A new type of nano-sized silicon/carbon composite was developed. It shows superior electrochemical cycling properties as negative electrode material for possible use in lithium-ion batteries with respect to high reversible and low irreversible capacity, and low fading.

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2+The Mg insertion into layered vanadium bronzes, MeV3Os(H20)~ (Me = Li, Na, K, Ca0.5, and Mg0.5), has been studied with regard to their use as positive electrodes of magnesium ion transfer batteries. In acetonitrile-based electrolytes maximum specific charges of -200 Ah/kg were measured but the charge decreases rapidly with the increasing cycle number. A salt melt (liquid at room temperature) based on MgC12, A1C13, and 1-ethyl-3-methylimidazolium chloride, offers an interesting alternative to common aprotic electrolytes. It is possible to insert Mg 2* electrochemically from the salt melt into the bronzes. The behavior of all bronzes is similar in this electrolyte with the exception of the first few cycles. Steady state is reached after about five cycles, and a reversible insertion and expulsion of Mg 2 § is observed for all bronzes. Specific charges of up to 150 Ah/kg for Mg 2* insertion were measured in the first cycle, and >80 Ah/kg can be utilized during 60 deep cycles. Variations in the content of bound lattice water in the bronzes are responsible for a difference in the electrochemical properties of the same starting material dried at different temperatures. The presence of this water seems to be essential. Unfortunately, the lattice water is removed during cycling.

Graphites, as well as other intercalation materials used in lithium-ion batteries, change their color upon electrochemical insertion of lithium ions. In this study, in situ colorimetry was developed as a straightforward technical method to measure the local state of charge of lithium-ion battery electrodes. A laboratory cell with a glass window was built for in situ characterization of intercalation materials. Calibration curves of red, green, and blue color values vs state of charge were acquired and used for mapping of lithium distribution in battery electrodes. The lithium distribution in anodes of aged lithium-ion batteries was found to be highly heterogeneous.

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