A positive electrode material and preparation method thereof

Abstract

A positive electrode material and its preparation method, belonging to the field of lithium-ion batteries, overcome the shortcomings of existing all-solid-state batteries in electrochemical performance, especially poor rate performance. The preparation method of the positive electrode material of the present invention comprises raw materials including a sulfur-containing argyrodite-type sulfide solid electrolyte, an active material, and a conductive agent. The preparation method comprises the following steps: weighing the raw materials, subjecting the sulfur-containing argyrodite-type sulfide solid electrolyte to secondary ball milling according to the mass content of the active material, and then mixing and grinding all the raw materials to produce the positive electrode material; when the mass content of the active material is 50% ≤ w < 70%, no secondary ball milling is performed, or the secondary ball milling conditions are: ball-to-material ratio z < 18, or ball milling time w < 3 hours; when the mass content of the active material is 70% ≤ w ≤ 80%, the secondary ball milling conditions are: ball-to-material ratio z satisfies 40> z ≥ 18, and ball milling time w satisfies 5 hours> w ≥ 3 hours.

Description

Technical Field

[0001] The present invention belongs to the field of lithium-ion batteries, and in particular relates to a positive electrode material and a preparation method thereof. Background Art

[0002] Lithium-ion batteries are one of the key technologies for solving energy problems. Over the past few decades, they have been widely used as high-performance energy storage devices. Energy density is the primary indicator of power battery performance, but the energy density of traditional lithium-ion battery cathode materials is currently approaching the theoretical value. In addition, with the growth of lithium-ion battery use, the frequency of safety accidents such as spontaneous combustion and explosion has also increased significantly. Safety issues have become a key issue hindering the further application and development of lithium-ion batteries. The main cause of lithium-ion battery safety accidents is the use of flammable organic electrolytes in the batteries, which are prone to combustion and fire when the batteries thermally run away.

[0003] All-solid-state batteries utilize solid electrolytes for ion conduction, making them non-flammable and non-volatile compared to traditional liquid batteries, significantly improving battery safety. While addressing safety concerns, solid-state lithium-ion battery systems also have the potential to increase energy density. As the next generation of high-energy-density mainstream technology, all-solid-state batteries have become a research hotspot.

[0004] Solid-state electrolytes are the core material of solid-state batteries. Due to their inherent physical and chemical properties, solid-state electrolytes are non-volatile, non-flammable, and mechanically strong. They offer unique advantages such as preventing internal short circuits, electrolyte leakage, and the absence of flammable or explosive components. They are expected to become the key to addressing the safety of lithium-ion secondary batteries. However, compared to liquid lithium-ion batteries, all-solid-state batteries suffer from higher interfacial impedance due to solid-solid contact, resulting in poor electrochemical performance, particularly rate capability. Summary of the Invention

[0005] Therefore, the technical problem to be solved by the present invention is to overcome the defect of poor rate performance in all-solid-state batteries in the prior art, thereby providing a positive electrode material and a preparation method thereof.

[0006] To this end, the present invention provides the following technical solutions.

[0007] The present invention provides a method for preparing a positive electrode material, wherein the raw materials include sulfur-containing argyrodite-type sulfide solid electrolyte, active material and conductive agent;

[0008] The preparation method comprises the following steps:

[0009] Weighing raw materials, ball-milling the sulfur-containing argyrodite-type sulfide solid electrolyte twice according to the mass content of the active material, and then mixing and grinding all the raw materials to obtain a positive electrode material;

[0010] When the mass content of the active material is 50%≤w<70%, the sulfur-containing argyrodite-type sulfide solid electrolyte is not subjected to secondary ball milling or the secondary ball milling conditions are: ball-to-material ratio z<18, or ball milling time w<3h;

[0011] When the mass content of the active material is 70%≤w≤80%, for the sulfur-containing argyrodite-type sulfide solid electrolyte, the secondary ball milling conditions are: the ball-to-material ratio z satisfies 40>z≥18, and the ball milling time w satisfies 5h>w≥3h.

[0012] The ball-to-material ratio refers to the mass ratio of the total mass of the ball to the mass of the sulfur-containing argyrodite-type sulfide solid electrolyte.

[0013] The secondary ball milling is performed under an inert atmosphere, preferably an argon atmosphere.

[0014] Furthermore, the mass ratio of the sulfur-containing argyrodite-type sulfide solid electrolyte to the conductive agent is (7-9):1.

