Performance Of Lithium-sulfur Batteries Research Articles

Novel DNA-based polysulfide sieves incorporated with MOF providing excellent 3D Li+ pathway for high-performance lithium-sulfur batteries

For enhancing the performance of lithium-sulfur batteries (LSBs), deoxyribonucleic acid (DNA) as a bio-macromolecular adsorbing agent was incorporated into metal–organic frameworks (MOFs) to fabricate a MOF/carbon nanotube (CNT)@DNA double interlayer (MCDDI). Simulation calculations show that the adsorption energy (Ea) increased in the order of CNT-Li2S8 (–0.051 eV) < DNA(=N)-Li2S8 (–1.095 eV) < DNA(–PO)-Li2S8 (–1.137 eV), confirming that DNA-functionalized conductive CNT (CNT@DNA) layer facing the cathode with abundant anchoring sites can block and inhibit the shuttle effect of lithium polysulfides. The MOF layer on the surface of the CNT@DNA layer provides 3D pathways to realize fast Li-ion transport and homogeneous Li deposition for inhibition of voltage polarization and dendritic Li growth. LSBs using the MCDDI exhibited a high specific capacity of 1126 mAh/g and stable cycling performance with a small capacity decay (851 mAh/g after 100 cycles) at 0.5C. A small polarization effect (ΔE = 0.33 V at 2C) is observed from the excellent rate performance. In addition, owing to the homogenous Li-ion fluxes, a high Li+ transference number (tLi+ = 0.62) and stable Li plating/stripping for a long cycle life (500 h, 1000 cycles) were achieved without Li dendrites.

CoMoO4 nanorods coated separator for high-performance lithium sulfur batteries

Since the separator commonly used in lithium sulfur batteries has a large pore size and the adsorption effect of polyolefin based materials on soluble polysulfides is not obvious, the research on the modification of separator has aroused great interest. In this paper, the effects of different sizes of CoMoO4 nanorods as functional coating materials on the performance of lithium-sulfur batteries were investigated. The results prove that there is a strong affinity between the Co-O-Mo polar bond of CoMoO4 and LiPSs, which can enhance the chemisorption of LiPSs; Moreover, compared with CoMoO4-12, CoMoO4-24 nanorods with smaller particle size can increase the contact area and reactive sites with electrolyte, and the electrolyte penetration is promoted in the CoMoO4-24 coated separator, and the rapid transformation of LiPSs during charge and discharge is realized. Therefore, the Li-S battery assembled with CoMoO4-24 coated separator can deliver an initial capacity of 1018.5 mAh g−1 at 0.2C and a capacity retention of 745.5 mAh g−1 after 200 cycles, higher than the cells assembled with CoMoO4-12 coated separator and blank separator, exhibiting more remarkable electrochemical performance.

CoSe-catalyzed growth of graphene sheath to construct CNF@graphene-CoSe cable/sheath heterostructure for high-performance Lithium–Sulfur batteries

Advanced hierarchical hybrid nanostructures of polar, conductive and catalytic chemical traps/carbon with rationally tailored components, structures, and chemistries are important in determining the performance of lithium-sulfur (Li–S) batteries. Herein we propose a facile strategy to prepare 3D-structured CNF@graphene-CoSe (CNF@GL-CoSe) cable/sheath heterostructure with the in-situ formed CoSe as a catalyst for graphene-like carbon growth and Se as a catalyst promoter. The architecture integrates high electrical conductivity, effective ion transport, notable polysulfide entrapment, and polysulfide redox kinetics, availing lithium/sulfur conversion when applied as an interlayer in a Li–S battery. As expected, the battery delivered a low decay of 0.053% per cycle over 700 cycles at 1 C. The capacity even remained 649.4 and 524.5 mA h g−1 at 4 and 6 C, respectively. Furthermore, an areal capacity of about 3 mA h cm−2 at 0.1 C after long-term tests can still maintain with sulfur loading of 4.5 mg cm−2.

Porous TiO2-x/C Nanofibers with Axially Aligned Tunnel Pores as Effective Sulfur Hosts for Stabilized Lithium-Sulfur Batteries.

