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Solid–state batteries based on Li7La3Zr2O12 (LLZO) garnet electrolyte are a robust and safe alternative to conventional lithium‐ion batteries. However, the large‐scale implementation of ceramic composite cathodes is still challenging due to a complex multistep manufacturing process. A new one‐step route for the direct synthesis of LLZO during the manufacturing of LLZO/LiCoO2 (LCO) composite cathodes based on cheap precursors and utilizing the industrially established tape casting process is presented. It is shown that Al, Ta:LLZO can be formed directly in the presence of LCO from metal oxide precursors (LiOH, La2O3, ZrO2, Al2O3, and Ta2O5) by heating to 1050 °C, eliminating the time‐ and energy‐consuming synthesis of preformed LLZO powders. In addition, performance‐optimized gradient microstructures can be produced by sequential casting of slurries with different compositions, resulting in dense and flat phase‐pure cathodes without unwanted ion interdiffusion or secondary phase formation. Freestanding cathodes with a thickness of 85 µm, a relative density of 95%, and an industrial relevant LCO loading of 15 mg show an initial capacity of 82 mAh g−1 (63% of the theoretical capacity of LCO) in a solid‐state cell with Li metal anodes, which is comparable to conventional LCO/LLZO cathodes and can be further improved in the future. [ABSTRACT FROM AUTHOR]

This study explores multi-component garnet-based materials as solid electrolytes for all-solid-state lithium batteries. Through a combination of computational and experimental approaches, we investigate the thermodynamic and structural properties of lithium lanthanum zirconium oxide garnets doped with various elements. Applying density functional theory, the influence of dopants on the thermodynamic stability of these garnets was studied. Probable atomic configurations and their impact on materials' properties were investigated with the focus on understanding the influence of these configurations on structural stability, phase preference, and ionic conductivity. In addition to the computational study, series of cubic-phase garnet compounds were synthesized and their electrochemical performance was evaluated experimentally. Our findings reveal that the stability of cubic phase in doped Li-garnets is primarily governed by enthalpy, with configurational entropy playing a secondary role. Moreover, we establish that the increased number of doping elements significantly enhances the cubic phase's stability. This in-depth understanding of materials' properties at atomic level establishes the basis for optimizing high-entropy ceramics, contributing significantly to the advancement of solid-state lithium batteries and other applications requiring innovative material solutions. [ABSTRACT FROM AUTHOR]

All-solid-state batteries are a hot research topic due to the prospect of high energy density and higher intrinsic safety, compared to conventional lithium-ion batteries. Of the wide variety of solid-state electrolytes currently researched, oxide ceramic lithium-ion conductors are considered the most difficult to implement in industrial cells. Although their high lithium-ion conductivity combined with a high chemical and thermal stability make them a very attractive class of materials, cost-cutting synthesis and scalable processing into full batteries remain to be demonstrated. Additionally, they are Fluorine-free and can be processed in air but require one or more high temperature treatment steps during processing counteracting their ecological benefits. Thus, a viable cell design and corresponding assessment of its ecological impact is still missing. To close this gap, we define a target cell combining the advantages of the two most promising oxidic electrolytes, lithium lanthanum zirconium oxide (LLZO) and lithium aluminium titanium phosphate (LATP). Even though it has not been demonstrated so far, the individual components are feasible to produce with state-of-the-art industrial manufacturing processes. This model cell then allows us to assess the environmental impact of the ceramic electrolyte synthesis and cell component manufacturing not just on an abstract level (per kg of material) but also with respect to their contributions to the final cell. The in-depth life cycle assessment (LCA) analysis revealed surprising similarities between oxide-based all-solid-state batteries and conventional Li-ion batteries. The overall LCA inventory on the material level is still dominated by the cathode active material, while the fabrication through ceramic manufacturing processes is a major contributor to the energy uptake. A clear path that identifies relevant research and development directions in terms of economic benefits and environmental sustainability could thus be developed to promote the competitiveness of oxide based all-solid-state batteries in the market. [ABSTRACT FROM AUTHOR]

