Material For Lithium-sulfur Batteries Research Articles

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.

Enhancing Lithium-Sulfur Battery Performance with MXene: Specialized Structures and Innovative Designs.

Established in 1962, lithium-sulfur (Li-S) batteries boast a longer history than commonly utilized lithium-ion batteries counterparts such as LiCoO2 (LCO) and LiFePO4 (LFP) series, yet they have been slow to achieve commercialization. This delay, significantly impacting loading capacity and cycle life, stems from the long-criticized low conductivity of the cathode and its byproducts, alongside challenges related to the shuttle effect, and volume expansion. Strategies to improve the electrochemical performance of Li-S batteries involve improving the conductivity of the sulfur cathode, employing an adamantane framework as the sulfur host, and incorporating catalysts to promote the transformation of lithium polysulfides (LiPSs). 2D MXene and its derived materials can achieve almost all of the above functions due to their numerous active sites, external groups, and ease of synthesis and modification. This review comprehensively summarizes the functionalization advantages of MXene-based materials in Li-S batteries, including high-speed ionic conduction, structural diversity, shuttle effect inhibition, dendrite suppression, and catalytic activity from fundamental principles to practical applications. The classification of usage methods is also discussed. Finally, leveraging the research progress of MXene, the potential and prospects for its novel application in the Li-S field are proposed.

Insight into the effect of N-doping level in N-doped carbons modified separator on improving the electrochemical performance of Li-S batteries

Carbon materials are widely applied in lithium-sulfur (Li-S) batteries due to their large specific surface area, high conductivity, and tunable properties. An appropriate heteroatom doping can enhance the adsorption ability and electrochemical activity toward lithium polysulfides, thus improving the overall performance of Li-S batteries. Herein, three nitrogen-doped carbons (NCs) with different nitrogen doping levels are firstly prepared and then used as the model materials to coat the common polypropylene (PP) separator, aiming to elaborate the effect of adsorption behavior from various N-doping level carbons surface toward lithium polysulfides on the subsequent catalytic conversion kinetics. The experimental data demonstrate that the NC800 with appropriate N-doped level shows the moderate adsorption of polysulfides as well as exhibits the best reaction kinetics on polysulfides conversion. In comparison, an assembled Li-S battery with NC800-PP separator delivers high capacity and good cycling stability, achieving an initial specific capacity of ∼ 1302.2 mAh g−1 at 0.2 C and a capacity fading rate of ∼ 0.061 % per cycle after 500 cycles at 1.0 C. Moreover, a Li-S battery using NC800-PP separator still delivers an initial specific capacity of ∼ 1147.6 mAh g−1 at 0.1 C and maintains a stable specific capacity of ∼ 833.5 mAh g−1 even with a sulfur loading of ∼ 3.9 mg cm−2. This study is believed to give better insight to reveal the internal correlation of adsorption and catalytic effect on polysulfides, as well as provide a guidance for rationally designing heteroatom doping carbon materials in Li-S batteries.

Amorphous MoS2/MoO3 nanosheets as high‐efficient polysulfide barrier in Li‐S batteries

Lithium‐sulfur batteries (LSBs) are seriously impeded by poor reaction kinetics and the polysulfides shuttling, leading to low utilization of sulfur and poor cycling performance. Herein, amorphous MoS2/MoO3 nanosheets are prepared by a one‐step formamide (FA)‐assisted strategy. Due to the merits of high adsorption capability and good catalytic activity of MoS2, relatively high electronic conductivity and strong polarity of MoO3, and abundant active sites of amorphous nanosheet structure, the LSBs based on amorphous MoS2/MoO3‐2 nanosheets coated separator exhibit an outstanding specific capacity (1420.2 mA h g‐1 at 0.1 C), excellent rate capacity (505.4 mA h g‐1 at 5 C), and long cycle life (a negligible decay rate of 0.063 % per cycle at 0.5 C). This work provides an idea for designing efficient amorphous catalytic materials in LSBs.

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.

Rational Design of Non-Noble Metal Single-Atom Catalysts in Lithium-Sulfur Batteries through First Principles Calculations.

