KR102525620B1 - Electrolyte for Secondary Battery and Secondary Battery Comprising the Same - Google Patents

Abstract

The present invention relates to an electrolyte solution for a secondary battery and a secondary battery including the same, and more particularly, to an electrolyte solution for a secondary battery by adding a cyclic sulfate compound and a trialkylsilyl compound to a normal voltage (4.2V) as well as a room temperature and high temperature lifetime at a high voltage. It relates to an electrolyte solution for a secondary battery having an effect of improving characteristics and a secondary battery including the same.

Description

Electrolyte for Secondary Battery and Secondary Battery Comprising the Same}

The present invention relates to an electrolyte solution for a secondary battery and a secondary battery including the same, and more particularly, to an electrolyte solution for a secondary battery by adding a cyclic sulfate compound and a trialkylsilyl compound to a normal voltage (4.2V) as well as a room temperature and high temperature lifetime at a high voltage. It relates to an electrolyte solution for a secondary battery having an effect of improving characteristics and a secondary battery including the same.

Secondary batteries are expanding their applications to medium and large-sized devices such as electric vehicles (EVs) and energy storage systems (ESSs) as well as small devices such as mobile phones, camcorders, and notebook PCs. Efforts towards development are becoming increasingly concrete. Among the secondary batteries currently applied, the lithium secondary battery developed in the early 1990s is a battery in which charging and discharging are repeated as lithium ions are intercalated and desorbed from the positive and negative electrodes, and can convert chemical energy into electrical energy through a redox reaction. there is.

In order to apply lithium secondary batteries to medium and large-sized devices such as electric vehicles and energy storage systems, it is essential to develop materials with excellent lifespan characteristics, high output and energy density. Research is being conducted to develop electrochemically stable electrolytes and electrolyte additives even in high-voltage environments.

However, in a high-voltage battery, as the charging voltage of a cathode material increases and the oxidative decomposition of the electrolyte deteriorates, the performance of the battery deteriorates. In addition, high-voltage batteries generally have positive electrode metal ion release during use, and in particular, when the battery is stored at a high temperature for a long time, the positive electrode metal ion release is further deteriorated and the capacity retention rate of the battery is lowered.

As a prior art, Korean Patent Publication No. 10-2017-0039369 discloses only the effect of improving output characteristics and high-temperature storage characteristics with an electrolyte containing a cyclic sulfate compound, and Korean Patent Publication No. 10-2016-0144123 discloses An electrolyte solution containing a cyclic sulfate compound has known effects on high-temperature stability, low-temperature discharge capacity and life characteristics (4.2V), but both of the present inventions are concerned about the effect of improving life characteristics at high voltage by adding a cyclic sulfate compound. nothing has been disclosed In addition, the present applicant also confirmed that the lifespan characteristics and high-temperature storage characteristics of the electrolyte containing the cyclic sulfate compound are significantly improved at room temperature and high temperature, but the improvement effect on the lifespan characteristics at high voltage is insignificant, so it is difficult to solve these problems. The composition of a new electrolyte solution for this study was continuously studied.

Korean Patent Publication No. 10-2012-0109407 discloses an electrolyte solution containing a trialkylsilyl compound (first additive), but the first additive is used in a non-aqueous electrolyte for a lithium secondary battery without deterioration in low-temperature characteristics and output characteristics. It can be confirmed that it was added to improve. In addition, Korean Patent Publication No. 10-2017-0067663 discloses a non-aqueous electrolyte solution for a lithium secondary battery containing four additives including 1,3-propanesultone and tris(trimethylsilyl)borate, but the additives are electrolytes. It can be seen that it was added to reduce the amount of gas generated during high-temperature storage by lowering the side reaction between the solvent and the cathode and anode.

Korean Patent Registration No. 10-1777917 discloses a secondary battery including a cathode active material surface-coated with a nano-film containing polyimide (PI) and conductive nanoparticles. In this case, the elution of metals in a high voltage environment can be prevented, but improvements are still needed to suppress side reactions with the electrolyte.

Accordingly, the present inventors have made diligent efforts to solve the above problems, and as a result, by adding a cyclic sulfate compound and a trialkylsilyl compound to a secondary battery electrolyte, it is possible to improve lifespan characteristics at room temperature and high temperature at high voltage as well as at normal voltage (4.2V). confirmed and completed the present invention.

