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This study investigates the synthesized NiO- and CuO-based carriers supported by Al 2 O 3 , CeO 2 , ZrO 2 and their combinations in chemical looping combustion (CLC). The oxygen carriers were tested in a thermogravimetric analyzer (TGA), where the results showed that the oxygen capacity increased using mixed support oxides in both NiO-based and CuO-based samples. The reducibility of CeO 2 played a role in the increase of oxygen capacity and in the case of NiO-based samples, the reduction of NiAl 2 O 4 phase as promoted by the formation of CeAlO 3 played a role, as well. For NiO-based samples, a significant increase of carbon deposition occurred for mixed support oxides (Al 2 O 3 -ZrO 2 , Al 2 O 3 -CeO 2 and Al 2 O 3 -ZrO 2 -CeO 2) at 750 °C in comparison with the use of one support while the differences were negligible at 950 °C. To examine the structure and properties of the oxygen carriers, they were characterized by XRD, SEM/EDX and XPS. Comparison of fresh and used samples revealed sintering of active-sites particles on the surface of supports as evident of EDX mapping images and the decrease in active-site to support ratio in the XPS analysis. NiO/Al 2 O 3 -ZrO 2 -CeO 2 was found to be a potential oxygen carrier for further CLC studies and scaleup. [Display omitted] • Reactivity, oxygen capacity and carbon formation were studied in this research. • Mixed support oxides in NiO and CuO carriers enhanced oxygen capacity. • NiAl 2 O 4 and CeAlO 3 found in XRD profiles participated in the reduction. • Reducibility of CeO 2 played a role in the enhancement of oxygen capacity. • Kinetic modeling was used to estimate activation energy. [ABSTRACT FROM AUTHOR]

The use of redox mediators is an effective strategy to enhance the redox reactions of sulfur species in lithium-sulfur batteries. Recent research on redox mediators has elucidated their relationships based on their reaction mechanisms and various categories. The detailed understanding provides guidance for the future development of high-performance redox mediators in lithium-sulfur batteries. [Display omitted] • The recent advancements in the use of redox mediators in lithium-sulfur batteries are summarized and discussed. • The application of redox mediators is classified and analyzed. • Future research directions for the development of high-performance redox mediators in lithium-sulfur batteries are proposed. Lithium-sulfur batteries are hailed as revolutionary energy storage mechanisms due to their high theoretical energy density. However, the high reaction barrier of lithium polysulfides hampers the practical application of lithium-sulfur batteries. Therefore, it is imperative to devise effective strategies to enhance the generation/transformation kinetics of lithium polysulfides from elemental sulfur or Li 2 S. Recently, redox mediators have emerged as promising agents to catalyze sulfur redox reactions, advancing the development of lithium-sulfur cells. This review comprehensively summarizes the operational principles of disclosed redox mediators, categorizing them based on their unique reaction systems and core functions in redox electrochemistry. Both solid and soluble redox mediators are examined, showcasing notable progress in molecule framework enhancement, novel reaction pathway proposals, and the development of innovative catalytic molecules. Additionally, the review outlines selection criteria, overarching design principles, current constraints, and future research directions for redox mediators. It is anticipated that this review will provide timely and comprehensive insights into the future study trajectories of redox mediators, thereby enhancing the efficacy of lithium-sulfur batteries. [ABSTRACT FROM AUTHOR]

The high-energy-density lithium-sulfur (Li-S) batteries (2600 Wh kg−1) are seriously hampered by the slow redox reaction kinetics and obnoxious shuttle effects of sulfur cathode. Introducing a catalytic host to promote sulfur redox kinetics is a promising way to inhibit polysulfide shuttling. Previous studies mainly focus on the unidirectional catalysis conversion from S 8 to Li 2 S, and usually ignore the inverse reaction. Herein, defective vanadium nitride (VN 1−x) is designed to promote the conversion of sulfur. The catalytic analysis suggests that introducing nitrogen vacancies effectively improves the nucleation and decomposition kinetics of Li 2 S, and prefers to promote the nucleation process, leading to superior capacity. Benefit from the bidirectional enhanced sulfur redox kinetics, the VN 1−x /S composite electrode presents an impressively high capacity of 1417 mAh g−1 at 0.1 C at the first charge/discharge process, which is very close to the theoretical capacity of sulfur cathode (1675 mAh g−1). The Coulombic efficiency of the composite electrode reaches 99.89% even after 1000 cycles, showing reversible redox reactions. The pouch cell using VN 1−x /S cathode shows a high initial discharge capacity (1180.3 mAh g−1) and can stably cycle over 100 cycles. This work can support the development of bidirectional catalytic host design for high-loading Li-S batteries. [Display omitted] • VN with nitrogen vacancies is employed as the host to confine sulfur. • The enhanced bidirectional catalytic ability due to nitrogen vacancy is confirmed. • The VN 1-x /S assembled pouch cell presents a high initial capacity of 1180.3 mAh/g. [ABSTRACT FROM AUTHOR]

Summary: A rational design of functional separators that include abundant active sites and high electrochemical stability without Li+ ion transport sacrifice is important for inhibiting the shuttle effect of lithium polysulfides (LiPSs) and improving the utilization efficiency of sulfur for high performance lithium sulfur batteries (LSB). Herein, we report a straightforward modification chemistry of separator through an in‐situ assembly of two‐dimensional nickel‐iron layered double hydroxide nanosheets onto the reticular functionalized carbon nanotubes surface (NiFe‐LDH@OCNT) with enriched active sites and interconnected conducting channels. As demonstrated by the spectroscopic and electrochemical characterizations, the NiFe‐LDH@OCNT composite features strong adsorption ability towards LiPSs and improvement of the LiPSs redox kinetics, thus effectively suppressing the shuttle effect. In this regard, the LSB cells assembled with the NiFe‐LDH@OCNT/PP composite separators achieve the excellent reversibility and good cycling stability over 600 cycles with a low capacity decay rate of 0.085% each cycle at 2 C. [ABSTRACT FROM AUTHOR]

Lithium−sulfur batteries (LSBs) are regarded as one of the most promising candidates for energy storage devices. However, the severe shuttling effect of soluble polysulfides (PSs) limits its further application. Metal−organic frameworks (MOFs) have emerged as a new kind of sulfur host for their talents in confining and trapping PSs. However, the shuttle effect has not been fully stressed as a significant drawback for most MOFs that leads to sluggish redox kinetics, resulting in low specific capacity and short lifetime, especially at high sulfur loading. In this work, a MOF‐sulfur copolymer (CNT@UiO‐66‐V‐S) is elaborated by copolymerization of sulfur with vinyl functionalized MOFs. Systematic electrochemical experiments and in situ Raman spectroscopy analysis indicate that the cathode exhibits a radical reaction mechanism and can accelerates LiPSs conversion. The CNT@UiO‐66‐V‐S cathode delivers over 100% improved discharge capacity and lowers decay rate at both low and high (5.6 mg cm–2) sulfur loadings compared to the physically mixed MOF/S cathode. The strategy of MOF‐sulfur copolymerization provides a new solution for promoting reaction kinetics and tackling the shuttle effect, and is expected to inspire the design of advanced sulfur hosts applied for high‐performance LSBs. [ABSTRACT FROM AUTHOR]

Lithium–sulfur batteries have aroused great interest in the context of rechargeable batteries, while the shuttle effect and sluggish conversion kinetics severely handicap their development. Defect engineering, which can adjust the electronic structures of electrocatalyst, and thus affect the surface adsorption and catalytic process, has been recognized as a good strategy to solve the above problems. However, research on phosphorus vacancies has been rarely reported, and how phosphorus vacancies affect battery performance remains unclear. Herein, CoP with phosphorus vacancies (CoP‐Vp) is fabricated to study the enhancement mechanism of phosphorus vacancies in Li–S chemistry. The derived CoP‐Vp features a low Co‐P coordination number and the introduced phosphorus vacancies mainly exist in the form of clusters. The obtained CoP‐Vp can reinforce the affinity to lithium polysulfides (LiPSs) and thus the shuttle effect can be restrained. In addition, the reduced reaction energy barriers and the promoted diffusion of Li+ can accelerate redox kinetics. Electrochemical tests and in situ Raman results confirm the advantages of phosphorus vacancies. The S/CNT‐CoP‐Vp electrode presents outstanding cycling performance and achieves a high capacity of 8.03 mAh cm−2 under lean electrolyte condition (E/S = 5 μLE mg−1S). This work provides a new insight into improving the performance of Li–S batteries through defect engineering. [ABSTRACT FROM AUTHOR]

