Development of a Lithium-Type Advanced Energy Storage Device

We have developed a device using a novel composite material as the negative electrode and ordinary activated carbon as the positive electrode. The composite material was obtained by heat-treatment of activated carbon with pitch. The structure of this composite was shown to be amorphous based on the X-ray diffraction pattern, and the surface area decreased from 2200 m 2 /g (activated carbon) to 250 m 2 /g (composite). This device can discharge at an extremely high current density of 10,000 mA/g based on the composite weight. The power density of around 2.2 kW/L was two times higher than EDLCs, and the energy density of around 20 Wh/L was three times higher. The discharge capacity maintained its initial capacity for at least 100,000 cycles. This device also had excellent storage characteristics at 60°C. © 2004 The Electrochemical Society. All rights reserved.