GTrusted

The LG G6 phone supports USB Power Delivery over its USB Type-C connector which means you should be able to use certain power banks like the  Anker PowerCore+ 26800mAh PD with 27W PD Portable Charger Bundle to charge the phone quickly. Unfortunately we have problems charging the phone using the Anker 30 watts based portable battery portion as seen below.

Here we connect a USB Type-C to Type-C cable between the LG G6 and the Anker battery charger when the battery is fully depleted on the phone.  Over USB Power Delivery negotiations, we can see that the Anker battery repeatedly declares 15 watts (5 volts @ 3 amps) and 30 watts (15 volts @ 2 amps) power profiles. However, we observe no communication between Anker and the LG G6 as charging continues.

We also observe that the LG G6 is not being charged by the Anker PowerCore+ 26800mAh PD's battery after the first 20 seconds which the phone pulls an initial 5.5 watts (5 volts @ 1.1 amps) when off at zero charge.