Carbon Sulfur Composites Research Articles

Mesoporous Carbons Produced from Tannin Biomass for Lithium-Sulfur Batteries

Lithium-sulfur batteries (LSBs) are promising alternatives since sulfur can provide a theoretical specific capacity of 1675 mA h g-1 when combined with lithium [1]. Thus, LSBs can achieve a theoretical energy density (2500 W h kg-1) that is much greater than that of conventional lithium-ion batteries [1]. However, several problems must be resolved to enable commercial production on a large scale, such as the formation of soluble species of lithium polysulfides [2]. Various approaches have been used to minimize this problem, including the development of carbon-based hosts capable of retaining these polysulfides. Among these, the development of cathodes based on carbon‒sulfur composites using carbon from biomass is an alternative that benefits from the possibility of obtaining materials with a modifiable surface area and porosity at low cost [2]. On this basis, this work reports the synthesis of mesoporous carbons (MCs) from tannin biomass, the incorporation of sulfur and the development of lithium-sulfur batteries. The MC sample was produced using the solvent-free method [3] and was named C. The incorporation of sulfur into mesoporous carbons was carried out using melt diffusion methodology [4]. Two quantities of sulfur were added to the carbon host by mass, and the materials were named CS1 and CS2 at ratios of 1:1 and 2:1, respectively, in relation to sulfur:MC. Coin cells (CR 2032) were assembled using the produced materials on the cathode, metallic Li on the anode and the electrolyte 1 M LiTFSI and 1% (w/v) LiNO3 in 1,2-dimethoxyethane/1,3-dioxolane (DME/DOL) and characterized by cyclic voltammetry (CV) and galvanostatic charge/discharge (GCD) cycling. The mesoporous carbon C presented a type IV isotherm characteristic of mesoporous materials, with a BET surface area of 539 m2g-1, average pore size of 7.7 nm and total pore volume of 0.747 cm3g-1. There was a decrease in the area and pore volume of the materials after sulfur incorporation, reaching 70 m2g-1 and 0.195 cm3g-1 for CS1 and 3 m2g-1 and 0.012 cm3g-1 for CS2, respectively. The sulfur contents were determined by thermogravimetric analysis (TGA) and were 39% and 61% for CS1 and CS2, respectively. The sulfur contents determined by TGA were close to those obtained by elemental analysis (CHNS), which were 45% and 63% for CS1 and CS2, respectively. The CV data showed that both cells presented cathodic and anodic potentials typical of Li-S batteries. The GCD data show that the cell containing the cathode with the material with a higher elemental sulfur content (CS 2) is stable and maintains specific capacities on the order of 550 mA h g-1 after 45 galvanostatic cycles at different current densities. However, this cell showed a more abrupt decrease in capacity at the highest rates (2C and 4C), Figure 1. Most likely, the higher sulfur content used in this sample did not result in total impregnation of the porous structure, resulting in sulfur deposition on the surface of the particles. As a result, the interparticle contact resistance in the electrodes increases, which limits the performance at higher current demands. For the cell built with the sample containing 39% S (CS1), excellent performance is obtained at high C rates. At 0.1 C, the cathode operates above 900 mA h g-1 in the initial cycles and above 550 mA h g-1 at 0.5 C, and no significant capacity drop is observed between 1 C and 2 C (≈500 mA h g-1). At 4C, a decrease in the specific capacity is noted, but the specific capacity remains above 350 mA h g-1. These results demonstrate the potential of carbon materials obtained from biomass for building high-performance Li-S batteries.Acknowledgments: The authors thank the financial support from the Rota 2030 Program at Fundep – Brazil.

