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• A new type of hot-pressed cathode is developed with electronic and ionic conductors. • Ionically conductive LLTO benefits the adsorption and conversion of polysulfides. • The incorporation of LLTO achieves a high active-material loading at lean electrolyte. • The incorporation of LLTO allows a long-term cycle stability at various rates. • The incorporation of LLTO attains high efficiency with a LiNO 3 -free electrolyte. Low-cost, high-energy-density lithium–sulfur electrochemical batteries have emerged as a promising solution for next-generation energy-storage technologies. To facilitate the practical application of such batteries, it is necessary to address the remaining scientific and engineering challenges, especially those associated with the high-loading sulfur cathode in a lean-electrolyte cell. In this study, we investigate the electrochemical and overall performance of lithium–sulfur cells with a high-loading sulfur cathode. Notably, this cathode is fabricated using a novel hot-pressing method and incorporates electronically and ionically conductive additives, specifically lithium lanthanum titanate (LLTO) and carbon black, respectively. Material analysis reveals the uniform distribution of additives in the cathodes, with the ionically conductive LLTO effectively adsorbing and converting polysulfides and carbon black enhancing the cathode conductivity. Electrochemical analysis of the lean-electrolyte cells shows that the incorporation of LLTO improves cell performance, with enhanced discharge capacity of 715–836 mAh g −1 at C/5–C/10 rates and notable capacity retention after 100 cycles, compared with cathodes without additives or with carbon black. Further investigations demonstrate the superior performance of the cell incorporating LLTO in a LiNO 3 -free electrolyte, attributable to the promotion of ion transport and polysulfide adsorption by LLTO, resulting in high discharge capacities (846 mAh g −1 at C/10), efficiency (93–99 %), and stability. Overall, this study compares the effects of electronically and ionically conductive additives on cell performance and highlights the effectiveness of the ionically conductive LLTO. The incorporation of such additives offers innovative solutions to the key challenges for the development of high-performance energy-storage devices. [Display omitted] [ABSTRACT FROM AUTHOR]

A type of bimetallic ZnTe-CoTe 2 heterostructure was synthesized adopting template-assisted method which was supported on N-doped carbon framework (NC) to serve as sulfur host for lithium sulfur batteries (LSBs). The NC structure not only could build efficient conductive channels for fast ion/electron transport, but also inhibit the polysulfides shuttling via multiple spatial confinement. Besides, the construction of ZnTe-CoTe 2 heterogeneous interface weakened the nucleation/decomposition barrier of Li 2 S and promoted the bidirectional conversion of sulfur. Benefiting from the advantages mentioned above, therefore, the assembled batteries delivered a high initial discharge capacity of 1250 mAh g-1 at 0.2 C and achieved enhanced long cycling performance with an attenuation rate of 0.047% at 1 C after 1000 cycles. Furthermore, even under sulfur loading of 4 mg cm-2 and E/S ratio of 6 μL mg-1, the area capacity could also reach to 3 mAh cm−2. [ABSTRACT FROM AUTHOR]

Li-sulfur batteries represent a promising class of next-generation batteries with high theoretical gravimetric capacity. Moreover, the absence of scarce elements such as nickel or cobalt makes them a sustainable alternative to Li-ion batteries. However, it is well known that the main problem of Li-sulfur batteries is the so-called polysulfide shuttle, which leads to self-discharge, capacity fading and low coulombic efficiency. In recent years, several mitigation strategies have been developed for Li-sulfur batteries to reduce the polysulfide shuttle effect. One promising approach is to covalently bond the sulfur to a polymer backbone. A well-known class of materials is sulfurized poly(acrylonitrile) (SPAN), for which long cycle life and high specific capacities have been reported. In this work, we present a novel continuum model for SPAN electrodes and demonstrate its application in Li-SPAN batteries. Within our simulation framework we include both red/ox reactions of covalently sulfur on PAN as well as transport and reactions of polysulfides in the solution. By combining simulations and experimental data we analyze the discharge mechanism and provide guidelines for electrode design. [Display omitted] • Continuum model of a Li-SPAN battery is presented for the first time. • Simulation results are compared to and in agreement with experimental data. • The model is able to describe the discharge mechanism of the SPAN material. • Transport in the electrolyte is limiting cell performance for thicker electrode with higher cell energy density. [ABSTRACT FROM AUTHOR]

• Sulfur particles are loaded on the surface of C/SnO 2 under high temperature. • C/SnS/S displays better cycling stability (1161 mAh⋅ g −1) than C/SnO 2 /S. • Good cycling stability is ascribed to strong surface activities of sulfur in SnS. Polysulfides are easily dissolved during the redox reaction process of Li-S batteries, which may be severe when current density and cycle number increase. Increasing capacity of the first platform effectively is beneficial for improving cycling stability. Physical sulfur loads are benefit for achieving high-capacity storage. However, the influence of composite electrodes with sulfur loads under high temperature on cycling stability of the first platform capacity has not been studied. Sulfur particles are loaded on the surface of C/SnO 2 under high temperature in this work. C/SnO 2 /S and C/SnS/S composite electrodes are obtained by controlling sulfur contents. Results show that C/SnS/S composite electrodes display better cycling stability (1161 mAh⋅ g −1) than C/SnO 2 /S composite electrodes at 1C after 100 cycles, especially in P1 platforms (724 mAh⋅ g −1). When cycling number increases to 1000, C/SnS/S composite electrodes still possess good cycling stability (274.8 mAh⋅ g −1) at 1C. Good cycling stability is ascribed to strong surface activities of sulfur in SnS and rapid electron transportation abilities during the cycling process. Studying sulfur-loading methods under high temperature is beneficial for obtaining high cycling performance composite electrodes for lithium-sulfur batteries. [Display omitted] [ABSTRACT FROM AUTHOR]

• The as-prepared hybrid membrane develops a unique adsorption/catalyst architecture. • MMS@CNTs is compatible with strong adsorption and efficient catalytic capability towards polysulfides. • The composite membrane enables high sulfur-loaded cell sustaining cycling stability and rate capability. Lithium sulfur (Li-S) batteries are considered a promising application device due to their high theoretical capacity and energy density. However, the commercialization of Li-S batteries is hindered by the rapid capacity fading caused by the shuttle effect of lithium polysulfide (LiPSs) and the sluggish redox reaction of sulfur cathodes. To address these issues, the hybrid membrane with combination of multiphasic molybdenum diselenide nanosheets (MMS) modified carbon nanotubes (MMS@CNTs) and utilized Li 2 S 6 catholyte for Li-S batteries. The conductivity CNTs facilitate fast electronic/ionic transport, while the polarity of MMS has a strong affinity for LiPSs, effectively anchoring them, facilitating the redox conversion of lithium polysulfides, and effectively diminishing reaction barriers. The cell with MMS@CNTs displays an initial discharge capacity of 1036.2 mAh g−1 and maintains 810.5 mAh g−1 after 300 cycles at 0.2 C with 5.4 mg sulfur loading. Remarkably, even at 10.8 mg sulfur loading, the MMS@CNTs membrane displays high capacity of 8.1 mAh and maintains 6.7 mAh over 100 cycles. The results show that the efficient chemical anchoring polysulfides and catalyzing redox reaction by multifunctional MMS@CNTs hybrid composites is promising for assembling with a high sulfur loading electrode, which exhibits a superior electrochemical performance in Li-S batteries. [Display omitted] [ABSTRACT FROM AUTHOR]

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 V 2 O 3 spheres were used as substrate templates, and ZIF-67 particles were grown on the surface of V 2 O 3 by in-situ growth method. ZIF-67 was calcined at high temperature to form N-doped porous carbon attached to the surface of V 2 O 3 spheres (Co-NC@V 2 O 3 -sp). The hollow structure of V 2 O 3 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@V 2 O 3 -sp has high electrochemical function in Li-S batteries. [ABSTRACT FROM AUTHOR]

