Sulfide all-solid-state battery positive electrode sheet having ion-electron dual continuous transport network and method of manufacturing the same

Abstract

The application belongs to the technical field of all-solid-state batteries, and relates to a sulfide all-solid-state battery positive electrode sheet with an ion-electron double-continuous transmission network and a preparation method thereof.The preparation method comprises the following steps: S1, in-situ interface modification of a positive electrode material: adding a ternary positive electrode material, an interface modifier and a fluorine-containing lithium salt into a non-polar solvent, reacting in an inert atmosphere, and recovering a surface passivated modified positive electrode material through centrifugation; S2, preparation of an electronic phase slurry and an ionic phase slurry: mixing the modified positive electrode material and a conductive polymer in a non-polar solvent and performing ball milling treatment to form an electronic phase slurry; dispersing a sulfide electrolyte and an ion conductive binder in a non-polar solvent to form an ionic phase slurry; S3, preparation of a composite slurry: low-speed mixing of the electronic phase slurry and the ionic phase slurry to form a double-continuous network slurry; and S4, coating and densification: coating the composite slurry on a current collector, drying, and performing warm pressing densification treatment to obtain a composite positive electrode sheet.

Description

Technical Field

[0001] This invention belongs to the field of all-solid-state lithium battery technology, and relates to a sulfide all-solid-state battery positive electrode with an ion-electron dual continuous transport network and its preparation method. Background Technology

[0002] With the rapid development of new energy vehicles and energy storage technologies, high-safety, high-energy-density all-solid-state lithium batteries have become an important development direction for the next generation of energy storage devices. Sulfide solid electrolytes are considered to be one of the most promising solid electrolyte systems due to their extremely high room-temperature ionic conductivity and good machinability. However, in the process of industrialization, the preparation of composite cathodes faces major technical challenges: (1) The polar solvents such as N-methylpyrrolidone (NMP) used in traditional wet processes will react violently with sulfide electrolytes (such as Li6PS5Cl), resulting in electrolyte decomposition, generation of H2S gas and conductivity decay; (2) The alkaline substances (such as LiOH, Li2CO3) remaining on the surface of high-nickel ternary cathode materials (NCM) will still undergo interfacial side reactions with sulfides even in neutral solvents, generating a high-resistivity interfacial layer; (3) Existing binder systems (such as PVDF) are difficult to balance electronic / ionic conductivity and mechanical flexibility, and are prone to forming high porosity structures during the drying process, which seriously restricts ion transport efficiency and electrode mechanical integrity. Although some studies have attempted to circumvent these problems by using nonpolar solvents or dry processes, they still cannot simultaneously solve key issues such as interface stability, densification, and multi-scale charge transport, which severely restricts the performance and commercial application of sulfide all-solid-state batteries.

[0003] Therefore, developing a new method for preparing composite cathodes that can be compatible with the chemical properties of sulfide electrolytes, achieve high-density electrode structures, and construct efficient ion / electron dual continuous transport networks is key to breaking through the technological bottleneck of sulfide all-solid-state batteries and is of great significance to promoting their industrialization. Summary of the Invention

[0004] Therefore, the present invention aims to provide a sulfide all-solid-state battery cathode electrode with an ion-electron dual continuous transport network and its preparation method. The method first involves adding an interface modifier and a fluorinated lithium salt to a non-polar solvent system. These two react synergistically with residual alkali on the surface of the ternary cathode material to generate a stable LiF-based composite protective layer, achieving in-situ interface passivation. Subsequently, a stepwise preparation process is used to construct an "electronic phase" cathode particle slurry coated with a conductive polymer shell and an "ionic phase" electrolyte slurry dispersed in an ion-conductive binder. These are then mixed at low speed to form a composite slurry with an ion-electron dual continuous transport network. Finally, a wet coating and graded drying-temperature-pressure densification process is used. During the solvent residue stage, the electrode is held at 60-100°C and 8-15 MPa for 5-15 minutes to achieve binder flow filling and in-situ densification of the electrode, resulting in a high-performance cathode electrode with low porosity. This method fundamentally solves problems such as solvent corrosion, interfacial side reactions, and transport bottlenecks.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] In a first aspect, the present invention provides a method for preparing a composite positive electrode sheet for a sulfide all-solid-state battery having an ion-electron dual continuous transport network, comprising the following steps:

[0007] S1. In-situ interface modification of cathode material: Ternary cathode material, interface modifier and fluorinated lithium salt are added to a non-polar solvent, reacted under an inert atmosphere, and centrifuged to obtain surface passivated modified cathode material.