[0015] Furthermore, at least one of the following conditions (1)-(3) is satisfied:

[0016] (1) The sulfur-containing argyrodite-type sulfide solid electrolyte is Li6PS5Cl;

[0017] (2) The active material is LiNi x Co y M 1-x-y O2, where M = Mn or Al, 0.6 ≤ x < 1, 0.01 < y ≤ 0.2;

[0018] (3) The conductive agent includes at least one of carbon black, conductive graphite, nanocarbon fiber, carbon nanotube or graphene.

[0019] Furthermore, when the mass content of the active substance is 50%≤w<70%, the conditions for the secondary ball milling are z<18, and the ball milling time w≤5h.

[0020] The active material is preferably NCM90, and the conductive agent is preferably VGCF.

[0021] Furthermore, the preparation method of the sulfur-containing argyrotechnical sulfide solid electrolyte includes: mixing precursor materials Li2S, P2S5 and LiCl according to the stoichiometric ratio of the sulfur-containing argyrotechnical sulfide solid electrolyte, ball milling for the first time, and sintering to obtain the sulfur-containing argyrotechnical sulfide solid electrolyte.

[0022] Furthermore, the first ball milling includes primary ball milling, manual milling and secondary ball milling; the mixture obtained by mixing the precursor materials is subjected to primary ball milling, and then manual milling and secondary ball milling are alternately performed until the powder color becomes uniform white.

[0023] Alternate between manual grinding and secondary ball milling. The sample in the ball mill jar can be manually chiseled off from the jar wall, and then placed on the ball mill for ball milling after manual grinding to ensure uniform ball milling.

[0024] Furthermore, the rotation speed of the first-stage ball mill is 200-220 r / min, and the ball milling time is 12-15 h; the rotation speed of the second-stage ball mill is 300-320 r / min, and the ball milling time is 12-15 h.

[0025] Furthermore, the sintering is carried out in a muffle furnace by heating the material at a rate of 3-5°C / min and keeping the temperature at 550±5°C for 12-15h.

[0026] Furthermore, the secondary ball milling is carried out under an inert atmosphere;

[0027] The speed of the secondary ball milling is 150-250 r / min. The powder after the secondary ball milling is manually ground and then sieved using a 400-600 mesh standard sample sieving method. The sample after ball milling is initially accumulated, which can be dispersed by manual grinding and sieving after ball milling.

[0028] A positive electrode material prepared according to the above method.

[0029] In a specific embodiment, the secondary ball milling is carried out in a zirconia ball milling jar, and large zirconia balls (3.254 g / piece) and small zirconia balls (0.394 g / piece) are placed in each ball milling jar in a ratio of 1:1. The mass of the solid electrolyte ball milled each time is 0.5 g to 4 g.

[0030] The use of a sample sieve for sulfur-containing argyrodite-type sulfide solid electrolyte can avoid the aggregation of electrolyte particles.

[0031] The technical solution of the present invention has the following advantages:

[0032] 1. The preparation method of the positive electrode material provided by the present invention comprises the following steps: weighing raw materials, performing secondary ball milling on the sulfur-containing argyrodite-type sulfide solid electrolyte according to the mass content of the active material, and then mixing all the raw materials to prepare the positive electrode material; when the mass content of the active material is 50%≤w<70%, the secondary ball milling conditions are: ball-to-material ratio <18, or ball milling time <3h; when the mass content of the active material is 70%≤w≤80%, the secondary ball milling conditions are: ball-to-material ratio z satisfies 40>z≥18, and ball milling time w satisfies 5h>w≥3h.

[0033] The content of active substances in the positive electrode material is generally 50% to 80%. As the content of active substances changes, different ball milling conditions of the sulfur-containing argyrodite-type sulfide solid electrolyte will cause changes in the ionic conductivity of the electrolyte and its contact with the active substances, thereby affecting the rate performance of the lithium-ion battery.

[0034] The higher the particle size of the sulfur-containing argyrodite-type sulfide solid electrolyte after secondary ball milling, the more significant the decrease in ionic conductivity. When the active material content is low, 50% ≤ w < 70%, the electrolyte's ionic conductivity is the dominant factor affecting lithium-ion battery performance. Insufficient ball milling or no ball milling of the sulfur-containing argyrodite-type sulfide solid electrolyte can improve the rate performance of the lithium-ion battery. When the active material content is high, 70% ≤ w ≤ 80%, the contact between the electrolyte and the active material is the dominant factor affecting lithium-ion battery performance. Insufficient ball milling of the sulfur-containing argyrodite-type sulfide solid electrolyte can improve the rate performance of the lithium-ion battery.