Hierarchically porous TiO2-x/C nanofibers (NFs) with axially aligned cylindrical tunnel pore channels were synthesized as a sulfur (S) host for lithium-sulfur batteries (LSBs) by a microemulsion electrospinning method. We explored a synergistic chemical trapping reinforced by coordinatively unsaturated Ti3+ nuclei with oxygen deficiency (or more broadly via polar O-Ti-O units) in combination with physical trapping in both narrow pores (<5 nm) and larger ordered pore tunnels (20-100 nm) separated by thin walls to allow for a large volume of active material and rapid diffusion within the channels while effectively blocking out the diffusion of soluble lithium polysulfides. Due to this unique architecture and enhanced conductivity, the prepared materials enabled a high S loading (∼72 wt %) and significantly reduced the shuttle effect. Hence, the composite TiO2-x/C@S cathodes exhibited a high utilization of active materials, excellent rate performance, and promising cycling stability (retention of up to ∼1010 mAh g-1 after 150 cycles for the aerial capacity of 1.5 mAh cm-2, with very stable performance even for the high S loading of 2.5 mg cm-2). By designing control nanomaterials that lack either the pore tunnels or the desired chemical compositions, we elucidated the importance of the synergistic effect of both factors. This work demonstrates a successful exploration of oxide NFs with tunnel pores via a simple single-needle microemulsion electrospinning method, which should pave the way for similar nanomaterials engineering with other chemistries for improved LSB performance.

In Situ Constructing a Catalytic Shell for Sulfur Cathode via Electrochemical Oxidative Polymerization.

Sluggish multiphase reaction kinetics and severe shuttle effect of lithium polysulfides (LiPSs) are two major challenges facing lithium-sulfur (Li-S) batteries, which largely prevent them from becoming a reality. Herein, a shell with catalytic function for sulfur cathode is in situ constructed through an ingenious electrochemical oxidative polymerization strategy by introducing hexafluorocyclotriphosphazene (HFPN) as additives, which suppresses the shuttle effect and promotes efficient sulfur conversion. The shell with abundant heteroatoms effectively confines polysulfides to the cathode matrix by chemically interacting with them to eliminate capacity degradation. Moreover, the shell exhibits high catalytic activities, which turns Li2S(2) into an activated state and facilitates its dissociation. The functionalized shell substantially advances the performance of Li-S batteries, thanks to efficient lithium-ion transportation and abundant adsorption-catalytic sites. As a result, Li-S batteries demonstrate superb resistance to self-discharge, ultrastable cycle performance, and greatly enhanced rate capability. Impressively, the batteries show an ultralow capacity decay rate of 0.034% throughout 700 cycles at 2C. They deliver a capacity of 517 mAh g-1 even at a 4C rate, exhibiting relieved electrochemical polarization and excellent sulfur utilization. This work provides an ingenious strategy to construct adsorption-catalytic nets for next-generation Li-S batteries with enhanced lifespan and electrochemical performance.

Spatial confinement of the cellular wall of yeast to the insertion of Co for enhanced electrochemical performance of Li-S batteries

Uniformly distributing Co crystalline particles within hierarchical pores of the microbial carbon stemmed from microorganisms is promising to improve a desirably electrochemical performance of Lithium-Sulfur (Li-S) batteries. Yeast as a representative microbial carbon, was used for making an exploration of spatial confinement of the cellular wall of yeast to the insertion of Co. On the basis of our previous paper, role of spatial confinement of the cellular wall of yeast to inserted Co was discussed, the difference of cobalt crystalline particles grown in the cellular wall and the cytoplasm was analyzed by high-resolution scanning electron microscopy. It showed that yeast cellular wall with compact structure could better keep fine cobalt particles from agglomeration and merging than yeast cytoplasm with loose structure. The as-prepared Co-YC-SDS-700/S electrode exhibited a higher reversible capacity of 1161.6 mAh g−1 as rate returned to 0.1 C and a better cycling life with a capacity fading rate of 0.099% per cycle at 0.2 C. The electrochemical reaction performance also further illustrated that the smaller and the more uniform distribution of the cobalt particles, the higher the utilization of sulfur, the better the cycle stability of the Li-S electrode.

