Method for preparing high-capacity silicon oxide-metal composite powder

Abstract

According to a desirable aspect of the present invention, a method for preparing a high-capacity and highly conductive silicon oxide-metal composite powder can be provided, the method enabling the generation of lithium silicate (LiSiO4) during charging and discharging of a lithium ion secondary battery to be effectively suppressed such that electrical conductivity can be improved while irreversibility of the lithium ion secondary battery can be increased.

Description

Method for producing high-capacity silicon oxide-metal composite powder

[0001] The present invention relates to a method for producing a silicon oxide-metal composite powder for use as a negative electrode material for a lithium ion secondary battery.

[0002] A lithium-ion secondary battery (LIB) is a rechargeable and reusable battery that generates electricity through a chemical reaction in which lithium ions move between the anode and cathode. A LIB consists of four key components: a cathode material, which constitutes the positive electrode; an anode material, which constitutes the negative electrode; an electrolyte, which acts as a path for lithium ions between the anode and cathode; and a separator, which does not participate in the electrochemical reaction but prevents physical contact between the anode and cathode. Cathode materials account for approximately 35% of a LIB and are a key component, and can be composed of one-component, ternary, or lithium iron phosphate depending on the composition of the metal salt. Recently, high-nickel materials with a high nickel content have become the mainstream to improve battery capacity, output, and lifespan. Anode materials store and release lithium ions generated at the positive electrode. Currently, materials such as natural graphite and artificial graphite are primarily used as anode active materials. However, graphite-based negative electrode materials, such as natural graphite and artificial graphite, have a low capacity limit of around 370 mAh per gram, so there is a high demand for new materials that can replace them, and silicon is being discussed as a next-generation negative electrode material.

[0003] Silicon can realize a battery capacity of 1,500 mAh per gram, has a higher energy density than graphite-based materials, and has a fast lithium-ion acceptance speed, which can effectively shorten the charging time of lithium-ion secondary batteries. Silicon anode active materials have already been used in small electronic devices such as smartphones and other devices since the early 2010s. However, compared to graphite-based anode active materials, the volume expansion rate is up to 40 times higher, so there are limitations in applying large amounts of silicon as anode active materials. Therefore, research and development on various methods to solve this issue are ongoing.

[0004] Meanwhile, silicon oxide (SiOx), which has a slightly lower initial capacity than silicon anode materials but superior charge-discharge stability, is attracting renewed attention. Irreversible lithium oxide (Li2O) and lithium silicate (Li4SiO4) produced during the lithiation process not only form a stable solid electrolyte interphase (SEI) layer but also act as a buffer against volume changes. However, the low electrical conductivity resulting from the insulating properties of silicon oxide can lead to deterioration of electrochemical performance, and irreversibility during initial charge-discharge, i.e., a rapid decrease in initial discharge capacity, can occur.

[0005] One aspect of the present invention is to provide a method for producing a high-capacity, high-conductivity silicon oxide-metal composite powder that can improve electrical conductivity while increasing irreversibility by suppressing the formation of lithium silicate (LiSiO4) during charge and discharge of a lithium ion secondary battery.

[0006] The objectives of the present invention are not limited to the above-described scope. Those skilled in the art will readily understand the additional objectives of the present invention from the overall content of this specification.

[0007] A method for producing a high-capacity silicon oxide-metal composite powder according to one aspect of the present invention may include a reaction step of reacting ethylene glycol and SiCl4 by dropping liquid SiCl4 at a preset injection rate into a reactor containing liquid ethylene glycol; a heating step of reacting ethylene glycol and SiCl4 in the reaction step to obtain a metastable silicon oxide obtained by heat-treating the obtained silicon oxide under atmospheric gas conditions to obtain a solid silicon oxide (SiOx); and a complexing step of adding at least one metal selected from Al, Ti, and Mn to the solid silicon oxide (SiOx) obtained in the heating step and performing dry milling to control the particle size of the silicon oxide (SiOx) and simultaneously complexing the silicon oxide (SiOx) with the metal.

