Applications of transition-metal sulfides in the cathodes of lithium–sulfur batteries

Design Unsaturated Selenium Coordinated NbSe2-x as Multifunctional Sulfur Electrocatalyst toward Fast and Durable Sulfur Reduction Reaction

Lithium-sulfur (Li-S) battery are considered as the next generation energy storage system owing to their ultra-high theoretical specific capacity and energy density. However, the commercialization of Li-S battery is still hindered by the intrinsically low conductivity of sulfur, sluggish catalytic conversion and notorious shuttle effect of polysulfides. The implantation of defects in sulfur electrocatalyst can effectively increase its conductivity and catalytic efficiency of lithium polysulfides, but the current mainstream defective materials are limited and lack of in-depth research. Herein, a defective niobium selenide (NbSe2-x) nanosheet sulfur electrocatalyst is constructed with enriched selenium defects, which demonstrates strong interaction with sulfur species, endowing NbSe2-x with rapid and reliable sulfur reduction reaction. As a result, the Li-S cell with NbSe2-x exhibits excellent multiplicative performance in both coin cell and pouch cell, which maintains stable cycling for over 2000 cycles under 5 C, corresponding to a low-capacity fading rate of 0.024% per cycle. Ah level pouch cell is also fabricated, showing a decent energy density of 378 Wh kg-1. This creative strategy not only emphasizes the importance of selenium defect engineering in Li-S batterie toward practical application, but also enlightens the material engineering to realize superior performance in related energy storage and conversion area.

Chelate Complexes of 3d Transition Metal Ions─A Challenge for Electronic-Structure Methods?

Different electronic-structure methods were assessed for their ability to predict two important properties of the industrially relevant chelating agent nitrilotriacetic acid (NTA): its selectivity with respect to six different first-row transition metal ions and the spin-state energetics of its complex with Fe(III). The investigated methods encompassed density functional theory (DFT), the random phase approximation (RPA), coupled cluster (CC) theory, and the auxiliary-field quantum Monte Carlo (AFQMC) method, as well as the complete active space self-consistent field (CASSCF) method and the respective on-top methods: second-order N-electron valence state perturbation theory (NEVPT2) and multiconfiguration pair-density functional theory (MC-PDFT). Different strategies for selecting active spaces were explored, and the density matrix renormalization group (DMRG) approach was used to solve the largest active spaces. Despite somewhat ambiguous multi-reference diagnostics, most methods gave relatively good agreement with experimental data for the chemical reactions connected to the selectivity, which only involved transition-metal complexes in their high-spin state. CC methods yielded the highest accuracy followed by range-separated DFT and AFQMC. We discussed in detail that even higher accuracies can be obtained with NEVPT2, under the prerequisite that consistent active spaces along the entire chemical reaction can be selected, which was not the case for reactions involving Fe(III). A bigger challenge for electronic-structure methods was the prediction of the spin-state energetics, which additionally involved lower spin states that exhibited larger multi-reference diagnostics. Conceptually different, typically accurate methods ranging from CC theory via DMRG-NEVPT2 in combination with large active spaces to AFQMC agreed well that the high-spin state is energetically significantly favored over the other spin states. This was in contrast to most DFT functionals and RPA which yielded a smaller stabilization and some common DFT functionals and MC-PDFT even predicting the low-spin state to be energetically most favorable.

Attenuating the Polysulfide Shuttle Mechanism by Separator Coating

Lithium-sulfur batteries have a high energy density but lack cycle stability to reach market maturity. This is mainly due to the polysulfide shuttle mechanism, i. e., the leaching of active material from the cathode into the electrolyte and subsequent side reactions. We demonstrate how to attenuate the polysulfide shuttle by magnetron sputtering molybdenum oxysulfide, manganese oxide, and chromium oxide onto microporous polypropylene separators. The morphology of the amorphous coatings was analyzed by SEM and XRD. Electrochemical cyclization quantified how these coatings improved Coulombic efficiency and cycle stability. These tests were conducted in half cells. We compare the different performances of the different coatings with the known chemical and adsorption properties of the respective coating materials.