Synergistic Effect of CNT-TiO2 Catalyst and 3D Electrode Architecture for Electrochemical Performance in Lithium-Sulfur Batteries

Lithium-sulfur batteries (LSBs) are a potential electrochemical storage system for the future with high capacity (1675 mAh g−1) and energy density (∼2600 Wh kg−1). The poor conductivity of sulfur, polysulfide shuttle effect, and volume expansion of the sulfur cathode are the main hurdles to their commercialization. To mitigate these issues, this work represents a rational composite of hybrid multiwalled carbon nanotubes (MWCNT) -TiO2 high surface area carbon-sulfur composite (CTHS) onto a 3D carbon fiber (CF) based free-standing electrode (CTHS@CF) architecture. TiO2 can effectively anchor the polysulfides by chemical bonding and improve cyclability. MWCNTs and CFs are the effective electron transport materials that accelerate the redox kinetics of polysulfides. The electrochemistry of CTHS@CF reveals an excellent discharge capacity of 910 mAh g−1 (1st cycle) at 100 mA g−1 compared to the conventional aluminum-coated (CTHS@Al) of 532 mAh g−1. The CTHS@CF (at 300 mA g−1) displays 514 mAh g−1 (initial discharge) capacity with 83% capacity retention up to 100 cycles, whereas CTHS@Al shows 394 mAh g−1 with 44% capacity retention. Combining 3D electrode architecture with the metal oxide (TiO2) plays a vital role in the electrochemistry of LSBs by improving the stability of the battery’s cycle life and overall energy density.

(Invited) New Synthesis Strategies to Develop High Performance Sulfur-Carbon Composites Cathodes for Lithium/Sulfur Batteries

Lithium/sulfur cells (Li/S) are recognized as a highly promising, inexpensive, and high-specific energy storage system due to the low cost of elemental sulfur and high theoretical specific capacity (1,675 mAh/g) of a sulfur cathode when paired with a lithium anode.1 However, practical applications of Li/S cells have been impeded by challenges related to sulfur cathodes, such as low sulfur conductivity of sulfur, the polysulfides shuttle, and changes in electrode microstructure during cycling.2-4 Sulfur-carbon (S-C) composites have been extensively studied as an effective approach to overcome these issues and improve the electrochemical performance of Li/S cells. Carbon materials, including graphene oxide, carbon nanotubes or nanofibers, and porous carbon, have been used in sulfur cathodes due to their high surface area, excellent electrical conductivity, and sulfur-immobilizing ability from their porous structure or surface functional groups.4 Designing high-performance S-C composites involves carefully considering various factors, such as the type of carbon materials, surface area or pore volume of carbon, sulfur-carbon weight ratio, and synthesis method, to achieve optimal performance. Key design strategies for high-performance S-C composites include: (1) confining nano-sized sulfur in porous carbon, (2) coating nano-sized sulfur onto sulfur-philic functional carbon surface, (3) engineering sulfur structures that form an adequate sulfur-electrolyte interface, and (4) preserving the electronically conductive carbon network in sulfur-carbon composite to minimize the electronic resistance of the sulfur cathode.4 S-C composites consisting of sulfur nanostructures confined in carbon porous structures or coated onto large sulfur-philic surface areas of carbon (e.g., graphene oxide) are promising composite designs as they can promote the kinetics and reversibility of the electrochemical process of the sulfur cathode. In this presentation, important recent findings about how to design and synthesize high performance S-C composite design will be introduced, and their effects on the electrochemical behavior of the sulfur cathode for Li/S cells will be discussed. References Bruce, P.G.; Freunberger, S.A.; Hardwick, L.J.; Tarascon, J.-M., Nat. Mater. 2012, 11, 19–29.Fotouhi, A.; Auger, D.J.; O’Neill, L.; Cleaver, T.; Walus, S., Energies 2017, 10, 1937.Peng, H.-J.; Huang, J.-Q.; Cheng, X.-B.; Zhang, Q., Adv. Energy Mater. 2017, 7, 1700260.Hwa, Y.; Cairn, E. J., ChemElectroChem 2020, 7, 3927-3942.

