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Substituted Li-layered transition-metal oxide (LTMO) electrodes such as LixNiyMnzCo1-y-zO2 (NMC) and LixNiyCo1-y-zAlzO2 (NCA) show reduced first cycle Coulombic efficiency (90-87% under standard cycling conditions) in comparison with the archetypal LixCoO2 (LCO; ∼98% efficiency). Focusing on LixNi0.8Co0.15Al0.05O2 as a model compound, we use operando synchrotron X-ray diffraction (XRD) and nuclear magnetic resonance (NMR) spectroscopy to demonstrate that the apparent first-cycle capacity loss is a kinetic effect linked to limited Li mobility at x > 0.88, with near full capacity recovered during a potentiostatic hold following the galvanostatic charge-discharge cycle. This kinetic capacity loss, unlike many capacity losses in LTMOs, is independent of the cutoff voltage during delithiation and it is a reversible process. The kinetic limitation manifests not only as the kinetic capacity loss during discharge but as a subtle bimodal compositional distribution early in charge and, also, a dramatic increase of the charge-discharge voltage hysteresis at x > 0.88. 7Li NMR measurements indicate that the kinetic limitation reflects limited Li transport at x > 0.86. Electrochemical measurements on a wider range of LTMOs including Lix(Ni,Fe)yCo1-yO2 suggest that 5% substitution is sufficient to induce the kinetic limitation and that the effect is not limited to Ni substitution. We outline how, in addition to a reduction in the number of Li vacancies and shrinkage of the Li-layer size, the intrinsic charge storage mechanism (two-phase vs solid-solution) and localization of charge give rise to additional kinetic barriers in NCA and nonmetallic LTMOs in general.

Nickel-rich layered oxides are promising positive electrode materials for lithium-ion batteries due to their high capacity and decreased cobalt content. The application of surface coatings is a common approach to slowing or potentially stopping deleterious reactions at the electrode-electrolyte interface of lower-Ni content layered oxides. However, their efficacy on Ni-rich LiNi0.8Mn0.1Co0.1O2 (NMC811) is less certain and knowledge on how to design effective coatings with favorable properties is sparse. In this work, we develop a convenient solution-based deposition method for the synthesis of aluminum oxide coatings NMC811 secondary particles and we study the effects of annealing temperature on their structure and electrochemical lifetime in lithium-ion batteries. Using energy dispersive X-ray spectroscopy (EDS) and X-ray fluorescence spectroscopy (XRF), we quantify the amount and distribution of aluminum oxide on the cathode particles. Changes in the coating phase and composition as a function of annealing temperature are tracked with solid-state nuclear magnetic resonance (SS-NMR) and X-ray photoelectron spectroscopy (XPS). 27Al NMR spectroscopy at very high field (23.5 T) provides direct evidence that after annealing up to 400 °C, 4-, 5- and 6-coordinate aluminum is present, here assigned to an amorphous alumina coating, but after annealing to 600 ºC, a γ-LiAlO2-like coating is observed. We further differentiate between Al in the bulk and surface phase and identify, for the first time, the critical temperature at which doping occurs in NMC811. Surface/bulk doping starts to occur in the range 500 – 600 °C, with considerable bulk doping being found at 800 °C. The onset of Al diffusion coincides with the decrease in capacity retention, contradicting previous studies and giving new insight into the relationship between lifetime and lithium-ion conductivity.

