Alistore

Lithium-ion (Li-ion) batteries that rely on cationic redox reactions are the primary energy source for portable electronics. One pathway toward greater energy density is through the use of Li-rich layered oxides. The capacity of this class of materials (>270 milliampere hours per gram) has been shown to be nested in anionic redox reactions, which are thought to form peroxo-like species. However, the oxygen-oxygen (O-O) bonding pattern has not been observed in previous studies, nor has there been a satisfactory explanation for the irreversible changes that occur during first delithiation. By using Li2IrO3 as a model compound, we visualize the O-O dimers via transmission electron microscopy and neutron diffraction. Our findings establish the fundamental relation between the anionic redox process and the evolution of the O-O bonding in layered oxides.

Largely based on its very high rechargeable capacity, silicon appears as an ideal candidate for the next generation of negative electrodes for Li-ion batteries. However, a crucial problem with silicon is the large volume expansion undergone upon alloying with lithium, which results in stability problems. Means to avoid such problems are largely linked to the understanding of the interfacial chemistry during charging/discharging. This is especially of great importance when using nanometric silicon particles. In this work, the interfacial mechanisms (reaction of surface oxide, Li–Si alloying process, and passivation layer formation) accompanying lithium insertion/extraction into Si/C/CMC composite electrodes have been scrutinized by X-ray photoelectron spectroscopy (XPS). A thorough nondestructive depth-resolved analysis was carried out by using both soft X-rays (100–800 eV) and hard X-rays (2000–7000 eV) from two different synchrotron facilities compared with in-house XPS (1487 eV). The unique combination utilizing hard and soft X-ray photoelectron spectroscopy accompanied with variation of the analysis depth allowed us to access interfacial phase transitions at the surface of silicon particles as well as the composition and thickness of the SEI (electrode/electrolyte interface layer).

The miniaturization of power sources aimed at integration into micro- and nano-electronic devices is a big challenge. To ensure the future development of fully autonomous on-board systems, electrodes based on self-supported 3D nanostructured metal oxides have become increasingly important, and their impact is particularly significant when considering the miniaturization of energy storage systems. This review describes recent advances in the development of self-supported 3D nanostructured metal oxides as electrodes for innovative power sources, particularly Li-ion batteries and electrochemical supercapacitors. Current strategies for the design and morphology control of self-supported electrodes fabricated using template, lithography, anodization and self-organized solution techniques are outlined along with different efforts to improve the storage capacity, rate capability, and cyclability.

Silicon is a very good candidate for the next generation of negative electrodes for Li-ion batteries, due to its high rechargeable capacity. An important issue for the implementation of silicon is the control of the chemical reactivity at the electrode/electrolyte interface upon cycling, especially when using nanometric silicon particles. In this work we observed improved performances of Li//Si cells by using the new salt lithium bis(fluorosulfonyl)imide (LiFSI) with respect to LiPF6. The interfacial chemistry upon long-term cycling was investigated by photoelectron spectroscopy (XPS or PES). A nondestructive depth resolved analysis was carried out by using both soft X-rays (100-800 eV) and hard X-rays (2000-7000 eV) from two different synchrotron facilities and in-house XPS (1486.6 eV). We show that LiFSI allows avoiding the fluorination process of the silicon particles surface upon long-term cycling, which is observed with the common salt LiPF6. As a result the composition in surface silicon phases is modified, and the favorable interactions between the binder and the active material surface are preserved. Moreover a reduction mechanism of the salt LiFSI at the surface of the electrode could be evidenced, and the reactivity of the salt toward reduction was investigated using ab initio calculations. The reduction products deposited at the surface of the electrode act as a passivation layer which prevents further reduction of the salt and preserves the electrochemical performances of the battery.

Several emerging battery technologies are currently on endeavour to take a share of the dominant position taken by Li-ion batteries in the field of energy storage. Among them, sodium-based batteries offer a combination of attractive properties i.e., low cost, sustainable precursors and secure raw material supplies. Na-based batteries include related battery concepts, such as Na-ion, all solid-state Na batteries, Na/O2 and Na/S, that differ in key components and in redox chemistry, and therefore result in separate challenges and metrics. Na-ion batteries represent an attractive solution which is almost ready to challenge Li-ion technology in certain applications; the other cell concepts represent a more disruptive innovation, with a higher performance gain, provided that major hurdles are overcome. The present review aims at highlighting the most promising materials in the field of Na-based batteries and challenges needed to be addressed to make this technology industrially appealing, by providing an in-depth analysis of performance metrics from recent literature. To this end, half-cell reported metrics have been extrapolated to full cell level for the more mature Na-ion technology to provide a fair comparison with existing technologies.

