Nitrogen-doped carbon nanotube in-situ loaded LiNbO3 anode with high capacitance contribution for lithium-ion capacitors

Abstract

LiNbO3 is an intercalation material with high theoretical specific capacity, which is promising for lithium-ion capacitor (LIC) anode. However, the poor charge transfer dynamics makes LiNbO3 unable to match the capacitive cathode in rate performance and cycle stability, resulting in poor electrochemical performance of the device. Herein, through the integrated process of in-situ nitrogen-doping with polypyrrole as the nitrogen source and hydrothermal deposition, the coaxial heterostructure of ultrafine LiNbO3 nanoparticles and nitrogen-doped carbon nanotubes (NCNT) was realized. The large lithium-ion accessible surface and the bonding with the conductive channel significantly enhance the pseudocapacitive behavior of LiNbO3 (capacitance contribution of 78.5% at 1 mV s−1). After 1000 cycles at a current density of 2 A g−1, NCNT@LiNbO3 still has a specific capacity of 154.9 mAh g−1 (89.8%). Thus, the assembled NCNT@LiNbO3//AC devices can charge and discharge up to 10000 cycles at a current density of 2 A g−1, and the capacity retention rate can still reach 90.3%, and can provide an energy density of 142 Wh kg−1. This work provides ideas for the interface and structure design of nanocomposite electrode materials.