Ion Intercalation Research Articles

Na+-doped WO3 double-layer resistive switching device for biomimetic applications

We report on polycrystalline double-layer NaWO3 thin films in a two-terminal device configuration showing resistive switching (RS) based on the neuronal ion Na+ for biomimetic applications. A top NayWO3 layer functions as a Na+ reservoir, enabling fast Na+ ion intercalation into a bottom NaxWO3 layer with x < y, giving good resistance control for analog processing. Operando Raman measurements show Na+ activation under 0.5 V and the electrical characterization proves that the switching is linked to the motion of Na+. The switching mechanism is investigated thoroughly by studying different film layer combinations. The observed RS performance can be explained by the change of electron emission/hopping site energy levels upon Na+ intercalation. The presented devices based on biocompatible materials constitute a promising route towards an analog processing building block for emulating neuronal ion channels for emerging biomimetic and potentially biomedical applications, as well as for flexible electronics.

One‐Step Electrodeposition of Iron Oxyhydroxide Onto 3D Porous Graphene Substrates for on Chip Asymmetric Micro‐Supercapacitors

AbstractElectrochemical capacitors based on redox active materials can achieve greater capacitance values than traditional electric double layer composites. Herein, electrodeposition of iron oxyhydroxide from a mildly acidic acetate precursor is reported. The one‐step deposition resulted in a submicron film composed of FeOOH phase, which was confirmed via Raman and x‐ray photoelectron spectroscopy. The capacitance increased linearly with loading amount and achieved a maximum at 1600 mC deposition with 120 mF cm−2 at 25 mV s−1 after which the film became more resistive, limiting electrolyte access to the porous graphene substrate. The deposited FeOOH demonstrated promising rate capability and good cycling stability, without phase changes, retaining 82 % of the initial capacitance after 5000 consecutive charge/discharge cycles. The charge storage mechanism of FeOOH was determined via in situ Raman spectroscopy, which followed reversible iron oxygen vibration changes upon cycling which become more intense upon reduction as a result of sodium ion intercalation. Furthermore, an asymmetric configuration full cell combining FeOOH/MnO2 allowed the working voltage to be extended to 2 V, maintaining an ideal capacitor behaviour, and achieving a maximum energy and power density of 21 μWh cm−2 and 2.5 mW cm−2 respectively.

Two-Dimensional ABS4 (A and B = Zr, Hf, and Ti) as Promising Anode for Li and Na-Ion Batteries.

Metal ion intercalation into van der Waals gaps of layered materials is vital for large-scale electrochemical energy storage. Transition-metal sulfides, ABS4 (where A and B represent Zr, Hf, and Ti as monolayers as anodes), are examined as lithium and sodium ion storage. Our study reveals that these monolayers offer exceptional performance for ion storage. The low diffusion barriers enable efficient lithium bonding and rapid separation while all ABS4 phases remain semiconducting before lithiation and transition to metallic states, ensuring excellent electrical conductivity. Notably, the monolayers demonstrate impressive ion capacities: 1639, 1202, and 1119 mAh/g for Li-ions, and 1093, 801, and 671 mAh/g for Na-ions in ZrTiS4, HfTiS4, and HfZrS4, respectively. Average voltages are 1.16 V, 0.9 V, and 0.94 V for Li-ions and 1.17 V, 1.02 V, and 0.94 V for Na-ions across these materials. Additionally, low migration energy barriers of 0.231 eV, 0.233 eV, and 0.238 eV for Li and 0.135 eV, 0.136 eV, and 0.147 eV for Na make ABS4 monolayers highly attractive for battery applications. These findings underscore the potential of monolayer ABS4 as a superior electrode material, combining high adsorption energy, low diffusion barriers, low voltage, high specific capacity, and outstanding electrical conductivity.

Electrochemical regulation of graphene infrared image display based on high-efficiency Lithium ions intercalation method

Electrochemical regulation of graphene infrared image display based on high-efficiency Lithium ions intercalation method

Quantum Spin Exchange Interactions Trigger O p Band Broadening for Enhanced Aqueous Zinc-Ion Battery Performance.

