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International audience; Hard carbon (HC) materials are commonly used as anode materials in Na-ion batteries. In most of the cases, their electrochemical performance is correlated only to their physicochemical properties, and the impact of the electrode additives (binders–conductive agent) and electrolyte is often neglected. In this work, a systematic study is performed to understand the role of electrode/electrolyte engineering on HC initial Coulombic efficiency (iCE), specific capacity, and cycle stability. Four HCs obtained by pyrolysis of several biopolymers, i.e., cellulose (HC-Cell), chitosan (HC-Chs), chitin (HC-Cht), and lignin (HC-Lig), are used. The binder was found to have an important impact on the electrochemical performance, with PVDF resulting in better performance than CMC. The carbon black additive had no significant impact on CMC-based electrochemical performance while it boosted the electrochemical performance of PVDF-based electrodes. For an optimized formulation (PVDF/carbon black), the best HC performance in NaPF6 in 1 EC:DEC was delivered by HC-Cell (83% iCE, 332 mAh g–1 at C/10, and 97% retention). This was attributed to its large graphene interlayer space, high purity, and low surface area. HC-Cht and HC-Chs exhibited similar good electrochemical performance (∼280 mAh g–1) whereas the use of HC-Lig resulted in low iCE and capacity fading overcycling due to the high level of impurities in its structure. This could be overcome by changing the electrolyte salt, by using NaClO4 (76% retention) instead of NaPF6 (52% retention). Based on the obtained results, the electrochemical performance could be correlated with the HC physicochemical properties and binder/conductive additive. It could be demonstrated that careful electrode engineering combined with proper electrolyte selection and tuned HC properties allowed all investigated materials achieving reasonable iCE (up to 83%), high specific capacity (∼280 to 332 mAh g–1), and high-capacity retention (72–97% after 50 cycles).

The model activated carbon spheres (ACSs) were optimized to be used as negative electrode in asymmetric electrochemical capacitors (ECs). A microporous commercial activated carbon was used as positive electrode. Carbon spheres (CSs) were synthesized by precipitation polymerization at room temperature followed by pyrolysis and activation. By enhancing the carbon:KOH ratio from 1:2 to 1:4, an increase in the specific surface area from 380 m2 g−1 to 2835 m2 g−1 (1:4) was achieved along with an increase in pore volume/size. Consequently, the electrochemical performance in the aqueous electrolyte was improved. After activation, low-temperature-pyrolyzed polymer spheres (400 °C) result in random-like particles with macroporous structure, while intermediate- and high-temperature-pyrolyzed materials (550 °C and 700 °C) lead to partially and totally conserved spheres. The interaction between the electrode material and electrolyte is important and is related to the texture, morphology, and surface chemistry of ACS. In 1 mol L−1 H2SO4, capacitance and rate handling are mostly affected by electrode morphology and wettability with the electrolyte. In 1 mol L−1 Li2SO4 electrolyte solution, texture and surface chemistry of the electrode material are crucial to obtain high-performance EC. Regardless of morphology, poor wetting properties of synthesized materials were found in Li2SO4, compared to the H2SO4 solution., Journal of Power Sources, 542, ISSN:0378-7753, ISSN:1873-2755

Despite the extensive research on Na-ion batteries little is known about the stability of the Na-metal counter electrode in a half-cell configuration. Therefore, in our study we focus on identifying the key factors responsible for its high interfacial resistance and often premature degradation in carbonate-based electrolytes.

Summary The promise of high-energy density and the predicted role of the Li–S batteries in electrochemical energy storage applications are largely based on sulfur's high theoretical specific charge. Unfortunately, to date the commercialization of Li–S battery is still hindered due to the complexity of the reaction mechanism involving a sequence of dynamically changing liquid and solid equilibria. Operando techniques have been widely employed to study these performance-limiting phase transformations; however, they often fall short in tracking and resolving simultaneously the solid and liquid phases. Here, we present a review summarizing the last efforts in the field.

