Negative electrode and secondary battery

Abstract

The present invention relates to a negative electrode for a secondary battery, which includes a current collector; and a negative electrode active material layer provided on the current collector and containing a negative electrode active material and a conductive material, wherein the conductive material includes a linear conductive material and a planar conductive material, and the negative electrode active material layer has an oriented structure, and a secondary battery including the same.

Description

Technical Field

[0001] This specification claims the benefit of the filing date of Korean Patent Application No. 10-2022-0131731, filed with the Korean Intellectual Property Office on October 13, 2022, and all the contents disclosed in the document of the Korean patent application are incorporated herein.

[0002] The present invention relates to a negative electrode for a secondary battery and a secondary battery including the same.

Background Art

[0003] Secondary batteries are widely applied not only to portable devices but also to electric vehicles (EVs), hybrid electric vehicles (HEVs), etc. driven by an electric drive source.

[0004] Such secondary batteries have not only the primary advantage of significantly reducing the use of fossil fuels but also the advantage of generating no by-products due to energy use, and thus are attracting attention as an environmentally friendly and new energy source for improving energy efficiency.

[0005] Generally, a secondary battery includes a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte. Also, an electrode such as a positive electrode or a negative electrode may have an electrode active material layer provided on a current collector.

[0006] As the utilization of secondary batteries increases, various battery performances are required. In order to improve battery performance, attempts have been made to control the composition of the active material or additive in the positive electrode active material layer or the negative electrode active material layer, but an incorrect combination of materials may rather have an adverse effect on the performance of the final battery. For this reason, research on improving battery performance by the combination of materials in the positive electrode and the negative electrode is needed.

Summary of the Invention

Problems to be Solved by the Invention

[0007] The present invention aims to provide a negative electrode for a secondary battery capable of providing a secondary battery with improved rapid charging characteristics, and a secondary battery including the same.

Means for Solving the Problems

[0008] One embodiment of the present invention is a current collector; and a negative electrode active material layer provided on the current collector and including a negative electrode active material and a conductive material, wherein the conductive material includes a linear conductive material and a planar conductive material, and the negative electrode active material layer has an oriented structure, providing a negative electrode for a secondary battery.

[0009] Another embodiment of the present invention provides a secondary battery including the negative electrode for a secondary battery, a positive electrode, and a separator.

Effects of the Invention

[0010] According to the embodiments described herein, the output characteristics can be improved by magnetically aligning the negative electrode active material layer and using both linear and planar conductive materials as the conductive material. Specifically, when using linear and planar conductive materials, compared with the case of applying a dot-shaped conductive material, the conductive material also exhibits an alignment effect due to the alignment of the negative electrode active material layer, and higher improvement in output characteristics can be obtained.

Brief Description of the Drawings

[0011]

Figure 1

Modes for Carrying Out the Invention

[0012] Hereinafter, in order to assist in the understanding of the present invention, the present invention will be described in more detail. The present invention can be embodied in various different forms and is not limited to the embodiments described herein. At this time, the terms or words used in this specification and the claims should not be construed as being limited to their ordinary or dictionary meanings, and the inventor should, in accordance with the principle that the concept of the terms can be appropriately defined in order to best explain his invention, be construed in a meaning and concept that conforms to the technical idea of the present invention.

[0013] In this specification, terms such as "including", "comprising", or "having" are intended to specify the presence of implemented features, numbers, steps, components, or combinations thereof, and are understood not to preclude the possibility of the presence or addition of one or other features, numbers, steps, components, or combinations thereof.

[0014] Also, when a certain part, such as a layer, is "on" another part, this includes not only the case where it is "directly on" the other part but also the case where there is another part in between. Conversely, when a certain part is "directly on" another part, it means that there is no other part in between. Note that being "on" the reference part refers to being located above or below the reference part and does not necessarily mean being located "upward" in the opposite direction of gravity.

[0015] The negative electrode for a secondary battery according to an embodiment of this specification includes a current collector; and a negative electrode active material layer provided on the current collector and including a negative electrode active material and a conductive material, the conductive material including a linear conductive material and a planar conductive material, and the negative electrode active material layer having a structure oriented by magnetic alignment. The inventors have found that, as described above, when a linear and a planar conductive material are used in combination as the conductive material, the improvement range of the cell resistance during the orientation of the negative electrode can be further increased, leading to the present invention.

