Catalytic Conversion Of Polysulfides Research Articles

Nitrogen-doped 3D carbon hybrids based on modified lignin as sulfur host for high-performance lithium-sulfur batteries

Constructing a sulfur host with strong adsorption and catalytic conversion of polysulfides is significant in improving the electrochemical performance of lithium-sulfur batteries. In this work, we obtained nitrogen-doped 3D carbon hybridized materials (lignin porous carbon/carbon nanotubes, LPC/CNTs) by self-assembly and in situ activation methods. This is the first time to achieve nitrogen-doped carbon hybrids by melamine modification lignin as raw material. The results show that the construction of the nitrogen-doped 3D carbon hybridization network is highly correlated with the modification treatment of lignin. As sulfur host material, it can reach a specific capacity of 1300.18 mAh g−1 at 0.1 C for the first time and still has a specific capacity of 582.84 mAh g−1 at 1 C for 400 cycles. In addition, carbon hybridized materials show excellent rate performance and high current adaptability in the rate performance test compared with the carbon materials prepared from unmodified lignin. The excellent electrochemical performance is mainly attributed to the synergistic effect within the 3D interconnection network, which enhances the physical confinement and chemical adsorption of polysulfides, as well as the catalytic conversion. This work provides new insights into biomass application in the sulfur hosts of lithium-sulfur batteries.

Oxygen deficient Eu2O3-δ synchronizes the shielding and catalytic conversion of polysulfides toward high-performance lithium sulfur batteries

Oxygen deficient Eu2O3-δ synchronizes the shielding and catalytic conversion of polysulfides toward high-performance lithium sulfur batteries

Synergistically accelerating capture and catalytic conversion of polysulfides by Co@NCNT-MoSe2 nanocomposite modified separator for advanced Lithium-Sulfur batteries

Lithium-sulfur (Li-S) battery with a high theoretical energy density (2600 Wh·kg−1) is considered as a promising energy storage system. However, the shuttle effect and the sluggish redox kinetics of lithium polysulfides (LiPSs) lead to low sulfur utilization. A multifunctional layer modified on separator, as a collaborator of capturer-catalyst-conductor, is be regarded as an effective strategy to solve these problems. Herein, the Co@NCNT-MoSe2 nanocomposite as a modified layer is synthesized with a mesoporous structure by the hydrothermal reaction, in which a large number of transparent MoSe2 nanosheets grow outside NCNT embedded with Co nanoparticles, forming a flower-like outer walls of tube. The modified layer displays the significant features of capturing and catalytic conversion toward LiPSs, attributing to strong adsorption abilities, abundant catalytic active sites, and efficient transferring pathway of electron/Li+. Benefitting from these alluring properties, the results demonstrate that the modified separator offers a high discharge capacity of 983.2 mAh·g−1 at 0.2C after 200 cycles. Even at 2C, after long-term 1000 cycles, it still shows a superb capacity of 725 mAh·g−1 accompanied by a low capacity fading of 0.042 % per cycle. More notably, at 0.2C, the modified separator can realize an ideal areal capacity of 5.24 mAh·cm−2 under high S load (5 mg·cm−2) and poor electrolyte (7.5 μL·mg−1). Therefore, this work will provide a new insight on the development of multifunctional separators to achieve a long-life battery with high sulfur utilization by restraining shuttle effect and accelerate redox kinetics of LiPSs.

Molecular engineering of N-rich ZIF-integrated graphene composite interface for efficient physiochemical confinement and catalytic conversion of polysulfides in lithium–sulfur batteries

