Negative electrode composition, negative electrode, and secondary battery

Abstract

The present specification provides a negative electrode comprising a negative electrode active material and a nano-metal structure, wherein the nano-metal structure includes at least one of a porous nano-metal structure or a 2D nano-metal structure.

Description

Cathode composition, cathode and secondary battery

[0001] This application claims the benefit of the filing date of Korean Patent Application No. 10-2024-0157796 filed with the Korean Intellectual Property Office on November 8, 2024, the entire contents of which are incorporated herein.

[0002] This specification relates to a cathode composition, a cathode including the same, and a secondary battery.

[0003] The rapid increase in the use of fossil fuels has led to a growing demand for alternative and clean energy. In response to this demand, one of the most actively researched fields is power generation and energy storage utilizing electrochemical reactions. Currently, secondary batteries are a representative example of electrochemical devices that utilize such electrochemical energy, and their scope of application is steadily expanding.

[0004] As technological development and demand for mobile devices increase, the demand for secondary batteries is also rising rapidly. Among secondary batteries, lithium-ion batteries, which possess high energy density and voltage, long cycle life, and low self-discharge rates, have been commercialized and are widely used. Furthermore, active research is underway to develop high-density electrodes with higher energy density per unit volume to manufacture electrodes for high-capacity lithium-ion batteries.

[0005] Generally, a secondary battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. The negative electrode contains a negative electrode active material that inserts and extracts lithium ions from the positive electrode, and silicon-based particles with a high discharge capacity can be used as this negative electrode active material.

[0006] In particular, with the recent increase in demand for high-density energy batteries, research is actively underway on methods to increase capacity by using silicon-based compounds, such as Si / C or SiOx, as anode active materials, which offer higher capacity compared to graphite-based materials. While silicon-based compounds, as high-capacity materials, have the advantage of higher capacity compared to conventionally used graphite, they present a problem in that they are vulnerable to thermal runaway within the cell in actual operating environments due to rapid volume expansion during the charging process.

[0007] Therefore, research is needed to develop secondary batteries with high capacity and improved thermal safety.

[0008] The present specification aims to provide a negative electrode active material, a negative electrode, and a secondary battery having high capacity and improved thermal safety in an operating environment.

[0009] According to one embodiment of the present invention, a cathode composition is provided comprising a cathode active material; and a nano metal structure, wherein the nano metal structure comprises at least one of a porous nano metal structure or a two-dimensional nano metal structure.

[0010] According to another embodiment, a cathode is provided comprising: a cathode current collector; and a cathode active material layer provided on the cathode current collector, wherein the cathode active material layer comprises a cathode composition according to one embodiment of the present invention.

[0011] According to another embodiment, a secondary battery is provided comprising: a positive electrode, a negative electrode according to one embodiment of the present invention; a separator provided between the positive electrode and the negative electrode; and an electrolyte.

[0012] According to another embodiment, a battery module or battery pack including a secondary battery according to an embodiment of the present invention is provided.

[0013] Finally, a battery pack including a battery module according to one embodiment of the present invention is provided.

[0014] When a cathode composition according to one embodiment of the present invention is applied to a cathode, high capacity can be maintained while thermal safety can be improved.

[0015] In the case of a secondary battery comprising a negative electrode composition according to one embodiment of the present invention, the oxidation reaction of lithium within the negative electrode during a thermal runaway reaction is suppressed by the metal nanostructure, thereby slowing down the thermal runaway time and speed.

[0016] FIG. 1 is a diagram showing a stacked structure of a cathode according to one embodiment of the present invention.

[0017] FIG. 2 is a diagram showing a stacked structure of a secondary battery according to one embodiment of the present invention.

[0018] <Explanation of Symbols>

[0019] 10: Cathode current collector

[0020] 20: Cathode active material layer

[0021] 30: Separator

[0022] 40: Positive active material layer

[0023] 50: Positive current collector

[0024] 100: Cathode

[0025] 200: Anode

[0026] Before describing the present invention, some terms are defined first.

[0027] In this specification, when a part is described as "comprising" a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0028] In this specification, "p to q" means a range of p or more and q or less.

[0029] In this specification, "specific surface area" or "BET specific surface area" refers to a measurement obtained by the BET method, specifically calculated from the amount of nitrogen gas adsorbed at a liquid nitrogen temperature (77K) using BEL SORP-mini II from BEL Japan. That is, in the present invention, the specific surface area may refer to the specific surface area measured by the above measurement method.

[0030] In this specification, "Dn" refers to the particle size distribution and represents the particle size at the n% point of the cumulative distribution of the number of particles according to particle size. That is, D50 is the particle size at the 50% point of the cumulative distribution of the number of particles according to particle size (central particle size), D90 is the particle size at the 90% point of the cumulative distribution of the number of particles according to particle size, and D10 is the particle size at the 10% point of the cumulative distribution of the number of particles according to particle size. Meanwhile, the central 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 (e.g., Microtrac S3500) and the difference in diffraction patterns according to particle size is measured as the particles pass through the laser beam to calculate the particle size distribution.

[0031] In this specification, "particle size (or particle diameter)" may refer to the average diameter or representative diameter of a particle. The particle may be in the form of a single particle or in the form of a secondary particle formed by the aggregation of multiple primary particles. Additionally, the central particle diameter of a particle may be used interchangeably with the average particle diameter, D50, or particle diameter, and the central particle diameter may refer to the size of a particle.

[0032] In this specification, "particle" may be in the form of a single particle, a pseudo-single particle, or a secondary particle.

[0033] In this specification, "single particle" may mean one primary particle and may include pseudo-single particles formed by aggregating, combining, or assembling 30 or fewer primary particles.

[0034] The term "secondary particles" used in the present invention refers to particles formed by the aggregation of dozens to hundreds, for example, more than 30 primary particles, by combining, bonding, or assembling.

[0035] In this specification, the meaning that a polymer contains a monomer in monomer units means that the monomer participates in a polymerization reaction and is included as a repeating unit within the polymer. In this specification, when it is stated that a polymer contains a monomer, this is interpreted as the same as the polymer containing the monomer in monomer units.

[0036] In this specification, the term "polymer" is understood to be used in a broad sense including copolymers unless specified as "homopolymer."

[0037] In this specification, the weight-average molecular weight (Mw) and the number-average molecular weight (Mn) are polystyrene equivalent molecular weights measured by gel permeation chromatography (GPC), using commercially available monodisperse polystyrene polymers of various degrees of polymerization (standard samples) for molecular weight measurement as standard materials. In this specification, the term "molecular weight" means weight-average molecular weight unless otherwise specified.

[0038] In this specification, "metal" includes both metals and metalloids such as silicon and germanium in an elemental or ionic state.

[0039] In this specification, "nano metal structure" refers to a metal or a structure in which pores within the metal are arranged at a nanometer-sized level. The nano metal structure may have various forms, such as a nano sheet or a nano porous structure.

[0040] The above nano sheet refers to a planar two-dimensional metal structure having an average thickness of nanometers. That is, the above nano sheet refers to a two-dimensional nano metal structure, and the sheet may have a structure comprising a single layer or multiple layers. The above nano sheet may be in the form of nano sheet flakes or in the form of a mesh containing multiple pores.

[0041] The above porous nanostructure refers to a metal structure containing a plurality of nanometer-sized pores. The above porous nanostructure may be a porous nanoparticle or a porous nanometal particle. A porous nanoparticle is a particle having nanometer-sized pores inside, and is distinguished from a nanoparticle whose particle size is nanometer-sized.

[0042] Hereinafter, the present invention will be described in detail with reference to the drawings so that those skilled in the art can easily practice the present invention. However, the present invention may be embodied in various different forms and is not limited to the description below.

[0043] Lithium-ion batteries can generate internal self-heating due to external shocks or abnormal cell behavior. If the internal temperature rises due to this heat, the electrodes are exposed to air, leading to a thermal runaway reaction. For instance, thermal runaway can occur as lithium embedded within the negative electrode active material oxidizes, or as the temperature increases, the positive electrode active material decomposes, releasing oxygen which then reacts with the negative electrode active material to accelerate the thermal runaway reaction. This phenomenon of thermal runaway causes a rapid increase in temperature and the generation of gases within the battery, posing a problem that can lead to serious fires or explosions.

[0044] In particular, with the recent increase in demand for electric vehicles and the resulting need for rechargeable batteries with high energy density and voltage, there have been ongoing attempts to apply silicon-based active materials to the anode to improve battery performance. While silicon-based active materials offer high energy density, they have lower thermal stability compared to carbon-based active materials, making them more vulnerable to thermal runaway. Therefore, additional measures are required to enhance high-temperature safety in order to improve the safety of lithium-ion batteries.

[0045] cathode composition

[0046] According to one embodiment of the present invention, a cathode composition is provided comprising a cathode active material; and a nano metal structure, wherein the nano metal structure comprises at least one of a porous nano metal structure or a two-dimensional nano metal structure.

[0047] The inventors of the present invention devised a method to suppress oxidation reactions within the cathode, which are expected to be the primary cause of thermal runaway reactions, by adding a solid-phase reducing metal to the cathode composition. Previously, methods such as including various additives in the cathode composition or forming a separate protective layer on the surface of the cathode active material layer were discussed. However, in the general operating environment of secondary batteries, lithium or silicon-based active materials, such as Si, contained in the cathode exhibit high reactivity at high temperatures. Consequently, the presence of general additives or protective layers alone cannot effectively suppress their oxidation reactions, and it was confirmed that the internal temperature of the battery rises rapidly in the temperature range where thermal runaway is a concern, leading to ignition within the cell.

[0048] The inventors have discovered that when a reducing metal is included in a cathode composition and the reducing metal is structured in nanometer units to form a porous nano metal structure or a two-dimensional nano metal structure, the reactivity between the reducing metal and oxygen within the cathode can be increased and the oxidation reaction of lithium can be suppressed. A secondary battery containing such a cathode composition has the characteristic that the time and speed of thermal runaway at the cathode can be delayed as the oxidation reaction within the cathode is suppressed.

[0049] A cathode composition according to one embodiment of the present invention comprises a cathode active material and a nano metal structure, wherein the nano metal structure comprises at least one of a porous nano metal structure or a two-dimensional nano metal structure. That is, the nano metal structure is a form distinct from nanoparticles or nanowires.

[0050] The above nanoparticle refers to a metal particle having a nano size, meaning a uniform solid metal mass without separate pores inside. The diameter of the above nanoparticle may be 10 nm to 1 µm, or 10 nm to 500 nm. The above nanoparticle may be in the form of a nano powder, which is an aggregate of multiple nanoparticles, and the multiple nanoparticles may exist independently within the nano powder. The above nanoparticle has a zero-dimensional (0D) structure that is shaped like a round ball and has volume, and is distinguished from porous nano metal structures.

