During fast charging, metallic lithium can form on the negative graphite electrode, compromising both cycle life and safety. After deposition, plated lithium can re‐intercalate within graphite, be disconnected or chemically oxidized. To better understand these reactions and their kinetics, operando measurements on cells with electrochemical performances close to commercial ones are essential. Herein, a dedicated pouch‐cell design is developed to follow the dynamic of lithium using 7 Li nuclear magnetic resonance (NMR) spectroscopy. These developments provide 7 Li NMR spectra every 6 min leading to a good temporal resolution. The dynamics of lithium is investigated for various charging scenarios and temperatures within NMC 811/graphite pouch cells with industry‐standard electrodes. Introduction of an original method allows assessing the mass of plated lithium formed in operando mode, offering insights on the competition between graphite lithiation, plating, and reintercalation processes. Interestingly, the lithium deposition occurs mainly during the constant‐current step and early stage of the constant‐voltage (CV) step, and lithium reintercalation, oxidation, or disconnection during the subsequent CV hold, highlighting the interest of reducing the current during fast‐charge scenario. Comparison with three‐electrode monolayer pouch cells provides an onset of plating located between −100 and –150 mV versus Li.

Improving the durability and safety of lithium-ion batteries (LIBs) is essential for large-scale green mobility. However, under specific conditions during charging, metallic lithium can deposit on the negative graphite electrode, which reduces cycle life and safety 1 . After deposition, reactive plated lithium can take various paths: reinsertion into graphite, disconnection leading to dead metallic lithium or chemical oxidation with electrolyte components. To understand these reactions and their kinetics, operando nuclear magnetic resonance (NMR) spectroscopy is a very interesting tool as it provides real-time access to the chemical shift of lithium of the electrolyte/SEI, lithium (de)intercalated in graphite, and lithium plating 2 . Nevertheless, characterization on cells with electrochemical performances close to commercial ones remains challenging. In this work, we develop a dedicated pouch-cell design and the associated instrumentation to follow the dynamic of lithium using 7 Li nuclear magnetic resonance (NMR) spectroscopy. These developments provide 7 Li NMR spectra every 3 min recorded in a static mode, offering a good temporal resolution over the charging process. The complex dynamics of lithium is investigated during various charging scenarios within LiNi 0.8 Mn 0.1 Co 0.1 O 2 (NMC 811)/graphite pouch cells with industry-standard electrodes (areal loading around 2.5 mAh/cm²). Despite the static NMR conditions, distinct signals from electrolyte, LiC x phases and metallic lithium deposition are visualized and quantified, offering insights on the competition between lithiation, plating and re-intercalation processes for various temperature and charging rates. Interestingly, the lithium deposition occurs mainly during the constant-current (CC) regime, while lithium re-intercalation, oxidation or disconnection are observed during the subsequent constant-voltage (CV) phase (See Figure 1), highlighting the interest of reducing the current during fast-charge scenario. Quantification of the deposited lithium metal shows that at temperature of 0°C and charge rate equal to 2C more than 60% of the exchanged capacity during the CC phase can be attributed to plated lithium. Furthermore, these experimental results were used to validate a multi-physics porous electrode model that includes an irreversible lithium deposition term in the lithium plating/stripping model 3 . The temporal resolution of the experiment provides insights on the evolution of the plating/stripping kinetics with temperature. [1] T. Waldmann, B.-I. Hogg and M. Wohlfahrt-Mehrens, Li plating as unwanted side reaction in commercial Li-ion cells – A review , J. Power Sources, 384, 107-124 (2018) [2] K. Marker, C. Xu, and C.P. Grey, Operando NMR of NMC811/Graphite Lithium-Ion Batteries: Structure, Dynamics, and Lithium Metal Deposition , J. Am. Chem. Soc, 142, 17447−17456 (2020) [3] C. von Lüders, J. Keil, M. Webersberger and A. Jossen, Modeling of lithium plating and lithium stripping in lithium-ion batteries, J. Power Sources, 414, 41-47 (2019) Figure 1

