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

Abstract

One embodiment of the invention provides a silicon composite negative electrode material. According to one embodiment of the present invention, a negative electrode material suitable for use in a lithium secondary battery is composed of a multi-component silicide matrix surrounding silicon nanoparticles, the matrix acting as a buffer during the volume expansion of silicon. Furthermore, by adding copper (Cu) into the multi-component silicide matrix, the stress relief and conductivity of the matrix can be improved, thereby enhancing the long-life characteristic of the material. Meanwhile, by setting the optimal ratio of copper (Cu) to boron (B), the strength and toughness characteristics are improved, and the stress is relieved, so that the problem of particle breakage of the silicon negative electrode material in the charge-discharge cycle process is solved.

Description

TECHNICAL FIELD

[0001] The present application relates to a silicon negative electrode material and a method of manufacturing the same. BACKGROUND

[0002] With the increase in the use of portable electronic devices and the expansion of the electric vehicle market, the demand for energy storage devices has sharply increased. Among them, lithium secondary batteries are attracting attention as one of the most popular energy storage devices due to their high operating voltage of 3.7 V on average, high energy density of 200 Wh / kg and 600 Wh / L.

[0003] In lithium secondary batteries, the most commercialized negative electrode material is graphite, and due to its low theoretical capacity (LiC6372 mAh / g), silicon is attracting attention as a next-generation negative electrode material due to its large charge and discharge capacity. However, the theoretical volume change rate due to lithium ion intercalation is 110% for carbon, and 280% for silicon (Li 15 Si4) at room temperature.

[0004] Due to this volume change, cracks and breakage of silicon particles occur, leading to an increase in the surface area of active material particles, destruction and regeneration of the solid electrolyte interface (SEI) layer formed on the surface, and thus a decrease in inter-cycle efficiency and a sharp degradation of capacity. Therefore, in view of this large volume change of silicon, many studies are being conducted to find a method of accommodation and suppression.

[0005] One of the methods is to reduce the size of silicon particles to the nanometer level to reduce the absolute volume expansion rate upon expansion, thereby alleviating physical stress due to volume change. Second, a conductive metal element that does not react with lithium is added to form a silicide, and the formed silicide matrix is utilized to alleviate the volume expansion of silicon. Another method is to manufacture porous silicon. Porous silicon not only buffers volume expansion through pores, but also increases the contact area of electrolyte with the electrode, thereby accelerating the diffusion of lithium ions. However, since it is difficult to control the specific surface area of silicon during etching, it is difficult to ensure the reliability of the powder, and problems such as a large amount of wastewater are generated during the manufacturing process. In order to improve the characteristics of silicon materials, various methods such as controlling the shape and particle size of the material, alloying, oxidation, and compounding with carbon materials have been attempted.

[0006] Among them, the silicon negative electrode material using the Silicide matrix is a powder formed of a plurality of phases due to the difference in melting point and mixing enthalpy of each element and alloy when the alloy melted in a furnace is cooled. By selecting the composition and alloy series, the silicon phase is separated from the Silicide matrix phase when the melt is cooled, thereby manufacturing the material.

[0007] For Si-Al-Ni or Si-Al-Fe-Ni three-component and four-component alloy powders, the microstructure is surrounded by the Silicide matrix phase around the silicon phase. Although such three-component and four-component alloys exhibit good characteristics in initial discharge capacity and efficiency, the capacity decreases as the cycle progresses, and good cycle life stability cannot be ensured. This is because the volume change of the silicon phase inside the powder is not sufficiently buffered by the surrounding Silicide matrix phase.

[0008] To realize the practicality of the silicon alloy negative electrode material, it is crucial to design a microstructure to enable the Silicide matrix phase to sufficiently buffer the volume expansion of the silicon phase.

[0009] Prior art documents

[0010] Patent Literature

[0011] Republic of Korea Laid-Open Patent Publication No. 10-2023-0096191. SUMMARY

[0012] Problems to be Solved by the Invention

[0013] The technical problem to be solved by the present application is to provide a multi-component silicon composite negative electrode material for a lithium secondary battery.

[0014] The technical problem to be solved by the present application 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 to which the present application belongs from the following description.

[0015] Means for Solving the Problem

[0016] To achieve the above technical problem, one embodiment of the present application provides a silicon composite negative electrode material.

[0017] According to one embodiment of the present application, the silicon composite negative electrode material includes: a multi-component Silicide matrix containing aluminum (Al), nickel (Ni), boron (B), copper (Cu), and silicon (Si); and crystalline silicon nanoparticles containing a plurality of particles immersed inside the silicon matrix.

[0018] Further, in one embodiment of the present application, the silicon composite negative electrode material is characterized in that the multi-component silicide base is composed of a substance represented by the following Chemical Formula 1.

[0019]

Chemical Formula 1

[0020] Si a (Al b NicCu d B e )

[0021] wherein a is a real number of 0.24 to 0.75, b is a real number of 0.18 to 0.33, c is a real number of 0.03 to 0.2, d is a real number of 0.03 to 0.13, and e is a real number of 0.01 to 0.1.

[0022] Further, in one embodiment of the present application, the aluminum (Al) content can be 18 atomic % or more to 33 atomic % or less of the total content of the multi-component silicon base.

[0023] Further, in one embodiment of the present application, the nickel (Ni) content can be 3 atomic % or more to 20 atomic % or less of the total content of the multi-component silicon base.

[0024] Further, in one embodiment of the present application, the boron (B) content can be 1 atomic % or more to 10 atomic % or less of the total content of the multi-component silicon base.

