Oxide Fuel Cell Cathode Materials Research Articles

The effects of sintering temperature and current contacting layer on the performance of lanthanum nickelate electrodes in Solid Oxide Fuel Cells

The Ruddlesden-Popper phase La2NiO4+δ (LNO214) has received a significant level of research attention with respect to its employment as a Solid Oxide Fuel Cell cathode material. However, it is known that there are many factors that are capable of influencing the performance of this phase when utilised in this role. One such factor that can impact on electrode behaviour is the choice of sintering temperature. In this paper, a study of this effect is detailed. This is achieved via the use of both symmetrical and single cell testing configurations, with additional investigation provided by ex-situ analysis. It is shown that a sizeable improvement in electrode performance can be achieved via an increase in sintering temperature. This is despite observations on the reactivity between LNO214 and the contact electrolyte material Ce0.9Gd0.1O2-δ. Further, it is also demonstrated that the addition of a noble metal contacting layer can dramatically improve the performance of an LNO214 electrode. In comparison, the impact of a contacting layer on a state-of-the-art La0.6Sr0.4Co0.2Fe0.8O3-δ composition is shown to be relatively minor. This has implications towards SOFC testing methodologies given the widespread employment of noble metal contacting pastes.

Fe-based double perovskite with Zn doping for enhanced electrochemical performance as intermediate-temperature solid oxide fuel cell cathode material.

This study aims to investigate the implications of transition-metal Zn doping at the B-site on the crystal structure, average thermal expansion coefficient (TEC), electrocatalytic activity, and electrochemical performance of LaBaFe2O5+δ by preparing LaBaFe2-xZnxO5+δ (x = 0, 0.05, 0.1, 0.15, 0.2, LBFZx). The X-ray diffraction (XRD) results show that Zn2+ doping does not change the crystal structure, the unit cell volume increases, and the lattice expands. The X-ray photoelectron spectroscopy (XPS) and mineral titration results show that the oxygen vacancy concentration and Fe4+ content gradually increase with the increase in doping amount. TEC decreases with the increase in Zn2+ doping amount, and the TEC of LBFZ0.2 is 11.4 × 10-6 K-1 at 30-750 °C. The conductivity has the best value of 103 S cm-1 at the doping amount of x = 0.1. The scanning electron microscopy (SEM) images demonstrate that the electrolyte CGO(Gd0.1Ce0.9O1.95) becomes denser after high-temperature calcination, and the cathode material is well attached to the electrolyte. The electrochemical impedance analysis shows that Zn2+ doping at the B-site can reduce the (Rp) polarization resistance, and the Rp value of the symmetric cell with LaBaFe1.8Zn0.2O5+δ as cathode at 800 °C is 0.014 Ω cm2. The peak power density (PPD) value of the anode-supported single cell is 453 mW cm-2, which shows excellent electrochemical performance.

In-situ segregation of A-site defect (La0.6Sr0.4)0.90Co0.2Fe0.8O3-δ to form a high-performance solid oxide fuel cell cathode material with heterostructure

As a potential cathode material for solid oxide fuel cells, the commercial application of La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) has to face the challenges in insufficient oxygen reduction reaction (ORR) activity, segregation of Sr element, and CO2 poisoning. Therefore, the effect of A-site non-stoichiometry on the electrochemical performance of (LS)1-xCFs (x = −0.05, 0, 0.05, 0.10, 0.15) from the aspect of microstructure/elemental surface chemical environment evolution is investigated in this paper. The results show that (LS)0.90CF has the best ORR activity and the highest electrochemical performance. The excellent electrochemical performance is attributed to the (LS)0.90CF/Co2FeO4/CoFe2O4-type heterostructure, formed by in-situ segregation induced by A-site defects, which improves the surface oxygen diffusion coefficient and chemical bulk diffusion coefficient of the cathode. At the same time, the A-site defect can effectively inhibit the segregation of Sr element in (LS)0.90CF, thereby improving the tolerance of CO2. At 800 °C, the area-specific resistance (ASR) of (LS)0.90CF (0.023 Ω cm2) is 66.7% lower than that of LSCF (0.069 Ω cm2), and the peak power density (1.57 Wcm−2) is 1.8 times higher than that of LSCF (0.87 Wcm−2). Therefore, perovskite A-site defect-induced B-site segregation to form heterostructures provides an effective strategy for the preparation of high-performance cathode materials.