Lithium and sodium (Na) mixed polyanion solid electrolytes for all-solid-state batteries display some of the highest ionic conductivities reported to date. However, the effect of polyanion mixing on the ion-transport properties is still not fully understood. Here, we focus on Na1+xZr2SixP3−xO12 (0 ≤ x ≤ 3) NASICON electrolyte to elucidate the role of polyanion mixing on the Na-ion transport properties. Although NASICON is a widely investigated system, transport properties derived from experiments or theory vary by orders of magnitude. We use more than 2000 distinct ab initio-based kinetic Monte Carlo simulations to map the compositional space of NASICON over various time ranges, spatial resolutions and temperatures. Via electrochemical impedance spectroscopy measurements on samples with different sodium content, we find that the highest ionic conductivity (i.e., about 0.165 S cm–1 at 473 K) is experimentally achieved in Na3.4Zr2Si2.4P0.6O12, in line with simulations (i.e., about 0.170 S cm–1 at 473 K). The theoretical studies indicate that doped NASICON compounds (especially those with a silicon content x ≥ 2.4) can improve the Na-ion mobility compared to undoped NASICON compositions. Battery solid-state electrolytes rely on mixed polyanion networks to attain high ionic conductivities. Here, the authors investigate the effect of polyanion mixing on the solid-state electrolyte ion conductivity via theoretical calculations and electrochemical measurements. [ABSTRACT FROM AUTHOR]

Phosphate lithium‐ion conductors are outstanding electrolyte materials for solid‐state lithium batteries. As polycrystalline ceramics, they must be sintered at high temperatures. Lithium tungstate Li2WO4 (LWO) is reported for the first time as an effective sintering aid to reduce the sintering temperature for one of the most common solid‐state lithium‐ion conductors, Li1.5Al0.5Ti1.5(PO4)3 (LATP). While densification of LATP without sintering aids requires temperatures of at least 950 °C to obtain a relative density of 90 %, here relative densities of 90–95 % are achieved even at 775 °C when 5 wt.% of LWO are added. At 800 °C the LATP containing 5–7 wt.% LWO densifies to a relative density of 97.2 %. The ionic conductivity of LWO containing LATP is generally higher than that of pure LATP sintered at the same temperature. LATP containing 7 wt.% LWO shows high ionic conductivity of 4.4×10−4 S/cm after sintering at 825 °C. A significant reduction in sintering temperature, an increase in density and in the ionic conductivity of LATP as well as its non‐toxicity render LWO a very promising sintering aid for the development of LATP‐based solid state batteries. [ABSTRACT FROM AUTHOR]

Highly efficient energy conversion and storage technologies such as high‐temperature solid oxide fuel and electrolysis cells, all‐solid‐state batteries, gas separation membranes, and thermal barrier coatings for advanced turbine systems depend on advanced materials. In all cases, processing of ceramics and metals starting from powders plays a key role and is often a challenging task. Depending on their composition, such powder materials often require high sintering temperatures and show an inherent risk of abnormal grain growth, evaporation, chemical reaction, or decomposition, especially in the case of long dwelling times. Electric current‐assisted sintering (ECAS) techniques are promising to overcome these restrictions, but a lot of fundamental and practical challenges must be solved properly to take full advantage of these techniques. A broad and long‐term expertise in the field of ECAS techniques and comprehensive facilities including conventional field‐assisted sintering technology/spark plasma sintering (FAST/SPS), hybrid FAST/SPS (with additional heater), sinter forging, and flash sintering (FS) devices are available at the Institute of Energy and Climate Research: Materials Synthesis and Processing (IEK‐1). Herein, main advantages and challenges of these techniques are discussed and the concept to overcome current limitations is introduced on selected examples. [ABSTRACT FROM AUTHOR]

The ionic conductivity of solid electrolytes is dependent on synthesis and processing conditions, ie, powder properties, shaping parameters, sintering time (ts), and sintering temperature (Ts). In this study, Na3Zr2(SiO4)2(PO4) was sintered at 1200 and 1250°C for 0‐10 hours and its microstructure and electrical performance were investigated by means of scanning electron microscopy and impedance spectroscopy. After sintering under all conditions, the sodium super‐ionic conductor‐type structure was formed along with ZrO2 as a secondary phase. The microstructure investigation revealed a bimodal particle size distribution and grain growth at both Ts. The density of samples increased from 60% at 1200°C for 0 hours to 93% at 1250°C for 10 hours. The ionic conductivity of the samples increased with ts due to densification and grain growth, ranging from 0.13 to 0.71 mS/cm, respectively. The corresponding equivalent circuit fitting for the impedance spectra revealed that grain boundary resistance is the prime factor contributing to the changing conductivity after sintering. The activation energy of the bulk conductivity (Ea,bulk) remained almost constant (0.26 eV) whereas the activation energy of the total conductivity (Ea) exhibited a decreasing trend from 0.37 to 0.30 eV for the samples with ts = 0 and 10 hours, respectively—both sintered at 1250°C. In this study, the control of the grain boundaries improved the electrical conductivity by a factor of 6. [ABSTRACT FROM AUTHOR]

