| abstract |
The present invention relates to a hybrid electrical energy storage system, which comprises a first electrode in which a first electrode layer is formed on a first current collector, a second electrode in which a second electrode layer is formed on a second current collector and an electrolyte. The hybrid electrical energy storage system of the present invention is characterized in that the first electrode layer comprises graphite, the second electrode layer comprises a lithium metal oxide in addition to an activated carbon, the first electrode stores energy though redox reaction, and the second electrode stores energy through both electric double layer reaction by the activated carbon and redox reaction of the lithium metal oxide. The lithium metal oxide added in the second electrode layer should satisfy the following conditions: (1) The lithium ions should be able to be intercalated and deintercalated reversibly by redox reactions; and (2) The reversible intercalation/deintercalation of the lithium ion by the redox reactions should occur within the electric double layer reaction potential of the activated carbon. The hybrid electrical energy storage system in accordance with the present invention offers an operating voltage of about 4 V and a high output. Moreover, differently from the conventional graphite/activated carbon hybrid electrical energy storage system, the hybrid electrical energy storage system in accordance with the present invention does not experience abrupt voltage rise or drop at the graphite electrode, thereby having improved discharging efficiency. |