Manipulating oxygen vacancy for controlling the kinetics of Nb2O5-based anode in Li-ion capacitor.

Modulation of oxygen vacancy concentration of Nb 2 O 5 anode, arising from quantitative regulation of oxygen content in the precursor, is developed, revealing the relationship between the oxygen vacancy concentration and kinetics for Li-ion storage. In addition, the integrated binder-free electrode with appropriate oxygen vacancies and highly conductive N-doped carbon porous framework results in improved kinetics for the anode of Li-ion capacitors. [Display omitted] • Oxygen vacancy concentration of Nb 2 O 5 @NC anode is quantitative regulation. • Revealing relationship between oxygen vacancy concentration and kinetics of Li-ion storage. • Nb 2 O 5 @NC binder-free electrode is constructed via electrophoretic deposition. • Binder-free electrode further improves kinetics for the anode of Li-ion capacitors. Introducing appropriate oxygen vacancies (OVs) improves the integral conductivity of the Nb 2 O 5 anode of Li-ion capacitors (LICs). Whereas a few recent studies link the OVs level and the kinetics of Nb 2 O 5 , the quantitative relationship between the OVs and the performance of Nb 2 O 5 remains elusive. Herein, we show that the OVs concentration in Nb 2 O 5 can be quantitatively manipulated by regulating the oxygen content in niobium complex (NbL) precursors, thus controlling the kinetics of the Nb 2 O 5 -based anode. The OVs concentration is inversely proportional to the oxygen content in the NbL, where it facilitates the electronic transfer and the Li-ion migration of Nb 2 O 5 with optimal introduction. In addition, the ligand in the NbL can also be used as a sacrificial template for creating an N-doped carbon coating wrapping Nb 2 O 5 nanoparticles with OVs to further improve the electronic conductivity of the composite. This was followed by depositing the NbL nanoparticles via electrophoretic deposition for assembling binder-free electrodes. The integrated electrode-based LICs deliver 76 μWh cm−2 at 550 μW cm−2 and retain 94 % of the capacity after 5000 cycles. This work provides a new recognition for the design of metal oxide electrodes with fast kinetics for LICs from material modification to electrode material assembly. [ABSTRACT FROM AUTHOR]