Adsorption Of Lithium Polysulfides Research Articles

Enhanced lithium-sulfur battery eilectrochemistry via Se-doped MoS2/rGO ultrathin sheets as sulfur hosts

In the pursuit of advancing lithium-sulfur (Li-S) battery technology, the intrinsic challenges of sulfur conductivity and the shuttle effect during charge-discharge cycles have posed significant barriers. Despite many efforts made through physical and chemical methodologies, the development of host materials with more active sites and good catalytic activities might still remain a challenging problem in Li-S batteries. This study presents a novel selenium-doped molybdenum disulfide (Se-MoS2) nanosheet, synthesized on reduced graphene oxide (rGO), which would address these issues. The Se-MoS2/rGO composite enhances conductivity and catalytic activity through the creation of anionic vacancies, facilitating lithium polysulfide adsorption. As a sulfur host, this material delivers an impressive initial capacity of 1008.1 mAh g−1 at 1C, maintaining 620.7 mAh g−1 after 500 cycles with a minimal capacity fade of 0.077 % per cycle, demonstrating superior coulombic efficiency and stability. The findings underscore the impact of heteroatom doping on the electrochemical performance of graphene-based materials for Li-S batteries.

Copper-nickel MOF-coated electrospun polyacrylonitrile membranes for Li–S batteries: Mitigating the shuttle effect and enhancing stability

Cu–Ni MOF nanoparticles were synthesized as coating materials for lithium–sulfur battery membranes, and the performance of batteries employing Cu–Ni MOF/PAN (CNMP) electrospinning membranes were examined. The modified membrane efficiently suppresses the shuttle effect, leveraging the synergistic catalysis and adsorption capabilities of the Cu–Ni MOF nanoparticles. The modified membrane exhibited relatively high porosity and outstanding electrolyte absorption capacity. The CNMP membrane battery demonstrated a remarkable first-cycle discharge capacity of 1529 mA h g⁻¹. The battery maintained an exceptional discharge capacity with 85.2 % retention and a minimal capacity decay rate of just 0.074 % per cycle after 200 cycles at 0.5 C. The capacity retention of the modified membrane battery remained at 74.6 % even after 2000 cycles at 2 C. The excellent performance of the modified membrane battery was due to the physical entrapment and strong chemical adsorption of lithium polysulfides by Cu–Ni MOF nanoparticles, significantly preventing the shuttle effect and facilitating rapid oxidation–reduction kinetics based on strong catalytic conversion.

Synergistic implementation of efficient adsorption-diffusion-conversion in lithium-sulfur batteries via built-in electric field constructed by transition metal selenides

The adsorption of lithium polysulfides (LiPSs), the transport of lithium ions, and the redox kinetics collectively play pivotal roles in determining the application of lithium-sulfur (Li-S) batteries. Herein, a defect-rich p-Co3Se4/n-ZnSe p-n junction (ZCSNC) is engineered by chemical vapor deposition (CVD)-selenation. The n-type semiconductor ZnSe and the p-type semiconductor Co3Se4 contained in ZCSNC effectively anchor LiPSs and promote the catalytic reaction kinetics through synergistic effects, respectively. Meanwhile, the presence of heterogeneous interfaces in the p-n junction and the difference in work functions spontaneously form a built-in electric field, which promotes the transport and transfer of lithium ions and LiPSs. Therefore, the ZCSNC functional material contributes to improving the electrochemical performance of Li-S batteries through the process of adsorption-diffusion-conversion. The Li-S cells with ZCSNC-modified separators show excellent rate performance (741.1 mAh/g at 5C) and long-lasting cycling performance (only 0.04 % capacity decay per cycle over 1000 cycles). Notably, the ZCSNC still has excellent rate discharge capacities (683.9 and 649.7 mAh/g at 2C, respectively) at high sulfur loading and low temperature of 0 °C. This study illustrates that a p-n junction containing a built-in electric field can effectively modulate the kinetics of redox reactions of LiPSs through synergistic interactions.

