KR20220000861A - Electrolyte Solution Additive, Electrolyte Solution For Battery And Secondary Battery Comprising The Same - Google Patents

Abstract

The present invention relates to an electrolyte additive, an electrolyte including the same, and a secondary battery, and more particularly, to an electrolyte additive including a compound represented by the following formula 1, an electrolyte including the electrolyte additive, and a secondary battery including the same. According to the present invention, the secondary battery has low charging resistance, which improves charging efficiency and output, and has an excellent long-term lifespan and high-temperature capacity retention. In formula 1, X_1 and X_2 are independently F, Cl, Br or I, and E_1 and E_2 are independently a substituted or unsubstituted hydrocarbon group having 1 to 3 carbon atoms, wherein the substitution is substituted with one or more selected from a group consisting of =O, -CX'_3 and -CH_2CX''_3, X' and X'' are independently F, Cl, Br or I, and a bond between carbons included in E_1 and E_2 is a single bond or a double bond.

Description

Electrolyte additive, battery electrolyte including same, and secondary battery including same {Electrolyte Solution Additive, Electrolyte Solution For Battery And Secondary Battery Comprising The Same}

The present invention relates to an electrolyte solution additive, an electrolyte solution including the same, and a secondary battery including the same, and more particularly, to improve the charging efficiency and output of the battery, to enable long-term storage, and to increase the capacity retention rate at high temperature It relates to an electrolyte solution additive that can be used.

Lithium secondary batteries enable smooth movement of lithium ions by putting an electrolyte between the positive and negative electrodes, and the use of electrical energy by the method in which electricity is generated or consumed by redox reactions following insertion and desorption from the positive and negative electrodes. make it easy

Meanwhile, as interest in the environment is growing, such as tightening environmental regulations around the world, interest in eco-friendly vehicles that can replace fossil fuel vehicles, which is one of the main causes of air pollution, is also increasing. Accordingly, in the domestic/foreign battery industry, the development of batteries for automobiles is being actively carried out.

In order to use a battery in a vehicle or an energy storage system (ESS), the output and capacity of the battery must be significantly increased, and the problem of output improvement and resistance increase at high and low temperatures must be solved in accordance with the use environment such as weather changes. , it is necessary to develop a battery with improved long-term charging and capacity retention in various environments, considering that automobiles are used outdoors regardless of seasons.

Japanese Patent Laid-Open No. 2008-300126 A Korean Patent Registration 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 a novel electrolyte solution additive, an electrolyte solution including the same, and a secondary battery including the same.

Another object of the present invention is to provide a secondary battery having reduced charging resistance, improved output of the battery, improved recovery capacity at high temperature, so that long-term storage is possible, 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.

The present invention provides an electrolyte solution additive comprising a compound represented by the following formula (1).

[Formula 1]

(In Formula 1, X ₁ and X ₂ are independently F, Cl, Br or I, and E ₁ and E ₂ are independently a substituted or unsubstituted hydrocarbon group having 1 to 3 carbon atoms, wherein the substitution is =O, -CX' ₃ and -CH ₂ CX" ₃ is substituted with one or more selected from the group consisting of, wherein X' and X" are independently F, Cl, Br or I, and are included in _{E 1} and E ₂ Bonds between carbons are single or double bonds.)

The compound represented by Formula 1 may include one selected from the group consisting of compounds represented by Formulas 2 and 3 below as an anion.

[Formula 2]

[Formula 3]

(In Formulas 2 and 3, a line is a bond, a point where a bond and a bond not describing a separate element meet is carbon, and the number of hydrogens satisfying the valence of the carbon is omitted.)

In addition, the present invention provides an electrolyte solution comprising an organic solvent, a lithium salt, and an electrolyte solution additive, wherein the electrolyte solution additive includes a compound represented by the following formula (1).

[Formula 1]

(In Formula 1, X ₁ and X ₂ are independently F, Cl, Br or I, and E ₁ and E ₂ are independently a substituted or unsubstituted hydrocarbon group having 1 to 3 carbon atoms, wherein the substitution is =O, -CX' ₃ and -CH ₂ CX" ₃ is substituted with one or more selected from the group consisting of, wherein X' and X" are independently F, Cl, Br or I, and are included in _{E 1} and E ₂ Bonds between carbons are single or double bonds.)

