Sulfide-based Solid-state Electrolytes Research Articles

Feature-rich electronic properties of three-dimensional ternary compound: Li7P3S11

PurposeThe theoretical findings serve as a foundation for further research into understanding sulfide-based solid-state electrolytes, ultimately advancing the progress of all-solid-state batteries.Design/methodology/approachThe electronic properties of Li7P3S11 are thoroughly explored through first-principles calculations.FindingsThis investigation encompasses the intricate atom-dominated valence and conduction bands, spatial charge density distribution and the breakdown of atom and orbital contributions to van Hove singularities. Additionally, the compound’s wide and discrete energy spectra reflect the substantial variations in bond lengths and its highly anisotropic geometric structure. The complex and nonuniform chemical environment indicates the presence of intricate hopping integrals.Originality/valueThis study provides valuable insights into the critical multiorbital hybridizations occurring in the Li-S and P-S chemical bonds. To validate the theoretical predictions, experimental techniques can be employed. By combining theoretical predictions with experimental data, a comprehensive understanding of the geometric and electronic characteristics of Li7P3S11 can be achieved.

Evolution Process of the Interfacial Chemical Reaction in Ni-Rich Layered Cathodes for All-Solid-State Batteries.

All-solid-state batteries (ASSBs) have attracted much attention in the fields of energy storage, electric vehicles, and portable electronic devices due to their safety and high energy density. Ni-rich layered ternary materials (LiNi1-y-zCoyMnzO2, 1 - y - z ≥ 0.7) are considered to be among the most promising candidates for cathode materials in ASSBs due to their unique advantages. Nevertheless, the interfacial chemical reaction between the ternary cathode (NCM) and solid-state electrolytes (SSEs) has become the main issue to limit the long-cycle stability of the cathode. Relative studies have shown that when NCM materials are in direct contact with sulfide-based SSEs, byproducts generated by the interfacial chemical reaction accumulate at the interface, resulting in increasing interfacial impedance. However, up to now, the formation mechanism of the NCM/SSE interfacial chemical reaction, as well as its properties and evolution process, still lacks detailed characterization. In this paper, batteries at different stages during the long-cycling process are characterized to reveal the dynamic evolution process of the chemical reaction from the cathode-electrolyte interface to the interior of the particle and to determine the chemical reaction effect on the irreversible degradation of the battery capacity. On this basis, a surface coating of LiNbO3 is adopted to establish a passivation protection layer at the cathode-electrolyte interface. The coated battery has been subjected to 2000 charge/discharge cycles at a rate of 1 C and achieved a capacity retention rate of up to 82%.

Investigation of Interfacial Behavior of Ni-Rich NCM Cathode Particles in Sulfide-Based Solid-State Electrolyte

All-solid-state batteries (ASSBs) are currently investigated as a future battery technology with conventional layered cathode materials because they can offer benefits in the gravimetric and volumetric energy densities compared to flammable liquid electrolyte lithium-ion batteries with graphite intercalation anode. The solid electrolyte is believed to suppress dendritic growth and low Coulombic efficiency on the lithium metal anode side, which are the key issues for the use of a lithium metal electrode in conventional batteries with liquid electrolyte. Moreover, layered transition metal oxides such as LiNixCoyMnzO2 (NCM, 0 < x, y, z < 1) are one of the most promising positive electrode active material candidates being developed to increase the energy density. In particular, recent studies have shown a tendency to decrease the cobalt content and increase the nickel content to increase energy density and price competitiveness, so high-nickel NCM can be the optimal material suitable for this purpose. However, the remaining interfacial challenges of the cathode / solid electrolyte interface still need to be solved.Herein, we investigated the kinetics such as charge transfer resistance at the interface between high nickel (Ni0.94) NCM particles and argyrodite (Li6PS5Cl) solid electrolytes using the microcavity electrode with the negative and positive pulsed current measurement technique and compared with liquid electrolytes using the same manner measurement technique. The cavity-electrode system is adopted to analyze the electrochemical properties of active particles and electrolytes confined in the cavity to exclude the effects of surrounding interfaces, barriers, and side reactions caused by battery components around the electrodes and the impact of loading and current collectors of the composite electrode. Therefore, understanding the electrode-electrolyte interface between cathode active particles and solid electrolytes is crucial for theoretical studies on the interfacial phenomenon in solid electrolyte batteries.

