Electrolyte Regulation towards Stable Lithium-Metal Anodes in Lithium–Sulfur Batteries with Sulfurized Polyacrylonitrile Cathodes

Lithium–sulfur (Li–S) batteries are highly regarded as the next-generation energy-storage devices because of their ultrahigh theoretical energy density of 2600 Wh kg⁻¹. Sulfurized polyacrylonitrile (SPAN) is considered a promising sulfur cathode to substitute carbon/sulfur (C/S) composites to afford higher Coulombic efficiency, improved cycling stability, and potential high-energy-density Li–SPAN batteries. However, the instability of the Li-metal anode threatens the performances of Li–SPAN batteries bringing limited lifespan and safety hazards. Li-metal can react with most kinds of electrolyte to generate a protective solid electrolyte interphase (SEI), electrolyte regulation is a widely accepted strategy to protect Li-metal anodes in rechargeable batteries. Herein, the basic principles and current challenges of Li–SPAN batteries are addressed. Recent advances on electrolyte regulation towards stable Li-metal anodes in Li–SPAN batteries are summarized to suggest design strategies of solvents, lithium salts, additives, and gel electrolyte. Finally, prospects for future electrolyte design and Li anode protection in Li–SPAN batteries are discussed.     

Electrochemical Reactivation of Dead Li2S for Li−S Batteries in Non-Solvating Electrolytes

The use of non-solvating, or as-called sparingly-solvating, electrolytes (NSEs), is regarded as one of the most promising solutions to the obstacles to the practical applications of Li−S batteries. However, it remains a puzzle that long-life Li−S batteries have rarely, if not never, been reported with NSEs, despite their good compatibility with Li anode. Here, we find the capacity decay of Li−S batteries in NSEs is mainly due to the accumulation of the dead Li₂S at the cathode side, rather than the degradation of the anodes or electrolytes. Based on this understanding, we propose an electrochemical strategy to reactivate the accumulated Li₂S and revive the dead Li−S batteries in NSEs. With such a facile approach, Li−S batteries with significantly improved cycling stability and accelerated dynamics are achieved with diglyme-, acetonitrile- and 1,2-dimethoxyethane-based NSEs. Our finding may rebuild the confidence in exploiting non-solvating Li−S batteries with practical competitiveness.     

Magnetic Solid-Phase Extraction and Ionic Liquid Dispersive Liquid–Liquid Microextraction Coupled with High-Performance Liquid Chromatography for the Determination of Hexachlorophene in Cosmetics

An efficient, simple, and fast method based on ionic liquid dispersive liquid–liquid microextraction (IL-DLLME) followed by magnetic solid-phase extraction (MSPE) was developed as a new technique for extracting and purifying hexachlorophene (HCP) in cosmetics prior to high-performance liquid chromatography (HPLC) determination. In this method based on IL-DLLME and MSPE, 1-hexyl-3-methylimidazolium hexafluorophosphate ([C₆MIM][PF₆]) is used as the extraction solvent and Fe₃O₄ nanoparticles are used to remove hydrophobic additives in the cosmetics by physical adsorption. The main parameters affecting the efficiency of the IL-DLLME and MSPE of HCP were investigated and optimized. Under the optimum conditions, the method was linear in the range 0.5–40 µg mL^?1 with a correlation coefficient (R ²) of 0.9976 and had a detection limit of 0.14 µg mL^?1 at a signal-to-noise ratio (S/N) of 3. The recoveries of HCP in three cosmetic samples using the proposed method were in the range 74.5–97.7%, and the relative standard deviations (RSD, n = 5) were in the range 3.8–6.7%. The developed method was successfully applied to the determination of HCP in cosmetics.     

