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Internal resistance of lithium-sulfur batteries was investigated with impedance spectroscopy. In order to understand the effect of various common solvents for Li-S battery preparation, the electrolyte in the cells was varied (ionic liquid [DEME][TFSI], sulfolane or TEGDME solvent). The impedance changes were followed at several points during discharge and charge of the batteries and through 50 cycles of their use. The resulting spectra were analyzed and fitted, extracting information on four different impedance contribution. The contributions were assigned to the electrolyte, anode or cathode. Their change through a single cycle and through multiples cycles of battery use was evaluated as well as compared between cells employing different electrolytes.

Nasl. z nasl. zaslona. Opis vira z dne 23. 1. 2023. Bibliografija: str. 62-63. Abstract.

Ca metal anode rechargeable batteries are seen as a sustainable high-energy density and high-voltage alternative to the current Li-ion battery technology due to the low redox potential of Ca metal...

Aqueous zinc-ion batteries are one of the most promising candidates for large-scale energy storage applications.

Final exploitation plan

Final report on the electrochemical and mechanistic studies of prepared carbonaceous and composite materials

Resumen del trabajo presentado a la XXXVIII Reunión Bienal de la Real Sociedad Española de Química, celebrada en el Palacio de Congresos de Granada, del 27 de junio al 30 de junio de 2022., Authors acknowledge the M-ERA.NET (NOEL) project, PCI2019-103637 funded by MCIN/AEI/10.13039/501100011033.

Insufficient understanding of the mechanism that reversibly converts sulfur into lithium sulfide (Li2S) via soluble polysulfides (PS) hampers the realization of high performance lithium-sulfur (Li-S) cells. Typically Li2S formation is explained by direct electroreduction of a PS to Li2S; however, this is not consistent with the size and shape of the insulating Li2S deposits. Here, we use operando small and wide angle X-ray scattering (SAXS/WAXS) and operando small angle neutron scattering (SANS) to track the growth and dissolution of solid deposits from atomic to sub-micron scales during charge and discharge. Stochastic modelling based on the SANS data allows quantification of the chemical phase evolution during discharge and charge. We show that the deposit is comprised of nanocrystalline Li2S and smaller, solid short-chain PS particles, which we argue are likely Li2S2. Our data are consistent with solid Li2S2 precipitating from solution and then being converted in the solid-state to Li2S, probably via direct electroreduction and chemical diffusion through the Li2S2 particle network. Solution-mediated Li2S2 precipitation, therefore, controls the Li2S/Li2S2 aggregate structure. Discharge capacity and rate capability in Li-S battery cathodes are limited by mass transport rather than electron transport through a thin passivating surface film. The found mechanism also explains why in practice not all S is converted to Li2S; a certain amount of Li2S2 remains as a second solid phase.

High-performance electrolytes are at the heart of magnesium battery development. Long-term stability along with the low potential difference between plating and stripping processes are needed to consider them for next-generation battery devices. Within this work, we perform an in-depth characterization of the novel Mg[Al(hfip)$_4$]$_2$ salt in different glyme-based electrolytes. Specific importance is given to the influence of water content and the role of additives in the electrolyte. Mg[Al(hfip)$_4$]$_2$-based electrolytes exemplify high tolerance to water presence and the beneficial effect of additives under aggravated cycling conditions. Finally, electrolyte compatibility is tested with three different types of Mg cathodes, spanning different types of electrochemical mechanisms (Chevrel phase, organic cathode, sulfur). Benchmarking with an electrolyte containing a state-of-the-art Mg[B(hfip)$_4$]$_2$ salt exemplifies an improved performance of electrolytes comprising the Mg[Al(hfip)$_4$]$_2$ salt and establishes Mg[Al(hfip)$_4$]$_2$ as a new standard salt for the future Mg battery research.

