Phosphorene / graphene composite positive electrode active material as well as preparation method and application thereof

Abstract

The invention discloses a phosphorene / graphene composite positive electrode active material as well as a preparation method and application thereof. The raw materials of the phosphorene / graphene composite positive electrode active material comprise phosphorene, graphene and sulfide solid electrolyte; the phosphorene is a few-layer phosphorene or a single-layer phosphorene; the number of the few layers of phosphorene is 2-10. The all-solid-state lithium battery with high energy density, high safety and excellent electrochemical performance is expected to be prepared by utilizing high theoretical specific capacity and excellent ion transmission performance of phosphorene as the positive electrode material and combining high ionic conductivity and safety of the sulfide solid electrolyte.

Description

Technical Field

[0001] The present invention belongs to the technical field of positive electrode materials, and in particular relates to a phosphorene / graphene composite positive electrode active material and a preparation method and application thereof. Background Art

[0002] Lithium-ion batteries have become the mainstream energy storage devices in portable electronic devices and electric vehicles due to their high energy density, long cycle life and light weight. However, traditional lithium-ion batteries usually use flammable liquid electrolytes, which pose safety risks such as leakage, combustion and even explosion, especially under high energy density and extreme working conditions.

[0003] All-solid-state lithium batteries are considered to be an important development direction for the next generation of high-safety, high-energy-density lithium batteries because they use solid electrolytes instead of flammable liquid electrolytes. Compared with traditional liquid electrolytes, solid electrolytes have the advantages of being non-flammable, non-leaking, high-temperature resistant, and having a wide electrochemical window, which can effectively improve the safety and energy density of batteries.

[0004] Sulfide solid electrolytes have become one of the most promising solid electrolyte systems due to their high ionic conductivity (comparable to liquid electrolytes), good mechanical properties and easy large-scale production.

[0005] The cathode material is a key component of lithium-ion batteries, and its performance directly determines the energy density, power density and cycle life of the battery. At present, commercial lithium-ion battery cathode materials mainly include lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate and ternary materials. However, these cathode materials still face some challenges when used in all-solid-state lithium batteries, such as low ion conductivity, poor contact with the solid electrolyte interface, and the need to improve rate performance and cycle performance.

[0006] As an emerging two-dimensional material, phosphorene is a single-layer or few-layer structure of black phosphorus with unique physical and chemical properties, such as high carrier mobility, adjustable band gap, excellent mechanical flexibility and large specific surface area. Theoretical studies have shown that phosphorene has a high theoretical specific capacity, and its two-dimensional layered structure is conducive to the rapid diffusion of lithium ions, making it show great application potential in the field of lithium-ion battery positive electrode materials. Summary of the invention

[0007] In view of this, the purpose of the present invention is to overcome the shortcomings of the prior art and provide a phosphorene / graphene composite positive electrode active material and a preparation method and application thereof, aiming to utilize the advantages of phosphorene as a positive electrode material, combined with the high ionic conductivity and safety of sulfide solid electrolytes, to develop an all-solid-state lithium battery with high energy density, high safety and excellent electrochemical performance.

[0008] The technical solution of the present invention is as follows:

[0009] <First aspect>

[0010] A phosphorusene-based cathode active material for all-solid-state lithium batteries, wherein the raw materials of the phosphorusene-based cathode active material include phosphorusene, graphene, and a sulfide solid electrolyte; the phosphorusene is few-layer phosphorusene or monolayer phosphorusene.

[0011] The few-layer phosphorusene is 2-10 layers of phosphorusene.

[0012] The sulfide solid electrolyte is selected from Li6PS5Cl or Li7P3S 11 .