Li-ion batteries (LIBs) are attractive and ubiquitous energy storage solutions, however, their lifetime is limited by gradual capacity loss or even full failure. A more holistic understanding of physical, chemical, and electrochemical processes in a functioning LIB is required to understand the origins of this performance loss. Therefore, it is crucial to conduct analytical measurements operando on a working battery. To date, most operando techniques face great technical challenges in cell design and experimental setup, which often leads to practical limitations. For example, only slow charging rates can be applied and/or “half-cells” are used where one electrode is replaced by Li metal. Such measurements are therefore often not suitable for studying the performance and degradation mechanisms of batteries in practical configurations and under realistic cycling conditions. In this contribution, we demonstrate that operando 7Li NMR spectroscopy can be applied to full LIBs while maintaining realistic and reproducible cycling performance at practical rates.[1] We exemplify this on LiNi0.8Mn0.1Co0.1O2 (NMC811)/graphite cells which are typical high-energy LIBs. Building up on our previous work on NMC811 cathodes in which we used ex situ magic-angle spinning 7Li NMR to study changes of structure and Li dynamics during electrochemical cycling,[2] we now present operando NMR studies of this highly paramagnetic material in full-cells. Using specially adapted NMR pulse sequences, we observe Li ions not only in the NMC811 cathode, but also in the graphite anode. This enables us to separately track Li insertion and extraction in both electrodes, making this the first operando NMR study of a full-cell in which both electrodes are investigated. Employing this setup, we study battery cycling at different rates and at temperatures between -20 and +55 °C, representing the varying operating conditions of LIBs. We describe the structural changes of the electrodes during charge and discharge, as well as the evolution of Li-ion mobility in the electrodes at different temperatures, an important factor for fast-charging applications. The operando NMR experiments also enable the observation of Li metal deposition on the graphite anode at low temperatures, which is a severe degradation mechanism and serious safety hazard in LIBs. Even small quantities of Li metal can be detected, which do not necessarily cause electrochemical features but still contribute to cell degradation. We observe Li metal plating during charge and stripping during discharge and investigate the dependence of these processes on charging current, voltage and temperature. Overall, these operando NMR experiments offer unique insights into the Li metal deposition process under different charging conditions and open up exciting possibilities for further studies of this serious degradation mechanism. References [1] K. Märker, C. Xu, C. P. Grey, submitted. [2] K. Märker, P. J. Reeves, C. Xu, K. J. Griffith, C. P. Grey, Chem. Mater. 2019, 31, 2545–2554. Figure 1

Ni-rich layered cathode materials are among the most promising candidates for high-energy-density Li-ion batteries, yet their degradation mechanisms are still poorly understood. We report a structure-driven degradation mechanism for NMC811 (LiNi0.8Mn0.1Co0.1O2), in which a proportion of the material exhibits a lowered accessible state of charge at the end of charging after repetitive cycling and becomes fatigued. Operando synchrotron long-duration X-ray diffraction enabled by a laser-thinned coin cell shows the emergence and growth in the concentration of this fatigued phase with cycle number. This degradation is structure driven and is not solely due to kinetic limitations or intergranular cracking: no bulk phase transformations, no increase in Li/Ni antisite mixing and no notable changes in the local structure or Li-ion mobility of the bulk are seen in aged NMCs. Instead, we propose that this degradation stems from the high interfacial lattice strain between the reconstructed surface and the bulk layered structure that develops when the latter is at states of charge above a distinct threshold of approximately 75%. This mechanism is expected to be universal in Ni-rich layered cathodes. Our findings provide fundamental insights into strategies to help mitigate this degradation process. Ni-rich layered cathode materials are promising for high-energy-density Li-ion batteries, but their degradation mechanisms are still poorly understood. A structure-driven mechanism with a lowered accessible state of charge after repetitive cycling is proposed for a typical NMC811 cathode.

Ni-rich layered cathode materials are among the most promising candidates for high energy density Li-ion batteries. However, the low cobalt containing materials suffer from rapid degradation, the underlying mechanism of which is still poorly understood. We herein report a novel structure-drive degradation mechanism for the NMC811(LiNi0.8Mn0.1Co0.1O2) cathode, in which a proportion of the material exhibits a lowered accessible state-of-charge (SoC) at the end of charge after repetitive cycling, i.e. becomes fatigued. Ex-situ and operando long- duration high-resolution X-ray diffraction enabled by a laser-thinned coin cell design clearly shows the emergence of the fatigued phase and the increase in its population as the cycling progresses. We show that the fatigue degradation is a structure-driven process rather than originating solely due to kinetic limitations or inter-granular cracking. No bulk phase transformations or increase in Li/Ni antisite mixing were observed by diffraction; no significant change in the local structure or Li-ion mobility of the bulk were observed by 7Li solid-state NMR spectroscopy. Instead, we propose that the fatigue process is a result of the high interfacial lattice strain between the reconstructed surface and the bulk layered structure when the latter is at SoCs above a distinct threshold of ~75 %. This mechanism is expected to be universal to Ni-rich layer cathodes, and our findings provide a fundamental guide for designing effective approaches to mitigate such deleterious processes.

International audience; A pathological hallmark of Huntington's disease (HD) is the formation of neuronal protein deposits containing mutant huntingtin fragments with expanded polyglutamine (polyQ) domains. Prior studies have shown the strengths of solid-state NMR (ssNMR) to probe the atomic structure of such aggregates, but have required in vitro isotopic labeling. Herein, we present an approach for the structural fingerprinting of fibrils through ssNMR at natural isotopic abundance (NA). These methods will enable the spectroscopic fingerprinting of unlabeled (e.g., ex vivo) protein aggregates and the extraction of valuable new long-range 13 C− 13 C distance constraints

Li metal anodes represent the ultimate energy density, but to address safety issues caused by dendrite formation, it is critical to understand the solid–electrolyte interphase (SEI) layer which forms on the metal surface. Dynamic nuclear polarisation (DNP) boosts sensitivity in NMR by harnessing the greater polarisation of unpaired electrons, however typical exogenous organic radicals are non-selective, could react with the SEI, and require cooling the sample to cryogenic temperatures. We instead exploit the inherent conduction electrons to hyperpolarise lithium metal at room temperature, utilising the Overhauser mechanism by which DNP was first discovered. This permits selective enhancement of the organic and inorganic SEI components, revealing their chemical nature and spatial distribution, via the 7Li, 1H and 19F NMR spectra.

