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 6Àx PS 5Àx Cl 1+x ,a nd combine electrochemical impedance spectroscopy, neutron diffraction, and 7 Li NMR MAS and PFG spectroscopytoshow that increasing the Cl À /S 2À ratio has as ystematic, and remarkable impact on Li-ion diffusivity in the lattice.T he phase at the limit of the solid solution regime, Li 5.5 PS 4.5 Cl 1.5 ,e xhibits ac old-pressed conductivity of 9.4 AE 0.1 mS cm À1 at 298 K( and 12.0 AE 0.2 mS cm À1 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 .W eakened interactions between the mobile Li-ions and surrounding framework anions incurred by substitution of divalent S 2À for monovalent Cl À play amajor role in enhancing Li + -ion diffusivity,a long with increased site disorder and ahigher lithium vacancy population. Figure 5. a) 7 Li MAS NMR for Li 6Àx PS 5Àx Cl 1+x (x = 0, 0.25, 0.375, 0.5) b) correlation of the activation energies from both techniques with the 7 Li isotropic chemical shift and the Haven ratio for all values of x under study.

High-resolution solid-state 1H NMR under fast magic angle spinning is used for the first time to study proton conductivity. The materials of interest, ethylene oxide tethered imidazole heterocycles (Imi-nEO), are characterized by variable temperature experiments, as well as 2D homonuclear double quantum (DQ) NMR and 2D exchange spectroscopy. Quantum chemical calculations provide a full assignment and understanding of the 1H chemical shifts, based on a single-crystal structure obtained for Imi-2EO. Three types of hydrogen-bonded N-1H resonances are observed by 1H MAS NMR at 30 kHz. Double quantum NMR experiments identify those hydrogen-bonded protons that are mobile on the time scale of the experiment, and thereby, those which are able to participate in charge transport. Characterized by their spin−spin relaxation ( ) behavior, the local mobility of these protons as a function of temperature is compared to the conductivity of the materials. Homonuclear 1H 2D DQ MAS spectra provide evidence for locally ordered domains within all the Imi-nEO materials. Disordered (mobile) and ordered components in Imi-2EO dramatically differ in their 1H spin−lattice relaxation times. 2D NOESY spectra show no evidence of chemical exchange processes between the ordered and disordered domains. These results indicate that the highly ordered regions of the materials do not (or only poorly) contribute to proton conductivity, which is rather taking place in the disordered regions. Molecules in the disordered domains are in a state of dynamic or fluctuating hydrogen-bonding, allowing for Grotthus mechanism proton transport, while molecules in the ordered domains do not experience exchange, and do not participate in long-range proton conductivity. At the interface between these regimes a small number of molecules undergo slow exchange. With increasing temperature, this exchange becomes fast on the NMR time scale, and the final chemical shift of 12.5 ppm in Imi-5EO implies the persistence of strongly and weakly hydrogen-bonded domains, which reorganize rapidly to support the proton transport process.

Solid-state electrode materials for Li-ion batteries are of considerable interest worldwide. Along with the intensively studied transition-metal oxides Li x MO 2 (M ) Co, Ni, and Mn) and Li x V 2 O 5 , polyanion structures built of corner-sharing MO 6 octahedra (M ) Fe, Ti, V, and Nb) and (XO 4 ) ntetrahedra (X ) S, P, As, Mo, and W) 1-11 have garnered much attention. Seminal studies on these materials focused on Fe 2 (XO 4 ) 3 (X ) S, 1 Mo, 2 and W 3 ). Materials such as Li x FePO 4 , 4 Li x MM′(XO 4 ) 3 , 5-10 Li x FeP 2 O 7 , 11 and Li x VOXO 4 12-14 were recently identified as good hosts for the extraction/intercalation of Li between 2.5 and 4 V vs Li/Li + . 6,15 Because of the lower covalence of the M-O bonds in these polyanion structures, the Fe 3+ /Fe 2+ and V 4+ /V 3+ redox couples lie at more useful potentials than in the simple oxides.The NASICON framework [MM′(XO 4 ) 3 ] ∞ , 16 which allows for extensive substitution on the octahedral (M and M′) and tetrahedral (X) sites, is particularly attrac-* To whom correspondence should be addressed.

