Glassy Solid Electrolytes Research Articles

Inverted Glasses As Ductile Lithium Ion Conductors for Solid State Batteries

Inorganic electrolytes for solid state batteries with Li metallic anodes must combine properties such as high ionic conductivity, chemical stability, and resistance to failure due to propagation of Li dendrites. Abundance of experimental evidence suggests that cracking of the solid electrolytes due to pressure exerted by lithium plating into the material defects is the primary source of failure [1]. This is due to inherent brittleness of the ceramic ionic conductors, i.e. their inability to reduce stress by means other than fracture. Unlike ceramics, plastic deformation in glass can be achieved via shear and (or) by densification. Both mechanisms can be operational in glasses with reduced content of glass formers relative to the content of glass modifiers – i.e. inverted glasses. Using the example of lithium phosphorous oxynitride, Lipon, we demonstrate how these two mechanisms are capable of accommodating applied stress while avoiding creation of new surfaces by cracking. We investigate the resistance to fracture in Lipon-like glasses and the underlying connection to their composition via instrumented nano-indentation, Raman spectroscopy, and numerical simulations. We observe enhancement of isochoric shear with increase of Li content, similarly to the reports of increased plasticity in sodium aluminoborate glases with high alkali content [2]. Nano-indentation demonstrates that Lipon is extremely resistant to fracture, compared to other inorganic solid electrolytes [3].[1] Porz, T. Swamy, B.W. Sheldon, D. Rettenwander, T. Fromling, H.L. Thaman, S. Berendts, R. Uecker, W.C. Carter, Y.-M. Chiang, Mechanism of lithium metal penetration through inorganic solid electrolytes. Adv. Energy Mater. 7, 1701003 (2017)[2] Sellappan, T. Rouxel, F. Celarie, E. Becker, P. Houizot, R. Conradt, Composition dependence of indentation deformation and indentation cracking in glass. Acta Mater. 61, 5949–5965 (2013)[3] Kalnaus, A. Westover, M. Kornbluth, E.J. Herbert, N.J. Dudney, Resistance to fracture in the glassy solid electrolyte Lipon. J. Mater. Research, 36, 787-795 (2021)

Structure and Properties of Na2S-SiS2-P2S5-NaPO3 Glassy Solid Electrolytes.

In the development of sodium all-solid-state batteries (ASSBs), research efforts have focused on synthesizing highly conducting and electrochemically stable solid-state electrolytes. Glassy solid electrolytes (GSEs) have been considered very promising due to their tunable chemistry and resistance to dendrite growth. For these reasons, we focus here on the atomic-level structures and properties of GSEs in the compositional series (0.6-0.08y)Na2S + (0.4 + 0.08y)[(1 - y)[(1 - x)SiS2 + xPS5/2] + yNaPO3] (NaPSiSO). The mechanical moduli, glass transition temperatures, and temperature-dependent conductivity were determined and related to their short-range order structures that were determined using Raman, Fourier transform infrared, and 31P and 29Si magic angle spinning nuclear magnetic resonance spectroscopies. In addition, the conductivity activation energies were modeled using the Christensen-Martin-Anderson-Stuart model. These GSEs appear to be highly crystallization-resistant in the supercooled liquid region where no measurable crystallization below 450 °C could be observed in differential scanning calorimetry studies. Additionally, these GSEs were found to be highly conducting, with conductivities on the order of 10-5 (Ω cm)-1 at room temperature, and processable in the supercooled state without crystallization. For all these reasons, these NaPSiSO GSEs are considered to be highly competitive and easily processable candidate GSEs for enabling sodium ASSBs.