Efficient Catalysis of Ultrathin Two-Dimensional Fe2 O3 -CoP Heterostructure Nanosheets for Polysulfide Redox Reactions

The "shuttle effect" and slow redox reactions of Li-S batteries limit their practical application. To solve these problems, a judicious catalyst design for improved battery cycle life and rate performance is essential. Herein, this issue is addressed by modifying the Li-S battery separator using a 2D Fe2 O3 -CoP heterostructure that combines the dual functions of polar Fe2 O3 and high-conductivity CoP. The synthesized ultrathin nanostructure exposes well-dispersed active sites and shortens the ion diffusion paths. Theoretical calculations, electrochemical tests, and in situ Raman spectroscopy measurements reveal that the heterostructure facilitates the inhibition of polysulfide shuttling and enhances the electrode kinetics. A sulfur cathode constructed using the Fe2 O3 -CoP-based separator provides an astonishing capacity of 1346 mAh g-1 at 0.2 C and a high capacity retention of ≈84.5%. Even at a high sulfur loading of 5.42 mg cm-2 , it shows an area capacity of 5.90 mAh cm-2 . This study provides useful insights into the design of new catalytic materials for Li-S batteries.

Effect of Heterostructure-Modified Separator in Lithium-Sulfur Batteries

Lithium-sulfur (Li-S) batteries with high energy density and low cost are the most promising competitor in the next generation of new energy reserve devices. However, there are still many problems that hinder its commercialization, mainly including shuttle of soluble polysulfides, slow reaction kinetics, and growth of Li dendrites. In order to solve above issues, various explorations have been carried out for various configurations, such as electrodes, separators, and electrolytes. Among them, the separator in contact with both anode and cathode is in a particularly special position. Reasonable design-modified material of separator can solve above key problems. Heterostructure engineering as a promising modification method can combine characteristics of different materials to generate synergistic effect at heterogeneous interface that is conducive to Li-S electrochemical behavior. This review not only elaborates the role of heterostructure-modified separators in dealing with above problems, but also analyzes the improvement of wettability and thermal stability of separators by modification of heterostructure materials, systematically clarifies its advantages, and summarizes some related progress in recent years. Finally, future development direction of heterostructure-based separator in Li-S batteries is given.

2D-2D heterostructure of ionic liquid-exfoliated MoS2/MXene as lithium polysulfide barrier for Li-S batteries

Suppressing the dissolution and shuttling of lithium polysulfides (LiPSs) in electrolytes in lithium-sulfur batteries (LSBs) is the focus of researchers. Herein, functional liquid phase exfoliated MoS₂ and MXene (IL-MoS₂/MX) interlayer is proposed as the separator of LSBs. The unique alternating intercalation structure of the IL-MoS₂/MX interlayer provides a channel for ion transport while achieving uniform Li⁺ deposition on the anode side. Moreover, IL-MoS₂ achieves physical and chemical anchoring to LiPSs and lowers the energy barrier for battery reactions. As a result, the separator in the coin cell delivers an initial capacity of 764.4 mAh·g^-1 at 1C and high retention of 58.7 % after 700 cycles, with a decay only 0.059 % per cycle. Simultaneously, the excellent stability is also verified under varying current densities. Beyond that, ionic conductivity and lithium-ion migration number are adopted to confirm unique ion transport channels and uniform deposition of lithium. X-ray photoelectron spectroscopy, S₈ and Li₂S decomposition and nucleation energy barrier analysis are performed to verify the adsorption and catalytic conversion mechanisms. The convenient preparation and excellent performance of IL-MoS₂/MX provide a design strategy for functionalized interlayers for LSBs, and the possibility for commercialization.

Self-Supporting Multicomponent Hierarchical Network Aerogel as Sulfur Anchoring-Catalytic Medium for Highly Stable Lithium-Sulfur Battery

