KR102537722B1 - Electrolyte Solution And Secondary Battery Comprising The Same - Google Patents

Abstract

The present invention relates to an electrolyte solution and a secondary battery including the same, and more particularly, to an electrolyte solution comprising an organic solvent, a lithium salt, a first additive and a second additive, wherein the first additive includes phosphorus pentoxide. And it relates to a secondary battery including the same.
According to the present invention, there is an effect of providing a secondary battery capable of improving charging efficiency and output due to low charging resistance, and having a long lifespan and high-temperature capacity retention rate.

Description

Electrolyte Solution And Secondary Battery Comprising The Same}

The present invention relates to an electrolyte and a secondary battery including the same, and more particularly, to an electrolyte for a battery capable of improving the charging efficiency and output of the battery, enabling long-term storage, and increasing the capacity retention rate at high temperatures. will be.

A lithium secondary battery enables smooth movement of lithium ions by putting an electrolyte solution between the positive and negative electrodes, and uses electric energy by generating or consuming electricity by oxidation-reduction reactions caused by intercalation and desorption at the positive and negative electrodes. facilitate

On the other hand, as interest in the environment has grown, such as the recent strengthening of environmental regulations worldwide, interest in eco-friendly vehicles that can replace fossil fuel vehicles, one of the main causes of air pollution, has also increased. Battery development is actively progressing.

In order to use a battery in a vehicle, not only the output and capacity of the battery must be greatly increased, but also the problem of improving output and increasing resistance at high and low temperatures must be solved in accordance with the use environment such as weather change, Considering that it is used outdoors, it is necessary to develop a battery with improved long-term charge and capacity retention rate in various environments.

Japanese Patent Publication 2008-300126 A Korean Registered Patent No. 10-1586199 B1

In order to solve the problems of the prior art as described above, an object of the present invention is to provide an electrolyte solution of a novel composition and a secondary battery including the same.

Another object of the present invention is to provide a secondary battery having improved battery output due to reduced charging resistance, improved recovery capacity at high temperature, enabling long-term storage, and excellent life retention rate at high temperature.

The above and other objects of the present invention can all be achieved by the present invention described below.

In order to achieve the above object, the present invention includes an organic solvent, a lithium salt, a first additive and a second additive, wherein the first additive includes phosphorus pentoxide. The second additive is vinylene carbonate, fluoroethylene carbonate, lithium difluorophosphate, lithium difluorobis (oxalato) phosphate, 1,3-propanesultone, ethylene sulfate, succinonitrile and vinyl ethylene carbonate It provides an electrolyte solution characterized in that it comprises at least one selected from the group consisting of.

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

When the electrolyte solution according to the present invention is applied as an electrolyte solution of a secondary battery, charging efficiency and output can be improved due to low charging resistance, and a secondary battery having a long lifespan and excellent capacity retention rate even when left at a high temperature has an effect of providing.

Hereinafter, the present invention will be described in detail, but the present invention is not limited thereto.

The electrolyte solution of the present invention includes an organic solvent, a lithium salt, a first additive and a second additive, wherein the first additive includes phosphorus pentoxide. The second additive is vinylene carbonate, fluoroethylene carbonate, lithium difluorophosphate, lithium difluorobis (oxalato) phosphate, 1,3-propanesultone, ethylene sulfate, succinonitrile and vinyl ethylene carbonate It is characterized in that it includes one or more selected from the group consisting of, in this case, the charging resistance is reduced to improve the output of the battery, the recovery capacity at high temperature is improved to enable long-term storage, and the life retention rate at high temperature is improved. It has an excellent effect.

In another example, the electrolyte solution of the present invention includes an organic solvent, a lithium salt, and a first additive, wherein the first additive includes phosphorus pentoxide, and the amount of phosphorus pentoxide is 0.01 to 5% by weight based on 100% by weight of the electrolyte solution. It is characterized by including, in this case, the charging resistance is reduced to improve the output of the battery, the recovery capacity at high temperature is improved to enable long-term storage, and the life retention rate at high temperature is excellent.

