Volume Expansion Of Sulfur Research Articles

A novel RuP2-infused heteroatom-doped porous carbon for high-durability lithium-sulfur batteries

Nitrogen and phosphorus co-doped three-dimensional porous carbon encapsulated ruthenium diphosphide (PCS900@RuP2-2) is successfully synthesized via a phytic acid-assisted phosphating process. The resulting RuP2 nanoparticles, ranging in size from 10 to 50 nm, are encapsulated within a carbon matrix, providing a stable catalytic structure. Nitrogen adsorption and desorption tests reveal that PCS900@RuP2-2/S possesses a high specific surface area and a rich micro/mesoporous structure. This high porosity facilitates multi-directional ion diffusion and offers ample buffer space to accommodate sulfur volume expansion during cycling. Density functional theory (DFT) calculations confirm that PCS900@RuP2-2/S enables efficient adsorption of soluble polysulfides, thereby minimizing the notorious "shuttle effect." Electrochemical testing demonstrates the remarkable durability of PCS900@RuP2-2/S. After 500 cycles at a 1 C current density, the reversible capacity remains at 511.6 mAh g⁻¹, with an average capacity decay rate of just 0.047 % per cycle. Even under heavy sulfur loading conditions (4.2 mg cm⁻²), the composite maintains a high reversible capacity of 386.6 mAh g⁻¹ after 500 cycles. The combination of high porosity, stable catalytic structure, and efficient redox reaction facilitation contributes to the exceptional performance and longevity of PCS900@RuP2–2/S.

A Review of Electrospun Carbon-Based Nanofibers Materials used in Lithium-Sulfur Batteries.

Commercial lithium-ion batteries are gradually approaching their theoretical specific energy, which cannot meet the fast-growing energy storage demands. Lithium-sulfur (Li-S) batteries are anticipated to supersede lithium-ion batteries as the next-generation energy storage system owing to their high atheoretical specific capacity (1675 mAh g-1) and energy density (2600 Wh kg-1). Nonetheless, Li-S batteries encounter several challenges, including the inadequate conductivity of sulfur and lithium sulfide, sulfur's volume expansion, and the shuttle effect of lithium polysulfides, all of which significantly impact the practical utilization of Li-S batteries. Electrospun carbon-based nanofibers can simultaneously resolve these issues with their economical preparation, distinctive nanostructure, and exceptional flexibility. This review presents the most recent research findings on electrospun carbon-based nanofibers materials serving as sulfur hosts and interlayer components in Li-S batteries. We analyzed the impact of the material's structural design on the performance of Li-S batteries and the relative underlying mechanism. Finally, the current challenges and issues faced by carbon-based nanofibers composites in the application of Li-S batteries are summarized, and the future development trajectory are outlined.

Preparation of MoSe2 nanosheets/nitrogen-doped carbon nanotubes and their electrochemical energy storage properties

Lithium-sulfur batteries can be used as excellent energy storage devices, but they still face some challenges in the practical application, such as the poor electrical conductivity of sulfur, the volume expansion of sulfur during the discharge process, and the dissolution of polysulfides. In this study, polypyrrole-coated molybdenum trioxide nanorods were used as templates for the simultaneous in-situ growth of MoSe2 nanosheets on the outer/inner sides of nitrogen-doped carbon nanotubes. When the MoSe2/N-carbon nanotubes (MoSe2/NC NTs) were used as sulfur carriers for lithium-sulfur battery, the large specific surface area of the N-carbon nanotubes facilitated the homogeneous loading of MoSe2 nanosheets and exposed more catalytically active sites of the MoSe2 nanosheets, increasing the contact area of electrolyte. In addition, the N-doped carbon nanotubes have excellent electrical conductivity, which greatly promotes the electrical conductivity of the cathode. The density functional theory calculations, adsorption experiments, and XPS results all confirm that the MoSe2/NC NTs are able to anchor lithium polysulfides through strong adsorption, thus effectively mitigating the shuttle effect of polysulfides. This study supplies a novel route for the preparation of sulfur host for advanced lithium-sulfur batteries.

