Sulfur Utilization Research Articles

Enhancement of Overall Kinetics by Se−Br Chemistry in Rechargeable Li−S Batteries

AbstractThe sluggish kinetics of lithium‐sulfur (Li−S) batteries severely impedes the application in extreme conditions. Bridging the sulfur cathode and lithium anode, the electrolyte plays a crucial role in regulating kinetic behaviors of Li−S batteries. Herein, we report a multifunctional electrolyte additive of phenyl selenium bromide (PhSeBr) to simultaneously exert positive influences on both electrodes and the electrolyte. For the cathode, an ideal conversion routine with lower energy barrier can be attained by the redox mediator and homogeneous catalyst derived from PhSeBr, thus improving the reaction kinetics and utilization of sulfur. Meanwhile, the presence of Se−Br bond helps to reconstruct a loose solvation sheath of lithium ions and a robust bilayer SEI with excellent ionic conductivity, which contributes to reducing the de‐solvation energy and simultaneously enhancing the interfacial kinetics. The Li−S battery with PhSeBr displays superior long cycling stability with a reversible capacity of 1164.7 mAh g−1 after 300 cycles at 0.5 C rate. And the pouch cell exhibits a maximum capacity of 845.3 mAh and a capacity retention of 94.8 % after 50 cycles. Excellent electrochemical properties are also obtained in extreme conditions of high sulfur loadings and low temperature of −20 °C. This work demonstrates the versatility and practicability of the special additive, striking out an efficient but simple method to design advanced Li−S batteries.

Lithiating cathodes for Li-S batteries: Regulating Li2S electrodeposition to enhance sulfur utilization

The passivation of the cathode substrate by Li2S during discharge is particularly pronounced in conditions such as high S content, crucial for practical Li-S batteries. Yet, actively regulating this phenomenon through cathode substrate exploration remains a challenging task. This study unveils that Li-intercalating oxides like Nb2O5, which undergo lithiation at discharge potentials, can induce passivation-free 3D Li2S growth, while oxides such as WO3 and MoO2, which do not undergo lithiation at discharge potentials, exhibit 2D growth. Specifically, during discharge, the electrodeposition of Li2S kinetically inhibits lithiation, prompting lithiation from Li2S instead of from the electrolyte Li salt; this process leads to the bulk diffusion of dissociated S2− and its 3D deposition. Utilizing a CNT cathode substrate incorporating lithiating oxides, we achieve high S utilization and high cell performance under conditions of high S loading with a lean electrolyte. This includes a discharge capacity of 1620 mAh g−1 at 0.03 C, equivalent to 97 % S utilization, and substantial capacities of 11.0 mAh cm−2 and 6.40 mAh cm−2 under high sulfur loadings of 14 mg cm−2 and a lean electrolyte of E/S = 5, respectively.

Hollow and Porous N‐Doped Carbon Framework as Lithium‐Sulfur Battery Interlayer for Accelerating Polysulfide Redox Kinetics

AbstractLithium‐sulfur batteries (LSBs) have become one of the most powerful candidates for next‐generation battery technologies due to their high theoretical energy density and low cost. However, the notorious shuttle effect of soluble lithium polysulfides (LiPSs) and sluggish conversion reaction kinetics cause low sulfur utilization and inferior cycle life. Rational catalyst design on hierarchical pore structures and composition optimization is highly desired to realize synergetic enrichment, accommodation, and catalytic redox capacity of sulfur species. In this consideration, the hollow and porous N‐doped carbon framework is prepared, in which Co nanoparticles (NPs) are evenly embedded (denoted as Co‐HMCF) to modulate electron cloud density of carbons. Electrochemical tests and density functional theory (DFT) calculations demonstrate that Co‐HMCF could simultaneously deliver superior catalytic activity in accelerating LiPSs conversion as well as Li2S nucleation/decomposition to improve overall sulfur redox kinetics. Consequently, the Co‐HMCF interlayer significantly improves the battery performance, including high discharge capacity output (1538 mAh g−1 at 0.2 C), stable long‐term cycle (0.047% capacity decay per cycle for 800 cycles at 1.0 C), and exceptional rate capacity (582 mAh g−1 at 5.0 C).