[0016] In the above embodiment, the negative electrode active material layer includes a linear conductive material and a planar conductive material as conductive materials. The linear and planar conductive materials can improve the output characteristics of the battery by being aligned by the alignment of the negative electrode active material layer. Further, by applying the linear conductive material and the planar conductive material together, a greater improvement in effect can be expected.

[0017] As the linear conductive material, conductive fibers such as carbon fibers and metal fibers; conductive tubes such as carbon nanotubes such as single-walled carbon nanotubes (SWCNT) and multi-walled carbon nanotubes (MWCNT); metal powders such as fluorocarbons, aluminum, and nickel powders; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; conductive materials such as polyphenylene derivatives can be used.

[0018] Examples of the planar conductive material include graphene.

[0019] If necessary, the conductive material may further include a dot-shaped conductive material. As the dot-shaped conductive material, for example, graphite such as natural graphite and artificial graphite; carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black may be used.

[0020] According to one embodiment, the conductive material may be 0.1 part by weight to 5 parts by weight based on 100 parts by weight of the negative electrode active material layer. At this time, the total amount of the above-described linear conductive material and planar conductive material may be 0.1 part by weight to 2 parts by weight based on 100 parts by weight of the negative electrode active material layer. The linear conductive material and the planar conductive material can be used in a smaller amount than the dot-shaped conductive material.

[0021] In one embodiment of the present specification, the negative electrode active material may include a silicon-based active material and a carbon-based active material, and the carbon-based active material may include artificial graphite and natural graphite.

[0022] In one embodiment of the present specification, the silicon-based active material is SiO x (0 ≦ x < 2), SiM y (M is a metal, 1 ≦ y ≦ 4) and at least one of Si / C. The silicon-based active material may contain only one type or two or more types may be included together. When both of the two layers of the negative electrode active material layer contain a silicon-based active material, the same type of silicon-based active material may be used for the two layers of the active material layer, or different types or different combinations of silicon-based active materials may be used.

[0023] In one embodiment of the present specification, based on 100 parts by weight in total of the negative electrode active material, the silicon-based active material may be included in an amount of 1 part by weight to 40 parts by weight, for example, 1 part by weight to 20 parts by weight.

[0024] The active material containing SiO x (0 ≦ x < 2) may be silicon-based composite particles containing SiO x (0 < x < 2) and pores.

[0025] The SiO x (0 < x < 2) corresponds to a matrix within the silicon-based composite particles. The SiO x (0 < x < 2) may be in a form containing Si and SiO2, and the Si may form a phase. That is, the x corresponds to the number ratio of O to Si contained in the SiO x (0 < x < 2). When the silicon-based composite particles contain the SiO x (0 < x < 2), the discharge capacity of the secondary battery can be improved.

[0026] The silicon-based composite particles may further contain at least one of a Mg compound and a Li compound. The Mg compound and the Li compound can correspond to a matrix within the silicon-based composite particles.

[0027] The Mg compound and / or the Li compound is the SiO xIt may be present inside and / or on the surface of (0 < x < 2). The initial efficiency of the battery can be improved by the Mg compound and / or Li compound.

[0028] The Mg compound may include at least one selected from the group consisting of Mg silicate, Mg silicide, and Mg oxide. The Mg silicate may include at least one of Mg2SiO4 and MgSiO3. The Mg silicide may include Mg2Si. The Mg oxide may include MgO.

[0029] In one embodiment of the present specification, the Mg element may be contained in an amount of 0.1% by weight to 20% by weight, or may be contained in an amount of 0.1% by weight to 10% by weight, based on 100% by weight of the total silicon-based active material. Specifically, the Mg element may be contained in an amount of 0.5% by weight to 8% by weight or 0.8% by weight to 4% by weight. When the above range is satisfied, the Mg compound can be contained in an appropriate content in the silicon-based active material, so that the volume change of the silicon-based active material can be easily suppressed during charging and discharging of the battery, and the discharge capacity and initial efficiency of the battery can be improved.

[0030] The Li compound may include at least one selected from the group consisting of Li silicate, Li silicide, and Li oxide. The Li silicate may include at least one of Li2SiO3, Li4SiO4, and Li2Si2O5. The Li silicide may include Li7Si2. The Li oxide may include Li2O.

