Self-assembled porous Ni(HCO3)2 microspheres with ultrahigh-capacity for battery-type supercapacitors

초록

Hybrid supercapacitors (HSCs) have attracted significant attention for their ability to integrate high energy density from battery-type electrodes with high power density from capacitor-type electrodes. Mesoporous microspheres, with high surface area and uniform pores, increase electroactive sites and enhance capacity and cycling stability compared to other electrode materials in HSCs. Nickel-based compounds are measured as promising redox-active materials for battery-type electrodes in HSC due to their high theoretical capacitances, excellent electrochemical stability, and favorable conductivity. In this study, nickel hydrogen carbonate (Ni (HCO3)2) microspheres, self-assembled from nanoparticles, were synthesized using a facile hydrothermal approach. Common nickel salts and urea were utilized as the starting materials for this process, offering a simple and efficient route to prepare advanced materials with enhanced performance. The structural, morphological, and surface properties of Ni(HCO3)2 were analyzed to understand their contribution to electrochemical performance. The microsphere morphology, characterized by a porous and granular structure, provided a larger surface area, improved ion accessibility, and faster charge/discharge kinetics. As a battery-type electrode for HSCs, Ni (HCO3)2 demonstrated ultra-high specific capacity of 2202.2 C g- 1 and significant rate capability even at higher current densities. Moreover, the electrode demonstrated exceptional cyclic stability, retaining 96 % of its initial capacity even after 3000 charge/discharge cycles at a high current density of 20 A g- 1. These findings demonstrate the promise of Ni(HCO3)2 as a highly efficient and stable battery-type electrode material, making a significant contribution to the advancement of HSCs for next-generation energy storage systems.

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