The pressing demand for large-scale energy storage solutions has propelled the development of advanced battery technologies, among which zinc-ion batteries (ZIBs) are prominent due to their resource abundance, high capacity, and safety in aqueous environments. However, the use of manganese oxide cathodes in ZIBs is challenged by their poor electrical conductivity and structural stability, stemming from the intrinsic properties of MnO2 and the destabilizing effects of ion intercalation. To overcome these limitations, our research delves into atomic-level engineering, emphasizing quantum spin exchange interactions (QSEI). These essential for modifying electronic characteristics, can significantly influence material efficiency and functionality. We demonstrate through density functional theory (DFT) calculations that enhanced QSEI in manganese oxides broadens the O p band, narrows the band gap, and optimizes both proton adsorption and electron transport. Empirical evidence is provided through the synthesis of Ru-MnO2 nanosheets, which display a marked increase in energy storage capacity, achieving 314.4 mAh g-1 at 0.2 A g-1 and maintaining high capacity after 2000 cycles. Our findings underscore the potential of QSEI to enhance the performance of TMO cathodes in ZIBs, pointing to new avenues for advancing battery technology.

Analysis of Battery-like and Pseudocapacitive Ion Intercalation Kinetics via Distribution of Relaxation Times

Abstract Improving the kinetics of electrochemical ion intercalation processes is of interest for realizing high-power electrochemical energy storage. This includes classical battery-like intercalation and pseudocapacitive intercalation processes with a capacitor-like electrochemical signature. Electrochemical methods are needed to probe the kinetics of such complex multistep processes in detail. Here, we present the use of the distribution of relaxation times (DRT) analysis of electrochemical impedance data to identify the kinetic limits of intercalation reactions. We study the lithium intercalation reaction in TiS2 from organic and aqueous electrolytes as a model system. The material can exhibit both battery-like and pseudocapacitive intercalation regimes depending on the potential range, variable diffusion lengths by adjusting its particle size, and a tunable degree of solvent cointercalation by choosing the electrolyte solvent. Using DRT, we can distinguish between the kinetic limitations imposed by solid-state ion diffusion, interfacial ion adsorption and transport, and ion desolvation processes. Thus, DRT analysis can complement existing methods, such as voltammetry or 3D-Bode analysis, to better understand the kinetics of intercalation reactions.

Optimizing Prussian Blue Analogues for Potassium‐Ion Batteries: Advanced Strategies

AbstractPotassium‐ion batteries (PIBs), with the merits of abundant resources and low cost, have rapidly garnered attention as a potential candidate for large‐scale energy storage. Among the various contenders, Prussian blue analogues (PBAs) are considered one of the most suitable cathode materials owing to their relatively easy and economical synthesis as well as the three‐dimensional open framework which facilitates fast potassium ions intercalation without causing drastic volume expansion. Despite these advantages, integrating PBA as a cathode material for PIBs presents substantial challenges, which hinder their further practical applications. Herein, a fundamental review on the development and advance of PBAs in PIBs is presented with the elucidation of their synthesis methods, structural characteristics, and optimization strategies. Particularly, key areas of focus include regulating crystal structures, doping transition metals, engineering interfaces, and employing innovative techniques such as high‐entropy approaches are highlighted. Finally, critical perspectives for future development of PBAs toward practical potassium‐based energy storage devices are proposed.

Gate-Controlled Potassium Intercalation and Superconductivity in Molybdenum Disulfide.

Intercalation of guest ions into a van der Waals (vdW) gap in layered materials is a powerful route to create novel material phases and functionalities. Ionic gating is a technique to control the motions and configuration of ions for both intercalation and surface electrostatic doping. The advance of ionic gating enables the in situ probe of dynamics of ion diffusion, carrier doping, and transport properties. Here we performed in situ resistivity and Raman experiments on the potassium ion (K+) intercalation of single-crystal MoS2 and constructed a temperature-carrier density phase diagram. The K+-intercalation induces a structural transition from the prismatically coordinated phase to the octahedrally coordinated phase, where anisotropic three-dimensional superconductivity and a possible charge density wave state were observed. The present ionic gating offers a comprehensive view of the intercalated phases and proves that the electrostatically induced superconductivity is distinct from that in the intercalated phase.

