KR20200002167A - Electrolyte composition for lithium secondary battery and lithium secondary battery using the same - Google Patents

Abstract

The present invention relates to an electrolyte composition for a lithium secondary battery and a lithium secondary battery including an electrolyte solution prepared from the electrolyte composition. The purpose of the present invention is to provide an electrolyte composition for a lithium secondary battery, which is capable of providing an electrolyte comprising an additive which can inhibit the formation of a by-product capable of acting as damage or resistance of an electrode interface due to HF by effectively removing HF formed by hydrolysis of LiPF6. The electrolyte composition for the lithium secondary battery comprises: a lithium salt including one selected from the group consisting of LiPF_6, LiClO_4, LiBF_4, LiFSI, LiTFSI, LiSO_3CF_3, LiPO_2F_2, lithium bis(oxalate)borate (LiBOB), lithium difluoro(oxalate)borate (LiFOB), lithium difluoro(bisoxalato) phosphate (LiDFBP), lithium tetrafluoro(oxalate) phosphate (LiTFOP), lithium fluoromalonato(difluoro) borate (LiFMDFB), and mixtures thereof; a carbonate-based solvent; and a side reaction inhibitor.

Description

ELECTROLYTE COMPOSITION FOR LITHIUM SECONDARY BATTERY AND LITHIUM SECONDARY BATTERY USING THE SAME

The present invention relates to an electrolyte composition for lithium secondary batteries, and more particularly to a method for producing an electrolyte composition for functional lithium secondary batteries that can suppress side reactions.

Today, portable devices such as smartphones and tablet PCs are deeply penetrating into our daily lives, and are becoming more and more essential to life. This is due to advances in all battery technology. In particular, since the mass production of lithium secondary batteries began in 1991, the lithium secondary battery has rapidly developed into a main power source with the spread of mobile devices such as mobile phones and notebook PCs with the superiority of high energy density and output voltage.

Lithium secondary batteries have not only achieved commercial success as a power source for portable electronic products, but also successfully entered the power tool market. In addition, it is expanding its base while pushing forward expansion to the electric vehicle and power storage market in the future.

In order to continuously expand the market, it is urgent to simultaneously secure high energy density, high output discharge and safety, and to secure fast charging characteristics. Currently, the direction of rapid charging performance development of lithium secondary batteries around the world is focused on electrode material development. Research is underway, and little research has been done on the electrolyte portion to develop fast charge performance. The current battery system is increasing the thickness and density of the electrode to increase the energy density, and when using a conventionally commercialized electrolyte solution on the electrode with a high thickness and density, there are areas that are not impregnated with the electrolyte solution to reduce the battery resistance There is a problem of increasing.

In addition, currently commercially available LiPF ₆ salts are hydrolyzed by moisture in the cell, resulting in the formation of HF and the problem of HF promoting degradation of the positive / cathode interface. For example, there is a problem of forming LiF acting as a resistive layer on the surface of the anode by reacting with Li ₂ CO ₃ formed due to decomposition of the electrolyte on the surface of the anode. In addition, it is the main cause of eluting the transition metal from the anode, the problem is that the eluted transition metal is deposited on the surface of the negative electrode, causing deterioration of the surface of the negative electrode. In other words, HF can be said to be a major material that promotes deterioration of the positive / cathode interface and degrades the electrochemical performance of the battery.

In the case of rapid charging using a conventionally available electrolytic solution, a film for easily transferring lithium ions is not formed on the surface of the electrode, thereby increasing the charge transfer resistance at the electrode interface, thereby causing a sharp decrease in cell performance. In order to develop a battery of high energy density, studies are being conducted to increase the operating voltage of the battery. However, commercially available electrolytes have low stability at low voltage and high voltage, and resistance at the positive / cathode-electrolyte interface increases. there is a problem. Accordingly, in order to solve problems such as a decrease in impregnation of the electrolyte during rapid charging, a decrease in lithium ion migration and electrolyte decomposition at low / high voltage, and formation of a resistive material at the positive / negative electrode, development of a rapid charging electrolyte is necessary.

Therefore, in order to implement a rechargeable battery capable of rapid charging, a low resistance film at the electrode-electrolyte interface should be formed. For this purpose, the formation of HF formed by the hydrolysis of LiPF ₆ is suppressed, and the HF at the positive / cathode interface is suppressed. Research should be conducted to improve the fast charging characteristics of the battery by minimizing the occurrence of resistance and interfacial deterioration.

