We present magnesium alginate as an aqueous polymer electrolyte for use in magnesium batteries. Alginates are polysaccharides extracted from algae, which form hydrogel materials upon interaction with divalent and trivalent cations. They are renewable, non-toxic, biocompatible materials that are widely used in the food and pharmaceutical industries. Mg2+ is weakly bound to an alginate polymer, which results in a hydrogel-like material that contains mobile magnesium ions. We propose that this is the ideal situation for an electrolyte that behaves in a similar way as a ‘water-in-salt’ system. Magnesium alginate was successfully synthesized and characterized by FTIR, XRD, and PDF. Ionic conductivity was measured with EIS measurements; a 2 wt% magnesium electrolyte shows a conductivity of 1.8 mS/cm. During conductivity experiments, we noticed the formation of a black layer on magnesium electrodes, which can improve the ionic conductivity between the electrodes. We carefully characterized this layer with XPS and saw that it mainly consists of alginate derivatives.@en

Ceramic membranes made of garnet Li7Zr3La2O12 (LLZO) are promising separators for lithium metal batteries because they are chemically stable to lithium metal and can resist the growth of lithium dendrites. Free-standing garnet separators can be produced on a large scale using tape casting and sintering slurries containing LLZO powder, but the quality of the separators is severely compromized by the protonation of the moisture-sensitive LLZO during processing and the irreversible loss of lithium during sintering. In this work, an approach is presented to mitigate the degradation of the LLZO and produce high quality separators using Li2CO3 as a source of excess lithium. By systematically investigating the effects of Li2CO3 addition during the different steps of the tape casting process and the intricate relationship between the protonation and relithiation of LLZO phase, the formation of highly protonated LLZO during ball milling was identified as the most critical step. It was shown that the addition of minimal amounts of Li2CO3 during wet milling effectively suppresses LLZO protonation and ensure the effectiveness of relithiation during subsequent sintering. Using this modified method, flat LLZO separators with a relative density of 95.3 % were prepared in a simplified process with a significantly reduced excess lithium of only 5 mol % with respect to the stoichiometric LLZO, exhibiting an ionic conductivity of 0.18 mS cm−1 at room temperature and a critical current density of 1 mA cm−2 at 60 °C for lithium stripping/plating.@en

The upcoming energy transition requires not only renewable energy sources but also novel electricity storage systems such as batteries. Despite Li-ion batteries being the main storage systems, other batteries have been proposed to fulfil the requirements on safety, costs, and resource availability. Moving away from lithium, materials such as sodium, magnesium, zinc, and calcium are being considered. Water-based electrolytes are known for their improved safety, environmentally friendliness, and affordability. The key, however, is how to utilize the negative metal electrode, as using water-based electrolytes with these metals becomes an issue with respect to oxidation and/or dendrite formation. This work studied magnesium, where we aimed to determine if it can be electrochemically deposited in aqueous solutions with alginate-based additives to protect the magnesium. In order to do so, atomic force microscopy was used to research the morphological structure of magnesium deposition at the local scale by using a probe—the tip of a cantilever—as the active electrode, during charging and discharging. The second goal of using the AFM probe technology for magnesium deposition and stripping was an extension of our previous study in which we investigated, for lithium, whether it is possible to measure ion current and perform nonfaradaic impedance measurements at the local scale. The work presented here shows that this is possible in a relatively simple way because, with magnesium, no dendrite formation occurs, which hinders the stripping process.

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We present a sustainable, inherently safe battery chemistry that is based on widely available and cheap materials, that is, iron and manganese hosted in alginate bio-material known from the food and medical industry. The resulting battery can be recycled to allow circularity. The electrodes were synthesised by the alginate caging the multi-valent metals to form a hydrogel in an aqueous environment. Characterisation includes FTIR, XPS and Mössbauer spectroscopy. The electrochemical performance of the electrodes was investigated by performing cyclic voltammetry (CV) and (dis)charge experiments. Mn and Fe ions show good co-ordination with the alginic acid with higher oxidation states demonstrating complex bonding behaviour. The non-optimised iron and manganese alginate electrodes already exhibit a cycling efficiency of 98% and 69%, respectively. This work shows that Fe and Mn atomically disperse in a bio-based host material and can act as electrodes in an aqueous battery chemistry. While demonstrated at cell level, it is furthermore explained how these materials can form the basis for a (semi-solid) flow cell.

