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Abstract This work was focused on studies of structural and electrochemical properties of the La-doped AB 2 -type Zr/Ti-based metal hydride anode alloys. The Ti 0.2 Zr 0.8 La 0-0.05 Ni 1.2 Mn 0.7 V 0.12 Fe 0.12 alloys were characterized using SEM, EDS and XRD, which concluded that the major C15 Laves type AB 2 compound co-exists with a minor La-Ni intermetallic. NPD study indicated that vanadium together with Ti and Zr partially fills the A site, while the rest of V together with Ni, Mn and Fe statistically fills the B site. NPD showed that in a trihydride (Ti,Zr,V)(Ni,Mn,Fe,V) 2 D 2.9 D atoms occupy A 2 B 2 tetrahedra. The alloys were characterized during high-rate discharge and on cycling. La addition resulted in a significant improvement of the activation performance caused by a catalytic influence of LaNi hydride. The highest content of La greatly accelerated the activation, but it also caused an obvious decrease in discharge capacity and cycling stability. The alloy with an optimized La addition (x = 0.03) demonstrated a maximum discharge capacity of 420 mAh g−1 and the discharge capacity maintained at 79% at 0.71 C, while the capacity retention after 500 cycles was also high, 63%. Based on the EIS results, we conclude that the decay of the alloy electrode is related to the irreversible capacity loss and its pulverization. Graphical abstract Image 1 Highlights • Annealed multi-component Zr/Ti-based alloy has a FCC C15 Laves type structure. • The maximum electrochemical discharge capacity of the alloy reaches 420 mAhg−1. • La addition significantly improves the electrochemical performance of AB 2 alloy. • D atoms occupy the 96 g sites only while V atoms occupy both 8 a and 16 d sites. [ABSTRACT FROM AUTHOR]

The reaction evolution and kinetics of the LiFePO 4 positive electrode material is dependent on the synthesis method and cycling conditions. In operando neutron powder diffraction is used investigate the structure-electrochemistry relationship of the electrode materials in a Valence Technology Inc. 18650 Energy cell (IFR18650EC) containing a graphite negative electrode and a Mg-doped LiFePO 4 (Li(MgFe)PO 4 ) positive electrode. Two cells were studied at ambient (298 K) and elevated (323 K) temperature, and higher temperatures were found to improve reaction kinetics and hence capacity. Rietveld refinement of structural models against the diffraction data revealed information about the nucleation of the lithiated and delithiated phases in the Li(MgFe)PO 4 positive electrode material as a function of each cell's state of charge. Polarisation was indicated by a shift in the potential at which the lithiated and delithiated (MgFe)PO 4 phases nucleate during cycling, the extent of which was found to be linearly proportional to the applied current. This work provides new evidence for polarisation of the positive electrode material in a Li-ion battery system. [ABSTRACT FROM AUTHOR]

Commercial 18650 lithium ion cells containing a blended positive electrode of layered LiNi 0.5 Mn 0.3 Co 0.2 O 2 and spinel Li 1.1 Mn 1.9 O 4 alongside a graphite negative electrode were stored at various depth-of-discharge (DoD) at 60 °C for 1, 2, 4, and 6 months. After storage, the cells were cycled at C/25 at 25 °C between 2.75 and 4.2 V for capacity determination and incremental capacity analysis (ICA). In addition to ICA analysis, the mechanism for capacity fade was investigated by combining the results of neutron powder diffraction under in-situ and operando conditions, in conjunction with post-mortem studies of the electrodes using synchrotron X-ray powder diffraction and inductively-coupled plasma optical emission spectroscopy. Among the cells, those stored at 25% DoD suffered the highest capacity fade due to their higher losses of active Li, NMC, and LMO than cells stored at other DoD. The cells stored at 0% DoD shows second high capacity fade because they exhibit the highest of active LMO and graphite anode among the stored cells and higher losses of active Li and NMC than cells stored at 50% DoD. [ABSTRACT FROM AUTHOR]

