Preparation method for battery positive electrode material, battery positive electrode, and all-solid-state battery

Abstract

A preparation method for a battery positive electrode material, a battery positive electrode, and an all-solid-state battery. The preparation method for a battery positive electrode material comprises: dissolving a sulfide solid-state electrolyte in an organic solvent to form a solution; and dispersing a positive electrode active material into the solution, and then carrying out drying treatment, to obtain a battery positive electrode material in which the positive electrode active material is coated with the sulfide solid-state electrolyte. The preparation method can increase the contact area between the solid-state electrolyte and the positive electrode active material, effectively solves the problem of small interfacial contact area between conventional solid-state electrolytes and positive electrode active materials, and thus enhances the capability of ions to rapidly intercalate into or deintercalate out of positive electrode active materials and facilitates transport of ions and utilization of capacity.

Description

Preparation method of battery positive electrode material, battery positive electrode and all-solid-state battery

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This patent application claims priority to the Chinese patent application filed on June 26, 2023, with application number 202310758999.5 and invention name “A method for preparing a battery positive electrode material, a battery positive electrode and an all-solid-state battery”. The full text of the application is incorporated herein by reference. Technical Field

[0003] The present application relates to the technical field of secondary batteries, and in particular to a method for preparing a battery positive electrode material, a battery positive electrode, and an all-solid-state battery. Background Art

[0004] Electrolyte is an indispensable component of all-solid-state batteries. It not only plays the role of conducting ions between the positive and negative electrodes, but also has a key impact on the battery's specific energy, safety, cycle performance, rate performance and cost.

[0005] Currently, the electrolytes in traditional all-solid-state batteries, such as lithium-ion batteries, are liquid electrolytes. However, since liquid electrolytes are organic substances with a low flash point, they can ignite under high-current discharge or overcharge conditions, causing the lithium-ion battery to catch fire and explode. Furthermore, organic liquids are prone to leakage, resulting in poor cycle performance and safety. Furthermore, the energy density of liquid lithium-ion batteries currently using a high-nickel positive electrode and silicon-based negative electrode system is approximately 350 Wh / kg, which may be close to the maximum energy density of liquid lithium-ion batteries. Therefore, the development of lithium-ion batteries with high safety performance and high energy density is urgent.

[0006] Summary of the Invention

[0007] The present application provides a method for preparing a battery positive electrode material, a battery positive electrode and an all-solid-state battery.

[0008] On the one hand, the present application provides a method for preparing a battery positive electrode material, comprising: dissolving a sulfide solid electrolyte in an organic solvent to form a solution; dispersing a positive electrode active material into the solution; and drying the solution to obtain a battery positive electrode material in which the positive electrode active material is coated with a sulfide solid electrolyte.

[0009] In one embodiment, the organic solvent comprises at least one of ethanol, acetonitrile, N-methylformamide, and tetrahydrofuran. Preferably, the organic solvent comprises ethanol.

[0010] In one embodiment, before dissolving the sulfide solid electrolyte in the organic solvent to form the solution, the method further comprises: adding a desiccant to the organic solvent and then allowing the solvent to stand to obtain an anhydrous organic solvent.

[0011] In one embodiment, the desiccant comprises molecular sieves.

[0012] In one embodiment, the water content of the anhydrous organic solvent is less than 50 ppm.

[0013] In one embodiment, the usage ratio of the sulfide solid electrolyte, the organic solvent, and the positive electrode active material is 0.002-0.03 g:5-10 mL:1 g.

[0014] Preferably, the usage ratio of the sulfide solid electrolyte, the organic solvent and the positive electrode active material is 0.002-0.01 g:5-10 mL:1 g.

[0015] In one embodiment, the thickness of the coating layer formed by the sulfide solid electrolyte coating the positive electrode active material is 1 to 10 nm.

[0016] In one embodiment, the sulfide solid electrolyte includes Li 7-a PS 6-a X a , Thio-LISICONs and Li 11-x M 2-x P 1+x S 12 wherein X is selected from at least one of chlorine, bromine, and iodine; 0.5≤a≤2; and M is selected from at least one of Ge, Sn, and Si.

[0017] In one embodiment, before dispersing the positive electrode active material into the solution, the positive electrode active material is further subjected to vacuum drying; the vacuum drying treatment temperature is 80 to 120° C., and the vacuum drying treatment time is 5 to 10 hours.

[0018] Preferably, the vacuum drying treatment time is 8 to 10 hours.

