Intercalation Of Species Research Articles

A review of the synthesis and application of azo dyes and metal complexes for emerging antimicrobial therapies

Antimicrobial resistance presents a formidable challenge to contemporary medicine, necessitating innovative therapeutic solutions. Azo dyes and their metal complexes have emerged as promising candidates due to their notable antimicrobial properties. This review comprehensively examines the synthesis and application of azo dyes and metal complexes for emerging antimicrobial therapies. Through various synthetic strategies and metallation, the chemical structure of azo derivatives allows for modifications that enhance their antimicrobial efficacy, making them promising candidates for pharmaceutical development against microbial infections. The study provides a comprehensive understanding of the mechanisms of antimicrobial action, including DNA intercalation, enzyme inhibition, membrane disruption, and reactive oxygen species generation. The role of metal ions is particularly significant, enhancing structural stability, reactivity, and the ability to target microbial enzymes effectively. Chelation effects, such as reduced polarity and increased lipophilicity, facilitate the penetration of microbial cell membranes and the disruption of enzyme activity. The review highlights novel azo-metal complexes’ significant antifungal and antibacterial activities, particularly their efficacy against pathogens such as Mycobacterium tuberculosis. The importance of structure-activity relationships is detailed, showing how specific functional groups and metal ions influence antimicrobial efficacy. Additionally, their potential sensing ability to detect and identify microorganisms highlights the multifaceted role of azo dye derivatives in infection management.

Improving cycling performance of the NaNiO2 cathode in sodium-ion batteries by titanium substitution

O3-type layered oxide cathodes, such as NaNi0.5Mn0.5O2, have garnered significant attention due to their high theoretical specific capacity while using abundant and low-cost sodium as intercalation species. Unlike the lithium analog (LiNiO2), NaNiO2 (NNO) exhibits poor electrochemical performance resulting from structural instability and inferior Coulomb efficiency. To enhance its cyclability for practical application, NNO was modified by titanium substitution to yield the O3-type NaNi0.9Ti0.1O2 (NNTO), which was successfully synthesized for the first time via a solid-state reaction. The mechanism behind its superior performance in comparison to that of similar materials is examined in detail using a variety of characterization techniques. NNTO delivers a specific discharge capacity of ∼190 mAh g−1 and exhibits good reversibility, even in the presence of multiple phase transitions during cycling in a potential window of 2.0‒4.2 V vs. Na+/Na. This behavior can be attributed to the substituent, which helps maintain a larger interslab distance in the Na-deficient phases and to mitigate Jahn–Teller activity by reducing the average oxidation state of nickel. However, volume collapse at high potentials and irreversible lattice oxygen loss are still detrimental to the NNTO. Nevertheless, the performance can be further enhanced through coating and doping strategies. This not only positions NNTO as a promising next-generation cathode material, but also serves as inspiration for future research directions in the field of high-energy-density Na-ion batteries.

Deciphering the Role of Nickel in Electrochemical Organic Oxidation Reactions

AbstractOrganic oxidation reactions (OORs) powered by renewable energy sources are gaining importance as a favorable alternative to oxygen evolution reaction, with the promise of reducing the cell potential and enhancing the overall viability of the water electrolysis. This comprehensive review delves into the electrochemical oxidation of diverse organic compounds, including alcohols, aldehydes, amines, and urea, as well as biomass‐derived renewable feedstocks such as hydroxymethylfurfural and glycerol. The key focus centers on the role of nickel (Ni)‐based catalysts for these OORs. The unique redox activity and chemical nature of Ni have been proven instrumental for the sustainable and cost‐effective oxidation of various organic molecules more efficiently and selectively. This review article discusses how strategic choices, such as the selection of foreign metals, intercalating species, vacancies, defects, and a secondary element (e.g. chalcogens and non‐metals), contribute to tuning the electrochemical performances of a Ni‐based (pre)catalyst for OORs. Moreover, this review provides insights into the active species in various reaction environments and further explores reaction mechanisms, to apparent phase changes of the catalyst with the most relevant examples. Finally, the review not only elucidates the limitations of the current approaches but also outlines potential avenues for future advancements in OOR.

