Method for improving air stability of sulfide solid electrolyte

Abstract

The present invention relates to the technical field of batteries, and particularly relates to a method for improving the air stability of a sulfide solid electrolyte. The method comprises the following steps: mixing a sulfide solid electrolyte with a solvent to form a slurry I; mixing mercaptan with a solvent to form a slurry II; and simultaneously spraying the slurry I and the slurry II to the center of a material mixing device that is provided with an air drying device, and drying same under the air drying device, so as to complete the improvement of the air stability of the sulfide solid electrolyte. By spraying the sulfide solid electrolyte and the mercaptan, the two collide with each other at a certain airflow rate; therefore, sulfydryl of the mercaptan is coordinated with metal cations or exposed sulfur vacancies on the surface of the sulfide solid electrolyte to form a stable thiolate or complex, thereby achieving a particle coating or semi-coating effect on the sulfide solid electrolyte.

Description

A method for improving the air stability of sulfide solid electrolytes Technical Field

[0001] This invention relates to the field of battery technology, and in particular to a method for improving the air stability of sulfide solid electrolytes. Background Technology

[0002] Solid-state batteries, as the next generation of high-energy-density and high-safety energy storage devices, are considered an important direction for replacing traditional liquid lithium-ion batteries. Their core advantage lies in using a solid electrolyte instead of a liquid electrolyte, thus completely eliminating the flammability and leakage risks of liquid electrolytes. Simultaneously, they allow the use of lithium metal anodes or high-voltage cathode materials, achieving a theoretical energy density of over 500 Wh / kg, significantly superior to current liquid batteries (approximately 300 Wh / kg). Furthermore, solid-state batteries exhibit high mechanical stability, a cycle life exceeding 45,000 cycles, and support rapid charging and discharging (fully charged in 15 minutes), making them promising for applications in electric vehicles, energy storage systems, and other fields.

[0003] In solid-state battery technology, sulfide solid electrolytes have attracted significant attention due to their ultra-high ionic conductivity and excellent interfacial contact. Furthermore, sulfide solid electrolytes can be synthesized via solid-phase or liquid-phase methods, enabling direct contact between the sulfide system and lithium metal, thereby significantly reducing interfacial impedance. However, the poor air stability of sulfide solid electrolytes remains a core bottleneck for their commercialization.

[0004] Therefore, existing technologies still need to be improved and developed. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of this invention is to provide a method for improving the air stability of sulfide solid electrolytes, aiming to solve the problem of poor air stability of existing sulfide solid electrolytes.

[0006] The technical solution of the present invention is as follows:

[0007] A method for improving the air stability of sulfide solid electrolytes includes the following steps:

[0008] S1. Mix the sulfide solid electrolyte with a solvent to form a slurry;

[0009] S2. Mix the thiol with the solvent to form slurry two;

[0010] S3. Spray slurry one and slurry two simultaneously into the same place of the mixing device equipped with an internal air drying device, and dry them under the air drying device to improve the air stability of the sulfide solid electrolyte.

[0011] Optionally, the mixing device includes a reactor, two sprayers, and a drying device. The sprayers are located on the top of the reactor on both sides and are connected to the reactor. The drying device is located on the top of the reactor and blows air downwards. The direction of the gas sprayed by the sprayers is inclined towards the center of the reactor.

[0012] Optionally, the temperature of the reactor is 100-200°C.

[0013] Optionally, the reactor is provided with a material silo at the bottom for convenient storage of the reacted materials.

[0014] Optionally, the solvent is an aromatic hydrocarbon solvent or an ester solvent. Xylene is preferred.

[0015] Optionally, the solid content of slurry one is 10-40%.

[0016] Optionally, the solid content of slurry two is 10-40%.

[0017] Optionally, the particle size of the sulfide solid electrolyte is 400 nm to 10 μm.

[0018] Optionally, the thiol is any one of hexamethylenetetramine, octanethiol, sec-butanethiol, cyclohexanethiol, n-octadecylthiol, and ethanethiol.