The electrolyte additive may be included in an amount of 0.1 to 10% by weight based on 100% by weight of the total electrolyte.

The compound represented by Formula 1 may have a symmetric structure.

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 And it may include at least one selected from the group consisting of ethylpropyl carbonate.

The lithium salt is LiPF ₆ , 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 SO ₃ Li and (CF ₃ SO ₂ ) ₂ NLi may include at least one selected from the group consisting of.

The electrolyte may include a metal phosphate-based compound.

The metal phosphate-based compound may include at least one selected from the group consisting of lithium difluoro (bisoxalato) phosphate, lithium tetrafluoro oxalato phosphate, lithium difluorophosphate and lithium trioxalato phosphate. can

In addition, the present invention provides a secondary battery comprising a negative electrode, a positive electrode, a separator interposed between the negative electrode and the positive electrode, and an electrolyte, wherein the electrolyte is the above-described electrolyte.

The secondary battery may have an HPPC charging resistance value of 40.0 mΩ or less at 60°C.

The secondary battery may have a recovery capacity of 853.1 mAh or more at 60°C.

The secondary battery may have a lifespan maintenance efficiency of 85% or more at 45°C.

The secondary battery may be an energy storage system (ESS) or a battery for a vehicle.

The secondary battery including the electrolyte including the electrolyte additive according to the present invention has a low charging resistance, so that charging efficiency and output can be improved, and there is an effect of providing a secondary battery excellent in long-term lifespan and high-temperature capacity retention.

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

The present inventors have been researching a secondary battery having improved output and excellent high-temperature recovery capacity and lifespan characteristics in order to manufacture a battery that can be used as an automobile battery. It was confirmed that all of the objects of the present invention can be achieved, and based on this, the present invention was completed.

The electrolyte additive according to the embodiments of the present invention is characterized in that it includes a compound represented by the following formula (1), and in this case, the charging resistance of the secondary battery is low, so that charging efficiency and output can be improved, long-term lifespan and high-temperature capacity There is an excellent effect of the retention rate.

[Formula 1]

(In Formula 1, X ₁ and X ₂ are independently F, Cl, Br or I, and E ₁ and E ₂ are independently a substituted or unsubstituted hydrocarbon group having 1 to 3 carbon atoms, wherein the substitution is =O, -CX' ₃ and -CH ₂ CX" ₃ is substituted with one or more selected from the group consisting of, wherein X' and X" are independently F, Cl, Br or I, and are included in _{E 1} and E ₂ Bonds between carbons are single or double bonds.)

The X ₁ , X ₂ , X' and X" are preferably independently F or Cl, and more preferably F, in this case, the charging resistance of the secondary battery is low, so that charging efficiency and output can be improved, and long-term There is an excellent effect of lifespan and high-temperature capacity retention rate.

E ₁ and E ₂ are preferably independently a substituted or unsubstituted hydrocarbon group having 2 or 3 carbon atoms, wherein the substitution is preferably 1 selected from the group consisting _{of 1 =O and 1 to 3 -CX′ 3} It is substituted with more than one species, and in this case, the charging resistance of the secondary battery is low, so that the charging efficiency and output can be improved, and long-term lifespan and high-temperature capacity retention rate are excellent.

In addition, when E ₁ and E ₂ do not include an =O (oxygen) substituent, _{the bond between the carbons of E 1} and E ₂ may include a double bond, and in this case, the bonding stability of the compound is improved This has the effect of further improving the battery life.

The compound represented by Formula 1 may preferably have a symmetrical structure with respect to the central P element, and in this case, the electron flow in the molecule is stabilized, and through this, molecular rigidity is increased, so that the battery performance is greatly improved. There is an advantage.

The compound represented by Formula 1 is an anion, and preferably at least one selected from the group consisting of compounds represented by Formulas 2 to 3, and in this case, charging efficiency and output can be improved due to low charging resistance of the secondary battery, , long lifespan and excellent high temperature capacity retention rate.

[Formula 2]

[Formula 3]

(In Formulas 2 to 3, a line is a bond, and if a separate element is not described, the point where the bond and the bond meet is carbon, and the number of hydrogens satisfying the valence of the carbon is omitted.)

