Nickel is not a cheap metal and NiFe batteries are not efficient[1]. Nickel is much more damaging to the environment to extract. LiFePO4 batteries have lifetim

Nickel is not a cheap metal and NiFe batteries are not efficient[1]. Nickel is much more damaging to the environment to extract. LiFePO4 batteries have lifetimes exceeding 15 years (no one really knows how long yet -- they were invented in 1996). Their efficiency is well above 90%. Its raw material costs are less than NiFe. [1] http://en.wikipedia.org/wiki/Nickel-iron_battery http://en.wikipedia.org/wiki/Nickel-iron_battery