Negative electrode composition for lithium secondary battery and lithium secondary battery manufactured using same

Abstract

A negative electrode composition for a lithium secondary battery according to an embodiment of the present invention comprises a metal-doped silicon oxide (SiOx, 0lt; xlt; 2) particles and an additive comprising aluminum hydroxide. Accordingly, the amount of gas generation may be reduced, and thus the life and capacity of the secondary battery may be improved.

Description

Technical Field

[0001] The present invention relates to a composition for a negative electrode of a lithium secondary battery and a lithium secondary battery including the composition. More specifically, the present invention relates to a composition for a negative electrode of a lithium secondary battery including different kinds of substances and a lithium secondary battery manufactured from the composition. Background Art

[0002] A secondary battery is a battery that can be repeatedly charged and discharged. With the development of the information communication and display industries, secondary batteries are widely used as power sources for portable electronic communication devices such as camcorders, mobile phones, and laptop computers. In addition, in recent years, battery packs including secondary batteries are being developed and used as power sources for eco-friendly vehicles such as hybrid vehicles.

[0003] Examples of secondary batteries include lithium secondary batteries, nickel-cadmium batteries, nickel-metal hydride batteries, etc. Among them, lithium secondary batteries have a high working voltage and energy density per unit weight, and are advantageous for charging speed and weight reduction, so they are being actively developed and applied.

[0004] For example, a lithium secondary battery may include an electrode assembly and an electrolyte impregnating the electrode assembly, and the electrode assembly includes a positive electrode, a negative electrode, and a separator (separating membrane). The lithium secondary battery may further include an exterior material for accommodating the electrode assembly and the electrolyte, such as an exterior material in the form of a pouch.

[0005] In recent years, with the expansion of the application targets of the lithium secondary battery, lithium secondary batteries with higher capacities and powers are being developed. For example, high-capacity silicon oxide (SiO x ) can be used as a negative electrode active material. However, when silicon is exposed to hydroxide ions in an aqueous slurry, hydrogen gas may be generated. Therefore, the stability of the slurry may deteriorate.

[0006] In addition, when doping a metal in silicon oxide (SiO x ), the viscosity decreases when preparing the negative electrode slurry, and gas is generated, making it difficult to fabricate an electrode, and there is a problem of deterioration of the power characteristics of the battery. For example, Korean Patent Nos. 10-1591698 and 10-1728171 disclose a negative electrode active material in which silicon oxide is doped with a metal (lithium), but do not disclose how to prevent the generation of the above gas. Summary of the Invention

[0007] (I) Technical Problems to be Solved

[0008] One technical problem of the present invention is to provide a negative electrode composition for a lithium secondary battery having excellent power characteristics and capacity efficiency.

[0009] One technical problem of the present invention is to provide a negative electrode manufactured using the composition.

[0010] One technical problem of the present invention is to provide a lithium secondary battery including a negative electrode manufactured using the composition.

[0011] (II) Technical Solutions

[0012] The negative electrode composition for a lithium secondary battery according to an exemplary embodiment includes metal-doped silicon oxide (SiO x , 0 < x < 2) particles and an additive containing aluminum hydroxide.

[0013] In some embodiments, the metal doped in the silicon oxide (SiO x , 0 < x < 2) particles may include at least one of lithium, magnesium, and calcium.

[0014] In some embodiments, in the negative electrode composition for a lithium secondary battery, the ratio of the total weight of aluminum to the total weight of silicon may be 0.002 to 0.06.

[0015] In some embodiments, relative to the total weight of the silicon oxide (SiO x , 0 < x < 2) particles, the content of the additive may be 0.5 - 5.0 wt%.

[0016] In some embodiments, in the total weight of the composition, the content of the silicon oxide (SiO x , 0 < x < 2) particles may be 3 - 40 wt%.

[0017] In some embodiments, the negative electrode composition for a lithium secondary battery may further include a graphite-based active material.

[0018] In some embodiments, the ratio of the total weight of the silicon oxide (SiO x , 0 < x < 2) particles and the additive to the content of the graphite-based active material may be 0.03 to 0.45.

[0019] In some embodiments, the negative electrode composition for a lithium secondary battery may further include a binder.

[0020] In some embodiments, in the total weight of the composition, the content of the additive may be 0.015 - 2 wt%.

[0021] In some embodiments, the binder may include at least one of an acrylic-based binder and styrene-butadiene rubber (SBR).

[0022] In some embodiments, the negative electrode composition for a lithium secondary battery may further include a conductive material and a thickening agent.

[0023] The negative electrode for a lithium secondary battery according to an exemplary embodiment includes: a current collector; and a negative electrode active material layer disposed on the current collector, wherein the negative electrode active material layer includes metal-doped silicon oxide (SiO x , 0 < x < 2) particles and aluminum hydroxide.

