Negative electrode composition, method for manufacturing the same, negative electrode, lithium secondary battery containing the same

Abstract

A negative electrode composition, a negative electrode for a lithium secondary battery including the same, a lithium secondary battery, and a method for manufacturing the negative electrode composition are provided. The negative electrode composition includes a silicon-carbon composite, graphite, and a negative electrode conductive material, where the silicon-carbon composite has a larger BET specific surface area than the graphite.

Description

[Technical Field]

[0001] This application claims the benefit as of the filing date of Korean Patent Application No. 10-2022-0136399, filed on 21 October 2022, and all content disclosed in the documents of said Korean Patent Application is included herein.

[0002] This description relates to a negative electrode composition, a negative electrode for a lithium secondary battery containing the same, a lithium secondary battery, and a method for producing the negative electrode composition. [Background technology]

[0003] Recently, with the rapid proliferation of battery-powered electronic devices such as mobile phones, laptops, electric vehicles, power tools, and vacuum cleaners, the demand for small, lightweight, yet relatively high-capacity and / or high-power rechargeable batteries has been rapidly increasing. In particular, lithium-ion batteries are attracting attention as a power source for electronic devices due to their light weight and high energy density. As a result, research and development efforts to improve the performance of lithium-ion batteries are being actively pursued.

[0004] In a lithium-ion secondary battery, an organic electrolyte or polymer electrolyte is filled between a positive electrode and a negative electrode containing an active material that allows for the insertion and deintercalation of lithium ions. Electrical energy is produced by oxidation and reduction reactions that occur when lithium ions are inserted into / deintercalated at the positive and negative electrodes.

[0005] For the positive electrode of a lithium secondary battery, metal oxides such as LiCoO2, LiMnO2, LiMn2O4, or LiNiO2 are used as the positive electrode active material, while for the negative electrode, carbon-based materials such as metallic lithium, graphite, or activated carbon, or silicon oxide (SiO2) are used as the negative electrode active material. x) and other materials are used. In the early days, metallic lithium was mainly used among the negative electrode active materials, but as the charge and discharge cycles progressed, lithium atoms grew on the surface of the metallic lithium, damaging the separator and causing the battery to break down. Therefore, in recent years, carbon-based materials have been mainly used.

[0006] Graphite is primarily used as the negative electrode active material for lithium-ion batteries. However, graphite has a low capacity of 372 mAh / g per unit mass, making it difficult to achieve high capacity lithium-ion batteries. Therefore, to increase the capacity of lithium-ion batteries, non-carbon negative electrode materials with higher energy densities than graphite, such as silicon, tin, and their oxides, have been developed. However, while these non-carbon negative electrode materials have high capacity, they suffer from low initial efficiency, large lithium consumption during initial charge and discharge, and significant irreversible capacity loss.

[0007] In particular, silicon-based active materials undergo transient volume changes during the battery's operation. This leads to a problem of reduced battery life. Therefore, there is a need to develop anodes that can effectively improve battery life characteristics while still using silicon-based anode active materials. [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] One aspect of this description relates to a lithium secondary battery, the type of active material and conductive material constituting the negative electrode composition, and the battery performance provided by an active material having a specific relationship with respect to the BET specific surface area value. [Means for solving the problem]

[0009] In one example, this description provides a negative electrode composition and a negative electrode for a lithium secondary battery comprising the negative electrode composition, a silicon-carbon composite, graphite, and a negative electrode conductive material. The BET specific surface area of ​​the silicon-carbon composite is greater than that of the graphite.

[0010] The graphite includes natural graphite and artificial graphite, and the BET specific surface area of ​​the natural graphite is greater than the BET specific surface area of ​​the artificial graphite.

[0011] In one example, this description provides a lithium secondary battery including the negative electrode and a method for producing the negative electrode composition.

[0012] In another example, this description provides a battery module and battery pack including the lithium secondary battery. [Effects of the Invention]

[0013] According to another example described herein, when a silicon-carbon composite, which is a high-capacity material, is used as the negative electrode composition to manufacture a high-capacity battery, by satisfying the interrelationship between the BET specific surface area of ​​the silicon-carbon composite and the graphite, it is possible to improve the lifespan of conventional secondary batteries, enable rapid charging, and have excellent electrode adhesion.

[0014] When single-walled carbon nanotubes (SWCNTs) are used together as a conductive material with the silicon-carbon composite, graphite, and conductive material contained in the aforementioned negative electrode composition, the conductive pathways between the negative electrode active material particles can be improved, thereby enhancing the battery's capacity, efficiency, and lifespan. [Modes for carrying out the invention]

[0015] The following provides a more detailed explanation of this document to aid in understanding it. The terms and words used in this description and in the claims should not be interpreted in a manner limited to their ordinary or dictionary meanings, but rather in a manner consistent with the technical idea of ​​the present invention.

[0016] The terms used herein are for illustrative purposes only and are not intended to limit this description. Unless otherwise clearly indicated in the context, singular expressions include plural expressions.

[0017] In this document, terms such as “includes,” “equip,” or “possess” are intended to specify the existence of a particular feature, number, stage, component, or combination thereof, and should be understood not to preemptively exclude the existence or possibility of adding one or more other features, numbers, stages, components, or combinations thereof.

[0018] Furthermore, when a layer or other part is said to be "on top of" or "above" another part, this includes not only when it is "directly above" the other part, but also when there is another part in between. Conversely, when a part is said to be "directly above" another part, it means that there is no other part in between. Also, being "on top of" or "above" a reference part means being located above or below the reference part, and does not necessarily mean being located "up" or "above" in the opposite direction of gravity.

[0019] In this description, "specific surface area" refers to the area measured by the BET method. This method involves using a BET measuring device (BEL-SORP-mini, Nippon Bell) to degass the object being measured at 130°C for 2 hours, followed by N2 adsorption / desorption at 77K. In other words, in this description, the BET specific surface area refers to the specific surface area of ​​the particle itself as measured by the aforementioned method.

[0020] In this description, the average length or diameter of the conductive material can be measured using SEM or TEM.

[0021] In this document, "pore size" refers to the size of the pores in the particle itself and can be measured using the BJH (Barrett-Joyer-Halenda) method via nitrogen adsorption. Using the BELSORP-mini II model from BEL Japan, the pore area was derived based on the pore size, and the pore size showing the largest pore area was used as representative. The BJH method can be used, and the plot of the measured values ​​shows the pore diameter (Dp / nm) on the X axis and dVp / dDp (cm) on the Y axis. 3 g -1 nm -1 )

[0022] In this description, "pore volume" can refer to the volume of the pores of the particle itself, and can be measured by a calculation formula using the adsorption / desorption isotherm method via nitrogen adsorption. Using the BELSORP-mini II model from BEL Japan, an N2 adsorption / desorption isotherm graph was derived, and the volume at the point where the P / P0 (closest to 1) was highest for adsorption was used as representative. The adsorption / desorption isotherm method can be used, and the plot of the measured values ​​is with pressure (P / P0) on the X axis and Va / cm on the Y axis. 3 (STP)g -1 That is the case.

[0023] Negative electrode composition The negative electrode composition according to the example described herein is a negative electrode composition comprising a silicon-carbon composite, graphite, and a negative electrode conductive material, wherein the BET specific surface area of ​​the silicon-carbon composite is greater than the BET specific surface area of ​​the graphite.

