KR102358449B1 - Negative electrode slurry composition for lithium secondary battery, and preparing method thereof - Google Patents

Abstract

The present invention is a silicon-based negative active material; at least one metal salt selected from the group consisting of NaCl, KCl, LiCl and Na ₂ CO ₃ ; And a solvent, wherein the metal salt is 0.01 wt% to 5 wt% based on the total weight of the silicon-based negative active material, a negative electrode slurry composition, and a negative electrode prepared using the same, and a lithium secondary battery comprising the negative electrode it's about

Description

Anode slurry composition for lithium secondary battery, and manufacturing method thereof

The present invention relates to a negative electrode slurry for a lithium secondary battery, and a method for manufacturing the same, and more particularly, to a negative electrode slurry containing a metal salt capable of forming a film on the surface of an anode active material and a method for manufacturing the same.

As technology development and demand for mobile devices increase, the demand for secondary batteries as an energy source is rapidly increasing. Among such secondary batteries, lithium secondary batteries exhibiting high energy density and operating potential, long cycle life, and low self-discharge rate. Batteries have been commercialized and widely used.

As a negative active material constituting the negative electrode of a lithium secondary battery, a material such as a carbon based meterial such as metal lithium, graphite, or activated carbon, or a material such as silicon oxide (SiO _x ) is being used Among the anode active materials, metallic lithium was mainly used in the beginning, but as the charging and discharging cycle proceeds, lithium atoms grow on the metallic lithium surface to damage the separator and damage the battery. Recently, carbon-based materials are mainly used. However, in the case of a carbon-based material, since the theoretical capacity is only about 400 mAh/g, it has a disadvantage that the capacity is small. Various studies have been conducted to replace the carbon-based material. Silicon oxide (SiO _x ) has a higher theoretical capacity (4,200 mAh/g) than graphite, but has a disadvantage in that the initial efficiency is low.

In a lithium secondary battery, charging and discharging proceed while repeating the process in which lithium ions of the positive active material of the positive electrode are intercalated into the negative active material of the negative electrode and deintercalated. Theoretically, lithium insertion and desorption reactions into the negative active material are completely reversible, but in practice, more lithium than the theoretical capacity of the negative active material is consumed, and only a part of it is recovered during discharge. Accordingly, after the second cycle, a smaller amount of lithium ions are inserted during charging, but most of the inserted lithium ions are desorbed during discharging. As described above, the difference in capacity that appears in the first charge and discharge reaction is called irreversible capacity loss. In a commercial lithium secondary battery, lithium ions are supplied from the positive electrode and lithium is not present in the negative electrode. It is important to minimize

It is known that this initial irreversible capacity loss is mostly due to an electrolyte decomposition reaction on the surface of the anode active material, and an SEI film (solid electrolyte membrane, Solid Electrolyte Interface) on the surface of the anode active material by an electrochemical reaction through the electrolyte decomposition. ) is formed. Since many lithium ions are consumed in the formation of the SEI film, there is a problem of causing irreversible capacity loss. ), it functions to pass only lithium ions, thereby suppressing further electrolyte decomposition reactions and contributing to the improvement of cycle characteristics of lithium secondary batteries. Therefore, there is a need for a method for improving the initial irreversibility caused by the formation of the SEI film or the like.

KR 2016-0040020 A

An object of the present invention is to provide a negative electrode slurry composition including a silicon-based negative electrode active material in which a film formed by the metal salt is positioned on the outer surface including the metal salt.

Another object of the present invention to be solved is to provide a method for preparing the negative electrode slurry composition.

Another problem to be solved by the present invention is a negative electrode for a lithium secondary battery comprising a negative electrode active material layer made of a negative electrode slurry containing a silicon-based negative electrode active material in which the film formed by the metal salt is located on the outer surface, and the negative electrode To provide a lithium secondary battery.

The present invention, in order to solve the above problems, a silicon-based negative active material; at least one metal salt selected from the group consisting of NaCl, KCl, LiCl and Na ₂ CO ₃ ; and a solvent, wherein the metal salt is 0.01 wt% to 5 wt%, based on the total weight of the silicon-based negative active material, to provide a negative electrode slurry composition.

The present invention, in order to solve the other problems, a negative active material; and mixing at least one metal salt selected from the group consisting of NaCl, KCl, LiCl, and Na ₂ CO ₃ , wherein the metal salt is 0.01 wt% to 5 wt% based on the total weight of the negative active material Phosphorus, provides a method for preparing the negative electrode slurry composition.

