KR20220168634A - Three phase-negative electrode active material for lithium rechargeable battery, method of preparing the same, and lithium rechargeable battery comprising the same - Google Patents

Abstract

One embodiment of the present invention provides a three-phase negative electrode active material and a manufacturing method thereof, wherein the three-phase negative electrode active material includes: a matrix composite having regular nanopores; a first functional layer positioned on the surface of the matrix composite; and a second functional layer positioned on the first functional layer and filling pores in the matrix composite. Accordingly, a silicon oxide-based negative electrode active material having improved coulombic efficiency, reversible capacity, and lifetime characteristics can be expected.

Description

Three-phase structure negative electrode active material, manufacturing method thereof, and lithium secondary battery using the same

The present invention relates to a negative electrode active material for a lithium secondary battery, and more particularly, to a negative electrode active material for a lithium secondary battery having a nanostructure and surface modified, a manufacturing method thereof, and a lithium secondary battery including the same.

A lithium ion battery is a type of secondary battery in which lithium ions move from a negative electrode to a positive electrode during a discharge process. During charging, lithium ions move back from the anode to the cathode to find their place. Lithium ion batteries are different from primary batteries in that they can be charged and reused, have high energy density, do not have a memory effect, and have a low degree of self-discharge even when not in use, so the frequency of use is increasing.

A lithium ion battery can be largely divided into three parts: positive electrode, negative electrode, and electrolyte. The negative electrode reversibly absorbs/releases lithium ions from the positive electrode while allowing current to flow through an external circuit. When the battery is in a charged state, lithium ions are present on the negative electrode. Therefore, if the anode, which is a place to store lithium ions, is not supported in a balanced manner, the efficiency will inevitably fall even if high energy is generated from the anode. In particular, the charging time can be shortened when the negative electrode can better accept lithium ions during charging. In this respect, the improvement of the negative electrode material constituting the negative electrode has been continued.

Graphite is the most commercially used anode material. Graphite has the advantage of being common and cheap, and because it has a layered structure, lithium ions can easily enter and exit the gap, so it is stable even after repeated charging/discharging. However, the disadvantage is that the charging speed is not fast, and graphite stores 1 lithium ion per 6 carbon atoms and has an energy capacity of 372 mAh/g, which does not meet the high-capacity batteries required by the battery industry.

In order to meet these demands, there have been examples of applying Si or Sn, which are metals that can be alloyed electrochemically with lithium, as anode active materials. is becoming an obstacle to In particular, Si has the advantage of being eco-friendly and abundantly present on the earth, but the Si anode material causes a phenomenon (lithiation) to increase the volume of the anode in the process of storing lithium ions. At this time, graphite increases in volume by about 10% to 20%, but silicon has a large volume expansion of 4 to 5 times. In addition, the silicon anode material has high crystal breakability. As a result, when charging/discharging is repeated, pulverization (particle cracking, destruction) of the silicon anode active material occurs and electrical separation from the current collector (Cu electrode plate, etc.) occurs, resulting in a rapid decrease in energy capacity and shortening the lifespan.

Various attempts have been made to solve the problem of Si, and among them, methods of suppressing expansion by forming a structure or a composite of a Si anode have been proposed. Specifically, as it has been revealed that the SiOx-based anode material, which introduces amorphous silicon oxide to buffer the volume expansion, can significantly improve the lifespan characteristics of a battery, research on SiOx-based materials is increasing. However, the low coulombic efficiency of the SiOx material itself and the low reversible capacity compared to Si are considered as other problems to be overcome. Therefore, modification and application of SiOx-based materials are indispensable research for next-generation high-capacity and high-stability lithium secondary batteries.

(Patent) Republic of Korea Patent No. 10-1840818

A technical problem to be achieved by the present invention relates to a silicon oxide-based negative electrode active material, and specifically, to improve coulombic efficiency, reversible capacity, and lifespan characteristics, a silicon oxide-based negative electrode active material having nanostructure formation and surface modification, and a manufacturing method thereof is to do

The technical problem to be achieved by the present invention is not limited to the above-mentioned technical problem, and other technical problems not mentioned can be clearly understood by those skilled in the art from the description below. There will be.

In order to achieve the above technical problem, one embodiment of the present invention provides a three-phase structure negative active material.

An embodiment of the present invention, a three-phase negative electrode active material, includes a matrix composite including an active material and a matrix capable of mitigating volume expansion including a plurality of regular nanopores; a first functional layer located in the form of a thin layer on the inner and outer surfaces of the matrix composite structure to increase the activity of the active material and to control an inactive layer that may be formed on the surface of the matrix composite; and a second functional layer positioned in a form filled with an active material in the pores of the matrix composite in which the first functional layer is formed.

In this case, the matrix of the matrix composite is a silicon oxide matrix, and the active material positioned on the matrix is a silicon crystal grain. In addition, the first functional layer is different from the material of the matrix composite and the second functional layer and is characterized in that it includes carbon, metal or metal oxide.

In addition, the metal or the metal of the metal oxide is characterized in that it includes at least one kind of metal selected from the group consisting of Ti, Sn, Ni, Mn, Co, Cu, Mo and Fe.

In addition, the active material of the second functional layer is different from the material of the first functional layer and is characterized in that it includes carbon, silicon, metal or metal oxide that can be used as an active material of a secondary battery.

In addition, the metal or the metal of the metal oxide is characterized in that it includes at least one kind of metal selected from the group consisting of Ti, Sn, Ni, Mn, Co, Cu, Mo and Fe.

In order to achieve the above technical problem, one embodiment of the present invention provides a method for manufacturing a three-phase negative electrode active material.

In an embodiment of the present invention, a method for manufacturing a three-phase negative electrode active material includes forming a matrix composite; forming a first functional layer on inner and outer surfaces of the matrix composite structure; and forming a second functional layer by filling the pores of the matrix composite in which the first functional layer is formed with an active material.

In this case, forming the matrix composite may include forming a silicon oxide matrix having regular pores; and forming silicon crystal grains on the silicon oxide matrix.