When the electrolyte solution additive represented by Formula 1 is added to the electrolyte solution of a battery, electrons are localized toward the O element due to the electronegativity difference between the P element and the O element directly connected thereto. Accordingly, the P element becomes in an e-poor (δ+) state and an oxidation reaction is induced in an electrolyte containing lithium ions, thereby forming a stable film on the electrode, in a specific example, the cathode. At this time, it is possible to prevent the decomposition of the electrolyte due to the stability of the film, and thereby cycle characteristics can be improved. There is an excellent effect of greatly improving.

In addition, since the increase in resistance is prevented, charging efficiency and output are improved, and gas generation due to a chemical reaction inside the battery is also suppressed, so that the safety of the battery can be improved.

In addition, the capacity retention is improved by preventing the structural collapse of the electrode active material of the positive electrode and the negative electrode at a high temperature, thereby extending the lifespan.

When the chemical structure of the compound represented by Formula 1 is symmetrical, the electron flow in the molecule is stabilized as a symmetrical cyclic structure, and through this, molecular rigidity is increased and the battery performance improvement effect is further improved. However, it is not limited thereto, and the above-described effects of the present invention can be exhibited even in an asymmetric structure.

The electrolyte additive represented by Formula 1 may be included in an amount of 0.1 to 10% by weight, preferably 0.2 to 5.0% by weight, more preferably 0.4 to 2.0% by weight, still more preferably based on 100% by weight of the total battery electrolyte. may be included in 0.5 to 1.5 wt%. Within the above range, the effect of improving the charging efficiency and high temperature life of the battery may be the most excellent.

The present invention also provides an electrolytic solution comprising the electrolytic solution additive of the present invention. The electrolyte is an electrolyte of a non-aqueous lithium secondary battery, and includes the electrolyte additive, an organic solvent, and a lithium salt.

The organic solvent may be, for example, a carbonate-based organic solvent, specifically ethylene carbonate (EC), diethyl carbonate (DEC), ethylmethyl carbonate (EMC), dimethyl carbonate (DMC), propylene carbonate (PC), di It may be an organic solvent comprising at least one selected from the group consisting of propyl carbonate (DPC), butylene carbonate, methylpropyl carbonate, and ethylpropyl carbonate.

The organic solvent may be, for example, one type or a mixed solvent of two or more types, and preferably, an organic solvent having high ionic conductivity and a viscosity of the solvent having high ionic conductivity so as to increase the charge/discharge performance of the battery to be applied to the battery. A low-viscosity organic solvent that can be adjusted to have an appropriate viscosity may be mixed and used as a mixed solvent.

EC and PC may be used as an example of the organic solvent having a high dielectric constant, and EMC, DMC, and DEC may be used as the low viscosity organic solvent, and the high dielectric constant and low viscosity organic solvent is 2: It is preferable to use the mixture in a volume ratio of 8 to 8:2. More specifically, it may be a ternary mixed solvent of EC or PC, EMC and DEC, and the ratio of EC or PC to EMC and DEC may be 3: 3 to 5: 2 to 4 by volume.

The organic solvent may be used, for example, in an amount remaining after subtracting the content of components other than the organic solvent in the electrolyte solution.

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

The lithium salt may be used without particular limitation as long as it is a compound capable of providing lithium ions used in a lithium secondary battery, and specifically, LiPF ₆ , LiBF 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 SO 3 Li and (CF ₃ SO ₂₎ may include at least one selected from the group consisting of ₂ NLi have. Preferably, it may be _{LiPF 6 .}

When the lithium salt is dissolved in the electrolyte, the lithium salt functions as a source of lithium ions in the lithium secondary battery, and may promote movement of lithium ions between the positive electrode and the negative electrode. Accordingly, the lithium salt is preferably contained in a concentration of about 0.6 to 2 M in the electrolyte. If the concentration of the lithium salt is less than 0.6 M, the conductivity of the electrolyte may be lowered, so that electrolyte performance may be deteriorated. 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 to 1.6 M, more preferably 0.8 to 1.5 M.

