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Nickel-rich layered oxide materials (LiNixMnyCo1–x–yO2, x ≥ 0.8, LiNMC) attract great interest for application as positive electrode in lithium ion batteries (LIBs) due to high specific discharge capacities at moderate upper cutoff voltages below 4.4 V vs Li/Li+. However, the comparatively poor cycling stability as well as inferior safety characteristics prevent this material class from commercial application so far. Against this background, new electrolyte formulations including additives are a major prerequisite for a sufficient electrochemical performance of Ni-rich NMC materials. In this work, we introduce triphenylphosphine oxide (TPPO) as electrolyte additive for the application in graphite/LiNi0.8Mn0.1Co0.1O2 (NMC811) cells. The addition of only 0.5 wt % TPPO into a carbonate-based electrolyte (LiPF6 in EC:EMC) significantly increases the first cycle Coulombic efficiency as well as the reversible specific capacity and improves the capacity retention of the LIB full cell cycled between 2.8 and 4.3 V...

Active lithium loss (ALL) resulting in a capacity loss (QALL), which is caused by lithium consuming parasitic reactions like SEI formation, is a major reason for capacity fading and, thus, for a reduction of the usable energy density of lithium-ion batteries (LIBs). QALL is often equated with the accumulated irreversible capacity (QAIC). However, QAIC is also influenced by non-lithium consuming parasitic reactions, which do not reduce the active lithium content of the cell, but induce a parasitic current. In this work, a novel approach is proposed in order to differentiate between QAIC and QALL. The determination of QALL is based on the remaining active lithium content of a given cell, which can be determined by de-lithiation of the cathode with the help of the reference electrode of a three-electrode set-up. Lithium non-consuming parasitic reactions, which do not influence the active lithium content have no influence on this determination. In order to evaluate this novel approach, three different anode materials (graphite, carbon spheres and a silicon/graphite composite) were investigated. It is shown that during the first charge/discharge cycles QALL is described moderately well by QAIC. However, the difference between QAIC and QALL rises with increasing cycle number. With this approach, a differentiation between “simple” irreversible capacities and truly detrimental “active Li losses” is possible and, thus, Coulombic efficiency can be directly related to the remaining useable cell capacity for the first time. Overall, the exact determination of the remaining active lithium content of the cell is of great importance, because it allows a statement on whether the reduction in lithium content is crucial for capacity fading or whether the fading is related to other degradation mechanisms such as material or electrode failure.

Long-term cycle aging experiments were performed on commercially available automotive type lithium-ion pouch cells under realistic conditions as found in electrical vehicles. The main mechanisms responsible for cell aging were identified based on a combined approach of electrochemical and post mortem analysis methods, and were attributed to the loss of lithium through lithium metal deposition on the graphite anode and electrolyte decomposition as a side reaction. Furthermore, the aging occurred spatially localized at different rates. Anode material located close to the tabs exhibited most progressed aging, as determined from the rather pronounced local heat generation over a long time period.

Spinel LiNi 0.5 Mn 1.5 O 4 material has been synthesized by a spray drying process and subsequent solid state reaction. Polyvinylpyrrolidone (PVP) is given as additive to the spray drying precursor solution and its effects on structural and electrochemical properties are evaluated. By using PVP in the synthesis process, the obtained sample displays a secondary plate morphology which is consisting of densely arranged primary octahedrally shaped particles. The new cathode material has a lesser degree of impurity phases, a higher discharge capacity, a superior rate capability, and a slightly better cycling performance than the sample synthesized without PVP. In more detail, by the use of PVP the ratio of Mn 3+ to Mn 4+ in the final product decreases from 20.8 to 9.2%. The initial discharge capacity at 0.1 C exhibits an increase of about 14%. The normalized capacity at 20 C is 84.1% instead of 67.0%. A slightly improved cycling performance with the capacity retention increase from 93.8 to 97.9% could be observed as well.

5-Aryl-3,3,4,4-tetramethyl-3,4-dihydro-3H-pyrrol-2-imines,conformationally restrained 1,3-diazabuta-1,3-diene derivatives, were easily prepared by treating aryllithium species with 2,2,3,3-tetramethylsuccinonitrile (1). Trapping the reaction intermediate with chlorotrimethylsilane gave N-silylated compounds 2a–e, whereas aqueous workup gave N-H derivatives 3a,b. Pyrenyl-substituted compound 3b was characterised by X-ray diffraction studies, revealing the presence of both intermolecular aromatic face-to-face contacts and the formation of homodimers by twofold H-bonding. N-Silylated derivatives 2a–d were used successfully as nucleophilic components in palladium-catalysed C–N bond-forming reactions to obtain N-arylated compounds 5b–h,j,k,m and 7a–d. The UV spectra of compounds 5 and 7 exhibit long wavelength absorptions up to 462 nm for 7d, thus indicating extended π–π* conjugation. Dihydropyrrolimine-based compounds with larger conjugated aryl substituents in the 5-position react with Bronsted and Lewis acids displaying a significant colour change that could be used to estimate the pKb of 3a to a value of –4.5. Derivatives 2c,e and 3a,b, which are not N-arylated, are fluorescent with a Stokes shift of 107 nm (6034 cm–1) for 3a. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