[0024] In some embodiments, the ratio of the total weight of aluminum to the total weight of silicon in the negative electrode for a lithium secondary battery may be from 0.002 to 0.06.

[0025] The lithium secondary battery according to an exemplary embodiment includes: a positive electrode; and the negative electrode as described above, the negative electrode being disposed opposite to the positive electrode.

[0026] The method for preparing a negative electrode composition for a lithium secondary battery according to an exemplary embodiment includes the following steps: preparing metal-doped silicon oxide (SiO x , 0 < x < 2) particles; mixing an additive containing aluminum hydroxide into the metal-doped silicon oxide (SiO x , 0 < x < 2) particles to form a primary composition; and mixing a binder into the primary composition.

[0027] (III) Beneficial Effects

[0028] The negative electrode composition for a lithium secondary battery according to an exemplary embodiment may include an additive containing aluminum hydroxide. Therefore, the additive can remove hydroxide ions, thereby blocking the reaction between silicon and hydroxide ions and suppressing the generation of hydrogen gas, thus improving the life and capacity of the secondary battery.

[0029] In the method for preparing a negative electrode composition according to some embodiments, a primary composition may be formed by mixing the additive before adding and mixing the binder. Therefore, the additive can be included before the negative electrode active material comes into contact with water, and the reaction between the hydroxide ions generated when the negative electrode active material comes into contact with water and silicon can be blocked. Therefore, a reduction in the capacity characteristics of the secondary battery can be prevented. Description of the Drawings

[0030] Figure 1 and Figure 2 are a schematic plan view and a schematic cross-sectional view showing a lithium secondary battery according to an exemplary embodiment, respectively. Detailed Description

[0031] According to an embodiment of the present invention, there is provided a negative electrode composition for a lithium secondary battery, the negative electrode composition for a lithium secondary battery comprising metal-doped silicon oxide (SiO x , 0 < x < 2) particles and an additive comprising aluminum hydroxide. In addition, an embodiment of the present invention provides a negative electrode manufactured from the negative electrode composition and a lithium secondary battery including the negative electrode.

[0032] Hereinafter, with reference to the accompanying drawings, embodiments of the present invention will be described in more detail. However, the drawings of this specification are used to illustrate preferred embodiments of the present invention and, together with the above-described summary of the invention, serve to further understand the technical idea of the present invention. Therefore, the present invention should not be construed as being limited to the content described in the drawings.

[0033] <Composition for negative electrode of lithium secondary battery>

[0034] The negative electrode composition for a lithium secondary battery according to an exemplary embodiment (hereinafter, may also be simply referred to as a negative electrode composition) may be provided in the form of a slurry and may include a negative electrode active material. For example, the negative electrode composition may further include a binder. For example, the negative electrode composition may further include a conductive material and a thickener.

[0035] The negative electrode active material may be silicon oxide (SiO x , 0 < x < 2) particles. In some embodiments, the negative electrode active material may further include a carbon-based active material. For example, the carbon-based active material may be a graphite-based active material such as natural graphite or artificial graphite.

[0036] In an exemplary embodiment, in order to improve the initial efficiency of a lithium secondary battery, a metal may be doped in the silicon oxide (SiO x , 0 < x < 2) particles.

[0037] For example, when a metal component is doped in the silicon oxide (SiO x , 0 < x < 2) particles, the metal may combine with the silicon oxide (SiO x , 0 < x < 2) particles and form a metal silicate region on the surface portion of the silicon oxide particles through an irreversible reaction.

[0038] Therefore, for example, the initial irreversible reaction of the silicon oxide particles during the insertion and extraction process of lithium ions during battery charging and discharging can be reduced. Therefore, the initial efficiency of the lithium secondary battery can be improved.

[0039] In some embodiments, the metal doped in the silicon oxide (SiO xIn the (SiO

[0040] For example, the silicon oxide (SiO x containing a lithium compound can be a silicon oxide (SiO x with 0 < x < 2) particles containing lithium silicate. The lithium silicate can be present in at least a part of the silicon oxide (SiO x with 0 < x < 2) particles. For example, the lithium silicate can be present inside and / or on the surface of the silicon oxide (SiO x with 0 < x < 2) particles. In one embodiment, the lithium silicate can include Li2SiO3, Li2Si2O5, Li4SiO4, Li4Si3O8, etc.

[0041] For example, metal hydroxides (e.g., LiOH or Mg(OH)2) can be formed on the surface of the silicon oxide (SiO x with 0 < x < 2) particles. Therefore, the metal hydroxide reacts with moisture in the atmosphere or water in the negative electrode paste to form hydroxide ions (OH - ), thereby increasing the pH of the negative electrode composition.