The electrolyte of the present invention, for example, in addition to the electrolyte additive represented by Formula 1 above, an additive (hereinafter, other additives ) may be further included.

Preferred examples of the other additive components include Vinylene Carbonate, Fluoro Ethylene Carbonate, Vinyl Ethylene Carbonate, Ethyl propionate, Propyl propionate, 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, Succinonitrile, 1-Ethyl-3-methylimidazolium dicyanamide, Trimethoxyboroxine, Lithium Bis(oxaleto)borate, Lithium DiFluro(Oxalato) Borate , Tris(trimethylsilyl) borate, Lithium Tetrafluoroborate, Triisopropyl borate, Lithium tetrafluro(oxalato) Phosphate, Lithium DiFluro(bisoxalato) Phosphate, lithium difluorophosphate, Diethyl (difluoromethyl)phosphonate, Tris(trimethylsilyl) Phosphite, Tripropagyl phosphate, 2propagyl phosphate ,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 , ethylene sulfate, 1-propene-1,3-sultone, 1,3-propylene sulf At least one selected from the group consisting of ate, 1,4-Butane sultone, Sulfolene, Biphenyl, Cyclo Hexyl Benzene, 4-Fluorotoluene, Triphenyl phosphate, Fluoro benzene, and 2-fluoro-biphenyl, and another preferred example is a metal phosphate-based compounds may be included.

The metal phosphate-based compound is selected from the group consisting of lithium difluoro (bisoxalato) phosphate (LiDFOP), lithium tetrafluoro oxalato phosphate (LiTFOP), lithium difluorophosphate and lithium trioxalato phosphate. more than one

The metal phosphate-based compound is a component added to improve the performance of a lithium secondary battery, a lithium ion capacitor, etc., and may be included in the electrolyte in an amount of 0.3 to 1.5 wt%, preferably 0.7 to 1.2 wt%. When the content of the metal phosphate-based compound satisfies the above range, it is preferable in terms of improving the low-temperature characteristics and cycle characteristics of the battery.

The secondary battery of the present invention is a negative electrode, a positive electrode. It characterized in that it comprises a separation foil interposed between the cathode and the anode, and the electrolyte.

The positive electrode may be prepared by, for example, mixing a positive electrode active material, a binder, and optionally a conductive agent to prepare a composition for forming a positive electrode active material layer, and then applying it to a positive electrode current collector such as aluminum foil.

The positive active material may be, for example, a typical NCM (lithium nickel manganese cobalt oxide, LiNiMnCoO ₂ ) positive electrode active material used in lithium secondary batteries, specifically, the formula Li[NixCo _1-xy Mn _y ]O ₂ (where 0 It may be a lithium composite metal oxide in the form of <x<0.5, 0<y<0.5), but is not limited thereto.

_{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 of the positive active material, a compound capable of reversible intercalation and de-intercalation of lithium (a lithiated intercalation compound) may be used.

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

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

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

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

As the metal alloyable 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 negative electrode active material. As the negative active material, in view of high stability, any one or more selected from the group consisting of crystalline carbon, amorphous carbon, carbon composite material, lithium metal, and an alloy containing lithium may be used.

In the secondary battery of the present invention, by adding the electrolyte additive represented by Formula 1 in addition to the metal phosphate-based compound added to the electrolyte to improve battery performance in the related art, compared to the case where only the conventional electrolyte additive is added, HPPC (Hybrid Pulse Power Characterization) ) method, such as battery charging resistance, output characteristics, capacity recovery characteristics and lifespan characteristics at a high temperature of 60 ° C. or higher, the effect of improving battery characteristics is further improved.

Specifically, in the secondary battery of the present invention, the discharge DC-IR resistance value measured at 60° C. may be 40.0 mΩ or less, preferably 38.0 mΩ, more preferably 32.8 to 35.3 mΩ. In addition, the secondary battery may have a recovery capacity (high temperature recovery capacity) of 850 mAh or more at 60°C, preferably 852 mAh or more, and more preferably 853.1 to 896.9 mAh. The lifetime maintenance efficiency (high temperature lifetime efficiency) of the secondary battery at 45° C. may be 85% or more, preferably 88% or more, and more preferably 89.9 to 94.4%.

