presentation ai ch e 2009
TRANSCRIPT
Silicon Nanowire Composite Anodes for Lithium-Ion Batteries
Wanli Xu and John C. FlakeCain Department of Chemical Engineering
Louisiana State University, Baton Rouge
LOUISIANA STATE UNIVERSITY 2
Comparison of the different battery technologies in terms of volumetric and gravimetric energy density.
Why Lithium-Ion Batteries ? Light-weight High energy storage capability High operating voltage
Lithium-Ion Rechargeable Batteries
Anode: xLi+ + 6C + xe- ↔ LixC6
Cathode: LiCoO2 ↔ xe- + Li(1-x)CoO2
Tarascon, J. M.; Armand, M., Issues and challenges facing rechargeable lithium batteries. Nature 2001, 414, (6861), 359-367.
LOUISIANA STATE UNIVERSITY 3
Graphite LiCoO2
Yoshio, M.; Tsumura, T.; Dimov, N., Electrochemical behaviors of silicon based anode material. Journal of Power Sources 2005, 146, (1-2), 10-14.
Target Anode Capacity: 1000-2000 mAhg-1
How to increase total capacity ?
LOUISIANA STATE UNIVERSITY 4
Silicon as Anode Material
Chan, C. K.; Hailin, P.; Gao, L.; McIlwrath, K.; Xiao Feng, Z.; Huggins, R. A.; Yi, C., High-performance lithium battery anodes using silicon nanowires. Nature Nanotechnology 2008, 3, (1), 31-35.
4200 mA·hg-1 for Li4.4Si phase (graphite 372 mA·hg-1 for LiC6 )
~300% silicon volumetric change causing anode pulverization and large capacity fade as cell cycles
VLS-grown silicon nanowire (SiNW) can avoid pulverization.
04/11/2023 LOUISIANA STATE UNIVERSITY 6
Nanowire Anodes• Nanowires can accommodate the volume changes
on cycling.• Only need ~15% Nanowires to double the cell
capacity.• Can we develop a composite anode with graphite
and nanowires?– Conductive– Resist Mechanical Failure– Cost Effective
• We propose a new nanowire composite anode made from electroless etching of Silicon (no vacuum processing).
Ag+e- →Ag Si + 6F- → SiF6
2- + 4e-
o Facile fabricationo Low cost o Mass production
Cross-section and top view SEM imagines of SiNWs on substrate
STEP 1: SiNW Fabrication via Electroless Etching
7
Anode Preparation:• Separation• Centrifugation• Mixing• Drying
A)SiNWs as fabricated by electroless etching.B) Graphite anode as fabricated .C) Silicon nanowire composite anode as fabricated.
A
B C
STEP 2: SiNW Composite Anode Preparation
LOUISIANA STATE UNIVERSITY 9
• 3 electrodes• Reference/Counter electrode: Li foil • Electrolyte: 1 M LiPF6 in EC/DMC • ~C/10 from 0.01 to 1.5 V vs. Li/Li+
• Anode capacity is the combination of both graphite and silicon components.
• The loss of capacity is mainly attributed to the silicon loss.
charge/discharge capacity of SiNW composite anode for the 1st 2nd and 5th cycles
STEP 3: Anode Assembly and Testing
Li Li
LiPF6 in EC/DMC
A
V
Working(SiNW composite)
Reference Counter
SEM image of SiNW composite anode
SiNW composite anode surface as prepared SiNW composite anode after 1 st charging cycle
• SiNW swells in diameter• No pulverization or cracking • An SEI layer covers the anode surface after first cycle
LOUISIANA STATE UNIVERSITY 10
Charge/discharge capacities versus cycle number
~2x
SiNW composite anode capacity vs. graphite
811mAhg-1
512 mAhg-1
310 mAhg-1
Conclusions Silicon nanowire composite anodes for lithium ion
battery are presented.
Nanowire structure can accommodate large volume change of silicon during the charge/discharge cycles.
2× capacity increase with only 15% silicon nanowire addition.
Facile and low-cost preparation of anodes for lithium ion battery.
LOUISIANA STATE UNIVERSITY 12
LOUISIANA STATE UNIVERSITY 13
Joel Nino BugayongSri Sai VeguntaPurnima Narayanan
SPONSORS:
Acknowledgements
Electrochemical behavior of the SiNW composite anode
• Anode capacity is the combination of both graphite and silicon components.
• The loss of capacity is mainly attributed to the silicon loss.
charge/discharge capacity of SiNW composite anode for the 1st 2nd and 5th cycles
Differential charge/discharge capacity of SiNW composite anode for the 1st 2nd and 5th cycles
04/11/2023 LOUISIANA STATE UNIVERSITY 15
A)Top-view of SiNWs as fabricated by electroless etching. B) Top-view of SiNWs after 11 cycles at both 25µA/cm2 charging and discharging rate. C) Tiled view of SiNWs as fabricated by electroless etching. D) Tilted view of SiNWs after 100 cycles at 12C scanning rate.
1 2 3 4 5 6 7 8 9 10 110.00
500.00
1000.00
1500.00
2000.00
2500.00
3000.00
3500.00
charging
discharging
cycle numberC
apac
ity
(mA
h/g
)
No binder or other special treatment was applied to prepare the sample. Charging and discharging rates are 25µAcm-2.
Free-standing Silicon Nanowire Anode