Preparation of carbon-coated lithium iron phosphate/titanium nitride for a lithium-ion supercapacitor

Carbon-coated lithium iron phosphate (C-LiFePO4) supported on a titanium nitride (TiN) substrate was designed as the electrode material for a lithium-ion supercapacitor for an energy storage application. C-LiFePO4 nanoparticles were prepared via a hydrothermal synthesis and carbonization treatment process. TiN nanowires were prepared using an anodization oxidation and nitridization process. A C-LiFePO4/TiN nanowire network was synthesized by loading C-LiFePO4 nanoparticles onto TiN nanowires through a chemical bath deposition method. The surface morphology and microstructure of C-LiFePO4/TiN were characterized using scanning electron microscopy, X-ray diffraction and Raman spectrum analysis. The lithium-ion insertion–extraction behavior of the C-LiFePO4/TiN in a Li2SO4 aqueous electrolyte was investigated by cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic charge–discharge measurements. C-LiFePO4/TiN exhibited a high capacitance of 972 F g−1 at the current density of 1.0 A g−1, presenting a capacity improvement of 210% when compared with 314 F g−1 for LiFePO4/TiN. The C-LiFePO4/TiN nanowire network also exhibited good cycle stability and high rate capability, presenting a promising application of the lithium-ion supercapacitor.