The sodiation and desodiation of sodium (Na) into the Super-P carbon anode material were investigated using electrochemical analyses, high-resolution transmission electron microscopy (HRTEM), and neutron powder diffraction (NPD). In the sodiated Super-P carbon, sodium is stored both in the graphite interlayer space of carbon nano-particles and pores between the particles. Sodium metal clusters found in micro-pores between the carbon particles are responsible for the large irreversible capacity of the Super-P electrode. The graphite interlayer distance increases on sodiation from 3.57 Å to two distinct values of ∼3.84 and 4.41 Å. The mechanism of the process is discussed. [ABSTRACT FROM AUTHOR]

Safety issues along with the substantially reduced energy and power capabilities of Li-ion cells, operated at low temperatures, pose a technical barrier limiting their use in electric vehicles and aerospace applications. A combined in situ high-resolution neutron powder diffraction and electrochemical study on Li-ion cells of the 18650-type over a temperature range from 230 K to 320 K is reported with a focus on the graphite anode and the low temperature performance of the cell. Instead of a quasi-continuous behavior as observed at ambient temperatures, an anomalous behavior occurs upon discharge at low temperature, primarily reflected in the abrupt character of the LiC 12 – to – graphite phase transformation and the unusual temperature dependence of the amount of LiC 6 . An instability of lithiated graphite phases at temperatures below 250 K is observed, which affects the performance of Li-ion batteries at low temperatures. [ABSTRACT FROM AUTHOR]

Abstract: Commercial NMC cells of 18650-type based on a Li x (Ni0.5Mn0.3Co0.2)O2 cathode and a graphitic anode were studied in situ using a combination of high-resolution monochromatic neutron powder diffraction and electrochemical analysis. The structural changes of the electrode materials during cell charge/discharge have been determined using Rietveld refinement and single profile decomposition techniques. A transformation of the graphitic anode to LiC12 and LiC6 through the formation of higher ordered lithium intercalated carbons was observed. A different behavior of electrochemically-driven lattice distortion was observed for NMC material in comparison to Li x CoO2 and its influence on the overall cell performance has been discussed in brief. Detailed analysis of the structural changes in the Li x (Ni0.5Mn0.3Co0.2)O2 cathode material revealed reversible Li/Ni cation mixing (5.6(8)%), which is state-of-charge independent below 1600 mAh and vanishing above 1800 mAh (∼0.8Q max). [Copyright &y& Elsevier]

Abstract: Spatially-resolved neutron diffraction has been applied to probe the lithium distribution in radial direction of a commercial Li-ion cell of 18650-type. The spatial evolution of selected Bragg reflections for LiCoO2 (positive electrode, “cathode”) and graphite and lithium intercalated graphite (negative electrode, “anode”) was observed and evaluated by taking beam attenuation and cell geometry effects into account. No evidences for lithium inhomogeneities have been found for the investigated set of cells. Computed neutron tomography using a monochromatic neutron beam confirmed the homogeneous lithium distribution. The relevance of the monochromatic beam to neutron imaging studies of Li-ion cells is discussed. [Copyright &y& Elsevier]

Abstract: In-situ neutron powder diffraction was employed to investigate the structural evolution of the electrode materials in a commercial lithium-ion battery used for electric buses in Taiwan. The battery, containing a vanadium-added LiFePO4 cathode, does not exhibit a delayed phase transition between LiFePO4 (triphylite) and FePO4 (heterosite) suggesting that the delayed phase transition can be suppressed through the use of vanadium-added LiFePO4 cathodes, which also enhances the capacity and prolongs the cycle life of these batteries. Furthermore, we characterize the readily reversible structural change of the anode (Li x C6 where 0 < x ≦ 1) and correlate this to battery voltage. [Copyright &y& Elsevier]

