KR100511519B1 - Nonaqueous electrolyte for battery and secondary battery comprising the electrolyte - Google Patents

Abstract

The present invention relates to a non-aqueous electrolyte for lithium batteries containing a novolak phenol or a multiphenol derivative in a carbonate-based organic mixed solvent (lithium salt-containing organic mixed solution) in which lithium salt is dissolved, and a lithium secondary battery including the same.

The non-aqueous electrolyte solution for lithium batteries according to the present invention has significantly less gas generation at a high temperature (85 ° C.) than conventional electrolyte solutions, and when applied to the battery, battery thickness due to gas generation inside the battery due to decomposition of the electrolyte solution at a high temperature. It is possible to prevent swelling, so-called bulging, and to have excellent capacity storage characteristics at high temperatures.

Description

Non-aqueous electrolyte for batteries and secondary batteries comprising the same

The present invention relates to a nonaqueous electrolyte solution for batteries, and more particularly, to a nonaqueous electrolyte solution for a lithium battery including a noblock phenol or a multiphenol derivative having a specific chemical formula in a carbonate-based organic mixed solvent in which a lithium salt is dissolved.

The miniaturized and slimmed lithium secondary battery used in consumer notebook computers, camcorders, mobile phones, etc. is a cathode composed of a lithium metal mixed oxide capable of detaching and inserting lithium ions, a cathode made of carbon material or metal lithium, and a mixed organic solvent. It consists of electrolyte solution in which lithium salt melt | dissolved in the suitable quantity. Such lithium batteries are generally used in the form of coins, 18650 cylinders, 063048 squares and the like. Since the lithium battery has an average discharge voltage of about 3.6 to 3.7 V, there is an advantage that high power can be obtained compared to other alkaline batteries or Ni-MH or Ni-Cd batteries. In order to exhibit such a high driving voltage, an electrochemically stable electrolyte composition is required in the charge and discharge region of 0 to 4.2 V. Therefore, ethylene carbonate (EC), dimethyl carbonate (DMC) and dicarbonate Fluorobenzene (FB) is suitably mixed and used as an electrolyte solvent in order to increase the absorbency between carbonate organic solvents such as ethyl carbonate (DEC) and the separator. As the solute of the electrolyte, lithium salts such as LiPF ₆ , LiBF ₄ , LiClO ₄ , or LiN (C ₂ F ₅ SO ₃ ) ₂ are commonly used. They act as a source of lithium ions in the battery, thereby operating the lithium battery. To make it possible. However, the non-aqueous electrolyte prepared as described above may have disadvantages in high rate charging and discharging because the ion conductivity is significantly lower than that of the aqueous electrolyte used in Ni-MH or Ni-Cd batteries. In the initial charging of a lithium battery, lithium ions from the lithium metal composite oxide used as the positive electrode move to the graphite (crystalline or amorphous) electrode used as the negative electrode and are intercalated between the layers of the graphite electrode. At this time, since lithium is highly reactive, the electrolyte and the carbon constituting the cathode react on the graphite cathode surface to form a compound such as Li ₂ CO ₃ , Li ₂ O, or LiOH. These compounds form a kind of passivation layer on the surface of the graphite cathode, which is called a solid electrolyte interface (SEI) film. Once formed, the SEI film functions as an ion tunnel to pass only lithium ions. The SEI film solvates lithium ions by the effect of this ion tunnel, and organic solvent molecules having a large molecular weight, such as EC, DMC, or DEC, which move together with lithium ions in the electrolyte are inserted together in the graphite cathode to form a graphite anode. It prevents the structure from collapsing. Once the SEI film is formed, lithium ions again do not react sideways with the graphite anode or other materials, and the amount of charge consumed to form the SEI film has a property of not reversibly reacting upon discharge with an irreversible capacity. Therefore, no further electrolyte decomposition occurs and the amount of lithium ions in the electrolyte is reversibly maintained so that charge and discharge are stably maintained (see J. Power Sources (1994) 51: 79 to 104). However, in the thin-film rectangular battery, gases such as CO, CO ₂ , CH ₄ , and C ₂ H ₆ are generated from decomposition of the carbonate-based organic solvent during the above-mentioned SEI formation reaction, causing a problem that the thickness of the battery expands during charging. (See J. Power Sources (1998) 72: 66-70). In addition, when stored at high temperature in a fully charged state (for example, left at 85 ° C. for 4 hours after being fully charged to 4.2 V), the SEI film gradually collapses due to increased electrochemical energy and thermal energy as time passes. The side reaction where the negative electrode surface reacts with the surrounding electrolyte continuously occurs. In this case, the internal pressure of the battery increases due to the continuous gas generation. As a result, in the case of the square battery and the polymer lithium ion (PLI) battery, the thickness of the battery increases, which makes it difficult to install the set itself.