Nickel-doped CNTs composite as cathode by sulfur vapor deposition for high-performance all-solid-state lithium‑sulfur batteries

Shuttle effect of polysulfide in the cathode and the safety issues arising from dendrite formation at Li metal anode are the main challenges of traditional liquid lithium‑sulfur batteries. In order to solve the shuttle effect and prevent short circuit, the all-solid-state lithium‑sulfur battery (ASSLSB) is proposed. However, the huge volume expansion of sulfur and the improvement of sulfur conversion efficiency during charge and discharge, which could lead to the limitation of electrochemical performance. Herein, a homogeneous Ni-doped carbon-nanotubes (H-Ni-SVD@CNT) composite cathode of ASSLSB is prepared by sulfur vapor deposition to confine sulfur and promote the conversion of sulfur and Li2S. In this work, SVD-5-S@CNT composite cathode demonstrates high reversible discharge capacity of 1001.1 mAh g−1 after 127 cycles and capacity retention rate of 78.6 % at the rate of 0.1C and 60 °C. Moreover, H-Ni-SVD@CNT composite cathode exhibits superior electrochemical performance, displaying the discharge specific capacity of 1519.3 mAh g−1 at 0.1C and 60 °C. Meanwhile, the discharge specific capacity of H-Ni-SVD@CNT composite cathode is 1060.9 mAh g−1 at room temperature. The synergistic effect of physical confinement and chemical catalysis improves the electrochemical performance of the all-solid-state lithium‑sulfur battery. This work proposes a new strategy for the cathode structure design of the all-solid-state lithium‑sulfur battery.

Nitrogen-doped hollow carbon sphere composite Mn3O4 as an advanced host for lithium-sulfur battery

As the most promising advanced energy storage system, lithium-sulfur batteries (LSBs) are highly favored by the researchers because of their advantages of high energy density (2500 W h kg−1), low cost and non-pollution. However, the low conductivity, volume expansion of sulfur, and shuttle effect are still the great hindrance to the practical application of LSBs. Herein, the above problems can be addressed through the following strategies: (1) Hollow carbon microspheres with high specific surface area were constructed as sulfur hosts to increase sulfur loading while also being able to enhance the physical adsorption of polysulfides; (2) the loading of Mn3O4 particles on the basis of hollow carbon microspheres facilitates the capture and adsorption of polysulfides; (3) the hollow carbon sphere structure as a conductive network can provide more pathways for rapid electrical/ionic transport and also accelerate electrolyte wetting. Moreover, the thinner shell of hollow carbon microsphere is conducive to ion diffusion and speed up the reaction rate. Thus, the NHCS/Mn3O4/S composites exhibit a high discharge specific capacity of 1010.3 mAh g−1 at first and still maintained a reversible capacity of 269.2 mAh g−1 after 500 cycles. This work presents a facile sustainable and efficient synergistic strategy for the development of advanced LSBs.

Enabling long cycle aluminum-sulfur batteries via structurally stable Co, N-doped graphene-CNTs covalently bonded hybrid

Al-S batteries offer advantages such as high energy density, low cost, and good safety. However, they face challenges including poor sulfur conductivity, volume expansion, and slow kinetics of polysulfides, leading to rapid capacity decay and short cycle life. Therefore, the design of materials with high conductivity, capable of anchoring polysulfides, and structurally robust is crucial for enhancing the overall performance of Al-S batteries. To address these issues, we propose the construction of a structurally stable graphene-carbon nanotubes (CNTs) covalently bonded hybrid and a three-dimensional (3D) conductive framework catalyzed by Co active sites. The porous Co, N-doped graphene-carbon nanotubes (CoN-GC) hybrid with excellent mechanical properties provides sufficient space for high sulfur loading, alleviating sulfur volume expansion. Co plays a key role in rapidly transporting electrons, adsorbing, and catalyzing aluminum polysulfides. The Al-S battery using S@CoN-GC cycles over 1500 cycles at a current density of 300 mA·g−1, maintaining a specific capacity of 315 mAh·g−1, and retains 278 mAh·g−1 after 2000 cycles. Additionally, utilizing the outstanding mechanical properties of CoN-GC, a flexible Al-S microbattery was successfully fabricated, maintaining a capacity retention of 90 % after folding 1000 times. These research findings are expected to accelerate the study of multivalent metal-sulfur batteries and their practical applications in various scenarios.

