Lithium secondary battery

Abstract

The present invention relates to a lithium secondary battery comprising a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the discharge potential of the negative electrode is controlled to 0-1.5 V (vs. Li / Li+) without using the full profile of the negative electrode, and the cut-off potential of the negative electrode is controlled to be less than the discharge potential of the negative electrode according to the type of the negative electrode, thereby leaving residual negative electrode capacity and thus improving lifespan characteristics.

Description

lithium secondary battery

[0001] This application claims the benefit of Korean Patent Application No. 10-2023-0164404, filed with the Korean Intellectual Property Office on November 23, 2023, the entire contents of which are incorporated herein by reference.

[0002] This application relates to a lithium secondary battery.

[0003] Due to the rapid increase in fossil fuel use, the demand for alternative or clean energy is increasing, and as part of this, the most actively researched field is power generation and storage using electrochemical reactions.

[0004] A representative example of an electrochemical device that currently utilizes this electrochemical energy is the secondary battery, and its application area is gradually expanding.

[0005] With the increasing technological development and demand for mobile devices, the demand for secondary batteries as an energy source is rapidly increasing. Among these secondary batteries, lithium secondary batteries, which boast high energy density and voltage, long cycle life, and low self-discharge rates, are commercialized and widely used. Furthermore, active research is being conducted on methods for manufacturing high-density electrodes with even higher energy density per unit volume as electrodes for these high-capacity lithium secondary batteries.

[0006] Typically, a secondary battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. The negative electrode includes a negative electrode active material that inserts and deintercalates lithium ions from the positive electrode. Silicon particles with a high discharge capacity can be used as the negative electrode active material.

[0007] In particular, due to the recent demand for high-density energy batteries, active research is being conducted on methods to increase capacity by using silicon-based compounds, such as Si / C or SiOx, as anode active materials, which have a capacity more than 10 times greater than graphite-based materials. However, in the case of silicon-based compounds, which are high-capacity materials, compared to the graphite used in the past, the capacity characteristics themselves are excellent, but the volume rapidly expands during the charging process, which cuts off the conductive path, deteriorating the battery characteristics, and consequently, the capacity drops from the beginning. In addition, when the silicon-based anode is repeated, lithium ions are not uniformly charged in the depth direction of the anode, and the reaction proceeds on the surface, accelerating surface degradation, so performance improvement in terms of the battery cycle is necessary.

[0008] Accordingly, in order to solve the above problems when using silicon-based compounds as negative electrode active materials, various methods are being discussed, such as a method of controlling the driving potential, a method of additionally coating a thin film on the active material layer, a method of suppressing the volume expansion itself such as a method of controlling the particle size of the silicon-based compound, or the development of a binder that will control the volume expansion of the silicon-based compound to prevent the conductive path from being cut off. In addition, research is also being conducted to supplement the life characteristics of silicon-based negative electrodes by limiting the proportion of silicon-based active materials used during initial charge and discharge and providing a reservoir role through a method of prelithiating the silicon-based active material layer.

[0009] However, the above methods may actually lower the performance of the battery, so their application is limited, and there are still limitations in the commercialization of negative electrode batteries with a high content of silicon compounds.

[0010] Recently, batteries using NCM cathode materials have been designed with an NP Ratio of around 100-105. This is due to the occurrence of cathode Li plating and the increased cost of excessive cathode use. Recently, designs are being developed to utilize the full profile of the cathode by eliminating residual cathode.

[0011] However, when using a full profile of the negative electrode to avoid leaving residual negative electrode material, problems arise in the life performance of the negative electrode, and in particular, problems arise due to the occurrence of a life degradation phenomenon depending on the type of negative electrode active material. In other words, when using a silicon-based active material with a large capacity in a full profile to secure capacity characteristics, the problem of a reduced lifespan occurred due to volume expansion.

[0012] Therefore, research is needed on how to improve cell performance without using the full profile of the cathode.

[0013] <Prior Art Literature>

[0014] (Patent Document 1) Japanese Patent Publication No. 2009-080971

[0015] The present application has found that cell characteristics can be improved along with life characteristics when the discharge depth of the cathode is controlled (cut-off potential control) without using the full profile of the cathode.

[0016] Accordingly, the present application seeks to provide a lithium secondary battery in which the discharge depth of the negative electrode is controlled.

[0017] One embodiment of the present specification provides a lithium secondary battery comprising a positive electrode; a negative electrode; a separator described between the positive electrode and the negative electrode; and an electrolyte, wherein the negative electrode has a discharge potential controlled to be 0 V or more and 1.5 V or less (vs Li / Li+), has a residual negative electrode capacity defined by the following equation 1 of 2.5% or more, and a cut-off potential of the negative electrode is less than the discharge potential of the negative electrode.

[0018] [Formula 1]

[0019]

[0020] In the lithium secondary battery according to the present application, the full profile of the negative electrode is not used, and the discharge potential of the negative electrode is controlled to be 0 V or more and 1.5 V or less (vs Li / Li+), and the cut-off potential of the negative electrode is adjusted to be lower than the discharge potential of the negative electrode, thereby leaving a residual negative electrode capacity of the negative electrode expressed by the above formula 1. That is, the main feature is that the lifespan characteristics are improved by leaving a residual negative electrode in the range of the above formula 1 without using the negative electrode full profile.

[0021] That is, in the case of the lithium secondary battery according to the present application, the main feature is that the life characteristics of the lithium secondary battery are improved by adjusting the cut-off voltage to leave a residual negative electrode within the range of Equation 1, rather than leaving a residual negative electrode by adjusting the NP ratio.

[0022] Figure 1 is a diagram showing a laminated structure of a lithium secondary battery according to one embodiment of the present application.

[0023] Figure 2 is a diagram showing the charge and discharge profiles and cut-off potential and residual cathode capacity (%) including a carbon-based cathode.

[0024] Figure 3 is a diagram showing the charge and discharge profiles and cut-off potential and residual cathode capacity (%) including a silicon-based cathode.