The present invention, in order to solve the another problem, a silicon-based negative active material; and at least one metal salt selected from the group consisting of NaCl, KCl, LiCl and Na ₂ CO ₃ , wherein a film formed by the metal salt is located on the outer surface of the silicon-based negative active material, and the metal salt is the silicon-based It provides a negative electrode for a lithium secondary battery and a lithium secondary battery including the negative electrode, comprising an anode active material layer in an amount of 0.01 wt% to 5 wt% based on the total weight of the anode active material.

The negative electrode slurry composition according to the present invention includes a silicon-based negative electrode material and a metal salt, and since the metal salt forms a film on the outer surface of the silicon-based negative active material, the film surrounds the surface of the negative electrode active material, thereby initial efficiency of the negative electrode can be improved, and electrolyte consumption due to continuous SEI generation and destruction and battery degradation due to lithium source loss can be improved.

Hereinafter, the present invention will be described in more detail to help the understanding of the present invention.

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. Based on the principle that there is, it should be interpreted as meaning and concept consistent with the technical idea of the present invention.

negative electrode slurry composition

The negative electrode slurry composition of the present invention may be a negative electrode slurry composition for forming a negative electrode for a lithium secondary battery, and may include a silicon-based negative electrode active material; at least one metal salt selected from the group consisting of NaCl, KCl, LiCl and Na ₂ CO ₃ ; and a solvent.

Since the negative electrode slurry composition of the present invention contains one or more metal salts selected from the group consisting of NaCl, KCl, LiCl and Na ₂ CO ₃ together with the silicon-based negative active material, when forming a negative electrode for a lithium secondary battery using this, the above Before the initial activation of the lithium secondary battery including the negative electrode is made, the metal salt may form a film on the outer surface of the silicon-based negative active material in advance. In the film formed by the metal salt, at least one metal salt selected from the group consisting of NaCl, KCl, LiCl and Na ₂ CO ₃ may itself constitute an inorganic layer, and a solid electrolyte interface formed on the electrode surface (Solid Electrolyte Interface, SEI, hereinafter also referred to as "SEI") may contain a component. For example, when a non-aqueous electrolyte is used in a lithium secondary battery including a negative electrode prepared by using the negative electrode slurry composition according to an example of the present invention, the metal salt is not dissolved and is present on the surface of the negative electrode active material as a salt film. can

Accordingly, the film formed by the metal salt partially replaces the solid electrolyte interface, or by allowing the component constituting the solid electrolyte interface to exist in the form of a film on the outer surface of the silicon-based negative active material, including a silicon-based negative active material It is possible to minimize the initial irreversibility of the negative electrode.

The metal salt may be in an amount of 0.01 wt% to 5 wt%, specifically 0.01 wt% to 1 wt%, and more specifically 0.05 wt% to 0.21 wt%, based on the total weight of the silicon-based negative active material. When the metal salt is included in the above content, it is possible to appropriately minimize the initial irreversibility of the negative electrode. When the content of the metal salt is insufficient compared to the above range, the film formed by the metal salt of the metal salt cannot be formed to an appropriate degree on the outer surface of the silicon-based negative active material, and the content of the metal salt is higher than the range. In this case, it may act as a resistor on the surface of the cathode.

The metal salt may surround the outer surface of the silicon-based negative active material in the negative electrode slurry composition. For example, a film may be formed on the outer surface of the silicon-based negative active material in the process of preparing the negative electrode slurry composition by mixing the components included in the negative electrode slurry composition.

The silicon-based particles may be one or more mixtures selected from the group consisting of Si, silicon oxide particles (SiO _x , 0<x≤2), Si-metal alloy, and silicon-carbon composite, specifically silicon oxide particles (SiO _x , may be 0<x≤2), and the silicon oxide particles (SiO _x , 0<x<2) may be a composite composed of crystalline SiO ₂ and amorphous Si.

The silicon-based negative active material may have an average particle diameter (D ₅₀ ) of 1 μm to 30 μm, specifically 3 μm to 20 μm, and more specifically, an average particle diameter (D ₅₀ ) of 4 μm to 10 μm. If the average particle _diameter (D ₅₀ ) of the silicon-based anode active material is too small, side reactions with the electrolyte may increase and lifespan performance may decrease. This may occur, so lifespan performance may be reduced. When the silicon-based anode active material satisfies the above range, excellent output and initial efficiency may be properly balanced, and excellent tap density may be exhibited, and an excellent loading amount may be exhibited during electrode coating.

