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Lithium‐sulfur batteries face challenges like polysulfide shuttle and slow conversion kinetics, hindering their practical applications in renewable energy storage and electric vehicles. Herein, a solution to solve this issue is reported by using a cation vacancy engineering strategy with rational synthesis of La‐deficient LaCoO3 (LCO‐VLa). The introduction of cation vacancies in LCO‐VLa modifies the geometric structure of coordinating atoms, exposing Co‐rich surface with more catalytically active surfaces. Meanwhile, the d‐band center of LCO‐VLa shifts toward the Fermi level, enhancing polysulfide adsorption. Furthermore, multivalent cobalt ions (Co3+/Co4+) induced by charge compensation enhance the electrical conductivity of LCO‐VLa, accelerating electron transfer processes and improving catalytic performance. Theoretical calculations and experimental characterizations demonstrate that La‐deficient LCO‐VLa effectively suppresses the polysulfide shuttle, reduces the energy barrier for polysulfide conversion, and accelerates redox reaction kinetics. LCO‐VLa‐based batteries demonstrate exceptional rate performance and cycling stability, retaining 70% capacity after nearly 500 cycles at 1.0 C, with a minimal decay rate of 0.055% per cycle. These findings highlight the significance of cation vacancy engineering for exploring precise structure‐activity relationships during polysulfides conversion, facilitating the rational design of catalysts at the atomic level for lithium‐sulfur batteries. [ABSTRACT FROM AUTHOR]

Hypothesis: Porous carbon microspheres (PCMs) with embedded tin di‐oxide (SnO2) quantum dots (QDs) (P‐SnO2@PCMs) are synthesized and employed as polysulfide barriers to enrich the electrochemical properties. Experiments: This composite structure is prepared by spray drying procedure and followed by heat‐treatment, resulting in well‐arranged macropores with a diameter of 59 nm generated by the polystyrene (PS) nanobeads (ϕ = 150 nm) decomposition. P‐SnO2@PCMs is functioned as an electrocatalytic interlayer and offer advantages such as reduced diffusion length for charged particles that guarantees immediate transfer, improved electrode wetting due to efficient electrolyte infiltration, and accommodation of large volume fluctuations during the redox reactions. Furthermore, the incorporation of polar SnO2 QDs within the microspheres allows for efficient chemical confinement and alteration of trapped polysulfide species due to catalytic activity, leading to an extensive use of the active material. Findings: Advancing from the nanostructural eminence, lithium–sulfur (Li–S) cells paired with P‐SnO2@PCMs‐coated separator and conventional sulfur electrode showed outstanding rate performance (321 mA h g−1 at 2.0 C) and prolonged cyclic steadiness at 0.1 C. This innovative synthesis strategy provides valuable insights for developing novel nanostructures applicable to various rechargeable devices. [ABSTRACT FROM AUTHOR]

Adjusting the morphology and structure of the catalyst to optimize the structure of the discharge product is an effective strategy for improving the electrocatalytic activity of lithium–oxygen batteries (LOBs). In this paper, a novel high‐orientation layered manganese‐based metal–organic frameworks (Mn‐MOFs) catalyst for the air cathode of a LOB is synthesized via a facile solvothermal method using 2,4‐pyridine dicarboxylic acid combined with the metal Mn2+ ion. The presence of layered structure increases the specific surface area of the catalytic material, and the interlayer spacing can be used as a channel for electron and oxygen transport, thus promoting ion diffusion and catalyzing reactions. Otherwise, the coordination of the N element and metal ion in the organic ligand significantly improves the electrical conductivity and oxygen reduction reaction/oxygen extraction reaction (ORR/OER) performance of LOB. The effective combination of Mn2+ and 2,4‐pyridine dicarboxylic acid improves the overall catalytic capacity of the material, leading to a high LiO2 adsorption capacity so as to induce the formation of film discharge products and extend the cycle life of LOBs. When using Mn‐MOFs at 140°C as the cathode catalyst, the specific discharge capacity of the LOB can achieve 5579 mAh/g with a 0.2 mA/cm2 current density and maintain 140 stable cycles, limiting the specific discharge capacity to 500 mAh/g. [ABSTRACT FROM AUTHOR]

Lithium‐sulfur batteries (LSBs) have become one of the most powerful candidates for next‐generation battery technologies due to their high theoretical energy density and low cost. However, the notorious shuttle effect of soluble lithium polysulfides (LiPSs) and sluggish conversion reaction kinetics cause low sulfur utilization and inferior cycle life. Rational catalyst design on hierarchical pore structures and composition optimization is highly desired to realize synergetic enrichment, accommodation, and catalytic redox capacity of sulfur species. In this consideration, the hollow and porous N‐doped carbon framework is prepared, in which Co nanoparticles (NPs) are evenly embedded (denoted as Co‐HMCF) to modulate electron cloud density of carbons. Electrochemical tests and density functional theory (DFT) calculations demonstrate that Co‐HMCF could simultaneously deliver superior catalytic activity in accelerating LiPSs conversion as well as Li2S nucleation/decomposition to improve overall sulfur redox kinetics. Consequently, the Co‐HMCF interlayer significantly improves the battery performance, including high discharge capacity output (1538 mAh g−1 at 0.2 C), stable long‐term cycle (0.047% capacity decay per cycle for 800 cycles at 1.0 C), and exceptional rate capacity (582 mAh g−1 at 5.0 C). [ABSTRACT FROM AUTHOR]

Lithium‐sulfur (Li‐S) batteries offer promising prospects due to their high energy density and cost‐effectiveness. However, the sluggish kinetics of lithium polysulfides (LiPSs) conversion, particularly the crucial stage from LiPSs to lithium sulfide (Li2S), hampers their development. Herein, a novel strategy for dynamically regulating LiPSs conversion by incorporating 4‐mercaptopyridine (4Mpy), as a LiPSs Redox Regulator (RR) in the electrolyte is introduced. This organic sulfur additive actively interacts with LiPSs during discharge, facilitating rapid conversion and promoting the formation of a three‐dimensional (3D) Li2S structure, thereby enhancing reaction kinetics. Both theoretical and experimental results reveal that the redox conversion mechanism with the 4Mpy additive differs from traditional electrolytes. Upon lithiation, 4Mpy forms lithium‐pyridinethiolate (Li‐pyS), which reversibly engages in the LiPSs conversion during the charging/discharging cycles, significantly improving the redox process. As a result, the Li‐S battery with 4Mpy additive demonstrates superior performances, achieving 10.05 mAh cm−2 under a high sulfur loading of 10.88 mg cm−2, surpassing industrial benchmarks. This study not only presents an approach to mitigating the shuttle effect in Li‐S batteries but also offers valuable insights into electrolyte design for other metal batteries. [ABSTRACT FROM AUTHOR]

Practical application of lithium–sulfur (Li–S) batteries is severely impeded by the random shuttling of soluble lithium polysulfides (LiPSs), sluggish sulfur redox kinetics, and uncontrollable growth of lithium dendrites, particularly under high sulfur loading and lean electrolyte conditions. Here, nitrogen‐doped bronze‐phase TiO2(B) nanosheets with oxygen vacancies (OVs) grown in situ on MXenes layers (N‐TiO2−x(B)‐MXenes) as multifunctional interlayers are designed. The N‐TiO2−x(B)‐MXenes show reduced bandgap of 1.10 eV and high LiPSs adsorption‐conversion‐nucleation‐decomposition efficiency, leading to remarkably enhanced sulfur redox kinetics. Moreover, they also have lithiophilic nature that can effectively suppress dendrites growth. The cell based on the N‐TiO2−x(B)‐MXenes interlayer under sulfur loading of 2.5 mg cm−2 delivers superior cycling performance with a high specific capacity of 690.7 mAh g−1 over 600 cycles at 1.0 C. It still has a notable areal capacity of 6.15 mAh cm−2 after 50 cycles even under a high sulfur loading of 7.2 mg cm−2 and a low electrolyte‐to‐sulfur (E/S) ratio of 6.4 µL mg−1. The Li‐symmetrical battery with the N‐TiO2−x(B)‐MXenes interlayer showcases a low over‐potential fluctuation with 21.0 mV throughout continuous lithium plating/stripping for 1000 h. This work offers valuable insights into the manipulation of defects and heterostructures to achieve high‐energy Li–S batteries. [ABSTRACT FROM AUTHOR]

