Sulfide electrolyte preparation method

Abstract

The present invention relates to a sulfide electrolyte preparation method. According to one aspect of the present invention, the sulfide electrolyte preparation method of the present invention comprises: a water control step for controlling water content in a solvent; a step for producing a precursor solution by stirring a precursor with the water content-controlled solvent; and a powder synthesis step for synthesizing an electrolyte powder using the precursor solution.

Description

Method for manufacturing sulfide electrolyte

[0001] The present invention relates to a method for manufacturing a sulfide electrolyte, and more particularly, to a method for manufacturing a sulfide electrolyte for an all-solid-state battery.

[0002] Currently, lithium-ion secondary batteries are used not only in small electronic devices but also in medium and large-sized devices such as electric vehicles, so their range of applications is wide.

[0003] Currently, extensive research is being conducted to increase the energy density and safety of lithium-ion secondary batteries. However, problems such as battery explosions and fires caused by excessive increases in energy density in high-voltage batteries continue to arise. To address these issues, active research is being conducted on all-solid-state batteries that utilize solid electrolytes, which offer superior heat resistance and durability compared to liquid electrolytes.

[0004] There are various types of solid electrolytes, including oxide-based, sulfide-based, and polymer-based solid electrolytes. Among them, sulfide-based solid electrolytes have the highest ionic conductivity and have advantages in processing, so much research is being conducted on them.

[0005] There are two methods for manufacturing solid electrolytes: solid-state method and liquid-state method.

[0006] The solid-state method synthesizes electrolyte powder by mixing solid starting materials using a ball mill or mixer, and then heat-treating them at high temperatures. However, it is difficult to control the particle size of the solid electrolyte, and since the particle size is not uniform, the problem of the ionic conductivity of the solid electrolyte being low may occur.

[0007] The liquid-phase method manufactures solid electrolytes by dissolving various starting materials in a solvent and then synthesizing electrolyte powder through solubility reduction or hydrolysis-condensation reactions. However, the liquid-phase method leaves residual solvent during the manufacturing process, and some raw materials may be diluted by this residual solvent, affecting the ionic conductivity of the solid electrolyte.

[0008] Accordingly, development of solid electrolyte manufacturing technology is required to overcome the limitations of solid-state and liquid-state methods.

[0009] Meanwhile, the background technology described above is technical information that the inventor possessed for the purpose of deriving the present invention or acquired during the process of deriving the present invention, and cannot necessarily be said to be publicly known technology disclosed to the general public prior to the application for the present invention.

[0010] One embodiment of the present invention aims to provide a method for producing a sulfide electrolyte having a low impurity content and high ionic conductivity.

[0011] As a technical means for achieving the above-described technical task, according to one aspect of the present invention, the method for producing a sulfide electrolyte of the present invention includes a moisture control step for controlling the moisture content in a solvent, a step for producing a precursor solution by stirring a precursor and the solvent in which moisture is controlled, and a powder synthesis step for synthesizing an electrolyte powder with the precursor solution.

[0012] According to another aspect of the present invention, the moisture control step may include a first moisture control step for controlling moisture in a first solvent including an aprotic solvent and a second moisture control step for controlling moisture in a second solvent including a protic solvent.

[0013] According to another aspect of the present invention, in the first moisture control step, the moisture content in the first solvent can be controlled to 135 ppm or less.

[0014] According to another aspect of the present invention, in the second moisture control step, the moisture content in the second solvent can be controlled to 35 ppm or less.

[0015] According to another aspect of the present invention, the aprotic solvent may include at least one selected from the group consisting of acetonitrile, tetrahydrofuran, hexane, acetone, dimethyl ether, and ethyl acetate.

[0016] According to another aspect of the present invention, the protic solvent may be an alcohol.

[0017] According to another aspect of the present invention, the moisture control step can be performed by any one of an adsorbent method, a membrane method, an electrolysis method, or a heating distillation method.

