High Li-ion Conductivity Research Articles

High-throughput screening of halide solid-state electrolytes for all-solid-state Li-ion batteries through structural descriptor

All-solid-state Li-ion batteries (ASSLIBs) have attracted great attention due to their intrinsic safety and high potential energy density. To realize ASSLIBs, the development of solid-state electrolytes (SSEs) with favorable electrochemical stability and high Li-ion conductivity is of utmost significance. Compared to trial-and-error searches, theoretical computation-based methods are recognized as a powerful tool for accelerating the exploration of SSEs. However, the development of appropriate descriptors is often the first hurdle toward implementing accurate and meaningful screening process. Here we quantified the structural properties pertaining to low Li-ion migration barriers and performed a high-throughput screening of 3119 Li-containing halides obtained from the Materials Project (MP) database to search for promising SSEs. After excluding previously reported SSEs, three candidate materials, Li4ZrF8, Li3ErBr6, and Li2ZnI4 with crystal structure exhibiting 3D diffusion pathway were obtained. Subsequent theoretical calculations of these materials were performed to evaluate their thermodynamic stability, chemical/electrochemical stability, and ionic conductivity. The three halide materials appeared to be promising SSE candidates due to their robust thermodynamical stability against cathodes, and high ionic conductivity. This research provides a new insight and a systematic quantitative understanding of the relationship between the structural properties and Li-ion migration barriers, which can motivate future computational studies on new fast-ion conductors and accelerate the discovery of high ionic conductivity SSEs for the use in ASSLIBs.

Surface modification of LiFePO4 cathode enabled by highly Li+ mobility wrapping layer towards high energy and power density

Surface-modified cathode materials have been developed to achieve high-performance lithium secondary batteries with higher capacity, rate capability, and longer cycle performance than bulk active materials. In this study, a new surface-modified active material was explored through a low-temperature in situ-solution wrapping method (LiFePO4@Li4SiO4 composite). In addition, high Li-ion and electronic conductivity materials with amorphous nanostructures, in which the bulk LiFePO4 nanoparticles were covered with a Li4SiO4 layer, were demonstrated. In lithium-ion batteries, the LiFePO4@Li4SiO4 composite demonstrated enhanced charge transfer kinetics, which lowered the interfacial resistance between electrode and electrolyte and resulted in enhanced electrochemical performance when compared to that of bulk LiFePO4. Furthermore, Li4SiO4 is introduced as a surface stabilizer and effective Li-ion conductor to avoid side reactions and prevent the dissolution of active materials into the electrolyte. The designed cathode delivers a high specific discharge capacity of 171.8 mAh g-1 at 0.1 C with 99.76 % capacity retention after 150 cycles and a high capacity of 121.2 mAh g-1 at 10 C. Moreover, Li-ion full batteries employing LiFePO4@Li4SiO4 and graphite displayed a high specific energy density of 416.078 Wh kg-1 at a power density of 69.34 W kg-1 at 5 C. In summary, this paper reports a new strategy based on low-temperature in situ solution phase wrapping materials for developing active materials for high energy-power density energy storage devices.

Universal-neural-network-potential molecular dynamics for lithium metal and garnet-type solid electrolyte interface

All-solid-state Li-metal batteries can conceivably improve the safety and extend the driving ranges of electric vehicles. In this regard, the garnet-type solid electrolyte Li7La3Zr2O12 (LLZ) has garnered considerable attention because of its high Li-ion conductivity and nonreactivity towards molten Li metal. Here, we perform molecular dynamics (MD) simulations using a universal neural network potential (UNNP) to analyse the Li-ion exchange at the LLZ/Li interface at the atomic scale. The UNNP-MD calculations show that Li ions traverse the LLZ/Li interface and that excess Li ions relative to the stoichiometric composition accumulate in an approximately 1 nm-thick zone near the LLZ phase interface, signifying the formation of a space-charge layer. Electronic structural analysis of the UNNP-MD-derived configuration, performed using density functional theory calculations, reveals band bending near the LLZ phase interface and the simultaneous suppression of Li metal reduction. These findings can help expedite the development of rationally designed all-solid-state Li-metal batteries.

