Four different types of nano-tin-polyaniline (nano-Sn-PAni) lithium-ion composite anode microstructures have been examined to investigate the relationship between this parameter and anode characteristics. Scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS) show that the electrochemical properties of nano-fin composite electrodes can be significantly affected by microstructure variation. To simultaneously obtain high capacity and long cycle fife, the active materials should be encased in a polymer matrix to accommodate volume changes during cycling, and porosity is required to offer low interfacial lithium insertion/extraction impedance. The polymer matrix should have a high binding strength to prevent the anode cracking.