Host For Lithium-sulfur Batteries Research Articles

Nickle-doped covalent organic frameworks/carbon nanotubes composite for high-performance lithium-sulfur batteries

Lithium-sulfur batteries (LSBs) are considered as one of the most promising next-generation energy storage systems. To mitigate the shuttle effect of lithium polysulfides (LiPSs) in LSBs, the rational design of sulfur hosts with high physical confinement and catalytic activity is critical to enhance the performance of LSBs. Here, we successfully prepare a nickle-doped covalent organic frameworks/carbon nanotubes composite (Ni/COFs/CNTs) as the sulfur host in LSBs. COFs can confine and immobilize sulfur species. Moreover, CNTs and Ni nanoparticles can provide fastelectrontransferpathways. Thus, Ni/COFs/CNTs composite can alleviate the shuttle effect during the cycling processes.The S/Ni/COFs/CNTs cathode displays a high initial reversible capacity of 1068.6 mAh g−1 and a high capacity retention (83.3 %) after 100 cycles at 0.1C. This work provides a useful strategy to the rational design of sulfur hosts for LSBs.

Synthesis of Nixp/C Nanofibers As Interlayer and Sulfur Host for Lithium-Sulfur Batteries

Lithium-sulfur batteries (LSB) have a high theoretical capacity (1675 mAh g − 1) and energy density (2600 Wh kg−1), making them one of the most promising energy storage systems. 1 However, it has some limitations, such as “shuttle effect” of polysulfides and high volume expansion, causing poor cycle performance of the battery.The transition metal phosphides with carbon materials as sulfur host for LSB have attracted extensive scientific focus due to the large surface area and strong chemisorption ability. Moreover, high electrical conductivity of carbon-based material and the chemical adsorption effect of Ni-P phase can reduce the “shuttle effect”, and improve the cyclability of the material. 2,3 In this work, nickel phosphide carbon composite (NixP/C) nanofibers were synthesized using a water-soluble carbon source polyvinylpyrrolidone (PVP) and cost-effective electrospinning method. The impact of humidity on the physical and electrochemical characteristics of the electrospun NixP/C nanofibers was studied, utilizing them as interlayer and sulfur host material for LSB.The NixP/C nanofibers were synthesized using an electrospinning machine from PVP, nickel nitrate hexahydrate, and phosphoric acid as precursors. The nanofibers were electrospun at 18 kV voltage and 0.8 mL h–1 flow rate. The electrospinning humidity (RH) varied between 19-35%. Obtained nanofibers were dried at 110 ºC for 11 h. Finally, prepared fibers were annealed at 700 ºC for 1 h with a heating rate of 5 ºC min-1 in the N2 + H2 (4%) atmosphere.The crystalline phases of the final products were observed using X-Ray diffraction (XRD, Miniflex, Rigaku). The microstructure was studied by transmission electron microscopy (TEM, JEM-1400 Plus, JEOL). According to the results shown in Figure 1, Ni2P with a hexagonal structure and the space group of P62m, and Ni12P5 with a tetragonal structure, space group of 87:I4/m were formed. Nanoparticles of NixP are uniformly distributed within the carbon fiber matrix (inset).The NixP/C freestanding mats were embedded as a sulfur host or interlayer for LSB in CR2032 coin-type cells. 1 M Li2S6 catholyte solution and 1 M LiTFSI in 1,3- dioxolane (DOL)/1,2 dimethoxyethane (DME) (v/v, 1:1) with 2 wt% of LiNO3 were used as a source of sulfur and electrolyte, respectively. Further details and obtained results will be presented at the conference. Acknowledgements This research was funded by the projects AP13068219 “Development of multifunctional free-standing carbon composite nanofiber mats”, and AP19675260 “Development of nanofibrous electrode materials for next-generation lithium-ion batteries” from the Ministry of Education and Science of the Republic of Kazakhstan.

Precisely Designed Ultra-Small CoP Nanoparticles-Decorated Hollow Carbon Nanospheres as Highly Efficient Host in Lithium-Sulfur Batteries.

