KR101420154B1 - Electrolyte for Lithium Secondary Battery and Lithium Secondary Battery containing the same - Google Patents

Abstract

The present invention relates to an electrolyte for a lithium secondary battery, and more particularly to an electrolyte for a lithium secondary battery, wherein the electrolyte comprises a linear monoacrylate compound, wherein the linear monoacrylate compound is an ether, ketone, Wherein the linear monoacrylate is a linear monoacrylate having any one of a linear structure, an ester structure and an amide structure. The present invention also provides an electrolyte for a lithium secondary battery and a lithium secondary battery using the same.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrolyte for a lithium secondary battery and a lithium secondary battery using the same.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrolyte for a lithium secondary battery and a lithium secondary battery using the same. More particularly, the present invention relates to an electrolyte separating active material from a current collector during charging and discharging in a secondary battery, will be.

Due to the rapid diffusion and demand of portable electronic devices such as mobile phones, notebook computers and portable game machines, the demand for lithium ion secondary batteries used as their supply devices is also increasing, and the need for high performance and large capacity lithium secondary batteries have. In response to such demands, researches on lithium secondary batteries having a high discharge voltage and a high energy density have been actively conducted.

The battery can be broadly divided into an anode, a cathode, and an electrolyte, and also includes components such as a separator and an exterior material. The general lithium ion battery is assembled by alternately stacking the positive electrode, the negative electrode and the separator with each other, inserting it into a can or pouch of a predetermined size and shape, and finally injecting the electrolyte. At this time, the injected electrolyte is impregnated between the anode, the cathode and the separator by a capillary force.

Among lithium secondary batteries, a lithium secondary battery using a non-aqueous electrolyte is used in which a cathode is coated with a lithium metal mixed oxide as a cathode active material, and a cathode is coated with a carbon material or metal lithium as a negative electrode active material And an electrolyte in which a lithium salt is dissolved in an organic solvent is used between these positive and negative electrodes.

The operation principle of the lithium secondary battery will be briefly described as follows. Lithium ions existing in the ion state in the electrolyte are generated from the anode to the cathode when charged and from the cathode to the anode when discharged.

Such lithium secondary batteries are used in various fields. Recently, lithium secondary batteries, which are being developed for electric vehicles, require much higher characteristics than lithium secondary batteries mounted on mobile phones or notebook computers. As an electrolyte suitable for a lithium secondary battery having such high-rate characteristics, a liquid electrolyte or gel polymer having high ion conductivity has been developed.

However, since the electrolyte having a high ionic conductivity merely accelerates the charging and discharging at a high rate when the charging and discharging proceeds at a high temperature at a high temperature, the movement of the electrolyte is accelerated, There arises a problem that a phenomenon of separation is caused.

Therefore, in the case of a lithium secondary battery in which charging and discharging is rapidly progressed, development of a technique for preventing the active material from being detached from the current collector in accordance with the movement of the electrolyte has been required.

Korean Patent Publication No. 2010-0109181 (published on October 10, 2010)

It is an object of the present invention to provide a technique capable of suppressing the phenomenon that the active material is separated from the electrode plate.

Another object of the present invention is to provide a lithium secondary battery in which the life of the battery can be prolonged by suppressing the desorption of the active material.

In order to achieve the above object, the present invention provides an electrolyte for a lithium secondary battery, wherein the electrolyte comprises a linear monoacrylate compound, wherein the linear monoacrylate compound has a linear structure selected from ether, ketone, ester and amide Linear monoacrylate and linear monoacrylate. The present invention also provides an electrolyte for a lithium secondary battery.

The present invention also provides an electrolyte for a lithium secondary battery, wherein the linear monoacrylate compound is a linear monoacrylate having any one of ether, ketone, ester and amide.

The present invention also provides an electrolyte for a lithium secondary battery, wherein the linear monoacrylate compound has a molecular weight (Mn) of 1,000 to 5,000.

