Experimental and theoretical evidence for hydrogen doping in polymer solution-processed indium gallium oxide.

The field-effect electron mobility of aqueous solution-processed indium gallium oxide (IGO) thin-film transistors (TFTs) is significantly enhanced by polyvinyl alcohol (PVA) addition to the precursor solution, a >70-fold increase to 7.9 cm2/Vs. To understand the origin of this remarkable phenomenon, microstructure, electronic structure, and charge transport of IGO:PVA film are investigated by a battery of experimental and theoretical techniques, including In K-edge and Ga K-edge extended X-ray absorption fine structure (EXAFS); resonant soft X-ray scattering (R-SoXS); ultraviolet photoelectron spectroscopy (UPS); Fourier transform-infrared (FT-IR) spectroscopy; time-of-flight secondary-ion mass spectrometry (ToF-SIMS); composition-/processing-dependent TFT properties; high-resolution solid-state 1H, 71Ga, and 115In NMR spectroscopy; and discrete Fourier transform (DFT) analysis with ab initio molecular dynamics (MD) liquid-quench simulations. The 71Ga{1H} rotational-echo double-resonance (REDOR) NMR and other data indicate that PVA achieves optimal H doping with a Ga···H distance of ∼3.4 Å and conversion from six- to four-coordinate Ga, which together suppress deep trap defect localization. This reduces metal-oxide polyhedral distortion, thereby increasing the electron mobility. Hydroxyl polymer doping thus offers a pathway for efficient H doping in green solvent-processed metal oxide films and the promise of high-performance, ultra-stable metal oxide semiconductor electronics with simple binary compositions.

High-performance all-solid-state batteries enabled by salt bonding to perovskite in poly(ethylene oxide).

Flexible and low-cost poly(ethylene oxide) (PEO)-based electrolytes are promising for all-solid-state Li-metal batteries because of their compatibility with a metallic lithium anode. However, the low room-temperature Li-ion conductivity of PEO solid electrolytes and severe lithium-dendrite growth limit their application in high-energy Li-metal batteries. Here we prepared a PEO/perovskite Li3/8Sr7/16Ta3/4Zr1/4O3 composite electrolyte with a Li-ion conductivity of 5.4 × 10-5 and 3.5 × 10-4 S cm-1 at 25 and 45 °C, respectively; the strong interaction between the F- of TFSI- (bis-trifluoromethanesulfonimide) and the surface Ta5+ of the perovskite improves the Li-ion transport at the PEO/perovskite interface. A symmetric Li/composite electrolyte/Li cell shows an excellent cyclability at a high current density up to 0.6 mA cm-2 A solid electrolyte interphase layer formed in situ between the metallic lithium anode and the composite electrolyte suppresses lithium-dendrite formation and growth. All-solid-state Li|LiFePO4 and high-voltage Li|LiNi0.8Mn0.1Co0.1O2 batteries with the composite electrolyte have an impressive performance with high Coulombic efficiencies, small overpotentials, and good cycling stability.

Interfacial Chemistry Enables Stable Cycling of All-Solid-State Li Metal Batteries at High Current Densities.

The application of flexible, robust, and low-cost solid polymer electrolytes in next-generation all-solid-state lithium metal batteries has been hindered by the low room-temperature ionic conductivity of these electrolytes and the small critical current density of the batteries. Both issues stem from the low mobility of Li+ ions in the polymer and the fast lithium dendrite growth at the Li metal/electrolyte interface. Herein, Mg(ClO4)2 is demonstrated to be an effective additive in the poly(ethylene oxide) (PEO)-based composite electrolyte to regulate Li+ ion transport and manipulate the Li metal/electrolyte interfacial performance. By combining experimental and computational studies, we show that Mg2+ ions are immobile in a PEO host due to coordination with ether oxygen and anions of lithium salts, which enhances the mobility of Li+ ions; more importantly, an in-situ formed Li+-conducting Li2MgCl4/LiF interfacial layer homogenizes the Li+ flux during plating and increases the critical current density up to a record 2 mA cm-2. Each of these factors contributes to the assembly of competitive all-solid-state Li/Li, LiFePO4/Li, and LiNi0.8Mn0.1Co0.1O2/Li cells, demonstrating the importance of surface chemistry and interfacial engineering in the design of all-solid-state Li metal batteries for high-current-density applications.

