Charge Storage Research Articles

Hollow Core-Shelled Na4Fe2.4Ni0.6(PO4)2P2O7 with Tiny-Void Space Capable Fast-Charge and Low-Temperature Sodium Storage.

Iron-based mixed polyanion phosphate Na4Fe3(PO4)2P2O7 (NFPP) is recognized as a promising cathode for Sodium-ion Batteries (SIBs) due to its low cost and environmental friendliness. However, its inherent low conductivity and sluggish Na+ diffusion limit fast charge and low-temperature sodium storage. This study pioneers a scalable synthesis of hollow core-shelled Na4Fe2.4Ni0.6(PO4)2P2O7 with tiny-void space (THoCS-0.6Ni) via a one-step spray-drying combined with calcination process due to the different viscosity, coordination ability, molar ratios, and shrinkage rates between citric acid and polyvinylpyrrolidone. This unique structure with interconnected carbon networks ensures rapid electron transport and fast Na+ diffusion, as well as efficient space utilization for relieving volume expansion. Incorporating regulation of lattice structure by doping Ni heteroatom to effectively improve intrinsic electron conductivity and optimize Na+ diffusion path and energy barrier, which achieves fast charge and low-temperature sodium storage. As a result, THoCS-0.6Ni exhibits superior rate capability (86.4 mAh g-1 at 25 C). Notably, THoCS-0.6Ni demonstrates exceptional cycling stability at -20 °C with a capacity of 43.6 mAh g-1 after 2500 cycles at 5 C. This work provides a universal strategy to design the hollow core-shelled structure with tiny-void space cathode materials for reversible batteries with fast-charge and low-temperature Na-storage features.

Mg‐ZnO/CNT Nanocomposite as Electrode Materials with Enhanced Electrochemical Performance for Supercapacitor Applications

AbstractThe present research work reported the study of nanocomposites of undoped and Mg‐doped ZnO with CNT as electrode materials for supercapacitor application. The undoped ZnO/CNT and Mg‐doped ZnO/CNT nanocomposites (i.e., 10 % Mg‐doped and 20 % Mg‐doped) were synthesized using a cost‐effective blending‐assisted hydrothermal method. The morphological (FESEM & TEM) studies revealed that the diameter of CNT was ~7 nm and the ZnO nanoparticles were spherical in shape with an average particle size of ~5 nm. In addition, it was also found that 10 % Mg‐ZnO and 20 % Mg‐ZnO had a sheet‐like structure. XRD and FTIR studies further confirmed the successful doping of Mg in ZnO and CNT nanocomposites. BET analysis showed that the value of specific capacitance increased with the increase in surface area. Further, the electrochemical performance of these nanocomposites revealed that the higher doping percentage, 20 % Mg‐ZnO/CNT nanocomposite achieved the highest specific capacitance value i.e., 458.5 F/g at 0.1 A/g current density in 3M H2SO4 electrolytic solution, having a retention of 99.8 % after 12,00 long cycles. In addition, the charge storage mechanism revealed that the as‐synthesized nanocomposites showed both the diffusion‐controlled and capacitive‐controlled behaviors. Thus, a higher value of specific capacitance with excellent cyclic stability indicated the higher efficiency of Mg‐doped ZnO/CNT nanocomposite for future supercapacitor applications.

Enhanced Electrochemical Performance and Cycling Stability of the (NH4)8[VIV12VV7O41(OH)9]·11H2O Cathode in Aqueous Zinc Ion Batteries.

Although vanadium-based compounds possess several advantageous characteristics, such as multivalency, open structure, and high theoretical specific capacity, which render them highly promising candidates for cathode materials in aqueous zinc ion batteries (AZIBs), their large-scale application still necessitates addressing the challenges posed by slow kinetics resulting from low conductivity and capacity degradation caused by material dissolution. Therefore, we have successfully synthesized high-purity mixed multivalent (NH4)8[VIV12VV7O41(OH)9]·11H2O (NVO) crystalline materials via a liquid-phase precipitation modulation method and employed it as an innovative AZIB cathode material for the first time. It exhibits a remarkable reversible specific capacity of 240 and 102.2 mAh g-1 after undergoing 1000 cycles at current densities of 1 and 5 A g-1, respectively, highlighting its exceptional cycling stability and electrochemical performance. The results from cyclic voltammetry (CV) and GITT tests demonstrate that the dominant factor influencing the charge storage is the pseudocapacitive behavior, which is accompanied by an exceptionally high diffusion coefficient of Zn2+ at a rate of 10-10 cm2 s-1. The highly reversible intercalation-deintercalation of Zn2+ in NVO/Zn cells is demonstrated through ex-situ TEM, XRD, and XPS analyses. This work provides a benchmark for the development of high-performance POV electrode materials.

