SnSb electrodes for Li-ion batteries: the electrochemical mechanism and capacity fading origins elucidated by using operando techniques

Abstract

SnSb was synthesized by ultra-fast microwave solid-state synthesis. The lithiation/delithiation mechanism of SnSb was fully revisited through operando X-ray diffraction (XRD) and ¹¹⁹Sn Mössbauer spectroscopy. While many studies have underlined the attractive electrochemical performance of SnSb as the electrode material for Li-ion batteries, only a few of them have focused on the complex electrochemical mechanism. In this work, the complementary results of operando XRD and Mössbauer spectroscopy were used to fully investigate this complex electrochemical system. The alloying mechanism with the reversible formation of Li₃Sb and Li_ySn lithiated phases was confirmed and complemented with additional information on the nature of the Li_ySn phases, namely Li₂Sn₅, LiSn, Li₅Sn₂ and Li₇Sn₂. Moreover, we demonstrated that the improved performance of SnSb compared to a physical mixture of Sn and Sb lies in the nature of the interfaces between the lithiated phases at the end of discharge. The progressive decrease of the availability/accessibility of Sn for the regeneration of SnSb at the end of the charge was also identified as a major failure mechanism for the long-term cycling stability of SnSb electrodes.