The present invention also relates to a lithium secondary battery, wherein the electrolyte comprises a non-aqueous organic solvent, a lithium salt and the linear monoacrylate compound, wherein the linear monoacrylate compound comprises 0.1 to 20 wt% Thereby providing an electrolyte.

The present invention also relates to a non-aqueous organic solvent, wherein the non-aqueous organic solvent is selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethylcarbonate (DEC), ethylmethylcarbonate (DME),? -Butyrolactone (BL), tetrahydrofuran (THF), 1,3-dioxolane (DOL), diethyl ether (DEE), methyl formate (MP), sulpholane (S), dimethylsulfoxide (DMSO), and acetonitrile (AN), or a mixture of at least one selected from the group consisting of methyl propionate do.

The present invention also provides a lithium secondary battery wherein the lithium salt is LiPF ₆ , LiBF ₄ , LiTFSI, LiSbF ₆ , LiAsF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , Li (CF ₃ SO ₂ ) ₂ N, LiC ₄ F ₉ SO ₃ , LiSbF ₆ , LiAlO ₄ , LiAlCl ₄ , LiN (C _x F _{2x + 1} SO ₂ ) (C _y F _{2y + 1} SO ₂ ) (where x and y are natural numbers), LiCl and LiI Wherein the electrolyte is a mixture of lithium secondary battery and lithium secondary battery.

The present invention also provides a lithium secondary battery comprising the electrolyte, the cathode, the anode and the separator.

The electrolyte for a lithium secondary battery and the lithium secondary battery using the same according to the present invention have an effect of suppressing a sudden micro-droplet phenomenon of the electrolyte in the vicinity of the current collector under severe charging and discharging conditions.

Also, the electrolyte for a lithium secondary battery according to the present invention and the lithium secondary battery using the same have the effect of inhibiting the phenomenon of the active material being removed from the electrode plate.

Also, the electrolyte for a lithium secondary battery according to the present invention and the lithium secondary battery using the same can suppress the desorption of the active material from the electrode plate, thereby prolonging the life of the battery.

Fig. 1 is a photograph showing the states of the positive electrode and the separator of Examples 1 to 8 and Comparative Example 1. Fig.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. First, it should be noted that, in the drawings, the same components or parts have the same reference numerals as much as possible. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted so as to avoid obscuring the subject matter of the present invention.

The terms " about ", " substantially ", etc. used to the extent that they are used herein are intended to be taken to mean an approximation of, or approximation to, the numerical values of manufacturing and material tolerances inherent in the meanings mentioned, Accurate or absolute numbers are used to help prevent unauthorized exploitation by unauthorized intruders of the referenced disclosure.

The present invention relates to an electrolyte capable of inhibiting the active material from being separated from the current collector, wherein the electrolyte contains a linear monoacrylate compound.

In the case of the polyfunctional acrylate compound, since it is difficult to impregnate into the micropores of the molecular skeleton active material, it is difficult to achieve the object to be achieved in the present invention.

The linear monoacrylate compound is preferably a monoacrylate in which ether, ketone, ester and amide are formed in a linear structure.

The structural formula of such a linear monoacrylate is as follows.

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The molecular size of the linear monoacrylate contained in the electrolyte according to the present invention should be smaller than the size of the fine gap between the active materials coated on the electrode plate. The size of such fine gaps is very much related to the average particle diameter of the active material constituting the electrode plate and the mixture density of the electrode plate.

The compound formed by the linear monoacrylate structure is excellent in affinity with the cathode active material and can be formed into a molecular structure having an appropriate size to enter into fine gaps between the active materials, thereby suppressing the rapid micro-scattering of the electrolyte near the current collector . Accordingly, the phenomenon that the active material is removed from the electrode plate can be suppressed.

More specifically, when the molecular weight (Mn) is 5,000 or less, a fine gel is formed between the active materials to form a gel-like polymer.

