Poly(ionic liquid) iongel membranes for all solid-state rechargeable sodium battery

Significant scientific and economic challenges are presented by developing battery systems with increased energy storage capacity. Geopolitical issues might pose supply chain risks for lithium (Li)-ion batteries, which are frequently used in portable electronics. As an alternative, sodium-ion batteries (NIBs), have drawn attention from researchers all over the world due to the perspective of being lower cost systems[1]. In comparison to lithium-ion batteries, solid-state sodium-ion batteries (SSSBs) promise as a safe, scalable, and environmentally friendly alternative. For the production of robust and adaptable SSSBs, the development of highly conductive, electrochemically stable, and chemically stable solid electrolytes (SEs) is essential [2]. With greater durability, adaptability, and safety, solid-state batteries with inorganic solid electrolytes are being heavily investigated as safer and perhaps more energy-dense alternatives to liquid electrolyte cells.Sulfides solid electrolytes have been extensively investigated due to their mechanical softness and high ionic conductivity. However, the electrochemical oxidation stability of those materials are as low as 2 V (vs. Na+/Na)[3]. Alternatively, the excellent ion conductivities and stability at high potentials have made halide compounds, intriguing candidates for solid electrolytes in batteries. These compounds offer fast ion transport, good stability at highly oxidative potentials, and are easily processed. A wide range of chemistries, such as A3MX6 (A = Li, Na; M = Sc, In, Y, Yb, Er, Hf, Ho, Dy, Al, Zr; X = F, Cl, Br, I), have been synthesized with tunable properties and the characterizations of those materials shows relevant electrochemical proprieties [2].In our work, we investigate different Na-based chloride compounds by Density Functional Theory (DFT). We expand beyond the reported compositions to consider possible cation-substituted compounds. Here, we report on the structures, ionic conduction pathways and ionic conductivity (computed by molecular dynamics methods) expected for such compounds. In the next months, we will also evaluate the compounds´ chemical and electrochemical stability. Our work moves us one step closer towards the development of stable and highly conductive solid electrolytes for Na-based solid-state batteries.References :[1] J. Mater. Chem. A, 2021,9, 281-292[2]J. Mater. Chem. A, 2022,10, 21565-21578[3] ACS Energy Lett. 2022, 7, 10, 3293–3301

Surface Stabilization of O3-type Layered Oxide Cathode to Protect the Anode of Sodium Ion Batteries for Superior Lifespan.

Ionic liquid based Fluoropolymer solid electrolytes for Lithium-ion batteries

Sodium is an earth abundant element, which makes sodium ion batteries a promising technology for grid-scale energy storage applications. Due to safety concerns with liquid electrolytes, extensive research has been carried out over the past decade to develop new solid-state electrolytes. However, developing solid-state electrolytes with relatively high ionic conductivity at room temperatures is a major challenge. Sulfide glasses have been reported to possess excellent ionic conductivity making them potential electrolytes for high performance sodium ion batteries. With an aim to develop novel electrolyte for high performance sodium ion batteries, our present work focuses on analyzing the local structure of sulfide glasses and its subsequent impact on transport properties through atomistic simulations, in conjunction with experimental characterization. As model systems, we studied x Na2S – (1-x) P2S5 glasses. The polarization and resonance effect of the P=S bonds in the glass complicates the parametrization of interatomic potentials necessary for classical MD simulations. Therefore, we employed ab initio MD simulations that perform quantum calculations on the fly while solving equations of motions at each MD step to accurately capture the complex chemistry. As model systems for our calculations, we considered a range of electrolytes with composition x Na2S – (1-x) P2S5 (x = 0, 0.33, 0.5, 0.6, 0.67, 0.75). The glasses were formed using melt-quench technique and the density of the glasses matched well (within 5%) with the experimentally measured value. We analyzed the local structure of these glasses by calculating the radial pair distribution functions (RDF’s) from ab initio MD and compared it to those obtained through X-ray scattering experiments to validate the model. The FTIR and NMR characterization of these glasses show presence of different structural units that effectively control the ionic conductivity of these glasses. We calculated the fractions of each of these functional units present in the glasses from ab initio MD. At 75% Na2S, all the sulfur present in the structure is non-bridging due to presence of purely [PS4]3- groups in the glass. At concentration lower than 75% Na2S, other structural units containing bridging sulfur such as [P2S7]4- dominate the local structure. On the other hand, at concentrations above 75% Na2S, additional structural units corresponding to [PS3]3- and polysulfides are observed along with [PS4]3- due to excess Na2S content. Increase in concentration of polysulfides leads to lower ionic conductivity. As a result, optimal ionic conductivity of these glasses is observed at 75 Na2S – 25 P2S5 composition. The calculated ionic conductivity of these glasses at room temperature was ~ 10-6 S/cm, which matches well in terms of order of magnitude with experimentally measured values. A relatively high ionic conductivity (~ 10-5 S/cm) can be achieved at slightly elevated temperatures of around 60 °C, making these sodium thiophosphate glasses promising electrolytes for solid-state sodium ion batteries.

