Loss Of Sulfur Research Articles

Catalytic Solid‐State Sulfur Conversion Confined in Micropores toward Superhigh Coulombic Efficiency Lithium‐Sulfur Batteries

AbstractAchieving the solid–solid conversion of sulfur is a fundamental solution to eliminating the shuttling of soluble polysulfides and improving the cycling stability of lithium‐sulfur batteries. However, the sluggish solid reaction kinetics seriously challenge the battery performance. In this work, a micropore‐confined catalysis strategy to achieve the smooth solid–solid conversion of sulfur is proposed. It is realized by storing sulfur in a microporous carbon host with narrow pore size and uniformly distributed single‐atom Co catalytic sites. The microporous structure avoids the contact of electrolyte solvents with the inner sulfur, preventing the formation and dissolution of polysulfides and efficiently suppressing sulfur loss during cycling. The introduced single‐atom Co catalytic sites promote the charge transfer to accelerate the solid–solid conversion of sulfur. When coupled with a liquid carbonate electrolyte, the battery exhibits a remarkably high Coulombic efficiency (CE) of ≈99.88% and a minimal capacity decay rate of ≈0.016% per cycle for 1000 cycles at 0.5 C. Even when coupled with the solid‐state electrolyte, the battery still delivers a significantly high capacity of 1100 mAh g−1 and a remarkably high CE of ≈99.83% over 200 cycles. This work reveals a promising solution for developing practical stable Li─S batteries.

Farmland Microhabitat Mediated by a Residual Microplastic Film: Microbial Communities and Function.

How the plastisphere mediated by the residual microplastic film in farmlands affects microhabitat systems is unclear. Here, microbial structure, assembly, and biogeochemical cycling in the plastisphere and soil in 33 typical farmland sites were analyzed by amplicon sequencing of 16S rRNA genes and ITS and metagenome analysis. The results indicated that residual microplastic film was colonized by microbes, forming a unique niche called the plastisphere. Notable differences in the microbial community structure and function were observed between soil and plastisphere. Residual microplastic film altered the microbial symbiosis and assembly processes. Stochastic processes significantly dominated the assembly of the bacterial community in the plastisphere and soil but only in the plastisphere for the fungal community. Deterministic processes significantly dominated the assembly of fungal communities only in soil. Moreover, the plastisphere mediated by the residual microplastic film acted as a preferred vector for pathogens and microorganisms associated with plastic degradation and the nitrogen and sulfur cycle. The abundance of genes associated with denitrification and sulfate reduction activity in the plastisphere was pronouncedly higher than that of soil, which increase the potential risk of nitrogen and sulfur loss. The results will offer a scientific understanding of the harm caused by the residual microplastic film in farmlands.

Sulfide-Based Solid-State Lithium-Sulfur Batteries: An in-Depth Study of the Li-Electrolyte Interface

The development of solid-state batteries has gained significant attention in recent years, owing to their potential to enhance the temperature range and energy density of energy storage devices. Sulfide-based electrolytes are some of the most promising candidates for solid-state batteries, thanks to their high ionic conductivity and low processing temperature. For lithium-sulfur (Li-S) batteries, the transition from liquid to solid electrolytes holds even greater promise. Sulfur is a readily available cathode material known for its high specific capacity, which endows Li-S batteries with remarkable specific energy and favourable environmental and economic impact. In liquid electrolytes however, the solubility of sulfur and lithium polysulfide causes a multitude of issues that hamper the performance of the Li-S system: rapid self-discharge, redox shuttle mechanism during charging, and loss of active sulfur and lithium material due to direct chemical reactivity. Solid-state Li-S cells are not prone to these issues, but they have, of course, issues of their own. Amongst them, the stability of the interface between the electrolyte and the lithium is of crucial importance to allow the use of this very high energy density negative electrode.In the present study, we compare two sulfide electrolytes, Li6PS5Cl and Li7P3S11, and assess their respective stability against lithium. We used innovative methods to characterize the interphase between the sulfide and the lithium without damaging it upon dismantling the cell. The nature and the properties of this interphase was characterised via EIS, XPS and ToF-SIMS.The EIS study showed that Li6PS5Cl forms a much more stable interphase with lithium than Li7P3S11, which is in accordance with most recent results in the literature. The XPS study confirmed the chemical composition of the interphase. Li2S and Li3P were present for both electrolytes. In the case of Li6PS5Cl, LiCl was also identified as expected. Gas cluster ion beam (GCIB) assisted abrasion of the interphase followed by in-situ XPS and ToF-SIMS suggested a separation of the components of the interphase depending on the depth of the abrasion. The interphase was found to be organised as Li2S-, Li3P- or LiCl-rich discrete layers, with the Li2S-rich layer being consistently the closest to lithium. This result confirms and completes the most recent research in the field published by Otto et al. in 2022 (doi: 10.1002/admi.202102387).To establish solid-state batteries as a practical energy storage option, it is essential to fully understand and effectively manage the Li-electrolyte interface. These findings suggest that thanks to the relative stability of its interface with lithium, Li6PS5Cl is the better option for solid-state lithium metal cells. It also sheds light on the reasons why this interface is more stable. The self-assembled lamellar structure of the interphase could also inspire strategies to better control the stability of solid electrolytes versus lithium.

