Reaction Mechanism of “SiO”-Carbon Composite-Negative Electrode for High-Capacity Lithium-Ion Batteries

The reaction mechanism of a "SiO"-carbon composite-negative electrode for high-capacity lithium-ion batteries is examined by Si K-edge X-ray absorption near edge structure (XANES), 7Li and 29Si nuclear magnetic resonance (NMR), and scanning transmission electron microscopy (STEM) with Si L-edge electron energy loss spectroscopy (EELS) and energy dispersive X-ray spectroscopy (EDX). According to the analytical results, "SiO" consisting of nano-size Si particles dispersed in amorphous SiO2 is converted to lithium-silicon alloys and lithium silicon oxides during the first charge in lithium-ion batteries, and the nano-size silicon particles surrounded by lithium silicon oxides are rechargeable for subsequent cycles. Molecular dynamics (MD) simulation of "SiO" is also carried out and shown that silicon particles grow during the first cycle and are surrounded by a good lithium-ion conductor of lithium silicon oxides. From these results, the reaction mechanism of "SiO" is discussed in terms of high-capacity negative electrodes for lithium-ion batteries.