Negative electrode composition, negative electrode for lithium secondary battery including the same, and lithium secondary battery including the negative electrode

Abstract

The present application relates to a negative electrode composition, a negative electrode for a lithium secondary battery, and a lithium secondary battery including the negative electrode.

Description

Technical Field

[0001] This application claims the benefit of the filing date of Korean Patent Application No. 10-2022-0177386, filed with the Korean Intellectual Property Office on December 16, 2022, and all of its content is incorporated herein by reference.

[0002] This application relates to a negative electrode composition, a negative electrode for a lithium secondary battery including the same, and a lithium secondary battery including the negative electrode.

Background Art

[0003] Due to the rapid increase in the use of fossil fuels, the demand for alternative and clean energy has been increasing. As part of this, the fields of power generation and energy storage using electrochemical reactions are the most actively studied.

[0004] Currently, a typical example of an electrochemical device using such electrochemical energy is a secondary battery, and its usage area is increasingly expanding.

[0005] As technology development and demand for mobile devices increase, the demand for secondary batteries as an energy source has been rapidly increasing. Among such secondary batteries, lithium secondary batteries having high energy density, high voltage, long cycle life, and low self-discharge rate have been commercialized and widely used. In addition, research on methods for manufacturing high-density electrodes with even higher energy density per unit volume as electrodes for such high-capacity lithium secondary batteries has been actively conducted.

[0006] Generally, a secondary battery is composed of a positive electrode, a negative electrode, an electrolyte, and a separator. The negative electrode includes a negative electrode active material that inserts and desorbs lithium ions emitted from the positive electrode, and as the negative electrode active material, silicon-based particles with a large discharge capacity can be used.

[0007] In particular, with the recent demand for high-density energy batteries, research has been actively conducted on methods to increase the capacity by using silicon-based compounds such as Si / C and SiOx, which have a capacity more than 10 times greater than that of graphite-based materials, as the negative electrode active material. However, in the case of silicon-based compounds, which are high-capacity materials, although the capacity is large compared to conventionally used graphite, there is a problem that the volume rapidly expands during the charging process, severing the conductive path and degrading the battery characteristics.

[0008] Therefore, in order to solve the problems when using silicon-based compounds as the negative electrode active material, methods such as adjusting the driving potential, additionally coating a thin film on the active material layer, methods to suppress the volume expansion itself such as adjusting the particle size of the silicon-based compound, or various methods to prevent the conductive path from being severed have been discussed. However, in the case of the above methods, since they may conversely degrade the performance of the battery, there are limitations to their application, and there are still limitations to the commercialization of manufacturing negative electrode batteries with a high content of silicon-based compounds.

[0009] Also, in the case of an electrode using a graphite-based or a composite of graphite and silicon as the active material, a dot-shaped conductive material is added to manufacture the electrode. However, conventionally used dot-shaped conductive materials react with lithium, clog the pores in the electrode structure, increase the diffusion resistance of Li ions, and such resistance causes a difference in the degree of degradation of the electrode during the lithium insertion and desorption reactions at the upper and lower ends of the electrode.

[0010] Therefore, in the process of manufacturing a silicon-based negative electrode to maximize the capacity characteristics, research is needed on an electrode that can maintain the porosity of the electrode equally and maximize the diffusion of Li ions.

Prior Art Documents

Patent Documents

[0011]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0012] Although various types of negative electrode conductive materials are used to maintain the conductive path, the above problems still remain unsolved. Therefore, by removing the dot-shaped conductive material which is a conventional conductive material, including a void securing material in the negative electrode composition to secure voids in the electrode, and inserting a linear conductive material to complement the void securing material which is a non-conductor as the conductive material, it has been found that the above problems can be solved.

[0013] Therefore, the present application relates to a negative electrode composition capable of solving the above problems, a negative electrode for a lithium secondary battery including the same, and a lithium secondary battery including the negative electrode.

Means for Solving the Problems

[0014] One embodiment of the present specification is a negative electrode composition including a silicon-based active material; a void securing material; a linear conductive material; and a negative electrode binder, wherein the silicon-based active material includes one or more selected from the group consisting of SiOx (x = 0) and SiOx (0 < x < 2), includes 90 parts by weight or more of the SiOx (x = 0) based on 100 parts by weight of the silicon-based active material, the void securing material is included in an amount of 0.1 part by weight or more and 20 parts by weight or less based on 100 parts by weight of the negative electrode composition, and a weight ratio of the linear conductive material to the void securing material is 1:10 to 1:120.

[0015] In another embodiment, a negative electrode for a lithium secondary battery is provided, which includes a negative electrode current collector layer; and a negative electrode active material layer including the negative electrode composition according to the present application formed on one or both sides of the negative electrode current collector layer.

[0016] Finally, a lithium secondary battery is provided, which includes a positive electrode; a negative electrode for a lithium secondary battery according to the present application; a separator provided between the positive electrode and the negative electrode; and an electrolyte.

Advantages of the Invention

[0017] In the case of the negative electrode composition according to the present application, it is characterized in that a void securing material is provided which can maintain the porosity of the electrode and maximize the diffusion of lithium ions. As a result, the conventional dot-shaped conductive material as a conductive material is removed, and by using the void securing material, the void securing material is located between the particles in the electrode, so that there is an advantage that voids can be secured to generate the diffusion of lithium ions.

[0018] Further, the above-described void securing material is an insulator, and a certain content portion is used for securing voids, and it is characterized in that it further contains a linear conductive material to complement this and lower the resistance of the electrode. As a result, voids can be maintained even during insertion and desorption of lithium in an electrode of pure silicon (Pure Si), and it has the characteristic that conductivity can be ensured and the resistance of the electrode can be lowered.

[0019] That is, the negative electrode composition according to the present invention mainly features that in a negative electrode to which a silicon-based active material is applied to maximize the capacity, a certain content of a void securing material is used to simplify the pore structure, which is a problem of pure Si, and the conductive network problem caused thereby is solved by including a linear conductive material with a specific content.