[0025] Further, in one embodiment of the present application, the copper (Cu) content can be 3 atomic % or more to 13 atomic % or less of the total content of the multi-component silicon base.

[0026] Further, in one embodiment of the present application, the sum of the atomic percentages of the copper (Cu) and boron (B) content can be 7 atomic % or more to 12 atomic % or less.

[0027] Further, in one embodiment of the present application, the ratio of Cu atomic % / (Cu atomic %+B atomic %) in the copper (Cu) and boron (B) content is 71 % or more to 83 % or less.

[0028] Further, in one embodiment of the present application, the silicon atomic % in the silicon composite negative electrode material is the remaining portion after the above-mentioned aluminum, nickel, boron, and copper content.

[0029] To achieve the above technical task, another embodiment of the present application provides a method of manufacturing a silicon composite negative electrode material.

[0030] An embodiment of the present invention describes a method for manufacturing silicon composite anode material, comprising: melting aluminum (Al), nickel (Ni), boron (B), copper (Cu), and silicon (Si) metals in a specific mixing ratio in a crucible to produce a melt; and rapidly cooling the melt by high-pressure water jetting, and then classifying the powder to produce silicon anode material powder containing crystalline silicon impregnated within a multi-component silicide matrix.

[0031] Furthermore, in one embodiment of the present invention, during the step of manufacturing the melt,

[0032] The aluminum (Al) content can be between 18 atomic% and 33 atomic% of the entire melt, the nickel (Ni) content can be between 3 atomic% and 20 atomic% of the entire melt, the boron (B) content can be between 1 atomic% and 10 atomic% of the entire melt, the copper (Cu) content can be between 3 atomic% and 13 atomic% of the entire melt, and the remainder is silicon.

[0033] Furthermore, in one embodiment of the present invention, in the step of manufacturing silicon anode material powder containing crystalline silicon impregnated within a multi-component silicide matrix, the rapid cooling rate can be 10. 5 K / s to 10 7 Between K / s.

[0034] In another embodiment of the present invention, the silicon composite anode material comprises aluminum (Al), nickel (Ni), boron (B), copper (Cu), and silicon (Si), wherein the atomic radii of each of the aluminum (Al), nickel (Ni), boron (B), copper (Cu), and silicon (Si) differ by more than 10% in a multi-component silicide matrix; and contains crystalline silicon nanoparticles impregnated within the silicon matrix.

[0035] Furthermore, according to another embodiment of the present invention, the silicon composite anode material is composed of a substance represented by the following chemical formula 1.

[0036] A silicon composite anode material, characterized in that it comprises crystalline silicon nanoparticles immersed in the silicon matrix.

[0037]

Chemical Formula 1

[0038] Si a (Al b Ni c Cu d B e )

[0039] Wherein, a is a real number from 0.24 to 0.75, b is a real number from 0.18 to 0.33, c is a real number from 0.03 to 0.2, d is a real number from 0.03 to 0.13, and e is a real number from 0.01 to 0.1.

[0040] To address the aforementioned technical challenges, another embodiment of the present invention provides a silicon anode active material.

[0041] The content of the silicon composite anode material is 5% to 10% by weight relative to the total silicon anode active material, and the content of the graphite is 90% to 95% by weight relative to the total silicon anode active material.

[0042] Invention Effects

[0043] In one embodiment of the present invention, the negative electrode material for a lithium secondary battery comprises a multi-component silicide matrix surrounding silicon nanoparticles, which has a buffering effect when silicon expands in volume. Simultaneously, by adding copper (Cu) to the multi-component silicide matrix, stress relief and conductivity of the matrix can be improved, thereby enhancing the long-life characteristics of the material. Furthermore, by setting an optimal ratio of copper (Cu) to boron (B), strength and toughness properties are improved, thereby relieving stress and solving the problem of particle breakage in silicon negative electrode materials during charge-discharge cycles.

[0044] The effects of the present invention are not limited to those described above, but should be understood to include all effects that can be derived from the invention's structure as described in the detailed description or claims of the present invention. Attached Figure Description

[0045] Figure 1 This is a schematic diagram illustrating a silicon composite anode material according to an embodiment of the present invention.

[0046] Figure 2 This is a cross-sectional and elemental analysis image of a silicon anode material according to an embodiment of the present invention.

[0047] Figure 3 This is an XRD pattern of a silicon anode material according to an embodiment of the present invention.

[0048] Figure 4 This is an FE-SEM image of the evaluation results of the morphology retention of a silicon anode material before and after cycling, according to an embodiment of the present invention.

[0049] Figure 5 This is an example diagram showing the conductivity of a silicon anode material according to an embodiment of the present invention.

[0050] Figure 6 This is an example diagram illustrating the single-electrode 1-Cycle characteristics of an embodiment of the present invention and a comparative example.

[0051] Figure 7 This is a graph evaluating the Cycle characteristics of a single electrode and a hybrid electrode according to an embodiment of the present invention. Detailed Implementation

[0052] The present invention will now be described with reference to the accompanying drawings. However, the present invention can be implemented in many different forms and is therefore not limited to the embodiments described herein. For clarity, parts irrelevant to the description have been omitted from the drawings, and similar reference numerals have been used for similar parts throughout the specification.

[0053] Throughout the specification, when a part is described as "connected (joined, contacted, or combined)" with other parts, this includes not only "direct connections" but also "indirect connections" where other components are present in between. Furthermore, when a part "contains" a component, unless specifically stated otherwise, the presence of other components is not excluded, meaning that other components may be included further.