Developing safe and high-energy-density batteries is a significant challenge, especially for Li-ion configurations. Using Li-metal as the negative electrode could greatly boost energy density but requires the replacement of liquid electrolytes by solid-state electrolytes (SSEs) to work properly and safely. Nonvolatile SSEs may prevent dendrite growth related to inhomogeneous Li electrodeposition leading to low-capacity retention and potential short circuit. Challenges persist in ensuring close electrode/SSE contact, enhancing ionic conductivities, electrochemical stability at operating temperatures, cycle life, and fast charging capabilities. Here, a composite SSE composed of a dispersion of ionic conductive ceramic particles in a polymer electrolyte matrix is studied to leverage different SSE types. Li+ ions migration is investigated at 60 degrees C with Li-isotopic tracing after applying an electrical field. High-resolution solid-state NMR and orthogonal time-of-flight secondary ion mass spectrometry are employed for characterizing the Li-isotopic relative abundance in the SSE at global and local levels, respectively. By differentiating Li in the polymer phase from ceramic particles, both techniques reveal that Li+ions preferentially diffuse through ceramic dispersion. Surprisingly, electrochemical impedance spectroscopy analyses indicate no enhancement in ionic conductivity between the polymer and composite electrolytes, highlighting the impact of other parameters such as percolation or polymer/ceramic interface properties.

Manufacturers aim to commercialize efficient and safe batteries by finding new strategies. Solid-state electrolytes can be seen as an opportunity to develop batteries with a high energy density. They allow the use of lithium foil as the anode, increasing the energy density. Also, they are composed of nonflammable materials making them safer than liquid electrolytes. However, to enhance the electrochemical performances of forthcoming solid-state lithium metal batteries, phenomena governing ionic conductivity have yet to be mastered in such devices. Lithium isotopic tracing was successfully used in previous works to further understand lithium ion transport mechanisms in batteries. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) and 6/7Li high-resolution solid-state nuclear magnetic resonance (ssNMR) spectroscopy are two complementary techniques probing local and global scale, respectively. Both techniques can distinguish lithium isotopes. Here, four polymer membranes were elaborated with the same lithium concentration, but with various isotopic enrichments from 7.6 to 95.4% of 6Li. The selected material was a poly(ethylene oxide) (PEO) membrane containing lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) as lithium salt. They are widely studied in the lithium battery field. First, reliable ToF-SIMS and ssNMR methodologies were validated in light of the converging results. They led to accurate determination of lithium isotopic abundance of polymer membranes with a 1 or a 2% uncertainty, respectively. Then, the developed methodologies were applied to characterize lithium self-diffusion in a polymer membrane. Furthermore, numerical simulations based on a two-dimensional diffusion model compared with ToF-SIMS analyses allowed us to extract a lithium self-diffusion coefficient of 1.6 × 10-12 m2·s-1 at 60 °C, which complements other published values. The robust methodologies described in this work can be extended to various applications and materials. They stand as powerful strategies to better understand lithium ionic transport, especially in multiphase materials, for example, in hybrid solid-state electrolytes.

The introduction of lithiated components with different 7Li/6Li isotopic ratios, also called isotopic tracing, can give access to better understanding of lithium transport and lithiation processes in lithium-ion batteries. In this work, we propose a simple methodology based on high-resolution solid-state NMR for the determination of the 7Li/6Li ratio in silicon electrodes following different strategies of isotopic tracing. The 6Li and 7Li MAS NMR experiments allow obtaining resolved spectra whose spectral components can be assigned to different moieties of the materials. In order to measure the ratio of the 6Li/7Li NMR integrals, a silicon electrode with a natural 7Li/6Li isotope abundance was used as a reference. This calibration can then be used to determine the 7Li/6Li ratio of any similar samples. This method was applied to study the phenomena occurring at the interface between a silicon electrode and a labeled electrolyte, which is an essential step for isotopic tracing experiments in systems after the formation of the solid electrolyte interphase (SEI). Beyond the isotopic exchanges between the SEI and the electrolyte already observed in the literature, our results show that isotopic exchanges also involve Li-Si alloys in the electrode bulk. Within a 52-hour contact, the electrolyte labeling disappeared: isotopic concentrations of the electrolyte and electrode become practically homogenized. However, at the electrode level, different silicides are characterized by rather different isotopic enrichment. In the present work, ToF SIMS and liquid state NMR were also used to cross-check and discuss the solid-state NMR method we have proposed.

