Life cycle assessment on sodium-ion cells for energy storage systems : A cradle-to-gate study including 16 environmental perspectives, focusing on climate change impact

Abstract: Because of the changing energy supply landscape, with the transition towards renewable energy, an emerging demand for energy storage systems (ESS) is expected in the near future. Battery energy storage is promising to contribute to mitigate the greenhouse gas emissions, but face issues considering resource use (IEA, 2023; IRENA, 2022). Sodium-ion batteries are a promising technology for the ESS-market, expected to take up 21 % of new installations by 2030. This means an anticipated demand of about 50 GWh of sodium-ion cells required in 2030. Key drivers for the expected entrance of sodium-ion storage are the low price, high abundance of cell materials and expectations of a more safe and sustainable battery. Lithium-ion technology is currently dominating the energy storage market, but have concerns with ethical resource supply and rising mineral prices combined with the growing demand. (BloombergNEF, 2023; IEA, 2023) There is a scarcity of information considering sodium-ion environmental reporting (Liu et al., 2021; Peters et al., 2021). Therefore, the purpose of this study is to evaluate the environmental aspect of sodium-ion storage technology. Thereby, with this study a life cycle assessment (LCA) is performed on a specific sodium-ion cell. The specific scope for the thesis is to look at 1 kWh of produced battery energy storage, in a cradle-to-gate perspective. The results are to be presented with a decomposition of the emissions across the value chain including materials, transport, and energy influence. As well a division of the cell materials impacts are demonstrated. For the assessed cell, it is assumed to be intended for a giga scale production (>1 GWh annual cell storage produced). Hypothetically this is to be placed in Europe, with both a global and a local supply chain presented. In order with European initiatives, there is a guideline called PEFCR, that recommends how to access the environmental footprint of different products. Among these guidelines, there is a certain standard for battery environmental assessment, which was pursued to be followed. According to these recommendations, the methodology of this assessment will include 16 environmental perspectives, called EF2.0. The EF2.0 emission categories presented as main result are Climate Change (total), Acidification, Resource Use (fossils), Resource Use (minerals & metals), and Particulate Matter, since these are considered relevant for batteries by PEFCR. (European Commission and ReCharge, 2018) Furthermore, it was chosen for this study to have its core in analysing the EF2.0 Climate Change impact, with the aim to identify measures on how to reduce the carbon footprint caused by the cell’s life cycle. With the perspective of the 16 environmental effects, a sodium-ion current state scenario was put in focus. On top of this, a decarbonized scenario is presented for the EF2.0 Climate Change impact. For the current state scenario, a comparison is made with a lithium-ion cell from industry, produced from fossil-free energy. This is framing the sodium-ion environmental results in the perspective of how a decarbonized lithium-ion cell performs environmentally. Both the sodium and lithium cells included in the comparison, have the aim to be used for energy storage system applications (ESS). Regarding the results for the 16 environmental categories, overall, the cathode is the main driver for emissions, followed by electrolyte and anode. Furthermore, in the decarbonized scenario, it is illustrated that implementing certain measures within the value chain could reduce the sodium-cell carbon emissions with potentially more than half of what is estimated today. Altogether, the sodium-ion value chain is in an emerging expansion phase (Rho motion, 2023), with a young supply chain starting to form. It is discussed that in the near future, with higher energy density on sodium cells commercialized (Peters et al., 2021), the environmental footprint for sodium-ion could significantly improve. Anyhow, the strongest indication from this study, is that the resource use from minerals and metals drastically would reduce with a technology switch from lithium to sodium. Among the 16 environmental impacts as a whole, the main trend is that sodium-ion cells induce less harm on the environment compared to lithium technologies. Certainly, in the future sodium-ion cells could be a low cost and sustainable option available for energy storage systems.