Solid Oxide Fuel Cell Applications Research Articles

Structural, thermal, dielectric and electrical behaviour of Ca doped La1-xCaxFe0.75Co0.25O3 {x = 0.05 & 0.35} ceramic material

La1-xCaxFe0.75Co0.25O3 {x = 0.05 & 0.35} ceramic material prepared by conventional method has been prepared for solid oxide fuel cell applications. Prepared material has been calcined for 12 h for 900 °C and sintered for 1250 °C for 4 h. The material's single phase and crystalline nature have been confirmed using an X-ray diffractometer. The material's morphology has been examined using scanning electron microscope. Density of the material has been obtained by Archimedes’s principle. Thermal behaviour of the material in respect of temperature has been studied by themogravimetric analysis. Dielectric and conductive nature of the material has been examined by impedence analyser. Conductivity of the material has been calculated greater than 100 Scm-1and also increased with Ca replacement of La in the present ceramic material. Results confirmed that the current prepared material is good to be used as cathode of solid oxide fuel cell.

Mechanical behavior of YSZ-glass composite seals for solid oxide fuel cell application

The long-term operation of solid oxide fuel cell stack critically depends on the joint strength between cells and interconnect alloy. In this work, 20 wt% YSZ (Y 2 O 3 stabilized ZrO 2 ) was added into different kinds of glass to form H1-20 and H4-20 composite seals. It was focused on the mechanical behavior between YSZ-glass composite seals and Fe–16Cr alloy under various thermal cycles by shear force testing and tensile force testing. The shear strength and the tensile strength between H4-20 seals and Fe–16Cr alloy were higher than that of H1-20. Two composite seals differed in characteristic temperature, viscosity, and crystalline phase with possible impacts on the joint strength. The interfacial composition between H1-20 and Fe–16Cr alloy was different from that of H4-20. Based on examination results, four possible fracture modes were proposed to illustrate the failure mechanism between composite seals and alloy.

Study on Preparation and Properties of La0.6Sr0.4Co0.2Fe0.8O3-Δ-mGd0.2Ce0.8O2 (M=0,30,40 and 50) Composite Cathode

Solid Oxide Fuel Cells (SOFCs) can convert chemical energy into electrical energy, with high energy conversion rate, safe operation, no pollutant emissions, and is one of the most potential new energy power generation devices in the future. However, at low and medium temperature (below 800℃), the cathode impedance of SOFCs will increase sharply, resulting in adverse effects on cell performance. Finding cathode materials that can work at low and medium temperature is the key to realize large-scale commercial application of SOFCs. LSCF cathode material is one of the commonly used cathode materials for solid oxide fuel cells because of its excellent electronic and ionic conductivity. However, its cathode performance cannot meet the requirements of commercial applications. At high temperature, solid-state reactions are easy to occur between LSCF and commonly used electrolyte materials such as YSZ, SSZ and LSGM, resulting in the formation of an intermediate phase that is not conducive to Oxygen Reduction Reaction (ORR). In this paper, LSCF and Gd0.2Ce0.8O2 (GDC) were combined by ball milling to prepare composite cathode. XRD test found that the two powders mixed at high temperature did not produce new substances, with good chemical compatibility. The electrical conductivity test showed that the electrical conductivity of the composite LSCF decreased significantly from 227 Sꞏcm-2 at 650℃ to 115, 90 and 77 Sꞏcm-2 at 550℃, respectively. The composite cathode with a composite ratio of 6:4 has the lowest polarization impedance, only 0.10 Ωꞏcm2 at 800℃. The discharge test shows that the cathode with the mass ratio of 6:4 LSCF to GDC has the best performance, and the power density is 328 and 256 mW/cm2 at 800 and 750℃, respectively. The performance of the cathode has good stability after working for 50h.