Nitrogen and phosphorus enriched nanoporous carbonaceous material for gas sorption and supercapacitor applications

Nitrogen and phosphorous-enriched heteroatoms-based nanoporous carbonaceous material (designated as HPHMC900) possesses a high surface area of 1668 m2 g−1 was synthesized. HPHMC900 captures 5.6 and 3 mmol g−1 of CO2 and CH4 at 273 K and 1 bar, respectively. Further, the material has 11.95 mmol g−1 of H2 adsorption capability at 77 K and 1 bar. HPHMC900 has been investigated for supercapacitor application. Further, a symmetric supercapacitor device (SSD) fabricated using the HPHMC900, has a specific capacitance (Csp) of 233 F g−1, energy (E) of 46.6 Wh kg−1, and power (P) of 289 W kg−1, respectively. The high Csp and high energy were achieved at low-concentrated aqueous electrolyte (0.5 M KOH), without using any redox-active agents. Further, it shows 100 % coulombic efficiency and initial capacitance retention (94.9 %) after 10,000 cycles. This research elucidates the correlation between high surface area and heteroatom enrichment with enhanced charge storage and gas adsorption efficiency.

Multi-Group Polymer Coating on Zn Anode for High Overall Conversion Efficiency Photorechargeable Zinc-Ion Batteries.

The solar-driven photorechargeable zinc-ion batteries have emerged as a promising power solution for smart electronic devices and equipment. However, the subpar cyclic stability of the Zn anode remains a significant impediment to their practical application. Herein, poly(diethynylbenzene-1,3,5-triimine-2,4,6-trione) (PDPTT) was designed as a functional polymer coating of Zn. Theoretical calculations demonstrate that the PDPTT coating not only significantly homogenizes the electric field distribution on the Zn surface, but also promotes the ion-accessible surface of Zn. With multiple N and C=O groups exhibiting strong adsorption energies, this polymer coating reduces the nucleation overpotential of Zn, alters the diffusion pathway of Zn2+ at the anode interface, and decreases the corrosion current and hydrogen evolution current. Leveraging these advantages, Zn-PDPTT//Zn-PDPTT exhibits an exceptionally long cycling time (≥4300 h, 1 mA cm-2). Zn-PDPTT//AC zinc-ion hybrid capacitors can withstand 50,000 cycles at 5 A/g. Zn-PDPTT//NVO zinc-ion battery exhibits a faster charge storage rate, higher capacity, and excellent cycling stability. Coupling Zn-PDPTT//NVO with high-performance perovskite solar cells results in a 13.12 % overall conversion efficiency for the photorechargeable zinc-ion battery, showcasing significant value in advancing the efficiency and upgrading conversion of renewable energy utilization.

Multi‐Group Polymer Coating on Zn Anode for High Overall Conversion Efficiency Photorechargeable Zinc‐Ion Batteries

