High-energy Materials Research Articles

Pb(II)-MOFs assembled with tetrazole-based carboxylic acids as a burn rate modifier

Three tetrazole-based carboxylic acids, 3,3-di(1H-tetrazol-5-yl)pentanedioic acid (H4L1), 2-(5-pyridin-4-yl-tetrazol-2-yl)propionic anion (HL2), and 5-(2-pyridyl)tetrazole-2-acetic acid (HL3), were selected as ligands to synthesize three new Pb(II)-coordination polymers, [Pb2(L1)] · H2O (1), [Pb(L2)(NO3 −)] (2), and [Pb(L3)2(H2O)] · H2O (3). These metal-organic frameworks have been characterized by elemental analysis, FT-IR, and single crystal X-ray diffraction. The results demonstrated that 1 displayed a 3-D network, while 2 and 3 show 2-D framework and 1-D chain, respectively. The differential scanning calorimetry and thermogravimetric analyses gave thermodynamic parameters (ΔH, ΔS, and ΔG). The results showed that 1–3 may be promising high-energy materials.

Conformational Effect of Catechol-Terephthalonitrile Emitters Leading to Ambient Violet Phosphorescence.

Organic ambient violet phosphorescent (AVP) materials are of great interest due to their involvement of high energy and longer-lived triplet excitons. Here, we show three fused ring functionalized donor-acceptor-donor (D-A-D/D-A-D') emitters (BPT1-BPT3), in which two catechol-based donors (3,4-dihydroxybenzophenone, catechol, or 3,5-ditert-butylcatechol) are covalently fused to the terephthalonitrile acceptor via four O-C single bonds. Spectroscopic analysis revealed that all the molecules show AVP (∼390-394 nm, τAVP = 73-101 μs) with phosphorescence quantum yields (ϕP) of 1.8-27.4% due to low singlet-triplet gaps (0.036-0.046 eV) and conformational effects. BPT3 with bulky tert-butyl groups increases AVP (ϕP = 27.4%). Quantum chemistry calculations reveal flat (F1) and twisted (F2) conformers (ground state) with a low energy difference (∼4-5 kcal/mol) for all molecules; the F1 conformer is responsible for efficient AVP, while weak blue thermally activated delayed fluorescence with longer-lived delayed components is realized from the F2 conformer. This approach may provide important clues for the design of high-energy organic phosphorescent materials.

Co-Valorisation Energy Potential of Wastewater Treatment Sludge and Agroforestry Waste

The growing demand for sustainable and environment-friendly energy sources resulted in extensive research in the field of renewable energy. Biomass, derived from organic materials such as agricultural waste, forestry products, and wastewater treatment plant (WWTP) sludge, holds great potential as a renewable energy resource that can reduce greenhouse gas emissions and offer sustainable solutions for energy production. This study focused on diverse biomass materials, including sludge from WWTPs, forest biomass, swine waste, cork powder, and biochar. Chemical and physicochemical characterizations were performed to understand their energy potential, highlighting their elemental composition, proximate analysis, and calorific values. Results showed that different biomasses have varying energy content, with biochar and cork powder emerging as high-energy materials with net heating values of 32.56 MJ/kg and 25.73 MJ/kg, respectively. WWTP sludge also demonstrated considerable potential with net heating values of around 14.87 MJ/kg to 17.44 MJ/kg. The relationships between biomass compositions and their heating values were explored, indicating the significance of low nitrogen and sulphur content and favourable carbon, hydrogen, and moisture balances for energy production. Additionally, this study looked into the possibility of mixing different biomasses to optimize their use and overcome limitations like high ash and moisture contents. Mixtures, such as “75% Santo Emilião WWTP Sludge + 25% Biochar,” showed impressive net heating values of approximately 21.032 MJ/kg and demonstrated reduced emissions during combustion. The study’s findings contribute to renewable energy research, offering insights into efficient and sustainable energy production processes and emphasizing the environmental benefits of biomass energy sources with low nitrogen and sulphur content.

Enhancing the Stability of 4.6 V LiCoO2 Cathode Material via Gradient Doping.

LiCoO2 (LCO) can deliver ultrahigh discharge capacities as a cathode material for Li-ion batteries when the charging voltage reaches 4.6 V. However, establishing a stable LCO cathode at a high cut-off voltage is a challenge in terms of bulk and surface structural transformation. O2 release, irreversible structural transformation, and interfacial side reactions cause LCO to experience severe capacity degradation and safety problems. To solve these issues, a strategy of gradient Ta doping is proposed to stabilize LCO against structural degradation. Additionally, Ta1-LCO that was tuned with 1.0 mol% Ta doping demonstrated outstanding cycling stability and rate performance. This effect was explained by the strong Ta-O bonds maintaining the lattice oxygen and the increased interlayer spacing enhancing Li+ conductivity. This work offers a practical method for high-energy Li-ion battery cathode material stabilization through the gradient doping of high-valence elements.