Solid-state sodium ion battery is a promising technology for energy storage in electrical grids. However, the characteristic low ionic conductivity of solid-state electrolytes is a major challenge towards commercialization of solid-state sodium ion batteries. Sulfide glasses have relatively high ionic conductivity at room temperature and are therefore considered promising as potential electrolytes. However, the energy barrier for ion hops in these electrolytes is highly sensitive to the chemical composition, which provides a tremendous opportunity to tailor the ionic conductivity. In-situ characterization of Na+ ion transport through experiments is extremely challenging. Atomistic simulations offer an economical route for determining the local structure of these glasses as well as Na+ ion transport mechanisms. Sodium sulfide – silicon sulfide [xNa2S – (1-x)SiS2] based electrolytes with varying compositions was chosen as a model system and atomistic simulations of various flavors were employed to determine ion conduction mechanism and evaluate ionic conductivity, each method having distinct advantages. Experimental X-ray scattering data was used for the purpose of model validation. Ab initio molecular dynamics (MD) simulations are able to accurately model the specific chemistry based on on-the-fly quantum mechanical calculations to determine interatomic interactions. Augmented with nudged elastic band analysis, these calculations can determine activation energies for ion hops. However, the maximum system size that can be realistically modeled using ab initio MD is limited to few hundred atoms and therefore cannot reliably calculate the bulk properties. On the other hand, classical MD simulations employ empirical forcefields to define pairwise interactions between constituent ions in these glasses. This method can simulate much larger systems comprising hundreds of thousands of atoms. However, the inability of these predefined forcefields to accurately capture the complex chemistry in sulfide glasses makes it extremely challenging to accurately model these glasses. Reactive force fields, such as ReaxFF, is based on a bond order potential in conjunction with charge equilibration that is based on extensive parameterization based on quantum mechanical calculations of structure and energies. ReaxFF forcefields are highly system specific. Classical MD simulations involving ReaxFF provide an effective route to accurately capture bond breakage and formation, while simulating considerably large systems (~ 100,000 atoms) and therefore accurately evaluates ionic conductivity. Based on simulation data from each of the above methods, their merits and demerits are discussed as pertains to the model system of sulfide glasses. We determined the ionic conductivities and activation energies for sodium ion hops and related them to the structural units and hop distances. Overall, these simulations provide fundamental insights into ion conduction mechanisms as well as correlate ionic conductivity with glass structure and composition. The combined approach demonstrates excellent promise in identifying optimal glassy electrolytes for sodium ion batteries.

