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 (NbB2) nanoparticles are synthesized via a salt-templated method and proposed for the first time as the anodes for LICs. NbB2 is a layered two-dimensional material similar to graphite, which is favorable to the intercalation and deintercalation of Li+. The NbB2 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 NbB2 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.