Cathode Material For Lithium-sulfur Batteries Research Articles

Accelerated Ion-Electron Transport in Bi-Heterostructures Constructed Based on Ohmic Contacts for Efficient Bi-Directional Catalysis of Lithium-Sulfur Batteries.

Although lithium-sulfur batteries have satisfactory theoretical specific capacity and energy density, they are difficult to further commercialize due to the shuttle effect of soluble polysulfides and slow sulfur oxidation kinetics. Based on this, in this work, the catalyst MXene-VS4-SnS2 (MVS), a dual heterostructured catalyst with ohmic contacts, is prepared by a one-step hydrothermal method and electrostatic self-adsorption for lithium-sulfur battery cathode materials. Experimental and theoretical results show that the ohmic contact induces spontaneous charge rearrangement, resulting in the formation of a fast charge transfer pathway at the MVS heterojunction interface, which helps to reduce the energy barrier for polysulfide reduction and Li2S oxidation during the discharge/charge process. In addition, the inherent sulfophilicity of VS4 and SnS2 promotes the conversion of S species, while the pleated MXene nanosheets not only provide a highly conductive network for the active sulfur but also retain a rich internal space to maintain the integrity of the cathode structure during the continuous cycling process. As a result, the MVS cathode exhibits excellent electrochemical performance even under high sulfur loading. The integration of excellent performance with a facile synthesis process provides a promising approach for designing highly efficient electrocatalysts suitable for the energy field.

Core-shell cobalt-iron@N-doped carbon: A high-performance cathode material for lithium-sulfur batteries.

Lithium-sulfur batteries hold great promise as energy storage systems, but the shuttle effect of lithium polysulfides (LiPS) and large volume variation limit their capacity and cycle life. We have developed CoFe alloy wrapped in N-doped porous carbon spheres (e-CF@NC) with a core-shell structure through simple copolymerization and pyrolysis. The nitrogen-doped porous carbon shell provides electron and ion transport channels and more active sites for electrolyte ion adsorption. The high chemically stable carbon can limit the segregation of polysulfides, further improving the battery cycling stability. Besides, the inside CoFe alloy particles catalyze the conversion between LiPS and Li2S, speeding up reaction kinetics and reducing solvation of active sites. Consequently, lithium-sulfur batteries with e-CF@NC-2 as the cathode display a high initial specific capacity of 1146 mA h g-1 at 0.1 C, excellent rate performance (891 mA h g-1 at 1 C, 741 mA h g-1 at 2 C), and satisfied cycle stability (average capacity decay rate of 0.033% per cycle at 1 C for 300 cycles), demonstrating significant application potential.

Asymmetrical TiSSe Monolayers as Catalytic Materials for Lithium-Sulfur Batteries: A DFT Study

Asymmetrical Janus TiSSe monolayers as cathode materials for lithium-sulfur batteries were studied by first-principles calculations, encompassing adsorption, catalytic, and conductive properties. The polarization effect, arising from the asymmetric arrangement of constituent elements, results in variability in adsorption energy and bonding processes across S/Se surfaces. The moderate adsorption energy of Lithium Polysulfides (LiPSs) on the TiSSe monolayer effectively mitigates the shuttle effect. The bond formation process investigated by charge transfer, physical/chemical adsorption, and projected crystal orbital Hamiltonian population (pCOHP), revealed its emergence in the early lithiation stage. The Gibbs free energies for the reduction reaction of sulfur on the S/Se surface demonstrate a significant enhancement in the transformation kinetics. The low decomposition and diffusion energy barriers for lithium atoms on the S/Se surface of the TiSSe monolayer indicate its catalytic potential in facilitating sulfur redox transformation. The TiSSe monolayer exhibits metallic properties before and after polysulfide absorption, thereby enhancing electron transport capacity in Li-S batteries. Therefore, the Janus TiSSe monolayer presents a new perspective for the selection of battery adsorption materials in lithium-sulfur batteries.