The lithium-sulfur battery has been regarded as a potential candidate for next-generation energy storage and conversion devices due to its high energy density, high theoretical capacity, and low cost of sulfur. However, its practical applications are still restricted by the polysulfide shuttle effect and the low redox kinetics. It has been demonstrated efficiency in ameliorating the polysulfide problem by utilizing the chemical bonds to realize chemical anchor of polysulfides through the design of molecular structures of sulfur copolymers. Herein, a sulfur copolymer is developed by directly copolymerizing sulfur to 2-methylimidazole through a hydrogen abstraction. In this sulfur copolymer, not only the abundant S-N bonds strongly anchored lithium polysulfides, restricting the polysulfide transportation, but also the generated sulfur-contained chemical bonds contribute to the decrease of the lithiation barrier, accelerating the slow redox kinetics. Therefore, this sulfur copolymer reveals a high initial capacity of 952 mAh g−1 at 0.5 C, and a high capacity of 1524 mAh g−1 at 0.1 C and improved rate capacities while composite with carbon nanotubes. A sulfur copolymer was developed by directly copolymerizing sulfur with 2-methylimidazole through a hydrogen abstraction. This prepared copolymer exhibited abundant S-N and S-C bonds to chemical anchor lithium polysulfide, and accelerated redox kinetics through sulfur contained molecular structure. Also, insoluble and stable imidazole ring structure promoted uniform electrochemical reactions during cycling. Thus, the sulfur copolymer exhibited improved performances including a high initial capacity and high rate performances. [Display omitted] [ABSTRACT FROM AUTHOR]

• CNFs implanted porous catalytic metal oxide electrode design is proposed. • Order porous Co-Al 2 O 3 facilitates the adsorption and catalytic conversion of LiPSs. • CNFs and Co nanoparticles in porous Co-Al 2 O 3 induce uniform lithium growth. • Excellent battery performance is achieved using the bifunctional electrode. The shuttling effect of lithium polysulfides (LiPSs) and uncontrolled dendrite formation of metal lithium anode are the two critical obstacles hindering the commercial application of lithium-sulfur (Li-S) batteries. Herein, a bifunctional electrode host design consists of carbon nanofibers implanted ordered porous Co-decorated Al 2 O 3 supported on carbon nanotube film (CNTF) is proposed to address these problems. As cathode sulfur host material, benefiting from the synergistic effect of porous Co-Al 2 O 3 and the embedded CNFs, the CNFs/Co-Al 2 O 3 @CNTF exhibits excellent conductivity, efficient LiPSs confinement and catalytic conversion performance. It shows a high initial capacity of 1165 mAh g−1 at 0.2 C, and holds a capacity of 594 mAh g−1 even up to 3 C. When serves as anode, the CNFs/Co-Al 2 O 3 @CNTF electrode exhibits excellent Li+ diffusion performance and uniform lithium growth behavior, achieving a dendrite-free lithium electrode. The anode also shows good cycle stability during an ultra-long cycle time of 1000 h. A flexible pack cell assembled from CNFs/Co-Al 2 O 3 @CNTF electrodes delivers a specific capacity of 972 mAh g −1 with capacity retention rate of 86.4% at 0.1 C. [ABSTRACT FROM AUTHOR]

Lithium-sulfur (Li–S) battery system shows immense potential as energy storage devices with high energy density. However, the soluble property of polysulfides into the electrolyte during charge/discharge process leads to low sulfur utilization, severe polarization and short cyclic life, which has been a serious obstacle for practical application. How to anchor the polysulfides onto the cathode materials and moreover, enhance its further conversion to the final products, have been important challenges for the utilization of Li–S batteries. Herein, a novel well crystallized nanosized Fe 7 S 8 possessing of a high specific surface area of 55.6 m2 g−1 fabricated by a simple microwave-assisted method combined with high temperature pyrolysis technique, is introduced into the S/C composite cathode for the first time. Strong interaction between polysulfides and the Fe 7 S 8 can be realized to relieve the shuttle effect. The redox reaction of polysulfides can also be promoted to reduce electrode polarization. As a result of the enhanced utilization of sulfur, the optimized S@GFS-15 electrode may deliver a high initial discharge capacity of 1307.2 mA h g−1 at 0.1 C (1 C = 1675 mA h g−1) and low decay rates of 0.047% and 0.037% per cycle after 1000 cycles at 1 and 2 C respectively when the sulfur loading is ordinary 1.1 mg cm−2. Even the sulfur loading rises up to 2.6 mg cm−2, a large initial discharge specific capacity of 1134.5 mA h g−1 can be achieved at 0.1 C. After 600 cycles, the specific capacity of 457.3 mA h g−1 with a relatively small average decay rate of 0.062% per cycle can be obtained. Thus, incorporation of the nanosized Fe 7 S 8 with graphene can help to achieve effective performance improvement route for Li–S batteries. Image 1 [ABSTRACT FROM AUTHOR]

We report a facile synthetic method to produce the interconnected hollow carbon spheres with various wall-thickness (as low as 9 nm). Instead of synthesizing and dispersing the silica hard templates in advance, we produce the templates in-situ to form the interconnected hollow-sphere structure. This interconnected structure provides a fast and efficient pathway for electron transfer. Meanwhile, decreasing the wall-thickness effectively shortens the distance of ion diffusion, which further promotes the high-rate performances of the interconnected hollow carbon spheres. For supercapacitor applications, at 1 A g−1, the MF-1.1-20 (with 9-nm wall-thickness) electrode demonstrates a high specific capacitance of 208 F g−1 and retains 93% of its initial capacity after 10000 cycles. Under a large current density of 20 A g−1, MF-1.1-20's specific capacity remains 153 F g−1, demonstrating excellent high-rate performances. In another aspect, as the electrode for lithium-sulfur battery, MF-1.1-20/S composite electrode demonstrates high specific capacity of 996 mAh g−1 and 465 mAh g−1 at 0.2C and 10C, respectively. The excellent electrochemical behavior of the interconnected hollow carbon spheres demonstrates their potential for applications in high-rate energy storage devices. Image 1 • A facile synthesis of hollow carbon spheres is developed by forming the hard template in-situ. • The interconnected carbon spheres effectively reduce the contact resistance. • The wall thickness of the hollow carbon spheres can be easily tuned to enhance rate performances. • The sample with 9 nm wall-thickness demonstrate 208 F g−1 at 1 A g−1 in supercapacitors. • The sulfur composite electrode exhibits highest capacity of 996 mAh g−1 at 0.2C for Li-S batteries. [ABSTRACT FROM AUTHOR]

Benefiting from the ultrahigh specific surface area, tunable pore size, and abundant surface functionality, biomass derived carbons (BC) are thriving as promising conductive matrices to host sulfur for Li S battery cathodes. Unfortunately, pristine BC still suffers from awful cycling performance rooted in their limited physical/chemical adsorption ability towards polysulfide. Herein, we proposed to construct Nickel Aluminum Layered Double Hydroxides (NiAl-LDH) fences coated on H 3 PO 4 activated BC (PAB) as an efficient sulfur host. The decorated NiAl-LDH fences could efficiently reinforce both chemical adsorption and physical confinement effects on polysulfides, and render as an electrocatalyst to significantly boost the redox reaction kinetics. Furthermore, the DFT simulation has been employed to illustrate enhanced interaction forces towards polysulfides. As a result, the prepared NiAl@PAB/S cell exhibits an improved performance of 1216.3 mAh g−1 initially at 0.2C (1C = 1672 mAh g−1), excellent cycling stability during 300 cycles at 1 C (0.13% decay rate per cycle), and superior rate capability up to 3 C (614.2 mAh g−1). This work provides a cost-efficient and effective method to significantly improve the overall performance of porous-carbon-based Li S battery cathode. [ABSTRACT FROM AUTHOR]