International audience; Dynamic nuclear polarization (DNP) has made feasible solid-state NMR experiments that were previously thought impractical due to sensitivity limitations. One such class of experiments is the structural characterization of organic and biological samples at natural isotopic abundance (NA). Herein, we describe the many advantages of DNP-enabled ssNMR at NA, including the extraction of long-range distance constraints using dipolar recoupling pulse sequences without the deleterious effects of dipolar truncation. In addition to the theoretical underpinnings in the analysis of these types of experiments, numerous applications of DNPenabled ssNMR at NA are discussed.

Dynamic nuclear polarization (DNP) has made feasible solid-state NMR experiments that were previously thought impractical due to sensitivity limitations. One such class of experiments is the structural characterization of organic and biological samples at natural isotopic abundance (NA). Herein, we describe the many advantages of DNP-enabled ssNMR at NA, including the extraction of long-range distance constraints using dipolar recoupling pulse sequences without the deleterious effects of dipolar truncation. In addition to the theoretical underpinnings in the analysis of these types of experiments, numerous applications of DNP-enabled ssNMR at NA are discussed.

The nickel-rich layered oxide LiNi0.8Mn0.1Co0.1O2 (NMC811) is a promising future cathode material for lithium-ion batteries in electric vehicles due to its high specific energy density. However, it exhibits fast voltage and capacity fading. In this article, we combine electrochemistry, operando synchrotron X-ray diffraction (XRD), and ex situ solid-state NMR spectroscopy to provide new insights into the structural changes and lithium dynamics of NMC811 during electrochemical charge and discharge, which are essential for a better understanding of its fast degradation. The evolution of the interlayer spacing is tracked by XRD, showing that it gradually increases upon delithiation before collapsing at high state-of-charge (SOC). Importantly, no two-phase O3 → O1 transition is observed at high SOC, demonstrating that this cannot be a major cause of degradation. A strong increase of Li dynamics accompanies the increase of the interlayer spacing, which is shown by 7Li NMR and electrochemical characterization. A...

The synthesis of photoswitchable glycooligomers is presented by applying solid-phase polymer synthesis and functional building blocks. The obtained glycoligands are monodisperse and present azobenzene moieties as well as sugar ligands at defined positions within the oligomeric backbone and side chains, respectively. We show that the combination of molecular precision together with the photoswitchable properties of the azobenzene unit allows for the photosensitive control of glycoligand binding to protein receptors. These stimuli-sensitive glycoligands promote the understanding of multivalent binding and will be further developed as novel biosensors.

Supercapacitors have the potential to play an important role in high-power energy storage solutions, in particular for power quality and stability applications which require fast cycling and long lifetimes. However, their underlying charging mechanisms and the interactions between the electrodes, the ions and the solvent are not fully understood. In situ NMR techniques can measure in-pore ion populations and can thus provide unique insights into the charging mechanisms, but have so far focused on measurements at equilibrium. Since one of the key advantages of supercapacitors is their fast charging/discharging rates, it is crucial to be able to study the dynamic charging behavior that more closely represents the performance of a working device. In this work, we develop an operando NMR technique based on the synchronization between NMR and electrochemical measurements and investigate the dynamic charging mechanism of electric double layer capacitors based on activated carbon electrodes. The novel method uncovers the significance of the so-called “weakly adsorbed” ion environment, which is shown to take part in the charging process and is thought to be associated with mesopores within the carbon electrode. These findings advance our current understanding of supercapacitor charging mechanisms and the role of the 3D electrode structure, and the synchronized operando NMR method can be applied to a wide range of reversible devices.

