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Sodium ion batteries, because of their sustainability attributes, could be an attractive alternative to Li-ion technology for specific applications. However, it remains challenging to design high energy density and moisture stable Na-based positive electrodes. Here, we report an O3-type NaLi1/3Mn2/3O2 phase showing anionic redox activity, obtained through a ceramic process by carefully adjusting synthesis conditions and stoichiometry. This phase shows a sustained reversible capacity of 190 mAh g-1 that is rooted in cumulative oxygen and manganese redox processes as deduced by combined spectroscopy techniques. Unlike many other anionic redox layered oxides so far reported, O3-NaLi1/3Mn2/3O2 electrodes do not show discernible voltage fade on cycling. This finding, rationalized by density functional theory, sheds light on the role of inter- versus intralayer 3d cationic migration in ruling voltage fade in anionic redox electrodes. Another practical asset of this material stems from its moisture stability, hence facilitating its handling and electrode processing. Overall, this work offers future directions towards designing highly performing sodium electrodes for advanced Na-ion batteries.

The intrinsic ionic conductivity of polyethylene oxide (PEO)-based block copolymer electrolytes is often assumed to be identical to the conductivity of the PEO homopolymer. Here, we use high-field 7Li nuclear magnetic resonance (NMR) relaxation and pulsed-field-gradient (PFG) NMR diffusion measurements to probe lithium ion dynamics over nanosecond and millisecond time scales in PEO and polystyrene (PS)-b-PEO-b-PS electrolytes containing the lithium salt LiTFSI. Variable-temperature longitudinal (T1) and transverse (T2) 7Li NMR relaxation rates were acquired at three magneticfield strengths and quantitatively analyzed for the first time at such fields, enabling us to distinguish two characteristic time scales that describe fluctuations of the 7Li nuclear electric quadrupolar interaction. Fast lithium motions [up to O(ns)] are essentially identical between the two polymer electrolytes, including sub-nanosecond vibrations and local fluctuations of the coordination polyhedra between lithium and nearby oxygen atoms. However, lithium dynamics over longer time scales [O(10 ns) and greater] are slower in the block copolymer compared to the homopolymer, as manifested experimentally by their different transverse 7Li NMR relaxation rates. Restricted dynamics and altered thermodynamic behavior of PEO chains anchored near PS domains likely explain these results. [ABSTRACT FROM AUTHOR]

Magic‐angle‐spinning (MAS) enhances sensitivity and resolution in solid‐state nuclear magnetic resonance (NMR) measurements. MAS is obtained by aerodynamic levitation and drive of a rotor, which results in large centrifugal forces that may affect the physical state of soft materials, such as polymers, and subsequent solid‐state NMR measurements. Here, we investigate the effects of MAS on the solid‐state NMR measurements of a polymer electrolyte for lithium‐ion battery applications, poly(ethylene oxide) (PEO) doped with the lithium salt LiTFSI. We show that MAS induces local chain ordering, which manifests itself as characteristic lineshapes with doublet‐like splittings in subsequent solid‐state 1H, 7Li, and 19F static NMR spectra characterizing the PEO chains and solvated ions. MAS results in distributions of stresses and hence local chain orientations within the rotor, yielding distributions in the local magnetic susceptibility tensor that give rise to the observed NMR anisotropy and lineshapes. The effects of MAS were investigated on solid‐state 7Li and 19F pulsed‐field‐gradient (PFG) diffusion and 7Li longitudinal relaxation NMR measurements. Activation energies for ion diffusion were affected modestly by MAS. 7Li longitudinal relaxation rates, which are sensitive to lithium‐ion dynamics in the nanosecond regime, were essentially unchanged by MAS. We recommend that NMR researchers studying soft polymeric materials use only the spin rates necessary to achieve the desired enhancements in sensitivity and resolution, as well as acquire static NMR spectra after MAS experiments to reveal any signs of stress‐induced local ordering. [ABSTRACT FROM AUTHOR]

The surface fluorination of lithium cobalt phosphate (LiCoPO4, LCP) using a one‐step, room temperature processable, easily up‐scalable and dry surface modification method with XeF2 as fluorine source was developed. After fluorination, fluorine‐rich nanoparticles were observed mainly on the particle surface, which facilitates the improvement of surface stability and electrochemical performance such as cycling stability and rate capability, as the fluorinated LCP can be protected against side reactions with electrolyte or by‐products of electrolyte decomposition at high voltage (5 V). More importantly, the direct surface fluorination proved more efficient than adding a fluorinated electrolyte additive (i. e., FEC). These results suggest that surface fluorination using XeF2 is of great promise for practical applications of high voltage positive materials for lithium‐ion batteries. [ABSTRACT FROM AUTHOR]