Sol-gel synthesis is an extensively used method for the preparation of nanopowders. However, complicated or expensive precursors, and the necessity of using organic solvent and/or heat assistance limit the method to laboratory-scaled level. An aqueous-based sol-gel method with spontaneous sol and gel formation is developed in this study. It can be applied on a large scale to synthesize compounds with Ti4+ and PO43− as major components with low cost. Al-substituted LiTi2( PO4)3 ( LATP) has been widely investigated as a promising candidate for solid electrolyte in Li-ion or Li-air batteries. Major challenges such as unsatisfactory phase purity, low sintering activity, and high production costs are faced during the fabrication of LATP. In this study, as a sample application, Li1.5Al0.5Ti1.5( PO4)3 ( LATP05) is conveniently prepared on a large scale by the novel sol-gel method with high phase purity, active densification behavior and high conductivity. [ABSTRACT FROM AUTHOR]

The correct affiliations, axis labels, numerical values of tables and labelling of equation components are now provided in the main text and supplementary information. In Supplementary Table 1, the numerical values "623.9" and "625.2" in the "AE SB end sb " column were missing the "-" sign, and the terms "Na(1)" and "Na(2)" were swapped. [Extracted from the article]

Front Cover: The Impact of Lithium Tungstate on the Densification and Conductivity of Phosphate Lithium-Ion Conductors (ChemElectroChem 5/2022) Keywords: Ceramics; Crystal growth; Lithium-ion conductor NASICON-type; Solid electrolyte EN Ceramics Crystal growth Lithium-ion conductor NASICON-type Solid electrolyte 1 1 1 03/17/22 20220311 NES 220311 B The Front Cover b shows LATP powder and a dense LATP pellet obtained after powder sintering, which typically requires high temperatures. Ceramics, Crystal growth, Lithium-ion conductor NASICON-type, Solid electrolyte. [Extracted from the article]

Oxide-ceramic based electrolytes such as Li 7 La 3 Zr 2 O 12 (LLZO), are one of the most promising solid electrolytes for application in all-solid-state batteries. However, most of its constituents are listed as critical raw materials, highlighting the need to minimize waste during synthesis and processing. Therefore, we investigated the re-use of aged LLZO powder and aged LLZO green foils produced by tape-casting, an industrial processing route suitable for ASSBs. We established a new synthesis route to fully recovery Li-poor LLZO and pyrochlore phase La 2 Zr 2 O 7 by simply adding a Li source during firing. By using recycled LLZO powder in a <200 μm thick cast tape, we were able to prove a similar ionic conductivity of 2.1 × 10−4 S cm−1 at room temperature and a critical current density of 0.75 mA cm−2 at 60 °C compared to fresh powder. This simple and efficient re-synthesis strategy might hold the potential to minimize waste streams of critical raw materials in future industrial production processes of solid-state batteries. • Investigation of re-use of production waste of the solid electrolyte Li 7 La 3 Zr 2 O 12. • Waste powder and tape loses Li and thus forms a pyrochlore phases. • A new processing route was developed to re-introduce the waste directly. • The performance was shown to be almost identical to freshly synthesized powders. • This approach minimizes waste of critical raw materials in future ASB production. [ABSTRACT FROM AUTHOR]

