Molten salts synthesis of NbB nanoparticles for lithium-ion capacitor applications

Lithium-ion capacitors (LICs), despite having great energy density and power density, possess many practical challenges, including matching optimization of kinetic imbalance. To address the issues, here, niobium monoboride (NbB) nanoparticles are presented as an anode material for LICs. The abundant pore size distribution and intercalation-type Li+ storage mechanism of NbB nanoparticles allow for fast redox kinetics in charge and discharge process. Therefore, the half-cells with NbB achieve excellent electrochemical performance, including a great capacity (197 mAh/g at 0.1 A g−1 for 1000 cycles) and superior cycle life (118 mAh/g at 1 A g−1 for 5000 cycles). Also, NbB//AC LIC-1 device fabricated with the NbB as anode and commercial activated carbon (AC) as cathode reveals a great specific capacitance of 28.1 F g−1 at 0.05 A/g, and remains over 70 % initial capacitance after 12,000 cycles. In this work, nanoscale NbB presents excellent lithium storage performance and matches well with carbon cathodes, indicating that transition metal borides (TMBs) have huge potential in the energy storage field.