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Lithium-sulfur batteries have great potential for next-generation electrochemical storage systems owing to their high theoretical specific energy and cost-effectiveness. However, the shuttle effect of soluble polysulfides and sluggish multi-electron sulfur redox reactions has severely impeded the implementation of lithium-sulfur batteries. Herein, we prepared a new type of Ti

Solid-state electrolytes attract great attention due to their advantages in safety, electrochemical stability and battery packaging. High-voltage cathode materials and the Li metal anode further increase the energy density and electrochemical cycling properties.

The S-LHCE strategy with the decoupling of ion pairing and ion conduction is proposed via a freeze-drying method, which realizes the recycling of solvents used and enables solid-state lithium-metal batteries with excellent electrochemical performance.

A unique integrated cathode of Co/CeO2–NCNA@CC, which displays high power density and superior cycling stability has been constructed for Zn–air battery applications.

Novel pyrazolyazoindole photoswitches with high to near-complete photoconversion, adjustable thermal half-lives, photochromic properties, and potential application value are developed.

Pairing different cations (R+) to stabilize cyclo-N5− is the main synthesis path for non-metallic cyclo-pentazolate (cyclo-N5−) salts.

Two trivalent metal pentazolate salts, namely, Fe(H2O)6(N5)3·9H2O (1) and Al(H2O)6(N5)3·9H2O (2) are prepared, and the coordination environment of the cyclo-N5− anions is discussed in detail.

The all-nitrogen cyclo-pentazolate (c-N5–) anion has attracted considerable attention because of its potential applications in high-energy density materials. However, achieving comprehensive insigh...

Large-scale implementation of all-solid-state lithium batteries is impeded by the physical limitations of the interface between the electrode and solid electrolyte; specifically, high resistance and poor stability, as well as poor compatibility with Li+ migration. We report double ionic-electronic transfer interface layers grown at electrode-electrolyte interfaces by in situ polymerization of 2,2'-bithiophene in polyethylene oxide (PEO) electrolyte. For all-solid-state LiFePO4 ∥PT-PEO-PT∥Li cells, the formation of a conductive polythiophene (PT) layer at the cathode-electrolyte interface resulted in an at least sevenfold decrease in interface resistance, and realized a capacity retention of about 94 % after 1000 cycles along with a lower polarization voltage under a rate of 2 C. The mixed ionic-electronic conductive layers imparted superior interface stability and contact while keeping good compatibility with the Li anode.

In this work, three novel nonmetallic pentazole salts (6–8) based on furazan or 4-nitropyrazole were synthesized. Some coplanar groups were introduced into the compounds to improve the planarity of...

Full-nitrogen energetic materials have excellent performance in the quest for higher-energy and greener explosive materials. Herein, the structure, properties under electric field, transition state, and unimolecular decomposition of octaazapentalene (o-N8), azidopentazole (a-N8), and bispentazole (N10) are studied in detail using density functional theory methods. The results show that three molecules are aromatic and each N atom is in the molecular plane. Applied electric field will change the bond length, atomic charge, and rate constant of thermal decomposition. The two pentazole rings of N10 immediately change from being in a plane (180°) to being perpendicular to each other (90.64°–91.81°) when the absolute value of the electric field intensity is greater than 40 × 10–4 a.u. The stability order of the three molecules is o-N8 > a-N8 > N10 judged by the activation energy of the initial decompostion. In addition to decompose to N2 in the azole ring, o-N8 was found to have a new pathway to eliminate N2 in the azide group. Moreover, ab initio molecular dynamics simulations were performed to further reveal the effect of different temperatures on the cleavage of single molecules.

