Kinetics of reaction products of silicon monoxide with controlled amount of li-ion insertion at various current densities for li-ion batteries

To understand the kinetics of the reaction products (Li-Si alloys, Li ₂O and Li₄ SiO₄) in SiO_x 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. SiO_x is charged when the amount of Li inserted into SiO_x is varied (0.1, 0.2, 0.5, and 4 mol per 1 mol of SiO_x, also called "mole control") and is discharged to 1.5 V at various Crates. The irreversible capacity of SiO_x 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 SiO_x during cycling.