiley-VCH GmbH.)

A robust imaging protocol utilizing laboratory XCT is presented. Hybrid 2D/3D imaging at different scales with real-time monitoring allowed to assess, in operation, the evolution of zinc electrodes within three environments, namely alkaline, near-neutral, and mildly acidic. Different combinations of currents were used to demonstrate various scenarios exhibiting both dendritic and smooth deposition of active material. Directly from radiograms, the volume of the electrode and therefore its growth/dissolution rate was estimated and compared against tomographic reconstructions and theoretical values. The protocol combines simplistic cell design with multiple three-dimensional and two-dimensional acquisitions at different magnifications, providing a unique insight into electrode's morphology evolution within various environments., Competing Interests: The authors declare no competing interests., (© 2023 The Author(s).)

It is of general interest to combine the faradaic processes based high energy density of a battery with the non-faradaic processes based high power density of a capacitor in one cell. Surface area and functional groups of electrode materials strongly affect these properties. For the anode material Li 4 Ti 5 O 12 (LTO), we suggest a polaron based mechanism that influences Li ion uptake and mobility. Here we show electrolytes containing a lithium salt induce an observable change in the bulk NMR relaxation properties of LTO nano particles. The longitudinal 7 Li NMR relaxation time of bulk LTO can change by almost an order of magnitude and, therefore, reacts very sensitively to the cation and its concentration in the surrounding electrolyte. The reversible effect is largely independent of the used anions and of potential anion decomposition products. It is concluded that lithium salt containing electrolytes increase the mobility of surface polarons. These polarons and additional lithium cations from the electrolyte can now diffuse through the bulk, induce the observed enhanced relaxation rate and enable the non-faradaic process. This picture of a Li + ion equilibrium between electrolyte and solid may help with improving the charging properties of electrode materials., (© 2023. The Author(s).)

The identification of fundamental relationships between atomic configuration and electronic structure typically requires experimental empiricism or systematic theoretical studies. Here, we provide an alternative statistical approach to gauge the importance of structure parameters, i.e. , bond lengths, bond angles, and dihedral angles, for hyperfine coupling constants in organic radicals. Hyperfine coupling constants describe electron-nuclear interactions defined by the electronic structure and are experimentally measurable, for example, by electron paramagnetic resonance spectroscopy. Importance quantifiers are computed with the machine learning algorithm neighborhood components analysis using molecular dynamics trajectory snapshots. Atomic-electronic structure relationships are visualized in matrices correlating structure parameters with coupling constants of all magnetic nuclei. Qualitatively, the results reproduce common hyperfine coupling models. Tools to use the presented procedure for other radicals/paramagnetic species or other atomic structure-dependent parameters are provided., Competing Interests: The authors declare no conflict of interest., (This journal is © The Royal Society of Chemistry.)

The addition of conductive additives during electrode fabrication is standard practice to mitigate a low intrinsic electronic conductivity of most cathode materials used in Li-ion batteries. To ensure an optimal conduction pathway, these conductive additives, which generally consist of carbon particles, need to be in good contact with the active compounds. Herein, we demonstrate how a combination of pulsed electron paramagnetic resonance (EPR) relaxometry and inverse Laplace transform (ILT) can be used to study such contact. The investigated system consists of PTMA (poly(2,2,6,6-tetramethylpiperidinyloxy-4-ylmethacrylate)) monomer radicals, which is a commonly used redox unit in organic radical batteries (ORB), mixed at different ratios with Super P carbon black (CB) as the conductive additive. Inversion recovery data were acquired to determine longitudinal ( T 1 ) relaxation time constant distributions. It was observed that not only the position and relative amplitude, but also the number of relaxation modes varies as the composition of PTMA monomer and CB is changed, thereby justifying the use of ILT instead of fitting with a predetermined number of components. A hypothesis for the origin of different relaxation modes was devised. It suggests that the electrode composition may locally affect the quality of electronic contact between the active material and carbon black.

