Sustainable cathode material screening for sodium-ion batteries using a hesitant fuzzy-intuitionistic MCDM framework

Sodium-ion batteries (SIBs) present a promising alternative to conventional lithium-ion batteries (LIBs), offering potential advantages in cost reduction and environmental sustainability. SIBs are in the early stages of development and numerous cathode materials are still being explored. A systematic screening is required to identify the most promising sustainable cathode materials of these early-stage technologies, in line with EU battery regulations and chemical safety strategies. To support such a screening, the evaluation considers major factors such as energy density, cost, greenhouse gas (GHG) emissions, supply risk, and input-related toxicity. As the number of evaluation criteria is high, both the complexity of finding an optimal solution and the impact of linguistic uncertainties in decision-making grow significantly. To address these challenges, a combination of hesitant-intuitionistic fuzzy multi-criteria decision-making (MCDM) is proposed. The hesitant fuzzy linguistic Analytic Hierarchy Process (HFL-AHP) is used to assign weights to the criteria, while the intuitionistic New Easy Approach to Fuzzy-PROMETHEE (NEAT-Fuzzy-PROMETHEE) method is used to rank the alternative materials. ... mehrObstacle degree analysis and comprehensive sensitivity assessments are additionally performed to find the field of improvement and ensure robustness with reliability of the results, respectively. The results highlight that the energy density of the cathode material is a critical factor in the screening of optimal solutions. Na$_2$FeSiO$_4$ is the optimal solution when input-related toxicity is not included, while Na$_{0.61}$Fe[Fe(CN)$_6$]$_{0.94}$   becomes a promising option with the inclusion of that factor under given assumptions and limitations of the approach. Furthermore, the analysis shows that energy density, GHG emissions and toxicity affect sustainable decision-making in material screening, indicating critical areas for improvement.