Effect of Chemical Doping on Ion Transport in Sulfide Solid Electrolytes

Rechargeable solid-state batteries (SSBs) offer tremendous promise as a safe and energy-dense storage technology for use in electric transportation, robotics, and portable electronics. Lithium argyrodites (e.g., Li7PS6, and its halogen-doped derivatives) have emerged as a lucrative class of solid-state electrolytes (SSEs) for SSBs owing to their high Li-ion conductivity (~10-3 S/cm), good elastic stiffness (~30 GPa), and low flammability. Meanwhile, sulfide-based solid electrolytes such as Na3SbS4 (NSS) also showcase substantial potential for SSBs with their high theoretical specific capacity, enhanced safety, and abundance of resources. Despite their promise, both lithium and sodium-based SSBs remain far from commercialization due to lack of atomic-scale understanding of ion-conduction, charge transport, structural evolution, and interfacial reactions (e.g., dendrite growth, electrolyte decomposition etc.). Here we employ a combination of density functional theory calculations, ab initio molecular dynamics simulations, and nudged elastic band calculations to understand ion transport mechanism in chemically doped lithium argyrodites and NSS.In lithium-based systems, using accurate materials modeling, we design fluorine-containing argyrodite electrolytes that offers enhanced Li-ion conduction facilitated by unique Li-disorder induced by fluorine and other halogen co-dopants. Our results show the opening up of new pathways for Li inter-cage hops in these fluorine -containing argyrodite electrolytes which increases the Li-ion conductivity. In the case of sodium-based systems, we focus on atomic-scale mechanisms underlying Na-ion conduction in the presence of cation dopants. Ab initio molecular dynamics simulations reveal the significant impact of cation dopants on NSS, where the introduction of charge-compensating Na-vacancies enhances Na-ion conduction. The size of the cation dopant is found to be a critical factor, with examples such as Ca-doped NSS (rCa2+ / rNa+ = 0.98) showing a conductivity approximately 10 times that of pristine NSS, while larger Ba2+ as a dopant (rBa2+ / rNa+ = 1.35) hinders Na-ion hops due to local strain, resulting in a Na-ion conductivity ~5 times that of NSS. We will discuss these results in the context of accelerating design of novel solid-state electrolytes for long-lived, stable, and high-energy density SSBs.

Scalable Synthesis and Electrochemical Study of Ceramic-Polymer Nanocomposite Solid Electrolytes for Solid-State Battery Manufacturing

Solid-state lithium batteries (SSBs) have the potential to achieve high energy and power densities due to the use of solid electrolytes (SEs) that are compatible with lithium metal or silicon-based anodes. However, fabrication of SEs with good ionic conductivity, mechanical strength, electrochemical stability, and interfacial contact with solid electrodes have been challenging. One promising approach is to combine ceramic lithium conductors that is expected to show a relatively high room-temperature Li-ion conductivity and a soft polymer matrix that facilitates mechanical integrity at the electrode-electrolyte interface during charge-discharge cycling. In this study, we report a scalable synthesis of Al0.25Li6.25La3Zr2O12 (LLZO) nanofibers and polyethylene oxide (PEO) composite SEs using roll-to-roll manufacturing. Our LLZO fibers showed 0.3 mS/cm conductivity at room temperature and the LLZO-PEO composites showed three times higher critical current density than a single PEO polymer electrolyte. Microstructural and electrochemical properties of the composite electrolytes will be discussed.