The electrolyte solution of the present invention includes, for example, two or more types of electrolyte solution additives, specifically, a first additive containing phosphorus pentoxide, and vinylene carbonate, fluoroethylene carbonate, lithium difluorophosphate, lithium difluorobis ( A second additive containing at least one selected from the group consisting of oxalato) phosphate, 1,3-propanesultone, ethylene sulfate, succinonitrile, and vinylethylene carbonate, in which case the battery output improvement effect described above , there is an advantage in that the effect of improving the high temperature recovery capacity and the effect of improving the high temperature life retention rate is excellent.

The first additive is, for example, 0.01 to 10% by weight, preferably 0.01 to 5% by weight, more preferably 0.02 to 2% by weight, and even more preferably 0.03 to 2% by weight based on 100% by weight of the total electrolyte solution. It may be included in 1% by weight, more preferably 0.05 to 0.5% by weight, and within this range, desired effects can be sufficiently obtained without deterioration of battery characteristics.

The first additive may further include, for example, at least one selected from the group consisting of methanesulfonic acid, sulfuric acid, and phosphoric acid. In this case, a synergistic effect is obtained due to the interaction of phosphorus pentoxide with methanesulfonic acid, sulfuric acid, or phosphoric acid. There is an advantage that the battery performance improvement effect is more outstanding.

As a preferred example, the first additive may be in the form of a solution in which phosphorus pentoxide is dissolved in methanesulfonic acid, and as a specific example, 1 to 20% by weight of phosphorus pentoxide and 80 to 80 to 20% by weight of methanesulfonic acid based on 100% by weight of the total amount of the first additive 99% by weight, preferably 2 to 15% by weight of phosphorus pentoxide and 85 to 98% by weight of methanesulfonic acid; More preferably, it may contain 5 to 13% by weight of phosphorus pentoxide and 87 to 95% by weight of methanesulfonic acid, and even more preferably 8 to 12% by weight of phosphorus pentoxide and 88 to 92% by weight of methanesulfonic acid, in this case It has excellent compatibility with the electrolyte solution, so that the manufacturing efficiency can be further improved and the battery output improvement effect is more excellent.

In another example, the first additive includes 1 to 20% by weight of phosphorus pentoxide and 80 to 99% by weight of phosphorus pentoxide and 80 to 99% by weight of phosphorus pentoxide, more preferably 2 to 15% by weight of phosphorus pentoxide and 85% by weight of methanesulfonate in the total 100% by weight of the first additive to 98% by weight, more preferably 5 to 13% by weight of phosphorus pentoxide and 87 to 95% by weight of methanesulfonate, even more preferably 8 to 12% by weight of phosphorus pentoxide and 88 to 92% by weight of methanesulfonate. In this case, a synergistic effect can be obtained due to the interaction of phosphorus pentoxide and methanesulfonate, so that the battery performance improvement effect is more excellent.

The methanesulfonate may be, for example, an alkali metal salt of methanesulfonic acid, and the alkali metal may preferably be lithium, sodium, or potassium, and more preferably lithium, in which case, without deteriorating other physical properties. There is an advantage that the battery performance improvement effect is more excellent.

The content of the phosphorus pentoxide contained in the electrolyte is, for example, 0.01 to 5% by weight, preferably 0.02 to 3% by weight, more preferably 0.03 to 1% by weight, and even more preferably, based on 100% by weight of the total electrolyte solution. It may be 0.05 to 0.5% by weight, preferably 0.05 to 0.1% by weight in one embodiment, and within this range, desired effects can be sufficiently obtained without deterioration of other physical properties.

The first additive may be added to the electrolyte solution of the secondary battery to form a stable film on the electrode. At this time, due to the stability of the film, it is possible to prevent the decomposition of the electrolyte solution, thereby improving the cycle characteristics, and in particular, the decomposition at high temperatures is suppressed, compared to the conventional electrode film decomposition at high temperatures, resulting in poor storage performance at high temperatures. There is an excellent effect of greatly improving storage stability. In addition, an increase in resistance is prevented to improve charging efficiency and output, and gas generation due to a chemical reaction inside the battery is also suppressed, thereby improving battery safety. In addition, the structure of the electrode active materials of the positive electrode and the negative electrode is prevented from collapsing at high temperatures, thereby improving the capacity retention rate, thereby prolonging the life of the battery.