17 O NMR Studies of Yeast Ubiquitin in Aqueous Solution and in the Solid State.

We report a general method for amino acid-type specific 17 O-labeling of recombinant proteins in Escherichia coli. In particular, we have prepared several [1-13 C,17 O]-labeled yeast ubiquitin (Ub) samples including Ub-[1-13 C,17 O]Gly, Ub-[1-13 C,17 O]Tyr, and Ub-[1-13 C,17 O]Phe using the auxotrophic E. coli strain DL39 GlyA λDE3 (aspC- tyrB- ilvE- glyA- λDE3). We have also produced Ub-[η-17 O]Tyr, in which the phenolic group of Tyr59 is 17 O-labeled. We show for the first time that 17 O NMR signals from protein terminal residues and side chains can be readily detected in aqueous solution. We also reported solid-state 17 O NMR spectra for Ub-[1-13 C,17 O]Tyr and Ub-[1-13 C,17 O]Phe obtained at an ultrahigh magnetic field, 35.2 T (1.5 GHz for 1 H). This work represents a significant advance in the field of 17 O NMR studies of proteins.

Fast Li+ Conduction Mechanism and Interfacial Chemistry of a NASICON/Polymer Composite Electrolyte.

The unclear Li+ local environment and Li+ conduction mechanism in solid polymer electrolytes, especially in a ceramic/polymer composite electrolyte, hinder the design and development of a new composite electrolyte. Moreover, both the low room-temperature Li+ conductivity and large interfacial resistance with a metallic lithium anode of a polymer membrane limit its application below a relatively high temperature. Here we have identified the Li+ distribution and Li+ transport mechanism in a composite polymer electrolyte by investigating a new solid poly(ethylene oxide) (PEO)-based NASICON-LiZr2(PO4)3 composite with 7Li relaxation time and 6Li → 7Li trace-exchange NMR measurements. The Li+ population of the two local environments in the composite electrolytes depends on the Li-salt concentration and the amount of ceramic filler. A composite electrolyte with a [EO]/[Li+] ratio n = 10 and 25 wt % LZP filler has a high Li+ conductivity of 1.2 × 10-4 S cm-1 at 30 °C and a low activation energy owing to the additional Li+ in the mobile A2 environment. Moreover, an in situ formed solid electrolyte interphase layer from the reaction between LiZr2(PO4)3 and a metallic lithium anode stabilized the Li/composite-electrolyte interface and reduced the interfacial resistance, which provided a symmetric Li/Li cell and all-solid-state Li/LiFePO4 and Li/LiNi0.8Co0.1Mn0.1O2 cells a good cycling performance at 40 °C.

Enhanced Surface Interactions Enable Fast Li+ Conduction in Oxide/Polymer Composite Electrolyte.

Li+ -conducting oxides are considered better ceramic fillers than Li+ -insulating oxides for improving Li+ conductivity in composite polymer electrolytes owing to their ability to conduct Li+ through the ceramic oxide as well as across the oxide/polymer interface. Here we use two Li+ -insulating oxides (fluorite Gd0.1 Ce0.9 O1.95 and perovskite La0.8 Sr0.2 Ga0.8 Mg0.2 O2.55 ) with a high concentration of oxygen vacancies to demonstrate two oxide/poly(ethylene oxide) (PEO)-based polymer composite electrolytes, each with a Li+ conductivity above 10-4  S cm-1 at 30 °C. Li solid-state NMR results show an increase in Li+ ions (>10 %) occupying the more mobile A2 environment in the composite electrolytes. This increase in A2-site occupancy originates from the strong interaction between the O2- of Li-salt anion and the surface oxygen vacancies of each oxide and contributes to the more facile Li+ transport. All-solid-state Li-metal cells with these composite electrolytes demonstrate a small interfacial resistance with good cycling performance at 35 °C.

