Lithium secondary battery and secondary battery module including same

Abstract

A lithium secondary battery according to one embodiment includes an electrode assembly (1) in which a first electrode group (2) and a second electrode group (4) are alternately assembled, the first electrode group (2) including one or more first cell cells (10), and the second electrode group (4) including one or more second cell cells (30). The first single cell (10) includes a first negative electrode (11). The first negative electrode (11) includes a first negative electrode mixture layer (111a) on a first negative electrode current collector (110) and a first negative electrode mixture layer (111b) on the first negative electrode mixture layer. The second single cell (30) comprises a second negative electrode (31), and the second negative electrode (31) comprises a second negative electrode mixture layer (311a) on a second negative electrode current collector (310) and a second negative electrode mixture layer (311b) on the second negative electrode mixture layer (311a). The first negative electrode mixture layer (111a) contains a carbon-based active material, and the first negative electrode mixture layer (111b), the second negative electrode mixture layer (311a), and the second negative electrode mixture layer (311b) each contain a silicon-based active material.

Description

Technical Field

[0001] The present invention relates to a lithium secondary battery and a secondary battery module comprising the lithium secondary battery. Background Art

[0002] In recent years, with the increasing concern about environmental issues, many studies are being conducted on electric vehicles (EVs) and hybrid electric vehicles (HEVs). Electric vehicles (EVs) and hybrid electric vehicles (HEVs) can replace vehicles that use fossil fuels, such as gasoline vehicles and diesel vehicles, which are one of the main causes of air pollution. As a power source for such electric vehicles (EVs) and hybrid electric vehicles (HEVs), lithium secondary batteries with high discharge voltage and power stability are mainly used. In addition, with the increasing demand for high-energy secondary batteries with high energy density, the development and research of high-capacity negative electrodes for this purpose are also being actively carried out. Summary of the Invention

[0003] (1) Technical issues to be resolved

[0004] An object of one aspect of the present invention is to provide a lithium secondary battery having excellent energy density.

[0005] Another object of the present invention is to provide a lithium secondary battery having excellent lifespan performance.

[0006] Another object of the present invention is to provide a lithium secondary battery having excellent rapid charging performance.

[0007] Another object of the present invention is to provide a lithium secondary battery having excellent power performance.

[0008] (2) Technical solution

[0009] A lithium secondary battery according to a specific embodiment of the present invention includes an electrode assembly, the electrode assembly being composed of a first electrode group and a second electrode group alternately assembled, the first electrode group including one or more first single cells, and the second electrode group including one or more second single cells. The first single cell includes a first negative electrode, the first negative electrode including a first negative electrode current collector and a first negative electrode mixture layer on the first negative electrode current collector, the first negative electrode mixture layer including a 1-1 negative electrode mixture layer on the first negative electrode current collector and a 1-2 negative electrode mixture layer on the 1-1 negative electrode mixture layer. The second single cell includes a second negative electrode, the second negative electrode including a second negative electrode current collector and a second negative electrode mixture layer on the second negative electrode current collector, the second negative electrode mixture layer including a 2-1 negative electrode mixture layer on the second negative electrode current collector and a 2-2 negative electrode mixture layer on the 2-1 negative electrode mixture layer.

[0010] The first 1-1 negative electrode mixture layer contains a carbon-based active material, and the first 1-2 negative electrode mixture layer, the second 2-1 negative electrode mixture layer, and the second 2-2 negative electrode mixture layer each contain a silicon-based active material. Based on the total weight of the first 1-2 negative electrode mixture layer, the content of the silicon-based active material contained in the first 1-2 negative electrode mixture layer is 7-23% by weight, and the weight of the silicon-based active material contained in the second 2-2 negative electrode mixture layer is greater than or equal to the weight of the silicon-based active material contained in the second 2-1 negative electrode mixture layer.

[0011] In some specific embodiments, the first 1-1 negative electrode mixture layer may contain a combination of artificial graphite and natural graphite as the carbon-based active material.

[0012] In some specific embodiments, the weight of the artificial graphite contained in the first 1-1 negative electrode mixture layer may be greater than or equal to the weight of the natural graphite.

[0013] In some specific embodiments, the first 1-1 negative electrode mixture layer may not contain a silicon-based active material.

[0014] In some specific embodiments, the first 1-2 negative electrode mixture layer, the second 2-1 negative electrode mixture layer, and the second 2-2 negative electrode mixture layer may each further contain a carbon-based active material. The weight of the carbon-based active material contained in the first 1-1 negative electrode mixture layer may be greater than or equal to the weight of the carbon-based active material contained in each of the first 1-2 negative electrode mixture layer, the second 2-1 negative electrode mixture layer, and the second 2-2 negative electrode mixture layer.

[0015] In some specific embodiments, the silicon-based active material may be at least any one selected from Si, SiOx (0 < x < 2), Si-Q alloy (where Q is an element selected from alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, Group 15 elements, Group 16 elements, transition metals, rare earth elements, and combinations thereof, and Q is not Si), and Si-C composite.

[0016] In some specific embodiments, the first 1-2 negative electrode mixture layer may contain a first 1-2 silicon-based active material as the silicon-based active material, the second 2-1 negative electrode mixture layer may contain a second 2-1 silicon-based active material as the silicon-based active material, and the second 2-2 negative electrode mixture layer may contain a second 2-2 silicon-based active material as the silicon-based active material. At least two of the first 1-2 silicon-based active material, the second 2-1 silicon-based active material, and the second 2-2 silicon-based active material may be different from each other.

[0017] In some specific embodiments, the first silicon-based active material, the second silicon-based active material, and the third silicon-based active material can all be different from each other.

[0018] In some specific embodiments, the first silicon-based active material can be a Si-C composite, the second silicon-based active material can be SiOx (0 < x < 2), and the third silicon-based active material can be SiOx (0 < x < 2) doped with metal.

[0019] In some specific embodiments, based on the total weight of the first negative electrode mixture layer, the content of the silicon-based active material in the first negative electrode mixture layer can be 0.1-30% by weight, and based on the total weight of the second negative electrode mixture layer, the content of the silicon-based active material in the second negative electrode mixture layer can be 0.1-30% by weight.

[0020] In some specific embodiments, based on the total weight of the second negative electrode mixture layer, the content of the silicon-based active material contained in the second negative electrode mixture layer can be 1-8% by weight, and based on the total weight of the third negative electrode mixture layer, the content of the silicon-based active material contained in the third negative electrode mixture layer can be 8-15% by weight.

[0021] In some specific embodiments, the first negative electrode mixture layer, the second negative electrode mixture layer, and the third negative electrode mixture layer can each further contain a conductive material.

[0022] In some specific embodiments, the electrode assembly can satisfy the conditions of the following formula 1.

[0023] [Formula 1]

[0024] 0.1 < A1 / A2 < 3.0

[0025] In formula 1, A1 is the total number of the first single cells, and A2 is the total number of the second single cells.

[0026] In some specific embodiments, the electrode assembly can satisfy the conditions of the following formula 2.

[0027] [Formula 2]

[0028] 0.1 < B1 / B2 < 3.0

[0029] In formula 2, B1 is the total number of the first electrode groups, and B2 is the total number of the second electrode groups.

[0030] The secondary battery module according to a specific embodiment includes the lithium secondary battery according to any one of the above specific embodiments.

[0031] (3) Beneficial effects

[0032] According to one embodiment of the present invention, the energy density of a lithium secondary battery can be increased.

[0033] According to another embodiment of the present invention, the lifespan performance of a lithium secondary battery can be improved.

[0034] According to another embodiment of the present invention, the fast charging performance of a lithium secondary battery can be improved.

[0035] According to another embodiment of the present invention, the power performance of a lithium secondary battery can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 is a schematic perspective view showing an assembled structure of a first battery cell and a second battery cell according to a specific embodiment.

[0037] Figure 2a is a cross-sectional view showing the structure of a first negative electrode according to a specific embodiment.

[0038] Figure 2b is a cross-sectional view showing the structure of a second negative electrode according to a specific embodiment.

[0039] Figure 3a and Figure 4a Each of the diagrams is a plan view showing the shape of the assembled structure of the first electrode group and the second electrode group according to a specific embodiment, as viewed from above.

[0040] Figure 3b and Figure 4b Each of the diagrams is a front view showing the shapes of the assembled structures of the first electrode group and the second electrode group according to a specific embodiment, as viewed with reference to the surface where the negative electrode uncoated portion protrudes.

[0041] Figure 3c and Figure 4c Each of the diagrams shows the shape of the assembled structure of the first electrode group and the second electrode group in the electrode assembly according to a specific embodiment, as viewed from the side.

[0042] Figure 3d and Figure 4d Each of the diagrams is a plan view showing the shape of a connection structure between a tab and an electrode lead of each electrode group in an electrode assembly according to a specific embodiment, as viewed from above.

[0043] Figure 3e and Figure 4eEach of the drawings is a diagram showing the shape of a connection structure between a tab and an electrode lead of each electrode group in an electrode assembly according to a specific embodiment, as viewed from the side.