High total Li-ion conductivity of LiTa2PO8 ceramics sintered using Bi2O3 as an additive

Lithium tantalum phosphate LiTa2PO8 ceramics have attracted significant attention as solid electrolytes in oxide-based all-solid-state batteries owing to their superior bulk conductivity of more than 1 mS cm−1 at room temperature. However, high-temperature sintering at 1050 °C, which is required to achieve a dense morphology, results in a high interfacial resistance at the grain boundaries. In this study, dense LiTa2PO8 ceramics were successfully synthesized via a conventional solid-state method at a low sintering temperature of 900 °C using Bi2O3 as the additive. A total lithium-ion conductivity of 1.41 × 10−3 S cm−1 at 25 °C was achieved. The microstructures of the sintered LiTa2PO8 ceramics were analyzed by X-ray diffraction and scanning electron microscopy with energy-dispersive X-ray spectroscopy. Large LiTa2PO8 grains grew in the dense solid-electrolyte body together with the interfacial BiPO4 phase, which acted as a sintering flux material, at a low sintering temperature of 900 °C. Thus, these LiTa2PO8 ceramics can serve as oxide solid electrolytes for all-solid-state lithium batteries owing to their high total Li-ion conductivity.

Intrinsically Safe Lithium Metal Batteries Enabled by Thermo-Electrochemical Compatible In Situ Polymerized Solid-State Electrolytes.

In situ polymerized solid-state electrolytes have attracted much attention due to high Li-ion conductivity, conformal interface contact, and low interface resistance, but are plagued by lithium dendrite, interface degradation, and inferior thermal stability, which thereby leads to limited lifespan and severe safety hazards for high-energy lithium metal batteries (LMBs). Herein, an in situ polymerized electrolyte is proposed by copolymerization of 1,3-dioxolane with 1,3,5-tri glycidyl isocyanurate (TGIC) as a cross-linking agent, which realizes a synergy of battery thermal safety and interface compatibility with Li anode. Functional TGIC enhances the electrolyte polymeric level. The unique carbon-formation mechanism facilitates flame retardancy and eliminates the battery fire risk. In the meantime, TGIC-derived inorganic-rich interphase inhibits interface side reactions and promotes uniform Li plating. Intrinsically safe LMBs with nonflammability and outstanding electrochemical performances under extreme temperatures (130°C) are achieved. This functional polymer design shows a promising prospect for the development of safe LMBs.

Elucidating the Impact of Li3InCl6-Coated LiNi0.8Co0.15Al0.05O2 on the Electro-Chemo-Mechanics of Li6PS5Cl-Based Solid-State Batteries.

Li6PS5Cl has attracted significant attention due to its high Li-ion conductivity and processability, facilitating large-scale solid-state battery applications. However, when paired with high-voltage cathodes, it experiences adverse side reactions. Li3InCl6 (LIC), known for its higher stability at high voltages and moderate Li-ion conductivity, is considered a catholyte to address the limitations of Li6PS5Cl. To extend the stability of Li6PS5Cl toward LiNi0.8Co0.15Al0.05O2 (NCA), we applied nanocrystalline LIC as a 180 nm-thick protective coating in a core-shell-like fashion (LIC@NCA) via mechanofusion. Solid-state batteries with LIC@NCA allow an initial discharge specific capacity of 148 mA h/g at 0.1C and 80% capacity retention for 200 cycles at 0.2C with a cutoff voltage of 4.2 V (vs Li/Li+), while cells without LIC coating suffers from low initial discharge capacity and poor retention. Using a wide spectrum of advanced characterization techniques, such as operando XRD, XPS, FIB-SEM, and TOF-SIMS, we reveal that the superior performance of solid-state batteries employing LIC@NCA is related to the suppression of detrimental interfacial reactions of NCA with Li6PS5Cl, delamination, and particle cracking compared to uncoated NCA.

