Lithium-ion batteries are widely developed and used as rechargeable power sources for portable electronic devices and will be essential in the field of automotive transportation. Kinetic processes at the electrodes during charging and discharging cycles play a key role for an understanding and optimization of these batteries. The aim of the present project is the quantitative description of lithium intercalation at negative electrodes of lithium ion batteries. Amorphous silicon with its high specific capacity (above 4000 mAh/g) will be used as a model system. For investigation, in-situ Neutron Scattering is used in combination with electrochemical methods (cyclic voltammetry, impedance spectroscopy, quartz crystal microbalance). Further, stable isotope tracer and chemical diffusion processes are studied by Secondary Ion Mass Spectrometry. All relevant aspects will be considered, including experimental determination of intercalation kinetics, of intercalation pathways, of diffusivities, and of associated structural modifications during cycling. Based on this data, reaction-diffusion models describing intercalation processes at electrodes will be checked, modified or alternatively developed.