Unexpected Behavior of the InSb Alloy in Mg-Ion Batteries: Unlocking the Reversibility of Sb

Electrochemical behavior and performance of negative electrodes in metal batteries can be modified and improved by combining different elements. Herein, a beneficial coupling of In and Sb in the alloying reaction with Mg was considered through the preparation of the InSb alloy by mechanochemical synthesis. Despite a strong inactivity of Sb as a sole element in Mg-ion batteries, the combination of Sb with In partially unlocks the reversibility of the alloying reaction of Sb with Mg to form Mg3Sb2. For the first time, this beneficial effect is observed not only during the first magnesiation but along few tens of cycles. The analysis of the behavior of InSb through electrochemical and X-ray diffraction measurements also revealed a more complex path than that reported in the literature. Uncommonly, a preferential electrochemically driven amorphization of MgIn is suggested in standard galvanostatic measurements. Crystallization of MgIn is, however, observed through a galvanostatic intermittent titration technique, suggesting strong kinetic effects on the microstructure, strain, or disorder in the InSb phase upon magnesiation.