[0051] In the case of the above nanoparticles, the surface area of ​​individual particles is fixed, so the specific surface area is limited; thus, the specific surface area is smaller compared to nanoporous particles or nanosheets of the same volume or particle size. In other words, the above nanoparticles have low reactivity with oxygen, making them unsuitable as nano metal structures for preventing thermal runaway. Furthermore, since a large number of the above nanoparticles may clump together within the negative electrode active material layer, it is difficult to disperse them evenly within the negative electrode active material layer. Therefore, when the above nanoparticles are applied as nano metal structures, the thermal runaway reaction cannot be effectively suppressed, and it is difficult to sufficiently absorb stress due to volume changes during the charging and discharging process. Consequently, if stress is concentrated due to charging and discharging, the particles may easily break or separate.

[0052] The above nanowire refers to a linear one-dimensional metal structure with a diameter (or diameter) in the nanometer range. The diameter of the nanowire may be 10 nm to 500 mm, and the length may be from 100 nm to several hundred micrometers. The nanowire has a one-dimensional (1D) structure having a very small diameter relative to its length. For example, the diameter-to-length ratio (aspect ratio) of the nanowire may be 1:100 to 1:10,000. The above nanoparticles and nanowires are distinguished from nanoporous particles having nanometer-sized pores inside the particles and two-dimensional nanometal structures in the form of nanometer-sized flakes or meshes.

[0053] In the case of the above nanowires, compared to nanosheets having a two-dimensional structure, they exist linearly, so the structure expands only in a single direction, which limits the increase in surface area. That is, even if the total surface area increases, the BET specific surface area relative to the total volume is low, which has the disadvantage of lower reaction efficiency with oxygen. In addition, since they may clump together within the cathode active material layer, it is difficult to disperse them evenly within the cathode active material layer. Accordingly, when nanowires are applied as the above nanometal structure, thermal runaway reactions cannot be effectively suppressed, and it is difficult to sufficiently absorb stress due to volume changes during the charging and discharging process; therefore, if stress is concentrated due to charging and discharging, the particles may easily break or separate.

[0054] That is, the present invention is characterized by adopting a porous nano metal structure or a two-dimensional nano metal structure as a nano metal structure to maximize the reactivity of the metal structure within the nano scale, thereby improving thermal stability, and improving structural stability when the nano metal structure is applied within the cathode active material layer.

[0055] Specifically, the nano metal structure is a reducing metal, and by including the nano metal structure in the cathode composition, when the cathode containing the cathode composition exhibits an abnormal temperature rise, the nano metal structure is preferentially oxidized over the lithium or cathode active material contained in the cathode to form a metal oxide, thereby reducing the amount of lithium oxide generated and delaying the thermal runaway time and speed.

[0056] In particular, the present invention is characterized by significantly improving reactivity with lithium by controlling the reducing metal to a nano-size. Since lithium is a highly reactive metal, there was a problem in that even when general reducing metals (such as Ni and Ti) were introduced to improve thermal stability, it was difficult for the reducing metal to form an oxide before lithium. As a result of research on this, it was discovered that structuring the metal to a nano-size can exhibit a reduction tendency different from the general reduction tendency. In particular, it was found that reactivity can be improved and the oxidation of lithium can be suppressed by structuring the metal into specific structures, such as porous nanoparticles or nanosheets.

[0057] The above-described nano-metal structure is a metal structure with high mechanical strength and is evenly dispersed in the negative electrode active material layer. That is, according to one embodiment of the present invention, the nano-metal structure with high mechanical strength is evenly dispersed in the negative electrode active material layer to mitigate volume changes during charging and discharging, and to prevent overheating and localized temperature rise caused by volume expansion during charging and discharging inside the battery. Since the above-described nano-metal structure has high electrical conductivity, it has the additional advantage of improving conductivity within the negative electrode and acting as a diffusion pathway for lithium ions.

[0058] In one embodiment of the present invention, the nano metal structure is included in an amount of 1 part by weight or more and 15 parts by weight or less based on 100 parts by weight of the cathode composition. When the nano metal structure is included in the above range, thermal safety can be improved without reducing the capacity of the battery. Preferably, in order to secure sufficient battery capacity, the nano metal structure is included in an amount of 1 part by weight to 10 parts by weight based on 100 parts by weight of the cathode composition. For example, it is included in an amount of 1 part by weight or more, 2 parts by weight or more, or 3 parts by weight or more, and in an amount of 15 parts by weight or less, 10 parts by weight or less, or 8 parts by weight or less. That is, the nano metal structure is included in an amount of 1 part by weight to 10 parts by weight, 3 parts by weight to 10 parts by weight, 3 parts by weight to 8 parts by weight, or 5 parts by weight to 8 parts by weight based on 100 parts by weight of the cathode composition.

[0059] In one embodiment of the present invention, the nano metal structure comprises a porous nano metal structure.

[0060] The porous nanometal structure described above includes pores, and the average pore size may be 8 nm to 600 nm. When the average pore size of the porous nanometal structure satisfies the above range, a sufficient number of pores is secured within the structure, resulting in a larger specific surface area compared to particles having the same particle size, thereby improving reactivity with oxygen and rapidly absorbing and dispersing heat generated inside the battery, which can suppress local temperature rise. Preferably, in terms of improving reactivity with oxygen, the average pore size may be 8 nm to 500 nm. For example, the average pore size may be 8 nm or more, 9 nm or more, or 10 nm or more, and 500 nm or less, 300 nm or less, 100 nm or less, 70 nm or less, or 50 nm or less. That is, the average pore size may be 8 nm to 500 nm, 8 nm to 300 nm, 8 nm to 100 nm, 8 nm to 50 nm, or 10 nm to 50 nm.

[0061] In this specification, the "pore size" or "average pore size" may be the average size of the pores measured through a BET method or an SEM image cross-sectional analysis method.

[0062] In one embodiment of the present invention, the pore size is measured by the BET method, and specifically, it may be calculated from the amount of nitrogen gas adsorbed at a liquid nitrogen temperature (77K) using BEL SORP-mini II of BEL Japan for the porous metal nanoparticles. That is, in the present invention, the pore size may refer to the average size of the pores measured by the above measurement method.

[0063] In another embodiment, the pore size is measured by a cross-sectional analysis method of SEM images, for example, through cross-sectional analysis of a cathode containing the cathode composition, and the cross-sectional analysis of the cathode can be performed using an ion milling device. Specifically, an electrode sample prepared by coating the cathode composition onto a copper foil (Cu Foil) is milled using a Hitachi IM4000 device. Afterward, an ion beam is fired at a voltage of 5 kV and treated for about 3 to 4 hours per sample, then a cross-sectional image is measured using a Hitachi S-4800 SEM, and the pore size can be measured for each particle observed in each SEM image obtained from the cross-sectional image. Five regions of the cross-section are randomly selected, and the cross-section is magnified by 100K to take a picture, and the average value of the pore size measured in each cross-sectional image obtained can be used.

[0064] The cross-sectional analysis of the above-mentioned cathode may be measured on the cathode before or after electrolyte impregnation in a secondary battery including the electrode, and may be measured before or after the charge and discharge of the secondary battery. Considering that particle deformation may occur after the charge and discharge of the secondary battery, the pore size may be measured before the initial charge and discharge of the secondary battery.

[0065] In one embodiment of the present invention, the BET specific surface area of ​​the porous nanometal body is 10 m² 2 / g to 200 m 2 It can be / g. For example, the BET specific surface area of ​​the porous nanometal is 10 m² 2 / g or more, 40 m 2 / g or more, 50 m 2 / g or more or 100 m 2 It can be more than / g, and 200 m 2 / g or less, 180 m 2 / g or less, 150 m 2 / g or less or 140 m 2 It may be less than / g. That is, the BET specific surface area of ​​the porous nanometal is 10 m² 2 / g to 200 m 2 / g, 40 m 2 / g to 200 m 2 / g, 50 m 2 / g to 200 m 2 / g, 100 m 2 / g to 200 m 2 / g, 50 m 2 / g to 150 m 2 / g or 100 m 2 / g to 150 m 2 It may be / g. The above BET specific surface area can be controlled according to the composition or average particle size of the porous nanometal body, and when the BET specific surface area is within the above range, the reactivity with oxygen is sufficiently high so that it can act as a reducing agent. If the above BET specific surface area exceeds the upper limit, the surface area relative to the particle increases excessively, which may cause particle breakage or electrode cracking in the operating environment.

[0066] In one embodiment of the present invention, the average particle size (D50) of the porous nano-metal body may be 10 nm to 5 μm. Alternatively, the average particle size (D50) of the porous nano-metal body may be 10 nm to 1.2 μm. For example, the average particle size (D50) of the porous nano-metal body may be 10 nm or more, 50 nm or more, 100 nm or more, 200 nm or more, 300 nm or more, or 400 nm, and may be 1.2 μm or less or 1 μm or less. That is, the average particle size of the porous nano-metal body may be 10 nm to 1.2 μm, 300 nm to 1.2 μm, 400 nm to 1.2 μm, or 400 nm to 1 μm. When the average particle size of the above porous nano metal body is below the lower limit, the particle size is excessively small, making it difficult to secure sufficient pores within the particle, which reduces reactivity and prevents it from performing its role as a reducing agent. When it exceeds the upper limit, the dispersibility within the cathode composition decreases, making it difficult to disperse evenly within the cathode active material layer, which may cause electrode cracking.

[0067] In one embodiment of the present invention, the porous nanometal structure may be a porous nanometal particle. For example, the porous nanometal structure may be a porous nano Ni particle.

[0068] In one embodiment of the present invention, the nano metal structure comprises a two-dimensional nano metal structure.

[0069] The above two-dimensional nano metal structure refers to a planar two-dimensional metal structure having a thickness of nanometers. The above two-dimensional nano metal structure (2D nano metal structure) may be a metal nanosheet.

[0070] The above nano sheet refers to a planar two-dimensional metal structure with an average thickness in the nanometer range. That is, the nano sheet refers to a two-dimensional nano metal structure, and the sheet may have a structure comprising a single layer or multiple layers. The nano sheet may be in the form of a flake or in the form of a mesh containing multiple pores. That is, the nano sheet is distinguished from a nano wire, which is a linear one-dimensional metal structure with a diameter (or diameter) in the nanometer range.

[0071] The average thickness of the metal nanosheet may be 10 nm to 100 nm. When the average thickness of the metal nanosheet falls within the above range, the metal nanosheet may be evenly dispersed in the cathode composition.