[0013] <Second aspect>

[0014] A preparation method of a phosphorusene / graphene composite cathode active material, comprising the following steps:

[0015] S1. Mix the black phosphorus raw material with a polar organic solvent, and perform ultrasonic dispersion to obtain a phosphorusene dispersion; separate the phosphorusene dispersion by density gradient centrifugation to obtain a few-layer phosphorusene dispersion;

[0016] Perform pre-oxidation, strong oxidant intercalation oxidation, hydrolysis exfoliation, and reduction treatment on the graphite raw material in sequence to obtain a carbon-based two-dimensional material dispersion;

[0017] S2. Mix the few-layer phosphorusene dispersion and the carbon-based two-dimensional material dispersion according to a mass ratio of (5:5) to (9:1), remove the solvent, and form a phosphorusene / graphene composite material;

[0018] S3. Mix the phosphorusene / graphene composite material, the sulfide solid electrolyte, and the conductive agent evenly, and grind to obtain the phosphorusene / graphene composite cathode active material.

[0019] In step S1:

[0020] The polar organic solvent is N-methylpyrrolidone (NMP); the duration of ultrasonic dispersion is 4-8 hours;

[0021] And / or, the density gradient centrifugation method uses a sucrose gradient medium, the centrifugation speed is 10,000-20,000 rpm, and the centrifugation time is 2-4 hours.

[0022] And / or, the pre-oxidation treatment is to react graphite powder with phosphorus pentoxide (P2O5) and potassium persulfate (K2S2O8) in concentrated sulfuric acid at 70-90 °C for 2-4 hours;

[0023] And / or, the strong oxidant is potassium permanganate (KMnO4), and the intercalation oxidation reaction is carried out under ice bath conditions, and the reaction temperature ≤ 30 °C.

[0024] In step S2:

[0025] The mixing mass ratio of the phosphorene dispersion liquid to the carbon-based two-dimensional material dispersion liquid is 5-7:3;

[0026] And / or, the method for removing the solvent is vacuum filtration or spray drying.

[0027] In the said step S3:

[0028] The sulfide solid electrolyte is Li6PS5Cl or Li7P3S 11 ;

[0029] And / or, the conductive agent is selected from at least one of carbon black, acetylene black, and carbon nanotubes;

[0030] And / or, the grinding conditions are ball milling under argon protection, the ball-to-material ratio is 10-20:1, the rotation speed is 300-500 rpm, and the grinding time is 8-10 hours.

[0031] In the said step S3, the mass ratio of the phosphorene / graphene composite material, the sulfide solid electrolyte, and the conductive agent is (6-8):(1-3):(0.5-1.5).

[0032] <The third aspect>

[0033] The present invention also provides a phosphorene / graphene composite cathode active material prepared by the preparation method as described above.

[0034] <The fourth aspect>

[0035] The present invention also provides an all-solid-state lithium battery containing the phosphorene / graphene composite cathode active material as described above.

[0036] The all-solid-state lithium battery further includes a negative electrode and a current collector. The negative electrode can be selected from a lithium metal negative electrode, an alloy negative electrode, a carbon negative electrode, a lithium titanate negative electrode, etc., and preferably a lithium metal negative electrode. The current collector can be selected from copper foil, aluminum foil, etc.

[0037] The present invention uses phosphorene as the cathode material of the all-solid-state lithium battery based on the following considerations:

[0038] High theoretical specific capacity: Phosphorene has a high theoretical specific capacity, which is expected to improve the energy density of the battery.

[0039] Two-dimensional layered structure and high ionic conductivity: The two-dimensional layered structure of phosphorene is beneficial to the rapid insertion and extraction of lithium ions, improving the rate performance of the battery. At the same time, phosphorene itself has a certain electronic conductivity, which can reduce the polarization of the cathode material.

[0040] Compatibility with sulfide solid electrolyte: There is good interfacial compatibility between phosphorene and sulfide solid electrolyte, which is beneficial to reducing the interfacial impedance and improving the electrochemical performance of the battery.

[0041] By compounding phosphorene with graphene, the electronic conductivity and structural stability of the cathode material can be further improved, and its electrochemical performance can be enhanced.

