Sulfur Host For Lithium-sulfur Batteries Research Articles

Catalytic Mo2C decorated hollow mesoporous carbon spheres as sulfur host for lithium-sulfur batteries with high sulfur loading

Hybrid structures as sulfur host materials have been proven to be an effective way to improve the electrochemical property of lithium-sulfur (Li–S) batteries. However, how to construct hybrid nanomaterials with reasonable structure and composition remains a challenge. Herein, the Mo2C nanoparticles grown on the surface of hollow mesoporous carbon spheres (HMCS@Mo2C) are synthesized as an effective sulfur host for Li–S batteries with high sulfur loading. In this hybrid structure, the HMCS can guarantee high sulfur loading, high-speed electron/ion transport, and sufficient buffer for volume change, and the Mo2C nanoparticles as effective catalysts significantly accelerate the conversion of polysulfides. Consequently, the as-prepared HMCS@Mo2C–S cathode demonstrates superb cyclic stability with a capacity decay rate of 0.065% for 500 cycles at 1 ​C. Impressively, HMCS@Mo2C–S cathode with high areal sulfur loading of 5.4 ​mg ​cm−2 can deliver a high specific capacity of 451.2 mAh g−1 after 500 cycles at 0.5 ​C. In addition, the preparation of HMCS@Mo2C is simple, feasible, and low cost. It is hoped that this work will provide new insight into the rational design of sulfur host materials integrating reasonable structure with an effective catalyst for Li–S batteries with high sulfur loading.

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

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

Molten salts approach of metal-organic framework-derived nitrogen-doped porous carbon as sulfur host for lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries have attracted significant attention as next-generation energy storage systems owing to their high theoretical specific capacity (1675 mAh g−1) and energy density (2567 Wh kg−1). However, the low electrical conductivity of S and the dissolution of polysulfides in organic electrolytes pose significant challenges for their industrial applications. Herein, we report a facile, scalable, and solvent-free synthetic method based on metal–organic-framework (MOF) for synthesizing N-doped carbon-based materials with hierarchical porous structures and large specific surface areas (2297 m2 g−1) as efficient cathode hosts for Li-S batteries. The cathode materials were synthesized via solvent-free mixing, followed by the direct carbonization of adenine and tetracarboxylic acid with zinc acetate using the molten salt method. Zinc salt was employed as a template for mesopores as well as binding sites for other organic materials. The irregular surface morphology and N-doping of the resulting porous carbons act as physical barriers to confine polysulfides within the carbon matrix. The S-loaded cathode was stable and exhibited a discharge capacity of 555 mAh g−1 over 290 cycles at a current density of 0.5C, corresponding to the capacity retention of 63%. The facile modified MOF synthetic strategy, assisted by molten salt processing, holds promise for the synthesis of noble cathode materials for high-performance Li-S batteries.

Synergistic Effect between Monodisperse Fe3O4 Nanoparticles and Nitrogen-Doped Carbon Nanosheets to Promote Polysulfide Conversion in Lithium-Sulfur Batteries.

Effective fabrication of electrocatalysts active in anchoring and converting lithium polysulfides is critical for the manufacturing of high-performance lithium-sulfur batteries (LSBs). In this study, original Fe3O4 nanospheres with diameters close to 12 nm were finely dispersed over a porous nitrogen-doped carbon matrix by the freeze-drying method to produce a three-dimensional composite material (nano-Fe3O4/PNC) suitable for application as a sulfur host in LSBs. Nano-Fe3O4/PNC loaded with sulfur (S@nano-Fe3O4/PNC) was used as a cathode in a Li-S cell, whose initial discharge specific capacity reached 1256 mA h g-1 at a 0.1 C rate. After 100 charge-discharge cycles at a 0.2 C rate, the reversible capacity of S@nano-Fe3O4/PNC remained at 745 mA h g-1, demonstrating a capacity retention rate of 70%. Importantly, a high Coulombic efficiency of more than 99% was achieved, indicating effective inhibition of the polysulfides' "shuttle effect" by nano-Fe3O4/PNC. The use of electrolytes containing lithium nitrate further reduces the "shuttle effect" of polysulfides. This study demonstrates the synergistic effect between metal oxide nanoparticles and N-doped carbon, which plays an important role in promoting the adsorption and conversion of polysulfides in LSBs.

