Molecular Intercalation Research Articles

Ordered and Expanded Li Ion Channels for Dendrite‐Free and Fast Kinetics Lithium–Sulfur Battery

AbstractThe uncontrolled polysulfide shuttling and lithium dendrite growth greatly impede the practical implementation of Li–S batteries. These issues can be alleviated by constructing an artificial layer that immobilizes soluble polysulfides and regulates Li+ flux. Here, a layer‐expanded lithium montmorillonite is fabricated through molecular intercalation to serve as a dual regulator for Li–S batteries. The lithiophilic montmorillonite, with its ordered and expanded Li+ diffusion channels, exhibits a high transference number, and promotes homogeneous Li deposition. Additionally, its moderate adsorption of polysulfides, combined with favorable Li diffusion behavior, enhanced the redox kinetics of sulfur species. This unique structure enables a prolonged lifespan of 1000 cycles at 0.5C with a low capacity decay of 0.04% per cycle for practical Li–S batteries.

(Invited) Van Der Waals Heterostructures and Superlattices: Boundless Opportunities at Bondless Boundaries

The advent of two-dimensional atomic crystals and van der Waals heterostructures (vdWHs) has catalyzed a bonding-free strategy for constructing heterostructures beyond the limits of traditional epitaxial heterostructures. In this talk, I start with a brief overview of the broad opportunities presented by exploring vdW interactions for the heterogeneous integration of diverse heterostructures with pristine electronic interfaces. I will then focus on our recent efforts in synthesizing and investigating a new family of vdW superlattices (vdWSLs) consisting of alternating crystalline atomic layers and self-assembled molecular layers of designable chemical compositions and structural motifs. I discuss how we may use the intercalated molecular layers to tailor the electronic and optical properties of various 2DACs, and particularly highlight a unique class of chiral molecular intercalation superlattices hosting exhibit robust chiral-induced spin selectivity and elusive chiral superconductivity. With the versatile molecular design and modular assembly strategies, the 2D-molecular vdWSLs allow boundless flexibility for weaving distinct building constituents into artificial solids with designable chemical modulation, structural topology and 3D potential landscape. It opens unprecedented ways to tailor the electronic, optical and quantum properties, thus defining a rich material platform for diverse emerging technologies.

The Hard Ferromagnetism in FePS3 Induced by Non‐Magnetic Molecular Intercalation

The Hard Ferromagnetism in FePS₃ Induced by Non‐Magnetic Molecular Intercalation

Charged organic ligands inserting/supporting the nanolayer spacing of vanadium oxides for high-stability/efficiency zinc-ion batteries.

Given their high safety, environmental friendliness and low cost, aqueous zinc-ion batteries (AZIBs) have the potential for high-performance energy storage. However, issues with the structural stability and electrochemical kinetics during discharge/charge limit the development of AZIBs. In this study, vanadium oxide electrodes with organic molecular intercalation were designed based on intercalating 11 kinds of charged organic carboxylic acid ligands between 2D layers to regulate the interlayer spacing. The negatively charged carboxylic acid group can neutralize Zn2+, reduce electrostatic repulsion and enhance electrochemical kinetics. The intercalated organic molecules increased the interlayer spacing. Among them, the 0.028EDTA · 0.28NH4 + · V2O5 · 0.069H2O was employed as the cathode with a high specific capacity (464.6mAhg-1 at 0.5Ag-1) and excellent rate performance (324.4mAhg-1 at 10Ag-1). Even at a current density of 20Ag-1, the specific capacity after 2000 charge/discharge cycles was 215.2mAhg-1 (capacity retention of 78%). The results of this study demonstrate that modulation of the electrostatic repulsion and interlayer spacing through the intercalation of organic ligands can enhance the properties of vanadium-based materials.