Germanium is a promising active material for high energy density anodes in Li-ion batteries thanks to its good Li-ion conduction and mechanical properties. However, a deep understanding of the (de)lithiation mechanism of Ge requires advanced characterizations to correlate structural and chemical evolution during charge and discharge. Here we report a combined operando X-ray diffraction (XRD) and ex situ 7Li solid-state NMR investigation performed on crystalline germanium nanoparticles (c-Ge Nps) based anodes during partial and complete cycling at C/10 versus Li metal. High-resolution XRD data, acquired along three successive partial cycles, revealed the formation process of crystalline core-amorphous shell particles and their associated strain behavior, demonstrating the reversibility of the c-Ge lattice strain, unlike what is observed in the crystalline silicon nanoparticles. Moreover, the crystalline and amorphous lithiated phases formed during a complete lithiation cycle are identified. Amorphous Li7Ge3 and Li7Ge2 are formed successively, followed by the appearance of crystalline Li15Ge4 (c-Li15Ge4) at the end of lithiation. These results highlight the enhanced mechanical properties of germanium compared to silicon, which can mitigate pulverization and increase structural stability, in the perspective for developing high-performance anodes.

This work sheds light on the role of the alkali cations, halide anion substitution as well as borohydride anion vacancies on the de-hydrogenation properties of ammine zinc borohydrides. A new liquid ammonia-based synthesis approach employed in this study enabled direct solvothermal synthesis of several novel and previously reported ammine zinc borohydride compounds such as A(x)Zn(BH4)(2+x)(NH3)(2) for x = 0; 1 and M = Li; Na; K. The experimental results are supported by first principle calculations and molecular dynamics techniques for the interpretation of inherently complex hydrogen release mechanisms. We demonstrate that the salt metathesis reaction heavily relied upon in literature for synthesis of these compounds can result in preferential halide anion substitution of certain borohydride sites in the structure which have significant consequences for hydrogen storage properties. Conclusions of this work is applicable not only to zinc system but to any ammine metal borohydride system. (C) 2022 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Cellulose ethers are an important class of biosourced polymers. They are typically obtained from by chemical modification of natural cellulose fibers in a heterogeneous process, resulting in heterogeneous distributions of the functional groups in the materials. A direct consequence is that batches with otherwise similar characteristics (molecular weights, degree of substitution, and particle size) can differ in their material properties. Here, we show that dynamic nuclear polarization (DNP)-enhanced nuclear magnetic resonance (NMR) spectroscopy can be used to reveal the spatial distribution of functional groups in cellulose ethers. Specifically, we show that we can clearly distinguish two samples of hydroxypropyl methylcellulose (HPMC) with otherwise almost identical chemical characteristics. We find that one of the samples exhibits a more homogeneous distribution of the substituents throughout the bulk material, while the second sample shows a more partitioned distribution of the hydroxypropyl moieties, which are found to be more present in the core than the surface of the HPMC particles. The method yields new insights into why different cellulose ether samples with almost identical chemical properties show significant variations in their physical properties. The heterogeneity of substituents in bulk polymers is a general analytical problem, and the method presented here is applicable to other polymers.

Nowadays, drug encapsulation and drug release from cellulose nanofibrils systems are intense research topics, and commercial grades of cellulose nanomaterials are currently available. In this work we present an ester-containing prodrug of metronidazole that is covalently bound to cellulose nanofibrils in aqueous suspension through a two-step immobilization procedure involving green chemistry principles. The presence of the drug is confirmed by several characterization tools and methods such as Raman spectroscopy, elemental analysis, Dynamic Nuclear Polarization enhanced NMR. This technique allows enhancing the sensitivity of NMR by several orders of magnitude. It has been used to study cellulose nanofibrils substrates and it appears as the ultimate tool to confirm the covalent nature of the binding through thiol-yne click chemistry. Moreover, the ester function of the immobilized prodrug can be cleaved by specific enzyme activity thus allowing controlled drug release.

