A high tensile strength, highly conductive flexible composite sheet
consisting of fibrillated PTFE polymers, performance enhancing dopants,
and carbon particles useful in electrochemical devices such as flow
through capacitors, capacitive deionization, electronic water
purification, fuel cells, capacitors, super-capacitors and a method of
preparation. The method consists of mixing the materials and calendering
to the desired thickness and strength all at room temperature and leaving
the material in a wet state without further drying.