Co-construction of sulfur vacancies and carbon confinement in V5S8/CNFs to induce an ultra-stable performance for half/full sodium-ion and potassium-ion batteries

Structure and Defect Engineering of V3S4-xSex Quantum Dots Confined in a Nitrogen-Doped Carbon Framework for High-Performance Sodium-Ion Storage

Constructing quantum dot-scale metal sulfides with defects and strongly coupled with carbon is significant for advanced sodium-ion batteries (SIBs). Herein, Se substituted V3S4 quantum dots with anionic defects confined in nitrogen-doped carbon matrix (V3S4-xSex/NC) are fabricated. Introducing element Se into V3S4 crystal expands the interlayer distance of V3S4, and triggers anionic defects, which can facilitate Na+ diffusions and act as active sites for Na+ storage. Meanwhile, the quantum dots tightly encapsulated by conductive carbon framework improve the stability and conductivity of the electrode. Theoretical calculations also unveil that the presence of Se enhances the conductivity and Na+ adsorption ability of V3S4-xSex. These properties contribute to the V3S4-xSex/NC with high specific capacity of 447 mAh g-1 at 0.2 A g-1, and prominent rate and cyclic performance with 504 mAh g-1 after 1000 cycles at 10 A g-1. The sodium-ion hybrid capacitors (SIHCs) with V3S4-xSex/NC anode and activated carbon cathode can achieve high energy/power density (maximum 144 Wh kg-1/5960 W kg-1), capacity retention ratio of 71% after 4000 cycles at 2 A g-1. This work not only synthesizes V3S4-xSex/NC, but also provides a promising opportunity for designing quantum dots and utilizing defects to improve the electrochemical properties.

Thermodynamic Origin-Based In Situ Electrochemical Construction of Reversible p-n Heterojunctions for Optimal Stability in Potassium Ion Storage

Heterojunctions in electrode materials offer diverse improvements during the cycling process of energy storage devices, such as volume change buffering, accelerated ion/electron transfer, and better electrode structure integrity, however, obtaining optimal heterostructures with nanoscale domains remains challenging within constrained materials. A novel in situ electrochemical method is introduced to develop a reversible CuSe/PSe p-n heterojunction (CPS-h) from Cu3PSe4 as starting material, targeting maximum stability in potassium ion storage. The CPS-h formation is thermodynamically favorable, characterized by its superior reversibility, minimized diffusion barriers, and enhanced conversion post K+ interaction. Within CPS-h, the synergy of the intrinsic electric field and P-Se bonds enhance electrode stability, effectively countering the Se shuttling phenomenon. The specific orientation between CuSe and PSe leads to a 35° lattice mismatch generates large space at the interface, promoting efficient K ion migration. The Mott-Schottky analysis validates the consistent reversibility of CPS-h, underlining its electrochemical reliability. Notably, CPS-h demonstrates a negligible 0.005% capacity reduction over 10,000 half-cell cycles and remains stable through 2,000 and 4,000 cycles in full cells and hybrid capacitors, respectively. This study emphasizes the pivotal role of electrochemical dynamics in formulating highly stable p-n heterojunctions, representing a significant advancement in potassium-ion battery (PIB) electrode engineering.

Electrochemical coupling in subnanometer pores/channels for rechargeable batteries

Subnanometer pores/channels (SNPCs) play crucial roles in regulating electrochemical redox reactions for rechargeable batteries. The delicately designed and tailored porous structure of SNPCs not only provides ample space for ion storage but also facilitates efficient ion diffusion within the electrodes in batteries, which can greatly improve the electrochemical performance. However, due to current technological limitations, it is challenging to synthesize and control the quality, storage, and transport of nanopores at the subnanometer scale, as well as to understand the relationship between SNPCs and performances. In this review, we systematically classify and summarize materials with SNPCs from a structural perspective, dividing them into one-dimensional (1D) SNPCs, two-dimensional (2D) SNPCs, and three-dimensional (3D) SNPCs. We also unveil the unique physicochemical properties of SNPCs and analyse electrochemical couplings in SNPCs for rechargeable batteries, including cathodes, anodes, electrolytes, and functional materials. Finally, we discuss the challenges that SNPCs may face in electrochemical reactions in batteries and propose future research directions.