Accordingly, there is a need in the art for the development of an electrolyte solution that can provide a lithium secondary battery having excellent high temperature performance and mounting performance without causing a problem of volume expansion occurring during high temperature storage in a lithium secondary battery.

The present inventors have made intensive studies to develop an electrolyte solution capable of providing a lithium secondary battery having improved high temperature performance and set mounting efficiency by solving the above problems. As a result, a novel phenol or multiphenol derivative having a specific chemical formula may be added to the battery nonaqueous electrolyte. In this case, it was confirmed that the swelling phenomenon in the battery was remarkably suppressed without affecting the battery characteristics in the battery using the nonaqueous electrolyte solution for the secondary battery.

As a result, the present invention is to provide a new non-aqueous electrolyte solution for lithium batteries by suppressing decomposition of the electrolyte at a high temperature, significantly reducing the thickness increase rate of the battery when left at a high temperature and improving capacity storage characteristics at a high temperature.

One aspect of the present invention for achieving the above object relates to a non-aqueous electrolyte for lithium batteries comprising a lithium salt-dissolved carbonate-based organic mixed solvent (lithium salt-containing organic mixed solution) and a noblock phenol or multiphenol derivative having the formula :

[Wherein n is an integer or a minority between 0 and 100,000, X and Y are hydrogen, a halogen group, an alkyl group having 1 to 12 carbon atoms, an aryl group having 1 to 12 carbon atoms, an alkenyl group having 1 to 12 carbon atoms, or fluorination Lower alkyl group or phenol group, and Z is hydrogen.]

Another aspect of the present invention relates to a lithium secondary battery including the nonaqueous electrolyte.

Hereinafter, the present invention will be described in more detail.

The nonaqueous electrolyte according to the present invention is prepared by adding 0.1 to 10.0 parts by weight of a noblock phenol or a multiphenol derivative represented by Formula 1 to 100 parts by weight of a carbonate mixed organic solvent in which lithium salt is dissolved.

The carbonate mixed organic solvent includes a cyclic carbonate organic solvent and a linear carbonate organic solvent. Preferably, the cyclic carbonate organic solvent is selected from the group consisting of ethylene carbonate, propylene carbonate and a mixture of both. The linear carbonate organic solvent is dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, Methylpropyl carbonate and mixtures thereof. More preferably, a mixture of ethylene carbonate and dimethyl carbonate or ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate is used. As the mixed organic solvent, one or two or more compounds selected from the group consisting of propyl acetate, methyl acetate, ethyl acetate, butyl acetate, methyl propionate, ethyl propionate and fluorobenzene may be further mixed and used as necessary. . The mixing ratio of the organic solvent selected from each group is not particularly limited as long as the object of the present invention is not impaired.

The mixed organic solvent contains a lithium salt compound, examples of the lithium salt include all known lithium salt compounds used in lithium batteries, preferably LiPF ₆ , LiClO ₄ , LiAsF ₆ , LiBF ₄ and LiN 1 or 2 or more selected from the group consisting of (C ₂ F ₅ SO ₃ ) ₂ is used. More preferably LiPF ₆ is used. The lithium salt compound is present in the carbonate-based mixed organic solvent in the range of 0.8 to 2.0M.