The low utilization rate of active materials, shuttle effect of lithium polysulfides (LiPSs), and slow reaction kinetics lead to the extremely low efficiency and poor high current cycle stability of lithium sulfur batteries (Li-S batteries). In this paper, a self-supporting multicomponent hierarchical network aerogel is proposed as the modified cathode (S/GO@MX@VS₄ ). It consists of graphene (GO) and MXene nanosheets (MX) loaded with VS₄ nanoparticles. The experimental results and first-principles calculations show that the GO@MX@VS₄ aerogel has strong adsorption and reversible conversion effects on LiPSs. It can not only inhibit the shuttle effect and improve the utilization rate of active substances by keeping the chain crystal structure of VS₄ , but also promote the reversibility and kinetics of the reaction by accelerating the liquid-solid transformation in the reduction process and the decomposition of insoluble Li₂ S in the oxidation process. The GO@MX@VS₄ aerogel modified cathode with a multicomponent synergy exhibits the capacity ratios (Q₁ /Q₂ ) at different discharge stages is close to the theoretical value (1:2.8), and the capacity decay per cycle is 0.019% in 1200 cycles at 5C. Also, a high areal capacity of 6.90 mAh cm^-2 is provided even at high sulfur loading (7.39 mg cm^-2 ) and low electrolyte/sulfur ratio (E/S, 8.0 µL mg^-1 ).

Phase Transitions and Stabilities among Three Phases of Di-p-tolyl Disulfides

Di-p-tolyl disulfides (p-Tol₂S₂) are employed as load-carrying additives because of their anti-wear and extreme load-bearing qualities. External pressure triggers conformational up-conversion (leads to phase transition) in the molecules of p-Tol₂S₂, by compensating for the stress and absorbing its energy. These features make p-Tol₂S₂ a potential candidate for next-generation energy storage devices. Upon lithiation, MoS₂ expands up to 103% which causes stress and affects battery stability and performance. Therefore, it is essential to study these materials under different physical conditions. In this work, we used density functional theory (DFT) at ωB97XD/6-31G* functional level, to calculate lattice parameters, Gibbs free energies, and vibrational spectra of three phases (i.e., α, β, and γ) of p-Tol₂S₂ under different pressure and temperature conditions. The phase transition between phases α and β occurred at a pressure and temperature of 0.65 GPa and 463 K, respectively. Furthermore, phase transition between phases α and γ was found at a pressure and temperature of 0.35 GPa and 400 K, respectively. Moreover, no phase transition was observed between phases β and γ under the pressure range studied (0 GPa to 5.5 GPa). We also computed and compared the FT-IR spectra of the three phases. These results can guide scientists and chemists in designing more stable battery materials.

Ultrathin Fe-ReS2 Nanosheets as Electrocatalysts for Accelerating Sulfur Reduction in Li-S Batteries

Lithium-sulfur batteries are promising next-generation energy storage systems with high theoretical specific capacity. Despite extensive research efforts, it is still challenging to rationally design electrocatalysts with fast kinetics and effective adsorption of polysulfides. Herein, Fe-doped ReS₂ (Fe-ReS₂) ultrathin nanosheets are prepared as an electrocatalyst to trap the intermediates and accelerate the sulfur reduction reaction kinetics. Density functional theory calculations combined with activation energies in the multistep sulfur reduction reaction reveal that the Fe-ReS₂ considerably reduces the activation energy and optimizes the optimum adsorption strength of polysulfides and catalytic activity. The Fe-ReS₂/S exhibits a highly reversible discharge capacity of 882.3 mA h g^-1 at 1 C. For 500 cycles, the capacity fade rate is 0.013% per cycle. Moreover, in situ Raman spectroscopy measurements further confirmed that both sulfur reduction and oxidation processes were significantly enhanced by Fe-ReS₂.

Unity of Opposites between Soluble and Insoluble Lithium Polysulfides in Lithium-Sulfur Batteries

Rechargeable batteries based on Li-S chemistry show promise as being possible for next-generation energy storage devices because of their ultrahigh capacities and energy densities. Research over the past decade has demonstrated that the morphology of lithium polysulfides (LPSs) in electrolytes (soluble or insoluble) plays a decisive role in battery performance. Early studies have focused mainly on inhibiting the dissolution of LPSs and invested considerable effort to realize this objective. However, in recent years, a completely different view that the dissolution of LPSs during battery discharge/charge should be promoted has emerged. At this critical juncture in the large-scale application of Li-S batteries, it is time to summarize and discuss both sides of the contradiction. Herein, an overview of these two opposite views pertaining to soluble and insoluble LPSs, including their historical environment, classical strategies, advantages, and disadvantages. Finally, the future morphology of LPSs in Li-S batteries is predicted based on a multiangle review of research studies conducted thus far, and the reasoning behind this conjecture is thoroughly discussed.

