Pseudocapacitive T-Nb2O5/N-doped carbon nanosheets anode enable high performance lithium-ion capacitors

Lithium ion capacitors combine the complementary advantageous characteristics of batteries and supercapacitors are expected to deliver both high energy and high power density. However, this technology suffers from the kinetics imbalance between battery electrode and capacitive electrode. Here, two dimensional T-Nb2O5/N-doped carbon nanosheets with a well-continuous ionic/electronic conducting network demonstrate superior rate capability of 142.3 mA h g−1 at 20 C (1 C = 200 mA g−1). A majority of charge storage in the T-Nb2O5/N-doped carbon nanosheets was proved to be intercalation pseudocapacitive processes by kinetic analysis, enabling fast charge storage performance. A lithium ion capacitor is based upon these T-Nb2O5/N-doped carbon nanosheets was successfully fabricated, demonstrating high energy density (70.3 W h kg−1) and high power density (16,014 W kg−1).