Sodium-ion batteries (SIBs) are expected to become alternatives to lithium-ion batteries (LIBs) as next-generation rechargeable batteries, owing to abundant sodium sources and low cost. However, SIBs still use liquid organic electrolytes (LOEs), which are highly flammable and have the tendency to leak. Although inorganic solid electrolytes (ISEs) and solid polymer electrolytes (SPEs) have been investigated for many years, given their higher safety level, neither of them is likely to be commercialized because of the rigidity of ISEs and the low room-temperature ionic conductivity of SPEs. During the last decade, composite polymer electrolytes (CPEs), composed of ISEs and SPEs, exhibiting both relatively high ionic conductivity and flexibility, have gained much attention and are considered as promising electrolytes. However, the ionic conductivities of CPEs are still unsatisfactory for practical application. Hence, this Review focuses on the principle of sodium ion conductors and particularly on recent investigations and development of CPEs., (© 2023 Wiley-VCH GmbH.)

The study of phase formation in the U-Te-O systems with mono and divalent cations under high-temperature high-pressure (HT/HP) conditions has resulted in four new inorganic compounds: K 2 [(UO 2 ) (Te 2 O 7 )], Mg [(UO 2 ) (TeO 3 ) 2 ], Sr [(UO 2 ) (TeO 3 ) 2 ] and Sr [(UO 2 ) (TeO 5 )]. Tellurium occurs as Te IV , Te V , and Te VI in these phases which demonstrate the high chemical flexibility of the system. Uranium VI) adopts a variety of coordinations, namely, UO 6 in K 2 [(UO 2 ) (Te 2 O 7 ), UO 7 in Mg [(UO 2 ) (TeO 3 ) 2 ] and Sr [(UO 2 ) (TeO 3 ) 2 ], and UO 8 in Sr [(UO 2 ) (TeO 5 )]. The structure of K 2 [(UO 2 ) (Te 2 O 7 )] is featured with one dimensional (1D) [Te 2 O 7 ] 4- chains along the c -axis. The Te 2 O 7 chains are further linked by UO 6 polyhedra, forming the 3D [(UO 2 ) (Te 2 O 7 )] 2- anionic frameworks. In Mg [(UO 2 ) (TeO 3 ) 2 ], TeO 4 disphenoids share common corners with each other resulting in infinite 1D chains of [(TeO 3 ) 2 ] 4- propagating along the a -axis. These chains link the uranyl bipyramids by edge sharing along two edges of the disphenoids, resulting in the 2D layered structure of [(UO 2 ) (Te 2 O 6 )] 2- . The structure of Sr [(UO 2 ) (TeO 3 ) 2 ] is based on 1D chains of [(UO 2 ) (TeO 3 ) 2 ] ∞ 2- propagating into the c -axis. These chains are formed by edge-sharing uranyl bipyramids which are additionally fused together by two TeO 4 disphenoids, which also share two edges. The 3D framework structure of Sr [(UO 2 ) (TeO 5 )] is composed of 1D [TeO 5 ] 4- chains sharing edges with UO 7 bipyramids. Three tunnels based on 6-Membered rings (MRs) are propagating along [001] [010] and [100] directions. The HT/HP synthetic conditions for the preparation of single crystalline samples and their structural aspects are discussed in this work., Competing Interests: Authors EL, BX and PK were employed by Institute of Energy and Climate Research (IEK-6), Forschungszentrum Jülich GmbH. Authors R-AE and EA were employed by Institute of Energy and Climate Research (IEK-9), Forschungszentrum Jülich GmbH. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Hao, Langer, Xiao, Kegler, Cao, Hu, Eichel, Wang and Alekseev.)

