Electrochemical Properties of Hollandite K1.5Fe1.5Ti6.5O16 with Carbon Coating

Iron-doped potassium titanate with a hollandite structure is synthesized by the solid-phase method. To reduce the contact resistance and to increase the diffusion coefficient of potassium ions, a conductive carbon coating is applied to the surface of the titanate synthesized in an argon atmosphere. The formation of the composite material is confirmed by the results of X-ray phase analysis, scanning electron microscopy, and IR spectroscopy. The half-cells with potassium metal in a CR2025 case, which are assembled on the basis of the synthesized composite, are tested electrochemically with subsequent calculation of the specific capacitance, power density, and energy density. It is found that the specific capacitance of an electrode with a carbon coating is 10–15% higher with low sweep rates (1 and 3 mV s–1). It is shown that the use of carbon coatings increases the diffusion coefficient of potassium to 1.77 × 10–14 cm2 s–1/2.