Selenium (Se) shows promise as a cathode candidate for all‐solid‐state lithium (Li) batteries due to its impressive theoretical volumetric energy density, much higher electronic conductivity, and improved safety in comparison to those for sulfur (S). An active cathode additive, lithium iodide (LiI) is demonstrated, to address the major challenge for all‐solid‐state Li–Se batteries, namely the sluggish redox kinetics resulting from the huge solid‐state conversion barrier. The LiI additive enhances Li+ transport and provides catalytic sites for Se cathode, thus endowing the batteries with accelerated reaction kinetics and extra capacity. DFT calculation and experimental analysis clearly reveal that LiI additive efficiently accelerates the conversion between polyselenide intermediates and Li2Se. With the above advantages, the battery with LiI using Li6PS5Br electrolyte gives an outstanding capacity of 862 mAh gSe−1 beyond the theoretical specific capacity of Se and a superlong life over 1800 cycles at 1C under room temperature. This work offers a simple strategy to facilitate the kinetics of all‐solid‐state Se cathodes and paves the way for the practicality of high‐capacity and long‐life all‐solid‐state Li–Se batteries. [ABSTRACT FROM AUTHOR]

Although the ultrahigh theoretical energy density and cost‐effectiveness, lithium–sulfur (Li‐S) batteries suffer from sluggish conversion kinetics and the shuttling effect of soluble lithium polysulfides (LiPSs). Herein, conductive hexagonal cobalt‐organic framework (Co‐HTP) nanosheets are anchored in situ on carboxyl graphene (CG) substrates and serve as host catalysts to modulate the polysulfide redox. Substantial characterizations identify that the local coordination environment of the quadrilateral Co–N4 units transforms into an asymmetric penta‐coordinated O–Co–N4 with axial Co─O coordination, which triggers spin polarization and remarkable electron delocalization of Co 3d orbital. The higher spin state and lower local electron density of the O–Co–N4 sites induce more active electronic states in Co‐HTP/CG and facilitate orbital hybridization with polysulfides to form more stable bond orders. Such optimized electronic structure significantly accelerates redox kinetics and enhances the adsorption strength of polysulfides. These merit the lithium–sulfur battery based on Co‐HTP/CG with a high reversible capacity, impressive rate capability, and prolonged cycling performance over 500 cycles. This work will enrich the design philosophy of modulating the spintronic structure of electrocatalysts for advanced Li–S batteries and beyond. [ABSTRACT FROM AUTHOR]

The heteroatom substitution is considered as a promising strategy for boosting the redox kinetics of transition metal compounds in hybrid supercapacitors (HSCs) although the dissimilar metal identification and essential mechanism that dominate the kinetics remain unclear. It is presented that d‐p orbital hybridization between the metal and electrolyte ions can be utilized as a descriptor for understanding the redox kinetics. Herein, a series of Co, Fe and Cu heteroatoms are respectively introduced into Ni3Se4 cathodes, among them, only the moderate Co‐substituted Ni3Se4 can hold the optimal d‐p orbital hybridization resulted from the formed more unoccupied antibonding states π*. It inevitably enhances the interfacial charge transfer and ensures the balanced OH− adsorption‐desorption to accelerate the redox kinetics validated by the lowest reaction barrier (0.59 eV, matching well with the theoretical calculations). Coupling with the lower OH− diffusion energy barrier, the prepared cathode delivers ultrahigh rate capability (~68.7 % capacity retention even the current density increases by 200 times), and an assembled HSC also presents high energy/power density. This work establishes the principles for determining heteroatoms and deciphers the underlying effects of the heteroatom substitution on improving redox kinetics and the rate performance of battery‐type electrodes from a novel perspective of orbital‐scale manipulation. [ABSTRACT FROM AUTHOR]

The redox‐active organic compounds including potassium 1,1′‐biphenyl‐4,4′‐dicarboxylate (K‐BPDC) are attracting considerable attention as anodes for potassium‐ion batteries (PIBs). Nevertheless, the practical applications of K‐BPDC organic anodes are severely hindered by short cycle life due to their relatively sluggish redox kinetics and instability. In this work, Ni single atoms (up to 6 wt.%) are implanted into K‐BPDC (NiSA@K‐BPDC) by using an electrochemical‐induced reconstruction (EIR) strategy to enhance the reaction kinetics and stability of PIBs. During the EIR process, Ni‐based metal‐organic framework (Ni‐BPDC) is in situ reconstructed into K‐BPDC by replacing Ni2+ with K+ to make the rest nickel species exist in the form of single atoms in K‐BPDC. By kinetic analysis and theoretical calculations, it is uncovered that the Ni single atoms supported on K‐BPDC efficiently redistribute the local charge of K‐BPDC to accelerate the K+ transport rate, and thermodynamically reduce the redox energy barrier. As a result, the NiSA@K‐BPDC anode exhibits outstanding cycle stability with 88.5% capacity retention during 4000 cycles at 1 A g−1 and an excellent rate capability (114 mAh g−1 at 2 A g−1). This study opens up a new door to the design of organic anodes with single atoms for high‐performance PIBs. [ABSTRACT FROM AUTHOR]

Highlights The interfacing between SnO2 and MXene alters electronic structures, shifting the d-band center in transition metals, enhancing catalytic efficiency by reducing electron filling in antibonding orbitals. A binder-free, ultrathin, laminar heterostructured interlayer on polypropylene separator is demonstrated. The ionic sieving mechanism and efficient adsorption–catalysis process enable deeper charge/discharge cycle and improved stability. The improved catalytic conversion and suppressed lithium dendrites formation enable a high loading of 7.5 mg cm−2 and an initial area capacity of 7.6 mAh cm−2.

Lithium-sulfur batteries are considered one of the most promising energy carriers due to their ultra-high theoretical energy density and low manufacturing cost. However, the limited diffusion of lithium ions at the electrode interface and the slow redox kinetics of the sulfur cathode easily led to frequent shuttle effects, affecting the electrochemical performance of the battery. In this paper, sulfur electrode materials with different structures of one-dimensional carbon as the carrier and MoS2 as the catalytic active material are designed by exploring the lithium ions diffusion and electrode reaction behaviors on the cathode surface. Among them, it is found that compared with carbon nanofibers and large-diameter carbon nanotubes, small-diameter carbon nanotubes (SD-CNT) have uniform hollow tubular morphology, abundant micropores, mesopores, and specific surface area, which is not only conducive to containing more active substances but also help the lithium ions diffusion inside the electrode material. Better electrochemical performance is obtained by constructing an interface environment that matches the ionic reaction and diffusion processes. It shows that the first discharge capacity of the obtained SD-CNT@MoS2-S cathode is as high as 1144 mAh g−1. The capacity retention rate reached more than 92.9% after 100 cycles at 0.5 C rate, further proving that SD-CNT@MoS2-S can promote the diffusion of lithium ions and the redox kinetics of sulfur. This study provides a new strategy for developing lithium-sulfur batteries with high electrochemical performance.

