The Effect of Ni on the Microstructures and Electrochemical Properties of Si-Ti Base Alloys for Lithium Secondary Batteries

Abstract

This paper presents the microstructures and electrochemical properties of Si-Ti-Ni alloys of various compositions prepared by a rapid solidification process. Si-15Ti-(0 similar to 25 at%)Ni alloy ingots prepared by arc-melting was melt-spun to produce thin strip of similar to 15 Om thickness. The Si-Ni-Ti alloy electrode were fabricated by mixing the active powdered materials (88 wt%) with ketjen black (4 wt%) as a conductive material and polyamide-imide binder (PAI, 8 wt.%) dissolved in N-methyl-2-pyrrolidinone (NMP). Results showed that the microstructures of melt-spun Si-Ti-Ni ribbons consist of silicon, TiSi2, Si7Ni4Ti4, and NiSi2 phases depending on the composition. As the content of nickel increased in silicon matrix, TiSi2 phase disappeared while Si7Ni4Ti4 and NiSi2 phases are generated. The cycle efficiency of Si65Ti15Ni20 and Si60Ti15Ni25 alloys was significantly improved because of the increased volume fraction of Si7Ni4Ti4 and NiSi2 phases and fine particulated silicon phase.