3D Nitrogen-doped Carbon Research Articles

Direct Pyrolysis of Supermolecules: An Ultrahigh Edge-Nitrogen Doping Strategy of Carbon Anodes for Potassium-Ion Batteries.

Most reported carbonaceous anodes of potassium-ion batteries (PIBs) have limited capacities. One approach to improve the performance of carbon anodes is edge-nitrogen doping, which effectively enhances the K-ion adsorption energy. It remains challenging to achieve high edge-nitrogen doping due to the difficulty in controlling the nitrogen dopant configuration. Herein, a new synthesis strategy is proposed to prepare carbon anodes with ultrahigh edge-nitrogen doping for high-performance PIBs. Specifically, self-assembled supermolecule precursors derived from pyromellitic acid and melamine are directly pyrolyzed. During the pyrolysis process, the amidation and imidization reactions between pyromellitic acid and melamine before carbonization enable the successful carbonization of pyromellitic acid-melamine supermolecule. The obtained 3D nitrogen-doped turbostratic carbon (3D-NTC) possesses a 3D framework composed of carbon nanosheets, turbostratic crystalline structure, and an ultrahigh edge-nitrogen-doping level up to 16.8 at% (73.7% of total 22.8 at% nitrogen doping). These features endow 3D-NTCs with remarkable performances as PIB anodes. The 3D-NTC anode displays a high capacity of 473 mAh g-1 , robust rate capability, and a long cycle life of 500 cycles with a high capacity retention of 93.1%. This new strategy will boost the development of carbon anodes for rechargeable alkali-metal-ion batteries.

3D hierarchical porous nitrogen-doped carbon/Ni@NiO nanocomposites self-templated by cross-linked polyacrylamide gel for high performance supercapacitor electrode

Three-dimensional nitrogen-doped carbon network incorporated with nickel@nickel oxide core-shell nanoparticles composite (3D NC/Ni@NiO) has been facilely prepared, self-templated by the cross-linked polyacrylamide aerogel precursor containing NiCl2. Characterizations reveal that the Ni@NiO nanoparticles distribute homogeneously in the 3D nitrogen-doped carbon matrix and the composite is of hierarchical porous structure. When used as supercapacitor electrode in a three-electrode system, the 3D NC/Ni@NiO exhibits enhanced electrical conductivity and excellent electrochemical performance, presenting a high specific capacitance (389F g−1 at 5 mV s−1), good rate capability (276 F g−1 at 100 mV s−1) and outstanding cycling performance (with the capacitance retention of 70.2% after 5000 charge-discharge cycles). This is due to the synergistic effects of conductive metallic nickel, pseudocapacitive nickel oxide as well as in situ nitrogen doping of carbon network. Moreover, an asymmetric supercapacitor (ASC) was fabricated with NC/Ni@NiO as positive electrode and active carbon as negative electrode. The ASC device exhibits a maximum energy density of 19.4 W h kg−1 at a power density of 700 W kg−1 and shows good cycling stability (73.8% capacity retention after 3000 cycles), indicating that it has great promise for practical energy storage and conversion application.

3D nitrogen-doped carbon supported non-precious metals electrocatalyst for oxygen reduction reaction

Sluggish oxygen reduction reaction (ORR) is a rate-limiting step in some electrochemical devices such as fuel cells. Thus, the synthesis and development of high performance, inexpensive and durable catalysts for ORR is a necessity. Metallic nanostructures decorated heteroatoms-doped carbons have been recognized as excellent catalysts in energy applications. However, nitrogen-doped partially oxidized three-dimensional carbonaceous supports were seldom studied for ORR. Herein, the synthesis of low Fe-Co bimetallic contents deposited on three-dimensional (3D) activated carbon (AC) is reported as an efficient and cost-effective catalyst for ORR in alkaline electrolyte. In the present work, AC was thermally treated by direct heat in air at 430 °C to enhance its electrochemical activity through increasing structure deficiency. AC and nitrogen doped AC (N-AC) were used to synthesize Fe-Co/AC and Fe-Co/N-AC. In both Fe-Co/AC and Fe-Co/N-AC, low amounts of non-precious Fe and Co nanoparticles were deposited on carbonaceous substrates. The air oxidation process, for partially oxidation of carbon structure and catalyst post treatment, was used for introducing defects to the catalyst structure. The performance of synthesized samples was evaluated by ORR process in alkaline medium.

