Zirconium doping facilitates a vertically aligned NiCoZr-layered hydroxide nanoneedle arrays electrode for hybrid supercapacitors exhibiting a 90,000 cycle durability

Abstract

LDHs (Layered Double Hydroxides) are a kind of promising cathode material for high-performance hybrid supercapacitor. Nevertheless, it suffers quick capacitance decay after only thousands of cycles, which greatly prevents it from further application. In this contribution, zirconium (Zr) is introduced to the host layer of NiCo-LDH via a simple one-pot hydrothermal process. Owing to the strong bonding energy of ZrO (760 kJ mol−1) and special electronic structure (fully empty 4d orbits), the doped Zr could not only act as a structural stabilized element, but also change the mechanism of the energy storage process to alleviate the Jahn-Teller distortion of NiCo-LDH. Moreover, the introduction of Zr boosts an orderly growth of the LDHs, changing from disorder stack structure to vertically aligned nanoneedle arrays, which improve their structural stability. By controlling a varying level of Zr content, the electrode NiCoZr-LDH@CC with a Zr content ratio of 6.4 % delivers the best comprehensive electrochemical performance with a specific capacitance of 1758 F g−1 and good rate performance (73 % capacitance retention at 10 A g−1). The assembled asymmetric supercapacitor shows a highest energy density of 42.3 Wh kg−1 at 504 W kg−1 and an ultralong cycling lifespan beyond 90,000 cycles with a 97 % capacitance retention. The results exhibit the great potential of NiCoZr-LDH as a qualified candidate for high-performance hybrid supercapacitors.