Jet mill system with improved pulverization efficiency

Abstract

To provide a jet mill system with improved pulverization efficiency.SOLUTION: A jet mill according to the present invention comprises: a compressor configured to compress gas introduced from the outside; a dehumidifier configured to remove moisture in the gas compressed by the compressor; a filter configured to filter foreign substances in the gas from which moisture has been removed by the dehumidifier; and a cooler configured to cool the gas filtered by the filter and supply the cooled gas into a milling main body of the jet mill.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a jet mill system with improved milling efficiency, and more specifically, to a jet mill system in which the temperature of compressed gas is controlled to 10°C or less when milling a sulfide-based solid electrolyte, thereby making it possible to easily adjust the particle size and prevent adhesion to the mill body, thereby improving the milling efficiency. [Background technology]

[0002] Recently, the use of secondary batteries in electronic devices such as smartphones has become common. A secondary battery has lithium as a positive electrode, is charged by lithium ions that move from the positive electrode to the negative electrode, and generates electricity by discharging in the process in which lithium moves from the negative electrode to the positive electrode.

[0003] Such lithium secondary batteries have the advantages of high energy density and the ability to achieve a long life, and therefore are commonly used in a variety of electronic devices. Recently, demand for such batteries has been expanding in line with the rapid growth of the electric vehicle market.

[0004] However, such lithium secondary batteries use an organic solvent as an electrolyte for ion migration, and therefore there is a risk of accidents occurring due to electrolyte leakage or evaporation, posing a safety problem.

[0005] In recent years, solid electrolyte technology that uses solid sulfide-based compounds as an alternative to conventional liquid electrolytes has been developed. This technology has the advantage that only lithium ions move within the electrolyte, so no side reactions occur and it is extremely safe and durable.

[0006] Among the solid electrolytes used in lithium secondary batteries, Li 7 -XPS 6The compound represented by -xClx has a cubic argyrodite-type crystal structure and has high ionic conductivity and electrochemical stability over a wide temperature range, so it is attracting attention as a sulfide-based solid electrolyte for mass production.

[0007] After synthesis, such solid electrolytes are processed into particles having a certain size by a milling process. In the conventional milling process for solid electrolytes, a ball mill is generally used. However, such a ball mill not only requires several tens of hours of processing to produce particles of less than 10 μm required for solid electrolyte particles, but also has problems such as the formation of carbon compounds due to the reaction of the solvent, which reduces electrical conductivity.

[0008] Accordingly, in order to control the particle size of the solid electrolyte, a method of dry pulverization of particles using a jet mill has been adopted recently. Such a jet mill is a device that injects compressed air through a nozzle to collide raw materials to be ground, and separates the raw materials according to particle size using a classifier at the top of the chamber where the raw materials collide, and is capable of grinding sulfide-based solid electrolyte (LPSCl).

[0009] However, due to the ductile characteristics of sulfide-based solid electrolytes, if they are milled at temperatures above room temperature, it becomes difficult to control the particle size and they become stuck inside the mill body, resulting in reduced process efficiency. Furthermore, if the compressed air supplied to the jet mill contains carbon dioxide, the carbon dioxide will act as an impurity, reducing the purity or generating secondary or tertiary by-products, which will reduce the performance of the solid electrolyte. Summary of the Invention [Problem to be solved by the invention]

[0010] The present invention has been devised to solve the above-mentioned problems of the conventional technology, and an object of the present invention is to provide a jet mill system that can easily adjust the particle size and improve the efficiency of milling by controlling the temperature of the compressed gas to 10°C or less when milling a sulfide-based solid electrolyte, thereby preventing adhesion to the mill body. [Means for solving the problem]

[0011] In order to achieve the above-mentioned object, the present invention provides a jet mill system with improved milling efficiency, which includes a compressor that compresses gas flowing in from the outside; a dehumidifier that removes moisture from the gas compressed by the compressor; a filter that filters out foreign matter from the gas from which moisture has been removed by the dehumidifier; and a cooler that cools the gas filtered by the filter and supplies the cooled gas into the mill body of the jet mill.

[0012] In this case, the gas is preferably any one of pure nitrogen, pure argon, and air. The dehumidifier is capable of dehumidifying to a dew point level of -90°C.