A Hydrogel Electrolyte with High Adaptability over a Wide Temperature Range and Mechanical Stress for Long-Life Flexible Zinc-Ion Batteries

Flexible zinc-ion batteries have garnered significant attention in the realm of wearable technology. However, the instability of hydrogel electrolytes in a wide-temperature range and uncontrollable side reactions of the Zn electrode have become the main problems for practical applications. Herein, N,N-dimethylformamide (DMF) to design a binary solvent (H2 O-DMF) is introduced and combined it with polyacrylamide (PAM) and ZnSO4 to synthesize a hydrogel electrolyte (denoted as PZD). The synergistic effect of DMF and PAM not only guides Zn2+ deposition on Zn(002) crystal plane and isolates H2 O from the Zn anode, but also breaks the hydrogen bonding network between water to improve the wide-temperature range stability of hydrogel electrolytes. Consequently, the symmetric cell utilizing PZD can stably cycle over 5600 h at 0.5 mA cm- 2 @0.5 mAh cm-2 . Furthermore, the Zn//PZD//MnO2 full cell exhibits favorable wide-temperature range adaptability (for 16000 cycles at 3 A g-1 under 25 °C, 750 cycles with 98 mAh g-1 at 0.1 A g-1 under -20 °C) and outstanding mechanical properties (for lighting up the LEDs under conditions of pressure, bending, cutting, and puncture). This work proposes a useful modification for designing a high-performance hydrogel electrolyte, which provides a reference for investigating the practical flexible aqueous batteries.

Enhancing Sodium-Ion Transport by Hollow Nanotube Structure Design of a V5S8@C Anode for Sodium-Ion Batteries

V5S8 has received extensive attention in the field of sodium-ion batteries (SIBs) due to its two-dimensional (2D) layered structure, and weak van der Waals forces between V-S accelerate the transport of sodium ions. However, the long-term cycling of V5S8 still suffers from volume expansion and low conductivity. Herein, a hollow nanotube V5S8@C (H-V5S8@C) with improved conductivity was synthesized by a solvothermal method to alleviate cracking caused by volume expansion. Benefiting from the large specific surface area of the hollow nanotube structure and uniform carbon coating, H-V5S8@C exhibits a more active site and enhanced conductivity. Meanwhile, the heterojunction formed by a few residual MoS2 and the outer layer of V5S8 stabilizes the structure and reduces the ion migration barrier with fast Na+ transport. Specifically, the H-V5S8@C anode provides an enhanced rate performance of 270.1 mAh g-1 at 15 A g-1 and high cycling stability of 291.7 mAh g-1 with a retention rate of 90.98% after 300 cycles at 5 A g-1. This work provides a feasible approach for the structural design of 2D layered materials, which can promote the practical application of fast-charging sodium-ion batteries.

External Fields Assisted Highly Efficient Oxygen Evolution Reaction of Confined 1T-VSe2 Ferromagnetic Nanoparticles

As a clean and effective approach, the introduction of external magnetic fields to improve the performance of catalysts has attracted extensive attention. Owing to its room-temperature ferromagnetism, chemical stability, and earth abundance, VSe2 is expected to be a promising and cost-effective ferromagnetic electrocatalyst for the accomplishment of high-efficient spin-related OER kinetics. In this work, a facile pulsed laser deposition (PLD) method combined with rapid thermal annealing (RTA) treatment is used to successfully confine monodispersed 1T-VSe2 nanoparticles in amorphous carbon matrix. As expected, with external magnetic fields of 800 mT stimulation, the confined 1T-VSe2 nanoparticles exhibit highly efficient oxygen evolution reaction (OER) catalytic activity with an overpotential of 228 mV for 10 mA cm-2 and remarkable durability without deactivation after >100 h OER operation. The experimental results together with theoretical calculations illustrate that magnetic fields can facilitate the surface charge transfer dynamics of 1T-VSe2 , and modify the adsorption-free energy of *OOH, thus finally improving the intrinsic activity of the catalysts. This work realizes the application of ferromagnetic VSe2 electrocatalyst in highly efficient spin-dependent OER kinetics, which is expected to promote the application of transition metal chalcogenides (TMCs) in external magnetic field-assisted electrocatalysis.

