KR20210127050A - Method of manufactureing anode of a lithium ion secondary battary for fast charging and anode - Google Patents

Abstract

Disclosed are a method for manufacturing an electrode of a lithium ion battery for rapid charging and an electrode of a lithium ion battery. According to one specific embodiment, a TiO_2(B) nano-belt is manufactured from titanium dioxide powder to form a channel for lithium ion transport and an active site in more open shape, the intrinsic properties of titanium dioxide are improved by doping with nitrogen to adjust an electronic structure of titanium dioxide, and an internal surface area and electrical conductivity can be increased, thereby improving the stable fast charging performance of a lithium ion secondary battery.

Description

Electrode manufacturing method of lithium ion battery for fast charging and electrode of lithium ion battery

The present invention relates to a method for manufacturing an electrode of a lithium ion battery for rapid charging and an electrode of a lithium ion battery, and more particularly, _{to manufacturing a TiO 2} (B) nano belt and then doping nitrogen to prepare a negative electrode of a lithium ion battery Accordingly, it relates to a technology for improving the fast charging performance of a lithium ion secondary battery and also maintaining stability.

In lithium-ion battery systems, titanium dioxide (TiO ₂ ) is a transition metal oxide and has excellent structural stability, high discharge voltage stability ( ^{over 1.7 V compared to Li/Li +} ), excellent cycling stability, environmental friendliness, and high safety, so it is used as an anode material. do.

However, the titanium dioxide shown in FIG. 1 has ^{limitations such as low theoretical capacity (330mAh g -1} ), low electrical conductivity, and insufficient speed performance. In order to solve these limitations, it is possible to design with appropriate phase selection and nanostructure, and form more extended channels and active sites for lithium ion transport through doping of heterogeneous atoms, as well as intrinsic electrical conductivity. Research is being actively conducted.

At this time, among the various phases of titanium dioxide (rutile, anatase, brookite, TiO ₂ (B), etc.), TiO ₂ (B) is a monoclinic crystal system, and has a more open structure than rutile and anatase. TiO ₂ (B) has a low backbone density compared to other phases, and exhibits large channels and pores. Therefore, TiO ₂ (B) exhibits a higher capacity of 250 mAh/g than rutile and anatase, which exhibit a capacity of about 168 mAh/g.

On the other hand, the nanostructure can promote lithium ion diffusion by shortening the desorption and insertion path of lithium ions. Among them, the titanium dioxide nanobelt is a one-dimensional (1D) material, which exhibits a short diffusion path, a relatively large surface area, and strong mechanical strength. This can form an efficient channel for fast transport of lithium ions and electrons.

Accordingly, the applicant TiO ₂ (B) By fabricating a nanobelt, channels and active sites for lithium ion transport can be formed more open, and by doping with nitrogen The purpose of this study is to propose a method for improving the intrinsic properties of titanium dioxide and increasing the internal surface area and electrical conductivity by adjusting the electronic structure of titanium dioxide.

Korea Patent Publication No. 2016-0001841 (2016.01.07)

Therefore, the technical task to be achieved by the present invention is TiO ₂ (B) Nanobelts were made to form more open channels and active sites for lithium ion transport, and nitrogen was doped to By adjusting the electronic structure of titanium dioxide, it is possible to improve the intrinsic properties of titanium dioxide and increase the internal surface area and electrical conductivity, thereby improving the fast charging performance of lithium ion secondary batteries and maintaining stability. An object of the present invention is to provide a method for manufacturing an electrode for an ion battery and an electrode for a lithium ion battery.

The object of the present invention is not limited to the object mentioned above, and other objects and advantages of the present invention not mentioned can be understood by the following description, and will be more clearly understood by the examples of the present invention. It will also be readily apparent that the objects and advantages of the present invention can be realized by means of the means and combinations thereof indicated in the claims.

According to an embodiment according to an embodiment, the electrode manufacturing method of a lithium ion battery for rapid charging is

_{TiO 2} (B) by performing hydrothermal synthesis of titanium dioxide powder a process of fabricating a nano-belt and then doping nitrogen to fabricate a negative electrode;

A process of dispersing a cathode agent, carbon black, and PVDF produced on a copper disk-shaped substrate in NMP in a mass ratio of 7:2:1, spin-coating and depositing a uniformly deposited film, followed by drying at 120°C to fabricate an anode ; and

_{Using a glass fiber dipped in an electrolyte of 1M LiPF 6} in which ethylene carbonate and dimethyl carbonate are mixed in a 1:1 ratio as a separator, and lithium metal as a counter electrode for the negative electrode. It is characterized by one thing.