The average particle diameter (D ₅₀ ) may be defined as a particle diameter based on 50% of the particle size distribution. The average particle diameter is not particularly limited, but may be measured using, for example, a laser diffraction method or a scanning electron microscope (SEM) photograph. In general, the laser diffraction method can measure a particle diameter of several mm from a submicron region, and can obtain a result having high reproducibility and high resolution.

The negative electrode slurry composition includes a solvent, and the solvent may be an aqueous solvent, specifically water. When the negative electrode slurry composition includes an aqueous solvent, the metal salt may be dissolved in the aqueous solvent to appropriately surround the outer surface of the silicon-based negative active material.

When the metal salt is dissolved in the aqueous solvent to form a film suitably surrounding the outer surface of the silicon-based negative active material, the film has Li ₂ CO ₃ , LiOCH ₃ , LiOC ₂ H ₅ , or Li ₂ O, such as Components constituting the SEI may be included. Since the components constituting the SEI are water-soluble, they are uniformly included in the film positioned on the outer surface of the silicon-based negative active material in the negative electrode slurry composition and exist together in the form of a film to perform the same or similar function as the solid electrolyte interface (SEI). It is possible to minimize the initial irreversibility of the negative electrode.

The negative electrode slurry composition may further include a thickener. The thickener may be a cellulosic compound, for example, may be at least one selected from the group consisting of carboxymethyl cellulose (CMC), hydroxy methyl cellulose, hydroxy ethyl cellulose and hydroxy propyl cellulose, specifically carboxy methyl cellulose (CMC).

The negative electrode slurry composition may include 0.1% to 3% by weight of the thickener based on the total weight of the solid content of the negative electrode slurry, specifically 0.2% to 2% by weight, more specifically 0.5% to 1.5% by weight % may be included. When the negative electrode slurry composition contains the thickener in the above range, it is possible to exhibit an appropriate thickening effect to ensure storage stability of the negative electrode slurry composition, and the thickener to be included in the negative electrode slurry in an amount that does not affect the performance of the battery can

The negative electrode slurry composition may further include a conductive material. The conductive material is not particularly limited as long as it has conductivity without causing a chemical change in the battery. Examples of the conductive material include graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and summer black; conductive fibers such as carbon fibers and metal fibers; 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; or conductive materials such as polyphenylene derivatives. The conductive material may be used in an amount of 0.1 wt% to 9 wt% based on the total weight of the solid content of the negative electrode slurry.

The negative electrode slurry composition may further include a binder. The binder is not particularly limited as long as it is a conventional binder used in preparing the slurry for the negative electrode active material, for example, any one selected from the group consisting of water-based binders such as acrylonitrile-butadiene rubber, styrene-butadiene rubber, and acrylic rubber. A mixture of two or more may be used.

The binder may be included in an amount of 10% by weight or less based on the total solids weight of the negative electrode slurry, and specifically 0.1 to 10% by weight, more specifically 0.5 to 4% by weight. If the content of the binder is less than 0.1% by weight, the effect of the use of the binder is insignificant, which is not preferable. Not desirable.

In addition, the negative electrode slurry composition may further include a dispersant, and the dispersant may specifically be an aqueous dispersant.

The dispersant includes a cellulose compound, polyvinyl alcohol, polyvinylpyrrolidone, polyvinyl acetal, polyvinyl ether, polyvinyl sulfonic acid, polyvinyl chloride (PVC), polyvinylidene fluoride, chitosans, starch, amyl Rose (amylose), polyacrylamide, poly-N-isopropylacrylamide, poly-N,N-dimethylacrylamide, polyethyleneimine, polyoxyethylene, poly(2-methoxyethoxyethylene), poly(acrylamide) -co-diallyldimethylammonium chloride), acrylonitrile/butadiene/styrene (ABS) polymer, acrylonitrile/styrene/acrylic ester (ASA) polymer, acrylonitrile/styrene/acrylic ester (ASA) polymer and propylene carbonate mixtures of, a styrene/acrylonitrile (SAN) copolymer, or a methylmethacrylate/acrylonitrile/butadiene/styrene (MABS) polymer, and any one or a mixture of two or more thereof may be used.

