Multi-component silicon composite negative electrode material for lithium secondary battery and manufacturing method thereof

Abstract

An embodiment of the present invention provides a silicon composite negative electrode material. In a negative electrode material for a lithium secondary battery according to an embodiment of the present invention, a multi-component silicide matrix surrounding silicon nanoparticles has a cushioning effect when silicon expands in volume. In addition, copper (Cu) is added to the multi-component silicide matrix, and thus long-life characteristics may be improved due to stress relaxation in the matrix phase and improved electrical conductivity. Moreover, an optimal ratio between copper (Cu) and boron (B) is set to achieve stress relaxation through improvement of strength and ductility properties, thereby solving the problem of particle destruction in a silicon negative electrode material during a charge-discharge cycle.

Description

Multi-component silicon composite negative electrode material for lithium secondary batteries and method for manufacturing the same

[0001] The present invention relates to a silicon negative electrode material and a method for manufacturing the same.

[0002] With the increasing use of portable electronic devices and the expansion of the electric vehicle market, demand for energy storage devices is rapidly increasing. Among these, lithium secondary batteries are attracting attention due to their high operating voltage (average 3.7 V), high energy density (200 Wh / kg), and high energy density (600 Wh / L).

[0003] In the case of graphite, which is currently the most commercialized anode material in lithium secondary batteries, silicon, which shows a large charge / discharge capacity, is attracting attention as a next-generation anode material due to its low theoretical capacity (LiC6372mAh / g). However, the theoretical volume change rate due to the intercalation of lithium ions during charge / discharge cycles is 110% for carbon, while silicon (Li) is 110%. 15 In the case of Si4), a volume change of 280% occurs at room temperature.

[0004] These volume changes cause cracking and breakage of silicon particles, increasing the surface area of ​​the active material particles. This, in turn, leads to the destruction and regeneration of the solid electrolyte interphase (SEI) layer formed on the surface, resulting in reduced cycle-to-cycle efficiency and rapid capacity degradation. Therefore, various studies are being conducted to accommodate and suppress these large volume changes in silicon.

[0005] One is to reduce the absolute volume expansion rate during expansion by reducing the silicon particle size to the nanoscale, thereby alleviating the physical stress caused by the volume change. Second, there is a method of forming silicide by adding a conductive metal element that does not react with lithium, and using the formed silicide matrix to alleviate the volume expansion of silicon. Another method is to manufacture porous silicon. Porous silicon has the advantage of not only buffering the volume expansion with pores, but also increasing the contact area between the electrolyte and the electrode, which allows for rapid diffusion of lithium ions. However, it is difficult to control the specific surface area of ​​silicon during etching, so it is difficult to ensure the reliability of the powder, and there are problems such as generating a large amount of wastewater during the manufacturing process. Various methods are being attempted to improve the properties of silicon materials, such as controlling the shape and particle size of the material, or alloying, oxidizing, and composites with carbon materials.

[0006] Among these, silicon anode materials using a silicide matrix are manufactured by selecting a composition and alloy system so that when the molten alloy in the melting furnace cools, a powder with multiple phases is formed due to the difference in melting points and mixing enthalpies of each element and alloy, and the silicon phase and the silicide matrix phase are phase separated when the molten metal is cooled.

[0007] In the case of ternary and quaternary alloy powders such as Si-Al-Ni or Si-Al-Fe-Ni, the silicon phase is surrounded by a silicate matrix phase, and although these ternary and quaternary systems show good characteristics in terms of initial discharge capacity and efficiency, capacity decreases as the cycle progresses, making it difficult to secure good cycle life stability. This is because the surrounding silicate matrix phase does not sufficiently buffer the volume change of the silicon phase inside the powder.

[0008] In order to commercialize silicon alloy anode materials, it is important to design a microstructure in which the silicide matrix phase can sufficiently buffer the volume expansion of the silicon phase.

[0009] <Prior Art Document> Republic of Korea Patent Publication No. 10-2023-0096191

[0010] The technical problem to be achieved by the present invention is to provide a multi-component silicon composite negative electrode material for a lithium secondary battery.

[0011] The technical problems to be solved by the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned can be clearly understood by a person having ordinary skill in the technical field to which the present invention belongs from the description below.

[0012] In order to achieve the above technical task, one embodiment of the present invention provides a silicon composite negative electrode material.

[0013] According to one embodiment of the present invention, the silicon composite anode material may include a multicomponent silicide matrix containing aluminum (Al), nickel (Ni), boron (B), copper (Cu), and silicon (Si); and crystalline silicon nanoparticles impregnated within the silicon matrix.

[0014] In addition, according to one embodiment of the present invention, the multi-component silicide matrix is ​​characterized in that it is composed of a material represented by the following chemical formula 1:

[0015] [Chemical Formula 1]

[0016] Si a (Al b Ni c Cu d B e )

[0017] The above a is a real number between 0.24 and 0.75, b is a real number between 0.18 and 0.33, c is a real number between 0.03 and 0.2, d is a real number between 0.03 and 0.13, and e is a real number between 0.01 and 0.1.

[0018] Additionally, according to one embodiment of the present invention, the aluminum (Al) content may be 18 atomic% or more and 33 atomic% or less relative to the total content of the entire multicomponent silicon matrix.

[0019] Additionally, according to one embodiment of the present invention, the nickel (Ni) content may be 3 atomic% or more and 20 atomic% or less relative to the total content of the entire multi-component silicon matrix.

[0020] Additionally, according to one embodiment of the present invention, the boron (B) content may be 1 atomic% or more and 10 atomic% or less relative to the total content of the entire multicomponent silicon matrix.

[0021] Additionally, according to one embodiment of the present invention, the copper (Cu) content may be 3 atomic% or more and 13 atomic% or less relative to the total content of the entire multi-component silicon matrix.