[0054] The terminology used in this specification is for illustrative purposes only and is not intended to limit the invention. Singular expressions should include plural expressions unless explicitly stated in the context as having a different meaning. In this specification, terms such as "comprising" or "having" refer to the presence of features, quantities, steps, actions, components, parts, or combinations thereof listed in the specification, without precluding the presence or additional possibilities of one or more other features, quantities, steps, actions, components, parts, or combinations thereof.

[0055] The invention will now be described with reference to the drawings shown in this specification. It should be noted that the drawings may be presented in an exaggerated manner to better illustrate the features of the invention. In such cases, it is recommended to interpret the invention according to its overall intent.

[0056] According to one embodiment of the present invention, a silicon composite anode material is provided.

[0057] Figure 1 This is a schematic diagram of a silicon composite anode material according to an embodiment of the present invention.

[0058] According to an embodiment of the present invention, a silicon composite anode material comprises: a multi-component silicide matrix containing aluminum (Al), nickel (Ni), boron (B), copper (Cu) and silicon (Si); and crystalline silicon nanoparticles impregnated within the silicon matrix.

[0059] The present invention is characterized by comprising a multi-component silicide matrix (100).

[0060] At this time, the multi-component silicide matrix may be composed of substances represented by the following chemical formula 1.

[0061]

Chemical Formula 1

[0062] Si a (Al b Ni c Cu d B e )

[0063] Wherein, a is a real number from 0.24 to 0.75, b is a real number from 0.18 to 0.33, c is a real number from 0.03 to 0.2, d is a real number from 0.03 to 0.13, and e is a real number from 0.01 to 0.1.

[0064] As described in the background section of this invention, conventional multi-component silicide compounds, such as three-component and four-component alloy powders like Si-Al-Ni or Si-Al-Fe-Ni, have a microstructure consisting of a silicide matrix surrounding the silicon phase. Although these three-component and four-component powders experience capacity reduction during cycling, thus failing to ensure good cycle life stability, this is because the volume change of the silicon phase within the powder is not adequately buffered by the surrounding silicide matrix.

[0065] The silicide matrix of the present invention is characterized by being composed of five components to solve the above-mentioned problems.

[0066] At this point, the atomic radius difference of each element contained in the silicide matrix of the present invention should exceed 10%.

[0067] Specifically, the atomic radii of each of them can be: Si (atomic radius: 117), Al (atomic radius: 143), Ni (atomic radius: 125), B (atomic radius: 88), and Cu (atomic radius: 128).

[0068] At this point, Cu can act as a catalyst in the initial silicon nucleation process, helping to micronize the silicon nuclei.

[0069] Furthermore, when the number of elements in the synthesized alloy is large and the difference in atomic radii exceeds 10%, the deformation in the liquid phase caused by these atomic size differences is mitigated by the inherent open structure of the liquid phase itself. Moreover, when the atomic size distribution is large, the atomic structure of the liquid phase becomes more dense.

[0070] If the five-component alloy composition consists of multiple alloying elements during solidification in order to generate crystal nuclei from the liquid solution, then all the internal atoms of the crystal will be arranged in a regular three-dimensional spatial arrangement. Therefore, when these nuclei attempt to crystallize, they must possess a correspondingly very complex crystal lattice structure.

[0071] For a nucleus with such a complex lattice structure to form, the atoms in the alloy composition must possess sufficient diffusion capability. However, the factor that inhibits this capability is the strain energy caused by the differences in atomic size between these alloying elements.

[0072] Thus, the more alloying elements with large size differences are involved, the greater the strain energy will be. Therefore, if more alloying elements are included, the probability of crystallization during alloy solidification will be greatly reduced, and the probability of forming relatively small grain sizes will increase.

[0073] The following describes the elements of the five-component alloy composition.

[0074] First, in the above-mentioned silicon anode material composition, aluminum (Al) can be used to improve the conductivity of the silicon anode material and exists as a silicide matrix to alleviate the stress caused by the volume expansion of silicon, while reacting with lithium to supplement the capacity of the silicon anode material.

[0075] At this point, the aluminum (Al) content can be between 18 atomic% and 33 atomic% of the overall multi-component silicon matrix content. If the aluminum content is less than 18 atomic%, the matrix's ductility will decrease, weakening its role as a supporting matrix in mitigating silicon volume expansion, and reducing conductivity. Conversely, when the aluminum content exceeds 33 atomic%, excessive silicide matrix formation will lead to reduced capacity.

[0076] Furthermore, nickel (Ni) is used as an additive to improve the conductivity of silicon anodes. Adding Ni can improve cycle stability and conductivity. Si-Ni alloy phases such as NiSi, NiSi2, Ni3Si2, and Ni3Si are inactive for lithium ions and only function as supporting materials. The higher the nickel content, the more it combines with silicon to form intermetallic compounds, thus leading to a decrease in battery capacity.

[0077] At this point, the nickel (Ni) content can be between 3 atomic% and 20 atomic% of the total content of the overall multi-component silicon-based matrix. When the nickel content is less than 3 atomic%, insufficient conductivity may occur; while when the nickel content exceeds 20 atomic%, excessive formation of inactive materials may occur, resulting in a reduction in the capacity of the silicon composite anode.

[0078] Furthermore, boron (B) has the smallest atomic radius among the elements added to the composition of silicon anode materials. Therefore, adding B can improve the amorphous forming ability of silicon anode materials, thereby refining the grain size of silicon particles and increasing strength during alloying with other metals.

