Pediatric mental health emergency department visits from 2017 to 2022: A multicenter study.

BACKGROUND: The COVID-19 pandemic adversely affected children's mental health (MH) and changed patterns of MH emergency department (ED) utilization. Our objective was to assess how pediatric MH ED visits during the COVID-19 pandemic differed from expected prepandemic trends. METHODS: We retrospectively studied MH ED visits by children 5 to <18 years old at nine U.S. hospitals participating in the Pediatric Emergency Care Applied Research Network Registry from 2017 to 2022. We described visit length by time period: prepandemic (January 2017-February 2020), early pandemic (March 2020-December 2020), midpandemic (2021), and late pandemic (2022). We estimated expected visit rates from prepandemic data using multivariable Poisson regression models. We calculated rate ratios (RRs) of observed to expected visits per 30 days during each pandemic time period, overall and by sociodemographic and clinical characteristics. RESULTS: We identified 175,979 pediatric MH ED visits. Visit length exceeded 12 h for 7.3% prepandemic, 8.4% early pandemic, 15.0% midpandemic, and 19.2% late pandemic visits. During the early pandemic, observed visits per 30 days decreased relative to expected rates (RR 0.80, 95% confidence interval [CI] 0.78-0.84), were similar to expected rates during the midpandemic (RR 1.01, 95% CI 0.96-1.07), and then decreased below expected rates during the late pandemic (RR 0.92, 95% CI 0.86-0.98). During the late pandemic, visit rates were higher than expected for females (RR 1.10, 95% CI 1.02-1.20) and for bipolar disorders (RR 1.83, 95% CI 1.38-2.75), schizophrenia spectrum disorders (RR 1.55, 95% CI 1.10-2.59), and substance-related and addictive disorders (RR 1.50, 95% CI 1.18-2.05). CONCLUSIONS: During the late pandemic, pediatric MH ED visits decreased below expected rates; however, visits by females and for specific conditions remained elevated, indicating a need for increased attention to these groups. Prolonged ED visit lengths may reflect inadequate availability of MH services.

Bioarchaeological investigation of individuals with suspected multibacillary leprosy from the mediaeval leprosarium of St Mary Magdalen, Winchester, Hampshire, UK.

Introduction. We have examined four burials from the St Mary Magdalen mediaeval leprosarium cemetery in Winchester, Hampshire, UK. One (Sk.8) was a male child, two (Sk.45 and Sk.52) were adolescent females and the fourth (Sk.512) was an adult male. The cemetery was in use between the 10th and 12th centuries. All showed skeletal lesions of leprosy. Additionally, one of the two females (Sk.45) had lesions suggestive of multi-cystic tuberculosis and the second (Sk.52) of leprogenic odontodysplasia (LO), a rare malformation of the roots of the permanent maxillary incisors.Gap statement. Relatively little is known of the manifestations of lepromatous leprosy (LL) in younger individuals from the archaeological record.Aims and Methodology. To address this, we have used ancient DNA testing and osteological examination of the individuals, supplemented with X-ray and microcomputed tomography (micro-CT) scan as necessary to assess the disease status.Results and Conclusions. The presence of Mycobacterium leprae DNA was confirmed in both females, and genotyping showed SNP type 3I-1 strains but with a clear genotypic variation. We could not confirm Mycobacterium tuberculosis complex DNA in the female individual SK.45. High levels of M. leprae DNA were found within the pulp cavities of four maxillary teeth from the male child (Sk.8) with LO, consistent with the theory that the replication of M. leprae in alveolar bone may interfere with root formation at key stages of development. We report our biomolecular findings in these individuals and review the evidence this site has contributed to our knowledge of mediaeval leprosy.

Early Administration of Steroids in the Ambulance Setting: An Observational Design Trial (EASI-AS-ODT).