[0018] According to another aspect of the present invention, the step of preparing the precursor solution of the present invention may include a first solution preparation step of stirring a first precursor containing lithium, phosphorus, and sulfur and the first solvent, a second solution preparation step of stirring a second precursor containing halogen and the second solvent, and a step of mixing the first solution and the second solution to prepare the precursor solution.

[0019] According to another aspect of the present invention, the first solvent may be configured to produce a precipitate of a seed formed by a liquid phase reaction of the first precursor, and the second solvent may be configured to dissolve the precipitate of the seed formed by a liquid phase reaction of the first precursor.

[0020] According to another aspect of the present invention, the powder synthesis step may include a spraying step in which the droplets are sprayed, a transporting step in which the droplets are transported to a heating furnace, and a pyrolysis synthesis step in which the transported droplets are pyrolyzed inside the heating furnace.

[0021] According to another aspect of the present invention, the spraying step can be performed using an ultrasonic sprayer.

[0022] According to another aspect of the present invention, the transporting step may include a step of transporting the droplets using an inert gas as a transporting gas.

[0023] According to another aspect of the present invention, in the thermal decomposition synthesis step, the synthesized electrolyte powder may be amorphous or crystalline.

[0024] According to any one of the aforementioned means for solving the problem of the present invention, a method for manufacturing a sulfide electrolyte according to one embodiment of the present invention is configured to manufacture a precursor solution using a solvent with controlled moisture content. This facilitates the formation and dissolution of precipitates within the solvent, thereby increasing powder yield. Furthermore, problems of compositional decomposition due to moisture or the generation of impurities due to residual substances are resolved, thereby improving the crystallinity of the powder and enhancing ionic conductivity.

[0025] According to any one of the aforementioned means for solving the problem of the present invention, a method for manufacturing a sulfide electrolyte according to one embodiment of the present invention is configured to control the moisture content of an aprotic solvent. At this time, as the moisture content in the aprotic solvent decreases, seeds are well formed from the precursor in the precursor solution, thereby reducing residual precursor and minimizing the generation of impurities. Accordingly, a sulfide electrolyte with improved powder crystallinity and high ionic conductivity can be provided.

[0026] According to any one of the aforementioned problem-solving means of the present invention, a method for manufacturing a sulfide electrolyte according to an embodiment of the present invention is configured to control the moisture content of a protic solvent. At this time, as the moisture content in the protic solvent decreases, the seed dissolves well in the precursor solution, thereby reducing residual precipitates, thereby minimizing the generation of impurities due to the residual precipitates. Accordingly, a sulfide electrolyte having a high powder yield, low impurity content, and high ionic conductivity can be provided.

[0027] The effects that can be obtained from the present invention are not limited to the effects mentioned above, and other effects not mentioned can be clearly understood by a person having ordinary skill in the art to which the present invention belongs from the description below.

[0028] Figure 1 is a flow chart of a method for manufacturing a sulfide electrolyte according to one embodiment of the present invention.

[0029] Figure 2 is a conceptual diagram for explaining the method for manufacturing the sulfide electrolyte of Figure 1.

[0030] Figure 3 is an XRD (X-Ray Diffraction) image of a sulfide electrolyte manufactured according to embodiments of the present invention.

[0031] Below, with reference to the attached drawings, embodiments of the present invention are described in detail so that those skilled in the art can easily implement them. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein. In the drawings, irrelevant parts have been omitted for clarity of description, and similar reference numerals have been used throughout the specification to indicate similar elements.

[0032] Throughout the specification, when a part is said to be "connected" to another part, this includes not only "directly connected" but also "indirectly connected" with other elements or components intervening between them. Furthermore, when a part is said to "include" a component, this does not exclude other components, but rather includes other components, unless otherwise specifically stated.

[0033] The present invention will be described in detail with reference to the attached drawings below.

[0034] The method for manufacturing a sulfide electrolyte of the present invention is a method for manufacturing a sulfide solid electrolyte for increasing the energy density and safety of a lithium ion secondary battery, and discloses a method for manufacturing a sulfide electrolyte having a low impurity content and high ionic conductivity.