[0019] In one embodiment, the vacuum degree of vacuum drying is -0.085 to -0.1 MPa.

[0020] In one embodiment, the positive electrode active material is dispersed in the solution and continuously stirred to ensure uniform dispersion.

[0021] In one embodiment, the average particle size of the sulfide solid electrolyte is 100 nm ≤ D50 ≤ 30 μm; and the average particle size of the positive electrode active material is 10 nm ≤ D50 ≤ 20 μm.

[0022] Preferably, the average particle size of the sulfide solid electrolyte is 1 μm≤D50≤5 μm; and the average particle size of the positive electrode active material is 1 μm≤D50≤8 μm.

[0023] In one embodiment, the positive electrode active material is LiNi x Co y Mn (1-x-y) O2.

[0024] In one embodiment, the shape of the positive electrode active material includes granular, rod-shaped, and sheet-shaped; preferably, the shape of the positive electrode material is granular.

[0025] In one embodiment, the positive electrode active material is a lithium-containing compound coating layer coated on LiNi x Co y Mn (1-x-y) The lithium compound coating layer includes at least one of lithium niobate, lithium tantalate, lithium zirconate, lithium germanate, lithium phosphate, lithium iron phosphate, lithium aluminum titanium phosphate (LATP), lithium lanthanum zirconium oxide (LLZO), lithium silicate, lithium carbonate, lithium oxide, and lithium aluminum oxide.

[0026] Preferably, the lithium compound coating layer includes at least one of lithium niobate and lithium phosphate.

[0027] On the other hand, the present application also provides a battery positive electrode, comprising a battery positive electrode material prepared by any of the above-mentioned methods for preparing a battery positive electrode material, a sulfide solid electrolyte, a conductive agent, and a binder; the mass proportion of the battery positive electrode material is 90% to 95%, the mass proportion of the sulfide solid electrolyte is 2.5% to 4%, the mass proportion of the conductive agent is 1.5% to 4%, and the mass proportion of the binder is 0.5% to 1%.

[0028] In one embodiment, the conductive agent may include at least one of a carbon material, metal particles, and a conductive polymer. Preferably, the conductive agent is a carbon material. The binder may be selected from polytetrafluoroethylene (PTFE) or polyvinylidene fluoride.

[0029] In one embodiment, the prepared battery positive electrode material, sulfide solid electrolyte, conductive agent and binder are mixed and pressed to obtain a battery positive electrode with high surface density.

[0030] On the other hand, the present application also provides an all-solid-state battery, including any of the battery positive electrodes described above.

[0031] In one embodiment, the all-solid-state battery further includes a battery negative electrode and a solid electrolyte membrane disposed between the battery negative electrode and the battery positive electrode.

[0032] In one embodiment, the battery negative electrode comprises lithium, lithium / indium alloy, graphite, silicon, silicon alloy, silicon dioxide, a mixture of silicon dioxide / graphite, or a mixture of silicon dioxide / graphite / silicon. DETAILED DESCRIPTION

[0033] In order to further understand the present application, the preparation method of the battery positive electrode material, the battery positive electrode and the all-solid-state battery provided in the present application are described in detail below in combination with the examples. The protection scope of the present application is not limited to the following examples.

[0034] In recent years, research on solid-state lithium-ion batteries has been highly favored. The electrolyte of a solid-state lithium-ion battery exists in the electrode in the form of a solid (solid-state electrolyte), which has the advantages of being non-volatile, non-combustible, and having fast ion conduction. In addition, solid-state lithium-ion batteries can adapt to higher-capacity positive and negative electrode materials, and the energy density can reach 500Wh / kg. However, the contact performance between the solid-state electrolyte and the positive electrode active material in a solid-state lithium-ion battery is poor. Therefore, it is required to set a larger solid electrolyte content ratio when preparing the positive electrode of a solid-state lithium-ion battery to achieve effective contact between the solid electrolyte and the active material. However, this will undoubtedly greatly reduce the energy density of the solid-state lithium-ion battery.

[0035] In order to solve these problems, the particle size of the solid electrolyte will be reduced. For example, if the particle size of the solid electrolyte is reduced to about 1 micron, the proportion of solid electrolyte in the positive electrode can be reduced to 20% to 15%. However, toxic solvents are usually used to mechanically crush the solid electrolyte, which not only increases the preparation process of solid-state lithium-ion batteries, but also pollutes the environment. Therefore, developing a method for preparing a high-area-density solid-state lithium-ion battery positive electrode to increase the loading capacity of the positive electrode active material is the key to preparing high-energy-density solid-state lithium-ion batteries.