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Here we present Positron Annihilation Doppler Broadening Spectroscopy (PADBS) as a powerful method to analyse the origin and development of defect processes in porous silicon structures as a result of alloying with lithium for the use in battery anode applications. Several prepared anodes were lithiated (discharged against Li⁺/Li) and de-lithiated (charged) with different capacities followed by a distinct treatment procedure and an analysis using the Delft Variable Energy Positron Beam. The results presented here show that we can distinguish two different processes attributed to (1) structural changes in silicon as a result of the alloying process, and (2) the formation of defects that initiate degradation of the material. The limit at which the porous material can be used for at least the first two cycles without the occurrence of damage can thus be accurately determined by using the PADBS technique.

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A novel protocol for the synthesis of perylene diimides (PDIs), by reacting perylene dianhydride (PDA) with aliphatic amines is reported. Full conversions were obtained at temperatures between 20 and 60 °C, using DBU as the base in DMF or DMSO. A "green"synthesis of PDIs, that runs at higher temperatures, was developed using K2CO3 in DMSO. The reaction sequence for the imidization process, via perylene amic acid intermediates (PAAs), has been confirmed experimentally aided by the synthesis and full characterization of stable model amic acid salts and amic esters. Kinetic studies, using absorption spectroscopy, have established that PDI formation proceeds via fast amic acid formation, followed by a slow conversion to imides. Solubility of the intermediate PAA salts is found to be low and rate-limiting. Based on this finding, quantitative PDI synthesis at room temperature was achieved by diluting the reaction mixture with water, the solvent in which PAA salts have better solubility. Thus, the otherwise harsh synthesis of PDIs has been transformed into an extremely convenient functional group tolerant and highly efficient reaction that runs at room temperature.

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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 TiO2 coatings on Si/SiO2 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.

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An Atomic Force Microscope (AFM) is combined with a special designed glovebox system and coupled to a Galvanostat/Potentiostat to allow measurements on electrochemical properties for battery research. An open cell design with electrical contacts makes it possible to reach the electrode surface with the cantilever so as to perform measurements during battery operation. A combined AFM-Scanning Electro-Chemical Microscopy (AFM-SECM) approach makes it possible to simultaneously obtain topological information and electrochemical activity. Several methods have been explored to provide the probe tip with an amount of lithium so that it can be used as an active element in a measurement. The “wet methods” that use liquid electrolyte appear to have significant drawbacks compared to dry methods, in which no electrolyte is used. Two dry methods were found to be best applicable, with one method applying metallic lithium to the tip and the second method forming an alloy with the silicon of the tip. The amount of lithium applied to the tip was measured by determining the shift of the resonance frequency which makes it possible to follow the lithiation process. A FEM-based probe model has been used to simulate this shift due to mass change. The AFM-Galvanostat/Potentiostat set-up is used to perform electrochemical measurements. Initial measurements with lithiated probes show that we are able to follow ion currents between tip and sample and perform an electrochemical impedance analysis in absence of an interfering Redox-probe. The active probe method developed in this way can be extended to techniques in which AFM measurements can be combined with mapping electrochemical processes with a spatial resolution.

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X-ray absorption and small-angle x-ray scattering spectra were simultaneously acquired under operando conditions in a joined technique approach, for the first time applied in the field of energy storage materials. This approach allows one to closely follow the electronic and local structure evolution, as well as monitor and quantify the morphological and nanostructural changes occurring during electrochemical cycling. Here we demonstrate its potential on the example of doped and non-doped Fe₂O₃ anode material vs. Li. Our results reveal that upon discharge Fe³⁺ is gradually reduced to the metallic state and segregated as nanoparticles. For the relithiation reaction, upon subsequent charge, we observe improved reversibility for the Sr-doped compared to non-doped and Ca-doped Fe₂O₃. We highlight that this combined technique approach is a reliable, facile and powerful tool to investigate electrode materials under realistic cycling condition. It provides an unbiased and holistic picture of the morphological and structural changes occurring during operation, which allows for adequate material tailoring.

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Developing multifunctional polymeric binders is key to the design of energy storage technologies with value-added features. We report that a multigram-scale synthesis of perylene diimide polymer (PPDI), from a single batch via polymer analogous reaction route, yields high molecular weight polymers with suitable thermal stability and minimized solubility in electrolytes, potentially leading to improved binding affinity toward electrode particles. Further, it develops strategies for designing copolymers with virtually any desired composition via a subsequent grafting, leading to purpose-built binders. PPDI dye as both binder and electroactive additive in lithium half-cells using lithium iron phosphate exhibits good electrochemical performance.