Preferably, the negative electrode preparation process is

_{TNB manufacturing step of producing TiO 2} (B) nano-belt TNB using the hydrothermal synthesis technique of titanium dioxide powder P25; and

The prepared TiO ₂ (B) nano-belt TNB may be doped with nitrogen to prepare an anode material.

Preferably, the TNB production step is

0.8 g of P25 was dispersed in 80 mL of a 10M NaOH solution, put in a Teflon-lined autoclave, heat-treated at 180° C. for 24 hours, cooled at room temperature, and then washed with distilled water and ethanol;

Dispersing the obtained product in 100 mL of 0.1M HCl at room temperature for 24 hours, washing with distilled water and ethanol until neutral;

After drying at 80° C. for 12 hours, calcining at 500° C. for 3 hours in an argon atmosphere may include preparing a TiO ₂ (B) nano-belt (TNB).

Preferably, the nitrogen doping step

Urea and TiO ₂ (B) nanobelts were mixed in a mass ratio of 3:1 and calcined at 500° C. for 2 hours in a mixed gas (argon/hydrogen) atmosphere to prepare TiO ₂ (B) nanobelts N-TNB doped with nitrogen. It may include a manufacturing step.

According to one embodiment, titanium dioxide _{TiO 2} (B) from powder Nanobelts were made to form more open channels and active sites for lithium ion transport, and nitrogen was doped to By adjusting the electronic structure of titanium dioxide, it is possible to improve the intrinsic properties of titanium dioxide, increase the internal surface area and electrical conductivity, and thereby improve the stable fast charging performance of the lithium ion secondary battery.

The following drawings attached to this specification illustrate preferred embodiments of the present invention, and serve to further understand the technical spirit of the present invention together with the detailed description of the present invention to be described later, so the present invention is a matter described in such drawings should not be construed as being limited only to
1 is a view showing the configuration of a general coin cell.
2 is an overall flowchart illustrating a process of manufacturing a coin cell according to an embodiment.
3 is a flowchart illustrating a detailed process of manufacturing an anode according to an embodiment.
4 is an embodiment of It is a diagram showing a scanning electron microscope (SEM) image.
5 is a diagram illustrating an X-ray diffraction pattern (XRD) according to an exemplary embodiment.
6 is a view showing the results of surface analysis of N-TNB using X-ray photoelectron spectroscopy (XPS) according to an embodiment.
7 is a graph showing the electrochemical dynamics characteristics of a lithium ion battery according to the cyclic current method according to an embodiment. are the ones shown
8 is a graph illustrating electrochemical dynamics characteristics of a lithium ion battery using a constant current charging and discharging method according to an embodiment. are the ones shown
9 is a speed performance of a lithium ion battery according to an embodiment; are the ones shown
10 is a diagram illustrating impedance spectroscopy according to an embodiment. The electrochemical and mechanical properties of lithium-ion batteries are the ones shown

Specific structural or functional descriptions of the embodiments are disclosed for purposes of illustration only, and may be changed and implemented in various forms. Accordingly, the embodiments are not limited to a specific disclosure form, and the scope of the present specification includes changes, equivalents, or substitutes included in the technical spirit.

Although terms such as first or second may be used to describe various components, these terms should be interpreted only for the purpose of distinguishing one component from another. For example, a first component may be termed a second component, and similarly, a second component may also be termed a first component.

When a component is referred to as being “connected to” another component, it may be directly connected or connected to the other component, but it should be understood that another component may exist in between.

The singular expression includes the plural expression unless the context clearly dictates otherwise. In this specification, terms such as "comprise" or "have" are intended to designate that the described feature, number, step, operation, component, part, or combination thereof exists, and includes one or more other features or numbers, It should be understood that the possibility of the presence or addition of steps, operations, components, parts or combinations thereof is not precluded in advance.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art. Terms such as those defined in a commonly used dictionary should be interpreted as having a meaning consistent with the meaning in the context of the related art, and should not be interpreted in an ideal or excessively formal meaning unless explicitly defined in the present specification. does not

Hereinafter, the present invention will be described in detail by describing preferred embodiments of the present invention with reference to the accompanying drawings.

