Solid electrolyte and preparation method and application thereof

Abstract

The invention discloses a solid-state electrolyte and a preparation method and application thereof, and relates to the technical field of solid-state batteries, and the solid-state electrolyte is obtained by doping an argyrodite electrolyte with fluorine and selenium. According to the solid electrolyte disclosed by the invention, fluorine and selenium are doped on the interface between the stable electrolyte and the positive and negative electrodes, and meanwhile, the ionic conductivity of the electrolyte is improved, so that the electrochemical performance of an all-solid-state electrolyte battery is improved.

Description

Technical Field

[0001] This application relates to the field of solid-state battery technology, and in particular to a solid electrolyte, its preparation method and application. Background Technology

[0002] Sulfide solid-state electrolytes are considered the most promising solid-state electrolyte development system due to their ultra-high ionic conductivity and good processing performance. Among them, the Li6PS5Cl (LPSCl) type silver-germanium sulfide electrolyte, represented by the Li2S-P2S5-LiCl system, is particularly outstanding. LPSCl electrolytes have the advantages of low raw material cost and high abundance of constituent elements, theoretically laying the foundation for their large-scale application. However, in practical applications, LPSCl electrolytes suffer from poor chemical stability, affecting the performance of solid-state batteries. Therefore, there is an urgent need for a silver-germanium sulfide electrolyte with high chemical stability. Summary of the Invention

[0003] The main purpose of this application is to propose a solid electrolyte, its preparation method and application, in order to address the problem of poor electrochemical stability of existing silver-germanium sulfide electrolytes.

[0004] To achieve the above objectives, the solid electrolyte proposed in this application includes silver-germanium sulfide ore, which is obtained by doping the silver-germanium sulfide ore electrolyte with fluorine and selenium.

[0005] Preferably, the dopant is a compound containing fluorine and selenium.

[0006] Preferably, the fluorine-containing compound is LiF, and the fluorine-containing compound is Li2Se.

[0007] Preferably, the solid electrolyte has the general chemical formula Li6PS. 5-x Se x Cl 1-y F y , where 0 < x < 5; 0 < x < 1.

[0008] This application also proposes a method for preparing the solid electrolyte proposed in this application, comprising: A mixture is obtained by mixing L2S, P2S5, LiCl, fluorine-containing compounds, and selenium-containing compounds in a predetermined molar ratio. The mixture is ball-milled and then compressed into tablets. The mixture after tableting is sintered to obtain a solid electrolyte.

[0009] Preferably, the fluorinated compound includes at least one of LiF, Al3F, and NH4F; The selenium-containing compound includes at least one of Li2Se and SeS2.

[0010] Preferably, the preset molar ratio is L2S:P2S5:LiCl:fluorine-containing compound:selenium-containing compound = 49:10:19:1:1~2:2:23:5:8.

[0011] Preferably, the ball-to-material ratio in the ball milling process is 25:1 to 15:1; The atmosphere for the ball milling process includes at least one of argon and nitrogen. The ball milling process is performed at a speed of 400-700 rpm for 18-36 hours.

[0012] Preferably, the sintering temperature is 400~700℃, the heating rate is 0.5~1℃ / min, and the holding time is 3~7 h.

[0013] This application also proposes an application of the solid electrolyte proposed in this application in the preparation of solid-state batteries.

[0014] Preferably, the solid-state battery is a coin cell solid-state symmetric battery or an all-solid-state battery.

[0015] Preferably, the all-solid-state battery includes a coin cell all-solid-state battery.