Inorganic fillers tailored Li+ solvation sheath for stable lithium metal batteries

Ionogel electrolytes based on gel scaffolds and ionic liquids (ILs) have garnered widespread attention for their processing compatibility, non-flammability, and exceptional thermal/electrochemical properties. While there have been many studies demonstrating the effectiveness of the bisalt approach in stabilizing lithium metal anode, the precise impact of skeleton-constrained dual-anion ionogels on interface modulation remains somewhat obscured and deserves further attention. Herein, we formulate a Li6.4La3Zr1.4Ta0.6O12 (LLZTO)-incorporated dual-anion ionogel to reveal the solvation chemistry in the presence of LLZTO and detail the Li+ transport mechanism and effect on the interfacial chemistries of Li-metal. The impact of inorganic substances on the solvation structure in IL-based solid electrolytes and their role in forming the SEI layer on lithium metal was unveiled. To be specific, the introduction of fillers exert a selective modulating influence on the anions species in the Li+-solvated shell and fine-tunes the local Li+ environment, thereby fostering a more robust interfacial layer. Modified ion environment in ionogels enables a preferable shift from vehicular to structural Li+ transport, whereby a high Li ion conductivity (1.24×10−3 S/cm) and high Li ion transference number of 0.42 is achieved. The synergistic solvent coordination and adjustment of the electrode-electrolyte interface enable the LiFePO4|PIL-10|Li cells to cycle steadily with capacity retention of 95.4 % after 500 cycles at 1C and 25 °C. The strategy of promoting transport mechanisms holds promise for designing the next-generation solid-state lithium metal batteries with high energy density.

Accelerating the Development of LLZO in Solid-State Batteries Toward Commercialization: A Comprehensive Review.

Solid-state batteries (SSBs) are under development as high-priority technologies for safe and energy-dense next-generation electrochemical energy storage systems operating over a wide temperature range. Solid-state electrolytes (SSEs) exhibit high thermal stability and, in some cases, the ability to prevent dendrite growth through a physical barrier, and compatibility with the "holy grail" metallic lithium. These unique advantages of SSEs have spurred significant research interests during the last decade. Garnet-type SSEs, that is, Li7La3Zr2O12 (LLZO), are intensively investigated due to their high Li-ion conductivity and exceptional chemical and electrochemical stability against lithium metal anodes. However, poor interfacial contact with cathode materials, undesirable lithium plating along grain boundaries, and moisture-induced chemical degradation greatly hinder the practical implementation of LLZO-based SSEs for SSBs. In this review, the recent advances in synthesis methods, modification strategies, corresponding mechanisms, and applications of garnet-based SSEs in SSBs are critically summarized. Furthermore, a comprehensive evaluation of the challenges and development trends of LLZO-based electrolytes in practical applications is presented to accelerate their development for high-performance SSBs.

Ce doped UiO-66(Hf) electrolyte for all-solid-state lithium metal batteries

Solid electrolytes have garnered significant attention as promising candidates for all-solid-state batteries due to their excellent safety, and cycling stability. However, the development of solid electrolytes faces challenges in achieving high ionic conductivity and low interfacial impedance. In this study, we prepared a Ce doped UiO-66(Hf)-base electrolyte using a solvothermal method. The resulting electrolyte exhibited remarkable properties, including high Li-ion conductivity (3.72 × 10−3 S cm−1), a high lithium ion transfer number (tLi+ = 0.66), and stability during stripping electroplating. These impressive results can be attributed to that the shorter length of the Ce-O bond in UiO-66(Hf) compared to the Hf-O bond, which enhances the transformation of Li+ ions. The incorporation of Ce as a dopant into UiO-66(Hf) in solid electrolytes holds great promise for future applications in solid-state batteries.