[0019] Optionally, the spray velocity of slurry one and slurry two is 1-5 m / s. 3 / h.

[0020] Optionally, the airflow rate of the air-drying device is set to 100-300 m³ / h. 3 / h.

[0021] Beneficial effects: This invention sprays sulfide solid electrolytes and thiols into the same mixing device, causing them to collide under a certain airflow. This allows the thiol's mercapto groups (-SH groups) to react with the metal cations (such as Li) on the surface of the sulfide solid electrolyte. + P 5+ The sulfur molecules coordinate with exposed sulfur vacancies to form stable thiols or complexes, thereby achieving particle coating or partial coating of the sulfide solid electrolyte. Simultaneously, the hydrophobic thiol molecules can self-assemble onto the surface of the sulfide solid electrolyte to form a monolayer or nanoscale protective film, thus physically blocking active molecules from the air.

[0022] Chemical compatibility optimization

[0023] Because thiols are hydrophobic (e.g., ethanethiol has a solubility of only 1.5 g / 100 mL in water), they can reduce hydrolysis reactions caused by contact between the electrolyte and water. Simultaneously, the flexibility of their molecular chains helps maintain the interfacial stability between sulfide solid electrolytes and electrode materials (such as lithium metal). Furthermore, the acidity of thiols (pKa ≈ 10) -10 (mol / L, stronger than alcohols) can bind to alkaline sites on the surface of sulfide solid electrolytes, enhancing the chemisorption strength of the coating layer.

[0024] Restorative protection mechanism

[0025] Because the thiol group (-SH) in thiols has strong reducing properties, it can preferentially react with oxidizing substances in the air (such as oxygen and water vapor) to form stable disulfides (SS bonds). For example, thiols react with oxygen to form peroxides or disulfides, thereby consuming reactive oxygen free radicals in the environment that trigger the decomposition of sulfide solid electrolytes and blocking PS4 in sulfide solid electrolytes. 3- The tetrahedral redox reaction (such as the formation of Li2S and Li3P) prevents the electrolyte structure from being destroyed. Therefore, the thiol of the present invention provides reducing protection for sulfide solid electrolytes.

[0026] physical barrier effect

[0027] Since thiol molecules can be physically adsorbed or chemically bonded (such as with Li on the surface of sulfide solid electrolytes), + (Or PS bond formation coordination) forms a dense protective layer on the electrolyte surface. This layer can effectively block the penetration of moisture and oxygen, and inhibit interfacial side reactions (such as hydrogen sulfide (H2S) release and lithium dendrite growth) caused by moisture absorption or oxidation of sulfide solid electrolytes. Attached Figure Description

[0028] Figure 1 is a flowchart of an embodiment of the present invention.

[0029] Figure 2 is a schematic diagram of the mixing device according to an embodiment of the present invention.

[0030] Figure 3 shows the relationship between the specific capacity and voltage of battery 1 (before treatment) during charging and discharging.

[0031] Figure 4 shows the relationship between the specific capacity and voltage of battery 2 (after treatment) during charging and discharging. Detailed Implementation

[0032] This invention provides a method for improving the air stability of sulfide solid electrolytes. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0033] The current sulfide solid electrolytes have poor air stability, mainly due to the following two points.

[0034] High chemical reactivity: Sulfides readily react with moisture and oxygen in the air to produce toxic hydrogen sulfide (H2S) gas, which not only harms human health but also leads to the destruction of electrolyte structure and a decrease in ionic conductivity.

[0035] Production and packaging are challenging: the synthesis, processing, and battery assembly of sulfides must be carried out under strict inert gas protection (such as argon), significantly increasing manufacturing costs. For example, an existing company's 100-ton-level sulfide production line requires a fully enclosed inert environment, and the cost per batch is still as high as 10,000-40,000 yuan / kg.

[0036] Currently, most practices in the industry to improve stability are coating, especially wet coating. Wet coating requires multiple process steps to form, which is complicated, costly, and difficult to scale up.

