KR20200048511A - Electrode active material for lithium secondary battery and lithium secondary battery using the same - Google Patents

Abstract

The present invention relates to an electrode active material for a lithium secondary battery and a lithium secondary battery using the same. More specifically, the electrode active material for a lithium secondary battery is manufactured using an organic compound based on tetrazine single molecule. The electrode active material for a lithium secondary battery made of a tetrazine single molecule-based organic compound enables easy control of the reduction potential while stable lithium redox is possible, thereby having excellent dissolution resistance.

Description

Electrode active material for lithium secondary battery and lithium secondary battery using the same {ELECTRODE ACTIVE MATERIAL FOR LITHIUM SECONDARY BATTERY AND LITHIUM SECONDARY BATTERY USING THE SAME}

Disclosed is an electrode active material for a lithium secondary battery and a lithium secondary battery using the same, and more specifically, a new electrode active material using an organic compound capable of stable redox, a new composite electrode active material having excellent dissolution resistance including the same, and using the same It relates to a lithium secondary battery.

Recently, lithium secondary batteries have been used in various fields including portable electronic devices such as mobile phones and laptop computers. Especially, as interest in environmental problems has increased, fossil fuels such as gasoline vehicles and diesel vehicles, which are one of the main causes of air pollution, have been used. Research into lithium secondary batteries having high energy density and discharge voltage as driving sources for electric vehicles that can replace used vehicles has been actively conducted, and some are in the commercialization stage.

In the past, metal oxide-based lithium secondary batteries have been commercially successful with many developments, but the growth of the Energy Storage System (ESS) and Electric Vehicle industries has led to the demand for higher levels of energy density. The theoretical capacity limit, the limited amount of rare metals must be used, and the environmental problems of heavy metals are emerging.

On the other hand, in order to use a lithium secondary battery as a driving source of such an electric vehicle, it must be able to stably maintain the output in a wide state of charge (SOC) in addition to high output.

As a positive electrode material for a high capacity lithium secondary battery, LiCoO ₂ , which is a typical representative positive electrode material, has reached the practical limit of increase in energy density and output characteristics, especially when used in high energy density applications, due to its structural instability, charging at high temperature In the state, it releases oxygen in the structure in addition to structural modification, causing an exothermic reaction with the electrolyte in the cell, which is the main cause of the battery explosion. In order to improve the safety problems of LiCoO _{2, the use} of lithium-containing manganese oxides such as LiMnO ₂ in a layered crystal structure and LiMn ₂ O _{4 in a} spinel crystal structure and a nickel-containing nickel oxide such as LiNiO ₂ have been considered, and recently, high-capacity materials As a necessary transition metal to layered lithium manganese oxide, many studies have been conducted on lithium manganese oxide (hereinafter abbreviated as "Mn-rich") in which manganese (Mn) is added in a larger amount than other transition metals (excluding lithium). Is going on.

In addition, research to apply an organic compound-based active material capable of producing at a low price while exhibiting better performance in addition to the lithium manganese oxide has been increasing, and research is currently actively conducted. Compared to this, studies have been conducted on relatively inexpensive and environmentally friendly organic compound active materials, and some material groups have approached commercialization.

The most representative organic compound active material is a group of carbonyl materials, which has a high theoretical capacity of 500 mAh / g in the case of benzoquinone, but has a very small molecular weight and is difficult to commercialize because it is well dissolved in an electrolyte. In terms of energy density, it has not yet reached a level that can replace the metal oxide active material, so research on a new active group is needed, and a battery with a higher energy density is required as more advanced high-performance secondary batteries are gradually required. Is becoming.

US Patent Publication No. US 20170226270 describes a large number of nitrogen-containing and high-energy tetrazine polymers, but reports the structure of various polymers based on tetrazine and describes only simple synthesis conditions. , US Patent Publication No. US 20170358748 describes a method for synthesizing a ladder tetrazine polymer and a ladder tetrazine polymer, and is described as being able to be used as a component of the active layer of an organic solar cell. Rather, it presents only the potential as an active layer of organic solar cells.