Preparation of Ti<sub>3</sub>C<sub>2</sub> nanowires with cross-linked network structure and its application in lithium-sulfur batteries

<p indent="0mm">Lithium-sulfur batteries are considered as one of the most promising next-generation energy storage devices due to their high energy density and low cost, but their development and application still face many challenges such as the shuttle effect of lithium polysulfide. Recently, a new type of two-dimensional material, MXene (e.g., Ti₃C₂), has attracted much attention. The high specific surface area, high electrical conductivity and polar surface of Ti₃C₂ make it an ideal sulfur host for lithium-sulfur batteries. However, two-dimensional Ti₃C₂ nanosheets (Ti₃C₂-NS) are easy to aggregate together, which reduces the contact area between them and sulfur, and results in the performance degradation of the sulfur electrode. In this work, Ti₃C₂ nanowires (Ti₃C₂-NW) with cross-linked structure are successfully synthesized by etching the exfoliated Ti₃C₂ nanosheets in NaOH solution. Subsequently, sulfur-loaded Ti₃C₂-NW (Ti₃C₂-NW@S) is prepared by the melt-impregnation method and used as the positive electrode material for lithium-sulfur batteries. Scanning electron microscope (SEM) and transmission electron microscope (TEM) images show that Ti₃C₂-NW is composed of cross-liked nanowires with a width of <sc>5–10 nm,</sc> and sulfur particles are successfully loaded in the cross-linked network structure of Ti₃C₂-NW. Moreover, the EDX element mapping images show that the elemental distribution of S is consistent with those of C, O and Ti, further confirming the high dispersion of sulfur particles in Ti₃C₂-NW. Subsequently, Ti₃C₂-NW is characterized by using nitrogen adsorption and desorption technique. The type IV isotherm indicates that Ti₃C₂-NW has a mesoporous structure and its specific surface area is <sc>124.6 m² g⁻¹.</sc> XPS analysis proves the interaction between Ti atoms on the surface of Ti₃C₂-NW and S atoms from sulfur particles because of the presence of Ti-S peak in the high-resolution Ti 2p and S 2p XPS spectra. The loading of sulfur in Ti₃C₂-NW@S (~71 wt%) is determined by thermogravimetric analysis (TGA). It is also found that the type of Ti₃C₂ precursor used for etching affects the structure of the product. Selecting the multilayer Ti₃C₂ particles as the Ti₃C₂ precursor for etching in NaOH solution can only obtain the composite of Ti₃C₂ nanowires and nanosheets (Ti₃C₂-NWS). For comparison, sulfur-loaded Ti₃C₂-NS (Ti₃C₂-NS@S) and sulfur-loaded Ti₃C₂-NWS (Ti₃C₂-NWS@S) are prepared and used as the positive electrode material for lithium-sulfur batteries. The cyclic voltammogram of Ti₃C₂-NW@S shows two reduction peaks and an oxidation peak, corresponding to lithiation of sulfur. Note that the potential difference of redox peak of Ti₃C₂-NW@S is smaller than that of Ti₃C₂-NWS@S, implying the smaller electrode polarization and faster redox reactions of sulfur within Ti₃C₂-NW. The electrochemical impedance spectroscopy (EIS) test results show that Ti₃C₂-NW@S has lower charge transfer resistance (<italic>R</italic>_ct = 7.35 Ω) than Ti₃C₂-NWS@S (<italic>R</italic>_ct = 28.38 Ω), also revealing the rapid reaction of sulfur with Li⁺ on Ti₃C₂-NW. Accordingly, compared to Ti₃C₂-NS@S and Ti₃C₂-NWS@S, Ti₃C₂-NW@S exhibits better electrochemical performance, such as a reversible capacity of <sc>658 mA h g⁻¹</sc> at <sc>0.2 C</sc> after 100 cycles, and a capacity of <sc>436 mA h g⁻¹</sc> at <sc>1 C</sc> after 300 cycles. The superior electrochemical performance of Ti₃C₂-NW@S is attributed to the large specific surface area and mesoporous structure of Ti₃C₂-NW@S, which effectively provide the space for high loading of sulfur and accommodate the volume expansion of sulfur during the lithiation process. Moreover, the large surface area of Ti₃C₂ nanowires is conducive to capturing the lithium polysulfide and thereby suppressing the shuttle effect of lithium polysulfides. Meanwhile, the cross-linked structure is also favorable to the diffusion of lithium ions. This study shows that modifying the morphology and structure of Ti₃C₂ can effectively improve its electrochemical performance as the sulfur host for lithium-sulfur batteries and expand its application in other energy fields.