All-solid-state lithium batteries (ASSBs) are considered like the next generation of electrochemical energy storage devices because of their safety and their high energy density up to 400Wh/kg. The all-solid-state battery is composed of a positive electrode (e.g., NMC (Li(Ni1∕3Mn1∕3Co1∕3)O2)), a negative one (Li), and a solid electrolyte, which is the critical component, composed of inorganic compound and/or solid polymer electrolyte (SPE) [1]. On the one hand, SPE have the advantage of an easy shaping with the technique already used in the manufacture of batteries and their flexibility allows obtaining a good interface with the electrode materials [2]. On the other hand, inorganic compounds generally have high ionic conductivity (10-3S/cm), they are stable electrochemically vs Li/Li+ and their transport number is close to 1 to promote the diffusion/migration of Li+ ions only. In order to combine the advantages of both types of materials, hybrid materials have been designed [3].First, a new adaptable polymer matrix based on PEO derivatives has been developed. A solvent-free synthesis has been designed from liquid and commercial precursors Poly(ethylene glycol) methyl methacrylate (PEGM) and Poly(ethylene glycol) dimethacrylate (PEGDM). These latter were copolymerized with Lithium 3-[(trifluoromethane)sulfonamidosulfonyl] propyl methacrylate (MTFSLi). The anion TFSI- is thus grafted to the PEO network, allowing exclusively the diffusion of the Li+ ion. This polymer matrix can be thus classified as single-ion conductor. In addition, the proportions between PEGM and PEGDM, acting as crosslinker, can be easily tuned. The PEGDM proportion controls the cross-linking density which modifies not only the glass transition temperature (Tg), but also the storage modulus (E’) and the free volume, and consequently the ionic conductivity of the polymer matrix which is the main property required for SPE. Finally, a ratio of PEGM:PEGDM (80:20) allows obtaining homogeneous SPE, self-standing and soft at room temperature, amorphous with a Tg of -41°C. The EO/Li ratio was then modulated in single-ion networks with the MTFSLi proportion, and an optimum in ionic conductivity of 2.10-7 S/cm @25°C has been measured for EO/Li ratio of about 20. The transport number measured by the Bruce and Vincent method [4] was t+=1,0 for the single ion conductor, demonstrating the effective grafting of the counter anion. This value has been validated by measuring the diffusion coefficients of 7Li and 19F in NMR. To our knowledge, this is the first time a real unity transport number is reported in the literature for a polymer electrolyte. Moreover, the electrochemical stability of this single ion system extends from 0 to 6V vs Li+/Li. These experiments suggest the interest of using the single-ion polymer in the formulation of composite positive electrode with high potential cathode materials, due to its stability in potential. Li metal is considered the ultimate anode for Li-batteries. The long-term electrochemical stability has been evaluated in symmetric Li/polymer electrolyte/Li cell. The cell is cycled at a constant current density of 0.2 mA/cm2. After 200 h of cycling the voltage reaches solely 2V. Accordingly, the grafting of the anion to the network limits an overpotential in the cell, allowing a more stable system over time.Second, the garnet Li6.4La3Zr2Al0.2O12 (LLZO) of the oxide family was associated to the previous polymer matrix. This garnet presents a high conductivity (10-4 S/cm @ 25°C), a good chemical stability not only against lithium metal but also against air and humidity, which is not the case of sulphides homologues. A 3D-fibrous network obtained by the electrospinning method was carried out with a solution containing the inorganic precursors, a polymer and an appropriate solvent [5]. Then this membrane is calcined at 850°C to obtain the 3D fibrous network of LLZO. The resulting self-standing porous inorganic material (~80% of porosity) exhibits a conductivity of the order of 10-6 S/cm @25°C. It was then impregnated with the polymer matrix precursors by capillarity and following by a polymerization. A self-standing membrane as thin as 80 µm containing 9%vol of LLZO was obtained. The conductivity of this hybrid membrane is comparable to that of the polymer (10-7S/cm @ 25°C). The resulting hybrid is mainly polymeric where the ionic conduction was realized by the polymeric matrix and the inorganic acts as a mechanical reinforcement. Preliminary results on high content of LLZO hybrid will also be presented, where a synergy of the both components is observed.[1] Janek. Nature Energy. 2016. Vol 1(9)p.16141. [2] Yue. Energy Storage Materials. 2016. Vol 5p.139-164. [3] Zheng. Chem Soc Rev. 2020. Vol 49p.8790-8839. [4] Bruce. Solid State Ion. 1988. Vol 28–30p.918–922. [5] A. La Monaca. Electrochemistry Communications. 2019. Vol 104p.106483. Figure 1

