Negative electrode active material for lithium secondary batteries, method for manufacturing the same, and lithium secondary battery containing the same

Abstract

The present embodiment relates to a silicon-based negative electrode active material, a manufacturing method thereof, and a lithium secondary battery including the same. The silicon-based negative electrode active material according to the embodiment may have a particle size fraction D1 of 1 μm or more, a particle size fraction D99 of 20 μm or less, and an oxidation degree in the range of 0.3% to 3.0%.

Description

Technical Field

[0001] The present disclosure relates to a negative electrode active material for a lithium secondary battery, a method for manufacturing the same, and a lithium secondary battery including the same.

Background Art

[0002] Silicon has attracted high attention as a negative electrode material for secondary batteries due to its very high theoretical capacity (Li 15 Si4: 3600 mAh / g) and low operating voltage (>0.1V vs. Li / Li + ). However, in the case of a general Si-based negative electrode material, it has a volume change reaching 300% during cycling and shows low discharge capacity characteristics, which is a demerit that makes it difficult to apply to an actual battery.

[0003] In order to solve such problems, recently, there have been attempts to utilize silicon coarse particles (several microns) and solve such problems by using less than the theoretical capacity.

[0004] However, in the process of pulverizing silicon, problems occur such that the pulverized fine particles are easily aggregated or reattached to the surface of the large particles, increasing the silicon particle size and increasing the film reaction due to side reactions with the electrolyte, resulting in an increase in irreversible capacity and a significant shortening of the life.

[0005] Therefore, there is a need to develop a technology that can improve the life characteristics of a battery while using a silicon-based negative electrode material.

Summary of the Invention

Problems to be Solved by the Invention

[0006] The present disclosure aims to provide a silicon-based negative electrode active material having excellent life characteristics, a method for manufacturing the same, and a lithium secondary battery including the same.

Means for Solving the Problems

[0007] In one embodiment, the silicon-based negative electrode active material has a particle size fraction D1 of 1 μm or more, a D99 of 20 μm or less, and an oxidation degree in the range of 0.3% to 3.0%.

[0008] A method for producing a silicon-based negative electrode active material according to another embodiment includes the steps of: preparing silicon particles and then grinding them so that the D99 is 20 μm or less; classifying the particles, whose D99 is controlled to be 20 μm or less, using a wet sorting device so that the D1 is 1 μm or more; and heat-treating the powder, whose particle size has been adjusted so that the D99 is 20 μm or less and the D1 is 1 μm or more, to produce a powder in which the degree of oxidation is in the range of 0.3 to 3.0.

[0009] An electrode for a lithium secondary battery according to another embodiment includes a negative electrode, a positive electrode, and an electrolyte according to one embodiment. [Effects of the Invention]

[0010] According to one embodiment, life degradation due to volume expansion of silicon particles during charging and discharging can be suppressed, and since an SiO2 layer develops on the surface, excellent life characteristics can be ensured by reducing reactivity with the electrolyte.

[0011] Furthermore, the surface of the silicon particles is given hydrophilic properties, improving dispersibility in aqueous systems and preventing a decrease in electrode plate quality during electrode fabrication, thus resulting in superior electrochemical performance. [Brief explanation of the drawing]

[0012] [Figure 1] Figure 1 schematically shows the apparatus used in a method for producing a silicon-based negative electrode active material according to one embodiment. [Figure 2] Figure 2 shows images taken with a camera after manufacturing a negative electrode plate using the negative electrode active material produced by Comparative Example 3, Example 1, and Example 5. [Modes for carrying out the invention]

[0013] The terms first, second, third, etc., are used to describe various parts, components, regions, layers, and / or sections, but are not limited to these. These terms are used solely to distinguish one part, component, region, layer, or section from other parts, components, regions, layers, or sections. Accordingly, the first part, component, region, layer, or section described below may be referred to as the second part, component, region, layer, or section, to the extent that it does not fall outside the scope of the invention.

[0014] The technical terms used herein are for the sole purpose of referring to specific embodiments and are not intended to limit the invention. The singular form used herein also includes the plural form unless the wording explicitly indicates otherwise. The meaning of “including” as used in this specification embodies certain characteristics, areas, integers, steps, operations, elements, and / or components, and does not exclude the presence or addition of other characteristics, areas, integers, steps, operations, elements, and / or components.

