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Article Reference Troff document (with manpage macros) Solid State NMR Study of Boron Coordination Environments in Silicone Boronate (SiBA) Polymers
Silicone polymers possess very unusual properties when compared to organic polymers. The addition of grafted boronic acid groups allows for elastomeric film formation through self-association and enhances compatibility with biological systems by increasing elastomer miscibility with aqueous systems, pH tunability, and the ability to bind to saccharides. Boronic acid dimerization was reported to be the origin of cross-linking in silicone boronic acids, but the boron environments involved in this process remain poorly understood. Solid state 11B NMR was used to investigate the boron coordination environments in these materials. 11B quadrupolar line shape fitting, a method previously used to characterize minerals and amorphous glasses, revealed structural information, including coordination number and coordination sphere symmetry. Chain extension in these materials was attributed to hydrogen bonding between boronic acids and could be identified by the presence of three-coordinate boron sites. Cross-linking between boronic acid sites through four-coordinate, dative bonded boron centers was found to be the origin of elastomer formation; the oxygen Lewis bases on the silicone backbone do not appear to play a role. The proportion of boronic acid in the material and location of the boronic acid sites—telechelic versus pendant—both impacted cross-linking in these materials.
Article Reference Troff document (with manpage macros) 7Li and 29Si NMR Enabled by High-Density Cellulose-Based Electrodes in the Lithiation Process in Silicon and Silicon Monoxide Anodes
To meet the energy density requirement for our next-generation electric vehicle applications, new electrode materials with higher capacity are required. Silicon monoxide (a-SiO) is one of the most promising anode materials because it can provide 1500 mAh/g specific capacity compared to 372 mAh/g for graphite and nevertheless overcome some of the inherent structural disadvantages of its parent material, silicon (Si) itself. The present work discusses the electrochemical reaction mechanisms of lithium insertion into a-SiO using multinuclear solid-state NMR (nuclear magnetic resonance). An in situ  7 Li NMR study on both Si and a-SiO using a jelly-roll-type battery design shows the intrinsic difference between the lithiation of those two materials. In addition,  29 Si MAS (magic-angle spinning) NMR data obtained at 20 T provide sufficient sensitivity to acquire these spectra on electrode active materials, in spite of the low natural abundance of  29 Si. Additionally, the electrochemical method developed here using porous cellulosic substrates provides a means to substantially enhance the amount of active material available for the NMR study of the cycled anode materials as a function of charge state. We demonstrate that this unorthodox cell design achieves reasonable capacity retention for the a-SiO anodes, and we suggest that this approach could be applied to a wide range of electrode materials.
Article Reference Troff document (with manpage macros) Boosting solid‐state diffusivity and conductivity in lithium superionic argyrodites by halide substitution
Developing high‐performance all‐solid‐state batteries is contingent on finding solid electrolyte materials with high ionic conductivity and ductility. Here we report new halide‐rich solid solution phases in the argyrodite Li 6 PS 5 Cl family, Li 6−x PS 5−x Cl 1+x , and combine electrochemical impedance spectroscopy, neutron diffraction, and  7 Li NMR MAS and PFG spectroscopy to show that increasing the Cl − /S 2−  ratio has a systematic, and remarkable impact on Li‐ion diffusivity in the lattice. The phase at the limit of the solid solution regime, Li 5.5 PS 4.5 Cl 1.5 , exhibits a cold‐pressed conductivity of 9.4±0.1 mS cm −1  at 298 K (and 12.0±0.2 mS cm −1  on sintering)—almost four‐fold greater than Li 6 PS 5 Cl under identical processing conditions and comparable to metastable superionic Li 7 P 3 S 11 . Weakened interactions between the mobile Li‐ions and surrounding framework anions incurred by substitution of divalent S 2−  for monovalent Cl −  play a major role in enhancing Li + ‐ion diffusivity, along with increased site disorder and a higher lithium vacancy population.
Article Reference Troff document (with manpage macros) Combining density functional theory and 23Na NMR to characterize Na2FePO4F as a potential sodium ion battery cathode
Sodium ion batteries offer an inexpensive alternative to lithium ion batteries, particularly for large-scale applications such as grid storage that do not require fast charging rates and high power output. Moreover, the use of polyanionic structures as cathode materials afford incredibly high structural stability relative to layered transition metal oxides that can undergo a structural collapse upon full removal of the charge carrying ions. Sodium iron fluorophosphate, Na 2 FePO 4 F, has demonstrated its viability as a potential cathode material for sodium ion batteries, having a robust framework even after multiple charge-discharge cycles. Although solid-state NMR has traditionally been an excellent method for the determination of local structure and dynamic properties of cathode materials during the electrochemical cycling process, reliable assignment of the  23 Na chemical shifts resulting from the paramagnetic hyperfine interaction can be difficult when using only empirical rules. Here we present the use of density functional theory calculations to assign the experimentally observed NMR shifts to the crystallographic sites in Na 2 FePO 4 F, where it is found that the results do not agree with the previously reported assignment based upon simple geometry arguments. Furthermore, we report the justification of the proposed desodiation mechanism in Na 2 FePO 4 F on the basis of theoretical arguments, in good agreement with experimental NMR results reported previously.