BACKGROUND: In the emergency department (ED), prompt administration of systemic corticosteroids for pediatric asthma exacerbations decreases hospital admission rates. However, there is sparse evidence for whether earlier administration of systemic corticosteroids by emergency medical services (EMS) clinicians, prior to ED arrival, further improves pediatric asthma outcomes. METHODS: Early Administration of Steroids in the Ambulance Setting: An Observational Design Trial is a multicenter, observational, nonrandomized stepped-wedge design study with seven participating EMS agencies who adopted an oral systemic corticosteroid (OCS) into their protocols for pediatric asthma treatment. Using univariate analyses and multivariable mixed-effects models, we compared hospital admission rates for pediatric asthma patients ages 2-18 years before and after the introduction of a prehospital OCS and for those who did and did not receive a systemic corticosteroid from EMS. RESULTS: A total of 834 patients were included, 21% of whom received a systemic corticosteroid from EMS. EMS administration of systemic corticosteroids increased after the introduction of an OCS from 14.7% to 28.1% (p < 0.001). However, there was no significant difference between hospital admission rates and ED length of stay before and after the introduction of OCS or between patients who did and did not receive a systemic corticosteroid from EMS. Mixed-effects models revealed that age 14-18 years (coefficient -0.83, p = 0.002), EMS administration of magnesium (coefficient 1.22, p = 0.04), and initial EMS respiratory severity score (coefficient 0.40, p < 0.001) were significantly associated with hospital admission. CONCLUSIONS: In this multicenter study, the addition of an OCS into EMS agency protocols for pediatric asthma exacerbations significantly increased systemic corticosteroid administration but did not significantly decrease hospital admission rates. As overall EMS systemic corticosteroid administration rates were low, further work is required to understand optimal implementation of EMS protocol changes to better assess potential benefits to patients.

Examination of disparities in prehospital encounters for pediatric asthma exacerbations.

Introduction: There are disparities in multiple aspects of pediatric asthma care; however, prehospital care disparities are largely undescribed. This study's objective was to examine racial and geographic disparities in emergency medical services (EMS) medication administration to pediatric patients with asthma. Methods: This is a substudy of the Early Administration of Steroids in the Ambulance Setting: An Observational Design Trial, which includes data from pediatric asthma patients ages 2-18 years. We examined rates of EMS administration of systemic corticosteroids and inhaled bronchodilators by patient race. We geocoded EMS scene addresses, characterized the locations' neighborhood-based conditions and resources relevant to children using the Child Opportunity Index (COI) 2.0, and analyzed associations between EMS scene address COI with medications administered by EMS. Results: A total of 765 patients had available racial data and 825 had scene addresses that were geocoded to a COI. EMS administered at least 1 bronchodilator to 84.7% (n = 492) of non-White patients and 83.2% of White patients (n = 153), P = 0.6. EMS administered a systemic corticosteroid to 19.4% (n = 113) of non-White patients and 20.1% (n = 37) of White patients, P = 0.8. There was a significant difference in bronchodilator administration between COI categories of low/very low versus moderate/high/very high (85.0%, n = 485 vs. 75.9%, n = 192, respectively, P = 0.003). Conclusions: There were no racial differences in EMS administration of medications to pediatric asthma patients. However, there were significantly higher rates of EMS bronchodilator administration for encounters in low/very low COIs. That latter finding may reflect inequities in asthma exacerbation severity for patients living in disadvantaged areas.

EMS Administration of Systemic Corticosteroids to Pediatric Asthma Patients: An Analysis by Severity and Transport Interval.

INTRODUCTION: Pediatric asthma exacerbations are a common cause of emergency medical services (EMS) encounters. Bronchodilators and systemic corticosteroids are mainstays of asthma exacerbation therapy, yet data on the efficacy of EMS administration of systemic corticosteroids are mixed. This study's objective was to assess the association between EMS administration of systemic corticosteroids to pediatric asthma patients on hospital admission rates based on asthma exacerbation severity and EMS transport intervals. METHODS: This is a sub-analysis of the Early Administration of Steroids in the Ambulance Setting: An Observational Design Trial (EASI AS ODT). EASI AS ODT is a non-randomized, stepped wedge, observational study examining outcomes one year before and one year after seven EMS agencies incorporated an oral systemic corticosteroid option into their protocols for the treatment of pediatric asthma exacerbations. We included EMS encounters for patients ages 2-18 years confirmed by manual chart review to have asthma exacerbations. We compared hospital admission rates across asthma exacerbation severities and EMS transport intervals using univariate analyses. We geocoded patients and created maps to visualize the general trends of patient characteristics. RESULTS: A total of 841 pediatric asthma patients met inclusion criteria. While most patients were administered inhaled bronchodilators by EMS (82.3%), only 21% received systemic corticosteroids, and only 19% received both inhaled bronchodilators and systemic corticosteroids. Overall, there was no significant difference in hospitalization rates between patients who did and did not receive systemic corticosteroids from EMS (33% vs. 32%, p = 0.78). However, although not statistically significant, for patients who received systemic corticosteroids from EMS, there was an 11% decrease in hospitalizations for mild exacerbation patients and a 16% decrease in hospitalizations for patients with EMS transport intervals greater than 40 min. CONCLUSION: In this study, systemic corticosteroids were not associated with a decrease in hospitalizations of pediatric patients with asthma overall. However, while limited by small sample size and lack of statistical significance, our results suggest there may be a benefit in certain subgroups, particularly patients with mild exacerbations and those with transport intervals longer than 40 min. Given the heterogeneity of EMS agencies, EMS agencies should consider local operational and pediatric patient characteristics when developing standard operating protocols for pediatric asthma.

