Local Effects of the Lithium Insertion into Cation-Deficient Tin−Indium Thiospinels Revealed by ¹¹⁹Sn Mössbauer Spectroscopy

Abstract

Three thiospinel phases of the In 2 S 3 −SnS−SnS 2 system solid solution domain have been selected for electrochemical lithium insertion and local investigation by means of 119 Sn Mössbauer spectroscopy. Two distinct insertion mechanisms, characterized by two plateaus, are evident from the obtained discharge curves. Mössbauer spectroscopy and X-ray diffraction results are consistent with this. The first insertion mechanism is characterized by the reduction of Sn IV and a cell expansion while the second one leads to an increased metallic-type Sn/Li interaction and a cell contraction, both accompanied by a migration of indium from tetrahedral to octahedral sites. The evolution of the hyperfine parameters is discussed to characterize the main differences between the three phases in terms of local and global guest−host interactions.