Negative electrode for secondary battery using locally different magnetic alignment and manufacturing method thereof

Abstract

According to a negative electrode for a secondary battery and a manufacturing method thereof, non-uniform magnetic alignment is applied when manufacturing the negative electrode, whereby non-uniform degradation of the negative electrode is prevented during charging and discharging of the secondary battery, and a secondary battery having excellent lifespan characteristics can be achieved.

Description

Negative electrode for a secondary battery with locally different magnetic alignment and method for manufacturing the same

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2024-0191431 dated December 19, 2024, and all contents disclosed in the literature of said Korean patent applications are incorporated herein as part of this specification.

[0002] The present invention relates to a negative electrode for a secondary battery with locally applied magnetic alignment and a method for manufacturing the same.

[0003] Recently, lithium-ion batteries are being widely applied not only to small devices such as portable electronic devices but also to medium-to-large devices such as battery packs or power storage systems for hybrid and electric vehicles. In particular, with the recent increase in concern for environmental issues, the demand base for high-capacity batteries is expanding due to the growth of the market for devices employing such batteries, including electric vehicles and hybrid electric vehicles, which can replace fossil fuel-using vehicles such as gasoline and diesel cars that are major causes of air pollution.

[0004] Generally, a lithium secondary battery is a rechargeable power generation device composed of a stacked structure of a positive electrode, a separator, and a negative electrode. During charging, a lithium extraction reaction occurs in the positive electrode, where lithium contained in the positive electrode active material is oxidized and released, while a lithium insertion reaction occurs in the negative electrode, where lithium is reduced and enters the negative electrode active material. Since the extraction reaction in the positive electrode active material is generally faster than the insertion reaction in the negative electrode active material, performance characteristics such as charging and discharging speeds are primarily determined by the negative electrode. Currently, materials containing graphite are widely used as the negative electrode active material. Additionally, silicon-based materials are partially applied as the negative electrode active material to increase the capacity of the negative electrode.

[0005] However, there is a problem in that the degree of degradation of the negative electrode varies by region during the charging and discharging process of secondary batteries. Specifically, during the repeated charging and discharging of a secondary battery, the active material located in the central region of the negative electrode participates more in the charging and discharging. Additionally, heat is generated during the charging and discharging process, and this degradation tends to concentrate in the central region of the negative electrode. Consequently, non-uniform degradation is induced between the active material located in the central region and the active material located in the edge region of the negative electrode. This non-uniform degradation of the negative electrode significantly reduces its lifespan characteristics, which in turn causes a decrease in the cell's capacity retention rate.

[0006] Accordingly, the present invention aims to provide a secondary battery with excellent lifespan characteristics by preventing uneven degradation of the negative electrode during the charging and discharging process of the secondary battery.

[0007] In order to solve the problem described above, in one embodiment, a negative electrode for a secondary battery according to the present invention comprises: a negative electrode current collector having an electrode tab formed on one side; and a negative electrode active layer provided on one or both sides of the negative electrode current collector and comprising a carbon-based negative electrode active material. Furthermore, when the negative electrode active layer is divided into an outer region including at least one of an upper region adjacent to the electrode tab and a lower region opposite thereto based on a planar structure; and a central region excluding the outer region, the value according to Formula 1 below is 0.5 or greater.

[0008] [Equation 1]

[0009] [DD out ] - [DD in ]

[0010] In the above Equation 1,

[0011] The above DD in represents the orientation degree (DD) of the central region, and the said DD out represents the orientation degree (DD) of the outer region, and

[0012] The above orientation degree (DD) is the sum of peak intensities (I) appearing at non-planar angles when XRD measuring the cathode active layer using CuKα rays. a ) and the sum of peak intensities appearing at all angles (I total The ratio of )(I a / I total It represents ).

[0013] As one example, the outer region may include an upper region adjacent to the electrode tab and a lower region on the opposite side. As another example, the outer region may include an upper region adjacent to the electrode tab.

[0014] For example, the value according to the above formula 1 is in the range of 0.5 to 30, 1 to 15, or 3 to 10.

[0015] In a specific example, in Equation 1 above, [DD out The value of ] is in the range of 20 to 70.

[0016] For example, the value according to the above Equation 1 is in the range of 2 to 25. Also, in the above Equation 1, [DD out The value of ] is in the range of 20 to 40.

[0017] In one embodiment, in the electrode, the area of ​​the outer region is in the range of 2% to 30% of the area of ​​the negative active layer.

[0018] In one embodiment, the carbon-based negative electrode active material includes one or more of natural graphite and artificial graphite.

