KR20230127728A - Electrolyte for secondary battery, manufacturing method thereof, and secondary battery comprising same - Google Patents

Abstract

An electrolyte for a secondary battery according to one embodiment of the present invention comprises a compound containing a functional group represented by the following chemical formula 1. [Chemical formula 1] In the above chemical formula 1, A is O or C and R1 and R2 are same or different and independently selected from hydrogen, a halogen, substituted or unsubstituted straight or branched chain with 30 or less carbon atoms, such as an alkyl group, a cycloalkyl group, an alkenyl group, a cycloalkenyl group, an alkynyl group, a cycloalkynyl group, an aryl group, a heteroaryl group, an arylalkyl group, and an arylalkenyl group. The electrolyte of the present invention can improve the electrochemical performance, reaction speed and stability of a secondary battery.

Description

Electrolyte for secondary battery and secondary battery including the same

The present invention relates to a novel secondary battery electrolyte capable of improving the performance of the secondary battery and a secondary battery including the same.

Batteries are used as power sources for portable electronic devices such as video cameras, mobile phones, and notebook computers. Rechargeable secondary batteries, especially lithium secondary batteries, have three times higher energy density per unit weight than conventional lead storage batteries, nickel-cadmium batteries, nickel-metal hydride batteries, and nickel-zinc batteries, and can be charged at high speed.

Demand for such secondary batteries, particularly lithium secondary batteries, is rapidly increasing, and accordingly, a lot of research has been conducted on lithium secondary batteries having high energy density and discharge voltage, and they have been commercialized and widely used.

Compared to other batteries, lithium secondary batteries have advantages such as light weight, small volume, high operating voltage, high energy density, high output power, high charging efficiency, no memory effect, and long lifespan. It has been widely applied in the field of digital products such as mobile phones and laptops, and is considered one of the best choices for electric vehicles and large-scale energy storage devices.

Recently, as the development of medium and large-sized lithium secondary batteries such as electric vehicles is progressing, various studies are being conducted to realize high voltage and high capacity lithium secondary batteries. This is where additives are needed.

International Publication No. WO 2019-013501 A1

The present invention is intended to provide a novel electrolyte for a secondary battery capable of improving the electrochemical performance, reaction rate and stability of the secondary battery.

An object of the present invention is to provide an electrolyte for a secondary battery having excellent charge/discharge characteristics, output characteristics, capacity characteristics, and voltage characteristics in a secondary battery by improving stability and durability of a negative electrode and a positive electrode.

In addition, the present invention is to provide an electrolyte for a secondary battery that sufficiently improves the capacity retention rate and life retention rate of the secondary battery by forming a protective film on the surface of the anode of the secondary battery.

An electrolyte for a secondary battery according to an embodiment of the present invention includes a compound including a functional group represented by Formula 1 below.

[Formula 1]

In Formula 1, A is O or C, R1 and R2 are the same as or different from each other and are each independently hydrogen; halogen; As a substituted or unsubstituted straight chain or branched chain having 30 or less carbon atoms, an alkyl group, a cycloalkyl group, an alkenyl group, a cycloalkenyl group, an alkynyl group, a cycloalkynyl group, an aryl group, a heteroaryl group, an arylalkyl group, and an arylalkenyl group; are selected from

As a more preferable example, the compound including the functional group represented by Formula 1 may be a compound represented by Formula 1-1 below.

[Formula 1-1]

In Formula 1-1, A, R1 and R2 are the same as defined in Formula 1, and R3 is a substituted or unsubstituted straight chain or branched chain having 10 or less carbon atoms, an alkylene group, an alkenylene group, an alkynylene group, an aryl It is selected from a rene group and a heteroarylene group, R4 is hydrogen; halogen; As a substituted or unsubstituted straight chain or branched chain having 10 or less carbon atoms, an alkyl group, a cycloalkyl group, an alkenyl group, a cycloalkenyl group, an alkynyl group, a cycloalkynyl group, an aryl group, a heteroaryl group, an arylalkyl group, and an arylalkenyl group; are selected from

As a more preferable example, the compound including the functional group represented by Formula 1 may be a compound represented by Formula 1-1-1.

