KR20230069816A - Lithium secondary battery improved safety - Google Patents

Abstract

The present invention relates to a secondary battery with improved high-temperature safety, wherein the secondary battery uses a cathode active material containing high concentrations of nickel and/or manganese and additives of specific components in a non-aqueous electrolyte solution to form a film on the electrode surface when the battery is activated. By uniformly forming it, it is possible to prevent generation of a large amount of gas under high-temperature conditions, and it is possible to effectively prevent an increase in cell resistance and a decrease in capacity due to elution of metal ions from the electrode, thereby improving battery performance and high-temperature safety. can be effectively improved.

Description

Lithium secondary battery with improved safety {LITHIUM SECONDARY BATTERY IMPROVED SAFETY}

The present invention relates to a lithium secondary battery with improved safety.

Recently, secondary batteries have been widely applied not only to small devices such as portable electronic devices, but also to medium and large devices such as battery packs or power storage devices of hybrid vehicles and electric vehicles. Examples of such secondary batteries include non-aqueous electrolyte batteries such as lithium ion batteries, lithium batteries, lithium ion capacitors, and sodium ion batteries.

Among these non-aqueous electrolyte batteries, lithium ion batteries include a positive electrode including a positive electrode active material capable of intercalating and deintercalating lithium, and a negative electrode capable of intercalating and deintercalating lithium. It is used by injecting an electrolyte solution into a battery cell including an anode containing an active material. In particular, an organic solvent in which lithium salt is dissolved is used as an electrolyte solution, and it is important in determining the stability and performance of a lithium secondary battery.

For example, LiPF ₆ , which is commonly used as a lithium salt of an electrolyte, reacts with an electrolyte solvent to promote solvent depletion and generate HF. The HF generated in this way not only generates a large amount of gas under high temperature conditions, but also can elute metal ions from the cathode active material. Since it causes degradation, etc., there is a problem of deteriorating the performance of the battery as well as the lifespan and high-temperature safety.

Accordingly, an object of the present invention is to form a film on the surface of the electrode to reduce the precipitation of metal ions on the surface of the electrode, thereby suppressing the generation of gas under high temperature conditions, while developing a technology that can improve the OCV drop of the battery is providing

In order to solve the above problems,

In one embodiment, the present invention

anode; cathode; An electrode assembly including a separator interposed between the positive electrode and the negative electrode, and

non-aqueous organic solvents; lithium salt; And an electrolyte solution composition comprising an electrolyte solution additive for a secondary battery containing a compound represented by Formula 1 below;

Provides a lithium secondary battery comprising:

[Formula 1]

In Formula 1,

이고,R ₁ is each independently a single bond, an alkylene group having 1 to 10 carbon atoms, or

ego,

R ₂ is each independently hydrogen, an acrylate group or a methacrylate group,

R ₃ is a single bond or an alkylene group having 1 to 4 carbon atoms;

a is an integer from 1 to 10;

이고,Specifically, the R ₁ is each independently a single bond, a methylene group, an ethylene group, a propylene group, or

ego,

R ₃ is a single bond or an ethylene group, and a may be an integer of 1 to 5.

More specifically, the compound represented by Formula 1 may be any one or more compounds of the following <Formula 1> to <Formula 8>:

In addition, the compound represented by Formula 1 may be included in an amount of 0.01 to 5% by weight based on the total weight of the electrolyte composition.

In addition, the electrolyte composition may further include a compound represented by Formula 2 below:

[Formula 2]

In Formula 2,

이고,R ₄ is independently an alkylene group having 1 to 10 carbon atoms or

ego,

R ₅ is independently hydrogen or an alkyl group having 1 to 4 carbon atoms;

R ₆ is independently a single bond or an alkylene group having 1 to 4 carbon atoms;

b is an integer from 1 to 10;

As an example, the compound represented by Formula 2 may include a compound represented by Formula 3 below:

.[Formula 3]

.

In addition, the compound represented by Chemical Formula 2 may be included in an amount of 0.01 to 3% by weight based on the total weight of the electrolyte composition.

In addition, the lithium salt is LiCl, LiBr, LiI, LiClO ₄ , LiBF ₄ , LiB10Cl ₁₀ , LiPF ₆ , LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , LiAsF ₆ , LiSbF ₆ , LiAlCl ₄ , CH ₃ SO ₃ Li and (CF ₃ SO ₂ ) ₂ It may include one or more selected from the group consisting of NLi.

