KR102498343B1 - Electrolyte for lithium secondary battery and lithium secondary battery including the same - Google Patents

Abstract

[화학식 2]

[화학식 3]

[화학식 4]

상기 화학식 1 내지 화학식 4에서, R₁ 내지 R₃₅는, 각각, 수소, 할로겐, 알킬기, 페닐기, 카르복실기 또는 에스터기이다.The present invention relates to an electrolyte solution for a lithium secondary battery and a lithium secondary battery including the same, and one aspect of the present invention is a lithium salt; organic solvents; And a functional additive including at least one selected from the group consisting of compounds represented by Formulas 1 to 4 below; provides an electrolyte solution for a lithium secondary battery comprising:
[Formula 1]

[Formula 2]

[Formula 3]

[Formula 4]

In Formulas 1 to 4, R ₁ to R ₃₅ are hydrogen, halogen, an alkyl group, a phenyl group, a carboxyl group or an ester group, respectively.

Description

Electrolyte for lithium secondary battery and lithium secondary battery containing the same

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

Among the components of a lithium secondary battery, a cathode material is a factor that determines the capacity and operating voltage of the battery, and in order to improve the energy density of a lithium secondary battery, it is essential to increase the capacity and voltage of the cathode material.

Accordingly, studies on cathode materials exhibiting high capacity and high voltage are being actively conducted, and Ni-rich cathode materials having a high Ni content are known to have high energy densities compared to widely commercialized LiCoO ₂ .

However, the Ni-rich anode material has a problem in that the electrolyte is decomposed due to the elution of the transition metal under a high voltage condition of 4.3V (vs Li/Li ⁺ ) or higher. This reaction is accelerated by high-temperature conditions or HF formed by the reaction of LiPF ₆ salt with trace amounts of moisture unavoidably present in the battery. In other words, as the transition metal is irreversibly eluted by the reaction between HF and the anode, the activated Ni ⁴⁺ ions on the surface of the anode induce an additional decomposition reaction of the electrolyte, which destroys the SEI layer of the cathode, resulting in performance degradation. . In addition, Ni ²⁺ produced by the reduction of Ni ⁴⁺ migrates to the Li layer of the anode and causes cation mixing, thereby making the anode structurally unstable.

To solve this problem, many studies have been conducted to suppress the elution of transition metals from the Ni-rich anode. Specific examples include doping the anode with metals such as Al and Zr, coating inorganic components such as SiO _x and ZrO ₂ , forming a stable film on the surface of the electrode through a protective film forming electrolyte additive, or removing HF in the electrolyte There is a method such as using an electrolyte solution additive that does.

However, in these methods, when transition metal ions are eluted onto an electrolyte, they are transferred to an electron-rich negative electrode by an electric field and deposited thereon, thereby preventing lithium from entering and leaving the negative electrode, and the electrodeposited transition metal is an electrochemical catalyst that promotes electrolyte decomposition. It is not possible to suppress the progression of performance deterioration for reasons such as playing a role.

Therefore, it is necessary to develop a functional additive capable of chelating the transition metal ions in the electrolyte solution before the transition metal ions already eluted in the electrolyte solution are electrodeposited to the cathode.

The above background art is possessed or acquired by the inventor in the process of deriving the disclosure of the present application, and cannot necessarily be said to be known art disclosed to the general public prior to the present application.

The present invention is to solve the above-mentioned problems, and an object of the present invention is to suppress the elution of transition metals, as well as to chelate the eluted transition metal ions and to reduce HF generation, and functional additives including the same It is to provide an electrolyte solution for a lithium secondary battery.

However, the problem to be solved by the present invention is not limited to those mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the description below.

One aspect of the present invention, a lithium salt; organic solvents; And a functional additive including at least one selected from the group consisting of compounds represented by Formulas 1 to 4 below; provides an electrolyte solution for a lithium secondary battery comprising:

[Formula 1]

[Formula 2]

[Formula 3]

[Formula 4]

In Formulas 1 to 4, R ₁ to R ₃₅ are hydrogen, halogen, an alkyl group, a phenyl group, a carboxyl group or an ester group, respectively.

