KR20220005112A - Electrolyte for lithium secondary battery and lithium secondary battery comprising the same - Google Patents

Abstract

An electrolyte additive for a secondary battery according to an embodiment of the present invention includes a compound represented by the following Chemical Formula 1. [Chemical Formula 1] (in Chemical Formula 1, R1, R2, R3, and R4 are the same as or different from each other, and each independently represent hydrogen, a substituted or unsubstituted C1-C6 alkyl group, a C1-C6 alkenyl group, a C1-C6 alkynyl group, or a C6-C10 aryl group, and R5 is a substituted or unsubstituted C1-C6 alkyl, C1-C6 alkenyl, C1-C6 alkynyl, or C6-C10 aryl group.) The present invention can improve an electrochemical performance, reaction rate, and stability of the battery.

Description

Electrolyte additive for lithium secondary battery and lithium secondary battery comprising same

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

Recently, interest in medium and large-capacity lithium secondary batteries for application to power sources for next-generation vehicles and the like is increasing.

In particular, when a layered oxide containing an excess of lithium (ie, lithium-rich) is used as a positive electrode active material, the charging and driving voltage of the battery can be improved, and a silicon-based material rather than a carbon-based material is used as the negative electrode active material. Because it can be used as a battery, the capacity of the battery can be improved.

On the other hand, in a general lithium secondary battery, lithium salt dissolved in a solvent is used as an electrolyte. The over-lithium positive electrode active material creates a high voltage environment while generating oxygen gas during the first charge, and the silicon-based negative electrode active material is subjected to repeated charging and discharging. Severe volume expansion occurs and cracks are formed on the surface, and eventually, electrolyte decomposition reaction is commonly induced on the surface of the electrode to which each active material is applied.

As a result, the electrolyte is gradually depleted, and the electrochemical performance of the battery is rapidly deteriorated, and as a thick film acting as a resistance is formed on the surface of each electrode, the electrochemical reaction rate of the battery is lowered. In addition, there is a problem in that the electrochemical stability of the battery is not guaranteed because an acidic material (eg, HF, etc.) generated as a result of the decomposition of the electrolyte melts each electrode film or damages the positive electrode active material.

However, additives such as 1,3-propanesultone and 1,3-propensultone, which have been extensively studied as electrolyte additives in the prior art, improve high-temperature storage characteristics of secondary batteries during long-term high-temperature storage, but high-temperature lifespan characteristics of secondary batteries. This diminishing problem arises.

On the other hand, in Laid-Open Patent Publication No. 10-2018-0015219, a propane sultone derivative compound in which a carbon at a specific position is substituted with a specific substituent is disclosed as an electrolyte additive for removing HF, an acidic material generated as a result of decomposition of the electrolyte, but the problem of cell swelling There is a problem that occurs.

Korean Patent Publication No. 10-2019-0022382 Republic of Korea Patent Publication No. 10-2018-0015219

The present invention is to solve the problem of cell swelling by adding a special additive to an electrolyte for a lithium secondary battery so that a by-product generated by reacting with HF becomes a liquid at room temperature.

In addition, it is an object of the present invention to provide an electrolyte additive having a function of efficiently removing HF in a secondary battery with a small amount of equivalent, and forming a passivation film on the surface of the anode as the produced material acts as a reductive decomposition additive.

In addition, an object of the present invention is to provide an electrolyte additive that can be efficiently applied to a perlithium positive electrode active material and a silicon-based negative electrode active material.

In addition, it is intended to implement a lithium secondary battery of high voltage and high capacity by applying the electrolyte additive.

The electrolyte additive for a secondary battery according to an embodiment of the present invention includes a compound represented by the following formula (1).

[Formula 1]

(In Formula 1, R1, R2, R3 and R4 are the same as or different from each other, and each independently represents hydrogen, a substituted or unsubstituted C1-C6 alkyl group, a C1-C6 alkenyl group, and a C1-C6 alkyl group. a nyl group or a C6-C10 aryl group, wherein R5 is a substituted or unsubstituted C1-C6 alkyl, C1-C6 alkenyl, C1-C6 alkynyl, or C6-C10 aryl group).

The electrolyte additive for a secondary battery according to an embodiment of the present invention may include at least one material selected from the following Chemical Formulas 1-1 to 1-9.

