Method for manufacturing si-based alloy for negative electrode active material of secondary battery and si-based alloy for negative electrode active material of secondary battery manufactured thereby

Abstract

Provided is a method for manufacturing a Si-based alloy for a negative electrode active material of a secondary battery. Accordingly, a Si-based alloy having a smaller thickness and being amorphous can be implemented more easily, and the use of the implemented Si-based alloy as a negative electrode active material of a secondary battery is highly suitable for achieving a high-capacity secondary battery and enables the maintenance of excellent charging and discharging efficiency for a long time even with repeated charging and discharging.

Description

Method for manufacturing Si-based alloy for secondary battery negative electrode active material and Si-based alloy for secondary battery negative electrode active material manufactured thereby

[0001] The present invention relates to a method for manufacturing a Si-based soft magnetic alloy and a Si-based alloy for use as a negative electrode active material for a secondary battery manufactured thereby.

[0002] With the recent increase in demand for electronic devices, including mobile devices, technological development for these devices is expanding. This has led to a significant increase in demand for secondary batteries, such as lithium-ion batteries and lithium-ion polymer batteries, to power these devices. Furthermore, with global regulations on automotive fuel efficiency and exhaust emissions becoming increasingly stringent, the growth of the electric vehicle market is accelerating. This, in turn, is driving a surge in demand for mid- to large-sized secondary batteries, such as those for electric vehicles (EVs) and energy storage systems (ESS).

[0003] Meanwhile, carbon-based anode materials with excellent cycle characteristics and a theoretical capacity of 372 mAh / g have been generally used as anode materials for secondary batteries. However, with the demand for higher capacity in secondary batteries, such as medium- to large-sized secondary batteries, active development is being conducted on various anode materials that can replace the theoretical capacity of carbon-based anode materials. For example, silicon-based anode materials are attracting attention. However, when silicon is used as an anode active material, there was a problem that cracks and breakage of silicon particles occurred due to volume changes in the process of lithium ion insertion and deintercalation through repeated charge and discharge. Due to this problem, the surface area of ​​the anode active material particles increased, and as a result, a thick film layer composed of decomposition products of the non-aqueous electrolyte was formed on the surface of the anode active material, which increased the interfacial resistance between the anode active material and the non-aqueous electrolyte, resulting in a problem of reduced charge and discharge cycle characteristics.

[0004] Accordingly, there is an urgent need to develop a negative electrode material that can achieve high capacity while increasing charge / discharge efficiency and extending cycle life even with repeated charge / discharge.

[0005] The present invention has been devised in consideration of the above points, and its purpose is to provide a method for manufacturing a Si-based alloy for a secondary battery negative electrode active material, which can be easily implemented to have an amorphous structure while achieving high capacity, excellent charge / discharge efficiency, and a high cycle life even in repeated charge / discharge cycles, and a Si-based alloy for a secondary battery negative electrode active material manufactured thereby.

[0006] In addition, another object of the present invention is to provide a secondary battery negative electrode active material composition that can further improve cycle life by using a Si-based alloy for negative electrode active material according to the present invention, and a secondary battery having a negative electrode implemented through the same.

[0007] In order to solve the above-mentioned problem, the present invention has an empirical formula of Si100-abc-dAl a Sn b C c M d (Where a, b, c, and d are at% (atomic percent) of the corresponding elements, 10≤a≤30, 0.5≤b≤5, 0 <c≤10, 0≤d≤35이고, M은 Fe, Ni, Cu 및 Mn 중 1종 이상의 원소임)로 표시되는 Si계 모합금을 제조하는 단계; 상기 Si계 모합금을 급속고화공정(RSP)을 통해서 Si계 비정질 리본시트로 제조하는 단계; 및 Si계 비정질 리본시트를 파쇄하는 단계;를 포함하는 이차전지 음극활물질용 Si계 합금 제조방법을 제공한다.

[0008] According to one embodiment of the present invention, the element M includes at least one element among Fe, Ni, Mn, and Cu, and Fe may be contained in an amount of 5 to 15 at% in the Si-based alloy, Ni may be contained in an amount of more than 0 to 5 at% in the Si-based alloy, Mn may be contained in an amount of more than 0 to 5 at% in the Si-based alloy, and Cu may be contained in an amount of more than 0 to 10 at% in the Si-based alloy.

[0009] Additionally, the above Si-based amorphous ribbon sheet may have a thickness of 10 μm or less.

[0010] In addition, the rapid solidification process can be performed through a melt spinning process in which a molten Si-based master alloy is discharged through a nozzle hole having a diameter of 0.1 to 0.6 mm onto a wheel having a surface speed of 20 to 50 m / s to manufacture a ribbon sheet.

