Sulfide Electrolyte Research Articles

Development of Argyrodite-Based Sulfide Electrolytes for Next-Generation Solid-State Li Batteries

Advances in solid electrolytes (SEs) with superionic conductivity and stabilized electrode-electrolyte interfaces are key enablers for all-solid-state batteries (SSBs) to meet the energy density and cost targets for next-generation batteries for electric vehicles. Argyrodite sulfide-based electrolytes with the nominal composition Li6PS5X; where X= Cl and/or Br, I provide several key advantages over other types of SE counterparts, including (i) exceptionally high ionic conductivities up to 10-2 S/cm at room temperature (comparable to nonaqueous liquid electrolytes), (ii) availability of low temperature and inexpensive synthesis routes to produce glass, glass-ceramic, and crystalline structures, and (iii) soft mechanical properties facilitating material processing and solid-state battery (SSB) fabrication.Several key challenges exist for the practical use of the argyrodite sulfide-based electrolyte in an SSB: (i) scale-up synthesis to produce phase-pure materials, (ii) rationale processing method development to produce free-standing thin film SSEs, and (iii) identifying buried interfacial side-reaction products at the electrode/electrolyte interfaces using advanced characterization tools.In this talk, we will present our recent achievements focusing on tackling each of these challenges, including (i) solution-based synthesis of Li6PS5X; (ii) optimizing binder, slurry composition, and processing method to make Li6PS5X thin film (<50 µm) SSEs, and (iii) combining in-situ Raman spectroscopy and microscopy with complementary electrochemical impedance spectroscopy (EIS) to explore electrode/ Li6PS5X interfacial stability. Acknowledgment This research conducted at Oak Ridge National Laboratory, managed by UT Battelle, LLC, for the U.S. Department of Energy (DOE) is sponsored by the Office of Energy Efficiency and Renewable Energy (EERE) in the Vehicle Technologies Office (VTO) through the Advanced Battery Materials Research (BMR) Program.

Combating Li metal deposits in all-solid-state battery via the piezoelectric and ferroelectric effects

All-solid-state Li-metal batteries (ASSLBs) are highly desirable, due to their inherent safety and high energy density; however, the irregular and uncontrolled growth of Li filaments is detrimental to interfacial stability and safety. Herein, we report on the incorporation of piezo-/ferroelectric BaTiO3 (BTO) nanofibers into solid electrolytes and determination of electric-field distribution due to BTO inclusion that effectively regulates the nucleation and growth of Li dendrites. Theoretical simulations predict that the piezoelectric effect of BTO embedded in solid electrolyte reduces the driving force of dendrite growth at high curvatures, while its ferroelectricity reduces the overpotential, which helps to regularize Li deposition and Li+ flux. Polarization reversal of soft solid electrolytes was identified, confirming a regular deposition and morphology alteration of Li. As expected, the ASSLBs operating with LiFePO4/Li and poly(ethylene oxide) (PEO)/garnet solid electrolyte containing 10% BTO additive showed a steady and long cycle life with a reversible capacity of 103.2 mAh g-1 over 500 cycles at 1 C. Furthermore, the comparable cyclability and flexibility of the scalable pouch cells prepared and the successful validation in the sulfide electrolytes, demonstrating its universal and promising application for the integration of Li metal anodes in solid-state batteries.

High-rate and durable sulfide-based all-solid-state lithium battery with in situ Li2O buffering

Sulfide electrolytes (SEs)-based all-solid-state lithium batteries (ASSLBs) are advantageous over traditional lithium-ion batteries (LIBs) because of high energy density and safety. Unfortunately, the commercialization of SEs-based ASSLBs is presently hindered by interfacial instability between SEs and active materials, sluggish dynamics and poor cycling performance. Here we report, for the first time, a stable and conductive Li2O buffering coating for Ni-rich LiNi0.8Co0.1Mn0.1O2 (NCM811) in ASSLBs using SEs of Li6PS5Cl via a facile one-step sintering. We show using judiciously combined computation and experiment that Li2O buffering improves the stability of NCM811 and significantly boosts transfer of Li+. Via tuning the thickness of the Li2O buffer, we demonstrate the high initial discharge capacity of 189.66 mAh g − 1 (0.1C) and rate capability of 61.71 mAh g − 1 (3C), together with outstanding long-term cycling performance of ∼ 2600 cycles at 1C with capacity retention of 81.47%, and Coulombic efficiency of 99.9%. We conclude that conductive Li2O buffering can be used to obviate interfacial instability between SEs and active materials and to boost dynamics and cycling performance. Findings will be of immediate benefit to a range of researchers in design for high-performance ASSLBs for practical application and commercialization.