[0035] 2. The present invention provides a method for preparing a cathode material, wherein the initial ball milling comprises primary ball milling, manual milling, and secondary ball milling. The mixture obtained by mixing the precursor materials is subjected to primary ball milling, and then manual milling and secondary ball milling are performed alternately until the powder color becomes uniform white. The combination of primary ball milling, manual milling, and secondary ball milling in the initial ball milling facilitates the sufficient refinement and mixing of the precursor materials, thereby promoting the improvement of the ionic conductivity of the electrolyte in the subsequent sintering process.

[0036] The present invention adopts a sulfur-containing argyrodite-type sulfide solid electrolyte that is subjected to secondary ball milling to prepare a ternary positive electrode material, thereby improving the energy density of the positive electrode material while ensuring the safety of the lithium-ion battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0038] Figure 1 is the XRD pattern of the Li6PS5Cl electrolyte in Examples 1-3;

[0039] Figure 2 1C charge-discharge curves of Example 1, Example 2 and Comparative Example 1;

[0040] Figure 3 2C charge-discharge curves of Example 1, Example 2, and Comparative Example 1;

[0041] Figure 4 1C charge and discharge curves of Example 3, Comparative Example 2, and Comparative Example 3. DETAILED DESCRIPTION

[0042] The following examples are provided for a better understanding of the present invention and are not intended to limit the best mode of implementation. They do not limit the content and scope of protection of the present invention. Any product identical or similar to the present invention obtained by anyone under the guidance of the present invention or by combining the features of the present invention with other prior arts shall fall within the scope of protection of the present invention.

[0043] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in this field can be used. If the manufacturer of the reagents or instruments is not specified, they are all commercially available conventional reagents.

[0044] Example 1

[0045] This embodiment provides a method for preparing a positive electrode material, wherein the active material NCM90 (i.e. LiNi 0.9 Co 0.05 M 0.05 The mass ratio of the electrolyte (O2), Li6PS5Cl and conductive agent (VGCF) (manufacturer: Shenzhen Kejing Zhida) is 60:35:5.

[0046] The following steps are involved:

[0047] (1) Preparation of Li6PS5Cl electrolyte:

[0048] In a glove box, the precursor materials Li2S, P2S5 and LiCl were mixed in a molar ratio of 2.5:0.5:1 and placed in a zirconia ball mill for the first ball milling.

[0049] The specific operation of the first ball milling is as follows: primary ball milling: place 15 large zirconia balls (3.254 g / piece) and 15 small zirconia balls (0.394 g / piece) in each ball mill jar, seal it, and then ball mill it in a vertical planetary ball mill at a speed of 200 r / min for 12 hours to mix it evenly; manual grinding: crush the powder and grind it into powder manually; secondary ball milling: after mixing evenly, put it into the ball mill again and ball mill it at a speed of 300 r / min. Take it out and grind it into powder manually every 12 hours, and alternate between manual grinding and secondary ball milling until the color of the powder becomes uniform white.

[0050] The powder was then placed in a muffle furnace and heated at a rate of 5°C / min and kept at 550°C for 12 h to obtain Li6PS5Cl electrolyte.

[0051] (2) Secondary ball milling of Li6PS5Cl electrolyte:

[0052] The Li6PS5Cl electrolyte prepared in (1) was placed in a zirconia ball mill for secondary ball milling. The zirconia ball mill contained a 1:1 ratio of large zirconia balls (3.254 g / ball) to small zirconia balls (0.394 g / ball). The mass of the electrolyte in the mill was 0.5 g to 4 g. The ball-to-material ratio was set to 9.12, the milling time was 5 h, and the speed was 200 r / min. After ball milling, manual grinding was performed.

[0053] (3) Use a 400-mesh standard sample sieve to avoid aggregation of electrolyte particles.

[0054] (4) The active material NCM90, the Li6PS5Cl electrolyte obtained in step (2), and the conductive agent VGCF are mixed in proportion, and the mixed material is ground in a mortar for half an hour to obtain a ternary positive electrode material.

[0055] Example 2

[0056] This embodiment provides a method for preparing a positive electrode material, which is basically the same as that of Example 1, except that this embodiment does not include (2) and the Li6PS5Cl electrolyte is not subjected to secondary ball milling.