[0035] Figure 1 is a flow chart of a method for manufacturing a sulfide electrolyte according to one embodiment of the present invention.

[0036] Figure 2 is a conceptual diagram for explaining the method for manufacturing the sulfide electrolyte of Figure 1.

[0037] Referring to FIG. 1, the method for manufacturing a sulfide electrolyte of the present invention controls the moisture content in the solvent (S110).

[0038] The moisture control step is a step to remove the moisture content in the solvent to a certain level through solvent purification.

[0039] The solvent used in the moisture control step is a solvent capable of reacting with the precursor to initiate a liquid-phase reaction to produce a sulfide-based all-solid-state electrolyte. Either an aprotic or protic solvent may be used. Other solvents include chemical solutions used in the battery or electronics industries, as well as electrolytes for lithium-ion batteries.

[0040] An aprotic solvent is a solvent that accepts a proton and solvates it, or conversely, gives up a proton without becoming an anion.

[0041] The aprotic solvent may include at least one selected from the group consisting of acetonitrile, tetrahydrofuran, hexane, acetone, dimethyl ether, and ethyl acetate, and preferably acetonitrile, tetrahydrofuran, and ethyl acetate may be used.

[0042] A protic solvent is a solvent that has the ability to donate protons.

[0043] The protic solvent can be selected from alcohols, and preferably, ethanol (Ethyl alcohol) or methanol (Methyl alcohol) can be used.

[0044] The solvent in the present invention may be used alone or in a form comprising two or more types of solvents. For example, both protic and aprotic solvents may be used, and the following description will be based on the case where two types of solvents are used.

[0045] Referring to Figure 2, the first solvent and the second solvent are each stored in a solvent storage tank (210), and the moisture is controlled through a solvent purification device (220).

[0046] The solvent storage tank (210) is a tank capable of storing the solvent before purification, and is preferably a sealed container.

[0047] A plurality of solvent storage tanks (210) may be provided depending on the combination and number of solvents to be used. For example, a solvent storage tank for a first solvent may be used solely with an aprotic solvent or may contain one or more other solvents. A solvent storage tank for a second solvent may be used solely with a protic solvent or may contain one or more other solvents.

[0048] The solvent storage tank (210) is connected to a solvent purification device (220). The solvent stored in the solvent storage tank (210) can be subjected to moisture control through a solvent purification device (220) connected to the solvent storage tank (210). For example, a first solvent storage tank (211) storing a first solvent may be connected to a first solvent purification device (221), and a second solvent storage tank (213) storing a second solvent may be connected to a second solvent purification device (223). However, the present invention is not limited thereto, and the first solvent storage tank (211) and the second solvent storage tank (213) may be connected to one solvent purification device (220). In this case, solvent purification of the first solvent and the second solvent can be performed in one solvent purification device (220), and a separate purge step using an inert gas, etc., may be performed at a time interval to prevent the solvents from mixing.

[0049] The moisture content of the solvent in the solvent storage tank (210) can be controlled to a specific content level through a solvent purification device (220).

[0050] The solvent purification device (220) is a device that can control the moisture content of a solvent to a specific level, and a solvent purification device (220) of an adsorbent type, a membrane type, an electrolysis type, or a heating distillation type can be used.

[0051] For example, the solvent purification device (220) may be a heated distillation type solvent purification device (220). The heated distillation method utilizes the difference in boiling points to remove moisture within the solvent. While it can simultaneously remove impurities and moisture, it has the disadvantage of requiring a significant amount of time to remove moisture. In addition, the heated distillation method entails the use of a suitable desiccant.

[0052] Additionally, the solvent purification device (220) may be a membrane-type solvent purification device (220). The membrane-type solvent purification device purifies the solvent through a membrane, and the membrane may include some adsorbent. Furthermore, the membrane-type solvent purification device may be effective in separating hydrocarbons or polar / non-polar organic solvents.