[0025] Figure 4 is a diagram showing the charge and discharge profiles and cut-off potential and residual cathode capacity (%) including carbon-based and silicon-based cathodes.

[0026] Figures 5 to 9 are diagrams showing three-electrode data for confirming information of examples and comparative examples of the present application.

[0027] Before explaining the present invention, some terms are first defined.

[0028] When a part of this specification is said to "include" a certain component, this does not mean that it excludes other components, but rather that it may include other components, unless otherwise stated.

[0029] In this specification, ‘p to q’ means a range of ‘p or more and q or less.’

[0030] In this specification, "specific surface area" is measured by the BET method, and specifically, is calculated from the nitrogen gas adsorption amount at liquid nitrogen temperature (77K) using BELSORP-mino II of BEL Japan. That is, in this application, the BET specific surface area may mean the specific surface area measured by the above measurement method.

[0031] In this specification, "Dn" means particle size distribution, and means the particle size at the n% point of the cumulative distribution of particle numbers according to particle size. That is, D50 is the particle size (average particle size, center particle size) at the 50% point of the cumulative distribution of particle numbers according to particle size, D90 is the particle size at the 90% point of the cumulative distribution of particle numbers according to particle size, and D10 is the particle size at the 10% point of the cumulative distribution of particle numbers according to particle size. Meanwhile, the particle size distribution can be measured using the laser diffraction method. Specifically, after the target powder is dispersed in a dispersion medium, it is introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac S3500) and the difference in diffraction pattern according to particle size is measured when the particles pass through a laser beam, thereby calculating the particle size distribution.

[0032] As used herein, the term "a polymer comprises a monomer as a monomer unit" means that the monomer participates in a polymerization reaction and is included as a repeating unit within the polymer. As used herein, "a polymer comprises a monomer" is interpreted to mean that the polymer comprises the monomer as a monomer unit.

[0033] In this specification, the term 'polymer' is understood to be used in a broad sense including copolymers unless 'homopolymer' is specified.

[0034] In this specification, the weight average molecular weight (Mw) and number average molecular weight (Mn) are polystyrene-converted molecular weights measured by gel permeation chromatography (GPC) using monodisperse polystyrene polymers (standard samples) of various degrees of polymerization commercially available for molecular weight measurement as standard materials. In this specification, molecular weight means weight average molecular weight unless otherwise specified.

[0035] Hereinafter, the present invention will be described in detail with reference to the drawings so that those skilled in the art can easily practice it. However, the present invention can be implemented in various different forms and is not limited to the following description.

[0036] One embodiment of the present specification provides a lithium secondary battery comprising a positive electrode; a negative electrode; a separator described between the positive electrode and the negative electrode; and an electrolyte, wherein the negative electrode has a discharge potential controlled to be 0 V or more and 1.5 V or less (vs Li / Li+), has a residual negative electrode capacity defined by the following equation 1 of 2.5% or more, and a cut-off potential of the negative electrode is less than the discharge potential of the negative electrode.

[0037] [Formula 1]

[0038]

[0039] In the lithium secondary battery according to the present application, the full profile of the negative electrode is not used, and the discharge potential of the negative electrode is controlled to be 0 V or more and 1.5 V or less (vs Li / Li+), and the cut-off potential of the negative electrode is adjusted to be lower than the discharge potential of the negative electrode, thereby leaving a residual negative electrode capacity of the negative electrode expressed by the above formula 1. That is, the main feature is that the lifespan characteristics are improved by leaving a residual negative electrode in the range of the above formula 1 without using the negative electrode full profile.

[0040] FIG. 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 negative electrode (100) including a negative electrode active material layer (20) on one surface of a negative electrode current collector layer (10) can be confirmed, and a lithium secondary battery positive electrode (200) including a positive electrode active material layer (40) on one surface of a positive electrode current collector layer (50) can be confirmed, and it is shown that the lithium secondary battery negative electrode (100) and the lithium secondary battery positive electrode (200) are formed in a laminated structure with a separator (30) interposed therebetween.

[0041] Below, the lithium secondary battery of the present invention is described in more detail.

[0042] 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 sides of the negative electrode current collector layer.

[0043] In the present application, the negative electrode active material layer includes a negative electrode active material layer composition, and the negative electrode active material layer composition may include a negative electrode active material; a negative electrode conductive material; and a negative electrode binder.

[0044] In the present application, a lithium secondary battery is provided, wherein the negative electrode active material includes at least one selected from the group consisting of a carbon-based active material, a silicon-based active material, a tin-based active material, a metal-based active material capable of being alloyed with lithium, lithium titanium oxide, and a lithium-containing nitride.

[0045] In one embodiment of the present application, the carbon-based active material is, as a representative example, natural graphite, artificial graphite, expanded graphite, carbon fiber, non-graphitizable carbon, graphitizable carbon, carbon black, carbon nanotubes, fullerene, or activated carbon, and can be used without limitation as long as it is commonly used as a carbon material for lithium secondary batteries, and specifically, can be processed into a spherical or dot-shaped form and used.

[0046] In one embodiment of the present application, the silicon-based active material is SiOx (x=0), SiOx (0 <x<2), SiC, 및 Si 합금으로 이루어진 군에서 선택되는 1 이상을 포함할 수 있다.

[0047] In one embodiment of the present application, the silicon-based active material is SiOx (0 <x<2), SiC, 및 Si 합금으로 이루어진 군에서 선택되는 1 이상을 포함하며, 상기 실리콘계 활물질 100 중량부 기준 SiOx (0<x<2)를 1 중량부 이상 포함할 수 있다.

[0048] In another embodiment, the silicon-based active material is SiOx (0 <x<2), SiC, 및 Si 합금으로 이루어진 군에서 선택되는 1 이상을 포함하며, 상기 실리콘계 활물질 100 중량부 기준 SiOx (0<x<2)를 1 중량부 이상, 10 중량부 이상 포함할 수 있으며, 99 중량부 이하 포함할 수 있다.