Tailoring dual redox pairs strategy on a defective spinel Mg0.4NixMn2.6−xO4+δ cathode for the boosting of SOFCs performance

The oxygen hopping through oxygen defect site plays an extremely important role in cathode catalysts of solid oxide fuel cells (SOFC) application. Herein, a dual Ni2+/Ni3+ and Mn2+/Mn3+/Mn4+ redox pairs strategy is developed to construct a series of defective spinel Mg0.4NixMn2.6−xO4+δ (abbreviated MN(x)MO) to gain insights in terms of oxygen nonstoichiometry. By regulating the stoichiometric proportion of Ni and Mn, it is possible to optimize electronic conductivity and oxygen-vacancy concentration. The optimized MN(1.4)MO provides electrical conductivity as high as 68 S·cm−1 at 800 °C, 2.72 folds that of MN(1.0)MO. Based on oxygen transport performance, the surface exchange coefficient of MN(1.4)MO at 900 °C is 162 folds that of commercial La0.7Sr0.3MnO3-δ (LSM). When a MN(1.4)MO cathode was used, the resulted SOFC exhibited extraordinarily high maximum power density of 0.34 W·cm−2 at 600 °C and 2.02 W·cm−2 at 800 °C. To the best of our knowledge, the performance is the best among the spinel-based cathodes ever reported for SOFC application. Endowed with optimal properties, MN(1.4)MO-based SOFC displays peak power density which is 2.27 and 1.44 folds that of LSM-based SOFC at 600 °C and 800 °C, respectively. A test of 50 h revealed the MN(1.4)MO-based SOFC is remarkably stable at 800 °C, continuously offering 2.02 W·cm−2 at 0.5 V. The excellent performance and stability of MN(1.4)MO-based SOFC suggests that MN(1.4)MO is a promising cathode material for the development of intermediate temperature SOFC technology.

Characterization of Plasma Sprayed Mn1.0Co1.9Fe0.1O4 Coating on Crofer 22 APU Interconnect for Solid Oxide Fuel Cell Application

Characterization of Plasma Sprayed Mn1.0Co1.9Fe0.1O4 Coating on Crofer 22 APU Interconnect for Solid Oxide Fuel Cell Application

Transport properties of LaYbO3-based electrolytes doped with alkaline earth elements

The rapid development of efficient high-temperature electrochemical devices stimulates the search for new electrolytic materials with high conductivity and excellent chemical stability. From this point of view, lanthanum-containing perovskites can be considered as suitable materials for solid oxide fuel cell applications. In this work, the successfully synthesis and comprehensive study of acceptor-doped lanthanum ytterbates, La1–xMxYbO3–δ (M = Ca, Sr, Ba; x = 0, 0.05, 0.1) is described. X-ray diffraction analysis showed all samples to possess an orthorhombic structure with the space group Pna21, whose stability was confirmed at temperatures up to 1000 °C. The high chemical stability of the materials with respect to carbon dioxide and water vapor was confirmed by SEM and XRD methods. The dilatometry data allowed the determination of thermal expansion coefficient values of ceramic samples, which are close to those for conventionally used YSZ electrolytes. The transport properties of the ceramic were studied in a wide range of temperatures (300–900°C) and oxygen partial pressures. It was found that ytterbates doped with 5 and 10 wt.% of strontium and 5 wt.% of barium exhibited the high electrical conductivity among other considered materials. Thus, these materials can be considered as promising proton-conducting electrolytes for various electrochemical devices.

Controlled synthesis of Bi2O3–YSZ composite powders and their sintering behavior for high‐performance electrolytes

AbstractBismuth oxide (Bi2O3) is a promising additive to decrease the sintering temperature of yttria‐stabilized zirconia (YSZ)‐based electrolyte for solid oxide fuel cell application. However, Bi2O3 tends to grow into large column bars (>50 µm) in a chemical coprecipitation method, which dramatically limits the mixing uniformity of Bi2O3 and YSZ, even much worse than that of mechanical mixing. In this study, the reaction temperature was increased from room temperature to 90°C to increase the number of nucleation during the violate reaction between Bi3+ solution and YSZ suspension in NaOH. On this basis, the violence of the reaction was further moderated by adding half of NaOH first, then YSZ powders and the other half of an NaOH solution. The size of Bi2O3 was further decreased to sub‐micrometer and Bi2O3 was homogeneously mixed with YSZ particles, even when its addition amount was as large as 20 mol%. These composite powders effectively promoted the sintering behavior of YSZ. The sintering temperature of YSZ was decreased to 900 and 1000°C with 10 and 5 mol% Bi2O3 doping, respectively. Increasing the doping ratio induced severe volatilization of Bi2O3 and pore formation. Raising the sintering temperature (no more than 1200°C) enhanced the doping effect of Bi2O3 into the YSZ lattice but induced instability in the YSZ crystal structure.

