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

Abstract

The present invention relates to a silicon oxide represented by SiO x (0 < x < 2); graphite; and a negative electrode composition containing a negative electrode conductive material, wherein the graphite includes natural graphite and artificial graphite, and the SiO x (0

Description

[Technical Field]

[0001] This application claims the benefit of the filing date of Korean Patent Application No. 10-2023-0117771 filed with the Korean Intellectual Property Office on September 5, 2023, and Korean Patent Application No. 10-2024-0120175 filed with the Korean Intellectual Property Office on September 4, 2024, the entire contents of which are incorporated herein by reference.

[0002] The present application relates to a negative electrode composition, a negative electrode for a lithium secondary battery including the same, a lithium secondary battery, and a method for producing the negative electrode composition. [Background technology]

[0003] In recent years, with the rapid spread of battery-powered electronic devices, such as mobile phones, laptops, and electric vehicles, as well as power tools and vacuum cleaners, the demand for secondary batteries that are small, lightweight, and have relatively high capacity and / or high output has been rapidly increasing. In particular, lithium secondary batteries, which are lightweight and have high energy density, have attracted attention as power sources for electronic devices. As a result, active research and development efforts are being made to improve the performance of lithium secondary batteries.

[0004] Lithium secondary batteries have an organic or polymer electrolyte between a positive electrode and a negative electrode, which are made of active materials that allow lithium ions to be inserted and deintercalated. Electrical energy is produced through oxidation and reduction reactions that occur when lithium ions are inserted into and deintercalated from the positive and negative electrodes.

[0005] The positive electrode active material of a lithium secondary battery is a metal oxide such as LiCoO2, LiMnO2, LiMn2O4, or LiNiO2, and the negative electrode active material is a carbon-based material such as metallic lithium, graphite, or activated carbon, or silicon oxide (SiOx Among the negative electrode active materials, metallic lithium was primarily used in the early days, but as charge and discharge cycles progressed, lithium atoms grew on the surface of the metallic lithium, damaging the separator and destroying the battery. Therefore, carbon-based materials have been primarily used in recent years.

[0006] Graphite is the primary negative electrode active material for lithium secondary batteries. However, its low capacity per unit mass (372 mAh / g) makes it difficult to increase the capacity of lithium secondary batteries. Therefore, to increase the capacity of lithium secondary batteries, non-carbon-based negative electrode materials such as silicon, tin, and their oxides have been developed as materials with higher energy densities than graphite. However, while these non-carbon-based negative electrode materials offer high capacity, they suffer from low initial efficiency, high lithium consumption during initial charging and discharging, and large irreversible capacity loss.

[0007] In particular, silicon-based active materials undergo excessive volume change during battery operation, resulting in a problem of reduced battery life. Therefore, there is a need to develop a negative electrode that uses silicon-based negative electrode active materials and can effectively improve battery life characteristics. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Korean Patent Publication No. 10-2021-0070933 Summary of the Invention [Problem to be solved by the invention]

[0009] The present inventors have discovered that in lithium secondary batteries designed within a limited space, optimal battery performance can be achieved by a specific combination of the types of active material and conductive material constituting the negative electrode composition, the content of each component, and the BET specific surface area, and have completed the present invention. [Means for solving the problem]

[0010] [[IP=]One embodiment of the present invention is a negative electrode composition comprising a silicon-based active material, graphite, and a negative electrode conductive material, wherein the graphite includes natural graphite and artificial graphite, and the silicon-based active material includes silicon oxide represented by SiO x (0 < x < 2), and the BET specific surface area values of the SiO x (0 < x < 2) silicon oxide, the natural graphite, and the artificial graphite are in the order of artificial graphite < natural graphite < silicon oxide represented by SiOx (0 < x < 2), and a negative electrode composition is provided.

[0011] Another embodiment of the present invention provides a method for manufacturing a lithium secondary battery and a negative electrode composition including the negative electrode.

[0012] Another embodiment of the present invention provides a battery module and a battery pack including the lithium secondary battery...

Effects of the Invention

[0013] In the case of the negative electrode composition according to one embodiment of the present invention, when using a silicon-based active material, which is a high-capacity material, to fabricate a high-capacity battery, by satisfying the mutual relationship of the BET specific surface areas of the SiO x (0 < x < 2) silicon oxide, the natural graphite, and the artificial graphite, it is possible to improve the reduction in the life of conventional secondary batteries, enable rapid charging, and have excellent electrode adhesion.

[0014] Also, by using together the SiO x (0 < x < 2) silicon oxide, graphite, and single-walled carbon nanotubes (SWCNT) as a conductive material included in the aforementioned negative electrode composition, the conductive path between the negative electrode active material particles can be improved, and the capacity, efficiency, and life performance of the battery can be enhanced.

Modes for Carrying Out the Invention

[0015] The present invention will now be described in more detail to aid in understanding the invention.

[0016] The terms and words used in this specification and claims should not be interpreted in a limited way to their ordinary or dictionary meanings, but should be interpreted in a way that is consistent with the technical idea of ​​the present invention, based on the principle that the inventors can appropriately define the concepts of terms in order to best explain their inventions.

[0017] The terms used in this specification are merely used to describe exemplary embodiments and are not intended to limit the present invention. The singular expressions include the plural expressions unless otherwise clearly indicated in the context.

[0018] It should be understood that in this specification, terms such as "comprises," "provides," or "has" specify the presence of embodied features, numbers, steps, components, or combinations thereof, but do not preclude the possibility of the presence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0019] Furthermore, when a part such as a layer exists "on" or "above" another part, it does not only mean that it is "directly above" that part, but also includes the case where there is another part between them. In contrast, when a part exists "directly above" another part, it means that there is no other part between them. Furthermore, when a part exists "on" or "above" a reference part, it does not necessarily mean that it is located above or below the reference part, and is not necessarily located "above" or "above" the direction opposite to gravity.

[0020] In this specification, the "specific surface area" is measured by the BET method, and specifically, the measurement can be performed by degassing the measurement object at 130°C for 2 hours using a BET measurement device (BEL-SORP-mini, Nippon Bell), and then performing N2 absorption / desorption at 77 K. That is, in this specification, the BET specific surface area can refer to the specific surface area of ​​the particle itself measured by the above measurement method.

[0021] In this specification, the average length or diameter of the conductive material can be measured using SEM or TEM.