Room-Temperature Pseudo-Solid-State Iron Fluoride Conversion Battery with High Ionic Conductivity.

Li-metal batteries (LMBs) employing conversion cathode materials (e.g., FeF3) are a promising way to prepare inexpensive, environmentally friendly batteries with high energy density. Pseudo-solid-state ionogel separators harness the energy density and safety advantages of solid-state LMBs, while alleviating key drawbacks (e.g., poor ionic conductivity and high interfacial resistance). In this work, a pseudo-solid-state conversion battery (Li-FeF3) is presented that achieves stable, high rate (1.0 mA cm-2) cycling at room temperature. The batteries described herein contain gel-infiltrated FeF3 cathodes prepared by exchanging the ionic liquid in a polymer ionogel with a localized high-concentration electrolyte (LHCE). The LHCE gel merges the benefits of a flexible separator (e.g., adaptation to conversion-related volume changes) with the excellent chemical stability and high ionic conductivity (∼2 mS cm-1 at 25 °C) of an LHCE. The latter property is in contrast to previous solid-state iron fluoride batteries, where poor ionic conductivities necessitated elevated temperatures to realize practical power levels. The stable, room-temperature Li-FeF3 cycling performance obtained with the LHCE gel at high current densities paves the way for exploring a range of architectures including flexible, three-dimensional, and custom shape batteries.

Tunable Intervalence Charge Transfer in Ruthenium Prussian Blue Analog Enables Stable and Efficient Biocompatible Artificial Synapses.

Emerging concepts for neuromorphic computing, bioelectronics, and brain-computer interfacing inspire new research avenues aimed at understanding the relationship between oxidation state and conductivity in unexplored materials. This report expands the materials playground for neuromorphic devices to include a mixed valence inorganic 3D coordination framework, a ruthenium Prussian blue analog (RuPBA), for flexible and biocompatible artificial synapses that reversibly switch conductance by more than four orders of magnitude based on electrochemically tunable oxidation state. The electrochemically tunable degree of mixed valency and electronic coupling between N-coordinated Ru sites controls the carrier concentration and mobility, as supported by density functional theory computations and application of electron transfer theory to in situ spectroscopy of intervalence charge transfer. Retention of programmed states is improved by nearly two orders of magnitude compared to extensively studied organic polymers, thus reducing the frequency, complexity, and energy costs associated with error correction schemes. This report demonstrates dopamine-mediated plasticity of RuPBA synapses and biocompatibility of RuPBA with neuronal cells, evoking prospective application for brain-computer interfacing.

Utilizing Near-Infrared Spectroscopy to Identify Pediatric Trauma Patients Needing Lifesaving Interventions: A Prospective Study.

