WO2024096275A1

WO2024096275A1 - Anode material for secondary battery, and method for preparing anode material for secondary battery

Info

Publication number: WO2024096275A1
Application number: PCT/KR2023/012087
Authority: WO
Inventors: 이덕연; 이창영; 이자은; 한연비
Original assignee: 주식회사 이노플라즈텍
Priority date: 2022-11-03
Filing date: 2023-08-16
Publication date: 2024-05-10
Also published as: KR102651795B1

Abstract

The present invention provides an anode material for a secondary battery, comprising: an anode active material powder comprising a conductive material powder and a plasma-surface-treated silicon powder; single-walled carbon nanotubes applied to the surface of the silicon powder in order to improve the conductivity of the anode material and inhibit the expansion of the silicon powder; and multi-walled carbon nanotubes mixed with the anode active material powder and the single-walled carbon nanotubes by using a binder. Therefore, since the single-walled carbon nanotubes encompass only silicon, which is partially added to an anode active material, so as to inhibit the expansion of silicon and serve as a conductive material, the amount of used single-walled carbon nanotubes is reduced such that costs are reduced enough to enable commercialization.

Description

Negative material for secondary batteries and method for manufacturing the negative electrode material for secondary batteries

The present invention relates to a negative electrode material for secondary batteries and a method of manufacturing the negative electrode material for secondary batteries. More specifically, in order to suppress expansion of the silicon powder included to increase capacity, a single-walled carbon nanotube with excellent physical properties is added to the surface of the silicon powder. Commercialization is possible by coating or additionally using multi-walled carbon nanotubes, which are relatively cheaper than single-walled carbon nanotubes, as a conductive material for the anode material to increase electrical conductivity while being structurally stable, and also reduce costs. It relates to a negative electrode material for secondary batteries and a method of manufacturing the negative electrode material for secondary batteries.

As the supply and spread of electric vehicles accelerates, the competition to develop materials to improve battery (secondary battery) performance is intensifying. In particular, among the core materials that make up batteries, the performance of anode materials, which play an important role in lifespan and charging speed, is improving more than before. As 'silicon anode material' emerges as a next-generation material, the development and commercialization of technology for it is gaining momentum. Silicon anode material is the optimal material to overcome the shortcomings of existing graphite anode materials and has a capacity more than 10 times higher than graphite. Using silicon instead of graphite in the anode material is expected to theoretically improve energy density by 25% and charging speed by 50%. It is known that it can be done.

However, silicon anode material has a high self-resistance and has the problem of reacting with lithium ions to expand its volume by about four times or more, which can cause performance and stability problems. In other words, as the volume expands through repeated charging and discharging, the particles are destroyed, and when a new electrolyte interface is formed along the broken surface, the electrolyte is depleted and lithium ion transfer slows down.

By adding single-walled carbon nanotubes (SWCNT) to silicon as a conductive material, the volume expansion of silicon can be suppressed and structural stability can be achieved during the charging and discharging process. In particular, SWCNT has high electrical conductivity and aspect ratio, so it is effective in forming a conductive network, has the characteristic of increasing the contact force of active materials with a high surface area, and can improve cycle performance with high flexibility and tensile strength.

However, despite its excellent performance, it is having difficulty commercializing it due to its high price (KRW 14,000/1g). Therefore, a solution is needed to enable commercialization by reducing costs while using anode materials for secondary batteries using insulating carbon nanotubes.

In order to suppress the expansion of the silicon powder included in order to increase capacity, the present invention coats the surface of the silicon powder with single-walled carbon nanotubes, which have excellent physical properties, or uses a conductive material for the anode material that is relatively expensive compared to single-walled carbon nanotubes. The purpose is to provide a negative electrode material for secondary batteries and a method of manufacturing the negative electrode material for secondary batteries that can be commercialized by additionally using inexpensive multi-walled carbon nanotubes to increase electrical conductivity while being structurally stable, and also reduce costs. do.

According to one aspect of the present invention, in a negative electrode material for a secondary battery, the present invention provides a negative electrode active material powder containing a conductive material powder and a plasma surface-treated silicon powder, improving the conductivity of the negative electrode material, and expanding the silicon powder. A secondary battery comprising single-walled carbon nanotubes coated on the surface of the silicon powder and multi-walled carbon nanotubes mixed with the negative electrode active material powder and the single-walled carbon nanotubes by a binder to suppress A cathode material is provided.

According to another aspect of the present invention, the present invention relates to a method for manufacturing a negative electrode material for a secondary battery, comprising the steps of plasma surface treatment on silicon powder, improving conductivity of the negative electrode material and suppressing expansion of the silicon powder, the plasma surface A secondary battery comprising the steps of coating single-walled carbon nanotubes on the surface of the treated silicon powder and mixing the silicon powder coated with the single-walled carbon nanotubes, the conductive material powder, and the multi-walled carbon nanotubes with a binder. A method for manufacturing an anode material is provided.