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Sodium-ion batteries have been considered as potential candidates for stationary energy storage because of the low cost and wide availability of Na sources. However, their future commercialization depends critically on control over the solid electrolyte interface formation, as well as the degree of sodiation at the positive electrode. Here we report an easily scalable ball milling approach, which relies on the use of metallic sodium, to prepare a variety of sodium-based alloys, insertion layered oxides and polyanionic compounds having sodium in excess such as the Na4V2(PO4)2F3 phase. The practical benefits of preparing sodium-enriched positive electrodes as reservoirs to compensate for sodium loss during solid electrolyte interphase formation are demonstrated by assembling full C/P'2-Na1[Fe0.5Mn0.5]O2 and C/'Na3+xV2(PO4)2F3' sodium-ion cells that show substantial increases (>10%) in energy storage density. Our findings may offer electrode design principles for accelerating the development of the sodium-ion technology.

Battery watch: UV/Vis spectrophotometry is demonstrated as a powerful analytical method for the in situ study of polysulfides. Through the interactions that occur between different chain-length polysulfide molecules and the UV/Vis radiation, quantitative and qualitative determination of the polysulfides formed during Li-S battery operation can be achieved.

Although promising improvements have been made in the field of Li–S rechargeable batteries, they are still far from reaching the market place due to several drawbacks. To combat the solubility of polysulphides, confinement approaches aiming to trap sulphur within the cathode side have been pursued, but success has been limited. Herein, we drastically deviate from this approach and use a liquid cathode obtained either by dissolving polysulphides within the electrolyte or by placing sulphur powders in contact with the Li negative electrode. Such approaches are shown to result in greater performance than confinement approaches. Such a strategy eliminates the detrimental Li2S formation inside a porous carbon matrix and moreover leads to the formation of a protective SEI layer at the Li electrode, as deduced by impedance spectroscopy and XPS, which seems beneficial to the cell cycling performance.

Abstract Increasing concerns regarding the sustainability of lithium sources, due to their limited availability and consequent expected price increase, have raised awareness of the importance of developing alternative energy-storage candidates that can sustain the ever-growing energy demand. Furthermore, limitations on the availability of the transition metals used in the manufacturing of cathode materials, together with questionable mining practices, are driving development towards more sustainable elements. Given the uniformly high abundance and cost-effectiveness of sodium, as well as its very suitable redox potential (close to that of lithium), sodium-ion battery technology offers tremendous potential to be a counterpart to lithium-ion batteries (LIBs) in different application scenarios, such as stationary energy storage and low-cost vehicles. This potential is reflected by the major investments that are being made by industry in a wide variety of markets and in diverse material combinations. Despite the associated advantages of being a drop-in replacement for LIBs, there are remarkable differences in the physicochemical properties between sodium and lithium that give rise to different behaviours, for example, different coordination preferences in compounds, desolvation energies, or solubility of the solid–electrolyte interphase inorganic salt components. This demands a more detailed study of the underlying physical and chemical processes occurring in sodium-ion batteries and allows great scope for groundbreaking advances in the field, from lab-scale to scale-up. This roadmap provides an extensive review by experts in academia and industry of the current state of the art in 2021 and the different research directions and strategies currently underway to improve the performance of sodium-ion batteries. The aim is to provide an opinion with respect to the current challenges and opportunities, from the fundamental properties to the practical applications of this technology.

