KR20230157111A - Additive for Nonaqueous Electrolyte, Nonaqueous Electrolyte and Secondary Battery Comprising the Same - Google Patents

Abstract

The present invention provides a non-aqueous electrolyte solution additive containing a compound of a specific structure, a non-aqueous electrolyte solution containing the same, and a secondary battery. The non-aqueous electrolyte additive according to the present invention has an excellent ability to form a protective film on the negative electrode surface even when a silicon-based negative electrode active material is used, thereby improving battery characteristics.

Description

Non-aqueous electrolyte additive, non-aqueous electrolyte containing the same, and secondary battery {Additive for Nonaqueous Electrolyte, Nonaqueous Electrolyte and Secondary Battery Comprising the Same}

The present invention relates to a non-aqueous electrolyte additive, a non-aqueous electrolyte solution containing the same, and a secondary battery. More specifically, a non-aqueous electrolyte additive that has excellent ability to form a protective film on the negative electrode surface even when using a silicon-based negative electrode active material, a non-aqueous electrolyte solution containing the same, and It is about secondary batteries.

Secondary batteries, specifically lithium secondary batteries, have been adopted as a power source for many portable devices due to their high energy density and ease of design. Recently, they have also been used as a power source for electric vehicles and as a power storage power source that can store electricity produced through the development of alternative energy. Expectations are rising.

A lithium secondary battery consists of a cathode, an anode, an electrolyte, and a separator.

Carbon-based materials such as graphite are widely known as negative electrode active materials used in the negative electrode. However, carbon-based materials have the problem of low capacity, and especially at high discharge voltages, side reactions with the electrolyte are prone to occur, which can lead to swelling of the battery. Accordingly, recently, silicon-based materials with high capacity as negative electrode active materials have been in the spotlight as substitutes.

In the positive electrode, an oxide of lithium and a transition metal with a structure capable of intercalation of lithium ions is used as the positive electrode active material. Recently, lithium-rich layered oxide has been used as the positive electrode to improve the charging driving voltage of the battery. A plan to use it as an active material was proposed. In this case, the capacity of the battery can be further improved because a silicon-based material rather than a carbon-based material can be used as the negative electrode active material.

Meanwhile, the electrolyte solution is one in which lithium salt is dissolved in a non-aqueous solvent. However, the silicon-based negative electrode active material undergoes severe volume expansion due to repeated charging and discharging, causing cracking to form on its surface, which ultimately causes a decomposition reaction of the electrolyte solution on the surface of the electrode.

As a result, the electrolyte is gradually depleted and the electrochemical performance of the battery rapidly deteriorates. Additionally, as a thick film that acts as resistance is formed on the electrode surface, the electrochemical reaction rate of the battery decreases. In addition, there is a problem that the electrochemical stability of the battery is not guaranteed because acidic substances, such as HF, generated as a result of decomposition of the electrolyte solution melt the electrode film or damage the positive electrode active material.

Accordingly, Republic of Korea Patent Publication No. 10-2011-0094578 prevents micronization due to volume changes of the high-capacity negative electrode active material that occurs during charging and discharging, and thus improves electrode cycle characteristics by containing trispentafluorophenylborane. An electrolyte for lithium secondary batteries has been proposed.

However, there is still a need for the development of a non-aqueous electrolyte additive that prevents cracking due to changes in the volume of the high-capacity negative electrode active material that occurs during charging and discharging and has an improved ability to form a protective film on the negative electrode surface.

Republic of Korea Patent Publication No. 10-2011-0094578

One object of the present invention is to provide a non-aqueous electrolyte solution additive that has excellent ability to form a protective film on the negative electrode surface even when a silicon-based negative electrode active material is used.

Another object of the present invention is to provide a non-aqueous electrolyte solution containing the non-aqueous electrolyte additive.

Another object of the present invention is to provide a secondary battery containing the non-aqueous electrolyte solution.

On the other hand, the present invention provides a non-aqueous electrolyte additive containing a compound represented by the following formula (1).

[Formula 1]

In the above equation,

n is an integer from 0 to 1.

In one embodiment of the present invention, the compound represented by Formula 1 may be one or more selected from compounds represented by Formulas 1-1 to 1-2 below.

[Formula 1-1]

[Formula 1-2]

The non-aqueous electrolyte additive according to an embodiment of the present invention may further include an additive that undergoes oxidative decomposition to form a protective film on the surface of the anode.