A Perovskite Electrolyte That Is Stable in Moist Air for Lithium-Ion Batteries.

Solid-oxide Li+ electrolytes of a rechargeable cell are generally sensitive to moisture in the air as H+ exchanges for the mobile Li+ of the electrolyte and forms insulating surface phases at the electrolyte interfaces and in the grain boundaries of a polycrystalline membrane. These surface phases dominate the total interfacial resistance of a conventional rechargeable cell with a solid-electrolyte separator. We report a new perovskite Li+ solid electrolyte, Li0.38 Sr0.44 Ta0.7 Hf0.3 O2.95 F0.05 , with a lithium-ion conductivity of σLi =4.8×10-4  S cm-1 at 25 °C that does not react with water having 3≤pH≤14. The solid electrolyte with a thin Li+ -conducting polymer on its surface to prevent reduction of Ta5+ is wet by metallic lithium and provides low-impedance dendrite-free plating/stripping of a lithium anode. It is also stable upon contact with a composite polymer cathode. With this solid electrolyte, we demonstrate excellent cycling performance of an all-solid-state Li/LiFePO4 cell, a Li-S cell with a polymer-gel cathode, and a supercapacitor.

Lithium-compatible and air-stable vacancy-rich Li9N2Cl3 for high-areal capacity, long-cycling all-solid-state lithium metal batteries.

Attaining substantial areal capacity (>3 mAh/cm2) and extended cycle longevity in all-solid-state lithium metal batteries necessitates the implementation of solid-state electrolytes (SSEs) capable of withstanding elevated critical current densities and capacities. In this study, we report a high-performing vacancy-rich Li9N2Cl3 SSE demonstrating excellent lithium compatibility and atmospheric stability and enabling high-areal capacity, long-lasting all-solid-state lithium metal batteries. The Li9N2Cl3 facilitates efficient lithium-ion transport due to its disordered lattice structure and presence of vacancies. Notably, it resists dendrite formation at 10 mA/cm2 and 10 mAh/cm2 due to its intrinsic lithium metal stability. Furthermore, it exhibits robust dry-air stability. Incorporating this SSE in Ni-rich LiNi0.83Co0.11Mn0.06O2 cathode-based all-solid-state batteries, we achieve substantial cycling stability (90.35% capacity retention over 1500 cycles at 0.5 C) and high areal capacity (4.8 mAh/cm2 in pouch cells). These findings pave the way for lithium metal batteries to meet electric vehicle performance demands.

Structural Evolution and Transition Dynamics in Lithium Ion Battery under Fast Charging: An Operando Neutron Diffraction Investigation.

Fast charging (<15 min) of lithium-ion batteries (LIBs) for electrical vehicles (EVs) is widely seen as the key factor that will greatly stimulate the EV markets, and its realization is mainly hindered by the sluggish diffusion of Li+ . To have a mechanistic understanding of Li+ diffusion within LIBs, in this study, structural evolutions of electrodes for a Ni-rich LiNi0.6 Mn0.2 Co0.2 O2 (NMC622) || graphite cylindrical cell with high areal loading (2.78 mAh cm-2 ) are developed for operando neutron powder diffraction study at different charging rates. Via sequential Rietveld refinements, changes in structures of NMC622 and Lix C6 are obtained during moderate and fast charging (from 0.27 C to 4.4 C). NMC622 exhibits the same structural evolution regardless of C-rates. For phase transitions of Lix C6 , the stage I (LiC6 ) phase emerges earlier during the stepwise intercalation at a lower state of charge when charging rate is increased. It is also found that the stage II (LiC12 ) → stage I (LiC6 ) transition is the rate-limiting step during fast charging. The LiC12 → LiC6 transition mechanism is further analyzed using the Johnson-Mehl-Avrami-Kolmogorov model. It is concluded as a diffusion-controlled, 1D phase transition with decreasing nucleation kinetics under increasing chargingrates.