Metal–nitrogen codoped cathode catalysts, such as M–N–C (M = Fe, Co, Mn, etc.) are considered most promising non-platinum group ORR catalysts, and have received widespread attention. However, the problem involving the high oxygen reduction performance and stability of the catalyst remains to be solved. The unique olefin oxidation polymerization and π–π stacking effect induced hemin to be evenly coated on polypyrrole nanotubes (PPy). Subsequent carbonization produces the Fe–NCNT catalyst with a monodispersed, uniform diameter and large inner cavity. The PPy not only serves as a template for the formation of the hemin polymer, but also provides C, N source to further improve the catalytic activity. The material exhibits excellent ORR activity attributed to the promotion of the π–π stacking effect between hemin and PPy, and the abundant active site of Fe–NX derived from hemin. Results show that the Fe–NCNT-800 catalyst with high performance exhibits a maximum onset potential (Eonset = 0.93 V) and half-wave potential (E1/2 = 0.79 V). The RRDE measures points out the complete four-electron transfer pathway of the Fe–NCNT-800 catalyst. The Fe–NCNT catalysts have higher durability of a negligible negative shift (10 mV) of E1/2 after a 5000 cycle ADT, and a remarkable methanol tolerance capability that is superior to that of the Pt/C catalyst. The synergy between the PPy-derived N-doped carbon nanotubes and Fe–NX facilitates oxygen reduction and electron conduction.

Both nitrogen-doping feature and pore structure are critical factors for developing nitrogen-doped carbons based catalysts with a high performance toward oxygen reduction reaction (ORR). Herein, a simple one-step CVD of acetylene and acetonitrile vapor method using silanized SBA-15 as a template has been developed to synthesize an ordered porous carbon (OPC) with dual nitrogen-doped interfaces. The optimized sample as prepared with the CVD of 4 h at 750 °C contains two types of ordered mesopores that one type is the ordered cylindrical pores inheriting from the pores of SBA-15 and has a pore width of 4.0∼5.0 nm, the other type is the ordered quasi-hexagonal pores with a width of 3.0∼4.0 nm produced by etching the pore walls of SBA-15. These two types of pores whose pore walls are built by the nitrogen doped carbon layers resulted by the CVD and thus it actually makes the dual nitrogen-doped interfaced OPC (DN-OPC). Meanwhile, DN-OPC contains a few of micropores and a large SSA of 1430 m2/g. This dual-ordered pores and dual nitrogen-doped interfaces cannot only facilitate mass transport but also utilize the active sites of DN-OPC for ORR. Therefore, as metal-free ORR catalyst, DN-OPC exhibits a good activity close to commercial Pt/C catalyst, and an excellent durability and methanol tolerance.

Pentazolate (cyclo-N5–) salts are actively pursued energetic nitrogen-rich compounds due to their potential as propellants and explosives. An in-depth understanding of the stabilizing forces betwee...

Pairing different cations (R

In hydrogen fuel cells, the sluggish oxygen reduction reaction (ORR) requires the catalysts used. Unfortunately, the precious platinum based catalysts still exhibit the best ORR activity in the commercial hydrogen fuel cells. Therefore, developing non-precious metal catalysts ORR become an important aspect for the utilization of hydrogen energy by using hydrogen fuel cells to develop non-precious catalysts and understand their active sites of ORR, herein the cobalt and nitrogen co-doped CNTs, nitrogen-doped CNTs and cobalt doped CNTs were prepared, respectively, and their catalytic properties toward ORR were tested and compared. The surface composition, microstructure and ORR performance of the samples were examined by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), pore/specific surface analyzer and electrochemical methods. The results demonstrate that as the catalyst, the cobalt and nitrogen co-doped CNTs owns the highest ORR limiting current density, the most positive ORR onset potential and the largest transfer electron number close to four, and thus exhibits the better ORR catalytic performance compared to the other two samples of the nitrogen-doped CNTs and the cobalt doped CNTs. The good ORR performance of cobalt and nitrogen co-doped CNTs can be attributed to its active sites of nitrogen containing functional groups, cobalt or cobalt oxides, Co-Nx structure, and the synergistic effect of these sites on ORR.

A breakthrough in polynitrogen chemistry was recently achieved by our bulk synthesis of (N5)6(H3O)3(NH4)4Cl in which the cyclo-pentazolate anions were stabilized extensively by hydrogen bridges with the NH4+ and OH3+ cations. Significant efforts have been carried out to replace these nonenergetic cations and the Cl– anion by more energetic cations. In this paper, the metathetical syntheses of cyclo-pentazolate salts containing the simple nitrogen-rich cations NH4+, NH3OH+, N2H5+, C(NH2)3+, and N(CH3)4+ are reported. These salts were characterized by their crystal structures; vibrational, mass, and multinuclear NMR spectra; thermal stability measurements; sensitivity data; and performance calculations. It is shown that the cyclo-pentazolates are more energetic than the corresponding azides but are thermally less stable decomposing in the range of 80 °C to 105 °C. As explosives, the hydrazinium and hydroxyl ammonium salts are predicted to match the detonation pressure of RDX but exhibit significantly higher...