Solid-state lithium metal batteries, SSLMBs, are widely sought after as the next generation battery technology due to their potential intrinsic safety and higher energy density. However, several challenges need to be addressed to achieve this goal. Previous studies have identified various challenges with the cathode electrode, including interphases, low active material contents, and limited overall ionic and electronic conductivity for high power density. [1] Additionally, there are different types of cathode materials that are currently under R&D for SSBs such as layered oxides, olivine phosphates, and spinel oxides. Among these, the spinel oxide LiNi0.5Mn1.5O4 (LNMO) has the highest voltage compared to other cathode materials, making it an attractive candidate for maximizing the energy density of active materials in solid-state batteries.However, most solid-state batteries require a catholyte,[2] solid electrolyte in the cathode electrode, to provide bulk ionic conductivity, but this, in turn, reduces energy density due to the addition of inactive materials.[3] Therefore, utilizing LNMO, a high energy density cathode, is a promising solution for solid-state batteries to compensate for this energy density loss.To ensure high voltage stability, it is crucial to have a well-designed catholyte composition that minimizes the use of solid electrolyte while ensuring excellent electronic and ionic conductivity to the cathode. In this work, we introduce a catholyte formulation that can effectively utilize LNMO and demonstrate promising cycling results with a Garnet-based solid electrolyte, having cycled over 100 times. This research opens up new possibilities for enhancing the performance of 5V solid-state lithium batteries using catholyte for the LMNO spinel cathode while maintaining high energy densities. Liang, Y., et al., Challenges, interface engineering, and processing strategies toward practical sulfide‐based all‐solid‐state lithium batteries. InfoMat, 2022. 4(5): p. e12292.Al-Salih, H., Houache, M.S.E., Baranova, E.A. and Abu-Lebdeh, Y. (2022), Composite Cathodes for Solid-State Lithium Batteries: “Catholytes” the Underrated Giants. Adv. Energy Sustainability Res., 3: 2200032.Yim, C.-H., et al., Understanding key limiting factors for the development of all-solid-state-batteries. Chemical Engineering Journal Advances, 2023. 13: p. 100436.

Three-dimensional Ag/carbon nanotube-graphene foam for high performance dendrite free lithium/sodium metal anodes

In the past decades, due to an always more electrification and the research of a greener environment, Li-ion Batteries (LIB) have taken an important place in worldwide research. Solid-state batteries (SSBs) have the potential to revolutionize the energy storage industry, offering superior safety and energy density in comparison to traditional LIBs[1, 2]. Our research aims to enhance the performance and safety of solid-state batteries at ambient temperature by incorporating electrodes with high specific capacity with a lithium lanthanum zirconate (LLZO) solid electrolyte.The integration of SiNW electrodes into the solid-state battery architecture offers several advantages. SiNWs are known for their large surface area and superior electrical conductivity and offer a strong platform for efficient lithium-ion transport and cell energy density optimization, theoretically almost 10 times the capacity of graphite[3, 4]. Furthermore, LLZO solid electrolytes are a stable and non-flammable alternative to conventional liquid electrolytes[2, 5], significantly improving battery safety.The main objectives of this study are to investigate the combined effects of silicon nanowires (SiNWs) electrodes and LLZO solid electrolyte and to determine the optimal amount of liquid electrolytes to improve cell safety.In this work, an LLZO thin solid electrolyte tape has been manufactured by casting technique. Precise volumes of liquid electrolyte have been added to the LLZO tape to improve surface contact and ion conductivity. Furthermore, the study will provide a view of the relationship between the quantity of liquid electrolytes introduced and their impact on cell stability and safety.Preliminary results show the preparation of a mechanically stable LLZO tape with high ionic conductivity (>10-4 S cm-1) through an easy and up-scalable procedure. Improvements have been reported in the electrochemical performance of SiNW-LLZO solid-state batteries compared to the relative Li-ion liquid cell.In conclusion, here we developed a new thin solid electrolyte tape with high ionic conductivity, used in solid-state LIBs with silicon nanowires as anode material. Moreover, we standardized a procedure to optimize the use of organic liquid electrolytes as an additive, without omitting the volume or using any excess that could lead to safety issues. This optimization process can contribute to the development of solid-state batteries that are not only high-performance but also safe and reliable for various applications, including electric vehicles and portable electronics. References Wu, F., J. Maier, and Y. Yu, Guidelines and trends for next-generation rechargeable lithium and lithium-ion batteries. Chem Soc Rev, 2020. 49(5): p. 1569-1614.Wang, C., et al., Garnet-Type Solid-State Electrolytes: Materials, Interfaces, and Batteries. Chem Rev, 2020. 120(10): p. 4257-4300.Chan, C.K., et al., High-performance lithium battery anodes using silicon nanowires. Nat Nanotechnol, 2008. 3(1): p. 31-5.Kennedy, T., M. Brandon, and K.M. Ryan, Advances in the Application of Silicon and Germanium Nanowires for High-Performance Lithium-Ion Batteries. Adv Mater, 2016. 28(27): p. 5696-704.Xu, L., et al., Garnet Solid Electrolyte for Advanced All ‐Solid ‐State Li Batteries. Advanced Energy Materials, 2020. 11(2).

