KR20210110186A - Additives for non-aqueous electrolyte, non-aqueous electrolyte and lithium secondary battery comprsing the same - Google Patents

Abstract

The present invention relates to an additive for a non-aqueous electrolyte capable of improving the lifespan characteristics of a lithium secondary battery by forming an electrode-electrolyte interface that is stable even at high temperatures and has low resistance, and specifically, to an additive for a non-aqueous electrolyte including a sultone-based compound represented by chemical formula 1, a non-aqueous electrolyte including the same, and a lithium secondary battery.

Description

Additive for non-aqueous electrolyte, non-aqueous electrolyte and lithium secondary battery containing same

The present invention relates to an additive for a non-aqueous electrolyte containing a sultone-based compound, a non-aqueous electrolyte containing the same, and a lithium secondary battery.

Recently, as the application area of lithium secondary batteries is rapidly expanding not only to the power supply of electronic devices such as electricity, electronics, communication, and computers, but also to the power storage supply of large-area devices such as automobiles and power storage devices, high capacity, high output and high stability. Demand for phosphorus secondary batteries is increasing.

Lithium secondary batteries are generally composed of a cathode active material made of lithium-containing transition metal oxide or a carbon material or silicon anode active material capable of occluding and releasing lithium ions, and a material mixed with a binder and a conductive material, respectively, as a cathode current collector, respectively. and a negative electrode current collector to prepare a positive electrode and a negative electrode, stacking them on both sides of a separator to form an electrode current collector having a predetermined shape, and then inserting the electrode current collector and a non-aqueous electrolyte into a battery case. Here, in order to secure the performance of the battery, formation (formation) and aging (aging) processes are almost essential.

The formation process is a step of activating the secondary battery by repeating charging and discharging after battery assembly. During the charging, lithium ions from the lithium-containing transition metal oxide used as the positive electrode move to and insert into the carbon material negative active material used as the negative electrode. do. At this time, the highly reactive lithium ions react with the electrolyte to form _{compounds such as Li 2} CO ₃ , Li ₂ O, and LiOH, and these compounds form a solid electrolyte interface (SEI) film on the surface of the anode.

On the other hand, especially in the lithium secondary battery for automotive use, high capacity, high output, and long life characteristics are becoming important. On the side of the positive electrode, as a positive active material with high energy density but low stability is used for high capacity, it is necessary to form an active material-electrolyte interface that can protect and stabilize the surface of the positive active material. The SEI layer used needs to be robust and low in resistance. Attempts have been made to introduce additives into the electrolyte in order to improve the performance of the battery by creating an interface between each electrode and the electrolyte.

On the other hand, as high-temperature driving and long-term life characteristics become important for the lithium secondary battery, electrolyte decomposition reactions caused by redox reactions occurring at the electrolyte and electrode interface during repeated cycles are accumulated, and due to this increased resistance, lifespan characteristics This deteriorating problem is accompanied.

As a result of multifaceted research to solve the above problem, in the present invention, a sultone-based compound is included as an additive for a non-aqueous electrolyte that can improve lifespan characteristics by forming an electrode-electrolyte interface that is stable even at high temperatures and has low resistance after decomposition. An object of the present invention is to provide an additive for a non-aqueous electrolyte.

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

In addition, the present invention is to provide a lithium secondary battery including the non-aqueous electrolyte.

In order to achieve the above object, the present invention provides an additive for a non-aqueous electrolyte, which includes a sultone-based compound represented by the following formula (1) as an additive for a non-aqueous electrolyte.

[Formula 1]

In Formula 1,

n is 1 or 2,

Ak is a single bond; Or a substituted or unsubstituted alkylene group having 1 to 6 carbon atoms;

X is Li, Na or K.

In addition, the present invention provides a non-aqueous electrolyte including the additive.

In addition, the present invention provides a lithium secondary battery including the non-aqueous electrolyte.

According to the present invention, when the additive for a non-aqueous electrolyte including the compound represented by Formula 1 is used, a low resistance and strong SEI layer is formed, thereby providing a lithium secondary battery having excellent high temperature and long life characteristics.

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

The terms or words used in the present specification and claims should not be construed as being limited to their ordinary or dictionary meanings, and the inventor may properly define the concept of the term in order to best describe his invention. It should be interpreted as meaning and concept consistent with the technical idea of the present invention based on the principle that there is.

The terms used in the present invention are only used to describe specific embodiments, and are not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly dictates otherwise. In the present invention, terms such as 'include' or 'have' designate the existence of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, but one or more other It is to be understood that this does not preclude the possibility of addition or presence of features or numbers, steps, operations, components, parts, or combinations thereof.