OBJECTIVES: The aim of this study was to prospectively investigate the role of near-infrared spectroscopy (NIRS) in identifying pediatric trauma patients who required lifesaving interventions (LSIs). METHODS: Prospective cohort study of children age 0 to 18 years who activated the trauma team response between August 15, 2017, and February 12, 2019, at a large, urban pediatric emergency department (ED).The relationship between the lowest somatic NIRS saturation and the need for LSIs (based on published consensus definition) was investigated. Categorical variables were analyzed by χ 2 test, and continuous variables were analyzed by Student t test. RESULTS: A total of 148 pediatric trauma patients had somatic NIRS monitoring and met the inclusion criteria. Overall, 65.5% were male with a mean ± SD age of 10.9 ± 6.0 years. Injuries included 67.6% blunt trauma and 28.4% penetrating trauma with mortality of 3.4% (n = 5). Overall, the median lowest somatic NIRS value was 72% (interquartile range, 58%-88%; range, 15%-95%), and 43.9% of patients had a somatic NIRS value <70%. The median somatic NIRS duration recorded was 11 minutes (interquartile range, 7-17 minutes; range, 1-105 minutes). Overall, 36.5% of patients required a LSI including 53 who required a lifesaving procedure, 17 required blood products, and 17 required vasopressors. Among procedures, requiring a thoracostomy was significant.Pediatric trauma patients with a somatic NIRS value <70% had a significantly increased odds of requiring a LSI (odds ratio, 2.11; 95% confidence interval, 1.07-4.20). Somatic NIRS values <70% had a sensitivity and specificity of 56% and 63%, respectively. CONCLUSIONS: Pediatric trauma patients with somatic NIRS values <70% within 30 minutes of ED arrival have an increased odds of requiring LSIs. Among LSIs, pediatric trauma patients requiring thoracostomy was significant. The role of NIRS in incrementally improving the identification of critically injured children in the ED and prehospital setting should be evaluated in larger prospective multicenter studies.

Imaging Phase Segregation in Nanoscale LixCoO2 Single Particles.

LixCoO2 (LCO) is a common battery cathode material that has recently emerged as a promising material for other applications including electrocatalysis and as electrochemical random access memory (ECRAM). During charge-discharge cycling LCO exhibits phase transformations that are significantly complicated by electron correlation. While the bulk phase diagram for an ensemble of battery particles has been studied extensively, it remains unclear how these phases scale to nanometer dimensions and the effects of strain and diffusional anisotropy at the single-particle scale. Understanding these effects is critical to modeling battery performance and for predicting the scalability and performance of electrocatalysts and ECRAM. Here we investigate isolated, epitaxial LiCoO2 islands grown by pulsed laser deposition. After electrochemical cycling of the islands, conductive atomic force microscopy (c-AFM) is used to image the spatial distribution of conductive and insulating phases. Above 20 nm island thicknesses, we observe a kinetically arrested state in which the phase boundary is perpendicular to the Li-planes; we propose a model and present image analysis results that show smaller LCO islands have a higher conductive fraction than larger area islands, and the overall conductive fraction is consistent with the lithiation state. Thinner islands (14 nm), with a larger surface to volume ratio, are found to exhibit a striping pattern, which suggests surface energy can dominate below a critical dimension. When increasing force is applied through the AFM tip to strain the LCO islands, significant shifts in current flow are observed, and underlying mechanisms for this behavior are discussed. The c-AFM images are compared with photoemission electron microscopy images, which are used to acquire statistics across hundreds of particles. The results indicate that strain and morphology become more critical to electrochemical performance as particles approach nanometer dimensions.

Understanding the Electrochemical Performance of FeS2 Conversion Cathodes.

Conversion cathodes represent a viable route to improve rechargeable Li+ battery energy densities, but their poor electrochemical stability and power density have impeded their practical implementation. Here, we explore the impact cell fabrication, electrolyte interaction, and current density have on the electrochemical performance of FeS2/Li cells by deconvoluting the contributions of the various conversion and intercalation reactions to the overall capacity. By varying the slurry composition and applied pressure, we determine that the capacity loss is primarily due to the large volume changes during (de)lithiation, leading to a degradation of the conductive matrix. Through the application of an external pressure, the loss is minimized by maintaining the conductive matrix. We further determine that polysulfide loss can be minimized by increasing the current density (>C/10), thus reducing the sulfur formation period. Analysis of the kinetics determines that the conversion reactions are rate-limiting, specifically the formation of metallic iron at rates above C/8. While focused on FeS2, our findings on the influence of pressure, electrolyte interaction, and kinetics are broadly applicable to other conversion cathode systems.