[0011] Additionally, the step of heat treatment after manufacturing the Si-based amorphous ribbon sheet may not be included.

[0012]

[0013] In addition, the present invention has an empirical formula of Si100-abc-dAl a Sn b C c M d (Where a, b, c, and d are at% (atomic percent) of the corresponding elements, 10≤a≤30, 0.5≤b≤5, 0 <c≤10, 0≤d≤35이고, M은 Fe, Ni, Cu 및 Mn 중 1종 이상의 원소임)로 표시되며 비정질인 이차전지 음극활물질용 Si계 합금을 제공한다.

[0014] According to one embodiment of the present invention, the element M includes at least one element among Fe, Ni, Mn, and Cu, and Fe may be contained in an amount of 5 to 15 at% in the Si-based alloy, Ni may be contained in an amount of more than 0 to 5 at% in the Si-based alloy, Mn may be contained in an amount of more than 0 to 5 at% in the Si-based alloy, and Cu may be contained in an amount of more than 0 to 10 at% in the Si-based alloy.

[0015] Additionally, the Si-based alloy may be a powder having an average particle diameter of 20 ㎛ or less.

[0016]

[0017] In addition, the present invention provides a negative electrode active material composition for a secondary battery, including a Si-based alloy-carbon composite including a Si-based alloy according to the present invention in powder form and carbon powder covering at least a portion of the surface of the Si-based alloy powder.

[0018] According to one embodiment of the present invention, the average particle diameter of the carbon powder may be smaller than the average particle diameter of the Si-based alloy powder.

[0019] Additionally, the carbon powder may be contained in an amount of 1 to 50 parts by weight per 100 parts by weight of the Si-based alloy.

[0020] Additionally, the carbon powder may contain at least one of carbon black and pitch.

[0021]

[0022] In addition, the present invention provides a secondary battery having a negative electrode including a current collector; and a negative electrode active material layer formed on the current collector using a negative electrode active material composition for a secondary battery according to the present invention.

[0023] The method for manufacturing a Si-based alloy for a secondary battery anode active material according to the present invention can more easily realize an amorphous Si-based alloy having a thinner thickness, and when the realized Si-based alloy is used as a secondary battery anode active material, it is very suitable for realizing a high-capacity secondary battery and can maintain excellent charge / discharge efficiency and capacity for a long time even after repeated charge / discharge. In addition, the Si-based alloy powder composited with graphite powder as an anode active material can significantly improve the cycle life of a secondary battery, and thus can be widely adopted as a secondary battery anode.

[0024] Figures 1 to 3 are SEM photographs of the side surfaces of Si-based ribbon sheets obtained in the process of manufacturing Si-based alloys according to one embodiment and a comparative example of the present invention, and

[0025] Figure 4 is an XRD pattern of a Si-based alloy according to one embodiment of the present invention.

[0026] Hereinafter, with reference to the attached drawings, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement the present invention. The present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0027]

[0028] According to one embodiment of the present invention, a Si-based alloy for a secondary battery negative electrode active material has an empirical formula of Si100-abc-dAl a Sn b C c M d (Where a, b, c, and d are at% (atomic percent) of the corresponding elements, 10≤a≤30, 0.5≤b≤5, 0 <c≤10, 0≤d≤35이고, M은 Fe, Ni, Cu 및 Mn 중 1종 이상의 원소임)로 표시되는 Si계 모합금을 제조하는 단계; 상기 Si계 모합금을 멜트스피닝 공정을 통해서 Si계 비정질 리본시트로 제조하는 단계; 및 Si계 비정질 리본시트를 파쇄하는 단계;를 포함하여 제조될 수 있다.

[0029]

[0030] First, as a first step, the empirical formula is Si100-abc-dAl a Sn b C c M d (Where a, b, c, and d are at% (atomic percent) of the corresponding elements, 10≤a≤30, 0.5≤b≤5, 0 <c≤10, 0≤d≤35이고, M은 Fe, Ni, Cu 및 Mn 중 1종 이상의 원소임)로 표시되는 Si계 모합금을 제조하는 단계를 수행한다.

[0031] A Si-based master alloy is an alloy composed of an element M that essentially contains the elements Si, Al, Sn and C, and optionally contains one or more of Fe, Ni, Cu and Mn, and may further contain impurities below the amount typically recognized as impurities.

[0032] Element Si in the Si-based master alloy is a main element involved in the insertion and de-insertion of lithium during charge and discharge by causing an alloying reaction with lithium ions dissociated from the positive electrode side in the secondary battery, and high theoretical capacity can be achieved in the use of negative electrode active materials through Si, Al, and Sn. Element Si can be included as a remainder considering the contents of Al, Sn, C, and M in the master alloy, and when element M is included, Si can be included at, for example, 45 to 75 at%. In addition, Al and Sn can be included at 10 to 30 at% and more than 0 to 5 at% in the Si-based master alloy, respectively, and through this, it can be more advantageous to achieve the purpose of the present invention, such as implementing a high-capacity secondary battery.

