Intercalation Chemistry Research Articles

Direct Solution Phase Synthesis and Functionalization of 2D WSe2 for Ambient Stability.

2H phase tungsten diselenide (WSe2) is a p-type 2D semiconductor from the transition metal dichalcogenides (TMDs) family with unique opto-electrical properties. Solution phase production of atomically thin WSe2is challenging due to its instability under ambient conditions. We present a highly efficient and scalable solution method for simultaneously exfoliating and functionalizingWSe2by leveraging the noncovalent interaction between mercapto-group and bulk WSe2.Single and few-layer 2H phase pure WSe2sheets of lateral size up to 5µm with minimal basal plane defects, as revealed by XPS, Raman and FTIR spectroscopy, are produced in water-ethanol mixture. Remarkably, WSe2dispersion remains stable even at high concentrations (10 mg/ml) and exhibited high colloidal stability with shelf-life exceeding a year. The findings from our study suggest that through precise manipulation of intercalation chemistry, mass production of solution processable phase-sensitive 2D materials such as WSe2can be achieved. This advancement holds great potential for facilitating their practical utilization in various real-world applications.

Transfer-free synthesis of large-area 2D boron films on non-wetting liquid gallium substrate

Two-dimensional (2D) boron films have been studied for their attractive physical and chemical properties in diverse technologies. However, the synthesis of large scale and high-quality boron films is still challenging, which limit its applications in high-performance devices. In this work, thin 2D boron films have been synthesized by chemical vapor deposition (CVD) on non-wetting liquid gallium (Ga) spheres by using boron and boron oxide powders as solid sources. The thin films were directly exfoliated onto SiO2/Si substrates to prepare smooth and uniform boron films by means of mechanical exfoliation method. The peak of boron at 618 cm−1 wave number is obtained by Raman characterization and the boron peak at 188.8 eV is obtained by XPS, which indicates that the film is elemental boron film. By controlling the intercalation chemistry, we obtained large-area 2D polycrystalline boron films with a thickness of 0.8 nm by using transfer-free Synthesis, which avoids the introduction of impurities. The research promotes the application of 2D boron thin film materials in electrical and optical devices.

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.

Dual-ion (de)intercalation into high-entropy perovskite oxides for aqueous alkaline battery-supercapacitor hybrid devices

High-entropy perovskite oxides (HEPOs) suffer from inferior stability in high-power battery-supercapacitor hybrid (BSH) devices. Therefore, revealing their energy storage mechanism is extremely important for optimizing appliance stability. Herein, La0.7Bi0.3Mn0.4Fe0.3Cu0.3O3 nano-HEPO exhibits the dual-ion energy storage mechanism in aqueous alkaline BSH devices. The rapid deintercalation of oxygen anions from the (sub)surface facilitates the intercalation of hydrogen cations into the bulk during charging; however, the deintercalation of hydrogen cations upon the discharge process is hindered because of the surface filling with oxygen vacancies, resulting in an irreversible phase transition and volumetric expansion. Meanwhile, the evolution of surface oxygen species leads to the weak binding between the surface metal-oxygen polyhedron and the bulk, causing severe capacity deterioration due to the active cation leaching and surface inactive La(OH)3 aggregation. Finally, optimal strategies are presented based on the dual-ion intercalation chemistry of HEPOs for application in high-performance BSH devices with long service life.

Reversible Switch in Charge Storage Enabled by Selective Ion Transport in Solid Electrolyte Interphase.

Solid-electrolyte interphases (SEIs) in advanced rechargeable batteries ensure reversible electrode reactions at extreme potentials beyond the thermodynamic stability limits of electrolytes by insulating electrons while allowing the transport of working ions. Such selective ion transport occurs naturally in biological cell membranes as a ubiquitous prerequisite of many life processes and a foundation of biodiversity. In addition, cell membranes can selectively open and close the ion channels in response to external stimuli (e.g., electrical, chemical, mechanical, and thermal), giving rise to "gating" mechanisms that help manage intracellular reactions. We wondered whether the chemistry and structure of SEIs can mimic those of cell membranes, such that ion gating can be replicated. That is, can SEIs realize a reversible switching between two electrochemical behaviors, i.e., the ion intercalation chemistry of batteries and the ion adsorption of capacitors? Herein, we report such SEIs that result in thermally activated selective ion transport. The function of open/close gate switches is governed by the chemical and structural dynamics of SEIs under different thermal conditions, with precise behaviors as conducting and insulating interphases that enable battery and capacitive processes within a finite temperature window. Such an ion gating function is synergistically contributed by Arrhenius-activated ion transport and SEI dissolution/regrowth. Following the understanding of this new mechanism, we then develop an electrochemical method to heal the SEI layer in situ. The knowledge acquired in this work reveals the possibility of hitherto unknown biomimetic properties of SEIs, which will guide us to leverage such complexities to design better SEIs for future battery chemistries.