For example, the second additive may be included in an amount of 0.01 to 5% by weight, preferably 0.1 to 4% by weight, more preferably 0.2 to 3.5% by weight , and even more preferably 0.01 to 5% by weight based on 100% by weight of the total electrolyte solution. 0.3 to 2.5% by weight, and more preferably 0.5 to 2.0% by weight, and within this range, the effect of improving battery output and improving battery life can be sufficiently obtained without deterioration of battery characteristics.

As another example, the second additive may be included in an amount of 0.01 to 5% by weight, preferably 0.1 to 4.5% by weight, and more preferably 0.5 to 4% by weight based on 100% by weight of the total electrolyte solution, within this range. The effect of improving battery output and improving battery life can be sufficiently obtained without deterioration of battery characteristics.

The second additive is vinylene carbonate, fluoroethylene carbonate, lithium difluorophosphate, lithium difluorobis (oxalato) phosphate, 1,3-propanesultone, ethylene sulfate, succinonitrile and vinyl ethylene carbonate It includes one or more selected from the group consisting of, and a preferred example may include two or more, and in this case, there is an advantage in that the battery performance improvement effect is more excellent due to the synergistic action between the additives.

As a preferred example, the second additive may include one or two selected from the group consisting of vinylene carbonate, fluoroethylene carbonate, lithium difluorophosphate, and 1,3-propanesultone. In this case, the additives There is an advantage that the battery performance improvement effect is more excellent due to the synergistic effect between the two.

The second additive may further include, for example, at least one selected from the group consisting of lithium tetrafluoro oxalato phosphate and lithium trioxalato phosphate, and in this case, improved low-temperature characteristics and cycle characteristics of the battery are more excellent. effect can be provided.

The organic solvent is, for example, ethylene carbonate (EC), diethyl carbonate (DEC), ethylmethyl carbonate (EMC), dimethyl carbonate (DMC), propylene carbonate (PC), dipropyl carbonate (DPC), butylene carbonate, methyl It may contain two or more selected from the group consisting of propyl carbonate, ethylpropyl carbonate, methyl propionate (MP), ethyl propionate (EP) and propyl propionate (PP), in which case the ionic conductivity of the electrolyte , viscosity, and the like are easy to control, so that the effect of improving battery performance is more excellent.

As a specific example, the organic solvent is a mixture of a high permittivity organic solvent having high ionic conductivity so as to increase the charge/discharge performance of a battery and a low viscosity organic solvent that can adjust the viscosity of the solvent to have a viscosity suitable for application to a battery. It can be used as a mixed solvent, and more specifically, EC and / or PC can be used as an example of the organic solvent of high dielectric constant, and the low viscosity organic solvent can be used as an example of EMC, DMC and DEC. One or more selected species may be used. It is preferable to mix the high dielectric constant and low viscosity organic solvent in a volume ratio of 2:8 to 8:2. More specifically, it may be a ternary mixed solvent of EC and/or PC, EMC and DEC, and the ratio of EC and/or PC:EMC:DEC may be 3:3 to 5:2 to 4.

When the organic solvent contains moisture, since lithium ions in the electrolyte may be hydrolyzed, the moisture content in the organic solvent is preferably controlled to 150 ppm or less, preferably 100 ppm or less.

The electrolyte solution may include, for example, at least one selected from the group consisting of LiPF ₆ and LiFSI as a lithium salt, and in this case, lithium ions are smoothly supplied to the battery, resulting in excellent battery performance.

The electrolyte is, for example, a lithium salt, LiF ₄ , LiCl, LiBr, LiI, LiClO ₄ , LiB ₁₀ Cl ₁₀ , LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , LiAsF ₆ , LiSbF ₆ , LiAlCl ₄ , CH ₃ SO ₃ Li, At least one selected from the group consisting of CF ₃ SO ₃ Li and (CF ₃ SO ₂ ) ₂ NLi may be further included, and in this case, the supply of lithium ions may be more smooth.