Screening of Metal-Ion Intercalated Yttrium Carbide and Nitride MXenes for Energy Storage Applications via Density Functional Theory

Rechargeable batteries and energy storage devices play a major role in many facets of human endeavour due to their efficiency and portability. In this work, we investigated the suitability of single-layer intercalated Yttrium-based MXenes Y2CT2 (T= Li, Mg, Al) and Y2NLi2 as potential energy storage materials using the first principle calculation within the framework of the density functional theory approach. Upon intercalation, the lattice constants of the MXenes expand due to the size of the intercalating species and the electrostatic repulsion. We obtained the theoretical gravimetric capacities, open circuit voltages and adsorption energies. The obtained open circuit voltages for Y2CT2 (T= Li, Mg) and Y2NLi2 falls within the voltage window of 0 − 1.0V which has been found to eliminate dendrites formation caused by alkaline metals during the discharge-charge cycle. The adsorption energies indicate the stability of the intercalating ion on the MXenes surfaces except for Al cation. The results are consistent with other studies on similar MXene families in the existing literature. The work may aid the understanding of the electrochemical properties of 2D materials and we recommend Y2CLi2, Y2NLi2 , and Y2CMg2 for future investigation as potential materials for rechargeable batteries.

Electrochemical Properties of MXene Electrodes in Aqueous Zinc Electrolytes

MXenes are a family of two-dimensional (2D) transition metal carbonitrides, with a general structure of M n +1X n T x , where M is the transition metal, X is carbon or nitrogen, T represents the surface terminations (F, O, OH), and n can vary from 1-4. MXenes have shown promise in multiple electrochemical systems including aqueous supercapacitors and non-aqueous batteries containing monovalent cations. However, there have been limited works studying the electrochemical properties of these materials in aqueous electrolytes with multivalent cations such as Zn2+ and Mg2+. MXenes have high (electro)chemical stability in halide zinc electrolyte systems unlike many oxide materials. Herein, the charge storage mechanism of Ti3C2T x was studied in multiple Zn containing aqueous electrolytes. In-situ XRD and in-situ UV-Vis were employed to monitor the intercalating species and redox response in the electrodes. Ti3C2T x electrodes could deliver battery-like performance at low rates with supercapacitor performance at high rates. This work demonstrates the potential of using MXenes in zinc ion capacitors and zinc hybrid energy storage devices.

Thermal Stability of Graphite Electrode as Cathode for Dual-Ion Batteries.

The increasing number of accidents relating to battery fire and explosion is raising people's attention towards safety of batteries. Abnormal battery operation can generate much heat and cause thermal runaway due to the exothermic reactions of the electrodes and electrolyte. Recently, dual-ion battery (DIB) has gained many interests because of its low cost and high working voltage compared with traditional lithium-ion battery (LIB). However, investigation on thermal stability of DIB is rare. In this paper, differential scanning calorimetry (DSC) was used to study the thermal stability of DIB using graphite as cathode with different states of charge (SOC) and with different amount of fluoroethylene carbonate as co-solvent in the electrolyte. Then, the thermal stability of graphite cathode for DIB was compared with those of LiCoO2 and LiNi0.5 Mn1.5 O4 at their fully charged states. Specifically, charged DIB using graphite as cathode in 3 m LiPF6 EMC showed superior thermal stability with no exothermic peaks in DSC tests, in contrast to traditional lithium-containing cathodes for LIB, which gave out significant amount of heat at evaluated temperature. In addition, the thermal stability of graphite depended on the type of intercalation species in it. While PF6 - intercalated graphite [Cn (PF6 )] showed an endothermic peak at about 320 °C, Li+ intercalated graphite [Cn (Li)] showed an exothermic peak at about 300 °C. Moreover, the type of electrolyte also affected heat generation from the charged electrodes and should be properly designed to improve thermal stability in the future.

High Entropy van der Waals Materials.

By breaking the restrictions on traditional alloying strategy, the high entropy concept has promoted the exploration of the central area of phase space, thus broadening the horizon of alloy exploitation. This review highlights the marriage of the high entropy concept and van der Waals systems to form a new family of materials category, namely the high entropy van der Waals materials (HEX, HE = high entropy, X = anion clusters) and describes the current issues and next challenges. The design strategy for HEX has integrated the local feature (e.g., composition, spin, and valence states) of structural units in high entropy materials and the holistic degrees of freedom (e.g., stacking, twisting, and intercalating species) in van der Waals materials, and is successfully used for the discovery of high entropy dichalcogenides, phosphorus tri‐chalcogenides, halogens, and MXene. The rich combination and random distribution of the multiple metallic constituents on the nearly regular 2D lattice give rise to a flexible platform to study the correlation features behind a range of selected physical properties, e.g., superconductivity, magnetism, and metal–insulator transition. The deliberate design of structural units and their stacking configuration can also create novel catalysts to enhance their performance in a bunch of chemical reactions.

