KR20230060965A - Composite active material for negative electrode, method for manufacturing the same, negative electrode and secondary battery comprising the same - Google Patents

Abstract

The present invention provides a composite negative electrode active material including: silicon (Si) particles; a coating layer formed on the surface of the silicon particles and including a carbonaceous material; and a linear conductive material, wherein the conductive material is attached to the coating layer, and a part of a conductive material body is spaced apart from the coating layer and includes a Li_xSi_yO_Z [x > 0, y > 0, 0 <= z <= 2 (x + 4y)] phase.

Description

Composite negative active material, manufacturing method thereof, negative electrode and secondary battery including the same

The present invention relates to a composite negative active material, a method for preparing the same, and a negative electrode and a secondary battery including the same.

Recently, with the rapid spread of electronic devices using batteries such as mobile phones, notebook computers, and electric vehicles, the demand for small, lightweight, and relatively high-capacity secondary batteries is rapidly increasing. In particular, lithium secondary batteries are in the limelight as a driving power source for portable devices because they are lightweight and have high energy density. Accordingly, research and development efforts to improve the performance of lithium secondary batteries are being actively conducted.

In general, a lithium secondary battery includes a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, an electrolyte, an organic solvent, and the like. In addition, an active material layer including a positive electrode active material or a negative electrode active material may be formed on the current collector for the positive electrode and the negative electrode. In the cathode, a lithium-containing metal oxide such as LiCoO ₂ or LiMn ₂ O ₄ is generally used as a cathode active material, and accordingly, a carbon-based active material that does not contain lithium or a silicon-based cathode active material is used as an anode active material.

In particular, among negative electrode active materials, silicon-based negative electrode active materials are attracting attention in that they have a capacity about 10 times higher than that of carbon-based negative electrode active materials, and have the advantage of being able to realize high energy density even with thin electrodes due to their high capacity. However, silicon-based negative active materials are not universally used due to problems such as volume expansion due to charging and discharging, cracking/damage of active material particles caused by this, and degradation of lifespan characteristics due to this.

In particular, the silicon-based negative electrode active material has problems in that the distance between active materials increases and an electrical short occurs due to volume expansion/contraction caused by charging and discharging, and thus, the passage of charge is lost and lithium ions are isolated, resulting in a decrease in capacity Lifespan deterioration may be accelerated.

Therefore, there is a need to develop a secondary battery capable of improving lifespan characteristics while realizing high capacity and energy density of a silicon-based negative electrode active material.

Korean Patent Registration No. 10-1906973 has the effect of preventing surface oxidation of silicon nanoparticles by adding a _lithium source and a _carbon source in the post-treatment process to form a film and a carbon coating layer on _the surface of silicon on the surface However, it has a disadvantage in that conductivity is poor and a heating process is additionally required after ball milling.

Korean Patent Registration No. 10-1906973

An object of the present invention is to provide an anode active material with improved lifespan characteristics and initial efficiency by reducing electrical shorts due to volume expansion/contraction by strongly bonding a conductive material to a silicon-based anode active material.

Another object of the present invention is to provide a method for producing the above-described composite negative electrode active material.

Another object of the present invention is to provide an anode and a secondary battery including the above-described composite anode active material.

The present invention, silicon (Si) particles; a coating layer formed on the surface of the silicon particle and containing carbonaceous material; and a linear conductive material, and a composite negative active material including a Li _x Si _y O _Z [x>0, y>0, 0≤z≤2(x+4y)] phase is provided.

In the composite negative electrode active material according to an embodiment of the present invention, the linear conductive material is attached to the coating layer, but a part of the body is spaced apart from the coating layer.

In one embodiment of the present invention, the linear conductive material is one or two selected from the group consisting of carbon nanotubes and carbon nanofibers.

In one embodiment of the present invention, the linear conductive material is one or two selected from the group consisting of vapor grown carbon fiber (VGCF) and multi-walled carbon nanotubes (MWCNT).

In one embodiment of the present invention, the average length of the long axis direction of the linear conductive material is 1 μm or more.

In one embodiment of the present invention, the silicon particles are 50% to 90% by weight based on the total weight of the composite negative electrode active material.

In one embodiment of the present invention, the linear conductive material is 2% to 30% by weight based on the total weight of the composite negative electrode active material.

In one embodiment of the present invention, the coating layer may be in the form of an island covering a portion of the surface of the silicon particle.

In another aspect, the present invention includes the steps of putting silicon, carbon precursor, lithium raw material and linear conductive material into a container; and a ball milling step of ball milling the mixture in the vessel, wherein the ball milling step converts the carbon precursor into carbonaceous material by a ball mill to form a coating layer containing carbonaceous material, and attaching the linear conductive material to the coating layer. It provides a method for producing a composite negative electrode active material characterized in that.

In one embodiment of the present invention, the ball mill step has a ball-to-powder weight ratio (BPR) of 1:1 to 10:1, a rotational speed of 50 rpm to 500 rpm, and ball milling for 1 hour to 36 hours.

In one embodiment of the present invention, the carbon precursor is glucose, sucrose, gum arabic, tannic acid, lignosulfonate, poly-aromatic oxide oxide), at least one selected from the group consisting of saccharides and polyphenols, coal-based pitch, petroleum-based pitch, coal-based oil, petroleum-based heavy oil, organic synthetic pitch, furan resin, and polyimide resin.

In one embodiment of the present invention, the lithium raw material is lithium metal, lithium oxide (Li ₂ O, LiO ₂ , Li ₂ O ₂ ), lithium hydroxide (LiOH), lithium carbonate (Li ₂ CO ₃ ) and lithium chloride ( LiCl) is one or a mixture of two or more selected from the group consisting of.

In one embodiment of the present invention, the conductive material is one or two selected from the group consisting of vapor grown carbon fiber (VGCF) and multi-walled carbon nanotubes (MWCNT).

In one embodiment of the present invention, the average length of the long axis direction of the conductive material is 1 μm or more.

In one embodiment of the present invention, in the inputting step, silicon (Si) is 50 to 90 parts by weight, carbon precursor is 3 to 10 parts by weight, lithium raw material is 3 to 15 parts by weight, and the conductive material is 5 to 30 parts by weight. are put in

In one embodiment of the present invention, the ball mill step is performed under an inert atmosphere.

