Li-Doping-Induced Structural and Electronic Structure Modulation in MgTiO₃ for an Electrochemical Energy Storage...

Correlation among the crystal structure, electronic structure, and electrochemical energy storage mechanism has been investigated for Li-doped MgTiO₃ ceramics, prepared using the solid-state reaction method. Li doping leads to an increase in the occupied density of states in the band structure of MgTiO₃, leading to a diminishing of the t_2g/e_g peak intensities in the O K-edge and Ti L-edge XANES spectra. Though Li doping did not change the Ti⁴⁺ and Mg²⁺ oxidation states, upon increasing Li content, the Mg₂TiO₄ phase thrived. Under the three-electrode configuration, with KOH as the electrolyte, the MgTiO₃, 5Li-MgTiO₃, and 10Li-MgTiO₃ samples have shown surface-plus-diffusion-based energy storage and offered high specific capacitances of 81.0 F/g, 190.5 F/g, and 309.0 F/g, respectively (at a scan rate of 5 mV/s). A Swagelok cell, a two-electrode-based symmetric supercapacitor device, has been investigated, which delivered an energy density of 46 Wh/kg at a power density of 5000 W/kg at a current density of 2.5A/g, retained greater than ∼71% capacity after 10,000 cycles, and powered an LED, indicating excellent practical energy storage performance.