[0022] Additionally, according to one embodiment of the present invention, the sum of the atomic % of Cu and the atomic % of B may be 7 atomic % or more and 12 atomic % or less.

[0023] In addition, according to one embodiment of the present invention, the ratio of Cu atom% / (Cu atom% + B atom%) with respect to the content of copper (Cu) and boron (B) may be 71% or more and 83% or less.

[0024] In addition, according to one embodiment of the present invention, the silicon atomic % of the silicon composite negative electrode material is characterized by containing the aluminum, nickel, boron and copper described above, and the remainder.

[0025] In order to achieve the above technical task, another embodiment of the present invention provides a method for manufacturing a silicon composite negative electrode material.

[0026] The method for manufacturing the silicon composite anode material according to one embodiment of the present invention may include the steps of: introducing aluminum (Al), nickel (Ni), boron (B), copper (Cu), and silicon (Si) metals into a crucible at a specific mixing ratio and then melting them to produce a melt; and the steps of rapidly cooling the melt with water sprayed at high pressure and then classifying the powder to produce a silicon anode material powder in which crystalline silicon is impregnated inside a multi-component silicide matrix.

[0027] In addition, according to one embodiment of the present invention, in the step of manufacturing the melt,

[0028] The content of the aluminum (Al) is 18 atomic% or more and 33 atomic% or less relative to the entire melt, the content of the nickel (Ni) is 3 atomic% or more and 20 atomic% or less relative to the entire melt, the content of the boron (B) is 1 atomic% or more and 10 atomic% or less relative to the entire melt, and the content of the copper (Cu) is 3 atomic% or more and 13 atomic% or less relative to the entire melt, and the remainder may be silicon.

[0029] In addition, according to one embodiment of the present invention, in the step of manufacturing a silicon anode material powder in which crystalline silicon is impregnated inside the multi-component silicide matrix, the rapid cooling rate is 10 5 K / Sec to 10 7 It could be K / Sec.

[0030] In addition, according to another embodiment of the present invention, the silicon composite anode material may include a multicomponent silicide matrix including aluminum (Al), nickel (Ni), boron (B), copper (Cu), and silicon (Si), wherein the difference in the size of the atomic radius of each of the aluminum (Al), nickel (Ni), boron (B), copper (Cu), and silicon (Si) is 10% or more; and crystalline silicon nanoparticles impregnated inside the silicon matrix.

[0031] In addition, according to another embodiment of the present invention, the silicon composite negative electrode material may be composed of a material represented by the following chemical formula 1.

[0032] A silicon composite anode material characterized by comprising crystalline silicon nanoparticles impregnated within the silicon matrix:

[0033] [Chemical Formula 1]

[0034] Si a (Al b Ni c Cu d B e )

[0035] The above a is a real number between 0.24 and 0.75, b is a real number between 0.18 and 0.33, c is a real number between 0.03 and 0.2, d is a real number between 0.03 and 0.13, and e is a real number between 0.01 and 0.1.

[0036] In order to achieve the above technical task, another embodiment of the present invention provides a silicon negative electrode active material.

[0037] The content of the above silicon composite negative electrode material may be 5 wt% to 10 wt% based on the total silicon negative electrode active material, and the content of the graphite may be 90 wt% to 95 wt% based on the total silicon negative electrode active material.

[0038] According to one embodiment of the present invention, a negative electrode material for a lithium secondary battery has a multi-component silicide matrix surrounding silicon nanoparticles, which has a buffering effect when the volume of silicon expands.

[0039] In addition, by adding copper (Cu) to the multicomponent silicide matrix, the long-life characteristics can be improved due to the stress relaxation of the matrix and the improvement of electrical conductivity, and by setting the optimal ratio of copper (Cu) and boron (B), stress relaxation is achieved through the improvement of strength and ductility characteristics, thereby solving the problem of particle destruction of the silicon anode material during the charge and discharge cycle.

[0040] The effects of the present invention are not limited to the effects described above, and should be understood to include all effects that can be inferred from the detailed description of the present invention or the composition of the invention described in the claims.

[0041] Figure 1 is a schematic diagram illustrating a silicon composite cathode material according to one embodiment of the present invention.

[0042] Figure 2 is a cross-sectional and elemental analysis image of a silicon anode material according to one embodiment of the present invention.

[0043] Figure 3 is an XRD graph of a silicon anode material according to an embodiment of the present invention.

[0044] Figure 4 is an FE-SEM image showing the evaluation results of maintaining the shape before and after the silicon anode material cycle according to one embodiment of the present invention.

[0045] Figure 5 is an exemplary diagram showing the electrical conductivity of a silicon anode material according to one embodiment of the present invention.

[0046] Figure 6 is an exemplary diagram showing the single electrode 1-cycle characteristics of one embodiment and a comparative example of the present invention.

[0047] Figure 7 is a graph evaluating the cycle characteristics of a single electrode and a mixed electrode of one embodiment of the present invention.

[0048] Hereinafter, the present invention will be described with reference to the attached drawings. However, the present invention can be implemented in various different forms and is therefore not limited to the embodiments described herein. In the drawings, irrelevant parts have been omitted for clarity of description, and similar parts have been designated with similar reference numerals throughout the specification.

[0049] Throughout the specification, when a part is said to be "connected (connected, contacted, or coupled)" to another part, this includes not only cases where it is "directly connected," but also cases where it is "indirectly connected" with another member in between. Furthermore, when a part is said to "include" a component, this does not mean that it excludes other components, but rather that it may include other components, unless otherwise specifically stated.

[0050] The terminology used herein is merely used to describe specific embodiments and is not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this specification, it should be understood that the terms "comprises" or "has" indicate the presence of a feature, number, step, operation, component, part, or combination thereof described in the specification, but do not exclude in advance the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0051]

[0052] Below, the present invention will be described with reference to the drawings presented in this specification. Note that the drawings may be exaggerated to illustrate the features of the present invention. In such cases, it is preferable to interpret them in light of the overall intent of this specification.