[0016] The solid-state electrolyte of this application is a traditional silver-germanium sulfide electrolyte doped with fluorine and selenium. This allows for microscopic control of the LPSCl crystal configuration. Fluorine doping mitigates side reactions between the solid-state electrolyte and the interface, improving the electrochemical stability of the solid-state electrolyte. Selenium, due to its similar ionic radius to sulfur, accelerates ion transport within the solid-state electrolyte, enhancing its conductivity. By simultaneously stabilizing the electrolyte-anode interface and improving the ionic conductivity of the electrolyte, the electrochemical performance of the all-solid-state electrolyte battery is enhanced. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0018] Figure 1 Electrochemical impedance side view of the coin cell solid-state symmetric battery prepared in Example 4 of this application; Figure 2 A side view of the electrochemical impedance of the coin-type solid-state symmetric cell prepared in Comparative Example 2 provided in this application; Figure 3Side view of the ionic conductivity of the coin-type solid-state symmetric cells prepared in Example 4 and Comparative Example 2 provided for this application; Figure 4 Battery cycle test diagram of the coin-type solid-state symmetric battery prepared in Example 4 of this application; Figure 5 Battery cycle test diagram of the coin-type solid-state symmetric battery prepared for Comparative Example 2 provided in this application; Figure 6 Long-cycle stability test graphs of the coin cells prepared in Example 5 and Comparative Example 3 provided in this application.

[0019] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0020] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0021] It should be noted that if the embodiments of this application involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a specific posture. If the specific posture changes, the directional indicators will also change accordingly.

[0022] Furthermore, if the embodiments of this application involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the use of "and / or" or "and / or" throughout the text includes three parallel solutions. For example, "A and / or B" includes solution A, solution B, or a solution that simultaneously satisfies A and B. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed in this application.

[0023] With the ever-increasing demand for energy, lithium-ion battery technology has become a top priority in the development of modern energy storage equipment. Traditional organic liquid electrolytes pose significant safety risks, exhibiting flammable and explosive properties and a risk of thermal runaway. When the battery temperature rises rapidly, the electrolyte decomposes quickly, releasing flammable gases and potentially causing combustion or even an explosion. Statistics show that approximately 80% of electric vehicle battery safety incidents worldwide are related to electrolyte leakage or thermal runaway. Furthermore, the interfacial reaction between the lithium metal anode and the liquid electrolyte in organic liquid electrolytes leads to dendrite growth, which not only reduces battery cycle life but may also puncture the separator, causing a short circuit and posing a safety hazard. Therefore, these factors necessitate further development of lithium battery technology.

[0024] In this context, all-solid-state lithium metal batteries (ASSLMB) have rapidly become the most promising lithium battery technology due to their high safety and high energy density. Solid-state batteries use solid electrolytes to replace traditional liquid electrolytes and separators, significantly improving the overall performance and safety of the battery. As a key material in solid-state batteries, the performance of the solid electrolyte plays a decisive role. Based on different properties, solid electrolytes are classified into polymer solid electrolytes, oxide solid electrolyte systems, sulfide solid electrolytes, and halide solid electrolytes. Sulfide solid electrolytes are considered the most promising solid electrolyte development system due to their ultra-high ionic conductivity and good processing performance. Among them, the Li6PS5Cl (LPSCl) type silver-germanium sulfide electrolyte, represented by the Li2S-P2S5-LiCl system, is particularly outstanding.

[0025] LPSCl electrolytes possess advantages such as low raw material cost and high abundance of constituent elements, theoretically laying the foundation for their large-scale application. However, in practical applications, LPSCl has revealed several problems that urgently need to be addressed: poor chemical stability; when directly matched with a strongly reducing lithium anode, it easily undergoes a reduction reaction, generating byproducts such as Li3P, Li2S, and LiCl. These byproducts accumulate continuously at the battery interface, significantly increasing interfacial impedance, leading to increased energy loss during battery charging and discharging, and a rapid decline in overall battery performance. Simultaneously, during battery charge-discharge cycles, electrons tend to accumulate at LPSCl grain boundaries, making the dissolution and deposition of lithium metal at these boundaries more frequent. This uneven lithium deposition phenomenon easily induces the growth and propagation of lithium dendrites within the electrolyte. With increasing cycle count, lithium dendrites may penetrate the electrolyte, causing internal short circuits, seriously threatening battery safety and lifespan, and greatly limiting the application and promotion of LPSCl in ASSLMB.

