I have tried changing the Device Type to match the ones that show the % sign, but TBH the ones that show the % were created either with Generic Z-Wave Contact Sensor or the Zooz ZSE41 Open Close Sensor - some show the % and some don't.
When I look at the device setting, they all show the battery level as a number, so I have no idea why this is happening or how to fix this. Any ideas?
On each of those device's Info page, at the top there's an Events button. Take a look at the Units column and verify all three have the % showing.
If it's not there, then the specific driver you're using doesn't store that bit of data. You'll have to report the Bug to the maintainer of the driver code.