In one embodiment of the present invention, the mixing ratio of the compound represented by Formula 1 and the additive that oxidizes and decomposes to form a protective film on the surface of the anode may be 10:90 to 90:10 by weight.

On the other hand, the present invention provides a non-aqueous electrolyte solution for a secondary battery containing a lithium salt, a non-aqueous solvent, and the non-aqueous electrolyte solution additive.

In one embodiment of the present invention, the non-aqueous electrolyte additive may be included in an amount of 0.1 to 20% by weight based on 100% by weight of the total electrolyte solution.

On the other hand, the present invention provides a secondary battery containing the non-aqueous electrolyte for secondary batteries.

The non-aqueous electrolyte additive according to the present invention has an excellent ability to form a protective film on the negative electrode surface even when a silicon-based negative electrode active material is used, thereby improving battery characteristics.

Hereinafter, the present invention will be described in more detail.

One embodiment of the present invention relates to a non-aqueous electrolyte solution additive containing a compound represented by the following formula (1).

[Formula 1]

In the above equation,

n is an integer from 0 to 1.

When applied as a non-aqueous electrolyte additive, the compound represented by Formula 1 significantly improves the electrochemical properties of the battery, including initial coulombic efficiency, speed performance, life performance, and capacity retention at high temperatures, and prevents side reactions at the interface between the cathode and electrolyte. This helps to form a uniform SEI layer. In particular, the compound represented by Formula 1 prevents cracking due to changes in the volume of the negative electrode active material that occurs during charging and discharging, even when using a silicon-based negative electrode active material, and has an excellent ability to form a protective film on the negative electrode surface, thereby improving battery characteristics. You can.

In one embodiment of the present invention, in terms of the ability to form a protective film on the cathode surface, low resistance, long life, and high temperature stability, the compound represented by Formula 1 is selected from compounds represented by Formulas 1-1 to 1-2 below. There may be more than one.

[Formula 1-1]

[Formula 1-2]

The compound represented by Formula 1 can be prepared and used by methods known in the art, or can be obtained and used as commercially available products.

The compound represented by Formula 1 may be included in an amount of 10% by weight or more, preferably 25 to 75% by weight, and more preferably 40 to 60% by weight, based on 100% by weight of the total non-aqueous electrolyte additive. When the compound represented by Formula 1 is included in the above range, decomposition of the electrolyte solution can be prevented and damage to the negative electrode active material can be prevented.

The compound represented by Formula 1 is an additive that forms a protective film (Solid Electrolyte Interphase, SEI) on the surface of the negative electrode by reduction and decomposition. When using a silicon-based negative electrode active material, especially when using a perlithium positive electrode active material and a silicon-based negative electrode active material, it is an additive that forms a protective film (Solid Electrolyte Interphase, SEI) on the negative electrode surface. Even under the above high voltage environment, the ability to form a protective film on the cathode surface is excellent. Accordingly, the compound represented by Formula 1 is used in a non-aqueous electrolyte for secondary batteries to improve the electrochemical performance, reaction speed, and stability of the battery, and to secure capacity maintenance rate and lifespan maintenance rate.

The non-aqueous electrolyte additive according to an embodiment of the present invention may further include other additives in addition to the compound represented by Formula 1 above.

Examples of the other additives include additives that are reduced and decomposed to form a protective film on the cathode surface, additives that are oxidized and decomposed to form a protective film on the anode surface, additives that can remove acidic substances, etc., and are commonly used in the art. It can be used without restrictions. In particular, it is preferable to use an additive that oxidizes and decomposes to form a protective film on the surface of the anode as the other additive.

The additives that form a protective film on the surface of the cathode by reduction decomposition include fluoroethylene carbonate (FEC), vinylene carbonate (VC), propanesultone (PS), and propenesultone. PRS) can be used as examples, and these can be used alone or in combination of two or more types.

The additives that oxidize and decompose to form a protective film on the surface of the anode include lithium difluorophosphate (LiPO ₂ F ₂ ) and lithium difluoro(oxalato)borate (LiFOB). , lithium bis(oxalato)borate (LiBOB), lithium tetrafluoro(oxalato)phosphate (LTFOP), lithium difluorobis (oxalato) ) Phosphate (lithium difluorobis(oxalato)phosphate, LDFOP), lithium tris(oxalato)phosphate, etc. are included as examples, and it is particularly preferable to use lithium difluorophosphate. These can be used individually or in combination of two or more types.

