Rumors suggest that the iPhone 16 may use a graphene heat sink and a metal battery case to promote better heat transfer.
This follows complaints by iPhone 15 users about overheating, which Apple fixed via software, but the iPhone 16 is rumored to have a hardware solution, too. Apple associated the overheating with poorly optimized software and issued a software fix, but more effective cooling may also help.
The iPhone has no fan, so heat has to be dissipated through the device frame into the air using passive heat transfer. Heat sinks remove heat from undesirable areas by having a more efficient thermal conduction value than the materials around it. Graphene could perform better than the existing cooling mechanism, thus allowing the iPhone to deal with more heat more efficiently.
Graphene-based cooling technology is already in commercial use in various devices, cell phones included. Examples of cell phones that use graphene thermal management tech include realme's GT 2 series, ZTE's Axon 30, Xiaomi's Mi 10 Ultra, various Huawei phones and more.