(Invited) Organic Binders for Rechargeable Lithium Batteries

Owing to the negative impact of the extensive utilization of batteries on the environment, sustainability of the cells needs to be included in the systemic research of batteries. Herein, a dissolvable ionic crosslinked polymer (DICP) is exploited as a binder for lithium–sulfur batteries by crosslinking the polyacrylic acid and polyethyleneimine through carboxy-amino ionic interaction. This interaction is pH-controlled, and therefore, the crosslinked binder network can be readily dissociated under basic conditions, providing a facile strategy enabling valuable components recycled through a convenient washing method. The sulfur cathode prepared using the recycled carbon–sulfur composite can deliver comparable capacity as that of fresh electrode. In addition, evidence from cell performance and characterizations, such as in situ X-ray absorption spectroscopy, in situ UV–visible spectroscopy, X-ray photoelectron spectroscopy, and density functional theory calculation, confirms that DICP is a more effective binder than its commercial counterpart on suppressing polysulfide dissolution in the electrolyte. Exploiting reversible crosslinked polymer binder for recyclable Li–S batteries with ameliorated electrochemical performance, this study illuminates sustainable development for large-scale energy storage systems.

Freeze-Drying-Assisted ZIF-67 Template-Derived Co@NCS Porous Composite as Sulfur Cathode Host for Improved Li-S Battery Performance: Deconvolution of Diffusive and Capacitive Li+ Storage.

A zeolitic imidazole framework (ZIF-67) template-derived cobalt@nitrogen-doped carbon-sulfur composite (ZIF-Co@NCS) was synthesized using a freeze-drying method and explored for lithium-sulfur (Li-S) batteries. Material characterizations confirmed the formation of the ZIF-Co@NCS composite. To fabricate the Li-S battery in a coin-type CR-2032 cell, the as-synthesized ZIF-Co@NCS composite having a sulfur content of ∼65% was used as a cathode material and coupled with a lithium metal anode. This battery demonstrated exceptional cycling stability over 600 charge-discharge cycles with a steady capacity of 550 mAh g-1 at 0.05 C-rate. The good electrochemical performance of the cathode was ascribed to the nanofeatures associated with the freeze-dried porous carbon structure, which offered enough space for the sulfur cathode. The enhanced trapping of polysulfide facilitated by the presence of the Co-N sites in the ZIF-Co@NCS composite led to excellent cycling stability. The derived cathode composite showed a high specific capacity, outstanding rate capability, and excellent cyclic stability rendering it a promising candidate for high-performance Li-S batteries. Detailed Li+ ion charge storage examined by means of Dunn's method revealed a significant capacitive mode of charge storage both at peak currents and nonpeak currents. The post-mortem analysis of the cycled cathode using X-ray diffraction and scanning electron microscopy at different depth-of-discharge (DOD) values revealed the stepwise formation of discharge products.

Development of Stable All-Solid-State Sodium-Sulfur Batteries

Sodium-sulfur (Na-S) batteries have been commercialized for stationary energy storage systems because of their low-cost fabrication and long-cycling stability. However, the Na-S batteries need to operate at high temperatures (> 300 oC) to maintain the molten state of sodium anode and sulfur cathode, which requires extra energy and raises safety issues when the solid electrolyte membrane fails. Therefore, low-temperature all-solid-state Na-S batteries (such as 60 oC) are highly desirable because of the improved safety and a lower operating temperature. To achieve high sulfur-specific capacity and long-cycling stability, the stable interfaces between electrodes and solid-state electrolyte are important for all-solid-state Na-S batteries. Herein, we demonstrate a strategy using Na alloy anodes to replace Na metal anode to solve the issues of unstable interface between Na metal and solid-state electrolytes. Na-Sn and Na-Sb alloys are first compared in terms of their alloying/dealloying process to identify the advantage of Na-Sb alloy as the anode. The Na-Sb alloy anode shows its superior stability against the solid electrolyte and undergoes a stable Na alloying/dealloying process at 0.04 mA cm-2 for over 500 hours. Sulfur-carbon composites with confined sulfur nanostructure were synthesized via the sulfur vapor deposition method and further utilized in full cells. Combining the optimized Na-Sb alloy anode and sulfur composite cathodes, the all-solid-state Na alloy-S battery shows improved rate performance and a high sulfur-specific capacity of 1377 mAh g-1 with good capacity retention of 70 % after 180 cycles at 60 oC (Figure 1a and b). Postmortem analysis of both the anode and cathode shows a reversible discharge/charge process after the first cycle and undergoes significantly rearranged distributions of carbon and solid electrolytes after 180 cycles due to severe volume change induced by repeated sodiation/desodiation process. These research results show a high sulfur specific capacity with long-cycling stability and shed light on further improving next-generation Na-S energy storage systems. Figure 1

