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Contact
Dr. Sylvio Indris
Section Head Functional Composite Materials

sylvio indrisJmf8∂kit edu

Tel.: 0721 608-28508

Functional Composite Materials

In our group, chemists, physicists, and materials scientists investigate materials that can serve as electrode or electrolyte materials for energy storage systems.
7Li-NMR-Spektren
7Li MAS NMR spectra of LiCoO2 at different lithiation states and cycle numbers revealing the highly reversible oxidation/reduction of Co3+/4+ and also the overlithiated states in the as-prepared sample and after deep discharge.
7Li-MAS-NMR-Messungen
7Li MAS NMR measurements on Li4Ti5O12 for different lithiation states revealing the reversible rearrangement of Li ions in the spinel structure (8a ® 16c) during Li insertion/removal.
7Li-NMR-Spektren
Temperature dependence of static 7Li NMR spectra of a LiAlO2 single crystal revealing the Li motion with hopping rates between 7.9∙103 and 1.6∙106 s-1

Different synthesis techniques are used, e.g. precipitation methods, solvo-/hydrothermal reactions, sol-gel techniques, and solid-state routes. Nanocomposites consisting of carbon nanofibers decorated with oxide materials are prepared by electro-spinning.

One focus is on rechargeable Li-ion batteries. The aim is to elucidate the electrochemical reaction mechanisms that occur during insertion and removal of Li into/from the electrode materials and that are responsible for function and degradation of the batteries. Besides standard battery testing we use solid-state NMR spectroscopy, Mössbauer spectroscopy, X-ray absorption spectroscopy, and diffraction methods to study the changes in the local/long-range structure of the host materials as well as the mobility of the Li ions. Finally, the results of these fundamental studies are used for optimization of the materials with respect to the battery performance.

Further projects are dealing with the proton and oxygen ion mobility in electrolytes for PEM and SOFC fuel cells, respectively. This mobility is investigated with temperature-dependent 1H/2H and 17O NMR spectroscopy and relaxation time measurements.

[1] N. Schweikert, R. Heinzmann, A. Eichhöfer, H. Hahn, S. Indris, Solid State Ionics 226, 15 (2012).

[2] H. Hain, R. Heinzmann, M. Scheuermann, L. Wünsche, H. Hahn, S. Indris, Solid State Nucl. Magn. Reson. 42, 9 (2012).

[3] S. Indris, P. Heitjans, R. Uecker, B. Roling, J. Phys. Chem. C 116, 14243 (2012).


Electro-spinning

Preparation of electrodes by electrospinning
Elektrospinning1
Laboratory scale electrospinning device
Elektrospinning2
An example for an electrospun fibre network.

Electrodes for electrochemical devices have to fulfill several functions. First of all, they provide matrices for the active species, e.g. lithium in Li-ion batteries. Secondly, they conduct electrons as well as reaction species allowing the access of reactants and the exit of products. A material, which has been successfully applied as the support material in fuel cells and Li-ion batteries is the electroconducting polymer PANI. However, the effect of support morphology - leaving the chemistry unchanged - on the electrochemical performance has not been investigated in detail, so far.

In this project, electrospinning is used as a method to obtain (aligned) polymer fibre networks in a controlled way. These are carbonized and impregnated using different potential electrode materials in order to allow for an intimate contact between electron and Li conducting phase. Using this combination, cathode materials which are not suitable for an application due to their low intrinsic electronic conductivity shall be applied for Li-ion batteries. Sophisticated methods are used to unravel the interaction between the different phases and the microstructure of the electrode.


Group Members
Name Title Phone E-Mail
M.Sc. +49 711 811 8896 nadine dannehlMwq5∂partner kit edu
Dipl.-Chem. +49 721 608 28502 lars esmezjanCtx7∂kit edu
M.Sc. +49 721 608 28502 ruth gieseckePzr1∂partner kit edu
M.Sc. +49 721 608 28509 weibo huaYmp8∂partner kit edu
M.Sc. +49 721 608 28509 xinyang liuCdu6∂kit edu
M.Sc. +49 721 608 23161 luo xianlinKuo3∂partner kit edu
Dr. +49 721 608 28508 bjoern schwarzVxo9∂kit edu
M.Sc. +49 721 608 28502 heike stoefflerNyk6∂kit edu
Dr. +49 721 608 28511 tatiana zinkevichAkv6∂kit edu