Brief Description of Drawings

[0020]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0021] Before explaining the present invention, first, several terms will be defined. In this specification, when a certain part "includes" a certain component, this means that, unless otherwise specified, it does not exclude other components, but may further include other components.

[0022] In this specification, "p to q" means a range of "p or more and q or less". In this specification, the "specific surface area" is measured by the BET method. Specifically, it is calculated from the nitrogen gas adsorption amount at liquid nitrogen temperature (77K) using BELSORP-mini II manufactured by BEL Japan. That is, in this application, the BET specific surface area may mean the specific surface area measured by the above measurement method.

[0023] In this specification, "Dn" means the particle size distribution and means the particle size at the n% point of the cumulative particle number distribution according to the particle size. That is, D50 is the particle size (median particle size) at the 50% point of the cumulative particle number distribution according to the particle size, D90 is the particle size at the 90% point of the cumulative particle number distribution according to the particle size, and D10 is the particle size at the 10% point of the cumulative particle number distribution according to the particle size. On the other hand, the median particle size can be measured using the laser diffraction method. Specifically, after dispersing the powder to be measured in a dispersion medium, it is introduced into a commercially available laser diffraction particle size measuring device (for example, Microtrac S3500), and the difference in the diffraction pattern according to the particle size is measured when the particles pass through the laser beam to calculate the particle size distribution.

[0024] In one embodiment of this application, the particle size or the particle diameter may mean the average diameter or the representative diameter of each individual particle forming the particle.

[0025] In this specification, when a polymer includes a certain monomer as a monomer unit, it means that the monomer participates in the polymerization reaction and is included as a repeating unit in the polymer. In this specification, when a polymer is said to include a monomer, this is interpreted in the same way as the polymer including the monomer as a monomer unit.

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

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

[0028] Hereinafter, a detailed description will be given with reference to the drawings so that those having ordinary knowledge in the technical field to which the present invention pertains can easily implement the present invention. However, the present invention may be realized in various different forms and is not limited to the following description.

[0029] One embodiment of this specification is a negative electrode composition including a silicon-based active material; a void-forming material; a linear conductive material; and a negative electrode binder, wherein the silicon-based active material includes one or more selected from the group consisting of SiOx (x = 0) and SiOx (0 < x < 2), contains 90 parts by weight or more of the SiOx (x = 0) based on 100 parts by weight of the silicon-based active material, the void-forming material is contained in an amount of 0.1 part by weight or more and 20 parts by weight or less based on 100 parts by weight of the negative electrode composition, and the weight ratio of the linear conductive material to the void-forming material is 1:10 to 1:120.

[0030] The negative electrode composition according to the present invention is mainly characterized in that, in a negative electrode applying a silicon-based active material to maximize the capacity, a certain content of a void-forming material is used to simplify the void structure, which is a problem of pure Si, and the resulting conductive network problem is solved by including a specific content of a linear conductive material.

[0031] Hereinafter, the negative electrode composition according to the present application will be described in detail. In one embodiment of the present application, the silicon-based active material includes one or more selected from the group consisting of SiOx (x = 0) and SiOx (0 < x < 2), and may contain 90 parts by weight or more of the SiOx (x = 0) based on 100 parts by weight of the silicon-based active material.

[0032] In another embodiment, based on 100 parts by weight of the silicon-based active material, the SiOx (x = 0) may be contained in an amount of 90 parts by weight or more, preferably 92 parts by weight or more, more preferably 93 parts by weight or more, and may be contained in an amount of 100 parts by weight or less, preferably 99 parts by weight or less, more preferably 95 parts by weight or less.

[0033] In one embodiment of the present application, the silicon-based active material may be SiOx (x = 0).

[0034] In one embodiment of the present application, the silicon-based active material may use particularly pure silicon (Si) as the silicon-based active material. Using pure silicon (Si) as the silicon-based active material may mean that, as described above, when based on a total of 100 parts by weight of the silicon-based active material, pure Si (SiOx (x = 0)) not bonded to other particles or elements is included within the above range.

[0035] That is, the silicon-based active material according to the present application uses pure Si and has the characteristic that the capacity to secure lithium is higher than when using SiOx (0 < x < 2). As a result, it can be excellent in rapid charging ability and capacity characteristics. However, since problems such as ensuring voids can occur in a pure Si negative electrode, it is mainly characterized by including the above-described void securing material and linear conductive material.

[0036] On the one hand, the average particle size (D50) of the silicon-based active material of the present invention may be 5 μm to 10 μm, specifically may be 5.5 μm to 8 μm, and more specifically may be 6 μm to 7 μm. When the average particle size is within the above range, the specific surface area of the particles is within an appropriate range, and the viscosity of the negative electrode slurry is formed within an appropriate range. As a result, the dispersion of the particles constituting the negative electrode slurry becomes smooth. Further, since the size of the silicon-based active material has a value equal to or greater than the lower limit value of the above range, the contact area between the silicon particles and the conductive material by the composite composed of the conductive material and the binder in the negative electrode slurry becomes good, and the possibility of the conductive network continuing is high, and the capacity retention rate increases. On the other hand, when the average particle size satisfies the above range, excessively large silicon particles are excluded, and the surface of the negative electrode is smoothly formed, thereby preventing the non-uniformity phenomenon of the current density during charge and discharge.

[0037] In one embodiment of the present application, the silicon-based active material has a generally characteristic BET specific surface area. The BET specific surface area of the silicon-based active material is preferably 0.01 m 2 / g to 150.0 m 2 / g, more preferably 0.1 m 2 / g to 100.0 m 2 / g, particularly preferably 0.2 m 2 / g to 80.0 m 2 / g, most preferably 0.2 m 2 / g to 18.0 m 2 / g. The BET specific surface area is measured in accordance with DIN 66131 (using nitrogen).

[0038] In one embodiment of the present application, the silicon-based active material may exist, for example, in a crystalline or amorphous form, and is preferably non-porous. The silicon particles are preferably spherical or flaky particles. Alternatively, although less convenient, the silicon particles may have a fibrous structure or exist in the form of a silicon-containing film or coating.