A solid-state lithium-ion battery with micron-sized silicon anode operating free from external pressure

Applying high stack pressure (often up to tens of megapascals) to solid-state Li-ion batteries is primarily done to address the issues of internal voids formation and subsequent Li-ion transport blockage within the solid electrode due to volume changes. Whereas, redundant pressurizing devices lower the energy density of batteries and raise the cost. Herein, a mechanical optimization strategy involving elastic electrolyte is proposed for SSBs operating without external pressurizing, but relying solely on the built-in pressure of cells. We combine soft-rigid dual monomer copolymer with deep eutectic mixture to design an elastic solid electrolyte, which exhibits not only high stretchability and deformation recovery capability but also high room-temperature Li-ion conductivity of 2×10−3 S cm−1 and nonflammability. The micron-sized Si anode without additional stack pressure, paired with the elastic electrolyte, exhibits exceptional stability for 300 cycles with 90.8% capacity retention. Furthermore, the solid Li/elastic electrolyte/LiFePO4 battery delivers 143.3 mAh g−1 after 400 cycles. Finally, the micron-sized Si/elastic electrolyte/LiFePO4 full cell operates stably for 100 cycles in the absence of any additional pressure, maintaining a capacity retention rate of 98.3%. This significantly advances the practical applications of solid-state batteries.

Mechanism of high Li-ion conductivity in poly(vinylene carbonate)-poly(ethylene oxide) cross-linked network based electrolyte revealed by solid-state NMR

Solid polymer electrolytes (SPEs) have become increasingly important in advanced lithium-ion batteries (LIBs) due to their improved safety and mechanical properties compared to organic liquid electrolytes. Cross-linked polymers have the potential to further improve the mechanical property without trading off Li-ion conductivity. In this study, focusing on a recently developed cross-linked SPE, i.e., the one based on poly(vinylene carbonate)-poly(ethylene oxide) cross-linked network (PVCN), we used solid-state nuclear magnetic resonance (NMR) techniques to investigate the fundamental interaction between the chain segments and Li ions, as well as the lithium-ion motion. By utilizing homonuclear/heteronuclear correlation, CP (cross-polarization) kinetics, and spin–lattice relaxation experiments, etc., we revealed the structural characteristics and their relations to lithium-ion mobilities. It is found that the network formation prevents poly(ethylene oxide) chains from crystallization, which could create sufficient space for segmental tumbling and Li-ion conduction. As such, the mechanical property is greatly improved with even higher Li-ion mobilities compared to the poly(vinylene carbonate) or poly(ethylene oxide) based SPE analogues.

Deciphering the Origin of Interface‐Induced High Li and Na Ion Conductivity in Nanocomposite Solid Electrolytes Using X‐Ray Raman Spectroscopy

AbstractSolid‐state electrolytes (SSEs) with high ionic conductivities are crucial for safer and high‐capacity batteries. Interface effects in nanocomposites of SSEs and insulators can lead to profound increases in conductivity. Understanding the composition of the interface is crucial for tuning the conductivity of composite solid electrolytes. Herein, X‐ray Raman Scattering (XRS) spectroscopy is used for the first time to unravel the nature of the interface effects responsible for conductivity enhancements in nanocomposites of complex hydride‐based electrolytes (LiBH4, NaBH4, and NaNH2) and oxides. XRS probe of the Li, Na, and B local environments reveals that the interface consists of highly distorted/defected and structurally distinct phase(s) compared to the original compounds. Interestingly, nanocomposites with higher concentrations of the interface compounds exhibit higher conductivities. Clear differences are observed in the interface composition of SiO2‐ and Al2O3‐based nanocomposites, attributed to differences in the reactivity of their surface groups. These results demonstrate that interfacial reactions play a dominant role in conductivity enhancement in composite solid electrolytes. This work showcases the potential of XRS in investigating interface interactions, providing valuable insights into the often complex ion conductor/insulator interfaces, especially for systems containing light elements such as Li, B, and Na present in most SSEs and batteries.

Influence of oxygen distribution on the Li-ion conductivity in oxy-sulfide glasses - taking a closer look.