Designing porous carbon materials with metal phosphides as host materials holds promise for enhancing the cyclability and durability of lithium-sulfur (Li-S) batteries by mitigating sulfur poisoning and exhibiting high electrocatalytic activity. Nevertheless, it is urgent to precisely control the size of metal phosphides to further optimize the polysulfide conversion reaction kinetics of Li-S batteries. Herein, a subtlety regulation strategy was proposed to obtain ultra-small CoP nanoparticles-decorated hollow carbon nanospheres (CoP@C) by using spherical polyelectrolyte brush (SPB) as the template with stabilizing assistance from polydopamine coating, which also works as carbon source. Leveraging the electrostatic interaction between SPB and Co2+, ultra-small Co particles with sizes measuring 5.5±2.6 nm were endowed after calcination. Subsequently, through a gas-solid phosphating process, these Co particles were converted into CoP nanoparticles with significantly finer sizes (7.1±3.1 nm) compared to state-of-the-art approaches. By uniformly distributing the electrocatalyst nanoparticles on hollow carbon nanospheres, CoP@C facilitated the acceleration of Li-ion diffusion and enhanced the conversion reaction kinetics of polysulfides through adsorption-diffusion synergy. As a result, Li-S batteries utilizing the CoP@C/S cathode demonstrated an initial specific discharge capacity of 850.0 mAh g-1 at 1.0 C, with a low-capacity decay rate of 0.03 % per cycle.

A Nitrogen/Oxygen Dual-Doped Porous Carbon with High Catalytic Conversion Ability toward Polysulfides for Advanced Lithium–Sulfur Batteries

Lithium–sulfur batteries (LSBs) have attracted widespread attention due to their high theoretical energy density and low cost. However, their development has been constrained by the shuttle effect of lithium polysulfides and their slow reaction kinetics. In this work, a nitrogen/oxygen dual-doped porous carbon (N/O-PC) was synthesized by annealing the precursor of zeolitic imidazolate framework-8 grown in situ on MWCNTs (ZIF-8/MWCNTs). Then, the N/O-PC composite served as an efficient host for LSBs through chemical adsorption and providing catalytic conversion sites of polysulfides. Moreover, the interconnected porous carbon-based structure facilitates electron and ion transfer. Thus, the S/N/O-PC cathode exhibits high cycling stability (a stable capacity of 685.9 mA h g−1 at 0.2 C after 100 cycles). It also demonstrates excellent rate performance with discharge capacities of 1018.2, 890.2, 775.1, 722.7, 640.4, and 579.6 mAh g−1 at 0.2, 0.5, 1.0, 2.0, 3.0, and 5.0 C, respectively. This work provides an effective strategy for designing and developing high energy density, long cycle life LSBs.

Hollow CoP-FeP cubes decorating carbon nanotubes heterostructural electrocatalyst for enhancing the bidirectional conversion of polysulfides in advanced lithium-sulfur batteries

The sluggish redox reaction kinetics and “shuttle effect” of lithium polysulfides (LPSs) impede the advancement of high-performance lithium-sulfur batteries (LSBs). Transition metal phosphides exhibit distinctive polarity, metallic properties, and tunable electron configuration, thereby demonstrating enhanced adsorption and electrocatalytic capabilities towards LPSs. Consequently, they are regarded as exceptional sulfur hosts for LSBs. Moreover, the introduction of a heterogeneous structure can enhance reaction kinetics and expedite the transport of electrons/ions. In this study, a composite of hollow CoP-FeP cubes with heterostructure modified carbon nanotube (CoFeP-CNTs) was fabricated and utilized as sulfur host in advanced LSBs. The presence of carbon nanotubes (CNTs) facilitates enhanced electron and Li+ transport. Meanwhile, the active sites within the heterogeneous interface of CoP-FeP suppress the “shuttle effect” and enhance the conversion kinetics of LPSs. Therefore, the CoFeP-CNTs/S electrode exhibited exceptional cycling stability and demonstrated a capacity attenuation of merely 0.051 % per cycle over 600 cycles at 1C. This study presents a highly effective tactic for synthesizing dual-acting transition metal phosphides with heterostructure, which will play a pivotal role in advancing the development of efficient LSBs.