A Review of X-ray Photoelectron Spectroscopy Technique to Analyze the Stability and Degradation Mechanism of Solid Oxide Fuel Cell Cathode Materials.

Nondestructive characterization of solid oxide fuel cell (SOFC) materials has drawn attention owing to the advances in instrumentation that enable in situ characterization during high-temperature cell operation. X-ray photoelectron spectroscopy (XPS) is widely used to investigate the surface of SOFC cathode materials because of its excellent chemical specificity and surface sensitivity. The XPS can be used to analyze the elemental composition and oxidation state of cathode layers from the surface to a depth of approximately 5–10 nm. Any change in the chemical state of the SOFC cathode at the surface affects the migration of oxygen ions to the cathode/electrolyte interface via the cathode layer and causes performance degradation. The objective of this article is to provide a comprehensive review of the adoption of XPS for the characterization of SOFC cathode materials to understand its degradation mechanism in absolute terms. The use of XPS to confirm the chemical stability at the interface and the enrichment of cations on the surface is reviewed. Finally, the strategies adopted to improve the structural stability and electrochemical performance of the LSCF cathode are also discussed.

Understanding the Role of Sr as a Dopant in a Double Perovskite Material for Solid Oxide Fuel Cells

LnBaCo2O5+d type of layered double perovskite materials has received much attention as solid oxide fuel cell cathode materials owing to their high oxygen ion concentration, high electronic conductivity, and catalytic activity towards oxygen reduction. In the present work, Nd-based double perovskites NdBa1-xSrxCo2O5+d (NBSCO, x= 0, 0.25 and 0.50) have been studied computationally.Plane-wave density functional theory-based calculations using VASP were performed to examine the electrochemical properties of NdBa1-xSrxCo2O5+d double perovskite material. Given the application of NBSCO material for SOFC cathodes, the bulk oxygen vacancy formation energies (Eov) have been calculated computationally for oxygen vacancy created in all possible planes (BaSr/O, Nd/O, and Co/O) and surface energies (γ) of the structure with different terminations (BaSr/Co, Nd/Co, Co/BaSr and Co/Nd) along (001) direction. Fig 1. and Fig. 2 shows the structure with oxygen vacancy created in various planes and with different terminal surfaces. Computed oxygen vacancy formation energies and surface energies in NBSCO are shown in table 1 and table 2. Nd/O plane observed to have the lowest oxygen vacancy formation energy among all the three possible planes in (001) direction of bulk NBSCO. This shows Nd/O plane to have high oxygen vacancy concentration. For x=0, 0.25, and 0.50, BaSr/O plane has the highest oxygen vacancy formation energies showing difficulty in oxygen vacancy creation in BaSr/O plane as compared to other planes. This suggested less oxygen anion diffusivity in the BaSr/O plane. However, doping one fourth and half of the Ba with Sr resulted in an improved bulk oxygen vacancy characteristic of the BaSr/O plane. Different energetics of different terminal surfaces shows the importance of terminations. The results of first-principles calculations for surface energies were analyzed and compared for different terminal surfaces. For NBCO material, low surface energies have been observed for Ba/Co termination. Due to lower surface energies, Ba ions have tendencies to segregate towards the surface. This is in accordance with the DFT based calculations of surface energies and molecular dynamics simulations for diffusivity and root mean square deviation values of other Ba containing LnBaCo2O5+d layered perovskites [1-5]. Doping the material with Sr has also shown a similar trend in surface energies of BaSr/Co terminal surface.