Insight of transport properties of glassy solid electrolytes for energy storage applications

The goal of developing battery systems has attracted researchers' attention for about 30 years, almost since the development of primary electrochemical systems with a lithium anode. To realize the benefits of lithium ion batteries (LIBs) and lithium metal anode batteries, several important issues need to be addressed. The use of liquid non-aqueous electrolytes based on aprotic solvents in lithium battery systems certainly offers advantages over traditional battery systems. However, due to the relatively low evaporation temperatures and high flammability of solvents, liquid electrolytes significantly limit the operating range of battery systems in the high-temperature range. Special measures are required to ensure the safe operation of a lithium-ion battery system. The use of inorganic solid electrolytes (SEs) is one of the most promising directions for improving lithium-ion and solid-state battery systems. The use of SEs will enable the safe cycling of battery systems with both lithium electrodes and intercalation anodes, significantly extend the temperature range of battery operation towards high temperatures and enable the creation of battery systems of new sizes and designs. The development of new solid oxide salt materials and technologies to produce battery systems with electrolytes based on them is an urgent task to solve the above problems.

Elucidating the Role of Anion Groups in Lithium-Ion Diffusion

Since the 1960s, the paddlewheel effect has been proposed as a way to enhance lithium-ion diffusion in inorganic materials by using rotor-like anion groups to assist lithium-ion movement(1–5). However, so far the physical mechanism behind how anion-group dynamics affect lithium-ion diffusion has not been clearly understood. In this talk, we clearly define various types of rotational motions of anion-groups. Based on such definition, we detect and differentiate such distinct anion-group rotational motions throughout a total of 10’s of ns ab-initio molecular dynamics trajectories. By performing rigorous statistical analysis of various rotational events as well as lithium-ion diffusion events, we reveal how each type of anion rotational motions are related to lithium-ion diffusion. Our research has finally resolved the ongoing debate about the existence of the paddlewheel effect and provide a clear physical understanding of how anion-group rotations are related to fast ionic diffusion in inorganic materials. L. Karlsson, R. L. McGreevy, Mechanisms of ionic conduction in Li2SO4 and LiNaSO4: Paddle wheel or percolation? Solid State Ionics. 76, 301–308 (1995).A. Kvist, A. Lundén, Electrical Conductivity of Solid and Molten Lithium Sulfate. Zeitschrift Für Naturforschung. 20, 235–238 (1965).Z. Zhang, L. F. Nazar, Exploiting the paddle-wheel mechanism for the design of fast ion conductors. Nat Rev Mater, 1–17 (2022).J. G. Smith, D. J. Siegel, Low-temperature paddlewheel effect in glassy solid electrolytes. Nat Commun. 11, 1483 (2020).M. Jansen, Volume Effect or Paddle‐Wheel Mechanism—Fast Alkali‐Metal Ionic Conduction in Solids with Rotationally Disordered Complex Anions. Angewandte Chemie Int Ed Engl. 30, 1547–1558 (1991).

Amorphous Chloride Solid Electrolytes with High Li-Ion Conductivity for Stable Cycling of All-Solid-State High-Nickel Cathodes.

Solid electrolytes (SEs) are central components that enable high-performance, all-solid-state lithium batteries (ASSLBs). Amorphous SEs hold great potential for ASSLBs because their grain-boundary-free characteristics facilitate intact solid-solid contact and uniform Li-ion conduction for high-performance cathodes. However, amorphous oxide SEs with limited ionic conductivities and glassy sulfide SEs with narrow electrochemical windows cannot sustain high-nickel cathodes. Herein, we report a class of amorphous Li-Ta-Cl-based chloride SEs possessing high Li-ion conductivity (up to 7.16 mS cm-1) and low Young's modulus (approximately 3 GPa) to enable excellent Li-ion conduction and intact physical contact among rigid components in ASSLBs. We reveal that the amorphous Li-Ta-Cl matrix is composed of LiCl43-, LiCl54-, LiCl65- polyhedra, and TaCl6- octahedra via machine-learning simulation, solid-state 7Li nuclear magnetic resonance, and X-ray absorption analysis. Attractively, our amorphous chloride SEs exhibit excellent compatibility with high-nickel cathodes. We demonstrate that ASSLBs comprising amorphous chloride SEs and high-nickel single-crystal cathodes (LiNi0.88Co0.07Mn0.05O2) exhibit ∼99% capacity retention after 800 cycles at ∼3 C under 1 mA h cm-2 and ∼80% capacity retention after 75 cycles at 0.2 C under a high areal capacity of 5 mA h cm-2. Most importantly, a stable operation of up to 9800 cycles with a capacity retention of ∼77% at a high rate of 3.4 C can be achieved in a freezing environment of -10 °C. Our amorphous chloride SEs will pave the way to realize high-performance high-nickel cathodes for high-energy-density ASSLBs.