Examining Electrochemical and Mechanical Behavior of Amorphous and Crystalline Sulfide-Based Solid-State Electrolytes

Traditional liquid electrolytes used in lithium-metal batteries have severe safety issues, poor power density, as well as thermal and electrochemical instability that prevent scaling to newer applications, such as electric vehicles. Sulfide-based solid-state electrolytes (SSEs) are viable for addressing many of the issues seen with liquid electrolytes. However, one of the key hindrances to the use of sulfide-based SSEs is the understanding of repeatable processing of highly conductive, stable material. There are limitations in producing electrolyte with known defect types and density, as well as degree of crystallinity. The degree of crystallinity greatly effects electrochemical properties, such as ionic conductivity, due to the change in ionic pathways through the electrolyte. However, other hindrances to SSE capabilities, such as interfacial stability and mechanical integrity, are not noted as a function of crystallinity. Here, multiple forms of characterization were utilized to confirm structural information on dry ball milled Li7P3S11 (LPS) SSEs. A range of crystallinity of pelletized electrolytes were then analyzed with different electrochemical and mechanical tests to evaluate the viability of SSEs in operation. There is particular interest in the near-amorphous regime of crystallinity, where minimal differences are seen in electrochemical capabilities, though there is uncertainty in the possible benefits observed for interfacial compatibility and in mechanical properties. Electrochemical impedance spectroscopy (EIS) and symmetric cell cycling were utilized to examine the bulk and interfacial capabilities of electrolytes, all operated under various loads with a specialty designed load cell. Mechanical properties were analyzed with mechanical testing on different scales, from bulk loading down to atomic force microscopy mapping and nanoindentation testing. With this wide array of characterizations, a wholistic understanding of slightly varied crystallinity of sulfide-based SSE is accomplished.

(Invited) Multiscale Interfacial Heterogeneity Explored by Advanced Spectroscopy and Imaging for Batteries Beyond Lithium-Ion

Keywords: solid-liquid interface, solid-state battery, surface-enhanced Raman spectroscopy (SERS), tip-enhanced Raman spectroscopy (TERS), neutron tomography, sulfide solid-state electrolyte, Raman imagingThe ever-growing needs for energy storage systems require batteries with even higher power and energy density with extended life and enhanced safety beyond the current Li-ion battery technologies. Fulfilling these needs requires new battery chemistries, including high-energy-density electrode materials, solid-state electrolytes, and efficient interphases to mitigate the side reactions between the electrodes and the electrolytes.Charge transport across the electrode and electrolyte interface is believed to be one of the charge/discharge rate-limiting steps. Although the composition, morphology, and structure of solid-electrolyte interphase (SEI) have been extensively studied, probing its evolution at the nanoscale is challenging to a large extent. Plasmon-enhanced Raman spectroscopy (PERS) is promising to solve this challenge. PERS is the resonant oscillation of conduction electrons at the interface between negative and positive permittivity molecules stimulated by incident light. It includes surface-enhanced Raman spectroscopy (SERS) and tip-enhanced Raman spectroscopy (TERS). In the first part of this talk, I will show that gap-mode SERS is ideal to probe salt solvation structure in the immediate vicinity (< 20 nm) of the electrode/electrolyte interface. SERS lacks the nanoscale resolution in the sample plane. This can be compensated by TERS. TERS analysis on cycled high-energy silicon anodes indicates that the nanometer scale SEI "islands" are unevenly distributed. Even for the same SEI "island", the composition is different from point to point with inter-point distance smaller than 10 nm.All-solid-state lithium metal batteries (SSBs) promise specific energy >500 Wh/kg. A solid-state electrolyte (SSE) plays an irreplaceable role in reaching such an energy-density goal. Sulfide-based SSEs have emerged as a prominent class of soft ionic conductors that have comparable room-temperature ionic conductivity to their liquid electrolyte counterparts. However, when paring with a high voltage cathode, such as lithium nickel manganese cobalt oxide (NMC), the (electro)chemical instability of the sulfide SSE at the electrode/SSE interfaces becomes a major challenge. The interfacial instability can result in >50% initial capacity loss in a Li/sulfide SSE/NMC battery, thereby keeping the sulfide SSEs from commercialization. In the second part of this talk, I will show how we synergistically use neutron computed tomography and in situ Raman imaging, with clustering analysis to track lithium displacement at the interface of a sulfide-based SSB. Acknowledgment This research was conducted at Oak Ridge National Laboratory, managed by UT Battelle, LLC, for the U.S. Department of Energy (DOE) and is supported by Asst. Secretary, Energy Efficiency and Renewable Energy (EERE), Vehicle Technologies Office (VTO) through the Advanced Battery Materials Research (BMR) Program. This research used resources at High Flux Isotope Reactor, a DOE Office of Science User Facilities operated by the Oak Ridge National Laboratory.

