Compositions and methods for energy storage device electrodes
An energy storage device can include a cathode, an anode, and a separator between the cathode and the anode, where the anode and/or electrode includes an electrode film having a super-fibrillized binder material and carbon. The electrode film can have a reduced quantity of the binder material while maintaining desired mechanical and/or electrical properties. A process for fabricating the electrode film may include a fibrillization process using reduced speed and/or increased process pressure such that fibrillization of the binder material can be increased. The electrode film may include an electrical conductivity promoting additive to facilitate decreased equivalent series resistance performance. Increasing fibrillization of the binder material may facilitate formation of thinner electrode films, such as dry electrode films.
1. A method for fabricating a dry energy storage device electrode film comprising:
forming a first dry electrode film mixture comprising dry carbon particles and dry fibrillizable binder particles;
super-fibrillizing the dry fibrillizable binder particles in the dry electrode film mixture to form a super-fibrillized matrix within the electrode film mixture, wherein super-fibrillizing the dry fibrillizable binder particles comprises:
fibrillizing the dry fibrillizable binder particles in the dry electrode film mixture to form a first fibrillized matrix;
destructuring the first fibrillized matrix to form a powdered mixture of carbon particles and fibrillized binder particles; and
fibrillizing the powdered mixture to form a super-fibrillized electrode film mixture comprising a second fibrillized matrix, wherein the second fibrillized matrix comprises the super-fibrillized matrix; and
calendering the super-fibrillized electrode film mixture to form a free-standing super-fibrillized electrode film.
2. The method of claim 1 , wherein the method is a dry method in which substantially no processing additives are used.
3. The method of claim 1 , further comprising contacting the free-standing super-fibrillized electrode film with a current collector to form a first electrode.
4. The method of claim 3 , further comprising forming a second electrode, and inserting a separator between the first electrode and the second electrode.
5. The method of claim 3 , wherein the first electrode is an anode.
6. The method of claim 1 , wherein calendering comprises compressing the free-standing super-fibrillized electrode film to a thickness of about 50 μm to about 120 μm.
7. The method of claim 6 , wherein calendering to the thickness of about 50 μm to about 120 μm comprises a single calendering step.
8. The method of claim 1 , wherein the super-fibrillized matrix comprises dry super-fibrillized binder particles, and wherein the dry super-fibrillized binder particles comprise about 5 wt % to about 7 wt % of the super-fibrillized matrix.
9. The method of claim 1 , wherein forming the first dry electrode film mixture further comprises adding conductive carbon particles to the first dry electrode film mixture.
10. The method of claim 9 , wherein the first dry electrode film mixture comprises the conductive carbon particles in about 1% to about 5% by mass.
11. The method of claim 4 , further comprising inserting the first electrode, separator and second electrode into a housing with an electrolyte to form an energy storage device.
12. The method of claim 11 , wherein the energy stroage device is a battery.
13. The method of claim 1 , wherein the dry fibrillizable binder particles comprise a binder selected from the group consisting of polytetrafluoroethylene (PTFE), ultra-high molecular weight polyethylene (UHMWPE), and combinations thereof.