According to one embodiment, R ₁ to R ₃₅ are each selected from hydrogen, halogen, a C _1-20 alkyl group substituted with an unsubstituted or halogen substituent, a C _6-20 phenyl group substituted with an unsubstituted or halogen substituent, It may be an unsubstituted or C _1-20 carboxyl group substituted with _a halogen substituent, or a C _1-20 ester group unsubstituted or substituted with a halogen substituent.

According to one embodiment, the lithium salt is LiPF ₆ , LiClO ₄ , LiBF ₄ , LiFSI, LiTFSI, LiSO ₃ CF ₃ , LiBOB, LiFOB, LiDFBP, LiTFOP, LiPO ₂ F ₂ , LiCl, LiBr, LiI, 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, LiSCN, and LiC(CF ₃ SO ₂ ) ₃ selected from the group consisting of It may contain one or more.

According to one embodiment, the concentration of the lithium salt may be 0.1 M to 3 M.

According to one embodiment, the organic solvent may include one or more selected from the group consisting of carbonate-based solvents, ester-based solvents, and ether-based solvents.

According to one embodiment, the carbonate crab solvent is ethylene carbonate, propylene carbonate, vinylene carbonate, vinyl ethylene carbonate, dimethyl carbonate, ethyl It includes at least one selected from the group consisting of methyl carbonate and diethyl carbonate, and the ester solvent includes methyl propionate, propyl propionate, Butyl propionate, Methyl butyrate, Ethyl butyrate, Propylbutyrate, Butylbutyrate, Methyl acetate, Ethyl acetate, Propyl Group consisting of Propyl acetate, Butyl acetate, Butyrolactone, Decanolide, Valerolactone, Mevalonolactone and Caprolactone It includes one or more selected from, and the ether solvent is dimethyl ether (Dimethyl ether), diethyl ether (diethyl ether), diisopropyl ether (diisopropyl ether), 1,2-dimethoxyethane (1, 2-dimethoxyethane), diethylene glycol dimethyl ether, triethylene glycol dimethyl ether and tetraethylene glycol dimethyl ether (tetr ethylene glycol dimethyl ether) may include one or more selected from the group consisting of

According to one embodiment, the content of the functional additive may be 0.01% by weight to 10% by weight.

According to one embodiment, the functional additive is to chelate the transition metal eluted in the electrolyte solution, form a complex with PF ₅ contained in the electrolyte solution, or form a film on the surface of a lithium secondary battery electrode can

Another aspect of the present invention is a positive electrode; cathode; an ion permeable separator between the anode and the cathode; It provides a lithium secondary battery containing; and the electrolyte solution for the lithium secondary battery.

According to one embodiment, the anode may include a Ni-rich composite metal oxide and be layered.

According to one embodiment, the composite metal oxide is LiNi _w Co _x Mn _y O ₂ (w+x+y+z=1) or LiNi _w Co _x Mn _y M _z O ₂ (w+x+y+z = 1), wherein M may be Ti, Zr, Nb, W, P, Al, Mg, V, Ca or Sr.

According to one embodiment, the negative electrode may include graphite, silicon, or both.

According to one embodiment, the driving voltage may be 3.0 V to 4.3 V, and the driving temperature may be 25 °C to 45 °C.

The electrolyte solution for a lithium secondary battery according to the present invention, by including a functional additive, not only chelates the transition metal ions eluted from the cathode on the electrolyte solution, but also forms a stable film on the electrode to suppress exposure of the transition metal. can

In addition, the nitrogen (N) element of the functional additive forms a complex with PF ₅ , which is the causative agent of HF generation, thereby reducing the generation of HF, and decomposition of salts and solvents that may occur during continuous charging and discharging at room temperature or high temperature. can be effectively reduced.

The lithium secondary battery according to the present invention can secure high capacity, high energy density, and excellent lifespan performance by suppressing the elution of transition metals under high voltage and high temperature conditions and catching the eluted transition metals by using an electrolyte solution containing functional additives. There are possible effects.