Dual-doping for enhancing chemical stability of functional anionic units in sulfide for high-performance all-solid-state lithium batteries

The sulfide-based solid-state electrolytes (SEs) reactivity toward moisture and Li-metal are huge barriers that impede their large-scale manufacturing and applications in all-solid-state lithium batteries (ASSLBs). Herein, we proposed an Al and O dual-doped strategy for Li3PS4 SE to regulate the chemical/electrochemical stability of anionic PS43− tetrahedra to mitigate structural hydrolysis and parasitic reactions at the SE/Li interface. The optimized Li3.08Al0.04P0.96S3.92O0.08 SE presents the highest σLi+ of 3.27 mS cm−1, which is ∼6.8 times higher than the pristine Li3PS4 and excellently inhibits the structural hydrolysis for ∼25 min @ 25% humidity at RT. DFT calculations confirmed that the enhanced chemical stability was revealed to the intrinsically stable entities, e.g., POS33− units. Moreover, Li3.08Al0.04P0.96S3.92O0.08 SE cycled stably in Li//Li symmetric cell over 1000 h @ 0.1 mA cm−2/0.1 mA h cm−2, could be revealed to Li-Al alloy and Li2O at SE/Li interface impeding the growth of Li-dendrites during cycling. Resultantly, LNO@LCO/Li3.08Al0.04P0.96S3.92O0.08/Li-In cell delivered initial discharge capacities of 129.8 mA h g−1 and 83.74% capacity retention over 300 cycles @ 0.2 C at RT. Moreover, the Li3.08Al0.04P0.96S3.92O0.08 SE presented >90% capacity retention over 200 and 300 cycles when the cell was tested with LiNi0.8Co0.15Al0.05O2 (NCA) cathode material vs. 5 and 10 mg cm−2 @ RT.

Matching silicon-based anodes with sulfide-based solid-state electrolytes for Li-ion batteries

Thanks to their high ionic conductivity and appropriate mechanical properties, sulfide-based solid electrolytes (SSE) are increasingly studied for a use in all-solid-state batteries (ASSBs). Silicon is abundant, non toxic and has a high theoretical capacity, and therefore is a promising active material in ASSBs. We first study the compatibility between two different solid electrolytes with similar ionic conductivity, Li10SnP2S12 (LSnPS) and Li6PS5Cl (LPSCl), and micron-sized silicon based anode. LPSCl appears to be less reactive than LSnPS and it is then used to determine the most appropriate silicon size and shape for efficient cycling. Two silicon materials are compared, micron-sized silicon particles (μSi) and silicon nanowires (SiNWs). Energy Dispersive X-ray spectroscopy (EDX) mapping of the composite powders shows a better dispersion of the SiNWs in the LPSCl matrix. Galvanostatic cycling and Electrochemical Impedance Spectroscopy (EIS) measurements highlight the greater compatibility of SiNWs compared to μSi in ASSBs with a high specific delithiation capacity of 2600 mAh/gSi at the first cycle, while limiting the polarization and maintaining a relatively stable lithiation mechanism during cycling.

Multifunctional Coatings on Sulfide-Based Solid Electrolyte Powders with Enhanced Processability, Stability, and Performance for Solid-State Batteries.

Sulfide-based solid-state electrolytes (SSEs) exhibit many tantalizing properties including high ionic conductivity and favorable mechanical properties for next-generation solid-state batteries. Widespread adoption of these materials is hindered by their intrinsic instability under ambient conditions, which makes them difficult to process at scale, and instability at the Li||SSE and cathode||SSE interfaces, which limits cell performance and lifetime. Atomic layer deposition is leveraged to grow thin Al2 O3 coatings on Li6 PS5 Cl powders to address both issues simultaneously. These coatings can be directly grown onto Li6 PS5 Cl particles with negligible chemical modification of the underlying material and enable exposure of powders to pure and H2 O-saturated oxygen environments for ≥4 h with minimal reactivity, compared with significant degradation of the uncoated powder. Pellets fabricated from coated powders exhibit ionic conductivities up to 2× higher than those made from uncoated material, with a simultaneous decrease in electronic conductivity and significant suppression of chemical reactivity at the Li-SSE interface. These benefits result in significantly improved room temperature cycle life at high capacity and current density. It is hypothesized that this enhanced performance derives from improved intergranular properties and improved Li metal adhesion. This work points to a completely new framework for designing active, stable, and scalable materials for next-generation solid-state batteries.

Stabilized Cathode/Sulfide Electrolyte Interface through Conformally Interfacial Nanocoating for All-Solid-State Batteries

All-solid-state lithium batteries (ASSLBs) composed of sulfide-based solid-state electrolyte and LiNixMnyCo1–x–yO2 (NMC) cathode are expected to become the promising next generation of energy storage systems due to their great potential in highly improved safety and energy density. However, the poor interfacial stability between the NMC cathode and sulfide-based electrolyte remains an important challenge for the commercialization of ASSLBs. In this study, a thin layer of fast lithium-ion conductor Li1.3Al0.3Ti1.7(PO4)3 (LATP) with a thickness of 8 nm was coated at the interface between LiNi0.8Co0.1Mn0.1O2 (NCM811) and Li5.5PS4.5Cl1.5 via a facile wet chemical method to improve interfacial stability. It has been found that the nanoscale LATP coating layer can not only accelerate lithium ions across the NCM811/Li5.5PS4.5Cl1.5 interface but also effectively alleviate the interfacial problems. The initial discharge capacity of the as-prepared LATP@NCM811/Li5.5PS4.5Cl1.5/Li batteries at 0.1 C is 151.5 mAh/g, and the capacity retention rate is 81.6% after 100 cycles at room temperature. The results indicate that interfacial modification with the nanosized LATP coating is an effective strategy for providing more possibilities for commercial application of ASSLBs.

