The cobalt goes in the NCM lithium batteries.
It also goes in lots of other stuff, and is basically a byproduct of Congolese copper production.
The kids are doing artisinal mining because when capitalism doesn't need you to make money, you are pretty fucked. The big mines can make plenty of money with very few workers, leaving no need to build a decent civil society. Something to bear in mind for when our glorious AI future arrives.
Every chance that some countries become the Norway of AI and everyone is rich while others become the resource cursed Congo of AI and a tiny minority become rich and others are left to rot.