In addition, the present invention is a negative electrode current collector; A negative electrode active material layer formed on the negative electrode current collector is provided, and the negative electrode active material layer provides a negative electrode including a negative electrode material including the above-described composite negative electrode active material, a binder, and a conductive material.

In addition, the present invention is the above-described negative electrode; an anode facing the cathode; a separator interposed between the cathode and the anode; And it provides a secondary battery comprising an electrolyte.

In the composite anode active material of the present invention, a linear conductive material is strongly attached/coupled to a carbonaceous coating layer on the surface of a silicon particle, but a part of the conductive material body is spaced apart from the coating layer, so that a conductive network between the composite anode active materials can be formed, electrical short circuit can be prevented due to the formation of the conductive network, and life characteristics and resistance of the negative electrode are reduced.

The manufacturing method of the composite negative electrode active material of the present invention can manufacture the composite negative electrode active material through a single process of a ball mill step, and thus has an effect of reducing manufacturing cost and time.

1 is a SEM picture of a composite anode active material according to Example 1.
2 is a SEM picture of an anode active material according to Comparative Example 2.
3 is a SEM picture of an anode active material according to Comparative Example 3.

The terms or words used in this specification and claims should not be construed as being limited to ordinary or dictionary meanings, and the inventors may appropriately define the concept of terms in order to explain their invention in the best way. It should be interpreted as a meaning and concept consistent with the technical idea of the present invention based on the principle that there is.

Terms used in this specification are only used to describe exemplary embodiments, and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise.

In this specification, terms such as "comprise", "comprise" or "having" are intended to indicate that there is an embodied feature, number, step, component, or combination thereof, but one or more other features or It should be understood that the presence or addition of numbers, steps, components, or combinations thereof is not precluded.

In the present specification, the average particle diameter (D ₅₀ ) may be defined as a particle diameter corresponding to 50% of the cumulative volume in the particle diameter distribution curve of the particles. The average particle diameter (D50) can be measured using, for example, a laser diffraction method. The laser diffraction method is generally capable of measuring particle diameters of several millimeters in the submicron region, and can obtain results with high reproducibility and high resolution.

Hereinafter, the present invention will be described in detail.

<Composite anode active material>

The present invention relates to a composite negative electrode active material. The composite anode active material may be preferably used in a lithium secondary battery.

The composite anode active material of the present invention includes silicon (Si) particles; a coating layer formed on the surface of the silicon particle and containing carbonaceous material; and a linear conductive material, including a Li _x Si _y O _Z [x>0, y>0, 0≤z≤2(x+4y)] phase.

The silicon-based negative electrode active material has a problem of lifespan deterioration due to volume expansion/contraction due to intercalation/desorption of lithium during charging and discharging. In particular, when the volume expansion / contraction of the silicon-based active material occurs due to charging and discharging, the electrical contact is deteriorated and an electrical short circuit occurs due to the increase in the distance between the active materials, resulting in loss of charge passage and isolation of lithium ions. etc. can cause rapid life degradation and capacity reduction of the negative electrode.

In order to solve this problem, in the composite anode active material of the present invention, a linear conductive material is strongly attached/bonded to a carbonaceous coating layer on the surface of a silicon particle. Accordingly, the linear conductive material may form a conductive network between the composite anode active materials.

In the composite negative electrode active material according to an embodiment of the present invention, the linear conductive material is attached to the coating layer, but a part of the body is spaced apart from the coating layer. Therefore, even if the silicon particles constituting the composite anode active material expand in volume due to charging and discharging and the distance between the composite anode active materials increases, the linear conductive material spaced apart from the coating layer remains in contact with the adjacent composite anode active material, thereby maintaining the conductivity. Due to the formation of a conductive network of the ash, an electrical short circuit can be prevented, which is preferable in terms of lifespan characteristics and resistance reduction of the negative electrode.

In addition, when the composite negative active material includes carbonaceous, there is a problem in that the initial efficiency is lowered due to the irreversible capacity generated from amorphous carbon and the irreversible capacity generated due to the oxygen component included in the carbonaceous material. The composite anode active material according to the present invention includes a Li _x Si _y O _Z [x>0, y>0, 0≤z≤2(x+4y)] phase by adding a material containing lithium, so that the initial It also has the effect of improving efficiency.

The silicon particles are capable of intercalating/deintercalating lithium, and may function as core particles of a composite anode active material.

The silicon particles may include a Li _x Si _y O _Z [x>0, y>0, 0≤z≤2(x+4y)] phase, and the Li _x Si _y O _Z [x>0, y >0, 0≤z≤2(x+4y)] may be partly distributed inside the silicon particles, partly on the surface of the silicon particles, and partly between the silicon particles and the coating layer containing carbonaceous material. there is.

In order to increase the efficiency of the active material by lowering the proportion of the non-reversible phase (eg, SiO ₂ ) in the composite anode active material of the present invention, a lithium raw material is added during the manufacturing process. Accordingly, the composite anode active material of the present invention is used. The active material includes a phase of Li _x Si _y O _Z [x>0, y>0, 0≤z≤2(x+4y)].

The average particle diameter (D ₅₀ ) of the silicon particles ensures structural stability of the active material during charging and discharging, better maintains electrical contact when used in combination with a conductive material, and expands volume as the particle diameter becomes excessively large. 0.5 μm to 10 μm is preferable in terms of preventing the problem of increasing the level of shrinkage, and preventing the problem of excessively low particle diameter, making it difficult to disperse, making the process after making a uniform thickness electrode difficult, or reducing the initial efficiency. It may be 1 μm to 5 μm.

The silicon particles may be included in an amount of 50 wt% to 90 wt%, preferably 60 wt% to 90 wt%, and more preferably 65 wt% to 90 wt%, based on the total weight of the composite anode active material. When it is within the above range, it is preferable in terms of improving the capacity of the negative electrode, and since the conductive network formed by the linear conductive material described later can be formed at a smooth level, it is preferable to prevent electrical short circuit due to volume expansion of the active material and improve lifespan characteristics. .

The coating layer containing carbonaceous is formed on the silicon particles, so that the volume expansion / contraction due to charging and discharging of the silicon particles is appropriately controlled, and the linear conductive material is attached to the silicon particles to conduct linear conduction. allow it to be combined with the material.

