Sulfide electrolyte material and preparation method thereof, positive plate, secondary battery, battery assembly and electric equipment

Abstract

The invention discloses a sulfide electrolyte material and a preparation method thereof, a positive plate, a secondary battery, a battery assembly and electric equipment. The carbon content of the sulfide electrolyte material provided by the invention is 1-20%, and the sulfide electrolyte material has good ionic conductivity and electronic conductivity, and is beneficial to improving the cycle performance of a battery.

Description

A sulfide electrolyte material and its preparation method, positive electrode, secondary battery, battery module and electrical device thereof. Technical Field

[0001] This application relates to the field of batteries, specifically to a sulfide electrolyte material and its preparation method, electrode sheet, secondary battery, battery assembly and electrical equipment. Background Technology

[0002] With the continuous development of battery technology, all-solid-state batteries have become a research hotspot in fields such as electric vehicles and energy storage systems due to their high safety and high energy density. Sulfide solid electrolytes have attracted much attention in all-solid-state battery research due to their high ionic conductivity and good processing performance.

[0003] Solid electrolytes lack fluidity and exhibit poor wettability to electrodes. To meet the ion transport requirements of composite electrodes, solid electrolyte materials need to be added to the positive / negative electrodes to improve ion transport. Composite electrodes typically contain components such as electrode materials, electrolyte materials, conductive carbon, and binders, usually existing in particulate form. Due to the poor physical contact between solid particles, it is difficult to achieve uniform dispersion of the three components—electrode, solid electrolyte, and conductive carbon—leading to limited local ion or electron conduction, which is detrimental to battery performance. Since solid electrolytes and conductive carbon are non-electrochemically active materials and do not contribute to capacity, adding excessive amounts is not conducive to improving battery energy density.

[0004] Therefore, improving the ionic and electronic conductivity of sulfide electrolyte materials and enhancing their cycling performance is a key research focus in this field. Summary of the Invention

[0005] A sulfide electrolyte material and its preparation method, positive electrode, secondary battery, battery module and electrical equipment are disclosed in this application. The sulfide electrolyte material provided in this application has both good ionic conductivity and electronic conductivity.

[0006] The first aspect of this application provides a sulfide electrolyte material, characterized in that the carbon content of the sulfide electrolyte material is 1% to 20%.

[0007] The sulfide electrolyte material provided in this application has a high carbon content and a low Young's modulus. It is easily deformed and coated on the surface of the electrode material, which is conducive to uniform mixing of the material. At the contact area between the electrolyte and the electrode particles, it can achieve rapid lithium-ion conduction and conduct electrons to promote redox reactions, thus possessing both good ionic conductivity and electronic conductivity.

[0008] A second aspect of this application provides a method for preparing the sulfide electrolyte material as described above, comprising:

[0009] The raw material system including lithium sulfide is mixed in stoichiometric ratio and sintered to obtain the sulfide electrolyte material, wherein the carbon content of the lithium sulfide is 2% to 60%.

[0010] This application selects lithium sulfide with high carbon content as one of the raw materials, and high carbon content sulfide electrolyte materials can be obtained by sintering. The process is simple and easy to scale up.

[0011] A third aspect of this application provides a positive electrode sheet, comprising the sulfide electrolyte material provided in the first aspect of this application or the sulfide electrolyte material prepared according to the method provided in the second aspect of this application.

[0012] In the positive electrode sheet provided in the third aspect of this application, the high-conductivity sulfide electrolyte material is uniformly distributed, which can reduce the amount of conductive agent used, avoid the problem of uneven mixing and local agglomeration of positive electrode components, and help reduce the internal resistance of the battery.

[0013] This application provides a fourth aspect of a secondary battery, comprising the sulfide electrolyte material provided in the first aspect of this application, or the sulfide electrolyte material prepared according to the method provided in the second aspect of this application, or the positive electrode sheet provided in the third aspect of this application. The battery provided by this application has high energy density and good cycle performance.

[0014] The fifth aspect of this application provides a battery assembly comprising at least two secondary batteries as described above, and the battery assembly provided by this application has excellent electrochemical performance.

