Sulfide Cathode Research Articles

Lithium‐Rich Li2TiS3 Cathode Enables High‐Energy Sulfide All‐Solid‐State Lithium Batteries

AbstractOutstanding interfacial issues exist between oxide cathodes and sulfide electrolytes in all‐solid‐state lithium batteries (ASSLBs), while high‐capacity Li‐rich sulfide cathodes are gaining attention for application. Herein, a sulfide cathode active material Li2TiS3 (LTS) that is chemically compatible with sulfide solid electrolytes, is used in high‐performance Li6PS5Cl‐based ASSLBs at room temperature. The batteries demonstrate a maximum discharge capacity of 423.2 mAh g−1 (910 Wh kg−1 based on Li2TiS3) with 95% capacity retention after 100 cycles at 0.1 C (0.33 mA cm−2). Traces of elemental sulfur on the surface of LTS are mainly responsible for the excessive Li‐intercalation and the capacity exceedance. The Li6PS5Cl is also found to offer a nonnegligible capacity (at least 27% of excess capacity) by comparing the Li6PS5Cl‐based and Li3YCl6‐based cells using Li2TiS3 as cathode active material. During long cycling, the amorphization and degradation of Li2TiS3 and Li6PS5Cl cause capacity decay. The electrochemical kinetics of Li6PS5Cl‐based cells are evaluated as a reference to further exploit the potential of Li2TiS3 material for practical applications in ASSLBs. Overall, this superior Li‐rich sulfide material is an attractive alternative to oxide cathodes for the development of high‐performance ASSLBs.

Ionic liquid electrolyte additive regulates the multi-species-insertion titanium sulfide cathode for magnesium batteries

Benefiting from the appealing Mg metal anodes, magnesium batteries (MBs) present attractive potential as sustainable batteries of tomorrow. However, the Mg metal anode-compatible electrolytes generally contain large-size and strongly bonded Mg-clusters ( i.e., Mg x Cl y 2x-y ), resulting in the inefficient cathode chemistries associated with the sluggish Mg-species insertion. Here, using the iconic TiS 2 cathode, we demonstrate the pronounced effect of ionic liquid on regulating Mg x Cl y 2x-y clusters in the MB electrolyte and promoting the high-kinetics multi-Mg-species insertion into TiS 2 . Specifically, the addition of 1-butyl-1-methylpiperidinium bis(trifluoromethylsulfonyl)imide (PP14TFSI) ionic liquid into the conventional Mg bis(hexamethyldisilazide)/4MgCl 2 electrolyte induces a nontrivial two-plateau charge/discharge profile of the TiS 2 electrode, in which Mg 2+ insertion is mainly disclosed at the high-potential plateau and MgCl + insertion dominates the low-potential plateau. Molecular dynamic simulations indicate that the PP14TFSI additive can dissociate large Mg x Cl y 2x-y clusters to produce MgCl + , which can be effectively stabilized by PP14 + and TFSI – . Meanwhile, PP14TFSI catalyzes the Mg-Cl dissociation, thus creating the desirable Mg 2+ species. These electrolyte-regulation effects consequently enable the TiS 2 cathode with a decent specific capacity (81 mAh g –1 at 10 mA g –1 ), high rate capability (63 mAh g –1 at 200 mA g –1 ), and long-term durability (86% capacity retention after 500 cycles).

A Stable Rechargeable Aqueous Zn-Air Battery Enabled by Heterogeneous MoS2 Cathode Catalysts.