1 is a graph showing life performance and coulombic efficiency at a driving temperature of 45° C. in batteries using the electrolytes of Example 1 and Comparative Example.
2 is a graph showing life performance and coulombic efficiency at a driving temperature of 25° C. in batteries using the electrolytes of Example 1 and Comparative Example.
3 is a graph showing life performance and coulombic efficiency when the driving temperature is 45 ° C. in the batteries using the electrolyte solutions of Example 2 and Comparative Example.
4 is a graph showing life performance and coulombic efficiency at a driving temperature of 25° C. in batteries using the electrolyte solutions of Example 3 and Comparative Example.
5 is a graph showing life performance and coulombic efficiency at a driving temperature of 45° C. in batteries using the electrolytes of Examples 4, 5, and Comparative Examples.
6 is a comparison of nickel elution amounts after chemical conversion cycles of each battery using the electrolyte solutions of Example 1 and Comparative Example.
Fig. 7 compares nickel elution amounts after chemical conversion cycles of batteries using the electrolyte solutions of Example 2 and Comparative Example.
Fig. 8 compares nickel elution amounts after chemical conversion cycles of batteries using the electrolytic solutions of Example 3 and Comparative Example.
Fig. 9 compares nickel elution amounts after chemical conversion cycles of batteries using the electrolyte solutions of Examples 4, 5, and Comparative Example.

Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. However, since various changes can be made to the embodiments, the scope of the patent application is not limited or limited by these embodiments. It should be understood that all changes, equivalents or substitutes to the embodiments are included within the scope of rights.

Terms used in the examples are used only for descriptive purposes and should not be construed as limiting. Singular expressions include plural expressions unless the context clearly dictates otherwise. In this specification, terms such as "include" or "have" are intended to designate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, but one or more other features It should be understood that the presence or addition of numbers, steps, operations, components, parts, or combinations thereof is not precluded.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by a person of ordinary skill in the art to which the embodiment belongs. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the related art, and unless explicitly defined in the present application, they should not be interpreted in an ideal or excessively formal meaning. don't

In addition, in the description with reference to the accompanying drawings, the same reference numerals are given to the same components regardless of reference numerals, and overlapping descriptions thereof will be omitted. In describing the embodiment, if it is determined that a detailed description of a related known technology may unnecessarily obscure the gist of the embodiment, the detailed description will be omitted.

In addition, in describing the components of the embodiment, terms such as first, second, A, B, (a), and (b) may be used. These terms are only used to distinguish the component from other components, and the nature, order, or order of the corresponding component is not limited by the term. When an element is described as being “connected,” “coupled to,” or “connected” to another element, that element may be directly connected or connected to the other element, but there may be another element between the elements. It should be understood that may be "connected", "coupled" or "connected".

Components included in one embodiment and components having common functions will be described using the same names in other embodiments. Unless stated to the contrary, descriptions described in one embodiment may be applied to other embodiments, and detailed descriptions will be omitted to the extent of overlap.

The present invention is a material parts technology development project supported by the Korea Evaluation Institute of Industrial Technology (development of ionic and nonionic compound-based electrolyte additive technology for high performance of electric vehicle batteries equipped with high-nickel (85% or more) anodes, 20007127, 2020.03.01 ~ 2020.12.31).

One aspect of the present invention, a lithium salt; organic solvents; And a functional additive including at least one selected from the group consisting of compounds represented by Formulas 1 to 4 below; provides an electrolyte solution for a lithium secondary battery comprising:

[Formula 1]

[Formula 2]

[Formula 3]

[Formula 4]

In Formulas 1 to 4, R ₁ to R ₃₅ are hydrogen, halogen, an alkyl group, a phenyl group, a carboxyl group or an ester group, respectively.

Specifically, in Formula 1, R ₁ to R ₈ are each hydrogen, a halogen, an alkyl group, a phenyl group, a carboxyl group, or an ester group, and in Formula 2, R ₉ to R ₁₆ are, respectively, hydrogen, a halogen, an alkyl group, , a phenyl group, a carboxyl group or an ester group.

Further, in Formula 3, R ₁₇ to R ₂₇ are each hydrogen, halogen, an alkyl group, a phenyl group, a carboxyl group, or an ester group, and in Formula 4, R ₂₈ to R ₃₅ are each hydrogen, a halogen, an alkyl group, It is a phenyl group, a carboxyl group, or an ester group.

According to one embodiment, R ₁ to R ₃₅ are each selected from hydrogen, halogen, a C _1-20 alkyl group substituted with an unsubstituted or halogen substituent, a C _6-20 phenyl group substituted with an unsubstituted or halogen substituent, It may be an unsubstituted or C _1-20 carboxyl group substituted with _a halogen substituent, or a C _1-20 ester group unsubstituted or substituted with a halogen substituent.

