Lithium secondary battery

Abstract

The present application relates to lithium secondary batteries.

Description

[Technical Field]

[0001] This application claims the benefit of the filing date of Korean Patent Application No. 10-2023-0159140, filed with the Korean Intellectual Property Office on November 16, 2023, the entire contents of which are incorporated herein by reference.

[0002] The present application relates to lithium secondary batteries. [Background technology]

[0003] The rapid increase in the use of fossil fuels has led to an increasing demand for alternative and clean energy, and one of the most actively researched fields in this area is power generation and storage using electrochemical reactions.

[0004] Currently, a typical example of an electrochemical element that uses electrochemical energy is a secondary battery, and the range of its use is expanding.

[0005] With the development of mobile device technologies and the increase in demand, the demand for secondary batteries as energy sources is rapidly increasing. Among such secondary batteries, lithium secondary batteries, which have high energy density and voltage, long cycle life, and low self-discharge rate, have been commercialized and are widely used. In addition, active research is being conducted on methods for manufacturing high-density electrodes with higher energy density per unit volume as electrodes for such high-capacity lithium secondary batteries.

[0006] Generally, a secondary battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. The negative electrode contains a negative electrode active material that inserts and extracts lithium ions from the positive electrode. The negative electrode active material may be silicon-based particles with a high discharge capacity.

[0007] In particular, in response to the recent demand for high-density energy batteries, active research is being conducted into methods for increasing capacity by using silicon-based compounds such as Si / C and SiOx as anode active materials, which have capacities more than 10 times greater than graphite-based materials. However, while silicon-based compounds, which are high-capacity materials, have higher capacities than conventional graphite and offer excellent capacity characteristics, they rapidly expand in volume during charging, disrupting the conductive pathway and reducing battery performance, resulting in a decrease in capacity from the start. Furthermore, when silicon-based anodes undergo repeated charge and discharge cycles, lithium ions are not uniformly charged throughout the anode depth, and reactions occur on the surface, accelerating surface degradation. This means that improvements in battery cycle performance are needed.

[0008] Therefore, various methods are being discussed to solve the above problems when using silicon-based compounds as negative electrode active materials, such as adjusting the driving potential, coating an additional thin film on the active material layer, suppressing the volume expansion itself by adjusting the particle size of the silicon-based compound, or developing a binder that controls the volume expansion of the silicon-based compound to prevent the conductive path from being broken.In addition, research is being conducted to improve the life characteristics of silicon-based negative electrodes by limiting the usage ratio of silicon-based active material used during initial charge and discharge through a method of pre-lithiating the silicon-based active material layer, thereby providing the role of a reservoir.

[0009] However, in the case of the above-mentioned method, there is a possibility that the performance of the battery may be deteriorated, so there is a limit to its application, and there is still a limit to the commercialization of the manufacture of anode batteries with a high content of silicon-based compounds.

[0010] Recent research has confirmed that when artificial graphite is used in the anode, although capacity is lower than that of a silicon-based anode, it has excellent cell characteristics. Therefore, the amount of natural graphite used has been reduced and the amount of artificial graphite used has been increased. However, in terms of cost, artificial graphite has a disadvantage in that it requires coke to be calcined and graphitized, which means that the processing costs are higher than those of natural graphite.

[0011] Therefore, ongoing development is underway to develop lithium secondary batteries that can reduce costs and have performance equivalent to or superior to that of conventional batteries. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-080971 Summary of the Invention [Problem to be solved by the invention]

[0013] In this application, we have discovered through research a cell that uses a carbon-based active material in the negative electrode while reducing the amount of artificial graphite used in terms of cost, and that can achieve the same or better cell characteristics as existing cells even with a reduced amount of artificial graphite.

[0014] Therefore, an object of the present application is to provide a lithium secondary battery in which an active material of a specific composition is used in the negative electrode and at the same time the NP ratio is adjusted. [Means for solving the problem]

[0015] One embodiment of the present specification provides a lithium secondary battery including a positive electrode; a negative electrode; a separator interposed between the positive electrode and the negative electrode; and an electrolyte, wherein the negative electrode includes a negative electrode current collector layer; and a negative electrode active material layer including a negative electrode active material layer composition provided on one or both sides of the negative electrode current collector layer, the negative electrode active material layer composition including a carbon-based active material, and including 1 part by weight to 50 parts by weight of artificial graphite having an initial capacity of 330 mAh / g or more, based on 100 parts by weight of the carbon-based active material, and an NP ratio of 110 or more. [Effects of the Invention]

[0016] Because artificial graphite has been shown to have excellent cell properties, the amount of natural graphite used has been reduced and the amount of artificial graphite used has been increased. However, this has led to problems in terms of cost and mass production, as the processing costs are high.

[0017] Therefore, in order to solve the problems of cost and mass production, the present application designed a cell by reducing the amount of artificial graphite used and increasing the amount of natural graphite, and solved the resulting problems by adjusting the NP ratio.

[0018] That is, in the case of the lithium secondary battery according to the present application, artificial graphite having an initial capacity of 330 mAh / g or more is contained in an amount of 1 part by weight to 50 parts by weight based on 100 parts by weight of carbon-based active material, and the NP ratio is adjusted to 110 or more, thereby allowing for a large amount of residual anode. Even if artificial graphite is used in the above range, the deterioration of the cell is not accelerated, thereby ensuring the life characteristics. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a diagram showing a stack structure of a lithium secondary battery according to an embodiment of the present application. DETAILED DESCRIPTION OF THE INVENTION

[0020] Before describing the present invention, some terms will first be defined.

[0021] In this specification, when a part is said to "comprise" a certain component, this does not mean that it may further include other components, unless specifically stated to the contrary, but rather that it does not exclude other components.

[0022] In this specification, "p to q" means "at least p and at most q."

[0023] In this specification, the "specific surface area" is measured by the BET method, and specifically, is calculated from the amount of nitrogen gas adsorption at liquid nitrogen temperature (77 K) using a BELSORP-mini II manufactured by BEL Japan Co., Ltd. That is, in the present application, the BET specific surface area can mean the specific surface area measured by the above-mentioned measurement method.