Driven by the rise of the electric automotive industry, the Li-ion battery market is in strong expansion. This technology does not only fulfill the requirements of electric mobility, but is also found in most portable electric devices. Even though Li-ion batteries are known for their numerous advantages, they undergo serious performance degradation during their aging, and more particularly when used in specific conditions such as at low temperature or high charging current rates. Depending on the operational conditions, different aging mechanisms are favored and can induce physical and chemical modifications of the internal components, leading to performance decay. In this article, the identification of the degradation mechanisms was carried out thanks to an in-depth ante- and post mortem study on three high power and high energy commercial 18,650 cells. Li-ion cells were aged using a battery electric vehicle (BEV) aging profile at −20 °C, 0 °C, 25 °C, and 45 °C in accordance with the international standard IEC 62-660, and in calendar aging mode at 45 °C and SOC 100%. Internal components recovered from fresh and aged cells were investigated through different electrochemical (half-coin cell), chemical (EDX, GD-OES, NMR), and topological (SEM) characterization techniques. The influence of power and energy cells’ internal design and Si content in the negative electrode on cell aging has been highlighted vis-à-vis the capacity and power fade.

Dynamic Nuclear Polarization MAS NMR is introduced to characterize model methylcellulose ether compounds at natural isotopic abundance. In particular an approach is provided to determine the position of the methyl ether group within the repeating unit. Specifically, natural abundance 13C-13C correlation experiments are used to characterize model 3-O-methylcellulose and 2,3-O-dimethylcellulose, and identify changes in chemical shifts with respect to native cellulose. We also probe the use of through space connectivity to the closest carbons to the CH3 to identify the substitution site on the cellulose ether. To this end, a series of methylcellulose ethers was prepared by a multistep synthesis approach. Key intermediates in these reactions were 2,6-O-diprotected thexyldimethylsilyl (TDMS) cellulose and 6-O-monoprotected TDMS cellulose methylated under homogeneous conditions. The products had degrees of substitution of 0.99 (3-O-methylcellulose) and 2.03 (2,3-O-dimethylcellulose) with exclusively regioselective substitution. The approaches developed here will allow characterization of the substitution patterns in cellulose ethers.

The coexistence of three different types of Na-ion motion has been revealed in the temperature range 300–750 K.

Chemical modifications of cellulose fibers as pretreatment for cellulose nanofibrils (CNF) production have been investigated to improve the production process and the quality of obtained cellulosic nanomaterial. In this study, phosphorylation of cellulose fibers was done in anticipation of a future nanofibrillation. Different phosphate salts, namely NH4H2PO4, (NH4)2HPO4, Na2HPO4, NaH2PO4 and LiH2PO4 with different constants of solubility (Ks) were used to increase the efficiency of the modification. Phosphorylated cellulose pulps were analyzed using elemental analysis, solid-state 13C and 31P NMR, or conductimetric titration method. No effect of Ks was observed whereas a counterion effect was pointed out. The study also reported the effect of pH, cellulose consistency, temperature and urea content in phosphorylation efficiency. Finally, chemical functionalization and penetration of phosphorylation reagents in the cellulose fibers were evaluated using XPS, SEM-EDX, ToF-SIMS and solid-state NMR.