Engineering Nickel/Palladium Heterojunctions for Dehydrogenation of Ammonia Borane: Improving the Catalytic Performance with 3D Mesoporous Structures and External Nitrogen-Doped Carbon Layers.

Catalysts based on metallic NPs have shown high activities in heterogeneous catalysis, due to their high fractions of surface-active atoms, which, however, will lead to the sacrifices in stability and recycle of catalysts. In order to balance well the relationship between activity, stability, and recovery, in this paper, we have constructed a 3D mesoporous sphere structure assembled by N-doped carbon coated Ni/Pd NP heterojunctions (Ni/Pd@N-C). This obtained Ni/Pd@N-C has shown high catalytic activity, durability and recyclability for the hydrolytic dehydrogenation of ammonia borane (AB). Further investigations, including experimental and theoretical results, have shown that the unique structural features, the synergistic effect between Ni and Pd, and the coating of N-doped carbon layer are responsible for the good catalytic performance of Ni/Pd@N-C mesoporous spheres.

Core@shell Sb@Sb2O3 nanoparticles anchored on 3D nitrogen-doped carbon nanosheets as advanced anode materials for Li-ion batteries.

Antimony (Sb) based materials are regarded as promising anode materials for Li-ion batteries (LIBs) because of the high capacity, appropriate working potential, and earth abundance of antimony. However, the quick capacity decay due to the huge volume expansion during the cycling process seriously hinders its practical applications. Here, a nanocomposite of core@shell Sb@Sb2O3 particles anchored on 3D porous nitrogen-doped carbon (3DNC) nanosheets is synthesized by freeze drying and sintering in a reducing atmosphere. Structural characterization shows that the developed Sb@Sb2O3/3DNC electrode has a high surface area (839.8 m2 g−1) and unique Sb–O–C bonding, both contributing to the excellent electrochemical performance. The initial charge and discharge specific capacities of the Sb@ Sb2O3/3DNC anode in LIB tests are 1109 mA h g−1 and 1810 mA h g−1, respectively. Also, it shows a charge capacity of 696.9 mA h g−1 after 500 cycles at 1 A g−1 and 458 mA h g−1 at a current density of 5 A g−1. Moreover, the assembled Sb@Sb2O3/3DNC‖LiNi0.6Co0.2Mn0.2O2 battery exhibits a discharge capacity of more than 100 mA h g−1 after 25 cycles at 100 mA g−1. The synthetic method can be extended to obtain other nanocomposites of metal and carbon materials for high-performance energy storage devices.

Large-Scale Synthesis of Three-Dimensional Reduced Graphene Oxide/Nitrogen-Doped Carbon Nanotube Heteronanostructures as Highly Efficient Electromagnetic Wave Absorbing Materials.

Herein, we use reduced graphene oxide as a substrate and NiFe as a catalyst to fabricate three-dimensional (3D) nitrogen-doped carbon nanotube (NCNT)/reduced graphene oxide heteronanostructures (3D NiFe/N-GCTs). The 3D NiFe/N-GCTs are composed of two-dimensional (2D) reduced graphene oxide-supported one-dimensional (1D) NiFe nanoparticle-encapsulated NCNT arrays. The NCNTs exhibit bamboo-like shapes with the length and diameter of 3-10 μm and 15-45 nm, respectively. Besides integration of advantages of 1D and 2D nanomaterials, the 3D NiFe/N-GCT heteronanostructure possesses interconnected network structures, sufficient interfaces, numerous defects, hundreds of void spaces enclosed by bamboo joints and the walls of the NCNT in an individual carbon nanotube, and large surface areas, which can improve their dielectric losses toward electromagnetic wave. Thus, the 3D NiFe/N-GCTs show satisfied property toward electromagnetic wave absorption. Typically, the optimized 3D NiFe/N-GCT displays excellent minimal reflection loss (-40.3 dB) and outstanding efficient absorption bandwidth (4.5 GHz), outperforming most of the reported absorbers. Remarkably, the synthesis of 3D NiFe/N-GCTs only involves vacuum freeze-drying and subsequent thermal treatment process at a high temperature, and thus, the large-scale production of 3D NiFe/N-GCTs can be achieved in each batch, affording the possibility of the practical applications of the 3D NiFe/N-GCTs.