[0042] Therefore, due to the reduction of the thickener, the viscosity of the negative electrode composition decreases, so the processability and productivity during electrode production may decrease. In addition, since the metal hydroxide on the surface of the silicon oxide (SiO x with 0 < x < 2) particles is removed, the excellent battery efficiency brought by metal doping may not be achieved.

[0043] For example, as shown in the following reaction formula, the hydroxide ions (OH - ) can react with silicon to produce hydrogen gas (H2gas).

[0044] [Reaction formula]

[0045] Si(s) + 2OH - (aq) + 2H2O(l) → Si(OH)4(ag) + H2(g) → SiO2(OH)2 2- (ag) + 2H2(g)

[0046] Therefore, if hydrogen gas is generated and bubbles are formed in the paste, it is difficult to uniformly coat on the current collector, and the silicon as a reversible phase is converted into silicon oxide as an irreversible phase (e.g., SiO2), which may lead to a decrease in the capacity characteristics of the negative electrode active material.

[0047] In an exemplary embodiment, the negative electrode composition for the lithium secondary battery may include an additive containing aluminum hydroxide.

[0048] For example, the additive may react with metal hydroxides such as LiOH, or react with or adsorb hydroxide ions dissolved in water, thereby reducing the concentration of hydroxide ions. Therefore, the reaction between silicon and hydroxide ions can be reduced, and the generation of hydrogen gas can be reduced. Accordingly, a decrease in processability and productivity during electrode fabrication can be prevented, and the lifespan and capacity of the lithium secondary battery can be improved.

[0049] In some embodiments, based on the total weight of the silicon oxide (SiO x , 0 < x < 2) particles, the content of the additive may be 0.5 - 5.0 wt%, for example, the content of the additive may be 0.4 - 6.0 wt%, 0.4 - 4.0 wt%, 0.4 - 2.5 wt%, 0.5 - 6.0 wt%, 0.5 - 4.0 wt%, 0.5 - 2.5 wt%. Within the above range, hydroxide ions can be removed by the aluminum compound, thereby suppressing the generation of hydrogen gas and improving the capacity, lifespan, and electrode adhesion of the lithium secondary battery.

[0050] When the content of the additive is less than 0.5 wt%, hydrogen gas may be generated, and the capacity and electrode adhesion may decrease. When the content of the additive exceeds 5.0 wt%, due to the excessive addition of the aluminum compound, the capacity and lifespan of the lithium secondary battery may decrease.

[0051] In a preferred embodiment, the negative electrode composition for the lithium secondary battery may include aluminum hydroxide. Based on the total weight of the silicon oxide (SiO x , 0 < x < 2) particles, the content of the aluminum hydroxide may be 0.5 - 5.0 wt%.

[0052] In some embodiments, in the negative electrode composition for the lithium secondary battery, the ratio of the total weight of aluminum to the total weight of silicon may be from 0.002 to 0.06, for example, the ratio of the total weight of aluminum to the total weight of silicon may be from 0.002 to 0.04, from 0.002 to 0.02, from 0.002 to 0.01. Within the above range, the generation of hydrogen gas can be reduced while ensuring the adhesion of the negative electrode active material, thereby improving the lifespan and capacity of the lithium secondary battery.

[0053] In some embodiments, in the total weight of the composition, the silicon oxide (SiO x, the content of particles with 0 < x < 2) can be 3 - 40% by weight. For example, in the total weight of the composition, the content of the silicon oxide (SiO x , the content of particles with 0 < x < 2) can be 5 - 35% by weight, 7 - 30% by weight, 10 - 25% by weight, 5 - 25% by weight. Within the above range, the initial efficiency and capacity of the lithium secondary battery can be improved.

[0054] In some embodiments, in the total weight of the composition, the content of the additive can be 0.015 - 2% by weight. For example, in the total weight of the composition, the content of the additive can be 0.02 - 1.8% by weight, 0.5 - 1.5% by weight, 0.8 - 1.3% by weight, 0.1 - 1% by weight. Within the above range, the capacity, lifespan, and electrode adhesion of the lithium secondary battery can be improved.

[0055] In some embodiments, the composition can further include a graphite - based active material. For example, the graphite - based active material can be natural graphite, artificial graphite, etc.

[0056] In some embodiments, for the silicon oxide (SiO x , 0 < x < 2) particles, the ratio of the total weight of the silicon oxide (SiO x , 0 < x < 2) particles and the additive to the content of the graphite - based active material can be 0.03 to 0.45. For example, for the silicon oxide (SiO

[0057] , 0 < x < 2) particles, the ratio of the total weight of the silicon oxide (SiO

[0058] , 0 < x < 2) particles and the additive to the content of the graphite - based active material can be 0.05 to 0.40, 0.10 to 0.35, 0.15 to 0.30, 0.20 to 0.28. Within the above range, the capacity and lifespan can be improved while maintaining the chemical stability of the lithium secondary battery.