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Intensive studies of an advanced energy material are reported and lithium polyacrylate (LiPAA) is proven to be a surprisingly unique, multifunctional binder for high‐voltage Li‐ion batteries. The absence of effective passivation at the interface of high‐voltage cathodes in Li‐ion batteries may negatively affect their electrochemical performance, due to detrimental phenomena such as electrolyte solution oxidation and dissolution of transition metal cations. A strategy is introduced to build a stable cathode–electrolyte solution interphase for LiNi0.5Mn1.5O4 (LNMO) spinel high‐voltage cathodes during the electrode fabrication process by simply using LiPAA as the cathode binder. LiPAA is a superb binder due to unique adhesion, cohesion, and wetting properties. It forms a uniform thin passivating film on LNMO and conducting carbon particles in composite cathodes and also compensates Li‐ion loss in full Li‐ion batteries by acting as an extra Li source. It is shown that these positive roles of LiPAA lead to a significant improvement in the electrochemical performance (e.g., cycle life, cell impedance, and rate capability) of LNMO/graphite battery prototypes, compared with that obtained using traditional polyvinylidene fluoride (PVdF) binder for LNMO cathodes. In addition, replacing PVdF with LiPAA binder for LNMO cathodes offers better adhesion, lower cost, and clear environmental advantages.

The impact of lithium bis(oxalate)borate (LiBOB) electrolyte additive on the performance of full lithium-ion cells pairing the high-voltage spinel cathode with the graphite anode was systematically investigated. Adding 1 wt % LiBOB to the electrolyte significantly improved the cycle life and Coulombic efficiency of the full-cells at 30 and 45 °C. As the LiBOB was preferentially oxidized and reduced compared with LiBOB-free electrolyte during cycling, their relative contributions to the improved capacity retention in full-cells was gauged by pairing fresh and LiBOB-treated electrodes with various combinations. The results indicated that a solid–electrolyte interphase (SEI) film on graphite produced by the reduction of the LiBOB additive is more robust and stable against Mn dissolution problem during cycling at 45 °C compared with the SEI formed by the reduction of the base (LiBOB-free) electrolyte. In addition, a 3 wt % LiBOB-added electrolyte showed reduced Mn dissolution compared with the base electrolyte after storing the fully charged Li1–x Ni0.42Fe0.08Mn1.5O4 (LNFMO) electrodes at 60 °C for one month. It is believed that LiBOB aids in stabilizing the electrolyte by trapping the PF5, i.e., sequestering the radical which tends to oxidize EC and DEC electrolyte solvents. Thus, oxidation is suppressed on the carbon black particles in the positive electrode, as evidenced by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR) analyses. As a result, HF generation is suppressed, which in turn results in less Mn dissolution from the spinel cathode.

Proton mobilities in Nafion and sulfonated poly(ether ether ketone) (S-PEEK) have been studied using high-resolution solid-state 1H NMR under fast magic angle spinning (MAS). These studies demonstrated proton exchange between sulfonic acid groups and water within both Nafion and S-PEEK. Variable temperature experiments were used to determine the activation energy for proton transport in pure Nafion, found to be 11.0 kJ/mol, which is lower than those determined for S-PEEKs with different degrees of sulfonation. Increasing proton exchange rates with increasing temperature indicate the expected dependence of proton mobility on temperature. A rotor-synchronized homonuclear double quantum filter sequence (BaBa) was used to disclose the nature of the H-bonding interactions in the two polymers, from which a model of the proton interactions in the polymers is developed.

The MXenes are a class of 2D materials composed of transition-metal sheets alternating with carbide/nitride sheets, stacked just a few atoms thick. MXenes discovered thus far also have a surface termination layer that is likely a mixture of hydroxides and fluorides. While reasonable structural models based on x-ray diffraction and transmission electron microscopy data exist, the exact nature and distribution of the surface termination species is not well understood. Here, 1 H, 19 F, and 13 C solid-state NMR spectroscopy is used to investigate the model MXene V 2 CT x , where T signifies the surface termination groups. 1 H NMR experiments provide direct proof of hydroxide moieties in the surface layer by measuring interactions with the MXene surface.Furthermore, 1 H NMR spectroscopy shows a significant amount of water hydrogen bonded to the surface hydroxide layer. 19 F NMR experiments show fluoride moieties bonded to the MXene surface, with extremely unusual 19 F spectra caused by strong interactions with the metallic/semi-conducting MXene. 13 C NMR observes the sample from the center of the MXene layer, and shows that the 13 C chemical shift is extremely sensitive to the MAX➞MXene transformation. Nuclear-spin magnetization transferred from 1 H nuclei in the hydroxide surface termination layer to 13 C nuclei in the center of the MXene sheet yields further evidence of this connectivity. The multinuclear NMR experiments provide direct experimental verification of the structural models, and depict the MXene V 2 CT x as infinite sheets of small-bandgap V 2 C sheets terminated by a mixed hydroxide/fluoride layer embedded in a matrix of strongly hydrogen-bonded water molecules.