[0022] In this specification, "pore size" refers to the size of the pores in the particle itself, and can be measured using a formula based on the BJH (Barrett-Joyer-Halenda) method using nitrogen adsorption. Specifically, the pore area according to the pore size was calculated using the BELSORP-mini II model manufactured by BEL Japan, and the pore size showing the largest pore area was used as the representative. The BJH method can be used, and the measured values ​​are plotted with the pore diameter (Dp / nm) on the X axis and the dVp / dDp (cm) on the Y axis. 3 g -1 nm -1 )

[0023] In this specification, "pore volume" refers to the volume of the pores in the particle itself, and can be measured using a formula based on the adsorption / desorption isotherm method using nitrogen adsorption. Specifically, a graph of the N2 adsorption / desorption isotherm was derived using a BELSORP-mini II model manufactured by BEL Japan, and the volume at the point where P / P0 (close to 1) was highest during adsorption was used as a representative volume. The adsorption / desorption isotherm method can be used, and the plot of the measured values ​​has pressure (P / P0) on the X axis and Va / cm on the Y axis. 3 (STP)g -1 is.

[0024] <Negative electrode composition > The negative electrode composition according to one embodiment of the present application is a negative electrode composition containing a silicon-based active material, graphite, and a negative electrode conductive material, wherein the graphite includes natural graphite and artificial graphite, and the silicon-based active material includes silicon oxide represented by SiO x (0 < x < 2), and the BET specific surface area values of the SiO x (0 < x < 2) silicon oxide, the natural graphite, and the artificial graphite are in the order of artificial graphite < natural graphite < silicon oxide represented by SiOx (0 < x < 2) and are large.

[0025] When the mutual relationship of the BET specific surface areas of the SiO x (0 < x < 2) silicon oxide, the natural graphite, and the artificial graphite is satisfied, the reduction of the life of the secondary battery is improved, rapid charging is possible, and the electrode adhesion is excellent.

[0026] In particular, the lithium secondary battery according to the present application uses silicon oxide represented by SiO x (0 < x < 2) among silicon-based active materials. Specifically, when using such an active material compared with other silicon-based active materials (for example, Si / C), it has the characteristic that the quality of the electrode, that is, the adhesion to the electrode, is improved. <000029​​​​​​​​​​​​​According to one embodiment of the present application, the SiO x (0 < x < 2) The BET specific surface area of silicon oxide represented by is 1 m 2 / g to 9 m 2 / g larger than the BET specific surface area of the natural graphite.

[0030] The BET specific surface area of the silicon oxide represented by the SiO x (0 < x < 2) 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 the BET specific surface area of the natural graphite. The BET specific surface area of the silicon oxide represented by the SiO x (0 < x < 2) 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 the BET specific surface area of the natural graphite.

[0031] According to one embodiment of the present application, the BET specific surface area of the silicon oxide represented by the SiO x (0 < x < 2) is 2 m 2 / g to 10 m 2 / g larger than the BET specific surface area of the artificial graphite.

[0032] The BET specific surface area of the silicon oxide represented by the SiO x (0 < x < 2) 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 the BET specific surface area of the artificial graphite.

[0033] The BET specific surface area of the silicon oxide represented by the SiO x (0 < x < 2) is 9.7 m 2 / g or less, 9.4 m 2 / g or less, 9.2 m 2 / g or less, or 9 m2 is less than / g.

[0034] According to one embodiment of the present application, the BET specific surface area of the natural graphite is 0.1 m 2 / g to 2 m 2 / g larger than that of the artificial graphite.

[0035] The BET specific surface area of the natural graphite is 0.2 m 2 / g or more, or 0.3 m 2 / g or more larger than that of the artificial graphite. The BET specific surface area of the natural graphite is 1.9 m 2 / g or less, 1.8 m 2 / g or less, or 1.7 m 2 / g or less larger than that of the artificial graphite.

[0036] 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, which can improve the electrode adhesion. The artificial graphite and SiO x (0 < x < 2) silicon oxide represented by affects rapid charging and life performance, and has a BET specific surface area of 0.1 m 2 / g or more and 2.5 m 2 / g or less, 3 m 2 / g or more and 15 m 2 / g or less respectively.

[0037] When the BET specific surface area value of the artificial graphite is larger than that of the natural graphite, when manufacturing an electrode using the negative electrode composition, more binders in the electrode will be consumed, and the electrode adhesion may decrease. Also, when the BET specific surface area of silicon oxide represented by SiO x (0 < x < 2) is smaller than the BET specific surface area of the natural graphite, the insertion and / or desorption of lithium into the silicon oxide represented by SiO<00​​​​According to a further embodiment of the present application, the negative electrode composition includes graphite, and the graphite may include natural graphite and artificial graphite.

[0039] According to one example, the natural graphite may satisfy the relationship between the content and the specific surface area, and more specifically, may have a sphericity of 0.9 or more and satisfy the above conditions.

[0040] In this specification, sphericity may be the value obtained by dividing the circumference of a circle having the same area as the projected image when a particle is projected by the perimeter of the projected image, and can be specifically expressed by the following formula 1. The sphericity can be determined from an SEM image or can be measured using a particle shape analyzer such as a Sysmex FPIA3000 manufactured by Malvern. Crystal size can also be confirmed by XRD analysis. [Formula 1] Sphericity = Circumference of a circle with the same area as the projected image of a particle / Perimeter of the projected image

[0041] The natural graphite refers to graphite that is naturally occurring, and examples thereof include flake graphite, scaly graphite, and soil graphite. Natural graphite has the advantages of being abundant, inexpensive, having a high theoretical capacity and a high compressed density, and being able to achieve high output.

[0042] The natural graphite may be selected to satisfy the above sphericity by checking the particle shape using an SEM and then checking it using a particle shape analyzer.

[0043] According to one example, the artificial graphite may satisfy the relationship between the content and the specific surface area, and more specifically, may be artificial graphite that has a sphericity of 0.9 or less and satisfies the above conditions.

[0044] The artificial graphite may be selected to satisfy the above sphericity by checking the particle shape using an SEM and then checking it using a particle shape analyzer.

[0045] According to a further embodiment of the present application, the negative electrode conductive material may include single-walled carbon nanotubes (SWCNTs). The term "SWCNTs" refers to a tubular carbon structure consisting of a single carbon layer. When the conductive material in the negative electrode composition includes the single-walled carbon nanotubes (SWCNTs), the charge / discharge capacity and / or lifespan of the battery may be improved. Specifically, the single-walled carbon nanotubes (SWCNTs) effectively connect the conductive paths between particles, thereby preventing the loss of the conductive paths due to swelling of the silicon-based negative electrode active material. As a result, when the single-walled carbon nanotubes (SWCNTs) are included, the lifespan of the battery may be improved.

[0046] In this specification, the length of a carbon nanotube refers to the length of the major axis passing through the center of a 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.

[0047] The average length of the single-walled carbon nanotubes (SWCNTs) may be 0.1 μm to 50 μm, specifically 0.5 μm to 25 μm or 0.5 μm to 20 μm, or more specifically 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.