[0053] In addition, the solvent purification device (220) may be an adsorbent-type solvent purification device (220). The adsorbent-type method is a method of adsorbing residual moisture and impurities in a solvent using an adsorbent. After the adsorbent is filled in a column, the solvent in the solvent storage tank (210) passes through the column due to the pressure of an inert gas.

[0054] At this time, multiple columns are used, and each column can be connected in series. When the solvent reaches the final column, the solvent can be sufficiently filtered.

[0055] Adsorbents that can be used include molecular sieves, activated alumina, silica gel, or copper catalysts.

[0056] As an example, a moisture control method using an adsorbent involves passing the solvent to be controlled through a first column filled with activated alumina and a second column filled with activated alumina and a copper catalyst. The first column can filter out polar impurities such as moisture and peroxides, while the second column can remove residual oxygen at the ppm level.

[0057] In some embodiments, the moisture control step described above may additionally remove polar impurities such as peroxide or oxygen in addition to the moisture content in the solvent when controlling the moisture content of the solvent.

[0058] When both an aprotic solvent and a protic solvent are used as solvents, the moisture control step can be performed for each solvent, and can be composed of a first moisture control step and a second moisture control step.

[0059] For example, the first moisture control step may include a step of controlling moisture in a first solvent comprising an aprotic solvent.

[0060] In the first moisture control step, the moisture content in the first solvent can be controlled to 135 ppm or less.

[0061] At this time, if the moisture content is controlled to exceed 135 ppm in the first moisture control step, the moisture content in the aprotic solvent increases, so that sulfide precipitates are not formed well, and the composition of the sulfide electrolyte may be partially decomposed by moisture, causing impurities to precipitate and affecting the crystallinity of the final solid electrolyte powder, making it difficult for the powder to become spherical and lowering the ionic conductivity.

[0062] The first moisture control step may be performed for an appropriate period of time so that the moisture content of the first solvent becomes 135 ppm or less. For example, the first moisture control step may be performed for 1 to 24 hours.

[0063] At this time, if moisture control is performed for less than 1 hour in the first moisture control step, it is difficult to expect improvement in ionic conductivity through moisture control, as moisture control is not performed for a sufficient period of time. Furthermore, if moisture control is performed for more than 24 hours in the first moisture control step, problems such as solvent evaporation or impurity contamination during the solvent purification process may occur.

[0064] Additionally, the second moisture control step may include a step of controlling moisture in a second solvent including a protic solvent.

[0065] In the second moisture control step, the moisture content in the second solvent can be controlled to 35 ppm or less.

[0066] At this time, if the moisture content is controlled to exceed 35 ppm in the second moisture control step, the moisture content in the protic solvent increases, and thus some of the sulfide-based precipitates are not dissolved in the protic solvent, thereby lowering the yield of the sulfide electrolyte powder, and impurities are generated due to compositional decomposition caused by the residual precipitates and moisture, which may lower the ionic conductivity of the final solid electrolyte.

[0067] The second moisture control step may be performed for an appropriate period of time so that the moisture content of the second solvent is 35 ppm or less. For example, the first moisture control step may be performed for 1 to 24 hours.

[0068] At this time, if moisture control is performed for less than 1 hour in the second moisture control step, it is difficult to expect improvement in ionic conductivity through moisture control, as moisture control is not performed for a sufficient period of time. Furthermore, if moisture control is performed for more than 24 hours in the second moisture control step, problems such as solvent evaporation or impurity contamination during the solvent purification process may occur.

[0069] Referring again to FIG. 1, the method for manufacturing a sulfide electrolyte of the present invention manufactures a precursor solution by stirring a precursor and a solvent (S120).

[0070] The step of preparing a precursor solution may include a first solution preparation step, a second solution preparation step, and a step of mixing the first solution and the second solution.

[0071] Referring to Figure 2, a first solution (250) is created by stirring an aprotic solvent that has passed through a solvent purification device (220) and a first precursor (230).