[0037] Based on this, embodiments of the present invention provide a method for improving the air stability of sulfide solid electrolytes, as shown in Figure 1, including the following steps:

[0038] S1. Mix the sulfide solid electrolyte with a solvent to form a slurry;

[0039] S2. Mix the thiol with the solvent to form slurry two;

[0040] S3. Spray slurry one and slurry two simultaneously into the same spot of the mixing device equipped with the air drying device 3, and dry them under the air drying device to improve the air stability of the sulfide solid electrolyte.

[0041] Because the thiol's mercaptan group (-SH group) has strong nucleophilicity, it can react with metal cations (such as Li) on the surface of sulfide solid electrolytes. + P 5+ This invention, through ingenious design of the process flow and apparatus, first mixes the sulfide solid electrolyte with a solvent to form slurry one, and mixes the thiol with a solvent to form slurry two. Then, slurry one and slurry two, containing sulfide solid electrolyte and thiol respectively, are sprayed to cause collisions between the two. Simultaneously, they are air-dried under a certain temperature and airflow, thereby allowing the thiol's mercapto group (-SH) to interact with the metal cations (such as Li) on the surface of the sulfide solid electrolyte. + P 5+ The sulfur vacancies may coordinate with the sulfur to form stable thiols or complexes, thereby achieving particle coating or semi-coating of the sulfide solid electrolyte.

[0042] Meanwhile, since thiol molecules are hydrophobic, when thiol comes into contact with sulfide solid electrolyte, it forms a monolayer or nanoscale protective film on the surface of the sulfide solid electrolyte through self-assembly, thereby achieving the effect of physically blocking active molecules in the air.

[0043] Chemical compatibility optimization

[0044] Because thiols are hydrophobic (e.g., ethanethiol has a solubility of only 1.5 g / 100 mL in water), they can reduce hydrolysis reactions caused by contact between the electrolyte and water. Simultaneously, the flexibility of their molecular chains helps maintain the interfacial stability between sulfide solid electrolytes and electrode materials (such as lithium metal). Furthermore, the acidity of thiols (pKa ≈ 10) -10 (mol / L, stronger than alcohols) can bind to alkaline sites on the surface of sulfide solid electrolytes, enhancing the chemisorption strength of the coating layer.

[0045] Restorative protection mechanism

[0046] Because the thiol group (-SH) in thiols has strong reducing properties, it can preferentially react with oxidizing substances in the air (such as oxygen and water vapor) to form stable disulfides (SS bonds). For example, thiols react with oxygen to form peroxides or disulfides, thereby consuming reactive oxygen free radicals in the environment that trigger the decomposition of sulfide solid electrolytes and blocking PS4 in sulfide solid electrolytes. 3- The tetrahedral redox reaction (such as the formation of Li2S and Li3P) prevents the electrolyte structure from being destroyed. Therefore, the thiol of the present invention provides reducing protection for sulfide solid electrolytes.

[0047] physical barrier effect

[0048] Since thiol molecules can be physically adsorbed or chemically bonded (such as with Li on the surface of sulfide solid electrolytes), + (Or PS bond formation coordination) forms a dense protective layer on the electrolyte surface. This layer can effectively block the penetration of moisture and oxygen, and inhibit interfacial side reactions (such as hydrogen sulfide (H2S) release and lithium dendrite growth) caused by moisture absorption or oxidation of sulfide solid electrolytes.

[0049] In one embodiment, as shown in FIG2, the mixing device includes a reactor 1, two sprayers 2 disposed on the top of the reactor 1 and connected to the reactor 1, and a drying device 3 disposed on the top of the reactor 1 and blowing air downwards. The gas sprayed by the sprayers 2 is inclined inwards.

[0050] In this embodiment, a sprayer is used to rapidly collide and react sulfide solid electrolyte and thiol in reactor 1, while also quickly drying them. When thiol comes into contact with sulfide solid electrolyte, it can self-assemble to form a monolayer or nanoscale protective film on the surface of sulfide solid electrolyte, thereby physically blocking active molecules in the air.