We explain how and under which conditions it is possible to obtain an efficient inversion of an entire sideband family of several hundred kHz using low-power, sideband-selective adiabatic pulses, and we illustrate with some experimental results how this framework opens new avenues in solid-state NMR for manipulating spin systems with wide spinning-sideband (SSB) manifolds. This is achieved through the definition of the criteria of phase and amplitude modulation for designing an adiabatic inversion pulse for rotating solids. In turn, this is based on a framework for representing the Hamiltonian of the spin system in an NMR experiment under magic angle spinning (MAS). Following earlier ideas from Caravatti et al. [J. Magn. Reson. 55, 88 (1983)], the so-called 'jolting frame' is used, which is the interaction frame of the anisotropic interaction giving rise to the SSB manifold. In the jolting frame, the shift modulation affecting the nuclear spin is removed, while the Hamiltonian corresponding to the RF field is frequency modulated and acquires a spinning-sideband pattern, specific for each crystallite orientation. [ABSTRACT FROM AUTHOR]

Adiabaticity plays a central role in modern magnetic resonance experiments, as excitations with adiabatic Hamiltonians allow precise control of the dynamics of the spin states during the course of an experiment. Surprisingly, many commonly used adiabatic processes in magnetic resonance perform well even though the adiabatic approximation does not appear to hold throughout the process. Here we show that this discrepancy can now be explained through the use of Berry’s superadiabatic formalism, which provides a framework for including the finite duration of the process in the theoretical and numerical treatments. In this approach, a slow, but finite time-dependent Hamiltonian is iteratively transformed into time-dependent diagonal frames until the most accurate adiabatic approximation is obtained. In the case of magnetic resonance, the magnetization during an adiabatic process of finite duration is not locked to the effective Hamiltonian in the conventional adiabatic frame, but rather to an effective Hamiltonian in a superadiabatic frame. Only in the superadiabatic frame can the true validity of the adiabatic approximation be evaluated, as the inertial forces acting in this frame are the true cause for deviation from adiabaticity and loss of control during the process. Here we present a brief theoretical background of superadiabaticity and illustrate the concept in the context of magnetic resonance with commonly used shaped radio-frequency pulses. [ABSTRACT FROM AUTHOR]

In this work, the physical, transport and electrochemical properties of various electrolytic solutions containing the 1-propyl-1-methylpyrrolidinium bis[fluorosulfonyl]imide ([C3C1pyr][FSI]) mixed with the lithium bis[(trifluoromethyl)sulfonyl]imide (Li[TFSI]) over a wide range of compositions are reported as a function of temperature at atmospheric pressure. First, the ionicity, lithium transference number, and transport properties (viscosity and conductivity) as well as the volumetric properties (density and molar volume) were determined as a function of lithium salt concentration from 293 to 343 K. Second, the self-diffusion coefficient of each ion in solution was measured by nuclear magnetic resonance (NMR) spectroscopy with pulsed field gradients (PFG). Moreover, an analysis of the collected nuclear Overhauser effect (NOE) data along with ab initio and COSMO-RS calculations was conducted to depict intra and intermolecular neighbouring within the electrolytic mixtures. Based on this analysis, and as expected, all activation energies increase with the Li[TFSI] concentration in solution, and all activation energies were determined from the self-diffusion data for all ions. Interestingly, regardless of the composition in solution, these activation energies were similar, except for those determined for the [FSI]− anion. The activation energy of [FSI]− self-diffusion relatively decreases compared to the other ions as the lithium salt concentration increases. Furthermore, the lithium transference was strongly affected by the lithium salt concentration, reaching an optimal value and an ionicity of approximately 50 % at a molality close to 0.75 mol · kg−1. Finally, these electrolytes were used in lithium-ion batteries (i.e. Li/NMC and LTO/NMC), demonstrating a clear relationship between the electrolyte formulation, its transport parameters and battery performance. [ABSTRACT FROM AUTHOR]