Recent advances in carbon-based sulfur host materials for lithium-sulfur batteries

Lithium-sulfur batteries (LSBs) have been brought into focus as the development direction of the next-generation power battery system due to their high energy density, eco-friendliness, and low cost, which has a broad application prospect in the field of energy storage. However, some problems are still unresolved in the sulfur cathode, e.g., poor electric conductivity, serious volume expansion of sulfur, shuttle effect caused by easy dissolution of lithium polysulfides in the electrolyte, and slow redox reaction kinetics of sulfur species. These issues lead to poor cycle stability and rate performance, making it hard to meet the requirement for LSBs in practical applications. Since the inherent nature of sulfur is the root cause of the above problems, reasonable design of functional sulfur hosts will be an effective way to break through the current bottlenecks of LSBs. The review covers the latest research progress on carbon-based sulfur host materials of LSBs, including structural design and functional optimization strategies, aiming to prepare multifunctional sulfur host materials by integrating physical confinement, chemical adsorption, and catalytic effect towards lithium polysulfides. The obstacles and future prospects of carbon-based sulfur hosts have also been brought forward, which provides in-depth guidance for practical application of LSBs.

A bifunctional double-layer Fe3O4-Polyvinylidene fluoride(PVDF)/PVDF separator with enhanced thermal stability for Li-S batteries

Li-S batteries, utilizing sulfur as the active material, have garnered significant attention due to their impressive theoretical specific capacity of 1675 mA h g−1. However, the commercialization of these batteries faces challenges primarily stemming from the volume expansion of sulfur and the shuttling effect caused by soluble polysulfides. In this study, we present a novel solution through the development of a bifunctional double-layer Fe3O4-PVDF/PVDF separator via electrospinning. The mesh structure of PVDF facilitates rapid lithium ion transport and effectively accommodates the volume expansion of sulfur during discharge/charge, leveraging its high thermal stability and mechanical properties. The incorporation of Fe3O4 within the PVDF matrix serves to trap polysulfides, mitigating the shuttle effect. Experimental results demonstrate that Li-S batteries employing the Fe3O4-PVDF/PVDF separator exhibit an initial discharge capacity of 1052.7 mA h g−1 at a current density of 0.5 C, with a commendably low capacity decay rate of 0.08 % per cycle after 250 cycles. This innovative separator design showcases promising advancements in addressing critical issues hindering the commercial viability of Li-S batteries.

Mn and N-doped RGO as a sulfur hosting accelerate electron transfer and redox reactions for Li–S batteries

The notorious polysulfides shuttling and slow redox reaction kinetics largely limit the Li–S battery commercial application as an effective energy storage system. In this report, Mn/N catalysts were co-doped on a high specific surface area reduced graphene oxide (RGO) scaffold by a simple formamide media-assisted method to develop the sulfur holding material for Li–S battery. The N-doped RGO with conductive layer structure not only facilitates the ion and electron transfer, but also provides superb reservoir space for sulfur volume expansion and intermediate polysulfides. Moreover, the introduction of Mn metal catalysts both paly the roles of chemical trappers and electrocatalysts to chemically anchor the polysulfides and accelerate the redox kinetics. It is a promising holding material to improve the reutilization of the polysulfides and suppression of the shuttle effect in lithium-sulfur batteries. As a result, the high initial discharge capacity for the Mn-NG modified Li–S battery is about 1124.7 mAh g−1 at 0.2 C, which can still reach to 914.3 mAh g−1 after 100 cycles, with a retention rate up to 81%. We believe that our method offers a significant approach to prepare multi-functional sulfur hosts for high performance Li–S batteries.