[0072] The metal nanosheet has a two-dimensional plane and an average thickness, and the width or major axis length of the two-dimensional plane may be 0.5 μm to 5 μm. The width (major axis length) of the two-dimensional plane may be 0.5 μm or more or 1 μm or more, and 5 μm or less or 3 μm or less. When the width (major axis length) of the metal nanosheet falls within the above range, the width of the two-dimensional plane may refer to the diameter of the two-dimensional plane if the two-dimensional plane is circular, and if the two-dimensional plane is non-circular, it may refer to the diameter of a circle calculated by approximating the non-spherical plane to a circle.

[0073] According to one embodiment of the present invention, the nano metal structure comprises one or more selected from the group consisting of Mg, Y, Al, Sn, Pb, V, Cr, Mn, Fe, Co, Ni, Zn, Zr, Nb, and Mo.

[0074] According to one embodiment of the present invention, the nano metal structure comprises one or more selected from the group consisting of Y, Al, Sn, Pb, Ti, V, Cr, Mn, Fe, Co, Ni, Zn, Zr, Nb, and Mo.

[0075] According to one embodiment of the present invention, the nano metal structure comprises one or more selected from the group consisting of Y, V, Cr, Mn, Fe, Co, Ni, Zn, Zr, Nb, and Mo.

[0076] Preferably, the nano metal structure comprises Ni. In particular, since Ni has a higher reactivity with oxygen compared to other metals and can more easily inhibit the oxidation reaction of Li, it is preferable for the nano metal structure to comprise Ni.

[0077] In one embodiment of the present invention, the nano metal structure may be of two or more types. That is, the nano metal structure may include two or more types of nano metal structures of different forms, or it may simultaneously include nano metal structures of the same form that contain different types of metals.

[0078] According to one embodiment of the present invention, the nano metal structure comprises an alkaline earth metal or a transition metal.

[0079] According to one embodiment of the present invention, the nano metal structure comprises an alkaline earth metal.

[0080] According to one embodiment of the present invention, the nano metal structure comprises a transition metal.

[0081] According to one embodiment of the present invention, the cathode composition comprises a cathode active material, the cathode active material comprises a silicon-based active material, and the silicon-based active material comprises Si, SiOx(0 <x<2) 및 Si / C로 이루어진 군에서 선택되는 1 이상을 포함한다.

[0082] According to one embodiment of the present invention, the cathode composition comprises a cathode active material, the cathode active material comprises a silicon-based active material, and the silicon-based active material comprises Si, SiOx(0 <x<2) 및 Si / C로 이루어진 군에서 선택되는 1 이상을 포함하며, 상기 실리콘계 활물질은 Si을 포함하고, 상기 Si는 상기 실리콘계 활물질 100 중량부 기준 40 중량부 이상 포함한다. 예컨대, 상기 Si는 상기 실리콘계 활물질 100 중량부 기준 40 중량부 이상, 45 중량부 이상, 50 중량부 이상 또는 60 중량부 이상 포함할 수 있고, 100 중량부 이하, 100 중량부 미만, 99 중량부 이하, 97 중량부 이하 또는 95 중량부 이하로 포함할 수 있다.

[0083] In one embodiment of the present invention, the silicon-based active material may be composed of silicon-based particles having 100 parts by weight of Si based on 100 parts by weight of the silicon-based active material.

[0084] In one embodiment of the present invention, the silicon-based active material may particularly include pure silicon (Si) particles. Using pure silicon (Si) particles as the silicon-based active material means that, when the negative electrode active material is based on 100 parts by weight of the total as described above, pure Si particles (Si) that are not combined with other particles or elements are included in the above range.

[0085] In one embodiment of the present invention, the silicon-based active material may include metal impurities, wherein the impurities may include metals that are generally included in the silicon-based active material, specifically 0.1 parts by weight or less based on 100 parts by weight of the silicon-based active material.

[0086] In one embodiment of the present invention, the silicon-based active material may be Si.

[0087] In one embodiment of the present invention, the silicon-based active material may be included in an amount of 5 parts by weight or more based on 100 parts by weight of the negative electrode active material. For example, the silicon-based active material may be included in an amount of 5 parts by weight or more, 10 parts by weight or more, 15 parts by weight or more, or 20 parts by weight or more based on 100 parts by weight of the negative electrode active material, and may be included in an amount of 100 parts by weight or less, less than 100 parts by weight, 99 parts by weight or less, 97 parts by weight or less, or 95 parts by weight or less.

[0088] In one embodiment of the present invention, the silicon-based active material may be included in an amount of 100 parts by weight based on 100 parts by weight of the negative electrode active material.

[0089] That is, in one embodiment of the present invention, the negative electrode active material may be the silicon-based active material.

[0090] In one embodiment of the present invention, the silicon-based active material generally has a characteristic BET surface area. The BET surface area of ​​the silicon-based active material is 0.01 m² 2 / g to 150.0 m 2 It can be / g. For example, the above BET specific surface area is 0.1 m 2 / g or more, 0.5 m 2 / g or more, 1 m 2 / g or more or 10 m 2 It may be greater than / g, and 150 m 2 / g or less, 130 m 2 / g or less, 100 m 2 / g or less, 80 m 2 / g or less, 50 m 2 / g or less or 40 m 2 It may be less than / g. The BET surface area is measured according to DIN 66131 (using nitrogen).

[0091] The above silicon-based active material has the above surface area, and the size of the surface area of ​​the silicon-based active material can be controlled by changing the process conditions during the manufacturing process and the growth conditions of the silicon-based active material.

[0092] In addition, when lithium ions are inserted, they are inserted uniformly, which can reduce the stress on the lithium ions inserted into the silicon particles and thereby mitigate particle breakage. As a result, it has the characteristic of improving the lifespan stability of the anode. If the surface area is less than the above range, even if the particle size is the same, the surface is formed smoothly, which reduces the bonding strength with the binder and causes electrode cracks. In this case, lithium ions are inserted unevenly into the particles, and the stress due to ion insertion increases, causing particle breakage.

[0093] In one embodiment of the present invention, the silicon-based active material generally has a characteristic average particle size (D50). The average particle size (D50) of the silicon-based active material is 1 μm to 15 μm. For example, the average particle size (D50) of the silicon-based active material may be 1 μm or more, 1.5 μm or more, or 3 μm or more, and may be 15 μm or less, 13 μm or less, 10 μm or less, 8 μm or less, or 6 μm or less.

[0094] In one embodiment of the present invention, the crystal grain size of the silicon-based active material may be 200 nm or less.

[0095] In another embodiment, the crystal grain size of the silicon-based active material may be 200 nm or less, 130 nm or less, 110 nm or less, 100 nm or less, 95 nm or less, or 91 nm or less. The crystal grain size of the silicon-based active material may have a range of 10 nm or more and 15 nm or more.

[0096] The above silicon-based active material has the aforementioned grain size, and the grain size of the silicon-based active material can be controlled by changing the process conditions during the manufacturing process. In this case, by satisfying the above range so that grain boundaries are widely distributed, lithium ions can be inserted uniformly, thereby reducing the stress required during lithium ion insertion into the silicon particles and mitigating particle breakage. As a result, it possesses the characteristic of improving the lifespan stability of the anode. If the grain size exceeds the above range, grain boundaries within the particles become narrowly distributed; in this case, lithium ions are inserted unevenly into the particles, and the stress caused by ion insertion increases, leading to particle breakage.

[0097] In one embodiment of the present invention, the silicon-based active material comprises a crystal structure having a crystal grain distribution of 1 nm or more and 200 nm or less, and the area ratio of the crystal structure relative to the total area of ​​the silicon-based active material may be 5% or less.

[0098] In another embodiment, the area ratio of the crystal structure based on the total area of ​​the silicon-based active material may be 5% or less, 3% or less, and 0.1% or more.

[0099] The silicon-based active material according to the present invention has a crystal grain size of 200 nm or less, so that the size of a single crystal structure is formed small and the above area ratio can be satisfied. Accordingly, the distribution of grain boundaries can be widened, and accordingly, the aforementioned effect can be exhibited.

[0100] In one embodiment of the present invention, the number of crystal structures included in the silicon-based active material may be 20 or more. In another embodiment, the number of crystal structures included in the silicon-based active material may be 20 or more, 30 or more, or 35 or more, and may satisfy a range of 60 or fewer, or 50 or fewer.

[0101] That is, as described above, when the silicon-based active material satisfies the above range for grain size and also satisfies the above range for the number of crystal structures, the strength of the silicon-based active material itself is within an appropriate range, thereby providing flexibility when included in the electrode and having the characteristic of efficiently suppressing volume expansion.

[0102] In the present invention, a grain refers to a crystal particle in a metal or material that consists of a collection of irregular shapes of microscopic size, and the grain size may refer to the diameter of the observed grain particle. That is, in the present invention, the grain size refers to the size of a domain within the particle that shares the same crystal orientation, and has a concept different from the particle size or particle diameter that expresses the size of the material.

[0103] In one embodiment of the present invention, the grain size can be calculated as the Full Width at Half Maximum (FWHM) value through XRD analysis. The remaining values, excluding L, are measured through XRD analysis of the silicon-based active material, and the grain size can be determined through the Debey-Scherrer equation, which indicates that FWHM and grain size have an inverse relationship. At this time, the Debey-Scherrer equation is as shown in Equation 1-1 below.

[0104] [Equation 1-1]

[0105] FWHM=Kλ / LCosθ

[0106] In the above Equation 1-1,

[0107] L represents the grain size, K is a constant, θ is the Bragg angle, and λ is the wavelength of the X-ray.

[0108] In addition, the shape of the crystal grains can be varied and measured in three dimensions, and generally, the size of the crystal grains can be measured using commonly used methods such as the circle method and the diameter measurement method, but is not limited thereto.

[0109] The above diameter measurement method can be performed by drawing 5 to 10 parallel lines, each with a length of L mm, on a micrograph of the target particle, counting the number of crystal grains z along the lines, and averaging them. In this case, only those that completely enclose the lines are counted, while those that overlap are excluded. If the number of lines is P and the magnification is V, the average particle diameter can be calculated using the following Equation 1-2.

[0110] [Equation 1-2]

[0111] Dm = (L*P*10 3 ) / (zV) (㎛)

[0112] In addition, the above-mentioned circle method is a method of calculating the average area of ​​a crystal grain by drawing a circle of a predetermined diameter on a micrograph of the target particle and determining the number of crystal grains inside the circle and the number of crystal grains overlapping the boundary line, which can be calculated using the following Equation 1-3.

