There are 2 documents that you need to obtain from a battery supplier wherever possible:
The battery specification sheet
The battery material safety data sheet (MSDS)
If your battery supplier cannot or will not provide you with this information, that’s a major red flag. You should consider these to be ‘the basics’ when it comes to purchasing batteries for use in today’s products.
Knowing how the batteries are made, their ingredients, and how they should be stored, handled, and shipped is important information for your own compliance.
Furthermore, if you do go on and get 3rd party lab tests done on the batteries, providing the testing lab with these will also be helpful for them and you can cross-check against what the supplier has provide in the spec sheet to assure that they’re providing the right type of battery with the correct voltage, etc, as promised.