Solution-recrystallization mechanism of g-C3N4 and its inhibitory effect on polysulfide shuttling through cross-linked porous network structure with carbon nanotubes

Lithium-sulfur batteries have the advantages of high specific capacitance density and high theoretical capacity, which are attracting more and more attention in the field of energy storage. However, in practice, there are still many difficulties, such as the poor conductivity of sulfur, the large volume expansion of sulfur, and the shuttle effect of polysulfides, which lead to rapid capacity degradation and poor cycling stability. Here, we utilize g-C3N4 which is soluble in concentrated H2SO4 and has a good solution-recrystallization reversible property, alcohol was used as deprotonation solvent, the g-C3N4/CNT composites were prepared by the method of solution-recrystallization as sulfur host. The dissolution and precipitation mechanism of g-C3N4 in concentrated sulfuric acid and the composite mechanism with CNT were revealed. The g-C3N4/CNT/S cathode exhibit excellent electrochemical properties. The capacity of SPCNT11 can still be maintained to 1013 mAh·g−1 after 200 cycles at 0.2 C, with a capacity retention rate of 73.2%. Even at rate of 4C, the SPCNT11 material still has a capacity of 547 mAh·g−1 after 450 cycles. The first-principle calculation results further reveal that the interaction between g-C3N4 and CNT produces conjugated effect, the constrain of g-C3N4 to electrons is weakened, enhances its conductivity, and thus realizes the effect of promoting polysulfide transformation.

Application of MXene-Based Materials for Cathode in Lithium-Sulfur Batteries.

The lithium-sulfur (Li-S) batteries have a high theoretical specific capacity of 1675 mAh ⋅ g-1 and have become the most promising high-energy storage system for the next generation batteries technology. However, their applications are hindered by insulated feature and volume expansion of sulfur, as well as the "shuttle effect" of polysulfides. MXenes own metallic conductivity and strong ability of polysulfides adsorption. Besides, their unique two-dimensional (2D) structure, large specific surface area, abundant functional groups, and adjustability are beneficial to overcome the drawbacks of the sulfur cathode. In this review, different mainstream preparation methods and excellent properties of MXenes are summarized. Significant achievements and recent progress of MXene-based cathodes and interlayers applied to Li-S cathodes are concluded later. Finally, the challenges, possible solutions and potential applications of MXenes for Li-S batteries are also presented.

Flexible self-supporting interconnected cobalt sulfide nanosheets enable high-loading and long-cycling Li-S batteries with high areal capacity

Lithium-sulfur batteries (LSB) with high theoretical specific capacity/energy density still face some practical challenges, for instance shuttle effect and sluggish redox kinetics, which leads to rapid capacity decay. To overcome these challenges, herein, a porous and flexible sulfur host composed of interconnected Co9S8 nanosheets grown on carbon cloth was constructed. The interconnected carbon fiber skeleton and porous conductive Co9S8 nanosheets can not only provide abundant electron/ion-transport channels, but also offer adequate void to accommodate volume expansion of sulfur, thus ensuring high sulfur utilization and remarkable cycle stability of electrode. Meanwhile, the abundant adsorption and catalytic sites provided by Co9S8 nanosheets can effectively inhibit dissolution of polysulfides and improve conversion kinetics of polysulfides, effectively suppressing “shuttle effect”. The Co9S8-CC/Li2S6 electrode achieves high discharge capacity (1315.1 mAh g−1, 0.1C), excellent rate capability (872.4 mAh g−1, 2C) and outstanding cyclic stability (decay of 0.02 %/cycle over 1500 cycles, 2C).