Tuning the Interfacial Chemistry for Stable and High Energy Density Aqueous Sodium-Ion/Sulfur Batteries

The environmental-related issues arising from the fossil fuel assorted industrial revolution and worldwide development have prompted the quest for rechargeable batteries. In these predicaments, lithium-ion batteries (LIBs) took ownership to reshape our lives. However, the limited abundance, non-uniform geographical distribution and severe flammability of organic electrolytes, increase the uncertainty over their large-scale application. Recently, aqueous rechargeable sodium-ion batteries (ARSIBs) have gained considerable curiosity for large-scale energy storage due to their much-assured safety, environment friendliness, high-rate capacity, and low cost. However, the prospects of ARSIBs seeing commercial success remained remote due to the narrow water stability window (1.23 V), which translates into low cell voltage (< 1.6 V), low energy density (< 70 Wh Kg-1), and compromised cycling stability. The aforesaid dilemmas can be resolved by generating a protective layer known as a solid electrolyte interface (SEI) like in organic electrolytes. However, the SEI concept in aqueous electrolytes is relatively unexplored, as water dissociation leads to O2 and H2, and will enhance the parasitic reactions. The SEI formed in WiSE due to salt reduction is often inhomogeneous with a porous mosaic structure and is susceptible to mechanical cracking, and increase the overall cost. Hence, high-capacity electrodes and high voltage electrolytes capable of forming a stable SEI are urgently required to fulfill the dream of the large-scale application of ARSIBs.Recently low cost, highly abundant sulfur-based electrode material has attracted significant research attention due to its high theoretical capacity (1675 mA h g-1) and energy density. However, sluggish sulfur redox kinetics, acute polysulfide shutting, dendritic growth on the metal-based anode and low conductivity of sulfur and its discharge products proves to be a major roadblock for its commercialization. Utilizing abundant sulfur in an aqueous electrolyte along with abundant Na+ can resolve the kinetics and conductivity anxieties and leads to a new greener and safer Na-ion/S batteries chemistry. However lower order polysulfide dissolution in water is more feasible, leading to the rapid capacity decay and active sulfur loss due to H2S formation. Polysulfide dissolution is an interfacial mechanism occurring at the electrode-electrolyte interface and depends on both electrode and electrolyte merits. Therefore, an effective approach will be to couple efficient sulfur host with an electrolyte capable of generating a stable SEI on the electrode surface to prevent the direct attack of water on polysulfide.Herein we have explored urchin-like CoWO4 as a sulfur host coupled with Na-W-U-D electrolyte. The CoWO4 exhibits high conductivity, strong chemical interaction for sulfur and its discharge products, and urchin-like morphology having exposed edges facilitate the charge transport results in excellent polysulfide redox kinetics. The high voltage Na-W-U-D electrolyte was prepared by mixing NaClO4, urea, and N, N-dimethylformamide DMF in 1:2:1 ratio in water. Each component in the electrolyte plays an important role. Urea has very high water solubility and tends to form stable SEI, while DMF has a high dielectric constant, good solvation ability, and develop stabilize SEI. As a result, Na-W-U-D shows a stability window close to the 3.1 V regime due to reduced water activity resulting from complex ion solvent interaction and stable and uniform SEI formation, consisting of Na2CO3, polyurea, and reduction products of DMF. Despite the addition of DMF, non-flammable features of aqueous electrolytes remain well maintained. Herein for the first time, the SEI concept was successfully used for the aq. Na-ion/S battery. We discovered that the lower water activity of Na-W-U-D electrolyte hindered polysulfide dissolution and stable SEI prevent the direct attack of water on polysulfide and results in extended cycling stability. At the same time, the urchin-like CoWO4 host enhances the sluggish polysulfide redox kinetics and provides an abundant anchoring site for polysulfide adsorption. We investigate the effect of time, C-rate, depth of discharge, and dissolved oxygen on polysulfide dissolution and self-discharge of the negative electrode. The high electrode capacity combined with the safety and stable SEI of Na-W-U-D electrolyte translated into a record high initial capacity of 834 mA h g-1 w.r.t sulfur, with remarkable cycling stability up to 500 cycles @ 0.5 C. Post analysis by SEM and XPS, evident that the stable SEI consists of Na2CO3, polyurea, and reduced products of DMF (CO and NHMe2), which also prevent the negative electrode from self-discharge by mitigating the parasitic reaction of dissolved oxygen in the electrolyte. Moreover, a full cell assembled by integrating S@CoWO4 anode and Na0.44MnO2 cathode showed remarkable stability and a high energy density of 119 Wh kg-1, making it a promising candidate for a future energy storage system. Figure 1

