Cathode Material For Lithium-sulfur Batteries Research Articles

Synthesis of Deliquescent Lithium Sulfide in Air.

In the field of lithium-sulfur batteries (LSBs) and all-solid-state batteries, lithium sulfide (Li2S) is a critical raw material. However, its practical application is greatly hindered by its high price due to its deliquescent property and production at high temperatures (above 700 °C) with carbon emission. Hereby, we report a new method of preparing Li2S, in air and at low temperatures (∼200 °C), which presents enriched and surprising chemistry. The synthesis relies on the solid-state reaction between inexpensive and air-stable raw materials of lithium hydroxide (LiOH) and sulfur (S), where lithium sulfite (Li2SO3), lithium thiosulfate (Li2S2O3), and water are three major byproducts. About 57% of lithium from LiOH is converted into Li2S, corresponding to a material cost of ∼$64.9/kg_Li2S, less than 10% of the commercial price. The success of conducting this water-producing reaction in air lies in three-fold: (1) Li2S is stable with oxygen below 220 °C; (2) the use of excess S can prevent Li2S from water attack, by forming lithium polysulfides (Li2Sn); and (3) the byproduct water can be expelled out of the reaction system by the carrier gas and also absorbed by LiOH to form LiOH·H2O. Two interesting and beneficial phenomena, i.e., the anti-hydrolysis of Li2Sn and the decomposition of Li2S2O3 to recover Li2S, are explained with density functional theory computations. Furthermore, our homemade Li2S (h-Li2S) is at least comparable with the commercial Li2S (c-Li2S), when being tested as cathode materials for LSBs.

Graphene/Heterojunction Composite Prepared by Carbon Thermal Reduction as a Sulfur Host for Lithium-Sulfur Batteries.

An interlayer nanocomposite (CC@rGO) consisting of a graphene heterojunction with CoO and Co9S8 was prepared using a simple and low-cost hydrothermal calcination method, which was tested as a cathode sulfur carrier for lithium-sulfur batteries. The CC@rGO composite comprises a spherical heterostructure uniformly distributed between graphene sheet layers, preventing stacking the graphene sheet layer. After the introduction of cobalt heterojunction on a graphene substrate, the Co element content increases the reactive sites of the composite and improves its electrochemical properties to some extent. The composite exhibited good cycling performance with an initial discharge capacity of 847.51 mAh/g at 0.5 C and a capacity decay rate of 0.0448% after 500 cycles, which also kept 452.91 mAh/g at 1 C and in the rate test from 3 C back to 0.1 C maintained 993.27 mAh/g. This article provides insight into the design of cathode materials for lithium-sulfur batteries.

Activation of Bulk Li2S as Cathode Material for Lithium-Sulfur Batteries through Organochalcogenide-Based Redox Mediation Chemistry.

Lithium sulfide (Li2S) is considered as a promising cathode material for sulfur-based batteries. However, its activation remains to be one of the key challenges against its commercialization. The extraction of Li+ from bulk Li2S has a high activation energy (Ea) barrier, which is fundamentally responsible for the initial large overpotential. Herein, a systematic investigation of accelerated bulk Li2S oxidation reaction kinetics was studied by using organochalcogenide-based redox mediators, in which phenyl ditelluride (PDTe) can significantly reduce the Ea of Li2S and lower the initial charge potential. Simultaneously, it can alleviate the polysulfides shuttling effect by covalently anchoring the soluble polysulfides and converting them into insoluble lithium phenyl tellusulfides (PhTe-SxLi, x > 1). This alters the redox pathway and accelerates the reaction kinetics of Li2S cathode. Consequently, the Li||Li2S-PDTe cell shows excellent rate capability and enhanced cycling stability. The Si||Li2S-PDTe full cell delivers a considerable capacity of 953.5 mAh g-1 at 0.2 C.

