I could be mistaken but I do believe you can throw a properly discharged lithium polymer battery in the trash, as there is nothing toxic in them. I don't think many laptops use LiPo though.
Most people have no idea what their discharged batteries are composed of or what is safe or not safe to throw with the rest of thrash and so good rule is to tell people to treat ALL batteries the same way.
I could be mistaken but I do believe you can throw a properly discharged lithium polymer battery in the trash, as there is nothing toxic in them. I don't think many laptops use LiPo though.