Polysulfides Capture-Copper Additive for Long Cycle Life Lithium Sulfur Batteries

Chemical Interactions between Dissolved Polysulfides and Potential Catalytic Host Materials for Li-S Batteries

Given that both elemental sulfur (S8) and lithium sulfide (Li2S) exhibit insulating properties, the involvement of conductive host materials becomes crucial for facilitating charge transfer in sulfur cathodes within lithium-sulfur (Li-S) batteries. Furthermore, there has been a recent surge in the exploration of host materials for sulfur cathodes to address the "polysulfide shuttle" effect. This effect arises from the formation of polysulfide species during the charge-discharge cycles of the Li-S batteries and can be mitigated through physical or chemical interactions with specific materials. To qualitatively and accurately assess the interactions between polysulfides and the potential host materials, this study utilized a well-established high-performance liquid chromatography method for polysulfide analysis. The objective was to monitor the changes in polysulfide solutions after contact with 44 different carbon and inorganic materials. Based on both qualitative and quantitative chromatographic results, it was determined that 20 out of the 44 materials exhibit significant interactions with polysulfides. The primary form of interaction observed is the irreversible disproportionation reaction with elemental sulfur being one of the resulting products.

Improved Performance in Li-S Batteries Due to In Situ CuS Formation from Cu Nanowires

Lithium-sulfur batteries offer theoretical capacities of 800-1600 mAh g-1 of active material and are therefore one of the most promising new battery chemistries currently under intensive study. However, the low electronic conductivity of the sulfur and the discharge products imposes energy penalties during the discharge and charge steps. In addition, the reduction of sulfur during discharge forms soluble polysulfides, which will diffuse to, and react with, the lithium metal anode. To address these two challenges, copper nanowires were introduced into the composite cathode to improve the electronic conductivity of the cathode and to provide electrostatic anchoring points for the formed polysulfide anions. The addition of the conductive copper nanowires resulted in the in situ formation of copper sulfide, which was shown to decrease the resistivity of the SEI layer on the anode, as manifested by diminished lithium plating and stripping overpotentials. Higher copper loadings exacerbated the dissolution of the copper sulfide during deep discharge and increased the concentration of displaced capping ligands in the electrolyte. Both phenomena generate species that react at the lithium anode, resulting in a more resistive SEI layer.

Recent Advances and Strategies toward Polysulfides Shuttle Inhibition for High-Performance Li-S Batteries

Lithium-sulfur (Li-S) batteries are regarded as the most promising next-generation energy storage systems due to their high energy density and cost-effectiveness. However, their practical applications are seriously hindered by several inevitable drawbacks, especially the shuttle effects of soluble lithium polysulfides (LiPSs) which lead to rapid capacity decay and short cycling lifespan. This review specifically concentrates on the shuttle path of LiPSs and their interaction with the corresponding cell components along the moving way, systematically retrospect the recent advances and strategies toward polysulfides diffusion suppression. Overall, the strategies for the shuttle effect inhibition can be classified into four parts, including capturing the LiPSs in the sulfur cathode, reducing the dissolution in electrolytes, blocking the shuttle channels by functional separators, and preventing the chemical reaction between LiPSs and Li metal anode. Herein, the fundamental aspect of Li-S batteries is introduced first to give an in-deep understanding of the generation and shuttle effect of LiPSs. Then, the corresponding strategies toward LiPSs shuttle inhibition along the diffusion path are discussed step by step. Finally, general conclusions and perspectives for future research on shuttle issues and practical application of Li-S batteries are proposed.

Rationally integrated nickel sulfides for lithium storage: S/N co-doped carbon encapsulated NiS/Cu2S with greatly enhanced kinetic property and structural stability

Nickel sulfides are promising anode materials for lithium-ion batteries (LIBs) due to their high theoretical capacities but suffer from the sluggish kinetic process and poor structural stability. Herein, we develop...

Etched ion-track membranes as tailored separators in Li-S batteries

Lithium-sulfur (Li-S) batteries are considered a promising next generation alternative to lithium-ion batteries for energy storage systems due to its high energy density. However, several challenges, such as the polysulfide redox shuttle causing self-discharge of the battery, remain unresolved. In this paper, we explore the use of polymer etched ion-track membranes as separators in Li-S batteries to mitigate the redox shuttle effect. Compared to commercial separators, their unique advantages lie in their very narrow pore size distribution, and the possibility to tailor and optimize the density, geometry, and diameter of the nanopores in an independent manner. Various polyethylene terephthalate membranes with diameters between 22 and 198 nm and different porosities were successfully integrated into Li-S coin cells. The reported coulombic efficiency of up to 97% with minor reduction in capacity opens a pathway to potentially address the polysulfide redox shuttle in Li-S batteries using tailored membranes.