(Invited) Investigating Transport Pathways on La0.6Sr0.4CoO3- δ Thin Films with Frequency-Resolved X-Ray Imaging

Enhancing oxygen electrode performance in SOFCs is generally hindered by insufficient understanding regarding the rates of surface exchange and ionic diffusion processes. Spatial averaging of rates taking place at different locations within the electrode structure prevent AC impedance and DC polarization techniques from unambiguously ascertaining mechanistic details. To probe local electrode rates, workers leveraged operando micro-X-ray absorption spectroscopy (µ-XAS) to capture one-dimensional images of oxygen chemical potential distributions in patterned thin film La0.6Sr0.4CoO3-δ electrodes under steady polarization.1–3 They directly measured the active region length for behavior co-limited by diffusion and kinetics, with surprising results regarding the role of three-phase boundaries (interface of gas, electrode, and electrolyte). Although measuring the active region length indicates relative contributions of kinetics and diffusion, measurements under co-limited conditions cannot determine their absolute rates.We recently extended those measurements into the frequency domain by collecting one-dimensional µ-XAS images under sinusoidal voltage perturbations. Therefore, we maintain the spatial resolution of µ-XAS and gain the benefit of probing physics by timescale (a feature of AC impedance spectroscopy). Our results from this technique – called frequency-resolved X-ray absorption spectroscopy (fr-XAS) – agree quantitatively with a one-dimensional Gerischer model, yielding transport and kinetic rate parameters from the images. Extracted parameters agree remarkably well with literature values from porous electrodes and show similar oxygen partial pressure dependence. AC impedance measurements of the patterned electrodes are not Gerischer-shaped, likely from parallel processes unrelated to oxygen exchange and transport, preventing meaningful interpretation.4,5 Contrasting interpretability showcases the power of local, frequency-resolved measurements for isolating pertinent phenomena amid extraneous factors.Higher harmonic distributions from the nonlinear response to moderate amplitude perturbations allow us to examine relative contributions of bulk and surface diffusion. Fr-XAS images collected over a range of perturbation amplitudes are analyzed analogously to nonlinear electrochemical spectroscopy data to extract amplitude independent coefficients.6 The sign and magnitude for the real and imaginary components of these coefficients indicate relative rates of bulk and surface diffusion. Ongoing work focuses on determining relative rates of these parallel transport pathways in patterned electrodes featuring triple-phase boundaries and double-phase boundaries (interface of electrode and electrolyte).(1) Fujimaki, Y.; Watanabe, H.; Terada, Y.; Nakamura, T.; Yashiro, K.; Hashimoto, S.; Kawada, T.; Amezawa, K. Direct Evaluation of Oxygen Chemical Potential Distribution in an SOFC Cathode by In Situ X-Ray Absorption Spectroscopy. ECS Trans. 2013, 57 (1), 1925–1932. https://doi.org/10.1149/05701.1925ecst.(2) Amezawa, K.; Fujimaki, Y.; Nakamura, T.; Bagarinao, K. D.-; Yamaji, K.; Nitta, K.; Terada, Y.; Iguchi, F.; Yashiro, K.; Yugami, H.; Kawada, T. (Invited) Determination of Effective Reaction Area in a Mixed-Conducting SOFC Cathode. ECS Trans. 2015, 66 (2), 129–135. https://doi.org/10.1149/06602.0129ecst.(3) Amezawa, K.; Fujimaki, Y.; Mizuno, K.; Kimura, Y.; Nakamura, T.; Nitta, K.; Terada, Y.; Iguchi, F.; Yugami, H.; Yashiro, K.; Kawada, T. (Invited) Triple Phase Boundary Reaction in a Mixed-Conducting SOFC Cathode. ECS Trans. 2017, 77 (10), 41–47. https://doi.org/10.1149/07710.0041ecst.(4) Lu, Y.; Kreller, C.; Adler, S. B. Measurement and Modeling of the Impedance Characteristics of Porous La1 − x Sr x CoO3 − δ Electrodes. J. Electrochem. Soc. 2009, 156 (4), B513–B525. https://doi.org/10.1149/1.3079337.(5) Søgaard, M.; Hendriksen, P. V.; Mogensen, M.; Poulsen, F. W.; Skou, E. Oxygen Nonstoichiometry and Transport Properties of Strontium Substituted Lanthanum Cobaltite. Solid State Ionics 2006, 177 (37), 3285–3296. https://doi.org/10.1016/j.ssi.2006.09.005.(6) Wilson, J. R.; Schwartz, D. T.; Adler, S. B. Nonlinear Electrochemical Impedance Spectroscopy for Solid Oxide Fuel Cell Cathode Materials. Electrochimica Acta 2006, 51 (8–9), 1389–1402. https://doi.org/10.1016/j.electacta.2005.02.109.