[0042] Using sulfide solid electrolyte can fully exert the high safety characteristics of all-solid-state lithium batteries. At the same time, by utilizing the high ionic conductivity of sulfide solid electrolyte, the problem of large ion transport resistance in solid-state batteries can be overcome, and the comprehensive performance of the battery can be improved.

[0043] Compared with all-solid-state lithium metal batteries in the prior art, the beneficial effects of the present invention are as follows:

[0044] (1) High energy density potential: By utilizing the high theoretical specific capacity of phosphorene, it is expected to significantly improve the energy density of all-solid-state lithium batteries.

[0045] (2) Excellent rate performance: The two-dimensional layered structure of phosphorene is conducive to the rapid diffusion of lithium ions. Combined with the high ionic conductivity of sulfide solid electrolyte, excellent rate performance is expected to be achieved.

[0046] (3) High safety: Using sulfide solid electrolyte essentially ensures the high safety of the battery and avoids the safety hazards of traditional liquid lithium batteries.

[0047] (4) Potential cost advantage: Phosphorus has relatively rich reserves, and the preparation technology of phosphorene is also constantly developing. In the future, it is expected to reduce costs and achieve large-scale application. Description of the Drawings

[0048] By reading the detailed description of the non-limiting embodiments with reference to the following drawings, other features, purposes, and advantages of the present invention will become more apparent:

[0049] Figure 1 SEM scanning image of the phosphorene composite material;

[0050] Figure 2 Long cycle performance comparison diagram between Example 1 and Comparative Example 1. Detailed Embodiments

[0051] 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 still be made. These all fall within the protection scope of the present invention.

[0052] Example 1

[0053] This embodiment is based on Li7P3S 11 All-solid-state lithium battery with sulfide solid electrolyte and phosphorus / graphene composite cathode.

[0054] 1. Preparation of active material for phosphorus / graphene composite cathode

[0055] 1.1 Preparation of phosphorus

[0056] Few-layer phosphorus is prepared by liquid-phase exfoliation method.

[0057] (1) Add bulk black phosphorus crystals to N-methylpyrrolidone (NMP) solvent, and ultrasonically treat for a certain time (6 hours) to obtain a phosphorus dispersion (1.2 mg / mL).

[0058] (2) Separate by gradient centrifugation; the specific operation is as follows: Use sucrose (density range 1.0 - 1.4 g / cm 3 ). Configure a 5% - 30% (w / v) sucrose gradient, layer it into a centrifuge tube, and ensure that the density gradually increases from top to bottom. Cover the phosphorus dispersion on top of the gradient medium to avoid disturbing the layering. Use an ultracentrifuge with a rotational speed of 10,000 - 20,000 rpm and a centrifugation time of 2 - 4 hours. After centrifugation, take the dispersion in the density range (2.6 g / cm 3 - 3.7 g / cm 3 ) and dispense it into a dialysis bag (cut-off molecular weight 10 kDa), and dialyze with deionized water for 24 hours to remove residual salts to obtain a purified few-layer phosphorus dispersion (3 - 7 layers are prepared in this embodiment).

[0059] 1.2 Preparation of graphene

[0060] Graphene oxide is prepared by the improved Hummers method; the specific steps are as follows:

[0061] (1) Mix graphite powder with phosphorus pentoxide (P2O5) and potassium persulfate (K2S2O8) in proportion (10 g graphite + 10 g P2O5 + 10 g K2S2O8), add concentrated sulfuric acid (35 mL), and stir and react in a water bath at 80°C for 4 hours. After cooling, filter by suction, wash until neutral, and dry at 60°C for 24 hours to obtain pre-oxidized graphite powder.

