Evaluation of Cu3N and CuO as Negative Electrode Materials for Sodium Batteries

Copper(I) nitride, produced by the ammonolysis of copper(II) pivalate at 250 degrees C, shows a competitive capacity and stable cycling behavior in sodium cells with a NaPF6/ethyl carbonate/diethyl carbonate electrolyte. Ex situ X-ray diffraction studies suggest that this material acts as a conversion electrode, with Cu3N reduced to copper metal, but that these reactions occur only at the surfaces of the particles. A higher capacity is observed in lithium cells, again with stable cycling behavior. Hydrolysis results in nanocrystalline CuO, which has a higher sodium cell capacity. However, this capacity gradually decays on cycling and, after 30 cycles, is similar to that observed with Cu3N.