Thickness Variation of Conductive Polymer Coatings on Si Anodes for the Improved Cycling Stability in Full Pouch Cells.

Si-dominant anodes for Li-ion batteries provide very high gravimetric and volumetric capacity but suffer from low cycling stability due to an unstable solid electrolyte interphase (SEI). In this work, we improved the cycling performance of Si/NCM pouch cells by coating the Si anodes with the conductive polymer poly(3,4-ethylenedioxythiophene) (PEDOT) prior to cell assembly via an electropolymerization process. The thicknesses of the PEDOT coatings could be adjusted by a facile process parameter variation. Glow-discharge optical emission spectroscopy was used to determine the coating thicknesses on the electrodes prior to the cell assembly. During electrochemical testing, improvements were observed closely linked to the PEDOT coating thickness. Specifically, thinner PEDOT coatings exhibited a higher capacity retention and lower internal resistance in the corresponding pouch cells. For the thinnest coatings, the cell lifetime was 18% higher compared to that of uncoated Si anodes. Postmortem analyses via X-ray photoelectron spectroscopy and cross-sectional scanning electron microscopy revealed a better-maintained microstructure and a chemically different SEI for the PEDOT-coated anodes.

GD-OES Investigations of Lithium-Ion Battery Graphite Anodes: Impact of Plasma Parameters and Electrode Properties.

Due to the demand of lithium-ion battery investigations with glow discharge optical emission spectroscopy (GD-OES), a fundamental study of the influence of essential GD-OES parameters toward graphite anodes in an argon plasma was conducted and compared to previous investigations of massive materials. It is shown that increased applied voltage (500-700 V) enhances the sputtering rate by up to 100%/100 V while keeping the crater shape unaffected. In contrast to this, gas pressure variation seems to be the main tool for crater shape adjustment. Enhancement of the gas pressure (160-300 Pa) pushes the crater profile from a concave to flat shape and to concave again. Known plasma effects are discussed and correlated with the observations. A set of measuring parameters providing a good balance between the crater shape and the sputtering rate is proposed. Additionally, an increase of the duty cycle in the pulsed glow discharge mode leads to a linear increase of the sputtering rate, while a pulse duration rise enhances the sputtering rate in a nonlinear fashion. Thus, different pulsing conditions represent instruments for enhancement of the sputtering rate without affecting the crater shape significantly. Our investigation of different electrode densities shows that lower densities lead to a larger sputtered volume as well as a larger concavity of the released crater.

p-Block metal complexes with bis(pyrazol-1-yl)acetato ligands.

The hetereoscorpionate ligands bis(pyrazol-1-yl)acetic acid (Hbpza) and bis(3,5-dimethylpyrazol-1-yl)acetic acid (Hbdmpza) are reacted with [Sn(OAc)2] or [Sn(acac)2] to yield the corresponding Sn(II) complexes. A single crystal X-ray determination for the in solution monomeric complex [Sn(bpza)2] (1a) revealed a dinuclear molecular structure [Sn2(bpza)4] (1b), with κ3-N,N,O-coordinated bpza ligands at each of the Sn(II) and two bpza ligands µ-bridging between the Sn(II) centres. The molecular structure of [Sn(bdmpza)2] (2) exhibits a homoleptic bisligand complex with both ligands displaced by the free electron pair, which is proven by DFT calculations. Oxidation of complex 2 in an attempt to synthesize a homoleptic Sn(IV) complex leads to the formation of [Sn(bdmpza)F3] (3). In addition, homoleptic bisligand gallium complexes [Ga(bdmpza)2][ClO4] (4) and [Ga(bpza)2][GaCl4] (5) were prepared and characterized by 71Ga NMR and IR spectroscopy as well as by X-ray crystallography.