Three-Dimensional Ordered Macroporous Metal-Organic Framework Single Crystal-Derived Nitrogen-Doped Hierarchical Porous Carbon for High-Performance Potassium-Ion Batteries.

The biggest challenge of potassium-ion batteries (KIBs) application is to develop high-performance electrode materials to accommodate the potassium ions large size. Herein, by rational design, we carbonize three-dimensional (3D) ordered macroporous ZIF-8 to fabricate 3D interconnected nitrogen-doped hierarchical porous carbon (N-HPC) that shows excellent rate performance (94 mAh g-1 at 10.0 A g-1), unprecedented cycle stability (157 mA g-1 after 12000 cycles at 2.0 A g-1), and superior reversible capacity (292 mAh g-1 at 0.1 A g-1). The 3D hierarchical porous structure diminishes the diffusion distance for both ions/electrons, while N-doping improves the reactivity and electronic conductivity via producing more defects. In addition, the bicontinuous structure possesses a large specific surface area, decreasing the current density, again improving the rate performance. In situ Raman spectra analysis confirms the potassiation and depotassiation in the N-HPC are highly reversible processes. The galvanostatic intermittent titration measurement and first-principles calculations reveal that the interconnected macropores are more beneficial to the diffusion of the K+. This 3D interpenetrating structure demonstrates a superiority for energy storage applications.

3D nitrogen-doped framework carbon for high-performance potassium ion hybrid capacitor

Post-lithium ion hybrid capacitors have great potential to serve as mid-to large-scale energy storage applications because of their high energy/power densities, abundant resources and low cost. Here we report a high-performance dual-carbon potassium ion hybrid capacitor (PIHC) based on two carbon electrode materials derived from a single precursor–ethylene diamine tetraacetic acid tetrasodium (EDTA-4Na). By means of a simple calcination, the EDTA-4Na can be directly converted to a three-dimensional (3D) nitrogen-doped framework carbon (3DNFC) that exhibits high reversible capacity and good electrochemical kinetic property for potassium ion storage. Such 3DNFC can be further converted to a 3D nitrogen-doped framework activated carbon (3DNFAC) that shows ultrahigh specific surface area (3839 m2 g−1) and excellent capacitance performance. Using the 3DNFC as battery-type anode and the 3DNFAC as capacitor-type cathode, a dual-carbon PIHC is fabricated, and it is able to normally work at 0–4.2 V, delivers high energy and power densities (163.5 Wh kg−1 at 210 W kg−1, and 76.4 Wh kg−1 at 21 000 W kg−1), and exhibits outstanding cycling stability (91.7% capacity retention after 10 000 cycles at 2.0 A g−1), which are all the best values for the state-of-the-art PIHCs.

Controllable synthesis of 3D nitrogen-doped carbon networks supported SnxPy nanoparticles as high performance anode for lithium ion batteries

SnxPy nanoparticles were controllably synthesized on 3D nitrogen-doped carbon networks (SnxPy/C) by a freeze drying and low-temperature phosphidation process. Interestingly, the product phase (Sn4P3, SnP0.94) could be varied by the SnCl4 concentrations and the doping of SnP0.94 could significantly enhance the cycling properties of Sn4P3 for lithium ion batteries (LIBs). The obtained SnxPy nanoparticles (5–10 nm) were anchored on the 3D nitrogen-doped carbon networks (N-CN), which protected SnxPy from serious agglomeration and large volume expansion. Meanwhile, the N-CN possessed a highly interconnected 3D network structure and good conductivity, so the transportation of Li+ would be speed up to enhance the electrochemical performance. As the LIBs anode, SnxPy/C displayed the best cycling performance with 2 M SnCl4 solution, which remained a high capacity of 718 mAh g−1 after 120 cycles (100 mA g−1). The strategy of synthesis SnxPy/C could be expanded to controllable synthesis of other metal phosphides on 3D nitrogen-doped carbon networks for LIBs, catalysis, hydrogen generation, etc.

Pyridinic-N Protected Synthesis of 3D Nitrogen-Doped Porous Carbon with Increased Mesoporous Defects for Oxygen Reduction.