In addition, the step of forming the first functional layer includes forming a carbon layer, a metal layer, or a metal oxide layer on the inner and outer surfaces of the matrix composite, different from the materials of the matrix composite and the second functional layer. to be characterized

In addition, the metal of the metal layer or metal oxide layer is characterized in that it includes at least one kind of metal selected from the group consisting of Ti, Sn, Ni, Mn, Co, Cu, Mo and Fe.

In addition, in the step of forming the second functional layer, carbon, silicon, metal, or metal oxide that is different from the material of the first functional layer and can be used as an active material of a secondary battery is placed inside the matrix composite on which the first functional layer is formed. It is characterized in that it comprises the step of filling the pores with an active material.

In addition, the metal of the metal or metal oxide is characterized in that it includes at least one kind of metal selected from the group consisting of Ti, Sn, Ni, Mn, Co, Cu, Mo and Fe.

In order to achieve the above technical problem, another embodiment of the present invention provides a negative electrode for a lithium secondary battery including the negative electrode active material having a three-phase structure.

In order to achieve the above technical problem, another embodiment of the present invention provides a lithium secondary battery including the anode active material for the lithium secondary battery.

According to an embodiment of the present invention, a matrix composite having regular nanopores includes a first functional layer located on the surface of the matrix composite and a second functional layer located on the first functional layer and filling the pores in the matrix composite. It is possible to provide a three-phase structure negative electrode active material characterized in that, through which the low coulombic efficiency, which is a problem when using a silicon oxide-based active material as a negative electrode, can be improved, and a negative electrode having a three-phase structure with improved reversible capacity and life characteristics Active material can be provided.

According to another embodiment of the present invention, a method for manufacturing an anode active material having the three-phase structure, an anode, and a secondary battery may be provided.

The effects of the present invention are not limited to the above effects, and should be understood to include all effects that can be inferred from the detailed description of the present invention or the configuration of the invention described in the claims.

1 is a schematic diagram of a three-phase negative electrode active material according to an embodiment of the present invention.
Figure 2 is a schematic diagram of the matrix composite of the present invention.
3 is a flow chart of a manufacturing method of a three-phase negative electrode active material.
4 is a flow chart of a method for preparing a matrix composite according to the present invention.
5 is a flowchart of a method of modifying the matrix composite of the present invention into a carbon layer.
6 is a flow chart of a method of modifying the matrix composite of the present invention into a metal layer or metal oxide layer.
7 is a schematic diagram showing the effect of mitigating volume expansion during charging and discharging of the m-Si/SiOx composite prepared according to Preparation Example 1.
8 is low-angle and high-angle XRD data of m-Si/SiOx with different m-HSQ and heat treatment temperatures.
9 is nitrogen absorption and desorption analysis curve data of m-Si/SiOx at different m-HSQ and heat treatment temperatures.
Figure 10 is the specific surface area and pore volume measurement data of m-Si/SiOx with different m-HSQ and heat treatment temperatures.
11 is a TEM image of m-HSQ and m-Si/SiOx.
12 is FTIR analysis result data of m-Si/SiOx with different m-HSQ and heat treatment temperatures.
13 is electrochemical evaluation data of m-Si/SiOx and Si NP with different m-HSQ and heat treatment temperatures.
14 is rate characteristic evaluation data of m-Si/SiOx and Si NP with different m-HSQ and heat treatment temperatures.
15 is impedance evaluation data of m-Si/SiOx 900° C. and Si NP.
16 is dilatometer analysis data of m-Si/SiOx and commercial SiOx.
17(a) is a schematic diagram of the m-Si/SiOx surface oxide layer etching process.
17(b) is a TEM image before etching the m-Si/SiOx surface.
17(c) is a TEM image after etching the m-Si/SiOx surface.
17(d) shows low-angle and high-angle XRD images before and after etching the m-Si/SiOx surface.
Figure 17(e) shows nitrogen adsorption and desorption curves before and after etching the m-Si/SiOx surface.
18(a) is data obtained by measuring the average oxidation number of XPS and Si before and after etching the m-Si/SiOx surface.
18(b) shows soft-XAS measurement data before and after etching the m-Si/SiOx surface.
19 is electrochemical evaluation data before and after etching the m-Si/SiOx surface.
20 is a schematic diagram of Me/m-Si/SiOx surface-modified using a metal precursor.
21 is a schematic diagram of Cm-Si/SiOx surface-modified using a carbon precursor.
22 is nitrogen absorption and desorption analysis result data of m-Si/SiOx and Ti-m-Si/SiOx.
23 is low-angle and high-angle XRD measurement data of m-Si/SiOx and Ti-m-Si/SiOx.
24 is CV analysis data of m-Si/SiOx and Ti-m-Si/SiOx.
25 is electrochemical evaluation data of m-Si/SiOx and Ti-m-Si/SiOx.
26 is voltage curve data of m-Si/SiOx and Ti-m-Si/SiOx.
27 is impedance analysis data of m-Si/SiOx and Ti-m-Si/SiOx.
Fig. 28(a) is a schematic diagram of introduction of m-Si/SiOx surface carbon layer.
28(b) shows Si2p XPS measurement data before and after introduction of the m-Si/SiOx surface carbon layer.
28(c) shows low-angle and high-angle XRD measurement data before and after introduction of the m-Si/SiOx surface carbon layer.
28(d) shows nitrogen absorption and desorption curve data before and after introduction of the m-Si/SiOx surface carbon layer.
29 is electrochemical evaluation data before and after introduction of the m-Si/SiOx surface carbon layer.
30 is a schematic diagram of a method for synthesizing MeOx/(C)/m-Si/SiOx material, which is a manufacturing example of the present invention.
31 to 34 are low-angle and high-angle XRD and nitrogen absorption and desorption experimental data of MeOx/(C)/m-Si/SiOx materials.
35 is specific surface area and pore volume measurement data of MeOx/(C)/m-Si/SiOx materials.
36 is a TEM image of the MeOx/(C)/m-Si/SiOx material.
37 is electrochemical evaluation data of MeOx/(C)/m-Si/SiOx materials.
38 is initial coulombic efficiency measurement data of MeOx/(C)/m-Si/SiOx materials.