Lithium (Li) is the lightest and most electronegative metallic element and has been considered the ultimate anode choice for energy storage systems with high energy density. However, uncontrollable dendrite formation caused by high ion transfer resistance and low Li atom diffusion, and dendrite growth with large volume expansion and high electronegative activity, result in severe safety concerns and poor coulombic efficiency. In this review, the latest progress is presented from the viewpoint of dendrite evolution (from dendrite formation to growth) as the main line to understand the factors that influence the deposition chemistry. For the dendrite formation, specific attention is focused on the four distinct but interdependent factors: (a) how the dielectric constant, donor number, viscosity and salt concentration affect the movement of solvated Li+ in nonaqueous electrolyte. (b) The effect of non-polar solvents and anions with polar groups or high concentration on the Li+ desolvation step. (c) The effect of the formation of solid electrolyte interphase (SEI), along with its specific adsorption and solvated structure, and its physical structure, chemical composition and growth thickness on Li+ diffusion. (d) The effect of the diffusion coefficient of the host material on Li atom migration. After dendrite formation, the attention is focused on two detrimental factors together with dendrite growth: (e) low coulombic efficiency; (f) large volume expansion. Correspondingly, the emphasis is placed on reducing the side reactions and minimizing the volume expansion. Conclusions and perspectives on the current limitations and future research directions are recommended. It is anticipated that the dynamic dendrite evolution can provide fresh insight into similar electrochemical reaction processes of other anode chemistries in nonaqueous electrolytes, ranging from a conversion-reaction metal anode (Li, Na, Al) and an alloying anode (LiAlx, NaAlx) to an intercalation-based anode (graphite, TiS2), as well as aqueous, ionic liquid and flow redox battery systems.

The all-nitrogen cyclo-pentazolate (c-N5ˉ) anion has attracted interest because of its promising application in high-energy materials. Now, nonmetallic pentazolate salts were prepared by assembling cyclo-N5ˉ and cations but it was shown to be challenging to balance excellent detonation performance and good stability, which results in restrictions for practical applications. However, we find the layer-by-layer crystal stacking structure can enhance the sensitivity of pentazolate salts. Herein, we designed and synthesized two targeted cyclo-pentazolate salts with layered stacking mode in their crystal structures based on two isomeric cations: 3,4,5-triamino-1,2,4-triazolium and 3-hydrazino-4-amino-1,2,4-triazolium. The results demonstrate that the aromaticity of triazole and pentazole rings arouse the π−π interaction force, promoting the formation of a layer-by-layer crystal stacking structure. Two compounds show very low sensitivity characteristics (FS>40 and IS>360) and good detonation properties (detonation velocity: 3, Dv= 8796m⋅s−1; 4, Dv=8574m⋅s−1. detonation pressure: 3, P = 26.6 GPa; 4, P = 25.1 GPa). Computational analysis based on noncovalent interaction index, localized orbital locator-π and electron density difference provide a better understanding about the effects of layer-by-layer stacking structure on the stabilities. These findings contribute to preparation of both high-energy and low sensitivity pentazolate salts.

In the area of polynitrogen anions, the only stable species synthesized as yet are the azide anion (N3−) and the pentazolate anion (cyclo-N5−). We here describe an unprecedented example of a spontaneous single-crystal to single-crystal transformation from the pentazolate salt [NH4]4[H3O]3(N5)6Cl to the known [NH4]N3 with concomitant release of N2 and H2O, which involves the cleavage of N–N bonds and a change in space group. This transformation is helpful for the understanding of the relationship between the long-known N3− and the recently synthesized cyclo-N5− polynitrogen anions.