[0062] (2) Mix the pre-oxidized graphite powder and concentrated sulfuric acid in proportion (3 g of pre-oxidized graphite powder + 69 ml of H2SO4), and slowly add potassium permanganate (such as 9 g of KMnO4) under ice bath conditions. Add it in 3 - 5 equal doses to avoid local overheating. After stirring for 30 minutes, raise the temperature to 35 °C and continue the reaction for 2 hours. Temperature control: Keep the reaction temperature ≤ 30 °C throughout the process (optimized conditions) to avoid excessive oxidation of graphite or equipment corrosion caused by high temperature. Hydrolysis and acidification: Slowly add deionized water drop by drop (such as 138 mL), control the temperature to rise to 80 - 90 °C, and keep warm for 15 minutes to promote interlayer delamination. Terminate oxidation: Add hydrogen peroxide (H2O2) until the solution turns bright yellow, and let it stand overnight for precipitation. Centrifugal washing: Centrifuge and separate the precipitate, and wash it successively with hydrochloric acid (HCl: water = 1:10) and deionized water until the pH is neutral to remove residual sulfate ions (SO4 2- ). Dialysis desalination: Disperse the precipitate in deionized water, put it into a dialysis bag with a molecular weight cut-off of 8000 - 14000, and continuously dialyze for 2 - 7 days, changing the deionized water every day until the pH is close to neutral. Ultrasonic dispersion: Treat the dialyzed GO dispersion with ultrasonic waves (such as 400 W, 100 kHz) for 30 minutes to promote sheet delamination. Centrifugation and drying: Centrifuge to remove the unpeeled graphite oxide, and freeze-dry the supernatant (-60 °C pre-freezing for 8 hours + vacuum drying for 24 hours) to obtain a sponge-like graphene oxide solid. Then reduce it by chemical reduction method to obtain a graphene dispersion.

[0063] 1.3, Phosphorene / graphene composite

[0064] Mix the phosphorene dispersion prepared in step 1.1 and the graphene dispersion prepared in step 1.2 according to (phosphorene: graphene mass ratio = 7:3), stir evenly, and then remove the solvent by methods such as vacuum filtration or spray drying to obtain a phosphorene / graphene composite material (such as Figure 1 ).

[0065] It is mainly composed of black phosphorene and graphene. The overall material shows an irregular sheet-like morphology, with obvious wrinkles and folds on the surface. The layered characteristics of black phosphorene and graphene are clearly visible in the image. The layer spacing of black phosphorene is relatively large, and its surface shows a certain degree of wrinkling, while graphene appears as thinner sheets, and in some areas, it may form close contact with black phosphorene. This layered structure helps to improve the conductivity and mechanical properties of the composite material. In some areas, an obvious interface can be seen between black phosphorene and graphene. There may be certain gaps or incompletely bonded areas at the interface, which may be due to the lattice mismatch of the two materials or the preparation process. Black phosphorene is prone to volume expansion during charge and discharge, resulting in electrode pulverization and capacity attenuation. The addition of graphene can provide mechanical support, relieve the volume expansion of black phosphorene, and improve the cycle stability of the composite material.

[0066] 2. Li7P3S 11 Preparation of Sulfide Solid Electrolyte

[0067] Prepare Li7P3S by mechanical ball milling method 11 Sulfide solid electrolyte. The specific steps are as follows: Mix Li2S and P2S5 powders according to the stoichiometric ratio, put them into a ball milling jar, and carry out high-energy ball milling for a certain time under an argon atmosphere (the abrasive ball is a zirconia ball, the ball-to-material ratio is 10:11, the rotation speed is 400 rpm, and the ball milling time is 20 hours) to obtain Li7P3S 11 Sulfide solid electrolyte powder

[0068] 3. Preparation of Cathode Active Material

[0069] Mix the phosphorene / graphene composite material, sulfide solid electrolyte (Li7P3S 11 ) and conductive agent (carbon black) evenly according to the mass ratio of 7:2:1, and grind (grinding conditions: ball-to-material ratio 10:1, zirconia grinding balls, 300 rpm, time: 8 h; protective atmosphere: high-purity argon) to obtain a phosphorene / graphene composite cathode active material