Hereinafter, the present invention will be described with reference to the accompanying drawings. However, the present invention may be embodied in many different forms and, therefore, is not limited to the embodiments described herein. And in order to clearly explain the present invention in the drawings, parts irrelevant to the description are omitted, and similar reference numerals are attached to similar parts throughout the specification.

Throughout the specification, when a part is said to be "connected (connected, contacted, combined)" with another part, this is not only "directly connected", but also "indirectly connected" with another member in between. "Including cases where In addition, when a part "includes" a certain component, it means that it may further include other components without excluding other components unless otherwise stated.

Terms used in this specification are only used to describe specific 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 "include" or "have" are intended to indicate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, but one or more other features It should be understood that the presence or addition of numbers, steps, operations, components, parts, or combinations thereof is not precluded.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a schematic diagram of a three-phase structure negative active material according to an embodiment of the present invention.

2 is a schematic diagram of a matrix composite constituting the three-phase negative electrode active material of the present invention.

Referring to FIG. 1, the three-phase negative electrode active material of the present invention includes a matrix composite 100 including an active material and a matrix capable of mitigating volume expansion including a plurality of regular nanopores; A first functional layer located in the form of a thin layer on the inner and outer surfaces of the matrix composite 100 structure, increasing the activity of the active material and controlling an inactive layer that can be formed on the surface of the matrix composite 100 ( 200); and a second functional layer 300 positioned in a form filled with an active material in the pores of the matrix composite 600 on which the first functional layer is formed.

At this time, the matrix of the matrix composite 100 is a silicon oxide matrix 400 and the active material located on the matrix is characterized in that the silicon crystal grains 500.

Specifically, the matrix composite 100 is a very ordered meso-porous material, and it is preferable that the ordered nanopores are 2 nm to 50 nm, but are not limited thereto, and the desired active material It can be changed considering the capacity per volume and the degree of suppression of volume expansion during charging and discharging of silicon. Looking closely, as the pores of the matrix composite 100 have a regular and small size, the specific surface area increases, the total volume of the pores increases, the amount of active material filling the pores increases, and the effect of modification by the active material filling the pores increases. In a lithium secondary battery using the three-phase structure negative electrode active material of the present invention, an electrochemical reaction with lithium ions can be maximized. In addition, the ability to mitigate the volume expansion during charging and discharging of silicon and the active materials constituting the negative electrode increases, and a physical buffer space is secured due to uniformly well-developed nanopores, so that the volume expansion of the electrode can be controlled more effectively. do. In addition, silicon corresponds to the active material of the matrix composite 100, and when electrons move through the matrix composite 100, a free path (which has an advantage in the path) is formed in the movement by the volume of the pore, so that the movement of electrons There is a quick advantage.

Looking at the structure of the matrix with reference to FIG. 2, the pores of the silicon oxide matrix 400 formed according to the manufacturing method of the present invention are formed in a very ordered manner, as will be separately described in the manufacturing examples below. In addition, silicon is grown and positioned in the form of crystal grains 500 on the surface of the silicon oxide matrix 400 .

Silicon 500 grown as crystal grains functions as a high-capacity electrode active material in a lithium secondary battery. Therefore, when the active material is used as an anode material of a lithium secondary battery, the more silicon in the active material, the more it can react with lithium, which acts as a factor determining the performance of the battery. At this time, the volume of silicon used as an active material expands 4 to 5 times according to the charging and discharging of the battery, which causes pulverization of the active material and electrical separation from the current collector, resulting in a rapid decrease in energy capacity. At this time, the silicon oxide matrix 400 constituting the composite of the present invention serves to buffer the volume expansion of the silicon crystal grains 500. In addition, the regular pores of the silicon oxide matrix 400 have a large pore volume, so that the volume expansion of the electrode can be more effectively controlled by securing a physical buffer space in addition to the role of buffering the volume expansion of the silicon crystal grains 500 described above. In addition, these regular pores have a large specific surface area, so that the electrochemical reaction with lithium ions can be maximized.

Next, referring to FIG. 1 again, the first functional layer 200 is different from the material of the matrix composite 100 and the second functional layer 300 and includes carbon, metal, or metal oxide. do.

In addition, the metal or the metal of the metal oxide is characterized in that it includes at least one kind of metal selected from the group consisting of Ti, Sn, Ni, Mn, Co, Cu, Mo and Fe.

Specifically, the first functional layer 200 is located on the surface of the matrix composite 100 and covers the entire outer surface of the outer structure and the outer surface of the internal structure forming the pores of the matrix composite 100 as if coating. formed in a way Formed as a thin layer, it serves to separate the matrix composite 100 and the second functional layer 300, and also may be formed naturally on the surface of the matrix composite 100, such as a silicon dioxide (SiO2) oxide film. The formation of the inactive layer can be controlled and prevented, and in forming the silicon crystal grains 500 on the surface of the silicon oxide matrix 400, the reduction of silicon is promoted to increase the coulombic efficiency of the negative electrode active material and increase the reversible capacity. do. In addition, when the first functional layer 200 includes a metal or a metal oxide, it additionally serves to increase conductivity. Here, the first functional layer 200 capable of performing the aforementioned role may be formed by including an active material, and in this case, the first functional layer 200 may also serve as an active layer.

Since the material of the first functional layer 200 serves to separate the matrix composite 100 and the second functional layer 300, the material of the matrix composite 100 and the second functional layer 300 It is characterized by being different from

Carbon, which can be used as a material of the first functional layer 200, prevents and controls the formation of an inactive layer formed on the surface of the silicon oxide matrix 400, as mentioned above, and forms the silicon crystal grains 500. Si plays a role in accelerating the reduction of silicon.

A manufacturing method of forming the first functional layer 200 as a carbon layer will be separately described below.