The Structure, Preparation, Characterization, and Intercalation Mechanism of Layered Hydroxides Intercalated with Guest Anions.

Since the intercalation of anions into layered hydroxides (LHs) has a great impact not only on their nucleation and growth but also on their structure, composition, and size, the intercalation chemistry of LHs has aroused the strong interest of researchers. However, the progress in the fundamental understanding of LHs intercalated with guest anions have not been paralleled by a concomitant development of the preparation and performance improvement of such materials. Considering the guidance of a timely in-depth review for scientists in this area, a systematic introduction about the development that is made on the above-mentioned issues is highly needed but yet missing so far. Herein, recent advances in understanding the chemical composition and structure of LHs intercalated with guest anions are systematically summarized. Meanwhile, typical and emerging bottom-up synthesis methods of LHs intercalated with anions are reviewed, and the potential impact of external reaction parameters on the intercalation of anions into LHs are discussed . Besides, different analytical characterization techniques employed in the examination of guest anion-intercalated LHs are deliberated upon. Finally, although progress is slow in exploring the intercalation mechanism, as many examples as possible are included in this review and inferred the possible intercalation mechanism.

Enabling selective zinc-ion intercalation by a eutectic electrolyte for practical anodeless zinc batteries

Two major challenges hinder the advance of aqueous zinc metal batteries for sustainable stationary storage: (1) achieving predominant Zn-ion (de)intercalation at the oxide cathode by suppressing adventitious proton co-intercalation and dissolution, and (2) simultaneously overcoming Zn dendrite growth at the anode that triggers parasitic electrolyte reactions. Here, we reveal the competition between Zn2+vs proton intercalation chemistry of a typical oxide cathode using ex-situ/operando techniques, and alleviate side reactions by developing a cost-effective and non-flammable hybrid eutectic electrolyte. A fully hydrated Zn2+ solvation structure facilitates fast charge transfer at the solid/electrolyte interface, enabling dendrite-free Zn plating/stripping with a remarkably high average coulombic efficiency of 99.8% at commercially relevant areal capacities of 4 mAh cm−2 and function up to 1600 h at 8 mAh cm−2. By concurrently stabilizing Zn redox at both electrodes, we achieve a new benchmark in Zn-ion battery performance of 4 mAh cm−2 anode-free cells that retain 85% capacity over 100 cycles at 25 °C. Using this eutectic-design electrolyte, Zn | |Iodine full cells are further realized with 86% capacity retention over 2500 cycles. The approach represents a new avenue for long-duration energy storage.

Materials and Processing of Lithium-Ion Battery Cathodes

Lithium-ion batteries (LIBs) dominate the market of rechargeable power sources. To meet the increasing market demands, technology updates focus on advanced battery materials, especially cathodes, the most important component in LIBs. In this review, we provide an overview of the development of materials and processing technologies for cathodes from both academic and industrial perspectives. We briefly compared the fundamentals of cathode materials based on intercalation and conversion chemistries. We then discussed the processing of cathodes, with specific focuses on the mechanisms of a drying process and the role of the binders. Several key parameters for the development of thick electrodes were critically assessed, which may offer insights into the design of next-generation batteries.

Comparative Study of Protection Efficiency of C-Steel Using Polystyrene Clay Nanocomposite Coating Prepared from Commercial Indian Clay and Local Khulays Clay