Lithium thiophosphates are a promising class of solid electrolyte (SE) materials for all-solid-state batteries (ASSBs) due to their high Li-ion conductivity. Yet, the practical application of lithium thiophosphates is hindered by their chemical instability, which remains a prevalent challenge in the field. Oxygen substitution has been discussed in the literature as a promising strategy to enhance stability. Nevertheless, the lack of understanding of the role of synthesis strategy on the resulting structure-property relationship makes it difficult to predict and control the material's behaviour, limiting our ability to fully utilize oxygen substitution as a viable solution. Here, we show that not only the total oxygen content but also the oxygen distribution within the material affects the ion conductivity. By carefully analysing the local structure of oxy-sulfide glasses, we find that few highly oxygenated structural units like [PO4]3- and [PO3S]3- are more detrimental to the ionic conductivity than a larger amount of less substituted units like [POS3]3-. Further, we demonstrate how the oxygen distribution is connected to the synthesis in high-energy ball milling by comparing two different sets of precursor materials. The results may explain the deviations in the past literature. The findings should be transferable to other Li-thiophosphate materials and enable more directed design of new materials.

Improved structure stability and performance of a LiFeSO4F cathode material for lithium-ion batteries by magnesium substitution.

Tavorite LiFeSO4F with high Li-ion conductivity has been considered a promising alternative to LiFePO4. However, its poor cycle stability and low electronic conductivity limit the practical application of Tavorite LiFeSO4F. In the present study, we employ a solvothermal method to produce magnesium-substitution LiMgxFe1-xSO4F (x = 0, 0.02, 0.04) cathode materials in which the Mg substitutes the Fe(2) sites. The first-principles calculations demonstrate that Mg-substitution could reduce the bandgap of LiFeSO4F and increase its electronic conductivity to 2.5 × 10-11 S cm-1. Meanwhile, CI-NEB and BV calculations reveal that the diffusion energy barrier of lithium along the (100) direction after Mg substitution is lower than the pristine sample, and the electrochemical inactive Mg2+ could improve the structure stability. The results show that the Mg-substituted LiFeSO4F exhibits enhanced cycle stability and rate performance compared with the pristine LiFeSO4F, suggesting that the use of electrochemically inactive ion substitution may be critical for the development of high-performance LiFeSO4F cathode materials for lithium-ion batteries.

Accelerated Single Li-Ion Transport in Solid Electrolytes for Lithium-Sulfur Batteries: Poly(Arylene Ether Sulfone) Grafted with Pyrrolidinium-Terminated Poly(Ethylene Glycol).

Polymeric solid electrolytes have attracted tremendous interest in high-safety and high-energy capacity lithium-sulfur (Li─S) batteries. There is, however, still a dilemma to concurrently attain high Li-ion conductivity and high mechanical strength that effectively suppress the Li-dendrite growth. Accordingly, a rapidly Li-ion conducting solid electrolyte is prepared by grafting pyrrolidinium cation (PYR+)-functionalized poly(ethylene glycol) onto the poly(arylene ether sulfone) backbone (PAES-g-2PEGPYR). The PYR+ groups effectively immobilize anions of Li-salts in Li-conductive PEGPYR domains phase-separated from PAES matrix to enhance the single-ion conduction. The tailored PAES-g-2PEGPYR membrane shows a high Li-ion transference number of 0.601 and superior ionic conductivity of 1.38mScm-1 in the flexible solid state with the tensile strength of 1.0MPa and Young's modulus of 1.5MPa. Moreover, this PAES-g-2PEGPYR membrane exhibits a high oxidation potential (5.5V) and high thermal stability up to 200(C. The Li/PAES-g-2PEGPYR/Li cell stably operates for 1000h without any short circuit, and the rechargeable Li/PAES-g-2PEGPYR/S cell discharges a capacity of 1004.7mAhg-1 at C/5 with the excellent rate capability and the prominent cycling performance of 95.3% retention after 200 cycles.

