Crystalline-amorphous double nickel-based composites for high-performance asymmetric supercapacitors to enhance rate performance

The low rate performance and limited energy density prevent hybrid supercapacitors (HSCs) from being used much further. Herein, a straightforward two-step procedure is used to create the rate-enhanced NiC₂O₄/NiCoB composites, which are composed of NiC₂O₄ nanorods and NiCoB. At the current density of 1 A g⁻¹, the NiC₂O₄/NiCoB electrode provides a high specific capacitance of 624C g⁻¹. The introduction of the NiCoB outer layer significantly enhances the electron transport capability and accelerates the ion/electron transfer rate. This design effectively addresses the inherently poor rate performance of NiC₂O₄ (with only 32.5 % capacity retention at a high current density of 10 A g⁻¹). With the NiCoB outer coating, the capacity retention is remarkably improved to 85.7 % at the current density of 10 A g⁻¹. The incorporation of the coating structure fundamentally resolves the issue of poor high-rate performance in the material. Therefore, based on the NiC₂O₄/NiCoB as the positive electrode and activated carbon (AC) as the negative electrode, NiC₂O₄/NiCoB||AC HSC is assembled. With the maximum potential window of 1.6 V, this HSC exhibits an energy density of 47.4 Wh kg⁻¹ and a power density of 881.47 W kg⁻¹. The innovative design of crystalline-amorphous double nickel-based composites offers an advanced and straightforward approach to enhancing the electron/ion transport kinetics in nickel-based materials, enabling the construction of high-performance HSCs.