Evaluation of compatibility in bio-oil and zinc oxide modified asphalt to facilitate waste recycling

The promotion of bio-oil (Bo) waste in road asphalt modification has significant potential for application and environmental benefits. The thermal storage stability, rheological properties, and nano-microstructural characteristics of the composite modified asphalt system were investigated. The Cole-Cole diagram effectively evaluated the compatibility of modified asphalt, demonstrating high sensitivity and accuracy. Significant interaction energy was observed between zinc oxide (ZnO) and asphaltene, with asphaltene primarily acting as an electron donor during its interaction with ZnO. The three organic small molecules in Bo primarily interacted with the polar molecules in asphalt through ester groups, exhibiting varied interaction effects with asphaltene. Bo influenced the colloidal structure of asphalt mainly through diffusion and molecular intercalation. When Bo constituted 4% of the composite modified asphalt system, the organic small molecules from Bo fully diffused within the asphalt matrix, inhibiting the stacking of aromatic rings in the asphaltene structure and enhancing the aromatic activity of asphaltene. Bo improved the compatibility between ZnO and asphalt primarily through dilution and balancing effects from the perspective of asphaltene components. The research results can promote the promotion and application of bio-oil waste in asphalt pavement engineering, which is an important measure to practice sustainable development.

Organic molecular intercalation regulated hydrated vanadate cathodes with improved electrochemical properties and fast kinetics for aqueous zinc-ion batteries

Due to the large hydrated zinc ion radius resulting from the stable solvation structure with six water molecules in electrolyte, the interlayer spacing of most vanadium-based materials fails to meet the requirements for efficient insertion and extraction of Zn2+. Therefore, it is crucial to optimize and reconstruct the VO layer structure in order to achieve rapid and stable zinc storage. In this paper, composites of phenylalanine methyl ester (PM) inserted hydrated V2O5 (PMVO) are prepared using a one-step hydrothermal method. With the increase of PM insertion, the electrochemical properties initially exhibit enhancement followed by subsequent decline. Notably, PMVO-1.6 presents exceptional electrochemical performance, including a high capacity of 464 mAh g−1 at 0.1 A g−1, excellent rate capability with 220 mAh g−1 at 7 A g−1, and superior cycling stability with 97.5 % capacity retention after 1000 cycles at 4 A g−1. The incorporation of PM not only serves as stable structural pillars, but also reduces the solubilization of vanadium, facilitates the diffusion kinetics of hydrated zinc ions, and enhances the surface pseudo-capacitance effect.

A library of 2D electronic material inks synthesized by liquid-metal-assisted intercalation of crystal powders

Solution-processable 2D semiconductor inks based on electrochemical molecular intercalation and exfoliation of bulk layered crystals using organic cations has offered an alternative pathway to low-cost fabrication of large-area flexible and wearable electronic devices. However, the growth of large-piece bulk crystals as starting material relies on costly and prolonged high-temperature process, representing a critical roadblock towards practical and large-scale applications. Here we report a general liquid-metal-assisted approach that enables the electrochemical molecular intercalation of low-cost and readily available crystal powders. The resulted solution-processable MoS2 nanosheets are of comparable quality to those exfoliated from bulk crystals. Furthermore, this method can create a rich library of functional 2D electronic inks ( >50 types), including 2D wide-bandgap semiconductors of low electrical conductivity. Lastly, we demonstrated the all-solution-processable integration of 2D semiconductors with 2D conductors and 2D dielectrics for the fabrication of large-area thin-film transistors and memristors at a greatly reduced cost.

Enhanced Superconductivity in 2H-TaS2 Devices through in Situ Molecular Intercalation.