High Li-ion diffusion coefficient in LiMn1.5Ni0.5O4 thin films for all-solid Li-ion battery applications

Among various choices of high-performance cathode materials, Ni substituted LiMn2O4 spinel LiMn1.5Ni0.5O4 (LMNO) has proved to be one of the solutions to yield a high-performance and high-energy density material, which can operate at a higher potential window. This study explores the high diffusion coefficient and electrochemical performance at wide current rates of LMNO thin films with less than 50 nm thickness, fabricated on SrTiO3 and SS substrates by the pulsed laser deposition method. The LMNO film with less thickness and the performance without binder and conducting carbon widen the Li-ion path and decrease diffusion length, resulting a higher diffusion coefficient on the order of 10−5 to 10−6 cm2/s, which is several orders higher than the previously obtained reports for bulk counterpart. The cycling stability and rate capability at different current densities of LMNO thin film electrodes are further investigated. Charge–discharge profile at varying current rates of 5, 10, 15, 20, 25, 50, 75, 100, and 125 mA/cm2 is obtained for 500 cycles. The as fabricated film shows a stable profile for 500 cycles with 1.3 and 2.3 μA h/cm2 areal discharge capacity at 25 and 5 mA current rates, respectively. Electrode interfacial properties of LMNO film (before and after cycles) are analyzed using impedance technique. This study indicates that the LMNO thin films can be employed as a cathode layer for fabricating the all-solid thin film batteries for energy applications.

Prolonging the Cycle Stability of Anion Redox P3-Type Na0.6Li0.2Mn0.8O2 through Al2O3 Atomic Layer Deposition Surface Modification.

Sodium-ion batteries (SIBs) are becoming an alternative option for large-scale energy storage systems owing to their low cost and abundance. The lattice oxygen redox (LOR), which has the potential to increase the reversible capacity of materials, has promoted the development of high-energy cathode materials in SIBs. However, the utilization of oxygen anion redox reactions usually results in harmful lattice oxygen release, which hastens structural deformation and declines electrochemical performance, severely hindering their practical application. Herein, a ribbon-ordered superstructured P3-type Na0.6Li0.2Mn0.8O2 (NLMO) cathode with a uniform Al2O3 coating through atomic layer deposition (ALD) was synthesized. The cycling stability and rate capability of the materials were improved by a proper thickness of the Al2O3 layer. Differential electrochemical mass spectrometry (DEMS) results clearly suggest that the Al2O3 coating can inhibit the CO2 release caused by the highly active surface of the NLMO material. Moreover, the results of transmission electron microscopy (TEM) and etching X-ray photoelectron spectroscopy (XPS) show that the Al2O3 coating can effectively prevent electrolyte and electrode side reactions and the dissolution of Mn. This surface engineering strategy sheds light on the way to prolong the cycling stability of anionic redox cathode materials.

Theoretical study on initial decomposition paths of energetic materials featuring RDX ring

AbstractThe molecular properties of RDX are affected by the introduction of different functional groups, and the decomposition process of these analogues is studied in this paper. DFT method is used to study the initial decomposition reaction paths of 30 high energy materials based RDX skeleton. In the nitro cleavage reaction, the energy barrier become relatively low by introducing CH(NO2)2 or C(NO2)3 groups on the C site of the six membered ring. In the ring opening reaction, the ring opening process is easier to proceed by introducing NH2 or NHNH2 groups on the C site of the six membered ring.

A novel synthesis method for nitrogen-rich energetic frameworks containing bistetrazoles: assembling an advanced high-energy density material with high nitrogen content and good oxygen balance

Target compound BDNTT exhibits excellent detonation performance and indicates the potential as a novel type of high-energy density material (HEDM).

Method of calculation of satellite flow parameters behind the point of Mach reflection

A mathematical model for the calculation and express analysis of triple configurations of air shock waves arising from an “elevated” explosion of a condensed high-energy material is presented. The considered blast waves with a long duration of the positive phase (compression phase) can take place in industrial and agricultural applications: in the explosion of fuel-air mixtures, explosive dust in elevators and granaries, as well as high-energy materials for agricultural and industrial applications based on ammonium nitrate and explosive saltpetre mixtures with petroleum products. The developed mathematical model uses exact and semi-empirical relationships developed earlier in the theory of optimal shock wave systems.

Direct ink writing of high explosive composites containing metal-organic frameworks.