Vanadium Nitride Nanoparticles Grown on Carbon Fiber Cloth as an Advanced Binder-Free Anode for the Storage of Sodium and Potassium Ions

The escalating demand for sustainable and high-performance energy storage systems has led to the exploration of alternative battery technologies for lithium-ion batteries. Sodium-ion batteries (SIBs) and potassium-ion batteries (PIBs) have emerged as promising candidates because of their abundant Na/K resources, inexpensive costs, and similar chemistries to lithium-ion batteries. However, inherent challenges, such as large ionic radii, sluggish kinetics, and serious volume expansion, necessitate the development of robust and efficient anode materials for SIBs and PIBs. Vanadium nitride has attracted increasing attention as a viable anode due to its high electronic conductivity and potential capacity. In this study, we report on a flexible electrode for SIBs and PIBs that creates binder-free anodes by synthesizing vanadium nitride nanoparticles grown directly on carbon fiber cloths (VN/CFC). The unique architecture and binder-free nature of this anode ensure a robust electrode-electrolyte interface and enhance its electron/ion transport kinetics. The results demonstrate that the material exhibits an outstanding specific discharge capacity of 227 mAh g-1 after undergoing 1000 cycles at a current density of 2 A g-1 for SIBs. An electrochemical analysis indicated that the excellent performance of the material is attributed to the bind-free structure of carbon fiber cloth and the fast kinetics of surface pseudo-capacitive contribution. Furthermore, the material continues to demonstrate an impressive performance, even for PIBs, with a specific discharge capacity of 125 mAh g-1 after 1000 cycles at a current density of 1 A g-1. This study provides a new perspective for designing and developing advanced binder-free anodes for the storage of sodium and potassium ions, paving the way for high-performance energy storage applications.

Metal-Organic Assembly Strategy for the Synthesis of Layered Metal Chalcogenide Anodes for Na+ /K+ -Ion Batteries

Layered transition metal chalcogenides (MX, M=Mo, W, Sn, V; X=S, Se, Te) have large ion transport channels and high specific capacity, making them promising for large-sized Na⁺ /K⁺ energy-storage technologies. Nevertheless, slow reaction kinetics and huge volume expansion will induce an undesirable electrochemical performance. Numerous efforts have been devoted to designing MX anodes and enhancing their electrochemical performance. Based on the metal-organic assembly strategy, nanostructural engineering, combination with carbon materials, and component regulation can be easily realized, which effectively boost the performance of MX anodes. In this Review, we present a comprehensive overview on the synthesis of MX nanostructure using the metal-organic assembly strategy, which can realize the design of MX nanostructures, based on self-sacrificial templates, host@guest tailored templates, post-modified layer and derivative templates. The preparation routes and structure evolution are mainly discussed. Then, Mo-, W-, Sn-, V-based chalcogenides used for Na⁺ /K⁺ energy storage are reviewed, and the relationship between the structure and the electrochemical performance, as well as the energy storage mechanism are emphasized. In addition, existing challenges and future perspectives are also presented.

Progressive activation of porous vanadium nitride microspheres with intercalation-conversion reactions toward high performance over a wide temperature range for zinc-ion batteries

Rechargeable aqueous zinc-ion batteries have great promise for becoming next-generation storage systems, although the irreversible intercalation of Zn²⁺ and sluggish reaction kinetics impede their wide application. Therefore, it is urgent to develop highly reversible zinc-ion batteries. In this work, we modulate the morphology of vanadium nitride (VN) with different molar amounts of cetyltrimethylammonium bromide (CTAB). The optimal electrode has porous architecture and excellent electrical conductivity, which can alleviate volume expansion/contraction and allow for fast ion transmission during the Zn²⁺ storage process. Furthermore, the CTAB-modified VN cathode undergoes a phase transition that provides a better framework for vanadium oxide (VO_x). With the same mass of VN and VO_x, VN provides more active material after phase conversion due to the molar mass of the N atom being less than that of the O atom, thus increasing the capacity. As expected, the cathode displays an excellent electrochemical performance of 272 mAh g^-1 at 5 A g^-1, high cycling stability up to 7000 cycles, and excellent performance over a wide temperature range. This discovery creates new possibilities for the development of high-performance multivalent ion aqueous cathodes with rapid reaction mechanisms.

