WO2017010820A1 - Electrolyte additive for secondary battery, electrolyte comprising same, and secondary battery - Google Patents

Abstract

The present invention relates to an electrolyte additive for a secondary battery, an electrolyte comprising the same, and a secondary battery. The electrolyte additive for a secondary battery of the present invention is contained in an electrolyte so as to provide a secondary battery having excellent physical properties in view of output characteristics, lifetime characteristics, storage characteristics, and withstand voltage characteristics, and therefore is suitable for use in a secondary battery for a mobile device, electric vehicle, power tool, electric bike, robot, or drone.

Description

Electrolyte Additive for Secondary Battery, Electrolyte and Secondary Battery Containing the Same

The present invention relates to an electrolyte additive for a secondary battery, an electrolyte including the same, and a secondary battery.

As technology development and demand for mobile devices increase, the demand for secondary batteries as an energy source is also rapidly increasing. Among secondary batteries, lithium secondary batteries that exhibit high energy density and operating potential, and have excellent cycle life and low self discharge rate have been commercialized and widely used.

In addition, recently, as interest in environmental problems grows, research on electric vehicles and hybrid electric vehicles, which can replace vehicles using fossil fuels such as gasoline and diesel vehicles, which are one of the main causes of air pollution, has been conducted. It's going on. Lithium ion secondary batteries are mainly used as power sources of such electric vehicles and hybrid electric vehicles, and researches to improve output stability and energy density of such lithium secondary batteries and corresponding materials are being actively conducted.

Such a lithium secondary battery is composed of a negative electrode such as a carbon material for adsorbing and releasing lithium ions, a positive electrode made of a lithium-containing oxide, or the like, and a non-aqueous electrolyte solution in which an appropriate amount of lithium salt is dissolved in a mixed organic solvent.

Conventionally, a number of techniques for adding a specific additive to an electrolyte for a secondary battery have been reported for the purpose of improving output characteristics or lifetime characteristics of a battery. For example, Korean Patent No. 1486618 discloses that low temperature cycle characteristics can be improved by using an electrolyte solution containing a sulfonic acid phenyl compound, and Korean Patent Publication No. 2015-0050493 discloses a high temperature by adding ethylene sulfate to an electrolyte solution. And improving the output characteristics of the battery at low temperatures. In addition, the Republic of Korea Patent Publication No. 2015-0050082 discloses that it is possible to improve the cycle characteristics of the battery by adding a compound containing a sulfinyl group to the electrolyte solution, Republic of Korea Patent No. 0976958 uses a sultone compound as an additive It is disclosed that the high temperature stability of the battery can be improved, and Japanese Patent No. 4190162 discloses that the high temperature stability of the battery can be improved by using an electrolyte solution containing propenesultone. Furthermore, WO 2012-053644 discloses that a high temperature storage capacity of a battery can be maintained by using an electrolyte solution containing a sulfate ester compound.

However, while the prior arts described above have some improvement in battery output characteristics or storage characteristics, the high output characteristics required in batteries for mobile, electric vehicles, power tools, electric bikes, robots or drones. And lack of sufficient lifespan characteristics. Therefore, there is still an urgent need to develop an electrolyte additive for a secondary battery, an electrolyte solution and a secondary battery including the same, which may further improve the output characteristics of the secondary battery and at the same time satisfy the life characteristics.

Accordingly, the inventors of the present invention have continuously conducted research, and have found a compound capable of improving output characteristics, improving storage characteristics, improving lifetime characteristics, and withstanding voltage characteristics of an electrolyte, and applying the same to a secondary battery electrolyte. The invention was completed.

Accordingly, it is an object of the present invention to provide an electrolyte additive which is included in an electrolyte for a lithium secondary battery to improve the output characteristics of the battery and lower the electrochemical decomposition of the electrolyte to improve life and storage characteristics.

Another object of the present invention is to provide a secondary battery electrolyte and a secondary battery including the improved withstand voltage characteristics.