[Formula 1-1-1]

In Formula 1-1-1, A, R1 and R2 are as defined in Formula 1 above.

As a more preferred example, the compound containing the functional group represented by Formula 1 may be a compound represented by Formula A or Formula B below.

[Formula A]

[Formula B]

As a more preferable example, the compound containing the functional group represented by Formula 1 may be included in an amount of 0.1 to 10% by weight based on the total weight of the electrolyte for a secondary battery.

As a more preferable example, the electrolyte for the secondary battery may include a lithium salt; menstruum; and additives other than the compound containing the functional group represented by Formula 1; It may further include any one or more selected from among.

A secondary battery according to an embodiment of the present invention includes a cathode including a cathode active material; a negative electrode including a negative electrode active material; and the secondary battery electrolyte included between the positive electrode and the negative electrode.

The present invention provides a novel electrolyte for a secondary battery capable of improving the electrochemical performance, reaction rate and stability of the secondary battery.

The electrolyte for a secondary battery improves stability and durability of a negative electrode and a positive electrode, so that the secondary battery has excellent charge/discharge characteristics, output characteristics, capacity characteristics, and voltage characteristics.

In addition, the secondary battery electrolyte has an effect of sufficiently improving the capacity retention rate and life retention rate of the secondary battery by forming a protective film on the surface of the anode of the secondary battery.

Embodiments of the technical idea of the present invention may provide various effects not specifically mentioned.

1 is an NMR analysis result of a compound prepared by Synthesis Example 1 of the present invention.
2 is an NMR analysis result of the compound prepared by Synthesis Example 2 of the present invention.

The advantages and features of the present invention, and how to achieve them, will become clear with reference to the detailed description of the embodiments below. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms.

As used herein, “comprising” should be understood as an open-ended term that connotes the possibility of including other embodiments.

As used herein, “preferred” and “preferably” refer to embodiments of the invention that may provide certain advantages under certain circumstances. However, other embodiments may also be preferred, under the same or other circumstances. Additionally, the recitation of one or more preferred embodiments does not imply that the other embodiments are not useful, nor is it intended to exclude the other embodiments from the scope of the present invention.

An electrolyte for a secondary battery according to an embodiment of the present invention includes a compound including a functional group represented by Formula 1 below.

[Formula 1]

In Formula 1, A is O or C, R1 and R2 are the same as or different from each other and are each independently hydrogen; halogen; As a substituted or unsubstituted straight chain or branched chain having 30 or less carbon atoms, an alkyl group, a cycloalkyl group, an alkenyl group, a cycloalkenyl group, an alkynyl group, a cycloalkynyl group, an aryl group, a heteroaryl group, an arylalkyl group, and an arylalkenyl group; are selected from

As used herein, 'substituted or unsubstituted' refers to a halogen, a cyano group, a nitro group, a hydroxyl group, a carbonyl group, an ester group, an imide group, an amino group, a phosphine oxide group, an alkoxy group, an aryloxy group, an alkylthioxy group, An arylthioxy group, an alkylsulfoxyl group, an arylsulfoxyl group, a silyl group, a boron group, an alkyl group, a cycloalkyl group, an alkenyl group, an alkynyl group, an aryl group, an aralkyl group, an aralkenyl group, an alkylaryl group, an alkylamine group. It is substituted or unsubstituted with one or more substituents selected from the group consisting of an aralkylamine group, a heteroarylamine group, an arylamine group, an arylphosphine group, and a heterocyclic group.

The secondary battery may be a lithium ion secondary battery, a lithium metal secondary battery, a lithium polymer secondary battery, a lithium ion polymer secondary battery, a lithium sulfur secondary battery, or an all-solid-state battery, but the secondary battery is not limited thereto.

In addition, the electrolyte for the secondary battery may be an electrolyte, a solid electrolyte, and/or a gel electrolyte, but is not limited thereto.

A compound containing a functional group represented by Formula 1 may be purchased or prepared.

As a more preferable example, the compound including the functional group represented by Formula 1 may be a compound represented by Formula 1-1 below.

