Constructing Co3S4 Nanosheets Coating N-Doped Carbon Nanofibers as Freestanding Sulfur Host for High-Performance Lithium-Sulfur Batteries

A Multifunctional Secondary Based on Heterogeneous Co-MnO@NC for Depth-Induced Deposition and Conversion of Polysulfides in Li─S Batteries

The conductive carbon-based interlayer, as the secondary current collector in the self-dissolving battery system, can effectively capture escaping cathode active materials, inducing deep release of remaining capacity. In the multi-step reactions of Li─S batteries, the environmental tolerance of the conductive carbon-based interlayer to polysulfides determines the inhibition of shuttle effects. Here, a modified metal-organic framework (Mn-ZIF67) is utilized to obtain nitrogen-doped carbon-coated heterogeneous Co-MnO (Co-MnO@NC) with dual catalytic center for the functional interlayer materials. The synergistic coupling mechanism of NC and Co-MnO achieves rapid deposition and conversion of free polysulfide and fragmented active sulfur on the secondary current collector, reducing capacity loss in the cathode. The Li─S battery with Co-MnO@NC/PP separator maintains an initial capacity of 1050 mAh g-1 (3C) and excellent cycle stability (0.056% capacity decay rate). Under extreme testing conditions (S load = 5.82 mg cm-2, E/S = 9.1 µL mg-1), a reversible capacity of 501.36 mAh g-1 is observed after 200 cycles at 0.2 C, showing good further practical reliability. This work demonstrates the advancement application of Co-MnO@NC bimetallic heterojunctions catalysts in the secondary current collector for high-performance Li─S batteries, thereby providing guidance for the development of interlayer in various dissolution systems.

Design of Coatings for Sulfur-Based Cathode Materials in Lithium-Sulfur Batteries: A review

Lithium-sulfur batteries (LSBs) are considered next-generation energy storage and conversion solutions owing to their high theoretical specific capacity and the high abundance/low-cost of sulfur-based cathode materials. However, LSBs still encounter significant challenges, including the low conductivities of sulfur-based materials, severe volumetric expansion of sulfur during the discharge process, and the persistent "shuttle effect" of polysulfides. In recent years, a tremendous amount of research has been conducted to address the above challenges by developing coating and compositing materials and corresponding fabrication strategies for sulfur-based cathode materials. In this study, the surface coating, compositing materials, and fabrication methodologies of LSB cathodes are comprehensively reviewed in terms of advanced materials, structure/component characterization, functional mechanisms, and performance validation. Some technical challenges are analyzed in detail, and possible future research directions are proposed to overcome the challenges toward practical applications of lithium-sulfur batteries.

Surface-coated AlF3 nanolayers enable polysulfide confinement within biomass-derived nitrogen-doped hierarchical porous carbon microspheres for improved lithium-sulfur batteries

The electrically insulating and volumetric deformation of sulfur and the shuttle effect of the intermediate lithium polysulfide (LiPSs) have severely hindered the development of lithium-sulfur batteries (LSBs). Herein, a synergistic strategy of hierarchical porous nitrogen-doped carbon microspheres (PNCM) derived from low-cost biomass with surface-coated AlF3 nanolayer as a multifunctional sulfur host (denoted as PNCM@S@AlF3) was developed. The PNCM not only possesses an abundant pore structure, large surface area, and high electrical conductivity but also features an intrinsic N-doped and fluorinated framework, which effectively enhances the physical adsorption and chemical anchoring to LiPSs. In addition, the AlF3 nanolayer protects the open surface of the porous carbon to isolate sulfur species from the electrolyte to reduce irreversible losses while accelerating the redox kinetics of LiPSs through strong polar adsorption and bonding. Hence, the PNCM@S@AlF3 cathode exhibits an initial capacity as high as 1176.2 mAh/g at 0.2C, and the cycling stability and rate capability are superior to that of PNCM@S without AlF3 coating. Impressively, the PNCM@S@AlF3 cathode delivers stable long-term cycling performance at a high rate of 2C, with 95.6% capacity retention after 500 cycles. This work presents a facile, sustainable, and efficient synergistic strategy for developing advanced LSBs.

