Original electrochemical mechanisms of CaSnO3 and CaSnSiO5 as anode materials for Li-ion batteries

Calcium stannate (CaSnO3) and malayaite (CaSnSiO5) were synthesized by means of a high temperature solid-state reaction. Their crystal structures and morphologies were characterized by X-ray diffraction (XRD) and Scanning Electron Microscopy; their electrochemical properties were analyzed by galvanostatic tests. The amorphization of the initial electrode materials was followed by XRD. The first discharge of the oxides CaSnO3 and CaSnSiO5 shows a plateau at low potential, which is due to the progressive formation of Li-Ca-Sn and/or Li-Sn alloys as shown by 119Sn Moessbauer spectroscopy. The results reveal similar electrochemical mechanisms for CaSnO3 and CaSnSiO5 but they completely differ from those related to SnO2. - Graphical abstract: 119Sn Moessbauer spectra at the end of the first discharge of CaSnO3 (dashed line) and CaSnSiO5 (solid line) anodes for Li-ion batteries. Inset shows that relative amounts of Sn(0) based alloys formed during the first discharge are similar for CaSnO3 and CaSnSiO5 pristine materials. Highlights: → CaSnSiO5 and CaSnO3 as anode materials for Li-ion batteries. → X-ray diffraction and Moessbauer spectroscopy, to explain the electrochemical mechanisms. → Similar mechanisms for the two compounds but different from those of SnO2 due to Ca.