In addition, the non-aqueous organic solvent is N-methyl-2-pyrrolidinone, ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-butyrolactone, 1,2-dimethoxy ethane, tetra Hydroxy franc, 2-methyl tetrahydrofuran, dimethylsulfoxide, 1,3-dioxorane, formamide, dimethylformamide, dioxorane, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphoric acid Triesters, trimethoxy methane, dioxolane derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl propionate and propionic acid may contain ethyl.

In addition, the positive electrode may include at least one positive electrode active material among lithium metal oxides represented by Formula 4 and Formula 5 below:

[Formula 4]

Li _x [Ni _y Co _z Mn _w M ¹ _v ] O ₂

[Formula 2]

LiM ² _p Mn _(2-5) O ₄

In Formula 4 and Formula 5,

M ¹ is W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and At least one element selected from the group consisting of Mo,

x, y, z, w and v are respectively 1.0≤x≤1.30, 0.5≤y<1, 0<z≤0.3, 0<w≤0.3, 0≤v≤0.1, and y+z+w+v= 1,

M ² is Ni, Co or Fe;

p is 0.05≤p≤0.6.

Specifically, the cathode active material is LiNi _0.8 Co _0.1 Mn _0.1 O ₂ , LiNi _0.6 Co _0.2 Mn _0.2 O ₂ , LiNi _0.9 Co _0.05 Mn _0.05 O ₂ , LiNi _0.6 Co _0.2 Mn _0.1 Al _0.1 O ₂ , LiNi _0.6 Co _0.2 Mn _0.15 Al _0.05 O ₂ , LiNi _0.7 Co _0.1 Mn _0.1 Al _0.1 O ₂ , LiNi _0.7 Mn _1.3 O ₄ , LiNi _0.5 Mn _1.5 O ₄ and LiNi _0.3 Mn _1.7 O ₄ It may contain at least one selected from the group consisting of there is.

In addition, the negative electrode material is composed of a negative electrode active material including a carbon material and a silicon material, and the silicon material is selected from among silicon (Si), silicon carbide (SiC) and silicon oxide (SiO _q , where 0.8≤q≤2.5). One or more may be included.

In addition, the silicon material may be included in an amount of 1 to 20% by weight based on the total weight of the negative electrode active material.

The secondary battery according to the present invention uses an additive of a specific component in a non-aqueous electrolyte together with a cathode active material containing high concentrations of nickel and/or manganese to uniformly form a film on the surface of the electrode when the battery is activated, resulting in a large amount of Generation of gas can be prevented, and since metal ions are eluted from the electrode to increase resistance and decrease in capacity of the cell, it is possible to effectively prevent battery performance and high-temperature safety.

Since the present invention can have various changes and various embodiments, specific embodiments will be described in detail in the detailed description.

However, this is not intended to limit the present invention to specific embodiments, and should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention.

In the present invention, the term "comprises" or "has" is intended to designate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, but one or more other features It should be understood that the presence or addition of numbers, steps, operations, components, parts, or combinations thereof is not precluded.

Further, in the present invention, when a part such as a layer, film, region, plate, etc. is described as being “on” another part, this includes not only the case where it is “directly on” the other part, but also the case where another part is present in the middle thereof. . Conversely, when a part such as a layer, film, region, plate, or the like is described as being “under” another part, this includes not only being “directly under” the other part, but also the case where there is another part in the middle. In addition, in the present application, being disposed "on" may include the case of being disposed not only on the upper part but also on the lower part.

In addition, in the present invention, 50% by weight or more, 60% by weight or more, 70% by weight or more, 80% by weight or more, 90% by weight or more, or 95% by weight or more of the components defined with respect to the total weight of "including as a main component" can mean including For example, "comprising graphite as a main component as a negative electrode active material" means that 50% by weight or more, 60% by weight or more, 70% by weight or more, 80% by weight or more, 90% by weight or more, or 95% by weight or more of graphite with respect to the total weight of the negative electrode active material It may mean that it contains more than weight%, and in some cases, it may mean that the entire negative electrode active material is composed of graphite and includes 100% by weight of graphite.

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

lithium secondary battery

Furthermore, the present invention, in one embodiment,

anode; cathode; An electrode assembly including a separator interposed between the positive electrode and the negative electrode, and

non-aqueous organic solvents; lithium salt; And an electrolyte solution composition comprising an electrolyte solution additive for a secondary battery containing a compound represented by Formula 1 below;

Provides a lithium secondary battery comprising:

[Formula 1]

In Formula 1,

이고,R ₁ is each independently a single bond, an alkylene group having 1 to 10 carbon atoms, or

ego,

R ₂ are each independently hydrogen, an acrylate group or a methacrylate group;

R ₃ is a single bond or an alkylene group having 1 to 4 carbon atoms;

a is an integer from 1 to 10;

The lithium secondary battery according to the present invention includes a positive electrode including a positive electrode active material, a negative electrode including a negative electrode active material, a separator interposed between the positive electrode and the negative electrode, and the lithium salt-containing non-aqueous electrolyte composition of the present invention described above.