[0113] [Equation 1-3]

[0114] Fm = (Fk * 10 6 ) / ((0.67n + z) V 2 ) (㎛ 2 )

[0115] In the above Equations 1-3, Fm represents the average particle area, Fk represents the measurement area on the photograph, z represents the number of particles inside the circle, n represents the number of particles on the arc, and V represents the magnification of the microscope.

[0116] According to one embodiment of the present invention, the cathode active material may provide a cathode composition further comprising a carbon-based active material.

[0117] That is, in one embodiment of the present invention, the negative electrode active material may include a silicon-based active material and a carbon-based active material.

[0118] The cathode active material of the cathode composition according to one embodiment of the present invention may be in the form of a mixture of a silicon-based active material and a carbon-based active material.

[0119] According to one embodiment of the present invention, the carbon-based active material is graphite. The graphite includes artificial graphite and natural graphite. When the carbon-based active material is graphite such as natural graphite or artificial graphite, the weight portion of the graphite used as the carbon-based active material is not considered when defining the total weight portion of the conductive material described below. Similarly, when the conductive material selected according to the cathode is graphite, the weight portion of the conductive material described is not included when defining the total weight portion of the carbon-based cathode active material. Therefore, when graphite is selected as both the carbon-based cathode active material and the cathode conductive material, the total weight portion of the graphite corresponds to the sum of the weight portion of the graphite used as the carbon-based cathode active material and the weight portion of the graphite used as the cathode conductive material.

[0120] In one embodiment of the present invention, the carbon-based active material may include at least one selected from the group consisting of artificial graphite and natural graphite. Specifically, the carbon-based active material may use natural graphite, artificial graphite, and a mixture of natural graphite and artificial graphite.

[0121] The above artificial graphite is generally manufactured by carbonizing raw materials such as coal tar, coal tar pitch, and petroleum-based heavy oils at temperatures above 2,500°C, and is used as a negative electrode active material after undergoing particle size adjustments such as grinding and secondary particle formation following this graphitization. In the case of artificial graphite, crystals are randomly distributed within the particles, and compared to natural graphite, it has a lower degree of sphericity and a somewhat pointed shape.

[0122] According to one embodiment of the present invention, when the graphite is artificial graphite, the average particle size (D50) of the artificial graphite may be 15 μm to 50 μm. If the average particle size (D50) of the artificial graphite is 15 μm or more, the cathode adhesion strength can be improved, and if it is 50 μm or less, the particle size can be effectively controlled to improve the cathode rapid charging performance.

[0123] The above natural graphite generally exists as plate-like aggregates before processing, and the plate-like particles are manufactured into a spherical shape with a smooth surface through post-processing, such as particle grinding and reassembly, in order to be used as an active material for electrode manufacturing.

[0124] In addition, the natural graphite may have an average particle size (D50) of 5 μm to 30 μm, or 7 μm to 25 μm.

[0125] When the above carbon-based active material is a mixture of artificial graphite and natural graphite, the weight ratio of the artificial graphite and natural graphite may be 9.99 : 0.01 to 0.01 : 9.99, or 9.7 : 0.3 to 7:3. When satisfying this weight ratio range, superior output may be exhibited.

[0126] According to one embodiment of the present invention, the carbon-based active material may comprise 70 parts by weight or more based on 100 parts by weight of the negative electrode active material. For example, the carbon-based active material may comprise 70 parts by weight or more, 80 parts by weight or more, 90 parts by weight or more, or 95 parts by weight or more based on 100 parts by weight of the negative electrode active material, and may comprise 100 parts by weight or less, less than 100 parts by weight, 99 parts by weight or less, 97 parts by weight or less, or 95 parts by weight or less.

[0127] According to one embodiment of the present invention, the natural graphite may be included in an amount of 10 to 50 parts by weight, for example, 10 to 45 parts by weight, based on 100 parts by weight of the negative electrode active material.

[0128] According to one embodiment of the present invention, the artificial graphite may be included in an amount of 50 to 99 parts by weight, for example, 50 parts by weight or more, 60 parts by weight or more, based on 100 parts by weight of the negative electrode active material, or 90 parts by weight or less, or 85 parts by weight or less. When the artificial graphite content is higher than the natural graphite content, it may be advantageous for improving rapid charging performance.

[0129] According to one embodiment of the present invention, when the negative electrode active material further comprises a carbon-based active material, the silicon-based active material may be included in an amount of 1 to 20 parts by weight based on 100 parts by weight of the negative electrode active material. For example, it may be included in an amount of 1 part by weight or more, 5 parts by weight or more, or 10 parts by weight or more, and may be included in an amount of 20 parts by weight or less, or 18 parts by weight or less. When the silicon-based active material is included in the above range, the capacity of the battery can be high, and volume expansion stability can be improved.

[0130] In one embodiment of the present invention, the silicon-based active material satisfies the range of Formula 2-1 below.

[0131] [Equation 2-1]

[0132] X1 / Y1 ≤ 0.960

[0133] In the above Equation 2-1,

[0134] X1 is the actual area of ​​the negative electrode active material, and

[0135] Y1 represents the area of ​​a spherical particle with the same perimeter as the cathode active material.

[0136] The measurement of Equation 2-1 above can be performed using a particle shape analyzer. Specifically, the cathode active material according to the present invention is scattered over a glass plate by air jetting, and the scattered particles are captured as shadow images to measure the shapes of 10,000 cathode active material particles within the photograph. In this case, Equation 2-1 represents the average value for 10,000 particles. Equation 2-1 according to the present invention can be measured from the above image, and Equation 2-1 can be expressed as the circularity of the cathode active material. The circularity is [4π (actual area of ​​the cathode active material) / (boundary) 2 It may also be displayed as ]

[0137] In one embodiment of the present invention, the degree of sphericity of the negative electrode active material may be, for example, 0.960 or less, 0.957 or less. The degree of sphericity of the negative electrode active material may be 0.8 or more, 0.9 or more, 0.93 or more, 0.94 or more, or 0.941 or more.

[0138] In one embodiment of the present invention, the negative electrode active material satisfies the range of Formula 2-2 below.

[0139] [Equation 2-2]

[0140] X2 / Y2 ≤ 0.995

[0141] In the above Equation 2-2,

[0142] Y2 is the actual circumference of the negative electrode active material and

[0143] X2 is the circumference of the circumscribed figure of the negative electrode active material.

[0144] The measurement of Equation 2-2 above can be performed using a particle shape analyzer. Specifically, the cathode active material according to the present invention can be scattered over a glass plate by blowing air, and the scattered particles can be photographed as shadow images to measure the shapes of 10,000 cathode active material particles within the photograph. In this case, Equation 2-2 represents the average value for 10,000 particles. Equation 2-2 according to the present invention can be measured from the above image, and Equation 2-2 can be expressed as the Convexity of the cathode active material.

[0145] In one embodiment of the present invention, the range X2 / Y2 ≤ 0.995 may be satisfied, and the range 0.8 ≤ X2 / Y2, 0.9 ≤ X2 / Y2, 0.95 ≤ X2 / Y2, or 0.98 ≤ X2 / Y2 may be satisfied.

[0146] The smaller the value of Equation 2-1 or Equation 2-2 above, the greater the roughness of the negative electrode active material. By using a negative electrode active material having such a range, the bonding strength with the binder increases, thereby providing the characteristic of mitigating cracks in the electrode due to repeated charge-discharge cycles.

[0147] In one embodiment of the present invention, the negative electrode active material has a particle size distribution of 0.01 μm or more and 30 μm or less.

[0148] The statement that the above-mentioned negative electrode active material includes negative electrode active material particles having a particle size distribution of 0.01 μm or more and 30 μm or less means that it includes a number of individual negative electrode active material particles having a particle size within the above range, and the number of negative electrode active material particles included is not limited.

[0149] The above particle size can be expressed by its diameter in the case of a spherical shape, but the particle size can also be measured in comparison to the case of a spherical shape even in the case of a non-spherical shape, and the particle size of individual particles can be measured using methods generally measured in the industry.

[0150] According to one embodiment of the present invention, a cathode composition is provided that comprises at least 60 parts by weight of the cathode active material based on 100 parts by weight of the cathode composition.

[0151] In another embodiment, the cathode active material may be 60 parts by weight or more, 65 parts by weight or more, 70 parts by weight or more based on 100 parts by weight of the cathode composition, and may be 97 parts by weight or less, 95 parts by weight or less, 91 parts by weight or less, or 90 parts by weight or less.

[0152] In one embodiment of the present invention, the conductive material may include one or more selected from the group consisting of point-type conductive materials, planar-type conductive materials, and linear-type conductive materials.

[0153] In one embodiment of the present invention, the point-shaped conductive material can be used to improve conductivity of the cathode and refers to a spherical or point-shaped conductive material that has conductivity without causing chemical changes. Specifically, the point-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, Farnes 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 achieving high conductivity and excellent dispersibility.

[0154] In one embodiment of the present invention, the point-shaped conductive material has a BET specific surface area of ​​40 m² 2 / g or more 70m 2 It may be less than / g, and 45m 2 / g or more 65m 2 / g or less, or 50m 2 / g or more 60m 2 It may be less than / g.

[0155] In one embodiment of the present invention, the point-shaped conductive material may 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.

[0156] In particular, when the functional group content of the point-shaped conductive material satisfies the above range, the functional group present on the surface of the point-shaped conductive material is present, so that the point-shaped conductive material can be smoothly dispersed within the solvent when water is used as the solvent.

[0157] In one embodiment of the present invention, the conductive material may include a planar conductive material.

[0158] The above-mentioned planar conductive material can be described as a plate-shaped conductive material or a bulk-shaped conductive material, as it can improve conductivity by increasing surface contact between silicon particles within the cathode and simultaneously suppress the interruption of conductive pathways due to volume expansion.

[0159] In one embodiment of the present invention, the planar conductive material may comprise at least one selected from the group consisting of plate-shaped graphite, graphene, graphene oxide, and graphite flakes, and preferably may be plate-shaped graphite.

[0160] In one embodiment of the present invention, the average particle size (D50) of the planar conductive material may be 2 μm to 7 μm, specifically 3 μm to 6 μm, and more specifically 4 μm to 5 μm. When the above range is satisfied, dispersion is easy without causing an excessive increase in the viscosity of the cathode composition due to the sufficient particle size. Therefore, when dispersion is performed using the same equipment and time, the dispersion effect is excellent.

[0161] In one embodiment of the present invention, the planar conductive material may be a planar conductive material with a high specific surface area having a high BET specific surface area; or a planar conductive material with a low specific surface area.

[0162] In one embodiment of the present invention, a planar conductive material with a high specific surface area or a planar conductive material with a low specific surface area may be used without limitation as the planar conductive material; however, since the planar conductive material according to the present invention may be affected to some extent by dispersion in electrode performance, it may be particularly preferable to use a planar conductive material with a low specific surface area that does not cause problems with dispersion.