Insufficient understanding of the mechanism that reversibly converts sulfur into lithium sulfide (Li2S) via soluble polysulfides (PS) hampers the realization of high performance lithium-sulfur (Li-S) cells. Typically Li2S formation is explained by direct electroreduction of a PS to Li2S; however, this is not consistent with the size and shape of the insulating Li2S deposits. Here, we use operando small and wide angle X-ray scattering (SAXS/WAXS) and operando small angle neutron scattering (SANS) to track the growth and dissolution of solid deposits from atomic to sub-micron scales during charge and discharge. Stochastic modelling based on the SANS data allows quantification of the chemical phase evolution during discharge and charge. We show that the deposit is comprised of nanocrystalline Li2S and smaller, solid short-chain PS particles, which we argue are likely Li2S2. Our data are consistent with solid Li2S2 precipitating from solution and then being converted in the solid-state to Li2S, probably via direct electroreduction and chemical diffusion through the Li2S2 particle network. Solution-mediated Li2S2 precipitation, therefore, controls the Li2S/Li2S2 aggregate structure. Discharge capacity and rate capability in Li-S battery cathodes are limited by mass transport rather than electron transport through a thin passivating surface film. Capacity and rate capability are thus influenced by are species solvation, mobility, and applied current density. The found mechanism also explains why in practice not all S is converted to Li2S; a certain amount of Li2S2 remains as a second solid phase.

Commercial LiMn2O4 powder was used as the base material for probing magnesiation, cycling behavior, and structural stability/changes in (MgxLi1-x)Mn2O4 spinel cathodes in aqueous Mg(NO3)2 and non-aqueous Mg(TFSI)2/diglyme and Mg(Mg(HFIP)2 − 2Al(HFIP)3/diglyme electrolytes. Each of the samples was delithiated and, then, magnesiated electrochemically in the corresponding electrolyte. The electrochemical activity of the cathode cycled in aqueous electrolyte showed high reversibility during the oxidation process, however, large polarization and a relatively fast capacity fading were the culprits of the system. Cycling in Mg(TFSI)2/diglyme electrolyte solution resulted in much lower initial specific capacity compared to an aqueous counterpart, as well as a much faster failure. On the other hand, cycling in Mg(HFIP)2 − 2Al(HFIP)3/diglyme electrolyte solution demonstrated excellent cycling performance with very low polarization in the first cycles. The observed voltages for this system were near theoretical values for the Mg insertion. Although the electrochemical measurements suggest reversible magnesiation, detailed structural and analytical STEM investigation revealed the differences in the atomic structure and Mn valence of all three cathode samples upon cycling. The electrolytes’ influence on the structural rearrangement during Mg insertion is discussed for each of the three systems.

Insights into the electrochemical processes occurring at the electrode-electrolyte interface are a crucial step in most electrochemistry domains and in particular in the optimization of the battery technology. However, studying potential-dependent processes at the interface is one of the biggest challenges, both for theoreticians and experimentalists. The challenge is pushed further when stable species also depend on the concentration of specific ligands in the electrolyte, such as chlorides. Herein, we present a general theoretical ab initio methodology to compute a Pourbaix-like diagram of complex electrolytes as a function of electrode potential and anion's chemical potential, that is, concentration. This approach is developed not only for the bulk properties of the electrolytes but also for electrode-electrolyte interfaces. In the case of chlorinated magnesium complexes in dimethoxyethane, we show that the stability domains of the different species are strongly shifted at the interface compared to the bulk of the electrolyte because of the strong local electric fields and charges occurring in the double layer. Thus, as the interfacial stability domains are strongly modified, this approach is necessary to investigate all interface properties that often govern the reaction kinetics, such as solvent degradation at the electrode. Interface Pourbaix diagram is used to give some insights into the improved stability at the Mg anode induced by the addition of chloride. Because of its far-reaching insights, transferability, and wide applicability, the methodology presented herein should serve as a valuable tool not only for the battery community but also for the wider electrochemical one.

