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Additive manufacturing of solid-state batteries is advantageous for improving the power density by increasing the geometric complexity of battery components, such as electrodes and electrolytes. In the present study, bulk three-dimensional Li _1+ _x Al _x Ti _2− _x (PO _4 ) _3 (LATP) electrolyte samples were prepared using the laser powder bed fusion (L-PBF) additive manufacturing method. Li _3 PO _4 (LPO) was added to LATP to compensate for lithium vaporization during processing. Chemical compositions included 0, 1, 3, and 5 wt. % LPO. Resulting ionic conductivity values ranged from 1.4 × 10 ^−6 –6.4 × 10 ^−8 S cm ^−1 , with the highest value for the sample with a chemical composition of 3 wt. % LPO. Microstructural features were carefully measured for each chemical composition and correlated with each other and with ionic conductivity. These features and their corresponding ranges include: porosity (ranging from 5% to 19%), crack density (0.09–0.15 mm mm ^−2 ), concentration of residual LPO (0%–16%), and concentration and Feret diameter of secondary phases, AlPO4 (11%–18%, 0.40–0.61 µ m) and TiO2 (9%–11%, 0.50–0.78). Correlations between the microstructural features and ionic conductivity ranged from −0.88 to 0.99. The strongest negative correlation was between crack density and ionic conductivity (−0.88), confirming the important role that processing defects play in limiting the performance of bulk solid-state electrolytes. The strongest positive correlation was between the concentration of AlPO4 and ionic conductivity (0.99), which is attributed to AlPO4 acting as a sintering aid and the role it plays in reducing the crack density. Our results indicate that additions of LPO can be used to balance competing microstructural features to design bulk three-dimensional LATP samples with improved ionic conductivity. As such, refinement of the chemical composition offers a promising approach to improving the processability and performance of functional ceramics prepared using binderless, laser-based additive manufacturing for solid-state battery applications.

Solid inorganic and polymeric electrolytes have the potential to enable rechargeable batteries with higher energy densities, compared to current lithium-ion technology, which uses liquid electrolyte. Inorganic materials such as ceramics and glasses conduct lithium ions well, but they are brittle, which makes incorporation into a battery difficult. Polymers have the flexibility for facile use in a battery, but their transport properties tend to be inferior to inorganics. Thus, there is growing interest in composite electrolytes with inorganic and organic phases in intimate contact. This article begins with a discussion of ion transport in single-phase electrolytes. A dimensionless number (the Newman number) is presented for quantifying the efficacy of electrolytes. An effective medium framework for predicting transport properties of composite electrolytes containing only one conducting phase is then presented. The opportunities and challenges presented by composite electrolytes containing two conducting phases are addressed. Finally, the importance and status of reaction kinetics at the interfaces between solid electrolytes and electrodes are covered, using a lithium-metal electrode as an example.

The design and production features of a solid oxide fuel cell greatly impact its microstructure and performance; however, these factors are frequently omitted in related studies. In this work, the influence of the design and formation factors of a solid oxide fuel cell on its performance and long-term stability is studied. The sintering process of multilayer half-cells is studied by heating microscopy and the optimal sintering strategy is identified. We show here the importance of the sintering strategy and suggest an approach for SOFC design that results in a stable in time performance. The electrochemical performance is evaluated by impedance spectroscopy and the distribution of relaxation times (DRT) technique. It is shown that the absence of the barrier layer leads to a decrease in the SOFC performance by 22.5% as-sintered and continues to drop down during the exposure of 850 °C for 400 h. The impregnation of the cathode and anode by Pr(NO3)3 and Ce(NO3)3 improves electrochemical performance by 15% and this increase withstands a heat treatment at least for 215 h without any noticeable degradation. The most stable in time performance of the cell with impregnated electrodes and the barrier layer is 515.3 mW × cm−2 (H2 + 3% H2O used as fuel, air + 3% H2O as oxidizer). [ABSTRACT FROM AUTHOR]

Glass-ceramics have gained considerable importance for applications in high-energy technology. Li- and Na-superionic ion-conducting ceramics find widespread use in lithium- and sodium-ion batteries as separators, solid electrolytes, and cathode materials. The ionic conductivity of these materials is influenced by crystal chemical parameters and can be further optimized via microstructural control using glass-ceramic processing. This article summarizes the most promising glass-ceramic material systems currently in use, detailing recent progress in understanding their structure–property–performance relationships. We also highlight the power and potential of solid-state nuclear magnetic resonance techniques for providing quantitative knowledge about structure, phase composition, and ion dynamics in these materials. [ABSTRACT FROM AUTHOR]

Solid-oxide fuel cells (SOFCs) are unique in their ability to directly convert the chemical energy of a wide variety of fuels to electric power with unmatched energy conversion efficiency. The articles in this issue of MRS Bulletin highlight the enormous potential of, and recent progress toward, operating SOFCs at lower temperatures (<650°C). Lower temperatures dramatically increase the number of potential applications for this technology as well as provide the opportunity to incorporate a wider variety of materials in SOFC power generation systems with greater reliability and lower cost. The articles in this issue describe materials development and processing for low-temperature SOFCs, including the enabling of nanotechnology and microelectromechanical systems-based cell designs, the development of highly active electrodes and their three-dimensional microstructural characterization, as well as the use of novel proton-conducting electrolytes, all of which provide new avenues of research. New fabrication methods are also being applied in the development of micro-SOFCs and microtubular SOFCs with higher power densities. Finally, advances in lowering performance degradation rates, a critical commercialization issue, are described. [ABSTRACT FROM AUTHOR]

