KR100810681B1 - Nonaqueous electrolyte for secondary battery and Li secondary battery thereby - Google Patents

Abstract

Provided is a nonaqueous electrolyte solution for a lithium secondary battery in which cycle characteristics and low temperature characteristics are improved when high voltage is applied. The non-aqueous electrolyte solution for a lithium secondary battery includes an organic solvent, a lithium salt, and at least one halogenated benzene selected from the group represented by the following general formula (1).

(Wherein X is F, Cl, Br, I and n is an integer of 1 to 3)

Lithium Secondary Battery, Electrolyte, Halogen Benzene

Description

Non-aqueous electrolyte for high voltage lithium secondary battery of 4.4V or more and lithium secondary battery comprising same {Nonaqueous electrolyte for secondary battery and Li secondary battery

1 is a graph showing the capacity retention rate (%) during the cycle of charging and discharging the embodiments and comparative examples of the present invention.

2 illustrates the use of aluminum (Al) as the positive electrode metal, copper (Cu) as the negative electrode 110 metal, LiCOO ₂ as the positive electrode 100 active material, and carbon (C) as the negative electrode active material. It is a schematic diagram which shows the lithium secondary battery which used this as electrolyte solution.

<Explanation of symbols for the main parts of the drawings>

100: positive electrode 110: negative electrode

130: electrolyte

The present invention relates to a non-aqueous electrolyte for secondary batteries, and more particularly to a non-aqueous electrolyte for secondary batteries for improving high voltage characteristics.

Secondary battery is a chemical battery that can be used semi-permanently because it can be recharged unlike a primary battery, and its market size is growing exponentially due to the recent mass distribution of laptops, mobile communication devices, and digital cameras. Recently, it is rapidly growing as one of the three parts industries in the 21st century along with semiconductors and displays.

Secondary batteries include lead-acid batteries, nickel-cadmium (Ni-Cd) batteries, nickel-hydrogen (Ni-MH) batteries, and lithium batteries, depending on the cathode and anode materials. The potential and energy density are determined by Among them, especially lithium secondary batteries are used as a driving power source for portable electronic devices because of their high energy density due to the low redox potential and molecular weight of lithium.

Among these lithium secondary batteries, a lithium secondary battery using a nonaqueous electrolyte, in particular, is coated with a lithium metal mixed oxide as a cathode active material on a metal as an anode, and as a cathode active material on a metal as a cathode. A carbon material or a metal lithium is coated and used, and an electrolyte in which lithium salt is appropriately dissolved in an organic solvent is disposed between these anodes and cathodes.

In brief, the operation principle of the lithium secondary battery, lithium ions (Li +) present in the ionic state in the electrolyte is moved from the positive electrode to the negative electrode during charging, and from the negative electrode to the positive electrode during discharge. The electrons then move along the wires that connect the anode and cathode, opposite to lithium ions.

Such lithium secondary batteries generate 4.2V of electromotive force and commercially available ones having a capacitance of 3000mA.

However, in recent years, there is an increasing demand for performance improvement of batteries, in particular, high capacity and high voltage of 3000 mA or more, and in order to satisfy this problem, development of a technology for improving characteristics by adding characteristic compounds to an electrolyte of a lithium secondary battery has been underway. . In particular, the high-voltage lithium secondary battery of 4.4V or more, compared to the existing 4.2V-class lithium secondary battery, the charge and discharge characteristics and cycle (cycle) characteristics are deteriorated, it is necessary to develop a technology for improving this.

The technical problem to be achieved by the present invention is a lithium secondary battery, in particular lithium secondary battery using a non-aqueous electrolyte by adding a halogenated benzene to the non-aqueous electrolyte lithium 2 which can have excellent cycle characteristics when applying a high voltage of 4.4V or more It is to provide a non-aqueous electrolyte solution for vehicle batteries.

Another object of the present invention is to provide a lithium secondary battery including the non-aqueous electrolyte of the present invention.

Technical problems to be achieved by the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art from the following description.

In order to solve the above technical problem, a nonaqueous electrolyte solution for a lithium secondary battery according to an embodiment of the present invention includes an organic solvent, a lithium salt, and at least one halogenated benzene selected from the group represented by the following Chemical Formula 1.

