Capacity Retention Research Articles

Three-Dimensional Array of Holey Graphene as a High-Performance Anode Material for Supercapacitors

Herein, a novel method is employed for the facile, and low-cost preparation of three-dimensional holey graphene (3DHG) starting from pristine graphite for supercapacitor applications. 3D nanopatterning of the holey graphene (HG), prepared via a jaggery-assisted ball mill exfoliation of graphite, is achieved here via heat treatment with urea, where the decomposition of urea causes more nanoholes on the graphene sheets. The structural and morphological analyses reveal the edge functionalization, less-defective nature, and extensive nanopores on graphene. Use of 3DHG as a supercapacitor electrode material is investigated and a high specific capacitance of 423 F/g (@3 A/g) is observed. The symmetric coin cell supercapacitor fabricated using the 3DHG delivers high energy density (7.5 Wh/kg), power density (106 W/kg), and long durability (100% capacitance retention after 8000 cycles). Furthermore, the asymmetric assembly with 3DHG as the anode material with HG cathode exhibits a higher cell voltage of 1.6 V, which diminishes the voltage limitation of aqueous electrolyte-based supercapacitors. The present study demonstrates exceptional supercapacitor performance of 3DHG architecture adequate for commercial energy storage applications.

A versatile, highly stretchable, and anti-freezing alginate/polyacrylamide/polyaniline multi-network hydrogel for flexible strain sensors and supercapacitors.

Conductive hydrogels have great potential as electrolyte materials for flexible strain sensors and supercapacitors. However, it remains a challenge to develop multifunctional hydrogels with excellent frost resistance, toughness, ionic conductivity, and electrochemical properties using simple methods. Herein, a "chemical-physical-ionic" cross-linked sodium alginate/polyacrylamide/polyaniline (SA/PAM/Ca2+/PANI) multi-network hydrogel was developed by in situ polymerization of aniline monomer within a Ca2+-crosslinked SA/PAM hydrogel network. The SA/PAM/Ca2+/PANI hydrogel shows excellent mechanical properties, (tensile strength of 0.577MPa at a strain of 1991%), high toughness (5.52 KJ·m-3), and high ionic conductivity (16.51S·m-1 at 25°C and 11.08S·m-1 at -20°C). The SA/PAM/Ca2+/PANI hydrogel-based strain sensor exhibited high sensitivity (gauge factor of 3.82 at 60-500% strain), an extensive detection range (0-2000%), and excellent frost resistance. The strain sensor can accurately monitor various human motions, as well as electrocardiograph (ECG) signals during both rest and exercise. The supercapacitor assembled with the SA/PAM/Ca2+/PANI hydrogel electrolyte exhibited a high surface capacitance (177.19 mF·cm-2 at 2mA·cm-2), maximum energy density (21.93Wh·kg-1), and high power density (3089W·kg-1). Moreover, it maintained satisfactory electrochemical stability with 77.8% capacitance retention after 4000cycles. Therefore, the versatile SA/PAM/Ca2+/PANI hydrogel shows promising potential for applications in flexible wearable electronic devices.

Building Li–S batteries with enhanced temperature adaptability via a redox-active COF-based barrier-trapping electrocatalyst

Covalent organic frameworks (COFs) are promising materials for mitigating polysulfide shuttling in lithium-sulfur (Li–S) batteries, but enhancing their ability to convert polysulfides across a wide temperature range remains a challenge. Herein, we introduce a redox-active COF (RaCOF) that functions as both a physical barrier and a kinetic enhancer to improve the temperature adaptability of Li–S batteries. The RaCOF constructed from redox-active anthraquinone units accelerates polysulfide conversion kinetics through reversible C=O/C-OLi transformations within a voltage range of 1.7 to 2.8 V (vs. Li+/Li), optimizing sulfur redox reactions in ether-based electrolytes. Unlike conventional COFs, RaCOF provides bidentate trapping of polysulfides, increasing binding energy and facilitating more effective polysulfide management. In-situ XRD and ToF-SIMS analyses confirm that RaCOF enhances polysulfide adsorption and promotes the transformation of lithium sulfide (Li2S), leading to better sulfur cathode reutilization. Consequently, RaCOF-modified Li–S batteries demonstrate low self-discharge (4.0% decay over a 7-day rest), excellent wide-temperature performance (stable from −10 to +60 °C), and high-rate cycling stability (94% capacity retention over 500 cycles at 5.0 C). This work offers valuable insights for designing COF structures aimed at achieving temperature-adaptive performance in rechargeable batteries.

