Sulfur-based Electrodes Research Articles

Surface-Dominated Potassium Storage Enabled by Single-Atomic Sulfur for High-Performance K-Ion Battery Anodes

Due to the large size and heavy mass of the K-ion, the pursuit of reliable anodes with outstanding comprehensive performance for K-ion batteries (KIBs) remains a formidable challenge. Typically, high-capacity potassium storage will lead to the electrodes’ serious volumetric expansion and elevated instability. Herein, it is identified that a single-atomic sulfur composite can act as a high-performance KIB anode with an excellent combination of capacity, cyclability, and rate. A high content (∼32 wt%) single-atomic sulfur can be covalently bonded into the carbon lattice of multi-shelled hollow nanospheres via a simple low-temperature pyrolyzation of the selected precursor. The superb redox reactivity of the single-atomic sulfur together with the porous architectures for the resultant S/C composite can not only enable a fast surface-dominated potassium storage but also ensure its structural resilience, thereby achieving high specific capacity together with outstanding rate and impressive cyclability. This study envisions new perspectives on designing high-performance sulfur-based electrodes.

One-pot Synthesis of High-capacity Sulfur Cathodes via In-situ Polymerization of a Porous Imine-based Polymer.

Lithium-ion batteries, essential for electronics and electric vehicles, predominantly use cathodes made from critical materials like cobalt. Sulfur-based cathodes, offering a high theoretical capacity of 1675mAhg-1 and environmental advantages due to sulfur's abundance and lower toxicity, present a more sustainable alternative. However, state-of-the-art sulfur-based electrodes do not reach the theoretical capacities, mainly because conventional electrode production relies on mixing of components into weakly coordinated slurries. Consequently, sulfur's mobility leads to battery degradation - an effect known as the "sulfur-shuttle". This study introduces a solution by developing a microporous, covalently-bonded, imine-based polymer network grown in-situ around sulfur particles on the current collector. The polymer network (i) enables selective transport of electrolyte and Li-ions through pores of defined size, and (ii) acts as a robust host to retain the active component of the electrode (sulfur species). The resulting cathode has superior rate performance from 0.1C (1360mAhg-1) to 3C (807mAhg-1). Demonstrating a high-performance, sustainable sulfur cathode produced via a simple one-pot process, our research underlines the potential of microporous polymers in addressing sulfur diffusion issues, paving the way for sulfur electrodes as viable alternatives to traditional metal-based cathodes.

Partially Ion-Paired Solvation Structure Design for Lithium-Sulfur Batteries under Extreme Operating Conditions.

Achieving increased energy density under extreme operating conditions remains a major challenge in rechargeable batteries. Herein, we demonstrate an all-fluorinated ester-based electrolyte comprising partially fluorinated carboxylate and carbonate esters. This electrolyte exhibits temperature-resilient physicochemical properties and moderate ion-paired solvation, leading to a half solvent-separated and half contact-ion pair in a sole electrolyte. As a result, facile desolvation and preferential reduction of anions/fluorinated co-solvents for LiF-dominated interphases are achieved without compromising ionic conductivity (>1 mS cm-1 even at -40 °C). These advantageous features were found to apply to both lithium metal and sulfur-based electrodes even under extreme operating conditions, allowing stable cycling of Li || sulfurized polyacrylonitrile (SPAN) full cells with high SPAN loading (>3.5 mAh cm-2 ) and thin Li anode (50 μm) at -40, 23 and 50 °C. This work offers a promising path for designing temperature-resilient electrolytes to support high energy density Li metal batteries operating in extreme conditions.

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

Inorganic Polysulfide Chemistries for Better Energy Storage Systems.