[0057] Example 3

[0058] This embodiment provides a method for preparing a positive electrode material, wherein the mass ratio of the active material NCM90, the Li6PS5Cl electrolyte, and the conductive agent VGCF is 80:17.5:2.5.

[0059] The following steps are involved:

[0060] (1) Preparation of Li6PS5Cl electrolyte:

[0061] In a glove box, the precursor materials Li2S, P2S5 and LiCl were mixed in a molar ratio of 2.5:0.5:1 and placed in a zirconia ball mill for the first ball milling.

[0062] The specific operation of the first ball milling is as follows: primary ball milling: place 15 large zirconia balls (3.254 g / piece) and 15 small zirconia balls (0.394 g / piece) in each ball mill jar, seal it, and then ball mill it in a vertical planetary ball mill at a speed of 200 r / min for 12 hours to mix it evenly; manual grinding: crush the powder and grind it into powder manually; secondary ball milling: after mixing evenly, put it into the ball mill again and ball mill it at a speed of 300 r / min. Take it out and grind it into powder manually every 12 hours, and alternate between manual grinding and secondary ball milling until the color of the powder becomes uniform white.

[0063] The powder was then placed in a muffle furnace and heated at a rate of 5°C / min and kept at 550°C for 12 h to obtain Li6PS5Cl electrolyte.

[0064] (2) Secondary ball milling of Li6PS5Cl electrolyte:

[0065] The Li6PS5Cl electrolyte prepared in (1) was placed in a zirconia ball mill for secondary ball milling. The zirconia ball mill was filled with large zirconia balls (3.254 g / ball) and small zirconia balls (0.394 g / ball) in a 1:1 ratio. The mass of the electrolyte in the ball mill was 0.5 g to 4 g. The ball-to-material ratio was set to 18.24, the ball milling time was 3 h, and the speed was 200 r / min. After ball milling, manual grinding was performed.

[0066] (3) Use a 400-mesh standard sample sieve to avoid aggregation of electrolyte particles.

[0067] (4) The active material NCM90, the Li6PS5Cl electrolyte obtained in step (2), and the conductive agent VGCF are mixed in proportion, and the mixed material is ground in a mortar for half an hour to obtain a ternary positive electrode material.

[0068] Example 4

[0069] This embodiment provides a method for preparing a positive electrode material, wherein the mass ratio of the active material NCM90, the Li6PS5Cl electrolyte, and the conductive agent VGCF is 50:45:5.

[0070] The following steps are involved:

[0071] (1) Preparation of Li6PS5Cl electrolyte:

[0072] In a glove box, the precursor materials Li2S, P2S5 and LiCl were mixed in a molar ratio of 2.5:0.5:1 and placed in a zirconia ball mill for the first ball milling.

[0073] The specific operation of the first ball milling is as follows: primary ball milling: place 15 large zirconia balls (3.254 g / piece) and 15 small zirconia balls (0.394 g / piece) in each ball mill jar, seal it, and then ball mill it in a vertical planetary ball mill at a speed of 220 r / min for 15 hours to mix it evenly; manual grinding: crush the powder and grind it into powder manually; secondary ball milling: after mixing evenly, put it into the ball mill again and ball mill it at a speed of 320 r / min. Take it out and grind it into powder manually every 15 hours, and alternate between manual grinding and secondary ball milling until the powder color becomes uniform white.

[0074] The powder was then placed in a muffle furnace and heated at a rate of 3°C / min and kept at 545°C for 15 h to obtain Li6PS5Cl electrolyte.

[0075] (2) Secondary ball milling of Li6PS5Cl electrolyte:

[0076] The Li6PS5Cl electrolyte prepared in (1) was placed in a zirconia ball mill for secondary ball milling. The zirconia ball mill contained a 1:1 ratio of large zirconia balls (3.254 g / ball) to small zirconia balls (0.394 g / ball). The mass of the electrolyte in the mill was 0.5 g to 4 g. The ball-to-material ratio was set to 15, the milling time was 3 h, and the speed was 150 r / min. After ball milling, manual grinding was performed.

[0077] (3) Use a 400-mesh standard sample sieve to avoid aggregation of electrolyte particles.

[0078] (4) The active material NCM90, the Li6PS5Cl electrolyte obtained in step (2), and the conductive agent VGCF are mixed in proportion, and the mixed material is ground in a mortar for half an hour to obtain a ternary positive electrode material.