In the present invention, the "coating layer" is a portion containing a carbonaceous component converted by a ball mill step to be described later in a carbon precursor, and means a layer covering some or all of the silicon particles, and the coating is "covered". should not be limited to the meaning of

The coating layer is formed by mixing and ball milling a linear conductive material, a carbon precursor, and a lithium raw material. In the process of ball milling these mixtures, a very high energy is generated locally by the collision of balls, so that Li _x Si _y O _Z [x>0, y>0, 0≤z≤2(x+4y )] phase is formed, the carbon precursor forms a carbonaceous coating layer, and the linear conductive material is strongly attached to the coating layer.

The coating layer may be included in an amount of 2 wt% to 30 wt%, preferably 3.5 wt% to 20 wt%, and more preferably 5 wt% to 10 wt%, based on the total weight of the composite negative electrode active material. When , it is preferable that the conductive material can be sufficiently attached to the coating layer while a part of the body of the conductive material is spaced apart from the coating layer.

The coating layer may cover the entire surface of the silicon particle, or may have a structure covering a portion of the silicon particle, such as an island shape.

The conductive material is a linear conductive material and is attached to the coating layer, but a part of the conductive material body is spaced apart from the coating layer. A part of the conductive material body may be spaced apart from the coating layer, and another part of the conductive material body may be attached to or adsorbed to the coating layer.

Here, the linear conductive material means a conductive material having an aspect ratio (long axis length/short axis length) of 10 or more. Specifically, the linear conductive material is made of carbon nanotubes and carbon nanofibers. It may be one or a mixture of two materials selected from the group, preferably a mixture of one or two materials selected from the group consisting of vapor grown carbon fiber (VGCF) and multi-walled carbon nanotubes (MWCNT). can be material.

Carbon nanotubes are formed in different shapes depending on the synthesis method, and depending on the number of layers of the graphite plate rolled, single walled (SW), double walled (DW), and multi walled carbon nanotubes carbon nanotube; MWNT). Single-walled carbon nanotubes are simply a rolled graphite layer with a diameter of 0.5 to 3 nm, and double-walled carbon nanotubes are two concentric single-walled carbon nanotubes with a diameter of 1.4 to 3 nm. Multi-walled carbon nanotubes have 3 to 15 layers of walls and have a diameter of 5 to 100 nm.

Multi-walled carbon nanotubes and gas-phase carbon fibers have the disadvantage of having a small surface area per weight due to their large diameter, but they can maintain a straight shape even after vigorous mixing, connecting long distances of several tens of micrometers between electrode films. This has the advantage of improving the overall conductivity of the electrode film, and multi-walled carbon nanotubes have a larger surface area than vapor-processed carbon fibers and are easily bendable, so it is easy to cover the surface of the composite anode active material, making up for the low conductivity, which is a disadvantage of silicon-based anode active materials. can do.

In the composite anode active material of the present invention, a portion of the linear conductive material body is spaced apart from the coating layer and exposed to the outside, and the portion of the conductive material body exposed to the outside has a long fiber length and flexibility of the conductive material. As a result, a conductive network that helps electrical contact between the composite anode active materials can be formed. Accordingly, in the composite anode active material of the present invention, even if the active materials expand in volume due to charging and discharging in the anode, the long conductive material can stably maintain electrical contact. Therefore, the composite anode active material of the present invention can effectively prevent the occurrence of an electrical short due to the volume expansion of the active material and the rapid deterioration of the lifespan of the active material, improve the lifespan characteristics of the anode, and prevent electrical short-circuiting between the active materials due to the long conductive material. Due to the smooth maintenance of the contact, it is also desirable in terms of reducing resistance and improving efficiency.

In addition, in the composite anode active material of the present invention, since the linear conductive material is attached to the coating layer, the conductive material can be uniformly distributed among the active materials, compared to a case where the active material and the conductive material are simply mixed, and the conductive material can be uniformly and stably conductive in the negative electrode. network can be formed.

The average length of the linear conductive material in the major axis direction is 1 µm or more, more preferably 3 to 30 µm, still more preferably 5 to 15 µm. When in the above range, it is preferable to smoothly maintain a conductive network between active materials.

The average length of the linear conductive material can be measured in the following way. A solution in which a conductive material and carboxymethylcellulose (CMC) are added to water in a weight ratio of 40:60 (solid content is 1% by weight based on the total weight of the solution) is diluted 1,000 times with water. Thereafter, 20 ml of the diluted solution is filtered through a filter, and the filter through which the conductive material is filtered is dried. 100 pictures of the dried filter are taken with a scanning electron microscope (SEM), the length of the conductive material is measured using the imageJ program, and the average value of the lengths is defined as the average length of the conductive material.

The average diameter of the linear conductive material may be 1 nm to 100 nm, preferably 3 nm to 50 nm. When the average diameter of the linear conductive material is within the above range, it is preferable in terms of preventing breakage of the conductive material and ensuring flexibility.

The average diameter of the linear conductive material can be measured in the following way. A solution in which a conductive material and carboxymethylcellulose (CMC) are added to water in a weight ratio of 40:60 (solid content is 1% by weight based on the total weight of the solution) is diluted 1,000 times with water. One drop of the diluted solution is applied to the TEM grid, and the TEM grid is dried. The dried TEM grid is observed with a TEM device (product name: H7650, manufacturer: Hitachi) to measure the average diameter of the conductive material.

The ratio of the average length of the linear conductive material to the average diameter may be, specifically, 60:1 or more, 100:1 to 500:1; It may be 1500: 1 to 5,000: 1, and when the conductive material is in the above range, it is preferable in terms of having high conductivity, preventing breakage, and improving flexibility.

The linear conductive material may be included in an amount of 2 wt% to 30 wt%, preferably 3.5 wt% to 20 wt%, and more preferably 5 wt% to 10 wt%, based on the total weight of the composite anode active material, When it is within the above range, it is possible to prevent aggregation of the active material while uniformly forming a conductive network.

<Method of manufacturing composite anode active material>

In addition, the present invention provides a method for preparing the composite anode active material described above.

Specifically, the manufacturing method of the composite anode active material of the present invention includes the steps of putting silicon, a carbon precursor, a lithium raw material, and a linear conductive material into a container; And a ball milling step of ball milling the mixture in the container, wherein the ball milling step converts the carbon precursor into carbonaceous by a ball mill to form a coating layer containing carbonaceous, and attaching the conductive material to the coating layer. to be characterized

According to the manufacturing method of the composite negative electrode active material of the present invention, a single process includes a Li _x Si _y O _Z [x>0, y>0, 0≤z≤2(x+4y)] phase, and on silicon particles A composite negative electrode active material in which a coating layer containing carbonaceous material is formed may be prepared.