[0079] At this point, the boron (B) content can be more than 1 atomic% and less than 10 atomic% of the total content of the overall multi-component silicon matrix. When the boron content is less than 1 atomic%, the amorphous forming ability decreases, which may lead to problems with silicon grain refinement. When it exceeds 10 atomic%, the brittleness increases, which may lead to problems with particle breakage.

[0080] Furthermore, as mentioned above, copper (Cu) has catalytic properties, high electrical conductivity, and high ductility. During alloying, it provides ductility to the matrix and acts as a buffer against stress during volume expansion. Additionally, the elements used in the silicon anode material melt at temperatures below those of silicon, thus eliminating the need for an additional melting process.

[0081] At this point, the content of copper (Cu) can be more than 3 atomic% and less than 13 atomic% of the overall multi-component silicon matrix. When the copper content is less than 3 atomic%, it may lead to the problem that the addition effect is not fully manifested. When it exceeds 13 atomic%, it may react excessively with other elements to form intermetallic compounds, thereby leading to the problem of capacity reduction.

[0082] At this point, the sum of the atomic percentages of copper (Cu) and boron (B) present in the aforementioned multi-component silicide matrix is ​​7 atomic percentages or more and 12 atomic percentages or less, and in particular, the ratio of Cu atomic percentages to (Cu atomic percentages + B atomic percentages) is 71% or more and 83% or less.

[0083] At this point, in this invention, when the content of copper (Cu) and boron (B) is less than 7 atomic%, the addition effect may not be fully realized; while when the content of copper (Cu) and boron (B) exceeds 12 atomic%, they may react excessively with other elements to form intermetallic compounds, thereby leading to problems of reduced capacity and increased brittleness.

[0084] Furthermore, the ratio of Cu atoms % / (Cu atoms % + B atoms %) refers to the proportion of copper (Cu) in the overall copper (Cu) and boron (B) content. This ratio can represent the improvement in the ductility and conductivity of the matrix. When this formula is satisfied, the excellent maintenance of the lifespan characteristics of the silicon composite anode can be observed.

[0085] In this case, the silicon content in the multi-component silicide matrix can be the remainder after containing the aforementioned aluminum, nickel, boron, and copper.

[0086] At this time, the multi-component silicide matrix contains crystalline silicon nanoparticles, which can play a buffering role when their volume expands.

[0087] The following will describe the silicon nanoparticles contained in silicon composite anode materials.

[0088] Based on the total atomic percentage of the entire silicon composite anode material, the atomic percentage of silicon may include the aforementioned aluminum, nickel, boron, and copper, and may then include the remainder.

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

[0090] The following describes a method for preparing silicon composite anode materials according to other embodiments of the present invention.

[0091] In one embodiment of the present invention, the method for manufacturing silicon composite anode material includes the following steps: melting aluminum (Al), nickel (Ni), boron (B), copper (Cu) and silicon (Si) metals in a specific mixing ratio in a furnace to prepare a melt; and rapidly cooling the melt by high-pressure water jetting, and then classifying the powder to manufacture silicon anode material powder containing crystalline silicon permeated in a multi-component silicide matrix.

[0092] Traditional silicon alloy anode materials form a crystalline phase with a regular atomic arrangement when solidified from a liquid state. However, if the cooling rate during solidification is fast enough, exceeding a critical value that limits the nucleation and growth of the crystalline phase, the irregular atomic structure of the liquid state can be directly maintained in the solid state. Such alloys are usually called amorphous alloys.

[0093] In addition, in the traditional method of manufacturing anode materials for lithium secondary batteries, various required raw materials are mixed and melted to form an ingot, which is then formed into an amorphous ribbon strip through a melt spinning process. The resulting ribbon strip is then pulverized and mixed with carbon, a polyimide coating solution, and NMP through a grinding process to prepare an alloy silicon anode material.

[0094] However, the process of pulverizing the silicon anode material after manufacturing amorphous strips is very complex and has limitations in shape and size, thus greatly restricting its practical application.

[0095] Furthermore, silicon anode materials manufactured via melt spinning are expensive, making silicon anode materials based on this alloy composition insufficiently competitive in terms of price. Additionally, amorphous alloys only exhibit their properties in their amorphous state; therefore, when introducing processes such as carbon coatings to prevent silicon side reactions, heat treatment can cause the amorphous structure to transform into a crystalline structure, thus adversely affecting battery performance.

[0096] On the other hand, the present invention relates to a method for preparing silicon anode material powder, wherein silicon and four other components are dissolved in a crucible in a certain mixing ratio, and the melt is rapidly cooled by high-pressure water jet through a nozzle, thereby containing crystalline silicon and a silicide matrix in the metal alloy.

[0097] The preparation method of the silicon composite anode material of the present invention will be described in detail below.

[0098] In the first step, aluminum (Al), nickel (Ni), boron (B), copper (Cu), and silicon (Si) metals are added to a crucible in a specific mixing ratio and melted to prepare a melt.

[0099] At this point, the aluminum (Al) content in the entire melt should be between 18 atomic% and 33 atomic%; the nickel (Ni) content should be between 3 atomic% and 20 atomic%; the boron (B) content should be between 1 atomic% and 10 atomic%; the copper (Cu) content should be between 3 atomic% and 13 atomic%; and the remainder should be silicon (Si).