[0053]

[0054] A silicon composite cathode material according to one embodiment of the present invention is described.

[0055] Figure 1 is a schematic diagram illustrating a silicon composite cathode material according to one embodiment of the present invention.

[0056] A silicon composite anode material according to one embodiment of the present invention may include a multicomponent silicide matrix containing aluminum (Al), nickel (Ni), boron (B), copper (Cu), and silicon (Si); and crystalline silicon nanoparticles impregnated within the silicon matrix.

[0057] The present invention is characterized by including a multi-component silicate matrix (100).

[0058] At this time, the multi-component silicate matrix may be composed of a material represented by the following chemical formula 1.

[0059] [Chemical Formula 1]

[0060] Si a (Al b Ni c Cu d B e )

[0061] The above a is a real number between 0.24 and 0.75, b is a real number between 0.18 and 0.33, c is a real number between 0.03 and 0.2, d is a real number between 0.03 and 0.13, and e is a real number between 0.01 and 0.1.

[0062] As described in the background of the invention, conventional multi-component silicide compounds are composed of a structure in which a silicide matrix phase surrounds a silicon phase in the case of ternary or quaternary alloy powders such as Si-Al-Ni or Si-Al-Fe-Ni. However, in the case of these ternary or quaternary systems, there was a problem in that capacity deterioration occurred over the cycle, making it impossible to secure good cycle life stability. The reason for this was that the surrounding silicide matrix phase did not sufficiently buffer the volume change of the silicon phase inside the powder.

[0063] The silicate matrix of the present invention is characterized by being composed of five components so as to solve the above-described problem.

[0064] At this time, the difference in the atomic radius of each element included in the silicate matrix of the present invention must be 10% or more.

[0065] At this time, the size of each atomic radius can be specifically Si (atomic radius: 117Å), Al (atomic radius: 143Å), Ni (atomic radius: 125Å), B (atomic radius: 88Å), and Cu (atomic radius 128Å).

[0066] At this time, in the case of the above Cu, it can play a catalytic role that can help atomize silicon nuclei during the initial silicon nuclei generation process.

[0067] In addition, when there are many elements constituting the alloy so that the difference in the size of the atomic radius is 10% or more, the deformation due to the difference in the size of these atoms in the liquid phase is reduced by the unique open structure of the liquid phase itself, and furthermore, when the atomic size distribution is large, the atomic structure of the liquid phase becomes dense.

[0068] If this quintuple alloy composition is composed of many types of alloying elements during solidification, and in order to generate crystalline nuclei from a liquid solution, the atoms must have a three-dimensionally regular spatial arrangement throughout the interior of the crystal, and the nuclei must also have a correspondingly complex lattice structure when attempting to crystallize.

[0069] In order for nuclei with such a complex lattice structure to be created, the alloying element atoms must have sufficient mobility to diffuse, but the factor that inhibits this is the strain energy caused by the difference in atomic size between the alloying elements.

[0070] As these elements with a large size difference are alloyed, the deformation energy increases, so when more alloying elements are included, the probability of crystallization when the alloy solidifies is greatly reduced, and the probability of forming a relatively small grain size increases.

[0071]

[0072] Below, each element of the above five-component alloy composition is described.

[0073] First, among the elements added to the above silicon anode material composition, aluminum (Al) improves the conductivity of the silicon anode material and exists as a silicide matrix to alleviate stress caused by silicon volume expansion, and can react with lithium to supplement the capacity of the silicon anode material.

[0074] At this time, the aluminum (Al) content may be 18 atomic% or more and 33 atomic% or less relative to the total content of the entire multi-component silicon matrix. If the aluminum content is less than 18 atomic%, the ductility of the matrix may be reduced, which may cause a reduction in the role of the support matrix that alleviates silicon volume expansion and a decrease in conductivity. If it exceeds 33 atomic%, a capacity reduction problem may occur due to excessive silicide matrix generation.

[0075] Additionally, nickel (Ni) acts as an additive to improve the conductivity of silicon anodes, and the addition of Ni can improve cycling stability and conductivity. Si-Ni alloy phases, NiSi, NiSi2, Ni3Si2, and Ni3Si, are inactive toward lithium ions and can only function as supporting materials. As the Ni content increases, it combines with silicon to form an intermetallic compound, which lowers battery capacity.

[0076] At this time, the nickel (Ni) content may be 3 atomic% or more and 20 atomic% or less relative to the total content of the entire multi-component silicon matrix. If the nickel content is less than 3 atomic%, there may be a problem of insufficient conductivity being provided, and if it exceeds 20 atomic%, there may be a problem of capacity reduction of the silicon composite cathode due to excessive formation of inactive materials.

[0077] In addition, since boron (B) has the smallest atomic radius among the elements added to the composition of silicon anode materials, adding B can improve the amorphous formation ability of the silicon anode material, thereby minimizing the silicon grain size, and has the property of increasing strength when alloyed with other metals.

[0078] At this time, the boron (B) content may be 1 atomic% or more and 10 atomic% or less relative to the total content of the entire multi-component silicon matrix. If the boron content is less than 1 atomic%, the amorphous forming ability may be reduced, causing a problem in refining silicon crystal grains. If it exceeds 10 atomic%, the brittleness may be increased, causing a problem in which particles are destroyed.

[0079] Additionally, as previously mentioned, copper (Cu) acts as a catalyst, possesses high electrical conductivity, and has high ductility. When alloyed, it imparts ductility to the matrix, thereby buffering stress during volume expansion. Furthermore, the elements applied to the silicon anode material melt at a lower temperature than silicon, eliminating the need for additional melting processes.

