Two-Dimensional Boron-Rich Monolayer BxN as High Capacity for Lithium-Ion Batteries: A First-Principles Study

A wide-bandgap graphene-like structure C6BN with ultra-low dielectric constant

This study introduces a new wide-bandgap graphene-like structure, denoted as C6BN, achieved by incorporating an eight-electron BN pair, substantially modifying its electronic properties. Utilizing extensive density functional calculations, we comprehensively analyzed the stability, electronic structure, mechanical properties, and optical-electrical characteristics of C6BN. Our investigations reveal the material's exceptional thermodynamic, mechanical, and dynamic stability. Notably, the calculated wide bandgap of 2.81 eV in C6BN, supported by analyses of energy levels, band structures, and density of states, positions it as a promising two-dimensional wide-bandgap semiconductor. Additionally, C6BN exhibits isotropic mechanical features, highlighting its inherent flexibility. Remarkably, our calculations indicate an ultra-low dielectric constant (k = 1.67) for C6BN, surpassing that of well-established third-generation semiconductors. Further exploration into the thermoelectric properties of C6BN demonstrates its promising performance, as evidenced by calculations of thermal conductivity (κ), power factor (P), and Seebeck coefficient (S). In summary, our findings underscore the significant potential of the proposed C6BN structure as a flexible two-dimensional material poised to drive future advancements in electronic and energy-related technologies.

Exploring the potential of MB2 MBene family as promising anodes for Li-ion batteries

In recent years, finding high-performance energy storage materials has become a major challenge for Li-ion batteries. B-based two-dimensional materials have become the focus of attention because of their abundant reserves and non-toxic characteristics. A series of two-dimensional transition metal borides (MBenes) are reported and their electrochemical properties as anode materials for Li-ion batteries are investigated by density functional theory (DFT) calculations. The surface of MB2 possesses medium adsorption strength and diffusion energy barrier for Li atoms, which are conducive to the insertion and extraction of Li-ions during the charge/discharge process of Li-ion batteries. Herein, we explore the potential of MB2 (M = Sc, Y, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Fe, Co, Ni, Cu and Zn) as the anode material for LIBs. Excitingly, the Li atom can be stably adsorbed on the surface of MB2 (M = Sc, Ti, V, Nb, Mo, W) monolayers, and the theoretical capacity of the MB2 monolayer is high (521.77-1610.20 mA h g-1). The average open circuit voltage range is within 0.10-1.00 V (vs. Li/Li+). The relationship between the p-band center of the B atom and the adsorption energy of Li on the surface of MB2 is also investigated. Furthermore, it is found that the charge transfer of Li atom and metallic center in the most stable position is strongly related to the corresponding value of diffusion energy barrier. These results confirm that MB2 monolayers are promising 2D anode materials for Li-ion batteries, demonstrating the application prospects of B-based 2D materials.

Alkali to alkaline earth metals: a DFT study of monolayer TiSi2N4 for metal ion batteries

A significant problem in the area of rechargeable alkali ion battery technologies is the exploration of anode materials with overall high specific capacities and superior physical properties. By using first-principles calculations, we have determined that monolayer TiSi2N4 is precisely such a potential anode candidate. Its demonstrated dynamic, thermal, mechanical, and energetic stabilities make it feasible for experimental realization. An important benefit of the electrode conductivity is that the electronic structure reveals that the pristine system experiences a change from a semiconductor to a metal throughout the entire alkali adsorption process. What's more interesting is that monolayer TiSi2N4 can support up to double-sided 3-layer ad-atoms, resulting in extremely high theoretical capacities for Li, Na, Mg, and K of 1004, 854, 492 and 531 mA h g-1 and low average open-circuit voltages of 0.55, 0.25, 0.55, and -1.3 V, respectively. Alkali diffusion on the surface has been demonstrated to occur extremely quickly, with migration energy barriers for Li, Na, Mg, and K as low as 0.25, 0.14, 0.10, and 0.07 eV, respectively. The results reveal that the migration barrier energy is the lowest for Li and Mg from path-2 and Na and K from path-1. Overall, these findings suggest that monolayer TiSi2N4 is a suitable anode candidate for use in high-performance and low-cost metal-ion batteries.