[0024] When the relationship between the BET specific surface area of ​​the silicon-carbon composite and the graphite is satisfied, the lifespan of the secondary battery is improved, rapid charging is possible, and electrode adhesion is excellent.

[0025] For example, the graphite comprises at least one of natural graphite or artificial graphite, and if the graphite comprises both natural graphite and artificial graphite, the BET specific surface area of ​​the natural graphite is greater than the BET specific surface area of ​​the artificial graphite. The graphite may comprise only natural graphite or only artificial graphite. Preferably, the graphite comprises both natural graphite and artificial graphite.

[0026] When artificial graphite has a smaller BET specific surface area than natural graphite, compared to when artificial graphite has a larger BET specific surface area than natural graphite, it is possible to obtain equivalent or greater electrode adhesion strength even with less binder.

[0027] Since artificial graphite consumes a relatively larger amount of binder compared to natural graphite, it can exhibit an effect of improving electrode adhesion when the BET specific surface area of ​​the artificial graphite is smaller than that of the natural graphite.

[0028] Furthermore, since silicon-carbon composites have relatively low reactivity with lithium ions, a silicon-carbon composite with a larger BET specific surface area than that of natural graphite is advantageous for the smooth insertion and removal of lithium ions.

[0029] Therefore, by satisfying the aforementioned BET specific surface area relationship, the electrode adhesion strength is improved when using an equivalent amount of binder, and the smooth insertion and removal of lithium ions is improved, thereby improving the lifespan characteristics and rapid charging performance of the secondary battery.

[0030] According to one example described herein, the BET specific surface area of ​​the silicon-carbon composite is 1 m² larger than the BET specific surface area of ​​the natural graphite. 2 / g~9m 2 / g is large.

[0031] Since the conductivity of silicon is lower than that of graphite, the reactivity of the silicon-carbon composite with lithium ions is relatively low. Therefore, when the BET specific surface area corresponding to the reaction area of the silicon-carbon composite is larger than that of natural graphite within the above range, it is advantageous for the smooth insertion and desorption of lithium ions.

[0032] The BET specific surface area of the silicon-carbon composite is 1.2 m 2 / g or more, 1.5 m 2 / g or more, 1.7 m 2 / g or more, or 1.9 m 2 / g or more larger than that of the natural graphite. The BET specific surface area of the silicon-carbon composite is 8.7 m 2 / g or less, 8.4 m 2 / g or less, 8.2 m 2 / g or less, or 8 m 2 / g or less larger than that of the natural graphite.

[0033] According to an example of this description, the BET specific surface area of the silicon-carbon composite is 2 m 2 / g to 10 m 2 / g larger than that of the artificial graphite.

[0034] Since the conductivity of silicon is lower than that of graphite, when the BET specific surface area corresponding to the reaction area of the silicon-carbon composite is larger than that of artificial graphite within the above range, it is advantageous for the smooth insertion and desorption of lithium ions.

[0035] The BET specific surface area of the silicon-carbon composite is 2.2 m 2 / g or more, 2.5 m 2 / g or more, 2.7 m 2 / g or more, or 2.9 m 2 / g or more larger than that of the artificial graphite.

[0036] The BET specific surface area of the silicon-carbon composite is up to 9.7 m 2 / g or less, 9.4 m 2 / g or less, 9.2 m2 / g or less, or 9m 2 Larger than / g

[0037] According to one example described herein, the BET specific surface area of ​​the natural graphite is 0.1 m² higher than the BET specific surface area of ​​the artificial graphite. 2 / g~2m 2 / g is large.

[0038] Within this range, if the BET specific surface area of ​​natural graphite is large, the BET specific surface area of ​​artificial graphite, which consumes a relatively large amount of binder, becomes relatively smaller, and when the same amount of binder is used, an improvement in electrode adhesion can be observed.

[0039] The BET specific surface area of ​​the aforementioned natural graphite is 0.2 m² higher than that of the aforementioned artificial graphite. 2 / g or more, or 0.3m 2 It is greater than or equal to / g. The BET specific surface area of ​​the natural graphite is 1.9m² greater than the BET specific surface area of ​​the artificial graphite. 2 / g or less, 1.8m 2 Less than / g, or 1.7m 2 Larger than / g

[0040] Natural graphite has a BET specific surface area of ​​1.5 m². 2 / g or more 3.5m 2 Having a value of less than / g, this can improve electrode adhesion. Artificial graphite and silicon-carbon composites affect fast charging and lifespan performance, with a BET specific surface area of ​​0.1m² each. 2 / g or more 2.5m 2 / g or less, 3m 2 / g or more 15m 2 It is less than / g.

[0041] If the BET specific surface area of ​​the artificial graphite is larger than that of the natural graphite, when manufacturing an electrode with the negative electrode composition, more binder will be consumed within the electrode, which may reduce the electrode adhesion strength. Also, if the BET specific surface area of ​​the silicon-carbon composite is smaller than that of the natural graphite, insertion and / or removal of lithium from the silicon-carbon composite becomes difficult, which may reduce the lifespan performance and rapid charging performance.

[0042] In this description, the silicon-carbon composite is a composite of Si and C, with Si and C (graphite) present respectively. For example, the peaks for Si and C can be observed by elemental analysis methods such as XRD or NMR. In this description, the silicon-carbon composite can be denoted as Si / C. The silicon-carbon composite may consist of Si and C that are not bonded to each other, but may contain additional components as needed. For example, the silicon-carbon composite may or may not contain silicon carbide, denoted as SiC. If the silicon-carbon composite contains silicon carbide, its content is 3% by weight or less. The silicon-carbon composite may exist in a crystalline, amorphous, or mixed state. For example, C in the silicon-carbon composite may exist in an amorphous state.

[0043] For example, the silicon-carbon composite may be a composite of silicon and graphite, and may have a structure in which a silicon-graphite composite core is surrounded by graphene or amorphous carbon. In the silicon-carbon composite, the silicon may be nanosilicon.

[0044] For example, the silicon-carbon composite comprises porous carbon-based particles and silicon located on the surface or in the pores of the porous carbon-based particles.

[0045] For example, the silicon-carbon composite can be manufactured by a method that includes the step of forming silicon on the surface and in the internal pores of porous carbon-based particles.

[0046] The porous carbon-based particles can be manufactured using methods known in the art. For example, they can be obtained by carbonizing organic materials, such as petroleum-based materials or polymers, or by chemically treating and then carbonizing naturally occurring substances, such as coconut bark. Another example is that the porous carbon-based particles can be obtained by a method that includes the step of etching carbon-based particles containing internal pores to expand the internal pores of the carbon-based particles.

[0047] The step of expanding the internal pores of the carbon-based particles can be carried out in a nitrogen (N2), oxygen (O2), or air atmosphere. The flow rate of the oxygen (O2) or the oxygen-containing air can be controlled from 0.1 L / min to 10 L / min.

[0048] The step of expanding the internal pores of the carbon-based particles can be carried out at a temperature range of 400°C to 1200°C for 30 minutes to 4 hours.

[0049] The pore properties of the resulting porous carbon-based particles may change depending on the conditions used to expand the internal pores of the carbon-based particles.