Design of Coatings for Sulfur-Based Cathode Materials in Lithium-Sulfur Batteries: A review.

Lithium-sulfur batteries (LSBs) are considered next-generation energy storage and conversion solutions owing to their high theoretical specific capacity and the high abundance/low-cost of sulfur-based cathode materials. However, LSBs still encounter significant challenges, including the low conductivities of sulfur-based materials, severe volumetric expansion of sulfur during the discharge process, and the persistent "shuttle effect" of polysulfides. In recent years, a tremendous amount of research has been conducted to address the above challenges by developing coating and compositing materials and corresponding fabrication strategies for sulfur-based cathode materials. In this study, the surface coating, compositing materials, and fabrication methodologies of LSB cathodes are comprehensively reviewed in terms of advanced materials, structure/component characterization, functional mechanisms, and performance validation. Some technical challenges are analyzed in detail, and possible future research directions are proposed to overcome the challenges toward practical applications of lithium-sulfur batteries.

Potassium Ion-Assisted Self-Assembled MXene-K-CNT Composite as High-Quality Sulfur-Loaded Hosts for Lithium-Sulfur Batteries.

We successfully synthesized hybrid MXene-K-CNT composites composed of alkalized two-dimensional (2D) metal carbide and carbon nanotubes (CNTs), which were employed as host materials for lithium-sulfur (Li-S) battery cathodes. The unique three-dimensional (3D) intercalated structure through electrostatic interactions by K+ ions in conjunction with the scaffolding effect provided by CNTs effectively inhibited the self-stacking of MXene nanosheets, resulting in an enhanced specific surface area (SSA) and ion transport capability. Moreover, the addition of CNTs and in situ-grown TiO2 considerably improved the conductivity of the cathode material. K+ ion etching created a more hierarchical porous structure in MXene, which further enhanced the SSA. The 3D framework effectively confined S embedded between nanosheet layers and suppressed volume changes of the cathode composite during charging/discharging processes. This combination of CNTs and alkalized nanosheets functioned as a physical and chemical dual adsorption system for lithium polysulfides (LiPSs). When subjected to a high current at 1.0C, S@MXene-K-0.5CNT with S-loaded of 1.2 mg cm-2 had an initial capacity of 919.6 mAh g-1 and capacity decay rate of merely 0.052% per cycle after 1000 cycles. Moreover, S@MXene-K-0.5CNT maintained good cycling stability even at a high current of up to 5.0C. These impressive results highlight the potential of alkalized 2D MXene nanosheets intercalated with CNTs as highly promising cathode materials for Li-S batteries. The study findings also have prospects for the development of next-generation Li-S batteries with high energy density and prolonged lifespans.

Flexible CNT-Interpenetrating Hierarchically Porous Sulfurized Polyacrylonitrile (CIHP-SPAN) Electrodes for High-Rate Lithium-Sulfur (Li-S) Batteries.

Sulfurized polyacrylonitrile (SPAN) is a promising cathode material for lithium-sulfur batteries owing to its reversible solid-solid conversion for high-energy-density batteries. However, the sluggish reaction kinetics of SPAN cathodes significantly limit their output capacity, especially at high cycling rates. Herein, a CNT-interpenetrating hierarchically porous SPAN electrode is developed by a simple phase-separation method. Flexible self-supporting SPAN cathodes with fast electron/ion pathways are synthesized without additional binders, and exceptional high-rate cycling performances are obtained even with substantial sulfur loading. For batteries assembled with this special cathode, an impressive initial discharge capacity of 1090 mAh g-1 and a retained capacity of 800 mAh g-1 are obtained after 1000 cycles at 1 C with a sulfur loading of 1.5 mg cm-2. Furthermore, by incorporating V2O5 anchored carbon fiber as an interlayer with adsorption and catalysis function, a high initial capacity of 614.8 mAh g-1 and a notable sustained capacity of 500 mAh g-1 after 500 cycles at 5 C are achieved, with an ultralow decay rate of 0.037% per cycle with a sulfur loading of 1.5 mg cm-2. The feasible construction of flexible SPAN electrodes with enhanced cycling performance enlists the current processing as a promising strategy for novel high-rate lithium-sulfur batteries and other emerging battery electrodes.

