Studies on the Reversibility of Electrolytic Tin Powder Obtained from an Ionic Liquid

A promising novel high-capacity anode material for lithium-ion batteries based on a highly dispersed tin powder is considered. The powder has been obtained using pulsed electrochemical cathodic reduction on a titanium vibrocathode in an electrolyte based on a choline chloride-ethylene glycol ionic liquid. The discharge capacity of the anode material is 817 (mAh)/g, which is close to the theoretical specific electrochemical capacity of tin amounting to 924 (mAh)/g. The powder dispersion level and the morphology of tin crystals are determined. The particle size distribution for the fractions with an increased content of particles having a size less than 0.1 mu m and the SEM images of grains having a rhombohedral shape are presented. For studying the reversibility of the aforementioned anode material, the following applied methods for electrochemical analysis under electrode charge and discharge have been used: cyclic voltammetry, galvanostatic cycling, and impedance spectroscopy. Changes in the characteristics of the electrode under study using equivalent circuits for impedance spectroscopy under the formation of a lithium-tin intermetallic compound, as well as change in the ratio between the diffusion coefficient of lithium ions at different stages of charge and at the initial stage are considered. It is shown that, when the charge capacity close to the theoretical value is reached, the intercalation can occur in two ways: through a solid-electrolyte film and through an intermetallic compound.