The intercalation of guest species into the gap of van der Waals materials often leads to the emergence of intriguing phenomena such as superconductivity. While intercalation-induced superconductivity has been reported in several bulk crystals, reaching a zero-resistance state in flakes remains challenging. Here, we show a simple method for enhancing the superconducting transition in tens-of-nanometers thick 2H-TaS2 crystals contacted by gold electrodes through in situ intercalation. Our approach enables measuring the electrical characteristics of the same flake before and after intercalation, permitting us to precisely identify the effect of the guest species on the TaS2 transport properties. We find that the intercalation of amylamine molecules into TaS2 flakes causes a suppression of the charge density wave and an increase in the superconducting transition with an onset temperature above 3 K. Additionally, we show that a fully developed zero-resistance state can be achieved in flakes by engineering the conditions of the chemical intercalation. Our findings pave the way for the integration of chemically tailored intercalation compounds in scalable quantum technologies.

Exploring the potential of Mbenes in energy storage

MBene, a layered metal boride similar to MXene, has garnered significant attention in recent times. Nevertheless, there is still a lack of comprehensive understanding regarding their structure and properties, necessitating further research and investigation. In this study, theoretical calculations were employed first to study the binding energy, band structures and density of states of three MBenes, namely MoB, MgB2, and ZrB2, providing insights into their electronic characteristics. In addition, open circuit voltage (OCV) and adsorption energy were also conducted using the three MBenes as cathode materials for zinc ion batteries, indicating their low ion migration barrier and potential in energy storage application. Subsequently, MoB, MgB2, and ZrB2 were experimentally synthesized using etching or exfoliation method and utilized as cathode materials for zinc ion batteries. Results demonstrates that the specific capacity of MoB is 60 mAh g-1 at 0.1 A g-1. Systematic investigation including kinetics simulation and ex situ XRD suggests the cation insertion mechanism of the MoB electrodes. Building upon these findings, attempts were made to enhance the performance of MoB through the incorporation of 1 T-MoS2 composites, urea molecular intercalation. Notably, the modified composite exhibited a specific capacity exceeding 150 mAh g-1 at 0.1 A g-1, with a stable Coulombic efficiency of 100% after 100 cycles. This study provides novel directions and insights for the research of MBene in the context of aqueous zinc-ion batteries.

Discovering the Order-Disorder Transition in Quinoline Intercalated Vanadium Oxide with Superior Calcium Storage via Polyhedral Distortion.

Calcium-ion batteries (CIBs) are considered as potential next-generation energy storage systems due to their abundant reserves and relatively low cost. However, irreversible structural changes and weak conductivity still hinder in current CIBs cathode materials. Herein, an organic molecular intercalation strategy is proposed, in which V2O5 regulated with quinoline, pyridine, and water molecules are studied as cathode material to provide fast ion diffusion channels, large storage host, and high conductivity for Ca ions. Among them, V2O5-quinoline (QVO) owns the largest interplanar spacing of 1.25 nm and the V-O chains are connected with organic molecular by hydrogen bond, which stabilizes the crystal structure. As a result, QVO exhibits a specific capacity of 168 mAh g-1 at 1 A g-1 and capacity retention of 80% after 500 cycles at 5 A g-1 than the other materials. Furthermore, X-Ray diffraction and X-ray absorption spectroscopy results reveal a reversible order-disorder transformation mechanism of Ca2+ for QVO, which can make full use of the abundant active sites for high capacity and simultaneously achieve fast reaction kinetics for excellent rate performance. These results demonstrate that QVO is a promising cathode material for CIBs, providing more choices for the development of high-performance CIBs.

Molecular Intercalation Enables Phase Transition of MoSe2 for Durable Na-Ion Storage.