[0059] For example, the solvent can be a water - based solvent such as water, hydrochloric acid aqueous solution, or sodium hydroxide aqueous solution.

[0060] For example, the binder can include at least one of organic binders such as polyacrylonitrile, polymethylmethacrylate, or water - based binders such as styrene - butadiene rubber (SBR).

[0061] In some embodiments, the negative electrode composition may further comprise a conductive material and a thickening agent.

[0062] For example, the conductive material may include carbon-based conductive materials such as graphite, carbon black, graphene, carbon nanotubes (CNT), etc. and / or perovskite materials such as tin, tin oxide, titanium oxide, LaSrCoO3, LaSrMnO3, etc.

[0063] For example, the thickening agent may include carboxymethyl cellulose (CMC).

[0064] Hereinafter, a method for preparing the negative electrode composition for the lithium secondary battery will be described.

[0065] In an exemplary embodiment, a metal may be doped into silicon oxide (SiO x , 0 < x < 2) particles to prepare metal-doped silicon oxide (SiO x , 0 < x < 2) particles containing a metal silicate region in the surface portion.

[0066] For example, an additive containing aluminum hydroxide may be directly mixed into the prepared metal-doped silicon oxide (SiO x , 0 < x < 2) particles to form a primary composition.

[0067] Therefore, the additive may be mixed before the metal hydroxide present on the surface of the metal-doped silicon oxide (SiO x , 0 < x < 2) particles reacts with water. Thereafter, the hydroxide ions generated by the reaction of the metal hydroxide with water may be blocked from reacting with the silicon in the metal-doped silicon oxide (SiO x , 0 < x < 2) particles. Therefore, the generation of hydrogen gas caused by the above reaction can be suppressed, and a reduction in the capacity characteristics of the battery can be prevented.

[0068] In some embodiments, a binder may be mixed into the primary composition. For example, a solvent and a binder may be mixed into the primary composition to obtain a negative electrode composition. For example, a solvent, a binder, a conductive material, and a thickening agent may be mixed into the primary composition. The materials of the solvent, the binder, the conductive material, and the thickening agent may be the same as those described above.

[0069] In some embodiments, the method for preparing the negative electrode composition for the lithium secondary battery may not include an acid washing process. Therefore, the generation of hydrogen gas in the negative electrode composition can be suppressed, thereby improving the battery life and capacity, reducing the process cost, achieving an environmentally friendly process, and preventing a reduction in the initial capacity efficiency due to the removal of the doped metal.

[0070] <Lithium secondary battery>

[0071] Figure 1 and Figure 2 are a schematic plan view and a schematic cross-sectional view showing a lithium secondary battery according to an exemplary embodiment, respectively.

[0072] Referring to Figure 1 and Figure 2 , the lithium secondary battery may include an electrode assembly including a positive electrode 100, a negative electrode 130, and a separator 140 disposed between the positive electrode and the negative electrode. The electrode assembly may be accommodated in a case 160 together with an electrolyte and immersed in the electrolyte.

[0073] The positive electrode 100 may include a positive electrode active material layer 110 formed by coating a positive electrode active material on a positive electrode current collector 105.

[0074] The positive electrode current collector 105 may be made of aluminum or an aluminum alloy, but is not limited thereto. The positive electrode current collector 105 may also be made of stainless steel, nickel, aluminum, titanium, or an alloy thereof, a material obtained by surface-treating the surface of aluminum or stainless steel with carbon, nickel, titanium, silver, etc.

[0075] The positive electrode active material may include a compound capable of reversibly inserting and extracting lithium ions.

[0076] In an exemplary embodiment, the positive electrode active material may include a lithium-transition metal oxide. For example, the lithium-transition metal oxide may include nickel (Ni), and may further include at least one of cobalt (Co) or manganese (Mn).

[0077] For example, the lithium-transition metal oxide may be represented by the following Chemical Formula 1.

[0078] [Chemical Formula 1]

[0079] Li x Ni 1-y M y O 2+z

[0080] In Chemical Formula 1, x may be 0.9 ≤ x ≤ 1.1, y may be 0 ≤ y ≤ 0.7, and z may be -0.1 ≤ z ≤ 0.1. M may represent one or more elements selected from Na, Mg, Ca, Y, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Co, Fe, Cu, Ag, Zn, B, Al, Ga, C, Si, Sn, or Zr.

[0081] In some embodiments, in Chemical Formula 1, the molar ratio or concentration (1 - y) of Ni may be 0.8 or more, and in a preferred embodiment, the molar ratio or concentration (1 - y) of Ni may exceed 0.8.

[0082] The positive electrode active material can be mixed and stirred with a binder, a conductive material, and / or a dispersion material, etc. in a solvent to prepare a slurry. After the slurry is coated on the positive electrode current collector 105, calendering and drying can be performed to manufacture the positive electrode 100.

