Negative electrode active material for secondary battery, negative electrode for secondary battery, and method for producing negative electrode for secondary battery

Abstract

A negative electrode active material for a secondary battery according to an embodiment of the present invention comprises: a negative electrode active material core; and a coating layer, which contains an aluminum-containing compound, and which is formed on the negative electrode active material core.

Description

Technical Field

[0001] Embodiments of the present invention relate to a negative electrode active material for a secondary battery, a negative electrode for a secondary battery, and a method for manufacturing the negative electrode for a secondary battery. Background Art

[0002] With the development of electronics, communications and aerospace industries, the demand for lithium secondary batteries as energy power sources is increasing dramatically. In particular, with the emphasis on the importance of global environmental protection policies, the electric vehicle market is developing rapidly, and research and development on lithium secondary batteries are being actively carried out at home and abroad.

[0003] A lithium secondary battery includes a positive electrode (cathode), a negative electrode (anode), and a separator between the positive electrode and the negative electrode. The positive electrode and the negative electrode respectively have active materials that can insert and extract lithium ions.

[0004] The negative electrode of a lithium secondary battery contains a binder, and as the binder migrates during the drying process of the negative electrode, a concentration gradient of the binder can be formed in the negative electrode. As a result, problems such as increased resistance of the negative electrode or reduced adhesion of the negative electrode may occur, so a solution that can control the distribution of the binder is needed. Summary of the invention

[0005] 1. Technical issues to be resolved

[0006] Embodiments of the present invention may provide a negative electrode active material for a secondary battery, a negative electrode for a secondary battery, and a method for manufacturing a negative electrode for a secondary battery, which can control the distribution of a binder in the negative electrode.

[0007] A secondary battery including the negative electrode for a secondary battery according to one embodiment of the present invention can be widely used in electric vehicles, battery charging stations, other green technology fields such as solar power generation and wind power generation using batteries.

[0008] (II) Technical solution

[0009] A negative electrode active material for a secondary battery according to an embodiment of the present invention includes: a negative electrode active material core; and a coating layer including an aluminum-containing compound and formed on the negative electrode active material core.

[0010] In one embodiment, the aluminum-containing compound may include one or more selected from Al(NO3)3, Al(OH)3, AlPO4, AlF3, Al2(SO4)3, AlCl3, and AlI3.

[0011] In one embodiment, the negative active material core may include a carbon-based material.

[0012] In one embodiment, the carbon-based substance may include one or more selected from artificial graphite, natural graphite, hard carbon, soft carbon, carbon black (acetylene black, Ketjen black, Super P) and graphene.

[0013] In one embodiment, the negative active material core may include a silicon-based material.

[0014] In one embodiment, the silicon-based material may include a material selected from SiO x (0≤x<2), one or more of Si / C composite and Si alloy.

[0015] In one embodiment, the negative active material may include 0.05-5.0 wt % of the aluminum-containing compound.

[0016] According to an embodiment of the present invention, a negative electrode for a secondary battery includes: a negative electrode collector; and a negative electrode active material layer, the negative electrode active material layer comprising a negative electrode active material and a binder, and the negative electrode active material layer is formed on at least one side of the negative electrode collector, wherein the negative electrode active material comprises: a negative electrode active material core; and a coating, the coating is formed on the negative electrode active material core and comprises an aluminum-containing compound.

[0017] In one embodiment, the binding force between the aluminum-containing compound and the binder may be greater than the binding force between the solvent that can dissolve the negative electrode active material and the binder and the binder, and the solvent may include one or more substances selected from water, methanol, ethanol, ethylene glycol, diethylene glycol and glycerol.

[0018] In one embodiment, in the negative active material layer, an average slope of the content of the binder according to the distance from the negative current collector may be 0.005 wt % / μm or less.

[0019] In one embodiment, the binder may include one or more selected from lithium polyacrylate (LiPAA), styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC), polyacrylic acid (PAA), polyethylene oxide (PEO), polyvinylidene fluoride (PVDF) and polyvinyl alcohol (PVA).