[0050] The step of forming the silicon can be carried out using chemical vapor deposition. In this process, silicon nanoparticles are deposited onto the surface and / or internal pores of the carbon-based particles with expanded internal pores to form silicon in film form, island form, or a mixture thereof.

[0051] The silicon nanoparticles may be crystalline, quasicrystalline, amorphous, or a combination thereof.

[0052] According to additional examples described herein, the negative electrode composition may contain graphite, and the graphite may include natural graphite and artificial graphite.

[0053] For example, the natural graphite may satisfy the relationship of specific surface area. Alternatively, the natural graphite may satisfy the above conditions while having a spheroidization degree of 0.7 or higher, or 0.9 or higher.

[0054] In this description, the degree of spheroidization may be the value obtained by dividing the circumference of a circle with the same area as the projected image by the circumference of the projected image, and specifically can be shown by the following formula 1. The degree of spheroidization can be determined from the SEM image, or it can be measured using a flow analyzer, such as the sysmex FPIA3000 manufactured by Malvern. Furthermore, the crystal size can be confirmed through XRD analysis. [Formula 1] Sphericity = Circumference of a circle with the same area as the projected image of the particle / Circumference of the projected image

[0055] The aforementioned natural graphite refers to graphite that is produced naturally, and examples include scaled graphite, flaky graphite, or soil graphite. This natural graphite has the advantages of being abundant, inexpensive, having high theoretical capacity and compaction density, and being able to achieve high output.

[0056] The aforementioned natural graphite can be selected and applied after confirming its particle shape using a scanning electron microscope (SEM) and then using a particle shape analyzer to determine if it meets the required degree of spheroidization.

[0057] For example, the artificial graphite may satisfy the relationship of specific surface area. Alternatively, the artificial graphite may satisfy the above conditions while having a spheroidization degree of 0.95 or less, or 0.9 or less.

[0058] The aforementioned artificial graphite can be selected and applied after confirming the particle shape using a scanning electron microscope (SEM) and then using a particle shape analyzer to confirm the spheroidization level.

[0059] The aforementioned silicon-carbon composite, natural graphite, and artificial graphite have a particle form. The average particle size (D50) of the silicon-carbon composite may be 1 μm or more, for example, 1 μm to 15 μm, 2 μm to 14 μm, or 3 μm to 13 μm. When the average particle size (D50) of the silicon-carbon composite is in the range of greater than 1 μm and less than 15 μm, the volume expansion and contraction rate due to charging and discharging is reduced, and the life performance can be improved. In addition, by preventing an excessive increase in specific surface area and preventing side reactions with the electrolyte as the cycle progresses, the life performance can be improved. The average particle size (D50) of the natural graphite and artificial graphite, respectively, is not particularly limited, but may be 1 μm or more, for example, 1 μm to 35 μm, 3 μm to 30 μm, or 5 μm to 25 μm.

[0060] In this description, "average particle size (D50)" can be defined as the particle size corresponding to 50% of the cumulative volume in the particle size distribution curve. The average particle size (D50) can be measured, for example, using the laser diffraction method. The laser diffraction method can generally measure particle sizes from the submicron region to several millimeters, and can obtain highly reproducible and high-resolution results.

[0061] The average particle size (D50) can be measured using a microtrac device (manufacturer: microtrac, model: S3500) with water and triton-X100 dispersant. The average particle size (D50) of the positive electrode active material can be measured in the range of refractive index 1.5 to 1.7, and the negative electrode active material can be measured under conditions of refractive index 1.97 or 2.42. For example, after dispersing the particles in a dispersion medium, they can be introduced into a commercially available laser diffraction particle size analyzer, irradiated with ultrasound at approximately 28 kHz at an output of 60 W, and after obtaining a volume cumulative particle size distribution graph, the particle size corresponding to 50% of the volume cumulative amount can be determined.

[0062] According to additional examples described herein, the negative electrode conductive material may include single-walled carbon nanotubes (SWCNTs). A single-walled carbon nanotube (SWCNT) means a tubular carbon structure consisting of a single layer of carbon. When the conductive material in the negative electrode composition includes single-walled carbon nanotubes (SWCNTs), the charge / discharge capacity and / or lifespan of the battery can be improved. The single-walled carbon nanotubes (SWCNTs) effectively connect the conductive paths between particles, thus preventing the loss of conductive paths due to the swelling of the silicon-based negative electrode active material. Consequently, when single-walled carbon nanotubes (SWCNTs) are included, the lifespan of the battery can be improved.

[0063] For example, the negative electrode composition may contain additional conductive materials in addition to single-walled carbon nanotubes. For instance, carbon black, multi-walled carbon nanotubes (MWCNTs), etc., may be included as additional conductive materials.

[0064] In this description, the length of a carbon nanotube refers to the length of the major axis passing through the center of the carbon nanotube unit, and the diameter of a carbon nanotube refers to the length of the minor axis passing through the center of the unit and perpendicular to the major axis.

[0065] The average length of the single-walled carbon nanotube (SWCNT) may be 0.1 μm to 50 μm, 0.5 μm to 25 μm, or 0.5 μm to 20 μm. The average length may also be 5 μm to 15 μm. The lower limit of the average length may be 0.1 μm, 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, or 8 μm, and the upper limit may be 50 μm, 30 μm, 25 μm, 20 μm, 15 μm, 14 μm, 13 μm, 12 μm, 11 μm, or 10 μm.

[0066] When single-walled carbon nanotubes (SWCNTs) having the above-described average length are used together with the silicon-carbon composite and the graphite, the connection of interparticle conductive paths becomes easier, which can improve the conductivity, strength, and / or electrolyte storage and retention of the negative electrode. On the other hand, if the length of the carbon nanotubes is too short, it may be difficult to efficiently form conductive paths, which may reduce conductivity, and if the length of the carbon nanotubes is too long, the dispersibility may decrease.

[0067] The average length of the aforementioned single-walled carbon nanotubes (SWCNTs) can be calculated using the average value of the results observed by SEM.

[0068] The average diameter of the single-walled carbon nanotube (SWCNT) may be 1 nm to 20 nm, or 1.5 nm to 15 nm. In other examples, the average diameter may be 1.5 nm to 5 nm. The lower limit of the average diameter may be 1 nm, 1.5 nm, or 2 nm, and the upper limit may be 20 nm, 18 nm, 16 nm, 14 nm, 12 nm, 10 nm, 8 nm, 6 nm, or 4 nm.

[0069] Single-walled carbon nanotubes (SWCNTs) that meet the above range have flexible properties, which has the effect of preventing the contact between negative electrode active material particles from easily breaking even if they are physically damaged. On the other hand, if the diameter of the carbon nanotubes (SWCNTs) is too large, the density of the electrode may decrease, and if the diameter of the carbon nanotubes (SWCNTs) is too small, dispersion may be difficult, which may reduce the ease of manufacturing the dispersion.

[0070] The average diameter of the aforementioned single-walled carbon nanotubes (SWCNTs) can be calculated using the average value observed by TEM.

[0071] The BET specific surface area of ​​the aforementioned single-walled carbon nanotube is 200 m². 2 / g~2,000m 2 It may also be / g, and in some examples, 250m 2 / g~1,500m 2 It may also be per g. When using single-walled carbon nanotubes (SWCNTs) that satisfy the above range, dispersion is easy even with a small amount of conductive material, and the particles can be effectively linked together.

