Lithium Storage Characteristics of Si–Graphite-Carbon Composite Anode Material using Pitch as an Internal Binder

Abstract

Recently, lithium secondary batteries are also gaining huge popularity in IT products based on high energy density and high power factors, but they are also used in a variety of medium and large-sized devices such as ESS and EVs. In the future markets, explosive expansion of the electric car market and the development of high-capacity batteries for energy storage systems will be essential. Si was expected to be a candidate for lithium-ion battery anode material because of its large theoretical capacity (10times higher capacity than graphite). However, the biggest disadvantage of commercializing silicon materials is that large volume expansion occur during charging. Expansion of silicon causes capacity fading and cycle performance degradation. As an effective strategy to improve the problem, silicon graphite carbon composite (SGC) was introduced which can prevent electrode volume expansion so that material shows excellent cycle performance. There are studies of various SGC materials, but I propose another SGC made by pitch as an internal binder to make high density material, which reduces electrode expansion in the material by controlling the si expansion in a full range. This research found the optimized pitch content that controls electrode expansion, and observe the change of expansion between the charge/discharge stages. SGC material also show excellent cycle performance and increase the conductivity of silicon with graphite and amorphous carbon to improve the initial efficiency and retaining high current density.