Potential High Energy Density Research Articles

Theoretical investigation on heats of formation, detonation properties and sensitivities of TANPy based energetic materials

A series of 2,4,6-triamino-3,5-dinitropyridine (TANPy) based energetic compounds were designed and optimized at the B3LYP/6-311G (d,p). The results show that all the designed compounds have high positive heats of formation, and the tetrazole ring/–N3 was an beneficial combination to increase the heats of formation. The introduction of furazan-furazan/-C(NO2)3/–CH(NO2)2 combination was effective to improve the densities and detonation properties while the furazan-furazan or furazan-tetrazine rings was beneficial to improving the values of heats of detonation. Considering the detonation properties and sensitivities, compounds D2, E2, F2 were finally screened as potential high energy density materials and their physicochemical properties were fully investigated.

One-Dimensional Non-coplanar Nitrogen Chains in Manganese Tetranitride under High Pressure.

Transition metal nitrides have great potential applications as incompressible and high energy density materials. Various polymeric nitrogen structures significantly affect their properties, contributing to their complex bonding modes and coordination conditions. Herein, we first report a new manganese polynitride MnN4 with bifacial trans-cis [N4]n chains by treating with high-pressure and high-temperature conditions in a diamond anvil cell. Our experiments reveal that MnN4 has a P-1 symmetry and could stabilize in the pressure range of 56-127 GPa. Detailed pressure-volume data and calculations of this phase indicate that MnN4 is a potential hard (255 GPa) and high energy density (2.97 kJ/g) material. The asymmetric interactions impel N1 and N4 atoms to hybridize to sp2-3, which causes distortions of [N4]n chains. This work discovers a new polynitride material, fills the gap for the study of manganese polynitride under high pressure, and offers some new insights into the formation of polymeric nitrogen structures.

An Amino Acid-Enabled Separator for Effective Stabilization of Li Anodes.

Fundamentally suppressing Li dendrite growth is known to be critical for realizing the potential high energy density for Li-metal batteries (LMBs). Inspired by the ionic transport function of proteins, we previously discovered that utilizing natural proteins was able to stabilize the Li anode but have not demonstrated how a specific amino acid of the protein enabled the function. In this study, we decorate the separator with Leucine (Leu) amino acid assisted by poly(acrylic acid) (PAA) for effectively stabilizing the Li-metal anode, so as to dramatically improve the cycling performance of LMBs. The decorated separator improves electrolyte wettability and effectively suppresses Li dendrite growth. As a result, the amino acid-enabled separator prolongs the cycle life of the symmetrical Li|Li cells, exhibits higher Coulombic efficiency in the Li|Cu cells, and improves the cycling performance in LMBs with the LiFePO4 cathode. This work is an initial study on applying a specific amino acid of proteins to enhance the performance of batteries, providing a new strategy on guiding Li+ deposition, and laying an important foundation for functional separator design of high-energy-density batteries.

Polyaniline packed activated carbon as pseudocapacitive negative electrodes

Hybrid supercapacitors (HSCs) are attracting more attentions due to their potential high power and energy density. To exploring high capacity negative electrode materials, especially the capacitive materials, is more critical for further enhancing the energy density of HSC in comparing with more reported advanced battery-type positive materials. For perfect combination of electrochemical double layer and pseudocapacitive capacitance in negative electrode, the method of evenly filling polyaniline on nanopores of activated carbon is developed herein with keeping large surface area, the suitable ion-diffusion structure of activated carbon and further obtaining rich surface redox-active sites. The polyaniline packed activated carbons exhibit high specific capacitance (437.9 F g−1 at 0.5 A g−1) in negative voltage window (0 to −1.0 V), superior rate performance (378.0 F g−1 at 30 A g−1), and excellent capacitance retention even at a high mass loading and a high current density (326.5 F g−1 at 10 mg cm−2 and 20 A g−1). Additionally, an aqueous HSC based on the polyaniline packed activated carbon negative electrode and Ni-Co-LDH positive electrode presents higher energy density of 44.6 Wh kg−1 at a power density of 377.1 W kg−1. The present study presents novel method and materials for developing high performance capacitive negative electrode materials.