[0049] In another embodiment, the silicon-based active material is SiOx (0 <x<2)를 포함할 수 있다.

[0050] In another embodiment, the silicon-based active material is SiOx (0 <x<2)로 이루어질 수 있다.

[0051] In one embodiment of the present application, the negative active material may be made of a carbon-based active material.

[0052] In one embodiment of the present application, the negative active material may be made of a silicon-based active material.

[0053] In one embodiment of the present application, a lithium secondary battery is provided in which the negative electrode active material includes a carbon-based active material and a silicon-based active material, and the silicon-based active material is included in an amount of 30 parts by weight or less based on 100 parts by weight of the negative electrode active material.

[0054] In particular, the silicon-based active material as described above has a particularly large change in discharge capacity from 0.2 V to 1.5 V, and when the discharge depth of the negative electrode is controlled as in the present application, the effect of improving cell characteristics can be maximized.

[0055] In addition, even if the composition and content of the negative electrode active material are changed as described above, the life characteristics can be improved by leaving residual negative electrode capacity by controlling the cut-off potential of the negative electrode described later, and the type of negative electrode used can be used without limitation.

[0056] In one embodiment of the present application, a lithium secondary battery is provided in which the negative electrode active material is included in an amount of 60 parts by weight or more based on 100 parts by weight of the negative electrode active material layer composition.

[0057] In another embodiment, the negative active material may be included in an amount of 60 parts by weight or more, 65 parts by weight or more, or 70 parts by weight or more, and may be included in an amount of 90 parts by weight or less, or 85 parts by weight or less, based on 100 parts by weight of the negative active material layer composition.

[0058] 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.

[0059] Previously, graphite compounds were typically used solely as negative electrode active materials. However, with the increasing demand for high-capacity batteries, attempts to mix silicon-based active materials to increase capacity have been increasing. However, even if the properties of silicon-based active materials themselves are adjusted as described above, the rapid expansion of volume during the charge / discharge process can cause some problems, damaging the conductive path formed within the negative electrode active material layer.

[0060] Therefore, in one embodiment of the present application, the negative electrode conductive material may include at least one selected from the group consisting of a dot-shaped conductive material, a planar conductive material, and a linear conductive material.

[0061] In one embodiment of the present application, the dot-shaped conductive material may be used to improve conductivity of the negative electrode, and refers to a dot-shaped or spherical conductive material having conductivity without causing chemical change. Specifically, the dot-shaped 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, paneth black, lamp black, thermal black, conductive fiber, fluorocarbon, aluminum powder, nickel powder, zinc oxide, potassium titanate, titanium oxide, and polyphenylene derivatives, and preferably may include carbon black in terms of implementing high conductivity and excellent dispersibility.

[0062] In one embodiment of the present application, the dot-shaped conductive material has a BET specific surface area of ​​40 m 2 / g or more than 70m 2 / g or less, preferably 45m 2 / g or more than 65m 2 / g or less, more preferably 50m 2 / g or more than 60m 2 / g can be less.

[0063] In one embodiment of the present application, the dot-shaped conductive material can satisfy a volatile matter content 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.

[0064] In particular, when the functional group content of the dot-shaped conductive material satisfies the above range, the functional groups present on the surface of the dot-shaped conductive material exist, so that when water is used as a solvent, the dot-shaped conductive material can be smoothly dispersed within the solvent. In particular, in the present invention, the functional group content of the dot-shaped conductive material can be reduced by using a specific silicon-based active material, thereby having an excellent effect in improving dispersibility.

[0065] In one embodiment of the present application, it is characterized by including a dot-shaped 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 controlled by adjusting the degree of heat treatment of the dot-shaped conductive material.

[0066] In one embodiment of the present application, the particle size of the dot-shaped conductive material may be 10 nm to 100 nm, preferably 20 nm to 90 nm, and more preferably 20 nm to 60 nm.

[0067] In one embodiment of the present application, the conductive material may include a planar conductive material.

[0068] The above-mentioned planar conductive material can improve conductivity by increasing planar contact between silicon particles within the cathode, and at the same time, suppress the disconnection of conductive paths due to volume expansion. The above-mentioned planar conductive material can be expressed as a plate-shaped conductive material or a bulk conductive material.

[0069] In one embodiment of the present application, the planar conductive material may include at least one selected from the group consisting of plate-shaped graphite, graphene, graphene oxide, and graphite flakes, and may preferably be plate-shaped graphite.

[0070] In one embodiment of the present application, the average particle diameter (D50) of the surface-shaped 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 above range is satisfied, dispersion is easy without causing excessive viscosity increase of the negative electrode slurry due to sufficient particle size. Therefore, the dispersion effect is excellent when dispersion is performed using the same equipment and time.

[0071] In one embodiment of the present application, the surface-shaped conductive material provides a negative electrode composition having 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.

[0072] In one embodiment of the present application, the planar conductive material may be a high-specific surface area planar conductive material having a high BET surface area; or a low-specific surface area planar conductive material.

[0073] In one embodiment of the present application, a high surface area surface conductive material or a low surface area surface conductive material may be used without limitation as the surface conductive material, but in particular, since the surface conductive material according to the present application may be affected to some extent by dispersion in electrode performance, it may be particularly preferable to use a low surface area surface conductive material that does not cause dispersion problems.

[0074] In one embodiment of the present application, the surface-shaped conductive material has a BET specific surface area of ​​0.25 m 2 / g can be more than that.

[0075] In another embodiment, the surface-shaped conductive material has a BET surface area of ​​1 m 2 / g or more than 500m 2 / g or less, preferably 5m 2 / g or more than 300m 2 / g or less, more preferably 5m 2 / g or more than 250m 2 / g can be less.

[0076] The planar conductive material according to the present application may be a planar conductive material with a high specific surface area; or a planar conductive material with a low specific surface area.