[0015] The sixth aspect of this application provides an electrical device, including a secondary battery provided in the fourth aspect of this application or a battery assembly provided in the fifth aspect of this application. The secondary battery or the battery assembly serves as the power supply for the electrical device. The electrical device provided by this application has excellent performance and strong product competitiveness. Attached Figure Description

[0016] 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 some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 is a schematic diagram of the synthesis of a sulfide electrolyte material in one embodiment of this application;

[0018] Figure 2. XRD pattern of the sulfide electrolyte material in Example 1 of this application;

[0019] Figure 3. XRD pattern of high carbon content lithium sulfide in Example 2 of this application.

[0020] Figure 4. XRD pattern of the sulfide electrolyte material in Example 2 of this application;

[0021] Figure 5. XRD pattern of the sulfide electrolyte material in Example 3 of this application;

[0022] Figure 6. XRD pattern of the sulfide electrolyte material in Example 4 of this application;

[0023] Figure 7. XRD pattern of the sulfide electrolyte material in Example 5 of this application;

[0024] Figure 8 shows the XRD pattern of the sulfide electrolyte material in Comparative Example 1 of this application. Detailed Implementation

[0025] To enable those skilled in the art to better understand the solutions of this application, a further detailed description of this application is provided below. The specific embodiments listed below are merely descriptions of the principles and features of this application; the examples are only for explaining this application and are not intended to limit its scope. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this application.

[0026] In recent years, all-solid-state lithium batteries have become a research hotspot for next-generation energy storage technologies due to their advantages such as high safety and high energy density. Among them, sulfide electrolytes are considered to be one of the electrolyte materials with great application potential due to their high room temperature ionic conductivity, good interfacial compatibility, and stability with lithium metal anodes, showing broad application prospects in fields such as electric vehicles and large-scale energy storage.

[0027] However, traditional sulfide electrolytes still face many challenges in practical applications, severely restricting the performance improvement and industrialization of all-solid-state lithium batteries. On the one hand, they have a high interfacial impedance with electrode materials, mainly due to insufficient physical contact and chemical compatibility between the electrolyte and electrode particle surfaces. This high interfacial impedance significantly affects lithium-ion transport efficiency, leading to a decrease in battery rate performance, increased polarization during charge and discharge, and consequently limiting cycle stability—after multiple cycles, the continuous increase in interfacial impedance may even cause rapid capacity decay.

[0028] Furthermore, most sulfide electrolytes possess only ionic conductivity, with extremely low electronic conductivity (typically below 10). -8The capacity (S / cm) is too low to adequately support electron conduction. This limits the redox reactions at the electrode / electrolyte interface to a limited number of contact points, severely restricting reaction kinetics. Especially under high-rate charge / discharge conditions, the active materials on the electrodes cannot fully participate in the reaction, resulting in the actual battery capacity being far lower than the theoretical value.

[0029] Although researchers have attempted to improve these problems through interface modification (such as introducing buffer layers), particle nano-sizing, and composite methods, existing solutions often suffer from drawbacks such as complex processes, high costs, or limited performance improvements. For example, the introduction of interface modification layers may increase lithium-ion transport resistance, while nano-sizing, although increasing the contact area, can exacerbate agglomeration due to excessively high material surface energy. Therefore, developing a sulfide electrolyte material that combines low Young's modulus, good ionic and electronic conductivity, and can form a stable and close contact with electrode materials has become crucial for advancing the practical application of all-solid-state lithium batteries.

[0030] To overcome the deficiencies in the prior art, this application provides a sulfide electrolyte material with a carbon content of 1% to 20%.

[0031] In terms of ion conductivity, sulfide electrolytes have good ion conductivity. Carbon exists in the form of a dispersed phase inside the sulfide and is uniformly dispersed. It does not disrupt the lithium ion migration path between the sulfide lattice and particles, and can still ensure that the material as a whole has good ion conductivity.