Construction of SnS2-modified multi-hole carbon nanofibers with sulfur encapsulated as free-standing cathode electrode for lithium sulfur battery

Lithium-sulfur (Li-S) batteries exhibit a huge potential in energy storage devices for the thrilling theoretical energy density (2600 Wh kg-1). Nevertheless, the serious shuttle effect rooted in polysulfides and retardative hysteresis reaction kinetics results in inferior cycling and rate performances of Li-S batteries, impeding commercial applications. In order to further promote the energy storage abilities of Li-S batteries, a unique binder-free sulfur carrier consisting of SnS2-modified multi-hole carbon nanofibers (SnS2-MHCNFs) has been constructed, where MHCNFs can offer abundant space to accommodate high-level sulfur and SnS2can promote the adsorption and catalyst capability of polysulfides, synergistically promoting the lithium-ion storage performances of Li-S batteries. After sulfur loading (SnS2-MHCNFs@S), the material was directly applied as a cathode electrode of the Li-S battery. The SnS2-MHCNFs@S electrode maintained a good discharge capacity of 921 mAh g-1after 150 cycles when the current density was 0.1 C (1 C = 1675 mA g-1), outdistancing the MHCNFs@S (629 mAh g-1) and CNFs@S (249 mAh g-1) electrodes. Meanwhile, the SnS2-MHCNFs@S electrode still exhibited a discharge capacity of 444 mAh g-1at 2 C. The good performance of SnS2-MHCNFs@S electrode indicates that combining multihole structure designation and polar material modification are highly effective methods to boost the performances of Li-S batteries.

Dually Sulphophilic Chromium Boride Nanocatalyst Boosting Sulfur Conversion Kinetics Toward High-Performance Lithium-Sulfur Batteries

The sluggish kinetics of sulfur conversions have long been hindering the implementation of fast and efficient sulfur electrochemistry in lithium-sulfur (Li-S) batteries. In this regard, herein the unique chromium boride (CrB) is developed via a well-confined mild-temperature thermal reaction to serve as an advanced sulfur electrocatalyst. Its interstitial-alloy nature features excellent conductivity, while the nano-lamination architecture affords abundant active sites for host-guest interactions. More importantly, the CrB nanocatalyst demonstrates a dual sulphophilicity with simultaneous Cr─S and B─S bondage for establishing strong interactions with the intermediate polysulfides. As a result, significant stabilization and promotion of sulfur redox behavior can be achieved, enabling an excellent Li-S cell cyclability with a minimum capacity fading rate of 0.0176% per cycle over 2000 cycles and a favorable rate capability up to 7 C. Additionally, a high areal capacity of 5.2 mAh cm-2 , and decent cycling and rate performances are still attainable under high sulfur loading and low electrolyte dosage. This work offers a facile approach and instructive insights into metal boride sulfur electrocatalyst, holding a good promise for pursuing high-efficiency sulfur electrochemistry and high-performance Li-S batteries.

Manipulating Sulfur Conversion Kinetics through Interfacial Built-In Electric Field Enhanced Bidirectional Mott-Schottky Electrocatalysts in Lithium-Sulfur Batteries

Efficient electrocatalysts and catalytic mechanisms remain a pressing need in Li-S electrochemistry to address lithium polysulfide (LiPS) shuttling and enhance conversion kinetics. This study presents the development of multifunctional VO2@rGO heterostructures, incorporating interfacial built-in electric field (BIEF) enhancement, as a Mott-Schottky electrocatalyst for Li-S batteries. Electrochemical experiments and theoretical analysis demonstrate that the interfacial BIEF between VO2 and rGO induces self-driven charge redistribution, resulting in accelerated charge transport rates, enhanced LiPS chemisorption, reduced energy barriers for Li2S nucleation/decomposition, and improved Li-ion diffusion behavior. The Mott-Schottky electrocatalyst, combining the strengths of VO2's anchoring ability, rGO's metallic conductivity, and BIEF's optimized charge transport, exhibits an outstanding "trapping-conversion" effect. The modified Li-S battery with a VO2@rGO-modified separator achieves a highly reversible capacity of 558.0 mAh g-1 at 2 C over 600 cycles, with an average decay rate of 0.048% per cycle. This research offers valuable insights into the design of Mott-Schottky electrocatalysts and their catalytic mechanisms, advancing high-efficiency Li-S batteries and other multielectron energy storage and conversion devices.