Prospects of Sulfide-Based Solid-State Electrolytes Modified by Organic Thin Films

Lithium-ion batteries are key to tackling today’s energy crisis. In recent years, compared with the research on other components of lithium-ion batteries, the research on solid-state electrolytes is particularly hot. Among various solid-state electrolyte modification measures, we found that the material design of organic/inorganic composite flexible solid-state electrolytes can achieve the best all-solid-state battery cycling performance. Based on the study of sulfide-based organic/inorganic composite solid-state electrolytes, this article firstly introduces the classification of inorganic solid electrolytes and the advantages and disadvantages of each type of materials. At the same time, the research progress of various oxide solid electrolyte materials and sulfide solid electrolyte materials in recent years is introduced as well as the advantages of organic/inorganic composite solid-state electrolyte materials. Then the influencing factors that affect the performance of solid-state electrolytes, such as material lattice, lattice defects, electrolyte interface problems, and electrolyte microcracks, are introduced. Finally, the superiority of the industrial electrochemical performance of the organic/inorganic composite solid electrolyte material and its future prospects are introduced.

Current Status and Future Directions in Environmental Stability of Sulfide Solid-State Electrolytes for All-Solid-State Batteries

Recently, sulfide-based solid-state electrolytes (SSEs) have attracted much attention owing to their high ionic conductivity and feasible mechanical features. The environmental stability of sulfide-based SSEs is one of the critical aspects due to the possible decomposition, and ionic conductivity change will affect the fabrication and electrochemical performance of the batteries. Thus, important efforts have been made to reveal and improve their environmental stability, and a timely summary of the progress is urgently needed. In this review, we first clarify the definition of environmental stability and its significance in the context of practical use. After indicating the degradation mechanisms of sulfide-based SSEs, we summarize several effective strategies to improve their stability and also highlight the related theoretical studies. The stability of organic solvents of sulfide SSEs is also summarized and discussed, which may help reliable sulfide SSEs in the battery system. The main target of this review is to gain insights and provide useful guidance to further improve the environmental stability of sulfide SSEs, which will finally promote the commercialization of sulfide-based all-solid-state batteries.

Indium doped sulfide solid electrolyte with tamed lithium dendrite and improved ionic conductivity for all-solid-state battery applications

Sulfide solid state electrolytes capture much attention owing to their high conductivity and decent mechanical property. Nevertheless, the moisture instability and poor interfacial compatibility against lithium metal anode remain challenging and hinder the practical application. Herein, we report a novel indium (In) doping strategy based on the hard-soft-acid-base theory to tackle these issues. Optimized Li7P2.9S10.9In0.1 electrolyte exhibits a high ionic conductivity of 4.1 × 10−3 S cm−1 and achieves an enhanced interfacial compatibility. Importantly, as In partially replaces the phosphorus (P), the amount of released hydrogen sulfide can be significantly decreased and the air stability is improved. The all-solid-state battery assembled with the Li7P2.9S10.9In0.1 electrolyte demonstrates a high discharge capacity and a good cycling stability under a high current density of 1.0 C. This work provides a practical and effective method to design sulfide-based solid-state electrolyte with high ionic conductivity and enhanced air stability for all-solid-state battery applications.

Review of various sulfide electrolyte types for solid-state lithium-ion batteries

Abstract The high sulfide ion polarization is known to cause increased ionic conductivity in the solid sulfide-type electrolytes. Three groups of sulfide-based solid-state electrolytes, namely, Li-P-S, Li6PS5X (X: Cl, Br, and I), and Li x MP x S x (M: Sn, Si, and Al) were reviewed systematically from several aspects, such as conductivity, stability, and crystal structure. The advantages and disadvantages of each electrolyte were briefly considered and compared. The method of the preparation was presented with experimental and theoretical studies. The analysis that has been carried out showed that the solid electrolyte Li10GeP2S12 is superior to others with an ionic conductivity of 12 × 10−2 S cm−1. This conductivity is comparable to that of conventional liquid electrolytes. However, the availability and high price of Ge are the problems encountered. Furthermore, because sulfide-based solid electrolytes have low chemical stability in ambient humidity, their handling is restricted to inert gas environments. When solid sulfide electrolytes are hydrolyzed, structural changes occur and H2S gas is produced. The review’s objective includes presenting a complete knowledge of sulfide-solid electrolyte synthesis method, characteristics, such as conductivity, structure, and stability, as well as generating more efficient and targeted research in enhancing the performance of the chemical substance.