[0048] Single-walled carbon nanotubes (SWCNTs), when used together with silicon oxide and graphite represented by (0 < x < 2), ensure a carbon nanotube length only corresponding to the distance between anode active material particles, making it easier to connect the conductive paths between the particles, and improving the electrical conductivity, strength, and / or electrolyte storage maintenance of the anode. In contrast, when the length of the carbon nanotubes is short, it is difficult to efficiently form conductive paths, which may reduce the electrical conductivity. When the length of the carbon nanotubes is excessively long, the dispersibility may decrease. x (0 < x < 2) When used together with silicon oxide and graphite represented by, since the length of the carbon nanotubes only corresponding to the distance between the anode active material particles is ensured, the connection of the conductive paths between the particles becomes easier, and the electrical conductivity, strength, and / or electrolyte storage maintenance of the anode can be improved. In contrast, when the length of the carbon nanotubes is short, it is difficult to efficiently form conductive paths, so the electrical conductivity may decrease. When the length of the carbon nanotubes is excessively long, the dispersibility may decrease.

[0049] The average length of the single-walled carbon nanotubes (SWCNTs) can be calculated as the average value of the results observed by SEM.

[0050] The average diameter of the single-walled carbon nanotubes (SWCNTs) may be 1 nm to 20 nm, specifically 1.5 nm to 15 nm, and more specifically 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.

[0051] Single-walled carbon nanotubes (SWCNTs) that meet the above range have flexible properties, so even when physically damaged, the connection between the anode active material particles is not easily severed. In contrast, when the diameter of the carbon nanotubes (SWCNTs) is excessively large, the electrode density may decrease. When the diameter of the carbon nanotubes (SWCNTs) is excessively small, it is difficult to disperse, and the manufacturability of the dispersion may decrease.

[0052] The average diameter of the single-walled carbon nanotube (SWCNT) can be calculated as the average value observed by TEM.

[0053] The BET specific surface area of the single-walled carbon nanotube may be 200 m 2 / g to 2,000 m 2 / g, specifically, it may also be 250 m 2 / g to 1,500 m 2 / g. When using single-walled carbon nanotubes (SWCNT) that satisfy the above range, even with a small amount of conductive material, dispersion is easy and there is an effect that particles can be effectively connected.

[0054] The single-walled carbon nanotube (SWCNT) may be contained in an amount of 0.01 parts by weight to 5 parts by weight based on 100 parts by weight of the negative electrode composition. Specifically, it may be contained in an amount of 0.01 parts by weight to 4 parts by weight, 0.01 parts by weight to 3 parts by weight, 0.01 parts by weight to 2 parts by weight, 0.01 parts by weight to 1 part by weight, or 0.05 parts by weight to 0.5 parts by weight.

[0055] When satisfying the above range, it is possible to facilitate the connection of the conductive path between the silicon-based negative electrode active material particles containing silicon oxide represented by SiO x (0 < x < 2) and graphite, and to minimize the side reaction of the electrolyte due to the high specific surface area.

[0056] According to a further embodiment of the present application, the BET specific surface area values of the silicon oxide represented by SiO x ((the natural graphite, and the artificial graphite may be in the order of artificial graphite < natural graphite < silicon oxide represented by SiOx (0 < x < 2).

[0057] According to one example, the specific surface area is measured by the BET method. Specifically, for the measurement target, using a BET measurement device (BEL-SORP-mini, Nippon Bell), the gas is removed (degassed) at 130 °C for 2 hours, and N2 adsorption / desorption is performed at 77 K for measurement. That is, in this specification, the BET specific surface area may mean the specific surface area of the particles themselves measured by the above measurement method.

[0058] According to one example, the negative electrode conductive material may include single-walled carbon nanotubes (SWCNT).

[0059] In the case of the negative electrode composition according to one embodiment of the present application, when using a silicon-based active material, which is a high-capacity material, to produce a high-capacity battery, SiO having the above-described content x (0 < x < 2) silicon oxide, natural graphite, artificial graphite, and single-walled carbon nanotubes (SWCNT), and by satisfying the mutual relationship of the BET specific surface areas of the SiO x (0 < x < 2) silicon oxide, the natural graphite, and the artificial graphite, it is possible to improve the life reduction of conventional secondary batteries, enable rapid charging, and have excellent electrode adhesion.

[0060] Also, by using together SiO x (0 < x < 2) silicon oxide, graphite, and single-walled carbon nanotubes (SWCNT) as a conductive material in the negative electrode composition having the above-described content, the conductive path between the negative electrode active material particles can be improved, and the capacity, efficiency, and life performance of the battery can be improved.

[0061] In one embodiment of the present application, the total pore volume of the SiO x (0 < x < 2) silicon oxide, the natural graphite, and the artificial graphite is provided in the order of artificial graphite ≤ natural graphite ≤ silicon oxide represented by SiOx (0 < x < 2) for the negative electrode composition.

[0062] According to a further embodiment of the present application, the SiO in the negative electrode composition x Silicon oxide represented by (0 < x < 2), natural graphite, and artificial graphite may contain pores.

[0063] According to one example, the volume of the pores means the volume of the pores in the particles themselves and can be measured by a calculation formula according to the absorption / desorption isotherm method by nitrogen adsorption. Specifically, after deriving a graph of the N2 absorption / desorption isotherm using a BELSORP-mini II model manufactured by BEL Japan, Inc., the volume at the point where P / P0 (close to 1) is the highest in absorption was taken as representative. The absorption / desorption isotherm method can be used, and the plot of the measured values has the pressure (P / P0) on the X-axis and Va / cm 3 (STP)g -1 on the Y-axis.

[0064] According to one example, the total pore volume of the silicon oxide represented by the SiO x (0 < x < 2) may be 7 cm 3 / g or more, the total pore volume of the natural graphite may be 3 cm 3 / g to 7 cm 3 / g, and the total pore volume of the artificial graphite may be 3 cm 3 / g or less.

[0065] The total pore volume of the silicon oxide represented by the SiO x (0 < x < 2) may be 1 cm 3 / g to 8 cm 3 / g larger than the total pore volume of the natural graphite.

[0066] The total pore volume of the silicon oxide represented by the SiO x (0 < x < 2) may be the same as the total pore volume of the natural graphite.

[0067] The SiO xThe pore volume of silicon oxide represented by (0 < x < 2) is 4 cm 3 / g to 11 cm 3 / g larger than the pore volume of the artificial graphite.

[0068] The pore volume of the natural graphite may be 1 cm 3 / g to 6 cm 3 / g larger than the pore volume of the artificial graphite.

