I've dissembled a Nokia BL-5F battery, which i thought is a fake one.
The battery has been used only several days, but i can see it has a seriously unshaped. The only thing i could certain is the core of it had wore out.
Tore off the sticky paper of the battery carefully, we will find a metal sealed core. That's it.
Due to this sucked quality core, the user will risking his life while using it.