In addition, in the metal or metal oxide that can be used as the material of the first functional layer 200, the metal prevents and controls the formation of the inactive layer formed on the surface of the silicon oxide matrix 400 as mentioned above, When the silicon crystal grains 500 are formed, they may include all metals that serve to promote reduction of silicon, and at least one selected from the group consisting of Ti, Sn, Ni, Mn, Co, Cu, Mo, and Fe mentioned above. It is not limited to the above metals.

A manufacturing method of forming the first functional layer 200 of metal or metal oxide will be separately described below.

Next, referring to FIG. 1 again, the second functional layer 300 is different from the material of the first functional layer 200 and includes carbon, silicon, metal, or metal oxide that can be used as an active material of a secondary battery. characterized by

At this time, the metal or the metal of the metal oxide is characterized in that it includes at least one kind of metal selected from the group consisting of Ti, Sn, Ni, Mn, Co, Cu, Mo and Fe.

Specifically, the second functional layer 300 is formed on the matrix composite 100 coated with the first functional layer 200, and is formed in such a way as to fill internal pores of the matrix composite 100. do. The degree of filling the pores is determined in consideration of the advantages obtained by introducing the second functional layer 300 and the advantages of the regular nanopores of the matrix composite 100. The second functional layer 300 functions to solve the opposite effect of reducing the capacity per unit volume as the matrix composite 100 has very ordered and small nanopores. Considering the secondary battery to which the three-phase structure negative electrode active material of the present invention is used, the capacity per volume of the secondary battery corresponds to a very important factor in determining the performance of the secondary battery according to the miniaturization trend of electronic devices. Therefore, as mentioned above, the second functional layer 300 serves to compensate for the problem of reducing capacity per volume that occurs along with the advantages of the very regular and small nanopores of the matrix composite 100. As the active material is introduced into the second functional layer 300, when the three-phase negative electrode active material of the present invention is used as a secondary battery, it enables additional reaction with lithium ions to increase the coulombic efficiency and increase the stability of the electrode depending on the specific material, thereby increasing the lifespan. characteristics and high reversible capacity. As mentioned above, the role of the second functional layer 300 may vary depending on the purpose of modification required to improve the performance of the lithium secondary battery to be used in the present invention, including supplementing the capacity per volume. As will be discussed separately in the experimental example below, when the second functional layer 300 is introduced, the overall capacity per volume of the three-phase negative electrode active material is improved.

The material of the second functional layer 300 is different from the material of the first functional layer 200 and may include carbon (graphite), silicon, metal, or metal oxide that can be used as an active material of a lithium secondary battery. In addition, the second functional layer 300 is not limited to an active material according to the purpose of modification of the present invention, and may include materials having other functions. The purpose of modification here may be to improve the capacity per volume mentioned above, and also to exhibit the inherent electrical characteristics of the second functional layer 300. However, this corresponds to an example and should be understood as a concept including the purpose of reforming that can be expected to improve the performance of a lithium secondary battery to which the present invention will be used. In this case, when the material of the second functional layer 300 is a metal or a metal oxide, the metal may include at least one metal selected from the group consisting of Ti, Sn, Ni, Mn, Co, Cu, Mo, and Fe. However, it is not limited thereto, and as mentioned above, various materials may be used as the material of the second functional layer 300 according to the purpose of modification.

Next, a method for manufacturing a three-phase negative electrode active material according to an embodiment of the present invention will be described with reference to FIGS. 3 to 6 .

Referring to FIG. 3 , a method for manufacturing a three-phase negative electrode active material according to the present invention includes forming a matrix composite (S100); forming a first functional layer on the inner and outer surfaces of the matrix composite structure (S200); and forming a second functional layer (S300) by filling the pores inside the matrix composite in which the first functional layer is formed with an active material.

Also, referring to FIG. 4, the forming of the matrix composite (S100) includes forming a silicon oxide matrix having regular pores (S110); and forming silicon crystal grains on the silicon oxide matrix (S120).

According to the manufacturing method of the present invention, it is possible to form pores that are very ordered and have a large specific surface area compared to a conventional matrix using silicon oxide. Specific manufacturing examples are separately described below.

Next, referring to FIGS. 5 and 6, in the step of forming the first functional layer (S200), a carbon layer, a metal layer, or a metal oxide layer is formed differently from the materials of the matrix composite and the second functional layer 300. It is characterized in that it comprises the step of forming on the inner and outer surfaces of the matrix composite (100).

At this time, the metal of the metal layer or metal oxide layer is characterized in that it includes at least one kind of metal selected from the group consisting of Ti, Sn, Ni, Mn, Co, Cu, Mo and Fe.

At this time, prior to the description of the method of modifying the surface by forming the carbon layer, metal layer, or metal oxide layer on the surface of the matrix composite 100, looking at another method of modifying the surface of the matrix composite 100, the matrix composite 100 After the composite forming step (S100), a step of etching the surface of the matrix composite 100 may be added. The etching step selectively removes an inactive layer that can be formed naturally, such as a silicon dioxide (SiO2) oxide film, on the surface of the matrix composite 100 by etching, thereby increasing coulombic efficiency, capacity per volume, activity level and electrical characteristics of the material. is to improve

Referring to FIG. 5 , the method for manufacturing a three-phase negative electrode active material according to the present invention is characterized by further comprising forming a carbon layer on the surface of the matrix composite 100 (S210).

Specific manufacturing examples are separately described below.

Referring to FIG. 6, the method of manufacturing a three-phase negative electrode active material according to the present invention includes preparing a silicon oxide matrix having regular pores (S110) and forming a metal layer or metal oxide layer on the silicon oxide matrix 400 (S220). ) and forming silicon crystal grains on the silicon oxide matrix 400 after the forming of the metal layer or metal oxide layer (S220) (S120).

At this time, the metal of the metal layer or the metal oxide layer is characterized in that it includes at least one kind of metal selected from the group consisting of Ti, Sn, Ni, Mn, Co, Cu, Mo and Fe.

Specific manufacturing examples are separately described below.

Next, referring to FIGS. 1 and 3 again, the step of forming the second functional layer (S300) is different from the material of the first functional layer 200, and carbon, silicon, and applying a metal or metal oxide to the surface of the matrix composite 600 on which the first functional layer is formed, and filling the pores of the matrix composite 600 on which the first functional layer is formed with an active material.