Leveraging doping strategies and interface engineering to enhance catalytic transformation of lithium polysulfides for high-performance lithium-sulfur batteries

The commercialization of lithium-sulfur (Li–S) batteries has faced challenges due to the shuttle effect of soluble intermediate polysulfides and the sluggish kinetics of sulfur redox reactions. In this study, a synergistic catalyst medium was developed as a high-performance sulfur cathode material for Li–S batteries. Termed A/R-TiO2@ Ni-N-MXene, this sulfur cathode material features an in-situ derived anatase–rutile homojunction of TiO2 nanoparticles on Ni-N dual-atom-doped MXene nanosheets. Using in-situ transmission electron microscopy (TEM) technique, we observed the growth process of the homojunction for the first time confirming that homojunctions facilitated charge transfer, while dual-atom doping offered abundant active sites for anchoring and converting soluble polysulfides. Theoretical calculations and experiments showed that these synergistic effects effectively mitigated the shuttle effect, leading to improved cycling performance of Li–S batteries. After 500 cycles at a 1C rate, Li–S batteries using A/R-TiO2@Ni-N-MXene as cathode materials exhibited stable and highly reversible capacity with a capacity decay of only 0.056 % per cycle. Even after 150 cycles at a 0.1C rate, a high-capacity retention rate of 62.8 % was achieved. Additionally, efficient sulfur utilization was observed, with 1280.76 mA h/g at 0.1C, 694.24 mA h/g at 1C, alongside a sulfur loading of 1.5–2 mg/cm2. The effective strategy based on homojunctions showcases promise for designing high-performance Li–S batteries.

Lithium cation-doped tungsten oxide as a bidirectional nanocatalyst for lithium-sulfur batteries with high areal capacity

Lithium-sulfur (Li-S) batteries are promising for high energy-storage applications but suffer from sluggish conversion reaction kinetics and substantial lithium sulfide (Li2S) oxidation barrier, especially under high sulfur loadings. Here, we report a Li cation-doped tungsten oxide (LixWOx) electrocatalyst that efficiently accelerates the S↔Li2S interconversion kinetics. The incorporation of Li dopants into WOx cationic vacancies enables bidirectional electrocatalytic activity for both polysulfide reduction and Li2S oxidation, along with enhanced Li+ diffusion. In conjunction with theoretical calculations, it is discovered that the improved electrocatalytic activity originates from the Li dopant-induced geometric and electronic structural optimization of the LixWOx, which promotes the anchoring of sulfur species at favourable adsorption sites while facilitating the charge transfer kinetics. Consequently, Li-S cells with the LixWOx bidirectional electrocatalyst show stable cycling performance and high sulfur utilization under high sulfur loadings. Our approach provides insights into cation engineering as an effective electrocatalyst design strategy for advancing high-performance Li-S batteries.

A novel mesoporous carbon pocket with single atom Cr sites for high performance Lithium-Sulfur battery

Lithium-sulfur batteries (LSBs) are considered one of the most promising next-generation energy storage devices. However, their practical application is limited by the sluggish conversion kinetics and shuttle behavior of lithium polysulfides (LiPSs). In this work, we employ a facile salt template and micelle-mediated co-assembly strategy to synthesize atomic Cr dispersed mesoporous N-doped carbon pocket (denoted as Cr-mNC pocket). The designed Cr-mNC pocket exhibits uniform and ordered mesoporous caged morphology with a high surface area (843.5 m2/g), large pore volume (0.184 cm3 g−1), and uniform mesopore size (3.7 nm). The mesoporous structure offers a facilitated pump to promote electron/ion transportation while exposing more catalytic sites. These advantages enable the Cr-mNC pocket modified membrane to facilitate Li+ diffusion, enhance LiPSs adsorption, and accelerate electrochemical reaction kinetics for polysulfide conversion. Consequently, LSBs with Cr-mNC modified separator show a high sulfur utilization (1405 mAh g−1 at 0.2 C), a remarkable rate performance (776 mAh g−1 at 5 C), a low capacity decay rate of 0.047 % per cycle at 2 C over 1000 cycles, and even remain at 4.47 mAh cm−2 after 100 cycles with a high sulfur load of 5.0 mg cm−2.