Synergistic effects of MXene and Co3O4 in composite electrodes: High-performance energy storage solutions

The development of high-performance electrode materials is crucial for advancing supercapacitor technology. The two-dimensional layered structure of MXene (Ti3C2Tx) presents high conductivity, abundant surface functional groups and accessible ion interaction between layers. However, the MXene suffers from the layer aggregation. To overcome this issue, we synthesized a composite material combining MXene with cobalt oxide (Co3O4) to enhance electrochemical performance in supercapacitors. MXene’s two-dimensional layered structure, high conductivity, and abundant surface functional groups allow for efficient ion intercalation, while Co3O4 contributes high theoretical capacitance and rich oxidation states. The resulted MXene/Co3O4 composite exhibits an impressive areal capacitance of 6.456F/cm2 at a current density of 3 mA/cm2, maintaining 90.52 % capacitance retention at 30 mA/cm2, and 81.37 % capacity after 5000 charge–discharge cycles. Additionally, the asymmetric supercapacitor (ASC) device fabricated using the MXene/Co3O4 composite achieves a power density of 6.41 mW/cm2 at an energy density of 0.37 mWh/cm2, with 82.3 % capacitance retention after 5000 cycles. These results demonstrate that the MXene/Co3O4 composite material is a promising candidate for high-performance supercapacitors, offering significant improvements in rate capability and long-term cycling stability.

Molybdenum-Modified Niobium Oxide: A Pathway to Superior Electrochromic Materials for Smart Windows and Displays

Electrochromic materials enable the precise control of their optical properties, making them essential for energy-saving applications such as smart windows. This study focuses on the synthesis of molybdenum-doped niobium oxide (Mo-Nb2O5) thin films using a one-step hydrothermal method to investigate the effect of Mo doping on the material’s electrochromic performance. Mo incorporation led to distinct morphological changes and a transition from a compact granular structure to an anisotropic rod-like feature. Notably, the MN-3 (0.3% Mo) sample displayed an optimal electrochromic performance, achieving 77% optical modulation at 600 nm, a near-perfect reversibility of 99%, and a high coloration efficiency of 89 cm2/C. Additionally, MN-3 exhibited excellent cycling stability, with only 0.8% degradation over 5000 s. The MN-3 device also displayed impressive control over color switching, underscoring its potential for practical applications. These results highlight the significant impact of Mo doping on improving the structural and electrochromic properties of Nb2O5 thin films, offering improved ion intercalation and charge transport. This study underscores the potential of Mo-Nb2O5 for practical applications in energy-efficient technologies.

Bottom-up stripping of graphene with controlled oxidation behaviors towards supercapacitors energy storage

Due to its distinctive two-dimensional planar structure, room temperature quantum Hall effect, and high strength, graphene has garnered significant interest in the fields of energy storage and conversion. In order to achieve high efficiency in the production of graphene, electrochemical peeling has been extensively investigated. Nevertheless, the intermolecular forces between graphite layers are disrupted during ion intercalation in solution, leading to inconsistent bonding forces and low yields. In order to address the issues above, this study introduces a novel bottom-up electrochemical peeling method, wherein graphite expansion occurs above the electrolyte. By preventing contact between the peeled graphene and the electrolyte, the oxidation of graphene is significantly minimized, resulting in a substantial yield of 88 %. At the current density of 1.0 A g−1, the Go-QAS displayed 225.5 F g−1, and kept about 220.2 F g−1 after 500 cycles. The well-designed bottom-up peeling process leads to graphene nanosheets with reduced structural degradation, high purity, and excellent conductivity. This technique is expected to introduce innovative concepts for the field.