The HOESY (Heteronuclear Overhauser Effect SpectroscopY) NMR experiment is commonly used to study interactions and structuring in ionic liquids (ILs) via the measurement of the cross relaxation rate σ between two spins. In the intermolecular case, σ is proportional to r−n, where r is the internuclear distance and n can vary between 1 and 6 depending on the frequency of the nuclei and their dynamics, thus σ can potentially provide detailed information on the liquid phase structure. However, in HOESY studies of ILs only relative values for σ are typically reported, making comparisons between different samples difficult. Herein we discuss the quantitative measurement of intermolecular cross relaxation rates based on the normalisation of HOESY signal intensities to the nuclear Boltzmann polarisation, demonstrated for 7Li–1H spin pairs in a lithium-containing pyrrolidinum-based ionic liquid electrolyte. We also use a simple model based on diffusing hard spheres for interpreting these quantities in terms of a distance of closest approach. [ABSTRACT FROM AUTHOR]

Abstract: Poly(2‐ethylhexyl acrylate) is synthesized by conventional radical bulk polymerization both with and without 1‐dodecane thiol as chain transfer agent (CTA) at temperatures from 4 to 140 °C. Electrospray‐ionization mass spectrometry is used to analyze the polymer. This reveals the occurrence of significant β‐scission at high temperature and confirms the presence of CTA‐capped polymers at all temperatures, as well as combination products from 4 to 65 °C. Subsequent 13C melt‐state NMR analysis allows quantification of branching and β‐scission. Both are reduced when CTA is present, consistent with a “patching” effect. As expected, the amounts of β‐scission and branching increase with synthesis temperature, although β‐scission dominates at the highest temperature. The backbiting rate coefficient of 2‐ethylhexyl acrylate is determined from NMR results, taking β‐scission into account for the first time. Remarkable agreement with literature kbb values is obtained, especially for activation energy. This strongly suggests family‐type behavior for acrylate kbb. [ABSTRACT FROM AUTHOR]

Selenium-rich Ge–Te–Se glasses have been synthesized along the GeSe4–GeTe4 pseudo-composition line and acquired by 77Se Hahn echo magic-angle spinning NMR. The comparison with the GeSe4 spectrum shows a drastic modification of the typical double-resonance lineshape even at low Te concentrations (＜10%). In order to rationalize this feature and to understand the effect of Te on the structure of our glasses, first-principles molecular dynamics simulations and gauge including projector augmented wave NMR parameter calculations have been performed. The distribution of the tellurium atoms in the selenium phase was shown to be mainly responsible for the 77Se lineshape changes. Another possible factor related to the perturbation of the δiso value due to Te proximity appears to be much more limited in the bulk, while the results obtained using molecular models suggest shifts of several hundreds of ppm. [ABSTRACT FROM AUTHOR]

Solid-state 77Se NMR measurements, first-principles molecular dynamics and DFT calculations of NMR parameters were performed to gain insight into the structure of selenium-rich GexSe(1−x) glasses. We recorded the fully-relaxed NMR spectra on natural abundance and 100% isotopically enriched GeSe4 samples, which led us to reconsider the level of structural heterogeneity in this material. In this paper, we propose an alternative procedure to initialise molecular dynamics runs for the chalcogenide glasses. The 77Se NMR spectra calculated on the basis of the structural models deduced from these simulations are consistent with the experimental spectrum. [ABSTRACT FROM AUTHOR]

Supercapacitors are electrochemical energy-storage devices that exploit the electrostatic interaction between high-surface-area nanoporous electrodes and electrolyte ions. Insight into the molecular mechanisms at work inside supercapacitor carbon electrodes is obtained with 13C and 11B ex situ magic-angle spinning nuclear magnetic resonance (MAS-NMR). In activated carbons soaked with an electrolyte solution, two distinct adsorption sites are detected by NMR, both undergoing chemical exchange with the free electrolyte molecules. On charging, anions are substituted by cations in the negative carbon electrode and cations by anions in the positive electrode, and their proportions in each electrode are quantified by NMR. Moreover, acetonitrile molecules are expelled from the adsorption sites at the negative electrode alone. Two nanoporous carbon materials were tested, with different nanotexture orders (using Raman and 13C MAS-NMR spectroscopies), and the more disordered carbon shows a better capacitance and a better tolerance to high voltages. [ABSTRACT FROM AUTHOR]

Chemical disorder can be characterized in silicate glasses using spectral editing in 29Si solid-state NMR. Resonances of the Qn(mX) (i.e.Si(OX)m(OSi)n−m) molecular motifs, which strongly overlap in the 29Si solid-state NMR spectra of silicate glasses, can be separated and quantified using 2 to n-quantum filters in INADEQUATE-like experiments, without prior knowledge of assigned chemical shifts, offering a new probe for the microscopic origins of residual entropy in glassy materials. [ABSTRACT FROM AUTHOR]

