JP2018520480A - Electrolytic solution additive for secondary battery, electrolytic solution containing the same, and secondary battery - Google Patents

Abstract

The present invention relates to an electrolytic solution additive for a secondary battery, an electrolytic solution containing the same, and a secondary battery. The electrolyte additive for secondary battery of the present invention is included in the electrolyte and can provide a secondary battery that is excellent in terms of output characteristics, life characteristics, storage characteristics, and withstand voltage characteristics. It is suitable for use in secondary batteries for electric vehicles, electric tools, electric motorcycles, robots, or drones. [Selection figure] None

Description

  The present invention relates to an electrolytic solution additive for a secondary battery, an electrolytic solution containing the same, and a secondary battery.

  As technology development and demand for mobile devices increase, the demand for secondary batteries as energy sources also increases rapidly. Among secondary batteries, lithium secondary batteries that exhibit high energy density and operating potential, have excellent cycle life and low self-discharge rate have been put into practical use and are widely used.

  In recent years, as interest in environmental issues has grown, research on electric vehicles, hybrid electric vehicles, etc. that can replace vehicles that use fossil fuels, such as gasoline vehicles and diesel vehicles, which are one of the main causes of air pollution. Is actively progressing. As a power source for such electric vehicles and hybrid electric vehicles, lithium ion secondary batteries are mainly used. Such lithium secondary batteries and the output stability and energy density of the materials are used. Research is going on actively to improve this.

  Such a lithium secondary battery includes a negative electrode made of a carbon material that adsorbs and releases lithium ions, a positive electrode made of a lithium-containing oxide, and a non-aqueous electrolyte solution in which an appropriate amount of lithium salt is dissolved in a mixed organic solvent. It is configured.

  Conventionally, many techniques for adding a specific additive to an electrolyte for a secondary battery have been reported for the purpose of improving the output characteristics or life characteristics of the battery. For example, Patent Document 1 discloses that low-temperature cycle characteristics are improved by using an electrolytic solution containing a sulfonic acid phenyl compound, and Patent Document 2 adds ethylene sulfate to the electrolytic solution. Discloses that the output characteristics of the battery are improved at high and low temperatures. Patent Document 3 discloses that the cycle characteristics of the battery can be improved by adding a compound containing a sulfinyl group to the electrolytic solution, and Patent Document 4 discloses a sultone-based compound as an additive. Patent Document 5 discloses that the high temperature stability of the battery is improved by using an electrolyte containing propene sultone. Disclosure. Furthermore, patent document 6 is disclosing that the high temperature storage capacity of a battery is maintained by using the electrolyte solution containing a sulfate ester compound.

  However, although the output characteristics and storage characteristics of the battery have been improved to some extent by the conventional techniques as described above, it is required for batteries for mobile use, electric vehicles, electric tools, electric motorcycles, robots, or drones. The high output characteristics and life characteristics that are achieved are not sufficiently ensured. Therefore, the development of the secondary battery electrolyte additive that can further improve the output characteristics of the secondary battery and satisfy the life characteristics, and the electrolyte and the secondary battery including the same are still urgent. .

Republic of Korea Registered Patent No. 1486618 Korean Published Patent No. 2015-0050493 Korean Published Patent No. 2015-0050082 Republic of Korea Registered Patent No. 0976958 Japanese Patent No. 4190162 International Publication No. 2012-053644

  As a result of continuous research, the present inventors have discovered compounds that can improve the output characteristics of secondary batteries, improve storage characteristics, improve life characteristics, and improve the withstand voltage characteristics of electrolytes. And this has been completed by applying this to the electrolyte solution for secondary batteries.

  The object of the present invention is to include an electrolyte solution that is contained in an electrolyte solution for a lithium secondary battery, improves the output characteristics of the battery, reduces the electrochemical decomposition of the electrolyte solution, and improves the life and storage characteristics. Is to provide an agent.

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

To achieve the above object, the present invention provides the following chemical formula 1:
The electrolyte solution additive for secondary batteries containing the compound represented by these is provided.

  Moreover, this invention provides the electrolyte solution for secondary batteries containing a non-aqueous solvent, lithium salt, and the said electrolyte solution additive.