[0080] At this time, the copper (Cu) content may be 3 atomic% or more and 13 atomic% or less relative to the total content of the entire multi-component silicon matrix. If the copper content is less than 3 atomic%, there may be a problem in that sufficient performance is not exhibited for the addition effect, and if it exceeds 13 atomic%, there may be a problem in that it excessively reacts with other elements to form an intermetallic compound, resulting in a decrease in capacity.

[0081] At this time, the sum of the atomic % of Cu and the atomic % of B present inside the multi-component silicide matrix is ​​7 atomic % or more and 12 atomic % or less, and in particular, the ratio of Cu atomic % / (Cu atomic % + B atomic %) is 71% or more and 83% or less.

[0082] At this time, in the present invention, if the content of copper (Cu) and boron (B) is less than 7 atomic%, there may be a problem that sufficient performance is not exhibited for the addition effect, and if the content of copper (Cu) and boron (B) exceeds 12 atomic%, there may be a problem that the capacity is reduced and the brittleness is increased due to excessive reaction with other elements to form an intermetallic compound.

[0083] In addition, the ratio of Cu at % / (Cu at % + B at %) above is a value for the content ratio of Cu compared to the total copper (Cu) and boron (B), and may mean improvement in ductility and conductivity within the matrix, and when the above formula is satisfied, the effect of maintaining excellent life characteristics of the silicon composite cathode can be derived.

[0084] At this time, the content of silicon in the multi-component silicide matrix may include the remainder after containing the above-described aluminum, nickel, boron, and copper.

[0085] At this time, the multi-component silicide matrix contains crystalline silicon nanoparticles therein and can perform a buffering role when the volume of the silicon nanoparticles expands.

[0086]

[0087] Below, silicon nanoparticles contained in the silicon composite cathode material are described.

[0088] The above silicon atomic % may include the remainder after containing the aluminum, nickel, boron and copper based on the total atomic % of the entire silicon composite negative electrode material.

[0089] Accordingly, the negative electrode material for a lithium secondary battery according to one embodiment of the present invention is characterized by the effect of a multi-component silicide matrix surrounding silicon nanoparticles buffering stress when the silicon expands in volume.

[0090]

[0091] A method for manufacturing a silicon composite cathode material according to another embodiment of the present invention is described.

[0092] A method for manufacturing a silicon composite anode material according to one embodiment of the present invention may include the steps of: introducing aluminum (Al), nickel (Ni), boron (B), copper (Cu), and silicon (Si) metals into a crucible at a specific mixing ratio and then melting them to produce a melt; and the steps of rapidly cooling the melt with water sprayed at high pressure and then classifying the powder to produce a silicon anode material powder in which crystalline silicon is impregnated inside a multi-component silicide matrix.

[0093] Conventional alloy-based silicon anode materials form a crystalline phase with a regular atomic arrangement upon solidification from the liquid phase. However, if the cooling rate during solidification is sufficiently high, exceeding a critical value, to limit the nucleation and growth of the crystalline phase, the irregular atomic structure of the liquid phase can be maintained in the solid phase. Such alloys are commonly referred to as amorphous alloys.

[0094] In addition, conventionally, as a method for manufacturing anode materials for lithium-ion batteries, a number of necessary raw materials are mixed and melted to create an ingot, and then an amorphous ribbon strip is formed by melt spinning, and the obtained ribbon strip is pulverized and mixed with carbon, a polyimide coating solution, and NMP through a milling process to manufacture an alloy silicon anode material.

[0095] However, the actual application of the silicon anode material is very limited because the process of manufacturing the amorphous ribbon strip and then powdering it is very complicated and there are limitations in shape and size.

[0096] Furthermore, silicon anode materials manufactured through the melt spinning process are expensive, making the formation of silicon anode materials based on this alloy composition a primary component a problem of low price competitiveness. Furthermore, amorphous alloys exhibit their properties only in the amorphous state. Therefore, when processes such as carbon coating to prevent silicon side reactions are introduced, the amorphous structure transforms into a crystalline structure through heat treatment, which can affect battery characteristics.

[0097] On the other hand, the present invention relates to a method for manufacturing a silicon anode powder containing crystalline silicon and a silicide matrix in a metal alloy by melting four component elements other than silicon in a crucible at a certain mixing ratio, and then rapidly cooling the molten material sprayed through a nozzle with water sprayed at high pressure.

[0098] Hereinafter, a method for manufacturing a silicon composite negative electrode material of the present invention will be described.

[0099] In the first step, the method may include a step of putting the aluminum (Al), nickel (Ni), boron (B), copper (Cu) and silicon (Si) metals in a specific mixing ratio into a crucible and then melting them to produce a melt.

[0100] At this time, the content of the aluminum (Al) is 18 atomic% or more and 33 atomic% or less relative to the entire melt, the content of the nickel (Ni) is 3 atomic% or more and 20 atomic% or less relative to the entire melt, the content of the boron (B) is 1 atomic% or more and 10 atomic% or less relative to the entire melt, and the content of the copper (Cu) is 3 atomic% or more and 13 atomic% or less relative to the entire melt, and the remainder may be silicon.

[0101] At this time, the aluminum (Al) content may be 18 atomic% or more and 33 atomic% or less relative to the total content of the entire multi-component silicon matrix. If the aluminum content is less than 18 atomic%, the ductility of the matrix may be reduced, which may result in a reduction in the supporting matrix role for alleviating silicon volume expansion and a decrease in conductivity. If it exceeds 33 atomic%, there may be a capacity reduction problem due to excessive silicide matrix generation.

[0102] At this time, the nickel (Ni) content may be 3 atomic% or more and 20 atomic% or less relative to the total content of the entire multi-component silicon matrix. If the nickel content is less than 3 atomic%, there may be a problem of insufficient conductivity being provided, and if it exceeds 20 atomic%, there may be a problem of reduced capacity of the silicon composite cathode due to excessive formation of inactive materials.