This work aimed to compare the coating protection efficiency of C-steel using two kinds of clay: a local Khulays clay (RCKh) from Saudi Arabia and a commercial clay (CCIn) from India. Clay-based polymer nanocomposites have a unique layered structure, rich intercalation chemistry, and availability at low cost. They are promising reinforcements for polymers. The raw clay for both clay types was washed before being treated with NaCl to produce sodium clay (NaC). The cationic surfactant cetylpyridinium chloride (CPC) was then used to convert the NaC into the organoclay (OC) form. Polystyrene/organoclay nanocomposites (PCNs) were prepared by combining different concentrations of organoclay (1%, 3%, and 5% OC) in toluene solvent and polystyrene (PS) as the matrix. To ensure the success of the PCN modification process, the organoclay and PCN films were characterized using a variety of techniques, including Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and transmission electron microscopy (TEM). The shifts in the FT-IR spectra after the CPC treatment of NaC confirmed the presence of CPC in the organoclay samples and the presence of OC in the PCNs. The exfoliated structure was obtained from the XRD spectrum for low clay loading (1–3% PCN), while the intercalated structure was the dominant form for the 5% PCN. The XRD results were confirmed by TEM images. To calculate the coating efficiency of the PCNs, various electrochemical methods were used. The electrochemical measurements included electrochemical impedance spectroscopy (EIS), the electrochemical frequency modulation (EFM) method, and Tafel plots. The PCN with a concentration of 1 wt.% OC has a fully exfoliated structure and higher coating efficiency than the PCNs with partially exfoliated structures (3 wt.% and 5 wt.%). It was found from the Tafel plots that commercial Indian clay has better corrosion protection (81.4%) than local Khulays clay (60.2%). A comparison with other studies using current density values shows that our results are superior to those of many studies.

Chemical-Mechanical Robustness of Single-Crystalline Ni-Rich Cathode Enabled by Surface Atomic Arrangement Control.

Layered transition metal oxide cathodes have been one of the dominant cathodes for lithium-ion batteries with efficient Li+ intercalation chemistry. However, limited by the weak layered interaction and unstable surface, mechanical and chemical failure plagues their electrochemical performance, especially for Ni-rich cathodes. Here, adopting a simultaneous elemental-structural atomic arrangement control based on the intrinsic Ni-Co-Mn system, the surface role is intensively investigated. Within the invariant oxygen sublattice of the crystal, a robust surface with the synergistic concentration gradient and layered-spinel intertwined structure is constructed on the model single-crystalline Ni-rich cathode. With mechanical strain dissipation and chemical erosion suppression, the cathode exhibits an impressive capacity retention of 82% even at the harsh 60 oC after 150 cycles at 1C. This work highlights the coupling effect of structure and composition on the chemical-mechanical properties, and the concept will spur more researches on the cathodes that share the same sublattice.

Chemical‐Mechanical Robustness of Single‐Crystalline Ni‐Rich Cathode Enabled by Surface Atomic Arrangement Control

AbstractLayered transition metal oxide cathodes have been one of the dominant cathodes for lithium‐ion batteries with efficient Li+ intercalation chemistry. However, limited by the weak layered interaction and unstable surface, mechanical and chemical failure plagues their electrochemical performance, especially for Ni‐rich cathodes. Here, adopting a simultaneous elemental‐structural atomic arrangement control based on the intrinsic Ni−Co−Mn system, the surface role is intensively investigated. Within the invariant oxygen sublattice of the crystal, a robust surface with the synergistic concentration gradient and layered‐spinel intertwined structure is constructed on the model single‐crystalline Ni‐rich cathode. With mechanical strain dissipation and chemical erosion suppression, the cathode exhibits an impressive capacity retention of 82 % even at the harsh 60 °C after 150 cycles at 1 C. This work highlights the coupling effect of structure and composition on the chemical‐mechanical properties, and the concept will spur more researches on the cathodes that share the same sublattice.

Precision intercalation chemistry: The next step for battery development?

Precision intercalation chemistry: The next step for battery development?

Ultrastable Cu2+ Intercalation Chemistry Based on a Niobium Sulfide Nanosheet Cathode for Advanced Aqueous Storage Devices

Exploring stable and durable cathodes for cost-effective reversible aqueous batteries is highly desirable for grid-scale energy storage applications, but significant challenges remain. Herein, we disclosed an ultrastable Cu2+ intercalation chemistry in mass-produced exfoliated NbS2 nanosheets to build ultralong lifespan aqueous batteries with cost advantages. Anisotropic interplanar expansion of NbS2 lattices balanced dynamic Cu2+ incorporation and the highly reversible redox reaction of Nb4+/Nb(4-δ)+ couple were illuminated by operando synchrotron X-ray diffraction and energy dispersive X-ray absorption spectroscopy, affording an extraordinary capacity of approximately 317 mAh g-1 at 1 A g-1 and a good stability of 92.2% capacity retention after 40000 cycles at 10 A g-1. Impressively, a budget NbS2||Fe hybrid ion cell involving an aqueous electrolyte/Fe-metal anode is established and provides a reliable energy supply of 225.4 Wh kg-1 at 750 W kg-1, providing insights for building advanced aqueous battery systems for large-scale applications.