Stabilized four-electron aqueous zinc-iodine batteries by quaternary ammonium complexation.

Four-electron aqueous zinc-iodine batteries (4eZIBs) leveraging the I-/I0/I+ redox couple have garnered attention for their potential high voltage, capacity, and energy density. However, the electrophilic I+ species is highly susceptible to hydrolysis due to the nucleophilic attack by water. Previous endeavors to develop 4eZIBs primarily relied on highly concentrated aqueous electrolytes to mitigate the hydrolysis issue, nonetheless, it introduced challenges associated with dissolution, high electrolyte viscosity, and sluggish electrode kinetics. In this work, we present a novel complexation strategy that capitalizes on quaternary ammonium salts to form solidified compounds with I+ species, rendering them impervious to solubilization and hydrolysis in aqueous environments. The robust interaction in this complexation chemistry facilitates a highly reversible I-/I0/I+ redox process, significantly improving reaction kinetics within a conventional ZnSO4 aqueous electrolyte. The proposed 4eZIB exhibits a superior rate capability and an extended lifespan of up to 2000 cycles. This complexation chemistry offers a promising pathway for the development of advanced 4eZIBs.

Cellulose nanofiber hydrogel with high conductivity electrolytes for high voltage flexible supercapacitors

Although flexible double layer capacitors based on hydrogels overcome the drawbacks of commercial double layer capacitors such as low safety and non-deformability, it is still considered as attractive challenges to achieve high conductivity for hydrogel electrolytes as well as high operating voltages for hydrogel flexible supercapacitors. In this paper, ion migration channels were engineered by immobilizing positive and negative charges on polymer skeleton and dispersing cellulose nanofibers in the polymerized polyelectrolyte network, providing ultra-high ionic conductivity (103 mS cm−1). In addition, K3[Fe(CN)6] was introduced through a soaking method, leading to redox reactions on the surface of carbon electrode during charging and discharging, supporting a relatively wide voltage window (1.8 V). Moreover, the specific capacitance at high current remained 55 % of the specific capacitance at low current, indicating excellent rate performance. In addition, the device displayed high cycling stability (80.05 % after 10,000 cycles). Notably, we successfully light up the red LED with only one device. Accordingly, this work provides a feasible design concept for the development of cellulose nanofibers (CNF) hydrogel-based solid-state electrolyte with high conductivity for flexible supercapacitors with wide potential window and high energy density.

Unveiling the catalytic potential of two-dimensional boron nitride in lithium–sulfur batteries

Lithium–sulfur (Li–S) batteries, renowned for their potential high energy density, have attracted attention due to their use of earth-abundant elements. However, a significant challenge lies in developing suitable materials for both lithium-based anodes, which are less prone to lithium dendrite formation, and sulfur-based cathodes. This obstacle has hindered their widespread commercial viability. In this study, we present a novel sulfur host material in the form of a two-dimensional semiconductor boron nitride framework, specifically the 2D orthorhombic diboron dinitride (o-B2N2). The inherent conductivity of o-B2N2 mitigates the insulating nature often observed in sulfur-based electrodes. Notably, the o-B2N2 surface demonstrates a high binding affinity for long-chain Li-polysulfides, leading to a significant reduction in their dissolution into the DME/DOL electrolytes. Furthermore, the preferential deposition of Li2S on the o-B2N2 surface expedites the kinetics of the lithium polysulfide redox reactions. Additionally, our investigations have revealed a catalytic mechanism on the o-B2N2 surface, significantly reducing the free energy barriers for various sulfur reduction reactions. Consequently, the integration of o-B2N2 as a host cathode material for Li–S batteries holds great promise in suppressing the shuttle effect of lithium polysulfides and ultimately enhancing the overall battery performance. This represents a practical advancement for the application of Li–S batteries.

