KR20180057928A - Electrolyte for secondary battery and secondary battery comprising same - Google Patents

Abstract

The present invention relates to an electrolyte for a secondary battery and a secondary battery having the same. According to an embodiment of the present invention, the electrolyte for a secondary battery comprises a carbonate-based solvent, lithium salt, a compound of chemical formula 1, and a compound of chemical formula 2. According to the present invention, the electrolyte for a secondary battery and the secondary battery having the same can provide a stable output feature of the battery.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an electrolyte for a secondary battery,

The present invention relates to an electrolyte for a secondary battery comprising glyoxal sulphate and vinylene carbonate and a secondary battery comprising the secondary battery, wherein the secondary battery has improved characteristics at a low temperature as well as a high temperature, and can realize high output.

As technology development and demand for mobile devices increase, the demand for secondary batteries as energy sources is rapidly increasing. Among secondary batteries, lithium secondary batteries having high energy density, excellent lifetime characteristics, and low self discharge rate are commercially available and widely used.

In recent years, interest in environmental problems has led to a great deal of research on electric vehicles and hybrid electric vehicles that can replace fossil-fueled vehicles such as gasoline vehicles and diesel vehicles, which are one of the main causes of air pollution . Researches on the use of lithium secondary batteries having excellent energy density, discharge voltage, and output stability as power sources for electric vehicles and hybrid electric vehicles have been actively conducted and some of them are being commercialized.

Such a lithium secondary battery is composed of a negative electrode made of a carbonaceous material or the like for storing and releasing lithium ions, a positive electrode made of a lithium-containing oxide or the like, and a nonaqueous electrolyte solution in which a suitable amount of lithium salt is dissolved in a mixed organic solvent. A number of additives and electrolytic solution composition techniques added to improve the output stability of the non-aqueous liquid electrolyte are known.

For example, U.S. Patent No. 5,626,981 discloses an electrolyte solution comprising vinylene carbonate. The electrolyte of the above-mentioned patent discloses that a coating film is formed on the surface of a negative electrode to insert and detach the lithium ion only into a graphite phase which is a negative electrode during charging and discharging of the secondary battery, thereby minimizing side reactions and charging and discharging stably. Japanese Patent No. 3157152 also discloses that vinylene carbonate reacts with lithium to form a thin film to improve the storage and lifetime characteristics of the battery. Furthermore, Japanese Patent Registration No. 3921836 discloses that vinylene carbonate improves not only the life characteristics but also the high temperature safety.

However, the vinylene carbonate improves the lifetime characteristics of the secondary battery and exhibits excellent performance at a high temperature, but there is a problem that the capacity and output of the battery are drastically deteriorated at a low temperature. In addition, when the secondary battery including vinylene carbonate is stored at a high temperature, there is a problem that it is difficult to apply to a field where a gas generation is large and an increase in resistance is large and a high output is required.

U.S. Patent No. 5,626,981 Japanese Patent No. 3157152 Japanese Patent No. 3921836

Therefore, research and development of an electrolyte capable of reducing gas generation and resistance increase at a high temperature while improving the low temperature characteristics of the secondary battery have been required.

Accordingly, an object of the present invention is to provide an electrolyte solution for a secondary battery having excellent output capacity at a low temperature and little increase in gas generation and resistance at the time of high temperature storage, and a secondary battery comprising the electrolyte solution.

In order to achieve the above object,

Carbonate-based solvent,

Lithium salt,

A compound of the formula

There is provided an electrolyte solution for a secondary battery comprising a compound represented by the following formula (2): < EMI ID =

The present invention also provides a secondary battery comprising the electrolyte for the secondary battery.

The secondary battery including the electrolyte for a secondary battery according to the present invention exhibits excellent output capacity and output characteristics due to stable output characteristics of the battery at a low temperature or a high temperature and has less gas generation and resistance increase at high temperature storage.

Hereinafter, the present invention will be described in detail.

The electrolyte for a secondary battery according to the present invention includes a carbonate-based solvent, a lithium salt, a compound represented by the following formula 1, and a compound represented by the following formula 2:

[Chemical Formula 1]

(2)

.

.