In addition, in the paper Tetrahedron, 2007, 63, 11189, a linear polymer composed of tetrazine and pyridine, a hyperbranced polymer, and a synthesis method thereof are reported, but the possibility of application as a high energy material containing a large amount of building block or nitrogen rather than a lithium secondary battery And J. Mater. Chem. A, 2016, 4, 11491-11497 describes the synthesis of naphthalimide-based linear polymers and evaluation of properties of sodium secondary batteries, but is composed of anthracene and naphthalimide rather than tetrazine. The polymer is synthesized and the application field is described as a sodium secondary battery rather than a lithium secondary battery.

Disclosed is to provide an electrode active material having excellent dissolution resistance, and a lithium secondary battery using the same, which is capable of stable redox and easy to control the reduction potential.

As one embodiment, the content of this disclosure describes an electrode active material for a lithium secondary battery based on a single molecule of a tetrazine derivative represented by Formula 1 below.

[Formula 1]

In Formula 1, R ₁ and R ₂ are the same or different substituents, and in Formula 1, R ₁ and R ₂ are each independently selected from the group consisting of alkoxy, phenyl, heterocyclic aromatic compound, chlorine, carboxyl group, and -COOM. M is a metal cation.

Preferably, the heterocyclic aromatic compound may be one or more compounds selected from the group consisting of pyridine, pyrimidine, thiophene, furan, pyrrole and imidazole.

More preferably, the electrode active material may further include a porous carbon material.

More preferably, the tetraazine derivative single molecule and the porous carbon material may have a weight ratio of 1: 0.5 to 2.

Even more preferably, the tetraazine derivative single molecule and the porous carbon material may have a weight ratio of 1: 2.

Even more preferably, the porous carbon material may be made of CMK-3.

As another example, the content of this disclosure describes a positive electrode for a lithium secondary battery, characterized in that the tetrazine single molecule is made of aluminum foil coated.

Preferably, the positive electrode for a lithium secondary battery is prepared by mixing the tetraazine single molecule, Super-P and polyvinylidene fluoride in dimethylformamide, and then coating the mixture on aluminum foil and drying it. Can be manufactured.

As another embodiment, the contents of this disclosure describe a lithium secondary battery comprising the positive electrode for a lithium secondary battery, a negative electrode made of lithium metal, an electrode separator made of a porous polypropylene membrane, and an electrolyte.

Preferably, the electrolyte is 1,3-dioxolane (DOL) / 1,2-dimethoxyethane (DME) (1: 1 v / v) 1M of 2M lithium bis (trifluoromethane) sulfone It may be made of a solution in which imide (LiTFSi) is dissolved.

The disclosed electrode active material for a lithium secondary battery and the lithium secondary battery using the same exhibit stable effects of stable redox and at the same time easy to control the reduction potential, and exhibit excellent effects of providing an electrode active material having excellent dissolution resistance and a lithium secondary battery using the same.

Figure 1 is a graph showing the measurement of the reduction potential according to the current of the tetrazine single molecule of Formulas 2 to 5 disclosed.
Figure 2 is a graph showing the measurement of the reduction potential according to the lowest non-occupied molecular orbital function of the tetrazine single molecule of Formula 2 to 5 disclosed.
FIG. 3 is a photograph showing a tetrazine single molecule having phenyl groups substituted on both sides by a scanning electron microscope (SEM).
4 is a photograph showing the disclosed CMK-3 by scanning electron microscope (SEM).
FIG. 5 is a photograph showing a positive electrode for a lithium secondary battery manufactured through Preparation Examples 3 to 5 photographed with a scanning electron microscope (SEM).
6 is a graph showing the transmittance according to the infrared wave number of the positive electrode for a lithium secondary battery prepared through the disclosed Preparation Examples 3 to 5.
7 is a graph showing physical properties of CR2032 coin-type lithium secondary batteries manufactured through Examples 1 to 2 as disclosed.
8 is a graph showing the characteristics of CR2032 coin-type lithium secondary batteries manufactured through Examples 3 to 5 disclosed.

Hereinafter, a preferred embodiment of the present invention and the physical properties of each component will be described in detail, but it is intended to be described in detail so that a person skilled in the art to which the present invention pertains can easily implement the invention. This does not mean that the technical spirit and scope of the present invention is limited.

The disclosed electrode active material for a lithium secondary battery is made of an organic compound based on a tetrazine single molecule, and the tetrazine single molecule is represented by Formula 1 below.

