Lithium Ion Battery (LIB)
Current generation PCs and mobile devices are powered by lithium ion batteries (LIB). In the near future, LIBs will be used extensively as a power source for Electric Vehicles (EV).
Rough outline for mechanism of LIB system
Active material: Graphite
Theoretical capacity: 370 mAh/g
C6 + Li+ + e- ⇔ C6Li
Active material: Silicon (Si)
Theoretical capacity: 4300 mAh/g
(Discharge ) (Charge)
Si + 4.4Li+ + 4.4e- ⇔ Li4.4Si
Si anode has potential more than decuple capability comparing with graphite anode.
Si anode technology is a highly anticipated development for LIB enhancement. Si anode technology will facilitate higher capacity and downsizing of the battery cell.
Difference between graphite and Silicon as anode
|Graphite anode||Silicon anode|
|Charge mode is intercalation system||Charge mode is an alloy formation of Si-Li|
|During charging, Li ions are inserted between layers of graphite. Currently, the graphite (anode) thickness does not change before/after a charging event.
WEA is good additive for SEI formation.
|During charging, Li ions combine with Si to form an alloy of Si-Li, The Si-Li complex expands 4x under charge, while the Si anode shrinks to 1/4 its original size in the discharge state. Si anodes are damaged through the constant expansion and contraction.|
The binder for Si is required a function to maintain the shape/size of Si anode.
FUJIFILM Wako develops CLPA in new binder for Si anode.
Additive for SEI formation
Relatively low LUMO (WEA-series)
→ formation of SEI with low electricity consumption
Cyclic Voltamograms of Electrolytes with Novel Additives (WEA)
WEA-67 ＞ WEA-14 ＞ WEA-36
(1.6V) (1.4V) (1.2V)
WEA-67 ＜ WEA-14 ＜ WEA-36
(1.44eV) (2.40eV) (2.50eV)
Performance of CLPA on Si and graphite composite electrode
The detailed results are reported on following letter.
Komaba, S. et al.: Journal of The Electrochemical Society, 162 (12) A2245-A2249 (2015)