The Structure And Performance Research Of Tin-based Material For Lithium Ion Batteries

The metallic tin and lithium can be formed of tin-lithium alloy, which makes the Sn have a theoretical capacity of994mAh/g. The capacity of Sn is about2.6times that of the graphite materials (372mAh/g), which makes the tin-based materials have more and more attention to be a new type of lithium-ion batteries anode materials. However, the most serious problem of tin-based anodes is the huge volume change (more than200%) during Li+insertion and extraction [11], which caused disintegration and pulverization of the electrodes. Therefore, the volume change leads the tin-based materials to very rapid capacity decay. To solve this so-called "pulverization" problem, we designed two kinds of tin-based materials/Carbon composites with special nanostructures in order to provide physical buffer areas for tin (tin dioxide) in charging and discharging process.1. In this paper, tin-based materials have been filled into lumens of carbon nanotubes to prepare Sn/MWCNT composite. Using the hydro-thermal method, the rupture of multi-walled carbon nanotubes and the formation of the tin dioxides happened at the same time. By the capillarity of the carbon nanotubes, tin resources could be filled into the lumens directly. The special structure of the Sn/MWCNT composite and the good conductivity of CNT mitigated the volume expansion effect of tin-based materials during the charging and discharging process. The composite had an excellent electrochemical performance in our work.2. In this paper, we designed a new nanostructure for anode materials: double-void-space SnO2/Carbon composite. The composite showed not only the internal void space inside the SnO2hollow spheres but also the exterior void space between SnO2and the synthesized carbon. The large void space made the materials have sufficient physical buffer zones for the tin-based materials during the cyclic process. Furthermore, this special void space makes every pore to be a "mini-area of anode material" and prevents the SnO2spheres extruding each other. As expected, the designed double-void-space SnO2/carbon composite manifest exceptional electrochemical performance even after50cycles.