[0031] In one embodiment of the present invention, the Li compound may include a lithium silicate form. The lithium silicate is Li a Si b O cIt is represented by (2 ≤ a ≤ 4, 0 < b ≤ 2, 2 ≤ c ≤ 5) and can be classified into crystalline lithium silicate and amorphous lithium silicate. The crystalline lithium silicate can exist in the form of at least one lithium silicate selected from the group consisting of Li2SiO3, Li4SiO4, and Li2Si2O5 within the silicon-based composite particles, and the amorphous lithium silicate is Li a Si b O c It may be in the form of (2 ≤ a ≤ 4, 0 < b ≤ 2, 2 ≤ c ≤ 5), and is not limited to the above form.

[0032] In one embodiment of the present specification, the Li element may be contained in an amount of 0.1 wt% to 20 wt%, or may be contained in an amount of 0.1 wt% to 10 wt% based on 100 wt% of the total silicon-based active material. Specifically, the Li element may be contained in an amount of 0.5 wt% to 8 wt%, and more specifically, may be contained in an amount of 0.5 wt% to 4 wt%. When the above range is satisfied, the Li compound can be contained in an appropriate content within the silicon-based active material, so that the change in the volume of the negative electrode active material can be easily suppressed during charging and discharging of the battery, and the discharge capacity and initial efficiency of the battery can be improved.

[0033] The content of the Mg element or Li element can be confirmed by ICP (Inductively Coupled Plasma) analysis. After accurately sampling a certain amount (about 0.01 g) of the negative electrode active material for the ICP analysis, it is transferred to a platinum crucible, and nitric acid, hydrofluoric acid, and sulfuric acid are added and completely decomposed on a hot plate. Then, using an inductively coupled plasma optical emission spectrometer (ICPAES, Perkin-Elmer 7300), the intensity of a standard solution (5 mg / kg) prepared using a standard solution at the specific wavelength of the Mg element or Li element is measured to create a calibration curve. Then, the pretreated sample solution and the background sample are introduced into the instrument, the intensities of each are measured to calculate the actual intensity, and after calculating the concentration of each component by comparing with the created calibration curve, it is converted so that the total sum becomes the theoretical value, and the content of the Mg element or Li element of the manufactured silicon-based active material can be analyzed.

[0034] In one embodiment of the present specification, a carbon layer may be provided on the surface and / or inside the pores of the silicon-based composite particles. The carbon layer imparts conductivity to the silicon-based composite particles, and the initial efficiency, life characteristics, and battery capacity characteristics of a secondary battery including a negative electrode active material containing the silicon-based composite particles can be improved. The total weight of the carbon layer may be included in an amount of 5% to 40% based on 100% by weight of the total silicon-based composite particles.

[0035] In one embodiment of the present specification, the carbon layer may include at least one of amorphous carbon and crystalline carbon.

[0036] The average particle size (D 50 ) of the silicon-based active material is 2 μm to 15 μm, specifically 3 μm to 12 μm, and more specifically may be 4 μm to 10 μm. When the above range is satisfied, the side reaction between the silicon-based composite particles and the electrolytic solution is controlled, and the discharge capacity and initial efficiency of the battery can be effectively realized.

[0037] In the present specification, the average particle size (D 50 ) can be defined as the particle size corresponding to 50% of the volume cumulative amount in the particle size distribution curve of the particles. The average particle size (D 50 ) can be measured, for example, using a laser diffraction method. The laser diffraction method can generally measure particle sizes in the submicron region to about several millimeters, and results with high reproducibility and high resolution can be obtained.

[0038] The active material containing Si / C as the silicon-based active material is a composite of Si and C, and is distinguished from silicon carbide denoted as SiC. The silicon-carbon composite may be a composite of silicon and graphite or the like, and may also form a structure in which a core in which silicon and graphite or the like are composite is surrounded by graphene or amorphous carbon or the like. In the silicon-carbon composite, the silicon may be nanosilicon.

[0039] In one embodiment of the present specification, the artificial graphite and the natural graphite may be contained in an amount of 60 parts by weight or more and 99 parts by weight or less based on 100 parts by weight of the negative electrode active material. The artificial graphite and the natural graphite may be contained in a weight ratio of 1:9 to 9:1, for example, 2:8 to 8:2.

[0040] In one embodiment of the present specification, the negative electrode active material in 100 parts by weight of the negative electrode active material layer may be contained in an amount of 80 parts by weight or more and 99.9 parts by weight or less, preferably 80 parts by weight or more and 90 parts by weight or less.

[0041] According to a further embodiment of the present specification, the negative electrode active material layer may further contain a negative electrode binder in addition to the negative electrode active material.