Article Reference Troff document (with manpage macros) In Situ Magic-Angle Spinning 7Li NMR Analysis of a Full Electrochemical Lithium-Ion Battery Using a Jelly Roll Cell Design
A new in situ magic angle spinning (MAS)  7 Li nuclear magnetic resonance (NMR) strategy allowing for the observation of a full lithium-ion cell is introduced. Increased spectral resolution is achieved through a novel jelly roll cell design, which allowed these studies to be performed for the first time under MAS conditions (MAS rate 10 kHz). The state of charge, metallic lithium plating and solid-electrolyte interface (SEI) formation was captured for the first charge/discharge cycle of a full electrochemical cell (LiCoO 2 /graphite). This strategy can be used to monitor both anode and cathode electrodes concurrently, which is valuable for tracking the lithium distribution in a full cell in real time and may also enable identification of causes of capacity loss that are not readily available from bulk electrochemical analyses, or other post-mortem strategies.
Article Reference Concentration Dependent Solution Structure and Transport Mechanism in High Voltage LiTFSI-Adiponitrile Electrolytes
The physiochemical properties of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in adiponitrile (ADN) electrolytes were explored as a function of concentration. The phase diagram and ionic conductivity plots show a distinct relationship between the eutectic composition of the electrolyte and the concentration of maximum ionic conductivity in the 25 degrees C isotherm. We propose a structure-based explanation for the variation of electrolyte ionic conductivity with LiTFSI concentration, where the eutectic concentration is a transitionary region at which the structure changes from solvated contact ion pairs to extended units of [Li-z(ADN)(x)TFSIy](z-y) aggregates. It is found through diffusion coefficient measurements using pulsed-field gradient (PFG) NMR that both D-Li/D-TFSI and D-Li/D-ADN increase with concentration until 2.9 M, where after Li+ becomes the fastest diffusing species, suggesting that ion hopping becomes the dominant transport mechanism for Li+. Variable diffusion-time (Delta) PFG NMR is used to track this evolution of the ion transport mechanism. A differentiation in Li+ transport between the micro and bulk levels that increases with concentration was observed. It is proposed that ion hopping within [Li-z(ADN)(x)TFSIy](z-y) aggregates dominates the micro-scale, while the bulk-scale is governed by vehicular transport. Lastly, we demonstrate that LiTFSI in ADN is a suitable electrolyte system for use in Li-O-2 cells. (c) 2020 The Electrochemical Society (''ECS''). Published on behalf of ECS by IOP Publishing Limited.
Article Reference Mapping of Lithium-Ion Battery Electrolyte Transport Properties and Limiting Currents with In Situ MRI
Given the electrochemical modelling and control systems challenges facing lithium-ion batteries in extreme operating conditions, such as low temperature and high C-rate, it is important to understand the transport dynamics in a polarized cell with large electrolyte concentration gradients. To this end, a combination of conventional magnetic resonance imaging (MRI) experiments and MRI experiments coupled with pulsed-field gradient NMR for diffusion measurements were performed on an in situ lithium-ion cell operating at a variety of temperatures and current densities. The aim was to quantify the electrolyte transport parameters with spatial resolution. Some progress was attained towards this aim, and the necessary framework for future studies along this direction was developed; however, it was determined that in order to accurately quantify the transference number, a very accurate measurement of the concentration gradient is necessary when the polarization is large. It was also observed that limiting current behavior in the electrolyte at low temperature arises as a consequence of diffusion limitation on the anodic side, rather than ion depletion on the cathodic side. The framework developed herein may be useful not only for electrochemical model validation, but potentially also comprehensive electrolyte transport characterization, should the identified experimental limitations be overcome.
Article Reference Discerning models of phase transformations in porous graphite electrodes: Insights from inverse modelling based on MRI measurements
Article Reference Characterizing the effect of superabsorbent polymer content on internal curing process of cement paste using calorimetry and nuclear magnetic resonance methods
Internal curing (IC) is used to mitigate autogenous shrinkage in low water-to-cement ratio (w/c) concrete. Although, superabsorbent polymers (SAP) have been shown to work well for IC, their effects on the kinetics of the cement chemical reaction and the amount of water they provide have not been fully quantified. An experimental program was performed using isothermal calorimetry and nuclear magnetic resonance (NMR) to study the behavior of cement paste with various levels of IC using SAP. The results revealed that the higher the amount of IC the more susceptible the cement paste became to SAP overdosing resulting in a significant decrease in the heat of hydration (HOH) and therefore loss of IC efficiency. The mass of SAP to entrained water greater than 5\% led to particles agglomeration and a 65\% decrease in its IC efficiency. The HOH is observed to be linearly proportional to the entrained w/c, and that its development is limited by the initial porosity of the paste which controls the water diffusion from the SAP. The NMR signal corresponding to IC water showed that the SAP absorbs 4-7\% more mixing water than initially estimated, and that pre-wetted SAP has larger amount of entrained water in comparison with dry SAP.
Article Reference Original Layered OP4-(Li,Na)(x)CoO2 Phase: Insights on Its Structure, Electronic Structure, and Dynamics from Solid State NMR
The OP4-(Li/Na)(x)CoO2 phase is an unusual lamellar oxide with a 1:1 alternation between Li and Na interslab spaces. In order to probe the loca structure, electronic structure, and dynamics, Li-7 and Na-23 magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy was performed in complementarity to X-ray diffraction and electronic and magnetic properties measurements. Li-7 MAS NMR showed that NMR shifts result from two contributions: the Fermi contact and the Knight shifts due to the presence of both localized and delocalized electrons, which is really unusual. Li-7 MAS NMR clearly shows several Li environments, indicating that, moreover, Co ions with different local electronic structures are formed, probably due to the arrangement of the Na+ ions in the next cationic layer. Na-23 MAS NMR showed that some Na(+ )ions are located in the Li layer, which was not previously considered in the structural model. The Rietveld refinement of the synchrotron XRD led to the OP4-[Li-0.42 Na-0.05]Na(0. 32 )CoO(2 )formula for the material. In addition, Li-7 and Na-23 MAS NMR spectroscopies provide information about the cationic mobility in the material: Whereas no exchange is observed for Li-7 up to 450 K, the( 23)Na spectrum already reveals a single average signal at room temperature due to a much larger ionic mobility.