[0024] In this specification, "Dn" refers to particle size distribution, and refers to the particle size at the n% point in the cumulative particle number distribution by particle size. That is, D50 is the particle size (average particle size, median particle size) at the 50% point in the cumulative particle number distribution by particle size, D90 is the particle size at the 90% point in the cumulative particle number distribution by particle size, and D10 is the particle size at the 10% point in the cumulative particle number distribution by particle size. Meanwhile, particle size distribution may be measured using the laser diffraction method. Specifically, the powder to be measured is dispersed in a dispersion medium and then introduced into a commercially available laser diffraction particle size analyzer (e.g., Microtrac S3500). When the particles pass through a laser beam, the difference in diffraction pattern due to particle size is measured to calculate the particle size distribution.

[0025] As used herein, when a polymer contains a certain monomer as a monomer unit, it means that the monomer participates in a polymerization reaction and is included as a repeating unit in the polymer. As used herein, when a polymer contains a monomer, this is interpreted as the same as when a polymer contains a monomer as a monomer unit.

[0026] In this specification, the term "polymer" is understood to be used in a broad sense, including copolymers, unless otherwise specified as a "homopolymer."

[0027] In this specification, the weight average molecular weight (Mw) and number average molecular weight (Mn) are polystyrene-equivalent molecular weights measured by gel permeation chromatography (GPC) using commercially available monodisperse polystyrene polymers (standard samples) with various degrees of polymerization that are commercially available for molecular weight measurement as standard substances. In this specification, molecular weight means weight average molecular weight unless otherwise specified.

[0028] DETAILED DESCRIPTION OF THE INVENTION The present invention will now be described in detail with reference to the accompanying drawings so that those skilled in the art can easily practice the present invention. However, the present invention may be embodied in many different forms and should not be construed as limited to the following description.

[0029] One embodiment of the present specification provides a lithium secondary battery including a positive electrode; a negative electrode; a separator interposed between the positive electrode and the negative electrode; and an electrolyte, wherein the negative electrode includes a negative electrode current collector layer; and a negative electrode active material layer including a negative electrode active material layer composition provided on one or both sides of the negative electrode current collector layer, the negative electrode active material layer composition including a carbon-based active material, and including 1 part by weight to 50 parts by weight of artificial graphite having an initial capacity of 330 mAh / g or more, based on 100 parts by weight of the carbon-based active material, and an NP ratio of 110 or more.

[0030] In the case of the lithium secondary battery according to the present application, artificial graphite having an initial capacity of 330 mAh / g or more is contained in an amount of 1 part by weight to 50 parts by weight based on 100 parts by weight of a carbon-based active material, and the NP ratio is adjusted to 110 or more, thereby allowing for a large amount of residual anode. Even if artificial graphite is used in the above range, the deterioration of the cell is not accelerated, thereby ensuring the life characteristics.

[0031] 1 is a diagram showing a laminated structure of a lithium secondary battery according to one embodiment of the present application. Specifically, a lithium secondary battery anode 100 including an anode active material layer 20 on one side of an anode current collector layer 10 can be seen, and a lithium secondary battery cathode 200 including a cathode active material layer 40 on one side of a cathode current collector layer 50 can be seen, and the lithium secondary battery anode 100 and lithium secondary battery cathode 200 are shown stacked with a separator 30 sandwiched between them.

[0032] The lithium secondary battery of the present invention will now be described in more detail.

[0033] In the present application, the negative electrode includes a negative electrode current collector layer; and a negative electrode active material layer including a negative electrode active material layer composition provided on one or both surfaces of the negative electrode current collector layer.

[0034] In the present application, the negative electrode active material layer composition includes a carbon-based active material, and may include 1 part by weight to 50 parts by weight of artificial graphite having an initial capacity of 330 mAh / g or more, based on 100 parts by weight of the carbon-based active material.

[0035] In yet another embodiment, the negative electrode active material layer composition includes a carbon-based active material, and may include 1 part by weight to 50 parts by weight, specifically 10 parts by weight to 50 parts by weight, more specifically 30 parts by weight to 50 parts by weight, of artificial graphite having an initial capacity of 330 mAh / g or more, based on 100 parts by weight of the carbon-based active material.

[0036] In one embodiment of the present application, the carbon-based active material may be any material commonly used in carbon materials for lithium secondary batteries, including, for example, natural graphite, artificial graphite, expanded graphite, carbon fiber, non-graphitizable carbon, carbon black, carbon nanotubes, fullerene, or activated carbon, and may be used without limitation. Specifically, the carbon-based active material may be processed into a spherical or dot-like shape before use.

[0037] The present application has the feature that by adjusting the NP ratio (NP Ratio) described below to 110 or more, it is possible to have a large amount of residual anode, and even if artificial graphite is used in the above range, the deterioration of the cell is not accelerated, thereby ensuring the life characteristics.

[0038] In the present application, the artificial graphite may have an initial capacity of 330 mAh / g or more.

[0039] In yet another embodiment, the artificial graphite may have an initial capacity of 330 mAh / g or more, preferably 335 mAh / g or more, and 450 mAh / g or less, preferably 400 mAh / g or less.

[0040] The artificial graphite according to the present application has an initial capacity within the above range, and is a material with a high initial capacity, unlike mesocarbon, which is a type of artificial graphite. In this case, it has the characteristic of being superior in capacitance characteristics to general artificial graphite.

[0041] In one embodiment of the present application, there is provided a lithium secondary battery, wherein the carbon-based active material includes artificial graphite and natural graphite, each having an initial capacity of 330 mAh / g or more, and the weight ratio of the artificial graphite to the natural graphite is 1:99 to 50:50, based on 100 parts by weight of the carbon-based active material.