Also, according to the manufacturing method, the linear conductive material may be attached to the coating layer, and a part of the linear conductive material body may be spaced apart from the coaching layer and exposed to the outside of the composite anode active material. A portion of the conductive material body exposed to the outside may form a conductive network that improves electrical contact between the composite anode active materials. Since the other portion of the conductive material body that is not spaced apart from the coating layer may be attached to and fixed to the coating layer, a conductive network between composite anode active materials may exist at a more stable and uniform level. Accordingly, it is possible to effectively prevent the problem of volume expansion due to the use of silicon particles as an active material, and the resulting electrical short circuit and reduction in lifespan.

The manufacturing method of the composite negative electrode active material of the present invention includes a step of putting silicon, a carbon precursor, a lithium raw material, and a linear conductive material into a container.

In this case, the silicon may be added in an amount of 50 to 90 parts by weight, preferably 60 to 90 parts by weight, and more preferably 65 to 90 parts by weight.

The carbon precursor may be added in an amount of 3 to 10 parts by weight, preferably 4 to 8 parts by weight, and more preferably 4.5 to 7.5 parts by weight.

The lithium raw material may be added at 3 to 20 parts by weight, preferably at 5 to 15 parts by weight, and more preferably at 7 to 12 parts by weight of the conductive material.

The linear conductive material may be added in an amount of 5 to 30 parts by weight, preferably 6 to 20 parts by weight, and more preferably 7 to 15 parts by weight. In the ball mill step, the linear conductive material is strongly attached to the carbonaceous layer by locally generating very high energy due to collision of balls. The average length of the linear conductive material in the long axis direction may be 1 μm or more, more preferably 3 to 30 μm, and even more preferably 5 to 15 μm, and in the ball mill step, a part of the linear conductive material is pulverized Since the length may be shortened, in consideration of this, it is preferable to insert those having an average length of 5 μm or more in the long axis direction of the linear conductive material introduced in the raw material input step.

The carbon precursor is for forming a coating layer containing carbonaceous on some or all of the silicon particles through a ball mill process, and specifically, glucose, sucrose, gum Arabic, tannic acid ( tannic acid), lignosulfonate, aromatic substance oxides including poly-aromatic oxide, sugars and polyphenols, coal-based pitch, petroleum-based pitch, coal-based oil, petroleum-based heavy oil, organic synthetic pitch , may be at least one selected from the group consisting of furan resin and polyimide resin, preferably glucose and sucrose.

The lithium raw material is added in order to increase the efficiency of the active material by lowering the ratio of the non-reversible phase (eg, SiO ₂ ), and reacts by the impact energy of the balls during the ball mill process to form Li _x Si _y O _Z [x >0, y>0, 0≤z≤2(x+4y)] phase material is formed.

The lithium raw material is 1 selected from the group consisting of lithium metal, lithium oxide (Li ₂ O, LiO ₂ , Li ₂ O ₂ ), lithium hydroxide (LiOH), lithium carbonate (Li ₂ CO ₃ ) and lithium chloride (LiCl). It may be species or a mixture of two or more species, preferably lithium oxide (Li ₂ O, LiO ₂ , Li ₂ O ₂ ).

The types and characteristics of the silicon particles and conductive material have been described above.

In the manufacturing method of the composite anode active material of the present invention, a linear conductive material for forming a conductive network can be attached to the coating layer through a single process of ball milling the mixed materials of the silicon, carbon precursor, lithium raw material, and linear conductive material. Accordingly, it is possible to effectively prevent the volume expansion problem due to the use of silicon particles as an active material, and the resulting electrical short circuit and lifespan reduction problems. In addition, since there is no need to go through a separate heat treatment step in addition to the ball mill step, there is an advantage in that the manufacturing cost can be reduced.

According to the input step, when silicon, carbon precursor, lithium raw material and conductive material are put into the container, a ball having a diameter of 0.5 to 10 mm may be put into the container, and the inside of the container may be filled with an inert gas, and the ball mill step may be performed with an inert gas It can be performed under an atmosphere. As the ball, a zirconia ball may be used.

The reason why the ball mill is performed under an inert atmosphere is to block contact between silicon and carbon precursors and oxygen, to prevent formation of silica on the surface of silicon, and to prevent oxidation of carbon to produce carbon oxides. As the inert atmosphere, nitrogen gas, argon gas, helium gas, krypton gas, or xenon gas is preferably used.

In one specific example, the ball mill step may be performed using a planetary mixer.

In the ball mill step, the ball-to-powder weight ratio (BPR) may be 1:1 to 10:1, preferably 2:1 to 10:1, and more preferably 3:1 to 8:1. there is.

In addition, the rotational speed in the ball mill step may be 50 rpm to 500 rpm, preferably 60 rpm to 300 rpm, and more preferably 75 rpm to 200 rpm.

In addition, the time for performing the ball mill may be 1 hour to 36 hours, preferably 2 hours to 24 hours, more preferably 3 hours to 12 hours.

<cathode>

In addition, the present invention provides an anode including the composite anode active material described above.

Specifically, the negative electrode of the present invention is a negative electrode current collector; An anode active material layer formed on the anode current collector is included, the anode active material layer includes an anode material, a binder, and a conductive material, and the anode material includes the composite anode active material described above.

The anode current collector is not particularly limited as long as it does not cause chemical change in the battery and has high conductivity. Specifically, the negative electrode current collector may be made of copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, or the like, aluminum-cadmium alloy, and the like. there is.

The negative current collector may typically have a thickness of 3 to 500 μm.

The negative electrode current collector may form fine irregularities on the surface to enhance bonding strength of the negative electrode active material. For example, the negative current collector may be used in various forms such as a film, sheet, foil, net, porous material, foam, or non-woven fabric.

The anode active material layer is formed on the anode current collector.

The anode active material layer may include an anode material and a binder, and the anode material includes the aforementioned composite anode active material.

The composite negative electrode active material can be included in the negative electrode and exhibit excellent capacity characteristics, and can contribute to improving the lifespan characteristics of the negative electrode by the conductive material included therein, and Li _x Si _y O _Z [x>0, y>0, 0≤ z≤2(x+4y)] phase improves the initial efficiency of the battery.