The Role of Electrolyte Composition in Enabling Li Metal-Iron Fluoride Full-Cell Batteries.

FeF3 conversion cathodes, paired with Li metal, are promising for use in next-generation secondary batteries and offer a remarkable theoretical energy density of 1947 Wh kg-1 compared to 690 Wh kg-1 for LiNi0.5 Mn1.5 O4 ; however, many successful studies on FeF3 cathodes are performed in cells with a large (>90-fold) excess of Li that disguises the effects of tested variables on the anode and decreases the practical energy density of the battery. Herein, it is demonstrated that for full-cell compatibility, the electrolyte must produce both a protective solid-electrolyte interphase and cathode-electrolyte interphase and that an electrolyte composed of 1:1.3:3 (m/m) LiFSI, 1,2-dimethoxyethane, and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether fulfills both these requirements. This work demonstrates the importance of verifying electrode level solutions on the full-cell level when developing new battery chemistries and represents the first full cell demonstration of a Li/FeF3 cell, with both limited Li and high capacity FeF3 utilization.

Mechanistic Insight and Local Structure Evolution of NiPS3 upon Electrochemical Lithiation.

Transition metal phosphorus trisulfide materials have received considerable research interest since the 1980-1990s as they exhibit promising energy conversion and storage properties. However, the mechanistic insights into Li-ion storage in these materials are poorly understood to date. Here, we explore the lithiation of NiPS3 material by employing in situ pair-distribution function analysis, Monte Carlo molecular dynamics calculations, and a series of ex situ characterizations. Our findings elucidate complex ion insertion and storage dynamics around a layered polyanionic compound, which undergoes intercalation and conversion reactions in a sequential manner. This study of NiPS3 material exemplifies the Li-ion storage mechanism in transition metal phosphorus sulfide materials and provides insights into the challenges associated with achieving reliable, high-energy phosphorus trisulfide systems.

Utilizing Near-Infrared Spectroscopy (NIRS) to Identify Pediatric Trauma Patients Needing Lifesaving Interventions (LSIs): A Retrospective Study.

OBJECTIVES: The aim of this study was to investigate the role of near-infrared spectroscopy (NIRS) in identifying pediatric trauma patients who required lifesaving interventions (LSIs). METHODS: Retrospective chart review of children age 0 to 18 years who activated the trauma team response between January 1, 2015 and August 14, 2017, at a large, urban pediatric emergency department. The lowest somatic NIRS saturation and the need for LSIs (based on published consensus definition) were abstracted from the chart. χ2 and descriptive statistics were used for analysis. RESULTS: The charts of 84 pediatric trauma patients were reviewed. Overall, 80% were boys with a mean age of 10.4 years (SD, 6.2 years). Injuries included 56% blunt trauma and 36% penetrating trauma with mortality of 10.7% (n = 9). Overall, the median lowest NIRS value was 67% (interquartile range, 51-80%; range, 15%-95%) and 54.8% of the patients had a NIRS value less than 70%. The median somatic NIRS duration recorded was 12 minutes (interquartile range, 6-17 minutes; range, 1-59 minutes). Overall, 50% of patients required a LSI, including 39 who required a lifesaving procedure, 11 required blood products, and 14 required vasopressors. Pediatric trauma patients with NIRS less than 70% had a significantly increased odds of requiring a LSI (odds ratio, 2.67; 95% confidence interval, 1.10-6.47). NIRS less than 70% had a sensitivity and specificity of 67% and 57% respectively. CONCLUSIONS: Pediatric trauma patients with somatic NIRS less than 70% within 30 minutes of emergency department arrival are associated with the need for LSIs. Continuous NIRS monitoring in the pediatric trauma population should be evaluated prospectively.

Understanding Stabilization in Nanoporous Intermetallic Alloy Anodes for Li-Ion Batteries Using Operando Transmission X-ray Microscopy.

