Aluminium’s Role in the Decarbonization of Batteries

Battery electric vehicles (BEVs) are seen as the cornerstone of a more sustainable future of transport. Batteries are the key technology for powering these vehicles. However, the production of battery cells involves energy-intensive processes that result in significant CO_2e emissions. As a result, BEVs have higher carbon footprint in production than internal combustion engine (ICE) vehicles. McKinsey’s projections¹ and industry targets indicate that CO_2e emissions from battery production can be significantly reduced.

*Figure 1: Current and projected CO_2e emissions of battery cell production per kWh according to McKinsey’s analysis ¹*

This study examines how aluminium components, such as the cell housing and the battery electrode foil, impact emissions today and what steps need to be taken to achieve meaningful carbon footprint reductions in future battery products.

Aluminium Utilization in State-of-the-Art Battery Cells

Aluminium’s unique properties make it the go-to material for battery applications. With its high conductivity, the battery’s internal and external electrical resistance can be kept low, allowing high charging speeds. Paired with its low specific weight, it is not by chance that aluminium plays a vital role in state-of-the-art lithium-ion batteries.

Aluminium is ubiquitous in lithium-ion batteries (LIBs), as it is used for the electrode foil, as the cell casing, or for different kinds of connectors. Depending on the cell chemistry, 0.5 to 0.7kg of aluminium is required to produce 1kWh of lithium-ion battery energy storage^2,3.

*Figure 2: Typical aluminium content of lithium-ion batteries featuring different cell chemistries considering cell level (electrode foil and cell housings)^2,3*

Greenhouse Gas Emissions Related to Aluminium

In the production of aluminium, the energy source and the amount of recycled material determine the carbon footprint.

As an example: Considering world average values, the production of 1kg of primary aluminium requires about 14kWh of electric energy. Using advanced technology, industry leaders might achieve a level of only 12.3kWh of energy used. Due to the high energy demand of aluminium primary production, the energy mix employed for its production is decisive for the greenhouse gas emissions. Using recycled aluminium can however offset the energy demand significantly as recycling of aluminium requires up to 95% less energy than the production of primary aluminium, where the use of external production scrap and end-of-life scrap allows for a significant reduction in greenhouse gas emissions^4-8.

More precisely, the CO_2e emissions for mine-to-slab production can range from 20 to 4kg of CO_2e per kg of aluminium depending on the employed electricity mix, while 100% recycled material could be produced with only 0.5kg of CO_2e per kg of aluminium, theoretically. On top of this, downstream processing needs to be added, although its contribution to the overall aluminium related CO_2e emissions is typically minor. For simplification reasons, the carbon footprint effects of semi-production processes such as rolling, cutting, and annealing, are considered within this study by a constant factor of 0.3kg of CO_2e per kg of aluminium, which is a typical value for aluminium semi-production⁷.

*Figure 3: Typical CO_2e emissions related to mine-to-slab production of aluminium^7-8.*

The contribution of aluminium to the total greenhouse gas emissions from lithium-ion battery cell production can be assessed exemplarily based on the foregoing evaluation considering the aluminium content per kWh of a lithium-ion battery with NMC 622 chemistry, the projected CO_2e emissions of cell production of 12 kg CO_2e per kWh in 2030 and the carbon footprint of aluminium associated with different production routes (Figure 4). It is evident that aluminium’s share of the projected CO_2e emissions of battery cell production would be excessively high with 75% when considering primary aluminium with world average carbon footprint. Employing primary aluminium produced with 100% carbon free renewable energies would reduce aluminium’s share to about 20%, while adopting a significant share of external and post-consumer scrap – like Speira ORBIS⁹ – cuts aluminium’s share to about 7%. It should be noted that this assessment makes use of the simplification that all aluminium components and grades could be produced at scale with high recycled content.

In practice, adopting low-carbon primary aluminium when needed and recycling-based aluminium where possible will be a necessity to achieve projected battery cell production CO_2e emissions.