Porosity vs carbon shell number: Key factor actually affecting the performance of multi-shelled hollow carbon nanospheres in Li-S batteries

• The pores in the carbon shells of HCNs play a key role in the Li + diffusion and Li 2 S x confinement. • Simply increasing the shell number in HCNs can not effectively confine the leakage of Li 2 S x from the S cathode. • Porous 1S-HCNs endow the S cathode with better cycling stability and rate capability than the oligoporous 2S-HCNs and 3S-HCNs do. • After 700 cycles, a capacity of 759 mAh g -1 with 63% retention is achieved for the S@1S-HCNs cathode at 0.2 C. As a type of sulfur host for lithium-sulfur batteries (LSBs), hollow carbon nanospheres (HCNs) are of particular interest due to their high electrical conductivity, available cavities, and unique morphology. However, there is a lack of in-depth study about the pivotal factors affecting their performance in LSBs. Herein, a series of multi-shelled HCNs have been prepared by a template-free method and the corresponding sulfur cathodes have been systematically investigated. A positive dependence of electrochemical properties on the specific surface area and pore volume of HCNs is confirmed. In case of low porosity of carbon shell, increasing the shell numbers in HCNs could not accelerate the Li + diffusion and restrict the dissolution of lithium polysulfide in the S@HCNs cathode. As a result, the highly porous 1S-HCNs endow the sulfur cathode with better cycling stability and rate performance than the oligoporous 2S-HCNs and 3S-HCNs do. This work may not only provide a useful reference in the design of novel sulfur hosts but also shed a light on the understanding of the complicated mechanism behind the sulfur redox reactions.

Design of spherical TiN/Nb4N5 heterostructure as bifunctional adsorption/catalytic material for lithium sulfur batteries

Lithium sulfur (Li-S) battery is the typical representative of the new generation secondary batteries, but its practical application is greatly hindered by the shuttle effect of lithium polysulfides (LiPSs) and sluggish electrochemical reaction kinetics. In this work, a spherical TiN/Nb 4 N 5 heterostructure is produced by nitridation of TiNb 2 O 7 microsphere and then used as an adsorption and catalytic material to fabricate modified polypropylene separator in Li-S batteries. Visual adsorption tests show that the TiN/Nb 4 N 5 heterostructure has better adsorption capacity of LiPSs than that of TiNb 2 O 7 microsphere precursor. The TiN/Nb 4 N 5 heterostructure also exhibits superior catalytic performance to accelerate the redox reaction kinetics of LiPSs conversion. The Li-S cell assembled with TiN/Nb 4 N 5 modified separator can deliver an initial discharge capacity of 917 mAh g -1 at 0.2 C, and a reversible capacity of 663.2 mAh g -1 after 200 cycles, higher than the cell assembled with TiNb 2 O 7 modified separator (555.4 mAh g -1 ) and pristine separator (385.1 mAh g -1 ). In short, this work provides a simple synthetic method to obtain a TiN/Nb 4 N 5 heterostructure with enhanced electrochemical performance of Li-S batteries. • TiN/Nb 4 N 5 heterostructure is synthesized by nitriding TiNb 2 O 7 microsphere; • TiN/Nb 4 N 5 heterostructure has strong adsorptive/catalytic conversion capability for polysulfides; • Li-S cell assembled with TiN/Nb 4 N 5 modified separator shows excellent electrochemical performance.

Tuning the Architecture of Hierarchical Porous CoNiO2 Nanosheet for Enhanced Performance of Li-S Batteries

As the desired components and crystal structure of a transition metal oxide catalyst are selected, architecture is a dominating factor affecting its electrocatalytic performance for applications in lithium-sulfur (Li-S) batteries. Nano-compounds with a hollow architecture are undoubtedly the ideal catalysts for enhancing cathodic performance for more exposed active sites and shortened path lengths than are other architectures. Additionally, the internal stress in hollow architecture is favorable for further performance enhancement, due to its regulation effects of driving the d-band center of the transition metal in the active sites to migrate toward the Fermi level, which will promote the chemical adsorption and catalytic conversion of the polysulfides (PSs). To this point, we select hierarchical porous dual transition metal oxide CoNiO2 nano-boxes (CoNiO2(B)) as the conceptual model; meanwhile, CoNiO2 nano-flakes (CoNiO2(F)) with identical stoichiometry and crystal structure are also analyzed as a comparison. Li-S batteries based on CoNiO2(B) deliver superior energy storage features, including a reversible discharge capacity of 1232 mAh g−1 at 0.05 C and a stable cycle performance with decay rate of 0.1% each cycle even after 300 cycles at 1 C. This research presents an alternative scheme for booting the performance of Li-S batteries.

