Structurally synergetic stabilization of polyvinylpyrrolidone and co-doping boosts robust interconnected Ni(OH)₂ nanosheets for high-performance asymmetric supercapacitor

The occurrence of microcracks hinders the capacity performance and lifetime of electrode materials in energy storage systems. Herein, we report PVP-modified and Co doped Ni(OH)₂ nanosheets with structurally robust interconnection fabricated on Ni foam by a facile hydrothermal process. Co-doping obviously makes the Ni(OH)₂ nanosheets have fewer microcracks while no observable microcracks appear under PVP modification. The obtained P-CoNi-0.5 LDHs (layered double hydroxides) electrode presents the optimal specific capacitance of 2350 F g⁻¹ (293.8 mA h g⁻¹) at 1 A g⁻¹ current density, which is about 3.12 times greater than that of CoNi-0 LDHs (pure Ni(OH)₂). The excellent rate capability is obtained since the retained specific capacitance of 1706 F g⁻¹ (213.3 mA h g⁻¹) is achieved at 16 A g⁻¹ current density. An asymmetric supercapacitor device is fabricated by using P-CoNi-0.5 LDHs and activated cow dung carbon (ACDC), as the positive and negative electrode materials respectively. It exhibits desirable energy and power densities up to 32.1 W h kg⁻¹ at 800 W kg⁻¹, and offers a fascinating electrochemical cyclic performance of 89.6 % capacitance retention after 4000 cycles. We suggest that the synergy of Co-doping and PVP modification makes it a promising electrode material for supercapacitor applications, and also provides a feasible strategy for the design and preparation of functional electrode materials.