Abstract: Substitution of La3+ by Sr2+ in the perovskite La2CoTiO6 yields materials of the La2−x Sr x CoTiO6 series. The dominant charge-compensating mechanism is oxidation of Co2+ if they are prepared at air. The as prepared oxides can be reduced inducing a large amount of oxygen vacancies while keeping the perovskite structure. The electrical behaviour of the La2−x Sr x CoTiO6 series is dominated by p-type electronic conduction in a wide pO2 range through non-adiabatic hopping of small-polarons. The electrical conductivity increases with x, except for the x = 0.5 material which shows an unexpectedly low conductivity due to microstructural and short-range ordering effects. The highest conductivity material, La1.60Sr0.40CoTiO6, is selected to study the electrochemical properties of the series. This compound is chemically compatible with YSZ up to 1373 K, in both oxidizing and reducing atmospheres. The preliminary evaluation of the electrode performance reveals that La1.60Sr0.40CoTiO6-based electrodes exhibit polarization resistances of typically 0.8 Ω cm2 at 1073 K in oxygen, which are close to the values obtained for LSM-based cathodes. Thus, the electrochemical behaviour of this oxide as cathode is particularly encouraging since the electrode microstructure is not optimized; it is expected that an improved microstructure will perform at least similarly to the state-of-art in SOFCs materials. [Copyright &y& Elsevier]

Abstract: Anode and cathode materials, graphite and LiCoO2, are studied by neutron diffraction under “in operando” conditions in commercial batteries (ICR 18650-type). The evolution of their crystal structure versus state of charge (SOC) and fatigue (state of health, SOH) has been analyzed using the Rietveld refinement technique. Neutron radiography data and their tomography reconstruction revealed the local neutron absorption density, which reflects mainly the Li-distribution density, but also further details of the battery design. Changes in the neutron absorption contrast have also been evaluated in dependence on SOC and SOH. [Copyright &y& Elsevier]

Abstract: Phase composition and electronic conductivity of La0.95Ni0.6Fe0.4O3−δ (LNF) modified by small additions (2–10mol%) of MnO2, TiO2, CeO2 and Sr-containing manganese perovskite were investigated. A-site deficiency was found to be only limited in extent with typically NiO precipitates compensating for the nominal A-site deficiency. The phase composition of modified LNF varies depending on the type and amount of oxide additives. A low level of doping (∼2mol%) does not change the value of conductivity and temperature of the semiconducting-metallic transition (∼300°C). However, electronic conductivity of the modified LNF decreases if it contains 5mol% of oxide additive or more. A decrease in conductivity was observed independently whether a secondary phase is present, solid solutions form or a change in symmetry of the modified LNF occurs. After reduction in argon atmosphere all compositions investigated exhibit semiconducting behaviour in a wide temperature range. Neutron powder diffraction measurements give insight into the mechanism of solid state interaction of LNF with small degrees of oxide additives. [Copyright &y& Elsevier]

Abstract: The knowledge of the thermal evolution of the crystal structure of a cathode material across the usual working conditions in solid oxide fuel cells is essential to understand not only its transport properties but also its chemical and mechanical stability in the working environment. In this regard, high-resolution neutron powder diffraction (NPD) measurements have been performed in air from 25 to 900°C on O2-treated (350°C/200bar) La2Ni0.6Cu0.4O4+δ . The crystal structure was Rietveld-refined in the tetragonal F4/mmm space group along all the temperature range. The structural data have been correlated with the transport properties of this layered perovskite. The electrical conductivity of O2-treated La2Ni0.6Cu0.4O4+δ exhibits a metal (high T)-to-semiconductor (low T) transition as a function of temperature, displaying a maximum value of 110Scm−1 at around 450°C. The largest conductivity corresponds, microscopically, to the shortest axial Ni–O2 distance (2.29(1)Å), revealing a major anisotropic component for the electronic transport. We have also performed a durability test at 750°C for 560h obtaining a very stable value for the electrical conductivity of 87Scm−1. The thermal expansion coefficient was 12.8×10−6 K−1 very close to that of the usual SOFC electrolytes. These results exhibit La2Ni0.6Cu0.4O4+δ as a possible alternative cathode for IT-SOFC. [Copyright &y& Elsevier]

