Three-Dimensional Porous Si with in Situ Decorated Carbon Nanotubes As Anode Materials for Li-Ion Batteries

Abstract

Rechargeable Li-ion Batteries have been widely used as energy storage devices for portable electronics owing to their higher energy density and long cycle life. However, higher capacity cathode and anode materials are required for their large-scale application in electrical vehicles (EVs)[1-3]. Currently, commercialized Li-ion batteries with graphite as an anode material are still far from practical use in EVs because of their limited capacity and unsatisfactory cycling performance. Many anode materials with higher theoretical capacities have been proposed. Among them, silicon is more attractive because of its highest theoretical specific capacity (~4200 mAh/g), low redox potential (< 0.5 V versus Li/Li+), and abundance as a mineral resource[4-5]. However, silicon has two main defects: low electronic conductivity and very large volume changes (~300%) during lithiation/delithiation. In this work, we prepared three-dimensional porous Si with in situ decorated carbon nanotubes. Si clusters were obtained from commercial Al-Si alloy spheres by pickling aluminum component. Then, carbon nanotubes were in situ grown on Si cluster by a chemical vapor deposition (CVD) process using toluene as a carbon source and Ni particles as a catalyst. The obtained material was denoted as Si cluster/CNTs. For comparison, Si cluster coated with carbon layers by the same CVD process without Ni catalyst was also prepared, denoted as Si cluster/C. The electrochemical results demonstrated that Si cluster/CNTs had longer life and higher rate cycling performance (2000 mAh g-1 at 0.5 A g-1 after 250 cycles) than Si cluster and Si cluster/C. The cluster structure could effectively relieve the volumetric change during charge-discharge process. The carbon nanotubes could improve the electronic conductivity and stabilize the structure of Si cluster in Si cluster/CNTs.