KR101602168B1 - Manufacturing method of natrium ion battery anode material - Google Patents

Abstract

The present invention relates to a method for preparing a negative electrode material for a sodium ion battery, and more particularly, to a method for manufacturing a negative electrode material for a sodium ion battery comprising a graphene-based paper having disordered orientation and high flexibility.
According to the present invention as described above, a paper electrode for a sodium ion battery which is disorderly oriented and highly flexible can be produced by vacuum filtration of graphene-based nanosheets permanently folded and crumpled by thionyl chloride treatment, The electrochemical performance is superior to that of the graphene-based paper, and an excellent electrochemical performance is obtained even without a conductive filler and a binder as a substrate.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a negative electrode material for a sodium ion battery,

The present invention relates to a method for preparing a negative electrode material for a sodium ion battery, and more particularly, to a method for manufacturing a negative electrode material for a sodium ion battery comprising a graphene-based paper having disordered orientation and high flexibility.

Thin, light, and flexible energy storage is critical to the next generation of flexible electronics. Lithium-ion batteries (LIBs) are being studied as a bendable power source for roll-up displays, wearable appliances and other portable electronics.

However, lithium reserves are not sufficient and are therefore less cost-competitive to meet the increased demand of LIBs, and are not biocompatible for application in applications such as implantable biomedical devices and electronic skin care with similar health checks There is a limit. On the other hand, sodium ion batteries (NIBs) are about ten times cheaper than LIBs and have attracted attention as an alternative to LIBs because of their abundant resources, biocompatibility, and similar electrochemical properties in lithium. A graphene-based carbon nanosheets powdered electrode (generic electrode form) randomly mixed on a substrate with a binder has been studied as an electrode material for NIBs, but no electrode material for NIBs using a flexible carbon-based electrode has been reported . Examples of related prior arts include Korean Unexamined Patent Publication No. 10-2013-0094366 (anode active material and lithium battery including the same) and Korean Patent No. 10-1192355 (sodium battery and its manufacturing method).

Essential differences between lithium and sodium should be considered for the preparation of NIBs. Sodium ions are 55% larger in ionic radius than lithium ions, which lower the energy density and exhibit adverse kinetic characteristics in the insertion and extraction of sodium ions. It is difficult to insert large-sized sodium ions into the graphite layer of the carbon material, so that the graphite material is not generally used as a negative electrode material in NIBs.

On the other hand, recently, we succeeded in applying graphene-based paper as an anode material for LIBs. Since a substrate or a binder is not required in the production of electrodes, independent paper electrodes are advantageous in energy density compared to conventional electrodes, and highly flexible paper electrodes can be applied to flexible devices and wearable devices. Non-heat-treated graphene paper is reported to exhibit a reversible capacity of each of 214, 151 and 84 mAhg ^-1 at a current density when used as anode for LIBs, 10, 20 and 50 mAg ^-1 bar. Graphene is much lower than the reversible capacity to reflect this problem folded structure of the reversible capacity of the negative electrode of the paper is more irregular way as traditional powders in the form of stacked graphene cathode (50 in ^-1 288 mAg mAhg ^-1) graphene paper electrode this development was showed a significantly larger reversible capacity (100 864 mAhg ^-1 in mAg ^-1). However, in the In 200, 500, 1000, 1500 mAg -1 in rate characteristic current density showed a capacity that corresponds to each of 557, 268, 169, 141 mAhg -1, were reported to have this way the output characteristics were not significantly improved . This is because the movement of lithium ions toward the inside and outside of the graphene layer is limited to the edge only, so that there is a great restriction on the removal and insertion speed of lithium ions. The flexible, pore-rich graphene paper electrode enhances the rate characteristics because it enhances diffusion of lithium ions into the overlapped layer, indicating that the structural design of the graphene sheet is important for the electrochemical performance of the electrode.

It is an object of the present invention to provide a negative electrode material for a sodium ion battery using a flexible carbon-based electrode.