[0033] In addition, in the Si-based master alloy, element C helps in the amorphization of the Si-based ribbon sheet implemented through the second step described below, while improving compatibility with carbon-based conductive materials that may be included in the negative electrode active material composition, improving electrical conductivity of the Si-based alloy, and playing a role in exhibiting a synergistic effect in improving cycle life when composited with graphite powder described below. The element C may be contained in the alloy in an amount of more than 0 and less than 10 at%, thereby more advantageously achieving the purpose of the present invention. If the element C is contained in the master alloy in excess of 10 at%, the content of other elements in the master alloy is relatively reduced, and thus, there is a concern that the effects exhibited through other elements may not be sufficient.

[0034]

[0035] Next, the element M that can be optionally contained is described. The element M includes at least one element among Fe, Ni, Cu, and Mn, and through the inclusion of these elements, the melting point of the Si-based alloy is lowered, the fluidity during melting is increased, and it is advantageous for implementing an amorphous Si-based alloy. In addition, the element M acts as a buffer matrix that alleviates volume expansion due to Si, etc., thereby improving the life characteristics of the negative electrode active material and additionally improving the initial efficiency and charge / discharge efficiency.

[0036] First, in the element M, Fe and / or Ni can achieve high electrical conductivity in addition to the effect of the element M described above, and can facilitate the production of an amorphous Si-based alloy. The Fe can be contained in the master alloy at 5 to 15 at%, and if Fe is contained at less than 5 at%, it may be difficult to control the volume expansion that may occur when reacting with Li ions due to the Si and Al elements described above. In addition, if Fe exceeds 15 at%, the content of other elements in the alloy is relatively reduced, and thus it may be difficult to achieve sufficient capacity or it may not be easy to achieve amorphousness. In addition, Ni can be contained at a content of more than 0 to 5 at%, and thereby it may be advantageous to sufficiently lower the melting point of the Si-based alloy. If Ni exceeds 5 at%, the content of other elements in the alloy is relatively reduced, and thus it may be difficult to achieve sufficient capacity or it may not be easy to achieve amorphousness, and there is a concern that the manufacturing cost may increase due to the high cost of raw materials.

[0037] Next, in the element M, Cu and Mn help to lower the melting point of the Si-based alloy and improve fluidity during melting, thereby helping to make the thickness of the ribbon sheet thinner, thereby facilitating the implementation of an amorphous Si-based alloy. The Cu may be included in the Si-based alloy in a content of 0 to 10 at%, and if Cu exceeds 10 at%, the content of other elements in the alloy is relatively reduced, making it difficult to achieve sufficient capacity and unsuitable for implementing a ribbon sheet.

[0038] In addition, Mn may be included in a Si-based alloy in a content of more than 0 to 5 at%, which may be advantageous in achieving the purpose of the present invention. If Mn exceeds 5 at%, the content of other elements in the alloy may be relatively reduced, which may make it difficult to achieve sufficient capacity.

[0039]

[0040] In addition, the Si-based master alloy can be produced by weighing and mixing the base materials containing each element to have the above-described experimental formula composition, and using a conventional alloy production method, such as an arc-melting method, the present invention is not particularly limited thereto.

[0041]

[0042] Next, as the second step of the present invention, a step of manufacturing the Si-based alloy into a Si-based amorphous ribbon sheet through a rapid solidification process (RSP) is performed.

[0043] The above rapid solidification process may be a known process of melting a master alloy and then rapidly cooling and solidifying it, and non-limiting examples thereof include a gas atomizing method in which a molten Si-based master alloy or Si-based alloy-forming composition is manufactured into a powder form by spraying high-pressure gas (Ex. Ar, N2, He, etc.) and / or high-pressure water, a centrifugal separation method in which a powder form is manufactured using a rapidly rotating disk of molten metal, and a melt spinning method in which a ribbon is manufactured by a roll rotating at a predetermined speed, and the like. The shape of the Si-based alloy formed through these methods may be a powder, a strip, or a ribbon. However, the melt spinning process may be used in which the process control is easy so that the Si-based alloy to be implemented has a uniform amorphous phase, and the Si-based alloy implemented in the second step has a ribbon sheet shape.

[0044]

[0045] In addition, when the rapid solidification process is a melt spinning process, the ribbon sheet manufactured through the two steps is a ribbon sheet having an amorphous structure of an alloy expressed by the above-described empirical formula, and preferably, in order to more easily realize an amorphous structure, the ribbon sheet may be formed to have a thickness of 10 μm or less, or for example, 6 to 10 μm. If the thickness of the ribbon sheet exceeds 10 μm, there is a concern that the frequency of manufacturing a ribbon sheet including crystals may increase.

