
Energy density for lithium-ion cells in electric cars has been improving at a rate of roughly 7% a year. But that rule, which has held for consumer cells for decades might be thrown to the wayside if a remark from CEO Elon Musk holds true. He noted that cells with 400 Wh/kg, produced in volume, might be just 3-4 years away. 400 Wh/kg *with* high...