[0083] The solvent can generally use a non-aqueous solvent. For example, the solvent can use N-methyl-2-pyrrolidone (NMP), dimethylformamide, dimethylacetamide, N,N-dimethylaminopropylamine, ethylene oxide, tetrahydrofuran, etc., but is not limited thereto.

[0084] The binder can include, for example, organic binders such as vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethyl methacrylate, etc. or aqueous binders such as styrene-butadiene rubber (SBR), and can be used together with thickeners such as carboxymethyl cellulose (CMC).

[0085] Preferably, a PVDF-based binder can be used as the positive electrode binder. In this case, the amount of the binder used to form the positive electrode active material layer can be reduced, and the amount of the positive electrode active material can be relatively increased, thereby improving the power and capacity of the secondary battery.

[0086] The conductive material can be included to promote electron migration between the active material particles. For example, the conductive material can include carbon-based conductive materials such as graphite, carbon black, graphene, carbon nanotubes (CNT), etc. and / or metal-based conductive materials including perovskite materials such as tin, tin oxide, titanium oxide, LaSrCoO3, LaSrMnO3, etc.

[0087] In some embodiments, the negative electrode 130 can include a negative electrode current collector 125 and a negative electrode active material layer 120, and the negative electrode active material layer 120 is formed by coating the above-mentioned negative electrode composition on at least one surface of the negative electrode current collector 125 and then performing calendering and drying.

[0088] In some embodiments, the negative electrode 130 can include a negative electrode current collector 125 and a negative electrode active material layer 120 located on the negative electrode current collector 125. The negative electrode active material layer 120 can include metal-doped silicon oxide (SiO x , 0 < x < 2) particles and aluminum hydroxide.

[0089] Since the negative electrode active material layer 120 is formed of the above-described negative electrode composition, it can contain the components of the composition. Regarding the description of the metal-doped silicon oxide (SiO x , 0 < x < 2) particles and aluminum hydroxide, it is the same as that described in the description of the negative electrode composition for a lithium secondary battery.

[0090] In some embodiments, the ratio of the total weight of aluminum to the total weight of silicon in the negative electrode 130 can be from 0.002 to 0.06. For example, the ratio of the total weight of aluminum to the total weight of silicon in the negative electrode 130 can be from 0.002 to 0.04, from 0.002 to 0.02, from 0.002 to 0.01. Within the above range, the life and capacity of the lithium secondary battery can be improved.

[0091] For example, the negative electrode current collector 125 can be made of any metal with high conductivity and to which the negative electrode composition can easily adhere, as long as it is not reactive within the voltage range of the battery. For example, the negative electrode current collector 125 can be made of copper or a copper alloy, stainless steel, nickel, copper, titanium, or their alloys, or a substance obtained by surface-treating the surface of copper or stainless steel with carbon, nickel, titanium, or silver.

[0092] The separator 140 can be disposed between the positive electrode 100 and the negative electrode 130. The separator 140 can include a porous polymer membrane made of a polyolefin-based polymer such as ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, ethylene / methacrylate copolymer, etc. The separator 140 can also include a non-woven fabric formed of glass fibers with a high melting point, polyethylene terephthalate fibers, etc.

[0093] In some embodiments, the area (e.g., the contact area with the separator 140) and / or volume of the negative electrode 130 can be larger than the area and / or volume of the positive electrode 100. Therefore, for example, lithium ions generated from the positive electrode 100 can migrate smoothly to the negative electrode 130 without precipitating in the middle. Therefore, it is easier to achieve the effects of improving capacity and power brought by the above-described silicon-based negative electrode active material.

[0094] According to an exemplary embodiment, the battery cell can be defined by the positive electrode 100, the negative electrode 130, and the separator 140, and an electrode assembly 150 in the form of, for example, a jelly roll can be formed by laminating a plurality of battery cells. For example, the electrode assembly 150 can be formed by winding, laminating, folding, etc. of the separator 140.

[0095] The electrode assembly 150 can be accommodated in the housing 160 together with the electrolyte, thereby defining a lithium secondary battery. According to an exemplary embodiment, the electrolyte can use a non-aqueous electrolyte.

[0096] The non-aqueous electrolyte solution may contain a lithium salt as an electrolyte and an organic solvent. The lithium salt may be represented, for example, by Li + X - indicating that, as the anion (X - ) of the lithium salt, examples include F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , PF6 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , CF3SO3 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - and (CF3CF2SO2)2N - and so on.

[0097] Examples of the organic solvent that can be used include propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), methyl propyl carbonate, dipropyl carbonate, dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, vinylene carbonate, sulfolane, γ-butyrolactone, propylene sulfite, and tetrahydrofuran. These can be used alone or in combination of two or more.

