A-site acceptor-doping strategy to enhance oxygen transport in sodium bismuth titanate perovskite

Sodium–bismuth–titanate (NBT) has recently been shown to contain high levels of oxide ion conductivity. Here we report the effect of A-site monovalent ions, M+ = K+ and Li+, on the electrical conductivity of NBT. The partial replacement of Bi3+ with monovalent ions improved the ionic conductivity by over one order of magnitude without an apparent change of the conduction mechanism, which is attributed to an increase in the oxygen vacancy concentration based on an acceptor-doping approach. The 18O tracer-diffusion coefficient (D*) determined by the isotope exchange depth profile method in combination with secondary ion mass spectrometry confirmed that oxygen ions are the main charge carriers in the system. Among these acceptor-doped samples, 4% Li doping provides the highest total conductivity, leading to a further discussion of doping strategies for NBT-based materials to enhance the electrical behavior, is discussed. Comparisons with other oxide-ion conductors and an oxygen-vacancy diffusivity limit model in perovskite lattice suggested that the doped NBT-based materials might already have achieved the optimization of the ionic conductivity

LaPr3Ni3O9.76 as a candidate solid oxide fuel cell cathode: Role of microstructure and interface structure on electrochemical performance

A new higher-order Ruddlesden-Popper phase composition LaPr3Ni3O9.76 was synthesised by a sol-gel route and studied for potential intermediate-temperature solid oxide fuel cell cathode properties by electrochemical impedance spectroscopy. The focus of the work was optimisation of the microstructure and interface structure to realise the best performance, and therefore symmetrical cells after impedance testing were subsequently studied by scanning electron microscopy for post-microstructural analysis. It was observed that the cathode ink prepared after ball milling the material and then triple roll milling the prepared ink gave the lowest area specific resistance (ASR) of 0.17Ωcm2 at 700◦C when a La0.8Sr0.2Ga0.8Mn0.2O3-δ (LSGM) electrolyte that had been previously polished was used. The post-microstructural studies, as expected, showed an improved interface structure and relatively good particle interconnectivity and much less sintering when compared to the symmetrical half-cells constructed using the ink prepared from the as-synthesised material. The interface structure was further improved significantly by adding a∼10μ m thick LSGM ink interlayer, which was reflected in the electrochemical performance, reducing the ASR of the material from 0.17Ωcm2 to 0.08Ω cm2 at 700◦C. This is to date the best performance reported for an n = 3 Ruddlesden-Popper phase material with LSGM as the electrolyte

The origin of chemical inhomogeneity in garnet electrolytes and its impact on the electrochemical performance

The interface between solid electrolytes and lithium metal electrodes determines the performance of an all-solid-state battery in terms of the ability to demand high power densities and prevent the formation of lithium dendrites. This interface depends strongly on the nature of the solid electrolyte surface in contact with the metallic anode. In the garnet electrolyte/Li system, most papers have focused on the role of current inhomogeneities induced by void formation in the Li metal electrode and the presence of insulating reaction layers following air exposure. However, extended defects in the solid electrolyte induced by chemical and/or structural inhomogeneities can also lead to uneven current distribution, impacting the performance of these systems. In this work, we use complementary surface analysis techniques with varying analysis depths to probe chemical distribution within grains and grain boundaries at the surface and in the bulk of garnet-type electrolytes to explain their electrochemical performance. We show that morphology, post-treatments and storage conditions can greatly affect the surface chemical distribution of grains and grain boundaries. These properties are important to understand since they will dictate the ionic and electronic transport near the interfacial zone between metal and electrolyte which is key to determining chemo-mechanical stability

Operando characterization and theoretical modeling of Metal|Electrolyte interphase growth kinetics in solid-state batteries. Part I: experiments

To harness all of the benefits of solid-state battery (SSB) architectures in terms of energy density, their negative electrode should be an alkali metal. However, the high chemical potential of alkali metals makes them prone to reduce most solid electrolytes (SE), resulting in a decomposition layer called an interphase at the metal|SE interface. Quantitative information about the interphase chemical composition and rate of formation is challenging to obtain because the reaction occurs at a buried interface. In this study, a thin layer of Na metal (Na0) is plated on the surface of an SE of the NaSICON family (Na3.4Zr2Si2.4P0.6O12 or NZSP) inside a commercial X-ray photoelectron spectroscopy (XPS) system while continuously analyzing the composition of the interphase operando. We identify the existence of a solid electrolyte interphase at the Na0|NZSP interface, and more importantly, we demonstrate for the first time that this protocol can be used to study the kinetics of interphase formation. A second important outcome of this article is that the surface chemistry of NZSP samples can be tuned to improve their stability against Na0. It is demonstrated by XPS and time-resolved electrochemical impedance spectroscopy (EIS) that a native NaxPOy layer present on the surface of as-sintered NZSP samples protects their surface against decomposition

Toward an Understanding of SEI Formation and Lithium Plating on Copper in Anode-Free Batteries.

