Physical properties of silicene electrodes for Li-, Na-, Mg-, and K-ion batteries

Ab Initio Study of the Electronic Properties of a Silicene Anode Subjected to Transmutation Doping

In the present work, the electronic properties of doped silicene located on graphite and nickel substrates were investigated by first-principles calculations method. The results of this modeling indicate that the use of silicene as an anode material instead of bulk silicon significantly improves the characteristics of the electrode, increasing its resistance to cycling and significantly reducing the volume expansion during lithiation. Doping of silicene with phosphorus, in most cases, increases the electrical conductivity of the anode active material, creating conditions for increasing the rate of battery charging. In addition, moderate doping with phosphorus increases the strength of silicene. The behavior of the electronic properties of doped one- and two-layer silicene on a graphite substrate was studied depending on its number and arrangement of phosphorus atoms. The influence of the degree of doping with silicene/Ni heterostructure on its band gap was investigated. We considered the single adsorption of Li, Na, K, and Mg atoms and the polyatomic adsorption of lithium on free-standing silicene.

Computational Modeling of Doped 2D Anode Materials for Lithium-Ion Batteries

Development of high-performance lithium-ion batteries (LIBs) is boosted by the needs of the modern automotive industry and the wide expansion of all kinds of electronic devices. First of all, improvements should be associated with an increase in the specific capacity and charging rate as well as the cyclic stability of electrode materials. The complexity of experimental anode material selection is now the main limiting factor in improving LIB performance. Computer selection of anode materials based on first-principles and classical molecular dynamics modeling can be considered as the main paths to success. However, even combined anodes cannot always provide high LIB characteristics and it is necessary to resort to their alloying. Transmutation neutron doping (NTD) is the most appropriate way to improve the properties of thin film silicon anodes. In this review, the effectiveness of the NTD procedure for silicene/graphite (nickel) anodes is shown. With moderate P doping (up to 6%), the increase in the capacity of a silicene channel on a Ni substrate can be 15-20%, while maintaining the safety margin of silicene during cycling. This review can serve as a starting point for meaningful selection and optimization of the performance of anode materials.

Electronic Properties and Structure of Silicene on Cu and Ni Substrates

Silicene, together with copper or nickel, is the main component of electrodes for solar cells, lithium-ion batteries (LIB) and new-generation supercapacitors. The aim of this work was to study the electronic properties and geometric structure of “silicene–Ni” and “silicene–Cu” systems intended for use as LIB electrodes. The densities of electronic states, band structures, adhesion energies and interatomic distances in the silicene–(Cu, Ni) systems were determined by ab initio calculations. Silicene on a copper substrate exhibited temperature stability in the temperature range from 200 to 800 K, while on a nickel substrate, the structure of silicene was rearranged. Adsorption energies and bond lengths in the “silicene–Cu” system were calculated in the range of Li/Si ratios from 0.125 to 0.5. The formation of the Li₂ isomer during the adsorption of lithium in a ratio to silicon of 0.375 and 0.5 was observed. Silicene was found to remain stable when placed on a copper substrate coated with a single layer of nickel. The charge redistribution caused by the addition of a nickel intermediate layer between silicene and a copper substrate was studied.

Charged lithium adsorption on pristine and defective silicene: a theoretical study

We investigated by first principle calculations the adsorption of Li^q(q= -1, 0 or +1) on a silicene single layer. Pristine and three different defective silicene configurations with and without Li doping were studied: single vacancy (SV), double vacancy (DV) and Stone-Wales (STW). Structural studies and the adsorption energies of various sites were obtained and compared in order to understand the stability of the Li on the surface. Moreover, electronic structure and charge density difference analysis were performed before and after adsorption at the most stables sites, which showed the presence of a magnetic moment in the undoped SV system, the displacement of the Fermi level produced by Li doping and a charge transfer from Li to the surface. Additionally, quantum capacity (QC) and charge density studies were performed on these systems. This analysis showed that the generation of defects and doping improves the QC of silicene in positive bias, because of the existence of 3p orbital in the zone of the defect. Consequently, the innovative calculations performed in this work of charged lithium doping on silicene can be used for future comparison with experimental studies of this Li-ion battery anode material candidate.

