Much of the material (lithium, cobalt, nickel, copper) in an EV battery can be recycled, although it is, at the moment, pricey. That will surely change as the number of batteries available for recycling increases. The batteries also can be repurposed (storing energy from solar panels, for example) once they can no longer hold enough charge for automotive use. From what I've read, Nissan is using old Leaf batteries to power streetlights in Japan, and GM is using old Volt packs for power backup.
What's more, EV batteries have shown remarkable longevity -- those in, say, the first-gen electric RAV 4 and Honda Insight hybrids are still plugging along.