Self-templated formation of CuCo2O4 triple-shelled hollow microspheres for all-solid-state asymmetric supercapacitors

The triple-shelled hollow CuCo2O4 (T-CuCo2O4) microspheres were synthesized by a solvothermal/calcination method. The unique structure with a large internal void volume and porous distribution shortened the ions/electrons transport distance and strengthened the electrochemical reaction. The triple-shelled architecture buffered the volume expansion/contraction to enhance structural stability due to the reduced stress and strain during the charge/discharge process. As a three-electrode cell, the T-CuCo2O4 electrode demonstrated a specific capacitance of 691 F/g (current density: 1 A/g), rate capability of 470 F/g (current density: 20 A/g) and capacitance retention of 93% after 6000 cycles. The all-solid-state asymmetrical supercapacitor achieved an energy density of 25.2 W h/kg at a power density of 1.05 kW/kg, using activated carbon as a negative electrode. The specific capacitance can still maintain 80.3 F/g at a current density of 2 A/g with 6% capacity loss after 2000 cycles.