[Formula 1-1]

[Formula 1-2]

[Formula 1-3]

[Formula 1-4]

[Formula 1-5]

[Formula 1-6]

[Formula 1-7]

[Formula 1-8]

[Formula 1-9]

.

.

The electrolyte additive for a secondary battery according to an embodiment of the present invention may react with HF in a lithium secondary battery to form a compound represented by the following formula (2).

[Formula 2]

(In Formula 2, R1, R2, R3 and R4 are the same as or different from each other, and each independently represents hydrogen, a substituted or unsubstituted C1-C6 alkyl group, a C1-C6 alkenyl group, and a C1-C6 alkyl group. a nyl group or a C6-C10 aryl group, wherein R5 is a substituted or unsubstituted C1-C6 alkyl, C1-C6 alkenyl, C1-C6 alkynyl, or C6-C10 aryl group).

The compound represented by Formula 2 according to an embodiment of the present invention may be in a liquid state at room temperature (25° C.).

The electrolyte for a secondary battery according to an embodiment of the present invention includes an electrolyte additive for a secondary battery represented by Chemical Formula 1; lithium salt; and a solvent;

The electrolyte for a secondary battery according to an embodiment of the present invention may further include an oxidative decomposition type additive.

In the electrolyte for a secondary battery according to an embodiment of the present invention, the electrolyte additive for a secondary battery represented by Formula 1 may be included in an amount of 0.01 to 10% by weight based on the total weight of the electrolyte.

A secondary battery according to an embodiment of the present invention includes a positive electrode; cathode; a separator interposed between the anode and the cathode; and an electrolyte for the secondary battery.

The positive electrode of the secondary battery according to an embodiment of the present invention may include a lithium-rich positive electrode active material.

The negative electrode of the secondary battery according to an embodiment of the present invention may include a silicon negative electrode active material.

An object of the present invention is to solve the problem of cell swelling by allowing the by-product generated by reacting with the electrolyte HF for a secondary battery according to an embodiment of the present invention to become a liquid at room temperature.

In addition, the electrolyte additive for a secondary battery can efficiently remove HF in a secondary battery with a small equivalent, and at the same time, the produced material acts as a reductive decomposition type additive to form a passivation film on the surface of the anode.

In addition, by applying the electrolyte additive for a secondary battery to a secondary battery, the electrochemical performance, reaction rate, and stability of the battery can be improved.

In addition, since it can be optimally applied to a secondary battery to which an overlithium positive electrode active material and a silicon-based negative electrode active material are applied, a higher voltage and higher capacity lithium secondary battery can be realized.

Hereinafter, the present invention will be described in more detail through examples. These examples are only for illustrating the present invention, and therefore, the scope of the present invention is not to be construed as being limited by these examples.

Expressions such as "comprising" as used herein should be understood as open-ended terms, including 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 desirable, under the same or other circumstances. Additionally, the recitation of one or more preferred embodiments does not imply that other embodiments are not useful, nor is it intended to exclude other embodiments from the scope of the invention.

The electrolyte additive for a secondary battery according to an embodiment of the present invention includes a compound represented by the following formula (1).

[Formula 1]

In Formula 1, R1, R2, R3 and R4 are the same as or different from each other, and each independently represents hydrogen, a substituted or unsubstituted C1-C6 alkyl group, a C1-C6 alkenyl group, and a C1-C6 alkynyl group. , or a C6-C10 aryl group, wherein R5 is a substituted or unsubstituted C1-C6 alkyl, C1-C6 alkenyl, C1-C6 alkynyl, or C6-C10 aryl group.

The electrolyte additive represented by Chemical Formula 1 may be purchased or manufactured, and the place of purchase or a manufacturing method thereof is not particularly limited.

In a more preferred embodiment, the electrolyte additive may be at least one material selected from the following Chemical Formulas 1-1 to 1-9.

[Formula 1-1]

[Formula 1-2]

[Formula 1-3]

[Formula 1-4]

[Formula 1-5]

[Formula 1-6]

[Formula 1-7]

[Formula 1-8]

[Formula 1-9]

.

.

The electrolyte additive may react with HF in the lithium secondary battery to form a compound represented by the following formula (2).

[Formula 2]

In Formula 2, R1, R2, R3 and R4 are the same as or different from each other, and each independently represents hydrogen, a substituted or unsubstituted C1-C6 alkyl group, a C1-C6 alkenyl group, and a C1-C6 alkynyl group. , or a C6-C10 aryl group, wherein R5 is a substituted or unsubstituted C1-C6 alkyl, C1-C6 alkenyl, C1-C6 alkynyl, or C6-C10 aryl group.