An object of the present invention is to provide an electrolyte solution for a secondary battery having excellent lifespan characteristics at room temperature and high temperature even at a high voltage as well as a normal voltage (4.2V).

Another object of the present invention is to provide a secondary battery having excellent lifespan characteristics at room temperature and high temperature even at high voltage as well as normal voltage (4.2V).

In order to achieve the above object, the present invention provides (A) a lithium salt; (B) a non-aqueous organic solvent; (C) a cyclic sulfate compound represented by Formula 1 below; And (D) it provides an electrolyte solution for a secondary battery containing a trialkylsilyl compound.

[Formula 1]

The present invention also provides a secondary battery including a positive electrode, a negative electrode, and the electrolyte solution.

The electrolyte solution for a secondary battery according to the present invention has an effect of improving lifespan characteristics at room temperature and high temperature even at a high voltage as well as at a normal voltage (4.2V) by adding a cyclic sulfate compound and a trialkylsilyl compound.

1 shows life characteristics at high voltage and high temperature according to an embodiment of the present invention.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In general, the nomenclature used herein is one well known and commonly used in the art.

The present applicant has confirmed that the lifespan characteristics and high-temperature storage characteristics of the electrolyte solution containing the cyclic sulfate compound are significantly improved at room temperature and high temperature, but the problem of reduced lifespan at high voltage in the secondary battery containing the electrolyte solution is solved Couldn't. However, in the present invention, it was confirmed that by adding a trialkylsilyl compound to a secondary battery electrolyte containing a cyclic sulfate compound, lifespan characteristics at room temperature and high temperature are remarkably improved at a high voltage as well as at a normal voltage (4.2V).

Accordingly, the present invention, in one aspect, (A) a lithium salt; (B) a non-aqueous organic solvent; (C) a cyclic sulfate compound represented by Formula 1 below; And (D) it relates to an electrolyte solution for a secondary battery containing a trialkylsilyl compound.

[Formula 1]

In another aspect, the present invention provides a secondary battery including a positive electrode, a negative electrode, and the electrolyte solution.

Hereinafter, the present invention will be described in detail.

In the present invention, the cyclic sulfate compound represented by Chemical Formula 1 is pentaerythritol disulfate.

In the present invention, the trialkylsilyl compound may include those in the form of borate, phosphate, phosphite or sulfate.

In the present invention, the trialkylsilyl compound is tris (trimethylsilyl) borate (tris (trimethylsilyl) borate), tris (trimethylsilyl) phosphite (tris (trimethylsilyl) phosphite), tris (trimethylsilyl) phosphate (tris (trimethylsilyl) )phosphate), bis(trimethylsilyl)sulfate, tris(triethylsilyl)borate, tris(triethylsilyl)phosphite, tris At least one selected from the group consisting of (triethylsilyl) phosphate (tris (triethylsilyl) phosphate) and bis (triethylsilyl) sulfate (bis (triethylsilyl) sulfate) is preferred, and tris (trimethylsilyl) borate (tris ( trimethylsilyl)borate (TMSB), tris(trimethylsilyl)phosphite (TMSPi), tris(trimethylsilyl)phosphate (TMSPa) and bis(triethylsilyl)sulphate (bis( It is more preferably at least one selected from the group consisting of triethylsilyl) sulfate, TESS).

In the present invention, the lithium salt used as the solute of the electrolyte is LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiClO ₄ , LiN(FSO ₂ ) ₂ , LiN(CF ₃ SO ₂ ) ₂ , LiN(C _{2 )} It may be at least one selected from the group consisting of F ₅ SO ₂ ) ₂ , CF ₃ SO ₃ Li, and LiC(CF ₃ SO ₂ ) ₃ . The concentration of the lithium salt is preferably used within the range of 0.1M to 2.0M, more preferably 0.7M to 1.6M, and when it is less than 0.1M, the conductivity of the electrolyte decreases and the performance of the electrolyte decreases, If it exceeds, there is a problem in that the mobility of lithium ions decreases due to an increase in the viscosity of the electrolyte solution. These lithium salts act as a source of lithium ions in the battery, enabling basic operation of the lithium secondary battery.