The compound of Formula 1 may be a known compound (CAS No. 496-45-7), such as bicyclo-glyoxal sulfate, glyoxal sulfate, or 3a, 6a-dihydro- [1,3,2] dioxathiolo [4,5-d] [1,3,2] dioxathiol 2,2,5,5-tetraoxide (3a, 6a-dihydro- [ 2] dioxathiolo [4,5-d] [1,3,2] dioxathiole 2,2,5,5-tetraoxide), which can be purchased commercially. In addition, the compound of formula (1) can be prepared by a known synthesis method, for example, by reacting 1,1,2,2-tetrachloroethane with fuming sulfuric acid or the like (US Patent No. 1,999,995 and US registered See Japanese Patent No. 2,415,397).

The compound of Formula 2 is a known compound, and the compound is vinylene carbonate (CAS No. 872-36-6), which may be purchased commercially or may be prepared by a known synthesis method.

The electrolytic solution may contain 0.1 to 10% by weight of the compound of Formula 1 and 0.05 to 10% by weight of the compound of Formula 2 based on the total weight. Specifically, the electrolytic solution may contain 0.1 to 8% by weight, 0.2 to 5% by weight, or 0.5 to 3% by weight based on the total weight of the compound of Formula 1; And 0.05 to 8% by weight, 0.1 to 5% by weight, or 0.2 to 3% by weight of the compound of Formula 2 above. When the compound of the formula (1) is contained in an amount within the above range, the effect of suppressing the increase of the resistance in a high temperature environment and the effect of preventing an excessive increase of the room temperature initial resistance are prevented. When the compound of the general formula (2) is contained in an amount within the above range, the surface of the electrode is coated with an appropriate thickness and the resistance of the secondary battery can be prevented from increasing.

It is preferable that the carbonate-based solvent has a high solubility in the lithium salt and the compound (additive) of the formulas (1) and (2). Specifically, the carbonate-based solvent is selected from the group consisting of diethyl carbonate (DEC), ethylmethyl carbonate (EMC), dimethyl carbonate (DMC), dipropyl carbonate (DPC) such as methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), propyl propionate propyl propionate (PP), and fluoroethylene carbonate (FEC). More specifically, the carbonate-based solvent is prepared by reacting diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC) and ethyl propyl carbonate At least one first carbonate-based solvent (linear carbonate) selected from the group consisting of: And at least one second carbonate solvent selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), propyl propionate (PP) and fluoroethylene carbonate (FEC) Or cyclic carbonates).

The carbonate-based solvent may be dehydrated. Specifically, the carbonate-based solvent may contain 30 ppm by weight or less of water.

The lithium salt is not particularly limited as long as it is usually used for an electrolyte solution for a secondary battery. Specifically, the lithium salt may be LiPF ₆ , LiBF ₄ , LiBF ₆ , LiSbF ₆ , LiAsF ₆ , LiClO ₄ , LiSO ₃ CF ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiN (SO ₂ F) ₂ and LiC (CF ₃ SO ₂ ) ₃ .

The electrolytic solution may contain 0.05 to 5.0 moles of lithium salt based on 1 liter of the carbonate-based solvent. Specifically, the electrolytic solution may contain 0.5 to 5.0 moles, 0.5 to 3.0 moles, 0.5 to 2.5 moles, 1.0 to 3.0 moles, or 1.0 to 2.5 moles of the lithium salt based on 1 liter of the carbonate-based solvent. When the lithium salt is contained in the content within the above range, ionic conductivity of the electrolytic solution is adequately secured, and the ionic conductivity of the electrolytic solution, which can be obtained with respect to the concentration of the added lithium salt, is high.

The electrolyte for a secondary battery according to the present invention can be prepared by simply mixing and stirring a carbonate-based solvent, a lithium salt, glyoxal sulphate represented by the formula (1) and vinylene carbonate represented by the formula (2).

The present invention provides a secondary battery comprising the electrolyte for the secondary battery. Specifically, the secondary battery includes: a positive electrode including a positive electrode active material; A negative electrode comprising a negative electrode active material; A separation membrane disposed between the anode and the cathode; And an electrolyte for the secondary battery.

The positive electrode includes a positive electrode active material capable of reversibly intercalating and deintercalating lithium ions. Wherein the cathode active material comprises at least one metal selected from the group consisting of cobalt, manganese, and nickel; And a composite metal oxide including lithium. The employment ratio between the metals may be varied and may be selected from the group consisting of Mg, Al, K, Na, Ca, Si, Ti, Sn, V, Ge, Ga, B, As, Zr, Cr, Fe, And one or more elements selected from the group consisting of elements.