Microwave heating enables near-carbonless liquid-phase-derived Li Argyrodites for all-solid-state batteries

The liquid-phase synthesis of sulfide solid electrolytes (SEs) is promising for the mass production of practical all-solid-state batteries (ASSBs). However, upon conventional furnace-based heat treatment of liquid-phase-derived intermediates, SEs contain deleterious carbon impurities from organic residues, negatively impacting the electrochemical performance of ASSBs and hindering their practical application. Herein, we present a novel approach utilizing ultrafast targeted heating through microwave-induced thermal shock, demonstrating the enhanced crystallization of SEs while effectively suppressing the carbonization of organic impurities during the liquid-phase synthesis of argyrodite SEs. Complementary analyses confirm the reduced sulfur loss and minimized impurity evolution achieved through microwave heating, as compared to conventional furnace heating. The microwave-derived argyrodite SEs exhibit high Li conductivities (Li5.5PS4.5Cl1.5: maximum 3.1 mS cm−1) and acceptably low electronic conductivities (Li6PS5Cl: 1.2 × 10−9 S cm−1), in stark contrast to the mixed conducting property of furnace-derived Li6PS5Cl (Li+ conductivity: 1.1 mS cm−1, electronic conductivity: 1.7 × 10−5 S cm−1). As a result, when utilized as SE layers or catholytes in LiNi0.70Co0.15Mn0.15O2||Li-In ASSB cells, the cells incorporating microwave-derived SEs significantly outperform those with furnace-derived SEs (e.g., the capacity retention after 250 cycles: 93.6% vs. 32.0%). Furthermore, a proof-of-concept for microwave self-heating of SEs is successfully demonstrated.

Metal‐Halide Gelated MXene and Its Use as a Bifunctional Sulfur Host Stabilizing Both Cathode and Anode for Practical Lithium–Sulfur Batteries

AbstractThe gelation of MXene promises to assemble a 3D conductive and catalytic monolith for various applications. However, controllable assembly and function customization are still challenging. Here, with a “killing two birds with one stone” initiator (metal halide, typically ZnI2), the controllable gelation of MXene is enabled, which produces a sulfur host that stabilizes not only the cathode but also the lithium metal anode for lithium‐sulfur batteries. Zn2+ cations trigger the gelation and act as linkers between MXene nanosheets (NSs), while the iodine anions as spacers avoid the NSs restacking, forming a monolith with a well‐tunable 3D structure. As a sulfur host, the formed 3D monolith with adsorptive Zn─O sites and highly accessible surface greatly enhances the sulfur redox kinetics, effectively suppressing the shuttling and sulfur loss. At the same time, iodine anions are released into the electrolyte as additives eliminating dead Li for the anode in cycling. Thus, the assembled battery shows high Coulombic efficiency (∼above 99%, even under high sulfur loading: 6.6 mg cm−2) and long cycling stability. Under the practical condition (E/S ratio: 5 µL mgs−1, sulfur loading: 5 mg cm−2), high capacity retention of &gt;70% for 200 cycles is achieved.