Sodium-ion batteries (SIBs) are emerging as a promising alternative to lithium-ion batteries, primarily due to their plentiful raw materials and cost-effectiveness. However, the use of traditional organic liquid electrolytes in sodium battery applications presents significant safety risks, prompting the investigation of solid electrolytes as a more viable solution. Despite their advantages, single solid electrolytes encounter challenges, including low conductivity of sodium ions at room temperature and incompatibility with electrode materials. To overcome these limitations, the researchers develop composite polymer solid electrolytes (CPSEs), which merge the strengths of high ionic conductivity of inorganic solid electrolytes and the flexibility of polymer solid electrolytes. CPSEs are usually composed of inorganic materials dispersed in the polymer matrix. The final performance of CPSEs can be further improved by optimizing the particle size, relative content, and form of inorganic fillers. CPSEs show great advantages in improving ionic conductivity and interface compatibility, making them an important direction for future solid-state sodium battery research. Therefore, this paper summarizes recent advancements in composite solid electrolytes, discusses the impact of their preparation processes on performance, and outlines potential future developments in sodium-ion solid-state batteries.

Solid-state sodium metal batteries have been proposed as an alternative to lithium-ion batteries (LIBs) for next-generation applications due to the high abundance and wide distribution of sodium resources.1 Sodium antiperovskites (Na3OX, X = Cl, Br, or BH4) have recently attracted great interest as solid electrolyte candidates due to the relatively low processing temperature (<500 oC), reasonable ionic conductivity (up to 4.4 x 10-3 S cm-1 at room temperature), and great chemical stability against sodium metal anodes.2,3 Typical solid-state ionic conductors have temperature-dependent ionic conductivity that follows Arrhenius behaviour over a broad range of temperatures, corresponding to a constant activation energy Ea. However, this is not the case in Na3OBr, and instead a phenomenon resulting in a higher ionic conductivity and lower activation energy is observed to occur at 255 oC. Similar non-Arrhenius ionic conductivity phenomenon has also been reported in the potassium antiperovskite K3OI. It has been proposed that this behaviour originated from anion disordering, but conclusive experimental evidence to support this claim has not been reported.4 An understanding of the origin of this behaviour could enable the synthesis route to be optimised such that higher ionic conductivities could be achieved.In this work, we combined temperature-resolved bulk and local characterisation methods including Pawley and Rietveld refinements of synchrotron x-ray diffraction (XRD), pair distribution function (PDF), solid-state nuclear magnetic resonance (NMR) spectroscopy, and electrochemical impedance spectroscopy (EIS) to gain an insight into the origin of this non-Arrhenius behaviour. We found that this phenomenon does not originate from anion disordering, as previously speculated, because the lattice parameter of Na3OBr changed linearly with temperature and no major intensity changes were observed in the Na-Br and Na-O signals in the PDF patterns. Other supporting findings that lead us to this conclusion will be discussed in the presentation.References Wang, X. et al. Ultra-stable all-solid-state sodium metal batteries enabled by perfluoropolyether-based electrolytes. Nat. Mater. 21, 1057–1066 (2022).Zheng, J., Perry, B. & Wu, Y. Antiperovskite Superionic Conductors: A Critical Review. ACS Mater. Au 1, 92–106 (2021).Sun, Y. et al. Rotational Cluster Anion Enabling Superionic Conductivity in Sodium-Rich Antiperovskite Na3OBH4. J. Am. Chem. Soc. 141, 5640–5644 (2019).Zheng, J. et al. Antiperovskite K3OI for K-Ion Solid State Electrolyte. J. Phys. Chem. Lett. 12, 7120–7126 (2021).