Electrochemical Characteristics of Novel Fluorinated Ether Solvent for Lithium-Sulfur Batteries

Introduction In recent years, the development of electric airplanes, large drones, and other equipment has created a need for batteries with high energy density and high power density. Lithium-sulfur batteries have been investigated as such batteries. Electrolyte solutions applying carbonate solvents and ether solvents have been developed as electrolyte for lithium-sulfur batteries1. An electrolyte with ether-based solvents is lighter than that with carbonate-based solvents, so the former is expected to be an electrolyte for lithium sulfur batteries with high energy density. However, lithium-sulfur batteries based on ether solvents have difficulty in reversible charge-discharge reactions due to the dissolution of lithium polysulfide (Li2S x ) that occurs during the charge-discharge process2. In this study, we investigate the electrochemical characteristics of electrolytes to apply a new fluorinated ether (C14) which is resistant to elution of Li2S x . Experimental Sulfur-carbon composite (S-C) was prepared by compositing activated carbon (C-novel, Toyo Tanso) and sulfur in a ratio of 35:65 by weight using a thermal impregnation method. S-C was used as the active material and mixed with acetylene black (AB, DENKA), carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR) to prepare a slurry. The cathode was obtained by coating the obtained slurry on an aluminum foil by a doctor blade method. An electrochemical cell was assembled with the obtained cathode as the working electrode, Li foil as the counter electrode, and LiTFSI dissolved in a mixture of dioxolane (DOL), dimethoxyethane (DME), and C14 at a concentration of 1 mol L-1 as the electrolyte. In order to clarify the electrochemical characteristics of the lithium sulfur battery with these electrolytes, constant current charge-discharge tests were conducted using the electrochemical cell described above. To clarify the coordination state of the solvent to lithium ions and lithium polysulfide in the electrolyte, IR spectra were measured for these electrolytes. Results and Discussion In the IR spectra for the solutions of Li2S x dissolved in DME, the intensity of the peak attributed to the asymmetric stretching of the C-O-C bond, which can be seen at around 1090 cm-1, increases with increasing concentration of Li2S x . The change in peak intensity appears to be due to the coordination of the structure of the diether in DME to the Li+ of Li2S x . On the other hand, in the IR spectra of Li2S x immersed in C14, the intensity of the corresponding peak was found to be similar to that of C14 only, regardless of the concentration of Li2S x . The results indicate that C14 is hard to coordinate to Li2Sx. This may be due to the fact that the functional group with fluorine in the structure of C14 is an electron-withdrawing group, which delocalizes the electrons located around O in the diether and weakens the coordinative force to Li2Sx. As a result of the constant-current charge-discharge test, it was confirmed that the voltage stagnated at about 2.3 V in the charge curves of the cell to which 1M LiTFSI / DOL : DME = 1 : 1 by vol.% was applied. The stagnation of the voltage is considered to be due to the shuttle reaction caused by the coordination of DME to lithium polysulfide and its dissolution into the electrolyte during the charge-discharge process. On the other hand, in the charge-discharge curves of the cell with 1M LiTFSI / C14, the stagnation of voltage that was observed in the cell with 1M LiTFSI / DME could not be confirmed, and it was turned out that the irreversible capacity was small. This should be due to the inability of C14 to coordinate with Li2S x . Acknowledgement A part of this research was conducted under a subcontract (JPNP15005) from the New Energy and Industrial Technology Development Organization (NEDO), a national research and development corporation. Reference 1) L. Gordin et al, ACS Appl. Mater. Interfaces, 6 (2014) 8006−80102) B. Zhang et al, ACS Energy Lett., 6 (2021) 537−546

