Design & Manufacture a Iphone Battery

AIM: Design a Iphone Battery Suitable: For Iphone 4, 4s, 5 Advantages: Battery should be built to expand the life of an iphone. Currently the iphones come with poor battery, and the phone constantly dies and doesn't last. People these days use facebook alot on their Devices and that drains the battery, & i think this will be the solution to expand the battery usage. The aim of this new product is to allow the iphone to last over 24 hours on a Full Charge, or possibly more if its on Standby. Product should Not be harmful to the Iphone in any way. (eg: shouldnt over heat the phone) If you think you can design and manufacture for me, please bid Thank-you