Modulating Electron Conducting Properties at Lithium Anode Interfaces for Durable Lithium-Sulfur Batteries.

The lithium (Li) ion and electron diffusion behaviors across the actual solid electrolyte interphase (SEI) play a critical role in regulating the Li nucleation and growth and improving the performance of lithium-sulfur (Li-S) batteries. To date, a number of researchers have pursued an SEI with high Li-ion conductivity while ignoring the Li dendrite growth caused by electron tunneling in the SEI. Herein, an artificial anti-electron tunneling layer with enriched lithium fluoride (LiF) and sodium fluoride (NaF) nanocrystals is constructed using a facile solution-soaking method. As evidenced theoretically and experimentally, the LiF/NaF artificial SEI exhibits an outstanding electron-blocking capability that can reduce electron tunneling, resulting in dendrite-free and dense Li deposition beneath the SEI, even with an ultrahigh areal capacity. In addition, the artificial anti-electron tunneling layer exhibits improved ionic conductivity and mechanical strength, compared to those of routine SEI. The symmetric cells with protected Li electrodes achieve a stable cycling of 1500 h. The LiF/NaF artificial SEI endows the Li-S full cells with long-term cyclability under conditions of high sulfur loading, lean electrolyte, and limited Li excess. This study provides a perspective on the design of the SEI for highly safe and practical Li-S batteries.

Separator modification of lithium-sulfur batteries based on Ni-Zn bimetallic MOF derived magnetic porous Ni-C composites

Because of its high theoretical specific capacity, lithium-sulfur batteries are regarded as one of the most promising secondary batteries. However, there are still a series of problems, which seriously affect the commercial application of lithium-sulfur batteries. Therefore, a magnetic porous carbon material was developed in this work for the modification of lithium-sulfur battery separators, which may reduce the shuttle effect of polysulfides and increase its electrochemical performances. The solvothermal preparation of Ni-Zn bimetallic MOF precursors was followed by a high-temperature carbonization in nitrogen environment to sublimate Zn ions and produce porous structures, achieving Ni@C(Zn) composite. In order to improve the electrochemical performances of lithium-sulfur batteries, the Ni@C(Zn) composite was coated on one side of the polyethylene (PE) separator. Ni@C(Zn) composite displays good physisorption and chemisorption properties, and it can also operate as a secondary current collector to promote the usage of active materials as well as inhibiting shuttle effect of polysulfides. By using Ni@C(Zn) coated PE separator, the initial discharge specific capacity of lithium sulfur battery is as high as 1278.6 mAh g−1 at a current density of 0.05 C when the S cathode is loaded with 3 mg cm−2 active materials. Furthermore, the discharge specific capacity in the first cycle at 0.5 C is 749.4 mAh g−1, which remains at 461 mAh g−1 after 500 long cycles, and the capacity retention rate is as high as 61.5%. Even when the S loading is as high as 5 mg cm−2, it can still experience a stable cycle of 100 cycles at 0.2 C.

Mott-Schottky electrocatalyst selectively mediates the sulfur species conversion in lithium-sulfur batteries

The lithium sulfur (Li-S) battery is an active research area in the field of energy storage systems, but the shuttle effect is a serious obstacle hindering its application. Herein, a CoSe2/CoO Mott-Schottky catalyst is blended with carbon nanotubes (CNTs) and subsequently coated onto a commercial separator as a modifier, whereby the synergy between the high electrocatalytic activity of the CoSe2/CoO heterostructure and high conductivity of the CNTs selectively mediate the conversion of sulfur species. As a result, a cell with a CoSe2/CoO-CNTs modified separator displays a high initial discharge capacity of 1573 and 910 mAh/g at 0.1 and 2C, respectively. Furthermore, a low decay rate of 0.070% per cycle can be obtained over 500 cycles at 2C. The results of this study suggest that the as-prepared CoSe2/CoO-CNTs is an effective modifier that can improve the performance of Li-S batteries for use in next-generation energy storage systems. This study provides fundamental insights into the rational design of Mott-Schottky catalysts for practical high-performance Li-S batteries.