Prediction of a planar BxP monolayer with inherent metallicity and its potential as an anode material for Na and K-ion batteries: a first-principles study

Borophene, the lightest two-dimensional material, exhibits exceptional storage capacity as an anode material for sodium-ion batteries (NIBs) and potassium-ion batteries (PIBs). However, the pronounced surface activity gives rise to strong interfacial bonding between borophene and the metal substrate it grows on. Incorporation of heterogeneous atoms capable of forming strong bonds with boron to increase borophene stability while preserving its intrinsic metallic conductivity and high theoretical capacity remains a great challenge. In this study, a particle swarm optimization (PSO) method was employed to determine several new two-dimensional monolayer boron phosphides (BxP, x = 3-6) with rich boron components. The obtained BxP has great potential to be used as an anode material for sodium-ion batteries/potassium-ion batteries (SIBs/PIBs), according to DFT calculations. BxP demonstrates remarkable stability compared with borophene which ensures their feasibility of experimental synthesis. Moreover, B5P and B6P exhibit high electronic conductivity and ionic conductivity, with migration energy barriers of 0.20 and 0.21 eV for Na ions and 0.07 eV for K ions. Moreover, the average open circuit voltage falls within a favorable range of 0.25-0.73 V, which results in a high storage capacity of 1119-2103 mA h g-1 for SIBs and 631-839 mA h g-1 for PIBs. This study paves the way for exploring boron-rich 2D electrode materials for energy applications and provides valuable insights into the functionalization and stabilization of borophene.

B3S2 monolayer as an anode material for Na/K-ion batteries: a first-principles study

Two-dimensional (2D) materials used as anodes in metal-ion batteries have attracted increased attention due to their high specific surface area, abundant active sites and good electronic properties. Searching for 2D materials with high storage capacities and low diffusion energy barriers is one of the most effective ways to design novel anode materials. In this work, based on first-principles calculations, we design a new 2D B3S2 monolayer with high thermodynamic and dynamic stability. The obtained B3S2 monolayer has a high cohesive energy, ensuring the feasibility of experimental synthesis. These characteristics of the B3S2 monolayer prompt us to explore its application as an anode material. The B3S2 monolayer exhibits not only a metallic nature but also a low diffusion energy barrier (0.037 eV) and open-circuit voltage (0.09 V). More importantly, the B3S2 monolayer shows a very high theoretical capacity of 1658 mA h g-1 as an anode material for sodium-ion batteries, which is comparable to other similar or common 2D materials. All of these intriguing properties make the B3S2 monolayer a promising 2D anode material for sodium-ion batteries.

Monolayer TiSi2P4as a high-performance anode for Na-ion batteries

Exploring anode materials with overall excellent performance remains a great challenge for rechargeable Na-ion battery technologies. Herein, we have identified that monolayer TiSi2P4is just such a prospective anode candidate via first-principles calculations. It is showed to be dynamically, thermally, mechanically, and energetically stable, which provides feasibility for experimental realization. The Na diffusion on the its surface is proved to be ultrafast, with a migration energy barrier as low as 73 meV. Electronic structure confirms that the pristine system undergoes a transition from the semiconductor to metal during the whole sodiation process, which is a significant advantage to the electrode conductivity. More excitingly, monolayer TiSi2P4can accommodate up to double-sided five-layer adatoms, resulting in an ultrahigh theoretical capacity of 1176 mA h g-1and a low average open-circuit voltage of 0.195 V. Moreover, the maximally sodiated electrode monolayer yields rather small in-plane lattice expansion of only 1.40%, which ensures reversible deformation and excellent cycling stability as further corroborated by structural relaxation andab initiomolecular dynamics simulation. Overall, all of these results point to the potential that monolayer TiSi2P4can serve as a promising anode candidate for application in high-performance low-cost Na-ion batteries.