[0039] In one embodiment of the present application, a negative electrode composition is provided, wherein the silicon-based active material is included in an amount of 60 parts by weight or more based on 100 parts by weight of the negative electrode composition.

[0040] In another embodiment, the silicon-based active material may be included in an amount of 60 parts by weight or more and 95 parts by weight or less based on 100 parts by weight of the negative electrode composition.

[0041] In still another embodiment, the silicon-based active material may be included in an amount of 60 parts by weight or more, preferably 60.5 parts by weight or more, more preferably 61 parts by weight or more, and may be included in an amount of 95 parts by weight or less, preferably 90 parts by weight or less, more preferably 85 parts by weight or less based on 100 parts by weight of the negative electrode composition.

[0042] The negative electrode composition according to the present application uses a silicon-based active material having a significantly high capacity within the above range. That is, when used beyond the above range, even if the combination of the linear conductive material and the void-providing material of the present invention is used, the life characteristics cannot be ensured, and instead, it results in poor cell performance evaluation. When used less than the above range, although the life characteristics can be ensured, the capacity characteristics and energy density are significantly reduced. When manufacturing a negative electrode having the same capacity, the thickness of the active material layer increases, and the rapid charging performance also deteriorates.

[0043] The present application uses a silicon-based active material within the above range that can control volume expansion and maximize capacity characteristics, and is characterized in that the contents of the linear conductive material and the void-providing material described below are optimized.

[0044] In one embodiment of the present application, the silicon-based active material may have a non-spherical shape, and its sphericity is, for example, 0.9 or less, for example, 0.7 to 0.9, for example, 0.8 to 0.9, for example, 0.85 to 0.9.

[0045] In the present application, the sphericity is determined by the following formula 1, where A is the area and P is the boundary line. [Formula 1] 4πA / P 2

[0046] In one embodiment of the present application, the negative electrode composition may include a void ensuring material. When having a silicon-based active material as described above, in order to ensure life stability, the insertion and desorption of lithium at the upper and lower ends of the electrode must occur uniformly. However, when using a dot-shaped conductive material as the conventionally used conductive material, the voids in the electrode structure are blocked, increasing the diffusion resistance of lithium ions. Due to such resistance, a difference in the degree of electrode deterioration will occur during the lithium insertion and desorption reactions at the upper / lower ends of the electrode.

[0047] In order to solve the above problems, the negative electrode composition according to the present application is characterized in that the dot-shaped conductive material is removed and includes 0.1 part by weight or more and 20 parts by weight or less of a void ensuring material based on 100 parts by weight of the negative electrode composition.

[0048] In another embodiment, the negative electrode composition includes 0.1 part by weight or more and 20 parts by weight or less, preferably 0.5 part by weight or more and 19 parts by weight or less, more preferably 0.7 part by weight or more and 19 parts by weight or less of a void ensuring material based on 100 parts by weight of the negative electrode composition.

[0049] That is, by including the void ensuring material that can ensure voids between particles and has no reactivity with lithium ions in the above-mentioned parts by weight, there is an advantage that a void structure that can generate the diffusion of lithium ions can be ensured. Further, the void ensuring material may be non-conductive metal oxide particles.

[0050] Particularly, when using the void ensuring material as described above, even if a side reaction layer is partially formed on the active material, the lithium ion path in the electrode can be ensured and uniformly distributed in the electrode. By including the above-mentioned content parts, the uniform reaction at the upper and lower ends in the electrode is induced, so that the life stability of the electrode can be ensured.

[0051] In one embodiment of the present application, there is provided a negative electrode composition in which the void securing material is an inorganic oxide having a lower reactivity with lithium than the silicon-based active material. That is, the void securing material may be an inorganic oxide having a lower reactivity or no reactivity with lithium compared to the silicon-based active material.

[0052] In one embodiment of the present application, the void securing material can exhibit amorphous (non-crystalline) or crystalline properties.

[0053] In one embodiment of the present application, the void securing material is composed of a non-transition metal and an oxide, or an oxide having a low reactivity with lithium ions, and can be used without limitation as long as it is an oxide whose composition and structure do not change due to the band structure between the electrode and the electrolyte even when charge and discharge occur between lithium ions and the silicon-based active material.

[0054] In one embodiment of the present application, the void securing material may be Al2O3; CaO; CeO2; MgO; or ZrO2, but is not limited thereto as long as it can be used for securing voids in the negative electrode described above.

[0055] Conventionally, it has been common to use only graphite-based compounds as the negative electrode active material. However, in recent years, as the demand for high-capacity batteries has increased, attempts have been made to mix and use silicon-based active materials to increase the capacity. However, in the case of silicon-based active materials, even if the characteristics of the silicon-based active material itself are partially adjusted as described above, 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.

[0056] Also, when the dot-shaped conductive material is removed as described above and the void securing material is used in the above-described parts by weight, since the void securing material exhibits the characteristics of a non-conductor, it may be difficult to secure a conductive path.

[0057] Therefore, the present application may include a linear conductive material as the negative electrode composition, and thus has the feature that it can complement the void securing material that is a non-conductor and reduce the resistance of the electrode.

[0058] Generally, conventional silicon-based anodes may contain both a punctiform conductive material and a sheet-like conductive material.

[0059] In one embodiment of the present application, the anode composition further includes an anode conductive material, and the anode conductive material is included in an amount of 5 parts by weight or more and 15 parts by weight or less based on 100 parts by weight of the anode composition, providing an anode composition.

[0060] In another embodiment, the anode conductive material may be 5 parts by weight or more and 15 parts by weight or less, preferably 13 parts by weight or less, and may also be 5 parts by weight or more, specifically 7 parts by weight or more, based on 100 parts by weight of the anode composition. At this time, the anode conductive material may include a punctiform conductive material or a sheet-like conductive material.

[0061] The punctiform conductive material can be used to improve the conductivity of the anode, does not cause chemical changes, and has conductivity, meaning a spherical or punctiform conductive material. Specifically, the punctiform 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 fibers, fluorocarbons, aluminum powder, nickel powder, zinc oxide, potassium titanate, titanium oxide, and polyphenylene derivatives, and preferably may include carbon black in terms of achieving high conductivity and excellent dispersibility.