The composite anode active material has been described above.

The anode material may further include a carbon-based active material together with the composite anode active material described above, and thus the degree of volume expansion of the entire anode material may be lowered by the carbon-based active material having a low degree of volume expansion during charging and discharging. The conductive network due to the linear conductive material in the negative electrode active material can surround the carbon-based active material, which is more desirable for improving resistance and efficiency.

The carbon-based active material may include at least one selected from the group consisting of artificial graphite, natural graphite, hard carbon, soft carbon, carbon black, acetylene black, Ketjen black, super P, graphene, and fibrous carbon, preferably Preferably, it may include at least one selected from the group consisting of artificial graphite and natural graphite.

The average particle diameter (D ₅₀ ) of the carbon-based active material may be 5 μm to 35 μm, preferably 10 μm to 20 μm, in terms of structural stability during charging and discharging and reducing side reactions with the electrolyte.

Specifically, the negative electrode material preferably uses both the composite negative active material and the carbon-based active material in terms of simultaneously improving capacity characteristics and cycle characteristics. : 95 to 30:70 in weight ratio, preferably 10:90 to 20:80 is preferably included. When the above range is preferred in terms of simultaneous improvement of capacity and cycle characteristics.

The negative electrode material may be included in the negative electrode active material layer in an amount of 80% to 99% by weight, preferably 90% to 98.5% by weight in the negative electrode active material layer.

The negative active material layer includes a binder.

In terms of further improving electrode adhesion and imparting sufficient resistance to volume expansion/contraction of the active material, the binder is styrene butadiene rubber (SBR), acrylonitrile butadiene rubber, and acrylic rubber (acrylic rubber), butyl rubber, fluoro rubber, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl alcohol (PVA) , polyacrylic acid (PAA), polyethylene glycol (PEG: polyethylene glycol), polyacrylonitrile (PAN: polyacrylonitrile), and polyacrylamide (PAM: polyacryl amide). can Preferably, the binder has high strength, has excellent resistance to volume expansion / contraction of the silicon-based negative electrode active material, and provides excellent flexibility to the binder to prevent distortion and bending of the electrode. It is preferable to include

The binder may be included in an amount of 0.5% to 10% by weight in the negative electrode active material layer, and when it is within the above range, it is preferable in terms of more effectively controlling the volume expansion of the active material.

If necessary, the negative electrode active material layer may further include a conductive material. The conductive material may be used to improve the conductivity of the negative electrode, and preferably has conductivity without causing chemical change. Specifically, the conductive material is natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, channel black, farnes black, lamp black, thermal black, conductive fiber, fluorocarbon, aluminum powder, nickel powder, zinc oxide, It may be at least one selected from the group consisting of potassium titanate, titanium oxide, and polyphenylene derivatives, and may preferably include carbon black in order to realize high conductivity.

The conductive material may be included in an amount of 0.5% to 10% by weight in the negative electrode active material layer.

The negative electrode active material layer may have a thickness of 30 μm to 100 μm, preferably 40 μm to 80 μm, in order to increase electrical contact with components of the negative electrode material due to the aforementioned linear conductive material.

The negative electrode is prepared by dispersing an anode material, a binder, and a conductive material on the negative electrode current collector in a solvent for forming the negative electrode slurry to prepare a negative electrode slurry, coating the negative electrode slurry on the negative electrode current collector, and then drying and rolling It can be.

The solvent for forming the anode slurry may include at least one selected from the group consisting of distilled water, ethanol, methanol, and isopropyl alcohol, preferably distilled water, in order to facilitate dispersion of components.

<Secondary Battery>

The present invention provides a secondary battery, specifically a lithium secondary battery, including the negative electrode described above.

Specifically, the secondary battery according to the present invention includes the aforementioned negative electrode; an anode facing the cathode; a separator interposed between the cathode and the anode; and electrolytes.

The positive electrode may include a positive electrode current collector; A cathode active material layer formed on the cathode current collector may be included.

The positive current collector is not particularly limited as long as it does not cause chemical change in the battery and has high conductivity. Specifically, the negative electrode current collector may be made of copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, or the like, aluminum-cadmium alloy, or the like. there is.

The cathode current collector may typically have a thickness of 3 to 500 μm.

The positive electrode current collector may form fine irregularities on the surface to enhance bonding strength of the negative electrode active material. For example, the negative current collector may be used in various forms such as a film, sheet, foil, net, porous material, foam, or non-woven fabric.

The cathode active material layer may include a cathode active material.

The cathode active material is a compound capable of reversible intercalation and deintercalation of lithium, and specifically, a lithium transition metal composite oxide containing lithium and at least one transition metal composed of nickel, cobalt, manganese, and aluminum, Preferably, a transition metal including nickel, cobalt, and manganese and a lithium transition metal composite oxide including lithium may be included.

More specifically, the lithium transition metal composite oxide includes lithium-manganese oxide (eg, LiMnO ₂ , LiMn ₂ O ₄ , etc.), lithium-cobalt oxide (eg, LiCoO _{2 ,} etc.), lithium-nickel based oxides (eg, LiNiO _{2 ,} etc.), lithium-nickel-manganese based oxides (eg, LiNi _1-Y Mn _Y O ₂ (where 0<Y<1), LiMn _2-z Ni _z O ₄ (here, 0<Z<2), etc.), lithium-nickel-cobalt-based oxide (eg, LiNi _1-Y1 Co _Y1 O ₂ (here, 0<Y1<1), etc.), lithium-manganese -Cobalt-based oxides (eg, LiCo _1-Y2 Mn _Y2 O ₂ (where 0<Y2<1), LiMn _2-z1 Co _z1 O ₄ (where 0<Z1<2), etc.), lithium -Nickel-manganese-cobalt-based oxide (eg, Li(Ni _p Co _q Mn _r1 ) O ₂ (here, 0<p<1, 0<q<1, 0<r1<1, p+q+ r1=1) or Li(Ni _p1 Co _q1 Mn _r2 )O ₄ (where 0<p1<2, 0<q1<2, 0<r2<2, p1+q1+r2=2), etc.), or Lithium-nickel-cobalt-transition metal (M) oxide (e.g., Li(Ni _p2 Co _q2 Mn _r3 M _S2 )O ₂ where M is Al, Fe, V, Cr, Ti, Ta, Mg and It is selected from the group consisting of Mo, and p2, q2, r3 and s2 are atomic fractions of independent elements, respectively, 0 <p2 <1, 0 <q2 <1, 0 <r3 <1, 0 <s2 <1, p2 +q2+r3+s2=1) and the like) and the like, and any one or two or more of these compounds may be included. Among them, in that the capacity characteristics and stability of the battery can be improved, the lithium transition metal composite oxide is LiCoO ₂ , LiMnO ₂ , LiNiO ₂ , lithium nickel-manganese-cobalt oxide (eg, Li(Ni _0.6 Mn _0.2 Co _0.2 )O ₂ , Li(Ni _0.5 Mn _0.3 Co _0.2 )O ₂ , Li(Ni _0.7 Mn _0.15 Co _0.15 )O ₂ or Li(Ni _0.8 Mn _0.1 Co _0.1 )O _{2 ,} etc.), or lithium nickel cobalt aluminum oxide (eg For example, it may be Li (Ni _0.8 Co _0.15 Al _0.05 ) O ₂ , etc.), and considering the remarkable effect of improving the type and content ratio control of the constituent elements forming the lithium transition metal composite oxide, the lithium transition metal Complex oxides are Li(Ni _0.6 Mn _0.2 Co _0.2 )O ₂ , Li(Ni _0.5 Mn _0.3 Co _0.2 )O ₂ , Li(Ni _0.7 Mn _0.15 Co _0.15 )O ₂ or Li(Ni _0.8 Mn _0.1 Co _0.1 )O ₂ And the like, any one or a mixture of two or more of them may be used.