[0042] That is, the lithium secondary battery according to the present application is characterized by using a carbon-based active material as the negative electrode active material, and by using a mixture of artificial graphite and natural graphite in the above-mentioned ratio, which satisfy a specific initial capacity, as described above. Specifically, using 100% artificial graphite results in excellent resistance and life characteristics, but such artificial graphite is not suitable for mass production due to its high cost and the time required for processing. Therefore, in the present application, natural graphite is mixed in the above-mentioned ratio, and the main objective of the present invention is to solve the resulting performance degradation by adjusting the NP ratio.

[0043] In the present application, the artificial graphite having an initial capacity of 330 mAh / g or more and the natural graphite may be crystalline carbon (Graphite).

[0044] Carbon-based active materials are divided into crystalline carbon (graphite) and amorphous carbon, and amorphous carbon is further divided into hard carbon and soft carbon. The artificial graphite and natural graphite according to the present application are mainly characterized by the use of crystalline carbon (graphite).

[0045] The carbon-based active material according to the present invention is a negative electrode material with a higher capacity than soft carbon or hard carbon, and has the characteristics of being excellent in initial efficiency and cycle characteristics.

[0046] In one embodiment of the present application, there is provided a lithium secondary battery, wherein the negative electrode active material layer composition further comprises at least one material selected from the group consisting of a silicon-based active material, a tin-based active material, a metal-based active material capable of forming an alloy with lithium, a lithium titanium oxide, and a lithium-containing nitride.

[0047] In particular, in the present application, the negative electrode active material layer composition may include a carbon-based active material and a silicon-based active material, and may include 50 parts by weight or less of the silicon-based active material based on 100 parts by weight of the negative electrode active material layer composition.

[0048] In the present application, the negative electrode active material layer composition includes a carbon-based active material and a silicon-based active material, and may include 30 parts by weight or less, preferably 20 parts by weight or less, or may include 1 part by weight or more and 10 parts by weight or more, of the silicon-based active material, based on 100 parts by weight of the negative electrode active material layer composition.

[0049] In the present application, the content of artificial graphite in the carbon-based active material is reduced, which can lead to problems such as reduced resistance and lifespan characteristics. As described above, the above problems can be solved by using a mixture of a carbon-based active material and a silicon-based active material or lithium titanium oxide in the negative electrode active material layer composition.

[0050] In one embodiment of the present application, the silicon-based active material may include one or more selected from the group consisting of SiOx (x = 0), SiOx (0 < x < 2), SiC, and Si alloys.

[0051] In one embodiment of the present application, the silicon-based active material includes one or more selected from the group consisting of SiOx (0 < x < 2), SiC, and Si alloys, and may include 1 part by weight or more of SiOx (0 < x < 2) based on 100 parts by weight of the silicon-based active material.

[0052] In another embodiment, the silicon-based active material includes one or more selected from the group consisting of SiOx (0 < x < 2), SiC, and Si alloys, and may include 1 part by weight or more and 30 parts by weight or more, and may include 99 parts by weight or less of SiOx (0 < x < 2) based on 100 parts by weight of the silicon-based active material.

[0053] In another embodiment, the silicon-based active material may include SiOx (0 < x < 2).

[0054] In another embodiment, the silicon-based active material may consist of SiOx (0 < x < 2).

[0055] In one embodiment of the present application, the negative electrode active material layer composition may include a negative electrode conductive material; and a negative electrode binder.

[0056] Conventionally, it has been common to use only graphite-based compounds as the negative electrode active material. However, recently, as the demand for high-capacity batteries has increased, attempts to use a silicon-based active material in combination to increase the capacity have been increasing. However, in the case of a graphite-based active material or a silicon-based active material, there may be a problem that the volume rapidly expands during the charge / discharge process, damaging the conductive path formed in the negative electrode active material layer.

[0057] Therefore, in one embodiment of the present application, the negative electrode conductive material may include one or more selected from the group consisting of dot-like conductive materials, planar conductive materials, and linear conductive materials.

[0058] In one embodiment of the present application, the dot-like conductive material refers to a dot-like or spherical conductive material that can be used to improve the conductivity of a negative electrode and has conductivity without inducing chemical changes. Specifically, the dot-like conductive material may be at least one selected from the group consisting of natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, conductive fiber, fluorocarbon, aluminum powder, nickel powder, zinc oxide, potassium titanate, titanium oxide, and polyphenylene derivatives, and preferably includes carbon black in view of realizing high conductivity and excellent dispersibility.

[0059] In one embodiment of the present application, the point-like conductive material has a BET specific surface area of ​​40 m 2 / g or more 70m 2 / g or less, preferably 45m 2 / g or more 65m 2 / g or less, more preferably 50m 2 / g or more 60m 2 / g or less.

[0060] In one embodiment of the present application, the dot-like conductive material may have a functional group content (volatile matter) of 0.01% or more and 1% or less, preferably 0.01% or more and 0.3% or less, and more preferably 0.01% or more and 0.1% or less.

[0061] In particular, when the content of functional groups in the dot-like conductive material satisfies the above range, the functional groups present on the surface of the dot-like conductive material exist, and when water is used as a solvent, the dot-like conductive material can be smoothly dispersed in the solvent. In particular, by using a specific silicon-based active material in the present invention, the content of functional groups in the dot-like conductive material can be reduced, thereby having an excellent effect in improving dispersibility.

[0062] In one embodiment of the present application, the active material is characterized by including a dot-like conductive material having a functional group content within the above range together with a silicon-based active material, and the functional group content can be adjusted by the degree of heat treatment of the dot-like conductive material.

[0063] In one embodiment of the present application, the particle size of the dotted conductive material may be 10 nm to 100 nm, preferably 20 nm to 90 nm, and more preferably 20 nm to 60 nm.

[0064] In one embodiment of the present application, the conductive material may include a planar conductive material.

[0065] The planar conductive material can improve conductivity by increasing surface contact between silicon particles in the negative electrode and simultaneously prevent the conductive path from being broken due to volume expansion. The planar conductive material may be referred to as a plate-type conductive material or a bulk-type conductive material.

[0066] In one embodiment of the present application, the planar conductive material may include at least one selected from the group consisting of platelet graphite, graphene, graphene oxide, and graphite flakes, and may preferably be platelet graphite.