Amorphous MoS2/MoO3 Nanosheets as High‐Efficient Polysulfide Barrier in Li−S Batteries

AbstractLithium‐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.

Hollow Defect-Rich Nanofibers as Sulfur Hosts for Lithium-Sulfur Batteries.

The slow redox kinetics of lithium-sulfur batteries severely limit their application, and sulfur utilization can be effectively enhanced by designing different cathode sulfur host materials. Herein, we report the hollow porous nanofiber LaNi0.6Co0.4O3 as a bidirectional host material for lithium-sulfur batteries. After Co is substituted into LaNiO3, oxygen vacancies are generated to enhance the material conductivity and enrich the active sites of the material, and the electrochemical reaction rate can be further accelerated by the synergistic catalytic ability of Ni and Co elements in the B-site of the active site of LaNi0.6Co0.4O3. As illustrated by the kinetic test results, LaNi0.6Co0.4O3 effectively accelerated the interconversion of lithium polysulfides, and the nucleation of Li2S and the dissolution rate of Li2S were significantly enhanced, indicating that LaNi0.6Co0.4O3 accelerated the redox kinetics of the lithium-sulfur battery during the charging and discharging process. In the electrochemical performance test, the initial discharge specific capacity of S/LaNi0.6Co0.4O3 was 1140.4 mAh g-1 at 0.1 C, and it was able to release a discharge specific capacity of 584.2 mAh g-1 at a rate of 5 C. It also showed excellent cycling ability in the long cycle test, with a single-cycle capacity degradation rate of only 0.08%. Even under the harsh conditions of high loaded sulfur and low electrolyte dosage, S/LaNi0.6Co0.4O3 still delivers excellent specific capacity and excellent cycling capability. Therefore, this study provides an idea for the future development of bidirectional high-activity electrocatalysts for lithium-sulfur batteries.

Comprehensive recovery of valuable elements from vanadium precipitation liquor using selective impurity removal-reduction precipitation process

The vanadium precipitation liquor produced by the vanadium slag extraction process contains various valuable elements, which are not utilized at high value. In this paper, chromium is recovered through aluminum salt impurity removal - chemical reduction precipitation method. Moreover, the ammonia nitrogen and sodium sulfur in the vanadium precipitation liquor are recovered by stripping and crystallization, thereby achieving comprehensive resource recovery and utilization. The aluminum salt slag removal reduction chemical precipitation method is used to separate Cr from Si, Ca and V impurities. As a result, the obtained Cr2O3 product has a purity of 98.20%, the chromium recovery efficiency is 97.58%, and the silicon removal efficiency reaches 99.66%. The ammonia nitrogen was recovered by stripping, which would be reused to the vanadium precipitation process, with an ammonia nitrogen stripping efficiency of 98%. The purity of NH4Cl is 99.13% and meets the 99-level national standard. The Na2SO4 was recovered by evaporation concentration - crystallization method, which would be reused to the vanadium slag roasting process, with a Na2SO4 recovery efficiency of 88.38%. And the purity of Na2SO4 is 98.85%, which meets the industrial standard for Class II Na2SO4 products. The final solution after comprehensive recovery of valuable elements would be reused to the leaching process, thereby achieving water circulation. This process realizes the high-value utilization of chromium, ammonia, nitrogen, sodium and sulfur, and has no wastewater discharge and is an environment-friendly route.

Isomeric dichloropyrazine of dual-function additives: Synergistic enhancement of lithium anode protection and sulfur redox kinetics in lithium–sulfur batteries

Lithium-sulfur batteries (LSBs) currently face challenges such as low sulfur utilization, inadequate cycling stability, and unstable lithium anode interfaces. In this study, dichloropyrazines (DCPs) are introduced as dual-functional additives into electrolyte and 2,5-DCP exhibits the most promising performance enhancement. This superiority can be attributed to its strong redox activity, lower molecular orbital energy gap, and more negative relative binding energy compared to the other DCP isomers. Specifically, DCPs demonstrate their dual functionality by promoting the formation of a stable organic-inorganic hybrid solid electrolyte interface (SEI) rich in LiCl on lithium anodes. This ensures uniform lithium deposition and suppresses dendrite growth. At sulfur cathodes, density functional theory (DFT) calculations confirm that DCPs facilitate lithium polysulfides (LiPSs) conversion kinetics through Li–N bond formation. LSBs with 2,5-DCP exhibit excellent stability at a 1C rate and retain 86.6 % capacity after 800 cycles. This study demonstrates DCPs' potential as effective dual-functional electrolyte additives in designing high-performance LSBs.

