Intercalation Of Cations Research Articles

Cationic vacancies as defects in honeycomb lattices with modular symmetries

Layered materials tend to exhibit intriguing crystalline symmetries and topological characteristics based on their two dimensional (2D) geometries and defects. We consider the diffusion dynamics of positively charged ions (cations) localized in honeycomb lattices within layered materials when an external electric field, non-trivial topologies, curvatures and cationic vacancies are present. The unit (primitive) cell of the honeycomb lattice is characterized by two generators, J_1, J_2 in mathrm{SL}_2({mathbb {Z}}) of modular symmetries in the special linear group with integer entries, corresponding to discrete re-scaling and rotations respectively. Moreover, applying a 2D conformal metric in an idealized model, we can consistently treat cationic vacancies as topological defects in an emergent manifold. The framework can be utilized to elucidate the molecular dynamics of the cations in exemplar honeycomb layered frameworks and the role of quantum geometry and topological defects not only in the diffusion process such as prediction of conductance peaks during cationic (de-)intercalation process, but also pseudo-spin and pseudo-magnetic field degrees of freedom on the cationic honeycomb lattice responsible for bilayers.

Enhancing the Dye-Rejection Efficiencies and Stability of Graphene Oxide-Based Nanofiltration Membranes via Divalent Cation Intercalation and Mild Reduction.

Laminar graphene oxide (GO) membranes have demonstrated great potential as next-generation water-treatment membranes because of their outstanding performance and physicochemical properties. However, solute rejection and stability deterioration in aqueous solutions, which are caused by enlarged nanochannels due to hydration and swelling, are regarded as serious issues in the use of GO membranes. In this study, we attempt to use the crosslinking of divalent cations to improve resistance against swelling in partially reduced GO membranes. The partially reduced GO membranes intercalated by divalent cations (i.e., Mg2+) exhibited improved dye-rejection efficiencies of up to 98.40%, 98.88%, and 86.41% for methyl orange, methylene blue, and rhodamine B, respectively. In addition, it was confirmed that divalent cation crosslinking and partial reduction could strengthen mechanical stability during testing under harsh aqueous conditions (i.e., strong sonication).

Cation-induced Ti3C2Tx MXene hydrogel for capacitive energy storage

To date, Ti3C2Tx MXene has been a promising candidate for energy storage field, however the construction of 3D MXene hydrogel with their inherent hydrophilicity and high conductivity remains a challenge. Herein, a series of Ti3C2Tx MXene hydrogel was fabricated successfully via a facile and fast cation-induced strategy. Typically, the formation of hydrogel is stem from the quick cross-linking of Ti3C2Tx nanosheets, accompanying with the intercalation of high-concentration cation between the layers. Characterization analyses have demonstrated that the cation-induced Ti3C2Tx hydrogel possesses 3D porous structure and controllable basal spacing, which could synergistically facilitate fast diffusion of electrolyte ions and accessibility of electrochemical active sites. Density functional theory (DFT) calculation shows that larger hydrated radii and more intercalated cation are favorable for the expansion of basal spacing thermodynamically. As a result, the excellent capacitance and high rate-capability are both realized in cation-induced Ti3C2Tx hydrogels. Especially, as-synthesized Al-Ti3C2Tx hydrogel delivery a remarkable capacitance of 675F/g at 1 A/g, along with a specific energy density of 46 Wh/kg when the power density is 349 h/kg, which is superior to the previous reported Ti3C2Tx electrodes. Besides, the well-designed H-Ti3C2Tx hydrogel still achieves 206F/g capacitance when the scan rate is up to 1 V/s, and it could withstand 5000 cycles with only 8% loss of capacitance. This work not only illuminates a straightforward way to construct high-performance MXene electrode for capacitive energy storage, but also provides a new guideline over the manipulation of interlayer spacing and morphology of 2D colloid materials.

Reversible Intercalation of Li Ions in an Earth-Abundant Phyllosilicate Clay.

The phyllosilicate family of clays is an intriguing collection of materials that make ideal models for studying the intercalation of alkali ions due to their layered topology and broadly tunable composition space. In this spirit, we present a hydrothermal method to prepare a layered iron phyllosilicate clay, Fe2Si4O10(OH)2, and an evaluation of its electrochemical performance for the (de)insertion of Li ions. Through careful structural refinement, we determined that this iron clay contains a 2:1 stacking sequence, which is directly analogous to the widely studied mineral montmorillonite, with the crystallites adopting a platelike morphology. Cyclic voltammetry and galvanostatic cycling reveal reversible insertion of lithium into the interstitial layers via a solid solution mechanism. Comparison of ion (de)intercalation with reports on other clay systems like muscovite, KFe2.75Si3.25O10(OH)2, which features a rigidly bound interlayer cation, demonstrates that controlling the net charge on the layers with phyllosilicate minerals is a route to enabling reversible cationic intercalation within the structure.