Additives that can remove the acidic substances include tris(trimethylsilyl)phosphite (TMSP) and tris(trimethylsilyl)phosphate (TMSPA), which can be used alone or in a mixture of two or more types. .

The other additives may be included in an amount of 90% by weight or less, preferably 25 to 75% by weight, and more preferably 40 to 60% by weight, based on 100% by weight of the total non-aqueous electrolyte additive. When the other additives are included in the above range, decomposition of the electrolyte solution can be prevented and damage to the electrode active material can be prevented.

The mixing ratio of the compound represented by Formula 1 and the other additives may be 10:90 to 90:10, preferably 25:75 to 75:25, and more preferably 40:60 to 60:40, based on weight. . Within the above mixing ratio range, decomposition of the electrolyte can be prevented and damage to each electrode active material can be efficiently prevented.

One embodiment of the present invention relates to a non-aqueous electrolyte solution for a secondary battery containing a lithium salt, a non-aqueous solvent, and the non-aqueous electrolyte solution additive.

In one embodiment of the present invention, the lithium salt serves as a source of lithium ions in the battery to enable basic operation of the secondary battery.

As the lithium salt, those commonly used in non-aqueous electrolytes for secondary batteries can be used without limitation, for example, LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , Li(CF ₃ SO ₂ ) ₂ N, LiN(SO ₂ CF ₃ ) ₂ , LiN(SO ₂ C ₂ F ₅ ) ₂ , LiC(SO ₂ CF ₃ ) ₃ , LiN(SO ₃ CF ₃ ) ₂ , LiC ₄ F ₉ SO ₃ , LiAlO ₄ , LiAlCl ₄ , LiCl, LiI, LiB(C ₂ O ₄ ) ₂ , Li(FSO ₂ ) ₂ N, etc. These can be used alone or in combination of two or more.

The concentration of the lithium salt is preferably in the range of 0.1 to 2.0M, and more preferably in the range of 0.7 to 1.6M. If the concentration of the lithium salt is less than 0.1M, the conductivity of the electrolyte may decrease and electrolyte performance may deteriorate, and if it exceeds 2.0M, the viscosity of the electrolyte may increase and the mobility of lithium ions may decrease.

In one embodiment of the present invention, the non-aqueous solvent serves as a medium through which ions involved in the electrochemical reaction of the battery can move.

As the non-aqueous solvent, those commonly used in non-aqueous electrolytes for secondary batteries can be used without limitation. For example, the non-aqueous solvents include carbonate-based solvents, ether-based solvents, and ester-based solvents, which can be used individually or in combination of two or more.

As the carbonate-based solvent, one or more of a cyclic carbonate-based solvent and a linear carbonate-based solvent may be used.

The cyclic carbonate-based solvents include ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2 , 3-pentylene carbonate, vinylene carbonate, fluoroethylene carbonate (FEC), etc.

Examples of the linear carbonate-based solvent include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethylmethyl carbonate (EMC), methylpropyl carbonate, and ethylpropyl carbonate.

Examples of the ether-based solvent include dimethyl ether, diethyl ether, dipropyl ether, methyl ethyl ether, methyl propyl ether, and ethyl propyl ether.

As the ester-based solvent, one or more of a linear ester-based solvent and a cyclic ester-based solvent may be used.

Examples of the linear ester solvent include methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, butyl propionate, etc.

Examples of the cyclic ester solvent include γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone, and ε-caprolactone.

In one embodiment of the present invention, the non-aqueous solvent may be included in a residual amount so that the total weight of the electrolyte solution is 100% by weight.

In one embodiment of the present invention, the non-aqueous electrolyte additive forms a protective film on the electrode surface as described above, thereby improving the electrochemical performance, reaction rate and stability of the battery, and ensuring capacity maintenance and life maintenance rate.

The non-aqueous electrolyte additive is included in an amount of 0.1 to 20% by weight, preferably 0.1 to 10% by weight, more preferably 0.5 to 5% by weight, and even more preferably 1 to 3% by weight, based on 100% by weight of the total electrolyte solution. You can. When the non-aqueous electrolyte additive is included in the above range, decomposition of the electrolyte solution can be prevented and damage to the electrode active material can be prevented.

