Hydrothermally Assisted Conversion of Switchgrass into Hard Carbon as Anode Materials for Sodium-Ion Batteries.

Sodium-ion batteries (SIBs) are emerging as a viable alternative to lithium-ion batteries, reducing the reliance on scarce transition metals. Converting agricultural biomass into SIB anodes can remarkably enhance sustainability in both the agriculture and battery industries. However, the complex and costly synthesis and unsatisfactory electrochemical performance of biomass-derived hard carbon have hindered its further development. Herein, we employed a hydrothermally assisted carbonization process that converts switchgrass to battery-grade hard carbon capable of efficient Na-ion storage. The hydrothermal pretreatment effectively removed hemicellulose and impurities (e.g., lipids and ashes), creating thermally stable precursors suitable to produce hard carbon via carbonization. The elimination of hemicellulose and impurities contributes to a reduced surface area and lower oxygen content. With the modifications, the initial Coulombic efficiency (ICE) and cycling stability are improved concurrently. The optimized hard carbon showcased a high reversible specific capacity of 313.4 mAh g-1 at 100 mA g-1, a commendable ICE of 84.8%, and excellent cycling stability with a capacity retention of 308.4 mAh g-1 after 100 cycles. In short, this research introduces a cost-effective method for producing anode materials for SIBs and highlights a sustainable pathway for biomass utilization, underscoring mutual benefits for the energy and agricultural sectors.

Self-terminating, heterogeneous solid-electrolyte interphase enables reversible Li-ether cointercalation in graphite anodes.

Ether solvents are suitable for formulating solid-electrolyte interphase (SEI)-less ion-solvent cointercalation electrolytes in graphite for Na-ion and K-ion batteries. However, ether-based electrolytes have been historically perceived to cause exfoliation of graphite and cell failure in Li-ion batteries. In this study, we develop strategies to achieve reversible Li-solvent cointercalation in graphite through combining appropriate Li salts and ether solvents. Specifically, we design 1M LiBF4 1,2-dimethoxyethane (G1), which enables natural graphite to deliver ~91% initial Coulombic efficiency and >88% capacity retention after 400 cycles. We captured the spatial distribution of LiF at various length scales and quantified its heterogeneity. The electrolyte shows self-terminated reactivity on graphite edge planes and results in a grainy, fluorinated pseudo-SEI. The molecular origin of the pseudo-SEI is elucidated by ab initio molecular dynamics (AIMD) simulations. The operando synchrotron analyses further demonstrate the reversible and monotonous phase transformation of cointercalated graphite. Our findings demonstrate the feasibility of Li cointercalation chemistry in graphite for extreme-condition batteries. The work also paves the foundation for understanding and modulating the interphase generated by ether electrolytes in a broad range of electrodes and batteries.

Reversible Switch in Charge Storage Enabled by Selective Ion Transport in Solid Electrolyte Interphase.

Solid-electrolyte interphases (SEIs) in advanced rechargeable batteries ensure reversible electrode reactions at extreme potentials beyond the thermodynamic stability limits of electrolytes by insulating electrons while allowing the transport of working ions. Such selective ion transport occurs naturally in biological cell membranes as a ubiquitous prerequisite of many life processes and a foundation of biodiversity. In addition, cell membranes can selectively open and close the ion channels in response to external stimuli (e.g., electrical, chemical, mechanical, and thermal), giving rise to "gating" mechanisms that help manage intracellular reactions. We wondered whether the chemistry and structure of SEIs can mimic those of cell membranes, such that ion gating can be replicated. That is, can SEIs realize a reversible switching between two electrochemical behaviors, i.e., the ion intercalation chemistry of batteries and the ion adsorption of capacitors? Herein, we report such SEIs that result in thermally activated selective ion transport. The function of open/close gate switches is governed by the chemical and structural dynamics of SEIs under different thermal conditions, with precise behaviors as conducting and insulating interphases that enable battery and capacitive processes within a finite temperature window. Such an ion gating function is synergistically contributed by Arrhenius-activated ion transport and SEI dissolution/regrowth. Following the understanding of this new mechanism, we then develop an electrochemical method to heal the SEI layer in situ. The knowledge acquired in this work reveals the possibility of hitherto unknown biomimetic properties of SEIs, which will guide us to leverage such complexities to design better SEIs for future battery chemistries.