Evaluations of Thermal Diffusivity and Electrochemical Properties for Lithium Hydride and Electrolyte Composites

There is ongoing research to develop lithium ion batteries as sustainable energy sources. Because of safety problems, solid state batteries, where electrolytes are replaced with solids, are attracting attention. Sulfide electrolytes, with a high ion conductivity of 10-3 S/cm or more, have the highest potential performance, but the price of the main materials is high. This study investigated lithium hydride materials, which offer economic advantages and low density. To analyze the change in ion conductivity in polymer electrolyte composites, PVDF, a representative polymer substance was used at a certain mass ratio. XRD, SEM, and BET were performed for metallurgical analyses of the materials, and ion conductivity was calculated through the EIS method. In addition, thermal conductivity was measured to analyze thermal stability, which is a major parameter of lithium ion batteries. As a result, the ion conductivity of LiH was found to be 10-6 S/cm, and the ion conductivity further decreased as the PVDF ratio increased when the composite was formed.

Revealing performance of 78Li2S-22P2S5 glass ceramic based solid-state batteries at different operating temperatures

78Li2S-22P2S5 are sulfide electrolytes with high lithium-ion conductivity and wide electrochemical windows in the Li2S-P2S5 system, making them attractive solid electrolytes for ASSLBs. However, the role and potential of 78Li2S-22P2S5 solid electrolytes over a wide temperature range are still not fully understood. Therefore, we constructed solid-state batteries with NCM622 as the positive electrode and 78Li2S-22P2S5 glass-ceramics as the electrolyte to investigate in depth the differences in battery performance over a wide temperature range and their intrinsic mechanisms. The in-situ impedance and relaxation time distribution (DRT) demonstrated the electrochemical stability of the electrolyte over a wide temperature range, while the in-situ stacking pressure observed a large volume change during cycling at 60 °C, leading to local solid-solid contact failure and poor cycling stability. This study provides insight into the advantages and problems of 78Li2S-22P2S5 in the wide temperature range as well as a basis for the construction of ASSLBs with high energy density and long cycle life.

Effects of lithium bis(oxalato)borate-derived surface coating layers on the performances of high-Ni cathodes for all-solid-state batteries

Instability of the cathode/solid electrolyte interface is a critical issue limiting the commercialization of all-solid-state batteries (ASSBs). Specifically, lithium thiophosphates (sulfide electrolytes), promising solid electrolytes, are highly reactive with oxide cathodes, leading to undesirable side reactions and electrolyte decomposition during cycling. Surface coating of oxide cathodes is an efficient approach to suppress undesirable interfacial reactions. Several ternary compounds, such as LiNbO3, LiTaO3, and Li2ZrO3, with suitable ionic conductivities have been applied as coating materials due to their appropriate stabilities against sulfide electrolytes. However, the fabrication of a coating layer containing ternary oxides requires high-temperature (over 600–800 °C) heat treatment for the homogeneous reaction of the constituent ions, which can deteriorate the performances of high-Ni cathodes. Accordingly, herein, a coating layer was synthesized using lithium bis(oxalato)borate (LiBOB) via low-temperature (below 400 °C) heat treatment. LiBOB formed thin and homogeneous coating layers on the surfaces of cathodes. LiBOB-coated cathode heat-treated at 350 °C presented higher discharge capacity, better rate capability, and lower impedance value as compared to those of the pristine cathode. Considering X-ray photoelectron spectra and energy-dispersive X-ray spectroscopy analyses of the composite cathodes, the LiBOB coating layer formed at 350 °C significantly reduced electrolyte decomposition and side reactions at the cathode/electrolyte interface, which enhanced the electrochemical performances of the LiBOB-coated cathodes. This result confirms that the LiBOB-based coating is an effective approach to improve the stability of the cathode/sulfide e Basically lectrolyte interface. Our simple and unique approach based on additives, such as LiBOB, has the potential to trigger new research on the fabrication of surface coatings at low temperatures (below 400 °C) for the cathodes of ASSBs.