The non-aqueous electrolyte solution for secondary batteries according to an embodiment of the present invention is generally stable in the temperature range of -20 to 60°C, and can maintain electrochemically stable characteristics even at a voltage in the 4.5V range, so it can be used in all types of batteries such as lithium ion batteries and lithium polymer batteries. It can be applied to lithium secondary batteries.

One embodiment of the present invention relates to a secondary battery containing the above-described non-aqueous electrolyte solution.

In one embodiment of the present invention, the secondary battery may be a lithium secondary battery, for example, a lithium ion secondary battery.

The lithium secondary battery includes a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and the non-aqueous electrolyte solution described above.

In one embodiment of the present invention, the positive electrode may include a positive electrode active material layer containing a positive electrode active material, and if necessary, the positive electrode active material layer may further include a conductive material and/or a binder.

The positive electrode active material is a compound capable of reversible intercalation and deintercalation of lithium, and may include a lithium transition metal oxide containing lithium and one or more metals selected from cobalt, manganese, nickel, or aluminum.

For example, the positive electrode active material may include a perlithium positive electrode active material, and the perlithium positive electrode active material may be a compound represented by the following formula (2).

[Formula 2]

Li _x Ni _y Mn _z Co _w O ₂

In the above formula, 1<x≤2, 0<y≤1, 0<z≤1, and 0<w≤1.

In addition, the positive electrode active materials include lithium-manganese oxides (e.g., LiMnO ₂ , LiMn ₂ O ₄ , etc.), lithium-cobalt oxides (e.g., LiCoO _{2 ,} etc.), and lithium-nickel oxides (e.g., For example, LiNiO _2, etc.), lithium-nickel-manganese oxide (for example, LiNi _1-Y Mn _Y O ₂ (0<Y<1), LiMn _2-z Ni _z O ₄ (0＜Z＜2) , lithium-nickel-cobalt-based oxide (for example, LiNi _1-Y1 Co _Y1 O ₂ (0<Y1<1), lithium-manganese-cobalt-based oxide (for example, LiCo _1-Y2 Mn _Y2 O ₂ ( 0<Y2<1), LiMn _2-z1 Co _z1 O ₄ (0＜Z1＜2), lithium-nickel-manganese-cobalt oxide (for example, Li(Ni _p Co _q Mn _r1 )O ₂ (0 ＜p＜1, 0＜q＜1, 0＜r1＜1, p+q+r1=1) or Li(Ni _p1 Co _q1 Mn _r2 )O ₄ (0＜p1＜2, 0＜q1＜2, 0＜r2＜2, p1+q1+r2=2), or lithium-nickel-cobalt-transition metal (M) oxide (for example, Li(Ni _p2 Co _q2 Mn _r3 M _S2 )O ₂ (M is Al , Fe, V, Cr, Ti, Ta, Mg and Mo, and p2, q2, r3 and s2 are each independent atomic fractions of elements, 0 < p2 < 1, 0 < q2 < 1, 0<r3<1, 0<s2<1, p2+q2+r3+s2=1), etc. can be used.

The positive electrode active material may be included in an amount of 80 to 98% by weight, more specifically, 85 to 98% by weight, based on the total weight of the positive electrode active material layer.

The conductive material is used to provide conductivity to the electrode, and can be used without particular limitation as long as it does not cause chemical change and has electronic conductivity in the battery being constructed.

For example, the conductive material includes carbon powder such as carbon black, acetylene black (or Denka black), Ketjen black, channel black, furnace black, and thermal black; Graphite powder such as natural graphite, artificial graphite, or graphite with a highly developed crystal structure; Conductive fibers such as carbon fiber and metal fiber; Metal powders such as carbon fluoride, aluminum, and nickel powder; Conductive whiskers such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives may be used.

The conductive material may be included in an amount of 0.1 to 10% by weight, preferably 0.1 to 5% by weight, based on the total weight of the positive electrode active material layer.

The binder serves to improve adhesion between positive electrode active material particles and adhesion between the positive active material and the current collector.

For example, the binder includes polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, and tetrafluoroethylene. , polyethylene, polypropylene, styrene-butadiene rubber, fluorine rubber, etc. can be used.

