Mechanism of Bilayer Polymer-Based Electrolyte with Functional Molecules in Enhancing the Capacity and Cycling Stability of High-Voltage Lithium Batteries.

Poly(ethylene oxide) (PEO)-based solid polymer electrolytes (SPEs) are favorable for all-solid-state lithium metal batteries (ASSLBs) to ensure safety and enhance energy density. However, their narrow work windows and unstable electrode/electrolyte interfaces hinder their practical application in high-voltage ASSLBs. Although introducing additives in SPEs has been proven to be effective to address the above issues, it could hardly optimize both cathode and anode interfaces by an individual additive. Herein, heterogeneously double-layer SPEs are constructed with two typical additives (LiPO2F2 and LiFSI), which are used to modify the LiNi0.6Co0.2Mn0.2O2 (NCM)-cathode/electrolyte interface (CEI) and lithium-anode/solid electrolyte interface (SEI), and further understand their respective mechanism in enhancing the capacity and cycling stability of ASSLBs. Specifically, LiPO2F2 not only leads to a uniform CEI layer to prevent the oxidation decomposition of PEO and LiTFSI but also ensures fast Li+ diffusion at high voltage (>3.9 V), improving the rate performances and life spans of the cells. The LiFSI contributes to a stable SEI layer with rich LiF, suppressing the growth of lithium dendrites and maximizing the specific capacity for ASSLBs. Integrating the advantages of the two functional molecules, the optimized ASSLB displays an excellent capacity of 141.4 mAh g-1 at 1C and an outstanding capacity retention of 81.6% after 400 cycles when using the NCM cathode, even reaching 154.2 mAh g-1 at 0.1 mA cm-2 with a high mass loading (6.4 mg cm-2). Additionally, the bilayer SPEs also match well with a LiFePO4 electrode with a high mass loading of 11.0 mg cm-2, displaying a high capacity of 155.7 mAh g-1 at 0.1 mA cm-2.

A Thin Composite Polymer Electrolyte Functionalized by a Novel Antihydrolysis Additive to Enable All-Solid-State Lithium Battery with Excellent Rate and Cycle Performance.

Composite solid-state electrolyte (CSE) incorporated with fluorine-containing functional additives usually endows the assembled cell with improved electrochemical performance by forming stable electrode/electrolyte interfaces. However, most of fluorine-containing additives are prone to hydrolysis, which is not suitable for the large-scale preparation of CSEs. In this work, an antihydrolysis and fluorine-containing additive of magnesium 2,3,4,5,6-pentafluorophenylacetate (MgPFPAA) is successfully synthesized and then used to regulate the properties of the electrode/electrolyte interfaces of the all-solid-state lithium batteries (ASSLBs). The antihydrolysis property of MgPFPAA facilitates the large-scale preparation of the ultrathin CSEs in atmospheric environment. Both theoretical calculations and experimental results indicate that MgPFPAA can effectively improve the composition and structure of the generated solid electrolyte interface film by providing rich F sources and Mg2+ , thus leading to a stable CSE/Li interface. Furthermore, an ultrathin PEO/PVDF-based CSE (≈30 µm) functionalized by this novel MgPFPAA additive enables the assembled LiFePO4 -based ASSLB with greatly enhanced electrochemical performances, with high discharge specific capacity of 93.7 mAh g-1 at 10 C and a high capacity retention of 74.9% after 1500 cycles at 5.0 C. Also, this MgPFPAA functionalized CSE can be compatible with the high-areal-capacity LiFePO4 and the high-voltage LiNi0.8 Co0.1 Mn0.1 O2 cathodes.

Ultrafine Co-Species Interspersed g-C3N4 Nanosheets and Graphene as an Efficient Polysulfide Barrier to Enable High Performance Li-S Batteries.

Lithium-sulfur (Li-S) batteries are regarded as one of the promising advanced energy storage systems due to their ultrahigh capacity and energy density. However, their practical applications are still hindered by the serious shuttle effect and sluggish reaction kinetics of soluble lithium polysulfides. Herein, g-C3N4 nanosheets and graphene decorated with an ultrafine Co-species nanodot heterostructure (Co@g-C3N4/G) as separator coatings were designed following a facile approach. Such an interlayer can not only enable effective polysulfide affinity through the physical barrier and chemical binding but also simultaneously have a catalytic effect on polysulfide conversion. Because of these superior merits, the Li-S cells assembled with Co@g-C3N4/G-PP separators matched with the S/KB composites (up to ~70 wt% sulfur in the final cathode) exhibit excellent rate capability and good cyclic stability. A high specific capacity of ~860 mAh g-1 at 2.0 C as well as a capacity-fading rate of only ~0.035% per cycle over 350 cycles at 0.5 C can be achieved. This bifunctional separator can even endow a Li-S cell at a low current density to exhibit excellent cycling capability, with a capacity retention rate of ~88.4% at 0.2 C over 250 cycles. Furthermore, a Li-S cell with a Co@g-C3N4/G-PP separator possesses a stable specific capacity of 785 mAh g-1 at 0.2 C after 150 cycles and a superior capacity retention rate of ~84.6% with a high sulfur loading of ~3.0 mg cm-2. This effective polysulfide-confined separator holds good promise for promoting the further development of high-energy-density Li-S batteries.

