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

Abstract

A 2D boron nanosheet that exhibits high theoretical capacitance, around four times that of graphene, is a significant supercapacitor electrode. However, its bulk structure with low interlaminar conduction and porosity restricts the charge transfer, ion diffusion, and energy density. Herein, we develop a new 2D hetero‐nanosheet made of anisotropic boron–carbon nanosheets (ABCNs) by B−C chemical bonds via gas‐phase exfoliation and condensation bottom‐up strategy. The ABCNs are constructed into high flexible supercapacitor electrode by microfluidic electrospinning. The ABCN electrode greatly promotes smooth migration and excessive storage of electrolyte ions due to large interlayer conductivity, ionic pathways, and accessible surfaces. The flexible supercapacitor delivers ultrahigh volumetric energy density of 167.05 mWh cm−3 and capacitance of 534.5 F cm−3. A wearable energy‐sensor system is designed to stably monitor physiological signals.

2D boron nanosheet architectonics: opening new territories by smart functionalization

“…Wu and Long et al prepared a boron nanosheets@carbon nanosheet composite, in which the B-C bond was conrmed by XPS analysis. 128,129 The B-C bond not only endows the composite with better charge transfer in three dimensions, but also stabilizes the boron nanosheets. The composite was identied as a good electrode material for a high performance supercapacitor.…”

“…The composite was identied as a good electrode material for a high performance supercapacitor. 128,129 The borophene-MoS 2 nanosheet is another extensively investigated composite. Shen et al theoretically designed a borophene/MoS 2 heterostructure and investigated the adsorption behaviors towards small gas molecules (CO, CO 2 , NO, NO 2 and NH 3 ) on the borophene surface.…”

Graphene Fiber‐Based Wearable Supercapacitors: Recent Advances in Design, Construction, and Application

“…In this aspect, we designed a wearable energy‐sensor system to detect the physiological signals by integrating FSC with a mechanical sensor. [ 126 ] This wearable system can monitor human activities with steadily physiological signals, including pulse (Figure 15i) and heart signals (Figure 15j).…”

A Covalent Black Phosphorus/Metal–Organic Framework Hetero‐nanostructure for High‐Performance Flexible Supercapacitors

“…Figure 4e and Figure S19 4f,t he E-BP/ZIF-67 exhibits ah igh capacitance of 506 Fcm À3 ,w hich is 763 %a nd 234 %i mprovements than those of bulk BP and E-BP FSCs.F igure S22 (Supporting Information) exhibits the coulombic efficiencies at different current densities.N otably,t he coulombic efficiencies rise from 66 %t o9 3% with the increase of current density from 0.5 to 10 Acm À3 .F igure 4g show the key parameters of energy and power densities for determining the practical applications. Significantly,t he E-BP/ ZIF-67 presents the high energy densities of 109.8 mWhcm À3 at power density of 0.675 Wcm À3 .T ot he best of our knowledge,s uch am aximum energy density evidently reaches one of the best levels among recently reported FSCs (Table S2, Supporting Information), such as SnO 2Àx B y (1.36 10 À3 mWhcm À3 ), [53] carbon nanocages (9.34 10 À2 mWh cm À3 ), [54] CNTs (1.2 mWhcm À3 ), [55] black phosphorus (2.47 mWhcm À3 ), [56] CNT/MXene (2.55 mWh cm À3 ), [57] CNT/RGO (6.3 mWhcm À3 ), [58] lithium thin-film battery (7.5 mWhcm À3 ), [10] carbon nanosheets (8.4 mWhcm À3 ), [5] graphene/PANI (8.8 mWhcm À3 ), [24]…”

“…On the other hand, the manufacture of FSCs that offers good interfacial adhesion of electrode and electrolyte layers, remarkable mechanical strength and flexibility,a nd largescale production is of fundamental importance for highperformance FSCs and back-end wearable applications. [24] Previous manufacturing procedures,i ncluding laser and printing technologies are highly efficient, convenient and patternable to fabricate FSCs.F or instance,l aser technologies,s uch as direct laser writing, [25] spatially shaped femtosecond laser, [26] and photoresist-free direct laser cutting [27] were used to construct chip-based FSCs with complete flexibility,d iverse planar geometry and capability of tunability-designed integrality. [28] Thep atterning of laser-induced FSCs kept excellent energy density of 23 mWhcm À3 due to high throughput pathways for ionic migration.…”