Abstract Rational design of modified separator is of great significance in effectively suppressing the shuttle of lithium polysulfides (LiPSs) and hence realizing fulfilling cycling performance of lithium-sulfur batteries (LSBs). In this paper, we developed a facile strategy to fabricate P-doped carbon coated CNT skeleton coupled with nickel phosphide (Ni 2 P) nanospheres (PCCNT@NPS), and then we employed the as-developed hybrid as a multifunctional modified interlayer onto PP separator (denoted as PCNPmPP) to face the challenge of LiPSs shuttling. The as-prepared hybrid provides abundant physical confinement and strong chemical adsorption for inhibiting polysulfides shuttling as well as efficient catalysis for accelerating LiPSs converting. As a result, the LSBs based on PCCNT@NPS modified PP separator have delivered a highly reversible cycling performance with high initial discharge capacity of 1067 mAh g−1 and low capacity decay rate of 0.077% per cycle within 500 cycles at 1 C. The promising results demonstrate that the PCCNT@NPS composite is capable of effectively inhibiting the diffusion and shuttle of LiPSs. This paper provides a novel thinking for the synthesis of multifunctional interlayer onto PP separator for advanced LSBs. [ABSTRACT FROM AUTHOR]

Abstract Practical application of Li S battery is greatly impeded by the critical challenges of large volume expansion, intrinsic insulation problem of active materials, and serious polysulfides shuttling. Thus, it is still quite essential for us to search an efficient strategy to synergistically overcome these problems. Herein, we design and in-situ deposit a functional δ-MnO 2 layer onto the outside surface of porous carbon foam/sulfur composites to synergetic inhibit the polysulfides shuttling and increase sulfur utilization, finally improve the electrochemical performance of Li S batteries. As verified by UV–vis and XPS results, the strong chemical interaction between the MnO 2 layer and polysulfide intermediates is characterized to be an internal disproportionation reaction by transferring the absorbed long-chain polysulfides into insoluble polythionate complex. Also, the unique structure possesses high conductivity and good volume expansion tolerance, further guaranteeing the electrode a good cycling stability, rate performance and low self-discharge behavior. The MnO 2 coated carbon foam/S electrode displays a remarkable capacity of 1547 mA g−1 at 0.1 C, and achieves a reversible capacity of 629 mA g−1 after 300 cycles at 1 C. Even with sulfur loading of 2.6 and 4.3 mg cm−2, the designed electrodes still deliver an initial discharge capacity of 1106 and 963 mA g−1 at 0.2 C. [ABSTRACT FROM AUTHOR]

Abstract Efficient redox conversions between polysulfides and sulfur or lithium sulfide have a significant impact on the electrochemical performance of lithium-sulfur batteries especially with high sulfur loading. Herein, a readily available cobalt-embedded carbon nanofiber (Co-CNF) is designed as the current collector for sulfur cathodes. It is shown that the Co-CNF promotes electron and Li-ion transfer, thus leading to fast redox conversion, which mitigates the dissolution and shuttling of polysulfides. Furthermore, the embedded cobalt metal facilitates the uniform nucleation of lithium sulfide on the surface of the carbon nanofiber, which reduces the polarization and leads to high specific capacity. The Co-CNF with 4.6 mg cm−2 sulfur loading delivers 970 mA h g−1 (4.5 mA h cm−2) at 0.1 C and 670 mA h g−1 at 1 C. Even when sulfur loading reaches as high as 9.6 mg cm−2, the reversible capacity of 730 mA h g−1 (7 mA h cm−2) is obtained. The Co-CNF/Li 2 S 6 cathode shows a degradation rate at 0.06% per cycle over 300 cycles. This work demonstrates the effect of cobalt metal catalysis and a simple but useful sulfur cathode design for high performance Li-S batteries. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

Abstracts Three-dimension ivy-structured MoS 2 nanoflakes @ nitrogen doped carbon nanofibers (MoS 2 @N-CNFs) composite membrane was designed by a combined electrospinning and hydrothermal technique. The MoS 2 @N-CNFs membrane is employed as a free-standing cathode for Li/polysulfides batteries. N-CNFs membrane with high electrical conductivity is used as a current collector to effectively reduce the internal resistance in the electrode and immobilize the dissolved lithium polysulfides with mesoporous N-CNFs with pyridine nitrogen. The MoS 2 nanoflakes introduced into N-CNFs membrane offer a hierarchical composite structure, in which the MoS 2 nanoflakes not only have chemical binding with the lithium polysulfides, but also promote fast redox reaction kinetics with high capacity and low voltage polarization. Meanwhile, the MoS 2 nanoflakes have been demonstrated to show strong binding energy and be capable of anchoring polysulfides based on density functional theory calculations. As a result, with a high sulfur loading of 7.11 mg, the assembled cell with MoS 2 @N-CNFs + Li 2 S 6 cathode demonstrates excellent electrochemical performances with a capacity decay rate of 0.08% per cycle over 250 cycles at 0.2C. Moreover, when the sulfur loading is further increased to 11.84 mg, a capacity decay rate of 0.25% per cycle over 100 cycles is achieved. Consequently, the method used in here provides a new insight to produce N-doped carbon nanofibers with metal sulfides/metal oxides nanoflakes composites as free-standing materials with the high sulfur loading for lithium-sulfur batteries. Graphical abstract Image 1 Highlights • 3D ivy-structured MoS 2 @N-CNFs has been synthesized for Li/polysulfides batteries. • The chemical interaction between LiPs and MoS 2 was revealed by DFT calculations. • The cathode with high sulfur loading exhibited stable electrochemical properties. [ABSTRACT FROM AUTHOR]

Abstract Rechargeable lithium-sulfur (Li−S) batteries are a significant energy-storage device owing to their eco-friendliness and high theoretical energy density. However, the shuttle effect of soluble polysulfides as well as the slow redox kinetics constrains the development of Li-S batteries. Herein, carbon nanodots-decorated alveolate N, O, S tridoped hierarchical porous carbon (a-NOSPC) material is synthesized via facile pyrolysis of tobacco stem. The coexistence of micropores, mesopores, and macropore in the hierarchical porous carbon are beneficial for physical accommodating/immobilizing active materials sulfur and rapid charge/ion transfer. Meanwhile, the N, O, S dopants provide rich electrocatalytic active site in chemical binding of polysulfides and their accelerated redox kinetics, thus guaranteeing high utilization on active materials. The resultant a-NOSPC/S cathode with an 2.7 mg cm−2 areal sulfur loading delivers a high reversible areal capacity of 2.90 mAh cm−2 at 0.1 C, maintaining 2.01 mAh cm−2 over 100 cycles, which is obviously superior to the most reported biochar-based electrodes. Our results provide an appealing avenue to the design of multifunctional sulfur host for advanced Li-S batteries. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

Abstract The mechanical degradation upon cycling of sulfur-based electrodes is investigated by operando acoustic emission (AE). The AE response of S-based electrodes using two different binders, polyvinylidene difluoride (PVdF) and carboxymethylcellulose (CMC), as well as two different current collectors, usual aluminum foil and porous non-woven carbon paper (CP), are compared. In all cases, AE signals are mainly detected during the 1st plateau of the 1st discharge, related to the initial dissolution of elemental sulfur into the electrolyte, causing a collapse of the electrode network. At the end of charge, the formation of micrometric sulfur on the surface of the electrode can be acoustically detected, in particular in the case of the CMC/Al formulation, where signals are also detected during subsequent cycles. This is believed to be a result of the good adhesion of CMC-based electrode to the current collector, which allows acoustic waves to propagate through the electrode to the AE sensor more easily. However, with CP current collector, no AE activity is detected upon charge, reflecting a lower mechanical stress attributed to a more homogeneous growth of the S particles in the electrode. It is also noted that inefficient electrode formulation/elaboration can be detected via AE, as AE signals are emitted at the end of the discharge when the cell polarizes more than usually observed. The use of CP as a current collector greatly improves the electrochemical performance of the cells, especially when combined with the better adhesion/cohesion strengths of CMC binder, reaching an initial capacity of 1180 mAh g−1 (∼4.5 mAh cm−2) stabilizing around 860 mAh g−1 after 50 cycles. Highlights • Sulfur electrodes of different compositions are studied by operando acoustic emission. • AE signals are mainly detected during the initial dissolution of sulfur particles. • The formation of micrometric sulfur upon charge are also acoustically detected. • The formation of Li 2 S is acoustically emissive only with highly polarized electrodes. [ABSTRACT FROM AUTHOR]