[0098] Such as Figure 1As shown, the tabs (the positive tab and the negative tab) can respectively protrude from the positive current collector 105 and the negative current collector 125 belonging to each battery cell and extend to one side of the outer casing 160. The tabs can be fused to the above-mentioned one side of the outer casing 170 and form electrode leads (the positive lead 107 and the negative lead 127) extending or exposed to the outside of the outer casing 170.

[0099] The lithium secondary battery can be made into, for example, a cylindrical shape using a can, a prismatic shape, a pouch type, or a coin type.

[0100] Hereinafter, in order to help understand the present invention, preferred embodiments are proposed. However, these embodiments are only used to illustrate the present invention and do not limit the claims. Various changes and modifications can be made to the embodiments within the scope and technical idea of the present invention, which are obvious to those skilled in the art, and such variations and modifications are naturally within the scope of the claims.

[0101] Example 1

[0102] Manufacture of the negative electrode

[0103] Lithium (Li) is doped into the synthesized silicon oxide (SiO x , 0 < x < 2) particles to prepare metal-doped silicon oxide (SiO x , 0 < x < 2) particles.

[0104] Aluminum hydroxide (Al(OH)3) is mixed into the metal-doped silicon oxide (SiO x , 0 < x < 2) particles such that the content of aluminum hydroxide (Al(OH)3) is 0.5% by weight relative to the total weight of the metal-doped silicon oxide (SiO x , 0 < x < 2) particles.

[0105] 20% by weight of a mixture composed of the metal-doped silicon oxide (SiO x , 0 < x < 2) particles and aluminum hydroxide (Al(OH)3), 75.5% by weight of artificial graphite, 1% by weight of flake type conductive material carbon nanotubes (CNT) as a conductive material, 2% by weight of styrene-butadiene rubber (SBR) as a binder, and 1.5% by weight of carboxymethyl cellulose (CMC) as a thickener are mixed to obtain a negative electrode composition.

[0106] The negative electrode composition is coated on a copper substrate and dried and calendered to produce a negative electrode.

[0107] Manufacture of a lithium half-cell

[0108] Manufacture a lithium secondary battery, which includes a negative electrode manufactured by the above method and uses lithium metal as the counter electrode (positive electrode).

[0109] A separator (polyethylene, thickness 20 μm) is disposed between the obtained negative electrode and the lithium metal (thickness 2 mm), thereby forming a lithium coin-type half cell.

[0110] The combination of lithium metal / separator / negative electrode is placed in a coin cell plate and an electrolyte is injected, and then the cap is covered and clamped. The electrolyte used is an electrolyte in which 1 M LiPF6 is dissolved in a mixed solvent of EC / FEC / EMC / DEC (20 / 10 / 20 / 50; volume ratio). After clamping, it is impregnated for more than 12 hours, and then charged and discharged in 3 cycles at 0.1C (charging condition CC-CV 0.1C 0.01V 0.01C cut-off (CUT-OFF), discharging condition CC 0.1C 1.5V cut-off).

[0111] Example 2

[0112] Manufacture a negative electrode and a lithium secondary battery including the negative electrode by the same method as in Example 1, except that aluminum hydroxide (Al(OH)3) is mixed into the metal-doped silicon oxide (SiO x , 0 < x < 2) particles such that the content of aluminum hydroxide (Al(OH)3) is 1.0 wt% relative to the total weight of the metal-doped silicon oxide (SiO x , 0 < x < 2) particles.

[0113] Example 3

[0114] Manufacture a negative electrode and a lithium secondary battery including the negative electrode by the same method as in Example 1, except that aluminum hydroxide (Al(OH)3) is mixed into the metal-doped silicon oxide (SiO x , 0 < x < 2) particles such that the content of aluminum hydroxide (Al(OH)3) is 3.0 wt% relative to the total weight of the metal-doped silicon oxide (SiO x , 0 < x < 2) particles.

[0115] Example 4

[0116] Manufacture a negative electrode and a lithium secondary battery including the negative electrode by the same method as in Example 1, except that aluminum hydroxide (Al(OH)3) is mixed into the metal-doped silicon oxide (SiO xin the particles of 0 < x < 2), such that the content of aluminum hydroxide (Al(OH)3) is 5.0% by weight relative to the total weight of the metal-doped silicon oxide (SiO x in the particles of 0 < x < 2).

[0117] Comparative Example 1

[0118] A negative electrode and a lithium secondary battery including the negative electrode were manufactured by the same method as in Example 1, except that aluminum hydroxide (Al(OH)3) was not used, and 20% by weight of metal-doped silicon oxide (SiO x in the particles of 0 < x < 2) was used.