[Display omitted] • InOOH nanoparticles are endowed with the prominent polysulfides adsorptivity. • InOOH nanoparticles present the potent bidirectional catalytic effects for polysulfides. • The electrocatalytic effects are verified by the theoretical and experimental results. • The Li–S cells with InOOH additive harvest the excellent electrochemical performance. Lithium–sulfur (Li–S) batteries with the prominent advantages are greatly expected to be the attractive alternatives in the next-generation energy-storage systems. However, the practical success of Li–S batteries suffers from the shuttle effect and depressed redox kinetics of polysulfides. Herein, for the first time, InOOH nanoparticles are employed as a potent catalytic additive in sulfur electrode to overcome these issues. As demonstrated by the theoretical and experimental results, the strong interactions between the InOOH nanoparticles and sulfur species enable the effective adsorption of polysulfides. More significantly, InOOH nanoparticles not only effectively expedite the reduction of sulfur during the discharge process, but also dramatically accelerate the oxidation of Li 2 S during the charge process, presenting the marvelous bidirectional catalytic effects. Benefited from these distinctive superiorities, the cells with InOOH nanoparticles harvest an excellent capacity retention of 69.5% over 500 cycles at 2C and a commendable discharge capacity of 891 mAh g−1 under a high-sulfur loading of 5.0 mg cm−2. The detailed investigations in this work provide a novel insight to ameliorate the Li–S electrochemistry by the bidirectional catalyst for high-performance Li–S batteries. [ABSTRACT FROM AUTHOR]

Lithiumâ€"sulfur (Liâ€"S) batteries with tremendous energy density possess great promise for the next-generation energy storage devices. Even though, the shuttle effect and sluggish redox kinetics of lithium polysulfides (LiPSs) seriously restrict practical applications of Liâ€"S batteries. Herein, a three-dimensionally ordered macro/mesoporous TiN (3DOM TiN) nanostructure is established via using poly (methyl methacrylate) PMMA spheres as template. The interconnected macro/mesoporous channels are constructed to effectively alleviate the stacking of composite materials and render a large portion of inherent active sites exposed on the surface region. Moreover, TiN exhibits high electrical conductivity, which efficiently enhances charge-transfer kinetics and guarantees the favorable electrochemical performance of sulfur cathode. More importantly, the as-prepared 3DOM TiN suppresses the shuttle effect and improves the redox kinetics significantly due to strong affinity toward LiPSs. Attributed to these unique features, the S/3DOM TiN electrode achieves an ultrahigh initial discharge capacity of 1187 mAh gâˆ'1 at 0.2 C, and stable cycling performance of 552 mAh gâˆ'1 over 500 cycles at 1 C. Meanwhile, the discharge capacity retention of 701 mAh gâˆ'1 (3.5 mAh cmâˆ'2) can be endowed for the S/3DOM TiN electrode under high sulfur loading of 5 mg cmâˆ'2 after 100 cycles at 0.1 C. Therefore, the 3DOM TiN nanostructure electrocatalyst provides a promising path for developing practically useable Liâ€"S batteries. [ABSTRACT FROM AUTHOR]

Redox input by subducted slab into mantle is important for deep cycle and isotopic evolution of volatile elements, whose stable forms are controlled by redox state. Given reduced condition in lower part of the upper mantle, taking redox budget from lithospheric mantle into consideration is crucial in redefining redox state there. To constrain to which extent subducted slab modified redox state of the uppermost mantle and how much oxygen budget slab carried into deep Earth, we investigated redox kinetics of olivine adopting diffusion couple method at 1 GPa and 1,373–1573 K in a piston cylinder apparatus. It is found that redox process in olivine is diffusion‐controlled, and diffusing on the order of 10−12 m2/s at 1473 K. Oxidation process in reduced part is oxygen fugacity (fO2)‐independent with activation enthalpy of 235 ± 56 kJ/mol, while reduction process in oxidized part is fO2‐dependent with an fO2 exponent of 2/5. Diffusion profile analysis reveals that for magnetite‐free couple, redox process is controlled by oxygen grain boundary diffusion (GBD) below ΔFMQ + 1, and rate‐limited by faster species which might be hydrogen related Mg vacancy above ΔFMQ + 1. However, for magnetite‐bearing couple, oxygen GBD dominates redox process across wide fO2 range. The extremely slow rate limits the homogenization of the slab with surrounding mantle so that redox state of the uppermost mantle remains unchanged in the past 3.5 Gyrs. A highly underestimated oxygen reservoir may have formed in deep Earth, when subducted slab transports oxidized components to region deeper than the mantle transition zone. Plain Language Summary: As oxidized slabs continue subducting into mantle, redox exchange proceeds between slabs and the surrounding mantle. Knowledge of redox kinetics of olivine is essential for understanding redox evolution of the uppermost mantle in the Earth's history and unraveling redox budget in slab residues that brought into deeper Earth. In this study, we conducted a series of diffusion experiments to determine rates of redox processes in olivine aggregates under high pressure and high temperature. Our results show that diffusion‐controlled redox processes in olivine aggregates are extremely slow. The extent of surrounding upper mantle which can be oxidized by slabs is very limited. The unchanging redox state of the uppermost mantle is not caused by its infinite redox capacity as previously supposed but due to its inability to digest oxidized components efficiently. Being not fully absorbed by the uppermost mantle, the oxidized slabs tend to transport a considerable amount of oxidized components into deeper mantle with further subducting. Key Points: Redox kinetics of olivine were investigated by diffusion couple method at 1 GPa and 1,373–1,573 KBelow ΔFMQ + 1, redox process is controlled by O grain boundary diffusion, while above that, by H diffusion related with Mg vacancySlow redox rate limits homogenization of subducted slab with mantle. A highly underestimated oxygen reservoir may be present in deep Earth [ABSTRACT FROM AUTHOR]

The oxidation of alcohols, n-propanol, 2-methoxy ethanol and 2-ethoxy ethanol by cerium (IV) in nitric acid leads to the formation of corresponding aldehydes. The reaction is first order with respect to Ce(IV). A Michaelis-Menten type kinetics is observed with respect to alcohols. The reaction is retarded by initial [Ce(IV)] with increase in concentration of oxidant. The reaction exhibits participation of 2 mole of cerium (IV) with 1 mole of alcohols. It has been concluded that Ce(IV)-dimer participate in the oxidation process and formation of free radical through complex ion formation in the nitric acid medium. [ABSTRACT FROM AUTHOR]

Benefiting from the merits of low cost, ultrahigh‐energy densities, and environmentally friendliness, metal–sulfur batteries (M–S batteries) have drawn massive attention recently. However, their practical utilization is impeded by the shuttle effect and slow redox process of polysulfide. To solve these problems, enormous creative approaches have been employed to engineer new electrocatalytic materials to relieve the shuttle effect and promote the catalytic kinetics of polysulfides. In this review, recent advances on designing principles and active centers for polysulfide catalytic materials are systematically summarized. At first, the currently reported chemistries and mechanisms for the catalytic conversion of polysulfides are presented in detail. Subsequently, the rational design of polysulfide catalytic materials from catalytic polymers and frameworks to active sites loaded carbons for polysulfide catalysis to accelerate the reaction kinetics is comprehensively discussed. Current breakthroughs are highlighted and directions to guide future primary challenges, perspectives, and innovations are identified. Computational methods serve an ever‐increasing part in pushing forward the active center design. In summary, a cutting‐edge understanding to engineer different polysulfide catalysts is provided, and both experimental and theoretical guidance for optimizing future M–S batteries and many related battery systems are offered. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fe 3 C-PBC is synthesized by a wet-impregnation strategy with subsequent calcination. • Fe 3 C-PBC couples the advantages of Fe 3 C and porous biomass-derived carbon. • The adsorptive and catalytic abilities of Fe 3 C-PBC are verified comprehensively. • Fe 3 C-PBC/S electrode delivers the commendable performances of Li–S batteries. Lithium–sulfur (Li–S) batteries are greatly expected to be the favored alternatives in the next-generation energy-storage technologies due to their exceptional advantages. However, the shuttle effect and sluggish reaction kinetics of polysulfides largely hamper the practical success of Li–S batteries. Herein, a unique iron carbide (Fe 3 C) nanoparticles-embedded porous biomass-derived carbon (Fe 3 C-PBC) is reported as the excellent immobilizer and promoter for polysulfides regulation. Such a distinctive composite strongly couples the vast active sites of Fe 3 C nanoparticles and the conductive network of porous biomass-derived carbon. Therefore, Fe 3 C-PBC is endowed with outstanding adsorptivity and catalytic effect toward inhibiting the shuttle effect and facilitating the redox kinetics of polysulfides, demonstrated by the detailed experimental demonstrations and theoretical calculation. With these synergistic effects, the Fe 3 C-PBC/S electrode embraces a superb capacity retention of 82.7% at 2C over 500 cycles and an excellent areal capacity of 4.81 mAh cm−2 under the high-sulfur loading of 5.2 mg cm−2. This work will inspire the design of advanced hosts based on biomass materials for polysulfides regulation in pursuing the superior Li–S batteries. [ABSTRACT FROM AUTHOR]