[Formula 1-1]

In Formula 1-1, A, R1 and R2 are the same as defined in Formula 1, and R3 is a substituted or unsubstituted straight chain or branched chain having 10 or less carbon atoms, an alkylene group, an alkenylene group, an alkynylene group, an aryl It is selected from a rene group and a heteroarylene group, R4 is hydrogen; halogen; As a substituted or unsubstituted straight chain or branched chain having 10 or less carbon atoms, an alkyl group, a cycloalkyl group, an alkenyl group, a cycloalkenyl group, an alkynyl group, a cycloalkynyl group, an aryl group, a heteroaryl group, an arylalkyl group, and an arylalkenyl group; are selected from

As a more preferable example, the compound including the functional group represented by Formula 1 may be a compound represented by Formula 1-1-1.

[Formula 1-1-1]

In Formula 1-1-1, A, R1 and R2 are as defined in Formula 1 above.

As a more preferable example, the compound containing the functional group represented by Formula 1 may be a compound represented by Formula A below.

[Formula A]

As an example, the compound represented by Formula A is reacted in an organic solvent by adding oxazolidone to prop-2-yn-1-yl 1H-imidazole-1-carboxylate or prop-2-yn-1-yl carbonochloridate ; removing hydrochloric acid salts or by-products produced after completion of the reaction; It can be prepared including; and removing the solvent.

As an example, the reaction may be carried out according to the following Scheme A-1 or A-2.

[Scheme A-1]

[Scheme A-2]

In addition, as a more preferable example, the compound including the functional group represented by Formula 1 may be a compound represented by Formula B below.

[Formula B]

As an example, the compound represented by Formula B is reacted in an organic solvent by adding 2-Pyrrolidone to prop-2-yn-1-yl 1H-imidazole-1-carboxylate or prop-2-yn-1-yl carbonochloridate. step of doing; removing hydrochloric acid salts or by-products produced after completion of the reaction; It can be prepared including; and removing the solvent.

As an example, the reaction may be carried out according to the following Scheme B-1 or B-2.

[Scheme B-1]

[Scheme B-2]

When preparing Formula A or B, the prop-2-yn-1-yl 1H-imidazole-1-carboxylate or prop-2-yn-1-yl carbonochloridate can be used both as a reagent and for industrial use, but high moisture is reactive Since it causes progress and a decrease in yield, the lower the moisture, the better.

In the above reaction, 1 to 4 equivalents, preferably 1 to 3 equivalents, and more preferably 1 to 2 equivalents of each of the carbonochloridate and carboxylate compounds can be used for 1 equivalent of oxazolidone or 2-Pyrrolidone.

The organic solvent may be any one or more selected from methylene chloride, dichloroethane, diethyl ether, diisopropyl ether, and toluene, and in addition, it may be synthesized in a water immiscible lipophilic organic solvent, and also mentioned in the present invention Solvents that are not used may also be used.

The water content of the organic solvent is preferably 10 to 1000 ppm. If the above range is exceeded, impurities such as carbonochloridate and carboxylate, which are raw materials, are decomposed by moisture.

The reaction temperature may be -5 to 100 °C, more preferably -5 to 50 °C. The reaction is preferably conducted under a nitrogen atmosphere.

In the reaction step, a base may be further added, and more preferably, an amine-based base may be added as an organic base. For example, when using carbonochloridate, triethylamine or pyridine may be added.

Next, a step of removing hydrochloride or by-products generated after completion of the reaction is performed, which may be performed through a filtration process or the like.

Next, a step of removing the solvent after completion of the reaction is performed. At this time, the step of removing residual amine such as residual triethylamine or pyridine in the step of removing the solvent may be further included.

Next, the solvent-free solution may be distilled to remove impurities.

Next, an organic solvent is introduced to extract the material, and this process can be repeated several times.

As an example, the solvent for extraction is an organic solvent capable of layer separation with water, and the organic solvent may be at least one selected from methylene chloride, dichloroethane, diethyl ether, diisopropyl ether, and toluene, and more preferably In addition to acetate and carbonate, lipophilic organic solvents immiscible with water are preferred. In addition, solvents not mentioned in the present invention can also be used.

Next, a step of removing the extraction solvent is performed. In this case, the step of removing the residual organic base may be further included in the step of removing the solvent.

After that, trace amounts of raw material residues and by-products can be removed through recrystallization, and in addition, methods such as column chromatography can be used.