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

  The electrolyte additive for secondary batteries of the present invention is contained in an electrolyte and provides a secondary battery excellent in terms of output characteristics, life characteristics, storage characteristics, and withstand voltage characteristics. Therefore, the secondary battery electrolyte additive of the present invention is useful for secondary batteries for mobiles, electric vehicles, electric tools, electric motorcycles, robots, or drones.

  Hereinafter, the present invention will be described in detail.

The secondary battery electrolyte additive of the present invention has the following chemical formula 1:
The compound represented by these is included.

  The electrolyte additive for secondary batteries according to the present invention reduces the interfacial resistance of the electrolyte, improves the output performance of the battery, improves the storage characteristics and life characteristics, enables the battery to be used for a long time, The withstand voltage characteristic of the liquid can be improved.

  The compound represented by the chemical formula 1 is a known compound (CAS No. 497-45-7), bicycloglyoxal 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] dioxathiole2,2,5,5-tetraoxide) and the like, and commercially available products can be purchased.

  In addition, the compound represented by the chemical formula 1 can be prepared by a known synthesis method, for example, a known synthesis method in which 1,1,2,2-tetrachloroethane is reacted with fuming sulfuric acid or the like as a starting material. (See U.S. Pat. No. 19999995 and U.S. Pat. No. 2,415,397).

  The compound represented by the chemical formula 1 can be used in an electrolytic solution alone or in combination with known electrolytic solution additives that can be generally used.

  Moreover, the electrolyte solution for secondary batteries of this invention contains a nonaqueous solvent, lithium salt, and the electrolyte solution additive for secondary batteries as mentioned above.

  The electrolyte solution for a secondary battery may further include a known electrolyte solution additive that can be generally used.

  The non-aqueous solvent is a linear or cyclic carbonate solvent or a lactone solvent, and preferably has a high solubility in the lithium salt and the electrolyte additive for secondary batteries. For example, the non-aqueous solvent may be diethyl carbonate, ethyl methyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, or methyl propyl carbonate. (Ethyl propylene carbonate), linear ethyl carbonate solvents such as methyl ethyl carbonate, ethylene carbonate, propylene carbonate, buty One solvent selected from the group consisting of cyclic carbonate solvents such as butylene carbonate and fluoroethylene carbonate, and lactone solvents such as γ-butyrolactone, or 2 It can be a mixed solvent of more than one species.

  Preferably, as the non-aqueous solvent, a dehydrated solvent can be used. Specifically, the water content of the non-aqueous solvent can be 150 ppm by weight or less. When the water content of the non-aqueous solvent is 150 ppm by weight or less, decomposition of the lithium salt in the battery and hydrolysis of the electrolytic solution additive can be suppressed, and the performance of the electrolytic solution can be further improved.

The lithium salt is for improving the ionic conductivity of the electrolytic solution. 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 or the like may be used alone or in combination. Can do.

  In the electrolytic solution, the concentration (content) of the lithium salt may be 0.9M to 3.0M (mol / L), specifically 1.0M to 2.0M. By including a lithium salt with a content in this range, it is advantageous to ensure the ionic conductivity of the electrolytic solution at an appropriate level, and the efficiency of improving the ionic conductivity of the electrolytic solution with respect to the amount of added lithium salt is further improved. Can be increased.

  According to the example of the present invention, the content of the electrolytic solution 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 of the total weight of the electrolytic solution. 0.1 to 10 wt%, 0.1 to 8 wt%, 0.1 to 6 wt%, 0.1 to 4 wt%, 0.1 to 3 wt%, 0.2 to 5 wt%, 0 5-15 wt%, 0.5-10 wt%, 0.5-8 wt%, 0.5-6 wt%, 0.5-4 wt%, 0.5-3 wt%, 1-10 Wt%, 1-8 wt%, 3-10 wt%, 3-8 wt%, 3-6 wt%, 4-10 wt%, 4-8 wt%, 4-7 wt%, or 5-7 wt% %. When the compound represented by the chemical formula 1 is included in the content range, the increase in resistance can be suppressed and the output characteristics can be further improved, and the storage characteristics and the electrolysis of the secondary battery including the electrolytic solution can be improved. This can be more effective in terms of improving the withstand voltage characteristics of the liquid.