Aqueous rechargeable zinc (Zn)-air batteries have recently attracted extensive research interest due to their low cost, environmental benignity, safety, and high energy density. However, the sluggish kinetics of oxygen (O2) evolution reaction (OER) and the oxygen reduction reaction (ORR) of cathode catalysts in the batteries result in the high over-potential that impedes the practical application of Zn-air batteries. Here, we report a stable rechargeable aqueous Zn-air battery by use of a heterogeneous two-dimensional molybdenum sulfide (2D MoS2) cathode catalyst that consists of a heterogeneous interface and defects-embedded active edge sites. Compared to commercial Pt/C-RuO2, the low cost MoS2 cathode catalyst shows decent oxygen evolution and acceptable oxygen reduction catalytic activity. The assembled aqueous Zn-air battery using hybrid MoS2 catalysts demonstrates a specific capacity of 330 mAh g-1 and a durability of 500 cycles (~180 h) at 0.5 mA cm-2. In particular, the hybrid MoS2 catalysts outperform commercial Pt/C in the practically meaningful high-current region (>5 mA cm-2). This work paves the way for research on improving the performance of aqueous Zn-air batteries by constructing their own heterogeneous surfaces or interfaces instead of constructing bifunctional catalysts by compounding other materials.

Enhancing the reversibility of Li deposition/dissolution in sulfur batteries using high-concentration electrolytes to develop anode-less batteries with lithium sulfide cathode

The reversibility of Li deposition/dissolution onto/from a copper substrate is analyzed herein for fabricating anodeless Li2S-cathode-based batteries using sulfolane (SL)-based sparingly solvating electrolytes to prevent lithium-polysulfide dissolution. The composition of electrolytes—binary lithium bis(trifluoromethanesulfonyl)amide/lithium bis(fluorosulfonyl)amide (LiTFSA/LiFSA; 9:1 molar ratio) in SL solvent—considerably affects the reversibility; a high-concentration electrolyte (HCE) and a localized high-concentration electrolyte (LHCE: HCE diluted by non-coordinating hydrofluoroether) exhibit superior reversibility than that of 1 M solution. Solid electrolyte interphases (SEI) with high F compositions and relatively low O concentrations are formed on the HCE- and LHCE-deposited Li surfaces. SEI formation via FSA decomposition is promoted in the HCE and LHCE, whereas SL decomposition is prohibited by the fluorine-rich SEI. The Li-deposit morphology is significantly affected by the nucleation overpotential at the initial deposition, which is influenced by the nature of the formed SEIs. Small-surface-area deposits with a low nucleation overpotential suppress the electrolyte decomposition and the formation of dead Li, resulting in high reversibility. Optimal reversibility is achieved by performing low-current-density initial deposition at 60 °C with the LHCE. The charge/discharge characteristics of anode-less Cu||Li2S batteries are determined under the reversibility-optimized conditions; 75 charge/discharge cycles and a 50-cycle capacity retention rate of 47.5% are achieved.

Encapsulate lithium sulfide cathodes with carbon-doped MoS2 for fast kinetics in lithium-sulfur batteries, a theoretical study

Li2S-based lithium-sulfur batteries represent a novel potential energy-storage device with high energy-density and superior safety. Metal sulfide surface coating has been regarded as an effective way to improve electrical and dynamic properties of Li2S cathode. We predict that encapsulate Li2S with MoS2 is a potential cathode material that outperforms Li2S@graphene in some aspects. The poor conductivity of MoS2 can be alleviated by doping carbon atoms, which also serve as the catalytic sites to catalyze the activation of Li2S. The doped C atoms in MoS2 surface greatly enhance the Li2S binding strength via the formation of S−C bonds, a pz-pz interaction that is not available in pristine MoS2. Such strong interaction facilitates the decomposition of adsorbed Li2S, thus lowering the activation voltage in the first charge cycle. Although increase the number of C atoms catalyze the decomposition of Li2S, the compact distribution and collective C atoms may hinder the diffusion of Li ion by forming an electrostatic potential well, split lithium polysulfides (LiPSs) by excessively strong S−C interaction, and raise the rate determining step free energy of the S8 to Li2S conversion during discharge process, thus a balance between them is required. Single carbon atom doped MoS2 model balances these factors and shows an excellent electrochemical performance, including improved conductivity, enhanced LiPSs affinity, lowered Li2S decomposition barrier, facilitated Li ion diffusion and fast kinetics of the conversion of LiPSs. This work is instructive in fabricating Li2S cathode with metal sulfides and doping architectures for practical Li-S batteries.