Hewettite ZnV6O16 ⋅ 8H2O with Remarkably Stable Layers and Ultralarge Interlayer Spacing for High-Performance Aqueous Zn-Ion Batteries

Aqueous Zn-ion batteries (ZIBs) are promising candidates for grid-scale energy storage because of their intrinsic safety, low-cost and high energy-intensity. Vanadium-based materials are widely used as the cathode of ZIBs, especially A₂V₆O₁₆ ⋅ nH₂O (AVO, A=NH₄⁺, Na, K). However, AVO suffers from serious dissolution, phase transformation and narrow gallery spacing (∼3 Å), leading to poor cycling stability and rate capability. Herein, we unveiled the root cause of the performance degradation in the AVO cathode and therefore developed a new high-performance cathode of ZnV₆O₁₆ ⋅ 8H₂O (ZVO) for ZIB. Through a method of ion exchange induced phase transformation, AVO was converted to hewettite ZVO with larger gallery spacing (∼6 Å) and more stable V₆O₁₆ layers. ZVO cathode thus constructed delivers a high capacity of 365 and 170 mAh g⁻¹ at 0.5 and 15 A g⁻¹, while 86 % and 70 % of its capacity are retained at 0.5 A g⁻¹ after 300 cycles and at 15 A g⁻¹ after 10000 cycles, substantially better than conventional AVO.     

Ionic Liquids as Mobile Phase Additives for Separation of Nucleotides in High-Performance Liquid Chromatography

Ionic liquids are a type of salts that are liquid at low temperature (＜100℃). Because of their some special properties, they have been widely used as new “green solvents” for many chemical reactions and liquid-liquid extraction in the past several years. In this paper, a new method for the separation of nucleotides is developed and the essential feature of the method is that 1-alkyl-3-methylimidazolium salts are used as mobile phase additives, resulting in a baseline separation of nucleotides without need of gradient elution and need of organic solvent addition as currently used in RP-HPLC. This study shows the potential application of ionic liquids as mobile phase additives in reversed-phase liquid chromatograohy.     

An Endogenous Prompting Mechanism for Sulfur Conversions Via Coupling with Polysulfides in Li−S Batteries

The sluggish kinetics process and shuttling of soluble intermediates present in complex conversion between sulfur and lithium sulfide severely limit the practical application of lithium-sulfur batteries. Herein, by introducing a designated functional organic molecule to couple with polysulfide intermediators, an endogenous prompting mechanism of sulfur conversions has thus been created leading to an alternative sulfur-electrode process, in another words, to build a fast “internal cycle” of promotors that can promote the slow “external cycle” of sulfur conversions. The coupling-intermediators between the functional organic molecule and polysulfides, organophosphorus polysulfides, to be the “promotors” for sulfur conversions, are not only insoluble in the electrolyte but also with higher redox-activity. So the sulfur-electrode process kinetics is greatly improved and the shuttle effect is eliminated simultaneously by this strategy. Meanwhile, with the endogenous prompting mechanism, the morphology of the final discharge product can be modified into a uniform covering film, which is more conducive to its decomposition when charging. Benefiting from the effective mediation of reaction kinetics and control of intermediates solubility, the lithium-sulfur batteries can act out excellent rate performance and cycling stability.     

Ionic Liquid Based Electrolyte with Mesoporous Silica SBA-15 as Framework for Quasi-solid-state Dye-sensitized Solar Cells

Quasi-solid-state electrolytes were fabricated with mesoporous silica SBA-15 as a framework material. Ionic conductivity measurements revealed that SBA-15 can enhance the conductivity of the quasi-solid-state electrolyte. The diffusion coefficients of polyiodide ions such as Ⅰ3ˉ and Ⅰ5ˉ which were confirmed by Raman spectroscopic measurement, were about twice larger than that of I-. The optimized photoenergy conversion efficiency of dye-sensitized solar cells （DSSC） with the quasi-solid-state electrolyte was 4.3% under AM 1.5 irradiation at 75 mW·cm^-2 light intensity.     

