Method for improving air stability and ionic conductivity of sulfide solid electrolyte

Abstract

The invention discloses a method for improving air stability and ionic conductivity of a sulfide solid electrolyte, which comprises the following steps: grinding a doped raw material and a solid electrolyte raw material in a mortar until powder is uniformly mixed to obtain mixed powder; the ground mixed powder is subjected to ball milling through a high-energy ball mill, and ball-milled powder is obtained; pressing the ball-milled powder into a blocky precursor by using a tablet press; and carrying out crystallization sintering on the pressed blocky precursor in an inert atmosphere, and grinding the sintered material into fine powder to obtain the solid electrolyte. According to the double-doped sulfide solid electrolyte, the ionic conductivity is remarkably improved on the basis of an original system, the preparation process is simple, the preparation raw materials are easy to obtain, the result repeatability is high, the material loss ratio is small, and the reaction is mild and easy to control. According to the double-doped sulfide solid electrolyte, the air stability is remarkably enhanced on the basis of an original system, the requirements of electrolyte production for low water and oxygen in the environment are reduced, the production cost is reduced, and the double-doped sulfide solid electrolyte is suitable for commercialized mass production.

Description

Technical Field

[0001] This invention relates to the field of solid-state batteries, and more specifically to a method for improving the air stability and ionic conductivity of sulfide solid electrolytes. Background Technology

[0002] Commercially available liquid lithium-ion batteries have achieved large-scale application in various aspects of our lives. However, with technological advancements and increasing demands in daily life, their development has encountered bottlenecks, including unresolved safety issues and the limitation of energy density reaching its theoretical limit. Of particular note is the fact that the use of organic electrolytes makes lithium-ion batteries susceptible to leakage, spontaneous combustion, and even explosions when subjected to impacts or pressure. Short circuits and overcharging are also present. Furthermore, the energy density of existing lithium-ion batteries has reached its theoretical limit, failing to meet the high-energy battery demands of daily life and travel.

[0003] All-solid-state batteries utilize non-flammable inorganic solid electrolytes, exhibiting excellent safety performance, high energy density, and broad application prospects. Among various solid electrolytes, sulfide electrolytes are considered the most suitable for large-scale energy storage devices due to their ultra-high ionic conductivity, with conductivity comparable to liquid electrolytes. Furthermore, the relatively soft nature of these materials allows for the achievement of a tight solid-solid contact interface through cold pressing during the assembly of all-solid-state batteries. These characteristics give sulfide electrolytes broad development prospects. Despite significant progress in sulfide electrolyte research, several issues still hinder their large-scale application. The primary problem lies in the poor air stability of sulfide electrolytes. (The text abruptly shifts to a seemingly unrelated topic about PS4 in sulfide electrolytes.) 3- P of the group 5+ It has a high affinity for O, S 2- It has a high affinity for hydrogen (H), making it readily react with H₂O in moist air to produce toxic H₂S gas. Furthermore, sulfide electrolytes reacting with H₂O are prone to structural damage and decreased ionic conductivity. Therefore, developing sulfide electrolytes with high air stability is crucial.

[0004] Element substitution is often used to solve the problem of air stability of sulfide electrolytes. According to the hard-soft acid-base theory, soft acids have a higher affinity for soft bases, while hard acids show a stronger tendency to bind to hard bases. 5+ It is a strong acid and reacts more readily with strong bases in the air, such as O₂. 2- The combination forms a PO bond, thereby breaking the PS bond, and the displaced weak base S 2- Tends to react with weak acid H + This combination generates H2S gas. Therefore, the soft acid Bi3+ can be used to partially replace the strong acid P. 5+A lithium-silver ore-based solid electrolyte with higher air stability was designed by utilizing the property that soft acids tend to combine with soft bases (S) rather than hard bases (O). Simultaneously, the introduction of bromide ions can induce S… 2- / Br - The disordered arrangement of Bi increases ionic conductivity. More importantly, the large ionic radius of Bi... 3+ ,Br - The introduction of [a specific ingredient] increases the cell volume, thereby promoting lithium-ion transport. This invention effectively improves the stability of sulfide solid electrolytes to water and oxygen, while enhancing their lithium-ion conductivity, providing a practical technical path and reference for the commercial application of this type of material. Summary of the Invention

[0005] To address the aforementioned problems, this invention aims to provide a method for improving the air stability and ionic conductivity of sulfide solid electrolytes.