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

In the present description, the recovery capacity indicates the capacity preservation 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 end-of-discharge voltage, and the discharged battery after recharging the battery to the end-of-discharge voltage. The discharged electric capacity at the time of discharging was measured, respectively, and the two capacity values were 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. This is a very important characteristic in a battery. When the electrolyte solution additive of the present invention is added to the electrolyte solution, the recovery capacity is improved by 9 to 28% compared to when only the conventional additive is used, so that it can be stored for a longer period of time with a single charge.

Therefore, when the battery of the present invention is used as a vehicle battery, the improvement of output, which becomes important depending on the size of the vehicle, and climate change, at low and high temperature, which is a problem due to the characteristics of the vehicle exposed to sunlight while driving or parking, performance is improved, and excellent performance as an automobile battery can be exhibited.

Hereinafter, preferred examples are presented to help the understanding of the present invention, but the following examples are merely illustrative of the present invention, and it will be apparent to those skilled in the art that various changes and modifications are possible within the scope and spirit of the present invention, It goes without saying that such variations and modifications fall within the scope of the appended claims.

Synthesis Example 1

A compound of Formula 2 below was synthesized.

[Formula 2]

Specifically, it was synthesized in the following two steps.

Specifically, 3 g (1eq) of lithium hexafluorophosphate was put into 50 ml of a three-necked flask prepared for drying, anhydrous SiCl ₄ (1.2eq) was added, and then _{6.6 g (2.1eq) of C 2} H ₂ O ₄ was slowly added dropwise for 1 hour. did

After completion of the dropwise addition, the mixture was purified by stirring at 120° C. for 30 minutes.

Then, 1 g (yield 15%) of the final material was obtained through purification of the synthesized material through fluorination treatment. As a result of confirming using IP spectroscopy, it was confirmed that the compound of Formula 2 was.

¹ H NMR (C ₆ D ₆ , 600 MHz) δ = 6.5 (m, 4H)

Example 1

As the organic solvent, a carbonate-based mixed solvent having a volume ratio of EC:EMC:CEC = 3:4:3 is used, and LiPF ₆ is dissolved to a concentration of 1.15M with a lithium salt, and is represented by Formula 2 as an electrolyte additive 0.5 wt% of the compound used was added to prepare an electrolyte for a battery. Here, the '0.5 wt% content' means an amount to be 0.5 wt% based on 100 wt% of the total solution after the electrolyte additive is added.

Example 2

As the organic solvent, a carbonate-based mixed solvent having a volume ratio of EC:EMC:CEC = 3:4:3 is used, and LiPF ₆ is dissolved to a concentration of 1.15M with a lithium salt, and is represented by Formula 2 as an electrolyte additive An electrolyte solution for a battery was prepared by adding 1.0 wt% of the compound to be used.

Example 3

As the organic solvent, a carbonate-based mixed solvent having a volume ratio of EC:EMC:CEC = 3:4:3 is used, and LiPF ₆ is dissolved to a concentration of 1.15M with a lithium salt, and is represented by Formula 2 as an electrolyte additive An electrolyte for a battery was prepared by adding 0.5 wt% of a compound represented by the following Chemical Formula 3 instead of the used compound.

[Formula 3]

Example 4

As the organic solvent, a carbonate-based mixed solvent having a volume ratio of EC:EMC:CEC = 3:4:3 is used, and LiPF ₆ is dissolved to a concentration of 1.15M with a lithium salt, and is represented by Formula 2 as an electrolyte additive An electrolyte for a battery was prepared by adding 1.0 wt% of the compound represented by Formula 3 instead of the used compound.

Comparative Example 1

It was carried out in the same manner as in Example 2, except that _{LiPO 2} F ₂ was used instead of the compound represented by Formula 2 as the electrolyte additive.