[0008] In the above reaction step, the mixing ratio of the ethylene glycol and the SiCl4 can be adjusted so that the oxygen value (x) of the silicon oxide (SiOx) obtained in the heating step satisfies 0.01 to 0.85.

[0009] In the above reaction step, the injection rate of SiCl4 may be 1 g / min to 1000 g / min.

[0010] In the above heating step, the atmospheric gas is at least one selected from oxygen, nitrogen, and argon, the flow rate of the atmospheric gas is 10 ml / sec to 1000 ml / sec, and the silicon oxide in the metastable state can be heated in a temperature range of 400°C to 900°C for 30 minutes to 8 hours.

[0011] In the above compounding step, the equipment used for the dry milling may be at least one selected from a jet mill, a planar mill, a specs mill, and / or an attritor, and the milling speed of the dry milling may be 50 rpm to 1000 rpm, and the milling time of the dry milling may be 30 minutes to 6 hours.

[0012] The average particle size of the silicon oxide (SiOx)-metal composite powder obtained in the above compounding step may be 1 µm to 10 µm.

[0013] The metal added in the above compounding step is a metal powder, and the metal powder can be added in an amount of 0.1 wt% to 10 wt%.

[0014] The above metal powder may be at least one selected from Al2O3 powder, TiO2 powder, or MnO2 powder.

[0015] According to one aspect of the present invention, a method for producing a high-capacity, high-conductivity silicon oxide-metal composite powder can be provided, which can improve electrical conductivity while increasing irreversibility by suppressing the formation of lithium silicate (LiSiO4) during charge / discharge of a lithium ion secondary battery.

[0016] The effects of the present invention are not limited to the above-described matters, and may include matters that can be reasonably inferred from the following description by a person of ordinary skill in the technical field to which the invention pertains.

[0017] Figure 1 is a graph showing the XRD analysis results for invention examples 1 to 6.

[0018] The present invention relates to a method for producing a high-capacity silicon oxide-metal composite powder. Preferred embodiments of the present invention will be described below. These embodiments may be modified in various ways, and the scope of the present invention should not be construed as being limited to the embodiments described below. These embodiments are provided to provide a more detailed description of the present invention to those skilled in the art.

[0019]

[0020] Hereinafter, a method for producing a high-capacity silicon oxide-metal composite powder according to one aspect of the present invention will be described in more detail.

[0021]

[0022] A method for producing a high-capacity silicon oxide-metal composite powder according to one aspect of the present invention may include a reaction step of reacting ethylene glycol and SiCl4 by dropping liquid SiCl4 at a preset injection rate into a reactor containing liquid ethylene glycol; a heating step of reacting ethylene glycol and SiCl4 in the reaction step to obtain a metastable silicon oxide obtained by heat-treating the obtained silicon oxide under atmospheric gas conditions to obtain a solid silicon oxide (SiOx); and a complexing step of adding at least one metal selected from Al, Ti, and Mn to the solid silicon oxide (SiOx) obtained in the heating step and performing dry milling to control the particle size of the silicon oxide (SiOx) and simultaneously complexing the silicon oxide (SiOx) with the metal.

[0023]

[0024] Reaction stage

[0025] Prepare liquid ethylene glycol and liquid SiCl4, place the ethylene glycol in a reactor, and then drop the SiCl4 into the reactor at a preset injection rate to react the ethylene glycol and SiCl4. If SiCl4 is placed in the reactor and then ethylene glycol is injected, there is a possibility that a large amount of hydrochloric acid gas will be generated due to the explosive oxidation reaction of SiCl4. Therefore, from the perspective of work safety, it is more preferable to place the ethylene glycol in the reactor and then inject the SiCl4.

[0026]

[0027] If SiCl4 is injected too slowly, the reaction time between silicon (Si) and oxygen becomes too long, and silicon oxide (SiOx) cannot be effectively generated. Therefore, it is preferable that SiCl4 be injected at an injection rate of 1 g / min or more. A more preferable injection rate of SiCl4 may be 10 g / min or more. On the other hand, if SiCl4 is injected too quickly, there is a concern that explosive emission of hydrochloric acid gas may occur due to the rapid reaction speed. Therefore, from the perspective of work safety, it is preferable that SiCl4 be injected at an injection rate of 1000 g / min or less. A more preferable injection rate of SiCl4 may be 500 g / min or less.