Lithium–sulfur (Li–S) batteries are regarded as one of the most promising energy storage systems because of their high theoretical specific capacity, energy density, low cost, and environmental benignancy. However, the practical application of Li–S batteries has been hindered by inevitable polysulfides shuttling behavior, the sluggish redox kinetics, and poor electrical conductivity of sulfur, which lead to rapid capacity decay and low active material utilization. In this study, we report a multifunctional layer consisting of N-rich zeolitic imidazolate frameworks (ZIF)/reduced graphene oxide (rGO) composite (NZG) as an electrocatalyst to overcome the drawbacks of Li–S batteries. During the preparation of NZG, deamination of the ZIF8A induces the incorporation of abundant N-containing moieties into rGO (pyridinic and pyrrolic N), which results in providing favorable active sites for polysulfides confinement and their rapid conversion via physiochemical interactions. Additionally, hierarchical pores with large surface area and interconnected conductive pathways in the as-prepared multifunctional layer accelerate the catalytic conversion kinetics of polysulfide species, leading to high sulfur utilization and enhanced Li–S battery electrochemical performance. This work suggests an efficient approach for designing multifunctional layers to achieve high-performance Li–S batteries.

Integrating Energy Band Alignment and Oxygen Vacancies Engineering of TiO2 Anatase/Rutile Homojunction for Kinetics‐Enhanced Li–S Batteries

AbstractThe inferior shuttle effect of intermediate lithium polysulfides and the sluggish kinetics of sulfur redox reaction are two serious puzzles for the application of lithium–sulfur batteries. Herein, energy band alignment is combined with oxygen vacancies engineering to obtain TiO2 anatase/rutile homojunction (A/R‐TiO2) with effective immobilization and high‐efficiency catalytic conversion of polysulfides. Theoretical calculations and experiments reveal that the near perfect energy band alignment in A/R‐TiO2 is conducive to fluent charge transfer and high catalytic activity, while the rich oxygen vacancies are engineered to provide abundant active sites for anchoring and accelerating conversion of soluble polysulfides. As a result, a battery with A/R‐TiO2‐modified separator delivers a marked sulfur utilization (1210 mAh g−1 at 0.1 C and 689 mAh g−1 at 1 C, 3.75 mg cm−2) and a high capacity retention of 63% over 300 cycles at 0.5 C (3.25 mg cm−2). More importantly, the A/R‐TiO2‐modified separator endows the pouch cell with a high capacity of 128.5 mAh at 0.05 C with a lean electrolyte/sulfur ratio for practical application (S loading: 4 mg cm−2).

Conductive metal-organic framework flowers facilitate the anchoring and conversion kinetics of polysulfides for lithium‑sulfur batteries

Enhancing the trapping and catalytic conversion of polysulfides is the main path to restrain their shuttling for durable lithium‑sulfur batteries (LSBs). Herein, we report a flower-like metal-organic framework (MOF) MIL-47 layer as an interlayer material to achieve this purpose. The proposed MOF material possesses a unique flower-like structure that is composed of two-dimensional nanosheets, which is conducive to the mass transfer and the exposure of active sites, enabling an efficient adsorption towards polysulfides. Moreover, the high conductivity combined with sufficient catalytic active centers are instrumental in accelerating the redox processes of polysulfides conversion. Consequently, this flowery MOF-based interlayer endows LSBs an amazing capacity of 1003.6 mAh g−1 and an ultralong cycling stability with a low attenuation rate of 0.029 % over 1000 cycles under 1C, together with an exceptional rate performance (a capacity high as 696.9 mAh g−1 under 5C). In addition to this, an elevated sulfur loading and reduced electrolyte content do not affect its excellent cycling and rate performance. This work provides a new mentality to exploit multi-role nanostructured materials for LSBs.

Catalytic conversion of polysulfides by atomic layer deposition derived titanium nitride for high‐performance lithium‐sulfur batteries

AbstractLithium‐Sulfur (Li‐S) batteries as the next‐generation battery system have an ultrahigh theoretical energy density. However, the limited conversion of polysulfides in sulfur cathodes deteriorates the performance of Li‐S batteries. In this study, we develop a novel titanium nitride (TiN) catalyst for sulfur cathodes via atomic layer deposition (ALD). The synthesized ALD‐TiN catalyst shows controllable ultrafine particle size (<2 nm) and uniform distribution at the nanoscale in the carbon matrix. Combined with electrochemical analysis and multiple post‐characterization techniques, ALD‐TiN demonstrates an excellent catalytic effect to facilitate the nucleation and deposition of Li2S, which effectively suppresses the dissolution and shuttle of polysulfides. The as‐prepared sulfur cathodes, with the assistance of TiN catalyst, exhibit excellent cycling performance at a high rate (4 C) and deliver 200% higher discharge capacity than the pristine Sulfur‐pristine porous carbon composite cathodes.

