Hi all. I was wondering, are lithium-ion batteries the best type of batteries for electric vehicles? I also remember watching a video of Elon Musk (from Tesla Motors and SpaceX) claiming that lithium-ion batteries are increasing their energy density by 8 to 9 percent every year. I googled this number and couldn't find any info on it. That seems unbelievably high. If lithium-ion batteries are becoming that much better so quickly, it seems like we could have an electric 747 flying in the sky sometime in the next 50 to 100 years.