Understanding the role played by Cu nanoparticles embedded in situ in a carbonaceous matrix as sulfur host for lithium-sulfur batteries

The lithium-sulfur (Li-S) battery is a promising alternative to Li-ion batteries as an energy storage system, owing to its higher capacity and specific energy values. To tackle its intrinsic problems, the element copper (Cu) is an attractive option given both its excellent conductivity and its ability to interact with highly reactive polysulfides. Here, we propose the use of a carbon/copper composite (90.5:9.5 wt ratio) obtained by thermal decomposition of a single precursor based on a Cu(II) oleate/oleic acid complex and eliminating the use of H2 as a reducing agent as commonly reported. Cu nanoparticles (mean particle size around 15 nm in diameter) which are highly dispersed on an amorphous carbon matrix derived from an organic framework, enhance both the conductivity and the ability for the chemical adsorption of lithium polysulfides (LiPSs), and thus increasing the reaction efficiency. Poor cycling stability, less specific capacity, and diminished rate capability were observed when the Cu content was reduced to around 70 % through treatment with concentrated nitric acid. This confirms the electrocatalytic role of the metal.

Synergistic improvement of the sulfur redox reaction by MOF-driven dual-defect polyhedral Mn-doped Co1-xS embedded in an N-doped carbon composite host for practical lithium-sulfur batteries

In the quest for practical sulfur hosts for lithium-sulfur batteries, a novel approach has been delineated. By meticulously adjusting the Mn:Co (1:5/1:9/1:1) ratio and the sulfidation temperature, a series of nitrogen-doped carbon nanopolyhedron composites have been synthesized, denoted as 1:9 Mn-Co1-xS-NC@NC, 1:5 Mn-Co1-xS-NC@NC, 1:1 Mn-Co1-xS-NC@NC, and Co1-xS-NC@NC. These materials, inheriting the polyhedral shape and a novel cavity structure from their precursors, exhibit enhanced lithium polysulfide adsorption and catalytic activity due to the introduction of Mn heteroatoms and cobalt vacancies. The resultant S@1:9 Mn-Co1-xS-NC@NC cathode excels in electrochemical performance, delivering an initial discharge capacity of 999.37 mA h g−1 at 1 C, and sustaining 715.65 mA h g−1 over 100 cycles. Notably, at an elevated sulfur loading of 3.05 mg cm−2 (E/S, 14.5 uL g−1), the cathode retains an areal capacity of 3.24 cmmA h cm−2 (corresponding specific capacity of 1067.59 mA h g−1) after 61 cycles at 0.2 C. The synergistic effect of manganese dopants and cobalt vacancies confers superior adsorptive and catalytic properties, presenting a promising avenue for the development of sulfur host materials with tailored morphologies and defect-rich structures.

Facile construction of porous carbon fibers from coal pitch for Li-S batteries

Coal pitch, an important by-product in the coal coking industry with a high output, is a low-cost and high-carbon yield precursor for the manufacturing of high-value carbon materials. Herein, N/O co-doped carbon fiber (CFCP), fabricated by electrospinning using pre-oxidized coal pitch as the precursor, was employed as the sulfur host for Li-S batteries. The presence of more pyrrolic N and graphic N in CFCP than carbon fiber made from polyacrylonitrile benefits the adsorption of lithium polysulfide and the battery’s life. Sulphur-CFCP cathode (S@CFCP) exhibited excellent specific capacity and cyclability, with a specific capacity of 701.1 mAh/g and a low capacity decay rate of 0.088% per cycle over 200 cycles at 2.0 C, respectively. The high ion diffusion rate, low charge transfer resistance, and effective conversion of lithium polysulfides enable the high electrochemical performance of S@CFCP.

Co3V2O8 composite carbon hollow spheres bidirectionally catalyze the conversion of lithium polysulfide to improve the capacity of lithium‐sulfur batteries