Enhancement of Organic Oxygen Atoms on Metal Cobalt for Sulfur Adsorption and Catalytic Polysulfide Conversion

Metals and their compounds effectively suppress the polysulfide shuttle effect on the cathodes of a lithium-sulfur (Li-S) battery by chemisorbing polysulfides and catalyzing their conversion. However, S fixation on currently available cathode materials is below the requirements of large-scale practical application of this battery type. In this study, perylenequinone was utilized to improve polysulfide chemisorption and conversion on cobalt (Co)-containing Li-S battery cathodes. According to IGMH analysis, the binding energies of DPD and carbon materials as well as polysulfide adsorption were significantly enhanced in the presence of Co. According to in situ Fourier transform infrared spectroscopy, the hydroxyl and carbonyl groups in perylenequinone are able to form O-Li bonds with Li2Sn, facilitating chemisorption and catalytic conversion of polysulfides on metallic Co. The newly prepared cathode material demonstrated superior rate and cycling performances in the Li-S battery. It exhibited an initial discharge capacity of 780 mAh g-1 at 1 C and a minimum capacity decay rate of only 0.041% over 800 cycles. Even with a high S loading, the cathode material maintained an impressive capacity retention rate of 73% after 120 cycles at 0.2 C.

O-doping induced abundant active-sites in MoS2 nanosheets for propelling polysulfide conversion of Li-S batteries

The oxygen doped MoS2 nanosheets were in-situ grown into the three-dimensional (3D) porous graphene frameworks (O-MoS2/G) through a facile hydrothermal method, and then used to coat the commercial PP separators for Li-S batteries. The relatively low hydrothermal temperature should be a key factor for achieving the O-doped MoS2. The O dopants could expand and disturb interlayer structures of MoS2 to produce abundant active edge sites for adsorption and catalytic conversion of polysulfides. Moreover, the basal planes of MoS2 should be also activated by the O doping and exhibit enhanced chemical adsorption strength towards polysulfides for propelling electrochemical conversion. Owing to the synergistic effects of the 3D porous graphene frameworks and the inlaid O-MoS2 nanosheets, the Li-S cells with high S areal loading cathodes and O-MoS2/G@PP separators exhibit excellent electrochemical performances with a high specific capacity of 1141 mAh g−1 at the 1st cycle at 0.1 C, reversible capacities of 772 mAh g−1 at the 50th cycle at 0.2 C and 583 mAh g−1 at the 100th cycle at 0.5 C. These encouraging results provide that the heteroatom doping should be a promising approach to improve the adsorption and catalytic activity of MoS2 for propelling the polysulfide conversion in Li-S batteries.

Surface reconstruction on Ni2P@CC to form an ultrathin layer of Ni(OH)2for enhancing the capture and catalytic conversion of polysulfides in lithium–sulfur batteries

An ultrathin layer of Ni(OH)2isin situintroduced to the Ni2P surface by an electrochemical method to realize the regulation of surface properties of Ni2P. The S/Ni(OH)2–Ni2P@CC based cell exhibits superior cycle stability and high areal capacity.

Construction of Co@N-CNTs grown on N-MoxC nanosheets for separator modification to enhance adsorption and catalytic conversion of polysulfides in Li–S batteries

A multi-dimensional hybrid Co@N-CNTs/N-MoxC framework is fabricated by using Mo2C MXenes as a conversion and growth template, and the mechanisms of inhibiting the shuttle effect and catalyzing the conversion of polysulfides are reasonably proposed.