[0044] Description of reference numerals:

[0045] 1: Electrode assembly

[0046] 2: 1st electrode group 4: 2nd electrode group

[0047] 10: 1st single cell 11: 1st negative electrode

[0048] 110: First negative electrode current collector 111: First negative electrode mixture layer

[0049] 111a: 1st-1st negative electrode mixture layer 111b: 1st-2nd negative electrode mixture layer

[0050] 13: 1st positive electrode 15: 1st separator

[0051] 21: First negative electrode uncoated portion 23: First positive electrode uncoated portion

[0052] 30: Second single cell 31: Second negative electrode

[0053] 310: Second negative electrode current collector 311: Second negative electrode mixture layer

[0054] 311a: 2-1st negative electrode mixture layer 311b: 2-2nd negative electrode mixture layer

[0055] 33: Second positive electrode 35: Second separator

[0056] 41: Second negative electrode uncoated portion 43: Second positive electrode uncoated portion

[0057] 211: 1st negative electrode tab 411: 2nd negative electrode tab

[0058] 51: First negative lead 53: Second negative lead DETAILED DESCRIPTION

[0059] In order to achieve a high-capacity and high-energy-density secondary battery, a lithium secondary battery negative electrode according to one embodiment may include a silicon-based active material having a higher discharge capacity than graphite. However, compared to graphite, the silicon-based active material has a larger volume expansion rate and causes relatively large shrinkage / expansion during repeated charge / discharge of the battery, which may cause peeling of the electrode mixture layer, increase in electrode internal resistance, side reactions with the electrolyte, and reduction in electrode life characteristics. In addition, in order to quickly charge the lithium secondary battery, a stable high-rate charging characteristic of the secondary battery may be required.

[0060] According to a specific embodiment of the present invention, a lithium secondary battery having high energy density, excellent life performance, and fast charging performance can be provided. The specific embodiment of the present invention is described in detail below, but its scope is not limited to the specific embodiment described below. In addition, the specific embodiment of the present invention can be applied not only by being limited to the composition of the specific embodiment described below, but also by being constituted by selectively combining all or part of each specific embodiment, thereby allowing various modifications.

[0061] In this specification, when a part is described as being connected to another part, this includes not only direct connections but also indirect connections with other devices interposed therebetween. Furthermore, unless otherwise specifically stated to the contrary, "including a component" means that other components may also be included, not excluding other components.

[0062] In this specification, a single cell is the smallest structural unit of a secondary battery including a positive electrode, a negative electrode, and a separator between the positive and negative electrodes. The first single cell and the second single cell described below refer to single cells that differ from each other in the design of the negative electrode, etc.

[0063] In this specification, an electrode group is a constituent unit including one or more single cells. The first electrode group and the second electrode group described below refer to groups of electrodes respectively including a structure assembled from the first and second single cells.

[0064] In this specification, the electrode assembly is a structural unit including one or more of the first electrode group and the second electrode group, and refers to a structure including a structure in which the first electrode group and the second electrode group are assembled.

[0065] In this specification, the uncoated portion is a portion on the surface of a negative electrode current collector or a positive electrode current collector where the electrode mixture layer is not coated, and refers to a portion located on at least one side of the current collector.

[0066] lithium secondary batteries

[0067] According to a specific embodiment, a lithium secondary battery includes an electrode assembly 1 , which is composed of a first electrode group 2 and a second electrode group 4 alternately assembled. The first electrode group 2 includes one or more first single cells 10 , and the second electrode group 4 includes one or more second single cells 30 .

[0068] The first single battery cell 10 includes a first negative electrode 11, which includes a first negative electrode current collector 110 and a first negative electrode mixture layer 111 on the first negative electrode current collector. The first negative electrode mixture layer 111 includes a 1-1 negative electrode mixture layer 111a on the first negative electrode current collector and a 1-2 negative electrode mixture layer 111b on the 1-1 negative electrode mixture layer.

[0069] The second single battery cell 30 includes a second negative electrode 31, which includes a second negative electrode current collector 310 and a second negative electrode mixture layer 311 on the second negative electrode current collector. The second negative electrode mixture layer 311 includes a 2-1 negative electrode mixture layer 311a on the second negative electrode current collector and a 2-2 negative electrode mixture layer 311b on the 2-1 negative electrode mixture layer.

[0070] The 1-1 negative electrode mixture layer 111a contains a carbon-based active material, and the 1-2 negative electrode mixture layer 111b, the 2-1 negative electrode mixture layer 311a and the 2-2 negative electrode mixture layer 311b each contain a silicon-based active material. Based on the total weight of the 1-2 negative electrode mixture layer 111b, the content of the silicon-based active material contained in the 1-2 negative electrode mixture layer 111b is 7-23% by weight, and the weight of the silicon-based active material contained in the 2-2 negative electrode mixture layer 311b is greater than or equal to the weight of the silicon-based active material contained in the 2-1 negative electrode mixture layer 311a.

[0071] See below Figure 1 , the structure of the electrode assembly included in the lithium secondary battery is described in detail.

[0072] Structure of electrode assembly

[0073] Figure 1 is a schematic perspective view showing an assembled structure of a first battery cell and a second battery cell according to a specific embodiment.

[0074] See also Figure 1 The lithium secondary battery includes an electrode assembly 1, which is composed of a first electrode group 2 and a second electrode group 4 alternately assembled. The first electrode group 2 includes one or more first single cells 10, and the second electrode group 4 includes one or more second single cells 30.

[0075] The first single cell 10 and the second single cell 30 can each have a dual-cell structure (positive electrode-diaphragm-negative electrode-diaphragm-positive electrode) or a single-cell structure (positive electrode-diaphragm-negative electrode), with electrodes of the same polarity located at both ends of the single cell. Depending on the design objectives, a single cell can be assembled from multiple dual cells and single cells. Therefore, the structures of the first and second single cells are not limited to the above scope.

[0076] The first battery cell 10 includes a first negative electrode 11 , and the second battery cell 30 includes a second negative electrode 31 . The first battery cell 10 may further include a first positive electrode 13 and a first separator 15 , and the second battery cell 30 may further include a second positive electrode 33 and a second separator 35 .

[0077] The first electrode group 2 and the second electrode group 4 each include a negative electrode having different active material contents and layer structures, and thus can have different electrochemical properties. Therefore, the electrode assembly including the first and second electrode groups can ensure excellent energy density, lifespan characteristics, power characteristics, rapid charging characteristics, and the like.

[0078] See below Figure 2a and Figure 2b , the first negative electrode 11 and the second negative electrode 31 included in the first electrode group 2 and the second electrode group 4, respectively, will be described in detail.

[0079] Negative electrode design

[0080] Figure 2a is a cross-sectional view showing the structure of a first negative electrode according to a specific embodiment.

[0081] Figure 2b is a cross-sectional view showing the structure of a second negative electrode according to a specific embodiment.

[0082] The first negative electrode 11 and the second negative electrode 31 are multilayer structures each including two or more electrode mixture layers. The first negative electrode includes a first negative electrode current collector 110 and a first negative electrode mixture layer 111 on the first negative electrode current collector. The first negative electrode mixture layer includes a 1-1 negative electrode mixture layer 111a on the first negative electrode current collector and a 1-2 negative electrode mixture layer 111b on the 1-1 negative electrode mixture layer.

[0083] In addition, the second negative electrode 31 includes a second negative electrode current collector 310 and a second negative electrode mixture layer 311 on the second negative electrode current collector. The second negative electrode mixture layer includes a 2-1 negative electrode mixture layer 311 a on the second negative electrode current collector and a 2-2 negative electrode mixture layer 311 b on the 2-1 negative electrode mixture layer.

[0084] According to a specific embodiment, a lithium secondary battery can be provided, which simultaneously includes a first negative electrode and a second negative electrode with different assembly structures using negative electrode mixture layers having different active material contents, etc., so that high-rate charging characteristics, energy density, life characteristics, etc. are excellent.

[0085] The composition of the first negative electrode current collector 110 and the second negative electrode current collector 310 is not particularly limited. For example, the first negative electrode current collector 110 and the second negative electrode current collector 310 can each be a plate or foil formed from one or more of indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), and alloys thereof. In some specific embodiments, the first negative electrode current collector 110 and the second negative electrode current collector 310 can each be copper foil (Cu-foil).

[0086] The thickness of the negative electrode current collector is not particularly limited. For example, the thickness of the negative electrode current collector may be 0.1 μm to 50 μm.

[0087] The 1-1 negative electrode mixture layer 111 a includes a carbon-based active material. Hereinafter, the 1-1 carbon-based active material refers to the carbon-based active material included in the 1-1 negative electrode mixture layer 111 a.

[0088] According to one specific embodiment, in the first negative electrode 11 included in the first electrode group 2, the lower layer 1-1 negative electrode mixture layer 111a may contain only a carbon-based active material as the negative electrode active material and may not contain a silicon-based active material. Therefore, in the first negative electrode 11 included in the first electrode group 2, the negative electrode mixture layer adjacent to the first negative electrode current collector 110 does not contain a silicon-based active material. This can alleviate electrode shedding caused by volume expansion / contraction of the silicon-based active material, and can provide excellent lifespan characteristics.

[0089] The first carbon-based active material may be at least one selected from the group consisting of artificial graphite, natural graphite, amorphous hard carbon, low-crystalline soft carbon, carbon black, acetylene black, Ketjen black, Super P, graphene, and fibrous carbon. Specifically, the first carbon-based active material may include a combination of artificial graphite and natural graphite. That is, according to one embodiment, the first negative electrode mixture layer 111a may include a combination of artificial graphite and natural graphite as the carbon-based active material.

[0090] The strength of the natural graphite is lower than that of artificial graphite, so the graphite particles can be easily compressed when the electrode is rolled. Therefore, in the negative electrode mixture layer comprising a combination of artificial graphite and natural graphite, the conduction path length between the graphite particles can be reduced. Therefore, in the first negative electrode mixture layer 111, when the 1-1 negative electrode mixture layer 111a as the lower layer comprises a combination of artificial graphite and natural graphite as a carbon-based active material and the 1-2 negative electrode mixture layer 111b as the upper layer comprises artificial graphite as a carbon-based active material but does not comprise natural graphite, the electrode density of the lower layer can be relatively greater than the electrode density of the upper layer. In this case, the cell resistance of the upper layer, i.e., the 1-2 negative electrode mixture layer 111b, having a relatively low electrode density can be reduced, thereby improving the high rate charge / discharge characteristics (fast charging performance) of the lithium secondary battery.

