Prospective hazard and toxicity screening of sodium-ion battery cathode materials†

Sodium-ion batteries (SiBs) are considered as a serious alternative to the current lithium-ion batteries (LiBs). However, SiBs are an emerging technology in the early stage of development with a wide set of potential cathode material candidates available. Therefore, a major challenge is to identify the most promising and sustainable cathode materials for further research and potential commercialization, simultaneously considering relevant regulations such as the recent new EU Battery Regulation and Europe's chemicals strategy. Herein, we provide a comprehensive hazard and toxicity screening of promising SIB cathode material, which includes three different toxicity and hazard perspectives: (i) hazard traffic lights (HTL), (ii) total hazard points (THP), and (iii) human toxicity potential (HTox). Over 20 different SiB cathode compositions were screened together with three state-of-the-art LiB-cathodes for comparison. Inputs such as gravimetric energy density and required precursors were based on a comprehensive literature review, laboratory data, and calculations. All cathode active materials were analysed via a bottom-up approach. The results clearly showed that the energy density is one of the most important factors determining the choice of materials for SiBs and their corresponding related impacts. This screening can support a preliminary assessment of cathodes and help substitute selected precursors if they are associated with increased toxic hazards, therefore contributing to the ongoing discussions on more sustainable batteries and their labelling.