Superoxide Anion Disproportionation Induced by Li+ and H+: Pathways to 1O2 Release in Li−O2 Batteries

We explore the disproportionation reaction of superoxide anions in the presence of H⁺ and Li⁺ cations with high quality multiconfigurational ab-initio methods. This reaction is of paramount importance in Li−O₂ battery chemistry as it represents the source of a major degrading impurity, singlet molecular oxygen. For the first time, the thermodynamic and kinetic data of the reaction are drawn from an accurate theoretical model where the electronic structure of the reactant and products is treated at the necessary level of theory. Overall, the H⁺ catalyzed O₂⁻+O₂⁻ disproportionation follows a very efficient thermodynamic and kinetic reaction path leading to neutral ³O₂, ¹O₂ and peroxide anions. On the contrary, we have found that the Li⁺ catalysis promotes only the release of ³O₂ whereas the ¹O₂ formation is energetically unfeasible at room temperature.     

B−N Co-Doped Biphenylene as a Metal-Free Cathode Catalyst for Li−O2 Batteries: a Computational Study

Lithium-oxygen batteries (LOBs) meet the growing demand for long-distance transportation over electric vehicles but face challenges because of the lack of high-performance cathode catalysts. Herein, using density functional theory calculations, we report a unique graphene allotrope, biphenylene, of which the doping structures exhibit great potential as metal-free catalysts for LOBs. Our modeling results demonstrate that the biphenylene nanosheets retain metallic properties after B doping, N doping, or B−N co-doping. Compared with the pristine biphenylene, the catalytic activity of the doped biphenylene is greatly improved due to charge redistributions. Notably, the overpotentials of the B−N co-doped biphenylene are as low as 0.19 and 0.18 V for the discharge and charge processes, respectively. Based on the electronic structure and bonding analysis, we identify two factors, i. e., Li−O bond strength and *Li₂O₂ adsorption energy, that can influence the Li−O₂ electrochemical reactions. This study not only proposes a promising cathode catalyst but also provides insights into optimizing cathode catalysts for LOBs.     

Dispersive Liquid–Liquid Microextraction Coupled with High-Performance Liquid Chromatography for Determination of Coumarin Compounds in Radix Angelicae Dahuricae

In this paper, two methods, organic solvent dispersive liquid–liquid microextraction (OS-DLLME) and ionic liquid dispersive liquid–liquid microextraction (IL-DLLME), coupled with high-performance liquid chromatography have been critically compared and introduced for the analysis of the eight coumarin compounds (psoralen, isopsoralen, bergapten, isobergapten, oxypeucedanin, imperatorin, osthole, and isoimperatorin) in Radix Angelicae Dahuricae samples. Experimental conditions have been investigated for both OS-DLLME and IL-DLLME. Under optimal conditions, the detection limits of the eight coumarin compounds obtained by OS-DLLME and IL-DLLME ranged between 0.002–0.026 ng mL⁻¹ and 0.013–0.66 ng mL⁻¹, respectively. The relative standard deviations (RSDs, n = 9) were lower than 8.7 and 8.4% with enrichment factors in the range of 145–380 and 130–230 folds for OS-DLLME and IL-DLLME, respectively. The results showed that there were no significant deviations between the two DLLME methods for the determination of the eight coumarin compounds. Both methods were simple, fast, efficient, and inexpensive. However, compared with IL-DLLME, the OS-DLLME technique exhibited a higher extraction capacity for the eight target analytes.

     

Binding FSI− to Construct a Self-Healing SEI Film for Li-Metal Batteries by In situ Crosslinking Vinyl Ionic Liquid

The solid electrolyte interphase (SEI) membrane on the Li metal anode tends to breakdown and undergo reconstruction during operation, causing Li metal batteries to experience accelerated decay. Notably, an SEI membrane with self-healing characteristics can help considerably in stabilizing the Li-electrolyte interface; however, uniformly fixing the repairing agent onto the anode remains a challenging task. By leveraging the noteworthy film-forming attributes of bis(fluorosulfonyl)imide (FSI⁻) anions and the photopolymerization property of the vinyl group, the ionic liquid 1-vinyl-3-methylimidazolium bis(fluorosulfonyl)imide (VMI-FSI) was crosslinked with polyethylene oxide (PEO) in this study to form a self-healing film fixing FSI⁻ groups as the repairing agent. When they encounter lithium metal, the FSI⁻ groups are chemically decomposed into LiF & Li₃N, which assist forming SEI membrane on lithium sheet and repairing SEI membrane in the cracks lacerated by lithium dendrite. Furthermore, the FSI⁻ anions exchanged from film are electrochemically decomposed to generate inorganic salts to strengthen the SEI membrane. Benefiting from the self-healing behavior of the film, Li/LiCoO₂ cells with the loading of 16.3 mg cm⁻² exhibit the initial discharge capacities of 183.0 mAh ⋅ g⁻¹ and are stably operated for 500 cycles with the retention rates of 81.4 % and the average coulombic efficiency of 99.97 %, operated between 3.0–4.5 V vs. Li⁺/Li. This study presents a new design approach for self-healing Li metal anodes and durable lithium metal battery.     