Understanding and Control of Activation Process of Lithium-Rich Cathode Materials

Lithium-rich materials (LRMs) are among the most promising cathode materials toward next-generation Li-ion batteries due to their extraordinary specific capacity of over 250 mAh g−1 and high energy density of over 1 000 Wh kg−1. The superior capacity of LRMs originates from the activation process of the key active component Li2MnO3. This process can trigger reversible oxygen redox, providing extra charge for more Li-ion extraction. However, such an activation process is kinetically slow with complex phase transformations. To address these issues, tremendous effort has been made to explore the mechanism and origin of activation, yet there are still many controversies. Despite considerable strategies that have been proposed to improve the performance of LRMs, in-depth understanding of the relationship between the LRMs’ preparation and their activation process is limited. To inspire further research on LRMs, this article firstly systematically reviews the progress in mechanism studies and performance improving attempts. Then, guidelines for activation controlling strategies, including composition adjustment, elemental substitution and chemical treatment, are provided for the future design of Li-rich cathode materials. Based on these investigations, recommendations on Li-rich materials with precisely controlled Mn/Ni/Co composition, multi-elemental substitution and oxygen vacancy engineering are proposed for designing high-performance Li-rich cathode materials with fast and stable activation processes.

Graphical abstract

The “Troika” of composition adjustment, elemental substitution, and chemical treatment can drive the Li-rich cathode towards stabilized and accelerated activation.

Electrolyte Salts and Additives Regulation Enables High Performance Aqueous Zinc Ion Batteries: A Mini Review

Aqueous zinc ion batteries (ZIBs) are regarded as one of the most ideally suited candidates for large-scale energy storage applications owning to their obvious advantages, that is, low cost, high safety, high ionic conductivity, abundant raw material resources, and eco-friendliness. Much effort has been devoted to the exploration of cathode materials design, cathode storage mechanisms, anode protection as well as failure mechanisms, while inadequate attentions are paid on the performance enhancement through modifying the electrolyte salts and additives. Herein, to fulfill a comprehensive aqueous ZIBs research database, a range of recently published electrolyte salts and additives research is reviewed and discussed. Furthermore, the remaining challenges and future directions of electrolytes in aqueous ZIBs are also suggested, which can provide insights to push ZIBs' commercialization.

Confined Co9S8 nanocrystals into N/S-Co-doped carbon nanofibers as a chainmail-like electrocatalyst for high-performance lithium-sulfur batteries with high sulfur loading

Accelerating phase transposition efficiency of lithium polysulfides (LiPSs) to L₂S and hampering the solution of LiPSs are the keys to stabilizing lithium-sulfur (Li-S) batteries. Hence, the sulfiphilic ultrafine Co₉S₈ nanoparticles embedded lithiophilic N, S co-doping carbon nanofibers (Co₉S₈/NSCNF) are prepared via the dual-template method, which are then used as sulfur host in Li-S batteries. Particularly, the double active sites (Co₉S₈ and N, S) in Co₉S₈/NSCNF are prone to form "Co-S", "Li-O" or "Li-N" bonds, and then simultaneously improving the chemisorption and interface transposition capability of LiPSs. In case of the S@ Co₉S₈/NSCNF composites with high sulfur loading of 89% are employed as cathode, the cell possesses optimized "sulfiphilicity" and "lithiophilicity", which achieves remarkable sulfur electrochemistry, including outstanding reversibility of 816.8mAhg^-1 over 500 cycles at 1.0C, excellent rate property of 742.2mAhg^-1at 5.0C, and long-term cycling with a low attenuation of 0.011% per cycle over 1800 cycles at 3.0C. Impressively, a remarkable areal capacity of 11.51mAhcm^-2 is retained under the sulfur loading of 15.3 mg cm^-2 for 50 cycles. This research will deepen the understanding of the complex LiPSs interface transposition procedure and provide new ideas for the design of new host materials.

