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

Abstract

• Electrochemical behavior of Ge nanowires in the temperature range from –40 to +20 o C is studied. • Formation of SEI on germanium nanowires was confirmed by IR spectra. • The activation energies of Rs, R SEI , and Rct are of 21.8, 24.1, and 36.5 kJ/mol, respectively. 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 (R s ), the resistance of the solid electrolyte film (R SEI ) on the surface of germanium nanowires, the capacitance of the solid electrolyte film (C SEI ), the charge transfer resistance (R ct ), 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 R SEI and R ct 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 R s, R SEI , and R ct 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.