At this time, the positive electrode includes lithium metal oxide containing nickel and / or manganese in high concentration / high content as a positive electrode active material, and the electrolyte composition contains an electrolyte solution additive of a specific component to prevent the generation of a large amount of gas under high temperature conditions. In addition, since metal ions are eluted from the electrode to effectively prevent an increase in cell resistance and a decrease in capacity, the performance and high-temperature safety of the battery can be effectively improved.

Specifically, the positive electrode includes a positive electrode composite material layer prepared by applying, drying, and pressing a positive electrode active material on a positive electrode current collector, and may optionally further include a conductive material, a binder, and other additives as needed.

Here, the positive electrode active material is a material that can cause an electrochemical reaction on the positive electrode current collector, and is one of lithium metal oxides represented by Chemical Formulas 4 and 5 capable of reversibly intercalating and deintercalating lithium ions. May include more than:

[Formula 4]

Li _x [Ni _y Co _z Mn _w M ¹ _v ] O ₂

[Formula 5]

LiM ² _p Mn _(2-p) O ₄

In Formula 1 and Formula 2,

M ¹ is W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and At least one element selected from the group consisting of Mo,

x, y, z, w and v are respectively 1.0≤x≤1.30, 0.5≤y<1, 0<z≤0.3, 0<w≤0.3, 0≤v≤0.1, and y+z+w+v= 1,

M ² is Ni, Co or Fe;

p is 0.05≤p≤0.6.

Lithium metal oxides represented by Chemical Formulas 4 and 5 are materials containing high amounts of nickel (Ni) and manganese (Mn), respectively, and can stably supply electricity of high capacity and/or high voltage when used as a cathode active material. There is an advantage to being In addition, a high charging potential of about 4.0V or more is required to form a film on the surface of the positive electrode and/or the negative electrode during activation of the secondary battery. Unlike conventional positive electrode active materials having a charging potential of less than 4.0V, such as iron phosphate, the lithium metal oxide Since they have a high charging potential of about 4.0 V or more, it may be easy to form a film on the electrode.

At this time, the lithium metal oxide represented by Chemical Formula 4 is LiNi _0.8 Co _0.1 Mn _0.1 O ₂ , LiNi _0.6 Co _0.2 Mn _0.2 O ₂ , LiNi _0.9 Co _0.05 Mn _0.05 O ₂ , LiNi _0.6 Co _0.2 Mn _0.1 Al _0.1 O ₂ , LiNi _0.6 Co _0.2 Mn _0.15 Al _0.05 O ₂ , LiNi _0.7 Co _0.1 Mn _0.1 Al _0.1 O ₂ , and the like, and the lithium metal oxide represented by Chemical Formula 5 is LiNi _0.7 Mn _1.3 O ₄ ; LiNi _0.5 Mn _1.5 O ₄ ; LiNi _0.3 Mn _1.7 O ₄ and the like may be included, and these may be used alone or in combination.

In addition, as the positive electrode current collector, one having high conductivity without causing chemical change in the battery may be used. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, etc. may be used, and aluminum or stainless steel may be surface-treated with carbon, nickel, titanium, silver, or the like. In addition, the average thickness of the current collector may be appropriately applied in the range of 3 to 500 μm in consideration of the conductivity and total thickness of the anode to be manufactured.

In addition, the negative electrode, like the positive electrode, includes a negative electrode mixture layer prepared by applying, drying, and pressing a negative electrode active material on a negative electrode current collector, and may optionally further include a conductive material, a binder, and other additives as needed. there is.

The anode active material may include a carbon material and a silicon material. Specifically, the carbon material refers to a material containing carbon atoms as a main component, and the carbon material is selected from the group consisting of natural graphite, artificial graphite, expanded graphite, non-graphitizable carbon, carbon black, acetylene black, and ketjen black It may include one or more species that are. In addition, the silicon material refers to a material containing silicon atoms as a main component, and the silicon material includes silicon (Si), silicon carbide (SiC), silicon monoxide (SiO) or silicon dioxide (SiO ₂ ) alone or or can be used in combination. When silicon monoxide (SiO) and silicon dioxide (SiO ₂ ) as the silicon (Si)-containing material are uniformly mixed or compounded and included in the negative electrode composite material layer, they are formed as silicon oxide (SiO _q , provided that 0.8≤q≤2.5). can be displayed

In addition, the silicon material may be included in 1 to 20% by weight based on the total weight of the negative electrode active material, specifically 3 to 10% by weight; 8 to 15% by weight; 13 to 18% by weight; or 2 to 8% by weight. The present invention can maximize the energy density of the battery by adjusting the content of the silicon material in the above content range.