FIG. 2 is an overall flowchart showing the manufacturing process of the coin cell shown in FIG. 1, and FIG. 3 is a flowchart showing the detailed process of the negative electrode manufacturing process 100 shown in FIG. 2, with reference to FIGS. 2 and 3, It may include a negative electrode manufacturing process 100 , a negative electrode manufacturing process 200 , and a half-cell manufacturing process 300 .

Here, the negative electrode manufacturing process 100 may include a TNB manufacturing step 110 and a nitrogen doping step 120 . _{Here, the TNB manufacturing step 110 is TiO 2} (B) using a hydrothermal synthesis technique of titanium dioxide powder P25. It can be provided to fabricate a nano-belt TNB. That is, in the TNB manufacturing step 110, 0.8 g of titanium dioxide powder P25 is dispersed in 80 mL of 10 M NaOH solution, put in a Teflon-lined autoclave, heat-treated at 180° C. for 24 hours, and then cooled at room temperature and then with distilled water and ethanol do.

And in the TNB production step 110, the obtained product is dispersed in 100 mL of 0.1M HCl at room temperature for 24 hours, washed with distilled water and ethanol until neutral, and then dried at 80° C. for 12 hours, and then in an argon atmosphere. _{The TiO 2} (B) nano belt (TNB) was prepared by calcining at 500° C. for 3 hours.

_{TiO 2} (B) produced thereafter A nitrogen doping step 120 of manufacturing an anode material (cathode) by doping nitrogen into the nano-belt TNB is performed.

That is, in the nitrogen doping step 120, urea and TiO ₂ (B) nanobelts are mixed in a mass ratio of 3:1 and calcined in a mixed gas (argon/hydrogen) atmosphere at 500° C. for 2 hours, and nitrogen-doped TiO ₂ (B) Nanobelt N-TNB can be produced.

Then, in the anode manufacturing process 200, a copper disk (diameter 15 mm) is prepared as a substrate, and 0.21 g of anode agent, 0.06 g of carbon black, and 0.03 g of PVDF are dispersed in 2.5 mL of NMP to uniformly deposit the resulting film by spin coating. Then, the film is deposited on the substrate and dried at 120° C. to prepare a cathode electrode.

_{In addition, the half-cell manufacturing process 300 uses a glass fiber dipped in an electrolyte of 1M LiPF 6} in which ethylene carbonate and dimethyl carbonate are mixed in a 1:1 ratio as a separator, and lithium metal is used as the counter electrode of the coin cell. Half cells can be crafted.

Figure 4 is titanium dioxide powder P25, TiO ₂ (B) Nanobelt TNB, Nitrogen-doped TiO ₂ (B) Nanobelt N-TNB as a scanning electron microscope image of each. Referring to FIG. 4 , P25, which is aggregated in the form of particles, is in the form of a nano belt through hydrothermal synthesis. It can be seen that the transformation into At this time, the nanobelt has a width of about 50-300 nm.

In addition, it can be confirmed that nitrogen doping did not affect the shape change of the nanobelts, as there was almost no change in shape when nitrogen-doped N-TNB and undoped TNB were compared.

5 is titanium dioxide powder P25, TiO ₂ (B) Nanobelt TNB, Nitrogen-doped TiO ₂ (B) As a figure showing the XRD pattern of each of the nanobelt N-TNB, referring to FIG. 5 , (a) is the θ-2θ bonding mode of P25, TNB, and N-TNB. of a view showing an X- ray diffraction pattern, with reference to (a), diffraction peak of P25 appears that 101 according to the TiO ₂ anatase at 2θ = 25.1˚ by daily doubles at 2θ = 27.2˚ (110 ) appears. In addition, TNB and N-TNB were _{transferred to the TiO 2 (B) phase by annealing at 500° C., and main diffraction peaks of the TiO 2} (B) phase appeared at 2θ = 29.6˚ and 2θ = 43.9˚, and monoclinic [JCPDS NO. 46-1237] has a decision system.

Referring to (b), the diffraction peak (110) shift of TNB and N-TNB is shown. N-TNB doped with nitrogen was shifted to the right, which means that d-spacing (interplanar distance) decreased due to nitrogen doping. The d-spacing is reduced due to the substitution of larger N ^{3 than O 2 -} and the formation of interstitial nitrogen due to charge compensation defects.

