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Ce0.8Gd0.2O2−δ-FeCo2O4 composites are attractive candidate materials for high-purity oxygen generation providing robust chemical stability. Aiming for future industrial applications, a feasible solid-state reaction process with one thermal processing step was used to synthesize 50 wt% Ce0.8Gd0.2O2−δ:50 wt% FeCo2O4 and 85 wt% Ce0.8Gd0.2O2−δ:15 wt% FeCo2O4 composites. Mechanical reliabilities of the sintered membranes were assessed based on the characterized mechanical properties and subcritical crack growth behavior. In general, the fracture strengths of as-sintered membranes were reduced by tensile residual stresses and microcracks. In particular, the enhanced subcritical crack growth behavior, which leads to limited stress tolerance and high failure probability after a 10-year operation, was evaluated in more detail. Further materials and processing improvements are needed to eliminate the tensile stress and microcracks to warrant a long-term reliable operation of the composites.

In this article, a versatile process based on microwave-assisted sol–gel synthesis is introduced in order to apply a surface coating on cathode material for lithium-ion batteries. Here, a nano-scaled ZnO:Al (AZO) layer is coated homogeneously onto Li(Ni1/3Mn1/3Co1/3)O2 (NMC111) powder at temperatures below 210°C within a few minutes. In contrast to other wet-chemical coating techniques, the method described here is conducted in a one-pot reaction and does not require a post-annealing step at elevated temperatures. Investigations via high resolution transmission electron microscopy (HR-TEM), scanning transmission electron microscopy (STEM) and inductively-coupled plasma optical emission spectroscopy (ICP-OES) promote a thorough understanding of coating microstructure and quality in dependence of reaction temperature, duration and precursor concentration. The AZO protective coating on NMC111 significantly reduces capacity fading during cycling in the voltage range of 3.0-4.5 V. Furthermore, applying optimal quantities of the coating agent on NMC111 lead to enhanced specific capacities compared to the uncoated material., Nano Select, 2 (1)

Journal of the American Ceramic Society (2021). doi:10.1111/jace.17715, Published by Wiley-Blackwell, Oxford [u.a.]

Sodium is a promising candidate for stationary storage applications, especially when the demand for lithium-ion batteries increases due to electromobility applications. Even though its energy density is lower, Na-ion technology is estimated to lead to a cost reduction of 30% compared to Li-ion technology. To improve safety as well as energy density, Na-based all-solid-state-batteries featuring solid electrolytes such as beta-alumina and sodium superionic conductors and cathode materials such as Na₃V₂(PO4)₃ and NaₓCoO₂ have been developed over the past years. However, the biggest challenge are mixed cathodes with highly conductive interfaces, especially when co-sintering the materials. For example, a promising sodium superionic conductor type Na₃Zr₂Si₂PO₁₂ electrolyte sinters at 1,250°C, whereas the corresponding Na₃V₂PO₁₂ cathode decomposes at temperatures higher than 900°C, posing a bottleneck. Thus in this paper, we synthesized Na₀.₆₂ [Ni₀.₁₀Fe₀.₁₀Mn₀.₈₀]O₂ as cathode material for all-solid-state sodium-ion batteries via a relatively cheap and easy solution-assisted solid state reaction processing route. The thermal investigations of the pure cathode material found no degradation up to 1,260°C, making it a perfect match for Na₃.₄Zr₂Si₂.₄P₀.₆O₁₂ electrolyte. In our aim to produce a co-sintered mixed cathode, electron microscopy investigation showed a highly dense microstructure and the elemental mapping performed via energy dispersive X-ray spectroscopy and secondary ion mass spectrometry confirm that Na₃.₄Zr₂Si₂.₄P₀.₆O₁₂ and Na₀.₆₂ [Ni₀.₁₀Fe₀.₁₀Mn₀.₈₀]O₂ do not react during sintering. However, the active cathode material forms a sodium rich and a sodium deficient phase which needs further investigation to understand the origin and its impact on the electrochemical performance. CA Extern

La(Co, Ni, Fe)O3 air-electrode for solid-oxide cells, from powder to stackQianli Ma,*a Qingping Fang,a Olivier Guillon,a,b Norbert H. Menzler aa Forschungszentrum Jülich GmbH, Institute of Energy and Climate Research (IEK), D-52425 Jülichb Jülich Aachen Research Alliance, JARA-Energy, D-52425 Jülich, Germany* E-mail: q.ma@fz-juelich.de Although the-state-of-the-art La1-xSrxFe1-yCoyO3 (LSCF) and La1-xSrxCoO3 (LSC) are mature air-electrodes for solid oxide cells (SOCs, including solid oxide fuel cells and solid oxide electrolysis), the continuous depletion of strontium in LSCF or LSC during operation of SOCs leads to deterioration of electrical conductivity and electrocatalytic activity of the air-electrode. It also causes detachment of the contact between the air-electrodes and the metallic interconnects used in SOC stacks. Therefore it is worth to search for alternative air-electrode materials. Among the possible candidates of Sr-free air-electrode materials, the system LaCoO3-LaNiO3-LaFeO3 shows high attractiveness because they have SOC-compatible physical properties, good electrochemical performance and chemical stability against chromium oxyhydroxides released from the metallic interconnects used in SOC stacks. [1]Based on the results obtained on the perovskites in the quasi-ternary system of LaFeO3-LaCoO3-LaNiO3,[1] A-site deficient La0.97Ni0.5Co0.5O3 (LNC97) is selected as the further optimized composition, which has an electronic conductivity of over 1000 S cm-1 at 800oC. [2] Compatibility of LNC97 with 8 mol% Y2O3 stabilized ZrO2 (8YSZ) is analyzed and compared with that of La0.58Sr0.4Co0.8Fe0.2O3-δ (LSCF) and 8YSZ. According to the requirements of the air electrode materials with qualified performance, i.e. 1) high electronic conductivity, 2) high ionic conductivity, and 3) high catalytic activity for the oxygen reduction reaction, LNC97 based electrodes are modified, characterized and optimized by symmetric cell tests. Mechanisms for explaining the electrode-processes of LNC97-based electrodes are raised.[2] Full cells based on optimized LNC97 air-electrode were tested under both fuel cell mode and electrolyzer mode. Mid-term operation of about 1000 h for SOCs in both modes primarily proved the stability of LNC97-based air electrodes. Impedance spectra were systematically applied to understand the polarization processes of the cells.[3] A stack based on LNC97 air electrode was also built and a long-term operation of 4000 h was investigated under fuel cell mode. The performance is comparable to the state-of-the-art LSCF air electrode based SOC stacks, and the degradation rate is as low as 0.9% kh-1, indicating a prospective future for the developed material and the relative SOCs. References[1] F. Tietz, I. ArulRaj, Q. Ma, S.Baumann, A.Mahmoud, R.P.Hermann, J. Solid State Chem. 237 (2016) 183–191.[2] Q. Ma, M. Balaguer, D. Pérez-Coll, L. G. J. de Haart, J. M. Serra, G. C. Mather, F. Tietz, N. H. Menzler, O. Guillon. ACS Appl. Energy Mater. 1 (2018) 2784−2792.[3] Q Ma, S Dierickx, V Vibhu, D Sebold, LGJ de Haart, A Weber, O Guillon, NH Menzler, J. Electrochem. Soc., 167 (2020) 084522.