The positive electrode active material may be included in an amount of 80% to 99% by weight, preferably 92% to 98.5% by weight in the positive electrode active material layer in consideration of exhibiting sufficient capacity of the positive electrode active material.

The positive electrode active material layer may further include a binder and/or a conductive material together with the positive electrode active material.

The binder is a component that assists in the binding of the active material and the conductive material and the binding to the current collector, specifically polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose Composed of rose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene-butadiene rubber and fluororubber. It may include at least one selected from the group, preferably polyvinylidene fluoride.

The binder may be included in an amount of 1% to 20% by weight, preferably 1.2% to 10% by weight in the positive electrode active material layer in order to sufficiently secure binding force between components such as the positive electrode active material.

The conductive material may be used to assist and improve the conductivity of a secondary battery, and is not particularly limited as long as it has conductivity without causing chemical change. Specifically, the conductive material is graphite such as natural graphite or artificial graphite; carbon black such as carbon black, acetylene black, ketjen black, channel black, farnes black, lamp black, and thermal black; conductive fibers such as carbon fibers and metal fibers; conductive tubes such as carbon nanotubes; metal powders such as fluorocarbon, aluminum, and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and polyphenylene derivatives, and may include at least one selected from the group consisting of, preferably, carbon black in terms of improving conductivity.

The conductive material may be included in an amount of 1 wt% to 20 wt%, preferably 1.2 wt% to 10 wt%, in the cathode active material layer in order to sufficiently secure electrical conductivity.

The thickness of the cathode active material layer may be 30 μm to 400 μm, preferably 50 μm to 110 μm.

The positive electrode may be prepared by coating a positive electrode slurry including a positive electrode active material and optionally a binder, a conductive material, and a solvent for forming the positive electrode slurry on the positive electrode current collector, followed by drying and rolling.

The solvent for forming the positive electrode slurry may include an organic solvent such as NMP (N-methyl-2-pyrrolidone), and may be used in an amount that provides a desired viscosity when including the positive electrode active material, and optionally a binder and a conductive material. can For example, the solvent for forming the positive electrode slurry is such that the concentration of the solid content including the positive electrode active material and optionally the binder and the conductive material is 50% to 95% by weight, preferably 70% to 90% by weight, so that the positive electrode slurry can be included in

The separator separates the negative electrode and the positive electrode and provides a passage for lithium ion movement, and can be used without particular limitation as long as it is normally used as a separator in a lithium secondary battery. Excellent is desirable. Specifically, a porous polymer film, for example, a porous polymer film made of polyolefin-based polymers such as ethylene homopolymer, propylene homopolymer, ethylene/butene copolymer, ethylene/hexene copolymer, and ethylene/methacrylate copolymer, or these A laminated structure of two or more layers of may be used. In addition, conventional porous non-woven fabrics, for example, non-woven fabrics made of high melting point glass fibers, polyethylene terephthalate fibers, and the like may be used. In addition, a coated separator containing a ceramic component or a polymer material may be used to secure heat resistance or mechanical strength, and may be selectively used in a single layer or multilayer structure.

In addition, the electrolyte used in the present invention includes an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel polymer electrolyte, a solid inorganic electrolyte, and a molten inorganic electrolyte that can be used in the manufacture of a secondary battery. It is not.

Specifically, the electrolyte may include an organic solvent and a lithium salt.

The organic solvent may be used without particular limitation as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, examples of the organic solvent include ester-based solvents such as methyl acetate, ethyl acetate, gamma-butyrolactone, and ε-caprolactone; ether solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; carbonate solvents such as dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); alcohol-based solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (R is a C2 to C20 straight-chain, branched or cyclic hydrocarbon group, and may include a double-bonded aromatic ring or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; Or sulfolane (sulfolane) and the like may be used. Of these, carbonate-based solvents are preferred, and cyclic carbonates (eg, ethylene carbonate or propylene carbonate, etc.) having high ionic conductivity and high permittivity that can improve the charge and discharge performance of batteries, and low-viscosity linear carbonates A mixture of compounds (e.g., ethyl methyl carbonate, dimethyl carbonate or diethyl carbonate) is more preferred. In this case, when the cyclic carbonate and the chain carbonate are mixed in a volume ratio of about 1:1 to about 1:9, the performance of the electrolyte may be excellent.

The lithium salt may be used without particular limitation as long as it is a compound capable of providing lithium ions used in a lithium secondary battery. Specifically, the lithium salt is LiPF ₆ , LiClO ₄ , LiAsF ₆ , LiBF ₄ , LiSbF ₆ , LiAlO 4 , LiAlCl ₄ , LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , LiN( _{C 2 F 5} SO ₃ ) ₂ , LiN(C ₂ F ₅ SO ₂ ) ₂ , LiN(CF ₃ SO ₂ ) ₂ , LiCl, LiI, or LiB(C ₂ O ₄ ) ₂ , and the like may be used. The concentration of the lithium salt is preferably used within the range of 0.1 to 2.0M. When the concentration of the lithium salt is within the above range, the electrolyte has appropriate conductivity and viscosity, so excellent electrolyte performance can be exhibited, and lithium ions can move effectively.