Sulfur-rich polymer/Ketjen Black composites as lithium-sulfur battery cathode with high cycling stability

Lithium-sulfur (Li-S) battery is considered as one of the most promising energy storage devices due to its exceptional energy density. However, its development is largely hampered by the shuttle effect of lithium polysulfide and the sluggish electrochemical kinetics of sulfur cathode. In this study, a novel sulfur-rich polymer is synthesized through the inverse vulcanization of sulfur with 2,4,6,8-tetravinyl-2,4,6,8-tetramethylcyclotetrasiloxane (TVTCSi) and used as cathode material for Li-S batteries, which can effectively immobilize the lithium polysulfides through covalent bonds to impede its shuttling, leading to marked improvement in the cycling performance of the batteries. Furtherly, with the addition of Ketjen Black, the resulting composite cathode exhibited faster electrochemical reaction kinetics and higher cycling stability, which could deliver a reversible discharge capacity of 652 mAh g−1 after 500 cycles at a high current density of 0.5 C,0.5C with quite a low capacity decay rate of only 0.037% per cycle, which indicates broad perspectives of sulfur-rich polymer/Ketjen Black composite as cathode material in lithium-sulfur battery.

Sulfur/hollow Carbon Nanofiber Composite as Cathode Material for Lithium-Sulfur Batteries

Sulfur/hollow Carbon Nanofiber Composite as Cathode Material for Lithium-Sulfur Batteries

Ultrafast Strategy to Fabricate Sulfur Cathodes for High-Performance Lithium-Sulfur Batteries.

Based on the different dielectric properties of materials and the selective heating property of microwaves, the ultrafast (30 s) preparation of S-NiS2@SP@Bitu as a cathode material for lithium-sulfur batteries was achieved using bitumen, sulfur, Super P, and nickel naphthenate as raw materials for the first time, under microwave treatment. NiS2@SP@Bitu forms Li-N, Li-O, Li-S, and Ni-S bonds with polysulfide, which contributes to promoting the adsorption of polysulfide, reducing the precipitation and decomposition energy barrier of Li2S, and accelerating the catalytic conversion of polysulfide, as result of inhibiting the "shuttle effect" and improving the electrochemical performance. S-NiS2@SP@Bitu as the sulfur cathode material demonstrates outstanding rate performance (518.6 mAh g-1 at 4C), and stable cycling performance. The lithium-sulfur battery with a sulfur loading of 4.8 mg cm-2 shows an areal capacity of 4.6 mAh cm-2. Based on the advantages of microwave selective and rapid heating, this method creatively realized that the sulfur carrier material was prepared and sulfur was fixed in it at the same time. Therefore, this method would have implications for the preparation of sulfur cathode materials.

Synergistic Effect of Zn–Co Bimetallic Selenide Composites for Lithium–Sulfur Battery

Compared with monometallic selenides, heterogeneous bimetallic selenides have rich phase boundaries and superior electrical conductivity. ZnSe/CoSe2 composites were prepared by introducing Zn metal and using ZIF-8/67 as the precursor through the synergistic effect between Zn and Co after selenification. The electrocatalytic conversion of polysulfide is accelerated by ZnSe through chemical adsorption and the catalytic effect. The conductive CoSe2 surface provides a rapid diffusion path for lithium ions, accelerating the conversion of the polysulfide. On the basis of their individual strengths, ZnSe and CoSe2 can jointly promote the smooth adsorptive–diffuse–catalytic conversion process of polysulfide and induce the growth of lithium sulfide around its heterogeneous interface, thus enhancing the electrochemical performance of the lithium–sulfur battery cathode materials. The ZnSe/CoSe2–S electrode, at the optimal Zn-to-Co ratio of 1:1, has a 790.06 mAh g−1 initial specific capacity at 0.2 C and excellent cycling stability at 1 C. After 300 cycles, the final capacity is 300.85 mAh g−1, and the capacity retention rate reaches 82.71%.

Construction of MoS2@reduced graphene oxide/carbon nanotubes three-dimensional network structure and its application in lithium-sulfur batteries

In order to enhance the electrochemical performance of lithium-sulfur batteries, reduced graphene oxide (rGO), and carbon nanotubes (CNTs) were used to construct a conductive and mechanical skeleton of the overall electrode composite. And molybdenum disulfide (MoS2) grew on the skeleton in situ. Thus, a composite MoS2@rGO/CNTs with a three-dimensional (3D) network structure was constructed. A series of corresponding structural characterizations and electrochemical performance tests were carried out. And the results showed that the 3D porous skeleton composed of rGO and CNTs could act as a 3D conductive network, which not only significantly improved the conductivity and structural stability of the cathode material for lithium-sulfur batteries but also provided a large number of active sites for the active substance S. MoS2 had a strong chemisorption effect on lithium polysulfides, which could effectively hinder their shuttle behavior. So, the MoS2@/CNTs/rGO/S cathode material showed good electrochemical performance. Its first discharge specific capacity was up to 1417.8 mAh/g at 0.1 C. After 200 cycles at 0.5 C, its capacity decay rate per cycle was only 0.09%. Its discharge capacity could still maintain at 803.2 mAh/g at 3 C, showing a good application prospect.