[0077] In another embodiment, the surface-shaped conductive material is a high surface area surface-shaped conductive material, and has a BET surface area of ​​50 m 2 / g or more than 500m 2 / g or less, preferably 80m 2 / g or more than 300m 2 / g or less, more preferably 100m 2 / g or more than 300m 2 / g can satisfy the range below.

[0078] In another embodiment, the surface-shaped conductive material is a low surface area surface-shaped conductive material, and has a BET surface area of ​​1 m 2 / g or more than 40m 2 / g or less, preferably 5m 2 / g or more than 30m 2 / g or less, more preferably 5m 2 / g or more than 25m 2 / g can satisfy the range below.

[0079] Other conductive materials may include linear conductive materials such as carbon nanotubes. The carbon nanotubes may be bundle-type carbon nanotubes. The bundle-type carbon nanotubes may include a plurality of carbon nanotube units. Specifically, the term "bundle type" herein refers to a secondary shape in the form of a bundle or rope, in which a plurality of carbon nanotube units are arranged in a substantially identical orientation in parallel or entangled with their longitudinal axes in the carbon nanotube unit direction, unless otherwise specified. The carbon nanotube units have a cylindrical shape of a graphite sheet with a nano-sized diameter and an sp2 bonding structure. At this time, the graphite sheets may exhibit conductor or semiconductor properties depending on the curling angle and structure. The above bundled carbon nanotubes can be uniformly dispersed during the manufacture of a cathode compared to entangled type carbon nanotubes, and can smoothly form a conductive network within the cathode, thereby improving the conductivity of the cathode.

[0080] In one embodiment of the present application, the negative electrode conductive material may be included in an amount of 0.1 parts by weight or more and 40 parts by weight or less based on 100 parts by weight of the negative electrode active material layer composition.

[0081] In another embodiment, the negative electrode conductive material may be included in an amount of 0.1 to 40 parts by weight, preferably 0.2 to 30 parts by weight, more preferably 0.4 to 25 parts by weight, and most preferably 0.4 to 10 parts by weight, based on 100 parts by weight of the negative electrode active material layer composition.

[0082] In one embodiment of the present application, a negative electrode composition is provided, wherein the negative electrode conductive material includes a planar conductive material or a linear conductive material.

[0083] In one embodiment of the present application, the negative electrode conductive material may include a planar conductive material and a linear conductive material.

[0084] In one embodiment of the present application, the negative electrode conductive material may include 80 parts by weight or more and 99.9 parts by weight or less of the planar conductive material and 0.1 parts by weight or more and 20 parts by weight or less of the linear conductive material based on 100 parts by weight of the negative electrode conductive material.

[0085] In another embodiment, the negative electrode conductive material may include 80 parts by weight or more and 99.9 parts by weight or less of the planar conductive material, 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, based on 100 parts by weight of the negative electrode conductive material.

[0086] In another embodiment, the negative electrode conductive material may include 0.1 to 20 parts by weight of the linear conductive material, preferably 0.1 to 15 parts by weight, and more preferably 0.2 to 5 parts by weight, based on 100 parts by weight of the negative electrode conductive material.

[0087] In one embodiment of the present application, since the negative electrode conductive material includes a planar conductive material and a linear conductive material and satisfies the above composition and ratio, it does not have a significant effect on the life characteristics of an existing lithium secondary battery, and in particular, when the planar conductive material and the linear conductive material are included, 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 cathode conductive material may be formed of a linear conductive material.

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

[0090] In one embodiment of the present application, when the negative electrode conductive material comprises a linear conductive material alone, the negative electrode conductive material may comprise 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 negative electrode conductive material according to the present application has a completely separate composition from the positive electrode conductive material applied to the positive electrode. That is, the negative electrode conductive material according to the present application serves to secure the contact between silicon-based active materials, which undergo a significant volume expansion of the electrode due to charging and discharging, and the positive electrode conductive material serves to provide some conductivity while acting as a buffer during rolling, and is completely different in composition and role from the negative electrode conductive material of the present invention.

[0092] In addition, the negative electrode conductive material according to the present application is applied to a silicon-based active material and has a completely different composition from the conductive material applied to a graphite-based active material. That is, the conductive material used in an electrode having a graphite-based active material simply has smaller particles than the active material, and thus has the characteristics of improving output characteristics and imparting some conductivity, and is completely different in composition and role from the negative electrode conductive material applied together with a silicon-based active material as in the present invention.

[0093] In one embodiment of the present application, the planar conductive material used as the aforementioned negative electrode conductive material has a structure and function different from those of carbon-based active materials generally used as negative electrode active materials. 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 processed into a spherical or dot-shaped form to facilitate the storage and release of lithium ions.

[0094] On the other hand, the planar conductive material used as the negative electrode conductive material is a material having a planar or plate-like shape, and can be expressed as plate-like graphite. In other words, it refers to a material included to maintain a conductive path within the negative electrode active material layer, and is not a material that plays a role in storing and releasing lithium, but rather a material that secures a conductive path in a planar shape within the negative electrode active material layer.

[0095] That is, in the present application, the use of plate-shaped graphite as a conductive material means that it is processed into a planar or plate-shaped form and used as a material that secures a conductive path rather than a role for storing or releasing lithium. In this case, the included negative electrode active material has high capacity characteristics for lithium storage and release, and serves to store and release all lithium ions delivered from the positive electrode.

[0096] On the other hand, in the present application, the use of a carbon-based active material as an active material means that it is processed into a dot or spherical shape and used as a material that plays a role in storing or releasing lithium.

[0097] That is, in one embodiment of the present application, the carbon-based active material, artificial graphite or natural graphite, is in a dot-like shape and has a BET specific surface area of ​​0.1 m 2 / g or more than 4.5 m 2 / g or less can be satisfied. In addition, the plate-shaped graphite, which is a planar conductive material, has a BET surface area of ​​5 m in the form of a planar surface. 2 / g can be more than that.