[0119] Comparative Example 2

[0120] A negative electrode and a lithium secondary battery including the negative electrode were manufactured by the same method as in Example 1, except that aluminum hydroxide (Al(OH)3) was mixed into the metal-doped silicon oxide (SiO x in the particles of 0 < x < 2), such that the content of aluminum hydroxide (Al(OH)3) was 0.3% by weight relative to the total weight of the metal-doped silicon oxide (SiO x in the particles of 0 < x < 2).

[0121] Comparative Example 3

[0122] A negative electrode and a lithium secondary battery including the negative electrode were manufactured by the same method as in Example 1, except that aluminum hydroxide (Al(OH)3) was mixed into the metal-doped silicon oxide (SiO x in the particles of 0 < x < 2), such that the content of aluminum hydroxide (Al(OH)3) was 10.0% by weight relative to the total weight of the metal-doped silicon oxide (SiO x in the particles of 0 < x < 2).

[0123] Comparative Example 4

[0124] A negative electrode and a lithium secondary battery including the negative electrode were manufactured by the same method as in Example 1, except that aluminum oxide (Al2O3) was used instead of aluminum hydroxide (Al(OH)3), and aluminum oxide (Al2O3) was mixed into the metal-doped silicon oxide (SiO x in the particles of 0 < x < 2), such that the content of aluminum oxide (Al2O3) was 0.5% by weight relative to the total weight of the metal-doped silicon oxide (SiO x in the particles of 0 < x < 2).

[0125] Comparative Example 5

[0126] The negative electrode and the lithium secondary battery including the negative electrode are manufactured by the same method as in Example 1, except that aluminum phosphate (AlPO4) is used instead of aluminum hydroxide (Al(OH)3), and aluminum phosphate (AlPO4) is mixed into the metal-doped silicon oxide (SiO x , 0 < x < 2) particles such that the content of aluminum phosphate (AlPO4) is 0.5% by weight based on the total weight of the metal-doped silicon oxide (SiO x , 0 < x < 2) particles.

[0127] Comparative Example 6

[0128] The negative electrode and the lithium secondary battery including the negative electrode are manufactured by the same method as in Example 1, except that aluminum silicate (Al2O(SiO4)) is used instead of aluminum hydroxide (Al(OH)3), and aluminum silicate (Al2O(SiO4)) is mixed into the metal-doped silicon oxide (SiO x , 0 < x < 2) particles such that the content of aluminum silicate (Al2O(SiO4)) is 0.5% by weight based on the total weight of the metal-doped silicon oxide (SiO x , 0 < x < 2) particles.

[0129] Experimental Example

[0130] (1) Evaluation of the silicon content and aluminum content in the negative electrode composition

[0131] The contents of silicon element and aluminum element in the negative electrode compositions prepared according to the Examples and Comparative Examples are measured by analysis with an Inductively Coupled Plasma Spectrometer (ICP).

[0132] (2) Measurement of the initial charge capacity and initial discharge capacity and calculation of the initial capacity efficiency

[0133] The lithium secondary batteries manufactured according to the above Examples and Comparative Examples are charged in a chamber at 25 °C (CC-CV 0.1C 0.01V 0.01C cut-off), and then the battery capacity (initial charge capacity) is measured. Then, after discharging (CC 0.1C 1.5V cut-off), the battery capacity (initial discharge capacity) is measured.

[0134] The initial capacity efficiency is calculated by dividing the measured initial discharge capacity by the measured initial charge capacity and multiplying by 100.

[0135] (3) Evaluation of the capacity retention rate

[0136] The lithium half-cells fabricated according to the above-described examples and comparative examples were subjected to constant current charging at a current of 0.1 C at 25 °C until the voltage reached 0.01 V (vs. Li). Subsequently, constant voltage charging was performed while maintaining 0.01 V, and the charging was cut off at a current of 0.01 C, and then discharged at a constant current of 0.1 C rate (C rate) until the voltage reached 1.5 V (vs. Li). The above charging and discharging were defined as one cycle.

[0137] Charging and discharging for one more cycle were further performed by the same method as the above method. Thereafter, except for changing the applied current to 0.5 C, charging and discharging for 48 more cycles were further performed by the same method as the above method, and a rest period of 10 minutes was set between each cycle.

[0138] The capacity retention rate was calculated by dividing the discharge capacity after a total of 50 cycles by the discharge capacity after the first cycle and then multiplying by 100.

[0139] (4) Evaluation of adhesive strength

[0140] For the negative electrodes fabricated according to the above-described examples and comparative examples, the adhesive strength of the negative electrode active material was measured. Specifically, the force when peeling at an angle of 90° after pasting the negative electrode onto the tape was measured using IMADA Z Link 3.1.

[0141] (5) Evaluation of gas generation amount

[0142] A certain amount of the negative electrode compositions prepared according to the examples and comparative examples was injected into an airtight syringe, and left at room temperature for 1 day with the injection port sealed. The volume of the negative electrode composition before and after leaving was measured, and the gas generation rate of the slurry was calculated according to the following calculation formula 1.