[0015] When one part is described as being "on top of" or "above" another part, it may be immediately on top of or above the other part, or the other part may be between them. In contrast, when one part is described as being "directly on top of" another part, there is no other part between them.

[0016] Unless otherwise defined, all terms used herein, including technical and scientific terms, have the same meaning as those generally understood by a person of ordinary skill in the art to which this invention pertains. Terms defined in commonly used dictionaries are further interpreted to have the meaning consistent with the relevant technical literature and the present disclosure, and are not interpreted in an ideal or highly formal sense unless otherwise defined.

[0017] Silicon-based negative electrode active material As mentioned above, silicon-based anode materials have the disadvantage of exhibiting a low discharge capacity ratio, making them difficult to apply to actual batteries.

[0018] Such silicon-based anode active materials have the problem of reduced lifespan due to volume expansion that occurs during charging and discharging. Therefore, in order to improve this problem, this disclosure aims to provide a silicon-based anode active material having a silicon particle size distribution and degree of oxidation that can achieve the most efficient lifespan characteristics when used with coarse silicon particles and with the State of Charge (SOC) limited to 20% or more and 80% or less.

[0019] Specifically, in one embodiment, a silicon-based negative electrode active material is provided in which the particle size fraction D1 is 1 μm or more, D99 is 20 μm or less, and the degree of oxidation is in the range of 0.3% to 3.0%.

[0020] In this embodiment, the particle size fraction D1 of the silicon-based anode active material may be 1 μm or more, more specifically, in the range of 1 μm to 3 μm or 1.5 μm to 2.5 μm. When the D1 of the silicon-based anode active material satisfies the above range, the electrochemical lifetime characteristics can be effectively improved when the SOC is restricted to 20% or more and 80% or less. Specifically, as described above, when coarse silicon particles within an appropriate range that do not contain fine powder are used, lifetime degradation due to the expansion of silicon particles can be prevented when charging and discharging with the SOC restricted. Furthermore, although the lithium charging reaction will be concentrated on the surface, at this time the internal core portion of the anode active material particles exists in the silicon state, and the surface is Li x This results in the Si form. In this embodiment, the unreacted internal core acts as a support against contraction and expansion during the charging reaction, improving the lifetime characteristics, and since the reaction mainly occurs only on the surface, the output characteristics are also improved.

[0021] However, in the case of fine silicon particles with a D1 size of less than 1 μm, the particles readily react with Li throughout their interior, making it difficult to achieve this effect. As a result, the lifetime characteristics are significantly reduced. Furthermore, fine silicon particles with a D1 size of less than 1 μm act as domains that increase side reactions with the electrolyte, which also reduces the lifetime characteristics.

[0022] These effects are manifested when SOC is used restrictively.

[0023] Furthermore, the D99 of the silicon-based negative electrode active material may be 20 μm or less, more specifically, in the range of 1 μm to 19 μm or 6 μm to 15 μm. When the D99 of the silicon-based negative electrode active material satisfies the above range, when manufacturing electrodes using the silicon-based negative electrode active material of this embodiment, it is possible to prevent the phenomenon of localized electrode compression during the rolling process, thereby improving the quality of the electrode plate and enabling the realization of a battery with excellent electrochemical performance.

[0024] The silicon-based negative electrode active material may have a D99 / D1 ratio in the range of 1.0 to 12.0. When the D99 / D1 value satisfies this range, it exhibits excellent lifespan characteristics and simplifies the electrode manufacturing process. Furthermore, the manufactured lithium secondary battery exhibits excellent electrochemical performance.

[0025] Next, the degree of spheroidization of the silicon-based negative electrode active material may be 0.9 or higher, more specifically in the range of 0.90 to 0.98. When the degree of spheroidization satisfies the above range, lithium charging on the surface can be uniformly controlled, thereby suppressing surface degradation during the charge and discharge process.