Highlights: The interfacing between SnO2 and MXene alters electronic structures, shifting the d-band center in transition metals, enhancing catalytic efficiency by reducing electron filling in antibonding orbitals. A binder-free, ultrathin, laminar heterostructured interlayer on polypropylene separator is demonstrated. The ionic sieving mechanism and efficient adsorption–catalysis process enable deeper charge/discharge cycle and improved stability. The improved catalytic conversion and suppressed lithium dendrites formation enable a high loading of 7.5 mg cm−2 and an initial area capacity of 7.6 mAh cm−2. Poor cycling stability in lithium–sulfur (Li–S) batteries necessitates advanced electrode/electrolyte design and innovative interlayer architectures. Heterogeneous catalysis has emerged as a promising approach, leveraging the adsorption and catalytic performance on lithium polysulfides (LiPSs) to inhibit LiPSs shuttling and improve redox kinetics. In this study, we report an ultrathin and laminar SnO2@MXene heterostructure interlayer (SnO2@MX), where SnO2 quantum dots (QDs) are uniformly distributed across the MXene layer. The combined structure of SnO2 QDs and MXene, along with the creation of numerous active boundary sites with coordination electron environments, plays a critical role in manipulating the catalytic kinetics of sulfur species. The Li–S cell with the SnO2@MX-modified separator not only demonstrates superior electrochemical performance compared to cells with a bare separator but also induces homogeneous Li deposition during cycling. As a result, an areal capacity of 7.6 mAh cm−2 under a sulfur loading of 7.5 mg cm−2 and a high stability over 500 cycles are achieved. Our work demonstrates a feasible strategy of utilizing a laminar separator interlayer for advanced Li–S batteries awaiting commercialization and may shed light on the understanding of heterostructure catalysis with enhanced reaction kinetics. [ABSTRACT FROM AUTHOR]

Aqueous rechargeable zinc‐sulfur (Zn‐S) batteries are a promising, cost‐effective, and high‐capacity energy storage technology. Still, they are challenged by the poor reversibility of S cathodes, sluggish redox kinetics, low S utilization, and unsatisfactory areal capacity. This work develops a facile strategy to achieve an appealing high‐areal‐capacity (above 5 mAh cm−2) Zn‐S battery by molecular‐level regulation between S and high‐electrical‐conductivity tellurium (Te). The incorporation of Te as a dopant allows for manipulation of the Zn‐S electrochemistry, resulting in accelerated redox conversion, and enhanced S utilization. Meanwhile, accompanied by the S‐ZnS conversion, Te is converted to zinc telluride during the discharge process, as revealed by ex‐situ characterizations. This additional redox reaction contributes to the S cathode's total excellent discharge capacity. With this unique cathode structure design, the carbon‐confined TeS cathode (denoted as Te1S7/C) delivers a high reversible capacity of 1335.0 mAh g−1 at 0.1 A g−1 with a mass loading of 4.22 mg cm−2, corresponding to a remarkable areal capacity of 5.64 mAh cm−2. Notably, a hybrid electrolyte design uplifts discharge plateau, reduces overpotential, suppresses Zn dendrites growth, and extends the calendar life of Zn‐Te1S7 batteries. This study provides a rational S cathode structure to realize high‐capacity Zn‐S batteries for practical applications. [ABSTRACT FROM AUTHOR]

The "shuttle effect" and sluggish conversion reaction kinetics of polysulfides seriously hinder the practical application of Li−S batteries. In this study, nano‐sized LaMnO3 (N‐LMO) with typical perovskite structure combined with highly‐conductive carbon black (SP) was introduced on the commercial separator to fabricate a functional surface modification. It is found that the polar N‐LMO with abundant active sites offers strong chemisorption towards the soluble polysulfides meanwhile accelerates their redox conversion, and the conductive SP contributes to extra spots to reactivate the trapped sulfur species. Consequently, the synergistic effect of adsorption‐catalysis‐conduction built by the cooperative N‐LMO/SP modification greatly enhances the sulfur redox kinetics as well as suppresses the polysulfide shuttling not at the expense of weakening Li‐ion transport, which endows the Li−S cell with a high initial discharge capacity of 1143.6 mAh g−1 at 0.2 C and a capacity decay rate of only 0.072 % per cycle at 1 C over 500 cycles. [ABSTRACT FROM AUTHOR]

The reduction of the dibromodicyanoaurate(III) ion by hexacyanoferrate(II)trihydrate was studied in an acidic medium. The reaction was first order in both Au(CN)2Br2− and Fe(CN)64− and a second order rate constant of k2 = 255 ± 5 M−1 s−1 at [H+] = 2.041 × 10−4 M, an ionic strength of 0.51 M (NaBr) and 20.0 ± 0.1 °C was found for the reaction. The reaction rate decreases with increasing [H+] in the region 0.0004 ≤ [H+] ≤ 0.065 M. An equilibrium constant of Ka = (3.00 ± 0.01) × 10−3 M (pKa = 2.52) at 20.0 ± 0.1 °C was found for the deprotonation of H2Fe(CN)62−. Activation parameters of ∆H# = 47.8 ± 0.9 kJ mol−1 and ∆S# = −37 ± 3 J K−1 mol−1 have been obtained by a least squares fit of temperature data directly to the Eyring equation. [ABSTRACT FROM AUTHOR]

Lithium‐sulfur (Li−S) batteries are one of the most potential new energy storage systems due to their high theoretical capacity (1675 mAh g−1) and high energy density (2600 Wh kg−1). However, the application of Li−S batteries is currently restricted due to the dissolution of polysulfides in the electrolyte, which leads to the shuttle effect of lithium polysulfides (LiPSs). Here, we present a Co@MXene‐derived TiO2 heterostructure decorated on carbon sheets derived from folic acid (Co@M‐TiO2/C) as a functional separator coating to trap polysulfide and accelerate redox kinetics in Li−S batteries. The interconnected porous structure with good electrical conductivity of the heterostructure boasts rapid ion diffusion and efficient electron transfer within the battery. By attaching Co and MXene‐derived dual‐phased TiO2 to two‐dimensional carbon sheets, heterostructures are formed, ensuring complete exposure of the active sites. These heterostructures exhibit catalytic effects on LiPSs and excellent adsorption capabilities, effectively inhibiting the shuttle effect and accelerating the redox kinetics. Considering these advantages, the Li−S battery with the optimized Co@M‐TiO2/C modified separator demonstrates a high specific capacity of 1481.7 mAh g−1 at 0.2 C, superior rate performance of 855.5 mAh g−1 at 2 C, and excellent cycling performance under a high sulfur load of 4.4 mg cm−2. [ABSTRACT FROM AUTHOR]

Lithium–sulphur batteries (LSBs) have elicited great interest due to their remarkably high energy density. However, challenges such as the dissolution of lithium polysulfides (LiPSs), low reaction kinetics, and safety concerns associated with LSBs impede large‐scale application. In this work, a multifunctional Co‐HP‐GC interlayer was prepared using evaporation, refluxing, and impregnation procedures. Notably, after ignition, this interlayer retained its structural integrity, indicative of excellent flame retardancy and thermal stability. Furthermore, the addition of cobalt atoms augmented the cyclic performance of the batteries by expediting the redox kinetics of LiPSs transformation and electron transfer at the interface. The electrodeposition capacity of Li2S cathode with Co‐HP‐GC interlayer reached up to 199.2 mAh g−1, higher than the 155.7 mAh g−1 achieved with a graphene oxide/carbonized fibre paper (G‐CCP) interlayer. This, in turn, curtails the shuttle effect whilst improving sulphur utilization. LSBs possessing a Co‐HP‐GC interlayer demonstrated superior cyclic and rate performance. At 0.5 C, the initial specific capacity of the battery fitted with a Co‐HP‐GC interlayer was 915.8 mAh g−1, with the rate of attenuation reduced by approximately half. The strategy integrates the multifunctional flame‐retardant interlayer into various battery systems, demonstrating wide‐ranging potential applicability within the realm of LSBs. [ABSTRACT FROM AUTHOR]