[0008] S2. Preparation of electronic and ionic phase slurries: Modified cathode material and conductive polymer are mixed in a non-polar solvent and ball-milled to form electronic phase slurry; sulfide electrolyte and ionic conductive binder are dispersed in a non-polar solvent to form ionic phase slurry.

[0009] S3. Preparation of composite slurry: The electronic phase slurry and the ionic phase slurry are mixed at low speed to form a double continuous network slurry; the mass ratio of the electronic phase slurry to the ionic phase slurry is (60-70):(40-30).

[0010] S4. Coating and densification: The composite slurry is coated onto the current collector, dried, and then densified by hot pressing to obtain the composite positive electrode sheet.

[0011] In step S1, the ternary cathode material is at least one of NCM111, NCM523, NCM622, and NCM811.

[0012] Preferably, the interface modifier comprises one or more of tris(trimethylsilyl)borate (TMSB), trimethylchlorosilane (TMCS), hexamethyldisilazane (HMDS), and hexamethyldisilazane (HMDSO).

[0013] The fluorinated lithium salt is at least one of LiPF6, LiBF4, LiTFSI, and LiDFOB.

[0014] A further improvement of this invention is that the conductive polymer in step 2 is one or more of poly(3-hexylthiophene) (P3HT), poly(3,4-ethylenedioxythiophene) (PEDOT), alkylated polyaniline (Alkylated PANI), or polypyrrole (PPy). The mass ratio of the modified cathode material to the conductive polymer is 100:(1-5); the ball milling speed is 200-300 rpm; and the ball milling time is 2-3 hours.

[0015] A further improvement of the present invention is that the sulfide electrolyte used in step S2 includes Li6PS5Cl (LPSCl), Li 10 GeP2S 12 (LGPS), Li7P3S 11 One or more of the following: Li3PS4, Li2S-P2S5 glass-ceramics;

[0016] The ion-conductive binder includes one or more of lithium-ion Nafion, lithium polyethylene oxide-bis(trifluoromethanesulfonyl)imide (PEO-LiTFSI), lithium-ion polystyrene sulfonate (Li-PSS), and polypropylene carbonate-lithium salt complex (PPC-Li Salt).

[0017] The mass ratio of sulfide electrolyte to ionic conductive binder is 100:(1-5); the speed of the high-speed disperser is 2000-3000 rpm; the dispersion time is 1-2 hours.

[0018] In step S1, the nonpolar solvent includes one or more of decane, dodecane, mesitylene, toluene, or mineral oil.

[0019] And / or, the mass ratio of ternary cathode material, interface modifier and fluorinated lithium salt is 100 : (0.5-2) : (0.1-1); the reaction temperature is 50-60℃; and the reaction time is 4-6 hours.

[0020] In step S3, the mass ratio of electronic phase slurry to ionic phase slurry is (60-70):(40-30); the stirring speed is 100-200 rpm; and the stirring time is 1-2 hours.

[0021] A further improvement of the present invention is that the drying temperature used in step S4 is 40-50℃; the drying time is 2-3 hours; the hot-press densification process is carried out in a hot press at a temperature of 80-90℃; the pressure is 10-20MPa; the hot pressing time is 5-10 minutes; the temperature is raised to 100-110℃ while maintaining the pressure; the drying time is continued for 1-2 hours; and the final thickness of the composite positive electrode sheet is 100-130μm.

[0022] The present invention involves first drying the electrode at a low temperature to evaporate most of the solvent; then transferring it to a hot press for hot pressing under certain temperature and pressure conditions; finally, maintaining the pressure while raising the temperature to continue drying, completely removing the residual solvent, and obtaining the final positive electrode.