AbstractThe solar‐driven photorechargeable zinc‐ion batteries have emerged as a promising power solution for smart electronic devices and equipment. However, the subpar cyclic stability of the Zn anode remains a significant impediment to their practical application. Herein, poly(diethynylbenzene‐1,3,5‐triimine‐2,4,6‐trione) (PDPTT) was designed as a functional polymer coating of Zn. Theoretical calculations demonstrate that the PDPTT coating not only significantly homogenizes the electric field distribution on the Zn surface, but also promotes the ion‐accessible surface of Zn. With multiple N and C=O groups exhibiting strong adsorption energies, this polymer coating reduces the nucleation overpotential of Zn, alters the diffusion pathway of Zn2+ at the anode interface, and decreases the corrosion current and hydrogen evolution current. Leveraging these advantages, Zn‐PDPTT//Zn‐PDPTT exhibits an exceptionally long cycling time (≥4300 h, 1 mA cm−2). Zn‐PDPTT//AC zinc‐ion hybrid capacitors can withstand 50,000 cycles at 5 A/g. Zn‐PDPTT//NVO zinc‐ion battery exhibits a faster charge storage rate, higher capacity, and excellent cycling stability. Coupling Zn‐PDPTT//NVO with high‐performance perovskite solar cells results in a 13.12 % overall conversion efficiency for the photorechargeable zinc‐ion battery, showcasing significant value in advancing the efficiency and upgrading conversion of renewable energy utilization.

Optimisation of Mo doping to form NiCoMo ternary sulphides for high performance charge storage.

Multi-component synergy and the rational design of structures are effective methods for preparing electrode materials for high-performance energy storage devices. Transition metal-based hydroxides offer advantages such as a large specific surface area, large interlayer spacing, multiple redox states, and high theoretical capacity, making them commonly used as positive materials for supercapacitors. However, challenges like low conductivity and severe agglomeration limit their practical application. This study focuses on the preparation of Ni, Co, and Mo ternary transition metal hydroxides by incorporating the Mo element to optimize their structure. Furthermore, sulfide ions were utilized in an ion exchange process to replace hydroxides, resulting in the formation of NiCoMo ternary sulfide electrode materials. By adjusting the amount of Mo added, a spherical nanoneedle-shaped N2C1MS0.2-2 electrode material was successfully synthesized. This electrode exhibited a specific capacity of 2094 F g-1 at a current density of 1 A g-1. In addition, an asymmetric supercapacitor was assembled with activated carbon as the negative electrode and N2C1MS0.2-2 as the positive electrode, which had an energy density of 46.2 W h kg-1 at a power density of 800 W kg-1, a capacity retention of 89.7% and a coulombic efficiency of 97.8% after 10 000 cycles. This study provides a reference for the design and preparation of ternary sulphide electrode materials.

Unveiling Na‐ion storage mechanism and interface property of layered perovskite Bi2TiO4F2@rGO anode in ether‐based electrolyte

AbstractTo unveil the charge storage mechanisms and interface properties of electrode materials is very challenging for Na‐ion storage. In this work, we report that the novel layered perovskite Bi2TiO4F2@reduced graphene oxides (BTOF@rGO) serves as a promising anode for Na‐ion storage in an ether‐based electrolyte, which exhibits much better electrochemical performance than in an ester‐based electrolyte. Interestingly, BTOF@rGO possesses a prominent specific capacity of 458.3–102 mAh g−1/0.02–1 A g−1 and a high initial coulombic efficiency (ICE) of 70.3%. Cross‐sectional morphology and depth profile surface chemistry indicate not only a denser reactive interfacial layer but also a superior solid electrolyte interface film containing a higher proportion of inorganic components, which accelerates Na+ migration and is an essential factor for the improvement of ICE and other electrochemical properties. Electrochemical tests and ex situ measurements demonstrate the triple hybridization Na‐ion storage mechanism of conversion, alloying, and intercalation for BTOF@rGO in the ether‐based electrolyte. Furthermore, the Na‐ion batteries assembled with the BTOF@rGO anode and the commercial Na3V2(PO4)2F3@C cathode exhibit remarkable energy densities and power densities. Overall, the work shows deep insights on developing advanced electrode materials for efficient Na‐ion storage.

A Charge Confinement Strategy for Boosting Interfacial Space Charge Storage in Manganese Ferrites Enabled by Highly Polarized Fluorinated‐Interfacial Layer for High‐Energy‐Density and Ultrafast Rechargeable Lithium‐Ion Batteries

A Charge Confinement Strategy for Boosting Interfacial Space Charge Storage in Manganese Ferrites Enabled by Highly Polarized Fluorinated‐Interfacial Layer for High‐Energy‐Density and Ultrafast Rechargeable Lithium‐Ion Batteries

One-pot synthesis of tungsten oxynitride/nitrogen-doped graphene with particle-sheet hybrid nanostructure as a highly effective binder-free supercapacitor electrode