Operando characterization and regulation of metal dissolution and redeposition dynamics near battery electrode surface.

Mn dissolution has been a long-standing, ubiquitous issue that negatively impacts the performance of Mn-based battery materials. Mn dissolution involves complex chemical and structural transformations at the electrode-electrolyte interface. The continuously evolving electrode-electrolyte interface has posed great challenges for characterizing the dynamic interfacial process and quantitatively establishing the correlation with battery performance. In this study, we visualize and quantify the temporally and spatially resolved Mn dissolution/redeposition (D/R) dynamics of electrochemically operating Mn-containing cathodes. The particle-level and electrode-level analyses reveal that the D/R dynamics is associated with distinct interfacial degradation mechanisms at different states of charge. Our results statistically differentiate the contributions of surface reconstruction and Jahn-Teller distortion to the Mn dissolution at different operating voltages. Introducing sulfonated polymers (Nafion) into composite electrodes can modulate the D/R dynamics by trapping the dissolved Mn species and rapidly establishing local Mn D/R equilibrium. This work represents an inaugural effort to pinpoint the chemical and structural transformations responsible for Mn dissolution via an operando synchrotron study and develops an effective method to regulate Mn interfacial dynamics for improving battery performance.

Spatial and Temporal Analysis of Sodium-Ion Batteries.

As a promising alternative to the market-leading lithium-ion batteries, low-cost sodium-ion batteries (SIBs) are attractive for applications such as large-scale electrical energy storage systems. The energy density, cycling life, and rate performance of SIBs are fundamentally dependent on dynamic physiochemical reactions, structural change, and morphological evolution. Therefore, it is essential to holistically understand SIBs reaction processes, degradation mechanisms, and thermal/mechanical behaviors in complex working environments. The recent developments of advanced in situ and operando characterization enable the establishment of the structure-processing-property-performance relationship in SIBs under operating conditions. This Review summarizes significant recent progress in SIBs exploiting in situ and operando techniques based on X-ray and electron analyses at different time and length scales. Through the combination of spectroscopy, imaging, and diffraction, local and global changes in SIBs can be elucidated for improving materials design. The fundamental principles and state-of-the-art capabilities of different techniques are presented, followed by elaborative discussions of major challenges and perspectives.

Recycling Polymeric Solid Wastes for Energy-Efficient Water Purification, Organic Distillation, and Oil Spill Cleanup.

Conventional approaches (e.g., pyrolysis) for managing waste polymer foams typically require highly technical skills and consume large amounts of energy resources. This paper presents an ultrafacile, cost-effective, and highly efficient alternative method for recycling waste packaging and cleaning foam (e.g., polymelamine-formaldehyde foam). The designed solar absorber, a polypyrrole-coated melamine foam (PMF), features a highly porous structure, excellent mechanical strength, low thermal conductivity, and rapid water transport capacity. These exceptional properties render the PMF suitable for multiple applications, including energy-efficient solar-powered water purification, ethanol distillation, and oil absorption. In water purification, the PMF yields a solar-thermal conversion efficiency as high as 87.7%, stability that is maintained for more than 35 operation cycles, and antifouling capabilities (when purifying different water types). In solar distillation, the PMF achieves a concentration increase up to 75 vol% when distilling a 10 vol% ethanol solution. In oil absorption, the PMF offers an oil-absorption capacity of ≈70 g g-1 with only a 7% loss in capacity after 100 absorbing-squeezing cycles. Thus, systems combining solar energy with various waste foams are highly promising as durable, renewable, and portable systems for water purification, organic distillation, and oil absorption, especially in remote regions or emergency situations.

Sub-nanometer confinement enables facile condensation of gas electrolyte for low-temperature batteries.