[0069] The pore volume of the natural graphite may be the same as the pore volume of the artificial graphite.

[0070] When the pore volumes (total pore V.) of the silicon oxide represented by SiO x (0 < x < 2), the natural graphite, and the artificial graphite satisfy the above range, it is possible to have the characteristics of improving the life reduction of the secondary battery, enabling rapid charging, and having excellent electrode adhesion.

[0071] In one embodiment of the present application, a negative electrode composition is provided in which the number of pores (pore intensity) having a size of 2 nm or more and 200 nm or less in the negative electrode composition is in the order of artificial graphite ≤ natural graphite ≤ silicon oxide represented by SiOx (0 < x < 2).

[0072] According to an example, the size of the pores means the size of the pores of the particles themselves, and can be measured by a calculation formula according to the BJH (Barrett - Joyer - Halenda) method by the nitrogen adsorption method. Specifically, after deriving the pore area corresponding to the pore size using a BELSORP - mini II model manufactured by BEL Japan, the size of the pores showing the largest pore area was used as a representative. The BJH method can be used, and the plot of the measured values has the X - axis as the pore diameter (Dp / nm) and the Y - axis as dVp / dDp (cm 3 g -1 nm -1 ).

[0073] <o:p>< / o:p> When the above range is satisfied, it is possible to have the characteristics of improving the life reduction of the secondary battery, enabling rapid charging, and having excellent electrode adhesion.

[0074] In one embodiment of the present application, 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, to provide a negative electrode composition.

[0075] 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, 1.5 m 2 / g or more and 3.3 m 2 / g or less, 1.5 m 2 / g or more and 3 m 2 / g or less, 1.5 m 2 / g or more and 2.8 m 2 / g or less, or 1.5 m 2 / g or more and 2.5 m 2 / g or less may also be acceptable.

[0076] The artificial graphite has a BET specific surface area of 0.1 m 2 / g or more and 2.2 m 2 / g or less, 0.1 m 2 / g or more and 2 m 2 / g or less, 0.1 m 2 / g or more and 1.8 m 2 / g or less, 0.1 m 2 / g or more and 1.5 m 2 / g or less, 0.3 m 2 / g or more and 2.5 m 2 / g or less may also be acceptable.

[0077] When the natural graphite and the artificial graphite satisfy the above BET specific surface area range, the negative electrode composition contains two types of graphite having different specific surface areas in addition to the silicon oxide represented by SiO x (0 < x < 2), so that the SiO xBy using silicon oxide represented by (0 < x < 2), it is possible to have the characteristics of increasing the battery capacity and having excellent output characteristics at a high C-rate, and it is possible to improve the problems of degradation of the lifespan of the negative electrode and the secondary battery that may occur due to the large volume change of the silicon-based particles.

[0078] Natural graphite can improve the electrode adhesion force within the BET specific surface area range, and artificial graphite can affect rapid charging and lifespan performance within the BET specific surface area range. Also, when the BET specific surface area value of artificial graphite is larger than that of natural graphite, during the production of an electrode using the negative electrode composition, a large amount of the binder within the electrode will be consumed, and the electrode adhesion force may decrease.

[0079] In one embodiment of the present application, the negative electrode conductive material includes single-walled carbon nanotubes (SWCNT). Among the negative electrode composition, SiO x Based on a total of 100 parts by weight of the contents of silicon oxide represented by (0 < x < 2), graphite, and single-walled carbon nanotubes, the SiO x Silicon oxide represented by (0 < x < 2): 0.5 to 50 parts by weight; the graphite: 45 to 99 parts by weight; and the single-walled carbon nanotubes (SWCNT): 0.01 to 5 parts by weight. Based on 100 parts by weight of the graphite, the natural graphite: 10 to 70 parts by weight; and the artificial graphite: 30 to 90 parts by weight are included, and a negative electrode composition is provided.

[0080] According to a further embodiment of the present application, the negative electrode composition includes SiO x Silicon oxide represented by (0 < x < 2); graphite; and a negative electrode conductive material. The graphite includes natural graphite and artificial graphite, and the negative electrode conductive material may include single-walled carbon nanotubes (SWCNT).

[0081] According to a further embodiment of the present application, among the negative electrode composition, based on a total of 100 parts by weight of the contents of silicon oxide represented by (0 < x < 2), graphite, and single-walled carbon nanotubes, the SiO x x0.5 to 50 parts by weight of silicon oxide represented by (0 < x < 2); 45 to 99 parts by weight of the graphite; and 0.01 to 5 parts by weight of the single-walled carbon nanotube (SWCNT) may be included.

[0082] According to one example, among the negative electrode compositions, SiO x Based on a total of 100 parts by weight of the contents of silicon oxide represented by (0 < x < 2), graphite, and single-walled carbon nanotubes, the SiO x The silicon oxide represented by (0 < x < 2) may be 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 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 nanotube (SWCNT) may be 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.

[0083] According to a further embodiment of the present application, based on 100 parts by weight of the graphite, 10 to 70 parts by weight of the natural graphite; and 30 to 90 parts by weight of the artificial graphite may be included.

[0084] According to one example, based on 100 parts by weight of the graphite, the natural graphite may be 11 to 68 parts by weight; and the artificial graphite may be 32 to 89 parts by weight.

[0085] When it is within the content range of the negative electrode composition, particularly, the SiO xWhen the content range of silicon oxide represented by (0 < x < 2) is satisfied, the capacitance characteristics can be improved. When the content range of graphite is satisfied, the rapid charging performance and the negative electrode adhesion can be improved. When the content range of single-walled carbon nanotubes (SWCNT) is satisfied, the efficiency and life performance of the battery can be improved. Therefore, it is possible to improve the reduction of the life of the secondary battery, increase the number of points where charging and discharging are possible, and have the characteristic of excellent output characteristics at a high C-rate.

[0086] One embodiment of the present application provides a negative electrode composition further including a binder.

[0087] The binder can play a role in improving the adhesion between the negative electrode active material particles and the adhesion force between the negative electrode active material particles and the negative electrode current collector. The binder may be a negative electrode binder. As the negative electrode binder, any known one in the technical field can be used. Non-limiting examples include polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluorine rubber, polyacrylic acid, and at least any one selected from the group consisting of substances in which hydrogen thereof is substituted with Li, Na, or Ca, etc., and various copolymers thereof may also be included.

[0088] The binder may be contained at 10% or less based on 100 parts by weight of the negative electrode composition, and preferably may be contained at 1% to 5%. For example, the binder may be contained at 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 contained at 0.5% or more, or 1% or more based on 100 parts by weight of the negative electrode composition.