[0020] According to an embodiment of the present invention, a method for manufacturing a negative electrode for a secondary battery includes the following steps: preparing a negative electrode active material having a coating material coated on a negative electrode active material core; and coating a negative electrode active material composition comprising the negative electrode active material, a binder and a solvent on at least one side of a negative electrode current collector, wherein the binding force between the coating material and the binder is greater than the binding force between the binder and the solvent.

[0021] In one embodiment, the step of preparing the negative active material may include the step of mixing the negative active material core and a coating material in the solvent to prepare a composition for preparing a negative active material.

[0022] In one embodiment, the composition for preparing a negative electrode active material may contain 30-90 wt % of solids.

[0023] In one embodiment, the coating material may comprise an aluminum-containing compound.

[0024] In one embodiment, the aluminum-containing compound may include one or more selected from Al(NO3)3, Al(OH)3, AlPO4, AlF3, Al2(SO4)3, AlCl3, and AlI3.

[0025] In one embodiment, the solvent may include one or more substances selected from the group consisting of water, methanol, ethanol, ethylene glycol, diethylene glycol, and glycerol.

[0026] (III) Beneficial effects

[0027] According to the present invention, there can be provided a negative electrode active material for a secondary battery, a negative electrode for a secondary battery, and a method for producing a negative electrode for a secondary battery, which can control the distribution of a binder in the negative electrode. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a diagram for explaining a negative electrode active material for a secondary battery according to an embodiment of the present invention.

[0029] Figure 2 It is a diagram for explaining a negative electrode for a secondary battery according to an embodiment of the present invention.

[0030] Figure 3 : is a flowchart for explaining a method for manufacturing a negative electrode for a secondary battery according to an embodiment of the present invention.

[0031] Figure 4 are images and graphs showing the distribution of a binder of a negative electrode for a secondary battery according to one embodiment of the present invention.

[0032] Figure 5It is a diagram for explaining a negative electrode for a secondary battery according to a comparative example of the present invention.

[0033] Figure 6 are an image and a diagram showing the distribution of a binder in a negative electrode for a secondary battery according to a comparative example of the present invention.

[0034] Figure 7 1 is a charge and discharge diagram of a secondary battery cell including a negative electrode for a secondary battery according to an embodiment of the present invention and a comparative example.

[0035] Description of reference numerals:

[0036] 10: Negative electrode active material

[0037] 11: Negative electrode active material core

[0038] 12: Coating

[0039] 20: Adhesive

[0040] 100: Negative electrode

[0041] 110: Negative electrode active material layer

[0042] 120: Negative electrode current collector DETAILED DESCRIPTION

[0043] The present invention will be described in detail below, but this is merely an exemplary embodiment, and the present invention is not limited to the specific embodiments described exemplarily.

[0044] Negative electrode active material for secondary batteries

[0045] One aspect of the present invention provides a negative electrode active material for a secondary battery, the negative electrode active material for a secondary battery comprising: a negative electrode active material core; and a coating layer comprising an aluminum-containing compound and formed on the negative electrode active material core.

[0046] Figure 1 1 is a diagram for explaining a negative electrode active material for a secondary battery according to an embodiment of the present invention. Figure 1 , a negative electrode active material for a secondary battery according to an embodiment of the present invention is described.

[0047] Reference Figure 1 The negative electrode active material 10 for a secondary battery includes a negative electrode active material core 11 and a coating layer 12 .

[0048] The negative electrode active material core 11 may be a material that can intercalate and deintercalate lithium ions.

[0049] In one embodiment, the negative active material core 11 may include a carbon-based material.

[0050] In one embodiment, the negative electrode active material core 11 may include a silicon-based material.

[0051] In one embodiment, the negative electrode active material core 11 may include a carbon-based material, or may include a silicon-based material, or may include both a carbon-based material and a silicon-based material.

[0052] In one embodiment, the carbon-based substance may include one or more selected from artificial graphite, natural graphite, hard carbon, soft carbon, carbon black (acetylene black, Ketjen black, Super P) and graphene.

[0053] In one embodiment, the silicon-based material may include a material selected from SiO x (0≤x<2), one or more of Si / C composite and Si alloy.

[0054] The coating layer 12 may be formed on the negative active material core 11. In the embodiment, by forming the coating layer 12 on the negative active material core 11, the negative active material 10 may form a core-shell structure.