[0062] The sheet-like conductive material can play a role in increasing the surface contact between silicon particles in the anode to improve conductivity and suppressing the interruption of the conductive path due to volume expansion, and can be represented as a plate-like conductive material or a bulk-like conductive material. The sheet-like conductive material may include at least one selected from the group consisting of plate-like graphite, graphene, graphene oxide, and graphite flakes, and preferably may be plate-like graphite.

[0063] First, when carbon black is used as the dot-shaped conductive material for the silicon-based negative electrode, it has the advantage of being inexpensive in terms of process, but in order to play its role, it must be contained in a high proportion in the negative electrode composition. Since such a high proportion of the dot-shaped conductive material has to be used, gas generation at high temperatures becomes a problem, and the problem of the stability of the negative electrode decreasing due to gas generation has occurred.

[0064] Also, in the case of plate-shaped graphite used as the sheet-shaped conductive material, it has an appropriate price, has appropriate rigidity, plays a buffering role during the rolling of the silicon-based negative electrode in a soft form, and also has a high specific surface area and the characteristic of being able to form a conductive network between the active materials. However, in the case of the sheet-shaped conductive material, since it must contain a certain amount or more with respect to the silicon-based active material used, despite having the above properties, there is a limitation in containing a high content of the silicon-based active material in the negative electrode active material, and as a result, the problem of not being able to achieve the maximization of the capacity characteristics has occurred.

[0065] In one embodiment of the present application, in particular, the linear conductive material is characterized by including single-walled carbon nanotubes (SWCNT); and multi-walled carbon nanotubes (MWCNT).

[0066] In the present application, the SWCNT has a specific surface area of 900 m 2 / g to 1500 m 2 / g, and the average diameter may be 0.5 μm or more and 3 μm or less.

[0067] In the case of the SWCNT, it has the characteristics of being long and having a high specific surface area as described above, and is most effective in forming a conductive network between the silicon-based active materials. However, in the case of the SWCNT, it has the disadvantage of being very expensive, and when the SWCNT is applied excessively, since the SWCNT dispersant used is included, the rigidity decreases.

[0068] In the present application, the MWCNT has a specific surface area of 100 m2 / g~500m 2 / g, and the average diameter (Mean diameter) may be 10 μm or more and 20 μm or less.

[0069] In one embodiment of the present application, the number of layers (Wall) of the MWCNT may satisfy 5 to 20.

[0070] In the case of the MWCNT, compared with the SWCNT, the specific surface area is small as described above and it is inferior in terms of length, but it corresponds to a substance having very excellent performance compared with the above-described dot-like conductive material and sheet-like conductive material.

[0071] In the present application, the SWCNT has a high specific surface area and a large aspect ratio. Relatively, the MWCNT is used in a bundled form (bundle form), located on the surface of the silicon-based active material, and it is difficult to connect between the active materials. That is, the SWCNT is used for long-distance connection, and the MWCNT is used as a role of mixing with the surface of the particles and the binder composite.

[0072] In one embodiment of the present application, based on 100 parts by weight of the negative electrode composition, the linear conductive material is 0.1 part by weight or more and 5 parts by weight or less, and a negative electrode composition is provided.

[0073] In another embodiment, based on 100 parts by weight of the negative electrode composition, the linear conductive material may be contained in an amount of 0.1 part by weight or more and 5 parts by weight or less, preferably 0.15 part by weight or more and 4 parts by weight or less, more preferably 0.15 part by weight or more and 1.0 part by weight or less.

[0074] In one embodiment of the present application, when the negative electrode composition contains a linear conductive material and satisfies the above-described composition and ratio, it does not significantly affect the life characteristics of a conventional lithium secondary battery, and there are many points where charging and discharging are possible, and it has a characteristic of excellent output characteristics at a high C-rate.

[0075] In one embodiment of the present application, there is provided a negative electrode composition in which, based on 100 parts by weight of the negative electrode composition, the total parts by weight of the void securing material and the linear conductive material is 0.1 part by weight or more and 30 parts by weight or less.

[0076] In another embodiment, based on 100 parts by weight of the negative electrode composition, the total parts by weight of the void securing material and the linear conductive material may be 0.1 part by weight or more and 30 parts by weight or less, preferably 0.5 part by weight or more and 25 parts by weight or less, more preferably 0.7 part by weight or more and 20 parts by weight or less.

[0077] The above parts by weight mean an optimal ratio capable of securing a conductive path while securing voids, and have the feature of being able to secure life characteristics and rapid charging characteristics while securing the capacity characteristics in a pure Si negative electrode.

[0078] In the case of the negative electrode conductive material according to the present application, it has a completely different configuration from the positive electrode conductive material applied to the positive electrode. That is, in the case of the negative electrode conductive material according to the present application, it serves as a contact between silicon-based active materials with very large volume expansion of the electrode during charging and discharging, while the positive electrode conductive material serves as a buffer with a buffering role during rolling and also serves to impart some conductivity, and the configuration and role of the negative electrode conductive material of the present invention are completely different.

[0079] Further, the negative electrode conductive material according to the present application is applied to a silicon-based active material and has a completely different configuration 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 configuration and role from the negative electrode conductive material applied together with a silicon-based active material as in the present invention.

[0080] In one embodiment of the present application, there is provided a negative electrode composition in which the negative electrode binder includes one or more selected from the group consisting of a rubber-based binder and an aqueous binder.

[0081] In one embodiment of the present application, the negative electrode binder includes 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, poly acrylic acid, and substances in which hydrogen thereof is substituted with Li, Na, Ca, etc., and may also include various copolymers thereof.

[0082] The negative electrode binder according to one embodiment of the present application serves to hold the active material and the conductive material in order to prevent distortion and structural deformation of the negative electrode structure during volume expansion and relaxation of the silicon - based active material. If the above - mentioned role is satisfied, any general binder can be applied. Specifically, an aqueous binder may be used, and more specifically, a PAM - based binder may be used.