[0026] To address the aforementioned issues with LPSCl, researchers have conducted extensive studies. Currently, strategies for improving the lithium stability of LPSCl mainly fall into two categories. The first is through composite structure design, combining LPSCl with materials possessing specific properties to improve the bulk performance of LPSCl at a macroscopic level. However, this method often introduces complex fabrication processes and interface issues, increasing battery manufacturing costs and the difficulty of performance control. The second method is elemental doping, which controls the crystal structure of LPSCl from a microscopic perspective; this method has received widespread attention. Previous research in liquid batteries has found that fluorinated lithium salts in the electrolyte can react with lithium metal to form a LiF-containing solid electrolyte interphase (SEI) film. LiF can promote the stability of the SEI film and the interface, inhibit lithium dendrite growth, and improve the electrolyte's stability for lithium. However, directly doping solid electrolytes with fluorine (F) leads to a decrease in the bulk ionic conductivity of the electrolyte, affecting the battery's electrochemical performance.

[0027] Based on this, this application proposes a solid electrolyte, which is obtained by doping silver-germanium sulfide solid electrolyte with fluorine and selenium. The general chemical formula of the silver-germanium sulfide solid electrolyte is Li. 7-x AB 6-x D x Where A includes at least one of P, Ge, and Sn, B includes S and / or Se, D includes at least one of F, Cl, and Br, and 0 < x < 5.

[0028] By doping traditional silver-germanium sulfide electrolytes with fluorine and selenium, the crystal structure of LPSCl can be controlled from a microscopic perspective. Fluorine doping can slow down side reactions between the solid electrolyte and the interface, thereby improving the electrochemical stability of the solid electrolyte. Selenium, due to its similar ionic radius to sulfur, can accelerate ion transport in the solid electrolyte and improve its conductivity.

[0029] In some embodiments, the dopant is a compound containing fluorine and selenium. Preferably, the fluorine-containing compound is LiF, and the fluorine-containing compound is Li₂Se.

[0030] In some embodiments, the general chemical formula of the solid electrolyte is Li6PS. 5-x Se x Cl 1-y F y , where 0 < x < 5; 0 < y < 1.

[0031] This application also proposes a method for preparing a solid electrolyte as described above, comprising the following steps: S1. Mix L2S, P2S5, LiCl, fluorine-containing compounds, and selenium-containing compounds in a predetermined molar ratio to obtain a mixture.

[0032] In some embodiments, the fluorinated compound includes at least one of LiF; the selenium-containing compound includes at least one of Li2Se.

[0033] In some implementations, the preset molar ratio is L2S:P2S5:LiCl:fluorinated compound:selenium compound = 49:10:19:1:1~2:2:23:5:8. For example, the molar ratio of L2S:P2S5:LiCl:fluorinated compound:selenium compound can be 49:10:19:1:1, 25:6:21:3:4, 7:3:20:2:5, or 2:2:23:5:8, etc.

[0034] S2. The mixture is ball-milled and then compressed into tablets.

[0035] The ball milling process may include placing the mixture in a zirconia jar containing zirconia balls and milling it on a planetary ball mill. The diameter of the zirconia balls is 8-12 mm. Zirconia is chemically inert, and using zirconia balls and a zirconia jar for ball milling ensures that no impurities are introduced during the process. Since the ball milling produces a loose powder mixture with numerous voids between particles, compaction can be used to compress the powder into a dense sheet-like blank. This tightly binds the reactant particles (Li₂S, P₂S₅, LiCl, etc.) together, increasing the contact points between the particles. Consequently, during subsequent sintering, this shortens the diffusion path of ions, resulting in a more complete, faster, and more uniform reaction.