[0028]

[0029] The mixing ratio of SiCl4 and ethylene glycol is not particularly limited, but the mixing ratio of SiCl4 and ethylene glycol can be adjusted so that the oxygen value (x) of silicon oxide (SiOx) obtained in the heating step satisfies the range of 0.01 to 0.85.

[0030]

[0031] The material obtained in the reaction step can maintain a semi-solid state, such as a foam or sponge, in a metastable state. Meanwhile, the reactor used in the reaction step may preferably be internally coated with a material with excellent acid resistance, such as Teflon, alumina, or zirconium, or be formed entirely in the form of a crucible.

[0032]

[0033] Heating stage

[0034] In the heating step, the metastable silicon oxide obtained in the reaction step can be heat-treated under atmospheric gas conditions to obtain solid silicon oxide (SiOx).

[0035]

[0036] The atmospheric gas may be one or more selected from oxygen, nitrogen, or argon, or a mixture thereof. To prevent a decrease in reactivity, the atmospheric gas may be supplied at a flow rate of 10 ml / sec or more, and a more preferable flow rate of 100 ml / sec or more may be provided. If the flow rate of the atmospheric gas is excessive, the reaction may occur only on the surface, resulting in non-uniform reaction. Therefore, the atmospheric gas may be supplied at a flow rate of 1000 ml / sec or less. A more preferable flow rate of the atmospheric gas may be 500 ml / sec or less.

[0037]

[0038] Under the condition where atmospheric gas is supplied, metastable silicon oxide can be heated to obtain black solid silicon oxide (SiOx). If the heating temperature is excessively low or the heating time is excessively short, sufficient solid-state reaction may not occur, resulting in the obtaining of silicon oxide in an intermediate state between solid and liquid. Therefore, it is preferable to heat at a heating temperature of 400°C or higher for 30 minutes or longer. A more preferable heating temperature may be 450°C or higher. On the other hand, if the heating temperature is excessively high or the heating time is excessively long, the particle size may become coarser due to particle growth after the formation of the solid phase. Therefore, it is preferable to heat at a heating temperature of 900°C or lower for 8 hours or less. A more preferable heating temperature may be 750°C or lower, and a more preferable heating time may be 2 hours or lower.

[0039]

[0040] Complexation stage

[0041] A metal source can be added to the black solid silicon oxide (SiOx) obtained in the heating step, and the particle size of the silicon oxide (SiOx) can be controlled through dry milling, while simultaneously complexing the silicon oxide (SiOx) and the metal to produce a silicon oxide (SiOx)-metal composite powder.

[0042]

[0043] The metal source may be at least one selected from Al, Ti, or Mn, which have excellent reactivity with oxygen, or may be any one selected from their oxides (Al2O3, TiO2, MnO2). If the amount of the metal source added is insufficient, the formation of lithium oxide cannot be sufficiently suppressed. Therefore, the amount of the metal source added is preferably 0.1 wt% or more. A more preferable amount of the metal source added may be 1.0 wt% or more. On the other hand, if the amount of the metal source added is excessive, the electrode reaction may be reduced due to metal precipitation, thereby reducing the battery charge / discharge capacity. Therefore, the amount of the metal source added is preferably 10 wt% or less. A more preferable amount of the metal source added may be 5 wt% or less.

[0044]

[0045] The equipment used in dry milling is not particularly limited, but one or more selected from a jet mill, a planetary mill, a spex mill, or an attritor mill may be used. However, to prevent the intrusion of impurities, it may be preferable for the bowl used in dry milling to have an interior made of ceramic.