Abstract In our study, TiC-TiO 2 /S composite was successfully prepared with a simple and effective method. For this special micro-mesoporous structure, TiC-TiO 2 can be used as an efficient sulfur storing material, and also restrain the volume expansion of sulfur to a certain degree for its suitable specific surface area. TiO 2 and TiC can suppress the diffusion of polysulfides due to their strong interaction with polysulfides. At the same time, TiC also can remedy the nonconductive defect of sulfur for its good conductivity. With the help of above advantages, the TiC-TiO 2 /S cathode delivers an initial discharge specific capacity of 1218 mAh g−1 at 1 C (1 C = 1675 mA g−1) with the sulfur loading of 1.5 mg cm−2. And when cycles at 0.5 C, a stable capacity of 714 mAh g−1 can be maintained after 500 cycles accompanied with the sulfur loading of 1.1 mg cm−2. Graphical abstract Here a simple and effective method was designed to prepare TiC-TiO 2 /S composite to achieve the aim that stabilize and prolong the life of Li-S batteries with the synergistic effect by TiC and TiO 2. When served as the cathode for Li-S batteries, the TiC-TiO 2 composite exhibited strong chemisorption to lithium polysulfides, and the cell with TiC-TiO 2 /S cathode delivered improved long life cyclability. Image 1 Highlights • The strong chemical trapping of TiC-TiO 2 /S to polysulfides minimizes the loss of polysulfides. • The cross-linked pores in TiC-TiO 2 /S can provide high efficiency for ion transport. • This host endows higher sulfur contents and better utilization of sulfur in the composite. • TiC-TiO 2 /S composite exhibits excellent electrochemical performances in Li-S batteries. [ABSTRACT FROM AUTHOR]

Abstract A Si 3 N 4 /graphene composite is designed as an interlayer for a carbon-nanotubes/sulfur cathode to improve electrochemical performance of lithium-sulfur batteries. In the interlayer, Si 3 N 4 nanoparticles suppress the migration of the dissolved polysulfides and graphene sheets construct a 3-dimensional charge-transfer network. The carbon-nanotubes/sulfur@Si 3 N 4 /graphene cathode delivers an initial discharge capacity of 1334.7 mAh g−1 at 0.1 C and retains a capacity as high as 745.8 mAh g−1 after 200 cycles, with a capacity fade ratio of 0.22% per cycle. The cathode shows good cycling life, delivering a discharge capacity of 413.3 mAh g−1 for 1 C after 1000 cycles. According to the results of density functional theory calculation, the anchoring of the Si 3 N 4 /graphene interlayer to lithium polysulfide can be attributed to a coefficient chemical binding of Li-N and Si-S bonds generating from electronic conjugation effect between the Si 3 N 4 supercell surface and the polysulfides. Generally, the improvement in electrochemical performance originates from the enhancements in Li+ diffusion coefficient and charge transfer, and from the restraining of the shuttle effect of the dissolved lithium polysulfide as a result of the Si 3 N 4 /graphene interlayer. Graphical abstract Image 1 Highlights • Si 3 N 4 /graphene interlayer anchors polysulfide via physical and chemical interactions. • Si 3 N 4 /graphene interlayer constructs a 3D network of charge transfer. • CNTs/S@Si 3 N 4 /graphene cathode exhibits ultralong cycling life. [ABSTRACT FROM AUTHOR]

Abstract Lithium-sulfur (Li-S) batteries are widely recognized as the most promising next generation energy storage system owing to the incredibly high theoretical energy density and specific capacity. Nevertheless, the practical application of Li-S batteries is hindered by the inevitable "shuttle effect" of the soluble lithium polysulfide, which leads to fast capacity degradation, low coulombic efficiency and severe self-discharge. To address these issues, we propose an ultralight carbon flakes modified separator (CFs@PP) that improves the conductivity and works as an effective polysulfide barrier for high-performance Li-S batteries. The CFs are easily obtained by the direct carbonization of sodium citrate, making it possible for large scale manufacture. With the CFs@PP separator employed, the Li-S battery delivers an initial discharge capacity of 1063 mAh g−1 and retains 683 mAh g−1 after 500 cycles at 0.5C with a low capacity decay rate of 0.071% per cycle. Moreover, great rate performance and small self-discharge are also acquired with the CFs@PP separator applied. The facile preparation of the CFs and the superior electrochemical performance of the CFs@PP separator may promote the commercialization of Li-S batteries. Graphical abstract Image 1 Highlights • Carbon flakes (CFs) are simply synthesized by the direct carbonization of sodium citrate. • The mass loading of the ultralight CFs coating on the PP separator is only 0.16 mg cm−2. • Conductivity and wettability of the separator are greatly enhanced due to the CFs coating. • CFs coating layer acts as an upper current collector and a polysulfide barrier simultaneously. • Li-S battery with the CFs@PP separator retains 683 mAh g−1 after 500 cycles at 0.5 C. [ABSTRACT FROM AUTHOR]

Abstract Lithium-sulfur batteries were investigated as promising next-generation energy storage devices owing to their high capacity in comparison to conventional lithium-ion batteries. Nevertheless, the serious shuttle effect and sluggish redox kinetics originated from dissolution of polysulfides and insulating property of sulfur and lithium sulfide, restricted their practical applications. To overcome these stubborn problems, a robust and environment-friendly biomass carbon fiber interlayer anchored with uniformly-distributed SiO 2 nanoparticles was demonstrated. Benefiting from the excellent conductivity of carbon fiber, together with the stable chemical adsorption of SiO 2 for soluble polysulfides, this low-cost and lightweight interlayer could not only remarkably enhance sulfur utilization, but also efficiently capture the polysulfides by chemical entrapment strategies. With this biomass carbon fiber@SiO 2 interlayer, the batteries delivered a high reversible capacity of 1352.8 mAh g−1 at 0.1 C and enhanced capacity of 618.4 mAh g−1 after 500 cycles at 1.0 C. Even up to 4.2 mg cm−2 sulfur loading, high cycling stability was also achieved by this interlayer. We believe this robust and low-cost interlayer has a great potential for practical applications of Li–S batteries. [ABSTRACT FROM AUTHOR]

Abstract Li-S batteries have shown great potential for next generation energy storage due to the high theoretical specific capacity and low cost. However, the issues of shuttle effect of polysulfide, poor conductivity of sulfur, and volume expansion during lithiation/delithiation seriously restrict the development of Li-S batteries. Inspired by the strong chemical absorption between metal oxides and polysulfides, a jujube pit like Fe 3 O 4 /C composite derived from iron-based metal-organic framework (Fe-MOF) are applied as efficient sulfur host in Li-S batteries in this work. Benefitting from the strong chemical bond between iron ion and polysulfides, as well as the interaction between oxygen anion and lithium ion, the Fe 3 O 4 /C composite can immobilize the sulfur and inhibit the diffusion of polysulfides efficiently. In addition, the carbon component not only improves the electrical conductivity, but also serves as buffer layer to accommodate the volume variation upon charging/discharging. Consequently, such Fe 3 O 4 /C/S cathode shows a high initial specific capacity of 1324 mAh/g at a current density of 0.05 C and could retain a specific capacity of 642 mAh/g after 300 cycles at current density of 1 C, corresponding to a low fading rate of 0.072% per cycle. Highlights • The jujube pit like Fe 3 O 4 /C composite would anchor polysulfides through both physical and chemical adsorption. • The hollow structure of the Fe 3 O 4 /C composites would furnish adequate space for sulfur reserve as well as provide ample interspace for the volume expansion during lithiation. • The Fe 3 O 4 /C contains abundant carbon improving the conductivity of the material. [ABSTRACT FROM AUTHOR]