The present invention is to solve the above problems, LiPF ₆ , LiClO ₄ , LiBF ₄ , LiFSI, LiTFSI, LiSO ₃ CF ₃ ,, LiPO ₂ F ₂ , Lithium bis (oxalate) borate (Lithium bis (oxalate) borate , LiBOB), lithium difluoro (oxalate) borate (LiFOB), lithium difluoro (bisoxalato) phosphate (Lithium difluoro (bisoxalato) phosphate, LiDFBP), lithium tetrafluoro ( Oxalate) phosphate (Lithium tetrafluoro (oxalate) phosphate (LiTFOP), lithium fluoromalonato (difluoro) borate (Lithium fluoromalonato (difluoro) borate, LiFMDFB) And it provides a lithium secondary battery electrolyte composition comprising a lithium salt, a carbonate-based solvent and a side reaction inhibitor containing at least one selected from the group consisting of a mixture thereof.

More specifically, the electrolyte composition for a lithium secondary battery effectively removes HF formed by hydrolysis of LiPF ₆ , and includes an additive capable of suppressing formation of byproducts that may act as damage and resistance of the electrode interface caused by HF. An electrolyte solution can be provided.

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 following description.

Lithium secondary battery electrolyte composition according to an embodiment of the present invention, LiPF ₆ , LiClO ₄ , LiBF ₄ , LiFSI, LiTFSI, LiSO ₃ CF ₃ ,, LiPO ₂ F ₂ , lithium bis (oxalate) borate (Lithium bis ( oxalate) borate, LiBOB), lithium difluoro (oxalate) borate (LiFOB), lithium difluoro (bisoxalato) phosphate (Lithium difluoro (bisoxalato) phosphate, LiDFBP), lithium tetra Fluoro (oxalate) phosphate (Lithium tetrafluoro (oxalate) phosphate (LiTFOP), Lithium fluoromalonato (difluoro) borate (LiFMDFB) And lithium salts, carbonate-based solvents and side reaction inhibitors including any one selected from the group consisting of a mixture thereof.

According to one embodiment of the invention, the carbonate solvent, ethylene carbonate (Ethylene carbonate, EC), propylene carbonate (propylene carbonate, PC), vinyl ethylene carbonate (vinyl ethylene carbonate, VC), fluoroethylene carbonate (fluoroethylene carbonate, FEC) and mixtures thereof.

According to one embodiment of the present invention, the carbonate solvent, any one selected from the group consisting of dimethyl carbonate (Dimethyl carbonate), ethyl methyl carbonate (Ethylmethyl carbonate), diethyl carbonate (diethyl carbonate) and mixtures thereof It may be to include.

According to an embodiment of the present invention, the side reaction inhibitor may include an isocyanate group (N = C = O) or an isothiocyanate group (N = C = S).

According to an embodiment of the present invention, the side reaction inhibitor may include a compound of Formula 1 below.

<Formula 1>

(A is sulfur (S) or oxygen (O), and R1 to R3 are C1 to C10 linear carbon chains.)

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

According to one embodiment of the present invention, the concentration of the side reaction inhibitor may be 0.1 wt% to 10 wt%.

According to one embodiment of the present invention, the side reaction may include a hydrolysis reaction and an electrode-electrolyte interface side reaction of the lithium salt on the surface of the positive electrode, the negative electrode, or both.

According to one embodiment of the invention, 1,2-dimethoxyethane (1,2-dimethoxyethane), 1,3-dioxolane (1,3-dioxolane), diethylene glycol (Diethylene glycol), dimethyl ether ( dimethyl ether, tereethylene glycol diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether and these It may further comprise any one ether solvent selected from the group consisting of a mixture of.

