CuFe0.4Mn1.6O4-MWCNT composites synthesized by solvothermal method as high-performance asymmetric supercapacitors

Supercapacitor has become a promising energy storage device because of its unique advantages, and the selection of appropriate electrode materials is the key to improve the performance of supercapacitor. A series of CuFe _xMn _2−xO ₄ -MWCNT-y (x = 0, 0.2, 0.4, 0.6, 0.8; y = 0, 2, 3, 4) spinel composites was successfully prepared by solvothermal method. Galvanostatic charge-discharge test confirmed that CuFe _0.4Mn _1.6O ₄ -MWCNT-3 modified electrode exhibited maximum specific capacitance of 656.7 F·g ⁻¹ at the current density of 1.0 A·g ⁻¹, and had good cycling stability with the capacitance retention rate of 80.6% after 5000 cycles at the current density of 8.0 A·g ⁻¹. Furthermore, the assembled CuFe _0.4Mn _1.6O ₄ -MWCNT-3//activated carbon (AC) asymmetric supercapacitor possesses higher capacitance of 104.0 F·g ⁻¹ at 1.0 A·g ⁻¹ and the maximum energy density of 30.43 Wh·kg ⁻¹ and power density of 3500 W·kg ⁻¹. The outstanding conductivity and capacitative performance of CuFe _0.4Mn _1.6O ₄-MWCNT-3 may be attributed to the fact that 2D CuFe _0.4Mn _1.6O ₄ is entangled by tubular MWCNTs, thus facilitating the rapid transport of electrolyte ions, and Ni doping in CuMn ₂O ₄ leads to increased defect sites of oxygen and increased ratio of Mn ⁴⁺ to Mn ²⁺. It also indicates that CuFe _0.4Mn _1.6O ₄-MWCNT-3 composite has a potential application prospect in energy storage devices.