[0042] The negative electrode binder can play a role in improving the adhesion between the negative electrode active material particles and the adhesion force between the negative electrode active material particles and the negative electrode current collector. As the negative electrode binder, those known in the art can be used. Non-limiting examples include polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene butadiene rubber (SBR), fluorine rubber, poly acrylic acid, and at least one selected from the group consisting of substances in which their hydrogens are substituted with Li, Na, or Ca, etc., and various copolymers thereof may also be included.

[0043] The negative electrode binder may be contained in an amount of 0.1 part by weight or more and 20 parts by weight or less, based on 100 parts by weight of the negative electrode active material layer. For example, it is preferably contained in an amount of 0.3 part by weight or more and 20 parts by weight or less, and more preferably 0.5 part by weight or more and 10 parts by weight or less.

[0044] In one embodiment of the present specification, the thickness of the negative electrode active material layer may be 5 μm or more and 300 μm or less, for example, 10 μm or more and 150 μm or less.

[0045] In one embodiment of the present specification, the negative electrode current collector may be any material that has conductivity without inducing a chemical change in the battery, and is not particularly limited. For example, as the current collector, copper, stainless steel, aluminum, nickel, titanium, fired carbon, or a material obtained by surface-treating the surface of aluminum or stainless steel with carbon, nickel, titanium, silver, etc. can be used. Specifically, a transition metal that can adsorb carbon such as copper or nickel can be used as the current collector. The thickness of the current collector can be 1 μm to 500 μm, but the thickness of the current collector is not limited thereto.

[0046] A further embodiment of the present specification provides a secondary battery including the negative electrode, positive electrode, and separator according to the foregoing embodiments.

[0047] In one embodiment of the present specification, the positive electrode includes a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector and containing the positive electrode active material. The thickness of the positive electrode active material layer may be 20 μm or more and 500 μm or less.

[0048] The positive current collector is not particularly limited as long as it has conductivity without inducing chemical changes in the battery. For example, stainless steel, aluminum, nickel, titanium, fired carbon, or those obtained by surface treatment with carbon, nickel, titanium, silver, etc. on the surface of aluminum or stainless steel can be used. Further, the positive current collector may usually have a thickness of 1 to 500 μm, and fine irregularities may be formed on the surface of the current collector to enhance the adhesive force of the positive electrode active material. For example, it may be used in various forms such as films, sheets, foils, nets, porous bodies, foams, non-woven bodies, etc.

[0049] In one embodiment of the present specification, the positive electrode may contain a lithium composite transition metal compound containing nickel (Ni) and cobalt (Co) as active materials. The lithium composite transition metal compound may further contain at least one of manganese and aluminum. The lithium composite transition metal compound may contain 80 mol% or more, for example, 80 mol% or more and less than 100 mol% of nickel among the metals excluding lithium.

[0050] In one embodiment, the positive electrode active material in 100 parts by weight of the positive electrode active material layer may be contained in an amount of 80 parts by weight or more and 99.9 parts by weight or less, preferably 90 parts by weight or more and 99.9 parts by weight or less, more preferably 95 parts by weight or more and 99.9 parts by weight or less, and still more preferably 98 parts by weight or more and 99.9 parts by weight or less.

[0051] According to a further embodiment of the present specification, the positive electrode active material layer according to the foregoing embodiment may further contain a positive electrode binder and a conductive material.

[0052] The anode binder can play a role in improving the adhesion between anode active material particles and the adhesive force between the anode active material particles and the anode current collector. As the anode binder, those known in the art can be used. Non-limiting examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, or various copolymers thereof. Among these, one kind alone or a mixture of two or more kinds may be used.

[0053] The anode binder may be contained in an amount of 0.1 part by weight or more and 50 parts by weight or less based on 100 parts by weight of the anode active material layer. For example, preferably, it may be contained in an amount of 0.3 part by weight or more and 35 parts by weight or less, and more preferably 0.5 part by weight or more and 20 parts by weight or less.

[0054] The conductive material contained in the anode active material layer is used to impart conductivity to the electrode, and can be used without particular limitation as long as it has electron conductivity without undergoing a chemical change in the battery. Specific examples include graphite such as natural graphite and artificial graphite; carbon-based materials such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fiber; metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives. Among these, one kind alone or a mixture of two or more kinds may be used.

[0055] Specifically, in one embodiment, the conductive material may include one or more of single-walled carbon nanotubes (SWCNT) and multi-walled carbon nanotubes (MWCNT). The conductive material may be included in an amount of 0.1 part by weight or more and 2 parts by weight or less based on 100 parts by weight of the composition for the positive electrode active material layer. For example, preferably, it may be included in an amount of 0.3 part by weight or more and 1.5 parts by weight or less, and more preferably 0.5 part by weight or more and 1.2 parts by weight or less.