[0013] Between the dehumidifier and the cooler, there are arranged, in order, a pre-treatment filter that filters out foreign matter in the compressed and dehumidified gas; a carbon dioxide gas purifier that purifies the carbon dioxide gas in the gas from which the foreign matter has been filtered out by the pre-treatment filter; and a post-treatment filter that filters out remaining foreign matter in the gas from which the carbon dioxide gas has been purified by the carbon dioxide gas purifier.

[0014] The temperature of the gas cooled by the cooling machine and supplied into the mill body of the jet mill is preferably controlled to -5°C to -10°C. A plurality of the cooling machines are provided and installed in series.

[0015] The material of the classifier installed at the upper end of the mill body of the jet mill for classifying particles according to size and the material of the mill base at the lower end of the mill body are preferably SUS (Steel Use Stainless) series or ceramic.

[0016] Details of other embodiments are set forth in the Detailed Description and accompanying Drawings. The advantages and / or features of the present invention, as well as the method for achieving the same, will become apparent from the following detailed description of the embodiments in conjunction with the accompanying drawings.

[0017] However, the present invention is not limited to the configurations of the embodiments disclosed below, but can be modified and embodied in various different forms. However, the embodiments disclosed in this specification are provided for the purpose of complete disclosure of the present invention and to enable those having ordinary skill in the art to which the present invention pertains to fully understand the scope of the present invention, and it should be understood that the present invention is defined by the scope of the claims set forth in the claims. Effect of the Invention

[0018] According to the means for solving the above-mentioned problems, the present invention has the following effects. According to the present invention, a cooling machine is further provided to cool the compressed gas whose temperature has increased due to processes such as compression and dehumidification, and the compressed gas is controlled to a temperature of 10° C. or less, whereby the particle size of the sulfide-based solid electrolyte can be easily adjusted and adhesion to the mill body can be prevented.

[0019] In addition, according to the present invention, by further providing a carbon dioxide gas purification machine, it is possible to prevent the carbon dioxide gas from acting as an impurity to reduce the purity, or from generating secondary or tertiary by-products that would reduce the performance of the solid electrolyte. [Brief description of the drawings]

[0020] [Figure 1]FIG. 1 is a diagram showing a schematic configuration of a jet mill system with improved grinding efficiency according to the present invention. [Diagram 2] 1 is a photograph showing the raw material input section of a jet mill system with improved milling efficiency according to the present invention (Examples 1 to 6) and the raw material input section of a jet mill system according to the prior art (Comparative Examples 1 and 2). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Hereinafter, preferred embodiments of the jet mill system with improved grinding efficiency according to the present invention will be described in detail with reference to the accompanying drawings. Incidentally, the terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted based on the meaning and concept that is consistent with the technical idea of ​​the present invention, in accordance with the principle that the inventor can appropriately define the concept of the term in order to best describe his / her invention. In addition, the embodiment described in this specification and the configuration shown in the drawings are merely preferred embodiments of the present invention, and do not fully represent the technical idea of ​​the present invention, so it should be understood that there may be various equivalents and modifications that can replace them at the time of this application.

[0022] FIG. 1 is a diagram showing a schematic configuration of a jet mill system with improved milling efficiency according to the present invention. The jet mill system with improved grinding efficiency according to the present invention is configured so that a compressor 10, a dehumidifier 20, filters 30 and 50, a cooler 60, and a jet mill 70 are arranged in this order.

[0023] The compressor 10 compresses gas that flows in from the outside after passing through a dust collecting filter. In this case, the gas is preferably any one of pure nitrogen, pure argon, and air.

[0024] The dehumidifier 20 removes moisture from the gas compressed by the compressor 10 . Such a dehumidifier 20 is capable of dehumidifying down to a dew point level of minus 90 degrees Celsius.

[0025] The filters 30 and 50 filter out foreign matter in the gas from which moisture has been removed by the dehumidifier. In the cooler 60, the gas filtered by the filters 30 and 50 is cooled and the cooled gas is supplied to the mill body of the jet mill 70, but multiple such coolers 60 may be provided and installed in series.

[0026] The reason for providing a plurality of chillers 60 in series in this manner is to efficiently cool the gas compressed by the compressor 10 to a desired temperature. That is, since each cooling machine (cooling equipment) has a different cooling temperature and a different cooling capacity, by connecting multiple cooling machines in series, cooling is performed in stages in each cooling machine.