Specifically, the surface of the matrix composite 600 on which the first functional layer is formed and the material constituting the second functional layer 300 is inserted into the pores in a precursor state so that phase-change and phase-separation occur in the pores . Precursors and processing methods used depending on the material may be different and may be understood as methods commonly used by those skilled in the art. Specific manufacturing examples are separately described below.

At this time, the metal of the metal or metal oxide is characterized in that it includes at least one kind of metal selected from the group consisting of Ti, Sn, Ni, Mn, Co, Cu, Mo and Fe.

Next, another embodiment of the present invention may include a negative electrode for a lithium secondary battery including the negative electrode active material having a three-phase structure. Here, the negative electrode for a lithium secondary battery may be interpreted as meaning a conventional negative electrode for a lithium secondary battery that can be understood by those skilled in the art of lithium secondary batteries.

Next, another embodiment of the present invention may include a lithium secondary battery including the negative electrode for the lithium secondary battery. Here, the lithium secondary battery may be interpreted as meaning a conventional lithium secondary battery that can be understood by a person skilled in the art of secondary batteries.

Preparation Example 1

Method for manufacturing mesoporous-Si/SiOx (hereinafter referred to as m-Si/SiOx), which is an embodiment of the matrix composite 100

(1) Silicon oxide matrix 400 manufacturing method (m-HSQ manufacturing method)

m-Si/SiOx, which is an example of preparing the silicon oxide matrix 400, is obtained by reducing mesoporous-HSQ (or HSiO1.5) (hereinafter referred to as m-HSQ).

The m-HSQ is prepared by adding a silicon precursor, a surfactant, and a NaCl complex to an acidic solution.

The silicon precursor refers to one that can be commonly used for manufacturing a silicon-based negative electrode active material.

The acidic solution includes, but is not limited to, a solution diluted with HCl.

The surfactant serves as a template (or template) for the silicon oxide matrix having regular nanopores. As the surfactant, a polymer material that forms micelles (or micelles) well is selected. The surfactant serves as a template for the silicon precursor by forming small and uniform micelles through a self-assembly reaction in the acidic solution. The silicon precursor is wrapped around the micelles formed by the surfactant as a template, and accordingly, uniform nanopores may be formed in the silicon oxide matrix 400 thereafter. If the silicon oxide matrix 400 is formed without using the surfactant, bulky, large-sized, and poorly uniform pores are formed.

In this preparation example, P123 (or PEO ₂₀ PPO ₇₀ PEO ₂₀ ) was used, but is not limited thereto, and includes a polymeric material that forms micelles well as described above.

The surfactant is removed through a subsequent washing process.

The NaCl complex refers to a material that can be added or subtracted according to specific process conditions, including NaCl. When the surfactant forms micelles through a self-assembly reaction, NaCl serves to form pores of a more uniform (ordered) and constant size.

Obtain m-HSQ powder through the above process. In the obtained m-HSQ powder, only the silicon oxide matrix 400 from which the surfactant is removed remains through a reduction heat treatment process and a washing process.

(2) Forming silicon crystal grains on the silicon oxide matrix 400 (S120)

When the silicon oxide matrix 400 (m-HSQ) from which the surfactant is removed is subjected to reduction heat treatment at a temperature and process condition of 500 ° C to 700 ° C, H is separated from the m-HSQ to form silicon oxide (SiOx) and oxidize On the surface of the silicon matrix 400, silicon is formed in the form of the silicon crystal grains 500. The degree of generation of the silicon crystal grains 500 may be controlled according to the temperature conditions of the reduction heat treatment.

(3) theorem

When the composite constituting the nanostructured negative electrode active material of the present invention is prepared according to the above process, uniform nanopores are formed in the silicon oxide matrix 400 produced due to the uniform nanopores formed by NaCl and the surfactant, It is possible to obtain the composite in which the degree of silicon crystal grains 500 formed on the silicon oxide matrix 400 is controlled by controlling the reduction heat treatment process conditions.

Experimental example 1

Description of the volume expansion relaxation effect of the m-Si/SiOx composite, which is an embodiment of the present invention

It will be described with reference to FIG. 7 .

The lower image of FIG. 7 is a schematic diagram showing the effect of mitigating volume expansion during charging and discharging of the m-Si/SiOx composite prepared according to Preparation Example 1.

According to FIG. 7, it can be confirmed that the silicon crystal grains 500 expand as the composite is filled. The silicon crystal grains 500 are fixed to the silicon oxide matrix 400 so that the degree of expansion is reduced compared to the case where the silicon crystal grains 500 are not fixed, so that micronization due to cracking of the silicon crystal grains 500 is suppressed and reduced, and also the silicon oxide matrix (400) Due to the pores existing inside, a physical free space remains despite the expansion of the silicon crystal grains 500, so that the problem of volume expansion during charging and discharging of the nanostructured negative electrode including the composite can be expected to be improved. there is.

Experimental Example 2

Low-angle and high-angle XRD measurement experiments of m-Si/SiOx with different m-HSQ and heat treatment temperatures

8 is low-angle and high-angle XRD data of m-Si/SiOx with different m-HSQ and heat treatment temperatures.

Referring to FIG. 8, it can be seen that all samples have uniform nanopores, and as the heat treatment temperature increases, the degree of crystallinity of silicon becomes stronger through an increase in the intensity of the Y-axis.

Experimental Example 3

Pore volume and specific surface area measurement experiments of m-Si/SiOx with different m-HSQ and heat treatment temperatures.

9 is nitrogen absorption and desorption analysis curve data of m-Si/SiOx at different m-HSQ and heat treatment temperatures.

Figure 10 is the specific surface area and pore volume measurement data of m-Si/SiOx with different m-HSQ and heat treatment temperatures.

Referring to FIG. 9, the blue curve is m-HSQ, the red curve is m-HSQ at 700°C, the purple curve is m-HSQ at 900°C, and the yellow curve is m-HSQ at 1100°C.

