Dynamics of changes in the kinetic parameters of germanium nanowires during lithiation/delithiation in a wide temperature range

Abstract Electrochemical impedance spectroscopy was used to study electrochemical lithium insertion into the electrodes based on germanium nanowires in a temperature range of +20 to −40 °C. Since such electrodes have a regular structure and do not contain binders and conductive additives, they are described by a relatively simple equivalent circuit including the electrolyte resistance (Rs), the resistance of the solid electrolyte film (RSEI) on the surface of germanium nanowires, the capacitance of the solid electrolyte film (CSEI), the charge transfer resistance (Rct), a constant phase element (CPE), reflecting the capacitance of the double layer, and the Warburg impedance (W), reflecting the diffusion of lithium in germanium. It is characteristic of the RSEI and Rct values to grow with an increase in the lithiation degree from 0.3 to 0.9, respectively, by 28% and 16%. A decrease in temperature leads to an increase in the values of Rs, RSEI, and Rct in accordance with the Arrhenius law with activation energies of 21.8, 24.1, and 36.5 kJ/mol, respectively. At the same time, the SEI capacity is independent of temperature.