[0046]

[0047] When the milling speed is excessively slow or the milling time is excessively short during dry milling, the particle size of the final powder becomes coarse and cannot be used for electrodes. Therefore, it is preferable to apply a milling speed of 50 rpm or more and a milling time of 30 minutes or more. On the other hand, when the milling speed is excessively fast or the milling time is excessively long, the particle size of the final powder becomes excessively small, causing a peeling phenomenon when applied to electrodes. Therefore, it is preferable to apply a milling speed of 1000 rpm or less and a milling time of 6 hours or less. The average particle size of the silicon oxide (SiOx)-metal composite powder finally obtained in the compounding step may be 1 μm to 10 μm, and a more preferable average particle size may be 3 μm to 7 μm.

[0048]

[0049] By doping a metal that oxidizes faster than silicon through a complexation process into the crystal structure of silicon oxide (SiOx), the production of lithium silicate (LiSiO4) can be effectively suppressed when applying silicon oxide (SiOx)-metal composite powder to a lithium-ion secondary battery.

[0050] Hereinafter, a method for producing a high-capacity silicon oxide-metal composite powder according to one aspect of the present invention will be described in more detail through examples. However, the examples below are merely illustrative examples to aid understanding of the present invention, and the scope of the present invention is not construed as being limited to the examples below.

[0051]

[0052] (Example)

[0053] Liquid SiCl4 and liquid ethylene glycol were prepared, and 100 g of ethylene glycol was placed in a ceramic reactor, and 200 g of SiCl4 was dropped into the reactor at an injection rate of 10 g / min to produce a metastable material. Afterwards, heating was performed at a temperature range of 600℃ for 1 hour in an atmosphere supplied with oxygen at a flow rate of 300 ml / sec to obtain black solid silicon oxide (SiOx). Afterwards, Al2O3, TiO2, and MnO2 were added to each solid silicon oxide (SiOx) as described in Table 1 below, and then dry milled in a plane mill at a milling speed of 150 rpm for 2 hours to obtain silicon oxide-metal composite powders having an average particle size of 5 μm. For comparative examples, commercial SiOx (shin-Etsu, x=0.7, 5±1 μm, Japan) was used.

[0054]

[0055] Classification SiCl4 (g) Ethylene glycol (g) Metal source Addition amount (wt%) Metal source Invention example 1 200 100 1 Al2O3 Invention example 2 200 100 5 Invention example 3 200 100 1 TiO2 Invention example 4 200 100 5 Invention example 5 200 100 1 MnO2 Invention example 6 200 100 5 Comparative example SiOx (Shin-Estu)

[0056]

[0057] XRD analysis was performed on Invention Examples 1 to 6 to confirm the crystal structure of each powder, and the results are as shown in Fig. 1. Meanwhile, although not shown in Fig. 1, XRD analysis was also performed on Comparative Examples, and it can be confirmed that Invention Examples 1 to 6 and the Comparative Examples have the same XRD diffraction peaks. That is, the XRD analysis results of the composite powders of Invention Examples 1 to 6 also confirm that Invention Examples 1 to 6 only have a crystal structure of silicon oxide (SiOx), and this is understood to be because the metal source was doped within the solid solution limit of the silicon oxide (SiOx) crystal structure.

[0058]

[0059] Meanwhile, for the electrochemical evaluation of the manufactured powders, the powders of each of Invention Examples 1 to 6 were mixed with acetylene black and polyamide (binder) at a weight ratio of 8:1:1, and mixed with N-methyl-2-pyrrolidone as a solvent to prepare a negative electrode slurry. The prepared negative electrode slurry was applied to a copper foil current collector at a concentration of 5 mg / cm. 2 The cathode was manufactured by applying the amount of , and drying at 400°C for 2 hours.

[0060]

[0061] A coin-type half-cell (2016 type) was manufactured using lithium metal foil as the positive electrode and an electrolyte containing 1.3 M LiP6 of ethyl carbonate (EC) / diethyl carbonate (DEC) in a 1:1 ratio and 5% fluorinated ethylene carbonate (FEC) added thereto.