Abstract Benefiting from the merits of low cost, ultrahigh‐energy densities, and environmentally friendliness, metal–sulfur batteries (M–S batteries) have drawn massive attention recently. However, their practical utilization is impeded by the shuttle effect and slow redox process of polysulfide. To solve these problems, enormous creative approaches have been employed to engineer new electrocatalytic materials to relieve the shuttle effect and promote the catalytic kinetics of polysulfides. In this review, recent advances on designing principles and active centers for polysulfide catalytic materials are systematically summarized. At first, the currently reported chemistries and mechanisms for the catalytic conversion of polysulfides are presented in detail. Subsequently, the rational design of polysulfide catalytic materials from catalytic polymers and frameworks to active sites loaded carbons for polysulfide catalysis to accelerate the reaction kinetics is comprehensively discussed. Current breakthroughs are highlighted and directions to guide future primary challenges, perspectives, and innovations are identified. Computational methods serve an ever‐increasing part in pushing forward the active center design. In summary, a cutting‐edge understanding to engineer different polysulfide catalysts is provided, and both experimental and theoretical guidance for optimizing future M–S batteries and many related battery systems are offered.

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 TiO 2 (B) nanosheets with oxygen vacancies (OVs) grown in situ on MXenes layers (N-TiO 2- 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-TiO 2- 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-TiO 2- 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-TiO 2- 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., (© 2024 The Author(s). Advanced Science published by Wiley‐VCH GmbH.)

The slow redox kinetics of lithium-sulfur batteries severely limit their application, and sulfur utilization can be effectively enhanced by designing different cathode sulfur host materials. Herein, we report the hollow porous nanofiber LaNi 0.6 Co 0.4 O 3 as a bidirectional host material for lithium-sulfur batteries. After Co is substituted into LaNiO 3 , oxygen vacancies are generated to enhance the material conductivity and enrich the active sites of the material, and the electrochemical reaction rate can be further accelerated by the synergistic catalytic ability of Ni and Co elements in the B-site of the active site of LaNi 0.6 Co 0.4 O 3 . As illustrated by the kinetic test results, LaNi 0.6 Co 0.4 O 3 effectively accelerated the interconversion of lithium polysulfides, and the nucleation of Li 2 S and the dissolution rate of Li 2 S were significantly enhanced, indicating that LaNi 0.6 Co 0.4 O 3 accelerated the redox kinetics of the lithium-sulfur battery during the charging and discharging process. In the electrochemical performance test, the initial discharge specific capacity of S/LaNi 0.6 Co 0.4 O 3 was 1140.4 mAh g -1 at 0.1 C, and it was able to release a discharge specific capacity of 584.2 mAh g -1 at a rate of 5 C. It also showed excellent cycling ability in the long cycle test, with a single-cycle capacity degradation rate of only 0.08%. Even under the harsh conditions of high loaded sulfur and low electrolyte dosage, S/LaNi 0.6 Co 0.4 O 3 still delivers excellent specific capacity and excellent cycling capability. Therefore, this study provides an idea for the future development of bidirectional high-activity electrocatalysts for lithium-sulfur batteries.

Controlling exposed crystal facets through crystal facet engineering is an efficient strategy for enhancing the catalytic activity of nanocrystalline catalysts. Herein, the active tin dioxide nano–octahedra enclosed by {332} crystal facets (SnO2 {332}) are synthesized on reduced graphene oxide and demonstrate powerful chemisorption and catalytic ability, accelerating the redox kinetics of sulfur species in lithium–sulfur chemistry. Attributed to abundant unsaturated–coordinated Sn sites on {332} crystal planes, SnO2 {332} has outstanding adsorption and catalytic properties. The material not only adsorbs and converts polysulfides efficiently, but also prominently lowers the decomposition energy barrier of Li2S. The batteries with these high active electrocatalysts exhibit excellent cycling stability with a low capacity attenuation of 0.021% every cycle during 2000 cycles at 2 C. Even with a sulfur loading of 8.12 mg cm−2, the batteries can still cycle stably and maintain a prominent areal capacity of 6.93 mAh cm−2 over 100 cycles. This research confirms that crystal facet engineering is a promising strategy to optimize the performance of catalysts, deepens the understanding of surface structure‐oriented electrocatalysis in Li–S chemistry, while aiding the rational design of advanced sulfur electrodes. [ABSTRACT FROM AUTHOR]

The sulfur redox kinetics critically matters to superior lithium–sulfur (Li–S) batteries, for which single atom catalysts (SACs) take effect on promoting Li2S redox process and mitigating the shuttle behavior of lithium polysulfide (LiPs). However, conventional trial‐and‐error strategy significantly slows down the development of SACs in Li–S batteries. Here, the Li2S oxidation processes over MN4@G catalysts are fully explored and energy barrier of Li2S decomposition (Eb) is identified to correlate strongly with three parameters of energy difference between initial and final states of Li2S decomposition, reaction energy of Li2S oxidation and LiS bond strength. These three parameters can serve as efficient descriptors by which two excellent SACs of MoN4@G and WN4@G are screened which give rise to Eb values of 0.58 and 0.55 eV, respectively, outperforming other analogues in adsorbing LiPs and accelerating the redox kinetics of Li2S. This method can be extended to a wider range of SACs by coupling MN4 moiety with heterostructures and heteroatoms beyond N where WN4@G/TiS2 heterointerface is predicted to exhibit enhanced catalytic performance for Li2S decomposition with Eb of 0.40 eV. This work will help accelerate the process of designing a wider range of efficient catalysts in Li–S batteries and even beyond, e.g. alkali‐ion‐Chalcogen batteries. [ABSTRACT FROM AUTHOR]

The oxidation of the tetrakisoxalatouranate(IV) ion by the octacyanometalate(V) ion of tungsten and molybdenum was studied in an oxalate buffer medium. The reaction was first order in both UIV(C2O4)44− and M(CN)83− (M = W, Mo), and a second order rate constant of k2 = 0.032 ± 0.002 M−1s−1 at pH 4.27 and 24.8 °C was found for the W(CN)83− reaction. For the Mo(CN)83− reaction the second order rate constant is k2 = 16.9 ± 0.1 M−1s−1 at pH 4.77 and 25.3 °C. The reactions are inversely proportional to [H+] and an equilibrium constant of Ka ≈ 1.3 × 10–6 M−1 (pKa ≈ 5.89) at 25 °C was found for the deprotonation of UIV(C2O4)3(H2O)22−. Activation parameters have been obtained by a least squares fit of temperature data directly to the Eyring equation. [ABSTRACT FROM AUTHOR]

Lithium sulfur batteries (LSBs) have been seen as of considerable potential candidate for lithium‐ion batteries (LIBs) to satisfy high energy density demand. However, the application of LSBs until now has been stubbornly dragged by the "shuttle effect" of lithium polysulfides (LiPSs) due to dissolution of LiPSs in electrolyte and reaction with the lithium anode, incurring a severe capacity decay. Herein, the straightforward separator modification method that multiphase and multicomponent nickel‐iron oxide heterostructure grown on oxidized carbon nanotube (NiFe2O4−NiO/OCNT) composites directly coated on the polypropylene (PP) separator, has been implemented, which effectively inhibits the migration of LiPSs, enhances the electron and lithium‐ion transfer, and promotes the redox kinetics by virtue of the heterostructure interfaces between NiFe2O4, NiO, and OCNT. In conclusion, the synthesized NiFe2O4−NiO/OCNT/PP separator delivers good rate capacities and high stability up to 1000 cycles at 2 C with a low‐capacity decay rate of approximately 0.065 % per cycle. [ABSTRACT FROM AUTHOR]

Abstract The sulfur redox kinetics critically matters to superior lithium–sulfur (Li–S) batteries, for which single atom catalysts (SACs) take effect on promoting Li2S redox process and mitigating the shuttle behavior of lithium polysulfide (LiPs). However, conventional trial‐and‐error strategy significantly slows down the development of SACs in Li–S batteries. Here, the Li2S oxidation processes over MN4@G catalysts are fully explored and energy barrier of Li2S decomposition (Eb) is identified to correlate strongly with three parameters of energy difference between initial and final states of Li2S decomposition, reaction energy of Li2S oxidation and LiS bond strength. These three parameters can serve as efficient descriptors by which two excellent SACs of MoN4@G and WN4@G are screened which give rise to Eb values of 0.58 and 0.55 eV, respectively, outperforming other analogues in adsorbing LiPs and accelerating the redox kinetics of Li2S. This method can be extended to a wider range of SACs by coupling MN4 moiety with heterostructures and heteroatoms beyond N where WN4@G/TiS2 heterointerface is predicted to exhibit enhanced catalytic performance for Li2S decomposition with Eb of 0.40 eV. This work will help accelerate the process of designing a wider range of efficient catalysts in Li–S batteries and even beyond, e.g. alkali‐ion‐Chalcogen batteries.