Abstract: Materials formulated La2Ni1−x Cu x O4+δ (0≤ x ≤1) have been prepared by the nitrate-citrate route, having an orthorhombic K2NiF4 structure with Fmmm (x =0) and Bmab (0.1≤ x ≤1) space groups. La2NiO4+δ , which resulted to be the compound with the highest capability to accommodate excess oxygen (δ =0.16), underwent heat treatments (873–1098K) under high oxygen pressure (200–250bar). This led to an increase of excess oxygen in the structure. Rietveld refinements on neutron powder diffraction data probe the excess of oxygen to be accommodated as interstitial defect at the atomic position (1/4, 1/4, z; z ≈1/4), which requires the displacement of four neighbouring oxygen atoms from their normal positions. This result is in agreement with a non-stoichiometry model which induces the stabilization of oxygen vacancies in the perovskite layer of these materials. The defect concentration determined from Rietveld refinement agrees well with the data obtained from thermogravimetric analysis. Results obtained herein reveal heat treatment under high oxygen pressure (873K, 200bar) as a promising method to enhance transport properties in K2NiF4-type structures. [Copyright &y& Elsevier]

Water exposure of layered nickel-rich transition metal oxide electrodes, widely used in high-energy lithium-ion batteries, has detrimental effects on the electrochemical performance, which complicates electrode handling and prevents implementation of environmentally benign aqueous processing procedures. Elucidating the degradation mechanisms in play may help rationally mitigate/circumvent key challenges. Here, the bulk structural consequences of long-term (>2.5 years) deuterated water (D 2 O) exposure of intercalation materials with compositions Li x Ni 0.5 Co 0. 2 Mn 0. 3 O 2 (NCM523) and Li x Ni 0.8 Co 0. 1 Mn 0. 1 O 2 (NCM811) are studied by neutron powder diffraction (NPD). Detailed inspection of the NPD data reveals gradual formation of a secondary crystalline phase in all exposed samples, not previously reported for this system. This unknown phase forms faster in liquid- compared to vapor-exposed compounds. Structural modelling of the NPD data shows a stable level of Li/Ni anti-site defects and does not indicate any significant changes in lattice parameters or hydrogen-lithium (D+/Li+) exchange in the structure. Consequently, the secondary phase formation must take place via transformation rather than modification of the parent material. X-ray photoelectron spectroscopy data indicate formation of LiHCO 3 /Li 2 CO 3 at the surface and a Li-deficient oxide in the sub-surface region of the pristine compounds, and the presence of adsorbed water and transition metal hydroxides at the exposed sample surfaces. • Deuterated water (D 2 O) exposure of NCM523 and NCM811 electrodes (>2.5 years). • Bulk structural evolution investigated by modeling of neutron powder diffraction data. • Gradual formation of new secondary crystalline phase observed. • Examination of Li/Ni anti-site defects and proton-lithium exchange concentrations. • Composition and chemistry of surface and sub-surface regions examined by XPS. Image 1 [ABSTRACT FROM AUTHOR]

18650-type cells with 2.5 Ah capacity are cycled at both 25 °C and 0 °C separately, and at 25 °C two charging protocols (constant current, and constant current-constant voltage charge) are used. Differential voltage analysis (dV/dQ) and alternating current (AC) impedance are mainly used to investigate battery degradation mechanisms quantitatively. The dV/dQ suggests that active cathode loss and loss of lithium inventory (LLI) are the dominating degradation factors. Significant microcracks are observed in the fatigued cathode particles from the scanning electron microscopy (SEM) images. Crystal structure parameters of selected fatigued batteries at fully charged state are determined by in situ high-resolution neutron powder diffraction. Obvious increases of ohmic resistance and solid electrolyte interphase (SEI) resistance occur when the battery capacity fade falls beneath 20%. Continuous charge transfer resistance and Warburg impedance coefficient (W.eff) increase are observed in the course of cycling. Correlation analysis is performed to bridge the gap between material loss as well as LLI and impedance increase. The increase of the charge transfer resistance is related to both active cathode loss and LLI, and a functional relationship is revealed between LLI and W.eff regardless of the used cycling protocols. • 18650-type Cells are cycled at 0 °C and 25 °C using two charging protocols. • Main degradation factors are loss of lithium inventory (LLI) and active cathode loss. • Neutron powder diffraction and post-mortem analysis are done for deep understanding. • Correlations between material loss and impedance parameters are revealed. • Warburg impedance coefficient could be correlated to LLI in the course of cycling. [ABSTRACT FROM AUTHOR]