[0026] Next, the degree of oxidation of the silicon-based negative electrode active material may be in the range of 0.3% to 3.0% by weight, more specifically 0.32% to 2.5% by weight or 0.34% to 2.3% by weight.

[0027] In this specification, the degree of oxidation refers to the oxygen content in the total active material, expressed in weight percent. The degree of oxidation of the silicon-based anode active material was measured using a LECO ONH836 Series.

[0028] In the silicon-based negative electrode active material of this embodiment, a certain amount of oxidation treatment causes an SiO2 layer to develop on the surface of the silicon particles. In other words, by controlling the degree of oxidation along with the D1 and D99 particle sizes within an appropriate range, the lifespan characteristics of the lithium secondary battery can be improved.

[0029] In this invention, when the D1 and D99 particle sizes of the silicon-based anode active material satisfy the aforementioned range, and the degree of oxidation also satisfies the aforementioned range, the silicon-based anode active material exhibits advantageous effects in that it allows for easy reversible expansion and contraction, and the electrode plate quality using the silicon-based anode active material of this embodiment is excellent. Furthermore, excellent life characteristics and electrochemical properties can be ensured for lithium secondary batteries to which the silicon-based anode active material of this embodiment is applied.

[0030] Method for manufacturing silicon-based negative electrode active material The following describes a method for producing a silicon-based negative electrode active material according to one embodiment.

[0031] A method for producing a silicon-based negative electrode active material according to another embodiment may include the steps of: preparing silicon particles and then grinding them so that the D99 is 20 μm or less; classifying the particles, whose D99 is controlled to be 20 μm or less, using a wet sorting device so that the D1 is 1 μm or more; and heat-treating the powder, whose particle size has been adjusted so that the D99 is 20 μm or less and the D1 is 1 μm or more, to produce a powder in which the degree of oxidation is in the range of 0.3 to 3.0.

[0032] First, after preparing the silicon particles, a step is performed in which they are ground so that the D99 size is 20 μm or less.

[0033] The silicon particles may be, for example, coarse silicon particles.

[0034] Furthermore, the step of grinding the silicon particles so that the D99 is 20 μm or less may be carried out using at least one of a wet bead mill, air jet mill, pin mill, or disc mill. When the D99 is ground using an air jet mill among the above methods, there is the advantage that the degree of particle sphericity is improved.

[0035] Next, the particles whose D99 is controlled to be 20 μm or less are classified using a wet sorting apparatus so that their D1 is 1 μm or more.

[0036] The step of classifying D1 to be 1 μm or larger may be performed using a tank, a stirrer, and an ultrasonic generator.

[0037] More specifically, the step of classifying the particles so that D1 is 1 μm or larger may be performed, for example, using the apparatus shown in Figure 1.

[0038] Referring to Figure 1, the process includes the steps of supplying the crushed raw material to a pipe 1 connected to a tank 7; dispersing the raw material supplied through the pipe 1 using a stirrer 6 and an ultrasonic generator 5; allowing the dispersed particles to settle to obtain a precipitate and a supernatant liquid; opening a valve connected to the bottom of the tank and discharging the precipitate through a pipe 2 located in one direction; discharging the supernatant liquid through a pipe 3 located in the opposite direction from which the precipitate was discharged; and drying the precipitate to obtain a powder with a particle size adjusted so that D99 is 20 μm or less and D1 is 1 μm or more.

[0039] The step of dispersing the particles using the aforementioned agitator and ultrasonic generator may be performed by irradiating with 300W to 500W 20kHz pulse ultrasonic waves for 30 minutes to 2 hours while stirring at 200 to 300 RPM.

[0040] Next, in the step of producing a powder with an oxidation degree in the range of 0.3 to 3.0 by heat-treating the powder whose particle size has been adjusted so that D99 is 20 μm or less and D1 is 1 μm or more, the heat treatment may be carried out in an air atmosphere at a temperature in the range of 300°C to 690°C for 1 to 2 hours. At this time, the heat treatment temperature may be more specifically in the range of 300°C to 650°C.

[0041] In another embodiment of the present invention, a lithium secondary battery is provided which includes a negative electrode, a positive electrode, and an electrolyte located between the negative electrode and the positive electrode, each containing a silicon-based negative electrode active material according to the above-described embodiment.