[0027] For example, two cooling machines may be provided, so that the first cooling machine cools the compressed gas to 0° C., and the second cooling machine cools the compressed gas to a desired sub-zero temperature. At this time, the temperature of the gas cooled by the cooler 60 and supplied to the inside of the mill body (the base of the mill) of the jet mill 70 is preferably controlled within a range of -5°C to -10°C.

[0028] In addition, between the dehumidifier 20 and the cooling device 60, a pre-treatment filter 30 that filters out foreign matter in the compressed and dehumidified gas, a carbon dioxide gas purifier 40 that purifies the carbon dioxide gas in the gas from which the foreign matter has been filtered by the pre-treatment filter 30, and a post-treatment filter 50 that filters out remaining foreign matter in the gas from which the carbon dioxide gas has been purified by the carbon dioxide gas purifier 40 may be arranged in this order.

[0029] In this way, the present invention further provides a cooling device 60 for cooling the compressed gas whose temperature has increased through processes such as compression and dehumidification, and controls the compressed gas to 10°C or lower (-5°C to -10°C), thereby easily adjusting the particle size of the sulfide-based solid electrolyte and preventing it from sticking to the mill body.

[0030] In addition, the present invention further provides a carbon dioxide gas purifier 40 between the dehumidifier 20 and the cooling device 60, thereby preventing the carbon dioxide gas from acting as an impurity to reduce the purity, or preventing the performance of the solid electrolyte from being reduced due to the generation of secondary or tertiary by-products. EXAMPLES

[0031] As shown in Table 1 below, the applicant conducted an experiment to compare the production volume and PSA depending on the temperature (temperature at the base of the mill) of the gas (air is used as the gas in this specification) supplied to the base of the mill in the mill body of the jet mill.

[0032] The experiment was carried out as follows: After the cooling machine is installed, the operation of the cooling equipment is stopped and compressed air is supplied to the jet mill through the bypass section.

[0033] At this time, the temperature of the compressed air is based on the temperature inside the mill body 20 minutes after the compressed air is supplied to the equipment. Data is collected for Comparative Example 1 and Comparative Example 2, where the compressed air temperature is 23°C.

[0034] The cooling equipment is operated to check the temperature inside the mill body, and experiments similar to those in Comparative Example 1 and Comparative Example 2 are carried out by changing only the temperature to -5°C, 0°C, 10°C, etc. (Examples 1 to 6). After the experiment, the production volume and the clogging condition at the raw material inlet of the mill body were checked and recorded as data.

[0035] Comparison of production volume and PSA by the jet mill system with improved grinding efficiency according to the present invention (Examples 1 to 6) and the conventional jet mill system (Comparative Examples 1 and 2); Comparison based on the temperature difference at the mill base

[0036] [Table 1]

[0037] The material of the classifier installed at the upper end of the mill body of the jet mill to separate particles according to size, and the material of the mill base at the lower end of the mill body, are preferably made of SUS (Steel Use Stainless) series or ceramic.

[0038] Here, PSA stands for Particle Size Analysis, which is an analytical method for measuring the size of particles and calculating the relative ratio of particles. That is, PSA is an analytical method that measures the minimum and maximum sizes, average values, and distribution of particles.

[0039] In this case, the concept of cumulative distribution is used. The values ​​that correspond to 10%, 50%, and 90% of the maximum value are defined as D10, D50, and D90, respectively, and the average value is D mean , the maximum value is D max It states that:

[0040] As shown in Table 1 above, it can be seen that the production amount and PSA in Example 3 are the best. That is, as the temperature of the mill base decreases, the production volume tends to increase, and the crushing process is smoother, resulting in smaller particle sizes.

[0041] FIG. 2 is a photograph showing the raw material input section of a jet mill system with improved milling efficiency according to the present invention (Examples 1 to 6) and the raw material input section of a jet mill system according to the prior art (Comparative Examples 1 and 2).

[0042] After the experiment was carried out under the experimental conditions shown in Table 1 above, it was confirmed that the raw material was stuck at the raw material inlet of the mill body of the jet mill, as shown in FIG. In Comparative Examples 1 and 2, in which the temperature of the mill base was 23° C., the raw material was clogged and stuck in the raw material inlet of the mill body.

[0043] In Examples 1 to 6, as the temperature of the base of the mill decreases, the phenomenon in which the raw material sticks to the raw material inlet portion of the mill body decreases significantly.

