Metallophthalocyanine-based electrode for sodium-ion batteries

Abstract

In this study, metallophthalocyanine-modified electrodes were fabricated and investigated for their electrochemical properties and energy storage performance. Six kinds of electrodes were prepared from indium tin oxide-coated glass (ITO-coated glass) substrates coated with titanium dioxide nanotube (TNT), poly(3,4-ethylenedioxythiophene) (PEDOT) and reduced graphene oxide (rGO) to improve conductivity of the substrates and surface area for the phthalocyanine-based materials. Target phthalocyanine monomers possess amino groups and Co(II) or Ni(II) central metals. On surface of each electrodes, films of the monomers were coated by a drop-casting technique, while those of their polymers were formed by electropolymerization. According to study on electrochemically active surface area of metallophthalocyanine-modified and unmodified electrodes, the presence of PEDOT significantly increases the electrochemically active surface area of the electrodes. Preliminary determination of specific capacitance of the electrodes by means of cyclic voltammetry (CV) and galvanostatic charge discharge (GCD) indicates that the metallophthalocyanine polymer films can more efficiently increase the specific capacitance of the electrodes than the monomers. TNT gives greater specific capacitance enhancement when used with the Ni(II)-phthalocyanine polymer films than when used with the Co(II)-phthalocyanine ones. Moreover, rGO also significantly improves the specific capacitance of the electrodes. Therefore, the electrode that give the optimum specific capacitance is the Ni(II)-phthalocyanine polymer film coated on PEDOT-rGO/TNT/ITO-coated glass. Further study for the energy storage performance of this electrode as a component of a sodium-ion battery shows that the specific capacitance of up to 60.22 mAh•g-1 was obtained at a C-rate of 3.94 μA with retention percentage of 79.86% after 125 charge/discharge cycles.