Carbon coated nano-LiTi2(PO4)3 electrodes for non-aqueous hybrid supercapacitors

Abstract

The Pechini type polymerizable complex decomposition method is employed to prepare LiTi₂(PO₄)₃ at 1000 °C in air. High energy ball milling followed by carbon coating by the glucose-method yielded C-coated nano-LiTi₂(PO₄)₃ (LTP) with a crystallite size of 80(±5) nm. The phase is characterized by X-ray diffraction, Rietveld refinement, thermogravimetry, SEM, HR-TEM and Raman spectra. Lithium cycling properties of LTP show that 1.75 moles of Li (∼121 mA h g⁻¹ at 15 mA g⁻¹ current) per formula unit can be reversibly cycled between 2 and 3.4 V vs. Li with 83% capacity retention after 70 cycles. Cyclic voltammograms (CV) reveal the two-phase reaction mechanism during Li insertion/extraction. A hybrid electrochemical supercapacitor (HEC) with LTP as negative electrode and activated carbon (AC) as positive electrode in non-aqueous electrolyte is studied by CV at various scan rates and by galvanostatic cycling at various current rates up to 1000 cycles in the range 0–3 V. Results show that the HEC delivers a maximum energy density of 14 W h kg⁻¹ and a power density of 180 W kg⁻¹.