[0067] In one embodiment of the present application, the average particle size (D50) of the sheet conductive material may be 2 μm to 7 μm, specifically 3 μm to 6 μm, and more specifically 3.5 μm to 5 μm. When the average particle size satisfies this range, the particle size is sufficient to facilitate dispersion without excessively increasing the viscosity of the negative electrode slurry. Therefore, when dispersing using the same device and time, the dispersion effect is excellent.

[0068] In one embodiment of the present application, there is provided a negative electrode composition in which the planar conductive material has a D10 of 0.5 μm or more and 2.0 μm or less, a D50 of 2.5 μm or more and 3.5 μm or less, and a D90 of 6.5 μm or more and 15.0 μm or less.

[0069] In one embodiment of the present application, the sheet conductive material may be a sheet conductive material having a high BET specific surface area; or a sheet conductive material having a low specific surface area.

[0070] In one embodiment of the present application, the sheet conductive material may be a sheet conductive material with a high specific surface area or a sheet conductive material with a low specific surface area without any restrictions. However, since the sheet conductive material according to the present application may have electrode performance that is affected to some extent by dispersion, it is particularly preferable to use a sheet conductive material with a low specific surface area that does not cause dispersion problems.

[0071] In one embodiment of the present application, the sheet conductive material has a BET specific surface area of ​​0.25 m 2 / g or more.

[0072] In another embodiment, the sheet conductive material has a BET specific surface area of ​​1 m 2 / g or more 500m 2 / g or less, and preferably 5m 2 / g or more 300m 2 / g or less, more preferably 5m 2 / g or more 250m 2 / g.

[0073] The sheet conductive material according to the present application may be a sheet conductive material with a high specific surface area or a sheet conductive material with a low specific surface area.

[0074] In another embodiment, the sheet conductive material is a sheet conductive material having a high specific surface area, and a BET specific surface area of ​​50 m 2 / g or more 500m 2 / g or less, preferably 80m 2 / g or more 300m 2 / g or less, more preferably 100m 2 / g or more 300m 2 / g or less.

[0075] In another embodiment, the sheet conductive material is a sheet conductive material having a low specific surface area, and a BET specific surface area of ​​1 m 2 / g or more 40m 2 / g or less, preferably 5m 2 / g or more 30m 2 / g or less, more preferably 5m 2 / g or more 25m 2 / g or less.

[0076] Other conductive materials include linear conductive materials such as carbon nanotubes. The carbon nanotubes may be bundled carbon nanotubes. The bundled carbon nanotubes may include multiple carbon nanotube units. Specifically, unless otherwise specified, the term "bundle type" refers to a secondary shape in which multiple carbon nanotube units are arranged parallel to each other or twisted together with the longitudinal axes of the carbon nanotube units aligned in substantially the same direction, forming a bundle or rope. The carbon nanotube units each have a cylindrical graphite sheet with a nanometer-sized diameter and an sp2 bonding structure. Depending on the angle and structure of the graphite sheet, the carbon nanotube unit may exhibit conductive or semiconductive properties. Compared to entangled carbon nanotubes, the bundled carbon nanotubes can be more uniformly dispersed during negative electrode fabrication and can smoothly form a conductive network within the negative electrode, thereby improving the conductivity of the negative electrode.

[0077] In one embodiment of the present application, the negative electrode conductive material may be contained in an amount of 0.1 parts by weight to 40 parts by weight, based on 100 parts by weight of the negative electrode active material layer composition.

[0078] In yet another embodiment, the negative electrode conductive material may be contained in an amount of 0.1 parts by weight or more and 40 parts by weight or less, preferably 0.2 parts by weight or more and 30 parts by weight or less, more preferably 0.4 parts by weight or more and 25 parts by weight or less, and most preferably 0.4 parts by weight or more and 10 parts by weight or less, based on 100 parts by weight of the negative electrode active material layer composition.

[0079] In one embodiment of the present application, the negative electrode conductive material may include a sheet conductive material; or a linear conductive material.

[0080] In one embodiment of the present application, the negative electrode conductive material may include a sheet conductive material and a linear conductive material.

[0081] In one embodiment of the present application, the negative electrode conductive material may include dot-shaped conductive material and linear conductive material.

[0082] In one embodiment of the present application, the negative electrode conductive material may include dot-like conductive material.

[0083] In one embodiment of the present application, the negative electrode conductive material may include, based on 100 parts by weight of the negative electrode conductive material, 80 parts by weight or more and 99.9 parts by weight or less of the sheet conductive material; and 0.1 parts by weight or more and 20 parts by weight or less of the linear conductive material.

[0084] In yet another embodiment, the negative electrode conductive material may contain 80 parts by weight or more and 99.9 parts by weight or less, preferably 85 parts by weight or more and 99.9 parts by weight or less, and more preferably 95 parts by weight or more and 98 parts by weight or less of the sheet conductive material, based on 100 parts by weight of the negative electrode conductive material.

[0085] In yet another embodiment, the negative electrode conductive material may contain 0.1 parts by weight or more and 20 parts by weight or less, preferably 0.1 parts by weight or more and 15 parts by weight or less, and more preferably 0.2 parts by weight or more and 5 parts by weight or less of the linear conductive material, based on 100 parts by weight of the negative electrode conductive material.

[0086] In one embodiment of the present application, the negative electrode conductive material may include, based on 100 parts by weight of the negative electrode conductive material, 80 parts by weight or more and 99.9 parts by weight or less of the dot-like conductive material; and 0.1 parts by weight or more and 20 parts by weight or less of the linear conductive material.

[0087] In one embodiment of the present application, the negative electrode conductive material comprises a planar conductive material and a linear conductive material; or a dotted conductive material and a linear conductive material; and by satisfying the above-mentioned compositions and ratios, respectively, the life characteristics of conventional lithium secondary batteries are not significantly affected, and in particular, when the negative electrode conductive material comprises a planar conductive material and a linear conductive material, the number of points at which charging and discharging are possible increases, resulting in excellent output characteristics at a high C rate and a reduced amount of high-temperature gas generation.

