An electrochemical energy storage device, lithium super-battery, comprising a positive electrode, a negative electrode, a porous separator disposed between the two electrodes, and a lithium-containing electrolyte in physical contact with the two electrodes, wherein the positive electrode comprises a plurality of chemically functionalized nano graphene platelets (f-NGP) or exfoliated graphite having a functional group that reversibly reacts with a lithium atom or ion. In a preferred embodiment, a lithium super-battery having a f-NGP positive electrode and Li4Ti5O12 negative electrode exhibits a gravimetric energy ˜5 times higher than conventional supercapacitors and a power density ˜10 times higher than conventional lithium-ion batteries. This device has the best properties of both the lithium ion battery and the supercapacitor.