Stable all-solid-state sodium-sulfur batteries for low-temperature operation enabled by sodium alloy anode and confined sulfur cathode

All-solid-state sodium-sulfur (Na-S) batteries are promising for stationary energy storage devices because of their low operating temperatures (less than 100 °C), improved safety, and low-cost fabrication. Using Na alloy instead of Na metal as an anode in Na-S batteries can prevent dendrite growth and improve interfacial stability between the anode and solid electrolytes to achieve long-cycling stability. A high-sulfur content cathode possessing high sulfur utilization is also important to enable an energy-dense Na-S battery. In this work, we studied Na-Sb and Na-Sn alloy anodes and demonstrated the superiority of Na3Sb alloy undergoing a stable Na alloying/dealloying process at 0.04 mA cm−2 for over 500 h. Combining the optimized Na3Sb alloy anode with sulfur-carbon composites prepared by the vapor deposition approach, the full cell shows a high sulfur specific capacity and improved rate performance. Moreover, the all-solid-state Na alloy-S battery can deliver a high initial discharge specific capacity of 1377 mAh g−1 and maintain good capacity retention of 70 % after 180 cycles at 60 °C. Post-cycle characterizations show that both the anode and cathode perform a reversible discharge/charge process after the 1st cycle, and the cathode undergoes significantly rearranged distributions of carbon and solid-state electrolytes after 180 cycles due to severe volume change induced by repeated sodiation/desodiation process. Data availabilityData will be made available on request.

Carbon Coated Metal-Based Composite Electrode Materials for Lithium Sulfur Batteries: A Review.

Lithium-sulfur battery is one of the most promising secondary battery systems due to their high energy density and low material cost. During the past decade, great progress has been achieved in promoting the performances of Li-S batteries by addressing the challenges at the laboratory-level model systems. With growing attention paid to the application of Li-S batteries, new challenges at practical cell scales emerge as the bottleneck. However, challenges remain for the commercialization of lithium-sulfur batteries. The current review mainly focused on metal-based catalysts decorated-carbon materials for enhanced lithium sulfur battery performance. Firstly, the synthesis methods of various carbon-sulfur composites are discussed, as well as the influence of different material structures on the electrochemical performance. Secondly, a variety of catalysts, including metal atoms, metal oxides, sulfides, phosphides, nitrides, and carbide-decorated carbon nanomaterials, are systematically introduced to determine how lithium can be enhanced by suppressing polysulfides and promoting redox conversion reactions. Also, analyzed the multi-step electrochemical reaction mechanism of the battery during the charging and discharging process, and provide a feasible path for the practical application of high energy density lithium-sulfur batteries.

Surfactant modified CNTs@S as cathode materials for high rate performance lithium sulfur batteries

The cathode materials are an important aspect of lithium sulfur battery research. This paper focuses on the electrochemical changes in the interface between cathode and electrolyte, via the surface modification of [email protected] composites by different types of surfactant. And the cause of this phenomenon is speculated through some comparative experiments. We find that the surfactant adsorbed on the surface of the [email protected] produce two effects in opposite directions on the interface between cathode and electrolyte: On the one hand, interaction between the hydrophilic group of surfactant and the electrolyte reducing the charge transfer impedance and improving the electrochemical reaction rate; On the other hand, the contact between the hydrophobic group of surfactant and [email protected] leads a new impedance creating. If these two opposite effects are properly controlled, the battery impedance can be substantially reduced. Finally, with the [email protected] cathode modified by APG, the charge transfer impedance decreased from 127.2 Ω to about 6.3 Ω, even with the newly generated contact impedance, the total impedance is approximately 1/9 of the original. This change increases the maximum charge and discharge current density of the [email protected] battery from 1 C to 7 C. Even both with a high sulfur loading of 5.3 mg cm−2 and a low electrolyte/sulfur ratio of 4.1 mL g−1, the Li-S batteries with [email protected] cathode modified by APG still deliver a high capacity of 2.38 mAh cm−2 (66% of initial capacity) after 50 cycles. Moreover, this simple modification strategy is suitable in different carbon-sulfur composites to improve the high current density charge and the discharge performance of Li-S batteries. It brings a new mentality to the industrial application of Li-S batteries.