Accelerated Conversion of Polysulfides for Ultra Long-Cycleof Li-S Batteryat High-Rateover Cooperative Cathode Electrocatalystof Ni0.261Co0.739S2/N-Doped CNTs.

Despite the very high theoretical energy density, Li-S batteries still need to fundamentally overcome the sluggish redox kinetics of lithium polysulfides (LiPSs) and low sulfur utilization that limit the practical applications. Here, highly active and stable cathode, nitrogen-doped porous carbon nanotubes (NPCTs) decorated with NixCo1-xS2 nanocrystals are systematically synthesized as multi-functional electrocatalytic materials. The nitrogen-doped carbon matrix can contribute to the adsorption of LiPSs on heteroatom active sites with buffering space. Also, both experimental and computation-based theoretical analyses validate the electrocatalytic principles of co-operational facilitated redox reaction dominated by covalent-site-dependent mechanism; the favorable adsorption-interaction and electrocatalytic conversion of LiPSs take place subsequently by weakening sulfur-bond strength on the catalytic NiOh 2+-S-CoOh 2+ backbones via octahedral TM-S (TM = Ni, Co) covalency-relationship, demonstrating that fine tuning of CoOh 2+ sites by NiOh 2+ substitution effectively modulates the binding energies of LiPSs on the NixCo1-xS2@NPCTs surface. Noteworthy, the Ni0.261Co0.739S2@NPCTs catalyst shows great cyclic stability with a capacity of up to 511 mAh g-1 and only 0.055% decay per cycle at 5.0 C during 1000 cycles together with a high areal capacity of 2.20 mAh cm-2 under 4.61mg cm-2 sulfur loading even after 200 cycles at 0.2 C. This strategy highlights a new perspective for achieving high-energy-density Li-S batteries.

First-Principles Investigation of Phosphorus-Doped Graphitic Carbon Nitride as Anchoring Material for the Lithium-Sulfur Battery.

The utilization of lithium-sulfur battery is hindered by various challenges, including the "shuttle effect", limited sulfur utilization, and the sluggish conversion kinetics of lithium polysulfides (LiPSs). In the present work, a theoretical design for the viability of graphitic carbon nitride (g-C3N4) and phosphorus-doping graphitic carbon nitride substrates (P-g-C3N4) as promising host materials in a Li-S battery was conducted utilizing first-principles calculations. The PDOS shows that when the P atom is introduced, the 2p of the N atom is affected by the 2p orbital of the P atom, which increases the energy band of phosphorus-doping substrates. The energy bands of PC and Pi are 0.12 eV and 0.20 eV, respectively. When the lithium polysulfides are adsorbed on four substrates, the overall adsorption energy of PC is 48-77% higher than that of graphitic carbon nitride, in which the charge transfer of long-chain lithium polysulfides increase by more than 1.5-fold. It is found that there are powerful Li-N bonds between lithium polysulfides and P-g-C3N4 substrates. Compared with the graphitic carbon nitride monolayer, the anchoring effect of the LiPSs@P-g-C3N4 substrate is enhanced, which is beneficial for inhibiting the shuttle of high-order lithium polysulfides. Furthermore, the catalytic performance of the P-g-C3N4 substrate is assessed in terms of the S8 reduction pathway and the decomposition of Li2S; the decomposition energy barrier of the P-g-C3N4 substrate decrease by 10% to 18%. The calculated results show that P-g-C3N4 can promote the reduction of S8 molecules and Li-S bond cleavage within Li2S, thus improving the utilization of sulfur-active substances and the ability of rapid reaction kinetics. Therefore, the P-g-C3N4 substrates are a promising high-performance lithium-sulfur battery anchoring material.