The negative electrode slurry may include 0.01% to 0.5% by weight of the dispersant based on the total solids weight of the negative electrode slurry, specifically 0.05% to 0.5% by weight, more specifically 0.1% to 0.3% by weight can do.

When the negative electrode slurry contains the dispersing agent in the above range, the dispersing agent may appropriately improve the dispersibility of the negative electrode active material, but the dispersing agent is included in the negative electrode slurry within a certain amount so as not to degrade the performance of the battery.

The negative electrode slurry composition may include a silicon-based negative electrode active material; And NaCl, KCl, LiCl, and Na ₂ CO ₃ It may be prepared by a manufacturing method comprising mixing at least one metal salt selected from the group consisting of, wherein the metal salt is in the total weight of the negative active material 0.01% to 5% by weight.

Specifically, the method for preparing the negative electrode slurry composition includes the steps of: (1) mixing a thickener, a conductive material, and a solvent; (2) mixing the silicon-based negative active material and the metal salt with the product of step (1); and (3) mixing a binder with the product of step (2).

The negative electrode slurry composition is prepared by first mixing the thickener and the conductive material in step (1), and then mixing the silicon-based negative active material and the metal salt with the product of step (1) in step (2) to the outer surface of the silicone-based negative active material The metal salt forms a film. The metal salt may be mixed with the silicon-based negative active material to surround the outer surface of the silicon-based negative active material.

In an example of the present invention, the mixing of the silicon-based negative active material and the metal salt may be made in an aqueous solvent, and thus the metal salt is dissolved in the aqueous solvent to surround the outer surface of the silicon-based negative active material dispersed in the aqueous solvent. Since components constituting the SEI, such as Li ₂ CO ₃ , LiOCH ₃ , LiOC ₂ H ₅ , or Li ₂ O, are water-soluble, the components constituting the SEI in the aqueous solvent are appropriately formed to be included in the outer surface film of the silicon-based negative electrode active material. can

In the method for preparing the negative electrode slurry composition according to an example of the present invention, the thickener and the conductive material in step (1) are mixed with a solvent.

As the thickener and binder, the above-mentioned kinds of materials may be used. Specifically, the thickener may include carboxymethyl cellulose (CMC), and the binder may include a water-soluble binder.

Next, a negative electrode slurry composition may be prepared by mixing a binder with the product of step (2).

A negative electrode for a lithium secondary battery can be manufactured using the negative electrode slurry composition prepared in this way, and thus the present invention provides a silicon-based negative electrode active material; and at least one metal salt selected from the group consisting of NaCl, KCl, LiCl and Na ₂ CO ₃ , wherein a film formed by the metal salt is located on the outer surface of the silicon-based negative active material, and the metal salt is the silicon-based It provides a negative electrode for a lithium secondary battery, comprising a negative electrode active material layer in an amount of 0.01% to 5% by weight based on the total weight of the negative electrode active material.

In addition, the present invention provides a lithium secondary battery including the negative electrode.

The lithium secondary battery may include a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode.

The negative electrode may be manufactured by a conventional method for manufacturing a negative electrode known in the art using the negative electrode slurry prepared by the above-described method for preparing the negative electrode slurry.

The amount of the aqueous solvent used is sufficient as long as it is capable of dissolving and dispersing the silicon-based negative active material, metal salt and binder, conductive material, and the like in consideration of the application thickness of the slurry and the production yield.

The negative electrode current collector used for the negative electrode according to an example of the present invention may have a thickness of 3 μm to 500 μm. The negative electrode current collector is not particularly limited as long as it has conductivity without causing a chemical change in the battery. For example, copper, gold, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface Carbon, nickel, titanium, one surface-treated with silver, an aluminum-cadmium alloy, etc. may be used. In addition, the bonding strength 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 films, sheets, foils, nets, porous bodies, foams, and nonwovens.

A filler may be included in the negative electrode slurry, if necessary.

The filler is an auxiliary component that suppresses the expansion of the electrode, and is not particularly limited as long as it is a fibrous material without causing a chemical change in the battery. For example, olefinic polymers such as polyethylene and polypropylene, glass fibers, carbon fibers It may be a fibrous material.