According to one embodiment of the present invention, Fluoroethylene carbonate (FEC), Vinylene carbonate (VC), Lithium oxalyldifluoroborate (LiDFOB), Lithium nitrate (LiNO3), 4-methyl-1,3-dioxol-2-one (MVC), 4-fluoro-1,3-dioxol-2-one (FVC), 4- (fluoranylmethyl) -1,3-dioxol-2-one (FMVC), 4- (trifluoromethyl) -1,3-dioxol- 2-one), FPVC (4- (4-fluorophenyl) -1,3-dioxol-2-one), TFPVC (4- (4- (trifluoromethyl) phenyl) -1,3-dioxol-2-one), PFPVC (4- (pentafluorophenyl) -1,3-dioxol-2-one), FTMSVC (4-((fluoro-((trimethylsilyl) oxy) alkoxy) methyl) -1,3-dioxol-2-one), PFMVC It may further include any one additional additive selected from the group consisting of (4-((perfluoroalkoxy) methyl) -1,3-dioxol-2-one) and mixtures thereof.

According to an embodiment of the present invention, the electrolyte composition may have a capacity retention of 80% to 99% after 100 cycles.

According to another embodiment of the present invention, a lithium secondary battery includes a positive electrode, a negative electrode, an ion permeable separator between the positive electrode and the negative electrode, and an electrolyte solution for a lithium secondary battery prepared according to the above-described embodiment.

The present invention, LiPF ₆ , LiClO ₄ , LiBF ₄ , LiFSI, LiTFSI, LiSO ₃ CF ₃ ,, LiPO ₂ F ₂ , Lithium bis (oxalate) borate (LiBOB), lithium difluoro (Oxalate) borate (Lithium difluoro (oxalate) borate, LiFOB), lithium difluoro (bisoxalato) phosphate (Lithium difluoro (bisoxalato) phosphate, LiDFBP), lithium tetrafluoro (oxalate) phosphate (Lithium tetrafluoro ( oxalate) phosphate, LiTFOP), lithium fluoromalonato (difluoro) borate, LiFMDFB And it can provide a lithium secondary battery electrolyte composition comprising a lithium salt, a carbonate-based solvent and a side reaction inhibitor comprising any one selected from the group consisting of a mixture thereof.

More specifically, it is possible to provide an electrolyte composition capable of improving the electrochemical performance of high-energy, high-density lithium ion batteries by introducing a functional additive that performs an HF removal function in an organic electrolyte composed of a carbonate solvent and a lithium salt. have.

1 is a graph of the life characteristics according to the fast charge rate of the lithium secondary battery manufactured according to an embodiment of the present invention.
Figure 2 shows the capacity retention rate after 100 times and 100 times the life of a lithium secondary battery prepared according to an embodiment of the present invention and a lithium secondary battery prepared according to a comparative example.
3 is a F 1s XPS analysis of the NCM622 positive electrode after chemical conversion of a lithium secondary battery manufactured according to an embodiment of the present invention.
4 is a by-product analysis of LiPF ₆ hydrolysis formed in the electrolyte prepared according to an embodiment of the present invention by ¹⁹ F NMR.

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

The terminology used herein is for the purpose of description and should not be construed as limiting. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this specification, terms such as "comprise" or "have" are intended to indicate that there is a feature, number, step, action, component, part, or combination thereof described on the specification, and one or more other features. It is to be understood that the present invention does not exclude the possibility of the presence or the addition of numbers, steps, operations, components, components, or a combination thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art. Terms such as those defined in the commonly used dictionaries should be construed as having meanings consistent with the meanings in the context of the related art and shall not be construed in ideal or excessively formal meanings unless expressly defined in this application. Do not.

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

When an element or layer is represented as "on", "connected to" or "coupled to" another element or layer, this is directly another element or layer. It may be understood that the layers may be present, connected or combined, or there may be intervening elements and layers.

Hereinafter, the electrolyte composition for a lithium secondary battery of the present invention and a lithium secondary battery manufactured according to the present invention will be described in detail with reference to Examples and drawings. However, the present invention is not limited to these embodiments and drawings.

Lithium secondary battery electrolyte composition according to an embodiment of the present invention, LiPF ₆ , LiClO ₄ , LiBF ₄ , LiFSI, LiTFSI, LiSO ₃ CF ₃ ,, LiPO ₂ F ₂ , lithium bis (oxalate) borate (Lithium bis ( oxalate) borate, LiBOB), lithium difluoro (oxalate) borate (LiFOB), lithium difluoro (bisoxalato) phosphate (Lithium difluoro (bisoxalato) phosphate, LiDFBP), lithium tetra Fluoro (oxalate) phosphate (Lithium tetrafluoro (oxalate) phosphate (LiTFOP), Lithium fluoromalonato (difluoro) borate (LiFMDFB) And lithium salts, carbonate-based solvents and side reaction inhibitors including any one selected from the group consisting of a mixture thereof.