[0089] <Method for manufacturing negative electrode composition> One embodiment of the present application is a method for manufacturing a negative electrode composition including the steps of mixing a negative electrode conductive material and water to form a first mixture; and mixing the mixture with a silicon-based active material and graphite, wherein the graphite includes natural graphite and artificial graphite, and the silicon-based active material includes silicon oxide represented by SiO x (0 < x < 2), and the BET specific surface area values of the SiO x (0 < x < 2) represented silicon oxide, the natural graphite, and the artificial graphite are in the order of artificial graphite < natural graphite < silicon oxide represented by SiOx (0 < x < 2). A method for manufacturing a negative electrode composition is provided.

[0090] According to a further embodiment of the present application, the method for manufacturing the negative electrode composition may include the step of mixing both the silicon oxide represented by SiO x (0 < x < 2) and graphite with the negative electrode conductive material.

[0091] In one embodiment of the present application, the negative electrode conductive material includes single-walled carbon nanotubes (SWCNT). Among the negative electrode composition, based on a total of 100 parts by weight of the contents of the silicon oxide represented by SiO x (0 < x < 2), graphite, and single-walled carbon nanotubes, the SiO x0.5 to 50 parts by weight of silicon oxide represented by (0 < x < 2); 45 to 99 parts by weight of the graphite; and 0.01 to 5 parts by weight of the single-walled carbon nanotube (SWCNT), based on 100 parts by weight of the graphite, including 10 to 70 parts by weight of the natural graphite; and 30 to 90 parts by weight of the artificial graphite, to provide a method for manufacturing a negative electrode composition.

[0092] In one embodiment of the present application, the SiO x The BET specific surface area of the silicon oxide represented by (0 < x < 2) is 1 m 2 / g to 9 m 2 / g larger than the BET specific surface area of the natural graphite, and the BET specific surface area of the SiO x The BET specific surface area of the silicon oxide represented by (0 < x < 2) is 2 m 2 / g to 10 m 2 / g larger than the BET specific surface area of the artificial graphite, and the BET specific surface area of the natural graphite is 0.1 m 2 / g to 2 m 2 / g larger.

[0093] In one embodiment of the present application, the SiO x Regarding the BET specific surface area and pore volume of the silicon oxide represented by (0 < x < 2), the natural graphite, and the artificial graphite, it is the same as that described in the negative electrode composition.

[0094] <Negative electrode> One embodiment of the present application provides a negative electrode for a lithium secondary battery, including a current collector; and a negative electrode active material layer formed on one or both surfaces of the current collector and including the above-described negative electrode composition.

[0095] According to a further embodiment of the present application, the current collector is a negative electrode current collector, which is not particularly limited as long as it does not cause a chemical change in the battery and has conductivity. For example, as the current collector, copper, stainless steel, aluminum, nickel, titanium, fired carbon, or a material obtained by surface-treating the surface of aluminum or stainless steel with carbon, nickel, titanium, silver, etc. may be used. Specifically, a transition metal that adsorbs carbon well, such as copper or nickel, may be used as the current collector. The thickness of the current collector may be 1 μm to 500 μm, but the thickness of the current collector is not limited thereto.

[0096] According to a further embodiment of the present application, a negative electrode active material layer containing the negative electrode composition according to the above-described embodiment may be formed on one or both surfaces of the current collector. According to an example, the thickness of the negative electrode active material layer may be 20 μm or more and 500 μm or less.

[0097] According to a further embodiment of the present application, the negative electrode for the lithium secondary battery can be manufactured by a normal method for manufacturing a negative electrode. The silicon oxide represented by SiO x (0 < x < 2) and graphite may be negative electrode active materials. Specifically, it can be manufactured by applying a negative electrode composition containing the negative electrode active material, the negative electrode conductive material, and optionally a binder onto a current collector, and then drying and rolling. At this time, the types and contents of the negative electrode active material, the negative electrode conductive material, and the binder are as described above.

[0098] The solvent may be a solvent commonly used in the art, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water. These may be used alone or in combination. The amount of solvent used is sufficient to dissolve or disperse the negative electrode active material, negative electrode conductive material, and binder, while maintaining a viscosity that allows excellent thickness uniformity during subsequent application to produce a negative electrode, taking into consideration the coating thickness of the slurry and the production yield. Alternatively, the negative electrode may be fabricated by casting the negative electrode composition on a separate support, peeling it off from the support, and laminating the resulting film on a current collector.

[0099] <Lithium secondary battery> One embodiment of the present application provides a lithium secondary battery including a positive electrode; a negative electrode for a lithium secondary battery according to the above-described embodiment; and a separator disposed between the positive electrode and the negative electrode.

[0100] According to a further embodiment of the present application, the negative electrode is the same as the negative electrode according to the above-described embodiment. Since the negative electrode has been described above, a detailed description thereof will be omitted.

[0101] According to a further embodiment of the present application, the positive electrode includes a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector and including a positive electrode composition.

[0102] 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.

[0103] The positive electrode current collector in the positive electrode is not particularly limited as long as it does not cause chemical changes in the battery and is conductive. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel whose surface has been treated with carbon, nickel, titanium, silver, or the like may be used. The positive electrode current collector may typically have a thickness of 3 μm to 500 μm, and fine irregularities may be formed on the surface of the current collector to enhance the adhesive strength of the positive electrode active material. The positive electrode current collector may be used in various forms, such as a film, sheet, foil, mesh, porous material, foam, or nonwoven fabric.

[0104] For 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, or these thicknesses may be the same.

[0105] The positive electrode active material may be a commonly used positive electrode active material. Specifically, the positive electrode active material may be a layered compound such as lithium cobalt oxide (LiCoO2) or lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; a lithium iron oxide such as LiFe3O4; 1+c1 Mn 2-c1 O4 (0≦c1≦0.33), lithium manganese oxides such as LiMnO3, LiMn2O3, and LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, V2O5, and Cu2V2O7; chemical formula LiNi 1-c2 M c2 Ni-site type lithium nickel oxide represented by the chemical formula LiMnO2 (wherein M is at least one selected from the group consisting of Co, Mn, Al, Cu, Fe, Mg, B, and Ga, and 0.01≦c2≦0.3 is satisfied); 2-c3 M c3Examples of the lithium manganese composite oxides include, but are not limited to, lithium manganese composite oxides represented by Li2Mn3MO8 (where M is at least one selected from the group consisting of Co, Ni, Fe, Cr, Zn, and Ta, and satisfying 0.01≦c3≦0.1), or Li2Mn3MO8 (where M is at least one selected from the group consisting of Fe, Co, Ni, Cu, and Zn); or LiMn2O4 in which part of the Li in the chemical formula is substituted with an alkaline earth metal ion. The positive electrode may be Li metal.

