Theoretical and experimental investigation of electrical double layer capacitance of LiClO4-interacted metal substrates and carbon-coated nickel electrode

Abstract

ABSTRACT Suitable transitional metal electrode substrate should keep high electroactivity and meanwhile suppress polarization effect. Theoretical calculation and experimental measurement are adopted to investigate interfacial interaction-dependent capacitance of lithium perchlorate-titanium and nickel (LiClO4-Ti, LiClO4-Ni) metal substrates. LiClO4-Ti reveals ideal electrical double layer capacitance due to electrochemical stability and LiClO4-Ni reveals the deviated electrical double layer capacitance due to polarization effect in potential range of 0–0.8 V. LiClO4-Ni reveals lower ohmic resistance, charge transfer resistance and Warburg resistance to present higher conductivity, more active interface, and more feasible ion diffusion properties than LiClO4-Ti. Titanium and nickel substrates achieve mean response current of 0.13–2.47 μA cm−2 and 1.03–22.20 μA cm−2 at 5200 mV s−1. The corresponding specific capacitances are 0.010–0.0095 mF cm−2 and 0.322–0.155 mF cm−2 at 0.01–0.10 mA cm−2. LiClO4-Ni keeps much higher capacitance but relatively lower electrochemical stability than LiClO4-Ti. Theoretical calculation proves interfacial electrostatic adsorption of LiClO4 on Ti and Ni substrates could change charge density distribution. LiClO4-Ni with the enlarged potential difference causes intensified polarization effect. LiClO4-Ni exhibits higher electrical conductivity and lower interface energy than LiClO4-Ti. Furthermore, carbon-coated nickel (C@Ni) was prepared to mostly restrain polarization effect and meanwhile keep high electroactivity of Ni substrate for the promising supercapacitor electrode application. It reveals specific capacitance of 25.9 mF cm−2 and cycling capacitance retention of 94.5% after 1000 charge-discharge cycles at 1.0 mA cm−2 in 1.0 M LiClO4. The C@Ni electrode accordingly exhibits superior electroactivity and electrical double layer capacitance for energy storage application.