[0072] The first precursor (230) is a compound containing lithium, phosphorus, and sulfur, and any compound capable of forming a matrix (hereinafter referred to as “seed”) of an argyrodite structure can be used.

[0073] The aprotic solvent functions as a matrix that provides an environment for seed formation through liquid phase reaction in the first solution (250).

[0074] The stirring of the first precursor (230) and the aprotic solvent can be performed at an appropriate temperature and time range so that a liquid phase reaction of the precursor can occur in the first solution (250) and a seed can be formed.

[0075] In the first solution (250), the first precursor (230) can form seeds and can be introduced at an appropriate concentration so that no problem occurs in droplet generation due to seed precipitation.

[0076] The preparation of the first solution (250) can be performed using various stirring devices capable of stirring under the conditions described above. For example, it can be performed using a heating stirrer such as a hot plate.

[0077] Referring to Figure 2, a second solution (260) is created by stirring a protic solvent that has passed through a solvent purification device (220) and a second precursor (240).

[0078] The second precursor (240) is a compound containing a halogen element, and examples thereof include LiF, LiCl, LiBr, and LiI. However, the present invention is not limited thereto, and any compound containing a halogen element that can react with the seed formed in the first solution (250) to form a sulfide electrolyte may be used.

[0079] The protic solvent serves to dissolve the seeds generated from the second precursor (240) and the first solution (250).

[0080] The stirring of the second precursor (240) and the protic solvent can be performed within an appropriate temperature and time range in which the second precursor (240) can be sufficiently dissolved in the protic solvent within the second solution (260).

[0081] The preparation of the second solution (260) can be performed using various stirring devices capable of stirring under the conditions described above. For example, the second precursor (240) and the protic solvent can be uniformly stirred and mixed using a stirrer.

[0082] In the second solution (260), the second precursor (240) can form powder particles and can be introduced at an appropriate concentration so as not to cause problems in droplet generation due to sediment.

[0083] Referring to FIG. 2, a precursor solution (270) is prepared by mixing the first solution (250) and the second solution (260).

[0084] The method of mixing the first solution (250) and the second solution (260) may include all mixing methods possible under the conditions described above.

[0085] Referring to FIG. 1, the method for manufacturing a sulfide electrolyte of the present invention synthesizes an electrolyte powder using a precursor solution (S130).

[0086] The powder synthesis step includes a spraying step in which droplets are sprayed, a transporting step in which the droplets are transported to a heating furnace, and a pyrolysis step in which the transported droplets are pyrolyzed inside the heating furnace.

[0087] Referring to FIG. 2, droplets are generated from a precursor solution (270) through an ultrasonic atomizer (280).

[0088] The droplets are droplets of a mixed solution containing seeds of a sulfide solid electrolyte and may have a size of 0.1 μm to 100 μm.

[0089] Droplets can be generated by various devices capable of generating and spraying droplets of sizes ranging from 0.1 μm to 100 μm, and for example, can be generated by an ultrasonic spraying device (280). In this case, ultrasonic spraying can be performed in the range of 1.7 MHz to 2.4 MHz.

[0090] When the heater (290) reaches the set temperature, the precursor solution (270) can be formed into droplets from the ultrasonic spray device (280).

[0091] Ultrasonic spraying is advantageous in producing fine droplets and particles with a narrow droplet size distribution through ultrasonic vibration, and can increase the dispersion stability of the generated droplets. In addition, since each particle is produced from a single droplet, if the droplet size is uniform, it has the advantage of being able to produce particles of uniform size and composition.

[0092] Afterwards, the droplets generated from the precursor solution (270) are moved to the heating furnace (290).

[0093] A carrier gas may be used when the droplets are moved to the heater (290).

[0094] An inert gas may be used as the carrier gas, preferably argon (Ar) or nitrogen (N2). By using an inert gas as the carrier gas, chemical stability can be improved.

[0095] Afterwards, the droplets moved to the heating furnace (290) are thermally decomposed and produced as sulfide electrolyte powder.

[0096] The material of the heater (290) may be heat-resistant quartz, alumina, or SUS.