Symmetric cells comprising either a pair of positive (sulfur), blocking or negative (lithium) electrodes were investigated by means of electrochemical impedance spectroscopy, to break down the complexity of the lithium–sulfur chemistry and to understand how the individual cell components influence the transport properties of a full cell. We thoroughly analyzed the ageing of the negative electrode (lithium metal) interface under open circuit conditions as a function of the nature of species present in the electrolyte, including the influence of dissolved binder and/or long-chain polysulfides. In a similar manner, we investigated the positive electrode interface. Herein, the objective was to understand the impact of an individual electrode component on the impedance response of the symmetric cell, and, more importantly, to discern the role of the sulfur in charge transfer reaction(s).

Char and Carbon Materials Derived from Biomass: Production, Characterization and Applications provides an overview of biomass char production methods (pyrolysis, hydrothermal carbonization, etc.), along with the characterization techniques typically used (Scanning Electronic Microscopy, X-Ray Fluorescence, Nitrogen adsorption, etc.) In addition, the book includes a discussion of the various properties of biomass chars and their suitable recovery processes, concluding with a demonstration of applications. As biomass can be converted to energy, biofuels and bioproducts via thermochemical conversion processes, such as combustion, pyrolysis and gasification, this book is ideal for professionals in energy production and storage fields, as well as professionals in waste treatment, gas treatment, and more.

Char and Carbon Materials Derived from Biomass: Production, Characterization and Applicationsprovides an overview of biomass char production methods (pyrolysis, hydrothermal carbonization, etc.), along with the characterization techniques typically used (Scanning Electronic Microscopy, X-Ray Fluorescence, Nitrogen adsorption, etc.) In addition, the book includes a discussion of the various properties of biomass chars and their suitable recovery processes, concluding with a demonstration of applications. As biomass can be converted to energy, biofuels and bioproducts via thermochemical conversion processes, such as combustion, pyrolysis and gasification, this book is ideal for professionals in energy production and storage fields, as well as professionals in waste treatment, gas treatment, and more.

Hard carbons (HCs) prepared from renewable precursors are promising cost-effective electrode-material candidates for the application in Na-ion battery. Usually these materials are derived from cellulose. Here, however, we demonstrate that other polysaccharides, such as chitin and chitosan, can be as well up-and-coming parent materials of HCs. Despite structural similarities, thermal decomposition of these two biopolymers proceeds differently, contributing to the discrepancies in physicochemical properties of resulting HCs. Although chitin- and chitosan-derived HCs have comparable d-spacings and crystallite sizes, solid-state pyrolysis of the former biopolymer leads to micromesoporous material with significant specific surface area, while that of chitosan yields nonporous carbon. Despite that, both materials deliver similar initial specific charge of 280 mAh g–1 (at C/10 rate), and their electrochemical performance starts to diverge only upon longer cycling at higher rate. With time, inorganic contaminants present in chitosan-derived HC presumably delay the diffusion of Na ions to and within the electrode and slow the rate of electrochemical reactions, eventually triggering polarization buildup. Further optimization of the chitosan-derived HC through acid treatment enables unblocking some of the micropores and increasing the carbon content in this material, therefore enhancing its active surface area and suppressing continuous fading of the specific charge.

International audience; Rapid development of the technologies based on electric energy in the last decades have stimulated intensive research on efficient power sources. Electrochemical energy conversion and storage systems are based on Faradaic reactions (charge transfer) and electrostatic attraction of ions at the electrode/electrolyte interface. The latter might be an interesting solution for applications requiring moderate energy density, high power rates, and long cycle life. Electrochemical capacitors (ECs) store the charge in a physical manner, hence, their energy density is moderate. At the same time, the lack of electrochemical reactions ensures very high power and long cycle life compared to batteries. Activated carbons with their versatile properties (like specific surface area, well-developed and suitable porosity, heteroatoms in the graphene matrix) are the most popular materials in EC application. This chapter provides a comprehensive overview of the carbon-based materials recently developed, with special attention devoted to those obtained by biomass carbonization and activation. Electrochemical properties demonstrated by such carbons are discussed in respect to their physicochemical characteristics

