Instead of using lithium ion, has anyone at Tesla considered using Reformed Methanol Fuel Cells (RMFC)? There's a company out there called Ultracell that has a portable version of this fuel cell that can power electronics. Couldn't this be scaled up and used in a Tesla?
Rather than having to recharge a battery, a car could just be filled up with a methanol/water mix. No need to wait for batteries to recharge. I'm not sure what the wearable parts are in this kind of fuel cell, but the bonus of no charging time should be pretty cool.