The binder may be included in an amount of 0.1 to 15% by weight, preferably 0.1 to 10% by weight, based on the total weight of the positive electrode active material layer.

The positive electrode can be manufactured according to a manufacturing method commonly known in the art. For example, the positive electrode may be prepared by applying a positive electrode slurry prepared by dissolving or dispersing the positive electrode active material, binder, and/or conductive material in a solvent onto the positive electrode current collector, followed by drying and rolling, or the positive electrode slurry is manufactured separately. It can be manufactured by casting on a support, then peeling off the support, and laminating the film obtained on the positive electrode current collector.

The positive electrode current collector is not particularly limited as long as it is conductive without causing chemical changes in the battery. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, or carbon on the surface of aluminum or stainless steel. , surface treated with nickel, titanium, silver, etc. can be used.

The positive electrode current collector may have various forms such as foil, net, or porous material, and may form fine irregularities on the surface to strengthen the bonding force of the positive electrode active material.

The solvent may be a solvent commonly used in the art, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water. and the like, and one type of these may be used alone or a mixture of two or more types may be used.

In one embodiment of the present invention, the negative electrode includes a negative electrode active material layer containing a negative electrode active material, and the negative electrode active material layer may further include a conductive material and/or a binder, if necessary.

The negative electrode active material may include a carbon-based negative electrode active material and/or a silicon-based negative electrode active material, and preferably includes a silicon-based negative electrode active material in terms of battery capacity.

Examples of the carbon-based negative electrode active material include graphite-based materials such as natural graphite, artificial graphite, and Kish graphite; Pyrolytic carbon, mesophase pitch based carbon fiber, meso-carbon microbeads, mesophase pitches and petroleum or coal tar pitch derived cokes. High-temperature calcined carbon, soft carbon, hard carbon, etc. may be used.

Examples of the silicon-based anode active material include silicon (Si), silicon oxide (SiOx, where 0<x≤2), silicon carbide (SiC), and Si-Y alloy (where Y is an alkali metal, alkaline earth metal, group 13). It is an element selected from the group consisting of elements, group 14 elements, transition metals, rare earth elements, and combinations thereof, but may include one or more types selected from the group consisting of Si. The element Y includes Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Ti, Ge, P, As, Sb, Bi, S, It may be selected from the group consisting of Se, Te, Po, and combinations thereof.

The negative electrode active material may be included in an amount of 80 to 99% by weight based on the total weight of the negative electrode active material layer.

The conductive material is a component to further improve the conductivity of the negative electrode active material, and is not particularly limited as long as it has conductivity without causing chemical changes in the battery.

For example, the conductive material includes graphite such as natural graphite or artificial graphite; Carbon black such as acetylene black, Ketjen black, channel black, furnace black, and thermal black; Conductive fibers such as carbon fiber and metal fiber; Metal powders such as carbon fluoride, aluminum, and nickel powder; Conductive whiskeys such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives may be used.

The conductive material may be added in an amount of 10% by weight or less, preferably 5% by weight or less, based on the total weight of the negative electrode active material layer.

The binder serves to assist bonding between the conductive material, the active material, and the current collector.

For example, the binder includes polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, and polypropylene. , ethylene-propylene-diene polymer, sulfonated-ethylene-propylene-diene polymer, styrene-butadiene rubber, nitrile-butadiene rubber, fluorine rubber, etc. can be used.

The binder may be added in an amount of 0.1% to 10% by weight based on the total weight of the negative electrode active material layer.

The cathode can be manufactured according to a cathode manufacturing method commonly known in the art. For example, the negative electrode may be prepared by applying a negative electrode slurry prepared by dissolving or dispersing the negative electrode active material and optionally a binder and a conductive material in a solvent onto the negative electrode current collector, followed by rolling and drying, or by applying the negative electrode slurry onto a separate support. It can be manufactured by casting and then peeling off the support and laminating the film obtained on the negative electrode current collector.

The negative electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery. For example, it can be used on the surface of copper, stainless steel, aluminum, nickel, titanium, fired carbon, copper or stainless steel. Surface treatment with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. can be used.

The negative electrode current collector may be used in various forms such as films, sheets, foils, nets, porous materials, foams, and non-woven fabrics, and may form fine irregularities on the surface to strengthen the bonding force of the negative electrode active material.

The solvent may be a solvent commonly used in the art, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water. etc. can be mentioned.