• TZM tool enables High-pressure Field Assisted Sintering. • High-pressure provides low-temperature sintering of components in Li batteries. • Low-temperature excludes undesirable reactions during synthesis of Li batteries. • High-pressure sintering enhances performance of all-solid-state Li batteries. High-pressure field assisted sintering (FAST/SPS) of half-cell for all-solid-state Li batteries was proposed and tested. The half-cell included the layer of lithium lanthanum zirconate (LLZO) electrolyte and the layer of mixed cathode. The mixed cathode consisted of lithium cobalt oxide (LCO) used as energy storage material and LLZO used as ionic conductor. A tool made of TZM molybdenum alloy was used to apply a high pressure of 440 MPa during FAST/SPS at a temperature of 675 °C ensuring stability of materials. An average relative density of sintered half-cell was around of 95%. The half-cell was assembled with a lithium anode and electrochemically tested. The results were compared with the performance of a half-cell sintered in an established graphite tool at the same temperature but under a lower pressure of 50 MPa and with a lower density (around of 78%). The battery with half-cell sintered at high pressure showed two-fold larger surface storage capacity. Further optimization of materials and processing is in progress. [ABSTRACT FROM AUTHOR]

NASICON-based solid electrolytes with exceptionally high Na-ion conductivities are considered to enable future all solid-state Na-ion battery technologies. Despite 40 years of research the interrelation between crystal structure and Na-ion conduction is still controversially discussed and far from being fully understood. In this study, microcontact impedance spectroscopy combined with single crystal X-ray diffraction, and differential scanning calorimetry is applied to tackle the question how bulk Na-ion conductivity σbulk of sub-mm-sized flux grown Na3Sc2(PO4)3 (NSP) single crystals is influenced by supposed phase changes (α, β, and γ phase) discussed in literature. Although we found a smooth structural change at around 140 °C, which we assign to the β → γ phase transition, our conductivity data follow a single Arrhenius law from room temperature (RT) up to 220 °C. Obviously, the structural change, being mainly related to decreasing Na-ion ordering with increasing temperature, does not cause any jumps in Na-ion conductivity or any discontinuities in activation energies Ea. Bulk ion dynamics in NSP have so far rarely been documented; here, under ambient conditions, σbulk turned out to be as high as 3 x 10-4 S cm-1 at RT (Ea, bulk = 0.39 eV) when directly measured with microcontacts for individual small single crystals. [ABSTRACT FROM AUTHOR]

As possible electrolyte materials for all-solid-state Na-ion batteries (NIBs), scandium-substituted Na3Zr2(SiO4)2(PO4) in the structure of NASICONs (Na superionic conductors) has received hardly any attention so far, although among all the trivalent cations, Sc3+ might be the most suitable substitution ion for Na3Zr2(SiO4)2(PO4) because the ionic radius of Sc3+ (74.5 pm) is the closest to that of Zr4+ (72.0 pm). In this study, a solution-assisted solid-state reaction (SASSR) method is described, and a series of scandium-substituted Na3Zr2(SiO4)2(PO4) with the formula of Na3+xScxZr2-x(SiO4)2(PO4) (NSZSPx, 0 ≤ x ≤ 0.6) have been prepared. This synthesis route can be applied for powder preparation on a large scale and at low cost. With increasing degrees of scandium substitution, the total conductivity of the samples also increases. An optimum total Na-ion conductivity of 4.0 x 10-3 S cm-1 at 25 °C is achieved by Na3.4Sc0.4Zr1.6(SiO4)2(PO4) (NSZSP0.4), which is the best value of all reported polycrystalline Na-ion conductors. The possible reasons for such high conductivity are discussed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Sheets of Na 5 YSi 4 O 12 Na+ ion superionic conductor were fabricated for the first time. • RT conductivity of Na 5 YSi 4 O 12 tape has reached 1 mS cm−1. • The electrochemical stability window is up to 8 V vs. Na+/Na. • The CCD can reach 2.2 mA cm−2 and galvanostatic cycling is > 280 h under 0.8 mA cm−2. • The aqueous based method is both cost-efficient and eco-friendly. All-solid-state sodium batteries (ASSNBs), which combine the benefits of high safety and low cost, are expected to be an alternative or complementary storage technology to lithium ion batteries. Herein, we developed an aqueous tape casting technique for the continuous fabrication of ceramic sheets made of silicate-based Na 5 YSi 4 O 12 (NYS) Na+ ion superionic conductor for the first time. After sintering, the ceramics showed a total conductivity of 1.0 mS cm−1 at room-temperature, low total activation energy of 0.30 eV, and wide electrochemical window of over 8 V. The critical current density of NYS tape against Na-metal electrodes can reach 2.2 mA cm−2 and the galvanostatic cycling time is over 280 h under 0.8 mA cm−2 and 0.8 mAh cm−2. The obtained tape has high crystalline purity, dense microstructure, favorable mechanical properties (hardness H of 2 GPa and elastic modulus E of 45 GPa). This work not only highlights the potential of the scarcely studied silicate-based NYS ionic conductor as a functional separator, but also presents a cost-efficient and eco-friendly continuous fabrication using the aqueous tape casting technique, thus being expected to boost the practical application of NYS as solid-state electrolyte in ASSNBs. [ABSTRACT FROM AUTHOR]