[0006] To achieve this technical objective, the present invention provides a method for improving the air stability and ionic conductivity of sulfide solid electrolytes, the specific steps of which are as follows:

[0007] S1. Grind the doping material and the solid electrolyte material in a mortar according to the proportion until the powder is evenly mixed to obtain a mixed powder.

[0008] S2. Place the ground mixed powder and zirconia balls into a zirconia sealed ball mill jar; use a high-energy ball mill to ball mill the mixed powder; after ball milling, separate the ball and material to obtain ball-milled powder.

[0009] S3. Use a tablet press to compress the ball-milled powder described in step S2 into a block precursor;

[0010] S4. The pressed block precursor is crystallized and sintered under an inert atmosphere to obtain the sintered product.

[0011] S5. Grind the sintered material after sintering into fine powder to obtain powdered solid electrolyte.

[0012] Preferably, the solid electrolyte raw material is a raw material powder used to prepare a sulfide solid electrolyte, and the sulfide solid electrolyte is Li. 10 GeP2S 12 Li3PS4, Li 6+x PS 5+x H 1-x One of them; Li 6+x PS 5+x H 1-x H is a halogen element, specifically one of F, Cl, Br, or I.

[0013] Preferably, the grinding time during the powder mixing process in step S1 is greater than or equal to 10 minutes.

[0014] Preferably, in step S2, the size of the zirconia balls is 10-15 mm, the ball-to-material ratio is greater than or equal to 20:1, the ball milling speed is 400-800 rpm, and the ball milling time is 10-20 h.

[0015] Preferably, during the pressing process in step S3, the pressing force of the tablet press is greater than or equal to 3 Tons, and the pressing time is greater than or equal to 5 minutes.

[0016] Preferably, in step S3, the sintering temperature is 400-600℃, the heating rate is 3℃ / min, and the sintering time is 2-10h; the inert gas in the inert atmosphere in step S3 is argon.

[0017] Preferably, in step S1, the doping material is BiBr3, wherein the molar ratio of the doping material to Bi and Li in the solid electrolyte material is 1:30-200.

[0018] The beneficial effects of this invention are that BiBr3 is used to prepare a double-doped sulfide solid electrolyte, which significantly improves the ionic conductivity compared to the original system. The preparation process is simple, the raw materials are easy to obtain, the results are highly reproducible, the material loss ratio is small, and the reaction is mild and easy to control.

[0019] The dual-doped sulfide solid electrolyte prepared in this application has significantly enhanced air stability compared to the original system, reducing the environmental requirements (low water and oxygen) for electrolyte production, lowering production costs, and making it suitable for commercial mass production. Attached Figure Description

[0020] Figure 1 Li, the present invention 5.46 P 0.96 Bi 0.04 S 4.38 C l1.5 Br 0.12 XRD pattern of electrolyte;

[0021] Figure 2 Li, the present invention 5.46 P 0.96 Bi 0.04 S 4.38 C l1.5 Br 0.12 SEM image of electrolyte;

[0022] Figure 3 Li, the present invention 5.46 P 0.96 Bi 0.04 S 4.38 C l1.5Br 0.12 Impedance diagram of electrolyte. Detailed Implementation

[0023] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0024] like Figure 1-3 As shown, the specific embodiment of the present invention is a method for improving the air stability and ionic conductivity of sulfide solid electrolytes, and the specific steps are as follows:

[0025] S1. Grind the doping material and the solid electrolyte material in a mortar according to the specified ratio until the powders are evenly mixed to obtain a mixed powder; the grinding time in the mortar should be greater than or equal to 10 minutes. The solid electrolyte material is a raw material powder used to prepare a sulfide solid electrolyte, and the sulfide solid electrolyte is Li. 10 GeP2S 12 Li3PS4, Li 6+x PS 5+x H 1-x One of them; Li 6+x PS 5+x H 1-x H represents a halogen element, specifically one of F, Cl, Br, or I. The doping material is BiBr3, with a molar ratio of Bi to Li in the solid electrolyte material of 1:30-200.