Additives for non-aqueous electrolytes

The additive for a non-aqueous electrolyte according to an embodiment of the present invention includes a sultone-based compound represented by the following formula (1). When an additive for a non-aqueous electrolyte including a compound represented by the following Chemical Formula 1 is used, a low resistance and strong SEI layer is formed, thereby providing a lithium secondary battery having excellent high temperature and long life characteristics.

[Formula 1]

In Formula 1,

n is 1 or 2,

Ak is a single bond; Or a substituted or unsubstituted alkylene group having 1 to 6 carbon atoms;

X is Li, Na or K.

According to an embodiment of the present invention, the -Ak-OSO ₃ ^- group may be bonded to the 3rd or 4th position of the cyclic structure of the sultone-based compound represented by Formula 1 above. In this case, since the reduction stability of the sultone-based compound represented by Formula 1 is high, SEI such as _{RSO 3} Li, RSO ₄ Li, Li ₂ SO ₃ , Li ₂ SO _{4 which is strong on the surface of the positive and negative electrodes and has high lithium salt conductivity} It can promote the production of substances. In addition, since the sultone-based compound represented by Formula 1 is reduced faster than the organic solvent in the electrolyte to form an SEI layer, a solid SEI can be formed before a side reaction occurs.

The reduction stability of the compound is evaluated by the following method using the Gaussian 09 program package (Gaussian 09 Revision C.01, Gaussian Inc., Wallingford, CT, 2009) to which the DFT calculation method is applied. After calculating the stable structural energy of the compound in the state before reduction (E _neut ) and the stable structural energy of the compound in the reduced state (E _red ), E _neut - E _red -1.45 eV is defined as reduction stability. At this time, the structural stabilization calculation is performed in the state that the PCM (Polarizable Continuum Model) method is applied.

According to an embodiment of the present invention, Ak may be a single bond or a methylene group. In this case, since the number of carbon atoms is small and the resistance is small, a low resistance and a strong SEI layer may be formed in a lithium secondary battery using the additive for a non-aqueous electrolyte including the compound represented by Formula 1 .

According to an embodiment of the present invention, X may be Li. Since lithium has high ionic conductivity, when X is Li, the supply and movement of lithium ions in the secondary battery may be improved.

According to an embodiment of the present invention, the sultone-based compound represented by Formula 1 may be at least one selected from the following Formulas 1a to 1c compounds.

[Formula 1a]

[Formula 1b]

[Formula 1c]

In Formulas 1a to 1c,

X may be Li, Na or K.

In Formulas 1a to 1c, the -Ak-OSO ₃ ^- group may be covalently bonded to the cyclic structure of the sultone-based compound, and X may be Li, Na, or K, but preferably Li.

According to an embodiment of the present invention, the sultone-based compound represented by Chemical Formula 1 may be at least one selected from the following Chemical Formulas 1aa to 1cc compounds.

[Formula 1aa]

[Formula 1bb]

[Formula 1cc]

The sultone-based compound represented by Formula 1 is oxidation-reductively decomposed on the surface of the electrode together with the electrolyte, and RSO ₃ Li, RSO ₄ Li, Li ₂ SO ₃ , Li ₂ SO ₄ and By creating the same SEI material, high-temperature long-life properties can help improve.

Meanwhile, the sultone-based compound represented by Formula 1 of the present invention includes 1) sulfonation of a diol-containing alkene compound or diol-containing halogen compound, and 2) sultone containing a hydroxyl group through condensation of one alcohol group and sulfonate group among diols. It can be prepared through the compound formation reaction, 3) introducing a sulfate salt to the remaining hydroxy group. However, the present invention is not limited thereto, and a known method capable of preparing a desired target compound may be applied. For example, a sultone compound containing a hydroxyl group can be prepared through the method described in Korean Patent No. 10-1736739 or Korean Patent No. 10-1777474, International Patent WO 02/055562A2, and a Li salt compound and chlorosulfonic acid are added thereto to obtain the chemical formula A sultone-based compound represented by 1, that is, a sultone-based compound in which a sulfate salt is substituted can be synthesized.

non-aqueous electrolyte

In addition, the non-aqueous electrolyte according to an embodiment of the present invention includes an additive for a non-aqueous electrolyte including the sultone-based compound represented by Formula 1 above.

The non-aqueous electrolyte may further include a lithium salt, an organic solvent, and other electrolyte additives.

(1) Additive for non-aqueous electrolyte containing sultone-based compound represented by Formula 1

Since the description of the sultone-based compound represented by Formula 1 overlaps with the above, description thereof will be omitted.

