A composite sulfide solid electrolyte material, preparation method and application

Abstract

The present invention discloses a composite sulfide solid electrolyte material, a preparation method and an application, which relate to the technical field of energy materials. By mixing a precursor material and a quantum dot material and then performing hot pressing and sintering treatment, a composite sulfide solid electrolyte material is obtained. The quantum dot material is a metal compound quantum dot or a carbon quantum dot with semiconductor properties. The mass ratio of the precursor material to the quantum dot material is 100:(1-10). The introduction of the quantum dot with semiconductor properties significantly improves the ion conductivity and interface stability of the material and other properties. The prepared electrolyte material has excellent interface compatibility, ionic conductivity, electrochemical stability, etc., and is suitable for application in all-solid-state soft-pack lithium metal batteries, effectively improving the cycle stability of the battery, enabling the battery to maintain a high capacity during long-term use, and extending the service life of the battery.

Description

Technical Field

[0001] The present invention relates to the technical field of energy materials, and particularly relates to a composite sulfide solid electrolyte material, a preparation method and an application thereof. Background Art

[0002] With the continuous growth of energy demand and the increasingly severe environmental problems, the development of energy storage devices with high energy density, high safety and long life has become an urgent need. Solid-state batteries, which use solid electrolytes to replace traditional liquid electrolytes, are considered to be the development direction of the next generation of energy storage devices due to their advantages such as higher safety, wider electrochemical window and higher energy density. However, current solid electrolyte materials still face some challenges.

[0003] Although oxide solid electrolytes have relatively high ionic conductivity, their brittleness, difficult processing and high interfacial impedance limit their application in solid-state batteries. Although polymer solid electrolytes have good flexibility and processability, their ionic conductivity is relatively low, making it difficult to meet the requirements of high-power density solid-state batteries. Sulfide solid electrolytes have become one of the most promising solid electrolyte materials due to their advantages such as high ionic conductivity, good flexibility and good contact with electrodes. As a new type of nanomaterial, quantum dots have unique physical and chemical properties, such as high specific surface area and tunable electronic energy level structure, and have also become potential substances for improving solid electrolyte materials. However, it has been found in research that the dispersion of quantum dots in solid electrolytes is difficult to ensure, and agglomeration is likely to occur, thus affecting the ion transport efficiency and the consistency of electrolyte performance. To improve these drawbacks, some measures have been taken in the prior art. For example, the dispersion of quantum dots in solid electrolyte materials is improved by adding dispersants, and the compatibility between quantum dots and solid electrolytes is enhanced by surface modification of quantum dots. However, these methods still have some drawbacks, such as limited dispersion effect and difficulty in maintaining the stability of surface modification in the long term. Another common improvement measure is the co-precipitation method, but this method is very sensitive to reaction conditions such as temperature, pH value, the addition rate and concentration of precipitants, etc. Small changes in process parameters may lead to large differences in the distribution and performance of quantum dots in solid electrolytes. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a composite sulfide solid electrolyte material, a preparation method and an application thereof.

[0005] The purpose of the present invention is achieved by the following technical solutions:

[0006] <First Aspect>

[0007] The present invention provides a method for preparing a composite sulfide solid electrolyte material modified with quantum dots, which is to mix a precursor material and a quantum dot material, and then perform hot pressing sintering treatment to obtain the composite sulfide solid electrolyte material, wherein,

[0008] the mass ratio of the precursor material to the quantum dot material is 100 : (1~10);

[0009] the precursor material is one or more mixtures of sulfide materials represented by the general formula Li x M y S b or a combination of two or more materials having the element ratio in the general formula Li x M y S b wherein M is one of P, Si, and Ge, and x:y:b = (1.3~2.4) : 1 : (2.6~3.7);

[0010] The quantum dot material is a metal compound quantum dot or a carbon quantum dot having semiconductor properties.