ConspectusSulfur-based cathode materials have become a research hot spot as one of the most promising candidates for next-generation, high-energy lithium batteries. However, the insulating nature of elemental sulfur or organosulfides has become the biggest challenge that leads to dramatic degradation and hinders their practical application. The disadvantage is more obvious for all-solid-state battery systems, which require both high electronic and ionic migration at the same sites to realize a complete electrochemical reaction. In addition to adding conductive components into the cathode composites, another effective way to realize high-reversibility sulfur-based cathodes is by optimizing the inherent nature of sulfur-based materials to make them "conductive". Inorganic polysulfide materials including polysulfide molecules, selenium-sulfur solid solutions, and (lithium) metal polysulfides are promising, as they have different structures that can make them intrinsically conductive or becoming conductive during lithiation. They all contain at least one -S-S- bridged bond, which is the intrinsic structural characteristic and the source of the chemical properties of these polysulfide compounds. For example, by balancing the conductivity and reversible capacity, researchers in the US National Aeronautics and Space Administration (NASA) have shown that 500 Wh/kg solid-state Li-Se/S batteries can power cars and even electric aircraft.We have long been focusing on the inorganic polysulfide component, reported the selenium-sulfur solid solutions, the first sulfur-rich phosphorus polysulfide molecules, and followed the research of metal polysulfide components. The proposed Account summarizes our current knowledge of the fundamental aspects of inorganic polysulfides in energy storage systems based on state-of-the-art publications on this topic. Both fast electron and ion migrations within the electrode materials are vital to achieving high-energy batteries. We begin by illustrating effective approaches to enhance the electronic/ionic conductivity of sulfur-based electrode materials. We then present some basic observations and properties (especially the intrinsic high conductivities) of the inorganic polysulfide electrode materials. The key chemical and structural factors dictating their conductive and electrochemical behaviors will be discussed. Finally, we show the advantages and broad applications of inorganic polysulfides in energy storage areas. The proposed Account will provide an insightful perspective on the current knowledge of inorganic polysulfide materials, as well as their future research directions and development potential, serving as a keynote reference for researchers in the field of energy storage.

Unveiling the catalytic potential of two-dimensional boron nitride in lithium–sulfur batteries

Lithium–sulfur (Li–S) batteries, renowned for their potential high energy density, have attracted attention due to their use of earth-abundant elements. However, a significant challenge lies in developing suitable materials for both lithium-based anodes, which are less prone to lithium dendrite formation, and sulfur-based cathodes. This obstacle has hindered their widespread commercial viability. In this study, we present a novel sulfur host material in the form of a two-dimensional semiconductor boron nitride framework, specifically the 2D orthorhombic diboron dinitride (o-B2N2). The inherent conductivity of o-B2N2 mitigates the insulating nature often observed in sulfur-based electrodes. Notably, the o-B2N2 surface demonstrates a high binding affinity for long-chain Li-polysulfides, leading to a significant reduction in their dissolution into the DME/DOL electrolytes. Furthermore, the preferential deposition of Li2S on the o-B2N2 surface expedites the kinetics of the lithium polysulfide redox reactions. Additionally, our investigations have revealed a catalytic mechanism on the o-B2N2 surface, significantly reducing the free energy barriers for various sulfur reduction reactions. Consequently, the integration of o-B2N2 as a host cathode material for Li–S batteries holds great promise in suppressing the shuttle effect of lithium polysulfides and ultimately enhancing the overall battery performance. This represents a practical advancement for the application of Li–S batteries.

One-Dimensional, Titania Lepidocrocite-Based Nanofilaments and Their Polysulfide Anchoring Capabilities in Lithium-Sulfur Batteries.

The high theoretical energy density of metal-sulfur batteries compared to their lithium-ion counter parts renders sulfur-based electrode chemistries attractive. Additionally, sulfur is relatively abundant and environmentally benign. Yet, issues like the low conductivity of sulfur, polysulfide (PS) formation, and shuttling have hindered the development of sulfur chemistries. Here, we react titanium carbide powders with tetramethylammonium hydroxide ammonium salts at 50 °C for 5 days and convert them into one dimensional, titania-based lepidocrocite (1DL) nanofilaments (NFs) using our facile bottom-up approach. This simple and scalable approach led to better electrode functionalization, facile tunability, and a higher density of active sites. The 1DL NFs self-assembled into a variety of microstructures─from individual 1DL NFs with minimal cross sections ≈5 × 7 Å2 to 2D flakes to mesoscopic particles. A composite was made with a 1:1 weight ratio of sulfur and 1DL NFs, which were hand-ground, mixed with carbon black and binder in a weight ratio of 70:20:10, respectively. We obtained a specific capacity of 750 mA h g-1 at 0.5C for 300 cycles. The 1DL NFs that, in this case assembled into 2D layers, trapped the polysulfides, PSs, by forming thiosulfate species and Lewis acid-base interactions with the Ti, as confirmed by post-mortem X-ray photoelectron spectroscopy. These interactions were also confirmed by PS adsorption via UV-vis spectroscopy and shuttle current measurements that showed lower PS shuttling in the 1DL NFs cells.