[0098] 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), fluoroelastomer, polyacrylic acid, and a material in which hydrogens thereof are substituted with Li, Na, Ca, or the like, and may also include various copolymers thereof.

[0099] The negative electrode binder according to one embodiment of the present application serves to hold the active material and conductive material in order to prevent distortion and structural deformation of the negative electrode structure when the volume of the silicon-based active material expands and relaxes. If the above-mentioned role is satisfied, all general binders can be applied, and specifically, an aqueous binder can be used, and more specifically, a PAM-based binder can be used.

[0100] In one embodiment of the present application, 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, and 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.

[0101] In one embodiment of the present application, a lithium secondary battery is provided, 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.

[0102] The above-described negative electrode current collector layer generally has a thickness of 1 μm to 100 μm. The negative electrode current collector layer is not particularly limited as long as it has high conductivity and does not cause chemical changes in the battery. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. can be used. In addition, the bonding strength of the negative electrode active material can be strengthened by forming fine unevenness on the surface, and can be used in various forms such as a film, sheet, foil, net, porous body, foam, non-woven fabric, etc.

[0103] However, the thickness can be varied depending on the type and purpose of the cathode used and is not limited thereto.

[0104] In one embodiment of the present application, the porosity of the negative electrode active material layer can satisfy a range of 10% or more and 60% or less.

[0105] In another embodiment, the porosity of the negative electrode active material layer can satisfy a range of 10% or more and 60% or less, preferably 20% or more and 50% or less, and more preferably 30% or more and 45% or less.

[0106] The above porosity varies depending on the composition and content of the active material, conductive material, and binder included in the negative electrode active material layer, and accordingly, the electrode is characterized by having an appropriate range of electrical conductivity and resistance.

[0107] 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 sides of the positive electrode current collector layer, wherein the positive electrode active material layer composition includes a positive electrode active material.

[0108] In the above positive electrode, the positive electrode current collector layer is not particularly limited as long as it is conductive and does not cause a chemical change in the battery, and 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. In addition, the positive electrode current collector layer may typically have a thickness of 3 to 500 ㎛, and fine unevenness may be formed on the surface of the positive electrode current collector to increase the adhesive strength of the positive electrode active material. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, or non-woven fabric.

[0109] The above 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), lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; lithium iron oxide such as LiFe3O4; or a compound having the chemical formula Li 1+c1 Mn 2-c1 Lithium manganese oxides such as O4(0≤c1≤0.33), LiMnO3, LiMn2O3, LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, V2O5, Cu2V2O7; chemical formula LiNi 1-c2 M c2Ni-site type lithium nickel oxide represented by O2 (wherein, M is at least one selected from the group consisting of Co, Mn, Al, Cu, Fe, Mg, B, and Ga, and satisfies 0.01≤c2≤0.3); chemical formula LiMn 2-c3 M c3 Lithium manganese composite oxide represented by O2 (wherein, M is at least one selected from the group consisting of Co, Ni, Fe, Cr, Zn, and Ta, and satisfies 0.01≤c3≤0.1) or Li2Mn3MO8 (wherein, M is at least one selected from the group consisting of Fe, Co, Ni, Cu, and Zn); LiMn2O4, etc., in which a part of Li in the chemical formula is replaced with an alkaline earth metal ion, but is not limited thereto. The positive electrode may be Li-metal.

[0110] 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 A lithium secondary battery is provided, which includes at least one selected from the group consisting of PO4 (M: Transition metal, x+y=1).

[0111] At this time, the positive electrode conductive material is used to provide conductivity to the electrode, and in the battery to be formed, as long as it does not cause a chemical change and has electronic conductivity, it can be used without any special restrictions. Specific examples 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, summer black, and carbon fiber; metal powder or metal fiber such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and the like, and one of these may be used alone or a mixture of two or more may be used.

[0112] In addition, the positive electrode binder plays a role of improving the adhesion between positive electrode active material particles and the adhesiveness between the positive electrode active material and the positive electrode current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluoroelastomer, or various copolymers thereof, and one of these may be used alone or a mixture of two or more thereof.

[0113] The present application relates to a lithium secondary battery comprising: a positive electrode; a negative electrode; a separator described between the positive electrode and the negative electrode; and an electrolyte, wherein the negative electrode has a discharge potential controlled to be 0 V or more and 1.5 V or less (vs Li / Li+).

[0114] In general, for the negative electrode, charge and discharge are performed at 0.005 V to 1.5 V depending on the composition and content of the active material used. However, in the case of Si or Sn, charge and discharge are performed at 0.005 V to 3 V to use a 3 V cut off profile. However, in this case, the positive electrode profile discharge potential meets the counter electrode of the full cell, so the voltage approaches 0 V and thus deviates from the actual usable voltage range of the lithium secondary battery. Therefore, the negative electrode for a lithium secondary battery according to the present application is characterized in that the discharge potential is controlled to be 0 V or more and 1.5 V or less (vs Li / Li+) regardless of the composition and content of the active material used.

[0115] At this time, the cathode according to the present application may have a residual cathode capacity represented by the above-described formula 1.

[0116] Having a residual cathode capacity represented by Equation 1 may mean that the cathode discharge capacity (vs Li / Li+) from 0 V to 1.5 V and the cathode discharge capacity to the cut-off potential are not equal, and specifically, Equation 1 may be applied without limitation if it has a value of 2.5% or more.

[0117] In the present application, a lithium secondary battery is provided in which the remaining negative electrode capacity represented by the above formula 1 of the negative electrode is 2.5% or more and 50% or less.

[0118] In the present application, the residual negative electrode capacity represented by the above formula 1 may be 2.5% or more, specifically 5% or more, more specifically 10% or more, and may be 80% or less, specifically 60% or less, more specifically 50% or less.