[0023] Secondly, the present invention provides a composite positive electrode sheet for a sulfide all-solid-state battery prepared by the preparation method described above.

[0024] Thirdly, the present invention provides an all-solid-state battery comprising the aforementioned composite positive electrode, sulfide solid electrolyte layer, and negative electrode layer.

[0025] The negative electrode active material of the negative electrode layer is one or more of micron-sized silicon, nano-sized silicon, graphite, and lithium-silicon alloy; the sulfide electrolyte is a solid electrolyte of type Li6PS5Cl.

[0026] The beneficial effects of this invention are as follows:

[0027] (1) By using a non-polar solvent system and in-situ interface modification technology, the chemical corrosion of the sulfide electrolyte by the solvent is fundamentally eliminated, and the generation of H2S gas during the preparation process is reduced. By reacting the interface modifier with the residual alkali on the NCM surface in situ, a stable LiF-BO protective layer is generated, which reduces the impedance of the cathode / electrolyte interface, reduces the interface side reaction, and significantly improves the interface stability.

[0028] (2) The dual continuous network structure of "electronic conductive layer / lithium-ion conductive layer" constructed by phase separation simultaneously optimizes the electron and ion transport paths, reduces the overall electrode impedance, and improves the battery rate performance.

[0029] (3) By using a combination of graded drying and warm-press densification processes, high densification of the electrode sheet (porosity as low as 5.4%) was achieved under low temperature and low pressure conditions, while maintaining the good flexibility of the electrode sheet, thereby increasing the compaction density of the prepared positive electrode sheet to 3.58 g / cm³. 3 The peel strength is 6.47 N / m, and the capacity retention rate is 98.7% after 30 cycles. It provides a reliable technical path for the industrialization of sulfide all-solid-state batteries and solves the core problems such as interface degradation, transport limitation and structural instability in the preparation of cathodes in sulfide systems. Attached Figure Description

[0030] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0031] Figure 1 SEM morphology image (magnification × 2000) of the modified NCM811 cathode prepared in Example 1 of the present invention.

[0032] Figure 2 SEM morphology image (magnification × 10000) of the modified NCM811 cathode prepared in Example 1 of the present invention. Detailed Implementation

[0033] The present invention will be described in detail below with reference to embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several adjustments and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0034] Example 1

[0035] A method for preparing a composite positive electrode sheet for a sulfide all-solid-state battery, comprising the following steps:

[0036] (1) Weigh 100g of single-crystal ternary cathode material NCM811, 1.5g of interface modifier tris(trimethylsilyl)borate (TMSB), and 0.5g of fluorinated lithium salt lithium difluorosulfonylimide (LiFSI); add the above materials together to a reactor containing 500g of decane solvent; under argon atmosphere protection, heat the reaction system to 55℃ and stir continuously at 300 rpm for 5 hours. After the reaction is completed, centrifuge the mixture, collect the solid product, and wash it three times with decane solvent to finally obtain the modified NCM811 cathode material with a LiF-BOF composite protective layer formed on the surface (SEM morphology image as shown). Figure 1 and Figure 2 );

[0037] (2) 100g of the modified NCM811 cathode material obtained above and 4g of conductive polymer poly(3-hexylthiophene) (P3HT) were added to 200g of decane solvent and mixed. The mixture was transferred to a planetary ball mill and ball milled at 250 rpm for 2.5 hours. Through the above treatment, P3HT was uniformly coated on the surface of the cathode particles to form an electronic phase slurry.

[0038] (3) Weigh 100g of sulfide electrolyte Li6PS5Cl (LPSCl) and 3g of ion-conductive binder lithium Nafion, add them to 200g of decane solvent and mix; use a high-speed disperser to perform high-speed shear dispersion of the mixture at a speed of 2500rpm for 1.5 hours; to form a uniform and stable ion phase slurry.