More specifically, when the molecular weight (Mn) is 5,000 or less, a gel-like polymer can be formed by entering a fine gap between the active materials.

Therefore, the molecular weight (Mn) is preferably 5,000 or less, more preferably 1,000 to 5,000.

Examples of the cathode active material include all carbon materials having a double layer capacity and can be used in one or more of the group consisting of activated carbon, natural fibers, amorphous carbon, fullerene, nanotubes, and graphene.

The monoacrylate having an excellent affinity with the cathode active material and having a proper molecular structure can be impregnated into the current collector layer inside the electrode plate using a gap between the active materials coated on the electrode plate to form a gel.

Therefore, the electrolyte is trapped in the gel-type electrode plate, so that it is possible to suppress the sudden micro-droplet phenomenon of the electrolyte in the vicinity of the current collector even under severe charging and discharging conditions. Accordingly, the phenomenon that the active material is removed from the electrode plate can be suppressed.

Meanwhile, the electrolyte for a lithium secondary battery according to the present invention includes a linear monoacrylate compound, a non-aqueous organic solvent, and a lithium salt.

The linear monoacrylate compound preferably comprises 0.1 to 20% by weight of the total electrolyte. Within the above range, it is possible to suppress the phenomenon that the gel is formed by being well impregnated into the current collector layer inside the electrode plate, and the active material is removed from the electrode plate.

The non-aqueous organic solvent may be at least one selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethylcarbonate (DEC), ethylmethylcarbonate (EMC), 1,2- (DME),? -Butyrolactone (BL), tetrahydrofuran (THF), 1,3-dioxolane (DOL), diethyl ether (DEE), methyl formate (MP), sulpholane (S), dimethylsulfoxide (DMSO), and acetonitrile (AN).

The lithium salt may be LiPF ₆ , LiBF ₄ , LiTFSI, LiSbF ₆ , LiAsF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , Li (CF ₃ SO ₂ ) ₂ N, LiC ₄ F ₉ SO ₃ , LiSbF ₆ , LiAlO ₄ , LiAlCl ₄ , LiN (C _x F _{2x + 1} SO ₂ ) (C _y F _{2y + 1} SO ₂ ) (where x and y are natural numbers), LiCl and LiI ≪ / RTI >

The electrolyte for a lithium secondary battery and the lithium secondary battery using the same according to the present invention have the effect of suppressing the phenomenon of abrupt microfiltration of the electrolyte in the vicinity of the current collector even under severe charging and discharging conditions and suppressing the phenomenon that the active material is separated from the electrode plate.

Hereinafter, embodiments of the present invention will be described.

Example  One

The electrolyte was prepared by mixing an organic solvent prepared by mixing ethylene carbonate (EC): diethyl carbonate (DEC) in a volume ratio of 30:70 and 1M LiPF ₆ , adding ether monoacrylate (Mn 1100) %. Then, a negative electrode, a positive electrode and a separator were constituted to manufacture a lithium secondary battery.

Charging and discharging were performed 50 times at 5 ° C at 60 ° C, and then the desorption phenomenon was observed on the electrode plate.

Example  2

The procedure of Example 1 was repeated,

Ether monoacrylate (Mn 1100) was added in an amount of 10% by weight based on the total electrolyte.

Example  3

The procedure of Example 1 was repeated,

Ether monoacrylate (Mn 1100) was added in an amount of 20% by weight based on the total electrolyte.

Example  4

The procedure of Example 1 was repeated,

Ester monoacrylate (Mn 1400) was used instead of ether monoacrylate (Mn 1100) and added at 4 wt% based on the total electrolyte.

Example  5

The procedure of Example 1 was repeated,

Ketone monoacrylate (Mn 1600) was used instead of ether monoacrylate (Mn 1100) and added at 4 wt% based on the total electrolyte.