[0036] An embodiment of the present application provides a method for preparing a battery positive electrode material, comprising: dissolving a sulfide solid electrolyte in an organic solvent to form a solution; dispersing a positive electrode active material into the solution; and drying the solution to obtain a battery positive electrode material in which the positive electrode active material is coated with a sulfide solid electrolyte.

[0037] For solid-state batteries, one of the current difficulties is the poor contact performance between particles (i.e., poor solid-solid contact). On the one hand, it will increase the internal resistance of the solid-state battery and reduce the rate of lithium ion deintercalation at the positive electrode, thereby affecting the capacity, rate performance and cycle performance of the positive electrode active material. In order to solve this problem, a larger content of sulfide solid electrolyte is usually used to construct an effective ion transmission channel. As the content of sulfide solid electrolyte increases, the amount of positive electrode active material will decrease, so the output capacity and energy density of the solid-state battery will also decrease accordingly.

[0038] In the above scheme of the present application, a sulfide solid electrolyte layer is constructed on the surface of the positive electrode active material by a wet method, which can increase the contact area between the solid electrolyte and the positive electrode active material, effectively solving the problem of reduced interface contact area between the traditional solid electrolyte and the positive electrode active material, thereby enhancing the ability of ions to quickly embed or de-embed the positive electrode active material, which is beneficial to the transmission of ions and the utilization of capacity. In addition, the formed sulfide solid electrolyte layer can reduce the volume expansion of the positive electrode material due to repeated embedding and de-embedding of ions to a certain extent, and try to avoid the problem of contact failure caused by repeated expansion of the positive electrode material. The preparation method of the positive electrode material of the battery is simple, efficient and low in preparation cost.

[0039] In some embodiments, the organic solvent comprises at least one of ethanol, acetonitrile, N-methylformamide, and tetrahydrofuran. Preferably, the organic solvent comprises ethanol.

[0040] In some embodiments, before dissolving the sulfide solid electrolyte in the organic solvent to form the solution, an organic solvent pretreatment step is further included: adding a desiccant to the organic solvent and then allowing it to stand to obtain an anhydrous organic solvent. This can minimize hydrolysis of the sulfide solid electrolyte.

[0041] In some embodiments, the desiccant includes molecular sieves, but the choice of desiccant is not limited thereto.

[0042] In some embodiments, the water content of the anhydrous organic solvent is less than 50 ppm, thereby ensuring that the water content in the organic solvent is as low as possible and minimizing the hydrolysis reaction of the sulfide solid electrolyte after dissolving in water.

[0043] In some embodiments, the ratio of the sulfide solid electrolyte, the organic solvent, and the positive electrode active material is 0.002-0.03 g: 5-10 mL: 1 g. This allows for the construction of a nanometer-thick solid electrolyte layer on the surface of the positive electrode active material. Preferably, the ratio of the sulfide solid electrolyte, the organic solvent, and the positive electrode active material is 0.002-0.01 g: 5-10 mL: 1 g.

[0044] In some embodiments, the coating layer formed by the sulfide solid electrolyte coating the positive electrode active material has a thickness of 1 to 10 nm. This can prevent the coating layer from being too thin and prone to cracking during charge and discharge, and from being too thick and inhibiting electron transport.

[0045] In some embodiments, the sulfide solid electrolyte includes Li 7-a PS 6-a X a , Thio-LISICONs and Li 11-x M 2-x P 1+x S 12 wherein X is selected from at least one of chlorine, bromine, and iodine; 0.5≤a≤2; and M is selected from at least one of Ge, Sn, and Si.

[0046] In some embodiments, prior to dispersing the positive electrode active material into the solution, the positive electrode active material is vacuum dried at a temperature of 80°C to 120°C for 5 to 10 hours. This prevents the positive electrode active material from being mixed with moisture, which could easily cause hydrolysis of the sulfide solid electrolyte after dispersion into the solution.

[0047] Preferably, the vacuum drying treatment time is 8 to 10 hours.

[0048] In some embodiments, the vacuum degree of vacuum drying is -0.085 to -0.1 MPa, thereby preventing the vacuum degree from being too low and affecting the drying efficiency, and preventing the vacuum degree from being too high and affecting the placement of the positive electrode active material.

