Hard X -Ray Photoelectron Spectroscopy (HAXPES) characterisation of electrochemical passivation oxide layers on Al-Cr-Fe Complex Metallic Alloys (CMA).

A Hard X-ray Photoelectron Spectroscopy (HAXPES) characterisation of the passivation layers formed by electrochemical polarisation of Al–Cr–Fe complex metallic alloys is presented. By employing X-ray excitation energies from 2.3 to 10.0 keV, the depth distributions of Al- and Cr-oxide and hydroxide species in the (Al,Cr)-containing passive layers could be determined. Simultaneous analyses of the shallow Al 2s and deep Al 1s core level lines (respectively, more bulk- and surface-sensitive) provided complementary information to effectively determine the depth-resolved contributions of hydroxide and oxide species within the passivation layer. A Cr threshold concentration of 18 (at.%) was found for effective passivation at pH 1

Electrolyte engineering for highly inorganic solid electrolyte interphase in high-performance lithium metal batteries

Electrolytes play pivotal roles in the stabilization of Li metal surface and operation at high voltages. In particular, localized high-concentration electrolytes have outperformed state-of-the-art electrolytes due to their unique solvation structures. However, a direct correlation between solvation structure in LHCEs, in particular for weakly coordinated diluents, and SEI composition is not well understood, yet it is highly critical to realize high Coulombic efficiency (CE) beyond 99.5%. Here, a class of electrolyte based on bis(2,2,2-trifluoroethoxy)methane and 1,2-dimethoxyethane was introduced to regulate anion decomposition to achieve ultra-high Li2O content of 63% in the SEI along with a highly uniform phase distribution. These unique features enabled a record-high CE of 99.72% and proved the impact of homogeneously distributed high Li2O SEI. The related Li|LiNi0.8Co0.1Mn0.1O2 full cell with a negative/positive capacity ratio of 2.5 achieved 90% capacity retention after 200 cycles at 1 C and 80% retention after 596 cycles at 3 C.N

Cost-effective sol-gel synthesis of porous CuO nanoparticle aggregates with tunable specific surface area

CuO nanoparticles (NPs) are applied in various key technologies, such as catalysis, energy conversion, printable electronics and nanojoining. In this study, an economic, green and easy-scalable sol-gel synthesis method was adopted to produce submicron-sized nanoporous CuO NP aggregates with a specific surface area > 18 m²/g. To this end, a copper-carbonate containing precursor was precipitated from a mixed solution of copper acetate and ammonia carbonate and subsequently calcinated at T ≥ 250 °C. The thus obtained CuO nanopowder is composed of weakly-bounded agglomerates, which are constituted of aggregated CuO NPs with a tunable size in the range of 100–140 nm. The CuO aggregates, in turn, are composed of equi-axed primary crystallites with a tunable crystallite size in the range of 20–40 nm. The size and shape of the primary CuO crystallites, as well as the nanoporosity of their fused CuO aggregates, can be tuned by controlled variation of the degree of supersaturation of the solution via the pH and the carbonate concentration. The synthesized submicron-sized CuO aggregates can be more easily and safely processed in the form of a solution, dispersion or paste than individual NPs, while still offering the same enhanced reactivity due to their nanoporous architecture.ISSN:2045-232

Substrate Purity Effect on the Defect Formation and Properties of Amorphous Anodic Barrier Al2O3

A comprehensive study concerning the effect of different Al metal substrate purities (i.e. 99.5 versus 99.99%) on the properties of amorphous anodic barrier Al2O3 is presented. The experimental findings demonstrate that only tiny variations in the purity of the employed Al materials lead to different oxide growth rate, surface charge, structural defect and impurities content. Below the ionic recombination potential characterized by Scanning Kelvin Probe Force Microscopy, an increase of the anodizing voltage leads to an improvement of the oxide barrier properties. The larger growth rate exhibited by the higher purity Al substrate however indicates the formation of highly disordered and inhomogeneous barrier oxides. A combination of photoelectrochemical and photoluminescence spectroscopies was used to characterize structural defect concentration and confirmed the presence of significantly higher concentrations in the oxide grown on the purer Al substrates. FT-IR and RBS/ERDA results indicate that H and C species are incorporated from the electrolyte solution in the barrier oxides with higher H amounts detected in the oxide grown on the purer Al substrate.ISSN:0013-4651ISSN:1945-711

Assessment of Critical Stack Pressure and Temperature in Li-Garnet Batteries

Stack pressure and temperature serve as effective means to induce deformation of the lithium metal anode toward the Li/solid-state-electrolyte interface, thereby mitigating the well-known issue of void formation during high-current-density stripping. In this study, a compelling methodology is systematically assessed for determining the critical stack pressure and temperature of Li metal anode in conjunction with Li7La3Zr2O12 (LLZO) solid-state electrolyte, which is the minimum set of values required to maintain conformal contact between Li and LLZO at a given current density. The methodology is based on the analysis of the second derivatives of the voltage profiles of identical Li/LLZO/Li symmetric cells measured during one half-cycle (3 mAh cm-2) at the same current density but different stack pressures. The effectiveness of the presented approach in assessing conditions for mitigating void formation during Li stripping is evaluated through cycle stability tests performed on Li/LLZO/Li symmetric cells.ISSN:2196-735

Assessment of Critical Stack Pressure and Temperature in Li‐Garnet Batteries

Abstract Stack pressure and temperature serve as effective means to induce deformation of the lithium metal anode toward the Li/solid‐state‐electrolyte interface, thereby mitigating the well‐known issue of void formation during high‐current‐density stripping. In this study, a compelling methodology is systematically assessed for determining the critical stack pressure and temperature of Li metal anode in conjunction with Li7La3Zr2O12 (LLZO) solid‐state electrolyte, which is the minimum set of values required to maintain conformal contact between Li and LLZO at a given current density. The methodology is based on the analysis of the second derivatives of the voltage profiles of identical Li/LLZO/Li symmetric cells measured during one half‐cycle (3 mAh cm‐2) at the same current density but different stack pressures. The effectiveness of the presented approach in assessing conditions for mitigating void formation during Li stripping is evaluated through cycle stability tests performed on Li/LLZO/Li symmetric cells

Study of the hydrogen uptake in deformed steel using the microcapillary cell technique

The microcapillary cell electrochemical method is capable of evaluating hydrogen (H) uptake in steel with respect to deformation, which is induced by various mechanical methods (cold rolling, bending and punching). A clear relation between the deformation degree and the local H-content is established for dual phase (DP600) steel. The magnitude of the deformation nearby a punched edge is quantitatively determined using electron backscatter diffraction technique. A shear-affected zone is identified at the edge of the punched hole. The dedicated local electrochemical measurements confirm the presence of high concentrations of local-H in this shear affected zone, which is likely detrimental for H-embrittlement