(Wherein X is F, Cl, Br, I and n is an integer of 1 to 3)

Lithium secondary battery according to an embodiment of the present invention for solving the above other technical problem is the electrode portion consisting of a positive electrode and a negative electrode which are located opposite to each other with the electrolyte solution, the electrolyte solution of the present invention, and the positive electrode and the negative electrode It includes a separator that electrically separates it.

Specific details of other embodiments are included in the detailed description and the accompanying drawings.

Advantages and features of the present invention and methods for achieving them will be apparent with reference to the embodiments described below in detail with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in various different forms, only these embodiments are intended to make the disclosure of the present invention complete, and common knowledge in the art to which the present invention pertains. It is provided to fully inform the person having the scope of the invention, which is defined only by the scope of the claims. Like reference numerals refer to like elements throughout.

The non-aqueous electrolyte solution for a lithium secondary battery according to an embodiment of the present invention does not contain water (H ₂ O) as the term, and only an organic solvent is used as a solvent.

The organic solvent is based on a carbonate organic solvent, and may further include an ester-based and / or aromatic hydrocarbon-based organic solvent and other organic solvents.

In addition, the organic solvent may further include 0.01 to 20% by weight of at least one selected from vinylene carbonate, succinic acid and fluoroethylbenzene in the carbonate-based organic solvent.

Examples of the carbonate organic solvent include at least one cyclic carbonate organic solvent composed of ethylene carbonate (EC), propylene carbonate (PC) and butylene carbonate (BC), dimethyl carbonate (DMC) and diethyl carbonate (DEC). ), It is preferable to use at least one linear carbonate organic solvent consisting of ethyl propyl carbonate (EPC), dipropyl carbonate (DPC), methyl ethyl carbonate (MEC) and methyl propyl carbonate (MPC).

However, the cyclic carbonate organic solvent and the linear carbonate organic solvent are preferably used in a ratio of 1: 1 to 1: 4 based on the volume ratio.

Ester organic solvents include butyrolactone, decanolide, valerolactone, mevalonolactone, caprolactone, n-methyl acetate, n-ethyl acetate, n-propyl acetate, and It is preferable to further use one or more selected from the group consisting of butyl acetate.

The aromatic hydrocarbon organic solvent specifically includes one or more selected from the group consisting of benzene, fluorobenzene, toluene, fluorotoluene, trifluorotoluene, and xylene.

In addition, the organic solvent preferably further comprises at least one selected from methyl propionic acid, ethyl propionic acid, and propyl propionic acid.

Lithium salt is used as a solute (salt) in the non-aqueous electrolyte solution for a lithium secondary battery according to an embodiment of the present invention. Specifically, one or two of LiPF ₆ , LiClO ₄ , LiAsF ₆ , LiBF ₄ , and LiCF ₃ SO ₃ are used. Lithium salts selected on paper are used.

At this time, the amount of the lithium salt is preferably added so that the concentration of the total electrolyte solution is in the range of 0.6 ~ 2.0M, the reason is that when the concentration of the lithium salt is less than 0.6M, the electrolyte performance is lowered by lowering the electrical conductivity of the electrolyte, 2.0 If it exceeds M, it is because there is a problem that the low-temperature performance due to the increase in viscosity at low temperature falls.

In addition to the organic solvent and the lithium salt, the non-aqueous electrolyte lithium secondary battery of the present invention is characterized in that it further comprises a halogenated benzene represented by the formula (1) of the group, more specifically fluorobenzene, difluorobenzene, Trifluorobenzene, chlorobenzene, dichlorobenzene, trichlorobenzene, bromobenzene, dibromobenzene, tribromobenzene, chlorofluorobenzene, bromofluorobenzene, and derivatives thereof. Species or a mixture of two or more thereof may be used, and preferably difluoro benzene is used.

(Wherein X is F, Cl, Br, I and n is an integer of 1 to 3)

At this time, the amount of halogenated benzene is added to the non-aqueous electrolyte of the present invention is preferably added to 0.1 to 30% by weight based on the total electrolyte.

The reason for determining the addition amount of the halogenated benzene as described above is that when the halogenated benzene is added in the non-aqueous electrolyte solution of the present invention, the characteristic is linearly improved up to 20% by weight, but the property is different between 20 to 30% by weight. Although it is improved, it shows a gentle improvement, but if it exceeds 30% by weight, even if halogenated benzene is added, there is almost no change in properties.