[0091] When the first negative electrode mixture layer 111a includes a combination of artificial graphite and natural graphite as the carbon-based active material, the weight of the artificial graphite included in the first negative electrode mixture layer 111a may be greater than or equal to the weight of the natural graphite. Specifically, the weight ratio of the artificial graphite to the natural graphite included in the first negative electrode mixture layer 111a may be 50:50 to 99:1 or 55:45 to 90:10. More specifically, the weight ratio of the artificial graphite to the natural graphite included in the first negative electrode mixture layer 111a may be 60:40 to 80:20.

[0092] When the content ratio of artificial graphite and natural graphite contained in the 1-1 negative electrode mixture layer 111a is adjusted as described above, the negative electrode mixture layer adjacent to the negative electrode current collector can contain an appropriate ratio of artificial graphite having excellent stability, etc. and natural graphite having excellent capacity characteristics, thereby ensuring a more excellent level of life characteristics and capacity characteristics, etc. of the secondary battery.

[0093] The carbon-based active material content of the negative electrode active material contained in the first negative electrode mixture layer 111a may be 90-100% by weight, 95-100% by weight, or 99-100% by weight. Specifically, the first negative electrode mixture layer 111a may contain only the carbon-based active material as the negative electrode active material, and the carbon-based active material content of the negative electrode active material contained in the first negative electrode mixture layer 111a may be substantially 100% by weight.

[0094] According to one embodiment, the first negative electrode mixture layer 111a may contain only a carbon-based active material as the negative electrode active material, and may contain a small amount of silicon-based active material to an extent that does not have a substantial effect, or may not contain any silicon-based active material at all. Therefore, the weight ratio of the carbon-based active material to the silicon-based active material contained in the first negative electrode mixture layer 111a may be 100:0.

[0095] In some specific embodiments, the carbon-based active material content in the 1-1 negative electrode mixture layer 111 a may be 95-99.9 wt %. Specifically, the carbon-based active material content in the 1-1 negative electrode mixture layer 111 a may be 97-99.9 wt %.

[0096] The first-second negative electrode mixture layer 111b, the first-second negative electrode mixture layer 311a, and the second-second negative electrode mixture layer 311b may each further include a carbon-based active material. In this case, the weight of the carbon-based active material included in the first-first negative electrode mixture layer 111a may be greater than or equal to the weight of the carbon-based active material included in each of the first-second negative electrode mixture layer 111b, the first-second negative electrode mixture layer 311a, and the second-second negative electrode mixture layer 311b.

[0097] When the 1-2 negative electrode mixture layer 111b, the 2-1 negative electrode mixture layer 311a and the 2-2 negative electrode mixture layer 311b each further contain a carbon-based active material, the following 1-2 carbon-based active material, 2-1 carbon-based active material and 2-2 carbon-based active material refer to the carbon-based active material contained in the 1-2 negative electrode mixture layer 111b, the 2-1 negative electrode mixture layer 311a and the 2-2 negative electrode mixture layer 311b, respectively.

[0098] Since the 1-2 negative electrode mixture layer 111 b, the 2-1 negative electrode mixture layer 311 a, and the 2-2 negative electrode mixture layer 311 b each contain a silicon-based active material, even if each further contains a carbon-based active material, the content ratio of the carbon-based active material can be lower than the content ratio of the carbon-based active material of the 1-1 negative electrode mixture layer 111 a.

[0099] The carbon-based active material content of the first-second negative electrode mixture layer 111 b may be 60-99.79 wt %. Specifically, the carbon-based active material content of the first-second negative electrode mixture layer 111 b may be 67-92.89 wt %.

[0100] The carbon-based active material content of the 2-1st negative electrode mixture layer 311 a may be 60-99.79 wt %, specifically, 82-92.89 wt %.

[0101] The carbon-based active material content of the 2-2 negative electrode mixture layer 311 b may be 60-99.79 wt %, specifically, 75-91.89 wt %.

[0102] The 1-2 carbon-based active material, the 2-1 carbon-based active material, and the 2-2 carbon-based active material may each be at least one selected from the group consisting of artificial graphite, natural graphite, amorphous hard carbon, low-crystalline soft carbon, carbon black, acetylene black, Ketjen black, SuperP, graphene, and fibrous carbon. Specifically, the 1-2 carbon-based active material, the 2-1 carbon-based active material, and the 2-2 carbon-based active material may each be artificial graphite.

[0103] Natural graphite has a relatively lower strength than artificial graphite. Therefore, when used with a silicon-based active material, the volume expansion of the silicon-based active material caused by battery charge and discharge may not be effectively suppressed. This can increase the internal resistance of the lithium secondary battery, potentially reducing the battery's power characteristics and rapid charging performance. Therefore, when the first-second negative electrode mixture layer 111b, the second-first negative electrode mixture layer 311a, and the second-second negative electrode mixture layer 311b contain both a silicon-based active material and artificial graphite, the occurrence of the above-mentioned problem can be suppressed.

[0104] Hereinafter, the silicon-based active material contained in each of the 1-2 negative electrode mixture layer 111 b , the 2-1 negative electrode mixture layer 311 a , and the 2-2 negative electrode mixture layer 311 b will be described in detail.

[0105] The first-second negative electrode mixture layer 111b, the first-second negative electrode mixture layer 311a, and the second-second negative electrode mixture layer 311b each contain a silicon-based active material. Specifically, the first-second negative electrode mixture layer 111b may contain the first-second silicon-based active material as the silicon-based active material, the second-first negative electrode mixture layer 311a may contain the second-first silicon-based active material as the silicon-based active material, and the second-second negative electrode mixture layer 311b may contain the second-second silicon-based active material as the silicon-based active material.

[0106] The silicon-based active materials may each be at least any one selected from Si, SiOx (0 < x < 2), Si-Q alloys (where Q is an element selected from alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, Group 15 elements, Group 16 elements, transition metals, rare earth elements, and combinations thereof, and Q is not Si), and Si-C composites. Specifically, the first to second silicon-based active materials may each be at least any one selected from the above substances.

[0107] The silicon-based active materials may include one or more silicon-based active material particles selected from the above substances. Among them, the silicon-based active materials may further include a carbon coating formed on the silicon-based active material particles. Thus, it is possible to prevent the silicon-based active material particles from contacting moisture in the atmosphere and / or water in the negative electrode slurry, and it is also possible to suppress a decrease in the discharge capacity of the secondary battery.

[0108] The carbon coating may include at least one selected from amorphous carbon, carbon nanotubes, carbon nanofibers, graphite, graphene, graphene oxide, and reduced graphene oxide.

[0109] In addition, the silicon-based active materials may include silicon-based active material particles doped with a metal. Among them, the metal may be one or more of alkali metals such as lithium (Li) and magnesium (Mg), or alkaline earth metals such as calcium (Ca).

[0110] Specifically, the silicon-based active materials may include silicon-based active material particles doped with magnesium (Mg). The silicon-based active material doped with a metal includes micropores, so it is possible to effectively suppress the expansion of the silicon-based active material during charging / discharging, and it is possible to prevent the phenomena of swelling and cracking of the electrode during charging and discharging, thereby improving the fast charging life characteristics and cycle characteristics at room temperature of the lithium secondary battery.

[0111] According to design purposes and the like, different silicon-based active materials may be applied to each single cell or each negative electrode mixture layer. Specifically, at least two of the first to second silicon-based active materials may be different from each other. According to a specific embodiment satisfying this point, the first to second negative electrode mixture layer 111b may include an Si-C composite as the silicon-based active material, and the second to first negative electrode mixture layer 311a may include SiOx (0 < x < ²) as the silicon-based active material. That is, the first to second silicon-based active material may be an Si-C composite, and the second to first silicon-based active material may be SiOx (0 < x < ²).

[0112] According to another specific embodiment, the first to second negative electrode mixture layer 111b may include a Si-C composite as the silicon-based active material, and the second to second negative electrode mixture layer 311b may include metal-doped SiOx (0 < x < 2) as the silicon-based active material. That is, the first to second silicon-based active material may be a Si-C composite, and the second to second silicon-based active material may be metal-doped SiOx (0 < x < 2).

[0113] According to another specific embodiment, the second to first negative electrode mixture layer 311a may include SiOx (0 < x < 2) as the silicon-based active material, and the second to second negative electrode mixture layer 311b may include metal-doped SiOx (0 < x < 2) as the silicon-based active material. That is, the second to first silicon-based active material may be SiOx (0 < x < 2), and the second to second silicon-based active material may be metal-doped SiOx (0 < x < 2).

[0114] The first to second silicon-based active material, the second to first silicon-based active material, and the second to second silicon-based active material may all be different from each other. Specifically, the first to second negative electrode mixture layer 111b may include a Si-C composite as the silicon-based active material, the second to first negative electrode mixture layer 311a may include SiOx (0 < x < 2) as the silicon-based active material, and the second to second negative electrode mixture layer 311b may include metal-doped SiOx (0 < x < 2) as the silicon-based active material. That is, the first to second silicon-based active material may be a Si-C composite, the second to first silicon-based active material may be SiOx (0 < x < 2), and the second to second silicon-based active material may be metal-doped SiOx (0 < x < 2).

[0115] In the first negative electrode 11 of the multilayer structure included in the first electrode group 2, when a Si-C composite having high-capacity characteristics is used as the silicon-based active material included in the first to second negative electrode mixture layer 111b as the upper layer, compared with a conventional silicon oxide-based (SiOx) active material, a relatively small content of the silicon-based active material may be included. Therefore, even if the first to first negative electrode mixture layer 111a as the lower layer substantially does not include the silicon-based active material, a high-capacity negative electrode can be easily designed. Therefore, the content of the silicon-based active material in the entire negative electrode is reduced, thereby alleviating the occurrence of problems caused by electrode swelling, and a first negative electrode 11 having improved high-rate charging characteristics and the like, a first single cell 10 including the first negative electrode 11, and a first electrode group 2 can be provided.