[0056] The positive electrode and the negative electrode can be manufactured according to the usual manufacturing methods of positive and negative electrodes, except for using the above-mentioned positive electrode active material and negative electrode active material. Specifically, after applying a composition for forming an active material layer, which contains the above-mentioned active material and optionally a binder and a conductive material, onto a current collector, it can be manufactured by drying and rolling. At this time, the types and contents of the positive electrode and negative electrode active materials, the binder, and the conductive material are as described above. The solvent may be a solvent generally used in the art, and examples include dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water, and one of these alone or a mixture of two or more thereof may be used. The amount of the solvent used is such that, considering the coating thickness of the slurry and the manufacturing yield, the active material, the conductive material, and the binder are dissolved or dispersed, and then it has a viscosity capable of showing excellent thickness uniformity during coating for manufacturing the positive electrode and the negative electrode. Also, as another method, the positive electrode and the negative electrode may be manufactured by casting the composition for forming the active material layer onto another support, and then laminating a film obtained by peeling from the support onto a current collector.

[0057] A further embodiment of the present specification provides a method for manufacturing a positive electrode for a secondary battery according to the above-described embodiment. The manufacturing method is as follows: A step of coating a composition containing a negative electrode active material and a conductive material on a current collector, magnetically aligning the composition simultaneously with or after the coating, and rolling the composition to form a negative electrode active material layer is included. The conductive material includes a linear conductive material and a planar conductive material.

[0058] By performing magnetic alignment according to the above manufacturing method together with the type of the conductive material of each of the negative electrode active material layers described above, the degree of orientation of the negative electrode active material layer can be controlled.

[0059] The separator separates the negative electrode and the positive electrode and provides a migration path for lithium ions. Usually, any material that can be used as a separator in a secondary battery can be used without particular limitation. In particular, it is preferably low resistance to the ion migration of the electrolyte while having excellent electrolyte moisture retention ability. Specifically, a porous polymer film, for example, a porous polymer film made of a polyolefin-based polymer such as a polyethylene homopolymer, a polypropylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer, or a laminate structure of two or more layers thereof may be used. Also, a normal porous nonwoven fabric, for example, a nonwoven fabric made of high melting point glass fibers, polyethylene terephthalate fibers, etc. may be used. Further, in order to ensure heat resistance or mechanical strength, a coated separator containing a ceramic component or a polymer substance can also be used, and it may be selectively used in a single layer or multilayer structure.

[0060] Examples of the electrolyte include, but are not limited to, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in the manufacture of lithium secondary batteries.

[0061] Specifically, the electrolyte may contain a non-aqueous organic solvent and a metal salt.

[0062] Examples of the non-aqueous organic solvent include aprotic organic solvents such as N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, triester phosphate, trimethoxymethane, dioxolane derivative, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivative, tetrahydrofuran derivative, ether, methyl propionate, ethyl propionate, etc. may be used.

[0063] In particular, ethylene carbonate and propylene carbonate, which are cyclic carbonates among the carbonate-based organic solvents, are organic solvents with high viscosity and high dielectric constant, which can dissociate lithium salts well, so they are preferably used. When such cyclic carbonates are mixed with linear carbonates with low viscosity and low dielectric constant such as dimethyl carbonate and diethyl carbonate in an appropriate ratio and used, an electrolyte having high electrical conductivity can be produced and can be more preferably used.

[0064] As the metal salt, a lithium salt can be used. The lithium salt is a substance that is easily dissolved in the non-aqueous electrolyte. For example, as the anion of the lithium salt, F - , Cl - , 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 - One or more selected from the group consisting of can be used.

[0065] In addition to the electrolyte components, the electrolyte may further contain one or more additives such as haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glyme, hexamethylphosphoric triamide, nitrobenzene derivatives, sulfur, quinoneimine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol or aluminum trichloride for the purpose of improving the life characteristics of the battery, suppressing the decrease in battery capacity, improving the discharge capacity of the battery, etc.

[0066] The secondary battery according to one embodiment of the present invention includes an assembly including a positive electrode, a negative electrode, a separator and an electrolyte, and this may be a lithium secondary battery.