The pentazolate anion, as a polynitrogen species, holds great promise as a high-energy density material for explosive or propulsion applications. Designing pentazole complexes that contain minimal non-energetic components is desirable in order to increase the material’s energy density. Here, we report a solvent-free pentazolate complex, AgN5, and a 3D energetic-framework, [Ag(NH3)2]+[Ag3(N5)4]ˉ, constructed from silver and cyclo-N5ˉ. The complexes are stable up to 90 °C and only Ag and N2 are observed as the final decomposition products. Efforts to isolate pure AgN5 were unsuccessful due to partial photolytical and/or thermal-decomposition to AgN3. Convincing evidence for the formation of AgN5 as the original reaction product is presented. The isolation of a cyclo-N5ˉ complex, devoid of stabilizing molecules and ions, such as H2O, H3O+, and NH4+, constitutes a major advance in pentazole chemistry.

Both SiC and porous carbons have been widely used in the fields of catalysts, ceramics, electrode materials and electromagnetic materials since their advantages of excellent chemical and thermal stability, good conductivity, flexibility and stiffness. However, pore construction of SiC still faces considerable difficulty comparing to carbon materials with a large variety of pores. Herein, by developing a novel method combining the silanization of SBA-15 template, acetylene CVD and magnesiothermic reduction reaction (MRR) technology, a novel porous material of OM-SiC@OMC that the ordered mesoporous SiC interfaces with the ordered mesoporous carbon has been successful synthesized. The silanization enhances the activity of carbon deposition into the pores of SBA-15 template, MRR results in the formation of SiC between the interface of SiO2 and carbon. After the template removal, a novel mesoporous composite material of OM-SiC@OMC has been successfully obtained. Interestingly, OM-SiC@OMC contains two types of ordered mesopores interfacing with each other by the pore wall of SiC phase and carbon phase, respectively. As electrode materials of supercapacitors, OM-SiC@OMC exhibits a capacitance of 194.8 F g−1 with an excellent retention rate of 97.8% after 10,000 cycles. The present study explores a novel ordered porous materials constructed by the interfaced pores of carbon and carbide, it is promising to find good applications of these multi-interfaced porous materials.

Silicon anode is considered as one of the candidates for graphite replacement due to its highest known theoretical capacity and abundant reserve on earth. However, poor cycling stability resulted from the “volume effect” in the continuous charge-discharge processes become the biggest barrier limiting silicon anodes development. To avoid the resultant damage to the silicon structure, some achievements have been made through constructing the structured space and pore design, and the cycling stability of the silicon anode has been improved. Here, progresses on designing nanostructured materials, constructing buffered spaces, and modifying surfaces/interfaces are mainly discussed and commented from spatial structure and pore generation for volumetric stress alleviation, ions transport, and electrons transfer improvement to screen out the most effective optimization strategies for development of silicon based anode materials with good property.

Rechargeable batteries are considered promising replacements for environmentally hazardous fossil fuel-based energy technologies. High-energy lithium-metal batteries have received tremendous attention for use in portable electronic devices and electric vehicles. However, the low Coulombic efficiency, short life cycle, huge volume expansion, uncontrolled dendrite growth, and endless interfacial reactions of the metallic lithium anode are major obstacles in their commercialization. Extensive research efforts have been devoted to address these issues and significant progress has been made by tuning electrolyte chemistry, designing electrode frameworks, discovering nanotechnology-based solutions, etc. This Review aims to provide a conceptual understanding of the current issues involved in using a lithium metal anode and to unveil its electrochemistry. The most recent advancements in lithium metal battery technology are outlined and suggestions for future research to develop a safe and stable lithium anode are presented.

A breakthrough in polynitrogen chemistry was recently achieved by our bulk synthesis of (N

The development of low-cost, highly efficient and stable non-precious metal electrocatalyst for the oxygen reduction reaction (ORR) substituting Pt has attracted much attention. Herein, we developed a promising structural platform for the fabrication of carbon nanospheres functionalized with hollow nanostructures of M-NHCS (M = Fe, Co and Mn) based on metallo-deuteroporphyrins (MDP). Benefited from the multi-layered active sites and hollow substrate with more exposed active surface area, convenient channels for the transport of electrons, the resulting Fe-NHCS electrocatalysts exhibit enhanced electrocatalytic performance in ORR with an onset potential of 0.90 V (versus RHE), and a high selectivity in the direct 4-electron pathway. The Fe-NHCS electrocatalysts also show a good methanol tolerance superior to Pt/C catalysts and an extremely high stability with only 13.0 mV negative after 5000 cycles in alkaline media. Experiments have verified that maintaining the multi-layered Fe−N−C active sites and hollow substrate were essential to deliver the high performance for ORR. The work opens new avenues for utilizing MDP-based materials in future energy conversion applications.