Mechanistic Study of Lithium Electrodeposition Using Dynamic Electrochemical Impedance Spectroscopy

Lithium metal batteries have increased energy density over standard graphite-based Li-ion anodes. However, Li metal anodes have difficulty forming stable passivation layer (called solid electrolyte interphase, SEI) leading to poor use of Li inventory. That is, LI metals require larger cathode loading, which reduces the energy density gain. A holistic approach to Li anode incorporation includes electrolyte design, mechanism understanding, and battery engineering. A factor that has not been fully appreciated is the nature of the Lithium metal itself, namely its SEI before incorporation into the battery device may affect the subsequent SEI formation. Here, we present a mechanistic study on lithium SEI formation on various lithium sources, as well as the Li cycling.We utilized dynamic impedance spectroscopy (dEIS) to probe the formation and evolution of the SEI during Li cycling of various Li sources. dEIS superimposes a multisine waveform atop the dc stimulus signal. After applying a sliding window FFT protocol that takes the complex ratio of the measured potential and current signals time-resolved complex impedance can be obtained. We will discuss the differences between the Li cycling profiles using Lipon (a glassy solid electrolyte) and a liquid electrolyte. We will relate the differences in cycling performance, particularly the SEI evolution to the surface chemistry of the as-received Li metal source.The US Department of Energy's Energy Efficiency and Renewable Energy Vehicles Technologies Office provided funding for this work under the US-German Cooperation on Energy Storage: Lithium-Solid-Electrolyte Interfaces program.

Controlling factor for fracture resistance and ionic conduction in glassy lithium borophosphate electrolytes

Glasses are promising candidates as solid electrolytes for all-solid-state batteries due to their isotropic ionic conduction, formability, as well as high chemical, thermal and electrochemical stability. However, their mechanical properties and ionic conductivity need to be improved. Here, based on molecular dynamics simulations and classification-based machine learning, we reveal that both fracture behavior and ionic conduction in glassy lithium borophosphate electrolytes are encoded in their static structures. By systematically varying the Li and B content, we demonstrate that the machine learning-based structural descriptor termed “softness” can be used as an indicator for both fracture resistance and ionic conductivity. The “softness” metric is calculated from the static local atomic environment, but well captures the long-term dynamics of individual atoms. Notably, the propensities for B atoms to undergo bond-switching (correlated with fracture) and for Li ions to migrate (correlated with ionic conductivity) increase with an increase in atomic softness. Specifically, the out-of-equilibrium interaction of B and Li with oxygen neighbors enhances the propensity for B and Li to undergo bond-switching or rearrangement when experiencing stimuli. These results enable finding the optimum chemical compositions for glassy solid electrolytes with high mechanical stability and high ionic conductivity.

Structure‐mechanical properties correlation in bulk LiPON glass produced by nitridation of metaphosphate melts