Cost-Effective Calculation of Collective Electronic Excitations in Graphite Intercalated Compounds.

Graphite/graphene intercalation compounds with good and improving electrical transport properties, optical properties, magnetic properties and even superconductivity are widely used in battery, capacitors and so on. Computational simulation helps with predicting important properties and exploring unknown functions, while it is restricted by limited computing resources and insufficient precision. Here, we present a cost-effective study on graphite/graphene intercalation compounds properties with sufficient precision. The calculation of electronic collective excitations in AA-stacking graphite based on the tight-binding model within the random phase approximation framework agrees quite well with previous experimental and calculation work, such as effects of doping level, interlayer distance, and interlayer hopping on 2D plasmon and 3D intraband plasmon modes. This cost-effective simulation method can be extended to other intercalation compounds with unlimited intercalation species.

High‐Performance Aqueous Rechargeable K/Zn Hybrid Batteries Based on Berlin Green Cathode Materials

AbstractAbstract: Aqueous rechargeable zinc‐based batteries with the advantages of sustainability, safety, and low cost, are suitable for large‐scale electrochemical energy storage applications. In this work, aqueous zinc‐based batteries with low defect Berlin green (FeHCF) cathode, a hybrid zinc triflate and potassium triflate electrolyte, and zinc anodes are developed. In the hybrid electrolyte, the K+ ions with the weak solvation effect and small electrostatic interaction are the dominant intercalation species in the FeHCF, resulting in the fast charge transfer process and rapid diffusion kinetics. The Zn2+ ions stay at the surface rather than penetrate into the bulk phase. Thus, the hybrid batteries deliver a high specific capacity of 169.2 mAh g−1 at 100 mA g−1, excellent rate performance with 45.7 mAh g−1 at 6 A g−1, and good long‐term cyclability with a capacity retention of 57 % over 1000 cycles at 1 A g−1. The results suggest using aqueous K/Zn hybrid electrolytes can improve the electrochemical performance of FeHCF.

Unraveling the multivalent aluminium-ion redox mechanism in 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA).

Rechargeable Aluminium-organic batteries are an exciting emerging energy storage technology owing to their low cost and promising high performance, thanks to the ability to allow multiple-electron redox chemistry and multivalent Al-ion intercalation. In this work, we use a combination of Density Functional Theory (DFT) calculations and experimental methods to examine the mechanism behind the charge-discharge reaction of the organic dye 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) in the 1,3-ethylmethylimidazolium (EMIm+) chloroaluminate electrolyte. We conclude that, contrary to previous reports claiming the intercalation of trivalent Al3+, the actual ionic species involved in the redox reaction is the divalent AlCl2+. While a less-than-ideal scenario, this mechanism still allows a theoretical transfer of four electrons per formula unit, corresponding to a remarkable specific capacity of 273 mA h g-1. However, the poor reversibility of the reaction and low cycle life of the PTCDA-based cathode, due to its solubility in the electrolyte, make it an unlikely candidate for a commercial application.

Ladder Mechanisms of Ion Transport in Prussian Blue Analogues.

Prussian blue (PB) and its analogues (PBAs) are drawing attention as promising materials for sodium-ion batteries and other applications, such as desalination of water. Because of the possibilities to explore many analogous materials with engineered, defect-rich environments, computational optimization of ion-transport mechanisms that are key to the device performance could facilitate real-world applications. In this work, we have applied a multiscale approach involving quantum chemistry, self-consistent mean-field theory, and finite-element modeling to investigate ion transport in PBAs. We identify a cyanide-mediated ladder mechanism as the primary process of ion transport. Defects are found to be impermissible to diffusion, and a random distribution model accurately predicts the impact of defect concentrations. Notably, the inclusion of intermediary local minima in the models is key for predicting a realistic diffusion constant. Furthermore, the intermediary landscape is found to be an essential difference between both the intercalating species and the type of cation doping in PBAs. We also show that the ladder mechanism, when employed in multiscale computations, properly predicts the macroscopic charging performance based on atomistic results. In conclusion, the findings in this work may suggest the guiding principles for the design of new and effective PBAs for different applications.