[0039] (4) Measure 120g of electronic phase paste and 80g of ionic phase paste and mix them in a mixing tank. Stir at a low speed of 150 rpm for 1.5 hours to ensure uniform mixing. Use a coating machine to coat the composite paste onto a 15μm thick aluminum foil current collector. The wet film thickness is controlled to be 150μm and the areal density is 30.15mg / cm³. 2 ;

[0040] (5) The coated electrode sheet was transferred to an oven at 45°C and dried at low temperature for 2.5 hours to remove most of the solvent. Then it was transferred to a hot press and hot-pressed at 85°C and 15MPa for 8 minutes. After that, the pressure was maintained at 15MPa and the temperature was raised to 105°C. The drying continued for 1.5 hours to completely remove the residual solvent. Finally, a composite positive electrode sheet with a thickness of 115μm was obtained.

[0041] Example 2

[0042] A method for preparing a composite positive electrode sheet for a sulfide all-solid-state battery, comprising the following steps:

[0043] (1) Weigh 100g of single-crystal ternary cathode material NCM811, 0.8g of interface modifier tris(trimethylsilyl)borate (TMSB), and 0.3g of fluorinated lithium salt lithium difluorosulfonylimide (LiFSI); add the above materials together to a reactor containing 400g of decane solvent; under argon atmosphere protection, heat the reaction system to 52℃ and stir continuously at 280 rpm for 4.5 hours. After the reaction is completed, centrifuge the mixture, collect the solid product, and wash it three times with fresh decane solvent to finally obtain the modified NCM811 cathode material with a LiF-BOF composite protective layer on the surface;

[0044] (2) Add 100g of the modified NCM811 material obtained above and 3g of conductive polymer poly(3-hexylthiophene) (P3HT) to 180g of decane solvent and mix. Transfer the mixed slurry to a planetary ball mill and treat it at a ball milling speed of 220 rpm for 3 hours to make P3HT uniformly coat the surface of the positive electrode particles and form an electronic phase slurry.

[0045] (3) Weigh 100g of sulfide electrolyte Li6PS5Cl (LPSCl) and 4g of ion-conductive binder lithium-ion, and add them to 200g of decane solvent; use a high-speed disperser to perform high-speed shear dispersion of the mixture at 2200 rpm for 2 hours to form a uniform and stable ionic slurry with an areal density of 30.84 mg / cm³. 2 ;

[0046] (4) Measure 130g of electronic phase paste and 70g of ionic phase paste and mix them in a mixing tank; stir at a low speed of 120 rpm for 2 hours to make them evenly mixed; use a coating machine to coat the composite paste onto a 15μm thick aluminum foil current collector, and control the wet film thickness to 150μm.

[0047] (5) The coated electrode sheet was transferred to an oven at 48°C and dried at low temperature for 3 hours to remove most of the solvent. Then it was transferred to a hot press and hot-pressed at 82°C and 12MPa for 10 minutes. After that, the pressure was maintained at 12MPa and the temperature was raised to 108°C. The drying continued for 1.2 hours to completely remove the residual solvent. Finally, a composite positive electrode sheet with a thickness of 110μm was obtained.

[0048] Comparative Example 1

[0049] In this comparative example, step (1) of Example 1 was omitted, and the cathode material was not modified using an interface modifier; all other steps remained unchanged. The impedance of this comparative example was 14.58 Ω, the ionic conductivity was 0.82 mS / cm, the discharge capacity at 0.2C was 176.4 mAh / g, the initial efficiency was 83.2%, the discharge capacity at 0.5C was 164.3 mAh / g, and the capacity retention after 30 cycles was 90.3%. In Example 1, the impedance was 7.45 Ω, the ionic conductivity was 3.32 mS / cm, the discharge capacity at 0.2C was 197.5 mAh / g, the initial efficiency was 87.4%, and the discharge capacity at 0.5C was 188.6 mAh / g. The capacity retention rate after 30 cycles was 98.7% (mAh / g). In Comparative Example 1, no in-situ interface modification was performed on the cathode material. A large number of residual alkaline lithium compounds (such as LiOH and Li2CO3) were present on the surface of the ternary cathode material. These substances would undergo irreversible acid-base reactions with the sulfide electrolyte, resulting in a sharp increase in interface impedance. Furthermore, repeated side reactions and interface degradation would continuously consume active lithium and electrolyte, leading to rapid capacity decay of the battery.