[0046] Meanwhile, in order to manufacture a ribbon sheet with a thickness of 10㎛ or less, the melt spinning process may be performed under process conditions in which the diameter of the nozzle hole through which the molten Si-based master alloy is discharged may be 0.1 to 0.8㎜, and the surface speed of the wheel that the discharged molten Si-based master alloy comes into contact with is 20 to 50 m / s. If the diameter of the nozzle hole and the surface speed of the wheel are outside the above ranges, it may be difficult to implement the thickness of the target ribbon sheet, and accordingly, it may be difficult for the implemented ribbon sheet to have an amorphous structure. Specifically, there is a concern that crystals may be generated on one side of the ribbon sheet that comes into contact with the air side after being discharged onto the wheel among the two opposite sides in the thickness direction of the manufactured ribbon sheet, and within a certain area in the thickness direction from the one side.

[0047]

[0048] Next, as the third step of the present invention, a step of crushing the Si-based amorphous ribbon sheet is performed. The crushed Si-based alloy can form a powder having a particle diameter of several to several tens of micrometers. The crushing of the amorphous ribbon sheet can be performed using known methods for crushing an alloy into a powder alloy, such as an atomizer, a vacuum mill, a ball mill, a planetary ball, a beads mill, and a jet mill. In addition, the size of the crushed powder can be controlled by controlling the milling process time or the diameter of the balls added during ball milling, and the present invention is not particularly limited thereto.

[0049] In addition, the Si alloy powder pulverized through the third step may have an average particle diameter of 20㎛ or less, which may be advantageous in achieving the purpose of the present invention.

[0050]

[0051] In addition, the Si-based alloy according to one embodiment of the present invention may not be heat-treated, thereby maintaining an amorphous structure and being more advantageous in achieving the purpose of the present invention. However, depending on the purpose, an additional heat treatment process may be further performed. In the case of the Si-based alloy represented by the above-described experimental formula 1, it is easy to realize an amorphous structure, and thus, it may be advantageous in creating smaller and more uniform crystal grains even after heat treatment.

[0052]

[0053] In addition, the present invention includes a Si-based alloy manufactured through the above-described manufacturing method. The Si-based alloy has an amorphous structure and may be in the form of a powder, for example.

[0054]

[0055] In addition, the present invention includes a negative electrode active material composition for a secondary battery including a manufactured Si-based alloy, and specifically, the Si-based alloy is introduced into the negative electrode active material composition as a Si-based alloy-carbon composite including a Si-based alloy in powder form and carbon powder covering at least a portion of the surface of the Si-based alloy powder, thereby enabling the composition to exhibit improved cycle life characteristics.

[0056] The above Si-based alloy is in powder form, and may have an average particle diameter of, for example, 20 ㎛ or less, or, for another example, 10 ㎛ or less.

[0057]

[0058] In addition, the carbon powder is coated to cover at least a portion of the surface of the Si-based alloy powder as a powder for improving the life characteristics due to the Si-based alloy, and is advantageous in exhibiting a synergistic effect related to the life characteristics with carbon atoms in the Si-based alloy or a compound containing the same. The carbon powder has the function of improving the life characteristics as described above, and this function is distinct from the improvement in electrical conductivity exhibited by a carbon material contained as a conductive material described below.

[0059] The carbon powder may be a powder of a known carbon material. For example, the carbon material may include at least one selected from the group consisting of artificial graphite, natural graphite, carbon black, pitch, Ketjen black, acetylene black, etc. Preferably, the carbon material may include at least one of carbon black and pitch, thereby more advantageously achieving the purpose of the present invention.

[0060]

[0061] In addition, the carbon powder may be contained in an amount of 1 to 50 parts by weight, or in another example, 3 to 30 parts by weight, relative to 100 parts by weight of the Si-based alloy, which may be advantageous in achieving the purpose of the present invention.

[0062]

[0063] Additionally, the carbon powder may have an average particle diameter smaller than the average particle diameter of the Si-based alloy. For example, the carbon powder may have an average particle diameter of 10 μm or less, preferably 5 μm or less.

[0064]

[0065] In addition, the average particle size ratio of the Si-based alloy and the carbon powder may be 1: 0.6 to 0.2, which makes it suitable for implementing a structure in which the carbon powder covers the surface of the Si-based alloy and may be more advantageous in improving the life characteristics. If the average particle size of the carbon powder is less than 0.2 times that of the Si-based powder, it may be difficult to sufficiently improve the life characteristics. In addition, if the average particle size of the carbon powder exceeds 0.6 times that of the Si-based powder, the number of carbon powders covering the surface of the Si-based alloy may decrease, the density between carbon powders may decrease, and the shedding of carbon powder may become severe, which may ultimately lead to a deterioration of the initially designed life characteristics.