First principles investigation on Na-ion storage in two-dimensional boron-rich B2N, B3N, and B5N

Na-ion batteries (SIBs) are emerging as a promising alternative to Li-ion batteries for large-scale energy storage in light of abundant Na resources and their low cost. Development of appropriate electrode materials that can conquer some critical issues such as low theoretical storage capacity and sluggish redox kinetics resulting from the larger radius of Na is urgently needed for their practical applications. In this work, boron-rich 2D B_xN (x = 2, 3, and 5) has been explored as promising anode materials for high-performance SIBs based on density functional theory calculations. B_xN electrodes exhibit moderate affinity toward Na-ions with adsorption energies of -0.41 to -1.21 eV, which allows stable Na-ion intercalation without the formation of metal dendrites. Moreover, both B₃N and B₅N deliver low diffusion barriers (0.28 and 0.08 eV) for Na-ion migration, guaranteeing a high charging/discharging rate. More importantly, these B_xN anodes exhibit not only a remarkably high theoretical capacity of 1129-1313 mA h g^-1 but also a low open-circuit voltage (0.45-0.87 V), which is important to achieve high energy density. AIMD simulations have confirmed the excellent cyclability of B_xN electrodes during reversible lithiation/delithiation. These results suggested that the B_xN electrode could be used as a new lightweight SIB anode with high capacity, cyclability, and desired rate performance.

A two-dimensional metallic SnB monolayer as an anode material for non-lithium-ion batteries

Na-, K- and Mg-ion batteries (NIBs, KIBs and MIBs) have drawn considerable interest due to their high abundance and excellent safety. However, the lack of high-performance anode materials is a major obstacle to its development. A metallic SnB planar monolayer is predicted by using the two-dimensional global minimum structure search method of swarm intelligence. Based on first-principles calculations, we proved that the metal SnB monolayer has high binding energy and excellent dynamical, thermal and mechanical stability. It is worth noting that the SnB monolayer has several stable adsorption sites for Na-, K- and Mg-ions, so it has a high theoretical capacity of 620.93, 517.44 and 620.93 mA h g^-1, respectively. For Na-, K- and Mg-ion batteries, the low diffusion barriers of the SnB monolayer are 0.22, 0.07 and 0.68 eV, and the low average open circuit voltages are 0.42, 0.49 and 0.23 V, which ensure long service life and fast charging in practical applications. In addition, it is proved that the SnB monolayer maintains excellent conductivity and stability during the charge-discharge process. The results show that the SnB monolayer offers innovative advantages for the development of new two-dimensional planar structures that further advance the development of anode materials for metal ion batteries.

A B2N monolayer: a direct band gap semiconductor with high and highly anisotropic carrier mobility

Two-dimensional materials with a planar lattice, suitable direct band gap, and high and highly anisotropic carrier mobility are desirable for the development of advanced field-effect transistors. Here we predict three thermodynamically stable B-rich 2D B-N compounds with the stoichiometries of B₂N, B₃N, and B₄N using a combination of crystal structure searches and first-principles calculations. Among them, B₂N has an ultraflat surface and consists of eight-membered B₆N₂ and pentagonal B₃N₂ rings. The eight-membered B₆N₂ rings are linked to each other through both edge-sharing (in the y direction) and bridging B₃N₂ pentagons (in the x direction). B₂N is a semiconductor with a direct band gap of 1.96 eV, and the nature of the direct band gap is well preserved in bilayer B₂N. The hole mobility of B₂N is as high as 0.6 × 10³ cm² V^-1 s^-1 along the y direction, 7.5 times that in the x direction. These combined novel properties render the B₂N monolayer as a natural example in the field of two-dimensional functional materials with broad application potential for use in field-effect transistors.