I'd like a reference on that because it seems completely implausible, and would make recycling almost anything impossible because glue is used everywhere, on tape bits to hold cables in place etc.

And if the batteries has to be glue free, then practically all laptop and cell phone batteries can't be recycled because the plastic battery case is glued together.

Turns out I got a bit mixed up: the problem with the glue exists with recycling the glass front panels of the iPhone and family.

OK, that's more understandable, since I guess that glue has to be pretty solid and has to cover the entire surface. And that's also bad from a servicability perspective (have to buy the entire display assembly).

Which seems very weird, given how many different layers and materials already go into a lithium battery. Why is a small dab of glue so problematic?

It's almost as if the recyclers are too lazy to keep their processes up to date. Nah, couldn't be.

Perhaps the glue can generates toxic derivatives in the recycling process that can nullify the benefits of the process by itself.

I would be interested in your source for that. Batteries are already made of very many different materials, it’s not as though glue is some sort of special material. (The label of, say, AAA batteries is glued to the metal container. The label of the Li-Ion battery of my Nokia phone is also glued to the plastic container. Maybe Apple uses a bit more glue – but glue shouldn’t be something completely new in battery recycling.)