When the lithium salt is dissolved in the electrolyte solution, the lithium salt functions as a source of lithium ions in the lithium secondary battery and can promote the movement of lithium ions between the positive electrode and the negative electrode. Accordingly, the lithium salt is preferably included in a concentration of about 0.6 mol% to 2 mol% in the electrolyte solution. When the concentration of the lithium salt is less than 0.6 mol%, the conductivity of the electrolyte may be lowered, resulting in deterioration in electrolyte performance, and when the concentration exceeds 2 mol%, the viscosity of the electrolyte may increase and mobility of lithium ions may be reduced. Considering the conductivity of the electrolyte and the mobility of lithium ions, the lithium salt may be included in the electrolyte in an amount of preferably 0.7 mol% to 1.6 mol%, more preferably 0.8 mol% to 1.5 mol%.

In addition to the first and second additives, the electrolyte solution of the present invention is an additive (hereinafter referred to as other additives) that can be generally used in the electrolyte solution for the purpose of improving lifespan characteristics of a battery, suppressing battery capacity decrease, and improving discharge capacity of a battery. ) may be further included.

Preferable specific examples of the other additive components include Succinic anhydride, Tetravinyl silane, Hexamethylenetetramine, 1,1,2,2-tetrafluoroethyl 2,2,2-trifluoroethyl ether, 1,2-bis((difluorophosphaneyl)oxy)ethane, 1 ,3,6-Hexanetricarbonitrile, 1-Ethyl-3-methylimidazolium dicyanamide, Trimethoxyboroxine, Lithium Bis(oxaleto)borate, Lithium DiFluro(Oxalato) Borate, Tris(trimethylsilyl) borate, Lithium Tetrafluoroborate, Triisopropyl borate, Diethyl (difluoromethyl)phosphonate, Tris(trimethylsilyl) Phosphite, Tripropagyl phosphate, 2,4,8,10-Tetraoxa-3,9-dithiaspiro[5.5]undecane 3,3,9,9-tetraoxide, Dimethyl sulfate, Ethylene dimethanesulfonate, methylene methyl disulfonate, Lithium bis (fluorosulfonyl)imide, 3-Fluoro-1,3-propansulton, 1-propene-1,3-sultone, 1,3-propylene sulfate, 1,4-Butane sultone, Sulfolene, Biphenyl, Cyclo Hexyl Benzene, 4-Fluorotoluene , triphenyl phosphate, fluoro benzene, and 2-fluoro-biphenyl may be one or more selected from the group consisting of.

The other additives may be preferably included in an amount of 0.3 to 1.5% by weight, preferably 0.5 to 1.2% by weight, based on the total weight of the electrolyte, and in this case, it is preferable in terms of improving low-temperature characteristics and cycle characteristics of the battery.

The secondary battery of the present invention includes a negative electrode and a positive electrode. It is characterized in that it comprises a separator interposed between the negative electrode and the positive electrode, and the electrolyte solution.

For example, the cathode may be prepared by preparing a composition for forming a cathode active material layer by mixing a cathode active material, a binder, and optionally a conductive agent, and then applying the composition to a cathode current collector such as aluminum foil.

For example, the cathode active material may be a conventional NCM (lithium nickel manganese cobalt oxide) cathode active material used in a lithium secondary battery, and preferably has the chemical formula Li[NixCo _1-xy Mn _y ]O ₂ (where 0<x< It may be a lithium composite metal oxide in the form of 0.5, 0<y<0.5), and as a specific example, it may be LiNiMnCoO ₂ , but is not limited thereto.

The variables x and y of the formula Li[NixCo _1-xy Mn _y ]O ₂ of the lithium composite metal oxide are, for example, 0.0001<x<0.5, 0.0001<y<0.5, or 0.001<x<0.3, 0.001<y<0.3 can be

As another example, a compound capable of reversible intercalation and deintercalation of lithium (lithiated intercalation compound) may be used as the cathode active material.

Among the above compounds, LiCoO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , LiNiO ₂ , LiNi _x Mn _(1-x) O ₂ (where 0<x<1), and LiM1 _x M2 _y O ₂ (where, 0≤x≤1, 0≤y≤1, 0≤x+y≤1, M1 and M2 are each independently selected from the group consisting of Al, Sr, Mg and La ) At least one selected from the group consisting of is preferred.