The positive electrode may be manufactured by a conventional method known in the art. For example, the positive electrode active material is mixed and stirred to prepare a slurry by mixing and stirring the solvent, the above-mentioned binder, conductive material, and dispersing agent, and then applying (coating) it to a current collector made of a metal material, compressing it, and drying it to prepare a positive electrode. .

The current collector of the metallic material is a metal with high conductivity, and is a metal to which the slurry of the positive electrode active material can be easily adhered. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, or a surface treated with carbon, nickel, titanium, silver, etc. on the surface of aluminum or stainless steel may be used. In addition, by forming fine irregularities on the surface of the current collector, the adhesive force of the positive electrode active material may be increased. The current collector may be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, a non-woven body, and the like, and may have a thickness of 3 μm to 500 μm.

The positive active material may include, for example, lithium cobalt oxide (LiCoO ₂ ); lithium nickel oxide (LiNiO ₂ ); Li[Ni _a Co _b Mn _c M ¹ _d ]O ₂ (Wherein, M ¹ is any one selected from the group consisting of Al, Ga, and In, or two or more of them, 0.3≤a<1.0, 0 ≤b≤0.5, 0≤c≤0.5, 0≤d≤0.1, a+b+c+d=1); Li(Li _e M ² _fe-f' M ³ _f' )O _2-g A _g (wherein, 0≤e≤0.2, 0.6≤f≤1, 0≤f'≤0.2, 0≤g≤0.2, and , M ² is Mn and Ni, Co, Fe, Cr, V, Cu, Zn and Ti includes at least one selected from the group, M ³ is Al, Mg and 1 selected from the group consisting of B more than one species, and A is at least one selected from the group consisting of P, F, S, and N) or a layered compound such as a compound substituted with one or more transition metals; Li _1+h Mn _2-h O ₄ (0≤h≤0.33 in the above formula), LiMnO ₃ , LiMn ₂ O ₃ , LiMnO ₂ Lithium manganese oxide such as; lithium copper oxide (Li ₂ CuO ₂ ); vanadium oxides such as LiV ₃ O ₈ , V ₂ O ₅ , and Cu ₂ V ₂ O ₇ ; Ni site type lithium nickel oxide represented by the formula LiNi _{1 - i} M ⁴ _i O ₂ (wherein M ⁴ is Co, Mn, Al, Cu, Fe, Mg, B or Ga, 0.01≤i≤0.3); Formula LiMn _{2 - j} M ⁵ _j O ₂ (wherein, M ⁵ is Co, Ni, Fe, Cr, Zn or Ta, 0.01≤j≤0.1) or Li ₂ Mn ₃ M ⁶ O ₈ (in the above formula, M ⁶ is a lithium manganese composite oxide represented by Fe, Co, Ni, Cu or Zn); LiMn ₂ O ₄ in which a part of Li in the formula is substituted with an alkaline earth metal ion; disulfide compounds; LiFe ₃ O ₄ , Fe ₂ (MoO ₄ ) ₃ , and the like may be mentioned, but are not limited thereto.

The positive active material may be included in an amount of 50 wt% to 99 wt%, specifically 70 wt% to 98 wt%, based on the total weight of the solid content of the cathode slurry.

Examples of the solvent for forming the positive electrode include organic solvents such as NMP (N-methyl pyrrolidone), DMF (dimethyl formamide), acetone, and dimethyl acetamide or water, and these solvents are used alone or in two or more types. can be mixed and used. The amount of the solvent used is sufficient as long as it is capable of dissolving and dispersing the positive electrode active material, the binder, and the conductive material in consideration of the application thickness of the slurry and the production yield.

The 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, Farness black, lamp black, and thermal black; conductive fibers such as carbon fibers and metal fibers; conductive tubes such as carbon nanotubes; metal powders such as fluorocarbon, 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 used in an amount of 1 wt% to 20 wt% based on the total weight of the solid content of the positive electrode slurry.

The dispersant may be an aqueous dispersant or an organic dispersant such as N-methyl-2-pyrrolidone. The dispersant may be used in an amount of 0.01 wt% to 10 wt% based on the total weight of the solid content of the cathode active material slurry.

On the other hand, as the separator, a conventional porous polymer film conventionally used as a separator, such as an ethylene homopolymer, a propylene homopolymer, an ethylene-butene copolymer, an ethylene-hexene copolymer, and an ethylene-methacrylate copolymer such as a polyolefin-based polymer The porous polymer film prepared with the above may be used alone or by laminating them, or a conventional porous nonwoven fabric, such as a nonwoven fabric made of high-melting glass fiber, polyethylene terephthalate fiber, or the like, may be used, but is not limited thereto.