Hexachloro-1,3-butadiene as a Functional Additive for Constructing an Efficient Solid Electrolyte Interface Layer for Long-Life Stable Li Anodes.

Lithium (Li) metal is considered as one of the attractive anodes for next-generation high-energy-density batteries due to its ultrahigh theoretical specific capacity and low potential. However, many great challenges including uncontrolled dendrite growth and undesired side reactions during repeated cycling still seriously hinder its practical application in Li metal secondary batteries. Herein, we report the hexachloro-1,3-butadiene (HCBD) molecule as a functional additive to stabilize the Li anode by forming a stable solid electrolyte interface (SEI) layer with high Li ion conductivity via in situ surface and electrochemical reactions. Density functional theory calculations demonstrate that HCBD can preferentially react with the Li anode, which generates an ionic conducting species (LiCl) into an SEI layer. The LiCl-rich SEI layer effectively regulates Li+ deposition/stripping kinetics and then induces uniform nucleation of Li+ and reduces the side reactions between the Li anode and electrolyte. With an optimal amount of HCBD in an ether-based electrolyte, an excellent cycling lifespan (7000 h) was achieved with a low hysteresis voltage of ∼10 mV at 1.0 mA cm-2 in a Li||Li symmetrical cell. Furthermore, the LiFePO4-based cell with the additive-functionalized Li anode displays obviously improved cycling stability (with a high specific capacity of 141.1 mAh g-1 after 350 cycles at 1 C).

A thin and multifunctional CoS@g-C3N4/Ketjen black interlayer deposited on polypropylene separator for boosting the performance of lithium-sulfur batteries.

The sluggish redox kinetic and shuttle effect of polysulfides still obstruct the commercial application of lithium-sulfur (Li-S) batteries. Herein, a nanocomposite consisting of well-dispersed and lamellar-like shape CoS anchored on g-C3N4 nanosheets (CoS@g-C3N4) is prepared firstly, and then it is integrated on a polypropylene membrane combined with little conductive Ketjen black (KB) to fabricate a multifunctional and quite thin interlayer, with a thickness of only âˆ¼ 2.1 um and areal mass loading of âˆ¼ 0.07 mg·cm-2. The as-prepared interlayer firstly can capture polysulfides by Li-N bond as well as Lewis acid-base interaction between CoS and polysulfide anions (Sn2-), and more importantly, it also displays a positive effect on catalyzing the redox conversion of intermediate polysulfides. As expected, a Li-S cell assembled with this modified separator and high sulfur content cathode displays an excellent electrochemical performance, with specific capacity of âˆ¼ 1290 mAh g-1 at 0.2C and a low fading rate of 0.03% per cycle after 500 cycles at 1.0C. Furthermore, a high sulfur mass loading of âˆ¼ 4.0 mg·cm-2 electrode paired with this multifunctional separator exhibits a stable specific capacity of âˆ¼ 600 mAh g-1 after 250 cycles under 0.1C. This work can give some guides to rational design a quite thin and light interlayer for improving the utilization of sulfur species, with little damage to the energy density and Li ion transportation in Li-S batteries.

Cyclodextrin-Integrated PEO-Based Composite Solid Electrolytes for High-Rate and Ultrastable All-Solid-State Lithium Batteries.

Poly(ethylene oxide) (PEO)-based composite solid electrolytes (CSEs) are considered as one of the most promising candidates for all-solid-state lithium batteries (ASSLBs). However, a key challenge for their further development is to solve the main issues of low ionic conductivity and poor mechanical strength, which can lead to insufficient capacity and stability. Herein, ß-cyclodextrin (ß-CD) is first demonstrated as a multifunctional filler that can form a continuous hydrogen bond network with the ether oxygen unit from the PEO matrix, thus improving the comprehensive performances of the PEO-based CSE. By relevant characterizations, it is demonstrated that ß-CD is uniformly dispersed into the PEO substrate, inducing adequate dissociation of lithium salt and enhancing mechanical strength through hydrogen bond interactions. In a Li/Li symmetric battery, the ß-CD-integrated PEO-based (PEO-LiTFSI-15% ß-CD) CSE works well at a critical current density up to 1.0 mA cm-2 and retains stable lithium plating/stripping for more than 1000 h. Such reliable properties also enable its superior performance in LiFePO4-based ASSLBs, with specific capacities of 123.6 and 114.0 mA h g-1 as well as about 100 and 81.8% capacity retention over 300 and 700 cycles at 1 and 2 C (1 C = 170 mA g-1), respectively.

