i see very little reason to believe they are. For instance the batteries for most smartphones made in the DRC are done under awful conditions for some miners, and amnesty international found LG don't give a damn. Actually no brand seems to be doing much about artisinal miners apart from Apple according to Amnesty, an independent charity representing miners in africa in this case.

Batteries are of course in every phone and an important part of the supply chain. So I think the amount of care brands have for the miners is quite indicative