[Formula 1]

In Formula 1, R ₁ and R ₂ are the same or different substituents, and in Formula 1, R ₁ and R ₂ are each independently selected from the group consisting of alkoxy, phenyl, heterocyclic aromatic compound, chlorine, carboxyl group, and -COOM. M is a metal cation.

Preferably, the heterocyclic aromatic compound may be one or more compounds selected from the group consisting of pyridine, pyrimidine, thiophene, furan, pyrrole and imidazole.

Tetragene is the first substance reported in the late 19th century, and many studies have been conducted to date, and it is known that it has a very stable electron exchange and redox activity. Based on this, there have been reports of transistors or solar cells, but no technology has been used as an electrode active material for lithium secondary batteries.

Tetragene single molecule used in the disclosed contents, as shown in the formula (1), alkoxy, phenyl, heterocyclic aromatic compound, chlorine, carboxyl group and -COOM, which have different electron-withdrawing ability, are each substituted symmetrically or asymmetrically. , Substances with chlorine, which has the strongest ability to pull electrons, are substituted on both sides and have the highest stabilized lowest non-occupied molecular orbital function (LUMO) level.

In this case, the alkoxy is preferably made of methoxy or ethoxy, and the heterocyclic aromatic compound is preferably made of at least one compound selected from the group consisting of pyridine, pyrimidine, thiophene, furan, pyrrole and imidazole.

In addition, it is possible to control the reduction potential by introducing a substituent based on the tetraazine structure and to provide a secondary battery with improved performance, and is made of a porous carbon nanomaterial, thereby improving the dissolution resistance of tetraazine having a low molecular weight. I can do it.

The reduction potential according to the current of the tetrazine single molecule having the formulas 2 to 5 and the reduction potential according to the lowest non-occupied molecular orbital function are measured and are shown in FIGS. 1 to 2 below.

Tetrazin monomolecules exhibiting the above-described effect may be prepared in the following formulas 2 to 5, for example.

[Formula 2]

As shown in Chemical Formula 2 (diphenyltetrazin, DPT), the tetraazine single molecule used in the disclosed electrode active material for lithium secondary batteries may be prepared in a form in which phenyl groups are substituted on both sides, as described above, phenyl groups are substituted on both sides. The tetraazine monomolecule was photographed with a scanning electron microscope (SEM) and is shown in FIG. 3 below.

[Formula 3]

In addition, as shown in Chemical Formula 3 (dichlorotetrazine, DCT), the tetrazine single molecule used in the disclosed electrode active material for a lithium secondary battery may be prepared in a form in which chlorine groups are substituted on both sides.

At this time, the method for synthesizing the tetrazine single molecule having Chemical Formula 3 is performed through the process of Scheme 1 below.

<Scheme 1>

[Formula 4]

In addition, as shown in Chemical Formula 4 (dimethoxytetrazin, DMT), the tetraazine single molecule used in the disclosed electrode active material for lithium secondary batteries may be prepared in a form in which methoxy groups are substituted on both sides.

At this time, the tetrazine single molecule represented by Chemical Formula 4 may be prepared by reacting the reactant prepared through Reaction Scheme 1 as shown in Reaction Scheme 2 below.

<Reaction Scheme 2>

[Formula 5]

In addition, as shown in Chemical Formula 5 (chloroethoxytetrazin, CET), the tetraazine monomolecule used in the disclosed electrode active material for lithium secondary batteries may be prepared in a form in which one side is substituted with chlorine and the other side is substituted with ethoxy group. It might be.

At this time, the electrode active material for the lithium secondary battery is 100 parts by weight of the tetraazine single molecule of Formulas 2 to 5, 90 to 110 parts by weight of Super-P, and 40 to 60 parts by weight of polyvinylidene fluoride as N-methylpyrrolidone. After mixing to prepare an organic compound based on a tetraazine single molecule, the organic compound may be coated on aluminum foil and dried in a vacuum oven at 20 to 30 ° C. for 7 to 9 hours.