A novel battery separator coated by a europium oxide/carbon nanocomposite enhances the performance of lithium sulfur batteries.

Lithium sulfur (Li-S) batteries represent one of the most promising future power batteries due to their remarkable advantages of low cost and ultrahigh theoretical energy density. However, the commercial applications of Li-S batteries have long been plagued by the shuttling effect of polysulfides and sluggish redox kinetics of these species. Herein, we designed a novel battery separator coated by a europium oxide-doped porous Ketjen Black (Eu2O3/KB) and tested its performance for the Li-S batteries for the first time. Experimental results and theoretical calculations reveal that the improved electrochemical performance can be attributed to the presence of Eu2O3. The strong binding effect between Eu2O3 and polysulfides is demonstrated in two aspects: (1) there exist strong interactions between Eu2O3 as a Lewis acid and polysulfides of strong Lewis basicity; (2) Eu2O3 with oxygen-vacancy defects provides active sites for catalyzing polysulfide conversion and polysulfide trapping. Thus, a Li-S battery with the Eu2O3/KB modified separator delivers highly stable cycling performance and excellent rate capability, with the capacity decay ratio of merely 0.05% per cycle under 1 C rate during 500 cycles, and high specific capacity of 563 mAh g-1 at 3 C rate. This work offers a meaningful exploration of the application of rare earth oxides for the modification of the separator towards high performance Li-S batteries.

A novel mutation in xanthine dehydrogenase in a case with xanthinuria in Hunan province of China.

Xanthinuria is a rare genetic metabolic disorder, the biochemical mechanism of xanthinuria is the disturbance of purine to uric acid metabolism due to the deficiency of xanthine dehydrogenase/xanthine oxidase (XDH/XO) and aldehyde oxidase 1 (AOX1). Xanthinuria has large clinical variability and only about half of all patients have urolithiasis. In this article, we present one xanthinuria case from an unrelated family, which diagnosed by clinical, biochemical and finally confirmed by molecular genetics. One mutation in XDH gene c.2737C > T (p.R913W) and another mutation in SEPT9 gene (c.655C > T (p.R219W)) were identified. To our knowledge, this is the first time that these novel mutations reported in the xanthinuria patients.

An environmentally friendly strategy to prepare nitrogen-rich hierarchical porous carbon for high-performance supercapacitors.

A green route modulated by the addition of CaCl2 during the potassium compound-assisted synthesis is developed for the first time for the synthesis of nitrogen-rich hierarchical porous carbon (NRHPC) with high external surface area and moderate total pore volume. The NRHPCN constructed by nanosheets is capable of simultaneously achieving high gravitational and volumetric capacity for supercapacitors (SCs).

Co(II)-Catalyzed Regioselective Pyridine C-H Coupling with Diazoacetates.

A Co(II)-catalyzed pyridyl C-H bond carbenoid insertion with α-diazoacetates has been realized. This transformation features a highly regioselective C-C bond formation at the C3-position of pyridines, providing an efficient access to diverse α-aryl-α-pyridylacetates.

Biomass waste-derived nitrogen-rich hierarchical porous carbon offering superior capacitive behavior in an environmentally friendly aqueous MgSO4 electrolyte.

Nitrogen-doped porous carbons have been extensively investigated to improve the specific capacitance in aqueous electrolytes by increasing the specific surface area and nitrogen content and by optimizing the pore structure. However, research on the effect of electrolyte cations on the specific capacitance of these materials is rare, especially for neutral electrolytes. Herein, a nitrogen-rich hierarchically porous carbon (NRHPC) with a high nitrogen content of 12.3 atm% is successfully prepared by pyrolyzing a mixture of bagasse, K2CO3 and urea in a mass ratio of 2:1:4. It is found that NRHPC shows superior electrochemical performance in MgSO4 than in Li2SO4 electrolyte, with specific capacitances of 315.0, 274.4, and 188.1 F g-1 at 1.0, 10.0, and 100 A g-1, respectively. Furthermore, it is found that the capacitance enhancement is closely related to the nitrogen content of the porous carbon materials. Theoretical calculation reveals that the Mg2+ ions have higher affinity towards the N atoms than Li+, producing higher charge storage capability via interaction between the Mg2+ and N atoms. When the 1.0 M MgSO4 is used as electrolyte, a symmetric capacitor based on the nitrogen-rich hierarchically porous carbon shows a high energy density of 39.5 Wh kg-1 at a power density of 0.9 kW kg-1. Moreover, this as-assembled device displays superior long-term cycling stability, with a capacitance retention of >96.2% after 10,000 cycles at 10.0 A g-1.

