Efficient Mineralization of Lithium Bis(pentafluoroethanesulfonyl)imide and Related Electrolyte Fluorochemicals Using...

Lithium bis(pentafluoroethanesulfonyl)imide, Li[N(SO₂C₂F₅)₂], a typical fluorochemical aimed at better electrochemical performance of battery electrolytes, in superheated water was studied for its waste treatment. When Li[N(SO₂C₂F₅)₂] was reacted in pure superheated water at 300 °C, little F^- ions were produced. In contrast, complete mineralization of the fluorine, sulfur, and nitrogen atoms in Li[N(SO₂C₂F₅)₂] was achieved when the reaction was performed in the presence of KMnO₄. Specifically, when Li[N(SO₂C₂F₅)₂] was treated for 18 h with 158 mM of KMnO₄, the F^- and SO₄^2- yields were 101 and 99%, respectively, and the sum of the NO₃^- and NO₂^- yields was 101%. In the gas phase, trace CO₂ was detected and no CHF₃, which has high global warming potential, was formed. Furthermore, the fluorine, sulfur, and nitrogen atoms in the analogues K[N(SO₂C₄F₉)₂] and K[N(SO₂CF₂)₂CF₂] also underwent complete mineralization using the same approach.