[0019] The above-described negative electrode active layer may further include a silicon-based component as an active material. Specifically, the above-described negative electrode active layer further includes a silicon-based negative electrode active material as a negative electrode active material. The content of the silicon-based negative electrode active material is in the range of 0.1 weight% to 30 weight% based on the total weight of the negative electrode active material contained in the negative electrode active layer.

[0020] For example, the silicon-based negative electrode active material is silicon (Si), silicon carbide (SiC), a composite of carbon and silicon (Si / C), and silicon oxide (SiO₂). q , provided that it includes at least one of 0.8≤q≤2.5).

[0021] For example, the above-mentioned negative electrode is a negative electrode for a pouch-type secondary battery.

[0022]

[0023] In addition, the present invention provides a method for manufacturing a negative electrode for a secondary battery as described above. In one embodiment, the method for manufacturing a negative electrode for a secondary battery according to the present invention comprises: a negative electrode slurry coating step of coating a negative electrode slurry onto the surface of a negative electrode current collector; and a magnetic field application step of applying a magnetic field to the coated negative electrode slurry.

[0024] When the above magnetic field application step is divided into an outer region including one or more of an upper region adjacent to the electrode tab and a lower region opposite it, and a central region excluding the outer region, the value according to Equation 2 below is 500 (G) or more.

[0025] [Equation 2]

[0026] [MF out ] - [MF in ]

[0027] In the above Equation 2,

[0028] The above MF in represents the strength (G) of the magnetic field applied to the central region, and the MF out represents the strength (G) of the magnetic field applied to the external region.

[0029] In one embodiment, in Equation 2 above, [MF out The value of ] is in the range of 1,000(G) to 20,000(G).

[0030] In another embodiment, after the magnetic field application step, the steps of drying the cathode and rolling may be further included.

[0031] In addition, the present invention provides a secondary battery comprising the negative electrode described above. Specifically, the secondary battery may be a pouch-type secondary battery. For example, the secondary battery is a battery for automobiles or for an Energy Storage System (ESS).

[0032] The negative electrode for a secondary battery according to the present invention prevents uneven degradation of the negative electrode during the charging and discharging process of the secondary battery and enables the realization of a secondary battery having excellent lifespan characteristics.

[0033] FIG. 1 is a schematic diagram showing the structure of a negative electrode for a secondary battery according to one embodiment of the present invention.

[0034] FIG. 2 is a schematic diagram showing the structure of a negative electrode for a secondary battery according to another embodiment of the present invention.

[0035] FIG. 3 is a graph showing the results of evaluating the capacity retention rate (%) for secondary batteries according to the embodiments and comparative examples of the present invention.

[0036] The present invention is capable of various modifications and may have various embodiments, and specific embodiments are to be described in detail in the detailed description.

[0037] However, this is not intended to limit the invention to specific embodiments, and it should be understood that it includes all modifications, equivalents, and substitutions that fall within the spirit and scope of the invention.

[0038] In the present invention, terms such as "comprising" or "having" are intended to specify the existence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not excluding in advance the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0039] Furthermore, in the present invention, when a part such as a layer, film, region, or plate is described as being "on" another part, this includes not only cases where it is "immediately above" the other part, but also cases where there is another part in between. Conversely, when a part such as a layer, film, region, or plate is described as being "under" another part, this includes not only cases where it is "immediately below" the other part, but also cases where there is another part in between. Additionally, in the present application, being "placed on" may include cases where it is placed on the lower part as well as on the upper part.

[0040]

[0041] The present invention will be described in more detail below.

[0042]

[0043] The present invention provides a negative electrode for a secondary battery. In one embodiment, the negative electrode according to the present invention comprises: a negative electrode current collector having an electrode tab formed on one side; and a negative electrode active layer provided on one or both sides of the negative electrode current collector and comprising a carbon-based negative electrode active material. Furthermore, the negative electrode active layer is divided, based on a planar structure, into an outer region including one or more of an upper region adjacent to the electrode tab and a lower region opposite thereto; and a central region excluding the outer region. The negative electrode has a value according to Formula 1 below of 0.5 or higher.

[0044] [Equation 1]

[0045] [DD out ] - [DD in ]

[0046] In the above Equation 1,

[0047] The above DD in represents the orientation degree (DD) of the central region, and the said DD out represents the orientation degree (DD) of the outer region, and

[0048] The above orientation degree (DD) is the sum of peak intensities (I) appearing at non-planar angles when XRD measuring the cathode active layer using CuKα rays. a ) and the sum of peak intensities appearing at all angles (I total The ratio of )(I a / I total It represents ).

[0049] As one example, the outer region may include an upper region adjacent to the electrode tab and a lower region on the opposite side. As another example, the outer region may include an upper region adjacent to the electrode tab.