[0067] A further embodiment of the present invention provides a battery module including the aforementioned secondary battery as a unit cell and a battery pack including the same. Since the battery module and the battery pack include the secondary battery having high capacity, high rate characteristics and cycle characteristics, they can be used as a power source for medium and large-sized devices selected from the group consisting of electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles and power storage systems.

[0068] The secondary battery according to an embodiment of the present invention can be used as a power source for not only portable devices such as mobile phones, notebook computers, and digital cameras, but also medium- and large-sized devices selected from the group consisting of electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and power storage systems, in order to stably exhibit excellent discharge capacity, output characteristics, and cycle performance. For example, the battery module or battery pack can be used as a power source for one or more medium- and large-sized devices among power tools; electric vehicles including electric vehicles (EV), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEV); or power storage systems.

[0069] Hereinafter, preferred examples are presented to assist in understanding the present invention. However, it is obvious to those skilled in the art that the examples are illustrative of the description and various changes and modifications are possible within the scope of the description and the scope of the technical idea. It goes without saying that such variations and modifications belong to the scope of the appended claims.

[0070] Example 1 After coating the negative electrode current collector with the negative electrode active material layer composition to a thickness of 100 μm, rolling and drying were performed at room temperature. A magnetic alignment process was applied during the coating process.

[0071] As a composition for manufacturing the negative electrode active material layer, a composition containing artificial graphite, natural graphite, a negative electrode active material containing SiO, a conductive material (including a linear conductive material (CNT) and a planar conductive material (graphene) in a weight ratio of 1:1), a binder (SBR), and a thickener in a weight ratio of 96:1:2:1 was used. The degree of orientation was confirmed by ratio calculation using XRD.

[0072] Li on the positive electrode current collector 1.0 Ni 0.86 Co 0.08 Mn 0.06After coating a composition containing O2, a conductive material (CNT), and a binder (PVDF) at a weight ratio of 97:1:2, respectively, a positive electrode was manufactured by drying and rolling.

[0073] The positive electrode and the negative electrode were laminated with a separator interposed therebetween, and an electrolytic solution was injected to fabricate a battery. The electrolytic solution contains 1M LiPF6, EC (ethylene carbonate) / EMC (ethyl methyl carbonate) (3 / 7 volume ratio), 1.5 wt% VC (vinylene carbonate), and 0.5 wt% PS (propane sultone).

[0074] Comparative Example 1 The procedure was the same as in Example 1, except that only a dot-shaped conductive material (carbon black) was used as the conductive material in the negative electrode active material layer.

[0075] The cell resistances of the negative electrodes of the batteries manufactured in the examples and comparative examples according to the SOC are shown in FIG. 1. According to FIG. 1, it was confirmed that, compared with the negative electrode to which only the dot-shaped conductive material was applied as in the comparative example, the negative electrode to which the linear and planar conductive materials were applied had a larger improvement width in cell resistance when magnetic alignment was applied.

Claims

1. A current collector, and a negative electrode active material layer provided on the current collector and containing a negative electrode active material and a conductive material, wherein the conductive material includes a linear conductive material and a planar conductive material, and the negative electrode active material layer has an oriented structure, a negative electrode for a secondary battery.

2. The negative electrode for a secondary battery according to Claim 1, wherein the negative electrode active material includes a silicon-based active material, artificial graphite, and natural graphite.

3. The negative electrode for a secondary battery according to Claim 2, wherein the silicon-based active material is contained in an amount of 1 part by weight to 40 parts by weight based on 100 parts by weight in total of the negative electrode active material.

4. The negative electrode for a secondary battery according to Claim 1, wherein the conductive material is contained in an amount of 0.1 part by weight to 5 parts by weight based on 100 parts by weight of the negative electrode active material layer.

5. A secondary battery including the negative electrode for a secondary battery according to any one of Claims 1 to 4, a positive electrode, and a separator.

6. The secondary battery according to Claim 5, wherein the positive electrode includes a lithium composite transition metal compound containing nickel (Ni) and cobalt (Co) as active materials.

7. The secondary battery according to Claim 6, wherein the lithium composite transition metal compound further includes at least one of manganese and aluminum.

8. A manufacturing method for manufacturing the negative electrode for a secondary battery according to any one of Claims 1 to 4, including coating a composition containing a negative electrode active material and a conductive material on a current collector, magnetically aligning simultaneously with or after the coating, rolling to form a negative electrode active material layer, and magnetically aligning the negative electrode active material layer, wherein the conductive material includes a linear conductive material and a planar conductive material, a manufacturing method.

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