Specifically, in Formula 1, R ₁ to R ₈ are each hydrogen, halogen, unsubstituted or halogen substituent-substituted C _1-20 alkyl group, unsubstituted or halogen substituent-substituted C _6-20 It may be a phenyl group, a C _1-20 carboxyl group unsubstituted or substituted with a halogen substituent, or _a C _1-20 ester group substituted with an unsubstituted or halogen substituent.

In Formula 2, R ₉ to R ₁₆ are hydrogen, halogen, a C _1-20 alkyl group substituted with an unsubstituted or halogen substituent, a C _6-20 phenyl group substituted with an unsubstituted or halogen substituent, It may be a C _1-20 carboxyl group substituted with _a ring or a halogen substituent, or a C _1-20 ester group substituted with an unsubstituted or halogen substituent.

In Formula 3, R ₁₇ to R ₂₇ are hydrogen, halogen, a C _1-20 alkyl group substituted with an unsubstituted or halogen substituent, a C _6-20 phenyl group substituted with an unsubstituted or halogen substituent, It may be a C _1-20 carboxyl group substituted with _a ring or a halogen substituent, or a C _1-20 ester group substituted with an unsubstituted or halogen substituent.

In Formula 4, R ₂₈ to R ₃₅ are hydrogen, halogen, a C _1-20 alkyl group substituted with an unsubstituted or halogen substituent, a C _6-20 phenyl group substituted with an unsubstituted or halogen substituent, It may be a C _1-20 carboxyl group substituted with _a ring or a halogen substituent, or a C _1-20 ester group substituted with an unsubstituted or halogen substituent.

According to one embodiment, each of R ₁ to R ₃₅ is hydrogen, an unsubstituted or halogen substituent-substituted C _1-10 alkyl group, an unsubstituted or halogen-substituted C _6-20 phenyl group, an unsubstituted Alternatively, it may be a C _1-10 carboxyl group substituted with a halogen substituent, or _a C _1-10 ester group substituted with an unsubstituted or halogen substituent.

According to one embodiment, the halogen substituent may be a fluorine substituent.

The functional additive according to the present invention can chelate the transition metal eluted from the positive electrode of a lithium secondary battery in an electrolyte, form a stable film on the positive electrode to suppress exposure of the transition metal, and nitrogen ( N) element reduces HF generation by forming a complex with PF ₅ , which is a causative agent of HF generation.

In addition, the electrochemical performance of the lithium secondary battery can be improved by effectively reducing the decomposition of salts and solvents that can occur at room temperature and high temperature.

For example, the functional additive may be a compound represented by Chemical Formulas 5 to 8 below.

[Formula 5]

[Formula 6]

[Formula 7]

[Formula 8]

According to one embodiment, the lithium salt is LiPF ₆ , LiClO ₄ , LiBF ₄ , LiFSI, LiTFSI, LiSO ₃ CF ₃ , LiBOB, LiFOB, LiDFBP, LiTFOP, LiPO ₂ F ₂ , LiCl, LiBr, LiI, 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, LiSCN, and LiC(CF ₃ SO ₂ ) ₃ selected from the group consisting of It may contain one or more.

The lithium salt may have high compatibility with materials such as aluminum and copper that can be used as a positive electrode current collector or a negative electrode current collector. At this time, certain lithium salts have low resistance to oxidation in the negative electrode and the risk of corroding the positive electrode. There may be a problem with this, but this problem can be solved by properly mixing two or more materials in the above lithium salt material group.

According to one embodiment, the concentration of the lithium salt may be 0.1 M to 3 M.

Preferably, the concentration of the lithium salt may be 0.5 M to 3 M, more preferably, 1 M to 3 M, and even more preferably, 1 M to 2 M. .

If the concentration of the lithium salt is less than the above range, the conductivity of the electrolyte solution may be lowered and the performance of the electrolyte solution may be deteriorated. If the concentration exceeds the above range, the viscosity of the electrolyte solution increases and the mobility of lithium ions is reduced, and overvoltage occurs from the beginning of the cycle. can

That is, it has the highest ionic conductivity in the concentration range of the lithium salt and excellent output performance due to high mobility of lithium ions in the electrolyte.