In addition, the anode current collector is not particularly limited as long as it does not cause chemical change in the battery and has high conductivity. For example, copper, stainless steel, nickel, titanium, fired carbon, etc. may be used, and copper However, in the case of stainless steel, surface treatment with carbon, nickel, titanium, silver, etc. may be used. In addition, the average thickness of the anode current collector may be appropriately applied in the range of 1 to 500 μm in consideration of the conductivity and total thickness of the anode to be manufactured.

On the other hand, the separator interposed between the anode and cathode of each unit cell is an insulating thin film having high ion permeability and mechanical strength, and is not particularly limited as long as it is commonly used in the art, but is specifically chemical-resistant and hydrophobic polypropylene. ; polyethylene; Polyethylene-propylene copolymers containing at least one polymer may be used. The separator may have the form of a porous polymer substrate such as a sheet or nonwoven fabric containing the above-described polymer, and in some cases may have the form of a composite separator coated with organic or inorganic particles on the porous polymer substrate with an organic binder. may be In addition, the separator may have an average pore diameter of 0.01 to 10 μm and an average thickness of 5 to 300 μm.

Furthermore, the secondary battery includes, as an electrolyte, the above-described non-aqueous electrolyte composition according to the present invention.

The electrolyte composition may be a non-aqueous electrolyte composition, and may be a liquid electrolyte having a configuration including a lithium salt and an electrolyte solution additive in a non-aqueous organic solvent. In this case, the electrolyte solution additive includes a compound represented by Formula 1 below:

[Formula 1]

In Formula 1,

이고,R ₁ is each independently a single bond, an alkylene group having 1 to 10 carbon atoms, or

ego,

R ₂ are each independently hydrogen, an acrylate group or a methacrylate group;

R ₃ is a single bond or an alkylene group having 1 to 4 carbon atoms;

a is an integer from 1 to 10;

The compound represented by Formula 1 includes a mother nucleus having a structure in which an acrylate group is bonded to two or more oxygen atoms in phosphate through an unsaturated hydrocarbon chain and/or an alkylene glycol unit, thereby forming a positive and/or negative electrode upon activation of a secondary battery. An organic and/or inorganic film may be uniformly formed on the surface. Through this, the electrolyte solution additive can suppress the generation of gas due to decomposition of the electrolyte when the battery is exposed to high temperature and can improve the phenomenon of resistance increase and / or capacity decrease of the battery, thereby improving battery performance and high-temperature safety. can be further improved.

To this end, in the compound represented by Formula 1,

이고,R ₁ is each independently a single bond, an alkylene group having 1 to 6 carbon atoms, or

ego,

R ₂ are each independently hydrogen, an acrylate group or a methacrylate group;

R ₃ is a single bond, a methylene group or an ethylene group;

a may be an integer from 1 to 10.

이고,Specifically, R ₁ is each independently a single bond, a methylene group, an ethylene group, a propylene group, or

ego,

R ₃ is a single bond or an ethylene group;

a may be an integer from 1 to 5.

As an example, the compound represented by Chemical Formula 1 may be any one or more compounds of the following <Formula 1> to <Formula 8>:

As described above, the electrolyte additive includes a mother nucleus having a structure in which an acrylate group is bonded to two or more oxygen atoms among oxygen atoms of phosphate through an unsaturated hydrocarbon chain and/or an alkylene glycol unit, so that when a battery is activated, even at a low potential By directly participating in the solvation shell of lithium ions, an inorganic film can be uniformly formed on the surface of the negative electrode through a reduction reaction, and at the same time, an inorganic film can be uniformly formed through an oxidation reaction on the surface of the positive electrode.

In addition, the compound represented by Formula 1 may be included in a specific amount in the electrolyte solution composition. Specifically, the compound represented by Formula 1 may be included in an amount of 0.01 to 5% by weight based on the total weight of the electrolyte composition, and more specifically, 0.05 to 3% by weight, 0.5 to 2.5% by weight, or 0.5 to 5% by weight based on the total weight of the electrolyte composition. 2.0% by weight or 0.7 to 1.8% by weight. According to the present invention, it is possible to prevent a decrease in capacity due to an increase in battery resistance at a high temperature due to the use of an excess amount of an electrolyte solution additive outside the above range. In addition, the present invention can prevent the effect of the additive from being implemented insignificantly due to the use of a small amount of the electrolyte solution additive outside the above range.