The secondary battery negative electrode material and the manufacturing method of the secondary battery negative electrode material according to the present invention have the following effects.

First, since single-walled carbon nanotubes surround only the silicon that is partially added among the anode active materials, thereby suppressing the expansion of silicon and acting as a conductive material, the amount of single-walled carbon nanotubes used is reduced, making commercialization possible. There is an advantage in saving money.

Second, when coating carbon nanotubes (multi-walled or single-walled) on silicon wet or dry, the surface of the silicon is pre-treated with plasma to improve the interfacial bonding between silicon and single-walled carbon nanotubes, thereby increasing coating efficiency. , it can prevent detachment of carbon nanotubes from the silicon surface even after the electrode manufacturing process or during battery operation.

Figure 1 is a perspective view showing a negative electrode material for a secondary battery according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing the surface of silicon, which is a negative electrode active material among the negative electrode materials for secondary batteries according to FIG. 1, being plasma treated and then coated with single-walled carbon nanotubes.

Figure 3 is a schematic diagram showing the negative electrode active material, conductive material, and binder separated from the negative electrode material for secondary batteries according to Figure 1.

Hereinafter, the present invention will be described in detail by explaining preferred embodiments of the present invention with reference to the attached drawings.

Referring to Figures 1 to 3, the negative electrode material 100 for a secondary battery according to an embodiment of the present invention includes a negative electrode active material powder 110 containing conductive material powder 111 and silicon powder 112, and single-walled carbon. It includes a conductive material 120 including a nanotube (Single-Walled Carbon NanoTube) 121 and a multi-walled carbon nanotube (122), a binder 130, and a substrate 140. However, the present invention is not limited to this, and only the single-walled carbon nanotube may be used by coating the silicon powder 112. That is, in this embodiment, as an example, single-walled carbon nanotubes are coated on silicon and the multi-walled carbon nanotubes are additionally used as a conductive material, but only the single-walled carbon nanotubes are coated on the silicon powder 112. , it can also be used without containing any other conductive materials such as the multi-walled carbon nanotubes. In FIG. 1 , for convenience of illustration, the anode active material powder 110, the conductive material 120, and the binder 130 are shown separately from the substrate 140.

In this embodiment, the conductive material 111 is graphite. And the graphite 111 and silicon 112 constituting the negative electrode active material powder 110 are in powder form as an example. And in this embodiment, the silicon powder 112 is an example of micro-sized particles or nano-sized particles.

And the surface of the silicon powder 112 is plasma treated (P). This improves the interfacial bonding force between the silicon powder 112 and the single-walled carbon nanotube 121 when coating the conductive single-walled carbon nanotube 121 on the surface of the non-conductive silicon powder 112. This is to ensure that the single-walled carbon nanotubes 121 are well coated with the silicon 112 and are not easily separated.

The conductive material 120 is included to improve the conductivity of the anode material 100 for a secondary battery. The single-walled carbon nanotube 121 is coated on the surface of the silicon powder 112. The single-walled carbon nanotube 121 performs a complex role of improving the conductivity of the anode material 100 for a secondary battery and suppressing expansion of the silicon powder 112.

The single-walled carbon nanotube 121 has a smaller diameter than the multi-walled carbon nanotube 122. Therefore, coating the single-walled carbon nanotube 121 on the surface of the silicon powder 112 can make the coating thickness thinner than coating the multi-walled carbon nanotube 122 on the surface of the silicon powder 112. There is an advantage. Additionally, the single-walled carbon nanotubes 121 are more flexible than the multi-walled carbon nanotubes 122. Therefore, the single-walled carbon nanotube 121 has the advantage of being coated on the surface of the silicon powder 112 having a micro or nano size.

Specifically, the single-walled carbon nanotube 121 is coated with non-conductive silicon powder 112 so that the portion where the silicon powder 112 is disposed within the anode material 100 for a secondary battery also has conductivity. Carbon nanotubes are hexagonal shapes made of 6 carbon atoms connected to each other to form a tube with space inside.

In this embodiment, as an example, a plurality of tube-shaped single-walled carbon nanotubes 121 are arranged to surround the outer surface of the silicon powder 112. However, the present invention is not limited to this, and the single-walled carbon nanotube 121 having the hexagonal tube shape may be cut in a specific direction (for example, longitudinal direction), spread out in a sheet form, and coated with the silicon powder 112. there is. When the single-walled carbon nanotube 121 is spread and coated with the silicon powder 112, the thickness can be reduced and the bonding strength with the silicon powder 112 can be improved.