Polyanthraquinonyl sulfide cathodes for rechargeable magnesium batteries: Effect of structure on the performance

Rechargeable magnesium batteries (RMBs) attract special interests as a low-cost and reliable energy-storage technology, but the development is hindered by the low capacities and sluggish Mg2+ diffusion kinetics of the traditional inorganic cathode materials. Organic polymers break the hindrance of inorganic lattice and deliver plenty of candidates for RMB cathodes with the flexible and designable frameworks. Herein, three organic polyanthraquinonyl sulfides (PAQSs) are fabricated and investigated comparatively as RMB cathodes to reveal the effect of structure on the electrochemical magnesium-storage performance. It is demonstrated that the capacity decay is primarily owing to the dissolution of the discharge products (magnesiation state) in the electrolyte. The degree of polymerization is an important factor for the cycling stability. Prominently, poly(2,6-anthraquinonyl sulfide) shows an outstanding comprehensive performance, providing a high capacity (145 mAh g−1 at 50 mA g−1), an outstanding rate capability (74 mAh/g at 10C) and an excellent cyclability (99 % capacity retained after 1000 cycles at 5C). Significantly, poly(2,6-anthraquinonyl sulfide) store Mg2+ rather than MgCl+, and exhibits a considerable specific energy density of 185 Wh kg−1. The present work would assist the rational design of advanced organic RMB electrode materials, and highlights the advantages of organic polymers based on enolization chemistry for high-performance magnesium-storage.

Boosting the cycling stability of rechargeable magnesium batteries by regulating the compatibility between nanostructural metal sulfide cathodes and non-nucleophilic electrolytes

Boosting the cycling stability of rechargeable magnesium batteries by regulating the compatibility between nanostructural metal sulfide cathodes and non-nucleophilic electrolytes

A Step Forward: Hydrogen Production on Cobalt Molybdenum Sulfide Electrocatalyst in Anion Exchange Membrane Water Electrolyzer

Cobalt molybdenum sulfide (Co0.5Mo0.5Sx) was evaluated, as an alternative cathode catalyst for hydrogen large scale production in an anion exchange membrane water electrolyzer (AEMWE). Performance testing in a Co0.5Mo0.5Sx//Ir single cell fed with 0.1 mol L–1 KOH exhibited the best activity reported to date for transition metal sulfide cathodes in alkaline media. The aforementioned cell presented good stability during 40 h of operation at 2 V; in addition, it has most of its current density degradation recovered in the beginning of the subsequent 10 h interval.

Kinetically optimized copper sulfide cathodes for rechargeable magnesium batteries

Copper sulfides have been recognized as one of the most promising cathode materials for rechargeable magnesium batteries due to their large theoretical capacity and unique conversion-type mechanism. However, the solid-state diffusion of bivalent Mg2+ ions in CuS host lattice is subjected to huge electrostatic interaction and thus sluggish kinetics. Herein, anion substitution strategy and crystal engineering are reported to regulate electrochemical reaction kinetics and reinforce magnesium storage performances of tubular CuS cathodes. Benefitting from anion substitution and crystal facet regulation, the lattice well-exposed Se-substituted CuS nanotube cathodes demonstrate excellent magnesium storage capacity (372.9 mAh g−1 at 100 mA g−1), remarkable cycling stability (1600 cycles at 2.0 A g−1), and a good rate capability (112.4 mAh g−1 at 2.0 A g−1). Electrochemical kinetics investigation further suggests that anionic Se-substitution and crystal facet regulation can significantly optimize electrochemical reaction kinetics and accelerate diffusion rate of Mg2+ ions. Ex-situ X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) characterizations reveal the conversion reaction mechanism of Se-substituted CuS cathodes. These novel findings provide an effective approach to construct high-performance cathode materials for rechargeable magnesium batteries and hold great promise for development of other new battery systems.

