High-Resolution Nanoanalytical Insights into Particle Formation in SnO2/ZnO Core/Shell Nanowire Lithium-Ion Battery Anodes.

Tin oxide (SnO2)/zinc oxide (ZnO) core/shell nanowires as anode materials in lithium-ion batteries (LIBs) were investigated using a combination of classical electrochemical analysis and high-resolution electron microscopy to correlate structural changes and battery performance. The combination of the conversion materials SnO2 and ZnO is known to have higher storage capacities than the individual materials. We report the expected electrochemical signals of SnO2 and ZnO for SnO2/ZnO core/shell nanowires as well as unexpected structural changes in the heterostructure after cycling. Electrochemical measurements based on charge/discharge, rate capability, and electrochemical impedance spectroscopy showed electrochemical signals for SnO2 and ZnO and partial reversibility of lithiation and delithiation. We find an initially 30% higher capacity for the SnO2/ZnO core/shell NW heterostructure compared to the ZnO-coated substrate without the SnO2 NWs. However, electron microscopy characterization revealed pronounced structural changes upon cycling, including redistribution of Sn and Zn, formation of ∼30 nm particles composed of metallic Sn, and a loss of mechanical integrity. We discuss these changes in terms of the different reversibilities of the charge reactions of both SnO2 and ZnO. The results show stability limitations of SnO2/ZnO heterostructure LIB anodes and offer guidelines on material design for advanced next-generation anode materials for LIBs.

Rapid wet-chemical oxidative activation of graphite felt electrodes for vanadium redox flow batteries.

To boost the performance of vanadium redox flow batteries, modification of the classically used felt electrodes is required to enable higher cycling performance and longer life cycles. Alternative approaches to the standard thermal oxidation procedure such as wet chemical oxidation are promising to reduce the thermal budget and thus the cost of the activation procedure. In this work we report a rapid 1 hour activation procedure in an acidified KMnO4 solution. We show that the reported modification process of the felt electrodes results in an increase in surface area, density of oxygenated surface functionalities as well as electrolyte wettability, as demonstrated by N2-physisorption, XPS, Raman spectroscopy as well as contact angle measurements. The activation process enables battery cycling at remarkably high current densities up to 400 mA cm-2. Stable cycling at 400 mA cm-2 over 30 cycles confirms promising stability of the reported activation procedure.

[The punishment of blinding and the life of the blind]. / Die Strafe der Blendung und das Leben blinder Menschen.

The article deals with a group of people who were deprived of their eyesight by private acts of force or by executions of lawful sentences. In early medieval texts blinding is frequently mentioned in connection with popes, kings, princes or bishops. However, since the High Middle Ages these dignitaries were increasingly spared the loss of their eyes. It may be said that on the whole, from the eighth to the twelfth century, blinding was overwhelmingly used to dispose of political adversaries, but did then rapidly turn into a criminal punishment. In the earliest 'Landfriedensordnungen' of the late eleventh century, the loss of the perpetrator's eyes crops up as punishment for breach of the peace, while later it was applied to a variety of more or less serious offences. The destiny of the blinded in the early Middle Ages is only highlighted by sketches of a few individual cases; for the High and late Middle Ages--apart from a few notable exceptions--it is only possible to reflect on the general situation of blind people in society, since the sources usually do not differentiate between those having lost their sight through human violence or due to other causes.