[0032] In terms of electronic conductivity, carbon, as a typical electronic conductor, forms a continuous electronic conduction network when uniformly dispersed in the sulfide electrolyte. When the carbon content is in the range of 1%-20%, effective contact can be formed between carbon particles, allowing electrons to be rapidly conducted within the electrolyte through the carbon phase. This electronic conduction network extends to the contact area between the electrolyte and electrode particles, providing ample electron supply for redox reactions at the electrode / electrolyte interface. In traditional composite electrodes, carbon black is an electronic conductor and an ionic insulator, while the sulfide electrolyte is an ionic conductor and an electronic insulator. Uniform mixing of the cathode, carbon black, and sulfide electrolyte is difficult to achieve in traditional composite electrodes; localized enrichment of electrolyte or carbon black leads to a loss of local electronic / ionic conductivity, which is detrimental to the reaction kinetics.

[0033] The sulfide electrolyte material provided in this application has a high carbon content and a low Young's modulus, making it easily deformable and coated on the surface of the electrode material. This facilitates uniform mixing of the material. At the contact area between the electrolyte and electrode particles, it enables both rapid lithium-ion conduction and electron conduction, promoting redox reactions. It exhibits both good ionic and electronic conductivity. Optionally, the carbon content of the sulfide electrolyte material can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, or any value between any two of the above.

[0034] For example, the carbon content of lithium sulfide and sulfide electrolyte materials can be tested by a carbon-sulfur analyzer. The working principle is to convert the carbon in the sample into corresponding gases (such as carbon dioxide) through combustion or other means, and then use gas detection technology (such as infrared absorption method) to quantitatively analyze these gases, thereby calculating the carbon content in the sample.

[0035] In a preferred embodiment, the carbon content of the sulfide electrolyte material is 10.5% to 20%. Within this range, carbon can form a more complete electron conduction network, enhancing electronic conductivity to promote interfacial redox reactions; at the same time, it ensures good ion transport, and the material is easily deformable, allowing for tighter coating of the electrode, further reducing interfacial impedance and improving battery cycle performance. Optionally, the carbon content of the sulfide electrolyte material can be 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, or any value between any two of the above.

[0036] In one embodiment, the ionic conductivity of the sulfide electrolyte material is greater than 6 mS / cm, and the electronic conductivity of the sulfide electrolyte material is greater than 5 × 10⁻⁶ mS / cm. -5 The ionic conductivity is greater than 8 mS / cm. High ionic conductivity ensures rapid migration of lithium ions in the electrolyte, reducing transport resistance and improving the rate performance of the battery; high electronic conductivity provides sufficient electrons for the redox reaction at the electrode / electrolyte interface, accelerating reaction kinetics. When this sulfide electrolyte material is used in the positive electrode, the amount of conductive agent can be reduced, which is beneficial for reducing the battery's internal resistance and increasing its energy density. In a preferred embodiment of this application, the ionic conductivity of the sulfide electrolyte material is greater than 8 mS / cm, and the electronic conductivity of the sulfide electrolyte material is greater than 5 mS / cm.

[0037] Specifically, sulfide electrolyte materials may include sulfide-type sulfides.

[0038] Sulfur-silver-germanium ore type sulfides include P and S.

[0039] Preferably, the sulfide of the silver-germanium sulfide further includes one or more of Li, X, and A, wherein X includes one or more of F, Cl, Br, and I, and A includes one or more of O, As, Sn, Se, Si, Bi, etc.

[0040] In some embodiments, the chemical formula of the argentite-germanium sulfide is Li 7-m+a-c-d M m / n P 1-a A a S 5-b D b Cl c X d M includes one or more of Na, Mg, Ca, Zn, and Al; A includes one or more of Si, Sn, and Ge; D includes one or more of O and Se; X includes one or more of Br and I; 0≤m≤1, 1≤n≤3, 0≤a≤1, 0≤b≤2, 0≤c<2, 0≤d<2, and 1≤c+d<2. The above-mentioned sulfide-silver-germanium ore type sulfides possess both good ionic and electronic conductivity, which helps improve the cycle performance of the battery.

[0041] This application also provides a method for preparing a sulfide electrolyte material, comprising: mixing a raw material system including lithium sulfide in a stoichiometric ratio and sintering to obtain a sulfide electrolyte material, wherein the carbon content of lithium sulfide is 2% to 60%.

[0042] This application uses carbon-containing lithium sulfide as a raw material, which simplifies the preparation process, eliminates the need for additional complex carbon doping steps, improves production efficiency, and allows for precise control of the carbon content of the final electrolyte material by controlling the carbon content of lithium sulfide in the raw material, thus ensuring its performance stability. Optionally, the carbon content of lithium sulfide can be 2%, 5%, 10%, 20%, 30%, 40%, 50%, 60%, or any value between any two of the above.

