For example, batteries that operate for extended periods at temperatures outside of standard operating conditions will degrade more rapidly. An electric vehicle battery is considered to have reached the end of its lifespan when its State of Health (SOH) reaches 70% to 80% (or 70% to 80% of its rated capacity). At this point, the battery may no longer be suitable for electric vehicles. Instead of discarding these batteries and wasting their remaining value, these retired batteries could be used for secondary applications with lower requirements than electric vehicles. This could include stationary energy storage or low-power electric vehicle applications.
Considerations for Battery Recyclers
Recyclers in the industry obtain lithium-ion electric vehicle batteries from automotive OEMs, typically with agreed-upon minimum state of harm (SOH). These recyclers may still conduct their own SOH and electrochemical impedance spectroscopy (EIS) tests. Batteries with low SOH and high internal resistance may not be suitable for reuse. These parameters can be estimated by extracting and processing data from the battery management system, or using machine learning or physics-based modeling techniques. Depending on the technology and the number of batteries to be tested, this can be a time-consuming process, thus increasing recycling costs.
Another crucial consideration is whether to disassemble the battery at the cell level or integrate it into the battery pack level. Disassembling to the cell level allows the best-performing cells to be used in new arrangements, making the rechargeable battery more competitive in performance with new lithium-ion stationary batteries. However, disassembling battery packs is not a simple task, and due to differences in battery pack designs between automotive OEMs, skilled labor is required to perform this safely. Therefore, manual labor is a key factor affecting reuse costs.
Due to the increased complexity and cost of disassembly, most recycling startups in North America and Europe are integrating retired electric vehicle batteries into battery packs for stationary storage applications. In some cases, battery packs from different OEMs can be connected in parallel to create larger kilowatt-hour to megawatt-hour containerized systems. This also provides recyclers with some advantages in terms of EV battery supplier flexibility. However, the performance of a battery pack will be limited by the worst-performing battery, so recyclers rely on OEMs to provide them with battery packs with pre-specified performance characteristics. Furthermore, recyclers will rely more heavily on battery analytics tools (rather than on battery operators relying on new batteries) to closely monitor battery performance. Additionally, because these batteries age and degrade during their initial use in electric vehicles, some battery packs are likely to fail before the intended lifespan of the stationary storage project. Recyclers must ensure they can replace these batteries with other rechargeable batteries of similar performance, which increases the overall cost of the project or service.
Mid-term electric vehicle battery design trends
Several emerging trends in electric vehicle battery pack design may offer opportunities for reusing higher-performance secondary systems at a lower cost, thus helping secondary batteries become more competitive with new lithium-ion batteries in stationary energy storage applications. The first of these trends is OEMs adopting battery-to-pack or battery-to-chassis designs for electric vehicles. Battery-to-pack designs, instead of being divided into several modules, stack the batteries together to reduce unnecessary materials and weight, thereby increasing the energy density of the battery pack. This also simplifies the manufacturing process and reduces costs. The absence of modules reduces the time recyclers spend disassembling to the battery level, thus lowering reuse costs. However, battery-to-chassis electric vehicle battery packs are structural components of the vehicle, so removing them can be a more challenging task. This is detrimental to recyclers.
The second trend is the use of larger battery sizes in electric vehicles. This simply reduces the total number of batteries in a battery pack, thus reducing the time required to remove them down to the battery level. The third trend is the increase in the average battery size of electric vehicles, resulting in increased driving range. Larger batteries have a lower depth of discharge per duty cycle, reducing battery degradation over time. Therefore, if retired after a given warranty period (mileage or years of use), more batteries can be retired with a higher State of Hypothesis (SOH) rather than when the battery reaches 70% to 80% SOH. This trend may be more applicable to the large electric vehicle batteries used in trucks or buses. These vehicles typically have greater range requirements than passenger electric vehicles, so if the battery SOH exceeds 90%, it may be forced to retire. While this may not necessarily happen now, recyclers may plan to procure such batteries in the near future to facilitate the remanufacturing of better-performing secondary systems.
prospect
Currently, most recyclers are integrating retired electric vehicle batteries into battery packs for secondary stationary energy storage applications. This avoids complex dismantling procedures and higher reuse costs. However, a drawback is that the performance of the secondary stationary energy storage system may be worse, as battery performance is limited by the worst-performing cell. Battery-level dismantling takes longer, and differences in battery pack design between OEMs further complicate this process. However, trends such as battery-to-pack and larger battery form factors may help reduce dismantling time to the battery level. This will reduce the cost for recyclers to design higher-performance secondary stationary energy storage batteries. Furthermore, this will make these systems more competitive with new lithium-ion stationary energy storage batteries in terms of both cost and performance.
The electric vehicle battery resale market is still in its infancy, with a few startups in North America and Europe primarily responsible for several pilot projects. In fact, only 11 GWh of resale batteries are projected to be installed globally by 2030, while the global demand for lithium-ion stationary energy storage that year is estimated at approximately 235 GWh. Most of the trends discussed are likely to benefit the resale market in the long run, thus promoting faster market growth. However, these trends are not driven by demand from the resale market itself, but rather by the need for improved electric vehicle battery performance. Resellers must adapt to these trends if they wish to produce cheaper, higher-performing resale battery systems.