N-doped porous carbon@CNT nanowire as effective polysulfides adsorption-catalysis interlayer for high-performance lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries have received tremendous attention from the energy sector which have emerged as one of the most potential electrochemical energy storage systems. However, the annoying shuttle effect and sluggish polysulfides conversion process are still determining factor for hindering their large-scale practical applications. Herein, one-dimensional N-doped porous carbon@CNT nanowires (CNT@NC) were prepared as a trapping-catalyzing bifunctional interlayer for PP separator in Li-S battery. The linear structure of nanowires forms a continuous conductive network, which provides a fast transmission channel for Li+/e–. Moreover, the adsorption capability and catalytic conversion of polysulfides are enhanced by N doping. The resulting CNT@NC could effectively suppress the shuttle effect and improve the redox reaction kinetics. Therefore, the Li-S battery exhibits outstanding rate performance in addition to a high initial capacity of 1395.4 mAh g−1 and a long-time cycling life with a decay rate of only 0.025 % after 700 cycles at 0.5 C. This study furnishes a feasible scheme for the reasonable optimization of the Li-S battery interlayer and promotes electrochemical applications.

Strong internal electric field enhanced polysulfide trapping and ameliorates redox kinetics for lithium-sulfur battery

The shuttle effect of polysulfides is a major challenge for the commercialization of lithium-sulfur battery. The systematic modification of separators has the potential to solve these problems by enhancing the adsorption and catalytic conversion of polysulfides. Herein, strong internal electric field bismuth oxycarbonate (Bi2O2CO3) nanoflowers decorated conductive carbon (DC + BOC) is proposed to be systematically modified on separator. This intermediate layer not only possesses a strong affinity for polysulfides, but also promotes the conversion of polysulfides and induces the formation of a stable solid electrolyte interphase (SEI) layer, thereby improving the rate performance and cycling stability of the battery. As expected, the modified membrane achieved a high specific capacity of 713 mA h g−1 at 5 C. At 1 C, high reversibility of 719 mA h g−1 was achieved after 550 cycles with only 0.044% decay per cycle. More importantly, under the sulfur loading of 5.1 mg cm−2, the area specific capacity remained at 4.1 mA h cm−2 after 200 cycles, and the attenuation rate per cycle was only 0.056%. This work provides a new strategy to overcome the shuttle effect of polysulfide, and shows great potential in the application of high-performance lithium-sulfur batteries.

Magnetron sputtering engineering of typha-like carbon nanofiber interlayer integrating brush filter and chemical adsorption for Li–S batteries

Enhancing the adsorption and catalytic conversion of polysulfides is critical in improving the cycling stability of lithium–sulfur (Li–S) batteries. Herein, an ultralight typha-like carbon nanofiber (CNF) based interlayer (MoS2/Al2O3@CNF) is constructed by scalable electrospinning and eco-friendly magnetron sputtering, to act as a “police constable” between the cathode and separator. The co-sputtering of MoS2 and Al2O3 endows the interlayer with both chemical adsorption and catalytic conversion active sites. Besides, the typha-like nanofibrous interlayer serves as both membrane and brush filters, leading to more efficient polysulfide blocking. The structural superiority of this interlayer compared to the CNF membrane results in a 693.8% higher specific surface area of 254 m2 g−1. In addition to these benefits, the unique structure allows for a 6.9-fold increase in exposure of active sites. The cell with such an interlayer delivers stable long-term cycling performance with an ultralow capacity decay rate of 0.035% per cycle over 1000 cycles at 0.5C. The long-term cycling performance can be attribute to the structural stability of the typha-like nanofibrous membrane, as evidenced by the postmortem SEM images. This work provides a valuable strategy for designing functional interlayers toward the long-term cycling stable Li–S batteries.