1T-MoSe2 is recognized as a promising anode material for sodium-ion batteries, thanks to its excellent electrical conductivity and large interlayer distance. However, its inherent thermodynamic instability often presents unparalleled challenges in phase control and stabilization. Here, a molecular intercalation strategy is developed to synthesize thermally stable 1T-rich MoSe2, covalently bonded to an intercalated carbon layer (1TR/2H-MoSe2@C). Density functional theory calculations uncover that the introduced ethylene glycol molecules not only serve as electron donors, inducing a reorganization of Mo 4d orbitals, but also as sacrificial guest materials that generate a conductive carbon layer. Furthermore, the C─Se/C─O─Mo bonds encourage strong interfacial electronic coupling, and the carbon layer prevents the restacking of MoSe2, regulating the maximum 1T phase to an impressive 80.3%. Consequently, the 1TR/2H-MoSe2@C exhibits an extraordinary rate capacity of 326mAhg-1 at 5Ag-1 and maintains a long-term cycle stability up to 1500 cycles, with a capacity of 365mAhg-1 at 2Ag-1. Additionally, the full cell delivers an appealing energy output of 194Whkg-1 at 208Wkg-1, with a capacity retention of 87.3% over 200 cycles. These findings contribute valuable insights toward the development of innovative transition metal dichalcogenides for next-generation energy storage technologies.

A Dual Active Site Organic–Inorganic Poly(O‐Phenylenediamine)/NH4V3O8 Composite Cathode Material for Aqueous Zinc‐Ion Batteries

AbstractAqueous zinc‐ion batteries, considered one of the important candidate technologies for green and environmentally friendly large‐scale energy storage, hinge upon the performance of cathode materials as the key factor driving their development. Vanadate oxide is a promising cathode material due to its high theoretical capacity; furthermore, in order to accelerate the reaction kinetics, ion or molecular intercalation is often utilized. However, non‐electrochemically active intercalants tend to cause capacity degradation. In this study, a one‐step hydrothermal method is employed to intercalate electrochemically active poly‐o‐phenylenediamine (PoPDA) into the interlayers of NH4V3O8 (NVO), with graphene oxide (GO) being used to further improve the conductivity of the composite material (NVO/PoPDA@GO). The insertion of PoPDA expands the interlayer spacing of the NVO, alters the charge distribution, and enhances the migration rate of Zn2+ among the hybrid materials. Additionally, PoPDA serves as a support within the interlayers, improving the material stability. Moreover, the reversible transformation and rearrangement of chemical bonds (C═N/C─N) in PoPDA allows for coordination with Zn2+, providing additional capacity. As a result, NVO/PoPDA@GO exhibits excellent electrochemical performance, releasing a specific capacity of 433 mAh g−1 at 0.5 A g−1, even with a capacity of 224 mAh g−1 at 5 A g−1. This work provides a promising direction for the preparation of organic–inorganic composite cathode materials with dual active components.

Effect of chemical intercalation on ferroelectricity in van der Waals layered CuInP2S6

Chemical intercalation brings about intriguing opportunities to tailor the properties of van der Waals (vdW) layered materials by crafting molecular composite at an atomic scale. Despite a plethora of reports on various materials, the chemical intercalation effect on long-range ferroelectric order remains scarcely explored. Herein, we report the construction of hybrid supercrystal based on a model vdW ferroelectric, CuInP2S6 by molecular intercalation. Although the out-of-plane lattice structure remains commensurate, its ferroelectric polarization is largely destroyed by the chemical intercalation, as confirmed by combined piezoresponse microscopy and Raman spectroscopy. Alternatively, we observed a dipole glass transition at about 280 K by dielectric spectroscopy and correlated it with the Raman analysis. This work highlights the impact of chemical intercalation on collective ferroic orders and paves the routes for creating artificial hybrid crystals by incorporating functional molecules.

Tandem molecular intercalation exfoliated TiSe2 nanosheets for enhanced sodium-ion storage