Feasibility study of Mg storage in a bilayer silicene anode via application of an external electric field

With the goal of developing a Si-based anode for Mg-ion batteries (MIBs) that is both efficient and compatible with the current semiconductor industry, the current research utilized classical Molecular Dynamics (MD) simulation in investigating the intercalation of a Mg²⁺ ion under an external electric field (E-field) in a 2D bilayer silicene anode (BSA). First principles density functional theory calculations were used to validate the implemented EDIP potentials. Our simulation shows that there exists an optimum E-field value in the range of 0.2–0.4 V Å⁻¹ for Mg²⁺ intercalation in BSA. To study the effect of the E-field on Mg²⁺ ions, an exhaustive spread of investigations was carried out under different boundary conditions, including calculations of mean square displacement (MSD), interaction energy, radial distribution function (RDF), and trajectory of ions. Our results show that the Mg²⁺ ions form a stable bond with Si in BSA. The effects of E-field direction and operating temperature were also investigated. In the X–Y plane in the 0°–45° range, 15° from the X-direction was found to be the optimum direction for intercalation. The results of this work also suggest that BSA does not undergo drastic structural changes during the charging cycles with the highest operating temperature being ∼300 K.

With the goal of developing a Si-based anode for Mg-ion batteries (MIBs), classical Molecular Dynamics (MD) was utilized in investigating the intercalation of a Mg²⁺ ion under an external electric field (E-field) in a 2D bilayer silicene anode (BSA).

Blue-AsP monolayer as a promising anode material for lithium- and sodium-ion batteries: a DFT study

Based on first-principle calculations, we proposed a one two-dimensional (2D) blue AsP (b-AsP) monolayer as an ideal anode material for lithium/sodium-ion (Li/Na-ion) batteries for the first time. The b-AsP monolayer possesses thermal and dynamic stabilities. The system undergoes the transition from semiconductor to metal after Li/Na atoms are embedded, which ensures good electric transportation. Most remarkably, our results indicate that the b-AsP monolayer exhibits high theoretical capacities of 1011.2 mA h g^-1 (for Li) and 1769.6 mA h g^-1 (for Na), low average open circuit voltages of 0.17 eV for Li₄AsP and 0.14 eV for Na₇AsP systems and ultrafast diffusivity with the low energy barriers of 0.17/0.15 eV and 0.08/0.07 eV of the P/As sides for Li and Na, respectively. Given these exceptional properties, the synthesis of a buckled b-AsP monolayer is desired to achieve a promising electrode material for Li- and Na-ion batteries.

Two-dimensional C3N/blue phosphorene vdW heterostructure for Li, Na and K-ion batteries

We investigate a van der Waals heterostructure constructed using BP and C₃N and investigate its use as an anode for lithium-, sodium- and potassium-ion batteries.

Approaching high-performance potassium-ion batteries via advanced design strategies and engineering

Potassium-ion batteries (PIBs) have attracted tremendous attention due to their low cost, fast ionic conductivity in electrolyte, and high operating voltage. Research on PIBs is still in its infancy, however, and achieving a general understanding of the drawbacks of each component and proposing research strategies for overcoming these problems are crucial for the exploration of suitable electrode materials/electrolytes and the establishment of electrode/cell assembly technologies for further development of PIBs. In this review, we summarize our current understanding in this field, classify and highlight the design strategies for addressing the key issues in the research on PIBs, and propose possible pathways for the future development of PIBs toward practical applications. The strategies and perspectives summarized in this review aim to provide practical guidance for an increasing number of researchers to explore next-generation and high-performance PIBs, and the methodology may also be applicable to developing other energy storage systems.

Understanding the Thermal Treatment Effect of Two-Dimensional Siloxene Sheets and the Origin of Superior Electrochemical Energy Storage Performances

Two-dimensional siloxene sheets are an emerging class of materials with an eclectic range of potential applications including electrochemical energy conversion and storage sectors. Here, we demonstrated the dehydrogenation/dehydroxylation of siloxene sheets by thermal annealing at high temperature (HT) and investigated their supercapacitive performances using ionic liquid electrolyte. The X-ray diffraction analysis, spectroscopic (Fourier transform infrared, laser Raman, and X-ray photoelectron spectroscopy) studies, and morphological analysis of HT-siloxene revealed the removal of functional groups at the edges/basal planes of siloxene, and preservation of oxygen-interconnected Si₆ rings with sheet-like structures. The HT-siloxene symmetric supercapacitor (SSC) operates over a wide potential window (0-3.0 V), delivers a high specific capacitance (3.45 mF cm^-2), high energy density of about 15.53 mJ cm^-2 (almost 2-fold higher than that of the as-prepared siloxene SSC), and low equivalent series resistance (compared to reported silicon-based SSCs) with excellent rate capability and long cycle life over 10 000 cycles.