[0043] The preparation method of the above-mentioned sulfide electrolyte material is simple to operate and easy to promote and apply.

[0044] Specifically, the sintering time is 1 hour to 24 hours. Sintering at the above temperatures promotes the complete reaction of the raw materials and the stable formation of the sulfide crystal structure, while avoiding excessively high temperatures that could lead to volatilization or structural damage, and also preventing incomplete reactions due to excessively low temperatures. Optionally, the sintering time can be 1 hour, 3 hours, 5 hours, 7 hours, 9 hours, 11 hours, 13 hours, 15 hours, 17 hours, 19 hours, 21 hours, 23 hours, or any value between any two of the above.

[0045] Specifically, the sintering temperature is 400–550℃. This temperature allows the reaction to proceed fully, promoting uniform dispersion of carbon in the material and forming an effective conductive network. This enables the efficient preparation of sulfide electrolyte materials with excellent performance and uniform carbon distribution, ensuring that their ionic conductivity, electronic conductivity, and mechanical properties meet the required standards. Optionally, the sintering temperature can be 400℃, 420℃, 440℃, 460℃, 480℃, 500℃, 520℃, 550℃, or any value between any two of the above.

[0046] Specifically, sintering is carried out under the protection of a protective gas, which includes at least one of helium, neon, argon, and nitrogen. Using protective gases such as helium, neon, argon, and nitrogen isolates the material from air, preventing sulfides from reacting with oxygen and water vapor during high-temperature sintering, avoiding oxidation of the carbon components, and ensuring the stability of the material structure.

[0047] In one embodiment, lithium sulfide is prepared by sintering a raw material system including a carbon source and lithium sulfate. The carbon source provides carbon during sintering, making the generated lithium sulfide naturally carbon-containing, eliminating the need for subsequent additional carbon doping and simplifying the process. At the same time, the carbon source's participation in the reaction can control the carbon content of lithium sulfide, and the carbon can be uniformly distributed in the lithium sulfide, giving the subsequently prepared electrolyte material good electronic conductivity and suitable mechanical properties.

[0048] In one embodiment, lithium sulfide can be prepared by carbothermal reduction. The carbon source used includes starch, glucose, sucrose, coconut shell carbon, etc. The molar ratio of carbon to lithium is between 3:1 and 7:1. Specifically, the carbon source and lithium sulfate are uniformly mixed and reacted at 600-900°C for 5-15 hours to obtain lithium sulfide raw material.

[0049] This application also provides a positive electrode sheet, comprising the above-described sulfide electrolyte material or a sulfide electrolyte material prepared according to the above method.

[0050] Based on the above-mentioned sulfide electrolyte material, the positive electrode sheet has a uniform distribution of sulfide electrolyte material, which can reduce the amount of conductive agent used and avoid the problem of uneven mixing and local agglomeration of positive electrode components. This is beneficial to reduce the internal resistance of the battery and improve cycle stability.

[0051] Furthermore, the positive electrode also includes a positive electrode active material, with a mass ratio of (50–99):(50–1) of the positive electrode active material to the sulfide electrolyte material. This ratio range avoids capacity loss due to insufficient active material and prevents ion transport obstruction caused by insufficient electrolyte. It also facilitates uniform mixing of the two materials, reduces interfacial impedance, and improves the cycle stability and rate performance of the battery.

[0052] It is understood that the positive electrode active material in this application may be at least one of ternary materials (such as NCM811), lithium iron phosphate (LFP), layered manganese-rich cathode (LRMO), or sulfur-based cathode (such as S / C composite).

[0053] This application also provides a secondary battery, including the above-described sulfide electrolyte material or a sulfide electrolyte material prepared according to the above-described method for preparing sulfide electrolyte material.

[0054] Specifically, secondary batteries can include solid-state batteries.

[0055] This application also provides a battery assembly, which includes at least two of the above-described secondary batteries.

[0056] This application also provides an electrical device, including the aforementioned secondary battery or battery assembly, wherein the secondary battery or battery assembly serves as the power supply for the electrical device.