In order to accomplish the above object, the present invention provides a method for producing a silver halide photographic light-sensitive material, comprising the steps of: (1) mixing graphene oxide powder and thionyl chloride; (2) vacuum-filtering the mixture to produce a graphene-based paper; And (3) heat treating the graphene-based paper. The present invention also provides a method of manufacturing a negative electrode material for a sodium ion battery.

In the step (1), the graphene oxide powder and the thionyl chloride are dispersed by ultrasonic dispersion at 20 to 70 ° C for 1 to 48 hours.

In the step (2), the mixture may contain one or more selected from the group consisting of chloroform, dimethylformamide, diethylformamide, and N-methyl-2-pyrrolidone. Or more, and vacuum filtration is performed.

In the step (3), the heat treatment is performed at 100 to 2500 ° C.

The present invention also provides a negative electrode material for a sodium ion battery produced by the above-described method.

According to the present invention as described above, a paper electrode for a sodium ion battery which is disorderly oriented and highly flexible can be produced by vacuum filtration of graphene-based nanosheets permanently folded and crumpled by thionyl chloride treatment, The electrochemical performance is superior to that of the graphene-based paper, and an excellent electrochemical performance is obtained even without a conductive filler and a binder as a substrate.

Figure 1 shows (a) SEM image of a UOGPs cross section, (b) UOGPs charge and discharge curves at 100 mAg ^-1 current density, (c) and (d) SEM images of ROGPs cross sections at various magnifications.
Figure 2 shows AFM (left) and TEM (right) images of the T-GNS.
FIG. 3 shows the XPS O 1 s spectrum of T-GNS, (d) the XPS Cl 2 p spectrum of T-GNS, (b) H ₂ N ₂ -GNS,
Figure 4 (a) GO, (b) H 2 N 2 -GNS, (c) FT-IR spectrum of the T-GNS.
FIG. 5 shows the results of the resistivity measurement according to the temperature of (a) and (b) the XPS spectrum of ROGPs-600, (c) Raman spectrum of ROGPs-600, and (d) ROGPs-600 and UOGPs.
6 shows XPS C 1 s spectrum of GO.
7 is a Raman measurement of each sample.
Figure 8 shows the charge / discharge curves of ROGPs-600 at 100 mAg ^-1 current density, (b) the capacitance of ROGPs-600 at various current densities, (c) the current density and capacity of ROGPs- (D) Cycle stability of ROGPs-600 at 1000 mAg ^-1 current density.
FIG. 9 is a photograph of ROGPs-600 before and after bending using custom-made equipment; (c) ROGPs-600 charge / discharge curve at 100 mAg ^-1 current density after 1000 bending cycles; ) Cycle stability of ROGPs-600 at 1000 mAg ^-1 current density after 1000 bending cycles.

Hereinafter, the present invention will be described in detail.

In the present invention, uni-oriented graphene-based papers (UOGPs) refer to unidirectionally graphene-based papers produced by vacuum filtration of graphene nanosheets reduced to hydrazine.

Randomly oriented graphene-based papers (ROGPs) in the present invention refer to graphene-based paper that is disorderly oriented and highly flexible produced by vacuum filtration of thionyl chloride treated graphene nanosheets.

In the present invention, H ₂ N ₂ -GNSs refers to graphene nanosheets reduced to hydrazine.

In the present invention, T-GNSs means graphene nanosheet treated with thionyl chloride.

(1) mixing graphene oxide powder with thionyl chloride; (2) vacuum-filtering the mixture to produce a graphene-based paper; And (3) heat treating the graphene-based paper. The present invention also provides a method of manufacturing a negative electrode material for a sodium ion battery.

In the step (1), the graphene oxide powder may be prepared by mixing graphene oxide obtained from graphite with distilled water, ethanol, methanol, chloroform, dimethylformamide A graphene oxide solution obtained by dispersing in at least one solution selected from the group consisting of diethylformamide, tert-butanol and N-methyl-2-pyrrolidone Is preferably prepared by lyophilization.

In the step (3), the heat treatment is preferably carried out at a temperature of 1 to 20 ° C / min under an inert gas atmosphere of 10 to 1,000 ml / min and at 100 to 2,500 ° C, preferably 200 to 1,500 ° C, Effect.