Meanwhile, according to an embodiment of the present invention, the additive for the non-aqueous electrolyte is used in an amount of 0.01 parts by weight to 10 parts by weight, specifically, 0.01 parts by weight to 5 parts by weight, 0.01 parts by weight to 100 parts by weight of the non-aqueous electrolyte. It may be included in an amount of 1 part by weight, or 0.01 parts by weight to 0.05 parts by weight. When the content of the additive for the non-aqueous electrolyte is within the above range, when the non-aqueous electrolyte is applied to a secondary battery, the content of the SEI layer derived from the sultone-based compound represented by Formula 1 is appropriate, so that stability can be improved, and the secondary battery By preventing the resistance from increasing, it is possible to prevent a decrease in the capacity of the battery.

(2) lithium salt

The lithium salt is used as an electrolyte salt in a lithium secondary battery, and is used as a medium for transferring ions. Typically, the lithium salt is LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiClO 4 , LiN(C ₂ F ₅ SO ₂ ) ₂ , LiN(CF ₃ SO ₂ ) ₂ , CF ₃ SO ₃ Li, LiC(CF _{3 )} SO ₂ ) ₃ , LiC ₄ BO ₈ , LiTFSI, LiFSI, and at least one compound selected from the group consisting of _{LiClO 4 may be included, preferably LiPF 6} , but is not limited thereto. On the other hand, the lithium salt may be used alone or as a mixture of two or more as needed.

According to an embodiment of the present invention, the lithium salt may be included in the non-aqueous electrolyte at a concentration of 0.5 M to 5 M, preferably, in a concentration of 0.5 M to 4 M. When the concentration of the lithium salt is within the above range, the concentration of lithium ions in the electrolyte is appropriate, so that charging and discharging of the battery can be performed properly, and the viscosity of the electrolyte is appropriate so that the wetting in the battery is excellent, so that the battery performance can be improved. .

(3) organic solvents

The organic solvent is a non-aqueous solvent commonly used in lithium secondary batteries, and includes, for example, ethers, esters (acetates, propionates), amides, linear carbonates or cyclic carbonates, nitriles (acetonitrile, SN, etc.), respectively. It can be used individually or in mixture of 2 or more types.

Among them, a carbonate-based electrolyte solvent including a carbonate compound that is a cyclic carbonate, a linear carbonate, or a mixture thereof may be typically used.

The organic solvent is not limited as long as it can minimize decomposition due to oxidation reaction and the like in the charging/discharging process of the secondary battery and exhibit desired properties together with the additive.

Specific examples of the cyclic carbonate compound include ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate , any one selected from the group consisting of 2,3-pentylene carbonate, vinylene carbonate, and fluoroethylene carbonate (FEC), or a mixture of two or more thereof.

In addition, specific examples of the linear carbonate compound include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethylmethyl carbonate (EMC), methylpropyl carbonate and the group consisting of ethylpropyl carbonate Any one selected from or a mixture of two or more of them may be used representatively, but is not limited thereto.

Specific examples of the linear ester compound include any one or two selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, and butyl propionate. The above mixtures and the like may be typically used, but the present invention is not limited thereto.

Specific examples of the cyclic ester compound include any one selected from the group consisting of γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone, ε-caprolactone, or two or more of them. A mixture may be used, but is not limited thereto.

Examples of the ether-based solvent include dimethyl ether, diethyl ether, dipropyl ether, methyl ethyl ether, methylpropyl ether, ethylpropyl ether, 1,3-dioxolane (DOL) and 2,2-bis(trifluoromethyl). Any one selected from the group consisting of )-1,3-dioxolane (TFDOL) or a mixture of two or more thereof may be used, but the present invention is not limited thereto.

The glyme-based solvent has a higher dielectric constant and a lower surface tension than the linear carbonate-based organic solvent, and is a solvent with less reactivity with metal, dimethoxyethane (glyme, DME), diethoxyethane, digylme, Tri-glyme (Triglyme), and tetra-glyme (TEGDME) may include at least one selected from the group consisting of, but is not limited thereto.

The nitrile solvent is acetonitrile, propionitrile, butyronitrile, valeronitrile, caprylonitrile, heptanenitrile, cyclopentane carbonitrile, cyclohexane carbonitrile, 2-fluorobenzonitrile, 4-fluorobenzonitrile , difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2-fluorophenylacetonitrile, may be at least one selected from the group consisting of 4-fluorophenylacetonitrile, but is not limited thereto.

In addition to the organic solvent, it may be at least one selected from the group consisting of dimethyl sulfoxide, sulfolane, propylene sulfite and tetrahydrofuran, but is not limited thereto.