Article Reference A Polymer-Rich Quaternary Composite Solid Electrolyte for Lithium Batteries
All-solid-state batteries continue to grow as an alternative to replace the traditional liquid-based ones not only because they provide increased safety but also higher power and energy densities. However, current solid-state electrolytes are either ceramics that are brittle but highly conducting (e.g. Li0.33La0.55TiO3, LLTO) or polymer electrolytes that are poorly conducting but form flexible films with desired mechanical properties (e.g. Poly(ethylene oxide):Lithium bis(trifluoromethanesulfonyl)imide, PEO:LiTFSI). In this work, we have developed quaternary composite solid-state electrolytes (CSEs) to combine the benefits of the two types along with Succinonitrile (SN) as a solid plasticizer. CSEs with different compositions have been fully characterized over the whole compositional range. Guided by neural network simulation results it has been found that a polymer-rich CSE film gives the optimal ionic conductivity (>10(-3)S cm(-1) at 55 degrees C) and mechanical properties (Tensile strength of 16.1 MPa; Elongation-at-break of 2360\%). Our solid-state coin-type cell which employs our in-house made cathode shows good cycling performance at C/20 and 55 degrees C maintaining specific discharge capacity at 143.2 mAh g(-1) after 30 cycles. This new approach of formulating quaternary CSEs is proven to give the best combination of properties and should be universal and be applied to other CSEs with different chemistry. (C) 2020 The Author(s). Published on behalf of The Electrochemical Society by IOP Publishing Limited.
Article Reference A Lithium Oxythioborosilicate Solid Electrolyte Glass with Superionic Conductivity
As potential next-generation energy storage devices, solid-state lithium batteries require highly functional solid state electrolytes. Recent research is primarily focused on crystalline materials, while amorphous materials offer advantages by eliminating problematic grain boundaries that can limit ion transport and trigger dendritic growth at the Li anode. However, simultaneously achieving high conductivity and stability in glasses is a challenge. New quaternary superionic lithium oxythioborate glasses are reported that exhibit high ion conductivity up to 2 mS cm(-1) despite relatively high oxygen: sulfur ratios of more than 1:2, that exhibit greatly reduced H2S evolution upon exposure to air compared to Li7P3S11. These monolithic glasses are prepared from vitreous melts without ball-milling and exhibit no discernable XRD pattern. Solid-state NMR studies elucidate the structural entities that comprise the local glass structure which dictates fast ion conduction. Stripping/plating onto lithium metal results in very low polarization at a current density of 0.1 mA cm(-2) over repeated cycling. Evaluation of the optimal glass composition as an electrolyte in an all-solid-state battery shows it exhibits excellent cycling stability and maintains near theoretical capacity for over 130 cycles at room temperature with Coulombic efficiency close to 99.9\%, opening up new avenues of exploration for these quaternary compositions.
Article Reference Real-Time Quantitative Detection of Lithium Plating by In Situ NMR Using a Parallel-Plate Resonator
The development and optimization of fast charging protocols requires detailed information about the lithium inventory inside the battery. We report the application of a parallel-plate NMR probe to the in situ monitoring of Li metal deposition on a graphite anode during the charging of a single layer prismatic cell constructed with electrodes harvested from a commercial electric vehicle battery. The probe provides an enhanced sensitivity and an ideal orientation of the electromagnetic field, which allows the quantification of the lithiation of the graphite anode throughout the duration of cell charging. The NMR data indicate that charging over a 4 h duration (C/4) occurs with well-defined stage transformations in the lithiated graphite, while the coexistence of several stages is observed when the cell charging occurs in 1 h (1C). We show that two types of lithium deposition can occur on graphite electrodes: (i) as a Li film on the surface of the electrode and (ii) as dendrites orthogonal to the electrode surface. Our data demonstrates that Li re-intercalation into the graphite electrode occurs primarily from the deposited Li metal film, while the lithium dendrites can partially dissolve into the electrolyte solution during the discharging of the cell subsequent to Li plating.
Article Reference Troff document (with manpage macros) Synthesis of Siliconized Photosensitizers for Use in 1O2-Generating Silicone Elastomers: An Electron Paramagnetic Resonance Study
Biomedical devices based on silicone are essential tools in modern healthcare but can be compromised by the development of device-acquired infections (DAIs). Unfortunately, the continued rise of antibiotic-resistant organisms makes current strategies to combat DAIs insufficient. Recently, the use of photoactive coatings that produce reactive oxygen species, specifically singlet oxygen (1O2), has attracted attention as a potential alternative to traditional strategies to prevent DAIs. However, the synthesis and characterization of silicone devices capable of 1O2 production are not trivial. Development is hindered by the incompatibility of photosensitizers with the silicone matrix and an incomplete understanding of how the method of incorporation impacts 1O2 production. Using the Piers–Rubinsztajn reaction, the photosensitizer 5,10,15,20-(tetra-3-methoxyphenyl)porphyrin (TPMP) was derivatized to be compatible with silicone matrices without the assistance of solvents and could be incorporated either covalently or physically within silicone elastomers. Electron paramagnetic resonance measurements indicated that 1O2 was more efficiently generated from elastomers containing a covalently cross-linked TPMP derivative than their physically dispersed counterparts, due to the minimization of aggregates.