[0100] At this point, the aluminum (Al) content can be between 18 atomic% and 33 atomic% of the entire multicomponent silicon matrix. If the aluminum content is less than 18 atomic%, it may lead to a decrease in the toughness of the matrix, thereby reducing the role of the supporting matrix in mitigating silicon volume expansion and potentially causing a decrease in conductivity; if the aluminum content exceeds 33 atomic%, it may lead to a decrease in capacity due to the formation of excessive silicide matrix.

[0101] At this point, the nickel (Ni) content can be between 3 atomic% and 20 atomic% of the entire multicomponent silicon substrate. If the nickel content is less than 3 atomic%, it may not provide sufficient conductivity; if the nickel content exceeds 20 atomic%, excessive formation of inactive material may occur, leading to a decrease in the capacity of the silicon composite anode.

[0102] At this point, the boron (B) content can be between 1 atomic% and 10 atomic% of the entire multicomponent silicon matrix. If the boron content is less than 1 atomic%, it may lead to a decrease in amorphous forming ability, thereby affecting the refinement of silicon grains; if the boron content exceeds 10 atomic%, it may lead to increased brittleness, thereby causing particle breakage.

[0103] At this point, the copper (Cu) content can be between 3 atomic% and 13 atomic% of the entire multi-component silicon-based matrix. If the copper content is less than 3 atomic%, the additive effect may not be fully realized; if the copper content exceeds 13 atomic%, it may react excessively with other elements to form intermetallic compounds, leading to a decrease in capacity.

[0104] Furthermore, the total percentage of copper (Cu) atoms and boron (B) atoms present within the multi-component silicide matrix should be between 7 and 12 atomic percent, particularly the ratio of copper atoms percent to (copper atoms percent + boron atoms percent) should be between 71% and 83%. When adjusting the ratio of copper (Cu) atoms to boron (B) atoms, the proportion of materials with both toughness and brittleness can be appropriately adjusted. This allows the brittle element B to increase particle strength, thus meeting the condition that the particles are not easily broken, while the toughness element Cu provides stress relief characteristics due to particle expansion.

[0105] At this time, the substance containing copper (Cu) can be copper (Cu), copper oxide (I) (Cu O), copper oxide (II) (CuO), copper-aluminum alloy (CuAl), bronze (Cu-Sn), brass (Cu-Zn) or a mixture of one or more of these, or one of these two.

[0106] In the second stage, the melt is rapidly cooled by high-pressure water jets, and then the powder is graded to produce silicon composite anode material powder impregnated with crystalline silicon within a multi-component silicide matrix.

[0107] When rapid cooling is achieved through high-pressure water jetting, the cooling rate should be at least 10%. 5 K / Sec to 10 7 Between K and Sec.

[0108] At this time, when the rapid cooling rate is less than 10 5 At K / Sec, excessive growth of the silicon single phase within the silicon anode material can lead to stress that cannot be relieved by the substrate, potentially causing damage to the silicon anode material. A low cooling rate can cause compounds to form with the substrate metal, resulting in low capacity and an inability to exhibit high-rate characteristics. Furthermore, when the rapid cooling rate exceeds 10... 7At K / Sec, some silicon crystals inside the silicon composite anode will be in a mixed state of crystalline and amorphous materials, which may lead to a decrease in the capacity of the silicon composite anode. Therefore, the rapid cooling rate should be controlled at 10 K / Sec. 5 K / Sec to 10 7 Between K and Sec.

[0109] In the silicon composite anode material of the present invention, a five-component anode material composition was designed to improve the size of silicon particles, wherein the difference in atomic radius between components exceeds 10%. In the liquid phase, the deformation caused by these differences in atomic size is mitigated by the inherent open structure of the liquid phase itself. Furthermore, when the atomic size distribution is large, the atomic structure of the liquid phase can be more dense than when this is not the case.

[0110] In this context, the reason why the atomic structure of the liquid phase can become more dense when the atomic size distribution is large is that, during the solidification of the five-component alloy composition, due to the presence of multiple alloying elements, the atoms must be arranged regularly in three-dimensional space to form crystal nuclei from the aforementioned liquid solution with structural characteristics. For these nuclei to also crystallize, they must possess a correspondingly complex lattice structure. To generate nuclei with such a complex lattice structure, the alloying atoms must possess sufficient diffusion capacity to allow them to move freely. However, this diffusion capacity is inhibited by the strain energy caused by differences in atomic size. As the differences in atomic size between alloying elements increase, the strain energy increases significantly, meaning that the probability of crystal formation during alloy solidification decreases significantly, thereby increasing the probability of forming relatively small grain sizes.

[0111] Therefore, the average particle size of the silicon composite anode material powder manufactured by the above-described silicon composite anode material manufacturing method can be 5 to 6 micrometers. This particle size was chosen because when the average particle size of the silicon composite anode material is less than 5 micrometers, the increased specific surface area necessitates the addition of a binder, and the small powder size may lead to insufficient dispersion between powder particles. During electrode fabrication, electrolyte migration becomes very difficult, potentially causing ionic conductivity issues and reducing battery capacity. Conversely, when the average particle size exceeds 6 micrometers, ion diffusion problems may arise due to the increased lithium-ion diffusion path, and intercalation issues may occur when mixed with natural graphite. Therefore, an average particle size between 5 and 6 micrometers is ideal, but it is not limited to the aforementioned range.

[0112] The present invention will be further described in detail below through manufacturing examples and experimental examples. These manufacturing examples and experimental examples are merely illustrative of the invention and do not limit the scope of the invention.