The Dual‐Site Adsorption and High Redox Activity Enabled by Hybrid Organic‐Inorganic Vanadyl Ethylene Glycolate for High‐Rate and Long‐Durability Lithium–Sulfur Batteries (Small 20/2023)

Lithium–Sulfur Batteries In article number 2206750, Kisoo Yoo, Jong-Hoon Kim, Hengyue Xu, and co-workers report a hybrid organic-inorganic vanadyl ethylene glycolate as a novel carbon-free cathode material for lithium-sulfur battery. The dual-site adsorption and fast electron/ion transport enable high anchoring efficiency and catalytic activity during the polysulfides conversion. Accordingly, excellent electrochemical performance could be achieved over a wide-range of temperatures.

“One Stone Two Birds” Strategy of Synthesizing the Battery Material Lithium Sulfide: Aluminothermal Reduction of Lithium Sulfate

Lithium sulfide (Li2S) is a critical material for clean energy technologies, i.e., the cathode material in lithium-sulfur batteries and the raw material for making sulfide solid electrolytes in all-solid-state batteries. However, its practical application at a large scale is hindered by its industrial production method of reducing lithium sulfate with carbon materials at high temperatures, which emits carbon dioxide and is time-consuming. We hereby report a method of synthesizing Li2S by thermally reducing lithium sulfate with aluminum. Compared with the carbothermal method, this aluminothermal approach has several advantages, such as operation at lower temperatures, completion in minutes, no emission of greenhouse gases, and valuable byproducts of aluminum oxide (Al2O3). The home-made Li2S demonstrates competitive performance in battery tests versus the commercial counterpart. Moreover, using the byproduct Al2O3 to coat the cathode side of the separator can enhance the battery's capacity without influencing its rate capability. Thus, this "one stone two birds" method has great potential for practical applications of developing Li-S batteries.

ZIF-67 on Sulfur-Functionalized Graphene Oxide for Lithium-Sulfur Batteries.

How to overcome the problem of fast capacity fading and low sulfur utilization is the key to promote the practical applications of lithium-sulfur (Li-S) batteries. Based on the fact that sulfur-functionalized graphene oxide (GO-S) can avoid the loss of sulfur/polysulfides through the strong C-S interaction, and the zeolitic imidazolate framework (ZIF-67) can capture sulfur and catalyze lithium polysulfide (Li2Sx, 4 ≤ x ≤ 8), the combination of ZIF-S (ZIF-67 after combining with sulfur) with GO-S can be expected to be an excellent electrode material for Li-S batteries due to the synergistic effect. Herein, ZIF-S@GO-S (n) nanocomposites (n = 1, 2, and 3 for the mass ratio of ZIF-67/GO of 4:1, 6:1, and 8:1, respectively) as the cathode materials in Li-S batteries were successfully fabricated, and ZIF-S@GO-S (2) showed better electrochemical performances and cycle stability with a high specific capacity of 1529.5 mA h g-1 at the initial cycle and 792 mA h g-1 after 500 cycles at 0.1 C (1 C = 1675 mA h g-1). The fact that ZIF-S@GO-S (n) can simultaneously improve the conductivity and utilization of S (C-S···S8 and C-S···SxLi2) and the conversion kinetics of Li2Sx (4 ≤ x ≤ 8) provides a new avenue for designing and fabricating promising cathodes for high-performance Li-S batteries.