[0066]

[0067] In addition, the carbon powder can be provided on the surface of the Si-based alloy powder through a known physical or chemical method. For example, the dry raw material put in a sealed container can be rotated by a blade to coat the carbon powder on the surface of the Si-based alloy powder. For example, this can be performed using a Spheric Coater (KMT) device. Specific conditions may vary depending on the specific method and device used. For example, when using a Spheric Coater, the conditions may be 2500 to 5000 RPM for 2 to 30 minutes to perform coating through mixing. At this time, the mixing and coating process may be performed continuously once during the above time, or may be divided into two or more times during the above time, and the present invention is not particularly limited thereto. In addition, a more specific method using a Spheric Coater can be performed with reference to the manufacturer's protocol, and the present invention is not particularly limited thereto.

[0068]

[0069] The above-described Si-based alloy-carbon composite can be mixed with known components to form a negative electrode active material composition.

[0070] For example, the above-mentioned known component may be a component capable of implementing a negative electrode active material layer typically formed on a negative electrode current collector, and may further include, for example, a binder component, a conductive material component, and a solvent.

[0071] The above binder component is a component for bonding the Si-based alloy-carbon composite contained as a negative electrode active material component with a conductive material described below, and for bonding the components in the negative electrode active material composition to a current collector. The above binder component can be used without limitation as a binder component used in a known negative electrode active material composition, and non-limiting examples thereof include polyvinylidene fluoride, polyvinylidene chloride, polybenzimidazole, polyimide, polyvinylacetate, polyacrylonitrile, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, polystyrene, polymethyl methacrylate, polyaniline, acrylonitrile butadiene styrene, phenol resin, epoxy resin, polyethylene terephthalate, polytetrafluoroethylene, polyphenyl sulfide, polyamideimide, polyetherimide, polyethylene sulfone, polyamide, polyacetal, polyphenylene oxide, polybutylene terephthalate, ethylene-propylene-diene terephthalate. Polymers (EPDM), sulfonated EPDM, styrene butadiene rubber, fluoroelastomer, and various copolymers can be used in combination of one or more types.

[0072] In addition, the binder component may be included in an amount of 1 to 50 parts by weight based on 100 parts by weight of the negative electrode active material component, but is not limited thereto, and it is to be noted that the content may be adjusted depending on the purpose.

[0073]

[0074] In addition, the conductive material is intended to provide a conductive path to the above-described negative electrode active material component to further improve electrical conductivity, and any known conductive material used in a negative electrode active material composition for a secondary battery may be used without limitation. For example, the conductive material may include a conductive material including a powder such as artificial graphite or natural graphite, and / or a fibrous carbon-based material; a metal-based material such as a metal powder or metal fiber such as copper, nickel, aluminum, or silver; a conductive polymer such as a polyphenylene derivative, or a mixture thereof. In addition, the content of the conductive material may be appropriately adjusted depending on the purpose, and for example, the weight ratio of the negative electrode active material and the conductive material may be added in a range of 99:1 to 90:10.

[0075]

[0076] In addition, the solvent may be used without limitation as long as it can perform this function of dissolving the binder component while appropriately dispersing the negative electrode active material component and the conductive agent. For example, the solvent may include, but is not limited to, N-methylpyrrolidone (NMP), acetone, water, etc. In addition, the solvent may be included in an amount of 1 to 30 parts by weight based on 100 parts by weight of the negative electrode active material component, but is not limited thereto.

[0077]

[0078] In addition, the present invention includes a negative electrode for a secondary battery having a negative electrode active material layer formed through the above-described negative electrode active material composition, or a secondary battery having the same.

[0079] The above-described negative electrode for a secondary battery includes a current collector and a negative electrode active material layer formed on the current collector, and the negative electrode active material layer is implemented using the above-described negative electrode active material composition.

[0080] The current collector is not particularly limited as long as it is conductive and does not cause a chemical change in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. can be used. In addition, the surface may be formed with fine irregularities to strengthen the bonding strength of the negative electrode active material, and can be used in various forms such as a film, sheet, foil, net, porous body, foam, non-woven fabric, etc. In addition, the thickness of the current collector may be 3 to 500㎛, but is not limited thereto.

[0081]

[0082] In addition, the negative electrode active material layer can be manufactured into a negative electrode by directly coating the above-described negative electrode active material composition on a current collector, or by casting the negative electrode active material film on a separate support and peeling it from the support and laminating it on a current collector.