[0050] Comparative Example 2

[0051] In this comparative example, step (2) in Example 1 was omitted, and the conductive polymer was not used to prepare the electronic phase slurry. The remaining steps remained unchanged. The impedance test of this comparative example was 11.26Ω, the ionic conductivity was 1.53mS / cm, the discharge capacity at 0.2C was 178.3 mAh / g, the initial efficiency was 82.5%, the discharge capacity at 0.5C was 163.2 mAh / g, and the capacity retention rate after 30 cycles was 88.6%. In Comparative Example 2, no electronic conductive phase was prepared. Since the sulfide solid electrolyte is an electronic insulator, and the electronic conductivity of the positive electrode active material itself is limited, without an additional electronic pathway, there will be huge electron transport resistance inside the electrode, resulting in severe polarization during charging and discharging, and the capacity cannot be effectively utilized, resulting in poor rate performance.

[0052] Comparative Example 3

[0053] In this comparative example, step (3) in Example 1 was omitted, and the ionic phase slurry was not prepared using an ionic conductive binder. The remaining steps remained unchanged. The impedance test of this comparative example was 16.83Ω, the ionic conductivity was 0.54mS / cm, the discharge capacity at 0.2C was 170.2 mAh / g, the initial efficiency was 81.7%, the discharge capacity at 0.5C was 158.4 mAh / g, and the capacity retention rate after 30 cycles was 89.9%. In this comparative example, no ionic conductive phase was prepared. Since the sulfide electrolyte particles and the positive electrode active material particles are in point-to-point contact, the ion transport path is tortuous. Even if there is an electron coating layer on the surface of the positive electrode particles, the ionic conductivity of this coating layer is poor, and lithium ions cannot smoothly enter and exit the active material, resulting in low overall ionic conductivity, high battery internal resistance, and poor rate performance.

[0054] Comparative Example 4

[0055] In this comparative example, in step (5) of Example 1, the low-temperature drying method was not used; instead, a hot press was used for processing, and the remaining steps remained unchanged. In this comparative example, the porosity of the electrode sheet was 14.6%, and the compaction density was 2.26 g / cm³. 3 The peel strength was 4.32 N / m, the discharge capacity at 0.2C was 183.4 mAh / g, the initial efficiency was 84.2%, the discharge capacity at 0.5C was 171.5 mAh / g, and the capacity retention rate after 30 cycles was 94.6%. In Example 1, the electrode porosity was 5.4%, and the compaction density was 3.58 g / cm³. 3The peel strength was 6.47 N / m, the discharge capacity at 0.2C was 197.5 mAh / g, the initial efficiency was 87.4%, the discharge capacity at 0.5C was 188.6 mAh / g, and the capacity retention rate after 30 cycles was 98.7%. The core function of the initial low-temperature drying is to gently and slowly remove most of the free solvent, creating the optimal material state and conditions for the subsequent critical "thermo-pressure densification" step, thereby ultimately achieving high densification of the electrode. In this comparative example, the initial low-temperature drying was not performed; instead, rapid drying was carried out directly at a higher temperature. The violent evaporation of the solvent would form a large number of pores and channels, generating huge capillary forces within the slurry, leading to uneven electrode shrinkage, internal stress, microcracks, and even curling, thus damaging the integrity of the electrode structure.

[0056] Comparative Example 5

[0057] In this comparative example, in step (5) of Example 1, the hot press is not used for processing, and the other steps remain unchanged; the impedance test of the electrode in this comparative example is 10.21Ω, the ionic conductivity is 1.86mS / cm, the porosity is 20.7%, and the compaction density is 2.04g / cm. 3 The peel strength was 3.51 N / m, the discharge capacity at 0.2C was 178.6 mAh / g, the initial efficiency was 83.1%, the discharge capacity at 0.5C was 168.4 mAh / g, and the capacity retention rate after 30 cycles was 94.8%. The purpose of hot pressing is to drive the binder flow and particle rearrangement by applying gentle heat and pressure when the electrode is in its optimal plastic state, thereby achieving in-situ densification of the electrode structure, minimizing porosity and enhancing interfacial contact. In this comparative example, no hot pressing was used. No matter how slow the drying process was, the electrode formed by natural evaporation alone was still a porous structure. The binder distribution may be uneven, a large number of nanoscale pores still exist, the particle arrangement is not the most compact, the solid-solid interface contact is poor, resulting in high interfacial impedance, hindering ion / electron transport, and limiting the battery capacity.