[0072] The single-walled carbon nanotubes (SWCNTs) may be included in amounts of 0.01 to 5 parts by weight based on 100 parts by weight of the negative electrode composition, specifically in amounts of 0.01 to 4 parts by weight, 0.01 to 3 parts by weight, 0.01 to 2 parts by weight, 0.01 to 1 part by weight, or 0.05 to 0.5 parts by weight.

[0073] When the aforementioned content range is met, it is possible to facilitate the connection of conductive paths between silicon-carbon composites and silicon-based negative electrode active material particles containing graphite.

[0074] According to the additional examples described herein, the BET specific surface area of ​​the silicon-carbon composite is greater than that of the natural graphite, and the BET specific surface area of ​​the natural graphite is greater than that of the artificial graphite.

[0075] For example, the specific surface area is measured by the BET method, which involves using BET measuring equipment (BEL-SORP-mini, Nippon Bell) on the object to be measured, degassing the gas at 130°C for 2 hours, and then performing N2 adsorption / desorption at 77K. In other words, in this description, the BET specific surface area can refer to the specific surface area of ​​the particle itself measured by the above measurement method.

[0076] For example, the negative electrode conductive material may include single-walled carbon nanotubes (SWCNTs).

[0077] In the case of the negative electrode composition according to the example described herein, when using a silicon-based active material, which is a high-capacity material, to manufacture a high-capacity battery, the composition includes a silicon-carbon composite having the above-mentioned content, natural graphite, artificial graphite, and single-walled carbon nanotubes (SWCNTs), satisfying the interrelationship of the BET specific surface areas of the silicon-carbon composite, natural graphite, and artificial graphite, thereby improving the lifespan of conventional secondary batteries, enabling rapid charging, and having excellent electrode adhesion.

[0078] Furthermore, by using a silicon-carbon composite, graphite, and single-walled carbon nanotubes (SWCNTs) as a conductive material together in the negative electrode composition having the aforementioned content, the conductive pathways between negative electrode active material particles can be improved, thereby enhancing the battery's capacity, efficiency, and lifespan.

[0079] In one example described herein, the total pore volume (total pore V.) of the silicon-carbon composite is the same as or greater than that of the natural graphite, and the total pore volume of the natural graphite is the same as or greater than that of the artificial graphite, providing a negative electrode composition.

[0080] Pore ​​volume, in the same principle as the BET specific surface area mentioned above, can affect the improvement of electrode adhesion and the smooth insertion and removal of lithium ions. Specifically, if the pore volume of natural graphite is equal to or greater than that of artificial graphite, the amount of binder consumed can be relatively reduced, thus improving electrode adhesion with the same amount of binder. Furthermore, if the pore volume of silicon-carbon composite is equal to or greater than that of natural graphite, it facilitates the insertion and removal of lithium ions in the silicon-carbon composite, which is advantageous for lifespan performance and rapid charging performance.

[0081] According to additional examples described herein, the silicon-carbon composite, natural graphite, and artificial graphite in the negative electrode composition may contain pores.

[0082] For example, the volume of the pores can refer to the volume of the pores of the particle itself, and can be measured by a calculation formula using the adsorption / desorption isotherm method via nitrogen adsorption. Specifically, using the BELSORP-mini II model from BEL Japan, an N2 adsorption / desorption isotherm graph was derived, and the volume at the point where the P / P0 (closest to 1) was highest for adsorption was used as representative. The adsorption / desorption isotherm method can be used, and the plot of the measured values ​​is with pressure (P / P0) on the X axis and Va / cm on the Y axis. 3 (STP)g -1 That is the case.

[0083] For example, the total pore volume (total pore V) of the silicon-carbon composite is 4-11 cm³. 3 The pore volume (total pore V.) of the aforementioned natural graphite is 2-8 cm³ / g. 3 The porosity (total pore volume V.) of the artificial graphite is 0.1 to 4 cm² / g. 3 It may be less than / g.

[0084] The pore volume of the silicon-carbon composite is 1 cm larger than that of the natural graphite. 3 / g~8cm 3 / g is large.

[0085] The pore volume of the silicon-carbon composite may be the same as that of the natural graphite.

[0086] The pore volume of the silicon-carbon composite is 4 cm² larger than that of the artificial graphite. 3 / g~11cm 3 / g is large.

[0087] The pore volume of the aforementioned natural graphite is 1 cm larger than that of the aforementioned artificial graphite. 3 / g~6cm 3 / g is large.

[0088] The pore volume of the natural graphite may be the same as that of the artificial graphite.

[0089] When the pore volume (total pore V.) of the silicon-carbon composite, the natural graphite, and the artificial graphite meets the above range, the secondary battery can have the characteristics of improving the lifespan, enabling rapid charging, and having excellent electrode adhesion.

[0090] In one example described herein, the number of pores (pore intensity) of the silicon-carbon composite having a size of 2 nm to 200 nm is the same as or greater than the number of pores of the natural graphite, and the number of pores of the natural graphite is the same as or greater than the number of pores of the artificial graphite, thereby providing a negative electrode composition.

[0091] For example, the pore size can refer to the size of the pores in the particle itself, and can be measured by a calculation formula using the BJH (Barrett-Joyer-Halenda) method via nitrogen adsorption. Specifically, using the BELSORP-mini II model from BEL Japan, the pore area was derived based on the pore size, and the pore size showing the largest pore area was used as representative. The BJH method can be used, and the plot of the measured values ​​is as follows: the X axis is the pore diameter (Dp / nm), and the Y axis is dVp / dDp (cm 3 g -1 nm -1 )

[0092] When the above range is met, the secondary battery can have the characteristics of improving the lifespan of the secondary battery, enabling rapid charging, and having excellent electrode adhesion.

[0093] In this example, the natural graphite has a BET specific surface area of ​​1.5 m². 2 / g or more 3.5m 2 The amount is less than or equal to / g, and the artificial graphite has a BET specific surface area of ​​0.1m². 2 / g or more 2.5m 2 The present invention provides a negative electrode composition that is less than or equal to / g.

[0094] The aforementioned natural graphite has a BET specific surface area of ​​1.5 m². 2 / g or more 3.5m 2 / g or less, 1.5m 2 / g or more 3.3m 2 / g or less, 1.5m 2 / g or more 3m 2 / g or less, 1.5m 2 / g or more 2.8m 2 / g or less, or 1.5m 2 / g or more 2.5m 2 It may be less than / g.

[0095] The aforementioned artificial graphite has a BET specific surface area of ​​0.1 m². 2 / g or more 2.2m 2 / g or less, 0.1m 2 / g or more 2m 2 / g or less, 0.1m2 / g or more 1.8m 2 / g or less, 0.1m 2 / g or more 1.5m 2 / g or less, 0.3m 2 / g or more 2.5m 2 It may be less than / g.

[0096] When the natural graphite and artificial graphite satisfy the BET specific surface area range, the negative electrode composition, by including two types of graphite with different specific surface areas other than the silicon-carbon composite, can have the characteristics of increased battery capacity and excellent output characteristics at a high C-rate, thereby improving the problem of reduced lifespan of the negative electrode and secondary battery that can occur due to large volume changes of silicon-based particles.