CeO2/Ce2S3 modified carbon nanotubes as efficient cathode materials for lithium-sulfur batteries

CeO2/Ce2S3 modified carbon nanotubes as efficient cathode materials for lithium-sulfur batteries

MoWS2 Nanosheet Composite with MXene as Lithium-Sulfur Battery Cathode Material

Due to their superior theoretical specific capacity and energy density, lithium-sulfur (L‒S) batteries are gaining popularity in order to achieve the growing terms for more power generation. However, drawbacks such as low electrical conductivity of the active ingredient sulfur, severe volume expansion and shuttle effect of polysulfides, rapidly decaying battery capacity, and short battery life have hampered their development. A MoWS2@MXene@CNT composite material is used as the main cathode material for L-S batteries in this study. MoWS2 can improve the electrochemical reaction rate by accelerating polysulfide conversion, whereas MXene can suppress electrode volume expansion. Furthermore, the addition of carbon nanotubes (CNT) with high electrical conductivity improves the rate of the electrochemical reaction. Therefore, the MoWS2@MXene@CNT composites have good capacity and versatility as cathode materials and enhance the behavior of L-S batteries.

Preparation of Co9S8-Mo2C nanoparticles and their application in lithium-sulfur batteries

Several critical issues, such as the shuttling effect and the sluggish reaction kinetics, exist in the design of high-performance lithium-sulfur (Li-S) batteries. To address these issues, Co9S8-Mo2C nanoparticles were synthesized by carburizing method with Co-Co PBA as the precursor, which was used to modify cathode materials in Li-S batteries. Strong sulfur fixation and catalytic effects on liquid-phase and liquid-solid transformation were demonstrated by Co9S8-Mo2C nanoparticles. In contrast, the positive electrode of Co9S8 nanoparticles is inferior to that of Co9S8-Mo2C nanoparticles in every way. This proves that the adsorption-catalytic function of Co9S8-Mo2C enhances polysulfide capture and conversion efficiency. By optimizing the proportion of Mo2C, we obtained a material with the best performance. The positive electrode that had the optimal ratio of Co9S8-Mo2C nanoparticles showed high specific capacity (0.2 C, 1010.8 mAh·g-1), excellent rate performance (1 C, 609.4 mAh·g-1 and 2 C, 590 mAh·g-1) and stable cycle performance.

Diphenylguanidine combined with high molecular weight polyacrylonitrile precursor for high-conductivity and high-sulfur-loading cathode of lithium-sulfur battery

Sulfurized polyacrylonitrile (SPAN) cathode have high discharge specific capacity, close to 100 % coulombic efficiency and excellent cycle stability, which is regarded as a very promising cathode material in lithium-sulfur batteries. However, polyacrylonitrile as vulcanization precursor have a great influence on the performance of SPAN. Therefore, the effects of different molecular weight polyacrylonitrile precursors while diphenylguanidine as vulcanization accelerator on the performance of SPAN cathodes are reported for the first time. Considering that diphenylguanidine as vulcanization accelerator can significantly increase the sulfur loading of SPAN. Prepared SPAN-1000k cathode by an ultra-high molecular weight polyacrylonitrile precursor (Mw = 1000k) has a sulfur-loading of up to 54.5 %. Surprisingly, a 22 % increase in conductivity resulting in a remarkable discharge capacity of 830 mAh gcomposite−1 at a high rate of 1C (0.7 A/g). This work demonstrates that diphenylguanidine as vulcanization accelerator prepared ultra-high molecular weight SPAN cathode can greatly improve sulfur loading and conductivity, and exhibit excellent electrochemical performance at a high rate.

Selenium-doped cathode materials with polyaniline skeleton for lithium-organosulfur batteries

Sulfur-containing polymer (SCP) is considered as an outstanding cathode material for lithium-sulfur batteries. However, undesirable soluble polysulfides may shuttle in electrolyte, concluding long-chain Li2Sn (n > 4) and short-chain Li2Sn (n ≤ 4), as well as the sluggish conversion kinetics are yet to be solved to enhance the performance of lithium-sulfur batteries. Here Se-doped sulfurized polyaniline with adjusted sulfur-chain −Sx− (x ≤ 6) contribute to ensure the absence of long-chain polysulfides, and the skeleton with quinoid imine can endow strongly adsorption towards short-chain polysulfides by the reversible transition between deprotonated/protonated imine (-NH+= and -N=), which offer double insurance against suppressing “shuttle effect”. Furthermore, Se atoms are doped into sulfurized polysulfides to accelerate the redox conversion and take a frontier orbital theory-oriented view into catalytic mechanism. Se-doped sulfurized polyaniline as active materials for lithium-organosulfur batteries delivers good electrochemical performance, including high rate, reversible specific capacity (680 mA h g−1 at 0.1 A g−1), and lower capacity decay rate only of 0.15% with near 100% coulomb efficiency during long-term cycle. This work provides a valuable guiding ideology and promising solution for the chemistry-oriented structure design and practical application for lithium-organosulfur batteries.