Lithium-sulfur batteries (LSBs) have great potential for development in next-generation storage devices, which are severely hampered by the shuttle effect of polysulfides and poor sulfur conductivity. To surmount these problems, a high specific carbon aerogel material (NiOQDs/HCA) modified by NiO quantum dots is constructed in this paper as a sulfur host, NiO quantum dots (NiOQDs) attached to porous carbon substrates provide active sites for the chemisorption and transformation of polysulfides. Meanwhile, HCA makes the entire substrate form a complete conductive network, increasing the speed of electron transport. Based on the above advantages, the LSBs with NiOQDs/HCA as the cathode still has a reversible capacity of 440 mA h g −1 after 900 cycles at 0.5 C and a capacity decay rate of 0.052% after 1000 cycles at 1.0 C. The discharge-specific capacity at 0.1 C also reaches up to 818 mA h g −1 at a high sulfur load of 3.3 mg cm−2, with a capacity retention rate of 66% after 100 cycles. [ABSTRACT FROM AUTHOR]

The polysulfides shuttle and the uncontrolled dendrite growth remain the biggest roadblocks to the extensive application of lithium-sulfur batteries (LSBs). Herein, we propose heterogeneous Al 2 O 3 -AlN nanosheets that rooted on carbon nanofiber film as bifunctional hosts for these troubles, which are prepared by the facile ammonification of two-dimension metal-organic framework MIL-101(Al). As the sulfur host, the Al 2 O 3 -AlN nanosheets exhibit a strong synergistic effect of physicochemical anchoring and outstanding electrocatalysis on polysulfides, which is strengthened by the superiorities of heterostructure. In the meantime, the excellent conductivity and fully exposed Al, N lithiophilic sites guarantee a fast and homogeneous Li deposition, thus suppressing the dendritic growth. Accordingly, with the assistance of these distinctive heterogeneous nanosheets, LSBs provide a striking capacity of 730 mAh g−1 and an outstanding cycling stability with a narrow decay of 0.025% per cycle for 1000 cycles under 5 C, and also excellent cycle and rate properties at high sulfur loadings with a reduced electrolyte. This work offers new viewpoints of heterostructures as both cathode and anode materials for advanced LSBs. [ABSTRACT FROM AUTHOR]

• Carbon nanotubes were branched onto steam activated reduced graphene oxide. • Hierarchically structured sGNC offered electronic pathways and low mechanical stress. • The redox kinetics of lithium polysulfides was facilitated. • sGNC-S cathode achieved excellent high-rate capability and cycling performance. Hierarchically structured carbon architecture is considered as a promising candidate of lithium-sulfur battery cathodes owing to its large surface area and percolated electron/ion pathways. However, the synthesis of hierarchical carbonaceous materials requires complicated processes and the resulting materials usually provide weak physical interactions to capture lithium polysulfides, which significantly hinders the performance of lithium-sulfur batteries. In order to resolve these problems, we have demonstrated a facile microwave-assisted synthesis of carbon nanotubes branches grown onto steam-activated reduced graphene oxide (sGNC) to simultaneously synthesize hierarchical carbon structure and nickel nanoparticles for the inhibition of lithium polysulfides shuttle. The hierarchical structure of carbon nanotubes branched from anchored nickel nanoparticle seeds, and uniform distribution of sulfur is attributed to the facilitated electron/ion diffusion pathway, sufficient space to impregnate sulfur, and the lithium polysulfides capturing sites. Accordingly, sGNC-sulfur (sGNC-S) cathode achieved the initial discharge capacity of 829.3 mAh g − 1 at 0.5 C, which is much higher than 531.8 mAh g − 1 of steam-activated reduced graphene oxide-sulfur (sG-S) cathode. When the current rates increased from 0.1 C to 1 C, the capacity retention of the sGNC-S cathode was 67.0%, greater than 62.5% of the sG-S cathode. The decay rate of 0.155%/cycle with the Coulombic efficiency of almost 100% over 200 cycles of the sGNC-S cathode was greater than 0.219%/cycle of the sG-S cathode, originating from facile kinetics and restricted polysulfide dissolution. [Display omitted] [ABSTRACT FROM AUTHOR]

A rate-dependent nucleation theory is developed to analyze the dependence of the capacity of lithium-sulfur (Li-S) batteries on discharge rates. The theory is based on expressing the nucleation rate of solid products in terms of the surface oversaturation of the precipitating species and rewriting the classical Kolmogorov-Avrami model in the form of a differential system of equations. By coupling this system of equations with the multicomponent transport equations we are able to explain qualitatively well the decrease of the specific capacity with increasing discharge rates and the characteristics of the discharge curves under variable discharge currents in Li-S batteries. Special attention is given to accurately determine the values of model parameters from experimental data, including the solubility constants of the solid products and the mobilities and diffusivities of the ions. The anodes of the batteries used in our analysis were made using Li foils and the cathodes were fabricated using freestanding carbon nanotube foams, on which solid sulfur was uniformly distributed to maximize the dissolution rate. The experimental data combined with the theoretical analysis show that the capacity limitation in our batteries is due to surface passivation by the final reaction products. In order to increase the specific capacity of Li-S batteries under normal discharge rates we conclude that it is better to avoid the solid precipitation of intermediate lithium polysulfides (LiPS) by using electrolytes with a high solubility of LiPS. In addition, it is better to use catalyst particles in the cathode that would promote the nucleation rate at specified locations. The number of catalyst particles should not be too small to avoid electrolyte oversaturation or too large to avoid the rapid passivation of the carbon surface with solid products. [ABSTRACT FROM AUTHOR]

To suppress the dissolution of polysulfides and maintain a high sulfur utilization of lithium-sulfur (Li-S) batteries, double-shelled hollow carbon sphere with a microporous outer carbon shell ( m -DSHCS) is designed and fabricated as an efficient sulfur host. Specially, the m -DSHCS with an outer microporous carbon shell and foam-like conductive carbon links is an ideal sulfur host. The foam-like carbon links between the shells and inside the hollow structure can not only provide enough space for sulfur loading and volume expansion, but also facilitate fast electron transfer and Li + diffusion. Additionally, the outer microporous carbon shell can also serve as an efficient physical barrier to suppress the diffusion of sulfur species derived from inner hollow carbon sphere. When used as cathode material for Li-S batteries, the m -DSHCS/S electrode delivered an outstanding reversible capacities (capacity fading of 0.16% per cycle at 0.2C after 200 cycles and 0.07% per cycle at 1C after 1000 cycles) and superior high-rate capabilities (900 mAh g −1 at 1C and 800 mAh g −1 at 2C) than that of graphene wrapped hollow carbon sphere/sulfur (rGO@HCS/S) electrode (100 cycles at 0.2C with 0.54% capacity fading per cycle, 670 mAh g −1 at 1C and 540 mAh g −1 at 2C). [ABSTRACT FROM AUTHOR]

The ultrafine Cr 2 O 3 modified carbon aerogel (Cr-CA) composites were successfully synthesized through in situ and sol-gel method as cathode material for lithium sulfur battery. The chromium doping remarkably controls structure, decreases carbon sphere size and promotes network interconnect. The nano Cr-CA composites with large pore volume and high specific surface present stronger adsorption ability and effectively immobilize polysulfides. The Cr-CA/S composite cathodes display excellent electrochemical performance with high specific capacity and long cycling stability. Especially, the Cr2-CA/S cathode with 65.9 wt% of sulfur delivers initial specific capacity of 1343 and 987 mAh g −1 at the rate of 0.2 C and 2 C, respectively. It exhibits the outstanding long-term cyclic stability with the discharge capacity of 873 mAh g −1  at 0.5 C for the 300th cycle. The excellent performance is mainly attributed to special anchoring role of Cr 2 O 3 to polysulfides and its catalytic effect for redox reaction process. Furthermore, the adsorb energy between polysulfides and Cr 2 O 3 and theoretic analysis by DFT definitely reveals and supports immobilizing and catalytic mechanism. [ABSTRACT FROM AUTHOR]