In particular, among the carbonate-based organic solvents, ethylene carbonate and propylene carbonate, which are cyclic carbonates, are highly viscous organic solvents and have a high dielectric constant, so they can be preferably used because they dissociate lithium salts in the electrolyte well, and these cyclic carbonates dimethyl carbonate and diethyl carbonate When a low-viscosity, low-dielectric constant linear carbonate is mixed in an appropriate ratio, an electrolyte having high electrical conductivity can be prepared, and thus can be used more preferably.

(4) other electrolyte additives

The other electrolyte additive is a known electrolyte additive that can be additionally added in addition to the sultone-based compound represented by Formula 1 of the present invention, for example, vinylene carbonate (Vinylene Carbonate), vinyl ethylene carbonate (vinyl ethylene carbonate) , propane sultone, succinonitrile, adiponitrile, ethylene sulfate, propene sultone, fluoroethylene carbonate, LiPO ₂ F ₂ , LiODFB (Lithium difluorooxalatoborate), LiBOB (Lithium bis-(oxalato)borate), TMSPa (3-trimethoxysilanyl-propyl-N-aniline), TMSPi (Tris(trimethylsilyl) Phosphite), LiBF _4, etc. can all be applied do.

The other electrolyte additives may be included in an amount of 0.01 parts by weight to 10 parts by weight based on 100 parts by weight of the non-aqueous electrolyte, preferably 0.05 parts by weight to 7.0 parts by weight, more preferably 0.05 parts by weight to 5.0 parts by weight. can

lithium secondary battery

In addition, the lithium secondary battery according to an embodiment of the present invention includes the non-aqueous electrolyte.

Specifically, the lithium secondary battery 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 above-described nonaqueous electrolyte.

In this case, the lithium secondary battery of the present invention may be manufactured according to a conventional method known in the art. For example, a positive electrode, a negative electrode, and a separator between the positive and negative electrodes are sequentially stacked to form an electrode assembly, the electrode assembly is inserted into the battery case, and the nonaqueous electrolyte according to the present invention may be injected. .

(1) anode

The positive electrode may be prepared by coating a positive electrode mixture slurry including a positive electrode active material, a binder, a conductive material, and a solvent on a positive electrode current collector.

The positive electrode current collector is not particularly limited as long as it has conductivity without causing a chemical change in the battery. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, or carbon on the surface of aluminum or stainless steel. , nickel, titanium, silver, etc. may be used.

The positive active material is a compound capable of reversible intercalation and deintercalation of lithium, and specifically, may include lithium metal oxide including lithium and one or more metals such as cobalt, manganese, nickel, or aluminum. . More specifically, the lithium metal oxide is a lithium-manganese oxide (eg, LiMnO ₂ , LiMn ₂ O _{4 ,} etc.), a lithium-cobalt-based oxide (eg, LiCoO ₂ etc.), a lithium-nickel-based oxide ( For example, LiNiO ₂ etc.), lithium-nickel-manganese oxide (for example, LiNi _1-Y Mn _Y O ₂ (here, 0<Y<1), LiMn _2-z Ni _z O ₄ (here , 0<Z<2), etc.), lithium-nickel-cobalt-based oxides (eg, LiNi _1-Y1 Co _Y1 O ₂ (here, 0<Y1<1), etc.), lithium-manganese-cobalt-based oxides Oxides (eg, LiCo _1-Y2 Mn _Y2 O ₂ (here, 0<Y2<1), LiMn _2-z1 Co _z1 O ₄ (here, 0<Z1<2), etc.), lithium-nickel- Manganese-cobalt oxide (for example, Li(Ni _p Co _q Mn _r1 )O ₂ (here, 0<p<1, 0<q<1, 0<r1<1, p+q+r1=1) ) or Li(Ni _p1 Co _q1 Mn _r2 )O ₄ (where 0<p1<2, 0<q1<2, 0<r2<2, p1+q1+r2=2), etc.), or lithium-nickel -Cobalt-transition metal (M) oxide (eg, Li(Ni _p2 Co _q2 Mn _r3 M _S2 )O ₂ , wherein M is composed of Al, Fe, V, Cr, Ti, Ta, Mg and Mo. is selected from the group, and p2, q2, r3 and s2 are atomic fractions of independent elements, respectively, 0<p2<1, 0<q2<1, 0<r3<1, 0<s2<1, p2+q2+ r3+s2=1), etc.), and any one or two or more of these compounds may be included.