[0119] In the present application, the negative electrode discharge capacity (vs Li / Li+) from 0 V to 1.5 V in the above formula 1 - the negative electrode discharge capacity (vs Li / Li+) to the cut-off potential of 0 V or more is 1 μAh / cm2 And, the cut-off potential of the above cathode may be 0 V or more and 1.4 V or less.

[0120] In the present application, the negative electrode discharge capacity (vs Li / Li+) from 0 V to 1.5 V in the above formula 1 - the negative electrode discharge capacity (vs Li / Li+) to the cut-off potential of 0 V or more is 1 μAh / cm 2 More than 20mAh / cm 2 Below, specifically 10μAh / cm 2 More than 15 mAh / cm 2 Below, more specifically 100μAh / cm 2 More than 10mAh / cm 2 The following ranges can be satisfied.

[0121] By leaving the remaining cathode capacity in the above range, the life characteristics can be improved by leaving the cathode as compared to using the full profile cathode.

[0122] In one embodiment of the present application, the cut off potential of the negative electrode may be less than the discharge potential of the negative electrode.

[0123] At this time, the cut-off potential of the cathode may be 0 V or more and 1.4 V or less.

[0124] In the present application, the degree of capacity of the remaining negative electrode represented by the above formula 1 can be determined according to the cut-off potential of the negative electrode.

[0125] In one embodiment of the present application, a lithium secondary battery is provided in which the negative electrode active material includes a carbon-based active material and the cut-off potential of the negative electrode is 0.1 V or more and 0.9 V or less.

[0126] Specifically, a negative electrode having 100% carbon-based active material is described as an example in FIG. 2, and when a cut-off potential of less than 0.5 V is set, the negative electrode can have the residual negative electrode capacity of Equation 1.

[0127] In one embodiment of the present application, a lithium secondary battery is provided in which the negative electrode active material includes a silicon-based active material and the cut-off potential of the negative electrode is 0.1 V or more and 1.4 V or less.

[0128] Specifically, a negative electrode having 100% silicon-based active material is described as an example in FIG. 3, and when a cut-off potential of less than 1.3 V is set, it can have the residual negative electrode capacity of Equation 1.

[0129] In one embodiment of the present application, a lithium secondary battery is provided in which the negative electrode active material includes a silicon-based active material and a carbon-based active material, and the cut-off potential of the negative electrode is 0.2 V or more and 1.3 V or less.

[0130] Specifically, in Fig. 4, a negative electrode having a mixture of a silicon-based active material and a carbon-based active material is described as an example, and when a cut-off potential of less than 0.7 V is set, the negative electrode can have the residual negative electrode capacity of Equation 1.

[0131] That is, FIGS. 2 to 4 are diagrams showing the charge and discharge profiles of the negative electrode according to the type of negative electrode. Specifically, the capacity value of the x-axis changes depending on the type of negative electrode, and the remaining negative electrode capacity according to the cut-off potential of the negative electrode can be compared. Specifically, in the case of a carbon-based negative electrode, there is almost no difference in capacity between 1.5 V and 1.4 V to 1.45 V, so no residual capacity remains. Accordingly, in the case of a carbon-based negative electrode, the cut-off potential can be adjusted to 0.1 V or more and 0.9 V or less to leave the remaining negative electrode within the range of Equation 1 described above. In addition, in the case of a silicon-based negative electrode, a capacity change occurs around 1.5 V, and a capacity difference appears around 1.3 V. Therefore, it can be seen that in the case of a silicon-based negative electrode, the cut-off potential can be adjusted to 0.1 V or more and 1.4 V or less to leave the remaining negative electrode within the range of Equation 1 described above.

[0132] For reference, the method of measuring the profile curves of the cathode and anode in FIGS. 2 to 4 can be secured by manufacturing a coin cell by filling the inside of the coin cell with a PE separator and an electrolyte, using the cathode or anode to be measured as the working electrode, lithium metal as the counter electrode, and charging and discharging the coin cell.

[0133] That is, the cut-off potential can be adjusted according to the type of cathode used as described above, and accordingly, the capacity of the remaining cathode can be adjusted within the range of Equation 1, thereby improving the lifespan characteristics along with the capacity characteristics, which is a main feature of the present invention.

[0134] The separator separates the negative and positive electrodes and provides a passage for lithium ions to move. Any separator commonly used in secondary batteries can be used without any particular restrictions, and in particular, one that has low resistance to ion movement of the electrolyte and excellent electrolyte moisture retention capacity is preferable. Specifically, a porous polymer film, for example, a porous polymer film made of a polyolefin polymer such as ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof, can be used. In addition, a conventional porous non-woven fabric, for example, a non-woven fabric made of high-melting-point glass fiber, polyethylene terephthalate fiber, etc. can also be used. In addition, a coated separator containing a ceramic component or a polymer material to secure heat resistance or mechanical strength can be used, and can optionally be used in a single-layer or multi-layer structure.

[0135] Examples of the electrolyte include, but are not limited to, 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 the manufacture of lithium secondary batteries.

[0136] Specifically, the electrolyte may include a non-aqueous organic solvent and a metal salt.

[0137] As the above non-aqueous organic solvent, for example, an aprotic organic solvent such as N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-butyrolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyl tetrahydrofuran, dimethylsulfoxide, 1,3-dioxolan, formamide, dimethylformamide, dioxolan, acetonitrile, nitromethane, methyl formate, methyl acetate, triester phosphate, trimethoxy methane, dioxolan derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl pyrropionate, ethyl propionate, etc. can be used.

[0138] In particular, among the above carbonate-based organic solvents, ethylene carbonate and propylene carbonate, which are cyclic carbonates, are high-viscosity organic solvents with high dielectric constants and thus can be preferably used because they easily dissociate lithium salts. In addition, when low-viscosity, low-dielectric constant linear carbonates such as dimethyl carbonate and diethyl carbonate are mixed and used in an appropriate ratio with these cyclic carbonates, an electrolyte with high electrical conductivity can be produced, so that they can be used even more preferably.

