LondonA ferrite-graphene cell held 86.53 Wh/kg at supercapacitor-level power.
Cheap, cobalt-free ferrites could give grids fast-response buffering without battery chemistry.
One electrode stores charge electrostatically, the other through fast surface redox, widening the voltage window.
The device held 10,000 cycles, but researchers tested only a coin cell, not a product.
Sources: Nature