Lithium salts that may be included as the electrolyte used in the present invention may be used without limitation, those commonly used in electrolytes for lithium secondary batteries, for example, as an anion of the lithium salt, F ^- , Cl ^- , Br ^- , I ^- , NO ₃ ^- , N(CN) ₂ ^- , BF ₄ ^- , ClO ₄ ^- , PF ₆ ^- , (CF ₃ ) ₂ PF ₄ ^- , (CF ₃ ) ₃ PF ₃ ^- , (CF ₃ ) ₄ PF ₂ ^- , (CF ₃ ) ₅ PF ^- , (CF ₃ ) ₆ P ^- , CF ₃ SO ₃ ^- , CF ₃ CF ₂ SO ₃ ^- , (CF ₃ SO ₂ ) ₂ N ^- , (FSO ₂ ) ₂ N ^- , CF ₃ CF ₂ (CF ₃ ) ₂ CO ^- , (CF ₃ SO ₂ ) ₂ CH ^- , (SF ₅ ) ₃ C ^- , (CF ₃ SO ₂ ) ₃ C ^- , CF ₃ (CF ₂ ) ₇ SO ₃ ^- , CF ₃ CO ₂ ^- , CH ₃ CO ₂ ^- , SCN ^- and (CF ₃ CF ₂ SO ₂ ) ₂ N ^- may be any one selected from the group consisting of.

In the electrolyte used in the present invention, as an organic solvent included in the electrolyte, those commonly used in electrolytes for secondary batteries may be used without limitation, and representatively, propylene carbonate (PC), ethylene carbonate (ethylene carbonate, EC) ), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethylmethyl carbonate (EMC), methylpropyl carbonate, dipropyl carbonate, dimethyl sulfur oxide, acetonitrile, dimethoxyethane, diethoxyethane , vinylene carbonate, sulfolane, gamma-butyrolactone, any one selected from the group consisting of propylene sulfite and tetrahydrofuran, or a mixture of two or more of these may be used representatively. Specifically, 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 and thus well dissociate lithium salts in the electrolyte. In these cyclic carbonates, dimethyl carbonate and di When a low-viscosity, low-dielectric constant linear carbonate such as ethyl carbonate is mixed in an appropriate ratio, an electrolyte having high electrical conductivity can be prepared, and thus it can be used more preferably.

Optionally, the electrolyte stored according to the present invention may further include additives such as an overcharge inhibitor included in a conventional electrolyte.

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.

The lithium secondary battery according to the present invention can be used not only in a battery cell used as a power source for a small device, but can also be preferably used as a unit cell in a medium or large battery module including a plurality of battery cells.

Example

Hereinafter, examples and experimental examples will be described in more detail to describe the present invention in detail, but the present invention is not limited by these examples and experimental examples. Embodiments according to the present invention may be modified in various other forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. The embodiments of the present invention are provided to more completely explain the present invention to those of ordinary skill in the art.

Example 1

1.5 parts by weight of carboxymethyl cellulose (CMC) and 2 parts by weight of carbon black as a conductive material were mixed in distilled water. 93.5 parts by weight of SiO particles having an average particle diameter (D ₅₀ ) of 7 μm were added thereto, and 0.09 parts by weight of LiCl was added and mixed. To this, 3 parts by weight of SBR binder as a binder was added and mixed to prepare a negative electrode slurry.

Example 2

A negative electrode slurry was prepared in the same manner as in Example 1, except that 0.09 parts by weight of NaCl was used instead of 0.09 parts by weight of LiCl.

Example 3

A negative electrode slurry was prepared in the same manner as in Example 1, except that 0.09 parts by weight of Na ₂ CO ₃ was used instead of 0.09 parts by weight of LiCl.

Example 4

A negative electrode slurry was prepared in the same manner as in Example 1, except that the LiCl content was changed to 0.19 parts by weight.

Example 5

A negative electrode slurry was prepared in the same manner as in Example 1, except that the content of LiCl was changed to 0.01 parts by weight.

Example 6

A negative electrode slurry was prepared in the same manner as in Example 1, except that the content of LiCl was changed to 3 parts by weight.

Comparative Example 1

A negative active material composition was prepared in the same manner as in Example 1, except that LiCl was not mixed in Example 1.