For the development of safe and long-lasting lithium-ion batteries we need electrolytes with excellent ionic transport properties. Argyrodite-type Li6PS5X (X: Cl, Br, I) belongs to a family of such a class of materials offering ionic conductivities, at least if Li6PS5Br and Li6PS5Cl are considered, in the mS cm-1 range at room temperature. Although already tested as ceramic electrolytes in battery cells, a comprehensive picture about the ion dynamics is still missing. While Li6PS5Br and Li6PS5Cl show an exceptionally high Li ion conductivity, that of Li6PS5I with its polarizable I anions is by some orders of magnitude lower. This astonishing effect has not been satisfactorily understood so far. Studying the ion dynamics over a broad time and length scale is expected to help shed light on this aspect. Here, we used broadband impedance spectroscopy and 7Li NMR relaxation measurements and show that very fast local Li ion exchange processes are taking place in all three compounds. Most importantly, the diffusion-induced NMR spin-lattice relaxation in Li6PS5I is almost identical to that of its relatives. Considering the substitutional disorder effects in Li6PS5X (X = Br, Cl), we conclude that in structurally ordered Li6PS5I the important inter-cage jump processes are switched off, hindering the ions from taking part in long-range ion transport.

The chemical stability of the Li–O2 battery components (cathode and electrolyte) in contact with lithium peroxide (Li2O2) was investigated using X-ray photoelectron spectroscopy (XPS). XPS is a versatile method to detect amorphous as well as crystalline decomposition products of both salts and solvents. Two strategies were employed. First, cathodes including carbon, α-MnO2 catalyst, and Kynar binder (PVdF-HFP) were exposed to Li2O2 and LiClO4 in propylene carbonate (PC) or tetraethylene glycol dimethyl ether (TEGDME) electrolytes. The results indicated that Li2O2 degrades TEGDME to carboxylate containing species and that the decomposition products, in turn, degraded the Kynar binder. The α-MnO2 catalyst was unaffected. Second, Li2O2 model surfaces were kept in contact with different electrolytes to investigate the chemical stability and also the resulting surface layer on Li2O2. Further, the XPS experiments revealed that the Li salts such as LiPF6, LiBF4, and LiClO4 decomposed to form LiF or LiCl together with P–O or B–O bond containing compounds when exposed to Li2O2. PC decomposed to carbonate and ether based species. The degradation of the electrolytes increased from short to long exposure time indicating that the surface layer on Li2O2 became thicker by increasing time. Overall, it was shown that a mixture of ethylene carbonate and diethyl carbonate (EC/DEC) is more robust in contact with Li2O2 compared to PC.

Abstract The production of hydrogen at a large scale by the environmentally-friendly electrolysis process is currently hampered by the slow kinetics of the oxygen evolution reaction (OER). We report a solid electrocatalyst α-Li 2 IrO 3 which upon oxidation/delithiation chemically reacts with water to form a hydrated birnessite phase, the OER activity of which is five times greater than its non-reacted counterpart. This reaction enlists a bulk redox process during which hydrated potassium ions from the alkaline electrolyte are inserted into the structure while water is oxidized and oxygen evolved. This singular charge balance process for which the electrocatalyst is solid but the reaction is homogeneous in nature allows stabilizing the surface of the catalyst while ensuring stable OER performances, thus breaking the activity/stability tradeoff normally encountered for OER catalysts.

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Solid-state electrolytes (SSEs) are promising candidates to circumvent flammability concerns of liquid electrolytes. However, enhancing energy densities by thinning SSE layers and enabling scalable coating processes remain challenging. While previous studies have addressed thin and flexible SSEs, mainly ionic conductivity was considered for performance evaluation, and no systematic research on the effects of manufacturing conditions on the quality of SSE films was performed. Here, both uniformity and ionic conductivity are considered for evaluating the SSE films under the guidance of machine learning (ML). Three algorithms, principal component analysis, K-means clustering, and support vector machine, are employed to decipher the interdependencies between manufacturing conditions and film performance. Guided by ML, a 40 μm SSE film with high ionic conductivity and good uniformity is used to construct a LiNi0.8Co0.1Mn0.1O2 || Li6PS5Cl || LiIn cell demonstrating 100 cycles. This study presents an efficient ML-assisted approach to optimize scalable production of high-quality SSE films.

A critical overview on electrolytes, anode and cathode materials for Mg batteries.