AbstractThe glassy solid electrolyte Lithium phosphorous oxynitride (LiPON) has been widely researched in thin film solid state battery format due to its outstanding stability when cycled against lithium. In addition, recent reports show thin film LiPON having interesting mechanical behaviors, especially its ability to resist micro‐scale cracking via densification and shear flow. In the present study, we have produced bulk LiPON glasses with varying nitrogen contents by ammonolysis of LiPO3 melts. The resulting compositions were determined to be LiPO3‐3z/2Nz, where 0 ≤ z ≤ 0.75, and the z value of 0.75 is among the highest ever reported for this series of LiPON glasses. The short‐range order structures of the different resulting compositions were characterized by infrared, Raman, 31P magic angle spinning nuclear magnetic resonance, and X‐ray photoelectron spectroscopies. Instrumented nano‐indentation was used to measure mechanical properties. It was observed that similar to previous studies, both trigonally coordinated (Nt) and doubly bonded (Nd) N co‐exist in the glasses in about the same amounts for z ≤ 0.36, the limit of N content in most previous studies. For glasses with z > 0.36, it was found that the fraction of the Nt increased significantly while the fraction of Nd correspondingly decreased. The incorporation of nitrogen increased both the elastic modulus and hardness of the glass by approximately a factor of 1.5 when N/P ratio reaches 0.75. At the same time, an apparent embrittlement of the glass was observed due to nitridation, which was revealed by nanoindentation with an extra sharp nanoindenter tip.

Optimized Thin Film Processing of Sodium Mixed Oxy-Sulfide-Nitride Glassy Solid Electrolytes for All-Solid-State Batteries

Na4P2S7–6xO4.62xN0.92x (NaPSON) glassy solid electrolytes (GSEs) were prepared and tested for their electrochemical properties and processability into thin films. The x = 0.2 composition (NaPSON-2) was found to be highly conducting, non-crystallizable, largely stable against Na-metal, and supports symmetric cell cycling up to >100 μA cm–2 without shorting. For these reasons, it was processed into thin films drawn to 50 μm and tested in symmetric and asymmetric cells. Measurements of the sodium ion conductivity using symmetric cells demonstrated that the conductivity of NaPSON-2 was unchanged by film forming. Galvanostatic cycling at 5 μA cm–2 of a 1.3 mm thick disc of NaPSON-2 showed stability over 450 h, while cycling a 50 μm thin film of NaPSON-2 showed a very slow growth in the resistance. Cyclic voltammetry and X-ray photoelectron spectroscopy of the NaPSON-2 thin film GSE revealed that it did not react with Na-metal at its surface, but rather in the bulk of the film, showing S, Na2S, and Na3P reaction products. The source of the surface stability was determined to be the preferential segregation of trigonally coordinated nitrogen. These low-cost and easily processed NaPSON GSEs provide a system of materials that could provide for significantly lower cost higher energy density grid-scale batteries.

Effects of LiPON Incorporation on the Structures and Properties of Mixed Oxy-Sulfide-Nitride Glassy Solid Electrolytes.

Glassy solid electrolytes (GSEs) are promising solid electrolytes in the development of all solid-state batteries. Mixed oxy-sulfide nitride (MOSN) GSEs combine the high ionic conductivity of sulfide glasses, the excellent chemical stability of oxide glasses, and the electrochemical stability of nitride glasses. However, the reports on the synthesis and characterization of these novel nitrogen containing electrolytes are quite limited. Therefore, the systematic incorporation of LiPON during glass synthesis was used to explore the effects of nitrogen and oxygen additions on the atomic-level structures in the glass transition (Tg) and crystallization temperature (Tc) of MOSN GSEs. The MOSN GSE series 58.3Li2S + 31.7SiS2 + 10[(1 - x)Li0.67PO2.83 + x LiPO2.53N0.314], x = 0.0, 0.06, 0.12, 0.2, 0.27, 0.36, was prepared by melt-quench synthesis. Differential scanning calorimetry was used to determine the Tg and Tc values of these glasses. Fourier transformation-infrared, Raman, and magic angle spinning nuclear magnetic resonance spectroscopies were used to examine the short-range order structures of these materials. X-ray photoelectron spectroscopy was conducted on the glasses to further understand the bonding environments of the doped nitrogen. Finally, N and S elemental analyses were used to confirm the composition of these GSEs. These results are used to elucidate the structure of these glasses and to understand the thermal property impact oxygen and nitrogen doping in these GSEs.