The negative electrode includes a negative electrode active material capable of intercalating and deintercalating lithium ions. The negative electrode active material may be a carbonaceous anode active material (thermally decomposed carbon, coke, graphite) of a crystalline or amorphous carbon or carbon composite; Burned organic polymer compounds; Carbon fiber; Tin oxide compounds; Lithium metal; Or a lithium alloy. For example, the amorphous carbon may be selected from the group consisting of hard carbon, coke, mesocarbon microbead (MCMB) calcined at 1500 ° C or less, mesophase pitch-based carbon fiber (MPCF) have. The crystalline carbon may be a graphite based material, for example, natural graphite, artificial graphite, graphitized coke, graphitized MCMB, graphitized MPCF, and the like. Other elements constituting the alloy with lithium in the lithium alloy may be aluminum, zinc, bismuth, cadmium, antimony, silicon, lead, tin, gallium or indium.

The separator is for preventing a short circuit due to a direct contact between the anode and the cathode. For example, the separator may be a polymer membrane such as polyolefin, polypropylene, or polyethylene, or a multi-layer thereof; Microporous film; web; And nonwoven fabrics. The separation membrane may have a metal oxide or the like coated on one or both sides thereof.

Hereinafter, the present invention will be described in more detail by way of specific examples and comparative examples. The following examples are intended to further illustrate the present invention and are not intended to limit the scope of the present invention.

[ Example ]

The compounds of formulas (1) and (2) used in the following Examples and Comparative Examples are all known compounds, and their structural formulas, chemical names and CAS No. are as follows:

(1) Compound of formula (I): glyoxal sulfate, bicyclo-glyoxal sulfate, CAS No. 496-45-7.

[Chemical Formula 1]

(2) Compound of formula (2): vinylene carbonate, vinylene carbonate, CAS No. 872-36-6.

(2)

Manufacturing example  One. Glyoxal Sulphate  Produce

The compound of formula (1) can be prepared according to the following known synthetic methods.

First, a 1,000 mL three-necked flask and a condenser were attached to an oil bath at 60 ° C. 70 g of 1,1,2,2-tetrachloroethane was added to the three-necked flask, and the temperature was stabilized at 60 ° C. Then, 320 g of sulfuric acid (60% fuming grade) was added to initiate the reaction. The reaction solution initially showed a clear to light brown viscosity, and a crystalline solid was formed after 4 hours from the initiation of the reaction. The oil bath was cooled to room temperature and stirred at low speed for an additional 3 hours. Thereafter, the mixture was replaced with a cold water bath at 5 to 7 ° C and stirred at a low speed for an additional 2 hours. The reaction was terminated when there was no further production of crystalline solid. The resulting slurry solution was subjected to solid-liquid separation using a filter, followed by vacuum drying at 20 Torr for 12 hours. As a result, 72.8 g of glyoxal sulphate represented by the above formula (1) was obtained (yield: 84.4%).

Example  1. Preparation of Electrolyte Solution

Ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) were mixed at a volume ratio of 25: 40: 35 to prepare a mixed solution. LiPF ₆ was dissolved in the mixed solution at a concentration of 1 mol / 1% by weight of glyoxal sulphate represented by Formula 1 and 1% by weight of vinylene carbonate represented by Formula 2 were added to the total weight of the electrolytic solution and mixed to prepare an electrolyte solution (electrolyte solution) for a secondary battery.

Example  2. Preparation of Electrolyte Solution

An electrolytic solution was prepared in the same manner as in Example 1, except that 1.5 weight% of glyoxal sulphate represented by Formula 1 and 1.5 weight% of vinylene carbonate represented by Formula 2 were used.

Example  3. Preparation of Electrolyte Solution

An electrolytic solution was prepared in the same manner as in Example 1, except that 2 wt% of glyoxal sulphate represented by the above formula (1) and 1 wt% of vinylene carbonate of the above formula (2) were used.

Comparative Example  1. Preparation of Electrolyte Solution

An electrolyte solution was prepared in the same manner as in Example 1, except that the vinylene carbonate represented by Formula 2 was not included.

Comparative Example  2. Preparation of Electrolyte Solution

An electrolyte solution was prepared in the same manner as in Example 3, except that the vinylene carbonate represented by the formula (2) was not included.

Comparative Example  3. Preparation of Electrolyte Solution

An electrolyte solution was prepared in the same manner as in Example 1, except that glyoxal sulphate represented by the above formula (1) was not included.