Lithium-sulfur (Li-S) batteries with a high theoretical energy density of 2600 Wh·kg-1 are hindered by challenges such as low S conductivity, the polysulfide shuttle effect, low S reduction conversion rate, and sluggish Li2S oxidation kinetics. Herein, single-atom non-noble metal catalysts (SACs) loaded on two-dimensional (2D) vanadium disulfide (VS2) as the potential host materials for the cathode in Li-S batteries were investigated systematically by using first-principles calculations. Based on the comparisons of structural stability, the ability to immobilize sulfur, electrochemical reactivity, and the kinetics of Li2S oxidation decomposition between these non-noble metal catalysts and noble metal candidates, Nb@VS2 and Ta@VS2 were identified as the potential candidates of SACs with the decomposition energy barriers for Li2S of 0.395 eV (Nb@VS2) and of 0.162 eV (Ta@VS2), respectively. This study also identified an exothermic reaction for Nb@VS2 and the Gibbs free energy of 0.218 eV for Ta@VS2. Furthermore, the adsorption and catalytic mechanisms of the VS2-based SACs in the reactions were elucidated, presenting a universal case demonstrating the use of unconventional graphene-based SACs in Li-S batteries. This study presents a universal surface regulation strategy for transition metal dichalcogenides to enhance their performance as host materials in Li-S batteries.

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.

Selecting non-metal doped FeS2 as efficient sulfur cathode host for enhanced Li-S redox chemistry.

Lithium-sulfur batteries (LSBs) are considered as the development direction of the new generation energy storage system due to their high energy density and low cost. The slow redox kinetics of sulfur and the shuttle effect of lithium polysulfide (LiPS) are considered to be the main obstacles to the practical application of LSBs. Transition-metal sulfide as the cathode host can improve the Li-S redox chemistry. However, there has been no investigation of the application of FeS2 host in Li-S redox chemistry. Applying the first-principles calculations, we investigated the formation energy, band gap, Li+ diffusion, adsorption energy, catalytic performance and Li2 S decomposition barrier of FeAx S2-x (A=N, P, O, Se; x=0, 0.125, 0.25, 0.375) to explore the Li-S redox chemistry and finally select excellent host material. FeA0.25 S1.75 (A=P, Se) has a low Li+ diffusion barrier and superior electronic conductivity. FeO0.25 S1.75 is more favorable for LiPS adsorption, followed by FeP0.25 S1.75 . FeP0.25 S1.75 (001) shows a low overpotential for the Li-S redox chemistry. In summary, FeP0.25 S1.75 has more application potential in LSBs due to its physical and chemical properties, followed by FeSe0.25 S1.75 . This work provides theoretical guidance for the design and selection of the sulfur cathode host materials in LSBs.

Hybrid Membrane Composed of Nickel Diselenide Nanosheets with Carbon Nanotubes for Catalytic Conversion of Polysulfides in Lithium-Sulfur Batteries.

Lithium-sulfur batteries demonstrate enormous energy density are promising forms of energy storage. Unfortunately, the slow redox kinetics and polysulfides shuttle effect are some of the factors that prevent the its development. To address these issues, the hybrid membrane with combination of nickel diselenide nanosheets modified carbon nanotubes (NSN@CNTs) and utilized Li2 S6 catholyte for lithium sulfur battery. The conductive CNTs facilitates fast electronic/ionic transport, while the polarity of NSN as a strong affinity to lithium polysulfides, effectively anchoring them, facilitating the redox conversion of polysulfide species, and effectively diminishing reaction barriers. The cell with NSN@CNTs delivers the first discharge capacity of 1123.8 mAh g-1 and maintains 786.5 mAh g-1 after 300 cycles (0.2 C) at the sulfur loading 5.4 mg. Its rate capability is commendable, enabling it to sustain a capacity of 559.8 mAh g-1 even at a high discharge rate of 2 C. In addition, its initial discharge capacity can remain 8.33 mAh even at 10.8 mg for duration of 100 cycles. This research indicates the potential application of NSN@CNTs hybrid materials in lithium-sulfur batteries.