[0011] As an embodiment, the precursor material is composed of Li2S and a sulfide of element M with a mass ratio of (0.45~0.7) : 1, and M is one of P, Si, and Ge.

[0012] As an embodiment, the sulfide of element M is P2S5, SiS2, or GeS2.

[0013] In some embodiments, the precursor material is Li2S and P2S5 with a mass ratio of 0.48:1.

[0014] In some embodiments, the precursor material is Li2S and SiS2 with a mass ratio of 0.49:1.

[0015] In some embodiments, the precursor material is Li2S and GeS2 with a mass ratio of 0.67:1.

[0016] As an embodiment, the average particle size of the quantum dot material is 1~100 nm.

[0017] As an embodiment, the average particle size of the quantum dot material is 1~50 nm.

[0018] In some embodiments, the average particle size of the quantum dot material is 2~20 nm.

[0019] As an embodiment, the metal compound quantum dot is a metal sulfide.

[0020] As an embodiment, the metal compound quantum dots are one or more of Ag2S, Cu2S, CdS, ZnS, and PbS.

[0021] As an embodiment, the carbon quantum dots are one or more of graphene quantum dots and carbon nanotube quantum dots.

[0022] In some embodiments, the quantum dot material is Ag2S, CdS, or carbon nanotube quantum dots.

[0023] As an embodiment, the mass ratio of the precursor material to the quantum dot material is 100 : (1 - 5).

[0024] As an embodiment, the parameters of the hot pressing sintering are: in an inert atmosphere, the pressure is 400 - 450 MPa, the temperature is 230 - 300 °C, and the time is 4 - 7 h.

[0025] In some embodiments, the parameters of the hot pressing sintering are: in an inert atmosphere, the pressure is 420 MPa, the temperature is 240 °C, and the time is 7 h.

[0026] As an embodiment, the precursor material is obtained by ball - milling Li2S and a sulfide of element M.

[0027] As an embodiment, the mixing of the precursor material and the quantum dots is carried out by ball - milling.

[0028] As an embodiment, both the ball - milling pot and the grinding balls in the ball - milling process are made of zirconia.

[0029] As an embodiment, the parameters of the ball - milling process are: the ball - to - material ratio is (15 - 40) : 1, and the ball - milling time is 15 - 30 h.

[0030] As an embodiment, the ball - milling process selects planetary ball - milling, and the rotation speed is 500 - 650 revolutions per hour.

[0031] In some embodiments, the ball - milling process for preparing the precursor material selects planetary ball - milling.

[0032] In some embodiments, the parameters of the ball - milling process for preparing the precursor material are: the ball - to - material ratio is 23:1, the rotation speed is 500 revolutions per hour, and the ball - milling time is 25 h.

[0033] As an embodiment, the ball - milling process for the precursor material and the quantum dots selects vibratory ball - milling.

[0034] As an embodiment, the parameters of the vibratory ball - milling process are: the vibration frequency is 1500 - 2000 revolutions per minute.

[0035] In some embodiments, the parameters of the vibratory ball milling treatment are as follows: the ball-to-material ratio is 20:1, the vibration frequency is 1800 revolutions per minute, and the ball milling time is 20 h.

[0036] <Second aspect>

[0037] The present invention provides a method for preparing a composite sulfide solid electrolyte membrane modified with quantum dots, which is further prepared based on the above-mentioned composite sulfide solid electrolyte material modified with quantum dots, and includes:

[0038] After step S3, the following steps are added:

[0039] S4. Grind the sintered product to obtain electrolyte powder;

[0040] S5. Coat the slurry obtained by mixing the electrolyte powder, binder, and solvent on a substrate under an inert atmosphere, and after drying, the composite sulfide solid electrolyte membrane can be formed on the substrate.

[0041] As an embodiment, the particle size of the electrolyte powder is in the micron range.

[0042] As an embodiment, the particle size of the electrolyte powder is 200 - 500 μm.