According to one embodiment, the organic solvent may include one or more selected from the group consisting of carbonate-based solvents, ester-based solvents, and ether-based solvents.

The carbonate-based solvent, the ester-based solvent, and the ether-based solvent have excellent electrochemical stability, that is, oxidation resistance and reduction resistance, so that decomposition can be minimized during charging and discharging of the battery.

According to one embodiment, the carbonate crab solvent is ethylene carbonate, propylene carbonate, vinylene carbonate, vinyl ethylene carbonate, dimethyl carbonate, ethyl It includes at least one selected from the group consisting of methyl carbonate and diethyl carbonate, and the ester solvent includes methyl propionate, propyl propionate, Butyl propionate, Methyl butyrate, Ethyl butyrate, Propylbutyrate, Butylbutyrate, Methyl acetate, Ethyl acetate, Propyl Group consisting of Propyl acetate, Butyl acetate, Butyrolactone, Decanolide, Valerolactone, Mevalonolactone and Caprolactone It includes one or more selected from, and the ether solvent is dimethyl ether (Dimethyl ether), diethyl ether (diethyl ether), diisopropyl ether (diisopropyl ether), 1,2-dimethoxyethane (1, 2-dimethoxyethane), diethylene glycol dimethyl ether, triethylene glycol dimethyl ether and tetraethylene glycol dimethyl ether (tetr ethylene glycol dimethyl ether) may include one or more selected from the group consisting of

According to one embodiment, the organic solvent may include ethylene carbonate, ethylmethyl carbonate, and dimethyl carbonate.

According to one embodiment, the content of the functional additive may be 0.01% by weight to 10% by weight.

According to one embodiment, the content of the functional additive may be 0.05 wt% to 5 wt%, preferably, 0.1 wt% to 5 wt%, and more preferably, 0.1 wt% to 3 wt%. may be %.

If the content of the functional additive is less than the above range, the transition metal eluted in the electrolyte may not be chelated, and a complex with PF ₅ contained in the electrolyte may be formed, or the surface of the lithium secondary battery electrode The lifespan performance of the battery may be deteriorated because the function such as forming a film may not be sufficiently performed.

On the other hand, when the content of the functional additive is included in excess of the above range, the functional additive may decompose the positive electrode and the negative electrode to form a resistive film, thereby deteriorating battery performance.

According to one embodiment, the functional additive is to chelate the transition metal eluted in the electrolyte solution, form a complex with PF ₅ contained in the electrolyte solution, or form a film on the surface of a lithium secondary battery electrode can

Here, the film may be formed on the positive and negative electrodes of the lithium secondary battery.

The film acts as a protective film of the anode and can suppress elution of the transition metal from the anode.

In addition, the eluted transition metal is chelated with a functional additive, thereby preventing electrodeposition of the transition metal on the cathode film.

Furthermore, by forming a complex with PF ₅ included in the electrolyte solution, the functional additive can suppress the generation of HF that accelerates the decomposition of the electrolyte solution.

The HF reacts with the anode to irreversibly elute the transition metal, and the transition metal ion activated through this not only induces an additional decomposition reaction of the electrolyte solution, but also destroys the SEI layer of the cathode, resulting in performance degradation. In addition, ions produced by reduction of eluted transition metal ions migrate to the anode and cause cation mixing, which may cause the anode to become structurally unstable.

The functional additive according to the present invention simultaneously performs the functions of chelating the transition metal eluted in the electrolyte, forming a complex with PF ₅ contained in the electrolyte, and forming a film on the surface of the electrode of a lithium secondary battery, Lithium secondary batteries, in particular, have characteristics that can effectively improve the electrochemical performance of lithium secondary batteries based on high-density energy cathodes.

Another aspect of the present invention is a positive electrode; cathode; an ion permeable separator between the anode and the cathode; It provides a lithium secondary battery containing; and the electrolyte solution for the lithium secondary battery.

According to one embodiment, the anode may include a Ni-rich composite metal oxide and be layered.

The lithium secondary battery according to the present invention, in particular, is characterized in that it can secure excellent lifespan performance under high voltage and high temperature conditions while having high energy density based on a positive electrode including a Ni-rich composite metal oxide.