Article Reference Troff document (with manpage macros) Efficiency measure of SAP as internal curing for cement using NMR & MRI
Nuclear magnetic resonance and imaging was used to quantify the absorbed and desorbed water by superabsorbent polymers (SAP) and the efficiency of SAP as internal curing. SAP pore solution absorption and desorption are found, respectively, 25 g/g SAP, and inversely proportional to time and SAP content. Cement hydration rate of mixes without SAP is statistically equal to mixes with 0.2% SAP and different for 0.3% SAP. Estimated SAP spacing for mixes with 0.2% and 0.3% SAP is 0.78 ± 0.03 and 0.67 ± 0.05 mm, respectively. The corresponding SAP efficiency drops from 98 ± 14% and 71 ± 14% to 84% and 41% when accounting for particles agglomeration.
Article Reference Troff document (with manpage macros) A parallel-plate RF probe and battery cartridge for 7Li ion battery studies
A new parallel-plate resonator for 7Li ion cell studies is introduced along with a removable cartridge-like electrochemical cell for lithium ion battery studies. This geometry separates the RF probe from the electrochemical cell permitting charge/discharge of the cell outside the magnet and introduces the possibility of multiplexing samples under test. The new cell has a geometry that is similar to that of a real battery, unlike the majority of cells employed for MR/MRI studies to this point. The cell, with electrodes parallel to the B1 magnetic field of the probe, avoids RF attenuation during excitation/reception. The cell and RF probe dramatically increase the sample volume compared to traditional MR compatible battery designs. Ex situ and in situ 1D 7Li profiles of Li ions in the electrolyte solution of a cartridge-like cell were acquired, with a nominal resolution of 35 µm at 38 MHz. The cell and RF probe may be employed for spectroscopy, imaging and relaxation studies. We also report the results of a T1-T2 relaxation correlation experiment on both a pristine and fully charged cell. This study represents the first T1-T2 relaxation correlation experiment performed in a Li ion cell. The T1-T2 correlation maps suggest lithium intercalated into graphite is detected by this methodology in addition to other Li species.
Article Reference Transient lithium metal plating on graphite: Operando 7Li nuclear magnetic resonance investigation of a battery cell using a novel RF probe
The development of optimal fast charging protocols requires detailed information regarding lithium inventory in a battery. We built a parallel-plate  resonator  RF probe and a cartridge-type single layer cell of improved designs. The probe has excellent sensitivity and homogeneity of electromagnetic field, while the cartridge allows easy cell assembly, straight-forward multiplexing, and excellent cell-to-cell data reproducibility. Herein we present our findings from  operando   7 Li NMR measurements on a graphite//NMC622 cell. The usual/expected sequencing of Li x C 6  phases from dilute to concentrated observed during charging at low (<C/5) rates is replaced at high (≥1C) rates by a direct transition to, and propagation of concentrated phases throughout the  graphite electrode , with no evidence for dilute phases. Concurrently, a peak attributed to lithium naphthalenide appears at ∼20 ppm. Lithium therefore accumulates on graphite surfaces, facilitating Li metal plating under fast charge conditions. While some of the deposited Li metal can intercalate into graphite after cell charging, a significant fraction accumulates during consecutive cycles, creating a barrier for Li +  transport, which decreases the amount of recoverable Li, and its intercalation rate into graphite. Thus, Li plating not only can create safety hazards through dendrite growth, but also irreversibly impairs the fast charging capability of cells.
Article Reference Troff document (with manpage macros) Structural Complexity and Evolving Lithium-Ion Dynamics within the Cathode Material LiFeV2O7 Revealed by Diffraction and Solid-State NMR
7 Li solid-state nuclear magnetic resonance (ssNMR) reveals unexpected structural complexity and substantive changes in the local dynamics of lithium exchange in monoclinic LiFeV 2 O 7  as a function of electrochemical lithium insertion. The one-dimensional (1D) NMR spectrum revealed a multiplicity of peaks beyond the three expected, which prompted a further structural investigation. A new sample was synthesized through a solid-state reaction, which revealed a change in the crystal structure. The single-crystal refinement showed an arrangement where the O8, V2, and V6 positions shift in a way that changes the geometry of the vanadium sites. With this new configuration, lithium sites are no longer equivalent, providing a reason why there are extra signals in the  7 Li ssNMR spectrum of the title compound. Ex situ  7 Li magic angle spinning ssNMR experiments were used to track structural changes of the LiFeV 2 O 7  electrode during electrochemical cycling. A new lithium arrangement was observed during the lithium insertion process, which occurs at a similar point of the electrochemical process as a notable increase of the lithium-ion dynamics as observed by 2D EXSY experiments.  7 Li selective inversion (SI) experiments were measured over a temperature range of 303–318 K to quantify the exchange rates and energy barriers of ion mobility for each exchange pair present in the structure. In general, the activation energy increases as a function of the lithiation, suggesting that the lithium vacancies play a significant role in the current dynamics.