According to the curve data of FIG. 9, it can be seen that the pore size and volume decrease as the temperature increases during the reduction treatment from m-HSQ to m-Si/SiOx, and mesopores are well developed in all samples at the experimental condition temperature. can confirm that it is.

Referring to the measurement data of FIG. 10, it can be seen that the pore volume and specific surface area decrease as the temperature increases during the reduction treatment.

Through the data results of FIG. 9 and FIG. 10, it can be seen that the size and volume of pores decrease and the specific surface area decreases according to the reduction treatment temperature. Through this, it can be confirmed that the nanostructured negative electrode active material of the present invention can design a desired volume expansion relief effect and a pore volume that meets the capacity per volume by controlling the reduction treatment temperature.

Experimental Example 4

TEM confirmation of m-HSQ and m-Si/SiOx

TEM images of m-HSQ and m-Si/SiOx can be confirmed with reference to FIG. 11 .

(a) to (c) are TEM images of m-HSQ, and (d) to (f) are TEM images of m-Si/SiOx. Through the TEM image, it can be confirmed that uniform nanopores are formed in both m-HSQ and m-Si / SiOx prepared according to Preparation Example 1, and crystalline Si is developed inside the pores in m-Si / SiOx. there is.

Experimental Example 5

FTIR analysis of m-Si/SiOx with different m-HSQ and heat treatment temperatures

Referring to FIG. 12, it can be confirmed that the reduction from m-HSQ to m-Si/SiOx was well performed at the temperature of the experimental conditions, as the Si-H bond and the O-Si-H bond disappeared in m-Si/SiOx. .

Experimental Example 6

Electrochemical evaluation of m-Si/SiOx and Si NPs with different m-HSQ and heat treatment temperatures

Referring to FIG. 13, Si NPs initially exhibit very high capacitance but have very poor lifetime characteristics, whereas m-Si/SiOx exhibit excellent lifetime characteristics. In particular, the sample reduced at 900 degrees showed the highest reversible capacity. On the other hand, in the case of the sample subjected to reduction treatment at the highest temperature of 1100 degrees, it can be seen that the reversible capacity is very low.

Experimental Example 7

Evaluation of rate characteristics of m-Si/SiOx and Si NPs with different m-HSQ and heat treatment temperatures

Referring to FIG. 14, it can be seen that the m-Si/SiOx 700 and 900 ° C samples exhibit excellent rate characteristics compared to the Si NP.

Experimental Example 8

Impedance evaluation of m-Si/SiOx 900℃ and Si NP

Referring to FIG. 15, it can be seen that m-Si/SiOx shows a lower resistance value at 900° C. than Si NP in the initial state and after 50 cycles.

Experimental Example 9

Dilatometer analysis of m-Si/SiOx and commercial SiOx

Referring to FIG. 16, it is confirmed that commercial Si / SiOx returns to about 120% after a volume change of about 200% during charging and discharging. On the other hand, in the case of m-Si / SiOx prepared according to the above preparation example, it can be seen that the volume change rate is within 10% even after a volume change of about 13% and a return of about 5%, and subsequent charge and discharge.

Experimental Example 10

Experiment to confirm improvement effect according to etching treatment

Referring to FIG. 17, (a) of FIG. 17 is a schematic view of the m-Si/SiOx surface oxide layer etching process.

17(b) is a TEM image before etching the m-Si/SiOx surface.

17(c) is a TEM image after etching the m-Si/SiOx surface.

17(d) shows low-angle and high-angle XRD images before and after etching the m-Si/SiOx surface.

Figure 17(e) shows nitrogen adsorption and desorption curves before and after etching the m-Si/SiOx surface.

Through the above experimental results, it can be confirmed that the material surface is roughened by etching, but uniform nanopores are well maintained even after etching.

Experimental Example 11

XPS before and after etching the m-Si/SiOx surface, average oxidation number of Si and soft-XAS measurements

18(a) is data obtained by measuring the average oxidation number of XPS and Si before and after etching the m-Si/SiOx surface.

18(b) shows soft-XAS measurement data before and after etching the m-Si/SiOx surface.

Through this, it was confirmed that the silicon dioxide oxide films on the surface were removed after etching, and as a result, it was confirmed that the oxidation number of silicon was reduced. Through this, it can be confirmed that etching is an effective surface modification method.

Experimental Example 12

Electrochemical evaluation before and after etching the m-Si/SiOx surface

Referring to FIG. 19, it can be confirmed through the graph data (a) that the reversible capacitance increases after surface etching, and it can be confirmed through the voltage curve of (b) that this is due to the increased activity of silicon.

Preparation Example 2

A method for producing a three-phase structure negative electrode active material in which a surface is modified by forming a carbon layer, a metal layer, or a metal oxide layer.

(1) Method for manufacturing a three-phase negative electrode active material by forming a carbon layer to modify the surface

It will be described with reference to Figs. 5 and 21. Referring to FIG. 5 , after the silicon oxide matrix forming step (S110) and the silicon crystal grain forming step (S120), the surface is modified in the order of forming the carbon layer.

The silicon oxide matrix forming step (S110) and the silicon crystal grain forming step (S120) follow Preparation Example 1 above. In the case of forming the carbon layer, as mentioned above, the formation of a naturally occurring inert silicon dioxide oxide film on the surface of the composite prepared according to Preparation Example 1 is suppressed, and SiOx is reduced to Si while carbon in the carbon layer is oxidized. promote the role of

Looking at a specific manufacturing example with reference to Figure 21, a carbon precursor is applied to the surface of the prepared composite. In this preparation example, 2,3-Dihydroxynaphthalene (hereinafter, DN) was used. In the case of using the DN, since a carbon layer is formed thinly, it is preferable but not limited thereto, and if a carbon layer can be formed on the surface of the m-Si/SiOx composite, it is considered to be included in the carbon precursor. DN is applied to the surface of the prepared composite, and dehydration is performed at about 373K. Accordingly, DN is chemisorbed and coats the m-Si/SiOx composite. Next, a carbonization process is performed on the DN-coated composite. The carbonization process is performed at a high temperature of about 1173K. A thin carbon layer is formed through the carbonization process, and at this time, the carbon is oxidized through the thermal reaction of the carbonization process and SiOx is additionally reduced.