All-solid-state sodium (Na) ion batteries (SiBs) are promising high-safety and low cost alternatives to current lithium (Li) ion batteries (LiBs), particularly suitable for the application to large-scale electrical energy storage systems. Development of inorganic solid Na-ion conducting materials used for solid electrolyte is most critical issue to realize all-solid-state SiBs. The solid electrolyte materials should have not only high Na-ion conductivity at room temperature but also chemical and electrochemical stabilities against both cathode and anode active materials. Oxide based solid electrolytes have lower conductivity and poorer deformability than sulfide based one, but they have other advantages such as their chemical stability in air and easiness for handling.Na2M2TeO6 (M = Zn, Mg, Ni, Co, etc.) with a P2-type honeycomb layered structure has been reported as a fast Na-ion conducting oxide [1]. Particularly, Na2Zn2TeO6 (NZTO) is an attractive candidate for a solid electrolyte material because of the high ionic conductivity well above 10-4 S cm-1 at room temperature, wide electrochemical potential window and lower densification temperature than other oxide-based Na-ion conductors such as NASICON and Na-β alumina [2–4]. On the other hand, Na2Ni2TeO6 (NNTO) has been investigated as a cathode active material for SiB operating at 3–4 V vs Na/Na+ [5,6]. Because of the similarity in their crystal structure and constituent elements, NNTO cathode and NZTO as solid electrolyte may be co-sintered without forming undesired secondary phases to fabricate all-solid-state SiBs.In this work, we investigated firstly the reactivity between NNTO and NZTO powders at annealing temperature between 500 ºC and 800 ºC in air. From XRD measurements, it was found that the reaction between NNTO and NZTO is negligible at annealing temperature below 700 ºC while when annealed at 800 ºC, they forms a solid-solution phase without forming any secondary phases. Based on this result, we fabricated NNTO-NZTO laminate via co-sintering NNTO and NZTO pellets at 700 ºC in air. Thicknesses of NNTO and NZTO layers in the laminate were set to 1 mm.From impedance measurements, apparent ionic conductivity of the NNTO-NZTO laminate was estimated to be approximately 0.1 mS cm-1 at 27 ºC, which is close to the prediction with taking into account only the conductivity of individually sintered NNTO (= 0.04 mS cm-1) and NZTO (= 0.36 mS cm-1) at 700 ºC. This indicates that the interfacial resistance between NNTO and NZTO layers is not so large. In addition, using the NNTO-NZTO laminate with NNTO layer thickness of 80 µm, electrochemical Na extraction reaction from NNTO layer through NZTO solid electrolyte was demonstrated via galvanostatic testing at room temperature. Obtained results are very fundamental but can be applied to fabricate all-solid-state SiBs with NNTO cathode and NZTO solid electrolyte via simple co-sintering process in future.