All-solid-state batteries with ceramic electrolytes and lithium metal anodes represent an attractive alternative to conventional ion battery systems. Conventional batteries still rely on flammable liquids as electronic insulators. Despite the great efforts reported over the last years, the optimum solid electrolyte has, however, not been found yet. One of the most important properties which decides whether a ceramic is useful to work as electrolyte is ionic transport. The various time-domain nuclear magnetic resonance (NMR) techniques might help characterize and select the most suitable candidates. Together with conductivity measurements it is possible to analyze ion dynamics on different length-scales, i.e., to differentiate between local, within-site hopping processes from long-range ion transport. The latter needs to be sufficiently fast in the ceramic, in the best case competing with that of liquid electrolytes. In addition to conductivity spectroscopy, NMR can help understand the relationship between local structure and dynamic parameters. Besides information on activation energies and jump rates the data also contain suggestions about the relevant elementary steps of ion hopping and, thus, diffusion pathways through the crystal lattice. Recent progress in characterizing ion dynamics in ceramic electrolytes by NMR relaxometry will be briefly reviewed. Focus is put on presently discussed solid electrolytes such as garnets, phosphates and sulfides, which have so far been studied in our lab.

The currently emerging sodium-ion battery technology is in need of an optimized standard organic solvent electrolyte based on solid and directly comparable data. With this aim we have made a systematic study of "simple" electrolyte systems consisting of two sodium salts (NaTFSI and NaPF6) dissolved in three different alkyl carbonate solvents (EC, PC, DMC) within a wide range of salt concentrations and investigated: (i) their more macroscopic physico-chemical properties such as ionic conductivity, viscosity, thermal stability, and (ii) the molecular level properties such as ion-pairing and solvation. From this all electrolytes were found to have useful thermal operational windows and electrochemical stability windows, allowing for large scale energy storage technologies focused on load levelling or (to a less extent) electric vehicles, and ionic conductivities on par with analogous lithium-ion battery electrolytes, giving promise to also be power performant. Furthermore, at the molecular level the NaPF6-based electrolytes are more dissociated than the NaTFSI-based ones because of the higher ionic association strength of TFSI compared to PF6- while two different conformers of DMC participate in the Na+ first solvation shells - a Na+ affected conformational equilibrium and induced polarity of DMC. The non-negligible presence of DMC in the Na+ first solvation shells increases as a function of salt concentration. Overall, these results should both have a general impact on the design of more performant Na-conducting electrolytes and provide useful insight on the very details of the importance of DMC conformers in any cation solvation studies.

Li–O2 cells composed of a carbon cathode containing an α-MnO2 nanowire catalyst and a Kynar (PVDF-HFP) binder were cycled with different electrolytes containing 0.5 M LiB(CN)4 salt in polyethylene glycol dimethyl ether (PEGDME) or tetraethylene glycol dimethyl ether (Tetraglyme) solvents. All cells exhibited fast capacity fading. To explain this, the surface chemistry of the carbon electrodes were investigated by synchrotron based hard X-ray photoelectron spectroscopy (HAXPES) using two photon energies of 2300 and 6900 eV. It is shown that the LiB(CN)4 salt and Kynar binder were degraded during cycling, forming a layer composed of salt and binder residues on the cathode surface. The degradation mechanism of the salt differed in the two tested solvents and, consequently, different types of boron compounds were formed during cycling. Larger amounts of the degraded salt was observed using Tetraglyme as the solvent. With a nonfluorined Li-salt, the observed formation of LiF, which might be a reason for the observed blockage of pores in the cathode and for the observed capacity fading, must be due to Kynar binder decomposition. The amount of LiF formed in the PEGDME cell was larger than that formed in the Tetraglyme cell. The results indicate that not only the electrolyte solvent, but also electrolyte salt as well as the binder used for the porous cathode must be carefully considered when building a successful rechargeable Li–O2 battery.

We report a novel procedure for the fabrication of vertical iron oxide nanowires with quite regular form and diameters ranging between 20 and 150 nm grown from a matrix of self-organized TiO2 nanotubes. The 3 μm thick nanocomposite electrode presented here shows relatively high areal capacities of 468 μAh cm−2 (1st reversible discharge) and 200 μA h cm−2 over 45 cycles at a rate of 25 μA cm−2 (specific capacities of 1190 and 510 mAh g−1, respectively). Additionally, studies performed at kinetics of 6, 12.5, and 50 μA cm−2 suggest that this architectured nanocomposite material reveals excellent electrochemical performance with promising potential applications as nano-architectured negative electrodes for Li-ion microbatteries.