Manipulating the d-band center of bimetallic molybdenum vanadate for high performance aqueous zinc-ion battery

Vanadium-based oxides have good application prospects in aqueous zinc ion batteries (AZIBs) due to their structures suitable for zinc ion extraction and intercalation. However, their poor conductivity limits their further development. The d-band center plays a key role in promoting adsorption of ions, which promotes the development of electrode materials. Here, a series of MoV2O8 compounds with oxygen defect (Od-MoV2O8) were synthesized by a simple hydrothermal process and a subsequent vacuum calcination process through strict control of the deoxidation time. Theoretical calculations reveal that the abundant oxygen vacancies in MoV2O8 effectively regulate the d-band center of the zinc ion adsorption site. This precise control of the d-band center enhances the zinc ion adsorption energy of MoV2O8, lowers the migration energy barrier for zinc ions, and ultimately significantly boosts zinc storage performance. The specific capacity is as high as 282.4 mAh/g after 100 cycles at 0.1 A/g, and it also shows excellent performance and outstanding cycle life. In addition, the maximum energy density of Od-MVO-0.5 (MoV2O8 sample deoxidized for 0.5 h) is 343.3 Wh kg−1. Importantly, the mechanism of Zn2+ storage in Od-MoV2O8 was revealed by the combination of in situ and ex situ characterization techniques.

Progress in aluminum-ion battery technology: innovations in cathode materials, electrolyte chemistry, and performance enhancement

The review explores recent advancements in aluminum-ion battery technology, focusing on innovations in cathode materials, electrolyte chemistry, and performance enhancement. Notable developments include new cathode materials like activated carbon and graphene composites, which improve surface area, conductivity, and overall battery performance. Advances in electrolyte formulations, particularly AlCl3-based ionic liquids, have optimized ion transport and stabilized electrochemical processes, extending cycle life and reliability. Studies on ion intercalation mechanisms using density functional theory and molecular dynamics have provided insights into electrode transformations during charge-discharge cycles, aiding in the design of cathode materials with higher ion storage capacities and improved cyclability. These advancements highlight AIBs' potential as a promising alternative for large-scale energy storage applications.

Highly efficient removal of trace thallium from surface water by Co@Fe Prussian blue analogue coated membrane

Super trace thallium(I) (Tl+) is still highly toxic and its removal from surface water is challenging. Here, we developed a new adsorptive membrane by immobilizing bimetal (cobalt and iron) Prussian blue analogues (Co@Fe-PBAs) on a polytetrafluoroethylene microporous membrane (Co@Fe-PBAs-M). The prepared membrane displayed precise adsorption of trace Tl+ (50 μg/L) from complex water. A variety of interfering factors, such as water pH, competitive adsorption of positive ions (Na+ and K+) and negative ions (CO32– and PO43-), natural organic matters (e.g., fulvic acid and bovine serum albumin) were evaluated during Tl removal. The composite membrane showed high removal efficiency (over 80 %) during long-term dynamic membrane separation of surface water containing super trace Tl+ (<2.0 μg/L), breaking through the adsorption limitation in ultralow concentration of Tl+. The unique bimetal electron transfer of Co@Fe-PBAs-M reinforced the adsorptive performance to Tl+ through dual ion exchange and intercalation. In the treatment of real Pearl River water containing 0.5 μg/L of Tl+, our membrane effectively reduced the Tl+ concentration to 0.04 μg/L during 6-h continuous separation, which was far below the required level for drinking water (i.e., 0.1 μg/L). This work offers a promising solution for safe drinking water by remedying ultralow Tl+ contaminated surface water.