[0055] The coating 12 may include a coating material. The coating material may be selected in consideration of the bonding strength with the binder used in manufacturing the negative electrode. In an embodiment, the coating material may be selected so that the bonding strength between the coating material and the binder is greater than the bonding strength between the binder and the solvent used in manufacturing the negative electrode. In an embodiment, the coating material may include an aluminum-containing compound, and in an embodiment, the aluminum-containing compound may include one or more selected from Al(NO3)3, Al(OH)3, AlPO4, AlF3, Al2(SO4)3, AlCl3, and AlI3.

[0056] In an embodiment, the negative active material 10 may include 0.05-5.0 wt % of the aluminum-containing compound.

[0057] When the content of the coating material is included in the above range, the coating material is sufficiently coated on the negative electrode active material core 11 , so that migration of the binder can be suppressed, and an excessive increase in resistance of the negative electrode active material layer can be prevented.

[0058] Negative electrode for secondary battery

[0059] Another aspect of the present invention provides a negative electrode for a secondary battery, the negative electrode for a secondary battery comprising: a negative electrode collector; and a negative electrode active material layer, the negative electrode active material layer comprising a negative electrode active material and a binder, and the negative electrode active material layer is formed on at least one side of the negative electrode collector, wherein the negative electrode active material comprises: a negative electrode active material core; and a coating, the coating is formed on the negative electrode active material core and comprises an aluminum-containing compound.

[0060] Figure 2 1 is a diagram for explaining a negative electrode for a secondary battery according to an embodiment of the present invention. Figure 2 , a negative electrode for a secondary battery according to an embodiment of the present invention is described.

[0061] Reference Figure 2 The negative electrode 100 for a secondary battery includes a negative electrode current collector 120 and a negative electrode active material layer 110 .

[0062] The negative electrode current collector 120 is not particularly limited as long as it does not cause chemical changes in the secondary battery and has conductivity. For example, the negative electrode current collector 120 can use copper, stainless steel, aluminum, nickel, titanium, calcined carbon, a material obtained by surface-treating the surface of copper or stainless steel with carbon, nickel, titanium, silver, etc., an aluminum-cadmium alloy, etc. In addition, the binding force with the negative electrode active material can be enhanced by forming fine concavo-convex on the surface, and can be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, a non-woven fabric, etc.

[0063] The negative electrode active material layer 110 may be formed on at least one side of the negative electrode collector 120. That is, the negative electrode active material layer 110 may be formed on one side of the negative electrode collector 120, or may be formed on both sides of the negative electrode collector 120.

[0064] The negative electrode active material layer 110 may include a negative electrode active material 10 and a binder 20 .

[0065] The negative electrode active material 10 may use the above-mentioned negative electrode active material 10. That is, the negative electrode active material 10 may include: a negative electrode active material core 11; and a coating layer 12, the coating layer 12 being formed on the negative electrode active material core 11 and including a coating material. In an embodiment, the coating material may include an aluminum-containing compound, and the aluminum-containing compound may include, for example, one or more selected from Al(NO3)3, Al(OH)3, AlPO4, AlF3, Al2(SO4)3, AlCl3, and AlI3.

[0066] The binder 20 may be a material that improves the bonding force between the negative electrode current collector 120 and the negative electrode active material 10. In the embodiment, the binder 20 may be a water-based binder. In the embodiment, the binder may include one or more selected from lithium polyacrylate (LiPAA), styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC), polyacrylic acid (PAA), polyethylene oxide (PEO), polyvinylidene fluoride (PVDF) and polyvinyl alcohol (PVA).

[0067] In the embodiment, the bonding force between the aluminum-containing compound contained in the coating 12 and the binder 20 may be greater than the bonding force between the binder 20 and the solvent used when manufacturing the negative electrode. The solvent is a substance that can dissolve the negative electrode active material 10 and the binder 20. In the embodiment, the solvent may be a water-based solvent. The water-based solvent may include, for example, one or more substances selected from water, methanol, ethanol, ethylene glycol, diethylene glycol, and glycerol.