Although layered transition metal dichalcogenides (TMDs) possess relatively high electrical and moderate ionic conductivities, their inclination to stack layered structure inevitably leads to a sluggish ion diffusion and limited cyclic life when used as anode materials. Therefore, the realization of few-layered structure with widened layer distance would facilitate the ion migration and thus help TMDs to gain enhanced performance. In this study, tandem molecular intercalation method was applied to fabricate few-layered TiSe2 nanosheets (ef-TiSe2) with pronounced expanded layer spacing (∼10 Å) using propylamine and hexylamine as intercalators. Density functional theory calculations disclose that there is a continuous charge accumulation between the TiSe2 interlayers, which enables Na+ to exhibit a strong adsorption tendency, thus forming a certain Coulombic force. Furthermore, the lowest Na+ diffusion barrier between interlayers guarantees TiSe2 to achieve rapid reaction kinetics. The effective exfoliation strategy renders the obtained ef-TiSe2 rich exposed reaction active sites, sufficient electrolyte penetration, shortened diffusion distance of ion/electron, suppressed stress caused by structural changes, and increased effective utilization of the material. Interestingly, compared with bulk TiSe2, few-layered ef-TiSe2 nanosheets exhibited a shorter activation cycling period, lower reaction polarization, and expedited reaction kinetics, therefore providing a high specific capacity (417 mA h g−1 at 1 A g−1) and cyclic stability (with a high-capacity retention of 95.36 % after 2000 cycles at 5 A g−1). In addition, the combined mechanism of intercalation and conversion in TiSe2 was closely elucidated by in situ X-ray diffraction and in situ electrochemical impedance spectroscopy.

Organic Molecular Intercalation Enabled Anionic Redox Chemistry with Fast Kinetics for High Performance Magnesium Storage.

Rechargeable magnesium-ion batteries possess desirable characteristics in large-scale energy storage applications. However, severe polarization, sluggish kinetics and structural instability caused by high charge density Mg2+ hinder the development of high-performance cathode materials. Herein, the anionic redox chemistry in VS4 is successfully activated by inducing cations reduction and introducing anionic vacancies via polyacrylonitrile (PAN)intercalation. Increased interlayer spacing and structural vacancies can promote the electrolyte ions migration and accelerate the reaction kinetics. Thanks to this "three birds with one stone" strategy, PAN intercalated VS4 exhibits an outstanding electrochemical performance: high discharge specific capacity of 187.2mAhg-1 at 200mAg-1 after stabilization and a long lifespan of 5000 cycles at 2Ag-1 are achieved, outperforming other reported VS4-based materials to date for magnesium storage under the APC electrolyte. Theoretical calculations confirm that the intercalated PAN can indeed induce cations reduction and generate anionic vacancies by promoting electron transfer, which can accelerate the electrochemical reaction kinetics and activate the anionic redox chemistry, thus improving the magnesium storage performance. This approach of organic molecular intercalation represents a promising guideline for electrode material design on the development of advanced multivalent-ion batteries.

Molecular intercalated graphene oxide with finely controllable interlayer spacing for fast dye separation

Molecular intercalation has been widely used for graphene oxide (GO) nanosheets to control interlayer spacing (d-spacing). However, further research is necessary to refine and enhance the precision of d-spacing control. In this study, we demonstrate a versatile strategy to create chitosan (CS) intercalated GO (GO@CS) nanosheets, whose d-spacing can be finely controlled by numbers of linked CS unit. This means the concentration of CS solution directly influences d-spacing of GO, and we can get the desired d-spacing for various applications by modulating the CS concentration. This is benefited from the linear structure of CS ensuring a consistent molecular length. The simulation of molecular structures with different numbers of linked CS unit supports this model. Then, the nanofiltration membranes prepared by these GO@CS nanosheets show high hydrophilicity, strong chemical bonding force, and abundant negative charges, which enhances permeability (water permeance of 91 L m−2 h−1 bar−1), stability, and anti-fouling ability during dye separation processes, even though they are ultrathin (∼70 nm). Notably, the contrasting filtration efficiencies observed for oppositely charged dye molecules indicate a great potential use in molecular sieving.