ZIF-67 derived material encapsulated V2O3 hollow sphere structure of Co-NC@V2O3-sp used as a positive electrode material for lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries receive considerable attention for their high energy density, but their slow reaction kinetics and poor shuttle effects raise concerns. Here, synthesized V2O3 spheres were used as substrate templates, and ZIF-67 particles were grown on the surface of V2O3 by in-situ growth method. ZIF-67 was calcined at high temperature to form N-doped porous carbon attached to the surface of V2O3 spheres (Co-NC@V2O3-sp). The hollow structure of V2O3 spheres provided abundant buffer space for sulfur volume expansion and enhanced the stability of the battery cycle. In addition, the great pore volume and specific surface area resulted in abundant active physical and chemical sites, the strong chemical adsorption of V4+ effectively trapped polysulfides, and the cobalt nanoparticles on the surface effectively consolidated the active sites. The rapid transformation between shuttle effect and polysulfides were limited by physical coordination and chemisorption, respectively. Owing to this double synergistic effect, the prepared composites had an initial discharge capacity of 1483 mAh g−1 (0.1 C). The initial specific capacity reached 1002 mAh g−1 (0.5 C), and it achieved 645 mAh g−1 after 500 cycles. These results showed that Co-NC@V2O3-sp has high electrochemical function in Li-S batteries.

Functional separator with 1 T/2H-MoSe2 nanosheets decorated nitrogen and sulfur co-doped mesoporous hollow carbon spheres for high-performance Li-S batteries

Due to the dissolution, shuttling, and tardy kinetics conversion of lithium polysulfides (LiPSs) during cycling, there are serious defects in the utilization of active material and capacity retention ability for lithium-sulfur batteries (LSBs). To inhibit effectively the shuttling effect of LiPSs, herein, we propose the dual design strategies, using 1 T/2H mixed phase MoSe2 (1 T/2H-MoSe2) nanosheets uniformly growing on the external surface and inner wall of nitrogen and sulfur co-doped mesoporous hollow carbon spheres (MoSe2-NSHC) as both sulfur host and modified material of conventional polypropylene (PP) separator. The hollow structure of MoSe2-NSHC has a large specific surface area and internal space, which not only loads a large amount of sulfur, but also buffers severe volume expansion of sulfur during charge/discharge process. Meanwhile, 1 T/2H-MoSe2 and co-doped nitrogen and sulfur in the carbon skeleton effectively anchor LiPSs and accelerate the kinetics conversion of LiPSs by forming chemical bond. Density-functional theory calculations indicate the corresponding mechanisms. Based on these advantages, lithium-sulfur battery assembled with a MoSe2-NSHC/S cathode and a MoSe2-NSHC-PP separator delivers an initial discharge capacity of 1402 mAh/g at 0.2C, and also exhibits the first discharge capacity of 1155 mAh/g at 0.5C with a capacity retention rate of 79 % after 100 cycles. And after 800 cycles at 1C, the outstanding long-term cyclability with a low capacity decay per cycle of 0.039 % is also obtained. Notably, even in case of sulfur loading of 3.2 mg cm−2 and electrolyte/sulfur ratio of 6 μL mg−1, lithium-sulfur battery still exhibits a good electrochemical performance. Importantly, this work provides a feasible approach for commercial application of LSBs.

Rational design of MoSSe nanosheets on N-doped carbon hollow spheres for accelerating polysulfide redox kinetics of high-performance lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries with high theoretical energy densities offer a promising alternative for next-generation energy storage. However, the poor conductivity, shuttle effect of lithium polysulfides (LiPSs), and large volume expansion upon cycling hinder their application. Hollow nanostructures can play an important role in achieving high sulfur loading, buffering volume expansion, and inhibiting LiPSs shuttling. In this work, MoSSe nanosheets grown on N-doped carbon hollow spheres (MoSSe/NC) are used as both sulfur host and separator to achieve catalytic adsorption and conversion of LiPSs. As a sulfur host, MoSSe/NC can enhance electron/ion transport and alleviate the volume expansion of sulfur during cycling, further accelerating the redox kinetics. The MoSSe/NC-modified separator can also induce interfacial charge modulation and expose more active sites, promoting rapid anchoring and conversion of LiPSs and uniform deposition of Li2S. Theoretical calculations and experiments verify that MoSSe/NC can catalyze the conversion of LiPSs, inhibit the shuttle effect, and effectively improve the electrochemical properties of sulfur. Therefore, the MoSSe/NC based Li-S battery exhibits high initial capacity (1455 mAh g−1), excellent rate performance (891 mAh g−1 at 2 C), and good cycling stability (0.049% capacity decay rate at 800 cycles at 1 C).