Atomically Strained Metal Sites for Highly Efficient and Selective Photooxidation.

Strain engineering is an attractive strategy for improving the intrinsic catalytic performance of heterogeneous catalysts. Manipulating strain on the short-range atomic scale to the local structure of the catalytic sites is still challenging. Herein, we successfully achieved atomic strain modulation on ultrathin layered vanadium oxide nanoribbons by an ingenious intercalation chemistry method. When trace sodium cations were introduced between the V2O5 layers (Na+-V2O5), the V-O bonds were stretched by the atomically strained vanadium sites, redistributing the local charges. The Na+-V2O5 demonstrated excellent photooxidation performance, which was approximately 12 and 14 times higher than that of pristine V2O5 and VO2, respectively. Complementary spectroscopy analysis and theoretical calculations confirmed that the atomically strained Na+-V2O5 had a high surficial charge density, improving the activation of oxygen molecules and contributing to the excellent photocatalytic property. This work provides a new approach for the rational design of strain-equipped catalysts for selective photooxidation reactions.

Electronic Structure Manipulation of the Mott Insulator RuCl3 via Single-Crystal to Single-Crystal Topotactic Transformation.

The core task for Mott insulators includes how rigid distributions of electrons evolve and how these induce exotic physical phenomena. However, it is highly challenging to chemically dope Mott insulators to tune properties. Herein, we report how to tailor electronic structures of the honeycomb Mott insulator RuCl3 employing a facile and reversible single-crystal to single-crystal intercalation process. The resulting product (NH4 )0.5 RuCl3 ⋅1.5 H2 O forms a new hybrid superlattice of alternating RuCl3 monolayers with NH4 + and H2 O molecules. Its manipulated electronic structure markedly shrinks the Mott-Hubbard gap from 1.2 to 0.7 eV. Its electrical conductivity increases by more than 103 folds. This arises from concurrently enhanced carrier concentration and mobility in contrary to the general physics rule of their inverse proportionality. We show topotactic and topochemical intercalation chemistry to control Mott insulators, escalating the prospect of discovering exotic physical phenomena.

Electronic Structure Manipulation of the Mott Insulator RuCl3 via Single‐Crystal to Single‐Crystal Topotactic Transformation

AbstractThe core task for Mott insulators includes how rigid distributions of electrons evolve and how these induce exotic physical phenomena. However, it is highly challenging to chemically dope Mott insulators to tune properties. Herein, we report how to tailor electronic structures of the honeycomb Mott insulator RuCl3 employing a facile and reversible single‐crystal to single‐crystal intercalation process. The resulting product (NH4)0.5RuCl3⋅1.5 H2O forms a new hybrid superlattice of alternating RuCl3 monolayers with NH4+ and H2O molecules. Its manipulated electronic structure markedly shrinks the Mott–Hubbard gap from 1.2 to 0.7 eV. Its electrical conductivity increases by more than 103 folds. This arises from concurrently enhanced carrier concentration and mobility in contrary to the general physics rule of their inverse proportionality. We show topotactic and topochemical intercalation chemistry to control Mott insulators, escalating the prospect of discovering exotic physical phenomena.

Enhanced electro-responsive electrorheological efficiency of polyethylene oxide-intercalated montmorillonite nanocomposite suspension

Polyethylene oxide (PEO)-salt complex is an important polymer electrolyte-based anhydrous electrorheological (ER) material. However, it is difficult to get PEO-based ER material in particle form owing to the low glass transition temperature. Cross-linking and copolymerization with other polymers are widely used ways to form polyether-salt complex with desired dimensions and stability. However, these ways are relatively complex, and the ionic conductivity of resulting products is also too high for ER application. In this paper, we report a simple way to form PEO-based nanocomposite ER particles by intercalation chemistry with montmorillonite (PEO-MMT) under the help of ethanol solvent. The structure and composition of samples were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetry, and so on. An increase in basal d001-spacings demonstrates successful intercalation of PEO in MMT. The electro-responsive ER effect of PEO-MMT suspension under electric fields was studied. It demonstrated that PEO intercalation not only effectively solved the problem of difficult granulation of PEO ER material but also replaced the absorbed water in the interlayer of MMT and greatly limited the ionic conductivity of MMT. Under electric fields, the suspension of PEO-MMT nanocomposite was found to show significant ER effect, weak current density, and wide working temperature range. A significant interfacial polarization process was observed by dielectric spectra measurement, which can explain the significant ER effect of PEO-MMT nanocomposite.