[0113] Manufacturing Example 1: Manufacturing of silicon composite anode material (atomic ratio of Al, Ni, B, Cu is 25:3:2:10)

[0114] First, 25 atomic percent aluminum (Al), 3 atomic percent nickel (Ni), 2 atomic percent boron (B), and 10 atomic percent copper (Cu) are added to a high-frequency melting furnace in a ratio of 60 atomic percent silicon (Si). These elements are melted in the high-frequency melting furnace at a temperature exceeding 1550°C and held for at least 45 minutes, specifically, at a time between 60 and 100 minutes, to achieve a uniform liquid state.

[0115] Next, powder is manufactured using a spray granulation method; more specifically, this involves atomizing and cooling the molten alloy using a high-pressure coolant. During this process, the cooling rate is 10... 5 K / Sec to 10 7 K / Sec.

[0116] Subsequently, after classification, silicon composite anode material powder with an average particle size of about 5 to 6 micrometers was obtained.

[0117] Manufacturing Example 2: Manufacturing of silicon composite anode material (atomic ratio of Al, Ni, B, Cu is 30:3:2:5)

[0118] In Preparation Example 2, the same method as in Manufacturing Example 1 was performed, except that it contained 30 atomic percent aluminum, 3 atomic percent nickel, 2 atomic percent boron, 5 atomic percent copper and the remainder silicon (60 atomic percent).

[0119] Manufacturing Example 3: Manufacturing of silicon composite anode material (atomic ratio of Al, Ni, B, Cu is 27:4:2:7)

[0120] In this preparation example 3, the same method as in manufacturing example 1 above was used, except that it contained 27 atomic% aluminum, 4 atomic% nickel, 2 atomic% boron, 7 atomic% copper and the remainder silicon (60 atomic%).

[0121] Comparative Example 1: Fabrication of silicon composite anode material (atomic ratio of Al, Ni, B, Cu is 28:3:1:8)

[0122] In Comparative Example 1, the same method as in Manufacturing Example 1 was used, except that it contained 28 atomic percent aluminum, 3 atomic percent nickel, 1 atomic percent boron, 8 atomic percent copper and the remainder silicon (60 atomic percent).

[0123] Comparative Example 2: Fabrication of silicon composite anode material (atomic ratio of Al, Ni, B, Cu is 32:3:2:3)

[0124] In this manufacturing example 2, the same method as in manufacturing example 1 was used, except that it contained 32 atomic percent aluminum, 3 atomic percent nickel, 2 atomic percent boron, 3 atomic percent copper and the remainder silicon (60 atomic percent).

[0125] Comparative Example 3: Fabrication of silicon composite anode material (atomic ratio of Al, Ni, B, Cu is 22:3:5:10)

[0126] In this Comparative Example 3, the same process as in Manufacturing Example 1 was carried out, except that it contained 22 atomic percent aluminum, 3 atomic percent nickel, 5 atomic percent boron, 10 atomic percent copper and the remainder silicon (60 atomic percent).

[0127] Comparative Example 4: Fabrication of silicon composite anode material (atomic ratio of Al, Ni, B, Cu is 28:4:1.2:6.8)

[0128] In this Comparative Example 4, the same method as in Manufacturing Example 1 was used, except that it contained 28 atomic% aluminum, 4 atomic% nickel, 1.2 atomic% boron, 6.8 atomic% copper and the remainder silicon (60 atomic%).

[0129] Comparative Example 5: Fabrication of silicon composite anode material (atomic ratio of Al, Ni, B, Cu is 23:6:3.5:7.5)

[0130] In this Comparative Example 5, the same method as in Manufacturing Example 1 was used, except that it contained 23 atomic% aluminum, 6 atomic% nickel, 3.5 atomic% boron, 7.5 atomic% copper and the remainder silicon (60 atomic%).

[0131] Table 1 below shows the percentage values ​​of atoms for the examples and comparative examples, as follows.

[0132] Table 1

[0133] Differentiation Si (at%) Al (at%) Ni (at%) B (at%) Cu (at%) Example 1 60 25 3 2 10 Example 2 60 30 3 2 5 Example 3 60 27 4 2 7 Comparative Example 1 60 28 3 1 8 Comparative Example 2 60 32 3 2 3 Comparative Example 3 60 22 3 5 10 Comparative Example 4 60 28 4 1.2 6.8 Comparative Example 5 60 23 6 3.5 7.5

[0134] Table 2 below shows the ratio of Cu to Cu+B, which is set to various ratios from 60% to 89%.

[0135] Table 2

[0136]

[0137] Example 1: Fabrication of a single electrode

[0138] In the above manufacturing example, the manufactured silicon anode material is mixed with binder PI and conductive agent in a weight ratio of 86.6:10:3.4 to prepare a negative electrode active material slurry.

[0139] At this point, the prepared slurry is coated onto the copper foil current collector to manufacture the negative electrode plate. After the coated electrode plate is dried at 110°C for 20 minutes, it is rolled to make the density of the negative electrode plate reach 1.5 g / cc.

[0140] Next, the dried negative electrode plate is heat-treated in an argon atmosphere at 350°C for 2 hours, and then the plate is cut into 14mm pieces to produce the negative electrode for a circular battery.

[0141] At this point, lithium metal was used as the counter electrode, and a 20mm thick polypropylene membrane was used. After injecting electrolyte, the membrane was compressed to manufacture a 2032-sized button battery.