Lithium-sulfur battery is one of the most prospective chemistries in secondary energy storage field due to its high energy density and theoretical capacity, but the rapid decay of capacity is still a huge challenge. Herein, we reported an ingenious design of nitrogen doped carbon nanofibers with honeycomb-like porous structure for the cathode of lithium-sulfur battery which can effectively suppress the “shuttle effect”. The special porous material with three dimensional (3D) interconnected pore structure is beneficial to enhance the adsorption of lithium polysulfides and accommodate the volume expansion of active materials. In addition, the doped nitrogen can not only improve the conductivity of cathode, but also form a strong interfacial interaction to trap lithium polysulfides. Therefore, the battery with the cathode exhibited a high reversible discharge capacity of 1093.9 mAh g −1 and good capacity retention of 76.0% after 300 cycles at 0.5C rate. After acidification, the cycling performance of the cathode could achieve upon 300 cycles with a very low decay rate of 0.027% at 0.5C. [ABSTRACT FROM AUTHOR]

Constructing 3D heteroatom-doped carbon framework from sp 2 -hybridized nanocarbon (graphene) and sp 3 -hybridized porous carbon (activated carbon) has been considered as an effective method to achieve excellent performance in energy conversion and storage due to the synergistic effect between building blocks. Herein, a facile assembly of graphene oxide and porous carbon is reported to fabricate the inherent nitrogen-doped porous carbon and graphene composited nanostructures. When used as the sulfur scaffold for lithium sulfur batteries, the materials suggest outstanding electrochemical properties, including a high reversible capacity (1372 mAh g −1 at 0.1C), excellent rate performance (451 mAh g −1 at 3C) and cycling stability (579 mAh g −1 at 1C after 500 cycles). The enhancement in electrochemical properties can be ascribed to the 3D hierarchical porous structure of the carbon hybrid, in which, besides, the inherent doping of nitrogen can generate homogeneous active sites and defects that can effectively improve the interfacial adsorption. Thus, the simple strategy of pyrolysis and self assembly of graphene oxide and porous carbon provided in this work opens a new avenue for combining different dimensional nanocarbons to construct nitrogen-doped, multi-dimensional carbon architecture for high performance lithium sulfur batteries. [ABSTRACT FROM AUTHOR]

Although lithium-sulfur batteries possess five-fold higher theoretical capacity than the state-of-the-art lithium-ion batteries, the migration of polysulfide between the electrodes remains as a problem area. In order to overcome this issue, numerous strategies have been adopted. Herein, we introduce a novel 1,3,5 benzene tricarboxylate-manganese (Mn-BTC) metal organic framework (MOF) coated-Celgard (2320) separator which acts as permselective in a Li-S cell. The Li-S cell with coated membrane exhibited higher discharge capacity than the uncoated one. The diffusion of polysulfides is successfully blocked by the separator due to the repulsive ionic forces provided by the COO that is present in the periphery of Mn-BTC MOF which was confirmed by XPS and XRD analyses. [ABSTRACT FROM AUTHOR]

A zeolitic imidazolate framework (ZIF)/graphene composite was prepared by the solvothermal reaction using different concentrations of graphene oxide to investigate the effect of graphene addition on the electroactivity of the composite. Field emission scanning electron microscopy (FE-SEM), field emission transmission electron microscopy (FE-TEM), and X-ray diffraction (XRD) were conducted to determine the morphology and micro-structure of the composite. Electrochemical characterizations were measured using the CR2016 type coin cell test. Based on the electrochemical properties and structural characteristics of the composite, the roles and effects of graphene in ZIF/graphene composite were studied. The concentration of graphene oxide used during the synthesis process affect the initial specific capacity and cycle performance of the composite. [ABSTRACT FROM AUTHOR]

Composite sulfur electrodes are prepared by high-temperature mechanical milling (443 K) for use in all-solid-state lithium–sulfur batteries, and their structures and electrochemical properties are investigated. Composites comprising sulfur, acetylene black, and a Li 3.25 Ge 0.25 P 0.75 S 4 solid electrolyte are fabricated by planetary ball milling using a temperature-controlled system. The composite electrode exhibits a high discharge capacity of greater than 1200 mAh g −1 and a good cycle capability. As a result of high-temperature milling, composites are formed, incorporating novel structural units from the reaction between sulfur and the solid electrolyte, along with their intrinsic characteristics. Hence, high-temperature milling demonstrates promise for the fabrication of a composite electrode exhibiting high, reversible electrochemical activities for use in an all-solid-state lithium–sulfur battery. [ABSTRACT FROM AUTHOR]

Lithium metal anodes covered by a thin (6–10 Å) solid electrolyte interphase (SEI) film at its initial nucleation stage modeled as a single component (Li 2 O, LiF, Li 2 SO 4 , and Li 3 N) are examined with density functional theory and ab initio molecular dynamics simulations. The combined metal anode/SEI surfaces are exposed to an electrolyte containing salt, solvent, and lithium polysulfides. The polysulfide species are found to be easily reduced by the metal slab, even in the presence of the model SEI films. Although the chemical nature of the film and geometry of the exposed facet induces different decomposition kinetics, the reaction mechanisms are shown to be similar for the various SEI models, and end with the formation of Li 2 S on the surface of the anode or inside the SEI film. The density of states of the films at this nascent stage of SEI formation in contact with the Li metal surface are very different than those of the bulk crystals, usually showing new intermediate states between the metal and conduction bands, which suggests a change to an electronically conductive character that favors continuous reactivity. [ABSTRACT FROM AUTHOR]

Lithium-sulfur (Li-S) battery is considered as the next-generation of cost-efficient rechargeable battery systems to fulfill clean energy transportation systems due to its remarkable high theoretical energy density. Nevertheless, capacity fading and poor cycling stability mostly caused by polysulfide shuttle and active sulfur materials loss play an obstacle role on large-scale viable commercialization. In this paper, a flower-like hierarchical carbon sphere (FHCS) is prepared and coated on commercialized PP separator for polysulfide trapper. This carbon sphere with multi-scale pores strongly absorbs the polysulfide, further tremendously enhances the cycling performances, and the conducted carbon sphere also acts as current collector for improving the conductivity of active materials. The results show the cell demonstrates an initial discharge specific capacity of up to 1427 mAh g −1 at 0.2C, and high reversible capacity of 730 mAh g −1 with degradation rate of only 0.061% per cycle after 500 cycles at 0.5C. [ABSTRACT FROM AUTHOR]

A dual functional interlayer consisted of composited two-dimensional MoS 2 and graphene has been developed as an efficient polysulfide barrier for lithium-sulfur batteries (LSBs). With such a configuration, LSBs show a superior rate capacity and improved cycling capacity. The excellent electrochemical performance can be attributed to the strong bonding interactions between the MoS 2 /graphene interlayer and the formed lithium polysulfides (LiPSs) as well as the good electrical conductivity of the MoS 2 /graphene composite. The MoS 2 /graphene interlayer can physically block LiPSs by the graphene nanosheets and chemically suppress the dissolution of LiPSs by the polar MoS 2 nanoflowers. Such a dual functional interlayer further provides a good contact with the surface of the sulfur cathode, acts as an upper current collector and greatly improves the sulfur utilization and the rate capability of LSBs. [ABSTRACT FROM AUTHOR]

Lithium-sulfur (Li-S) batteries have been recognized as one of the promising next-generation energy storage devices owing to their high energy density, low cost and eco-friendliness. As for cathode’s performance, the main challenges for developing highly-efficient and long-life Li-S batteries are to retard the polysulfides diffusion into electrolyte and the reaction with metallic lithium (Li). Especially, the safety issues, derived from metallic Li in anode, must be overcome. Herein, we fabricated lithium sulfide@porous carbon composites (Li 2 S@PC) by an in-situ reaction between the lithium sulfate (Li 2 SO 4 ) and the pyrolytic carbon from glucose. The nanosized Li 2 S particles were uniformly distributed in the carbon matrix, which not only significantly improve electronic conductivity of the electrode but also effectively trap the dissolved polysulfides. Furthermore, on the basis of the graphite’s electrochemical features in ether-based electrolyte, we assembled graphite-Li 2 S@PC full cells using the obtained Li 2 S@PC composites as the cathode, graphite as the anode and the DOL/DME with LiNO 3 additive as the electrolyte. A unique strategy was proposed to activate the full-cells in descending order using constant voltage and current to charge the cut-off voltage. This Li-S full cell exhibits stable cycling performance at 0.5 C over 100 cycles. Because graphite-Li 2 S batteries are suitable to the lithium-ion batteries industry, our preliminary results here will shed a new light on the cell design and industrial production. [ABSTRACT FROM AUTHOR]

