iPhones are physically closed devices: neither flash memory or battery are expandable. Solutions to both of these limitations exist, but Mophie has the only single solution to both problems: Space Pack adds battery & up to 64 GB of flash memory in a protective case.
Mophie web site:
http://www.mophie.com/shop/space-pack#powerandstorage / new iPhones lowest storage model upgrade cost file files music SD cards card 16 32 extra gigabytes storage new space pack iPhone 5S mophie space pack 100% extra battery life 8 hours extra talk time extra power mophie cases adds extra storage 16 32 64 GB free iOS Space app collections favorites recent file storage battery usage /