Long‐Cycling All‐Solid‐State Batteries Achieved by 2D Interface between Prelithiated Aluminum Foil Anode and Sulfide Electrolyte

All-solid-state batteries (ASSBs) with alloy anodes are expected to achieve high energy density and safety. However, the stability of alloy anodes is largely impeded by their large volume changes during cycling and poor interfacial stability against solid-state electrolytes. Here, a mechanically prelithiation aluminum foil (MP-Al-H) is used as an anode to construct high-performance ASSBs with sulfide electrolyte. The dense Li-Al layer of the MP-Al-H foil acts as a prelithiated anode and forms a 2D interface with sulfide electrolyte, while the unlithiated Al layer acts as a tightly bound current collector and ensures the structural integrity of the electrode. Remarkably, the MP-Al-H anode exhibits superior lithium conduction kinetics and stable interfacial compatibility with Li6 PS5 Cl (LPSCl) and Li10 GeP2 S12 electrolytes. Consequently, the symmetrical cells using LPSCl electrolyte can work at a high current density of 7.5mA cm-2 and endure for over 1500 h at 1mA cm-2 . Notably, ≈100% capacity is retained for the MP-Al-H||LPSCl||LiCoO2 full cell with high area loadings of 18mg cm-2 after 300 cycles. This work offers a pathway to improve the interfacial and performance issues for the application of ASSBs.

The Contact Interface Engineering of All‐Sulfide‐Based Solid State Batteries via Infiltrating Dissoluble Sulfide Electrolyte

All‐solid‐state lithium batteries (ASSLBs) based on sulfide solid electrolytes (SEs) are one of the most promising strategies for next‐generation energy storage systems and electronic devices. However, the poor chemical/electrochemical stability of sulfide SEs with oxide cathode materials and high interfacial impedance, particularly due to physical contact failure, are the major limiting factors to the development of sulfide SEs in ASSLBs. Herein, the composite cathode of MOF‐derived Fe7S8@C and Li6PS5Br fabricated by an infiltration method (IN–Fe7S8) with dissoluble sulfide electrolyte (dissoluble SE) is reported. Dissoluble SE can easily infiltrate the porous sheet‐type Fe7S8@C cathode to homogeneously contact with Fe7S8 nanoparticles that are embedded in the surrounding carbon matrixes and form a fast ionic transport network. Benefiting from applying dissoluble SE and Fe7S8@C, the IN‐Fe7S8‐based cells displayed a reversible capacity of 510 mAh g−1 after 180 cycles at 0.045 mA cm−2 at 30 °C. This work demonstrates a novel and practical method for the development of high‐performance all‐sulfide‐based solid state batteries.

Control of side reactions using LiNbO3 mixed/doped solid electrolyte for enhanced sulfide-based all-solid-state batteries