According to one side, the lithium salt, LiPF ₆ , LiClO ₄ , LiBF ₄ , LiFSI, LiTFSI, LiSO ₃ CF ₃ ,, LiPO ₂ F ₂ , lithium bis (oxalate) borate (Lithium bis (oxalate) borate, LiBOB), Lithium difluoro (oxalate) borate (LiFOB), Lithium difluoro (bisoxalato) phosphate (Lithium difluoro (bisoxalato) phosphate (LiDFBP), Lithium tetrafluoro (oxalate) Lithium tetrafluoro (oxalate) phosphate (LiTFOP), Lithium fluoromalonato (difluoro) borate (LiFMDFB) In the group consisting of two or more may be used in combination.

According to one side, such lithium salts can have a high compatibility with materials such as aluminum, copper, etc., which can be used as a positive electrode current collector or a negative electrode current collector, wherein certain lithium salts have low resistance to oxidation at the negative electrode and There may be a problem of the risk of corrosion of the anode, which can be solved by properly mixing two or more of the materials in the lithium salt group above.

According to one embodiment of the invention, the carbonate solvent, ethylene carbonate (Ethylene carbonate, EC), propylene carbonate (propylene carbonate, PC), vinyl ethylene carbonate (vinyl ethylene carbonate, VC), fluoroethylene carbonate (fluoroethylene carbonate, FEC), and mixtures thereof.

According to one side, the ethylene carbonate (EC), propylene carbonate (PC), vinyl ethylene carbonate (VC), fluoroethylene carbonate (FEC) and mixtures thereof One selected from the group consisting of cyclic carbonate (cyclic carbonate).

According to one side, fluoroethylene carbonate (FEC) among the carbonate-based solvents as an electrolyte additive used in secondary batteries, the main use is to participate in the reaction of the electrolyte and the electrode, in particular the reaction of the negative electrode to the surface of the negative electrode It may be a material that contributes to the generation of even SEI film to contribute to the stability of the charge / discharge.

According to one side, the vinyl ethylene carbonate may be effective in improving the interfacial stability of the negative electrode material including the graphite negative electrode and silicon.

According to one side, it may further include a non-aqueous organic solvent in the carbonate solvent.

According to one side, the carbonate solvent, most preferably, in order to compensate for the high melting point, high viscosity, etc. of the disadvantages of the cyclic carbonate having a high dielectric constant linear carbonate (linear carbonate) solvent (linear carbonate) You can mix and use.

According to an embodiment of the present invention, the side reaction inhibitor may include an isocyanate group (N = C = O) or an isothiocyanate group (N = C = S).

According to one side, the isocyanate group (N = C = O) or isothiocyanate group (N = C = S) functional group of the side reaction inhibitor effectively removes HF formed by the hydrolysis of LiPF _{6 in} the electrolyte solution. , Minimizing the deterioration of the positive / negative surface caused by HF and suppressing the formation of LiF, which can act as a resistive layer, thereby improving the lifespan performance at high speed of battery charging.

According to one side, since the side reaction inhibitor containing the isocyanate group (N = C = O) or the isothiocyanate group (N = C = S) has a lower reduction potential than that of the carbonate-based electrolyte solvent, In the initial charge, it may be reduced on the surface of the negative electrode material before the electrolyte solvent to form a solid and dense SEI film. As a result, the electrolyte solvent can be prevented from intercalating into the negative electrode active material layer or decomposed at the negative electrode interface to participate in side reactions such as SEI film regeneration, thereby improving charge and discharge efficiency of the battery.

According to one side, the side reaction inhibitor including the isocyanate group (N = C = O) or isothiocyanate group (N = C = S) is because the SEI film formed is a low chemically reactive passivation layer. The long life cycle can be achieved by showing high stability even in a long cycle.

According to an embodiment of the present invention, the side reaction inhibitor may include a compound of Formula 1 below.

<Formula 1>

(A is sulfur (S) or oxygen (O), and R1 to R3 are C1 to C10 linear carbon chains.)

According to one side, the side reaction inhibitor, preferably may include the following formula (2), (3) or both.