[0163] In one embodiment of the present invention, the planar conductive material has a BET specific surface area of ​​5 m² 2 It can be more than / g.

[0164] In another embodiment, the planar conductive material has a BET specific surface area of ​​5m² 2 / g or more than 500m 2 It may be less than / g, preferably 5m 2 / g or more than 300m 2 / g or less, more preferably 5m 2 / g or more 250m 2 It may be less than / g.

[0165] In another embodiment, the planar conductive material is a high specific surface area planar conductive material, and has a BET specific surface area of ​​50 m² 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 It can satisfy a range of / g or less.

[0166] In another embodiment, the planar conductive material is a low specific surface area planar conductive material, and the BET specific surface area is 5m² 2 / g or more 40m 2 / g or less, preferably 5m2 / g or more 30m 2 / g or less, more preferably 5m 2 / g or more 25m 2 It can satisfy a range of / g or less.

[0167] Other conductive materials may include linear conductive materials such as carbon nanotubes. The carbon nanotubes may be bundled carbon nanotubes. The bundled carbon nanotubes may comprise a plurality of carbon nanotube units. Specifically, "bundle type" here refers to a secondary shape in the form of a bundle or rope in which a plurality of carbon nanotube units are arranged parallel or intertwined with the axes along the longitudinal direction of the carbon nanotube units having substantially the same orientation, unless otherwise noted. The carbon nanotube units have a graphite sheet having a cylindrical shape with a nano-sized diameter, and sp 2 It has a bonded structure. At this time, depending on the angle and structure in which the graphite plane is rolled, it may exhibit conductive or semiconductor characteristics. Compared to entangled type carbon nanotubes, the bundled carbon nanotubes can be uniformly dispersed during cathode manufacturing and smoothly form a conductive network within the cathode, thereby improving the conductivity of the cathode.

[0168] In one embodiment of the present invention, the linear conductive material may include SWCNT; or MWCNT.

[0169] In one embodiment of the present invention, the cathode conductive material is provided in an amount of 0.01 parts by weight or more and 40 parts by weight or less based on 100 parts by weight of the cathode composition.

[0170] In another embodiment, the cathode conductive material may comprise 0.01 parts by weight or more and 40 parts by weight or less, 0.01 parts by weight or more and 30 parts by weight or less, or 0.05 parts by weight or more and 25 parts by weight or less, based on 100 parts by weight of the cathode composition.

[0171] The cathode conductive material according to the present invention has a completely separate composition from the anode conductive material applied to the anode. That is, the cathode conductive material according to the present invention serves to hold the contact points between silicon-based active materials, which undergo significant volume expansion of the electrodes due to charging and discharging, whereas the anode conductive material serves as a buffer during rolling and provides some conductivity; thus, their composition and roles are completely different from those of the cathode conductive material of the present invention.

[0172] Furthermore, the cathode conductive material according to the present invention is applied to silicon-based active materials and has a completely different composition from that of a conductive material applied to graphite-based active materials. That is, a conductive material used in an electrode having a graphite-based active material simply has particles smaller than the active material, thereby providing improved output characteristics and some conductivity; thus, its composition and role are completely different from that of a cathode conductive material applied together with a silicon-based active material as in the present invention.

[0173] In one embodiment of the present invention, the cathode binder may comprise at least one selected from the group consisting of polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethylmethacrylate, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene butadiene rubber (SBR), fluororubber, polyacrylic acid, and materials in which hydrogens thereof are substituted with Li, Na, or Ca, etc., and may also comprise various copolymers thereof.

[0174] A negative electrode binder according to one embodiment of the present invention serves to hold the active material and the conductive material to prevent distortion and structural deformation of the negative electrode structure during volume expansion and relaxation of the silicon-based active material. Any general binder that satisfies the above role can be applied, and specifically, an aqueous binder or a non-aqueous binder can be used.

[0175] In one embodiment of the present invention, the cathode composition is provided such that the cathode binder comprises 5 parts by weight or more and 12 parts by weight or less based on 100 parts by weight of the cathode composition.

[0176] In another embodiment, the cathode binder may be 5 parts by weight or more and 12 parts by weight or 7 parts by weight or more and 11 parts by weight or 8 parts by weight or more and 11 parts by weight or less, based on 100 parts by weight of the cathode composition.

[0177] In the case of the negative electrode for a lithium secondary battery according to the present invention, a silicon-based active material is used in the above weight portion to maximize capacity characteristics, and compared to the case where only a conventional carbon-based active material is used as the active material, the volume expansion during charging and discharging is significantly increased. Accordingly, by including the negative electrode binder in the above content portion, it has the characteristic of being able to efficiently control the volume expansion of the silicon-based active material with high rigidity during charging and discharging.

[0178] cathode

[0179] According to one embodiment of the present invention, a cathode is provided comprising a cathode current collector and a cathode active material layer provided on the cathode current collector, wherein the cathode active material layer comprises a cathode composition according to one embodiment of the present invention.

[0180] FIG. 1 is a diagram showing a stacked structure of a cathode according to one embodiment of the present invention. Specifically, a cathode (100) including a cathode active material layer (20) on one surface of a cathode current collector (10) can be seen, and FIG. 1 shows that the cathode active material layer is formed on one surface, but it can be included on both surfaces of the cathode current collector.

[0181] According to one embodiment of the present invention, a cathode is provided comprising a cathode current collector and a cathode active material layer provided on one or both sides of the cathode current collector, wherein the cathode active material layer comprises a cathode composition according to one embodiment of the present invention.

[0182] According to one embodiment of the present invention, the cathode active material layer provides a cathode comprising a metal oxide represented by the following formula 1.

[0183] [Equation 1]

[0184] MaOb (1≤a≤5, 1≤b≤5)

[0185] In the above formula 1, M includes one or more selected from the group consisting of Mg, Y, Al, Sn, Pb, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Nb, and Mo.

[0186] According to one embodiment of the present invention, since the cathode composition includes a nano metal structure, the nano metal structure within the cathode oxidizes at an abnormal temperature to form a metal oxide, thereby improving the thermal runaway phenomenon.

[0187] According to one embodiment of the present invention, the M comprises one or more selected from the group consisting of Mg, Y, Al, Sn, Pb, Ti, V, Cr, Mn, Fe, Co, Ni, Zn, Zr, Nb, and Mo.

[0188] According to one embodiment of the present invention, M comprises one or more selected from the group consisting of Y, Al, Sn, Pb, Ti, V, Cr, Mn, Fe, Co, Ni, Zn, Zr, Nb, and Mo.

[0189] According to one embodiment of the present invention, M comprises one or more selected from the group consisting of Y, Ti, V, Cr, Mn, Fe, Co, Ni, Zn, Zr, Nb, and Mo.

[0190] According to one embodiment of the present invention, M includes Ni. For example, the metal oxide may be NiO.

[0191] In one embodiment of the present invention, the metal oxide may be of two or more types. That is, the metal oxide may include two or more different metal oxides represented by Formula 1. For example, the metal oxide may simultaneously include TiO2 and NiO.

[0192] The metal oxide represented by Formula 1 above may be included in an amount of 1 to 15 parts by weight based on 100 parts by weight of the negative electrode active material layer. For example, it may be included in an amount of 5 to 15 parts by weight, 5 to 10 parts by weight, 6 to 15 parts by weight, or 6 to 10 parts by weight. When included within the above range, it can be evaluated that the oxidation reaction of lithium is effectively suppressed without degrading battery performance. If the above range is exceeded, it may adversely affect the capacity.

[0193] In one embodiment of the present invention, the cathode may be formed by applying and drying the cathode composition on one or both sides of a cathode current collector.

[0194] In one embodiment of the present invention, the cathode may be formed by applying and drying a cathode slurry containing the cathode composition on one or both sides of a cathode current collector.

[0195] At this time, the cathode slurry may include the aforementioned cathode composition; and a slurry solvent.

[0196] In one embodiment of the present invention, the solid content of the cathode slurry may satisfy a range of 5% or more and 55% or less. In another embodiment, the solid content of the cathode slurry may satisfy a range of 5% or more and 55% or less, 7% or more and 35% or less, or 10% or more and 30% or less.

[0197] The solid content of the above cathode slurry may refer to the content of the cathode active material, cathode conductive material, and cathode binder excluding the solvent within the above cathode slurry, and may refer to the sum of the cathode active material, cathode conductive material, and cathode binder based on 100 parts by weight of the cathode composition.

[0198] When the solid content of the above cathode slurry satisfies the above range, the viscosity is suitable when forming the cathode active material layer, thereby minimizing particle aggregation and enabling the cathode active material layer to be formed efficiently.

[0199] In one embodiment of the present invention, the cathode slurry solvent may be used without limitation as long as it is used in the art, and specifically, water (distilled water), acetone, or NMP may be used.

[0200] In one embodiment of the present invention, the negative current collector generally has a thickness of 1 μm to 100 μm. Such a negative current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface treated with carbon, nickel, titanium, silver, etc., or aluminum-cadmium alloy may be used. In addition, fine irregularities may be formed on the surface to strengthen the bonding strength of the negative active material, and it may be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0201] In one embodiment of the present invention, a negative electrode for a secondary battery is provided, wherein the thickness of the negative current collector is 1 μm or more and 100 μm or less, and the thickness of the negative active material layer is 10 μm or more and 500 μm or less.

[0202] In the present invention, the negative electrode active material layer may refer to the thickness of a single layer of negative electrode active material layer when it is formed on one surface of a negative electrode current collector.

[0203] However, the thickness may vary depending on the type and application of the cathode used, and is not limited thereto.

[0204] In one embodiment of the present invention, a negative electrode for a secondary battery is provided, wherein the porosity of the negative electrode active material layer is 40% or more and 60% or less.

[0205] In another embodiment, the porosity of the cathode active material layer may satisfy a range of 40% or more and 60% or less, 45% or more and 60% or less, or 50% or more and 55% or less.

[0206] The above porosity varies according to the composition and content of the silicon-based active material, carbon-based active material, cathode conductive material, and cathode binder included in the cathode active material layer, and in particular, satisfies the above range by including the silicon-based active material, carbon-based active material, cathode conductive material, and cathode binder according to the present invention in specific compositions and contents, and accordingly, the electrical conductivity and resistance of the electrode have an appropriate range.

[0207] secondary battery

[0208] According to one embodiment of the present invention, a lithium secondary battery is provided comprising a positive electrode, a negative electrode for a secondary battery according to the present invention, a separator provided between the positive electrode and the negative electrode, and an electrolyte.