In addition, the vacancy formed when ^{O 2 -} is ^{replaced with N 3 -} _{forms a defect in the TiO 2} lattice and creates a passage for electrons to move, thereby increasing the mobility of electrons, thereby increasing electrical conductivity.

6 is a view showing the surface analysis result of N-TNB using X-ray photoelectron spectroscopy (XPS). Referring to FIG. 6, (a) is a Ti-O bond (Ti ⁴⁺ ) in the Ti 2p region binding energy due to It can be seen that the peaks appear at 458.8eV and 464.5eV, and it can be confirmed that the Ti-N binding energy peak by nitrogen doping also appears at 457.5eV.

Referring to (b), in the O 1s region, it can be seen that a specific peak due to Ti-O bonding is shown at 530.2 eV.

(c) is a diagram showing high-resolution XPS of the N 1s region by nitrogen doping. Referring to (c), the ratio of doped nitrogen is about 0.67 atom%, and O-Ti-N bonding by inter-terminal doped nitrogen. At 400.6 eV, the Ti-N bond by the substitutional doped nitrogen is shown at 396.2 eV, and in the case of the intercalation dopant, the electron density for the nitrogen atom is decreased due to the high electronegativity of the oxygen atom, which is higher than the substituted Ti-N bond. It exhibits high binding energy. Also, it can be seen that intercalation doping of nitrogen is more dominant than substitution doping.

7 is a view showing the results of evaluation of electrochemical dynamics of a lithium ion battery incorporating N-TNB using cyclic voltammetry, where P25, TNB, and N-TNB are used as anodes to evaluate electrochemical dynamics. Cyclic voltammetry was performed on the used lithium-ion half-cell.

^{That is, the cyclic voltammetry was performed at a scan rate of 0.1-0.5 mV s -1} in the potential range of 1-3V to measure the lithium ion diffusion coefficient, thereby showing the change in current with respect to voltage (CV curve).

Accordingly, referring to FIG. 7, in P25, which is a mixed phase of anatase phase and rutile phase, a reduction peak due to lithium ion insertion is generated at about 1.7 V, and an oxidation peak due to lithium ion desorption occurs at about 2.1 V. It can be seen that, TiO ₂ (B) phase TNB and N-TNB can be confirmed that the redox peak appears around 1.5V.

In addition, the CV curve measured at each scan rate is expressed as the peak intensity with respect to the square root of the scan rate, so the lithium ion diffusion coefficient can be derived using the following Randles-Sevcik equation, and the lithium ion diffusion coefficient can satisfy the following equation.

Lithium ions of N-TNB diffusivity can be seen that about two times increased than 4.189 × 10 ^-5 cm ² s ^-1 undoped ^{TNB (2.292 × 10 -5 cm 2} s -1) to. This means that nitrogen doping increases the efficiency of the lithium ion storage behavior of the N-TNB electrode, which can greatly improve the electrochemical dynamics performance of N-TNB when used in lithium-ion batteries.

8 is a view showing the evaluation results of electrochemical dynamics characteristics of a lithium ion battery incorporating N-TNB using a constant current charging and discharging method, wherein the charging and discharging cycling is performed in the 1-3V potential range.

(a) to (c) are diagrams showing the outline of charging and discharging of P25, TNB, and N-TNB at 1C to 40C (1C=300mA g ^{-1 ). Referring to the CV curve shown, P25 is about 1.7V} It can be seen that at about 2.1V, a flat surface occurs due to lithium ion removal and insertion, and TNB and N-TNB are S-curves in which lithium ion removal and insertion occurs around 1.5V.

In addition, P25 and TNB showed ^{discharge capacities of 120 mAh g -1} and 148 mAh g ^-1 at 1C, but near zero at 40 C. In contrast to the N-TNB it is showed a discharge capacity of 160mAh g ^-1 at 1C, 40C shows the capacity of 40mAh g ^-1.

(d) is a diagram comparing cycle performance at ^{100 mA g -1} . P25 showed an initial discharge capacity of ^{about 140 mAh g -1.} More overvoltage is required to maintain 50% or less of the initial capacity after 100 cycles. TNB initially showed about 146mAh g ^-1 , but showed a large decrease compared to N-TNB. On the other hand, N-TNB has an initial discharge capacity of 179.4 mAh g ^-1 and maintains more than 66% of the initial capacity after 100 cycles. Through this, it can be confirmed that the electrochemical dynamics and electrical conductivity of TNB are improved by nitrogen doping.