In addition, the electrolyte solution composition may further include a compound represented by Formula 2 together with an electrolyte solution additive represented by Formula 1:

[Formula 2]

In Formula 2,

이고,R ₄ is independently an alkylene group having 1 to 10 carbon atoms or

ego,

R ₅ is independently hydrogen or an alkyl group having 1 to 4 carbon atoms;

R ₆ is independently a single bond or an alkylene group having 1 to 4 carbon atoms;

b is an integer from 1 to 10;

이고,Specifically, R ₄ is independently a methylene group, an ethylene group, a propylene group or

ego,

R ₅ is independently hydrogen, a methyl group or an ethyl group;

R ₆ is independently a single bond or a methylene group;

b is an integer from 1 to 4;

As an example, the compound represented by Formula 2 may include a compound represented by Formula 3 below:

[Formula 3]

.

.

The compound represented by Formula 2 includes a double bond at the terminal and participates in the formation of a film on the surface of the electrode when the battery is activated together with the electrolyte additive, thereby suppressing metal elution generated from the cathode active material, and containing a phosphate group and an amide group. Battery durability and electrical performance can be improved at high temperatures.

In this case, the compound represented by Chemical Formula 2 may be included in a specific amount in the electrolyte solution composition. Specifically, the compound represented by Formula 2 may be included in an amount of 0.01 to 3% by weight based on the total weight of the electrolyte composition, and more specifically, 0.05 to 3% by weight, 0.1 to 1% by weight, or 0.3 to 3% by weight based on the total weight of the electrolyte composition. 0.8% by weight. In the present invention, it is possible to prevent deterioration of wettability of an electrode and a separator by increasing the viscosity of an electrolyte composition when an excessive amount of the compound represented by Formula 4 is used outside the above range. In addition, the present invention can prevent the effect of the additive from being implemented insignificantly due to the use of a small amount of the electrolyte solution additive outside the above range.

Meanwhile, the lithium salt used in the electrolyte composition may be applied without particular limitation as long as it is used in a non-aqueous electrolyte in the art. Specifically, the lithium salt is LiCl, LiBr, LiI, LiClO ₄ , LiBF ₄ , LiB10Cl ₁₀ , LiPF ₆ , LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , LiAsF ₆ , LiSbF ₆ , LiAlCl ₄ , CH ₃ SO ₃ Li and (CF ₃ SO ₂ ) ₂ It may include one or more selected from the group consisting of NLi.

The concentration of these lithium salts is not particularly limited, but the lower limit of the appropriate concentration range is 0.5 mol/L or more, specifically 0.7 mol/L or more, more specifically 0.9 mol/L or more, and the upper limit is 2.5 mol/L or more. It is the range of L or less, specifically, 2.0 mol/L or less, and more specifically, 1.5 mol/L or less. When the concentration of the lithium salt is less than 0.5 mol/L, there is a possibility that the cycle characteristics and output characteristics of the non-aqueous electrolyte battery may decrease due to a decrease in ionic conductivity. In addition, when the concentration of the lithium salt exceeds 2.5 mol / L, the viscosity of the electrolyte for non-aqueous electrolyte battery increases, so there is a possibility that the ion conductivity is also reduced, and the cycle characteristics and output characteristics of the non-aqueous electrolyte battery may be reduced. .

In addition, when a large amount of lithium salt is dissolved in a non-aqueous organic solvent at one time, the liquid temperature may rise due to the heat of dissolution of the lithium salt. In this way, when the temperature of the non-aqueous organic solvent is significantly increased due to the heat of dissolution of the lithium salt, in the case of the lithium salt containing fluorine, decomposition is accelerated and hydrogen fluoride (HF) may be generated. Hydrogen fluoride (HF) is undesirable because it causes deterioration in battery performance. Accordingly, the temperature at which the lithium salt is dissolved in the non-aqueous organic solvent is not particularly limited, but may be adjusted to -20 to 80 °C, specifically 0 to 60 °C.

In addition, the non-aqueous organic solvent used in the electrolyte composition may be applied without particular limitation as long as it is used in a non-aqueous electrolyte in the art. Specifically, examples of the non-aqueous organic solvent include N-methyl-2-pyrrolidinone, ethylene carbonate (EC), propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, and gamma-butyrolactone. , 1,2-dimethoxy ethane, tetrahydroxy franc, 2-methyl tetrahydrofuran, dimethyl sulfoxide, 1,3-dioxorane, formamide, dimethylformamide, dioxorane, acetonitrile, Nitromethane, methyl formate, methyl acetate, phosphoric acid triesters, trimethoxy methane, dioxolane derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran An aprotic organic solvent such as a derivative, ether, methyl propionate or ethyl propionate may be used.