Although lithium‐sulfur batteries have a high theoretical energy density that is higher than lithium‐ion batteries, their development is limited by the slow kinetics of lithium polysulfide conversion. In this research, we utilize the excellent bidirectional catalysis and adsorption of lithium polysulfide by the bimetallic oxide Co3V2O8 composite carbon hollow sphere to address the kinetic obstacle of lithium‐sulfur battery. On the one hand, the carbon hollow sphere substrate provides a cavity that can hold a large amount of sulfur. On the other hand, it can limit the diffusion of lithium polysulfide by van der Waals forces. The combination of the above two points improves the capacity and stability of lithium‐sulfur batteries. It has a specific capacity of 1237.2 mAh g‐1 at 0.2 C current density and retains 603 mAh g‐1 after 100 cycles. At a high current density of 2 C, the specific capacity is 976.2 mAh g‐1. After 1000 cycles, it holds at 338.3 mAh g‐1, and the capacity retention rate per cycle is 99.89%. This work discovers the new potential of Co3V2O8 as an electrocatalyst and proposes a process that can widely prepare carbon materials with complex uniform distribution of electrocatalysts to achieve high specific capacity of lithium‐sulfur batteries.

Oxygen-defect-rich ZnV2O4/ZnO heterojunction as multifunctional separator to boost lithium polysulfide adsorption and conversion for superior lithium‑sulfur batteries

Lithium‑sulfur (Li-S) batteries have been recognized as one of the promising energy systems which can meet the large amounts of energy demanding. However, its practical application has been seriously hindered due to the instinct drawbacks such as low conductivity, large volume expansion and notorious “shuttle effect”. Herein, multi-structure lamellar flower-like zinc vanadate/zinc oxide heterojunction (CoNi@ZnV2O4/ZnO-N,C) with abundant oxygen vacancies, CoNi nanoalloys and N-doped carbon (C) layer has been successfully constructed. XPS and ex-situ XRD analysis reveal that the oxygen vacancies can replace lattice oxygen to adsorb lithium polysulfides (LPS), then stabilize the crystal structure. Additionally, with the synergistic catalysis of CoNi nanoalloys and N-doped C layer, the heterojunction can effectively accelerate the conversion of LPS and promote the precipitation of Li2S. When the lamellar flower-like heterojunction is applied as separator modifier, the “shuttle effect” of LPS can be effectively hindered, leading to synergistic enhancement of long cycle performance of Li-S batteries: the initial discharging capacities of 1468.9 and 1394.9 mAh g−1 can be obtained at 0.1 and 1C, respectively. After 1000 long-term cycles at 3C, the discharging capacity can be still maintained at 467.9 mAh g−1, with a capacity loss rate of 0.049 % per cycle, showing a stable high-rate performance.

Melamine Polymerization Promotes Compact Phosphorus/Carbon Composite for High-Performance and Safe Lithium Storage.

Phosphorus is regarded as a promising material for high-performance lithium-ion batteries (LIBs) due to its high theoretical capacity, appropriate lithiation potential, and low lithium-ion diffusion barrier. Phosphorus/carbon composites (PC) are engineered to serve as high-capacity high-rate anodes; the interaction between phosphorus and carbon, long-term capacity retention, and safety problems are important issues that must be well addressed simultaneously. Herein, an in situ polymerization approach to fabricate a poly-melamine-hybridized (pMA) phosphorus/carbon composite (pMA-PC) is employed. The pMA hybridization enhances the density and electrical conductivity of the PC, improves the structural integrity, and facilitates stable electron transfer within the pMA-PC composite. Moreover, the pMA-PC composite exhibits efficient adsorption of lithium polysulfides, enabling stable transport of Li+ ions. Therefore, the pMA-PC anode demonstrates a high specific charging capacity of 1,381mAhg-1 at 10Ag-1, and a great capacity retention of 86.7% at 1Ag-1 over 500 cycles. The synergistic effect of phosphorus and nitrogen further confers excellent flame retardant properties to the pMA-PC anode, including self-extinguishing in 2.5s, and a much lower combustion temperature than PC. The enhanced capacity and safety performance of pMA-PC show potential in future high-capacity and high-rate LIBs.

Ion/Electron Co-Conductive Triple-Phase Interface Enabling Fast Redox Reaction Kinetics in Lithium-Sulfur Batteries.