[0106] The positive electrode active material layer may contain a positive electrode conductive material and a positive electrode binder in addition to the above-described positive electrode active material.

[0107] In this case, the positive electrode conductive material is used to impart conductivity to the electrode, and can be any material that has electronic conductivity without causing chemical changes in the battery that is constructed. Specific examples include graphite such as natural graphite and artificial graphite; carbon-based materials such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fiber; metal powder or metal fiber such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive polymers such as polyphenylene derivatives. These may be used alone or in combination of two or more.

[0108] The positive electrode binder improves adhesion between positive electrode active material particles and between the positive electrode active material and the positive electrode current collector. Specific examples of the positive electrode binder include polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, and various copolymers thereof. These binders may be used singly or in combination.

[0109] According to a further embodiment of the present application, the lithium secondary battery may include a separator provided between the positive electrode and the negative electrode.

[0110] The separator separates the negative electrode and the positive electrode and provides a path for lithium ions to move. Any separator typically used in secondary batteries can be used without particular limitation. It is particularly preferable that the separator exhibits low resistance to electrolyte ion migration and has excellent electrolyte humidifying ability. Specifically, porous polymer films, such as those made from polyolefin polymers such as ethylene homopolymers, propylene homopolymers, ethylene / butene copolymers, ethylene / hexene copolymers, and ethylene / methacrylate copolymers, or laminate structures of two or more layers thereof, may be used. Conventional porous nonwoven fabrics, such as nonwoven fabrics made from high-melting-point glass fibers or polyethylene terephthalate fibers, may also be used. To ensure heat resistance or mechanical strength, a coated separator containing a ceramic component or a polymeric material may be used, and it may be selectively used as a single-layer or multi-layer structure.

[0111] According to one embodiment of the present application, the lithium secondary battery may include an electrolyte solution.

[0112] 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 manufacturing lithium secondary batteries.

[0113] Specifically, the electrolyte may include a non-aqueous organic solvent and a metal salt.

[0114] Examples of the non-aqueous organic solvent that can be used include aprotic organic solvents such as N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphoric acid triester, trimethoxymethane, dioxolane derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl propionate, and ethyl propionate.

[0115] In particular, among the carbonate organic solvents, ethylene carbonate and propylene carbonate, which are cyclic carbonates, can be preferably used as high-viscosity organic solvents, because they have a high dielectric constant and dissociate lithium salts well. When such cyclic carbonates are mixed with linear carbonates having low viscosity and low dielectric constants, such as dimethyl carbonate and diethyl carbonate, in an appropriate ratio, an electrolyte having high electrical conductivity can be prepared, and therefore such cyclic carbonates can be more preferably used.

[0116] The metal salt may be a lithium salt, which is a substance that is easily dissolved in the non-aqueous electrolyte solution. For example, the anion of the lithium salt may be F - , Cl - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , PF6 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , CF3SO3 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - , and (CF3CF2SO2)2N - One or more selected from the group consisting of:

[0117] In addition to the constituent components of the electrolyte, the electrolyte may further include one or more additives, such as a haloalkylene carbonate compound such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ether, ethylenediamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivative, sulfur, quinoneimine dye, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, or aluminum trichloride, in order to improve the life characteristics of the battery, suppress a decrease in battery capacity, and improve the discharge capacity of the battery.

[0118] In one embodiment of the present application, the lithium secondary battery is a cylindrical battery.

[0119] According to one example, the cylindrical battery refers to a battery having a cylindrical shape, which includes an assembly including a positive electrode, a negative electrode, a separator, and an electrolyte. Specifically, the cylindrical battery may be composed of a cylindrical can, a battery assembly provided inside the cylindrical can, and a top cap.

[0120] One embodiment of the present application provides a battery module including the lithium secondary battery.

[0121] One embodiment of the present application provides a battery pack including a battery module according to the above-described embodiment.

[0122] In a further embodiment of the present invention, there is provided a battery module including the cylindrical battery as a unit cell, and a battery pack including the same. The battery module and battery pack include the secondary battery having high capacity, high rate characteristics, and high cycle characteristics, and therefore can be used as a power source for medium- to large-sized devices selected from the group consisting of electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and power storage systems.

[0123] The lithium secondary battery according to an embodiment of the present invention can be used as a power source for not only portable devices such as mobile phones, notebook computers, and digital cameras, but also 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, in order to stably exhibit excellent discharge capacity, output characteristics, and cycle performance. For example, the battery module or battery pack can be used as a power source for any one or more of medium and large-sized devices including power tools; electric vehicles including electric vehicles (EV), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEV); or power storage systems.

Example

[0124] Hereinafter, preferred examples are presented to assist in understanding the present invention. However, the following examples are merely for illustrative purposes of this description, and it is obvious to those skilled in the art that various changes and modifications can be made within the scope of this description and the scope of the technical idea. It is natural that such variations and modifications belong to the scope of the appended claims.

[0125] <Examples and Comparative Examples> <Example 1> Manufacture of Negative Electrode In the negative electrode composition, silicon oxide represented by SiO x (0 < x < 2); graphite; and based on a total of 100 parts by weight of the content of the negative electrode conductive material, SiO x10 parts by weight of silicon oxide represented by (0 < x < 2), 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. Based on 100 parts by weight of the negative electrode composition, it contains 1.15 parts by weight of styrene-butadiene rubber (SBR) and 1 part by weight of carboxymethyl cellulose (CMC) as binders. In addition, it contains a CNT pre-dispersion liquid containing 0.09 parts by weight of a dispersant and 0.06 parts by weight of single-walled CNTs, and a negative electrode composition was produced. At this time, in the said composition, the BET specific surface areas of artificial graphite, natural graphite, and silicon oxide are respectively 0.8 m 2 / g, 1.8 m 2 / g, 7 m 2 / g.

[0126] That is, using distilled water as a dispersion medium and carboxymethyl cellulose (CMC) as a dispersant, silicon oxide, graphite, carboxymethyl cellulose (CMC) as a binder, and styrene-butadiene rubber (SBR) were added to the single-walled carbon nanotube dispersion liquid and stirred. Then, distilled water was added to produce a negative electrode composition (solid content = 50 parts by weight).

[0127] The said negative electrode composition was applied and dried on a copper (Cu) metal thin film which is a negative electrode current collector with a thickness of 15 μm. At this time, the temperature of the circulating air was 60°C. Next, it was roll-pressed and dried in a vacuum oven at 130°C for 12 hours to produce a negative electrode in which a negative electrode active material layer was disposed on the negative electrode current collector.