Solid-state sintering at high temperatures is commonly used to densify solid electrolytes. Yet, optimizing phase purity, structure, and grain sizes of solid electrolytes is challenging due to the lack of understanding of relevant processes during sintering. Here, we use an in situ environmental scanning electron microscopy (ESEM) to monitor the sintering behavior of NASICON-type Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 (LATP) at low environmental pressures. Our results show that while no major morphological changes are observed at 10 -2 Pa and only coarsening is induced at 10 Pa, environmental pressures of 300 and 750 Pa lead to the formation of typically sintered LATP electrolytes. Furthermore, the use of pressure as an additional parameter in sintering allows the grain size and shape of electrolyte particles to be controlled., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)

Li 7 La 3 Zr 2 O 12 (LLZO)-based all-solid-state Li batteries (SSLBs) are very attractive next-generation energy storage devices owing to their potential for achieving enhanced safety and improved energy density. However, the rigid nature of the ceramics challenges the SSLB fabrication and the afterward interfacial stability during electrochemical cycling. Here, a promising LLZO-based SSLB with a high areal capacity and stable cycle performance over 100 cycles is demonstrated. In operando transmission electron microscopy (TEM) is used for successfully demonstrating and investigating the delithiation/lithiation process and understanding the capacity degradation mechanism of the SSLB on an atomic scale. Other than the interfacial delamination between LLZO and LiCoO 2 (LCO) owing to the stress evolvement during electrochemical cycling, oxygen deficiency of LCO not only causes microcrack formation in LCO but also partially decomposes LCO into metallic Co and is suggested to contribute to the capacity degradation based on the atomic-scale insights. When discharging the SSLB to a voltage of ≈1.2 versus Li/Li + , severe capacity fading from the irreversible decomposition of LCO into metallic Co and Li 2 O is observed under in operando TEM. These observations reveal the capacity degradation mechanisms of the LLZO-based SSLB, which provides important information for future LLZO-based SSLB developments., (© 2022 The Authors. Advanced Science published by Wiley-VCH GmbH.)

With the ever-increasing use of Li-ion batteries, especially due to their adoption in electric vehicles, their safety is in prime focus. Thus, the all-solid-state batteries (ASSBs) that use solid electrolytes instead of liquid electrolytes, which reduce the risk of flammability, have been the center stage of battery research for the last few years. However, in the ASSB, the ion transportation through the solid-solid electrolyte-electrode interface poses a challenge due to contact and chemical/electrochemical stability issues. Applying a suitable coating around the electrode and/or electrolyte particles offers a convenient solution, leading to better performance. For this, researchers are screening potential electronic/ionic conductive and nonconductive coatings to find the best coatings with suitable thickness for long-term chemical, electrochemical, and mechanical stability. Operando transmission electron microscopy (TEM) couples high spatial resolution with high temporal resolution to allow visualization of dynamic processes, and thus is an ideal tool to evaluate electrode/electrolyte coatings via studying (de)lithiation at a single particle level in real-time. However, the accumulated electron dose during a typical high-resolution in situ work may affect the electrochemical pathways, evaluation of which can be time-consuming. The current protocol presents an alternative procedure in which the potential coatings are applied on Si nanoparticles and are subjected to (de)lithiation during operando TEM experiments. The high volume changes of Si nanoparticles during (de)lithiation allow monitoring of the coating behavior at a relatively low magnification. Thus, the whole process is very electron-dose efficient and offers quick screening of potential coatings.

A Pt-nanoparticle-decorated 1T-MoS 2 layer is designed as a sacrificial electrocatalyst by carbothermal shock (CTS) treatment to improve the energy efficiency and lifespan of seawater batteries. The phase transition of MoS 2 crystals from 2H to metallic 1T─induced by the simple but potent CTS treatment─improves the oxygen-reduction-reaction (ORR) activity in seawater catholyte. In particular, the MoS 2 -based sacrificial catalyst effectively decreases the overpotential during charging via edge oxidation of MoS 2 , enhancing the cycling stability of the seawater battery. Furthermore, Pt nanoparticles are deposited onto CTS-MoS 2 via an additional CTS treatment. The resulting specimen exhibits a significantly low charge/discharge potential gap of Δ0.39 V, high power density of 6.56 mW cm -2 , and remarkable cycling stability up to ∼200 cycles (∼800 h). Thus, the novel strategy reported herein for the preparation of Pt-decorated 1T-MoS 2 by CTS treatment could facilitate the development of efficient bifunctional electrocatalysts for fabricating seawater batteries with long service life.