Excellent Cathode Interfaces Achieved by Atomic/Molecualr Layer Depositions for Sulfide-Based All-Solid-State Batteries

All-solid-state Lithium batteries (ASSLBs) are attracting a large amount of attention due to the improved safety and high energy density compared with conventional liquid electrolyte-based Li-ion batteries (LIBs). Sulfide-based solid-state electrolytes (SSEs) exhibit ultrahigh ionic conductivity up to 10-2 S cm-1 at room temperature (RT). [1] However, the interface between sulfide SSEs and oxide cathode materials is considered unstable. The reason of the poor cathode interface stability is originated form the low oxidation potential of sulfide SSEs. This causes big chemical-potential gap between sulfides and oxide cathode materials, which would cause the formation of space-charge layer and increase the interfacial impedance. [1] Additionally, the low oxidation limit of sulfides leads to severe decomposition of SSEs at the cathode interface, thus affecting the interfacial Li+ transport. Designing coating materials for cathode particles is the most common strategy to alleviate the cathode interface problems. [2]Atomic/molecular layer deposition (ALD/MLD) is an advanced film fabricating technique, capable of tuning the interface property with atomic-level thickness control at relatively low temperature (< 400 oC). Compared with the conventional wet chemical method (e.g., sol-gel method), the ALD/MLD method can not only show the ability of developing Li-containing ternary oxides and organic coatings with uniform and conformal features, but also completely avoid the negative effects of using solvents and high-temperature treatments. [2-4] In our work, we employed ALD/MLD to elaborately design LiNbOx, LiZrOx, LiPOx, and PEDOT coating materials to solve the interface problem between sulfide SSEs and oxide cathode materials. [5-8] Ion-conducting and electron-insulating ALD coating layers can prevent the interfacial side reactions and improve the Li+ transport, while the semiconductor MLD layer can suppress the interfacial degradation. Therefore, excellent performance of sulfide-based ASSLBs was obtained. Ex/in-situ synchrotron X-ray characterizations (XANES, EXAFS, STXM) were used to analyze the local structure of ALD/MLD coatings and reveal the working mechanism of designed interfaces. The flexible design of functional cathode interface realized by ALD/MLD coatings paves the way to achieve advanced sulfide-based ASSLBs. Re ferences C. Yu, F. Zhao, X. Sun*, et al. Recent Development of lithium argyrodite solid-state electrolytes for solid-state batteries: synthesis, structure, stability and dynamics. Nano Energy 2021, 83, 105858.Y. Zhao, F. Zhao, X. Sun*, et al. Atomic/molecular layer deposition for energy storage and conversion. Chem. Soc. Rev., 2021, 50, 3889-3956.Y. Zhao, X. Sun*, et al. Addressing interfacial issues in liquid-based and solid-state batteries by atomic and molecular layer deposition, Joule 2018, 2, 2583-2604.Y. Zhao, X. Sun*. Molecular Layer Deposition for Energy Conversion and Storage, ACS Energy Lett. 2018, 3, 899-914.F. Zhao, X. Sun*, et al. Tuning bifunctional interface for advanced sulfide-based all-solid-state batteries. Energy Storage Mater. 2020, 33, 139-146.C. Wang, F. Zhao, X. Sun* et al. Manipulating Interfacial Nanostructure to Achieve High-Performance All-Solid-State Lithium-Ion Batteries, Small M e thods, 2019, 3, 1900261.S. Deng, X. Sun*, et al. Dual-functional interfaces for highly stable Ni-rich layered cathodes in sulfide all-solid-state batteries Energy Storage Mater. 2020, 27, 117-123.S. Deng, X. Sun*, et al. Eliminating the Detrimental Effects of Conductive Agents in Sulfide-Based Solid-State Batteries, ACS Energy Lett. 2020, 5, 1243-1251.