Investigation of Glass-Ceramic Lithium Thiophosphate Solid Electrolytes Using NMR and Neutron Scattering.

Solid-state Li batteries require solid electrolytes which have high Li+ conductivity and good chemical/mechanical compatibility with Li metal anodes and high energy cathodes. Structure/function correlations which relate local bonding to macroscopic properties are needed to guide development of new solid electrolyte materials. This study combines diffraction measurements with solid-state nuclear magnetic resonance spectroscopy (ssNMR) and neutron pair distribution function (nPDF) analysis to probe the short-range vs. long-range structure of glass-ceramic Li3PS4-based solid electrolytes. This work demonstrates how different synthesis conditions (e.g., solvent selection and thermal processing) affect the resulting polyanionic network. More specifically, structures with high P coordination numbers (e.g., PS4 3- and P2S7 4-) correlate with higher Li+ mobility compared to other polyanions (e.g., (PS3)n n- chains and P2S6 4-). Overall, this work demonstrates how ssNMR and nPDF can be used to draw key structure/function correlations for solid-state superionic conductors.

Loss of EGR-1 uncouples compensatory responses of pancreatic ß cells.

Rationale: Subjects unable to sustain ß-cell compensation develop type 2 diabetes. Early growth response-1 protein (EGR-1), implicated in the regulation of cell differentiation, proliferation, and apoptosis, is induced by diverse metabolic challenges, such as glucose or other nutrients. Therefore, we hypothesized that deficiency of EGR-1 might influence ß-cell compensation in response to metabolic overload. Methods: Mice deficient in EGR-1 (Egr1-/-) were used to investigate the in vivo roles of EGR-1 in regulation of glucose homeostasis and beta-cell compensatory responses. Results: In response to a high-fat diet, Egr1-/- mice failed to secrete sufficient insulin to clear glucose, which was associated with lower insulin content and attenuated hypertrophic response of islets. High-fat feeding caused a dramatic impairment in glucose-stimulated insulin secretion and downregulated the expression of genes encoding glucose sensing proteins. The cells co-expressing both insulin and glucagon were dramatically upregulated in islets of high-fat-fed Egr1-/- mice. EGR-1-deficient islets failed to maintain the transcriptional network for ß-cell compensatory response. In human pancreatic tissues, EGR1 expression correlated with the expression of ß-cell compensatory genes in the non-diabetic group, but not in the diabetic group. Conclusion: These results suggest that EGR-1 couples the transcriptional network to compensation for the loss of ß-cell function and identity. Thus, our study highlights the early stress coupler EGR-1 as a critical factor in the development of pancreatic islet failure.

Li Distribution Heterogeneity in Solid Electrolyte Li10GeP2S12 upon Electrochemical Cycling Probed by 7Li MRI.

All-solid-state rechargeable batteries embody the promise for high energy density, increased stability, and improved safety. However, their success is impeded by high resistance for mass and charge transfer at electrode-electrolyte interfaces. Li deficiency has been proposed as a major culprit for interfacial resistance, yet experimental evidence is elusive due to the challenges associated with noninvasively probing the Li distribution in solid electrolytes. In this Letter, three-dimensional 7Li magnetic resonance imaging (MRI) is employed to examine Li distribution homogeneity in solid electrolyte Li10GeP2S12 within symmetric Li/Li10GeP2S12/Li batteries. 7Li MRI and the derived histograms reveal Li depletion from the electrode-electrolyte interfaces and increased heterogeneity of Li distribution upon electrochemical cycling. Significant Li loss at interfaces is mitigated via facile modification with a poly(ethylene oxide)/bis(trifluoromethane)sulfonimide Li salt thin film. This study demonstrates a powerful tool for noninvasively monitoring the Li distribution at the interfaces and in the bulk of all-solid-state batteries as well as a convenient strategy for improving interfacial stability.