[0051] In some embodiments, the temperature of the reactor 1 is 100-200°C, and can be 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C, 200°C or other temperatures.

[0052] Because the reactor is relatively large, in order to make the overall temperature inside the reactor uniform, a number of temperature control zones (such as an upper temperature control zone and a lower temperature control zone) are generally set along the longitudinal direction of the reactor, and the temperature of the upper temperature control zone and the lower temperature control zone are set to be the same.

[0053] In some embodiments, the reactor 1 is provided with a material hopper 4 at the bottom for convenient storage of the fully reacted materials.

[0054] In some embodiments, the solvent is an aromatic hydrocarbon solvent or an ester solvent. The aromatic hydrocarbon solvent is preferably toluene, ethylbenzene, or naphtha; the ester solvent is preferably ethyl acetate, butyl acetate, or isoamyl acetate.

[0055] In some embodiments, the solid content of slurry one is 10-40%, and the solid content of slurry one can be selected as 10%, 20%, 30%, 40%, and any other solid content within the range.

[0056] In some embodiments, the solid content of slurry two is 10-40%, and the solid content of slurry two can be selected as 10%, 20%, 30%, 40%, or any other solid content within the range. If the solid content is too low, a large amount of solvent will be used, which is not only environmentally unfriendly but also very costly. If the solid content is too high, the outlet of the sprayer is easily blocked, affecting subsequent reactions.

[0057] In some embodiments, the sulfide solid electrolyte is Li7P2S8X, where X is Cl, Br, I, and / or F; it can also be Li3PS4 or Li 10 GeP2S12, preferably Li 5.5 PS 4.5 Cl 1.5 (Chinese name: Lithium Phosphate Sulfate Chloride, abbreviated as LPSC).

[0058] In some embodiments, the particle size of the sulfide solid electrolyte is 400 nm to 10 μm. The preferred particle size is 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, or any particle size within this range. The method of this invention is applicable to sulfide solid electrolytes of various particle sizes, whether small (400 nm) or large (10 μm), and can improve their air stability. However, since small-particle-size sulfide solid electrolytes are more prone to water absorption, improving the air stability of small-particle-size sulfide solid electrolytes has greater industrial application value and prospects, and is therefore more significant.

[0059] In some embodiments, thiols refer to a class of non-aromatic compounds containing a mercapto functional group (-SH). In this embodiment, the thiols are any one of hexamethylenetetramine, octanethiol, sec-butanethiol, cyclohexanethiol, n-octadecylthiol, and ethanethiol.

[0060] In some embodiments, the spray velocity of slurry one and slurry two is 1-5 m / s. 3 / h. The preferred flow rate is 1m. 3 / h, 1.5m 3 / h、2m 3 / h, 2.5m 3 / h、3m 3 / h, 3.5m 3 / h、4m 3 / h、5m 3 / h. If the spray flow rate is too low and the discharge speed is too slow, the prepared slurry will settle before it is sprayed out, which may result in different solid content in the sprayed material and poor coating effect. If the spray flow rate is too high and the discharge speed is too fast, the two materials will not come into complete contact, and if the temperature is not well matched, there is even a risk of not drying.

[0061] In some embodiments, the airflow rate of the drying device is 100-300 m³ / h. 3 / h. The preferred airflow rate is 100m³ / h. 3 / h, 150m 3 / h、200m 3 / h, 250m 3 / h, 300m 3 / h. Too low an air velocity will cause uneven contact of the material and incomplete reaction; too high an air velocity will cause the material to come into contact too quickly and be blown away before it has time to react, which will also result in incomplete reaction.

[0062] The present invention will be further described below with reference to specific embodiments.

[0063] Example 1

[0064] A method for improving the air stability of sulfide solid electrolytes includes the following steps:

[0065] A slurry with a solid sulfide electrolyte (LPSC) and a solvent (xylene) was prepared, with a solid content of 20%.