Improving the conversion efficiency of lithium polysulfides (LiPSs) within the interlayer plays a significant role in inhibiting the shuttle effect of polysulfides for lithium-sulfur (Li-S) batteries, and this can be addressed by constructing highly exposed catalytic active sites. Herein, a feather-like interlayer material featured with highly exposed active sites is prepared by combining electrospinning technology and chemical vapor deposition. In the interlayer design, the growth of carbon nanotubes (CNTs) on the nitrogen-doped carbon fiber (N CF) surface greatly exposes the active Co and N-dopant adsorption-catalytic sites and forms a feather-like Co/CNT@N CF composite. The feather-like structure design endows the interlayer with good blockage effect for LiPSs shuttling. Meanwhile, the abundant active catalytic sites can effectively promote the conversion of polysulfides, and thus further suppress the shuttle of LiPSs. The cell with Co/CNT@N CF interlayer achieves excellent discharge performance (901.5 mAh g −1) with low capacity decay (0.025% per cycle) after 500 cycles at 1 C. Moreover, the cell exhibits a discharge capacity of 809 mAh g −1 at 5 C and an areal capacity of 5.05 mAh cm−2 under a sulfur loading of 6.9 mg cm−2. This work offers a facile interlayer design from the perspective of high active sites exposure in Li-S cells. [ABSTRACT FROM AUTHOR]

Poly (3, 4-ethyleendioxythiophene) (PEDOT) coated titanium dioxide (TiO 2 ) nanoparticles were prepared through a soft chemistry approach-assisted in situ synthesis route. The as synthesized PEDOT/TiO 2 nanocomposites (NCs) are characterized by XRD, Raman, BET, XPS, SEM, TEM and EDX analysis/elemental mapping. The formation mechanism of PEDOT/TiO 2 NCs is also illustrated. The uniformly TiO 2 nanoparticles dispersed in PEDOT matrix improving the electrochemical performance of the ternary PEDOT/TiO 2 /sulfur composite, which exhibits higher reversible capacity and better rate capability compared with the PEDOT/S and TiO 2 /S composites. The reversible capacity of PEDOT/TiO 2 NCs can be up to 1110 mAh g −1 and was retained 532.1 mAh g −1 after 500 charge-discharge cycles at the rate of 1C, which confirms the good cycling behavior. The superior electrochemical performance of the PEDOT/TiO 2 NCs could be attributed to the uniform conducting polymer layer and improving the electrical conductivity of TiO 2 , the lower charge-transfer resistance and larger lithium ion diffusion coefficient. [ABSTRACT FROM AUTHOR]

Electrolyte choice is an important decision on the quest for higher-energy batteries. Besides general guidelines on the required properties of an electrolyte suitable for use in lithium–sulfur batteries, the influence of more specific physicochemical properties on its characteristics is not well understood. For this purpose, binary mixtures based on the [DEME][TFSI] and dioxolane electrolyte system for lithium–sulfur batteries was investigated in this work. Selected physicochemical properties were determined for different mixtures of solvents and lithium salt concentrations. All the electrolytes prepared were also tested in the lithium–sulfur battery system. The capacity, Coulombic efficiency, overpotentials and impedance spectra were analyzed and a connection between them and the determined electrolyte properties elucidated. We show that the electrolyte's conductivity does not have a direct connection to any of the battery system properties measured. The highest specific capacities were obtained with batteries compromising 1.0 M LiTFSI and the highest ratio of dioxolane in the binary solvent mixture. On the other hand, the best Coulombic efficiencies were obtained with batteries having high ratios of ionic liquid. Resistance and overpotential are connected parameters and are a function of the ionic liquid content. None of the monitored parameters prevail, since the best electrochemical performance in terms of specific capacity and stability was obtained with the 1.0 M LiTFSI in X[DEME][TFSI] = 0.199 electrolyte. [ABSTRACT FROM AUTHOR]

Although the cathode of lithium-sulfur (Li-S) batteries has a theoretical specific capacity of 1,672 mAh g −1 , its practical capacity is much smaller than this value and depends on the electrolyte/sulfur ratio. The operation of Li-S batteries under lean electrolyte conditions can be challenging, especially in the case when the solubility of lithium polysulfide (LiPS) sets an upper bound for polysulfide dissolution. In this work, specially designed cathode structures and electrolyte configurations were built in order to analyze the effects of LiPS solubility on cell capacity. Two reaction pathways involving the reduction of LiPS in liquid and solid phase are proposed and analyzed. We show that at discharge rates above 0.4 mA cm −2 the reaction in the liquid phase dominates the discharge process. Once the electrolyte becomes saturated, the solid phase LiPS cannot be further reduced and does not contribute to the capacity of the cells. This phenomenon prevents Li-S batteries from achieving their high theoretical specific capacity. Finally, the specific energy of the Li-S cell is reevaluated and discussed considering the limitation imposed by LiPS solubility. [ABSTRACT FROM AUTHOR]

Experimental data elucidating the time-dependent composition of the electrolyte within a standard lithium-sulfur battery cell are presented. The electrolyte employed consisted of a solution of LiTFSI in a 1:1 mixture of dimethoxyethane and dioxolane, including nitrate salts. In order to track the decomposition reactions of the electrolyte components, the cells were run for a fixed number of cycles, after which they were opened and the remaining electrolyte was extracted with an excess amount of 1,4-dioxane. The amount of each of the components (namely LiTFSI, dimethoxyethane and dioxolane) within these mixtures was determined by means of gas chromatography and 19 F-NMR. It was found that the amount of electrolyte accessible to extraction remains relatively constant during the first 25 cycles, but then continuously decreases within the subsequent 40 investigated cycles. The ratio of the organic constituents of the electrolyte does not change considerably, which means there is no preferred decomposition pathway for either of the two components dioxolane and dimethoxyethane, respectively. These results demonstrate that the capacity fading of a lithium-sulfur cell coincides with the loss of the electrolyte within the cell and there is a strong correlation between the failure of a lithium-sulfur cell and the decomposition reactions of its electrolyte. These findings are supported by a detailed analysis of the gaseous decomposition products after specified cycle numbers. Realistic pouch bag cells are used as test vehicles. Such cells do resemble industrially viable, commercial cells much closer as e.g. coin-type cells: Much lower electrolyte/active mass ratios can be used, thus allowing for a more realistic picture of the failure mechanisms involved. [ABSTRACT FROM AUTHOR]

The micromorphology characteristics of carbon host materials play an important role in stabilizing the structure and restricting the polysulphides in lithium-sulfur batteries. In our work, four kinds of biomass carbon materials derived from mushroom have been synthesized by a facile activation method using H 3 PO 4 , K 2 CO 3 , KOH and ZnCl 2 as activators and the correlation between micromorphology characteristics and electrochemical properties in these biomass carbon materials have been systematically investigated. The electrochemical performance of lithium sulfur batteries is highly dependent on pore size, pore volume and surface area of activated carbon matrixes. The H 3 PO 4 -, K 2 CO 3 -, KOH- and ZnCl 2 - activated carbon materials exhibit the fluffy, dense, anomalous and molten morphologies, respectively, which induce the initial discharge capacities of 1357, 943, 1013 and 860 mAh g −1 in their S/C composites; and their capacity retentions at 0.1C are 54%, 37%, 38% and 35% after experiencing 100 cycles, respectively. These may be attributed to the combination effects of surface area and pore size/volume in their carbon matrixes. Our study show that activator can effectively tailor pore size, pore volume and surface area of biomass carbon host materials and thus improve electrochemical performance of S/C composites for lithium sulfur batteries. [ABSTRACT FROM AUTHOR]

