[ The future of both electric vehicles and utility-scale energy storage are depending on lithium-ion batteries because of their high energy-density (though that is not as important for energy storage, but that’s where most research money is going).
This EPA study looked at the impact of several kinds of lithium-ion batteries, on resource depletion, global warming potential, acidification potential, eutrophication potential, ozone depletion potential, photochemical oxidation potential, ecological toxicity potential, human toxicity potential, occupation cancer hazard, occupational non-cancer hazard.
The lifetime of an auto li-ion battery was assumed to be 10 years, and that ways to recycle most of the materials will be found. Also, “Because the market for recovered and recycled material from lithium-ion batteries is not well developed for large battery packs, we assumed an optimistic scenario for the reuse and recycling of materials, essentially modeling all recovered materials as being directly reinserted into the applicable commodity market and displacing virgin materials”. The results are therefore optimistic, but the reader can decide how to modify the results to reflect current reality. Also, certain life-cycle stages were emphasized and characterized more than others.
A worst case scenario with a battery life of 5-years is presented on page 102: “Halving the lifetime of the battery has a significant adverse effect on impact categories, including occupational cancer and non-cancer, ecotoxicity, and ozone depletion.”
The paper has many interesting sections not covered below, i.e. how batteries are made, the energy used, the supply chains, and environmental impacts.
April 24, 2013. Application of Life- Cycle Assessment to Nanoscale Technology: Lithium-ion Batteries for Electric Vehicles. United States Environmental Protection Agency. 126 pages.
Below are sections from this paper:
The study showed that the 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.
A number of groups have quantified the life-cycle impacts of lithium-ion batteries for use in vehicle applications, based primarily on secondary data sources. In general, the results of this study are fairly similar to these prior LCA studies. In terms of upstream materials extraction and battery manufacture stages, our estimates of primary energy use and greenhouse gas emissions ranged from 870-2500 MJ/kWh.
As of 2007, batteries accounted for 25% of lithium resource consumption; this amount is projected to increase significantly.
Water is the main material input at 500-5400 kg/kWh (24-67% of total) and second is the lithium brine taken from saline lakes in Chile at 540-750 kg/kWh (9-28% of total). See page 70 for the other inputs, and page 72 for energy use, most of which comes from the materials extraction stage in the life cycle.
Lifetime of the battery is a significant determinant of impact results; halving the lifetime of the battery results effectively doubles the non-use stage impacts, resulting in substantial increases in global warming potential, acidification potential, ozone depletion potential, and photochemical oxidation potential (e.g., smog); this is true even for PHEV-40s batteries, which are 3.4 times smaller in terms of capacity.
Lithium-ion (Li-ion) batteries will be critical to improving the marketability of electric vehicles, due to their large energy storage capability in comparison to other types of batteries, including nickel-metal- hydride (Ni-MH) batteries primarily used in HEVs. The share of Ni-MH batteries is anticipated to decrease in proportion to Li-ion batteries as more PHEVs and EVs come on the market. Li-ion batteries in HEVs are expected to grow to 30% of the HEV fleet by 2015, and 70% by 2020 and the demand for automotive Li-ion batteries is projected to parallel the growth of PHEVs and EVs, growing from about 1 billion USD in 2010 to 30 billion USD by 2018.
Though the use stage of the battery dominates in most impact categories, upstream and production is non-negligible in all categories, and relatively important with regard to eutrophication potential, ozone depletion potential, ecological toxicity potential, and the occupational cancer and non-cancer hazard impact categories. The extraction and processing of metals, specifically aluminum used in the cathode and passive cooling system and steel used in the battery pack housing and battery management system (BMS), are key drivers of impacts.
Recovery of materials in the EOL stage significantly reduces overall life-cycle impacts, as the extraction and processing of virgin materials is a key contributor to impacts across battery chemistries. This is particularly the case for the cathode and battery components using metals (e.g., passive cooling system, BMS, pack housing and casing). Therefore, the analysis underscores the importance of curtailing the extraction of virgin lithium to preserve valuable resources and reduce environmental impacts.
Battery Chemistries, Components, and Materials
Across battery chemistries, the choice of active material for the cathode affects human health and toxicity results. For example, the nickel cobalt manganese lithium-ion (Li-NCM) chemistry relies on rare metals like cobalt and nickel, for which the data indicated significant non-cancer and cancer toxicity impact potential. The other two chemistries use the low er toxicity metals, manganese and iron.
The cathode active materials appear to all require large quantities of energy to manufacture. However, the Li-NCM cathode active material requires 1.4 to 1.5 times as much primary energy as the other two active materials.
The choice of materials for cell and battery casing and housing (e.g., steel or aluminum), which are primarily chosen for weight and strength considerations, are among the top process flow contributors to impacts in the upstream and manufacturing stages.