Atomically dispersed Co/Mn immobilized on O, N dual doped hollow carbon spheres as sulfur host for lithium sulfur batteries

The regulation of the chemical coordination environment in the electrocatalyst can effectively suppress the shuttle effect of sulfur species in lithium-sulfur batteries. However, the mechanism of the atomically dispersed dual metal atom with the coordination of various heteroatoms used as the sulfur cathode catalyst and trapper remains unknown. This study introduces, for the first time, atomically dispersed Co and Mn in-situ immobilized on O, N dual-doped hollow carbon spheres (SACoMn/C-(N, O)) as sulfur host. Experiments combined with density functional theory calculations reveal that the synergy between Co-(N, O) and Mn-(N, O) sites enhances the nucleation/deposition and decomposition capabilities of Li2S. This enhancement is attributed to the anchoring-coupling-conversion behavior of sulfur species on the SACoMn/C-(N, O) surface, which effectively restrains the shuttle effect and facilitates the conversion kinetics. Moreover, the cooperation of dual metal atoms with O, N non-metal atoms embedded in the carbon network structure accelerates electric transport and ion diffusion kinetics. The cathode demonstrates a high initial specific capacity of 890 mAh·g−1 at 1 C and show exceptional long-term cycling durability, with a low capacity degradation of 0.037 % per cycle after 1700 cycles. This research may offer novel insights into the design of dual metal atom-decorated, functionalized carbon materials to improve the conversion reaction in sulfur cathodes.

Tube‐in‐Tube Structure Design and In‐situ Growth of Fe3C for Efficient Reaction Kinetics in Lithium‐Sulfur Batteries

AbstractTo improve the sulfur reaction kinetics and inhibit the notorious shuttle effects, a tube‐in‐tube structure decorated by carbon nanotubes (CNT) and Fe3C nanoparticles (TIT/Fe3C‐CNT) is designed as sulfur host for lithium‐sulfur batteries (LSBs) in this work. The construction of tube‐in‐tube structure increases the active sites and the specific surface area of the material. Additionally, Fe3C nanoparticles can effectively adsorb the soluble lithium polysulfides and promote their catalytic conversion, thus greatly alleviating the shuttle effects. As a result of these advantages, the TIT/Fe3C‐CNT‐based cathode exhibits a high reversible capacity of 841 mAh g−1 after 200 cycles with a low decay of 0.056 % per cycle at 0.5 C. This work provides a promising and reasonable approach to the rational design of sulfur host for LSBs.

Iron, cobalt co-embedded in situ graphitized xerogel-derived carbon as sulfur host for ultrahigh rate and high-performance lithium-sulfur batteries

Lithium‑sulfur battery (LSB) is an enticing technology because of its high specific capacity, potential energy density, and natural abundance of sulfur in the earth's crust. However, some notorious issues need to mitigate before commercialization. Here we report a novel and scalable iron, cobalt co-embedded resorcinol formaldehyde derived carbon framework as sulfur host for high-performance LSB. To further increase the specific surface area and porosity of carbon, polyvinyl alcohol (PVA) is used as a sacrificial polymer. One pot synthesis method is used for preparing the Fe, Co co-embedded PVA incorporated RF xerogel-derived carbon (FC-PRFC) framework. The first-principles calculations suggest the advantage of bimetallic doping in enhancing the binding energy and reducing the energy gap of the carbon host for polysulfide anchoring. The porous structure and higher specific area of FC-PRFC enable high sulfur loading in the composite and show excellent rate performance and cyclability, as suggested by detailed electrochemical analysis. Moreover, the FC-PRFC cathode host with a high areal sulfur loading of 4.2 mg cm−2 delivers a high initial discharge capacity of 1283 mAh g−1 at 0.1C. During long-cycling at a high current rate of 4C, it retains a capacity of 372 mAh g−1 after 400 charge-discharge cycles with a capacity retention of 73 %. This scalable, innovative, low-cost fabrication technique has the potential to pave the way for developing an outstanding xerogel-derived carbon framework for high-performance LSBs for commercial applications.