[0057] The present application will be further described below through specific embodiments and comparative examples. Unless otherwise specified, the reagents, materials and instruments used below are all conventional reagents, materials and instruments, all of which are commercially available, and the reagents and materials involved can also be synthesized by conventional synthetic methods.

[0058] Example 1

[0059] Preparation of sulfide electrolyte materials: Sucrose and lithium sulfate were mixed in a C:Li ratio of 3.1:1 and reacted at 800℃ for 10 h to obtain carbon-containing lithium sulfide materials. The carbon-containing lithium sulfide materials were then reacted with P2S5 and LiCl in a Li... 5.5 PS 4.5 Cl 1.5 The stoichiometric proportions of the ingredients were measured and ball-milled at 400 r / min for 10 h. The mixture was then cold-pressed under 400 MPa to obtain a green body with a diameter of 10 mm and a thickness of 0.5 mm. The green body was placed in a high-temperature furnace and heated to 450 °C at a rate of 5 °C / min under an argon atmosphere. After holding at this temperature for 6 h, the mixture was cooled in the furnace to obtain Li. 5.5 PS 4.5 Cl 1.5 Sulfide solid electrolyte materials.

[0060] Solid-state battery fabrication: The positive electrode active material is lithium nickel cobalt manganese oxide (LiNi). 0.8 Co 0.1 Mn 0.1O2 and solid electrolyte are mixed and ground evenly in a ratio of 80:20 and set aside. 100 mg of the above sulfide electrolyte material is placed into a mold with a diameter of 1 cm and pressed under a pressure of 300 MPa. Then, the composite positive electrode powder is evenly spread on one side of the solid electrolyte layer and pressed under a pressure of 500 MPa. Next, the lithium indium negative electrode is placed on the other side of the solid electrolyte layer and pressed under a pressure of 200 MPa. The prepared mold battery is tested under a pressure of 200 MPa. The above battery fabrication process must be carried out in an inert atmosphere glove box with a water content <1 ppm and an oxygen content <1 ppm.

[0061] Examples 2-7

[0062] It is basically the same as Example 1, with the differences shown in Table 1.

[0063] Comparative Example 1

[0064] Preparation of sulfide electrolyte materials: Lithium sulfide (Aladdin, CAS: 12136-58-2) was purchased as raw material, and its carbon content was found to be 0.09%. The carbon-containing lithium sulfide material was then mixed with P2S5 and LiCl according to the Li... 5.5 PS 4.5 Cl 1.5 The ingredients were stoichiometrically proportioned and ball-milled at 400 r / min for 10 h. The mixture was then cold-pressed under 400 MPa pressure to obtain a blank with a diameter of 10 mm and a thickness of 0.5 mm.

[0065] The billet was placed in a high-temperature furnace and heated to 450°C at a rate of 5°C / min under an argon atmosphere. After holding at this temperature for 6 hours, it was cooled with the furnace to obtain Li. 5.5 PS 4.5 Cl 1.5 Sulfide solid electrolyte materials.

[0066] Solid-state battery fabrication: The positive electrode active material is lithium nickel cobalt manganese oxide (LiNi). 0.8 Co 0.1 Mn 0.1 O2 and solid electrolyte are mixed and ground evenly in a ratio of 80:20 and set aside. 100 mg of the above sulfide electrolyte material is placed into a mold with a diameter of 1 cm and pressed under a pressure of 300 MPa. Then, the composite positive electrode powder is evenly spread on one side of the solid electrolyte layer and pressed under a pressure of 500 MPa. Next, the lithium indium negative electrode is placed on the other side of the solid electrolyte layer and pressed under a pressure of 200 MPa. The prepared mold battery is tested under a pressure of 200 MPa. The above battery fabrication process must be carried out in an inert atmosphere glove box with a water content <1 ppm and an oxygen content <1 ppm.