Funder: Blavatnik Family Foundation"Anode-free" batteries present a significant advantage due to their substantially higher energy density and ease of assembly in a dry air atmosphere. However, issues involving lithium dendrite growth and low cycling Coulombic efficiencies during operation remain to be solved. Solid electrolyte interphase (SEI) formation on Cu and its effect on Li plating are studied here to understand the interplay between the Cu current collector surface chemistry and plated Li morphology. A native interphase layer (N-SEI) on the Cu current collector was observed with solid-state nuclear magnetic resonance spectroscopy (ssNMR) and electrochemical impedance spectroscopy (EIS). Cyclic voltammetry (CV) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) studies showed that the nature of the N-SEI is affected by the copper interface composition. An X-ray photoelectron spectroscopy (XPS) study identified a relationship between the applied voltage and SEI composition. In addition to the typical SEI components, the SEI contains copper oxides (Cu x O) and their reduction reaction products. Parasitic electrochemical reactions were observed via in situ NMR measurements of Li plating efficiency. Scanning electron microscopy (SEM) studies revealed a correlation between the morphology of the plated Li and the SEI homogeneity, current density, and rest time in the electrolyte before plating. Via ToF-SIMS, we found that the preferential plating of Li on Cu is governed by the distribution of ionically conducting rather than electronic conducting compounds. The results together suggest strategies for mitigating dendrite formation by current collector pretreatment and controlled SEI formation during the first battery charge

Operando characterization and theoretical modeling of metal|electrolyte interphase growth kinetics in solid-state batteries. Part II: Modeling

Understanding the interfacial dynamics of batteries is crucial to control degradation and increase electrochemical performance and cycling life. If the chemical potential of a negative electrode material lies outside of the stability window of an electrolyte (either solid or liquid), a decomposition layer (interphase) will form at the interface. To better understand and control degradation at interfaces in batteries, theoretical models describing the rate of formation of these interphases are required. This study focuses on the growth kinetics of the interphase forming between solid electrolytes and metallic negative electrodes in solid-state batteries. More specifically, we demonstrate that the rate of interphase formation and metal plating during charge can be accurately described by adapting the theory of coupled ion-electron transfer (CIET). The model is validated by fitting experimental data presented in the first part of this study. The data was collected operando as a Na metal layer was plated on top of a NaSICON solid electrolyte (Na3.4Zr2Si2.4P0.6O12 or NZSP) inside an XPS chamber. This study highlights the depth of information which can be extracted from this single operando experiment and is widely applicable to other solid-state electrolyte systems

Large memcapacitance and memristance at Nb:SrTiO3/La0.5Sr0.5Mn0.5Co0.5O3-d topotactic redox interface

The possibility to develop neuromorphic computing devices able to mimic the extraordinary data processing capabilities of biological systems spurs the research on memristive systems. Memristors with additional functionalities such as robust memcapacitance can outperform standard devices in key aspects such as power consumption or miniaturization possibilities. In this work, we demonstrate a large memcapacitive response of a perovskite memristive interface, using the topotactic redox ability of La0.5Sr0.5Mn0.5Co0.5O3-d (LSMCO, 0 = d = 0.62). We demonstrate that the multi-mem behavior originates at the switchable n-p diode formed at the Nb:SrTiO3/LSMCO interface. We found for our Nb:SrTiO3/LSMCO/Pt devices a memcapacitive effect CHIGH/CLOW ~100 at 150 kHz. The proof-of-concept interface reported here opens a promising venue to use topotactic redox materials for disruptive nanoelectronics, with straightforward applications in neuromorphic computing technology

Effectiveness of a multifactorial intervention in increasing adherence to the mediterranean diet among patients with diabetes mellitus type 2: a controlled and randomized study (EMID Study)

The Mediterranean diet (MD) is recognized as one of the healthiest dietary patterns and has benefits such as improving glycaemic control among patients with type 2 diabetes (T2DM). Our aim is to assess the effectiveness of a multifactorial intervention to improve adherence to theMD, diet quality and biomedical parameters. The EMID study is a randomized and controlled clinical trial with two parallel groups and a 12-month follow-up period. The study included 204 subjects between 25–70 years with T2DM. The participants were randomized into intervention group (IG) and control group (CG). Both groups received brief advice about healthy eating and physical activity. The IG participants additionally took part in a food workshop, five walks and received a smartphone application for three months. The population studied had a mean age of 60.6 years. At the 3-month follow-up visit, there were improvements in adherence to the MD and diet quality of 2.2 and 2.5 points, compared to the baseline visit, respectively, in favour of the IG. This tendency of the improvement was maintained, in favour of the IG, at the 12-month follow-up visit. In conclusion, the multifactorial intervention performed could improve adherence to the MD and diet quality among patients with T2DM.Regional Health Management through the 2016 grants to carry out research projects in biomedicine, health management and socio-health care (GRS 1276/B/16), the 2016 program for the professional development of nurses in their research activity (BOCYL-D-11022016-2) and the 2015 incentive program for nurses who have completed their residency (ORDER SAN / 360/2015). The study was also co-financed by the Carlos III Health Institute and the European Regional Development Fund (ERDF) (RD 16/0007/0003)

The role of ion solvation in lithium mediated nitrogen reduction

Since its verification in 2019, there have been numerous high-profile papers reporting improved efficiency of lithium-mediated electrochemical nitrogen reduction to make ammonia. However, the literature lacks any coherent investigation systematically linking bulk electrolyte properties to electrochemical performance and Solid Electrolyte Interphase (SEI) properties. In this study, we discover that the salt concentration has a remarkable effect on electrolyte stability: at concentrations of 0.6 M LiClO4 and above the electrode potential is stable for at least 12 hours at an applied current density of −2 mA cm−2 at ambient temperature and pressure. Conversely, at the lower concentrations explored in prior studies, the potential required to maintain a given N2 reduction current increased by 8 V within a period of 1 hour under the same conditions. The behaviour is linked more coordination of the salt anion and cation with increasing salt concentration in the electrolyte observed via Raman spectroscopy. Time of flight secondary ion mass spectrometry and X-ray photoelectron spectroscopy reveal a more inorganic, and therefore more stable, SEI layer is formed with increasing salt concentration. A drop in faradaic efficiency for nitrogen reduction is seen at concentrations higher than 0.6 M LiClO4, which is attributed to a combination of a decrease in nitrogen solubility and diffusivity as well as increased SEI conductivity as measured by electrochemical impedance spectroscopy