[0070] Example 2

[0071] This example provides an all-solid-state lithium battery based on Li6PS5Cl sulfide solid electrolyte and phosphorene / graphene composite cathode

[0072] The difference between Example 2 and Example 1 is that in steps 3.1 and 3.2.1, the preparation of Li7P3S 11 sulfide solid electrolyte is replaced with Li6PS5Cl sulfide solid electrolyte

[0073] Preparation of Li6PS5Cl sulfide solid electrolyte: Prepare Li6PS5Cl sulfide solid electrolyte by mechanical ball milling method combined with sintering method; the specific steps are as follows: Mix Li2S, P2S5 and LiCl powders according to the stoichiometric ratio, put them into a ball milling jar, and carry out high-energy ball milling for a certain time ((the abrasive ball is a zirconia ball, the ball-to-material ratio is 10:11, the rotation speed is 400 rpm, and the ball milling time is 20 hours)) to obtain sulfide solid electrolyte powder, then cold press the powder into an electrolyte sheet at 200 MPa, place the electrolyte sheet in a muffle furnace for sintering (480 °C, 10 h, under an argon atmosphere), and finally obtain Li6PS5Cl sulfide solid electrolyte powder

[0074] 3. Preparation of Cathode Active Material

[0075] The phosphorusene / graphene composite material, sulfide solid electrolyte (Li6PS5Cl), and conductive agent (carbon black) are mixed evenly in a mass ratio of 7:2:1, ground (grinding conditions: ball-to-material ratio of 10:1, zirconia grinding balls, 300 rpm for 8 h; protective atmosphere: high-purity argon), and then used as the positive electrode active material.

[0076] Comparative Example 1

[0077] This comparative example provides an all-solid-state lithium battery based on the Li6 P S5Cl sulfide solid electrolyte and NCM811 composite positive electrode. The NCM811 composite positive electrode is composed of NCM811 coated with 70% lithium niobate, 28.5% Li6PS5Cl, and 1.5% graphene.

[0078] Preparation of lithium niobate-coated NCM811: The NCM811 ternary material (Ni:Co:Mn = 8:1:1) and niobium nitrate (Nb(NO3)5) are mixed in a mass ratio of 9:1, added to an ethanol solution and ball-milled for 4 hours (ball-to-material ratio of 10:1, rotation speed of 300 rpm), dried, and then calcined in an oxygen atmosphere at 600 °C for 6 hours to obtain lithium niobate-coated NCM811 particles.

[0079] Preparation of Li6PS5Cl: The same as in Example 2.

[0080] Preparation of the positive electrode composite material: By mass percentage: 70% lithium niobate-coated NCM811, 28.5% Li6PS5Cl solid electrolyte powder, and 1.5% graphene are mixed and ball-milled for 8 hours (under argon protection, ball-to-material ratio of 10:1, rotation speed of 300 rpm) to form a uniform positive electrode active material.

[0081] Comparative Example 2

[0082] This comparative example provides an all-solid-state lithium battery based on Li7P3S 11 sulfide solid electrolyte and NCM811 composite positive electrode. The NCM811 composite positive electrode is composed of 70% lithium niobate-coated NCM811 and 28.5% Li7P3S 11 and 1.5% graphene.

[0083] Preparation of lithium niobate-coated NCM811: The same as in Comparative Example 2;

[0084] Li7P3S 11 Preparation: The same as in Example 1;

[0085] Preparation of the positive electrode composite material: By mass percentage: 70% lithium niobate-coated NCM811, 28.5% Li7P3S 11The solid electrolyte powder is mixed with 1.5% graphene and ball-milled for 8 hours (under argon protection, ball-to-material ratio of 10:1, rotation speed of 300 rpm) to form a uniform positive electrode active material.

[0086] Comparative Example 3

[0087] This comparative example provides an all-solid-state lithium battery based on a Li6PS5Cl sulfide solid electrolyte and a phosphorene positive electrode. The phosphorene positive electrode is directly prepared from the few-layer phosphorene prepared by the liquid-phase exfoliation method in Example 1.