[0116] In the second negative electrode 31 of the multilayer structure included in the second electrode group 4, when doped metal-containing SiOx (0 < x < 2) is used as the silicon-based active material contained in the upper second-2 negative electrode mixture layer 311b, specifically, when SiO doped with magnesium (Mg) x (0 < x < 2) is used as the silicon-based active material contained in the upper second-2 negative electrode mixture layer 311b, even when a relatively large amount of the silicon-based active material is contained in the upper layer, the occurrence of phenomena such as swelling of the electrode during charge and discharge can be effectively suppressed. Therefore, the content of the silicon-based active material in the upper layer can be easily designed to be relatively higher than that in the lower layer. Therefore, a second negative electrode 31 having excellent capacity characteristics and improved life retention rate, a second single cell 30 including the second negative electrode 31, and a second electrode group 4 can be provided.

[0117] Based on the total weight of the first negative electrode mixture layer, the content of the silicon-based active material contained in the first negative electrode mixture layer 111 can be 0.1 - 30% by weight. Based on the total weight of the second negative electrode mixture layer, the content of the silicon-based active material contained in the second negative electrode mixture layer 311 can be 0.1 - 30% by weight. Specifically, based on the total weight of the first negative electrode mixture layer, the content of the silicon-based active material contained in the first negative electrode mixture layer 111 can be 1 - 15% by weight. Based on the total weight of the second negative electrode mixture layer, the content of the silicon-based active material contained in the second negative electrode mixture layer 311 can be 1 - 15% by weight.

[0118] In some specific embodiments, the content of the silicon-based active material in the above negative electrode mixture layer of each negative electrode can be adjusted differently as follows.

[0119] Based on the total weight of the first-2 negative electrode mixture layer, the content of the silicon-based active material contained in the first-2 negative electrode mixture layer 111b can be 7 - 23% by weight. Specifically, based on the total weight of the first-2 negative electrode mixture layer, the content of the silicon-based active material contained in the first-2 negative electrode mixture layer 111b can be 8% or more or 10% or more, and can be 20% or less or 15% or less.

[0120] Based on the total weight of the second-1 negative electrode mixture layer, the content of the silicon-based active material contained in the second-1 negative electrode mixture layer 311a can be 1 - 8% by weight.

[0121] Based on the total weight of the second-2 negative electrode mixture layer, the content of the silicon-based active material contained in the second-2 negative electrode mixture layer 311b can be 8 - 15% by weight.

[0122] By adjusting the silicon-based active material content characteristics of the first-second negative electrode mixture layer 111b as described above, the content of the silicon-based active material in the upper layer (the first-second negative electrode mixture layer) directly in contact with the electrolyte is adjusted to an appropriate range, thereby smoothly inducing lithium ion migration and ensuring excellent high-rate characteristics. Consequently, the first negative electrode 11, first battery cell 10, and first electrode assembly 2, including the first-second negative electrode mixture layer 111b, can improve the problems caused by the volume expansion / contraction of the silicon-based active material while also exhibiting excellent rapid charging characteristics.

[0123] When the silicon-based active material content characteristics of each of the 2-1 negative electrode mixture layer 311a and the 2-2 negative electrode mixture layer 311b are adjusted as described above, by adjusting the silicon-based active material content in the lower layer (2-1 negative electrode mixture layer) directly in contact with the second negative electrode current collector 310 to a relatively low content, the occurrence of phenomena such as appearance distortion and outermost layer shedding due to volume expansion / contraction of the silicon-based active material can be alleviated, and the battery can have excellent life retention. Furthermore, by adjusting the silicon-based active material content in the upper layer (2-2 negative electrode mixture layer) directly in contact with the electrolyte to a relatively high content, the overall negative electrode capacity can be increased. Consequently, the second negative electrode 31, the second single cell 30, and the second electrode group 4, including the negative electrode mixture layers, can all have excellent energy density and lifespan characteristics.

[0124] According to a specific embodiment, a lithium secondary battery includes an electrode assembly 1, which introduces a structure composed of a first electrode group 2 with excellent high-rate charging characteristics and low volume expansion rate and a second electrode group 4 with relatively excellent life retention rate and energy density, etc., which are alternately assembled. Therefore, the life characteristics, energy density, fast charging characteristics, etc. can be excellent.

[0125] In addition, even if a specific single cell expands due to a negative electrode that is relatively more affected by the volume expansion of the silicon-based active material, single cells including a negative electrode that is relatively less affected by this effect are assembled at the upper and lower parts, so that the volume expansion of the silicon-based active material in the Z axis (thickness direction) can be uniformly suppressed by its physical pressure, etc.

[0126] Furthermore, the loading weight (LW) ratio of each layer in the first negative electrode mixture layer 111 and the loading weight (LW) ratio of each layer in the second negative electrode mixture layer 311 can be adjusted, taking into account the content characteristics of the silicon-based active material in each negative electrode mixture layer. The loading weight (LW) refers to the amount of the negative electrode mixture layer formed on the current collector, i.e., the layer containing the active material, binder, conductive material, etc., expressed in units of weight per unit area. The area is based on the area of ​​the current collector, and the weight is based on the total weight of the negative electrode mixture layer formed.

[0127] The load weight (LW) ratio of the 1-1 negative electrode mixture layer 111a to the 1-2 negative electrode mixture layer 111b may be 1:3 to 3:1. In addition, the load weight (LW) ratio of the 2-1 negative electrode mixture layer 311a to the 2-2 negative electrode mixture layer 311b may be 1:3 to 3:1.

[0128] The total load weight (LW) of the first negative electrode mixture layer 111 can be 4-15 mg / cm 2 Specifically, the load weight (LW) of the 1-1 negative electrode mixture layer 111a may be 1.38-7.5 mg / cm 2 The load weight (LW) of the first-second negative electrode mixture layer 111b may be 1.38-7.5 mg / cm 2 .

[0129] The total load weight (LW) of the second negative electrode mixture layer 311 can be 5-20 mg / cm 2 Specifically, the load weight (LW) of the 2-1st negative electrode mixture layer 311a may be 2-10.5 mg / cm 2 The load weight (LW) of the 2-2 negative electrode mixture layer 311b may be 2-10.5 mg / cm 2 .

[0130] When the load weight (LW) values ​​and their proportions of each negative electrode mixture layer of each negative electrode are adjusted as described above, even if the content ratios of the silicon-based active material in each layer are different from each other, the content of the silicon-based active material can be adjusted to be within an appropriate range based on the entire negative electrode, thereby enabling a high-capacity negative electrode to be manufactured without causing problems due to volume expansion / contraction of the silicon-based active material.

[0131] The first negative electrode 11 and the second negative electrode 31 may each further include a binder. Specifically, the 1-1 negative electrode mixture layer 111a, the 1-2 negative electrode mixture layer 111b, the 2-1 negative electrode mixture layer 311a, and the 2-2 negative electrode mixture layer 311b may each include a binder.

[0132] Illustrative examples of the binder may be rubber-based binders such as styrene-butadiene rubber (SBR), fluorine-based rubber, ethylene-propylene rubber, butyl acrylate rubber, butadiene rubber, isoprene rubber, acrylonitrile rubber, acrylic rubber, silane rubber, and / or water-soluble polymer-based binders such as carboxymethyl cellulose (CMC), hydroxypropyl methylcellulose, methylcellulose, polyacrylic acid (PAA), polyvinyl alcohol (PVA), and polyvinyl alcohol-polyacrylic acid copolymer (PVA-PAA Copolymer).

[0133] The content of the binder contained in the 1-1 negative electrode mixture layer 111a, the content of the binder contained in the 1-2 negative electrode mixture layer 111b, the content of the binder contained in the 2-1 negative electrode mixture layer 311a, and the content of the binder contained in the 2-2 negative electrode mixture layer 311b may each be 0.1 to 5% by weight. In a specific embodiment in which the 1-1 negative electrode mixture layer 111a does not contain a conductive material, the weight of the binder contained in the 1-1 negative electrode mixture layer 111a may be greater than or equal to the weight of the binder contained in each of the 1-2 negative electrode mixture layer 111b, the 2-1 negative electrode mixture layer 311a, and the 2-2 negative electrode mixture layer 311b.

[0134] The first negative electrode 11 and the second negative electrode 31 may each further include a conductive material. Specifically, the first-second negative electrode mixture layer 111b, the second-first negative electrode mixture layer 311a, and the second-second negative electrode mixture layer 311b may each further include a conductive material. In this case, the first-first negative electrode mixture layer 111a may include a trace amount of conductive material to an extent that does not have a substantial effect, or may not include any conductive material at all.

[0135] The 1-1 negative electrode mixture layer 111a may contain a carbon-based active material, and may substantially contain only a carbon-based active material as a negative electrode active material, without containing a silicon-based active material. In addition, in some specific embodiments, the 1-1 negative electrode mixture layer 111a may contain a combination of artificial graphite and natural graphite as a carbon-based active material. Therefore, even if the 1-1 negative electrode mixture layer 111a does not contain a conductive material, the conductivity inside the mixture layer may be sufficiently high, and may further contain other components such as a binder in the same amount as the content of the excluded conductive material. Therefore, the bonding force between the carbon-based active materials contained in the 1-1 negative electrode mixture layer 111a and the bonding force between the first negative electrode current collector 110 and the 1-1 negative electrode mixture layer 111a in the first negative electrode mixture layer 111 can be improved.

[0136] Examples of the conductive material include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, and carbon nanotubes; 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, etc. These can be used alone or as a mixture of two or more. In some specific embodiments, the conductive material can be at least one selected from multi-walled carbon nanotubes (MWCNTs), single-walled carbon nanotubes (SWCNTs), and graphite.