<Formula 2>

<Formula 3>

According to one side, the side reaction inhibitor, by minimizing the damage to the positive / negative electrode interface through the removal of HF, can improve the battery life performance, it is possible to improve the fast charging characteristics by reducing the LiF component in the positive electrode film.

According to one side, the side reaction inhibitor, by effectively suppressing the HF in the electrolyte, it is possible to suppress the formation of LiF that can be formed by the reaction of LiOCO ₂ R, Li ₂ CO ₃ and HF present in the surface of the positive electrode.

According to one side, by the side reaction inhibitor in the electrolyte composition, HF removal function to minimize the damage of the positive / negative electrode interface, and suppress the formation of the resistive material LiF by the carbon-based negative electrode and layered positive electrode It can provide a foundation to improve the electrochemical high-speed charging characteristics and life performance of the high energy, high density lithium ion battery composed of.

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

According to one side, the higher the concentration of the lithium salt may increase the initial efficiency of the lithium electrodeposition / desorption reaction, while the higher the concentration of the lithium salt may be higher in viscosity and lower in ionic conductivity. Therefore, it may be important to properly control the concentration of the lithium salt in the present invention.

According to one side, when the concentration of the lithium salt is higher than 3M, the viscosity may increase, while the ionic conductivity may decrease, which is due to the increase in the amount of the lithium salt does not dissociate in the electrolyte composition increases the electrolyte composition It may be to increase the viscosity of, thereby reducing the ionic conductivity.

According to one side, the concentration of the lithium salt within the numerical range may be the concentration of the lithium salt that can exhibit the optimum efficiency in the electrolyte composition.

According to one side, when the concentration of the lithium salt is less than 0.1 M, as the concentration of the lithium salt is too low may cause a problem that the charge carrier in the electrolyte is reduced, the ion conductivity is lowered.

According to one side, if the concentration of lithium salt is more than 3M, the viscosity is too high may cause overvoltage from the beginning of the operating cycle, or the performance of the cell deteriorated later in the charge and discharge cycle Can occur.

According to one embodiment of the present invention, the concentration of the side reaction inhibitor may be 0.1 wt% to 10 wt%.

According to one side, if the content of the side reaction inhibitor is too small, all of it is consumed during the initial operation, deterioration of life during charging and discharging or long-term storage and at the same time the removal of HF does not occur sufficiently, the quality may deteriorate, the content If too much, an excessive amount of film is formed on the electrode surface, which may act as a resistance to the movement of lithium ions.

 According to one side, when the concentration of the side reaction inhibitor is less than 0.1% by weight, there may be a problem that the effect of suppressing the side reaction to be implemented in the present invention is insignificant, when the concentration of the side reaction inhibitor exceeds 10% by weight As the charge / discharge cycle proceeds, a thick resistive film is formed on the surface of the lithium metal, thereby reducing cell performance and causing a large overvoltage in the cell.

According to one side, in the case of having a concentration of the side reaction inhibitor within the above numerical range, the removal of HF occurs sufficiently in the range that is not consumed during the initial operation to minimize the damage of the positive / cathode interface, the formation of the resist material LiF By suppressing the electrochemical fast charging characteristics and life performance of a high energy, high density lithium ion battery composed of a carbon-based negative electrode and a layered positive electrode can be improved.

According to one embodiment of the present invention, the side reaction may include a hydrolysis reaction and an electrode-electrolyte interface side reaction of the lithium salt on the surface of the positive electrode, the negative electrode, or both.

According to one side, the side reaction is preferably a reaction of LiOCO ₂ R, Li ₂ CO ₃ and HF, more specifically, the following formula (1) and formula (2).

<Equation 1>

LiOCO ₂ R + HF → LiF + ROH + CO ₂

<Equation 2>

Li ₂ CO ₃ + 2HF → 2LiF + CO ₂ + H ₂ O

According to one embodiment of the invention, 1,2-dimethoxyethane (1,2-dimethoxyethane), 1,3-dioxolane (1,3-dioxolane), diethylene glycol (Diethylene glycol), dimethyl ether ( dimethyl ether, tertraethylene glycol diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether and these It may further comprise any one ether solvent selected from the group consisting of a mixture of.

According to one side, may further comprise a non-aqueous organic solvent in the ether solvent.

According to one side, by using the ether solvent can be obtained an effect that can be minimized decomposition by reduction and the like during the charge and discharge of the battery.