In other words, by solving the problem of elution of transition metals when a high-energy-density Ni-rich composite metal oxide-based anode operates under high-voltage and high-temperature conditions, functional additives are introduced into the electrolyte, resulting in high capacity, high energy density, and excellent lifespan. performance can be obtained.

According to one embodiment, the composite metal oxide is LiNi _w Co _x Mn _y O ₂ (w+x+y+z=1) or LiNi _w Co _x Mn _y M _z O ₂ (w+x+y+z = 1), wherein M may be Ti, Zr, Nb, W, P, Al, Mg, V, Ca or Sr.

According to one embodiment, the composite metal oxide is LiNi _w Co _x Mn _y O ₂ (w+x+y+z=1) or LiNi _w Co _x Mn _y Al _z O ₂ (w+x+y+z = 1) can be included.

Here, w may be greater than or equal to 0.5.

The composite metal oxide is characterized by having a higher energy density than commercially available LiCoO ₂ , and through this, high voltage and high capacity of a lithium secondary battery can be implemented.

According to one embodiment, the negative electrode may include graphite, silicon, or both.

According to one embodiment, a solid electrolyte interphase (SEI) layer may be formed on the surface of the negative electrode during charging and discharging.

The solid electrolyte mesophase is formed at the interface between the anode and the electrolyte to protect the anode from degradation and enable stable cathode behavior.

The ion permeable separator may be an insulating thin film having high ion permeability and mechanical strength.

According to one embodiment, the driving voltage may be 3.0 V to 4.3 V, and the driving temperature may be 25 °C to 45 °C.

The lithium secondary battery according to the present invention has an effect of securing excellent lifespan performance even under high voltage conditions and high temperature conditions.

Hereinafter, the present invention will be described in more detail by examples and comparative examples.

However, the following examples are only for illustrating the present invention, and the content of the present invention is not limited to the following examples.

<Example> Preparation of functional electrolyte solution for lithium secondary battery

Lithium salt (LiPF ₆ ) was added at a concentration of 1.15 M to an organic solvent containing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a volume ratio of 2: 4: 4, and vinylene carbonate (VC ) was added at 1% by volume to prepare a standard electrolyte solution.

An electrolyte solution for a lithium battery was prepared by adding a functional additive to the standard electrolyte solution in an amount of 0.01 wt % to 10 wt %.

The chemical structures of the functional additives used are shown in Table 1 below.

functional additives content Example 1

0.5% by weight Example 2

0.1% by weight Example 3

0.1% by weight Example 4

0.1% by weight Example 5

0.5% by weight

<Comparative Example> Preparation of standard electrolyte solution

As a comparative example, an electrolyte solution having the same composition as the reference electrolyte solution of Example without using a functional additive was prepared.

<Experimental Example 1> Lithium secondary battery performance evaluation

LiNi _0.84 Co _0.11 Mn _0.05 O ₂ /16 ㎛ separator/Graphite coin-type full cells (positive | cathode loading: 14.0 mg/cm ² | 10.4 mg/cm ² ) were prepared with the electrolytes of Examples 1 to 3 and Comparative Example The lifetime performance and coulombic efficiency of each used battery were measured.

At this time, the performance of the batteries was compared under a driving voltage range of 4.3 - 3.0 V, a charge/discharge rate of 0.5C/0.5C, and a driving temperature of 25 °C or 45 °C.

The life performance and coulombic efficiency measurement results of each battery are shown in FIGS. 1 to 4 .

1 is a graph showing life performance and coulombic efficiency at a driving temperature of 45° C. in batteries using the electrolytes of Example 1 and Comparative Example.

2 is a graph showing life performance and coulombic efficiency at a driving temperature of 25° C. in batteries using the electrolytes of Example 1 and Comparative Example.

1 and 2, life characteristics at high temperature (45 ° C.) and room temperature (25 ° C.) in the case of using the electrolyte solution of Example 1 (functional additive 0.5% by weight) compared to the reference electrolyte solution of Comparative Example. You can see that this improves.

3 is a graph showing life performance and coulombic efficiency when the driving temperature is 45 ° C. in the batteries using the electrolyte solutions of Example 2 and Comparative Example.

Referring to FIG. 3, it can be confirmed that the lifespan characteristics at high temperature (45 ° C.) are improved when the electrolyte solution of Example 2 (functional additive 0.1% by weight) is used compared to the standard electrolyte solution of Comparative Example.

