Hi na na,
Yes, you can take out the battery without removing the screen. It's a safety procedure to ensure the display cables aren't damaged in the process of fiddling with the battery. As a matter of fact, the introduction in the battery replacement guide comes right out and tells you that it can be done without taking off the display.
[quote]This guide instructs you to detach the front panel assembly; this is intended to prevent damage to the display cables. If you feel comfortable supporting the display carefully while peeling the battery out of the iPhone, you can skip the display removal and go directly to the battery removal steps.[/quote]
[guide|51380|iPhone 6s Plus Battery Replacement - iFixit Repair Guide|new_window=true]
It also suggests that removing the Taptic engine is optional as well, but I'd suggest doing so. It's not difficult and will give you a flatter angle to pull the battery adhesives out, which helps keep them from breaking as you're trying to remove them.
Good luck with it; let us know how it goes!