[0036] In some embodiments, the ball-to-material ratio in the ball milling process is 20:1. For example, the ball-to-material ratio in the ball milling process is 25:1 to 15:1. For example, the ball-to-material ratio in the ball milling process can be 25:1, 20:1, or 15:1, etc. The atmosphere for the ball milling process includes at least one of argon and nitrogen. The ball milling speed is 400 to 700 rpm, and the time is 18 to 36 h. For example, the ball milling speed can be 400 rpm, 450 rpm, 500 rpm, 550 rpm, 600 rpm, 650 rpm, or 700 rpm, etc. The time can be 18 h, 24 h, 30 h, or 36 h, etc.

[0037] S3. The mixture after tableting is sintered to obtain a solid electrolyte.

[0038] The sintering process can be as follows: the mixture after tableting is sealed in a quartz tube, and the quartz tube is transferred to a muffle furnace for sintering.

[0039] In some embodiments, the sintering temperature is 400~700℃, the heating rate is 0.5~1℃ / min, and the holding time is 3~7 h. For example, the sintering temperature can be 400℃, 450℃, 500℃, 550℃, 600℃, 650℃, or 700℃, etc. The heating rate can be 0.5℃ / min, 0.6℃ / min, 0.7℃ / min, 0.8℃ / min, 0.9℃ / min, or 1℃ / min, etc. The holding time can be 3 h, 4 h, 5 h, 6 h, or 7 h, etc.

[0040] In some embodiments, the method for preparing solid electrolytes further includes the step of: S4. Grind the sintered mixture.

[0041] Grinding can transform the solid electrolyte obtained by sintering from a block or cake into a powder, which facilitates the characterization and confirmation of the product and subsequent battery assembly.

[0042] This application also proposes the application of a solid electrolyte in the preparation of solid-state batteries.

[0043] In some implementations, the solid-state battery is a coin cell solid-state symmetric battery or an all-solid-state battery.

[0044] Preferably, the all-solid-state battery includes a coin cell all-solid-state battery.

[0045] The following specific examples provide further details.

[0046] Example 1 This embodiment provides a method for preparing a solid electrolyte made from silver-germanium sulfide, comprising the following steps: In an argon-filled glove box, Li₂S, Li₂Se, P₂S₅, LiCl, and LiF were weighed out in a molar ratio (4:1:1:1.4:0.6) and added to an agate mortar. The mixture was ground for 30 minutes to ensure homogeneity. The mixed material was then transferred to a zirconia ball mill jar (ball-to-material ratio of 20:1) and ball-milled at 550 rpm for 18 hours under argon protection. The ball-milled mixture was pressed into sheets in the glove box, transferred to a quartz tube, and then flame-sealed. The sealed quartz tube was then transferred to a muffle furnace and heated to 550°C at a rate of 0.5°C / min, held at that temperature for 5 hours, and allowed to cool naturally to room temperature. The quartz tube was then opened in the glove box, and the calcined material was removed and ground finely in an agate mortar for 30 minutes to obtain the solid electrolyte LPSSeClF.

[0047] Example 2 This embodiment provides a method for preparing a solid electrolyte made from silver-germanium sulfide, comprising the following steps: In an argon-filled glove box, Li₂S, Li₂Se, P₂S₅, LiCl, and LiF were weighed out in a molar ratio (49:10:19:1:1) and added to an agate mortar. The mixture was ground for 30 minutes to ensure homogeneity. The mixed material was then transferred to a zirconia ball mill jar (ball-to-material ratio of 25:1) and ball-milled at 400 rpm for 18 hours under argon protection. The ball-milled mixture was pressed into sheets in the glove box, transferred to a quartz tube, and then flame-sealed. The sealed quartz tube was then transferred to a muffle furnace and heated to 700°C at a rate of 1°C / min, held at that temperature for 3 hours, and allowed to cool naturally to room temperature. The quartz tube was then opened in the glove box, and the calcined material was removed and ground finely in an agate mortar for 30 minutes to obtain the solid electrolyte LPSSeClF.