Encapsulation of sulfur in MoS2-modified metal-organic framework-derived N, O-codoped carbon host for sodium–sulfur batteries

Room-temperature sodium–sulfur batteries (RT Na-S) are promising energy storage systems with high energy densities and low costs. Nevertheless, drawbacks, including the limited cycle life and sluggish redox kinetics of sodium polysulfides, hinder their implementation. Herein, a heterostructure of MoS2 nanosheets coated on a metal–organic framework (MOF)-derived N, O-codoped flower-like carbon matrix (NOC) was designed as a sulfur host for advanced RT Na-S batteries. The NOC@MoS2 hierarchical host provided a sufficient space to guarantee a high sulfur loading and confinement for the volume expansion of sulfur during the charge/discharge process. According to first-principle calculations, the NOC@MoS2 composite exhibited metallic conductivity because electronic states crossed the Fermi level, which indicates that the introduction of NOC significantly improved the electronic conductivity of MoS2. Furthermore, electron transfer from MoS2 to the O-doped carbon sites was observed owing to the strong electronegativity of O, which can effectively increase the Lewis acidity of MoS2 and weaken the sodium–sulfur bonds in sodium polysulfides after adsorption on the cathode, leading to reductions in the Na2S dissociation energy barrier and Gibbs free energy for the rate-limiting step of the sulfur reduction process. Therefore, with the synthetic effects of MoS2 and N, O-codoped carbon, the obtained cathode exhibited a superior electrochemical performance.

Polyaniline-coated Ni3N microflowers as sulfur host for advanced Li–S battery

This paper presents novel polyaniline-coated Ni3N/S (Ni3N/S@PANI) microflowers as sulfur host for lithium–sulfur battery to solve the problems of cathode, such as poor electrical conductivity caused by sulfur and shuttle effect caused by multi-sulfide dissolution. Microflower-like Ni3N is synthesized using hydrothermal reaction followed by a nitridation procedure. The Ni3N/S@PANI microflowers are obtained by compounding the Ni3N microflowers with sulfur powder, followed by polyaniline coating. The as-prepared Ni3N/S@PANI microflowers exhibit the first capacity of 935 mAh/g at 0.5 A/g and retain 678 mAh/g after 200 cycles. The high electrochemical property is due mainly to the porous hierarchical structure of the Ni3N and the highly conductive polyaniline coating, which provide sufficient interspace to mitigate the volume expansion of sulfur and trap polysulfides, and inhibit the dissolution of polysulfides, respectively.

Competing polysulfides conversion between edge-N and embedded CoS2 within multichannel carbon nanofibers

The practical application of lithium-sulfur batteries (LSBs) is hindered by a range of challenges, including slow conversion kinetics and inevitable shuttle effect of lithium polysulfide (LiPSs) intermediates, low electrical conductivity and rigorous volume expansion of sulfur. To address these challenges, we initiatively propose a competing catalytic mechanism dominated by two functional components, which aims to accelerate the liquid–liquid–solid conversion for the sulfur reduction reaction (SRR). To achieve this goal, we construct multichannel carbon fibers decorated with edge nitrogen and CoS2 nanoparticles (CoS2/NMCNF) as the cathode host for LSBs. The internal channels provide spatial constraints towards alleviating volume expansion and accelerating electron/ion transmission. Moreover, based on theoretical calculations and experiments, there is a competition between edge nitrogen and embedded CoS2 for catalytic conversion of LiPSs, of which CoS2 plays a major role in the liquid–liquid conversion (Li2S6–Li2S4), while edge-N accelerates the liquid–solid conversion (Li2S4–Li2S2). Consequently, the prepared CoS2/NMCNF electrode has an excellent performance with high initial specific capacity (1,437.9 mAh/g at 0.2C), excellent cycling stability at 3.0C (only about 0.032% capacity decay per cycle after 650cycles), and maintaining good cycling stability even when the sulfur loading increases to 4.10 mg cm−2. This work demonstrates a unique competing catalytic mechanism for the liquid–liquid–solid conversion process of LSBs.