Ethyl 2-butene phosphite as a film-forming additive for high voltage lithium-ion batteries

Increasing the charge cutoff voltage can significantly improve the capacity of lithium-ion batteries. However, the structural degradation of Ni-rich cathodes and high reactivity of electrolytes at the high-potential cathodes greatly affect the cycling stability. In this paper, a new type of cathode film-forming additive, ethyl 2-butene phosphite (EBP), is synthesized based on the molecular design of phosphite by increasing the functional group of carbon-carbon double bond and ring structure. Theoretical calculation shows that EBP has a higher HOMO level and can form a cathode electrolyte interphase (CEI) on the cathode electrode surface before the electrolyte in theory. The electrochemical performance of NCM622/Li half-cells is significantly enhanced by incorporating EBP into the electrolyte, achieving 72.52% capacity retention over 100 cycles at 0.5C. Scanning Electron Microscope (SEM), X-Ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS) and Energy Dispersive Spectroscopy (EDS) are used to characterize the morphology of the anode and cathode, revealing that EBP forms a dense and complete CEI film on the surface of the LiNi0.6Co0.2Mn0.2O2 electrode. This film effectively blocks direct contact between the electrolyte and the cathode active material, prevents the dissolution of transition metals, improves interfacial stability, and consequently enhances the high-voltage cycling performance of the battery.

Ensemble Machine Learning for Predictive Accuracy and Experimental Corroboration on transition metal-based electrodes for Supercapacitor

Machine learning (ML) proves highly effective in refining the electrochemical performance of electrode materials through precise tuning of compositional parameters. This study employs a data-driven ensemble learning approach, integrating classification and regression techniques to investigate the electrochemical behavior of transition metal-based electrodes with varying Ni:Co stoichiometry. A resample filter is introduced to the dataset to enhance predictive accuracy, yielding closely aligned classification and regression predictions. ML predictions discern that Ni-rich electrodes are apt for high-capacity, while Co-rich excels in high-rate applications. The characterizations of developed electrode materials XRD, FT-IR, EDS, and XPS confirmed the formation of desired compositions. The XPS analysis indicates that nickel and cobalt are in variable Ni2+/Ni3+ and Co2+/Co3+ oxidation states, enabling a reversible charge storage mechanism, while phosphorus is present in the pentavalent state. The TEM micrograph suggests that the nanoparticle size is extremely small, in the range of 1-3 nm, which is significant for providing a high surface-to-volume ratio, thereby enhancing specific capacitance (Csp). Experimental findings highlight N1C2 as the superior electrode, exhibiting impressive capacitance (2247.6 F g−1 at 3 A g−1), robust rate retention (78.6% from 3 to 20 A g−1), and substantial capacitance retention (91.3% after 10,000 charge-discharge cycles), which is in line with ML prediction. The experimental validation highlights the excellent agreement (percentage error: 2.48 to 8.46%) between the capacitance that was predicted, and the capacitance achieved experimentally. Predicted rate and cyclic retention curves align closely with experimental results, with minimal errors (0.03 to 19.3% and 3.95 to 19.64%, respectively). Lastly, the introduction of reverse structural and operational feature engineering contributes to the optimization of electrode material performance.