Formation of 2D Amorphous Lithium Sulfide Enabled by Mo2C Clusters Loaded Carbon Scaffold for High-Performance Lithium Sulfur Batteries.

Lithium-sulfur (Li-S) batteries, operated through the interconversion between sulfur and solid-state lithium sulfide, are regarded as next-generation energy storage systems. However, the sluggish kinetics of lithium sulfide deposition/dissolution, caused by its insoluble and insulated nature, hampers the practical use of Li-S batteries. Herein, leaf-like carbon scaffold (LCS) with the modification of Mo2C clusters (Mo2C@LCS) is reported as host material of sulfur powder. During cycles, the dissociative Mo ions at the Mo2C@LCS/electrolyte interface are detected to exhibit competitive binding energy with Li ions for lithium sulfide anions, which disrupts the deposition behavior of crystalline lithium sulfide and trends a shift in the configuration of lithium sulfide toward an amorphous structure. Combining the related electrochemical study and first-principle calculation, it is revealed that the formation of amorphous lithium sulfides shows significantly improved kinetics for lithium sulfide deposition and decomposition. As a result, the obtained Mo2C@LCS/S cathode shows an ultralow capacity decay rate of 0.015% per cycle at a high mass loading of 9.5mg cm-2 after 700 cycles. More strikingly, an ultrahigh sulfur loading of 61.2mg cm-2 can also be achieved. This work defines an efficacious strategy to advance the commercialization of Mo2C@LCS host for Li-S batteries.

Sulfur confinement into highly porous banana peduncle-derived carbon for high-rate performance lithium‑sulfur battery

In this work, we introduce a facile route to synthesize an eco-friendly and inexpensive cathode host material to address the critical challenges of insulating sulfur, polysulfide shutting, and volume changes for lithium‑sulfur batteries (LSBs). The cathode uses banana peduncle, a biomass as a carbon precursor, to enhance the specific surface area and porosity after chemical activation. The two approaches (with/without the outer layer and with/without activation) have been compared to substantiate the role of banana skin and activation in boosting the performance of LSB. The carbon‑sulfur composite prepared with a sulfur loading of 75 % yields a significantly high initial discharge capacity of 1498 mA h g−1 at 0.1C, which remains stable with a very minimal capacity decay for the subsequent 100 charge-discharge cycles. Even at a high current rate (2C), the electrode shows a remarkable discharge capacity of 1076 mA h g−1, reflecting the efficacy of the as-fabricated cathode for LSB for high current applications. Further, the cycling performance is corroborated with high aerial sulfur loading (4 mg cm−2) to investigate the commercial feasibility. This confirms the advantage of the highly porous cathode matrix (surface area: 3148.42 m2 g−1 and pore volume: 2.51 cm3 g−1) in confining the lithium polysulfides and the volume expansion during charge-discharge cycles. To the best of our knowledge, this is the first-time banana peduncle has been used as a source of electrode material, and the present approach may pave the path for developing a green and sustainable, low-cost, highly porous carbon made from waste material as a sulfur host for high-performance LSB.

Preparation and application of NiS2/NiSe2 heterostructure as a sulfur host in lithium-sulfur batteries

The introduction of heterostructure in the cathode material of Li-S battery is an effective method to improve the redox reaction kinetics and suppress the shuttle effect of polysulfide. A metal sulfide/metal selenide (NiS2/NiSe2) heterostructure with hollow tetrahedral structure is prepared as a sulfur host of lithium-sulfur batteries. The prepared NiS2/NiSe2 heterostructure exhibits efficient charge transfer at the heterojunction interface, thereby enhancing catalytic activity for redox reactions of polysulfides and facilitating their rapid conversion. Moreover, the unique hollow tetrahedral structure, along with abundant surface pores, enables high sulfur loading capacity, providing abundant electrochemical reaction sites to enhance sulfur utilization efficiency. The results demonstrate that the NiS2/NiSe2 heterostructure material exhibits a remarkable initial capacity of 1338.9 mAh/g at 0.2 C, along with exceptional cycling stability (maintaining a capacity of 517.6 mAh/g after 200 cycles at 0.2 C, with only a negligible decay rate of 0.3% per cycle, retaining a capacity of 462.6 mAh/g after 500 cycles at 1 C, with an insignificant decay rate of merely 0.12% per cycle). The facile preparation of this NiS2/NiSe2 heterostructure not only enables the realization of lithium-sulfur batteries with exceptional capacity, but also opens up broader avenues for exploring high-performance heterogeneous materials.