The single-walled carbon nanotube 121 is coated on the surface of the silicon powder 112 in a dry or wet manner. In this embodiment, the single-walled carbon nanotube 121 is dry-coated on the surface of the silicon powder 112 through a dry electrode manufacturing process. When the single-walled carbon nanotubes 121 are wet-coated on the surface of the silicon powder 112, a process is required to additionally dry the silicon powder 112 coated with the single-walled carbon nanotubes 121. do. Additionally, during the additional drying, a problem may occur in which the single-walled carbon nanotubes 121 aggregate again. Therefore, an additional process of splitting the aggregated single-walled carbon nanotubes 121 again is required. Therefore, when the single-walled carbon nanotube 121 is wet-coated with the silicon powder 112, there is a disadvantage in that time efficiency and cost-efficiency are reduced compared to when the single-walled carbon nanotube 121 is coated dry.

However, when dry coating the single-walled carbon nanotubes 121 with the silicon powder 112, there is a problem in that it is difficult for the single-walled carbon nanotubes 121 to be well bonded to the silicon powder 112. However, since the anode material 100 for a secondary battery according to this embodiment is coated with the single-walled carbon nanotubes 121 while the silicon powder 112 is plasma-treated, the single-walled carbon nanotubes (121) can be formed even through a dry process. 121) is well coated on the silicon powder 112 and is not easily separated even after coating, so dry coating is possible.

Additionally, the single-walled carbon nanotube 121 entirely surrounds the silicon powder 112. This is because the single-walled carbon nanotube 121, which has strong rigidity, has a structure surrounding the silicon powder 112, so that expansion of the silicon powder 112 as the secondary battery is repeatedly charged is suppressed by physical force. It is for this purpose. When the single-walled carbon nanotube 121 is sufficiently decomposed, its physical properties are superior to those of the multi-walled carbon nanotube 122, so its mechanical properties are maintained despite repeated charging and discharging of the secondary battery. There is an advantage in that the expansion inhibition force and conductivity of the silicon powder 112 can be continuously maintained compared to coating the silicon powder 112 with the multi-walled carbon nanotube 122. Therefore, compared to the case where the anode material 100 for a secondary battery according to this embodiment contains only the graphite powder 111, the battery capacity is significantly increased by including the silicon powder 112, enabling high-speed charging and depending on the cycle. It has the advantage of excellent capacity retention rate.

However, the single-walled carbon nanotube 121 is expensive, reaching approximately 14,000 won per gram. Therefore, if only the single-walled carbon nanotubes 121 are used as a conductive material for secondary battery anode materials considering only the excellent physical properties of the single-walled carbon nanotubes 121, the cost increases rapidly, making commercialization difficult. Therefore, in this embodiment, the single-walled carbon nanotube 121 is coated only on the surface of the silicon powder 112 to effectively expand the silicon and reduce the amount of use, thereby reducing the cost. Ultimately, the single-walled carbon nanotube 121 is coated only on the surface of the silicon powder 112. This allows commercialization of secondary battery anode material 100 using carbon nanotubes 121.

And the silicon powder 112 coated with the single-walled carbon nanotube 121 has a smaller weight percent (wt%) than the graphite powder 111 in the anode active material powder 110. However, in this embodiment, the silicon powder 112 coated with the single-walled carbon nanotube 121 is included in an amount of 5% by weight or more based on the total weight of the negative electrode active material powder 110. However, the present invention is not limited to this, and the silicon powder 112 coated with the single-walled carbon nanotube 121 may be included in an amount of 5 to 20 weight percent based on the total weight of the negative electrode active material powder 110.

The multi-walled carbon nanotubes 122 are included to improve the conductivity of the anode material 100 for secondary batteries. The multi-walled carbon nanotubes 122 are combined with the negative electrode active material powder 110 and the single-walled carbon nanotubes 111 by the binder 130.

The graphite powder 111 has conductivity, and as described above, the single-walled carbon nanotube 121 is arranged in a structure surrounding the silicon powder 112, so that the portion where the silicon powder 112 is placed is also conductive. have Therefore, since the negative electrode active material powder 110 has overall conductivity, an additional conductive material is not necessarily required.

However, by including a separate conductive material in addition to the single-walled carbon nanotube 121, it is possible to secure stable conductivity of the entire negative electrode material 100 for a secondary battery. In this regard, in this embodiment, the conductivity of the negative electrode material 100 for a secondary battery can be improved by disposing the multi-walled carbon nanotubes 122 between the negative electrode active material powders 110. At this time, since the multi-walled carbon nanotubes 122 are cheaper than the single-walled carbon nanotubes 121, even if a large amount of the multi-walled carbon nanotubes 122 are included, the single-walled carbon nanotubes 121 It is possible to produce the anode material 100 for secondary batteries at a much lower cost than when using it as a whole.