[0088] In one embodiment of the present application, the negative electrode conductive material may be made of a linear conductive material.

[0089] In particular, when a linear conductive material is used alone, the tortuosity of the electrode, which is a problem with carbon-based or silicon-based negative electrodes, can be simplified, improving the electrode structure and thereby reducing the resistance to lithium ion migration within the electrode.

[0090] In one embodiment of the present application, when the negative electrode conductive material contains only a linear conductive material, the negative electrode conductive material may be contained in an amount of 0.1 parts by weight or more and 5 parts by weight or less, preferably 0.2 parts by weight or more and 3 parts by weight or less, and more preferably 0.4 parts by weight or more and 1 part by weight or less, based on 100 parts by weight of the negative electrode active material layer composition.

[0091] The anode conductive material according to the present application has a completely different structure from the cathode conductive material used in the cathode. That is, the anode conductive material according to the present application controls the contact points between the silicon-based active material, which experiences a large volume expansion of the electrode during charging and discharging, while the cathode conductive material acts as a buffer during rolling and also provides partial conductivity, and thus has a completely different structure and role from the anode conductive material of the present invention.

[0092] In one embodiment of the present application, the planar conductive material used as the negative electrode conductive material has a structure and function different from that of a carbon-based active material typically used as a negative electrode active material. Specifically, the carbon-based active material used as the negative electrode active material may be artificial graphite or natural graphite, and refers to a material that is processed into a spherical or dot-like shape to facilitate the storage and release of lithium ions.

[0093] Meanwhile, the planar conductive material used as the negative electrode conductive material is a material having a planar or plate-like shape, which may be expressed as plate-like graphite. That is, it is a material contained in the negative electrode active material layer to maintain a conductive path, and it does not function to store and release lithium, but rather to ensure a planar conductive path within the negative electrode active material layer.

[0094] That is, in this application, the use of plate-shaped graphite as a conductive material means that it is processed into a planar or plate-like shape and used as a material to ensure a conductive path rather than to store or release lithium. In this case, the negative electrode active material included therein has high capacity characteristics for storing and releasing lithium and plays a role in storing and releasing all lithium ions transferred from the positive electrode.

[0095] Meanwhile, in the present application, the term "carbon-based active material is used as an active material" means that the carbon-based active material is processed into a dotted or spherical shape and used as a material that stores or releases lithium.

[0096] That is, in one embodiment of the present application, the carbon-based active material, artificial graphite or natural graphite, is dot-like and has a BET specific surface area of ​​0.1 m 2 / g or more 4.5m 2 The plate-shaped graphite, which is a planar conductive material, may have a planar shape and a BET specific surface area of ​​5 m 2 / g or more.

[0097] In one embodiment of the present application, the negative electrode binder may include at least one selected from the group consisting of polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethylmethacrylate, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, polyacrylic acid, and substances in which hydrogen is substituted with Li, Na, Ca, or the like, or may include various copolymers thereof.

[0098] The negative electrode binder according to one embodiment of the present application serves to control the active material and conductive material in order to prevent twisting and deformation of the negative electrode structure during volume expansion and relaxation of the silicon-based active material. As long as the binder fulfills the above-mentioned role, any conventional binder may be used. Specifically, a water-based binder may be used, and more specifically, a PAM-based binder may be used.

[0099] In one embodiment of the present application, the amount of the negative electrode binder may be 30 parts by weight or less, preferably 25 parts by weight or less, more preferably 20 parts by weight or less, or may be 5 parts by weight or more, or 10 parts by weight or more, based on 100 parts by weight of the negative electrode active material layer composition.

[0100] In one embodiment of the present application, there is provided a lithium secondary battery, wherein the thickness of the negative electrode current collector layer is 1 μm or more and 100 μm or less, and the thickness of the negative electrode active material layer is 5 μm or more and 500 μm or less.

[0101] The negative electrode current collector layer typically has a thickness of 1 μm to 100 μm. Such a negative electrode current collector layer is not particularly limited as long as it has high conductivity without inducing chemical changes in the battery, and examples thereof include copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloys. Furthermore, the surface may be provided with fine irregularities to strengthen the binding force of the negative electrode active material, and the negative electrode current collector layer may be used in various forms such as a film, sheet, foil, net, porous material, foam, or nonwoven fabric.

[0102] However, the thickness may vary depending on the type and application of the negative electrode used, and is not limited thereto.

[0103] In one embodiment of the present application, the porosity of the negative electrode active material layer may be in the range of 10% to 60%.

[0104] In another embodiment, the porosity of the negative electrode active material layer may satisfy the range of 10% to 60%, preferably 20% to 50%, more preferably 30% to 45%.

[0105] The porosity varies depending on the composition and content of the active material, conductive material, and binder contained in the negative electrode active material layer, and the electrode is characterized by having an appropriate range of electrical conductivity and resistance.

[0106] In one embodiment of the present application, the positive electrode includes a positive electrode current collector layer; and a positive electrode active material layer including a positive electrode active material layer composition provided on one or both surfaces of the positive electrode current collector layer, and the positive electrode active material layer composition includes a positive electrode active material.

[0107] The positive electrode current collector layer in the positive electrode is not particularly limited as long as it is conductive and does not induce chemical changes in the battery. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. may be used. The positive electrode current collector layer may typically have a thickness of 3 μm to 500 μm, and fine irregularities may be formed on the surface of the current collector to enhance adhesion of the positive electrode active material. The positive electrode current collector layer may be used in various forms, such as a film, sheet, foil, net, porous material, foam, or nonwoven fabric.