Among them, the lithium metal oxide is LiCoO ₂ , LiMnO ₂ , LiNiO ₂ , lithium nickel manganese cobalt oxide (for example, Li(Ni _1/3 Mn _1/3 Co _{1 / 3} )O ₂ , Li(Ni _0.6 Mn _0.2 Co _0.2 )O ₂ , Li(Ni _0.5 Mn _0.3 Co _0.2 )O ₂ , Li(Ni _0.7 Mn _0.15 Co _0.15 )O ₂ and Li(Ni _0.8 Mn _0.1 Co _0.1 )O _{2 ,} etc.), or lithium nickel cobalt aluminum oxide (eg, Li (Ni _0.8 Co _0.15 Al _0.05 )O ₂ etc.), etc.), and the lithium composite metal oxide is Li(Ni _0.6 Mn _0.2 Co _0.2 )O ₂ , Li(Ni _0.5 Mn _0.3 Co _0.2 )O ₂ , Li(Ni _0.7 Mn _0.15 Co _0.15 )O _{2 ,} and Li(Ni _0.8 Mn _0.1 Co _0.1 )O ₂ , and the like, and any one or a mixture of two or more thereof may be used. have.

The positive active material may be included in an amount of 60 to 99% by weight, preferably 70 to 99% by weight, more preferably 80 to 98% by weight based on the total weight of the solid material excluding the solvent in the positive electrode mixture slurry.

The binder is a component that assists in bonding of the active material and the conductive material and the like to the current collector.

Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene (PE), polypropylene , ethylene-propylene-diene monomer, sulfonated ethylene-propylene-diene monomer, styrene-butadiene rubber, fluororubber, and various copolymers.

Typically, the binder may be included in an amount of 1 to 20 wt%, preferably 1 to 15 wt%, more preferably 1 to 10 wt%, based on the total weight of the solid material excluding the solvent in the positive electrode mixture slurry.

The conductive material is a component for further improving the conductivity of the positive electrode active material.

The conductive material is not particularly limited as long as it has conductivity without causing a chemical change in the battery. For example, graphite; carbon-based materials such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fibers and metal fibers; 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; A conductive material such as a polyphenylene derivative may be used.

Typically, the conductive material may be included in an amount of 1 to 20% by weight, preferably 1 to 15% by weight, more preferably 1 to 10% by weight based on the total weight of the solid material excluding the solvent in the positive electrode mixture slurry.

The solvent may include an organic solvent such as NMP (N-methyl-2-pyrrolidone), and may be used in an amount having a desirable viscosity when the positive active material and, optionally, a binder and a conductive material are included. . For example, it may be included so that the concentration of the solid content including the positive active material, and optionally the binder and the conductive material is 50 to 95% by weight, preferably 70 to 95% by weight, more preferably 70 to 90% by weight. .

(2) cathode

The negative electrode may be prepared by, for example, coating a negative electrode mixture slurry containing a negative electrode active material, a binder, a conductive material and a solvent on the negative electrode current collector, or using a graphite electrode made of carbon (C) or a metal itself as the negative electrode. have.

For example, when the negative electrode is prepared by coating the negative electrode mixture slurry on the negative electrode current collector, the negative electrode current collector generally has a thickness of 3 to 500 μm. Such a negative current collector is not particularly limited as long as it has high conductivity without causing a chemical change in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel. The surface treated with carbon, nickel, titanium, silver, etc., an aluminum-cadmium alloy, etc. may be used. In addition, like the positive electrode current collector, the bonding force of the negative electrode active material may be strengthened by forming fine irregularities on the surface, and may be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a non-woven body.

Examples of the negative active material include natural graphite, artificial graphite, carbonaceous material; lithium-containing titanium composite oxide (LTO), Si, SiOx, Sn, Li, Zn, Mg, Cd, Ce, Ni or Fe metals (Me); alloys composed of the metals (Me); oxides (MeOx) of the metals (Me); and one or more negative active materials selected from the group consisting of a composite of the metal (Me) and carbon.

The negative active material may be included in an amount of 60 to 99% by weight, preferably 70 to 99% by weight, more preferably 80 to 98% by weight, based on the total weight of the solid material excluding the solvent in the negative electrode mixture slurry.

The binder is a component that assists in bonding between the conductive material, the active material, and the current collector. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoro and roethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer, sulfonated ethylene-propylene-diene monomer, styrene-butadiene rubber, fluororubber, and various copolymers thereof.

Typically, the binder may be included in an amount of 1 to 20% by weight, preferably 1 to 15% by weight, more preferably 1 to 10% by weight based on the total weight of the solid excluding the solvent in the negative electrode mixture slurry.

The conductive material is a component for further improving the conductivity of the anode active material. Such a conductive material is not particularly limited as long as it has conductivity without causing a chemical change in the battery. For example, graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fibers and metal fibers; 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; A conductive material such as a polyphenylene derivative may be used.

The conductive material may be included in an amount of 1 to 20% by weight, preferably 1 to 15% by weight, more preferably 1 to 10% by weight based on the total weight of the solid excluding the solvent in the negative electrode mixture slurry.