Core–shell structured S@CuO/δ-MnO2 composites as cathodes for lithium–sulfur batteries

Novel core–shell structured S@CuO/δ-MnO2 composites have been developed as cathodes for lithium sulfur batteries. They exhibited an excellent electrochemical performance with an initial specific capacity of 848.1 mAh g−1 at 0.1 C.

A Four-Electron Sulfur Electrode Hosting a Cu2+ /Cu+ Redox Charge Carrier

The elemental sulfur electrode with Cu²⁺ as the charge carrier gives a four-electron sulfur electrode reaction through the sequential conversion of S↔CuS↔Cu₂ S. The Cu-S redox-ion electrode delivers a high specific capacity of 3044 mAh g^-1 based on the sulfur mass or 609 mAh g^-1 based on the mass of Cu₂ S, the completely discharged product, and displays an unprecedently high potential of sulfur/metal sulfide reduction at 0.5 V vs. SHE. The Cu-S electrode also exhibits an extremely low extent of polarization of 0.05 V and an outstanding cycle number of 1200 cycles retaining 72 % of the initial capacity at 12.5 A g^-1 . The remarkable utility of this Cu-S cathode is further demonstrated in a hybrid cell that employs an Zn metal anode and an anion-exchange membrane as the separator, which yields an average cell discharge voltage of 1.15 V, the half-cell specific energy of 547 Wh kg^-1 based on the mass of the Cu₂ S/carbon composite cathode, and stable cycling over 110 cycles.

Viromimetic STING Agonist-Loaded Hollow Polymeric Nanoparticles for Safe and Effective Vaccination against Middle East Respiratory Syndrome Coronavirus

The continued threat of emerging, highly lethal infectious pathogens such as Middle East respiratory syndrome coronavirus (MERS-CoV) calls for the development of novel vaccine technology that offers safe and effective prophylactic measures. Here, a novel nanoparticle vaccine is developed to deliver subunit viral antigens and STING agonists in a virus-like fashion. STING agonists are first encapsulated into capsid-like hollow polymeric nanoparticles, which show multiple favorable attributes, including a pH-responsive release profile, prominent local immune activation, and reduced systemic reactogenicity. Upon subsequent antigen conjugation, the nanoparticles carry morphological semblance to native virions and facilitate codelivery of antigens and STING agonists to draining lymph nodes and immune cells for immune potentiation. Nanoparticle vaccine effectiveness is supported by the elicitation of potent neutralization antibody and antigen-specific T cell responses in mice immunized with a MERS-CoV nanoparticle vaccine candidate. Using a MERS-CoV-permissive transgenic mouse model, it is shown that mice immunized with this nanoparticle-based MERS-CoV vaccine are protected against a lethal challenge of MERS-CoV without triggering undesirable eosinophilic immunopathology. Together, the biocompatible hollow nanoparticle described herein provides an excellent strategy for delivering both subunit vaccine candidates and novel adjuvants, enabling accelerated development of effective and safe vaccines against emerging viral pathogens.

Molecular-Level CuS@S Hybrid Nanosheets Constructed by Mineral Chemistry for Energy Storage Systems

The transition-metal sulfide, CuS, is deemed a promising material for energy storage, mainly derived from its good chemisorption and conductivity, although serious capacity fading limits its advancement within reversible lithium storage. Learning from the gold extraction method utilizing the lime-sulfur-synthetic-solution, a CuS@S hybrid utilizing CaS _x as both sulfur resource and reductant-oxidant is prepared, which is an efficient approach to apply the metallurgy for the preparation of electrode materials. Regulating the amount of CuCl₂, the CuS@S is induced to reach a molecular-level hybrid. When utilized as an anode within a lithium-ion battery, it presents the specific capacity of 514.4 mA h g^-1 at 0.1 A g^-1 over 200 cycles. Supported by the analyses of pseudo-capacitive behaviors, it is confirmed that the CuS matrix with the suitable content of auxiliary sulfur could improve the durability of the CuS-based anode. Expanding the wider application within lithium-sulfur batteries, the synchronous growth of CuS@S exhibits stronger chemisorption with polysulfides than the mechanical mixture of CuS and S. A suite of in situ electrochemical impedance spectroscopy studies further investigates the stable resistances of the CuS@S within the charge/discharge process, corresponding to the reversible structure evolution. This systematic work may provide a practical fabricating route of metal sulfides for scalable energy storage applications.