In summary, the structure of the non-aqueous electrolyte solution of the present invention is shown in the form of the most preferred embodiment. As the organic solvent, ethylene carbonate (EC), dimethyl carbonate (DMC), and diethyl carbonate (DEC) are each represented by 3: 6. LiPF ₆ was dissolved in an organic solvent mixed at a ratio of 1 to a concentration of 1.15 M as a basic electrolyte, and the halogenated benzene of the general formula (1) was added to the basic electrolyte at less than 50% by weight. will be.

Hereinafter, various embodiments of the present invention will be described.

<Example 1>

LiPF ₆ dissolved in a concentration of 1.15 M as a solute in a solvent mixed with ethylene carbonate, dimethyl carbonate, and diethyl carbonate in a ratio of 3: 6: 1 was used as a base electrolyte, and 10% by weight of florobenzene was used as the base electrolyte. The final electrolyte solution was added to evaluate the charge and discharge life and are shown in Table 1 and the graph of FIG. 1. In this case, carbon was used as the active material of the negative electrode, polyvinylidene fluoride resin (PVDF) was used as the binder, LiCoO ₂ was used as the active material of the positive electrode, PVDF was used as the binder, and acetylene black was used as the conductor. Used.

<Example 2>

Except for using 10% by weight of difluorobenzene as an additive was carried out in the same manner as in Example 1 to evaluate the charge and discharge life, it is shown in the graph of Table 1 and FIG.

<Example 3>

Except for using 10% by weight of trifluorobenzene as an additive was carried out in the same manner as in Example 1 to evaluate the charge and discharge life, shown in the graph of Table 1 and FIG.

<Example 4>

Except that 10 wt% of chlorobenzene was used as an additive, the same procedure as in Example 1 was carried out to evaluate the charge and discharge life, and are shown in the graphs of Table 1 and FIG. 1.

Example 5

Except for using 10% by weight of bromobenzene as an additive was carried out in the same manner as in Example 1 to evaluate the charge and discharge life, shown in the graph of Table 1 and FIG.

<Example 6>

Except that 10% by weight of benzene iodide was used as an additive, the same procedure as in Example 1 was carried out to evaluate the charge and discharge life, and are shown in the graphs of Table 1 and FIG. 1.

Comparative Example 1

Except for using only the basic electrolyte solution without the use of additives after the same as in Example 1 to evaluate the charge and discharge life, shown in the graph of Table 1 and FIG.

Comparative Example 2

Except that 10 wt% of benzene was used as the additive, the same procedure as in Example 1 was carried out to evaluate the charge and discharge life, and are shown in the graphs of Table 1 and FIG. 1.

As described above, referring to Table 1 and FIG. 1, in the case of the non-aqueous electrolyte containing the halogenated benzene of the present invention, even if the cycle is repeated, the capacity reduction rate is superior to that of the comparative examples, in particular, 300 cycles. Later, in the case of Example 2, the capacity of 81% is maintained, whereas in Comparative Example 1, only 8% of the capacity can be seen that.

2 shows that aluminum (Al) is used as the positive electrode 100 metal, copper (Cu) is used as the negative electrode 110 metal, LiCoO ₂ is used as the positive electrode 100 active material, and carbon (C) is used as the negative electrode active material. It is a schematic diagram which shows the lithium secondary battery which used the nonaqueous electrolyte solution as electrolyte solution 130. FIG.

As shown in FIG. 2, a lithium secondary battery according to an exemplary embodiment of the present invention includes a positive electrode 100, a negative electrode 110, an electrolyte 130, and a separator 140.

However, since the electrolyte 130 used in the lithium secondary battery according to the embodiment of the present invention is used, the non-aqueous electrolyte according to the embodiment of the present invention has been described above. .

The positive electrode 100 and the negative electrode 110 are disposed to face each other with the electrolyte 130 interposed therebetween.

The positive electrode 100 was coated with LiCoO ₂ , as an active material on a metal, but in addition, LiMnO ₂ , LiMn ₂ O ₄ , LiNiO ₂ , and LiNi _1-xy Co _x Mn _y O ₂ (0 ≦ _x ≦ ₁ , One or more active materials selected from the group consisting of 0 ≦ y ≦ 1 and 0 ≦ x + y ≦ 1) may be used.

The negative electrode 110 is coated with one or more active materials selected from the group consisting of crystalline carbon, amorphous carbon, carbon composite, lithium metal, and lithium alloy.

