A new compliant polymer seal and process for sealing sodium conducting energy storage devices and batteries are disclosed. Compliant polymer seals become viscous at the operation temperature which seals cathode and anode chambers and other components together following assembly. Seals can accommodate thermal expansion mismatches between selected components during operation.
STATEMENT REGARDING RIGHTS TO INVENTION MADE UNDER FEDERALLY-SPONSORED RESEARCH AND DEVELOPMENT
 This invention was made with Government support under Contract DE-AC05-76RLO1830 awarded by the U.S. Department of Energy. The Government has certain rights in the invention.