Electrochemical Intercalation of Lithium into Carbon: A Relaxation Study

Basic kinetic parameters of electrochemical intercalation of lithium into thin carbon films are determined by relaxation methods of current and potential steps. The overall electrode polarization is theoretically and experimentally divided into kinetic and diffusion constituents. The former is connected with the hindered ion transfer in a surface solid-electrolyte layer. The latter is due to the slow diffusion of lithium inside the carbon matrix. Concentration dependences of parameters of a solid-electrolyte layer and those of the diffusion coefficient for lithium in carbon are determined at lithium concentrations in the electrode varied from 2 to 16 M. The kinetic current is dependent on polarization in the interval 0.01 to 2.5 V, the dependence being identical to that for a lithium electrode.