BC6NA monolayer as an ideal anode material for high-performance sodium-ion batteries

Selecting an appropriate anode material (AM) has been considered to be a crucial initial step in advancing high-performance batteries. Within this piece of research, we examine the suitability of the BC6NA monolayer (referred to as BC6NAML) as an AM by first-principles calculations. The BC6NAML exhibits metallic behavior consistently, even with varying concentrations of Na atoms, making it an ideal choice for battery usages. Our findings revealed that the theoretical storage capacity for Na-adhered BC6NAML was 406.36 mAhg-1, surpassing graphite, TiO2, BC6NA, and numerous other 2D materials. The BC6NAML also demonstrates a diffusion barrier of 0.39 eV and favorable diffusivity of Na-ions. Although the open-circuit voltage (OCV) of BC6NAML was temperate and lower compared to the OCV of other AMs like TiO2, our results suggested that it is possible to utilize BC6NAML as one of the encouraging host materials for sodium-ion batteries (SIBs). Consequently, this investigation into the potential anodic application of BC6NAML proves valuable for future experimental studies into sodium storage for SIBs.

Atomistic understanding on desalination performance of pristine graphenylene nanosheet membrane at high applied pressures

Molecular dynamics (MD) simulations are conducted to assess pristine graphenylene membranes' effectiveness in seawater desalination, explicitly focusing on their salt rejection and water permeability capabilities. This study investigates the potential of the graphenylene for separation of the Na+ as monovalent cation, in order to evaluate its further application for separation of the other type of contaminants. To this end, the pristine graphenylene nanosheet is introduced into the simulation box which included the water molecules, sodium and chlorine ions. Subsequently, MD simulations were conducted by applying different amounts of external pressures in which the temperature changes are investigated as another effective parameter in water permeability and salt rejection properties. Furthermore, the water density map, radial distribution functions, and water density elucidate the performance of the considered membrane in the presence of water molecules, Na+ ions, and Cl- ions. The optimum performance of the pristine graphenylene for seawater desalination is achieved at P = 400 MPa and T = 298 K that results in the water flux of 2920 L/m2 h bar and 98.8 % salt rejection. The pristine graphenylene nanosheet shows significant potential in effectively separating salt ions, which has elucidated its importance and subsequently, the functionalized membrane for this application.

Synthesis and Characterization of Zinc/Iron Composite Oxide Heterojunction Porous Anode Materials for High-Performance Lithium-Ion Batteries

Environmental pollution caused by the use of fossil fuels is becoming increasingly serious, necessitating the adoption of clean energy solutions. Lithium-ion batteries (LIBs) have attracted great attention due to their high energy density and currently occupy a dominant commercial position. Metal oxide materials have emerged as promising anode materials for the next generation of LIBs, thanks to their high theoretical capacity. However, the practical application of these materials is hindered by their substantial volume expansion during lithium storage and poor electrical conductivity. In this work, a zinc/iron bimetallic hybrid oxide composite, ZnO/ZnFe2O4/NC, is prepared using ZIF-8 as a precursor (ZIF-8, one of the metal organic frameworks). The N-doped porous carbon composite improves the volume change and optimizes the lithium-ion and electron transport. Meanwhile, the ZnFe2O4 and ZnO synergistically enhance the electrochemical activity of the anode through the built-in heterojunction to promote the reaction kinetics at the interface. As a result, the material delivers an excellent cycling performance of 604.7 mAh g-1 even after 300 cycles of 1000 mA g-1. This study may provide a rational design for the heterostructure and doping engineering of anodes for high-performance lithium-ion batteries.

Exploring the role of 2D-C2N monolayers in potassium ion batteries

CONTEXT

In recent years, undivided attention has been given to the unique properties of layered nitrogenated holey graphene (C₂N) monolayers (C₂NMLs), which have widespread applications (e.g., in catalysis and metal-ion batteries). Nevertheless, the scarcity and impurity of C₂NMLs in experiments and the ineffective technique of adsorbing a single atom on the surface of C₂NMLs have significantly limited their investigation and thus their development. Within this research study, we proposed a novel model, i.e., atom pair adsorption, to inspect the potential use of a C₂NML anode material for KIBs through first-principles (DFT) computations. The maximum theoretical capacity of K ions reached 2397 mA h g^-1, which was greater in contrast with that of graphite. The results of Bader charge analysis and charge density difference revealed the creation of channels between K atoms and the C₂NML for electron transport, which increased the interactions between them. The fast process of charge and discharge in the battery was due to the metallicity of the complex of C₂NML/K ions and because the diffusion barrier of K ions on the C₂NML was low. Moreover, the C₂NML has the advantages of great cycling stability and low open-circuit voltage (approximately 0.423 V). The current work can provide useful insights into the design of energy storage materials with high efficiency.