In order to achieve the above object, the present invention provides a secondary battery electrolyte additive containing a compound of formula (1).

[Formula 1]

In addition, the present invention is a non-aqueous solvent; Lithium salts; And it provides a secondary battery electrolyte comprising the electrolyte additive.

In addition, the present invention provides a secondary battery comprising the secondary battery electrolyte.

The electrolyte additive for a secondary battery of the present invention can be provided in the electrolyte to provide a secondary battery having excellent physical properties in terms of output characteristics, life characteristics, storage characteristics and withstand voltage characteristics, it can be used for mobile, electric vehicles, power tools, electric It can be usefully used for secondary batteries for bikes, robots or drones.

Hereinafter, the present invention will be described in detail.

The present invention provides a secondary battery electrolyte additive, comprising a compound of formula (1).

[Formula 1]

The electrolyte additive for a secondary battery according to the present invention can improve the output performance of the battery by lowering the interfacial resistance of the electrolyte, improve the storage characteristics and life characteristics, enable long-term use of the battery, and improve the withstand voltage characteristics of the electrolyte.

The compound of Formula 1 is a known compound (CAS No. 496-45-7), 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- [1,3,2 ] dioxathiolo [4,5-d] [1,3,2] dioxathiole 2,2,5,5-tetraoxide), etc., and can be purchased commercially.

In addition, the compound of Formula 1 may be prepared by a known synthesis method, for example, 1,1,2,2-tetrachloroethane as a starting material may be prepared by a known synthesis method to react with fuming sulfuric acid and the like ( US Patent No. 1,999,995 and US Patent No. 2,415,397).

The compound of Formula 1 may be used alone or in combination with a known electrolyte additive commonly used.

In addition, the present invention is a non-aqueous solvent; Lithium salts; And it provides a secondary battery electrolyte comprising a secondary battery electrolyte additive as described above.

The secondary battery electrolyte may further include a known electrolyte additive commonly used.

The non-aqueous solvent is a linear or cyclic carbonate solvent or a lactone solvent, and preferably has high solubility in lithium salt and electrolyte additive for a secondary battery. For example, the non-aqueous solvent may be diethyl carbonate, ethyl methyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, Linear carbonate solvents such as ethyl propyl carbonate and methyl ethyl carbonate; Cyclic carbonate solvents such as ethylene carbonate, propylene carbonate, butylene carbonate, and fluoroethylene carbonate; And it may be one solvent selected from the group consisting of lactone solvents such as gamma-butyrolactone (gamma-butyrolactone) or two or more mixed solvents.

Preferably, the non-aqueous solvent may be dehydrated, and specifically, the water content of the non-aqueous solvent may be 150 ppm by weight or less. When the moisture content of the non-aqueous solvent is 150 ppm by weight or less, the decomposition of lithium salts in the battery and the hydrolysis of the electrolyte additive may be suppressed to further improve the electrolyte performance.

The lithium salt is to improve the ionic conductivity of the electrolyte, for example, LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiN (SO ₂ F) ₂ , LiN (SO ₂ CF ₃ ) _2, LiN (SO ₂ C ₂ F ₅ ) ₂ , LiClO ₄ , LiAlO ₂ , LiAlCl ₄ , LiSO ₃ CF ₃ , LiI, LiCl, LiB (C ₂ O ₄ ) _2, etc. may be used alone or in combination.

The concentration (content) of the lithium salt in the electrolyte may be 0.9 M to 3.0 M (mol / liter), specifically 1.0 M to 2.0 M. By including the lithium salt in the content range, it is advantageous to ensure the ionic conductivity of the electrolyte at an appropriate level, it is possible to further increase the efficiency of improving the ion conductivity of the electrolyte compared to the amount of the added lithium salt.