Nitrogen (N)-doped carbons are potential nonprecious metal catalysts to replace Pt for the oxygen reduction reaction (ORR). Pyridinic-N-C is believed to be the most active N group for catalyzing ORR. In this work, using zinc phthalocyanine as a precursor effectively overcomes the serious loss of pyridinic-N, which is commonly regarded as the biggest obstacle to catalytic performance enhancement upon adopting a second pyrolysis process, for the preparation of a 3D porous N-doped carbon framework (NDCF). The results show only ≈14% loss in pyridinic-N proportion in the Zn-containing sample during the second pyrolysis process. In comparison, a loss of ≈72% pyridinic-N occurs for the non-Zn counterpart. The high pyridinic-N proportion, the porous carbon framework produced upon NaCl removal, and the increased mesoporous defects in the second pyrolysis process make the as-prepared catalyst an excellent electrocatalyst for ORR, exhibiting a half-wave potential (E1/2 = 0.88 V) up to 33 mV superior to state-of-the-art Pt/C and high four-electron selectivity (n > 3.83) in alkaline solution, which is among the best ORR activities reported for N-doped carbon catalysts. Furthermore, only ≈18 mV degradation in E1/2 occurs after an 8000 cycles' accelerating stability test, manifesting the outstanding stability of the as-prepared catalyst.

Well-defined cobalt sulfide nanoparticles locked in 3D hollow nitrogen-doped carbon shells for superior lithium and sodium storage

Hollow nanostructured materials present a class of promising electrode materials for energy storage and conversion. Herein, 3D hollow nitrogen-doped carbon shells decorated with well-defined cobalt sulfide nanoparticles (Co9S8/HNCS) have been constructed for superior lithium and sodium storage. Two steps are involved in the designed preparation procedure. First, hollow intermediates with preserved cobalt components are controllably fabricated by simultaneously dissociating cobalt containing zeolitic-imidazolate-frameworks-67 (ZIF-67), and polymerizing dopamine in a Tris–HCl solution (pH = 8.5). The polydopamine (PDA) wrapped intermediates inherits the polyhedral structure of the ZIF-67 crystals. In the second step, the final Co9S8/HNCS composite is obtained via a combined carbonization and sulfurization treatment of the intermediates, allowing the formation of hollow polyhedrons of nitrogen-doped carbon shells (900±100 nm) derived from PDA and the encapsulation of highly uniform cobalt sulfide nanoparticles (11±2 nm). This configuration is believed to not only shorten the lithium or sodium ion diffusion distance and accommodate volume change during lithium or sodium ion insertion/extraction, but also to enhance the overall electrical conductivity and the number of active sites. As a result, the Co9S8/HNCS composite exhibits an impressive reversible capacity of 755 mA h g-1 at 500 mA g-1 after 200 cycles for lithium ion storage, and capacities of 327 mA h g-1 at 500 mA g-1 after 200 cycles and 224 mA h g-1 at 1000 mA g-1 after 300 cycles for sodium ion storage. Essential factors especially the structural stability during cycling have been identified, and the discharge/charge mechanism is discussed.

Assembling Carbon Pores into Carbon Sheets: Rational Design of Three-Dimensional Carbon Networks for a Lithium-Sulfur Battery.

The conversion reaction-based lithium-sulfur battery features an attractive energy density of 2600 W h/kg. Nevertheless, the unsatisfied performance in terms of poor discharge capacity and cycling stability still hinders its practical applications. Recently, porous carbon materials have been widely reported as promising sulfur reservoirs to promote the sluggish reaction kinetics of sulfur conversion, tolerate volume expansion of sulfur, and suppress polysulfide shuttling. However, porous carbon with a simply designed nanostructure is hard to satisfy all of these aspects simultaneously. Herein, we have applied a dual-template strategy that assembles carbon pores into carbon sheets to prepare three-dimensional (3D) nitrogen-doped porous carbon nanosheets (N-PCSs) as the multifunctional sulfur host for the Li-S battery. By arranging carbon pores within an interconnected 3D architecture, the porous carbon sheets enable rapid electron/ion transfer. Moreover, the micro/mesopores and nitrogen dopant in N-PCS provide both physical and chemical restrictions to polysulfide species. With these advances, the N-PCS/S cathode delivers a large initial discharge capacity of 1360 mA h/g at 0.1 C. When performed at 0.5 C for 1000 cycles, the cathode can still remain ∼50% of its capacity with a low decay rate of 0.05% per cycle, showing the important role of the 3D carbon material in the Li-S battery.