As a more preferred example, the compound containing the functional group represented by Chemical Formula 1 may be included in an amount of 0.1 to 10% by weight, 0.5 to 5% by weight, or 1 to 3% by weight based on the total amount of the electrolyte for a secondary battery. When included within the above content range, it is possible to prevent decomposition of the electrolyte and damage to the positive electrode active material, thereby improving the capacity retention rate and life retention rate of the battery.

As an example, the secondary battery electrolyte may further include a lithium salt and a solvent.

As an example, the lithium salt is LiPF ₆ , LiBF ₄ , LiB ₁₂ F ₁₂ , LiAsF ₆ , LiFSO ₃ , Li ₂ SiF ₆ , LiCF ₃ CO ₂ , LiCH ₃ CO ₂ , LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , LiCF ₃ CF ₂ SO ₃ , LiCF ₃ (CF ₂ ) ₇ SO ₃ , LiCF ₃ CF ₂ (CF ₃ ) ₂ CO, Li(CF ₃ SO ₂ ) ₂ CH, LiNO ₃ , LiN(CN) ₂ , LiN (FSO ₂ ) ₂ , LiN(F ₂ SO ₂ ) ₂ , LiN(CF ₃ SO ₂ ) ₂ , LiN(C ₂ F ₅ SO ₂ ) ₂ , LiC(CF ₃ SO ₂ ) ₃ , LiP(CF ₃ ) ₆ , LiPF(CF ₃ ) ₅ , LiPF ₂ (CF ₃ ) ₄ , LiPF ₃ (CF ₃ ) ₃ , LiPF ₄ (CF ₃ ) ₂ , LiPF ₄ (C ₂ F ₅ ) ₂ , LiPF ₄ (CF ₃ SO ₂ ) ₂ , LiPF ₄ (C ₂ F ₅ SO ₂ ) ₂ , LiBF ₂ C ₂ O ₄ , LiBC ₄ O ₈ , LiBF ₂ (CF ₃ ) ₂ , LiBF ₂ (C ₂ F ₅ ) ₂ , LiBF ₂ (CF ₃ SO ₂ ) ₂ , LiBF ₂ (C ₂ F ₅ SO ₂ ) ₂ , LiSbF ₆ , LiAlO ₄ , LiAlF ₄ , LiSCN, LiClO ₄ , LiCl, LiF, LiBr, LiI, LiAlCl ₄ It may be any one or more selected, but It is not limited.

As an example, the solvent is preferably an organic solvent in which the electrolyte additive can be dissolved, and all solvents that can be commonly used in secondary batteries may be used, and are not particularly limited thereto. As an example, carbonate-based, ester-based, ether-based, ketone-based, alcohol-based, or aprotic solvents may be used. In addition, as an embodiment, at least one or more of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) may be included.

In addition, the electrolyte for a secondary battery may further include another additive. As an example, the additive may be at least one selected from carbonate-based compounds, sultone-based compounds, and phosphazene-based compounds, but is not limited thereto. More preferably, the electrolyte of the linear phosphinate structure according to an embodiment of the present invention is an oxalatoborate-based, oxalatophosphate-based, fluorine-substituted carbonate-based, vinylidene carbonate-based, and sulfyic acid electrolyte. It is possible to improve the stability and durability of the negative electrode and the positive electrode of the secondary battery compared to the case of further including any one or more additives selected from the group consisting of yl group-containing compounds.

A secondary battery according to an embodiment of the present invention includes a cathode including a cathode active material; a negative electrode including a negative electrode active material; and the secondary battery electrolyte included between the positive electrode and the negative electrode.