In Situ Filling of the Oxygen Vacancies with Dual Heteroatoms in Co3O4 for Efficient Overall Water Splitting

Electrocatalytic water splitting is a crucial area in sustainable energy development, and the development of highly efficient bifunctional catalysts that exhibit activity toward both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is of paramount importance. Co₃O₄ is a promising candidate catalyst, owing to the variable valence of Co, which can be exploited to enhance the bifunctional catalytic activity of HER and OER through rational adjustments of the electronic structure of Co atoms. In this study, we employed a plasma-etching strategy in combination with an in situ filling of heteroatoms to etch the surface of Co₃O₄, creating abundant oxygen vacancies, while simultaneously filling them with nitrogen and sulfur heteroatoms. The resulting N/S-V_O-Co₃O₄ exhibited favorable bifunctional activity for alkaline electrocatalytic water splitting, with significantly enhanced HER and OER catalytic activity compared to pristine Co₃O₄. In an alkaline overall water-splitting simulated electrolytic cell, N/S-V_O-Co₃O₄ || N/S-V_O-Co₃O₄ showed excellent overall water splitting catalytic activity, comparable to noble metal benchmark catalysts Pt/C || IrO₂, and demonstrated superior long-term catalytic stability. Additionally, the combination of in situ Raman spectroscopy with other ex situ characterizations provided further insight into the reasons behind the enhanced catalyst performance achieved through the in situ incorporation of N and S heteroatoms. This study presents a facile strategy for fabricating highly efficient cobalt-based spinel electrocatalysts incorporated with double heteroatoms for alkaline electrocatalytic monolithic water splitting.

Fast-Charging Zn-Air Batteries with Long Lifetime Enabled by Reconstructed Amorphous Multi-Metallic Sulfide

Developing fast-charging Zn-air batteries is crucial for widening their application but remains challenging owing to the limitation of sluggish oxygen evolution reaction (OER) kinetics and insufficient active sites of electrocatalysts. To solve this issue, a reconstructed amorphous FeCoNiS_x electrocatalyst with high density of efficient active sites, yielding low OER overpotentials of 202, 255, and 323 mV at 10, 100, and 500 mA cm^-2 , respectively, is developed for fast-charging Zn-air batteries with low charging voltages at 100-400 mA cm^-2 . Furthermore, the fabricated 3241.8 mAh (20 mA cm^-2 , 25 °C) quasi-solid Zn-air battery shows long lifetime of 500 h at -10 and 25 °C as well as 150 h at 40 °C under charging 100 mA cm^-2 . The detailed characterizations combine with density functional theory calculations indicate that the defect-rich crystalline/amorphous ternary metal (oxy)hydroxide forms by the reconstruction of amorphous multi-metallic sulfide, where the electron coupling effect among multi-active sites and migration of intermediate O* from Ni site to the Fe site breaks the scaling relationship to lead to a low theoretical OER overpotential of 170 mV, accounting for the outstanding fast-charging property. This work not only provides insights into designing advanced OER catalysts by the self-reconstruction of the pre-catalyst but also pioneers a pathway for practical fast-charging Zn-air batteries.

Atomic-Scale Laminated Structure of O-Doped WS2 and Carbon Layers with Highly Enhanced Ion Transfer for Fast-Charging Lithium-Ion Batteries

WS₂ anode materials show huge potential for fast-charging lithium-ion batteries (LIBs) due to the naturally good 2D diffusion pathways but suffer from large Li⁺ diffusion barrier energy and poor intrinsic electrical conductivity. Here, a defect-rich atomic-scale laminated structure of WS₂ and C (D-WS₂ -C) with O doping and enlarged interlayer distance from 0.62 to 1.06 nm of WS₂ is first fabricated, which is assembled into micron-sized spheres to prepare WS₂ /C composite microspheres. D-WS₂ -C with maximized molecular layer contact area between WS₂ and carbon and large interlayer spacing greatly enhances the electrical conductivity of WS₂ and reduces Li-ion diffusion energy barrier, confirmed by density functional theory calculations. Besides, the unique D-WS₂ -C enables the formation of vast superfine W nanoparticles (1-2 nm) during the conversation reaction, resulting in the construction of a space charge zone on W surface. Based on these characteristics of D-WS₂ -C, the prepared WS₂ /C composite microspheres show superior fast-charging capability with a high capacity of 647.8 mAh g^-1 at 20 C in half cells. For full cells, a high-energy density of 100.9 Wh kg^-1 is achieved at a charge time of only 8.5 min at 5 C, representing the best fast-charging performances in WS₂ -based anode materials to date.

