Advanced Electrode Materials Comprising of Structure‐Engineered Quantum Dots for High‐Performance Asymmetric Micro‐Supercapacitors

Abstract

Micro‐supercapacitors (MSCs) as a new class of energy storage devices have attracted great attention due to their unique merits. However, the narrow operating voltage, slow frequency response, and relatively low energy density of MSCs are still insufficient. Therefore, an effective strategy to improve their electrochemical performance by innovating upon the design from various aspects remains a huge challenge. Here, surface and structural engineering by downsizing to quantum dot scale, doping heteroatoms, creating more structural defects, and introducing rich functional groups to two dimensional (2D) materials is employed to tailor their physicochemical properties. The resulting nitrogen‐doped graphene quantum dots (N‐GQDs) and molybdenum disulfide quantum dots (MoS2‐QDs) show outstanding electrochemical performance as negative and positive electrode materials, respectively. Importantly, the obtained N‐GQDs//MoS2‐QDs asymmetric MSCs device exhibits a large operating voltage up to 1.5 V (far exceeding that of most reported MSCs), an ultrafast frequency response (with a short time constant of 0.087 ms), a high energy density of 0.55 mWh cm−3, and long‐term cycling stability. This work not only provides a novel concept for the design of MSCs with enhanced performance but also may have broad application in other energy storage and conversion devices based on QDs materials.

An Aqueous Anti‐Freezing and Heat‐Tolerant Symmetric Microsupercapacitor with 2.3 V Output Voltage

“…k) Comparison of the areal energy density of the constructed symmetric MSC‐CP with that of other high‐performance asymmetric MSCs reported previously. [ 8,11,15–22,62,73–81 ]…”

“…Impressively, the specific areal capacitance of the MSC‐CP was calculated to be 66.1, 63.8, 54.4, 49.7, and 47.1 mF cm −2 at scan rates of 10, 20, 50, 80 and 100 mV s −1 , with corresponding specific volumetric capacitances of 44.4, 42.8, 36.5, 33.3, and 31.6 F cm −3 , respectively (Figure S19d,e, Supporting Information). Thanks to the 2.3 V operating voltage enabled by the HVTT‐PAM‐10.5, the MSC‐CP achieved a record high areal energy density of 48.6 μWh cm −2 at the power density of 760.2 μW cm −2 , far outperforming all reported symmetric MSCs with aqueous electrolytes based on carbon materials, [ 12,25–27,43–61 ] conductive polymers, [ 13,62–64 ] MXene, [ 14,65–68 ] metal oxides, [ 69–72 ] (Figure 4e; Table S1, Supporting Information) and high‐energy AMSCs with aqueous electrolytes [ 8,11,15–22,62,73–81 ] (Figure 4k; Figure S19g and Table S1, Supporting Information). Even if the power density was increased to 5416.5 μW cm −2 , a high energy density of 34.6 μWh cm −2 was still maintained.…”

Anisotropic Boron–Carbon Hetero‐Nanosheets for Ultrahigh Energy Density Supercapacitors

“…Clearly,t he peaks at 532.6, 531.6, and 533.1 eV belong to the B À Ob ond, O = Cb ond, and O À Cb ond, respectively,which is highly consist with B1sand C1sspectra of ABCNs. [31] Thecrystalline structure of ABCNs is evaluated by X-ray diffraction (XRD). TheX RD spectrum of g-C 3 N 4 in boron nanosheets are shown in the Supporting Information, Figure S14.…”

Recent developments of advanced micro-supercapacitors: design, fabrication and applications

“…One strategy is to make capacitive asymmetric MSCs with both EDLC and pseudocapacitor materials. For example, Liu et al 118 reported an asymmetric MSC using nitrogen-doped graphene quantum dots (N-GQDs) as negative electrode and molybdenum disulfide quantum dots (MoS 2 -QDs) as positive electrode, and achieved a large operating voltage up to 1.5 V and a high energy density of 0.55 mWh cm −3 . In addition, Gao et al 61 prepared an integrated MSC array based on MnO 2 @Ppy@MWCNT (multiwalled carbon nanotube) anode and Ppy@MWCNT cathode.…”