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High-fidelity and facile ex situ transmission electron microscopy (TEM) characterization of lithium−oxygen (Li−O₂) batteries is still limited by challenges in preserving the native environment of Li−O₂ discharge products. The extreme reactivity and moisture sensitivity of the discharge products means that they are quickly altered during sample retrieval from cycled batteries and transfer for TEM analysis, resulting in loss of original information. We here demonstrate that by using a TEM specimen grid directly in Li−O₂ batteries as both support electrode and sample collector overlaid on a standard oxygen diffusion electrode, discharge products that are formed on the grid can be kept pristine.

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With operando transmission electron microscopy visualizing the solid-solid electrode-electrolyte interface of silicon active particles and lithium oxide solid electrolyte as a model system, we show that (de)lithiation (battery cycling) does not require all particles to be in direct contact with electrolytes across length scales of a few hundred nanometers. A facile lithium redistribution that occurs between interconnected active particles indicates that lithium does not necessarily become isolated in individual particles due to loss of a direct contact. Our results have implications for the design of all-solid-state battery electrodes with improved capacity retention and cyclability. ©

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All-solid-state Li-ion batteries promise safer electrochemical energy storage with larger volumetric and gravimetric energy densities. A major concern is the limited electrochemical stability of solid electrolytes and related detrimental electrochemical reactions, especially because of our restricted understanding. Here we demonstrate for the argyrodite-, garnet- and NASICON-type solid electrolytes that the favourable decomposition pathway is indirect rather than direct, via (de)lithiated states of the solid electrolyte, into the thermodynamically stable decomposition products. The consequence is that the electrochemical stability window of the solid electrolyte is notably larger than predicted for direct decomposition, rationalizing the observed stability window. The observed argyrodite metastable (de)lithiated solid electrolyte phases contribute to the (ir)reversible cycling capacity of all-solid-state batteries, in addition to the contribution of the decomposition products, comprehensively explaining solid electrolyte redox activity. The fundamental nature of the proposed mechanism suggests this is a key aspect for solid electrolytes in general, guiding interface and material design for all-solid-state batteries.

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The unique capability of TEM to resolve the microstructural and chemical evolution of electrode materials during battery operation at high temporal and spatial resolution makes it the method of choice for operando battery experiments. However, the widely used open-cell setup, that uses oxidized lithium as the electrolyte due to its inherent design, does not allow Li-ions to be (de)inserted from every part of the electrode particle, which imposes restrictions on the (de)intercalation process. This may lead to the formation of a mechanistic hypothesis based on incomplete information about the (de)lithiation of the electrode material under investigation. Using LiFePO₄ as a model electrode material we propose here a MEMS based cell-on-a-chip design comprising of a thin coating of amorphous electrolyte, which can be utilized to overcome the said issue.

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The global quest for intermittent renewable energy sources (wind, solar), consumer goods (mobile phones, notebooks), and electrification of the transport sector (electric vehicles), requires a strong increase in the use of rechargeable energy storages devices, such as batteries. Hence, novel types of rechargeable batteries are to be found that are cost-effective, consist of environmentally friendly materials and non-critical materials, and deliver a high performance in terms of energy density and power, during a long cycle and service life, taking current legislation laws into account. Here we concentrate on various types of batteries and their materials, their typical sectors of application, and their forecast, including potential market share. It turns out that metals will still remain the predominant type of battery material, irrespective of the choice of battery system. From the required materials that are important for future rechargeable batteries, a number are critical in terms of scarcity, geopolitics, supply risk, competition with the food industry, carbon footprint, and/or ethical mining. With respect to the critical elements, particularly once those concern scarcity and supply risks, recycling is of utmost relevance, and needs to be regarded as an industrial sector of paramount importance.@en

To this day, elucidating the charge transfer process in electrode materials upon electrochemical cycling remains a challenge, primarily due to the complexity of chemical reactions at the electrode surfaces. Here, we present an elegant and reliable method to probe bulk-sensitive soft edges for elucidating anodic and cathodic charge compensation contribution via X-ray Raman scattering spectroscopy. By using a hard X-ray incident beam, this technique circumvents surface limitations and is practically free of self-absorption due to its nonresonant nature. In addition, it does not require complex sample preparation or experimental setups, making it an ideal tool for potential in situ analysis of the electronic structure of electrode materials. In this study, we monitored, for the first time, bulk soft edges of both oxygen and transition metal (iron) of the cathode material Li₂FeSiO₄ during one complete electrochemical cycle concurrently. Our results reveal that the redox mechanism relies primarily on the iron (cathodic) contribution. Nevertheless, a change in electron confinement of the oxygen suggests its active involvement in the charge compensation process (anodic). Moreover, we were able to support the experimentally observed changes in the electronic structure with ab initio-based simulation.