All-solid-state lithium batteries offer promising advantages in energy density and safety compared to conventional lithium ion batteries. However, the majority of this type of batteries suffers from a low cycling stability, which might originate from mechanical fatigue caused by mechanical stresses and strains in the rigid structure. We introduce a general approach to model and analyse the stresses in rigid cathode/electrolyte electrodes on a cell level, which enables to develop optimised cell designs with an improved mechanical stability. We apply this approach on composite cathodes with a Li 7 La 3 Zr 2 O 12 (LLZO) ceramic electrolyte and LiCoO 2 (LCO) active material. Using the 3D microstructure of a real cathode, the stresses inside a free-standing electrode and model cells with a thin and a thick LLZO separator are calculated for the charging cycle considering isotropic and anisotropic material properties of LCO as well as non-textured and textured crystallographic alignment. Compared to randomly oriented crystals, the textured crystallographic alignment of LCO grains, introduced by the manufacturing process, has a significant effect and yields considerably better stress distributions in all cell configurations investigated. The design of optimised all-solid-state cells with reduced separator thickness leads to a significantly more favourable stress state than a typical lab scale separator-supported cell. Image 1 [ABSTRACT FROM AUTHOR]

One of the necessary prerequisites to advance the electrochemical performance of Li 7 La 3 Zr 2 O 12 (LLZ) based all-solid-state lithium batteries is the manufacturing of dense composite cathodes from cathode active material (CAM) and the LLZ ceramic solid electrolyte. However, free co-sintering of LLZ and CAM mixtures requires temperatures above 1000 °C which often leads to decomposition and secondary phase formation, especially for high energy CAMs. In our study we present a completely dry processing route which is fast, free of any sintering additives and coatings and suitable to fabricate dense mixed cathodes, pure LLZ separators and multilayers of the two. Through application of high mechanical pressure during Field-Assisted Sintering we were able to reduce the sintering temperature down to 675–750 °C with dwell times as low as 10 min, while still obtaining 95% theoretical density for LCO/LLZ mixtures. The low sintering temperature is suitable for high energy CAMs, but leads to a significant effect of surface impurities, especially from powder handling in air, and affects the crystallinity of the CAM/LLZ interface. In the present paper we investigate the impact of resulting interfaces on the ionic conductivity, the interfacial impedance and the cycling stability of produced cells and propose the optimization strategy. Image 1 • High-pressure spark plasma sintering enables low-T sintering of LLZ at 675 °C. • Surface impurities significantly decrease ionic conductivity of low-T sintered LLZ. • Amorphous grain boundaries between LCO and LLZ lead to high interface impedance. • Crystallization of interface reduces impedance and improves battery performance. • Low-T fabricated LLZ based all-solid-state batteries with high capacity. [ABSTRACT FROM AUTHOR]

The mobility of Na+ ions in Na 3+ x Sc 2 (SiO 4) x (PO 4) 3 − x (0.1 < x < 0.8) was investigated by temperature-dependent 23Na NMR spectroscopy and relaxometry. These measurements are probing the local motion of the Na+ ions and give information about the average hopping rate of the ions and the activation barriers these ions have to overcome for single jumps. The results are compared with those obtained by impedance spectroscopy that is probing the long-range transport of the Na+ ions. A consistent picture is obtained with the fastest motion of the Na+ ions observed for the sample with x = 0.4. • Solid electrolytes Na 3+x Sc 2 (SiO 4) x (PO 4) 3 − x show high Na ion conductivity. • The increase of silicate content facilitates local Na+ hopping. • The highest conductivity was observed for Na 3.5 Sc 2 (SiO 4) 0.5 (PO 4) 2.5. • Excessive saturation of the structure with Na ions leads to lower conductivity. [ABSTRACT FROM AUTHOR]