Tin-based alloying anodes are exciting due to their high energy density. Unfortunately, these materials pulverize after repetitive cycling due to the large volume expansion during lithiation and delithiation; both nanostructuring and intermetallic formation can help alleviate this structural damage. Here, these ideas are combined in nanoporous antimony-tin (NP-SbSn) powders, synthesized by a simple and scalable selective-etching method. The NP-SbSn exhibits bimodal porosity that facilitates electrolyte diffusion; those void spaces, combined with the presence of two metals that alloy with lithium at different potentials, further provide a buffer against volume change. This stabilizes the structure to give NP-SbSn good cycle life (595 mAh/g after 100 cycles with 93% capacity retention). Operando transmission X-ray microscopy (TXM) showed that during cycling NP-SbSn expands by only 60% in area and then contracts back nearly to its original size with no physical disintegration. The pores shrink during lithiation as the pore walls expand into the pore space and then relax back to their initial size during delithiation with almost no degradation. Importantly, the pores remained open even in the fully lithiated state, and structures are in good physical condition after the 36th cycle. The results of this work should thus be useful for designing nanoscale structures in alloying anodes.

Updates on pediatric sepsis.

Sepsis, defined as an infection with dysregulated host response leading to life-threatening organ dysfunction, continues to carry a high potential for morbidity and mortality in children. The recognition of sepsis in children in the emergency department (ED) can be challenging, related to the high prevalence of common febrile infections, poor specificity of discriminating features, and the capacity of children to compensate until advanced stages of shock. Sepsis outcomes are strongly dependent on the timeliness of recognition and treatment, which has led to the successful implementation of quality improvement programs, increasing the reliability of sepsis treatment in many US institutions. We review clinical, laboratory, and technical modalities that can be incorporated into ED practice to facilitate the recognition, treatment, and reassessment of children with suspected sepsis. The 2020 updated pediatric sepsis guidelines are reviewed and framed in the context of ED interventions, including guidelines for antibiotic administration, fluid resuscitation, and the use of vasoactive agents. Despite a large body of literature on pediatric sepsis epidemiology in recent years, the evidence base for treatment and management components remains limited, implying an urgent need for large trials in this field. In conclusion, although the burden and impact of pediatric sepsis remains substantial, progress in our understanding of the disease and its management have led to revised guidelines and the available data emphasizes the importance of local quality improvement programs.

Filament-Free Bulk Resistive Memory Enables Deterministic Analogue Switching.

Digital computing is nearing its physical limits as computing needs and energy consumption rapidly increase. Analogue-memory-based neuromorphic computing can be orders of magnitude more energy efficient at data-intensive tasks like deep neural networks, but has been limited by the inaccurate and unpredictable switching of analogue resistive memory. Filamentary resistive random access memory (RRAM) suffers from stochastic switching due to the random kinetic motion of discrete defects in the nanometer-sized filament. In this work, this stochasticity is overcome by incorporating a solid electrolyte interlayer, in this case, yttria-stabilized zirconia (YSZ), toward eliminating filaments. Filament-free, bulk-RRAM cells instead store analogue states using the bulk point defect concentration, yielding predictable switching because the statistical ensemble behavior of oxygen vacancy defects is deterministic even when individual defects are stochastic. Both experiments and modeling show bulk-RRAM devices using TiO2- X switching layers and YSZ electrolytes yield deterministic and linear analogue switching for efficient inference and training. Bulk-RRAM solves many outstanding issues with memristor unpredictability that have inhibited commercialization, and can, therefore, enable unprecedented new applications for energy-efficient neuromorphic computing. Beyond RRAM, this work shows how harnessing bulk point defects in ionic materials can be used to engineer deterministic nanoelectronic materials and devices.

NMR Relaxometry and Diffusometry Analysis of Dynamics in Ionic Liquids and Ionogels for Use in Lithium-Ion Batteries.