Interfacial synergy of nanoengineered PANI/MnO2 for strong anchoring and fast conversion of polysulfides in Li-S batteries

The shuttle of polysulfides and slow sulfur redox kinetics are the two main issues in the practical application of lithium sulfur (Li-S) batteries. The interface-induced electric fields produced in MnO2-based conductive composites are proposed to solve the above obstacles. Herein, a novel hybrid structure of birnessite-MnO2 nanosheets in situ formed inside polyaniline nanotubes (NSs-MnO2@PANI) is prepared and applied as a catalytic host in Li-S batteries. The DFT calculation combined with experiments reveal the interface-induced electric field with a direction pointing from PANI to birnessite-MnO2 is created, which would induce interface charge redistribution and result in electron-rich MnO2 region and electron-deficient PANI region, optimizing the strong anchoring of polysulfides and their fast catalytic conversions. Owing to the interfacial synergy, the NSs-MnO2@PANI/S cathode delivers higher capacity than PANI/S at rates from 0.1 C (1473.7 vs. 467.5 mAh g−1) to 5 C (513.2 vs. 38.1 mAh g−1), with a low decay rate of 0.054% during 500 cycles at 0.2 C. Further, at an extremely high sulfur loading of 15.9 mg cm−2, the areal capacity achieves a high level of 10.2 mAh cm−2 at 0.05 C, with stable cycling at 1 C. Our work provides new insights for attaining high-energy and stable Li-S batteries.

Cherry blossom derived micron carbon sheets loaded with Co based particles served as sulfur host for lithium sulfur batteries

In order to effectively alleviate the shuttle effect in lithium-sulfur batteries (LSBs), cherry blossom-derived micron carbon sheets loaded with a small amount of Co-based nano-particles are synthesized in this work. After the thermal decomposition of ZIF-67, the composite shows a high specific surface area (2768.2 m² g−1) and pore volume (1.63 cm³ g−1), which can enhance the physical adsorption of polysulfides. Moreover, the Co-N and Co nano-particles obtained by ZIF-67 have strong catalytic and polar adsorption abilities. Not only can they accelerate the electrochemical reaction, but also effectively inhibit the shuttle effect of polysulfides, which in turn improves the electrochemical performance of lithium-sulfur batteries. Thus, the initial discharge capacity of the Co-PB@S electrodes reached 933 mAh g−1, with a remaining capacity of 550 mAh g−1 after 500 cycles at 0.5 C. This work may provide a practical way for the application of LSBs and the field of electrocatalysis.

Defect Strategy‐Regulated MoSe2‐Modified Self‐Supporting Graphene Aerogels Serving as Both Cathode and Interlayer of Lithium‐Sulfur Batteries

AbstractThe severe shuttle effect and the sluggish redox reaction kinetics are the two most urgent issues with lithium‐sulfur batteries (LSBs). In this work, Se vacancy‐rich molybdenum selenide‐modified graphene aerogels are designed to serve as both cathode host (MoSe2‐x@GA/S) and freestanding interlayers (MoSe2‐x@GA) for LSBs. The graphene network‐supported binder‐free sulfur host maximizes electron conductivity/Li+ migration rate and alleviates bulk expansion. The defect‐rich MoSe2‐x with sulfiphilic‐lithiophilic properties accelerates the nucleation and dissociation of Li2S, while the insertion of a bifunctional interlayer not only facilitates the adsorption and conversion of polysulfides but also regulates the uniform lithium deposition and inhibit the growth of lithium dendrites. As a result, the assembled MoSe2‐x@GA/S+interlayer electrode obtains good feedback in terms of capacity enhancement and cycling stability, possessing a high initial discharge capacity of 1256.9 mA h g−1 at 0.2 C and a slow decay ratio of 0.024% per cycle at a high current density of 1 C after 1000 long‐term cycling, and achieve high specific capacity (720.6 mA h g−1) at high sulfur loading (4.8 mg cm−2) and lean electrolyte (5.5 µL mg−1) conditions. This insightful work contributes new ideas for the design of binder‐free sulfur host and the application of defective electrocatalytic engineering.