[0050] For example, the value according to Equation 1 above is in the range of 0.5 to 30, 1 to 15, or 3 to 10. The numerical range according to Equation 1 above means controlling the orientation degree (DD) value of the outer region to be high when the surface of the cathode active layer is divided into an outer region and a central region. The present invention is characterized by increasing the orientation degree (DD) by applying a stronger magnetic field to the outer region or increasing the magnetic field application time when manufacturing the cathode. In the central region, a relatively weaker magnetic field is applied or the magnetic field application time is reduced to lower the orientation degree (DD). The present invention may also include cases where no magnetic field is applied to the central region.

[0051] Generally, during the charging and discharging process of a secondary battery, the negative electrode exhibits different degrees of degradation depending on the region. The present invention controls the orientation degree (DD) of the negative electrode active layer differently for each region during the manufacture of the negative electrode. Through this, it is implemented so that the entire negative electrode active layer exhibits the same or equivalent degree of degradation after undergoing charging and discharging of the secondary battery.

[0052] In a specific example, in Equation 1 above, [DD out The value of ] is in the range of 20 to 70. Specifically, in Equation 1 above, [DD outThe value of ] is in the range of 25 to 70, 20 to 40, 25 to 40, 30 to 40, or 25 to 38. At the same time, in the above Equation 1, [DD in The value of ] is in the range of 10 to 60, 15 to 60, 10 to 40, or 15 to 38.

[0053] For example, the value according to the above Equation 1 is in the range of 2 to 25 or in the range of 2 to 10. Also, in the above Equation 1, [DD out The value of ] is in the range of 20 to 40.

[0054] In one embodiment, the area of ​​the outer region of the electrode is in the range of 2% to 30% of the area of ​​the cathode active layer. In the electrode, the area of ​​the outer region is in the range of 2% to 20%, 5% to 30%, 5% to 20%, 8% to 30%, 15% to 25%, or 5% to 15% of the area of ​​the cathode active layer. The outer region may include both an upper region adjacent to the electrode tab and a lower region on the opposite side. As another example, the outer region may include only the upper region adjacent to the electrode tab.

[0055] FIG. 1 is a schematic diagram showing a negative electrode for a secondary battery according to one embodiment of the present invention. The negative electrode (100) for the secondary battery has a structure in which a negative active layer (130) is formed on a negative current collector. In addition, a negative tab (101) is formed protrudingly on the upper end of the negative electrode (100) for the secondary battery. The negative electrode (100) for the secondary battery includes an outer region (111, 112) that includes an upper region (111) adjacent to the negative tab (101) and a lower region (112) on the opposite side, based on the negative active layer (130). In addition, the negative active layer (130) includes a central region (120) located between the upper region (111) and the lower region (112). Based on the total length (D1) of the negative active layer (130), the length (D) of the upper region (111)1A ) is at the 10% level, and the length (D) of the lower region (112) 1B ) is at the 10% level. In this case, the negative electrode (100) for the secondary battery has an area of ​​the outer region (111, 112) that is 20% of the area of ​​the negative electrode active layer (130).

[0056] FIG. 2 is a schematic diagram showing a negative electrode for a secondary battery according to another embodiment of the present invention. The negative electrode (200) for the secondary battery has a structure in which a negative active layer (230) is formed on a negative current collector. In addition, a negative tab (201) is formed protrudingly on the upper end of the negative electrode (200) for the secondary battery. The negative electrode (200) for the secondary battery includes an outer region (211) that includes an upper region (211) adjacent to the negative tab (201), based on the negative active layer (230). In addition, the negative active layer (230) includes a central region (220) located below the upper region (211). Based on the total length (D2) of the negative active layer (230), the length (D) of the upper region (211) 2A ) is at the 10% level. In this case, the negative electrode (200) for the secondary battery has an area of ​​the outer region (211) that is 10% of the area of ​​the negative electrode active layer (230).

[0057] In one embodiment, the carbon-based negative electrode active material comprises one or more of natural graphite, artificial graphite, Kish graphite, pyrolytic carbon, carbon microbeads, mesophase calcined carbon made from tar and pitch, and graphitized coke.

[0058] In another embodiment, the negative active layer may further include a silicon-based negative active material as the negative active material. Specifically, the content of the silicon-based negative active material is in the range of 0.1 wt% to 30 wt%, 1 wt% to 30 wt%, 1 wt% to 10 wt%, 0.1 wt% to 5 wt%, 5 wt% to 30 wt%, or 6 wt% to 20 wt%, based on the total weight of the negative active material contained in the negative active layer. The silicon-based negative active material has the advantage of increasing electrode capacity compared to carbon-based negative active materials. On the other hand, the silicon-based negative active material has the problem of causing volume changes during the charge-discharge process. Therefore, it is desirable to control the content of the silicon-based negative active material by considering the application field or form of the secondary battery.