[0103] At this time, the boron (B) content may be 1 atomic% or more and 10 atomic% or less relative to the total content of the entire multi-component silicon matrix. If the boron content is less than 1 atomic%, the amorphous forming ability may be reduced, causing a problem in refining silicon crystal grains. If it exceeds 10 atomic%, the brittleness may be increased, causing a problem in which particles are destroyed.

[0104] At this time, the copper (Cu) content may be 3 atomic% or more and 13 atomic% or less relative to the total content of the entire multi-component silicon matrix. If the copper content is less than 3 atomic%, there may be a problem in that sufficient performance is not exhibited for the addition effect, and if it exceeds 13 atomic%, there may be a problem in that it excessively reacts with other elements to form an intermetallic compound, resulting in a decrease in capacity.

[0105] In addition, the sum of the atomic % of Cu and the atomic % of B present inside the multi-component silicide matrix is ​​7 atomic % or more and 12 atomic % or less, and in particular, the ratio of Cu atomic % / (Cu atomic % + B atomic %) is 71% or more and 83% or less, and when the ratio of the copper (Cu) atoms and the boron (B) atoms is adjusted, the brittle element B increases the particle strength through the appropriate ratio adjustment of materials having ductility and brittleness, thereby satisfying the condition of not breaking the particles, and the ductile Cu can have a relaxation characteristic for stress due to particle expansion.

[0106] At this time, the material containing copper (Cu) may be copper (Cu), copper(I) oxide (Cu2O), copper(II) oxide (CuO), copper aluminum (Cu2Al3), bronze (Cu-Sn), brass (Cu-Zn), a mixture containing one or more of these, or one of the two.

[0107]

[0108] In the second step, the method may include a step of rapidly cooling the melt with water sprayed at high pressure and then classifying the powder to manufacture a silicon anode material powder in which crystalline silicon is impregnated inside a multi-component silicide matrix.

[0109] The rapid cooling rate when rapidly cooling with the water sprayed at the above high pressure is 10 5 K / Sec to 10 7 It is characterized by K / Sec.

[0110] At this time, the rapid cooling rate is 10 5If the cooling rate is less than K / Sec, excessive growth of silicon alone inside the silicon anode material occurs, which may cause stress that cannot be relieved in the matrix, ultimately leading to destruction of the silicon anode material. A slow cooling rate causes compounds to be formed with silicon and metals in the matrix, resulting in a low level of capacity, and thus, high-capacity characteristics cannot be achieved. In addition, if the rapid cooling rate is less than 10 7 If it exceeds , some of the silicon crystals inside the silicon composite cathode may become a mixed state of crystalline and amorphous, which may cause a problem of reduced capacity of the silicon composite cathode. Therefore, the rapid cooling rate is set to 10 5 K / Sec to 10 7 You can do it with K / Sec.

[0111] At this time, in the case of the silicon composite anode material of the present invention, a five-component anode material composition was designed to improve the silicon particle size, and the difference in the size of the mutual atomic radii is 10% or more, and in the liquid phase, the deformation due to the size difference of these atoms is reduced due to the unique open structure of the liquid phase itself, and furthermore, in the case where the atomic size distribution is large, the atomic structure of the liquid phase can become denser than in other cases.

[0112] Here, the reason why the liquid atomic structure can become dense when the atomic size distribution is large is that the quintuple alloy composition is composed of many types of alloying elements during solidification. In order to create crystalline nuclei from the liquid solution with the aforementioned structural characteristics, the atoms are arranged in a three-dimensionally regular space throughout the interior of the crystal, and the nuclei must also have a very complex lattice structure corresponding to this when attempting to crystallize. In order for nuclei with such a complex lattice structure to be created, the alloying component atoms must have mobility sufficient to diffuse, but the factor that inhibits this is the strain energy due to the atomic size difference between these alloying elements. The greater the size difference between elements that are alloyed, the greater this strain energy. Therefore, if more alloying elements are included, the probability of crystallization when the alloy solidifies is greatly reduced, and the probability of forming a relatively small grain size is greatly increased.

[0113] Accordingly, the average particle size of the silicon composite anode material powder manufactured by the above silicon composite anode material manufacturing method may be 5 um to 6 um, and the reason for the particle size of the powder described above is that when the average particle size of the silicon composite anode material is less than 5 um, a problem occurs in which a binder must be added due to an increase in the specific surface area, and there is a high possibility that the powder particles are not sufficiently dispersed due to the small powder size, and when the electrode is manufactured, the movement of the electrolyte is very difficult, which may cause difficulties in ion conduction, and thus a problem in which the capacity development of the battery is reduced may occur, and when the average particle size exceeds 6 um, a problem in ion diffusion may occur due to an increase in the diffusion length of lithium ions, and an intercalation problem may occur when mixed with natural graphite, so that the average particle size is most preferably 5 um or more and 6 um or less, but is not limited to the above numerical range.

[0114]

[0115] Hereinafter, the present invention will be described in more detail through manufacturing examples and experimental examples. These manufacturing examples and experimental examples are intended solely to illustrate the present invention, and the scope of the present invention is not limited by these manufacturing examples and experimental examples.

[0116] Manufacturing Example 1: Manufacturing of silicon composite cathode material (Al, Ni, B, Cu = 25:3:2:10 atomic %)

[0117] First, the aluminum (25 atomic%), nickel (3 atomic%), boron (2 atomic%), copper (10 atomic%), and the remainder (60 atomic%) were put into a high-frequency melting furnace, and then melted into a liquid state at a high-frequency melting temperature of 1,550 degrees or higher for 45 minutes or more and 120 minutes or less, and specifically for 60 minutes or more and 100 minutes or less, to create a uniform state.