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The high Li-ion conductivity of the Li₇P₃S₁₁ sulfide-based solid electrolyte makes it a promising candidate for all-solid-state lithium batteries. The Li-ion transport over electrode-electrolyte and electrolyte-electrolyte interfaces, vital for the performance of solid-state batteries, is investigated by impedance spectroscopy and solid-state NMR experiments. An all-solid-state Li-ion battery is assembled with the Li₇P₃S₁₁ electrolyte, nano-Li₂S cathode and Li-In foil anode, showing a relatively large initial discharge capacity of 1139.5 mAh/g at a current density of 0.064 mA/cm² retaining 850.0 mAh/g after 30 cycles. Electrochemical impedance spectroscopy suggests that the decrease in capacity over cycling is due to the increased interfacial resistance between the electrode and the electrolyte. 1D exchange ⁷Li NMR quantifies the interfacial Li-ion transport between the uncycled electrode and the electrolyte, resulting in a diffusion coefficient of 1.70(3)⋅10⁻¹⁴ cm²/s at 333 K and an energy barrier of 0.132 eV for the Li-ion transport between Li₂S cathode and Li₇P₃S₁₁ electrolyte. This indicates that the barrier for Li-ion transport over the electrode-electrolyte interface is small. However, the small diffusion coefficient for Li-ion diffusion between the Li₂S and the Li₇P₃S₁₁ suggests that these contact interfaces between electrode and electrolyte are relatively scarce, challenging the performance of these solid-state batteries.

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The Sulfonated Poly (Ether Ether Ketone) (sPEEK) is used in many of the developments of polymer electrolyte membranes for fuel cells. In this publication, it is proven that the water in the sPEEK membrane creates channels in the sulfonated clusters by interacting with the sulfonic groups, and changing the glass transition temperature (Tg) of the material. It is shown that, for conductivity, apart from water in the membrane, order is needed in the water channels because it has an impact on how fast the protons pass through the membrane. This research focuses on how various thermal treatment, performed under a pre-stated conditioning; allow the free alignment of the inner phases, influencing their order. It is demonstrated how is possible to use of differential calorimetry, dielectric measurements and X-ray to follow these changes, and how to used Broadband Dielectric Spectroscopy to forecast the most optimal and stable thermal treatment for the highest proton conduction in sPEEK. The methodology is also test successfully on a hybrid sPEEK/Boron Phosphate membrane.

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We developed a dedicated Atomic Force Microscopy set-up in a hermetically closed environment, coupled with a Galvanostat/Potentiostat which will be able to perform in-situ and operando measurements at the cathode-electrolyte and anode-electrolyte interface to monitor the interphase processes. The setup was tested in first measurements to prove the abilities for monitoring changes in morphology, impedance, and performing a combination of AFM-SECM for operando monitoring redox processes. First results of operando Atomic Force Microscopy will be presented in this paper to indicate the possibilities of the new build facility for visualising the forming of the Solid Electrolyte Interphase (SEI), which proved to be responsible for the most important ageing meganisms, and thus the cycle and calendar life of the battery. The measurements proved the possibilities of the setup to monitor SEI processes operando and visualizing impedance distribution on cathode-electrolyte and anode-electrolyte interfaces.

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A successful sol-gel process to encapsulate molybdenum di-silicide MoSi₂ particles with a closed and thermally stable Al₂O₃ layer using aluminium tri-sec-butoxide as a precursor is presented. The processing conditions such as precursor selection and temperature were optimized through analysing the interaction of the MoSi₂ particles with the sol. The application of the sol-gel based coating was followed by calcining the coated particles at temperatures between 900 and 1200 °C in Ar. The shell composition and the mechanical stability of the microcapsule were analysed by means of X-ray diffraction, scanning electron microscopy and thermogravimetric analysis. Upon calcining at 1200 °C in Ar, the MoSi₂ core remains intact as it is, covered by an α - alumina shell with a thickness of about 0.6 μm. The stability tests proved that the encapsulate particles are about five times more oxidation resistant than the uncoated MoSi₂ particles.

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