According to one embodiment of the present invention, Fluoroethylene carbonate (FEC), Vinylene carbonate (VC), Lithium oxalyldifluoroborate (LiDFOB), Lithium nitrate (LiNO3), 4-methyl-1,3-dioxol-2-one (MVC), 4-fluoro-1,3-dioxol-2-one (FVC), 4- (fluoranylmethyl) -1,3-dioxol-2-one (FMVC), 4- (trifluoromethyl) -1,3-dioxol- 2-one), FPVC (4- (4-fluorophenyl) -1,3-dioxol-2-one), TFPVC (4- (4- (trifluoromethyl) phenyl) -1,3-dioxol-2-one), PFPVC (4- (pentafluorophenyl) -1,3-dioxol-2-one), FTMSVC (4-((fluoro-((trimethylsilyl) oxy) alkoxy) methyl) -1,3-dioxol-2-one), PFMVC It may further include any one additional additive selected from the group consisting of (4-((perfluoroalkoxy) methyl) -1,3-dioxol-2-one) and mixtures thereof.

According to one side, by further including the additional additives can be expected to more effectively suppress the side reactions on the surface of the electrolyte and the positive electrode, the negative electrode or both.

According to one side, the additional additives to increase the reversibility of lithium electrodeposition and desorption reaction, to suppress the formation of dendritic lithium to minimize the loss of reversible lithium can improve the electrochemical performance of the battery.

According to an embodiment of the present invention, the electrolyte composition may have a capacity retention of 80% to 99% after 100 cycles.

According to one side, it is possible to maintain the capacity retention ratio within the above range, because the protective film formed on the positive / cathode surface formed by mixing the side reaction inhibitor or the side reaction inhibitor with the additional additive prevents the side reaction between the electrolyte and the anode / cathode interface. This is because HF in the electrolyte is effectively removed while being effectively suppressed to improve the reversibility of the cell.

According to another embodiment of the present invention, a lithium secondary battery includes a positive electrode, a negative electrode, an ion permeable separator between the positive electrode and the negative electrode, and an electrolyte solution for a lithium secondary battery prepared according to the above-described embodiment.

According to one side, the negative electrode is not particularly limited as long as lithium ions can be occluded and released as a negative electrode active material.

According to one side, the positive electrode, a variety of materials can be used as the positive electrode active material, the component is not particularly limited.

According to one side, the separator is interposed between the anode and the cathode, it is not particularly limited as long as it can be used as an insulating thin film having high ion permeability and mechanical strength.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples.

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

Example 1.

In an embodiment of the present invention, a secondary battery cell was prepared in the form of LiNi _0.6 Co _0.2 Mn _0.2 O ₂ / Graphite coin type full cell.

Loading amount of the positive and negative electrodes each were to 19.1mg / cm ² and 9.3mg / cm ^2, the reference electrolyte is an _{1.15M LiPF 6 in EC / DMC (} 5/95, vol%) + 10% FEC.

As a side reaction inhibitor, 0.1% of a side reaction inhibitor containing the isothiocyanate group of the above formula (2) was added.

Example 2.

A cell was prepared in the same manner as in Example 1 except that the content of the side reaction inhibitor was 0.2%.

Example 3.

A cell was prepared in the same manner as in Example 1 except that the content of the side reaction inhibitor was 0.3%.

Example 4 Preparation of Electrolyte

In Example 4 of the present invention, an electrolyte for NMR analysis was prepared. Reference electrolyte is 1.15 M LiPF ₆ in EC / DMC (5/95, vol%) + 10% FEC. As a side reaction inhibitor, 0.1% of a side reaction inhibitor containing the isothiocyanate group of the above formula (2) was added.

Comparative Example 1.

A cell was prepared in the same manner as in Example 1 except that no side reaction inhibitor was added.

Comparative Example 2. Preparation of Negative Control

An electrolyte was prepared in the same manner as in Example 4, except that no side reaction inhibitor was added.