In addition, the non-aqueous solvent used in this invention may be used individually by 1 type, and may mix and use two or more types in arbitrary combinations and ratios according to a use. Among these, in terms of their electrochemical stability against redox and chemical stability against reaction with heat or solute, propylene carbonate, ethylene carbonate, fluoroethylene carbonate, diethyl carbonate, dimethyl carbonate, and ethylmethyl carbonate are particularly preferred. desirable.

Meanwhile, the electrolyte composition may further include additives in addition to the basic components described above. As long as the gist of the present invention is not impaired, additives generally used in the non-aqueous electrolyte solution of the present invention may be added in any proportion. Specifically, prevention of overcharge of cyclohexylbenzene, biphenyl, t-butylbenzene, vinylene carbonate, vinylethylene carbonate, difluoroanisole, fluoroethylene carbonate, propanesultone, succinonitrile, dimethylvinylene carbonate, etc. A compound having an effect, a negative electrode film-forming effect, and a positive electrode protective effect is exemplified. It is also possible to pseudo-solidify the electrolyte solution for a non-aqueous electrolyte battery with a gelling agent or a crosslinked polymer and use it, as in the case of being used for a non-aqueous electrolyte battery called a lithium polymer battery.

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

However, the following Examples and Experimental Examples are merely illustrative of the present invention, and the contents of the present invention are not limited to the following Examples and Experimental Examples.

Preparation Example 1~. Preparation of electrolyte composition

LiPF ₆ as a lithium salt was dissolved at a concentration of 1M in a solvent in which ethylene carbonate (EC) and ethylmethyl carbonate (EMC) were mixed in a 3:7 volume ratio, and the electrolyte additive represented by Formula 1 and the compound represented by Formula 3 were added to the total weight of the electrolyte As shown in Table 1 below, a non-aqueous electrolyte composition was prepared by dissolving to a weight.

Unit: % by weight Compound of Formula 1 Compound of Formula 3 Usage type content Preparation Example 1

0.1 - Preparation Example 2 0.5 - Preparation Example 3 One - Production Example 4 2 - Preparation Example 5 5 - Preparation Example 6

0.1 - Preparation Example 7 0.5 - Preparation Example 8 One - Preparation Example 9 2 - Preparation Example 10 5 - Preparation Example 11

One - Preparation Example 12

One 0.5

[Formula 3]

.

.

Examples 1 to 12. Manufacture of lithium secondary battery

As a cathode active material, LiNi _0.8 Co _0.1 Mn _0.05 Al _0.05 O ₄ having a particle size of 5 μm was prepared, and N-methyl pyrrolidone was mixed with polyvinylidene fluoride as a carbon-based conductive agent and binder in a weight ratio of 94:3:3. (NMP) to form a slurry, cast on a thin aluminum plate, dry in a vacuum oven at 120° C., and then rolled to prepare a positive electrode.

Separately, a negative electrode active material in which artificial graphite and silicon oxide (SiO ₂ ) are mixed in a weight ratio of 9:1 is prepared, and 97 parts by weight of the negative electrode active material and 3 parts by weight of styrene butadiene rubber (SBR) are mixed with water to form a slurry. Then, it was cast on a thin copper plate, dried in a vacuum oven at 130° C., and then rolled to prepare a negative electrode.

A separator made of 18 μm polypropylene was interposed between the obtained positive and negative electrodes, inserted into a case, and then, as shown in Table 2 below, the electrolyte composition (5 ml) prepared in Preparation Examples 1 to 12 was injected to form a pouch. A 2.1Ah class small lithium secondary battery was manufactured.

Electrolyte composition type Example 1 Electrolyte composition of Preparation Example 1 Example 2 Electrolyte composition of Preparation Example 2 Example 3 Electrolyte composition of Preparation Example 3 Example 4 Electrolyte composition of Preparation Example 4 Example 5 Electrolyte composition of Preparation Example 5 Example 6 Electrolyte composition of Preparation Example 6 Example 7 Electrolyte composition of Preparation Example 7 Example 8 Electrolyte composition of Preparation Example 8 Example 9 Electrolyte composition of Preparation Example 9 Example 10 Electrolyte composition of Preparation Example 10 Example 11 Electrolyte composition of Preparation Example 11 Example 12 Electrolyte composition of Preparation Example 12

Comparative Example 1. Manufacturing of Lithium Secondary Battery

Except for using an electrolyte solution in which LiPF ₆ as a lithium salt was dissolved at a concentration of 1M in a solvent in which ethylene carbonate (EC) and ethylmethyl carbonate (EMC) were mixed in a 3:7 volume ratio without an electrolyte additive, Example 1 and A lithium secondary battery was prepared in the same manner.

experimental example.