4 is a graph showing life performance and coulombic efficiency at a driving temperature of 25° C. in batteries using the electrolyte solutions of Example 3 and Comparative Example.

Referring to FIG. 4, it can be confirmed that the lifespan characteristics at room temperature (25 ° C.) are improved when the electrolyte solution of Example 3 (functional additive 0.1% by weight) is used compared to the standard electrolyte solution of the comparative example.

<Experimental Example 2> Lithium secondary battery performance evaluation

LiNi _0.85 Co _0.10 Mn _0.05 O ₂ /16 ㎛ separator/Graphite coin-type full cell (positive | cathode loading: 14.0 mg/cm ² | 10.4 mg/cm ² ) of Example 4, Example 5 and Comparative Example The life performance and coulombic efficiency of the batteries each using the electrolyte were measured.

At this time, the performance of the batteries was compared under a driving voltage range of 4.2 - 3.0 V, a charge/discharge rate of 0.5C/0.5C, and a driving temperature of 45 °C.

5 is a graph showing life performance and coulombic efficiency at a driving temperature of 45° C. in batteries using the electrolytes of Examples 4, 5, and Comparative Examples.

Referring to FIG. 5 , it can be confirmed that the lifespan characteristics at high temperature (45 ° C.) are improved when the electrolyte solutions of Examples 4 and 5 are used compared to those using the standard electrolyte solution of Comparative Example.

In addition, it can be seen that the high-temperature lifespan characteristics are improved both when the content of the functional additive is included at 0.1% by weight and when the content of the functional additive is included at 0.5% by weight.

<Experimental Example 3> Confirmation of inhibition of transition metal elution electrodeposition

LiNi _0.85 Co _0.10 Mn _0.05 O ₂ /16 μm separator/Graphite coin-type full cell (positive | cathode loading: 14.0 mg/cm ² | 10.4 mg/cm ² ) was prepared with the electrolytes of Examples 1 to 5 and Comparative Example. Each used battery was prepared. Each battery was disassembled after the conversion cycle and stored at 60 °C for 1 day, and then the nickel elution amount was analyzed.

6 is a comparison of nickel elution amounts after chemical conversion cycles of each battery using the electrolyte solutions of Example 1 and Comparative Example.

Fig. 7 compares nickel elution amounts after chemical conversion cycles of batteries using the electrolyte solutions of Example 2 and Comparative Example.

Fig. 8 compares nickel elution amounts after chemical conversion cycles of batteries using the electrolytic solutions of Example 3 and Comparative Example.

Fig. 9 compares nickel elution amounts after chemical conversion cycles of batteries using the electrolyte solutions of Examples 4, 5, and Comparative Example.

Referring to FIGS. 6 to 9 , it can be seen that the nickel elution amount was all reduced when the electrolyte solutions of Examples 1 to 5 were used compared to when the electrolyte solutions of Comparative Examples were used.

Through this, it can be seen that the amount of elution of nickel was reduced by forming a stable film on the anode when the example electrolyte was used.

That is, it can be seen that the amount of nickel ions electrodeposited is significantly reduced by the formation of a stable film on the anode through the functional additive and the trapping phenomenon of the transition metal eluted in the electrolyte.

As described above, although the embodiments have been described with limited drawings, those skilled in the art can apply various technical modifications and variations based on the above. For example, the described techniques may be performed in an order different from the method described, and/or components of the described system, structure, device, circuit, etc. may be combined or combined in a different form than the method described, or other components may be used. Or even if it is replaced or substituted by equivalents, appropriate results can be achieved.

Therefore, other implementations, other embodiments, and equivalents of the claims are within the scope of the following claims.