Developing silicon based anode of lithium-ion battery (LIB) is seriously blocked by the huge volume change of lithiation and delithiation and the corresponded high cost paying to solve it, although Si with the theoretical capacity of 4200 mAh g−1 for Li+ storage. In this study, natural diatomite with low cost was using as precursor and self-template to produce Si and construct porous structure, a coral-like porous Si/C (CLP-Si/C) material has been successfully synthesized through the NaCl added magnesiothermic reduction reaction (MRR) technology and acetylene CVD method. The hierarchical structure of macro-/mesopores in CLP-Si/C are inherited from diatomite itself and produced by removing the unreacted SiO2 in diatomite and the byproduct of MgO of MRR. Acetylene CVD further constructs a shell-core structure of carbon layers and Si particles. The hierarchical pores and core-shell structure make CLP-Si/C exhibit a stable cycling performance as LIB anode that the capacity of 990.6 mAh g−1 can be kept after 100 cycles at a rate of 250 mA g−1. This work provides a simple, low-cost and scalable strategy for producing porous Si/C anode materials with high-performance by using diatomite as both precursor and template, and is promising in the development of practical application of Si based anode materials of lithium-ion battery.

A series of mono-, di- and tri-substituted arylpentazoles were obtained via different synthetic routes. The effects of the number and position of the substituents on the arylpentazoles stability have been investigated at different temperatures. Investigators used electrospray ionization tandem mass spectrometry to infer the decomposition pathway of arylpentazoles. The article examines the relationship between the arylpentazole stability and the relative intensity of the generated pentazolate anion.

The reactions of (N5)6(H3O)3(NH4)4Cl with Co(NO3)2⋅6 H2O at room temperature yielded Co(N5)2(H2O)4⋅4 H2O as an air-stable orange metal complex. The structure, as determined by single-crystal X-ray diffraction, has two planar cyclo-N5− rings and four bound water molecules symmetrically positioned around the central metal ion. Thermal analysis demonstrated the explosive properties of the material.

A salty route to an all-nitrogen ring The flip side of the robust stability of N 2 is the instability of any larger molecules composed exclusively of nitrogen. These molecules nonetheless remain enticing targets for explosive and propellant applications. Zhang et al. successfully prepared the pentazolate ion, a negatively charged ring of five nitrogens, by oxidative cleavage of a C–N bond in an aryl-substituted precursor (see the Perspective by Christe). The molecule was stabilized and isolated in the solid state as a hydrated ammonium chloride salt. Spectroscopic and crystallographic characterization confirmed the ring's planar geometry. Science , this issue p. 374 ; see also p. 351

Solid polymer electrolytes (SPEs) are being intensively pursued as a means to develop safe, stable and long-life Li-ion batteries. However, the low Li+ conductivity and transference number in SPEs still impede all-solid-state polymer batteries from practical commercialization. Here, lithium polysulfides that cause a shuttle effect problem in Li–S batteries are reduced on a Poly(ethylene oxide) (PEO) chain as an effective way to stimulate Li+ transport. It is shown that the product of the reduction (main –S4Li) dramatically increases Li+ transport while forming a strong interaction with the PEO matrix through intermolecular interactions. In contrast to PEO electrolytes, the –S4Li grafted electrolyte membranes have a lithium transfer number almost 3 times higher, and the LiFePO4|ScPEO|Li cell shows an ultra-long cycle life exceeding 1200 cycles with a capacity decay of 0.024% per cycle at 1 C. The results reveal lithium polysulfides tremendous potential in a solid-state electrolyte system for improving the ion transport and cycling stability.