Sponge-like hierarchical porous carbon decorated by Fe atoms for high-efficiency sodium storage and diffusion

Hierarchical pores with accessible active sites in carbon are highly desired for enhancing sodium storage in sodium ion batteries (SIBs). However, it is still challenging to construct such materials with tunable architectures. Herein, a sponge-like 3D hierarchical porous Fe-doped carbon (Fe@NCS) was successfully assembled from an energetic framework. The continuous distribution of micro/meso/macro-pores in the range of 5 nm-2 μm and homogenously decorated Fe atoms were achieved, which greatly enhanced the storage and diffusion of Na⁺ ions and displayed brilliant high-rate capability and cycling stability.

Recent Advances in Metal-Gas Batteries with Carbon-Based Nonprecious Metal Catalysts

Metal-gas batteries draw a lot of attention due to their superiorities in high energy density and stable performance. However, the sluggish electrochemical reactions and associated side reactions in metal-gas batteries require suitable catalysts, which possess high catalytic activity and selectivity. Although precious metal catalysts show a higher catalytic activity, high cost of the precious metal catalysts hinders their commercial applications. In contrast, nonprecious metal catalysts complement the weakness of cost, and the gap in activity can be made up by increasing the amount of the nonprecious metal active centers. Herein, recent work on carbon-based nonprecious metal catalysts for metal-gas batteries is summarized. This review starts with introducing the advantages of carbon-based nonprecious metal catalysts, followed by a discussion of the synthetic strategy of carbon-based nonprecious metal catalysts and classification of active sites, and finally a summary of present metal-gas batteries with the carbon-based nonprecious metal catalysts is presented. The challenges and opportunities for carbon-based nonprecious metal catalysts in metal-gas batteries are also explored.

Constructing Artificial SEI Layer on Lithiophilic MXene Surface for High-Performance Lithium Metal Anodes

MXene has been found as a good host for lithium (Li) metal anodes because of its high specific surface area, lithiophilicity, good stability with lithium, and the in situ formed LiF protective layer. However, the formation of Li dendrites and dead Li is inevitable during long-term cycle due to the lack of protection at the Li/electrolyte interface. Herein, a stable artificial solid electrolyte interface (SEI) is constructed on the MXene surface by using insulating g-C₃ N₄ layer to regulate homogeneous Li plating/stripping. The 2D/2D MXene/g-C₃ N₄ composite nanosheets can not only guarantee sufficient lithiophilic sites, but also protect the Li metal from continuous corrosion by electrolytes. Thus, the Ti₃ C₂ T_x /g-C₃ N₄ electrode enables conformal Li deposition, enhanced average Coulombic efficiency (CE) of 98.4%, and longer cycle lifespan over 400 cycles with an areal capacity of 1.0 mAh cm^-2 at 0.5 mA cm^-2 . Full cells paired with LiFePO₄ (LFP) cathode also achieve enhanced rate capacity and cycling stability with higher capacity retention of 85.5% after 320 cycles at 0.5C. The advantages of the 2D/2D lithiophilic layer/artificial SEI layer heterostructures provide important insights into the design strategies for high-performance and stable Li metal batteries.

Heterogeneous cobalt polysulfide leaf-like array/carbon nanofiber composites derived from zeolite imidazole framework for advanced asymmetric supercapacitors

Developing new electrode materials is one of the keys to improving the energy density of supercapacitors. In this article, a novel cobalt polysulfide/carbon nanofibers (C,N-Co_xS_y/CNF) film derived from zeolitic imidazolate framework is first prepared by a facile strategy. The composite material with two-dimensional leaf-shaped nanoarray neatly grown on the surface of carbon nanofibers is composed of CoS, CoS₂, Co₉S₈, N-doped carbon nanosheets, and carbon nanofibers. It is found that the composite can not only increase the contact area with the electrolyte but also provide abundant redox-active sites and a Faraday capacitance for the entire electrode. The C,N-Co_xS_y/CNF composite exhibits excellent electrochemical properties, including a high capacity of up to 1080F g ^-1 at 1 A g ^-1 and a good rate capability (80.4 % from 1 A g ^-1 to 10 A g ^-1). A C,N-Co_xS_y/CNF//AC asymmetric supercapacitor device is assembled using C,N-Co_xS_y/CNF as the positive electrode and activated carbon as the negative electrode, showing high energy density (37.29 Wh kg ^-1@813.6 W kg ^-1) and good cycle stability (90.5% of initial specific capacitance at 10 g^-1 after 5000 cycles). This C,N-Co_xS_y/CNF composite material may also be used as a potential electrode for future lithium-ion batteries, zinc-ion batteries, lithium-sulfur batteries, etc.