Elucidating the Charge Storage Mechanism of MnO2 in Aqueous Aluminum Batteries

The rapid development of renewable energy technologies entails the demand for high-performance energy storage devices for effective on-demand utilization. The sustainable future of the commonly used lithium-ion battery is critically debatable, as a result of the imminent exhaustion of the Li and Co resources and their geopolitically restricted abundance. To this end, rechargeable aluminum-ion batteries (AIBs) are gaining considerable attention owing to the favorable characteristics of aluminum (Al) metal, including high natural abundance, low cost, ease of handling in an ambient environment as well as a high theoretical gravimetric and volumetric capacity (2981 mAh g−1 and 8046 mAh cm−3, respectively).Existing chloroaluminate ionic liquid electrolyte employed in AIBs serve as (i) a medium for ion transportation, and concurrently, (ii) as an active material known as liquid anode/anolyte. This fundamentally limits the achievable capacity of chloroaluminate IL-based AIBs at the cell level. Moreover, drawbacks including ambient sensitivity, high cost, toxicity, high corrosivity, and low conductivity limit the non-aqueous AIBs for large-scale application. To address these limitations, research attention has therefore been shifted towards aqueous electrolytes lately, owing to their stability in ambient environment, cost-effectiveness, and high ionic conductivity. Transitional metal oxide-based materials of high theoretical capacity were being explored in the aqueous aluminum electrolytes with appreciable electrochemical performance attained. However, the underlying charge storage mechanism involved remains equivocal.In this work, we comprehensively investigate the electrochemical performance and intercalation mechanism of alpha manganese dioxide (α-MnO2) electrode in aqueous aluminum trifluoromethanesulfonate (Al(OTF)3) electrolyte through various electrochemical techniques and extensive spectroscopic characterizations, and an alternative charge storage mechanism is proposed. With a combination of the electrochemical and the spectroscopic analysis, we observe that H3O+ is the dominant intercalation species and H3O+ intercalation/de-intercalation contributes to the reversible capacity of α-MnO2 over cycles in aqueous aluminum electrolytes, while a small amount of Al3+ could also intercalate into α-MnO2. The formation of the surface complex during discharge is observed, which may contain Al3+, OH-, and OTF-. After charge, this surface complex would dissolve. Lastly, we offer recommendations on prospective electrode and electrolyte design using the insights obtained from this study. We expect that our findings will shed light on achieving high-performance aluminum-based energy storage devices.

Influence of the Nanotube Morphology and Intercalated Species on the Sorption Properties of Hybrid Layered Vanadium Oxides: Application for Cesium Removal from Aqueous Streams.

The present paper examines the impact that the nanotube morphology and organic or inorganic intercalated species may have on the cesium sorption by layered vanadium oxides prepared with the use of hexadecylamine as a structure-directing agent. The hybrid material represented by a chemical formula of (V2O5)(VO2)1.03(C16H36N)1.46(H2O)x was achieved through accelerated microwave-assisted synthesis carefully optimized to ensure the best compromise between the scroll-like morphology and the hydrophobic character. To enhance its dispersibility in water, this sample was subsequently modified by progressive replacement of the C16H36N+ units by NH4+ cations. The final materials represented a stacking of lamellar sheets with a worse scroll-like morphology. Both the optimization procedure and the template removal were monitored on the basis of scanning and transmission electronic microscopy, X-ray diffraction, infra-red spectroscopy, inductively coupled plasma-optical emission spectrometry, X-ray photoelectron spectroscopy, and elemental analysis, supplemented by adequate simulations methods providing the reference IR spectra and XRD patterns for comparison or the textural parameters of the samples. The comparison of the cesium sorption from either a 4:1 ethanol–water mixture or aqueous solutions pointed toward the solubility of intercalated cations in the bulk solution as the main factor limiting their displacement from the interlayer space by the oncoming cesium ones. The sample obtained after 70% exchange with NH4+ exhibited a maximum sorption capacity of 1.4 mmol g−1 from CsNO3 aqueous solutions and its retention efficiency remained significant from low-concentration Cs solutions in river or sea water.

In-situ polymerization into the basal spacing of LDH for selective and enhanced uranium adsorption: A case study with real life uranium alkaline leach liquor

