Help with aluminum wires

I'm planning to add can lights in my basement the is a junction box that is all aluminum wires I found the hot that is

Feeding the old light switch with power but I'm planning to disconnect that wire from there and running all new copper wire too the new switch but I've been lookin how to cap off the old wire so that everything that is still running off the old wire but can seem to find how to do that properly without starting a fire