Ford, LG Chem team reports 1st cradle-to-gate LCA for mass-produced battery pack in commercial BEV; cell manufacturing key GHG contributor
A team from Ford’s Research and Innovation Center and LG Chem’s Corporate R&D group has reported the first cradle-to-gate (i.e., the factory gate—before delivery to the consumer) emissions assessment for a mass-produced battery in a commercial battery electric vehicle (BEV)—the lithium-ion battery pack used in the Ford Focus BEV. Their paper is published in the ACS journal Environmental Science & Technology.
The researchers based their assessment on the bill of materials and energy and materials input data from the battery cell and pack supplier (LG). They calculated that the cradle-to-gate greenhouse gas (GHG) emissions for the 24 kWh Ford Focus lithium-ion battery are 3.4 metric tonnes of CO2-eq (140 kg CO2-eq per kWh or 11 kg CO2-eq per kg of battery). Cell manufacturing is the key contributor accounting for 45% of the GHG emissions.
Extending the system boundary to include the entire vehicle, they estimated a 39% increase in the cradle-to-gate GHG emissions of the Focus BEV compared to the Focus internal combustion engine vehicle (ICEV), which falls within the range of literature estimates of 27–63% increases for hypothetical non-production BEVs.
A number of LCAs [life cycle assessments] have been conducted to understand the benefits of electric mobility. Most studies have focused on the vehicle use phase, particularly on the grid mix that powers PHEVs and BEVs as it is a key determinant of emissions and energy use. However, it is important to also include the environmental impact of electrified vehicle (EV) powertrain production especially the traction battery which is energy intensive to produce. Energy use and greenhouse gas (GHG) emissions associated with EV battery production are not well established.—Kim et al.
The battery pack in the Focus Electric consists of 430 cells with a nominal voltage of 3.7 V and has a specific energy of 0.08 kWh/kg. LG Chem in South Korea provides the cells, while Piston Group in Michigan manufactures the final pack.
The cradle-to-gate assessment covers battery materials production, cell and component manufacturing, and battery pack assembly, including transportation.
The cathode material is a mixture of LMO/NCM, which is combined with solven, binder and conductive carbon to make a cathode slurry. The anode uses an aqueous slurry system, and combines the active material graphite with a mixture of styrene butadiene rubber (SBR) and carboxymethyl cellulose (CMC). The slurry mixtures are coated and dried onto aluminum and copper current collectors.
Cathodes and anodes are assembled in stacks, separated by a ceramic coated polyolefin separator, and tabbed. The electrode stacks are packaged into laminated aluminum pouches and injected with electrolyte. Most of the electrode production and cell assembly operations are housed in a dry room with stringent air filtration requirements.
Cells are cycled and stored at different temperatures during the formation step and, after degassing and resealing processes, the formed cells are tested before being shipped out for pack manufacturing.
Pack manufacturing combines the cells and the balance of battery (electrical system including sensors, battery management system (BMS), thermal management system, and enclosure) into the final pack.
Cell materials account for 55% of the total mass; electrodes and collectors represent 73% of the cell mass. Steel used mostly for structural integrity and battery enclosure comprises 30% of the total mass. Plastics and composites (8%) are used in the enclosures and module components while nonferrous metals such as copper and aluminum alloys (3%) are used for the electrical architecture (bus bars, wiring etc.) and thermal management system. The BMS which consists of printed circuit board, electronics, and wiring harness accounts for the remaining 4% of the battery mass.
Running second to cell manufacturing as a leading contributor of GHG emissions, producing and manufacturing the cell materials and components including cathode, anode, current collectors, electrolyte, separator, and pouch materials accounted for 19% of the GHG emissions. Module and pack enclosures, electrical system wiring and components, and thermal manage- ment system account for 22% of the cradle-to-gate GHG emissions.
Similar to GHG emissions, cell manufacturing, cell components, and battery enclosure dominate criteria pollutant emissions, accounting for 82%−92% depending on pollutant.
|Cradle-to-gate GHG emissions for ICEVs and BEVs from different studies, including the current Ford/LG work. Credit: ACS, Kim et al. Click to enlarge.|
Despite their higher cradle-to-gate GHG emissions, switching from ICEVs to BEVs potentially saves a large amount of GHG emissions during their life cycle. Published studies have estimated approximately 30−40% life cycle GHG emissions reduction for BEVs powered by the average US or European electric grid mix.
Using our GHG estimate for BEV battery production, 11 kg CO2-eq/kg battery, in place of those in the literature gives an estimate of 31−37% life cycle GHG benefits for BEVs over gasoline ICEVs. Our results confirm the potential for BEVs to curb GHG emissions from the transportation sector.
Current trends of increasing vehicle energy efficiency, decreasing burdens associated with battery production, decreasing burdens for electricity production, and increasing burdens for oil production are expected to increase the GHG emission benefits of electrification technology. We highlight the importance of further LCA studies for BEVs using real world data to capture future improvements in vehicle performance and battery materials.— Kim et al.
Hyung Chul Kim, Timothy J. Wallington, Renata Arsenault, Chulheung Bae, Suckwon Ahn, and Jaeran Lee (2016) “Cradle-to-Gate Emissions from a Commercial Electric Vehicle Li-Ion Battery: A Comparative Analysis” Environmental Science & Technology doi: 10.1021/acs.est.6b00830