[0059] Specifically, the silicon-based negative electrode active material comprises silicon (Si), silicon carbide (SiC), a carbon-silicon composite (Si / C), and silicon oxide (SiO₂). q , provided that it includes at least one of 0.8≤q≤2.5).

[0060] As an example, the cathode active material may include graphite and silicon (Si)-containing particles together, and the graphite may include one or more of natural graphite having a layered crystal structure and artificial graphite having an isotropic structure, and the silicon (Si)-containing particles may include silicon (Si) particles, silicon oxide (SiO, SiO2) particles, or a mixture of silicon (Si) particles and silicon oxide (SiO, SiO2) particles as a metal component.

[0061]

[0062] In addition, the present invention provides a method for manufacturing a negative electrode for a secondary battery as described above. In one embodiment, the method for manufacturing a negative electrode for a secondary battery according to the present invention comprises: a negative electrode slurry application step of applying a negative electrode slurry to the surface of a negative electrode current collector; and a magnetic field application step of applying a magnetic field to the applied negative electrode slurry. When the magnetic field application step is divided into an outer region including one or more of an upper region adjacent to an electrode tab and a lower region opposite thereto, and a central region excluding the outer region, the value according to Equation 2 below can be controlled to be 500 or more.

[0063] [Equation 2]

[0064] [MF out ] - [MF in ]

[0065] In the above Equation 2,

[0066] The above MF in represents the strength (G) of the magnetic field applied to the central region, and the MF out represents the strength (G) of the magnetic field applied to the external region.

[0067] Specifically, the value according to the above Equation 2 is in the range of 500 to 8,000(G), 1,000 to 8,000(G), 1,500 to 6,000(G), 2,000 to 5,000(G), or 2,800 to 4,000(G).

[0068] The present invention applies a stronger magnetic field to the outer region of the electrode active layer and applies a weak magnetic field to the central region. In the present invention, the meaning of applying a weak magnetic field includes all methods such as reducing the magnetic field strength (G) and applying it, reducing the magnetic field application time (s), and forming a magnetic field shielding structure or a shielding film.

[0069] In one example, in Equation 2 above, [MF outThe value of ] is in the range of 1,000 to 20,000 (G). Specifically, in Equation 2 above, [MF out The value is in the range of 1,000 to 15,000 (G), 2,000 to 20,000 (G), 5,000 to 18,000 (G), 1,000 to 7,000 (G), or 3,000 to 12,000 (G). The present invention is characterized by applying a strong magnetic field to an outer region of the electrode active layer.

[0070] In this regard, in Equation 2 above, [MF in The value of ] is [MF out The control is made to be smaller than the ] value. In the present invention, in Equation 2 above, [MF in ] includes cases where the value is 0, which means cases where no magnetic field is applied to the central region or where the magnetic field is completely shielded.

[0071] In the present invention, after the step of applying a magnetic field, the steps of drying the cathode and rolling are further included. The step of drying the cathode involves drying the cathode slurry to which a magnetic field has been applied at a high temperature to form a cathode active layer on a cathode current collector. The step of drying the cathode can be performed, for example, by applying hot air at a temperature of 160°C to 200°C. The step of rolling the cathode can be performed by applying pressure to the cathode that has undergone the drying process on one or both sides. The method of applying pressure can be performed using a roll press or a plate press, etc. For example, the step of rolling the cathode is performed by rolling with a roll press so that the rolling porosity of the cathode active layer becomes 25±5%.

[0072]

[0073] secondary battery

[0074] The present invention provides a secondary battery comprising the negative electrode described above. In one example, the secondary battery may be a cylindrical, prismatic, or pouch-type secondary battery. For example, the secondary battery is a pouch-type secondary battery. The pouch-type secondary battery comprises an electrode assembly in which a unit structure in which a positive electrode, a separator, and a negative electrode are stacked is repeated.

[0075] The above secondary battery includes an electrode assembly comprising a positive electrode, a negative electrode, and a separator located between the positive and negative electrodes, and a case surrounding the electrode assembly.

[0076] The secondary battery according to the present invention includes an electrode assembly having a structure in which a plurality of positive electrodes and a plurality of negative electrodes are alternately arranged and a separator is located between them. The lithium secondary battery is equipped with the negative electrode of the present invention described above, and has the advantage of having excellent rapid charging performance by improving lithium ion diffusion ability, as well as high energy density.