Insight into the effects of gas molecules-adsorbed on 2D-FeS2: A DFT study

Lithium-sulfur (Li-S) batteries are especially competitive in the energy sector due to their excellent performances, like preferable energy density and economic benefits. Studying the adsorption of gas molecules on electrode materials has potential engineering significance for Li-S batteries since they have a highly osmotic potential, which causes unavoidable damage to batteries. In this work, the adsorption phenomenon of common gas molecules (H2O, N2, H2, CO2, and O2) on the two-dimensional pyrite (2D-FeS2) cathode material surface, as well as the effects on the electronic and electrochemical properties, were investigated by the first-principles calculations. The adsorption capabilities were estimated by adsorption energy and Mulliken population analysis. Simulation results demonstrated that whole adsorption energies were less than -1.0 eV and larger than -0.6 eV, which shows a physisorption nature. Among them, the O-S bond of O2/2D-FeS2 has the strongest strength. Electronic structure calculations suggested that 2D-FeS2 maintained good conductivity after gas molecules were adsorbed, achieving efficient transfer between electron, lithium, and sulfur intermediates. Additionally, ab initio molecular dynamics (AIMD) simulations showed that Li+ exhibits excellent diffusion performance and low activation energy at different temperatures. 2D-FeS2 still has a stable electrochemical working window (1.87 ∼ 2.47 V), while the theoretical open current voltage is damaged by gas molecule adsorption. Consequently, this work theoretically reveals the effect of gas molecules on the cathode materials for Li-S batteries, which has guide meaning for engineering.

Sulfur Encapsulation into Carbon Nanospheres as an Effective Technique to Limit Sulfide Dissolution and Extend the Cycle Life of Lithium–Sulfur Batteries

Sulfur Encapsulation into Carbon Nanospheres as an Effective Technique to Limit Sulfide Dissolution and Extend the Cycle Life of Lithium–Sulfur Batteries

Theoretical screening of electrocatalytic performance of Fe@BNC materials in lithium-sulfur batteries

Advanced cathode materials can suppress the shuttle effect and improve the slow sulfur reduction kinetics during discharge in lithium-sulfur batteries. The catalytic performance of Fe@BNC single-atom catalysts as cathode materials was evaluated through simulations based on density functional theory in this article. By calculating the Gibbs free energy curve and adsorption energy of polysulfides on the substrate, it was found that Fe@BNC has a reasonable adsorption energy range and good catalytic activity. Moreover, calculations of reaction energy barriers indicate that Fe@B1N3 performs well in delithiation when charged. The Research investigates in detail the electrocatalytic properties and electronic structure properties of Fe@BNC as a cathode material for lithium-sulfur batteries. This paper highlights its potential to improve battery performance by reducing the shuttle effect and accelerating the redox kinetics.

Mixed valence Mo2C-MoC/C catalyst enhances polysulfides conversion kinetics in lithium–sulfur batteries

