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A critical and detailed assessment of using Shell Isolated Nanoparticles for Enhanced Raman Spectroscopy (SHINERS) on different electrode substrates was carried out, providing relative enhancement factors, as well as an evaluation of the distribution of shell-isolated nanoparticles upon the electrode surfaces. The chemical makeup of surface layers formed upon lithium metal electrodes and the mechanism of the oxygen reduction reaction on carbon substrates relevant to lithium-oxygen cells are studied with the employment of the SHINERS technique. SHINERS enhanced the Raman signal at these surfaces showing a predominant Li 2 O based layer on lithium metal in a variety of electrolytes. The formation of LiO 2 and Li 2 O 2 , as well as degradation reactions forming Li 2 CO 3 , upon planar carbon electrode interfaces and upon composite carbon black electrodes were followed under potential control during the reduction of oxygen in a non-aqueous electrolyte based on dimethyl sulfoxide.

A closer look: Solid-state (7) Li and (17) O NMR spectroscopy is a valuable tool in the characterization of products formed in the lithium-oxygen battery, a necessary step in the development of a viable cell. Since lithium peroxide, the desired discharge product, has a unique (17) O NMR signature, it can be clearly identified., (Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Abstract: We report on the origin of the surface structural disordering in graphite anodes induced by lithium intercalation and deintercalation processes. Average Raman spectra of graphitic anodes reveal that cycling at potentials that correspond to low lithium concentrations in Li x C (0≤ x <0.16) is responsible for most of the structural damage observed at the graphite surface. The extent of surface structural disorder in graphite is significantly reduced for the anodes that were cycled at potentials where stage-1 and stage-2 compounds (x >0.33) are present. Electrochemical impedance spectra show larger interfacial impedance for the electrodes that were fully delithiated during cycling as compared to electrodes that were cycled at lower potentials (U <0.15V vs. Li/Li+). Steep Li+ surface-bulk concentration gradients at the surface of graphite during early stages of intercalation processes, and the inherent increase of the Li x C d-spacing tend to induce local stresses at the edges of graphene layers, and lead to the breakage of C–C bonds. The exposed graphite edge sites react with the electrolyte to (re)form the SEI layer, which leads to gradual degradation of the graphite anode, and causes reversible capacity loss in a lithium-ion battery. [Copyright &y& Elsevier]

Abstract: Anatase type TiO2 has been previously largely reported as a candidate negative electrode material for lithium-ion batteries. We report here for the first time the complete in situ Raman study of lithium insertion and de-insertion into three variously nano-sized TiO2 anatase powders (Prolabo, ca. 80nm, AK1, ca. 15nm and MTi5 ca. 8nm), of which AK1 and MTi5 show superior capacity and cyclability. From these measurements realized in a galvanostatic mode between 3 and 1V versus Li/Li+, the phase transition from a tetragonal to an orthorhombic structure was clearly observed to take place at different quantities of x in Li x TiO2. These results confirm the extension of the solid solution domain as particle size is reduced. For the smaller TiO2 nano-sized materials (AK1 and MTi5), a more pronounced decrease in band intensity when x >0.3 for Li x TiO2, was observed and may be related to the decrease in the optical skin depth linked to the conductivity increase as lithiation proceeds. [Copyright &y& Elsevier]