Nitrogen-doped MoS2 as a catalytic sulfur host for lithium-sulfur batteries

Lithium-sulfur batteries (LSBs) are the leading candidates for the next-generation lithium-ion batteries because of their large energy densities and low price. However, LSBs have a critical problem in that specific capacity continuously decreases due to the shuttle effect, so it has not been commercialized. Herein, we propose an N-doped MoS2 composite (nMC) with the dual functions of a chemisorption host and a conversion catalyst to inhibit the shuttle effect and thus improve the scalability of LSBs. The nMC increases the chemisorption energy of lithium polysulfide and promotes electron transfer, resulting in improved cycle stability and electrochemical performance. In addition, it controls the redox kinetics of lithium polysulfides by acting as a catalyst of the cathode. The nMC cathode accelerates the reaction rates by reducing the activation energy barrier of the Li2Sn to Li2S conversion and inhibits the shuttle effect by rapidly reducing highly soluble Li2Sn. Consequently, we developed the N-doped MoS2 composite, a catalytic host material for LSBs, that provides high initial capacity, outstanding cycle stability, and fast charging ability as cathode materials of LSBs. Especially, LSBs based on S@nMC cathode demonstrate high cycle stability with a low-capacity decay rate of 0.025% per cycle after 1000 cycles.

A COF-coated MOF framework polysulfide barrier design for enhanced performance in lithium-sulfur batteries

The shuttle effect of lithium polysulfide (LiPS) and slow sulfur reaction kinetics is a key problem hindering the application of lithium-sulfur (Li-S) batteries. To address these problems, herein, a novel multifunctional sulfur cathode design strategy of coating microsporous covalent organic framework (COF) onto metal organic framework (MOF)-derived carbon/transition metal composite is developed. This strategy is proofed by coating a TpPa-1 COFs layer on the UIO-66-NH2-derived N-doped Co/Zr-NC, forming core-shell structured Co/Zr-NC@TpPa composite. The Co/Zr-NC core consists of Co nanoparticles and ZrO2 that offers effective sulfur trapping and catalysis effect for sulfur redox reaction, whereas the microsporous COF shell with polar functional groups further reduces the shuttling of LiPS. The S/Co/Zr-NC@TpPa cathode achieves an initial capacity of 792 mAh g−l at 1 C with 76.4% capacity retention after 500 cycles. More importantly, under the high sulfur loading of 5.10 mg cm−2, it has a high specific surface area capacity of 4.15 mAh cm−2 at 0.2 C. This study provides a promising alternative design strategy for the development of efficient sulfur host in Li-S batteries.

Ordered macroporous V-doped ZnO framework impregnated with microporous carbon nanocages as multifunctional sulfur reservoir in lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries are considered as a promising energy storage device. However, their practical application is still hindered by the unsatisfactory cyclability and slow reaction kinetics. Here, we propose a conductive oxide-based macro-microporous framework, where ZIF-8-derived N-doped carbon (NC) nanocages are embedded within the three-dimensionally ordered macroporous (3DOM) V-doped ZnO matrix, as a high-performance sulfur host for Li-S batteries. The unique framework provides large surface area and high porosity for sulfur accommodation, while the V-doped ZnO skeleton enables a highly conducive substrate for electrochemical reactions. More importantly, such hybrid structure imposes strong fixation and effective catalysis of polysulfides, rendering reversible and rapid sulfur redox reactions. Due to these synergistic effects, the 3DOM [email protected]/S cathode exhibits an excellent cycling stability with a low capacity fading rate of 0.043 % per cycle during 500 cycles at 1C and a good rate capability of 767.6 mAh g−1 at 3C. Moreover, a high initial areal capacity of 4.4 mAh cm−2 was also achieved under a high sulfur loading of 5.8 mg cm−2 with a low E/S ratio of 4.4 μL mg−1 in coin cells, as well as decent flexibility and stable cycling in Li-S pouch cell configuration.

