T-Nb2O5 embedded carbon nanosheets with superior reversibility and rate capability as an anode for high energy Li-ion capacitors

Abstract

Li-ion capacitors (LICs), structured with an energy-type lithium-ion battery (LIB) anode and a power-type electrochemical capacitor (EC) cathode, have attracted great attention owing to the combined advantages of high energy density of LIBs and high power density of ECs. Unfortunately, the imbalance in reaction kinetics between the sluggish faradaic lithium-intercalation anode and rapid non-faradaic capacitive cathode is the main impediment in developing high-performance LICs. Herein, a new type of LIC with an orthorhombic T-Nb₂O₅/graphene-like carbon nanosheet (T-Nb₂O₅/GCN) anode and graphene-like carbon nanosheet (GCN) cathode is designed and fabricated. Benefiting from the merits of the structure and pseudocapacitive properties of the T-Nb₂O₅/GCN nanocomposite, a high capacity of ∼170 mA h g⁻¹ at 0.1 A g⁻¹ (1.0–3.0 V vs. Li/Li⁺) and a superior capacity retention of 90% after 500 cycles are obtained in a half-cell. In the voltage range of 0–3.5 V, the LIC exhibits a superior energy density of 129 W h kg⁻¹ and power density of 32 kW kg⁻¹. In addition, the capacity retention of the LIC is 80% after 10 000 cycles. This design provides an effective way to fabricate high-performance LICs.