High-performance nanoscale composites have achieved predominance as promising materials for supercapacitor applications. Graphene nanosheets decorated with transition metal oxynitride nanoparticles can be highly beneficial in improving supercapacitor properties. However, they are hardly retrieved, and their electrochemical characterizations and inherent charge-storage mechanisms have not been deeply investigated. Herein, tungsten oxynitride decorated nitrogen-doped graphene (WON-NG) is synthesized by a facile one-pot strategy in a particle-sheet hybrid nanostructure. The nanocomposite is grown directly on a nickel foam (NF) as the current collector through the synthesis process. X-ray photoelectron spectroscopy and TEM images have confirmed the particle-sheet hybrid nanostructure of the prepared nanocomposite with tungsten oxynitride nanoparticles and nitrogen-doped graphene nanosheet. The oxygen and nitrogen-based redox groups, which synergistically coexist in the hybrid network, inherently cooperate in the electrochemical activities of the nanocomposite. The electrochemical measurements show that the WON-NG|NF electrode can deliver a superior specific capacitance of 1079.4 F g−1 (4.6 F cm−2) at 1 A g−1 in 1 M KOH aqueous electrolyte. In-depth investigations suggest that the diffusive-controlled process governs the charge storage mechanism at all scan rates in the composite for the advantageous porous morphology. The assembled all-solid-state asymmetric supercapacitor device exhibits a high energy density of 81.6 Wh kg−1 and a power density of 5005.4 W kg−1. Also, the designed devise shows an excellent cycle life with 87.7% capacitance retention of 10,000 cycles.

Zeolitic imidazolate framework derived stellate shaped cobalt-molybdenum hybrid sulfide microflower for enhanced supercapacitor properties

Zeolitic imidazolate frameworks (ZIFs) represent a class of material exhibiting a well-defined geometry. The ZIF derivatives are known to inherit the parent morphology and have emerged as a potential platform for developing superior electrode materials. In this study, leaf-like ZIF-67 is synthesized using a chemical route and employed as the sacrificial template in one-pot hydrothermal sulfurization for preparing Co3S4-Mo15S19, cobalt‑molybdenum hybrid sulfide (CMS/NF). The unique stellate-shaped architecture of the CMS/NF microflowers enhances the exposure of the redox active sites, improving charge storage and exhibiting superior performance. On account of the synergy of the metal ions and stellate-shaped hierarchical architecture, the CMS/NF hybrid sulfide shows an excellent specific capacitance value of 3283 F g−1 at a current density of 1 A g−1 with capacitance retention of 77.7 % at 10 A g−1. An asymmetric supercapacitor device based on CMS/NF hybrid sulfide with aqueous KOH electrolyte exhibits a high specific energy of 40.8 Wh kg−1 at 400 W kg−1 with excellent cycling life of 81 % after 5000 cycles with ∼100 % coulombic efficiency. In addition, the density functional theory-based simulations have been carried out for the Co3S4-Mo15S19 hybrid system to develop a better understanding. From the total density of states, it is concluded that compared to the pristine structures, the hybrid system has enhanced states close to the Fermi level, confirming the conductivity improvement. Computed quantum capacitance for the pristine and hybrid systems corroborates the experimental capacitance consequences. Hence, the theoretical examinations warrant our electrochemical results and provide insight into developing high-performance supercapacitor electrodes.

Electrochemical Charge Transfer Kinetics of Ferrocene in the Light of Different Working Electrodes.

Ferrocene is an accidentally discovered organometallic compound that serves as a crucial redox probe in investigating electrochemical charge transfer dynamics. Besides solution phase studies, ferrocene derivatives are well-explored in molecular thin films, including self-assembled monolayers on various electrodes for understanding on-surface redox behavior, molecular electronics, and charge storage applications. Heterogeneous charge transfer is an imperative parameter for efficient charge transport in spin-dependent electrochemistry, photoelectrochemistry, and molecular electronic devices. In this work, we aim to study the electrochemical charge transfer of ferrocene on various electrodes such as commercially obtained glassy carbon, graphite rod, indium tin oxide (ITO), and as-prepared gold, and nickel to determine the impact of the nature of the working electrode on the electron transfer rate, diffusion coefficient, and reversibility of the redox process. Both the direct current and alternating current-based electrochemical experiments are performed, followed by digitization of the experimental results. The kinetics of electron transfer and electrochemical reversibility reveal a strong dependence on the nature of the working electrode, as the electrochemically driven oxidation and reduction of the material of interest are directly related to the Fermi energy and electronic structure of the working electrode.