Halide Solid-State Electrolytes: Synthesize and the Atmospheric Stability Study

Rechargeable all-solid-state Li batteries (ASSLBs) are considered as the next generation of electrochemical energy storage systems. Development of solid-state electrolytes (SSEs), which are key materials for ASSLBs, is therefore one of the most important subjects in modern energy storage chemistry. Thus, various types of electrolytes such as polymer-, oxide-, and sulfide-based SSEs have been developed to date and the development of new superionic conductors is still ongoing. Halide SSEs (Li-M-X, M is a metal element, and X is a halogen) are emerging as promising candidates with a number of attractive properties (oxidative stability and interfacial compatibility, etc.). [1] For example, halide SSEs show advantages including high ionic conductivity, wide electrochemical stability windows (0.36-6.71 V vs. Li/Li+), and improved chemical stability toward cathode materials compared to other SSEs. [2-4] Moreover, some of the halide SSEs (such as Li3InCl6 developed by our group) can be directly synthesized in a water solvent with the capability of large-scale production, thus removing the need for special apparatus or handling in an inert atmosphere.In this talk, (i) I will demonstrate the new and salable water-mediated synthesis method of the highly conductive Li3InCl6 halide SSE [5]. (ii) I will report the anion sublattice evolution effect on Li+ conductivity for halide SSEs [6]. I will also show the humidity stability and degradation chemistry of metal halide SSEs investigated by advanced in-situ and operando synchrotron techniques [6-7]. In the end, direct synthesis of halide SSEs on cathode materials by the water-mediated route that has been used to eliminate the interfacial challenges of ASSLBs or act as an interfacial modifier for high-performance all-solid-state Li-O2 batteries will be discussed [8-9].References X. Li, J. Liang, X. Yang, K. R. Adair, C. Wang, F. Zhao, X. Sun, Progress and Perspectives of Halide-based Lithium Conductors for All-Solid-State Lithium Batteries. Energy Environ. Sci., 2020, 13, 1429-1461. J. Liang, X. Li, S. Wang, K. R. Adair, W. Li, Y. Zhao, C. Wang, Y. Hu, L. Zhang, S. Zhao, S. Lu, H. Huang, R. Li, Y. Mo, X. Sun. Site-Occupation-Tuned Superionic LixScCl3+x Halide Solid Electrolytes for All-Solid-State Batteries. J. Am. Chem. Soc., 2020, 142, 7012-7022. X. Li, J. Liang, J. Luo, M. Banis, C. Wang, W. Li, S. Deng, C. Yu, F. Zhao, Y. Hu, T. Sham, L. Zhang, S. Zhao, S. Lu, H. Huang, R. Li, K. R. Adair, X. Sun, Air-stable Li3InCl6 electrolyte with high voltage compatibility for all-solid-state batteries, Energy Environ. Sci., 2019, 12, 2665-2671. C. Yu, Y. Li, K. R. Adair, W. Li, K. Goubitz, Y. Zhao, M. J. Willans, M. A. Thijs, C. Wang, F. Zhao, Q. Sun, S. Deng, J. Liang, X. Li, R. Li, T. Sham, H. Huang, S. Lu, S. Zhao, L. Zhang, L. Eijck, Y. Huang, X. Sun, Tuning ionic conductivity and electrode compatibility of Li3YBr6 for high-performance all solid-state Li batteries, Nano Energy, 2020, 77, 105097. X. Li, J. Liang, N. Chen, J. Luo, K. R. Adair, C. Wang, M. Banis, T. Sham, L. Zhang, S. Zhao, S. Lu, H. Huang, R. Li, X. Sun, Water-Mediated Synthesis of Superionic Halide Solid Electrolyte, Angew. Chem. Int. Ed., 2019, 58, 16427-16432. X. Li, J. Liang, K. R. Adair, J. Li, W. Li, F. Zhao, Y. Hu, T. Sham, L. Zhang, S. Zhao, S. Lu, H. Huang, R. Li, N. Chen, X. Sun, “Origin of Superionic Li3Y1-xInxCl6 Halide Solid-Electrolytes with High Humidity Tolerance” Nano Lett., 2020, 20, 4384-4392. W. Li, J. Liang, M. Li, K. Adair, X. Li, Y. Hu, Q. Xiao, R. Feng, R. Li, L. Zhang, S. Lu, H. Huang, S. Zhao, T. Sham, X. Sun, Unraveling the Origin of Air Stability of Halide Solid-State Electrolytes by In situ and Operando Synchrotron X-ray analytical techniques, Chem. Mater., 2020, 32, 7019–7027. C. Wang, J. Liang, M. Jiang, X. Li, S. Mukherjee, K. Adair, M. Zheng, Y. Zhao, F. Zhao, S. Zhang, R. Li, H. Huang, S. Zhao, L. Zhang, S. Lu, C. Singh, X. Sun, Interface-Assisted In-situ Growth of Halide Electrolytes Eliminating Interfacial Challenges of All-Inorganic Solid-State Batteries. Nano Energy, 2020, 76, 105015. C. Zhao, J. Liang, X. Li, N. Holmes, C. Wang, J. Wang, F. Zhao, S. Li, Q. Sun, X. Yang, J. Liang, X. Lin, W. Li, R. Li, S. Zhao, H. Huang, L. Zhang, S. Lu, X. Sun, Halide-based solid-state electrolyte as an interfacial modifier for high performance solid-state Li–O2 batteries. Nano Energy, 2020, 75, 105036.

High-Performance Sulfide-based Solid-state Electrolytes and Interfaces for All-solid-state Li Batteries