[0097] The natural graphite can improve electrode adhesion within the BET specific surface area range, while artificial graphite may affect rapid charging and lifespan performance within the BET specific surface area range. Furthermore, if the artificial graphite has a larger BET specific surface area than the natural graphite, when manufacturing electrodes with the negative electrode composition, more binder in the electrode may be consumed, which can reduce electrode adhesion.

[0098] In the example described herein, the negative electrode conductive material comprises single-walled carbon nanotubes (SWCNTs), and the negative electrode composition comprises, based on a total of 100 parts by weight of silicon-carbon composite, graphite, and single-walled carbon nanotubes, 0.5 to 50 parts by weight of silicon-carbon composite; 45 to 99 parts by weight of graphite; and 0.01 to 5 parts by weight of single-walled carbon nanotubes (SWCNTs), and based on 100 parts by weight of graphite, 10 to 70 parts by weight of natural graphite; and 30 to 90 parts by weight of artificial graphite.

[0099] According to additional examples described herein, the anode composition may comprise a silicon-carbon composite; graphite; and a negative electrode conductive material, wherein the graphite comprises natural graphite and artificial graphite, and the negative electrode conductive material may comprise single-walled carbon nanotubes (SWCNTs).

[0100] According to the additional examples described herein, the negative electrode composition may contain, based on a total of 100 parts by weight of silicon-carbon composite, graphite, and single-walled carbon nanotubes, 0.5 to 50 parts by weight of silicon-carbon composite; 45 to 99 parts by weight of graphite; and 0.01 to 5 parts by weight of single-walled carbon nanotubes (SWCNTs).

[0101] For example, based on a total of 100 parts by weight of silicon-carbon composite, graphite, and single-walled carbon nanotubes in the negative electrode composition, the silicon-carbon composite may be in amounts of 1 to 40 parts by weight, 2 to 30 parts by weight, 3 to 20 parts by weight, 4 to 10 parts by weight, or 5 to 10 parts by weight. The graphite may be in amounts of 50 to 99 parts by weight, 55 to 99 parts by weight, 60 to 99 parts by weight, 65 to 99 parts by weight, 70 to 99 parts by weight, or 75 to 95 parts by weight. The single-walled carbon nanotubes (SWCNTs) may be in amounts of 0.01 to 4 parts by weight, 0.01 to 3 parts by weight, 0.01 to 2 parts by weight, 0.01 to 1 part by weight, or 0.05 to 0.5 parts by weight.

[0102] According to the additional examples described herein, the natural graphite may be 10 to 70 parts by weight, and the artificial graphite may be 30 to 90 parts by weight, based on 100 parts by weight of graphite.

[0103] For example, based on 100 parts by weight of graphite, the amount of natural graphite may be 11 to 68 parts by weight, and the amount of artificial graphite may be 32 to 89 parts by weight.

[0104] When the content range of the negative electrode composition satisfies the content range of the silicon-carbon composite, the capacity characteristics can be improved; when the content range of the graphite is satisfied, the rapid charging performance and negative electrode adhesion can be improved; and when the content range of the single-walled carbon nanotube (SWCNT) is satisfied, the battery efficiency and lifespan can be improved. As a result, the reduction in the lifespan of the secondary battery can be improved, the number of points where charging and discharging is possible can be increased, and the battery can have the characteristic of having excellent output characteristics at a high C-rate.

[0105] In one example described herein, a negative electrode composition is provided, further comprising a binder.

[0106] The binder can play a role in improving the adhesion between negative electrode active material particles and the adhesion between the negative electrode active material particles and the negative electrode current collector. The negative electrode binder may be one of those known in the art, and non-limiting examples include at least one selected from the group consisting of polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, polyacrylic acid, and substances in which the hydrogens of these are substituted with Li, Na, or Ca, and may also include a variety of copolymers thereof.

[0107] The binder may be present in an amount of 10% or less, preferably 1% to 5%, based on 100 parts by weight of the negative electrode composition. For example, the binder may be present in an amount of 9% or less, 8% or less, 7% or less, 6% or less, or 5% or less, based on 100 parts by weight of the negative electrode composition. The binder may be present in an amount of 0.5% or more, or 1% or more, based on 100 parts by weight of the negative electrode composition.

[0108] Method for manufacturing the negative electrode composition One example described herein is a method for producing a negative electrode composition, comprising the steps of: adding water to a negative electrode conductive material and mixing to form a first mixture; and mixing a silicon-carbon composite and graphite with the first mixture to form a second mixture, wherein the BET specific surface area of ​​the silicon-carbon composite is greater than the BET specific surface area of ​​the graphite.

[0109] According to additional examples described herein, the method for producing the negative electrode composition may include the step of mixing the silicon-carbon composite and graphite together with the negative electrode conductive material.

[0110] For example, the graphite comprises at least one of natural graphite and artificial graphite, and if the graphite comprises both natural graphite and artificial graphite, the BET specific surface area of ​​the natural graphite is greater than the BET specific surface area of ​​the artificial graphite. Preferably, the graphite comprises both natural graphite and artificial graphite.

[0111] In one example described herein, the negative electrode conductive material includes single-walled carbon nanotubes (SWCNTs), and the negative electrode composition contains, based on a total of 100 parts by weight of silicon-carbon composite, graphite, and single-walled carbon nanotubes, 0.5 to 50 parts by weight of silicon-carbon composite; 45 to 99 parts by weight of graphite; and 0.01 to 5 parts by weight of single-walled carbon nanotubes (SWCNTs), and based on 100 parts by weight of graphite, 10 to 70 parts by weight of natural graphite; and 30 to 90 parts by weight of artificial graphite, in a method for producing the negative electrode composition.

[0112] In the example described herein, the BET specific surface area of ​​the silicon-carbon composite is 1 m² larger than the BET specific surface area of ​​the natural graphite. 2 / g~9m 2 Furthermore, the BET specific surface area of ​​the silicon-carbon composite is 2m² greater than that of the artificial graphite. 2 / g~10m 2 Furthermore, the BET specific surface area of ​​the natural graphite is 0.1 m² greater than that of the artificial graphite. 2 / g~2m 2 / g is even larger.

[0113] In the examples described herein, the proportions of the silicon-carbon composite, natural graphite, and artificial graphite relative to the BET specific surface area are as described above for the negative electrode composition.

[0114] negative electrode One example described herein provides a negative electrode for a lithium secondary battery, comprising a current collector and a negative electrode active material layer containing the aforementioned negative electrode composition formed on one or both sides of the current collector.

[0115] As additional examples described herein suggest, the current collector is not particularly limited as a negative electrode current collector, as long as it is conductive without inducing chemical changes in the battery. For example, the current collector may be made of copper, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel with a surface treatment of carbon, nickel, titanium, silver, etc. Transition metals that readily adsorb carbon, such as copper and nickel, may also be used as current collectors. The thickness of the current collector may be between 1 μm and 500 μm, but is not limited thereto.

[0116] According to additional examples described herein, a negative electrode active material layer containing the negative electrode composition described in the above examples can be formed on one or both sides of the current collector. For example, the thickness of the negative electrode active material layer may be 20 μm or more and 500 μm or less.

[0117] According to the additional examples described herein, the negative electrode for the lithium secondary battery can be manufactured by a conventional negative electrode manufacturing method. It can be manufactured by coating a negative electrode composition, comprising the aforementioned active material, conductive material, and selectively a binder, onto a current collector, followed by drying and rolling. In this case, the types and contents of the negative electrode active material, conductive material, and binder are as described above.