Most of the ceramic ionic conductors typically conduct one ion. For example, AgI conducts Ag+ ion, Sodium β”-alumina conducts Na+ ion and Yttria-stabilized zirconia (YSZ) conducts O2- ions. Some selected materials such as alkaline earth cerates or zirconates conduct both protons and O2- ions. In such materials also, conductivity of one species is not independent of the other species. Thus, temperature and atmosphere determine the total conductivity. All of such materials are single phase materials. We have been investigating two phase materials such that one phase conducts one ion (Na+) while the other phase conducts another ion (O2-). The materials in such cases is a composite with the two phases forming an interpenetrating network. The volume ratios of the two phases can be adjusted as necessary. Since the two phases essentially constitute a mixture, conduction of one species occurring through one phase is independent of the conduction of the other species through the second phase. Yet, the condition of electroneutrality is applicable globally across multiple phases. Transport equations can then be written down in the usual manner but accounting for different volume fractions for the two phases. A mixed Na+ ion and O2- ion two phase conductor is fabricated by first making a sintered dense composite containing α-alumina and YSZ such that both phases are contiguous. YSZ and α-alumina are immiscible. This allows the fabrication of fine-grained, dense, strong composites. Subsequently, the sample is packed in Na-β”-alumina + YSZ powder and heat treated in air over a range of temperatures from 1200oC to 1400oC. During this process, α-alumina is converted into Na-β”-alumina by the incorporation of Na2O into α-alumina by coupled transport in which Na+ transports through the formed Na-β”-alumina and O2- ions transport through YSZ. The reaction front over time sweeps through the sample forming a two phase composite of Na-β”-alumina + YSZ. Such a material is now capable of conducting two ions; Na+ and O2-. Materials capable of transporting other alkali ions can be made by an ion exchange process in molten salts. For example, by ion exchanging in lithium salts, it is possible to make mixed Li-ion and O2- ion conducting materials. The oxygen ion conductivity is negligible at low temperatures. Thus, the materials at room temperature are predominantly alkali ion conductors with possible use in all solid state lithium ion and sodium ion batteries. Another mixed ion conductor was made by a similar process using a composite of Ga2O3 and YSZ. It was similarly packed in Na-β”-alumina powder and heat treated. In this case a two phase mixture containing YSZ and sodium zirconium gallate formed, the latter with a chemical formula of Na0.7Ga4.7Zr0.3O8 with a monoclinic structure. This compound is isostructural with Na0.7Ga4.7Ti0.3O8 which is known to be one dimensional sodium ion conductor. Measurement of ionic conductivity on Na0.7Ga4.7Zr0.3O8 + YSZ showed it to be a mixed Na+ ion and O2- ion conductor. Sodium ion conductivity of Na0.7Ga4.7Zr0.3O8 is much lower than that of Na-β”-alumina. The activation energy for Na+ ion transport is much lower than for O2- ion transport in YSZ. As a result, the two phase mixture is predominantly a Na+ ion conductor at low temperatures and an O2- ion conductor at elevated temperatures. Both Na-β”-alumina + YSZ and Na0.7Ga4.7Zr0.3O8 + YSZ are mixed Na+ ion and O2- ion conductors. This allows one two explore electrochemical transport of two species and examine the applicability of Goldman-Hotchkin-Katz trype of an equation, routinely used in aqueous electrochemistry, for solid-state systems. Preliminary results of experiments conducted by maintaining different chemical potentials of Na2O at the two electrodes and different chemical potentials of oxygen (by testing in a fuel cell mode) will be described. Possible degradation of Na-β”-alumina in reducing atmosphere will also be addressed. Acknowledgements: This work was supported by the National Science Foundation under Grant Number DMR-1407048.

<p indent="0mm">In order to deal with the increasingly severe global energy crisis as well as serious environmental pollution, it is urgent to develop new energy resources. Although lithium-ion batteries have only been successfully introduced into the market since 1990s, there is still an exponentially growing demand for lithium-ion batteries all over the world. As a considerable novel energy source, lithium-ion batteries have significant potential, which is widely used in electric vehicles, energy-storage systems, metallurgy, ceramic production, glass manufacturing and aviation fuel industries. Among them, the solid-state lithium-ion batteries (SSLIBs) represent a promising evolution in battery technology, offering superior safety, energy density, and longevity compared to conventional liquid electrolyte batteries. Traditional lithium-ion batteries, which use liquid electrolytes, suffer from safety issues such as leakage, flammability and thermal runaway. SSLIBs replace these liquid electrolytes with solid electrolytes, mitigating these risks and enabling higher energy densities due to the ability to accommodate lithium metal anodes. The SSLIB consists of a positive electrode, a negative electrode and a solid electrolyte. Compared with liquid electrolytes, solid electrolytes avoid the direct contact between positive electrodes and negative electrodes, fundamentally eliminating the risk of lithium dendrites piercing the separator, so as to enhance the safety of lithium batteries greatly. Furthermore, the SSLIBs are expected to be a hot spot in future lithium battery research due to the advantages of high energy density, wide operating voltage range and long cycle life. Advancements in SSLIBs technology are crucial for the next generation of electric vehicles, portable electronics, and large-scale energy storage systems, pushing the boundaries of battery performance, safety and sustainability. Solid electrolytes are regarded as the key component of SSLIBs, serving dual functions as both separators and electrolytes. The currently developed solid electrolytes can be divided into two categories: Polymer solid electrolytes and inorganic solid electrolytes, in which the oxide solid electrolytes, as the earliest developed inorganic solid electrolytes, play an indispensable role in the development of solid-state battery industry. The typical oxide solid electrolytes, including sodium super ionic conductor (NASICON), garnet (LLZO), inorganic perovskite (LLTO), and LiPON films, are reviewed in this paper. NASICON, for example, is known for its high ionic conductivity and structural stability. Garnet-type electrolytes, such as LLZO, possess high ionic conductivity and chemical stability with lithium. Inorganic perovskite (LLTO) provides a good balance between ionic conductivity and mechanical strength. LiPON films, widely used in thin-film batteries, have excellent electrochemical stability and compatibility with lithium metal. In addition, the crystal structures and ion-transport mechanism, the solutions to improve conductivity and measures to improve the compatibility between electrodes and electrolytes are introduced, along with a comparation of oxide solid electrolytes. Finally, several suggestions for future development directions are proposed. These include enhancing the ionic conductivity of solid electrolytes, improving the interface compatibility between the electrolytes and electrodes, and developing cost-effective and scalable manufacturing processes. Additionally, further research is needed to understand the degradation mechanisms and long-term stability of solid-state batteries. These recommendations aim to provide a more comprehensive reference for ongoing and future research on oxide solid electrolytes, supporting the broader goal of advancing solid-state lithium battery technology.