  In addition, the secondary battery electrolyte may be other known additives such as vinylene carbonate, fluoroethylene carbonate, succinonitrile, adiponitrile, vinylethylene. Carbonate, lithium difluorodioxalate phosphate, lithium tetrafluorooxalate phosphate, lithium difluorooxalate borate (lithium difluorooxalato phosphate) including fluoroxalato borate, lithium difluorophosphate, propene sultone, propane sultone, ethylene sulphate, or ethylene sulphate be able to. The known additives can be added within a range that does not affect the efficacy of the compound represented by the chemical formula 1 and the performance of the electrolytic solution. % To 10% by weight can be added.

  The electrolyte solution for a secondary battery of the present invention can be prepared by mixing and stirring a non-aqueous solvent, a lithium salt, and the electrolyte additive for a secondary battery. At this time, a known electrolytic solution additive usually used for the electrolytic solution may be further mixed.

  Furthermore, the secondary battery of this invention contains the electrolyte solution for secondary batteries as mentioned above. As the secondary battery of the present invention, all kinds of secondary batteries including the secondary battery electrolyte are possible. 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 separation membrane disposed between the positive electrode and the negative electrode, and the electrolyte for the secondary battery. It can be included as a component.

  The positive electrode includes a positive electrode active material capable of reversibly adsorbing and desorbing lithium ions, and the positive electrode active material is selected from the group consisting of cobalt, manganese, iron, aluminum, and nickel. One or more or lithium composite metal oxides can be used. Various metal compounds can be used for the positive electrode active material. In addition to these metals, K, Na, Ca, Sn, V, Ge, Ga, B, As, Zr, Cr, Sr, V, And a component selected from the group consisting of rare earth elements.

  The negative electrode includes a negative electrode active material capable of adsorbing and desorbing lithium ions. Examples of the negative electrode active material include crystalline or amorphous carbon, carbon-based carbon negative electrode active material (heat Decomposed carbon, coke, graphite), burned organic polymer compounds, carbon fibers, tin oxide compounds, lithium metals, or lithium alloys can be used. For example, examples of the amorphous carbon include hard carbon, coke, mesocarbon microbead (MCMB) fired at 1500 ° C. or less, and mesophase pitch-based carbon fiber (MPCF). It is done. Examples of the crystalline carbon include graphite-based materials, and specific examples include natural graphite, artificial graphite, graphitized coke, graphitized MCMB, and graphitized MPCF. Among the lithium alloys, silicon, titanium, zinc, bismuth, cadmium, antimony, lead, tin, gallium, or indium can be used as another element that forms an alloy with lithium.

  The separation membrane is for preventing a short circuit between the positive electrode and the negative electrode, a polymer membrane made of polyolefin resin polypropylene, polyethylene or the like, or a multi-layer membrane, a microporous film, a woven fabric, and Nonwoven fabrics and the like can be used.

  Hereinafter, the present invention will be described in detail with reference to examples. However, the following examples are for illustrating the present invention, and the present invention is not limited thereto.

The following chemical formula used in the examples:
The bicycloglyoxal sulfate represented by the formula is a known compound (CAS No. 496-45-7) and is sold by ATOMAX (China), CHEMOS (Germany), ABICHEM (Germany), PEWAX (China), etc. You can purchase the products you have. The compound represented by the chemical formula 1 can be prepared by a known synthesis method such as Preparation Example 1 below.

<Preparation Example 1: Preparation of bicycloglyoxal sulfate>
A 1000 mL three-necked flask and a condenser were attached to a 60 ° C. oil bath. 70 g of 1,1,2,2-tetrachloroethane was added to the three-necked flask to stabilize the temperature, and then 320 g of sulfuric acid (60% fusing grade) was added to initiate the reaction. The reaction solution initially showed a clear or 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 further stirred at low speed for 3 hours. Thereafter, the bath was replaced with a cold water bath at 5 ° C to 7 ° C, and further stirred at low speed for 2 hours. The reaction was terminated when no additional crystalline solid was formed. The obtained slurry solution was subjected to solid-liquid separation with a filter and then vacuum-dried for 12 hours under 20 Torr. As a result, 72.8 g of bicycloglyoxal sulfate represented by Chemical Formula 1 was obtained (yield: 84.4%).