[0043] As an embodiment, the grinding treatment is a roll pressing and crushing method, and the rotational speed of the roller is 50 - 100 revolutions per minute and the pressure is 3 - 5 MPa.

[0044] In some embodiments, the parameters of the grinding treatment are as follows: the rotational speed of the roller is 70 revolutions per minute and the pressure is 3 MPa.

[0045] As an embodiment, the mass ratio of the electrolyte powder, binder, and solvent is (70 - 95) : (5 - 30) : 100.

[0046] As an embodiment, the binder is selected from one or more of polyethylene oxide, polyvinylidene fluoride, polyacrylonitrile, and polymethyl methacrylate.

[0047] In some embodiments, the binder is selected as polyvinylidene fluoride.

[0048] As an embodiment, the slurry is mixed for 10 - 15 h using a drum ball mill or a shearer.

[0049] As an embodiment, the coating is to uniformly coat the slurry on the substrate under an inert atmosphere.

[0050] As an embodiment, the drying is carried out in an inert atmosphere at 70 °C.

[0051] In some embodiments, the substrate is made of copper tape with a parameter of 10 μm.

[0052] <The third aspect>

[0053] The present invention provides a composite sulfide solid electrolyte material, comprising: a substance represented by the general formula Li x M y N c S z wherein M is one of P, Si, and Ge, N is one of Ag, Cd, Zn, Pb, and C, and x:y:c:z = (1.3 - 2.4) : 1 : (0.01 - 0.6) : (2.6 - 3.7).

[0054] <The fourth aspect>

[0055] The present invention provides an application of the composite sulfide solid electrolyte material in a all-solid-state flexible battery.

[0056] As an embodiment, the all-solid-state flexible battery includes: a positive electrode, a negative electrode, and an electrolyte membrane prepared from the composite sulfide solid electrolyte material.

[0057] As an embodiment, the negative electrode includes lithium metal or a metal lithium composite.

[0058] As an embodiment, the positive electrode includes NCM811.

[0059] Compared with the prior art, the present invention has the following beneficial effects:

[0060] The present invention provides a preparation method of a composite sulfide solid electrolyte material. By the method of stepwise ball milling, the mixing process of raw materials can be better controlled. First, the sulfide is preliminarily ball milled to reach a certain particle size and uniformity, and then quantum dots are added for the second-stage ball milling, which can ensure the uniform distribution of quantum dots in the sulfide matrix to achieve better optimization of mixing performance.

[0061] Furthermore, the present invention also provides that the activation energy of the reaction is reduced by ball milling the reactants, thereby initiating the reaction to form a sulfide solid electrolyte precursor, and then quantum dots are added for further treatment, which can make the final solid electrolyte material have a more uniform composition and structure. Further, sintering is carried out to form good interfacial contact between the quantum dots and the sulfide material.

[0062] By introducing quantum dots with semiconductor properties (such as metal compound quantum dots or carbon quantum dots) into the sulfide solid electrolyte, the ionic conductivity and interface stability of the material can be significantly improved, as follows:

[0063] (1) Higher ionic conductivity: The introduction of quantum dots can increase the interface area in the composite solid electrolyte membrane, promote the transport and diffusion of lithium ions, and thus improve the ionic conductivity. In addition, quantum dots can interact with the sulfide matrix, changing the electronic structure of the matrix and further enhancing the ionic conductivity.

[0064] (2) Better interface compatibility: Quantum dots can act as interface modifiers to improve the interface contact between the composite solid electrolyte membrane and the electrode, reduce the interface impedance, and enhance the cycle stability and rate performance of the solid-state battery.

[0065] (3) Enhanced mechanical properties: The introduction of polymer binders and quantum dots can strengthen the mechanical strength and toughness of the composite solid electrolyte membrane, making it more resistant to volume changes during charge and discharge of the solid-state battery and reducing the short-circuit risk of the solid-state battery.

[0066] (4) Higher electrochemical stability: Quantum dots can act as stabilizers to inhibit the decomposition and side reactions of the sulfide matrix during the electrochemical cycling process, improve the electrochemical stability of the solid electrolyte, and extend the life of the solid-state battery.

