Amorphous Engineering and In Situ Atomic-Scale Deciphering of Lithium-Ion Storage Mechanism in Tellurium

Lithium-ion batteries (LIBs) using tellurium (Te) as electrode material are appealing because of their high capacities, conductivities, and lithium-ion diffusivity relative to those of silicon. However, crystalline Te electrode suffers from mechanical instability and poor cyclability during Li⁺ insertion and extraction. Moreover, the reaction mechanisms governing Te electrode during the electrochemical charge and discharge are poorly understood. Here, an amorphous Te phase is deliberately conducted and the results of comparative operando experiments on the crystalline and amorphous Te phases are reported. The lithiation of the crystalline Te phase results in grains with concomitant pulverization. On the lithiation-induced volumetric expansion and aggregation of the intrinsic stress, the Te crystalline phase undergoes bending, fracture, and finally collapse. In addition to the Li-rich phase (Li₂Te), a new Li-deficient phase (LiTe₃) that may be associated with incomplete lithiation owing to the poor ion conductivity of pulverized lithiation product is also detected. However, the amorphous Te specimens show promising lithiation/delithiation properties, particularly no pulverization behavior or structural damage, suggesting better capacity and reversibility. The different performances of crystalline and amorphous Te can be ascribed to the ordered and disordered structures. The findings will serve as a reference for the design of Te-containing LIBs.