The battery chemistries used by the manufacturers include a lithium-manganese oxide, lithium-nickel-cobalt-manganese-oxide, and a lithium-iron phosphate chemistry.
The study assumes that the anticipated lifetime of the battery is the same as the anticipated lifetime of the vehicle for which it is used (10 years). Ten years is the anticipated lifetime the battery manufacturers seek to achieve. Therefore, our study assumes one ten-year Li -ion battery per vehicle life-time. There is uncertainty with respect to the actual lifetime of batteries in automobiles however.
- Raw materials extraction/acquisition. Activities related to the acquisition of natural resources, including mining non-renewable material, harvesting biomass, and transporting raw materials to processing facilities.
- Materials processing. Processing natural resources by reaction, separation, purification, and alteration steps in preparation for the manufacturing stage; and transporting processed materials to product manufacturing facilities.
- Product manufacture : Manufacture of components of battery cells and battery packs.
- Product use. Use of batteries in vehicles (PHEVs and EV s
- Final disposition/end-of -life (EOL): Recovery of the batteries at the end of their useful life.
Also included are the activities that are required to affect movement between the stages (e.g., transportation). The inputs (e.g., resources and energy) and outputs (e.g., product and waste) within each life cycle stage, as well as the interaction between each stage (e.g., transportation), are evaluated to determine the environmental impacts.
Battery recycling issues
Although metals are recovered from Li-ion batteries, they are currently not fed back into the battery cell manufacturing process. To do so, the recovered battery materials (including lithium) would need to be processed so they are “battery grade” which means they can be used as secondary material in the battery cell manufacturing process. However, there are a few key obstacles to achieving this goal, including:
- The battery manufacturers frequently modify their battery chemistries, which makes it difficult to incorporate recovered materials. This is especially a concern for EV batteries, which may be recovered 10 to 15 years after the battery is manufactured. The battery companies continually modify their chemistries to try to obtain market distinction and to improve charge capacity and energy density, which generate benefits in the use stage of the battery.
- The battery manufacturers are hesitant to use secondary materials, as they fear it will not be of high enough quality to meet the battery specifications required by the original equipment manufacturers (OEMs) that purchase the batteries and manufacture the vehicles.
Batteries may be capable of having a –second life or use as part of another product, such as to provide energy storage for an electricity grid; however, there is limited information on characterizing spent batteries in a secondary application, so the potential second life was not included in this study.
What a 22-26.5 lb (10-12 kg) Li-ion battery is made of
% Mass Component / Material (s)
15-24 Anode / Copper foil (collector) 1-12%, graphite/carbon 8-13%, polymer 1%, solvent 1-6%
29-39 Cathode / aluminum 4-9%, lithium 22-31%, polymer 1-3%, solvent 1-11%
2-3 Separator / polymer
3-20 Cell Casing / aluminum and polymer
8-15 Electrolyte / carbonate solvents 7-13%, lithium hexafluorophosphate 1-2%
2 Battery Management System / copper wiring 1%, steel 1%, printed wire board <1%
17-23 Battery Pack Casing/housing / polypropylene
17-20 Passive Cooling System / steel and aluminum.
In order to estimate transportation distances and impacts, assumptions are made with respect to where the raw materials will likely be obtained throughout the supply chain.
Overall, the LCA assumed that raw materials were obtained from where they are typically produced. For instance, we assumed that the basic lithium salts would come from Chile, cobalt and nickel would come from the Congo, battery-grade graphite would come from China, and the cathode active material would be obtained from Japan. Other, more common basic inputs were assumed to be globally sourced.
Materials and products produced or shipped domestically would be transported 95% by mass, at an average distance of 260 miles in a for-hire truck, and 5% by mass, at an average distance of 853 miles in railcars. The distance estimates are based on the U.S. Bureau of Labor Statistics “Hazmat Shipment by Mode of Transportation”.
Summary of results and conclusions
4.1 Battery Chemistry, Components, and Materials
Battery chemistry appears to influence the results in a number of impact categories, due to impacts associated with upstream materials extraction and processing, and energy use. Overall, the study found that the choice of active material for the cathode influences the results across most of the impact categories. For example, the Li-NCM chemistry relies on rare metals, such as cobalt and nickel, for which the data indicate significant non-cancer and cancer toxicity impact potential; this is reflected in the occupational hazard categories. The other two battery chemistries use the relatively lower toxicity metals, manganese and iron.
Other material choices also produce differences in impact results. One choice that stands out in particular is the use of aluminum in various battery components, from the cathode substrate to the cell casing. Battery chemistries that use larger quantities of aluminum, such as LiMnO2 and LiFePO4 , show distinctly higher potential for ozone depletion impacts than the battery chemistry that does not, Li-NCM. As discussed before, this is a direct outcome of the CFC 11 releases during the upstream processes that lead to aluminum end-products.