[0137] In some specific embodiments, the conductive material contained in the 1-2 negative electrode mixture layer 111b and the 2-2 negative electrode mixture layer 311b may be different from the conductive material contained in the 2-1 negative electrode mixture layer 311a. Specifically, the 1-2 negative electrode mixture layer 111b and the 2-2 negative electrode mixture layer 311b may contain single-walled carbon nanotubes (SWCNTs) as the conductive material, and the 2-1 negative electrode mixture layer 311a may contain at least one of multi-walled carbon nanotubes (MWCNTs) and graphite as the conductive material.

[0138] In this case, the first-second negative electrode mixture layer 111b and the second-second negative electrode mixture layer 311b, which are the upper layers of the negative electrode containing a silicon-based active material, contain single-walled carbon nanotubes (SWCNTs), a conductive material with high crystallinity, excellent conductivity, and dispersibility, thereby making it easier to form and maintain a conductive path that can increase electrical contact between the components contained in the negative electrode mixture layer. Therefore, the rapid charging performance of the lithium secondary battery can be improved.

[0139] Furthermore, the 2-1st negative electrode mixture layer 311a as the negative electrode lower layer containing the carbon-based active material contains at least one of graphite and multi-walled carbon nanotubes (MWCNTs), which are conductive materials with low crystallinity, thereby alleviating the problem caused by the volume expansion of the silicon-based active material.

[0140] The content of the single-walled carbon nanotube (SWCNT) included in the 1-2 negative electrode mixture layer 111 b and the 2-2 negative electrode mixture layer 311 b may be 0.05-0.5 wt %, respectively.

[0141] The content of the multi-walled carbon nanotubes (MWCNTs) included in the 2-1st negative electrode mixture layer 311 a may be 0.2-1.5 wt %.

[0142] The content of graphite included in the 2-1st negative electrode mixture layer 311 a may be 2-4 wt %.

[0143] The content of the conductive material included in the 1-2 negative electrode mixture layer 111 b , the content of the conductive material included in the 2-1 negative electrode mixture layer 311 a , and the content of the conductive material included in the 2-2 negative electrode mixture layer 311 b may each be 0.01 to 5 wt %.

[0144] The method for manufacturing the first negative electrode 11 and the second negative electrode 31 is not particularly limited and can be performed using known methods. For example, the first negative electrode 11 can be manufactured by applying a 1-1 negative electrode slurry containing a 1-1 solvent, a 1-1 carbon-based active material, and a 1-1 binder to a first negative electrode current collector 110 by bar coating, casting, or spraying, and drying to form a 1-1 negative electrode mixture layer 111a. Then, applying a 1-2 negative electrode slurry containing a 1-2 solvent, a 1-2 carbon-based active material, a 1-2 silicon-based active material, a 1-2 binder, and a 1-2 conductive material to the 1-1 negative electrode mixture layer by bar coating, casting, or spraying, and drying to form a 1-2 negative electrode mixture layer 111b. The second negative electrode 31 can also be manufactured using the same method.

[0145] The solvent may be, for example, dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water. The amount of the solvent used may be sufficient to dissolve or disperse the active material, the conductive material, and the binder and to provide the composition for forming the negative electrode mixture layer with a viscosity that allows excellent thickness uniformity to be exhibited when the composition is subsequently coated to form the negative electrode mixture layer, taking into account the coating thickness and manufacturing yield of the composition for forming the negative electrode mixture layer.

[0146] There is no particular limitation on the first positive electrode 13 and the second positive electrode 33. For example, the positive electrode may include a positive electrode current collector and a positive electrode mixture layer formed on at least one side of the positive electrode current collector. The positive electrode mixture layer may include a positive electrode active material.

[0147] The composition of the positive electrode current collector is not particularly limited. For example, the positive electrode current collector can be a plate or foil formed from one or more of indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), and alloys thereof. In some specific embodiments, the positive electrode current collector can be aluminum foil (Al-foil).

[0148] The thickness of the positive electrode current collector is not particularly limited. For example, the thickness of the positive electrode current collector may be 0.1 μm to 50 μm.

[0149] In some specific embodiments, the positive electrode mixture layer may include a positive electrode active material. The positive electrode active material is an active material generated from the above-mentioned active material precursor, and is not particularly limited. The positive electrode active material may include a compound that can reversibly intercalate and deintercalate lithium ions. Exemplarily, the positive electrode active material may include lithium-nickel metal oxide. The lithium-nickel metal oxide may further include at least one of cobalt (Co), manganese (Mn), and aluminum (Al).

[0150] In some specific embodiments, the positive active material or the lithium-nickel metal oxide may include a layered structure or a crystal structure represented by the following Chemical Formula 1.

[0151] [Chemical Formula 1]

[0152] Li x Ni a M b O 2+z

[0153] In the chemical formula 1, 0.9≤x≤1.2, 0.6≤a≤0.99, 0.01≤b≤0.4, and -0.5≤z≤0.1 may be satisfied. As described above, M may include Co, Mn, and / or Al.

[0154] The chemical structure represented by the chemical formula 1 represents the bonding relationship contained in the layered structure or crystal structure of the positive electrode active material, and does not exclude other additional elements. For example, M may include Co and / or Mn, and Co and / or Mn may be provided together with Ni as the main active element (main active element) of the positive electrode active material. The chemical formula 1 is provided to represent the bonding relationship of the main active elements, and it should be understood that the chemical formula 1 is a formula including the introduction and substitution of additional elements.

[0155] In some specific embodiments, in addition to the main active element, an auxiliary element for enhancing the chemical stability of the positive electrode active material or the layered structure / crystal structure may be further included. The auxiliary element may be mixed into the layered structure / crystal structure to form a bond, and it should be understood that this situation is also included in the chemical structure represented by Chemical Formula 1.

[0156] For example, the auxiliary element may include at least one of Na, Mg, Ca, Y, Ti, Hf, V, Nb, Ta, Cr, Mo, W, Fe, Cu, Ag, Zn, B, Al, Ga, C, Si, Sn, Sr, Ba, Ra, P, or Zr. The auxiliary element may also function as an auxiliary active element that contributes to the capacity / power activity of the positive electrode active material together with Co or Mn, such as Al.

[0157] Illustratively, the positive active material or the lithium-nickel metal oxide may include a layered structure or a crystal structure represented by the following Chemical Formula 1-1.

[0158] [Chemical Formula 1-1]

[0159] Li x Ni a M1 b1 M2 b2 O 2+z

[0160] In Chemical Formula 1-1, M1 may include Co, Mn, and / or Al. M2 may include the auxiliary elements described above. In Chemical Formula 1-1, 0.9≤x≤1.2, 0.6≤a≤0.99, 0.01≤b1+b2≤0.4, and -0.5≤z≤0.1 may be sufficient.

[0161] The positive electrode active material may further include a coating element or a doping element. For example, an element substantially identical to or similar to the auxiliary element may be used as the coating element or the doping element. For example, one or a combination of two or more of the above elements may be used as the coating element or the doping element.

[0162] The coating element or the doping element may be present on the surface of the lithium-nickel metal oxide particle, or may be permeated through the surface of the lithium-nickel metal oxide particle and included in the bonding structure represented by Chemical Formula 1 or Chemical Formula 1-1.

[0163] The positive electrode active material may include a nickel-cobalt-manganese (NCM)-based lithium oxide. In this case, an NCM-based lithium oxide with an increased nickel content may be used.

[0164] In the NCM-based lithium oxide, the Ni content (e.g., the molar fraction of nickel in the total moles of nickel, cobalt, and manganese) may be greater than 0.6, greater than 0.7, or greater than 0.8. In some embodiments, the Ni content may be 0.8 to 0.95, 0.82 to 0.95, 0.83 to 0.95, 0.84 to 0.95, 0.85 to 0.95, or 0.88 to 0.95.

[0165] In some specific embodiments, the positive electrode active material may further include a lithium cobalt oxide-based active material, a lithium manganese oxide-based active material, a lithium nickel oxide-based active material, or a lithium iron phosphate (LFP)-based active material (e.g., LiFePO4).

[0166] In some specific embodiments, the positive electrode active material may include a Mn-rich-based active material having a chemical structure or crystal structure represented by Chemical Formula 2, a Li rich layered oxide (LLO) / Over Lithiated Oxide (OLO)-based active material, or a Co-less-based active material.

[0167] [Chemical Formula 2]

[0168] p[Li2MnO3]·(1-p)[Li q JO2]

[0169] In Chemical Formula 2, 0 < p < 1, 0.9 ≤ q ≤ 1.2, and J may include at least one element selected from Mn, Ni, Co, Fe, Cr, V, Cu, Zn, Ti, Al, Mg, and B.

[0170] In some specific embodiments, the positive electrode mixture layer may further include an adhesive. The adhesive is not particularly limited. Exemplarily, the adhesive may include one or more of polyvinylidene fluoride (PVDF), styrene-butadiene rubber (SBR), polytetrafluoroethylene (PTFE), polyvinylidene fluoride / hexafluoropropylene copolymer, polyacrylonitrile, and polymethyl methacrylate. According to a specific embodiment, the adhesive may include polyvinylidene fluoride (PVDF).

[0171] The content of the adhesive included in the positive electrode mixture layer is not particularly limited. Exemplarily, the content of the adhesive included in the positive electrode mixture layer may be 0.1 wt% to 10 wt%.

[0172] In some specific embodiments, the positive electrode mixture layer may further include a conductive material. The conductive material is not particularly limited. Exemplarily, the conductive material may include one or more of the following substances: graphite such as natural graphite or artificial graphite; carbon-based substances such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, carbon fiber, and carbon nanotube (CNT); 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.

[0173] The content of the conductive material in the positive electrode mixture layer is not particularly limited. For example, the content of the conductive material in the positive electrode mixture layer may be 0.1 wt % to 10 wt %.