Advances in sulfide-based all-solid-state lithium-sulfur battery: Materials, composite electrodes and electrochemo-mechanical effects

Sulfide-based all-solid-state lithium-sulfur batteries (ASSLSBs) have recently attracted great attention. The “shuttle effect” caused by the migration of polysulfides in conventional liquid lithium-sulfur batteries could be eliminated. Therefore, the utilization of active materials and cycling stability, as well as battery safety, can be significantly improved. Impressive progress has been made in the research of materials for sulfide-based ASSLSBs, including sulfide solid-state electrolytes (SSEs), sulfur-based cathode materials, and anode materials. However, challenges such as scalable fabrication of large-scale, high-areal capacity composite electrodes and robust, high-conductivity thin SSE films, as well as the serious electrochemo-mechanical issues in sulfur-based electrodes, still hinder the practical application and development of sulfide-based ASSLSBs. In this review, recent research progress on sulfide-based ASSLSBs materials is summarized and discussed. In addition, the challenges in the practical application of sulfide-based ASSLSBs, such as scalable composite electrodes/SSE membranes fabrication and complicated electrochemo-mechanical coupling effects, are also systematically overviewed.

CeO2 nanoparticles decorated CMK-3 as high-performance sulfur host for Li-S batteries

The development of Li-S batteries is hindered by some inherent drawbacks such as the shuttle effect of lithium polysulfides and the volume expansion of sulfur. Herein, 3–6 nm CeO2 nanoparticles decorated CMK-3 (CMK-3 @CeO2) is prepared and used as the sulfur host for Li-S batteries. As a conductive carbon support, CMK-3 can improve the electrical conductivity of sulfur-based electrode, and its mesopores provide the space required for the volume expansion of sulfur. Meanwhile, the decorative CeO2 nanoparticles can not only change the non-polar carbon surface into the polar CeO2 surface for capturing lithium polysulfides, but also accelerate the redox reaction of lithium polysulfides, which effectively inhibits the shuttle effect of lithium polysulfides. Therefore, compared to pure CMK-3 supported sulfur (CMK-3 @S), CMK-3 @CeO2 supported sulfur (CMK-3 @CeO2 @S) exhibits better electrochemical performance, such as a discharge capacity of 686 mA h g−1 after 800 cycles at 1 C. Besides, the size effect of CeO2 nanoparticles on the electrochemical performance of CMK-3 @CeO2 @S is also studied. This work provides a simple method for improving the electrochemical performance of CMK-3 as the sulfur host, and this strategy can be extended to the other metal oxides decorated sulfur host materials.

Understanding the lithium–sulfur battery redox reactions via operando confocal Raman microscopy

The complex interplay and only partial understanding of the multi-step phase transitions and reaction kinetics of redox processes in lithium–sulfur batteries are the main stumbling blocks that hinder the advancement and broad deployment of this electrochemical energy storage system. To better understand these aspects, here we report operando confocal Raman microscopy measurements to investigate the reaction kinetics of Li–S redox processes and provide mechanistic insights into polysulfide generation/evolution and sulfur deposition. Operando visualization and quantification of the reactants and intermediates enabled the characterization of potential-dependent rates during Li–S redox and the linking of the electronic conductivity of the sulfur-based electrode and concentrations of polysulfides to the cell performance. We also report the visualization of the interfacial evolution and diffusion processes of different polysulfides that demonstrate stepwise discharge and parallel recharge mechanisms during cell operation. These results provide fundamental insights into the mechanisms and kinetics of Li–S redox reactions.