For example, the negative electrode may be prepared by preparing a composition for forming a negative electrode active material layer by mixing a negative electrode active material, a binder, and optionally a conductive agent, and then applying the composition to a negative electrode current collector such as copper foil.

As the negative electrode active material, for example, a compound capable of reversible intercalation and deintercalation of lithium may be used.

Specific examples of the negative electrode active material may be a carbonaceous material such as artificial graphite, natural graphite, graphitized carbon fiber, or amorphous carbon. In addition to the carbonaceous material, a metallic compound capable of alloying with lithium or a composite including a metallic compound and a carbonaceous material may also be used as an anode active material, and for example, graphite may be used.

As the metal capable of alloying with lithium, for example, at least one of Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloy, Sn alloy, or Al alloy may be used.

In addition, a metal lithium thin film may be used as the anode active material. As the negative electrode active material, one or more selected from the group consisting of crystalline carbon, amorphous carbon, carbon composites, lithium metal, and lithium-containing alloys may be used in view of high stability.

In the secondary battery of the present invention, by adding the first and second additives, the battery charging resistance, output characteristics, and high temperature of 45 ° C. or higher measured by HPPC (Hybrid Pulse Power Characterization) method are higher than when only the conventional electrolyte solution additive is added. There is an effect of further improving the effect of improving battery characteristics such as capacity recovery characteristics and life characteristics.

As a specific example, the secondary battery of the present invention may have an HPPC charging resistance value measured at 60 ° C. of 50 mΩ or less, preferably 48 mΩ or less, more preferably 45 mΩ or less, and most preferably 43 mΩ or less. there is. In addition, the secondary battery may have a recovery capacity of 805 mAh or more, preferably 810 mAh or more, and more preferably 815 mAh or more at 60 °C. The life maintenance efficiency of the secondary battery at 45° C. may be 80% or more, preferably 85% or more, and more preferably 87% or more.

As a specific example, the HPPC charging resistance value measured at 60° C. may be expressed as a resistance value of the battery measured after the secondary battery is left at 60° C. for 5 hours in a fully charged state.

As a specific example, the recovery capacity at 60 ° C. is measured by charging and discharging the secondary battery at room temperature (25 ° C.) to measure the initial discharge capacity, charging it again under the same conditions, storing it at 60 ° C. for 4 weeks, and then at room temperature again. It can be expressed as the measured residual capacity when discharged.

As a specific example of the life maintenance efficiency at 45 ° C., the secondary battery is charged and discharged 300 cycles at 45 ° C., and the discharge capacity after 300 cycles of the initial discharge capacity is expressed as a percentage (%) value.

In this disclosure, the HPPC charging resistance value can be measured by the method prescribed in the document “Battery test manual for plug-in hybrid electric vehicles,” (2010, Idaho National Laboratory for the U.S. Department of Energy.), It is an important indicator of battery characteristics such as battery output. In addition, charging resistance is a resistance value measured during charging of the battery, and the lower the charging resistance, the smaller the energy loss, so that the charging speed can be increased and the output of the battery can be improved. The secondary battery of the present invention has a low HPPC charging resistance value as described above, and is excellent in charging speed and output, so it is suitable for use as, for example, an automobile battery.

In the present description, the recovery capacity represents the capacity conservation characteristics of a battery left for a long time, and the discharged electric capacity when the battery left for a long time is discharged to the discharge end voltage, and the discharge end voltage after recharging the discharged battery. The discharged capacitance when discharged to , respectively, is measured, and the two capacitance values are compared. The higher the recovery capacity, the smaller the amount of natural discharge due to battery preservation (storage), which means that the battery can be stored for a long time. In particular, the higher the storage temperature of the battery, the faster the natural discharge rate. This is a very important characteristic in batteries. When the electrolyte solution additive of the present invention is added to the electrolyte solution, the recovery capacity is improved by 5 to 20% compared to the case of using only the conventional additives, and there is an effect that can be stored for a longer period of time with one charge.

Therefore, when the battery of the present invention is used as a battery for an electric vehicle, improvement in output, which is important depending on the size of the vehicle, climate change, low temperature and Performance improvement at high temperatures is achieved, and thus excellent performance can be exhibited as an automobile battery.

