LowCost HighPerformance Battery for StartStop Applications

For use in congested traffic, start stop vehicle technology (microhybrid) offers the promise of significant increases in fuel economy and reduction of pollutant emissions, without large increase in the vehicle sales price. A key enabling component of the start stop system is the battery. Present start stop systems employ lead acid batteries because of their low initial cost and excellent low temperature performance, but these batteries suffer from life limitations especially when subjected to repeated deep cycling and high charge rates. Consequently, alternate battery systems with improved life characteristics are the key to enable widespread adoption of start stop vehicles. Liion technology is the leading candidate to replace lead acid batteries in start stop systems and several battery companies have announced Liion batteries for start stop applications. However, most Liion battery systems offered today suffer from one or more disadvantages such as poor low temperature performance, poor high rate charge acceptance, or high cost relative to lead acid batteries. This is at least in part because the materials in these batteries are not optimized for the specific requirements of start stop applications. TIAX is developing Liion technology for start stop applications that overcomes the limitations of the current Liion systems by tailoring its proprietary CAM7 cathode material for use opposite lithium titanate anode (LTO) anode in pouch cells that provide excellent cold cranking capability, elevated temperature stability, cycle life and safety for 12V start stop batteries. In Phase I, TIAX showed that CAM7 cathode/LTO anode pouch cell technology provides excellent 30 °C cold cranking capability and elevated temperature stability (without pouch cell gassing/swelling), that the performance could be improved by CAM7 material modifications that specifically targeted the start/stop implementation, and that CAM7 cells had superior performance to competing cathodes. In Phase II we will optimize the CAM7 material and the cathode and anode electrode designs for the 12V start stop battery application. We will develop a cell design for 12V start stop batteries based on automobile company input and our internal results. We will assemble scaled versions of these cells into 12V modules that achieve USABC 12V start stop vehicle battery stability and scaled power and energy targets, and we will demonstrate the excellent abuse tolerance of these cells under standard thermal, electrical and mechanical abuse tests. The TIAX start stop battery technology will facilitate widespread commercialization of start stop microHEVs by enhancing the available energy, dynamic charge acceptance, and life of Liion batteries used in microHEVs. Rapid, widespread adoption of affordable microHEVs in traffic congested areas of the country can yield benefits including reduced adverse health impacts from pollution in urban and other high traffic areas, reduced adverse environmental and economic impacts of global warming, and reduced economic impacts of fluctuations in global petroleum supply and price. Key Words Start stop vehicle battery, microhybrid vehicle battery, lithiumion. TIAX is developing low cost microhybrid vehicle battery technology that will facilitate widespread commercialization of start stop vehicles by presenting a compelling value proposition for drivers in congested traffic areas. This will reduce the fuel consumption and pollutant emission associated with idling in traffic, yielding public health, environmental quality, and economic benefits.