Synthesis of 4-in. multilayer molybdenum disulfide via space-confinement thermolysis

Two-dimensional (2D) semiconductors like molybdenum disulfide (MoS2) exhibit superior performance at nanometer-scale thickness compared to silicon. Notably, multilayers are more resistant to breakage during transfer and boast enhanced electrical properties over monolayers. In this study, we synthesized 4-in. multilayer MoS2 using a rapid thermal processing system through the ammonium tetrathiomolybdate precursor thermolysis. A 200 nm-scale space confinement on the sample surface was used to reduce sulfur loss during annealing and to facilitate vacancy healing by self-feeding sulfur atoms. Various characterizations confirmed good crystallinity, surface flatness, and continuity, including Raman spectroscopy, x-ray photoelectron spectroscopy, scanning transmission electron microscopy, and atomic force microscopy. Moreover, these samples showed a significant enhancement in electron mobility. Our approach benefits efficiency, scalability, and procedural simplicity, paving a promising path toward large-scale production of multilayer 2D semiconductors.

2D Nano-Channeled Molybdenum Compounds for Accelerating Interfacial Polysulfides Catalysis in Li-S Battery.

The shuttle effect, which causes the loss of active sulfur, passivation of lithium anode, and leads to severe capacity attenuation, is currently the main bottleneck for lithium-sulfur batteries. Recent studies have disclosed that molybdenum compounds possess exceptional advantages as a polar substrate to immobilize and catalyze lithium polysulfide such as high conductivity and strong sulfiphilicity. However, these materials show incomplete contact with sulfur/polysulfides, which causes uneven redox conversion of sulfur and results in poor rate performance. Herein, a new type of 2D nano-channeled molybdenum compounds (2D-MoNx) via the 2D organic-polyoxometalate superstructure for accelerating interfacial polysulfide catalysis toward high-performance lithium-sulfurbatteries is reported. The 2D-MoNx shows well-interlinked nano-channels, which increase the reactive interface and contact surface with polysulfides. Therefore, the battery equipped with 2D-MoNx displays a high discharge capacity of 912.7 mAh g-1 at 1 C and the highest capacity retention of 523.7 mAh g-1 after 300 cycles. Even at the rate of 2 C, the capacity retention can be maintained at 526.6 mAh g-1 after 300 cycles. This innovative nano-channel and interfacial design of 2D-MoNx provides new nanostructures to optimize the sulfur redox chemistry and eliminate the shuttle effect of polysulfides.

Electrochemical reduction of carbon dioxide to formate in a flow cell on CuSx grown by atomic layer deposition

Transition metal chalcogenides (TMCs) are promising pre-catalysts for tuning the selectivity of electrochemical carbon dioxide (CO2) reduction (CO2R). Atomic layer deposition (ALD) enables well-controlled growth of thin TMC films on various gas diffusion electrodes. Herein, we have studied the CO2R performance of ALD-grown copper sulfide (CuSx) in a flow cell. The effects of electrode configuration, electrolyte concentration, temperature, and electrolysis time were carefully studied, combined with pre- and post-electrolysis physico-chemical analyses of the films. The unique selectivity of sulfur-doped Cu towards formate was retained with Faradaic efficiencies between 40 and 60%, but slow selectivity changes were observed over time. Major loss of sulfur was encountered during the initial 5-min reduction period, and after that, progressive formation of nanoparticles could be observed. Comparisons to ALD-grown Cu thin film and CuSx-modified Cu foam electrodes verified the importance of sulfur and suggested that other electrocatalyst films could be easily realized with ALD.