Bifunctional biomass-derived 3D nitrogen-doped porous carbon for oxygen reduction reaction and solid-state supercapacitor

Biomass-derived carbon materials have garnered intensive consideration in energy fields, such as fuel cells and supercapacitors, due to their inexpensive precursors, abundant resources and facile synthesis. Herein, we report a facile strategy based on taro stem precursor to synthesize a 3D nitrogen-doped porous carbon (3DNPC) with micropores, mesopores, macropores, large specific surface area (1012 m2 g−1) and nitrogen content (4.8 at%), which displays high catalytic activity and stability for oxygen reduction reaction and good electrochemical properties for supercapacitors. Compared with the commercial Pt/C catalysts, the 3DNPC-800 with 3D porous structure, proper total doped N and high graphitic N content, presents brilliant long-term stability (96.5% retention after 20,000 s) and resistance to methanol crossover for oxygen reduction reaction. With respect to electrode material of supercapacitor, the 3DNPC-800 possesses high specific capacitance (236.4F g−1 at 0.1 A g−1) and outstanding long cycle durability (89.3% retention after 10,000 cycles at 20 A g−1). Moreover, the prepared symmetric solid-state supercapacitor devices achieve outstanding power density (5 kW kg−1 at 5.56 Wh kg−1). Consequently, economically and sustainably utilization nature of materials to fabricate heteroatom-doped carbon materials, having great potential in electrochemical applications, is presented.

Large-scale template-free synthesis of nitrogen-doped 3D carbon frameworks as low-cost ultra-long-life anodes for lithium-ion batteries

Finding novel anode materials in place of the current commonly used but performance-limited graphite is the top priority for the remarkable development of lithium-ion batteries (LIBs). Although impressive reports have been published, certain problems, such as complicated synthesis processes, limited production, high cost of raw materials, and lack of truly durable and high-capacity performance, are still hindering the actual applications of LIBs. In this work, we report a mass-produced 3D nitrogen-doped carbon framework (NCF) that uses low-cost polyacrylonitrile (PAN) as the precursor. A simple sol–gel method is used to prepare the anode materials for ultra-long life LIBs, through which 24.35 g samples can be easily prepared at the laboratory level. This method also ensures that samples with certain morphologies, crystal structures, and nitrogen of specific contents and species can be prepared by the simple control of the pyrolysis temperature. Benefitting from the unique structure, NCFs-800 exhibits excellent rate performance, with its lithium ion storage capacity maintained as high as 41.4% from 675 mAh g−1 to 279 mAh g−1 when the current density increases 100-fold from 0.1 A g−1 to 10 A g−1. Furthermore, the electrode of NCFs-800 possesses an ultra-long lifespan of over 10,000 cycles with stable capacity retention exceeding 54%, corresponding to a remarkably slow capacity loss of 0.0046% per cycle. After deep cycling at 10 A g−1, a relatively high capacity of 124 mAh g−1 can be retained, which is consistent with the theoretical capacity of cathode materials. Therefore, this kind of material is perfect for industrialization, given the low cost of raw materials, easily scaled up methods, and excellent lithium storage performance.

In situ growth of amorphous Fe2O3 on 3D interconnected nitrogen-doped carbon nanofibers as high-performance anode materials for sodium-ion batteries

In this work, a novel porous amorphous Fe2O3/nitrogen-doped carbon composite as a promising anode material for sodium-ion batteries has been fabricated by in situ growing amorphous Fe2O3 on 3D interconnected nitrogen-doped carbon nanofibers. The as-prepared composite exhibits superior sodium storage properties. It delivers a high reversible capacity of 408 mA h g−1 after 350 cycles at a current density of 100 mA g−1 and a good rate capability of 183 mA h g−1 at 3 A g−1. The excellent electrochemical performance is owing to the synergistic effects of the amorphous structure of Fe2O3 and the 3D interconnected nitrogen-doped carbon network with high nitrogen doping content (10 atom%), which do not only relieve the internal stress of the electrode and accommodate more electrochemical active sites for Na+ storage, but also buffer the volume changes of amorphous Fe2O3 as well as facilitate the electronic and ionic transportation during cycling.