Lifting the redox potential of layered sulfide cathodes for sodium-ion batteries

Lifting the redox potential of the cathode material is an important target to increase the energy density of sodium-ion batteries. Wang et al. report that this can be achieved for layered sulfides by careful combination of two different transition metals. The mixed compound NaTi_1-yV_yS₂ shows a higher redox potential compared to the pure materials NaTiS₂ and NaVS₂. The synergistic effect is believed to be due to an unusually strong covalency in the Ti–V–S system. Among various improvements, this approach leads to a 15% increase in energy density.

(Digital Presentation) Lithiation/De-Lithiation of a Unique C-S Species in Amorphous FeS4/C Cathodes for Li Batteries

When paired with Li metal anodes, Fe-based conversion cathodes like iron sulfide present a promising material for creating energy dense rechargeable batteries for energy storage. While iron sulfide cathodes (e.g. FeS2) typically suffer from deleterious polysulfide formation, recent work with a class of amorphous iron sulfide-carbon composites (e.g. FeS4/C) has shown minimal evidence of polysulfide formation during lithiation and de-lithiation, and thus it may represent a pathway to stable, polysulfide-free iron sulfide batteries. Prior reports indicate that the active component of the composite is the FeS4 and that the amorphous carbon does not exhibit any electrochemical response. While studying this material, however, we have found evidence to suggest that the cycling of FeS4 alone does not fully explain the electrochemical and chemical behavior observed for the FeS4/C cathode, and that the carbon plays a significant role in the overall electrochemistry of the composite.In this presentation, we will present a study of this amorphous FeS4/C composite as a cathode for use in Li batteries and provide evidence of the electrochemical lithiation and de-lithiation of a previously unstudied and unreported C-S compound found in the composite material. Our results indicate that this C-S species is amorphous and is (electro)chemically similar to sulfurized poly(acrylonitrile) (SPAN) and carbyne polysulfide (C-PS). By coupling ex situ Raman and X-ray photoelectron spectroscopy (XPS) to galvanostatic battery cycling, we show how chemical changes in the FeS4/C cathode correspond to electrochemical features associated with the lithiation and de-lithiation of both iron sulfide and the C-S species. Our results indicate that the C-S species is electrochemically active at all stages of cycling, while the FeS4 loses activity within approximately 15-20 cycles. This differs significantly from earlier reports and suggests that the lack of polysulfide formation when testing the FeS4/C composite may in fact be due to the cycling of this C-S species rather than iron sulfide. These results serve as an initial foray into the electrochemistry of this new material and should provide a basis for additional study of this new and promising C-S based cathode material for Li batteries.This work was supported by the Laboratory Directed Research and Development program at Sandia National Laboratories, a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-NA-0003525. The views expressed herein do not necessarily represent the views of the U.S. Department of Energy or the United States Government.

Scalable Preparation and Improved Discharge Properties of FeS2@CoS2 Cathode Materials for High-Temperature Thermal Battery.

Long-time thermal batteries with high specific energy are crucial for improving the fast response ability of long-range weapons. Due to its high capacity, safety, and stability, the new sulfide cathode has attracted extensive attention. In this study, an FeS2@CoS2 composite cathode with a core–shell structure was prepared via a combination of hydrothermal and high-temperature vulcanization processes. The novel FeS2@CoS2 cathode not only delivers a high discharge voltage and output capacity, but also has high thermal stability and excellent conductivity. Benefiting from the synergistic effect of FeS2 and CoS2, the as-synthesized cathode yields a high specific capacity. At a large current density of 1 A/cm2, the utilization rate of FeS2@CoS2 cathode material can reach 72.33%, which is 8.23% higher than that of FeS2. Moreover, the maximum output capacity is up to 902 As/g, with a utilization rate of 79.02% at 500 mA/cm2. This novel design strategy holds great promise for the development and application of high-performance thermal batteries in the future.

