Power-only USB connection to charge my phone - as simple as cutting the data lines?
The data lines should be shorted together to identify the charger as a dedicated charging port (DCP). Some phone manufacturers, however, have their own non-standard ways of identifying charging ports.
Now, the phone charger may not like being treated like a DCP, but alternatives are it is a standard downstream port (SDP), which is slow and allows data transfer, or a charging downstream port (CDP), which is fast and also allows data transfer, or something non-standard. Some devices can change how they appear. Your phone may refuse to change if it does not like how the USB port is configured.
Definitions for DCP, SDP, CDP can all be found in Maxim's Tutorial 4803, The Basics of USB Battery Charging: A Survival Guide.

Source: https://www.maximintegrated.com/en/app-notes/index.mvp/id/5801