[0083] In one embodiment of the present application, the negative electrode binder includes an aqueous binder, and the negative electrode binder is 5 parts by weight or more and 15 parts by weight or less based on 100 parts by weight of the negative electrode composition, to provide a negative electrode for a lithium secondary battery.

[0084] In another embodiment, the negative electrode binder may be 5 parts by weight or more and 15 parts by weight or less, preferably 7 parts by weight or more and 13 parts by weight or less, more preferably 9 parts by weight or more and 12 parts by weight or less based on 100 parts by weight of the negative electrode composition.

[0085] In one embodiment of the present application, based on 100 parts by weight of the silicon-based active material, the negative electrode binder may be included in an amount of 3 parts by weight or more and 10 parts by weight or less.

[0086] In another embodiment, based on 100 parts by weight of the silicon-based active material, the negative electrode binder may be 3 parts by weight or more and 10 parts by weight or less, preferably 3.5 parts by weight or more and 10 parts by weight or less, more preferably 5 parts by weight or more and 10 parts by weight or less.

[0087] In the case of the negative electrode for a lithium secondary battery according to the present application, in order to maximize the capacity characteristics, a silicon-based active material is used in the above-described parts by weight, and the volume expansion during charge and discharge is larger compared to the case where a conventional carbon-based active material is used as the main active material. Accordingly, by including the negative electrode binder in the above-described content parts, it has the characteristic that the volume expansion due to charge and discharge of the highly rigid silicon-based active material can be efficiently suppressed.

[0088] In one embodiment of the present application, there is provided a negative electrode for a lithium secondary battery, including: a negative electrode current collector layer; and a negative electrode active material layer including the negative electrode composition according to the present application formed on one or both sides of the negative electrode current collector layer.

[0089] FIG. 1 is a diagram showing a laminated structure of a negative electrode for a lithium secondary battery according to an embodiment of the present application. Specifically, a negative electrode 100 for a lithium secondary battery including a negative electrode active material layer 20 on one side of a negative electrode current collector layer 10 can be confirmed. FIG. 1 shows a case where the negative electrode active material layer is formed on one side, but it may be included on both sides of the negative electrode current collector layer.

[0090] In one embodiment of the present application, the negative electrode for the lithium secondary battery may be formed by applying and drying a negative electrode slurry including the negative electrode composition on one or both sides of the negative electrode current collector layer.

[0091] At this time, the negative electrode slurry may include the above-described negative electrode composition and a slurry solvent.

[0092] In one embodiment of the present application, the solid content of the negative electrode slurry may satisfy 5% or more and 55% or less.

[0093] In another embodiment, the solid content of the negative electrode slurry may satisfy the range of 5% or more and 55% or less, preferably 7% or more and 35% or less, more preferably 10% or more and 30% or less.

[0094] The solid content of the negative electrode slurry means the content of the negative electrode composition contained in the negative electrode slurry, and may mean the content of the negative electrode composition based on 100 parts by weight of the negative electrode slurry.

[0095] When the solid content of the negative electrode slurry satisfies the above range, the viscosity during the formation of the negative electrode active material layer is appropriate, the particle aggregation phenomenon of the negative electrode composition is minimized, and the negative electrode active material layer can be efficiently formed. Further, the negative electrode composition according to the present application contains a linear conductive material and a high content of a silicon-based active material, and has characteristics of excellent rapid charging performance and cell performance.

[0096] In one embodiment of the present application, the slurry solvent can be used without limitation as long as it can dissolve the negative electrode composition. Specifically, water, acetone, or NMP may be used.

[0097] In one embodiment of the present application, the negative electrode current collector layer generally has a thickness of 1 μm to 100 μm. Such a negative electrode current collector layer is not particularly limited as long as it does not cause a chemical change in the battery and has high conductivity. For example, copper, stainless steel, aluminum, nickel, titanium, fired carbon, those obtained by surface treatment of the surface of copper or stainless steel with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. may be used. Further, fine irregularities may be formed on the surface to strengthen the binding force of the negative electrode active material, and it may be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, a non-woven fabric body, etc.

[0098] In one embodiment of the present application, there is provided a negative electrode for 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 10 μm or more and 500 μm or less.

[0099] In the present application, when the negative electrode active material layer is formed on one side of the negative electrode current collector layer, that is, it can mean the thickness of a single-layer negative electrode active material layer.

[0100] However, the thickness can be variously deformed according to the type and use of the negative electrode used, and is not limited thereto.

[0101] In one embodiment of the present application, the porosity of the negative electrode active material layer may satisfy the range of 30% or more and 60% or less.

[0102] In another embodiment, the porosity of the negative electrode active material layer may satisfy the range of 30% or more and 60% or less, preferably 35% or more and 55% or less, more preferably 39% or more and 54% or less.

[0103] The porosity varies according to the composition and content of the silicon-based active material, conductive material, and binder contained in the negative electrode active material layer. In particular, by including the silicon-based active material, void ensuring material, and linear conductive material according to the present application in specific compositions and content parts, the above range is satisfied. Thereby, the electric conductivity and resistance in the electrode have an appropriate range.

[0104] In one embodiment of the present application, there is provided a lithium secondary battery including a positive electrode; a negative electrode for a lithium secondary battery according to the present application; a separator provided between the positive electrode and the negative electrode; and an electrolyte.

[0105] FIG. 2 is a diagram showing a stacked structure of a lithium secondary battery according to an embodiment of the present application. Specifically, a negative electrode 100 for a lithium secondary battery including a negative electrode active material layer 20 can be confirmed on one side of a negative electrode current collector layer 10, and a positive electrode 200 for a lithium secondary battery including a positive electrode active material layer 40 can be confirmed on one side of a positive electrode current collector layer 50, indicating that the negative electrode 100 for the lithium secondary battery and the positive electrode 200 for the lithium secondary battery are stacked with a separator 30 interposed therebetween.

[0106] A secondary battery according to an embodiment of the present specification may particularly include the negative electrode for a lithium secondary battery described above. Specifically, the secondary battery may include a negative electrode, a positive electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte, and the negative electrode is the same as the negative electrode described above. Since the negative electrode has been described above, a specific description thereof will be omitted.