Graphene supported In2S3 nanostructure as electrode material for lithium sulfur batteries and supercapacitors

A facile one-pot fabrication of reduced graphene oxide (rGO) supported In2S3-rGO is presented here with improved electrochemical performance in lithium-sulfur (Li–S) batteries and supercapacitors (SCs). Increasing the concentration of rGO in the nanostructures successfully mitigated the conversation kinetics, polysulfide shuttle effect and improved the overall cyclability in Li–S batteries. A battery made from In2S3-rGO30 electrode loses only 8 % of its discharge capacity after 250 continuous charge-discharge cycles, compared to a 36 % loss from a bare In2S3 electrode. It presented a high discharge capacity of 947.3 mA h g−1 at 1C, superb rate performance of 821.65 mA h g−1 at 5C, excellent capacity retention and Columbic efficiency of ⁓100 % over 250 cycles are achieved. The In2S3-rGO30 electrode provides a specific capacitance of 645.2 F g−1 at a current density of 2 A g−1 for SC application. The electrode retains 96 % of its capacity after 1000 continuous discharge cycles at a higher current density of 5 A g−1, performing well and staying ahead of other nanocomposites. This study successfully demonstrates the integration of In2S3 with a two-dimensional conductive substrate as a multifunctional and cost-effective host for designing high-performance cathode for Li–S batteries and battery-type electrode material for SC application.

Enhancing performance of lithium-sulfur batteries through porous carbon network integration in carbonized cotton

A novel material, Cporous@CC, has been developed by incorporating a porous conductive network into carbonized cotton (CC). This modification significantly enhances the surface area of the material, increasing it from 29.1 to 163.0 m2 g−1. The introduction of the porous network significantly enhances the connection between carbon fibers, resulting in a substantial improvement in electronic conduction, up to 2–3 times greater than bare CC. To evaluate its potential, Cporous@CC was utilized as a conductive host for the cathode-active material in lithium-sulfur batteries. The battery utilizing Cporous@CC as the cathode host demonstrated a higher initial capacity of 1200 mAh g−1 at 0.2C and exhibited superior rate capability across the range of 0.1C to 1.0C, outperforming the CC-based battery. The factors contributing to the enhanced electrochemical performance of the Cporous@CC cell were further elucidated through the utilization of the galvanostatic intermittent titration technique.

Enhancing performance of NiCo Sulfide composite cathode by Mn doping in Li-S batteries

A sulfurophilic Ni-Co bimetallic sulfide (NiCo2S4) with Mn doping is synthesized as the electrocatalyst for the cathode of lithium-sulfur batteries. The characterization showed that the incorporation of Mn into the NiCo2S4 effectively altered the size and crystallinity of the particles. The NiCoMn-S/CNT composite were further produced as the sulfur host by combining the Mn-doped NiCo2S4 with space-rich CNTs. This structure physically restricts polysulfides and improves the redox reaction kinetics of polysulfide conversion. Therefore, the NiCoMn-S/CNT@S (4:6) as optimal ratio enables stable cycling with an initial capacity of ∼1149 mAh g−1 at 0.2 C and a lower capacity fade rate (∼0.08% per cycle upon 500 cycles) at 0.5 C. Additionally, the cathode with a sulfur loading of 2.1 mg cm−2 delivers a reversible areal capacity (597.2mAh g−1) over 200 cycles. The results indicate that doping metallic ions into the NiCo2S4 lattice is an effective strategy for enhancing the electrochemical performance of the material in lithium-sulfur batteries.

In situ synthesis of VS4/Ti3C2Tx MXene composites as modified separators for lithium-sulfur battery

Lithium-sulfur (Li-S) batteries are regarded as highly prospective energy storage devices. However, problems such as low sulfur utilization, poor cycle performance, and insufficient rate capability hinder the commercial development of Li-S batteries. Three-dimensional (3D) structure materials have been applied to modify the separator of Li-S batteries to suppress the diffusion of lithium polysulfides (LiPSs) and inhibit the transmembrane diffusion of Li+. A vanadium sulfide/titanium carbide (VS4/Ti3C2Tx) MXene composite with a 3D conductive network structure has been synthesized in situ by a simple hydrothermal reaction. VS4 is uniformly loaded on the Ti3C2Tx nanosheets through vanadium-carbon(V-C) bonds, which effectively inhibits the self-stacking of Ti3C2Tx. The synergistic action of VS4 and Ti3C2Tx substantially reduces the shuttle of LiPSs, improves interfacial charge transfer, and boosts the kinetics of LiPSs conversion, consequently increasing the rate performance and cycle stability of the battery. The assembled battery has a specific discharge capacity of 657 mAhg-1 after 500 cycles at 1C, with a high capacity retention rate of 71%. The construction of VS4/Ti3C2Tx composite with a 3D conductive network structure provides a feasible strategy for the application of polar semiconductor materials in Li-S batteries. It also provides an effective solution for the design of high-performance Li-S batteries.