 The nonaqueous electrolyte of the present invention is prepared by adding 0.1 to 10.0 parts by weight, preferably 0.1 to 1.0 parts by weight of a noble phenol or a multiphenol derivative of Formula 1 to 100 parts by weight of the organic mixed solvent including the lithium salt compound described above.

When the phenol derivative is added, the generation of gas at a high temperature is significantly reduced, and the swelling phenomenon is greatly reduced even when the battery is left at a high temperature.

By using the nonaqueous electrolyte solution for lithium batteries according to the present invention, a lithium battery can be manufactured according to a conventional method, and the lithium battery thus produced can generate gas inside the battery due to decomposition of the electrolyte when left at a high temperature (85 ° C). Since it is suppressed, the swelling phenomenon that the thickness of the battery expands is prevented and the capacity storage characteristic at high temperature is also excellent.

EXAMPLE

Hereinafter, the structure and effect of the present invention will be described in more detail with specific examples and comparative examples, but these examples are only intended to more clearly understand the present invention, and are not intended to limit the scope of the present invention.

Examples 1 to 3

0.5 parts by weight of electrolyte based on 100 parts by weight of an electrolyte solution containing 1 M of LiPF ₆ in a 3: 6: 1 mixed solvent of ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC). (Example 1), 0.25 parts by weight (Example 2), 0.1 parts by weight (Example 3) of the noblock phenol (wherein n is 3 in the general formula (1), X, Y, and Z are all hydrogen) To prepare an electrolyte solution.

The prepared electrolyte was applied to a square 02350 battery. In this case, the active material of the used negative electrode was graphite, and PVDF was used as the binder. LiCoO ₂ was used as an active material, PVDF was used as a binder, and acetylene black was used as a conductive material. After carrying out the process of charging and discharging the standard and the standard charging and discharging with the prepared battery, the experiment was inflated at a high temperature (85 ℃, 72 hours) in 4.2V full charge state. The results are shown in Table 1.

Comparative Example 1

An electrolyte was prepared in the same manner as in Example 1 except that no-block phenol was used, and a battery was prepared using the inflated test. The results are shown in Table 1.

From Table 1, it can be seen that when the electrolyte according to the present invention is used, the chemical conversion efficiency and the standard efficiency are high, and the rate of increase in thickness at high temperature is significantly reduced.

The non-aqueous electrolyte solution for lithium batteries according to the present invention has significantly less gas generation at a high temperature (85 ° C.) than conventional electrolyte solutions, and when applied to the battery, battery thickness due to gas generation inside the battery due to decomposition of the electrolyte solution at a high temperature. It is possible to prevent swelling, so-called bulging, and to have excellent capacity storage characteristics at high temperatures.

Claims (4)

In the carbonate-based organic mixed solvent (lithium salt-containing mixed organic solution) in which a lithium salt compound is dissolved, include a noblock phenol or a multiphenol derivative represented by the following formula (1), The lithium salt compound is present in the carbonate mixed organic solvent in the range of 0.8 to 2.0 M, and the noblock phenol or multiphenol derivative is 0.1 to 1 parts by weight in the lithium salt-containing mixed organic solution, characterized in that the non-aqueous electrolyte for lithium batteries : [Formula 1] [Wherein n is an integer and a minority between 0 and 100,000, X and Y are hydrogen, a halogen group, an alkyl group having 1 to 12 carbon atoms, an aryl group having 1 to 12 carbon atoms, an alkenyl group having 1 to 12 carbon atoms, or fluorinated Lower alkyl group or phenol group, and Z is hydrogen.] delete The compound according to claim 1 or 2, wherein the lithium salt compound is at least one compound selected from the group consisting of LiPF ₆ , LiClO ₄ , LiAsF ₆ , LiBF ₄ and LiN (C ₂ F ₅ SO ₃ ) ₂ . , The carbonate-based organic mixed solvent is a mixture of linear and cyclic carbonate-based organic solvent, wherein the linear carbonate-based organic solvent is selected from the group consisting of ethylene carbonate, propylene carbonate and a mixture of both And the linear carbonate organic solvent is selected from the group consisting of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, and mixtures thereof. A lithium battery comprising the electrolyte according to claim 1 or 2.