[0068] In one embodiment, the content of the binder in the negative electrode active material layer 110 may be 10.0 wt % or less relative to the total solid content of the negative electrode active material layer 110, and in another embodiment, the content of the binder in the negative electrode active material layer 110 may be 5.0 wt % or less. In addition, the content of the binder in the negative electrode active material layer 110 may be 0.05 wt % or more relative to the total solid content of the negative electrode active material layer 110, and in another embodiment, the content of the binder in the negative electrode active material layer 110 may be 0.1 wt % or more. When the content of the binder satisfies the above range, the secondary battery cell can maintain sufficient charge and discharge performance, while maintaining excellent adhesion between the negative electrode active material layer 110 and the negative electrode current collector 120.

[0069] According to the embodiment, in the negative electrode active material layer 110, the absolute value of the average slope of the content of the binder 20 according to the distance from the negative electrode collector 120 may be 0.005 wt % / μm or less. That is, in one embodiment, the average slope of the content of the binder 20 according to the distance from the negative electrode collector 120 may be -0.005 wt % / μm to 0.005 wt % / μm, and in another embodiment, the average slope of the content of the binder 20 according to the distance from the negative electrode collector 120 may be 0 wt % / μm to 0.005 wt % / μm. The average slope value of the content of the binder 20 may be a value for the total thickness of the negative electrode active material layer 110. That is, the average slope value of the content of the binder 20 according to the distance from the negative electrode collector 120 may be an average slope value of the content of the binder 20 from the surface of the negative electrode collector 120 to the surface of the negative electrode active material layer 110.

[0070] By combining the coating material with the binder 20, the migration of the binder 20 in the negative electrode active material layer 110 to the surface side of the negative electrode 100 due to the evaporation of the solvent can be suppressed. As a result, sufficient binder 20 exists at the interface between the negative electrode active material layer 110 and the negative electrode current collector 120, so the binding force between the negative electrode active material layer 110 and the negative electrode current collector 120 can be improved.

[0071] In addition, in order to improve the bonding force between the negative electrode active material layer 110 and the negative electrode current collector 120, there may be no need to separately provide an adhesive layer disposed between the negative electrode active material layer 110 and the negative electrode current collector 120. The adhesive layer may be a region where the content of the adhesive 20 is relatively higher than that of the negative electrode active material layer 110, and the adhesive layer may function as a resistor between the negative electrode active material layer 110 and the negative electrode current collector 120, thereby increasing the resistance within the secondary battery cell.

[0072] Furthermore, even if the amount of binder 20 included in the negative electrode active material layer 110 is relatively small compared with the conventional method, sufficient binding force between the negative electrode active material layer 110 and the negative electrode collector 120 can be ensured. Therefore, the energy density in the secondary battery cell can be increased.

[0073] Furthermore, since the binder 20 in the negative electrode active material layer 110 is suppressed from migrating to the surface of the negative electrode 100 , there is no excessive binder 20 on the surface of the negative electrode 100 , thereby improving the problem of excessive increase in resistance of the negative electrode 100 .

[0074] In an embodiment, the negative electrode active material layer 110 may further include a conductive material that can impart conductivity to the negative electrode 100. The conductive material may include, for example, one or more selected from metal-based conductive materials, carbon-based conductive materials, and conductive polymers. The metal-based conductive material may be, for example, a metal powder or metal fiber such as copper, nickel, aluminum, silver, etc.; a conductive whisker such as zinc oxide, potassium titanate, etc.; or a conductive metal oxide such as titanium oxide. The carbon-based conductive material may be, for example, graphite, carbon black, graphene, or carbon nanotubes. The conductive polymer may be, for example, a polyphenyl derivative, etc.

[0075] In the embodiment, in order to ensure the advantages in the manufacturing process, the negative electrode active material layer 110 may optionally further include a thickener. The thickener can improve the problem of cracks on the negative electrode surface by enhancing the cohesive force of the binder 20. The thickener may include, for example, one or more selected from carboxymethyl cellulose, methyl cellulose, hydroxypropyl cellulose, methyl hydroxypropyl cellulose, ethyl hydroxyethyl cellulose, methyl ethyl hydroxyethyl cellulose and cellulose gum.