[0066] Thiol (hexamethylene mercaptan) and solvent (xylene) are mixed to form slurry II with a solid content of 20%;

[0067] Slurry 1 and slurry 2 are simultaneously sprayed into the center of a mixing device equipped with a drying device 3 and dried under the drying device 3 to improve the air stability of the sulfide solid electrolyte.

[0068] As shown in Figure 2, the mixing device includes a reactor 1, two sprayers 2, and a drying device 3. The sprayers 2 are located on the top of the reactor 1 on both sides and are connected to the reactor 1. The drying device 3 is located on the top of the reactor 1 and blows air downwards. The direction of the gas sprayed by the sprayers 2 is inclined towards the center of the reactor 1.

[0069] The temperature of reactor 1 is 120°C.

[0070] The bottom of the reactor 1 is provided with a material bin 4 for collecting materials.

[0071] The sulfide solid electrolyte has a particle size of 500 nm.

[0072] The spray velocity of slurry one and slurry two is 2.5m. 3 / h.

[0073] The airflow rate of the air drying device is 200 m³ / h. 3 / h.

[0074] Example 2

[0075] The difference between Example 2 and Example 1 is that the temperature of reactor 1 is 100°C.

[0076] Example 3

[0077] The difference between Example 3 and Example 1 is that the temperature of reactor 1 is 140°C.

[0078] Example 4

[0079] The difference between Example 4 and Example 1 is that the temperature of reactor 1 is 160°C.

[0080] Performance testing

[0081] 1. Before treatment, the charging capacity, discharging capacity and first-efficiency test of Example 1.

[0082] The sulfide solid electrolyte (LPSC) sample that has not undergone the performance improvement of the embodiments of the present invention is referred to as before LPSC treatment.

[0083] Powder tableting: First, the untreated sulfide solid electrolyte and the sulfide solid electrolyte treated in Example 1 are respectively tableted to form tablets before LPSC treatment and tablets of Example 1. During tableting, the tablets are cold-pressed at 400 MPa to a thickness of about 0.5 mm and a diameter of 10 mm to ensure density (porosity ≤ 5%). The tablets must be pressed with uniform force to avoid breakage or dents, which would affect the test results. Then, the 811 cathode material (811 cathode material refers to the high-nickel ternary material in nickel-cobalt-manganese ternary lithium-ion batteries with a chemical ratio of nickel (Ni):cobalt (Co):manganese (Mn) = 8:1:1, and the chemical formula is LiNi) is tested separately. 0.8 Co 0.1 Mn 0.1 Both O2 and graphite anode materials are subjected to a pressure of 300 MPa to form 811 cathode material sheets and graphite anode material sheets;

[0084] Batteries 1 (before treatment) and 2 (after treatment) were synthesized by pressing 811 positive electrode material sheets + pre-LPSC treated sheets + graphite negative electrode material sheets, and combining 811 positive electrode material sheets + sheets from Example 1 + graphite negative electrode material sheets with a pressure of 4 MPa. These batteries were then placed in a battery cabinet for testing. The test procedure was a uniform 0.1C constant current charge-discharge. Figure 3 shows the specific capacity and voltage relationship of battery 1 (before treatment), and Figure 4 shows the specific capacity and voltage relationship of battery 2 (after treatment). Table 1 shows the charging capacity, discharging capacity, and first-efficiency test results of battery 1 (before treatment) and battery 2 (after treatment). From Figures 3 and 4 and Table 1, it can be seen that the method of this embodiment does not significantly affect the charging, discharging, and first-efficiency of the sulfide solid electrolyte itself. The charging capacity, discharging capacity, and first-efficiency test results obtained in other embodiments are similar to those of Example 1, indicating that the method of this invention does not significantly affect the charging, discharging, and first-efficiency of the sulfide solid electrolyte itself.

[0085] Table 1. Charging capacity, discharging capacity, and first-efficiency test results of Battery 1 (before treatment) and Battery 2 (after treatment).