[0048] Example 3 This embodiment provides a method for preparing a solid electrolyte made from silver-germanium sulfide, comprising the following steps: In an argon-filled glove box, Li₂S, Li₂Se, P₂S₅, LiCl, and LiF were weighed out in a molar ratio (2:2:23:5:8) and added to an agate mortar. The mixture was ground for 30 minutes to ensure homogeneity. The mixed material was then transferred to a zirconia ball mill jar (ball-to-material ratio of 15:1) and ball-milled at 700 rpm for 36 hours under argon protection. The ball-milled mixture was pressed into sheets in the glove box, transferred to a quartz tube, and then flame-sealed. The sealed quartz tube was then transferred to a muffle furnace and heated to 400°C at a rate of 0.7°C / min, held at that temperature for 7 hours, and allowed to cool naturally to room temperature. The quartz tube was then opened in the glove box, and the calcined material was removed and ground finely in an agate mortar for 30 minutes to obtain the solid electrolyte LPSSeClF.

[0049] Example 4 Using LPSSeClF obtained in Example 1 as a solid electrolyte and lithium metal as the negative electrode, a coin cell solid-state symmetric battery was assembled using conventional processes.

[0050] Example 5 Using LPSSeClF obtained in Example 1 as a solid electrolyte, lithium metal as a negative electrode, and lithium cobalt oxide as a positive electrode, a coin cell all-solid-state battery was assembled using conventional processes.

[0051] Comparative Example 1 This embodiment provides a method for preparing a solid electrolyte made from silver-germanium sulfide, comprising the following steps: In an argon-filled glove box, Li₂S, P₂S₅, and LiCl were weighed in a molar ratio (5:1:2) and added to an agate mortar. The mixture was ground for 30 minutes to ensure homogeneity. The mixed material was then transferred to a zirconia ball mill jar (ball-to-material ratio 20:1) and ball-milled at 550 rpm for 18 hours under argon protection. The ball-milled mixture was pressed into sheets in the glove box, transferred to a quartz tube, and then flame-sealed. The sealed quartz tube was then transferred to a muffle furnace and heated to 550°C at a rate of 0.5°C / min, held at that temperature for 5 hours, and allowed to cool naturally to room temperature. The quartz tube was then opened in the glove box, and the calcined material was removed and ground finely in an agate mortar for 30 minutes to obtain LPSCl.

[0052] Comparative Example 2 Using LPSCl prepared in Comparative Example 1 as a solid electrolyte and lithium metal as the negative electrode, a coin cell solid-state symmetric battery was assembled using conventional processes.

[0053] Comparative Example 3 Using LPSCl prepared in Comparative Example 1 as a solid electrolyte, lithium metal as the negative electrode, and lithium cobalt oxide as the positive electrode, a coin cell all-solid-state battery was assembled using conventional processes.

[0054] Electrochemical impedance spectroscopy was performed on the coin-type solid-state symmetric cells prepared in Example 4 and Comparative Example 2. The results are as follows: Figure 1 and Figure 2 As shown. From Figure 1 and Figure 2 As can be seen, the coin-type solid-state symmetric cell prepared in Comparative Example 2 has a slightly higher impedance, thus indicating that the solid electrolyte LPSSeClF prepared in Example 1 of this application has the effect of reducing the impedance of the solid-state cell. Based on the measured impedance, the ionic conductivity of the coin-type solid-state symmetric cells prepared in Example 4 and Comparative Example 2 was calculated, and the results are as follows: Figure 3 As shown. From Figure 3 As can be seen from the above, the coin-type solid-state symmetric battery prepared in Example 4 has a higher ionic conductivity, which shows that the solid electrolyte LPSSeClF prepared in Example 1 of this application can effectively improve the ionic conductivity of the solid-state battery.