Cocklebur-like ZnSe-VO2@rGO nanostructures as host to boost the performance of lithium-sulfur batteries

Although lithium sulfur batteries (LSBs) have high theoretical capacity and energy density, low conductivity of sulfur and the discharge species (Li2S2, Li2S), the polysulfide shuttle and the large volume change hinder the commercialization of LSBs. To tackle the problem, we hydrothermally prepared a special cocklebur-like ZnSe-VO2@rGO nanostructure, in which graphene oxide (GO) is active in inducing thorn-like VO2 nanorods grown on carambola-like VO2 nanostructures. In this structure, the polar VO2 and ZnSe quantum dots (QDs) have strong chemical adsorption that can catalyze the polysulfide conversion and alleviate the shuttle effect; besides, the thorn-like VO2 nanorods act like numerous tentacles that capture polysulfides by increasing the contact area, and the reduced graphene oxide (rGO) nanosheets not only buffer the volume change, but also enhance the conductivity of the framework and improve the ion and electron transfer. Boosted by the synergetic effects of VO2, rGO and ZnSe QDs, the ZnSe-VO2@rGO/S cathode achieves a high specific capacity of 1026.1 mA h g−1 at 0.2 C and 712.3 mA h g−1 at 2 C. Good cyclic stability was obtained as well, with a high reversible capacity of 820 mA h g−1 and high retention of 89.1 % after cycling at 0.5 C for 150 cycles. Such outstanding performance indicated its good potential for use in advanced LSBs.

Asymmetric N-coordinated iron single-atom catalysts supported on graphitic carbon for polysulfide conversion in lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries with extremely high theoretical energy density are expected to be the next-generation energy storage systems. However, the electrochemical performance of Li-S batteries is still restricted by the shuttle effect of lithium polysulfides (LiPSs) resulting from their sluggish conversion kinetics. Herein, we demonstrated a coordination-confinement-pyrolysis strategy to fabricate iron single-atom catalysts (Fe SACs) supported on graphitic carbon nanocapsules (GCNC) by using imine (-RC = N-)-enriched polymer as precursors, aiming at suppressing the shuttle effect in Li-S batteries via simultaneously enhancing LiPSs confinement and catalytic conversion. The in-depth experiment investigations have revealed that the as-obtained N-doped carbon nanocapsules with ample hollow channels and large specific surface area (SSA) enable efficient adsorption and confinement for LiPS intermediates. Further, the isolated Fe SACs anchored on highly conductive graphitic carbon frameworks show an asymmetric N-coordinated active moiety (Fe-N5) that ensures fast redox kinetics of LiPSs and solid Li2S/Li2S2 products. As a result, the Li-S cell with a functional separator modified by the Fe-N5/GCNC exhibits a much-increased specific capacity of 1125 mAh/g at 0.1 C, excellent rate capability of 627 mAh/g at 2 C, and remarkable long-term cycling stability with a low capacity decay of 0.0386 % per cycle upon 1000 cycles. This work presents a useful strategy to fabricate high-activity SACs coupled with hollow graphitic carbon frameworks and to accelerate the catalytic conversion kinetics of LiPS intermediates for high-performance Li-S batteries.