Mott Schottky heterojunction Co/CoSe2 electrocatalyst: Achieved rapid conversion of polysulfides and Li2S deposition dissolution via built-in electric field interface effect

Rechargeable lithium-sulfur (Li-S) batteries are considered ideal candidates for the next generation of energy storage devices. However, the insulation properties of S and Li2S, as well as the notorious “shuttle effect” of lithium polysulfide, result in severe loss of active sulfur, poor redox kinetics, and rapid capacity decline. To overcome these limitations, this paper designs a self-supporting electrocatalytic electrode based on Co/CoSe2 Mott Schottky heterojunction coated carbon nanofibers (Co/CoSe2@NCNFs), and engineers it for capturing and converting polysulfides. Density functional theory calculations show that the introduction of Co/CoSe2 heterojunction effectively reduces the redox barrier of Li2S. The electron current and electron interaction at the Co/CoSe2 interface induce the redistribution of charge density in the depletion region, thus increasing the chemical reactivity of the metal semiconductor heterojunction interface, which is conducive to the ion/electron transport, polysulfide conversion and Li2S oxidation process. Therefore, the Li-S battery assembled by Co/CoSe2@NCNFs/S electrode exhibited a high initial specific capacity of 1043.3 mAh/g at 1C, and maintained a capacity of 709.9 mAh/g after 1000 cycles, with a capacity decay rate of only 0.032% per cycle. The proposed Mott Schottky heterojunction as an electrocatalyst deepens the promotion of polysulfides and Li2S in long-life Li-S batteries.

Preparation of Co–Co9S8–MoS2 catalyst for efficient deoxygenation of lignin-derived aromatic oxy-compounds into arenes

The formidable challenge for the deoxygenation of lignin-derived aromatic oxy-compounds into arenes under mild conditions is how to engineer a robust catalyst. In this study, Co–Co9S8–MoS2 catalyst was prepared via thermal decomposition, in–situ sulfidation and following by H2 reduction, where Co was highly dispersed and mainly existed in the species of metallic Co and Co9S8. This catalyst exhibited high activity, allowing the reaction temperature for cleaving Caromatic–O bond lowered to 120 °C, which was attributed to that metallic Co accelerated the H2 dissociation and then enhanced the deoxygenation activity. Co–Co9S8–MoS2 also presented a high stability: both the conversion and product selectivity were unchanged after 8 continuous cycles, and the characterization results evidenced almost no structure change and sulfur loss during the deoxygenation reaction. In addition, other 20 aromatic oxy-compounds including acid, ester, guaiacol and dimer lignin linkages were also successfully deoxygenated, and the arenes selectivity could maintain higher than 98 %. This work offered a new strategy for constructing metal–sulfide–MoS2 type catalysts and provided an efficient route towards the practical application in bio-oil upgrading.

Ceramic Fillers for Improved Lithium-Sulfur Batteries

With the decarbonization of transportation, the demand for electric vehicles (EVs) and batteries that can power these EVs has been increasing. Lithium-ion-based batteries are already well-established and are considered the main chemistries to power current EVs. However, limited specific energy (< 300 Wh/kg) prevents these batteries from having high mileage vehicles. Lithium-sulfur batteries are considered the most promising next-generation energy storage system as they high theoretical capacity (~1675 mAhg-1), low cathode materials cost, and cell energy densities that can exceed 700 Wh/kg [1,2]. However, some major drawbacks prevent the Li-S battery system from being applicable in energy devices and hinder its commercialization, that include low power density and rapid capacity degradation during their cycling life. In addition, the lithium metal anode in Li-S batteries bring various issues to the forefront such as continuous solid electrolyte interface growth, dendrite formation, and loss of active lithium and electrolyte. These issues are further exacerbated at high C-rates which increases the possibility of an internal short-circuit and sudden cell failure [3]. In order to promote longer life cycles and prevent sudden cell failure, a thorough understanding of the cell’s electrochemical behavior is crucial for the development of a stable and practical Li-S battery system. The introduction of oxide fillers such TiO2, Al2O3, SiO2, etc. has been previously studied in various lithium-ion systems and has been shown to improve the cell’s lithium-ion transport properties, which in turn improve the performance of Li-S cells [4]. When used as interlayers they can also trap soluble polysulfides diffusing out of the cathode and reduce their crossover to the anode which helps reduce the shuttle effect of said polysulfides.In the present study, the use of a polysulfide immobilizing system to reduce sulfur loss and improve capacity retention has been demonstrated. The galvanostatic charge-discharge cycling study shows that cells retain higher capacity during the course of cycling. The initial capacity for Li-S cells with the filler average 1300+ mAh/g (C/10) while the capacity stabilizes around 1000 mAh/g after 3 cycles (C/5). The capacity retention at C/5 after 75 cycles was approximately 875 mAh/g which represents a rate 0.17% drop per cycle. When compared to control cells, the cells containing no fillers had lower initial capacity that averaged 1050 mAh/g and that rapidly declined to stabilize around 650 mAh/g. However, after this major drop, the cells remained stable no with measurable drop after 75 cycles. The behavior indicates that the cells with fillers delayed the effect of sulfur loss experienced in cells without fillers; however, the slow capacity drop that ensued, indicates that while polysulfide trapping was efficient it was unable to fully prevent it. The effect of fillers on the Coulombic efficiency (CE) also supports the polysulfide “trapping” mechanism and shows the ability of the cell to reduce the shuttle effect that contributes to lower CE values. Further electrochemical studies have been performed to understand the mechanisms of the improvement of the cell.