Amorphous Titanium Polysulfide Composites with Electronic/Ionic Conduction Networks for All-Solid-State Lithium Batteries.

All-solid-state lithium/sulfide batteries are considered as next-generation high-energy-density batteries with unrivaled safety. However, sulfide cathodes generally suffer from insulating properties and huge volume expansion in all-solid-state lithium batteries. Based on amorphous TiS4 (a-TiS4), a certain proportion of Super P is introduced to suppress the volume expansion and increase the electronic conductivity. Meanwhile, a Li7P3S11 solid electrolyte is in situ coated on the surface of 20% Super P/a-TiS4, and the close interfacial contact between the active material and the solid electrolyte constructs a favorable ionic conduction path. As a result, a Li/75% Li2S-24% P2S5-1% P2O5/Li10GeP2S12/20% Super P/a-TiS4@Li7P3S11 battery shows a high reversible capacity of 507.4 mAh g-1 after 100 cycles at 0.1 A g-1. Even the current density increases to 1.0 A g-1, and it can also provide a reversible capacity of 349.8 mAh g-1 after 200 cycles. These results demonstrate a promising 20% Super P/a-TiS4@Li7P3S11 cathode material with electronic/ionic conduction networks for all-solid-state lithium batteries.

Promoting Reversibility of Multielectron Redox in Alkali-Rich Sulfide Cathodes through Cryomilling

Promoting Reversibility of Multielectron Redox in Alkali-Rich Sulfide Cathodes through Cryomilling

High‐Temperature Solid‐State Synthesis and Electrochemical Properties of Transition Metal Sulfides for Thermal Batteries

Transition metal sulfide is the most widely used cathode material for thermal batteries. The development of modern weapons requires higher quality and output of transition metal sulfide cathode materials. However, the current synthesis processes have some limitations for large‐scale industrial production due to the long production cycle and low production efficiency. Herein, by controlling the synthesis temperature and adopting a high‐temperature solid‐state method, sulfide FeS2, CoS2, and NiS2 with single‐phase and good crystalline structure are synthesized. This method with a simple production process, short production cycle, and high single output is suitable for engineering production. Hence, guidance for large‐scale industrial synthesis of pure phase FeS2, NiS2, and CoS2 is provided, embodying important scientific significance and application value.

Li+ assisted fast and stable Mg2+ reversible storage in cobalt sulfide cathodes for high performance magnesium/lithium hybrid-ion batteries

Rechargeable magnesium/lithium hybrid-ion batteries (MLHBs) are one of the more promising future energy storage systems based on Mg2+/Li+ dual salt electrolytes, magnesium anodes and typical cathodes. In this work, we describe a set of MLHBs that use CoS cathodes coupled with the all-phenyl complex (APC) and 0.8 M lithium chloride in tetrahydrofuran (THF) derived APC-0.8 LiCl electrolyte. This electrolyte facilitates better Mg stripping/plating coincident with more uniform deposition on Mg vs. APC electrolyte alone and enhances significantly the electrochemical performance of CoS cathodes, offering capacities of 538 mAh g−1 at 0.1 A g−1 after 80 cycles and 320 mAh g−1 at 1 A g−1 after 1000 cycles. Multiple characterization methods indicate that Co9S8 forms as an intermediate during MLHB cycling with a lattice structure similar to target products of Li2S and MgS (Fm-3m), differentiated from CoS (P63/mmc). Moreover, Mg2+ and Li+ participate in the cathode reactions during cycling and capacities mainly come from Li+ reactions with CoS during initial cycles but Mg2+ reactions with Co9S8 after sufficient activation. It appears that superior MLHB performance can be achieved by using simple Mg2+/Li+ dual salt electrolytes and cathodes having similar crystal structure before and after Mg2+/Li+ storage.