Lithium-sulfur batteries (LSBs) are promising next-generation energy storage systems because of their high energy densities and high theoretical specific capacities. However, most catalysts in the LSBs are based on carbon materials, which can only improve the conductivity and are unable to accelerate lithium-ion transport. Therefore, it would be worthwhile to develop a catalytic electrode exhibiting both ion and electron conductivity. Herein, a triple-phase interface using lithium lanthanum titanate/carbon (LLTO/C) nanofibers to construct ion/electron co-conductive materials was used to afford enhanced adsorption of lithium polysulfides (LiPSs), high conductivity, and fast ion transport in working LSBs. The triple-phase interface accelerates the kinetics of the soluble LiPSs and promotes uniform Li2S precipitation/dissolution. Additionally, the LLTO/C nanofibers decrease the reaction barrier of the LiPSs, significantly improving the conversion of LiPSs to Li2S and promoting rapid conversion. Specifically, the LLTO promotes ion transport owing to its high ionic conductivity, and the carbon enhances the conductivity to improve the utilization rate of sulfur. Therefore, the LSBs with LLTO/C functional separators deliver stable life cycles, high rates, and good electrocatalytic activities. This strategy is greatly important for designing ion/electron conductivity and interface engineering, providing novel insight for the development of the LSBs.

Could Commercially Available Aqueous Binders Allow for the Fabrication of Highly Loaded Sulfur Cathodes with a Stable Cycling Performance?

In this review, the application of five commercially available aqueous-based binders including sodium carboxyl methyl cellulose (CMC), polyacrylic acid (PAA), polyvinyl alcohol (PVA), polyethylene oxide (PEO), and polyethyleneimine (PEI) as well as some representative custom (or purpose) synthesized functional binders used in lithium sulfur (Li-S) batteries is summarized based on the main evaluation criteria of cycling capacity, battery lifetime, and areal sulfur loading (and, consequently, energy density of the battery). CMC with SBR (styrene butadiene rubber) has been reported with promising results in highly loaded sulfur cathodes (>5 mg cm−2 sulfur loading). PVA and PEI were confirmed to provide an enhanced adsorption of lithium polysulfides due to the interaction with hydroxyl and amine groups. No competitive advantage in electrochemical performance was demonstrated through the use of PAA and PEO. Water-based binders modified with polysulfide-trapping functional groups have complex fabrication processes, which hinders their commercial application. In general, achieving a high capacity and long cycling stability for highly loaded sulfur cathodes using commercial aqueous-based binders remains a significant challenge. Additionally, the scalability of these reported sulfur cathodes, in terms of complexity, cost, and stable electrochemical cycling, should be evaluated through further battery testing, particularly targeting pouch cell performance.

Bidirectional enhancement of Li2S redox reaction by NiSe2/CoSe2-rGO heterostructured bi-functional catalysts

The high activity barriers of Li2S nucleation and deposition limit the redox reaction kinetics of lithium polysulfides (LiPSs), meanwhile, the significant shuttle effect of LiPSs hampers the advancement of Li-S batteries (LSBs). In this work, a NiSe2/CoSe2-rGO (NiSe2/CoSe2-G) sulfur host with bifunctional catalytic activity was prepared through a hard template method. Electrochemical experiment results confirm that the combination of NiSe2 and CoSe2 not only facilitates the bidirectional catalytic function during charge and discharge processes, but also increases the active sites toward LiPSs adsorption. Simultaneously, the highly conductive rGO network enhances the electronic conductivity of NiSe2/CoSe2-G/S and provides convenience for loading NiSe2/CoSe2 catalysts. Benefitting from the exceptional catalytic-adsorption capability of NiSe2/CoSe2 and the presence of rGO, the NiSe2/CoSe2-G/S electrode exhibits excellent electrochemical properties. At 1C, it demonstrates a low capacity attenuation of 0.087 % per cycle during 500 cycles. The electrode can maintain a discharge capacity of 927 mAh/g at a sulfur loading of 3.3 mg cm−2. The bidirectional catalytic activity of NiSe2/CoSe2-G offers a prospective approach to expedite the redox reactions of active S, meanwhile, this work also offers an ideal approach for designing efficient S hosts for LSBs.

A review of metal phosphides with catalytic effects in Li-S batteries: boosting the redox kinetics.