The Solid Electrolyte Interphase (SEI) has been considered as “the Most Important and the Least Understood Solid Electrolyte in Rechargeable Li Batteries” by Winter in 2009 [1]. Being aware that its stability has a significant impact on their performance, lifespan and safety, the scientific community tries to improve knowledge on this interface. Experimental studies have been achieved to observe the global composition of the SEI on common anodes (lithium, graphite and silicon) [2], [3]. LiF, Li 2 CO 3 , polyolefins and semicarbonates detected in the SEI derives from electrolyte compounds degradation. Several SEI models have been discussed (mosaic, super capacitor, multi-layers, etc), but they are still being debated. Finding the “perfect” model is challenging because this model should be able to explain conductive (ions) and resistive (electrons) properties of the SEI, as well as its formation and ageing. As of today, most of the knowledge concerning Li transport properties and SEI formation comes from theoretical studies and are based on simulations. Li isotopic tracing has already been successfully employed to study the Li dynamics in components of Li-ions accumulators. Since 2011 [4], Li isotope tracing has been used about 10 times in this field. In all literature, isotopes are introduced in specific parts of a cell (anode, cathode or electrolyte). In our study, we have added them at different states of charge (100% or 0%) in order to label selectively the SEI. This study aims at investigating the lithium dynamics within the SEI during the first cycles of charge and discharge. Trapped lithium (in the SEI) can be distinguished from active lithium by using its natural isotopes 6 Li and 7 Li. Two specific systems have been studied: SEI on graphite and SEI on silicon. During a first step, the SEI have been generated in 7 Li. Then, the electrode has been recovered and re-used in a new cell in front of a 6 Li-enriched counter electrode and electrolyte. By using time-of-flight secondary ion mass spectrometry (ToF-SIMS), we have been able to track 7 Li and 6 Li distribution in the electrode. First results on graphite electrode have shown that “trapped” Li is eventually highly mobile, even when the system is down (without polarization of the electrode). Indeed, when electrolyte and electrode are in contact without any electric field, lithium initially present in the electrolyte have been detected in the SEI. The same kind of experiments have been carried out on silicon-based electrodes. In addition to ToF-SIMS characterization, 7 Li and 6 Li Solid State Nuclear Magnetic Resonance (NMR) analyses have been performed. ToF-SIMS allows probing the surface chemistry on a small sample of the electrode (~1000 µm²), while NMR spectroscopy investigates the whole sample and allows knowing the chemical environment of the probed nucleus. The same observation has been made in these experiments: lithium “trapped” in the SEI is highly mobile. As no self-discharge has been observed, it is probably mainly related to isotope exchanges. These results paves the way for calculations of diffusion coefficients, as well as for the estimation of a characteristic length and thickness of the probed SEI. Other isotope experiments have also been carried out. However, natural isotope exchanges, even without polarization of the electrode, tend to hide information by homogenizing isotope concentrations. Optimization of experiments and operando measurements may overcome such issues. [1] M. Winter, Zeitschrift für Physikalische Chemie , 223 , 1395–1406 (2009). [2] E. Peled and S. Menkin, Journal of The Electrochemical Society , 164 , A1703–A1719 (2017). [3] S. J. An et al., Carbon , 105 , 52–76 (2016). [4] P. Lu and S. J. Harris, Electrochemistry Communications , 13 , 1035–1037 (2011). Figure 1

Conservation treatment of degraded archaeological osseous materials is still an open challenge, since no specific conservation protocol is currently available for restorers or museum curators. This work aims to test the efficiency of two original consolidant solutions in consolidating archaeological material. Archaeological osseous materials remain rare and sparsely available, it is a real drawback for optimization of conservation treatments, therefore in the present work a set of representative samples was chosen. The consolidants tested were a solution of disodium sebacate and a novel polyalcohol (SG1.2) obtained by esterification of 5 succinic diacids with 6 molecules of glycerol at 150°C. Characterization studies of archaeological bones, combining SEM microscopy, IR spectroscopy and high-resolution solid-state 13 C NMR investigations, have been carried out to assess the effective permeation of bone by the consolidant solutions and to determine their chemical interactions with the residual components of archaeological bones. Although both water solutions significantly impregnate bone, we show that, the solution with disodium sebacate leads to chemical attack on the mineral component due to preferential precipitation of endogenous calcium by the sebacate ions. Such deleterious behaviour is not observed at all with the SG1,2 chemicals. The added value of the polyalcohol treatment as strengthening agent suitable for archaeological bony materials should be further demonstrated by mechanical and ageing tests.

