Studies on the structural control and surface modification of high capacity anode for enhancing the performance of lithium secondary batteries

Abstract

For over a decade, lithium-ion batteries (LIBs) have been the preferred source of electric power for mobile devices such as digital cameras, smart phones, and laptop computers. This is owing to their high energy density per volume (volumetric) and weight (gravimetric). However, the depletion of petroleum resources coupled with regulations to reduce environmental pollution has created a new demand for large-scale LIBs for electrical vehicles (EVs) and for sustainable energy storage systems (ESSs) to store energy from renewable sources (water, sun, biomass, geothermal, and hydrogen). These large-scale LIBs should ideally exhibit a variety of reversible capacities, cyclabilities, and power capabilities in order to meet this demand. Graphitic carbon has been widely used as a commercial anode material because of its high coulombic effi-ciency and superior cyclability. However, owing to its relatively low theoretical capacity (372 mAh $g^{-1}$), significant efforts have been dedicated to finding high-capacity anode materials that exhibit high efficiencies and long-term stability. Among the various candidate materials, Si and Li metal have been investigated extensively because of those extremely high theoretical capacities (Si: 4200 mAh $g^{-1}$, Li: 3860 mAh $g^{-1}$). The practical use of Si-based anodes is hindered by the fact that the Si particles in the anodes undergo pulverization accompanied by large volume changes (up to 300%) during cycling, resulting in electrically isolated and dead Si anodes. This is accompanied by the continuous growth of a solid electrolyte interphase (SEI) layer on the newly exposed surfaces of the Si anodes owing to electrolyte decomposition. Various nanosized or nanostructured Si materials, whose electrochemical performances are significantly better than those of micron-sized Si materials, have been proposed to address this problem. In particular, nanoscaled Si structures such as nanowires, hollow nanoparticles and nanotubes can eff...