A Novel Nickel and Cobalt-Layered Double Hydroxide@Nickel Borate with Three-Dimensional Flower-like Structure as Electrode Material for High-performance Hybrid Supercapacitor

It is crucial for enhancing electrochemical properties of existing supercapacitors to design and develope electrode materials with unique structures. Herein, a novel design of nickel and cobalt-layered double hydroxide@nickel borate (NiCo-LDH@Ni(BO2)2) with three-dimensional flower-like structure as the positive by a two-step method for asymmetric supercapacitor is reported. The synthesis strategy of the unique structure formed by stacking two-dimensional lamels provides efficient mesoporous networks, ion diffusion channels for quicker electron transfer, and enhances more active sites for nickel and cobalt-layered double hydroxide (NiCo-LDH) and nickel borate (Ni(BO2)2). The specific electric capacity of optimized NiCo-LDH@Ni(BO2)2 composite achieves 1373 F·g−1 at 0.5 A·g−1 in a three-electrode system. The self-assembled hybrid supercapacitors (HSC) NiCo-LDH@Ni(BO2)2//AC owns the an maximum energy density of 46.5 Wh·kg-1 at the power density 850 W·kg-1. Meanwhile, it displays significant cycle stability with an impressive capacitance retention rate of 84.9% over 5000 charging/discharging cycles. In the end, two serial-connected HSC devices can light up (Light Emitting Diodes) LEDs with difference color (red, yellow and green). Hence, the present research can match the demand of high-property electrode materials for energy storing equipment in the future.

Enhancing electrochemical properties of PNb9O25 anodes at elevated temperature via surface modification by nitrogen-doped carbon

Improving the performance of electrode materials is a crucial step for enhancing the intrinsic safety of batteries, especially during high operating temperature and rapid charge/discharge processes. The aggravation of side reactions caused by electro-thermal behaviors especially at high operating temperature is the main factor causing the instability of surface structure. In this work, we focus on the titanium-free, coarse-grained PNb9O25 (PNO) anode and enhance its electrochemical performance at an elevated temperature of 45 °C using a nitrogen-doped carbon (N-C) surface modification strategy. The homogeneous N-C passivation layer provides favorable electronic conductivity and fast Li+ diffusion kinetics, significantly reducing chemical reactivity and improving the interfacial charge transfer capability. As a result, PNO@N-C demonstrates exceptional high-rate capacity retention (249 mAh g–1 at 0.1 A g–1 and 173 mAh g–1 at 6 A g–1 under 45 °C) and superior cycling stability, maintaining a high capacity of 147 mAh g–1 after 1000 rapid charging cycles at a current density of 4 A g–1 (∼20 C, 45 °C). This approach provides a practical strategy for further development of electrode materials for high-rate lithium-ion batteries operating at high temperatures.

In situ establishment of rapid lithium transport pathways at the electrolytes-electrodes interface enabling dendrite-free and long-lifespan solid-state lithium batteries

Composite solid-state electrolytes (CSEs) exhibit the high ionic conductivity of ceramic electrolytes and the facile processing and good flexibility of polymer electrolytes, representing the most promising class of solid-state electrolytes for the industrialization of lithium batteries. Nevertheless, CSEs continue encountering substantial interfacial resistance, which impedes their practical deployment. In response to these issues, a Li6.4La3Zr1.4Ta0.6O12/poly(vinylidene fluoride) (LLZTO/PVDF) solid electrolyte membranes with a thickness of 25 μm were prepared by the doctor blade method. In situ polymerization of 1,3-dioxolane (DOL) at the electrolyte–electrode interface was initiated by lithium hexafluorophosphate (LiPF6) and lithium difluoro(oxalate)borate (LiDFOB) dual-salts to produce poly(1,3-dioxolane) (PDOL). The presence of PDOL in LLZTO/PVDF@PDOL results in a high room temperature ionic conductivity of 3.578 mS cm−1. Moreover, the Li||LLZTO/PVDF@PDOL||LiFePO4(LFP) battery exhibits a discharge-specific capacity of 143 mAh g−1 and capacity retention of 81.7 % after 1000 cycles at 2 C, and the pouch cell with LLZTO/PVDF@PDOL achieved a high energy density of 190 Wh kg−1. The findings of this study may facilitate the industrial application of CSEs.

