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Since 20 years, titanium oxide materials and in particular, lithium titanate spinel Li4Ti5O12 (LTO) were considered as promising negative electrode materials for lithium-ion cells. In the case of the TiNb2O7 compound (TNO), which has a larger theoretical lithiation capacity of 388 mAh g−1, few studies have focused on the outgassing of the material. In this work, we quantified the volume produced as a function of different cycling parameters and then characterized the produced species and show a prevalence of H2 gas. The use of carbon coating as a mitigation strategy and its limitation is also discussed. [ABSTRACT FROM AUTHOR]

Nearly half of the elements in the periodic table are extracted, refined, or plated using electrodeposition in high-temperature melts. However, operando observations and tun- ing of the electrodeposition process during realistic electrolysis operations are extremely difficult due to severe reaction conditions and complicated electrolytic cell, which makes the improvement of the process very blind and inefficient. Here, we developed a mul- tipurpose operando high-temperature electrochemical instrument that combines oper- ando Raman microspectroscopy analysis, optical microscopy imaging, and a tunable magnetic field. Subsequently, the electrodeposition of Ti—which is a typical polyvalent metal and generally shows a very complex electrode process—was used to verify the sta- bility of the instrument. The complex multistep cathodic process of Ti in the molten salt at 823 K was systematically analyzed by a multidimensional operando analysis strategy involving multiple experimental studies, theoretical calculations, etc. The regulatory effect and its corresponding scale-span mechanism of the magnetic field on the electro- deposition process of Ti were also elucidated, which would be inaccessible with existing experimental techniques and is significant for the real-time and rational optimization of the process. Overall, this work established a powerful and universal methodology for in- depth analysis of high- temperature electrochemistry. [ABSTRACT FROM AUTHOR]

The reported study was devoted to the investigation of viscoelastic behavior for solid and porous ultra-high molecular weight polyethylene (UHMWPE) under compression. The obtained experimental stress curves were interpreted using a two-term Prony series to represent the superposition of two coexisting activation processes corresponding to long molecular (~160 s) and short structural (~20 s) time scales, respectively, leading to good statistical correlation with the observations. In the case of porous polymer, the internal strain redistribution during relaxation was quantified using digital image correlation (DIC) analysis. The strongly inhomogeneous deformation of the porous polymer was found not to affect the relaxation times. To illustrate the possibility of generalizing the results to three dimensions, X-ray tomography was used to examine the porous structure relaxation at the macro- and micro-scale levels. DIC analysis revealed positive correlation between the applied force and relative density. The apparent stiffness variation for UHMWPE foams with mixed open and closed cells was described using a newly proposed three-term expression. Furthermore, in situ tensile loading and X-ray scattering study was applied for isotropic solid UHMWPE specimens to investigate the evolution of internal structure and orientation during drawing and stress relaxation in another loading mode. [ABSTRACT FROM AUTHOR]

Electrochemical dilatometry is used to investigate Li plating/stripping on Cu foil and porous carbon paper substrates. Experiments are performed in standard electrolyte for Li–S batteries at a current density of 1 mA cm−2 with a Li plating charge fixed at 1 mAh cm−2. A fully dense Li film (4.8 μm thick) is initially electrodeposited on the Cu electrode. However, from the 2nd Li plating/stripping cycle, Li deposit becomes porous to reach a thickness of 9.6 µm at the 27th cycle, corresponding to a film porosity of 50%, favoring its collapse during the subsequent cycles. When a carbon paper with a low surface area (0.02 m2 g−1) is used as a substrate, Li deposition occurs preferentially in the pores of the carbon paper during the first few cycles. However, this does not prevent the formation of Li dendrites, which progressively extend on the top of the substrate, resulting in the degradation of the electrode cyclability after about 40 cycles. The use of a carbon paper with a higher surface area (4.2 m2 g−1) favors Li deposition inside the electrode, with no apparent loss of cyclability after 50 cycles. However, this does not prevent the formation of dead Li, as suggested by the continuous and irreversible expansion of the electrode over cycling at a mean rate of 1.3 μm per cycle. Additionally, a large and irreversible expansion of 38 μm is observed during the first cycle, which is attributed to the lithium-solvent co-intercalation in the graphitic part of the carbon paper substrate. [ABSTRACT FROM AUTHOR]

The reported study was devoted to the investigation of viscoelastic behavior for solid and porous ultra-high molecular weight polyethylene (UHMWPE) under compression. The obtained experimental stress curves were interpreted using a two-term Prony series to represent the superposition of two coexisting activation processes corresponding to long molecular (~160 s) and short structural (~20 s) time scales, respectively, leading to good statistical correlation with the observations. In the case of porous polymer, the internal strain redistribution during relaxation was quantified using digital image correlation (DIC) analysis. The strongly inhomogeneous deformation of the porous polymer was found not to affect the relaxation times. To illustrate the possibility of generalizing the results to three dimensions, X-ray tomography was used to examine the porous structure relaxation at the macro- and micro-scale levels. DIC analysis revealed positive correlation between the applied force and relative density. The apparent stiffness variation for UHMWPE foams with mixed open and closed cells was described using a newly proposed three-term expression. Furthermore, in situ tensile loading and X-ray scattering study was applied for isotropic solid UHMWPE specimens to investigate the evolution of internal structure and orientation during drawing and stress relaxation in another loading mode.

