If you don't plan on replacing the battery then I'd suggest to remove it from the laptop and discard of it properly (there are usually local collection centers or a battery store). It can be tricky removing the battery in the 13. To do it properly you have to disassemble a decent portion of the system. You can take a few shortcuts but I wouldn't suggest it if you don't have experience. If you're careful you can sneak it out without as much disassembly.  It's perfectly fine left in the system but I would at least unplug it from the motherboard.  You can find aftermarket batteries online for these models and they work pretty well.  If you decide to remove or replace the battery then have a read of the guides below [URL] [URL] [URL]    
I have an Alienware 13 R3 laptop hooked up to the Alienware Graphics Amplifier (external GPU) with a RTX 2070 inside and an external monitor. I haven't used my computer in a few months because I've been away, and when I booted it up today I got a message in BIOS that my "battery has experienced permanent failure." I clicked the option to continue, and my computer turned on as normal. It says, however, that I have 0% battery (and charging, although it never goes past 0%), but my computer's running fine. Should I just continue to use it as usual or is this gonna either damage my computer or eventually shut down?
13 R3, battery at 0% with external GPU but still running