Comparative Example  4. Preparation of Electrolyte Solution

An electrolytic solution was prepared in the same manner as in Example 1, except that the glyoxal sulfate represented by the formula (1) was not added and the vinylene carbonate represented by the formula (2) was added in an amount of 2 wt%.

Comparative Example  5. Preparation of Electrolyte Solution

An electrolyte solution was prepared in the same manner as in Example 1, except that the glyoxal sulphate represented by Formula 1 and the vinylene carbonate represented by Formula 2 were not used.

Experimental Example  1. Output Characteristics of Lithium Secondary Battery at High Temperature Storage

Assembling a 1.4 Ah pouch cell by an ordinary method using the anode material used to 1 weight ratio of positive electrode active material of LiNi _1/3 Co _1/3 Mn cathode material with _1/3 and the negative electrode active material of artificial graphite and natural graphite 1 , And 6.5 g of each of the electrolytes of Examples 1 to 3 and Comparative Examples 1 to 5 were injected to complete the secondary battery. The 1.4 Ah pouch battery obtained through the above battery charging process was discharged at 3 C (coulomb) for 10 seconds while maintaining a 60% charged state voltage at 25 ° C as compared to full charge. The voltage difference generated at this time was measured with a PNE-0506 charge / Manufactured by: PNE Co., Ltd.), and the initial resistance was calculated from the measured value.

The battery was stored for 3 days in a high temperature oven at 80 占 폚 after the battery was fully charged, and the resistance after 3 days was measured in the same manner as described above and shown in Table 1.

Content of additive in electrolyte DC-IR (mΩ) Initial 25 ℃ After 3 days at 80 ° C Example 1 1% by weight of formula (1) + 1% by weight of formula 35.3 36.7 Example 2 1.5% by weight of formula (1) + 1.5% by weight of formula 36.7 36.7 Example 3 2% by weight of formula (1) + 1% by weight of formula 35.5 35.8 Comparative Example 1 1% by weight of formula 1 34.6 36.0 Comparative Example 2 2% by weight of formula (1) 35.1 36.1 Comparative Example 3 1% by weight of formula (2) 37.1 52.9 Comparative Example 4 2% by weight of formula (2) 38.0 47.4 Comparative Example 5 No additive 32.9 57.0

As shown in Table 1, the electrolytic solutions of Examples 1 to 3 had no internal additives (Comparative Example 5) or Comparative Examples 3 and 4 (Comparative Examples 3 and 4) in which the additive was not added (Comparative Example 5) or the case where one kind of additive of vinylene carbonate Which is lower than that of the others. This shows that the output characteristics of the battery are improved by suppressing an increase in the resistance of the interface between the electrode and the electrolyte during the battery discharge process by using the electrolyte solution containing the combination of the compounds of the above formulas (1) and (2).

Experimental Example  2. Gas Generation Characteristics of Lithium Secondary Battery at High Temperature Storage

A secondary battery (1.4 Ah pouch battery) was obtained in the same manner as in Experimental Example 1 to charge the battery at 4.2 V / 140 mA at a constant current / constant voltage (CC / CV) Respectively. Thereafter, the discharge capacity was measured using a PNE-0506 charge / discharge device (manufactured by PNE Co., Ltd.) at a constant current (CC) condition of 1 V to 3 V.

In addition, the initial cell thickness was measured after charging the same cell. Thereafter, the cell was stored in an oven at 80 ° C. for 3 days, and the thickness of the cell after one week was measured to calculate the volume expansion ratio with respect to the initial thickness. Electrical thickness was measured using Mitutoyo Indicator Model ID-C1012XB.

Content of additive in electrolyte After 3 days at 80 ° C
Thickness Expansion Rate Example 1 1% by weight of formula (1) + 1% by weight of formula 3.4% Example 2 1.5% by weight of formula (1) + 1.5% by weight of formula 2.9% Example 3 2% by weight of formula (1) + 1% by weight of formula 1.9% Comparative Example 1 1% by weight of formula 1 4.5% Comparative Example 2 2% by weight of formula (1) 2.4% Comparative Example 3 1% by weight of formula (2) 12.2% Comparative Example 4 2% by weight of formula (2) 5.9% Comparative Example 5 No additive 45.1%

As shown in Table 2, the electrolytic solution of Examples 1 to 3 contained no additives (Comparative Example 5), compared with the case of using one type of vinylene carbonate additive (Comparative Examples 3 and 4) The thickness expansion rate after storage at high temperature (80 캜) was remarkably excellent. This shows that the use of an electrolyte solution containing a combination of the compounds of the above formulas (1) and (2) significantly reduced side reactions and gases during high-temperature storage of the battery. As a result, it was confirmed that the secondary battery including the electrolyte of the present invention can stably maintain the electrolyte at a high temperature and prevent the battery from being swollen at high temperatures.