In situ formed Organic Sodium Salt/rGO Nanocomposite as Anode Material for Sodium Ion Batteries.

Sodium-ion batteries (SIBs) are expected to be the next-generation large-scale energy storage technology. Organic anode materials are potential for efficient SIBs because they are not sensitive to the size of metal ions. Yet they still suffer from shortcomings such as low electrical conductivity, and solubility in electrolyte. Formation of nanocomposite with carbon materials is an efficient way to address these issues. Herein, we design a thiophene-based carboxylate compound STT, and the STT@rGO nanocomposite is also in situ formed as anode material for SIBs. The reduced graphene oxide (rGO) could improve conductivity and decrease the solubility of the anode material. Compared to the pristine STT electrode, STT@rGO delivers a reversible specific capacity of 178 mAh g-1, with a capacity retention rate of 86% after 1000 cycles. Moreover, full batteries are successfully assembled using the nanocomposite anode and the commercial cathode Na3V2(PO4)3, manifesting the potential applications of the nanocomposite as organic electrode materials.

Enhancing micro-scale SiOx anode durability: Electro-mechanical strengthening of binder networks via anchoring carbon nanotubes with carboxymethyl cellulose

With the increasing prevalence of lithium-ion batteries (LIBs) applications, the demand for high-capacity next-generation materials has also increased. SiOx is currently considered a promising anode material due to its exceptionally high capacity for LIBs. However, the significant volumetric changes of SiOx during cycling and its initial Coulombic efficiency (ICE) complicate its use, whether alone or in combination with graphite materials. In this study, a three-dimensional conductive binder network with high electronic conductivity and robust elasticity for graphite/SiOx blended anodes was proposed by chemically anchoring carbon nanotubes and carboxymethyl cellulose binders using tannic acid as a chemical cross-linker. In addition, a dehydrogenation-based prelithiation strategy employing lithium hydride was utilized to enhance the ICE of SiOx. The combination of these two strategies increased the CE of SiOx from 74% to 87% and effectively mitigated its volume expansion in the graphite/SiOx blended electrode, resulting in an efficient electron-conductive binder network. This led to a remarkable capacity retention of 94% after 30 cycles, even under challenging conditions, with a high capacity of 550 mA h g−1 and a current density of 4 mA cm−2. Furthermore, to validate the feasibility of utilizing prelithiated SiOx anode materials and the conductive binder network in LIBs, a full cell incorporating these materials and a single-crystalline Ni-rich cathode was used. This cell demonstrated a ∼27.3% increase in discharge capacity of the first cycle (∼185.7 mA h g−1) and exhibited a cycling stability of 300 cycles. Thus, this study reports a simple, feasible, and insightful method for designing high-performance LIB electrodes.

Polyimide/cellulose composite membrane with excellent heat-resistance and fast lithium-ion transport for lithium-ion batteries.

Polyimide membranes have long been of great interest in the battery industries due to their outstanding thermal stability and flame retardancy. However, the preparation of polyimide membranes with ideal pore structure and excellent lithium-ion transference remains a challenge. In this study, we reported for the first time, that a nano-porous fluorinated and partially carboxylated polyimide/cellulose composite membrane was successfully synthesized by selected monomers and prepared by thermal imidization, phase separation, and alkaline hydrolysis method. Particularly, an appropriate addition of cellulose acetate (CA) during the synthesis process can optimize the pore structure of the membrane. Besides, CA was converted to cellulose after alkaline hydrolysis, further enhancing the electrolyte affinity and lithium-ion transference of the membrane. Hence, this composite membrane exhibited distinct heat-resistance, high porosity (78 %), electrolyte absorption (344 %), and lithium-ion transfer number (0.84). Most importantly, thanks to the above characteristics of the membrane, the assembled LiFePO4/Li cells demonstrated excellent cycling stability compared with the cell with PP membrane, showing a capacity retention rate of as high as 93 % after 500 cycles at 1C. We anticipate that this composite membrane with superior physical and electrochemical properties would shed light on the development of next-generation membranes for high-power and high-safety batteries.