Nickel-doped lanthanum cerate nanomaterials as highly active electrocatalysts.

The efficient oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) catalyst materials are crucial in the energy research domain due to their tunability. Structural modification in perovskites such as lanthanum cerates (LaCeO3) upon doping at A or B sites significantly affects the surface activity and enhances the catalysis efficacy. Herein, B-site nickel-doped lanthanum cerate (LaCe1-xNixO3±δ) nanopowders were applied as ORR indicators in high-temperature electrochemical impedance spectroscopy for solid-oxide fuel cell (SOFC) tests and in cyclic voltammetric OER investigations in alkaline medium. The integration into SOFC applications, via solid-state EIS in a co-pressed three-layered cell with LCNiO as cathode, is investigated in an oxygen-methane environment and reveals augmented conductivity with temperatures of 700-850°C. The higher electrokinetic parameters-including diffusion coefficients, Do heterogeneous rate constant, ko, and peak current density for OER in KOH-methanol at a LCNiO-9-modified glassy carbon electrode-serve as robust gauges of catalytic performance. CV indicators and EIS conductivities of LaCe1-xNixO3±δ nanomaterials indicate promising potencies for electrocatalytic energy applications.

Investigation on high entropy alloys as interconnect material for intermediate temperature solid oxide fuel cells

Investigation of Solid Oxide Fuel Cells (SOFCs) is receiving great attention due to its higher efficiency and zero environmental pollution during operation. Interconnects are a critical part of the SOFC stack which connects the cells in series and combines the electricity produced. The present study aims to investigate High Entropy Alloys (HEAs) for interconnect application in intermediate temperature SOFC. Towards this, FeCoCrNi, FeCoCrNiMn0.1, FeCoCrNiMn0.5, and FeCoCrNiMn HEAs are prepared by vacuum arc melting and examined for its phase evaluation. Thermal stability, thermal expansion, resistivity, oxidation, and Area Specific Resistance (ASR) are investigated up to 800 °C. Oxidation studies show the formation of multicomponent oxide in the HEAs which suppresses the growth of Cr2O3 layer. FeCoCrNiMn0.1, FeCoCrNiMn0.5, and FeCoCrNiMn HEAs possess ASR values less than 100 mΩ.cm2 in the temperature range of 600–800 °C which ensure the superior performance of the SOFC stack.

Effect of Sn loading variation on the electrochemical performance of dry internal reforming of biogas in solid oxide fuel cells

Solid Oxide Fuel Cells (SOFC) operations at 750 °C by using direct-biogas fuel without pre-reforming or steam addition on undoped Ni/YSZ and tin-doped Ni/YSZ (Sn-Ni/YSZ) anodes with varied Sn loadings were tested. High CH4/CO2 ratio (2:1) was used as simulated biogas with the absence of steam. The average current density of the undoped Ni/YSZ cells at 0.7 V and 750 °C was approximately 150 mA/cm2, while that of Sn-Ni/YSZ cells produced 300–420 mA/cm2 depending on Sn/Ni dopant concentration. Repeated cell tests revealed that the SOFC electrochemical performance is very sensitive to the quantity of Sn doped into the Ni/YSZ anode even with dopant amount as low as 0.10 wt% Sn/Ni. The highest electrochemical performance in H2 and biogas was obtained from Sn-Ni/YSZ with 0.38 wt% Sn/Ni loading in the anode. The SEM micrographs of the tested anode surface showed no apparent sign of carbon deposition on the anode while small amount of carbon quantified on the SOFC tested cells with Temperature Programmed Oxidation (TPO). The successful operation of SOFC using biogas as fuel broadens the application of SOFC to directly produce electricity at places where biogas produced from anaerobic digestion of waste is available. However, due to the gradual degradation in the long durability test (150 h) shown in biogas there are further studies need to be carried out.