Chip-Inspired Design of High-Performance Lithium-Sulfur Batteries by Integrating Monodisperse Sulfur Nanoreactors on Graphene.

For practical application of lithium-sulfur batteries (LSBs), designing devices with an overall optimal structure instead of modifying electrode materials is significant. Herein, we report a chip-inspired design of a vertically integrated structure as an LSB cathode by implanting Mo2C nanoparticles and nanosulfur into the reduced graphene oxide (rGO) matrix. This configuration enabled the synthesis of isolated sulfur nanoreactors (S-NRs) integrated in a tandem array on the rGO, generating chip-like integrated LSBs. The spatial confinement/protection and concentration gradient of the S-NRs effectively avoided the dissolution, diffusion, and loss of polysulfides, thereby enhancing the sulfur utilization and redox reaction kinetics. Additionally, the adaptive storage energy can be improved by utilizing the tandem, isolation, and synergistic multiplicative effect among the nanoreactor units. As a result, the integrated LSB cathode obtained excellent electrochemical performances with an initial capacity of 1392 mAh g-1 at 0.1C, a low capacity decay rate of 0.017% per cycle during 1500 cycles of operation at 0.5C, and a superior rate performance. This work provides a rational design idea and method of further advancing the precise preparation of high-performance energy storage devices.

Phloroglucinol–2,6‐Diaminoanthraquinone as a Durable Redox Mediator for Enhancing Conversion Reaction Kinetics in Lithium‐Sulfur Batteries

AbstractLithium‐sulfur batteries, despite being a promising solution for next‐generation secondary batteries, require substantial efforts to overcome the challenges of sluggish sulfur redox kinetics, polysulfides shuttling, and Li metal instability before achieving practical viability. Conventional strategies that utilize metal catalysts or soluble redox mediators (RMs) are limited by either impractical producing processes or unsatisfactory service life. Herein, an electrochemically active organic material, phloroglucinol – 2,6‐diaminoanthraquinone (PG‐DAAQ) is synthesized through a green and facile polymerization process to better resolve these issues. Serving as an RM at the cathode, PG‐DAAQ exhibits enduring redox activity within the sulfur operating potential window, leading to enhanced redox kinetics and sulfur utilization. Remarkably, even without any metal elements, PG‐DAAQ exhibits an excellent affinity to polysulfides, thereby suppressing the shuttling and facilitating the formation of a more favorable solid‐electrolyte interface to stabilize Li deposition at the anode. As a result, Li‐S cells employing PG‐DAAQ show significantly enhanced cycling and rate performances than the control cells. Even with a low electrolyte‐to‐sulfur ratio of 6, pouch cells with PG‐DAAQ deliver a reversible discharge capacity of 821 mA h g−1 after 100 cycles at a C/10 rate.

Quasi-Solid-State Electrolyte Induced by Metallic MoS2 for Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) batteries are a promising high-energy-density technology for next-generation energy storage but suffer from an inadequate lifespan. The poor cycle life of Li-S batteries stems from their commonly adopted catholyte-mediated operating mechanism, where the shuttling of dissolved polysulfides results in active material loss on the sulfur cathode and surface corrosion on the lithium anode. Here, we report in situ formation of a quasi-solid-state electrolyte (QSSE) on the metallic 1T phase molybdenum disulfide (MoS2) host that extends the lifetime of Li-S batteries. We find that the metallic 1T phase MoS2 host is able to initiate the ring-opening polymerization of 1,3-dioxolane (DOL), forming an integrated QSSE inside batteries. Nuclear magnetic resonance analysis reveals that the QSSE consists of ∼13% liquid DOL in a solid polymer matrix. The QSSE efficiently mediates sulfur redox reactions through dissolution-conversion chemistry while simultaneously suppressing polysulfide shuttling. Therefore, while ensuring high sulfur utilization, it avoids degradation of both electrodes, as well as the concomitant electrolyte consumption, leading to enhanced cycling stability. Under a practical lean electrolyte condition (electrolyte-to-sulfur ratio = 2 μL mg-1), Li-S pouch cell batteries with the QSSE demonstrate a capacity retention of 80.7% after 200 cycles, much superior to conventional liquid electrolyte cells that fail within 70 cycles. The QSSE also enables Li-S pouch cell batteries to operate across a wider temperature range (5 to 45 °C), together with improved safety under mechanical damage.