Lithium-sulfur batteries have received extensive attention in the field of electrochemical energy storage systems due to their extremely high theoretical energy density (2600 Wh·kg−1) and low cost. However, poor electrical conductivity, shuttle effect, and volume expansion effect still need to be addressed. Here, we controllably synthesized hollow spherical Mo2C-MoC/C structure as the cathode material for lithium-sulfur batteries. Through high-temperature calcination, the synthesis of graphitized reticular carbon matrix and the loading of Mo2C and MoC nanoparticles with mixed valence of Mo2+ and Mo3+ were simultaneously achieved. The two synergistically improved the electronic conductivity and ensured excellent battery performance. From the experimental results, Mo2C-MoC/C structure strongly adsorbed polysulfides and promoted the conversion of polysulfides to lithium sulfide, accelerating the reaction kinetics and enhancing the battery performance. The initial discharge specific capacity of Mo2C-MoC/C electrode with 57.12 wt% sulfur content was 870.4 mAh·g−1 at 0.2 C, and remained at 770.7 mAh·g−1 at 0.5 C, which was significantly better than that of Mo2C/C/S. The rational design of the Mo2C-MoC/C structure in this study can be generalized to the advanced electrode materials of other Mo-based nanomaterials.

Heterokaryotic transition-metal dimers embedded monolayer g-C3N3 as promising anchoring and electrocatalytic materials for lithium-sulfur battery: First-principles calculations

g-C3N3 not only has high content of pyridine nitrogen, but also has a special two-dimensional porous structure, which is an ideal diatomic catalytic host materials. In this work, homonuclear and heteronuclear dual-atom catalysts (DACs, TM-TM@g-C3N3, TM = Mn, Fe, Co, Ni) were constructed using single-layer g-C3N3 as the carrier material of DACs, and their potential as sulfur-hosting materials and electrocatalytic materials for lithium-sulfur batteries was explored through first principles comprehensively. The results show that the coupling between the two metal atoms in heteronuclear DACs can regulate the spin state of each other's d-electrons, so that the anchoring and catalytic effects of heteronuclear DACs on polysulfide are more excellent than that of homonuclear DACs. Co-Mn@g-C3N3, when utilized as the cathode material in lithium-sulfur batteries, offers exceptional properties due to the hybridization between Mn2+ high-spin state d electron and Co2+ half-filled dz2 orbital. This unique interaction not only enables the polysulfide to exhibit the lowest Gibbs free energy during conversion, but also results in the lowest reaction energy barrier of 0.26 eV for the conversion of Li2S2 to Li2S. Furthermore, it is found that when 3d transition metal atoms act as heteronuclear DACs, the coupling between metal ions with high-spin states at the active site and metal ions with empty orbitals or half-full d-electrons has the most significant catalytic effect on polysulfides.

Hybrid Organosulfur Network/MWCNT Composite Cathodes for Li-S Batteries.

Lithium-sulfur (Li-S) batteries hold a promising position as candidates for next-generation high-energy storage systems. Here, we combine inverse vulcanization of sulfur with multiwalled carbon nanotubes (MWCNTs) to increase the conductivity of cathode materials for Li-S batteries. The mixing process of inversely vulcanized sulfur copolymer networks with MWCNTs is aided by shear in a two-roll mill to take advantage of the soft nature of the copolymer. The high-throughput mixing method demands a source of conductive carbon that can be intimately mixed with the S copolymer, rendering MWCNTs an excellent choice for this purpose. The resulting sulfur copolymer network-MWCNTs composites were thoroughly characterized in terms of structure, chemical composition, thermal, and electronic transport properties, and finally evaluated by electrochemical benchmarking. These promising hybrids yielded electrodes with high sulfur content and demonstrate stable electrochemical performance exhibiting a specific capacity of ca. 550 mAh·gsulfur-1 (380 mAh·gelectrode-1) even after 500 charge-discharge cycles at specific current of 167 mA·g-1 (corresponds to 0.1C discharge rate), and thus are superior to melt-infiltrated reference samples.

Uniaxial Tensile Strain Impact on 1T-NbS2 Monolayers as Cathode Material for Lithium-Sulfur Batteries

In this work, we report our study on asymmetrical Janus TiSSe monolayers as cathode materials for lithium-sulfur batteries by first-principles calculations, encompassing adsorption, catalytic, and conductive properties. The results indicate...

Theoretical investigation of synergistically boosting the anchoring and electrochemical performance of lithiophilic/sulfiphilic transition metal carbides for lithium-sulfur batteries.