[0042] The negative electrode may be manufactured by mixing a negative electrode active material, a binder, and a conductive material to produce a composition for forming a negative electrode active material layer, and then applying this composition to a negative electrode current collector.

[0043] The negative electrode current collector may be, for example, copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, or a combination thereof.

[0044] The negative electrode active material is the same as that described in the previous embodiment of the present invention, so it will be omitted here.

[0045] The binder may be, but is not limited to, polyvinyl alcohol, carboxymethylcellulose / styrene-butadiene rubber, hydroxypropylene cellulose, diacetylene cellulose, polyvinyl chloride, polyvinylpyrrolidone, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, or polypropylene. The binder may be mixed in an amount of 1% to 30% by weight relative to the total amount of the negative electrode active material layer forming composition.

[0046] The conductive material is not particularly limited as long as it has conductivity without causing a chemical change in the battery. Specifically, it may include graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, or thermal black; conductive fibers such as carbon fibers or metal fibers; metal powders such as carbon fluoride, aluminum, or nickel powder; conductive whiskey such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; or conductive materials such as polyphenylene derivatives. The conductive material may be mixed in an amount of 0.1% to 30% by weight relative to the total amount of the negative electrode active material layer forming composition.

[0047] Next, the positive electrode can be manufactured by mixing a positive electrode active material, a binder, and a conductive material to produce a composition for forming a positive electrode active material layer, and then applying this composition to a positive electrode current collector. In this case, the binder and conductive material are the same as those used for the negative electrode described above.

[0048] The positive electrode current collector may be made of, for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel with a surface treatment of carbon, nickel, titanium, silver, etc.

[0049] The positive electrode active material may be a compound capable of reversible intercalation and deintercalation of lithium (a lithium-intercalated intercalation compound).

[0050] The positive electrode active material may specifically be one or more composite oxides of a metal such as cobalt, manganese, nickel, or a combination thereof, and lithium. A specific example of such a compound may be one represented by any one of the following chemical formulas.

[0051] Li a A 1-b R bD2 (in the above formula, 0.90 ≤ a ≤ 1.8 and 0 ≤ b ≤ 0.5); Li a E 1-b R b O 2-c D c (in the above formula, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, and 0 ≤ c ≤ 0.05); LiE 2-b R b O 4-c D c (in the above formula, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); Li a Ni 1-b-c Co b R c D α (in the above formula, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05 and 0 < α ≤ 2); Li a Ni 1-b-c Co b R c O 2-α Z α (in the above formula, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05 and 0 < α < 2); Li a Ni 1-b-c Co b R c O 2-α Z2 (in the above formula, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05 and 0 < α < 2); Li a Ni 1-b-c Mn b R c D α (in the above formula, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05 and 0 < α ≤ 2); Li a Ni 1-b-c Mn b RcO 2-α Z α (in the above formula, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05 and 0 < α < 2); Li a Ni 1-b-c Mn b R c O 2-α Z2 (in the above formula, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05 and 0 < α < 2); Li a Ni bE c G d O2(In the above equation, 0.90≦a≦1.8, 0≦b≦0.9, 0≦c≦0.5, and 0.001≦d≦0.1.);Li a Ni b Co c Mn d G e O2(In the above equation, 0.90≦a≦1.8, 0≦b≦0.9, 0≦c≦0.5, 0≦d0.5, and 0.001≦e≦0.1.);Li a NiG b O2(In the above equation, 0.90≦a≦1.8 and 0.001≦b≦0.1.);Li a CoG b O2(In the above equation, 0.90≦a≦1.8 and 0.001≦b≦0.1.);Li a MnG b O2(In the above equation, 0.90≦a≦1.8 and 0.001≦b≦0.1.);Li a Mn2G b O4 (In the above formula, 0.90 ≤ a ≤ 1.8 and 0.001 ≤ b ≤ 0.1.); QO2; QS2; LiQS2; V2O5; LiV2O5; LiTO2; LiNiVO4; Li (3-f) J2(PO4)3(0≦f≦2);Li (3-f) Fe2(PO4)3 (0≦f≦2); and LiFePO4.