We report on a detailed structural versus electrochemical property investigation of the corncob-derived non-graphitizable carbons prepared at different carbonization temperatures using a combination of structural characterization methodology unique to this field. Non-graphitizable carbons are currently the most viable option for the negative electrode in sodium-ion batteries. However, many challenges arise from the strong dependence of the precursor’s choice and carbonization parameters on the evolution of the carbon matrix and its resulting electrochemistry. We followed structure development upon the increase in carbonization temperature with thorough structural characterization and electrochemical testing. With the increase of carbonization temperature from 900 to 1600 °C, our prepared materials exhibited a trend toward increasing structural order, an increase in the specific surface area of micropores, the development of ultramicroporosity, and an increase in conductivity. This was clearly demonstrated by a synergy of small- and wide-angle X-ray scattering, scanning transmission electron microscopy, and electron-energy loss spectroscopy techniques. Three-electrode full cell measurements confirmed incomplete desodiation of Na+ions from the non-graphitizable carbons in the first cycle due to the formation of a solid–electrolyte interface and Na trapping in the pores, followed by a stable second cycle. The study of cycling stability over 100 cycles in a half-cell configuration confirmed the observed high irreversible capacity in the first cycle, which stabilized to a slow decrease afterward, with the Coulombic efficiency reaching 99% after 30 cycles and then stabilizing between 99.3 and 99.5%. Subsequently, a strong correlation between the determined structural properties and the electrochemical behavior was established.

Electrochemical capacitors are attractive power sources, especially when they are able to operate at high frequency (high current regime). In order to meet this requirement their constituents should be made of high conductivity materials with a suitable porosity. In this study, enhanced power and simultaneously high capacitance (120 F g−1 at 1 Hz or 10 A g−1) electrode material obtained from carbonized adenine precursor is presented. A micro/mesoporous character of the carbon with optimal pore size ratio and high surface area was proven by the physicochemical characterization. The beneficial pore structure and morphology resembling highly conductive carbon black, together with a significant nitrogen content (5.5%) allow for high frequency response of aqueous capacitor to be obtained. The carbon/carbon symmetric capacitor (in 1 mol L−1 Li2SO4) has been tested to the voltage of 1.5 V. The cyclic voltammetry indicates a good electrochemical response even at high scan rate (50 mV s−1). The cyclability of the capacitor is comparable to the one operating with commercial carbon (YP50F). The adenine-based capacitor is especially favourable for stationary applications requiring high power., Partners acknowledge M-ERA.NET network, MCIN/AEI/10.13039/501100011033 (Ref. PCI2019–103637), CIBER-BBN, ICTS ‘‘NANBIOSIS’’, ICTS ELECMI node "Laboratorio de Microscopias Avanzadas", National Science Centre, Poland (2018/30/Z/ST4/00901), and Ministrstvo za izobraževanje, znanost in šport for financial support and the grant of Ministry of Science and Higher Education in Poland, no. 0911/SBAD/2101. A.V., B.T., E.T. and R.D. additionally acknowledge financial support from the Slovenian Research Agency (ARRS) research core funding P2–0393.

International audience; Mastering the metal-electrolyte interface is mandatory for the development of reliable rechargeable magnesium batteries. Nevertheless, most of the current electrolytes contain chlorides species to bypass the surface passivation of magnesium, making them corrosive to other cell components and potentially irrelevant for industrial application. Here, we demonstrate a novel approach to bypass the use of such electrolytes via the mediation of an alloy-type interface prepared by coating the surface of a magnesium electrode with liquid gallium. The chemical alloying induces the formation of a surface layer, mainly composed of the intermetallic Mg2Ga5, enabling significantly improved electrochemical performance with a simple chloride-free Mg(TFSI)2/DME electrolyte. Sensibly less-polarized and more stable plating/stripping is observed with symmetric cells, and longer cycle life is achieved in full cells with positive electrodes based on sulphur- and organic composites. This alloy-based surface protection opens the door to electrolytes firstly considered as non-compatible with magnesium metal, and consequently paves the way to the application of metal electrodes in practical magnesium batteries.