Enhancing sulfur absorption in soybean rhizosphere through arbuscular mycorrhizal fungi inoculation: Implications for soil health and crop growth

Soybean, a sulfur-loving cash crop, suffers from declining soil sulfur with continuous cropping, hindering its growth and development. Arbuscular mycorrhizal fungi (AMF) form beneficial partnerships with plant roots, aiding in nutrient uptake and promoting plant growth. Recent research has increasingly focused upon AMF's potential to enhance sulfur absorption through increased rhizosphere microbial activity. This study investigated the impact of AMF inoculation on soil organic sulfur mineralization, microbial community composition, and sulfur cycle function genes in the continuous cropping soybean rhizosphere. 16 S rRNA sequencing and high-throughput qPCR revealed changes in microbial community composition and the expression of sulfur cycle genes. ICP-MS measured total soil sulfur, and the BaSO4 turbidimetric method determined available sulfur. Following inoculation of continuous cropping soybean soil with AMF, it was observed that OTU1851, OTU1897, OTU2148, OTU3303, and OTU3738, five specific rhizospheric soil sulfur cycling microbial communities, were enriched. And AMF inoculation enhanced sulfur cycle function, the abundance of aspA, soxY and yedZ increased by 143.23 %, 236.04 % and 436.64 %. This led to increased soil arylsulfatase (S-ASF) activity (from 39.17 to 49.82 μg/(mL·h)), available sulfur content (from 12.88 to 17.55 mg/kg), and ultimately, improved soybean sulfur absorption and growth. Therefore, this study holds significant implications for improving available sulfur content and utilization in sulfur-deficient soils. Furthermore, it provides a theoretical basis for using AMF as a biofertilizer to remediate sulfur -deficiency, offering a sustainable and environmentally friendly solution.

Ru Single Atom Dispersed on MoS2/MXene for Enhanced Sulfur Reduction Reaction in Lithium-Sulfur Batteries.

The high theoretical energy density (2600 Whkg-1) and low cost of lithium-sulfur batteries (LSBs) make them an ideal alternative for the next-generation energy storage system. Nevertheless, severe capacity degradation and low sulfur utilization resulting from shuttle effect hinder their commercialization. Herein, Single-atom Ru-doped 1T/2H MoS2 with enriched defects decorates V2C MXene (Ru-MoS2/MXene) produced by a new phase-engineering strategy employed as sulfur host to promote polysulfide adsorption and conversion reaction kinetics. The Ru single atom-doped adjusts the chemical environment of the MoS2/MXene to anchor polysulfide and acts as an efficient center to motivate the redox reaction. In addition, the rich defects of the MoS2 and ternary boundary among 1T/2H MoS2 and V2C accelerate the charge transfer and ion movements for the reaction. As expected, the Ru-MoS2/MXene/S cathode-based cell exhibits a high-rate capability of 684.3 mAh g-1 at 6 C. After 1000 cycles, the Ru-MoS2/MXene/S cell maintains an excellent cycling stability of 696 mAh g-1 at 2 C with a capacity degradation as low as 0.02% per cycle. Despite a high sulfur loading of 9.5mg cm-2 and a lean electrolyte-to-sulfur ratio of 4.3, the cell achieves a high discharge capacity of 726 mAh g-1.

Steering bidirectional polysulfide conversion in virtue of interface microenvironment of Ni/porous carbon Mott-Schottky heterojunctions