The solvent may include water or an organic solvent such as NMP (N-methyl-2-pyrrolidone), and may be used in an amount to achieve a desirable viscosity when the negative electrode active material and, optionally, a binder and a conductive material are included. can For example, it may be included so that the concentration of the solids including the negative active material, and optionally the binder and the conductive material is 50 wt% to 95 wt%, preferably 70 wt% to 90 wt%.

When a metal itself is used as the negative electrode, it may be manufactured by physically bonding, rolling, or depositing a metal on the metal thin film itself or the negative electrode current collector. As the deposition method, an electrical deposition method or a chemical vapor deposition method for metal may be used.

For example, the metal to be bonded/rolled/deposited on the metal thin film itself or the negative electrode current collector is lithium (Li), nickel (Ni), tin (Sn), copper (Cu), and indium (In). It may include one kind of metal or an alloy of two kinds of metals selected from

(3) separator

In addition, as the separator, a conventional porous polymer film conventionally used as a separator, for example, an ethylene homocopolymer, a propylene homocopolymer, an ethylene/butene copolymer, an ethylene/hexene copolymer, and an ethylene/methacrylate copolymer, etc. A porous polymer film made of the same polyolefin-based polymer may be used alone or by laminating them, or a conventional porous nonwoven fabric, for example, a nonwoven fabric made of high-melting glass fiber, polyethylene terephthalate fiber, etc. may be used, but this It is not limited. In addition, a coated separator including a ceramic component or a polymer material may be used to secure heat resistance or mechanical strength, and may optionally be used in a single-layer or multi-layer structure.

The external shape of the lithium secondary battery of the present invention is not particularly limited, but may be a cylindrical shape using a can, a prismatic shape, a pouch type, or a coin type.

According to another embodiment of the present invention, there is provided a battery module including the lithium secondary battery as a unit cell and a battery pack including the same. Since the battery module and the battery pack include the lithium secondary battery having high capacity, high rate-rate characteristics and cycle characteristics, mid-to-large selected from the group consisting of electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and power storage systems It can be used as a power source for the device.

Hereinafter, the present invention will be described in more detail through specific examples. However, the following examples are only examples to help the understanding of the present invention, and do not limit the scope of the present invention. It is obvious to those skilled in the art that various changes and modifications are possible within the scope and spirit of the present disclosure, and it is natural that such variations and modifications fall within the scope of the appended claims.

Synthesis example

Synthesis Example 1. Preparation of compound (A1) of Formula 1aa

In a 500 mL round-bottom flask, 50 g of 3-Chloro-1,2-propanediol, 60 g of Na ₂ SO ₃ and 200 mL of water were added, and the mixture was heated and stirred at 65 °C for 7 hours. After concentration of the solution by distillation under reduced pressure, 300 mL of methanol was added to form a precipitate. The precipitate was filtered under reduced pressure, washed with methanol, and dried under vacuum to obtain sodium 2,3-dihydroxypropane sulfonate (yield 105 g, purity 80%). In a 500 mL round-bottom flask, 30 g of dried sodium 2,3-dihydroxypropane sulfonate, 0.5 g of DMF, and 75 mL of toluene were placed, and 48 g of thionyl chloride was slowly added dropwise at room temperature. After the dropping was completed, the reaction was heated at 65 °C for 5 hours. After the reaction was cooled to room temperature, 50 mL of MeOH was added and stirred for 3 hours. After removing the residual solvent from the reaction mixture under reduced pressure, it was passed through a silica gel column to obtain 2-Hydroxy-1,3-propane sultone (Eluent: Ethyl acetate, 8.8 g). 0.31 g of LiCl was added to 8 mL of dimethyl carbonate to prepare a slurry, and 0.84 g of chlorosulfonic acid was slowly added thereto. After about 1 hour, 1 g of 2-Hydroxy-1,3-propane sultone was dissolved in 5 mL of dimethyl carbonate and slowly added. After stirring at room temperature for 3 hours, the reaction solution was precipitated in methylene chloride and filtered under reduced pressure to obtain 1.1 g of a compound of Formula 1aa.

¹ H-NMR (500 MHz, DMSO-d6) δ (ppm): 3.2 (1H), 3.7 (1H), 4.3 (1H), 4.5 (1H), 4.8 (1H)

Synthesis Example 2. Preparation of Formula 1bb Compound (A2)

In a 250 mL round-bottom flask, 5 g of 3-Butene-1,2-diol, _{11.9 g of Na 2} S ₂ O ₅ , and 10 mL of water were added, and the mixture was stirred at 65 °C for 9 hours while maintaining pH 7.3. The reaction solution was concentrated by distillation under reduced pressure, and 50 mL of methanol was added to obtain a precipitate. The precipitate was filtered under reduced pressure and dried in a vacuum oven to obtain sodium 3,4-dihydroxybutane sulfonate (10 g). After the sultonation reaction was carried out under hydrochloric acid conditions, a sulfate salt introduction reaction was performed as in Synthesis Example 1 to prepare 1.1 g of a compound of Formula 1bb.