Vanadium (oxy)nitride as a new category of anode for direct ammonia solid oxide fuel cells cells

Ammonia (NH3) is considered a potential energy carrier to be used as a fuel in energy conversion devices, such as solid oxide fuel cells (SOFCs). Nonetheless, in the presence of NH3, traditional Ni-containing anodes may suffer from poor chemical stability, resulting in its partial conversion to nickel nitride. We, therefore, propose a new composite anode for direct ammonia solid oxide fuel cells made of a metallic conducting phase, vanadium (oxy)nitride (VON), and an oxygen-ion conducting phase, (ZrO2)0.92(Y2O3)0.08 (YSZ). X-ray diffraction (XRD) reveals that the VON material is chemically compatible with YSZ. Good thermal stability was also shown under reducing conditions by thermogravimetry (TGA). Electrochemical impedance spectroscopy (EIS) showed that peak performing composition is composed of 50:50% vol of VON:YSZ at 850 °C, yielding comparable performance to that of previous reports on traditional Ni-YSZ cermets. The electrode mechanism under NH3 fuel was found to be similar to that of traditional Ni-based cermet compositions using hydrogen fuel, due to the predicted thermal decomposition of ammonia under the studied operation temperatures, i.e., ≥650 °C, while sensitivity to flow rate considerations was also highlighted. To the best of our knowledge, this work reports a completely new category of anodes for SOFC applications.

Efficiently enhance the proton conductivity of YSZ-based electrolyte for low temperature solid oxide fuel cell

Yttrium stabilized zirconia (YSZ) as a typical oxygen ionic conductor has been widely used as the electrolyte for solid oxide fuel cell (SOFC) at the temperature higher than 1000 °C, but its poor ionic conductivity at lower temperature (500–800 °C) limits SOFC commercialization. Compared with oxide ionic transport, protons conduction are more transportable at low temperatures due to lower activation energy, which delivered enormous potential in the low-temperature SOFC application. In order to increase the proton conductivity of YSZ-based electrolyte, we introduced semiconductor ZnO into YSZ electrolyte layer to construct heterointerface between semiconductor and ionic conductor. Study results revealed that the heterointerface between ZnO and YSZ provided a large number of oxygen vacancies. When the mass ratio of YSZ to ZnO was 5:5, the fuel cell achieved the best performance. The maximum power density (Pmax) of this fuel cell achieved 721 mW cm−2 at 550 °C, whereas the Pmax of the fuel cell with pure YSZ electrolyte was only 290 mW cm−2. Further investigation revealed that this composite electrolyte possessed poor O2− conductivity but good proton conductivity of 0.047 S cm−1 at 550 °C. The ionic conduction activation energy of 5YSZ-5ZnO composite in fuel cell atmosphere was only 0.62 eV. This work provides an alternative way to improve the ionic conductivity of YSZ-based electrolytes at low operating temperatures.

Synthesis, characterization, and electrochemical properties of Sm0.5Sr0.5Zr1−xNixO3.25−x for solid oxide fuel cell applications

Synthesis, characterization, and electrochemical properties of Sm0.5Sr0.5Zr1−xNixO3.25−x for solid oxide fuel cell applications

Reactive Sputtered NiO-YSZ Anode Functional Layer for Thin Film Low-Temperature Solid Oxide Fuel Cell

Solid oxide fuel cell (SOFC) is one of the most promising next-generation electrochemical energy conversion devices because of its wide choice of fuels, cleanliness and, high efficiency of up to 70-85%( with heat utilization). Recently, low-temperature SOFC (< 600 ℃) has been studied to overcome the limitations of conventional SOFC, e.g., thermal stability, cost, and limited application. However, lowering operated temperature is challenging due to slow charge transfer and ion transport rates. Therefore, SOFC design with thin-film stacks, namely thin-film SOFC (TF-SOFC) fabricated on porous anode support, have been usually adopted for sufficient power density even at this temperature regime.A ceramic-metal composite (cermet) of Ni and YSZ (yttria-stabilized zirconia) is the most common anode or anode functional layer (AFL) material of TF-SOFC, because Ni-YSZ cermet has reasonable cost, chemical stability in a reducing atmosphere at high temperature, and similar thermal expansion coefficient to that of YSZ electrolyte. Various thin-film techniques have been reported for AFL fabrication, e.g., pulsed laser deposition (PLD), RF sputtering, etc. Among those, reactive sputtering method, which uses metal target in controlled gas conditions (e.g., oxygen condition for oxide deposition), is a versatile method to deposit various types of thin films with fast deposition speed (up to > 1um/hr), which is beneficial in manufacturability regarding the usual thickness range of AFL (a few microns).In this study, therefore, we studied physical and chemical properties of nanocomposite Ni-YSZ films fabricated by using the reactive sputtering deposition technique, focusing on the effect of sputter parameters. In particular, Oxygen partial pressure significantly affects deposition speed, surface morphology, composition, electrochemical performance, and thermal durability at 450 ℃. It is shown that excessive O2/Ar partial pressure ratio (> 0.2) significantly reduces the deposition speed by approximately one order of magnitude compared to the lower ratio case. In morphological analysis, O2/Ar partial pressure ratio affect nano-structured of anode, after annealing process at 1200℃ with air. Also, the Ni-YSZ anode sputtered at the environment of O2/Ar partial pressure ratio of 0.1 sample shows the lowest activation resistance when applied to LT-SOFC’s anode. The O2/Ar 0.5 sample shows surface Ni agglomeration due to high NiO-to-metallic Ni ratio.

