High-performance hybrid electrochemical capacitor with binder-free Nb₂O₅@graphene

Abstract

Hybrid electrochemical capacitors (HECs) are capable of storing more energy than supercapacitors while providing more power compared to lithium-ion batteries (LIBs). The development of Li-intercalating materials is critical to organic electrolyte based HECs, which generally give larger potential output than aqueous electrolyte based HECs. This article reports on a simple binder-free Nb 2 O 5 @graphene composite that exhibited excellent HEC performance as compared with other Li intercalating electrode materials. The composite exhibited enhanced cyclability with a capacity retention of 91.2% compared to 74.4% of the pure Nb 2 O 5 half-cell when tested at a rate of 2000 mA g À1 (10 C). The composite displayed a lower polarization effect when cycled at increasing scan rates (1-10 mV s À1 ). The enhanced rate capability could be ascribed to the use of a highly conductive graphene support. As a result, the HEC composed of the Nb 2 O 5 @graphene composite and activated carbon (AC) delivered a maximum energy and power density of 29 W h kg À1 and 2.9 kW kg À1 . The performance is better than most reported HECs with other Li-intercalating electrode materials.

Electrode Materials, Electrolytes, and Challenges in Nonaqueous Lithium‐Ion Capacitors

“…However, due to the poor electrical conductivity of Nb 2 O 5 (≈3.4 × 10 −6 S cm −1 at 300 K), a poor rate capability and low electrochemical utilization were observed . Tremendous research efforts have been made to solve these issues, frequently by coating Nb 2 O 5 with conducting materials, such as in carbon‐coated T‐Nb 2 O 5, mesoporous Nb 2 O 5 /carbon nanocomposites, Nb 2 O 5 @graphene composites, rGO‐wrapped mesoporous T‐Nb 2 O 5 nanospheres, SnO 2 –rGO, and MoS 2 –RGO …”

Amorphous carbon layer contributing Li storage capacity to Nb2O5@C nanosheets

“…12 The lithium storage properties of Nb 2 O 5 -based electrode, have been intrinsically limited by its poor electrical conductivity (s z 3 Â 10 À6 S cm À1 ) and slow ion diffusion, which results in low rate performance. [24][25][26][27] Recently, our group found that an amorphous carbon coating layer can effectively enhance the capacity, cycle life, and rate performance of electrode materials, in which the amorphous carbon layer not only improved the electronic conductivity of the electrode material, but also contributed to high capacity. [24][25][26][27] Recently, our group found that an amorphous carbon coating layer can effectively enhance the capacity, cycle life, and rate performance of electrode materials, in which the amorphous carbon layer not only improved the electronic conductivity of the electrode material, but also contributed to high capacity.…”

Conducting polymer hydrogel materials for high-performance flexible solid-state supercapacitors

“…The performance of a flexible supercapacitor mainly depends on the properties of electrode materials and the device configuration [6]. The electrode materials of supercapacitor include various nanocarbons, conducting polymers and transition metal oxides [7][8][9][10][11][12]. Conducting polymer electrodes possess several merits, such as high electric conductivity, large capacitance, inherent flexibility and easy to processing [13][14][15][16][17][18].…”