Silicon (Si) is an attractive anode material for Li-ion batteries (LIBs) due to its high theoretical specific capacity. However, the solid-electrolyte interphase (SEI) formation, caused by liquid electrolyte decomposition, often befalls Si electrodes. The SEI layer is less Li-ion conductive, which would significantly inhibit Li-ion transport and delay the reaction kinetics. Understanding the interaction between the SEI components and Li-ion diffusion is crucial for further improving the cycling performance of Si. Herein, different liquid electrolytes are applied to investigate the induced SEI components, structures, and their role in Li-ion transport. It is found that Si electrodes exhibit higher discharge capacities in LiClO 4 -based electrolytes than in LiPF 6 -based electrolytes. This behavior suggests that a denser and more conductive SEI layer is formed in LiClO 4 -based electrolytes. In addition, a coating of a Li 3 PO 4 artificial SEI layer on Si suppresses the formation of natural SEI formation, leading to higher capacity retentions. Furthermore, galvanostatic intermittent titration technique (GITT) measurements are applied to calculate Li-ion diffusion coefficients, which are found in the range of 10 -23 -10 -19 m 2 /s., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)

Liquid phase transmission electron microscopy (TEM) provides a useful means to study a wide range of dynamics in solution with near-atomic spatial resolution and sub-microsecond temporal resolution. However, it is still a challenge to control the chemical environment (such as the flow of liquid, flow rate, and the liquid composition) in a liquid cell, and evaluate its effect on the various dynamic phenomena. In this work, we have systematically demonstrated the flow performance of an in situ liquid TEM system, which is based on 'on-chip flow' driven by external pressure pumps. We studied the effects of different chemical environments in the liquid cell as well as the electrochemical potential on the deposition and dissolution behavior of Cu crystals. The results show that uniform Cu deposition can be obtained at a higher liquid flow rate (1.38 μ l min -1 ), while at a lower liquid flow rate (0.1 μ l min -1 ), the growth of Cu dendrites was observed. Dendrite formation could be further promoted by in situ addition of foreign ions, such as phosphates. The generality of this technique was confirmed by studying Zn electrodeposition. Our direct observations not only provide new insights into understanding the nucleation and growth but also give guidelines for the design and synthesis of desired nanostructures for specific applications. Finally, the capability of controlling the chemical environment adds another dimension to the existing liquid phase TEM technique, extending the possibilities to study a wide range of dynamic phenomena in liquid media., (© 2022 IOP Publishing Ltd.)

The development of highly selective adsorbents for CO 2 is a key part to advance separation by adsorption as a viable technique for CO 2 capture. In this work, polyacrylonitrile (PAN) based carbon nanofibers (CNFs) were investigated for their CO 2 separation capabilities using dynamic gas adsorption. The CNFs were prepared by electrospinning and subsequent carbonization at various temperatures ranging from 600 to 1000 °C. A thorough investigation of the CO 2 /N 2 selectivity resulted in measured values of 53-106 at 1 bar and 25 °C on CNFs carbonized at 600, 700, or 800 °C. Moreover, the selectivity increased with lower measurement temperatures and lower CO 2 partial pressures, reaching values up to 194. Further analysis revealed high long-term stability with no degradation over 300 cycles and fast adsorption kinetics for CNFs carbonized at 600 or 700 °C. These excellent properties make PAN-based CNFs carbonized at 600 or 700 °C promising candidates for the capture of CO 2 ., (© 2022 The Authors. ChemSusChem published by Wiley-VCH GmbH.)