In recent years, the atom‐doping strategy has attracted extensive attention in lithium‐sulfur batteries. The reasonable structure design and introduction of doping atoms into sulfur cathode materials not only improve the utilization rate of active materials but also catalyze the redox kinetics of polysulfides, which greatly improves the electrochemical performance of the lithium‐sulfur batteries. However, the understanding of the functional mechanism and conversion mechanism of the doping atoms at micro levels is still limited. Hence, it is very crucial to explore the influence of doping atoms on the electronic arrangement and electrochemical active sites. Herein, the development of atomic doping in lithium‐sulfur batteries is reviewed, and the structure‐activity relationship between doped atoms and the adsorption of lithium polysulfide is analyzed. Furthermore, the catalytic mechanisms of catalytic materials were unmasked from microscopic perspectives, namely ion transport, surface electronic structure, energy band structure and state density. [ABSTRACT FROM AUTHOR]

[Display omitted] In this work, SnS 2 -SnO 2 -CNTs heterostructure was constructed to modify both the separator and cathode, which promotes the movement of the P band center of the tin atom to the Fermi level, realizing the association process of adsorption, capture, and conversion of LPSs, thus achieving high-performance Li-S battery. • SnS 2 -SnO 2 heterostructure is designed to modify both separator and cathode for Li-S battery. • The formation of heterostructure regulates the movement of the P band center of Sn. • SnS 2 -SnO 2 reduces the deposition barrier of Li 2 S and promotes redox kinetics. • Superior performance achieved under high rate or high S loading. Lithium-sulfur batteries (LSBs) are considered a strong contender for the new-generation secondary energy storage system due to their high capacity and energy density. However, the sluggish reaction kinetics and the shuttle effect of lithium polysulfides (LPSs) severely hinder the cycle stability. The robust design of both the separator and cathode exhibit an effective role in restricting the shuttle effect and accelerating redox kinetics through the LPSs trapping and catalyzing effect. In this paper, a CNT-modified tin sulfide and tin oxide (SnS 2 -SnO 2 -CNTs) heterostructure was constructed as a multifunctional catalyst to modify both the separator and cathode to achieve high-performance LSBs. The formation of SnS 2 -SnO 2 heterostructure promotes the movement of the P band center of the tin atom to the Fermi level, which realizes the association process of adsorption, capture, and conversion of LPSs, thus effectively suppressing the shuttle effect. The SnS 2 -SnO 2 heterogeneous interface can also reduce the deposition barrier of Li 2 S, thus greatly promoting the redox kinetics. Together with the improved electron transfer, the resulting LSBs with the robust electrode and separator exhibit superior electrochemical performance with a high initial capacity of 930.2 mAh g−1 at 1 C with a high sulfur loading of 4.3 mg cm−2 and a remarkable capacity of up to 580.3 mAh g−1 at an ultrahigh rate of 7.4 C. [ABSTRACT FROM AUTHOR]

The controversial lithium-sulfur (Li-S) batteries still have too many challenges to be commercially developed. The electrical conductivity of elemental sulfur is poor. Moreover, the shuttle effect caused by soluble polysulfides can reduce sulfur utilization and produce lithium dendrites at the anode. To address the above disadvantages, Bi 2 Se 3 @CoSe composite is in-situ synthesized on carbon nanotubes through one-step hydrothermal method and applied to the cathodes. The strong metallicity of Bi 2 Se 3 @CoSe composite improves the electrical conductivity. In comparison with pure metal selenides, the attached CoSe particles on lamellar Bi 2 Se 3 surface increase the adsorption sites of lithium polysulfides to effectively alleviate the shuttle effect. Combined with these advantages, S/Bi 2 Se 3 @CoSe/CNTs cathode exhibits a long cycling stability. Over 700 cycles, the cathode shows a capacity decay rate of 0.049 % per cycle at 0.5 C. In addition, the cathode shows high initial capacity (840.4 mA h g−1) with sulfur content of 2.31 mg cm−2 at 0.1 C. This study demonstrates the efficacy of Bi 2 Se 3 @CoSe composite in improving the conductivity of the sulfur cathodes and polysulfides chemisorption. [Display omitted] • The Bi 2 Se 3 @CoSe/CNTs composite is synthesized as a multifunctional sulfur host by one-step hydrothermal method. • The electrical conductivity of the sulfur cathodes is greatly improved due to the strong metallicity of Bi 2 Se 3 @CoSe. • The shuttle effect is suppressed by enhanced chemisorption and abundant catalytic sites. • S/Bi 2 Se 3 @CoSe/CNTs cathode with sulfur loading of 2.31 mg cm−2 delivers excellent performance. [ABSTRACT FROM AUTHOR]

[Display omitted] • Co@NCNT-MoSe 2 nanocomposite, as a multifunctional layer, is used to modify separator. • The nanocomposites show a flower-like tube walls and tube embedded in Co nanoparticles. • The multifunctional separator, as trapper-catalyst-conductor, is used in Li-S battery. • The separator efficiently capture, catalyze conversion for LiPSs, and transfer e-/Li+. • This Li-S battery achieves a high sulfur utilization and a long cycling stability. Lithium-sulfur (Li-S) battery with a high theoretical energy density (2600 Wh·kg−1) is considered as a promising energy storage system. However, the shuttle effect and the sluggish redox kinetics of lithium polysulfides (LiPSs) lead to low sulfur utilization. A multifunctional layer modified on separator, as a collaborator of capturer-catalyst-conductor, is be regarded as an effective strategy to solve these problems. Herein, the Co@NCNT-MoSe 2 nanocomposite as a modified layer is synthesized with a mesoporous structure by the hydrothermal reaction, in which a large number of transparent MoSe 2 nanosheets grow outside NCNT embedded with Co nanoparticles, forming a flower-like outer walls of tube. The modified layer displays the significant features of capturing and catalytic conversion toward LiPSs, attributing to strong adsorption abilities, abundant catalytic active sites, and efficient transferring pathway of electron/Li+. Benefitting from these alluring properties, the results demonstrate that the modified separator offers a high discharge capacity of 983.2 mAh·g−1 at 0.2C after 200 cycles. Even at 2C, after long-term 1000 cycles, it still shows a superb capacity of 725 mAh·g−1 accompanied by a low capacity fading of 0.042 % per cycle. More notably, at 0.2C, the modified separator can realize an ideal areal capacity of 5.24 mAh·cm−2 under high S load (5 mg·cm−2) and poor electrolyte (7.5 μL·mg−1). Therefore, this work will provide a new insight on the development of multifunctional separators to achieve a long-life battery with high sulfur utilization by restraining shuttle effect and accelerate redox kinetics of LiPSs. [ABSTRACT FROM AUTHOR]

• A universal protocol produces microcrystalline hard carbon (MHC) from cheap anthracite. • MHC shows a high electrical conductivity of 13,065 S m−1 and enhanced electrochemical kinetics. • A practical lithium-ion capacitor using MHC anode delivers an energy density of 46.7 Wh kg−1. As a promising electrochemical energy storage system, lithium-ion capacitors (LICs) exhibit alluring theoretical merits of high energy density, high power density and long cycle life. However, most of the LIC cells can hardly surpass the practical energy density threshold of 30 Wh kg−1, which greatly hinders their employments in various energy-oriented fields. Anthracite shows great prospect as low-cost and abundant carbon precursor to prepare anode material with plentiful Li-ion anchoring sites for high performance LICs. In this work, a scalable low-temperature hydrothermal disordering strategy is proposed to achieve balanced structural modification of anthracite into short-ranged turbostratic carbon precursor, which further transforms into microcrystalline hard carbon (MHC) with high electrical conductivity (13065 S m−1) and substantially improved energy storage kinetics. A practical large-capacity LIC pouch cell is fabricated using MHC anode and activated carbon cathode to deliver a maximum gravimetric and volumetric energy density of 46.7 Wh kg−1 and 66.8 Wh/L based on the total weight of cell, outperforming the commercially available LIC products from relevant enterprises. Moreover, the cell reveals an exceptional capacity retention of 94.7 % after 10,000 cycles at high current density. The work herein would emerge as a universal and feasible protocol to fabricate high-end carbon electrode for practical LICs in numerous energy-intensive occasions. [ABSTRACT FROM AUTHOR]

