Thermal Stability of Sb and Cu2Sb Anodes in Lithium-Ion Batteries

Abstract

The thermal stability and reactions of Sb and the intermetallic Cu2Sb in lithium-ion batteries has been investigated and analyzed relative to graphite electrodes under the same conditions. Bulk and surface layer products of the thermal reactions have been characterized by ex situ X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Differential scanning calorimetry (DSC) has been employed to investigate the relative heat generation with these electrodes and their potential to enhance lithium-ion battery safety by reducing the low-temperature exothermic driving force for thermal runaway. Sb and Cu2Sb are both found to undergo low-temperature reactions similar to graphite, with reactions at, respectively, ∼90 and 130°C related to solid-electrolyte interphase (SEI) layer breakdown. The heat generation per unit capacity for both Sb and Cu2Sb at < 150°C is ∼37% lower than that with graphite, which is a critical range for prevention of thermal runaway. Because neither Sb nor Cu are shown to be present in the SEI layer in appreciable quantities, this reduction in heat generation is largely attributed to the greater volumetric capacities of antimony and Cu2Sb that allow for greater lithium storage with less surface exposure for the formation of a thermally unstable SEI layer.