Life developed on Earth probably about 3.8 billion years ago, on a planet that was already largely covered by oceans and where the atmosphere was very humid. The reactions, which may have led to the formation of the first polymers, particularly to the first peptides and nucleic acids, must have been compatible with these conditions. This is the case of the reaction of nitriles with aminothiols, such as cysteine and homocysteine. Since aminonitriles are the probable precursors of amino acids, this condensation reaction has been able to rapidly yield dipeptides, tripeptides, oligomers and even true polymers, each containing thiol functions. These thiol-rich peptides (TRP's) would then have assumed the various catalytic roles that the peptides containing cysteine residues play today. They allowed a rapid bloom of life in the primitive ocean. In this scenario, RNA's are not the first polymers, but have been synthesized, like DNA's, thanks to the catalytic properties of thiols in a mostly TRP world. In this world, due to its ability to form a thiolactone, homocysteine may have played the leading role in enabling the previously formed oligomers to be stappled together, thus accelerating the formation of long peptide chains.

The low natural abundance of 13C combined with MAS-DNP enables 13C–13C polarization transfer up to ∼7 Å and observation of π-stacking., The self-assembly of small organic molecules is an intriguing phenomenon, which provides nanoscale structures for applications in numerous fields from medicine to molecular electronics. Detailed knowledge of their structure, in particular on the supramolecular level, is a prerequisite for the rational design of improved self-assembled systems. In this work, we prove the feasibility of a novel concept of NMR-based 3D structure determination of such assemblies in the solid state. The key point of this concept is the deliberate use of samples that contain 13C at its natural isotopic abundance (NA, 1.1%), while exploiting magic-angle spinning dynamic nuclear polarization (MAS-DNP) to compensate for the reduced sensitivity. Since dipolar truncation effects are suppressed to a large extent in NA samples, unique and highly informative spectra can be recorded which are impossible to obtain on an isotopically labeled system. On the self-assembled cyclic diphenylalanine peptide, we demonstrate the detection of long-range internuclear distances up to ∼7 Å, allowing us to observe π-stacking through 13C–13C correlation spectra, providing a powerful tool for the analysis of one of the most important non-covalent interactions. Furthermore, experimental polarization transfer curves are in remarkable agreement with numerical simulations based on the crystallographic structure, and can be fully rationalized as the superposition of intra- and intermolecular contributions. This new approach to NMR crystallography provides access to rich and precise structural information, opening up a new avenue to de novo crystal structure determination by NMR.

International audience; 2D double-quantum single-quantum correlation spectra with arbitrary spectral widths can be recorded with SR26 and related supercycled recoupling sequences when applying Supercycle-Timing-Compensation (STiC) phase shifts. This concept widely extends the applicability of supercycled sequences, most importantly for obtaining long-range distance constraints for structure determination with solid-state NMR.

Dynamic nuclear polarization exploits electron spin polarization to boost signal-to-noise in magic-angle-spinning (MAS) NMR, creating new opportunities in materials science, structural biology, and metabolomics studies. Since protein NMR spectra recorded under DNP conditions can show improved spectral resolution at 180-200 K compared to 110 K, we investigate the effects of AMUPol and various deuterated TOTAPOL isotopologues on sensitivity and spectral resolution at these temperatures, using proline and reproducibly prepared SH3 domain samples. The TOTAPOL deuteration pattern is optimized for protein DNP MAS NMR, and signal-to-noise per unit time measurements demonstrate the high value of TOTAPOL isotopologues for Protein DNP MAS NMR at 180-200 K. The combined effects of enhancement, depolarization, and proton longitudinal relaxation are surprisingly sample-specific. At 200 K, DNP on SH3 domain standard samples yields a 15-fold increase in signal-to-noise over a sample without radicals. 2D and 3D NCACX/NCOCX spectra were recorded at 200 K within 1 and 13 hours, respectively. Decreasing enhancements with increasing (2)H-content at the CH2 sites of the TEMPO rings in CD3-TOTAPOL highlight the importance of protons in a sphere of 4-6 Å around the nitroxyl group, presumably for polarization pickup from electron spins.

International audience; NMR crystallography of organic molecules at natural isotopic abundance (NA) strongly relies on the comparison of assigned experimental and computed NMR chemical shifts. However, a broad applicability of this approach is often hampered by the still limited H-1 resolution and/or difficulties in assigning C-13 and N-15 resonances without the use of structure-based chemical shift calculations. As shown here, such difficulties can be overcome by C-13-C-13 and for the first time N-15-C-13 correlation experiments, recorded with the help of dynamic nuclear polarization. We present the complete de novo C-13 and N-15 resonance assignment at NA of a self-assembled 2'-deoxyguanosine derivative presenting two different molecules in the asymmetric crystallographic unit cell. This de novo assignment method is exclusively based on aforementioned correlation spectra and is an important addition to the NMR crystallography approach, rendering firstly H-1 assignment straightforward, and being secondly a prerequisite for distance measurements with solid-state NMR.