[0058] Comparative Example 6

[0059] In this comparative example, all other steps of Example 1 were kept unchanged, except that the interface modifier tris(trimethylsilyl)borate (TMSB) in step (1) was replaced with LiPO3 (lithium phosphate), which is commonly used in the art. The remaining process parameters and operating steps were the same as in Example 1. The impedance test of this comparative example was 8.97Ω, the ionic conductivity was 2.43mS / cm, the discharge capacity at 0.2C was 181.5 mAh / g, the first-time efficiency was 83.7%, the discharge capacity at 0.5C was 160.3 mAh / g, and the capacity retention rate after 30 cycles was 93.9%. Although lithium phosphate reacts with the alkaline compounds remaining on the surface of the ternary cathode material to reduce its side reactions with the sulfide electrolyte, it cannot form a stable protective layer of LiF-BO on the surface of the active material to reduce the cathode / electrolyte interface impedance, resulting in a low capacity utilization and capacity retention rate of the battery.

[0060] Performance testing

[0061] The various embodiments and comparative examples were tested using the following methods:

[0062] 1. Ionic conductivity test: The prepared positive electrode sheet was cut into small circular pieces with a diameter of 10 mm, and then loaded into a pressure battery mold. It was pressed under a pressure of 1 ton and held for 1 minute. The AC impedance was tested at room temperature and in a normal atmospheric atmosphere using an electrochemical workstation with specification model CHI660E, and the ionic conductivity was calculated. The results are shown in Table 1.

[0063] Table 1

[0064]

[0065] 2. Porosity Testing of the Positive Electrode: A high-performance fully automated mercury porosimeter, model MicromeriticsAutoPore V 9620, was used in the experiment. The pressure applied in the low-pressure station (LP) was approximately 0.6 to 50 PSI, and the pressure applied in the high-pressure station (HP) was 20 to 60,000 PSI. A glass cone probe was used as the sample container to apply pressure to the sample, which was 1 cm x 1 cm in size. The porosity of the positive electrode was calculated based on the volume of mercury entering the pores.

[0066] 3. 180° Peel Test of Positive Electrode: A universal tensile testing machine was used. The sample size was 1cm*10cm. A flat, thin steel plate was taken, and a strip of double-sided tape was first applied to the center of the steel plate, smoothing it firmly to ensure a tight fit. The double-sided tape was then peeled off, and the electrode was attached to the tape, ensuring a perfect match between the electrode and the tape. The steel plate with the attached electrode was inserted into the lower clamp of the tensile testing machine and fixed vertically. The electrode without tape was inserted into the upper clamp and fixed, so that the electrode attached to the tape was at a 180° angle to the electrode fixed in the upper clamp. After fixing the test sample, the peel speed was 0.2mm / s, and the test began.

[0067] The test results of porosity, peel strength and compaction density of the positive electrode sheet are shown in Table 2.

[0068] Table 2

[0069]

[0070] 4. Full Battery Performance Test: 100 mg of Li6PS5Cl sulfide electrolyte was weighed and placed in a pressure mold, and a pressure of 1 ton was applied and held for 1 minute. Then, a small circular positive electrode sheet with a diameter of 10 mm was placed on one side of the electrolyte. After assembly, a pressure of 1 ton was applied and held for 1 minute. Next, 30 mg of negative electrode active material (micron silicon D50 = 5 μm) was weighed and spread evenly on the other side of the electrolyte. Copper foil was used as the negative electrode current collector. After assembly, a pressure of 1 ton was applied and held for 1 minute. Finally, a sulfide all-solid-state lithium-ion battery was obtained for testing and backup. The Xinwei Battery Testing System, model CT-4000, was used to conduct charge and discharge tests on the all-solid-state battery. The charge and discharge rate steps were 0.2C-0.5C, the voltage range was 4.3-2.5V, and the temperature was 28℃. The charge and discharge capacity of the sulfide all-solid-state battery was tested, and the test results are shown in Table 3.

