Sulfide solid electrolyte membrane layer and preparation method and application thereof

Abstract

The invention provides a sulfide solid-state electrolyte membrane layer and a preparation method and application thereof, and relates to the technical field of solid-state batteries. Specifically, the method comprises the following steps: preparing a mixed solution containing a binder for the sulfide solid electrolyte, the sulfide solid electrolyte and an organic solvent, dispersing the mixed solution onto a polyfluortetraethylene plate, and carrying out hot pressing treatment after drying to obtain the sulfide solid electrolyte membrane layer. According to the preparation method, the specific binder with a self-healing effect is adopted, and the solid electrolyte membrane is prepared by a specific process, so that the sulfide solid electrolyte membrane with good binding performance, dispersing performance and mechanical strength is obtained, and the sulfide solid electrolyte membrane has a good application prospect.

Description

Technical Field

[0001] This invention relates to the field of solid-state battery technology, and more specifically, to a sulfide solid electrolyte film, its preparation method, and its application. Background Technology

[0002] Slurry casting is a mature lithium-ion battery manufacturing technology that demonstrates certain advantages in solid electrolyte membrane (SEM) preparation. This is because it is highly compatible with existing lithium-ion battery slurry coating equipment (such as slot coaters and blade coaters), allowing for large-scale production of SEMs directly on existing production lines, avoiding the cost pressures of large-scale equipment upgrades. Furthermore, slurry casting enables large-area continuous production, with a significantly lower unit area manufacturing cost compared to dry processes. Simultaneously, parameters such as membrane thickness, porosity, and ionic conductivity can be optimized and adjusted by modifying the slurry formulation (e.g., solid content, viscosity, solvent type).

[0003] However, sulfide solid electrolytes are highly reactive and can undergo nucleophilic reactions with polar solvents, which can destroy the electrolyte structure and reduce its ionic conductivity. Therefore, only a few weakly polar or non-polar solvents can be selected for their use, which further severely limits the choice of binders.

[0004] Extensive efforts have been made to develop polymer binders for sulfide solid electrolyte membranes manufactured using slurry casting; for example, rubber-based and acrylic-based binders that are soluble in nonpolar solvents and dispersible have been selected. Furthermore, achieving uniform distribution and strong adhesion of the solid electrolyte within the polymer binder matrix is ​​crucial for efficient lithium-ion conductivity pathways. However, the interaction between nonpolar binder-solvent systems containing low electronegativity groups and sulfide solid electrolyte particles is weak, leading to binder aggregation in the membrane and a significant reduction in ionic conductivity. Finally, the mechanical strength of the binder is crucial for maintaining the integrity and flexibility of the electrolyte membrane and suppressing dendrite growth, but mechanical strength-related properties have not been considered in the prior art.

[0005] In view of this, the present invention is hereby proposed. Summary of the Invention

[0006] The primary objective of this invention is to provide a method for preparing a sulfide solid electrolyte membrane, which mainly addresses the following problems: weak interaction between conventional non-polar binders and sulfide solid electrolyte particles, leading to binder aggregation in the electrolyte membrane, a significant reduction in ionic conductivity, and non-dense electrolyte membranes with insufficient mechanical properties.

[0007] A second objective of this invention is to provide a sulfide solid electrolyte membrane layer.

[0008] A third objective of this invention is to provide a solid-state battery.

[0009] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted: A method for preparing a sulfide solid electrolyte membrane includes the following steps: A mixture containing a binder for sulfide solid electrolyte, sulfide solid electrolyte, and organic solvent is prepared, and the mixture is dispersed on a polytetrafluoroethylene plate. After drying, it is subjected to hot pressing to obtain the sulfide solid electrolyte film layer.

[0010] Preferably, the adhesive comprises a polyurethane material.

[0011] Preferably, the sulfide solid electrolyte includes at least one of Li6PS5F, Li6PS5Cl, Li6PS5Br, Li6PS5I, Li3PS4, Li7P3S11, Li10GeP2S12, Li10SnP2S12, and Li9.54Si1.74P1.44S11.7C10.3.

[0012] Preferably, the organic solvent includes one or both of dibromomethane and dichloromethane.

[0013] Preferably, the concentration of the sulfide solid electrolyte in the mixture is 5 mg / mL to 20 mg / mL.

[0014] Preferably, in the mixture, the concentration of the binder for the sulfide solid electrolyte is 1.5 wt.% to 7 wt.%.

[0015] Preferably, the thickness of the sulfide solid electrolyte membrane layer is 0.05 mm to 0.25 mm.