Visualization of the Lithium Sulfur Electrochemistry

Taken advantage of a high theoretical energy density of 2567 Wh kg-1, lithium sulfur batteries (LSBs) have been considered promising candidates for next-generation energy storage systems. Tremendous efforts have been devoted to improving the battery performance by preparing smart nanostructures. However, detailed reaction mechanisms and the principles of tailoring reaction paths remain unclear. In-situ transmission electron microscopy (TEM) is a powerful technique to probe the dynamic processes of electrochemical reactions at a high spatial resolution and in real-time. Through in-situ TEM study with a solid cell, we revealed the correlation between sulfur volume expansion and the porosity of carbon nanofibers. Further, by developing an in-situ TEM equiped with a graphene-based liquid cell (GLC), where liquid electrolyte and TiN-C/S nanoparticles are encapsulated between two graphene sheets, we disclosed the nucleation and growth dynamics of solid Li2S from soluble polysulfides. Very recently, using operando optical microscopy, we found liquid sulfur droplets formation during charging at room temperature, which is much lower than the melting point of sulfur. The liquid sulfur indicates superior kinetic features from its flowing and reshaping natures. More interestingly, the preservation of liquid sulfur is strongly linked to the substrate chemistry, where solid sulfur forms from the edge of 2D materials. It is believed that in-situ microscopic investigation of sulfur cathodes would not only shed new light on understanding of reaction mechanisms but also provide fundamental guidelines to design better LSBs.

Multifunctional Ni-doped CoSe2 nanoparticles decorated bilayer carbon structures for polysulfide conversion and dendrite-free lithium toward high-performance Li-S full cell

The commercial application of lithium-sulfur batteries is severely hampered by polysulfide shuttle effects, sluggish redox kinetics, and uncontrollable lithium dendrite growth. Herein, a unique Ni-doped CoSe2 nanoparticle decorated bilayer carbon (Ni-CoSe2/BC) structure is synthesized for both the sulfur cathode and lithium anode, which introduces bi-functionalities including Ⅰ) the internal carbon conductive network skeleton of carbon nanotubes is capable of physically confining, storing, and alleviating volume expansion of sulfur; and Ⅱ) Ni-CoSe2 nanoparticles decorated on the external carbon nanoarrays contribute to efficient chemical anchoring and accelerated polysulfide conversion for the cathode, and serve as lithiophilic sites to induce homogeneous lithium deposition for the anode. As a result, Ni-CoSe2/BC effectively inhibits the shuttle effect and induces dendrite-free lithium deposition. The Ni-CoSe2/BC-S delivers a high discharge specific capacity of 806 mAh g−1 after 400 cycles at 1 C, with a low capacity decay rate of 0.07% per cycle. Moreover, the Ni-CoSe2/BC-Li exhibits an impressively long cycle life of 2000 h at 10 mA cm−2/10 mAh cm−2. Notably, the lithium-sulfur full cell assembled with Ni-CoSe2/BC as universal hosts for both anode and cathode possesses an average discharge capacity of 6.07 mAh cm−2 in 50 cycles (Sulfur loading=12.8 mg cm−2, Electrolyte/Sulfur=7.8 μL mg−1, and Negative/Positive=1.56). This work provides novel structural design and mechanism insights for the practical application of lithium-sulfur batteries.