In the present invention, the non-aqueous organic solvent may be at least one selected from the group consisting of cyclic carbonate, chain carbonate and propionate, and the cyclic carbonate is ethylene carbonate (ethyl carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylene carbonate (VC), γ-butyrolactone, and mixtures thereof. It may be one or more carbonates selected from the group, and the chain carbonate is dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), ethylmethyl carbonate (EMC), and one or more carbonates selected from the group consisting of mixtures thereof. In addition, the propionate includes methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), and butyl propionate (BP) And it may be one or more propion esters selected from the group consisting of mixtures thereof.

In the electrolyte solution according to an embodiment of the present invention, the non-aqueous organic solvent is a mixed solvent of a cyclic carbonate-based solvent and a linear carbonate-based solvent, and the mixed volume ratio of the linear carbonate-based solvent:cyclic carbonate-based solvent is 1:1 to 9: It may be 1, preferably 1.5: 1 to 4: 1 may be mixed and used in a volume ratio.

In the present invention, the content of the cyclic sulfate compound is preferably 0.05 to 5% by weight, more preferably 0.05 to 3% by weight, based on the total amount of the electrolyte solution. The effect of improving life characteristics is insignificant, and when it exceeds 5% by weight, the resistance of the battery increases, and secondary battery characteristics such as life and output degradation and high-temperature storage characteristics are rather deteriorated.

In the present invention, the content of the trialkylsilyl compound is preferably 0.05 to 5% by weight, more preferably 0.05 to 3% by weight, based on the total amount of the electrolyte, and when less than 0.05% by weight, room temperature and high temperature at high voltage The effect of improving life characteristics is insignificant, and when it exceeds 5% by weight, the resistance of the battery increases, resulting in a problem in that secondary battery characteristics such as life and output degradation and high-temperature storage characteristics are rather deteriorated.

In the present invention, lithium difluorophosphate, lithium difluorobis (oxalato) phosphate, lithium bis (oxalato) borate, Lithium difluoro(oxalato)borate, lithium bis(fluorosulfonyl)imide, ethylene sulfate, 1,3-propane sultone (1,3-propane sultone), 1,3-propene-1,3-sultone, vinylene carbonate, vinylethylene carbonate 1 selected from the group consisting of fluoroethylene carbonate, succinonitrile, adiponitrile and 1,3,6-hexanetricarbonitrile It may further include one or more additives, but is not limited thereto.

The electrolyte solution for a secondary battery of the present invention maintains stable characteristics in a temperature range of -20 to 50 °C. The electrolyte solution of the present invention can be applied to lithium ion secondary batteries, lithium ion polymer batteries, and the like.

In the present invention, the cathode material of the secondary battery is LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , or LiNi _1-xy Co _x M _y O ₂ (0≤x≤1, 0≤y≤1, 0≤ x+y≤1, M is a metal such as Al, Sr, Mg, La, etc.), and crystalline or amorphous carbon, carbon composite, lithium metal, or lithium alloy is used as the anode material. . The active material is applied to a thin current collector with an appropriate thickness and length or the active material itself is applied in the form of a film to form an electrode group by winding or laminating together with a separator, which is an insulator, and then putting it in a can or similar container and then forming a ring. A secondary battery is prepared by injecting an electrolyte solution to which a sulfate compound and a trialkylsilyl compound are added. Resins such as polyethylene and polypropylene may be used as the separator.

Hereinafter, the present invention will be described in more detail through examples. These examples are only for exemplifying the present invention, and it will be apparent to those skilled in the art that the scope of the present invention is not limited by these examples.

Example 1

1.0 M of LiPF ₆ was added to a non-aqueous organic solvent in which ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed in a ratio of 3:7 (v/v), and 1% by weight of a cyclic sulfate compound of Formula 1 and An electrolyte solution for a secondary battery was prepared by adding 1% by weight of tris(trimethylsilyl)borate.

[Formula 1]

Example 2

An electrolyte solution for a secondary battery was prepared in the same manner as in Example 1, except that 1% by weight of tris(trimethylsilyl)phosphite was added instead of 1% by weight of tris(trimethylsilyl)borate.

Example 3

An electrolyte solution for a secondary battery was prepared in the same manner as in Example 1, except that 1% by weight of tris(trimethylsilyl)phosphate was added instead of 1% by weight of tris(trimethylsilyl)borate.

Example 4

An electrolyte solution for a secondary battery was prepared in the same manner as in Example 1, except that 1% by weight of bis(triethylsilyl)sulphate was added instead of 1% by weight of tris(trimethylsilyl)borate.