[0118] Next, the powder was manufactured using the atomizing method, and more specifically, the molten alloy was differentiated and cooled using a high-pressure coolant. At this time, the cooling rate was 10 5 K / Sec to 10 7 It represents the cooling rate in K / Sec.

[0119] Afterwards, the powder was classified to produce silicon anode powder with an average particle size of approximately 5 um to 6 um.

[0120]

[0121] Manufacturing Example 2: Manufacturing of silicon composite cathode material (Al, Ni, B, Cu = 30:3:2:5 atomic %)

[0122] In this Manufacturing Example 2, the same method as in the Manufacturing Example 1 process was performed except that aluminum was included in a ratio of 30 atomic%, nickel in a ratio of 3 atomic%, boron in a ratio of 2 atomic%, copper in a ratio of 5 atomic%, and silicon in a ratio of 60 atomic%.

[0123]

[0124] Manufacturing Example 3: Manufacturing of silicon composite cathode material (Al, Ni, B, Cu = 27:4:2:7 atomic %)

[0125] In this Manufacturing Example 3, the same method as in the Manufacturing Example 1 process was performed except that aluminum (27 atomic%), nickel (4 atomic%), boron (2 atomic%), copper (7 atomic%), and the remainder silicon (60 atomic%) were included.

[0126]

[0127] Comparative Example 1: Manufacturing of silicon composite cathode material (Al, Ni, B, Cu = 28:3:1:8 atomic %)

[0128] In this comparative example 1, the same method was performed as in the manufacturing example 1 process except that aluminum was included in a ratio of 28 atomic%, nickel in a ratio of 3 atomic%, boron in a ratio of 1 atomic%, copper in a ratio of 8 atomic%, and silicon in a ratio of 60 atomic%.

[0129]

[0130] Comparative Example 2: Manufacturing of silicon composite cathode material (Al, Ni, B, Cu = 32:3:2:3 atomic %)

[0131] In this Manufacturing Example 2, the same method as in the Manufacturing Example 1 process was performed except that the proportions of aluminum (32 atomic%), nickel (3 atomic%), boron (2 atomic%), copper (3 atomic%), and the remainder silicon (60 atomic%) were included.

[0132]

[0133] Comparative Example 3: Manufacturing of silicon composite cathode material (Al, Ni, B, Cu = 22:3:5:10 atomic %)

[0134] In this comparative example 3, the same method was performed as in the manufacturing example 1 process except that aluminum was included in a ratio of 22 atomic%, nickel in a ratio of 3 atomic%, boron in a ratio of 5 atomic%, copper in a ratio of 10 atomic%, and silicon in a ratio of 60 atomic%.

[0135]

[0136] Comparative Example 4 Manufacturing of silicon composite cathode material (Al, Ni, B, Cu = 28:4:1.2:6.8 atomic %)

[0137] In this comparative example 4, the same method was performed as in the manufacturing example 1 process except that aluminum was included in a ratio of 28 atomic%, nickel in a ratio of 4 atomic%, boron in a ratio of 1.2 atomic%, copper in a ratio of 6.8 atomic%, and silicon in a ratio of 60 atomic%.

[0138]

[0139] Comparative Example 5: Manufacturing of silicon composite cathode material (Al, Ni, B, Cu = 23:6:3.5:7.5 atomic %)

[0140] In this comparative example 5, the same method was performed as in the manufacturing example 1 process except that aluminum was included in a ratio of 23 atomic%, nickel 6 atomic%, boron 3.5 atomic%, copper 7.5 atomic%, and the remainder silicon (60 atomic%).

[0141]

[0142] Table 1 below shows the atomic % ratio values ​​of examples and comparative examples, and the numerical values ​​are as follows.

[0143]

[0144] Classification Si(at%) Al(at%) Ni(at%) B(at%) Cu(at%) Example 160253210 Example 26030325 Example 36027427 Comparative Example 16028318 Comparative Example 26032323 Comparative Example 360223510 Comparative Example 4602841.26.8 Comparative Example 5602363.57.5

[0145] Table 2 below shows the ratio of Cu to Cu+B, set at various ratios from 60% to 89%.

[0146]

[0147] Classification Si + Al (at%) Cu + B (at%) Cu / (Cu+B) % Example 1851283% Example 290771% Example 387978% Comparative Example 188989% Comparative Example 292560% Comparative Example 3821567% Comparative Example 488885% Comparative Example 5831168%

[0148] Example 1: Fabrication of a single electrode

[0149] The silicon negative electrode material manufactured in the above manufacturing example and PI as a binder and a conductive material were mixed in a weight ratio of 86.6:10:3.4 to manufacture a negative electrode active material slurry.

[0150] At this time, the manufactured slurry was coated on a copper foil current collector to manufacture a negative electrode plate, and the coated electrode plate was dried at 110°C for 20 minutes and then rolled to make the density of the negative electrode plate 1.5 g / cc.

[0151] Next, the dried negative electrode plate was heat-treated in an Ar atmosphere at 350°C for 2 hours, and then the plate was cut into a size of 14 mm to manufacture a negative electrode to be applied to a coin cell.

[0152] At this time, Li metal was used as the counter electrode, a polypropylene separator with a thickness of 20 mm was used, and a coin cell of the 2032 standard was manufactured by injecting and compressing the electrolyte.

[0153] At this time, the electrolyte was used by adding 10% of FEC, an electrolyte additive, to a mixed solvent of ethylene carbonate and diethyl carbonate, and dissolving LiPF6 to a concentration of 1.0 M.

[0154]

[0155] Example 2: Manufacturing of silicon composite cathode material

[0156] First, the silicon negative electrode material manufactured in Example 1 was mixed with graphite at a weight ratio of 9:1, and the SBR / CMC conductive material as a binder was mixed at a weight ratio of 95:4.8:0.2 to manufacture a negative electrode active material slurry.