Article Reference Troff document (with manpage macros) Fluorinated Rocksalt Cathode with Ultra-high Active Li Content for Lithium-ion Batteries
The key to increasing the energy density of lithium-ion batteries is to incorporate high contents of extractable Li into the cathode. Unfortunately, this triggers formidable challenges including structural instability and irreversible chemistry under operation. Here, we report a new kind of ultra-high Li compound: Li 4+x MoO 5 F x  (1≤ x ≤3) for cathode with an unprecedented level of electrochemically active Li (>3 Li +  per formula), delivering a reversible capacity up to 438 mAh g −1 . Unlike other reported Li-rich cathodes, Li 4+x MoO 5 F x  presents distinguished structure stability to immunize against irreversible behaviors. Through spectroscopic and electrochemical techniques, we find an anionic redox-dominated charge compensation with negligible oxygen release and voltage decay. Our theoretical analysis reveals a “reductive effect” of high-level fluorination stabilizes the anionic redox by reducing the oxygen ions in pure-Li conditions, enabling a facile, reversible, and high Li-portion cycling.
Article Reference Ti4O7-Enhanced Carbon Supports to Stabilize NaO2 in Sodium-Oxygen Batteries
Sodium-oxygen batteries (NaOBs) have been investigated extensively over the past decade as a high-energy-density alternative to the Li-ion battery system. However, the instability of the main discharge product, sodium superoxide (NaO 2 ), toward the carbon cathode has limited the rechargeability and cycle life of the cell. Here, Magnéli-phase Ti 4 O 7  is studied as a stable coating for carbon paper cathodes in NaOBs. Ti 4 O 7  is shown to be stable toward NaO 2  attack via  23 Na magic angle spinning (MAS) solid-state nuclear magnetic resonance (ssNMR). Subsequently, NaOB coin cells are constructed with cathodes made from slurries of various Ti 4 O 7  wt % cast onto carbon paper substrates. It is found that cycle life increases dramatically with Ti 4 O 7  content. Characterization of the discharged cathodes by  23 Na ssNMR shows that NaO 2  is the main electrochemical product in both pure carbon and Ti 4 O 7 -coated systems, although the degradation of NaO 2  is significantly hindered in Ti 4 O 7 -containing cells. Scanning electron microscopy (SEM) data acquired for the discharged cathodes demonstrates that NaO 2  is indeed formed electrochemically on the Ti 4 O 7  surface, confirming that the stability of Ti 4 O 7  is able to contribute to the observed extended cell lifetime. A discharge/charge model is proposed where NaO 2  precipitates and reversibly dissociates on the Ti 4 O 7  surface through the previously reported solution-based formation and decomposition mechanisms. Characterization of lifetime-cycled cathodes using the two-dimensional  23 Na- 1 H dipolar heteronuclear multiple quantum correlation ( 23 Na{ 1 H} D-HMQC) and  23 Na triple quantum magic angle spinning (3QMAS) experiments shows that eventual cell death is caused by the buildup of carbonaceous NaO 2  degradation products such as sodium carbonate (Na 2 CO 3 ) and sodium formate (NaHCO 2 , NaFormate), but is delayed in Ti 4 O 7  systems as a higher proportion of NaO 2  is formed on the stable Ti 4 O 7  surface, which agrees with the proposed formation–decomposition mechanism.
Article Reference Troff document (with manpage macros) Structure of the Solid-State Electrolyte Li3+2xP1–xAlxS4: Lithium-Ion Transport Properties in Crystalline vs Glassy Phases
The search for new solid electrolyte materials and an understanding of fast-ion conductivity are crucial for the development of safe and high-power all-solid-state battery technology. Herein, we present the synthesis, structure, and properties of a crystalline lithium-ion conductor, Li 3.3 Al 0.15 P 0.85 S 4  (i.e., Li 9.9 Al 0.45 P 2.55 S 12 ), found in the compositional range Li 3+2x P 1–x Al x S 4  ( x  = 0.15, 0.20, and 0.33).  31 P magic-angle spinning nuclear magnetic resonance (MAS-NMR) aided in identifying the successful introduction of Al into the lattice. At high values of  x  (>0.15), crystalline Li 5 AlS 4  and a glassy amorphous component exsolve to yield a multiphase mixture. The crystal structure of Li 3.3 Al 0.15 P 0.85 S 4  was elucidated by single-crystal X-ray diffraction and powder neutron diffraction, demonstrating that it belongs to the thio-LISICON family with the  Pnma  space group,  a  = 12.9572(13) Å,  b =  8.0861(8) Å,  c  = 6.1466(6) Å, and  V  = 644.00(11) Å 3 . The Li + -ion conductivity and diffusivity in this bulk material (which contains about 10 wt % of an amorphous phase, as prepared) were studied by electrochemical impedance spectroscopy and  7 Li pulsed-field gradient nuclear magnetic resonance spectroscopy (PFG-NMR). The total ionic conductivity of Li 3.3 Al 0.15 P 0.85 S 4  is 0.22(2) mS·cm –1  at room temperature with an activation energy of 0.30(1) eV. A two-component analysis method based on the Kärger equations was developed to analyze the diffusive exchange between the bulk and amorphous phases of Li 3.3 Al 0.15 P 0.85 S 4  detected via the PFG-NMR signal attenuation curves. This approach was employed to quantitatively compare different sample morphologies (glass powder, crystalline powder, and crystalline pellets of Li 3.3 Al 0.15 P 0.85 S 4 ) and assess the influence of the macroscopic state on microscopic ion transport, as supported by NMR relaxation measurements.