Negative sulfur-based electrodes and their application in battery cells: Dual-ion batteries as an example

In this work, a cell concept comprising of an anion intercalating graphite-based positive electrode (cathode) and an elemental sulfur-based negative electrode (anode) is presented as a transition metal- and in a specific concept even Li-free cell setup using a Li-ion containing electrolyte or a Mg-ion containing electrolyte. The cell achieves discharge capacities of up to 37 mAh g−1 and average discharge cell voltages of up to 1.9 V. With this setup, more than 100 cycles with a high capacity retention (> 90% of the highest achieved value) and Coulombic efficiencies up to 95% could be achieved, which opens a broad new field for energy storage approaches.

Operando X-ray absorption tomography for the characterization of lithium metal electrode morphology and heterogeneity in a liquid Li/S cell

Lithium/sulfur batteries have been under intense study for the last two decades, due to the high specific capacity promised by elemental sulfur as an active material. Sulfur is also cheap, abundant and non-toxic compared to conventional transition metal oxides. The Li/S electrochemical cell is traditionally composed of a sulfur-based electrode, an organic liquid electrolyte and a lithium metal electrode. Lithium metal technologies have received a renewed interest, due to the light weight and low operating voltage of the lithium electrode, which makes it the ultimate choice to be combined with high-energy positive electrode materials. In this paper, operando X-ray absorption and phase contrast tomography were employed to characterize the lithium metal electrode morphology and heterogeneity in a liquid Li/S cell. It was observed that oxidation of the lithium foil occurs in a heterogeneous fashion with pit formation from the beginning of discharge, with the pits growing in diameter, depth and quantity during the discharge. Using Faraday's law, the local current density distribution was calculated to confirm the strongly heterogeneous behavior of the lithium metal electrode. We demonstrate that decreasing the current density leads to lithium stripping/plating occurring more homogenously, with the formation of a smaller number of pits. • X-ray absorption tomography is a powerful tool to characterize the lithium. • Presence of large number of pits during lithium oxidation at high current density. • Determination of the local current density distribution. • Lithium heterogeneity starts at the beginning of the cell life.

A polymer sulfur-based electrode for high energy Li batteries. Influence of the materials of current collector and electrode design on the performance of lithium-sulfur batteries

Various compositions and types of materials based on the sulfur are used for the cathode of Li–S batteries with the aim to improve the performance of this system. In the present study, we investigated Li batteries with cathode based on polymer sulfur. Our development and evaluation confirm that the performance of Li–S batteries is also heavily dependent on the electrode technology, some extraneous materials like current collector, and the design of electrodes. The modification of the aluminum current collector of the sulfur electrode dramatically decreases the interface resistance of interface between sulfur cathode and current collector. Total impedance of Li-S batteries decreases, and the operating power increases. The modification of the design of electrodes results in increasing the energy of Li-S battery and stabilizing the battery parameters during cycling. In our article, these effects are confirmed by the results of Li-S battery testing with the polymer sulfur-based cathode: impedance spectroscopy, cyclic voltammetry, and galvanostatic cycling.

Melanin’s Semiconductor Nature and His Polymer Structure Successfully Modifies Sulfur Cathode and Increases Efficiency on Li-S Batteries

Dynamics of change in impedance spectra and electrochemical parameters of the Li-S rechargeable batteries with non-aqueous liquid electrolyte 0.7 M LiIm, 0.25 M LiNO3, DME: DOL (2:1) during storage after assembly and cycling have been shown. For modification of the Sulfur cathode, we used the different types of melanin. Our results confirm that melanin can be used as a promising component of sulfur-based electrodes

Impact of the Binder Nature on the Morphological Change of Sulfur Electrodes upon Cycling Investigated By in Situ Characterization Methods