According to an example of the present invention, the electrolyte additive according to the present invention is 0.05 to 20% by weight, 0.05 to 15% by weight, 0.05 to 10% by weight, 0.1 to 10% by weight, 0.1 to 8% by weight, 0.1 to the total weight of the electrolyte 6 wt%, 0.1-4 wt%, 0.1-3 wt%, 0.2-5 wt%, 0.5-15 wt%, 0.5-10 wt%, 0.5-8 wt%, 0.5-6 wt%, 0.5-4 wt% %, 0.5 to 3 wt%, 1 to 10 wt%, 1 to 8 wt%, 3 to 10 wt%, 3 to 8 wt%, 3 to 6 wt%, 4 to 10 wt%, 4 to 8 wt%, It may be included in an amount of 4 to 7% by weight or 5 to 7% by weight. When the compound of Formula 1 is included in the content range, it is possible to further improve output characteristics by suppressing an increase in resistance, and more effective in maintaining storage characteristics of the secondary battery including the electrolyte and improving the withstand voltage characteristics of the electrolyte. Can be.

In addition, the secondary battery electrolyte is other known additives (vinylene carbonate), fluoroethylene carbonate (fluoroethylene carbonate), succinonitrile (succinonitrile), adiponitrile (adiponitrile), vinyl ethylene carbonate (vinylethylene carbonate) ), Lithium difluorodioxalato phosphate, lithium tetrafluorooxalato phosphate, lithium difluorooxalato borate, and lithium difluorophosphate (lithium difluorodioxalato phosphate) lithium difluorophosphate, propene sultone, propane sultone, ethylene sulfate or ethylene sulfite may be included alone or in combination. The known additive may be added in a content range that does not affect the efficacy of the compound of Formula 1 and the performance of the electrolyte solution, for example, 0.1 wt% or more, for example, 0.1 to 10 wt% of the electrolyte solution, respectively. Can be added.

The secondary battery electrolyte of the present invention may be prepared by mixing and stirring a non-aqueous solvent, a lithium salt and the secondary battery electrolyte additive, and at this time, a known electrolyte additive commonly used in the electrolyte may be further mixed.

Furthermore, the present invention provides a secondary battery comprising the secondary battery electrolyte as described above. The secondary battery of the present invention can be any kind of secondary battery including the above-described secondary battery electrolyte. For example, the secondary battery of the present invention includes a positive electrode including a positive electrode active material; A negative electrode including a negative electrode active material; A separator disposed between the anode and the cathode; And the above-described secondary battery electrolyte as a component.

The positive electrode includes a positive electrode active material capable of reversibly adsorbing and detaching lithium ions, and the positive electrode active material includes at least one selected from the group consisting of cobalt, manganese, iron, aluminum, and nickel; Or lithium composite metal oxides. The metal compound used for the positive electrode active material may be variously selected and selected from the group consisting of K, Na, Ca, Sn, V, Ge, Ga, B, As, Zr, Cr, Sr, V and rare earth elements in addition to these metals. It may further comprise a component.

The negative electrode includes a negative electrode active material capable of adsorbing and desorbing lithium ions, and the negative electrode active material includes crystalline or amorphous carbon; Carbon-based negative electrode active material (thermally decomposed carbon, coke, graphite) of the carbon composite; Burnt organic polymer compound; Carbon fiber; Tin oxide compounds; Lithium metal; Or lithium alloys. For example, the amorphous carbon may include hard carbon, coke, mesocarbon microbead (MCMB) fired at 1,500 ° C. or lower, mesophase pitch-based carbon fiber (MPCF), or the like. Can be. Examples of the crystalline carbon include a graphite material, and specific examples thereof include natural graphite, artificial graphite, graphitized coke, graphitized MCMB, graphitized MPCF, and the like. Among the lithium alloys, silicon, titanium, zinc, bismuth, cadmium, antimony, lead, tin, gallium, or indium may be used as another element forming an alloy with lithium.