Strategies on Enabling High Areal Sulfur Loading in Lithium Sulfur Batteries

Needs for energy storage devices in modern-day applications such as electric vehicles and other high energy consuming portable electronics make the Lithium sulfur batteries (LSBs) to be one of the most attractive types since they offer a high theoretical energy density (2600 Wh kg-1), which is about an order of magnitude higher than the theoretical specific capacity of the lithium ion batteries. In addition, Sulfur is one of the most abundant materials in nature and moreover, a non-toxic element which makes the lithium sulfur battery a suitable candidate for commercialization. However, obstacles to overcome include the loss of active sulfur due to various phenomena mainly represented by polysulfide diffusion and reactivity on the lithium anode. Another serious issue observed in so many ways is the low electronic conductivity of Sulfur and its products such as Li2S as a result of cycling. These problems are often exacerbated at higher sulfur loading and lower electrolyte to sulfur ratios (E/S). One way to increase the sulfur loading is to increase the thickness of the cathode which in return increases the risk of low utilization of active material because of the high thickness and low wettability by electrolyte. Another way is to increases the ratio of the sulfur in respect to conductive host material without increasing the thickness of the cathode. By doing so, sulfur is going to fill all the pores existing in the host material and therefore, this structure cannot provide enough volume expansion during discharge process and as a result, the cathode structure may collapse and the whole cell fail. Therefore, to come up with a high performance and stable battery during cycling, there is no doubt that we have to focus on the structure of the cathode and the host material to effectively confine the sulfur and produced polysulfide and at the same time, alleviate the way of the electron transfer through the conductive network.In this research, we investigate some of the most influential parameters mainly associated with the morphology of the cathode to improve capacity retention. Optimizing the sulfur loading, E/S content, pore structure and pore volume, and the thickness of the cathode lead to an overarching understanding of the physical transitions that occur during the discharge and charge operation of the battery. In addition, various electrochemical testing to evaluation the loss of activity of the cathode surface is also carried it to correlate to the proposed physical model.

Redistribution of d-orbital in Fe-N4 active sites optimizing redox kinetics of the sulfur cathode

Redistributing the d-orbital of single Fe atom catalysts (SFeACs) has been challenging to optimize redox kinetics of lithium sulfur batteries (LSBs). Here, the Fe-N4/S2C with mounting energy level of dz2 and partial occupation of dxz is controllably fabricated. The increased dz2, originating from thiophene sulfur, upshifts d band center compared to the Fe-N4/C with planar symmetric structure. That promotes electron transfer between Fe-N4 and sulfur, enhancing conversion of polysulfides and solid products. The lower fill of dxz develops hybridization between Fe and S atoms via the form of bonding and antibonding, with alleviating the loss of sulfur. Thus, the sulfur cathode with Fe-N4/S2C delivers a high capacity of 749 mAh g−1 at 2.0 C, accompanied by excellent stability with a lower capacity decay of 0.07% per cycle. This work has developed a novel coordination configuration towards SFeACs and uncovered the intrinsic mechanism of facilitated redox kinetics with SFeACs for LSBs.