[0077] At this time, since the cathode active material included in the above cathode has the same composition as described above, a detailed description is omitted. The above cathode may include a cathode current collector and a cathode active material layer located on the cathode current collector and containing a cathode active material. Specifically, the above cathode is manufactured by coating, drying, and rolling a cathode active material on a cathode current collector, and may optionally further include a conductive material, an organic binder polymer, a filler, etc., as needed.

[0078] In this case, the negative electrode active material may comprise 80 to 98 parts by weight of a carbon-based negative electrode active material per 100 parts by weight of the entire negative electrode active layer. Alternatively, the negative electrode active material may comprise 80 to 95 parts by weight of a carbon-based negative electrode active material; and 1 to 20 parts by weight of a silicon (Si)-based negative electrode active material. By controlling the content of graphite and silicon (Si)-containing particles included in the negative electrode active material to the above range, the present invention can improve the charge capacity per unit mass while reducing lithium consumption and irreversible capacity loss during the initial charge and discharge of the battery.

[0079] The above conductive material may include one or more types of carbon black such as acetylene black, Denka black, Ketjen black, Super-P, furnace black, lamp black, and thermal black; graphene; carbon nanotubes and carbon fibers, but is not limited thereto.

[0080] As an example, the above-mentioned cathode active layer may contain carbon black, carbon nanotubes, carbon fibers, etc., as a conductive material, either alone or in combination.

[0081] At this time, the content of the conductive material may be 0.1 to 10 parts by weight per 100 parts by weight of the entire cathode active layer. Specifically, the conductive material may be 0.1 to 8 parts by weight, 0.1 to 5 parts by weight, 0.1 to 3 parts by weight, 2 to 6 parts by weight, or 0.5 to 2 parts by weight per 100 parts by weight of the entire cathode active layer. By controlling the content of the conductive material within the above range, the present invention can prevent the decrease in charging capacity caused by an increase in the resistance of the cathode due to a low content of the conductive material. Furthermore, the present invention can prevent problems such as a decrease in charging capacity due to a decrease in the content of the cathode active material caused by an excessive amount of conductive material exceeding the above range, or an increase in electrical resistance due to an increase in the loading amount of the cathode active layer.

[0082] In addition, the binder is a component that assists in the bonding of the cathode active material and the conductive material, and the bonding to the current collector, and can be appropriately applied within a range that does not degrade the electrical properties of the cathode. For example, the binder may include one or more of vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidenefluoride (PVdF), polyacrylonitrile, polymethylmethacrylate, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene-propylene-diene monomer, sulfonated ethylene-propylene-diene monomer, styrene butadiene rubber (SBR), and fluororubber.

[0083] The content of the binder may be 0.1 to 10 parts by weight per 100 parts by weight of the entire cathode active layer. Specifically, the binder may be 0.1 to 8 parts by weight, 0.1 to 5 parts by weight, 0.1 to 3 parts by weight, or 2 to 6 parts by weight per 100 parts by weight of the entire cathode active layer. By controlling the content of the binder contained in the cathode active layer to the above range, the present invention can prevent the adhesion of the active layer from being reduced due to a low content of binder or the electrical properties of the cathode from being reduced due to an excessive amount of binder.

[0084] In addition, the cathode active material layer may have an average thickness of 100㎛ to 800㎛, and specifically, may have an average thickness of 100㎛ to 780㎛; 100㎛ to 550㎛; 120㎛ to 500㎛; 140㎛ to 200㎛ or 140㎛ to 160㎛.

[0085] In addition, the above-mentioned negative current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, copper, stainless steel, nickel, titanium, calcined carbon, etc. may be used, and in the case of copper or stainless steel, surface-treated carbon, nickel, titanium, silver, etc. may be used.

[0086] In addition, the above-mentioned negative current collector, like the positive current collector, may form fine irregularities on its surface to strengthen the bonding force with the negative active material, and can take various forms such as films, sheets, foils, nets, porous bodies, foams, and nonwoven fabrics. Furthermore, the average thickness of the above-mentioned negative current collector can be appropriately applied in the range of 3 to 500 μm, taking into consideration the conductivity and total thickness of the manufactured negative electrode.

[0087] In addition, the anode comprises an anode active layer containing an anode active material on an anode current collector, and the anode active layer may optionally further include a conductive material, a binder, other additives, etc., as needed.