Abstract: We present here the first 3D homonuclear/heteronuclear correlation experiment applied to quadrupolar nuclei and making use of the sole scalar J-coupling. This experiment, based on the 2D-Homonuclear–Heteronuclear Single Quantum Correlation (H–HSQC) experiment, uses a relayed transfer from the 27Al central transition to neighbouring 31P spins and to the central transition of a second 27Al. It confirms the correlation map characterizing the two 27Al and the 31P NMR signatures of 27Al–O–31P–O–27Al chemically bonded molecular motifs. [Copyright &y& Elsevier]

Creating high‐energy‐density cathodes is crucial for building next‐generation lithium‐ion batteries. However, materials exploration along two main directions, namely Li‐rich or Ni‐rich oxides, has encountered bottlenecks. To get rid of the impasse, here a “Li‐rich Ni‐rich” route is consolidated by designing a new family of Li1+yNi(3‐5y)/3W2y/3O2 oxides with high‐voltage cycling stability up to 4.5 V and high capacities over 230 mAh g−1. It is discovered that W6+ is largely incorporated into the LiNiO2 lattice, forming W/Ni(Li) inverse honeycomb‐ordered nano‐domains. These Li‐rich domains enable reversible anionic redox, clearly demonstrated by X‐ray absorption spectroscopy, resonant inelastic X‐ray scattering, transmission electron microscopy, and nuclear magnetic resonance, which is linked to improved electrochemical performance. Furthermore, the incorporation of W6+ into the lattice proves to be the key to generating electrochemically active Li‐rich domains irrespective of Li stoichiometry given that a similar local structure is found in W‐substituted non‐Li‐rich oxides. This therefore implies the underestimated role of high‐valence cations in tuning the structure and electrochemistry of Ni‐rich oxides. These results underline the necessity of a Li‐rich composition in the request for reversible high capacity, reinforcing the promise of a “Li‐rich Ni‐rich” avenue for developing advanced cathodes. [ABSTRACT FROM AUTHOR]

Abstract: Phase separation in glasses has been extensively studied due to its occurence in silica-rich glasses; however, some aspects as the first steps of the nucleation of domains with different compositions remain to be clarified as they are difficult to characterize with most analytical techniques. Thereafter, it will be demonstrated that these first steps of phase separation can be studied using solid-state magic angle spinning nuclear magnetic resonnance (MAS-NMR). First, the measurement of the spin–lattice relaxation (T 1) in such glasses without added paramagnetic impurities helps for the identification of phase separation and of small Q4 clusters. Second, two-dimensional 29Si–29Si correlation experiments characterize the Si O Si network after various heat treatments and are used to obtain the compositions of the two demixing phases. The first phase is made of nearly pure silica (SiO2) and the second with a composition that tends towards the Na2Si2O5 composition. A link can be made with the crystallizing phases when longer heat-treatments are applied. [Copyright &y& Elsevier]

Abstract: Dipolar-Heteronuclear Multiple Quantum Correlation (D-HMQC) experiment based on SR42 1 recoupling was shown as a very efficient probe of spatial proximities in ordered or disordered materials. As crystalline sodium silicates have been extensively studied using 1D and 2D MAS NMR experiments and DFT calculations, they have been used as candidate model systems to perform this D-HMQC experiment. In this work, we demonstrate that the combination of 29Si and 23Na NMR at high magnetic field and DFT calculations makes it possible to revisit the assignment of the NMR signature of the δ-Na2Si2O5 polymorph. A D-HMQC experiment performed on this crystalline sample reveals lineshape distortions on the 23Na powder patterns extracted from the 2D correlation. Numerical simulations showed that these distortions result from an effect of the relative orientation between the 23Na quadrupolar tensor and the 23Na–29Si dipolar vector at the origin of the magnetization transfer. [Copyright &y& Elsevier]