METHODS

In this research, we used B3LYP-D3 functional and 6-31 + G* basis with GAMESS program to calculate adsorption energy, open-circuit voltage, and maximum theoretical capacity of K ions on the C₂NML.

On the Road to the Frontiers of Lithium-Ion Batteries: A Review and Outlook of Graphene Anodes

Graphene has long been recognized as a potential anode for next-generation lithium-ion batteries (LIBs). The past decade has witnessed the rapid advancement of graphene anodes, and considerable breakthroughs are achieved so far. In this review, the aim is to provide a research roadmap of graphene anodes toward practical LIBs. The Li storage mechanism of graphene is started with and then the approaches to improve its electrochemical performance are comprehensively summarized. First, morphologically engineered graphene anodes with porous, spheric, ribboned, defective and holey structures display improved capacity and rate performance owing to their highly accessible surface area, interconnected diffusion channels, and sufficient active sites. Surface-modified graphene anodes with less aggregation, fast electrons/ions transportation, and optimal solid electrolyte interphase are discussed, demonstrating the close connection between the surface structure and electrochemical activity of graphene. Second, graphene derivatives anodes prepared by heteroatom doping and covalent functionalization are outlined, which show great advantages in boosting the Li storage performances because of the additionally introduced defect/active sites for further Li accommodation. Furthermore, binder-free and free-standing graphene electrodes are presented, exhibiting great prospects for high-energy-density and flexible LIBs. Finally, the remaining challenges and future opportunities of practically available graphene anodes for advanced LIBs are highlighted.

Energy Storage Mechanism of C12-3-3 with High-Capacity and High-Rate Performance for Li/Mg Batteries

The low specific capacity and Mg non-affinity of graphite limit the energy density of ion rechargeable batteries. Here, we first identify that the monolayer C12-3-3 in sp2-sp3 carbon hybridization with high Li/Mg affinity is an appropriate anode material for Li-ion batteries and Mg-ion batteries via the first-principles simulations. The monolayer C12-3-3 can achieve high specific capacities of 1181 mAh/g for Li and 739 mAh/g for Mg, higher than those of most previous anodes. The Li storage reaction is an "adsorption-conversion-intercalation mechanism", while the Mg storage reaction is an "adsorption mechanism". The 2D carbon material of C12-3-3 displays fast diffusion kinetics with low diffusion barriers of 0.41 eV for Li and 0.21 eV for Mg. As a new carbon-based anode material, the monolayer C12-3-3 will promote the practical application of batteries with high-capacity and high-rate performance.

Effective high-throughput screening of two-dimensional layered materials for potential lithium-ion battery anodes

Lithium-ion batteries (LIBs) are considered the promising next-generation advanced energy storage devices. It is very important to quickly screen out ideal anode materials for LIBs with excellent performance. In this work, an effective procedure is designed for the high-throughput screening of the three kinds of LIB anode materials from 131 613 inorganic compounds in the Materials Project database. The high throughput screen procedure was not only reliable but was also easily realized. Three ideal anode materials were obtained by considering remarkable thermodynamic stability, Li capacity larger than 372 mA h g^-1, band gap smaller than 1.0 eV, and two-dimensional constraint. Furthermore, open-circuit voltage, volume expansion ratio, and the diffusion energy barrier were calculated by the DFT-D corrected density functional method. We believe that our high throughput screen procedure can effectively and accurately search for other kinds of anode materials, which can strongly support the theoretical basis for experimental research.

First-principles study of graphenylene/MoX2 (X = S, Te, and Se) van der Waals heterostructures

New van der Waals (vdW) heterostructures obtained by stacking monolayers of recently synthesized graphenylene (Gr) and two-dimensional 1H-MoX2 (X = S, Te, and Se) are proposed and analyzed using ab initio calculations. These heterostructures are stable under normal conditions and have unique crystalline lattices. The study of electronic properties shows that the proposed materials are direct-gap semiconductors with a narrow band gap, which can be controlled by in-plane tensile strain or a transverse electric field. The considered vdW heterostructures demonstrate the transition of band alignments between types I, II and III, when in-plane stress or a transverse electric field is applied, and hold great potential for creating multifunctional devices for stretched electronics. Computations based on the non-equilibrium Green's function method indicate a high rectification factor of the order of 103-104 for a diode based on the Gr/MoS2 vdW junction. The studied structures exhibit broad optical absorption across the entire visible range and represent a promising material for optoelectronic applications.

