Heterogeneous Contraction-Mediated Asymmetric Carbon Colloids

Abstract

Introducing asymmetry in carbon colloids can enrich their already broad merits; however, the tailored synthesis of asymmetric carbon colloids remains a great challenge. Herein, we report the synthesis of asymmetric semi-yolk−shell carbon spheres (semi-YSCS) with rich N-doping (3.9 at%), raspberry-like rough surface, abundant mesopores, and uniform particle size (∼600 nm). An interfaceinduced heterogeneous contraction mechanism is proposed. The unique structural features endow the semi-YSCS a high specific capacitance (283 F g −1 at 1 A g −1 ), favorable cycling stability, and superior rate performance in aqueous supercapacitors. This work provides new insights into the rational design of asymmetric carbon colloids. C arbon colloids have received increasing researchinterest because of their widespread potential applications in sorption, biomedicine, catalysis, electrocatalysis, secondary batteries, as well as supercapacitors. 1−3 Significant progress has been made in the rational design of carbon colloids with tailored morphology, microstructure, size, porosity, and surface functionality as their physicochemical properties are highly dependent on these structural parameters. 4−8 Conventional carbon colloids, such as microporous/mesoporous carbon spheres, 4,9,10 hollow carbon spheres, 11−14 and core-shell carbon spheres, 15,16 possess highly symmetric spherical shape, which is restricted to the primary principle of symmetry in nature.Recently, considerable efforts have been devoted to the construction of asymmetric carbon colloids due to not only the structural complexity but also the possible enhanced properties caused by the anisotropic effect. 17 For example, in the field of energy storage and conversion, asymmetric bowl-like mesoporous carbon particles manifested excellent electrocatalytic performance for oxygen reduction reaction. 17 N-doped hollow carbon bowls delivered favorable electrochemical performance in Li−S batteries. 18 Asymmetric flasklike hollow carbon colloids demonstrated impressive supercapacitor performance. 19 In the field of biomedicine, mesoporous carbon hemispheres demonstrated excellent thermal generation property under near-IR irradiation. 20 Asymmetric invaginated

Oxygen Vacancy Modulated LiMnxOy@C Three-Dimensional Nanosheet Arrays on Nickel Foam for Lithium-Ion Capacitor with High Performance

“…The excellent electrochemical performance of LMO@C­(Ar/H 2 ) in lithium-ion storage can be owed to the possible synergistic effect between LMO, the carbon-shell, and plenty of oxygen vacancies in the Ni foam@LMO@C composite. In addition, the better electrochemical performance of LMO@C­(Ar/H 2 ) than LMO­(Ar/H 2 ), shown in Figure a–d, further reflects that the unique chemiphysical structure of LMO@C­(Ar/H 2 ) which possesses the strong synergistic effect between the conductive carbon-shell and LMO in the LMO@C composites . On the basis of the XPS data (Figure ) and electrochemical properties of LMO@C­(Ar/H 2 ) in Figure a–d, we may find that the carbon layer not only introduces some oxygen vacancies during heat treatment which contributes to a part of capacitance but also increases conductivity and cycling stability.…”

“…In addition, the better electrochemical performance of LMO@C(Ar/H 2 ) than LMO(Ar/H 2 ), shown in Figure 7a−d, further reflects that the unique chemiphysical structure of LMO@C(Ar/H 2 ) which possesses the strong synergistic effect between the conductive carbon-shell and LMO in the LMO@C composites. 47 On the basis of the XPS data (Figure 5) and electrochemical properties of LMO@C(Ar/H 2 ) in Figure 7 a−d, we may find that the carbon layer not only introduces some oxygen vacancies during heat treatment which contributes to a part of capacitance but also increases conductivity and cycling stability. The result further confirms the contribution of the double-reduction effect of the carbon layer and calcination in the Ar/H 2 atmosphere on the electrochemical properties of LMO@C(Ar/H 2 ).…”

Anisotropic Self-Assembly of Asymmetric Mesoporous Hemispheres with Tunable Pore Structures at Liquid–Liquid Interfaces

“…Until now, extensive efforts have been directed to fabricate carbon spheres with asymmetric geometries such as interface-induced shrinking, island assembly, , epitaxial growth, , and preferential etching . However, most of the formed asymmetric carbon hemispheres are of nonporosity, greatly limiting the utilization of their internal matrixes.…”

Recent advances in carbon nanostructures prepared from carbon dioxide for high-performance supercapacitors

“…For most of the state-of-the-art commercial supercapacitors, numerous carbon materials with contrasting physical and chemical properties act as typical active materials in electrodes [17][18][19]. Among them, activated carbon (AC) is widely used as a practical electrode material due to its advantages of high specific surface area, low cost and mature preparation technologies [20][21][22][23]. However, supercapacitors based on AC usually present a much lower energy density (~15-20 Wh kg À1 ) than lithium-ion batteries (up to 250-300 Wh kg À1 ) [24][25][26][27], which is considered as a great obstacle for its further application in electronic devices requiring high energy and high power simultaneously.…”