Control of side reactions is a critical issue for obtaining all-solid-state lithium batteries (ASSLBs) with comparable performance to lithium-ion batteries (LIBs). In particular, the interfacial reaction at the cathode/sulfide electrolyte interface and decomposition of the sulfide electrolyte lead to a significant deterioration in the electrochemical performance of ASSLBs. Surface-coated cathodes have been used in ASSLBs to mitigate these side reactions. However, the generally used LiNbO3 coating, a representative coating for ASSLBs, is expensive because of the high price of the source materials, and perfect coverage of the entire cathode surface by coating is practically very difficult. In this study, we introduced a LiNbO3 mixed/doped Li6PS5Cl solid electrolyte, instead of surface coating on the cathodes, to improve the resistance against side reactions concerning the sulfide electrolyte. The source material used for LiNbO3 mixing/doping is cheaper than that used for LiNbO3 coating. Partial doping of LiNbO3 was confirmed by laser Raman spectroscopy and field-emission scanning electron microscopy with energy dispersive X-ray spectroscopy (EDS) analysis. An optimum LiNbO3 mixed/doped electrolyte (4 mol.% of electrolyte) showed enhanced ionic conductivity than that of Li6PS5Cl solid electrolyte without LiNbO3. Moreover, the interfacial reaction at the cathode/electrolyte interface and the sulfide electrolyte decomposition were decreased owing to the LiNbO3 mixing/doping effect. The suppression of ion exchange between the cathode and electrolyte was also confirmed by the scanning transmission electron microscopy - energy dispersive X-ray spectroscopy (STEM-EDS) line profile. These results contributed to the increased discharge capacity and improved rate capability of the cell using 96LPSCl-4LNO (4 mol.% LiNbO3 mixing/doping), compared to those of the cell using pristine Li6PS5Cl.

Self‐densified ultrathin solid electrolyte membrane fabricated from monodispersed sulfide electrolyte nanoparticles

AbstractReducing particle size of sulfide electrolytes to nanoscale is essential for preparing ultrathin sulfide electrolyte membrane of all‐solid‐state batteries. However, there lacks effective way to synthesize sulfide electrolyte nanoparticles with good morphology uniformity. In this work, a dual precursor sol route is developed to speed up the synthesis of lithium thiophosphate (LPS) from tens of hours by conventional liquid‐phase routes to &lt;50 min. The promoted reaction kinetics inhibit the overgrowth of the product particles so that monodispersed LPS nanoparticles with sizes of 44 ± 6 nm are prepared. Membranes fabricated from the nanoparticles achieve a thickness of 0.5–1.0 μm, which are reduced by one order of magnitude in comparison with those of reported sulfide electrolyte membranes. Moreover, the monodispersity makes the nanoparticles closely packed in the green membrane, so that the membrane can be self‐densified without applying pressure, whereas 100‐MPa‐level pressure is indispensable for conventional membrane fabrication technologies. The ultrathin LPS membrane is also successfully employed in all‐solid‐state LiFePO4 thin film batteries. This work not only provides a heuristic strategy to synthesis sulfide electrolyte nanoparticles but also develops a pressing‐free fabrication route of sulfide electrolyte membranes, which is eagerly demanded for high‐energy‐density all‐solid‐state batteries.

Liquid Copper and Iron Production from Chalcopyrite, in the Absence of Oxygen

Clean energy infrastructure depends on chalcopyrite: the mineral that contains 70% of the world’s copper reserves, as well as a range of precious and critical metals. Smelting is the only commercially viable route to process chalcopyrite, where the oxygen-rich environment dictates the distribution of impurities and numerous upstream and downstream unit operations to manage noxious gases and by-products. However, unique opportunities to address urgent challenges faced by the copper industry arise by excluding oxygen and processing chalcopyrite in the native sulfide regime. Through electrochemical experiments and thermodynamic analysis, gaseous sulfur and electrochemical reduction in a molten sulfide electrolyte are shown to be effective levers to selectively extract the elements in chalcopyrite for the first time. We present a new process flow to supply the increasing demand for copper and byproduct metals using electricity and an inert anode, while decoupling metal production from fugitive gas emissions and oxidized by-products.

Nanostructure of the Interphase Layer between a Single Li Dendrite and Sulfide Electrolyte in All-Solid-State Li Batteries

Nanostructure of the Interphase Layer between a Single Li Dendrite and Sulfide Electrolyte in All-Solid-State Li Batteries

Effects of I and W co-doping on the structural and electrochemical characteristics of Na3SbS4 glass-ceramic electrolytes

Sodium-ion batteries are becoming a feasible choice for large-scale energy storage because of their low cost and vast selection of cathode materials. Here we report the design and synthesis of Na3SbS4–Na2W0.77S4I0.6 glass-ceramic electrolyte. A high room-temperature conductivity of 4.97 mS cm−1 was achieved by I doping. In this sulfide super-ionic conductor structure, I-substitution loosened the local bonding between Na and S (or I). The Sb in the SbS43− unit was replaced by W with a higher valence state, producing sodium vacancies while maintaining the 3D conduction pathways and resulting in fast ion transport. Additionally, the electrolyte Na3SbS4–Na2 W0.77S4I0.6 exhibited advantage of air stability against the humid atmosphere, which is a promising sulfide electrolyte for all solid-state sodium battery application.