Slightly ruthenium doping enables better alloy nanoparticle exsolution of perovskite anode for high-performance direct-ammonia solid oxide fuel cells

• Slightly Ru doping promotes the exsolution of alloy nanoparticles in perovskite anode. • Ru doping greatly reduces the particle size and increase the amount of exsolved alloy nanoparticles. • Ru doped perovskite anode shows superior catalytic activity for NH 3 decomposition and anti-sintering capability. • DA-SOFCs with Ru doped perovskite anode exhibits a superior operational stability to Ru-free counterpart. Fuel flexibility is one of the most distinguished advantages of solid oxide fuel cells (SOFCs) over other low-temperature fuel cells. Furthermore, the combination of ammonia fuel and SOFCs technology should be a promising clean energy system after considering the high energy density, easy transportation/storage, matured synthesis technology and carbon-free nature of NH 3 as well as high efficiency of SOFCs. However, the large-scale applications of direct-ammonia SOFCs (DA-SOFCs) are strongly limited by the inferior anti-sintering capability and catalytic activity for ammonia decomposition reaction of conventional nickel-based cermet anode. Herein, a slightly ruthenium (Ru) doping in perovskite oxides is proposed to promote the alloy nanoparticle exsolution, enabling better DA-SOFCs with enhanced power outputs and operational stability. After treating Ru-doped Pr 0.6 Sr 0.4 Co 0.2 Fe 0.75 Ru 0.05 O 3-δ single-phase perovskite in a reducing atmosphere, in addition to the formation of two layered Ruddlesden-Popper perovskites and Pr 2 O 3 nanoparticles (the same as the Ru-free counterpart, Pr 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ ), the exsolution of CoFeRu-based alloy nanoparticles is remarkably promoted. Such reduced Pr 0.6 Sr 0.4 Co 0.2 Fe 0.75 Ru 0.05 O 3-δ composite anode shows superior catalytic activity and stability for NH 3 decomposition reaction as well as anti-sintering capability in DA-SOFCs to those of reduced Pr 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ due to the facilitated nanoparticle exsolution and stronger nanoparticle/substrate interaction. This work provides a facile and effective strategy to design highly active and durable anodes for DA-SOFCs, promoting large-scale applications of this technology.

Ni doped SrFe12O19 nanoparticles synthesized via micro-emulsion route and photocatalytic activity evaluation for the degradation of crystal violet under visible light irradiation

A series of Ni doped SrNixFe12-xO19 (x = 0.0, 0.05, 0.10, 0.15, 0.20, 0.25) hexaferrites were fabricated through facile micro-emulsion approach and doping content effect was investigated based on structural, dielectric, optical and photocatalytic properties. The prepared materials were characterized via X-ray diffraction (XRD), Raman, Fourier transformed infrared (FTIR), photoluminescence (PL) and UV–vis techniques. The Ni doped SrFe12O19 structure was hexagonal having space group P63/mmc with mean crystallite size in 34–50 nm range. Ferroelectric polarization, coercivity and Remnant polarizations were increased with Ni doping. Dielectric analysis showed the higher values of dielectric parameters with dispersion in low frequency region, which were independent of at high frequency. Optical bandgap was reduced on substitution, which was in 2.31–1.66 eV range, which was in good association with decline in PL analysis. The PCA (photocatalytic activity) of pure SrFe12O19 (SFO) and doped SFNO5 (x = 0.25) material was assessed for removal of crystal violet (CV) dye under visible light illumination. The SFNO5 showed much better PCA and 91 % dye was removed in 90 min with a rate constant of 2.337 × 10-2 min−1 versus pristine SFO (only 55 % with rate constant 8.02 × 10-3 min−1). Results revealed that tuned bandgap and enhanced AC conductivity of doped materials make it crucial candidates for optoelectronic and SOFCs (Solid oxide fuel cell) applications. Owing to the excellent PCA and magnetically separable nature, SrNixFe12-xO19 has potential for the dyes removal from the effluents under solar light irradiation, which could be more economically versus UV based photocatalytic process.

