High-Performance MxSb-Al2O3-C (M=Fe, Ni, and Cu) Nanocomposite-Alloy Anodes for Sodium-Ion Batteries

MxSb-Al2O3-C (M=Fe, Ni, and Cu) nanocomposites were synthesized by mechanochemical reduction of Sb2O3 with Al and other metals (Fe, Ni, and Cu) in the presence of carbon and they were subsequently assessed as potential anode materials for sodium-ion batteries. Various characterization methods, including XRD and transmission electron microscopy (TEM), reveal that the as-prepared nanocomposites consist of nanostructured MxSb particles in a matrix of amorphous Al2O3 and conductive carbon. The incorporation of Al2O3 and a conductive metal-support into the Sb-C composite leads to an improved cycle life. The Cu2Sb-Al2O3-C and NiSb-Al2O3-C electrodes show, respectively, 80 and 90% capacity retention after 70 cycles at a current rate of 100 mAg(-1), and the MxSb-Al2O3-C composite anodes display > 70% retention at high current densities of 10 000 mAg(-1). These characteristics are attributed to the presence of both a metal framework to support the electrochemically active Sb, which results in a low electrode impedance, and a ceramic oxide and conductive carbon matrix, which reduce the agglomeration of nanoparticles as well as buffer the volume expansion/contraction during alloying/dealloying. Ex situ XRD analysis of the sodium-storage mechanism in MxSb-Al2O3-C composite anodes confirms the formation of a Na3Sb phase during sodiation.