[0016] Preferably, the hot pressing temperature is 30℃~80℃, the hot pressing pressure is 10MPa~400MPa, and the hot pressing time is 3h~48h.

[0017] A sulfide solid electrolyte membrane layer is obtained by the preparation method described above.

[0018] A solid-state battery, comprising the aforementioned sulfide solid electrolyte membrane layer.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention provides a method for preparing a sulfide solid electrolyte membrane. On one hand, the invention employs a highly elastic polar elastomer binder material, represented by polyurethane, which possesses self-healing properties. This self-healing property allows for the breaking and recombination of hydrogen bonds at relatively low temperatures, achieving a self-healing effect. In conventional wet film formation processes, solvent evaporation leads to porosity within the electrolyte membrane, resulting in low ionic conductivity and increasing the risk of short circuits due to dendrite growth in the full cell. By introducing the hot-pressing method and the self-healing binder of this invention, the porosity of the electrolyte can be reduced and its density increased under certain conditions using the self-healing function. On the other hand, the binder of this invention possesses strong mechanical strength, resulting in a more intact electrolyte membrane and inhibiting dendrite growth. When the binder of this invention is used to prepare an electrolyte membrane containing a sulfide solid electrolyte, through optimization of the preparation process, the binder can be uniformly distributed within the sulfide electrolyte membrane after hot pressing, forming a dense electrolyte membrane with excellent adhesion, dispersion, and mechanical strength. Attached Figure Description

[0020] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0021] Figure 1 The self-healing effect test diagram of Embodiment 1 of the present invention is provided; Figure 2 A schematic diagram illustrating the principle of self-healing adhesive in this invention is provided; Figure 3 Symmetrical battery cycle diagrams corresponding to Embodiment 1 and Comparative Example 1 of the present invention are provided; Figure 4 The critical current density test diagrams of the symmetrical cells corresponding to Embodiment 1 and Comparative Example 1 of the present invention are provided. Detailed Implementation

[0022] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially. In addition, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0023] The first aspect of the present invention is to provide a method for preparing a sulfide solid electrolyte membrane, which mainly includes the following steps: preparing a mixture containing a binder for sulfide solid electrolyte, sulfide solid electrolyte, and organic solvent; dispersing the mixture onto a polytetrafluoroethylene plate; and performing hot pressing after drying to obtain the sulfide solid electrolyte membrane.

[0024] In a preferred embodiment, the binder for the sulfide solid electrolyte includes a polyurethane material; the polyurethane material is obtained by addition polymerization of an organic diisocyanate or polyisocyanate with a dihydroxy or polyhydroxy compound, and optionally includes functional groups such as ethers, esters, ureas, biurets, and urethane esters in addition to urethane esters.

[0025] In a more preferred embodiment, the polyurethane material has a melting point of 160°C to 180°C and a glass transition temperature of -40°C to -60°C.

[0026] In a more preferred embodiment, the elasticity of the polyurethane material is 0.04 GPa to 0.06 GPa.

[0027] In a more preferred embodiment, the polyurethane material is obtained by polymerization of monomers including toluene diisocyanate and polytetrahydrofuran.

[0028] In a preferred embodiment, the sulfide solid electrolyte includes Li6PS5F, Li6PS5Cl, Li6PS5Br, Li6PS5I, Li3PS4, and Li7P3S. 11 Li 10 GeP2S 12 Li 10 SnP2S 12 Li 9.54 Si 1.74 P 1.44 S11.7 C 10.3 At least one of them.

[0029] In a preferred embodiment, the organic solvent includes one or both of dibromomethane and dichloromethane, and the volume ratio of the two includes, but is not limited to, 0:100, 10:90, 20:80, 30:70, 40:60, 50:50, 60:40, 70:30, 80:20, 90:10, 100:0, etc., but is not limited to the listed values. Other unlisted values ​​within this data range are also applicable.

[0030] In a preferred embodiment, the concentration of the sulfide solid electrolyte in the mixture is 6 mg / mL to 20 mg / mL, including but not limited to any one or any two of the following values: 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, and 20 (mg / mL).

[0031] In a preferred embodiment, the concentration of the binder for the sulfide solid electrolyte in the mixture is 1.5 wt.% to 5 wt.%, including but not limited to any one or any two of the following values: 1.5, 1.75, 2, 2.25, 2.5, 2.75, 3, 3.25, 3.5, 3.75, 4, 4.25, 4.5, 4.75, and 5 (wt.%).