The internal temperature of a Li-ion battery is one of the critical parameters for monitoring cell performance, ageing and safety. The development of new sensor technologies to control the internal temperature of cells without compromising performance and safety remains a challenge. It is one of the objectives of the European INSTABAT project in the framework of the Battery2030+ initiative. The objective of this paper is to describe the development of a new optical fibre sensor based on a thermoluminescent material to monitor internal cell temperature. The development of the sensor, its thermal characterisation and its calibration are presented here. This sensor was inserted into a commercial Li-ion cell and its response during cycling at high charge and discharge rates (2C in charge and 4C in discharge) was investigated. The comparison between external and internal temperature measurements shows good agreement. These results demonstrate the ability of this type of sensor to monitor the internal temperature of a Li-ion battery without affecting its performance at high loading. [Display omitted] • Thermo-luminescent optical fibre sensor. • Smart cell with embedded optical sensor. • Li-ion battery internal temperature monitoring. • In-situ operando monitoring. [ABSTRACT FROM AUTHOR]

Renewable technologies, and in particular the electric vehicle revolution, have generated tremendous pressure for the improvement of lithium ion battery performance. To meet the increasingly high market demand, challenges include improving the energy density, extending cycle life and enhancing safety. In order to address these issues, a deep understanding of both the physical and chemical changes of battery materials under working conditions is crucial for linking degradation processes to their origins in material properties and their electrochemical signatures. In situ and operando synchrotron-based X-ray techniques provide powerful tools for battery materials research, allowing a deep understanding of structural evolution, redox processes and transport properties during cycling. In this review, in situ synchrotron-based X-ray diffraction methods are discussed in detail with an emphasis on recent advancements in improving the spatial and temporal resolution. The experimental approaches reviewed here include cell designs and materials, as well as beamline experimental setup details. Finally, future challenges and opportunities for battery technologies are discussed.

A wide variety of analytical methods are used for studying the behavior of lithium-ion batteries and particularly the lithium ion distribution in the electrodes. However, the development of in situ / operando techniques proved powerful to understand the mechanisms responsible for the lithium trapping and then the aging phenomenon. Herein, we report the design of an electrochemical cell to profile operando lithium concentration in LiFePO 4 electrodes using Ion Beam Analysis techniques. The specificity of the cell resides in its ability to not only provide qualitative information about the elements present but above all to measure quantitatively their content in the electrode at different states of charge of the battery. The nuclear methods give direct information about the degradation of the electrolyte and particularly reveal inhomogeneous distributions of lithium and fluorine along the entire thickness of the electrode. Higher concentrations of fluorine is detected near the electrode/electrolyte interface while a depletion of lithium is observed near the current collector at high states of charge. [ABSTRACT FROM AUTHOR]

Nearly half of the elements in the periodic table are extracted, refined, or plated using electrodeposition in high-temperature melts. However, operando observations and tuning of the electrodeposition process during realistic electrolysis operations are extremely difficult due to severe reaction conditions and complicated electrolytic cell, which makes the improvement of the process very blind and inefficient. Here, we developed a multipurpose operando high-temperature electrochemical instrument that combines operando Raman microspectroscopy analysis, optical microscopy imaging, and a tunable magnetic field. Subsequently, the electrodeposition of Ti-which is a typical polyvalent metal and generally shows a very complex electrode process-was used to verify the stability of the instrument. The complex multistep cathodic process of Ti in the molten salt at 823 K was systematically analyzed by a multidimensional operando analysis strategy involving multiple experimental studies, theoretical calculations, etc. The regulatory effect and its corresponding scale-span mechanism of the magnetic field on the electrodeposition process of Ti were also elucidated, which would be inaccessible with existing experimental techniques and is significant for the real-time and rational optimization of the process. Overall, this work established a powerful and universal methodology for in-depth analysis of high-temperature electrochemistry.

Elucidating the NO x purification mechanism of exhaust gas catalysts such as Rh nanoparticles is essential for the development of air purification technology required for environmentally conscious automobiles. In this study, operando observations of Rh nanoparticles in NO gas were performed to understand the Rh surface structure and dynamics. A system comprising a high-voltage electron microscope (HVEM) connected to a high-sensitivity quadrupole mass spectrometer (QMS) (HVEM-QMS system), which was newly developed by Nagoya University and JEOL, was used for gas analysis. While confirming the onset of the NO reduction reaction using the QMS, structural changes in the Rh nanoparticles in the presence of NO gas with increasing temperature were investigated. The repeated appearance and disappearance of a surface oxide film was observed for the first time, suggesting that the metastable surface oxidation state contributes to the uptake and release of oxygen during NO decomposition. [Display omitted] • State-of-the-art HVEM-QMS system performs operando TEM. • Temperature-driven structural changes in Rh nanoparticles during NO reduction. • First observation of repeated appearance and disappearance of a surface oxide film. • Catalyst surface dynamics studied for improved air-purification technologies. [ABSTRACT FROM AUTHOR]