The cathode includes a current collector and a cathode active material layer formed on the current collector, and the cathode active material layer may further include a binder or a conductive material in addition to the cathode active material. The cathode active material is not particularly limited as long as it is a compound capable of intercalation and deintercalation of ions. As an example, the cathode active material is LiNi _x Co _y Mn _z L _(1-xyz) O ₂ (0≤x≤1, 0≤y≤1, 0≤z≤1, and L is Al, Sr, Mg, At least one selected from Ti, Nb, V, Ca, Zr, Zn, Sn, Si and Fe), LiNi _x Co _y Al _z L _(1-xyz) O ₂ (0≤x≤1, 0≤y≤1 , 0≤z≤1 and L is at least one selected from Al, Sr, Mg, Ti, Nb, V, Ca, Zr, Zn, Sn, Si and Fe), wLi ₂ MnO ₃ (1-w)LiMn _a Ni _b Co _c L _(1-abc) O ₂ (0<w<1, 0≤a≤1, 0≤b≤1, 0≤c≤1, and L is Al, Sr, Mg, Ti, Nb, At least one selected from V, Ca, Zr, Zn, Sn, Si, Sb, and Fe), Li _1.2 Mn _0.8-a L _a O ₂ (0≤a≤0.8, and L is Al, Sr, Mg, Ca, At least one selected from Ti, V, Cr, Ni, Co, Fe, Cu, Nb, W, Zr, Zn, Sn, Sb and Si), LiMPO ₄ (M is any one selected from Fe, Co, Ni, and Mn) one or more), LiMn _2-x M _x O ₄ (0≤x<1 and M is any one or more selected from Ni, Co, Fe, Cr, V, Ti, Nb, Cu, Sn, Sb and Si), Li ₂ N _1-x M _x O ₃ (0≤x<1, N is at least one selected from Mn, Ni, Sn, Fe, Ru, and Ir, and M is Ti, Mn, Sn, Sb, Ru, and Te At least one selected from), and Li _1+x N _yz M _z O ₂ (0≤x≤1, N is at least one selected from Ti and Nb, M is any one selected from V, Ti, Mo and W or more) may be any one or more selected from among.

The negative electrode includes a current collector and a negative active material layer formed on the current collector, and the negative active material layer may further include a binder or a conductive material in addition to the negative active material. The negative electrode active material is not particularly limited as long as it is a material capable of reversibly intercalating and deintercalating ions. As an example, a carbon-based or silicon-based negative electrode active material may be used.

However, more preferably, the cathode active material may be an overlithiated layered oxide (OLO) system. In addition, the anode active material may be silicon-based.

In a general lithium secondary battery, a lithium salt dissolved in an organic solvent is used as an electrolyte, and an overlithiated layered oxide (OLO)-based cathode active material creates a high voltage environment while generating oxygen gas during first charge. In addition, the silicon-based negative electrode active material undergoes serious volume expansion due to repeated charging and discharging, and cracking is formed on its surface. Therefore, in the end, the decomposition reaction of the electrolyte is commonly induced on the surface of the electrode to which each of the active materials is applied. As a result, the electrochemical performance of the battery is rapidly degraded due to the gradual depletion of the electrolyte solution, and the electrochemical reaction rate of the battery is lowered as a thick film acting as resistance is formed on the surface of each electrode, resulting in the decomposition of the electrolyte solution. There is a problem in that the electrochemical stability of the battery is not guaranteed because acidic substances (eg, HF, etc.) that dissolve each electrode film or damage the cathode active material.

The electrolyte for a secondary battery containing a compound containing a functional group represented by Formula 1 of the present invention is particularly well generated in a secondary battery including an overlithiated layered oxide (OLO)-based positive electrode active material and/or a silicon-based negative electrode active material By solving such a problem, the electrochemical performance can be improved.

When the secondary battery further includes a separator, the separator is a porous polymer film, for example, ethylene homopolymer, propylene homopolymer, ethylene/butene copolymer, ethylene/hexene copolymer, and ethylene/methacrylate copolymer. Porous polymer films made of polyolefin-based polymers may be used alone or by laminating them, or ordinary porous nonwoven fabrics such as high melting point glass fibers and polyethylene terephthalate fibers may be used, but are limited thereto. It is not.

As a more preferable example, the average charging voltage of the secondary battery may be 4.5V or more. This is a high-range voltage that can be developed as the positive electrode including the lithium positive electrode active material and/or the negative electrode including the silicon-based negative electrode active material is applied, and can be stably maintained by the functional additive included in the electrolyte of the present invention. can

The manufacturing method of the secondary battery is based on a known manufacturing method, and a detailed description thereof will be omitted.

Hereinafter, the present invention will be described in more detail through examples. Embodiments of the present invention may be modified in many different forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. This embodiment is provided to more completely explain the present invention to those skilled in the art.