[0139] The metal salt may be a lithium salt, and the lithium salt is a substance that is easily dissolved in the non-aqueous electrolyte, for example, as an anion of the lithium salt, F - , Cl - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , PF6 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 -, (CF3)5PF - , (CF3)6P - , CF3SO3 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - and (CF3CF2SO2)2N - One or more selected from the group consisting of may be used.

[0140] In addition to the electrolyte components, the electrolyte may further include one or more additives, such as, for example, a haloalkylene carbonate compound such as difluoroethylene carbonate, pyridine, triethylphosphite, triethanolamine, a cyclic ether, ethylene diamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinone imine 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 battery capacity decrease, and improving the discharge capacity of the battery.

[0141] One embodiment of the present invention provides a battery module including the secondary battery as a unit cell and a battery pack including the same. The battery module and battery pack include the secondary battery having high capacity, high rate characteristics, and cycle characteristics, and thus 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.

[0142] Hereinafter, preferred embodiments are presented to help understand the present invention, but the above embodiments are only illustrative of the present disclosure, and it is obvious to those skilled in the art that various changes and modifications are possible within the scope and technical idea of ​​the present disclosure, and it is natural that such changes and modifications fall within the scope of the appended patent claims.

[0143] <Manufacturing Example>

[0144] <Example 1>

[0145] <Manufacturing of secondary batteries>

[0146] A carbon-based active material (artificial graphite (D50: 18㎛): natural graphite (D50: 18㎛) = 50:50), carbon black, SBR as a binder, and CMC as a thickener were added to distilled water as a solvent for forming a negative electrode slurry at a weight ratio of 95.7:1:2.3:1 to prepare a negative electrode slurry (solid content concentration 50 wt%).

[0147] As a mixing method, the carbon black, binder, and distilled water were dispersed using a homo mixer at 2500 rpm for 30 minutes, and then the active material was added and dispersed at 2500 rpm for 30 minutes to produce a slurry.

[0148] The above negative electrode slurry was coated on both sides of a copper current collector (thickness: 15 μm) as a negative electrode current collector, dried in a vacuum oven at 130°C for 1 hour, and rolled to form a negative electrode active material layer (porosity: 35%).

[0149] LiNi as a cathode active material 0.6 Co 0.2 Mn 0.2 O2 (average particle size (D50): 15㎛), carbon black (product name: Super C65, manufacturer: Timcal) as a conductive agent, and polyvinylidene fluoride (PVdF) as a binder were added to N-methyl-2-pyrrolidone (NMP) as a solvent for forming a cathode slurry at a weight ratio of 95:2.5:2.5 to prepare a cathode slurry (solid content concentration: 63 wt%).

[0150] The positive electrode slurry was coated on both sides of an aluminum current collector (thickness: 12 μm) as a positive electrode collector, dried in a vacuum oven at 130°C for 1 hour, and rolled to produce a positive electrode active material layer (porosity: 30%).

[0151] A lithium secondary battery was manufactured by interposing a polyethylene separator between the positive electrode and the negative electrode and injecting an electrolyte.

[0152] The above electrolyte was an organic solvent containing fluoroethylene carbonate (FEC) and diethyl carbonate (DEC) mixed in a volume ratio of 30:70, vinylene carbonate added at 3 wt% based on the total weight of the electrolyte, and LiPF6 added as a lithium salt at a concentration of 1 M.

[0153] <Example 2>

[0154] <Manufacturing of secondary batteries>

[0155] A negative electrode slurry was prepared in the same manner as in Example 1, except that carbon-based active material (artificial graphite (D50: 18㎛): natural graphite (D50: 18㎛): SiOx (D50: 7㎛) = 49.5:49.5:1), carbon black, and SBR as a binder and CMC as a thickener were added to distilled water as a solvent for forming a negative electrode slurry in a weight ratio of 95.7:1:2.3:1.

[0156] <Example 3>

[0157] <Manufacturing of secondary batteries>

[0158] A negative electrode slurry was prepared in the same manner as in Example 1, except that carbon-based active material (artificial graphite (D50: 18㎛): natural graphite (D50: 18㎛): SiOx (D50: 7㎛) = 48.75:48.75:2.5), carbon black, and SBR as a binder and CMC as a thickener were added to distilled water as a solvent for forming a negative electrode slurry in a weight ratio of 95.7:1:2.3:1.

[0159] <Example 4>

[0160] <Manufacturing of secondary batteries>

[0161] A negative electrode slurry was prepared in the same manner as in Example 1, except that carbon-based active material (artificial graphite (D50: 18㎛): natural graphite (D50: 18㎛): SiOx (D50: 7㎛) = 48:48:4), carbon black, and SBR as a binder and CMC as a thickener were added to distilled water as a solvent for forming a negative electrode slurry in a weight ratio of 95.7:1:2.3:1.

[0162] <Comparative Example 1>

[0163] <Manufacturing of secondary batteries>

[0164] A negative electrode slurry was prepared in the same manner as in Example 1, except that carbon-based active material (artificial graphite (D50: 18㎛): natural graphite (D50: 18㎛): SiOx (D50: 7㎛) = 47.25:47.25:5.5), carbon black, and SBR as a binder and CMC as a thickener were added to distilled water as a solvent for forming a negative electrode slurry in a weight ratio of 95.7:1:2.3:1.

[0165] In the above examples and comparative examples, the cathode and anode were controlled with the information shown in Table 1 below.