Article Reference Troff document (with manpage macros) Atomic Layer Deposition ZnO-Enhanced Negative Electrode for Lithium-Ion Battery: Understanding of Conversion/Alloying Reaction via 7Li Solid State NMR Spectroscopy
Understanding the mechanism for capacity delivery in conversion/alloying materials (CAM) electrodes, such as ZnO, in lithium-ion batteries (LIBs) requires careful investigation of the electrochemical reactions. Here, we used magic angle spinning (MAS at 60 kHz)  7 Li nuclear magnetic resonance (NMR) as a sensitive analytical means to probe the reactions occurring between electrode materials and Li +  ions. The ZnO nanolayer generated on carbon substrate by atomic layer deposition (ALD) enhanced the cyclic capacity of half cell LIB up to 40%.  7 Li NMR revealed Li x Zn alloy formation through an irreversible conversion reaction during discharge. MAS results revealed the dealloying of Li x Zn at the full charge step which left atomic zinc nanograins that do not undergo the re-oxidation of zinc atoms according to the cyclic voltammetry. An  in situ  formation of elemental zinc at the initial cycles facilitates uniform lithium deposition on subsequent cycles due to the reduced energy barrier for lithium nucleation on pure zinc as compared to ZnO. X-ray diffraction analysis indicated the crystalline formation of the Li x Zn alloy while scanning electron microscope showed the uniform morphology for the lithiated discharge products. Cyclic voltammetry and differential capacity functions initially predicted the conversion and alloying reactions.
Article Reference Troff document (with manpage macros) The parallel-plate resonator: An RF probe for MR and MRI studies over a wide frequency range
We explore the use of the parallel-plate resonator for the study of thin cuboid samples over a wide range of  magnetic resonance  frequencies. The parallel-plate resonator functions at frequencies from tens to hundreds of MHz. Seven parallel-plate resonators are presented and discussed in a frequency range from 8 to 500 MHz. Magnetic resonance experiments were performed on both horizontal and vertical bore magnet systems with lithium and hydrogen nuclei. Parallel-plate  radiofrequency  (RF) probes are easy to build and easy to optimize. Experiments and simulations showed good sensitivity of the parallel-plate RF probe geometry with a small decrease in sensitivity at higher frequencies.
Article Reference Troff document (with manpage macros) Quantitative Operando 7Li NMR Investigations of Silicon Anode Evolution during Fast Charging and Extended Cycling
The development and optimization of fast battery charging protocols require detailed information regarding lithium speciation inside a battery. Nuclear magnetic resonance (NMR) spectroscopy has the unique capability of identifying the Li phases formed in an anode during Li-ion cell operation and quantifying their relative amounts. In addition, both Li metal films and dendrites are readily detected and quantified. Here, our recently reported parallel-plate resonator radio frequency (RF) probe and the cartridge-type single-layer full cell were used to track the behavior of Si electrodes during cycling and during fast charging. The Li x Si compounds formed during electrochemical cycling exhibit an unexpected intrinsic nonequilibrium behavior at both slow and fast rates, evolving toward increasingly disordered local environments. The evolution with time of lithiated phases is nonlinear during both charging and discharging at constant current, unlike the case for pure graphite, and asymmetric between charge and discharge. During charging at rates of 1C, 2C, and 3C, metallic Li in both films and (to a lesser extent) dendritic forms are deposited on the Si anode. Part of the Li metal film formation is reversible, but a fraction remains on the electrode surface as dead Li, while all of the dendritic Li, even though formed in a considerably smaller amount, is entirely irreversible. Such performance-governing properties are critical to the development of fast-charging protocols for lithium-ion batteries (LIBs) and are exceptionally well evaluated and quantified by  7 Li magnetic resonance strategies such as those presented here.
Article Reference Troff document (with manpage macros) Na4–xSn2–xSbxGe5O16, an Air-Stable Solid-State Na-Ion Conductor
The structure of a Na 4 Sn 2 Ge 5 O 16  phase was established via single-crystal X-ray diffraction. Unusually large displacement parameters of Na atoms suggested the possibility of Na +  ionic conductivity. To create Na deficiencies and thus increase the Na +  mobility in Na 4 Sn 2 Ge 5 O 16 , Sn 4+  cations were partially substituted with Sb 5+ . A series of Na 4–x Sn 2–x Sb x Ge 5 O 16  samples ( x  = 0, 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, or 0.35) were prepared by solid-state reactions and characterized with electrical impedance spectroscopy in the range of 25–200 °C. The highest ionic conductivity value was achieved in the Na 3.8 Sn 1.8 Sb 0.2 Ge 5 O 16  sample (1.6 mS cm –1  at 200 °C). Na +  migration pathways were calculated using the bond-valence energy landscape approach, and two-dimensional conductivity channels with low energy barriers (≈0.4 eV) were found in the structure. Three-dimensional conductivity can also be achieved in the structure; however, it has a much higher energy barrier. The pristine phase and Na 3.8 Sn 1.8 Sb 0.2 Ge 5 O 16  sample were studied via  23 Na and  119 Sn solid-state nuclear magnetic resonance. A faster exchange between the Na sites was observed in the doped sample.
Article Reference Accurate Measurements of Li+ Dynamics in Pressure-Treated Solid Electrolytes by Powder X-ray Diffraction and 7Li Magnetic Resonance Diffusometry
Applying fabrication pressure is an inevitable step when preparing solid electrolytes (SEs) for all-solid-state batteries (ASSBs). Utilizing  7 Li diffusometry and relaxometry nuclear magnetic resonance (NMR) measurements, this study demonstrates that the long-range ion transport in sulfide SEs, measured by diffusometry, is slowed by 20% following the application of pressure of 500 MPa. The local range relaxometry measurements show a more modest change. It is notable that the NMR and structural measurements are taken on samples after the applied pressure is removed, while the sample remains in the pellet form. The fact that this change in ion dynamics remains evident even when the pressure is no longer actively applied is an important finding that will impact the consideration of the role of pressure in altering the ion dynamics in ASSBs. Powder X-ray diffraction (PXRD) was performed on powder and compressed thiophosphate Li 10 SnP 2 S 12  (LSnPS) samples to reveal the grain morphology change after pressure treatment. The PXRD analysis reveals the change in the peak shapes of the LSnPS materials, consistent with a significant microstrain imparted to the material by the fabrication pressure. A comparative investigation was performed for the reference ceramic oxide Li 1.5 Al 0.5 Ge 1.5 (PO 4 ) 3  (LAGP) phase, where no significant changes were observed in either the ion dynamics or the micromorphology. This is expected due to the significantly larger Young’s modulus of the oxide relative to that of the sulfide SEs. This study demonstrates the accuracy with which diffusometry and relaxometry NMR can measure changes in ion dynamics under mechanical modification, opening a new window to link macroscopic material engineering with particle-level dynamics and ion transport.
