A Scalable Furnace Technique to Grow Silicon Nanoparticles for High-Performance Li-Ion Battery Anodes

Abstract

Lithium-ion battery (LIB) technology is one of the key technologies to lower the emission from fossil fuel while maintaining stable supply of energy to the society. One way to increase the capacity of LIBs is to add silicon to the graphite anode, since silicon can store much more lithium ions than graphite. Silicon does however expand and contract during lithiation and delithiation, leading to cracks which deteriorates the performance of the LIB anode. Mechanical cracking can be avoided by using sufficiently small silicon nanoparticles. Several high-performance schemes utilizing silicon nano materials such as nanoparticles, nanotubes, nanorods etc. have been demonstrated but industrial-scale implementation of these solutions still poses a challenge. The Siemens process is one of the most commonly used methods to create silicon nanoparticles and uses chemical vapor deposition (CVD) processes involving silane or silane derivatives as precursors. Due to the flammable and toxic nature of silane, the CVD process requires special handling care and expensive instrumentation. In this work, a novel scalable furnace technique to create silicon nanoparticles attached to graphene flakes LIB anode applications is presented. With this technique, we can avoid the silane precursor. In addition, the instrumentation requirements of the furnace technique are quite simple and inexpensive and the technology is compatible with already established industrial-scale electrode manufacturing techniques.In the work presented here we demonstrate how silicon nanoparticles are grown from micro sized silicon powder onto graphene flakes using simple thermal treatment. Thermal gravitometry, mass spectrometry and differential scanning calorimetry was used to show how silicon powder and a binder can be converted to silicon nanoparticles by simple pyrolysis. The silicon nanoparticles are grown on top of graphene flakes to create a LIB anode. The anode, when tested in a half cell assembly shows a capacity that is considerably higher than standard graphene/graphite electrodes.