[0209] FIG. 2 is a diagram showing a stacked structure of a secondary battery according to one embodiment of the present invention. Specifically, a negative electrode (100) including a negative active material layer (20) on one surface of a negative electrode current collector (10) can be seen, and a positive electrode (200) for a lithium secondary battery including a positive active material layer (40) on one surface of a positive electrode current collector (50) can be seen, and the negative electrode (100) and the positive electrode (200) are formed in a stacked structure with a separator (30) in between.

[0210] A secondary battery according to one embodiment of the present specification may particularly include a negative electrode for a secondary battery as 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, wherein the negative electrode is identical to the negative electrode described above. Since the negative electrode has been described above, a detailed description thereof is omitted.

[0211] The above positive electrode may include a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector and comprising the positive electrode active material.

[0212] In the above-mentioned positive electrode, the positive current collector is not particularly limited as long as it is conductive without causing chemical changes 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 above-mentioned positive current collector may typically have a thickness of 3 to 500 μm, and fine irregularities may be formed on the surface of the current collector to increase the adhesion of the positive active material. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0213] The above-mentioned positive electrode active material may be a commonly used positive electrode active material. Specifically, the above-mentioned positive electrode active material may be a layered compound such as lithium cobalt oxide (LiCoO2) or lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; lithium iron oxide such as LiFe3O4; or a compound with the chemical formula Li 1+c1 Mn 2-c1 Lithium manganese oxides such as O4 (0≤c1≤0.33), LiMnO3, LiMn2O3, LiMnO2, etc.; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, V2O5, Cu2V2O7, etc.; chemical formula LiNi 1-c2 M c2 Ni-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, satisfying 0.01≤c2≤0.6); chemical formula LiMn 2-c3 M c3Examples include lithium manganese composite oxides represented by O2 (where M is at least one selected from the group consisting of Co, Ni, Fe, Cr, Zn and Ta, satisfying 0.01≤c3≤0.6) or Li2Mn3MO8 (where M is at least one selected from the group consisting of Fe, Co, Ni, Cu and Zn); and LiMn2O4 in which a portion of the Li in the chemical formula is substituted with alkaline earth metal ions, but are not limited thereto. The anode may also be Li-metal.

[0214] In one embodiment of the present invention, the positive active material comprises a lithium composite transition metal compound comprising nickel (Ni), cobalt (Co) and manganese (Mn), and the lithium composite transition metal compound comprises single particles or secondary particles, and the average particle size (D50) of the single particles may be 1 μm or more.

[0215] For example, the average particle size (D50) of the above single particle may be 1 μm or more and 12 μm or less, 1 μm or more and 8 μm or less, 1 μm or more and 6 μm or less, greater than 1 μm and 12 μm or less, greater than 1 μm and 8 μm or less, or greater than 1 μm and 6 μm or less.

[0216] Even if the above single particles are formed with an average particle size (D50) of 1㎛ or more and 12㎛ or less, their particle strength can be excellent. For example, the above single particles have a strength of 650 kgf / cm² 2 When rolled with the force, it can have a particle strength of 100 to 300 MPa. Accordingly, the above single particle is 650 kgf / cm² 2 Even if rolled with strong force, the phenomenon of increased fine particles within the electrode due to particle breakage is mitigated, and thereby the lifespan characteristics of the battery are improved.

[0217] The above single particle can be manufactured by mixing a transition metal precursor and a lithium raw material and calcining them. The above secondary particle can be manufactured by a different method than the above single particle, and its composition may be the same as or different from the composition of the single particle.

[0218] The method of forming the above single particles is not particularly limited, but generally, they can be formed by increasing the firing temperature to underfire, or by using additives such as grain growth promoters that aid in underfire, or by changing the starting material.

[0219] For example, the above calcination is performed at a temperature capable of forming single particles. To form these, calcination must be performed at a higher temperature than that used for manufacturing secondary particles; for example, when the precursor composition is the same, calcination must be performed at a temperature approximately 30°C to 100°C higher than that used for manufacturing secondary particles. The calcination temperature for forming the single particles may vary depending on the metal composition within the precursor; for example, when forming single particles of a high-nickel (High-Ni) NCM-based lithium composite transition metal oxide with a nickel (Ni) content of 80 mol% or more, the calcination temperature may be approximately 700°C to 1000°C, preferably 800°C to 950°C. When the calcination temperature satisfies the above range, an anode active material containing single particles with excellent electrochemical properties can be manufactured. If the calcination temperature is less than 790℃, a positive electrode active material containing a lithium complex transition metal compound in the form of secondary particles can be manufactured, and if it exceeds 950℃, excessive calcination occurs, and the layered crystal structure is not properly formed, which may degrade the electrochemical properties.

[0220] In this specification, the term "single particle" is used to distinguish it from a secondary particle formed by the aggregation of tens to hundreds of conventional primary particles, and is a concept that includes a single particle consisting of one primary particle and a pseudo-single particle form which is an aggregate of 30 or fewer primary particles.

[0221] Specifically, in the present invention, the single particle may be in the form of a single particle consisting of one primary particle or a pseudo-single particle which is an aggregate of 30 or fewer primary particles, and the secondary particle may be in the form of an aggregate of hundreds of primary particles.

[0222] In one embodiment of the present invention, the lithium composite transition metal compound that is the positive electrode active material further comprises secondary particles, and the average particle size (D50) of the single particle is smaller than the average particle size (D50) of the secondary particles.

[0223] In the present invention, the single particle may be in the form of a single particle consisting of one primary particle or a pseudo-single particle which is an aggregate of 30 or fewer primary particles, and the secondary particle may be in the form of hundreds of primary particles aggregated.

[0224] The aforementioned lithium complex transition metal compound may further include secondary particles. Secondary particles refer to forms formed by the aggregation of primary particles and can be distinguished from the concept of single particles, which includes a single primary particle, a single particle, or a pseudo-single particle form which is an aggregate of 30 or fewer primary particles.

[0225] The particle size (D50) of the secondary particle may be 1 μm to 20 μm, 2 μm to 17 μm, preferably 3 μm to 15 μm. The specific surface area (BET) of the secondary particle is 0.05 m² 2 / g to 10 m 2 It can be / g, preferably 0.1 m 2 / g to 1 m 2 It can be / g, and more preferably 0.3 m 2 / g to 0.8 m 2 / g can be.

[0226] In a further embodiment of the present invention, the secondary particle is an aggregate of the primary particle, and the average particle size (D50) of the primary particle is 0.5 μm to 3 μm. Specifically, the secondary particle may be in the form of hundreds of primary particles aggregated, and the average particle size (D50) of the primary particle may be 0.6 μm to 2.8 μm, 0.8 μm to 2.5 μm, or 0.8 μm to 1.5 μm.

[0227] If the average particle size (D50) of the primary particles satisfies the above range, a single-particle cathode active material with excellent electrochemical properties can be formed. If the average particle size (D50) of the primary particles is too small, the number of aggregates of primary particles forming lithium nickel-based oxide particles increases, and the effect of suppressing particle breakage during rolling decreases; if the average particle size (D50) of the primary particles is too large, the lithium diffusion path within the primary particles becomes longer, which may increase resistance and decrease output characteristics.

[0228] According to a further embodiment of the present invention, the average particle size (D50) of the single particle is smaller than the average particle size (D50) of the secondary particle. Thus, even if the single particle is formed with a small particle size, the particle strength can be excellent, and as a result, the phenomenon of increased fine particles within the electrode due to particle breakage is mitigated, and the lifespan characteristics of the battery can be improved.

[0229] In one embodiment of the present invention, the average particle size (D50) of the single particle is 1 μm to 18 μm smaller than the average particle size (D50) of the secondary particle.

[0230] For example, the average particle size (D50) of the above single particle may be 1 μm to 16 μm smaller than the average particle size (D50) of the above secondary particle, 1.5 μm to 15 μm smaller, or 2 μm to 14 μm smaller.

[0231] When the average particle size (D50) of the single particle is smaller than the average particle size (D50) of the secondary particle, for example, when the above range is satisfied, the particle strength of the single particle can be excellent even if it is formed with a small particle size, and as a result, the phenomenon of increased fine particles within the electrode due to particle breakage is mitigated, thereby improving the lifespan characteristics and energy density of the battery.

[0232] According to a further embodiment of the present invention, the single particle is included in an amount of 15 to 100 parts by weight per 100 parts by weight of the positive active material. The single particle may be included in an amount of 20 to 100 parts by weight, or 30 to 100 parts by weight, per 100 parts by weight of the positive active material.

[0233] When including single particles within the above range, excellent battery characteristics can be exhibited in combination with the aforementioned cathode material. In particular, when the single particles are 15 parts by weight or more, the phenomenon of increased fine particles within the electrode due to particle breakage during the rolling process after electrode fabrication can be mitigated, and thereby the lifespan characteristics of the battery can be improved.

[0234] In one embodiment of the present invention, the lithium composite transition metal compound may further include secondary particles, and the secondary particles may be 85 parts by weight or less per 100 parts by weight of the positive electrode active material. The secondary particles may be 80 parts by weight or less, 75 parts by weight or less, or 70 parts by weight or less per 100 parts by weight of the positive electrode active material. The secondary particles may be 0 parts by weight or more per 100 parts by weight of the positive electrode active material.

[0235] When the above range is satisfied, the aforementioned effect caused by the presence of a single-particle positive active material can be maximized. In the case of including a secondary particle positive active material, the component may be the same as that exemplified by the single-particle positive active material described above, may be a different component, and may refer to a form in which the single particle shape is aggregated.

[0236] In one embodiment of the present invention, the positive active material in 100 parts by weight of the positive active material layer may be included in an amount of 80 parts by weight or more and 99.9 parts by weight or less, preferably 90 parts by weight or more and 99.9 parts by weight or less, more preferably 95 parts by weight or more and 99.9 parts by weight or less, and even more preferably 98 parts by weight or more and 99.9 parts by weight or less.

[0237] The above-described positive active material layer may include a positive conductive material and a positive binder together with the positive active material described above.

[0238] At this time, the positive electrode conductive material is used to impart conductivity to the electrode, and in the battery being constructed, any material that has electronic conductivity without causing chemical changes can be used without special limitations. 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, thermal black, and carbon fiber; metal powder or metal fiber such as copper, nickel, aluminum, or 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 one of these alone or a mixture of two or more may be used.

[0239] In addition, the anode binder serves to improve adhesion between anode active material particles and adhesion between the anode active material and the anode current collector. Specific examples include polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluororubber, or various copolymers thereof, and one of these alone or a mixture of two or more may be used.