The mechanism of generating HF in the lithium secondary battery and the mechanism in which the electrolyte additive represented by Formula 1 reacts with HF in the lithium secondary battery to form the compound represented by Formula 2 are as follows.

[Mechanism 1]

As gases such as HF are generated in the secondary battery, the thickness of the battery expands during charging. In addition, when left at a high temperature in a fully charged state, the negative electrode passivation film is gradually collapsed by the increased electrochemical energy and thermal energy over time, and a side reaction in which the surrounding electrolyte reacts with the newly exposed surface of the negative electrode continues to occur. . Due to the continuous gas generation, the internal pressure of the secondary battery increases, and performance degradation occurs such as a decrease in the lifespan of the secondary battery at a high temperature due to volume expansion of the secondary battery.

The electrolyte additive according to an embodiment of the present invention can suppress the shortening of the battery life by removing HF generated by moisture as in the above mechanism.

In addition, since 1 equivalent of the electrolyte additive can remove 2 equivalents of HF, it is possible to more efficiently remove HF in the lithium secondary battery.

In addition, the compound represented by Formula 2 generated by the reaction of the electrolyte additive with HF may be in a liquid state at room temperature (25° C.).

The existing HF skivenzer has a problem in that the cell swells due to the formation of gas due to the low boiling point of the generated by-product. The present invention can solve the problem of cell swelling by generating a by-product in a liquid state.

In addition, the electrolyte additive may form a solid electrolyte interphase (SEI) on the surface of the anode by removing the HF and simultaneously forming a compound represented by Chemical Formula 2 as a reductive decomposition additive. These SEIs have ion conductivity and serve to help lithium ions move. In addition, due to the passivation film generated by the electrolyte additive, it is possible to suppress the further decomposition of the electrolyte and improve the reversible capacity.

In addition, when the additive according to the embodiment of the present invention is applied to a lithium secondary battery, the electrochemical performance, reaction rate and stability of the lithium secondary battery can be improved, and the capacity and lifespan maintenance rate can be sufficiently improved.

The lithium secondary battery electrolyte of the present invention is generally stable in a temperature range of -20 to 60 °C, and can maintain electrochemically stable characteristics even at a voltage of 4.5V, so it can be applied to all lithium secondary batteries such as lithium ion batteries and lithium polymer batteries. can

The electrolyte for a secondary battery according to an embodiment of the present invention includes an electrolyte additive for a secondary battery represented by Chemical Formula 1; lithium salt; and a solvent;

The electrolyte additive for a secondary battery represented by Chemical Formula 1 is the same as described above.

The electrolyte additive may be included in an amount of 0.01 to 10% by weight, or 0.01 to 5% by weight, or 0.01 to 3% by weight based on the total weight of the electrolyte. When the electrolyte additive is included in the above content, it is possible to form an appropriate amount of a passivation film formed on the surface of the negative electrode formed at the same time as removing HF in the secondary battery.

In one embodiment, the lithium salt is preferably LiPF ₆ , LiBF ₄ , LiClO ₄ , 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, LiN(SO ₂ C ₂ F ₅ ) ₂ , Li(CF ₃ SO ₂ ) ₂ N, LiC ₄ F ₉ SO ₃ , LiB(C ₆ H ₅ ) ₄ , Li(SO ₂ F) ₂ N(LiFSI) and (CF ₃ SO ₂ ) ₂ NLi may be at least one selected from, but not particularly limited to.

The concentration of the lithium salt in the electrolyte of the present invention may be 0.1 to 2 M.

The solvent may be a carbonate-based, ester-based, ether-based, ketone-based, alcohol-based, aprotic solvent, or a combination thereof.

In one embodiment, the solvent is preferably ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (dimethyl catbonate, DMC), diethyl carbonate (diethyl catbonate, DEC), Or it may be a combination thereof, but is not particularly limited thereto.

The electrolyte for a secondary battery according to an embodiment of the present invention may further include an oxidative decomposition type additive.

In one embodiment, the oxidative decomposition additive may be the following LiFOB, LiBOB, WCA1, WCA2, WCA3.

The electrolyte for a secondary battery according to an embodiment of the present invention may further include a reductive decomposition additive.