Solid-oxide fuel cells (SOFCs) are an energy conversion technology with unique potential to have the highest energy conversion efficiency with the least environmental impact, as well as broad fuel flexibility from renewable to conventional fuels. Lowering the SOFC operating temperature will further lower system and operational costs, increase long-term durability, and allow more rapid start-up, providing feasibility for load following and transportation applications. Unfortunately, at reduced temperatures, the thermally activated nature of ionic conduction and electrochemical reactions increase polarization resistances, thus decreasing cell and system performance. However, lower operating temperatures also create the opportunity to employ nanostructured materials with higher surface area-to-volume ratios and greater interphase and interfacial regions, which can greatly enhance electrochemical performance. Here, we review recent progress in the development of various nanostructured electrodes and electrolytes and discuss their effects on the enhancement of the electrocatalytic activity of oxygen reduction and fuel oxidation, as well as oxygen-ion conduction, in order to achieve high-performance low-temperature SOFCs. [ABSTRACT FROM AUTHOR]

The need for reducing the operating temperature of solid-oxide fuel cells (SOFCs) imposed by cost reduction has pushed significant progress in fundamental understanding of the individual components, as well as materials innovation and device engineering. Proton-conducting oxides have emerged as potential alternative electrolyte materials to oxygen-ion conducting oxides for operation at low and intermediate temperatures. This article describes major recent developments in electrolytes, electrodes, and complete fuel cell performance for SOFCs based on proton-conducting electrolytes. Although the performance of such fuel cells is still relatively modest, significant improvements in the power density output have been made during the last couple of years, and this trend is expected to continue. [ABSTRACT FROM AUTHOR]

Solid oxide fuel cells (SOFCs) offer an efficient energy conversion technology for alleviating current energy problems. High temperature proton-conducting (HTPC) oxides are promising electrolytes for this technology, since their activation energy is lower than that of conventional oxygen-ion conductors, enabling the operating temperature reduction at 600 °C. Among HTPC oxides, doped BaZrO3 materials possess high chemical stability, needed for practical applications. Though, poor sinterability and the resulting large volume of highly resistive grain boundaries hindered their deployment for many years. Nonetheless, the recently demonstrated high proton conductivity of the bulk revived the attention on doped BaZrO3, stimulating research on solving the sintering issues. The proper selection of dopants and sintering aids was demonstrated to be successful for improving the BaZrO3 electrolyte sinterability. We here briefly review the synthesis strategies proposed for preparing BaZrO3-based nanostructured powders for electrolyte and electrodes, with the aim to improve the SOFC performance. [ABSTRACT FROM PUBLISHER]

(1−x) Ce0.8Gd0.2O2−δ+x Al2O3 ceramics with compositions x=0 to 0.2 were prepared by the conventional mixed-oxide method from high purity (>99.9%) of commercial powders, and sintered at 1550 °C for 5 h in air. Sintered density, crystal phase, and microstructure were characterized. The ionic conductivity was measured over 200 to 800 °C in air using an impedance analyzer in the frequency range of 0.001 to 100 Hz. Microhardness and indentation fracture toughness were also determined. A new phase (i.e., GdAlO3) has been detected in the samples with Al content greater than 5% AlO1.5. Ce0.8Gd0.2O2−δ ceramic has a Vickers hardness of ∼9.23±0.15 GPa, and an indentation fracture toughness of ∼1.47±0.2 MPa m1/2. A remarkable improvement in both fracture toughness and microhardness can be observed for the samples with over 10% AlO1.5. However, the addition of Al2O3 exhibits a detrimental effect on the conductivities, especially on grain boundary conductivity, which is possibly related to the formation of GdAlO3. [Copyright &y& Elsevier]

The elaboration of Na+ super-ionic conductor (NaSICON) ceramics is studied in this work. These solid electrolytes can be used as sensor for detection of polluted gases in air. Two sorts of ceramics with different chemical compositions are synthesised by soft chemistry route: a zirconium-based NaSICON and a hafnium-based NaSICON. DTA-TG and temperature depending X-ray diffractometry were used to follow the thermal decomposition of the precursor phases. The electrical properties of these ceramic sodium ionic conductors are investigated by complex impedance spectroscopy (CIS). The substitution of the zirconium by the hafnium increases the ceramic conductivity and decreases the activation energy E a (from 0.29 to 0.12 eV). [ABSTRACT FROM AUTHOR]

By using powders obtained via hydrothermal synthesis, a high-density sintered Na 3 Al 2 (PO 4) 3 ceramic with enhanced electric conductivity was successfully synthesized. Precursor materials containing sodium phosphates as well as some hydrates and other phosphates were synthesized using a hydrothermal method. X-ray diffraction (XRD) patterns showed that crystalline Na 3 Al 2 (PO 4) 3 powder could be prepared by post-heating of the hydrothermal precursor at 600 °C for 3 h. Thermogravimetry-differential thermal analysis (TG-DTA) suggested that the crystallization temperature was about 600 °C. Powder samples were pressed into discs with a diameter of 13 mm and a thickness of 3 mm under a pressure of 50 MPa and sintered in an electric furnace at 600 °C for 24 h. When the hydrothermally synthesized powdered precursor was used as the raw material for sintering, a high-density Na 3 Al 2 (PO 4) 3 ceramic was formed, which exhibited enhanced electric conductivity. Image 1 • Dense Na 3 Al 2 (PO 4) 3 ceramics was prepared by reaction sintering at a low temperature. • The hydrothermally synthesized precursor powder was a mixture of several phosphates. • It was pressure-molded and fired at 600 °C for 24 h to be a dense sintered body. • The ceramics had a fine structure and the total electrical conductivity was increased. [ABSTRACT FROM AUTHOR]