The kinetics of the reduction of tetrachloroaurate(III) by the cyano complexes of Fe(II), W(IV) and Mo(IV) have been studied in aqueous acidic medium. The reactions of Fe(CN)64− and W(CN)84− display first-order kinetics in both [AuCl4−] and [M(CN)n4−] (M = Fe and n = 6, W and n = 8) while [H+] has a retarding effect on the reaction rate for both the Fe and W reactions. An acid dissociation constant, Ka1, for the Fe(CN)64− reaction has been established kinetically to be Ka1 = (9.1 ± 0.5) × 10−3 M (pKa1 = 2.04) at µ = 1.2 M while the previously unknown Ka1 for the W(CN)84− reaction was found to be Ka1 = 0.33 ± 0.09 M (pKa1 = 0.48). Alkali metal cations such as Na+ and Cs+ and denoted as (cat+) accelerate the reaction. Some reactions were performed under second order (stoichiometric) conditions while other were performed under pseudo-first order conditions; rate constants utilizing these two techniques were mutually consistent. From the acid dependence and variation of the ionic strength of the reaction medium and the Bronsted-Bjerrum equation it has been established that AuIIICl4− and H(cat+)M(CN)n2− (M = Fe and n = 6 or M = W and n = 8) are the reactive species during the course of the reactions. The reaction between Mo(CN)84− and AuCl− is first order in [AuCl−] and second order in Mo(CN)84−. Reactions were performed under stoichiometric conditions and kinetic data was treated with a third order integrated rate law. The reaction is independent of [H+] and [cat+]. From the retarding effect of Cl− and Mo(CN)83− on the rate of the AuIIICl4− reduction, it is concluded that the molecular formula of the intermediate gold(II) species en route to AuICl2− is AuIICl3−. Activation parameters for all three reactions have been obtained from the Eyring equation. It was concluded that all three reactions follow the same mechanism but that the reverse reaction in the equilibrium between the intermediate gold(II) species, AuIICl3−, and the product MoV(CN)83− is only significant in the MoIV(CN)84− reduction of AuIIICl4−. This was also the cause for Mo(CN)84− showing a second order dependency. [ABSTRACT FROM AUTHOR]

Abstract Practical application of lithium–sulfur (Li–S) batteries is severely impeded by the random shuttling of soluble lithium polysulfides (LiPSs), sluggish sulfur redox kinetics, and uncontrollable growth of lithium dendrites, particularly under high sulfur loading and lean electrolyte conditions. Here, nitrogen‐doped bronze‐phase TiO2(B) nanosheets with oxygen vacancies (OVs) grown in situ on MXenes layers (N‐TiO2−x(B)‐MXenes) as multifunctional interlayers are designed. The N‐TiO2−x(B)‐MXenes show reduced bandgap of 1.10 eV and high LiPSs adsorption‐conversion‐nucleation‐decomposition efficiency, leading to remarkably enhanced sulfur redox kinetics. Moreover, they also have lithiophilic nature that can effectively suppress dendrites growth. The cell based on the N‐TiO2−x(B)‐MXenes interlayer under sulfur loading of 2.5 mg cm−2 delivers superior cycling performance with a high specific capacity of 690.7 mAh g−1 over 600 cycles at 1.0 C. It still has a notable areal capacity of 6.15 mAh cm−2 after 50 cycles even under a high sulfur loading of 7.2 mg cm−2 and a low electrolyte‐to‐sulfur (E/S) ratio of 6.4 µL mg−1. The Li‐symmetrical battery with the N‐TiO2−x(B)‐MXenes interlayer showcases a low over‐potential fluctuation with 21.0 mV throughout continuous lithium plating/stripping for 1000 h. This work offers valuable insights into the manipulation of defects and heterostructures to achieve high‐energy Li–S batteries.

Aqueous Redox Flow Batteries (ARFB) are the most prominent technology for large-scale energy storage applications. The energy density of the ARFBs is mainly determined by the electrolyte components, which highly influence the flow battery performance. In the present work, we acutely investigated the various electrolyte compositions and optimized the best electrolyte for realizing the high performance of Zn-Br2 ARFBs. The electrode kinetics, such as rate constant, exchange current density, conductivity, and diffusion coefficient, were analyzed using electrochemical techniques, cyclic voltammetry, and electrochemical impedance analysis. It was observed that zinc bromide (ZnBr2) + perchloric acid (HClO4) + 1-Ethyl-1-methylmorpholinium bromide (MEM) + N-ethyl-N-methylpyrrolidinium bromide (MEP) and ZnBr2 + zinc chloride (ZnCl2) + MEM + MEP electrolytes showed improved performance, where the redox kinetics of 2Br-/Br2 redox couple is greatly enhanced. The presence of perchloric acid unlocks the capacity of full electro-oxidation of bromide (Br-) to bromine (Br2) as it involves 1e- per Br-, which would be highly beneficial to attain high energy density. Further, Zn-Br2 RFB adopted with optimized electrolyte formulation ZnBr2 + HClO4 + MEM+ MEP shows a better round-trip efficiency and displays a stable long cycling performance over 200 cycles with an energy (EE) and coulombic efficiency (CE) of > 68% and > 92%, respectively.

Abstract Aqueous rechargeable zinc‐sulfur (Zn‐S) batteries are a promising, cost‐effective, and high‐capacity energy storage technology. Still, they are challenged by the poor reversibility of S cathodes, sluggish redox kinetics, low S utilization, and unsatisfactory areal capacity. This work develops a facile strategy to achieve an appealing high‐areal‐capacity (above 5 mAh cm−2) Zn‐S battery by molecular‐level regulation between S and high‐electrical‐conductivity tellurium (Te). The incorporation of Te as a dopant allows for manipulation of the Zn‐S electrochemistry, resulting in accelerated redox conversion, and enhanced S utilization. Meanwhile, accompanied by the S‐ZnS conversion, Te is converted to zinc telluride during the discharge process, as revealed by ex‐situ characterizations. This additional redox reaction contributes to the S cathode's total excellent discharge capacity. With this unique cathode structure design, the carbon‐confined TeS cathode (denoted as Te1S7/C) delivers a high reversible capacity of 1335.0 mAh g−1 at 0.1 A g−1 with a mass loading of 4.22 mg cm−2, corresponding to a remarkable areal capacity of 5.64 mAh cm−2. Notably, a hybrid electrolyte design uplifts discharge plateau, reduces overpotential, suppresses Zn dendrites growth, and extends the calendar life of Zn‐Te1S7 batteries. This study provides a rational S cathode structure to realize high‐capacity Zn‐S batteries for practical applications.