Hereinafter, the present invention will be described in more detail with reference to Examples. It is to be understood by those skilled in the art that these embodiments are merely illustrative of the present invention and that the scope of the present invention is not construed as being limited by these embodiments.

Examples.

Grafton oxide (G-O) was prepared from graphite purchased from Sigma-Aldrich using the Hummers method known per se. The aqueous solution of G-O was then frozen in liquid nitrogen and lyophilized for 72 hours at 50 DEG C and 0.045 mbar using a freeze dryer (LP3, Jouan, France). After lyophilization, a GO powder with a density of 1.58 loosely piled up at low density was obtained. By using a GO powder having a low density, it is possible to manufacture a paper having a very thin thickness by minimizing GO aggregation in a high temperature heat treatment process have.

100 mg of G-0 powder prepared above was dispersed in 50 ml of thionyl chloride (≥99%, Sigma-aldrich) while ultrasonication. The G-O dispersion was treated at 60 DEG C for 12 hours. The resultant was diluted with dimethylformamide and vacuum filtered with anodisc membrane filter (47 mm diameter, 0.2 μm pore size; Whatman) to produce graphene-based paper ROGPs. In addition, ROGPs were heated in a tube furnace at room temperature to 600 ° C and maintained for 2 hours (heating rate 10 ° C / min, argon gas injection rate 200 ml / min). The thus prepared ROGPs-600 was stored in a vacuum oven at 30 ° C.

Comparative Example.

The graphene oxide powder prepared according to the known Hummers method was dispersed in distilled water, and hydrazine was added to the dispersed graphene oxide solution at a ratio of 1: 2. (H ₂ N ₂ -GNSs) was prepared by stirring the mixture at 90 ° C. for 1 hour to prepare reduced graphene nanosheets (H ₂ N ₂ -GNSs), and the H ₂ N ₂ -GNSs was subjected to anodisc membrane filter (47 mm in diameter, UOGPs were prepared by vacuum filtration.

Experimental example.

(1) Physical properties

The morphology of the prepared samples was analyzed by field emission scanning electron microscopy (FE-SEM, S-4300, Hitachi, Japan) and field emission scanning electron microscopy (FE-TEM, JEM2100F, JEOL, Japan). Topographical images of T-GNS were measured by atomic force microscope (AFM, NT-MDT, Russia). The cantilever was measured using NSG-10 (NT-MDT, Russia) and semi-contact operation mode. Raman spectrum analysis was performed using a NTEGRA spectrometer and backscattering at 473 nm (2.62 eV). The spectral resolution was set to ~ 2 cm ^-1 using a 600-groove / mm grating and the objective lens of 100 magnification had a laser spot size of up to 330 nm. For non-destructive measurement, the laser intensity was kept below 0.3 mW, and monochromated Al K radiation (hv = 1486.6 eV) was used for X-ray photoelectron spectroscopy (XPS, PHI 5700 ESCA) analysis. Fourier Transform-Infrared spectroscopy (FT-IR) was measured with a VERTEX 80v (Bruker Optics, Germany). Temperature-dependent IV characteristics were determined using the four probe methods traditionally used in the Janis cryo-system as a semiconductor characterization system (4200-SCS, Keithley). This electrical measurement was done after degassing (< 2 x 10 &lt; ^-6 &gt; Torr) for 12 hours in vacuum.

(2) Electrochemical properties

Electrochemical performance was measured using Wonatec automatic battery cycler and CR2032-type coin cells. The coin cells were collected in a glove box filled with argon and metallic sodium and 1 M NaClO ₄ (Aldrich 99.99%) were used as electrolyte in the aqueous solution of propylene carbonate.

Experiment result.

(1) inter-layer morphology of UOGPs represents a dense interlayer accumulation (~ 3 μm) of H ₂ N ₂ -GNSs (Fig. 1a), is reversible Li UOGPs capacity of 170 mAhg ^-1 at a current density of 100 mAg ^-1 (Fig. 1B). This value is similar to the previous report on LIBs. However, the reversible Na capacity was very low at 10 mAhg ^-1 at the same current density. This indicates that insertion and release of Na ions into UOGPs is difficult in the current range of practical NIBs. Therefore, a graphene-based structural design is needed to provide a suitable structure for easy insertion and release of Na ions.