The oxidation of the tetrakisoxalatouranate(IV) ion by the hexacyanoferrate(III) ion was studied in an oxalate buffer medium. The reaction was first order in both UIV(C2O4)44– and Fe(CN)63–, and a second order rate constant of k2av = (5.46 ± 0.04) × 10–2 M−1 s−1 at 34.9 °C was obtained. The reaction is inversely proportional to [H+] and a pKa of 5.99 was found for the deprotonation of UIV(C2O4)3(H2O)22−. Activation parameters have been obtained by application of the Eyring equation. Minimum excess concentrations of UIV(C2O4)44– over Fe(CN)63– for the kinetic study under pseudo-order conditions were evaluated following literature guidelines and also compared to results from a direct second order treatment of data. Contradictory to general beliefs, a fivefold excess of UIV(C2O4)44– was found to be sufficient for a pseudo-order kinetic treatment. The need to obtain results from traditional approximation methods, for example utilizing the linearized Eyring equation to obtain activation enthalpies (∆H#) and entropies (∆S#), was demonstrated not to be required anymore as modern computational capabilities utilizing least square fitting programs allows ∆H# and ∆S# to be obtained directly from temperature and rate constant data utilising the exponential Eyring equation easily and more accurately. A reaction mechanism for the reaction is proposed. [ABSTRACT FROM AUTHOR]

Inhalation of particulate matter is hypothesized to contribute to health effects by overproducing reactive oxygen species (ROS) and inducing oxidative stress. Fe(II) has been shown to contribute to ROS generation in acellular simulated lung fluids. Atmospheric humic-like substances (HULIS) have been shown to chelate Fe(II) and significantly enhance this ROS generation. Here, we investigate Fe(II)-mediated . OH generation from the iron active proteins in lung fluid, albumin and transferrin, and fulvic acid, a surrogate for HULIS, in human bronchoalveolar lavage fluid (BALF). We find that albumin enhances . OH generation from inorganic Fe(II) and that transferrin attenuates this enhancement. We estimate the rate constants for albumin-Fe(II) and fulvic acid-Fe(II) mediated O 2 . - reduction (1.9 ± 0.3) M−1 s−1 and (2.7 ± 0.3) M−1s−1 (pH = 5.5, T = 37 °C), 17–25 times the rate for free iron, which we measured to be (110 ± 20) × 10−3 M−1s−1, in agreement with the literature. . OH generation measured from fulvic acid-Fe(II) in BALF from 8 individuals with added fulvic acid is successfully predicted rates of . OH generation by mixtures of Fe(II), albumin, transferrin, fulvic acid, and ascorbate in saline solution. This indicates that fulvic acid enhances . OH formation in BALF, and that albumin and transferrin in BALF moderate the effect. We propose that fulvic acid, and thereby HULIS, is capable of mobilizing Fe(II) away from albumin and transferrin and this increases the formation rate of O 2 . - and ultimately of . OH. Furthermore, we find that albumin and transferrin have significantly different impacts on Fe(II)-mediated . OH than citrate, a common component of simulated lung fluids, a factor that should be considered carefully in the interpretation of results obtained from solutions containing citrate. [Display omitted] • o Albumin complexes inorganic iron enhancing reactive oxygen species generation. • o Fulvic acid takes iron from proteins in lung fluids enhancing.OH generation. • o Citrate in simulated lung fluids does not accurately mimic lung proteins. • o Albumin and fulvic acid increase iron O 2 .- generation rates by factors of about 20. [ABSTRACT FROM AUTHOR]

Sb 2 Se 3 based anodes are widely studied for advanced Na-ion batteries. However, their Na storage performance at high rates is limited to 2000 mA g−1 because of poor kinetics of redox reactions. Here, the heterointerfacial interactions taking place between Sb 2 Se 3 and functionalized CNTs are probed to understand the formation of Sb–O–C and Se–C bonds in the amorphous a-Sb 2 Se 3 /CNT composite using the density functional theory and ab-initio molecular dynamics simulations. The distinct morphologies and thicknesses of solid electrolyte interface layers formed on crystalline c-Sb 2 Se 3 and a-Sb 2 Se 3 /CNT composite electrodes are revealed by advanced cryogenic transmission electron microscopy and their influences on the kinetics of redox reactions in the corresponding electrodes are identified. The structurally robust a-Sb 2 Se 3 /CNT composite electrode exhibits four orders of magnitude higher Na-ion diffusion coefficient than the crystalline c-Sb 2 Se 3 counterpart, giving rise to an exceptional high-rate capacity of 454 mA h g−1 at 12800 mA g−1 and capacity retention of over 62% after 200 cycles at 10000 mA g−1. The full cells containing the composite electrodes present energy and power densities of ∼175 Wh kg−1 at 0.5C and ∼5784 W kg−1 at 80C, respectively, and stable cyclic performance up to 120 cycles. Image 1 • Cryo-TEM reveals a thin and uniform SEI layer formed on the a-Sb 2 Se 3 /CNT anode. • DFT calculations support the presence of Sb–O–C and Se–C bonds in the composite. • The morphology of SEI layer is critical for kinetics of electrochemical reactions. • Ultrahigh rate capability up to 12.8 A g−1 is achieved in the composite anodes. • The full cell delivers an outstanding power density of ∼5784 W kg−1 at 80C. [ABSTRACT FROM AUTHOR]

Despite extensive research on flexible/wearable power sources, their structural stability and electrochemical reliability upon mechanical deformation and charge/discharge cycling have not yet been completely achieved. A new class of galvanically replaced single‐bodied lithium‐ion battery (LIB) fabric electrodes is demonstrated. As a proof of concept, metallic tin (Sn) is chosen as an electrode active material. Mechanically compliable polyethyleneterephthalate (PET) fabrics are conformally coated with thin metallic nickel (Ni) layers via electroless plating to develop flexible current collectors. Driven by the electrochemical potential difference between Ni and Sn, the thin Ni layers are galvanically replaced with Sn, resulting in the fabrication of a single‐bodied Sn@Ni fabric electrode (Sn is monolithically embedded in the Ni matrix on the PET fabric). Benefiting from the chemical/structural uniqueness and rationally designed bicontinuous ion/electron transport pathways, the single‐bodied Sn@Ni fabric electrode provides exceptional redox reaction kinetics and omnidirectional deformability (notably, origami‐folding boats), which lie far beyond those attainable with conventional LIB electrode technologies. [ABSTRACT FROM AUTHOR]

[Display omitted] • Efficient Ni-Co bimetallic oxygen carriers were crafted via sol–gel auto-combustion. • Co enters the NiO lattice, enabling the formation of Ni-Co alloy upon reduction. • Co addition enhances the oxidation kinetics of oxygen carrier during redox cycles. • Ni-Co oxygen carriers retain reduction degree higher than 80% over 20 redox cycles. • Bimetallic materials have more stable steam reforming activity than monometallic one. This work deals with the synthesis of bimetallic Ni-Co oxygen carriers with ZrO 2 as structure stabilizer via a one-pot sol–gel auto-combustion method and the evaluation of their redox properties and catalytic activity of their reduced state for steam methane reforming. Fresh materials were composed of Ni-Co mixed monoxides, which could be reduced to form a Ni-Co alloy. Conducting reforming experiments for 10 h time-on-stream at 650 °C showed that Ni-Co alloy sites of reduced bimetallic materials, in addition to the high reforming activity, can improve the stability compared to Ni sites of a monometallic material, due to a higher tendency of the latter toward sintering and coke formation. Redox behavior was tested via CH 4 reduction and air oxidation cycles in a thermogravimetric analyzer. Increasing the Co content led to a slight decrease of reduction degree, which, however, was not altered over cycles. Both reduction and oxidation steps were found to proceed via a nucleation and nuclei growth reaction mechanism, with Co addition promoting the oxidation kinetics. Ultimately, addition of Co with low Co/(Ni + Co) ratios (≤0.20) could balance adequate degree of reduction (≥80 %) and oxygen transfer capacity (≥0.07 g O/g material) in tandem with stable catalytic activity for steam methane reforming in the reduced state of oxygen carrier. [ABSTRACT FROM AUTHOR]