Selective catalytic oxidation of pollutant H2S over Co-decorated hollow N-doped carbon nanofibers for high-performance Li-S batteries

Hydrogen sulfide (H2S) is one of the most harmful pollutants to human health and the environment. Using carbon-based catalysts, H2S can be selectively oxidized to elemental sulfur (S) at room temperature and carbon-sulfur composites are produced, which enlightens a facile solution combining desulfurization with cathode preparation for high-performance lithium-sulfur batteries (LSBs). Herein, a heterogeneous catalyst of cobalt decorated N-doped hollow carbon nanofibers (Co-NHCFs) is designed for realizing the integrated application, in which the electron redistribution arising from long-range interactions of Co/N-doped carbon significantly promotes the oxygen radical generation and H2S dissociation, leading to its robust catalytic activity for H2S oxidation. Benefiting from the hollow framework with capacious storage space for rapid gas diffusion, the in-situ fabrication of high S-loading carbon-based cathodes (S@Co-NHCFs) used for LSBs is achieved during the H2S oxidation processing. Due to the more favorable diffusion of H2S gas than liquid S, this kind of chemical reaction-induced deposition can realize a more uniform distribution of solid S upon carbon than the traditional method by molten infusion, which, coupled with the catalysis of heterogeneous effect on the reversible sulfur-redox reaction, results in superior electrochemical performance of S@Co-NHCFs in LSBs.

Lithium Iron Phosphate Reconstruction Facilitates Kinetics in High-Areal-Capacity Sulfur Composite Cathodes

Lithium-sulfur (Li-S) batteries have been recognized as one of the most promising choices beyond lithium-ion batteries (LIB), because of its low cost and high theoretical specific energy (~2510 Wh/kg or ~10 times of LIB). However, Li-S batteries still face a few challenges, including large volume expansion, poor conductivity, low active material loading, inert end products, and polysulfide crossover called the “shuttle effect”, etc.To address these challenges, we have incorporated lithium iron phosphate (LFP) into our sulfur composite cathode. The addition of LFP enabled a more uniform slurry rheology, which allowed mass loading to double the amount of typical sulfur cathodes. Meanwhile, LFP can effectively adsorb polysulfides, which restricted the shuttle effects common in high-sulfur-loading batteries. Our LFP-hybrid Li-S batteries showed high areal capacity for 300 cycles under both low- and high-current charge-discharge cycles. More importantly, our characterizations demonstrated that LFP in Li-S batteries can reconstruct into Fe2P during cycling. We propose that Fe2P is an effective electrocatalyst for anchoring polysulfides.To unveil the role of Fe2P, we have directly incorporated these materials into the sulfur composite cathode. Using a hydrothermal synthesis, we showed that Fe2P nanoparticles can be directly anchored on the sulfur-carbon composite. This approach caused minimal phase separation and enabled a uniform morphology. We presented the analysis of the cathodes by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA). These results allow us to develop a mechanistic hypothesis and a comparison between Fe2P and LFP in terms of the electrochemical performances.

Sulfur-acetylacetone based solutions for precipitation of quasi-core–shell microparticles or hybrid structures

A methodology to produce quasi-core–shell or hybrid microstructured sulfur particles is introduced in this study. Dissolution of sulfur in acetylacetone (AcAc) suspensions at high temperatures and recrystallization upon cooling enables production of quasi-spherical carbon–sulfur composites or carbon nanotube (CNT)/graphite encapsulated sulfur particles. Particle sizes are in the range of several micrometers in all cases. The particle formation mechanism relies on temperature dependent solubility of sulfur in AcAc. AcAc provides dissolution of sulfur at relatively high quantities (greater than25 g L-1), and it also allows homogenous dispersion of nanoparticles. This medium provides interaction of sulfur crystallites with carbon particles during recrystallization in colloid. Several techniques were employed to elucidate the solubility behavior of sulfur in AcAc and structure of composites including fluorescence spectroscopy, dynamic light scattering (DLS) and atomic force microscopy (AFM). It was found that sulfur presents in the form of homocyclic rings in AcAc near room temperature under ambient pressure as verified through assignments using UV–Visible absorption (UV–Vis) and Raman spectroscopy techniques. This study has wide implications. Because exploitation of high solubility of sulfur in polar and non-volatile solvents may provide new opportunities for composite particle production with tailored properties.