Therefore, when the electrolyte solution additive according to the embodiments of the present invention and the electrolyte solution containing the same are applied to a secondary battery, it can be seen that the charging resistance, output, recovery capacity and lifetime efficiency are improved, making it suitable for use as a secondary battery for automobiles. can

Hereinafter, preferred embodiments are presented to aid understanding of the present invention, but the following examples are merely illustrative of the present invention, and various changes and modifications are possible within the scope and spirit of the present invention. It is obvious to those skilled in the art, It goes without saying that these variations and modifications fall within the scope of the appended claims.

[Example: Preparation of Electrolyte for Battery]

Example 1

As the organic solvent, a carbonate-based mixed solvent having a volume ratio of EC: EMC: DEC = 3:4:3 was used, and as the lithium salt, a solution containing LiPF ₆ at a concentration of 1.15 M, phosphorus pentoxide as an electrolyte additive ( An electrolyte solution was prepared by adding 0.05 wt% of P ₂ O ₅ compound), 0.5 wt% of methane sulfonic acid, and 1.0 wt% of lithium difluorophosphate.

Example 2

Example 1 was carried out in the same manner as in Example 1, except that 0.05% by weight of the P ₂ O ₅ compound, 0.5% by weight of methanesulfonic acid, and 1.0% by weight of vinylene carbonate were added as electrolyte additives. .

Example 3

In Example 1, the same procedure as in Example 1 was performed except that 0.05% by weight of the P ₂ O ₅ compound, 0.5% by weight of methanesulfonic acid, and 1.0% by weight of fluoroethylene carbonate were added as electrolyte additives. did

Example 4

In Example 1, except that 0.05 wt% of the P ₂ O ₅ compound, 0.5 wt% of methanesulfonic acid, and 1.0 wt% of 1,3-propane sultone were added as electrolyte additives. It was carried out in the same way as in Example 1.

Example 5

Example 1 was carried out in the same manner as in Example 1, except that 0.1% by weight of the P ₂ O ₅ compound, 1.0% by weight of methanesulfonic acid, and 1.0% by weight of vinylene carbonate were added as electrolyte additives.

Example 6

In Example 1, the P ₂ O ₅ compound as an electrolyte solution additive 0.1% by weight, 1.0% by weight of methanesulfonic acid and 1.0% by weight of lithium difluorophosphate were added, but the same procedure as in Example 1 was performed.

Comparative Example 1

Example 1 was carried out in the same manner as in Example 1, except that 0.05% by weight of the P ₂ O ₅ compound and 0.5% by weight of methanesulfonic acid were added as electrolyte additives.

Comparative Example 2

Example 1 was carried out in the same manner as in Example 1, except that 0.1% by weight of the P ₂ O ₅ compound and 1.0% by weight of methanesulfonic acid were added as electrolyte additives.

Comparative Example 3

Example 1 was carried out in the same manner as in Example 1, except that 1.0% by weight of lithium difluorophosphate was added as an electrolyte solution additive.

Comparative Example 4

Example 1 was carried out in the same manner as in Example 1, except that 1.0% by weight of lithium difluorophosphate and 1.0% by weight of vinylene carbonate were added as electrolyte additives.

Comparative Example 5

Example 1 was carried out in the same manner as in Example 1, except that 1.0% by weight of lithium difluorophosphate, 1.0% by weight of vinylene carbonate, and 1.0% by weight of methanesulfonic acid were added as electrolyte additives.

manufacture of batteries

92% by weight of Li(Ni _0.5 Co _0.2 Mn _0.3 )O ₂ as a cathode active material, 4% by weight of carbon black as a conductive agent, and 4% by weight of polyvinylidene fluoride (PVdF) as a binder were mixed with N-methyl- as a solvent. A positive electrode mixture slurry was prepared by adding 2-pyrrolidone (NMP). The positive electrode mixture slurry was coated on an aluminum (Al) thin film, which is a positive electrode current collector, and dried to have a thickness of about 20 μm, and then a roll press was performed to prepare a positive electrode.