Coupled effect of TiO2-x and N defects in pyrolytic waste plastics-derived carbon on anchoring polysulfides in the electrode of Li-S batteries

Lithium-sulfur (Li-S) batteries have the potential to provide high energy density but they suffer from shuttling phenomena that are detrimental to cyclic stability in such a way that lithium polysulfides gradually diffuse out from the cathode interface. We employed the pyrolysis residue from waste plastics for a carbon source and applied it as a cathode sulfur host for Li-S batteries to limit the shuttle effect. Annealing with the aid of KOH and the subsequent ammonia thermal treatment endowed the residue with hierarchical porosity that reached 30% mesoporosity of the total pore volume. N-defects were significantly introduced in carbon networks with edge-positioned states, which helped them chemically interact with Li moieties in the polysulfides. Furthermore, titanium sub-dioxide (TiO2-x) was formed as impurities after the thermal treatment effectively suppressed diffusion of the intermediates. Based on the coupled effect of both N-defects and TiO2-x, the prepared carbon contributed to retarding the decay rate of discharge capacity, and its decay rate decreased to 0.089% per cycle at 1 C until 500 cycles with a capacity of higher than 500 mAh g−1. This study offers a precedent for practical green design of waste plastic residues as a carbon source.

Templated spherical coassembly strategy to fabricate MoS2/C hollow spheres with physical/chemical polysulfides trapping for lithium-sulfur batteries

• Novel heterogenous MoS 2 /C hollow spheres as a sulfur host material are constructed. • The composite allows both physical confinement and chemical adsorption for LiPSs. • The hollow structure enables fast ion transport and a high sulfur loading. • The MoS 2 /C-based sulfur cathode exhibits superior comprehensive performance. Rational design of advanced polar hosts with high sulfur loading, facilitated ionic/electronic transport and effectively suppressed shuttling effect has great potential for high performance lithium-sulfur batteries, yet it remains challenging. Here we propose a novel templated spherical coassembly strategy to fabricate the MoS 2 /C hollow spheres as an efficient sulfur host material. The unique hollow structure provides enough interior space for accommodating a substantial amount of sulfur, and effectively suppresses the diffusion of dissolved polysulfides by both physical confinement and chemical adsorption. Moreover, the ionic transport as well as the ability to mitigate volume variation upon cycling is also improved, thereby maximizing the utilization of sulfur. Owing to these merits, when evaluated as a sulfur host for lithium-sulfur batteries, the MoS 2 /C hollow spheres exhibit appealing electrochemical performance with an impressive specific capacity of 1082 mA h g −1 at 0.1 C, excellent rate capability and superior cycling stability with a low fading rate of 0.04% per cycle.

Molten Salts Approach of Metal-Organic Framework-Derived Nitrogen-Doped Porous Carbon as Sulfur Host for Lithium-Sulfur Batteries

Molten Salts Approach of Metal-Organic Framework-Derived Nitrogen-Doped Porous Carbon as Sulfur Host for Lithium-Sulfur Batteries

MOF-derived cobalt Disulfide/Nitrogen-doped carbon composite polyhedrons linked with Multi-walled carbon nanotubes as sulfur hosts for Lithium-Sulfur batteries

Lithium sulfur batteries (LSBs) are regarded as one of the most promising energy storage devices because of their ultrahigh theoretical energy densities (2500 Wh kg−1), low cost, and environmental friendliness. Nevertheless, several detrimental drawbacks, including shuttling effects caused by soluble lithium polysulfides (LiPS), sluggish conversion kinetics between LiPS, and poor conductivities of sulfur, prevent commercialization of LSBs. To takle the above issues, MOF-derived cobalt disulfide/nitrogen-doped carbon (NC) composite polyhedrons linked with multi-walled carbon nanotubes (MWCNTs), CoS2@NC/MWCNT, were developed as an effective sulfur host for LSBs. It was fabricated through first in-situ growth of nanoporous ZIF-67 on surface treated MWCNTs, followed by carbonization and sulfurization. CoS2@NC/MWCNT combines the advantages of outstanding conductivities of MWCNTs, excellent chemical adsorption of NC and CoS2 toward LiPS, and high catalytic efficiency of CoS2 toward LiPS conversion, effectively addressing the shuttling, sluggish conversion, and low conductivity issues. The CoS2@NC/MWCNT electrode delivered a high specific capacity of 1133 mAh g−1 at 0.1C and maintained a decent specific capacity of 607 mAh g−1 at 2.0C. Its cycling stability is excellent, with a capacity retention rate of 77% after 300cycles at 1.0C, i.e., an average capacity decay rate of 0.078% per cycle. The cycling stability was further improved through increasing N-doping levels of the carbons for enhanced chemical adsorption toward LiPS and through incorporation of inter-linked reduced graphene oxide sheets as a physical barrier to reduce the diffusion loss of LiPS, achieving even smaller capacity decay rates of 0.066 and 0.064 % per cycle, respectively.