The electrochemical carbon dioxide reduction on copper attracted considerable attention within the last decade, since Cu is the only elemental transition metal that catalyses the formation of short-chain hydrocarbons and alcohols. Research in this field is mainly focused on understanding the reaction mechanism in terms of adsorbates and intermediates. Furthermore, dynamic changes in the micro-environment of the catalyst, i.e. local pH and [Formula: see text] concentration values, play an equivalently important role in the selectivity of product formation. In this study, we present an in operando [Formula: see text] nuclear magnetic resonance technique that enables the simultaneous measurement of pH and [Formula: see text] concentration in electrode vicinity during electroreduction. The influence of applied potential and buffer capacity of the electrolyte on the formation of formate is demonstrated. Theoretical considerations are confirmed experimentally and the importance of the interplay between catalyst and electrolyte is emphasised., (© 2022. The Author(s).)

High interfacial resistance and unstable interphase between cathode active materials (CAMs) and solid-state electrolytes (SSEs) in the composite cathode are two of the main challenges in current all-solid-state batteries (ASSBs). In this work, the all-phosphate-based LiFePO 4 (LFP) and Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 (LATP) composite cathode is obtained by a co-firing technique. Benefiting from the densified structure and the formed redox-active Li 3- x Fe 2- x - y Ti x Al y (PO 4 ) 3 (LFTAP) interphase, the mixed ion- and electron-conductive LFP/LATP composite cathode facilitates the stable operation of bulk-type ASSBs in different voltage ranges with almost no capacity degradation upon cycling. Particularly, both the LFTAP interphase and LATP electrolyte can be activated. The cell cycled between 4.1 and 2.2 V achieves a high reversible capacity of 2.8 mAh cm -2 (36 µA cm -2 , 60 °C). Furthermore, it is demonstrated that the asymmetric charge/discharge behaviors of the cells are attributed to the existence of the electrochemically active LFTAP interphase, which results in more sluggish Li + kinetics and more expansive LFTAP plateaus during discharge compared with that of charge. This work demonstrates a simple but effective strategy to stabilize the CAM/SSE interface in high mass loading ASSBs., (© 2022 The Authors. Small published by Wiley-VCH GmbH.)

Supporting electrolytes contain inert dissolved salts to increase the conductivity, to change microenvironments near the electrodes and to assist in electrochemical reactions. This combined experimental and computational study examines the impact of supporting salts on the ion transport and related limited currents in electrochemical cells. A physical model that describes the multi-ion transport in liquid electrolytes and the resulting concentration gradients is presented. This model and its parameterization are evaluated by the measured limited current of the copper deposition in a CuSO 4 electrolyte under a gradually increasing amount of Na 2 SO 4 that acts as a supporting salt. A computational sensibility analysis of the transport model reveals that the shared conductance between the ions lowers the limited currents with larger supporting salt concentrations. When the supporting salt supplies most of the conductance, the electric-field-driven transport of the electrochemically active ions becomes negligible so that the limited current drops to the diffusion-limited current that is described by Fick's first law. The transition from diluted supporting electrolyte to the case of ionic liquids is elucidated with the transport model, highlighting the different physical transport mechanisms in a non-conducting (polar) and a conducting (ionic) solvent., (© 2022. The Author(s).)

Conformal coating of silicon (Si) anode particles is a common strategy for improving their mechanical integrity, to mitigate battery capacity fading due to particle volume expansion, which can result in particle crumbling due to lithiation induced strain and excessive solid-electrolyte interface formation. Here, we use operando transmission electron microscopy in an open cell to show that TiO 2 coatings on Si/SiO 2 particles undergo thickness dependent rupture on battery cycling where thicker coatings crumble more readily than thinner (∼5 nm) coatings, which corroborates the difference in their capacities.