[0067] Comparative Example 2

[0068] Preparation of sulfide electrolyte material: Sucrose and lithium sulfate were mixed in a C:Li ratio of 7.7:1 and reacted at 800℃ for 10 h to obtain a carbon-containing lithium sulfide material with a carbon content of 66.65%. The carbon-containing lithium sulfide material was then reacted with P2S5 and LiCl in a Li... 5.5 PS 4.5 Cl 1.5 The ingredients were stoichiometrically proportioned and ball-milled at 400 r / min for 10 h. The mixture was then cold-pressed under 400 MPa pressure to obtain a blank with a diameter of 10 mm and a thickness of 0.5 mm.

[0069] The billet was placed in a high-temperature furnace and heated to 450°C at a rate of 5°C / min under an argon atmosphere. After holding at this temperature for 6 hours, it was cooled with the furnace to obtain Li. 5.5 PS 4.5 Cl 1.5 The sulfide solid electrolyte material has a carbon content of 23.0% as tested.

[0070] Solid-state battery fabrication: The positive electrode active material is lithium nickel cobalt manganese oxide (LiNi). 0.8 Co 0.1 Mn 0.1 O2 and solid electrolyte are mixed and ground evenly in a ratio of 80:20 and set aside. 100 mg of the above sulfide electrolyte material is placed into a mold with a diameter of 1 cm and pressed under a pressure of 300 MPa. Then, the composite positive electrode powder is evenly spread on one side of the solid electrolyte layer and pressed under a pressure of 500 MPa. Next, the lithium indium negative electrode is placed on the other side of the solid electrolyte layer and pressed under a pressure of 200 MPa. The prepared mold battery is tested under a pressure of 200 MPa. The above battery fabrication process must be carried out in an inert atmosphere glove box with a water content <1 ppm and an oxygen content <1 ppm.

[0071] Table 1

[0072]

[0073] Test case

[0074] The following parameters of the sulfide electrolyte materials in each embodiment and comparative example were tested:

[0075] 1) Electrolyte ionic conductivity test: Place a piece of carbon-coated aluminum foil at the bottom of a Φ=10mm mold battery, weigh a certain amount of electrolyte powder, vibrate to spread the powder evenly, and apply a pressing pressure of 300MPa. Then place another piece of carbon-coated aluminum foil on the surface of the pressed electrolyte and apply a pressure of 600MPa. Perform PEIS testing on an electrochemical workstation under 300MPa pressure, with a frequency of 1MHz-100Hz and an amplitude of 10mV. Take the real part of the inflection point in the low-frequency region and the arc segment as the resistance value. The ionic conductivity of the solid electrolyte can be calculated using the following formula:

[0076]

[0077] In the formula:

[0078] L: Thickness of the solid electrolyte sheet (cm);

[0079] R: Solid electrolyte resistance (Ω), which can be measured by the EIS spectrum of a symmetrical cell assembled with blocked electrodes.

[0080] A: Solid electrolyte sheet end face area (cm²) 2 );

[0081] 2) Electrolyte electronic conductivity test:

[0082] A carbon-coated aluminum foil was placed at the bottom of a Φ=10mm mold battery, and 0.125g of electrolyte powder was weighed in. The powder was vibrated to spread evenly, and a pressing pressure of 300MPa was applied. Then, another carbon-coated aluminum foil was placed on the surface of the pressed electrolyte, and a pressure of 600MPa was applied. DC polarization tests were performed at 300MPa pressure using an electrochemical workstation, with polarization voltages of 0.2V and 0.3V, each for 6 hours. The current at the voltage endpoint was taken as the steady-state current, and the difference in steady-state current between the two voltages was calculated. The electronic conductivity of the solid electrolyte can be calculated using the following formula:

[0083]

[0084] In the formula:

[0085] L—Thickness of the solid electrolyte sheet (cm);

[0086] △I: Steady-state current difference at voltages of 0.2V and 0.3V; A: Area of ​​the solid electrolyte sheet end face (cm²) 2 )

[0087] 3) Cyclic performance test:

[0088] The positive and negative electrode materials are LiNi, respectively. 0.8 Co 0.1 Mn0.1 Using O2 and lithium indium anodes, the solid-state mold battery was tested for 0.2C charge-discharge performance at room temperature, with a test voltage range of 2.5-4.2V. The first discharge capacity was tested, and the capacity retention rate after 200 cycles was calculated.

[0089] The following conclusions can be drawn from the above embodiments and comparative examples.