An Ionic Liquid Loaded β-Cyclodextrin-Cross-Linked Polymer as the Solid Phase Extraction Material Coupled with High-Performance Liquid Chromatography for the Determination of Rhodamine B in Food

A novel method for separation and determination of rhodamine B in food samples is described. The work is based on the utilization of an ionic liquid loaded β-cyclodextrin cross-linked polymer coupled with high-performance liquid chromatography for the determination of rhodamine B. The inclusion interaction of the ionic liquid-β-cyclodextrin cross-linked polymer with rhodamine B was studied by FTIR. Under optimum conditions, the preconcentration factor achieved for this method was approximately 20. The linear range, detection limit, and relative standard deviation were 0.80 to 130.0 µg L^?1, 0.09 µg L^?1, and 0.66% (n = 3, concentration = 10.0 µg L^?1), respectively. The technique was successfully applied for determination of rhodamine B in food samples.     

New Oxyhalide Solid Electrolytes with High Lithium Ionic Conductivity >10 mS cm−1 for All-Solid-State Batteries

All-solid-state batteries (ASSBs) with inorganic solid electrolytes (SEs) have attracted significant interest as next-generation energy storage. Halides such as Li₃YCl₆ are promising candidates for SE because they combine high oxidation stability and deformability. However, the ionic conductivities of halide SEs are not as high as those of other SEs, especially sulfides. Here, we discover new lithium-metal-oxy-halide materials, LiMOCl₄ (M=Nb, Ta). They exhibit extremely high ionic conductivities of 10.4 mS cm⁻¹ for M=Nb and 12.4 mS cm⁻¹ for M=Ta, respectively, even in cold-pressed powder forms at room temperature, which are comparable to or surpass those of organic liquid electrolytes used in lithium-ion batteries. Bulk-type ASSB cells using the oxyhalides as the cathode SE demonstrate an outstanding rate capability with a capacity retention of 80 % at 5 C/0.1 C. We believe that the proposed oxyhalides are promising SE candidates for the practical applications of ASSBs.     

Pre-intercalation of Ammonium Ions in Layered δ-MnO2 Nanosheets for High-Performance Aqueous Zinc-Ion Batteries

Layered manganese dioxide is a promising cathode candidate for aqueous Zn-ion batteries. However, the narrow interlayer spacing, inferior intrinsic electronic conductivity and poor structural stability still limit its practical application. Herein, we report a two-step strategy to incorporate ammonium ions into manganese dioxide (named as AMO) nanosheets as a cathode for boosted Zn ion storage. K⁺-intercalated δ-MnO₂ nanosheets (KMO) grown on carbon cloth are chosen as the self-involved precursor. Of note, ammonium ions could replace K⁺ ions via a facile hydrothermal reaction to enlarge the lattice space and form hydrogen-bond networks. Compared with KMO, the structural stability and the ion transfer kinetics of the layered AMO are enhanced. As expected, the obtained AMO cathode exhibits remarkable electrochemical properties in terms of high reversible capacity, decent rate performance and superior cycling stability over 10000 cycles.     