Hydrogen Bond-Enabled High-ICE Anode for Lithium-Ion Battery Using Carbonized Citric Acid-Coated Silicon Flake in PAA Binder

A silicon-based lithium-ion battery (LIB) anode is extensively studied because of silicon's abundance, high theoretical specific capacity (4200 mAh/g), and low operating potential versus lithium. Technical barriers to large-scale commercial applications include the low electrical conductivity and up to about 400% volume changes of silicon due to alloying with lithium. Maintaining the physical integrity of individual silicon particles and the anode structure is the top priority. We use strong hydrogen bonds between citric acid (CA) and silicon to firmly coat CA on silicon. Carbonized CA (CCA) enhances electrical conductivity of silicon. Polyacrylic acid (PAA) binder encapsulates silicon flakes by strong bonds formed by abundant COOH functional groups in PAA and on CCA. It results in excellent physical integrity of individual silicon particles and the whole anode. The silicon-based anode shows high initial coulombic efficiency, around 90%, and the capacity retention of 1479 mAh/g after 200 discharge-charge cycles at 1 A/g current. At 4 A/g, the capacity retention of 1053 mAh/g was achieved. A durable high-ICE silicon-based LIB anode capable of high discharge-charge current has been reported.

Anchoring polysulfides via a CoS2/NC@1T MoS2 modified separator for high-performance lithium–sulfur batteries

CoS2/NC@1T MoS2 synthesized by a one-step hydrothermal method forms a unique hierarchical configuration with simultaneous internal and external modifications. A lithium–sulfur battery with a CoS2/NC@1T MoS2-PP separator shows superior cycling performance.

Carbon Quantum Dot Modified Reduced Graphene Oxide Framework for Improved Alkali Metal Ion Storage Performance

Organic materials with redox-active oxygen functional groups are of great interest as electrode materials for alkali-ion storage due to their earth-abundant constituents, structural tunability, and enhanced energy storage properties. Herein, a hybrid carbon framework consisting of reduced graphene oxide and oxygen functionalized carbon quantum dots (CQDs) is developed via the one-pot solvothermal reduction method, and a systematic study is undertaken to investigate its redox mechanism and electrochemical properties with Li-, Na-, and K-ions. Due to the incorporation of CQDs, the hybrid cathode delivers consistent improvements in charge storage performance for the alkali-ions and impressive reversible capacity (257 mAh g^-1 at 50 mA g^-1 ), rate capability (111 mAh g^-1 at 1 A g^-1 ), and cycling stability (79% retention after 10 000 cycles) with Li-ion. Furthermore, density functional theory calculations uncover the CQD structure-electrochemical reactivity trends for different alkali-ion. The results provide important insights into adopting CQD species for optimal alkali-ion storage.

Sb-Doped metallic 1T-MoS2 nanosheets embedded in N-doped carbon as high-performance anode materials for half/full sodium/potassium-ion batteries

Metal 1T phase molybdenum disulfide (1T-MoS₂) is being actively considered as a promising anode due to its high conductivity, which can improve electron transfer. Herein, we elaborately designed stable Sb-doped metallic 1T phase molybdenum sulfide (1T-MoS₂-Sb) with a few-layered nanosheet structure via a simple calcination technique. The N-doping of the carbon and Sb-doping induce the formation of T-phase MoS₂, which not only effectively enhances the entire stability of the structure, but also improves its cycling performance and stability. When employed as an anode of sodium-ion batteries (SIBs), 1T-MoS₂-Sb exhibits a reversible capacity of 493 mA h g^-1 at 0.1 A g^-1 after 100 cycles and delivers prominent long-term performance (253 mA h g^-1 at 1 A g^-1 after 2200 cycles) along with decent rate capability. Paired with a Na₃V₂(PO₄)₃ cathode, it displays a superior capacity of 242 mA h g^-1 at 0.5 A g^-1 over 100 cycles, which is one of the best performances of a MoS₂-based full cell for SIBs. Employed as the anode for potassium-ion batteries (PIBs), it exhibits a satisfactory specific capacity of 343 mA h g^-1 at 0.1 A g^-1 after 100 cycles. This facile strategy will provide new insights for designing T-phase advanced anode materials for SIBs/PIBs.