[0090] (1) By synthesizing lithium sulfide raw materials with different carbon contents, the carbon content of the sulfide electrolyte can be controlled from 1.0% to 20.0%, thereby affecting the ionic / electronic conductivity. Preferably, when the carbon content of the sulfide electrolyte is in the range of 10.5%-20.0%, the ionic conductivity is >8mS / cm and the electronic conductivity is >5mS / cm.

[0091] (2) The high-carbon solid electrolyte prepared in this application can simultaneously possess high ionic conductivity and high electronic conductivity. When applied to composite cathodes, it does not require the addition of additional conductive carbon black and exhibits good discharge capacity and cycle performance. Preferably, when the carbon content of the sulfide electrolyte is in the range of 10.5%-20.0% and the ratio of cathode active material to sulfide electrolyte is 80:20, the initial discharge capacity of the battery is ≥166mAh / g, and the capacity retention rate after 200 cycles at 0.2C rate is ≥85%.

[0092] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still 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. Such 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 this application.

Claims

1. A sulfide electrolyte material, characterized in that, The carbon content of the sulfide electrolyte material is 1% to 20%.

2. The sulfide electrolyte material according to claim 1, characterized in that, The carbon content of the sulfide electrolyte material is 10.5% to 20%.

3. The sulfide electrolyte material according to claim 1 or 2, characterized in that, The sulfide electrolyte material has an ionic conductivity greater than 6 mS / cm, and an electronic conductivity greater than 5 × 10⁻⁶ mS / cm. -5 mS / cm.

4. The sulfide electrolyte material according to any one of claims 1-3, characterized in that, The sulfide electrolyte material includes sulfide of the silver-germanium type.

5. The sulfide electrolyte material according to claim 4, characterized in that, The chemical formula of the silver-germanium sulfide is Li. 7-m+a-c-d M m / n P 1-a A a S 5-b D b Cl c X d M includes one or more of Na, Mg, Ca, Zn, and Al; A includes one or more of In, Bi, Si, Sn, and Ge; D includes one or more of O and Se; X includes one or more of F, Br, and I; 0≤m≤1, 1≤n≤3, 0≤a≤1, 0≤b≤2, 0≤c<2, 0≤d<2, and 1≤c+d<2.

6. A method for preparing a sulfide electrolyte material according to any one of claims 1-5, characterized in that, include: The raw material system including lithium sulfide is mixed in stoichiometric ratio and sintered to obtain the sulfide electrolyte material, wherein the carbon content of the lithium sulfide is 2% to 60%.

7. The method for preparing the sulfide electrolyte material according to claim 6, characterized in that, include: The sintering time is 1h to 24h; and / or the sintering temperature is 400 to 550℃.

8. The method for preparing the sulfide electrolyte material according to claim 6 or 7, characterized in that, The sintering is carried out under the protection of a protective gas, which includes at least one of helium, neon, argon, and nitrogen.

9. The method for preparing the sulfide electrolyte material according to any one of claims 6-8, characterized in that, The lithium sulfide is obtained by sintering a raw material system including a carbon source and lithium sulfate.

10. A positive electrode plate, characterized in that, The positive electrode comprises the sulfide electrolyte material according to any one of claims 1-5 or the sulfide electrolyte material obtained by the preparation method of the sulfide electrolyte material according to any one of claims 6-9.

11. The positive electrode sheet according to claim 10, characterized in that, The positive electrode sheet also includes a positive electrode active material, and the mass ratio of the positive electrode active material to the sulfide electrolyte material is (50-99):(50-1).

12. A secondary battery, characterized in that, Includes the sulfide electrolyte material according to any one of claims 1-5, or the sulfide electrolyte material obtained according to the preparation method of the sulfide electrolyte material according to any one of claims 6-9, or the positive electrode sheet according to claim 10 or 11.

13. The secondary battery according to claim 12, characterized in that, The secondary battery includes a solid-state battery.

14. A battery assembly, characterized in that, The battery assembly includes at least two secondary batteries as described in claim 12 or 13.

15. An electrical appliance, characterized in that, The device includes the secondary battery as described in claim 12 or 13 or the battery assembly as described in claim 14, wherein the secondary battery or the battery assembly serves as the power supply for the electrical device.

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