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 about 1-25 μm;
wherein the microparticulate non-fibrillizable binder is selected from at least one of cellulose and a cellulose derivative;
wherein the dry electrode film is free-standing; and
wherein the dry electrode film has a tensile strength of at least about 1 N.
2. The dry electrode film of claim 1 , wherein the microparticulate non-fibrillizable binder has a D 50 particle size of about 5-15 μm.
3. The dry electrode film of claim 1 , wherein the dry binder comprises up to 50 wt. % of the microparticulate non-fibrillizable binder.
4. 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.
5. 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.
6. The dry electrode film of claim 1 , wherein the dry electrode film comprises a thickness of at least about 250 μm.
7. The dry electrode film of claim 1 , wherein the cellulose or the cellulose derivative has a number average molecular weight of about 10,000 to about 500,000.
8. The dry electrode film of claim 1 , wherein the cellulose derivative has a degree of substitution of about 0.7 to about 1.5.
9. The dry electrode film of claim 1 , wherein the fibrillizable binder comprises polytetrafluoroethylene (PTFE).
10. The dry electrode film of claim 1 , wherein the dry electrode film is substantially free of holes, cracks and surface pits.
11. The dry electrode film of claim 1 , wherein the dry electrode film has a tensile strength of at least about 1.5 N.
12. The dry electrode film of claim 1 , wherein the dry active material comprises graphite.
13. An electrode comprising the dry electrode film of claim 1 in contact with a current collector.
14. A lithium ion battery comprising the electrode of claim 13 .
15. The dry electrode film of claim 6 , wherein the additional non-fibrillizable binder comprises polyvinylidene fluoride (PVDF).
16. The dry electrode film of claim 1 , wherein the dry binder further comprises an additional non-fibrillizable binder.
17. The dry electrode film of claim 1 , wherein the dry electrode film comprises at least about 92 wt. % of the dry active material.
18. The lithium ion battery of claim 14 , wherein the lithium ion battery has a first cycle efficiency of at least about 90%.