Anchoring stable FeS2 nanoparticles on MXene nanosheets via interface engineering for efficient water splitting

Exploring highly-efficient, economical and environment friendly electrocatalysts towards hydrogen and oxygen evolution reaction (HER and OER) is necessary but challenging for water splitting. Herein, FeS2 nanoparticles were anchored on the...

Dynamic 1T-2H Mixed-Phase MoS2 Enables High-Performance Li-Organosulfide Battery

Achieving high energy density and long cycle life in realistic batteries is still an unmet need, which has triggered research into the discoveries of new electrode materials as well as new storage mechanisms. As a kind of new cathode materials for rechargeable lithium batteries, organosulfide compounds R-S_n -R (n = 3-6) based on conversion chemistries of SS bonds have many advantages and promising prospects; however, poor electric/ionic conductivity and sluggish redox kinetics is a major hinder for their applications. Here an organic-inorganic hybrid cathode by introducing 1T MoS₂ grown on reduced graphene oxide to hybridize with phenyl tetrasulfide (Ph-S₄ -Ph, theoretical specific capacity 570 mAh g^-1 ), enhancing the battery performance is reported. This includes the improved charge transfer, stable long cycles, and close-to-practical energy density in coin cells and pouch cells, which also show high mass loadings and contents, and low electrolyte dependence. Furthermore, the dynamic 1T-2H mixed-phase during the charge/discharge is revealed to be critical for the improved performance. This study proves the hybrid nanomaterials as a promising solution to address the challenges facing lithium-organosulfide batteries.

Surface Atomic Decoration of a Manganite to a Modulable Oxygen Evolution Reaction

Aiming at the fundamental understanding of oxygen evolution reaction (OER) in epitaxial perovskite transition metal oxide (TMO) thin films, we evaluate the surface decoration conditions, including lattice orientation and surface morphology, of La_2/3Sr_1/3MnO₃ (LSMO) related to its modulable OER performance. The LSMOs with orientations of (001), (110), and, (111) exhibit different OER activities owing to the discrepant surface density of Mn. Furthermore, tuning of the surface atomic terrace width of LSMO shows a more efficient path to modulate the OER performance by introducing a high-valence Mn state owing to the surface dangling bonds of LSMO. As the electrochemical process is dominated by the interface of the TMO surface and electrolyte, our investigation can approach the fundamental understanding of a perovskite-type TMO surface state and its OER performance while highlighting the role of the nonbulk electron state in a promising TMO electrocatalyst in abundant electrochemical processes.

The Synergetic Effect Induced High Electrochemical Performance of CuO/Cu2O/Cu Nanocomposites as Lithium-Ion Battery Anodes

Due to the high theoretical capability, copper-based oxides were widely investigated. A facile water bath method was used to synthesis CuO nanowires and CuO/Cu₂O/Cu nanocomposites. Owing to the synergetic effect, the CuO/Cu₂O/Cu nanocomposites exhibit superior electrochemical performance compared to the CuO nanowires. The initial discharge and charge capacities are 2,660.4 mAh/g and 2,107.8 mAh/g, and the reversible capacity is 1,265.7 mAh/g after 200 cycles at 200 mA/g. Moreover, the reversible capacity is 1,180 mAh/g at 800 mA/g and 1,750 mAh/g when back to 100 mA/g, indicating the excellent rate capability. The CuO/Cu₂O/Cu nanocomposites also exhibit relatively high electric conductivity and lithium-ion diffusion coefficient, especially after cycling. For the energy storage mechanism, the capacitive controlled mechanism is predominance at the high scan rates, which is consistent with the excellent rate capability. The outstanding electrochemical performance of the CuO/Cu₂O/Cu nanocomposites indicates the potential application of copper-based oxides nanomaterials in future lithium-ion batteries.