Example  6

The procedure of Example 1 was repeated,

Amide monoacrylate (Mn 1300) was used instead of ether monoacrylate (Mn 1100) and added at 4 wt% based on the total electrolyte.

Example  7

The procedure of Example 1 was repeated,

The molecular weight (Mn) of the ether monoacrylate was 4200, and 4 wt% of the total electrolyte was added.

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Comparative Example  One

The procedure of Example 1 was repeated,

The electrolyte was prepared by mixing only an organic solvent mixed with ethylene carbonate (EC): diethyl carbonate (DEC) in a volume ratio of 30:70 and 1M LiPF ₆ alone.

division Linear acrylate Molecular weight (Mn) Linear acrylate content Pole plate condition 5C lifetime Example 1 Ether monoacrylate 1100 4 wt% Vitali 85% Example 2 Ether monoacrylate 1100 10 wt% Vitali 65% Example 3 Ether monoacrylate 1100 20 wt% Vitali 55% Example 4 Ester monoacrylate 1400 4 wt% Vitali 79% Example 5 Ketone monoacrylate 1600 4 wt% Vitali 82% Example 6 Amide monoacrylate 1300 4 wt% Vitali 75% Example 7 Ether monoacrylate 4200 4 wt% Vitali 63% Comparative Example 1 - - - Tally 50%

- "5C lifetime" in Table 1 is a value indicating the remaining capacity after 50 cycles at 60 ° C. That is, the charge / discharge ratio is expressed as a percentage of the maximum charge capacity after 50 cycles at 60 ° C. For example, in the case of Example 1, it means that only up to 85% is charged after 50 cycles of charging and discharging.

Fig. 1 is a photograph showing the states of the positive electrode and the separator of Examples 1 to 7 and Comparative Example 1. Fig.

Referring to Table 1 and FIG. 1, it can be seen that the linear monoacrylate according to the present invention does not desorb the active material from the electrode plate even in a severe charging / discharging state, and the lifetime is increased as compared with Comparative Example 1.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the inventions. It will be clear to those who have knowledge of.

Claims (6)

In an electrolyte for a lithium secondary battery,
Wherein the electrolyte comprises a linear monoacrylate compound,
The linear monoacrylate compound is a linear monoacrylate having a linear structure of any one of ether, ketone, ester and amide,
Wherein the linear monoacrylate compound is capable of entering fine gaps between the active materials. The method according to claim 1,
Wherein the linear monoacrylate compound has a molecular weight (Mn) of 1,000 to 5,000. The method according to claim 1,
Wherein the electrolyte comprises a non-aqueous organic solvent, a lithium salt and the linear monoacrylate compound,
Wherein the linear monoacrylate compound comprises 0.1 to 20 wt% of the total electrolyte. The method of claim 3,
The non-aqueous organic solvent may be at least one selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethylcarbonate (DEC), ethylmethylcarbonate (EMC), 1,2- (DME),? -Butyrolactone (BL), tetrahydrofuran (THF), 1,3-dioxolane (DOL), diethyl ether (DEE), methyl formate Wherein the electrolyte is one or a mixture of at least one selected from the group consisting of nitrile (MP), sulpolane (S), dimethylsulfoxide (DMSO) and acetonitrile (AN). The method of claim 3,
The lithium salt is selected from the group consisting of LiPF ₆ , LiBF ₄ , LiTFSI, LiSbF ₆ , LiAsF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , Li (CF ₃ SO ₂ ) ₂ N, LiC ₄ F ₉ SO ₃ , LiSbF ₆ , LiAlO ₄ , ₄ , LiN (C _x F _{2x + 1} SO ₂ ) (C _y F _{2y + 1} SO ₂ ) (where x and y are natural numbers), LiCl and LiI Characterized in that the electrolyte is a lithium secondary battery. A lithium secondary battery comprising an electrolyte according to any one of claims 1 to 5, a negative electrode, a positive electrode and a separator.

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