[0108] The positive electrode active material may be a commonly used positive electrode active material. Specifically, the positive electrode active material may be a layered compound such as lithium cobalt oxide (LiCoO2) or lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; a lithium iron oxide such as LiFe3O4; 1+c1 Mn 2-c1 O4 (0≦c1≦0.33), lithium manganese oxides such as LiMnO3, LiMn2O3, and LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, V2O5, and Cu2V2O7; chemical formula LiNi 1-c2 M c2 Ni-site type lithium nickel oxide represented by the chemical formula LiMnO2 (wherein M is at least one selected from the group consisting of Co, Mn, Al, Cu, Fe, Mg, B, and Ga, and 0.01≦c2≦0.3 is satisfied); 2-c3 M c3 Examples of the lithium manganese composite oxide include, but are not limited to, lithium manganese composite oxides represented by Li2Mn3MO8 (where M is at least one selected from the group consisting of Co, Ni, Fe, Cr, Zn, and Ta, and satisfying 0.01≦c3≦0.1) or Li2Mn3MO8 (where M is at least one selected from the group consisting of Fe, Co, Ni, Cu, and Zn); and LiMn2O4, in which part of the Li in the chemical formula is substituted with an alkaline earth metal ion. The positive electrode may be Li metal.

[0109] In the present application, the positive electrode active material is LiNi x Co y Mn z O2(x+y+z=1);LiNi a Co b Mn c Al d O2(a+b+c+d=1);LiMn2O4;LiNi 0.5 Mn 1.5 O2; and LiM x Fe y The present invention provides a lithium secondary battery containing one or more selected from the group consisting of PO4 (M: transition metal, x+y=1).

[0110] In the present application, the positive electrode active material layer composition is LiNi x Co y Mn z O2(x+y+z=1);LiNi a Co b Mn c Al d The lithium secondary battery includes O2 (a+b+c+d=1), wherein z is 0.5 or more and c is 0.4 or more.

[0111] That is, the lithium secondary battery according to the present application is characterized by using a Mn-rich positive electrode active material.

[0112] The positive electrode active material layer may contain a positive electrode conductive material and a positive electrode binder in addition to the positive electrode active material described above.

[0113] In this case, the positive electrode conductive material is used to impart conductivity to the electrode and can be any material that does not cause chemical changes in the battery and has electronic conductivity. Specific examples include graphite such as natural graphite and artificial graphite; carbon-based materials such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fiber; metal powder or metal fiber such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive polymers such as polyphenylene derivatives. These may be used alone or in combination.

[0114] The positive electrode binder improves adhesion between positive electrode active material particles and between the positive electrode active material and the positive electrode current collector. Specific examples of the positive electrode binder include polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, and various copolymers thereof. These may be used alone or in combination.

[0115] In the present application, the lithium secondary battery may have an NP ratio of 110 or more.

[0116] In another embodiment, the NP ratio may be 110 or more and 200 or less, 113 or more and 150 or less, or 115 or more and 140 or less.

[0117] By adjusting the NP content within the above range, it is possible to reduce the amount of artificial graphite and increase the amount of natural graphite, while still achieving cell performance comparable to or superior to existing products. That is, when the NP content is adjusted within the above range, it is possible to have a large amount of residual negative electrode, and even when the amount of artificial graphite is reduced and the amount of natural graphite is increased, it is possible to prevent accelerated cell degradation.

[0118] In general, the NP ratio may satisfy the following formula A: [Formula A] N / P ratio = discharge capacity per unit area of ​​negative electrode / discharge capacity per unit area of ​​positive electrode × 100

[0119] In the present invention, the "discharge capacity per unit area" refers to the discharge capacity per unit area of ​​the negative electrode or positive electrode in the first cycle.

[0120] The discharge capacity per unit area of ​​the negative electrode can be obtained as follows. Specifically, a half-cell is prepared using a negative electrode sample containing a negative electrode active material and a counter electrode (e.g., a lithium metal electrode) facing the negative electrode sample. The half-cell is charged and discharged, and the measured discharge capacity is divided by the weight of the negative electrode active material to obtain the "discharge capacity of the negative electrode sample per unit weight of the negative electrode active material." A secondary battery is prepared using a negative electrode containing the same negative electrode active material as the negative electrode active material used in the half-cell and a positive electrode containing the same positive electrode active material. The "discharge capacity of the negative electrode sample per unit weight of the negative electrode active material" is multiplied by the weight of the negative electrode active material contained in the secondary battery, and the result is divided by the area of ​​the negative electrode contained in the secondary battery to obtain the discharge capacity per unit area of ​​the negative electrode.

[0121] The discharge capacity per unit area of ​​the positive electrode can be obtained by the following method. Specifically, a half-cell is prepared using a positive electrode sample containing a positive electrode active material and a counter electrode (e.g., a lithium metal electrode) facing the positive electrode sample. The half-cell is charged and discharged, and the measured discharge capacity is divided by the weight of the positive electrode active material to obtain the "discharge capacity of the positive electrode sample per unit weight of the positive electrode active material." A secondary battery is prepared using a positive electrode containing the same positive electrode active material as the positive electrode active material used in the half-cell and a negative electrode containing the same negative electrode active material. The "discharge capacity of the positive electrode sample per unit weight of the positive electrode active material" is multiplied by the weight of the positive electrode active material contained in the secondary battery, and the result is divided by the area of ​​the positive electrode contained in the secondary battery to obtain the discharge capacity per unit area of ​​the positive electrode.

[0122] The separator separates the negative electrode and the positive electrode and provides a path for lithium ions to move. Any separator typically used in secondary batteries can be used without particular limitations. In particular, a separator with low resistance to ion migration and excellent humidifying ability for the electrolyte is preferred. Specifically, a porous polymer film, such as a porous polymer film made of a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, or an ethylene / methacrylate copolymer, or a laminate structure of two or more layers thereof, can be used. Conventional porous nonwoven fabrics, such as nonwoven fabrics made of high-melting-point glass fibers or polyethylene terephthalate fibers, can also be used. Furthermore, a coated separator containing a ceramic component or a polymeric material to ensure heat resistance or mechanical strength can be used, and it can be selectively used in a single-layer or multi-layer structure.

[0123] Examples of the electrolyte include organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in manufacturing lithium secondary batteries, but are not limited to these.

[0124] Specifically, the electrolyte may include a non-aqueous organic solvent and a metal salt.