Even though the lithium-sulfur (Li/S) battery system is one of the most promising candidates to become the successor of the current Li-ion battery, its insufficient cycle life needs to be resolved before envisioning their commercial use. Several phenomena are reported to be involved in the capacity fading of the Li/S cells upon cycling, among which important structural changes in the sulfur electrode. The binder material plays a crucial role in maintaining the integrity of the electrode through cycling, and the use of innovative in situ characterization techniques enables to get a better understanding of its complex mechanisms. In the present study, operando acoustic emission (AE) and dilatometry techniques, and in situ synchrotron X-ray tomography are used to study the degradation mechanism of sulfur-based electrodes depending on their binder formulation [1-3]. In particular, the impact of using a polyelectrolyte binder (poly(diallyldimethylammonium) bis(trifluromethane sulfonyl)imide), previously known for its polysulfide-retaining and ionic conductive abilities [4], on the morphological degradation of the sulfur electrode is evaluated and compared to more conventional binders (poly(vinylidene difluoride) (PVdF) and carboxymethyl cellulose (CMC)) in the present studyTo date, AE technique has been used to characterize the degradation mechanisms (crack growth, friction, delamination, matrix cracking, corrosion, etc) of various materials subjected to a stress by mechanical, pressure or thermal means, and has been used in our previous work to monitor the mechanical degradation (e.g. cracking, collapsing) of electrodes upon cycling. The operando electrochemical dilatometry technique allows to measure thickness variation of an electrode material undergoing electrochemical reactions and has been used to study various battery electrode materials such as graphite or Si anodes. Finally, X-Ray computed tomography (XRCT) is certainly one of the most powerful analytical tools enabling non-destructive 3D imaging of objects with complex and porous morphologies such as S-based electrodes. Using appropriate image processing, segmentation and analysis procedures, quantitative parameters can be extracted such as the volume fraction, the size distribution, the connectivity and the geometrical tortuosity of the constitutive phases of the sulfur electrodes. A spatial resolution of a few tens of nm can be reached with a synchrotron X-ray source. Operando dilatometry is used for one the very first times on sulfur-based electrodes and shows that during the initial sulfur dissolution process, the polyelectrolyte-based electrode displays a lower irreversible thickness contraction of ~16% compared to ~22% and ~31% for CMC and PVdF, respectively. This is confirmed by the XRT measurements showing a reduced thickness variation for the polyelectrolyte electrode compared to the CMC electrode. The same trend is found in the AE results, where a lower acoustic activity attributed to the rupture of the binder/carbon/sulfur network is detected during the 1st discharge plateau for the polyelectrolyte electrode. All these results confirm the major role of the binder for the Li/S system as well as the highly promising performance of the present polyelectrolyte binder. Thanks to its multifunctionality, it impacts both the diffusion of the active material outside the electrode and the electrode integrity and therefore the conduction paths and accessible active surface for electrochemical processes.[1] Q. Lemarié, H. Idrissi,E. Maire, P.X. Thivel, F. Alloin, L. Roué. Impact of the binder nature on the morphological change of sulfur electrodes upon cycling investigated by in-situ characterization methods, J. Power Sources 477 (2020) 228374.[2] Q. Lemarié, E. Maire, H. Idrissi, P.X. Thivel, F. Alloin, L. Roué,Sulfur-based electrode using a polyelectrolyte binder studied via coupled in situ synchrotron X-ray diffraction and tomography, ACS-Applied Energy Materials 3 (2020) 2422-2431.[3] Q. Lemarié, F. Alloin, P.X. Thivel, H. Idrissi, L. Roué, Study of sulfur-based electrodes by operando acoustic emission, Electrochim. Acta 299 (2019) 415-422[4] L. Li, T.A. Pascal, J.G. Connell, F.Y. Fan, S.M. Meckler, L. Ma, Y.-M. Chiang, D. Prendergast, B.A. Helms, Molecular understanding of polyelectrolyte binders that actively regulate ion transport in sulfur cathodes, Nat. Commun. 8 (2017) 1–10. Figure 1

Quantum Chemical Calculation of Lithium Polysulfide in EMI-Tfsi Solution: SMD(Universal Solvation Model Based on Solute Electron Density and a Continuum Model of the Solvent) Model

One of the problem of the sulfur-based electrode for the all-solid-Lithium-Sulfur battery cells is the chemical (or electrochemical) decomposition of lithium polysulfide Li2S n . Kinoshita et al have shown that the EMI-TFSI (1-Ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide) ionic liquid contained all-solid-Lithium-Sulfur battery has a good battery performance. In this study we have calculated the quantum chemical calculation of lithium polysulfide Li2S n . in continuum which has the dielectric constant and optical constant is the same as EMI-TFSI ionic liquid. The solvation effect is included by the SMD (Universal Solvation Model Based on Solute Electron Density and a Continuum Model of the Solvent) model. The Austin-Frisch-Petersson functional with dispersion is used in the calculation. From the total energy difference of the enthalpy of the reaction 2Li+ + Sn → (LiSn)2+, 2Li+ + Sn 2- → LiSn, and decomposition reactions. The enthalpy of the reactions have been compared with the experimental results given by Uchimoto and Yamamoto.Reference [1] S. Kinoshita, K. Okuda. N. Machida and T. Shigematsu, J. Power Sources, 269, (2014) 727-734.[2] Y. Uchimoto, K. Yamamoto, private communication