[0107] The positive electrode may include a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector and including the positive electrode active material.

[0108] In the positive electrode, the positive electrode current collector is not particularly limited as long as it does not cause a chemical change in the battery and has conductivity. For example, stainless steel, aluminum, nickel, titanium, fired carbon, or a material obtained by surface treatment with carbon, nickel, titanium, silver, etc. on the surface of aluminum or stainless steel may be used. Further, the positive electrode current collector may usually have a thickness of 3 μm to 500 μm, and fine irregularities may be formed on the surface of the current collector to enhance the adhesion of the positive electrode active material. For example, it may be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, a non-woven fabric body, etc.

[0109] The positive electrode active material may be a commonly used positive electrode active material. Specifically, as the positive electrode active material, layered compounds such as lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), and compounds substituted with one or more transition metals; lithium iron oxide such as LiFe3O4; chemical formula Li 1+c1 Mn 2-c1Lithium 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 c2 O2 (where 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), nickel site-type lithium nickel oxide represented by; chemical formula LiMn 2-c3 M c3 O2 (where 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 lithium manganese composite oxide represented by Li2Mn3MO8 (where M is at least one selected from the group consisting of Fe, Co, Ni, Cu, and Zn); examples include, but are not limited to, LiMn2O4 in which part of the Li in the chemical formula is substituted with alkaline earth metal ions. The positive electrode may be metallic lithium (Li-metal).

[0110] The positive electrode active material layer may include a positive electrode conductive material and a positive electrode binder together with the aforementioned positive electrode active material.

[0111] At this time, the positive electrode conductive material is used to impart conductivity to the electrode, and in the battery to be configured, it can be used without particular limitation as long as it has electron conductivity without causing a chemical change. Specific examples include graphite such as natural graphite and artificial graphite; carbon-based substances such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, carbon fiber; metal powders or metal fibers such as copper, nickel, aluminum, silver; conductive whiskers such as zinc oxide, potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives. One of these or a mixture of two or more thereof may be used.

[0112] In addition, the positive electrode binder plays a role in improving the adhesion between the positive electrode active material particles and the adhesive force 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, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber (SBR), fluororubber, or various copolymers thereof. Among these, one kind alone or a mixture of two or more kinds may be used.

[0113] The separator separates the negative electrode and the positive electrode and provides a migration path for lithium ions. Generally, any material that is usually used as a separator in a secondary battery can be used without particular limitation. In particular, it is preferably low in resistance to the ion migration of the electrolyte and excellent in electrolyte moisture retention ability. Specifically, a porous polymer film, for example, a porous polymer film made of polyolefin-based polymers 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 may be used. Also, a normal porous non-woven fabric, for example, a non-woven fabric made of high-melting-point glass fibers, polyethylene terephthalate fibers, etc. may be used. Further, in order to ensure heat resistance or mechanical strength, a coated separator containing a ceramic component or a polymer substance may be used, and it may be selectively used as a single-layer or multi-layer structure.

[0114] 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. Specifically, the electrolyte may contain a non-aqueous organic solvent and a metal salt.

[0115] Examples of the non-aqueous organic solvent include aprotic organic solvents such as N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, triphosphate ester, trimethoxymethane, dioxolane derivative, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivative, tetrahydrofuran derivative, ether, methyl propionate, ethyl propionate, etc.

[0116] In particular, ethylene carbonate and propylene carbonate, which are cyclic carbonates among the carbonate-based organic solvents, can be preferably used as high-viscosity organic solvents because they have a high dielectric constant and can dissociate lithium salts well. When such cyclic carbonates are mixed with linear carbonates such as dimethyl carbonate and diethyl carbonate having low viscosity and low dielectric constant at an appropriate ratio, an electrolyte having high electrical conductivity can be produced, so they can be more preferably used.

[0117] As the metal salt, a lithium salt may be used. 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.

[0118] 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, hexamethylphosphoric triamide, nitrobenzene derivatives, sulfur, quinoneimine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride for improving the life characteristics of the battery, suppressing the decrease in battery capacity, and improving the discharge capacity of the battery.

[0119] 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. Since the battery module and the battery pack include the secondary battery having a high capacity, high rate characteristics, and cycle characteristics, they 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.

Examples

[0120] Hereinafter, preferred embodiments are presented to assist in understanding the present invention. However, these embodiments are merely illustrative of the description, and it is obvious to those skilled in the art that various changes and modifications are possible within the scope of the description and the scope of the technical idea. Needless to say, such variations and modifications belong to the scope of the appended claims.

[0121] <Production Example> <Manufacture of Negative Electrode> <Example 1> As a silicon-based active material, Si (average particle size (D50): 5 μm), a void-forming material (Al2O3), a second conductive material, SWCNT as a linear conductive material, and polyacrylamide (PAM) as a binder were added to distilled water as a solvent for forming a negative electrode slurry at a weight ratio of 79:0.75:10:0.25:10 to produce a negative electrode slurry (solid content concentration: 28% by weight).

[0122] The SWCNT had a BET specific surface area of 1000 m 2 / g to 1500 m 2 / g, an aspect ratio of 10,000 or more, and an average diameter of 1.0 μm or more. As the SWCNT, a solution dispersed in CMC was used. As the second conductive material, plate-shaped graphite (specific surface area: 17 m 2 / g, average particle size (D50): 3.5 μm) was used.

[0123] As a specific mixing method, the SWCNT, the second conductive material, the void-forming material, the binder, and water were dispersed at 2500 rpm for 30 minutes using a homomixer, and after adding the silicon-based active material, they were dispersed at 2500 rpm for 30 minutes to prepare a negative electrode slurry.

[0124] The negative electrode slurry was coated on both sides of a copper current collector (thickness: 15 μm) as a negative electrode current collector layer at a loading amount of 87.7 mg / 25 cm 2 and rolled (roll press), and dried in a vacuum oven at 130 °C for 10 hours to form a negative electrode active material layer (thickness: 27 μm), which was used as the negative electrode (thickness of the negative electrode: 42 μm).