Optimizing electrosynthetic reactions requires fine tuning of a vast chemical space, including charge transfer at electrocatalyst/electrode surfaces, engineering of mass transport limitations, and complex interactions of reactants and products with their environment. Hybrid electrolytes, in which supporting salt ions and substrates are dissolved in a binary mixture of organic solvent and water, represent a new piece of this complex puzzle as they offer a unique opportunity to harness water as the oxygen or proton source in electrosynthesis. In this work, we demonstrate that modulating water-organic solvent interactions drastically impacts the solvation properties of hybrid electrolytes. Combining various spectroscopies with synchrotron small-angle X-ray scattering (SAXS) and force field-based molecular dynamics (MD) simulations, we show that the size and composition of aqueous domains forming in hybrid electrolytes can be controlled. We demonstrate that water is more reactive for the hydrogen evolution reaction (HER) in aqueous domains than when strongly interacting with solvent molecules, which originates from a change in reaction kinetics rather than a thermodynamic effect. We exemplify novel opportunities arising from this new knowledge for optimizing electrosynthetic reactions in hybrid electrolytes. For reactions proceeding first via the activation of water, fine tuning of aqueous domains impacts the kinetics and potentially the selectivity of the reaction. Instead, for organic substrates reacting prior to water, aqueous domains have no impact on the reaction kinetics, while selectivity may be affected. We believe that such a fine comprehension of solvation properties of hybrid electrolytes can be transposed to numerous electrosynthetic reactions.

Hybrid solid electrolytes (HSEs) aim to combine the superior ionic conductivity of inorganic fillers with the scalable process of polymer electrolytes in a unique material for solid-state batteries. Pursuing the goal of optimizing the key metrics (σ ion ≥ 10 -4 S·cm -1 at 25 °C and self-standing property), we successfully developed an HSE based on a modified poly(ethylene oxide):LiTFSI organic matrix, which binds together a high loading (75 wt %) of Li 6 PS 5 Cl particles, following a solvent-free route. A rational study of available formulation parameters has enabled us to understand the role of each component in conductivity, mixing, and mechanical cohesion. Especially, the type of activation mechanism (Arrhenius or Vogel-Fulcher-Tammann (VFT)) and its associated energy are proposed as a new metric to unravel the ionic pathway inside the HSE. We showed that a polymer-in-ceramic approach is mandatory to obtain enhanced conduction through the HSE ceramic network, as well as superior mechanical properties, revealed by the tensile test. Probing the compatibility of phases, using electrochemical impedance spectroscopy (EIS) alongside 7 Li nuclear magnetic resonance (NMR), reveals the formation of an interphase, the quantity and resistivity of which grow with time and temperature. Finally, electrochemical performances are evaluated by assembling an HSE-based battery, which displays comparable stability as pure ceramic ones but still suffers from higher polarization and thus lower capacity. Altogether, we hope these findings provide valuable knowledge to develop a successful HSE, by placing the optimization of the right metrics at the core of the formulation.

This paper describes the simple, highly reproducible, and robust synthesis of a new solid organic/inorganic electrolyte based on the ionic liquid (IL) 1-butyl-3-(carboxyundecyl)imidazolium bis(trifluoromethylsulfonyl)imide tethered to zirconia nanoparticles (15-25 nm) by coordination and named ZrO 2 @IL. The IL monolayer formation, ensured by two-dimensional solid-state NMR, at the nanoparticles' surface considerably reduces both the IL's consumption and the IL amount at the ZrO 2 surface compared to the IL-based hybrid electrolytes reported in the literature. After LiTFSI, used as a lithium source, content optimization (26 wt %), the hybrid exhibits unprecedented stable conductivity passing from 0.6 × 10 -4 S.cm -1 to 0.15 × 10 -4 S.cm -1 , respectively, from 85 °C to room temperature (25 °C). Unlike silica which is commonly adopted for this type of hybrid material, zirconia makes it possible to produce more impact-resistant pellets that are easier to compact, thus being favorable for accurate conductivity studies and battery development by electrode/composite/solid electrolyte layer stacking. The ZrO 2 @IL/LiTFSI solid hybrid electrolyte's thermal stability (up to 300 °C) and performance make this electrolyte suitable for lithium conduction in all-solid-state batteries.

Aqueous biphasic systems (ABSs), in which two aqueous phases with different compositions coexist as separate liquids, were first reported more than a century ago with polymer solutions. Recent observations of ABS forming from concentrated mixtures of inorganic salts and ionic liquids raise the fundamental question of how "different" the components of such mixtures should be for a liquid-liquid phase separation to occur. Here we show that even two monovalent salts sharing a common cation (lithium) but with different anions, namely, LiCl and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), may result in the formation of ABSs over a wide range of compositions at room temperature. Using a combination of experimental techniques and molecular simulations, we analyze the coexistence diagram and the mechanism driving the phase separation, arising from the different anion sizes. The understanding and control of ABS may provide new avenues for aqueous-based battery systems., Competing Interests: The authors declare no competing financial interest.