¹ H-NMR (500 MHz, DMSO-d6) δ (ppm): 2.3 (1H), 2.55 (1H), 3.4 (2H), 3.8-3.9 (2H), 4.8 (1H)

Synthesis Example 3. Preparation of Formula 1cc Compound (A3)

In a 250 mL round-bottom flask, 5 g of 3-Butene-1,2-diol, _{11.9 g of Na 2} S ₂ O ₅ , and 10 mL of water were added, and the mixture was stirred at 65 °C for 9 hours while maintaining pH 7.3. The reaction solution was concentrated by distillation under reduced pressure, and 50 mL of water was added to obtain a precipitate. The precipitate was filtered under reduced pressure and dried in a vacuum oven to obtain sodium 3,4-dihydroxybutane sulfonate (10 g). Then, as in Synthesis Example 1, a sultonation reaction and a sulfate salt introduction reaction were performed to prepare 1.1 g of a compound of Formula 1cc.

¹ H-NMR (500 MHz, DMSO-d6) δ (ppm): 2.2 to 2.4 (2H), 3.2 to 3.4 (2H), 4.2 (1H), 4.4 to 4.6 (2H)

Example

Example 1.

(Preparation of non-aqueous electrolyte)

In 96.5 g of 1 M LiPF ₆ dissolved organic solvent (ethylene carbonate (EC): ethylmethyl carbonate (EMC) = 3:7 volume ratio), 3 g of vinylene carbonate and 0.5 g of compound (A1) of Formula 1aa were added to the non-aqueous electrolyte was prepared. (See Table 1 below).

(Lithium secondary battery manufacturing)

Positive active material (LiNi _0.8 Co _0.1 Mn _0.1 O ₂ ; NCM): conductive material (carbon black): binder (polyvinylidene fluoride) in a weight ratio of 90:5:5 to N-methyl-2-pyrrolidone as a solvent ( NMP) to prepare a positive electrode slurry (solid content: 40 wt%). The positive electrode slurry was applied to one surface of a positive electrode current collector (Al thin film) having a thickness of 20 μm, dried and rolled to prepare a positive electrode. Next, negative electrode active material (artificial graphite): conductive material (carbon black): binder (polyvinylidene fluoride) was added to N-methyl-2-pyrrolidone (NMP) as a solvent in a weight ratio of 90:5:5 to the negative electrode. A slurry (40 wt% solids) was prepared. The negative electrode slurry was applied to one surface of a negative electrode current collector (Cu thin film) having a thickness of 20 μm, and dried and roll press were performed to prepare a negative electrode.

Then, a coin-type battery was prepared by sequentially stacking the prepared positive electrode and negative electrode together with a polyethylene porous film, and then, a lithium secondary battery (battery capacity 340 mAh) was prepared by injecting the prepared non-aqueous electrolyte. did.

Example 2.

A non-aqueous electrolyte was prepared and injected in the same manner as in Example 1, except that the compound of Formula 1bb (A2) was used instead of the compound of Synthesis Example 1 to prepare a lithium secondary battery.

Example 3.

A non-aqueous electrolyte was prepared in the same manner as in Example 1, except that the compound of Formula 1cc (A3) was used instead of the compound of Synthesis Example 1, and a lithium secondary battery was prepared by injecting it.

Comparative Example 1.

A non-aqueous electrolyte was prepared in the same manner as in Example 1, except that 1,3-propane sultone (B1) was used instead of the compound of Synthesis Example 1, and a lithium secondary battery was prepared by injecting it.

Comparative Example 2.

A non-aqueous electrolyte was prepared in the same manner as in Example 1, except that 2-Hydroxy-1,3-propane sultone (B2) was used instead of the compound of Synthesis Example 1, and a lithium secondary battery was prepared by injecting it.

Experimental example

Experimental Example 1. Cycle life characteristic experiment

Each of the secondary batteries prepared in Examples 1 to 3 and Comparative Examples 1 to 2 was charged at 1C to 4.25V/55mA under constant current/constant voltage (CC/CV) conditions at 45°C, and then 2C to 3.0V under CC conditions. to measure the 400 cycle life at high temperature (400 cycles/1 cycle Х 100), and the results are shown in Table 1 below.

