Poly-vinylidene difluoride anode binder in a lithium ion capacitor
A lithium ion capacitor, including: an anode including: a conductive support; a first mixture coated on the conductive support including: a carbon sourced from coconut shell flour; a conductive carbon black; and a PVDF binder in amounts as defined herein, and where the PVDF binder has a weight average molecular weight of from 300,000 to 400,000; and a second mixture coated on the first mixture, the second mixture comprising micron-sized lithium metal particles having an encapsulating shell comprised of LiPF 6 , mineral oil, and a thermoplastic binder. Also disclosed is a method of making and using the lithium ion capacitor.
1. A lithium ion capacitor, comprising:
an anode comprising:
a conductive support;
a first mixture coated on the conductive support comprising:
a carbon sourced from coconut shell flour in from 85 to 95 wt %;
a conductive carbon black in from 1 to 8 wt %; and
a PVDF binder in from 3 to 10 wt %, where the wt % is based on the total weight of the first mixture, and where the PVDF binder has a weight average molecular weight of from 300,000 to 400,000; and
a second mixture coated on the first mixture, the second mixture comprising micron-sized lithium metal particles having an encapsulating shell comprised of LiPF 6 , mineral oil, and a thermoplastic binder.
2. The capacitor of claim 1 wherein the conductive support is copper foil or aluminum foil.
3. The capacitor of claim 1 further comprising:
a separator;
a cathode electrode coupled with the separator, the cathode electrode comprising an alkali activated carbon sourced from wheat flour in from 80 to 95 wt %, a fluorinated polymer in from 3 to 12 wt %, and carbon black in from 1 to 8 wt %; and
an electrolyte comprising an inorganic lithium salt in a non-aqueous and aprotic solvent.
4. The capacitor of claim 3 wherein the electrolyte comprising an inorganic lithium salt is LiPF 6 , and the non-aqueous and aprotic solvent is a mixture of major amounts of ethylene carbonate, dimethyl carbonate, methyl propionate, and a minor amount of fluorinated ethylene carbonate.
5. The capacitor of claim 4 wherein the LiPF 6 is present in from 0.8 to 1.5 M and the non-aqueous and aprotic solvent is a mixture of 20:20:60 (by vol %) of ethylene carbonate: dimethyl carbonate:methyl propionate, and 3 to 8 wt % by superaddition of fluorinated ethylene carbonate.
6. The capacitor of claim 1 wherein the capacitor has a higher operating power density of from 15 to 50 W/l at 100 C. rate compared to the same capacitor having an anode made of a PVDF binder having a higher weight average molecular weight of greater than 480,000.
7. A method of using the capacitor of claim 1 , comprising:
discharging the capacitor to provide a power density of from 15 to 50 W/l at 100 C. rate.
8. The method of claim 7 further comprising discharging the capacitor in combination with at least one of: a vehicle, an electronic appliance, a consumer electronic device, a component of an electrical grid system, or a combination thereof.