This is so simple. Continuance is a set of batteries with a USB interface on the side. Designed by Haimo Bao, Hailong Piao, Yuancheng Liu and Xiameng Hu, Continuance is a reliable USB rechargeable battery and it was designed for emergency usage and at places where power supply is absent.
The unknown issues are, of course, how long it would take to fully charge one single AA battery. It would make more sense to have a USB cable base to charge multiple batteries at once, since most devices never use just one AA battery.