Three-Dimensionally Hierarchical Ni/Ni3S2/S Cathode for Lithium-Sulfur Battery

Lithium-sulfur (Li-S) batteries have attracted interest as a promising energy-storage technology due to their overwhelming advantages such as high energy density and low cost. However, their commercial success is impeded by deterioration of sulfur utilization, significant capacity fade, and poor cycle life, which are principally originated from the severe shuttle effect in relation to the dissolution and migration of lithium polysulfides. Herein, we proposed an effective and facile strategy to anchor the polysulfides and improve sulfur loading by constructing a three-dimensionally hierarchical Ni/Ni₃S₂/S cathode. This self-supported hybrid architecture is sequentially fabricated by the partial sulfurization of Ni foam by a mild hydrothermal process, followed by physical loading of elemental sulfur. The incorporation of Ni₃S₂, with high electronic conductivity and strong polysulfide adsorption capability, can not only empower the cathode to alleviate the shuttle effect, but also afford a favorable electrochemical environment with lower interfacial resistance, which could facilitate the redox kinetics of the anchored polysulfides. Consequently, the obtained Ni/Ni₃S₂/S cathode with a sulfur loading of ∼4.0 mg/cm² demonstrated excellent electrochemical characteristics. For example, at high current density of 4 mA/cm², this thick cathode demonstrated a discharge capacity of 441 mAh/g at the 150th cycle.

CuV2S4: A High Rate Capacity and Stable Anode Material for Sodium Ion Batteries

The ternary compound CuV₂S₄ exhibits an excellent performance as anode material for sodium ion batteries with a high reversible capacity of 580 mAh g^-1 at 0.7 A g^-1 after 300 cycles. A Coulombic efficiency of ≈99% is achieved after the third cycle. Increase of the C-rate leads to a drop of the capacity, but a full recovery is observed after switching back to the initial C-rate. In the early stages of Na uptake first Cu⁺ is reduced and expelled from the electrode as nanocrystalline metallic Cu. An increase of the Na content leads to a full conversion of the material with nanocrystalline Cu particles and elemental V embedded in a Na₂S matrix. The formation of Na₂S is evidenced by ²³Na MAS NMR spectra and X-ray powder diffraction. During the charge process the nanocrystalline Cu particles are retained, but no crystalline materials are formed. At later stages of cycling the reaction mechanism changes which is accompanied by the formation of copper(I) sulfide. The presence of nanocrystalline metallic Cu and/or Cu₂S improves the electrical conductivity, leading to superior cycling and rate capability.

Microporous Carbon Polyhedrons Encapsulated Polyacrylonitrile Nanofibers as Sulfur Immobilizer for Lithium-Sulfur Battery

Microporous carbon polyhedrons (MCPs) are encapsulated into polyacrylonitrile (PAN) nanofibers by electrospinning the mixture of MCPs and PAN. Subsequently, the as-prepared MCPs-PAN nanofibers are employed as sulfur immobilizer for lithium-sulfur battery. Here, the S/MCPs-PAN multicomposites integrate the advantage of sulfur/microporous carbon and sulfurized PAN. Specifically, with large pore volume, MCPs inside PAN nanofibers provide a sufficient sulfur loading. While PAN-based nanofibers offer a conductive path and matrix. Therefore, the electrochemical performance is significantly improved for the S/MCPs-PAN multicomposite with a suitable sulfur content in carbonate-based electrolyte. At the current density of 160 mA g^-1_sulfur, the S/MPCPs-PAN composite delivers a large discharge capacity of 789.7 mAh g^-1_composite, high Coulombic efficiency of about 100% except in the first cycle, and good capacity retention after 200 cycles. In particular, even at 4 C rate, the S/MCPs-PAN composite can still release the discharge capacity of 370 mAh g^-1_composite. On the contrary, the formation of the thick SEI layer on the surface of nanofibers with a high sulfur content are observed, which is responsible for the quick capacity deterioration of the sulfur-based composite in carbonate-based electrolyte. This design of the S/MCPs-PAN multicomposite is helpful for the fabrication of stable Li-S battery.