[0052] In the above chemical formula, A is Ni, Co, Mn or a combination thereof; R is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements or a combination thereof; D is O, F, S, P or a combination thereof; E is Co, Mn or a combination thereof; Z is F, S, P or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V or a combination thereof; Q is Ti, Mo, Mn or a combination thereof; T is Cr, V, Fe, Sc, Y or a combination thereof; and J is V, Cr, Mn, Co, Ni, Cu or a combination thereof.

[0053] The electrolyte comprises a non-aqueous organic solvent and a lithium salt.

[0054] The aforementioned non-aqueous organic solvent acts as a medium through which ions involved in the electrochemical reaction of the battery can move.

[0055] The aforementioned lithium salt dissolves in an organic solvent and acts as a source of lithium ions within the battery, enabling the basic operation of a lithium secondary battery and playing a role in promoting the movement of lithium ions between the positive and negative electrodes.

[0056] Depending on the type of lithium secondary battery, a separator may be present between the positive and negative electrodes. Such separators may be polyethylene, polypropylene, polyvinylidene fluoride, or multilayer films of two or more layers thereof. Needless to say, mixed multilayer films such as polyethylene / polypropylene two-layer separators, polyethylene / polypropylene / polyethylene three-layer separators, or polypropylene / polyethylene / polypropylene three-layer separators may also be used.

[0057] Lithium secondary batteries can be classified into lithium-ion batteries, lithium-ion polymer batteries, and lithium polymer batteries depending on the type of separator and electrolyte used. They can also be classified by shape into cylindrical, prismatic, coin-type, pouch-type, etc., and by size into bulk type and thin-film type. The structure and manufacturing methods of these batteries are widely known in this field, so a detailed explanation will be omitted. [Examples]

[0058] The following describes embodiments of the present invention in detail. However, these are presented as examples only and do not limit the present invention, which is defined solely by the scope of the claims described below.

[0059] Example 1 Si raw materials with a particle size of 100 μm or less were subjected to air-jet milling using an air jet mill until the D99 particle size was 10 μm or less. The pulverized Si powder was mixed with ethaneol at a weight ratio of 10% to produce a slurry.

[0060] As described above, the pulverized slurry was transferred to the tank of a wet sorting machine, and while being stirred at 1000 RPM, it was irradiated with ultrasound at 300 W 20 kHz pulse mode for 30 minutes.

[0061] Next, stirring and ultrasonic treatment were stopped, and the mixture was left to stand for 1 hour to allow the heavier particles to settle. After this period, 10 vol% of the input amount was recovered from the bottom. The recovered precipitate was then transferred back to the tank, and the same procedure was repeated twice to obtain silicon-based anode active materials having particle sizes D1, D10, D50, D90, and D99 as listed in Table 1 below.

[0062] Example 2 The silicon-based anode active material was manufactured in the same manner as in Example 1, except that a wet classification process was performed once.

[0063] Example 3 The negative electrode active material was produced in the same manner as in Example 1, except that the D99 was ground during air-jet pulverization so that it had an average particle size of 20 μm.

[0064] Comparative Example 1 Silicon with D99 ​​pulverized to 10 μm or less was used as the negative electrode active material without wet classification.

[0065] Comparative Example 2 Silicon, pulverized to an average size of 20 μm, was used as the negative electrode active material without wet classification.

[0066] Comparative Example 3 Si raw materials with a particle size of 100 μm or less were used as the negative electrode active material without any separate pretreatment.

[0067] Example 4 The silicon-based negative electrode active material obtained in Example 1 was heat-treated at 300°C for 1 hour in an air atmosphere.

[0068] Example 5 The silicon-based negative electrode active material obtained in Example 1 was heat-treated at 400°C for 1 hour in an air atmosphere.

[0069] Example 6 The silicon-based negative electrode active material obtained in Example 1 was heat-treated at 500°C for 1 hour in an air atmosphere.

[0070] Example 7 The silicon-based negative electrode active material obtained in Example 1 was heat-treated at 600°C for 1 hour in an air atmosphere.