[0097] Afterwards, the sulfide electrolyte generated in the heating furnace (290) is dried while passing through the heating furnace (290) and is collected in the form of a solid powder in a powder obtainer.

[0098] It is preferable that the above powder has an argyrodite phase, but a process to increase the crystallinity of the powder through an additional heat treatment process after the process may be added.

[0099] As described above, the method for producing a sulfide electrolyte of the present invention is configured to produce a precursor solution using a solvent with controlled moisture content. Since the method for producing a sulfide electrolyte of the present invention uses a solvent with controlled moisture content, precipitates can be easily formed and dissolved within the solvent, thereby increasing the powder yield. Furthermore, problems of compositional decomposition due to moisture or the generation of impurities due to residual substances are resolved, thereby improving the crystallinity of the powder and enhancing its ionic conductivity.

[0100] In addition, the method for manufacturing a sulfide electrolyte of the present invention is configured to control the moisture content of the aprotic solvent. At this time, as the moisture content in the aprotic solvent decreases, seeds are well formed from the precursor in the precursor solution, so that residual precursor is reduced, thereby minimizing the generation of impurities. Accordingly, a sulfide electrolyte with improved powder crystallinity and high ionic conductivity can be provided. If the moisture content is not controlled, some of the composition may be decomposed by moisture, or the crystallinity of the final powder may be reduced due to impurities caused by residual precursor, resulting in low ionic conductivity.

[0101] Furthermore, the method for manufacturing a sulfide electrolyte of the present invention is configured to control the moisture content of the protic solvent. As the moisture content in the protic solvent decreases, the seed dissolves well in the precursor solution, thereby reducing residual precipitates. Consequently, the generation of impurities due to residual precipitates can be minimized. Consequently, a sulfide electrolyte with a high powder yield, low impurity content, and high ionic conductivity can be provided.

[0102] Hereinafter, a method for manufacturing a sulfide electrolyte according to a preferred embodiment of the present invention will be described in more detail.

[0103] <Manufacturing Example 1 - Preparation of Purification Solvent>

[0104] First, aprotic and protic solvents were used to manufacture sulfide electrolytes. Ethyl acetate was selected as the aprotic solvent, and ethanol was selected as the protic solvent. The moisture content of both solvents was purified through an adsorbent method. Specifically, the moisture-controlled solvent was passed through a first column filled with activated alumina and a second column filled with activated alumina and a copper catalyst.

[0105] For the two types of solvents described above, solvent samples of Comparative Examples 1 to 6 were prepared by varying the degree of moisture purification as shown in [Table 1] below. Specifically, in Comparative Example 1, moisture control was not performed for any solvents, and for Examples 1, 3, 4, and 5, solvent purification was performed by setting the moisture control levels to 5 ppm, 30 ppm, 60 ppm, and 130 ppm for all solvents. For Examples 2 and 6, moisture control was performed within 5 ppm only for the aprotic solvent and the protic solvent, respectively, so that comparison with Example 1 could be made.

[0106] Comparative Example 1 Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Control Level (ppm) -55 30 60 130 5 Moisture Content (ppm) Aprotic Solvent 192.75 2.73 43 1.136 2.24 13 1.33 18 9.17 Protic Solvent 43.62 3.82 43.23 0.62 20.19 10.75 3.68 Whether Solvent Controlled Aprotic Solvent XOOOOOX Protic Solvent XOXOOOO

[0107]

[0108] <Manufacturing Example 2 - Preparation of Precursor Solution>

[0109] After the moisture control step of the solvent, a first solution was prepared by stirring the first precursor selected from Li2S and P2S5 with an aprotic solvent with controlled moisture, and a second solution was prepared by stirring the second precursor selected from Li2S and LiCl with an aprotic solvent with controlled moisture. Thereafter, the first solution and the second solution were mixed to prepare a precursor solution.

[0110] Detailed manufacturing conditions are as shown in [Table 2] below.