[0062]

[0063] In order to confirm the final characteristic evaluation and uniformity, coin-type half-cells were manufactured five times using the method described above (Invention Example 1' to Invention Example 6'), and then electrochemical evaluations were performed, and the results are shown in Table 2. Comparative Example' in Table 2 used commercial SiOx (shin-Etsu, x=0.7, 5±1㎛, Japan) as in Table 1, and the same coin-type half-cell (2016 type) manufacturing conditions and evaluation conditions as Invention Example 1' to Invention Example 6' were applied.

[0064]

[0065] Category 1 st Charging capacity (mAh / g)1 st Discharge capacity (mAh / g) 300 th Discharge capacity (mAh / g)1 stInitial Efficiency (%) Invention Example 1'19451888181193.1 Invention Example 2'19261856179996.3 Invention Example 3'18891812178895.9 Invention Example 4'18971779169994.8 Invention Example 5'19121865182093.7 Invention Example 6'18541778171295.9 Comparative Example'19121523100979.6

[0066]

[0067] As shown in Table 2, it can be confirmed that the invention examples 1' to 6' in which the metal source is doped have higher capacity characteristics and lifespan characteristics compared to the comparative example.

[0068]

[0069] Therefore, it can be seen that the silicon oxide-metal composite powder manufactured according to one aspect of the present invention can effectively improve the irreversible properties and lifespan of a negative electrode for a secondary battery.

[0070]

[0071] While the present invention has been described in detail through examples above, other embodiments are possible. Therefore, the technical spirit and scope of the claims set forth below are not limited to the examples.

Claims

1. Liquid SiCl is placed in a reactor containing liquid ethylene glycol. 4 Dropping ethylene glycol and SiCl at a preset injection rate 4 A reaction step that causes a reaction; In the above reaction step, ethylene glycol and SiCl 4 A heating step for obtaining a solid silicon oxide (SiOx) by heat-treating the metastable silicon oxide obtained by reacting under atmospheric gas conditions; and A method for producing a high-capacity silicon oxide-metal composite powder, comprising a compounding step of adding at least one metal selected from Al, Ti, and Mn to solid silicon oxide (SiOx) obtained in the above heating step, controlling the particle size of silicon oxide (SiOx) through dry milling, and simultaneously complexing the silicon oxide (SiOx) with the metal.

2. In paragraph 1, In the above reaction step, The oxygen value (x) of the silicon oxide (SiOx) obtained in the above heating step is 0.01 to 0.85, so that the ethylene glycol and the SiCl 4 A method for producing a high-capacity silicon oxide-metal composite powder by controlling the mixing ratio.

3. In paragraph 1, In the above reaction step, The above SiCl 4 A method for producing a high-capacity silicon oxide-metal composite powder, wherein the injection speed is 1 g / min to 1000 g / min.

4. In paragraph 1, In the above heating step, The above atmospheric gas is at least one selected from oxygen, nitrogen or argon, The flow rate of the above atmospheric gas is 10 ml / sec to 1000 ml / sec, A method for producing a high-capacity silicon oxide-metal composite powder, wherein the above-mentioned metastable silicon oxide is heated in a temperature range of 400°C to 900°C for 30 minutes to 8 hours.

5. In paragraph 1, In the above compounding step, The equipment used for the above dry milling may be at least one selected from a jet mill, a planar mill, a specs mill, and / or an attritor. The milling speed of the above dry milling is 50 rpm to 1000 rpm, A method for producing a high-capacity silicon oxide-metal composite powder, wherein the milling time of the above dry milling is 30 minutes to 6 hours.

6. In paragraph 5, A method for producing a high-capacity silicon oxide-metal composite powder, wherein the average particle size of the silicon oxide (SiOx)-metal composite powder obtained in the above compounding step is 1 ㎛ to 10 ㎛.

7. In paragraph 1, A method for producing a high-capacity silicon oxide-metal composite powder, wherein the metal added in the above compounding step is a metal powder, and the metal powder is added in an amount of 0.1 wt% to 10 wt%.

8. In paragraph 7, The above metal powder is Al 2 O 3 Powder, TiO 2 Powder or MnO 2 A method for producing a high-capacity silicon oxide-metal composite powder, wherein at least one powder is selected from among the following.

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