Lithium-sulfur batteries (Li-S batteries) are being widely studied as promising energy-storage solutions for the next generation owing to their excellent properties including high energy density, eco-friendliness, and low cost. Nevertheless, drawbacks, especially the severe "shuttle effect" and slow transformation of polysulfides, hinder the road to commercialization of Li-S batteries. The functional utilization of metal compounds in Li-S batteries has been verified, such as enhancing the conductivity, adsorption of lithium polysulfides (LPSs) and improving the kinetics of electrode processes. Benefiting from the outstanding catalytic capability and relatively good conductivity, metal phosphides have gradually received intense attention over the past few years. Consequently, significant progress has been achieved in the optimization of phosphides for Li-S batteries in recent years. This review introduces the application of metal phosphides in Li-S batteries from the aspects of their own characteristics, material structure design, and material interface control. The aim of this review is to enhance the understanding of the operational mechanism of metal phosphides and provide guidance for the development of Li-S batteries.

Recent advances in copper-based materials for robust lithium polysulfides adsorption and catalytic conversion

Lithium–sulfur (Li–S) batteries are considered one of the most promising next-generation secondary batteries owing to their ultrahigh theoretical energy density. However, practical applications are hindered by the shuttle effect of soluble lithium polysulfides (LiPSs) and sluggish redox kinetics, which result in low active material utilization and poor cycling stability. Various copper-based materials have been used to inhibit the shuttle effect of LiPSs, owing to the strong anchoring effect caused by the lithiophilic/sulphilic sites and the accelerated conversion kinetics caused by excellent catalytic activity. This study briefly introduces the working principles of Li–S batteries, followed by a summary of the synthetic methods for copper-based materials. Moreover, the recent research progress in the utilization of various copper-based materials in cathodes and separators of Li–S batteries, including copper oxides, copper sulfides, copper phosphides, copper selenides, copper-based metal-organic frameworks (MOFs), and copper single-atom, are systematically summarized. Subsequently, three strategies to improve the electrochemical performance of copper-based materials through defect engineering, morphology regulation, and synergistic effect of different components are presented. Finally, our perspectives on the future development of copper-based materials are presented, highlighting the major challenges in the rational design and synthesis of high-performance Li–S batteries.

A Facile Molten Salt Method for Diverse TiC/C Hybrid as Effective Polysulfide Confinement toward Stable Lithium–Sulfur Batteries

Traditional carbon materials suffer from weak adsorption of lithium polysulfides and excessive consumption of electrolyte. A simple and feasible molten salt method is applied for constructing an active nanocrystalline TiC shell on the surface of porous carbon. The highly active TiC nanoshells endow the core–shell composite with efficient chemical–physical synergistic adsorption, which can effectively confine and convert polysulfides, thereby improving the electrochemical performance of lithium–sulfur batteries. The lithium–sulfur batteries assembled with modified separator deliver a high initial discharge specific capacity of 1396 mAh g−1 at a discharge rate of 0.5 C and a high capacity retention of 747.1 mAh g−1 after 500 cycles, with a high coulombic efficiency of 98% during cycling. Besides, this molten salt method can be applied to modify the porous carbon materials of various composite sulfur cathodes such as graphene, carbon nanotubes, and 3D nonwoven carbon fabrics.

Reinforcing the Adsorption and Conversion of Polysulfides in Li-S Battery by Incorporating Molybdenum into MnS/MnO Nanorods.

The Sabatier principle suggests that an excessive adsorption of lithium polysulfides (LiPSs) by metal compounds may hinder their conversion in the absence of a conversion module. Therefore, it is imperative to establish a synergetic effect mechanism between "strong adsorption" and "rapid conversion" for LiPSs. To achieve this coexistence, a molybdenum-doped MnS/MnO@C porous structure is designed as a multifunctional coating on the polypropylene (PP) separator. The incorporation of MnS/MnO@C enhances the adsorption capacity towards LiPSs, while molybdenum facilitates subsequent conversion. Benefiting from the synergistic effect of each component and its large specific surface area, the cell with Mo-doped MnS/MnO@C coating achieves smooth adsorption-diffusion-conversion processes and exhibits an appreciable rate performance with outstanding cycling stability. Even when sulfur loading increases to 9.68 mg cm-2 , the modified battery delivers an excellent initial areal capacity of 11.69 mAh cm-2 and maintains 6.97 mAh cm-2 after 50 cycles at 0.1 C. This study presents a promising approach to simultaneously accomplish "strong adsorption" and "rapid conversion" of polysulfides, offering novel perspectives for devising dual-functional modified separators.

