The study on the formation of lithium alloying with Bi thin layer electrode and its kinetics was carried out in 1 mol/dm(3) LiClO4/PC electrolyte. In situ XRD and chronopotentiometry results confirmed the formation of LiBi and Li3Bi alloy phases with the open circuit potentials of 0.830 and 0.805 V, respectively. The formation of Li3Bi alloy rather than LiBi alloy was found to be responsible for the mechanical degradation of Li-Bi alloy electrode. Lithium diffusion coefficient in LiBi alloy was evaluated to be in the order of 10(-13) cm(2)/s by ac impedance measurement. This smaller lithium diffusion coefficient in thin layer electrode than that in the common sheet electrode was attributed to the intrinsic properties of the thin layer electrode. Furthermore, a mechanism involving the adsorption process at the electrode surface was proposed for lithium alloying with bismuth.