[0067] (5) Lower cost: The preparation cost of quantum dots is relatively low, and the preparation method provided by the present invention is simple and easy to implement, suitable for large-scale production. Therefore, the manufacturing cost of the solid electrolyte can be reduced, promoting the commercial application of solid-state batteries. Description of the Drawings

[0068] Figure 1 XRD pattern of the electrolyte powder obtained in step S4 of Example 1 of the present invention;

[0069] Figure 2 XRD pattern of the electrolyte powder obtained in step S4 of Example 2 of the present invention;

[0070] Figure 3 XRD pattern of the electrolyte powder obtained in step S4 of Example 3 of the present invention;

[0071] Figure 4 XRD pattern of the electrolyte powder obtained in step S4 of Example 4 of the present invention;

[0072] Figure 5 XRD pattern of the electrolyte powder obtained in step S4 of Example 5 of the present invention;

[0073] Figure 6XRD pattern of the electrolyte powder obtained in step S4 of Comparative Example 1 of the present invention;

[0074] Figure 7 XRD pattern of the electrolyte powder obtained in step S4 of Comparative Example 2 of the present invention;

[0075] Figure 8 XRD pattern of the electrolyte powder obtained in step S4 of Comparative Example 3 of the present invention. Detailed Description of the Invention

[0076] The present invention will be described in detail below with reference to the embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several adjustments and improvements can be made. These all fall within the protection scope of the present invention.

[0077] Example 1

[0078] This example provides a method for preparing a quantum dot Ag2S-modified Li-P-S composite sulfide solid electrolyte membrane. The raw materials used include:

[0079] Sulfide electrolyte precursor: Li2S and P2S5 with a mass ratio of 0.48:1;

[0080] Quantum dots: Ag2S, with an average particle size of 10 nm;

[0081] Polymer: polyvinylidene fluoride (PVDF). Specifically used in this example is: grade: TA-60512 / 0000, manufacturer: Solvay, USA, characteristic level: low viscosity, origin: USA, drying temperature: 120 - 180 °C, drying time: 5 hours to 8 hours;

[0082] Among them, the mass ratio of the precursor, quantum dots, and polymer is 82:3:15.

[0083] The preparation steps are as follows:

[0084] S1. Under an inert atmosphere, the precursor is mixed and loaded into a zirconia ball milling jar together with 5 mm zirconia grinding balls, and ball milling is carried out in a planetary ball mill for 25 h, where the ball-to-material ratio is 23:1 and the rotation speed is 500 revolutions per hour to obtain a first ball mill product;

[0085] Specifically, the molecular weight of Li2S is 45.942, and the molecular weight of P2S5 is 222.27. Then, in Li2S and P2S5 with a mass ratio of 0.48:1, the molar ratio of the three elements Li, P, and S is approximately 2.32:1:3.66. The first ball mill product is expressed as Li 2.32 PS3.66 。

[0086] S2. Under an inert atmosphere, load the quantum dots and the first ball-milled product together with 10 mm zirconia grinding balls into a zirconia ball mill jar, and perform high-energy mechanical grinding in a vibratory ball mill for 20 h. Among them, the ball-to-material ratio is 20:1, the amplitude is 5 mm, and the vibration frequency is 1800 revolutions per minute to obtain a second ball-milled product;

[0087] Specifically, the molecular weight of Ag2S is 247.8. Then, after adding the quantum dots, the molar ratio of the four elements Li, P, Ag, and S in the second ball-milled product is approximately 2.32:1:0.05:3.69. Then the second ball-milled product is expressed as Li 2.32 PAg 0.05 S 3.69 。

[0088] S3. Sinter the second ball-milled product in a muffle furnace under an inert atmosphere at a temperature of 240 °C, a pressure of 420 MPa, and a sintering time of 7 h to obtain a sintered product;