PPy-encapsulated hydrangea-type 1T MoS2 microspheres as catalytic sulfur hosts for long-life and high-rate lithium-sulfur batteries

Lithium-sulfur batteries are regarded as promising candidates for next-generation energy storage applications owing to their high theoretical specific capacity, low cost, and eco-friendliness. However, the poor conductivity, large volume variation of sulfur species during the charging/discharging process, complicated conversion reactions of sulfur species, shuttle effect of lithium polysulfide, and low sulfur loading greatly hinder the practical application of lithium-sulfur batteries. In this study, we propose an efficient approach to design polypyrrole (PPy)-encapsulated 1T-MoS2 microspheres with a hydrangea-like structure as catalytic sulfur hosts for lithium-sulfur batteries. The catalytic effect of 1T-MoS2 and the high conductivity of the PPy layer accelerated the adsorption/conversion of lithium polysulfides. The hydrangea-like structure of the 1T-MoS2 microspheres provided adequate number of active sites and sufficient space for sulfur loading. Meanwhile, the specific inter-porous/outer-coating layer structure could also restrain the expansion of sulfur electrode during the electrochemical reaction process. The obtained 1T-MoS2-S@PPy cathode material exhibited outstanding electrochemical performance with an excellent reversible capacity of 1434 mAh g−1 at 0.1C rate, a considerable capacity of 1023 mAh g−1 at 1C rate, and excellent cycling stability for over 800 cycles with a low cycling decay rate of 0.051% per cycle.

Mn2O3 Incorporated Carbonized Bacterial Cellulose As Sulfur Host for Lithium-Sulfur Batteries

Early development and commercialization of lithium-ion batteries (LIBs) have enabled the portable electronic devices and powered the world. However, the ever-increasing demand for higher energy batteries have led to the quest for further improvement. Lithium-sulfur batteries (LSBs), with lithium anode and sulfur-based composite as cathode, have high theoretical specific energy of 2600 W h kg-1 (around 10 folds higher than LIBs system). Moreover, sulfur is produced as a by-product from petroleum refineries making research in LSBs more lucrative. However, there are a few critical challenges which restrict the commercialization of LSBs. First, insulating nature of sulfur (5 × 10-30 S cm-1) and lithium sulfide (Li2S, 10-13 S cm-1) impedes the electronic conductivity which results in low utilization of active sulfur. Secondly, the dissolution and diffusion of long-chain lithium polysulfides in electrolyte to lithium anode under concentration gradient causes series of severe issues such as loss of active sulfur, pulverization of lithium anode. Thirdly, the volume change during lithiation (up to 80%) results in degradation of cathode.To tackle aforementioned issues, we have utilized Mn2O3 incorporated carbonized bacterial cellulose (Mn2O3@CBC) as sulfur host for LSB. A facile melt-diffusion approach was adopted to encapsulate sulfur into Mn2O3@CBC matrix. The material was characterized using various physicochemical techniques - X-ray diffraction spectroscopy, Raman spectroscopy, Thermal gravimetric analysis, and Surface area analyzer. The Mn2O3@CBC system developed in this work offers the following benefits: (a) interconnected carbon nanofiber assembly which helps in fast diffusion of Li-ion and electrons; (b) porous morphology to accommodate volume change and to act as a reservoir for long-chain lithium polysulfides accumulation; (c) Mn2O3 as long-chain lithium polysulfide binding site and catalyst for conversion of long-chain lithium polysulfides to short-chain lithium polysulfides.To investigate the electrochemical property of the material, the performance is compared to bare sulfur and sulfur incorporated carbonized bacterial cellulose (S-CBC). Various electrochemical characterization such as cyclic voltammograms, galvanostatic charge-discharge, rate capability, long-term cycling was performed to investigate the performance of the materials. The material (S-Mn2O3@CBC) exhibited initial reversible capacity of 1150 mA h g-1 at 0.1C and retained 254.4 mA h g-1 at the extremely high current rate of 15C which is far ahead than the bare sulfur and S-CBC. Furthermore, the cycle life of LSB with low and high-sulfur loading was performed to further establish the advantage of using Mn2O3 as electro catalyst. Moreover, first-principles calculation was carried out to understand the functional mechanism for interaction of Mn2O3@CBC and intermediate lithium polysulfides. The excellent electrochemical performance substantiates that the S-Mn2O3@CBC is a good choice for cathode for LSBs. Figure 1