Smart weapon systems are being miniaturised for widespread application in high-energy materials, necessitating the development of processable and printable high explosive (HEs) composites that can be detonated with a small critical diameter. This study presents an efficient strategy for fabricating HE composites with exceptional detonation performance. We developed an HE ink based on 1,3,5-trinitro-1,3,5-triazinane (RDX), consisting of a glycidyl azide polymer (GAP) as a binder and a metal-organic framework (MOF) as an additive. This ink was deposited on an aluminium plate using direct ink writing (DIW). The resulting RDX/MOF composite demonstrated a significantly lower critical diameter (∼720 μm) for detonation compared to a composite without the MOF. This reduction in critical diameter is attributed to the pores inside the MOFs, which enhanced the transfer of heat during detonation, creating an artificial hot-spot that sustained continuous explosion. The fabricated RDX/MOF composite offers a promising approach for developing miniaturized smart weapon systems with improved detonation characteristics.

High-pressure high-temperature induced polymerization of nitrogen molecules under restricted condition

Polymeric nitrogen has been recognized to be a new type of high-energy density material (HEDM). However, the polymeric nitrogen structure formed under high-pressure and high-temperature conditions is usually in poor thermodynamic stability. Confinement strategy is conductive to the stabilization of the high-pressure phase of polymeric nitrogen structures, providing a new modulation approach for realizing the polymerization of nitrogen. In this work, nitrogen molecules are confined into the boron nitride nanotubes (N<sub>2</sub>@BNNTs) under high-pressure condition. The pressure-induced polymerization of nitrogen in N<sub>2</sub>@BNNT samples with varying nitrogen content and the stabilities of polymeric nitrogen structure are characterized by high-pressure <i>in situ</i> Raman spectroscopy method. In the N<sub>2</sub>@BNNT sample with higher nitrogen content, the N<sub>2</sub> confined to boron nitride nanotubes exhibits different Raman spectral pressure response behaviors compared with that of non confined N<sub>2</sub>, but both of them are transformed into cg-N structure after laser heating at about 123 GPa. With pressure decreasing to 40 GPa, the unconfined cg-N decomposes and releases huge energy, which affects the stability and results in the decomposition of the confined cg-N. Under ambient conditions, the confined N<sub>2</sub> is stabilized in the liquid phase. In the N<sub>2</sub>@BNNTs sample with lower nitrogen content, the confined N<sub>2</sub> is transformed into new polymeric nitrogen structure, which possesses N=N double bonds with different bond lengths close to the those in the <inline-formula><tex-math id="Z-20240409215933">\begin{document}${\mathrm{N}}_3^- $\end{document}</tex-math><alternatives><graphic specific-use="online" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="8-20240173_Z-20240409215933.jpg"/><graphic specific-use="print" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="8-20240173_Z-20240409215933.png"/></alternatives></inline-formula> anion and <inline-formula><tex-math id="Z-20240409215942">\begin{document}${\mathrm{N}}_4^+ $\end{document}</tex-math><alternatives><graphic specific-use="online" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="8-20240173_Z-20240409215942.jpg"/><graphic specific-use="print" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="8-20240173_Z-20240409215942.png"/></alternatives></inline-formula> clusters, respectively, after laser-heating in the pressure range of 122–150 GPa. This polynitrogen structure is stable with pressure decreasing to 25 GPa. This work provides new insights into the synthesis and stabilization of polymeric nitrogen structures, opening up new avenues for developing these advanced structures.

Intramolecular assembly of dinitromethyl and bistetrazole: a strategy for constructing advanced and environmentally friendly high-energy density materials

Target compound BDNBT exhibits excellent detonation performance, indicating its potential as a novel type of high-energy density material (HEDM).

Quantum tunneling instability of the mythical hexazine and pentazine.

Through computational analysis we found that pentazine and hexazine, two hypothetical high-energy density materials, exhibit inherent instability due to quantum tunneling effects. This instability remains even near the absolute zero, and therefore they can be deemed as unsynthesizable. We propose substituents that could potentially stabilize pentazine, especially dimethylamine.

Nitrogen-rich Ce-N compounds under high pressure.

Four high-pressure N-rich compounds (Pmn21-CeN7, Amm2-CeN9, P1̄-CeN10, and P1̄-II-CeN10) are proposed using first-principles calculations. Novel polymeric units (a heart shaped layered structure, chain-like N8 rings, and two new banded structures) in four cerium nitrides are reported for the first time in this study. The analyses of electronic structures and bonding properties show that the charge transfer between Ce and N atoms promotes the formation of the Ce-N ionic bond and N-N covalent bond, which play an important role in stabilizing the nitrogen skeleton. Four new phases possess high energy densities (3.24-3.86 kJ g-1), indicating that they are favorable high-energy density materials. Moreover, P1̄-CeN10 possesses ultra-incompressibility along the [1 0 0] direction. Finally, infrared and Raman spectra are analyzed to provide guidance for experimental synthesis.

