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With the continued increase in Li‐metal anode rate capability, there is an equally important need to develop high‐rate cathode architectures for solid‐state batteries. A proposed method of improving charge transport in the cathode is introducing a mixed electronic and ionic conductor (MEIC) which can eliminate the need for conductive additives that occlude electrolyte–electrode interfaces and lower the net additive required in the cathode. This study takes advantage of a reduced perovskite electrolyte, Li0.33La0.57TiO3 (LLTO), to act as a model MEIC. It is found that the ionic conductivity of reduced LLTO is comparable to oxidized LLTO (σbulk = 10−3–10−4 S cm−1, σGB = 10−5–10−6 S cm−1) and the electronic conductivity is 1 mS cm−1. The ionic transference numbers are 0.9995 and 0.0095 in the oxidized and reduced state, respectively. Furthermore, two methods for controlling the transference numbers are evaluated. It is found that the electronic conductivity cannot easily be controlled by changing O2 overpressures, but increasing the ionic conductivity can be achieved by increasing grain size. This work identifies a possible class of MEIC materials that may improve rate capabilities of cathodes in solid‐state architectures and motivate a deeper understanding of MEICs in the context of solid‐state batteries. [ABSTRACT FROM AUTHOR]

Abstract The potential for safe, high energy-density Li-ion batteries has motivated the development of the solid electrolyte Li 7 La 3 Zr 2 O 12 (LLZO) to physically stabilize the Li-electrolyte interface. Although dense LLZO is a relatively hard ceramic, it has been observed that above a certain critical current density (CCD), Li metal can still propagate through both polycrystalline and single crystalline LLZO. However, reported values of CCD are still well below the current density regimes relevant to applications like electric vehicles (≥3 mA cm−2). The relationship between CCD and temperature was studied using recently developed methods for achieving consistently low interfacial impedances without interfacial coatings that can complicate the analysis of what controls interface stability. By analyzing the flux of Li+ ions at the Li-electrolyte interface, it is hypothesized here that solid-state diffusivity of Li in the Li electrode may be a governing mechanism that controls the CCD. These results demonstrate an improvement for dendrite-free cycling in LLZO up to ∼1 mA cm−2 at room temperature and ∼7 mA cm−2 at 100 °C without the need for coatings to achieve low interface resistances (∼10 Ω cm2). Furthermore, the presented analysis may provide additional insight on the role of Li diffusivity in Li propagation through ceramic electrolytes. [ABSTRACT FROM AUTHOR]

Cubic garnet LiLaZrAlO (LLZO) is a candidate material for use as an electrolyte in Li-Air and Li-S batteries. The use of LLZO in practical devices will require LLZO to have good mechanical integrity in terms of scratch resistance (hardness) and an adequate stiffness (elastic modulus). In this paper, the powders were fabricated by powder processing of cast ingots. All specimens were then densified via hot pressing. The room temperature elastic moduli (Young's modulus, shear modulus, bulk modulus, and Poisson's ratio) and hardness were measured by resonant ultrasound spectroscopy, and Vickers indentation, respectively. For volume fraction porosity, P, the Young's modulus was 149.8 ± 0.4 GPa ( P = 0.03) and 132.6 ± 0.2 GPa ( P = 0.06). The mean Vickers hardness was 6.3 ± 0.3 GPa for P = 0.03 and 5.2 ± 0.4 for P = 0.06. [ABSTRACT FROM AUTHOR]

The lattice and total Li-ionic conductivity of LiLaTiO ceramic (LLTO) sintered at 1200 °C were determined as functions of powder calcination temperature and sintering duration, and these results were correlated with the relative degrees of Li-ordering, Li-content, grain size, and bulk density to assess the relative impact of these parameters on material performance. Under all conditions, LLTO formed with a high degree of tetragonal superstructure to its perovskite related framework, and the lattice conductivity closely followed the relative amounts of the superstructure, as evaluated via determination of the sample ordering parameter from X-ray diffraction data. LLTO powders that were calcined at 900 °C for 1 h and sintered at 1200 °C for 6 h gave lattice conductivity values (~1.14 × 10S cm) comparable within the highest ranges reported in the literature. This coincided with the lowest degree of tetragonal superstructure formation, and it was also found to be largely independent of the values of Li-content measured on sintered ceramic despite significant LiO volatilization at longer sintering times (up to 23 % after 12 h at 1200 °C). Samples of LLTO powder that were calcined at 1100 °C and sintered at 1200 °C for 12 h resulted in the highest total Li-ion conductivity value ~6.30 × 10S cm. The total conductivity of LLTO varied inversely with grain size when the grains were <20 μm but was insensitive to that parameter above that size threshold. The strongest influence on total conductivity was primarily the bulk ceramic density. It was estimated from measured values that as the bulk ceramic density approached the full theoretical value for LLTO the total conductivity could near the lattice conductivity of ~1.2 × 10S cm. [ABSTRACT FROM AUTHOR]

The Na-ion conducting solid electrolyte NASICON is a promising solid state electrolyte (SSE) for use in Na based electrochemical systems. The effects of particle morphology and synthesis of von Alpen type NASICON via hot-pressing were investigated. Spray dried particles were shown to improve mechanical and electrochemical properties. X-ray diffraction, scanning electron microscopy, impulse excitation measurements, Vickers hardness, and impedance spectroscopy were used to correlate relationships between phase purity, microstructure, mechanical properties, and electrochemical properties. Scanning electron microscopy showed the presence of a glass phase as between 19.08% and 28.23% area percentage and a ZrO 2 phase between 0.46% and 3.51% area percentage in the hot-pressed samples. Impulse excitation showed elastic modulus varying from 83.65 to 97.65 GPa. The first values of Poisson's ratio and shear modulus of NASICON are reported as between 0.23 and 0.26 and 33.87 to 38.79 GPa, respectively. Vickers hardness and fracture toughness measurements showed Vickers hardness ranging from 4.30 to 4.68 GPa and fracture toughness ranging from 1.05 to 1.09 MPa m½. Impedance spectroscopy showed grain conductivities ranging from 1.023 to 1.287 mS/cm, with grain boundary resistance percentages between 73.22 and 47.5%. Total conductivities ranged from 0.292 to 0.596 mS/cm, with 0.596 mS/cm being achieved at room temperature for the spray dried powders with lower grain boundary resistance percentages. • Densified spray dried von Alpen NASICON powders using hot-pressing. • Smaller and more uniform spray dried particles and hot-pressing reduce glassy phase. • First experimental values of Poisson's ratio of NASICON, between 0.23 and 0.26. • First experimental values of shear modulus of NASICON, between 33.87 and 38.79 GPa. • Hot-pressed NASICON total conductivities ranged from 0.292 to 0.595 mS/cm. [ABSTRACT FROM AUTHOR]