Exploring the electrochemical behavior of Mo1.33CTz MXene in aqueous sulfates electrolytes: Effect of intercalating cations on the stored charge

MXenes have been introduced as a high energy and power density electrochemical supercapacitor material owing to their high specific capacitance and electrochemical stability. The operating potential window and, in turn, energy density of MXene based symmetric and asymmetric supercapacitors can be effectively enhanced by the proper choice of aqueous electrolyte. Herein, we investigate the electrochemical behavior of vacancy-containing i-MXene (Mo1.33CTz) in sulfate based aqueous electrolytes with univalent (Li+, Na+, or K+) or divalent (Mg2+, Mn2+, or Zn2+) cations. The results show that the Mo1.33CTz MXene electrodes can be operated in a potential window higher than 1 V without degradation in these sulfate electrolytes. The Mo1.33CTz MXene electrodes deliver a high volumetric capacitance up to ∼677 F cm−3 as measured in 1.0 M MnSO4 solution. Furthermore, symmetric (Mo1.33CTz//Mo1.33CTz) and asymmetric (Mo1.33CTz//nitrogen-doped activated carbon (NAC)) devices in 0.5 M K2SO4 solution can be operated with a cell voltage of about 1.1 V and 1.8 V, respectively. The asymmetric devices retain about 97% of their initial capacitance after 5000 charge/discharge cycles. Overall, the results reveal that the choice of the intercalating cations is a viable route to boost the performance of Mo1.33CTz MXene and to construct energy storage devices.

Effect of different alkali metal cations on the oxygen evolution activity and battery capacity of nickel electrodes in concentrated hydroxide electrolytes

The effect of different alkali metal cations on the oxygen evolution activity and battery capacity of nickel electrodes has recently been studied in low concentration alkali hydroxide electrolytes. As high concentration hydroxide electrolytes are favored in applications due to their high conductivity, we investigate if the cation effects observed in low concentration electrolytes translate to more industrially relevant conditions for both alkaline water electrolysis and nickel iron batteries. We investigate the alkali metal cation effect on the electrochemical properties of nickel electrodes in highly concentrated hydroxide electrolytes by adding Li+, Na+, Cs+ and Rb+ cations to a 6.5 M KOH electrolyte, while keeping the hydroxide concentration constant. For OER we find a trend in activity similar to that at low concentrations Rb+>Cs+>K+>Na+>Li+, where especially larger additions of Rb+ and Cs+ (1 M or 0.5 M) cause a significant decrease in OER potential. Smaller cations interact with the layered hydroxide structures in NiOOH to stabilize the α/γ phases and increase the potential for OER. The intercalation of small cations also causes an increase in battery electrode capacity because of the higher average valence of the Ni(OH)2/NiOOH α/γ pair. Small concentrations of Li+ added to a concentrated KOH electrolyte can therefore be beneficial for the nickel electrode battery functionality and for an integrated battery and electrolyser system, where it increases the battery capacity without a significant increase in OER onset potential.

Hierarchical Intercalation of Spiro-bipyrrolidinium Cation into Graphite Electrode from Propylene Carbonate

The intercalation of spiro-(1,1′)-bipyrrolidinium (SBP) cation into a graphite electrode from propylene carbonate (PC) is performed in graphite/activated carbon capacitors. The effect of the electrolyte salt concentration on the storage behavior of PC-solvated SBP+ cation in graphite electrode is investigated by electrochemical tests, in situ X-ray diffraction and electrochemical quartz crystal microbalance measurements.