High-Energy and Long-Cycling All-Solid-State Lithium-Ion Batteries with Li- and Mn-Rich Layered Oxide Cathodes and Sulfide Electrolytes

High-Energy and Long-Cycling All-Solid-State Lithium-Ion Batteries with Li- and Mn-Rich Layered Oxide Cathodes and Sulfide Electrolytes

A facile path from fast synthesis of Li-argyrodite conductor to dry forming ultrathin electrolyte membrane for high-energy-density all-solid-state lithium batteries

All-solid-state lithium batteries (ASSLBs), utilizing sulfide solid electrolyte, are considered as the promising design on account of their superior safety and high energy density, whereas the time-consuming preparation process of sulfide electrolyte powders and the thickness of electrolyte layer hinder their practical application. Herein, an innovative ultimate-energy mechanical alloying plus rapid thermal processing approach is employed to rapidly synthesize the crystalline Argyrodite-type conductor Li5.3PS4.3ClBr0.7 (LPSClBr) with superior ionic conductivity (11.7 mS cm−1). Furthermore, to realize the higher energy density of the battery, an ultrathin LPSClBr sulfide electrolyte membrane with superior ionic conductivity of 6.5 mS cm−1 is fabricated with the aid of polytetrafluoroethylene (PTFE) binder and the reinforced cellulose mesh. Moreover, a simple solid electrolyte interphase (SEI) is constructed on the surface of lithium metal to enhance anodic stability. Benefiting from the joint efforts of these merits, the modified ASSLBs with a high cell-level energy density of 311 Wh kg−1 show an excellent cyclic stability. The assembled all-solid-state Li2S/Li pouch cell can operate even under the severe conditions of bending and cutting, demonstrating the enormous potential of the sulfide electrolyte membrane for ASSLBs application.

Deciphering Fast Ion Transport in Glasses: A Case Study of Sodium and Silver Vitreous Sulfides.

High-capacity solid-state batteries are promising future products for large-scale energy storage and conversion. Sodium fast ion conductors including glasses and glass ceramics are unparalleled materials for these applications. Rational design and tuning of advanced sodium sulfide electrolytes need a deep insight into the atomic structure and dynamics in relation with ion-transport properties. Using pulsed neutron diffraction and Raman spectroscopy supported by first-principles simulations, we show that preferential diffusion pathways in vitreous sodium and silver sulfides are related to isolated sulfur Siso, that is, the sulfur species surrounded exclusively by mobile cations with a typical stoichiometry of M/Siso ≈ 2. The Siso/Stot fraction appears to be a reliable descriptor of fast ion transport in glassy sulfide systems over a wide range of ionic conductivities and cation diffusivities. The Siso fraction increases with mobile cation content x, tetrahedral coordination of the network former and, in case of thiogermanate systems, with germanium disulfide metastability and partial disproportionation, GeS2 → GeS + S, leading to the formation of additional sulfur, transforming into Siso. A research strategy enabling to achieve extended and interconnected pathways based on isolated sulfur would lead to glassy electrolytes with superior ionic diffusion.

Air Stability of Solid-State Sulfide Batteries and Electrolytes

Air Stability of Solid-State Sulfide Batteries and Electrolytes

Immense Reduction in Interfacial Resistance between Sulfide Electrolyte and Positive Electrode.

