Not all laptops. The only I know of at the moment is Lenovo ThinkPads. The slice battery is like a dock for your laptop. You can dock the laptop onto the battery to extend its life. You can just leave it attached always as well. It's essentially adding a second battery to laptop, thereby doubling the battery life. Most other manufacturers require you to remove the existing battery and replace it with a new one if you want to extend the battery life. Lenovo lets you stack them live.
https://www.youtube.com/watch?v=3wYIHfjNA3A
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