[0088] The above-mentioned positive active material is a material capable of causing an electrochemical reaction on a positive current collector and may include one or more of lithium metal oxides represented by the following Chemical Formula 1 and Chemical Formula 2, which are capable of reversibly intercalating and deintercalating lithium ions:

[0089] [Chemical Formula 1]

[0090] Li l [Ni m Co n Mn w M 1 v ]O2

[0091] [Chemical Formula 2]

[0092] LiM 2 p Mn q P r O4

[0093] In the above Chemical Formulas 1 and 2,

[0094] M 1 It is one or more elements selected from W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo, and

[0095] l, m, n, w, and v are 1.0≤l≤1.30, 0.5≤m<1, 0, respectively. <n≤0.3, 0<w≤0.3, 0≤v≤0.1이되, m+n+w+v=1이고,

[0096] M 2 is Ni, Co, or Fe, and

[0097] p is 0.05≤p≤1.0, and

[0098] q is 2-p, and

[0099] r is 0 or 1.

[0100] The lithium metal oxides represented by the above chemical formulas 1 and 2 are materials containing high amounts of nickel (Ni) and manganese (Mn), respectively, and when used as cathode active materials, they have the advantage of being able to stably supply high capacity and / or high voltage electricity compared to conventionally used cathode active materials such as lithium iron phosphate oxide (LiFeO4).

[0101] In this case, LiNi is used as the lithium metal oxide represented by the above chemical formula 1. 0.8 Co 0.1 Mn 0.1 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.9 Co 0.05 Mn 0.05 O2, LiNi 0.6 Co 0.2 Mn 0.1 Al 0.1 O2, LiNi 0.6 Co 0.2 Mn 0.15 Al 0.05 O2, LiNi 0.7 Co 0.1 Mn0.1 Al 0.1 The lithium metal oxide represented by the above chemical formula 2 may include O2, etc., and is LiNi 0.7 Mn 1.3 O4; LiNi 0.5 Mn 1.5 O4; LiNi 0.3 Mn 1.7 It may include O4, etc., and can be used alone or in combination.

[0102] In addition, the above-mentioned positive active material may be included in an amount of 85 parts by weight or more based on 100 parts by weight of the total positive active layer. Specifically, the above-mentioned positive active material may be included in an amount of 90 parts by weight or more, 93 parts by weight or more, or 95 parts by weight or more based on 100 parts by weight of the total positive active layer.

[0103] In addition, the above-mentioned positive active layer may further include a conductive material, a binder, other additives, etc., along with the positive active material.

[0104] At this time, the conductive material is used to improve the electrical performance of the anode, and while commonly used in the industry may be applied, specifically, it may include one or more of natural graphite; artificial graphite; carbon black such as acetylene black, Denka black, Ketjen black, Super-P, furnace black, lamp black, and thermal black; graphene; and carbon nanotubes.

[0105] In addition, the conductive material may be included in an amount of 0.1 to 5 parts by weight based on 100 parts by weight of each positive active layer. Specifically, the conductive material may be included in an amount of 0.1 to 4 parts by weight; 2 to 4 parts by weight; 1.5 to 5 parts by weight; 1 to 3 parts by weight; 0.1 to 2 parts by weight; or 0.1 to 1 part by weight based on 100 parts by weight of each positive active layer.

[0106] In addition, the binder serves to bind the cathode active material, cathode additive, and conductive material together, and any binder having this function can be used without particular limitation. Specifically, the binder may include one or more resins selected from polyvinylidenefluoride-hexafluoropropylene copolymer (PVdF-co-HFP), polyvinylidenefluoride (PVdF), polyacrylonitrile, polymethylmethacrylate, and copolymers thereof. As an example, the binder may include polyvinylidenefluoride.

[0107] In addition, the binder may be included in an amount of 1 to 10 parts by weight based on 100 parts by weight of each anode active layer. Specifically, the binder may be included in an amount of 2 to 8 parts by weight or 1 to 5 parts by weight based on 100 parts by weight of the anode active layer.

[0108] The total thickness of the anode active layer is not particularly limited, but specifically may be in the range of 50㎛ to 800㎛, and more specifically may be in the range of 100㎛ to 800㎛; 80㎛ to 150㎛; 120㎛ to 170㎛; 150㎛ to 300㎛; 200㎛ to 600㎛; or 150㎛ to 390㎛.

[0109] In addition, the anode may be used as an anode current collector that has high conductivity without causing chemical changes in the battery. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, etc. may be used, and in the case of aluminum or stainless steel, surface-treated materials such as carbon, nickel, titanium, silver, etc. may be used. Furthermore, the average thickness of the current collector may be appropriately applied from 3㎛ to 500㎛, taking into consideration the conductivity and total thickness of the anode being manufactured.