Originating from the notorious shuttle effect and intrinsically sluggish redox kinetics of polysulfides (especially under the conditions of high sulfur loadings and low electrolytes), the low capacity and sulfur utilization efficiency, unsatisfactory rate performance, and unremarkable cycle performance severely hinder the practical commercialization of lithium-sulfur batteries (LSBs). Furnishing rapid electron transfer and mass diffusion in virtue of interface modulation and nanostructure design is an effective strategy to enhance the activity of catalysts. Herein, a Mott-Schottky heterojunction composed of porous carbon (PC)-supported nickel (Ni) nanoparticles was fabricated on a functionalized carbon nanotube sponge (Ni/PC/FCNTS) via adjusting the geometric structure such as the particle size, aggregation state and pore volume (based on the different solvothermal reaction temperature of the Ni-MOF precursor and the high-temperature pyrolysis process). Transmission electron microscope (TEM) and X-ray photoelectron spectroscopy (XPS) demonstrated the charge redistribution and a self-generated built-in electric field accelerated electron transfer at the heterogeneous interface between Ni and PC. Meanwhile, the high pore volume of Ni/PC/FCNTS-170 provided a reaction space for rapid ion diffusion and sulfur redox process. Benefiting from the synergistic effect, the derived S@Ni/PC/FCNTS-170 cells manifested excellent rate performance with a capacity of 784.2 mAh g-1 at 2 C and a high areal capacity of 8.09 mAh cm-2 with a high sulfur loading of 17.6 mg cm-2 and low electrolyte/sulfur of 11.3 µL mg-1.

Polyoxomolybdate-Based Metal-Organic Framework-Derived Cu-Embedded Molybdenum Dioxide Hybrid Nanoparticles as Highly Efficient Electrocatalysts for Al-S Batteries.

High-performance rechargeable aluminum-sulfur batteries (RASB) have great potential for various applications owing to their high theoretical capacity, abundant sulfur resources, and good safety. Nevertheless, the practical application of RASB still faces several challenges, including the polysulfide shuttle phenomenon and low sulfur utilization efficiency. Here, we first developed a synergistic copper heterogeneous metal oxide MoO2 derived from polymolybdate-based metal-organic framework as an efficient catalyst for mitigating polysulfide diffusion. This composite enhances sulfur utilization and electrical conductivity of the cathode. DFT calculations and experimental results reveal the catalyst Cu/MoO2@C not only effectively anchors aluminum polysulfides (AlPSs) to mitigate the shuttle effect, but also significantly promotes the catalytic conversion of AlPSs on the sulfur cathode side during charging and discharging. The unique nanostructure contains abundant electrocatalytic active sites of oxide nanoparticles and Cu clusters, resulting in excellent electrochemical performance. Consequently, the established RASB exhibits an initial capacity of 875 mAh g-1 at 500 mA g-1 and maintains a capacity of 967 mAh g-1 even at a high temperature of 50 °C.

Modulating the d-band center of single-atom catalysts for efficient Li2S2-Li2S conversion in durable lithium-sulfur batteries

Enhancing the conversion of insoluble Li2S2-Li2S to improve sulfur utilization has become an essential strategy for Lithium-Sulfur (Li-S) batteries. The proposed approach employs single-atom catalysts (SACs) known for their high atomic usage efficiency to enable in-situ reactions with Li2S2. However, the origin and mechanisms of various SACs involved in the Li2S2 to Li2S reduction reaction are not fully elucidated. Herein, we reveal the underlying mechanism of Li2S2-Li2S reduction catalysis on Mn atoms by examining the electronic structure of d orbitals. Theoretical calculations indicate that substituting a S atom for N in the first coordination structure of Mn SACs elevates the Mn d-band center and simultaneously enhances the hybridization between the Mn d orbitals and the p orbitals of sulfur species. This alteration not only improves the anchoring of lithium polysulfides, leading to better adsorption but also accelerates the conversion kinetics of Li2S2 to Li2S due to the improved intrinsic catalytic activity of SACs. As a result, the Li-S batteries equipped with the SAMn-based cathode deliver an impressive initial capacity of 1343.9 mAh g−1 at 0.1 C, exceptional rate capability of 782.4 mAh g−1 at 3 C, and maintain a low degradation rate of approximately 0.025% per cycle over 1000 cycles at 1.0 C. Furthermore, with a sulfur loading of 6 mg cm−2, the S/SAMn@NSC cathode achieves a reversible areal capacity of 4.4 mAh cm−2 at 0.1 C. This study significantly advances the kinetics of solid-solid transformation in Li-S battery cathodes through catalysis facilitated by single-atom d-band regulation.