Molybdenum carbide nanoparticle-decorated 3D nitrogen-doped carbon flowers as an efficient electrode for high-performance, all-solid-state symmetric supercapacitors

Electrode materials with high electro-catalytic activity and tailored nanostructures are of great importance for high performance energy storage devices. We develop a novel 3D nanostructured electrode with highly stable, and catalytically-active molybdenum carbide nanoparticles decorated on nitrogen-doped carbon flowers (Mo2C/NCF). The controlled synthesis of Mo2C/NCF provides a uniform distribution of Mo2C nanoparticles of ∼80 nm on carbon microflowers with a self-assembled petal-like structure. The Mo2C/NCF achieves excellent electrochemical performance, with a specific capacitance of 1250 F/g at the current density of 1 A/g in a liquid electrolyte. A device consisting of all-solid-state symmetric supercapacitors (SSC) that used this novel electrode exhibits a high energy density of 54 Wh/kg along with remarkable cycling stability (100% retention after 5000 cycles). We believe that these results provide a new way for carbide materials to be used in high-performance energy storage devices.

Co Nanoparticles Confined in 3D Nitrogen-Doped Porous Carbon Foams as Bifunctional Electrocatalysts for Long-Life Rechargeable Zn-Air Batteries.

Proper design and simple preparation of nonnoble bifunctional electrocatalysts with high cost performance and strong durability for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) is highly demanded but still full of enormous challenges. In this work, a spontaneous gas-foaming strategy is presented to synthesize cobalt nanoparticles confined in 3D nitrogen-doped porous carbon foams (CoNCF) by simply carbonizing the mixture of citric acid, NH4 Cl, and Co(NO3 )2 ·6H2 O. Thanks to its particular 3D porous foam architecture, ultrahigh specific surface area (1641 m2 g-1 ), and homogeneous distribution of active sites (C-N, Co-Nx , and Co-O moieties), the optimized CoNCF-1000-80 (carbonized at 1000 °C, containing 80 mg Co(NO3 )2 ·6H2 O in precursors) catalyst exhibits a remarkable bifunctional activity and long-term durability toward both ORR and OER. Its bifunctional activity parameter (ΔE) is as low as 0.84 V, which is much smaller than that of noble metal catalyst and comparable to state-of-the-art bifunctional catalysts. When worked as an air electrode catalyst in rechargeable Zn-air batteries, a high energy density (797 Wh kg-1 ), a low charge/discharge voltage gap (0.75 V), and a long-term cycle stability (over 166 h) are achieved at 10 mA cm-2 .

A flexible 3D nitrogen-doped carbon foam@CNTs hybrid hosting TiO2 nanoparticles as free-standing electrode for ultra-long cycling lithium-ion batteries

Free-standing electrodes have stood out from the electrode pack, owing to their advantage of abandoning the conventional polymeric binder and conductive agent, thus increasing the specific capacity of lithium-ion batteries. Nevertheless, their practical application is hampered by inferior electrical conductivity and complex manufacturing process. To this end, we report here a facile approach to fabricate a flexible 3D N-doped carbon foam/carbon nanotubes (NCF@CNTs) hybrid to act as the current collector and host scaffold for TiO2 particles, which are integrated into a lightweight free-standing electrode (NCF@CNTs-TiO2). In the resulting architecture, ultra-fine TiO2 nanoparticles are homogeneously anchored in situ into the N-doped NCF@CNTs framework with macro- and meso-porous structure, wrapped by a dense CNT layer, cooperatively enhances the electrode flexibility and forms an interconnected conductive network for electron/ion transport. As a result, the as-prepared NCF@CNTs-TiO2 electrode exhibits excellent lithium storage performance with high specific capacity of 241 mAh g−1 at 1 C, superb rate capability of 145 mAh g−1 at 20 C, ultra-long cycling stability with an ultra-low capacity decay of 0.0037% per cycle over 2500 cycles, and excellent thermal stability with ∼94% capacity retention over 100 cycles at 55 °C.

Sulfur vacancy-rich CdS loaded on filter paper-derived 3D nitrogen-doped mesoporous carbon carrier for photocatalytic VOC removal

A new strategy is explored to fabricate a sulfur vacancy-rich CdS composite photocatalyst with a nitrogen-doped 3D porous carbon matrix for VOC removal.

Flexible quasi-solid-state 2.4 V aqueous asymmetric microsupercapacitors with ultrahigh energy density

A simple and cost-effective cut-and-transfer method is demonstrated to fabricate flexible 2.4 V asymmetric microsupercapacitors by adopting hierarchical Na-MnOx nanosheets on 3D nitrogen-doped carbon fibers as the cathode and VN nanosheet arrays as the anode.