All-solid-state Lithium metal batteries (ASSLMBs) cannot only maximize the energy density, but also show improved safety compared with the conventional liquid electrolyte-based Li-ion batteries. Solid-state electrolytes (SSEs), as the most important component in the ASSLMBs, can determine the electrochemical performance. High ionic conductivity is one of the most basic requirements for an excellent SSE. Sulfide-based SSEs exhibit ultrahigh ionic conductivity (> 10-2 S cm-1 at room temperature) that can be comparable to the liquid electrolytes, making this kind of SSEs popular and promising.1 However, air sensitivity and Li metal incompatibility are two major obstacles, which are together with the problematic cathode interface, hindering the development of sulfide SSEs for practical ASSLMBs.2, 3 In our work, we employed the strategy of element substitution to design F-substituted Li6PS5Cl, Sn-substituted Li6PS5I, and Sn-substituted Li3PS4 as high-performance Li-metal compatible sulfide SSEs.4-6 Using these element doping SSEs can derive functional interphases that contain LiF, LiI, and Li-Sn alloy, respectively. These interfacial contents were demonstrated as important to achieve stable Li plating/stripping. Importantly, we found that replacing P with Sn could significantly improve the air stability and ionic conductivity at the same time. The high reaction energy between the Sn-substituted PS4 tetrahedra and moisture was regarded as the main reason for the improved air stability, while the expanded unit cell and increased Li+ concentration led to superior ionic conductivity. Our modifications on various common-used sulfide SSEs with multi-function elements provide more choices of sulfide SSEs for practical ASSLMBs. At the cathode side,7-10 we used interface modification (coating strategy) to improve the interfacial Li+ transport and chemical inertness. Thus, excellent electrochemical performance was achieved. Re ferences N. Kamaya, R. Kanno*, et al. A lithium superionic conductor, Nat. Mater. 2011, 10, 682-686.C. Yu, F. Zhao, X. Sun*, et al. Recent Development of lithium argyrodite solid-state electrolytes for solid-state batteries: synthesis, structure, stability and dynamics. Nano Energy, 2021, 83, 105858.Y. Zhao, F. Zhao, X. Sun*, et al. Atomic/molecular layer deposition for energy storage and conversion. Chem. Soc. Rev., 2021, 50, 3889-3956.F. Zhao, X. Sun*, et al. Ultrastable anode interface achieved by fluorinating electrolytes for all-solid-state Li metal batteries, ACS Energy Lett. 2020, 5, 1035-1043F. Zhao, X. Sun*, et al. A Versatile Sn-Substituted Argyrodite Sulfide Electrolyte for All-Solid-State Li Metal Batteries, Adv. Energy Mater. 2020, 10, 1903422.F. Zhao, X. Sun*, et al. An Air-Stable and Li-Metal-Compatible Glass-Ceramic Electrolyte enabling High-Performance All-Solid-State Li-Metal Batteries. Adv. Mater. 2021, 33, 2006577.F. Zhao, X. Sun*, et al. Tuning bifunctional interface for advanced sulfide-based all-solid-state batteries. Energy Storage Mater. 2020, 33, 139-146.C. Wang, F. Zhao, X. Sun* et al. Manipulating Interfacial Nanostructure to Achieve High-Performance All-Solid-State Lithium-Ion Batteries, Small Methods, 2019, 3, 1900261.S. Deng, X. Sun*, et al. Dual-functional interfaces for highly stable Ni-rich layered cathodes in sulfide all-solid-state batteries Energy Storage Mater. 2020, 27, 117-123.S. Deng, X. Sun*, et al. Eliminating the Detrimental Effects of Conductive Agents in Sulfide-Based Solid-State Batteries, ACS Energy Lett. 2020, 5, 1243-1251.

Current status and future directions of all-solid-state batteries with lithium metal anodes, sulfide electrolytes, and layered transition metal oxide cathodes

All-solid-state batteries (ASSBs) offer great promise as a next-generation energy storage technology with higher energy density, wider operating temperature range, and improved safety for electric vehicles. ASSBs employing lithium metal anodes (Li), sulfide-based solid-state electrolytes (SSE), and Ni-rich layered transition metal oxide cathodes (LiMO 2 , M = Ni, Mn, Co, Al) are particularly promising due to its superior electrochemical performance compared to other solid-electrolyte systems. However, the battery cycle life at high cathode mass loading and high current is still limited because the failure mechanism is not fully understood. Lithium dendrite growth at the anode or inside a solid electrolyte still represents as a serious risk of cell failure. Interfacial resistance increases attributed to electrolyte decomposition and interfacial void formation at both cathode−electrolyte and anode−electrolyte interfaces lead to gradual capacity fading. In this Review, we present the fundamental challenges and recent scientific understandings of each component in ASSBs. The novel diagnostic tools for these components, especially the interfaces buried under the surface that are often hard for characterization are mainly examined. Finally, we offer a perspective for future research directions. We hope this Review will provide a timely snapshot of state-of-the-art research progress in ASSBs to accelerate the development of ASSBs. • Progress and challenges of lithium metal anodes, sulfide electrolytes, and layered ternary oxide cathodes in solid-state batteries. • Origins of the failures in lithium metal anodes, Li-electrolyte interface, sulfide electrolytes, electrolyte-cathode interface, and layered metal oxide cathodes. • Summarize the state-of-the art diagnostic tools for investigating interfaces buried under the surface. • Future research directions for the solid-state battery architectures.

Metal Halide Superionic Conductors for All-Solid-State Batteries.

