Title: Sustainable eco-friendly sub-micron NaCl crystal powder-assisted method to synthesize SiO_x/C as anode materials originated from rice husk for lithium-ion batteries

Author: Se Hun Lee^a,†, Youngseul Cho^b,†, Young Pyo Jeon^a,†, Yujin Chang^c, Kyu Sang Lee^c, Dongpyo Hong^a, Ok Sung Jeon^a, Yongyeol Park ^a,c, Hyun Seo Yang ^a, Young Joon Yoo ^a,*, Sang Yoon Park^a,d,*, and Yuanzhe Piao^c,*

aCenter for Applied Electromagnetic Research for Advanced Institute of Convergence Technology, Seoul National University, Gyeonggi-do 16229, Republic of Korea

^bProgram in Nano Science and Technology, Graduate School of Convergence Science and Technology, Seoul National University, 145 Gwanggyo-ro, Yeongtong-gu, Suwon-Si, Gyeonggi-do 16229, Republic of Korea

^cDepartment of Applied Bioengineering, Graduate School of Convergence Science and Technology, Seoul National University, 145 Gwanggyo-ro, Yeongtong-gu, Suwon-Si, Gyeonggi-do 16229, Republic of Korea

^dSchool of Electronic Engineering, Kyonggi University 154-42 Gwanggyosan-ro, Yeongtong-gu, Suwon-si, Gyeonggi-do 16227, Republic of Korea

Abstract: 

Graphite is the mainstay for lithium-ion battery anodes. However, its energy density originating from its low gravimetric capacity still remained as challenge and synthesizing graphite generally requires complex procedures with toxic chemicals. Hence, the research focus should shift towards mitigating the environmental risks associated with battery anode material development while simultaneously enhancing the low energy density of graphite. In the present study, we produced SiO_x/C from rice husk by the NaCl sub-micron crystal-assisted synthesis method which can mitigate environmental degradation and hazards, simplify preparation, and improve electrochemical performance. During synthesis, NaCl induces catalytic graphitization, carbon activation, and amorphous silica formation. Moreover, it is only partially consumed and can be recrystallized and reused indefinitely. Our NaCl sub-micron crystal powder-assisted method created lithium-ion batteries (LIBs) with rice husk-derived SiO_x/C anodes that exhibited a high initial charge/discharge capacity of 422.05/915.93 mAh∙g^-1 at 0.05 A∙g^-1 current density and stable cycling performance. In addition, the SiO_x/C electrode produced by the NaCl micro-crystal method had 333.96 mAh∙g^-1 capacity at 0.05 A∙g^-1 current density. By contrast, bare rice husk electrode exhibited a lower capacity of 333.96 mAh∙g^-1_­at the same condition.

Keywords: lithium-ion battery, rice husk, SiO_x/C, sodium chloride activation, sodium chloride sub-micron crystal powder-assisted synthesis method