Cation/Anion Dual-Vacancy Pair Modulated Atomically-Thin Sex -Co3 S4 Nanosheets with Extremely High Water Oxidation Performance in Ultralow-Concentration Alkaline Solutions

The density functional theory calculation results reveal that the adjacent defect concentration and electronic spin state can effectively activate the Co^III sites in the atomically thin nanosheets, facilitating the thermodynamic transformation of *O to *OOH, thus offering ultrahigh charge transfer properties and efficiently stabilizing the phase. This undoubtedly evidences that, for metal sulfides, the atom-scale cation/anion vacancy pair and surface electronic spin state can play a great role in enhancing the oxygen evolution reaction. Inspired by the theoretical prediction, interconnected selenium (Se) wired ultrathin Co₃ S₄ (Se_x -Co₃ S₄ ) nanosheets with Co/S (Se) dual-vacancies (Se_1.0 -Co₃ S₄ -V_S/Se -V_Co ) pairs are constructed by a simple approach. As an efficient sulfur host material, in an ultralow-concentration KOH solution (0.1 m), Se_1.0 -Co₃ S₄ -V_S/Se -V_Co presents outstanding durability up to 165 h and a low overpotential of 289.5 mV at 10 mA cm^-2 , which outperform the commercial Co₃ S₄ nanosheets (NSs) and RuO₂ . Moreover, the turnover frequency of Se_1.0 -Co₃ S₄ -V_S/Se -V_Co is 0.00965 s^-1 at an overpotential of 0.39 V, which is 5.7 times that of Co₃ S₄ NSs, and 5.8 times that of commercial RuO₂ . The finding offers a rational design strategy to create the multi-defect structure in catalysts toward high-efficiency water electrolysis.

Enhanced stability of nitrogen doped porous carbon fiber on cathode materials for high performance lithium–sulfur batteries

Lithium–sulfur (Li–S) batteries are considered to be one of the candidates for high-energy density storage systems due to their ultra-high theoretical specific capacity of 1675 mA h g⁻¹. However, problems of rapid capacity decay, sharp expansion in volume of the active material, and the shuttle effect have severely restricted their subsequent development and utilization. Herein, we design a nitrogen-doped porous carbon nanofiber (NPCNF) network as a sulfur host by the template method. The NPCNF shows a feather-like structure. After loading sulfur, the NPCNF/S composite can maintain a hierarchically porous structure. A high discharge capacity of 1301 mA h g⁻¹ is delivered for the NPCNT/S composite at 0.1C. The reversible charge/discharge capacity at 2C is 576 mA h g⁻¹, and 700 mA h g⁻¹ is maintained after 500 cycles at 0.5C. The high electrochemical performance of this NPCNT/S composite is attributed to the synergy effects of abundant N active sites and high electrical conductivity of the material.

The conductive network of nitrogen-doped porous carbon nanofibers was successfully prepared by the template method. The doping of nitrogen and the synergistic effect of mesopores and micropores reduce the energy barrier of Li⁺ migration in the material.

Facile preparation of flexible porous carbon fibers as self-supporting sulfur cathode hosts for high-performance Li–S batteries

A makeup cotton derived self-supporting porous carbon fibers with a specific surface area of 2124.9 m2 g−1 are prepared. The optimized S/C cathode with a sulfur loading of 3.0 mg cm−2 delivers the first discharge capacity of 778 mA h g−1 at 0.2 C.

InOOH as an efficient bidirectional catalyst for accelerated polysulfides conversion to enable high-performance lithium-sulfur batteries

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 Li₂S 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.