The commercial application of lithium–sulfur (Li–S) batteries is severely impeded by abominable shuttle effects, sluggish redox kinetics, and poor safety performance under high loading conditions. Herein, a novel adsorption‐mediator synergistic polymer binder (PAT) is reported to regulate the conversion of lithium polysulfides (LiPSs) through close intermolecular synergy. The abundant polar groups provide strong anchor ability for LiPSs to effectively inhibit the shuttle effect, and the anchored LiPSs are accelerated by adjacent mediator catalytic sites to facilitate their redox kinetics. Moreover, PAT itself features excellent flame retardant properties, which effectively enhance the safety performance of Li–S cells. Benefiting from these attributes, PAT‐based Li–S cells exhibit outstanding rate performance with an average capacity of 617.34 mAh g−1 at 5 C and excellent cycling stability maintaining a capacity of 629.1 mAh g−1 after 800 cycles at 2 C. Even under the harsh conditions of high loading (9.84 mg cm−2) and lean electrolyte (E/S = 3.56 µL mg−1), PAT‐based cell delivers a high average areal capacity of 9.58 mAh cm−2 and an ultralow overpotential of 3 mV, confirming the application potential of adsorption‐mediator synergistic polymer binder in high performance Li–S batteries. [ABSTRACT FROM AUTHOR]

Lithium–sulfur batteries (LSB) show excellent potential as future energy storage devices with high energy density, but their slow redox kinetics and the shuttle effect seriously hinder their commercial application. Herein, a 0D@2D composite was obtained by anchoring polar nano-TiO2 onto a 2D layered g-C3N4 surface in situ, and a functional separator was prepared using multi-walled carbon nanotubes as a conductive substrate. Due to their long-range conductivity, multi-walled carbon nanotubes make up for the low conductivity of TiO2@g-C3N4 to some extent. A lithium–sulfur battery prepared with a modified separator exhibited excellent long-term cycle performance, a good lithium ion diffusion rate, and rapid redox kinetics. The initial specific discharge capacity of the composite was 1316 mAh g−1 at 1 C, and a high specific discharge capacity of 569.9 mAh g−1 was maintained after 800 cycles (the capacity decay rate per cycle was only 0.07%). Even at the high current density of 5 C, a specific capacity of 784 mAh g−1 was achieved. After 60 cycles at 0.5 C, the modified separator retained the discharge capacity of 718 mAh g−1 under a sulfur load of 2.58 mg cm−2. In summary, the construction of a heterojunction significantly improved the overall cycle stability of the battery and the utilization rate of active substances. Therefore, this study provides a simple and effective strategy for further improving the overall performance and commercial application of lithium–sulfur batteries. [ABSTRACT FROM AUTHOR]

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This paper explores the reaction kinetics of NiO supported on YSZ (Yttria Stabilized Zirconia) as an oxygen carrier for chemical looping combustion. Nickel particles with size less than 1 μm mixed with YSZ nano-powders are used to prepare the solid mixture, with 45% mol of NiO. Redox reactivity and oxygen carrying capacity are measured in a laboratory scale fixed bed reactor in the temperature range 500–1000 °C with different concentrations of the reactive gasses. Samples are subjected to repeated redox cycles using synthetic air (O 2 +Ar) for oxidation, and H 2 /H 2 O/Ar mixtures for reduction. NiO/YSZ demonstrates superb cyclic regenerability starting with the 2nd cycle, with full utilization of its oxygen carrying capacity. Compared to pure nickel, pronounced improvement is achieved in the kinetics and oxygen utilization. Full reduction is achieved, and the presence of H 2 O does not affect the reduction rate. Reactivity is also determined as a function of conversion. Global models of redox conversion are developed, in which surface chemistry and solid diffusion are considered. Oxidation exhibits the characteristics of a shrinking-core model with internal reactions at the Ni/NiO interface being the rate limiting step, and it is weakly temperature dependent. Reduction with H 2 generally exhibits surface chemistry limitation (adsorption-desorption), with surface product formation being the rate limiting step. YSZ significantly enhances ionic transport during oxidation and reduction. Reaction rate dependencies on conversion during the two steps suggest an optimal range for the oxygen carrying capacity of the material. [ABSTRACT FROM AUTHOR]

Abstract The chief culprit impeding the commercialization of lithium–sulfur (Li–S) batteries is the parasitic shuttle effect and restricted redox kinetics of lithium polysulfides (LiPSs). To circumvent these key stumbling blocks, incorporating electrocatalysts with rational electronic structure modulation into sulfur cathode plays a decisive role in vitalizing the higher electrocatalytic activity to promote sulfur utilization efficiency. Breaking the stereotype of contemporary electrocatalyst design kept on pretreatment, field‐assisted electrocatalysts offer strategic advantages in dynamically controllable electrochemical reactions that might be thorny to regulate in conventional electrochemical processes. However, the highly interdisciplinary field‐assisted electrochemistry puzzles researchers for a fundamental understanding of the ambiguous correlations among electronic structure, surface adsorption properties, and catalytic performance. In this review, the mechanisms, functionality explorations, and advantages of field‐assisted electrocatalysts including electric, magnetic, light, thermal, and strain fields in Li–S batteries have been summarized. By demonstrating pioneering work for customized geometric configuration, energy band engineering, and optimal microenvironment arrangement in response to decreased activation energy and enriched reactant concentration for accelerated sulfur redox kinetics, cutting‐edge insights into the holistic periscope of charge‐spin‐orbital‐lattice interplay between LiPSs and electrocatalysts are scrutinized, which aspires to advance the comprehensive understanding of the complex electrochemistry of Li–S batteries. Finally, future perspectives are provided to inspire innovations capable of defeating existing restrictions.

The brownmillerite-structured Ca 2 Fe 2 O 5 oxygen carrier has shown its great potential in chemical looping processes, due to it can be completed regeneration in a H 2 O or CO 2 atmosphere without the air reactor. However, the low reaction reactivity of Ca 2 Fe 2 O 5 restricts its application. In this study, Ca 2 Fe 2 O 5 oxygen carrier was prepared by sol-gel method. The reduction and oxidation kinetics of Ca 2 Fe 2 O 5 were evaluated in H 2 and CO 2 atmospheres, respectively. The reduction of Ca 2 Fe 2 O 5 in H 2 atmosphere in good agreement with the random nucleation and growth model with E a and A of 53.82 kJ/mol and 2.65 s−1, respectively. The dimension of the model increases with conversion (A1.5 → A2 → A3 → A4). The oxidation of reduced Ca 2 Fe 2 O 5 in CO 2 atmosphere can be described by the zero-order contraction model with E a and A of 11.66 kJ/mol and 0.05 s−1, respectively. The kinetics analysis showed that both the reduction of H 2 and the oxidation of CO 2 are one-step reactions, as evidenced by the fact that only Fe0 and Fe3+ phases were detected in semi-in situ XRD analysis. It was inferred that the release and recovery of lattice oxygen is from inside to outside for Ca 2 Fe 2 O 5 oxygen carrier in the redox process. By reducing the migration energy barrier of lattice oxygen between bulk and surface would be an effective means to improve the reactivity of Ca 2 Fe 2 O 5 oxygen carriers. [Display omitted] • The OC was evaluated by comprehensive kinetic parameters and redox performance. • Both the reduction and oxidation of Ca 2 Fe 2 O 5 are one-step reaction. • The oxidation and reduction of OC were controlled by Avrami–Erofeev and F0 models. • The release and recovery of lattice oxygen is from inside to outside for Ca 2 Fe 2 O 5. [ABSTRACT FROM AUTHOR]