Boosting lithium–sulfur battery performance using a phosphating nano-sulfur anchored on graphene framework anode

The shuttle effect of the intermediate lithium polysulfide and low sulfur utilization rate are two core issues restricting the further development of lithium–sulfur batteries (LSBs). Herein, a hierarchical sandwich superstructure (abbreviate as P-NS/GQDs/MGO) compose of phosphating nano-sulfur (P-NS) particles disperse and anchor on monolayer graphene oxide (MGO) with graphene quantum dots (GQDs) as the intermediate phase is constructed by hydrothermal method under oxygen-assist atmosphere and apply to the cathodes of LSBs. Notably, the phosphating and the robustly anchored P-NS effectively restricts the dissolution of intermediates in ether-based electrolytes and boosts charge/ion transport, which promotes the redox kinetics and maintains the electrode integrity during electrochemical cycling. Moreover, GQDs can facilitate the formation of specific bonding environments and interfacial interactions, resulting in accelerate heterogeneous nucleation, which effectively prevents P-NS agglomeration and volume change, improves sulfur utilization. Density functional theory (DFT) calculations reveal that the synergy of strategies relate to phosphating and interfacial interactions lead to high energy density and ultra-long cycle life with specific discharge capacities of 1117 and 838 mAh g−1 at 0.1 and 1.68A g−1, respectively. The capacity decay rate per cycle is 0.041% after 1000 charge–discharge cycles at 1.68A g−1.

FeCoNi Ternary Nano-Alloys Embedded in a Nitrogen-Doped Porous Carbon Matrix with Enhanced Electrocatalysis for Stable Lithium-Sulfur Batteries.

The application of composite materials that combine the advantages of carbonaceous material and metal alloy proves to be a valid method for improving the performance of lithium-sulfur batteries (LSBs). Herein iron-cobalt-nickel (FeCoNi) ternary alloy nanoparticles (FNC) that spread on nitrogen-doped carbon (NC) are obtained by a strategy of low-temperature sol-gel followed by annealing at 800 °C under an argon/hydrogen atmosphere. Benefiting from the synergistic effect of different components of FNC and the conductive network provided by the NC, not only can the "shuttle effect" of lithium polysulfides (LiPS) be suppressed, but also the conversion of LiPS, the diffusion of Li+, and the deposition of Li2S can be accelerated. Taking advantage of those merits, the batteries assembled with an FNC@NC-modified polypropylene (PP) separator (FNC@NC//PP) can deliver a high reversible specific capacity of 1325 mAh g-1 at 0.2 C and maintain 950 mAh g-1 after 200 cycles, and they can also achieve a low capacity fading rate of 0.06% per cycle over 500 cycles at 1 C. More impressively, even under harsh test conditions (the ratio of electrolyte to sulfur (E/S) = 6 μL mg-1 and sulfur loading = 4.7 mg cm-2 and E/S = 10 μL mg-1 and sulfur loading = 5.9 mg cm-2), the area capacity of batteries is still much higher than 4 mAh cm-2.

Surface Defect Engineering of a Bimetallic Oxide Precatalyst Enables Kinetics-Enhanced Lithium-Sulfur Batteries.

Developing efficient electrocatalysts to accelerate the sluggish conversion of lithium polysulfides (LiPSs) is of paramount importance for improving the performances of lithium-sulfur (Li-S) batteries. However, a consensus has not yet been reached on the in situ evolution of the electrocatalysts as well as the real catalytic active sites. Herein, defective MnV2O6 (D-MVO) is designed as a precatalyst toward LiPSs' adsorption and conversion. We reveal that the introduction of surface V defects can effectively accelerate the in situ sulfurization of D-MVO during the electrochemical cycling process, which acts as the real electrocatalyst for LiPSs' retention and catalysis. The in situ-sulfurized D-MVO demonstrates much higher electrocatalytic activity than the defect-free MVO toward LiPSs' redox conversion. With these merits, the Li-S batteries with D-MVO separators achieve superior long-term cycling performance with a low decay rate of 0.056% per cycle after 1000 cycles at 1C. Even under an elevated sulfur loading of 5.5 mg cm-2, a high areal capacity of 4.21 mAh cm-2 is still retained after 50 cycles at 0.1C. This work deepens the cognition of the dynamic evolution of the electrocatalysts and provides a favorable strategy for designing efficient precatalysts for advanced Li-S batteries using defect engineering.