The low sulfur utilization and notorious polysulfides shuttling of Li-S battery (LSBs) largely limit the practical implementation as an effective energy storage system. Herein, we designed a coaxial electrospinning process to prepare cobaltous selenide/carbon tube (CoSe 2 /CTs) with hollow tubular structures to hold sulfur activity for the cathode of LSBs. This CoSe 2 /CTs material with superior hollow tubular structures and high specific surface area is able to tolerate the sulfur volume expansion/contraction and make the intimate contact with sulfur at the micro level. Moreover, the uniformly dispersed CoSe 2 on the CTs both as catalysts and trappers can significantly facilitate the reaction kinetics in the LSBs and chemically immobilize lithium polysulfides. In order to optimize the CoSe 2 /CTs/S cathode, we investigated the effects of the Co concentration and carbon tube porosities on batteries performance to achieve the satisfactory discharge specific capacity and a long duration at a high current density. We believe that our method can provide a significant strategy to prepare Co-based cathodes and enhance the performance of LSBs. [Display omitted] • The Polar, catalytic, volume-tolerant CoSe 2 /CTs material is designed and prepared. • The CoSe 2 /CTs are prepared by coaxial electrospinning and in-suit selenylation. • CoSe 2 /CTs both as catalysts and trappers facilitate the reaction kinetics in LSBs. [ABSTRACT FROM AUTHOR]

• This review presents an overview of the key techniques for optimizing crystal growth direction. • The structure–activity relationship between crystal orientation design and Na storage performance is discussed. • The prevalent challenges and new developments in regulating crystal orientation are given. Low-cost Na-ion batteries (NIBs) have manifested enormous potential for stationary energy storage and low-speed vehicles. Despite their potential advantages, the use of large and heavy Na+ ions as charge carriers in NIBs results in relatively slow kinetics and an inferior rate capacity. Moreover, Na+ de-intercalation is commonly accompanied by irreversible phase transition and sizeable volume changes, leading to structural degradation and capacity decay. Recent advancements have shown that tailoring the crystal growth direction and employing specific exposed crystal facets can bring about significant improvement in the electrochemical performance of electrode materials for NIBs. This review presents an overview of the key techniques for optimizing crystal growth direction, including surfactant addition, template-assisted synthesis, and foreign ion doping, followed by a detailed discussion pertaining to the corresponding regulatory mechanisms. Subsequently, the structure–activity relationship between crystal orientation design and Na storage performance is thoroughly examined with regards to the crystal anisotropy of cathode and anode materials. The prevalent challenges and new developments in regulating crystal orientation have been discussed given the development of high-performance NIB electrodes. [ABSTRACT FROM AUTHOR]

Sluggish sulfur redox kinetics and incessant shuttling of lithium polysulfides (LiPSs) greatly influence the electrochemical properties of lithium-sulfur (Li-S) batteries and their practical applications. For this reason, ammonium thiosulfate (AMTS) with effective redox regulation capability has been proposed as a functional electrolyte additive to promote the bidirectional conversion of sulfur species and inhibit the shuttle effect of soluble LiPSs. During discharging, the S 2 O 3 2- in AMTS can trigger the rapid reduction of LiPSs from long chains to short chains by a spontaneous chemical reaction with sulfur species, thereby decreasing the accumulation of LiPSs in the electrolyte. During charging, the NH 4 + in the AMTS enhances the dissociation/dissolution of Li 2 S by hydrogen-binding interactions, which alleviates the electrode surface passivation and facilitates the reversible oxidation of short-chain sulfides back to long chains. The enhanced bidirectional redox kinetics brought about by AMTS endows Li-S cells with high reversible capacity, excellent cycle stability, and rate capability even under lean electrolyte conditions. This work not only illustrates an effective redox regulation strategy by an electrolyte additive but also investigates its catalytic reaction mechanism and Li corrosion behavior. The crucial criteria for screening additives that enable bidirectional redox mediation analogous to AMTS are summarized, and its application perspectives/challenges are further discussed.2 /Li 2 S by hydrogen-binding interactions, which alleviates the electrode surface passivation and facilitates the reversible oxidation of short-chain sulfides back to long chains. The enhanced bidirectional redox kinetics brought about by AMTS endows Li-S cells with high reversible capacity, excellent cycle stability, and rate capability even under lean electrolyte conditions. This work not only illustrates an effective redox regulation strategy by an electrolyte additive but also investigates its catalytic reaction mechanism and Li corrosion behavior. The crucial criteria for screening additives that enable bidirectional redox mediation analogous to AMTS are summarized, and its application perspectives/challenges are further discussed.

Highlights • Experimental evidence that NO is involved both in the reduction step and in the oxidation step. • A redox rate equation is developed with inhibiting effect of NH 3 and promoting effect of NO. • Multiscale testing (from powders to commercial plates) for model validation. Abstract This study addresses a kinetic investigation of NH 3 -SCR on commercial SCR catalysts with composition V 2 O 5 /MoO 3 /TiO 2. Objective of the study is an improved kinetic description of the reaction, based on the recognition of the redox nature of the V-site; which calls for an understanding of the effect of O 2. At this scope, an extensive experimental investigation over a powdered catalyst was performed at largely varying concentrations of O 2 (from 0.06 to 8%) both at high and at low NO and NH 3 concentration. It was found that the increase of the O 2 feed content promoted NO conversion with asymptotic trend: the promotion was important in the range 0.06–3%, but became moderate in the range 3–8%. Unexpectedly, the effect of O 2 was equally important at high NO and NH 3 concentration as well as at low NO and NH 3 concentration (where a kinetic control from the reduction step and thus a negligible role of the oxidation step were expected). The kinetic analysis revealed that the observed experimental trends can be described by a Mars-van Krevelen rate expression assuming that the rate of re-oxidation depends on NO concentration as well as the rate of reduction does. A molecular rate equation which incorporates a simple linear dependence on NO concentration in the re-oxidation kinetics fully describes the whole bulk of data and is suitable to engineering purposes. The existence of an NH 3 inhibiting effect was also included. The global rate expression was successfully validated against independent pilot-scale experiments on slabs. [ABSTRACT FROM AUTHOR]

lithium–selenium (Li–Se) batteries are recognized as an attractive candidate for energy storage owing to its high volumetric capacity (3253 mA h cm−3). However, the sluggish electrochemical redox reaction and the accompanying enormous volume fluctuation greatly impede the application of Li–Se batteries. Herein, a catalyst of nickel disulfide (NiS 2) nanoparticles decorated hierarchical porous carbon (HPC) has been fabricated and applied as the cathode for Li-Se batteries. The porous structure offers large amount of viod to buffer the volume change during charge/discharge. At the same time, the NiS 2 nanoparticles exhibit strong adsorption capabilities towards lithium polyselenides and aslo promote the conversion of these intermediates. As a consequence, the NiS 2 -HPC cathode delivers a superior rate capacity (569 mAh g−1 at 0.5 C and 549 mAh g−1 at 1 C) and good cycling stability (289 mAh g−1 after 1000 cycles at 2 C with a Coulombic efficiency of ∼100%). This work demonstrates the viability of employing metal sulfide-anchored porous carbon materials for high-performance lithium-selenium batteries. [Display omitted] [ABSTRACT FROM AUTHOR]