Confining molecules in the nanoscale environment can lead to dramatic changes of their physical and chemical properties, which opens possibilities for new applications. There is a growing interest in liquefied gas electrolytes for electrochemical devices operating at low temperatures due to their low melting point. However, their high vapor pressure still poses potential safety concerns for practical usages. Herein, we report facile capillary condensation of gas electrolyte by strong confinement in sub-nanometer pores of metal-organic framework (MOF). By designing MOF-polymer membranes (MPMs) that present dense and continuous micropore (~0.8 nm) networks, we show significant uptake of hydrofluorocarbon molecules in MOF pores at pressure lower than the bulk counterpart. This unique property enables lithium/fluorinated graphite batteries with MPM-based electrolytes to deliver a significantly higher capacity than those with commercial separator membranes (~500 mAh g-1 vs. <0.03 mAh g-1) at -40 °C under reduced pressure of the electrolyte.

Self-Healing and Anti-CO2 Hydrogels for Flexible Solid-State Zinc-Air Batteries.

Flexible solid-state zinc-air batteries (ZABs) generally suffer from poor electrolyte/electrode contact and mechanical degradation in practical applications. In addition, CO2 corrosion is also a common issue for ZABs with alkaline electrolyte. Herein, we report a thermoreversible alkaline hydrogel electrolyte that can simultaneously solve the aforementioned problems. Through a simple cooling process, the hydrogel electrolyte transforms from solid state to liquid state that can not only restore the deformed electrolyte layer to its original state but also rebuild intimate contact between electrode and electrolyte. Moreover, the ZAB based on this hydrogel electrolyte exhibits an unprecedented anti-CO2 property. As a result, such a battery shows almost 2.5 times discharge duration than that of ZAB based on liquid electrolyte.

Rational Synthesis of "Grape-like" Ni2 V2 O7 Microspheres as High-capacity Anodes for Rechargeable Lithium Batteries.

Vanadates have received booming attention recently as promising materials for extensive electrochemical devices such as batteries and electrocatalysis. However, the enormous difficulties of achieving pure-phase transition metal vanadates, especially for nickel-based, hinder their exploitations. Herein, for the first time, by controlling the amount of ethylene glycol (EG) and reaction time, grape-like Ni2 V2 O7 (or V2 O5 /Ni2 V2 O7 ) microspheres were rationally fabricated. It is demonstrated that the EG can chelate both Ni2+ and VO3 - to form organometallic precursors. As anode in lithium-ion batteries (LIBs), it could deliver superior reversible capacity of 1050 mAh/g at 0.1 A/g and excellent rate capability of 600 mAh/g at 4 A/g. The facile hydrothermal synthesis broadens the material variety of nickel vanadates and offers new opportunities for their wider applications in electrochemistry.

An ester electrolyte for lithium-sulfur batteries capable of ultra-low temperature cycling.

A novel lithium bis(fluorosulfonyl)imide in a methyl propionate/fluoroethylene carbonate (LiFSI MP/FEC) electrolyte was designed for high compatibility with the Li metal and sulfurized polyacrylonitrile (SPAN). The resulting Li||SPAN cells can charge and discharge at -20 °C and -40 °C with over 91% and 78% room temperature capacity retention.

Pure-phase ß-Mn2V2O7 interconnected nanospheres as a high-performance lithium ion battery anode.

This work primarily exhibits a systematic study of the large-scale hydrothermal synthesis of ß-Mn2V2O7 interconnected nanospheres without templates. An optimal combination of hydrothermal/annealing/atmosphere parameters is identified for the pure phase, which exhibits an excellent cycling performance of 760 mA h g-1 at 0.5 A g-1 over 120 cycles and a rate capability of 470 mA h g-1 at 2 A g-1 as an anode for a lithium ion battery. Guidelines have been provided for the first time for the synthesis of ß-Mn2V2O7, which opens broad opportunities for this earth-abundant chemical in electrochemical devices.

