Japan's JNC
reports that Sony has a new line-up of lithium-ion batteries, boasting the industry's highest level of energy density:
The G8 Series, a cylindrical lithium ion battery with a diameter of 18mm and height of 65mm, offers a high capacity with 2550mAh (a 6% increase from the conventional battery) while the A8 series, a a lithium ion polymer battery offers a power supply of 830mAh (a 9% increase from Sony's conventional model of the same size). Both are geared towards mobile products, and shipment will start from December 2004 onwards.
A 2550mAh definitely sounds great, but somehow it is hard to imagine a 18mm x 65mm battery inside a handheld.