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In the field of all-solid-state Li-ion batteries, understanding and controlling contact loss and interfacial reactions in composite electrodes over long-term cycling remains challenging. This study investigated how various physicochemical phenomena individually affect the discharge profile upon cycling for a solid-state cell with the following composition: LiNbO3-coated LiCoO2 + Li10GeP2S12|Li10GeP2S12|In-Li alloy. Two specially designed cells were prepared to separately characterise contact loss or interfacial chemical reactions, by means of electrochemical measurements and chemical analysis. It was found that in the discharge process, contact loss induced a certain overpotential compared to the initial value, while the chemical reaction accounted for the capacity loss caused by an additionally increased overpotential in the final stage of the discharge process. The overpotential from the undesired chemical reaction was proposed to be due to the high Li-ion transfer/migration resistance induced by sulphate formation and the decrease in the lithium content at the LiNbO3/Li10GeP2S12 interface. [ABSTRACT FROM AUTHOR]

Epitaxial thin films of the lithium ionic conductor Li0.17La0.61TiO3 have been successfully synthesized on Al2O3(0001) and Nb:SrTiO3(001) substrates at working temperatures below 750°C using pulsed laser deposition. The application of high laser fluence in conjunction with low oxygen pressure was identified as the key to obtaining highly crystalline Li0.17La0.61TiO3 films. The use of low temperatures prevents the loss of lithium during the deposition process and generates films with no compositional deviation from the target, as confirmed by chemical analyses. The Li0.17La0.61TiO3 film deposited on Al2O3(0001) exhibits a high total ionic conductivity of 3.76 × 10-4 S cm-1 at room temperature, which is comparable to the bulk ionic conductivity of polycrystalline Li0.18La0.16TiO3. The low temperature synthetic process described herein should allow the use of new configurations to fabricate electrode-electrolyte interfaces for use in high power all solid-state batteries incorporating Li0.17La0.16TiO3 as the solid electrolyte. [ABSTRACT FROM AUTHOR]

Although LiFePO4-based chemistry has been extensively studied and developed in the last decade due to its promise for the next generation of Li-ion battery applications, the impact of ambient air exposure and the concomitant aging mechanism is still a controversial matter. In the present study, we describe quantitatively the aging process in terms of the successive phase formation, distribution and iron local environments. Formation and growth of a disordered ferric phosphate phase are directly observed for the first time from the surface of particles toward the core, preceding the crystallization of tavorite LiFePO4(OH) as observed through the combination of amorphous phase quantification by XRD, and by Mössbauer and Electron Energy Loss spectroscopies. Structural and electrochemical characterization prove that the amorphous ferric phosphate formed in the early aging stage exhibits already tavorite composition and structure at the local scale and shed light on a crucial step of the aging mechanism. Based on the correlation we establish here between the amounts of Fe(iii) and hydroxyls groups present in aged samples and specific capacity of the corresponding electrodes, we show that the degradation of active material upon storage and the electrochemical performance can be predicted easily through simple TGA measurements. [ABSTRACT FROM AUTHOR]

Epitaxial Li4Ti5O12thin-films were successfully synthesized on SrTiO3single-crystal substrates with (111), (110), and (100) lattice plane orientations using pulsed laser deposition (PLD). Thin-film X-ray diffraction (XRD) revealed that the Li4Ti5O12films had the same orientation as the SrTiO3substrates: Li4Ti5O12(111) on SrTiO3(111), Li4Ti5O12(110) on SrTiO3(110), and Li4Ti5O12(100) on SrTiO3(100). These epitaxial films contained island structures, and the morphology of the (111), (110), and (100) films, observed by field emission scanning electron microscopy (FE-SEM), exhibited angular, needle-like, and circular shapes, respectively. The electrochemical properties of 20 nm thick Li4Ti5O12(111) and (110) films were investigated by cyclic voltammetry. Reversible intercalation proceeded through both lattice planes due to the three-dimensional diffusion pathway of lithium in the spinel framework. Reduction peaks in the first cathodic scan appeared at different positions from those in subsequent scans, suggesting a surface reconstruction at the Li4Ti5O12surface due to interfacial reactions. [ABSTRACT FROM AUTHOR]

Magic angle spinning solid state NMR is generally used to characterize bulk materials. We show here that it is also a promising tool to detect and characterize the diamagnetic surface layer on a paramagnetic material, which is a novel development. We apply this technique to the very hot topic of positive electrode/electrolyte characterization in the field of lithium rechargeable batteries. We report a 7Li MAS NMR study of physisorbed surface layers on LiNi1/2Mn1/2O2, a positive electrode material for lithium ion batteries. 7Li MAS NMR signals arising from surface layers formed by mixing the material with lithium carbonate or from contact of the material with ambient atmosphere, as well as with electrolyte are collected and analyzed. The progressive broadening of the line shape of the MAS NMR spectra reflects the increasing intimacy of the surface layer or secondary phase with the bulk material and therefore gives extremely useful complementary structural information on the surface not available using XPS or IR. We show that relaxation time measurements can be used as a probe of surface layers, allowing for discrimination of interphases from different origins. We propose a detailed analysis of the relaxation curves with a stretched exponential model allowing the description of the distribution of environments inside the surface layer. Our work indicates that MAS NMR can provide useful information for fine surface characterization of materials. [ABSTRACT FROM AUTHOR]