New Insights of Infiltration Process of Argyrodite Li6PS5Cl Solid Electrolyte into Conventional Lithium-Ion Electrodes for Solid-State Batteries

All-solid-state lithium-ion batteries based on solid electrolytes are attractive for electric applications due to their potential high energy density and safety. The sulfide solid electrolyte (e.g., argyrodite) shows a high ionic conductivity (10−3 S cm−1). There is an open question related to the sulfide electrode’s fabrication by simply infiltrating methods applied for conventional lithium-ion battery electrodes via homogeneous solid electrolyte solutions, the structure of electrolytes after drying, chemical stability of binders and electrolyte, the surface morphology of electrolyte, and the deepening of the infiltrated electrolyte into the active materials to provide better contact between the active material and electrolyte and favorable lithium ionic conduction. However, due to the high reactivity of sulfide-based solid electrolytes, unwanted side reactions between sulfide electrolytes and polar solvents may occur. In this work, we explore the chemical and electrochemical properties of the argyrodite-based film produced by infiltration mode by combining electrochemical and structural characterizations.

Tellurium with Reversible Six-Electron Transfer Chemistry for High-Performance Zinc Batteries.

Chalcogens, especially tellurium (Te), as conversion-type cathodes possess promising prospects for zinc batteries (ZBs) with potential rich valence supply and high energy density. However, the conversion reaction of Te is normally restricted to the Te2-/Te0 redox with a low voltage plateau at ∼0.59 V (vs Zn2+/Zn) rather than the expected positive valence conversion of Te0 to Ten+, inhibiting the development of Te-based batteries toward high output voltage and energy density. Herein, the desired reversible Te2-/Te0/Te2+/Te4+ redox behavior with up to six-electron transfer was successfully activated by employing a highly concentrated Cl--containing electrolyte (Cl- as strong nucleophile) for the first time. Three flat discharge plateaus located at 1.24, 0.77, and 0.51 V, respectively, are attained with a total capacity of 802.7 mAh g-1. Furthermore, to improve the stability of Ten+ products and enhance the cycling stability, a modified ionic liquid (IL)-based electrolyte was fabricated, leading to a high-performance Zn∥Te battery with high areal capacity (7.13 mAh cm-2), high energy density (542 Wh kgTe-1 or 227 Wh Lcathdoe+anode-1), excellent cycling performance, and a low self-discharge rate based on 400 mAh-level pouch cell. The results enhance the understanding of tellurium chemistry in batteries, substantially promising a remarkable route for advanced ZBs.

Succinonitrile-Lithium Salt Composite As a Solid Catholyte for Llzo-Based All-Solid-State Batteries

All-solid-state batteries (ASSB) have come into the spotlight as next-generation batteries because of their potential high energy density and low flammability. LLZO (Li7La3Zr2O12) is a prominent solid electrolyte material for ASSBs due to its high ionic conductivity (>1 x 10-4 S/cm at room temperature) and compatibility with Li metal. However, for its use in ASSBs, there are challenges including forming intimate contact with the active electrode material. Because both LLZO and the cathode active material are rigid, employing a soft solid catholyte between them can be a solution to ensure intimate contact. The solid catholyte must be ionically conductive, and stable against oxidation (> 4.5 V vs. Li/Li+).Organic Ionic Plastic Crystals (OIPC) are a class of materials that is soft and waxy at room temperature. When the OIPC is mixed with Li salts, the mixture has high ionic conductivity and a wide electrochemical window. Succinonitrile (SN) is an OIPC material, and SN with Li salts are reported to have high ionic conductivities (> 1x10-4 S/cm), good oxidation stability (>5 V vs. Li/Li+), and low flammability as well [1][2]. Despite the favorable properties of the SN-Li salt composite, poor chemical stability with Li metal makes it difficult to use it alone as a solid electrolyte [1]. For its use as a solid catholyte, chemical stability with Li metal is not an issue, making it a prominent candidate material. However, studies for its use as a solid catholyte with LLZO are limited.In this talk, we describe the properties of Succinonitrile-Lithium salt composites focusing on their suitability as solid catholytes in LLZO-based ASSBs. SN is mixed with different kinds of Li salts including LiTFSI and LiBOB to form composites. Their electrochemical properties are compared and the contact between the composite and LLZO is observed. The performance of all-solid-state cells with the mixtures will also be evaluated at room temperature. It is hoped that this work can motivate efforts toward developing LLZO cells using OIPC materials.[1] Alarco P.J, et al Nat. Mater., 3, 476 (2004)[2] Effat M.B, et al J. Power Sources, 226802, 436 (2019)