[0026] S2. Place the ground mixed powder and zirconia balls into a zirconia sealed ball mill jar; use a high-energy ball mill to ball mill the mixed powder. After ball milling, separate the ball and material to obtain ball-milled powder; the size of the zirconia balls is 10-15mm, the ball-to-material ratio is greater than or equal to 20:1, the ball milling speed is 400-800rpm, and the ball milling time is 10-20h.

[0027] S3. Use a tablet press to compress the ball-milled powder described in step S2 into a block precursor; the pressing force of the tablet press is greater than or equal to 3 Tons, and the pressing time is greater than or equal to 5 minutes.

[0028] S4. The pressed block precursor is crystallized and sintered under an inert atmosphere to obtain a sintered product. The sintering temperature is 400-600℃, the heating rate is 3℃ / min, and the sintering time is 2-10h. The inert gas in the inert atmosphere in step S3 is argon.

[0029] S5. Grind the sintered material after sintering into fine powder to obtain powdered solid electrolyte.

[0030] Example 1

[0031] Step S101: Place 1.1463g P2S5, 0.9775g Li2S, 0.6833g LiCl, and 0.1928g BiBr3 in a mortar and grind for 20 minutes to ensure thorough mixing.

[0032] Step S102: The uniformly mixed powder and 75g of zirconia balls are packaged in a sealed ball mill jar filled with argon gas.

[0033] Step S103: Use a high-energy ball mill to ball mill the mixed ball material at a speed of 500 rpm / min for 60 min. After ball milling, ball mill at a speed of 800 rpm / min for 600 min. After the ball milling is completed, separate the powder from the ball milling beads.

[0034] Step S104: The powder from step 3 is pressed into a block precursor using a tablet press under a force of 5 Tons.

[0035] Step S105: The pressed block precursor is placed in a corundum crucible and sintered in a tube furnace at 500°C for 8 hours, wherein the heating rate is 3°C / min.

[0036] Step S106: Grind the sintered mixture into powder.

[0037] All of the above work was carried out under an Ar atmosphere (H2O, O2 < 1 ppm).

[0038] The Li prepared above 5.46 P 0.96 Bi 0.04 S 4.38 Cl 1.5 Br 0.12 Solid-state electrolytes were assembled into an all-solid-state lithium-ion battery, and its electrochemical performance was measured. The assembly process was as follows: A positive electrode mixture (NCM811:solid electrolyte:VGCF = 70:27:3) was stirred until homogeneous. 20 mg of the positive electrode mixture powder was evenly sprinkled into a mold to form the positive electrode layer. Then, 120 mg of solid electrolyte was filled in. Next, a negative electrode material with an N / P ratio of 1:1.2 (graphite:solid electrolyte = 6:4) was filled into the mold. The battery was then pressed into shape under a 3.5 Tons force using a tablet press. The performance was as follows: Figure 1-3 .

[0039] This application utilizes BiBr3 and solid electrolyte raw materials to prepare a dual-doped sulfide solid electrolyte. The ionic conductivity of this dual-doped sulfide solid electrolyte is significantly improved compared to the original system. The preparation process is simple, the raw materials are readily available, the results are highly reproducible, the material loss ratio is low, and the reaction is mild and easily controlled. Simultaneously, the air stability of this dual-doped sulfide solid electrolyte is significantly enhanced compared to the original system, reducing the environmental requirements (low water, low oxygen) for electrolyte production, lowering production costs, and making it suitable for commercial mass production.

[0040] Example 2

[0041] In step S201, 1.0754g P2S5, 1.2109g Li2S, 0.4364g LiCl, and 0.2772g BiBr3 are placed in a mortar and ground for 20 minutes to ensure thorough mixing.

[0042] Step S202: The uniformly mixed powder and 75g of zirconia balls are packaged in a sealed ball mill jar filled with argon gas.

[0043] Step S203: Use a high-energy ball mill to ball mill the mixed ball material at a speed of 500 rpm / min for 60 min. After ball milling, ball mill at a speed of 800 rpm / min for 600 min. After the ball milling is completed, separate the powder from the ball milling beads.

[0044] Step S204: The powder from step 3 is compressed into a block precursor using a tablet press under a force of 5 Tons.