[0142] At this point, the electrolyte is a mixture of ethylene carbonate and diethyl carbonate with 10% electrolyte additive FEC added, and dissolved to a LiPF6 concentration of 1.0M.

[0143] Example 2: Manufacturing of silicon composite anode material

[0144] First, the silicon anode material manufactured in Example 1 is mixed with graphite at a mass ratio of 9:1, and the SBR / CMC conductive agent is mixed at a mass ratio of 95:4.8:0.2 to manufacture anode active material slurry.

[0145] Next, the prepared slurry is coated onto a copper foil current collector to manufacture a negative electrode. The coated electrode is dried at 110°C for 20 minutes and then rolled to achieve a density of 1.5 g / cc.

[0146] Next, the dried negative electrode sheet is heat-treated in a vacuum environment at 180°C for 10 hours, and then the electrode sheet is cut into 14mm sizes to manufacture the negative electrode suitable for button batteries.

[0147] At this point, lithium metal is used as the counter electrode, a 20mm thick polypropylene membrane is used, electrolyte is injected and compressed to manufacture a 2032 specification button battery.

[0148] At this point, the electrolyte is made by adding 10% electrolyte additive FEC to a mixed solvent of ethylene carbonate and diethylene carbonate, and dissolving LiPF6 to make its concentration 1.0M, thereby creating a separate electrode.

[0149] Experimental Example

[0150] Figure 2This is a cross-sectional and elemental analysis image of a silicon anode material according to an embodiment of the present invention.

[0151] from Figure 2 It can be confirmed that crystalline silicon nanoparticles are contained within the multi-component silicide matrix.

[0152] Figure 3 This is the XRD pattern of a silicon composite anode material according to an embodiment of the present invention.

[0153] refer to Figure 3 It can be confirmed that the new peaks between 2θ° are due to the formation of a new phase by the addition of copper, and TEM / EDS analysis confirms that a copper phase has been formed in the matrix.

[0154] Figure 4 According to one embodiment of the present invention, FE-SEM images show the evaluation results of the morphology retention of silicon composite anode materials before and after cycling.

[0155] refer to Figure 4 By comparing the surface characteristics of the silicon composite anode materials before and after charge-discharge cycles in Example 3 and Comparative Example 2, and after cycle life evaluation, it can be confirmed that the silicon volume expansion of the silicon composite anode materials in the examples is buffered by the surrounding matrix structure, thereby avoiding powder breakage.

[0156] Figure 5 This is a schematic diagram illustrating the conductivity of the silicon anode material in one embodiment of the present invention.

[0157] refer to Figure 5 Impedance analysis confirmed that the internal impedance of the silicon anode material decreased from 450Ω to 210Ω. This confirms that the presence and increased content of copper within the material contribute to its excellent conductivity.

[0158] The following describes the charge-discharge experimental results of the lithium secondary battery using the silicon composite anode material included in this invention.

[0159] In this charge-discharge experiment, a current density equivalent to Cycle: 0.2C was used for charging in CC mode (constant current mode), and when the voltage dropped to 0.005V, it was switched to CV mode (constant voltage mode) to continue charging to 0.005C.

[0160] Then, discharge is performed at a current density of 0.2 Crate, and the above charge and discharge reaction is repeated 50 times to complete the cycle, with a 1-hour rest period between each charge and discharge.

[0161] Figure 6 This is a schematic diagram of the single-electrode cycle characteristics of an embodiment and comparative example of the present invention.

[0162] refer toFigure 6 Based on the initial charge-discharge diagram of Example 3, the discharge capacity of Example 3 is 1,923 mAh / g, while the discharge capacity of Comparative Example 2 is 2,312 mAh / g.

[0163] Figure 7 This is a graph evaluating the cycling characteristics of a single electrode and a hybrid electrode according to an embodiment of the present invention.

[0164] refer to Figure 7 In (a), the single-electrode lifetime retention rate of Example 3 was 83%, while that of Comparative Example 2 was 62%, thus confirming the superior lifetime retention rate of the examples. Furthermore, refer to... Figure 7 (b) The lifetime retention rate of the hybrid electrode in Example 3 was 93%, while that in Comparative Example 2 was 79%. It can be seen that Example 3 showed excellent retention rates in both single-electrode and hybrid-electrode applications.

[0165] Table 3 below shows the evaluation results of the single-electrode electrochemical characteristics of the examples and comparative examples.

[0166] Table 3

[0167]

[0168] The initial discharge capacity increases with increasing Si+Al content. Furthermore, the effects of Cu and B on cycle life characteristics were investigated.

[0169] Cu+B has an atomic percentage content of 2 atomic% or more and 15 atomic% or less, with excellent lifetime characteristics confirmed at contents of 7 atomic% or more and 12 atomic% or less.

[0170] Furthermore, when the content of Cu atoms % / (Cu atoms % + B atoms %) was confirmed, it was found that the lifetime characteristics were excellent at ratios of 71% or higher and 83% or lower.

[0171] Table 4 below shows the evaluation results of the electrochemical characteristics of the hybrid electrodes in the examples and comparative examples.

[0172] Table 4

[0173]

[0174] Based on the single-electrode results, 10 wt% silicon anode material was mixed with graphite to prepare an electrode, and the electrochemical properties were evaluated. The results showed a similar trend to those of the single-electrode method.

[0175] In Example 1, even when internal stress is generated during cycling, the shape of the silicon anode material is maintained due to the buffering effect of the silicide matrix on the silicon structure; while in Comparative Example 1, the silicon anode material cannot withstand the internal stress as cycling continues, resulting in its destruction.

