Dry sintered macroporous Si electrodes for Li-ion batteries are first studied using spectral impedance measurements (EIS). The obtained EIS spectra in the lithiated and delithated state are modeled by an equivalent electrical circuit, the parameters of which make it possible to determine the main stages of the electrochemical process of lithium incorporation / extraction caused by the surface layer of solid-state electrolyte (SEI), a double electric layer, and diffusion in the solid phase of the electrode material. It was shown that the effective diffusion coefficient of Li in Si increases with rising degree of lithiation from D = 6.5·10 ^ (-12) cm2/s to D = 2.6·10^ (-10) cm2/s. The effect of carbonization by sucrose pyrolysis was studied, which led to a decrease in impedance and an increase in the diffusion coefficient of lithium to D = 2.2·10^(-10) - 1.7·10^(-9) cm2/s.