Porous hydrogen substituted graphyne as a promising anode for lithium-ion batteries

Porous hydrogen substituted graphyne (HsGY) has been considered as a promising candidate for anode material due to its excellent electrochemical properties. In this work, we found that monolayer and bilayer HsGY are good electrodes for high charge capacity lithium-ion batteries based on density functional theory calculations. Mechanical tests reveal that monolayer and bilayer HsGY exhibit excellent mechanical properties, including large critical strains (>25%) and high in-plane stiffness (>200 N m⁻¹). The bilayer HsGY displays ultrahigh stiffness (400.27 N m⁻¹). Li adsorption on bilayer HsGY is stronger than that on the monolayer HsGY. Moreover, Li diffusion on the surfaces of monolayer and bilayer HsGY has low energy barriers (<0.5 eV). Our calculation results suggest that HsGY may contain the highest theoretical charge capacity among two-dimensional (2D) materials studied so far, with ultrahigh Li capacities of 3378 and 2895 mA h g⁻¹ for monolayer and bilayer HsGY, respectively. Given these advantages, including large critical strain, high mechanical stiffness, strong adsorption, low diffusive energy barrier, and high charge capacity, we conclude that both monolayer and bilayer HsGY could be promising anode materials for lithium-ion batteries.

Porous hydrogen substituted graphyne (HsGY) has been considered as a promising candidate for anode material due to its excellent electrochemical properties.

DFT-Guided Design and Fabrication of Carbon-Nitride-Based Materials for Energy Storage Devices: A Review

Carbon nitrides (including CN, C₂N, C₃N, C₃N₄, C₄N, and C₅N) are a unique family of nitrogen-rich carbon materials with multiple beneficial properties in crystalline structures, morphologies, and electronic configurations. In this review, we provide a comprehensive review on these materials properties, theoretical advantages, the synthesis and modification strategies of different carbon nitride-based materials (CNBMs) and their application in existing and emerging rechargeable battery systems, such as lithium-ion batteries, sodium and potassium-ion batteries, lithium sulfur batteries, lithium oxygen batteries, lithium metal batteries, zinc-ion batteries, and solid-state batteries. The central theme of this review is to apply the theoretical and computational design to guide the experimental synthesis of CNBMs for energy storage, i.e., facilitate the application of first-principle studies and density functional theory for electrode material design, synthesis, and characterization of different CNBMs for the aforementioned rechargeable batteries. At last, we conclude with the challenges, and prospects of CNBMs, and propose future perspectives and strategies for further advancement of CNBMs for rechargeable batteries.

Assessing electrochemical properties and diffusion dynamics of metal ions (Na, K, Ca, Mg, Al and Zn) on a C2N monolayer as an anode material for non-lithium ion batteries

We perform first-principles molecular dynamics (FPMD) simulations together with a CI-NEB method to explore the structure, electrochemical properties and diffusion dynamics of a C2N monolayer saturated with various univalent, bivalent and trivalent metal ions. A characteristic irregular adsorption structure consisting of an inner coplanar layer at the large atomic pore and loosely bound outer layer is discovered for all six types of ions. The predicted specific capacities and mean open circuit voltages (OCVs) for them are: 600 mA h g-1, and 0.26 V (Na); 385 mA h g-1, and 1.56 V (K); 600 mA h g-1, and 0.96 V (Mg); 713 mA h g-1, and 1.31 V (Ca); 411 mA h g-1, and 1.40 V (Zn); 1175 mA h g-1, and 0.78 V (Al). For the energy favorable migration pathway, the diffusion energy barrier height for each ionic species is found to be 0.24 eV (Na+), 0.10 eV (K+), 0.25 eV (Mg2+) and 0.10 eV (Ca2+). The values are larger than 1.0 eV for both Zn2+ and Al3+. FPMD simulation at 400 K further predicted that the diffusion coefficients of Na and K atoms absorbed on the C2N monolayer are 5.33 × 10-9 m2 s-1 and 8.52 × 10-9 m2 s-1, respectively, which are one order of magnitude higher than those of other remaining ions discussed in our work. The C2N monolayer shows promising electrochemical properties and ion diffusion dynamics for use as the anode material in alkali metal ion batteries.