Effects of interstitial water and alkali cations on the expansion, intercalation potential, and orbital coupling of nickel hexacyanoferrate from first principles

Prussian blue analogs (PBAs) are an important material class for aqueous electrochemical separations and energy storage owing to their ability to reversibly intercalate monovalent cations. However, incorporating interstitial H2O molecules in the ab initio study of PBAs is technically challenging, though essential to understanding the interactions between interstitial water, interstitial cations, and the framework lattice that affect intercalation potential and cation intercalation selectivity. Accordingly, we introduce and use a method that combines the efficiency of machine-learning models with the accuracy of ab initio calculations to elucidate mechanisms of (1) lattice expansion upon intercalation of cations of different sizes, (2) selectivity bias toward intercalating hydrophobic cations of large size, and (3) semiconductor–conductor transitions from anhydrous to hydrated lattices. We analyze the PBA nickel hexacyanoferrate [NiFe(CN)6] due to its structural stability and electrochemical activity in aqueous electrolytes. Here, grand potential analysis is used to determine the equilibrium degree of hydration for a given intercalated cation (Na+, K+, or Cs+) and NiFe(CN)6 oxidation state based on pressure-equilibrated structures determined with the aid of machine learning and simulated annealing. The results imply new directions for the rational design of future cation-intercalation electrode materials that optimize performance in various electrochemical applications, and they demonstrate the importance of choosing an appropriate calculation framework to predict the properties of PBA lattices accurately.

Reunderstanding the Reaction Mechanism of Aqueous Zn-Mn Batteries with Sulfate Electrolytes: Role of the Zinc Sulfate Hydroxide.

Rechargeable aqueous Zn-Mn batteries have garnered extensive attention for next-generation high-safety energy storage. However, the charge-storage chemistry of Zn-Mn batteries remains controversial. Prevailing mechanisms include conversion reaction and cation (de)intercalation in mild acid or neutral electrolytes, and a MnO2 /Mn2+ dissolution-deposition reaction in strong acidic electrolytes. Herein, a Zn4 SO4 ·(OH)6 ·xH2 O (ZSH)-assisted deposition-dissolution model is proposed to elucidate the reaction mechanism and capacity origin in Zn-Mn batteries based on mild acidic sulfate electrolytes. In this new model, the reversible capacity originates from a reversible conversion reaction between ZSH and Znx MnO(OH)2 nanosheets in which the MnO2 initiates the formation of ZSH but contributes negligibly to the apparent capacity. The role of ZSH in this new model is confirmed by a series of operando characterizations and by constructing Zn batteries using other cathode materials (including ZSH, ZnO, MgO, and CaO). This research may refresh the understanding of the most promising Zn-Mn batteries and guide the design of high-capacity aqueous Zn batteries.

Regulation of dual-ion batteries via the defects design in carbon electrode based on the different storage behaviors of PF6− and Li+

Dual-ion batteries (DIBs) have aroused much attention due to their high energy density, low cost, and environmental friendliness compared to conventional alkali metal-ion batteries. However, there are still two severe challenges to confront, including structural collapse for the graphitic carbon cathode due to the intercalation of anions with large size and limited specific capacity of cations intercalation for the graphitic carbon anode, rendering poor rate performance, unsatisfactory cyclability, and insufficient energy density. Herein, a simple design is proposed to prepare cathode and anode materials for PF6− and Li+ intercalation in one synthesis system by regulating boron content in the complex of amino acid with iron (III). The graphitic mesoporous carbon cathode with minimal defect sites shows a superior rate performance and cycling stability for PF6− intercalation. The boron-doped porous carbon anode shows a high capacity of up to 606 mAh g−1 for Li + storage by introducing abundant defects. The DIB assembled by the above cathode and anode can exhibit a maximum energy density of 130 Wh kg−1 at a power density of 580 W kg−1 and an energy density of 74 Wh kg−1 at an ultrahigh power density of 29000 W kg−1.

Self-Driven Electrochromic Window System Cu/WOx-Al3+/GR with Dynamic Optical Modulation and Static Graph Display Functions.

Electrochromic devices with unique advantages of electrical/optical bistability are highly desired for energy-saving and information storage applications. Here, we put forward a self-driven Al-ion electrochromic system, which utilizes WOx films, Cu foil, and graphite rod as electrochromic optical modulation and graph display electrodes, coloration potential supplying electrodes, and bleaching potential supplying electrodes, respectively. The inactive Cu electrode can not only realize the effective Al3+ cation intercalation into electrochromic WOx electrodes but also eliminate the problem of metal anode consumption. The electrochromic WOx electrodes cycled in Al3+ aqueous media exhibit a wide potential window (∼1.5 V), high coloration efficiency (36.0 cm2/C), and super-long-term cycle stability (>2000 cycles). The dynamic optical modulation and static graph display function can be achieved independently only by switching the electrode connection mode, thus bringing more features to this electrochromic system. For a large-area electrochromic system (10 × 10 cm2), the absolute transmittance value in its color-neutral state can reach about 41% (27%) at 633 nm (780 nm) by connecting the Cu and WOx electrodes for 140 s. The original transparent state can be readily recovered by replacing the Cu foil with the graphite rod. This work throws light on next-generation electrochromic applications for optical/thermal modulation, privacy protection, and information display.