A review of Solid Oxide Fuel Cell cathode materials with respect to their resistance to the effects of chromium poisoning

Solid Oxide Fuel Cell (SOFC) cathode materials have been shown to be susceptible to a ‘chromium poisoning’ phenomenon that can significantly deteriorate cell output during operation. Chromium-containing species, released from stack and system materials, migrate to the SOFC cathode where they are able to form new phases through reaction with the cathode material. Such phases have been shown to diminish the catalytic and conductive performance of the electrodes and even block the pathways through which oxygen must diffuse. To date, there has been a significant body of research afforded to this subject area. Efforts have been made towards understanding the chromium poisoning effect, whilst also considering how it may be mitigated. In this review, we discuss the effects of chromium-containing phases on both conventional and non-conventional cathode materials. This is in order to understand the most successful approaches towards developing chromium-tolerant cathode materials. The influences of environmental parameters such as temperature and humidity are also discussed. This is to explore how degradation rates may be affected by the operating conditions themselves and the extent to which the phenomenon can be mitigated by suitable control of such factors. In the most part, these environmental effects are studied in relation to the most common cathode materials, La1-xSrxCo1-yFeyO3 and La1-xSrxMnO3, where there has been the largest body of work conducted.

Strain-induced structure and oxygen transport interactions in epitaxial La0.6Sr0.4CoO3\u2212\u03b4 thin films

The possibility to control oxygen transport in one of the most promising solid oxide fuel cell cathode materials, La0.6Sr0.4CoO3−δ, by controlling lattice strain raises questions regarding the contribution of atomic scale effects. Here, high-resolution transmission electron microscopy revealed the different atomic structures in La0.6Sr0.4CoO3−δ thin films grown under tensile and compressive strain conditions. The atomic structure of the tensile-strained film indicated significant local concentration of the oxygen vacancies, with the average value of the oxygen non-stoichiometry being much larger than for the compressive-strained film. In addition to the vacancy concentration differences that are measured by isotope exchange depth profiling, significant vacancy ordering was found in tensile-strained films. This understanding might be useful for tuning the atomic structure of La0.6Sr0.4CoO3−δ thin films to optimize cathode performance.

Characterisation of indentation microstructures for porous SOFC cathodes

In this study, high-resolution focused ion beam sectioning assisted with SEM imaging was used to study the indentation microstructures of porous bulks and films of a solid oxide fuel cell cathode material (La0.6Sr0.4Co0.2Fe0.8O3-δ) sintered at different temperatures. The crack morphologies and pore-filling densification caused by crushing of particle networks were studied in details. Analysis showed distinct permanent deformation mechanisms of the indentation microstructures between porous bulks and films. Whilst remarkable porosity gradient was found for the porous films under both Berkovich and spherical indenters, the porous bulks were found to behave more like dense materials. Results also showed that radial cracks induced by Berkovich indentation on the bulks could not generate observable pop-in/pop-out events in the loading-unloading curves. However, when indenting with the spherical indenter on a thick film, the shear sliding of the particle networks immediately under the indenter could cause phenomenal disruption in the loading unloading curves shown.

Dynamic X-ray Spectroscopy of La0.6Sr0.4CoO3-δ Thin Film Electrodes

Dense thin films of the solid oxide fuel cell cathode material La0.6Sr0.4CoO3-δ were studied by operando X-ray absorption spectroscopy under sinusoidal voltage perturbations. This approach showed good agreement with previous steady-state μ-XAS measurements, but with high effective p(O2) resolution over several orders of magnitude. Co oxidation state varied strongest under a 0.5 Hz perturbation suggesting, in agreement with linear impedance, that oxygen exchange kinetics are most active at this timescale. Furthermore, the local structure around Co atoms response varied at different timescales; however, interpretation was limited with only preliminary analysis. Altogether, this approach was shown as a successful step towards developing a technique sensitive to local chemical state that can also separate processes by timescale.