Multicomponent gas separation and purification using advanced 2D carbonaceous nanomaterials

Multicomponent gas separation and purification is an important pre- or post-processing step in industry. Herein, we employed a multiscale computational approach to investigate the possibility of multicomponent low-weight gas (H₂, O₂, N₂, CO₂, CH₄) separation and purification using novel porous 2D carbonaceous nanomaterials, namely Graphdiyne (GD), Graphenylene (GN), and Rhombic-Graphyne (RG). The dispersion-corrected plane-wave density functional theory (DFT) calculation combined with the Climbing Image Nudged Elastic Band (CI-NEB) method was employed to study the gas/membrane interaction energy and diffusion barrier of different gases passing through the geometrically optimized membranes. The results from CI-NEB calculations were then fitted to the Morse potential function to construct a bridge between quantum mechanics calculations and non-equilibrium molecular dynamics (NEMD) simulation. The selectivity of each membrane for all binary mixtures was calculated using the estimated diffusion energy barriers based on the Arrhenius equation. Finally, a series of extensive NEMD simulations were carried out to evaluate the real word and time dependent separation process. According to the results, CH₄ molecules can be completely separated from the other gases using a GD membrane, O₂ molecules from CH₄, N₂, and CO₂ by a GN membrane, and H₂ molecules from all other gases using a RG membrane.

High-efficiency helium separation through an inorganic graphenylene membrane: a theoretical study

Appropriate interactions between an IGP membrane and He molecules result in efficient helium separation.

Graphenylene-supported single-atom (Ru and Mo) catalysts for CO and NO oxidations

Based on density functional theory (DFT) calculations, the adsorption geometries, stability and catalytic properties of single-atom Ru and Mo anchored on graphenylene sheets (gra-Ru and gra-Mo) are comparatively investigated.

Graphenylene-based nanoribbons for novel molecular electronic devices

In the last decade, graphene has been frequently cited as one of the most promising materials for nanoelectronics. However, despite its outstanding mechanical and electronic properties, its use in the production of real nanoelectronic devices usually imposes some practical difficulties. This happens mainly due to the fact that, in its pristine form, graphene is a gapless material. We investigate theoretically the possibility of obtaining rectifying nanodevices using another carbon based two dimensional material, namely the graphenylene. This material has the advantage of being an intrinsic semiconductor, posing as a promising material for nanoelectronics. By doping graphenylene, one could obtain 2-dimensional p-n junctions, which can be useful for the construction of low dimensional electronic devices. We propose 2-dimensional diodes in which a clear rectification effect was demonstrated, with a conducting threshold of approximately 1.5 eV in direct bias and current blocking with opposite bias. During these investigations were found specific configurations that could result in devices with Zener-like behavior. Also, one unexpected effect was identified, which was the existence of transmission dips in electronic conductance plots. This result is discussed as a related feature to what was found in graphene nanoribbon systems under external magnetic fields, even though the external field was not a necessary ingredient to obtain such effect in the present case.

Carbon Nitride Transforms into a High Lithium Storage Capacity Nitrogen-Rich Carbon

We describe here the metal-templated transformation of carbon nitride (C₃N₄) into nitrogen-containing carbons as anodes for Li-ion batteries (LIBs). Changing the template from the carbon- and nitrogen-immiscible Cu powder to the carbon- and nitrogen-miscible Fe powder yields different carbons; while Fe templating produces graphitized carbons of low (<10%) nitrogen content and moderate pore volume, Cu templating yields high defect-density carbons of high (32-24%) nitrogen content and larger pore volume. The Li⁺ storage capacity of the high nitrogen content and larger pore volume Cu-templated carbons exceeds that of the more graphitic Fe-templated carbons due to added contribution from Li⁺ insertion/extraction from pores and defects and to reversible faradaic Li⁺ reaction with nitrogen atoms. The Cu-templated carbon annealed at 750 °C delivers the highest specific capacity of 900 mAh g^-1 at 0.1 A g^-1 and 275 mAh g^-1 at 20 A g^-1, while also achieving a 96% capacity retention after 2000 cycles at 2 A g^-1. The fabrication of higher mass loading electrodes (4.5 mg cm^-2) provided a maximum areal capacity of 2.6 mAh cm^-2 at 0.45 mA cm^-2 (0.1 A g^-1), comparable to the capacities of commercial LIB cells and favorable compared to other reported carbon materials.