[0032] In a preferred embodiment, the preparation of the mixture can be aided by methods such as shaking, stirring, shaking table, centrifugation, ultrasonication, and heating, which helps to accelerate dispersion and obtain a relatively uniform dispersion system. In a more preferred embodiment, the sulfide solid electrolyte is mixed with a binder, the sulfide solid electrolyte, and the organic solvent by stirring at a frequency of 200 rpm to 1000 rpm for a duration of 3 h to 36 h.

[0033] In a preferred embodiment, during the dispersion of the mixture onto the polytetrafluoroethylene (PTFE) plate, the ratio of the amount of the mixture to the area of ​​the PTFE plate is 65-200 (unit: μL / cm²). 2 ).

[0034] In a preferred embodiment, the thickness of the sulfide solid electrolyte membrane layer is 0.05 mm to 0.25 mm.

[0035] In a preferred embodiment, the drying is achieved by allowing the sample to stand at room temperature.

[0036] In a preferred embodiment, the hot pressing temperature is 30℃~80℃, the hot pressing pressure is 10MPa~400MPa, and the hot pressing time is 3h~48h.

[0037] As an optional implementation, the temperature of the hot pressing treatment includes, but is not limited to, any one or any two of the following numerical ranges: 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80 (°C); the pressure of the hot pressing treatment includes, but is not limited to, any one or any two of the following numerical ranges: 10, 20, 50, 100, 150, 200, 250, 300, 350, 400 (MPa); and the time of the hot pressing treatment includes, but is not limited to, any one or any two of the following numerical ranges: 3, 5, 8, 10, 15, 20, 25, 30, 35, 40, 45, 48 (h).

[0038] As a preferred embodiment, the process further includes cutting the dried film precursor to a suitable shape and area before performing the hot pressing treatment.

[0039] A second aspect of the present invention is to provide a sulfide solid electrolyte membrane layer, which is prepared by a method comprising the preparation method of the sulfide solid electrolyte membrane layer as described in the first aspect.

[0040] It should be noted that the sulfide solid electrolyte film layer described in this invention corresponds to the solid electrolyte layer in a solid-state battery, and this layer necessarily contains a sulfide electrolyte. In some solid-state batteries, a small amount of solid electrolyte component is incorporated into the solid electrode; however, the sulfide solid electrolyte film layer described in the second aspect of this invention is not equivalent to a solid electrode containing a sulfide electrolyte. Furthermore, this invention does not limit whether other types of solid electrolyte components besides sulfide electrolytes are included.

[0041] A third aspect of the present invention is to provide a solid-state battery comprising a sulfide solid electrolyte membrane layer as described in the second aspect.

[0042] It is understood that, apart from the sulfide solid electrolyte membrane layer, the solid-state battery should include a solid positive electrode, a solid negative electrode, and other necessary or non-essential functional elements or packaging components, which can be arbitrarily selected and combined by those skilled in the art; when the solid-state battery includes the sulfide solid electrolyte membrane layer described in this invention, regardless of whether other electrolyte layers are used, it can be considered as an embodiment of this invention.

[0043] Example 1 The polyurethane adhesive was dissolved in a mixed solvent of dibromomethane and dichloromethane (volume ratio 70:30) to prepare a solution with a concentration of 10 mg / mL; the sulfide electrolyte Li6PS5F was dissolved in the adhesive solution and stirred.

[0044] 200 μL of the stirred solution was poured onto a circular polytetrafluoroethylene plate with a diameter of 14 mm. After the solvent dried, the electrolyte membrane precursor was peeled off, with a binder dosage of 3 wt.%. It was then placed in a hot press mold and hot-pressed at a temperature of 80 °C, a pressure of 300 MPa, and a time of 12 h to obtain the sulfide solid electrolyte membrane of this embodiment.

[0045] Example 2 The only difference from Example 1 is that the sulfide electrolyte is replaced with Li6PS5Cl.

[0046] Example 3 The only difference from Example 1 is that the sulfide electrolyte is replaced with Li6PS5Br.

[0047] Example 4 The only difference from Example 1 is that the sulfide electrolyte is replaced with Li6PS5I.

[0048] Example 5 The only difference from Example 1 is that the sulfide electrolyte is replaced with Li3PS4.

[0049] Example 6 The only difference from Example 1 is that the sulfide electrolyte is replaced with Li7P3S11.

[0050] Example 7 The only difference from Example 1 is that the sulfide electrolyte is replaced with Li10GeP2S12.

[0051] Example 8 The only difference from Example 1 is that the sulfide electrolyte is replaced with Li9.54Si1.74P1.44S11.7C10.3.

[0052] Example 9 The only difference from Example 1 is that the hot pressing temperature is 40°C, the hot pressing pressure is 400MPa, and the hot pressing time is 20h.