HNO3 pre-oxidation-tuned microstructures of porous carbon derived from high-sulfur coal for enhancing capture and catalytic conversion of polysulfides

Heteroatoms-doped carbon materials have received increasing interest as promising sulfur hosts for lithium-sulfur (Li-S) batteries. Herein, high-sulfur coal was selected as the low cost and earth-abundant precursor and HNO3 pre-oxidation was adopted to tune the microstructure of N,O,S-multidoped three-dimensional porous carbon (NOSTPC) to facilitate affinity and conversion toward polysulfides. HNO3 pretreatment significantly increases the specific surface area, pore volume, and the content of pyrrolic nitrogen and the defects in NOSTPCs. HNO3 pre-oxidation increases the specific capacity of Li-S battery with NOSTPC as the sulfur host from 559.3 to 860.4 mAh g−1 at 1C, and the capacity retention from 67% to 81% after 200 cycles. The satisfying performance benefits from that oxidation pretreatment improves the chemical adsorption of polysulfides by NOSTPC(O), and accelerates the kinetic conversion of polysulfides together with the catalytic oxidation of Li2S. Accordingly, the good performance of high-sulfur coal-based NOSTPCs can not only promote practical application of Li-S batteries, but also facilitate the efficient utilization of high-sulfur coal.

Single Mo–N4 Atomic Sites Anchored on N‐doped Carbon Nanoflowers as Sulfur Host with Multiple Immobilization and Catalytic Effects for High‐Performance Lithium–Sulfur Batteries

AbstractRational design of sulfur hosts for effectively confining lithium polysulfides (LiPS) and optimizing the sluggish sulfur kinetics is still a major challenge in lithium–sulfur batteries (LSBs). In this work, a simple strategy of introducing single Mo–N4 atoms into N‐doped carbon nano‐flower matrix (Mo‐N‐CNF) as sulfur host cathode materials is developed to realize high‐performance LSBs. These single Mo–N4 atoms have been demonstrated to regulate the hydrophilic nature, Li‐ion diffusion, adsorption capacity, and catalytic conversion of polysulfides via experimental evidences and theoretical calculations. The resulting Mo‐N‐CNF with high loading content of sulfur (>72 wt.%) exhibits a high specific capacity (1248 mAh g–1 at 0.2 C) and excellent rate capability (715 mAh g–1 at 5 C). More importantly, the outstanding cycling performance with a low attenuation rate of only 0.004% per cycle over 400 cycles at 4.27 mA cm–2 is achieved with the area sulfur loading of 5.1 mg cm–2. This work demonstrates a viable strategy for using single atoms‐based carbon materials with high exposed sites as multiple captors for LiPS and an efficient accelerator for sulfur redox kinetics toward next‐generation LSBs with boosted electrochemical performance.

Enhancing anchoring and catalytic conversion of polysulfides by nitrogen deficient cobalt nitride for advanced lithium-sulfur batteries

While lithium-sulfur (Li-S) battery has attracted remarkable attention owing to the high theoretical capacity, its practical application is still hindered by the shuttle and sluggish conversion kinetics of intermediate lithium polysulfides (LiPSs). Defect engineering, which can regulate the electronic structure and in turn influence the surface adsorption and catalytic capability, has been regarded as a feasible strategy to deal with the above challenges. However, few studies on nitrogen vacancies and their mechanisms are reported. Herein, cobalt nitride with nitrogen vacancies grown on multi-walled carbon nanotube (CNT-CoN-VN) is designed and applied as the separator modification material to investigate the enhancing mechanism of nitrogen vacancies on Li-S batteries. The experimental evidence and theoretical calculation indicate that the introduction of nitrogen vacancies into cobalt nitride can enhance the chemical affinity to LiPSs and effectively hamper the shuttle effect. Meanwhile the reduced band gap of the d-band center of Co and p-band center of N for CNT-CoN-VN and the promoted diffusion of Li+ can expedite the solid–liquid and liquid–liquid conversions of sulfur species. Due to these superiorities, the cell with CNT-CoN-VN modified separator delivers a favorable initial capacity of 901 mAh g−1 and a capacity of 660 mAh g−1 can be achieved after 250 cycles at 2 C. This work explores the application of metal nitride with nitrogen vacancies and sheds light on the development of functional separators for high-efficient Li-S batteries.