[0128] At this time, among the said CMC, the weight of CMC added as a binder: the weight of CMC added as a dispersant = 1.14:0.06. The average length of the single-walled carbon nanotube unit in the negative electrode active material layer was 10 μm, and the average diameter was 2 nm.

[0129] <Examples 2 to 14> The artificial graphite, natural graphite, and SiO x The BET specific surface area of silicon oxide represented by (0 < x < 2) contained in the negative electrode composition, and among the negative electrode compositions, SiOx Silicon oxide represented by (0 < x < 2); graphite; and except for using those described in Table 1 below as the respective weight ratios based on a total of 100 parts by weight of the contents of single-walled carbon nanotubes, a negative electrode was produced in the same manner as in Example 1.

[0130] <Comparative Examples 1 to 5> The BET specific surface area of artificial graphite, natural graphite, and silicon oxide contained in the negative electrode composition, and except for using those described in Table 1 below as the respective weight ratios based on a total of 100 parts by weight of the contents of silicon oxide; graphite; and single-walled carbon nanotubes, a negative electrode was produced in the same manner as in Example 1.

[0131] The negative electrodes produced in the above Examples and Comparative Examples are as shown in Table 1 below.

[0132]

Table 1

[0133] The specific surface area was measured using a BET measuring device (BEL-SORP-mini, Nippon Bell), removing the gas (degassing) at 130 °C for 2 hours, and performing N2 adsorption / desorption at 77K.

[0134] <Experimental Example> Lithium secondary batteries containing the negative electrodes of the Examples and Comparative Examples were produced.

[0135] 〔Evaluation of Life (Capacity Retention Rate) Characteristics〕 Charge and discharge were performed on the produced batteries to evaluate the capacity retention rate, which is shown in Table 2 below.

[0136] For the first cycle and the second cycle, charge and discharge were performed at 0.1C, and from the third cycle, charge and discharge were performed at 0.5C. The 300th cycle ended in a charged state (with lithium in the negative electrode). Charging conditions: CC (constant current) / CV (constant voltage) (4.25V / 0.05C current cut-off) Discharge condition: CC (constant current) condition 2.5V

[0137] The capacity retention rate was calculated as follows. Capacity retention rate (%) = (100 discharge capacity / 1 discharge capacity) × 100

[0138] Table 2 below shows values ​​for energy density (based on Example 1, %) and capacity retention rate (300 cycles, %) for Examples 1 to 14 and Comparative Examples 1 to 5.

[0139] [Evaluation at the time of re-plating] The manufactured negative electrode was placed in a 1.4875cm 2 A lithium (Li) metal thin film cut into a circular shape was used as the positive electrode. A porous polyethylene separator was placed between the positive electrode and the negative electrode, and an electrolyte solution prepared by dissolving 0.5 parts by weight of vinylene carbonate in a 7:3 volumetric ratio mixture of methyl ethyl carbonate (EMC) and ethylene carbonate (EC) and dissolving 1M LiPF6 was injected to fabricate a lithium coin half-cell.

[0140] After the first charge-discharge cycle was completed, the lithium plating time was measured under a 1.8C charge condition. Charging conditions: CC (constant current) / CV (constant voltage) (5mV / 0.005C current cut-off) Discharge condition: CC (constant current) condition 1.5V

[0141] [Evaluation of electrode adhesive strength] Each negative electrode was punched out to a size of 20 mm x 150 mm and fixed to the center of a glass slide with tape. The negative electrode current collector was then peeled off using a UTM, and the 180° peel strength was measured. The peel strength was measured for five or more negative electrodes and averaged to evaluate the results. The results are shown in Table 2 below.

[0142]

Table 2

[0143] The negative electrode composition according to the present invention includes a silicon-based active material, graphite, and a negative electrode conductive material. The graphite includes natural graphite and artificial graphite. The SiO x (0 < x < 2) The BET specific surface area values of silicon oxide, the natural graphite, and the artificial graphite are characterized in that the BET specific surface area of the artificial graphite < the natural graphite < the silicon oxide represented by SiOx (0 < x < 2) is in this order. When using the silicon-based active material, which is a high-capacity material, to produce a high-capacity battery, the negative electrode composition satisfies the mutual relationship of the BET specific surface areas of the SiO x (0 < x < 2) silicon oxide, the natural graphite, and the artificial graphite, can improve the life reduction of conventional secondary batteries, enable rapid charging, and have excellent electrode adhesion. In particular, the negative electrode composition of the present invention satisfies not only the BET specific surface area of artificial graphite and natural graphite but also the mutual relationship of the BET specific surface area of SiO to realize optimal battery performance at the "optimum point" for controlling side reactions from an electrochemical perspective. Also, by using together the silicon oxide represented by SiO x (0 < x < 2), graphite, and single-walled carbon nanotubes (SWCNT) as the conductive material, the conductive path between the negative electrode active material particles can be improved, and the capacity, efficiency, and life performance of the battery can be improved. [[ID=!7]]

[0144] Natural graphite has a BET specific surface area of 1.5 m 2 / g or more and 3.5 m 2 / g or less, which can improve the electrode adhesion. Artificial graphite and SiO x (0 < x < 2) silicon oxide affect rapid charging and life performance, and their BET specific surface areas are 0.1 m 2 / g or more and 2.5 m 2 / g or less, 3 m 2 / g or more and 15 m 2 / g or less, respectively.

[0145] When the BET specific surface area value of artificial graphite is larger than that of natural graphite, when manufacturing an electrode using the negative electrode composition, a large amount of the binder in the electrode will be consumed, and the electrode adhesion may decrease. Also, when the BET specific surface area of silicon oxide is smaller than the BET specific surface area of natural graphite, x insertion and / or desorption of lithium into silicon oxide represented by SiO(0 < x < 2) becomes difficult, and the life performance and rapid charging performance may decrease.

[0146] Examples 1 to 14 use a negative electrode composition that satisfies a specific specific surface area ratio, and it can be confirmed that they are excellent in all of life performance, rapid charging, and electrode adhesion.

[0147] On the other hand, Comparative Example 1 does not satisfy the specific specific surface area ratio of the negative electrode composition used in the present invention. Since the BET specific surface area value of artificial graphite is larger than that of natural graphite, when manufacturing an electrode using the negative electrode composition, a large amount of the binder in the electrode will be consumed, the electrode adhesion will decrease, and the life performance may decrease.

[0148] Comparative Example 2 does not satisfy the specific specific surface area ratio of the negative electrode composition used in the present invention. x Since the BET specific surface area of silicon oxide represented by SiO(0 < x < 2) is smaller than the BET specific surface area of natural graphite, insertion and / or desorption of lithium into silicon oxide becomes difficult, and the life performance and rapid charging performance may decrease.