Chemically Binding Vanadium Sulfide in Carbon Carriers to Boost Reaction Kinetics for Potassium Storage

Potassium-ion batteries (PIBs) have received widespread interest on account of low redox potential, low price, and high abundance of potassium. However, attributing to the large radius of K⁺ ions, the structure of electrode material is easily damaged during the potassiation/depotassiation process. Herein, the unique chemical bonding of encapsulating V_5.45S₈ nanoparticles in N,S codoped multichannel carbon nanofibers (CB-VS@NSCNFs) is designed through electrospinning and in situ vulcanization techniques. The anchoring effect (V-C chemical bonding) of the V_5.45S₈ nanoparticles with carbon carriers assists in shortening the K⁺/e^- transport path and alleviating the structural changes, which is highlighted to acquire a stable cycle lifespan. Also, codoped multichannel carbon nanofibers provide abundant active sites for pseudocapacitive behavior to achieve fast kinetics. As a synergistic result, when CB-VS@NSCNFs are evaluated as anode material for PIBs, they exhibit a high reversible capacity of 411 mA h g^-1 at 0.1 A g^-1, decent rate property with a capacity of up to 123 mA h g^-1 at 6 A g^-1, and good cycling stability of 500 cycles at 1 A g^-1.

Co-intercalation strategy of constructing partial cation substitution of ammonium vanadate {(NH4)2V6O16} for stable zinc ion storage

Recently, aqueous zinc-ion batteries have become a hot research topic in the field of grid-scale application, which can be attributed to their low-cost, aqueous electrolyte and dominant theoretical reversible capacity. Nevertheless, the lack of suitable cathode materials greatly hinders the development of aqueous zinc-ion batteries. In this work, we adopt a simple one-step synthesis strategy to prepare (NH₄)₂V₆O₁₆ with an intercalation of Na⁺ and H₂O, which exhibits a novel crystal structure in which the ammonium ion, crystal water, and sodium ion co-locate in the V₃O₈ layers. The co-intercalation not only effectively enhances the binding energy between V-O layers to suppress vanadium dissolution but also successfully improves the structural stability to alleviate the structural collapse during the cyclic process. As result, (NH₄)₂V₆O₁₆ with the intercalation of crystal water and Na⁺ presents a remarkable reversible discharge capacity of 423.9 mA h g^-1 after 90 cycles at 0.1 A g^-1 with an excellent energy density of 350.3 W h kg^-1 and demonstrates an outstanding specific capacity of 182.5 mA h g^-1 at the high current density of 5 A g^-1 upon 1400 cycles during the ultra-wide voltage window of 0.1-2.0 V.

Vanadium nitride@carbon nanofiber composite: Synthesis, cascade enzyme mimics and its sensitive and selective colorimetric sensing of superoxide anion

Nanozymes featuring with favorable activity, good stability and easy scale-up production, are promising to replace natural enzymes for various applications. However, it remains a challenge to explore the cascade reactions of multi-enzyme mimics, aiming at synergistic catalysis for various applications. Herein, vanadium nitride nanoparticles deposited on carbon nanofibers (VN@CNFs) composite was facilely prepared by typical electrospinning route with subsequently ammonia reduction process. The nanocomposite showed excellent peroxidase (POD)-like and superoxide dismutase (SOD)-like activities. Additionally, their catalytic mechanisms were systematically researched. Coupling of SOD-like with POD-like as cascade enzyme, a selective and sensitive colorimetric detection of superoxide anion (O₂^•-) was explored, which has two linear parts, 0.05-30 μM and 30-250 μM O₂^•- with the LOD of 0.0167 μM (S/N = 3). The as-proposed method was applicable to practical samples detection with satisfactory accuracy and recovery. Therefore, the VN@CNFs composite shows great prospect in biosensing, superoxide anion removal and biocatalysis.