Enhancing the Reversibility of Li Deposition/Dissolution in Sulfur Batteries Using High-Concentration Electrolytes to Develop Anode-Less Batteries with Lithium Sulfide Cathode

Enhancing the Reversibility of Li Deposition/Dissolution in Sulfur Batteries Using High-Concentration Electrolytes to Develop Anode-Less Batteries with Lithium Sulfide Cathode

Heavily Tungsten-Doped Sodium Thioantimonate Solid-State Electrolytes with Exceptionally Low Activation Energy for Ionic Diffusion.

A strategy for modifying the structure of solid-state electrolytes (SSEs) to reduce the cation diffusion activation energy is presented. Two heavily W-doped sodium thioantimonate SSEs, Na2.895 W0.3 Sb0.7 S4 and Na2.7 W0.3 Sb0.7 S4 are designed, both exhibiting exceptionally low activation energy and enhanced room temperature (RT) ionic conductivity; 0.09 eV, 24.2 mS/cm and 0.12 eV, 14.5 mS/cm. At -15 °C the Na2.895 W0.3 Sb0.7 S4 displays a total ionic conductivity of 5.5 mS/cm. The 30 % W content goes far beyond the 10-12 % reported in the prior studies, and results in novel pseudo-cubic or orthorhombic structures. Calculations reveal that these properties result from a combination of multiple diffusion mechanisms, including vacancy defects, strongly correlated modes and excessive Na-ions. An all-solid-state battery (ASSB) using Na2.895 W0.3 Sb0.7 S4 as the primary SSE and a sodium sulfide (Na2 S) cathode achieves a reversible capacity of 400 mAh g-1 .

Heavily Tungsten‐Doped Sodium Thioantimonate Solid‐State Electrolytes with Exceptionally Low Activation Energy for Ionic Diffusion

AbstractA strategy for modifying the structure of solid‐state electrolytes (SSEs) to reduce the cation diffusion activation energy is presented. Two heavily W‐doped sodium thioantimonate SSEs, Na2.895W0.3Sb0.7S4 and Na2.7W0.3Sb0.7S4 are designed, both exhibiting exceptionally low activation energy and enhanced room temperature (RT) ionic conductivity; 0.09 eV, 24.2 mS/cm and 0.12 eV, 14.5 mS/cm. At −15 °C the Na2.895W0.3Sb0.7S4 displays a total ionic conductivity of 5.5 mS/cm. The 30 % W content goes far beyond the 10–12 % reported in the prior studies, and results in novel pseudo‐cubic or orthorhombic structures. Calculations reveal that these properties result from a combination of multiple diffusion mechanisms, including vacancy defects, strongly correlated modes and excessive Na‐ions. An all‐solid‐state battery (ASSB) using Na2.895W0.3Sb0.7S4 as the primary SSE and a sodium sulfide (Na2S) cathode achieves a reversible capacity of 400 mAh g−1.

Understanding LiI-LiBr Catalyst Activity for Solid State Li2S/S Reactions in an All-Solid-State Lithium Battery.

Li||MoS2 solid-state batteries have higher volumetric energy density and power density than Li||Li2S batteries. However, they suffer from energy and power decay due to the formation of lithium sulfide that has low ionic/electronic conductivity and a strong Li-S bond. Herein, we overcome these challenges by incorporating the catalytic LiI-LiBr compound and carbon black into MoS2. The comprehensive simulations, characterizations, and electrochemical evaluations demonstrated that LiI-LiBr significantly reduces Li+/S2- interaction and increases the ionic conductivity of Li2S, thus enhancing the reaction kinetics and Li2S/S redox reversibility. MoS2@LiI-LiBr@C||Li cells with an areal capacity of 0.87 mAh cm-2 provide a reversible capacity of 816.2 mAh g-1 at 200 mA g-1 and maintain 604.8 mAh g-1 (based on the mass of MoS2) for 100 cycles. At a high areal capacity of 2 mAh cm-2, the battery still delivers reversible capacity of 498 mAh g-1. LiI-LiBr-carbon additive can be broadly applied for all transition-metal sulfide cathodes to enhance the cyclic and rate performance.