[0076] Method for manufacturing negative electrode for secondary battery

[0077] Another aspect of the present invention provides a method for manufacturing a negative electrode for a secondary battery, the manufacturing method comprising the following steps: preparing a negative electrode active material having a coating material coated on a negative electrode active material core; and coating a negative electrode active material composition comprising the negative electrode active material, a binder and a solvent on at least one side of a negative electrode current collector, wherein the binding force between the coating material and the binder is greater than the binding force between the binder and the solvent.

[0078] Figure 3 Flow chart for explaining a method for manufacturing a negative electrode for a secondary battery according to an embodiment of the present invention. Figure 3 , a method for manufacturing a negative electrode for a secondary battery according to an embodiment of the present invention is described.

[0079] Reference Figure 3 In step S100 , a negative electrode active material having a coating material coated on a negative electrode active material core may be prepared.

[0080] In an embodiment, step S100 may include a step of mixing the negative electrode active material core and the coating material in a first solvent to prepare a composition for preparing the negative electrode active material. In an embodiment, the first solvent may be a substance that can dissolve the negative electrode active material core and the coating material, for example, the first solvent may include one or more substances selected from water, methanol, ethanol, ethylene glycol, diethylene glycol, and glycerol.

[0081] The composition for preparing the negative electrode active material may contain 30-98 wt % of solids, more specifically, 50-95 wt % of solids. The solids may include a negative electrode active material core and a coating material.

[0082] When the solid content is less than 30 wt %, the content of the negative electrode active material is too small, so the negative electrode manufactured thereby may not function properly. When the solid content exceeds 98 wt %, it may be difficult to evenly coat the negative electrode active material.

[0083] In addition, step S100 may further include a step of drying the composition for preparing the negative electrode active material. By drying the negative electrode active material composition, a negative electrode active material having a coating material coated on the negative electrode active material core may be formed. This negative electrode active material may be Figure 1 and Figure 2 The negative electrode active material is the same as described in .

[0084] Next, in step S200 , a negative electrode active material composition including a negative electrode active material, a binder, and a second solvent may be coated on at least one side of the negative electrode current collector.

[0085] The negative electrode active material may be the negative electrode active material prepared in step S100 .

[0086] In an embodiment, the binder may be a material that improves the adhesion between the negative electrode current collector and the negative electrode active material, for example, the binder may include one or more selected from lithium polyacrylate (LiPAA), styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC), polyacrylic acid (PAA), polyethylene oxide (PEO), polyvinylidene fluoride (PVDF) and polyvinyl alcohol (PVA).

[0087] In an embodiment, the second solvent may be a substance that can dissolve the negative electrode active material and the binder. For example, the second solvent may include one or more substances selected from water, methanol, ethanol, ethylene glycol, diethylene glycol, and glycerol.

[0088] In embodiments, the bonding force between the coating material and the binder may be greater than the bonding force between the binder and the second solvent.

[0089] In one embodiment, the coating material may be an aluminum-containing compound, which may include, for example, one or more selected from Al(NO3)3, Al(OH)3, AlPO4, AlF3, Al2(SO4)3, AlCl3, and AlI3.

[0090] After step S200 , the method may further include drying the negative electrode active material composition coated on at least one side of the negative electrode current collector.

[0091] The second solvent contained in the negative electrode active material composition can be evaporated by drying the negative electrode active material composition. However, even if the second solvent evaporates, migration of the binder can be suppressed.

[0092] Therefore, before the step of coating the negative electrode active material composition, the step of coating the binder composition on the negative electrode current collector, which is conventionally performed, may not be required. The binder composition is a composition having a relatively higher content of the binder than the negative electrode active material composition, and in order to improve the bonding force between the negative electrode current collector and the negative electrode active material, it may be coated on the negative electrode current collector before coating the negative electrode active material composition.

[0093] Furthermore, even if the amount of the binder included in the negative electrode active material composition is relatively smaller than that in the past, sufficient binding force between the negative electrode active material and the negative electrode current collector can be ensured.

[0094] Secondary battery

[0095] In addition, another aspect of the present invention may provide a secondary battery including the above-mentioned negative electrode for a secondary battery.