Structure Engineering of BiSbSx Nanocrystals Embedded within Sulfurized Polyacrylonitrile Fibers for High Performance of Potassium-Ion Batteries

Potassium-ion batteries (PIBs) are regarded as promising candidates in next-generation energy storage technology; however, the electrode materials in PIBs are usually restricted by the shortcomings of large volume expansion and poor cycling stability stemming from a high resistance towards diffusion and insertion of large-sized K ions. In this study, BiSbS_x nanocrystals are rationally integrated with sulfurized polyacrylonitrile (SPAN) fibres through electrospinning technology with an annealing process. Such a unique structure, in which BiSbS_x nanocrystals are embedded inside the SPAN fibre, affords multiple binding sites and a short diffusion length for K⁺ to realize fast kinetics. In addition, the molecular structure of SPAN features robust chemical interactions for stationary diffluent discharge products. Thus, the electrode demonstrates a superior potassium storage performance with an excellent reversible capacity of 790 mAh g^-1 (at 0.1 A g^-1 after 50 cycles) and 472 mAh g^-1 (at 1 A g^-1 after 2000 cycles). It's one of the best performances for metal dichalcogenides anodes for PIBs to date. The unusual performance of the BiSbS_x @SPAN composite is attributed to the synergistic effects of the judicious nanostructure engineering of BiSbS_x nanocrystals as well as the chemical interaction and confinement of SPAN fibers.

Stabilizing V2O3 in carbon nanofiber flexible films for ultrastable potassium storage

Vanadium oxides, such as V2O3 and VO2, are expected to be potential anode materials for potassium-ion batteries (KIBs) on account of their high theoretical capacity, low price and natural abundance....

Recent Advances and Perspectives of Battery-Type Anode Materials for Potassium Ion Storage

Potassium ion energy storage devices are competitive candidates for grid-scale energy storage applications owing to the abundancy and cost-effectiveness of potassium (K) resources, the low standard redox potential of K/K⁺, and the high ionic conductivity in K-salt-containing electrolytes. However, the sluggish reaction dynamics and poor structural instability of battery-type anodes caused by the insertion/extraction of large K⁺ ions inhibit the full potential of K ion energy storage systems. Extensive efforts have been devoted to the exploration of promising anode materials. This Review begins with a brief introduction of the operation principles and performance indicators of typical K ion energy storage systems and significant advances in different types of battery-type anode materials, including intercalation-, mixed surface-capacitive-/intercalation-, conversion-, alloy-, mixed conversion-/alloy-, and organic-type materials. Subsequently, host-guest relationships are discussed in correlation with the electrochemical properties, underlying mechanisms, and critical issues faced by each type of anode material concerning their implementation in K ion energy storage systems. Several promising optimization strategies to improve the K⁺ storage performance are highlighted. Finally, perspectives on future trends are provided, which are aimed at accelerating the development of K ion energy storage systems.

Facile fabrication of WS2 nanocrystals confined in chlorella-derived N, P co-doped bio-carbon for sodium-ion batteries with ultra-long lifespan

Sodium-ion batteries (SIBs) have been regarded as a promising substitute for lithium-ion batteries but there are still formidable challenges in developing an anode material with adequate lifespan and outstanding rate performance. Transition metal dichalcogenides (TMDs) are promising anode materials for SIBs due to their high theoretical capacities. However, their severe volume expansions and low electronic conductivity impede their practical developments. In addition, the synthesis of energy storage materials from waste biomass has aroused extensive attention. Herein, we synthesize WS₂ nanocrystals embedded in N and P co-doped biochar via a facile bio-sorption followed by sulphurization, employing waste chlorella as the adsorbent and bio-reactor. The WS₂ nanocrystals are beneficial for storing more sodium ions and expediting the transportation of sodium ions, thus improving the capacity and reaction kinetics. Chlorella acts as a reactor and not only inhibits the stacking of WS₂ nanocrystals during the synthesis process but also alleviates the mechanical pressure of composite during the charge/discharge process. As a result, the WS₂/NPC-2 electrode delivers a high specific capacity (436 mA h g^-1 at 0.1 A g^-1) and superior rate performance of 311 mA h g^-1 at 3 A g^-1 for SIBs. It also exhibits excellent stability even up to 6000 cycles at 5 A g^-1, which is one of the optimal long-cycle properties reported for WS₂-based materials to date.