[0174] The first diaphragm 15 and the second diaphragm 35 can be polyolefin-based polymer diaphragms such as polyethylene, polypropylene, glass fiber, polyester, polytetrafluoroethylene, or combinations thereof, and can be in the form of non-woven fabrics or woven fabrics. In addition, to ensure heat resistance or mechanical strength, the diaphragms can be coated with a composition containing a ceramic component, etc., and can optionally be provided as a single-layer structure or a multi-layer structure. As described above, as the first diaphragm 15 and the second diaphragm 35, diaphragms known in the art can be used, and are not limited to the above range.

[0175] See below Figure 1 and Figures 3a to 4e , the assembly structure of the first electrode group 2 and the second electrode group 4 is described in detail.

[0176] Assembly structure of electrode group

[0177] Figure 1 is a schematic perspective view showing an assembled structure of a first battery cell and a second battery cell according to a specific embodiment.

[0178] Figure 3a and Figure 4a Each of the diagrams is a plan view showing the shape of the assembled structure of the first electrode group and the second electrode group according to a specific embodiment, as viewed from above.

[0179] Figure 3b and Figure 4b Each of the diagrams is a front view showing the shapes of the assembled structures of the first electrode group and the second electrode group according to a specific embodiment, as viewed with reference to the surface where the negative electrode uncoated portion protrudes.

[0180] Figure 3c and Figure 4c Each of the diagrams shows the shape of the assembled structure of the first electrode group and the second electrode group in the electrode assembly according to a specific embodiment, as viewed from the side.

[0181] Figure 3d and Figure 4d Each of the diagrams is a plan view showing the shape of a connection structure between a tab and an electrode lead of each electrode group in an electrode assembly according to a specific embodiment, as viewed from above.

[0182] Figure 3e and Figure 4e Each of the drawings is a diagram showing the shape of a connection structure between a tab and an electrode lead of each electrode group in an electrode assembly according to a specific embodiment, as viewed from the side.

[0183] In the lithium secondary battery according to a specific embodiment, the first battery cell 10 and the second battery cell 30 may each include an uncoated portion protruding in the same direction relative to the electrodes of the same polarity (see Figure 1 、 Figure 3a to Figure 3b 、 Figures 4a to 4b Specifically, the first negative electrode 11 and the second negative electrode 31 may include a first negative electrode uncoated portion 21 and a second negative electrode uncoated portion 41, respectively, protruding in the same direction. In addition, the first positive electrode 13 and the second positive electrode 33 may include a first positive electrode uncoated portion 23 and a second positive electrode uncoated portion 43, respectively, protruding in the same direction (a direction different from the direction in which the first negative electrode uncoated portion 21 and the second negative electrode uncoated portion 41 protrude).

[0184] The first negative electrode uncoated portion 21 and the second negative electrode uncoated portion 41 may be formed at different positions relative to the protruding surface. Specifically, the first negative electrode uncoated portion 21 may be formed at the right side relative to the protruding surface, and the second negative electrode uncoated portion 41 may be formed at the left side relative to the protruding surface (see Figure 1 、 Figure 3a to Figure 3b 、 Figures 4a to 4b ), or it could be the other way around.

[0185] The first positive electrode uncoated portion 23 and the second positive electrode uncoated portion 43 may be formed at different positions relative to the protruding surface. Specifically, the first positive electrode uncoated portion 23 may be formed at the left side relative to the protruding surface, and the second positive electrode uncoated portion 43 may be formed at the right side relative to the protruding surface (see Figure 1 、 Figure 3a to Figure 3b 、 Figures 4a to 4b ), or it could be the other way around.

[0186] As described above, the first negative electrode uncoated portion 21 and the second negative electrode uncoated portion 41 as well as the first positive electrode uncoated portion 23 and the second positive electrode uncoated portion 43 are respectively formed at different positions relative to each other in the protruding surface direction of the electrodes of the same polarity (specifically, biased to the left / right side, respectively). Therefore, the internal space utilization can be maximized by connecting each electrode ear described below to a plurality of independent electrode leads, and the energy density of each electrode group and electrode assembly can be greatly improved.

[0187] The width of the first negative electrode uncoated portion 21 and the second negative electrode uncoated portion 41 may be 15 mm to 45 mm. In addition, the width of the first positive electrode uncoated portion 23 and the second positive electrode uncoated portion 43 may be 15 mm to 45 mm.

[0188] The thickness of the first negative electrode uncoated portion 21 and the second negative electrode uncoated portion 41 may be 6 μm to 20 μm. In addition, the thickness of the first positive electrode uncoated portion 23 and the second positive electrode uncoated portion 43 may be 8 μm to 20 μm.

[0189] In addition, the assembly structure of the electrode group according to a specific embodiment is a structure in which the first electrode group 2 including one or more first single cells 10 and the second electrode group 4 including one or more second single cells 30 are alternately assembled, and can be arranged in the order of "~ first electrode group - second electrode group - first electrode group - second electrode group ~" (ABAB) (see Figures 3a to 3e ).

[0190] In addition, according to another specific embodiment, the assembly structure of the electrode group is a structure in which the second electrode group 4 including one or more second single cells 30, the first electrode group 2 including one or more first single cells 10, and the second electrode group 4 including one or more second single cells 30 are alternately assembled, and can be a structure arranged in the order of "~ second electrode group-first electrode group-second electrode group-second electrode group-first electrode group-second electrode group~" (BABBAB) (see Figures 4a to 4e ).

[0191] A lithium secondary battery according to one embodiment may include an electrode assembly 1 satisfying the following Formula 1.

[0192] [Formula 1]

[0193] 0.1 <A1 / A2<3.0

[0194] In Formula 1, A1 is the total number of the first battery cells, and A2 is the total number of the second battery cells.

[0195] Specifically, the A1 / A2 value may be 1.0 to 2.5, or 1.5 to 2.0. In addition, the A1 value may be 1 to 40, or 10 to 30. In addition, the A2 value may be 1 to 20, or 5 to 15.

[0196] A lithium secondary battery according to one embodiment may include an electrode assembly 1 satisfying the following Formula 2.

[0197] [Formula 2]

[0198] 0.1 <B1 / B2<3.0

[0199] In Formula 2, B1 is the total number of the first electrode group, and B2 is the total number of the second electrode group. Specifically, the value of B1 / B2 may be 0.3 to 1.0.

[0200] When the ratio of the total number of the first single cells 10 and the second single cells 30, the ratio of the total number of the first electrode group 2 and the second electrode group 4, etc. are within the above ranges, the number of first single cells and the first electrode group having excellent high-rate characteristics and volume expansion control characteristics, and the number of second single cells and the second electrode group having excellent capacity characteristics and life characteristics, etc. can be appropriately adjusted, thereby manufacturing a hybrid secondary battery having excellent high-rate characteristics, volume expansion control characteristics, capacity characteristics, life characteristics, etc.

[0201] In the first electrode group 2 including one or more first battery cells 10, the first negative electrode uncoated portions 21 included in each first battery cell 10 may be combined to form a first negative electrode tab 211. That is, the lithium secondary battery may include a first negative electrode tab 211 formed by combining one or more first negative electrode uncoated portions 21. Similarly, in the second electrode group 4 including one or more second battery cells 30, the second negative electrode uncoated portions 41 included in each second battery cell 30 may be combined to form a second negative electrode tab 411. That is, the lithium secondary battery may include a second negative electrode tab 411 formed by combining one or more second negative electrode uncoated portions 41.

[0202] The first negative electrode tab 211 and the second negative electrode tab 411 can be connected to different first and second negative electrode leads, 51 and 53, respectively. Specifically, the first and second negative electrode leads can be arranged parallel to each other, and the first and second negative electrode leads 51 and 53 can be connected to a single lead film 600. Thus, the first and second battery cells 10 and 30 can be connected to separate electrode leads, respectively, and different currents can be input and output from a single battery simultaneously or independently, depending on the design purpose.

[0203] The first negative electrode tab 211 and the first negative electrode lead 51 can be connected via a first connecting portion 511 formed therebetween, and the second negative electrode tab 411 and the second negative electrode lead 53 can be connected via a second connecting portion 533 formed therebetween. The first connecting portion 511 and the second connecting portion 533 constitute paths for current input and output, and can be formed to have different dimensions (thickness, width, length, etc.) to reduce internal resistance.

[0204] The first coupling portion 511 and the second coupling portion 533 may be made of different materials. For example, only one of the first coupling portion 511 and the second coupling portion 533 may include a coating layer for reducing electrical resistance, but the present invention is not limited thereto.

[0205] In the case of the assembled structure of the electrode group according to one specific embodiment ( Figures 3a to 3e ), the first negative electrode tab 211 located at the upper portion in the thickness direction based on the first negative electrode lead 51 can be coupled to the upper portion of the first negative electrode lead 51, and thus the first coupling portion 511 can be formed at the upper portion of the first negative electrode lead 51. On the other hand, the second negative electrode tab 411 located at the lower portion in the thickness direction based on the second negative electrode lead 53 can be coupled to the lower portion of the second negative electrode lead 53, and thus the second coupling portion 533 can be formed at the lower portion of the second negative electrode lead 53.

[0206] In the case of the assembled structure of the electrode group according to another specific embodiment ( Figures 4a to 4e ), the first negative electrode tab 211 located at the upper portion in the thickness direction based on the first negative electrode lead 51 can be bonded to the upper portion of the first negative electrode lead 51, and thus the first bonding portion 511 can be formed at the upper portion of the first negative electrode lead 51. On the other hand, the second negative electrode tab 411 located at the upper portion in the thickness direction based on the second negative electrode lead 53 can be bonded to the upper portion of the second negative electrode lead 53, and the second negative electrode tab 411 located at the lower portion in the thickness direction based on the second negative electrode lead 53 can be bonded to the lower portion of the second negative electrode lead 53. Therefore, the second bonding portion 533 can be formed at both the upper and lower portions of the second negative electrode lead 53.