• A metallic cobalt-doped ZSM-5 zeolite with extra-framework Li+ is innovatively constructed. • The functionalized zeolite-modified separator endows lithium–sulfur batteries with fast redox conversion and low shuttle effect. • Superior cyclic stability, excellent rate capability, and negligible self-discharge behavior are achieved. Lithium–sulfur (Li–S) batteries are among the most promising next-generation rechargeable battery systems because of their high theoretical energy density and low cost. Nevertheless, the notorious shuttle effect of polysulfides and poor redox kinetics significantly limit their practical applications. Herein, a metallic cobalt-doped ZSM-5 zeolite with extra-framework Li+ is constructed to inhibit the migration of polysulfides and simultaneously enhance their conversion kinetics via a separator coating strategy. The ZSM-5 zeolite possessing a sub-nanometer channel structure acts as an ionic sieve, and effectively suppresses the undesired polysulfide migration by spatial constraint. The negatively charged zeolite framework with Li+ as counterions helps to facilitate the fast Li+ transport. More importantly, Co dopants further strengthen the interaction with polysulfides and work as active sites to improve the kinetics of sulfur redox reactions, which is verified by theoretical calculations and experiments. As expected, a Li–S battery employing the modified separator delivers superior long-term cyclic stability (only 0.04% capacity decay per cycle over 500 cycles at 1.0 C) and excellent rate capability (706 mAh g−1 at 3.0 C). In addition, the stable operation of an assembled Li–S pouch cell under various bending angles demonstrates its feasibility in practical applications. This work offers a new insight into the design of advanced separator modifiers for high-performance Li–S batteries. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel nano-scale polyimide-based COF (PI-COF) with hierarchical porous structure was fabricated by dehydration reaction. • Aqueous Zn2+ storage capacity of the PI-COF electrode was remarkably enhanced by the lithium ion-induced behavior. • In-situ investigation technologies were employed to reveal the high reversibility of double redox-active units in PI-COF. Rechargeable aqueous zinc ion batteries (AZIBs) have the great potential as a safe, economical, sustainable, and environmentally friendly energy storage system. Despite being one of the most promising electrode materials for AZIBs, organic molecules are plagued by poor conductivity and structural instability due to their low molecular weight and short-range conjugated structure. Herein, a novel polyimide-based covalent organic framework (PI-COF) compound with affluent C=O and C=N electroactive groups is synthesized and employed as the cathode to achieve rapid aqueous Zn2+ storage. Results of electrochemical measurements and in-situ characterizations reveal a lithium ion-induced Zn2+ storage behavior and high reversibility of redox-active units in PI-COF electrode, which favor to extend the Zn2+ storage capability and ensure the cycle stability. As a result, the PI-COF delivers an ultrahigh and ultrafast Zn2+ storage properties in aqueous hybrid-ions electrolyte, in terms of remarkable charging/discharging capacity of 464.2 mA h g−1 at 1.0 A g−1 and high-rate capacity of 220.2 mA h g−1 at 10.0 A g−1 as well as superior cycling stability over 1000 cycles with a capacity retention of 85.3 %. This work lays the groundwork to develop the highly stable organic electrode materials for advanced AZIBs. [ABSTRACT FROM AUTHOR]

Redistributing the d -orbital of single Fe atom catalysts (SFeACs) has been challenging to optimize redox kinetics of lithium sulfur batteries (LSBs). Here, the Fe-N 4 /S 2 C with mounting energy level of d z 2 and partial occupation of d xz is controllably fabricated. The increased d z 2 , originating from thiophene sulfur, upshifts d band center compared to the Fe-N 4 /C with planar symmetric structure. That promotes electron transfer between Fe-N 4 and sulfur, enhancing conversion of polysulfides and solid products. The lower fill of d xz develops hybridization between Fe and S atoms via the form of bonding and antibonding, with alleviating the loss of sulfur. Thus, the sulfur cathode with Fe-N 4 /S 2 C delivers a high capacity of 749 mAh g−1 at 2.0 C, accompanied by excellent stability with a lower capacity decay of 0.07% per cycle. This work has developed a novel coordination configuration towards SFeACs and uncovered the intrinsic mechanism of facilitated redox kinetics with SFeACs for LSBs. [Display omitted] • A novel configuration (Fe-N 4 S 2) of single Fe atom catalysts (SFeACs) for lithium sulfur batteries was developed. • The increased d z 2 upshifts d band center, promoting the electron transfer between Fe-N 4 and sulfur and redox kinetics. • The lower fill of d xz develops hybridization between Fe and S atoms, with alleviating the loss of active sulfur. • A new insight on the relation among energy level of d -orbital, catalysis of SFeACs and conversion of sulfur was provided. • The sulfur cathode with Fe-N 4 /S 2 C delivers a high capacity of 749 mAh g−1 at 2 C and low-capacity decay of 0.07% per cycle. [ABSTRACT FROM AUTHOR]

Highly Graphitized and Nitrogen-Doped Carbon Nanotube-Encased FeNi Bimetallic Alloy Catalyst for Efficient Separator Modification in Lithium-Sulfur Batteries. [Display omitted] • A highly graphitized and carbon-tubule-rich FeNi@NC was successfully synthesized. • FeNi@NC with ultra-low resistivity can accelerate charge transfer kinetics. • FeNi@NC promotes the kinetics of redox reactions. Lithium-sulfur batteries (LSBs) are constrained by the shuttle effect and slow kinetics of lithium polysulfides (LPSs). Herein, we introduces a novel FeNi bimetallic catalyst, encapsulated within a structure of highly graphitized and nitrogen-doped carbon tubules, denoted as FeNi@NC. The synthesis employs a straightforward high-temperature calcination and freeze-drying technique, tailored to modify the functional separator layer in LSBs. FeNi@NC includes a diverse range of carbon tube morphologies, facilitating quick electron and lithium-ion transfer. Notably, it displays remarkable catalytic activity towards LPSs. Specifically engineered, the FeNi@NC catalyst prompts the generation of S•3− radicals, providing an alternative pathway for polysulfide transformation, ultimately enhancing the redox kinetics of the polysulfides. As a result, a battery incorporating the FeNi@NC catalyst-modified separator layer attains a notable initial specific capacity of 1378.8 mAh/g at 0.1C, and a negligible capacity decay rate of only 0.11% per cycle after 500 cycles at 1C. The robust performance extends to areal capacity, which reaches a high value of 6.25 mAh cm−2 with a high sulfur loading of 4.99 mg cm−2. Even after 100 cycles, the areal capacity remains significant at 4.28 mAh cm−2. These findings showcase the promising potential for the application of bimetallic alloy catalysts in LSBs. [ABSTRACT FROM AUTHOR]

Lithium-sulfur (Li–S) battery with high theoretical energy density is recognized as a promising energy storage device, while its commercial applications are still hampered by the severe shuttling effect and sluggish kinetics of lithium polysulfides (LiPSs). Heteroatoms doping, which can adjust the electronic configuration and regulate the adsorption and catalytic properties, is realized as an effective strategy to solve the above problems. Herein, sulfur-doped CoP nanoparticles embedded in hollow carbon microspheres (C@S–CoP) is designed and employed as the modification material for separator. The introduction of sulfur atom into CoP leads to enhanced chemisorption for LiPSs and favorable conversion kinetics of sulfur species. In addition, the hollow porous structure of C@S–CoP is beneficial to the penetration of electrolyte and the alleviation of the sulfur species expansion during cycles. Theoretical calculation is further utilized to elucidate the enhanced mechanisms of S–CoP in Li–S chemistry at molecular level. The cell with C@S–CoP-separator delivers a superior rate performance of 761 mAh g−1 at 5C and excellent cyclability over 400 cycles at 2C with a low-capacity decay rate of 0.060%. This work furnishes a feasible strategy to boost the electrochemical performance and promotes the development of functional separators for highly efficient Li–S battery. [Display omitted] • The sulfur atoms are doped into CoP to realize the regulation of electronic structure. • ● The sulfur-doped CoP can enhance the chemical affinity toward LiPSs. • ● The introduction of S atoms into CoP is beneficial to promoting LiPSs conversions. • ● The cells with C@S–CoP modified separator exhibit superior rate performance and cycle stability. [ABSTRACT FROM AUTHOR]

Sulfur-based cathode chemistries are essential for the development of high energy density alkali-ion batteries. Here, we elucidate the redox kinetics of sulfur confined on carbon nanotubes, comparing its performance in ether-based and carbonate-based electrolytes at room temperature. The solvent is found to play a key role for the electrochemical reactivity of the sulfur cathode in sodium−sulfur (Na−S) batteries. Ether-based electrolytes contribute to a more complete reduction of sulfur and enable a higher electrochemical reversibility. On the other hand, an irreversible solution-phase reaction is observed in carbonate solvents. This study clearly reveals the solvent-dependent Na−S reaction pathways in room temperature Na−S batteries and provides an insight into realizing their high energy potential, via electrolyte formulation design.