An anode mixture slurry was prepared by adding 96% by weight, 3% by weight, and 1% by weight of carbon powder as an anode active material, PVdF as a binder, and carbon black as a conductive agent to NMP as a solvent. The negative electrode mixture slurry was coated on a copper (Cu) thin film as a negative electrode current collector having a thickness of 10 μm, dried to prepare a negative electrode, and then rolled pressed to prepare a negative electrode.

After preparing the positive electrode and the negative electrode prepared as described above with a separator composed of three layers of polypropylene / polyethylene / polypropylene (PP / PE / PP) in a conventional method, a pouch-type battery was prepared, and the Examples 1 to 6 and Comparative Examples The preparation of the lithium secondary battery was completed by injecting the electrolyte solution prepared in 1 to 5.

test example

In order to evaluate the performance of each secondary battery prepared above, the performance was evaluated by the following method, and the results are summarized in Table 1 below.

[HPPC charging resistance evaluation]

It was measured by the method prescribed in the literature "Battery test manual for plug-in hybrid electric vehicles," (2010, Idaho National Laboratory for the U.S. Department of Energy.).

After the secondary battery fully charged with 100% SOC was left at 60°C for 5 hours, the measured voltage value, the charge/discharge current value corresponding to the C-rate, the current change (ΔI), and the discharge voltage change (ΔV) , charge voltage change (ΔV), discharge resistance, and charge resistance were measured, and the charge/discharge current was briefly flowed for a certain period of time for each C-rate, and the resistance value was calculated with the slope obtained from the current and voltage change.

[Evaluation of high temperature recovery capacity]

The charging conditions were charged until the charging current became 1/10C at a constant current of 1.0C and a voltage of 4.2V. Discharge conditions were performed by charging and discharging by discharging up to 3.0V at a constant current of 1.0C, and then the discharge capacity was measured.

After charging under the same charging/discharging conditions, storing in a thermostat at 60° C. for 4 weeks, discharging to a discharge voltage of 3V at room temperature at 25° C., the remaining capacity was measured. Thereafter, the recovery capacity was measured after 100 cycles under the same charging and discharging conditions, and the average value thereof was calculated.

[High temperature life evaluation]

The secondary battery is charged with a constant current at 45° C. at a current of 1C rate until the voltage reaches 4.20V (vs. Li), and then cut-off at a current of 0.05C rate while maintaining 4.20V in constant voltage mode. did Subsequently, the discharge was performed at a constant current at a rate of 1C until the voltage reached 3.0V (vs. Li) during discharge (1st cycle). The above cycle was repeated 300 times and the average value thereof was calculated.

division Additives (% by weight) HPPC charging resistance
(mΩ) recovery capacity
(mAh) lifetime efficiency
(%) 1st additive 2nd additive Example 1 P ₂ O ₅
(0.05) Methane sulfonic acid
(0.5) lithium difluorophosphate
(1.0) 41.1 816.3 88.1 Example 2 P ₂ O ₅
(0.05) Methane sulfonic acid
(0.5) Vinylene carbonate
(1.0) 42.8 825.6 88.5 Example 3 P ₂ O ₅
(0.05) Methane sulfonic acid
(0.5) Fluoroethylene carbonate
(1.0) 40.3 826.4 88.8 Example 4 P ₂ O ₅
(0.05) Methane sulfonic acid
(0.5) 1,3-propane sultone
(1.0) 42.8 836.5 87.9 Example 5 P ₂ O ₅
(0.1) Methane sulfonic acid
(1.0) Vinylene carbonate
(1.0) 39.3 832.5 89.1 Example 6 P ₂ O ₅
(0.1) Methane sulfonic acid
(1.0) lithium difluorophosphate
(1.0) 41.0 830.6 86.3 Comparative Example 1 P ₂ O ₅
(0.05) Methane sulfonic acid
(0.5) - 52.6 749.3 81.3 Comparative Example 2 P ₂ O ₅
(0.1) Methane sulfonic acid
(1.0) - 58.4 723.8 80.6 Comparative Example 3 - - lithium difluorophosphate
(1.0) 65.7 780.5 84.2 Comparative Example 4 - - lithium difluorophosphate (1.0)
Vinylene carbonate (1.0) 53.3 805.1 82.4 Comparative Example 5 - Methane sulfonic acid
(1.0) lithium difluorophosphate (1.0)
Vinylene carbonate (1.0) 70.5 764.2 80.5