The separator 140 is one of a single layer separator made of polyethylene or polypropylene, a two layer separator made of polyethylene / polypropylene, and one of three layer separators made of polyethylene / polypropylene / polyethylene or polypropylene / polyethylene / polypropylene. do.

In this case, the metal used in the positive electrode 100 and the negative electrode 110 is a portion to which a voltage is applied from the outside during charging and supplies a voltage to the outside during discharge, and the positive electrode active materials are a collector and a negative electrode that collect positive charges. The active material serves as a current collector for collecting negative charges.

Although the embodiments of the present invention have been described above with reference to the accompanying drawings and tables, the present invention is not limited to the above embodiments, but may be manufactured in various forms, and common knowledge in the art to which the present invention pertains. Those skilled in the art can understand that the present invention can be implemented in other specific forms without changing the technical spirit or essential features of the present invention. Therefore, it should be understood that the embodiments described above are exemplary in all respects and not restrictive.

According to the nonaqueous electrolyte solution for a lithium secondary battery according to an embodiment of the present invention, even when high voltage is applied, the lithium secondary battery has an effect of improving cycle characteristics and low temperature characteristics without degrading the performance of the basic electrolyte solution.

Claims (12)

A lithium secondary battery electrolyte using a graphite negative electrode, comprising: an organic solvent, a lithium salt, and 5-15% by weight of a fluorobenzene represented by the following general formula (1): a non-aqueous electrolyte solution for a high voltage lithium secondary battery for 4.4V or higher.

(In Formula 1, n is an integer of 1 to 3) The method of claim 1, The fluorobenzenes are non-aqueous electrolyte solution for a high-voltage lithium secondary battery of 4.4 V or more, characterized in that at least one selected from fluorobenzene, difluorobenzene, trifluorobenzene, and derivatives thereof. The method of claim 1, A non-aqueous electrolyte solution for a high voltage lithium secondary battery of 4.4 V or higher, characterized in that 0.1 to 30% by weight of fluorobenzenes are contained in the total electrolyte solution. The method of claim 1, The organic solvent is at least one cyclic carbonate organic solvent consisting of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl propyl carbonate (EPC) 4.4V, characterized in that one or more linear carbonate organic solvents consisting of dipropyl carbonate (DPC), methyl ethyl carbonate (MEC) and methyl propyl carbonate (MPC) are mixed at a volume ratio of 1: 1 to 1: 4. The above non-aqueous electrolyte solution for high voltage lithium secondary batteries. delete The method of claim 4, wherein The carbonate organic solvent is butyrolactone, decanolide, valerolactone, mevalonolactone, caprolactone, n-methyl acetate, n-ethyl acetate, n-propyl acetate, and 4.4 V or more non-aqueous electrolyte for high voltage lithium secondary battery, characterized in that it further comprises at least one selected from the group consisting of butyl acetate. The method of claim 4, wherein The carbonate-based organic solvent further comprises at least one selected from the group consisting of at least one aromatic hydrocarbon solvent consisting of benzene, fluorobenzene, toluene, fluorotoluene, trifluorotoluene, and xylene, lithium 2 for high voltage of at least 4.4V Non-aqueous electrolyte solution for vehicle batteries. The method of claim 4, wherein The carbonate-based organic solvent is 4.4V or higher non-aqueous electrolyte for lithium secondary battery, characterized in that it further comprises at least one selected from methyl propionic acid, ethyl propionic acid and propyl propionic acid. The method of claim 1, The lithium salt is at least one selected from LiPF ₆ , LiClO ₄ , LiAsF ₆ , LiBF ₄ , and LiCF ₃ SO ₃ and the concentration is 0.6 to 2.0M non-aqueous for high voltage lithium secondary battery, characterized in that Electrolyte solution. The electrolyte of claim 1; And An electrode unit including positive and negative electrodes positioned to face each other with the electrolyte interposed therebetween; And 4.4V or higher high-voltage lithium secondary battery comprising a separator for electrically separating the positive electrode and the negative electrode. The method of claim 10, The positive electrode is LiCoO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , LiNiO ₂ , and LiNi _1-xy Co _x Mn _y O ₂ (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1). 4.4V or higher high-voltage lithium secondary battery, characterized in that at least one active material selected from the group consisting of. The method of claim 10, The negative electrode is at least 4.4V high-voltage lithium secondary battery, characterized in that at least one selected from the group consisting of crystalline carbon, amorphous carbon, carbon composite, lithium metal and lithium alloy.

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