The secondary battery may be manufactured according to a conventional secondary battery manufacturing method by injecting an electrolyte solution after interposing a separator between the above-described negative electrode and positive electrode.

The secondary battery according to the present invention is useful for portable devices such as mobile phones, notebook computers, and digital cameras, and electric vehicles such as hybrid electric vehicles (HEVs), and is particularly preferable as a battery component of a medium or large-sized battery module. can be used Accordingly, the present invention also provides a medium or large-sized battery module including the above secondary battery as a unit battery.

Such medium- or large-sized battery modules can be preferably applied to power sources requiring high output and large capacity, such as electric vehicles, hybrid electric vehicles, and power storage devices.

Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement the present invention. However, the present invention may be embodied in many different forms and is not limited to the embodiments described herein.

Example 1

In an airtight container, 1.4 g of silicon particles with an average particle diameter (D ₅₀ ) of 1 µm, 0.1 g of VGCF with an average length of 8 µm, 0.1 g of multi-walled carbon nanotubes with an average length of 8 µm, 0.12 g of sucrose and 0.18 g of Li ₂ O The mixture was put into an airtight container made of zirconia. 5.7 g of zirconia balls with a diameter of 5 mm (three times the weight of the mixture) are put into the airtight container, and the airtight container is filled with argon gas by opening and closing the airtight container in a glove box filled with argon gas. did Thereafter, the airtight container was ball milled at a speed of 150 rpm for 12 hours by vigorously shaking the container using a planetary mixer to prepare a composite negative active material.

Anode slurry was prepared by mixing the composite anode active material, PAA binder, and superC (carbon black) conductive material in a weight ratio of 8: 1: 1 in distilled water as a solvent, and the anode slurry was prepared using a blade-type coating machine, a Mattis coater After coating to a uniform thickness on a copper foil having a thickness of 20 μm using a copper foil, it was dried at 80° C. to prepare a negative electrode (thickness of the negative electrode: 57 μm, area 1.4875 cm 2 , circular shape).

Example 2

In an airtight container, 1.5 g of silicon particles with an average particle diameter (D ₅₀ ) of 1 μm, 0.1 g of VGCF with an average length of 8 μm, 0.1 g of multi-walled carbon nanotubes with an average length of 8 μm, 0.15 g of sucrose and 0.15 g of Li ₂ O The mixture was put into an airtight container made of zirconia. 6 g of zirconia balls having a diameter of 5 mm (three times the weight of the mixture) were put into the airtight container, and the airtight container was opened and closed in a glove box filled with argon gas to fill the inside of the airtight container with argon gas. . Thereafter, the airtight container was ball-milled at a speed of 150 rpm for 24 hours by vigorously shaking the container using a planetary mixer to prepare a composite negative active material.

A negative electrode slurry was prepared by mixing the composite negative electrode active material, PAA binder, and superC (carbon black) conductive material in a weight ratio of 6: 2: 2 in distilled water as a solvent, and the negative electrode slurry was prepared using a blade-type coating machine, a Mattis coater After coating to a uniform thickness on a copper foil having a thickness of 20 μm using a copper foil, it was dried at 80° C. to prepare a negative electrode (thickness of the negative electrode: 57 μm, area 1.4875 cm 2 , circular shape).

Comparative Example 1

As raw materials for the composite negative electrode active material, 1.8 g of Si and 0.27 g of sucrose were placed in an airtight container (lithium raw material and conductive material were not added), and then a negative electrode was manufactured in the same manner as in Example 1.

Comparative Example 2

As raw materials for the composite negative electrode active material, 1.8 g of Si, 0.15 g of sucrose, and 0.2 g of Li ₂ O were placed in an airtight container (no conductive material was added), and then a negative electrode was prepared in the same manner as in Example 1.

Comparative Example 3

In an airtight container, 1.5 g of Si, 0.15 g of VGCF, and 0.15 g of carbon nanotubes were put, and pulverized to prepare a mixed active material of silicon particles and a conductive material. A negative electrode slurry was prepared by mixing the negative electrode active material mixed with the conductive material, the PAA binder, and the superC (carbon black) conductive material in a weight ratio of 8:1:1, and then a negative electrode was prepared in the same manner as in Example 1.

<Scanning electron microscope analysis>

SEM images of the anode active materials according to Example 1, Comparative Example 2, and Comparative Example 3 are shown in FIGS. 1 to 3, respectively.

Referring to FIG. 1 , in the composite anode active material prepared in Example 1, it can be observed that the surface of the silicon particle is covered with carbonaceous material. In addition, carbon nanotubes or vapor-processed carbon fibers are attached to the surface of the silicon particles.

Referring to FIG. 2 , in the anode active material prepared in Comparative Example 2, carbon nanotubes or vapor-processed carbon fibers were not added when raw materials for preparing the anode active material were added, so they could not be observed.

Referring to FIG. 3, in the negative electrode active material prepared in Comparative Example 3, since carbon and lithium sources were not added when the raw materials for preparing the negative electrode active material were added, the surface of the silicon particles was clean, and the carbon nanotube or vapor phase method was used. It can be observed that the carbon fibers exist independently in a form that is not attached to the silicon particles.

<Manufacture of coin type half cell>

A coin-type half-cell (half- cell) A secondary battery was manufactured. As the electrolyte, 0.5% by weight of vinylene carbonate (VC) was dissolved in a solution of ethyl methyl carbonate (EMC) and ethylene carbonate (EC) mixed at a volume ratio of 7: 3, and LiPF ₆ was dissolved at a concentration of 1 M. used

Using the negative electrodes prepared in Example 2 and Comparative Examples 1 to 3, coin-type half cells were manufactured in the same manner as described above.

<Evaluation of initial efficiency>

For each of the half-cells manufactured in Examples 1 to 2 and Comparative Examples 1 to 3, initial efficiencies were evaluated using an electrochemical charge/discharger.

Discharge was performed at room temperature in CC-CV mode at 0.1 C until 5 mV was reached, and discharging was terminated at the time of reaching 0.005 C. After charging up to 1.5V with a constant current of 0.1C and performing a single charge/discharge experiment, the initial efficiency was measured, and the results are shown in Table 1.