Synthesis and Characterizations of Ce0.5Sr0.5Co0.8Fe0.2O3-? (CSCF)Solid Oxide Fuel Cell Cathode Material by Sol-Gel method

Synthesis and Characterizations of Ce0.5Sr0.5Co0.8Fe0.2O3-? (CSCF)Solid Oxide Fuel Cell Cathode Material by Sol-Gel method

In situ study of strontium segregation in La0.6Sr0.4Co0.2Fe0.8O3−δ in ambient atmospheres using high-temperature environmental scanning electron microscopy

Samples of the solid oxide fuel cell cathode material La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF) were annealed using HT-ESEM from room temperature to 1000 °C in atmospheres of pure oxygen, pure water and ambient lab air.

Structural and Electronic Features of Nb-Doped SrCoO3: Insight from First-Principles Calculations

The present work reports a systematic investigation into the structural and electronic features of tetragonal and cubic structured undoped and Nb-doped SrCoO3 using first-principles calculations. The results suggest that the tetragonal structure is more stable than the cubic structure as a result of the Jahn–Teller distortion effect. In the Nb-Doped SrCoO3 system, the structural analysis reveals a gradual tetragonal-to-cubic transition with Nb-doping. Nb-ions show no occupational preference over Co-sites in the SrCoO3 host structure. Co-ions become more easily reduced by Nb-doping due to the filling of excess electrons from Nb-ions into Co-3d orbitals, thus decreasing the magnetic moment of Co-ions. Furthermore, the rich electronic states at the Fermi level in Nb-doped SrCoO3 enable a high electronic conductivity, making the material suitable for a solid oxide fuel cell cathode material.

Synthesis and characterization of Sr0.75Y0.25Co0.9Ru0.1O3−δ perovskite as a solid oxide fuel cell cathode material

The oxygen-deficient Sr0.75Y0.25Co0.9Ru0.1O3−δ (SYCR) cathode is systematically evaluated for the application of solid oxide fuel cells. X-ray diffraction analysis indicates that SYCR presents a tetragonal structure with space group of I4/mmm (139). In the measured high oxygen partial pressure (pO2) region (0.01–0.21 atm), the conductivity increases with increasing pO2 because of the oxygen vacancy annihilation and hole creation, relating to a general p-type semiconducting mechanism. To get an insight into the rate-limiting step of SYCR cathode, behaviors of individual polarization resistance (R 1 and R 2) are investigated in different pO2. The obtained fitting results reveal that R 1 is nearly independent on the pO2, while R 2 presents a (pO2)−0.5 dependence. At 800 °C, SYCR cathode exhibits an R p value of 0.14 Ω cm2, moreover, when using the wet hydrogen (∼ 3% H2O) as fuel and ambient air as oxidant, the maximum power density of single cell Ni-YSZ (yttria-stabilized zirconia)|YSZ|SYCR reaches 452.9 W cm−2.

Cationic Interdiffusion at the SOFC Electrolyte/Cathode Interface in La2Mo2O9/La0.8Sr0.2MnO3‐δ

AbstractIn this work cation diffusion between a La2Mo2O9 (LM) ionic conductor and the conventional Solid Oxide Fuel Cell (SOFC) cathode material La0.8Sr0.2MnO3‐δ (LSM), was probed using secondary ion mass spectrometry (SIMS), and diffusion coefficients of Sr, Mo and Mn cations within both materials evaluated. Diffusion coefficients extracted from samples with a Sr solution deposited on the LM pellets and from a Mo solution deposited on LSM pellets were found to be orders of magnitude higher than the cross‐diffusion through the interface between two dense pellets in direct contact. These differences may be due to uncertainty in determining the interface position, or to a real dependence on the source of the diffusing cation. In the most favorable case, that of pellets in direct contact, extrapolation of diffusion coefficients down to a typical SOFC operating temperature, 800 °C, show that Mo diffusion in LSM (diffusion coefficient ∼ 10−14 cm2.s−1) is much higher than Sr or Mn diffusion in LM, and incompatible with use in a SOFC device, unless an efficient buffer layer is used.