[0166] Positive electrode active material Negative electrode active material Positive electrode discharge loading (mAh / cm 2 )Cathode discharge loading (mAh / cm 2 )Cathode cut-off potential (V)Cell operating voltage (V)Cathode discharge potential control (V)Example 1LiNi 0.6 Co 0.2 Mn 0.2 O2Graphite3.1194.430.244.35V-2V0-1.5(vs Li / Li+)Example 2LiNi 0.6 Co 0.2 Mn 0.2 O2Graphite+SiO 1%3.1194.430.394.35V-2V0-1.5(vs Li / Li+)Example 3LiNi 0.6 Co 0.2 Mn 0.2O2Graphite+SiO2 2.5%3.1194.430.554.35V-2V0-1.5(vs Li / Li+)Example 4LiNi 0.6 Co 0.2 Mn 0.2 O2Graphite+SiO 4%3.1194.430.704.35V-2V0-1.5(vs Li / Li+)Comparative example 1LiNi 0.6 Co 0.2 Mn 0.2 O2Graphite+SiO 5.5%3.1194.430.864.35V-2V0-1.5(vs Li / Li+)

[0167] Specifically, to confirm the cut-off potential of Table 1, a bi-cell three-electrode evaluation was conducted as shown in Figs. 5 to 9, and the results were derived as shown in Table 1.

[0168] Experimental example

[0169] For the above examples and comparative examples, the results shown in Table 2 below were obtained.

[0170] At this time, in Table 2, the 0.33C capacity retention rate was evaluated at a high temperature of 45°C using an electrochemical charger / discharger. The secondary battery was subjected to an in-situ cycle test at 1C / 0.5C according to the cell operating voltages listed in Table 1, and the calculation was made as follows based on 300 cycles.

[0171] Capacity retention rate (%) = {(discharge capacity in the Nth cycle) / (discharge capacity in the first cycle)} Х 100

[0172] Initial 0.33C capacity (mAh) Residual cathode capacity (Formula 1) (%) Residual cathode capacity (mAh / cm 2 )0.33C Capacity Retention Rate (%, 300th)Example 138.710.40.4686Example 238.150.2283Example 337.74.10.1882Example 438.130.1380Comparative Example 137.52.40.1078

[0173] As can be seen in Table 2 above, in all cases of Examples 1 to 4 of the present invention, it was confirmed that when the negative electrode Cut-off potential was controlled to leave the remaining negative electrode capacity within the range of Equation 1, the life characteristics were also improved. In other words, it was confirmed that the life characteristics were improved by controlling the Cut-off potential without being greatly affected by the type of negative electrode, and that it was important to design the battery to include the remaining negative electrode through Equation 1. Specifically, Example 1 corresponds to a carbon-based negative electrode, and Examples 2 to 4 correspond to a carbon-based and silicon-based mixed negative electrode.

[0174] In the case of Comparative Example 1, although the cut-off potential was controlled, the residual cathode capacity remained at 2.4%. In this case, it was confirmed that the initial capacity was also reduced to some extent, and the capacity retention rate was not maintained at 80% or higher, i.e., the life characteristics were reduced.

Claims

1. A lithium secondary battery comprising a positive electrode; a negative electrode; a separator described between the positive electrode and the negative electrode; and an electrolyte, The above cathode is controlled to have a discharge potential of 0 V or more and 1.5 V or less (vs Li / Li+). It has a residual cathode capacity of 2.5% or more, as defined by the following equation 1, A lithium secondary battery, wherein the cut off potential of the negative electrode is lower than the discharge potential of the negative electrode. [Formula 1] 2. In claim 1, A lithium secondary battery having a residual negative electrode capacity represented by the above formula 1 of 2.5% or more and 50% or less.

3. In claim 1, In the above formula 1, the negative electrode discharge capacity (vs Li / Li+) from 0 V to 1.5 V - the negative electrode discharge capacity (vs Li / Li+) to the cut-off potential of 0 V or higher is 1 μAh / cm 2 That's it, A lithium secondary battery, wherein the cut-off potential of the negative electrode is 0 V or more and 1.4 V or less.

4. In claim 1, The above negative electrode comprises a negative electrode current collector layer; and a negative electrode active material layer provided on one or both sides of the negative electrode current collector layer, The above negative electrode active material layer comprises a negative electrode active material layer composition, The above negative electrode active material layer composition comprises a negative electrode active material; a negative electrode conductive material; and a negative electrode binder. A lithium secondary battery, wherein the negative electrode active material comprises at least one selected from the group consisting of a carbon-based active material, a silicon-based active material, a tin-based active material, a metal-based active material capable of being alloyed with lithium, lithium titanium oxide, and a lithium-containing nitride.

5. In claim 4, The above negative active material includes a carbon-based active material, A lithium secondary battery having a cut-off potential of the negative electrode of 0.1 V or more and 0.9 V or less.

6. In claim 4, The above negative active material includes a silicon-based active material, A lithium secondary battery having a cut-off potential of the negative electrode of 0.1 V or more and 1.4 V or less.

7. In claim 4, The above negative active material includes a silicon-based active material and a carbon-based active material. A lithium secondary battery having a cut-off potential of the negative electrode of 0.2 V or more and 1.3 V or less.

8. In claim 4, The above negative active material includes a carbon-based active material; and a silicon-based active material, A lithium secondary battery comprising 30 parts by weight or less of the silicon-based active material based on 100 parts by weight of the negative active material.

9. In claim 4, A lithium secondary battery, wherein the negative electrode active material is contained in an amount of 60 parts by weight or more based on 100 parts by weight of the negative electrode active material layer composition.

10. In claim 1, The above positive electrode comprises a positive electrode current collector layer; and a positive electrode active material layer comprising a positive electrode active material layer composition provided on one or both sides of the positive electrode current collector layer, The above positive electrode active material layer includes a positive electrode active material; a positive electrode conductive material; and a positive electrode binder. The above positive electrode active material 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 PO 4 A lithium secondary battery comprising at least one selected from the group consisting of (M: transition metal, x+y=1).

11. In claim 4, The thickness of the above negative electrode current collector layer is 1 μm or more and 100 μm or less, A lithium secondary battery, wherein the thickness of the negative active material layer is 5 μm or more and 500 μm or less.

12. In claim 10, The thickness of the above positive electrode current collector layer is 1 μm or more and 100 μm or less, A lithium secondary battery, wherein the thickness of the positive electrode active material layer is 5 μm or more and 500 μm or less.

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