A boron-doped unzipped carbon nanotubes/sulfur (BUCNTs/S-1) composite was first prepared via a one-pot facile hydrothermal process by using oxidized unzipped carbon nanotubes (O-UCNTs), boron acid and element sulfur as the carbon precursor, B and S sources, respectively. The morphology, structure and composition of the BUCNTs/S-1 composite were characterized and the effect of B doping and sulfur loading were also investigated in details. The results demonstrated that the participation of B atom and sulfur loading achieved by hydrothermal method endowed the BUCNTs host with enhanced conductivity, promoted sulfur dispersibility and strengthened adsorbability for the sulfur species. The electrochemical performances of the BUCNTs/S-1 used as lithium-sulfur cathodes were then studied. Benefitting from all the merits, the BUCNTs/S-1 cathode delivered a high initial capacity of ∼1251 mAh/g at 0.2C, retaining as high as ∼750 mAh/g after 400 cycles, displaying significantly enhanced cycling stability. Hence, this work provides a facile method to fabricate a promising sulfur cathode candidate for high performance lithium-sulfur batteries. [ABSTRACT FROM AUTHOR]

Lithium-sulfur (Li-S) batteries are attractive and promising energy storage devices due to the large theoretical energy density (2600 Wh kg −1 ) and natural abundance of sulfur. However, several intrinsic drawbacks hamper broader application, for example, the poor conductivity, serious shuttle effect, as well as large volume expansion. In this work, hierarchical porous carbon materials (HPCMs) are prepared from natural bamboo leaves by carbonization and HF etching. The biogenetic SiO 2 nanoparticles (NPs) with abundant mesopores in the carbonized bamboo leaves are etched by HF producing hierarchical meso-/microporous carbon that can be exploited to load sulfur on the nanoscale. The HPCMs/S composite loaded with 70.26 wt. % sulfur shows a high initial discharge capacity of 1487 mAh g −1 at a rate of 0.05C (1C = 1675 mA g −1 ) and the capacity of 707 mAh g −1 is maintained at 1C for over 200 cycles with a capacity decay of only 0.014% per cycle. When the current density is increased from 0.2 to 4C, 62.3% of the capacity is retained, suggesting good rate capability and promising application to advanced Li-S batteries. [ABSTRACT FROM AUTHOR]

There is an ever-increasing interest in utilization of natural biomass for rational design and fabrication of advanced carbon materials towards energy-related storage/conversion application. In this work, we successfully prepared an in-situ nitrogen-doped porous carbon nanosheet (NPCN) materials derived from renewable silk cocoon via a facile simultaneous activation and carbonization approach using metal salt FeCl 3 and ZnCl 2 as chemical activating agent. The as-prepared carbon materials were fully characterized to determine their morphology and structure features, and it was found that the obtained NPCN has a unique interconnected sheet-like morphology and a hierarchically porous structure with a relatively high specific surface area of 1540 m 2 g −1 and a large pore volume of 1.85 cm 3 g −1 . Owing to the inherent nitrogen-containing functional groups existing in the silk cocoon, in-situ doping of nitrogen heteroatom can be realized by the carbonization treatment, which can efficiently boost the electrical conductivity of the porous carbon nanosheets. By employing the NPCP as a reservoir to impregnate sulfur for lithium-sulfur batteries, the resulting carbon/sulfur composite (NPCN/S) shows a remarkably improved rate performance and superior long-term cycling stability with an extremely low decay rate (0.1% per cycle) up to 300 cycles at a high rate of 2C (3350 mA g −1 ). What is more, a Coulombic efficiency of approximatively 100% is obtained. Taking into consideration various factors including sustainable development, low-cost carbon source, and facile mass production, this work shows a great scientific significance and promising prospect in scalable preparation of advanced carbon-based host matrix for the efficient immobilization of sulfur towards developing high performance lithium-sulfur batteries. [ABSTRACT FROM AUTHOR]

To limit the shuttle effect in lithium-sulfur batteries (LSBs), a porous carbon microsphere with high specific surface area is prepared as sulfur hosts with an additional TiO 2 coating on the exterior of the host. The average thickness of the coating is about 4.4 nm, but some areas are too thin to fully cover the sulfur. With the progress of the charging and discharging, sulfur inside the shell will spill out of the shell but confined on the surface. Cracks on the electrode surface did not increase significantly after long cycles. And no obvious damage to the spherical structure of the active material can be observed. Benefiting from high stability and strong adsorption of TiO 2 coating, the electrode shows a high initial capacity of 888.16 mA h g−1 at 0.5 C, and 443.63 mA h g−1 after 1000 cycles. Even at charge-discharge rate of 1 C, it also delivers a high initial capacity of 691.32 mA h g−1, and 369.25 mA h g−1 after 1000 cycles. [ABSTRACT FROM AUTHOR]

Although lithium-sulfur (Li-S) batteries have an unparalleled specific capacity, the notorious shuttle effect, and slow reaction kinetics severely inhibit their development. Herein, a composite composed of ZnSe nanoparticles with a nitrogen-doped (N-doped) carbon shell uniformly dispersed in reduced graphene oxide (ZnSe/NC@rGO) is designed as a separator modifier for Li-S batteries. The underlying mechanism of the ZnSe/NC@rGO modified separator is confirmed by both systemic electrochemical characterization and density functional theory (DFT) calculations. Graphene as a highly conductive skeleton promotes electrical conductivity, while N-doping provides additional adsorption sites for the immobilization of lithium polysulfides (LiPSs). Moreover, the polar ZnSe has good chemical adsorption capabilities for LiPSs and could lower the decomposition energy barrier of Li 2 S, which effectively facilitates the catalytic conversion of polysulfides. In addition, the separator modifier is beneficial to the uniform deposition of lithium. Thus, the delicate catalyst can effectively suppress the shuttle effect and accelerate the redox reaction kinetics during the charging and discharging processes. When used as a separator modifier of Li-S batteries, ZnSe/NC@rGO delivers enhanced electrochemical performance, including a high capacity (1057 mAh g–1 at 0.2 C after 100 cycles) and excellent rate performance of 685 mAh g–1 at 3 C. The negligible capacity decay per cycle within 900 cycles at 1 C is as low as 0.043%. These findings not only provide a feasible method for boosting the electrochemical performance of Li-S batteries but also reveal that transition metal selenides have potential in energy storage as electrocatalysts. [ABSTRACT FROM AUTHOR]

In this study, by using commercial melamine foam as a starting material, we report a facile method to prepare N-doped carbon framework loaded with graphene (NCF-G), in which graphene nanosheets are homogeneously coated on the N-doped carbon framework. After sulfur is infused into this composite, the electrode delivers an initial capacity of 1,359.7 mA h g −1 at 0.1C (1st cycle), and maintains a specific capacity of 629.3 mA h g −1 for 150 cycles at 0.5C for lithium-sulfur batteries. The improved electrochemical performances are attributed to the capping effect exerted by N-doping for polysulfides and high electrical conductivity of the carbon framework with highly conductive graphene. [ABSTRACT FROM AUTHOR]

Transition metal vanadium (V)-based oxides with various morphologies have been used in lithium-sulfur (Li-S) batteries to restrain the polysulfide shuttling because of their strong chemical interaction with polysulfides and the high catalytic activity toward the polysulfide transformation. Herein, hollow vanadium oxide spheres (VOOH) with several integrated merits are prepared and used to construct an interlayer between separator and cathode. The mesopore-abundant thin shells of VOOH are beneficial for the fast ion transport. Combined with nitrogen (N)-doped graphene sheets (NG), the as-obtained VOOH/NG interlayer allows fast electron/ion transport, finally enhancing polysulfide transformation kinetics. The Li-S batteries with the VOOH/NG exhibit a high initial discharge capacity (1441.1 mAh g−1 at 0.1C), low capacity decay rate (0.075% per cycle at 1C after 600 cycles), good rate capability, and high areal discharge capacity exceeding that of commerical lithium ion batteries. In addition, the real application of such VOOH-based interlayer is further demonstrated by the successful assembly and good performance of the corresponding pouch cells. [ABSTRACT FROM AUTHOR]