Pseudocapacitances such as the hydrogen adsorption on platinum (HAoPt) are associated with faradaic chemical processes that appear as capacitive in their potentiodynamic response, which was reported to result from the kinetics of adsorption processes. This study discusses an alternative interpretation of the partly capacitive response of the HAoPt that is based on the proton transport of ad- or desorbed hydrogen in the double layer. Potentiodynamic perturbations of equilibrated surface states of the HAoPt lead to typical double layer responses with the characteristic resistive-capacitive relaxations that overshadow the fast adsorption kinetics. A potential-dependent double layer representation by a dynamic transmission line model incorporates the HAoPt in terms of capacitive contributions and can computationally reconstruct the charge exchanged in full range cyclic voltammetry data. The coupling of charge transfer with double layer dynamics displays a novel physicochemical theory to explain the phenomenon of pseudocapacitance and the mechanisms in thereon based supercapacitors., (© 2022. The Author(s).)

The interface between ceramic particles and a polymer matrix in a hybrid electrolyte is studied with high spatial resolution by means of Electrochemical Strain Microscopy (ESM), an Atomic Force Microscope (AFM)-based technique. The electrolyte consists of polyethylene oxide with lithium bis(trifluoromethanesulfonyl)imide (PEO 6 -LiTFSI) and Li 6.5 La 3 Zr 1.5 Ta 0.5 O 12 (LLZO:Ta). The individual components are differentiated by their respective contact resonance, ESM amplitude and friction signals. The ESM signal shows increased amplitudes and higher contact resonance frequencies on the ceramic particles, while lower amplitudes and lower contact resonance frequencies are present on the bulk polymer phase. The amplitude distribution of the hybrid electrolyte shows a broader distribution in comparison to pure PEO 6 -LiTFSI. In the direct vicinity of the particles, an interfacial area with enhanced amplitude signals is found. These results are an important contribution to elucidate the influence of the ceramic-polymer interaction on the conductivity of hybrid electrolytes.

Choline-based electrolytes have been proposed as environmentally friendly and low-cost alternatives for secondary zinc air batteries. Choline acetate [Ch] + [OAc] - in protic (D 2 O) and aprotic (DMSO-d 6 ) solvents has been studied by means of concentration-dependent 1 H NMR, viscosity, and density measurements. The viscosities have been calculated on the basis of the Jones-Dole equation and showed that the dominant contribution originates from short-range ion-solvent interactions. Site-specific association affinities were assigned from NMR chemical shift titrations. In DMSO-d 6 , the hydroxyl group of choline was found to have the smallest dissociation constant followed by the methyl group of acetate. The corresponding Gibbs energies at low concentration were found to be in agreement with a solvent-separated ion pair (2SIP) configuration, whereas at concentrations above 300 mM, a solvent-shared ion pair (SIP) configuration was assigned. For [Ch] + [OAc] - in D 2 O, association effects were found to be weaker, attributed to the high dielectric constant of the solvent. On time scales on the order of 100 ms, NMR linewidth perturbations indicated a change in the local rotational dynamics of the ions, attributed to short-range cation-solvent interactions and not to solvent viscosity. At 184 mM, ∼ 40 % of the cations in DMSO-d 6 and ∼ 10 % in D 2 O were found to exhibit short-range interactions, as indicated by the linewidth perturbations. It was found that at about 300 mM, the ions in DMSO-d 6 exhibit a transition from free to collective translational dynamics on time scales on the order of 400 ms. In DMSO-d 6 , both ions were found to be almost equally solvated, whereas in D 2 O solvation of acetate was stronger, as indicated by the obtained effective hydrodynamic radii. For [Ch] + [OAc] - in DMSO-d 6 , the results suggest a solvent-shared ion association with weak H-bonding interactions for concentrations between 0.3-1 M. Overall, the extent of ion association in solvents such as DMSO is not expected to significantly limit charge transport and hinder the performance of choline-based electrolytes., (© 2021 The Authors. ChemPhysChem published by Wiley-VCH GmbH.)

