Monday, March 10, 2014

Getting better battery range in your EV

Right now, range anxiety and price are still the main barriers to entry for most people looking at electric cars. The batteries don't charge fast enough and there's no battery-swap capability which leads many - myself included - to still shy away from a fully electric car because there's the nagging "what if" problem. Sure my EV has a range of 80 miles - plenty for a day's driving or more, usually. But "what if" I need to go a couple of extra errands? Blam. Dead, with no way to get home and no way to recharge. In a petrol car, that's not a problem - fill up and keep going.
Battery capacity has been slow to catch up with the needs of electric vehicles but there's a possibility that could change. A couple of weeks ago, researchers at UNC Chapel Hill stumbled on a discovery whilst trying to design a material to keep sea life from sticking to boat hulls. Lithium-Ion batteries - the most common type used today - are great but do rather have a habit of going up in flames. The discovery made in Chapel Hill would replace the unstable, fire-prone chemicals in the electrolyte with a very stable polymer instead. It's called perfluoropolyether (PFPE) and it dissolves lithium salt - something required to produce conductivity in batteries. Most polymers don't mix with salt, but this one does and as a bonus, it's nonflammable.
So why is this important? Well the entire way a battery works is by moving ions around between the electrode and cathode, the direction being dependent on whether the battery is being charged or discharged. The rate of movement of the ions is called "transference rate" and typically it's around 0.2 for the average Li-Ion battery. The PFPE electrolyte, however, has a transference rate closer to 0.9. Not only that but it has an operating temperature range of -90°C to +200°C - far lower and higher than you'd ever find in a passenger car in daily use.
So what does this mean? Simple - higher transference means better capacity, meaning a Volt or a Tesla could instantaneously get over a 4x increase in range by using batteries with a PFPE electrolyte.
Range anxiety will still be there, but quadrupling the mileage means that odd unexpected errands and diversion will no longer be cause for concern.
Now if we could get swappable PFPE Li-Ion battery packs for cars - 600 mile range and instant swapover? THEN we'll see mass market adoption because at that point, road trips and long-distance journeys become possible without having to stop every 150 miles or so to hang around a charging station for an hour or more.