The separation membrane is for preventing a short circuit between the positive electrode and the negative electrode, a polyolefin-based polymer membrane such as polypropylene, polyethylene, or a multilayer thereof; Microporous film; web; And nonwoven fabrics may be used.

Hereinafter, the present invention will be described in detail by way of examples. However, the following examples are only for illustrating the present invention, and the present invention is not limited thereto.

Bicycloglyoxalsulfate of formula 1 used in the following examples is a known compound (CAS No. 496-45-7), ATOMAX (China), CHEMOS (Germany), ABICHEM (Germany), PEWAX (China) You can buy products sold by companies such as). In addition, the compound of Formula 1 may be prepared according to a known synthesis method such as Preparation Example 1.

[Formula 1]

Preparation Example 1 Preparation of Bicycloglyoxalsulfate

A 1,000 mL three neck flask and condenser were mounted in a 60 ° C. oil bath. 70 g of 1,1,2,2-tetrachloroethane was added to the three neck flask and the temperature was stabilized. Then, 320 g of sulfuric acid (60% fuming grade) was added to initiate a reaction. The reaction solution initially exhibited a clear to light brown viscosity, and a crystalline solid was formed after 4 hours from the start of the reaction. The oil bath was cooled to room temperature and stirred slowly for an additional 3 hours. It was then replaced with a cold water bath at 5-7 ° C. and stirred slowly for an additional 2 hours. The reaction was terminated in the absence of further production of crystalline solids. The resulting slurry solution was solid-liquid separated with a filter, and then vacuum dried at 20 Torr for 12 hours. As a result, 72.8 g of bicycloglyoxalsulfate represented by Chemical Formula 1 was obtained (yield: 84.4%).

Example 1 Preparation of Electrolyte

429 g of ethylene carbonate (EC), 589 g of ethyl methyl carbonate (EMC), and 380 g of diethyl carbonate (DEC) were mixed to prepare a mixed liquid. 167.1 g of LiPF ₆ was added to the mixed liquid, and 1.1 M of LiPF _{6 was added.} After the solution was prepared, bicycloglyoxal sulfate of Chemical Formula 1 was added in an amount of 0.5% by weight as an additive to prepare an electrolyte solution for a secondary battery.

Example 2 Preparation of Electrolyte

An electrolyte solution was prepared in the same manner as in Example 1, except that bicycloglyoxal sulfate of Chemical Formula 1 was added in an amount of 1.5 wt%.

Example 3. Preparation of Electrolyte

An electrolyte solution was prepared in the same manner as in Example 1, except that bicycloglyoxal sulfate of Chemical Formula 1 was added in an amount of 3% by weight.

Example 4 Preparation of Electrolyte

An electrolyte solution was prepared in the same manner as in Example 1, except that bicycloglyoxal sulfate of Chemical Formula 1 was added in an amount of 10% by weight.

Example 5. Preparation of Electrolyte

An electrolyte solution was prepared in the same manner as in Example 1, except that bicycloglyoxal sulfate of Chemical Formula 1 was added in an amount of 15% by weight.

Example 6 Preparation of Electrolyte

An electrolyte solution was prepared in the same manner as in Example 1, except that bicycloglyoxal sulfate of Chemical Formula 1 was added in an amount of 0.01% by weight.

Comparative Example 1. Preparation of Electrolyte

An electrolyte solution was prepared in the same manner as in Example 1, except that bicycloglyoxal sulfate of Chemical Formula 1 was not added.

Comparative Example 2. Preparation of Electrolyte

An electrolyte solution was prepared in the same manner as in Example 1, except that 1,3-trimethylene sultone was added in an amount of 3% by weight instead of the bicycloglyoxalsulfate of Formula 1. .

Comparative Example 3. Preparation of Electrolyte

An electrolyte solution was prepared in the same manner as in Example 1, except that bis (carboxymethyl) disulfide was added in an amount of 3% by weight instead of bicycloglyoxalsulfate of Chemical Formula 1.