We have investigated the charge transport dynamics of a novel solid-like electrolyte material based on mixtures of the ionic liquid (IL) 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([BMIM] TFSI) and various concentrations of lithium salt bis(trifluoromethylsulfonyl)imide (LiTFSI) confined within a SiO2 matrix, prepared via a sol-gel method. The translational diffusion coefficients of BMIM+, TFSI-, and Li+ in ILs and confined ILs (ionogels, IGs) with different concentrations of lithium salt have been measured at variable temperatures, covering the 20-100 °C range, using nuclear magnetic resonance (NMR) pulsed field gradient diffusion spectroscopy. The mobility of BMIM+, TFSI-, and Li+ was found to increase with the [BMIM] TFSI/LiTFSI ratio, exhibiting an almost liquid-like mobility in IGs. Additionally, the effect of confinement on IL rotational dynamics has been analyzed by measuring 1H, 19F, and 7Li spin-lattice relaxation rate dispersions of IGs at different temperatures, using fast field-cycling NMR relaxometry. The analysis of the experimental data was performed assuming the existence of two fractions of the liquid: a bulk fraction (at least several ionic radii from the silica particles) and a surface fraction (close to the silica particles) and using two different models based on translational and rotational diffusion and reorientation mediated by translational displacements. The existence and weighting of these two fractions of ions were obtained from the direct diffusion measurements. The results show that the ion dynamics slowed only modestly under confinement, which evidences that IGs preserve IL transport properties, and this behavior is an encouraging indication for using IGs as a solid electrolyte for Li+ batteries.

Electrochemical and Spectroscopic Analysis of the Ionogel-Electrode Interface.

Ionogels, pseudo-solid-state electrolytes consisting of an ionic liquid electrolyte confined in a mesoporous inorganic matrix, have attracted interest recently due to their high ionic conductivity and physicochemical stability. These traits, coupled with their inherent solution processability, make them a viable solid electrolyte for solid-state battery systems. Despite the promising properties of ionogels, there have been very few investigations of the electrode-ionogel interface. In the present study, X-ray photoelectron spectroscopy, Raman spectroscopy, and electrochemical measurements were utilized to probe the surface reactions occurring at the electrode-ionogel interface for several electrode materials. Our results indicate that the sol acidity initiates breakdown of the organic constituents of the sol and reduction of the transition metals present in the electrode materials. This chemical attack forms an organic surface layer and affects the electrode composition, both of which can impede Li+ access. By modifying the silica sol-gel reaction via a two-step acid-base catalysis, these interfacial reactions can be avoided. Results are shown for a LiCoO2 electrode in which a high Li-ion capacity and stable cycling were achieved.

Conformal Ultrathin Film Metal-Organic Framework Analogues: Characterization of Growth, Porosity, and Electronic Transport.

Thin-film formation and transport properties of two copper-paddlewheel metal-organic framework (MOF) -based systems (MOF-14 and MOF-399) are investigated for their potential integration into electrochemical device architectures. Thin-film analogs of these two systems are fabricated by the sequential, alternating, solution-phase deposition of the inorganic and organic ligand precursors that result in conformal films via van der Merwe-like growth. Atomic force microscopy reveals smooth film morphologies with surface roughnesses determined by the underlying substrates and linear film growth of 1.4 and 2.2 nm per layer for the MOF-14 and MOF-399 systems, respectively. Electrochemical impedance spectroscopy is used to evaluate the electronic transport properties of the thin films, finding that the MOF-14 analog films demonstrate low electronic conductivity, while MOF-399 analog films are electronically insulating. The intrinsic porosities of these ultrathin MOF analog films are confirmed by cyclic voltammetry redox probe characterization using ferrocene. Larger peak currents are observed for MOF-399 analog films compared to MOF-14 analog films, which is consistent with the larger pores of MOF-399. The layer-by-layer deposition of these systems provides a promising route to incorporate MOFs as thin films with nanoscale thickness control and low surface roughness for electrochemical devices.

Probing ion current in solid-electrolytes at the meso- and nanoscale.

We present experimental approaches to probe the ionic conductivity of solid electrolytes at the meso- and nanoscales. Silica ionogel based electrolytes have emerged as an important class of solid electrolytes because they maintain both fluidic and high-conductivity states at the nanoscale, but at the macroscale they are basically solid. Single mesopores in polymer films are shown to serve as templates for cast ionogels. The ionic conductivity of the ionogels was probed by two experimental approaches. In the first approach, the single-pore/ionogel membranes were placed between two chambers of a conductivity cell, in a set-up similar to that used for investigating liquid electrolytes. The second approach involved depositing contacts directly onto the membrane and measuring conductivity without the bulk solution present. Ionic conductivity determined by the two methods was in excellent agreement with macroscopic measurements, which suggested that the electrochemical properties of ionogel based electrolytes are preserved at the mesoscale, and ionogels can be useful in designing meso-scaled energy-storage devices.