[Preparation of Electrolyte Additives]

[Synthesis Example 1] Preparation of prop-2-yn-1-yl 2-oxooxazolidine-3-carboxylate

Install a magnetic bar and thermometer in a 1L flask, and add 8.6g of 2-Oxazolidone. When 300 ml of acetonitrile (ACN) with a water content of 100 ppm or less is added as a solvent and completely dissolved after stirring, 16.3 g of prop-2-yn-1-yl 1H-imidazole-1-carboxylate is added and stirred to dissolve. When all solids are dissolved in the reactor, 3 g of 1,8-Diazabicyclo (5.4.0) undec-7-ene (DBU) is added and the progress of the reaction is monitored by GC or TLC. After the overnight reaction, 500 ml of 1M HCl aqueous solution was added and quenched to complete the reaction. Then, EA (100gX3) is added to try extraction, and brine (100g) is added to the organic layer to wash again. The obtained organic layer was filtered after adding MgSO ₄ to remove moisture. The filter filtrate is concentrated under reduced pressure to obtain a solid crude product. After this, EA was added again, refluxed, completely dissolved, and then recrystallization was attempted and filtered to obtain prop-2-yn-1-yl 2-oxooxazolidine-3-carboxylate, with a yield of about 68%.

[Synthesis Example 2] Preparation of prop-2-yn-1-yl 2-oxopyrrolidine-1-carboxylate

Install a magnetic bar and thermometer in a 1L flask, and add 8.4g of 2-Pyrrolidone. When 300 ml of acetonitrile (ACN) with a water content of 100 ppm or less is added as a solvent and completely dissolved after stirring, 16.3 g of prop-2-yn-1-yl 1H-imidazole-1-carboxylate is added and stirred to dissolve. When all solids are dissolved in the reactor, 3 g of 1,8-Diazabicyclo (5.4.0) undec-7-ene (DBU) is added and the progress of the reaction is monitored by GC or TLC. After the overnight reaction, 500 ml of 1M HCl aqueous solution was added and quenched to complete the reaction. Then, EA (100gX3) is added to try extraction, and brine (100g) is added to the organic layer to wash again. The obtained organic layer was filtered after adding MgSO ₄ to remove moisture. The filter filtrate is concentrated under reduced pressure to obtain a solid crude product. After that, EA was added again, refluxed, completely dissolved, recrystallized, and filtered to obtain prop-2-yn-1-yl 2-oxopyrrolidine-1-carboxylate, with a yield of about 65%.

[Preparation of Electrolyte]

[Example 1]

1 weight of 1M LiPF6 and fluoroethylene carbonate (FEC) in a non-aqueous organic solvent in which ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a ratio of 2:5:5 (v/v/v) %, and 2% by weight of the additive of Synthesis Example 1 was added to prepare an electrolyte solution for a secondary battery.

[Example 2]

1M LiPF ₆ and fluoroethylene carbonate (FEC) 1 in a non-aqueous organic solvent in which ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a ratio of 2:5:5 (v/v/v) An electrolyte solution for a secondary battery was prepared by adding 2% by weight of the additive of Synthesis Example 2, and adding 2% by weight of the additive by weight.

[Comparative Example 1]

An electrolyte solution for a secondary battery was prepared in the same manner as in Example 1, except that the additive of Synthesis Example 1 was not added.

[Manufacture of secondary battery]

A cathode was prepared using a composition for forming a cathode active material layer containing 94 wt% of LiCoO ₂ as a cathode active material, 3 wt% of polyvinylidene fluoride (PVDF) as a binder, and 3% of carbon black as a conductive material. In addition, a negative electrode was prepared using a composition for forming a negative electrode active material layer containing 96% by weight of graphite as a negative electrode material, 3% by weight of PVDF as a binder, and 1% by weight of carbon black as a conductive material.

After placing the separator on the positive electrode prepared above and placing the negative electrode on it again, the electrolyte solutions prepared in Examples 1 and 2 and Comparative Example 1 were injected, respectively, and vacuum packed to prepare a lithium secondary battery.

[Experimental Example] Secondary Battery Characteristics

Battery characteristics of the prepared secondary battery were evaluated as follows, and the results are shown in Table 1 below.