[0125] Examples of the non-aqueous organic solvent that can be used include aprotic organic solvents such as N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-butyrolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphoric acid triester, trimethoxymethane, dioxolane derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl propionate, and ethyl propionate.

[0126] In particular, among the carbonate-based organic solvents, cyclic carbonates such as ethylene carbonate and propylene carbonate are preferably used because they are high-viscosity organic solvents with high dielectric constants and good dissociation of lithium salts. Furthermore, when such cyclic carbonates are mixed with linear carbonates having low viscosity and low dielectric constants, such as dimethyl carbonate and diethyl carbonate, in an appropriate ratio, an electrolyte having high electrical conductivity can be produced, and therefore these cyclic carbonates are more preferably used.

[0127] The metal salt may be a lithium salt, which is a substance that is easily dissolved in the non-aqueous electrolyte solution. For example, the anion of the lithium salt may be F - , Cl - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , PF6 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 -, (CF3)5PF - , (CF3)6P - , CF3SO3 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - and (CF3CF2SO2)2N - One or more selected from the group consisting of:

[0128] In addition to the constituent components of the electrolyte, the electrolyte may further contain one or more additives, such as haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinoneimine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride, for the purpose of improving the life characteristics of the battery, suppressing a decrease in battery capacity, and improving the discharge capacity of the battery.

[0129] According to one embodiment of the present invention, there is provided a battery module including the secondary battery as a unit cell, and a battery pack including the same. The battery module and the battery pack include the secondary battery having high capacity, high rate characteristics, and high cycle characteristics, and therefore can be used as a power source for medium- to large-sized devices selected from the group consisting of electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and power storage systems. [Example]

[0130] In the following, preferred embodiments will be presented to aid in understanding the present invention. However, the above embodiments are merely illustrative of the present description, and it will be apparent to those skilled in the art that various changes and modifications are possible within the scope of the present description and technical ideas. Naturally, such changes and modifications fall within the scope of the claims.

[0131] <Production example> <Secondary battery manufacturing> <Example> A carbon-based active material (artificial graphite (D50 = 18 μm): natural graphite (D50 = 18 μm) = 50:50), carbon black, SBR as a binder, and CMC as a thickener were added in a weight ratio of 95.7:1:2.3:1 to distilled water as a solvent for forming a negative electrode slurry to prepare a negative electrode slurry (solid concentration 50 wt%).

[0132] As a mixing method, carbon black, binder, and water were dispersed using a homomixer at a speed of 2500 rpm for 30 minutes, and then the active material (artificial graphite, natural graphite) was added, and then the mixture was dispersed at a speed of 2500 rpm for 30 minutes to prepare a slurry.

[0133] The negative electrode slurry was applied to both sides of a copper current collector (thickness: 15 μm) as a negative electrode current collector at 5.48 mAh / cm 2 The coated material was dried in a vacuum oven at 130°C for 1 hour and roll pressed to form a negative electrode active material layer (negative electrode porosity: 35%).

[0134] As the positive electrode active material, LiNi 0.6 Co 0.2 Mn 0.2O2 (average particle size (D50): 15 μm), carbon black (product name: Super C65, manufacturer: Timcal) as a conductive material, and polyvinylidene fluoride (PVdF) as a binder were added in a weight ratio of 95:2.5:2.5 to N-methyl-2-pyrrolidone (NMP) as a solvent for forming a positive electrode slurry to prepare a positive electrode slurry (solid concentration: 63 wt%).

[0135] The positive electrode current collector was an aluminum current collector (thickness: 15 μm) and the positive electrode slurry was applied to both sides of the collector at 4.0 mAh / cm. 2 The coated material was dried in a vacuum oven at 130°C for 1 hour and roll pressed to form a positive electrode active material layer, thereby preparing a positive electrode (the porosity of the positive electrode was 25%).

[0136] A polyethylene separator was interposed between the positive electrode and the negative electrode of the example, and an electrolyte was injected to prepare a lithium secondary battery (4.2V to 2V, NP ratio 137).

[0137] <Comparative Example> A carbon-based active material (artificial graphite (D50 = 18 μm): natural graphite (D50 = 18 μm) = 80:20), carbon black, SBR as a binder, and CMC as a thickener were added in a weight ratio of 95.7:1:2.3:1 to distilled water as a solvent for forming a negative electrode slurry to prepare a negative electrode slurry (solid concentration 50 wt%).

[0138] As a mixing method, carbon black, binder, and water were dispersed using a homomixer at a speed of 2500 rpm for 30 minutes, and then the active material (artificial graphite, natural graphite) was added, and then the mixture was dispersed at a speed of 2500 rpm for 30 minutes to prepare a slurry.

[0139] The negative electrode slurry was applied to both sides of a copper current collector (thickness: 15 μm) as a negative electrode current collector at 5.48 mAh / cm 2The coated material was dried in a vacuum oven at 130°C for 1 hour and roll pressed to form a negative electrode active material layer (negative electrode porosity: 35%).

[0140] As the positive electrode active material, LiNi 0.6 Co 0.2 Mn 0.2 O2 (average particle size (D50): 15 μm), carbon black (product name: Super C65, manufacturer: Timcal) as a conductive material, and polyvinylidene fluoride (PVdF) as a binder were added in a weight ratio of 95:2.5:2.5 to N-methyl-2-pyrrolidone (NMP) as a solvent for forming a positive electrode slurry to prepare a positive electrode slurry (solid concentration: 63 wt%).

[0141] The positive electrode current collector was an aluminum current collector (thickness: 15 μm) and the positive electrode slurry was applied to both sides of the collector at 4.0 mAh / cm. 2 The coated layer was dried in a vacuum oven at 130°C for 1 hour and then roll pressed to form a positive electrode active material layer (positive electrode porosity: 25%).

[0142] A polyethylene separator was interposed between the positive electrode and the negative electrode of the comparative example, and an electrolyte was injected to prepare a lithium secondary battery (4.2V to 2V, NP ratio 137).