Scalable wet-slurry fabrication of sheet-type electrodes for sulfide all-solid-state batteries and performance enhancement via optimization of Ni-rich cathode coating layer

All-solid-state Li or Li-ion batteries (ASSLBs) have attracted much attention due to their potential high energy density, high safety, and low manufacturing costs compared to commercial liquid electrolyte Li-ion batteries. However, the rate capacity and cycling performance could not satisfy the practical application. Here, an island-like amorphous Li2O–ZrO2 (LZO) was coated on the surface of LiNi0.88Co0.10Al0.02 (NCA) via a sol-gel method and low-temperature sintering. The electrochemical performance and density functional theory calculation results demonstrate that the LZO coating layer significantly boosts Li-ions transfer. Targeting large-scale production, a sheet-type cathode was prepared by a wet-slurry process with PVDF-HFP as a binder, which exhibits an initial specific capacity of 181.91 mAh·g−1 at 0.13C and 25 °C. Remarkably, the wet-slurry cathode with a high NCA loading of 20 mg cm−2 delivers an initial areal capacity of 2.936 mAh·cm−2 and capacity retention of 69.93% after 1000 cycles at a rate of 0.64C. By employing X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy, we reveal that the LZO coating layer and PVDF-HFP binder inhibited the decomposition of sulfide electrolyte and detrimental structure evolution of NCA active material. This work would guide designing high-performance ASSLBs for practical application and commercialization.

New carbon–nitrogen–oxygen compounds as high energy density materials

Molecular crystals are complex systems exhibiting various crystal structures, and accurately modeling the crystal structures is essential for understanding their physical behaviors under high pressure. Here, we perform an extensive structure search of ternary carbon-nitrogen-oxygen (CNO) compound under high pressure with the CALYPSO method and first principles calculations, and successfully identify three polymeric CNO compounds with Pbam, C2/m and symmetries under 100 GPa. More interestingly, these structures are also dynamically stable at ambient pressure, and are potential high energy density materials (HEDMs). The energy densities of Pbam, C2/m and phases of CNO are about 2.30 kJ/g, 1.37 kJ/g and 2.70 kJ/g, respectively, with the decompositions of graphitic carbon and molecular carbon dioxide and α-N (molecular N2) at ambient pressure. The present results provide in-depth insights into the structural evolution and physical properties of CNO compounds under high pressures, which offer crucial insights for designs and syntheses of novel HEDMs.

Cryo-TEM studies of binder free high performance FeF2 cathode based full cells enabled by surface engineering

Iron-based fluorides (IBFs, typically FeF3 and FeF2) are potential next generation high energy density cathodes for lithium-ion batteries (LIBs) due to their high specific capacity, cost effectiveness and crustal abundance. However, IBFs decompose electrolyte violently which impedes their practical implementation in LIBs. Herein we report a strategy to embed FeF2 nanoparticles in an interconnected cyclic polyacrylonitrile (cPAN) network to passivate the cathode/electrolyte interface. Moreover, cPAN affords strong adhesion to both the FeF2 nanoparticles and the current collector, essentially acting as a binder that is superior to polyvinylidene fluoride (PVDF). Cryo-transmission electron microscopy reveals that the amorphous cPAN was uniformly coated on the FeF2 surface with a thickness of 5 nm, acting as an effective (cathode electrolyte interphase) CEI layer that inhibited the growth of excessive CEI, thus achieved stable cycling in lean electrolyte. When paired with the high capacity SiO/C anode, the FeF2-cPAN|SiO/C full cell delivered a capacity of 400 mAh/g after 100 cycles at 0.5C. Density functional theory (DFT) calculation indicates that the cPAN is inert to the electrolyte, thus suppresses the catastrophic electrolyte decomposition caused by FeF2. DFT further suggests that the existence of vacancies on the carbon surface will cause H transfer reaction of the solvent, leading to the degradation of the electrolyte. This study provides a viable technology to enable high energy density FeF2 cathode-based LIBs for energy storage applications.

Novel high-pressure phases of nitrogen-rich Y-N compounds.