In order to evaluate the gas generation reduction effect and high-temperature safety of the lithium secondary battery according to the present invention, the following experiments were performed.

A) Analysis of resistance and capacity change of secondary battery after high temperature storage

Each of the secondary batteries prepared in Examples and Comparative Examples was stored at 60° C. for 12 weeks, and changes in resistance and capacity of the batteries were observed.

Specifically, the activation charge/discharge of each secondary battery is performed twice at 0.2C/0.5C, the standard charge/discharge current density is 0.5C/0.2C, the charge end voltage is 4.8V (Li/graphite), and the discharge A charge/discharge experiment with a termination voltage of 3.0 V (Li/graphite) was performed once each.

Then, the battery was fully charged at 4.2V of 0.33C, and the resistance and capacity of the battery were measured at intervals of 2 weeks while being stored at a high temperature of 60°C. Here, after measuring the resistance and capacity of the battery, the battery was charged to a full state and stored. Based on the measured resistance and capacity of the battery, the amount of change based on the initial resistance and initial capacity of the battery was calculated, and the results are shown in Table 3 below.

B) Analysis of gas generation from secondary batteries stored at high temperatures

Each secondary battery manufactured in Examples and Comparative Examples was stored at 60° C. for 12 weeks, and the amount of gas generated from the battery was analyzed at 2-week intervals. Specifically, the activation charge/discharge of each secondary battery is performed twice at 0.2C/0.5C, the standard charge/discharge current density is 0.5C/0.2C, the charge end voltage is 4.8V (Li/graphite), and the discharge A charge/discharge experiment with a termination voltage of 3.0 V (Li/graphite) was performed once each.

Then, it was fully charged with 4.2V of 0.33C and stored for 12 weeks at a high temperature of 60°C. After 12 weeks, the surface of the secondary battery was pressurized and degassed, and the amount of degassed gas was measured. The results are shown in Table 3 below.

gas generation resistance increase rate capacity retention rate Example 1 2955 μl 5.79% 94.60% Example 2 2530 μl -0.43% 95.58% Example 3 2511 μl -0.39% 95.62% Example 4 2327 μl -0.53% 95.06% Example 5 2321 μl -1.85% 94.18% Example 6 3003 μl 6.07% 94.03% Example 7 2936 μl -0.34% 94.45% Example 8 2932 μl 2.7% 94.35% Example 9 2546 μl -0.35% 94.61% Example 10 2523 μl -3.12% 93.99% Example 11 2485 μl -0.42% 95.70% Example 12 2350 μl -0.46% 95.78% Comparative Example 1 3269 μl 8.89% 94.14%

As shown in Table 3, the secondary batteries of the examples include an electrolyte solution composition including a compound represented by Formula 1 as an electrolyte additive together with a cathode active material containing a high amount of nickel, so that electrical performance and safety at high temperatures can be seen. there is

Specifically, compared to the secondary batteries of Comparative Examples, the amount of gas was significantly less, the increase in resistance of the battery was small, and the capacity retention rate was high even when exposed to high temperature conditions.

From these results, the secondary battery according to the present invention uniformly forms a film on the surface of the electrode when the battery is activated by using an additive of a specific component in a non-aqueous electrolyte together with a cathode active material containing high concentration of nickel and/or manganese, It is possible to prevent the generation of a large amount of gas under the condition and effectively prevent the elution of metal ions from the electrode to increase the resistance of the cell and decrease the capacity, thereby effectively improving the performance and high-temperature safety of the battery. .

Although the above has been described with reference to preferred embodiments of the present invention, those skilled in the art or those having ordinary knowledge in the art do not deviate from the spirit and technical scope of the present invention described in the claims to be described later. It will be understood that various modifications and changes can be made to the present invention within the scope.

Therefore, the technical scope of the present invention is not limited to the contents described in the detailed description of the specification, but should be defined by the claims.