Operando EPR for Simultaneous Monitoring of Anionic and Cationic Redox Processes in Li-Rich Metal Oxide Cathodes.

Anionic redox chemistry offers a transformative approach for significantly increasing specific energy capacities of cathodes for rechargeable Li-ion batteries. This study employs operando electron paramagnetic resonance (EPR) to simultaneously monitor the evolution of both transition metal and oxygen redox reactions, as well as their intertwined couplings in Li2MnO3, Li1.2Ni0.2Mn0.6O2, and Li1.2Ni0.13Mn0.54Co0.13O2 cathodes. Reversible O2-/O2n- redox takes place above 3.0 V, which is clearly distinguished from transition metal redox in the operando EPR on Li2MnO3 cathodes. O2-/O2n- redox is also observed in Li1.2Ni0.2Mn0.6O2, and Li1.2Ni0.13Mn0.54Co0.13O2 cathodes, albeit its overlapping potential ranges with Ni redox. This study further reveals the stabilization of the reversible O redox by Mn and e- hole delocalization within the Mn-O complex. The interactions within the cation-anion pairs are essential for preventing O2n- from recombination into gaseous O2 and prove to activate Mn for its increasing participation in redox reactions. Operando EPR helps to establish a fundamental understanding of reversible anionic redox chemistry. The gained insights will support the search for structural factors that promote desirable O redox reactions.

On the origin of high ionic conductivity in Na-doped SrSiO3.

Understanding the local structure and ion dynamics is at the heart of ion conductor research. This paper reports on high-resolution solid-state 29Si, 23Na, and 17O NMR investigation of the structure, chemical composition, and ion dynamics of a newly discovered fast ion conductor, Na-doped SrSiO3, which exhibited a much higher ionic conductivity than most of current oxide ion conductors. Quantitative analyses reveal that with a small dose (<10 mol%) of Na, the doped Na integrates into the SrSiO3 structure to form Na x Sr1-x SiO3-0.5x , and with >10 mol% Na doping, phase separation occurs, leading to the formation of an amorphous phase ß-Na2Si2O5 and a crystalline Sr-rich phase. Variable-temperature 23Na and 17O magic-angle-spinning NMR up to 618 °C have shown significant changes in Na ion dynamics at high temperatures but little oxide ion motion, suggesting that Na ions are responsible for the observed high ionic conductivity. In addition, ß-Na2Si2O5 starts to crystallize at temperatures higher than 480 °C with prolonged heating, resulting in reduction in Na+ motion, and thus degradation of ionic conductivity. This study has contributed critical evidence to the understanding of ionic conduction in Na-doped SrSiO3 and demonstrated that multinuclear high-resolution and high-temperature solid-state NMR is a uniquely useful tool for investigating ion conductors at their operating conditions.

Dehydration induced 2D-to-3D crystal-to-crystal network re-assembly and ferromagnetism tuning within two chiral copper(II)-tartrate coordination polymers.

The synthesis of two homochiral l-tartrate-copper(II) coordination polymers, [Cu2(C4H4O6)2(H2O)2·xH2O]n (1), and [Cu(C4H4O6)]n (2), under hydrothermal conditions, is reported. Compound 1 adopts a 2D layered network structure with a space group of P21, while compound 2 features a 3D network structure with a space group P21212. Interestingly, the 2D layered structure of compound 1 can undergo a crystal-to-crystal network reassembly, with the formation of the 3D network structure of compound 2 under dehydration conditions. Variable temperature and field magnetic studies reveal the existence of a distinct ferromagnetic interaction between Cu(2+) ions as the result of distinct syn-anti carboxylate bridging coordination modes.