As an embodiment, the reductive decomposition additive is selected from fluoroethylene carbonate (FEC) and vinylene carbonate (VC), propanesultone (PS), and propanylsultone (PRS) It may be at least any one or more.

The reductive decomposition additive may be included in an amount of 0.1 to 10% by weight, preferably 0.5 to 5% by weight, more preferably 1 to 3% by weight relative to the total weight of the electrolyte. When the reductive decomposition additive is included in the above content, it is possible to prevent decomposition of the electrolyte and prevent damage to the negative electrode active material.

A secondary battery according to an embodiment of the present invention includes a positive electrode; cathode; a separator interposed between the anode and the cathode; and an electrolyte for the secondary battery.

The secondary battery may be a lithium secondary battery, and may be classified into a lithium ion battery, a lithium ion polymer battery, and a lithium polymer battery according to the type of a separator and an electrolyte.

In addition, the lithium secondary battery may be classified into a cylindrical shape, a prismatic shape, a coin type, a pouch type, etc. according to the shape, and may be divided into a bulk type and a thin film type according to the size.

The structure and manufacturing method of these batteries are not particularly limited, and since they are widely known in the technical field to which the present invention pertains, a detailed description thereof will be omitted.

As an embodiment, the lithium secondary battery may have a form in which a negative electrode, a separator, and a positive electrode are sequentially stacked and then accommodated in a battery container while being wound on a spiral.

The positive electrode may include a current collector and a positive electrode active material layer formed on the current collector, and the positive electrode active material layer may include a positive electrode active material.

The cathode active material is a compound capable of reversible intercalation and deintercalation of lithium (lithiated intercalation compound), and any cathode active material available in the art may be used.

As an example, the positive electrode active material is a lithium-containing transition metal oxide, that is, lithium cobalt-based oxide, lithium manganese-based oxide, lithium copper oxide, lithium nickel-based oxide, lithium manganese composite oxide, and lithium-nickel-manganese-cobalt-based oxide. It may be at least any one or more selected from the group consisting of.

In addition, as an example, the cathode active material is LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , Li(Ni _a Co _b Mn _c )O ₂ (0<a<1, 0<b<1, 0<c<1, a+b+c=1), LiNi _{1 - y} Co _y O ₂ (O<y<1), LiCo _{1 -y} Mn _y O ₂ (O<y<1), LiNi _{1 - y} Mn _y O ₂ (O?y<1), Li(Ni _a Co _b Mn _c )O ₄ (0<a<2, 0<b<2, 0<c<2, a+b+c=2), _{LiMn 2-z Ni z O 4} (0 <z <2), LiMn 2 - z Co z O 4 (0 <z <2), can at least be at least one selected from the group consisting of LiCoPO ₄ and LiFePO _4.

Also, more preferably, the positive electrode active material may include a lithium-rich positive electrode active material.

In addition, the positive electrode active material is a perlithium positive electrode active material, and may include a compound represented by the following formula (3).

[Formula 3]

Li _x Ni _y Mn _z Co _w O ₂

In Formula 3, 1<x≤2, 0<y≤1, 0<z≤1, and 0<w≤1.

Recently, a technique for improving the charging and driving voltage of a battery by using a perlithium layered oxide containing an excess of lithium as a positive electrode active material has been studied. In this case, since a silicon-based material rather than a carbon-based material can be used as the negative electrode active material, the capacity of the battery can be further improved.

The positive electrode active material layer may also include a binder and/or a conductive material.

The binder serves to well adhere the positive electrode active material particles to each other and the positive electrode active material to the current collector. In one embodiment, as the binder, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymer including ethylene oxide, poly Vinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride (PVDF), polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, etc. can be used. , but is not particularly limited thereto.

The conductive material serves to impart conductivity to the electrode. As the conductive material, any electronically conductive material that does not cause chemical change in the battery may be used. As an example, metal powders such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, copper, nickel, aluminum, silver, and metal fibers, metal fibers, etc. may be used, and conductive materials such as polyphenylene derivatives may be used alone or in combination of one or more.

The negative electrode may include a current collector and an anode active material layer formed on the current collector, and the anode active material layer may include an anode active material.

The negative active material is a material capable of reversibly intercalating and deintercalating lithium ions, and includes a carbon-based material, lithium metal, an alloy of lithium metal, a material capable of doping and de-doping lithium, a silicon-based or transition metal. oxides and the like can be used.