In one embodiment of the present invention, the separator serves to separate the cathode and the anode and provide a passage for lithium ions to move.

The separator may be used without particular limitation as long as it is commonly used in the field. In particular, it is preferable that the separator has low resistance to ion movement in the electrolyte and has excellent electrolyte moisturizing ability.

Specifically, the separator includes commonly used porous polymer films, such as polyolefin-based polymers such as ethylene homopolymer, propylene homopolymer, ethylene/butene copolymer, ethylene/hexene copolymer, and ethylene/methacrylate copolymer. The porous polymer film prepared can be used alone or by stacking them. Alternatively, the separator may be a conventional porous nonwoven fabric, for example, a nonwoven fabric made of high melting point glass fiber, polyethylene terephthalate fiber, etc.

The pore diameter of the separator is generally 0.01 to 50㎛, and the porosity may be 5 to 95%.

Additionally, the thickness of the separator may generally range from 5 to 300㎛.

The average charging voltage of the secondary battery may be 4.5 V or more. This is a high range of voltage that can be developed by applying a positive electrode containing a perlithium positive electrode active material and a negative electrode containing a silicon-based negative electrode active material, and can be stably maintained by using a non-aqueous electrolyte additive containing the compound represented by Formula 1. You can.

The external shape of the secondary battery may be cylindrical, prismatic, pouch-shaped, or coin-shaped.

The secondary battery can be manufactured by injecting the non-aqueous electrolyte solution of the present invention into an electrode assembly composed of sequentially stacking a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode.

The secondary battery can be usefully used in portable devices such as mobile phones, laptop computers, and digital cameras, and electric vehicles such as hybrid electric vehicles (HEV).

Hereinafter, the present invention will be described in more detail through examples, comparative examples, and experimental examples. These examples, comparative examples, and experimental examples are only for illustrating the present invention, and it is obvious to those skilled in the art that the scope of the present invention is not limited thereto.

Example 1: Preparation of non-aqueous electrolyte solution

Ethylene carbonate (EC), ethylmethyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a ratio of 2:5:5 (v/v/v). LiPF ₆ was added to the mixed solution at a concentration of 1M, and as additives, LiPO ₂ F ₂ and a compound represented by the following formula 1-1 were added in an amount of 1% by weight based on 100% by weight of the total electrolyte solution, and then mixed to form a non-aqueous solution. An electrolyte solution was prepared.

[Formula 1-1]

Example 2: Preparation of non-aqueous electrolyte solution

A non-aqueous electrolyte solution was prepared in the same manner as Example 1, except that a compound represented by the following Formula 1-2 was used instead of the compound represented by the Formula 1-1.

[Formula 1-2]

Example 3: Preparation of non-aqueous electrolyte solution

The same procedure as in Example 1 was carried out, except that LiPO ₂ F ₂ and the compound represented by Formula 1-1 were added as additives in amounts of 0.5 wt% and 1.5 wt%, respectively, based on 100 wt% of the total electrolyte solution. A non-aqueous electrolyte solution was prepared.

Example 4: Preparation of non-aqueous electrolyte solution

The same procedure as Example 1 was performed, except that LiPO ₂ F ₂ and the compound represented by Formula 1-1 were added as additives in amounts of 1.5 wt% and 0.5 wt%, respectively, based on 100 wt% of the total electrolyte solution. A non-aqueous electrolyte solution was prepared.

Comparative Example 1: Preparation of non-aqueous electrolyte solution

A non-aqueous electrolyte solution was prepared in the same manner as in Example 1, except that the compound represented by Formula 1-1 was not added.

Comparative Example 2: Preparation of non-aqueous electrolyte solution

A non-aqueous electrolyte solution was prepared in the same manner as in Example 1, except that a compound represented by the following formula (a) was used instead of the compound represented by the formula (1-1).

[Formula a]

Comparative Example 3: Preparation of non-aqueous electrolyte solution

A non-aqueous electrolyte solution was prepared in the same manner as in Example 1, except that a compound represented by Formula b below was used instead of the compound represented by Formula 1-1.

[Formula b]

Experimental Example 1:

A secondary battery was manufactured as follows using the non-aqueous electrolyte solution prepared in the above Examples and Comparative Examples, and the initial direct current resistance, room temperature life maintenance rate, and high temperature life maintenance rate were measured by the following methods. The results are shown in Table 1 below.