Energy use is another chemistry-specific driver. Across battery chemistries, the cathode is a dominant contributor to upstream and component manufacturing impacts. The cathode active materials appear to all require large quantities of energy to manufacture. However, the data indicate that the Li-NCM cathode active material requires approximately 50% more primary energy than the other two active materials.
4.2 Vehicle/Battery Type
In looking at the impacts for PHEV and EV Li-ion batteries, this study found that, in general, global warming potential is one of the few categories in which EV batteries show lower impacts than PHEV batteries; however, this is not unequivocal. A true net benefit in global warming potential for EV batteries only appears when the grid is not coal-centric, and battery production does not represent a substantial proportion of primary energy consumption (e.g., LiMnO2 . Drawing on the average U.S. grid, EV batteries show a small average net benefit over PHEV batteries across all battery chemistries (about 25 g CO 2 -eq./km). However, the electricity grid in Illinois, which is more representative of the Southeast, Appalachia, and Midwest, shows PHEV-40 batteries more favorable than EV batteries, on a GWP-basis. In other words, given present grid conditions, it might be preferable for people living in these regions to buy PHEV-40s if mitigation of global warming impacts are highly valued (based on assessment of the battery life cycle, including its use — not the entire vehicle).
Abiotic depletion and eutrophication potential impacts are the only other impact categories in which EV batteries show lower impacts; however, there are some caveats. Specifically, lower impacts for EV batteries are only evident in these categories when the grid is comp ri sed to a large extent of natural gas- based generation facilities, and battery production does not represent a substantial proportion of the overall primary energy use (e.g., for LiMnO 2 batteries). It is likely that most of the impacts across categories would be lower for EV batteries if the average electricity grid were less dependent on fossil fuels, and relied more on renewable sources of energy.
4.3 Life-Cycle Stages
Impacts vary significantly across life-cycle stages for all battery chemistries and vehicle battery types. Though the use stage of the battery dominates in nearly all impact categories, upstream materials extraction and processing and battery production are non-negligible in all categories, and are significant contributors to eutrophication potential, ozone depletion potential, ecological toxicity potential, and the occupational cancer and non-cancer hazard impact categories.
During the upstream materials extraction and processing stages, which are implicated in a number of impact categories, common metals drive stage-specific impacts. Aluminum used in manufacture of the cathode and passive cooling system comes up as a driver in a number of impact categories, especially in ozone depletion potential. Steel, which is used in the battery pack housing and BMS, is another metal that shows up in a number of different impact categories as a driver, including global warming potential and ecological toxicity potential, due to cyanide emissions.
Lifetime of the battery is a significant determinant of impact results, as it directly modifies the proportion of the impact attributable to all non-use stages. Halving the lifetime of the battery results in sizeable changes in global warming potential, acidification potential, ozone depletion potential, and photochemical oxidation potential (e.g., smog); this is true even for PHEV-40 batteries that are 3.4 times smaller in terms of capacity. Longevity by battery chemistry should be assessed in future research, because of the correlation of greater battery lifetimes with reduced environmental impacts.
4.5 Implications for the Electricity Grid
One factor that has the potential to significantly change the outcome of an electric vehicle battery LCA is the choice of average versus marginal electricity generation to generate impact estimates. U.S. LCI data and GaBi data currently apply an average mix of electricity generation for different regions. Though average electricity provisions may make more sense when thinking about the impact of battery product systems in static, long-run analyses, the electricity grid is subject to cyclical as well as structural changes in the distribution of underlying energy generation processes. Marginal generation considers the deployment of new technology that may draw a lot more electricity at different times from the electric grid. With the increase in use of electric cars, it will likely change the make-up of the grid from its current mix. So, it may be important to consider the “marginal” generation, instead of focusing only on the “average” generation. Accordingly, attribution of the average grid mix to battery charging may not accurately reflect the impact of the batteries on overall electricity production.
Key improvements needed
Increase the lifetime of the battery
- Reduce cobalt and nickel use (high toxicity)
- Reduce the percentage of metals by mass.
- Use recycled material
- Use a solvent-less process to make batteries
- Reassess manufacturing process and upstream materials selection to reduce primary energy use for the cathode.
The biggest contributor to most impact categories — larger in most cases than the upstream, and component and battery manufacturing stages combined — was the electricity grid. The sensitivity analysis conducted in the study showed that distinctive patterns emerged when electricity was derived primarily from coal (Illinois smart charging scenario), versus when it was derived primarily from natural gas (WECC and ISO-NE unconstrained charging).