Uranium is used as a fuel for nuclear power plant and can be extracted from different ores, mainly acidic (silicious ore) and alkaline (carbonate ore). Recovery of uranium through acid leaching from silicious ore is well established, whereas, alkaline leaching from carbonate ore is challenging due to the excessive salinity of leach liquor and high concentration of carbonate, bicarbonate and sulphate. Herein, two monomers, acrylic acid (AA) and N, N-methylene bisacrylamide (BAM), selective towards uranyl were intercalated in-situ into the interlayer, followed by their polymerization and cross-linking to form novel polymer intercalated hybrid layered double hydroxide (LDH). The LDH acts as a backbone to overcome coiling and swelling of polymer and anchors them as free-standing. Various parameters, like, the type of metal ions, monomer ratio (AA: BAM) and metal ion ratio (M2+:M3+), were studied to determine the optimum conditions for effective intercalation and polymerization of monomers. Magnesium aluminum (MgAl) LDH with a cross-linked polymer having a monomer ratio of 3:2 (AA: BAM) as intercalating species showed maximum efficiency of uranyl adsorption (1456 mg/g at 30 °C) with highest capacity so far. The distribution coefficient (Kd, l/mg) in the order of 105 suggested that the adsorbent was highly selective for uranyl in the presence of different cations, anions and humic acid. The adsorbent extracts uranium effectively and selectively from a real-life alkaline leach liquor with an efficiency of 96% at 5 g/l dose. Uranium can be recovered from the adsorbent in the form of sodium di-uranate using 2(M) NaOH and was reused for eight cycles.

Intercalated Iron Chalcogenides: Phase Separation Phenomena and Superconducting Properties.

Organic molecule-intercalated layered iron-based monochalcogenides are presently the subject of intense research studies due to the linkage of their fascinating magnetic and superconducting properties to the chemical nature of guests present in the structure. Iron chalcogenides have the ability to host various organic species (i.e., solvates of alkali metals and the selected Lewis bases or long-chain alkylammonium cations) between the weakly bound inorganic layers, which opens up the possibility for fine tuning the magnetic and electrical properties of the intercalated phases by controlling both the doping level and the type/shape and orientation of the organic molecules. In recent years, significant progress has been made in the field of intercalation chemistry, expanding the gallery of intercalated superconductors with new hybrid inorganic–organic phases characterized by transition temperatures to a superconducting state as high as 46 K. A typical synthetic approach involves the low-temperature intercalation of layered precursors in the presence of liquid amines, and other methods, such as electrochemical intercalation, intercalant or ion exchange, and direct solvothermal growths from anhydrous amine-based media, are also being developed. Large organic guests, while entering a layered structure on intercalation, push off the inorganic slabs and modify the geometry of their internal building blocks (edge-sharing iron chalcogenide tetrahedrons) through chemical pressure. The chemical nature and orientation of organic molecules between the inorganic layers play an important role in structural modification and may serve as a tool for the alteration of the superconducting properties. A variety of donor species well-matched with the selected alkali metals enables the adjustment of electron doping in a host structure offering a broad range of new materials with tunable electric and magnetic properties. In this review, the main aspects of intercalation chemistry are discussed, involving the influence of the chemical and electrochemical nature of intercalating species on the crystal structure and critical issues related to the superconducting properties of the hybrid inorganic–organic phases. Mutual relations between the host and organic guests lead to a specific ordering of molecular species between the host layers, and their effect on the electronic structure of the host will be also argued. A brief description of a critical assessment of the association of the most effective chemical and electrochemical methods, which lead to the preparation of nanosized/microsized powders and single crystals of molecularly intercalated phases, with the ease of preparation of phase pure materials, crystal sizes, and the morphology of final products is given together with a discussion of the stability of the intercalated materials connected with the volatility of organic solvents and a possible degradation of host materials.

Nominal Effect of Mg Intercalation on the Superconducting Properties of 2H-NbSe2.

2H-NbSe2 is a phonon-mediated, Fermi-surface topology-dependent multiband superconductor with an incommensurate charge-density wave (CDW) that coexists at a local level with superconductivity. Usually, the intercalation in 2H-NbSe2 enriches the CDW, enhances the c-axis lattice parameter, and distorts the Fermi surface, which result in a decrease in the superconducting transition temperature (Tc). The rate of decrease of Tc depends on the electronic structure, size, valence, magnetic nature, and electronegativity of the intercalating species. Herein, we report an unusual effect of Mg intercalation on the superconductivity of 2H-MgxNbSe2 (x = 0.0, 0.02, 0.06, 0.08, 0.10, and 0.12) synthesized by a high-temperature solid-state reaction method. Unlike other s- and p-block elements/species as intercalants (Rb, Sn, Ga, and Al) that have a sharp detrimental effect on the Tc of 2H-NbSe2 within 1-5% of intercalation, Mg is found to be an exception. Upon Mg intercalation up to x = 0.06, no remarkable changes in Tc as compared to the parent 2H-NbSe2 (Tc ∼ 6.7 K) are observed, and further intercalation results in a small decrease in Tc (for x = 0.12, Tc = 6.2 K). From heat-capacity measurements, it is inferred that superconducting Mg-intercalated 2H-NbSe2 exhibits strong electron-phonon coupling. Electronic structure calculations on two s-block element intercalated compounds of formula M0.125NbSe2 (M = Mg, Rb) show that Rb s-, p-, and d-states completely overlap with the Nb d states, while the Mg s states lie in a low-energy region as compared to Nb d states, indicating a weak interaction between the intercalant and the Nb sublattice in Mg0.125NbSe2 as compared to Rb0.125NbSe2. These results suggest that the electronic states of the Nb network in 2H-NbSe2 are least altered with Mg intercalation, which could be one of the reasons for the minimal effect on the Tc with intercalation.