[0143] [Calculation formula 1]

[0144] Gas generation rate of slurry = (Volume of slurry after 1 day - Initial volume of slurry) / (Initial volume of slurry)

[0145] The evaluation results are shown in Tables 1 and 2.

[0146] [Table 1]

[0147]

[0148] [Table 2]

[0149]

[0150] Referring to Table 2, in the secondary battery manufactured using the negative electrode composition of the example, compared with the comparative example, the generation of gas is suppressed, while having good adhesion of the negative electrode active material, and the capacity and life of the secondary battery are improved.

[0151] In the case of Comparative Example 1 and Comparative Example 2 without aluminum hydroxide or with a small amount of aluminum hydroxide, hydrogen gas is generated, resulting in poor capacity and electrode adhesion of the secondary battery.

[0152] In the case of Comparative Example 3 containing an excessive amount of aluminum hydroxide, the capacity of the secondary battery is low, and the precipitation generated by the reaction of metal hydroxides such as LiOH with aluminum hydroxide increases, resulting in a decrease in electrode adhesion.

[0153] In the case of Comparative Examples 4 to 6 using other aluminum compounds instead of aluminum hydroxide, compared with aluminum hydroxide, the reactivity of aluminum oxide, aluminum phosphate, and aluminum silicate with metal hydroxides such as LiOH is relatively low, so the effect of suppressing hydrogen gas is low.

Claims

1. A negative electrode composition for a lithium secondary battery, comprising: Metal-doped silicon oxide SiO x particles, wherein the x of the SiO x is 0 < x < 2; and An additive, wherein the additive comprises aluminum hydroxide.

2. The negative electrode composition for a lithium secondary battery according to claim 1, wherein, Doped in the silicon oxide SiO x The metal in the particles includes at least one of lithium, magnesium, and calcium, and the x of the SiO x is 0 < x < 2.

3. The negative electrode composition for a lithium secondary battery according to claim 1, wherein, The ratio of the total weight of aluminum to the total weight of silicon is from 0.002 to 0.

06.

4. The negative electrode composition for a lithium secondary battery according to claim 1, wherein, Relative to the total weight of the silicon oxide SiO x , the content of the additive is 0.5 - 5.0 wt%, and for the SiO x , x satisfies 0 < x < 2.

5. The negative electrode composition for a lithium secondary battery according to claim 1, wherein, In the total weight of the negative electrode composition for the lithium secondary battery, the content of the silicon oxide SiO x particles is 3 to 40% by weight, and x of the SiO x is 0 < x < 2.

6. The negative electrode composition for a lithium secondary battery according to claim 1, wherein, The negative electrode composition for a lithium secondary battery further comprises a graphite-based active material.

7. The negative electrode composition for a lithium secondary battery according to claim 6, wherein, The silicon oxide SiO x The ratio of the total weight of the particles and the additive to the content of the graphite-based active material is from 0.03 to 0.45, and for the SiO x , x satisfies 0 < x < 2.

8. The negative electrode composition for a lithium secondary battery according to claim 1, wherein, The negative electrode composition for a lithium secondary battery further comprises a binder.

9. The negative electrode composition for a lithium secondary battery according to claim 8, wherein In the total weight of the negative electrode composition for a lithium secondary battery, the content of the additive is 0.015 - 2% by weight.

10. The negative electrode composition for a lithium secondary battery according to claim 8, wherein The binder comprises at least one of an acrylic-based binder and styrene-butadiene rubber (SBR).

11. The negative electrode composition for a lithium secondary battery according to claim 1, wherein The negative electrode composition for a lithium secondary battery further comprises a conductive material and a thickener.

12. A negative electrode for a lithium secondary battery, comprising: A current collector; And A negative electrode active material layer disposed on the current collector, Wherein, the negative electrode active material layer contains metal-doped silicon oxide SiO x particles and aluminum hydroxide, and x of the SiO x is 0 < x < 2.

13. The negative electrode for a lithium secondary battery according to claim 12, wherein, The ratio of the total weight of aluminum to the total weight of silicon is from 0.002 to 0.

06.

14. A lithium secondary battery, comprising: A positive electrode; And The negative electrode for a lithium secondary battery according to claim 12, wherein the negative electrode for a lithium secondary battery is disposed opposite to the positive electrode.

15. A method for preparing a negative electrode composition for a lithium secondary battery, comprising the following steps: Prepare metal-doped silicon oxide SiO x particles, where x in SiO x satisfies 0 < x < 2; Mix an additive containing aluminum hydroxide into the metal-doped silicon oxide SiO x particles to form a primary composition, where x of the SiO x is 0 < x < 2; And Mixing a binder into the primary composition.

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