Porous Anatase-TiO2(B) Dual-Phase Nanorods Prepared from in Situ Pyrolysis of a Single Molecule Precursor Offer High Performance Lithium-Ion Storage.

To overcome the problems faced by TiO2 materials for lithium-ion batteries usage, such as easy nanoparticles agglomeration during cycling and poor cycling performance, in this study, TiO2 nanorods with the controlled phase compositions are prepared via direct pyrolysis of single molecule precursors in combination with a simple washing process. By tuning the external cations in the single source precursors, three TiO2 samples in a nanorod shape with the compositions of pure anatase, anatase-rutile dual phase, and anatase-TiO2(B) dual phase are synthesized successfully. High-resolution transmission electron microscopy, X-ray powder diffraction, and Raman measurements confirm the phase structures and compositions of the three prepared samples. The electrochemical results manifest that all the three nanorod-shaped TiO2 samples show the long-term cycling stability as negative materials for LIBs. Among them, the TiO2 sample with the combination of the anatase and TiO2-B phase shows the best performance, with the specific capacity of ∼184, 164, 140, 105, 80, and 60 mAh g-1 at 0.1, 0.3, 0.5, 1.5, 3.0, and 5.0 A g-1, respectively, and showing no capacity loss and low resistance after 1000 cycles at 1.5 A g-1. By the analysis of the cyclic voltammetry results recorded from different scan rates, the lithium-ion storage mechanism is clarified, which is dominated by the semi-infinite linear diffusion (anatase phase) in combination with the partial surface pseudocapacitive contribution [TiO2(B) phase]. As a result, this sample shows a great potential as a negative material for LIBs because of its electrochemical stability, high specific capacity, and superior rate capability. The proof-of-concept design of the anatase and TiO2-B dual phase may provide a new strategy for the synthesis of high performance TiO2-based anode material for LIBs.

Zn(OAc)2-Catalyzed C3-Carbonylacetylation of Indoles with α-Diazoketones Involving Wolff Rearrangement.

Zn(OAc)2-catalyzed highly regioselective carbonylacetylation of indoles and pyrroles with α-diazoketones has been developed. This transformation involves a combination of Wolff rearrangement/cross-coupling relay and provides an efficient approach to versatile 3-carbonylacetylindoles and 2-carbonylacetylpyrroles with a broad range of functional group tolerance.

Carbon-Encapsulated Sn@N-Doped Carbon Nanotubes as Anode Materials for Application in SIBs.

Carbon-encapsulated Sn@N-doped carbon tubes with submicron diameters were obtained via the simple reduction of C@SnO2@N-doped carbon composites that were fabricated by a hydrothermal approach. Sn nanoparticles encapsulated in carbon layers were distributed uniformly on the surfaces of the N-doped carbon nanotubes. The electrochemical performances of the composites were systematically investigated as anode materials in sodium-ion batteries (SIBs). The composite electrode could attain a good reversible capacity of 398.4 mAh g-1 when discharging at 100 mA g-1, with capacity retention of 67.3% and very high Coulombic efficiency of 99.7% over 150 cycles. This good cycling performance, when compared to only 17.5 mAh g-1 delivered by bare Sn particles prepared via the same method without the presence of N-doped carbon, could be mainly ascribed to the uniform distribution of the precursor SnO2 on the substrate of N-doped carbon tubes with three-dimensional structure, which provides more reaction sites to reduce the diffusion distance of Na+, further facilitating Na+-ion diffusion and relieves the huge volume expansion during charging/discharging. These outcomes imply that such a Sn/C composite would provide more options as an anode candidate for SIBs.

Resilient Energy Storage under High-Temperature with In-Situ-Synthesized MnOx@Graphene as Anode.

