Iron oxide encapsulated in nitrogen-rich carbon enabling high-performance lithium-ion capacitor

Abstract

Lithium-ion capacitors (LICs) could combine the virtues of high power capability of conventional supercapacitors and high energy density of lithium-ion batteries. However, the lack of high-performance electrode materials and the kinetic imbalance between the positive and negative electrodes are the major challenge. In this study, Fe 3 O 4 nanoparticles encapsulated in nitrogen-rich carbon (Fe 3 O 4 @NC) were prepared through a self-assembly of the colloidal FeOOH with polyaniline (PANI) followed by pyrolysis. Due to the well-designed nanostructure, conductive nitrogen-rich carbon shells, abundant micropores and high specific surface area, Fe 3 O 4 @NC-700 delivers a high capacity, high rate capability and long cycling stability. Kinetic analyses of the redox reactions reveal the pseudocapacitive mechanism and the feasibility as negative material in LIC devices. A novel LIC was constructed with Fe 3 O 4 @NC-700 as the negative electrode and expanded graphene (EGN) as the positive electrode. The wellmatched two electrodes effectively alleviate the kinetic imbalance between the positive and negative electrodes. As a result, Fe 3 O 4 @NC-700//EGN LIC exhibits a wide operating voltage window, and thus achieves an ultrahigh energy density of 137.5 W h kg −1. These results provide fundamental insights into the design of pseudocapacitive electrode and show future research directions towards the next generation energy storage devices.

Nitrogen and phosphorous co-doped hierarchical meso—microporous carbon nanospheres with extraordinary lithium storage for high-performance lithium-ion capacitors

“…The Ragone plots in Fig. 6g show that the energy and power densities of the as-fabricated LIC are highly comparable or even exceeded those of many LICs that have been reported (Table S3), including Li 4 Ti 5 O 12 (LTO)// AC [48], Li 4 Ti 5 O 12 /C//porous graphene macroform (PGM) [49], graphitic carbon (GC)//AC [50], Li 2 TiSiO 5 (LTSO)/C//AC [51], m-Nb 2 O 5 -C//AC [52], SnO 2 -C//C [53], H 2 Ti 6 O 13 //CMK-3 [54], Fe 3 O 4 /C@MXenes//AC [55], Fe 2 TiO 5 /super conducting carbon black (SCCB) [56], N-doped carbon//AC [57], TiNb 2 O 7 //AC [58], Ti 3 C 2 T x /rGO//AC [59], and soft carbon (SC)//AC [60].…”

Porous 3D Architecture of Carbon‐Encapsulated Fe3O4 Nanospheres Anchored on Networks of Carbon Nanotubes as Anodes for Advanced Lithium‐Ion Batteries

“…As can be seen from Figure 5e, the Fe 3 O 4 /CNTs@C delivers a discharge specific capacity of 775 mA h g −1 under a current density of 200 mA g −1 . When the current density soars stepwise to 0.5, 1.0, 2.0 and 5.0 A g −1 , the specific capacity decreases gradually to approximately 705, 633, 598 and 523 mA h g −1 , respectively, which is superior than some reported results (Figure 5f) [45–53] . After the fast charge/discharge for 50 cycles and the current density is restored to 200 mA g −1 , the capacity for the Fe 3 O 4 /CNTs@C composite rise to 776 mA h g −1 .…”

Study on the Alternative Solvent of Methylbenzene in the Total Acid Number Titration of Current Jet Fuels

“…As shown in Tables S1 and S2, 0.23, 0.14, 0.28, and 0.32 mL of KOH solution are consumed by the titration solvents of methylbenzene, isopropanol, and water ( V methylbenzene / V isopropanol / V water = 100:99:1), absolute ethanol and water ( V absolute ethanol / V water = 99:1), isopropanol and water ( V isopropanol / V water = 99:1), and cyclohexane, isopropanol, and water ( V cyclohexane / V isopropanol / V water = 100:99:1), respectively. Note that in the titration solvents, the organic solvents are used to extract the organic acids in the jet fuel, such as naphthenic acids, and the water is used to extract the water-soluble acids. − Meanwhile, the organic solvents can also improve the solubility of water in the jet fuel because the hydrocarbon chains of organic solvents interact with the fuel physicochemically, and the hydroxyl group forms hydrogen bonds with water molecules. , …”