Experimental Example  3. Low temperature characteristics of lithium secondary battery

A secondary battery (1.4 Ah pouch battery) was obtained in the same manner as in Experimental Example 1 to obtain a secondary battery (1.4 Ah pouch battery), which was then charged to 1 C at a constant current / constant voltage (CC / CV) condition of 4.2 V / Next, discharge was performed at 1 C to 3 V under constant current (CC) condition, and the initial capacity was measured with a PNE-0506 charge / discharge device.

The same cell was charged at 1 C up to 4.2 V / 140 mA under the constant current / constant voltage (CC / CV) condition at -10 ° C. and discharged at 1 C up to 3 V under the constant current (CC) condition. Discharge capacity was measured with a discharger. This was repeated 10 times, and the discharge capacity measured after 10 cycles was calculated as the capacity retention ratio relative to the initial capacity of the battery, and is shown in Table 3.

Content of additive in electrolyte 25 ℃ initial capacity ratio
-10 ℃ 10 times capacity maintenance rate Example 1 1% by weight of formula (1) + 1% by weight of formula 69.1% Example 2 1.5% by weight of formula (1) + 1.5% by weight of formula 63.2% Example 3 2% by weight of formula (1) + 1% by weight of formula 67.8% Comparative Example 1 1% by weight of formula 1 70.1% Comparative Example 2 2% by weight of formula (1) 68.8% Comparative Example 3 1% by weight of formula (2) 58.7% Comparative Example 4 2% by weight of formula (2) 52.1% Comparative Example 5 No additive 72.2%

As shown in Table 3, the electrolytic solutions of Examples 1 to 3 exhibited a low-temperature capacity as compared with the case where the additive was not added (Comparative Example 5) or the case where one kind of additive of vinylene carbonate was used (Comparative Examples 1 to 3) The characteristics were improved. This is a result of using the electrolytic solution containing the combination of the compounds of the formulas (1) and (2) to prevent the capacity decrease caused by continuous use of the battery at a low temperature, especially the capacity drop due to vinylene carbonate. As a result, it has been confirmed that the secondary battery including the electrolyte of the present invention maintains the ion conductivity of the electrolyte at a certain level or higher even at a low temperature, thereby realizing excellent capacity characteristics.

Claims (7)

Carbonate-based solvent,
Lithium salt,
A compound of the formula
An electrolyte solution for a secondary battery comprising a compound represented by the following formula (2): < EMI ID =
[Chemical Formula 1]

(2)

.
The method according to claim 1,
The carbonate-based solvent is selected from the group consisting of diethyl carbonate, ethylmethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate ), At least one member selected from the group consisting of ethylene carbonate, propylene carbonate, butylene carbonate, propyl propionate and fluoroethylene carbonate, An electrolyte for a secondary battery.
3. The method of claim 2,
The carbonate-based solvent
At least one first carbonate-based solvent selected from the group consisting of diethyl carbonate, ethyl methyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate and ethylpropyl carbonate, and
And at least one second carbonate-based solvent selected from the group consisting of ethylene carbonate, propylene carbonate, butylene carbonate, propyl propionate, and fluoroethylene carbonate.
The method according to claim 1,
The lithium salt _{LiPF 6, LiBF 4, LiBF 6} , LiSbF 6, LiAsF 6, LiClO 4, LiSO 3 CF 3, LiN (CF 3 SO 2) 2, LiN (C 2 F 5 SO 2) 2, LiN (SO ₂ F) _2, and LiC (CF ₃ SO ₂ ) ₃ .
The method according to claim 1,
Wherein the electrolytic solution contains 0.1 to 10% by weight of the compound of Formula 1 and 0.05 to 10% by weight of the compound of Formula 2 based on the total weight of the electrolytic solution.
The method according to claim 1,
Wherein the electrolytic solution contains 0.05 to 5.0 moles of a lithium salt based on 1 liter of the carbonate-based solvent.
A secondary battery comprising an electrolyte solution for a secondary battery according to any one of claims 1 to 6.