Intercalation of Zinc Monochloride Cations by Deep Eutectic Solvents for High-Performance Rechargeable Non-aqueous Zinc Ion Batteries.

Zinc ion batteries have been extensively studied with an aqueous electrolyte system. However, the batteries suffer from a limited potential window, gas evolution, cathode dissolution, and dendrite formation on the anode. Considering these limitations, we developed an alternative electrolyte system based on deep eutectic solvents (DESs) because of their low cost, high stability, biodegradability, and non-flammability, making them optimal candidates for sustainable batteries. The DES electrolyte enables reversible Zn plating/stripping and effectively suppresses zinc dendrite formation. Furthermore, in-depth characterizations reveal that the energy storage mechanism can be attributed to [ZnCl]+ ion intercalation and the intermediate complex ion plays a pivotal role in electrochemical reactions, which deliver a high reversible capacity of 310 mAh g-1 at 0.1 A g-1and long-term stability (167 mAh g-1 at a current density of 0.3 A g-1 after 300 cycles, Coulombic efficiency: ∼98%). Overall, this work represents our new finding in rechargeable batteries with the DES electrolyte.

Interlayer Structure Manipulation of Iron Oxychloride by Potassium Cation Intercalation to Steer H2O2 Activation Pathway.

Structural regulation of the active centers is often pivotal in controlling the catalytic functions, especially in iron-based oxidation systems. Here, we discovered a significantly altered catalytic oxidation pathway via a simple cation intercalation into a layered iron oxychloride (FeOCl) scaffold. Upon intercalation of FeOCl with potassium iodide (KI), a new stable phase of K+-intercalated FeOCl (K-FeOCl) was formed with slided layers, distorted coordination, and formed high-spin Fe(II) species compared to the pristine FeOCl precursor. This structural manipulation steers the catalytic H2O2 activation from a traditional Fenton-like pathway on FeOCl to a nonradical ferryl (Fe(IV)═O) pathway. Consequently, the K-FeOCl catalyst can efficiently remove various organic pollutants with almost 2 orders of magnitude faster reaction kinetics than other Fe-based materials via an oxidative coupling or polymerization pathway. A reaction-filtration coupled process based on K-FeOCl was finally demonstrated and could potentially reduce the energy consumption by almost 50%, holding great promise in sustainable pollutant removal technologies.

Alkali cation intercalation manganese phosphate hydrate boosting electrochemical kinetics for pseudocapacitive energy storage

New insight into the effect on the alkali cations of Li+, Na+, and K+ pre-intercalated between adjacent layers of Mn3(PO4)2·3H2O towards the charge storage mechanism and their electrochemical kinetics of intercalation/deintercalation in three alkali electrolytes is demonstrated. The electrochemical performance of the designed LiMn3(PO4)2·3H2O material outperforms that most of Mn-based pseudocapacitive electrode materials. The designed unique stratified structure is attractive for quick charge migration, which confirms that the appropriate pre-intercalation of alkali cation between layers is an efficient strategy to improve kinetics for the high-power density pseudocapacitive supercapacitor energy storage application.

Regulating the electrolyte ion types and exposed crystal facets for pseudocapacitive energy storage of transition metal nitrides

Pseudocapacitance is a charge storage behavior dominated by the surface kinetics of electrode materials, and it can differentiate into adsorption pseudocapacitance associated with surface redox reactions and intercalation pseudocapacitance associated with ion insertion in bulk without structural change. Despite major efforts to develop pseudocapacitive materials of transition metal nitrides (TMNs) and understand their energy storage mechanism, they are limited to identifying the specific pseudocapacitance that the target TMNs occurs, a probe into the internal matching relationship between the pseudocapacitance of TMNs and electrolyte ions as well as exposed crystal facets is still lacking. Here, we use mesoporous Mo2N nanowires as a subject of study to reveal the influences of the ion type of aqueous electrolytes and exposed crystal facets on the pseudocapacitive behavior of TMNs. Our results show that almost only solvated cations occur intercalation pseudocapacitance in acid and neutral electrolytes; solvated cations and anions both contribute energy in alkaline electrolyte by means of intercalation pseudocapacitance and adsorption pseudocapacitance, respectively. Crystal facet regulation further elucidates that the (111) crystal facet can provide larger interstitial sites for cation intercalation and more active terminations for anion adsorption compared with the (200) counterpart, thereby achieving a higher capacity. These findings offer a new insight on the pseudocapacitive energy storage, and for the first time emphasize the importance of crystal facet regulation for the rational design of pseudocapacitive materials.