[0083]

[0084] In addition, the secondary battery including the above-described negative electrode further includes a known secondary battery configuration in addition to the negative electrode. For example, the secondary battery may further include a positive electrode, a separator, an electrolyte, and an outer material encapsulating the positive electrode, the separator, the negative electrode, and the electrolyte. Meanwhile, the present invention is not particularly limited to the various components constituting the above-described secondary battery, and a detailed description thereof will be omitted.

[0085] The present invention will be described in more detail through the following examples, but the following examples do not limit the scope of the present invention, and should be interpreted as helping to understand the present invention.

[0086]

[0087] <Example 1>

[0088] Empirical formula Si 70The raw materials of Si, Al, Sn, C, Fe, Cu, Mn, and Ni were weighed and then the Si-based master alloy, represented by Al9Sn1C3Fe9Cu6Mn1Ni1, was manufactured using the arc melting method. After that, the manufactured Si-based master alloy was melted and then discharged on a wheel with a surface speed of 50 m / s through a nozzle hole with a diameter of 0.5 mm in an Ar atmosphere, and 10 6 A Si-based amorphous alloy with a ribbon shape of approximately 7 μm in thickness and 2 mm in width was manufactured by rapid cooling at a rate of 100 K / sec. The Si-based amorphous ribbon sheet was then crushed using a ball mill to manufacture a Si-based alloy in powder form with an average particle size of 7.3 μm.

[0089]

[0090] Comparative Examples 1-2

[0091] The same process as Example 1 was performed to manufacture the ribbon sheet, but the melt spinning conditions and the thickness of the ribbon sheet to be manufactured were changed to manufacture the Si-based ribbon sheet as shown in Table 1 below, and through this, a Si-based alloy in powder form with an average particle diameter of 6.9 μm was manufactured.

[0092]

[0093] Experimental Example 1

[0094] SEM photographs were taken of the side surfaces of the Si-based ribbon sheets manufactured according to Example 1, Comparative Examples 1 and 2, and the results are shown in Fig. 1 (Example 1), Fig. 2 (Comparative Example 1), and Fig. 3 (Comparative Example 2), and the presence or absence of crystals formed is shown in Table 1.

[0095]

[0096] Additionally, the XRD pattern for Example 1 was analyzed and the results are shown in Fig. 4.

[0097]

[0098] In addition, a negative electrode was manufactured using the Si-based alloy obtained according to Example 1, Comparative Examples 1 and 2 according to Manufacturing Example 1 below, and a coin cell secondary battery was implemented through this.

[0099] < Manufacturing Example 1 >

[0100] A composition for a negative electrode active material was prepared by mixing a carbon black conductive agent having an average particle size of 2.8㎛ into a Si-based alloy at a weight ratio of 90:10, then mixing 5 parts by weight of a binder composed of styrene-butadiene rubber and polyamide-imide in a 5:5 ratio per 100 parts by weight of the Si-based alloy, and then mixing n-hexane as a solvent. The prepared negative electrode slurry was applied to one surface of a coin-shaped copper current collector having a diameter of 14 pi and a thickness of 18㎛, and then dried in a vacuum oven at 130℃ for 12 hours to prepare a negative electrode having a negative electrode active material layer having a thickness of 20㎛.

[0101] In addition, a circular Li metal with a diameter of 14 pi and a thickness of 0.5 mm was prepared as the positive electrode. Afterwards, a porous polyethylene (PE) separator (thickness: approximately 16 ㎛) was interposed between the prepared positive and negative electrodes, and electrolyte A was injected to manufacture a coin cell. Here, electrolyte A refers to an electrolyte solution in which lithium hexafluorophosphate (LiPF6, 1.0 M) and vinyl carbonate (VC, 2 wt%) are mixed in a mixture of ethylene carbonate (EC), dimethyl carbonate (DMC), and diethyl carbonate (DEC) in a volume ratio of 1:1:1.

[0102]

[0103] The following physical properties of the coin cells manufactured thereafter were evaluated, and the results are shown in Table 1 below.

[0104] 1. Initial charge / discharge capacity and initial efficiency

[0105] The manufactured coin cell was charged at a temperature of 25℃ with a charge current of 0.05C to a charge terminal voltage of 4.2 to 4.25 V, and then activated by charging until the current density became 0.01C at 0.02 V. Afterwards, it was discharged to a terminal voltage of 2 V with a discharge current of 0.05C, and the resistance of the electrode and the initial charge / discharge capacity per unit mass were measured. The initial efficiency was calculated according to the measured charge / discharge capacity and Equation 1 below.

[0106] [Formula 1]

[0107] Initial efficiency (%) = (discharge capacity in 1 cycle / charge capacity in 1 cycle) × 100

[0108] At this time, the initial charge / discharge capacity was expressed as a relative percentage based on the measured value of Example 1 as 100% and the measured values ​​of the remaining examples and comparative examples.

