Preparation and capacitive properties of lithium manganese oxide intercalation compound

Lithium manganese oxide intercalation compound (Li_0.7MnO₂) supported on titanium nitride nanotube array (TiN NTA) was applied as cathode electrode material for lithium-ion supercapacitor application. Li_0.7MnO₂/TiN NTA was fabricated through electrochemical deposition and simultaneous intercalation process using TiN NTA as a substrate, Mn(CH₃COO)₂ as manganese source, and Li₂SO₄ as lithium source. The morphology and microstructure of the Li_0.7MnO₂/TiN NTA were characterized by scanning electron microscopy and X-ray diffraction analysis. The electrochemical performance of the Li_0.7MnO₂/TiN NTA was investigated by electrochemical impedance spectroscopy, cyclic voltammetry, and galvanostatic charge/discharge measurements. Li_0.7MnO₂/TiN NTA exhibited higher capacitive performance in Li₂SO₄ electrolyte solution rather than that in Na₂SO₄ electrolyte solution, which was due to the different intercalation effects of lithium-ion and sodium-ion. The specific capacitance was improved from 503.3 F g⁻¹ for MnO₂/TiN NTA to 595.0 F g⁻¹ for Li_0.7MnO₂/TiN NTA at a current density of 2 A g⁻¹ in 1.0 M Li₂SO₄ electrolyte solution, which was due to the intercalation of lithium-ion for Li_0.7MnO₂. Li_0.7MnO₂/TiN NTA also kept 90.4 % capacity retention after 1000 cycles, presenting a good cycling stability. An all-solid-state lithium-ion supercapacitor was fabricated and showed an energy density of 82.5 Wh kg⁻¹ and a power density of 10.0 kW kg⁻¹.