Conductive vanadium-based metal-organic framework nanosheets membranes as polysulfide inhibitors for lithium-sulfur batteries

The polysulfide shuttle is regarded as the most critical challenge that hinders the commercial process of lithium-sulfur batteries (LSBs). Herein, a vanadium-based MIL-47 nanosheets membrane is fabricated on carbon nanotube film for this trouble, which serves as a versatile interlayer material in LSBs. With a good electrolyte wettability, thin thickness and appropriate pore diameter, MIL-47 nanosheets membrane is capable of efficaciously blocking polysulfides and enabling the fast transport of Li ions via the selectively sieving effect. Furthermore, the excellent conductivity and fully exposed catalytic metal centers contribute to enhance the reaction kinetics and sulfur utilization. Therefore, this MOF-based interlayer provides a wonderful capacity of 1044.6 mAh g−1 and a durable cyclic performance with a numbered decay of 0.03 % per cycle for 1000 cycles at 1 C. Even under harsh conditions of high sulfur loading and lean electrolyte, excellent cycle and rate performances are still acquired. This work boosts the development of multi-functional materials in LSBs.

Dual-additives enable stable electrode-electrolyte interfaces for long life Li-SPAN batteries

Sulfurized polyacrylonitrile (SPAN) is proposed as a promising cathode material for lithium sulfur batteries. However, the continuous side reactions at the electrolyte-electrode interfaces as well as the slow redox kinetics of SPAN cathode deteriorate the electrochemical performance. In this study, an electrolyte with dual-additives comprising 2-fluoropyridine (2-FP) and lithium difluorobis (oxalato) phosphate (LiDFBOP) was used to improve the performance of Li||SPAN cells. 2-FP has a lower lowest occupied molecular orbital energy than that of the solvents in the electrolyte, leading to its prior reduction. A LiF-rich film can be formed on the electrode, effectively improving the stability of the electrolyte-electrode interfaces and prolonging the life. Simultaneously, LiDFBOP could form an electrolyte-electrode interface film containing a large amount of LixPOyFz species, compensating for the kinetic deterioration caused by the lower ionic conductive of LiF formed at the electrolyte-electrode interface. Hence, an electrode-interface film with good chemical stability and high Li+ transport was established by LiF and LixPOyFz-rich species. The Li||SPAN cell with the electrolyte containing dual-additives demonstrates an excellent capacity retention of 97.5% after 200 cycles at 1.0 C, 25 °C, comparing to 56.2% capacity retention without additives. Moreover, the rate capacities of cells with dual-additives can reach 1128.1 mAh/g at 5 C, comparing to only 813.5 mAh/g using electrolyte without additives. Our results shown that the dual-additives in electrolyte provide a promising strategy for practical application of lithium sulfur batteries with SPAN cathodes.

Superfine SnO2–x Particles Embedded in a Porous Carbon Matrix as a Separator-Modifying Material for High-Performance Lithium Sulfur Batteries

The commercialization of lithium sulfur batteries faces great challenges, such as shuttle effect and low conductivity. Herein, we explore embedding anoxic oxide SnO2–x in a porous carbon matrix as a separator-modifying material for lithium sulfur batteries. This material can limit the size of SnO2–x particles and reduce their agglomeration through confining by the porous carbon (PC). As a result, more adsorption and catalytic sites can be obtained. Moreover, the oxygen vacancies in SnO2–x can change the electronic environment to enhance the adsorption and catalysis of polysulfides, resulting in the depression of the shuttle effect of the battery. Therefore, the lithium sulfur battery with the SnO2–x/PC-modified separator has excellent cycling performance. At a current rate of 1 C, it can provide a high initial discharge capacity of 1049.4 mAh g–1 and maintain a reversible specific capacity of 798.4 mAh g–1 after 300 cycles.

Green Production of Biomass-Derived Carbon Materials for High-Performance Lithium-Sulfur Batteries.