Uncovering the lithium-embedded behavior and catalytic mechanism of g-C3N4 as a sulfur host of lithium‑sulfur batteries in the initial discharge reaction

Due to its excellent anchoring properties to lithium polysulfide (LiPSs), g-C3N4 has been widely studied as anode material for lithium‑sulfur batteries (LSBs). g-C3N4 as the electrode material has an obvious irreversible capacity during the initial discharge progress. The mechanism of this irreversible reaction and its effect on the adsorption of LiPSs and cycling performance of g-C3N4 are not clear. Using first-principle calculations, founding that during the initial discharge progress, the binding energy of lithium to the heptazine ring is larger than the binding energy of lithium to sulfur resulting in this part of lithium entering the center of the heptazine ring and being unable to desorption form Li@g-C3N4, which is the main reason for the irreversible capacity. However, compared with g-C3N4, the conductivity of Li@g-C3N4 is enhanced and the diffusion of lithium atoms is facilitated not only by avoiding the strong interaction of other Li atoms with g-C3N4 because the vacancies have been filled. And the adsorption of LiPSs is also appropriately weakened, which can better maintain the structure integrity of the Li2S6 and Li2S8 molecules and lead to a lower reaction free energy during the discharge process.

Cations Mediate Lithium Polysulfide Adsorption in Metal–Organic Frameworks for Lithium–Sulfur Batteries

Cations Mediate Lithium Polysulfide Adsorption in Metal–Organic Frameworks for Lithium–Sulfur Batteries

Synergizing Spatial Confinement and Dual-Metal Catalysis to Boost Sulfur Kinetics in Lithium-Sulfur Batteries.

Sluggish kinetics and parasitic shuttling reactions severely impede lithium-sulfur (Li-S) battery operation; resolving these issues c ould enhance the capacity retention and cyclability of Li-S cells. Therefore, an effective strategy featuring core-shell-structured Co/Ni bimetal-doped metal-organic framework (MOF)/sulfur nanoparticles is reported herein for addressing these problems; this approach offers unprecedented spatial confinement and abundant catalytic sites by encapsulating sulfur within an ordered architecture. The protective shells exhibit long-term stability, ion screening, high lithium-polysulfide adsorption capability, and decent multistep catalytic conversion. Additionally, the delocalized electrons of the MOF endow the cathodes with superior electron/lithium-ion transfer ability. Via multiple physicochemical and theoretical analysis, the resulting synergistic interactions are proved to significantly promote interfacial charge-transfer kinetics, facilitate sulfur conversion dynamics, and inhibit shuttling. The assembled Li-S batteries deliver a stable, highly reversible capacity with marginal decay (0.075% per cycle) for 400 cycles at 0.2C, a pouch-cell areal capacity of 3.8 mAh cm-2 for 200 cycles under a high sulfur loading, as well as remarkably improved pouch-cell performance. This article is protected by copyright. All rights reserved.

Preparation and application of carbon nanotubes loaded atomic-level Ni–N4 catalyst for lithium-sulfur battery

Lithium-sulfur batteries (LSBs) are promising candidates as next-generation secondary batteries due to their advantages with respect to cost and energy density. However, their practical application is hindered by their slow kinetics and the shuttle behavior of soluble polysulfide ions. Herein, we successfully prepared a three-dimensional porous conductive catalyst material with an atomic-level Ni–N4 structure. The results showed that a strong adsorption of lithium polysulfides (LiPSs) by the Ni–N4 catalytic active sites and a strong catalytic effect on the conversion of LiPSs in the sulfur reduction reaction (SRR) as well as the lithium sulfide oxidation reaction (SOR) were achieved, effectively inhibiting the shuttle effect of polysulfide ions and promoting the sulfur cathode kinetics process. Thus, the LSBs exhibited an excellent performance with a specific capacity of 829.8 mAh g–1 and an average coulombic efficiency of 98.8 % after 420 cycles at a high rate of 1 C. Our work provides new insights and novel efforts to solve the shuttle effect in LSBs.