Ultrahigh-energy sodium ion capacitors enabled by the enhanced intercalation pseudocapacitance of self-standing Ti2Nb2O9/CNF anodes

In order to increase the capacity and improve the sluggish Na⁺-reaction kinetics of anodes as sodium ion capacitors (SICs), a Ti₂Nb₂O₉/CNF self-standing film electrode comprised of Ti₂Nb₂O₉ nanosheets and carbon nanofibers has been fabricated via electrospinning HTiNbO₅ nanosheets with PAN and subsequent carbonization treatment. The as-prepared Ti₂Nb₂O₉/CNF film electrode possesses fast Na-ion intercalation kinetics and high conductivity during Na-ion storage, and it displays a high reversible capacity of 324 mA h g^-1 at 0.1 A g^-1. Additionally, it also delivers a superior rate capability of 204 mA h g^-1 at a high current density of 4 A g^-1, as well as an excellent cycling stability of 97% retention after 2000 cycles at 1 A g^-1 in a half-cell test. A prototype Ti₂Nb₂O₉/CNF//AC SIC full device was assembled by employing the presodiated Ti₂Nb₂O₉/CNF anode and AC cathode, and it exhibits an high energy density of 129 W h kg^-1 at a power density of 75 W kg^-1 and a high power density (7560 W kg^-1 with 63 W h kg^-1), a good cycling performance of 85% capacitance retention after 10 000 cycles at 1 A g^-1, suggesting that the Ti₂Nb₂O₉/CNF electrode with excellent performance would be a very promising candidate as the anode for high-performance SICs.

Facile self-assembly of carbon-free vanadium sulfide nanosheet for stable and high-rate lithium-ion storage

Metal sulfides are recognized as potential candidates for the anode materials of lithium ion batteries (LIBs) because of their high theoretical capacity. However, the low reaction kinetics of metal sulfides leads to their poor cycle life and rate performance, which limits their practical application in the field of energy storage. In this work, we synthesized a self-assembled carbon-free vanadium sulfide (V₃S₄) nanosheet via a facile and efficient method. The unique mesoporous nanostructure of V₃S₄ can not only accelerate the migration of ions/electrons, but also alleviate the volume expansion during the lithium ion insertion/extraction process. When used as the anode material of LIBs, the carbon-free V₃S₄ electrode exhibits remarkable electrochemical performance with ultra-high charge capacity (1099.3 mAh g^-1 at 0.1 A g^-1), superior rate capability (668.8 mAh g^-1 at 2 A g^-1 and 588.8 mAh g^-1 at 5 A g^-1) and impressive cycling ability (369.6 mAh g^-1 after 200 cycles at 10 A g ^-1), which is very competitive compared with those of most metal sulfides-based anode materials reported so far. The strategy in this work provides inspiration for the rational design of advanced nanostructured electrode materials for energy storage devices.

Realizing Fast Diffusion Kinetics Based on Three-Dimensional Ordered Macroporous Cu9S5@C for Potassium-Ion Batteries

Recently, potassium-ion batteries (PIBs) have been deemed to be a potential next-generation energy storage system for large-scale application because of the similar metal-ion storage mechanism as lithium-ion batteries and rich potassium resources. However, the large-sized potassium ion will cause sluggish reaction kinetics of K⁺ during charge/discharge processes, hindering the development of high-performance PIBs. In this work, copper sulfide embedded in three-dimensional ordered macroporous carbon framework (3DOM Cu₉S₅@C) was prepared through a sulfidation and subsequent ion exchange strategy with 3D ordered macropore Zn-based metal-organic frameworks as a precursor for an advanced PIBs anode. In particular, the interconnected 3D ordered macroporous structure can provide rapid transport channels for the large potassium ions and create a sufficient contact area for solid electrode materials and the liquid electrolyte, which is conducive to improve the ionic diffusion kinetics of batteries. Consequently, when the prepared 3DOM Cu₉S₅@C composite was used as a PIBs anode material, it shows a remarkable potassium storage rate capacity of 170 mA h g^-1 at 2.0 A g^-1 and an excellent cycling stability of 316 mA h g^-1 at 100 mA g^-1 after 200 cycles.