[0088] Preparation of pure phosphorene positive electrode material:

[0089] 1. Preparation of phosphorene

[0090] Few-layer phosphorene powder is obtained by the liquid-phase exfoliation method in Step 1.1 of Example 1, but not compounded with graphene.

[0091] 2. Mixing of positive electrode composite materials

[0092] The pure phosphorene powder, Li6PS5Cl solid electrolyte powder and carbon black conductive agent are mixed in a mass ratio of 7:2:1 and ball-milled for 8 hours (under argon protection, ball-to-material ratio of 10:1).

[0093] Preparation of Li6PS5Cl sulfide electrolyte: The same as Step 2 of Example 2.

[0094] Comparative Example 4

[0095] The difference between this comparative example and the example is that graphene is replaced by carbon nanotubes.

[0096] It includes the following steps:

[0097] 1.1 Preparation of phosphorene dispersion: The same as Example 1

[0098] 1.2 Preparation of carbon nanotube dispersion:

[0099] Multi-walled carbon nanotubes are added to an aqueous surfactant solution containing 0.5 wt% sodium dodecyl sulfate, and the solid content is controlled to be 2 mg / mL. First, magnetic stirring is carried out for 2 hours to pre-disperse the solution, and then it is transferred to an ultrasonic cell disruptor for ultrasonic treatment. The ultrasonic power is set to 500 W and the treatment time is 4 hours to obtain a uniform and stable carbon nanotube dispersion.

[0100] 1.3 Preparation of composite material:

[0101] The phosphorene dispersion prepared in Step 1.1 and the carbon nanotube dispersion prepared in Step 1.2 were mixed at a solid mass ratio of 7:3 and continuously stirred at a speed of 2000 rpm for 6 hours under a nitrogen atmosphere. Subsequently, solid-liquid separation was carried out through a vacuum filtration device (the pore size of the filter membrane was 0.22 μm), and the obtained filter cake was treated in a vacuum drying oven at 60 °C for 12 hours to finally obtain a phosphorene / carbon nanotube composite material.

[0102] Performance test example

[0103] The products prepared in the above examples and comparative examples were assembled as follows:

[0104] 1. Preparation of the positive electrode sheet

[0105] In an inert gas glove box with a water and oxygen content ≤ 0.01 ppm, 14.29 mg of positive electrode active powder was taken out and cold-pressed into a positive electrode sheet in a stainless steel mold with a diameter of 10 mm at 400 Mpa; the loading per unit area was 10 mg·cm -2 .

[0106] 2. Negative electrode layer

[0107] Lithium metal sheet (size 8 cm × 10 cm, thickness 100 μm, surface pretreatment of lithium hydride)

[0108] 3. Electrolyte layer

[0109] 120 mg of a sulfide electrolyte (Li7P3S 11 electrolyte) was weighed and pressed into a tablet, and all were pressed into a thin sheet with an area of 0.785 cm 2 and a thickness of 1 mm as the electrolyte layer.

[0110] 4. Current collector

[0111] Positive electrode side: Aluminum foil current collector

[0112] Negative electrode side: Stainless steel current collector (316L stainless steel sheet, thickness 0.2 mm, surface sandblasted);

[0113] 5. Stacking and encapsulation

[0114] In a dry argon atmosphere glove box; the all-solid-state lithium battery was assembled in the following stacking order.

[0115] Stainless steel current collector → Lithium metal negative electrode → Li7P3S 11 Electrolyte layer → Positive electrode sheet → Aluminum foil current collector.

[0116] Finally, cyclic discharge was carried out. First, charge and discharge at 0.1C for two cycles, and then perform long-term cyclic testing at 1C. The initial efficiency, number of cyclic cycles, and capacity retention rate in subsequent tests were measured, and the results are shown in Table 1: Figure 2It is a comparison chart of the long cycle performance between Example 1 and Comparative Example 1.