Comparative Example 4. Preparation of Electrolyte

An electrolyte was prepared in the same manner as in Example 1, except that ethylene sulfite was added in an amount of 3% by weight instead of bicycloglyoxalsulfate of Chemical Formula 1.

Experimental Example 1. Measurement of impedance (mΩ) of secondary battery

A 1.3 Ah pouch battery was assembled in a conventional manner using a positive electrode mixed with LiNi _0.5 Co _0.2 Mn _0.3 and LiMnO ₂ in a 1: 1 weight ratio and a negative electrode mixed with artificial graphite and natural graphite in a 1: 1 weight ratio. Then, 6 g of the electrolyte solution prepared in Examples 1 to 6 and Comparative Examples 1 to 4 were injected to complete a secondary battery.

The impedance obtained when the obtained secondary battery was discharged at 3C for 10 seconds while maintaining a 60% state of charge voltage compared to full charge at room temperature was measured (used equipment: PNE-0506 charger / discharger). After measuring the initial impedance at room temperature of the secondary battery in the above manner, it was stored in a 70 ℃ high temperature oven and after 1 week and 2 weeks, each discharge impedance was measured.

Table 1 shows the comparison of the impedance of the battery using an electrolyte solution containing a bicycloglyoxal sulfate of Formula 1 or a non-containing electrolyte, Table 2 shows an electrolyte solution containing the additive of Formula 1 or other additives of the same content The impedances of the batteries used are compared.

division Impedance (mΩ) Room temperature (initial) 70 degrees Celsius (one week passage) 70 degrees Celsius (after two weeks) Example 1 32 39 46 Example 2 34 36 39 Example 3 38 39 40 Example 4 41 40 42 Example 5 42 43 46 Example 6 34 49 73 Comparative Example 1 34 55 80

division Impedance (mΩ) Room temperature (initial) 70 degrees Celsius (one week passage) 70 degrees Celsius (after two weeks) Example 3 38 39 40 Comparative Example 2 44 51 58 Comparative Example 3 47 56 96 Comparative Example 4 35 51 70

As shown in Table 1, when the additive of Formula 1 was added to the electrolyte (Examples 1 to 6), it was confirmed that the impedance during battery discharge is lower than when the additive is not added (Comparative Example 1). In addition, as shown in Table 2, when the additive of the formula (1) is added to the electrolyte solution (Example 3) compared with the case of adding another kind of additive in the same amount (Comparative Examples 2 to 4), the battery discharge When the impedance was lowered it was confirmed. This shows that by adding the additive of the formula (1) to the electrolyte, the output characteristics of the battery is improved due to the low resistance characteristics of the interface between the electrode and the electrolyte during the battery discharge process.

Experimental Example 2. Measurement of Life Characteristics of Secondary Battery

Using the electrolyte solutions prepared in Examples 1 to 6 and Comparative Examples 1 to 4 to prepare a secondary battery in the form of 1.3 Ah pouch in the same manner as in Experimental Example 1, the high temperature of 70 ℃ in a fully charged state with respect to the secondary battery Charge / discharge were performed at a rate of 4.2 V charge 1.3 A and 2.7 V discharge 1.3 A at. The discharge capacity during 200 charges / discharges performed in the above manner was measured with a PNE-0506 charger / discharger (manufacturer: PNE Solution Co., Ltd.) to calculate the ratio (%) relative to the initial capacity.