Mechanism enhancement of V3O7/V6O13 heterostructures to achieve high-performance aqueous Zn-Ion batteries

Vanadium oxides are the most promising cathode materials for aqueous Zn-ion batteries (AZIBs). A major restriction of vanadium oxides in practical applications is their poor utilization due to the limited migration depth of Zn2+. Mechanism enhancement through modifying Zn2+ intercalation chemistry is the key to boost the performance of vanadium oxides, but yet has rarely been reported. Through a series of ex situ characterizations, we demonstrate here a new two-process reversible transition mechanism in V3O7/V6O13 heterostructures. We observe an unusual reversible transition between V3O7/V6O13 and Zn3V2O7(OH)2·2H2O (ZVO, also a known Zn2+ and proton intercalation material), both of which can be the active materials for subsequent energy storage. This suggests that the Zn2+ intercalation pressure can be shared by the two hosts at deep discharging, that is, the active materials may be better utilized as compared to the only host, which is conducive to improving the available capacity. In addition, the generated ZVO also aids in Zn2+/H+ diffusion due to its open layered structure and water-lubricated channels. With the advanced energy storage mechanism, 2D defective heterostructures, and a facile and energy-efficient synthesis, the V3O7/V6O13 nanosheets are expected to be a high-performance and mass-produced cathode material for commercial AZIBs.

Giant Redox Entropy in the Intercalation vs Surface Chemistry of Nanocrystal Frameworks with Confined Pores.

Redox intercalation involves coupled ion-electron motion within host materials, finding extensive application in energy storage, electrocatalysis, sensing, and optoelectronics. Monodisperse MOF nanocrystals, compared to their bulk phases, exhibit accelerated mass transport kinetics that promote redox intercalation inside nanoconfined pores. However, nanosizing MOFs significantly increases their external surface-to-volume ratios, making the intercalation redox chemistry into MOF nanocrystals difficult to understand due to the challenge of differentiating redox sites at the exterior of MOF particles from the internal nanoconfined pores. Here, we report that Fe(1,2,3-triazolate)2 possesses an intercalation-based redox process shifted ca. 1.2 V from redox at the particle surface. Such distinct chemical environments do not appear in idealized MOF crystal structures but become magnified in MOF nanoparticles. Quartz crystal microbalance and time-of-flight secondary ion mass spectrometry combined with electrochemical studies identify the existence of a distinct and highly reversible Fe2+/Fe3+ redox event occurring within the MOF interior. Systematic manipulation of experimental parameters (e.g., film thickness, electrolyte species, solvent, and reaction temperature) reveals that this feature arises from the nanoconfined (4.54 Å) pores gating the entry of charge-compensating anions. Due to the requirement for full desolvation and reorganization of electrolyte outside the MOF particle, the anion-coupled oxidation of internal Fe2+ sites involves a giant redox entropy change (i.e., 164 J K-1 mol-1). Taken together, this study establishes a microscopic picture of ion-intercalation redox chemistry in nanoconfined environments and demonstrates the synthetic possibility of tuning electrode potentials by over a volt, with profound implications for energy capture and storage technologies.

Exploiting Cation Intercalating Chemistry to Catalyze Conversion-Type Reactions in Batteries

Effective harvest of electrochemical energy from insulating compounds serves as the key to unlocking the potential capacity from many materials that otherwise could not be exploited for energy storage. Herein, an effective strategy is proposed by employing LiCoO2, a widely commercialized positive electrode material in Li-ion batteries, as an efficient redox mediator to catalyze the decomposition of Na2CO3 via an intercalating mechanism. Differing from traditional redox mediation processes where reactions occur on the limited surface sites of catalysts, the electrochemically delithiated Li1-xCoO2 forms NayLi1-xCoO2 crystals, which act as a cation intercalating catalyzer that directs Na+ insertion-extraction and activates the reaction of Na2CO3 with carbon. Through altering the route of the mass transport process, such redox centers are delocalized throughout the bulk of LiCoO2, which ensures maximum active reaction sites. The decomposition of Na2CO3 thus accelerated significantly reduces the charging overpotential in Na-CO2 batteries; meanwhile, Na compensation can also be achieved for various Na-deficient cathode materials. Such a surface-induced catalyzing mechanism for conversion-type reactions, realized via cation intercalation chemistry, expands the boundary for material discovery and makes those conventionally unfeasible a rich source to explore for efficient utilization of chemical energy.