[0207] The assembly structure of the electrode group, the connection structure between the tabs and the electrode leads, etc. of the technology disclosed in this specification are not limited to the above-mentioned specific embodiments and can be configured differently according to design purposes, etc.

[0208] When the above-mentioned assembly structure and connection structure are applied, even if a plurality of electrode groups are assembled, asymmetric expansion of the uncoated portion and the like can be prevented, thereby substantially alleviating the occurrence of problems such as breakage of the uncoated portion and the like.

[0209] The technical features of the above-mentioned negative electrode tab, negative electrode lead, joint, etc. can be similarly applied to the positive electrode, and the detailed description thereof is a repetitive description, so the relevant description is omitted.

[0210] According to a specific embodiment, a lithium secondary battery can be manufactured by inserting the electrode assembly 1 including a structure in which the first electrode group 2 and the second electrode group 4 are alternately assembled into a battery case and then injecting an electrolyte.

[0211] The electrode assembly 1 may be a stacked type electrode assembly, a laminated / stacked type electrode assembly, or a stacked / folded type electrode assembly.

[0212] The battery housing can be a housing commonly used in the art. For example, the battery housing can be cylindrical, prismatic, soft-pack or coin-shaped, preferably soft-pack. In addition, the battery housing can be a structure assembled from an insulating layer, an adhesive layer, a metal film, etc. In order to ensure the mechanical strength of the housing and block moisture and oxygen, the metal film can include aluminum (Al) or the like.

[0213] The electrolyte contains an organic solvent and a lithium salt. The organic solvent acts as a medium that allows the migration of ions involved in the electrochemical reaction of the battery. Exemplarily, the organic solvent can be a carbonate-based solvent, an ester-based solvent, an ether-based solvent, a ketone-based solvent, an alcohol-based solvent or an aprotic solvent, and these can be used alone or in combination of two or more. The mixing ratio when two or more organic solvents are mixed can be appropriately adjusted according to the desired battery performance. The lithium salt is a substance that is dissolved in an organic solvent and serves as a supply source of lithium ions in the battery, can realize the basic operation of the lithium secondary battery and promote the migration of lithium ions between the positive electrode and the negative electrode. As the lithium salt, a well-known substance can be used at a concentration suitable for the purpose. The electrolyte can further contain a well-known solvent as needed, and can contain well-known additives to improve the charge and discharge characteristics and flame retardant properties, etc.

[0214] Battery modules and battery packs

[0215] A secondary battery module according to one embodiment includes the lithium secondary battery described above. Specifically, the secondary battery module is a battery module including a plurality of the lithium secondary batteries described above. By including a plurality of electrode assemblies formed by alternating two electrode groups having different electrochemical properties, the module can achieve excellent lifespan characteristics, rapid charging characteristics, energy density, etc.

[0216] A secondary battery pack according to a specific embodiment includes the secondary battery module. Specifically, the secondary battery pack can be used as a battery pack formed by combining and connecting multiple secondary battery modules including the above-mentioned lithium secondary batteries, and can have excellent usability as a power device for medium and large-scale equipment, such as power tools (power tools), electric vehicles (Electric Vehicles, EVs), hybrid electric vehicles (Hybrid Electric Vehicles, HEVs) and plug-in hybrid electric vehicles (Plug-in Hybrid Electric Vehicles, PHEVs).

[0217] Example

[0218] 1) Manufacturing of single battery cells

[0219] The first and second single-cell batteries including the multi-layer negative electrode structures of the embodiments and comparative examples were manufactured respectively. The coating ratio (based on the loading weight) of each negative electrode mixture layer in the multi-layer negative electrode structure, the type and content characteristics of the silicon-based active material and the carbon-based active material are shown in Tables 1 and 2 below, respectively.

[0220] 2) Manufacturing of electrode assemblies

[0221] A first electrode group consisting of 20 first single cells and two second electrode groups consisting of 11 second single cells are alternately assembled to produce Figures 4a to 4e The stacked electrode assembly shown. In addition, the assembly is performed in such a manner that the uncoated portions of the same polarity form protrusion directions in parallel in the same direction, and the protruding positions of the uncoated portions are set at different positions from each other according to the structure of the single cell. Specifically, the uncoated portion of the first electrode group composed of the first single cell (the first negative electrode uncoated portion) is set to be biased to the right, and the uncoated portion of the second electrode group composed of the second single cell (the second negative electrode uncoated portion) is set to be biased to the left. Taking into account the safety during charging and discharging, the interval between the first negative electrode uncoated portion in the first electrode group and the second negative electrode uncoated portion in the second electrode group is set to maintain 8.0 mm, the width of the first negative electrode uncoated portion is made to 35.0 mm, and the width of the second negative electrode uncoated portion is made to 25.0 mm.

[0222] Next, the first negative electrode tab formed by joining the first negative electrode uncoated portions in the first electrode group is connected to the first negative electrode lead, and the second negative electrode tab formed by joining the second negative electrode uncoated portions in the second electrode group is connected to the second negative electrode lead. The first negative electrode tab is connected so as to be located at the upper portion in the thickness direction based on the first negative electrode lead, and the second negative electrode tab is connected so as to be located at the upper and lower portions in the thickness direction based on the second negative electrode lead (see Figure 4e As described above, when ultrasonically welding the negative electrode tab to the negative electrode lead, by welding the negative electrode tab to the upper and lower portions of the negative electrode lead, the degree of stretching of the multiple uncoated portions can be adjusted to be the same, thereby minimizing the occurrence of defects such as tearing of the substrate.

[0223] 3) Manufacturing of secondary batteries

[0224] The prepared electrode assemblies were respectively placed into soft-pack housings, and three surfaces other than the electrolyte injection surface were sealed. At this time, the sealing was performed in such a way that the part with the tab was included in the sealing portion. The electrolyte was injected through the remaining surfaces other than the sealing portion, and the remaining surfaces were sealed, and then impregnated for more than 12 hours. The electrolyte used was an electrolyte in which 1.1 M LiPF6 was dissolved in a mixed solvent of EC / EMC (25 / 75; volume ratio), and then 8 wt% of fluoroethylene carbonate (FEC), 0.5 wt% of 1,3-propylene sultone (PRS), and 1.0 wt% of 1,3-propane sultone (PS) were added. After that, heat press pre-charging was performed at a current corresponding to an average of 0.5C for 60 minutes. After being stable for more than 12 hours, degassing was carried out, and it was aged for more than 24 hours, and then formation charge and discharge were performed (charging conditions: CC-CV, 0.25C, 4.2V, 0.05C, cut-off; discharging conditions: CC, 0.25C, 2.5V, cut-off). After that, standard charge and discharge were performed (charging conditions: CC-CV, 0.33C, 4.2V, 0.05C, cut-off; discharging conditions: CC, 0.33C, 2.5V, cut-off).

[0225] In Table 1 and Table 2, "○" indicates the inclusion of a conductive material, and "X" indicates the non-inclusion of a conductive material.

[0226] [Table 1]

[0227]

[0228] ※ Carbon-based active material: A = artificial graphite, B = natural graphite

[0229] ※ Silicon-based active material: A = SiOx (0 < x < 2), B = Mg-doped SiOx (0 < x < <2), C = Si-C composite

[0230] ※ Upper-layer conductive material: single-walled carbon nanotube (SWCNT)

[0231] ※ Lower-layer conductive material: multi-walled carbon nanotube (MWCNT)

[0232] [Table 2]

[0233]

[0234] ※ Carbon-based active material: A = artificial graphite

[0235] ※ Silicon-based active material: A = SiOx (0 < x < 2), B = Mg-doped SiOx (0 < x < 2), C = Si-C composite

[0236] ※Upper layer conductive material: single-walled carbon nanotube (SWCNT)

[0237] ※ Bottom layer conductive material: Multi-walled carbon nanotubes (MWCNT)

[0238] 4) Performance evaluation

[0239] (1) Energy density

[0240] The lithium secondary batteries manufactured according to Examples 1 to 5 and Comparative Examples 1 to 5 were charged at a constant current rate of 0.3C until the voltage reached 4.2V, then charged at a constant voltage rate of 4.2V in a constant voltage mode, and then cut off at a current rate of 0.05C. After that, they were discharged at a constant current rate of 0.3C until the voltage reached 2.5V. The discharge capacity (Ah) and energy (Wh) were measured, and the volume of each battery in the 4.2V charged state was measured to calculate the volume-energy density. The results are shown in Table 3 below.

[0241] [Table 3]

[0242]

[0243] (2) Evaluation of electrode volume expansion rate and electrode detachment

[0244] The lithium secondary batteries manufactured according to Examples 1 to 5 and Comparative Examples 1 to 5 were charged at room temperature (25°C) (CC / CV 0.1C 0.01V (vs. Li) 0.01C cutoff) and then disassembled. The thicknesses of the charged first and second single cells were measured.

[0245] The thickness of the negative electrode of the first and second single cells that were not charged (SOC 0%, t1) and the thickness of the negative electrode of the first and second single cells that were charged (SOC 100%, t2) were measured, and the electrode volume expansion rate was calculated using the following formula 3. The results are shown in Table 4 below.

[0246] [Formula 3]

[0247] Expansion rate (%) = (t2-t1) / (t1-thickness of current collector) × 100

[0248] In Formula 3, the thickness of the current collector is the thickness of the negative electrode current collector used in manufacturing the negative electrode of the secondary battery.

[0249] The charged first and second single cells were left at room temperature (25° C.) for 10 minutes without undergoing a separate washing process, and the state of the adhesive surface between the negative electrode current collector and the negative electrode mixture layer was confirmed by appearance. The results are shown in Table 4 below. If no electrode was detached during the appearance confirmation of the charged first and second single cells, "-" was indicated.