Sandwich-type CoSe2-CNWs@NG as host for lithium-sulfur batteries with high sulfur loading, ultrahigh rate, and long lifespan

While lithium-sulfur batteries (LSBs) have tremendous potential in capacity and energy, their application in practice is limited by short cycle life, slow reaction kinetics, and underutilization of sulfur. To tackle these challenges, we have developed a multifunctional host consisting of sandwich-type CoSe2-CNWs@NG that were hydrothermally synthesized through self-assembly of CoSe2-embedded carbon nanowires (CoSe2-CNWs) with N-doped graphene (NG). Through the implementation of CoSe2-CNWs@NG as a host material, active sulfur can be effectively intercalated within the interlayer spaces of neighboring NG layers. The extensive contact area between sulfur and NG sheets facilitates rapid electron transfer, thereby maximizing sulfur utilization. N-doped graphene and polar CoSe2 provide sufficient chemisorption sites for polysulfides, while the catalytic activity of CoSe2 promotes polysulfide conversion. In addition to building a good conductivity structure for fast carrier transport and electrolyte diffusion, the sandwich structure of CoSe2-CNWs@NG physically restricts polysulfides and buffers substantial sulfur volume changes during cycling. As a result, the CoSe2-CNWs@NG/S cathode possessing high-load sulfur capacity (4.06 mg cm−2) exhibits superior cell performance at an ultrahigh rate as well as low E/S ratio. After 1000 cycles at 10 C, it achieves a remarkable reversible capacity of 314.4 mAh g−1 with an impressively low average fading rate of 0.023 % per cycle. Even at a low E/S ratio of 5 μL mg−1, the cathode exhibits remarkable performance, retaining a reversible capacity of 628.2 mAh g−1 after 150 cycles at the rate of 1 C.

Transition Metal Phosphides: The Rising Star of Lithium-Sulfur Battery Cathode Host.

Lithium-sulfur batteries (LSBs) with ultra-high energy density (2600Whkg-1) and readily available raw materials are emerging as a potential alternative device with low cost for lithium-ion batteries. However, the insulation of sulfur and the unavoidable shuttle effect leads to slow reaction kinetics of LSBs, which in turn cause various roadblocks including poor rate capability, inferior cycling stability, and low coulombic efficiency. The most effective way to solve the issues mentioned above is to rationally design and control the synthesis of the cathode host for LSBs. Transition metal phosphides (TMPs) with good electrical conductivity and dual adsorption-conversion capabilities for polysulfide (PS) are regarded as promising cathode hosts for new-generation LSBs. In this review, the main obstacles to commercializing the LSBs and the development processes of their cathode host are first elaborated. Then, the sulfur fixation principles, and synthesis methods of the TMPs are briefly summarized and the recent progress of TMPs in LSBs is reviewed in detail. Finally, a perspective on the future research directions of LSBs is provided.

Synergistic effect in the ZIF67-derived core shell structure towards the improved electrochemical performances in lithium-sulfur batteries

A ZIF-67 core could be grown within the hollow carbon sphere to further develop the hierarchical core shell structure, which displays synergistic effects as sulfur host in lithium sulfur batteries (LSB). The carbon shell with N active sites exhibits strong anchoring capability towards lithium polysulfide (LiPS), and the electrochemical conversion kinetic is favorably accelerated by the ZIF-67 derived carbon core. By virtue of the unique core shell structure and advantageous active species of the host material, the resulting composite cathode exhibits the high initial reversible capacity of 1308 mAh g−1 at 0.1C and outstanding long-term stability at 2C with a mere 0.039 % decay rate over 600 cycles. This work may shed a light on rational designing of novel sulfur host material towards the synergistic improvement of electrochemical performances of LSB.