[0118] The solvent may be any solvent commonly used in the art, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water, and one or more of these may be used. The amount of solvent used should be such that, considering the coating thickness and production yield of the slurry, it has a viscosity that allows for excellent thickness uniformity when dissolving or dispersing the active material, conductive material, and binder, and then coating them to manufacture the negative electrode. Alternatively, the negative electrode may be manufactured by casting the active material layer-forming composition onto a separate support, peeling it off the support, and then laminating the resulting film onto a current collector.

[0119] Lithium-ion battery One example described herein provides a lithium secondary battery comprising a positive electrode; a negative electrode for a lithium secondary battery according to one or more examples described above; and a separator between the positive electrode and the negative electrode.

[0120] According to the additional examples described herein, the negative electrode is identical to the negative electrode in the previously mentioned examples. Since the negative electrode has already been described, a detailed explanation is omitted.

[0121] According to additional examples described herein, the positive electrode includes a positive electrode current collector and a positive electrode active material layer comprising a positive electrode composition formed on the current collector. The current collector may be a positive electrode current collector.

[0122] According to one example, the positive electrode may include a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector and including the positive electrode composition. The positive electrode composition may include a positive electrode active material.

[0123] In the positive electrode, the positive electrode current collector is not particularly limited as long as it has conductivity without inducing a chemical change in the battery. For example, stainless steel, aluminum, nickel, titanium, fired carbon, or a material obtained by surface treatment of the surface of aluminum or stainless steel with carbon, nickel, titanium, silver, etc. may be used. Further, the positive electrode current collector may usually have a thickness of 3 μm to 500 μm, and fine irregularities may be formed on the surface of the current collector to increase the adhesion force of the positive electrode active material. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, non-woven fabric body, etc.

[0124] According to one example, the thickness of the negative electrode active material layer may be 20 μm or more and 500 μm or less, and the thickness of the positive electrode active material layer may be 90% to 110%, for example 95% to 105%, of the thickness of the negative electrode active material layer. Also, these thicknesses may be the same.

[0125] The positive electrode active material may be a commonly used positive electrode active material. Specifically, the positive electrode active material is a layered compound such as lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; lithium iron oxide such as LiFe3O4; chemical formula Li 1+c1 Mn 2-c1 O4 (0 ≦ c1 ≦ 0.33), lithium manganese oxides such as LiMnO3, LiMn2O3, LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, V2O5, Cu2V2O7; chemical formula LiNi 1-c2 M c2 O2 (where M is at least one selected from the group consisting of Co, Mn, Al, Cu, Fe, Mg, B, and Ga, and satisfies 0.01 ≦ c2 ≦ 0.3) represented by Ni-site type lithium nickel oxide; chemical formula LiMn 2-c3 Mc3 Lithium manganese composite oxides represented as O2 (where M is at least one selected from the group consisting of Co, Ni, Fe, Cr, Zn, and Ta, satisfying 0.01 ≤ c3 ≤ 0.1) or Li2Mn3MO8 (where M is at least one selected from the group consisting of Fe, Co, Ni, Cu, and Zn); LiMn2O4 in which part of the Li in the chemical formula is substituted with an alkaline earth metal ion, etc., are examples, but are not limited to these. The positive electrode may also be metallic lithium (Li-metal).

[0126] The positive electrode active material layer may also include a positive electrode conductive material and a positive electrode binder, along with the positive electrode active material described above.

[0127] In this case, the positive electrode conductive material is used to impart conductivity to the electrode, and can be used without particular limitations as long as it has conductivity in the battery without causing a chemical change. 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 powders or metal fibers such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives. One of these alone or a mixture of two or more may be used.

[0128] Furthermore, the positive electrode binder plays a role in improving the adhesion between positive electrode active material particles and the adhesion between the positive electrode active material and the positive electrode current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber (SBR), fluororubber, or various copolymers thereof, and one or more of these may be used.

[0129] According to additional examples described herein, the lithium secondary battery may include a separator between the positive electrode and the negative electrode.

[0130] The separator separates the negative electrode and the positive electrode and provides a passage for lithium ions to move. Any separator commonly used in secondary batteries can be used without particular limitations, but those with low resistance to ion movement of the electrolyte and excellent electrolyte moisture absorption capacity are particularly preferred. Specifically, porous polymer films, such as those made from polyolefin polymers like ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, or laminated structures of two or more layers thereof, may be used. Alternatively, ordinary porous nonwoven fabrics, such as those made from high-melting-point glass fibers or polyethylene terephthalate fibers, may be used. Furthermore, to ensure heat resistance or mechanical strength, coated separators containing ceramic components or polymeric substances may be used, and these may be selectively used in single-layer or multi-layer structures.

[0131] According to one example described herein, the lithium secondary battery may contain an electrolyte.

[0132] Examples of the electrolyte include, but are not limited to, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in the manufacture of lithium secondary batteries.

[0133] Specifically, the electrolyte may include a non-aqueous organic solvent and a metal salt.

[0134] As the 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, γ-butyrolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, triester phosphate, trimethoxymethane, dioxolane derivatives, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ether, methyl propionate, and ethyl propionate may be used.

[0135] In particular, among the carbonate-based organic solvents, ethylene carbonate and propylene carbonate, which are cyclic carbonates, can be preferably used as high-viscosity organic solvents because they have high dielectric constants and dissociate lithium salts well. Furthermore, when such cyclic carbonates are mixed with linear carbonates with low viscosity and low dielectric constant, such as dimethyl carbonate and diethyl carbonate, in appropriate proportions, an electrolyte with high conductivity can be produced, and therefore they can be used even more preferably.

[0136] As the metal salt, a lithium salt may be used, and the lithium salt is a substance that is easily soluble 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 selected from the group consisting of may be used.

[0137] In addition to the components constituting the electrolyte solution, the electrolyte may further contain one or more additives such as haloalkylene carbonate-based compounds such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glyme, triamide hexaline, nitrobenzene derivatives, sulfur, quinoneimine dyes, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride for the purpose of improving the life characteristics of the battery, suppressing the decrease in battery capacity, improving the discharge capacity of the battery, etc.

[0138] In an example of this description, the lithium secondary battery is a cylindrical battery.

[0139] For example, the cylindrical battery can mean that the form of the battery itself, which includes an assembly comprising a positive electrode, a negative electrode, a separator, and an electrolyte, is cylindrical, and may include a cylindrical can, a battery assembly provided inside the cylindrical can, and a top cap.

[0140] In one example described herein, a battery module including the aforementioned lithium secondary battery is provided.

[0141] In this example, a battery pack is provided that includes a battery module as described above.

[0142] An additional example described herein provides a battery module and a battery pack containing the same, which includes the aforementioned cylindrical battery as a unit cell. Since the battery module and battery pack include the secondary battery having high capacity, high rate characteristics, and cycle characteristics, they can be used as a power source for medium to large devices selected from the group consisting of electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and power storage systems.

[0143] The lithium secondary batteries described herein exhibit excellent discharge capacity, output characteristics, and cycle performance, and can therefore be used as power sources for portable devices such as mobile phones, laptops, and digital cameras, as well as for medium- and large-sized devices selected from the group consisting of electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and power storage systems. For example, the battery module or battery pack can be used as a power source for one or more medium- and large-sized devices, including power tools; electric vehicles (EVs), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEVs); or power storage systems.