Nitrogen sulfur dual-doped porous biochar fibers for high performance lithium-sulfur battery

Porous carbons have gained great attention for applications in lithium-sulfur (Li-S) batteries. However, achieving high specific surface area, hierarchical porosity, and abundant heteroatom-doping with facile approaches is still challenging. Herein, nitrogen, sulfur dual-doped hierarchical porous carbons (PBF@N@S) are obtained via a simple and sustainable activation process of cotton fibers. The as-prepared PBF@N@S exhibits a hierarchically interconnected network porous structure and large specific surface area. Meanwhile, abundant nitrogen, sulfur atoms are simultaneously doped in the carbons. These characteristics make the carbon favorable for hosting sulfur. The PBF@N@S sample with 50 wt% sulfur content (PBF@N@S-S-50%) delivers a high initial capacity with excellent cycling performance. Such high performance suggests that the PBF@N@S-S could be a promising cathode material for Li-S batteries.

Theoretical identification of the superior anchoring effect and electrochemical performance of Ti2CS2 by single atom Zn doping for lithium-sulfur batteries.

As one of the promising next-generation energy storage systems, lithium-sulfur (Li-S) batteries have been the subject of much recent attention. However, the polysulfide shuttle effect remains problematic owing to the dissolution of intermediate polysulfide species in the electrolyte and the sluggish reaction dynamics in Li-S batteries. To overcome these issues, this work reports an effective strategy for enhancing the electrochemical performance of Li-S batteries using single atom Zn doping on the S-terminated Ti2C MXenes (Ti2-xZnxCS2). Spin-polarized density functional theory (DFT) calculations were performed to elucidate the interactions of lithium polysulfides (LiPSs) and the Ti2-xZnxCS2 surface in terms of geometric and electronic properties, as well as the delithiation process of Li2S on the Ti2-xZnxCS2 surface. It is found that doping single atom Zn could induce a new Lewis acid-based sites, which could provide proper affinity toward LiPSs. Combined with the metallic character, a low Li diffusion barrier and high catalytic activity for the delithiation process of Li2S, makes Ti2-xZnxCS2 a promising cathode material for Li-S batteries. The results demonstrate the importance of surface chemistry and the electronic structure of MXenes in LiPSs' adsorption and catalysis capability. We believe that our findings provide insights into the recent experimental results and guidance for the preparation and practical application of MXenes in Li-S batteries.

Water Kefir Grains-Microbial Biomass Source for Carbonaceous Materials Used as Sulfur-Host Cathode in Li-S Batteries.

Nowadays, the use of biomass to produce cathode materials for lithium-sulfur (Li-S) batteries is an excellent alternative due to its numerous advantages. Generally, biomass-derived materials are abundant, and their production processes are environmentally friendly, inexpensive, safe, and easily scalable. Herein, a novel biomass-derived material was used as the cathode material in Li-S batteries. The synthesis of the new carbonaceous materials by simple carbonization and washing of water kefir grains, i.e., a mixed culture of micro-organisms, is reported. The carbonaceous materials were characterized morphologically, texturally and chemically by using scanning electron microscopy, N2 adsorption-desorption, thermogravimetric analysis, X-ray diffraction, and both Raman and X-ray photoelectron spectroscopy. After sulfur infiltration using the melt diffusion method, a high sulfur content of ~70% was achieved. Results demonstrated that the cell fitted with a cathode prepared following a washing step with distilled water after carbonization of the water kefir grains only, i.e., not subjected to any chemical activation, achieved good electrochemical performance at 0.1 C. The cell reached capacity values of 1019 and 500 mAh g-1 sulfur for the first cycle and after 200 cycles, respectively, at a high mass loading of 2.5 mgS cm-2. Finally, a mass loading study was carried out.

Integration of PDAAQ and Non-stoichiometric MgO as Host Cathode Materials for Lithium-Sulfur Batteries with Superior Cycle Stability: Density Functional Theory Calculations and Experimental Validations

Integration of PDAAQ and Non-stoichiometric MgO as Host Cathode Materials for Lithium-Sulfur Batteries with Superior Cycle Stability: Density Functional Theory Calculations and Experimental Validations