Misfit Ca-cobaltite from a mixture of mollusk shells and cobalt oxide as potential SOFC cathode material

Abstract Misfit Ca-cobaltites of nominal composition Ca 3 Co 4 O 9-δ (C349) have attracted great attention as Solid Oxide Fuel Cell (SOFC) cathode material. The present work reports, for the first time, the solid-state synthesis of C349 powders from a mixture of cobalt oxide and mollusk shells, a natural source of calcium carbonate. The synthesized material was studied by X-ray diffraction, with Rietveld refinement of the XRD data, and Transmission Electron Microscopy (TEM). Screen-printed C349 porous electrodes were fired on both sides of dense gadolinia-doped ceria ceramics and electrochemically characterized by impedance spectroscopy at 700–800 °C in air. The measured area specific resistance (ASR of 1.47 Ω cm 2 at 800 °C in air) is in line with literature data for similar cathodes prepared by other synthetic routes.

(Invited) Electrochemical Characterization of Complete La0.6Sr0.4Co1-XFeXO3-δ Composition Phase Space By Microelectrode Impedance Spectroscopy

Solid oxide fuel cells are a promising clean energy technology due to their high efficiency and fuel flexibility, but current commercialization efforts are limited by expensive components needed to withstand high operating temperatures [1]. Attempts to decrease operating temperature have been stymied in large part by cathode materials with high polarization resistance [2], and efforts to improve performance through composite electrode morphologies [3] lead to complex geometries that prevent rigorous comparisons between different materials. We present a case study employing a novel methodology [4] for electrode characterization that enables fundamental property determination of multiple electrode compositions and allows for rigorous performance comparisons. In this work, the entire composition phase space of a state-of-the-art ion- and electron-conducting solid oxide fuel cell cathode material (La0.6Sr0.4Co1-xFexO3-δ) is examined with unprecedented compositional resolution (x=0 to x=1 with Δx=0.05). Gradient pulsed laser deposition was employed to obtain a compositionally graded thin film on a (100)-oriented 8 mol% Y2O3-ZrO2 electrolyte substrate. The film was patterned using photolithography and ion milling to obtain electronically isolated circular microdot electrodes ranging from 80-500 µm in diameter. Microelectrode impedance spectroscopy was performed with a robotic scanning probe in an environmental chamber to obtain relevant electrochemical parameters. The measured impedance spectra are consistent with a two-phase boundary electrochemical pathway including bulk ionic conduction through the oxide. A monotonic increase in electrochemical resistance is observed from La0.6Sr0.4CoO3–δ (LSC) to La0.6Sr0.4FeO3–δ (LSF) along with a decrease in chemical capacitance corresponding to a decrease in reducibility and oxygen vacancy concentration. This case study demonstrates the rich insights that can be gleaned from this high-throughput approach and its promising application toward searching for new high-performance solid oxide fuel cell electrode materials. 1. Yang, Z.G., Recent advances in metallic interconnects for solid oxide fuel cells. International Materials Reviews, 2008. 53(1): p. 39-54. 2. Kuklja, M.M., et al., Combined theoretical and experimental analysis of processes determining cathode performance in solid oxide fuel cells. Physical Chemistry Chemical Physics, 2013. 15(15): p. 5443-5471. 3. Sun, C.W., R. Hui, and J. Roller, Cathode materials for solid oxide fuel cells: a review. Journal of Solid State Electrochemistry, 2010. 14(7): p. 1125-1144. 4. Usiskin, R.E., et al., Probing the reaction pathway in (La0.8Sr0.2)(0.95)MnO3+delta using libraries of thin film microelectrodes. Journal of Materials Chemistry A, 2015. 3(38): p. 19330-19345.

