Department of Chemical Engineering, National Chung Cheng ...
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Synthesis of Porous Silicon from Rice Husks as Anode Material for Li-ion Batteries Material Identification Electrochemical performance Chung-Chu, Chou (周盅車) and Chao-Hong, Wang (王朝弘)* Department of Chemical Engineering, National Chung Cheng University, Chia-yi, Taiwan (MOST 104-2218-E-194-005) In this study, we demonstrated a new and simple method for successfully preparing the porous Si powders from the agricultural waste - rice husks, which contains up to ~ 20% silica. A mixture of Si and Li x Si y O z is synthesized by thermal treatment of blending biogenic silica and reducing agents. After the removal of Li 4 SiO 4 , the pure Si particles characterized by FIB microscopy clearly revealed the porous structure with pore sizes of about 0.3-1.2 μm. Notably, the homogenous and high-porosity microstructure can accommodate the volume expansion of Si and enhance the lithiation/delithiation during the cycling. In addition, fluoroethylene carbonate (FEC) was added to the electrolyte, leading to the formation of a dense and less resistant SEI film on porous Si particle. The Si electrode exhibited the high capacity of ~2000 mAh/g, (0.1C) and good cycle life (69% capacity retention after 100 cycles) ). The approach has a scalable synthetic potential for the transformation of rice husk to obtain high-performance porous Si for many applications. Heat treatment Leaching with Acid Rice Husks- SiO 2 Etching with B.O.E. Morphology Capacity (mAh/g) 1 st cycle 1 st CE% Max. capacity 100 th cycle 100 th retention No FEC addition 2048.26 80.23% 2104.09 642.07 30.52% 5wt% FEC addition 1770.17 78.37% 1992.64 1365.75 68.54% 0 40 80 120 160 200 240 0 40 80 120 160 200 240 -Z(ohm) Z(ohm) After 100th cycle test 5wt% FEC addition no FEC addition Introduction We synthesized porous Si via thermal reduction of SiO 2 . The significant improvement of electrochemical performance could be achieved by electrolyte addition. The porous Si electrode have a good reversible capacity of 1365.75 mAh/g at the current density of 0.1C. Surface area : 48.5 m 2 /g Abstract Cross section Experimental Method Reducing agent Li 4 SiO 4 Porous Si Rice Husks- SiO 2 Pyrolysis Ball milled Calcination Rice Husks Leaching Si Pore MTES Rice Husks TEOS Sand Magnesiothermic Reduction Porous Si Etching Pore SiO 2 Assembling Cross section Zoom In Zoom In Conclusion New Thermal Reduction Carbothermic Magnesiothermic Aluminothermic Calciothermic New method Si Etching Etching MgO Si Si SiO 2 Li 4 SiO 4 SiO 2 Si a b c d (a) (b) (c) (d) 10 20 30 40 50 60 70 80 90 Leaching with Acid ● ● ● ● ● ● ● ● ● ● ● Li 2 SiO 3 ● Li 4 SiO 4 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● Si Intensity (a.u.) 2 (degree) Etching with B.O.E. Heat treatment Rice Husk - SiO 2
Transcript of Department of Chemical Engineering, National Chung Cheng ...
Synthesis of Porous Silicon from Rice Husks as Anode Material for Li-ion Batteries
Material Identification
Electrochemical performance
Chung-Chu, Chou (周盅車) and Chao-Hong, Wang (王朝弘)*
Department of Chemical Engineering, National Chung Cheng University, Chia-yi, Taiwan
(MOST 104-2218-E-194-005)
In this study, we demonstrated a new and simple method for successfully preparing the porous Si powders from the agricultural waste - rice husks, which
contains up to ~ 20% silica. A mixture of Si and LixSiyOz is synthesized by thermal treatment of blending biogenic silica and reducing agents. After the
removal of Li4SiO4, the pure Si particles characterized by FIB microscopy clearly revealed the porous structure with pore sizes of about 0.3-1.2 µm.
Notably, the homogenous and high-porosity microstructure can accommodate the volume expansion of Si and enhance the lithiation/delithiation during the
cycling. In addition, fluoroethylene carbonate (FEC) was added to the electrolyte, leading to the formation of a dense and less resistant SEI film on porous
Si particle. The Si electrode exhibited the high capacity of ~2000 mAh/g, (0.1C) and good cycle life (69% capacity retention after 100 cycles) ). The
approach has a scalable synthetic potential for the transformation of rice husk to obtain high-performance porous Si for many applications.
Heat treatment
Leaching with Acid
Rice Husks- SiO2
Etching with B.O.E.
Morphology
Capacity (mAh/g) 1st cycle 1st CE% Max. capacity 100th cycle 100th retention
No FEC addition 2048.26 80.23% 2104.09 642.07 30.52%
5wt% FEC addition 1770.17 78.37% 1992.64 1365.75 68.54%
0 40 80 120 160 200 240
0
40
80
120
160
200
240
-Z(
ohm
)
Z(ohm)
After 100th cycle test
5wt% FEC addition
no FEC addition
Introduction
We synthesized porous Si via thermal reduction of SiO2. The significant improvement
of electrochemical performance could be achieved by electrolyte addition. The porous Si
electrode have a good reversible capacity of 1365.75 mAh/g at the current density of 0.1C.
Surface area : 48.5 m2/g
Abstract
Cross section
Experimental Method
Reducing
agent Li4SiO4
Porous Si
Rice Husks- SiO2
Pyrolysis Ball milled
Calcination
Rice Husks
Leaching
Si
Pore
MTES
Rice Husks
TEOS
Sand
Magnesiothermic Reduction
Porous Si
Etching
Pore
SiO2
Assembling
Cross section
Zoom In
Zoom In
Conclusion
New Thermal Reduction
Carbothermic
Magnesiothermic
Aluminothermic
Calciothermic
New method
Si
Etching
Etching
MgO
Si
Si SiO2
Li4SiO4
SiO2 Si
a b
c
d
(a)
(b) (c)
(d)
10 20 30 40 50 60 70 80 90
Leaching with Acid
●
●●
●●●
● ● ●
●
● Li2SiO
3
●
Li4SiO
4
●●
●
●
●●
●
●● ●
●
●
●
●
●
● Si
Inte
nsi
ty (
a.u
.)
2(degree)
Etching with B.O.E.
Heat treatment
Rice Husk - SiO2
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