Lithium‐sulfur (Li−S) batteries are considered as promising candidates for next‐generation energy storage systems in view of the high theoretical energy density and low cost of sulfur resources. The suppression of polysulfide diffusion and promotion of redox kinetics are the main challenges for Li−S batteries. Herein, we design and prepare a novel type of ZnCo‐based bimetallic metal–organic framework nanoboxes (ZnCo‐MOF NBs) to serve as a functional sulfur host for Li−S batteries. The hollow architecture of ZnCo‐MOF NBs can ensure fast charge transfer, improved sulfur utilization, and effective confinement of lithium polysulfides (LiPSs). The atomically dispersed Co−O4 sites in ZnCo‐MOF NBs can firmly capture LiPSs and electrocatalytically accelerate their conversion kinetics. Benefiting from the multiple structural advantages, the ZnCo‐MOF/S cathode shows high reversible capacity, impressive rate capability, and prolonged cycling performance for 300 cycles. [ABSTRACT FROM AUTHOR]

Zn−I2 batteries stand out in the family of aqueous Zn‐metal batteries (AZMBs) due to their low‐cost and immanent safety. However, Zn dendrite growth, polyiodide shuttle effect and sluggish I2 redox kinetics result in dramatically capacity decay of Zn−I2 batteries. Herein, a Janus separator composed of functional layers on anode/cathode sides is designed to resolve these issues simultaneously. The cathode layer of Fe nanoparticles‐decorated single‐wall carbon nanotubes can effectively anchor polyiodide and catalyze the redox kinetics of iodine species, while the anode layer of cation exchange resin rich in −SO3− groups is beneficial to attract Zn2+ ions and repel detrimental SO42−/polyiodide, improving the stability of cathode/anode interfaces synergistically. Consequently, the Janus separator endows outstanding cycling stability of symmetrical cells and high‐areal‐capacity Zn−I2 batteries with a lifespan over 2500 h and a high‐areal capacity of 3.6 mAh cm−2. [ABSTRACT FROM AUTHOR]

For practical lithium–sulfur batteries (LSBs), the high sulfur loading and lean‐electrolyte are necessary conditions to achieve the high energy density. However, such extreme conditions will cause serious battery performance fading, due to the uncontrolled deposition of Li2S and lithium dendrite growth. Herein, the tiny Co nanoparticles embedded N‐doped carbon@Co9S8 core–shell material (CoNC@Co9S8NC) is designed to address these challenges. The Co9S8NC‐shell effectively captures lithium polysulfides (LiPSs) and electrolyte, and suppresses the lithium dendrite growth. The CoNC‐core not only improves electronic conductivity, but also promotes Li+ diffusion as well as accelerates Li2S deposition/decomposition. Consequently, the cell with CoNC@Co9S8NC modified separator delivers a high specific capacity of 700 mAh g−1 with a low‐capacity decay rate of 0.035% per cycle at 1.0 C after 750 cycles under a sulfur loading of 3.2 mg cm−2 and a E/S ratio of 12 µL mg−1, and a high initial areal capacity of 9.6 mAh cm−2 under a high sulfur loading of 8.8 mg cm−2 and a low E/S ratio of 4.5 µL mg−1. Besides, the CoNC@Co9S8NC exhibits an ultralow overpotential fluctuation of 11 mV at a current density of 0.5 mA cm–2 after 1000 h during a continuous Li plating/striping process. [ABSTRACT FROM AUTHOR]

Abstract For practical lithium–sulfur batteries (LSBs), the high sulfur loading and lean‐electrolyte are necessary conditions to achieve the high energy density. However, such extreme conditions will cause serious battery performance fading, due to the uncontrolled deposition of Li2S and lithium dendrite growth. Herein, the tiny Co nanoparticles embedded N‐doped carbon@Co9S8 core–shell material (CoNC@Co9S8NC) is designed to address these challenges. The Co9S8NC‐shell effectively captures lithium polysulfides (LiPSs) and electrolyte, and suppresses the lithium dendrite growth. The CoNC‐core not only improves electronic conductivity, but also promotes Li+ diffusion as well as accelerates Li2S deposition/decomposition. Consequently, the cell with CoNC@Co9S8NC modified separator delivers a high specific capacity of 700 mAh g−1 with a low‐capacity decay rate of 0.035% per cycle at 1.0 C after 750 cycles under a sulfur loading of 3.2 mg cm−2 and a E/S ratio of 12 µL mg−1, and a high initial areal capacity of 9.6 mAh cm−2 under a high sulfur loading of 8.8 mg cm−2 and a low E/S ratio of 4.5 µL mg−1. Besides, the CoNC@Co9S8NC exhibits an ultralow overpotential fluctuation of 11 mV at a current density of 0.5 mA cm–2 after 1000 h during a continuous Li plating/striping process.

CoSe 2 /CoO-CNTs catalyst was rationally designed as separator modifier for Li-S battery to selectively catalyze the sulfur species conversion via Mott-Schottky effect. [Display omitted] • CoSe 2 /CoO Mott-Schottky catalyst has been rationally designed and blended with CNTs for using as a separator modifier in Li-S battery. • CoSe 2 /CoO-CNTs synergistically utilizes the high electrocatalytic activity of CoSe 2 /CoO heterostructure and high conductivity of CNTs to selectively catalyze the sulfur species conversion via Mott-Schottky effect. • The Li-S battery with a CoSe 2 /CoO-CNTs modified separator displays a high initial discharge capacity of 1236 mAh/g at 0.5C and a low decay rate of 0.070% per cycle over 500 cycles at 2C. The lithium sulfur (Li-S) battery is an active research area in the field of energy storage systems, but the shuttle effect is a serious obstacle hindering its application. Herein, a CoSe 2 /CoO Mott-Schottky catalyst is blended with carbon nanotubes (CNTs) and subsequently coated onto a commercial separator as a modifier, whereby the synergy between the high electrocatalytic activity of the CoSe 2 /CoO heterostructure and high conductivity of the CNTs selectively mediate the conversion of sulfur species. As a result, a cell with a CoSe 2 /CoO-CNTs modified separator displays a high initial discharge capacity of 1573 and 910 mAh/g at 0.1 and 2C, respectively. Furthermore, a low decay rate of 0.070% per cycle can be obtained over 500 cycles at 2C. The results of this study suggest that the as-prepared CoSe 2 /CoO-CNTs is an effective modifier that can improve the performance of Li-S batteries for use in next-generation energy storage systems. This study provides fundamental insights into the rational design of Mott-Schottky catalysts for practical high-performance Li-S batteries. [ABSTRACT FROM AUTHOR]

Regulating redox kinetics is able to spur the great‐leap‐forward development of room‐temperature sodium–sulfur (RT Na–S) batteries, especially on propelling their Na‐ion storage capability. Here, an innovative metal oxide kinetics accelerator, orthorhombic Nb2O5 Na‐ion conductor, is proposed to functionalize porous carbon nanoreactors (CNR) for S cathodes. The Nb2O5 is shown to chemically immobilize sodium polysulfides via strong affinity. Theoretical and experimental evidence reveals that the Nb2O5 can bidirectionally regulate redox behaviors of S cathodes, which accelerates reduction conversions from polysulfides to sulfides as well as promotes oxidation reactions from sulfides to S. In situ and ex situ characterization techniques further verify its electrochemical lasting endurance in catalyzing S conversions. The well‐designed S cathode demonstrates a high specific capacity of 1377 mA h g−1 at 0.1 A g−1, outstanding rate capability of 405 mA h g−1 at 2 A g−1, and stable cyclability with a capacity retention of 617 mA h g−1 over 600 cycles at 0.5 A g−1. An ultralow capacity decay rate of 0.0193% per cycle is successfully realized, superior to those of current state‐of‐the‐art RT Na–S batteries. This design also suits emerging Na–Se batteries, which contribute to outstanding electrochemical performance as well. [ABSTRACT FROM AUTHOR]