Designing polysulfides adsorption‐conversion on g‐C3N4‐based separator via doping heteroatoms boron and phosphorus toward high‐performance lithium‐sulfur batteries

AbstractThe notorious “shuttle effect” of lithium polysulfides (LiPSs) has suppressed the large‐scale commercial application of lithium‐sulfur batteries (LSBs). Also, the intrinsic advantages including inhibiting the shuttling‐circulation and promoting the conversion of LiPSs, on the separator are deemed as stimulating blocks on the exploitation of LSBs. Herein, guided by theoretical calculations, we have designed doping‐heteroatoms boron (B) and phosphorus (P) on graphitic carbon nitride (g‐C3N4), to suppress the “shuttle effect” of LiPSs and improve the battery cycling performance. Theoretical calculations show strong chemical bonding between Li atom and N substance of g‐C3N4, and corroborates synergistic mechanism of electron transfer and van der Waals interaction. The high adsorption energies with doping B/P atoms enable LiPSs adsorption on the separators inhibiting shuttle loss. As expected, the experiment data also demonstrate that superior electrochemical performance are achieved by utilizing B‐doped g‐C3N4 (BCN) separator. Incorporating the B‐doped g–C3N4 (BCN) separator in LSBs delivered an initial specific capacity of 1050 mAh g−1 at 1 C and 920 mAh g−1 at 2 C. Notably, it achieved a decay rate of 0.08% and 0.1% at 1 and 2 C, respectively, after 500 cycles. This study furthers our understanding of B/P doping separator enhancement and restraining LiPSs shuttling loss for an improved LSBs performance.

Porous Activated Carbons Derived from Coffee Waste for Use as Functional Separators in Lithium-Sulfur Batteries

A novel approach has been proposed for improving the performance of lithium-sulfur batteries (LSBs) with a carbon-based material as an interlayer between the cathode and separator. With this method, the cross-over of lithium polysulfides (LiPS) to the anode is suppressed, increasing reutilization of the sulfur cathode. In this study, activated carbons (ACs) were prepared using coffee waste as a carbon source and potassium hydroxide (KOH) as an activation agent at various reaction temperatures ranging from 500 to 800 °C. With the rise in heating temperature, the specific surface areas, micro-surface areas, and micro-pore volumes of the AC samples gradually increased. In particular, the AC sample prepared at 800 °C and used as a functional separator for LSB exhibited improved capacity and cycling performance while suppressing the LiPS shuttle effect.

Enhanced Performance of Li-S Batteries due to Synergistic Adsorption and Catalysis Activity within a Separation Coating Made of Hybridized BNNSs/N-Doping Porous Carbon Fibers.

Lithium-sulfur (Li-S) batteries with high theoretical energy density are considered as the most promising devices for rechargeable energy-storage systems. However, their actual applications are rather limited by the shuttle effect of lithium polysulfides (LiPSs) and the sluggish redox kinetics. Here, the boron nitride nanosheets are homodispersedly embedded into N-doping porous carbon fibers (BNNSs/CHFs) by an electrospinning technique and a subsequent in situ pyrolysis process. The hybridized BNNSs/CHFs can be smartly designed as a multifunctional separation coating onto the commercial PP membrane to enhance the electrochemical performance of Li-S batteries. As a result, the Li-S batteries with extra BNNSs/CHF modification deliver a highly reversible discharge capacity of 830.4 mA h g-1 at a current density of 1 C. Even under 4 C, the discharge specific capacity can reach up to 609.9 mA h g-1 and maintain at 553.9 mA h g-1 after 500 cycles, showing a low capacity decay of 0.01836% per cycle. It is considered that the excellent performance is attributed to the synergistic effect of adsorption and catalysis of the BNNSs/CHF coating used. First, this coating can efficiently reduce the charge transfer resistance and enhance Li-ion diffusion, due to increased catalytic activity from strong electronic interactions between BNNSs and N-doping CHFs. Second, the combination of polar BNNSs and abundant pore structures within the hybridized BNNSs/CHF networks can highly facilitate an adsorption for LiPSs. Here, we believed that this work would provide a promising strategy to increase the Li-S batteries' performance by introducing hybridized BNNSs/N-doping carbon networks, which could efficiently suppress the LiPSs' shuttle effect and improve the electrochemical kinetics of Li-S batteries.