Let's see here how you can use the dual role power enabled LG G7 ThinQ phone to charge up your Apple iPhone 5s just in case it's running low on battery with no access to AC power. The Android based LG G7 ThinQ comes with Qualcomm Quick Charge 4+ technology to support USB Power Delivery 3.0, PPS (Programmable Power Supply), and Qualcomm Quick Charge 3.0 technology over USB Type-C, and with its dual role power capabilities can be used for charging other compatible devices when there's no AC power available as well as being able to be charged itself. The Apple iPhone and iPad Pro's on the other hand can only consume and not supply power.
The LG G7 ThinQ should be acting as a power bank to the iPhone 5s when connected over a Apple USB-C to Lightning Cable. Since this will force the LG phone to deplete its own battery charge to support charging the iPhone, it's important that the LG G7 ThinQ has enough battery charge to last through the entire process.
With a 17% charged battery, the iPhone 5s was observed to level out charging at around 2.5 watts when connected to the 78% charged LG G7 ThinQ over USB Power Delivery. You will also need to check that 'Charge connected device' is selected from the LG phone's USB charging options. The iPhone when connected automatically just supports charging in. Click here to download the trace captured by the GRL-A1 power analyzer to see more details.
Even when the iPhone 5s is able to charge faster using its own shipped 5W USB Type-A charger given that it doesn't support USB Power Delivery, it's still good to know that certain Android phones like the LG G7 ThinQ can be used as an alternative power supply for the iPhone albeit very slow charging.