International audience; Complex battery degradation is an interplay of different processes correlated to the thermodynamic, chemical, and mechanical instability of materials. Their degradation kinetics and mechanisms are functions of several intrinsic and environmental conditions. The degradation of the battery cell can be minimized by using preventive steps, like artificial interphases, coatings, additives, or materials that operate within the thermodynamic stability voltage window. Like in most systems/applications degradation processes/aging cannot be avoided since battery cells operate in different environments. Self-healing functionalities have been proved in different areas of material science and they can significantly improve the performance of battery cells. Some of them have been demonstrated on the laboratory scale, while other degradation processes have been tackled only by the development of preventive approaches. Since self-healing functionalities add additional weight and cost to the battery cell, directions of development should be focused on modification of nonactive materials, preferably based on biosourced materials to lower environmental impact. Important issues include detection of degradation using sensors and the vectorization of self-healing components and their controlled release. In addition to this, a triggering process of extrinsic self-healing components together with manufacturability and recyclability should be considered from the early stages of the development phase.

International audience; This roadmap presents the transformational research ideas proposed by "BATTERY 2030+", the European large-scale research initiative for future battery chemistries. In this paper we outline a "chemistry-neutral" roadmap to advance battery research, particularly at low TRL, with a time horizon of about ten years. The roadmap is centered around six themes: 1) accelerated materials discovery platform, 2) battery interface genome, with the integration of smart functionalities such as 3) sensoring and 4) self-healing processes. Beyond chemistry related aspects we also include crosscutting research regarding 5) manufacturability and 6) recyclability. This roadmap should be seen as an important enabling complement to the many global battery roadmaps which focus on expected ultrahigh battery performance, especially for the future of transports. Batteries are used in many other applications and are considered to be one of Europe's key technologies necessary to reach the climate goals. Currently the market is dominated by lithium-ion batteries, which performs well in most applications, but despite new generations coming in near time, soon will approach their performance limits. Without major breakthroughs, battery performance and production requirements will not be sufficient to enable the building of a climate-neutral society. Through our "chemistry neutral" approach we aim to create a generic toolbox transforming the way we develop and design batteries, which later benefit into the development of specific battery chemistries and technologies. The goal is to integrate modeling and high-through-put experimental results in a closed integrated loop and manage the large amounts of data we generate to learn more about complex processes on different levels affecting the function of a battery cell or a battery system. Based on this we suggest concrete actions with the ambition to be part of and support the implementation of the European Green Deal, the UN Sustainable Development Goals, as well as the European Strategic Action plan on Batteries and the Strategic Energy Technology Plan.

New era heteroatom-doped carbons, relying on different biomass residues, play a rising role in contemporary carbon energy storage technology. Herein, an abundant waste of viticulture industry – vine shoots (VS) was carbonized and examined as electrode material for supercapacitors with non-conventional aqueous electrolyte. Biochar obtained by pre-carbonization treatment of vine shoots (at 300 °C) is impregnated with ZnCl2 at 600 °C (ACvs600) and 700 °C (ACvs700), to synthesize carbon with developed specific surface area, close to 1500 m2 g−1. The high specific capacitance of ACvs is achieved in Al-based electrolyte, which allows working voltage of 1.8 V ACvs700/Al2(SO4)3/ACvs700 cell delivers the energy density of 24 Wh kg−1 at 1 A g−1, which is higher than one measured in typical Na2SO4 (∼16 Wh kg−1) and H2SO4 electrolyte (∼11 Wh kg−1). By using Trasatti&Dunn surface charge distribution models, the reallocation of inner vs. outer charge in Al-based electrolyte is found to be different from that in H2SO4 electrolyte. The nature of the interaction between pristine/defective graphene and hydrated Al3+ ion is examined by Density Functional Theory (DFT) and discussed. Gathered experimental and theoretical data open novel perspectives for using carbon in more sustainable energy storage devices.

The use of impedance spectroscopy in the field of modern batteries is demonstrated on three systems: lithium ion batteries represented by lithium iron phosphate (LFP) and lithium cobalt oxide (LCO) electrodes, a porous carbon cathode in contact with polysulfides and a metallic lithium anode exhibiting dendritic growth. In all cases, systematic experiments are shown where the type and composition of electrochemical cell is varied in order to identify the main processes contributing to the impedance response. The experiments are upgraded with appropriate models, using mainly the transmission line approach. The approach allows establishment of clear correlations between the composition and morphology of electrodes on one hand and the measured impedance features on the other. As the transmission line models are based on the use of physically well-defined elements, the approach allows a quantitative description of the main processes (diffusion, reaction, migration across films and contacts) taking place in modern battery electrodes.

