Improvement in Si active material particle performance for lithium-ion batteries by surface modification of an inductivity coupled plasma-chemical vapor deposition

The high capacity and optimal cycle characteristics of silicon render it essential in lithium-ion batteries. The authors have attempted to realize a composite material by coating individual silicon (Si) particles of a few micrometers in diameter with a silicon oxide film to serve as an active material in the anode and so optimize the charge–discharge characteristics of the lithium-ion battery. Particle coating was achieved using an inductively coupled plasma-chemical vapor deposition (ICP-CVD) process that realized a homogenous coating of silicon oxide film on each Si particle. The film was synthesized based on tetraethyl orthosilicate (TEOS), with hydrogen (H2) gas used as a reducing agent to deoxidize the silicon dioxide. This enabled the control of the silicon oxidation number in the layers produced by adjusting the H2 flow during the silicon oxidization deposition with ICP-CVD. The silicon oxide covering the Si particles included both silicon monoxide and suboxide, which served to optimize the charge–discharge characteristics. The authors have succeeded in realizing a favorable active material using Si which is abundant in nature in the anode of a lithium-ion battery with highly charged, optimized cycle properties.