9 is a view showing the results of charging and discharging rate performance evaluation. Referring to (a), it can be seen that N-TNB exhibits the highest discharge capacity at all current densities. In particular, N-TNB maintained a capacity of ^{40 mAh g -1 at 40C.} Moreover, it shows a reversible capacity of ^{132mAh g -1} when it is performed again at a rate of 1C.

Referring to (b), P25 and TNB maintained only about 34% and 40% of the initial discharge capacity even at a long cycle cycle at ^{1A g -1 , whereas the N-TNB had 51% of the initial discharge capacity, about 68 mAh g.} represents ^-1.

Referring to (c), the cycle performance can also be confirmed in fast discharging (lithium ion insertion) and slow charging (lithium ion desorption). P25 exhibits an initial discharge capacity of 77.8 mAh g ^-1 and maintains 61% after 100 cycles, whereas N-TNB exhibits ^{an initial discharge capacity of 131.5 mAh g -1} and maintains 80% or more.

10 is a view showing the electrochemical dynamics characteristic evaluation result of a lithium ion battery incorporating N-TNB using electrochemical impedance spectroscopy. Referring to FIG. 9 , the resistance (R _ct ) by charge transport is determined by the electrochemical impedance spectroscopy method. (EIS) and presented as a Nyquist plot.

And although the resistance (R _s ) by the electrolyte was almost similar, the resistance by charge transport showed the lowest value for N-TNB at 66.8Ω. _{In addition, the line representing the resistance (R mt} ) by material transport in the low frequency region shows the largest slope, which is attributed to the fast lithium ion diffusion rate.

_{Thus TiO 2} (B) from titanium dioxide powder Nanobelts were made to form more open channels and active sites for lithium ion transport, and nitrogen was doped to By adjusting the electronic structure of titanium dioxide, it is possible to improve the intrinsic properties of titanium dioxide, increase the internal surface area and electrical conductivity, and thereby improve the stable fast charging performance of the lithium ion secondary battery.

Claims (5)

titanium dioxide _{TiO 2} (B) by performing hydrothermal synthesis of the powder a process of fabricating a nano-belt and then doping nitrogen to fabricate a negative electrode;
A process of dispersing a cathode agent, carbon black, and PVDF produced on a copper disk-shaped substrate in NMP in a mass ratio of 7:2:1, spin-coating and depositing a uniformly deposited film, followed by drying at 120°C to fabricate an anode ; and
_{Using a glass fiber dipped in an electrolyte of 1M LiPF 6} in which ethylene carbonate and dimethyl carbonate are mixed in a 1:1 ratio as a separator, lithium metal is used as a counter electrode for the negative electrode. A method for manufacturing an electrode of a lithium ion battery for rapid charging, characterized in that. According to claim 1, wherein the manufacturing process of the negative electrode agent,
_{TiO 2} (B) titanium dioxide powder P25 using hydrothermal synthesis technique TNB manufacturing step of manufacturing nano-belt TNB; and
Fabricated TiO ₂ (B) A method of manufacturing an electrode for a rapid charging lithium ion battery, comprising a nitrogen doping step of preparing an anode agent by doping the nanobelt TNB with nitrogen. According to claim 2, wherein the TNB manufacturing step
0.8 g of P25 was dispersed in 80 mL of a 10M NaOH solution, put in a Teflon-lined autoclave, heat-treated at 180° C. for 24 hours, cooled at room temperature, and then washed with distilled water and ethanol;
Dispersing the obtained product in 100 mL of 0.1M HCl at room temperature for 24 hours, washing with distilled water and ethanol until neutral; and
After drying at 80° C. for 12 hours, calcining at 500° C. for 3 hours in an argon atmosphere to prepare a TiO ₂ (B) nano belt (TNB). Electrode manufacturing method. According to claim 2, wherein the nitrogen doping step
Urea and TiO ₂ (B) nanobelts were mixed in a mass ratio of 3:1 and calcined at 500° C. for 2 hours in a mixed gas (argon/hydrogen) atmosphere to prepare TiO ₂ (B) nanobelts N-TNB doped with nitrogen. An electrode manufacturing method of a lithium ion battery for fast charging, characterized in that it comprises the step of manufacturing. An electrode of a lithium ion battery manufactured by using the electrode manufacturing method of any one of claims 1 to 4 for a rapid charging lithium ion battery.

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