ConspectusRechargeable all-solid-state Li batteries (ASSLBs) are considered to be the next generation of electrochemical energy storage systems. The development of solid-state electrolytes (SSEs), which are key materials for ASSLBs, is therefore one of the most important subjects in modern energy storage chemistry. Various types of electrolytes such as polymer-, oxide-, and sulfide-based SSEs have been developed to date and the discovery of new superionic conductors is still ongoing. Metal-halide SSEs (Li-M-X, where M is a metal element and X is a halogen) are emerging as new candidates with a number of attractive properties and advantages such as wide electrochemical stability windows (0.36-6.71 V vs Li/Li+) and better chemical stability toward cathode materials compared to other SSEs. Furthermore, some of the metal-halide SSEs (such as the Li3InCl6 developed by our group) can be directly synthesized at large scales in a water solvent, removing the need for special apparatus or handling in an inert atmosphere. Based on the recent advances, herein we focus on the topic of metal-halide SSEs, aiming to provide a guidance toward further development of novel halide SSEs and push them forward to meet the multiple requirements of energy storage devices.In this Account, we describe our recent progress in developing metal halide SSEs and focus on some newly reported findings based on state-of-the-art publications on this topic. A discussion on the structure of metal-halide SSEs will be first explored. Subsequently, we will illustrate the effective approaches to enhance the ionic conductivities of metal halide SSEs including the effect of anion sublattice framework, the regulation of site occupation and disorder, and defect engineering. Specifically, we demonstrated that proper structural framework, balanced Li+/vacancy concentration, and reduced blocking effect can promote fast Li+ migration for metal halide SSEs. Moreover, humidity stability and degradation chemistry of metal halide SSEs have been summarized for the first time. Some examples of the application of metal halide SSEs with stability toward humidity have been demonstrated. Direct synthesis of halide SSEs on cathode materials by the water-mediated route has been used to eliminate the interfacial challenges of ASSLBs and has been shown to act as an interfacial modifier for high-performance all-solid-state Li-O2 batteries. Taken together, this Account on metal halide SSEs will provide an insightful perspective over the recent development and future research directions that can lead to advanced electrolytes.

Micromechanism in All-Solid-State Alloy-Metal Batteries: Regulating Homogeneous Lithium Precipitation and Flexible Solid Electrolyte Interphase Evolution.

Sulfide-based solid-state electrolytes (SSEs) matched with alloy anodes are considered as promising candidates for application in all-solid-state batteries (ASSBs) to overcome the bottlenecks of the lithium (Li) anode. However, an understanding of the dynamic electrochemical processes on alloy anode in SSE is still elusive. Herein, in situ atomic force microscopy gives insights into the block-formation and stack-accumulation behaviors of Li precipitation on an Li electrode, uncovering the morphological evolution of nanoscale Li deposition/dissolution in ASSBs. Furthermore, two-dimensional Li-indium (In) alloy lamellae and the homogeneous solid electrolyte interphase (SEI) shell on the In electrode reveal the precipitation mechanism microscopically regulated by the alloy anode. The flexible and wrinkle-structure SEI shell further enables the electrode protection and inner Li accommodation upon cycles, elucidating the functional influences of SEI shell on the cycling behaviors. Such on-site tracking of the morphological evolution and dynamic mechanism provide an in-depth understanding and thus benefit the optimizations of alloy-based ASSBs.

A novel air-stable Li7Sb0.05P2.95S10.5I0.5 superionic conductor glass-ceramics electrolyte for all-solid-state lithium-sulfur batteries

The blend of air stability and high lithium-ion (Li+) conductivity is not a simplistic approach to attain for sulfide-based solid-state electrolytes (SSEs), which hinders the exploitation of high energy all-solid-state lithium-sulfur batteries (ASSLSBs). Herein we report a novel lithium superionic conductor of Li7Sb0.05P2.95S10.5I0.5 as solid-state glass-ceramics electrolytes obtained by an annealing treatment in a solid-state reaction route. It systematically explores the impact of facile aliovalent dual doping into the newly synthesized solid electrolytes, which have influenced higher Li+ conductivity of 2.55 × 10−3 Scm−1 at room temperature, and wide range of voltage stability vs. Li/Li+ up to 7 V. Except that, an activation barrier of Li7Sb0.05P2.95S10.5I0.5 for Li+ migration drops expressively due to optimizing the dopant contents, and subsequently defects produced. The electrolyte also achieved significant air stability based on Hard and Soft Acid/Base (HSAB) theory. The intrinsic structural aspects of the air stability for Li7P3S11 and Li7Sb0.05P2.95S10.5I0.5 solid-state electrolytes are premeditated using a combination of ex-situ X-ray photoelectron spectroscopy, XRD as well as Raman spectroscopy and SEM. The Li2S-VGCF-SSE composite cathode with Li7Sb0.05P2.95S10.5I0.5 SSE exhibited a high initial discharge capacity of 622.3 mAhg−1 at 0.060 mAcm−2, and ASSLSB was retained over 683.3 mAh g−1 after 15th cycle at room temperature, better than pristine Li7P3S11 SSE-based cell. This research provides a novel concept on the design of air-stable and superionic conductor solid-state electrolytes for high-performance ASSLSBs.