High performance nickel-metal hydride and lithium-ion batteries

The development of high performance traction batteries is a key issue for the future market acceptance of electric and hybrid vehicles. Tile Nickel-Metal Hydride (NiMH) system is besides Lithium-Ion (Li-Ion) the most promising battery system for electric vehicles. NiMH batteries have already penetrated the consumer market worldwide. Due to its high design flexibility and robustness the NiMH battery system is an ideal candidate for the whale range of battery applications from small consumer cells up to large traction batteries. Because of its high power capability for charging and discharging, the NiMH system is regarded as the optimum battery system for hybrid vehicles. VARTA is developing three different NiMH product lines: high energy, high power and ultra-high power cells. The specific energy of these products exceeds 80 Wh/kg (high energy cells) and a specific power of more than 1000 W/kg (ultra high power cells) can be achieved. Since the first announcement of commercialization of Li-Ion as a rechargeable consumer battery in 1991 by SONY, the Li-Ion technology has seen an unprecedented rise to what is now considered to be the most promising rechargeable battery technology of the future. Not only in the consumer sector where Li-Ion type batteries have gained already a substantial market share but also for applications such as electric vehicles, load leveling and aerospace systems this technology is under intense development. The most prominent feature of the Li-Ion battery system is its high gravimetric and volumetric energy density. Although still in the early stage of development, large prismatic Li-Ion cells reach specific energies of more than 120 Wh/kg and energy densities over 300 Wh/l. There is a predicted potential for a further increase of the specific energy of more than 30 % and for the energy density of above 60 % during the next 4 years. The system works within a wide temperature range of -20 to +60 degrees C and can run up to 1200 cycles. The Li-Ion system represents the latest battery technology. It is expected to be the dominating technology for electric vehicles and aerospace applications. Therefore, VARTA has developed large prismatic cells up to 240 Wh employing low cost manganese spinell cathodes and carbon anodes. This talk describes VARTA's high performance NiMH and Li-Ion cells as well as complete batteries.