Lithium (Li) metal has been considered as an important anode candidate to reach more powerful energy storage devices with higher gravimetric and volumetric capacities. Nevertheless, the growth of h...

Aluminum (Al) batteries are fundamentally a promising future post-Li battery technology. The recently demonstrated concept of an Al-graphite battery represents some significant progress for the technology, but the cell energy density is still very modest and limited by the quantity of the AlCl3 based electrolyte, as it relies on AlCl4‒ intercalation. For further progress, cathode materials capable of an electrochemical reaction with Al positively charged species are needed. Here such a concept of an Al metal anode ‒ organic cathode battery based on anthraquinone (AQ) electrochemistry with a discharge voltage of 1.1 V is demonstrated. Further improvement of both the cell capacity retention and rate capability is achieved by nano-structured and polymerized cathodes. The intricate electrochemical mechanism is proven to be that the anthraquinone groups undergo reduction of their carbonyl bonds during discharge and become coordinated by AlCl2+ species. Altogether the Al metal anode – AQ cathode cell has almost the double energy density of the state-of-the-art Al-graphite battery.

The journal of physical chemistry / C 126(12), 5435 - 5442 (2022). doi:10.1021/acs.jpcc.1c10622, X-ray Raman spectroscopy (XRS) is an emerging spectroscopic technique that utilizes inelastic scattering of hard X-rays to study X-ray absorption edges of low Z elements in bulk material. It was used to identify and quantify the amount of carbonyl bonds in a cathode sample, in order to track the redox reaction inside metal–organic batteries during the charge/discharge cycle. XRS was used to record the oxygen K-edge absorption spectra of organic polymer cathodes from different multivalent metal–organic batteries. The amount of carbonyl bond in each sample was determined by modeling the oxygen K-edge XRS spectra with the linear combination of two reference compounds that mimicked the fully charged and the fully discharged phases of the battery. To interpret experimental XRS spectra, theoretical calculations of oxygen K-edge absorption spectra based on density functional theory were performed. Overall, a good agreement between the amount of carbonyl bond present during different stages of battery cycle, calculated from linear combination of standards, and the amount obtained from electrochemical characterization based on measured capacity was achieved. The electrochemical mechanism in all studied batteries was confirmed to be a reduction of double carbonyl bond and the intermediate anion was identified with the help of theoretical calculations. X-ray Raman spectroscopy of the oxygen K-edge was shown to be a viable characterization technique for accurate tracking of the redox reaction inside metal–organic batteries., Published by Soc., Washington, DC

Insufficient understanding of the mechanism that reversibly converts sulphur into lithium sulphide (Li2S) via soluble polysulphides (PS) hampers the realization of high performance lithium-sulphur cells. Typically Li2S formation is explained by direct electroreduction of a PS to Li2S; however, this is not consistent with the size of the insulating Li2S deposits. Here, we use in situ small and wide angle X-ray scattering (SAXS/WAXS) to track the growth and dissolution of crystalline and amorphous deposits from atomic to sub-micron scales during charge and discharge. Stochastic modelling based on the SAXS data allows quantification of the chemical phase evolution during discharge and charge. We show that Li2S deposits predominantly via disproportionation of transient, solid Li2S2 to form primary Li2S crystallites and solid Li2S4 particles. We further demonstrate that this process happens in reverse during charge. These findings show that the discharge capacity and rate capability in Li-S battery cathodes are therefore limited by mass transport through the increasingly tortuous network of Li2S / Li2S4 / carbon pores rather than electron transport through a passivating surface film.