The intermolecular interactions in a hybrid electrolyte based on various compositions of the ionic liquid N -methyl- N -propyl pyrrolidinium bis-fluorosulfonylimide (C 3 mpyrFSI), LiFSI salt and an ether-based additive, 1,2-dimethoxy ethane (DME), have been investigated using the HOESY (Heteronuclear Overhauser Effect SpectroscopY) NMR experiment. This NMR technique allows a quantification of the intermolecular interactions in ionic liquids (ILs) by measuring the cross-relaxation rate (σ) between different pairs of nuclei. Thereby, we compare the cross-relaxation rates between the cations, anions and DME in these hybrid electrolyte systems using 1 H- 7 Li and 1 H- 19 F HOESY experiments, and interpret the measured parameters in terms of ionic and molecular associations. The results give insights into the local coordination environment of the Li + cations and their solvation by the FSI anions and DME.

The HOESY NMR experiment is commonly used to probe ion associations in ionic liquids and their mixtures. The parameter measured in this experiment is the heteronuclear cross-relaxation rate σ, which has dimensions of s -1 . For intramolecular NOEs this scales as r -6 where r is the internuclear distance, but in the intermolecular case (as typically probed in studies of ionic liquids), theory predicts a more complex behavior including a distance dependence that is affected by the relative frequencies of the nuclei involved. Specifically, for nuclei with similar resonance frequencies such as 1 H and 19 F, it has been predicted that intermolecular NOEs will be sensitive to longer range distances than for nuclei with very different frequencies such as 1 H and 7 Li. In this contribution, we test this theory using a combination of quantitative HOESY analysis and molecular dynamics simulations carried out on two different ionic liquid electrolyte systems. In agreement with theoretical predictions, we find excellent correlations between the experimentally measured 1 H- 7 Li NOEs and carbon-lithium distances below 4 Å, while longer distances (>6 Å) must be considered in order to obtain good correlations between 1 H- 19 F NOEs and carbon-fluorine coordination numbers. This demonstrates the utility of HOESY NMR in understanding structure and interactions in ionic liquids while also illustrating that care must be taken in interpreting the measured cross-relaxation rates.

Dynamic nuclear polarization (DNP)-enhanced solid-state NMR spectroscopy has been used to study an ionic liquid salt solution (N-methyl-N-propyl-pyrrolidinium bis(fluorosulfonyl)imide, C 3 mpyrFSI, containing 1.0 m lithium bis(fluorosulfonyl)imide, 6 LiFSI) in its glassy state at a temperature of 92 K. The incorporation of a biradical to enable DNP signal enhancement allowed the proximities of the lithium to the individual carbon sites on the pyrrolidinium cation to be probed using a 13 C- 6 Li REDOR pulse sequence. Distributions in Li-C distances were extracted and converted into a 3D map of the locations of the Li + relative to the C 3 mpyr that shows remarkably good agreement with a liquid-phase molecular dynamics simulation.

The intrinsic ionic conductivity of polyethylene oxide (PEO)-based block copolymer electrolytes is often assumed to be identical to the conductivity of the PEO homopolymer. Here, we use high-field 7 Li nuclear magnetic resonance (NMR) relaxation and pulsed-field-gradient (PFG) NMR diffusion measurements to probe lithium ion dynamics over nanosecond and millisecond time scales in PEO and polystyrene (PS)-b-PEO-b-PS electrolytes containing the lithium salt LiTFSI. Variable-temperature longitudinal (T 1 ) and transverse (T 2 ) 7 Li NMR relaxation rates were acquired at three magnetic field strengths and quantitatively analyzed for the first time at such fields, enabling us to distinguish two characteristic time scales that describe fluctuations of the 7 Li nuclear electric quadrupolar interaction. Fast lithium motions [up to O(ns)] are essentially identical between the two polymer electrolytes, including sub-nanosecond vibrations and local fluctuations of the coordination polyhedra between lithium and nearby oxygen atoms. However, lithium dynamics over longer time scales [O(10 ns) and greater] are slower in the block copolymer compared to the homopolymer, as manifested experimentally by their different transverse 7 Li NMR relaxation rates. Restricted dynamics and altered thermodynamic behavior of PEO chains anchored near PS domains likely explain these results.