[0157] Next, the manufactured slurry was coated on a copper foil current collector to manufacture a negative electrode plate. The coated plate was dried at 110°C for 20 minutes and then rolled to make the density of the negative electrode plate 1.5 g / cc.

[0158] Next, the dried negative electrode plate was heat-treated in a vacuum atmosphere at 180°C for 10 hours, and then the plate was cut into 14 mm sizes to manufacture a negative electrode to be applied to a coin cell.

[0159] At this time, Li metal was used as the counter electrode, a polypropylene separator with a thickness of 20 mm was used, and a coin cell of the 2032 standard was manufactured by injecting and compressing the electrolyte.

[0160] At this time, the electrolyte was prepared by adding 10% FEC, an electrolyte additive, to a mixed solvent of ethylene carbonate and diethyl carbonate, and dissolving LiPF6 to a concentration of 1.0 M to manufacture a single electrode.

[0161]

[0162] Experimental example

[0163] Figure 2 is a cross-sectional and elemental analysis image of a silicon anode material according to one embodiment of the present invention.

[0164] Referring to Figure 2, it can be confirmed that crystalline silicon nanoparticles are included within the multicomponent silicate matrix.

[0165]

[0166] Figure 3 is an XRD graph of a silicon anode material according to an embodiment of the present invention.

[0167] Referring to the above Figure 3, the new peak existing between 2θ° was confirmed to be a new phase due to the addition of Cu, and it can be confirmed through TEM / EDS analysis that a Cu phase is formed in the matrix.

[0168]

[0169] Figure 4 is an FE-SEM image showing the evaluation results of maintaining the shape before and after the silicon anode material cycle according to one embodiment of the present invention.

[0170] Referring to FIG. 4, the surface characteristics of the silicon composite anode material before and after the charge / discharge cycles of Example 3 and Comparative Example 2 were confirmed, and after the cycle life evaluation, it was confirmed that in the case of the silicon composite anode material of the example, the volume expansion of the silicon was buffered by the surrounding matrix tissue, so that the powder was not destroyed.

[0171]

[0172] Figure 5 is an exemplary diagram showing the electrical conductivity of a silicon anode material according to one embodiment of the present invention.

[0173] Referring to Figure 5, it was confirmed that the internal resistance of the silicon anode material decreased from 450Ω to 210Ω in the case of electrical conductivity through impedance analysis. This confirmed that it has excellent electrical conductivity characteristics due to the presence and increased content of internal Cu.

[0174]

[0175] Hereinafter, the results of a charge / discharge experiment of a lithium ion battery including the silicon composite negative electrode material of the present invention will be described.

[0176] In this charge-discharge experiment, charging was performed in CC Mode with a current density corresponding to Cycle: 0.2C, and charging was performed in CV Mode from the point where it reached 0.005V to the point where it reached 0.005C.

[0177] Afterwards, the discharge was performed at a current density corresponding to 0.2C rate, and the above charging and discharging reactions were performed 50 times to perform the cycle stage, with a rest time of 1 hour between each charge and discharge.

[0178]

[0179] Figure 6 is an exemplary diagram showing the single electrode 1-cycle characteristics of one embodiment and a comparative example of the present invention.

[0180] Referring to FIG. 6, based on the initial charge / discharge graph of Example 3, the discharge capacity of Example 3 was 1,923 mAh / g, and the discharge capacity of Comparative Example 2 was 2,312 mAh / g.

[0181]

[0182] Figure 7 is a graph evaluating the cycle characteristics of a single and mixed electrode of one embodiment of the present invention.

[0183] Referring to Fig. 7(a), the single electrode life maintenance rate value of Example 3 is 83%, and the single electrode life maintenance rate value of Comparative Example 2 is 62%, confirming that the life maintenance rate of the Example is excellent. In addition, referring to Fig. 7(b), the mixed electrode life maintenance rate value of Example 3 is 93%, and the mixed electrode life maintenance rate value of Comparative Example 2 is 79%, confirming that Example 3 shows excellent life maintenance rates in both the single electrode and the mixed electrode.

[0184]

[0185] Table 3 below shows the results of the evaluation of the electrochemical characteristics of single electrodes for examples and comparative examples.

[0186] Category 1 Cycle 50 Cycle Discharge capacity (mAh / g) Coulomb efficiency (%) Capacity retention rate (%) Coulomb efficiency (%) Example 11,89390.081.898.3 Example 22,27890.878.097.4 Example 31,92389.983.698.5 Comparative example 11,97390.175.698.1 Comparative example 22,31290.162.797.4 Comparative example 31,82288.964.597.5 Comparative example 41,97090.174.097.9 Comparative example 51,85489.873.998.0

[0187] It was confirmed that the initial discharge capacity increased as the content of Si+Al increased, and the effects of Cu and B for improving cycle life characteristics were additionally confirmed.

[0188] The atomic% content of Cu+B was adjusted to be 2 atomic% or more and 15 atomic% or less, and it was confirmed that the life characteristics were excellent when the content was 7 atomic% or more and 12 atomic% or less.

[0189] In addition, when the content of Cu atomic % / (Cu atomic %+B atomic %) was confirmed, it was confirmed that the life characteristics were excellent at a ratio of 71% or more and 83% or less.

[0190] Table 4 below shows the results of evaluating the electrochemical characteristics of the mixed electrodes of examples and comparative examples.

[0191] Category 1 Cycle 50 Cycle Discharge capacity (mAh / g) Coulomb efficiency (%) Capacity retention rate (%) Coulomb efficiency (%) Example 151492.292.399.7 Example 254092.688.599.8 Example 352092.593.699.7 Comparative example 152991.986.499.7 Comparative example 254492.078.299.5 Comparative example 349491.881.199.5 Comparative example 453091.986.099.7 Comparative example 550691.984.599.6

[0192] Based on the results of the single electrode, an electrode was manufactured by mixing 10 wt% of silicon anode material into graphite, and the electrochemical characteristics were evaluated, and a similar trend to the single electrode was confirmed.