The fast Li + transportation of "polymer-in-ceramic" electrolytes is highly dependent on the long-range Li + migration pathways, which are determined by the structure and chemistry of the electrolytes. Besides, Li dendrite growth may be promoted in the soft polymer region due to the inhomogeneous electric field caused by the commonly low Li + transference number of the polymer. Herein, a single-ion-conducting polymer electrolyte is infiltrated into intertwined Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 (LATP) nanofibers to construct free-standing electrolyte membranes. The composite electrolyte possesses a large electrochemical window exceeding 5 V, a high ionic conductivity of 0.31 mS cm -1 at ambient temperature, and an extraordinary Li + transference number of 0.94. The hybrid electrolyte in the lithium symmetric cell shows stable Li plating/stripping up to 2000 h under 0.1 mA cm -2 without dendrite formation. The Li|hybrid electrolyte|LiFePO 4 battery exhibits enhanced rate capability up to 1 C and a stable cycling performance with an initial discharge capacity of 131.8 mA h g -1 and a retention capacity of 122.7 mA h g -1 after 500 cycles at 0.5 C at ambient temperature. The improved electrochemical performance is attributed to the synergistic effects of the LATP nanofibers and the single-ion-conducting polymer. The fibrous fast ion conductors provide continuous ion transport channels, and the polymer improves the interfacial contact with the electrodes and helps to suppress the Li dendrites.

Lithium titanium phosphate LiTi 2 (PO 4 ) 3 is an electrode material for lithium-ion batteries with a specific capacity of 138 mA h g -1 . Owing to its potential of 2.5 V vs. Li/Li + it provides an electrochemically stable interface when used as an anode in all-solid state batteries with NASICON type lithium aluminium titanium phosphate electrolyte. High performance has been identified for in situ carbon coated LiTi 2 (PO 4 ) 3 synthesized via a hydrothermal route, resulting in micro-scaled spindle shaped particles consisting of nano-scaled sub-particles. To elucidate the internal microstructure of these spindle-like particles in three dimensions we applied tomographic Focused Ion Beam - Scanning Electron Microscopy. For more detailed chemical analysis we performed electron-energy loss spectroscopy and energy dispersive X-ray spectroscopy in the scanning electron microscope as well as high resolution (scanning) transmission electron microscopy for structural insight. It could be clearly shown that the spindle-like particles mainly are made up of LiTi 2 (PO 4 ) 3 sub-particles in the 100 to 400 nm range. Additionally, two types of secondary phase materials were identified. LiTiOPO 4 , which shows different surface morphology, as a volume component of the spindles and TiO 2 nanoparticles (anatase), which are not only present at the particle surface but also inside the spindle, were detected. Reconstruction from tomography reveals the nanoparticles form a three-dimensionally interconnected network even though their phase fraction is low., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

An innovative approach for the design of air electrodes for metal-air batteries are free-standing scaffolds made of electrospun polyacrylonitrile fibres. In this study, cobalt-decorated fibres are prepared, and the influence of carbonisation temperature on the resulting particle decoration, as well as on fibre structure and morphology is discussed. Scanning electron microscopy, Raman spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, elemental analysis, and inductively coupled plasma optical emission spectrometry are used for characterisation. The modified fibre system is compared to a benchmark system without cobalt additives. Cobalt is known to catalyse the formation of graphite in carbonaceous materials at elevated temperatures. As a result of cobalt migration in the material the resulting overall morphology is that of turbostratic carbon. Nitrogen removal and nitrogen-type distribution are enhanced by the cobalt additives. At lower carbonisation temperatures cobalt is distributed over the surface of the fibres, whereas at high carbonisation temperatures it forms particles with diameters up to 300 nm. Free-standing, current-collector-free electrodes assembled from carbonised cobalt-decorated fibre mats display promising performance for the oxygen reduction reaction in aqueous alkaline media. High current densities at an overpotential of 100 mV and low overpotentials at current densities of 333 μA·cm -2 were found for all electrodes made from cobalt-decorated fibre mats carbonised at temperatures between 800 and 1000 °C., (Copyright © 2021, Gehring et al.)

