ChargeTech recently sent me the ThinCharge, the thinnest iPhone charger case in the world. It doubles your battery life and was barely thicker than the plastic case I had been carrying around. I asked and right now the ThinCharge (available for iPhone 6/6s) is 53% off for a limited time only on Amazon. You can learn more about the ThinCharge and order yours at the link below.
ThinCharge: World’s Thinnest iPhone 6 / 6S Battery Case [Black]