[0193] In Example 1, the shape of the silicon anode material was maintained due to the buffering role of the Silicide matrix surrounding the silicon tissue even when internal stress occurred according to the cycle. On the other hand, in Comparative Example 1, the silicon anode material was destroyed as it could not withstand the internal stress as the cycle progressed.

[0194] The even distribution of silicon and Cu in the matrix during the manufacture of silicon anode materials was confirmed through TEM / EDS.

[0195]

[0196] The foregoing description of the present invention is for illustrative purposes only, and those skilled in the art will readily appreciate that the present invention can be readily modified into other specific forms without altering the technical spirit or essential characteristics of the present invention. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive. For example, each component described as a single entity may be implemented in a distributed manner, and similarly, components described as distributed may be implemented in a combined manner.

[0197] The scope of the present invention is indicated by the claims described below, and all changes or modifications derived from the meaning and scope of the claims and their equivalent concepts should be interpreted as being included in the scope of the present invention.

[0198] [Explanation of symbols]

[0199] 100: Multicomponent silicate matrix

[0200] 200: Silicon nanoparticles

Claims

A multicomponent silicide matrix containing aluminum (Al), nickel (Ni), boron (B), copper (Cu), and silicon (Si); and A silicon composite anode material characterized by comprising crystalline silicon nanoparticles impregnated within the silicon matrix. In the first paragraph, The above multi-component silicide matrix is ​​characterized by being composed of a material represented by the following chemical formula 1: [Chemical Formula 1] And a (Al b us c With d B e ) The above a is a real number between 0.24 and 0.75, b is a real number between 0.18 and 0.33, c is a real number between 0.03 and 0.2, d is a real number between 0.03 and 0.13, and e is a real number between 0.01 and 0.

1. In the first paragraph, A silicon composite anode material characterized in that the aluminum (Al) content is 18 atomic% or more and 33 atomic% or less relative to the total content of the entire multi-component silicon matrix. In the first paragraph, A silicon composite anode material characterized in that the nickel (Ni) content is 3 atomic% or more and 20 atomic% or less relative to the total content of the entire multi-component silicon matrix. In the first paragraph, A silicon composite anode material characterized in that the above boron (B) content is 1 atomic% or more and 10 atomic% or less relative to the total content of the entire multi-component silicon matrix. In the first paragraph, A silicon composite cathode material characterized in that the copper (Cu) content is 3 atomic% or more and 13 atomic% or less relative to the total content of the entire multi-component silicon matrix. In the first paragraph, A silicon composite cathode material characterized in that the sum of the atomic % of copper (Cu) and the atomic % of boron (B) is 7 atomic % or more and 12 atomic % or less. In the first paragraph, A silicon composite cathode material characterized in that the ratio of Cu atomic% / (Cu atomic% + B atomic%) with respect to the content of copper (Cu) and boron (B) is 71% or more and 83% or less. In the first paragraph, A silicon composite anode material characterized in that the atomic % of silicon of the silicon composite anode material is the remainder after containing the aluminum, nickel, boron, and copper. A multi-component silicide matrix comprising aluminum (Al), nickel (Ni), boron (B), copper (Cu), and silicon (Si), wherein the difference in the sizes of the atomic radii of each of the aluminum (Al), nickel (Ni), boron (B), copper (Cu), and silicon (Si) is 10% or more; and A silicon composite anode material characterized by comprising crystalline silicon nanoparticles impregnated within the silicon matrix. A multicomponent silicide matrix characterized by being composed of a material represented by the following chemical formula 1; and A silicon composite anode material characterized by comprising crystalline silicon nanoparticles impregnated within the silicon matrix: [Chemical Formula 1] And a (Al b us c With d B e ) The above a is a real number between 0.24 and 0.75, b is a real number between 0.18 and 0.33, c is a real number between 0.03 and 0.2, d is a real number between 0.03 and 0.13, and e is a real number between 0.01 and 0.

1. A step of producing a melt by putting aluminum (Al), nickel (Ni), boron (B), copper (Cu) and silicon (Si) metals in a specific mixing ratio into a crucible and then melting them; and A method for manufacturing a silicon composite anode material, characterized by comprising a step of rapidly cooling the molten material with water sprayed at high pressure and then classifying the powder to manufacture a silicon anode material powder in which crystalline silicon is impregnated inside a multi-component silicide matrix. In paragraph 12, In the step of manufacturing the above melt, The content of the above aluminum (Al) is 18 atomic% or more and 33 atomic% or less compared to the entire molten material, The content of the above nickel (Ni) is 3 atomic% or more and 20 atomic% or less compared to the entire melt, The content of the above boron (B) is 1 atomic% or more and 10 atomic% or less compared to the entire melt, The above copper (Cu) content is 3 atomic% or more and 13 atomic% or less compared to the entire melt, A method for manufacturing a silicon composite cathode material, characterized in that the remainder is silicon. In paragraph 12, In the step of manufacturing a silicon anode material powder in which crystalline silicon is impregnated inside the multicomponent silicide matrix, The above rapid cooling rate is 10 5 K / Sec to 10 7 A method for manufacturing a silicon composite cathode material characterized by having a K / Sec. A silicon negative electrode active material characterized by comprising the silicon composite negative electrode material of claim 1 and graphite. In Article 15, The content of the above silicon composite negative electrode material is 5 to 10 wt% based on the total silicon negative electrode active material, A silicon negative electrode active material characterized in that the content of the graphite is 90 to 95 wt% based on the total silicon negative electrode active material.

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