[0240] The above separator separates the negative electrode and the positive electrode and provides a pathway for the movement of lithium ions. Any separator commonly used in secondary batteries can be used without special limitations, and it is particularly desirable that it has low resistance to the movement of electrolyte ions and excellent electrolyte moisture retention capacity. Specifically, a porous polymer film, such as a porous polymer film made of a polyolefin-based polymer like 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. In addition, a conventional porous nonwoven fabric, such as a nonwoven fabric made of high-melting-point glass fiber or polyethylene terephthalate fiber, may be used. Furthermore, a coated separator containing ceramic components or polymer materials may be used to ensure heat resistance or mechanical strength, and it may optionally be used in a single-layer or multi-layer structure.

[0241] Examples of the above electrolytes that can be used in the manufacture of lithium secondary batteries include organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, molten inorganic electrolytes, etc., but are not limited to these.

[0242] Specifically, the electrolyte may include a non-aqueous organic solvent and a metal salt.

[0243] As the above-mentioned non-aqueous organic solvent, for example, aprotic organic solvents such as N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-butyl lactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyl tetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolone, formamide, dimethylformamide, dioxolone, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphate triester, trimethoxymethane, dioxolone derivative, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivative, tetrahydrofuran derivative, ether, methyl propionate, ethyl propionate, etc. may be used.

[0244] 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 that effectively dissociate lithium salts, so they can be used preferably. Furthermore, if low-viscosity, low-dielectric constant linear carbonates such as dimethyl carbonate and diethyl carbonate are mixed with these cyclic carbonates in appropriate proportions, an electrolyte with high electrical conductivity can be produced, making it even more preferable to use.

[0245] The metal salt mentioned above may be a lithium salt, and the lithium salt is a substance that dissolves well in the non-aqueous electrolyte; for example, as the 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 types selected from the group consisting of can be used.

[0246] In addition to the above electrolyte components, the above electrolyte may further include one or more additives for the purpose of improving the lifespan characteristics of the battery, suppressing the decrease in battery capacity, and improving the discharge capacity of the battery, such as, for example, a haloalkylene carbonate-based compound such as difluoroethylene carbonate, pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, triamide hexaphosphate, nitrobenzene derivative, sulfur, quinone imine dye, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, or aluminum trichloride.

[0247] Although the present invention has been described with reference to embodiments thereof, those skilled in the art will be able to make various applications and modifications within the scope of the present invention based on the above description.

[0248] Battery modules and battery packs

[0249] One embodiment of the present invention provides a battery module including a secondary battery according to one embodiment of the present invention.

[0250] One embodiment of the present invention provides a battery pack including a secondary battery according to one embodiment of the present invention.

[0251] One embodiment of the present invention provides a battery pack including a battery module according to one embodiment of the present invention.

[0252] One embodiment of the present invention provides a battery module comprising the secondary battery as a unit cell and a battery pack comprising the secondary battery or the battery module. Since the battery module and the battery pack include the secondary battery having high capacity, high rate capability and cycle capability, they can be used as a power source for a medium-to-large device selected from the group consisting of electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and power storage systems.

[0253] Hereinafter, preferred embodiments are presented to aid in understanding the present invention; however, the above 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 and spirit of the description, and that such variations and modifications fall within the scope of the appended claims.

[0254] <Preparation Example>

[0255] Example 1

[0256] 1) Preparation of cathode composition

[0257] A negative electrode active material was prepared by mixing graphite (synthetic graphite (average particle size (D50): 21㎛) : natural graphite (average particle size (D50): 9㎛) = 7:3 weight ratio) and Si powder (average particle size (D50): 5㎛) in a weight ratio of 85:15. Based on 100 parts by weight of the negative electrode composition, a negative electrode composition was prepared comprising 90.6 parts by weight of the negative electrode active material, 5 parts by weight of porous nano Ni particles which are porous nano metal structures as a nano metal structure, 1 part by weight of carbon black (product name: Super C65, manufacturer: Timcal) as a conductive material, 2.3 parts by weight of SBR (styrene butadiene rubber) and 1.1 parts by weight of CMC (carboxymethylcellulose) as binders. That is, in the manufactured cathode composition, the cathode active material: porous nano metal structure: conductive material: binder:thickener are included in a weight ratio of 90.6:5:1:2.3:1.1.

[0258] The average pore size of the porous nano Ni particles used is 10 nm, the average particle diameter (D50) is 0.5 µm, and the BET specific surface area is 140 m². 2 / g was.

[0259] 2) Preparation of the cathode

[0260] A cathode slurry was prepared by adding distilled water as a solvent for forming the cathode slurry to the cathode composition of 1) (solid content 26 wt%).

[0261] 87.7 mg / 25 cm of the above cathode slurry is applied to both sides of a copper current collector (thickness 26 μm) as a cathode current collector. 2 A cathode was manufactured by coating with a loading amount, rolling, and drying in a vacuum oven at 130°C for 10 hours to form a cathode active material layer (thickness 33 μm) (cathode thickness 41 μm, porosity 55.0%).

[0262] 3) Manufacturing of secondary batteries

[0263] LiNi as a positive electrode active material 0.6 Co 0.2Mn 0.2 An anode composition was prepared comprising O2 (average particle size (D50): 15㎛), carbon black as a conductive material (product name: Super C65, manufacturer: Timcal), and polyvinylidene fluoride (PVdF) as a binder in a weight ratio of 97:1.5:1.5, and an anode slurry was prepared by adding N-methyl-2-pyrrolidone (NMP) as a solvent for forming an anode slurry to the anode composition (solid content concentration 78 wt%).

[0264] 537 mg / 25 cm of the anode slurry is applied to both sides of an aluminum current collector (thickness: 12 μm) as an anode current collector. 2 A positive electrode was manufactured by coating with a loading amount, rolling, and drying in a vacuum oven at 130°C for 10 hours to form a positive electrode active material layer (thickness: 65㎛) (positive electrode thickness: 77㎛, porosity 26%).

[0265] A lithium secondary battery was manufactured by interposing a polyethylene separator between the anode and cathode and injecting an electrolyte.

[0266] The above electrolyte was used by adding vinylene carbonate (VC) at 3% by weight based on the total weight of the electrolyte to an organic solvent in which fluoroethylene carbonate (FEC) and diethyl carbonate (DEC) were mixed in a volume ratio of 10:90, and adding LiPF6 as a lithium salt at a concentration of 1M.

[0267] Example 2

[0268] In the process of manufacturing the cathode composition, as a porous nanometal structure, the average pore size is 50 nm, the average particle diameter (D50) is 1 μm, and the BET specific surface area is 105 m² 2 A secondary battery was prepared in the same manner as in Example 1, except that porous nano Ni particles with a particle size of 1 / g were used.

[0269] Example 3

[0270] A secondary battery was manufactured in the same manner as in Example 2, except that in the process of manufacturing the cathode composition, the cathode active material:porous nanometal structure:conductive material:binder:thickener were included in a weight ratio of 87.6:8:1:2.3:1.1.

[0271] That is, Example 3 used a nano metal structure with a different content from Example 2.

[0272] Example 4

[0273] A secondary battery was manufactured in the same manner as in Example 2, except that in the process of manufacturing the cathode composition, the cathode active material:porous nanometal structure:conductive material:binder:thickener were included in a weight ratio of 80.6:15:1:2.3:1.1.

[0274] That is, Example 4 used a nano metal structure with a different content from Example 2.

[0275] Example 5

[0276] In the process of manufacturing the cathode composition, as a porous nanometal structure, the average pore size is 600 nm, the average particle diameter (D50) is 5 μm, and the BET specific surface area is 65 m² 2 A secondary battery was prepared in the same manner as in Example 1, except that porous nano Ni particles with a particle size of 1 / g were used.

[0277] That is, Example 5 used porous nano Ni particles with a different average pore size than Example 1.

[0278] Example 6

[0279] In the process of manufacturing the cathode composition, as a porous nanometal structure, the average pore size is 10 nm, the average particle diameter (D50) is 1 μm, and the BET specific surface area is 60 m² 2 A secondary battery was prepared in the same manner as in Example 1, except that porous nano Ag particles with a particle size of 1 / g were used.

[0280] That is, Example 6 used a different type of porous nanometal structure than Example 1.

[0281] Example 7

[0282] In the process of manufacturing the cathode composition, a nano-metal structure with a BET specific surface area of ​​95 m² 2 A secondary battery was manufactured in the same manner as in Example 1, except that a Ni nanosheet (average thickness 50 nm, major axis length 1 μm) with a thickness of 1 g was used.

[0283] That is, Example 7 used a different type of nano metal structure than in Example 1.

[0284] Example 8

[0285] A secondary battery was manufactured in the same manner as in Example 1, except that only Si powder (average particle size (D50): 5㎛) was used as the negative electrode active material in the process of manufacturing the negative electrode composition.

[0286] That is, Example 8 used a negative electrode active material containing only pure Si as in Example 1.

[0287] Example 9

[0288] In the process of manufacturing the cathode composition, as a porous nanometal structure, the average pore size is 50 nm, the average particle diameter (D50) is 1 µm, and the BET specific surface area is 105 m² 2 A secondary battery was prepared in the same manner as in Example 8, except that porous nano Ni particles were used in / g.

[0289] That is, Example 9 used a porous nano Ni particle with a different average pore size than Example 8.

[0290] Example 10

[0291] A secondary battery was manufactured in the same manner as in Example 1, except that porous nano Cu particles were used as porous nano metal structures in the process of manufacturing the cathode composition.

[0292] That is, Example 10 used a different type of porous nano-metal structure than Example 1.

[0293] Example 11

[0294] A secondary battery was manufactured in the same manner as in Example 1, except that porous nano Ti particles were used as porous nano metal structures in the process of manufacturing the cathode composition.

[0295] That is, Example 11 used a different type of porous nano-metal structure than Example 1.

[0296] Example 12

[0297] A secondary battery was manufactured in the same manner as in Example 1, except that porous nano TiO2 particles were used as porous nano metal structures in the process of manufacturing the cathode composition.

[0298] That is, Example 12 used a different type of porous nano-metal structure than Example 1.

[0299] Comparative Example 1

[0300] 1) Preparation of cathode composition

[0301] A negative electrode active material was prepared by mixing graphite (synthetic graphite (average particle size (D50): 21㎛) : natural graphite (average particle size (D50): 9㎛) = 7:3 weight ratio) and Si powder (average particle size (D50): 5㎛) in a weight ratio of 85:15. Based on 100 parts by weight of the negative electrode composition, a negative electrode composition was prepared comprising 95.6 parts by weight of the negative electrode active material, 1 part by weight of carbon black (product name: Super C65, manufacturer: Timcal) as a conductive agent, 2.3 parts by weight of SBR (styrene butadiene rubber) as a binder, and 1.1 parts by weight of CMC (carboxymethylcellulose). That is, in the prepared negative electrode composition, the negative electrode active material : porous nano metal structure : conductive agent : binder : thickener are included in a weight ratio of 95.6 : 0 : 1 : 2.3 : 1.1. Subsequently, a secondary battery was manufactured using the same method as in Example 1.

