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Lithium-ion batteries (LIBs) are the most crucial part of energy storage systems. The lower molar weight of anodes can achieve a higher theoretical capacity. We explore the performance of a Be2B monolayer as an anode for LIBs. By first-principles calculations, we reveal that the Be2B monolayer shows excellent tensile strength, which suggests that it can deal with the volume expansion during the adsorption process. Furthermore, the Be2B monolayer can stably adsorb Li atoms with an adsorption energy of −0.98 eV. Moreover, the Be2B monolayer exhibits a low diffusion barrier (0.066 eV), an ultra-high theoretical capacity (3717 mA h g−1), and a moderate open circuit voltage (0.59 V). We also confirm the wettability of the Be2B monolayer in common electrolytes and investigate the adsorption and diffusion properties of Li on Be2B/graphene heterostructure. The introduction of graphene enhances the migration behavior of Li, suggesting the fast charging/discharging capability. Based on the above-mentioned properties, we propose that the Be2B monolayer can act as a high-performance anode material. [ABSTRACT FROM AUTHOR]

Developing two-dimensional (2D) carbon electrode materials with high performance has become an increasingly fascinating pursuit. However, the most popular carbon allotrope, graphene, possesses chemical inertness arising from its delocalized π-electron network. Breaking of the hexagonal symmetry in graphene can disrupt its π-conjugated system, thus increasing the surface reactivity. Here, by employing first-principles calculations, we predict a 2D carbon allotrope (called QH-graphene), which exhibits remarkable stability across the dynamic, thermal, and mechanical aspects. It has several advantages as an anode material for sodium-ion batteries (SIBs), including a high theoretical capacity (1116.7 mA h g−1), a moderate Na migration barrier (0.35–0.60 eV), a suitable average open-circuit voltage (0.55 V), and a small change in lattice parameters (∼3%). When contacted with electrolyte solvents, the Na adsorption and diffusion capabilities are enhanced. Moreover, introducing a monovacancy defect in QH-graphene improves the adsorption strength of Na but reduces its mobility. Compared with single-layer QH-graphene, QH-graphene bilayer has a stronger binding affinity for Na while maintaining rapid ion diffusion on its exterior surface. [ABSTRACT FROM AUTHOR]

Potassium-ion batteries (PIBs) demonstrate significant potential for future renewable energy storage systems, given the high natural richness and economic benefits of potassium resources. Nevertheless, the primary challenge hindering the development of PIBs is the scarcity of appropriate anode materials capable of delivering high performance. Using first-principles calculations, we theoretically design a two-dimensional graphene allotrope, termed TTH-graphene, constructed from assembled tetracyclo[6.6.0.02,6.010,14]tetradeca-1(8),2,4,6,9,11,13-heptaene (C14H8) structural units, which demonstrates good dynamical, thermal, and mechanical stability. The non-hexagonal symmetry can enhance the surface reactivity, making TTH-graphene a high-performance anode for PIBs with a low K migration barrier (0.22 eV), a moderate average open-circuit voltage (0.42 V), a high theoretical capacity (956.33 mA h g−1), and a small lattice expansion (1.2%). Furthermore, the appearance of vacancy defects enhances the K adsorption strength but induces the decrease in ionic diffusivity. Compared with the monolayer, the TTH-graphene bilayer exhibits an enhancement of the adsorption and diffusion performance of K on the outer surface. [ABSTRACT FROM AUTHOR]

As one of the most important energy storage systems, lithium-ion batteries (LIBs) attract much attention recently. Materials composed of beryllium or boron, due to the lighter molar weight, offer natural advantages for high energy density anode of LIBs. Here, we propose a two-dimensional tetragonal Be2B (T-Be2B) and investigate the performance as a potential anode for LIBs. Through first-principles calculations, T-Be2B exhibits excellent thermal, dynamic, and mechanical stability. As a semiconductor material with the bandgap of 0.303 eV, T-Be2B shows a strong capability to adsorb Li atoms. Furthermore, T-Be2B monolayer demonstrates a low diffusion barrier of 0.26 eV, a moderate theoretical capacity of 929 mA h g−1, and an average open-circuit voltage of 0.88 V. Additionally, the presence of vacancy defects weakens the adsorption ability and migration behavior of Li on T-Be2B, which should be carefully handled in the experimental preparation process of T-Be2B monolayer. Based on these properties, the T-Be2B monolayer has significant potential as an anode material for LIBs. [ABSTRACT FROM AUTHOR]