Quantitative pre-intercalation of alkali metal ions enables precisely modulating Li+ storage of MXenes

Ion intercalation is crucial for improving energy storage performance, but controlling the content of intercalated ions is challenging for two-dimensional (2D) electrode materials although it enables clarifying individual intercalation behaviors and thereof pinpointing the intercalation mechanism. Herein, the equal‐content alkali metal ions were successfully manipulated to intercalate into Mo2CTx MXene electrodes via an electrochemistry‐driven approach via the anti‐battery principle. Based on a variety of alkali metal ions pre‐intercalation into the Mo2CTx MXene (M+‐Mo2CTx) electrodes, the lithium storage performance was largely improved. Li+‐Mo2CTx electrode exhibits an outstanding capacity of 395.49 mAh g−1 at 200 mA g−1 after 100 cycles due to the enhanced redox activity induced by high-valence Mo and low -F interlayer exposed surface. Besides, the K+‐Mo2CTx electrode delivers excellent rate performance due to faster ion transfer kinetics originating from the pillaring effect of pre-intercalated K+ ions. In a broader sense, our study opens up a new route to accurately improve the electrochemical performance via precisely tuning the content of ions intercalated into 2D intercalation‐type materials.

Rational design of MoS2 nanoflowers-decorated carbon nanofibers with enhanced electronic transmission for boosting capacitive deionization

Capacitive deionization (CDI) has sparked considerable interest for its promising application in handling brackish water. Unfortunately, most traditional carbonaceous materials are still plagued by the limited desalination capacity and sluggish adsorption kinetics with the single adsorption mechanism and irrational pore structure. Herein, we developed a facile and affordable strategy to integrate electrospinning with hydrothermal method to fabricate MoS2 nanoflowers-decorated carbon nanofibers (MoS2/CNF) composite for boosting desalination performance. CNF not only serves as a supportive framework to inhibit the agglomeration of MoS2 nanosheets favoring the full contact with salt solutions, but also typically diminishes the charge transfer resistance of the composite. By taking advantage of the double layer adsorption of CNF and the hierarchically micro-mesoporous structure of MoS2 nanoflowers with large interlayer spacer for salt ions intercalation, the optimized sample MoS2/CNF-1 employed as a cathode for the asymmetric hybrid CDI cell showed an eminent capacity for desalination of 30.9 mg·g−1, an ultrafast rate for desalination of 3.7 mg·g−1·min−1, and an attractive circulation stability for desalination with the capacity reservation remaining at 94.8 % after 30 cycles in the solution of 500 mg·L−1 NaCl at 1.2 V. This research sheds fresh light on the evolution of advanced CDI electrode materials for practical utilization.

Fast-switching electrochromic smart windows based on WO3 doped NiO thin films

Nickel oxide (NiO) is a very promising material for the counter electrode in electrochromic devices (ECDs). In the current research, WO3 incorporated NiO thin films were fabricated via RF sputtering to enhance the electrochromic performance of NiO thin films. An XRD analysis revealed that the addition of WO3 to the cubic NiO thin film disrupts its long-range crystalline structure, resulting in an amorphous state. FESEM revealed the formation of columnar structure which favours ECDs. XPS analysis revealed that the addition of WO3 into NiO enhanced the hole concentration by creating nickel vacancies (nickel defects). Compared to pristine NiO, WO3 mixed NiO thin films showed enhanced optical modulation (66 %) with rapid switching speed (0.6 s/1.0 s for bleaching/colouring). This is mainly because the defect- induced amorphous structure of the nickel tungsten oxide thin film can provide large number of diffusion channels which facilitates the rapid ion intercalation process, and can accommodate large number of ions, and hence enhances the electrochromic performance. This advancement might have a substantial impact on the development of nickel tungsten oxide as a potential counter electrode in high-performance energy saving smart windows.

Competition for Ion Intercalation in Prussian Blue Analogues as Cathode Materials for Calcium Ion Batteries