[0110] In addition, the separator interposed between the positive and negative electrodes of the lithium secondary battery is an insulating thin film having high ion permeability and mechanical strength, and is not particularly limited as long as it is one commonly used in the industry. Specifically, the separator may be one comprising one or more polymers selected from chemically resistant and hydrophobic polypropylene; polyethylene; and polyethylene-propylene copolymer. The separator may have the form of a porous polymer substrate, such as a sheet or nonwoven fabric, containing the aforementioned polymer, and in some cases, may have the form of a composite separator in which organic or inorganic particles are coated on the porous polymer substrate by an organic binder. Furthermore, the separator may have an average pore diameter of 0.01 μm to 10 μm and an average thickness of 5 μm to 300 μm.

[0111] Meanwhile, the secondary battery according to the present invention is not particularly limited, but may be a secondary battery of a form that includes a stack type; a zigzag type; or a zigzag-stack type electrode assembly.

[0112] In addition, the secondary battery according to the present invention may include a lithium salt-containing electrolyte. The lithium salt-containing electrolyte may consist of an electrolyte and a lithium salt, and the electrolyte may be a non-aqueous organic solvent, an organic solid electrolyte, an inorganic solid electrolyte, etc.

[0113] As the above-mentioned non-aqueous organic solvent, for example, aprotic organic solvents such as N-methyl-2-pyrrolidinone, ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-butyrolactone, 1,2-dimethoxyethane, tetrahydroxyfranc, 2-methyl tetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolone, formamide, dimethylformamide, dioxolone, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphate triester, trimethoxymethane, dioxolone derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ether, methyl propionate, ethyl propionate, etc. may be used.

[0114] The above organic solid electrolyte may be, for example, a polyethylene derivative, a polyethylene oxide derivative, a polypropylene oxide derivative, a phosphate ester polymer, agitation lysine, polyester sulfide, polyvinyl alcohol, polyvinylidene fluoride, a polymer containing an ionic dissociator, etc.

[0115] As the above-mentioned inorganic solid electrolyte, for example, nitrides, halides, sulfates of Li such as Li3N, LiI, Li5Ni2, Li3N-LiI-LiOH, LiSiO4, LiSiO4-LiI-LiOH, Li2SiS3, Li4SiO4, Li4SiO4-LiI-LiOH, Li3PO4-Li2S-SiS2, etc., may be used.

[0116] The above lithium salt is a substance that dissolves well in a non-aqueous electrolyte, for example, LiCl, LiBr, LiI, LiClO4, LiBF4, LiB10Cl 10LiPF6, LiCF3SO3, LiCF3CO2, LiAsF6, LiSbF6, LiAlCl4, CH3SO3Li, (CF3SO2)2NLi, lithium chloroborane, lithium lower aliphatic carboxylate, lithium 4-phenylboronicate, imide, etc. may be used.

[0117] In addition, for the purpose of improving charge / discharge characteristics and flame retardancy, the electrolyte may be further enriched with, for example, pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylenediamine, n-glyme, triamide hexaphosphate, nitrobenzene derivative, sulfur, quinone imine dye, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, aluminum trichloride, etc. In some cases, to impart non-flammability, halogen-containing solvents such as carbon tetrachloride and trifluoroethylene may be further enriched, carbon dioxide gas may be further enriched to improve high-temperature storage characteristics, and FEC (Fluoro-Ethylene Carbonate), PRS (Propene Sultone), etc.

[0118] Meanwhile, in one embodiment, the present invention provides a module including the secondary battery described above to a battery pack including the module.

[0119] The above battery pack can be used as a power source for medium-to-large devices requiring high temperature stability, long cycle characteristics, and high rate characteristics. Specific examples of such medium-to-large devices include power tools that are powered by an electric motor; electric vehicles including electric vehicles (EVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs); electric two-wheeled vehicles including electric bicycles (E-bikes) and electric scooters (E-scooters); electric golf carts; and power storage systems. More specifically, hybrid electric vehicles (HEVs) can be cited, but are not limited thereto.

[0120] Furthermore, the above-mentioned positive and negative electrodes may be wound into a jelly roll shape and stored in a cylindrical battery, a prismatic battery, or a pouch-type battery, or stored in a pouch-type battery in a folding or stack-and-folding form. For example, the secondary battery according to the present invention may be a pouch-type battery.

[0121] As described above, the secondary battery according to the present invention can be used in a battery module or battery pack comprising a plurality of unit cells. Specifically, it is useful in fields such as portable devices like mobile phones, laptop computers, and digital cameras, and electric vehicles such as hybrid electric vehicles (HEVs).

[0122]

[0123] Experimental Example 3: Evaluation of Life Characteristics

[0124] For secondary batteries using the positive electrodes of Example 2 and Comparative Example 3, charge and discharge cycles were repeated at room temperature (25°C) under 1 / 3C conditions. The capacity retention rate (%) according to the number of cycles (N) was evaluated. The capacity retention rate at room temperature (25°C) is shown in FIG. 3.

