(699b) Carbon Oxide-Thermic Oxidation Process for Synthesis of Porous Silicon-Carbon Composite Anodes for Lithium-Ion Batteries

Mohamed A. Elharati^a, Younghwan Cha^b, Qusay Bkour^a, Steven R. Saunders^a, M. Grant Norton^b, Min-Kyu Song^b,*, Su Ha^a,*

^aVoiland School of Chemical Engineering and Bioengineering, Washington State University,
Pullman, WA 99164-2710, USA

^bSchool of Mechanical and Materials Engineering, Washington State University, P.O. Box 642920, Pullman, WA 99164-2920, USA

Abstract

The silicon-based compounds have been investigated as a promising anode material for lithium-ion (Li-ion) batteries. In this work, we show that a novel carbon oxide thermic oxidation (CO_x-OP) process is not only a facile and low-cost technique to synthesize porous silicon-carbon (Si-C) composites for high-energy Li-ion batteries but also is the novel utilization technology of greenhouse gas. Furthermore, we demonstrate that the morphology/microstructure and performance of Si-C composites can be controlled by using different gas compositions (CO, CO₂, and H₂).

In-situ high-temperature X-ray diffraction analyses were performed to elucidate the phase transition during CO_x-OP. The pulsing experiments were conducted to illustrate the mechanism of the CO_x-OP process. The electron microscopy and X-ray microanalysis were carried out to investigate the effects of processing conditions on the morphology and microstructures of Si-C. The TGA and Raman analysis were performed to determine the amount and type of carbonaceous materials.

The synthesized porous Si-C via CO_x-OP process showed good electrochemical performance for Li-ion batteries, and their performance is strongly affected by the gas composition used in the CO_x-OP process. For example, the first lithiation and delithiation capacities of Si-C prepared with CO₂-rich gas stream were 2481 mAh/g and 2061 mAh/g, respectively, resulting in high coulombic efficiency of 83.1% . In contrast, the first lithiation and delithiation capacities were 2148 mAh/g and 1356 mAh/g, respectively, resulting in low coulombic efficiency of 63.2.% for Si-C prepared with CO-rich gas stream.

Keywords:

Porous silicon-carbon (Si-C) composites, carbon oxide thermic oxidation (CO_x-OP) process, lithium-ion battery.