Nanostructured La0.75Sr0.25Cr0.5Mn0.5O3-Ce0.8Sm0.2O2 Heterointerfaces as All-Ceramic Functional Layers for Solid Oxide Fuel Cell Applications.

The use of nanostructured interfaces and advanced functional materials opens up a new playground in the field of solid oxide fuel cells. In this work, we present two all-ceramic thin-film heterostructures based on samarium-doped ceria and lanthanum strontium chromite manganite as promising functional layers for electrode application. The films were fabricated by pulsed laser deposition as bilayers or self-assembled intermixed nanocomposites. The microstructural characterization confirmed the formation of dense, well-differentiated, phases and highlighted the presence of strong cation intermixing in the case of the nanocomposite. The electrochemical properties—solid/gas reactivity and in-plane conductivity—are strongly improved for both heterostructures with respect to the single-phase constituents under anodic conditions (up to fivefold decrease of area-specific resistance and 3 orders of magnitude increase of in-plane conductivity with respect to reference single-phase materials). A remarkable electrochemical activity was also observed for the nanocomposite under an oxidizing atmosphere, with no significant decrease in performance after 400 h of thermal aging. This work shows how the implementation of nanostructuring strategies not only can be used to tune the properties of functional films but also results in a synergistic enhancement of the electrochemical performance, surpassing the parent materials and opening the field for the fabrication of high-performance nanostructured functional layers for application in solid oxide fuel cells and symmetric systems.

Stability of infiltrated cathodes using Pr2NiO4+delta precursor for low-temperature fuel cell applications

The electrochemical performance and stability of infiltrated praseodymium nickelate (PNO) as the cathode for solid oxide fuel cell (SOFC) applications was studied. PNO cathode (Pr2NiO4+δ) was infiltrated into gadolinium-doped ceria (GDC) scaffolds and tested in two different anode-supported cells with tubular geometry: i) tubular cell A with Ni-YSZ support, Ni-YSZ anode functional layer (AFL), and thin (∼7 μm) electrolyte and; ii) microtubular cell B with Ni-YSZ support, without AFL and thick (34 μm) electrolyte. Both cells were stable during 91 h and 260 h of stability testing at 650 °C and experienced a reduction in total polarization resistances. Post-mortem X-ray diffraction (XRD) analysis confirmed PNO's partial transformation into the Pr4Ni3O10 phase with higher electrical conductivity and thermal stability. Improvement in the oxygen reduction reaction was confirmed using DRT analysis. This finding confirms that PNO infiltrated into GDC scaffold can be considered a promising cathode for SOFC applications.

Development and Characterization of Ba0.5Sr0.5(Co1−xMgx)0.2Fe0.8O3 Cathode Materials System for Low-Temperature Solid Oxide Fuel Cell (LT-SOFC) Applications

Development and Characterization of Ba0.5Sr0.5(Co1−xMgx)0.2Fe0.8O3 Cathode Materials System for Low-Temperature Solid Oxide Fuel Cell (LT-SOFC) Applications

Cold sintering of ceria-based solid electrolyte with the assistance of a core-shell structure

Due to its strong ionic conductivity, doped ceria has been employed as an electrolyte in medium-temperature solid oxide fuel cell applications. For the first time, we demonstrated the feasibility of cold sintering high-density Ce0.8Sm0.2O1.9 (SDC)@Na2CO3 composite electrolytes with Na2CO3 as a shell at temperatures less than 200 °C. The effects of Na2CO3 and water content on cold-sintered samples’ relative density, microstructure, and ionic conductivity were examined. The core-shell structure is significant in densification, but water addition has an opposite effect. The bulk and grain-boundary conductivities of cold-sintered SDC@Na2CO3 electrolytes were studied at 350−700 °C and analyzed in detail based on carbonate and water effects. This work presents a significant and scalable method for synthesizing dense solid electrolytes by forming a core-shell structure by cold sintering.