Invited Presentation: Innovative Batteries for Sustainable Mobility

The rapid economic growth, the ever-increasing populations and the increase in the number of vehicles have accelerated the consumption of fossil fuels in the world; automobile industries are now expected to tackle with reduction of CO₂ emissions by developing vehicles driven by sustainable energy sources such as hybrid vehicles (HVs), plug-in hybrid vehicles (PHVs), electric vehicles (EVs) and fuel-cell hybrid vehicles (FCHVs).  Since Toyota Motor Corporation introduced the first-generation Prius in 1997, we have sold more than 3 million HVs with 17 models all over the world, reducing CO₂ emissions by 14 million tons (as of May 2010).  And now, we are going to develop next-generation vehicles with more energy efficiency; for this reason we need to develop innovative batteries with higher energy densities than traditional batteries.  Figure 1 represents a rough sketch of Ragone plots for traditional Ni-MH and Li-ion batteries together with next-generation batteries such as all-solid-state batteries and Li-air batteries.  Although we have already developed prototype cells of all-solid-state batteries and Li-air batteries with energy densities of 400 Wh/L and 1000 Wh/L, respectively, it is also true that there are still many issues to be overcome until their practical application.  In the presentation, we will overview our recent effort on developing innovative batteries.