In addition, each of the secondary batteries prepared in Examples 1 to 3 and Comparative Examples 1 to 2 were charged at 1C up to 4.25V/55mA at 25°C under CC/CV conditions, and then discharged at 2C up to 3.0V under CC conditions. 400 cycle life characteristics at room temperature were measured (400 cycles/1 cycle Х 100), and the results are shown in Table 1 below.

Experimental Example 2. High-temperature storage characteristics test

Each of the secondary batteries prepared in Examples 1 to 3 and Comparative Examples 1 to 2 were stored at a high temperature of 60° C. for 16 weeks, then charged at 1 C to 4.25 V/55 mA at room temperature under CC/CV conditions, and then under CC conditions. Discharged to 2.5V at 2C, and after 16 weeks, the discharge capacity was calculated as a percentage (capacity after 16 weeks/initial discharge capacity Х 100 (%)), and the capacity after high temperature storage was measured. The results are shown in Table 1 below.

In addition, each secondary battery prepared in Examples 1 to 3 and Comparative Examples 1 to 2 was stored at a high temperature of 60° C. for 16 weeks, and then discharged for 10 seconds at 3C at 50% SOC at room temperature. It was calculated and calculated as the output percentage after 16 weeks of storage (output after 16 weeks / initial output Х 100), and the results are shown in Table 1 below.

Non-aqueous electrolyte additive composition ^a Life characteristics (%) ^b High temperature storage characteristics (%) ^c Additives (wt%) room temperature High temperature Volume Print Example 1 VC/A1 = 3/0.5 91 88 93 95 Example 2 VC/A2 = 3/0.5 91 86 92 93 Example 3 VC/A3 = 3/0.5 90 85 92 93 Comparative Example 1 VC/B1= 3/0.5 81 78 82 80 Comparative Example 2 VC/B2 = 3/0.5 77 76 80 77

a. Non-aqueous electrolyte composition other than additives EC/EMC 30/70 vol%, LiPF ₆ 1MVC: Vinylene Carbonate

b. 400 cycle life characteristics

c. Characteristics after storage at 60℃ for 16 weeks

As shown in Table 1, looking at the lifespan characteristics after 400 cycles, it was confirmed that the secondary batteries prepared in Examples 1 to 3 had significantly superior cycle life characteristics at room temperature and high temperature than the secondary batteries manufactured in Comparative Examples 1 and 2 can

In addition, looking at the high temperature storage characteristics, it can be seen that the capacity and output characteristics of the secondary batteries manufactured in Examples 1 to 3 are improved compared to the secondary batteries manufactured in Comparative Examples 1 and 2.

This property is believed to be because the sultone-based additives of Examples 1 to 3 efficiently produce SEI films with high stability and low resistance.

Therefore, when the additive for a non-aqueous electrolyte containing the compound represented by Formula 1 according to an embodiment of the present invention is used, a low resistance and strong SEI layer is formed, thereby providing a lithium secondary battery having excellent high temperature and long life characteristics. It can be seen that there is

Claims (10)

An additive for a non-aqueous electrolyte comprising a sultone-based compound represented by the following formula (1):
[Formula 1]

In Formula 1,
n is 1 or 2,
Ak is a single bond; Or a substituted or unsubstituted alkylene group having 1 to 6 carbon atoms;
X is Li, Na or K.
The method according to claim 1,
The -Ak-OSO ₃ ^- group is an additive for a non-aqueous electrolyte that is bonded to the 3rd or 4th position of the cyclic structure of the sultone-based compound represented by Formula 1 above.
The method according to claim 1,
wherein Ak is a single bond or a methylene group.
The method according to claim 1,
wherein X is Li, an additive for a non-aqueous electrolyte.
The method according to claim 1,
The sultone-based compound represented by Formula 1 is an additive for a non-aqueous electrolyte that is at least one selected from the following Formulas 1a to 1c compounds:
[Formula 1a]

[Formula 1b]

[Formula 1c]

In Formulas 1a to 1c,
X is Li, Na or K.
The method according to claim 1,
The sultone-based compound represented by Formula 1 is an additive for a non-aqueous electrolyte that is at least one selected from the following Formulas 1aa to 1cc compounds:
[Formula 1aa]

[Formula 1bb]

[Formula 1cc]

.
A non-aqueous electrolyte comprising the additive according to any one of claims 1 to 6.
8. The method of claim 7,
The additive is included in an amount of 0.01 parts by weight to 10 parts by weight based on 100 parts by weight of the non-aqueous electrolyte.
8. The method of claim 7,
The non-aqueous electrolyte further comprises a lithium salt,
The lithium salt is a non-aqueous electrolyte contained in a concentration of 0.5 M to 5 M.
A lithium secondary battery comprising the non-aqueous electrolyte according to claim 7.