Lithium-sulfur (Li-S) batteries have ultrahigh theoretical specific capacity, but the practical application is hindered by the severe shuttle effect and the sluggish redox kinetics of the intermediate lithium polysulfides (LiPSs). Effectively enhancing the conversion kinetics of LiPSs is essential for addressing these issues. Herein, the redox kinetics of LiPSs are effectively improved by introducing 6-azauracil (6-AU) molecules to the organic electrolyte to modulate the molecular orbital energy level of LiPSs. The 6-AU as a soluble catalyst can form complexes with LiPSs via Li-O bonds. These complexes are liable to transform because of the elevated HOMO and the reduced LUMO energy levels as compared to the dissociative LiPSs, resulting in small energy gaps ( E gap ) and exhibiting stronger redox activity. Benefiting from the rapid conversion kinetics, the shuttling effect of LiPSs is alleviated to a great extent, so that sulfur utilization is improved and the lithium electrode is protected. In addition, the introduction of 6-AU modulates the deposition behavior of Li 2 S and eases the coverage of the cathode surface by the insulating Li 2 S layer. The Li-S battery containing 6-AU provides superior capacity retention of 853 mAh g -1 after 150 cycles at 0.2 C and shows remarkable high-rate performance and retains a specific discharge capacity of 855 mAh g -1 at 5 C. This study accelerates the kinetics of Li-S batteries by tuning the HOMO and LUMO energy levels of LiPSs, which opens an avenue for designing functional electrolyte additives.

Rechargeable aqueous Zn-I 2 batteries (ZIB) are regarded as a promising energy storage candidate. However, soluble polyiodide shuttling and rampant Zn dendrite growth hamper its commercial implementation. Herein, a hetero-polyionic hydrogel is designed as the electrolyte for ZIBs. On the cathode side, iodophilic polycationic hydrogel (PCH) effectively alleviates the shuttle effect and facilitates the redox kinetics of iodine species. Meanwhile, polyanionic hydrogel (PAH) toward Zn metal anode uniformizes Zn 2+ flux and prevents surface corrosion by electrostatic repulsion of polyiodides. Consequently, the Zn symmetric cells with PAH electrolyte demonstrate remarkable cycling stability over 3000 h at 1 mA cm -2 (1 mAh cm -2 ) and 800 h at 10 mA cm -2 (5 mAh cm -2 ). Moreover, the Zn-I 2 full cells with PAH-PCH hetero-polyionic hydrogel electrolyte deliver a low-capacity decay of 0.008 ‰ per cycle during 18 000 cycles at 8 C. This work sheds light on hydrogel electrolytes design for long-life conversion-type aqueous batteries., (© 2023 Wiley-VCH GmbH.)

Lithium-sulfur (Li-S) batteries hold great promise as next-generation high-energy storage devices owing to the high theoretical specific capacity of sulfur, but polysulfide shuttling and lithium dendrite growth remain key challenges limiting cycling life. In this work, we propose a polyacrylonitrile-derived asymmetric (PDA) separator to enhance Li-S battery performance by accelerating sulfur redox kinetics and guiding lithium plating and stripping. A PDA separator was constructed from two layers: the cathode-facing side consists of polyacrylonitrile nanofibers carbonized at 800 °C and doped with titanium nitride, which can achieve rapid polysulfide conversion via electrocatalysis to suppress their shuttling; the anode-facing side consists of polyacrylonitrile oxidized at 280 °C, on which the abundant electronegative groups guide uniform lithium ion plating and stripping. Li-S batteries assembled with the PDA separator exhibited enhanced rate performance, cycling stability, and sulfur utilization, retaining 426 mA h g -1 capacity at 1 C over 1000 cycles and 632 mA h g -1 at 4 C over 200 cycles. Attractively, the PDA separator showed high thermal stability, which could mitigate the risk of internal short circuits and thermal runaway. This work demonstrates an original path to addressing the most critical issues with Li-S batteries.

Lithium-sulfur (Li-S) batteries are widely studied because of their high theoretical specific capacity and environmental friendliness. However, the further development of Li-S batteries is hindered by the shuttle effect of lithium polysulfides (LiPSs) and the sluggish redox kinetics. Since the adsorption and catalytic conversion of LiPSs mainly occur on the surface of the electrocatalyst, regulating the surface structure of electrocatalysts is an advisable strategy to solve the obstacles in Li-S batteries. Herein, CoP nanoparticles with high oxygen content on surface embedded in hollow carbon nanocages (C/O-CoP) is employed to functionalize the separators and the effect of the surface oxygen content of CoP on the electrochemical performance is systematically explored. Increasing the oxygen content on CoP surface can enhance the chemical adsorption to lithium polysulfides and accelerate the redox conversions kinetics of polysulfides. The cell with C/O-CoP modified separator can achieve the capacity of 1033 mAh g -1 and maintain 749 mAh g -1 after 200 cycles at 2 C. Moreover, DFT calculations are used to reveal the enhancement mechanism of oxygen content on surface of CoP in Li-S chemistry. This work offers a new insight into developing high-performance Li-S batteries from the perspective of surface engineering., (© 2023 Wiley-VCH GmbH.)

Abstract Lithium-sulfur (Li-S) battery is recognized as one of the most promising high-energy-density storage system. However, the poor cycle life and low sulfur utilization originating from the shuttling process involving lithium polysulfide (LiPSs) significantly hinder the practical application of Li-S battery. Various approaches have been introduced to retard the shuttle of LiPSs. Herein, a polar cobalt disulfide embedded in porous nitrogen doped carbon frameworks (CoS 2 -N-C) is synthesized from a single metal-organic framework ZIF-67. When used as a sulfur host for Li-S battery cathode, the CoS 2 -N-C frameworks can not only limit the dissolution of LiPSs by chemisorption, but also buffer the volume expansion during cycling. More importantly, the electrochemical reaction kinetics is greatly improved. As a result, the Li-S battery based on the S/CoS 2 -N-C electrode exhibits a high initial discharge capacity of 1288 mAh g−1 at 0.2 C and a superior long cycle life for 500 cycles with a degradation rate as low as 0.064% per cycle at 1 C rate. Even with a high sulfur loading of 5.25 mg cm−2, the battery still delivers a better cycle performance. [ABSTRACT FROM AUTHOR]

Abstract Lithium–sulfur (Li–S) batteries have been regarded as promising candidates for current energy-storage technologies due to their remarkable advantages in energy density and theoretical capacity. However, one of the daunting challenges remained for advanced Li–S systems thus far deals with the synchronous suppression of polysulfide (LiPS) shuttle and acceleration of redox kinetics. Herein, a cooperative interface bridging adsorptive V 2 O 3 and conductive graphene is constructed in-situ by virtue of direct plasma-enhanced chemical vapor deposition (PECVD), resulting in the design of a novel V 2 O 3 -graphene hybrid host to synergize the LiPS entrapment and conversion. The redox kinetics and electrochemical performances of thus-derived cathodes were accordingly enhanced owing to the smooth adsorption-diffusion-conversion of LiPSs even at a sulfur mass loading of 3.7 mg cm–2. Such interfacial engineering offers us a valuable opportunity to gain insight into the comprehensive regulation of LiPS anchoring ability, electrical conductivity and ion diffusive capability in hybrid hosts on suppressing the LiPS shuttle and propelling the redox kinetics. Our devised PECVD route might pave a new route toward the facial and economic design of hetero-phased multi-functional hosts for high-performance Li–S systems. Graphical abstract fx1 Highlights • Graphene-V 2 O 3 hybrid host was designed in-situ based on PECVD route. • Thus-derived cathode showed a low capacity decay of merely 0.046% per cycle at 2 C after 1000 cycles. • Cathodes with a relatively high sulfur mass loading (3.7 mg cm–2) were fabricated. • The smooth adsorption-diffusion-conversion of polysulfides was thoroughly probed via experimental studies and DFT simulations. [ABSTRACT FROM AUTHOR]

Abstract: Lithium–sulfur (Li–S) batteries deliver a high theoretical energy density of 2600 Wh kg−1, and hold great promise to serve as a next‐generation high‐energy‐density battery system. Great progress has been achieved in cathode design to deal with the intrinsic problems of sulfur cathodes, including low conductivity, the dissolution of polysulfide intermediate, and volume fluctuation. However, aiming at the practical applications of Li–S batteries, the weight percentage of sulfur in cathode materials and the overall areal sulfur loading need to be significantly increased, which inevitably complicate the process and cause heavy shuttle effect, slow redox kinetics, and more undesirable reaction pathways. Recently, rationally designing efficient mediators, as well as incorporating them into a working battery, emerges to be a promising method to construct high‐energy‐density Li–S batteries. The influence of mediators on Li–S batteries appears to be the enhancement in redox kinetics and the increase in reaction efficiency. In this feature article, the mechanistic understanding of redox kinetics in Li–S reactions is discussed, and then a comprehensive analysis of the recent advances in both heterogeneous and homogeneous mediator design is provided. A mediator perspective in building high‐energy‐density Li–S batteries is also included. [ABSTRACT FROM AUTHOR]