[0089] S4. Crush and grind the sintered product under an inert atmosphere to increase the reaction area of the electrolyte powder. In this embodiment, a vertical roller mill is used to crush the sintered product at a roller speed of 70 revolutions per minute and a pressure of 3 MPa, and the crushed powder is sieved and classified to obtain electrolyte powder with a particle size of 200 - 500 μm;

[0090] S5. Mix the solid electrolyte powder, polymer (as a binder), and p-xylene (as a solvent) with a mass ratio of 17:3:20 under an inert atmosphere. Then load them together with 20 mm zirconia ball milling beads into a zirconia ball mill jar. The ball-to-material ratio is 10:1, and a drum ball mill (Miqi horizontal DMS-4) is used to mix for 10 h at a rotation speed of 300 revolutions per hour to ensure the uniformity of the mixed slurry;

[0091] S6. Place the slurry in an inert atmosphere glove box, and use a coater to evenly coat the slurry on a copper tape with a doctor blade. Among them, the copper tape is 10 μm thick, 9 cm wide, and 11 cm long. The height of the doctor blade is 220 μm, the angle is 90°, and the coating speed is 5 mm / s;

[0092] S7. Dry the coated copper tape in an inert atmosphere environment at 70 °C for 6 h to form a composite solid electrolyte membrane on the copper tape. The formed composite solid electrolyte membrane has a thickness of 200 μm, a width of 8 cm, and a length of 10 cm.

[0093] It should be noted that in this embodiment, the inert atmosphere is an argon gas environment with a water and oxygen content ≤ 0.01 ppm.

[0094] Example 2

[0095] This example provides a preparation method for a quantum dot CdS-modified Li-Si-S composite sulfide solid electrolyte membrane. The raw materials used include:

[0096] Sulfide electrolyte precursor: Li2S and SiS2 with a mass ratio of 0.49:1;

[0097] Quantum dots: CdS, with an average particle size of 20 nm;

[0098] Polymer: polyvinylidene fluoride;

[0099] Among them, the mass ratio of the precursor, quantum dots, and polymer is 89:1:10.

[0100] The preparation steps are basically the same as those in Example 1, with the difference being:

[0101] In step S1, the obtained first ball-milled product is denoted as Li 1.97 SiS 2.98 ;

[0102] In step S2, the second ball-milled product is denoted as Li 1.97 SiCd 0.01 S 2.99 .

[0103] Example 3

[0104] This example provides a preparation method for a quantum dot carbon nanotube-modified Li-Si-S composite sulfide solid electrolyte membrane. The raw materials used include:

[0105] Sulfide electrolyte precursor: Li2S and SiS2 with a mass ratio of 0.49:1;

[0106] Quantum dots: carbon nanotubes, with an average particle size of 2.1 nm;

[0107] Polymer: polyvinylidene fluoride;

[0108] Among them, the mass ratio of the precursor, quantum dots, and polymer is 80:4:16.

[0109] The preparation steps are basically the same as those in Example 1, with the difference being:

[0110] In step S1, the obtained first ball-milled product is denoted as Li 1.97 SiS 2.98 ;

[0111] In step S2, the second ball-milled product is denoted as Li 1.97 SiC 0.57 S 2.98 .

[0112] Example 4

[0113] This example provides a method for preparing a quantum dot carbon nanotube modified Li-Ge-S composite sulfide solid electrolyte membrane. The raw materials used include:

[0114] Sulfide electrolyte precursor: Li2S and GeS2 with a mass ratio of 0.67:1;

[0115] Quantum dots: Carbon nanotubes with an average particle size of 2.1 nm;

[0116] Polymer: Polyvinylidene fluoride;

[0117] Among them, the mass ratio of the precursor, quantum dots, and polymer is 85:4:11.

[0118] The preparation steps are basically the same as those in Example 1, and the differences are as follows:

[0119] In step S1, the obtained first ball-milled product is designated as Li 1.34 GeS 2.67 ;

[0120] In step S2, the second ball-milled product is designated as Li 1.34 GeC 0.30 S 2.67 .