Lithium-ion batteries (LIBs) using organic liquid electrolytes have been applied in portable devices such as laptops and cellular phones owing to its wide electrochemical stability, high voltages, and excellent energy density. LiNi0.5Co0.2Mn0.3O2 (NCM523) cathode have attracted significant interest as the cathode materials for LIBs owing to their high capacity, excellent rate capability and low cost. NCM523 cathode materials have a disadvantage of structural instability, which caused by the reduction of Ni ions releases oxygen from the crystal structure at the high temeprature or high charged state, which can lead thermal runaway by reacting with the flammable electrolyte. The use of organic liquid electrolytes in LIBs raises safety issues due to its flammable character and the impact on the explosion is greater in particular for relatively large systems such as electrical vehicles and grid storage. To overcome the safety issues, solid state batteries (SSBs) using a non-combustible solid state Li-ion conductor are regarded as the realistic alternative to prohibit the leakage of liquid electrolytes and the resultant fire hazards. However, due to the large resistance in the electrode-electrolyte interface, the capacity retention and cycle effieciency of the SSBs become worse. Previous studies on SSBs have been mainly focused on developing solid state electrolytes with high ion conductivity. Despite growing interest in stability, the systematic studies of safety of SSBs depending on the type of electrolyte has never been evaluated so far. It is necessary for understanding structural deformations on the cathode material in the effects of the reactions beween the electrode and various types of electrolytes, which is essential for ensuring the safety of the batteries. In this study, we investigate the structural degradation and thermal stability on NCM523 cathode materials by taking an advantage of in situ transmission electron microscopy (TEM) in various electrolyte conditions, including conventional liquid electrolyte, poly(ethylene oxide) (PEO) complexes with LiClO4 (PEO-based solid electrolyte), and PEO/LiClO4/Li1.3Al0.3Ti1.7(PO4)3 (LATP) composite electrolyte (PEO-inorganic composite electrolyte). Since the LATP oxide electrolyte has brittleness and the PEO has flexibility, it adopts a composite electrolyte having inorganic and organic phases with good interface contact with the cell electrode. A cell composed of each electrolyte was prepared and charged with cut-off voltages of 3.9 V and 4.3 V at a rate of 0.05 C after the second formation process for stabilzing the cell. The capacity at the same cut-off voltage decreases in the order of conventional liquid electrolyte, PEO-based solid electrolyte, and PEO-inorganic composite electrolytes. To understand the thermal stability and the degradation mechanism, modifications in selected-area electron diffraction (SAED) and electron energy-loss (EEL) spectra of oxygen K-edge and transition metal (Ni, Co, Mn) L-edges of each of charged NCM523 cathode materials are monitored in real time at the range from room temperature to 300°C. Our work demonstrated that contact resistance at the interface between the electrode and electrolyte is important factor. This work provides important information on the relationship with structural deformation and thermal stability of the cathode materials, which is an essential part of the rational design to develope for high engergy densities and safe SSBs. All the details will be available at the meeting. Acknowledgement This work was supported by the Korea Institute of Science and Technology (KIST) Institutional Program (Project 2E28142). This work was also supported by the National Research Foundation of Korea (NRF) grant (No. 2018R1A2B2005205).