[0071] Comparative Example 4 The silicon-based negative electrode active material obtained in Example 1 was heat-treated at 700°C for 1 hour in an air atmosphere.

[0072] Experimental Example 1 - Evaluation of the properties of the negative electrode active material (1) Manufacturing of coin-type full cell batteries After manufacturing a CR2032 coin cell using the silicon-based negative electrode active material produced as described above, an electrochemical evaluation was performed.

[0073] Specifically, 1.2 g of PAA (polyacrylic acid) binder was mixed with 11 g of de-ionized water and stirred in a thinky mixer for 10 minutes. Then, 2.4 g of negative electrode active material and 0.4 g of super-P conductive material were added and mixed, and the mixture was stirred for an additional 10 minutes.

[0074] Next, the slurry was coated onto the Cu current collector, dried, and then rolled to produce the negative electrode plate. The loading amount of the negative electrode was approximately 3 mg / cm³. 2 The electrode density was 1.2-1.3 g / cc.

[0075] For the cathode used as the counter electrode, 50.15g of super-C6 and 1.67g of PVdF binder were added and stirred for 3 minutes in a thinky mixer. Then, 9.65g of cathode active material NCM and 1.5g of NMP were added and stirred for an additional 3 minutes.

[0076] Next, the slurry was coated onto the Al current collector, dried, and then rolled to produce a positive electrode plate. The loading amount of the positive electrode was 18 mg / cm². 2 The electrode density was 3.5-3.6 g / cc.

[0077] A 2032 coin-type full cell battery was manufactured using the aforementioned negative electrode, positive electrode, electrolyte, and polypropylene separator by a conventional method. The electrolyte was prepared by dissolving 1 M LiPF6 in a mixed solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) (mixing ratio EC:EMC = 3:7 vol%) to produce a mixed solution, to which 1.5 wt% vinylene carbonate (VC) and 10 wt% FEC were added.

[0078] (2) Evaluation of life characteristics The coin-type half-cell batteries manufactured in step 1 were aged at room temperature (25°C) for 10 hours, and then their lifespan characteristics were evaluated.

[0079] Capacity evaluation was performed using 2500mAh / g as the baseline capacity. Charge and discharge tests were conducted in the operating voltage range of 4.25V to 2.5V, and the charge and discharge current was measured at 0.1C in the initial cycle. Using the initial 1C capacity as a baseline, the lifespan was measured over 100 cycles by applying a current of 0.5C during charge and discharge. At this time, the charge cut-off current was set to 0.005C.

[0080] When evaluated under the aforementioned conditions, the negative electrode will be charged and discharged at approximately a SOC level of 40%.

[0081] [Table 1]

[0082] Referring to Table 1, Comparative Example 3, which used silicon raw material without pretreatment, was measured to have the worst lifetime characteristics. Furthermore, while reducing the maximum particle size through wet grinding, as in Comparative Examples 2 and 3, improved the lifetime characteristics somewhat, reducing the D99 particle size to approximately 10 μm, as in Comparative Example 1, did not have a significant effect. Therefore, it was confirmed that reducing fine particles smaller than 1 μm by wet ultrasonic classification effectively improved the lifetime characteristics, as in Examples 1 and 2.

[0083] It can be confirmed that the lifespan is further improved when the powder obtained from Example 1 is subjected to oxidation treatment through a heat treatment process as in Examples 4 and 5.

[0084] However, as in Comparative Example 4, when the heat treatment temperature is increased to 700°C, it can be confirmed that the degree of oxidation increases excessively, and the life characteristics actually decrease.

[0085] Experimental Example 2 - Evaluation of Electrode Quality The negative electrode plates were manufactured using the negative electrode active materials produced in Comparative Example 3, Example 1, and Example 5, in the manner described in Experimental Example 1 (1).

[0086] Next, the surface of the negative electrode plate manufactured as described above was photographed using a camera and then inspected with the naked eye. The image is shown in Figure 2.

[0087] Referring to Figure 2, the negative electrode plate manufactured using the negative electrode active material of Comparative Example 3, which used raw materials without pretreatment, showed the most frequent phenomenon of localized compression after rolling.