[0125] In Example 1, a negative electrode was produced in the same manner as in Example 1, except that the parts by weight in Table 1 below were changed.

[0126]

Table 1

[0127] In Table 1 above, the porosity of the negative electrode including the volume of the void securing material was calculated as follows.

[0128]

Equation

[0129] <Comparative Example 5> As the silicon-based active material, Si (average particle size (D50): 5 μm), as the linear conductive material, SWCNT, carbon black C (specific surface area: 58 m 2 / g, diameter: 37 nm), a second conductive material, and polyacrylamide (PAM) as a binder were added to distilled water as a solvent for forming a negative electrode slurry at a weight ratio of 70:9.79:10:0.21:10 to produce a negative electrode slurry (solid content concentration 28% by weight).

[0130] The SWCNT has a BET specific surface area of 1000 m 2 / g to 1500 m 2 / g, an aspect ratio of 10,000 or more, and an average diameter of 1.0 μm or more. As the SWCNT, a solution dispersed in CMC was used.

[0131] As a specific mixing method, the SWCNT, carbon black C, binder, and water were dispersed at 2500 rpm for 30 minutes using a homomixer, and after adding the silicon-based active material, they were dispersed at 2500 rpm for 30 minutes to prepare a negative electrode slurry.

[0132] The negative electrode slurry was applied to both sides of a copper current collector (thickness: 26 μm) as a negative electrode current collector layer at 87.7 mg / 25 cm 2Coated with the loading amount of , roll pressed, and dried in a vacuum oven at 130 °C for 10 hours to form a negative electrode active material layer (thickness: 33 μm), which was used as the negative electrode (negative electrode thickness: 41 μm).

[0133] <Comparative Example 6> As the silicon-based active material, Si (average particle size (D50): 5 μm), carbon black C (specific surface area: 58 m 2 / g, diameter: 37 nm), a void ensuring material, and polyacrylamide (PAM) as a binder were added to distilled water as a solvent for forming the negative electrode slurry at a weight ratio of 70:10:10:10 to produce a negative electrode slurry (solid content concentration: 28% by weight).

[0134] As a specific mixing method, the carbon black C, the void ensuring material, the binder, and water were dispersed at 2500 rpm for 30 minutes using a homomixer, and after adding the silicon-based active material, it was dispersed at 2500 rpm for 30 minutes to prepare a negative electrode slurry.

[0135] The negative electrode slurry was coated on both sides of a copper current collector (thickness: 26 μm) as the negative electrode current collector layer at a loading amount of 87.7 mg / 25 cm 2 Coated with the loading amount of , roll pressed, and dried in a vacuum oven at 130 °C for 10 hours to form a negative electrode active material layer (thickness: 33 μm), which was used as the negative electrode (negative electrode thickness: 41 μm).

[0136] <Experimental Example> Experimental Example 1: Lifetime Evaluation of Monocells The secondary batteries containing the negative electrodes manufactured in the above Examples and Comparative Examples were evaluated for their life using an electrochemical charge / discharge device, and the capacity retention rate was evaluated. The secondary batteries were subjected to an In-situ cycle test at 4.2 - 3.0 V, 1C / 0.5C, and charged / discharged at 0.33C / 0.33C (4.2 - 3.0 V) every 50 cycles during the test to measure the capacity retention rate, and the results are shown in Table 2.

[0137] Lifetime maintenance rate (%) = {(Discharge capacity in the Nth cycle) / (Discharge capacity in the first cycle)} × 100

[0138]

Table 2

[0139] Experimental Example 2: Tortuosity Evaluation After fabricating a symmetric coin cell with the same electrode as each electrode, the ionic resistance (R ion ) was measured through the section showing a 45° slope in the low-frequency range in the Nyquist plot by EIS (Electrochemical impedence spectroscopy) measurement. The tortuosity was calculated from such ionic resistance by the following formula respectively.

[0140]

Equation

[0141] In the above formula, τ is the tortuosity, R ion is the ionic resistance, ε is the porosity of the electrode, A is the area of the electrode, κ is the conductivity of the electrolyte, and t is the thickness of the electrode.

[0142]

Table 3

[0143] The tortuosity evaluation is an index indicating how easy it is for ion transfer through the path of voids in the electrode. The lower the value, the easier it is for the actual electrochemically reactive substances to penetrate into the electrode. At this time, it is possible to ensure the voids of the electrode through the void ensuring material. It can be confirmed that when the porosity increases, the number of passages through which the electrolyte can move increases, and the value of the tortuosity is improved (in the above table, it is judged that the lower the value of the tortuosity, the more improved).

[0144] Experimental Example 3: Initial Cycle @ SOC50 2.5C 0.1s Discharge Resistance Evaluation (Measurement of Resistance of Electrodes Using Monocells) In the above Experimental Example 1, during the test, charge and discharge were performed at 0.33C / 0.33C (4.2 - 3.0V) every 50 cycles to measure the capacity retention rate. After that, when discharging at a 2.5C pulse at SOC50, the resistance value measured for a certain period (0.1 s) was measured, and the results are shown in Table 4 below.

[0145] [Table 4]

[0146] Experimental Example 4: Measurement Evaluation of Conductivity of Electrodes The resistance of the electrode was measured by the four - point probe measurement method. Specifically, as can be confirmed from Figure 3, among the four probes separated at the same interval, a direct current was passed between the two outer probes, and the voltage drop was measured through the two inner probes, and the resistance was calculated from the current and voltage values. Then, using the calculated resistance value and the distance between the probes, the conductivity of the electrode was calculated, and the results are as shown in Table 5 below.

[0147] [Table 5]

[0148] Experimental Example 5: PC Penetration Experiment A certain amount (10 ml) of PC (propylene carbonate) was injected onto the surface of the electrode punched out to a certain area through a syringe so that droplets of PC were formed on the surface. Then, after covering the container so that the injected PC did not evaporate, the time until the solvent completely penetrated into the electrode and the droplets disappeared was compared, and the results are shown in Table 6.