Ionically Active MXene Nanopore Actuators.

Reversible electrochemical intercalation of cations into the interlayer space of 2D materials induces tunable physical and chemical properties in them. In MXenes, a large class of recently developed 2D carbides and nitrides, low intercalation energy, high storage capacitance, and reversible intercalation of various cations have led to their improved performance in sensing and energy storage applications. Herein, a coupled nanopore-actuator system where an ultrathin free-standing MXene film serves as a nanopore support membrane and ionically active actuator is reported. In this system, the contactless MXene membrane in the electric field affects the cation movement in the field through their (de)intercalation between individual MXene flakes. This results in reversible swelling and contraction of the membrane monitored by ionic conductance through the nanopore. This unique nanopore coupled to a mechanical actuation system could provide new insights into designing single-molecule biosensing platforms at the nanoscale.

Tuning the magnetic properties of NiPS3 through organic-ion intercalation.

Atomically thin van der Waals magnetic crystals are characterized by tunable magnetic properties related to their low dimensionality. While electrostatic gating has been used to tailor their magnetic response, chemical approaches like intercalation remain largely unexplored. Here, we demonstrate the manipulation of the magnetism in the van der Waals antiferromagnet NiPS3 through the intercalation of different organic cations, inserted using an engineered two-step process. First, the electrochemical intercalation of tetrabutylammonium cations (TBA+) results in a ferrimagnetic hybrid compound displaying a transition temperature of 78 K, and characterized by a hysteretic behavior with finite remanence and coercivity. Then, TBA+ cations are replaced by cobaltocenium via an ion-exchange process, yielding a ferrimagnetic phase with higher transition temperature (98 K) and higher remanent magnetization. Importantly, we demonstrate that the intercalation and cation exchange processes can be carried out in bulk crystals and few-layer flakes, opening the way to the integration of intercalated magnetic materials in devices.

Mechanistic insights into the pseudocapacitive performance of bronze-type vanadium dioxide with mono/multi-valent cations intercalation

Mechanistic understanding of mono/multi-valent cations' behaviors upon intercalation into solvothermally prepared VO2(B), which enables rational design of layered oxides with excellent charge storage performance.

Supercapacitance in graphene oxide materials modified with tetrapyrrole dyes: a mechanistic study.

The global increase in mobile technology usage has created a need for better energy storage systems. With standard batteries reaching their technological limits, alternate energy storage methods are gaining momentum. In this study, we demonstrate a cheap and efficient way of building from scratch high-performance supercapacitors based on graphene oxide (GO) functionalized with tetrapyrrole derivatives: porphyrins and phthalocyanines. We present supercapacitors with capacitances about 30 times larger than those of the pristine graphene oxide-based counterparts. Experimental characterisation methods including X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), ultraviolet-visible spectroscopy (UV-VIS), electron paramagnetic resonance (EPR), and density functional theory (DFT) calculations revealed correlations between the structural, magnetic, electronic and thermodynamic properties of these materials and their performance as supercapacitors. Electrochemical studies indicate the complex and versatile nature of capacitive effects associated with thin layers of supramolecular composites of graphene oxide. The electrical double layer (EDL) capacitance, cation intercalation and faradaic processes are coupled. Moreover, differences in the electronic interactions between GO and tetrapyrrolic modifiers have a profound effect on the observed capacitance. At the same time, these interactions are sufficiently weak to induce only subtle spectral changes, as well as a small increase of the interlayer distance as determined by XRD measurements. The present work offers a viable strategy for manufacturing high-performance supercapacitive materials that are superior to the state of the art nanocarbon-based supercapacitors using benign electrolytes in terms of capacitance per mass unit and have the potential for application in future green energy storage technologies. Our study provides insight into the multifarious origins of supercapacitance beyond the well-known EDL mechanism.

Intercalation of cobalt cations into Co9S8 interlayers for highly efficient and stable electrocatalytic hydrogen evolution

A one-step solvothermal method is demonstrated to synthesize layered Co9S8 intercalated with Co cations. The as-prepared electrocatalyst exhibits outstanding performance for the hydrogen evolution reaction as well as remarkable long-term catalytic durability.