Table 3 shows a comparison of the life characteristics of the battery using an electrolyte solution containing a bicycloglyoxal sulfate of Formula 1 or a non-containing electrolyte, Table 4 is an electrolyte solution containing the additive of Formula 1 or other additives of the same content It is shown by comparing the life characteristics of the battery using.

division Discharge capacity (%) at 200 ℃ / discharge at 70 ℃ against initial capacity Example 1 81 Example 2 86 Example 3 87 Example 4 85 Example 5 86 Example 6 60 Comparative Example 1 57

division Discharge capacity (%) at 200 ℃ / discharge at 70 ℃ against initial capacity Example 3 87 Comparative Example 2 71 Comparative Example 3 56 Comparative Example 4 69

As shown in Table 3, when the additive of Formula 1 was added to the electrolyte solution (Examples 1 to 6), the 70 ° C lifespan characteristics of the battery were significantly improved compared to the case where no additive was added (Comparative Example 1). . In addition, as shown in Table 4, when the additive of the formula (1) is added to the electrolyte solution (Example 3) compared with the case where other kinds of additives are added in the same amount (Comparative Examples 2 to 4), The 70 ° C. lifespan characteristics were significantly improved. This shows that the addition of the additive of Formula 1 to the electrolytic solution, the electrochemical electrode capacity decrease significantly generated during the charge / discharge of the battery at 70 ℃.

Experimental Example 3. Measurement of Storage Characteristics (Capacity Recovery) of Secondary Battery

Using the electrolyte prepared in Examples 1 to 6 and Comparative Examples 1 to 4 to prepare a secondary battery in the form of 1.3 Ah pouch in the same manner as Experimental Example 1, the secondary battery is stored in a 70 ℃ oven in a fully charged state After that, after one week and two weeks, the discharge capacity relative to the initial charge capacity was measured (used equipment: PNE-0506 charger / discharger).

Table 5 shows a comparison of the life characteristics of the battery using an electrolyte solution containing the bicycloglyoxal sulfate of Formula 1 or a non-containing electrolyte, Table 6 is an electrolyte solution containing the additive of Formula 1 or other additives of the same content It is shown by comparing the life characteristics of the battery using.

division Storage characteristics (capacity recovery,%) Early(%) 70 degrees Celsius (one week passage) 70 degrees Celsius (after two weeks) Example 1 100 91 81 Example 2 100 94 83 Example 3 100 95 91 Example 4 100 93 85 Example 5 100 91 84 Example 6 100 86 78 Comparative Example 1 100 85 74

division Storage characteristics (capacity recovery,%) Early(%) 70 degrees Celsius (one week passage) 70 degrees Celsius (after two weeks) Example 3 100 95 91 Comparative Example 2 100 90 81 Comparative Example 3 100 84 67 Comparative Example 4 100 86 79

As shown in Table 5, when the additive of Formula 1 is added to the electrolyte solution (Examples 1 to 6), the discharge capacity after storage at 70 ° C compared to the initial charge capacity of the battery than when the additive is not added (Comparative Example 1) This was markedly stabilized. In addition, as shown in Table 6, when the additive of the formula (1) is added to the electrolyte solution (Example 3) compared with the case where other kinds of additives are added in the same amount (Comparative Examples 2 to 4), It was confirmed that the discharge capacity after the storage temperature 70 ℃ compared to the charging capacity was significantly stabilized. This shows that the addition of the additive of Formula 1 to the electrolyte solution significantly reduced the electrochemical electrode capacity generated during high temperature storage of the battery. As a result, it was confirmed that the charging and discharging capacity was realized at a high temperature by using the additive of Chemical Formula 1.

The electrolyte additive for a secondary battery of the present invention can be provided in the electrolyte to provide a secondary battery having excellent physical properties in terms of output characteristics, life characteristics, storage characteristics and withstand voltage characteristics, it can be used for mobile, electric vehicles, power tools, electric It can be usefully used for secondary batteries for bikes, robots or drones.

Claims (4)

Comprising a compound of formula 1, the secondary battery electrolyte additive. [Formula 1]

Non-aqueous solvents; Lithium salts; And Electrolyte additive including the compound of formula Containing, the secondary battery electrolyte. [Formula 1]

The electrolyte solution for a secondary battery of claim 2, wherein the electrolyte solution contains the electrolyte additive in an amount of 0.05 to 20% by weight based on the total weight of the electrolyte solution. A secondary battery comprising the secondary battery electrolyte according to claim 2.