[0302] That is, Comparative Example 1 is characterized by not including a nano metal structure in the cathode composition.

[0303] Comparative Example 2

[0304] A secondary battery was manufactured in the same manner as in Example 1, except that Ag nanoparticles (average particle size (D50): 10 nm) were used as the nano metal structure in the process of manufacturing the cathode composition.

[0305] That is, Comparative Example 2 is characterized by having a different type of nano metal structure compared to Example 1.

[0306] Comparative Example 3

[0307] A secondary battery was manufactured in the same manner as in Example 1, except that Ag nanowires (diameter 20 nm, length 2 μm) were used as the nano metal structure in the process of manufacturing the cathode composition.

[0308] That is, Comparative Example 3 is characterized by having a different type of nano metal structure compared to Example 1.

[0309] Comparative Example 4

[0310] A secondary battery was manufactured in the same manner as Comparative Example 1, except that only pure Si powder (average particle size (D50): 5㎛) was used as the negative electrode active material in the process of manufacturing the negative electrode composition.

[0311] That is, Comparative Example 4 used a negative electrode active material containing only pure Si, as in Comparative Example 1.

[0312] <Experimental Example 1>

[0313] The following items were evaluated for the manufactured examples and comparative examples, and the results are shown in Table 1.

[0314] Evaluation of thermal runaway duration and maximum temperature

[0315] Each manufactured secondary battery was heated using a heat pad at a rate of 20°C / min. Subsequently, the time from when the secondary battery ignited as the temperature rose until the ignition continued and then naturally extinguished was measured, and the maximum temperature of the secondary battery was measured during this process.

[0316] In addition, the amount of metal oxide inside the secondary battery was measured after natural digestion. Since metal oxide is formed by the oxidation of nano-metal structures during the thermal runaway process, the amount of said metal oxide can be understood as the extent to which the nano-metal structures contributed to the thermal stability of the secondary battery. The amount of said metal oxide was expressed in parts by weight relative to the content of silicon-based active material in the negative electrode composition.

[0317] Content of Si-based active material in cathode active material (parts by weight) Duration of thermal runaway (seconds) Maximum temperature (°C) Amount of metal oxide (parts by weight) Example 1 152.26 207.2 Example 2 153.56 506.5 Example 3 152.86 309.8 Example 4 152.46 2516.6 Example 5 154.66 905.8 Example 6 155.17 105.2 Example 7 154.068 06.3 Comparative Example 1 156.07 400 Comparative Example 2 155.27 005.4 Comparative Example 3 155.47 155.3 Example 8 1004.58 158.0 Example 9 1005.88 857.4 10155.37805.7 Example 11155.77156.2 Example 12156.27655.9 Comparative Example 41008.410500

[0318] Referring to Table 1, in the case of Examples 1 to 9 according to one embodiment of the present invention, compared to Comparative Examples 1 to 4, the thermal runaway duration was shorter, the maximum temperature of the secondary battery was relatively lower, and the amount of metal oxide was smaller. Through this, it can be confirmed that the thermal safety of the battery according to one embodiment of the present invention has been improved.

[0319] Comparative Examples 1 and 4 applied a cathode composition that does not include a nano metal structure, and since it does not include a separate component capable of suppressing the oxidation reaction of lithium within the battery, it can be confirmed that the thermal stability is inferior, as the thermal runaway time is longer and the maximum temperature within the battery is higher when ignition occurs in the battery.

[0320] Comparative Example 2 uses nanoparticles as the nanometal structure, and Comparative Example 3 uses nanowires as the nanometal structure. Since the form of the nanometal structure is not porous nanoparticles or nanosheets, the BET specific surface area is smaller compared to the form of porous nanoparticles or nanosheets, and the reactivity with oxygen at the same content is relatively lower, resulting in a negligible improvement in thermal stability.

[0321] In addition, when comparing Examples 1, 2, and 5 with Examples 8 and 9, it can be observed that Examples 1 and 8, in which the average pore size of the porous nanoparticles is relatively smaller, exhibit shorter thermal runaway durations and lower maximum temperatures compared to Examples 2, 5, and 9, in which the average pore size is larger. This is understood to be because when the average pore size of the porous nanoparticles is smaller, a greater number of pores within the porous nanoparticles is secured, resulting in a larger BET specific surface area; consequently, the reactivity between the porous nanoparticles and oxygen increases, which can effectively suppress the oxidation reaction of lithium. In particular, in the case of Example 5, it can be observed that the thermal stability characteristics are relatively degraded compared to Examples 1 and 2 because the average pore size of the porous nanoparticles is excessively large, failing to secure sufficient pores within the particles.

[0322] Comparing Examples 1 and 6, Example 6, which contains Ag porous nanoparticles as the nanometal structure, exhibits a higher thermal runaway duration and maximum temperature compared to Example 1, indicating that the thermal stability characteristics are relatively degraded. This is understood to be because the Ni porous nanoparticles of Example 1 have greater reactivity with oxygen than the Ag porous nanoparticles of Example 6, which can more easily suppress the oxidation reaction of Li.

[0323] Likewise, when comparing Examples 10 to 12 with Example 1, it was confirmed that Example 1 of the present application, which uses Ni porous nanoparticles, has an excellent effect. This is understood to be because the cases using Examples 10 to 12 have poor reactivity with oxygen compared to Ni, and consequently, Example 1 has greater reactivity with oxygen, which allows for easier inhibition of the oxidation reaction of Li.

[0324] Comparing Examples 1 and 7, Example 7, which includes nanosheets as the nanometal structure, exhibits a higher thermal runaway time and maximum temperature compared to Example 1, indicating that the thermal stability characteristics are relatively degraded. This is understood to be because the porous nanoparticle form of Example 1 is easier to secure a BET specific surface area and a form that can maximize reactivity with oxygen compared to the nanosheet form of Example 7.

[0325] <Experimental Example 2>

[0326] For Examples 2 to 4, the dosage retention rate was evaluated in the following manner, and the results are shown in Table 2.

[0327] Lifetime evaluation and capacity retention rate were evaluated for the secondary batteries of Examples 2 to 4 using an electrochemical charge / discharger. The secondary batteries were subjected to in-situ cycle tests at 4.2-2.5V, 1C charge, and 1C discharge. The test was terminated after 200 cycles of discharge, and the capacity retention rate was measured by performing 0.33C / 0.33C charge / discharge (4.2-2.5V) every 50 cycles and is shown in Table 1.

[0328] Capacity Retention Rate (%) = {(Discharge Capacity at the Nth Cycle) / (Discharge Capacity at the 1st Cycle)} * 100 %

[0329] Nano metal structure capacity retention rate (%) Thermal runaway duration (sec) Maximum temperature (°C) Type Form Content (parts by weight) Example 2 Ni porous nanoparticles 597 3.5650 Example 3 Ni porous nanoparticles 894 2.8630 Example 4 Ni porous nanoparticles 1588 3.0640

[0330] Referring to Table 2, it can be seen that the capacity retention rate of Example 4 is inferior compared to Examples 2 and 3. This is understood to be because when the content of the nano metal structure in the cathode deviates from the optimal range, the content of the cathode active material in the cathode becomes relatively low, resulting in an inferior capacity retention rate. In other words, it is important to appropriately control the content of the nano metal structure to provide a secondary battery with excellent capacity retention rate while simultaneously improving thermal stability.

[0331] The above detailed description is intended to illustrate and explain the present invention. Furthermore, the foregoing merely illustrates and describes preferred embodiments of the present invention, and as described above, the present invention may be used in various other combinations, modifications, and environments, and may be modified or altered within the scope of the invention disclosed herein, the scope equivalent to the foregoing disclosure, and / or the scope of the art or knowledge. Accordingly, the above detailed description of the invention is not intended to limit the present invention to the disclosed embodiments. Additionally, the appended claims should be interpreted as including other embodiments.

Claims

1. Cathode active material; and Includes nano metal structures, A cathode composition wherein the above nano metal structure comprises at least one of a porous nano metal structure or a two-dimensional nano metal structure.

2. In Claim 1, The above negative electrode active material includes a silicon-based active material, and The above silicon-based active material is Si, SiOx (0 <x<2) 및 Si / C로 이루어진 군에서 선택되는 1 이상을 포함하는, 음극 조성물.

3. In Claim 2, The above silicon-based active material includes Si, and A cathode composition comprising at least 40 parts by weight of the above Si based on 100 parts by weight of the above silicon-based active material.

4. In Claim 2, A cathode composition comprising at least 5 parts by weight of the silicon-based active material based on 100 parts by weight of the cathode active material.

5. In Claim 2, The above-mentioned cathode active material is a cathode composition further comprising a carbon-based active material.

6. In Claim 5, A cathode composition comprising at least 70 parts by weight of the carbon-based active material based on 100 parts by weight of the cathode active material.

7. In Claim 1, The cathode composition wherein the nano metal structure is included in an amount of 1 to 10 parts by weight based on 100 parts by weight of the cathode composition.

8. In Claim 1, A cathode composition having an average pore size of 8 nm to 500 nm of the porous nanometal structure.

9. In Claim 1, The above two-dimensional nano metal structure is a metal nano sheet, and A cathode composition having an average thickness of 10 nm to 100 nm of the metal nanosheet.

10. In Claim 1, The above nano metal structure is, A cathode composition comprising one or more selected from the group consisting of Mg, Y, Al, Sn, Pb, V, Cr, Mn, Fe, Co, Ni, Zn, Zr, Nb, and Mo.

11. A negative electrode current collector; and a negative electrode active material layer provided on the negative electrode current collector, comprising The cathode, wherein the cathode active material layer comprises a cathode composition according to any one of claims 1 to 10.

12. In Claim 11, The above cathode active material layer comprises a metal oxide represented by the following formula 1, cathode: [Equation 1] M a O b (1≤a≤5, 1≤b≤5) In the above formula 1, M includes one or more selected from the group consisting of Mg, Y, Al, Sn, Pb, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Nb, and Mo.

13. A secondary battery comprising: a positive electrode; a negative electrode according to claim 11; a separator provided between the positive electrode and the negative electrode; and an electrolyte.

14. A battery module comprising a secondary battery according to claim 13.

15. A battery pack comprising a secondary battery according to claim 13.

16. A battery pack comprising a battery module according to claim 14.

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