[0055] Furthermore, the coin-type solid-state symmetric cells prepared in Example 4 and Comparative Example 2 were compared at 0.2 mAh·cm⁻¹. -1 Battery cycle testing was conducted at a current density, and the results are as follows: Figure 4 and Figure 5 As shown. From Figure 4 and Figure 5 As can be seen from the data, the coin-type solid-state symmetric battery prepared in Comparative Example 2 has poor cycle stability and a larger polarization voltage.

[0056] The coin-type all-solid-state batteries prepared in Example 5 and Comparative Example 3 were subjected to long-term cycling stability tests at a rate of 0.2C. The results are as follows: Figure 6 As shown. From Figure 6 As can be seen, the coin cell all-solid-state battery prepared in Example 5 has more stable cycling, which shows that the LPSSeClF solid-state electrolyte has higher chemical stability compared with the LPSCl solid-state electrolyte.

[0057] In summary, the solid-state battery prepared using the fluorine- and selenium-doped silver-germanium ore solid-state electrolyte provided in this application exhibits lower battery impedance, higher ionic conductivity, and more stable cycle performance compared to solid-state batteries prepared using traditional LPSCl solid-state electrolytes. This demonstrates that the fluorine- and selenium-doped silver-germanium ore solid-state electrolyte provided in this application improves the ionic conductivity of the electrolyte while stabilizing the interface between the electrolyte and the positive and negative electrodes, thereby enhancing the electrochemical performance of the all-solid-state electrolyte battery.

[0058] The above description is merely an exemplary embodiment of this application and does not limit the patent scope of this application. Any equivalent structural transformations made based on the technical concept of this application and the contents of the specification and drawings of this application, or direct / indirect applications in other related technical fields, are included within the patent protection scope of this application.

Claims

1. A solid electrolyte comprising argentite, characterized in that, The solid electrolyte is obtained by doping silver-germanium ore electrolyte with fluorine and selenium.

2. The solid electrolyte as described in claim 1, characterized in that, The solid electrolyte includes a dopant, which is a compound containing F and Se; Preferably, the F-containing compound is LiF, and the Se-containing compound is Li2Se.

3. The solid electrolyte as described in claim 1, characterized in that, The general chemical formula of the silver-germanium sulfide electrolyte is [chemical formula not provided in the original text]. The general chemical formula of the solid electrolyte is Li6PS. 5-x Se x Cl 1-y F y , where 0 < x < 5; 0 < x < 1.

4. A method for preparing a solid electrolyte according to any one of claims 1 to 3, characterized in that, include: A mixture is obtained by mixing L2S, P2S5, LiCl, fluorine-containing compounds, and selenium-containing compounds in a predetermined molar ratio. The mixture is ball-milled and then compressed into tablets. The mixture after tableting is sintered to obtain a solid electrolyte.

5. The method for preparing a solid electrolyte as described in claim 4, characterized in that, The fluorine-containing compound includes at least one of LiF, Al3F, and NH4F; The selenium-containing compound includes at least one of Li2Se and SeS2.

6. The method for preparing a solid electrolyte as described in claim 4, characterized in that, The preset molar ratio is L2S:P2S5:LiCl:fluorine-containing compound:selenium-containing compound = 49:10:19:1:1~2:2:23:5:

8.

7. The method for preparing a solid electrolyte as described in claim 4, characterized in that, The ball-to-material ratio in the ball milling process is 25:1 to 15:

1. The atmosphere for the ball milling process includes at least one of argon and nitrogen. The ball milling process is performed at a speed of 400-700 rpm for 18-36 hours.

8. The method for preparing a solid electrolyte as described in claim 4, characterized in that, The sintering treatment is performed at a temperature of 400~700℃, a heating rate of 0.5~1℃ / min, and a holding time of 3~7 h.

9. The use of the solid electrolyte according to any one of claims 1 to 3 in the preparation of solid-state batteries.

10. The application as described in claim 9, characterized in that, The solid-state battery is a coin cell solid-state symmetric battery or an all-solid-state battery; Preferably, the all-solid-state battery includes a coin cell all-solid-state battery.

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