Wide-temperature and high-voltage Li||LiCoO2 cells enabled by a nonflammable partially-fluorinated electrolyte with fine-tuning solvation structure

Efficient, safe, and reliable energy output from high-energy-density lithium metal batteries (LMBs) at all climates is crucial for portable electronic devices operating in complex environments. The performance of corresponding cathodes and lithium (Li) metal anodes, however, faces significant challenges under such demanding conditions. Herein, a nonflammable electrolyte for high-voltage Li||LCO cells has been designed, including partially-fluorinated ethyl 4,4,4-trifluorobutyrate (ETFB) as the key solvent, guided by theoretical calculations. With this ETFB-based electrolyte, Li||LCO cells exhibit enhanced reversible capacities and superior capacity retention at an elevated charge voltage of 4.5 V and a wide operating temperature range spanning from −60 °C to 70 °C. The cells achieve 67.1% discharge capacity at −60 °C, relative to room temperature capacity, and 85.9% 100th-cycle retention at 70 °C. The outstanding properties are attributed to the LiF-rich interphases formed in the ETFB-based electrolyte with a fine-tuned solvation structure, in which the coordination environment in the vicinity of Li+ cations and the distance between anion and solvents are subtly adjusted by introducing ETFB. This solvation structure has been mutually elucidated through joint spectra characterizations and atomistic simulations. This work presents a new strategy for the design of electrolytes to achieve all-climate reliable and safe application of LMBs.

Zinc Single-Atom Catalysts Encapsulated in Hierarchical Porous Bio-Carbon Synergistically Enhances Fast Iodine Conversion and Efficient Polyiodide Confinement for Zn-I2 Batteries.

Aqueous zinc iodine (Zn-I2) batteries have attracted attention due to their low cost, environmental compatibility, and high specific capacity. However, their development is hindered by the severe shuttle effect of polyiodides and the slow redox conversion kinetics of the iodine (I2) cathode. Herein, a long-life Zn-I2 battery is developed by anchoring iodine within an edible fungus slag-derived carbon matrix encapsulated with Zn single-atom catalysts (SAZn@CFS). The high N content and microporous structure of SAZn@CFS provide a strong iodine confinement, while the Zn-N4-C sites chemical interact with polyiodides effectively mitigating the iodine dissolution and the polyiodide shuttle effect. Additionally, the uniformly distributed SAZn sites significantly enhance the redox conversion efficiency of I-/I3 -/I5 -/I2, leading to improved capacity. At a high current density of 10Ag-1, the designed Zn-I2 battery delivers an excellent capacity of 147.2mAhg-1 and a long lifespan of over 80000 cycles with 93.6% capacity retention. Furthermore, the battery exhibits stable operation for 3500 times even at 50°C, demonstrating significant advances in iodine reversible storage. This synergistic strategy optimizes composite structure, offering a practical approach to meet the requirements of high-performance Zn-I2 batteries.

Selectively fluorinated aromatic lithium salts regulate the solvation structure and interfacial chemistry for all-solid-state batteries.

Solid polymer electrolytes suffer from the polymer-dominated Li+ solvation structure, causing unstable electrolyte/electrode interphases and deteriorated battery performance. Here, we design a class of selectively fluorinated aromatic lithium salts (SFALS) as single conducting lithium salts to regulate the solvation structure and interfacial chemistry for all-solid-state lithium metal batteries. By tuning the anionic structure, the Li+-polyether coupling is weakened, and the Li+-anion coordination is enhanced. The hydrogen bonding between the SFALS and polymer matrix induces a special "triad"-type solvation structure, which improves the electrolyte homogeneity and mechanical strength, and promotes the formation of an ultrathin and robust Li2O-rich solid electrolyte interphase. Therefore, the stable cycling of more than 1650 cycles (Coulombic efficiency, 99.8%) for LiFePO4/Li half cells and 580 cycles (97.4% capacity retention) for full cells is achieved. This molecular engineering strategy could inspire further advancements of functional lithium salts for practical application of all-solid-state lithium metal batteries.