[0149] [Table 6]

[0150] As can be confirmed from Examples 1 to 8, this application is characterized by containing a void securing material that maintains the porosity of the electrode and maximizes the diffusion of lithium ions. As a result, by removing the dot-shaped conductive material, which is a conventional conductive material, and using the void securing material, the void securing material is positioned between the particles in the electrode, thereby having the advantage of being able to secure voids that can generate the diffusion of lithium ions.

[0151] Further, the void securing material as described above is a non-conductor, and a certain content is used for securing voids. It is further characterized by further including a linear conductive material to complement this and lower the resistance of the electrode. As a result, voids can be maintained even during the insertion and desorption of lithium in a pure Si electrode, and it has the characteristics of ensuring conductivity and lowering the resistance of the electrode.

[0152] That is, the negative electrode composition according to the present invention uses a certain content of a void securing material to simplify the void structure, which is a problem of pure Si, in a negative electrode to which a silicon-based active material is applied to maximize the capacity, and the main feature is that the problem of the conductive network caused thereby is solved by including a linear conductive material with a specific content.

[0153] In the case of Comparative Examples 1 and 2, although a void securing material is included, it corresponds to the case where the ratio of the linear conductive material and the void securing material according to this application is not satisfied. In the case of Comparative Examples 3 and 4, although a void securing material is included, it corresponds to the case where the content exceeds the weight according to this application. Further, Comparative Example 5 corresponds to the case where no void securing material is included. Furthermore, Comparative Example 6 does not use a linear conductive material and a void securing material, but corresponds to the case where a dot-shaped conductive material and a void securing material are used.

[0154] In this case, when compared with the examples, voids can be ensured between the particles. For the void-forming material that has no reactivity with lithium ions, Comparative Examples 1 and 2 contain a small amount of it and cannot fully play its role, making it difficult to ensure the void structure and resulting in poor evaluation results. Comparative Examples 3 and 4 contain a relatively large amount of the non-conductive void-forming material. Even when a linear conductive material is included, it is difficult to ensure conductivity, and it can be confirmed that the evaluation results are not good.

[0155] In the case of Comparative Example 5, no void-forming material is used, making it difficult to ensure the desired void structure. In the case of Comparative Example 6, no linear conductive material is used, but a dot-shaped conductive material is used. In this case, a side reaction layer is formed on the dot-shaped conductive material at the nanometer level, which instead blocks the voids. As a result, lithium ions cannot enter the lower end of the electrode, leading to non-uniform lithium ion distribution at the upper and lower ends. As a result, it can be confirmed that the silicon at the upper end is charged more with respect to the depth of charge, causing cracks in the active material and reducing the life stability of the electrode.

Explanation of Reference Numerals

[0156] 10 ··· Negative electrode current collector layer 20 ··· Negative electrode active material layer 30 ··· Separator 40 ··· Positive electrode active material layer 50 ··· Positive electrode current collector layer 60 ··· External probe 70 ··· Internal probe 100 ··· Negative electrode for lithium secondary battery 200 ··· Positive electrode for lithium secondary battery

Claims

1. A negative electrode composition comprising a silicon-based active material, a void-forming material, a linear conductive material, and a negative electrode binder, wherein the silicon-based active material contains one or more selected from the group consisting of SiO x (x = 0) and SiO x (0 < x < 2), and contains 90 parts by weight or more of the SiO x (x = 0) based on 100 parts by weight of the silicon-based active material, the void-forming material is contained in an amount of 0.1 part by weight or more and 20 parts by weight or less based on 100 parts by weight of the negative electrode composition, the negative electrode composition in which the weight ratio of the linear conductive material to the void-forming material is 1:2 to 1:

120.

2. The negative electrode composition according to Claim 1, wherein the silicon-based active material is contained in an amount of 60 parts by weight or more based on 100 parts by weight of the negative electrode composition.

3. The negative electrode composition according to Claim 1, wherein the total weight of the void-forming material and the linear conductive material is 0.1 part by weight or more and 30 parts by weight or less based on 100 parts by weight of the negative electrode composition.

4. The negative electrode composition according to Claim 1, wherein the linear conductive material is 0.1 part by weight or more and 5 parts by weight or less based on 100 parts by weight of the negative electrode composition.

5. The negative electrode composition according to Claim 1, wherein the linear conductive material is SWCNT or MWCNT.

6. The specific surface area of the MWCNT is 100 m ２ / g to 500 m ２ / g, and The negative electrode composition according to Claim 5, having a mean diameter of 10 μm or more and 20 μm or less.

7. The SWCNT has a specific surface area of 900 m ２ / g to 1500 m ２ / g, and The negative electrode composition according to Claim 5, having a mean diameter of 0.5 μm or more and 3 μm or less.

8. The negative electrode composition according to Claim 1, wherein the negative electrode binder contains one or more selected from the group consisting of a rubber-based binder and an aqueous binder.

9. The negative electrode composition further contains a negative electrode conductive material, The negative electrode composition according to Claim 1, wherein the negative electrode conductive material is contained in an amount of 5 parts by weight or more and 15 parts by weight or less based on 100 parts by weight of the negative electrode composition.

10. The negative electrode composition according to Claim 1, wherein the void-forming material is an inorganic oxide having a lower reactivity with lithium than the silicon-based active material.

11. A negative electrode current collector layer; and a negative electrode active material layer including the negative electrode composition according to any one of Claims 1 to 10 formed on one or both sides of the negative electrode current collector layer; A negative electrode for a lithium secondary battery comprising the same.

12. The thickness of the negative electrode current collector layer is 1 μm or more and 100 μm or less, The thickness of the negative electrode active material layer is 10 μm or more and 500 μm or less. The negative electrode for a lithium secondary battery according to claim 11.

13. The porosity of the negative electrode active material layer is 30% or more and 60% or less. The negative electrode for a lithium secondary battery according to claim 11.

14. Positive electrode; The negative electrode for a lithium secondary battery according to claim 11; A separator provided between the positive electrode and the negative electrode; and Electrolyte; A lithium secondary battery comprising the same.

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