Sustainable synthesis of SiS2 for solid-state electrolytes by cascaded metathesis

Sulfide-based electrolytes containing silicon offer high ionic conductivity and are employed in emerging solid-state batteries that are promising for electric vehicles due to their improved energy density and safety. However, their deployment is constrained by the high cost and low availability of the SiS2 precursor. Here we introduce a green, solution-based synthesis of SiS2 through coupled metathesis reactions. First, the key Li2S precursor is synthesized from the room-temperature reaction between abundant Na2S and LiCl in ethanol. Next, the Li2S is recovered from solution and combined with SiCl4 in ethyl acetate to form a SiS2 solution and regenerate LiCl. The synthesized Li2S and SiS2 are characterized and then combined to form a glassy solid electrolyte with a conductivity of 0.11 mS cm-1 at 30 °C, validating the utility of metathesis-derived metal sulfides to solid electrolyte synthesis. In this cascaded metathesis scheme the expensive components, LiCl and solvents, are recovered and recycled in a circular economy. The cascaded metathesis process can in principle be used to synthesize nearly any metal sulfide of interest to a wide range of applications including energy conversion/storage, catalysis, electronics, and optics.

Inorganic–organic hybrid solid electrolytes in the tetramethylammonium iodide–LiI–Li2S–P2S5 system for all-solid-state lithium batteries

A new type of glassy solid electrolyte was prepared by doping tetramethylammonium iodide (TMAI) in Li7P2S8I. TMAI can suppress the large volume change of a Si electrode during cycling.

Cover Feature: Grain‐Boundary‐Free Glassy Solid Electrolytes based on Sulfide Materials: Effects of Oxygen and Nitrogen Doping on Electrochemical Performance (Batteries & Supercaps 11/2022)

The Cover Feature illustrates the amorphous nature of fast ion conducting mixed oxy-sulfide-nitride glassy solid-state electrolytes synthesized through melt quenching. The grain-boundary-free nature of the monolithic glass, combined with the stability improvements from oxygen and nitrogen doping, allows for high current rates without shorting due to dendrite growth. More information can be found in the Research Article by S. W. Martin and co-workers.

Development and Optimization of Composite Cathode Materials for Use with Thin-Film Glassy Solid Electrolytes in Solid-State Batteries

The electrochemical properties and thermal behavior of thin-film glassy solid electrolytes (GSE) in the [Li2S - SiS2 - LiPO3] system make them viable candidates for inclusion in solid-state batteries. To properly assess these electrolytes in the full-cell format, compatible composite cathode materials must be developed. These materials must be electronically and ionically conductive, and form a stable interface in contact with the GSE. A composite blend of redox-active lithium iron phosphate (LiFePO4), a mixed-oxy-sulfide glassy electrolyte, carbon nanotubes, a lithium solvate ionic liquid (SIL), and styrene butadiene rubber binder (SBR) was utilized to create the cathode material. Mixing time and order of component mixing were controlled in order to optimize for ionic and electronic conductivities within the bulk composite powder. With the addition of the SIL and SBR, a composite cathode blend capable of stably cycling in contact with the GSE was created.

Preparation of Li-Si-P-S-O-N Glasses: The Impact of Lipon Incorporation on Ionic Conductivity

Lithium glassy solid electrolytes (GSEs) are an alternative to liquid electrolytes in the development of solid-state batteries. Mixed oxy-sulfide nitride GSEs incorporate the useful properties of sulfide glasses, which show high ionic conductivity, of oxide glasses which display excellent chemical stability, and of nitride glasses which exhibit good electrochemical stability. In our investigation of these new GSEs, the following compositional series was explored Li2S + SiS2 + [(1-x)Li0.67PO2.83 + xLiPON]. Differential scanning calorimetry (DSC) was employed to determine the crystallization and glass temperatures of these GSEs. In addition, electrochemical impedance spectroscopy (EIS) was used to determine the temperature-dependent ionic conductivity of theses GSEs. X-ray Photoelectron Spectroscopy (XPS) was conducted on the glasses to further understand the chemical bonding environment of nitrogen. It was found that x = 0.2 displayed the highest ionic conductivity suggesting that nitrogen incorporation can be used to optimize mixed oxy-sulfide glasses.Support of this research by NSF Grant NSF-DMR-1936913 is acknowledged.