Experimental Example 1. Evaluation of Fast Charge Characteristics of NCM622 / Graphite Full Cells

First, during the one-time charging and discharging, the full cell is charged at a constant current at 25 ° C. with a current of 0.1 C rate until the voltage reaches 4.2 V (vs. Li), and then in constant voltage (CV) mode. Cut-off at 0.05C current was maintained at 4.2V. Subsequently, it discharged at the constant current of 0.1C rate until the voltage reached 3.0V (vs. Li) at the time of discharge (chemical conversion step, 1st cycle). The full cell, which has undergone the 1st cycle of the formation step, is charged at a constant current until the voltage reaches 4.2V (vs. Li) at a current of 0.2C at 25 ° C., and the current is 0.05C while maintaining 4.2V in the constant voltage mode. Cut-off at. Subsequently, the battery was discharged at a rate of 0.2 C until the voltage reached 3.0 V (vs. Li). This process is called the standard course, and this process is repeated three times. The full cell, which had undergone the standard procedure, was charged by 50 cycles with different charging current conditions of 2C-rate and 3C-rate, respectively, and the discharge current condition was fixed at 1C-rate. Voltage and cutoff conditions in addition to current conditions were performed in the same manner as in Mars and Standard.

Evaluation results for the fast charge characteristics are shown in FIGS. 1 to 2.

1 to 2 below is based on Experimental Example 1 of the cell prepared according to Examples 1 to 3 and Comparative Example 1 provided in one aspect of the present invention, the side reaction inhibitor of the provided in one aspect of the present invention It is to grasp the effect and proper content on the fast charging performance improvement.

As the side reaction inhibitor is applied, it can be seen that the life performance is improved in the 3C (20 minutes charge) / 1C discharge life characteristics. It is believed that the side reaction inhibitor effectively removes HF in the electrolyte, thereby minimizing deterioration of the electrode-electrolyte interface, thereby improving fast charging characteristics of the battery.

Experimental Example 2. NCM622 Anode Surface F 1s XPS Analysis After Mars of NCM622 / Graphite Full Cells

First, during the one-time charging and discharging, the full cell is charged at a constant current at 25 ° C. with a current of 0.1 C rate until the voltage reaches 4.2 V (vs. Li), and then in constant voltage (CV) mode. Cut-off at 0.05C current was maintained at 4.2V. Subsequently, at the time of discharge, the battery was discharged at a constant current of 0.1 C rate until the voltage reached 3.0 V (vs. Li) (the formation step, 1st cycle). The full cell that passed the 1st cycle of the formation step was placed in an argon glove box. After dismantling at, separate the NCM622 anode. The separated positive electrode was washed / dried in DMC and then F 1s XPS analysis was performed.

3 is a cell prepared according to Examples 1 to 3 and Comparative Example 1 provided in one aspect of the present invention based on Experimental Example 2, by using a side reaction inhibitor provided in one aspect of the present invention to the positive electrode surface It is confirmed through the F 1s XPS analysis that the LiF formation that can be formed by HF is inhibited.

In addition, since the PVDF peak used as the positive electrode binder appears more strongly when the side reaction inhibitor is applied, it is judged that the film formed on the surface of the positive electrode is thinner than the positive electrode using the reference electrolyte solution. As the thin film is formed, the anode interface resistance decreases, and thus, the fast charging property may be improved.

Experimental Example 3. ¹⁹ HF and LiPF of side reaction inhibitors by F NMR analysis ₆  Confirmation of hydrolysis inhibition effect

Example 4 and Comparative Example 2 After the addition of 1wt% of water to the electrolyte solution and stored at room temperature for 24 hours, the hydrolysis side reaction product of LiPF ₆ salt was analyzed by ¹⁹ F NMR analysis.

Figure 4 is based on Experimental Example 3 of the electrolyte prepared according to Example 4 and Comparative Example 2 provided in one aspect of the present invention, by using a side reaction inhibitor provided in one aspect of the present invention, the valence of LiPF ₆ salt PO ₃ F exploded side reaction products ^- will verify that the significantly reduced PO ₂ F ₂ ^2- and HF.

Through this, it can be confirmed that by inhibiting the hydrolysis of the side reaction inhibitor additive LiPF ₆ to suppress the formation of side reaction products such as HF.

The foregoing description of the present invention is intended for illustration, and it will be understood by those skilled in the art that the present invention may be easily modified in other specific forms without changing the technical spirit or essential features of the present invention. will be. Therefore, it should be understood that the embodiments described above are exemplary in all respects and not restrictive. For example, each component described as a single type may be implemented in a distributed manner, and similarly, components described as distributed may be implemented in a combined form.