Room‐temperature sodium–sulfur (RT/Na–S) batteries are regarded as promising large‐scale stationary energy storage systems owing to their high energy density and low cost as well as the earth‐abundant reserves of sodium and sulfur. However, the diffusion of polysulfides and sluggish kinetics of conversion reactions are still major challenges for their application. Herein, we developed a powerful and functional separator to inhibit the shuttle effect by coating a lightweight three‐dimensional cellulose nanofiber‐derived carbon aerogel on a glass fiber separator (denoted NSCA@GF). The hierarchical porous structures, favorable electronic conductivity, and three‐dimensional interconnected network of N,S‐codoped carbon aerogel endow a multifunctional separator with strong polysulfide anchoring capability and fast reaction kinetics of polysulfide conversion, which can act as the barrier layer and an expanded current collector to increase sulfur utilization. Moreover, the hetero‐doped N/S sites are believed to strengthen polysulfide anchoring capability via chemisorption and accelerate the redox kinetics of polysulfide conversion, which is confirmed from experimental and theoretical results. As a result, the assembled Na–S coin cells with the NSCA@GF separator showed a high reversible capacity (788.8 mAh g−1 at 0.1 C after 100 cycles) and superior cycling stability (only 0.059% capacity decay per cycle over 1000 cycles at 1 C), thereby demonstrating the significant potential for application in high‐performance RT/Na–S batteries. [ABSTRACT FROM AUTHOR]

Zinc-bromine (Zn–Br) flow battery is a promising option for large scale energy storage due to its scalability and cost-effectiveness. However, the sluggish reaction kinetics of Br 2 /Br− have hindered further advances. In this study, we report that a nitrogen-doped carbon felt electrode derived from a metal-organic framework can facilitate the adsorption of N-methyl N-ethyl pyrrolidinium polybromide (MEP-pBr) complex droplet dispersed in aqueous electrolyte. Density functional theory (DFT) calculation and Zeta potential measurement suggest that the adsorption is primarily due to the positively charged surface induced by graphitic nitrogen defects. Electrochemical analysis indicates that the enhanced adsorption of MEP-pBr droplet significantly boosts the redox kinetics and decreases the crossover of bromine-bearing species. Consequently, the cell performance improves, achieving an energy efficiency of over 79 % during 900 cycles at a current density of 100 mA cm−2. Our work underscores the importance of providing access of MEP-pBr droplet to the electrode surface in augmenting the energy efficiency of Zn–Br flow battery. [Display omitted] • A nitrogen-doped carbon felt cathode derived from a metal-organic framework (ZIF-8). • A positively charged surface on cathode induced by graphitic nitrogen defects. • A positively charged cathode surface facilitates the anchoring of MEP-pBr droplet to boost the redox kinetics. • Optimized nitrogen-doped carbon felt cathode exhibits superior performance and durability. [ABSTRACT FROM AUTHOR]

Lithium–sulfur batteries (LSB) show excellent potential as future energy storage devices with high energy density, but their slow redox kinetics and the shuttle effect seriously hinder their commercial application. Herein, a 0D@2D composite was obtained by anchoring polar nano-TiO2 onto a 2D layered g-C3N4 surface in situ, and a functional separator was prepared using multi-walled carbon nanotubes as a conductive substrate. Due to their long-range conductivity, multi-walled carbon nanotubes make up for the low conductivity of TiO2@g-C3N4 to some extent. A lithium–sulfur battery prepared with a modified separator exhibited excellent long-term cycle performance, a good lithium ion diffusion rate, and rapid redox kinetics. The initial specific discharge capacity of the composite was 1316 mAh g−1 at 1 C, and a high specific discharge capacity of 569.9 mAh g−1 was maintained after 800 cycles (the capacity decay rate per cycle was only 0.07%). Even at the high current density of 5 C, a specific capacity of 784 mAh g−1 was achieved. After 60 cycles at 0.5 C, the modified separator retained the discharge capacity of 718 mAh g−1 under a sulfur load of 2.58 mg cm−2. In summary, the construction of a heterojunction significantly improved the overall cycle stability of the battery and the utilization rate of active substances. Therefore, this study provides a simple and effective strategy for further improving the overall performance and commercial application of lithium–sulfur batteries.

Abstract As one of the most promising candidates for next‐generation energy storage systems, lithium‐sulfur (Li‐S) batteries have gained wide attention owing to their ultrahigh theoretical energy density and low cost. Nevertheless, their road to commercial application is still full of thorns due to the inherent sluggish redox kinetics and severe polysulfides shuttle. Incorporating sulfur cathodes with adsorbents/catalysts has been proposed to be an effective strategy to address the foregoing challenges, whereas the complexity of sulfur cathodes resulting from the intricate design parameters greatly influences the corresponding energy density, which has been frequently ignored. In this review, the recent progress in design strategies of advanced sulfur cathodes is summarized and the significance of compatible regulation among sulfur active materials, tailored hosts, and elaborate cathode configuration is clarified, aiming to bridge the gap between fundamental research and practical application of Li‐S batteries. The representative strategies classified by sulfur encapsulation, host architecture, and cathode configuration are first highlighted to illustrate their synergetic contribution to the electrochemical performance improvement. Feasible integration principles are also proposed to guide the practical design of advanced sulfur cathodes. Finally, prospects and future directions are provided to realize high energy density and long‐life Li‐S batteries.

With the increasing penetration of renewable energy sources in the past decades, stationary energy storage technologies are critically desired for storing electricity generated by non-dispatchable energy sources to mitigate its impact on power grids. Redox flow batteries (RFBs) stand out among these technologies due to their salient features for large-scale energy storage. The primary obstacle to the successful industrialization and broad deployment of RFBs is now their high capital costs. A feasible route to cost reduction is to develop high-power RFBs, since the increase in power performance has a pronounced impact on the cost of RFB systems. In this review, an in-depth inspection of the power performance of RFBs is presented. Perspectives for the future development of high-power RFBs along with implementable strategies addressing both the intrinsic and extrinsic limiting factors are summarized, which are expected to provide useful references steering the further improvement in the power density of RFBs.

Abstract Regulating redox kinetics is able to spur the great‐leap‐forward development of room‐temperature sodium–sulfur (RT Na–S) batteries, especially on propelling their Na‐ion storage capability. Here, an innovative metal oxide kinetics accelerator, orthorhombic Nb2O5 Na‐ion conductor, is proposed to functionalize porous carbon nanoreactors (CNR) for S cathodes. The Nb2O5 is shown to chemically immobilize sodium polysulfides via strong affinity. Theoretical and experimental evidence reveals that the Nb2O5 can bidirectionally regulate redox behaviors of S cathodes, which accelerates reduction conversions from polysulfides to sulfides as well as promotes oxidation reactions from sulfides to S. In situ and ex situ characterization techniques further verify its electrochemical lasting endurance in catalyzing S conversions. The well‐designed S cathode demonstrates a high specific capacity of 1377 mA h g−1 at 0.1 A g−1, outstanding rate capability of 405 mA h g−1 at 2 A g−1, and stable cyclability with a capacity retention of 617 mA h g−1 over 600 cycles at 0.5 A g−1. An ultralow capacity decay rate of 0.0193% per cycle is successfully realized, superior to those of current state‐of‐the‐art RT Na–S batteries. This design also suits emerging Na–Se batteries, which contribute to outstanding electrochemical performance as well.