Comparative Example 2

As an electrolyte additive, it was carried out in the same manner as in Example 1, except that 0.5 wt% of lithium difluoro (oxalato) phosphate, which is a phosphate having an asymmetric structure, was added instead of the compound represented by Formula 2 above.

manufacture of batteries

_{Li (Ni 0.5} Co _0.2 Mn _0.3 )O ₂ 92 wt% as a positive active material, 4 wt% of carbon black as a conductive agent, and 4 wt% of polyvinylidene fluoride (PVdF) as a binder N-methyl- as a solvent It was added to 2-pyrrolidone (NMP) to prepare a positive electrode mixture slurry. The positive electrode mixture slurry was applied to an aluminum (Al) thin film as a positive electrode current collector having a thickness of about 20 μm, dried to prepare a positive electrode, and then a positive electrode was manufactured by performing a roll press.

Carbon powder as an anode active material, PVdF as a binder, and carbon black as a conductive agent in 96 wt%, 3 wt%, and 1 wt%, respectively, were added to NMP as a solvent to prepare an anode mixture slurry. The negative electrode mixture slurry was applied to a 10 μm-thick copper (Cu) thin film as a negative electrode current collector, dried to prepare a negative electrode, and then roll press was performed to prepare a negative electrode.

After preparing a pouch-type battery in a conventional manner with a separator consisting of three layers of polypropylene/polyethylene/polypropylene (PP/PE/PP) for the positive and negative electrodes prepared as described above, Examples 1 to 4, Comparative Examples Preparation of the lithium secondary battery was completed by injecting the electrolyte solution prepared in 1 and 2.

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 document “Battery test manual for plug-in hybrid electric vehicles,” (2010, Idaho National Laboratory for the U.S. Department of Energy.).

After standing at 60 ℃ for 5 hours, the measured voltage value, the charge/discharge current value corresponding to the C-rate, the current change amount (∆I), the discharge voltage change amount (∆V), the charge voltage change amount (∆V), the discharge resistance, the charge resistance was measured, and the initial resistance value (initial DCIR value) was calculated with the slope value obtained from the amount of change in current and voltage by briefly flowing charge/discharge current for each C-rate for a certain period of time.

[High temperature recovery capacity evaluation]

The charging conditions were a constant current of 1.0C and a voltage of 4.2V until the charging current became 1/10C. 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 and discharging conditions, it was stored in a thermostat at 60°C for 4 weeks, and then discharged to a discharge voltage of 3V at room temperature at 25°C, and the remaining capacity was measured. After performing 100 times under the same charge/discharge conditions, the recovery capacity was measured and the average value thereof was calculated.

[High temperature life evaluation]

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

The high-temperature lifetime efficiency (%) in the item was calculated by substituting the discharge capacity measured at the initial cycle (1 cycle) and the discharge capacity measured at the end (300 cycle) cycle into the following Equation 1.

[Equation 1]

High temperature lifetime efficiency (%) = {discharge capacity at 300 cycles / discharge capacity at 1 cycle} X 100

division Additive type additive
Content (wt%) initial discharge resistance
(Initial DCIR)
(mΩ) high temperature recovery
Volume
(mAh) high temperature life
efficiency
(%) Example 1 Formula 2 0.5 33.6 853.1 89.8 Example 2 Formula 2 1.0 32.8 854.2 89.9 Example 3 Formula 3 0.5 35.3 895.7 94.3 Example 4 Formula 3 1.0 34.4 896.9 94.4 Comparative Example 1 LiPO ₂ F ₂ 1.0 45.0 780.0 85.7 Comparative Example 2 Lithium difluoro(oxalato)phosphate 0.5 110.0 650.0 80.0

As shown in Table 1, in the case of the secondary battery using the compound represented by the specific formula 1 according to the present invention, the initial discharge resistance value was 32.8 to 35.3 mΩ, but a comparison using only the _{conventional electrolyte additive LiPO 2} F ₂ In the case of Example 1, it was 45.0 mΩ, and in Comparative Example 2 using only lithium difluoro (oxalato) phosphate, which is an asymmetric phosphate, it was high as 110.0 mΩ. % was found to be lowered.

In addition, as a result of high temperature recovery capacity evaluation, it was found that the secondary battery using the electrolyte additive of the present invention was 853.1 to 896.9 mAh, whereas Comparative Examples 1 and 2 were 780 mAh and 650 mAh compared to the Example of the present invention. can This means that, by using the electrolyte additive of the present invention, the recovery power of the battery is also improved while repeating 300 cycles at a high temperature compared to when only the conventional electrolyte additive is used, and thus the cycle characteristics of the battery in a high-temperature environment using the electrolyte additive of the present invention and It can be seen that the lifetime efficiency is improved.