In this work, a fluoride-selective electrode (FSE) was applied with regard to the analysis of fluoride in lithium hexafluorophosphate-based lithium-ion battery (LIB) electrolytes. The influence of linear organic carbonate solvents dimethyl carbonate (DMC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) which are used as co-solvents in battery electrolytes was investigated. The developed FSE method for the analysis of battery electrolytes was comprehensively validated in view of the (1) trueness and recovery rates (nominal vs. actual comparison; influence of different amounts of electrolytes on the performance of the electrode; recovery rates of defined differences in concentration), (2) precision (intra-day precision and inter-day precision), (3) selectivity (influence of the carbonate solvents on different fluoride concentrations; interferents) and (4) linearity and range. Statistical analysis was performed to evaluate the data and to characterize the reproducibility of the method. The determination of the commercially available LP30 (1 mol LiPF6 and ethylene carbonate/dimethyl carbonate (EC : DMC, 50 : 50 wt%)) electrolyte stored over 47 days and at 80 °C, by the FSE technique was compared to the fluoride analysis by ion chromatography (IC). While interferences in the IC method resulted in false-high concentrations, the FSE operated free from interferences, selective and specific. The validation of the method was successfully carried out and enables new areas of application.

Lithium consuming parasitic reactions which induce active lithium loss (ALL) are a major reason for capacity fading in lithium ion batteries (LIBs).[1, 2] As a consequence of capacity fading, the usable energy density is reduced. Typically, the ALL is set equal to the accumulated irreversible capacity (sum of the differences between charge and discharge capacity in each cycle, AIC). However, regarding the AIC it is known that it includes all parasitic reactions which generate a parasitic current. Hence, the AIC cannot be directly equated with ALL. Due to this, we proposed a novel approach in the following named as IRLC method, which is based on the remaining active lithium content of the cell, in order to determine the ALL with a higher accuracy. Therefore, a cell with a three electrode set-up is cycled and afterwards the positive electrode is de-lithiated with help of the former reference electrode in order to obtain the remaining active lithium content. Finally, the ALL can be calculated by using the remaining and the initial active lithium content. In order to evaluate the IRLC method we investigated different anode materials. It can be shown that within the first cycles the ALL can be described moderately well with help of AIC. However, with increasing cycle number the difference between ALL and AIC increases, most likely attributed to the fact that the impact of SEI formation and repair becomes smaller in comparison to other parasitic reactions which do not consume lithium. Furthermore, one additional advantage of the IRLC method is that it allows a statement whether the reduction of lithium content is crucial for capacity fading or whether the fading is related to host material losses or other degradation mechanisms e.g. a higher charge transfer resistances due to a growing SEI film. 1. Krueger, S., et al., How Do Reactions at the Anode/Electrolyte Interface Determine the Cathode Performance in Lithium-Ion Batteries? Journal of the Electrochemical Society, 2013. 160(4): p. A542-A548. 2. Vetter, J., et al., Ageing mechanisms in lithium-ion batteries. Journal of Power Sources, 2005. 147(1-2): p. 269-281.

The interaction of Mercurochrome, a medical preparation based on the mercury organic compound merbromin, with free thiols in low molecular weight peptides and in proteins has been investigated by means of liquid chromatography (LC) and electrospray mass spectrometry (ESI-MS). Beta-lactoglobulin A (beta-LGA) from bovine milk (18.4 kDa) has been used as the model protein. It was found that, in contrast to assumptions in literature, the commercial product itself is a heterogeneous mixture of moderate chemical stability, which may contain precipitated Hg salts depending on storage time and conditions. Further variability results from different degrees of bromination of the fluorescein backbone of the compound. The formation of mercury compound-protein adducts was detected. The peptide sequence T13 containing a free thiol residue was identified as the binding site for mercury species after tryptic digestion of beta-lactoglobulin A. While fresh Mercurochrome tends to the formation of a Hg(II)-beta-LGA adducts due to excess Hg(2+) in solution, investigations after precipitation of Hg salts yield Hg(merbromin)(beta-LGA) as the major product.