Abstract Room‐temperature sodium–sulfur (RT/Na–S) batteries are regarded as promising large‐scale stationary energy storage systems owing to their high energy density and low cost as well as the earth‐abundant reserves of sodium and sulfur. However, the diffusion of polysulfides and sluggish kinetics of conversion reactions are still major challenges for their application. Herein, we developed a powerful and functional separator to inhibit the shuttle effect by coating a lightweight three‐dimensional cellulose nanofiber‐derived carbon aerogel on a glass fiber separator (denoted NSCA@GF). The hierarchical porous structures, favorable electronic conductivity, and three‐dimensional interconnected network of N,S‐codoped carbon aerogel endow a multifunctional separator with strong polysulfide anchoring capability and fast reaction kinetics of polysulfide conversion, which can act as the barrier layer and an expanded current collector to increase sulfur utilization. Moreover, the hetero‐doped N/S sites are believed to strengthen polysulfide anchoring capability via chemisorption and accelerate the redox kinetics of polysulfide conversion, which is confirmed from experimental and theoretical results. As a result, the assembled Na–S coin cells with the NSCA@GF separator showed a high reversible capacity (788.8 mAh g−1 at 0.1 C after 100 cycles) and superior cycling stability (only 0.059% capacity decay per cycle over 1000 cycles at 1 C), thereby demonstrating the significant potential for application in high‐performance RT/Na–S batteries.

The oxidation of the uranium tetrachloride (UCl4) by the octacyanometalate(V) ion of tungsten and molybdenum was studied in a perchloric acid medium at an ionic strength of 1.5 M (NaClO4). The reaction was first order in both UIV(H2O)84+ and MV(CN)83– (M = W, Mo). A second order rate constant of k2 = 0.111 ± 0.002 M−1s−1 at [H+] = 0.932 M and 15.0 °C was found for the W(CN)83– reaction and for the Mo(CN)83– reaction, k2 = 32.9 ± 0.9 M−1s−1 at [H+] = 1.008 M and 29.7 °C. The reactions are proportional to [H+]–2 and an equilibrium constant of Ka2 ≈ 1.18 × 10−3 M−1 (pKa ≈ 6.7) at µ = 1.5 M was found for the deprotonation of UIV(H2O)84+. Activation parameters have been obtained by a least squares fit of temperature data directly to the Eyring equation. [ABSTRACT FROM AUTHOR]

The practical application of lithium–sulfur batteries (LSBs) is limited by the shuttle effect of lithium polysulfides (LiPSs), large volume expansion, and sluggish conversion kinetics of sulfur. Herein, the crystallinity regulation of NixFey alloy anchored on oxidized carbon nanotube/nitrogen‐doped graphene (NixFey@OCNT/NG) for application of a functional separator into LSBs is demonstrated. A low crystalline NixFey@OCNT/NG (LC‐NixFey@OCNT/NG) modified polypropylene separator is systematically compared with its highly crystalline counterpart (HC‐NixFey@OCNT/NG), demonstrating superior LiPS absorbability, redox mediating capability into facilitated conversion kinetics, and uniform flux of Li+ into the anode. Furthermore, theoretical calculations confirm that the LC‐NixFey alloy features high adsorption energies and low diffusion energy barriers toward LiPSs, as well as a decreased energy gap and larger electron density near Fermi level. Accordingly, the LSB cells with LC‐NixFey@OCNT/NG modified separators deliver a high specific capacity of 1379.13 mA h g−1 at 0.1 C and a low decay ratio of 0.04%/cycle over 600 cycles at 5.0 C with a high capacity of 410 mA h g−1. Even under high sulfur loading (5.37 mg cm−2) and lean electrolyte (E/S = 4.9 µL mg−1) conditions, the LSB cells with LC‐NixFey@OCNT/NG/PP deliver a high areal capacity of 4.1 mAh cm−2 at 0.2 C. [ABSTRACT FROM AUTHOR]

Lithium-sulfur batteries (LSBs) have become strong competitors in secondary battery systems because of their superior theoretical capacity and energy density. However, due to the serious shuttle effect of soluble long-chain lithium polysulfides (LiPSs) and the slow solid-solid reaction kinetics, LSBs face some specific challenges, such as a short cycle life and low rate performance. The introduction of selenide/carbon composites derived from zeolite imidazolate frameworks (ZIFs) into separator coatings is a direct and effective solution to the aforementioned problems. Here, a zinc selenide/carbon catalyst material (ZnSe@C) was constructed and employed to modify commercial polypropylene (PP) separators to accelerate the conversion of intermediates. The highly polar ZnSe effectively fixes the active material on the cathode side by transferring electrons between elements with LiPSs and improves the utilization rate of sulfur. Concurrently, the highly conductive carbon nanoskeleton generated following the pyrolysis of ZIF-8 ensures the rapid transfer of charges during the catalytic reaction. The prepared ZnSe@C has a large specific surface area (250.07 m 2 g -1 ) and mesoporous ratio (78.03%), which not only enhances adsorption and catalysis but also promotes the penetration of the electrolyte and the transport of Li + . Based on this, ZnSe@C/PP separator cells exhibit a low average capacity decay rate of 0.051% per cycle after 500 cycles at 1 C.

Ionic hybrid perovskites face challenges in maintaining their structural stability against non-equilibrium phase degradation, therefore, it is essential to develop effective ways to reinforce their corner-shared [PbI 6 ] 4- octahedral units. To strengthen structural stability, redox-active functional polyoxometalates (POMs) are developed and incorporated into perovskite solar cells (PSCs) to form a robust polyoxometalates/perovskite interlayer for stabilizing the perovskite phase. This approach offers several advantages: 1) promotes the formation of an interfacial connecting layer to passivate interfacial defects in addition to stabilize the [PbI 6 ] 4- units through exchanged ammonium cations in POMs with perovskites; 2) facilitates continuous structural repairing of Pb 0 - and I 0 -rich defects in the [PbI 6 ] 4- unit through redox electron shuttling of the electroactive metal ions in POMs; 3) provides guidance for selecting suitable redox mediators based on the kinetic studies of POM's effectiveness in reacting with targeted defects. The POM-reinforced device maintains 97.2% of its initial PCE after 1500 h of shelf-life test at 65 °C, while also enhancing the long-term operational stability. Additionally, this approach can be generally applicable across scalable sizes and various bandgap perovskites in devices, showing the promise of using functional POMs to enhance perovskite photovoltaic performance., (© 2024 Wiley‐VCH GmbH.)

The advancement of lithium-sulfur (Li-S) batteries is severely retarded by lithium polysulfides (LiPSs) shuttling behavior and sluggish redox kinetics. Herein, the heterogeneous composite with defective Bi2Se3−x nanosheets and porous nitrogen-doped carbon (Bi2Se3−x/NC) is prepared by selenizing bismuth metal-organic frameworks as a multifunctional sulfur host. The highly efficient immobilization-conversion on LiPSs is realized by the synergistic effect of structure construction strategy and defect engineering. It is found that Bi2Se3−x with the suitable amount of selenium vacancies achieves the best electrochemical performance due to the advantages of its structure and composition. These results confirm the intrinsic correlation between defects and catalysis, which are revealed by computational and experimental studies. Due to these superiorities, the developed sulfur electrodes exhibited admirable stability and a fairly lower capacity decay rate of approximately 0.0278% per cycle over 1,000 cycles at a 3 C rate. Even at the high sulfur loading of 6.2 mg·cm−2, the cathode still demonstrates a high discharge capacity of 455 mAh·g−1 at 1 C. This work may enlighten the development of mechanism investigation and design principles regarding sulfur catalysis toward high-performance Li-S batteries. [ABSTRACT FROM AUTHOR]