[0176] During the fabrication of silicon anode materials, TEM / EDS confirmed the uniform distribution of silicon and Cu in the matrix.

[0177] The above description of the present invention is merely illustrative, and those skilled in the art will understand that it can be readily modified into other specific forms without altering the technical concept or essential features of the invention. Therefore, the embodiments described above should be understood as exemplary in all respects and not restrictive. For example, the various components described in a single form may be implemented separately, and similarly, the components described separately may be implemented in combination.

[0178] The scope of this invention is defined by the patent claims described below, and any changes or modifications derived from the meaning and scope of the claims and their equivalents shall be construed as being included within the scope of this invention.

[0179] List of reference signs

[0180] 100: Multi-component silicide matrix; 200: Silicon nanoparticles.

Claims

1. A silicon composite negative electrode material, characterized by, The material comprises: a multi-component silicide matrix comprising aluminum (Al), nickel (Ni), boron (B), copper (Cu), and silicon (Si); and crystalline silicon nanoparticles immersed inside the silicon matrix. 2.The silicon composite negative electrode material according to claim 1, characterized in that, the multi-component silicide matrix is composed of a substance represented by the following Chemical Formula 1: Chemical Formula 1 Si a (Al b Ni c Cu d B e ) wherein a is a real number of 0.24 to 0.75, b is a real number of 0.18 to 0.33, c is a real number of 0.03 to 0.2, d is a real number of 0.03 to 0.13, and e is a real number of 0.01 to 0.

1. 3.The silicon composite negative electrode material according to claim 1, characterized in that, the content of the aluminum (Al) is 18 atomic% or more and 33 atomic% or less of the total content of the multi-component silicide matrix. 4.The silicon composite negative electrode material according to claim 1, characterized in that, the content of the nickel (Ni) is 3 atomic% or more and 20 atomic% or less of the total content of the multi-component silicide matrix. 5.The silicon composite negative electrode material according to claim 1, characterized in that, the content of the boron (B) is 1 atomic% or more and 10 atomic% or less of the total content of the multi-component silicide matrix. 6.The silicon composite negative electrode material according to claim 1, characterized in that, the content of the copper (Cu) is 3 atomic% or more and 13 atomic% or less of the total content of the multi-component silicide matrix. 7.The silicon composite negative electrode material according to claim 1, characterized in that, the sum of the atomic% of the copper (Cu) and the atomic% of the boron (B) is 7 atomic% or more and 12 atomic% or less. 8.The silicon composite negative electrode material according to claim 1, characterized in that, the ratio of Cu atomic% / (Cu atomic%+B atomic%) in the content of the copper (Cu) and the boron (B) is 71% or more and 83% or less. 9.The silicon composite negative electrode material according to claim 1, characterized in that, the atomic% of silicon in the silicon composite negative electrode material is the remaining part after containing the aluminum, the nickel, the boron, and the copper.

10. A silicon composite negative electrode material, characterized by, The material comprises: a multi-component silicide matrix comprising aluminum (Al), nickel (Ni), boron (B), copper (Cu), and silicon (Si), wherein the difference between the atomic radii of the aluminum (Al), the nickel (Ni), the boron (B), the copper (Cu), and the silicon (Si) exceeds 10%; and crystalline silicon nanoparticles immersed inside the silicon matrix.

11. A silicon composite negative electrode material, characterized by, The material comprises: a multi-component silicide matrix composed of a substance represented by the following Chemical Formula 1; and crystalline silicon nanoparticles immersed inside the silicon matrix: [Chemical Formula 1] Si a (Al b Ni c Cu d B e ) wherein a is a real number of 0.24 to 0.75, b is a real number of 0.18 to 0.33, c is a real number of 0.03 to 0.2, d is a real number of 0.03 to 0.13, and e is a real number of 0.01 to 0.

1.

12. A method for producing a silicon composite negative electrode material, characterized by, comprising the following steps: putting aluminum (Al), nickel (Ni), boron (B), copper (Cu), and silicon (Si) metals into a crucible in a specific mixing ratio to prepare a melt; and The molten material is rapidly cooled with high-pressure jetted water, and then powder classification is performed, to produce a silicon negative electrode material powder containing crystalline silicon immersed inside a multi-component silicide matrix.

13. The method for manufacturing a silicon composite negative electrode material according to claim 12, characterized in that, in the step of manufacturing the molten material, the content of the aluminum (Al) is 18 atomic% or more and 33 atomic% or less of the entire molten material; the content of the nickel (Ni) is 3 atomic% or more and 20 atomic% or less of the entire molten material; the content of the boron (B) is 1 atomic% or more and 10 atomic% or less of the entire molten material; the content of the copper (Cu) is 3 atomic% or more and 13 atomic% or less of the entire molten material; the remainder is silicon.

14. The method for manufacturing a silicon composite negative electrode material according to claim 12, characterized in that, in the step of manufacturing a silicon negative electrode material powder with crystalline silicon impregnated inside a multi-component silicide matrix, 15. A silicon negative electrode active material, characterized by, containing the silicon composite negative electrode material according to claim 1 and graphite. The rapid cooling speed is 10 5 K / Sec to 10 7 K / Sec.

16. The silicon negative electrode active material according to claim 15, characterized in that, the content of the silicon composite negative electrode material is 5 to 10% by weight of the entire silicon negative electrode active material; the content of the graphite is 90 to 95% by weight of the entire silicon negative electrode active material. ​ ​

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