Benchmarking study of different electrolytes for Na, Mgand Ca batteries

Milestone 6:Set up for characterization of all four battery systems

In this work, valence-to-core (VtC) Kβsulfur X-ray emission spectroscopy (XES) was used to perform quantitative analysis of different sulfur compounds produced in a lithium sulfur (Li–S) battery during discharge. The analysis is based on the theoretical sulfur KβXES spectra obtained from ab initio quantum chemical calculations based on density functional theory. The emphasis is given to the Kβsulfur XES spectra of the polysulfide molecules (Li2Sx, x = 2,…,8) produced electrochemically within the Li–S battery. Ab initio molecular dynamics calculations are used further to calculate also the Kβspectra of Li2Sx dissolved in a model solvent. Calculated spectra were directly compared with the experimental ones collected with a Johansson type tender XES spectrometer on laboratory synthesized Li2Sx reference standards and pre-cycled battery cathodes. These results demonstrate that sulfur VtC XES can be used effectively to quantitatively analyze electrochemical sulfur conversion, also in a smaller laboratory without the need for large scale synchrotron facilities.

IR spectroscopy can be a non-destructive and straightforward probing tool in the battery research. However, its application has been limited due to the difficulties related to the handling and interpretation of ex situ samples along with the lack of widely applicable in situ and operando cells. Herein, we show a simple, operando ATR-IR two electrode pouch cell with an IR-transmissive silicon window and discuss its advantages and limitations. This setup is applied to the study of the polyanthraquinone (PAQ) reaction mechanism in Li- and Mg-organic batteries. During the reduction/oxidation process of the PAQ, not only the conversion of both C O groups into C–O– species is observed, but also the formation of an intermediate semiquinone radical anion as an intermediate product. Furthermore, continuous measurement of IR spectra allows visualization of the gradual solid-electrolyte interphase (SEI) buildup on the cathode during cycling.

Mg rechargeable batteries are a highly perspective battery system for the future post Li-ion batteries. However, their practical application seems quite distant due to poor Mg2+ insertion into inorganic cathode materials. Organic cathodes offer an opportunity for realization of practical Mg rechargeable batteries due to circumvention of insertion limitations encountered in inorganic hosts. Herein, we investigate the electrochemical performance of polyanthraquinone (PAQ) organic cathode in two Mg electrolytes based on different combinations of the salts, Mg(TFSI)2-2MgCl2 and MgCl2-AlCl3. PAQ in electrolyte containing Mg(TFSI)2-2MgCl2 exhibits good capacity retention and utilization. MgCl2-AlCl3 based electrolyte shows poorer electrochemical performance and a peculiar upshift of the voltage plateau for 300 mV, which is caused by the presence of AlCl3 in the electrolyte. Mg anode morphology after cycling reveals the formation of pits and cracks on the Mg foil anode as well as uneven Mg deposits several μm in size in both electrolytes. The maximum capacity and capacity retention are referenced with polyanthraquinone performance in Li battery and show that at 1C cycling rate 75% of the maximum capacity in Li battery can be obtained in Mg battery. Long-term capacity fade is comparable, demonstrating the potential for practical realization of Mg‒organic battery.

The transport-reaction mechanism taking place in porous cathodes used in lithium-sulfur battery cells is systematically investigated using impedance spectroscopy. The adverse effects of metallic lithium are excluded by using symmetrical carbon-carbon cells. The results obtained on two types of porous electrodes, a carbon felt and a conventional mesoporous carbon electrode, are compared to those previously obtained on a flat glassy carbon electrode. The thickness of both porous electrodes as well as the thickness of porous separator are varied and impedance spectra studied in detail. The shapes, magnitudes and trends of various impedance features could well be reproduced by a proposed transmission line model. The model is upgraded with respect to known transmission line models in two ways: diffusion in pores of electrode is taken into account and a coupling of this diffusion to diffusion in separator is carried out. The results consistently show that the migration, reaction and diffusion impedances due to processes taking place inside a typical cathode are one to two orders of magnitude smaller than the impedance due to diffusion of active species in the porous separator. However, the present findings strongly indicate that if one could suppress the leakage of polysulfides into the separator, the total impedance would drop dramatically, regardless of the actual thickness or porosity of the cathode.