Interfacial Degradation Processes in Solid-State Batteries during High Temperature Processing and the Mitigation Strategies

Garnet-type solid electrolytes have been extensively investigated in recent times as potential candidates for solid-state batteries. Among them, garnets with nominal composition Li7La3Zr2O12(LLZO) have received particular attention due to their high Li-ion conductivity (10-3 Scm-1) at room temperature and chemical stability against metallic lithium besides possessing a large electrochemical window >5V.[1] Despite of striking properties, LLZO suffers from several challenges such as interfacial instability with cathodes, e.g., LCO, during high temperature processing, resulting in a huge interface resistance, which is one of the fundamental reasons for the failure of solid-state batteries based on LLZO.[2-4] So far, the high interfacial impedance has been related to LLZO|LCO interface decomposition occurring due to diffusion of Co across the cathode-electrolyte interface. Herein, we investigated the hypothesis that interfacial degradation originate from the incorporation of Co into the LLZO lattice. The solubility limit of Co is determined to be 0.16 per formula unit, whilst the concentrations beyond promote phase transition (cubic LLZO-to-tetragonal LLZO). We investigated in detail the temperature-dependent Co diffusion into LLZO and concluded that detrimental cross diffusion could take place at any relevant process condition. Besides, the optimal protective Al2O3 coating thickness for relevant temperatures was studied, which allowed to create a process diagram to provide mitigation strategies towards enabling stable LCO|LLZO interface in all-solid-state batteries. Keywords: Solid-state batteries, Interfaces, cross diffusion, interfacial degradation AcknowledgementsD.R. acknowledges financial support by the Austrian Federal Ministry for Digital and Economic Affairs, the National Foundation for Research, Technology and Development and the Christian Doppler Research Association (Christian Doppler Laboratory for Solid-State Batteries). D.R. and J. F. acknowledges financial support by the Austrian Science Fund (FWF) in the frame of the project InterBatt (P 31437). D.K. acknowledges funding by the European Union’s Horizon 2020 Research and Innovation Programme (Grant No. 823717, project “ESTEEM3”) and by the Zukunftsfond Steiermark.Reference[1] Murugan, R., Thangadurai, V. and Weppner, W., 2007. Fast Lithium Ion Conduction in Garnet‐type Li7La3Zr2O12. Angew. Chemie. Int. Edt., 46(41), 7778-7781.[2] Chen, X., Xie, J., Zhao, X., & Zhu, T., 2021. Electrochemical Compatibility of Solid‐State Electrolytes with Cathodes and Anodes for All‐Solid‐State Lithium Batteries: A Review. Adv. Energy Sustain. Res., 2(5), 2000101.[3] Sakuda, A., Hayashi, A., Tatsumisago, M., 2010. Interfacial Observation Between LiCoO2 Electrode and Li2S-P2S5 Solid Electrolytes of All-Solid-State Lithium Secondary Batteries Using Transmission Electron Microscopy. Chem. Mater., 22(3), 949–956.[4] Ihrig, M., Kuo, L.Y., Lobe, S., Laptev, A.M., Lin, C.A., Tu, C.H., Ye, R., Kaghazchi, P., Cressa, L., Eswara, S. and Lin, S.K., 2023. Thermal Recovery of the Electrochemically Degraded LiCoO2/Li7La3Zr2O12: Al, Ta Interface in an All-Solid-State Lithium Battery. ACS Appl. Mater. Interfaces.

Mixed Ionic Electronic Conduction Caused by Phase Transformation and Interfacial Segregation in an Entropy Stabilized Oxide