What insertion species is electrochemically intercalated into the LiNiO2 electrode in aqueous solutions?

The mechanism of the electrochemical intercalation of LiNiO2 (LNO) electrodes in an aqueous LiNO3 electrolyte was investigated with special focus on the electrode/electrolyte interfacial reaction including the hydration state of Li+ ions. Electrochemical measurements, the Nernst equation, and in situ X-ray diffraction analysis revealed that lithium ion was main intercalation species, instead of proton, into LNO in aqueous electrolytes. In addition, calculation of the lattice parameters of LNO during charge/discharge processes indicated the co-intercalation of Li+ ions with H2O molecules, supported by the activation energy of Li+ ions estimated for the intercalation. Furthermore, in situ Raman spectra showed that partially hydrated Li+ ions were co-intercalated into LNO.

In Situ Dynamics during Heating of Copper-Intercalated Bismuth Telluride

Summary The presence of a van der Waals gap within layered materials enables the intercalation of guest species, which can be used for tuning properties. The introduction of intercalant species may also lead to structural transformations across a range of temperatures and use conditions, but we have a limited understanding of the high-temperature evolution of intercalated layered materials. Here, we use in situ transmission electron microscopy to investigate temperature-dependent structural evolution of Bi2Te3, a layered material with well-known application as a thermoelectric, which contains intercalated Cu. As temperature is increased, the initially disordered Cu undergoes local ordering within the van der Waals gap, along with anisotropic sublimation behavior of the crystals. As the temperature is raised further, layered Cu2Te crystals nucleate and grow with a crystallographic relationship to the Bi2Te3 lattice. Notably, the presence of Cu decreases the thermal stability of the Bi2Te3 and substantially alters the transformation pathways during heating.

EQCM analysis of intercalation species into graphite positive electrodes for Al batteries

AlCl4− ions are considered the intercalated species, reversibly intercalated/deintercalated between graphite layers, when graphite is used as an active material for Al batteries; however, the reaction mechanism of intercalated species in Al batteries has not yet been fully understood. In order to understand the process, we quantitatively evaluated the charge/discharge reactions of graphite in an ionic liquid consisting of 1-ethyl-3-methylimidazolium chloride and AlCl3 by electrochemical quartz crystal microbalance and density functional theory calculations. The presence of AlCl4− and Al2Cl7− as the intercalated species in the graphite interlayer was confirmed at a ratio of 0.76:0.24. Additionally, the capacity was retained after the destruction of the graphite structure because of its pseudocapacitive behavior.

First-Principles Understanding of the Staging Properties of the Graphite Intercalation Compounds towards Dual-Ion Battery Applications.

Graphite-based dual-ion batteries are a promising alternative to the lithium-ion batteries for energy storage because of its potentially lower cost, higher voltage, and better safety. Among the most important materials in the dual-ion battery are the graphite and graphite intercalation compounds (GICs), whose properties determine the performance of electrodes. The GICs are formed at both anode and the cathode sides during the charging process in which the graphene sheets and the intercalants are arranged in an ordered way called the staging of GICs. Staging is one of the important structural features of GICs related to the volume expansion of the electrodes, the charging rate, and the capacity of the battery. However, the details of the staging mechanism, such as the structural properties, the electronic structure, and the voltage dependence on the stages are still poorly understood. In this regard, we perform density functional theory studies to explore these issues in GICs. Using staging models, we examine the stability of GICs at different stages of intercalation with a range of species (i.e., Li, Na, K, PF6, BF4, TFSI, AlCl4, and ClO4). We then study the contribution of intercalants to the electronic band structures in GICs. In addition, the voltage profiles of the dual-ion batteries with different intercalation species, intercalation stages, and battery capacities are also analyzed. The present work is important for the better understanding of graphite-based dual-ion batteries and helpful in development of novel energy storage systems.