Molten Salt Electrochemical Modulation of Iron–Carbon–Nitrogen for Lithium–Sulfur Batteries

Sulfur hosts with rationally designed chemistry to confine and convert lithium polysulfides are of prime importance for high-performance lithium-sulfur batteries. A molten salt electrochemical modulation of iron-carbon-nitrogen is herein demonstrated as formation of hollow nitrogen-doped carbon with grafted Fe3 C nanoparticles (Fe3 C@C@Fe3 C), which is rationalized as an excellent sulfur host for lithium-sulfur batteries. Fe3 C over nitrogen-doped carbon contributes to enhanced adsorption and catalytic conversion of lithium polysulfides. The sulfur-loaded Fe3 C@C@Fe3 C electrodes hence show a high capacity, good cyclic stability, and enhanced rate performance. This work highlights the unique chemistry of metal carbides on facilitating adsorption-conversion process of lithium polysulfides, and also extends the scope of molten salt electrolysis to elaboration of energy materials.

Self-supported VN arrays coupled with N-doped carbon nanotubes embedded with Co nanoparticles as a multifunctional sulfur host for lithium-sulfur batteries

Rational design and synthesis of advanced sulfur host materials has been regarded as an effective strategy to address the critical challenges of lithium-sulfur (Li-S) batteries including shuttle effect of lithium polysulfides (LiPSs), sluggish reaction kinetics, and huge volume change of sulfur. In this work, we demonstrate the rational construction of a multifunctional sulfur host grown on carbon cloth consisting of self-supported porous VN arrays coupled with MOF-derived N-doped carbon nanotubes embedded with tiny Co nanoparticles (named CC/VN/Co@NCNTs). This unique electrode design possesses a series of advantages such as high electrical conductivity, strong physical/chemical confinement of LiPSs, favorable catalytic activity, fast reaction kinetics, effective volumetric accommodation, good mechanical stability and high sulfur loading. As expected, when evaluated as self-standing and binder-free cathode for Li-S batteries, the CC/VN/Co@NCNTs/S exhibits a high initial discharge capacity of 1130.4 mAh g−1 at 0.1C and maintains 864.1 mAh g−1 after 100 cycles, along with outstanding rate performance (625.3 mAh g−1 at 5C) and superior long-term cycling stability with a low capacity decay rate of 0.063% per cycle at 1C for 500 cycles. Moreover, the CC/VN/Co@NCNTs/S delivers high reversible capacities of 847.6, 668.3, and 581.1 mAh g−1 at 0.1C after 100 cycles at different high sulfur loadings of 2.8, 5.2, and 7.8 mg cm−2, respectively. The present work might provide an effective strategy to directly construct multifunctional sulfur host materials on current collectors for high-performance Li-S batteries.

Hollow Ni-Co-S Nanocubes as Superior Sulfur Host for High-Performance Lithium-Sulfur Batteries

In this work, hollow Ni-Co-S nanocubes were designed and successfully prepared as a superior sulfur host for lithium-sulfur batteries (LSBs) by means of facile synthesis methods. The prepared hollow Ni-Co-S nanocubes possess multiple merits, including good electrical conductivity, sulfur encapsulated nanostructure and LiPS adsorbability. By employing Ni-Co-S nanocubes as the sulfur host, the electron transfer efficiency is incresed and the volume expansion during repeated cycling can be buffered. Besides, the shuttling effect is limited effectively due to the strong lithium polysulfides (LiPS) adsorbability. As a result, the sulfur utilization is significantly improved for better performance. Benefiting from these advantages, the LSBs exhibited a fairly high initial capacity of 1482 m Ah g-1, a retained capacity of 669 m Ah g-1 over 200 cycles and impressive discharge capacities of 710, 565, 370 and 186 m Ah g-1 even at 1C, 2C, 3C and 4C, respectively.