Lithium-sulfur (Li-S) battery is one of the most promising next-generation energy-storage systems with a high energy density and low cost. However, their commercial applications face several challenges, such as the shuttle effect caused by the soluble lithium polysulfide (LiPSs) intermediates and the sluggish sulfur redox reaction. In this article, we systematically investigated the anchoring and electrochemical performance of a series of transition metal carbides (TMCs: TiC, VC, ZrC, NbC, HfC, TaC) as cathode materials for Li-S batteries by theoretical calculations. The lithiophilic/sulfiphilic non-polar (001) surfaces of TMCs can offer moderate binding strength with LiPS intermediates, ensuring good performance of sulfur immobilization. These TMCs can also facilitate lithium diffusion, indicating the good rate performance of Li-S batteries. We also demonstrated that the studied TMCs can be classified into two classes according to their catalytic activity for Li2S decomposition which originated from their different electronic structural features. Furthermore, TiC, ZrC, and HfC exhibited excellent bifunctional electrochemical activity through reducing the Gibbs free energy for sulfur reduction reactions (SRRs) and lowering the barrier for Li2S decomposition which facilitates accelerating electrode kinetics and elevating utilization of sulfur. Our results offer a systematic approach to designing and screening non-polar materials for high-performance Li-S batteries, based on the rational electronic structure and lattice match strategy.

N-doped CNTs wrapped sulfur-loaded hierarchical porous carbon cathode for Li-sulfur battery studies.

Lithium-sulfur (Li-S) batteries are considered promising next-generation energy storage devices due to their low cost and high energy density (2600 W h kg-1). However, the practical applicability of Li-S batteries is hindered by the insulating nature of sulfur cathodes, and the high solubility of polysulfides (Li2Sx, 3 < x ≤ 8) which are formed during the electrochemical process. Integrating sulfur into the carbon host is an effective way to enhance the conductivity of the electrode which hampers the shuttling effect of the polysulfides. Here in this study, hierarchical porous carbon structures (HPC) are prepared from spent coffee waste (SCW) by the KOH activation process and are encapsulated with sulfur (SHPC) which increases the interaction between sulfur and carbon and enhances both the electronic and ionic conductivities. Further wrapping of SHPC with N-doped multi-walled carbon nanotubes (NCNTs) gives a SHPC-NCNT composite, which alleviates the shuttling of polysulfides by trapping them and ensures the required conductivity to the sulfur cathode during the Li+ reactions. When studied as a cathode material for Li-S batteries, the prepared cathode showed 664 and 532 mA h g-1 specific capacities after 150 cycles at 0.2C and 0.5C, respectively. The stable cyclability and rate capability properties of SPHCNCNT suggest that the prepared sulfur composite is suitable as a cathode material for Li+ energy storage applications.

First-row transition metal carbide nanosheets as high-performance cathode materials for lithium-sulfur batteries.

Despite the prodigious potential of lithium-sulfur (Li-S) batteries as future rechargeable electrochemical systems, their commercial implementation is hindered by several vital issues, including the shuttle effect and sluggish migration of lithium-polysulfides leading to rapid capacity fading. Here, we systematically investigate the potential of first-row two-dimensional transition metal carbides (TMCs) as sulfur cathodes for Li-S batteries. The adsorption strength of lithium-polysulfides on TMCs is induced by the amount of charge transfer from the former to the latter and the proposed periodic relationship between sulfur in Li2S and 3d-transition metals. Our findings show that the VC nanosheet possesses immense anchoring potential and exhibits a comparatively low migration energy barrier for lithium-ion and Li2S molecules. Additionally, we report ab initio molecular dynamics simulations for lithiated polysulfide species anchored on a TMC-based model with a liquid-electrolyte medium. The microscopic reaction mechanism, revealed by the evolution of the reaction voltage during lithiation, demonstrates that the dissolution of high-order lithium-polysulfides in the electrolytes can be prevented due to their robust interaction with TMC-based cathode materials. These appealing features suggest that TMCs present colossal performance improvements for anchoring lithium-polysulfides, stimulating the active design of sulfur cathodes for practical Li-S batteries.

