Lithium migration in nanostructured electrode materials is important for an understanding and improvement of high energy density lithium batteries. An approach to measure lithium transport through nanometer thin layers of relevant electrochemical materials is presented using amorphous silicon as a model system. A multilayer consisting of a repetition of five [(6)LiNbO3(15 nm)/Si (10 nm)/(nat)LiNbO3 (15 nm)/Si (10 nm)] units is used for analysis, where LiNbO3 is a Li tracer reservoir. It is shown that the change of the relative (6)Li/(7)Li isotope fraction in the LiNbO3 layers by lithium diffusion through the nanosized silicon layers can be monitored nondestructively by neutron reflectometry. The results can be used to calculate transport parameters.