[0111] Common conditions 1st solution 2nd solution Precursor type Li2SP2S5Li2SLiCl Amount (g) 3.44975.61291.72482.6502 Solvent type Ethyl acetate Ethanol

[0112]

[0113] <Manufacturing Example 3 - Manufacturing of Electrolyte Powder>

[0114] Sulfide electrolyte powder was manufactured by spraying and heating the precursor solutions according to Comparative Example 1 and Examples 1 to 6 under the process conditions of [Table 3] below.

[0115] Common conditions Mixed solution heating furnace temperature 200~300℃ Carrier gas type Nitrogen (N2) or argon (Ar) Flow rate 5~20L / min

[0116]

[0117] <Experimental Example 1 - XRD Measurement>

[0118] X-ray diffraction analysis (XRD) was performed to compare the particle structure of the sulfide electrolyte powders according to Comparative Example 1 and Examples 1 to 6.

[0119] Figure 3 is an XRD (X-Ray Diffraction) image of a sulfide electrolyte manufactured according to embodiments of the present invention.

[0120] As can be seen with reference to FIG. 3, compounds having an argyrodite structure were detected in both Comparative Example 1 and Examples 1 to 6, indicating that sulfide electrolyte powder particles were properly obtained. It can be seen that Comparative Example 1 has a relatively low peak compared to Examples 1 to 6. This is thought to be because some of the composition of the sulfide electrolyte was decomposed by moisture in the solvent of Comparative Example 1, affecting the crystallinity of the sulfide electrolyte. In particular, Li2S was not detected in Example 1. This is thought to be because, as the moisture content in the solvent was controlled to 5 ppm or less in Example 1, the seeds were well formed and dissolved in the precursor solution, resolving the problem of composition decomposition or residual precipitates and minimizing the generation of impurities.

[0121]

[0122] <Experimental Example 2 - Ionic Conductivity Measurement>

[0123] To compare the ionic conductivity of the sulfide electrolyte powders according to Comparative Example 1 and Examples 1 to 6, the ionic conductivity was measured.

[0124] Electrochemical impedance spectra (EIS) were measured to evaluate ionic conductivity. EIS was measured using AC impedance spectroscopy equipment (Biologic SP-300). The measurement was performed at a frequency of 1 Hz to 7 MHz and an AC amplitude of 20 mV. The measured impedance values ​​were converted to ionic conductivity values ​​using EIS (Electrochemical impedance spectroscopy) analysis, Nyquist plots, and equivalent circuits. Specifically, the bulk resistance values ​​obtained from plotting and the dimensions of the LPSCl pellets made using a pressurized cell were measured, and the ionic conductivity was measured using the following relationship.

[0125] σ = t / (A*R)

[0126] Here, σ represents ionic conductivity, t represents the thickness of the pellet, R represents ionic resistance, and A represents the area of ​​the pellet.

[0127] [Table 4] is a chart showing the results of ionic conductivity measurements for sulfide electrolytes manufactured according to embodiments of the present invention.

[0128] Comparative Example 1 Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Control Level (ppm) -55 30 60 130 5 Moisture Content (ppm) Aprotic Solvent 192.75 2.73 43 1.136 2.24 13 1.33 18 9.17 Protic Solvent 43.62 3.82 43.23 0.62 20.19 10.75 3.68 Solvent Control Aprotic Solvent XOOOOOX Protic Solvent XOXOOOO Ionic Conductivity (mS / cm) 2.67 3.82 3.12 3.0 43.12 2.95 2.95

[0129] As can be seen from [Table 4], it can be seen that Examples 1 to 6 all have excellent ionic conductivity of 2.95 mS / cm or more. In particular, it can be observed that the best ionic conductivity value of 3.58 mS / cm is shown in Example 2, where the moisture content in the solvent was controlled to 5 ppm or less in both aprotic and protic solvents.