[0071] Table 3

[0072]

[0073] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A method for preparing a composite positive electrode sheet for a sulfide all-solid-state battery with an ion-electron dual continuous transport network, characterized in that, Includes the following steps: S1. In-situ interface modification of cathode material: Ternary cathode material, interface modifier and fluorinated lithium salt are added to a non-polar solvent and reacted under an inert atmosphere. The modified cathode material with surface passivation is obtained by centrifugation. The interface modifier includes tris(trimethylsilyl)borate. S2. Preparation of electronic and ionic phase slurries: Modified cathode material and conductive polymer are mixed in a non-polar solvent and ball-milled to form electronic phase slurry; sulfide electrolyte and ionic conductive binder are dispersed in a non-polar solvent to form ionic phase slurry. S3. Preparation of composite slurry: The electronic phase slurry and the ionic phase slurry are mixed at low speed to form a double continuous network slurry; the mass ratio of the electronic phase slurry to the ionic phase slurry is 60-70:40-30. S4. Coating and densification: The composite slurry is coated onto the current collector, dried, and then densified by hot pressing to obtain the composite positive electrode sheet.

2. The preparation method according to claim 1, characterized in that, In step S1, the ternary cathode material includes at least one of NCM111, NCM523, NCM622, and NCM811.

3. The preparation method according to claim 1, characterized in that, In step S1, the fluorinated lithium salt is at least one of LiPF6, LiBF4, LiTFSI, and LiDFOB.

4. The preparation method according to claim 1, characterized in that, In step S2, the conductive polymer includes one or more of poly(3-hexylthiophene), poly(3,4-ethylenedioxythiophene), alkylated polyaniline, and polypyrrole; And / or, the mass ratio of modified cathode material to conductive polymer is 100:1-5; the ball milling speed is 200-300 rpm; and the ball milling time is 2-3 hours.

5. The preparation method according to claim 1, characterized in that, In step S2, the sulfide electrolyte includes Li6PS5Cl and Li 10 GeP2S 12 Li7P3S 11 One or more of the following: Li3PS4, Li2S-P2S5 glass-ceramics; And / or; the ionic conductive binder includes one or more of lithium-ion Nafion, lithium ethylene oxide-bis(trifluoromethanesulfonyl)imide, lithium-ionized polystyrene sulfonate, and polypropylene carbonate-lithium salt composite; And / or, the mass ratio of sulfide electrolyte to ionic conductive binder is 100:1-5; the high-speed dispersion speed is 2000-3000 rpm; and the dispersion time is 1-2 hours.

6. The preparation method according to claim 1, characterized in that, In step S1, the nonpolar solvent includes one or more of decane, dodecane, mesitylene, toluene, and mineral oil.

7. The preparation method according to claim 1, characterized in that, The mass ratio of ternary cathode material, interface modifier, and fluorinated lithium salt is 100 : (0.5-2) : 0.1-1; the reaction temperature is 50-60℃; and the reaction time is 4-6 hours.

8. The preparation method according to claim 1, characterized in that, The drying temperature used in step S4 is 40-50℃, and the drying time is 2-3 hours; the hot-press densification process is carried out in a hot press at a temperature of 80-90℃ and a pressure of 10-20MPa for 5-10 minutes, and the temperature is raised to 100-110℃ while maintaining the pressure, and the drying time is continued for 1-2 hours, resulting in a final composite positive electrode sheet thickness of 100-130μm.

9. A composite positive electrode sheet for a sulfide all-solid-state battery prepared by the preparation method according to any one of claims 1-8.

10. An all-solid-state battery, characterized in that, It includes the composite positive electrode sheet, sulfide solid electrolyte layer and negative electrode layer as described in claim 9.

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