In Operando Raman Spectroscopy Reveals Li-Ion Solvation in Lithium Metal Batteries.

Inhomogeneous lithium (Li) deposition and unstable solid electrolyte interphase are the main causes of short cycle life and safety issues in Li metal batteries (LMBs). Developing a 3D structured matrix current collector and novel electrolyte are feasible strategies to tackle these issues. Ether-based electrolytes are widely used in LMBs. However, a fundamental understanding of Li-ion coordination and solvent remains incomplete. Here, lithiophilic Ag-Cu mesh is designed as the current collector to boost rapid Li-ion flux and Li metal nucleation. Meanwhile, dimethoxyethane (DME)/dioxolane (DOL) are used as complex solvents to enable lower interfacial resistance. The solvation structures at the interfaces of different collectors with different electrolytes are investigated. By applying in operando Raman spectroscopy, it is demonstrated that bis(trifluoromethylsulfonyl)imide TFSI-and DME molecules are highly coordinated with Li+ compared with DOL molecules. Furthermore, lithiophilic 3D Ag-Cu mesh tunes Li+ solvation/desolvation, resulting in a uniform deposition. The Ag-Cu mesh/Li symmetric cells demonstrate long-term cycling life up to 1200h and Coulombic efficiency of 98.6% over 200 cycles at 1mAcm-2. The Ag-Cu mesh/Li||LiNi0.8Co0.1Mn0.1O2 cells exhibit an initial discharge capacity of 208.7mAhg-1 at 1.0 C with a capacity retention of 76.1% after 500 cycles.

Ultrafast Li-Rich Transport in Composite Solid-State Electrolytes.

Solid-state lithium (Li) metal batteries (SSLMBs) have garnered considerable attention due to their potential for high energy density and intrinsic safety. However, their widespread development has been hindered by the low ionic conductivity of solid-state electrolytes. In this contribution, a novel Li-rich transport mechanism is proposed to achieve ultrafast Li-ion conduction in composite solid-state electrolytes. By incorporating cation-deficient dielectric nanofillers into polymer matrices, it is found that negatively charged cation defects effectively intensify the adsorption of Li ions, resulting in a high Li-ion concentration enrichment on the surface of fillers. More importantly, these formed Li-rich layers are interconnected to establish continuous ultrafast Li-ion transport networks. The composite electrolyte exhibited a remarkably low ion transport activation energy (0.17eV) and achieved an unprecedented ionic conductivity of approaching 1×10⁻3Scm⁻1 at room temperature. The Li||LiNi0.8Co0.1Mo0.1O2 full cells demonstrated an extended cycling life of over 200 cycles with a capacity retention of 70.7%. This work provides a fresh insight into improving Li-ion transport by constructing interconnected Li-rich transport networks, paving the way for the development of high-performance SSLMBs.

Four-Electron-Transferred Pyrene-4,5,9,10-tetraone Derivatives Enabled High-Energy-Density Aqueous Organic Flow Batteries.

Multielectron-transferred molecules hold great potential to enhance the energy density and reduce the cost for aqueous organic flow batteries (AOFBs). However, the extended conjugated units required for increasing redox-active sites and stabilizing the multielectron reaction always decrease the molecular polarity, limiting the solubility in the electrolyte. Herein, we presented an asymmetrical pyrene-4,5,9,10-tetraone-1-sulfonate (PTO-PTS) monomer which not only could reversibly store four electrons but also exhibited a high theoretical electron concentration of 4.0 M and the strongly heat-resistant intermediate semiquinone free radical. As a result, PTO-PTS-based AOFBs demonstrated a high energy density of 59.6 Wh Lcatholyte-1 (89 Ah L-1) with an ultrastable capacity retention of nearly 100% for above 5200 cycles (60 days). Moreover, the heat-stable PTO-PTS structure further enabled both symmetric and full cells to achieve remarkable cycling durability for over a thousand cycles at 60 °C. The outstanding cell performance and high thermal stability suggest its promising application in large-scale energy storage.