<Evaluation of capacity retention rate>

For each of the half-cells manufactured in Examples 1 to 2 and Comparative Examples 1 to 3, the cycle capacity retention rate was evaluated using an electrochemical charger and discharger.

The first cycle was charged/discharged at 0.1C, and from the second cycle, charged/discharged at 0.5C (discharge condition: CC/CV, 5mV cut-off current 0.02C), charging condition: CC, 1.0V cut-off )

The capacity retention rate was calculated as follows.

Capacity retention rate (%)={(Charging capacity in the Nth cycle)/(Charging capacity in the 1st cycle)} Х 100

(In the above formula, N is an integer greater than or equal to 1)

The 10th cycle capacity retention rate (%) is shown in Table 1 below.

initial efficiency capacity retention rate Example 1 87 61 Example 2 86 63 Comparative Example 1 57 28 Comparative Example 2 80 43 Comparative Example 3 51 38

Referring to Table 1, the batteries of Comparative Example 1 and Comparative Example 3 in which the lithium raw material was not added showed significantly lower initial efficiency and capacity retention rate compared to Example 1. This seems to be due to the reduction of the irreversible phase according to the addition of the lithium raw material in the preparation of the composite negative electrode active material of the present invention.

In addition, Comparative Example 2, in which the linear conductive material was not added, was found to have a poor capacity retention rate compared to Example. This means that the composite anode active material of the present invention can prevent electrical shorts between active materials against volume expansion/contraction due to charging and discharging of the silicon active material, and can stably form a conductive network in the anode, thereby improving the lifespan of the anode and secondary battery. interpreted as being able to

In addition, Comparative Example 3, in which silicon particles and a conductive material are simply mixed, contains the same conductive material as Example 1, but since the conductive material does not sufficiently form a conductive network between active materials, compared to Example 1, the initial efficiency and capacity The retention rate appears to be declining.

In addition, compared to Example 1, the content ratio of Li ₂ O and linear conductive material (VGCF, multi-walled carbon nanotubes) was slightly lowered in the preparation of the composite negative electrode active material, and the conductive material (carbon black) in the preparation of the negative electrode slurry Example 2 prepared by increasing the content ratio by 2 times showed a slight decrease in the initial efficiency of the battery compared to Example 1, which is because the input ratio of Li ₂ O was slightly lowered, so the effect of reducing the irreversible phase was relatively small. It appears that this is because On the other hand, in Example 2, the content of the conductive material is doubled compared to Example 1 when preparing the negative electrode slurry, but the capacity retention rate is only slightly increased due to the effect of reducing the linear conductive material added to the composite negative electrode active material.

Claims (18)

silicon (Si) particles;
a coating layer formed on the surface of the silicon particle and containing carbonaceous material; and
Including a linear conductive material,
A composite negative active material comprising a Li _x Si _y O _Z [x>0, y>0, 0≤z≤2(x+4y)] phase.
The composite anode active material of claim 1, wherein the linear conductive material is attached to the coating layer, and a part of the body is spaced apart from the coating layer.
The composite anode active material according to claim 1, wherein the linear conductive material is one or two selected from the group consisting of carbon nanotubes and carbon nanofibers.
The composite anode active material according to claim 1, wherein the linear conductive material is one or two selected from the group consisting of vapor grown carbon fiber (VGCF) and multi-walled carbon nanotube (MWCNT).
The composite anode active material according to claim 1, wherein the linear conductive material has an average length in a major axis direction of 1 μm or more.
The composite anode active material of claim 1 , wherein the silicon particles are present in an amount of 50% to 90% by weight based on the total weight of the composite anode active material.
The composite anode active material of claim 1 , wherein the linear conductive material is present in an amount of 2% to 30% by weight based on the total weight of the composite anode active material.
The composite anode active material of claim 1 , wherein the coating layer has an island shape covering a portion of the surface of the silicon particle.
An input step of putting silicon, a carbon precursor, a lithium raw material, and a linear conductive material into a container; and
A ball mill step of ball milling the mixture in the container,
In the ball mill step, a carbon precursor is converted into carbonaceous by a ball mill to form a coating layer containing carbonaceous material, and the conductive material is attached to the coating layer.
10. The method of claim 9, wherein the ball mill step has a ball-to-powder weight ratio (BPR) of 1:1 to 10:1, a rotational speed of 50 rpm to 500 rpm, and ball milling for 1 hour to 36 hours. Method for producing a composite anode active material to be.
10. The method of claim 9, wherein the carbon precursor is glucose, sucrose, gum arabic, tannic acid, lignosulfonate, poly-aromatic oxide Composite anode, characterized in that at least one selected from the group consisting of aromatic substance oxides, sugars and polyphenols, coal-based pitch, petroleum-based pitch, coal-based oil, petroleum-based heavy oil, organic synthetic pitch, furan resin and polyimide resin. Methods for manufacturing active materials.
10. The method of claim 9, wherein the lithium source material is lithium metal, lithium oxide (Li ₂ O, LiO ₂ , Li ₂ O ₂ ), lithium hydroxide (LiOH), lithium carbonate (Li ₂ CO ₃ ) and lithium chloride (LiCl) Method for producing a composite negative electrode active material, characterized in that one or a mixture of two or more selected from the group consisting of.
10. The composite anode active material of claim 9, wherein the linear conductive material is one or two selected from the group consisting of vapor grown carbon fiber (VGCF) and multi-walled carbon nanotubes (MWCNT). manufacturing method.
10. The method of claim 9, wherein the linear conductive material has an average length in a major axis direction of 1 μm or more.
10. The method of claim 9, wherein, in the inputting step, 50 to 90 parts by weight of silicon, 3 to 10 parts by weight of carbon precursor, 3 to 15 parts by weight of lithium raw material, and 5 to 30 parts by weight of conductive material are added. Method for producing a composite anode active material to be.
10. The method of claim 9, wherein the ball milling step is performed under an inert atmosphere.
negative current collector; A negative electrode comprising a negative electrode active material layer formed on the negative electrode current collector, wherein the negative electrode active material layer includes the composite negative electrode active material of claim 1.
a negative electrode according to claim 17; an anode facing the cathode; a separator interposed between the cathode and anode; and a lithium secondary battery comprising an electrolyte.

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