[0130] Comparing Example 2 in which moisture in an aprotic solvent was controlled, Example 6 in which moisture in a protic solvent was controlled, and Comparative Example 1 in which moisture in the solvent was not controlled, it can be confirmed that when moisture in the solvent was controlled, less impurities were generated in the precursor solution and the ionic conductivity of the sulfide electrolyte tended to increase. In addition, it can be confirmed that the ionic conductivity tended to increase more when moisture in an aprotic solvent was controlled than in a protic solvent. This is because, considering the functions of each solvent, the effect of preventing residual precursors through moisture control in an aprotic solvent is thought to have a greater effect on the ionic conductivity of the sulfide electrolyte than the effect of preventing residual precipitates through moisture control in a protic solvent because it can control impurities better.

[0131] The scope of the present invention is indicated by the claims described below rather than the detailed description above, and all changes or modifications derived from the meaning and scope of the claims and their equivalent concepts should be interpreted as being included in the scope of the present invention.

[0132] The present invention, as a method for manufacturing a sulfide electrolyte, can be widely utilized in industries utilizing secondary batteries. For example, the present invention can be widely used not only in small electronic devices but also in medium- to large-sized devices such as electric vehicles, and can be applied to diverse fields such as home appliances, medical devices, robots, aerospace, energy storage systems, wearable devices, and IoT devices.

Claims

1. Moisture control step for controlling the moisture content in the solvent; A step of preparing a precursor solution by stirring the precursor and the solvent with controlled moisture content; and Comprising a powder synthesis step of synthesizing electrolyte powder using the above precursor solution, Method for manufacturing sulfide electrolyte.

2. In paragraph 1, The above moisture control step is, A first moisture control step for controlling moisture in a first solvent including an aprotic solvent; and Comprising a second moisture control step for controlling moisture in a second solvent including a protic solvent, Method for manufacturing sulfide electrolyte.

3. In paragraph 2, In the above first moisture control step, The moisture content in the first solvent is controlled to 135 ppm or less, Method for manufacturing sulfide electrolyte.

4. In paragraph 2, In the second moisture control step, The moisture content in the second solvent is controlled to 35 ppm or less, Method for manufacturing sulfide electrolyte.

5. In paragraph 2, The aprotic solvent comprises at least one selected from the group consisting of acetonitrile, tetrahydrofuran, hexane, acetone, dimethyl ether, and ethyl acetate. Method for manufacturing sulfide electrolyte.

6. In paragraph 2, The above protic solvent is an alcohol. Method for manufacturing sulfide electrolyte.

7. In paragraph 1, The above moisture control step It is performed by any one of the following methods: adsorption method, membrane method, electrolysis method or heating distillation method. Method for manufacturing sulfide electrolyte.

8. In paragraph 2, The step of preparing the above precursor solution is: A first solution preparation step of stirring a first precursor containing lithium, phosphorus, and sulfur and the first solvent; A second solution preparation step of stirring a second precursor containing halogen and the second solvent; and A step of preparing the precursor solution by mixing the first solution and the second solution, Method for manufacturing sulfide electrolyte.

9. In paragraph 8, The first solvent is configured to produce a precipitate of the seed formed by the liquid phase reaction of the first precursor, The second solvent is configured to dissolve the seed precipitate formed by the liquid phase reaction of the first precursor. Method for manufacturing sulfide electrolyte.

10. In paragraph 1, The above powder synthesis step is, Spraying step where droplets are sprayed; A transport step for transporting the above droplets to a heating furnace; and Comprising a thermal decomposition synthesis step of synthesizing electrolyte powder by inducing a reaction of the liquid droplets transported inside the heating furnace, Method for manufacturing sulfide electrolyte.

11. In paragraph 10, The above spraying step is, Performed using an ultrasonic nebulizer, Method for manufacturing sulfide electrolyte.

12. In paragraph 10, The above transport steps are: Comprising a step of transporting the droplets using an inert gas as a carrier gas, Method for manufacturing sulfide electrolyte.

13. In paragraph 10, In the above thermal decomposition synthesis step, The above-mentioned synthesized electrolyte powder is amorphous or crystalline. Method for manufacturing sulfide electrolyte.

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