[0096] As described above, the negative electrode for a secondary battery may include a negative electrode current collector and a negative electrode active material layer. The negative electrode active material layer may include a negative electrode active material and a binder, and the negative electrode active material layer may be formed on at least one side of the negative electrode current collector. The negative electrode active material may include a negative electrode active material core and a coating layer, the coating layer being formed on the negative electrode active material core and including an aluminum-containing compound.

[0097] In addition to the negative electrode according to the present invention, the secondary battery also includes a positive electrode and a separator. The positive electrode may include a positive electrode current collector and an active material layer disposed on the positive electrode current collector. The active material layer may include an active material. For example, the positive electrode active material layer may include a positive electrode active material, and the positive electrode active material may be a material that can embed and de-embed lithium ions.

[0098] The positive electrode active material may be a lithium metal oxide. For example, the positive electrode active material may be one of a lithium manganese-based oxide, a lithium nickel-based oxide, a lithium cobalt-based oxide, a lithium nickel manganese-based oxide, a lithium nickel cobalt aluminum-based oxide, a lithium iron phosphate-based compound, a lithium manganese phosphate-based compound, a lithium cobalt phosphate-based compound, and a lithium vanadium phosphate-based compound, and is not necessarily limited to the specific examples.

[0099] The separator may be between the negative electrode and the positive electrode. The separator is configured to prevent a short circuit between the negative electrode and the positive electrode and to generate a flow of ions. The separator may include a porous polymer film or a porous nonwoven fabric. Among them, the porous polymer film may be composed of a single layer or multiple layers of polyolefin-based polymers such as ethylene polymers, propylene polymers, ethylene / butene copolymers, ethylene / hexene copolymers, and ethylene / methacrylate copolymers. The porous nonwoven fabric may include high melting point glass fibers, polyethylene terephthalate fibers. However, it is not limited thereto, and according to an embodiment, the separator may be a high heat-resistant separator (ceramic coated separator, CCS) comprising ceramic.

[0100] The negative electrode, the positive electrode and the separator can be made into an electrode assembly by winding, lamination, folding or zigzag stacking. In addition, the electrode assembly can be provided together with an electrolyte to make a secondary battery according to the present invention. The secondary battery can be any one of a cylindrical, prismatic, pouch and coin-shaped using a can, but is not limited thereto.

[0101] The electrolyte may be a non-aqueous electrolyte. The electrolyte may include a lithium salt and an organic solvent. The organic solvent may include at least one of propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), methyl propyl carbonate (MPC), dipropyl carbonate (DPC), vinylene carbonate (VC), dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, sulfolane, gamma-butyrolactone, propylene sulfide or tetrahydrofuran.

[0102] Example

[0103] The embodiments of the present invention are further described below with reference to specific experimental examples. The embodiments and comparative examples included in the experimental examples are only used to illustrate the present invention and are not used to limit the claims. Various modifications and variations can be made to the embodiments within the scope of the present invention and the technical concept, which is obvious to those skilled in the art, and it is natural that such modifications and variations belong to the scope of the claims.

[0104] <Preparation Example 1>-Preparation of negative electrode active material

[0105] A negative electrode active material core prepared by mixing artificial graphite and natural graphite in a weight ratio of 7:3 is added to an aqueous solution in which aluminum nitrate (Al(NO3)3) is dissolved. The amount of the negative electrode active material core is adjusted so that the solid content contained in the aqueous solution to which the negative electrode active material core is added is 50-95% by weight.

[0106] The aqueous solution added to the negative electrode active material core was mixed for a certain period of time using a mixer and then vacuum dried to prepare a negative electrode active material having a coating layer containing aluminum nitrate formed on the negative electrode active material core.

[0107] <Example 1>-Manufacturing of negative electrode

[0108] The negative electrode active material of Preparation Example 1, multi-walled carbon nanotubes, carboxymethyl cellulose, and styrene-butadiene rubber were mixed in water at a ratio of 95.8:0.4:1.2:2.6 (based on weight) to prepare a negative electrode active material composition.

[0109] The prepared negative electrode active material composition was coated on a copper thin film as a negative electrode current collector, and then dried under vacuum at 130° C. for 1 hour, thereby manufacturing a negative electrode having a negative electrode active material layer formed on the copper thin film.

[0110] The structure of the negative electrode of Example 1 can refer to Figure 2 Come to understand.