Comparative Example 1

An electrolyte solution for a secondary battery was prepared by adding 1.0 M LiPF ₆ to a non-aqueous organic solvent in which ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed in a ratio of 3:7 (v/v).

Comparative Example 2

An electrolyte solution for a secondary battery was prepared in the same manner as in Comparative Example 1, except that 1% by weight of tris(trimethylsilyl)borate was added.

Comparative Example 3

An electrolyte solution for a secondary battery was prepared in the same manner as in Comparative Example 1, except that 1% by weight of tris(trimethylsilyl)phosphite was added.

Comparative Example 4

An electrolyte solution for a secondary battery was prepared in the same manner as in Comparative Example 1, except that 1% by weight of tris(trimethylsilyl)phosphate was added.

Comparative Example 5

An electrolyte solution for a secondary battery was prepared in the same manner as in Comparative Example 1, except that 1% by weight of bis(triethylsilyl)sulfate was added.

Comparative Example 6

An electrolyte solution for a secondary battery was prepared in the same manner as in Comparative Example 1, except that 1% by weight of the cyclic sulfate compound represented by Formula 1 was added.

[Formula 1]

Experimental Example 1: Evaluation of secondary battery life characteristics

In this experimental example, after completing the formation of the secondary battery into which the electrolytes prepared in Examples 1 to 4 and Comparative Examples 1 to 6 were injected, 1C charge to 4.2V or 4.35V, and then 2C discharge to 3V. This process was repeated 500 times to measure life characteristics (cycle performance). Cycle performance evaluation was evaluated at room temperature (25 ℃) and high temperature (45 ℃), discharge capacity at 500 cycles, percentage of initial capacity and percentage of initial capacity increased compared to Comparative Example 1 were measured, specific experimental conditions are shown in Table 1 below Same as

4.2V Cycle condition 4.35V Cycle condition Charge (CC/CV) 4.2V/1C, 0.1C cut-off
(rest time=10min) 4.35V/1C, 0.1C cut-off
(rest time=10min) Discharge (CC) 2C/3V cut-off
(rest time=10min) 2C/3V cut-off
(rest time=10min)

Tables 2 to 5 below show the results of evaluating life characteristics by the above evaluation method using the electrolyte solutions prepared according to Examples 1 to 4 and Comparative Examples 1 to 6 of the present invention under 4.2V and 4.35V conditions, respectively. will be.

As shown in Tables 2 and 3, the life characteristics of the electrolytes prepared according to Examples 1 to 4 of the present invention at 4.2V and room temperature (25 ° C.) were compared to the initial capacity at 500 cycles, compared to Comparative Examples 1 to 6 It can be seen that the improved stable life characteristics are exhibited, and in particular, the life characteristics of Examples 1 and 4 including tris (trimethylsilyl) borate and bis (triethylsilyl) sulfate as trialkylsilyl compounds (improvement rate 3.07 compared to Comparative Example 1) % and 3.19%) were excellent. In addition, life characteristics at 4.2V and high temperature (45 ° C) also showed improved life characteristics than Comparative Examples 1 to 6, as at room temperature, and of Example 2 containing tris (trimethylsilyl) phosphite as a trialkylsilyl compound. It can be seen that the lifespan characteristics (5.83% improvement compared to Comparative Example 1) are the most excellent.

From the above results, it can be seen that the electrolyte solution for a secondary battery according to the present invention includes a cyclic sulfate compound represented by Formula 1 and a trialkylsilyl compound, so that life characteristics are improved under a 4.2V condition. In particular, life characteristics at high temperatures are improved. I was able to confirm that it was excellent.

As shown in Tables 4 and 5, the life characteristics of the electrolytes prepared according to Examples 1 to 4 of the present invention at 4.35V and room temperature (25 ° C.) were compared to the initial capacity at 500 cycles, compared to Comparative Examples 1 to 6 It can be seen that it exhibits more improved and stable life characteristics, and the life characteristics of Examples 2 and 4 containing tris (trimethylsilyl) phosphite and bis (triethylsilyl) sulfate as trialkylsilyl compounds (improvement rate 6.81 compared to Comparative Example 1) %) was found to be the best. In addition, life characteristics at 4.35V and high temperature (45 ℃) also showed improved life characteristics than Comparative Examples 1 to 6, as at room temperature, and it was confirmed that the improvement rate of Examples 1 to 4 compared to Comparative Example 1 was 37.16% to 44.23. can

