Titanium sulfide thin film coated titanium foil for high-performance symmetric supercapacitor

Abstract

Electrodes are the central component in determining the performance of electrochemical supercapacitors (ESCs). Thin-film electrodes, characterized by a layer of active material ranging from nanometers to hundreds of micrometers in thickness, raise particular interest in developing ESCs. This is because thin-film electrodes enable rapid electrochemical response during ESC charging/discharging induced by the shorter ion diffusion length. Herein, a thin film of titanium sulfide (TiS2) nanoparticle aggregates-modified Ti foil is prepared by the in situ electrochemical method, aiming to assemble a high-performance symmetric supercapacitor. Bare Ti foil is partially converted to TiS2 thin film by potentiostatic electrolysis at +6.0 V in sodium sulfide (Na2S) solution. Morphological and spectroscopic analyses reveal the formation of a thin film of TiS2 nanoparticle aggregates on Ti foil with good crystallinity (average crystalline size of 35.40 nm) and purity. In a three-electrode system, the optimized TiS2/Ti electrode exhibits a pseudocapacitive energy storage mechanism with good reversibility and high areal capacitance (136.75 mF/cm2 at the applied current density of 0.312 mA/cm2). The symmetric supercapacitor based on the identical TiS2/Ti electrode also displays high areal capacitance (68.62 mF/cm2 at an applied current density of 0.375 mA/cm2), high energy density (34.35 mWh/cm2), and power density (675.10 mW/cm2). Furthermore, the symmetric supercapacitor reveals excellent cycling stability with only a 4 % loss of areal capacitance after 5000 charge/discharge cycles. These findings suggest that TiS2/Ti electrode is promising in advancing the performance of ESCs with flexibility and miniature-ability, suitable for modern-day IoT and electronic devices.