You can read about it here. Big hat tip to B Cole for sniffing this out.
Hitachi, Ltd. (NYSE:HIT / TSE:6501,hereinafter Hitachi) today announced that Hitachi, Ltd. and Hitachi Vehicle Energy, Ltd. which develops and manufactures lithium-ion batteries for automotive applications, such as hybrid electric vehicles, have developed a lithium-ion battery having the world's highest power density of 4,500W/kg, 1.7 times the output of the company's mass-produced, automotive lithium-ion batteries. Sampling of the new battery by domestic and overseas car manufacturers will start in the fall.
To reduce internal resistance, the battery employs a new manganese cathode and an original Hitachi battery structure, in such as thinner electrodes, power collection method and effective configurations to achieve the world's highest output.
The new battery will be on display at the Automotive Engineering Exposition 2009 held at PACIFICO Yokohama from May 20 to May 22. Right now.