Enhancing the Interfacial Stability of Thin Solid Polymer Electrolyte with Fluorinated Covalent Organic Framework Nanosheets.

Thin poly(ethylene oxide) (PEO)-based electrolytes with higher energy density face challenges such as low ionic conductivity, deterioration of lithium dendrites, and severe side reactions. To address these issues, a surface modification strategy was developed to enhance the electrode-electrolyte interfacial stability by introducing fluorinated covalent organic framework nanosheets (CONs) to construct a thin PEO-based electrolyte with a mere 14 μm thickness. Characterization and DFT calculation indicated that the CON layer promotes concentration enrichment and averaging of free Li+ and mitigates side reactions at the interface. The electrode/electrolyte interface stability is significantly improved compared to the unmodified group (Li symmetric cells stabilized for more than 1000 h, and the full cell of LiFePO4∥Li exhibited a satisfactory capacity retention of 97.3% at 0.5 C after 150 cycles at 60 °C. This interface modification strategy provides a valuable reference for applying thin polymer electrolytes in high-energy solid-state lithium metal batteries.

Exploring Vanadium Disulfide (VS2) Nanosheets as High‐Efficiency Supercapacitor Electrodes

Transition metal dichalcogenides (TMDs) emerge as promising electrode materials for next‐generation electrochemical energy‐storage devices. In the present study, vanadium disulfide (VS2), an underexplored TMD, is investigated as an electrode material for supercapacitors. VS2 nanosheets are synthesized via a single‐step hydrothermal method at 220 °C for 24 h. Multiple characterization techniques, including Fourier‐transform infrared, Raman spectroscopy, scanning electron microscope–energy dispersive X‐ray analysis, and transmission electron microscope, confirm the formation of phase‐pure VS2 nanosheets with a hexagonal structure. The specific surface area, measured using Brunauer–Emmett–Teller analysis, is 12 m2 g−1. A specific capacitance of 106 F g−1 at a current density of 1 A g−1 is demonstrated using symmetric supercapacitors fabricated using these VS2 nanosheets. Using this device, an energy density of 34 Wh kg−1 at a power density of 800 W kg−1 is achieved. Moreover, the supercapacitor maintains 94% capacitance retention after 9000 charge–discharge cycles at 5 A g−1, highlighting the potential of VS2 nanosheets as efficient electrode materials for supercapacitor applications.

Rational Design of Cobalt-Based Prussian Blue Analogues via 3d Transition Metals Incorporation for Superior Na-Ion Storage.

Understanding the relationship between structure regulation and electrochemical performance is key to developing efficient and sustainable sodium-ion batteries (SIBs) materials. Herein, seven Cobalt-M-based (M=V, Mn, Fe, Co, Ni, Cu, Zn) Prussian blue analogues (CoM-PBAs) are designed as anodes for SIBs via a universal low-energy co-precipitation approach with the strategic inclusion of 3d transition metals. Density Functional Theory (DFT) simulation and experimental validation reveal that a moderate p-band center of cyanide linkages (-CN-) is more favorable for Na+ intercalation and diffusion, while the d-band center of metal cations is linearly related to electrode stability. Among seven CoM-based PBAs, CoV-PBAs possess the best sodium-ion adsorption/diffusion kinetics and overall cycling performance, including high specific capacity (565 mAh/g at 0.1 A/g), cycling stability (over 15000 cycles with 97.7% capacity retention), and superior rate capability (174.7 mAh/g at 30 A/g). In-situ/ex-situ techniques further demonstrate that the π-electron regulation by V introduction enhances the reversibility and kinetics of redox reactions. Moreover, the study identified the "p-band center" and "d-band center" may serve as key descriptors for quantifying the capability and stability of other-type bimetal Co-based anodes (oxides, phosphides, sulfides, and selenides) with similar theoretical capacity, offering a potentially transformative approach for selecting practical SIB electrode materials.