Sulfurized Carbon Composite with Unprecedentedly High Tap Density for Sodium Storage

AbstractA novel sulfurized carbon decorated by terephthalic acid (TPA) and polyacrylonitrile (PAN), with unprecedently high tap density (≈1.02 g cm−3), is investigated. Room‐temperature sodium–sulfur batteries offer high energy density; however, the dissolution of the polysulfide is a major factor hindering their commercialization. This dissolution problem can be tolerated by inhibiting the formation of polysulfide through binding sulfur to the carbon structure of PAN. Low sulfur content and low volumetric energy density in the composite are other drawbacks to be resolved. Heat‐treated TPA induces a high‐density carbonaceous material with high conductivity. This TPA is partly replaced by PAN, and the produced carbon and sulfur are composited with dehydrated polyacrylonitrile (CS–DPAN), which exhibits higher conductivity and surface area than the sulfurized dehydrated polyacrylonitrile (S–DPAN). The CS–DPAN composite electrode exhibits excellent electrochemical performance, and the resulting volumetric capacity is also superior to that of the S–DPAN material electrode. Operando Raman and operando X‐ray diffraction analyses confirm that the increased capacity is realized via the avoidance of parasitic C60Na3 formation formed below 1 V, by adjusting the operation voltage range. This finding demonstrates the feasibility of carbon–sulfur composites as a high‐energy electrode material for rechargeable sodium batteries.

Potato Peel Based Carbon-Sulfur Composite as Cathode Materials for Lithium Sulfur Battery.

Lithium sulfur battery has become one of the promising rechargeable battery systems to replace the conventional lithium ion battery. Commonly, it uses carbon-sulfur composites as cathode materials. Biomass based carbons has an important role in enhancing its electrochemical characteristics due to the high conductivity and porous structures. Here, potato peel wastes have been utilized to prepare porous carbon lithium sulfur battery through hydrothermal carbonization followed by the chemical activation method using KOH. After sulfur loading, as prepared carbon-sulfur composite shows stable coulombic efficiencies of above 98% and a reversible specific capacity of 804 mAh g-1 after 100 cycles at current density of 100 mA g-1. These excellent electrochemical properties can be attributed to the unique structure of PPWC showing mesoporous structure with large specific surface areas. These results show the potential application of potato peel waste based porous carbon as electrode's materials for lithium sulfur battery.

Operando characterization of active surface area and passivation effects on sulfur-carbon composites for lithium-sulfur batteries

Sulfur electrodes for lithium-sulfur batteries necessarily contain a conductive additive, typically carbon, to enable the electrochemical reactions, since sulfur and the discharge product, Li2S, are insulators. Consequently, the full passivation of carbon, by deposition of sulfur and/or Li2S, would necessarily produce the death of the battery. However, here we demonstrate that for high-performance lithium-sulfur batteries operated under lean electrolyte conditions (electrolyte to sulfur ratio of 6 µL mgS−1 in Li-S coin cells), the extent of passivation of carbon is not severe enough to limit performance. This is shown by performing impedance measurements of fully charged lithium-sulfur batteries, from which we demonstrate that we can evaluate the specific surface area of carbon, and we find that the capacity fade with cycling is not due to a decrease in the electrochemically active surface area of carbon. These results show that introducing a higher surface area carbon in the sulfur electrode formulation is not needed to prevent passivation, and that the focus of lithium-sulfur development should be directed towards other issues, such as mitigating undesirable reactions at the lithium electrode and achieving robust sulfur electrode structures enabling fast transport of electrolyte species and, thus, more homogeneous reactions.