Starch-Based Superabsorbent Hydrogel with High Electrolyte Retention Capability and Synergistic Interface Engineering for Long-Lifespan Flexible Zinc−Air Batteries

The advent of wearable electronics has strongly stimulated advanced research into the exploration of flexible zinc−air batteries (ZABs) with high theoretical energy density, high inherent safety, and low cost. However, the half-open battery structure and the high concentration of alkaline aqueous environment pose great challenges on the electrolyte retention capability and the zinc anode stability. Herein, a starch-based superabsorbent hydrogel polymer electrolyte (SSHPE) with high ionic conductivity, electrolyte absorption and retention capabilities, strong alkaline resistance and high zinc anode stability has been designed and applied in ZABs. Experimental and calculational analyses probe into the root of the superiority of SSHPEs, confirming the significance of the carboxyl functional groups along their polymer chains. These features endow the as-fabricated ZAB a long cycle life of 300 h, much longer than that with commonly used poly(vinyl alcohol)-based electrolyte.     

Engineering Na−Mo−O/Graphene Oxide Composites with Enhanced Electrochemical Performance for Lithium Ion Batteries

Sodium molybdate (Na−Mo−O) wrapped by graphene oxide (GO) composites have been prepared via a simple in-situ precipitation method at room temperature. The composites are mainly constructed with one dimension (1D) ultra-long sodium molybdate nanorods, which are wrapped by the flexible GO. The introduction of GO is expected to not merely provide more active sites for lithium-ions storage, but also improve the charge transfer rate of the electrode. The testing electrochemical performances corroborated the standpoint: The Na−Mo−O/GO composites delivers specific capacities of 718 mAh g⁻¹ after 100 cycles at 100 mA g⁻¹, and 570 mAh g⁻¹ after 500 cycles at a high rate of 500 mA g⁻¹; for comparison, the bare Na−Mo−O nanorod shows a severe capacity decay, which deliver only 332 mAh g⁻¹ after 100 cycles at 100 mA g⁻¹. In view of the cost-efficient and less time-consuming in synthesis, and one-step preparation without further treatment, these Na−Mo−O nanorods/GO composites present potential and prospective anodes for LIBs.     

Revealing the CO2 Conversion at Electrode/Electrolyte Interfaces in Li–CO2 Batteries via Nanoscale Visualization Methods

Lithium–carbon dioxide (Li–CO₂) battery technology presents a promising opportunity for carbon capture and energy storage. Despite tremendous efforts in Li–CO₂ batteries, the complex electrode/electrolyte/CO₂ triple-phase interfacial processes remain poorly understood, in particular at the nanoscale. Here, using in situ atomic force microscopy and laser confocal microscopy-differential interference contrast microscopy, we directly observed the CO₂ conversion processes in Li–CO₂ batteries at the nanoscale, and further revealed a laser-tuned reaction pathway based on the real-time observations. During discharge, a bi-component composite, Li₂CO₃/C, deposits as micron-sized clusters through a 3D progressive growth model, followed by a 3D decomposition pathway during the subsequent recharge. When the cell operates under laser (λ=405 nm) irradiation, densely packed Li₂CO₃/C flakes deposit rapidly during discharge. Upon the recharge, they predominantly decompose at the interfaces of the flake and electrode, detaching themselves from the electrode and causing irreversible capacity degradation. In situ Raman shows that the laser promotes the formation of poorly soluble intermediates, Li₂C₂O₄, which in turn affects growth/decomposition pathways of Li₂CO₃/C and the cell performance. Our findings provide mechanistic insights into interfacial evolution in Li–CO₂ batteries and the laser-tuned CO₂ conversion reactions, which can inspire strategies of monitoring and controlling the multistep and multiphase interfacial reactions in advanced electrochemical devices.     