Claims (13)

lithium salt;
organic solvents; and
A functional additive comprising at least one selected from the group consisting of compounds represented by Formulas 3 to 4 below;
Electrolyte for lithium secondary battery:
[Formula 3]

[Formula 4]

In Formulas 3 to 4,
R ₁₇ to R ₃₅ are, respectively, hydrogen, halogen, a C _1-20 alkyl group substituted with an unsubstituted or halogen substituent, a C _6-20 phenyl group substituted with an unsubstituted or halogen substituent, an unsubstituted or halogen substituent, and A substituted C _1-20 carboxyl group _, or an unsubstituted or C _1-20 ester group substituted with a halogen substituent.
According to claim 1,
R ₁₇ to R ₃₅ are, respectively, hydrogen, an unsubstituted or halogen substituent-substituted C _1-20 alkyl group, an unsubstituted or halogen substituent-substituted C _6-20 phenyl group, unsubstituted or halogen substituent substituted _A C _1-20 carboxyl group, or an unsubstituted or C _1-20 ester group substituted with a halogen substituent,
Electrolyte for lithium secondary batteries.
According to claim 1,
The lithium salt,
LiPF ₆ , LiClO ₄ , LiBF ₄ , LiFSI, LiTFSI, LiSO ₃ CF ₃ , LiBOB, LiFOB, LiDFBP, LiTFOP, LiPO ₂ F ₂ , LiCl, LiBr, LiI, 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, LiSCN, and LiC(CF ₃ SO ₂ ) ₃ Which includes one or more selected from the group consisting of,
Electrolyte for lithium secondary batteries.
According to claim 1,
The concentration of the lithium salt is,
0.1 M to 3 M,
Electrolyte for lithium secondary batteries.
According to claim 1,
The organic solvent,
To include at least one selected from the group consisting of carbonate-based solvents, ester-based solvents and ether-based solvents,
Electrolyte for lithium secondary batteries.
According to claim 5,
The carbonate solvent is ethylene carbonate, propylene carbonate, vinylene carbonate, vinyl ethylene carbonate, dimethyl carbonate, ethylmethyl carbonate And it includes one or more selected from the group consisting of diethyl carbonate (Diethyl carbonate),
The ester-based solvent is methyl propionate, propyl propionate, butyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate ), Butyl Butyrate, Methyl Acetate, Ethyl Acetate, Propyl Acetate, Butyl Acetate, Butyrolactone, Decanolide, It contains at least one selected from the group consisting of valerolactone, mevalonolactone and caprolactone,
The ether-based solvent is dimethyl ether, diethyl ether, diisopropyl ether, 1,2-dimethoxyethane, diethylene glycol dimethyl ether (diethylene glycol dimethyl ether), triethylene glycol dimethyl ether (triethylene glycol dimethyl ether) and tetraethylene glycol dimethyl ether (tetraethylene glycol dimethyl ether) containing at least one selected from the group consisting of,
Electrolyte for lithium secondary batteries.
According to claim 1,
The content of the functional additive,
0.01% by weight to 10% by weight,
Electrolyte for lithium secondary batteries.
According to claim 1,
The functional additive,
chelating the transition metal eluted in the electrolyte,
Forming a complex with PF ₅ contained in the electrolyte, or
Forming a film on the surface of a lithium secondary battery electrode,
Electrolyte for lithium secondary batteries.
anode;
cathode;
an ion permeable separator between the anode and the cathode; and
Including; electrolyte solution for a lithium secondary battery,
The electrolyte is
lithium salt;
organic solvents; and
A functional additive comprising at least one selected from the group consisting of compounds represented by Formulas 3 to 4 below;
The drive voltage is 3.0 V to 4.3 V,
A lithium secondary battery having a driving temperature of 25 ° C to 45 ° C:
[Formula 3]

[Formula 4]

In Formulas 3 to 4,
R ₁₇ to R ₃₅ are, respectively, hydrogen, halogen, a C _1-20 alkyl group substituted with an unsubstituted or halogen substituent, a C _6-20 phenyl group substituted with an unsubstituted or halogen substituent, an unsubstituted or halogen substituent, and A substituted C _1-20 carboxyl group _{, or an unsubstituted or C 1-20 ester} group substituted with a halogen substituent.
According to claim 9,
The anode is
It contains a Ni-rich composite metal oxide and is layered,
lithium secondary battery.
According to claim 10,
The composite metal oxide,
LiNi _w Co _x Mn _y O ₂ (w+x+y+z=1) or LiNi _w Co _x Mn _y M _z O ₂ (w+x+y+z=1);
Wherein M is Ti, Zr, Nb, W, P, Al, Mg, V, Ca or Sr,
lithium secondary battery.
According to claim 9,
The cathode is
containing graphite, silicon or both,
lithium secondary battery.
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