Low interfacial resistance between the solid sulfide electrolyte and the electrode is critical for developing all-solid-state Li batteries; however, the origin of interfacial resistance has not been quantitatively reported in the literature. This study reports the resistance values across the interface between an amorphous Li3PS4 solid electrolyte and a LiCoO2(001) epitaxial thin film electrode in a thin-film Li battery model. High interfacial resistance is observed, which is attributed to the spontaneous formation of an interfacial layer between the solid electrolyte and the positive electrode upon contact. That is, the interfacial resistance originates from an interphase mixed layer instead of a space charge layer. The introduction of a 10 nm thick Li3PO4 buffer layer between the solid electrolyte and positive electrode layers suppresses the formation of the interphase mixed layer, thereby leading to a 2800-fold decrease in the interfacial resistance. These results provide insight into reducing the interfacial resistance of all-solid-state Li batteries with sulfide electrolytes by utilizing buffer layers.

Wet-slurry fabrication using PVdF-HFP binder with sulfide electrolytes via synergetic cosolvent approach for all-solid-state batteries

Polymeric binders are a crucial component of large-format all-solid-state Li batteries (ASLBs) that employ sulfide solid electrolytes. However, the severe dissolution of sulfide solid electrolyte materials into conventional polar solvents restricts the suitability of slurry-processing solvents to less polar molecules, and in turn, the suitability of materials for polymeric binders to rubbers, such as nitrile butadiene rubber (NBR). In this study, a synergistic cosolvent approach is employed, to render poly(vinylidene fluoride-hexafluoropropylene) (PVdF-HFP), which is sulfide-slurry-incompatible, amenable to slurry fabrication. The synergistic combination of highly volatile ethyl acetate, and less volatile hexyl butyrate allows for the utilization of PVdF-HFP as it is soluble in the former but not in the latter, while avoiding the binder migration problem. A comparative investigation of sheet-type LiNi0.70Co0.15Mn0.15O2 electrodes comprising PVdF-HFP or NBR, demonstrates the superior performance of the former. Specifically, it is revealed that the effective volume fraction and binder distribution in the electrodes are key factors for determining the electrochemical performance. The advantageous features of PVdF-HFP over NBR are highlighted, particularly at a low temperature of 0 °C or under a low external operating pressure of 2 MPa. Finally, the encouraging performance of pouch-type LiNi0.70Co0.15Mn0.15O2/graphite ASLB full cells fabricated using PVdF-HFP, is successfully demonstrated.

Constructing Favorable Microstructures in Solid-State Organic Cathodes Via Mechanical Property Manipulation

Organic electrode materials, due to their low environment footprint and high material-level specific capacities, have become competitive alternatives to inorganic materials for solid-state batteries (SSB) in recent years. Additionally, the soft nature of organic compounds ensures consistent and intimate contact with solid sulfide electrolytes during cycling, which is beneficial for battery longevity. However, the low-modulus organic materials and high-modulus sulfide electrolytes, upon mixing and compression, would form unfavorable composite microstructure where sulfide particles are encapsulated by organics and cannot form an efficient ion conduction path. This mismatch in mechanical property prevents a high fraction of organic compounds to be used in a solid-state cathode, limiting the energy density of organic solid-state batteries.Here we report the formation of favorable microstructures of organic cathodes by “softening” the sulfide electrolytes. Solvent treatment of the sulfide electrolyte Li6PS5Cl more than halves its modulus from 28.6 ± 8.5 GPa to 16.0 ± 1.6 GPa. Thermal gravimetric analysis, Raman spectroscopy, and X-ray diffraction were used to elucidate the evolution of the sulfide electrolyte during the softening and recovering process. The organic cathode formed by mixing organic materials with this softened electrolyte shows a favorable microstructure where the electrolyte forms a percolated domain. As a result, the utilization of an organic material, pyrene-4,5,9,10-tetraone (PTO), is increased by 133.6% and 90.8% compared with cells with a re-hardened and the pristine Li6PS5Cl, respectively. The mass fraction of PTO can be improved from 20 to 40wt% while maintaining high utilization (85.7%). Our exploration of softened electrolyte builds the correlation among structure, mechanical property, microstructure engineering and battery performance, and the strategy is applicable to other active materials with low modulus.