(1) Capacity retention rate (%)

Each of the secondary batteries manufactured according to Examples 1 and 2 and Comparative Example 1 was charged at room temperature (25°C) to 4.5V at 1C, discharged at 2.75V at 1C, and then charged at 0.5C to 4.2V at high temperature (45°C). After being left for 1 week, 1C charging up to 4.2V and 2.75V 1C discharging were performed, and the discharged capacity of the 2nd cycle was measured.

(2) Room temperature life retention rate (%)

Each of the secondary batteries manufactured according to Examples 1 and 2 and Comparative Example 1 was charged at room temperature (25° C.) at 1C to 4.5V, then discharged at 2C to 2.75V to measure the initial capacity, and after repeating this 500 times The capacity was measured, and the life retention rate at room temperature was calculated from the formula: life retention rate = (capacity after 500 repetitions/initial capacity) * 100.

(3) High temperature life retention rate (%)

Each of the secondary batteries manufactured according to Examples 1 and 2 and Comparative Example 1 was charged 1C to 4.5V at a high temperature (45° C.) and then discharged 2C to 2.75V to measure the initial capacity, and after repeating this 500 times The capacity was measured, and the high-temperature life retention rate was calculated from the formula: life retention rate = (capacity after 500 repetitions/initial capacity) * 100.

Example 1 Example 2 Comparative Example 1 Capacity retention rate (%) 87.1 84.3 61.3 Room temperature life retention rate (%) 91.4 91.2 67.0 High temperature life retention rate (%) 90.2 89.7 62.3

In the case of using the electrolyte solution containing the electrolyte additive of the present invention, it can be seen that the capacity retention rate and life retention rate of the lithium secondary battery are significantly improved compared to the case where the additive is not added.

Claims (7)

Including a compound containing a functional group represented by Formula 1 below,
Electrolyte for secondary battery:
[Formula 1]

In Formula 1, A is O or C,
R1 and R2 are the same as or different from each other and are each independently hydrogen; halogen; As a substituted or unsubstituted straight chain or branched chain having 30 or less carbon atoms, an alkyl group, a cycloalkyl group, an alkenyl group, a cycloalkenyl group, an alkynyl group, a cycloalkynyl group, an aryl group, a heteroaryl group, an arylalkyl group, and an arylalkenyl group; are selected from
According to claim 1,
The compound containing the functional group represented by Formula 1 is a compound represented by Formula 1-1 below,
Electrolyte for secondary battery:
[Formula 1-1]

In Formula 1-1, A, R1 and R2 are as defined in Formula 1,
R3 is a substituted or unsubstituted straight or branched chain having 10 or less carbon atoms, and is selected from an alkylene group, an alkenylene group, an alkynylene group, an arylene group, and a heteroarylene group;
R4 is hydrogen; halogen; As a substituted or unsubstituted straight chain or branched chain having 10 or less carbon atoms, an alkyl group, a cycloalkyl group, an alkenyl group, a cycloalkenyl group, an alkynyl group, a cycloalkynyl group, an aryl group, a heteroaryl group, an arylalkyl group, and an arylalkenyl group; are selected from
According to claim 1,
The compound containing the functional group represented by Formula 1 is a compound represented by Formula 1-1-1,
Electrolyte for secondary battery:
[Formula 1-1-1]

In Formula 1-1-1, A, R1 and R2 are as defined in Formula 1 above.
According to claim 1,
The compound containing the functional group represented by Formula 1 is a compound represented by Formula A or Formula B below,
[Formula A]

[Formula B]

According to claim 1,
The compound containing the functional group represented by Formula 1 is included in 0.1 to 10% by weight of the total electrolyte for a secondary battery,
Electrolyte for secondary batteries.
According to claim 1,
The electrolyte for the secondary battery may include a lithium salt; menstruum; and additives other than the compound containing the functional group represented by Formula 1; Further comprising any one or more selected from
Electrolyte for secondary batteries.
A cathode containing a cathode active material;
A negative electrode containing a negative electrode active material; and
Including, the electrolyte for a secondary battery of claim 1 included between the positive electrode and the negative electrode.
secondary battery.