[0121] Example 5

[0122] This example provides a method for preparing a modified Li-P-S composite sulfide solid electrolyte membrane, which is basically the same as the steps in Example 1, and the differences are as follows:

[0123] In step S1, the precursor, quantum dots, and zirconia grinding balls are jointly loaded into a zirconia ball mill jar for ball milling, and the ball milling parameters are the same;

[0124] Step S2 is cancelled.

[0125] Comparative Example 1

[0126] This example provides a method for preparing an unmodified Li-P-S composite sulfide solid electrolyte membrane, which is basically the same as the steps in Example 1, and the differences are as follows:

[0127] In step S2, the first ball-milled product and zirconia grinding balls are jointly loaded into a zirconia ball mill jar for ball milling, without quantum dots, and the ball milling parameters are the same.

[0128] Comparative Example 2

[0129] This example provides an unmodified Li -The preparation method of the Si-S composite sulfide solid electrolyte membrane is basically the same as that of Example 2, except that:

[0130] In step S2, the first ball-milled product and zirconia grinding balls are jointly placed into a zirconia ball mill jar for ball milling, without quantum dots, and the ball milling parameters are the same.

[0131] Comparative Example 3

[0132] This example provides a preparation method of an unmodified Li-Ge-S composite sulfide solid electrolyte membrane, which is basically the same as that of Example 4, except that:

[0133] In step S2, the first ball-milled product and zirconia grinding balls are jointly placed into a zirconia ball mill jar for ball milling, without quantum dots, and the ball milling parameters are the same.

[0134] Battery assembly

[0135] Positive electrode plate: The positive electrode material is NCM811, the positive electrode current collector is 10-μm aluminum foil, and the binder is polyvinylidene fluoride, with a mass ratio of 99:1. After being mixed evenly, it is coated on the positive electrode current collector, and the loading amount of the positive electrode material is 10 mg / cm 2 , the width of the positive electrode plate is 8 cm and the length is 10 cm;

[0136] Negative electrode plate: The negative electrode material is a lithium-indium alloy negative electrode (indium foil with a thickness of 200 μm and lithium foil with a thickness of 50 μm). The width of the negative electrode plate is 8 cm and the length is 10 cm, which is attached to the negative electrode current collector. The negative electrode current collector is 10-μm copper foil;

[0137] Preparation of the polymer electrolyte membrane: Use the composite solid electrolyte membranes prepared in the above examples and comparative examples;

[0138] Battery assembly: In an inert atmosphere, the positive electrode, negative electrode, and polymer electrolyte membrane are stacked together in sequence, and then vacuum-sealed to assemble a full-solid-state soft-pack lithium metal battery.

[0139] Parameter test conditions: Cut a 200-μm-thick electrolyte membrane into a 10-mm-diameter disc, and place it in a PEEK mold with stainless steel on both sides to measure the ionic conductivity and impedance. The test method is to use an electrochemical workstation EC-Lab, model VSP-300. At an initial potential of 0 V and a scan rate of 5 mV / s, from 0.1 Hz to 10 6Testing was carried out in the range of Hz. The ionic conductivity of the sample was measured according to the formula σ = l / (S*R), where l is the thickness of the electrolyte, S is the cross-sectional area of the electrolyte, and R represents the charge transfer resistance; Mechanical strength test: A tensile testing machine with the brand of Litao and model LT was used to conduct the test at a tensile rate of 0.1 mm / min. The test sample was a solid electrolyte membrane with a thickness of 200 μm, a length of 2 cm, and a width of 1 cm.

[0140] It should be noted that the inert atmosphere for the assembly environment is an argon environment with a water and oxygen content ≤ 0.01 ppm, and the test conditions are all in an incubator at 25°C.

[0141] Performance detection

[0142] The XRD patterns of the electrolyte powders prepared in each example and comparative example are as Figures 1 to 8 shown.