In addition, the electrode active material for a lithium secondary battery, after melting a tetrazine single-molecule-based organic compound prepared through the above process in a solvent, mixed with CMK-3 and subjected to sonic treatment, vacuum at 20 to 30 ° C It can be prepared by drying in an oven. More specifically, the tetrazine single-molecule-based organic compound is completely dissolved in a solvent, dimethylformamide, and then mixed with CMK-3 and sonicated for 1 hour. It may be produced through a process of drying in a vacuum oven at 25 ℃ after the implementation.

At this time, the organic compound based on the tetraazine derivative single molecule and the porous carbon material CMK-3 are mixed in a weight ratio of 1: 0.5 to 2, and most preferably in a weight ratio of 1: 2.

The electrode active material for a lithium secondary battery manufactured through the above process has excellent dissolution resistance because it is manufactured by intrusion of an organic compound based on a single molecule of tetraazine derivative into the porous carbon material CMK-3.

The CMK-3 was photographed with a scanning electron microscope (SEM) and is shown in FIG. 4 below.

4, it can be seen that CMK-3 has a porous structure exhibiting a large specific surface area.

Hereinafter, a method for manufacturing a positive electrode for a lithium secondary battery to which the electrode active material for a disclosed lithium secondary battery is applied and the properties of a lithium secondary battery to which the positive electrode is applied will be described with reference to examples.

<Production Example 1> Preparation of a positive electrode for a lithium secondary battery

After preparing a mixture by mixing 100 parts by weight of tetraazine single molecule, 100 parts by weight of Super-P and 50 parts by weight of polyvinylidene fluoride in dimethylformamide as shown in Chemical Formula 2 above, the mixture is prepared. A positive electrode for a lithium secondary battery was prepared by coating on an aluminum foil using a doctor blade and drying in a vacuum oven at 25 ° C. for 8 hours.

<Production Example 2> Preparation of a positive electrode for a lithium secondary battery

The same procedure as in Preparation Example 1 was performed, and an anode for a lithium secondary battery was manufactured using an organic compound based on the tetraazine single molecule represented by Chemical Formula 3.

<Production Example 3> Preparation of a positive electrode for a lithium secondary battery

After preparing a mixture by mixing 100 parts by weight of an organic compound based on a tetrazine single molecule represented by Chemical Formula 2, 100 parts by weight of Super-P and 50 parts by weight of polyvinylidene fluoride in dimethylformamide, After mixing 50 parts by weight of CMK-3 and adding 15 kHz sound waves for 1 hour to 1 hour, the mixture was coated on an aluminum foil using a doctor blade, and dried in a vacuum oven at 25 ° C. for 8 hours for a lithium secondary battery. An anode was prepared.

<Production Example 4> Preparation of a positive electrode for a lithium secondary battery

The same procedure as in Preparation Example 3 was performed, but 100 parts by weight of CMK-3 was mixed to prepare a positive electrode for a lithium secondary battery.

<Production Example 5> Preparation of a positive electrode for a lithium secondary battery

The same procedure as in Production Example 3 was performed, and 200 parts by weight of CMK-3 was mixed to prepare a positive electrode for a lithium secondary battery.

The positive electrode for a lithium secondary battery manufactured through Preparation Examples 3 to 5 was photographed with a scanning electron microscope (SEM) and is shown in FIG. 5 below, and the transmittance according to the infrared wave number was measured and shown in FIG. 6 below. As shown in FIG. 5 below, the cross-sectional area of the positive electrode for a lithium battery prepared through Preparation Example 5, in which the content of CMK-3 is twice that of the tetraazine single molecule in which the phenyl group is substituted on both sides, is formed most widely and outside the CMK-3 nanostructure. It can be seen that the remaining tetrazine single molecule is the smallest, and the positive electrode for a lithium secondary battery prepared through Preparation Example 5 as shown in FIG. 6 below is an organic based on a tetraazine derivative single molecule in the porous carbon material CMK-3. Since the rate of penetration of the compound is high, it can be seen that the rate of infrared absorption inherent in the tetraazine single molecule is low.

<Example 1>

The positive electrode for a lithium secondary battery prepared in Preparation Example 1, a lithium metal as a negative electrode, a porous polypropylene membrane as an electrode separator, and 1,3-dioxolane (DOL) / 1,2-dimethoxyethane as an electrolyte. (DME) (1: 1 v / v) A CR2032 coin-type lithium secondary battery was prepared using a solution in which 2M of lithium bis (trifluoromethane) sulfonimide (LiTFSi) was dissolved in 1M.