Polyacrylonitrile-based carbon nanofibers (PAN-based CNFs) have great potential to be used for carbon dioxide (CO 2 ) capture due to their excellent CO 2 adsorption properties. The porous structure of PAN-based CNFs originates from their turbostratic structure, which is composed of numerous disordered stacks of graphitic layers. During the carbonization process, the internal structure is arranged toward the ordered graphitic structure, which significantly influences the gas adsorption properties of PAN-based CNFs. However, the relation between structural transformation and CO 2 capture is still not clear enough to tune the PAN-based CNFs. In this paper, we show that, with increasing carbonization temperature, the arrangement of the PAN-based CNF's structure along the stack and lateral directions takes place independently: gradually aligning and merging along the stack direction and enlarging along the lateral direction. Further, we correlate the structural arrangement and the CO 2 adsorption properties of the PAN-based CNFs to propose a comprehensive structural mechanism. This mechanism provides the knowledge to understand and tailor the gas adsorption properties of PAN-based CNFs.

Routinely, cyclic voltammetry (CV) or electrochemical impedance spectroscopy (EIS) are used in electrochemistry to probe the current response of a specimen. For the interpretation of the response, constant phase elements (CPEs) are used in the frequency domain based impedance calculus to parameterize the double layer. In this study, the double layer responses to the two measurement techniques are compared by probing a model-type polished gold electrode under potential and amplitude variation. The equivalent circuit that describes the double layer includes a CPE and is parameterized by impedance data, while a computational impedance-based Fourier transform model (source code disclosed) is used to describe the CV response. With CV, the measured and modelled responses show good agreement at amplitudes below 0.2 V and within a certain scan rate window. At larger amplitudes, the ion arrangement in the double layer is actively changed by the measurement, leading to potential dependencies and deviations from the CPE behaviour. These varying contributions to the impedance measurements are not respected in the impedance calculus that relies on a sinusoidal response. The transition from perturbations of the double layer equilibrium to distortions of the ion arrangements is analysed with both measurement methods.

Developing high-performance Fe-based ammonia catalysts through simple and cost-efficient methods has received an increased level of attention. Herein, we report for the first time, the synthesis of two-dimensional (2D) FeOOH nanoflakes encapsulated by mesoporous SiO 2 (mSiO 2 ) via a simple solution-based method for ammonia synthesis. Due to the sticking of the mSiO 2 coating layers and the limited spaces in between, the Fe after reduction retains the 2D morphology, showing high resistance against the sintering in the harsh Haber-Bosch process. Compared to supported Fe particles dispersed on mSiO 2 spheres, the coated catalyst shows a significantly improved catalytic activity by 50% at 425 °C. Thermal desorption spectroscopy (TDS) reveals the existence of a higher density of reactive sites for N 2 activation in the 2D Fe catalyst, which is possibly coupled to a larger density of surface defect sites (kinks, steps, point defects) that are generally considered as active centers in ammonia synthesis. Besides the structural impact of the coating on the 2D Fe, the electronic one is elucidated by partially substituting Si with Al in the coating, confirmed by 29 Si and 27 Al magic-angle spinning nuclear magnetic resonance (MAS NMR). An increased apparent activation energy ( E a ) of the Al-containing catalyst evidences an influence on the nature of the active site. The herein-developed stable 2D Fe nanostructures can serve as an example of a 2D material applied in catalysis, offering the chance of a rational catalyst design based on a stepwise introduction of various promoters, in the coating and on the metal, maintaining the spatial control of the active centers.