Enhanced efficiency of solid-state NMR investigations of energy materials using an external automatic tuning/matching (eATM) robot

We have developed and explored an external automatic tuning/matching (eATM) robot that can be attached to commercial and/or home-built magic angle spinning (MAS) or static nuclear magnetic resonance (NMR) probeheads. Complete synchronization and automation with Bruker and Tecmag spectrometers is ensured via transistor-transistor-logic (TTL) signals. The eATM robot enables an automated “on-the-fly” re-calibration of the radio frequency (rf) carrier frequency, which is beneficial whenever tuning/matching of the resonance circuit is required, e.g. variable temperature (VT) NMR, spin-echo mapping (variable offset cumulative spectroscopy, VOCS) and/or in situ NMR experiments of batteries. This allows a significant increase in efficiency for NMR experiments outside regular working hours (e.g. overnight) and, furthermore, enables measurements of quadrupolar nuclei which would not be possible in reasonable timeframes due to excessively large spectral widths. Additionally, different tuning/matching capacitor (and/or coil) settings for desired frequencies (e.g.7Li and 31P at 117 and 122MHz, respectively, at 7.05 T) can be saved and made directly accessible before automatic tuning/matching, thus enabling automated measurements of multiple nuclei for one sample with no manual adjustment required by the user. We have applied this new eATM approach in static and MAS spin-echo mapping NMR experiments in different magnetic fields on four energy storage materials, namely: (1) paramagnetic 7Li and 31P MAS NMR (without manual recalibration) of the Li-ion battery cathode material LiFePO4; (2) paramagnetic 17O VT-NMR of the solid oxide fuel cell cathode material La2NiO4+δ; (3) broadband 93Nb static NMR of the Li-ion battery material BNb2O5; and (4) broadband static 127I NMR of a potential Li–air battery product LiIO3. In each case, insight into local atomic structure and dynamics arises primarily from the highly broadened (1–25MHz) NMR lineshapes that the eATM robot is uniquely suited to collect. These new developments in automation of NMR experiments are likely to advance the application of in and ex situ NMR investigations to an ever-increasing range of energy storage materials and systems.

Ab initio study of vacancy formation in cubic LaMnO3 and SmCoO3 as cathode materials in solid oxide fuel cells.

Doped LaMnO3 and SmCoO3 are important solid oxide fuel cell cathode materials. The main difference between these two perovskites is that SmCoO3 has proven to be a more efficient cathode material than LaMnO3 at lower temperatures. In order to explain the difference in efficiency, we need to gain insight into the materials' properties at the atomic level. However, while LaMnO3 has been widely studied, ab initio studies on SmCoO3 are rare. Hence, in this paper, we perform a comparative DFT + U study of the structural, electronic, and magnetic properties of these two perovskites. To that end, we first determined a suitable Hubbard parameter for the Co d-electrons to obtain a proper description of SmCoO3 that fully agrees with the available experimental data. We next evaluated the impact of oxygen and cation vacancies on the geometry, electronic, and magnetic properties. Oxygen vacancies strongly alter the electronic and magnetic structures of SmCoO3, but barely affect LaMnO3. However, due to their high formation energy, their concentrations in the material are very low and need to be induced by doping. Studying the cation vacancy concentration showed that the formation of cation vacancies is less energetically favorable than oxygen vacancies and would thus not markedly influence the performance of the cathode.

Electrochemical and morphological characterizations of La2⿿xNiO4±d (x = 0.01, 0.02, 0.03 and 0.05) as new cathodes materials for IT-SOFC

A new IT-SOFC (Intermediate Temperature Oxide Fuel Cell) cathode material, La2⿿xNiO4±δ (x=0.01, 0.02, 0.03 and 0.05), was tested along with the electrolyte material yttria-stabilized zirconia (YSZ). The low deficit materials have good electrochemical properties. L2NO has shown the lowest resistance values meanwhile L1NO has shown the lowest energy activation. Particle size decrease according to the percentage of deficiency as increased interaction force between atoms causes shrinkage of the crystal lattice. In addition, porosity is reduced. Nevertheless this phenomenon adversely affects the electrochemical properties of the material by increasing its polarization resistance. That was observed in the case of materials whose deficiency varies between 3 and 5%. The mixed conducting materials were prepared by the citrate method. They were characterized by SEM and XRD while their electric properties were studied by impedance spectroscopy. Eventually improvements in the electrochemical properties of the cathode are certainly due to the morphological properties of materials.