US Patent 8663841 Power storage device

A power storage device in which charge capacity and discharge capacity are high and deterioration in battery characteristics due to charge/discharge is small is provided. A power storage device in which charge capacity and discharge capacity are high and output characteristics are excellent is provided. A power storage device in which charge capacity and discharge capacity are high and cycle characteristics are excellent is provided. A power storage device includes a negative electrode. The negative electrode includes a current collector, an active material including a plurality of protrusions protruding from the current collector and an outer shell in contact with and attached to surfaces of the plurality of protrusions, and graphene in contact with and attached to the outer shell. Axes of the plurality of protrusions are oriented in the same direction. A common portion may be provided between the current collector and the plurality of protrusions.