Coordinated Adsorption and Catalytic Conversion of Polysulfides Enabled by Perovskite Bimetallic Hydroxide Nanocages for Lithium-Sulfur Batteries

Catalysis is an effective remedy for the fast capacity decay of lithium-sulfur batteries induced by the shuttling of lithium polysulfides (LiPSs), but too strong adsorption ability of many catalysts toward LiPSs increases the risk of catalyst passivation and restricts the diffusion of LiPSs for conversion. Herein, perovskite bimetallic hydroxide (CoSn(OH)₆ ) nanocages are prepared, which are further wrapped by reduced graphene oxide (rGO) as the catalytic host for sulfur. Because of the coordinated valence state of Co and Sn and the intrinsic defect of the perovskite structure, such bimetallic hydroxide delivers moderate adsorption ability and enhanced catalytic activity toward LiPS conversion. Coupled with the hollow structure and the wrapped rGO as double physical barriers, the redox reaction kinetics, and sulfur utilization are effectively improved with such a host. The assembled battery delivers a good rate performance with a high capacity of 644 mAh g^-1 at 2 C and long stability with a capacity decay of 0.068% per cycle over 600 cycles at 1 C. Even with a higher sulfur loading of 3.2 mg cm^-2 and a low electrolyte/sulfur ratio of 5 µL mg^-1 , the battery still shows high sulfur utilization and good cycling stability.

Sandwiched Cathodes Assembled from CoS2 -Modified Carbon Clothes for High-Performance Lithium-Sulfur Batteries

Structural design of advanced cathodes is a promising strategy to suppress the shuttle effect for lithium-sulfur batteries (LSBs). In this work, the carbon cloth covered with CoS2 nanoparticles (CC-CoS2 ) is prepared to function as both three-dimensional (3D) current collector and physicochemical barrier to retard migration of soluble lithium polysulfides. On the one hand, the CC-CoS2 film works as a robust 3D current collector and host with high conductivity, high sulfur loading, and high capability of capturing polysulfides. On the other hand, the 3D porous CC-CoS2 film serves as a multifunctional interlayer that exhibits efficient physical blocking, strong chemisorption, and fast catalytic redox reaction kinetics toward soluble polysulfides. Consequently, the Al@S/AB@CC-CoS2 cell with a sulfur loading of 1.2 mg cm-2 exhibits a high rate capability (≈823 mAh g-1 at 4 C) and delivers excellent capacity retention (a decay of ≈0.021% per cycle for 1000 cycles at 4 C). Moreover, the sandwiched cathode of CC-CoS2 @S/AB@CC-CoS2 is designed for high sulfur loading LSBs. The CC-CoS2 @S/AB@CC-CoS2 cells with sulfur loadings of 4.2 and 6.1 mg cm-2 deliver high reversible capacities of 1106 and 885 mAh g-1 , respectively, after 100 cycles at 0.2 C. The outstanding electrochemical performance is attributed to the sandwiched structure with active catalytic component.

Highly Effective Trapping-Conversion Interface Based on Nickel-Modified Versatile Carbon Skeleton Enabled High-Performance Li-S Battery

The development of comprehension in the mechanism of lithium-sulfur (Li-S) batteries creates more opportunities and potential for the application of interlayer. However, the viable design of versatile interlayer to retard the shuttling effects and improve the sluggish kinetics is still a focus and paramount challenge. Herein, we present a tentacles-like metallic nickel-modified and nitrogen-doped carbon skeleton (NCS) to serve as adsorbent and catalyst in the lithium-sulfur battery (LSBs). The carbonized skeleton and derived carbon tubes jointly construct conductive networks and adequate ion pathways. Meanwhile, abundant metallic nickel nanoparticles synergistically build a multifunctional interface with polar networks for the fixation and conversion of polysulfides, giving rise to significant improvement of cyclic stability and reaction kinetics of LSBs. As a result, the Li-S batteries using NCS as an interlayer could possess superior electrochemical performance including cyclic stability, high specific capacity (1204.8 mAh g^-1 at 0.2C, 998.7 mAh g^-1 at 1C), and good Coulombic efficiency. More importantly, even with the areal sulfur loading of up to 6.1 and 7.5 mg cm^-2, it still demonstrates superior electrochemical performance with the areal capacity of 4.2 and 5.9 mAh cm^-2 with steady cycling, respectively. In conclusion, we confirm this work provides a promising way to explore and expand the application of metal nanoparticles in interlayers for advanced Li-S batteries.