With the gradual development of renewable energy, search for high-performance energy storage materials as anodes for lithium-ion batteries (LIBs) has become urgent. Two-dimensional (2D) materials are considered as candidates for anode materials due to their unique structure and physicochemical properties. Based on first-principles calculations, we propose a 2D material, BC12 monolayer, as an excellent anode for LIBs. BC12 exhibits outstanding dynamic, mechanical, and thermal stability. In addition, BC12 monolayers show not only remarkably high storage capacity (2767.57 mA h g−1) but also low diffusion barrier energy (0.175 eV) and appropriate open circuit voltage (0.3 V). A small volume expansion (0.38%) is also observed during the lithiation process. Furthermore, we undertake a comprehensive analysis on the impact of carbon vacancy in BC12. The presence of carbon vacancy makes the adsorption and diffusion of Li relatively weak, which should be carefully handled in the experimental synthesis process. The above-mentioned investigation offers valuable insights and guidance for the future development and application of 2D anode materials in metal-ion batteries. [ABSTRACT FROM AUTHOR]

Using first-principles calculations, we propose a new two-dimensional Ge2S (space group P21212) with unique mechanical and electronic properties. Monolayer Ge2S has excellent thermal, mechanical, and dynamic stabilities, exhibiting a semiconducting behavior with an indirect bandgap and anisotropic carrier mobility. The uniaxial strain along the zigzag direction can induce an indirect-to-direct bandgap transition. Remarkably, Ge2S possesses large in-plane negative Poisson's ratios, comparable with that of well-known penta-graphene. Moreover, we identify Ge2S as a high-performance anode material for metal-ion batteries. It shows metallic features after adsorbing Na, K, and Mg, providing good electrical conductivity during the charge/discharge process. The diffusion of metal ions on Ge2S is anisotropic with modest energy barriers in the armchair direction of 0.12, 0.39, and 0.76 eV for Na, K, and Mg, respectively. Ge2S can adsorb metal atoms up to a stoichiometric ratio of 1:1, which yields storage capacities of 151.17, 151.17, and 302.35 mA h g−1 for Na, K, and Mg, respectively. The volume of Ge2S shrinks slightly upon the adsorption of metal ions even at high concentrations, ensuring a good cyclic stability. Besides, the average open circuit voltage (0.30–0.70 V) falls within the acceptable range (0.1–1.0 V) of the anode materials. These results make Ge2S a promising anode material for the design of future metal-ion batteries. [ABSTRACT FROM AUTHOR]

Unique structure of two-dimensional (2D) pentagonal materials makes them potentially valuable for applications in many fields, especially in electrode applications for lithium-ion batteries (LIBs). By means of first-principles calculations, we propose a 2D pentagonal material with an indirect bandgap of 2.551 eV, named a-BCP, exhibiting excellent thermodynamic, kinetic, and mechanical stabilities. Additionally, the structure remains stable with a cohesive energy of −5.827 eV at temperatures up to 1400 K, indicating the great chemical stability of a-BCP. Most importantly, a-BCP acting as the anode of LIBs demonstrates an ultra-high theoretical capacity of 2989.51 mA h g−1, a very low diffusion barrier of 0.13 eV, and small volume changes (−6.5%) in the intercalation/decalcification process, suggesting the potential of high energy density and high charge/discharge rate of LIBs. Furthermore, a-BCP possesses the appropriate reduction and oxidation potentials during water decomposition, making it an ideal material for photocatalytic water splitting. [ABSTRACT FROM AUTHOR]

High-performance sodium-ion batteries (SIBs) require anode materials with high capacity and fast kinetics. Based on first-principles calculations, we propose BC3N2 and BC3N2/graphene (B/G) heterostructure as potential SIB anode materials. The BC3N2 monolayer exhibits intrinsic metallic behavior. In addition, BC3N2 possesses a low Na+ diffusion barrier (0.15 eV), a high storage capacity (777 mA h g−1), a low open-circuit voltage (0.72 V), and a tiny axial expansion (0.36%). Compared with the BC3N2 monolayer, the B/G heterostructure exhibits a lower diffusion barrier of 0.027 eV, suggesting a much faster diffusion. More importantly, although the B/G heterostructure possesses heavier molar weight, its theoretical capacity (689 mA h g−1) is comparable to that of the BC3N2 monolayer. Based on the above-mentioned properties, we hope both the BC3N2 monolayer and the B/G heterostructure would be promising anodes for SIBs. [ABSTRACT FROM AUTHOR]