The inter-layer morphology of ROGPs shows a structure in which graphene-based components are randomly oriented (Fig. 1c-d). ROGPs are flexible and have a thickness of about 30 μm, which is a structure made of T-GNSs. The morphological differences between ROGPs and UOGPs lead to large differences in sodium storage performance. The lyophilized G-O powder was immediately added to thionyl chloride (≥99%, Sigma-Aldrich) solution. The internucleophilic functional group of thionyl chloride interacts with carboxylic acid, and acyl chloride is formed on the basal plane and edge of G-O. Some of the acyl chloride above G-O is also reactive to nucleophilic attack by carboxylic acid and other G-O hydroxyl groups, which occurs between the intersheet and the intrasheet of G-O. As a result, the G-O sheet was permanently folded or creased.

Figure 2 shows a corrugated surface morphology with a side dimension of several micrometers in the T-GNS and a height of 10 nm. T-GNS was reduced by thionyl chloride, and FIG. 3 shows O 1s XPS of GO, H ₂ N ₂ -GNS, and T-GNS. The distinctive peaks of O 1s show the presence of carbonyl groups and various other oxygen functionalities. The oxygen of the GO was lowered through the treatment of hydrazine or thionyl chloride, and T-GNS was doped with several Cl elements. In Cl 2p XPS of T-GNS, two distinct binding energies at 199.0 eV and 200.9 eV were measured, which indicate C-Cl and O = C-Cl, respectively. The FT-IR data of T-GNS show the chemical bonding between graphene and Cl (Fig. 4).

(2) Figure 5a shows the XPS C 1s spectrum of ROGPs-600 after heat treatment at 600 ° C. A major sp ² C = C peak at 284.2 eV and an sp ³ CC peak at 285.1 eV were observed in the C 1s spectrum of ROGPs-600. In addition, the remaining C (O) O oxygen peak was found at 290.1 eV. This sp ³ CC peak at 285.1 eV is distinct from the XPS C 1s of GO with a CO peak at 287.5 eV (FIG. 6). The chemical arrangement of oxygen groups inside ROGPs-600 was similar to that of T-GNS, but the content of carbonyl groups was higher for ROGPs-600 (FIG. 5b). The C / O ratio of ROGPs is 11.5, which is much higher than the other values of GO (2.3), T-GNS (6.9), and H ₂ N ₂ -GNS (7.9), suggesting that ROGPs- .

Raman spectroscopy was used to identify the atomic structure of ROGPS-600. Figure 5c shows Raman spectra, with D and G peaks at ~ 1367 cm ^-1 and ~ 1599 cm ^-1 , respectively. The D-peak is related to the defect breaking symmetry in the infinite honeycomb-shaped lattice in the ideal graphene structure, and the G-peak originates from the double degeneration of E2g in the Brillouin zone center. The intensity of the D peak and the intensity of the G peak are ~ 1.07, which is lower than the values of UOGPs (~ 1.23) and ROGPs (~ 1.11), indicating that the defects in ROGPs-600 are relatively small. Also, as shown in FIG. 7, attention was paid to Raman measurement values of H ₂ N ₂ -GNS, T-GNS and T-GNS-600 nanosheets.

The resistivity of the c-axis (nonplanar) and a-axis (plane), which depends on the temperature of the ROGPs-600, was measured to confirm the structural effect of electrical and electrical properties (FIG. UOPGs were similarly obtained. Both samples showed non-metallic behavior with negative d ρ (T) / d T over the entire temperature range. As expected, the resistivity of UOPGs was higher than that of ROGPs-600. Δ ρ = ( ρ _a - ρ _c ) / ρ _a was measured to be low (0.769) at ROGPs-600, but this value is much lower than that of UOPG (2.928). This means that there are more conduction channels in the c-axis direction in ROPGs-600 compared to UOPGs, which is due to the randomly oriented structure of ROGPs-600. Therefore, it was found that the structure of ROGPs-600 improves the electrical characteristics by improving the rate characteristic of the NIBs cathode.