The scope of the present invention is represented by the following claims, and it should be construed that all changes or modifications derived from the meaning and scope of the claims and their equivalents are included in the scope of the present invention.

Claims (12)

LiPF ₆ , LiClO ₄ , LiBF ₄ , LiFSI, LiTFSI, LiSO ₃ CF ₃ ,, LiPO ₂ F ₂ , Lithium bis (oxalate) borate (LiBOB), Lithium difluoro (oxalate) Lithium difluoro (oxalate) borate (LiFOB), Lithium difluoro (bisoxalato) phosphate (Lithium difluoro (bisoxalato) phosphate, LiDFBP), Lithium tetrafluoro (oxalate) phosphate, LiTFOP), Lithium fluoromalonato (difluoro) borate (LiFMDFB) And a lithium salt comprising any one selected from the group consisting of a mixture thereof;
Carbonate solvents; And
Side reaction inhibitors, including
Electrolyte composition for lithium secondary battery. The method of claim 1,
The carbonate solvent,
Ethylene carbonate (EC), propylene carbonate (PC), vinyl ethylene carbonate (VC), fluoroethylene carbonate (FEC), and a mixture thereof. Including one,
Electrolyte composition for lithium secondary battery. The method of claim 1,
The carbonate solvent,
Dimethyl carbonate, ethylmethyl carbonate (Ethylmethyl carbonate), diethyl carbonate (Diethyl carbonate) and any one selected from the group consisting of a mixture thereof,
Electrolyte composition for lithium secondary battery. The method of claim 1,
The side reaction inhibitor,
One containing an isocyanate group (N = C = O) or an isothiocyanate group (N = C = S),
Electrolyte composition for lithium secondary battery. The method of claim 1.
The side reaction inhibitor,
To include a compound of formula (1)
Electrolyte composition for lithium secondary battery.
<Formula 1>

(A is sulfur (S) or oxygen (O), and R1 to R3 are C1 to C10 linear carbon chains.) The method of claim 1,
Concentration of the lithium salt is 0.1 M to 3M,
Electrolyte composition for lithium secondary battery. The method of claim 1,
Concentration of the side reaction inhibitor is 0.1 to 10% by weight,
Electrolyte composition for lithium secondary battery. The method of claim 1,
The side reaction is,
It comprises a hydrolysis reaction of the lithium salt on the surface of the positive electrode, the negative electrode or both and the electrode-electrolyte interface side reaction,
Electrolyte composition for lithium secondary battery. The method of claim 1,
1,2-dimethoxyethane (1,2-dimethoxyethane), 1,3-dioxolane (1,3-dioxolane), diethylene glycol, dimethyl ether, teraethylene glycol ( tetraethylene glycol) selected from the group consisting of diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, and mixtures thereof One ether-based solvent; further comprising,
Electrolyte composition for lithium secondary battery. The method of claim 1,
Fluoroethylene carbonate (FEC), vinyl carbonate (VC), lithium oxalyldifluoroborate (LiDFOB), lithium nitrate (LiNO3), 4-methyl-1,3-dioxol-2-one (MVC), 4-fluoro-1,3 -dioxol-2-one), FMVC (4- (fluoranylmethyl) -1,3-dioxol-2-one), TFMVC (4- (trifluoromethyl) -1,3-dioxol-2-one), FPVC (4- (4-fluorophenyl) -1,3-dioxol-2-one), TFPVC (4- (4- (trifluoromethyl) phenyl) -1,3-dioxol-2-one), PFPVC (4- (pentafluorophenyl) -1 , 3-dioxol-2-one), FTMSVC (4-((fluoro-((trimethylsilyl) oxy) alkoxy) methyl) -1,3-dioxol-2-one), PFMVC (4-((perfluoroalkoxy) methyl) -1,3-dioxol-2-one) and any one additional additive selected from the group consisting of a mixture thereof;
Electrolyte composition for lithium secondary battery. The method of claim 1,
The electrolyte composition has a capacity retention rate of 80.0% to 99% after 100 cycles.
Electrolyte composition for lithium secondary battery. anode;
cathode;
An ion permeable separator between the anode and the cathode; And
Claim 1 to claim 11, comprising the electrolyte solution for lithium secondary battery of any one of
Lithium secondary battery.

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