Lithium Ion Battery (LIB)

Lithium-ion batteries are used in a wide range of products around us because of their high energy density and voltage. Because of the development of electric vehicles and mobile devices, demand for high-capacity, high-voltage, and safe secondary batteries is growing. FUJIFILM Wako deal with various materials that constitute lithium-ion batteries. Our CLPA series of binders are polyacrylic acid (PAH) and its cross-linked polymer; these binders are synthesized by our technology and lead to significantly improved battery properties compared to those of polyvinylidene fluoride (PVdF). Furthermore, the addition of our WEA series of products [bis(sulfonate) type of materials] to an electrolyte of a secondary battery improves the battery properties.

More Information

Rough outline for mechanism of LIB system

[Current]
Active material: Graphite
Theoretical capacity: 370 mAh/g

(Discharge)  (Charge)
C6 + Li+ + e- ⇔ C6Li

[Next generation]
Active material: Silicon (Si)
Theoretical capacity: 4300 mAh/g

LIB-img02.jpg

(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

    Charge mode is intercalation system

    LIB-img03.jpg

    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.

  • Silicon anode

    Charge mode is an alloy formation of Si-Li

    LIB-img04.jpg

    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)

  • LIB-img06.jpg
  • LIB-img07.jpg
  • LIB-img08.jpg
  • Reduction potential

    WEA-67 > WEA-14 > WEA-36
    (1.6V)   (1.4V)   (1.2V)

    LUMO energy

    WEA-67 < WEA-14 < WEA-36
    (1.44eV)  (2.40eV)  (2.50eV)


Performance of CLPA on Si and graphite composite electrode

LIB-img09.jpg

The detailed results are reported on following letter.

Reference

Komaba, S. et al.: Journal of The Electrochemical Society, 162 (12) A2245-A2249 (2015)

Author: H. Mizuta

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