(3) The electrochemical properties of ROGPs-600 were measured by current charging / discharging cycling while varying the current density in the potential range of 0.005 to 2.5 V. As a result, the charge / discharge curves (insertion / extraction of Na) of ROGPs-600 did not show a distinct potential plateaus (FIG. 8A). This means that the reaction at the surface takes place in the presence of electrochemically, geometrically unequal Na ions. A voltage plateau between 0.5 and 0.7 V can contribute to the decomposition of the electrolyte and the formation of a solid electrolyte film on the electrode surface. The reversible capacity of the first cycle was 180 mAg ^-1 at a current density of 100 mAg ^-1 similar to the reduced GO powder deposited randomly on a commonly used copper substrate.

FIG. 8B shows the rate characteristic of ROGPs-600, and FIG. 8C shows plot of ROGPs-600 (red line) and reference density vs. capacity. ROGPs-600 has very good rate and reversibility characteristics. Nevertheless, a very stable cathode capacity of 60 mAhg ^-1 at 8 Ag ^-1 current density was obtained. The cycle stability of ROGPs-600 was measured 500 times at a current density of 1 Ag &lt; ^{-1 &} gt ;. A repetitive 500 stable charge / discharge cycles were maintained, with Coulomb efficiency nearing 100% in all but the initial cycle (FIG. 8d). The electrochemical performance did not change after 1000 bend tests.

(4) The bending test results of ROGPs-600 using the customized equipment are shown in FIG. After more than 1000 repetitive bending tests, the NIB half cell experiment was performed using the central part of ROGPs-600. The charge / discharge curve closely matched the ROGPs-600 prior to the bend test, and the cycle stability was also maintained over 500 times.

(5) In conclusion, it can be seen that the permanently folded or corrugated structure of T-GNS plays an important role electrochemically in flexible ROGPs-600. ROGPs-600 has a C / O ratio of 11.5 and an I _D / I _G of 1.07, indicating that the sp ² carbon structure is well developed and that ROGPs-600 exhibits good electrical conductivity in both planar and non- (19 and 12 S cm ^-1 , respectively). In addition, the unique structure and well-developed carbon structure of ROGPs-600 showed good electrochemical properties in spite of the absence of a binder such as filler or substrate. ROGPs-600 has good cycle stability with high coulomb efficiency, despite 500 charge / discharge cycles, and this electrochemical property was maintained during 1000 bend tests, demonstrating the high flexibility of ROGPs-600.

Having described specific portions of the present invention in detail, it will be apparent to those skilled in the art that this specific description is only a preferred embodiment and that the scope of the present invention is not limited thereby. It will be obvious. Accordingly, the actual scope of the present invention will be defined by the appended claims and their equivalents.

Claims (5)

(1) mixing a graphene oxide powder and thionyl chloride to prepare a mixture;
(2) vacuum-filtering the mixture to produce a graphene-based paper; And
(3) heat treating the graphene-based paper
The graphene oxide powder is prepared by dissolving graphene oxide in distilled water, ethanol, methanol, chloroform, dimethylformamide, diethylformamide, tertiary butanol wherein the solution is prepared by lyophilizing a graphene oxide solution obtained by dispersing in at least one solution selected from the group consisting of tert-butanol and methyl-2-pyrrolidone. A method of manufacturing a negative electrode material.
The method according to claim 1,
Wherein the graphene oxide powder and the thionyl chloride are dispersed by ultrasonic dispersion at 20 to 70 ° C for 1 to 48 hours in the step (1).
The method according to claim 1,
In the step (2), the mixture may contain one or more selected from the group consisting of chloroform, dimethylformamide, diethylformamide, and N-methyl-2-pyrrolidone. By weight, and then vacuum filtration is performed.
The method according to claim 1,
Wherein the heat treatment in the step (3) is performed at a temperature of 100 to 2500 占 폚.
A negative electrode material for a sodium ion battery produced by the method of any one of claims 1 to 4.

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