Two-dimensional carbazole-based COFs for high-performance lithium-sulfur batteries.

Carbazole-based COFs were synthesized and applied as the sulfur-host in cathode materials for lithium-sulfur batteries (LSBs), which effectively mitigate the shuttle effect of lithium polysulfides. A high initial capacity of 1232 mAh g-1 at 0.1C is achieved, while also showing excellent capacity retention and stability in cyclic experiments. This work highlights the potential application of carbazole-based COFs for LSBs.

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

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

Tandem Carbon Hollow Spheres with Tailored Inner Structure as Sulfur Immobilization for Superior Lithium–Sulfur Batteries

AbstractThe construction of lithium–sulfur battery cathode materials while simultaneously achieving high areal sulfur‐loading, adequate sulfur utilization, efficient polysulfides inhibition, rapid ion diffusion, etc. remains a major challenge. Herein, an internal regulatory strategy to fabricate the unique walnut‐like yolk–shell carbon flower@carbon nanospheres is presented (WSYCS) as sulfur hosts. The internal carbon flower, suitable cavity, and external carbon layer effectively disperse the insulate sulfur, accommodate volumetric expansion, and confine polysulfides, thus improving the performance of lithium–sulfur batteries. The finite element simulation method also deduces the enhanced Li+ diffusion and lithium–sulfur reaction kinetics. More importantly, WSYCS2 is grafted onto carbon fiber (CF) by electro‐spinning method to form a tandem WSYCS2@CF 3D film as a sulfur host for the free‐standing electrode. The corresponding battery exhibits an extremely high areal capacity of 15.5 mAh cm−2 with a sulfur loading of 13.4 mg cm−2. Particularly, the flexible lithium–sulfur pouch cell delivers a high capacity of 8.1 mAh cm−2 and excellent capacity retention of 65% over 800 cycles at a relatively high rate of 1C, corresponding to a calculated energy density of 539 Wh kg−1 and 591 Wh L−1. This work not only provides guidance for tailoring thick carbon/sulfur electrodes but also boosts the development of practical lithium–sulfur batteries.

Theoretically unraveling the performance of 2D-FeS2 as cathode material for Li-S batteries

The construction of electrode materials with high conductivity and satisfactory safety for lithium-sulfur (Li-S) batteries remains critical to enhancing the performance of energy storage devices. In recent years, two-dimensional (2D) materials with layered structures have been a hot spot for research due to their unique electronic properties and large specific surface area. As an emerging electrochemically active material, 2D-FeS2 has short ion diffusion paths and a high specific surface area. Based on theoretical calculations, we have systematically studied the performance of the 2D-FeS2 monolayer as cathode material for Li-S batteries from five aspects: obtainability of structure, thermodynamic stability, electrical, surface activity, and electrochemical properties. Simulation results show that the 2D-FeS2 monolayer structure is easy to form due to the small exfoliation energy and interlayer binding energy. The layered structure surface enhances the anchoring effect of polysulfide. Excellent stability was verified by tdynamics simulation. Additionally, the DOS results show that the 2D-FeS2 monolayer has higher conductivity, which effectively improves the mobility of Li+ and electrons. The theoretical specific capacity of the 2D-FeS2 monolayer is 446.96 mAh/g, and the lower Li+ diffusion barrier is 0.19 eV. Compared to traditional FeS2, the 2D-FeS2 monolayer has higher conductivity and stability. In brief, the 2D-FeS2 monolayer is a promising cathode material for Li-S batteries. This work opens up a new path for the application of 2D materials to new energy batteries and also deepens our understanding of 2D materials at the nanoscale.