Kinetics of Reaction Products of Silicon Monoxide with Controlled Amount of Li-Ion Insertion at Various Current Densities for Li-Ion Batteries

Abstract

To understand the kinetics of the reaction products (Li-Si alloys, Li2O and Li-4 SiO4) in SiOx anodes for Li-ion batteries, the irreversible behavior of the batteries is studied while controlling the amount of Li-ion insertion at various current densities. SiOx is charged when the amount of Li inserted into SiOx is varied (0.1, 0.2, 0.5, and 4 mol per 1 mol of SiOx, also called "mole control") and is discharged to 1.5 V at various Crates. The irreversible capacity of SiOx increases at high mole rate, but decreases at high Crates. To observe the formation of the reaction products after mole control at various current densities, impedance and X-ray photoelectron spectroscopy are used. Also, the relative quantity of irreversible products (Li4SiO4) after mole control at various current densities is detected by Fast Fourier transform (FFT). Upon evaluating the dQ/dV curves, it was determined that the elevated rate of the overpotential of the irreversible products (Li2O, Li4SiO4) was higher than that of the reversible products (Li-Si alloys) as the current density increased. The use of the Butler-Volmer equation shows that the activation energy of the reaction products is affected by the current density, which changes the irreversible capacity of SiOx during cycling. (C) 2014 The Electrochemical Society.