<Example 2>

CR2032 coin-type lithium secondary battery was manufactured in the same manner as in Example 1, using the positive electrode for a lithium secondary battery prepared in Preparation Example 2.

The physical properties of the CR2032 coin-type lithium secondary battery manufactured through Examples 1 to 2 were measured and are shown in FIG. 7 below.

As shown in FIG. 7 below, as a result of performance evaluation of the coin-type lithium secondary battery prepared through Examples 1 to 2, it can be seen that the new material group tetrazine has redox activity and operates as a battery.

<Example 3>

CR2032 coin-type lithium secondary battery was prepared in the same manner as in Example 1, using the positive electrode for a lithium secondary battery prepared in Preparation Example 3.

<Example 4>

CR2032 coin-type lithium secondary battery was manufactured in the same manner as in Example 1, using the positive electrode for a lithium secondary battery prepared in Preparation Example 4.

<Example 5>

CR2032 coin-type lithium secondary battery was manufactured in the same manner as in Example 1, using the positive electrode for a lithium secondary battery prepared in Preparation Example 5.

The characteristics of the CR2032 coin-type lithium secondary battery manufactured through Examples 3 to 5 were evaluated and are shown in FIG. 8 below.

As shown in FIG. 8 below, as a result of evaluating the properties of the CR2032 coin-type lithium secondary battery prepared through the disclosed Examples 3 to 5, it was confirmed that the charge / discharge cycle was also improved while the new material group tetrazine had redox activity. Particularly, in the case of Example 5, in which the organic compound based on the tetraazine single molecule prepared through Preparation Example 1 and the weight part of CMK-3 were prepared at a ratio of 1: 2, the best cycle retention was shown.

Accordingly, the disclosed electrode active material for a lithium secondary battery and the lithium secondary battery using the same provide stable electrode oxidation and easy control of the reduction potential, and provide an electrode active material having excellent dissolution resistance and a lithium secondary battery using the same.

Claims (11)

Electrode active material for a lithium secondary battery, characterized in that it comprises a single molecule of tetraazine derivative represented by the following formula (1).
[Formula 1]

(In Formula 1, R ₁ and R ₂ are the same or different substituents)
The method according to claim 1,
In Formula 1, R ₁ , R ₂ are each independently selected from the group consisting of alkoxy, phenyl, heterocyclic aromatic compound, chlorine, carboxyl group, and -COOM, wherein M is a metal cation electrode active material for a lithium secondary battery .
The method according to claim 2,
The heterocyclic aromatic compound is an electrode active material for a lithium secondary battery, characterized in that it comprises at least one compound selected from pyridine, pyrimidine, thiophene, furan, pyrrole and imidazole.
The method according to claim 1,
An electrode active material for a lithium secondary battery, further comprising a porous carbon material.
The method according to claim 4,
The tetraazine derivative single molecule and the porous carbon material has an electrode active material for a lithium secondary battery, characterized in that the weight ratio is made of 1: 0.5 to 2.
The method according to claim 5,
The tetraazine derivative single molecule and the porous carbon material is an electrode active material for a lithium secondary battery, characterized in that the weight ratio is made of 1: 2.
The method according to any one of claims 4 to 6,
The porous carbon material is an electrode active material for a lithium secondary battery, characterized in that CMK-3.
A positive electrode for a lithium secondary battery, characterized in that it is made of aluminum foil coated with the tetraazine single molecule of claim 1.
The method according to claim 8,
The positive electrode for a lithium secondary battery is prepared by mixing the tetraazine single molecule, Super-P and polyvinylidene fluoride in dimethylformamide, and then coating the mixture on aluminum foil and drying it. A positive electrode for a lithium secondary battery.
A lithium secondary battery comprising a positive electrode for a lithium secondary battery according to any one of claims 8 to 9, a negative electrode made of lithium metal, an electrode separator made of a porous polypropylene membrane, and an electrolyte.
The method according to claim 10,
The electrolyte is 1,3-dioxolane (DOL) / 1,2-dimethoxyethane (DME) (1: 1 v / v) 1M to 2M lithium bis (trifluoromethane) sulfonimide (LiTFSi Lithium secondary battery, characterized in that made of a dissolved solution.

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