High‐Performance Sodium‐Ion Hybrid Supercapacitor Based on Nb₂O₅@Carbon Core–Shell Nanoparticles and Reduced Graphene Oxide Nanocomposites

Abstract

Sodium‐ion hybrid supercapacitors (Na‐HSCs) have potential for mid‐ to large‐scale energy storage applications because of their high energy/power densities, long cycle life, and the low cost of sodium. However, one of the obstacles to developing Na‐HSCs is the imbalance of kinetics from different charge storage mechanisms between the sluggish faradaic anode and the rapid non‐faradaic capacitive cathode. Thus, to develop high‐power Na‐HSC anode materials, this paper presents the facile synthesis of nanocomposites comprising Nb2O5@Carbon core–shell nanoparticles (Nb2O5@C NPs) and reduced graphene oxide (rGO), and an analysis of their electrochemical performance with respect to various weight ratios of Nb2O5@C NPs to rGO (e.g., Nb2O5@C, Nb2O5@C/rGO‐70, ‐50, and ‐30). In a Na half‐cell configuration, the Nb2O5@C/rGO‐50 shows highly reversible capacity of ≈285 mA h g−1 at 0.025 A g−1 in the potential range of 0.01–3.0 V (vs Na/Na+). In addition, the Na‐HSC using the Nb2O5@C/rGO‐50 anode and activated carbon (MSP‐20) cathode delivers high energy/power densities (≈76 W h kg−1 and ≈20 800 W kg−1) with a stable cycle life in the potential range of 1.0–4.3 V. The energy and power densities of the Na‐HSC developed in this study are higher than those of similar Li‐ and Na‐HSCs previously reported.

Sodium ion storage in reduced graphene oxide

“…A pronounced reduction peak at 0.82 and 0.92 V can be seen from Fe-RGO and Sn-RGO, respectively. This reduction peak was due to the degradation of the electrolyte and the formation of solid electrolyte interphase (SEI) [45]. A sharp cathodic peak near ~0.015 V was observed for both RGOs.…”

Advanced Functional Carbons and Their Hybrid Nanoarchitectures towards Supercapacitor Applications

“…[96,97] The differencei n crystalline and amorphous phasesl ed to an extra contribution of pseudocapacitance. [99] This hybrid materialw as tested in as odium-ionh alfcell configuration, and provided ac apacity of 285 mAh g À1 at 0.025 Ag À1 over the potential window of 0.01-3.0 V( vs. Na/ Na + ). Because Nb 2 O 5 has ah igh theoreticalc apacity,a ppropriate voltage range,a nd low cost, it was fabricated with variousm orphologies and architectures.…”

“…[98] Furthermore, they synthesized a Nb 2 O 5 @carbonc ore-shell structure combined with rGO nanosheets. [99] This hybrid materialw as tested in as odium-ionh alfcell configuration, and provided ac apacity of 285 mAh g À1 at 0.025 Ag À1 over the potential window of 0.01-3.0 V( vs. Na/ Na + ). Then, it was installed into aN aH SC as an anode material with AC as the cathode material;t his gave ah igh energy density of 76 Wh kg À1 at ap ower density of 80 Wkg À1 .…”

Performance of Na-ion Supercapacitors Under Non-ambient Conditions—From Temperature to Magnetic Field Dependent Variation in Specific Capacitance

“…Typical energy densities that have been reported are ∼210-600 W h kg −1 . Intriguingly, its capacitive behavior remains ignored or mostly limited (Lu et al, 2015;Lim et al, 2016;Zhang et al, 2017;Ramakrishnan et al, 2018). For application in supercapacitors, tuning of morphology, surface area, pore size/dimension, and redox sites becomes essential.…”