Furthermore, as a result of evaluation of high temperature life efficiency, in the case of the secondary battery using the electrolyte additive of the present invention, 89.8 to 94.4%, whereas in Comparative Examples 1 and 2, 85.7% and 80.0%, 14.4% maximum compared to the embodiment of the present invention It can be seen that p (% point) is low. This means that by using the electrolyte additive of the present invention, the capacity retention rate of the battery is improved while repeating 300 cycles at a high temperature of 45° C. compared to when only the conventional electrolyte additive is used. It can be seen that the cycle characteristics and life efficiency of

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

Claims (14)

An electrolyte solution additive comprising a compound represented by the following formula (1).
[Formula 1]

(In Formula 1, X ₁ and X ₂ are independently F, Cl, Br or I, and E ₁ and E ₂ are independently a substituted or unsubstituted hydrocarbon group having 1 to 3 carbon atoms, wherein the substitution is =O, -CX' ₃ and -CH ₂ CX" ₃ is substituted with one or more selected from the group consisting of, wherein X' and X" are independently F, Cl, Br or I, and included in _{E 1} and E ₂ The bonds between the two carbons are single or double bonds.) The method of claim 1,
The compound represented by the formula (1) is an electrolyte solution additive, characterized in that at least one selected from the group consisting of compounds represented by the following formulas (2) to (3).
[Formula 2]

[Formula 3]

(In Formulas 2 and 3, a line is a bond, a point where a bond and a bond not describing a separate element meet is carbon, and the number of hydrogens satisfying the valence of the carbon is omitted.) An electrolyte comprising an organic solvent, a lithium salt and an electrolyte additive, comprising:
The electrolyte solution additive is an electrolyte solution comprising a compound represented by the following formula (1).
[Formula 1]

(In Formula 1, X ₁ and X ₂ are independently F, Cl, Br or I, and E ₁ and E ₂ are independently a substituted or unsubstituted hydrocarbon group having 1 to 3 carbon atoms, wherein the substitution is =O, -CX' ₃ and -CH ₂ CX" ₃ is substituted with one or more selected from the group consisting of, wherein X' and X" are independently F, Cl, Br or I, and are included in _{E 1} and E ₂ Bonds between carbons are single or double bonds.) 4. The method of claim 3,
The electrolyte solution additive is an electrolyte, characterized in that it is included in an amount of 0.1 to 10% by weight based on 100% by weight of the total electrolyte. 4. The method of claim 3,
The compound represented by Formula 1 is an electrolyte solution, characterized in that it has a symmetrical structure. 4. The method of claim 3,
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 and at least one selected from the group consisting of ethylpropyl carbonate. 4. The method of claim 3,
The lithium salt is LiPF ₆ , 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 SO ₃ Li and (CF ₃ SO ₂ ) ₂ An electrolyte comprising at least one selected from the group consisting of NLi. 4. The method of claim 3,
The electrolyte solution, characterized in that it comprises a metal phosphate-based compound. 4. The method of claim 3,
The metal phosphate-based compound comprises at least one selected from the group consisting of lithium difluoro (bisoxalato) phosphate, lithium tetrafluoro oxalato phosphate, lithium difluorophosphate and lithium trioxalato phosphate. Electrolyte, characterized in that. A secondary battery comprising a negative electrode, a positive electrode, a separator interposed between the negative electrode and the positive electrode, and an electrolyte,
The electrolyte is a secondary battery, characterized in that the electrolyte of any one of claims 3 to 9. 11. The method of claim 10,
The secondary battery, characterized in that the HPPC charging resistance value of 40.0 mΩ or less at 60 ℃. 11. The method of claim 10,
The secondary battery is a secondary battery, characterized in that the recovery capacity at 60 ℃ 853.1 mAh or more. 11. The method of claim 10,
The secondary battery is a secondary battery, characterized in that the lifespan efficiency at 45 ℃ 85% or more. 11. The method of claim 10,
The secondary battery is a secondary battery, characterized in that the battery for a vehicle or an energy storage system (ESS).