The carbon-based material includes crystalline carbon and amorphous carbon. Examples of the crystalline carbon include graphite such as amorphous, plate-like, flake, spherical or fibrous natural graphite or artificial graphite, and examples of the amorphous carbon include soft carbon (low-temperature calcined carbon). or hard carbon, mesophase pitch carbide, and calcined coke.

The lithium metal alloy includes lithium and Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al and Sn from the group consisting of Alloys of metals of choice may be used.

As the silicon-based material, a combination of graphite and silicon, a material in which silicon is coated on the surface of graphite particles, or a material in which silicon and carbon are simultaneously coated on the surface of graphite particles may be SiO _x , Si may be carbon-based.

Examples of the transition metal oxide include vanadium oxide and lithium vanadium oxide.

Among the anode active materials, a carbon-based material such as graphite is widely known as a material capable of reversibly intercalating and deintercalating lithium ions. Graphite has a low discharge voltage of -0.2V compared to lithium, and a battery using graphite as an anode active material exhibits a high discharge voltage of 3.6V, providing an advantage in terms of energy density of a lithium battery. In addition, secondary batteries using graphite as an anode active material are the most widely used because they guarantee a long lifespan of lithium secondary batteries with excellent reversibility.

However, the graphite anode active material has a problem with low capacity in terms of energy density per unit volume of the electrode plate due to the low density of graphite (theoretical density 2.2 g/cc) during the manufacture of the electrode plate, and a side reaction with the organic electrolyte at a high discharge voltage is easy to occur, and the battery There is a problem of swelling and capacity degradation. Therefore, in recent years, as a material capable of doping and de-doping lithium, a silicon-based material having a high capacity has been in the spotlight as an alternative.

However, as an electrolyte of a general lithium secondary battery, a lithium salt dissolved in a solvent is used as an electrolyte. The over-lithium positive electrode active material creates a high voltage environment while generating oxygen gas during the first charge, and the silicon-based negative electrode active material is repeatedly charged and discharged. As a result, serious volume expansion occurs and cracks are formed on the surface, and eventually, a decomposition reaction of the electrolyte solution is commonly induced on the surface of the electrode to which each of the active materials is applied.

As a result, the electrolyte is gradually depleted, and the electrochemical performance of the battery is rapidly deteriorated, and as a thick film that acts as a resistance is formed on the surface of each electrode, the electrochemical reaction rate of the battery is reduced. In addition, there is a problem in that the electrochemical stability of the battery is not guaranteed because an acidic material (eg, HF, etc.) generated as a result of the decomposition of the electrolyte melts each electrode film or damages the positive electrode active material. However, the electrolyte according to the embodiment of the present invention can be efficiently applied to an overlithium positive electrode active material and a silicon-based negative electrode active material.

The anode active material layer may further include a binder and/or a conductive material.

For the binder and the conductive material, the roles and representative examples described in the positive electrode active material for the negative electrode active material are similarly applied, and there is no particular limitation as long as the binder and the conductive material can be used in the related field.

The average charging voltage of the lithium secondary battery may be 4.5 V or more. This is a high-range voltage that can be expressed when the positive electrode containing the overlithium positive electrode active material and the negative electrode containing the silicon-based negative electrode active material are applied, and can be stably maintained by the functional additive included in the electrolyte solution of the present invention. have.

[Example] Preparation of electrolyte comprising each of the following electrolyte additives

_{1M LiPF 6} and FEC (fluoroethylene carbonate) in a non-aqueous organic solvent in which ethylene carbonate (EC), ethylmethyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a ratio of 2:5:5 (v/v/v) ) 1% by weight, and 1% by weight of the electrolyte additives according to Examples 1 to 7 were respectively added to prepare an electrolyte solution for a secondary battery.

