Following years of hype and underwhelming products, the plug-in vehicle market had a breakout year in 2016. Not only do consumers now have the option to buy an electric vehicle with more than 200 miles of range and pay less than US$40,000, but the year was littered with announcements of automotive OEMs committing serious resources to building their own electric vehicles – and not just compliance cars. Cost reduction in Li-ion batteries has enabled this revolution, as have better performing batteries optimised specifically for electric vehicles. Increasing Li-ion demand will help to continue to lower energy storage costs, but also bring up an important issue: what should be done with the batteries after they are used in vehicles?
Historically batteries are recycled, and the lead-acid battery remains one of the most recycled products humans produce, but the high cost of processing most Li-ion chemistries makes this process unprofitable. This has fostered interest in reusing batteries for other applications, mostly for stationary energy storage applications, which would delay but not eliminate the need for battery recycling. On the surface this seem like an excellent opportunity to recapture value that would otherwise be wasted in Li-ion recycling batteries. While this is true in some applications, there are several reasons why reusing EV batteries is not ideal for most stationary energy storage applications.
Complexities of second-life use
Reusing Li-ion batteries in second-life applications is not as simple as removing a battery from a vehicle then installing it directly into a stationary system. Before a battery can be reused, it first must be manually removed from a vehicle and the pack disassembled into individual cells. The cells must then be tested to determine the battery’s state of health, sending batteries without sufficient remaining capacity to be recycled. Even within the batteries suitable for reuse, cells must be sorted by similar remaining capacity, or else the second-life system performance would suffer. These are labor and energy intensive processes, but efforts in both academia and industry are underway to reduce costs. Introducing automation in the process will reduce time and labor costs, as will convincing battery manufacturers to use clearer labels and design for disassembly.
Even with better processing techniques there are some limitations to our current understanding of the second-life battery opportunity. As the first mass-market electric vehicle was released about six years ago, and few vehicles have reached the end of their life, there isn’t a clear indication of how much remaining capacity can be expected from these batteries after typical use. There will be further variation among the different chemistries being used in the Li-ion batteries: the nickel cobalt aluminum oxide (NCA) batteries preferred by Tesla are unsuitable for most stationary applications, even when new, due to poor cycling characteristics. Other chemistries such as lithium iron phosphate (LFP) and nickel manganese cobalt oxide (NMC) preferred by other manufacturers in batteries made by LG Chem, Samsung SDI and BYD are better suited for second-life applications.