A review of size engineering-enabled electrocatalysts for Li-S chemistry

Li-S batteries (LSBs) have received extensive attention owing to their remarkable theoretical capacity (1672 mA h g^-1) and high energy density (2600 W h kg^-1), which are far beyond those of the state-of-the-art Li-ion batteries (LIBs). However, the retarded sulfur reaction kinetics and fatal shuttle effect have hindered the practical implementations of LSBs. In response, constructing electrocatalysts for Li-S systems has been considered an effective strategy to date. Particularly, size engineering-enabled electrocatalysts show high activity in the sulfur redox reaction, considerably contributing to the latest advances in Li-S system research. In this tutorial review, we provide a systematic summary of nano- to atomic-scale electrocatalysts employed in Li-S chemistry, aiming at figuring out the working mechanism of size engineering-enabled electrocatalysts in the sulfur redox reaction and guiding the rational construction of advanced LSBs toward practically viable applications.

Self-Healing Nucleation Seeds Induced Long-Term Dendrite-Free Lithium Metal Anode

Seeded lithium (Li) nucleation has been considered as a promising strategy to achieve uniform Li deposition. However, problems of agglomeration and pulverization quickly invalidate the nucleation seeds, resulting in Li dendrite growth during repeated charge/discharge processes. Herein, liquid gallium-indium (GaIn) nanoparticles with structural self-healing properties are utilized to guide uniform metallic Li nucleation and deposition. Ultrafine GaIn nanoparticles (∼25 nm) uniformly decorated on the surface of carbon layers effectively homogenize the lithium-ion flux. After fully Li stripping, lithiophilic GaIn nanoparticles return to the liquid binary eutectic phase, thereby healing the deformed structure and enabling them to continuously guide dendrite-free Li deposition. Li metal anodes with such nucleation seeds exhibit nearly zero nucleation overpotential even after hundreds of cycles and a high average Coulombic efficiency of 99.03% for more than 400 cycles. The design of self-healing nucleation seeds provides important insights for obtaining high-performance lithium metal anodes.

An in-situ electrodeposited cobalt selenide promotor for polysulfide management targeted stable Lithium-Sulfur batteries

Lithium-sulfur batteries (LSBs) have attracted much attention due to their high theoretical specific capacity, energy density and low cost. However, the commercial application of LSBs is hindered due to the lithium polysulfide (LiPS) shuttle as well as the sluggish reaction kinetics. Herein, cobalt selenide (Co_0.85Se) nanowire arrays have been constructed on a carbon-modified separator by an in-situ electrodeposition technique without any other post-treatments such as coating with other ancillary materials. The introduced three-dimensional (3D) conductive carbon layer comprising of carbon nanotube (CNT) and acetylene black (AB) not only serves as the effective support for Co_0.85Se (CS) but also builds a hierarchical structure to promote the e^- transfer. The as-obtained CS-CNT/AB presents a strong anchoring effect on LiPSs and high electrocatalytic activity for sulfur reaction kinetics. As a result, the LSBs inserted with electrodeposition-enabled CS modified separator exhibit an outstanding rate capability (1560.4 mAh g^-1 at 0.1 C) and relatively low capacity decay of only 0.068% per cycle over 500 cycles at 2.0 C. This study provides a promising strategy to realize the rational construction of high-efficiency and long-life LSBs.

Metal Sulfide Nanoparticle Synthesis with Ionic Liquids - State of the Art and Future Perspectives

Metal sulfides are among the most promising materials for a wide variety of technologically relevant applications ranging from energy to environment and beyond. Incidentally, ionic liquids (ILs) have been among the top research subjects for the same applications and also for inorganic materials synthesis. As a result, the exploitation of the peculiar properties of ILs for metal sulfide synthesis could provide attractive new avenues for the generation of new, highly specific metal sulfides for numerous applications. This article therefore describes current developments in metal sulfide nanoparticle synthesis as exemplified by a number of highlight examples. Moreover, the article demonstrates how ILs have been used in metal sulfide synthesis and discusses the benefits of using ILs over more traditional approaches. Finally, the article demonstrates some technological challenges and how ILs could be used to further advance the production and specific property engineering of metal sulfide nanomaterials, again based on a number of selected examples.