XPS 17 9700, battery screw (8) M2X4, what type of screwdriver?

If they are not Torx screws, most screws I've seen on Dell laptops take a Phillips #1 bit. #0 is only for tiny screws that are part of components like drives and fans (not the screws that secure them to the board), which you wouldn't normally need to remove. And from the image in the service manual, the battery screws look like Phillips #1.

When removing or installing laptop screws:

• Ensure that the screwdriver bit is the correct size. If it's a bit loose, use a larger bit. If it seems to slip, try a smaller bit.
• Use a quality screwdriver with a good bit that will make contact evenly with the screw head, even at the tip. Cheaper drivers don't fit as well.
• The driver must be aligned in the same plane as the screw, not on an angle to it.
• Apply firm pressure and turn slowly.

When you're ready to tackle it, take your time and be careful. The reason screws get stripped is that people (and sometimes paid technicians) use the wrong tool or don't use it properly. On laptop screws, I would never use power drivers, only hand screwdrivers.

Whenever touching components or working inside a computer, wear a grounded wrist strap, also called anti-static wrist strap, ESD wrist strap, or ground bracelet. It's a cheap and sensible precaution. Rest the laptop on an anti-static mat or at least a reasonable alternative such as corrugated cardboard. (Repeatedly touching a metal case part is not sufficient mitigation with modern components.)