|The energy and power densities of the Lithium Ion Capacitor compared to other storage technologies. Click to enlarge.|
JM Energy, originally a 50-50 joint venture between MIPOX and JSR Corporation formed in August 2007 (now 100% owned by JSR Corporation), has developed a new lithium-ion capacitor (LIC) that combines the electrode coating technique of MIPOX’s ultra-fine coating technology and new material technologies of JSR Corporation. The new LIC offers about four times the energy density of a conventional electric double-layer capacitor (EDLC) and has a voltage of 3.8V, compared to the 2.5V of a conventional EDLC.
For automotive and transportation, JM Energy is targeting LIC usage in regenerative breaking as well as start/stop applications, among others.
|The electrochemical difference between EDLC and Lithium Ion Capacitors. Click to enlarge.|
The lithium-ion capacitor achieves its 4x increase in energy density by using a lithium-ion pre-doping technique to increase the capacity and lower the potential of the anode. JM Energy says safety testing shows that runaway heat reactions do not occur in the LIC because the electrode and electrolyte do not react significantly.
Capacitors are characterized by very long cycle life, high power density and instantaneous charge and discharge, but with low energy densities. The JM Energy LICs—the company is introducing two series initially based on capacitance (1100F and 2200F)—improves the energy density, offering volumetric density of 21-25 Wh/L, and gravimetric density of 12-14 Wh/kg.
The LICs feature a self-discharge of less than 5% after 3 months, and less than a 10% drop in capacity after 100,000 cycles.
|Basic properties of JM Energy LIC. Click to enlarge.|
JM Energy has begun LIC production at a pilot plant (10,000 cells per year) and is building a full-scale production facility scheduled for completion in October 2008.
A number of automakers and suppliers are investigating the potential of lithium-ion capacitors, notably Fuji Heavy for its Subaru vehicles. (Earlier post.)
Shibuya Hideki, Hato Yukinori, Hatozaki Osamu, Ando Nobuo, Kojima Kenji, Tasaki Shink’ichi, Miyagawa Risa (2006) Lithium Ion Capacitor Pre-doping and High Performance. Subaru Technical Review, No. 33, pages 80-87