Five new high-pressure phases (I4̄3d-Y4N3, R3c-Y2N3, P1̄-II-YN4, P1̄-YN6, and P31c-YN8) are proposed by the crystal structure prediction. A series of polynitrogen forms were achieved in the nitrogen-rich Y-N compounds, including diatomic N2, an isolated N8 chain, an infinite N chain with an N6 unit, and an infinite N layer with bent N18 rings. The high energy densities of P1̄-II-YN4 (1.98 kJ g-1), P1̄-YN6 (2.35 kJ g-1), and P31c-YN8 (3.77 kJ g-1) make them potential high energy density materials. More importantly, P1̄-II-YN4, P1̄-YN6, and P31c-YN8 exhibit excellent explosive performance, with detonation pressures 4-8 times that of TNT (19 GPa) and detonation velocities 1-2 times that of TNT (6.90 km s-1). The electronic structure and bonding properties show that the high stability of Y-N compounds originates from the strong N-N covalent bond and the weak Y-N ionic bond interaction. The increase in the transferred charge quantity as the pressure decreased is more conducive to stabilizing the polymeric nitrogen structure, which leads to the metastable properties of P1̄-II-YN4 and P1̄-YN6 under ambient conditions. Finally, the infrared (IR) spectra of P1̄-II-YN4, P1̄-YN6, and P31c-YN8 are calculated to provide a reference in experimental synthesis.

Synthesis, Characterization and DFT Study of a New Family of High-Energy Compounds Based on s-Triazine, Carborane and Tetrazoles.

An efficient one-pot synthesis of carborane-containing high-energy compounds was developed via the exploration of carbon-halogen bond functionalization strategies in commercially available 2,4,6-trichloro-1,3,5-triazine. The synthetic pathway first included the substitution of two chlorine atoms in s-triazine with 5-R-tetrazoles (R = H, Me, Et) units to form disubstituted tetrazolyl 1,3,5-triazines followed by the sequential substitution of the remaining chlorine atom in 1,3,5-triazine with carborane N- or S-nucleophiles. All new compounds were characterized by IR- and NMR spectroscopy. The structure of four new compounds was confirmed by single crystal X-ray diffraction analysis. The density functional theory method (DFT B3LYP/6-311 + G*) was used to study the geometrical structures, enthalpies of formation (EOFs), energetic properties and highest occupied and lowest unoccupied molecular orbital (HOMO and LUMO) energies and the detonation properties of synthesized compounds. The DFT calculation revealed compounds processing the maximum value of the detonation velocity or the maximum value of the detonation pressure. Theoretical terahertz frequencies for potential high-energy density materials (HEDMs) were computed, which allow the opportunity for the remote detection of these compounds.

Improving performances of oxide solid electrolytes by a magnetic field for all-solid-state lithium-metal batteries

All-solid-state lithium-metal batteries have been regarded as the next-generation energy storage due to the potential high safety and high energy density. However, for oxide solid electrolytes (SEs), the relatively low ionic conductivities and the growth of lithium dendrite leading to safety issues limit their commercialization. Here, we systematically investigate the influences of external magnetic field on electrochemical performances of oxide SEs. It reveals that the magnetic field can improve ionic conductivity of SEs and the cycle performance in Li symmetric cells. The enhanced performance is because the magnetohydrodynamics effect can promote diffusion in SEs and homogenize distribution of lithium deposition to avoid the propagation of lithium dendrite. This strategy can be extent to other types of SEs or various energy applications.

Polymer hydrogel based quasi-solid-state sodium-ion supercapacitor with 2.5 V wide operating potential window and high energy density

The present work reports a quasi-solid state sodium ion-based asymmetric supercapacitor (ASC) device with nitrogen-doped reduced graphene oxide (NrGO) and boron-doped reduced graphene oxide (BrGO) electrodes. The choice of NrGO (BrGO) for the cathode (anode) is accomplished through a computational investigation of electrode quantum capacitances based on density functional theory (DFT). Nanocellulose is used as an electrode binder due to its biodegradability, enhanced wettability, good ion permeability, and low cost. The NaClO4-PVA based hydrogel membrane is the separator-less quasi-solid state gel electrolyte in the fabricated device. The specific capacitance of the NrGO || BrGO ASC device is obtained as 251.2 F g−1, at a current density of 1 A g−1 with a wide potential window of 2.5 V which is better than the previous reports. This device offers a better performance in comparison to the rGO||rGO, NrGO||NrGO and BrGO||BrGO symmetric supercapacitor (SSC) devices due to the synergistic effect of non-faradic capacitance and pseudocapacitance. The ASC device shows an energy density of 54.5 Wh kg−1 at a power density of 1.25 kW kg−1 and significant capacitance retention of 84.8% after 10,000 cycles at a high current density of 15 A g−1.