[0049] In some embodiments, the positive electrode active material is dispersed in the solution and then continuously stirred to uniformly disperse the positive electrode active material. It should be noted that the stirring method may be magnetic stirring and / or mechanical stirring, but is not limited thereto.

[0050] In some embodiments, the average particle size of the sulfide solid electrolyte is 100 nm ≤ D50 ≤ 30 μm; and the average particle size of the positive electrode active material is 10 nm ≤ D50 ≤ 20 μm.

[0051] Preferably, the average particle size of the sulfide solid electrolyte is 1 μm≤D50≤5 μm; and the average particle size of the positive electrode active material is 1 μm≤D50≤8 μm.

[0052] In some embodiments, the positive electrode active material includes LiNi x Coy Mn (1-x-y) O2.

[0053] In some embodiments, the shape of the positive electrode active material includes granular, rod-shaped, and sheet-shaped; preferably, the shape of the positive electrode material is granular.

[0054] In some embodiments, the positive electrode active material is coated on LiNi by a lithium compound coating layer. x Co y Mn (1-x-y) O2 is formed. The lithium compound coating layer includes at least one of lithium niobate, lithium tantalate, lithium zirconate, lithium germanate, lithium phosphate, lithium iron phosphate, lithium aluminum titanium phosphate (LATP), lithium lanthanum zirconium oxide (LLZO), lithium silicate, lithium carbonate, lithium oxide, and lithium aluminum oxide. Thus, the lithium compound coating layer can significantly reduce the occurrence of side reactions between the active material in the positive electrode active material and the sulfide solid electrolyte.

[0055] Preferably, the lithium compound coating layer includes at least one of lithium niobate and lithium phosphate.

[0056] For further understanding, examples are listed below to illustrate in detail the preparation method of the battery positive electrode material provided by the present application. The protection scope of the present application is not limited to the following examples.

[0057] Example 1

[0058] S1: LiNi coated with LiNbO3 as the positive electrode active material 0.8 Co 0.1 Mn 0.1 O2(LNO@NCM811) was vacuum dried at 120℃, with the vacuum degree controlled at about -0.1MPa, and the drying time was 5h. After the ethanol was passed through a molecular sieve for water removal, a moisture test was performed, and the moisture value of the ethanol after the water was removed was 50ppm.

[0059] S2: Dissolve 0.02g of sulfide solid electrolyte Li6PS5Cl in 20mL of organic solvent ethanol, shake thoroughly, and form a solution after complete dissolution; disperse 10g of dried LNO@NCM811 into the solution and stir magnetically at a rate of 500rpm / min for 30min. Then, dry the solution in a vacuum oven with a vacuum setting of -0.1MPa, a drying temperature of 90°C, and a drying time of 8h to prepare a battery positive electrode material in which the positive electrode active material LNO@NCM811 is coated with the sulfide solid electrolyte Li6PS5Cl. The battery positive electrode material is numbered NCM-1.

[0060] Example 2

[0061] The difference between Example 2 and Example 1 is that the sulfide solid electrolyte is Li 10 GeP2S 12 , other preparation methods and conditions are the same as those in Example 1.

[0062] Sulfide solid electrolyte Li 10 GeP2S 12 The battery positive electrode material coated with the positive electrode active material LNO@NCM811, the battery positive electrode material is numbered NCM-2.

[0063] Example 3

[0064] The difference between Example 3 and Example 1 is that the sulfide solid electrolyte is Li 3.833 Sn 0.833 As 0.166 S4, other preparation methods and conditions are the same as those in Example 1.

[0065] Sulfide solid electrolyte Li 3.833 Sn 0.833 As 0.166 S4 is a battery positive electrode material coated with the positive electrode active material LNO@NCM811, and the number of the battery positive electrode material is NCM-3.

[0066] Example 4

[0067] The difference between Example 4 and Example 1 is that the positive electrode active material is Li3PO4 coated LiNi 0.8 Co 0.1 Mn 0.1 O2(LPO@NCM811), other preparation methods and conditions are the same as those in Example 1.

[0068] A battery positive electrode material was obtained, in which the positive electrode active material LPO@NCM811 was coated with the sulfide solid electrolyte Li6PS5Cl. The battery positive electrode material was numbered NCM-4.

[0069] Example 5

[0070] The difference between Example 5 and Example 1 is that the amount of sulfide solid electrolyte Li6PS5Cl used is 0.1 g, and the other preparation methods and conditions are the same as those of Example 1.