The binder 130 serves to adhere the anode active material powder 110 and the conductive material 120 to the substrate 140. In other words, the binder 130 functions as a type of adhesive. The binder 130 may be a fluorine-containing binder or a SBR/CMC, PAA, or PI-based binder. When using an SBR binder, an additional thickener may be included. At this time, the thickener may be one or more selected from the group consisting of carboxymethyl cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose, and hydroxypropyl cellulose.

Hereinafter, a method of manufacturing the anode material 100 for a secondary battery according to FIGS. 1 to 3 will be described.

First, prepare the materials necessary to manufacture the anode material 100 for a secondary battery. That is, a negative electrode active material 110 containing conductive material powder 111 and silicon powder 112, a conductive material 120 containing single-walled carbon nanotubes 121 and multi-walled carbon nanotubes 122, and a binder. (130) and base material (140) are prepared. The conductive material powder 111 is prepared from graphite powder 111.

Next, the silicon powder 112 is surface treated with plasma. And in order to improve the conductivity of the negative electrode material 100 for a secondary battery and suppress expansion of the silicon powder 112, single-walled carbon nanotubes 121 are formed on the surface of the plasma surface-treated silicon powder 112. Coat.

Then, the silicon powder 112 coated with the single-walled carbon nanotubes 121, the conductive material powder 111, and the multi-walled carbon nanotubes 122 are mixed with the binder 130. Then, silicon powder 112 coated with the mixed single-walled carbon nanotubes 121, conductive material powder 111, and multi-walled carbon nanotubes are formed on the substrate 140.

The present invention has been described with reference to the embodiments shown in the drawings, but these are merely illustrative, and those skilled in the art will understand that various modifications and equivalent other embodiments are possible therefrom. Therefore, the true scope of technical protection of the present invention should be determined by the technical spirit of the attached patent claims.

Using the present invention, single-walled carbon nanotubes surround only the silicon that is partially added among the anode active materials, thereby suppressing the expansion of silicon and acting as a conductive material. Therefore, the amount of single-walled carbon nanotubes used is reduced, making commercialization possible. It is possible to manufacture anode materials for secondary batteries that reduce costs.

Claims

In the anode material for secondary batteries,

Negative active material powder including conductive material powder and silicon powder subjected to plasma surface treatment;

Single-walled carbon nanotubes coated on the surface of the silicon powder to improve conductivity of the anode material and suppress expansion of the silicon powder; and

Containing multi-walled carbon nanotubes mixed with the negative electrode active material powder and the single-walled carbon nanotubes by a binder,

Anode material for secondary batteries.
In claim 1,

The silicone is,

Formed from microparticles or nanoparticles,

Anode material for secondary batteries.
In claim 2,

The single-walled carbon nanotubes are,

In order to suppress the expansion of the silicon particles by physical force, disposed on the surface of the silicon particles to surround the silicon particles,

Anode material for secondary batteries.
In claim 3,

The single-walled carbon nanotubes are,

Dry or wet coated on the surface of the silicon particles,

Anode material for secondary batteries.
In claim 1,

The conductive material powder is formed of graphite powder,

Anode material for secondary batteries.
In claim 5,

The silicon powder coated with the single-walled carbon nanotubes is,

The negative electrode active material has a weight percent (wt%) smaller than that of the graphite powder, but contains more than 5 weight percent based on the total weight of the negative electrode active material.

Anode material for secondary batteries.
In claim 1,

The multi-walled carbon nanotubes are,

Disposed between the negative electrode active material powder to improve the conductivity of the conductive material powder,

Anode material for secondary batteries.
In claim 1,

In order to minimize the amount of single-walled carbon nanotubes used, the single-walled carbon nanotubes are disposed only on the silicon surface.

Anode material for secondary batteries.
In the method of manufacturing a negative electrode material for a secondary battery,

Plasma surface treatment of silicon powder;

coating single-walled carbon nanotubes on the surface of the plasma surface-treated silicon powder to improve conductivity of the anode material and suppress expansion of the silicon; and

Comprising the step of mixing the silicon powder coated with the single-walled carbon nanotubes, the conductive material powder, and the multi-walled carbon nanotubes with a binder,

Method for manufacturing anode materials for secondary batteries.
In claim 9,

The silicon is formed of micro particles or nanoparticles,

The single-walled carbon nanotubes are disposed on the surface of the silicon particle to surround the silicon particle in order to suppress expansion of the silicon particle by physical force,

The conductive material powder is formed of graphite powder,

Method for manufacturing anode materials for secondary batteries.