[0109]

[0110] 2. Cycle life

[0111] For coin cell secondary batteries, the lifespan after 30 cycles was calculated based on Equation 2 below.

[0112] [Formula 2]

[0113] 30 cycle life (%) = (discharge capacity after 30 cycles / discharge capacity after 1 cycle) × 100

[0114]

[0115] Example 1 Comparative Example 1 Comparative Example 2 Si-based alloy composition Si 70 Al9Sn1C3Fe9Cu6Mn1Ni1Melt spinning nozzle hole diameter (mm)0.51.51.0Melt spinning wheel surface speed (m / s)503040Ribbon sheet thickness (㎛)71812Ribbon sheet structureAmorphousCrystallineAmorphous+CrystallineSecondary battery propertiesInitial charge / discharge capacity (%)10072.380.5Initial efficiency (%)85.576.081.230Cycle life (%)80.467.769.0

[0116] As can be seen from FIGS. 1 to 4 and Table 1, the Si-based alloys according to Comparative Examples 1 and 2 formed crystals at least on one side located on the air side, but the Si-based alloy according to Example 1 did not include crystals in the entire thickness direction, and it can be seen that a thin ribbon sheet was implemented in an amorphous phase compared to Comparative Examples 1 and 2.

[0117] In addition, when the negative electrode and secondary battery were implemented using Example 1, which is an amorphous Si-based alloy, it was confirmed that the properties were superior in terms of initial capacity, initial efficiency, and 30-cycle life compared to when the negative electrode and secondary battery were implemented using Comparative Examples 1 and 2, which are crystalline Si-based alloys.

[0118]

[0119] <Example 2>

[0120] According to Example 1, 9 parts by weight of carbon black having an average particle diameter of 2.8 ㎛ was mixed with 100 parts by weight of Si-based alloy powder, and then placed in a Spheric Coater (KMT), and the blades were selected to be arranged on the same plane so that the linear blades formed a 60° angle between adjacent blades, and the operation conditions were repeated twice at 4000 RPM for 10 minutes to obtain a Si-based alloy-carbon composite in which carbon black powder was coated on the surface of the Si-based alloy powder.

[0121]

[0122] <Example 3>

[0123] A Si-based alloy-carbon composite was obtained by manufacturing the same method as in Example 2, but by changing the carbon black to pitch graphite having an average particle diameter of 3.0 ㎛, and coating the Si-based alloy powder surface with pitch graphite powder.

[0124]

[0125] <Example 4>

[0126] A Si-based alloy-carbon composite was obtained by manufacturing in the same manner as in Example 2, but replacing carbon black with artificial graphite having an average particle diameter of 3.1 μm, thereby coating the surface of the Si-based alloy powder with artificial graphite powder.

[0127]

[0128] <Example 5>

[0129] The same process as in Example 2 was used to manufacture the mixture, but the mixture was simply mixed without being put into a Spheric Coater (KMT) to manufacture a Si-based alloy-carbon mixture.

[0130]

[0131] <Comparative Example 3>

[0132] A Si-based alloy-carbon mixture was manufactured by performing the same process as in Example 2, but omitting carbon from the composition of the Si-based alloy.

[0133]

[0134] Experimental Example 2

[0135] For Examples 2 to 5, secondary batteries were manufactured in the same manner as in Manufacturing Example 1, and the initial charge / discharge capacity, initial efficiency, and cycle life were evaluated in the same manner as in Experimental Example 1, and the results are shown in Table 2 below.

[0136] At this time, the content of the carbon black, which is a conductive material, was changed to include only 2.1 parts by weight per 100 parts by weight of the Si alloy, taking into account the carbon content in the Si alloy-carbon composite.

[0137] In addition, the initial charge / discharge capacity was expressed as a relative percentage of the initial charge / discharge capacity of the remaining examples based on the initial charge / discharge capacity of Example 5 as 100%.

[0138] Additionally, the cycle life was evaluated at 30 and 50 cycles, respectively.

[0139]

[0140] Example 5 Example 2 Example 3 Example 4 Comparative Example 3 Negative active material Si-based alloy Si 70 Al9Sn1C3Fe9Cu6Mn1Ni1Si 70 Al 10 Sn2Fe 10 Cu6Mn1Ni1Carbon powder type / mixed type carbon black / simple mixed carbon black / coated pitch graphite / coated artificial graphite / coated carbon black / coated secondary battery propertiesInitial charge / discharge capacity (%)100134.3130.9118.282.0Initial efficiency (%)85.589.589.988.480.230cycleslife (%)80.490.091.587.578.050cycleslife (%)68.583.485.080.150.6

[0141] As can be seen in Table 2, compared to Example 5, which simply mixed carbon black, Examples 2 to 4 showed significantly improved initial charge / discharge capacity and initial efficiency, as approximately 81% of the carbon powder was implemented to cover the surface of the Si-based alloy powder, despite the total carbon content being similar to that of Example 5. In addition, it can be confirmed that Examples 2 to 4 showed a further improved effect compared to Example 5 in terms of cycle life characteristics.