1 shows life characteristics of secondary batteries into which electrolytes prepared in Examples 1 to 4 and Comparative Examples 1 to 6 of the present invention were injected under conditions of 4.35V and high temperature (45° C.). As a result, while all exhibited similar behavior up to the initial 100 to 200 cycles, after repeating 350 to 450 cycles, it was confirmed that the life efficiency of Comparative Examples 1 to 6 was significantly reduced. However, Examples 1 to 4 including the cyclic sulfate compound and the trialkylsilyl compound according to the present invention maintained life efficiency of 65.77% to 72.85% after 500 cycles, and was significantly superior to Comparative Example 1 (28.61%). It can be confirmed that the life characteristics are displayed.

From the above results, it can be seen that the electrolyte solution for a secondary battery according to the present invention includes a cyclic sulfate compound represented by Formula 1 and a trialkylsilyl compound, so that life characteristics are improved under the condition of 4.35V, and similarly to the condition of 4.2V, at high temperature. It was confirmed that the life characteristics of were remarkably excellent.

From these results, it can be confirmed that the electrolyte solution for a secondary battery containing a cyclic sulfate compound and a trialkylsilyl compound according to the present invention has excellent lifespan characteristics under conditions of 4.2V and 4.35V, room temperature (25°C) and high temperature (45°C). can

Having described specific parts of the present invention in detail above, it will be clear to those skilled in the art that these specific descriptions are only preferred embodiments, and the scope of the present invention is not limited thereby. will be. Accordingly, the substantial scope of the present invention will be defined by the claims and their equivalents.

Claims (11)

Electrolyte for secondary batteries containing:
(A) a lithium salt;
(B) a non-aqueous organic solvent;
(C) a cyclic sulfate compound represented by Formula 1 below; and
[Formula 1]

(D) from the group consisting of tris(trimethylsilyl)borate, tris(trimethylsilyl)phosphite, and bis(trimethylsilyl)sulfate At least one selected trialkylsilyl compound.
delete delete The method of claim 1, wherein the lithium salt is LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiClO ₄ , LiN(FSO ₂ ) ₂ , LiN(CF ₃ SO ₂ ) ₂ , LiN(C ₂ F ₅ SO ₂ ) ₂ , CF ₃ SO ₃ Li and LiC (CF ₃ SO ₂ ) ₃ An electrolyte solution for a secondary battery, characterized in that at least one selected from the group consisting of.
The electrolyte for a secondary battery according to claim 1, wherein the organic solvent is at least one selected from the group consisting of cyclic carbonate, chain carbonate, and propionate.
The method of claim 5, wherein the cyclic carbonate is at least one carbonate selected from the group consisting of ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, γ-butyrolactone, and mixtures thereof, and the chain carbonate is dimethyl An electrolyte solution for a secondary battery, characterized in that it is at least one carbonate selected from the group consisting of carbonate, diethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, ethylmethyl carbonate, and mixtures thereof.
The method of claim 5, wherein the propionate is methyl propionate (methyl propionate), ethyl propionate (ethyl propionate), propyl propionate (propyl propionate), butyl propionate (butyl propionate) and mixtures thereof Electrolyte for a secondary battery, characterized in that at least one propion ester selected from the group consisting of.
The electrolyte for a secondary battery according to claim 1, wherein the content of the cyclic sulfate compound is 0.05 to 5% by weight based on the total amount of the electrolyte.
The electrolyte for a secondary battery according to claim 1, wherein the content of the trialkylsilyl compound is 0.05 to 5% by weight based on the total amount of the electrolyte.
The method of claim 1, wherein lithium difluorophosphate, lithium difluorobis (oxalato) phosphate, lithium bis (oxalato) borate , lithium difluoro(oxalato)borate, lithium bis(fluorosulfonyl)imide, ethylene sulfate, 1,3-propane 1,3-propane sultone, 1,3-propene-1,3-sultone, vinylene carbonate, vinylethylene carbonate ), fluoroethylene carbonate, succinonitrile, adiponitrile and 1,3,6-hexanetricarbonitrile (1,3,6-hexanetricarbonitrile) selected from the group consisting of An electrolyte solution for a secondary battery further comprising at least one additive.
A secondary battery comprising a positive electrode, a negative electrode, and the electrolyte of any one of claims 1 and 4 to 10.

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