Lithium-metal polysulfide batteries with free-standing MoSxCy thin-film cathodes

Free-standing thin film electrodes hold huge promise for solid-state and micro batteries required by a range of portable electronic devices. However, for lithium-sulfur (Li–S) and lithium-metal polysulfide (Li-MSx; M = Mo, V, Ti, etc.) batteries, the promising thin film electrodes are not possible yet because of low melting point of sulfur. Here, for the first time, we have developed amorphous molybdenum sulfide (MoSx) – carbon (Cy) composite thin-films using a magnetron sputtering method with novel co-deposition of molybdenum metal and sulfur-carbon composite. The thin films were used as the free-standing cathode for Li-MSx cells that demonstrates excellent cycling performance and rate capability without any shuttle effect. The Li-MoSx cells exhibit a high areal-capacity of 115 μAh/cm2 at the current density of 20 μA/cm2, an excellent stability of 500 cycles and remarkable rate capability with no traces of shuttle effect. Density functional theory (DFT)-Molecular dynamics (MD) based calculations reveal the insertion of lithium via an optimal mix of conversion and intercalation reactions without breaking the base Mo-Sx structure, eliminating the shuttle effect, and producing stable cycling performance.

Shuttle-effect-free sodium–sulfur batteries derived from a Tröger's base polymer of intrinsic microporosity

Room-temperature sodium–sulfur (RT Na–S) batteries have recently gained attention as next-generation energy storage devices owing to their low cost, the abundance of sodium, and the high theoretical capacity of sulfur. However, the notorious shuttle effect, caused by the dissolution of intermediate polysulfides during cycling, limits the long-term performance of Na–S batteries. In this study, intrinsically microporous Tröger's base based polymer (PIM-EA-TB)-based carbon–sulfur composites are prepared for shuttle-effect-free RT Na–S batteries by utilizing the combination of physical confinement and covalent bonding in a single material. The composites demonstrate excellent electrochemical performance, including a negligible capacity fading over 350 cycles and a high coulombic efficiency of approximately greater than 99%.

Biomass Based Porous Carbons As Cathode's Component for Room Temperature Sodium Sulfur Battery

Porous carbons originated from microalgae powder, were synthesized using a hydrothermal carbonization followed by the chemical-activation process. Porous carbons are the used as cathode's components with sulfur for Sodium Sulfur (NaS) Batteries. the presence of the carbons in the composites can increase the electrical conductivity and assist the sodium ion transfer in the cell since it can allow the electrolyte to permeate easily. The micropores (<2 nm) of porous carbons are the main sulfur host and help to adsorb the small sulfur molecules , so it can improve the electrochemical performance of carbon-sulfur composites as cathodes for NaS batteries at room temperature. The porous carbons can form more actives site that improves the electrical conductivity and prevent the shuttle effect of polysulfide The composite cathodes can give a high initial discharge capacity of 1267 mAh g−1 at 0.1 C and a superior capacity retention of 267 mAh g−1 after 100 cycles at 1 C. This study suggest that microalgae can be used in the application of the room temperature NaS battery.

Sulfur/carbon binding with polar MoS3 as cathode materials for lithium-sulfur batteries

MoS3 is in situ grown on sulfur carbon composite (S/C-MoS3) surface by chemical oxidative reaction of (NH4)2MoS4. Based on the synergistic role of porous carbon and polar MoS3 with sulfur-like characteristic, polysulfides are effectively anchored and shuttle effect is greatly reduced. In particular, 10 wt% MoS3 bridged S/C composite exhibits the best electrochemical performance. After 100 cycles at 0.2C, the discharge specific capacity remains 727.6 mA h g−1, and the capacity retention rate is 59.0%. When cycling 300 times at 1C, the capacity is still maintained at 546.9 mA h g−1, and the coulomb efficiency is around 97.0%. The results show that MoS3 effectively improves the cyclic property of S/C composite for lithium‑sulfur battery.