[0045] Step S205: The pressed block precursor is placed in a corundum crucible and sintered in a tube furnace at 500°C for 8 hours, wherein the heating rate is 3°C / min.

[0046] Step S206: Grind the sintered mixture into powder to prepare Li. 6.12 P 0.94 Bi 0.06 S 4.28 ClBr 0.18 Solid electrolyte. All the above work was carried out under an Ar atmosphere (H2O, O2 < 0.01 ppm).

[0047] Example 3

[0048] Step S301: Place 1.6615g P2S5, 1.0591g Li2S and 0.2792g BiBr3 in a mortar and grind for 20 minutes to mix them thoroughly.

[0049] Step S302: The uniformly mixed powder and 75g of zirconia balls are packaged in a sealed ball mill jar filled with argon gas.

[0050] Step S303: Use a high-energy ball mill to ball mill the mixed ball material at a speed of 500 rpm / min for 60 min. After ball milling, ball mill at a speed of 800 rpm / min for 600 min. After the ball milling is completed, separate the powder from the ball milling beads.

[0051] Step S304: The powder from step 3 is pressed into a block precursor using a tablet press under a force of 5 Tons.

[0052] Step S305: The pressed block precursor is placed in a corundum crucible and sintered in a tube furnace at 500°C for 8 hours, wherein the heating rate is 3°C / min.

[0053] Step S306: Grind the sintered mixture into powder to prepare Li. 2.96 P 0.96 Bi 0.04 S 3.88 Br 0.12 Solid electrolyte. All the above work was carried out under an Ar atmosphere (H2O, O2 < 1 ppm).

[0054] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any minor modifications, equivalent substitutions, and improvements made to the above embodiments based on the technical essence of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for improving the air stability and ionic conductivity of sulfide solid electrolytes, characterized in that, The specific steps are as follows: S1. Grind the doping material and the solid electrolyte material in a mortar according to the proportion until the powder is evenly mixed to obtain a mixed powder. S2. Place the ground mixed powder and zirconia balls into a zirconia sealed ball mill jar; use a high-energy ball mill to ball mill the mixed powder; after ball milling, separate the ball and material to obtain ball-milled powder. S3. Use a tablet press to compress the ball-milled powder described in step S2 into a block precursor; S4. The pressed block precursor is crystallized and sintered under an inert atmosphere to obtain the sintered product. S5. Grind the sintered material after sintering into fine powder to obtain a powdered dual-doped solid electrolyte.

2. The method for improving the air stability and ionic conductivity of sulfide solid electrolytes according to claim 1, characterized in that: The solid electrolyte raw material is a raw material powder used to prepare sulfide solid electrolytes, and the sulfide solid electrolyte is Li. 10 GeP2S 12 Li3PS4, Li 6+x PS 5+x H 1-x One of them; Li 6+x PS 5+x H 1-x H is a halogen element, specifically one of F, Cl, Br, or I.

3. The method for improving the air stability and ionic conductivity of sulfide solid electrolytes according to claim 1, characterized in that: In step S1, the grinding time for the powder mixed in the mortar is greater than or equal to 10 minutes.

4. The method for improving the air stability and ionic conductivity of sulfide solid electrolytes according to claim 1, characterized in that: In step S2, the size of the zirconia balls is 10-15mm, the ball-to-material ratio is greater than or equal to 20:1, the ball milling speed is 400-800rpm, and the ball milling time is 10-20h.

5. The method for improving the air stability and ionic conductivity of sulfide solid electrolytes according to claim 1, characterized in that: During the compression process in step S3, the compression force of the tablet press is greater than or equal to 3 Tons, and the compression time is greater than or equal to 5 minutes.

6. The method for improving the air stability and ionic conductivity of sulfide solid electrolytes according to claim 1, characterized in that: In step S3, the sintering temperature is 400-600℃, the heating rate is 3℃ / min, and the sintering time is 2-10h; the inert gas in the inert atmosphere in step S3 is argon.

7. The method for improving the air stability and ionic conductivity of sulfide solid electrolytes according to claim 1, characterized in that: In step S1, the doping material is BiBr3, wherein the molar ratio of the doping material to Bi and Li in the solid electrolyte material is 1:30-200.

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