High tensile strength paper suitable for use in electrochemical cells
A paper suitable for use as a separator paper in electrochemical cells and an electrochemical cell comprising same, the paper comprising as the sole fibrous components 95 to 100 weight percent fibrils and 0 to 5 weight percent aramid fibrids and having a thickness of 10 to 40 micrometers and a tensile strength of at least 15 megapascals or greater, the fibrils comprising a polymer blend of 80 to 96 weight percent polyparaphenylene terephthalamide and 4 to 20 weight percent of polyvinylpyrrolidone; the fibrils having a diameter of 10 to 2000 nanometers, a length of 0.2 to 3 millimeters, a surface area of 3 to 40 square meters/gram, and a Canadian Standard Freeness of 0 to 10 milliliters.
1. A paper suitable for use as a separator paper in electrochemical cells comprising, as the sole fibrous components:
a) 95 to 100 weight percent fibrils, and
b) 0 to 5 weight percent aramid fibrids;
the paper having a thickness of 10 to 40 micrometers and a tensile strength of at least 15 megapascals or greater,
wherein the fibrils comprise a polymer blend of 80 to 96 weight percent polyparaphenylene terephthalamide and 4 to 20 weight percent of polyvinylpyrrolidone,
the fibrils having
i) diameter of 10 to 2000 nanometers,
ii) a length of 0.2 to 3 millimeters,
iii) a specific surface area of 3 to 40 square meters/gram, and
iv) a Canadian Standard Freeness of 0 to 10 milliliters.
2. The paper of claim 1 having a tensile strength of 100 megapascals or less.
3. The paper of claim 2 having a tensile strength of 50 megapascals or less.
4. The paper of claim 1 having a mean flow pore size of 0.05 to 0.5 micrometers.
5. The paper of claim 1 , wherein the fibrils have a diameter of 10 to 1200 nanometers.
6. An electrochemical cell comprising the paper of claim 1 .