Revealing Ion Adsorption and Charging Mechanisms in Layered Metal-Organic Framework Supercapacitors with Solid-State Nuclear Magnetic Resonance.

Conductive layered metal-organic frameworks (MOFs) have demonstrated promising electrochemical performances as supercapacitor electrode materials. The well-defined chemical structures of these crystalline porous electrodes facilitate structure-performance studies; however, there is a fundamental lack in the molecular-level understanding of charge storage mechanisms in conductive layered MOFs. To address this, we employ solid-state nuclear magnetic resonance (NMR) spectroscopy to study ion adsorption in nickel 2,3,6,7,10,11-hexaiminotriphenylene, Ni3(HITP)2. In this system, we find that separate resonances can be observed for the MOF's in-pore and ex-pore ions. The chemical shift of in-pore electrolyte is found to be dominated by specific chemical interactions with the MOF functional groups, with this result supported by quantum mechanics/molecular mechanics (QM/MM) and density functional theory (DFT) calculations. Quantification of the electrolyte environments by NMR was also found to provide a proxy for electrochemical performance, which could facilitate the rapid screening of synthesized MOF samples. Finally, the charge storage mechanism was explored using a combination of ex-situ NMR and operando electrochemical quartz crystal microbalance (EQCM) experiments. These measurements revealed that cations are the dominant contributors to charge storage in Ni3(HITP)2, with anions contributing only a minor contribution to the charge storage. Overall, this work establishes the methods for studying MOF-electrolyte interactions via NMR spectroscopy. Understanding how these interactions influence the charging storage mechanism will aid the design of MOF-electrolyte combinations to optimize the performance of supercapacitors, as well as other electrochemical devices including electrocatalysts and sensors.

Spinel nickel ferrite (NiFe2O4) materials synthesized via spray-pyrolysis for electrochemical supercapacitor application

To explore potential applications of NiFe2O4-based supercapacitors in various energy storage systems, including portable electronic devices, electric vehicles, and grid energy storage, highlighting the advantages and challenges of using NiFe2O4 in these applications. To identify and propose future research directions for further improving the performance of NiFe2O4 supercapacitors. In the study focuses on optimizing concentration of synthesis to achieve desirable structural and electrochemical properties, characterizing the synthesized materials, and assessing their specific capacitance, energy density, power density, cycle stability, and rate capability. The different molar precursor solutions were utilized for the formation of NiFe2O4 thin films by using the cost-effective spray pyrolysis technique. The impact of different molarities on the structural, morphological, elemental, optical, and charge storage performance of NiFe2O4 thin films has been studied. In the XRD studies identified the cubic crystalline structure with Fd-3 m space group symmetry of NiFe2O4. The FE-SEM shows the grain-like surface morphology of NiFe2O4 thin films. The EDAX study reveals that NiFe2O4 thin films were stoichiometric. Bandgap energy values of the thin films were observed in the range of 1.97 to 2.2 eV with allowed direct band gap transitions. The maximum specific capacitance for NiFe2O4 thin film was found to be 707 Fg−1 at 2 mVs−1 with the wider potential window of − 0.8 to + 1 .6 V in 1 M KOH aqueous electrolyte. GCD study confirms the pseudocapacitive behavior of NiFe2O4 thin films. The maximum specific energy and specific power were found to be 83.88 WhKg−1 and 5.294 KWkg−1 at a current density of 0.002 Ag−1. Such as spinel ferrite NiFe2O4 thin film electrodes as an excellent candidate material for electrochemical supercapacitor applications.