[0144] Examples The following are preferred embodiments to aid in understanding this description, but these embodiments are merely illustrative, and it will be obvious to those skilled in the art that various changes and modifications are possible within the scope of this description and the technical idea, and such variations and modifications will naturally fall within the scope of the attached claims.

[0145] <Examples and Comparative Examples> Example 1 Manufacturing of negative electrodes A negative electrode composition comprising a silicon-carbon composite, graphite, and a negative electrode conductive material was prepared. In the negative electrode composition, based on 100 parts by weight of the total content of the silicon-carbon composite, graphite, and negative electrode conductive material, 10 parts by weight of silicon-carbon composite, 89.5 parts by weight of graphite (artificial graphite:natural graphite = 89:11 by weight ratio), and 0.5 parts by weight of single-walled carbon nanotubes were included. Based on 100 parts by weight of the negative electrode composition, 1.15 parts by weight of SBR (styrenebutadiene rubber) and 1 part by weight of CMC (carboxymethyl cellulose) were included as binders. The negative electrode conductive material was added in the form of a CNT predispersion, based on 100 parts by weight of the negative electrode composition, containing 0.09 parts by weight of dispersant and 0.06 parts by weight of single-walled carbon nanotubes. In this case, the BET specific surface area of ​​the artificial graphite, natural graphite, and silicon-carbon composite in the composition was 0.8 m² each. 2 / g, 1.8m 2 / g, 6.8m 2 Manufactured in / g

[0146] Specifically, a single-walled carbon nanotube predispersion was prepared using distilled water as the dispersion medium and CMC (carboxymethyl cellulose) as the dispersant. The silicon-carbon composite, graphite, carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR) as binders were added, the mixture was stirred, and then distilled water was added to produce the negative electrode composition (solid content = 50 parts by weight).

[0147] The aforementioned negative electrode composition was applied to a copper (Cu) metal thin film, which was a negative electrode current collector with a thickness of 15 μm, and dried. The temperature of the circulating air during this process was 60°C. Subsequently, the film was rolled (rolled in a roll press) and dried in a vacuum oven at 130°C for 12 hours to produce a negative electrode in which the negative electrode active material layer was placed on the negative electrode current collector.

[0148] In this case, the ratio of the weight of CMC added to the binder to the weight of CMC added to the dispersant was 1.14:0.06. The average length of the single-walled carbon nanotube units in the negative electrode active material layer was 10 μm, and the average diameter was 2 nm.

[0149] <Examples 2-23> The anode was manufactured in the same manner as in Example 1, except that the BET specific surface area of ​​the artificial graphite, natural graphite, and silicon-carbon composite contained in the anode composition, and the weight ratios of the silicon-carbon composite, graphite, and single-walled carbon nanotubes in the anode composition, based on a total of 100 parts by weight, were as shown in Table 1 below.

[0150] <Comparative Examples 1-6> The anode was manufactured in the same manner as in Example 1, except that the BET specific surface area of ​​the artificial graphite, natural graphite, and silicon-carbon composite contained in the anode composition, and the weight ratios of the silicon-carbon composite, graphite, and single-walled carbon nanotubes in the anode composition, based on 100 parts by weight of the sum of their contents, were as shown in Table 1 below. <Reference Examples 1 and 2> The negative electrode was manufactured in the same manner as in Example 1, except that multi-walled carbon nanotubes (MWCNTs) and carbon black were used instead of single-walled carbon nanotubes in the negative electrode composition.

[0151] The negative electrodes manufactured in the above examples and comparative examples are shown in Table 1 below.

[0152] [Table 1]

[0153] The pore volumes of the materials used in Examples 1 and 23, and Comparative Examples 1, 2, and 6 are shown in Table 2 below.

[0154] [Table 2]

[0155] The specific surface area was measured using a BET measuring device (BEL-SORP-mini, Nippon Bell) by degassing the gas at 130°C for 2 hours, followed by N2 adsorption / desorption at 77K.

[0156] The aforementioned pore volume was determined using the BELSORP-mini II model from BEL Japan. After deriving an N2 adsorption / desorption isotherm graph, the volume at the point where the P / P0 ratio (closest to 1) was highest for adsorption was used as representative.

[0157] Experimental example Using the negative electrode active materials from the examples and comparative examples, a negative electrode and a lithium secondary battery containing the same were manufactured.

[0158] Lifespan (capacity retention rate) characteristic evaluation The capacity retention rate was evaluated by charging and discharging the manufactured batteries, and this is shown in Table 3 below.

[0159] The first and second cycles were charged and discharged at 0.1C, and from the third cycle onwards, the charge and discharge were performed at 0.5C. The 300th cycle ended in a charged state (lithium was in the negative electrode).

[0160] Charging conditions: CC (constant current) / CV (constant voltage) (4.25V / 0.05C current cut-off) Discharge condition: CC (constant current) condition 2.5V

[0161] The capacity retention rates were derived using the following calculations. Capacity retention rate (%) = (100th discharge capacity / 1st discharge capacity) × 100

[0162] Table 3 below lists the values ​​for energy density (referenced to Example 1, %) and capacity retention rate (300 cycles, %) for Examples 1 to 23, Comparative Examples 1 to 6, and Reference Examples 1 and 2.

[0163] Evaluation at the time of re-plating 1.4875cm 2 A circularly cut lithium (Li) metal thin film was used as the positive electrode. A porous polyethylene separator was interposed between the positive and negative electrodes, and a lithium coin half-cell was manufactured by dissolving vinylene carbonate dissolved at a volume ratio of 7:3 in a mixed solution of methyl ethyl carbonate (EMC) and ethylene carbonate (EC), at a concentration of 0.5 parts by weight, and injecting an electrolyte solution containing 1M LiPF6.

[0164] After the first charge / discharge cycle was completed, the Li-plating time was measured under a charging condition of 1.8C. Charging conditions: CC (constant current) / CV (constant voltage) (5mV / 0.005C current cut-off) Discharge condition: CC (constant current) condition 1.5V

[0165] Electrode adhesion strength evaluation For each manufactured negative electrode, the negative electrode was punched out to 20 mm x 150 mm and fixed to the center of a glass slide using tape. Then, the peel strength at 180 degrees was measured while peeling off the negative electrode current collector using a UTM. The evaluation was determined by measuring the peel strength of five or more samples and taking the average value. This is shown in Table 3 below.

[0166] [Table 3]

[0167] The negative electrode composition described herein comprises a silicon-carbon composite, graphite, and a negative electrode conductive material, wherein the graphite includes natural graphite and artificial graphite, and the BET specific surface area of ​​the silicon-carbon composite is larger than that of the natural graphite, and the BET specific surface area of ​​the natural graphite is larger than that of the artificial graphite. When using a silicon-based active material, which is a high-capacity material, to manufacture a high-capacity battery, the negative electrode composition satisfies the interrelationship of the BET specific surface areas of the silicon-carbon composite, the natural graphite, and the artificial graphite, thereby improving the lifespan reduction of conventional secondary batteries, enabling rapid charging, and having excellent electrode adhesion. From Table 3, it can be confirmed that the examples appear at a higher SOC% at the Li plating stage compared to the comparative example, which means that lithium is deposited more slowly during charging. Since lithium is deposited more slowly during charging, it can be seen that the rapid charging performance is superior.