Claims (13)

anode; cathode; An electrode assembly including a separator interposed between the positive electrode and the negative electrode, and
non-aqueous organic solvents; lithium salt; And an electrolyte solution composition comprising an electrolyte solution additive for a secondary battery containing a compound represented by Formula 1 below;
A lithium secondary battery containing:
[Formula 1]

In Formula 1,
R ₁ is each independently a single bond, an alkylene group having 1 to 10 carbon atoms, or

ego,
R ₂ are each independently hydrogen, an acrylate group or a methacrylate group;
R ₃ is a single bond or an alkylene group having 1 to 4 carbon atoms;
a is an integer from 1 to 10;
According to claim 1,
R ₁ is each independently a single bond, a methylene group, an ethylene group, a propylene group, or

ego,
R ₃ is a single bond or an ethylene group;
a is an integer of 1 to 5, the lithium secondary battery.
According to claim 1,
The compound represented by Formula 1 is a lithium secondary battery that is any one or more compounds of the following <Structural Formula 1> to <Structural Formula 8>:

According to claim 1,
A lithium secondary battery comprising the compound represented by Formula 1 in an amount of 0.01 to 5% by weight based on the total weight of the electrolyte composition.
According to claim 1,
The electrolyte composition is a lithium secondary battery further comprising a compound represented by Formula 2 below:
[Formula 2]

In Formula 2,
R ₄ is independently an alkylene group having 1 to 10 carbon atoms or

ego,
R ₅ is independently hydrogen or an alkyl group having 1 to 4 carbon atoms;
R ₆ is independently a single bond or an alkylene group having 1 to 4 carbon atoms;
b is an integer from 1 to 10;
According to claim 5,
The compound represented by Formula 2 is a lithium secondary battery including a compound represented by Formula 3 below:
[Formula 3]

.
According to claim 5,
A lithium secondary battery comprising the compound represented by Formula 2 in an amount of 0.01 to 3% by weight based on the total weight of the electrolyte composition.
According to claim 1,
Lithium salts are LiCl, LiBr, LiI, LiClO ₄ , LiBF ₄ , LiB10Cl ₁₀ , LiPF ₆ , LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , LiAsF ₆ , LiSbF ₆ , LiAlCl ₄ , CH ₃ SO ₃ Li and (CF ₃ SO ₂ ) A lithium secondary battery comprising at least one selected from the group consisting of ₂ NLi.
According to claim 1,
Non-aqueous organic solvents include N-methyl-2-pyrrolidinone, ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-butyrolactone, 1,2-dimethoxy ethane, tetrahydroxy franc (franc), 2-methyl tetrahydrofuran, dimethyl sulfoxide, 1,3-dioxorane, formamide, dimethylformamide, dioxorane, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphoric acid triesters, Including trimethoxy methane, dioxolane derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl propionate and ethyl propionate Lithium secondary battery that does.
According to claim 1,
The positive electrode is a lithium secondary battery including at least one positive electrode active material among lithium metal oxides represented by Formula 4 and Formula 5:
[Formula 4]
Li _x [Ni _y Co _z Mn _w M ¹ _v ] O ₂
[Formula 5]
LiM ² _p Mn _(2-p) O ₄
In Formula 4 and Formula 5,
M ¹ is W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and At least one element selected from the group consisting of Mo,
x, y, z, w and v are respectively 1.0≤x≤1.30, 0.5≤y<1, 0<z≤0.3, 0<w≤0.3, 0≤v≤0.1, and y+z+w+v= 1,
M ² is Ni, Co or Fe;
p is 0.05≤p≤0.6,
According to claim 10,
Cathode active materials are LiNi _0.8 Co _0.1 Mn _0.1 O ₂ , LiNi _0.6 Co _0.2 Mn _0.2 O ₂ , LiNi _0.9 Co _0.05 Mn _0.05 O ₂ , LiNi _0.6 Co _0.2 Mn _0.1 Al _0.1 O ₂ , LiNi _0.6 Co _0.2 Mn _0.15 Al _0.05 O ₂ , LiNi _0.7 Co _0.1 Mn _0.1 Al _0.1 O ₂ , LiNi _0.7 Mn _1.3 O ₄ , LiNi _0.5 Mn _1.5 O ₄ and LiNi _0.3 Mn _1.7 O ₄ A lithium secondary battery including one or more selected from the group consisting of.
According to claim 1,
The negative electrode is composed of a negative electrode active material including a carbon material and a silicon material,
The silicon material is a lithium secondary battery including at least one of silicon (Si), silicon carbide (SiC) and silicon oxide (SiO _q , where 0.8≤q≤2.5).
According to claim 12,
A lithium secondary battery in which the silicon material is included in an amount of 1 to 20% by weight based on the total weight of the negative electrode active material.