Quantum Scape -
http://www.quantumscape.com/ - A secretive start-up company in Silicon Valley (where it's popular to be a secretive start-up) focusing on electric vehicle batteries. The batteries are supposed to have the energy density of gasoline The Valley's next big battery play: QuantumScape which would be amazing if possible. The company's technology is licensed from Stanford University, and uses a new method for stacking trace amounts of materials together, which can lead to high energy and power densities, and also higher cycle life than standard lithium ion batteries. Khosla Ventures lists QuantumScape on its website as an investment.
Researchers at Stanford University seek to develop an "All-Electron Battery" that would enable a completely new class of electrical energy storage devices for electric vehicles. The All-Electron Battery has the potential to provide ultra-high energy and power densities, while enabling extremely high cycle life. This novel battery stores energy by moving electrons, rather than ions, and uses electron/hole redox instead of capacitive polarization of a double-layer. This technology uses a novel architecture that has potential for very high energy density because it decouples the two functions of capacitors: charge separation and breakdown strength. If successful, this project will develop a completely new paradigm in energy storage for electric vehicles that could revolutionize the electric vehicle industry.
TBD [[[ Envia Systems promises 400 Wh/kg lithium ion batteries ]]] is a start-up company in Newark, CA targeting a 400 Wh/kg energy density at $125/kWh cost. They are expecting commercialization by 2014-5ish or so. If this pans out, it will more than double energy density and drastically lower the cost of lithium ion battery packs.
Peacebay Power Co, Ltd.
http://www.peacebay.com/ "...the super high energy and reliable Ni-MH rechargeable battery manufacturer, that meets your every requirement for the battery power. Based in Tianjin China, Peacebay has provided the high quality products to many countries around the world. The world-class production facilities, strong technical support and intelligent people build Peacebay into one of the best-reputed Ni-MH rechargeable battery manufacturers in China. ... "
http://www.pwtcbattery.com/ - Power Technology Incorporated - The web site doesn't contain enough detail, but it discusses using lead but being lighter than conventional batteries. They have patents so those ought to be tracked down (see this page).
http://a123systems.com has developed a Lithium ION battery cell. They claim 100C peak discharges and 5 minute recharges. Unfortunately their site is a little weak on details.