International audience; Imaging techniques are increasingly used to study Li-ion batteries and, in particular, post-Li-ion batteries such as Li–S batteries, Na-ion batteries, and all-solid-state batteries. Results that appear impressive owing to good image design and reconstruction are frequently published in high-impact-factor journals; however, questions have arisen about the added value of such results and the information they reveal about reaction mechanisms occurring in batteries during operation and/or degradation. We present here a review of imaging techniques and the knowledge acquired from these techniques for three systems: Li–S batteries, Na-ion batteries, and all-solid-state batteries. There are always advantages and disadvantages associated with these techniques, but beam damage remains the bottleneck to characterization. This factor needs to be considered seriously in order to obtain valuable outcomes that will enable improvements of battery performance and lifetime.

A novel microporous separator for lithium–sulphur batteries, in the form of an asymmetric membrane with cation-exchange functional groups, was synthesised by a one-step plasma-induced graft co-polymerisation. This separator consists of commercial porous polypropylene modified with styrene sulfonate at or near the surface of the material. Both successful grafting and membrane asymmetry were confirmed by attenuated total reflectance Fourier transform infrared spectroscopy. Morphological changes as a function of graft level were analysed using scanning electron microscopy. Additionally, the separators were tested for their ability to inhibit polysulphide diffusion, which showed a strong dependence on the amount of negatively charged –SO3− groups introduced onto the hydrophobic substrate. Cycling tests in model Li–S cells with the modified separators showed improved coulombic efficiency.

In the on going quest towards lithium-battery chemistries beyond the lithium-ion technology, the lithium–sulfur system is emerging as one of the most promising candidates. The major outstanding challenge on the route to commercialization is controlling the so-called polysulfide shuttle, which is responsible for the poor cycling efficiency of the current generation of lithium–sulfur batteries. However, the mechanistic understanding of the reactions underlying the polysulfide shuttle is still incomplete. Here we report the direct observation of lithium polysulfides in a lithium–sulfur cell during operation by means of operando X-ray diffraction. We identify signatures of polysulfides adsorbed on the surface of a glass-fibre separator and monitor their evolution during cycling. Furthermore, we demonstrate that the adsorption of the polysulfides onto SiO2 can be harnessed for buffering the polysulfide redox shuttle. The use of fumed silica as an electrolyte additive therefore significantly improves the specific charge and Coulombic efficiency of lithium–sulfur batteries. The presence of polysulfides in Li–S batteries is highly relevant to the battery performance, but their formation and evolution during battery operation are not well understood. Here the authors design an operando X-ray diffraction experiment to reveal their reaction mechanisms.

Asymmetric separators with polysulfide barrier properties consisting of porous polypropylene grafted with styrenesulfonate (PP-g-PLiSS) were characterized in lithium-sulfur cells to assess their practical applicability. Galvanostatic cycling at different C-rates with and without an electrolyte additive and cyclic voltammetry were used to probe the electrochemical performance of the cells with the PP-g-PLiSS separators and to compare it with the performance of the cells utilizing state-of-the-art separator, Celgard 2400. Overall, it was found that regardless of the applied cycling rate, the use of the grafted separators greatly enhances the Coulombic efficiency of the cell. An appropriate Li-exchange-site (-SO3(-)) concentration at and near the surface of the separator was found to be essential to effectively suppress the polysulfide shuttle without sacrificing the Li-ion mobility through the separator and to improve the practical specific charge of the cell.

A series of novel complexes [Ni(η(5)-C5H4R)(L)(NHC)](+)A(-)2a-2j and [Ni(η(5)-C5H5)(A)(NHC)] 3a-3c has been obtained by anion metathesis from the corresponding chlorides 1a-1d, depending on the anion binding properties and reaction conditions. Solid-state structures of two cationic complexes (2c, 2j) and two complexes with a coordinated anion (3a, 3c) have been determined by X-ray diffraction revealing a trigonal planar geometry in all cases. Unexpectedly, 3c displayed unprecedented for this type of compounds temperature-dependent NMR spectra that were interpreted in terms of spin equilibrium. The cationic complexes 2 were less efficient in styrene polymerization than the parent chlorides 1. However, the activity of 2 and 3 in Suzuki cross-coupling did not depend considerably on the counterion.