Article Reference Troff document (with manpage macros) Multinuclear MR and MRI study of lithium-ion cells using a variable field magnet and a fixed frequency RF probe
An exploratory multinuclear  magnetic resonance  (MR) and magnetic resonance imaging (MRI) study was performed on lithium-ion battery cells with  7 Li,  19 F, and  1 H measurements. A variable field superconducting magnet with a fixed frequency parallel-plate  radiofrequency  (RF) probe was employed in the study. The magnetic field was changed to set the resonance frequency of each nucleus to the fixed RF probe frequency of 33.7 MHz. Two cartridge-like lithium-ion cells, with graphite anodes and LiNi 0.5 Mn 0.3 Co 0.2 O 2  (NMC) cathodes, were interrogated. One cell was pristine, and one was charged to a cell voltage of 4.2 V. The results presented demonstrate the great potential of the variable field magnet approach in multinuclear measurement of lithium-ion  batteries . These methods open the door for developing faster and simpler methods for detecting, quantifying, and interpreting MR and MRI data from lithium-ion and other batteries.
Article Reference Troff document (with manpage macros) Effective recovery of the air-exposed Ni-rich lithium transition metal oxide cathodes with a coating-stabilized surface
The electrochemical cycling performance of Ni-rich  cathode materials  is adversely affected by the exposure of the active materials to the ambient environment, especially for a harsh cycling condition. To mitigate this degradation, Li x B y C 1-y O z  (LBCO) was synthesized where B and C are with identical chemical bonding structures and a 0.5 at%  LBCO  sol-gel  coating process  is introduced. Here we provide a comprehensive characterization of the  coating material  and the effect of coating. We confirm the effectiveness of the coating method and optimize processing parameters from both chemical and electrochemical perspectives. The coating and following process can regenerate the deteriorated surface and recover the capacity. After extended cycling, we demonstrate that the  LBCO coating  stabilized the surface and protected the bulk from severe structural degradation, with multiscale  electron microscopy  and spectroscopy characterization techniques. Our in-depth investigation provides a promising approach to recovering the degraded surface structure and  electrochemical performance  by applying LBCO coatings.
Article Reference Troff document (with manpage macros) Impact of functional groups on lithium salt dispersion and mobility in polymer electrolytes
Solid Polymer electrolytes are versatile, highly processible and electrochemically compatible with solid electrode materials. The versatility of these materials is a result of the existence of many possible conductive polymer-salt, polymer-polymer and salt-salt combinations. Despite the wide array of available lithium salts, most polymer electrolyte materials are made using lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) due to its long history of achieving relatively high ionic conductivities in polymer electrolyte systems with the most famous being poly(ethylene oxide) (PEO). It is however possible that better ionic conductivities can be achieved with different salts and/or in polymer matrices containing different functional groups. This is because ionic conductivity in polymer electrolytes is partially based on the ability of the polymer matrix to dissolve and bond to the salt. These interactions impact local-scale ion mobility which can be measured via NMR spectroscopy using pulsed field gradient experiments. In this work, polymer electrolytes are prepared using PEO, hydrogenated nitrile butadiene rubber and poly(propylene) carbonate. Ion mobility, lithium conductivity and salt-polymer interactions are investigated to compare interactions between LiTFSI and lithium cyano(trifluorosulfonyl)imide in polymers with common salt-dissociating functional groups such as ethyl, nitrile and carbonate to determine the impact of these interactions on ionic conductivity.
Article Reference Combined 7Li NMR, density functional theory and operando synchrotron X-ray powder diffraction to investigate a structural evolution of cathode material LiFeV2O7
In our recent study, we demonstrated using  7 Li solid-state Nuclear Magnetic Resonance (ssNMR) and single-crystal X-ray diffraction that the cathode LiFeV 2 O 7  possesses a defect associated with the positioning of vanadium atoms. We proposed that this defect could be the source of extra signals detected in the  7 Li spectra. In this context, we now apply density functional theory (DFT) calculations to assign the experimental signals observed in  7 Li NMR spectra of the pristine sample. The calculation results are in strong agreement with the experimental observations. DFT calculations are a useful tool to interpret the observed paramagnetic shifts and understand how the presence of disorder affects the spectra behavior through the spin-density transfer processes. Furthermore, we conducted a detailed study of the lithiated phase combining  operando  synchrotron powder X-ray diffraction (SPXRD) and DFT calculations. A noticeable volume expansion is observed through the first discharge cycle which likely contributes to the enhanced lithium dynamics in the bulk material, as supported by previously published ssNMR data. DFT calculations are used to model the lithiated phase and demonstrate that both iron and vanadium participate in the redox process. The unusual electronic structure of the V 4+  exhibits a single electron on the 3d xy  orbital perpendicular to the V–O–Li bond being a source of a negative Fermi contact shift observed in the  7 Li NMR of the lithiated phase.
