Compositions and methods for dry electrode films including microparticulate non-fibrillizable binders
Provided herein are dry process electrode films, and energy storage devices incorporating the same, including a microparticulate non-fibrillizable binder having certain particle sizes. The electrode films exhibit improved mechanical and processing characteristics. Also provided are methods for processing such microparticulate non-fibrillizable electrode film binders, and for incorporating the microparticulate non-fibrillizable binders in electrode films.
1 . A dry electrode film of an energy storage device, comprising:
a dry active material; and
a dry binder comprising a fibrillizable binder and a microparticulate non-fibrillizable binder having a D 50 particle size of 1-25 μm;
wherein the dry electrode film is self-supporting.
2 . The dry electrode film of claim 1 , wherein the microparticulate non-fibrillizable binder has a D 50 particle size of 5-15 μm.
3 . The dry electrode film of claim 1 , wherein the fibrillizable binder comprises polytetrafluoroethylene (PTFE).
4 . The dry electrode film of claim 1 , wherein the dry binder comprises up to 50 wt. % of the microparticulate non-fibrillizable binder.
5 . The dry electrode film of claim 1 , wherein the microparticulate non-fibrillizable binder is selected from at least one of cellulose and a cellulose derivative.
6 . The dry electrode film of claim 5 , wherein the cellulose or the cellulose derivative has a number average molecular weight of 10,000 to 500,000.
7 . The dry electrode film of claim 5 , wherein the cellulose derivative has a degree of substitution of 0.7 to 1.5.
8 . The dry electrode film of claim 1 , wherein the microparticulate non-fibrillizable binder is selected from at least one of cellulose, a cellulose ester, a cellulose ether, cellulose nitrate, a carboxyalkylcellulose, a cellulose salt and a cellulose salt derivative.
9 . The dry electrode film of claim 1 , wherein the microparticulate non-fibrillizable binder is selected from at least one of cellulose, cellulose acetate, methylcellulose, ethylcellulose, hydroxylpropylcellulose (HPC), hydroxyethylcellulose (HEC), cellulose nitrate, carboxymethylcellulose (CMC), carboxyethylcellulose, carboxypropylcellulose, carboxyisopropylcellulose, sodium cellulose, sodium cellulose nitrate and sodium carboxyalkylcellulose.
10 . The dry electrode film of claim 1 , wherein the microparticulate non-fibrillizable binder comprises polyvinylidene fluoride (PVDF).
11 . The dry electrode film of claim 1 , wherein the dry electrode film is substantially free of holes, cracks and surface pits.
12 . The dry electrode film of claim 1 , wherein the dry active material comprises graphite.
13 . The dry electrode film of claim 1 , wherein the dry electrode film comprises a thickness of at least about 250 μm.
14 . The dry electrode film of claim 1 , wherein the dry binder further comprises an additional non-fibrillizable binder.
15 . The dry electrode film of claim 1 , wherein the dry electrode film comprises at least about 92 wt. % of the dry active material.
16 . The dry electrode film of claim 1 , wherein the dry electrode film is substantially free from solvent residues.
17 . An electrode comprising the dry electrode film of claim 1 in contact with a current collector.
18 . A lithium ion battery comprising the electrode of claim 17 .
19 . The lithium ion battery of claim 18 , wherein the lithium ion battery has a first cycle efficiency of at least about 90%.
20 . A method of fabricating a dry electrode film of an energy storage device, comprising:
processing a dry non-fibrillizable binder at high shear to form a dry microparticulate non-fibrillizable binder;
mixing the dry microparticulate non-fibrillizable binder with a first dry active material by a first nondestructive mixing process to form a dry bulk active material mixture;
combining a dry fibrillizable binder with the dry bulk active material mixture to form a dry electrode film mixture; and
producing from the dry electrode film mixture a self-supporting dry electrode film.
21 . The method of claim 20 , wherein processing the dry non-fibrillizable binder at high shear is selected from the group consisting of high shear jet milling, blending, and combinations thereof.
22 . The method of claim 20 , wherein the dry microparticulate non-fibrillizable binder has a D 50 particle size of 0.5-40 μm.
23 . The method of claim 20 , wherein combining the dry fibrillizable binder with the dry bulk active material mixture comprises a second nondestructive mixing process.
24 . The method of claim 20 , wherein the first nondestructive mixing process is selected from the group consisting of nondestructive jet milling, tumbling, paddle mixing, blade blending, acoustic mixing, and combinations thereof.
25 . The method of claim 20 , wherein producing the self-supporting dry electrode film comprises processing the dry electrode film mixture by a process selected from the group consisting of pressing, calendering, and combinations thereof.
26 . The method of claim 25 , wherein the producing the self-supporting dry electrode film comprises heated calendering the dry electrode film mixture.
27 . The method of claim 20 , wherein the method is a dry fabrication process.
28 . The dry electrode film of claim 14 , wherein the additional non-fibrillizable binder comprises polyvinylidene fluoride (PVDF).