In the continuously developing field of lignocellulosic biomass, high-yield lignin depolymerization processes are sought to optimize its productivity and profitability. Recently, formaldehyde stabilization during lignin extraction and biomass pretreatment has been found to drastically enhance subsequent lignin upgradeability but can affect cellulose digestibility. The exact role and/or form of formaldehyde on the residual biomass surface is still not fully understood. Here, we use magic angle spinning (MAS) dynamic nuclear polarization (DNP) methods to characterize the components that remain inside the residual cell wall after the lignin extraction process and reveal the topochemistry of the solid residue. The regioselectivity of relayed DNP allows the observation of hyperpolarization in a range of 40–200 nm from the surface of the cell wall for poplar wood materials. That regioselectivity allows us to distinguish between the external secondary cell wall and the inner middle lamellae. In that respect, for the untreated wood, we confirm that there is less lignin in the outer part of the cell wall than deeper inside. In treated wood, we determine that the role of dioxane during the process is to enable the extraction of the modified products from the cell wall. We show that the modified lignins which were not extracted in the absence of dioxane accumulate in a 40 nm region at the surface of the cell wall. Also, using carbon-13 enriched formaldehyde during the process, we show that 1% of the total amount of carbon in the material is assigned to self-polymerization and that no covalent bonds to cellulose are observed.

We investigate water infiltration in porous matrices made of bitumen and salts with different solubilities. Dispersion, inside bitumen, of either SrSO4 or MgSO4 at 40% mass fraction was achieved, as a way to model materials used in the context of nuclear waste conditioning. Pulsed field gradient nuclear magnetic resonance (PFG-NMR) and environmental scanning electron microscopy (ESEM) measurements allow us to characterize the evolution of the porous structure as a consequence of water infiltration (due to a leaching phenomenon) for durations up to 1.5 year. PFG-NMR enables performing 1D-imaging of water at different times to monitor its slow seeping inside the material. Profiles observed at the maximum time interval (1.5 year) demonstrate that different leaching behaviors exist depending on whether the salts dispersed inside bitumen are of the soluble or insoluble type. NMR relaxation and diffusion measurements were also taken. Remarkably, when performed in combination with 1D-imaging, such measurements yield information on the surface-to-volume ratio of the water-filled porous network, at different times, as a function of depth. In the case of the matrix-containing insoluble salts, relaxation measurements lead to discrimination between two different water populations differing by their T-2 or T-1 values. These values are described in the framework of surface-driven relaxation. A two-step model of leaching is proposed that globally accounts for the different observations (NMR 1D-imaging, relaxation/diffusion, as well as ESEM). The present work gives insight into the leaching behavior of porous bitumen-salt matrices and could be used as an input for modeling their evolution on longer timescales.

In this work, new gelled electrolytes were prepared based on a mixture containing phosphonium ionic liquid (IL) composed of trihexyl(tetradecyl)phosphonium cation combined with bis(trifluoromethane)sulfonimide [TFSI] counter anions and lithium salt, confined in a host network made from an epoxy prepolymer and amine hardener. We have demonstrated that the addition of electrolyte plays a key role on the kinetics of polymerization but also on the final properties of epoxy networks, especially thermal, thermo-mechanical, transport, and electrochemical properties. Thus, polymer electrolytes with excellent thermal stability (>300 °C) combined with good thermo-mechanical properties have been prepared. In addition, an ionic conductivity of 0.13 Ms·cm−1 at 100 °C was reached. Its electrochemical stability was 3.95 V vs. Li0/Li+ and the assembled cell consisting in Li|LiFePO4 exhibited stable cycle properties even after 30 cycles. These results highlight a promising gelled electrolyte for future lithium ion batteries.

NMR can be used for in situ studies of lipidic components, mainly triacylglycerols (TAG), in mature seeds. Lipids can be one of the most abundant constituents of seeds in oleaginous crops. The inputs of high-resolution solid-state 1H or 13C NMR and pulsed field gradient 1H NMR (PFG NMR) are presented in this chapter. By combining single pulse excitation (SP) and cross-polarization (CP) experiments, both liquid and solid domains of plant seeds can be characterized and the assignments of the corresponding 13C and 1H can be performed. As TAG are confined in oil bodies (OBs), analysis of their diffusion properties, determined with PFG NMR, is a well-suited experimental approach to determine OB sizes. In fact, at long diffusion time, TAG mean squared displacement is limited by the OB size. In order to access the OB size distribution, strong intensities of magnetic field gradients are generally required. However, using a standard liquid-phase NMR probe equipped with a weak-intensity gradient coil, the mean size of OBs can be determined. OB diameters obtained by PFG NMR were fully consistent with previously published values obtained by microscopy techniques.