<Example 1: Preparation of electrolyte solution>
A mixed solution was prepared by mixing 429 g of ethylene carbonate (EC), 589 g of ethyl methyl carbonate (EMC), and 380 g of diethyl carbonate (DEC). 167.1 g of LiPF ₆ was added to the mixed solution to prepare a 1.1M LiPF ₆ solution, and then bicycloglyoxal sulfate represented by the above chemical formula 1 was added as an additive at a content of 0.5% by weight. Then, an electrolyte solution for a secondary battery was prepared.

<Example 2: Preparation of electrolyte solution>
An electrolytic solution was prepared in the same manner as in Example 1 except that the bicycloglyoxal sulfate represented by the chemical formula 1 was added at a content of 1.5% by weight.

<Example 3: Preparation of electrolyte solution>
An electrolyte solution was prepared in the same manner as in Example 1 except that the bicycloglyoxal sulfate represented by the chemical formula 1 was added at a content of 3% by weight.

<Example 4: Preparation of electrolyte solution>
An electrolytic solution was prepared in the same manner as in Example 1 except that the bicycloglyoxal sulfate represented by the chemical formula 1 was added at a content of 10% by weight.

<Example 5: Preparation of electrolyte solution>
An electrolyte solution was prepared in the same manner as in Example 1 except that the bicycloglyoxal sulfate represented by the chemical formula 1 was added at a content of 15% by weight.

<Example 6: Preparation of electrolyte solution>
An electrolytic solution was prepared in the same manner as in Example 1 except that the bicycloglyoxal sulfate represented by the chemical formula 1 was added at a content of 0.01% by weight.

<Comparative Example 1: Preparation of electrolyte solution>
An electrolytic solution was prepared in the same manner as in Example 1 except that the bicycloglyoxal sulfate represented by the chemical formula 1 was not added.

<Comparative Example 2: Preparation of electrolyte solution>
Example 1 except that 1,3-trimethylene sultone was added in a content of 3% by weight instead of the bicycloglyoxal sulfate represented by Chemical Formula 1. An electrolytic solution was prepared in the same manner.

<Comparative Example 3: Preparation of electrolyte solution>
The same as in Example 1 except that bis (carboxymethyl) disulfide (bis (carboxymethyl) disulphide) was added at a content of 3% by weight instead of the bicycloglyoxal sulfate represented by Formula 1. The electrolyte solution was prepared by the method.

<Comparative Example 4: Preparation of electrolyte solution>
An electrolyte solution was prepared in the same manner as in Example 1 except that ethylene sulfite was added at a content of 3% by weight instead of the bicycloglyoxal sulfate represented by Formula 1. did.

<Experimental Example 1: Measurement of impedance (mΩ) of secondary battery>
A positive electrode in which LiNi _0.5 Co _0.2 Mn _0.3 and LiMnO ₂ are mixed at 1: 1 (weight ratio), and a negative electrode in which artificial graphite and natural graphite are mixed at 1: 1 (weight ratio). Then, a 1.3 Ah pouch battery was assembled by a normal method, and 6 g of the electrolyte solutions 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 voltage in a charged state of 60% of full charge at room temperature was measured (device used: PNE-0506 charger / discharger). . After measuring the normal temperature initial impedance of the secondary battery by the above method, it was stored in a high-temperature oven at 70 ° C., and after 1 week and 2 weeks, each discharge impedance was measured.

  Table 1 shows a comparison of the impedances of the batteries using the bicycloglyoxal sulfate-containing or non-containing electrolyte represented by the chemical formula 1. Table 2 shows a comparison of the impedances of the batteries using the electrolytic solution containing the additive represented by Chemical Formula 1 or another additive having the same content.

  As shown in Table 1, when the additive represented by Chemical Formula 1 was added to the electrolyte (Examples 1 to 6), the battery was more effective than when the additive was not added (Comparative Example 1). It was confirmed that the impedance at the time of discharging was low. Moreover, as shown in Table 2, when the additive represented by the chemical formula 1 is added to the electrolyte (Example 3), other types of additives are added at the same content (Comparative Example 2). It was confirmed that the impedance at the time of discharging the battery was lower than that of ~ 4). This indicates that by adding the additive represented by the chemical formula 1 to the electrolytic solution, the output characteristics of the battery are improved due to the low resistance characteristic of the interface between the electrode and the electrolytic solution in the discharge process of the battery.

