The US Environmental Protection Agency has recently published a life cycle assessment of lithium-ion batteries such as are used in many electric and hybrid vehicles. In addition to providing advice on environmentally desirable improvements to battery design and systems, the study is an excellent illustration of one of the important uses of LCA – determining the steps necessary to reduce the environmental footprint of our activities and technologies.
While the study did not compare electric vehicle batteries with other systems for powering vehicles, comparison of the data in this report with other published information does indicate that vehicle batteries have a smaller environmental footprint than other vehicle energy systems, though use of coal-based electricity for charging the batteries significantly increases their environmental footprint.
Findings of this study include:
- Vehicle batteries that use cathodes with nickel and cobalt, as well as solvent-based electrode processing, have the highest potential for environmental impacts. These impacts include resource depletion, global warming, ecological toxicity, and human health impacts. The largest contributing processes include those associated with the production, processing, and use of cobalt and nickel metal compounds, which may cause adverse respiratory, pulmonary, and neurological effects in those exposed. Environmental improvements to technologies and manufacturing processes can help reduce these impacts.
- Global warming potential and other environmental and health impacts are influenced by the source of the electricity used to charge the batteries prior to vehicle operation. Specifically, the study results indicate that the use stage is an important driver of impacts for the life cycle of the battery, particularly when batteries are used with more carbon-intensive sources of electricity.
- Single-walled carbon nanotube (SWCNT) anode technology shows promise for improving the energy density and ultimate performance of Li-ion batteries in vehicles. However, the energy needed to produce these anodes in these early stages of development is significant (i.e., may outweigh potential energy efficiency benefits in the use stage). If researchers focus on reducing the energy intensity of the manufacturing process before commercialization, the overall environmental profile of the technology has the potential to improve dramatically.
- Current recycling processes do not recycle large volumes of Li-ion batteries for vehicles at present.
Opportunities for improvement include:
- Increase the lifetime of the battery.
- Reduce cobalt and nickel material use.
- Reduce the percentage of metals by mass.
- Incorporate recovered material in the production of the battery.
- Use a solvent-less process in battery manufacturing.
- Reassess manufacturing process and upstream materials selection to reduce primary energy use for the cathode.
A brief project description is available at http://www.epa.gov/dfe/pubs/projects/lbnp/
The full 115 page report is available at http://www.epa.gov/dfe/pubs/projects/lbnp/final-li-ion-battery-lca-report.pdf