Sodium‐Sulfur Batteries with Unprecedented Capacity, Cycling Stability and Operation Temperature Range Enabled by a CoFe2O4 Catalytic Additive Under an External Magnetic Field

AbstractThe electrochemical performance of room‐temperature sodium‐sulfur batteries (SSBs) is limited by slow reaction kinetics and sulfur loss in the form of sodium polysulfides (SPSs). Here, it is demonstrated that through electron spin polarization, at no additional energy cost, an external magnetic field (M on) generated by a permanent magnet can significantly improve the SPSs adsorption capacity and reaction dynamics of a ferrimagnetic sulfur host. More specifically, the preparation of a carbon nanofiber/CoFe2O4/S (CNF/CoFe2O4/S) cathode with unprecedented performance and stability at ambient temperature is detailed when M on. It is experimentally and theoretically demonstrated that the magnetic field polarizes the electrons of Co ions, enhancing the adsorption of SPSs and their catalytic conversion. CNF/CoFe2O4/S cathodes with spin polarization provide unprecedented decay rates down to 0.0039% per cycle at 1.0 C for 2700 cycles. The performance of SSBs is further tested, which has 248 mAh g−1 under 1.0 C after 100 cycles when M on. Furthermore, it is evidenced that even when removing the external magnetic field, the magnetic polarization effect persists, opening the door for practical applications. This study not only demonstrates an effective strategy to improve electrochemical performance in SSBs, but also contributes to the enrichments of spin effects in the fields of electrocatalysis.

Revealing the Electrochemistry of All-Solid-State Li-SeS2 Battery via Transmission Electron Microscopy

Li-SeS2 batteries balance the opposing and complimentary qualities of Li-S and Li-Se batteries by having a high specific capacity and high electrical conductivity. However, there is still a lack of knowledge regarding the electrochemical characteristics of Li-SeS2 all-solid-state batteries (ASSB). Herein, transmission electron microscopy (TEM) is used to reveal the electrochemistry of a Li-SeS2 battery. It is discovered that, without the Polyethylene glycol (PEG), amorphous SeS2 in Li-SeS2 ASSB change into crystalline selenium and a small amount of sulfur. The continuous loss of sulfur from the active material may be related to the failure of the cell at 15 cycles and the severe instability of the Coulombic efficiency. It was found that the PEG coating selenium disulfide graphene composite (PEG@rGO-SeS2) cathode maintained a specific capacity of 258 mAh g−1 and a stable Coulombic efficiency of about 97% after 50 cycles. TEM analysis shows that the charging product remains as a granular amorphous selenium disulfide with a constant Se/S ratio during cycling. The PEG-protected selenium disulfide can effectively limit the loss of elemental sulfur and regulate the reaction mechanism of the Li-SeS2 batteries.

Effect of SnCl2 heat treatment on SnS thin films deposited by RF sputtering

In this study, the effect of SnCl2 treatment on SnS thin films was investigated. SnS thin films were grown by RF sputtering and SnCl2 treatment was applied by wet chemical processing. The samples grouped as SnCl2 heat treated, annealed, as dep. were subjected to annealing in air atm. The as dep. sample grew in the orthorhombic SnS phase. Annealing of the SnS sample in air environment led to the formation of orthorhombic SnS as well as non-dominant SnS2 and SnO2 phases. It was found that applying SnCl2 heat treatment to SnS deteriorated the crystallization and especially the SnO2 oxide phase became more dominant. Raman spectra confirmed the presence of SnS and SnS2 phases in the samples, but no evidence of SnO2 phase was found. SEM images showed bladelike, dense grain formation in the as dep. and annealed samples. However, SnCl2 heat treatment completely changed the surface morphology of the sample, causing it to transform into a structure consisting of several domains split by deep fractures. EDS revealed a distinct Sn-rich composition of the as dep. and annealed samples (Sn/S~1.2). On the other hand, SnCl2 heat treatment caused a massive loss of sulfur in the atomic distribution of the SnS and it was seen that the Sn/S ratio increased to around 7.5. The band gaps of the as dep. and annelaed samples were calculated as 1.43 eV and 1.45, respectively. However, SnCl2 heat treatment led to an increase to 1.56 eV of the band gap. Analysis results show that SnCl2 treatment by the wet processing causes a significant change on the characteristics of SnS thin film. In this context, it can be said that SnCl2 heat treatment can be further improved with optimization processes.