Article Reference Troff document (with manpage macros) A facile route to plastic inorganic electrolytes for all-solid state batteries based on molecular design
Solid-state lithium batteries are on the threshold of commercialization as an alternative to liquid electrolyte batteries. Glassy or amorphous solid electrolytes could bring crucial benefits, but their lack of periodicity impedes structure-derived material design. Here, we report an approach for glassy electrolyte design based on well-defined lithium metal oxychloride linear oligomers. By packing these oligomers formed by oxygen-bridged chloroaluminates, a glassy solid model is constructed. Li ions in mixed-anion coordination with distorted polyhedra favor good lithium conductivity (1.3 mS cm −1  at 30 °C). The frustrated Li-ion geometry and non-crystallinity promote conformational dynamics of the oligomer backbone that generates mechanical plasticity.  Ab initio  molecular dynamics simulations depict the conformational motion that resembles that of organic molecules. Our all-solid-state battery based on this solid electrolyte shows exceptional long term electrochemical stability with a high-nickel NCM cathode. This work shows the impact of targeted structure models for rational design of glassy plastic electrolytes.
Article Reference Troff document (with manpage macros) Stable NaTFSI-Based Highly Concentrated Electrolytes for Na-Ion and Na–O2 Batteries
Sodium bis(trifluoromethanesulfonyl)imide (NaTFSI) and adiponitrile (ADN) have attractive high stability and safety properties for application as electrolytes in Na-ion batteries, but are unusable in modern cells due to significant Al corrosion by NaTFSI, and spontaneous ADN degradation by Na metal. Herein, the electrochemical properties of NaTFSI–ADN electrolytes are investigated as a function of concentration. The ionic conductivity and phase diagram of NaTFSI–ADN is measured, and molecular dynamics (MD) simulations give insight into the solution structure of the electrolyte. The reductive stability of the electrolyte is found to increase drastically with concentration in cyclic voltammetry (CV) experiments, and the parasitic dissolution of Al by TFSI decreases with concentration in linear sweep voltammetry (LSV) and chronoamperometry (CA) tests. In Na-ion cells, the dual effect of reductive stability enhancement and Al corrosion suppression allows the 4.4 M electrolyte to reversibly intercalate high voltage Na 3 V 2 (PO 4 ) 2 F 3  (NVPF) cathodes for multiple cycles, while no NVPF intercalation is observed with the standard 1.0 M electrolyte. Na–O 2  cells also benefit from the highly concentrated electrolyte, showing significantly longer lifetimes in CV experiments on Na–O 2  coin cells. Concentrating NaTFSI–ADN electrolytes offers practical benefits to Na batteries and should be implemented with further stabilizing strategies going forward.
Article Reference Troff document (with manpage macros) Quantitative Investigation of Lithium Metal Plating via Operando 7Li NMR Spectroscopy of a Unique Three Electrode Lithium-Ion Battery
This work represents the first investigation that simultaneously uses both 7Li NMR chemical analysis and three-electrode (3E) electrochemical analysis in real time to observe SiO-graphite anodes experiencing lithium plating during fast charge. NMR has the unparalleled ability to distinguish lithium in various forms, such as plated metal, alloyed lithium-silicon, or intercalated lithium-graphite compounds. This permits a detailed accounting of the whereabouts of lithium in an anode undergoing high-rate charge. This highly specialized technique comes at a high cost, however, in terms of time, equip-ment, and expertise. Establishing correlation between NMR and the more common and readily implemented 3E tech-nique for detecting the onset of plating allows the latter to be applied with confidence to the type of extensive testing required to build fast charge tables. NMR provides additional insight into the disposition of lithium after plating has occurred, allowing a clear analysis of the fraction of lithium metal that is spontaneously re-dissolved and taken up by the anode (reversible lithium plating).
Article Reference Troff document (with manpage macros) Revealing Na+ Dynamics in the Na4Sn2Ge5O16 Solid Electrolyte Material Using 23Na Solid-State NMR Spectroscopy and Computational Methods
Na 4 Sn 2 Ge 5 O 16  is a novel Na +  conductor that can be utilized in the next generation of all-solid-state Na +  batteries (ASSNIBs).  23 Na ssNMR experiments were carried out on the Na 4 Sn 2 Ge 5 O 16  phase to investigate the Na +  dynamics for the three unique crystallographic Na sites under multiple field strengths (20, 11.7, and 7 T). However, completely resolving the fast exchange Na2 and Na3 pair (4c sites) in the  23 Na NMR spectra (Na2–3 resonance) was nontrivial under the available experimental conditions. The subsequent relaxation study supports that the Na2–3 peaks are dynamically mediated, in contrast to immobile Na1 peaks. To further understand the dynamic effects on the  23 Na NMR spectra, 1D and 2D 3QMAS  23 Na spectra under various magnetic field strengths were analyzed to establish possible ranges of “averaged” quadrupolar parameter values for the two sites. With the assistance of density functional theory (DFT)-based CASTEP calculations, simulated lineshapes of the Na1 site (8d) are established, which exhibit excellent agreement with the experimentally determined ones. Subsequently, the EXchange Program for RElaxing Spin Systems (EXPRESS) script was employed to simulate the Na2–3 peaks under dynamic conditions, with a final estimated exchange rate of 2 × 10 5  Hz. This work paves the way for future studies of Na +  transport at the molecular level in fast-conducting Na-based solid electrolytes (SEs).

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