[Example 1] Synthesis of 4,4'-((Ethane-1,2-diylbis(dimethylsilanediyl))bis(oxy))bis(1,2-oxathiolane 2,2-dioxide)

4-Hydroxy-1,2-oxathiolane-2,2-dioxide synthesized in a reaction vessel (8 g, 57.9 mmol, Journal of the Society of Dyers and Colorists, 1998, 114(5-6), 160-164 method used) Synthesis) and Imidazole (4 g, 58.8 mmol, 2.02 eq) were added to DMF (80 mL) and cooled to 0 °C with stirring. To the cooled reaction mixture, 1,2-Bis(chlorodimethylsilyl)ethane (5.7 g, 26.4 mmol, 0.91 eq) is slowly added. Raise the temperature of the reactant to room temperature (20 °C to 25 °C) and then stir for 5 hours. The reaction solvent is concentrated, purified water (100 mL) is added to the reaction mixture, extracted with dichloromethane (100 mL), and the organic layer is washed with Brine (100 mL). The organic layer was dried over anhydrous Na ₂ SO ₄ , the organic solvent was concentrated, and the concentrate was purified using column chromatography to obtain the white powder compound (5.8 g, 48 % yield).

[Example 2] Synthesis of (E)-4,4'-((ethene-1,2-diylbis(dimethylsilanediyl))bis(oxy))bis(1,2-oxathiolane 2,2-dioxide)

1,2-Bis(chlorodimethylsilyl)ethene was synthesized using the literature method (Russian journal of General Chemistry, 2012, 82(5), 944-945) and synthesized by the method of Example 1 (4-Hydroxy-1,2 -oxathiolane-2,2-dioxide 8 g, 57.9 mmol) to obtain the compound (4.9 g, 41 % yield).

[Example 3] Synthesis of 4,4'-((Ethyne-1,2-diylbis(dimethylsilanediyl))bis(oxy))bis(1,2-oxathiolane 2,2-dioxide)

Bis(chlorodimethylsilyl)ethyne (5.8 g, 27.7 mmol, 0.95 eq.) and Triethylamine (10.1 mL) synthesized using the literature method (J. Organomet. Chem., 1998, 562(2), 207-215) in a reaction vessel , 72.8 mmol, 2.5 eq.) was added to DC (60 mL) and cooled to 0 °C with stirring. To the cooled reaction mixture, a solution of 4-Hydroxy-1,2-oxathiolane-2,2-dioxide (8 g, 57.9 mmol in MC 40 mL) is slowly added for 30 minutes. Raise the temperature of the reactant to room temperature (20 ℃ ~ 25 ℃) and then stir for 3 hours. The precipitate generated during the reaction was removed by filtration, and the organic layer was washed with purified water (100 mL ×2). The organic layer was dried over anhydrous Na2SO4, the organic solvent was concentrated, and the concentrate was purified using column chromatography to obtain the white powder compound (5.2 g, 43 % yield).

[Example 4] Synthesis of 4,4'-((1,4-Phenylenebis(dimethylsilanediyl))bis(oxy))bis(1,2-oxathiolane 2,2-dioxide)

1,4-Phenylenebis(chlorodimethylsilane) was synthesized by the method of Example 3 (4-Hydroxy-1,2-oxathiolane-2,2-dioxide 8 g, 57.9 mmol) by purchasing a material from Combi-Block Company, and preparing the compound (6.0 g, 45% yield) was obtained.

[Example 5] Synthesis of 4,4'-((Ethane-1,2-diylbis(diethylsilanediyl))bis(oxy))bis(1,2-oxathiolane 2,2-dioxide)

1,2-Bis(chlorodiethylsilyl)ethene was synthesized using the literature method (Russian journal of General Chemistry, 2008, 78(9), 1668-1674) and synthesized by the method of Example 1 (4-Hydroxy-1,2 -oxathiolane-2,2-dioxide 8 g, 57.9 mmol) to obtain the compound (5.3 g, 39 % yield).

[Example 6] 4-(((2-(((2,2-dioxido-1,2-oxathiolan-4-yl)oxy) (methyl)(phenyl)silyl)ethyl)dimethylsilyl)oxy)-1, Synthesis of 2-oxathiolane 2,2-dioxide

Synthesis and implementation of chloro(2-(chloro(methyl)(phenyl)silyl)ethyl)dimethylsilane by reacting chlorodimethylsilane with chloromethylphenylsilane using the literature method (Russian journal of General Chemistry, 2008, 78(9), 1668-1674) By the method of Example 1 (4-Hydroxy-1,2-oxathiolane-2,2-dioxide 8 g, 57.9 mmol), the compound (4.8 g, 35 % yield) was obtained.