Synergistic catalysis of MoS2-Ni3S2 heterojunctions to accelerate polysulfide conversion for high-performance Li-S battery

The sluggish conversion kinetics of polysulfides and its unprevented dissolution will lead to loss of active sulfur and act as the biggest obstacle for the widespread use of lithium-sulfur (Li-S) batteries. However, it is a great challenge to simultaneously response to the above-mentioned multiple requirements by the adoption of single catalyst. Herein, by incorporating the merits of strong adsorption and high electron conductivity of Ni3S2 with good catalytic of MoS2, a self-supported heterojunction MoS2-Ni3S2 catalyst has been developed with uniform rod-like morphology, which can provide larger specific surface area, better compensation of electrons, more effective catalysis, and faster solid phase transformation compare to its single component catalyst. Theoretical calculations and mechanism analyses suggest that the heterojunctions exhibit a synergistic process of “adsorption-diffusion-conversion” for polysulfides (LiPSs) and effectively facilitate the liquid-solid phase conversion(Li2S6→Li2S2/Li2S). Integrating the merits of Ni3S2 and MoS2, MoS2-Ni3S2 heterojunctions catalytic cathode deliver a good cycling stability with 70 % capacity retention after 150 cycles at 0.2 C with a high sulfur loading of 5.0 mg cm−2. Therefore, this work proposed a feasible catalyst design of bi-metal sulfides heterostructure which can simultaneously meet multiple kinetics requirements of Li-S system.

Cu2ZnSnS4 films properties deposited by spray pyrolysis, subjected to a combined novel thermal treatment: CSS sulfurization and RTA post-treatment

CZTS films were obtained by spray pyrolysis, a low-cost technique implemented on an industrial scale. Sulfurization processes generally enhance CZTS properties for its use in solar cells; however, these require high temperatures and long times. In this work, CZTS films properties were studied after being subjected to a combined novel thermal treatment which involved two stages. Sulfur incorporation using close space sublimation technique (CSS) at a temperature (TCSS) in the 350–500 °C range for 60 s, and after a rapid thermal annealing post-treatment (RTA) at TRTA = 500 °C for 10 s, with a heating ramp of 5 °C/s under argon atmosphere. Morphological, structural, chemical composition, optical and electrical properties were studied for CZTS films subjected to CSS as CSS+RTA treatments for all TCSS values. From the results, efficient sulfur incorporation by CSS was obtained without substantial sulfur concentration loss after RTA treatment, associated with the short treatment time. In addition, significant enhancement of crystalline quality and electrical resistivity diminished of the films is obtained after the CSS+RTA process for all TCSS. CZTS films with the best properties are those obtained at TCSS of 400 °C, having Cu/(Zn+Sn) = 0.79 and Zn/Sn = 1.3 ratios, a direct bandgap value of 1.5 eV, and resistivity of 4 Ω-cm. These films can be candidates for their characteristics as an absorbent layer in solar cells.

Structural Transformation in a Sulfurized Polymer Cathode to Enable Long-Life Rechargeable Lithium–Sulfur Batteries

Sulfurized polyacrylonitrile (SPAN) represents a class of sulfur-bonded polymers, which have shown thousands of stable cycles as a cathode in lithium-sulfur batteries. However, the exact molecular structure and its electrochemical reaction mechanism remain unclear. Most significantly, SPAN shows an over 25% 1st cycle irreversible capacity loss before exhibiting perfect reversibility for subsequent cycles. Here, with a SPAN thin-film platform and an array of analytical tools, we show that the SPAN capacity loss is associated with intramolecular dehydrogenation along with the loss of sulfur. This results in an increase in the aromaticity of the structure, which is corroborated by a >100× increase in electronic conductivity. We also discovered that the conductive carbon additive in the cathode is instrumental in driving the reaction to completion. Based on the proposed mechanism, we have developed a synthesis procedure to eliminate more than 50% of the irreversible capacity loss. Our insights into the reaction mechanism provide a blueprint for the design of high-performance sulfurized polymer cathode materials.