[0086] 2. Air stability test

[0087] The powders before LPSC treatment (control group) and after LPSC treatment in Examples 1-4 were divided into multiple portions and placed in an air stability test chamber with a humidity of 5%. The corresponding powders were taken out at different time points (1h, 2h, 3h, 4h, 8h, 18h, 24h) to test the ionic conductivity.

[0088] The specific testing method is as follows:

[0089] Sample preparation

[0090] The control group and the LPSC-treated powders from Examples 1-4 at different time points were cold-pressed into sheets at a pressure of 400 MPa, with a thickness of approximately 0.5 mm and a diameter of 10 mm. The thickness of the resulting sulfide solid electrolyte sheets was then measured using a micrometer.

[0091] Electrochemical impedance spectroscopy (EIS)

[0092] The sample is held in place using a blocking electrode (stainless steel, or sputtered metal film) and an AC voltage is applied (amplitude 10mV, frequency range 1MHz to 0.1Hz).

[0093] The bulk resistance R is obtained by fitting the semicircular intercept in the high-frequency region using EIS. bulk The low-frequency region reflects the interfacial resistance and the double-layer effect.

[0094] Geometric parameter measurement

[0095] Thickness (L): The thickness of the compressed tablet is measured directly using a micrometer;

[0096] Area (A): Calculated based on the electrode diameter;

[0097] The ionic conductivity of the corresponding material was calculated according to formula (1), and the results are shown in Table 2. As can be seen from Table 2, the control group (before LPSC treatment) that was not treated by Examples 1-4 of the present invention was almost insulated after 18 hours. Compared with the control group (before LPSC treatment), the initial ionic conductivity of the material treated by Examples 1-4 of the present invention decreased. However, as the exposure time in air increased, the LPSC of Examples 1-4 of the present invention still had an order of magnitude advantage in ionic conductivity. In fact, Example 1 still maintained an ionic conductivity of 1.885 mS / cm after 24 hours. It can be seen that the method of the present invention can improve the air stability of sulfide solid electrolytes.

[0098] Table 2. Conductivity of each embodiment and control group at different time points under air stability.

[0099] In summary, the method for improving the air stability of sulfide solid electrolytes provided by this invention can enhance the air stability of sulfide solid electrolytes and has significant implications for their commercialization.

[0100] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A method for improving the air stability of sulfide solid electrolytes, characterized in that, Includes the following steps: The sulfide solid electrolyte is mixed with a solvent to form a slurry. Thiol is mixed with solvent to form slurry two; Slurry 1 and slurry 2 are sprayed simultaneously into the same spot of the mixing device equipped with the air drying device (3), and dried under the air drying device (3) to improve the air stability of the sulfide solid electrolyte.

2. The method according to claim 1, characterized in that, The mixing device includes a reactor (1), two sprayers (2), and a drying device (3). The sprayers (2) are located on the top of the reactor (1) on both sides and are connected to the reactor (1). The drying device (3) is located on the top of the reactor (1) and blows air downwards. The direction of the gas sprayed by the sprayers (2) is inclined towards the center of the reactor (1).

3. The method according to claim 2, characterized in that, The temperature of the reactor (1) is 100-200℃.

4. The method according to claim 2, characterized in that, The bottom of the reactor (1) is provided with a material bin (4) for collecting materials.

5. The method according to claim 1, characterized in that, The solvent is an aromatic hydrocarbon solvent or an ester solvent.

6. The method according to claim 1, characterized in that, The solid content of slurry one is 10-40%; the solid content of slurry two is 10-40%.

7. The method according to claim 1, characterized in that, The particle size of the sulfide solid electrolyte is 400 nm to 10 μm.

8. The method according to claim 1, characterized in that, The thiol is any one of hexamethylenetetramine, octanethiol, sec-butanethiol, cyclohexanethiol, n-octadecylthiol, and ethylthiol.

9. The method according to claim 1, characterized in that, The spray velocity of slurry one and slurry two is 1-5m. 3 / h.

10. The method according to claim 1, characterized in that, The airflow rate of the air-drying device (3) is set to 100-300 m³ / h. 3 / h.

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