[0111] <Comparative Example 1>-Manufacturing of Negative Electrode

[0112] Figure 5 It is a diagram for explaining a negative electrode for a secondary battery according to a comparative example of the present invention.

[0113] A negative electrode was manufactured by the same method as in Example 1, except that, as the negative electrode active material, a negative electrode active material in which artificial graphite and natural graphite were mixed at a weight ratio of 7:3 was used instead of the negative electrode active material of Preparation Example 1.

[0114] Unlike the negative electrode active material prepared in Preparation Example 1, the negative electrode active material used in Comparative Example 1 has no coating layer on the graphite.

[0115] The structure of the negative electrode of Comparative Example 1 can be referred to Figure 5 Come to understand.

[0116] <Experimental Example 1>-Confirmation of Adhesive Distribution and Adhesive Strength

[0117] Figure 4 are images and graphs showing the distribution of a binder of a negative electrode for a secondary battery according to one embodiment of the present invention.

[0118] Figure 6 are an image and a diagram showing the distribution of a binder in a negative electrode for a secondary battery according to a comparative example of the present invention.

[0119] In order to detect the binder in the negative electrode, the negative electrodes manufactured in Example 1 and Comparative Example 1 were stained with osmium tetroxide (OsO4). That is, osmium tetroxide (OsO4) was bound to the binder in the negative electrode. After that, the cross section of the negative electrode was cut and analyzed using Energy Dispersive X-ray Spectroscopy. The results of Example 1 are shown in FIG. Figure 4 The results of Comparative Example 1 are shown in Figure 6 The results of analysis using energy dispersive X-ray spectroscopy showed that the distribution of osmium (Os) in the negative electrode cross section represented the distribution of styrene-butadiene rubber as a binder.

[0120] In addition, based on the analysis results of energy dispersive X-ray spectroscopy, a graph showing the content of the binder according to the distance from the negative electrode current collector is shown in FIG. Figure 4 and Figure 6 , and the absolute values ​​of the slopes in the respective graphs are shown in the following Table 1.

[0121] [Table 1]

[0122]

[0123] In the above Table 1, the first side and the second side refer to the two sides of the negative electrode current collector on which the negative electrode active material layer is formed.

[0124] See also Figure 4 , Figure 6 As shown in Table 1, in the case of Comparative Example 1 using a negative electrode active material without a coating layer, it can be confirmed that the content of the binder according to the distance from the negative electrode current collector exceeds 0.005 wt % / μm. Figure 4 and Figure 6 , a relatively high binder content is shown near the negative electrode current collector, which is expected to be due to the error caused by osmium tetroxide (OsO4) added only to confirm the binder content.

[0125] That is, in the case of the negative electrode active material without forming a coating layer, it can be seen that the binder migrates to the negative electrode surface in the step of drying after coating the negative electrode active material composition (see Figure 5 ).

[0126] On the other hand, in the case of Example 1 using the negative electrode active material of Preparation Example 1, it can be confirmed that the content of the binder according to the distance from the negative electrode current collector is 0.005 wt % / μm or less, and the binder is relatively uniformly distributed throughout the negative electrode active material layer. That is, in the case of using the negative electrode active material of Preparation Example 1, it can be seen that the migration of the binder is suppressed.

[0127] <Experimental Example 2>-Evaluation of Adhesive Strength

[0128] The negative electrode manufactured in Example 1 and Comparative Example 1 was punched into a size of 20 mm × 150 mm and fixed to the center of a 25 mm × 75 mm glass slide using double-sided tape. Then, the 90-degree peel strength (adhesion) was measured while peeling the negative active material layer from the negative current collector using UTM (manufacturer: LLOYD Instruments LTD., instrument name: LF Plus). The results are shown in Table 2 below.

[0129] [Table 2]

[0130]

[0131] Referring to Table 2, although the negative electrode of Example 1 and the negative electrode of Comparative Example 1 both contain the same amount of binder, in the negative electrode of Example 1 using the negative electrode active material of Preparation Example 1, it can be confirmed that the binding force between the negative electrode current collector and the negative electrode active material layer is significantly excellent.