Improving the electro-optical properties of MoS2/rGO hybrid nanocomposites using liquid crystals

Hybrid systems of two-dimensional (2D) materials (such as graphene-family materials and 2D transition metal dichalcogenides) are attracting much attention due to their distinctive optoelectronic, thermal, mechanical, and chemical properties. The application perspectives of these materials in various fields further expand when enriching those with liquid crystals (LCs) primarily due to their enhanced tunability and functionality. In this study, we report on the hydrothermal synthesis of hybrid nanocomposites composed of MoS2 and rGO and discuss tuning possibilities of their electro-optical properties by incorporating thermotropic LCs. In particular, we demonstrate that the incorporation of 5CB LC increases the sensitivity and charge storage efficiency of the hybrid nanocomposites. In addition, we also present the responsivity, detectivity, and response time properties of the hybrid nanocomposites of MoS2/rGO, both with and without the inclusion of nematic LCs. Furthermore, we demonstrate that the system exhibits a 5CB-induced photocurrent switching effect. We believe the findings will open new doors for applications of these materials in optoelectronics and photonics.

Facile fabrication of Mn doped WSe2 as an electrode material for supercapacitor application

The world is currently confronted with major challenges of energy scarcity and environmental deterioration. Prioritising the development and storage of eco-friendly energy sources is imperative given the finite availability of non-renewable resources. Under these circumstances, the production and utilization of environmentally friendly energy have become widely recognized as of utmost significance. Lately, researchers have shown a strong fascination with supercapacitors owing to exceptional energy/power density and prolonged cycle life. In this work, we have fabricated Mn doped WSe2 through the hydrothermal route for supercapacitor applications. Utilization of Mn2+ as a dopant increases the conductivity of the WSe2 lattice by adding charge carriers, hence enhancing electron mobility. The incorporation of Mn2+ enhanced the electrochemical characteristics of Mn-doped WSe2, resulting in an overall improvement in electrochemical efficacy. The Mn doped WSe2 exhibited Cs of 1908 F/g at 1 A g-1, surpassing the Cs of pure WSe2 (593 F/g). This enhancement was attributed to the rise in the quantity of active sites, lower resistance and improved morphology resulting from to successful doping of Mn2+. It enhances the material's conductivity and charge storage capacity, compelling to increase in capacitance. After 5000th cycle at 10 mV/s, the material showed great cyclic stability due to doping. The superior performance of Mn doped WSe2 electrode suggests its potential for supercapacitor electrodes. The widespread implementation of Mn doped WSe2 can considerably enhance the performance, durability, and cost-effectiveness for it to be utilized further in next-generation energy storage processes.

Unraveling the Capacitive Behaviors in Nanoconfined Ionophilic Carbon Pores.

Intensifying the synergy between confined carbon nanopores and ionic liquids (ILs) and a deep comprehension of the ion behavior is required for enhancing the capacitive storage performance. Despite many theoretical insights on the storage mechanism, experimental verification has remained lacking due to the intricate nature of pore texture. Here, a compressed micropore-rich carbon framework (CMCF) with tailored monolayer and bilayer confinement pores is synthesized, which exhibits a compatible ionophilic interface to accommodate the IL [EMIM][BF4]. By deploying in situ Raman spectroscopy, in situ Fourier-transform infrared spectroscopy, and solid-state nuclear magnetic resonance, the effect of the pore textures on ions storage behaviors is elucidated. A voltage-induced ion gradient filling process in these ionophilic pores is proposed, in which ion exchange and co-ion desorption dominate the charge storage process. Moreover, it is established that the monolayer confinement of ions enhances the capacity, and bilayer confinement facilitates the charging dynamics. This work may guide the design of nanoconfinement carbon for high-energy-density supercapacitors and deepen the understanding of the charge storage mechanism in ionophilic pores.