[0125] Referring to FIG. 3, it can be seen that the secondary battery of Example 2 has a superior capacity retention rate compared to Comparative Example 3.

[0126]

[0127] Although the present invention has been described above with reference to preferred embodiments, those skilled in the art or those with ordinary knowledge in the art will understand that various modifications and changes can be made to the present invention without departing from the spirit and technical scope of the invention as described in the claims set forth below.

[0128] Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification, but should be determined by the claims.

[0129]

[0130] [Explanation of the symbol]

[0131] 100, 200: Negative electrode for secondary battery

[0132] 101, 201: Cathode tab

[0133] 111, 211: Upper area

[0134] 112: Sub-region

[0135] 120, 220: Central area

[0136] 130, 230: Cathode active layer

[0137] D1, D2: Total length of the cathode active layer

[0138] D 1A , D 2A : Length of the upper area

[0139] D 1B: Length of the lower area

Claims

1. In a negative electrode for a secondary battery, the negative electrode is, A negative current collector having an electrode tab formed on one side; and A negative active layer is provided on one or both sides of a negative current collector and includes a carbon-based negative active material. The above-mentioned cathode active layer, based on a planar structure, When divided into an outer region including at least one of an upper region adjacent to the electrode tab and a lower region on the opposite side; and a central region excluding the outer region, A negative electrode for a secondary battery having a value of 0.5 or higher according to Formula 1 below: [Equation 1] [DD out ] - [DD in ] In the above Equation 1, The above DD in represents the orientation degree (DD) of the central region, and the said DD out represents the orientation degree (DD) of the outer region, and The above orientation degree (DD) is the sum of peak intensities (I) appearing at non-planar angles when XRD measuring the cathode active layer using CuKα rays. a ) and the sum of peak intensities appearing at all angles (I total The ratio of )(I a / I total It represents ).

2. In Paragraph 1, A negative electrode for a secondary battery, wherein the value according to the above Equation 1 is in the range of 0.5 to 30.

3. In Paragraph 1, In Equation 1 above, [DD out A negative electrode for a secondary battery characterized by a value in the range of 20 to 70.

4. In Paragraph 1, The value according to the above Equation 1 is in the range of 2 to 25, and In Equation 1 above, [DD out A negative electrode for a secondary battery in which the ] value is in the range of 20 to 40.

5. In Paragraph 1, A negative electrode for a secondary battery, wherein the area of ​​the outer region is in the range of 2% to 30% of the area of ​​the negative active layer.

6. In Paragraph 1, The above carbon-based negative electrode active material is a negative electrode for a secondary battery comprising one or more of natural graphite, artificial graphite, Kish graphite, pyrolytic carbon, carbon microbeads, mesophase calcined carbon made from tar and pitch, and graphitized coke.

7. In Paragraph 1, The above-mentioned negative electrode active layer further comprises a silicon-based negative electrode active material as a negative electrode active material, and A negative electrode for a secondary battery, wherein the content of the silicon-based negative electrode active material is in the range of 0.1% to 30% by weight based on the total weight of the negative electrode active material contained in the negative electrode active layer.

8. In Paragraph 7, The above silicon-based negative electrode active material is silicon (Si), silicon carbide (SiC), a composite of carbon and silicon (Si / C), and silicon oxide (SiO₂). q A negative electrode for a secondary battery comprising at least one of the following: , provided that 0.8≤q≤2.5).

9. A cathode slurry application step of applying a cathode slurry to the surface of a cathode current collector; The method includes a magnetic field application step of applying a magnetic field to the coated cathode slurry, wherein The above magnetic field application step is, When divided into an outer region including one or more of an upper region adjacent to the electrode tab and a lower region on the opposite side, and a central region excluding said outer region, A method for manufacturing a negative electrode for a secondary battery, wherein the value according to Formula 2 below is 500 or more: [Equation 2] [MF] out ] - [MF in ] In the above Equation 2, The above MF in represents the strength (G) of the magnetic field applied to the central region, and the MF out represents the strength (G) of the magnetic field applied to the external region.

10. In Paragraph 9, In Equation 2 above, [MF out A method for manufacturing a negative electrode for a secondary battery, characterized in that the value of ] is in the range of 1,000 to 20,000 (G).

11. In Paragraph 9, After the above magnetic field application step, A method for manufacturing a negative electrode for a secondary battery, further comprising the steps of drying the negative electrode and rolling it.

12. A secondary battery comprising a negative electrode according to claim 1.

13. In Paragraph 12, The above secondary battery is characterized by being a pouch-type battery.

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