The Li-ion chemistry is thus far the most advanced chemistry employed in battery technology. To date, Li-ion batteries dominate the market of the electronics and portables devices. However, in the field of electric and hybrid vehicles further improvements are required in terms of performance, safety, and cost. The same set of criteria concerns other systems based on alternative chemistries such as Na-ion and Lithium–Sulfur (Li–S) batteries. Advanced Li-ion batteries and the pre-cited novel systems utilize less understood electroactive materials and thus show new reaction mechanisms during electrochemical cycling, the understanding of which requires new characterization tools and techniques. Development of a reliable electrochemical cells is thus of a prime importance when studying battery materials in in situ or operandomode during cycling. This is never an easy task, since the design of such cells has to be adequate to the technique of a choice and meet all necessary requirements (i.e. the use of a Be window for operando X-ray diffraction measurement to ensure “transparency” to the X-ray beam). However, once a proper design is found, the surface, the bulk, the interfaces, and finally the combination of those can be studied and lead to the elucidation of the reaction mechanisms, thus further improving the battery technology. Unfortunately, in most cases the electrochemical cells used for operando measurement are not ideal and suffer from low internal pressure (i.e. poor contact between the electrodes). It shortes the lifespan of the cell and as a consequence most of the studies presented in the literature focus on the first/second cycle. Herein we present different cell designs developed in our laboratory and used for operando/in situ studies. Having overcome earlier mentioned obstacle our operando/in situ cells are able to sustain more than 100 cycles and simultaneously to perform structural studies such as X-ray and neutron diffraction. For the latter one, we also developed a new set-up called stroboscopic mode. It allows operando study of the batteries that are cycling at very high rates (e.g. 10C) with a neutron patterns collected each 1 s along 200 cycles and more. All these efforts lead us closer to understand the aging phenomena occurring during cycling and to gain the insights into the failure of both new battery technologies, such as 5 V cathode materials, and more academic systems like Na-ion and Li-S batteries. An example of the results obtained from our advanced neutron diffraction cell is shown in Figure 1. Based on the design adapted from an 18650 cell, we cycled 4.5 g of active material, 5 V cathode spinel LiNi0.5Mn1.5O4, in full cell configuration versus graphite counter electrode over 120 cycles to study the aging mechanisms. The neutron diffraction patterns were collected during the 1st and 120th cycle. As expected, along the first cycle (Figure 1a) we detected all the different stages of graphite lithiation (Figure 1b). Interestingly, after 120 cycles we were unable to detect LiC6. Thus, we concluded that the fading of the cell is mainly caused by the lack of lithium in the system. Figure 1. Operando neutron powder diffraction measurements performed in a full cell LiNi0.5Mn1.5O4 (spinel) vs. graphite. Evolution of the main peak of the graphite (002) along the 1st (a) and the 120th cycle (b); Operando X-ray diffraction measurement performed on Li2MnO3at 50°C along the first cycle (c). Another example might be Li2MnO3 (Figure 1c). It is known that the optimal cycling of this active material requires the activation at elevated temperature. We modified our X-ray diffraction cell to be able to cycle it at temperatures higher than 25°C and thus to study the activation mechanisms of Li2MnO3. These and other examples based on different operando/in situtechniques such as X-ray diffraction, neutron diffraction, neutron imaging, and Raman spectroscopy used to characterize Li-ion, Na-ion, and Li-S batteries will be presented during the talk. Acknowledgment: The authors would like to express their gratitude to Dr. Denis Sheptiakov from HRPT, SINQ, PSI beamline and fruitful help/discussions regarding neutron experiments. Mr. Hermann Kaiser and Christoph Junker are acknowledged for their help in all technical aspects of this study and the development of the cells. SAFT, SNF and SCCER Heat and Storage are thanked for financial support. Figure 1