Synthesis and pseudocapacitive investigation of LiCrxMn2-xO4 cathode material for aqueous hybrid supercapacitor

A series of Cr-substituted LiMn 2 O 4 samples (LiCr x Mn 2- x O 4 , 0 ≤ x ≤ 0.3) were synthesized by a urea-assisted combustion method to enhance pseudocapacitive properties of LiMn 2 O 4 material in aqueous electrolyte. Their structure and morphology were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The LiCr x Mn 2- x O 4 and activated carbon (AC) electrode were used as the cathode and anode in hybrid supercapacitors, respectively, which capacitive properties were determined by cyclic voltammetry (CV), galvanostatic charge/discharge test, and electrochemical impedance spectroscopy (EIS) in Li 2 SO 4 solution. The results revealed that the partial substitution of Mn 3+ by Cr 3+ decreased initial capacity, but it prevented capacity fading. In the working voltage of 0–1.4 V, the AC/LiCr 0.1 Mn 1.9 O 4 capacitor delivered an initial specific capacitance of 41.6 F g −1 (based on the total active mass of two electrodes) at a current density of 100 mA g −1 in 1 M Li 2 SO 4 solution. After 1,000 cycles, its capacity loss was only 1.7 %.