[0250] [Table 4]

[0251]

[0252] (3) Resistance characteristics

[0253] The lithium secondary batteries manufactured according to Examples 1 to 5 and Comparative Examples 1 to 5 were adjusted to an SOC of 50% at 25° C., allowed to stand for 1 hour, and then discharged at a current of 1 C for 10 seconds. The resistance characteristics were measured, and the results are shown in Table 5. Specifically, the resistance values ​​of the lithium secondary battery samples were measured according to the following formula 4, and the results are shown in Table 5.

[0254] [Formula 4]

[0255] R=(V0-V1) / I

[0256] In Formula 4, R is the resistance value of the lithium secondary battery, V0 is the voltage of the lithium secondary battery measured after a 1-hour rest period after adjustment to SOC 50% at 25°C, V1 is the voltage of the lithium secondary battery measured after discharging at a current of 1C for 10 seconds, and I is the current value of 1C.

[0257] (4) Power characteristics

[0258] The lithium secondary batteries manufactured in Examples 1 to 5 and Comparative Examples 1 to 5 were charged (CC / CV 0.3C 4.2V 0.05C cut-off) and discharged (CC 0.3C 2.5V cut-off) twice at room temperature (25°C). Subsequently, the batteries were discharged (CC 0.3C) to a SOC of 50% while still charged (CC / CV 0.3C 4.2V 0.05C cut-off). The power (W / kg) during discharge and charge at SOC 50% was measured, and the results are shown in Table 5 below.

[0259] [Table 5]

[0260]

[0261] (5) Lifespan characteristics (normal lifespan / fast charge lifespan)

[0262] [Evaluation of general life characteristics]

[0263] In a chamber maintained at 25°C, the lithium secondary batteries manufactured according to Examples 1 to 5 and Comparative Examples 1 to 5 were evaluated for normal charge life characteristics in the range of SOC 4%-98%. After charging at 0.3C under constant current / constant voltage (CC / CV) conditions to a voltage corresponding to SOC 98%, the battery was cut off at 0.05C, and then discharged at 0.3C under constant current (CC) conditions to a voltage corresponding to SOC 4%, and the discharge capacity was measured. This was repeated 500 cycles, and then the discharge capacity retention rate of the normal (normal temperature) life characteristic evaluation was measured, and the results are shown in Table 6 below.

[0264] [Evaluation of fast charge life characteristics]

[0265] The lithium secondary batteries manufactured according to Examples 1 to 5 and Comparative Examples 1 to 5 were charged at a rate (C-rate) in the range of 3.25C / 3.0C / 2.75C / 2.5C / 2.25C / 2.0C / 1.75C / 1.5C / 1.25C / 1.0C / 0.75C / 0.5C and in a step charging manner so as to reach DOD 72 within 25 minutes, and then discharged at 1 / 3C. The above-mentioned charge and discharge were regarded as one cycle, and fast charging evaluation was performed by repeated cycles. A 10-minute rest time was set between the charge and discharge cycles, and the cycles were repeated 300 times. The fast charging capacity retention rate was then measured, and the results are shown in Table 6 below.

[0266] If the discharge capacity decreased to a level that was difficult to measure before 300 cycles of charge and discharge, it was indicated as “-”.

[0267] [Table 6]

[0268]

[0269] Referring to Tables 1 to 6, when the content of the silicon-based active material in the first-second negative electrode mixture layer exceeded 23% by weight based on the total weight of the first-second negative electrode mixture layer (Comparative Example 1), it was confirmed that the volume expansion rate of the first single cell was very large, and electrode shedding occurred in the first single cell. Furthermore, when the content of the silicon-based active material in the first-second negative electrode mixture layer was less than 7% by weight based on the total weight of the first-second negative electrode mixture layer, it was confirmed that the power characteristics were relatively poor (Comparative Example 2) or the energy density was low (Comparative Example 3).

[0270] Furthermore, in Comparative Examples 4 and 5, in which the second negative electrode mixture layer had a single-layer structure, it was confirmed that the volume expansion rate of the second single cell was very large and the power characteristics were relatively poor. In particular, in Comparative Example 5, electrode detachment was also confirmed in the second single cell.

[0271] On the other hand, in the cases of Examples 1 to 5 in which the content of the silicon-based active material contained in the 1-2 negative electrode mixture layer is 7-23 weight % based on the total weight of the 1-2 negative electrode mixture layer and the weight of the silicon-based active material contained in the 2-2 negative electrode mixture layer is greater than or equal to the weight of the silicon-based active material contained in the 2-1 negative electrode mixture layer, it can be confirmed that the energy density, resistance characteristics, power characteristics, life characteristics, fast charging characteristics, etc. of the lithium secondary battery are excellent.

Claims

1. A lithium secondary battery, the lithium secondary battery comprising an electrode assembly, the electrode assembly being alternately assembled from a first electrode group and a second electrode group, the first electrode group including one or more first monomer cells, the second electrode group including one or more second monomer cells, in, The first monomer cell includes a first negative electrode, the first negative electrode including a first negative electrode current collector and a first negative electrode mixture layer on the first negative electrode current collector, The first negative electrode mixture layer includes a first-1 negative electrode mixture layer on the first negative electrode current collector and a first-2 negative electrode mixture layer on the first-1 negative electrode mixture layer, The second monomer cell includes a second negative electrode, the second negative electrode including a second negative electrode current collector and a second negative electrode mixture layer on the second negative electrode current collector, The second negative electrode mixture layer includes a second-1 negative electrode mixture layer on the second negative electrode current collector and a second-2 negative electrode mixture layer on the second-1 negative electrode mixture layer, The first-1 negative electrode mixture layer contains a carbon-based active material, The first-2 negative electrode mixture layer, the second-1 negative electrode mixture layer, and the second-2 negative electrode mixture layer each contain a silicon-based active material, Based on the total weight of the first-2 negative electrode mixture layer, the content of the silicon-based active material contained in the first-2 negative electrode mixture layer is 7-23% by weight, The weight of the silicon-based active material contained in the second-2 negative electrode mixture layer is greater than or equal to the weight of the silicon-based active material contained in the second-1 negative electrode mixture layer.

2. The lithium secondary battery according to claim 1, wherein The first-1 negative electrode mixture layer contains a combination of artificial graphite and natural graphite as the carbon-based active material.

3. The lithium secondary battery according to claim 2, wherein The weight of the artificial graphite contained in the first-1 negative electrode mixture layer is greater than or equal to the weight of the natural graphite.

4. The lithium secondary battery according to claim 1, wherein The first-1 negative electrode mixture layer does not contain a silicon-based active material.

5. The lithium secondary battery according to claim 1, wherein The first-2 negative electrode mixture layer, the second-1 negative electrode mixture layer, and the second-2 negative electrode mixture layer each further contain a carbon-based active material, The weight of the carbon-based active material contained in the first-1 negative electrode mixture layer is greater than or equal to the weight of the carbon-based active material contained in each of the first-2 negative electrode mixture layer, the second-1 negative electrode mixture layer, and the second-2 negative electrode mixture layer.

6. The lithium secondary battery according to claim 1, wherein The silicon-based active material is at least any one selected from Si, SiOx, Si-Q alloy, and Si-C composite, where 0 < x < 2, the Q is an element selected from alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, Group 15 elements, Group 16 elements, transition metals, rare earth elements, and combinations thereof, and the Q is not Si.

7. The lithium secondary battery according to claim 1, wherein The first-2 negative electrode mixture layer contains a first-2 silicon-based active material as the silicon-based active material, The second-1 negative electrode mixture layer contains a second-1 silicon-based active material as the silicon-based active material, The second-2 negative electrode mixture layer contains a second-2 silicon-based active material as the silicon-based active material, At least two of the first-2 silicon-based active material, the second-1 silicon-based active material, and the second-2 silicon-based active material are different from each other.

8. The lithium secondary battery according to claim 7, wherein The 1-2 silicon-based active material, the 2-1 silicon-based active material, and the 2-2 silicon-based active material are all different from each other.

9. The lithium secondary battery according to claim 8, wherein The first-second silicon-based active material is a Si-C complex, the second-first silicon-based active material is SiOx, and the second-second silicon-based active material is SiOx doped with a metal, wherein 0 <x<2。 10. The lithium secondary battery according to claim 1, wherein Based on the total weight of the first negative electrode mixture layer, the content of the silicon-based active material in the first negative electrode mixture layer is 0.1-30% by weight. The content of the silicon-based active material in the second negative electrode mixture layer is 0.1-30 wt % based on the total weight of the second negative electrode mixture layer.

11. The lithium secondary battery according to claim 1, wherein Based on the total weight of the 2-1st negative electrode mixture layer, the content of the silicon-based active material contained in the 2-1st negative electrode mixture layer is 1-8% by weight. The content of the silicon-based active material in the 2-2 negative electrode mixture layer is 8-15 wt % based on the total weight of the 2-2 negative electrode mixture layer.

12. The lithium secondary battery according to claim 1, wherein The 1-2 negative electrode mixture layer, the 2-1 negative electrode mixture layer, and the 2-2 negative electrode mixture layer each further contain a conductive material.

13. The lithium secondary battery according to claim 1, wherein The electrode assembly satisfies the following conditions: [Formula 1] 0.1 <A1 / A2<3.0 In Formula 1, A1 is the total number of the first battery cells, and A2 is the total number of the second battery cells.

14. The lithium secondary battery according to claim 1, wherein The electrode assembly satisfies the following equation 2: [Formula 2] 0.1 <B1 / B2<3.0 In Formula 2, B1 is the total number of the first electrode group, and B2 is the total number of the second electrode group. 15 . A secondary battery module comprising the lithium secondary battery according to claim 1 .

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