As shown in Table 1, in the case of the secondary battery including the electrolytes of Examples 1 to 6 according to the present invention, the charging resistance is 39.3 to 42.8 mΩ, the high-temperature recovery capacity is 816.3 to 830.6 mAh, and the high-temperature life efficiency is While 86.3 to 89.1%, in the case of Comparative Examples 1 to 5 outside the present invention, the charging resistance is at least about 10 mΩ higher than that of Examples 1 to 6, and the high-temperature recovery capacity is at least about 11 mAh or lower, The high-temperature lifetime efficiency was lowered by at least about 2%.

Therefore, it was confirmed that the electrolyte solution of the present invention has an effect of improving the charging efficiency and output of the secondary battery, and improving the long-term storage efficiency and capacity retention rate at high temperatures.

Claims (13)

organic solvent;
lithium salt;
a first additive; and
A second additive; including,
The first additive is a phosphorus pentoxide methanesulfonic acid solution containing 1 to 20% by weight of phosphorus pentoxide and 80 to 99% by weight of methanesulfonic acid based on 100% by weight of the total first additive,
The second additive is vinylene carbonate, fluoroethylene carbonate, lithium difluorophosphate, lithium difluorobis (oxalato) phosphate, 1,3-propanesultone, ethylene sulfate, succinonitrile and vinyl ethylene carbonate An electrolyte solution characterized in that it comprises at least one selected from the group consisting of.
According to claim 1,
The electrolyte solution for a battery, characterized in that the first additive is included in 0.01 to 10% by weight based on 100% by weight of the total electrolyte solution.
delete According to claim 1,
The second additive is an electrolyte solution for a battery, characterized in that contained in 0.01 to 5% by weight based on 100% by weight of the total electrolyte solution.
According to claim 1,
The organic solvent is ethylene carbonate (EC), diethyl carbonate (DEC), ethylmethyl carbonate (EMC), dimethyl carbonate (DMC), propylene carbonate (PC), dipropyl carbonate (DPC), butylene carbonate, methylpropyl carbonate , Ethylpropyl carbonate, methyl propionate (MP), ethyl propionate (EP) and propyl propionate (PP) characterized in that it comprises two or more selected from the group consisting of electrolyte solution.
According to claim 1,
The lithium salt is an electrolyte solution, characterized in that it comprises at least one selected from the group consisting of LiPF ₆ and LiFSI [Lithium bis (FluoroSulfonyl) Imide].
According to claim 1,
The electrolyte is a lithium salt, LiF ₄ , LiCl, LiBr, LiI, LiClO ₄ , LiB ₁₀ Cl ₁₀ , LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , LiAsF ₆ , LiSbF ₆ , LiAlCl ₄ , CH ₃ SO ₃ Li, CF ₃ An electrolyte solution comprising at least one selected from the group consisting of SO ₃ Li and (CF ₃ SO ₂ ) ₂ NLi.
According to claim 1,
The electrolyte solution, characterized in that the second additive further comprises at least one selected from the group consisting of lithium tetrafluoro oxalato phosphate and lithium trioxalato phosphate.
A secondary battery comprising a negative electrode, a positive electrode, a separator interposed between the negative electrode and the positive electrode, and an electrolyte solution,
The electrolyte solution is a secondary battery, characterized in that the electrolyte solution of any one of claims 1, 2 and 4 to 8.
According to claim 9,
The secondary battery is a lithium secondary battery, characterized in that HPPC (Hybrid Pulse Power Characterization) charging resistance value is 50 mΩ or less at 60 ℃.
According to claim 9,
The secondary battery, a lithium secondary battery, characterized in that the recovery capacity at 60 ℃ 805 mAh or more.
According to claim 9,
The secondary battery, the lithium secondary battery, characterized in that the life maintenance efficiency at 45 ℃ 80% or more.
According to claim 9,
The secondary battery is a lithium secondary battery, characterized in that the vehicle battery.