Electrochemistry of Pyrite‐Based Cathodes for Ambient Temperature Lithium Batteries

Abstract

The charge and discharge mechanisms of and cells near room temperature are studied by in situx‐ray diffraction and in situ ⁵⁷Fe Mössbauer spectroscopy. The electrochemical behavior of these cells are compared, and their cell reactions are described. For , the cycling behavior of is reversible. However, for , structural decomposition of occurs, and disproportionation to nonstoichiometric and S is observed. Similarly, when cells are recharged to 2.8V, the cathode is a mixture of and S. Examination of the mixture by differential scanning calorimetry shows that and S react to form above 200°C. This explains why high temperature cells cycle reversibly while ambient temperature cells show poor reversibility.