Reduced graphene oxide wrapped ZnCo layered double hydroxides microsphere as efficient sulfur host in lithium-sulfur batteries

The practical application of lithium-sulfur (Li-S) batteries is impeded by the shuttling of the polysulfide and slow sulfur electrochemical reaction. In this study, a reduced graphene oxide (rGO) wrapped hollow ZnCo layered double hydroxides (ZnCo-LDH) microsphere is fabricated as sulfur host material. The rGO nanosheets offer efficient charge transportation pathways. Meanwhile, the porous rGO and hollow ZnCo-LDH provide sufficient space for sulfur storage and mitigates the volume variation during battery charging and discharging. In addition, ZnCo-LDH exhibits excellent chemical adsorption capacity for polysulfides, and promotes their electrochemical conversion reactions. Benefited from these advantages, the S/ZnCo-LDH@rGO cathode delivers a high rate performance of 796.5 mAh g−1 at 5.0 C, and excellent stability performance with a capacity decay of 0.036 % per cycle after 500 cycles at 1.0 C. This study shows that the porous microsphere design of rGO wrapped layered double hydroxides has excellent application prospects as efficient sulfur host for Li-S batteries.

A coral-like composite of CoP-modified polyaniline-derived carbon chain skeleton as an efficient sulfur host for lithium-sulfur batteries

Lithium-sulfur batteries (LSBs) have attracted wide attention in the field of rechargeable batteries due to their high theoretical energy density. However, the severe “shuttle effect” of lithium polysulfides (LiPSs) and the slow conversion kinetics are key factors restricting the commercial application of LSBs. To address these issues, we designed and prepared a coral-like composite of CoP-modified polyaniline-derived carbon chain skeleton (CoP/C) as the sulfur host for LSBs. The carbon chains can provide multidirectional channels for the transport of Li+ and electron; and the uniformly scattered CoP can adsorb the LiPSs through chemical adsorption and simultaneously promote their conversion, thus the “shuttle effect” can be effectively alleviated. Meanwhile, the effect of the amount of aniline monomer on the electrochemical performance of sulfur cathode were studied. After sulfur loading, the CoP/C-300/S (with aniline monomer addition of 300 μL) exhibits the best electrochemical performance. At 1 C, after 500 cycles, it still maintains a reversible specific capacity of 478 mA h g−1, with a decay rate of 0.074% per cycle, indicating its excellent cycling stability. This work provides a new approach for the application of CoP material in advanced LSBs.

Synergistic effect of Fe3C quantum dots, N-doped carbon and selenium on high conductive stable host for lithium sulfur batteries

Lithium-sulfur batteries are considered as one of the most promising energy storage devices. However, their development is still hindered by significant obstacles, particularly the well-known "shuttle effect". To overcome the issues, a three-dimensional porous biochar composite GC(Fe3C)x with Fe3C quantum dots/ C heterostructure is prepared by a simple one-stage chemical activation method as a sulfur host. A small amount of selenium is also added to form GC/Fe3C@SSe and improved electrochemical performances are obtained. The influence of Fe3C content on the structure and properties of the composites is investigated. It has been observed that an increase in Fe3C content leads to a reduction in specific surface area, thereby enhancing chemical adsorption while simultaneously weakening physical adsorption. When the Fe3C content reached 2.7%, the composite achieved a specific surface area of 1150.0 m² g−1. The synergistic effect of Fe3C quantum dots, N-doped carbon, and selenium resulted in outstanding electrochemical properties exhibited by the composite. At 1 C, GC/(Fe3C)2.7@SSe provides an initial specific discharge capacity of 803.7 mAh g−1. After 1000 long cycles, the specific discharge capacity is maintained at 363.1 mAh g−1, and the per-cycle capacity loss rate is 0.055%. Even at the current density of 5 C, the initial discharge capacity is 424.5 mAh g−1, and the capacity after 500 cycles is 322.9 mAh g−1, with a single cycle capacity decay rate of 0.048%. This work provides guidance for the design of lithium-sulfur battery cathode materials with synergetic physisorption and chemisorption for inhibiting shuttle effect.