(Invited) How Does One Enable High Energy Li Metal Batteries a Case Study with Lipon

The next generation of high energy batteries using Li metal as an anode and utilizing a solid electrolyte requires good interfacial stability, reasonable ionic conductivity, and most importantly the ability to eliminate dendrites.i While most solid-state electrolytes suffer from both interfacial instability and Li penetration resulting in cell shorting,ii,iii The solid electrolyte Lipon has a remarkable ability to suppress dendrites, and enable solid state batteries that can cycle for more than 1000 cycles and support current densities as high as 10 mA/cm2.iii,iv Recent efforts have started to illuminate the origin of Lipon’s ability to enable high-energy solid-state Li metal batteries. This presentation will highlight the unique structure of Lipon and Lipon like materials, the interfacial structure of Lipon with Li metal, and the mechanics that enable high quality performance in Lipon based solid-state batteries.v,vi,vii Finally, the presentation will connect these findings from Lipon to outline key underlying principles that answer the question, how do we enable high energy Li metal batteries? Acknowledgements: Work for this presentation was funded by ARPA-E under contract #DE-AR0000775, and the US Department of Energy Office of Energy Efficiency and Renewable Energy for the Vehicle Technologies Office’s US-German Cooperation on Energy Storage: Interfaces and Interphases In Rechargeable Li-metal based Batteries Program and the Battery Materials Research Program under program managers Tien Duong and Simon Thompson. P. Albertus et al., “Challenges for and pathways toward Li-metal-based all-solid-state batteries”, ACS Energy Letters, 6, 4, 1399-1404, Mar. 2021.Fudong Han, Andrew S Westover, Jie Yue, Xiulin Fan, Fei Wang, Miaofang Chi, Donovan N Leonard, Nancy J Dudney, Howard Wang, Chunsheng Wang, “High electronic conductivity as the origin of lithium dendrite formation within solid electrolytes”, Nature Energy, 1, Jan. 2019. Andrew S Westover, Nancy J Dudney, Robert L Sacci, Sergiy Kalnaus, “Deposition and Confinement of Li Metal along an Artificial Lipon–Lipon Interface”, ACS Energy Letters, 4, 651-655, Feb. 2019.Juchuan Li, Cheng Ma, Miaofang Chi, Chengdu Liang, and Nancy J. Dudney. "Solid electrolyte: the key for high‐voltage lithium batteries." Advanced Energy Materials5, 4, 1401408, 2015. Andrew S Westover* Valentina Lacivita,* , Andrew Kercher, Nathan D Phillip, Guang Yang, Gabriel Veith, Gerbrand Ceder, Nancy J Dudney, “Resolving the amorphous structure of lithium phosphorus oxynitride (Lipon)”, Journal of the American Chemical Society 140 (35), 11029-11038, July 2018. Andrew S Westover, Robert L Sacci, Nancy Dudney, “Electroanalytical measurement of interphase formation at a Li metal–solid electrolyte interface”, ACS Energy Letters, 5, 12, 3860-3867, Nov. 2020.Sergiy Kalnaus, Andrew S Westover, Mordechai Kornbluth, Erik Herbert, Nancy J Dudney, “Resistance to fracture in the glassy solid electrolyte Lipon”, Journal of Materials Research, 36, 4, 787-796, Feb. 2021.