[0117] Table 1

[0118]

[0119] It can be seen from Table 1 that the experimental results show that black phosphorus is prone to volume expansion during charge and discharge, leading to electrode pulverization and capacity decay. The addition of graphene can provide mechanical support, relieve the volume expansion of black phosphorus, and improve the cycle stability of the composite material. The all-solid-state lithium battery prepared in this example can exhibit a high specific capacity, good cycle performance and rate performance, as well as excellent safety.

[0120] 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 does not affect the essence of the present invention.

Claims

1. A phosphorus / graphene composite cathode active material for all-solid-state lithium batteries, characterized in that, The raw materials of the phosphorusene / graphene composite cathode active material include phosphorusene, graphene, and a sulfide solid electrolyte; the phosphorusene is few-layer phosphorusene or monolayer phosphorusene.

2. The phosphorene / graphene composite cathode active material according to claim 1, wherein The few-layer phosphorusene is 2-10 layers of phosphorusene.

3. The phosphorusene / graphene composite cathode active material according to claim 1, wherein, The sulfide solid electrolyte is selected from Li6PS5Cl or Li7P3S 11 .

4. A preparation method of a phosphorene / graphene composite cathode active material, characterized in that, It includes the following steps: S1. Mix the black phosphorus raw material with a polar organic solvent and disperse it by ultrasonic treatment to obtain a phosphorusene dispersion; separate the phosphorusene dispersion by density gradient centrifugation to obtain a few-layer phosphorusene dispersion; Perform pre-oxidation, intercalation oxidation with a strong oxidant, hydrolysis exfoliation, and reduction treatment on the graphite raw material in sequence to obtain a carbon-based two-dimensional material dispersion; S2. Mix the few-layer phosphorusene dispersion and the carbon-based two-dimensional material dispersion according to a mass ratio of (5:5) to (9:1), and remove the solvent to form a phosphorusene / graphene composite; S3. Mix the phosphorusene / graphene composite, the sulfide solid electrolyte, and the conductive agent evenly and grind them to obtain the phosphorusene / graphene composite cathode active material.

5. The preparation method according to claim 4, characterized in that, In the step S1: The polar organic solvent is N-methylpyrrolidone; the duration of ultrasonic dispersion is 4-8 hours; And / or, the density gradient centrifugation method uses a sucrose gradient medium, the centrifugation speed is 10,000-20,000 rpm, and the centrifugation time is 2-4 hours; And / or, the pre-oxidation treatment is to react graphite powder with phosphorus pentoxide and potassium persulfate in concentrated sulfuric acid at 70-90 °C for 2-4 hours; And / or, the strong oxidant is potassium permanganate, and the intercalation oxidation reaction is carried out under ice bath conditions, and the reaction temperature ≤ 30 °C.

6. The preparation method according to claim 4, characterized in that, In the step S2: The mass ratio of the phosphorusene dispersion to the carbon-based two-dimensional material dispersion is 5-7:3; And / or, the method for removing the solvent is vacuum filtration or spray drying.

7. The preparation method according to claim 4, characterized in that, In the step S3, The sulfide solid electrolyte is Li6PS5Cl or Li7P3S 11 ; And / or, the conductive agent is selected from at least one of carbon black, acetylene black, and carbon nanotubes; And / or, the grinding conditions are ball milling under argon protection, the ball-to-material ratio is 10-20:1, the rotation speed is 300-500 rpm, and the grinding time is 8-10 hours.

8. The preparation method according to claim 4, characterized in that, In the step S3, the mass ratio of the phosphorusene / graphene composite, the sulfide solid electrolyte, and the conductive agent is (6-8):(1-3):(0.5-1.5).

9. A phosphorusene / graphene composite cathode active material prepared by the preparation method according to any one of claims 4-8.

10. A all-solid-state battery containing the phosphorusene / graphene composite cathode active material according to claim 9.

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