Sulfur-Based Electrode Using a Polyelectrolyte Binder Studied via Coupled in Situ Synchrotron X-ray Diffraction and Tomography

Polyelectrolytes are promising binders for sulfur cathodes of Li/S batteries, with an ability to control the diffusion of polysulfides into the electrolyte, but their impact on the microstructural ...

Sway of MnO2 with poly(acrylonitrile) in the sulfur-based electrode for lithium–sulfur batteries

Lithium–sulfur batteries have achieved a vast development in electric vehicles, laptops and portable devices. Sulfur has theoretical specific capacity of 1675 mAh g−1 and high theoretical energy density of 2600 Wh kg−1. The sulfur-based cathode material has been prepared by solid-state reaction method. The composites were characterized by XRD, SEM, RAMAN and electrochemical measurements. The as-prepared cathode material exhibits an initial capacity of 1285 mAh g−1 at a scan rate of 0.1 C. The metal oxide MnO2 suppresses the polysulfide shuttle and maintains the capacity of the electrode. The porous nature of polymer matrix could confine the sulfur in the pores to prevent the active material loss.

Liquid-phase exfoliated-graphene-supporting nanostructural sulfur as high-performance lithium–sulfur batteries cathode

Abstract Lithium-sulfur (Li–S) batteries with high energy density are promising candidates to satisfy emerging energystorage demands. Nevertheless, the poor conductivity of sulfur and fast capacity decay of the sulfur-based electrodes restrict its practical applications. Here, we report a facile and simple titration method to synthesize nano-sulfur@liquid-phase exfoliated graphene (Nano-S@LEGr) composites by in situ growth of nanostructural sulfur on the LEGr surface. The as-prepared Nano-S@LEGr with tunable sulfur morphologies exhibited excellent electrochemical performance as the cathode material for Li–S batteries. In particular, the spherical Nano-S@LEGr composites with 68 wt% sulfur displayed a reversible capacity of 552.8 mAh g −1 after 100 cycles at a current density of 0.5C. Even at a high current density of 1C, a discharge capacity of 532.8 mAh g−1 could be delivered. Compared to rod-like Nano-S@LEGr and the graphene oxide derived cathode, the as-prepared spherical Nano-S@LEGr showed higher specific capacity, superior cycling stability and rate capability.

Modulating molecular orbital energy level of lithium polysulfide for high-rate and long-life lithium-sulfur batteries

Despite high energy density, lithium-sulfur (Li-S) battery suffers from severe capacity fading due to the dissolution and the slow reaction kinetics of lithium polysulfides (LiPSs). Novel strategies to limit LiPSs are greatly desired by high-performance lithium-sulfur batteries towards practical applications. Here, modulating molecular orbital energy level of LiPSs by adding 2,5-di-tert-butyl-1,4-benzoquinone (DBBQ) into organic electrolyte is reported to improve the electrochemical performance of Li-S batteries. The soluble catalyst DBBQ is able to form complexes with LiPSs via medium-strength Li-O bonding. Compared with LiPSs, the complexes have higher HOMO energies and lower LUMO energies, and therefore shows the stronger redox activity, indicating that DBBQ can facilitate the electrochemical reactions of LiPSs. This strategy leads to a long cycling stability and excellent rate performance of sulfur-based electrodes. The Li-S battery with DBBQ not only delivers the capacity of 745 mA h g−1 at 10C rate, but also retains the capacity of 850 mA h g −1 after 500 cycle at 1C rate. Moreover, the DBBQ additive enables the cathode to achieve steadily cyclable at high sulfur content (78 wt%) and sulfur loading (7 mg cm−2).