[0088] In contrast, when large silicon particles are crushed to reduce the D99 particle size to 10 μm or less, as in Example 1, it can be confirmed that the phenomenon of localized pressing during the manufacturing of the negative electrode plate is significantly improved.

[0089] Furthermore, it was confirmed that the negative electrode plate manufactured using the negative electrode active material of Example 5, in which the surface of the negative electrode active material was oxidized, showed improved affinity with the binder and improved dispersion of the negative electrode active material within the electrode, thus resulting in further improvement in electrode quality.

[0090] The present invention is not limited to the embodiments described above and can be manufactured in a variety of different forms. Those with ordinary skill in the art to which the present invention pertains should understand that the invention can be implemented in other specific forms without altering the technical idea or essential features of the invention. Therefore, the embodiments described above should be understood to be illustrative and not limiting in all respects.

Claims

1. The particle size fraction D1 is 1 μm or larger. D99 is 20 μm or less. A silicon-based negative electrode active material with an oxidation degree in the range of 0.3% by weight to 3.0% by weight.

2. The silicon-based anode active material according to claim 1, wherein the degree of sphericity of the silicon-based anode active material is 0.9 or higher.

3. The silicon-based anode active material according to claim 1, wherein the silicon-based anode active material has a D99 / D1 ratio in the range of 1.0 to 12.

0.

4. The silicon-based negative electrode active material according to claim 1, wherein the degree of oxidation is in the range of 0.32% by weight to 2.5% by weight.

5. After preparing the silicon particles, the step is to grind them so that the D99 is 20 μm or less, The steps include: classifying particles whose D99 is controlled to be 20 μm or less using a wet sorting apparatus so that D1 is 1 μm or more; The process involves heat-treating a powder whose particle size has been adjusted so that D99 is 20 μm or less and D1 is 1 μm or more, in order to produce a powder in which the degree of oxidation is in the range of 0.3% to 3.0% by weight. A method for producing a silicon-based negative electrode active material containing [the specified material].

6. The step of grinding so that the D99 is 20 μm or less is, A method for producing a silicon-based anode active material according to claim 5, wherein the method is carried out using at least one of a wet bead mill, an air jet mill, a pin mill, and a disc mill.

7. The step of classifying such that D1 is 1 μm or larger is: A method for producing a silicon-based anode active material according to claim 5, comprising using a tank, a stirrer, and an ultrasonic generator.

8. The step of classifying such that D1 is 1 μm or larger is: The steps include supplying the crushed raw material to a pipe connected to a tank, The steps include: dispersing particles of the raw material supplied through the pipe using a stirrer and an ultrasonic generator; The steps include allowing the dispersed particles to settle to obtain a precipitate and a supernatant liquid, The steps include opening a valve connected to the bottom of the tank and discharging the sediment through a pipe located in one direction, The steps include: discharging the supernatant liquid through a pipe located in the opposite direction from which the precipitate was discharged; The steps include drying the precipitate to obtain a powder whose particle size is adjusted so that D99 is 20 μm or less and D1 is 1 μm or more, A method for producing a silicon-based negative electrode active material according to claim 7, including the method described in claim 7.

9. The step of dispersing particles using the aforementioned stirrer and ultrasonic generator is: A method for producing a silicon-based negative electrode active material according to claim 8, wherein the process is carried out while stirring at 200 RPM to 300 RPM.

10. The step of dispersing particles using the aforementioned stirrer and ultrasonic generator is: A method for producing a silicon-based negative electrode active material according to claim 8, comprising irradiating with 300W to 500W 20kHz pulse ultrasound for 30 minutes to 2 hours.

11. In the step of producing a powder having an oxidation degree in the range of 0.3% to 3.0% by weight, the powder is heat-treated to adjust the particle size such that D99 is 20 μm or less and D1 is 1 μm or more. The method for producing a silicon-based negative electrode active material according to claim 5, wherein the heat treatment is performed in an atmospheric environment at a temperature in the range of 300°C to 690°C for 1 to 2 hours.

12. A negative electrode comprising the silicon-based negative electrode active material described in claim 1, Positive electrode and, Electrolytes, Lithium-ion batteries, including lithium-ion batteries.

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