The demand for high-performance energy storage systems has stimulated intensive research on high-performance electrode materials for lithium-ion batteries (LIBs). Two-dimensional (2D) materials have emerged as promising candidates for anode materials due to their unique structural and physicochemical properties. Based on first-principles calculations, we propose a 2D material, B5C8 monolayer, as an excellent anode material for LIBs. B5C8 monolayer exhibits inherent metallicity and outstanding dynamic, mechanical, and thermal stability. Furthermore, B5C8 monolayer shows not only remarkably high storage capacity (2856 mA h g−1) but also low barrier energy (0.25 eV) and small volume change (2.1%). More importantly, B5C8 possesses strong wettability toward commonly used electrolytes in LIBs, namely, solvent molecules and metal salts, indicating prime compatibility. Based on the above distinguished findings, we hope B5C8 monolayer can act as a well-balanced performance anode material for LIBs. [ABSTRACT FROM AUTHOR]

Sodium-ion batteries (SIBs) have attracted much attention due to their abundant earth-reserves and low cost. Two-dimensional (2D) Dirac materials show great application prospects as anodes for SIBs because of their excellent electronic conductivity. We explore the performances of AlB4 (Al2B2) monolayers and bilayers as anodes for SIBs by using first-principles calculations. The AlB4 (Al2B2) monolayer exhibits a high theoretical storage capacity of 954.15 (709.17) mA h g−1 and a low diffusion barrier of 0.36 (0.03) eV. The calculated average open-circuit voltage (0.68/0.18 V) falls within the acceptance range of 0.1–1.0 V for anode materials. The fully sodiated AlB4 (Al2B2) monolayer shows a tiny lattice expansion of 0.9% (2.4%), suggesting good reversibility. Furthermore, in comparison with the AlB4 (Al2B2) monolayer, the AlB4 (Al2B2) bilayer can provide stronger binding with Na on the outside surface. These results contribute to a better understanding of the AlB4 (Al2B2) monolayers and bilayers as potential high-performance anode materials for SIBs. [ABSTRACT FROM AUTHOR]

Lithium-ion batteries (LIBs) remain irreplaceable for clean energy storage applications. The intrinsic metallic nature of penta-SiCN ensures its promising application in the electrodes of LIBs. Using first-principles calculations, we evaluate the performance of the intrinsic metallic penta-SiCN monolayer as the anode material for LIBs. Penta-SiCN exhibits a low diffusion energy barrier (0.107 eV) for Li atom migration on Si18C18N18, while the diffusion energy barrier for vacancy migration on Li17Si18C18N18 is only 0.006 eV. Additionally, penta-SiCN possesses a high theoretical capacity of 1485.98 mA h g−1, average open-circuit voltage of 0.97 V, and small volume expansion of 1%. Remarkably, penta-SiCN exhibits robust wettability towards the electrolytes (solvent molecules and metal salts) widely used in commercial LIBs, indicating the excellent compatibility in electrode applications. These intriguing theoretical findings make penta-SiCN a high performance anode material for LIBs. [ABSTRACT FROM AUTHOR]