(2) Method of manufacturing a three-phase negative electrode active material by forming a metal layer or a metal oxide layer to modify the surface

A description will be made with reference to Figs. 6 and 20.

Referring to FIG. 6, the method of modifying the surface by forming a metal layer or metal oxide layer is slightly different from the method of modifying the surface by forming the carbon layer. After forming the silicon oxide matrix (S110), forming a metal layer or metal oxide layer (S220) is performed, followed by forming silicon crystal grains (S120).

Specifically, with reference to FIG. 20 , a metal impregnating process is performed using a metal precursor on the silicon oxide matrix 400 prepared according to (1) the silicon oxide matrix manufacturing method of Preparation Example 1. Through the metal impregnation process, a metal precursor is applied to the outer surface of the internal structure constituting the surface of the silicon oxide matrix 400 and the outer surface of the external structure. Thereafter, a reduction thermal reaction is performed on the silicon oxide matrix 400 coated with the metal precursor in an atmosphere of hydrogen and argon. Through the reduction heat reaction, the metal precursor is coated on the silicon oxide matrix 400 in the form of a metal or metal oxide. In addition, through the reduction heat reaction process, the silicon crystal grains 500 from SiOx are formed between the silicon oxide matrix 400 and the coated metal layer or metal oxide layer and at a position corresponding to the silicon oxide matrix 400 at the same time. formed by reduction.

Looking at specific manufacturing conditions with reference to FIG. 20, the metal precursor is a nitrided or sulfurized metal powder, which is commonly used in an impregnation process, and should be interpreted as including a commercially available powdered metal precursor. In this preparation example, a Ti, Sn or Fe precursor was used. However, it is not limited thereto. The reduction heat reaction was carried out in a 5% hydrogen and 95% argon atmosphere and at a temperature of 300 ° C to 800 ° C in this preparation example.

Experimental Example 13

Analysis of nitrogen adsorption and desorption of m-Si/SiOx and Ti-m-Si/SiOx

22 is nitrogen absorption and desorption analysis result data of Ti-m-Si/SiOx with different m-Si/SiOx and Ti contents.

According to FIG. 22, the Ti content performed in this experimental example did not show any tendency according to the Ti content, and all samples had uniform nanopores within a certain range, and the specific surface area and pore volume did not change significantly even after surface modification. sound could be ascertained.

Experimental Example 14

Low angle high angle XRD measurement of m-Si/SiOx and Ti-m-Si/SiOx

23 is low-angle and high-angle XRD measurement data of m-Si/SiOx and Ti-m-Si/SiOx.

Referring to FIG. 23, it was confirmed that all samples had a well-ordered nanostructure in the Ti content performed in this experimental example, and crystalline Si appeared on XRD after surface modification.

Experimental Example 15

Electrochemical evaluation of m-Si/SiOx and Ti-m-Si/SiOx

24 is CV analysis data of m-Si/SiOx and Ti-m-Si/SiOx.

Referring to FIG. 24, it can be seen that the activity of Si increased after surface modification according to the increase in Ti content.

Experimental Example 16

Electrochemical evaluation of m-Si/SiOx and Ti-m-Si/SiOx

25 is electrochemical evaluation data of m-Si/SiOx and Ti-m-Si/SiOx.

Referring to FIG. 25 , it can be confirmed that the reversible capacity almost doubled after surface modification and the initial Coulombic efficiency was greatly improved.

Experimental Example 17

Voltage measurement of m-Si/SiOx and Ti-m-Si/SiOx

26 is voltage curve data of m-Si/SiOx and Ti-m-Si/SiOx.

Referring to FIG. 26, it can be seen that after surface modification, a voltage flat surface corresponding to the operating voltage of Si clearly developed.

Experimental Example 18

Impedance analysis of m-Si/SiOx and Ti-m-Si/SiOx

27 is impedance analysis data of m-Si/SiOx and Ti-m-Si/SiOx.

Referring to FIG. 27, it can be confirmed that the material shows a low resistance value after surface modification.

Experimental Example 19

Measurement of m-Si/SiOx and C-coated m-Si/SiOx characteristics after introduction of carbon layer

Fig. 28(a) is a schematic diagram of introduction of m-Si/SiOx surface carbon layer.

28(b) shows Si2p XPS measurement data before and after introduction of the m-Si/SiOx surface carbon layer.

28(c) shows low-angle and high-angle XRD measurement data before and after introduction of the m-Si/SiOx surface carbon layer.

28(d) shows nitrogen absorption and desorption curve data before and after introduction of the m-Si/SiOx surface carbon layer.

Combining the measurement data, it can be confirmed that uniform nanopores are well maintained even after the introduction of the surface carbon layer, as in the case of surface modification with Ti, and the XPS measurement data show that the activity of Si is increased through carbon thermal reaction. You can check.

Experimental Example 20

Electrochemical evaluation before and after introduction of m-Si/SiOx surface carbon layer

29 is electrochemical evaluation data before and after introduction of the m-Si/SiOx surface carbon layer.

Referring to FIG. 29 , it can be confirmed through the voltage curve that the reversible capacity greatly increased after the introduction of the surface carbon layer and the separation of Si occurred more easily after the introduction of the carbon layer.

Preparation Example 3

Method for manufacturing a three-phase structure anode active material with surface modification by forming Metal Oxide or Metal/(C)/m-Si/SiOx (hereinafter, MeOx/(C)/m-Si/SiOx)

30 is a schematic diagram of a method for synthesizing MeOx/(C)/m-Si/SiOx.

Referring to FIG. 30 , the matrix composite 600 having the first functional layer according to Manufacturing Example 1 or 2 is impregnated with a carbon precursor, a metal precursor, or a metal oxide precursor to form a matrix composite having the first functional layer. An example of manufacturing the second functional layer 300 may be confirmed by uniformly applying the layer 600 to the surface and pores and performing heat treatment. Here, the carbon precursor, the metal precursor, or the metal oxide precursor should be interpreted as meaning including a precursor that can be commonly used by a person skilled in the art to prepare an active material. In addition, the impregnation process or the heat treatment process is not limited thereto, and in order to apply the precursors to the matrix composite 600 on which the first functional layer is formed, a person skilled in the art of the present invention can typically use in preparing an active material It should be interpreted as meaning including fairness.