[Example 7] Synthesis of 4,4'-((ethane-1,2-diylbis(methyl(vinyl)silanediyl))bis(oxy))bis(1,2-oxathiolane 2,2-dioxide)

1,2-bis(chloro(methyl)(vinyl)silyl)ethane was synthesized by reacting chloromethyldivinylsilane and chloromethylvinylsilane using the literature method (Russian journal of General Chemistry, 2008, 78(9), 1668-1674) and Examples The compound (4.8 g, 38 % yield) was obtained by the synthesis (4-Hydroxy-1,2-oxathiolane-2,2-dioxide 8 g, 57.9 mmol) in the method of 1.

1H NMR and GC-Mass results of the compounds represented by Formulas 1-1 to 1-9 synthesized by the above preparation method are shown in Table 1 below.

chemical formula 1H NMR (400 MHz, DMSO-d6): δ GC-Mass (m/z) 1-1 4.54 to 4.29 (m, 4H), 4.17 (dd, 2H), 3.46 to 3.21 (m, 4H) 1,12 (s, 4H), 0.21 (s. 12H) 418.06 1-2 4.54 to 4.29 (m, 4H), 4.17 (dd, 2H), 3.46 to 3.21 (m. 4H) 1.4 (m, 2H), 1.08 (m, 4H), 0.21 (s, 12H) 432.08 1-3 4.52 to 4.29 (m, 4H), 4.17 (dd, 2H), 3.46 to 3.21 (m, 4H) 1.30 to 1.28 (m, 8H), 1.08 (m, 4H), 0.21 (s, 12H) 474.12 1-4 5.3(s, 2H), 4.54~4.29 (m, 4H), 4.17~4.13(m, 2H) 3.46~3.21(m, 4H), 0.14(s, 12H) 416.05 1-5 4.54 to 4.29 (m, 4H), 4.17 to 4.13 (m, 2H) 3.46 to 3.21 (m, 4H), 0.14 (s, 12H) 414.03 1-6 7.18(s, 4H), 4.54~4.29 (m, 4H), 4.17~4.13(m, 2H) 3.46~3.21(m, 4H), 0.66(s, 12H) 466.06 1-7 4.52 to 4.29 (m, 4H), 4.17 to 4.13 (m, 2H), 3.46 to 3.21 (m, 4H) 1.12 to 1.08 (m, 12H), 0.92 to 0.88 (m, 12H) 474.12 1-8 7.45~7.18(m, 5H), 4.52~4.29(m, 4H), 4.17~4.13(m, 2H), 3.46~3.21(m, 4H), 1.5(t, 2H), 1.12(t,2H), 0.66(s,3H), 0.21(s, 6H) 480.08 1-9 5.42~16 (dd, 4H), 5.3(s, 2H), 4.54~4.29(m, 4H), 4.17~4.13(m, 2H), 3.46~3.21(m, 4H) 1.12(s, 4H), 0.14 (s, 6H) 442.06

[Comparative Example 1]

An electrolyte solution was prepared in the same manner as in Examples 1 to 7 except that the additives of Examples 1 to 7 were not added.

[Comparative Example 2]

An electrolyte solution was prepared in the same manner as in Examples above, except that an additive represented by the following Chemical Formula 4 was added instead of the additives of Examples 1 to 7.

[Formula 4]

[Comparative Example 3]

An electrolyte solution was prepared in the same manner as in Examples above, except that an additive represented by the following Chemical Formula 5 was added instead of the additives of Examples 1 to 7.

[Formula 5]

[Production Example] Preparation of secondary battery

_{A positive electrode was prepared using a composition for forming a positive electrode active material layer comprising 94% by weight of LiCoO 2} as a positive electrode active material, 3% by weight of PVDF (polyvinylidene fluoride) as a binder, and 3% by weight of carbon black as a conductive material. In addition, an anode was prepared by including a composition for forming an anode active material layer comprising 96 wt% of graphite as an anode active material, 3 wt% of PVDF as a binder, and 1 wt% of carbon black as a conductive material.

After placing the separator on the prepared positive electrode and placing the prepared negative electrode there again, the electrolyte solution according to the Examples and Comparative Examples was injected, respectively, and vacuum packaging was performed to prepare a lithium secondary battery.

[Experimental Example 1] Evaluation of capacity retention rate (%)

The battery prepared in Preparation Example was charged at 1C to 4.5V at room temperature (25°C), discharged at 2.75V at 1C, charged at 0.5C to 4.2V, left at high temperature (45°C) for 1 week, and then charged at 1C to 4.2V, 2.75 After 2 cycles of V 1C discharge, the capacity discharged in the 2nd cycle was measured and compared.

