Level the Conversion/Alloying Voltage Gap by Grafting the Endogenetic Sb2Te3 Building Block into Layered GeTe to Build Ge2Sb2Te5 for Li-Ion Batteries.

Many research efforts for advanced Li-ion batteries have been made to design new material with large capacity and long cycle life, but little attention has been paid to regulate the voltage platform until now. Although quite attractive for the binary Ge-based chalcogenides, challenge is that a large potential gap as well as incongruous reaction kinetics is typically found between their conversion step (>1.6 V) and alloying region (<0.4 V). Herein, we propose an endogenetic structural design by grafting Sb2Te3 building block into layered GeTe to establish a ternary Ge2Sb2Te5 compound, which can effectively level such a big potential gap. Turning from semiconductive GeTe into metallic conductive Ge2Sb2Te5, the reaction kinetics can be enhanced. The LixTe formation step in Ge2Sb2Te5 is found declined to 1.30 V, and the enlistment of Sb (∼0.78 V) bridges the conversion and alloying plateau; thus, the incongruous reaction kinetics and large potential gap between the conversion-alloying step can be alleviated. Furthermore, there is a spatially confined and synergistic effect among Te, Sb, and Ge components, conducting the LixTe and LixGe processes in a more harmonious and gentle way. Therefore, Ge2Sb2Te5 exhibites much enhanced cyclability and rate performance, with 546 mAh/g remained at 2000 mA/g. This unique design strategy can be leveraged to manipulate the voltage profile of other compounds.