An novel exfoliation strategy to few-layered graphene (FLG) combined with in situ synthesized amorphous MnOx has been established via a facile and robust ball milling route in the presence of KMnO4. The facile synthesis approach has the features of low cost, environmentally friendly nature and scalable capability. As an anode for lithium-ion batteries, amorphous MnOx@FLG delivered a wonderful electrochemical performance under extremely operational conditions, that is, an excellent reversible capacity of 856 mAh g-1 at a high current density of 1 A g-1 after 75 cycles under a high temperature of 85 °C. Those excellent electrochemical performances could be ascribed to elaborately designed three-dimensional nanostructure, the well-chosen electrolyte, significant incorporation of in situ Mn(IV) nanocrystal and few-layered graphene, and the contribution of pseudocapacitance. Remarkable electrochemical performance under a widely operational temperature window makes the amorphous MnOx@FLG composites promising anode of Li-ion batteries for heavy-duty application.

Co(II)-Catalyzed Regioselective Cross-Dehydrogenative Coupling of Aryl C-H Bonds with Carboxylic Acids.

A cobalt(II)-catalyzed regioselective aryl C-H bond oxygenation between arenes and aryl or aliphatic carboxylic acids under bidendate-chelation assistance is developed. This method provides an efficient approach to acyoxy-substituted arenes with a broad range of functional group tolerance. Furthermore, this reaction system could be further applied to the preparation of polyfunctional naphthylenes.

An Unprecedented Case: A Low Specific Surface Area Anatase/N-Doped Carbon Nanocomposite Derived from a New Single Source Precursor Affords Fast and Stable Lithium Storage.

A nanocomposite of ultrafine anatase nanoparticles (<5 nm) embedded N-doped carbon (TiO2-NPs/NC) with a relatively low specific surface area was successfully synthesized by in situ pyrolysis of a new and cheap single source precursor of (H2en)3[Ti4(O2)4(Hcit)2(cit)2]·12H2O (en = ethylenediamine and H4cit = citric acid) under 550 °C and an inert atmosphere. The precursor in crystalline state was isolated from an aqueous solution containing of titanium butoxide, citric acid, hydrogen peroxide, and ethylenediamine and was characterized. The crystal structure was determined by X-ray single crystal diffraction. To our surprise, the low surface area TiO2-NPs/NC exhibits a high specific capacity, superior rate capability, excellent cycle performance, and good processability as a negative material for rechargeable lithium-ion batteries (LIBs). A large reversible capacity of 360 and 125 mA h g-1 and a high Coulombic efficiency (the average value is ∼99.8%) could be kept even after 1000 cycles under a current density of 0.3 and 6 A g-1, respectively. An analysis of the voltammetric sweep data shows that the pseudocapacitive behavior occurred at the surface of the material and the lithium intercalation processes contribute to the total stored charge, resulting in the high capacity of the TiO2-NPs/NC nanocomposite. The potentiostatic intermittent titration technique used to determine the lithium ion diffusion (DLi+) suggested the TiO2-NPs/NC nanocomposite displays a high DLi+. In addition, the high electric conductivity provided by the NC substrate and the ultrafine anatase particles can mitigate the diffusion path for electrons and ions and tolerate higher strain, and thus effectively decrease pulverization and improve the rate and cycle performance. In particular, the observed superior lithium storage properties, resulting from the low surface area nanocomposite with ultrafine nanoparticles embedded NC substrate, are expected to have fundamental and practical implications for the preparation of high performance electrodes in LIBs or other cells.

Rh(III)-Catalyzed Carboamination of Propargyl Cycloalkanols with Arylamines via Csp2-H/Csp3-Csp3 Activation.

A Rh(III)-catalyzed carboamination of alkynyl cycloalkanols with arylamines has been developed. This transformation involves a novel Csp2-H/Csp3-Csp3 activation relay and provides an efficient approach to versatile 1,2,3-trisubstituted indoles with a broad range of functional group tolerance.

An Ir(iii)-catalyzed aryl C-H bond carbenoid functionalization cascade: access to 1,3-dihydroindol-2-ones.

An Ir(iii)-catalyzed relay aryl C-H bond carbenoid insertion cascade of N-aryl-2-pyridinamines with diazo Meldrum's acid has been developed. This method provides an efficient approach to multifunctionalized 1,3-dihydroindol-2-ones with a broad range of functional group tolerance. Furthermore, this protocol could be applied for the concise synthesis of bioactive hematopoietic growth factor analogues.

A [4 + 1] Cyclative Capture Access to Indolizines via Cobalt(III)-Catalyzed Csp(2)-H Bond Functionalization.

A Co(III)-catalyzed [4 + 1] cycloaddition of 2-arylpyridines or 2-alkenylpyridines with aldehydes through Csp(2)-H bond activation has been developed. This protocol provides a facile approach to structurally diverse indolizines including benzoindolizines with a broad range of functional group tolerance.