The battery characteristics of the secondary batteries according to Examples and Comparative Examples were evaluated as follows, and the results are shown in Table 2 below.

[Experimental Example 2] Evaluation of room temperature life retention rate (%)

The battery prepared in Preparation Example 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 the capacity after repeating this 500 times was measured. Next, from the formula: life retention = (capacity / initial capacity after 500 repetitions) * 100, life retention at room temperature was calculated and shown in Table 2 below.

[Experimental Example 3] Evaluation of high temperature life retention rate (%)

The battery prepared in Preparation Example was charged at 1C to 4.5V at a high temperature (45°C), then discharged at 2C to 2.75V to measure the initial capacity, and the capacity after repeating this 500 times was measured. Next, from the formula: life retention = (capacity / initial capacity after 500 repetitions) * 100, life retention at room temperature was calculated and shown in Table 2 below.

Example
One Example
2 Example
3 Example
4 Example
5 Example
6 Example
7 comparative example
One comparative example
2 comparative example
3 Volume
retention rate
(%) 86.6 83.3 84.5 84.5 85.0 83.9 84.2 52.2 80.0 85.8 room temperature life
retention rate
(%) 91.2 90.5 91.8 93.2 92.4 91.2 91.1 67.1 82.0 85.5 high temperature life
retention rate
(%) 90.1 89.5 88.7 90.8 90.5 89.3 89.7 61.7 76.2 78.7

According to Table 2, in the case of the secondary battery manufactured using the electrolyte containing the additive according to the embodiment of the present invention, it can be confirmed that the capacity retention ratio and the life retention ratio are excellent compared to the case according to the comparative example.

Claims (10)

comprising a compound represented by the following formula (1),
Electrolyte additives for secondary batteries:
[Formula 1]

(In Formula 1, R1, R2, R3 and R4 are the same as or different from each other, and each independently represents hydrogen, a substituted or unsubstituted C1-C6 alkyl group, a C1-C6 alkenyl group, and a C1-C6 alkyl group. a nyl group, or a C6-C10 aryl group,
R5 is a substituted or unsubstituted C1-C6 alkyl, C1-C6 alkenyl, C1-C6 alkynyl, or C6-C10 aryl group).
The method of claim 1,
At least one material selected from the following Chemical Formulas 1-1 to 1-9,
Electrolyte additives for secondary batteries:
[Formula 1-1]

[Formula 1-2]

[Formula 1-3]

[Formula 1-4]

[Formula 1-5]

[Formula 1-6]

[Formula 1-7]

[Formula 1-8]

[Formula 1-9]

.
The method of claim 1,
The electrolyte additive for a secondary battery reacts with HF in a lithium secondary battery to form a compound represented by the following Chemical Formula 2,
Electrolyte additives for secondary batteries:
[Formula 2]

(In Formula 2, R1, R2, R3 and R4 are the same as or different from each other, and each independently represents hydrogen, a substituted or unsubstituted C1-C6 alkyl group, a C1-C6 alkenyl group, and a C1-C6 alkyl group. a nyl group, or a C6-C10 aryl group,
R5 is a substituted or unsubstituted C1-C6 alkyl, C1-C6 alkenyl, C1-C6 alkynyl, or C6-C10 aryl group).
4. The method of claim 3,
The compound represented by Formula 2 is in a liquid state at room temperature (25° C.),
Electrolyte additive for secondary batteries.
An electrolyte additive for a secondary battery represented by the formula (1) of claim 1;
lithium salt; and
solvent; containing,
Electrolyte for secondary batteries.
6. The method of claim 5,
The electrolyte for the secondary battery further comprises an oxidative decomposition type additive,
Electrolyte for secondary batteries.
6. The method of claim 5,
The electrolyte additive for a secondary battery represented by Formula 1 is included in an amount of 0.01 to 10% by weight based on the total weight of the electrolyte,
Electrolyte for secondary batteries.
anode; cathode; a separator interposed between the anode and the cathode; and
Including the electrolyte for a secondary battery according to claim 5,
secondary battery.
9. The method of claim 8,
The positive electrode comprises a lithium-rich positive electrode active material,
secondary battery.
9. The method of claim 8,
The negative electrode includes a silicon negative electrode active material,
secondary battery.