Experimental Example 21

Low- and high-angle XRD and nitrogen adsorption and desorption experiments of MeOx/(C)/m-Si/SiOx materials

31 to 34 are data for low-angle and high-angle XRD and nitrogen absorption and desorption experiments of MeOx/(C)/m-Si/SiOx materials.

31 to 34, when the second functional layer 300 is composed of FeOx or SnOx, it can be confirmed that as the content of FeOx or SnOx increases, the nanopores are filled and the specific surface area and pores are reduced, and XRD Through this, it can be confirmed that the metal and metal oxide are well developed.

Experimental Example 22

Measurement of specific surface area and pore volume of MeOx/(C)/m-Si/SiOx materials

35 is the result data for the specific surface area and pore volume measurement experiments of MeOx/(C)/m-Si/SiOx materials.

Referring to FIG. 35 , when the second functional layer 300 is composed of FeOx or SnOx, it can be confirmed that as the content of FeOx or SnOx increases, the nanopores are filled and the specific surface area and pores are reduced.

Experimental Example 23

TEM confirmation experiment of MeOx/(C)/m-Si/SiOx materials

36 is a TEM image of MeOx/(C)/m-Si/SiOx materials.

Referring to FIG. 36, it can be seen that the metal layer and the metal oxide layer, which are the second functional layer 300, are developed in the nanopore to form a well-aligned structure.

Experimental Example 24

Electrochemical evaluation of MeOx/(C)/m-Si/SiOx materials

37 is electrochemical evaluation data of MeOx/(C)/m-Si/SiOx materials.

Referring to FIG. 37, it can be confirmed that the SiOx-based three-phase composite anode active material synthesized according to the above manufacturing method exhibits stable life characteristics and high reversible capacity.

Experimental Example 25

Initial coulombic efficiency measurement experiment of MeOx/(C)/m-Si/SiOx materials

38 is initial coulombic efficiency measurement data of MeOx/(C)/m-Si/SiOx materials.

Referring to FIG. 38, it can be seen that the coulombic efficiency is greatly improved in the SiOx-based three-phase composite negative electrode active material synthesized according to the above manufacturing method.

The above description of the present invention is for illustrative purposes, and those skilled in the art can understand that it can be easily modified into other specific forms without changing the technical spirit or essential features of the present invention. will be. Therefore, the embodiments described above should be understood as illustrative in all respects and not limiting. For example, each component described as a single type may be implemented in a distributed manner, and similarly, components described as distributed may be implemented in a combined form.

The scope of the present invention is indicated by the following claims, and all changes or modifications derived from the meaning and scope of the claims and equivalent concepts should be interpreted as being included in the scope of the present invention.

100: matrix complex
200: first functional layer
300: second functional layer
400: silicon oxide matrix
500: silicon crystal grains
600: matrix composite on which the first functional layer is formed
700: matrix composite with a second functional layer formed thereon

Claims (14)

a matrix composite comprising an active material and a matrix capable of mitigating volume expansion including a plurality of regular nanopores;
a first functional layer located in the form of a thin layer on the inner and outer surfaces of the matrix composite structure to increase the activity of the active material and to control an inactive layer that may be formed on the surface of the matrix composite; and
A three-phase structure negative electrode active material, characterized in that it comprises a second functional layer positioned in a form filled with an active material in the pores inside the matrix composite in which the first functional layer is formed. According to claim 1,
The three-phase structure negative electrode active material, characterized in that the matrix of the matrix composite is a silicon oxide matrix, and the active material located on the matrix is a silicon crystal grain. According to claim 1,
The first functional layer is different from the material of the matrix composite and the second functional layer and includes carbon, metal or metal oxide. According to claim 3,
The metal or the metal of the metal oxide includes at least one metal selected from the group consisting of Ti, Sn, Ni, Mn, Co, Cu, Mo, and Fe. According to claim 1,
The active material of the second functional layer is different from the material of the first functional layer and includes carbon, silicon, metal or metal oxide that can be used as an active material of a secondary battery. According to claim 5,
The metal or the metal of the metal oxide includes at least one metal selected from the group consisting of Ti, Sn, Ni, Mn, Co, Cu, Mo, and Fe. forming a matrix complex;
forming a first functional layer on inner and outer surfaces of the matrix composite structure; and
and forming a second functional layer by filling the pores of the matrix composite in which the first functional layer is formed with an active material. According to claim 7,
Forming the matrix composite may include forming a silicon oxide matrix having regular pores; and
A method for producing a three-phase negative electrode active material comprising the step of forming silicon crystal grains on the silicon oxide matrix. According to claim 7,
The step of forming the first functional layer includes forming a carbon layer, a metal layer, or a metal oxide layer on the inner and outer surfaces of the matrix composite, different from the materials of the matrix composite and the second functional layer. A method for producing a three-phase structure negative active material. According to claim 9,
The metal of the metal layer or metal oxide layer comprises at least one metal selected from the group consisting of Ti, Sn, Ni, Mn, Co, Cu, Mo, and Fe. According to claim 7,
In the step of forming the second functional layer, carbon, silicon, metal, or metal oxide, which is different from the material of the first functional layer and can be used as an active material of a secondary battery, is applied to pores inside the matrix composite in which the first functional layer is formed. A method for producing a three-phase structure negative electrode active material comprising the step of filling and forming an active material. According to claim 11,
The metal of the metal or metal oxide is a three-phase structure negative electrode active material manufacturing method, characterized in that it comprises at least one or more metals selected from the group consisting of Ti, Sn, Ni, Mn, Co, Cu, Mo and Fe. An anode for a lithium secondary battery comprising the three-phase structure anode active material of claim 1. A lithium secondary battery comprising the anode active material for a lithium secondary battery of claim 13.

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