[0071] A battery positive electrode material was prepared, in which the positive electrode active material LNO@NCM811 was coated with the sulfide solid electrolyte Li6PS5Cl. The battery positive electrode material was numbered NCM-5.

[0072] Example 6

[0073] The difference between Example 6 and Example 1 is that the sulfide solid electrolyte is Li6PS5Br, the organic solvent is N-methylformamide, and the other preparation methods and conditions are the same as those in Example 1.

[0074] A battery positive electrode material was prepared, in which the positive electrode active material LNO@NCM811 was coated with the sulfide solid electrolyte Li6PS5Br. The battery positive electrode material was numbered NCM-6.

[0075] Example 7

[0076] The difference between Example 7 and Example 1 is that the sulfide solid electrolyte is Li6PS5I, and the other preparation methods and conditions are the same as those of Example 1.

[0077] A battery positive electrode material was prepared, in which the positive electrode active material LNO@NCM811 was coated with the sulfide solid electrolyte Li6PS5I. The battery positive electrode material is numbered NCM-7.

[0078] Example 8

[0079] The difference between Example 8 and Example 1 is that the amount of sulfide solid electrolyte Li6PS5Cl used is 0.05 g, the organic solvent is acetonitrile, and the other preparation methods and conditions are the same as those in Example 1.

[0080] A battery positive electrode material was prepared, in which the positive electrode active material LNO@NCM811 was coated with the sulfide solid electrolyte Li6PS5Cl. The battery positive electrode material is numbered NCM-8.

[0081] Example 9

[0082] The difference between Example 9 and Example 1 is that the positive electrode active material is LiNbO3 coated LiNi 0.6 Co 0.2 Mn 0.2 O2, other preparation methods and conditions are the same as those in Example 1; the prepared battery positive electrode material is numbered NCM-9.

[0083] Example 10

[0084] The difference between Example 10 and Example 1 is that the positive electrode active material is LiNi 0.8 Co 0.1 Mn 0.1 O2, other preparation methods and conditions are the same as those in Example 1; the prepared battery positive electrode material is numbered NCM-10.

[0085] Example 11

[0086] The difference between Example 11 and Example 1 is that the positive electrode active material is LiNi 0.6 Co0.2 Mn 0.2 O2, other preparation methods and conditions are the same as those in Example 1; the prepared battery positive electrode material is numbered NCM-11.

[0087] Comparative Example 1

[0088] The difference between Comparative Example 1 and Example 1 is that the comparative example is a battery positive electrode material composed of the positive electrode active material LNO@NCM811, numbered NCM-A.

[0089] Comparative Example 2

[0090] The difference between Comparative Example 2 and Example 1 is that the battery positive electrode material in this comparative example is composed of the positive electrode active material LPO@NCM811, which is numbered as NCM-B.

[0091] Comparative Example 3

[0092] The difference between Comparative Example 3 and Example 1 is that the comparative example is composed of the positive electrode active material LNO@NCM622 (LiNbO3 coated LiNi 0.6 Co 0.2 Mn 0.2 O2) composed of battery positive electrode materials, numbered NCM-C.

[0093] The present application also provides a battery positive electrode, comprising a battery positive electrode material prepared by the method for preparing a battery positive electrode material according to any of the above embodiments of the present application, a sulfide solid electrolyte, a conductive agent, and a binder. The mass proportion of the battery positive electrode material is 90% to 95%, the mass proportion of the sulfide solid electrolyte is 2.5% to 4%, the mass proportion of the conductive agent is 1.5% to 4%, and the mass proportion of the binder is 0.5% to 1%. As a result, the loading amount of the positive electrode active material can be increased, greatly improving the capacity performance.

[0094] In the above solution, the sulfide solid electrolyte can first contact the battery positive electrode material to promote the migration of lithium ions to further improve the ionic conductivity.

[0095] In some embodiments, the conductive agent may include at least one of a carbon material, metal particles, and a conductive polymer. This can improve the electronic conductivity of the battery's positive electrode. Preferably, the conductive agent is a carbon material. The binder may be selected from polytetrafluoroethylene (PTFE) or polyvinylidene fluoride.

[0096] In some embodiments, the prepared battery positive electrode material, sulfide solid electrolyte, conductive agent and binder are mixed and pressed to obtain a battery positive electrode with high surface density.

[0097] An embodiment of the present application also provides an all-solid-state battery, comprising the battery positive electrode described in any of the above embodiments of the present application.

