Synthesis and Nitrogen-Plasma Treatment of Silicon/Carbon Nanotube/Graphene Composites As Anode Materials for Lithium-Ion Batteries
Authors: Lin Chuen-Chang , Chang Jyun-Wei 
Published: February 2020

Lithium-ion batteries compared to other batteries (such as Ni-Cd, Lead-Acid, and Ni-MH) possess higher energy densities (100 – 150 Wh/kg), higher voltage, and lower maintenance [1]. To increase the accessibly specific surface area and the stability as well as conductivity between the carbon nanotube bundles as well as the nickel foam, three dimensional few layer graphene/multi-walled carbon nanotube architectures were fabricated on oxygen-plasma treated nickel foam coated with Fe catalysts by e-beam evaporation through a one-step ambient pressure chemical vapor deposition (CVD) process using a mixture of acetylene and hydrogen [2]. Silicon thin films with loose microstructure deposited on Cu foil by radio frequency (RF) magnetron sputtering as well as used as anode materials for Li-ion rechargeable batteries can not only be help to buffering the volume changes of Si films during discharge/charge cycles, but also provide with effective pathways for Li ions transportation and consequently lead to higher energy density as well as good cycling stability of electrodes [3]. Silicon nitride thin films deposited by plasma enhanced chemical vapor deposition (PECVD) as anode materials for Li-ion batteries possessed high reversible capacity since a ductile and conductive Li3N matrix buffered volume expansion of the Si-Li alloy as well as prevented aggregation of the Si nanoparticles, however, the specific capacity of silicon nitride was very sensitive to RF power, the higher the power, the lower the specific capacity [4]. Silicon nitride derived from silicon nanoparticles by vacuum CVD with ammonia within graphene matrixes as anode materials for Li-ion batteries displayed stable electrochemical performance at 500 mA/g rate of cycling due to the improved stress management and conductive Li3N matrix which was primarily derived from SiN0.73 [5].
Carbon nanotube/graphene composites were directly grown on cobalt (Co) catalysts-coated nickel foam by one-step ambient pressure CVD. Next, The silicon film was deposited on the carbon nanotube/graphene composites by RF magnetron sputtering at different power levels (150 and 200 W). Finally, the silicon/carbon nanotube/graphene composites were modified by RF nitrogen-plasma treatment at different power levels (50, 75, and 100 W). The silicon film sputtered on the carbon nanotube/graphene composites at a lower power level possessed higher specific capacity and cyclic stability due to the silicon thin film sputtered on the carbon nanotube/graphene composites at 150 W with loose microstructure [3]. Furthermore, the higher the nitrogen-plasma power, the higher the cyclic stability because a conductive Li3N matrix primarily was derived from SiN0.73 [5], the higher the power, the higher the percentage of SiN0.73 as well as then the higher the percentage of ductile and conductive Li3N which buffered volume expansion of the Si-Li alloy as well as prevented aggregation of the Si nanoparticles [4, 5]. However, the higher the nitrogen-plasma power, the lower the specific capacity since the higher the power, the higher the percentage of nonconductive SiN1.33 which led to the lower specific capacity [4]. Moreover, silicon/carbon nanotube/graphene composites modified by nitrogen-plasma showed a stable cyclic performance in comparison to silicon/carbon nanotube/graphene composites since the incorporation of nitrogen improved the cyclic stability of the anode [4, 5].
Keywords: silicon/carbon nanotube/graphene composites; chemical vapor deposition; magnetron sputtering; nitrogen-plasma treatment; lithium-ion batteries

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