Enhanced immobilization and accelerated conversion of polysulfides by functionalized separator for advanced lithium sulfur batteries

Lithium-sulfur (Li–S) batteries have attracted much attention due to high energy density and low cost. However, some vital issues, especially the notorious shuttle effect of polysulfides has greatly hindered the practical development of Li–S batteries. Reasonable design of electrocatalysts to improve the electrochemical performance of Li–S batteries by enhancing the chemical immobilization and catalytic conversion of polysulfides is considered as a promising solution. Herein, an integrated structure consisting of reduced graphene oxide (RGO) nanosheets modified with Co9S8 nanoparticles is reported, which is expected to be used as a mediator for Li–S batteries to improve the anchoring and catalyzing of polysulfides. The Co9S8 nanoparticles not only have excellent chemisorption capability to capture polysulfides, but also can be used as catalysts to accelerate the conversion of polysulfides. Highly conductive RGO nanosheets can provide appropriate ion/electron diffusion path length, facilitate interfacial reaction kinetics and physically limit polysulfide diffusion. Accordingly, the as-assembled Li–S battery has excellent cycling stability with a low capacity decay rate of 0.041% per cycle over 1000 cycles at 3 A g−1. Importantly, it enables the device to operate over a wide temperature range, with an area specific capacity of 6.4 mAh cm−2 at a sulfur load of 5.8 mg cm−2.

Synergistic effect of NiCo alloy and NiCoS integrated with N doped carbon for superior rate and ultralong-lifespan lithium sulfur batteries

The transition-metal-based alloy and chalcogenides have been widely investigated as efficient sulfur host for lithium sulfur batteries (LSB), yet the synergistic effect of both has been rarely reported. Herein, nickel cobalt alloy (NiCo) and nickel cobalt sulfides (NiCoS) have been simultaneously constructed on the nitrogen-doped carbon substrate (NiCo-NiCoS/NC) via facile calcination-sulfurization of NiCo Prussian blue analogue (NiCo-PBA). The abundantly exposed NiCo alloy and NiCoS domains act as adsorption and catalytic sites that enable effective capture and catalytic conversion of polysulfides, and the highly conductive NiCo-NiCoS integrated with N-doped carbon provides a facile Li+ transfer channel. As a result, S@NiCo-NiCoS/NC electrode delivers a high initial discharge capacity of 1345.1 mA h g−1 at the current density of 0.1 C, superior rate capability of 692.1 mA h g−1 up to 5 C, and ultralong lifespan over 1500 cycles with a small capacity decay of 0.055% per cycle at the current density of 1.0 C.

Enhanced multiple anchoring and catalytic conversion of polysulfides by SnO2-decorated MoS2 hollow microspheres for high-performance lithium-sulfur batteries

Lithium-Sulfur (Li-S) batteries are very competitive in energy storage equipment due to their high theoretical capacity and low cost of raw materials. However, the serious polysulfide "shuttle effect", volume expansion effect and slow conversion reaction kinetics of Li−S batteries during the charge/discharge cycle process still need to be resolved urgently. Herein, we prepared a novel sulfur host of SnO2-decorated MoS2 hollow microspheres (SnO2-MoS2 HMSs). The unique hollow structure provides enough space to accommodate a large amount of sulfur and effectively adapts to its large volume expansion during charge and discharge process. On the other hand, the SnO2 nanoparticles that attached to the surface of the MoS2 nanosheets will accelerate the catalysis of MoS2 and enhance the bonding strength with the polysulfide intermediates through the S−Sn−O chemical bond, which further inhibits the shuttle effect. The newly synthesized SnO2-MoS2 HMSs cathode has achieved excellent electrochemical performance. The initial discharge specific capacity of 1326.4 mAh g−1 was obtained at 0.2 C, and after 100 cycles, the specific capacity of the SnO2-MoS2 HMSs/S cathode only decreased slightly to 1183.8 mAh g−1, its capacity retention rate reaching as high as 89.2%. We expect the newly synthesized hollow structured MoS2 with SnO2 decoration provides a new strategy for the construction of Li-S battery cathode materials.