[0053] Comparative Example The only difference from Example 1 is that the hot pressing temperature is 20°C (cold pressing).

[0054] Test case (1) The ionic conductivity and tensile strength of the sulfide solid electrolyte membranes of each embodiment and comparative example were tested and the results are shown in Table 1.

[0055] Table 1

[0056] (2) The electrolyte membrane precursor described in Example 1 was manually broken from the middle and then placed in a hot press mold for hot pressing. The hot pressing temperature was 80°C, the hot pressing pressure was 300 MPa, and the hot pressing time was 12 h. The product was then observed under an optical microscope, and the results were as follows: Figure 1 As shown, it can be observed that the electrolyzed electrolyte membrane exhibits a self-healing effect, such as... Figure 2 The diagram shows the principle of self-healing. Through the high toughness and resilience of the polyurethane adhesive material, a certain degree of shear thinning occurs during hot pressing, which fills the electrolyte gap and forms an electrolyte film layer with good adhesion, dispersion and mechanical strength, while further enhancing the electrochemical performance of the electrolyte layer.

[0057] (3) The sulfide solid electrolyte membranes obtained by hot pressing and cold pressing in Example 1 and Comparative Example 1, respectively, were placed in a battery mold, and circular lithium foils were attached to both sides of the electrolyte; without applying additional pressure, a symmetrical battery cycle test was performed on the blue battery; at 0.1 mA / cm 2 0.5mA / cm 2 Get Figure 3 The voltage-time curve is shown. And in Figure 3 Hot pressing corresponds to the hot pressing of Example 1, and cold pressing corresponds to the cold pressing of Comparative Example 1. Through Figure 3 It is evident that Example 1 exhibits good cycle stability, while Comparative Example 1 fails to produce a battery with good electrochemical performance.

[0058] Furthermore, the symmetrical cells prepared in Example 1 and Comparative Example 1 were subjected to critical current density (CCD) testing, and the results are as follows: Figure 4 As shown, similarly, Hot Pressing corresponds to the hot pressing of Example 1, and Cold Pressing corresponds to the cold pressing of Comparative Example 1. The critical current density is the minimum current density at which lithium dendrites can penetrate the solid electrolyte and cause a short circuit in the battery; through Figure 4 It is evident that Example 1 has a better ability to suppress lithium dendrites, and the battery corresponding to Example 1 has higher short-circuit resistance and cycle stability.

[0059] Although the present invention has been illustrated and described with specific embodiments, it should be understood that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; those skilled in the art should understand that modifications can be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein, without departing from the spirit and scope of the present invention; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention; therefore, this means that all such substitutions and modifications that fall within the scope of the present invention are included in the appended claims.

Claims

1. A method for preparing a sulfide solid electrolyte membrane, characterized in that, Includes the following steps: A mixture containing a binder for sulfide solid electrolyte, sulfide solid electrolyte, and organic solvent is prepared, and the mixture is dispersed on a polytetrafluoroethylene plate. After drying, it is subjected to hot pressing to obtain the sulfide solid electrolyte film layer.

2. The preparation method according to claim 1, characterized in that, The adhesive includes polyurethane materials; Preferably, the polyurethane material has a melting point of 160°C to 180°C and an elasticity of 0.04 GPa to 0.06 GPa.

3. The preparation method according to claim 1, characterized in that, The sulfide solid electrolyte includes at least one of Li6PS5F, Li6PS5Cl, Li6PS5Br, Li6PS5I, Li3PS4, Li7P3S11, Li10GeP2S12, Li10SnP2S12, and Li9.54Si1.74P1.44S11.7C10.

3.

4. The preparation method according to claim 1, characterized in that, The organic solvent includes one or both of dibromomethane and dichloromethane.

5. The preparation method according to claim 1, characterized in that, In the mixture, the concentration of the sulfide solid electrolyte is 5 mg / mL to 20 mg / mL.

6. The preparation method according to claim 1, characterized in that, In the mixture, the concentration of the binder for the sulfide solid electrolyte is 1.5 wt.% to 7 wt.%.

7. The preparation method according to claim 1, characterized in that, The thickness of the sulfide solid electrolyte membrane layer is 0.05 mm to 0.25 mm.

8. The preparation method according to claim 1, characterized in that, The hot pressing temperature is 30℃~80℃, the hot pressing pressure is 10MPa~400MPa, and the hot pressing time is 3h~48h.

9. A sulfide solid electrolyte membrane layer, characterized in that, It is obtained by the preparation method described in any one of claims 1 to 8.

10. A solid-state battery, characterized in that, Includes the sulfide solid electrolyte membrane layer as described in claim 9.

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