If you can live with a 21.3mm-thick LG G4, get this 8500mAh battery pack from Zerolemon
As some may already know, the LG G4 comes with a 3000mAh battery. If that's not nearly enough for your needs, then the Zerolemon battery pack for the LG G4 can help you extend the battery capacity to a whopping 8500mAh, or about 2.83 times the capacity of the original battery.
Unlike most smartphones, the LG G4 has the navigational and power button on the back. For Zerolemon, this translated in a design challenge that the company overcame by making its own soft-touch plastic back case that implements back-mounted buttons. To make sure that the case doesn't hinder future NFC payment capabilities via Android Pay, the case also includes an NFC chip.
The 8500mAh battery pack takes about 3 hours to fully charge, but you're probably going to enjoy about three days of moderate usage. Just think of how many hours of video recording you can squeeze out the LG G4 with an 8500mAh battery.
As you can imagine, installing such a large battery doesn't come without its drawbacks. With the battery pack installed, the LG G4 measures 21.3mm across the waist and weighs 178g, up from 9.8mm and 155g. For a visual representation of how thick the LG G4 becomes with the battery pack installed, check out these official images: