The electrochemical model coupled parameterized life cycle assessment for the optimized design of EV battery pack

• Published in: The international journal of life cycle assessment 2022-02, Vol.27 (2), p.267-280
• Main Authors: Ma, Ruifei, Deng, Yelin
• Format: Article
• Language: English
• Subjects: Carbon dioxide; Carbon dioxide emissions; Cathodes; Charging; Cobalt; Composition; Design optimization; Discharge; Earth and Environmental Science; Efficiency; Electric vehicles; Electrochemistry; Emissions; Environment; Environmental Chemistry; Environmental Economics; Environmental Engineering/Biotechnology; Environmental impact; Flux density; Greenhouse gases; Lci Methodology and Databases; Life cycle analysis; Life cycle assessment; Life cycles; Lithium; Lithium-ion batteries; Manganese; Nickel; Parameterization; Rechargeable batteries; Sustainable design; Sustainable energy; Thickness
• ISSN: 0948-3349; 1614-7502
• DOI: 10.1007/s11367-022-02026-z

Purpose With the increasing market share of electric vehicles (EVs), many studies have been devoted to the life cycle assessment (LCA) of lithium-ion batteries. However, current LCA results are diverse, leading to various material compositions, energy densities, and charging/discharging efficiencies. All of these performance indicators can have a significant influence on environmental impacts. This study establishes a parametric LCA model that can reflect the most current understanding of battery cell/pack design and greenhouse gas (GHG) emissions. Methods First, a practical parameterized life cycle inventory (LCI) of nickel-manganese-cobalt (NMC) battery cells and packs used in EVs is designed to integrate the simplified electrochemical method. By adjusting the cathode thickness and bilayer number, the changes in the composition of the battery cell and pack are studied. Next, a kinetic model of the battery cell and the pack is established to calculate their area-specific impedances (ASIs), internal resistance, sustainable power, and efficiency in the use phase. Finally, the GHG emissions of the battery pack in the entire life cycle are analyzed using Ecoinvent 3 — allocation, cut-off by classification — unit database in Simapro 9.1.1. Results and discussion The increase of cathode thickness (30–150 µm) leads to significant expansions of mass proportion attributed to the positive active materials (from 26.2 to 38.5%) and negative active materials (from 17.0 to 24.9%). Thus, the energy density of the pack can be improved from 144 to 202 Wh/kg. On the other hand, a thicker cathode thickness triggers an increased internal resistance from 28.8 to 64.8 m Ω , which correspondingly degrades the charging/discharging efficiency from 96.5 to 90.2%. For the carbon emissions from the LCA, the CO 2 equivalent per km exhibits a minimal point (70–90 µm) under the cathode thickness range of 30–150 µm. Moreover, CO 2 eq/km is reduced by 9–16% for every additional 50,000 km mileage. Conclusions The model in this study reflects the change of parameters in practice according to the current and future requirements, increasing the transparency of LCA and benefitting future green design of the battery pack. The results indicate that cathode thickness should be 70 µm for a 200,000-km total mileage. The optimized CO 2 emissions are 16.0 CO 2 eq/km, where the pack is configured to have a 400-km driving range per charge and 94.6–95.0% charging/discharging efficiency.