Catalytic Chemistry Derived Artificial Solid Electrolyte Interphase for Stable Lithium Metal Anodes Working at 20 mA cm−2 and 20 mAh cm−2

A stable solid electrolyte interphase (SEI) layer is crucial for lithium metal anode (LMA) to survive in long-term cycling. However, chaotic structures and chemical inhomogeneity of natural SEI make LMA suffering from exasperating dendrite growth and severe electrode pulverization, which hinder the practical application of LMAs. Here, we design a catalyst-derived artificial SEI layer with an ordered polyamide-lithium hydroxide (PA-LiOH) bi-phase structure to modulate ion transport and enable dendrite-free Li deposition. The PA-LiOH layer can substantially suppress the volume changes of LMA during Li plating/stripping cycles, as well as alleviate the parasitic reactions between LMA and electrolyte. The optimized LMAs demonstrate excellent stability in Li plating/stripping cycles for over 1000 hours at an ultra-high current density of 20 mA cm⁻² in Li||Li symmetric cells. A high coulombic efficiency up to 99.2 % in Li half cells in additive-free electrolytes is achieved even after 500 cycles at a current density of 1 mA cm⁻² with a capacity of 1 mAh cm⁻².     

Characteristics of Pt Electrode Activated by Tb1 − xCexO2 − α Films in Contact with ZrO2 + 10 mol % Y2O3 Electrolyte

Porous platinum electrodes on ZrO₂ + 10 mol % Y₂O₃ solid electrolyte (YSZ) are activated by Tb_{1 ? x}Ce_xO_{2 ? α} (x = 0; 0.15; 0.33; 0.5; 1.0) mixed oxides by impregnation, and their polarization characteristics are studied. The activation is carried out under the conditions that an oxide activator nanofilm forms on the electrolyte surface as a result of heat treatment of the electrode. The activation is performed by impregnating the electrodes with low-concentrated alcohol solution of terbium and cerium nitrates (1.5% as recalculated to the oxides) and subsequent slow heating (≤50°C/h) to 850°C. An average thickness of the film on the electrolyte after a single activation (≈0.1 mg oxides/cm²) is estimated at 10–20 nm. The electrodes of Pt|YSZ|Pt cell activated by Tb_{1 ? x}Ce_xO_{2 ? α} films are studied by the impedance method in the oxidative and reductive atmospheres in the range of 700 to 500°C. The polarization conductivities of the activated electrodes increase by 2–3 orders of magnitude. The studied electrodes are discussed within the model of compact oxide electrodes, where platinum plays the role of collector. The advantage of these electrodes is that they can work both in the oxidative and reductive conditions. According to the aggregate of the properties, Tb_{1 ? x}Ce_xO_{2 ? α} compounds at x = 0.3–0.5 are recommended for activation.

     

Understanding the High-Performance Anode Material of CoC2O4⋅2 H2O Microrods Wrapped by Reduced Graphene Oxide for Lithium-Ion and Sodium-Ion Batteries

Metal oxalate has become a most promising candidate as an anode material for lithium-ion and sodium-ion batteries. However, capacity decrease owing to the volume expansion of the active material during cycling is a problem. Herein, a rod-like CoC₂O₄⋅2 H₂O/rGO hybrid is fabricated through a novel multistep solvo/hydrothermal strategy. The structural characteristics of the CoC₂O₄⋅2 H₂O microrod wrapped using rGO sheets not only inhibit the volume variation of the hybrid electrode during cycling, but also accelerate the transfer of electrons and ions in the 3 D graphene network, thereby improving the electrochemical properties of CoC₂O₄⋅2 H₂O. The CoC₂O₄⋅2 H₂O/rGO electrode delivers a specific capacity of 1011.5 mA h g⁻¹ at 0.2 A g⁻¹ after 200 cycles for lithium storage, and a high capacity of 221.1 mA h g⁻¹ at 0.2 A g⁻¹ after 100 cycles for sodium storage. Moreover, the full cell CoC₂O₄⋅2 H₂O/rGO//LiCoO₂ consisting of the CoC₂O₄⋅2 H₂O/rGO anode and LiCoO₂ cathode maintains 138.1 mA h g⁻¹ after 200 cycles at 0.2 A g⁻¹ and has superior long-cycle stability. In addition, in situ Raman spectroscopy and in situ and ex situ X-ray diffraction techniques provide a unique opportunity to understand fully the reaction mechanism of CoC₂O₄⋅2 H₂O/rGO. This work also gives a new perspective and solid research basis for the application of metal oxalate materials in high-performance lithium-ion and sodium-ion batteries.