[0079] Example 5

[0080] This embodiment provides a method for preparing a positive electrode material, wherein the mass ratio of the active material NCM90, the Li6PS5Cl electrolyte, and the conductive agent VGCF is 75:22:3.

[0081] The following steps are involved:

[0082] (1) Preparation of Li6PS5Cl electrolyte:

[0083] In a glove box, the precursor materials Li2S, P2S5 and LiCl were mixed in a molar ratio of 2.5:0.5:1 and placed in a zirconia ball mill for the first ball milling.

[0084] The specific operation of the first ball milling is as follows: primary ball milling: place 15 large zirconia balls (3.254 g / piece) and 15 small zirconia balls (0.394 g / piece) in each ball mill jar, seal it, and then ball mill it in a vertical planetary ball mill at a speed of 210 r / min for 14 hours to mix it evenly; manual grinding: crush the powder and grind it into powder manually; secondary ball milling: after mixing evenly, put it into the ball mill again and ball mill it at a speed of 310 r / min. Take it out and grind it into powder manually every 14 hours, and alternate between manual grinding and secondary ball milling until the color of the powder becomes uniform white.

[0085] The powder was then placed in a muffle furnace and heated at a rate of 4°C / min and kept at 555°C for 13 h to obtain Li6PS5Cl electrolyte.

[0086] (2) Secondary ball milling of Li6PS5Cl electrolyte:

[0087] The Li6PS5Cl electrolyte prepared in (1) was placed in a zirconia ball mill for secondary ball milling. The zirconia ball mill contained a 1:1 ratio of large zirconia balls (3.254 g / ball) to small zirconia balls (0.394 g / ball). The mass of the electrolyte in the mill was 0.5 g to 4 g. The ball-to-material ratio was set to 2:4, the milling time was 4 h, and the speed was 250 r / min. After ball milling, manual grinding was performed.

[0088] (3) Use a 400-mesh standard sample sieve to avoid aggregation of electrolyte particles.

[0089] (4) The active material NCM90, the Li6PS5Cl electrolyte obtained in step (2), and the conductive agent VGCF are mixed in proportion, and the mixed material is ground in a mortar for half an hour to obtain a ternary positive electrode material.

[0090] Comparative Example 1

[0091] This comparative example is basically the same as Example 1, except that, in this comparative example, the ball-to-material ratio is set to 18.24 and the ball milling time is 3 h.

[0092] Comparative Example 2

[0093] This comparative example is basically the same as Example 3, except that, in this comparative example, the ball-to-material ratio is set to 9.12 and the ball milling time is 5 h.

[0094] Comparative Example 3

[0095] This comparative example is basically the same as Example 3, except that (2) is not included in this comparative example, and the Li6PS5Cl electrolyte is not subjected to secondary ball milling in this comparative example.

[0096] Test example

[0097] (1) The electrolytes obtained after step (2) in Example 1 and Example 3 and the electrolyte not subjected to secondary ball milling in Example 2 were subjected to structural analysis by X-ray diffractometer, and the following results were obtained: Figure 1 The standard XRD pattern was calculated using the Vesta software using the cif file of the Li6PS5Cl electrolyte with the ICSD database number 131109. Since Li6PS5Cl is unstable in air, a layer of plastic wrap was wrapped around the sample tank to isolate it from air during the analysis.

[0098] pass Figure 1It can be seen that the positions of the diffraction peaks in Examples 1-3 are consistent with the calculated standard XRD patterns, indicating that the Li6PS5Cl electrolyte was successfully prepared and that the subsequent secondary ball milling did not affect its crystal structure. In addition, the XRD peak intensity of the Li6PS5Cl electrolyte was significantly reduced after the secondary ball milling, with a wider half-peak width, indicating that the grain size of the Li6PS5Cl electrolyte decreased after the ball milling treatment.

[0099] (2) Electrochemical performance test

[0100] The electrochemical performance test was carried out in a 55° C. constant temperature box using the positive electrode materials in the examples and comparative examples as the positive electrode, with a positive electrode loading of 5 mg and lithium metal as the negative electrode.

[0101] The test results of Examples 1, 2 and Comparative Example 1 are as follows: Figure 2 、 Figure 3 At high rates of 1C and 2C, the first-cycle discharge specific capacity of Comparative Example 1 is lower than that of Examples 1 and 2, and the first-cycle discharge specific capacity of Example 2 without secondary ball milling is the highest.