[0132] <Experimental Example 3>-Confirmation of charge and discharge performance

[0133] Making of coin half cell

[0134] A CR2032 type coin half cell was manufactured using the negative electrode of Example 1 and the negative electrode of Comparative Example 1. As the counter electrode, metallic lithium was used, as the separator, a polyethylene (PE) separator was used, and as the electrolyte, an electrolyte in which 1.0 M LiPF6 was dissolved in a mixed solvent of EC (ethylene carbonate): DEC (diethyl carbonate): DMC (dimethyl carbonate) (volume ratio of 3:5:2) was used.

[0135] Confirmation of charge and discharge performance

[0136] Figure 7 1 is a charge and discharge diagram of a secondary battery cell including a negative electrode for a secondary battery according to an embodiment of the present invention and a comparative example.

[0137] The fabricated coin half-cells were charged to 1.5 V (vs. Li / Li at 25 °C at 0.1 C) and + ) and discharged to 0.05V at 0.1C (vs. Li / Li + ) and is shown in Figure 7 , and the reversible capacity was calculated based on the charge capacity and discharge capacity and is shown in the following Table 3.

[0138] [Table 3]

[0139]

[0140] See also Figure 7 From Table 3, it can be confirmed that the reversible capacity of Example 1 is 348.87 mAh / g, and the charge and discharge performance is better than that of Comparative Example 1, which has a reversible capacity of 343.81 mAh / g.

[0141] Example 1 has relatively excellent adhesion between the negative electrode current collector and the negative electrode active material layer, so that the negative electrode active material can be prevented from falling off and peeling off, while in the case of Comparative Example 1, the negative electrode active material may fall off and peel off. This difference may lead to a difference in charge and discharge performance.

[0142] In addition, in Example 1, the binder is uniformly distributed throughout the negative electrode, while in Comparative Example 1, excessive binder may be concentrated on the surface of the negative electrode, so the resistance of the surface of the negative electrode in Comparative Example 1 may be relatively increased. This difference can also lead to differences in charge and discharge performance.

Claims

1. A negative electrode active material for a secondary battery, comprising: A negative electrode active material core; and A coating layer includes an aluminum-containing compound and is formed on the negative electrode active material core.

2. The negative electrode active material for a secondary battery according to claim 1, wherein The aluminum-containing compound comprises one or more selected from Al(NO3)3, Al(OH)3, AlPO4, AlF3, Al2(SO4)3, AlCl3, and AlI3.

3. The negative electrode active material for a secondary battery according to claim 1, wherein The negative electrode active material core includes a carbon-based material.

4. The negative electrode active material for a secondary battery according to claim 3, wherein The carbon-based substance includes at least one selected from artificial graphite, natural graphite, hard carbon, soft carbon, carbon black and graphene.

5. The negative electrode active material for a secondary battery according to claim 4, wherein The carbon black includes acetylene black, Ketjen black and Super P.

6. The negative electrode active material for a secondary battery according to claim 1, wherein The negative electrode active material core includes a silicon-based material.

7. The negative electrode active material for a secondary battery according to claim 6, wherein The silicon-based material comprises a material selected from SiO x , one or more of Si / C composite and Si alloy, 0≤x<2.

8. The negative electrode active material for a secondary battery according to claim 1, wherein The negative electrode active material includes 0.05-5.0 wt % of the aluminum-containing compound.

9. A negative electrode for a secondary battery, comprising: Anode current collector; as well as a negative electrode active material layer, the negative electrode active material layer comprising a negative electrode active material and a binder, and the negative electrode active material layer is formed on at least one side of the negative electrode current collector, The negative electrode active material comprises: a negative electrode active material core; and a coating layer, which is formed on the negative electrode active material core and comprises an aluminum-containing compound.

10. The negative electrode for a secondary battery according to claim 9, wherein In the negative electrode active material layer, an absolute value of an average slope of the content of the binder according to a distance from the negative electrode collector is 0.005 wt % / μm or less.

11. The negative electrode for a secondary battery according to claim 9, wherein The binder includes one or more selected from lithium polyacrylate (LiPAA), styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC), polyacrylic acid (PAA), polyethylene oxide (PEO), polyvinylidene fluoride (PVDF) and polyvinyl alcohol (PVA).

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