Electrochemical Characterization of a Drawn Thin-Film Mixed Oxy-Sulfide Glassy Electrolyte Material for Solid-State Battery Applications

Solid-state batteries are a promising avenue for next-generation lithium-ion batteries due to their enabling of the lithium metal anode, while simultaneously removing the flammable organic electrolyte. Glassy materials are particularly interesting as solid-state electrolytes due to their intrinsic lack of grain boundaries, their low temperature forming capabilities, and their highly tunable chemistries. Much work has been done to study the electrochemical properties of glasses in the Li2S – SiS2 – LixMOy phase space, and several compositions have shown high ionic conductivities (~ 10-3 S/cm), large electrochemical stability windows (0-5 V vs. Li/Li+), and good glass forming ability. These glasses, however, have not been well studied at thicknesses that are viable for commercialization of solid electrolytes (< 100 μm). Utilizing a glass working method known as the redraw process, a rectangular preform of glass can be reheated and drawn from ~ 5 mm in thickness to thin films of less than 100 μm. The electrochemical behavior of thin-film glasses in the Li2S – SiS2 – LiPO3 phase space created through the glass redraw process are studied utilizing electrochemical impedance spectroscopy, cyclic voltammetry, and galvanostatic symmetric cell cycling. These results show that thin-film glassy solid electrolytes made through the glass redraw method are a viable new research direction for generation of highly conducting thin-film solid-state electrolytes.

Grain‐Boundary‐Free Glassy Solid Electrolytes based on Sulfide Materials: Effects of Oxygen and Nitrogen Doping on Electrochemical Performance

AbstractWhile much of the current research on glassy solid electrolytes (GSEs) has focused on the binary Li2S+P2S5 system, compositions with Si are of interest because Si promotes stronger glass formation and allows low‐cost melt‐quenching (MQ) synthesis under ambient pressure. Another advantage is that they can be formed in homogeneous and continuous glass forms, as a result they are free of grain boundaries. In this work, we have examined the structures and electrochemical properties of bulk glass pieces of sulfide and oxy‐sulfide GSE compositions and have also expanded the study by using LiPON glass as a dopant to produce an entirely new class of nitrogen doped mixed oxy‐sulfide nitride (MOSN) GSEs. Upon doping with oxygen and nitrogen, the solid electrolyte interface (SEI) is stabilized and the doped MOSN GSE exhibits a critical current density (CCD) of 1.8 mA cm−2 at 100 °C. We also report on improving the glass quality, the SEI engineering and its limitations, and future plans of improving the electrochemical performance of these homogeneous MQ MOSN GSEs. These fundamental results can help to understand the structures and doping effects of the bulk GSEs, and as such can provide a guide to design improved homogeneous grain‐boundary‐free GSEs.

Cation-assisted lithium ion diffusion in a lithium oxythioborate halide glass solid electrolyte

Due to their absence of grain boundaries that limit Li ion transport and provoke dendritic growth, glass materials are considered promising solid electrolytes for all-solid-state lithium batteries. However, understanding of ion transport in glassy solid electrolytes is limited on account of their disordered structure. This study reports the Li ion diffusion mechanism in lithium oxythioborate halide (Li2S–B2S3–LiI–SiO2) quaternary glasses with different SiO2 contents. Oxygen in the glass can increase and decrease Li ion conductivity by collapsing local LiI crystals and forming strong bonds with Li ions, respectively. This conductivity is determined by the competition between the two effects of oxygen at each SiO2 content, resulting in a maximum conductivity of 14.6 mS cm−1 in the 30Li2S∙25B2S3∙45LiI∙25SiO2 composition, which is comparable to about 10 mS cm−1 for liquid electrolytes. Li ion hopping readily occurs in cation-rich environments, as the cations facilitate the breaking of the bonds of Li with anions, especially oxygen, by attracting the anions around Li, which is suggested to be the cation-assisted Li ion diffusion mechanism. This work suggests that precise control of the oxygen:sulfur ratio in glassy solid electrolytes is key to promoting Li ion diffusion while minimizing immobilized Li ions and improving moisture stability.

Progress, challenges and perspectives of computational studies on glassy superionic conductors for solid-state batteries

This review summarizes the computational studies of lithium and sodium sulfide-type glassy solid electrolytes, and provides our understandings of the challenges and potential future developments in the computational study of new glassy SSEs.