Polymerization of nitrogen in two theoretically predicted high-energy compounds ScN6 and ScN7 under modest pressure

Materials under high pressure usually exhibit unique chemical and physical properties. Polynitrogen compounds have received widespread attention as potential high energy density materials. This paper uses CALYPSO crystal structure prediction method to study the structures of ScN6 and ScN7 in 0–100 GPa. Theoretical calculations show that ScN6 is thermodynamically stable above 80 GPa, while ScN7 is thermodynamically stable from 30 GPa to 90 GPa. Furthermore, ScN7 is metastable under ambient conditions, demonstrating that it can be quenched to ambient conditions after high pressure synthesis. The P -ScN6 is a three-dimensional extended fold multi-nitrogen network, and the P -ScN7 contains a five-membered ring and a curved N4 molecular unit. Both P -ScN6 and P -ScN7 contain a lot of N–N single bonds and N=N double bonds. The energy densities of P -ScN6 and P -ScN7 are 3.97 kJ g−1 and 3.12 kJ g−1, respectively. The detonation velocity and detonation pressure of the P -ScN6 phase and P -ScN7 phase are also higher than that of TNT. Excellent energy storage properties and detonation performance show that they can be used as potential high-energy materials. These results opened up a new way for the synthesis of nitrogen-rich compounds.

Density functional theory investigation of triazole substituted nitro borazine derivatives as high energy density material

This work involves Density Functional Theory (DFT) investigation for prediction of nitrogen enriched boron based heterocyclic molecules for potential application as high energy density materials (HEDMs). The development of environment benign energetic materials as propellants, explosives, construction, military purposes and safety equipments are of immense interest. Boron based heterocyclic molecules with high nitrogen content have remarkable explosive properties. They are safe to the environment as their decomposition produces safe nitrogen gas instead of toxic hydrocarbons. In this work we have performed DFT calculations of thermodynamic properties and explosive characteristics of triazole substituted nitro borazine derivatives to assess their role as possible HEDMs. Effects of substitution of triazole group along boron atom and nitrogen atom have been investigated. Energetic properties that are important in deciding the explosive characteristics have been computed. Calculation of heat of formation through isodesmic reaction, detonation properties, heat of combustion etc. has been carried out. Further, crystal density, chemical stability and impact sensitivity have been analyzed. The designed molecules have nitrogen content of more than 48% and density in the range of 1.74–1.78 g/cm3. Impact sensitivity of the molecules indicates them as highly insensitive towards impact. Computed results in our investigation suggests that substitution of triazole ring along boron atom of the nitro borazine derivatives could be a potential high energy density material.

Synthesis of KVPO4F/Carbon Porous Single Crystalline Nanoplates for High-Rate Potassium-Ion Batteries.

With high theoretical capacity and operating voltage, KVPO4F is a potential high energy density cathode material for potassium-ion batteries. However, its performance is usually limited by F loss, poor electronic conductivity, and unsteady electrode/electrolyte interface. Herein, a simple one-step sintering process is developed, where vanadium-oxalate-phosphite/phosphate frameworks and fluorinated polymer are used to synthesize carbon-coated KVPO4F nanoplates. It is found that the V-F-C bond generated by fluorinated-polymer-derived carbon at the interface of KVPO4F/C nanoplates diminishes the F loss, as well as enhances K-ions migration ability and the electronic conductivity of KVPO4F. The as-synthesized KVPO4F/C cathode delivers a reversible capacity of 106.5 mAh g-1 at 0.2 C, a high working voltage of 4.28 V, and a rate capability with capacity of 73.8 mAh g-1 at the ultrahigh current density of 100 C. In addition, a KVPO4F/C//soft carbon full cell exhibits a high energy density of 235.5 Wh kg-1.