Effects of In Situ Graphitic Nanocarbon Coatings on Cycling Performance of Silicon-Flake-Based Anode of Lithium Ion Battery

Yonhua Tzeng,Wei-Chih Huang,Cheng-Ying Jhan,Yi-Hsuan Wu

doi:10.3390/coatings11020138

Abstract

We coated graphitic nanocarbons by thermal chemical vapor deposition (CVD) on silicon flakes recycled from the waste of silicon wafer manufacturing processes as an active material for the anode of lithium ion battery (LIB). Ferrocene contains both iron catalyst and carbon, while camphor serves as an additional carbon source. Water vapor promotes catalytic growth of nanocarbons, including carbon nanotubes (CNTs), carbon fibers (CFs), and carbon films made of graphitic carbon nanoparticles, at temperatures ranging from 650 to 850 °C. The container of silicon flakes rotates for uniform coatings on silicon flakes of about 100 nm thick and 800–1000 nm in lateral dimensions. Due to short CVD time, besides CNTs and CFs, surfaces of silicon flakes deposit with high-density graphitic nanoparticles, especially at a low temperature of 650 °C. Nanocarbon coatings were characterized by SEM, EDX, ESCA, and Raman spectroscopy. Half-cells were characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and retention of capacity in discharge/charge cycling. Silicon-flake-based anode with nanocarbon coatings at both 650 and 850 °C exhibited capacity retention of 2000 mAh/g after 100 cycles at 0.1 C, without needing any conductivity enhancement material such as Super P.

Highlights

The lithium ion battery (LIB) is characterized as having high potential, energy density, and power and being capable of having a long cycling life for repetitive charging and discharging in a wide temperature range
We report the effects of in situ thermal chemical vapor deposition (CVD) of graphitic nanocarbon coatings, including carbon nanotubes (CNTs)-like and carbon-fiber-like one-dimensional nanocarbon nanostructures on silicon flakes, on sustainable cycling performance and improved retention of capacity of silicon-based anode
These results clearly demonstrated that high-density CNTs grew in 15 min under the thermal CVD conditions

Summary

Introduction

The lithium ion battery (LIB) is characterized as having high potential, energy density, and power and being capable of having a long cycling life for repetitive charging and discharging in a wide temperature range. The commonly used anode material for LIB is graphite, which has a theoretical capacity of 372 mAh/g. The capacity of graphite does not meet the high demands by long-range electric vehicles (EVs) and large-scale storage of intermittent renewable energy [1,2,3]. Silicon provides some hope for greatly increased capacity of LIB anode because its theoretical capacity of 4200 mAh/g is more than ten times of that for graphite [4]. Unlike delithiation and lithiation of graphite anode during charge and discharge cycling, lithium forms alloys with silicon during discharging. The alloying reactions and the subsequent dissociation of alloys result in as high as 420% volume changes of silicon [7]

Methods

Results

Conclusion