[0168] Furthermore, by using single-walled carbon nanotubes (SWCNTs) together with the silicon-carbon composite, graphite, and conductive material contained in the aforementioned negative electrode composition, the conductive pathways between negative electrode active material particles can be improved, thereby enhancing the battery's capacity, efficiency, and lifespan.

[0169] Natural graphite has a BET specific surface area of ​​1.5 m². 2 / g or more 3.5m 2 Having a value of less than / g, this can improve electrode adhesion. Artificial graphite and silicon-carbon composites affect fast charging and lifespan performance, with a BET specific surface area of ​​0.1m² each. 2 / g or more 2.5m 2 / g or less, 3m 2 / g or more 15m 2 It is less than / g.

[0170] If the BET specific surface area of ​​artificial graphite is larger than that of natural graphite, more binder will be consumed in the electrode when manufacturing the electrode with the negative electrode composition, which may reduce the electrode adhesion strength. Also, if the BET specific surface area of ​​the silicon-carbon composite is smaller than that of natural graphite, the insertion and / or removal of lithium from the silicon-carbon composite becomes difficult, which may reduce the lifespan performance and fast charging performance.

[0171] Examples 1 to 23 demonstrate the use of negative electrode compositions that satisfy a specific specific surface area ratio, confirming superior lifespan performance, rapid charging capabilities, and electrode adhesion.

[0172] On the other hand, Comparative Examples 1 and 3-6 are cases where the specific specific surface area ratio of the negative electrode composition used in this description is not met. In these cases, the artificial graphite has a larger BET specific surface area than natural graphite, and when an electrode is manufactured using the negative electrode composition, more binder is consumed within the electrode, which can reduce the electrode adhesion strength and thus reduce the lifespan performance.

[0173] Comparative Example 2 is a case where the specific specific surface area ratio of the negative electrode composition used in this description is not met, and the BET specific surface area of ​​the silicon-carbon composite is smaller than that of natural graphite, making it difficult to insert and / or remove lithium from the silicon-carbon composite, which may reduce lifespan performance and rapid charging performance.

[0174] Reference Examples 1 and 2 show cases where multi-walled carbon nanotubes (MWCNTs) and carbon black are used as the negative electrode conductive material instead of single-walled carbon nanotubes (SWCNTs) as described herein, which may affect the battery's lifespan, rapid charging performance, and electrode adhesion strength.

Claims

1. A negative electrode composition comprising a silicon-carbon composite, graphite, and a negative electrode conductive material, The graphite includes both natural graphite and artificial graphite, and the BET specific surface area of ​​the natural graphite is greater than the BET specific surface area of ​​the artificial graphite. The BET specific surface area of ​​the silicon-carbon composite is greater than the BET specific surface area of ​​the natural graphite. The anode conductive material is an anode composition containing single-walled carbon nanotubes (SWCNTs).

2. The graphite includes the natural graphite, and the BET specific surface area of ​​the silicon-carbon composite is 1 m² greater than the BET specific surface area of ​​the natural graphite. ２ / g~9m ２ The negative electrode composition according to claim 1, which is larger in g / g.

3. The graphite includes the artificial graphite, and the BET specific surface area of ​​the silicon-carbon composite is 2 m² greater than the BET specific surface area of ​​the artificial graphite. ２ / g to 10m ２ The negative electrode composition according to claim 1, which is larger in g / g.

4. The BET specific surface area of ​​the natural graphite is 0.1 m² greater than the BET specific surface area of ​​the artificial graphite. ２ / g~2m ２ The negative electrode composition according to claim 1, which is larger in g / g.

5. The negative electrode composition according to claim 1, wherein the pore volume of the silicon-carbon composite is the same as or greater than that of the natural graphite, and the pore volume of the natural graphite is the same as or greater than that of the artificial graphite.

6. The natural graphite has a BET specific surface area of 1.5 m ２ / g or more and 3.5 m ２ / g or less, and the artificial graphite has a BET specific surface area of 0.1 m ２ / g or more and 2.5 m ２ / g or less. The negative electrode composition according to claim 1.

7. The anode composition according to claim 1, wherein, based on a total content of 100 parts by weight of silicon-carbon composite, graphite, and single-walled carbon nanotubes, the silicon-carbon composite is contained in an amount of 0.5 to 50 parts by weight; the graphite is contained in an amount of 45 to 99 parts by weight; and the single-walled carbon nanotubes (SWCNTs) are contained in an amount of 0.01 to 5 parts by weight.

8. The negative electrode composition according to claim 1, wherein the natural graphite is contained in an amount of 10 to 70 parts by weight, based on 100 parts by weight of graphite; and the artificial graphite is contained in an amount of 30 to 90 parts by weight.

9. The negative electrode composition according to claim 1, further comprising a binder.

10. A step of mixing a negative electrode conductive material with water to form a first mixture; and A step of mixing the first mixture with a silicon-carbon composite and graphite to form a second mixture; A method for producing a negative electrode composition, comprising: The graphite includes both natural graphite and artificial graphite, and the BET specific surface area of ​​the natural graphite is greater than the BET specific surface area of ​​the artificial graphite. The BET specific surface area of ​​the silicon-carbon composite is greater than the BET specific surface area of ​​the natural graphite. The negative electrode conductive material includes single-walled carbon nanotubes (SWCNTs), and the method for producing the negative electrode composition.

11. A method for producing the anode composition according to claim 10, wherein, based on a total content of 100 parts by weight of silicon-carbon composite, graphite, and single-walled carbon nanotubes, the silicon-carbon composite is contained in an amount of 0.5 to 50 parts by weight; the graphite is contained in an amount of 45 to 99 parts by weight; and the single-walled carbon nanotubes (SWCNTs) are contained in an amount of 0.01 to 5 parts by weight.

12. A method for producing a negative electrode composition according to claim 10, wherein the natural graphite is included in an amount of 10 to 70 parts by weight, based on 100 parts by weight of graphite, and the artificial graphite is included in an amount of 30 to 90 parts by weight.

13. The BET specific surface area of ​​the silicon-carbon composite is 1 m² greater than the BET specific surface area of ​​the natural graphite. ２ / g~9m ２ A method for producing the negative electrode composition according to claim 10, with a larger / g value.

14. The BET specific surface area of ​​the silicon-carbon composite is 2 m² greater than the BET specific surface area of ​​the artificial graphite. ２ / g to 10m ２ A method for producing the negative electrode composition according to claim 10, with a larger / g value.

15. The BET specific surface area of ​​the natural graphite is 0.1 m² greater than the BET specific surface area of ​​the artificial graphite. ２ / g~2m ２ A method for producing the negative electrode composition according to claim 10, with a larger / g value.

16. Current collector; and A negative electrode active material layer comprising a negative electrode composition according to any one of claims 1 to 9 is provided on one or both sides of the current collector. A negative electrode for lithium secondary batteries, including...

17. positive electrode; A negative electrode for a lithium secondary battery according to claim 16; and A separator provided between the positive electrode and the negative electrode; Lithium-ion batteries, including lithium-ion batteries.

18. The lithium secondary battery according to claim 17, wherein the lithium secondary battery is a cylindrical battery.

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