There comes a time when a lithium ion battery is no longer suitable for use in an electric car. It comes down to the difference in power and energy. Energy is the ability to do work. Power is the ability to do work quickly. The battery in an electric car has to be able to do both. Over time, the battery may have plenty of energy remaining but very little power.
It stands to reason that there will be a lots and lots of lithium ion batteries in the future that have enough remaining energy to serve as storage batteries for residential, commercial, or even grid scale use. Why not just remove them from the cars they were originally installed in and put them to use as storage batteries? A recent study by Lux Research looked at the question and decided it makes more economic sense to recycle used batteries rather than re-purpose them.
According to Lux Research, reused plug-in electric vehicle batteries will “deliver questionable returns on account of reduced performance, limiting them to application with less frequent and shallower depth of discharge cycles. With present technology, recycling old batteries for new materials is the more economical option for creating the most value from existing materials,” stated Christopher Robinson, Lux Research Associate, and lead author of the new report. “That said, innovations in areas like packaging and testing could tip the balance in the future, so companies should have plans for both recycling and reuse.”
The findings are in line with the thoughts of JB Struubel, chief technology officer of Tesla Motors. Earlier this year, he said his company has examined this question and decided that recycling is the best approach.
“We’ve looked at reuse or kind of the second life of automotive batteries for grid applications very closely, and you know, ultimately, every time we’ve studied this we’ve come to the conclusion that it’s not a very economical or very good use of those assets.
“You know, by the time they come out of a vehicle that’s lived its life, the technology will be quite old. We expect 10 maybe 15 year life at a minimum from these batteries. And, you know, the degradation is not entirely linear. By the end of their life, the efficiency has degraded on every cycle, you see lower efficiency, the capacity will have somewhat degraded, and for a lot of reasons, it makes it very difficult to deploy those efficiently back into a grid setting, where you want high reliability and you do want predictability.
“So, my view is that we’ll see new batteries dedicated to that market, that also have slightly different characteristics — they should have higher cycle life. In an electric vehicle that has 200+ miles of range, you don’t need as many cycles as you do on a battery that’s designed to charge and discharge every single day on the grid. There’s perhaps a factor of about 4 or 5 difference in the cycle life — so that’s one aspect.”
Lux Research offers the example of an 11.2 kilowatt-hour home energy storage system composed of second-life electric vehicle batteries. Such a system would cost $4,600 using repurposed batteries. A 7 kilowatt-hour system using new batteries would cost $6,000. But with round-trip efficiency and cycle life factored in, the system that uses new batteries is the better option once all the numbers are crunched according to Lux. Here are more specifics from the Lux study:
- Recycling technologies are varied. Of all the recycling technologies, pyrometallurgical processing, or smelting, is the most mature and can recover key metallic elements. Mechanical processing can recover valuable cathode materials directly, and hydrometallurgical processing can be lower cost.
- Tesla backs recycling. Automakers are choosing a wide array of applications for reuse of batteries. BMW and Nissan are commercializing residential storage products, while Daimler has started operating a large 13 MWh system. Tesla, on the other hand, pursues recycling as its NCA cathodes are not suitable for most stationary storage needs.
- Reuse options are limited. Second-life batteries offer only limited cost savings, especially as new cell prices continue to fall. Still, with more efficient testing, sorting, and repackaging, second-life systems could be made more competitive for applications like demand response and backup power.
Lux Research estimates that by 2035 some 65 gigawatt-hours worth of batteries will be retired from service every year.
Source: Cleantechnica Image credit: Lux Research