Research on entropy-stabilized oxides (ESO) [1] has primarily focused on exploring new single-phase structures with diverse chemistries, or unique properties, such as high Li-ion conductivity, high dielectric constant, low thermal conductivity, good electrochemical cycling stability, and high storage capacity retention [2]. However, few studies discuss the impact of secondary phase formation on functionality such as electrical conductivity [3] despite the fact that annealing this single-phase ESO causes it to undergo a phase transformation leading to the formation of Cu-rich and Co-rich secondary phases [4]. To address this gap, this work [5] investigates the electrical transport mechanisms in the canonical entropy-stabilized oxide (Co,Cu,Mg,Ni,Zn)O as a function of secondary phase content. Here, the structure and composition of single-phase and multiphase ESOs, and their GBs and HIs are probed using atomic-resolution imaging by scanning transmission electron microscopy (STEM) coupled with nanoscale spectroscopy by electron energy-dispersive spectroscopy (EDS) and electron energy-loss spectroscopy (EELS). Our findings suggest that when single-phase, the oxide is an oxygen ion conductor. After 2 h of heat treatment, Cu-rich tenorite particles form at some grain boundaries, turning the grain interior rocksalt oxide into a mixed ionic-electronic conductor via oxygen ions and small hole polaron Co2+/Co3+ and Cu2+/Cu+ pairs. 24 h of heat treatment leads to the full coverage of Cu-rich tenorite particles at all grain boundaries and the formation of anisotropic Cu-rich tenorite and equiaxed Co-rich spinel particles in the grains. While the grain interiors exhibit similar mixed ionic-electronic conduction, Cu-rich tenorite grain boundary phases create a pathway for Cu2+/Cu3+ small hole polarons. The ability to selectively grow secondary phases nucleated at grain boundaries enables tuning of electrical properties in entropy-stabilized and complex concentrated oxides using microstructure design, nanoscale engineering, and heat treatment, paving the way to develop many novel materials.[1] C. M. Rost, J.-P. Maria, Nat Commun, 2015.[2] A. Salian, S. Mandal, Critical Reviews in Solid State and Materials Sciences, 2022.[3] M. Moździerz, K. Świerczek, Acta Materialia, 2021.[4] A. D. Dupuy, J. M. Schoenung, Journal of the European Ceramic Society, 2021.[5] H. Vahidi...W. J. Bowman (submitted). Acknowledgments This research was primarily supported by the National Science Foundation Materials Research Science and Engineering Center program through the UC Irvine Center for Complex and Active Materials (DMR-2011967). WJB and HV acknowledge partial support from the UCI new faculty startup funding. The authors acknowledge the use of facilities and instrumentation at the UC Irvine Materials Research Institute (IMRI) supported in part by the National Science Foundation Materials Research Science and Engineering Center program through the UC Irvine Center for Complex and Active Materials (DMR-2011967).

A nanocrystal garnet skeleton-derived high-performance composite solid-state electrolyte membrane

Composite solid-state electrolytes (SSEs) can improve the flexibility of the oxide SSEs to decrease the interfacial resistance between the electrolytes and the electrodes. However, the ceramic nanofillers within the composite SSEs suffer from the agglomeration at high concentrations, decreasing the ion conductivities. In this study, a continuous nanocrystal Li6.5La3Zr1.5Ta0.5O12 (LLZTO) skeleton is prepared by the ultrafast high-temperature sintering (UHS) together with tape-casting. Due to the short sintering time of ∼5 s from precursors, the LLZTO grains are restrained to ∼300 nm with limited Li loss. Even with trace solvent (3 wt%), the composite SSE membrane exhibits an ion conductivity of 5 × 10−4 S⋅cm−1, ∼50 times higher than the DOL electrolyte (1 × 10−5 S⋅cm−1, 8 wt% solvent), which further proves the high Li-ion conductivity of the nanocrystal LLZTO skeleton. The composite SSE membrane exhibits a critical current density of 3.4 mA⋅cm−2, among the highest reported values for ceramic-polymer SSEs. The Li/composite SSEs/Li symmetric cells can cycle ∼ 120 h at the current density from 0.2 to 0.4 mA⋅cm−2. The LiFePO4/LLZTO-PEGDA composite SSEs/Li full cell exhibits a high specific discharge capacity of ∼150 mAh⋅g−1 for ∼50 cycles with a Coulombic efficiency of ∼97%. To explore the processability of the membrane with large size, we also demonstrate a pouch cell (2 cm × 5 cm) with a high specific capacity of ∼150 mAh⋅g−1 for ∼25 cycles and a capacity retention of ∼94.5%. This work paves a new way to manufacture the nanocrystal ceramic SSE skeleton for high energy density all-solid-state batteries.