Lithium-sulfur batteries (LSBs) with a high energy density have been regarded as a promising energy storage device to harness unstable but clean energy from wind, tide, solar cells, and so on. However, LSBs still suffer from the disadvantages of the notorious shuttle effect of polysulfides and low sulfur utilization, which greatly hider their final commercialization. Biomasses represent green, abundant and renewable resources for the production of carbon materials to address the aforementioned issues by taking advantages of their intrinsic hierarchical porous structures and heteroatom-doping sites, which could attribute to the strong physical and chemical adsorptions as well as excellent catalytic performances of LSBs. Therefore, many efforts have been devoted to improving the performances of biomass-derived carbons from the aspects of exploring new biomass resources, optimizing the pyrolysis method, developing effective modification strategies, or achieving further understanding about their working principles in LSBs. This review firstly introduces the structures and working principles of LSBs and then summarizes recent developments in research on carbon materials employed in LSBs. Particularly, this review focuses on recent progresses in the design, preparation and application of biomass-derived carbons as host or interlayer materials in LSBs. Moreover, outlooks on the future research of LSBs based on biomass-derived carbons are discussed.

“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.

The quinone-based conjugated microporous polymer as an effective electrode additive for activated graphene host material in lithium-sulfur batteries

Lithium-Sulfur (Li-S) battery is receiving increasing attention for next-generation energy storage system due to its promising features such as high theoretical energy density and cost-effectiveness. However, sluggish redox reaction and fatal polysulfide dissolution have been considered as significant challenges which limit the practical application of Li-S batteries. Recently, anthraquinone-based organic molecule was used in the Li-S battery and exhibited good electrochemical performance with enhanced redox chemistry and structural stability. Herein, we used anthraquinone-based conjugated microporous polymer (CMP), namely PAQTA, as an electrode additive for activated graphene (AG) host material in Li-S batteries. Conjugated network of PAQTA with high surface area and porosity provided efficient redox activity and stable electrochemical performance compared to non-conjugated quinone material. We prepared reduced AG/sulfur (rAG/S) electrodes by varying amounts of PAQTA addition and the optimized rAG1h/S + PAQTA 5% showed the best electrochemical performance, proving a synergistic effect between rAG and PAQTA additive. In detail, rAG act as effective host material by taking advantage of in-plane nanopores and high surface area, resulting in enhanced polysulfide adsorption. The PAQTA additive, which improves redox kinetic, could further make intimate contact with rAG via π–π stacking interaction, thereby enhancing the cycling stability. Thus, it is important to note that the synergistic effect between AG host and PAQTA additive enabled improved redox chemistry and structural stability for good electrochemical performance. This study suggests the usage of PAQTA as effective electrode additive for high-performance Li-S batteries with improved long-term cycling stability.

Cobalt-loaded three-dimensional ordered Ta/N-doped TiO2 framework as conductive multi-functional host for lithium-sulfur battery

The low electrical conductivity of sulfur and severe shuttling effect of lithium polysulfides (LiPSs) have hindered the practical application of lithium-sulfur (Li-S) batteries. In this work, a conductive Ta/N co-doped TiO2 framework featured with three-dimensional ordered macroporous (3DOM) structure embedded with ZIF-67 derived Co-anchored N-doped carbon (Co-NC) is synthesized as efficient sulfur host material in Li-S batteries. The 3DOM Ta/N-TiO2 backbone has good structural stability, which benefits the electrolyte penetration and sulfur accommodation. Meanwhile, the Ta/N co-doping not only improves the conductivity of TiO2, but also strengthens the adsorption of LiPSs. In addition, the embedded Co-NC increases the active site of 3DOM skeleton towards LiPSs conversion, facilitates the diffusion of Li+ ion, and at the same time provides additional microspores for sulfur confinement. Attributed to these features, the sulfur electrode based on 3DOM Ta/N-TiO2@Co-NC achieves excellent electrochemical performance. The S/3DOM Ta/N-TiO2@Co-NC cell maintains a discharge capacity of 789.2 mAh g−1 after 500 cycles at 1C with a low decay rate of 0.06 % per cycle. Additionally, an initial area capacity of 5.67 mAh cm−2 is obtained under areal sulfur loading of 6.55 mg cm−2. This multistage porous sulfur cathode design has the potential to expedite the development of feasible Li-S battery.