<Manufacture of secondary batteries>

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

A separator was placed on the positive electrode prepared above and a negative electrode was placed on it, and then the non-aqueous electrolytes prepared in the examples and comparative examples were injected and vacuum-packed to prepare a secondary battery.

The manufactured secondary battery was charged to 4.5 V at 0.2 C-rate and then underwent a chemical charge/discharge step under discharge conditions to 2.75 V at 0.2 C-rate.

(1) Initial direct current resistance (direct current-internal resistance, DC-IR)

The secondary battery was discharged to SOC 50% at a constant current of 0.2C in a fully charged state, and after a 1-hour rest period, it was discharged at a constant current of 1.5C for 10 seconds. In the next process, after a pause of 40 seconds, it was charged with a constant current of 1.125C. The initial direct current resistance (DC-IR, R _dis ) was calculated from the discharge data using Equation 1 below.

[Equation 1]

R _dis = ΔV/I

In the above equation, ΔV represents OCV _dis (voltage just before 10 second discharge starts) - V _dis (10 second discharge end voltage), and I is the current value during discharge.

(2) Room temperature life maintenance rate

The secondary battery was charged at room temperature (25°C) by 1C to 4.5V, then discharged at 1C to 2.75V to measure the initial capacity. After repeating this 100 times, the capacity was measured, and the lifespan maintenance rate (%) was calculated using Equation 2 below. was calculated.

[Equation 2]

Life maintenance rate = (discharge capacity after 100 repetitions/initial discharge capacity) × 100

(3) High temperature life maintenance rate

The secondary battery was charged at 1C to 4.5V at high temperature (45°C), then discharged at 1C to 2.75V to measure the initial capacity, and the capacity was measured after repeating this 100 times, and the lifespan maintenance rate (%) was calculated using Equation 2 above. was calculated.

Initial direct current resistance (mΩ) Room temperature life maintenance rate (%) High temperature life maintenance rate (%) Example 1 35.8 92.5 83.7 Example 2 32.5 93.2 84.5 Example 3 36.5 91.5 82.8 Example 4 37.8 88.7 82.5 Comparative Example 1 45.2 67.7 61.0 Comparative Example 2 43.1 86.8 79.2 Comparative Example 3 42.4 83.8 78.9

As shown in Table 1, the secondary batteries manufactured using the non-aqueous electrolytes of Examples 1 to 4 using the compound represented by Formula 1 as an additive according to the present invention are those that do not use the compound represented by Formula 1. It was confirmed that the secondary batteries manufactured using the non-aqueous electrolytes of Comparative Examples 1 to 3 had superior initial direct current resistance, room temperature life maintenance rate, and high temperature life maintenance rate.

As the specific parts of the present invention have been described in detail above, it is clear to those skilled in the art that these specific techniques are merely preferred embodiments and do not limit the scope of the present invention. do. Anyone skilled in the art to which the present invention pertains will be able to make various applications and modifications within the scope of the present invention based on the above contents.

Accordingly, the actual scope of the present invention will be defined by the appended claims and their equivalents.

Claims (7)

Non-aqueous electrolyte additive containing a compound represented by the following formula (1):
[Formula 1]

In the above equation,
n is an integer from 0 to 1. The non-aqueous electrolyte solution additive according to claim 1, wherein the compound represented by Formula 1 is at least one selected from compounds represented by the following Formulas 1-1 to 1-2:
[Formula 1-1]

[Formula 1-2]
The non-aqueous electrolyte solution additive of claim 1, further comprising an additive that undergoes oxidative decomposition to form a protective film on the surface of the anode. The non-aqueous electrolyte solution additive according to claim 3, wherein the mixing ratio of the compound represented by Formula 1 and the additive that is oxidatively decomposed to form a protective film on the anode surface is 10:90 to 90:10 by weight. A non-aqueous electrolyte for a secondary battery comprising a lithium salt, a non-aqueous solvent, and the non-aqueous electrolyte additive according to any one of claims 1 to 4. The non-aqueous electrolyte solution of claim 5, wherein the non-aqueous electrolyte additive is contained in an amount of 0.1 to 20% by weight based on 100% by weight of the total electrolyte solution. A secondary battery containing a non-aqueous electrolyte for secondary batteries according to paragraph 5.