<Experimental example 2: Measurement of life characteristics of secondary battery>
Using the electrolytic solutions prepared in Examples 1 to 6 and Comparative Examples 1 to 4, 1.3 Ah pouch-shaped secondary batteries were manufactured in the same manner as in Experimental Example 1. The secondary battery was charged / discharged at a high charge of 70 ° C. in a fully charged state at a charge rate of 1.3 A at 4.2 V and a discharge rate of 1.3 A at 2.7 V. The discharge capacity at the time of 200 charge / discharge performed by this method was measured with a PNE-0506 charger / discharger (manufacturer: PNE Solution Co., Ltd.), and the ratio (%) to the initial capacity was calculated.

  Table 3 shows a comparison of the life characteristics of batteries using the bicycloglyoxal sulfate-containing or non-containing electrolyte represented by Chemical Formula 1. Table 4 shows a comparison of the life characteristics of the batteries using the electrolytic solution containing the additive represented by Chemical Formula 1 or other additives having the same content.

  As shown in Table 3, when the additive represented by Chemical Formula 1 was added to the electrolyte (Examples 1 to 6), the battery was more effective than when the additive was not added (Comparative Example 1). The life characteristics at 70 ° C. were significantly improved. Moreover, as shown in Table 4, when the additive represented by the chemical formula 1 was added to the electrolyte (Example 3), other types of additives were added at the same content (Comparative Example 2). Compared with ˜4), the battery life characteristics at 70 ° C. were remarkably improved. This indicates that by adding the additive represented by the chemical formula 1 to the electrolytic solution, the decrease in the electrochemical electrode capacity generated during the charging / discharging process of the battery at 70 ° C. is remarkably alleviated.

<Experimental Example 3: Measurement of Storage Characteristics (Capacity Recovery) of Secondary Battery>
Using the electrolytic solutions prepared in Examples 1 to 6 and Comparative Examples 1 to 4, 1.3 Ah pouch-shaped secondary batteries were manufactured in the same manner as in Experimental Example 1. After the secondary battery was stored in a 70 ° C. oven in a fully charged state, the discharge capacity relative to the initial charge capacity was measured after 1 week and 2 weeks (equipment used: PNE-0506 charge / discharge). Electric).

  Table 5 compares the storage characteristics of the batteries using the bicycloglyoxal sulfate-containing or non-containing electrolyte represented by Chemical Formula 1. Table 6 shows a comparison of the storage characteristics of the batteries using the electrolyte represented by the chemical formula 1 or an electrolyte containing other additives having the same content.

  As shown in Table 5, when the additive represented by Chemical Formula 1 was added to the electrolyte (Examples 1 to 6), the battery was more effective than when the additive was not added (Comparative Example 1). It was confirmed that the discharge capacity after storage at 70 ° C. with respect to the initial charge capacity was significantly stabilized. Moreover, as shown in Table 6, when the additive represented by the chemical formula 1 was added to the electrolyte (Example 3), other types of additives were added at the same content (Comparative Example 2). It was confirmed that the discharge capacity after storage at 70 ° C. with respect to the initial charge capacity of the battery was significantly stabilized as compared with ˜4). This indicates that the addition of the additive represented by the chemical formula 1 to the electrolytic solution remarkably mitigates the decrease in electrochemical electrode capacity that occurs during high-temperature storage of the battery. Thus, it was confirmed that by using the additive represented by the chemical formula 1, a stable charge / discharge capacity was realized even at a high temperature.

The electrolyte additive for secondary battery of the present invention is included in the electrolyte and can provide a secondary battery that is excellent in terms of output characteristics, life characteristics, storage characteristics, and withstand voltage characteristics. It is useful for secondary batteries for electric vehicles, electric tools, electric motorcycles, robots, or drones.

Claims (4)

The following chemical formula 1:
The electrolyte solution additive for secondary batteries containing the compound represented by these. A non-aqueous solvent,
Lithium salt,
The following chemical formula 1:
The electrolyte solution for secondary batteries containing the electrolyte solution additive containing the compound represented by these.   The electrolyte solution for secondary batteries according to claim 2, wherein the content of the electrolyte solution additive is 0.05 wt% to 20 wt% of the total weight of the electrolyte solution. The secondary battery containing the electrolyte solution for secondary batteries of Claim 2 or 3.