Niobium boride (NbB2): Salt-templated synthesis, pseudocapacitive electrode and lithium-ion capacitor applications.

Lithium-ion capacitors (LICs), which combine great power and energy density, have become promising energy storage and have been well studied recently. Developing novel battery-type anode materials is the key to mitigating the kinetic mismatch between the anode and cathode electrodes. In this paper, niobium diboride (NbB 2) nanoparticles are synthesized via a salt-templated method and proposed for the first time as the anodes for LICs. NbB 2 is a layered two-dimensional material similar to graphite, which is favorable to the intercalation and deintercalation of Li+. The NbB 2 with high conductivity delivers outstanding long cycling stability (254.1 mAh g−1 after 800 cycles at 0.1 A g−1) and great rate capability. Moreover, a high-performance LIC is assembled employing the prepared NbB 2 as anode and commercialized activated carbon (AC) as cathode, which can display an energy density of 68.76 Wh kg−1, a power density of 7.02 kW kg−1, and a capacity retention ratio of 98% after 10,000 cycles. The work presents the great potential of transition metal borides as electrode materials and accelerates the development of LICs. [Display omitted] • Niobium diboride are synthesized via a simple and facile molten salt method. • The NbB 2 nanoparticles are first reported as anodes for Lithium-ion capacitors. • The optimized NbB 2 electrode shows superior specific capacity and rate capability. • The surface capacitance dominates the NbB 2 electrode kinetics process. [ABSTRACT FROM AUTHOR]