Intermetallic and alloy materials have been investigated as potential anode materials in lithium and sodium ion batteries. These materials are often morphologically and electrochemically unstable during extended cycling in lithium ion batteries. The intermetallic compound Cu2Sb is unusual because of its exceptional reversibility, despite a large volume change upon cycling and conversion-type mechanism. Available methods for probing the transformation mechanisms of multi-composition materials are unable to identify microscopic changes in the active material composition. This has led to difficulty in determining the dynamics of the copper during electrochemical cycling. Further complications arise when the phase of the active material is amorphous, as is the case with intermetallic anodes in sodium ion cells. To help elucidate the mechanism of this material, we have developed a unique method for probing the morphological evolution of this material by electrodepositing the compound onto special grids designed for transmission electron microscopy. Using energy dispersive spectroscopy in a scanning electron microscope, we show how nanoscale particles of Cu2Sb transform during the charge and discharge of lithium and sodium ions. This approach allows a direct method for imaging the migration of copper into and out of the copper-antimony matrix as the former is extruded and reincorporated during cycling.

Investigation of the morphology evolution of nanoscale Cu2Sb electrodes during electrochemical cycling via ex situ electron microscopy

249th National Meeting (2015)

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