Effects of electrochemical ageing of lithium-ion battery electrolyte on its in vitro genotoxicity: a special focus on sultones

Lithium-ion batteries (LIBs) play a key role in the transformation of society away from fossil fuels. Despite extensive research on their behaviour and improvement, toxicological aspects are often neglected, in particular regarding the liquid organic electrolyte. This study aimed to investigate the genotoxic and mutagenic potential as well as cell cycle effects of LIB electrolytes including one of the three sulphur-containing additives 1,3‑propanesultone (PS), prop‑1‑ene‑1,3‑sultone (PES) and 1,3,2‑dioxathiolane‑2,2‑dioxide (DTD). These additives are used in LIB to improve performance. Genotoxicity was assessed in HepG2 cells by two different versions of the in vitro micronucleus assay, whereas for mutagenicity testing, the bacterial reverse mutation assay in Salmonella typhimurium strains was used. The study focussed mainly on the investigation of the electrolyte and its constituents in different electrochemical ageing stages. Pure additives and one suspected degradation product each were investigated as well. It was shown that the toxicity of the pristine electrolyte related to that of the present additive. However, ageing led to electrolyte decomposition and the formation of new species, which had a major influence on toxicity. In sum, the extent to which toxicity was reduced depended on the additive. The results suggested that for the application in LIBs, DTD should be preferred over PS and PES from a toxicological point of view.