[0102] It is proved that when the content w of the positive electrode active material is in the range of 50%≤w<70%, the solid electrolyte content in the positive electrode material is sufficient and the contact between the electrolyte and the active material is sufficient. However, under a larger current density, sufficient ball milling makes the ionic conductivity of the electrolyte decrease more significantly, resulting in the lithium ions in the active material unable to be released and embedded in time, thereby resulting in the discharge specific capacity performance of the sufficiently ball-milled comparative example 1 at a high rate being worse than that of the insufficiently ball-milled example 1 and the un-ball-milled example 2.

[0103] The test results of Example 3, Comparative Examples 2 and 3 are as follows: Figure 4 At a relatively high charge and discharge rate, the first cycle discharge specific capacity of Example 3, which was sufficiently ball-milled, was significantly greater than that of Comparative Example 2, which was insufficiently ball-milled, and Comparative Example 3, which was not subjected to secondary ball milling.

[0104] The results demonstrate that fully ball-milling the Li6PS5Cl electrolyte within the range of 70% ≤ w ≤ 80% positive electrode active material content can improve the rate performance of lithium-ion batteries. Increasing the positive electrode active material content reduces the electrolyte content in the positive electrode material, which in turn reduces the lithium ion transport capacity of the positive electrode material. However, in Example 3, where the electrolyte was fully ball-milled, although its conductivity was reduced, the electrolyte particle size was effectively refined, thereby improving the contact between the electrolyte and the active material in the positive electrode material, enhancing the lithium ion transport efficiency of the positive electrode, and thus increasing the battery's specific discharge capacity.

[0105] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A method for preparing a positive electrode material, characterized in that: The raw materials include sulfur-containing argyrogermanite-type sulfide solid electrolyte, active material and conductive agent; The preparation method comprises the following steps: Weighing raw materials, ball-milling the sulfur-containing argyrodite-type sulfide solid electrolyte twice according to the mass content of the active material, and then mixing and grinding all the raw materials to obtain a positive electrode material; When the mass content of the active substance is 50%≤w<70%, the conditions for secondary ball milling are: ball-to-material ratio z<18, and ball milling time w≤5h; when the mass content of the active substance is 70%≤w≤80%, the conditions for secondary ball milling are: ball-to-material ratio z satisfies 40>z≥18, and ball milling time w satisfies 5h>w≥3h; The sulfur-containing argyrodite-type sulfide solid electrolyte is Li6PS5Cl; The active material is LiNi x Co y M 1-x-y O2, where M = Mn or Al, 0.6 ≤ x < 1, 0.01 < y ≤ 0.

2.

2. The method for preparing the positive electrode material according to claim 1, wherein: The mass ratio of the sulfur-containing argyrodite-type sulfide solid electrolyte to the conductive agent is (7-9):

1.

3. The method for preparing the positive electrode material according to claim 1, wherein: The conductive agent includes at least one of carbon black, conductive graphite, nano-carbon fiber, carbon nanotube or graphene.

4. The method for preparing the positive electrode material according to claim 3, wherein: The preparation method of the sulfur-containing argyrodite-type sulfide solid electrolyte comprises: mixing precursor materials Li2S, P2S5 and LiCl according to the stoichiometric ratio of the sulfur-containing argyrodite-type sulfide solid electrolyte, ball milling for the first time, and sintering to obtain the sulfur-containing argyrodite-type sulfide solid electrolyte.

5. The method for preparing the positive electrode material according to claim 4, wherein: The first ball milling includes primary ball milling, manual milling and secondary ball milling; the mixture obtained by mixing the precursor materials is subjected to primary ball milling, and then manual milling and secondary ball milling are alternately performed until the powder color becomes uniform white.

6. The method for preparing the positive electrode material according to claim 5, wherein: The rotation speed of the first-stage ball mill is 200-220 r / min, and the ball milling time is 12-15 h; the rotation speed of the second-stage ball mill is 300-320 r / min, and the ball milling time is 12-15 h.

7. The method for preparing the positive electrode material according to claim 4, wherein: The sintering is carried out in a muffle furnace by heating the temperature at a rate of 3-5°C / min and keeping the temperature at 550±5°C for 12-15h.

8. The method for preparing a positive electrode material according to any one of claims 1 to 3, characterized in that: The secondary ball milling is carried out under an inert atmosphere; The rotation speed of the secondary ball milling is 150-250 r / min. The powder after the secondary ball milling is manually ground and then sieved using a standard 400-500 mesh sieve.

9. A positive electrode material prepared by the method according to any one of claims 1 to 8.

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