Lithium secondary batteries have been actively investigated during the past ten years and small cells with liquid electrolytes have been commercialized. In view of the concerns about safety, solid state batteries that use solid polymers in place of both the electrolyte and the separator offer a unique design for a high rate battery for implantable medical devices. The solid electrolyte has a low vapor pressure and should be relatively safe with respect to problems that could result from the vaporization of a volatile liquid electrolyte. The solid polymeric electrolyte may be fabricated in the form of a thin film and, in combination with thin electrode structures, can exhibit good high rate performance and improved lithium plating morphology.