Strain and collapse during lithiation of layered transition metal oxides: a unified picture

Developing long-life, high-energy density materials such as the Ni-rich LiNixMnyCozO2 (NMCxyz) is needed to manufacture advanced Li-ion batteries.

Asymmetric functionalized modification of bi(1,2,4-triazole) towards high-energy insensitive materials

Asymmetric single trinitromethyl group-modified bi(1,2,4-triazole) balanced the energy and sensitivity for novel energetic materials.

Synthesis of C-C bonded trifluoromethyl-based high-energy density materials via the ANRORC mechanism.

A trifluoromethyl group substituted C-C bonded nitrogen rich energetic material 3-(3-nitro-1H-pyrazol-4-yl)-5-(trifluoromethyl)-1,2,4-oxadiazole (4), its hydroxyl amine (5) and 3,6,7-triamino-7H-[1,2,4]triazolo[4,3-b][1,2,4]triazol-2-ium (6) salts and hydrazinium 5-(3-nitro-1H-pyrazol-4-yl)-3-(trifluoromethyl)-1,2,4-triazol-1-ide (7) were synthesized and fully characterized using infrared spectroscopy (IR), multinuclear magnetic resonance (NMR) spectroscopy (1H, 13C, and 19F), high-resolution mass spectrometry (HRMS), elemental analysis (EA) and differential scanning calorimetry (DSC) studies. Furthermore, compounds 4 and 7 were confirmed using single-crystal X-ray diffraction studies (SC-XRD). All compounds possess good density (1.70-1.80 g cm-3), detonation velocity (6432-7144 m s-1), pressure (16.38-20.31 GPa), and thermal stability (>170 °C). They are insensitive towards mechanical stimuli, impact (IS > 35 J) and friction (FS > 288 N). Overall, due to their balanced performance, these compounds can be a better replacement for presently used explosives such as trinitrotoluene (TNT).

Recent developments, advances and strategies in heterogeneous photocatalysts for water splitting.

Photocatalytic water splitting (PWS) is an up-and-coming technology for generating sustainable fuel using light energy. Significant progress has been made in the developing of PWS innovations over recent years. In addition to various water-splitting (WS) systems, the focus has primarily been on one- and two-steps-excitation WS systems. These systems utilize singular or composite photocatalysts for WS, which is a simple, feasible, and cost-effective method for efficiently converting prevalent green energy into sustainable H2 energy on a large commercial scale. The proposed principle of charge confinement and transformation should be implemented dynamically by conjugating and stimulating the photocatalytic process while ensuring no unintentional connection at the interface. This study focuses on overall water splitting (OWS) using one/two-steps excitation and various techniques. It also discusses the current advancements in the development of new light-absorbing materials and provides perspectives and approaches for isolating photoinduced charges. This article explores multiple aspects of advancement, encompassing both chemical and physical changes, environmental factors, different photocatalyst types, and distinct parameters affecting PWS. Significant factors for achieving an efficient photocatalytic process under detrimental conditions, (e.g., strong light absorption, and synthesis of structures with a nanometer scale. Future research will focus on developing novel materials, investigating potential synthesis techniques, and improving existing high-energy raw materials. The endeavors aim is to enhance the efficiency of energy conversion, the absorption of radiation, and the coherence of physiochemical processes.

Exploring the unexpected electrochemical dynamics of lithium vanadyl phosphate electrodes in zinc battery systems

Our study explores the potential of β-LiVOPO4 as a high-energy and stable cathode material for zinc-ion batteries, achieving a high working voltage through comprehensive characterization techniques.

Enhancing the ultra-high rate capability of manganese-based olivine cathode by in situ catalytic growth of graphene carbon layer

Manganese-based olivine is a high energy and low-cost cathode material for lithium-ion batteries. However, its low electronic and ionic conductivity limits its further application. Herein the graphene-modified LiMn0.8Fe0.2PO4 (LMFP/C-Fe) composites are prepared by in-situ pyrolysis and catalytic graphitization through trace ferrocene as catalyst precursor. The average thickness of graphene carbon layer grown in situ is about 2–3 nm, which forms a dense and uniform carbon layer along the face of LMFP granules. It has been found that this unique structure can make a significant improvement to the electrical conductivity of LMFP. The as-prepared LMFP/C-Fe composite has a high discharge capacity of 155.9 mAh/g at 0.5C, and the capacity retention is 93.8 % after 300 charge-discharge cycles. In addition, the material can still provide reversible capacity of 94.4 mAh/g even at an ultra-high current rate of 30C. Therefore, this work offers new tactics for layout and preparation of long-life, low cost and high-energy density lithium-ion batteries, which will present a promising application in electric automobile and other applications.