Figure 4: Top-down estimate of aluminium contribution to the battery cell carbon footprint for different aluminium sources and NMC 622 chemistry without differentiating the applicability of grades, based on the McKinsey’s 2030 scenario^1-3,7-8

Aluminium Grades used in Batteries

Traditionally and at present, aluminium grades used for battery electrode foil, cell housings and connectors are made from primary based alloys such as 1050, 1060, 1085, 3003 or 8021. Although, these materials are well-established, the applicability of less pure and hence, more recycling friendly alloys should be evaluated on a case-by-case basis to unlock the sustainability benefits of recycling.

Here, it is important to realize that the requirements of a component are decisive for the applicability of alloys based on primary or recycled aluminium. For instance, applications with highest conductivity requirements can only be satisfied with commercial pure aluminium (1xxx). Hence, these products will typically be primary aluminium-based. Regarding the battery cell, the same is to be expected for electrode foil and cell-to-cell connectors.

Contrary, battery cell housings pose increased possibilities for reducing greenhouse gas emissions. Currently, battery cell housings are made of the aluminium alloy AA3003. While this material is established and fulfils all the technical requirements of a deep-drawn cell housing, it has one distinct disadvantage. Its restricted chemical composition requires a high content of primary material. Consequently, the use of recycled content will be limited and greenhouse gas emission reductions below 4.0kg of CO_2e per kg of aluminium are hard to achieve. Alternative material concepts like Speira ION Cell 3-CS R or Speira ION Cell 3-PS R enable a significantly increased share of recycled content in conjunction with very low greenhouse gas emissions, while fulfilling all the requirements of a battery cell housing material such as formability, strength, electrolyte compatibility, and weldability.

The foregoing evaluation highlights the importance of sustainable aluminium for sustainable battery cell production. Developing such aluminium grades can only be successful in a joint effort of the battery and aluminium industry. Considering 2030 targets and typical development cycles, the evaluation of alternative material concepts needs to launch as soon as possible.

Additional details are available at: Speira learn – Whitepaper Decarbonization of Batteries

About Speira

Speira is a leading aluminium rolling and recycling company, driven by its purpose to build a circular world that works, and it strives to fully decarbonize its business by 2045. Speira produces one million tons of aluminium rolled products per year. Speira operates eleven manufacturing facilities and one R&D center across Germany and Norway, including various aluminium recycling facilities, its joint venture of the world’s largest aluminium rolling mill at Alunorf, and the world’s largest rolled aluminium finishing mill at Grevenbroich. Speira has approximately 5,400 employees. Speira is proud to serve some of the most well-known companies in the global automotive, packaging, printing, engineering, building, and construction industries. Speira is headquartered in Grevenbroich, Germany.

Speira is a volume supplier of material solutions for battery systems to leading global battery manufactures and offers an extensive product portfolio under the ION brand that covers the entire spectrum from battery electrode foils to cell connectors, heat exchangers, and housing materials.

References

The race to decarbonize electric-vehicle batteries, McKinsey
From Dirty Oil to Clean Batteries, Transport and Environment
Visualizing the Key Minerals in an EV Battery, Elements
Primary Aluminium Smelting Energy Intensity, International Aluminium Institute
The world’s most energy-efficient aluminium production technology, Hydro
Aluminium Recycling – Sustainability, Alu, The International Aluminium Institute
Greenhouse Gas Emissions – Aluminium Sector, International Aluminium Institute
ORBIS EN – Sustainability, Speira
Recycled Aluminium ORBIS: at least 75 % recycled content, Speira

Benefits of Aluminium Cell Housing for Cylindrical Li-ion Batteries

In summary, the simulation reveals clear advantages in thermal management for 4680 cells featuring an aluminium cell housing compared to a NPS cell housing. Thereby, efficient heat transfer and a homogenous temperature distribution within the cell enable improved temperature levels and enable enhanced fast-charging performance and slower aging of the cell.

See also: Aluminium