Flower-like Ni3S2 hollow microspheres as superior sulfur hosts for lithium-sulfur batteries

Due to high theoretical capacity, lithium sulfur (Li–S) batteries are regarded as aussichtsreich batteries for future energy storage devices. Several factors, such as low usage effectiveness of sulfur and “shuttle effect” of polysulfides, restrain the development of Li–S batteries. Porous sulfur carriers have been developed to remit these shortcomings to some extent. In this paper, a simple strategy is reported to prepare porous Ni 3 S 2 hollow microspheres as sulfur hosts for Li–S batteries by an easy hydrothermal and calcination method. The as-fabricated Ni 3 S 2 /S cathodes present excellent cycling performance (959.7 mA h g −1 at 0.1 C after 100 cycles) as well as good rate property and cyclability (557.5 mA h g −1 at 1 C after 400 cycles). Such excellent energy storage properties can be ascribed to the unique hollow microsphere structure with high specific surface area, which is conducive to the capture of polysulfides during cycling. The study also provides a simple route to develop transition metal sulfide with hollow structures as superior sulfur hosts which may promote the development of various hollow structures for Li–S batteries application. • Porous Ni 3 S 2 hollow microspheres are prepared as sulfur hosts for Li–S batteries. • Ni 3 S 2 /S exhibit good electrochemical performance as Li–S battery cathodes. • Porous Ni 3 S 2 hollow structure is conducive to capture polysulfide. • Large specific surface area of electrode can well adapt volume change of S.

Array-Structured Double-Ion Cooperative Adsorption Sites as Multifunctional Sulfur Hosts for Lithium-Sulfur Batteries with Low Electrolyte/Sulfur Ratio.

Low electrolyte/sulfur ratio (E/S) is a crucial factor that promotes the development of lithium-sulfur batteries (LSBs) with desired energy density. However, it causes multiple problems, including a strong "shuttle effect" during both the cycle and storage process, and limited sulfur utilization. Herein, we develop a Na2Ti6O13 (NTO) nanowire array as a multifunctional sulfur host to simultaneously tackle both the above problems. The synergistic coordination between Na and Ti cations in NTO can accelerate the conversion of soluble polysulfides (PSs) to insoluble sulfides and significantly enhance their adsorption. Therefore, accumulation of PSs, which is the primary cause of the "shuttle effect", can be avoided in two ways. One is fast conversion kinetics during cycles; another is strong PS adsorption, which can suppress the disproportionation of PSs during storage. The as-prepared array represents an easy-to-infiltrate structure with efficient electron transport that allows good wetting ability of the conductive surface toward the electrolyte. Therefore, it helps improve sulfur utilization that is mainly limited by the presence of unwetted conductive surface. Consequently, NTO/sulfur array cathodes exhibit high sulfur utilization and extended cycle- and shelf-lives at a low E/S (5:1). Our work suggests that array materials featuring cooperative multi-ion adsorption sites are promising hosts for LSBs.

Hollow urchin-like Mn3O4 microspheres as an advanced sulfur host for enabling Li-S batteries with high gravimetric energy density

Lithium-sulfur (Li-S) batteries are considered to be promising candidates for next-generation storage systems. However, the practical applications are still hindered by the severe capacity decay, mainly caused by the large volume change, polysulfide shuttle and sluggish sulfur conversion kinetics. Herein, hollow urchin-like Mn3O4 (HU-Mn3O4) microspheres as sulfur hosts have been synthesized by the hydrothermal method and calcination treatment, aiming to prevent the polysulfide dissolution (benefiting from the strong polysulfide anchoring effect of Mn3O4) and alleviate the volume expansion of sulfur (benefiting from the special hollow structure). Meanwhile, the urchin-like thorny surface also facilitates the rapid ion/electron transfer and the abundant active sites for the fast sulfur redox kinetics. When used as the sulfur host in Li-S batteries, the S@HU-Mn3O4 cathode delivers a high initial capacity of 1137.4 mAh g−1 with a slow capacity decay of 0.042% after 200 cycles at 0.2 C. Even under the conditions of lean electrolyte (E/S = 7 mL g−1) and low N/P ratio (N/P = 2.1), the S@HU-Mn3O4 cathode still enables a stable cycling performance with a high gravimetric energy density (202 Wh kg cell−1), demonstrating its great potential in the development of future practical Li-S battery materials.