[0143] Figure 1 The XRD pattern of the electrolyte powder material prepared in Example 1. After analysis by XRD software, it was found that the synthesized substance had characteristic peaks of Li3PS4 (PDF#04-010-1784 Li3PS4) and Ag2S (PDF#04-007-1178 Ag2S).

[0144] Figure 2 The XRD pattern of the electrolyte powder material prepared in Example 2. After analysis by XRD software, it was found that the synthesized substance had characteristic peaks of Li2SiS3 (PDF#04-005-3853 Li2SiS3) and Cd4SiS6 (PDF#04-002-4379 Cd4SiS6).

[0145] Figure 3 The XRD pattern of the electrolyte powder material prepared in Example 3. After analysis by XRD software, it was found that the synthesized substance had some characteristic peaks of Li2SiS3 (PDF#04-005-3853 Li2SiS3) and carbon nanotubes (PDF#04-007-2081 CNTs).

[0146] Figure 4 The XRD pattern of the electrolyte powder material prepared in Example 4. After analysis by XRD software, it was found that the synthesized substance had a characteristic peak of Li4GeS4 (PDF#04-011-5080 Li4GeS4) and carbon nanotubes (PDF#04-007-2081 CNTs).

[0147] Figure 5XRD pattern of the electrolyte powder material prepared in Example 5. After analysis by XRD software, it was found that the synthesized substance had characteristic peaks of Li3PS4 (PDF#04-010-1784 Li3PS4) and Ag2S (PDF#04-007-1178 Ag2S), and the peak intensity was much stronger than that in Example 1.

[0148] Figure 6 XRD pattern of the electrolyte powder material prepared in Comparative Example 1. After analysis by XRD software, it was found that the synthesized substance had a characteristic peak of Li3PS4 (PDF#04-010-1784 Li3PS4).

[0149] Figure 7 XRD pattern of the electrolyte powder material prepared in Comparative Example 2. After analysis by XRD software, it was found that the synthesized substance had some characteristic peaks of Li2SiS3 (PDF#04-005-3853 Li2SiS3).

[0150] Figure 8 XRD pattern of the electrolyte powder material prepared in Comparative Example 3. After analysis by XRD software, it was found that the synthesized substance had a characteristic peak of Li4GeS4 (PDF#04-011-5080 Li4GeS4).

[0151] It should be noted that in Example 1, the synthesis of Li 2.32 PAg 0.05 S 3.69 was carried out according to the stoichiometric ratio. The synthesized substance was doped with Ag2S on the basis of the crystal structure of Li3PS4. Although the existing material database is huge, it still cannot cover all known compounds and materials. Therefore, Li3PS4 was selected as the comparison peak for XRD. Moreover, the newly doped interstitial atoms would exert pressure on the surrounding atoms, resulting in a change in the lattice constant and thus a shift in the position of the XRD peak. The same is true for other examples and comparative examples, which will not be elaborated here.

[0152] The assembled battery was subjected to cyclic charge-discharge tests at 0.1C. The results of its initial charge-discharge efficiency (first efficiency) and capacity retention rate after 100 cycles are listed in Table 1. It can be seen that after adding quantum dots to the solid electrolyte membrane, the first efficiency of the battery increased by about 20%, which means that the energy conversion efficiency of the battery during the first charge-discharge process was improved and the energy loss was reduced.

[0153] When quantum dots are not added to the solid electrolyte membrane, after 39 cycles for the battery corresponding to Comparative Example 1 and 40 cycles for the battery corresponding to Comparative Example 2, the capacity retention rates of both are approximately 70%. However, after 100 cycles for the battery with added quantum dots, the capacity retention rate is above 90%. This shows that quantum dots can effectively improve the cycling stability of the battery, enabling the battery to maintain a high capacity during long-term use and extending the service life of the battery.