Opioid-Induced Hyperalgesia in the Nonsurgical Setting: A Systematic Review.

BACKGROUND: Opioid-induced hyperalgesia (OIH) is a phenomenon that causes an increased pain sensitization and perception of pain to noxious stimuli secondary to opioid exposure. While this clinical effect has been described in the surgical setting, it is unclear if OIH occurs in the nonsurgical setting. STUDY QUESTION: To review the available literature which evaluated OIH in nonsurgical settings. DATA SOURCES: A comprehensive literature search was performed using PubMed (January 1946-July 2017) using a variety of keywords for OIH. This review included randomized controlled trials with objectives to identify OIH in the nonsurgical setting. The clinical outcomes of interest were identification of OIH, adverse events, and impact of OIH on opioid consumption. RESULTS: The search identified 8 studies that fulfilled the criteria. Six studies enrolled healthy male volunteers, 1 study used chronic low-back patients, and another used heroin-dependent treatment-seeking adults. Studies used various opioids and dosages, including remifentanil, alfentanil, fentanyl, morphine, methadone, and buprenorphine. Three primary experimental pain induction models were used to evaluate for OIH. Measured outcomes included hyperalgesia area, pain threshold, and pain tolerance. All 5 studies that used the electrical stimulation model identified OIH as a significant outcome. However, only 2 of 5 studies using the cold pressor model and 1 of 3 studies using the heat pressor model identified OIH. None of the trials explored clinical outcomes, such as effects on opioid consumption. CONCLUSIONS: Most included studies identified OIH as a significant outcome within the nonsurgical setting. However, due to conflicting conclusions and various limitations, the clinical impact of OIH could not be assessed. Clinicians should monitor for effects of OIH in the nonoperative setting because there is insufficient evidence from the available literature to conclude that OIH is consistently observed in this setting.

Enhanced Electrochemical and Thermal Transport Properties of Graphene/MoS2 Heterostructures for Energy Storage: Insights from Multiscale Modeling.

Graphene has been combined with molybdenum disulfide (MoS2) to ameliorate the poor cycling stability and rate performance of MoS2 in lithium ion batteries, yet the underlying mechanisms remain less explored. Here, we develop multiscale modeling to investigate the enhanced electrochemical and thermal transport properties of graphene/MoS2 heterostructures (GM-Hs) with a complex morphology. The calculated electronic structures demonstrate the greatly improved electrical conductivity of GM-Hs compared to MoS2. Increasing the graphene layers in GM-Hs not only improves the electrical conductivity but also stabilizes the intercalated Li atoms in GM-Hs. It is also found that GM-Hs with three graphene layers could achieve and maintain a high thermal conductivity of 85.5 W/(m·K) at a large temperature range (100-500 K), nearly 6 times that of pure MoS2 [∼15 W/(m·K)], which may accelerate the heat conduction from electrodes to the ambient. Our quantitative findings may shed light on the enhanced battery performances of various graphene/transition-metal chalcogenide composites in energy storage devices.

A Facile Approach to Tune the Electrical and Thermal Properties of Graphene Aerogels by Including Bulk MoS2.

Graphene aerogels (GAs) have attracted extensive interest in diverse fields, owing to their ultrahigh surface area, low density and decent electrical conductivity. However, the undesirable thermal conductivity of GAs may limit their applications in energy storage devices. Here, we report a facile hydrothermal method to modulate both the electrical and thermal properties of GAs by including bulk molybdenum disulfide (MoS2). It was found that MoS2 can help to reduce the size of graphene sheets and improve their dispersion, leading to the uniform porous micro-structure of GAs. The electrical measurement showed that the electrical conductivity of GAs could be decreased by 87% by adding 0.132 vol % of MoS2. On the contrary, the thermal conductivity of GAs could be increased by ~51% by including 0.2 vol % of MoS2. The quantitative investigation demonstrated that the effective medium theories (EMTs) could be applied to predict the thermal conductivity of composite GAs. Our findings indicated that the electrical and thermal properties of GAs can be tuned for the applications in various fields.