[0143] [Table 1]

[0144] [Experimental Example 1: Lifespan characteristic evaluation] For the secondary batteries including the negative electrodes prepared in the Examples and Comparative Examples, a lifespan evaluation was performed on three cells at a time using an electrochemical charger / discharger, and the capacity retention was evaluated. The secondary batteries were subjected to an in-situ cycle test at 4.2-2.0 V and 1 C / 0.5 C. During the test, the secondary batteries were charged / discharged at 0.33 C / 0.33 C (4.2-2.0 V) every 50 cycles, and the capacity retention was measured. Table 2 below lists the in-situ capacity retention, not the RPT capacity retention.

[0145] Capacity retention rate (%) = {(discharge capacity at Nth cycle) / (discharge capacity at first cycle)} x 100

[0146] [Experimental Example 2: Resistance Increase Rate Measurement Evaluation] In Experimental Example 1, the capacity retention was measured by charging / discharging at 0.33C / 0.33C (4.2-3.0V) every 50 cycles during the test, and then the resistance was measured by discharging at 2.5C pulses at SOC50, and the resistance increase rate was compared and analyzed.

[0147] Furthermore, data were calculated for the life characteristics evaluation and the resistance increase rate measurement evaluation at 100 cycles, 200 cycles, and 400 cycles, respectively, and the results are shown in Table 2 below.

[0148] In Table 2 below, three life evaluations were performed on each of the secondary batteries of the examples, and the results are indicated as Examples 1 to 3. Three life evaluations were performed on each of the secondary batteries of the comparative examples, and the results are indicated as Comparative Examples 1 to 3. The average and standard deviation values ​​of Examples 1 to 3 and Comparative Examples 1 to 3 were entered, respectively.

[0149] [Table 2]

[0150] As can be seen from Tables 1 and 2, in the case of the lithium secondary battery according to the present invention, artificial graphite having an initial capacity of 330 mAh / g or more is contained in an amount of 1 part by weight to 50 parts by weight based on 100 parts by weight of carbon-based active material, and the NP ratio is adjusted to 110 or more, thereby allowing for a large amount of residual anode. Even when artificial graphite is used in the above range, cell degradation is not accelerated, and it has been confirmed that the life characteristics and resistance characteristics are equivalent or improved.

[0151] Additionally, in the comparative example, where artificial graphite was used beyond the scope of the present application, it was difficult to handle and fabricate the electrodes, resulting in a larger standard deviation in the electrochemical performance values ​​than in the examples. In other words, the batteries of the comparative example were not suitable for mass production and had poor processability. Therefore, when the NP ratio is 110 or more, it is preferable to include natural graphite, which is easy to handle, and use a specific weight of artificial graphite according to the present application. [Explanation of symbols]

[0152] 10 Negative electrode current collector layer 20...Negative electrode active material layer 30...Separation membrane 40...Cathode active material layer 50 Positive electrode current collector layer 100...Negative electrode 200...Positive electrode

Claims

1. A lithium secondary battery comprising: a positive electrode; a negative electrode; a separator interposed between the positive electrode and the negative electrode; and an electrolyte, the negative electrode includes a negative electrode current collector layer; and a negative electrode active material layer provided on one or both surfaces of the negative electrode current collector layer, the negative electrode active material layer including a negative electrode active material layer composition, the negative electrode active material layer composition contains a carbon-based active material, Based on 100 parts by weight of the carbon-based active material, the carbon-based active material contains 1 part by weight or more and 50 parts by weight or less of artificial graphite having an initial capacity of 330 mAh / g or more, A lithium secondary battery having an NP ratio of 110 or more.

2. The carbon-based active material includes artificial graphite and natural graphite having an initial capacity of 330 mAh / g or more, 2. The lithium secondary battery of claim 1, wherein a weight ratio of the artificial graphite to the natural graphite is 1:99 to 50:50 based on 100 parts by weight of the carbon-based active material.

3. 2. The lithium secondary battery of claim 1, wherein the negative electrode active material layer composition further comprises at least one selected from the group consisting of a silicon-based active material, a tin-based active material, a metal-based active material capable of forming an alloy with lithium, a lithium-titanium oxide, and a lithium-containing nitride.

4. 2. The lithium secondary battery according to claim 1, wherein an NP ratio is 110 or more and 200 or less.

5. the negative electrode active material layer composition contains a carbon-based active material and a silicon-based active material, The lithium secondary battery according to claim 3 , wherein the silicon-based active material is contained in an amount of 50 parts by weight or less based on 100 parts by weight of the negative electrode active material layer composition.

6. 3. The lithium secondary battery according to claim 2, wherein the artificial graphite having an initial capacity of 330 mAh / g or more and the natural graphite are crystalline carbon.

7. the positive electrode includes a positive electrode current collector layer; and a positive electrode active material layer provided on one or both surfaces of the positive electrode current collector layer, the positive electrode active material layer including a positive electrode active material layer composition, The positive electrode active material layer composition is LiNi ｘ Co ｙ Mn ｚ O ２ (x+y+z=1);LiNi ａ Co ｂ Mn ｃ Al ｄ O ２ (a+b+c+d=1);LiMn ２ O ４ ;LiNi ０．５ Mn １．５ O ２ and LiM ｘ Fe ｙ P.O. ４ 2. The lithium secondary battery according to claim 1, comprising one or more positive electrode active materials selected from the group consisting of (M: transition metal, x+y=1).

8. The positive electrode active material layer composition is LiNi ｘ Co ｙ Mn ｚ O ２ (x + y + z = 1); or LiNi ａ Co ｂ Mn ｃ Al ｄ O ２ (a+b+c+d=1), The z is 0.5 or more, 8. The lithium secondary battery according to claim 7, wherein c is 0.4 or more.

9. the thickness of the negative electrode current collector layer is 1 μm or more and 100 μm or less, 2. The lithium secondary battery according to claim 1, wherein the negative electrode active material layer has a thickness of 5 μm or more and 500 μm or less.

10. the thickness of the positive electrode current collector layer is 1 μm or more and 100 μm or less, 8. The lithium secondary battery according to claim 7, wherein the thickness of the positive electrode active material layer is 5 μm or more and 500 μm or less.

Images