[0154] The calculation formula for the capacity retention rate is: 。

[0155] Table 1 Battery performance test table corresponding to each example and comparative example

[0156]

[0157] The AC impedance method was used to test its ionic conductivity, and a tensile test was carried out using a tensile machine to record the tensile force at break. The experimental data are shown in Table 2. It can be seen that the addition of quantum dots improves both the ionic conductivity and mechanical properties, and reduces the interfacial impedance. From the perspective of material properties, this effect of quantum dots in fields such as batteries and electronic devices helps to improve the overall performance, efficiency, and stability of the devices.

[0158] Table 2 Parameter test table corresponding to each example and comparative example

[0159]

[0160] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various deformations or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A method for preparing a composite sulfide solid electrolyte material, characterized in that: The following steps are involved: The precursor material and the quantum dot material are mixed, and then hot-pressed and sintered to obtain the composite sulfide solid electrolyte material, wherein: The mass ratio of the precursor material to the quantum dot material is 100: (1-10); The precursor material is a general formula Li x M y S b One or more of the sulfide materials shown are mixed, or the mixed sulfide materials have a general formula of Li x M y S b It is composed of two or more materials with the same element ratio, M is one of P, Si and Ge, x:y:b=(1.3~2.4) : 1 : (2.6~3.7); The quantum dot material is a metal sulfide quantum dot or a carbon quantum dot having semiconductor properties; The metal sulfide quantum dots are one or more of Ag2S, Cu2S, CdS, ZnS, and PbS, and the carbon quantum dots are one or more of graphene quantum dots and carbon nanotube quantum dots; The parameters of the hot pressing sintering are: in an inert atmosphere, a pressure of 400-450 MPa, a temperature of 230-300° C., and a time of 4-7 hours.

2. The method for preparing the composite sulfide solid electrolyte material according to claim 1, characterized in that: The precursor material is prepared by mixing Li2S and a sulfide of an element M in a mass ratio of (0.45-0.7):1, where M is one of P, Si, and Ge.

3. The method for preparing the composite sulfide solid electrolyte material according to claim 1, characterized in that: The average particle size of the quantum dot material is 1-100 nm.

4. A composite sulfide solid electrolyte material, characterized in that: It is prepared by the method according to any one of claims 1 to 3, including the general formula Li x M y N c S z For the substance shown, M is one of P, Si, and Ge, N is one of Ag, Cd, Zn, Pb, and C, and x:y:c:z=(1.3~2.4) : 1 : (0.01~0.6) : (2.6~3.7).

5. The use of the composite sulfide solid electrolyte material according to claim 4 in the manufacture of all-solid-state soft-pack batteries, characterized in that: The all-solid-state soft-pack battery comprises: a positive electrode, a negative electrode and an electrolyte membrane prepared from the composite sulfide solid electrolyte material.

6. A method for preparing a composite sulfide solid electrolyte membrane, characterized in that: It is prepared using the composite sulfide solid electrolyte material according to claim 4, comprising: A slurry obtained by mixing electrolyte powder, binder and solvent is coated on a substrate under an inert atmosphere, and after drying, the composite sulfide solid electrolyte membrane can be formed on the substrate. The electrolyte powder is ground from a solid electrolyte material, and the solid electrolyte material includes the composite sulfide solid electrolyte material as described in claim 4.

7. The method for preparing a composite sulfide solid electrolyte membrane according to claim 6, characterized in that: Includes one or more of the following technical features: A. The electrolyte powder particle size is micron-sized; B. The grinding process is a roller crushing method, with a roller speed of 50-100 rpm and a pressure of 3-5 MPa.

8. The method for preparing a composite sulfide solid electrolyte membrane according to claim 7, characterized in that: Includes one or more of the following technical features: A. The mass ratio of the electrolyte powder, the binder and the solvent is (70-95): (5-30): 100; B. The binder is selected from one or more of polyethylene oxide, polyvinylidene fluoride, polyacrylonitrile and polymethyl methacrylate.

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