[0044] Comparison of production volume, electrical conductivity, and ionic conductivity with the operation of the carbon dioxide gas purifier on and off

[0045] [Table 2]

[0046] In the evaluation of the retention rate of ionic conductivity, the samples were double-vacuum-packed using aluminum pouches, and samples were taken under the same conditions as in Comparative Example 1 and Example 1. Since initial contact with moisture is necessary to evaluate the retention rate of ionic conductivity, the ionic conductivity was measured for 0 hours under a dew point of -20° C., and the container was immediately sealed.

[0047] Sampling for measuring electrical conductivity was carried out at a dew point of -60°C. As a result, when grinding was performed with the carbon dioxide gas purification machine off, there was no significant difference in production volume between Comparative Example 1 and Example 1, but the ionic conductivity in Example 1 was reduced compared to Comparative Example 1, and the electrical conductivity in Example 1 was increased compared to Comparative Example 1.

[0048] A method for verifying the change in ionic conductivity and electrical conductivity due to the presence or absence of carbon dioxide gas will be briefly described below.

[0049] [Verification method 1] Comparison of the rate of deterioration of ionic conductivity depending on whether or not carbon dioxide is included The hydrolysis reaction of argyrodite is as follows: Li 6 P.S. 5 Cl+6H 2 O → LiCl + Li 3 PO 4 +5H2 S+2LiOH

[0050] Here, carbon dioxide (CO 2 ) is added, the neutralization reaction is as follows: 2LiOH+CO 2 →Li 2 CO 3 +H 2 O When carbon dioxide is contained and exposed to moisture, it undergoes a neutralization reaction to produce H 2 Further production of O leads to degradation and lower ionic conductivity.

[0051] [Verification method 2] Change in electrical conductivity depending on whether or not carbon dioxide is present The higher the electrical conductivity of the electrolyte, the higher the possibility of self-discharge during the cell process. Therefore, the lower the electrical conductivity, the better the physical properties.

[0052] If carbon gas is present, the electrical conductivity will increase, so by analyzing the sample under the same conditions, it is possible to indirectly confirm whether or not carbon dioxide gas is present. The present invention as described above is not limited to the above-described embodiments and the accompanying drawings, and it will be easily understood by those having ordinary knowledge in the technical field to which the present invention pertains that various substitutions, modifications, and changes can be made within the scope that does not deviate from the technical idea of ​​the present invention. [Explanation of symbols]

[0053] 10: Compressor 20:Dehumidifier 30: Pre-processing filter 40: Carbon dioxide gas purifier 50: Post-processing filter 60: Cooler 70: Jet mill

Claims

1. A compressor that compresses gas flowing in from the outside; a dehumidifier for removing moisture from the gas compressed by the compressor; A filter that filters foreign matter in the gas from which moisture has been removed by the dehumidifier; and a cooler for cooling the gas filtered by the filter and supplying the cooled gas into a mill body of a jet mill; A jet mill system having improved grinding efficiency, comprising:

2. 2. The jet mill system with improved grinding efficiency as claimed in claim 1, wherein the gas is any one of pure nitrogen, pure argon, and air.

3. 2. The jet mill system with improved milling efficiency according to claim 1, wherein the dehumidifier performs dehumidification to a dew point level of minus 90 degrees Celsius.

4. Between the dehumidifier and the cooler, a pre-treatment filter for filtering foreign matter in the compressed and dehumidified gas; A carbon dioxide gas purifier that purifies the carbon dioxide gas in the gas from which foreign matter has been filtered by the pretreatment filter; and a post-treatment filter for filtering out remaining foreign matter in the gas obtained by purifying the carbon dioxide gas in the carbon dioxide gas purifier; 2. The jet mill system with improved grinding efficiency according to claim 1, wherein:

5. 5. The jet mill system with improved grinding efficiency according to claim 4, wherein the temperature of the gas cooled by the cooler and supplied into the mill body of the jet mill is controlled to be between -5°C and -10°C.

6. The jet mill system with improved grinding efficiency according to claim 5 , wherein a plurality of the coolers are provided and installed in series.

7. 2. The jet mill system with improved pulverization efficiency according to claim 1, wherein a material of a classifier installed at an upper end of the mill body of the jet mill for classifying particles according to size and a material of a mill base at a lower end of the mill body are made of SUS series or ceramic.

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