Carbonaceous materials are considered the most promising anode materials for sodium-ion batteries (SIBs) due to their abundant active sites, high electronic conductivity, and good mechanical stability. However, two typical types of carbon materials, graphite and graphene, are unsuitable for Na storage arising from π-electron delocalization. The introduction of Janus structure in graphene can disrupt the extended sp2 conjugated network and thus enhance the surface reactivity. Herein, inspired by the dissymmetric structural characteristics of triquinacene, we construct a metallic two-dimensional Janus carbon allotrope, termed TQ-graphene. After confirming its dynamical, thermal, and mechanical stability, we find that TQ-graphene is an auxetic material with large in-plane negative Poisson's ratios. Furthermore, it exhibits excellent performance as an anode material for SIBs with an extremely high capacity of 2436 mA h g–1, a small diffusion barrier (0.01∼0.34 eV), and a low average voltage (0.32 V). [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) carbon materials integrated with planar tetracoordinate carbon (ptC) and negative Poisson's ratio (NPR) provide a cornerstone for constructing multifunctional energy-storage devices. As a typical 2D carbon material, the pristine graphene is chemically inert, hindering its application in metal-ion batteries. Introducing the ptC in graphene can break the extended conjugation of π-electrons and lead to an enhanced surface reactivity. Inspired by the unique geometry of [4.6.4.6] fenestrane skeleton with ptC, we theoretically design a ptC-containing 2D carbon allotrope, namely THFS-carbon. It is intrinsically metallic with excellent dynamical, thermal, and mechanical stabilities. The Young's modulus along the x direction (311.37 N m−1) is comparable to that of graphene. Intriguingly, THFS-carbon possesses an in-plane half-NPR distinct from most other 2D crystals. As a promising anode for sodium-ion batteries, THFS-carbon delivers an ultra-high theoretical storage capacity (2233 mA h g−1), a low diffusion energy barrier (0.03–0.05 eV), a low open-circuit voltage (0.14–0.40 V), and a good reversibility for Na insertion/extraction. [ABSTRACT FROM AUTHOR]

Magnesium-ion batteries (MIBs) are expected to be an alternative to lithium-ion batteries due to the lower cost and immanent safety of Mg. Presently, the major difficulty in breaking through MIBs technology is the lack of desirable anode materials. Based on first-principles calculations, we predict a two-dimensional material named the Be2B monolayer as an excellent anode material. The structural stability is confirmed by superior cohesive energy, positive phonon modes, excellent thermal stability, and strong mechanical stability. Afterward, we explore the performance of the Be2B monolayer as the anode material for MIBs. It exhibits stable Mg atom adsorption with an energy of −0.7 eV, low diffusion barrier (0.1 eV), ultra-high specific capacity (7436 mA h g−1), tiny lattice expansion (0.3%), and low average open-circuit voltage (0.29 V). Thereby, the above-mentioned intriguing findings suggest that the Be2B monolayer can act as a promising anode material for high performance MIBs. [ABSTRACT FROM AUTHOR]

Na-ion batteries (NIBs) have attracted a great deal of attention for large-scale electric energy storage due to their inherent safety, natural abundant resources, and low cost. The exploration of suitable anode materials is the major challenge in advancing NIB technology. On the basis of first-principles calculations, we systematically explore the potential performance of two-dimensional (2D) TiCl2 as an electrode material for NIBs. Monolayer TiCl2 can be easily exfoliated from the bulk structure with a small exfoliation energy of 0.64 J m−2. It shows good stability, as demonstrated by its high cohesive energy, positive phonon modes, and high thermal stability. Monolayer TiCl2 has high storage capacity (451.3 mA h g−1), low diffusion energy barrier (0.02–0.14 eV), moderate average open-circuit voltage (0.81 V), and small lattice change (2.37%). Moreover, bilayer TiCl2 can significantly enhance the Na adsorption strength but reduce the Na-ion diffusion ability. These results suggest that TiCl2 is a promising anode candidate for NIBs. [ABSTRACT FROM AUTHOR]

Sodium-ion batteries (SIBs) are promising candidates for large-scale energy storage due to the abundance and low cost of sodium. However, graphite, the primary anode for commercial lithium-ion batteries, cannot be applied to SIBs. Its two-dimensional (2D) counterpart graphene is also inactive toward Na ions because of the delocalized π-electron network. We propose an idea to tackle this problem by introducing kagome topology into the honeycomb lattice, creating localized electronic states for improving the Na storage performance. Herein, we design a form of 2D carbon allotrope (named FSL-graphene), consisting of a kagome and a honeycomb sublattice. It has excellent stability, which is confirmed by the superior cohesive energy, positive phonon modes, high thermal stability, and strong mechanical stability. FSL-graphene exhibits an ultra-high theoretical Na storage capacity of 3347.1 mA h g−1, superior to most previously reported 2D anode materials. In addition, it possesses low diffusion energy barriers (0.19–0.23 eV), low open-circuit voltages (0.59–0.61 V), and small changes in lattice constants (1.3%). Furthermore, the electrolytes with high dielectric constants (e.g., ethylene carbonate) could improve the adsorption and migration of Na on FSL-graphene. This study provides an insight for designing high-performance carbon anode materials for SIBs by focusing on the topological lattices. [ABSTRACT FROM AUTHOR]