With multivalent ion batteries being considered viable post‐lithium energy storage technologies, the last few years have seen increasing interest in intercalation type cathode materials for Ca‐ion batteries (CIBs). Prussian blue analogues (PBAs) display many positive attributes such as open structural framework, large interstitial sites, and versatile transition metal redox activity. The PBA cathodes reported for CIBs often contain K‐ion or Na‐ion due to the syntheses involving the use of potassium or sodium hexacyanoferrate. It has been long overlooked whether the presence of K‐ion or Na‐ion in pristine PBAs could affect the Ca‐ion storage in the PBAs when assessing their CIB performance. Through a combined experimental and computational investigation, this work reports that when K+/Na+ is present in the pristine PBAs, K/Na intercalation is preferred by the PBA structure over Ca intercalation even in the Ca cells. Ca‐ion intercalation can be increased when the K+/Na+ content in the pristine PBAs is reduced, shifting from a K or Na‐dominated intercalation process to a Ca/K or Ca/Na co‐intercalation process. This work consolidates that PBAs are an interesting and versatile intercalation host for several ions, but investigating PBAs as intercalation cathodes requires careful consideration of all ions present in the battery system.

Potential difference-induced electrodeposition of defect-rich α-cobalt hydroxide on porous copper (PCu): High-voltage performance of supercapacitor

Designing electrode materials for aqueous battery-type supercapacitors to extend the operating voltage window remains a significant challenge to increase the energy density of aqueous supercapacitors. In this work, a directional electrodeposition method without any additives was employed to deposit α-Co(OH)2 onto a porous copper (PCu) current collector substrate, which involves the fabrication of a supercapacitor electrode material with a cross-linked network structure named α-Co(OH)2@PCu900. The potential difference between copper and cobalt facilitated the formation of a larger interlayer spacing for α-Co(OH)2. In addition, crystals of α-Co(OH)2 with different orientations exert stress on one another, leading to lattice distortion and vacancy formation. The morphology and microstructure of materials were analyzed through techniques such as SEM, HRTEM, XRD, and XPS, confirming the validity of the experimental design. This defect-rich, large interlayer spacing structure facilitates ion intercalation and deintercalation during the charge-discharge process, thereby expanding the operating voltage window. In a three-electrode system, α-Co(OH)2@PCu900 exhibited a potential range from −0.45 V to 0.55 V and demonstrated an areal capacitance of 2580 mF cm−2 and specific capacitance of 600 A g−1 at 2 mA cm−2. The α-Co(OH)2@PCu900 was used as the cathode material and commercial reduced graphene oxide (rGO) was used as the anode material in an asymmetric supercapacitor, and the ASC device exhibited an areal capacitance of 295.3 mF cm−2 and a specific capacitance of 87.89 F g−1. Notably, it retained a high energy density of 0.12 mW h cm−2 (35.27 Wh kg−1) at a power density of 1.7 mW cm−2 (505.95 W kg−1). This method established α-Co(OH)2@PCu900 as a promising supercapacitor electrode material, providing a viable strategy for designing and fabricating functional electrode materials.

Magnetic, electrochemical properties and probable mechanism of charge storage in the pristine and Cr-doped CeO2

The emergence of cerium oxide (CeO2) has garnered significant interest as an energy storage gadget owing to its inspiring electrochemical, electrical and mechanical properties. Current work, we have synthesized Ce1-xCrxO2x=0,0.025,0.05,0.1 via simple auto-combustion method. The structure–property relations were characterized by several physicochemical characterizations such as XRD, FESEM, EDAX, vibrational spectroscopy, XPS, BET and UV–visible spectroscopy. The suds-like CeO2 morphology and oxygen defects were highly suitable for the electrolytic ion intercalation to the electrode. By employing the Trassati model, Power law establishment and Dunn’s model, the innate charge storage mechanisms in the synthesized materials were revealed. The specific capacitance of pristine CeO2 attained 30.42F/g and it enhances to 73.56F/g for Ce0.925Cr0.025O2 at 0.5 A/g. Further Ce0.925Cr0.025O2 possesses a capacitance retention of 108.85 % even after 1000 GCD cycles at a current density of 4 A/g. The electrochemical results suggest Ce1-xCrxO2x=0.025 as a good material for supercapacitor applications. The magnetic measurements on the doped and undoped samples show no long-range ordering indicating zero hysteresis loss. Further, magnetic studies suggests the suitability of Ce1-xCrxO2x=0.1 for supercapacitance applications.