Experimental Example 1

Each negative electrode active material slurry prepared in Examples 1 to 6 and Comparative Example 1 was coated on one surface of a copper current collector to form an active material layer having a thickness of 65 μm, dried, and then punched to a predetermined size after rolling to each negative electrode was prepared.

Li metal was used as a counter electrode, and a polyolefin separator was interposed between each negative electrode prepared above and Li metal, and then ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed in a volume ratio of 30:70. An electrolyte in which 0.5 wt% of vinylene carbonate and 1M LiPF ₆ were dissolved in the mixed solvent was injected to prepare coin-type half-cells, respectively.

Table 1 shows the ratio of the 0.1 C constant current 0.005 V constant voltage charge amount and the 0.1 C/1.5 V constant current discharge capacity of the coin-type half-cells.

Experimental Example 2

Each of the coin-type half-cells prepared in Experimental Example 1 was charged with a constant current of 0.33 C and a constant voltage of 4.2 V (current limit: 0.05 C), and then discharged with a constant current of 0.33 C and 2.5 V. Fully charge in the same way, discharge only 50% of the previous 0.33 C discharge capacity, rest for 1 hour, and then apply a 2.5 C discharge current for 10 seconds. was measured and shown in Table 1 below.

Initial Efficiency (%) initial resistance
(DCIR@SOC50, ohm) Example 1 88 1.1 Example 2 87 1.0 Example 3 89 1.0 Example 4 90 1.2 Example 5 83 1.0 Example 6 89 1.8 Comparative Example 1 82 1.0

As can be seen in Table 1, the lithium secondary battery including the negative electrode prepared by using the negative electrode slurry composition of Examples 1 to 6 containing the metal salt has increased initial efficiency, which means that the metal salt is the negative electrode active material. It is considered that this is because the initial irreversible capacity of the negative electrode was reduced by creating a solid electrolyte interface (SEI) on the surface.

Claims (11)

silicon oxide particles (SiOx, 0<x≤2); at least one metal salt selected from the group consisting of NaCl, KCl, LiCl and Na ₂ CO ₃ ; and a solvent,
The metal salt is 0.05 wt% to 0.21 wt% based on the total weight of the silicon oxide particles (SiOx, 0<x≤2), the negative electrode slurry composition.
The method of claim 1,
A film formed by the metal salt is located on the outer surface of the silicon oxide particles (SiOx, 0 < x ≤ 2), the negative electrode slurry composition.
3. The method of claim 2,
The film formed by the metal salt comprises a component constituting a solid electrolyte interface (SEI), negative electrode slurry composition.
delete The method of claim 1,
The silicon oxide particles (SiOx, 0<x≤2) have an average particle diameter (D ₅₀ ) of 1 μm to 30 μm, a negative electrode slurry composition.
The method of claim 1,
The solvent is an aqueous solvent, the negative electrode slurry composition.
silicon oxide particles (SiOx, 0<x≤2); and one or more metal salts selected from the group consisting of NaCl, KCl, LiCl and Na ₂ CO ₃ , and a film formed by the metal salt on the outer surface of the silicon oxide particles (SiOx, 0<x≤2) is is located,
The metal salt is a negative electrode for a lithium secondary battery comprising a negative active material layer in an amount of 0.05 wt% to 0.21 wt% based on the total weight of the silicon oxide particles (SiOx, 0<x≤2).
A lithium secondary battery comprising the negative electrode of claim 7.
silicon oxide particles (SiOx, 0<x≤2); and mixing at least one metal salt selected from the group consisting of NaCl, KCl, LiCl, and Na ₂ CO ₃ ,
The method of claim 1, wherein the metal salt is 0.05 wt% to 0.21 wt% based on the total weight of the silicon oxide particles (SiOx, 0<x≤2).
10. The method of claim 9,
The method for preparing the negative electrode slurry composition,
(1) mixing a thickener, a conductive material, and a solvent;
(2) mixing the silicon oxide particles (SiOx, 0<x≤2) and the metal salt with the product of step (1); and
(3) mixing a binder with the product of step (2)
A method for producing a negative electrode slurry composition comprising a.
10. The method of claim 9,
The mixing of the silicon oxide particles (SiOx, 0<x≤2) and the metal salt is made in an aqueous solvent, a method of producing a negative electrode slurry composition.