[0149] Comparative Example 3 does not satisfy the specific specific surface area ratio of the negative electrode composition used in the present invention, and particularly corresponds to the case where the relationship of the BET specific surface area of the present application is reversed. Also in this case, insertion and / or desorption of lithium into the negative electrode becomes difficult, and the life performance and rapid charging performance may decrease.

[0150] Comparative Example 4 is SiO xThis corresponds to the case where silicon oxide represented by (0 < x < 2) is not used. In this case, the thickness of the electrode increases, the rapid charging performance deteriorates, and a relatively high C-rate cycle evaluation of 0.5C / 0.5C is performed. In this case, it was confirmed that due to the deterioration of the rapid charging performance, the life performance, which can be grasped in terms of accumulation, also deteriorates.

[0151] Comparative Example 5 corresponds to the case where no negative electrode conductive material is used for reference. In particular, when comparing the above Examples and Comparative Examples, it corresponds to the case where SWCNT is not included as the negative electrode conductive material. The negative electrode of the present application requires a negative electrode conductive material for securing a conductive path such as long SWCNT due to a silicon-based substance that is a non-conductor. However, in Comparative Example 5, a substance capable of securing the conductive path is not included, and it was confirmed that the life performance deteriorates.

Claims

1. 1. A negative electrode composition comprising: a silicon-based active material; graphite; and a negative electrode conductive material, The graphite includes natural graphite and artificial graphite, The silicon-based active material is SiO ｘ (0<x<2) The SiO ｘ The BET specific surface area values ​​of the silicon oxide represented by (0<x<2), the natural graphite, and the artificial graphite are in the order of artificial graphite < natural graphite < silicon oxide represented by SiOx (0<x<2).

2. The SiO ｘ The BET specific surface area of ​​silicon oxide expressed by (0<x<2) is 1 m 2 larger than the BET specific surface area of ​​the natural graphite. ２ / g~9m ２ The negative electrode composition according to claim 1 , wherein the Cr content is greater than 1 / g.

3. The SiO ｘ 2. The negative electrode composition of claim 1, wherein the silicon oxide represented by (0<x<2) is doped with magnesium metal or lithium metal.

4. The SiO ｘ The BET specific surface area of ​​silicon oxide expressed by (0<x<2) is 2 m 2 larger than the BET specific surface area of ​​the artificial graphite. ２ / g to 10m ２ The negative electrode composition according to claim 1 , wherein the Cr content is greater than 1 / g.

5. The BET specific surface area of ​​the natural graphite is 0.1 m less than the BET specific surface area of ​​the artificial graphite. ２ / g to 2m ２ The negative electrode composition according to claim 1 , wherein the Cr content is greater than 1 / g.

6. The SiO ｘ 2. The negative electrode composition according to claim 1, wherein the pore volumes (total pore V.) of the silicon oxide represented by (0<x<2), the natural graphite, and the artificial graphite are in the order of artificial graphite≦natural graphite≦silicon oxide represented by SiOx (0<x<2).

7. The natural graphite has a BET specific surface area of ​​1.5 m ２ / g or more 3.5m ２ / g or less, and the artificial graphite has a BET specific surface area of ​​0.1 m ２ / g or more 2.5m ２ The negative electrode composition according to claim 1 , wherein the SiO 2 content is 0.1 wt % or less.

8. the negative electrode conductive material includes single-walled carbon nanotubes (SWCNTs), In the negative electrode composition, SiO ｘ (0<x<2) Based on 100 parts by weight of the total content of silicon oxide, graphite, and single-walled carbon nanotubes, ｘ 0.5 to 50 parts by weight of silicon oxide represented by (0<x<2); 45 to 99 parts by weight of the graphite; and 0.01 to 5 parts by weight of the single-walled carbon nanotubes (SWCNTs), 2. The negative electrode composition according to claim 1, comprising, based on 100 parts by weight of the graphite, 10 to 70 parts by weight of the natural graphite; and 30 to 90 parts by weight of the artificial graphite.

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

10. mixing a negative electrode conductive material and water to form a first mixture; and mixing the mixture with a silicon-based active material and graphite to form a second mixture; A method for producing a negative electrode composition comprising: The graphite includes natural graphite and artificial graphite, The silicon-based active material is SiO ｘ (0<x<2) The SiO ｘ wherein the BET specific surface area values ​​of the silicon oxide represented by (0<x<2), the natural graphite, and the artificial graphite are greatest in the order of artificial graphite < natural graphite < silicon oxide represented by SiOx (0<x<2).

11. the negative electrode conductive material includes single-walled carbon nanotubes (SWCNTs), In the negative electrode composition, SiO ｘ (0<x<2) Based on 100 parts by weight of the total content of silicon oxide, graphite, and single-walled carbon nanotubes, ｘ 0.5 to 50 parts by weight of silicon oxide represented by (0<x<2); 45 to 99 parts by weight of the graphite; and 0.01 to 5 parts by weight of the single-walled carbon nanotubes (SWCNTs), The method for producing a negative electrode composition according to claim 10, comprising, based on 100 parts by weight of the graphite, 10 to 70 parts by weight of the natural graphite; and 30 to 90 parts by weight of the artificial graphite.

12. The SiO ｘ The BET specific surface area of ​​silicon oxide expressed by (0<x<2) is 1 m 2 larger than the BET specific surface area of ​​the natural graphite. ２ / g~9m ２ The method for producing a negative electrode composition according to claim 10 , wherein the SiO 2 content is 0.015 wt % or more.

13. The SiO ｘ The BET specific surface area of ​​silicon oxide expressed by (0<x<2) is 2 m 2 larger than the BET specific surface area of ​​the artificial graphite. ２ / g to 10m ２ The method for producing a negative electrode composition according to claim 10 , wherein the SiO 2 content is 0.015 wt % or more.

14. The BET specific surface area of ​​the natural graphite is 0.1 m less than the BET specific surface area of ​​the artificial graphite. ２ / g to 2m ２ The method for producing a negative electrode composition according to claim 10 , wherein the SiO 2 content is 0.015 wt % or more.

15. a current collector; and A negative electrode for a lithium secondary battery, comprising a negative electrode active material layer formed on one or both surfaces of the current collector and comprising the negative electrode composition according to any one of claims 1 to 9.

16. positive electrode; The negative electrode for a lithium secondary battery according to claim 15; and A separator provided between the positive electrode and the negative electrode A lithium secondary battery comprising:

17. The lithium secondary battery according to claim 16, wherein the lithium secondary battery is a cylindrical battery.

18. A battery module comprising the lithium secondary battery according to claim 16.

19. A battery pack comprising the battery module of claim 18.

20. A battery pack comprising the lithium secondary battery according to claim 16.

Images