Magnetic properties of intercalated quasi-2D Fe3-xGeTe2 van der Waals magnet

Among several well-known transition metal-based compounds, cleavable van der Waals (vdW) Fe3-xGeTe2 (FGT) magnet is a strong candidate for use in two-dimensional (2D) magnetic devices due to its strong perpendicular magnetic anisotropy, sizeable Curie temperature (TC ~154 K), and versatile magnetic character that is retained in the low-dimensional limit. While the TC remains far too low for practical applications, there has been a successful push toward improving it via external driving forces such as pressure, irradiation, and doping. Here we present experimental evidence of a room temperature (RT) ferromagnetic phase induced by the electrochemical intercalation of common tetrabutylammonium cations (TBA+) into quasi-2D FGT. We obtained Curie temperatures as high as 350 K with chemical and physical stability of the intercalated compound. The temperature-dependent Raman measurements, in combination with vdW-corrected ab initio calculations, suggest that charge transfer (electron doping) upon intercalation could lead to the observation of RT ferromagnetism. This work demonstrates that molecular intercalation is a viable route in realizing high-temperature vdW magnets in an inexpensive and reliable manner, and has the potential to be extended to bilayer and few-layer vdW magnets.

Terephthalic Acid Intercalated CoNi-LDH Materials for Improved Li-O2 Battery.

CoNi-LDH (layered CoNi double hydroxides) hollow nanocages with specific morphology are obtained by Ni ion etching of ZIF-67 (Zeolitic imidazolate framework-67). The structure of the layered materials is further modified by molecular intercalation. The original interlayer anions are replaced by the ion exchange effect of terephthalic acid, which helps to increase the interlayer distance of the material. The intercalated cage-like structures not only benefit for the storage of oxygen, and the discharge product reaction, but also have more support between the material layers. The experimental results show that the excessive use of intercalation agent will affect structural stability of the intercalated CoNi-LDH. By adjusting the amount of terephthalic acid, the intercalated CoNi-LDH-2 (with 0.02mmol terephthalic acid intercalated) is not easy to collapse after 209 cycles and shows the best electrochemical performance in Li-O2 battery.

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A solution‐based electrochemically driven molecular intercalation exfoliation has been developed by Cho et al., to produce wafer‐scale films of platinum diselenide (PtSe2) with layer‐dependent controlled electronic properties. Semiconducting or semimetallic PtSe2 nanosheets were separated using centrifugation‐based thickness classification. Semiconducting nanosheets were used to fabricate gate‐tunable photodetector arrays for visible and near‐infrared light, and semimetallic films served as catalytic electrodes for long‐term stable water splitting. image

Electrochemical molecular intercalation and exfoliation of solution-processable two-dimensional crystals.

Electrochemical molecular intercalation of layered semiconducting crystals with organic cations followed by ultrasonic exfoliation has proven to be an effective approach to producing a rich family of organic/inorganic hybrid superlattices and high-quality, solution-processable 2D semiconductors. A traditional method for exfoliating 2D crystals relies on the intercalation of inorganic alkali metal cations. The organic cations (e.g., alkyl chain-substituted quaternary ammonium cations) are much larger than their inorganic counterparts, and the bulky molecular structure endows distinct intercalation and exfoliation chemistry, as well as molecular tunability. By using this protocol, many layered 2D crystals (including graphene, black phosphorus and versatile metal chalcogenides) can be electrochemically intercalated with organic quaternary alkylammonium cations. Subsequent solution-phase exfoliation of the intercalated compounds is realized by regular bath sonication for a short period (5-30 min) to produce free-standing, thin 2D nanosheets. It is also possible to graft additional ligands on the nanosheet surface. The thickness of the exfoliated nanosheets can be measured by using atomic force microscopy and Raman spectroscopy. Modifying the chemical structure and geometrical configuration of alkylammonium cations results in different exfoliation behavior and a family of versatile organic/inorganic hybrid superlattices with tunable physical/chemical properties. The whole protocol takes ~6 h for the successful production of stable, ultrathin 2D nanosheet dispersion in solution and another 11 h for depositing thin films and transferring them onto an arbitrary surface. This protocol does not require expertise beyond basic electrochemistry knowledge and conventional colloidal nanocrystal synthesis and processing.