Piezoelectric Response of Porous Nanotubes Derived from Hexagonal Boron Nitride under Strain Influence

A computational study via periodic density functional theory of porous nanotubes derived from single-layer surfaces of porous hexagonal boron nitride nanotubes (PBNNTs) and inorganic graphenylene-like boron nitride nanotubes (IGP-BNNTs) has been carried out with the main focus in its piezoelectric behavior. The simulations showed that the strain provides a meaningful improve in the piezoelectric response on the zigzag porous boron nitride nanotubes. Additionally, its stability, possible formation, elastic, and electronic properties were analyzed, and for comparison purpose, the porous graphene and graphenylene nanotubes were studied. From the elastic properties study, it was found that IGP-BNNTs exhibited a higher rigidity because of the influence of the superficial porous area, as compared to PBNNTs. The present study provides evidence that the strain is a way to maximize the piezoelectric response and make this material a good candidate for electromechanical devices.

Nitrogen and Phosphorus Codoped Porous Carbon Framework as Anode Material for High Rate Lithium-Ion Batteries

Slow kinetics and low specific capacity of graphite anode significantly limit its applications in the rapidly developing lithium-ion battery (LIB) markets. Herein, we report a carbon framework anode with ultrafast rate and cycling stability for LIBs by nitrogen and phosphorus doping. The electrode structure is constructed of a 3D framework built from 2D heteroatom-doped graphene layers via pyrolysis of self-assembled supramolecular aggregates. The synergistic effect from the nanostructured 3D framework and chemical doping (i.e., N- and P-doping) enables fast kinetics in charge storage and transport. A high reversible capacity of 946 mAh g^-1 is delivered at a current rate of 0.5 A g^-1, and excellent rate capability (e.g., a capacity of 595 mAh g^-1 at 10 A g^-1) of the electrode is shown. Moreover, a moderate surface area from the 3D porous structure contributes to a relatively high initial Coulombic efficiency of 74%, compared to other graphene-based anode materials. The electrode also demonstrates excellent cycling stability at a current rate of 2 A g^-1 for 2000 cycles. The synthetic strategy proposed here is highly efficient and green, which can provide guidance for large-scale controllable fabrication of carbon-based anode materials.

Nitrogen-Deficient Graphitic Carbon Nitride with Enhanced Performance for Lithium Ion Battery Anodes

Graphitic carbon nitride (g-C₃N₄) behaving as a layered feature with graphite was indexed as a high-content nitrogen-doping carbon material, attracting increasing attention for application in energy storage devices. However, poor conductivity and resulting serious irreversible capacity loss were pronounced for g-C₃N₄ material due to its high nitrogen content. In this work, magnesiothermic denitriding technology is demonstrated to reduce the nitrogen content of g-C₃N₄ (especially graphitic nitrogen) for enhanced lithium storage properties as lithium ion battery anodes. The obtained nitrogen-deficient g-C₃N₄ (ND-g-C₃N₄) exhibits a thinner and more porous structure composed of an abundance of relatively low nitrogen doping wrinkled graphene nanosheets. A highly reversible lithium storage capacity of 2753 mAh/g was obtained after the 300th cycle with an enhanced cycling stability and rate capability. The presented nitrogen-deficient g-C₃N₄ with outstanding electrochemical performances may unambiguously promote the application of g-C₃N₄ materials in energy-storage devices.

Biphenylene and Phagraphene as Lithium Ion Battery Anode Materials

We present results of density functional theory calculations on the lithium (Li) ion storage capacity of biphenylene (BP) membrane and phagraphene (PhG) which are two-dimensional defected-graphene-like membranes. Both membranes show a larger capacity than graphene, Li₂C₆ and Li_1.5C₆ compared to LiC₆. We find that Li is very mobile on these materials and does not interact as strongly with the membranes. In the case of BP we also investigated the possible volume expansion on Li insertion. We find a 11% expansion, which is very similar to the one found in graphite. Our findings show that both membranes are suitable materials for lithium ion battery anodes.

Structural characterization and electrochemical performance of macroporous graphite-like C3N3 prepared by the Wurtz reaction and heat treatment

g-C₃N₃ is synthesized by a facile method and further heat treatment can improve the initial coulombic efficiency and reversible capacity.

Two-dimensional GeP3 as a high capacity electrode material for Li-ion batteries

Monolayer GeP₃ is predicted to be an ideal anode material for lithium battery with ultrahigh-capacity, low diffuse barrier and low average open-circuit voltage.