Molten salt-mediated hierarchical porous carbon derived from biomass waste for high-performance capacitive storage

Biomass-derived carbon (BDC) materials are the suitable precursors for the fabrication of carbon electrodes of supercapacitors because of the sustainability, environmental friendliness, power capability, and structural diversity. The fabrication of BDC with low cost and excellent electrochemical properties is important for the practical applications of BDC in energy storage fields. Herein, ambrosia melon peels are used as carbon precursors for the fabrication of sustainable BDC electrodes through the molten salt-mediated pyrolysis procedure. The ambrosia melon peels-derived porous carbon (AMPPC) possesses high specific surface area of 529.9 m2 g−1. The AMPPC electrode shows the charge storage behavior of electrical double-layer capacitance with high ionic conductivity, high specific capacitance (218.3 F g−1 at 0.5 A g−1) and outstanding rate performance. In addition, the symmetric supercapacitor based on the AMPPC electrodes presents high specific energy density and specific power density (8 kW kg−1). It can be used as energy source to power helicopter model, clock, and calculator. Thus, the work gives an inspiration of design of BDC from the low-cost biomass waste and provides a simple way for the fabrication of BDC for the carbon electrodes of supercapacitors, lithium-ion batteries and so on.

Chemical preintercalation of magnesium ions into ⍺-MoO3 structure for improved electrochemical stability in Li-ion cells

Chemical preintercalation of layered materials, used as electrodes in intercalation-based energy storage devices, represents a promising strategy to enhance electrochemical stability and extend cycle life. However, standardized synthesis approaches for the chemical preintercalation of diverse ions into various layered materials are lacking, necessitating the development of specific synthesis routes for each ion and layered phase combination. In this study, we present the first successful demonstration of Mg2+ ion chemical preintercalation into the interlayer region of α-MoO3, revealing its stabilizing effect during cycling in non-aqueous Li-ion cells. Using ethanol during hydrothermal treatment facilitated molybdenum reduction, which was critical for Mg2+ ion preintercalation. Interestingly, we found that Mg preintercalation was accompanied by the incorporation of water. Mg-preintercalated α-MoO3 exhibited enhanced charge storage capacity, electrochemical stability, and power capability compared to pristine α-MoO3 electrodes. This improved performance is attributed to the structural stabilization provided by Mg2+ pillars, which prevent undesirable phase transformations during repeated Li intercalation/deintercalation, and increased Li+ ion diffusion due to the shielding of electrostatic interactions between electrochemically cycled ions and the α-MoO3 lattice, enabled by structural water. Our study offers new insights into developing chemical preintercalation synthesis approaches that can be broadly applied to a wide range of pillaring ions and layered material hosts.

Synthesis and electrochemical performance of CeO2/NiS nanocomposite for enhanced asymmetric supercapacitor device applications

A novel CeO2/NiS nanocomposite, combining the advantageous properties of transition metal sulfides (high conductivity) and rare-earth metal oxides (excellent stability), was successfully synthesized using a simple hydrothermal method. This composite leverage synergistic effects to potentially achieve superior electrochemical performance in supercapacitor applications. To evaluate its suitability for supercapacitors, the electrochemical performance of the CeO2/NiS electrode was comprehensively investigated using a series of techniques, including cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) curves, electrochemical impedance spectroscopy (EIS), and cyclic stability analysis. The results demonstrate that the as-prepared CeO2/NiS electrode exhibits significantly improved supercapacitor performance compared to the bare CeO2 electrode. The CV curves of the CeO2/NiS electrode reveal a high specific capacitance of 825.53 F/g at a low scan rate of 5 mV/s, indicating good charge storage capability. Further insights into the charge storage mechanism were obtained using the Trasatti method. This analysis revealed that the total stored capacitance of the CeO₂/NiS electrode is 1250 F/g, with contributions from both outer surface capacitance (94 F/g) and inner diffusion capacitance (1156 F/g). Notably, the dominant contribution (92.5 %) originates from capacitive processes, highlighting the efficient charge storage at the electrode surface. The CeO2/NiS electrode also demonstrates exceptional rate capability, delivering a specific capacitance (Csp) of 710 F/g at a high current density of 1 A/g. Additionally, it exhibits impressive cycling stability, retaining approximately 96.56 % of its initial capacitance even after undergoing 3000 continuous GCD cycles at a high current density of 10 A/g. These results suggest that the CeO2/NiS composite can maintain its performance during extended charge-discharge cycles, a crucial characteristic for practical supercapacitor applications. Finally, an asymmetric supercapacitor device was fabricated using the CeO2/NiS nanocomposite. This device achieved a specific capacitance of 157 F/g, demonstrating the potential of the CeO2/NiS composite for practical energy storage applications.