Abstract
Silicon (Si) draws great attention as a candidate material for high-capacity negative-electrodes of next-generation lithium-ion batteries (LIBs) due to about 10 times larger capacity than that of graphite, which is widely used for negative electrodes in conventional LIBs. Si, however, has several serious problems which hinder its practical usage. The first problem is a limitation of charge/discharge rate due to lower electrical conductivity and lower reaction rate with lithium (Li) than those of graphite. In order to improve this problem, it is effective to decrease the particle size to the nano range and make composites with conductive materials like carbon. Second, the cyclability is very poor due to destructions of the electrode structure by Si's volume change during charge/discharge. In this thesis, we designed nano-structures of Si-containing electrodes having buffer “nano-spaces” around nanosized Si. And their properties as negative electrodes were evaluated. In each of the three chapters, three completely different kinds of “nano-spaces” were investigated: “nano-space” prepared around Si nanoparticles by a template method, dynamically transforming “nano-space” during charge/discharge cycle and “nano-space” formed by electrical Li extraction from eutectic Li–Si alloy. Considering their charge/discharge properties and structure changes, new guidelines for structure designs of Si-containing electrodes were proposed.