[0142]

[0143] In addition, Comparative Example 3 does not include carbon in the Si-based alloy, and thus, it can be confirmed that there is a synergistic effect on the cycle life between the carbon in the Si-based alloy and the carbon powder covering the Si-based alloy surface compared to Example 2.

[0144]

[0145] Although one embodiment of the present invention has been described above, the spirit of the present invention is not limited to the embodiment presented in this specification, and a person skilled in the art who understands the spirit of the present invention will be able to easily propose other embodiments by adding, changing, deleting, or adding components within the scope of the same spirit, but this will also be considered to fall within the spirit of the present invention.

Claims

1. Empirical formula Si100-abc-dAl a Sn b C c M d (Where a, b, c, and d are at% (atomic percent) of the corresponding elements, and 10≤a≤30, 0.5≤b≤5, 0 <c≤10, 0≤d≤35이고, M은 Fe, Ni, Cu 및 Mn 중 1종 이상의 원소임)로 표시되는 Si계 모합금을 제조하는 단계; A step of manufacturing the above Si-based alloy into a Si-based amorphous ribbon sheet through a rapid solidification process (RSP) process; and A method for manufacturing a Si-based alloy for a secondary battery negative electrode active material, comprising the step of crushing a Si-based amorphous ribbon sheet.

2. In paragraph 1, The above Si-based amorphous ribbon sheet is a method for manufacturing a Si-based alloy for use as a secondary battery negative electrode active material having a thickness of 10㎛ or less.

3. In paragraph 1, The above rapid solidification process is a method for manufacturing a Si alloy for a secondary battery negative electrode active material, which is performed through a melt spinning process in which a molten Si alloy is discharged through a nozzle hole having a diameter of 0.1 to 0.6 mm onto a wheel having a surface speed of 20 to 50 m / s to manufacture a ribbon sheet.

4. In paragraph 1, Contains at least one element among Fe, Ni, Mn and Cu as the element M, A method for manufacturing a Si alloy for use as a secondary battery negative electrode active material, wherein Fe is contained in an amount of 5 to 15 at% in the Si alloy, Ni is contained in an amount of more than 0 to 5 at% in the Si alloy, Mn is contained in an amount of more than 0 to 5 at% in the Si alloy, and Cu is contained in an amount of more than 0 to 10 at% in the Si alloy.

5. In paragraph 1, A method for manufacturing a Si-based alloy for use as a secondary battery negative electrode active material, characterized in that it does not include a step of performing heat treatment after manufacturing a Si-based amorphous ribbon sheet.

6. Experimental formula Si100-abc-dAl a Sn b C c M d (Where a, b, c, and d are at% (atomic percent) of the corresponding elements, and 10≤a≤30, 0.5≤b≤5, 0 <c≤10, 0≤d≤35이고, M은 Fe, Ni, Cu 및 Mn 중 1종 이상의 원소임)로 표시되며 비정질인 이차전지 음극활물질용 Si계 합금.

7. In paragraph 6, Contains at least one element among Fe, Ni, Mn and Cu as the element M, A Si alloy for use as an anode active material for secondary batteries, containing Fe in an amount of 5 to 15 at% in the Si alloy, Ni in an amount of more than 0 to 5 at% in the Si alloy, Mn in an amount of more than 0 to 5 at% in the Si alloy, and Cu in an amount of more than 0 to 10 at% in the Si alloy.

8. In paragraph 6, Si-based alloy is a Si-based alloy for use as a secondary battery negative electrode active material, which is a powder with an average particle size of 20㎛ or less.

9. A secondary battery negative active material composition comprising a Si-based alloy-carbon composite including a Si-based alloy according to claim 6 of the powder merchant and a carbon powder covering at least a portion of the surface of the Si-based alloy powder; 10. In paragraph 9, A composition of a negative electrode active material for a secondary battery, wherein the average particle diameter of the carbon powder is smaller than the average particle diameter of the Si-based alloy powder.

11. In paragraph 9, A composition for a negative electrode active material for a secondary battery, wherein the carbon powder is contained in an amount of 1 to 50 parts by weight per 100 parts by weight of a Si-based alloy.

12. In paragraph 9, The above carbon powder is a negative electrode active material composition for a secondary battery containing at least one of carbon black and pitch.

13. The entire house; and A secondary battery having a negative electrode including a negative electrode active material layer formed of a negative electrode active material composition for a secondary battery according to claim 9 on the above-mentioned collector.

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