[0098] The all-solid-state battery prepared from the battery positive electrode provided in this application has excellent cycle performance and rate performance.

[0099] In some embodiments, the all-solid-state battery further includes a battery negative electrode and a solid electrolyte membrane disposed between the battery negative electrode and the battery positive electrode.

[0100] In some embodiments, the battery negative electrode comprises lithium, a lithium / indium alloy, graphite, silicon, a silicon alloy, silicon dioxide, a mixture of silicon dioxide / graphite, or a mixture of silicon dioxide / graphite / silicon.

[0101] For further understanding, examples are listed below to describe in detail the battery positive electrode and all-solid-state battery provided in this application. The scope of protection of this application is not limited to the following examples.

[0102] Experimental Example 1

[0103] S1: Preparation of positive electrode sheet.

[0104] Add 9g of battery positive electrode material NCM-1 powder, 0.5g of sulfide solid electrolyte Li6PS5Cl, and 0.4g of carbon material (such as VGCF, vapor-phase grown carbon fiber) to a blender, stir in a pulsed manner at low speed (300rpm) for 10 minutes to mix evenly, then add 0.1g of binder (for example, PTFE), stir in a pulsed manner at low speed (300rpm) for 10 minutes to mix evenly. Then, stir in a pulsed manner at high speed (20000rpm) for the fiberization process, stir for 10 minutes, and the mass proportion of the battery positive electrode material is 90%. The mixed powder is placed in a roller press, rolled into a film at a temperature of 150°C, and finally hot-rolled with the current collector aluminum foil to obtain a positive electrode sheet.

[0105] S2: Preparation of negative electrode sheet: lithium-indium alloy sheet.

[0106] The specific preparation method of the lithium-indium alloy sheet can be found in the relevant technology and will not be described here in detail.

[0107] S3: Preparation of solid electrolyte membrane.

[0108] 4.95g of the sulfide solid electrolyte Li6PS5Cl and 0.05g of PTFE were added to a blender and pulsed at low speed (300 rpm) for 10 minutes to mix thoroughly. Then, high speed (20,000 rpm) pulsed stirring was applied to initiate the fiberization process. The mixed powder was placed in a roller press and rolled at 150°C to form a solid electrolyte membrane.

[0109] S4: The positive electrode sheet, solid electrolyte membrane and negative electrode sheet are stacked and assembled, and an external pressure of 5MPa is applied to form a solid-state battery.

[0110] Battery testing: The solid-state battery was subjected to 100 cycles of constant current charge and discharge at 0.1C (1C = 180 mAh / g) at 25°C. The two-probe method was also used to measure the battery impedance. The test results are shown in Table 1.

[0111] Experimental Example 2

[0112] Experimental Example 2 differs from Experimental Example 1 in that the battery positive electrode material is 9.5g of NCM-2, the amount of sulfide solid electrolyte Li6PS5Cl is 0.25g, the amount of VGCF is 0.15g, and the amount of PTFE binder is 0.1g. The mass proportion of the battery positive electrode material is 95%. Other preparation methods and conditions are the same as those of Experimental Example 1.

[0113] Experimental Example 3

[0114] Experimental Example 3 differs from Experimental Example 1 in that the battery positive electrode material is 9.2g of NCM-3, the amount of sulfide solid electrolyte Li6PS5Cl is 0.4g, the amount of VGCF is 0.3g, and the amount of PTFE binder is 0.1g, with the weight proportion of the battery positive electrode material being 92%. Other preparation methods and conditions are the same as those in Experimental Example 1.

[0115] Experimental Examples 4 to 16

[0116] The difference compared to Experimental Example 1 is that the battery positive electrode materials used in Experimental Examples 4 to 16 are NCM-4, NCM-5, NCM-6, NCM-7, NCM-8, NCM-9, NCM-10, NCM-11, NCM-A, NCM-B, NCM-C, NCM-A, and NCM-A, respectively. In Experimental Example 15, the amount of NCM-A used is 7g, and the amount of sulfide solid electrolyte Li6PS5Cl used is 2.5g; in Experimental Example 16, the amount of NCM-A used is 8g, and the amount of sulfide solid electrolyte Li6PS5Cl used is 1.5g. The other preparation methods and preparation conditions of Experimental Examples 4 to 16 are the same as those of Experimental Example 1.

[0117] Table 1 Test results of solid-state batteries prepared in Experimental Examples 1 to 16

[0118] By comparing Experimental Examples 1 to 11 in Table 1 with Experimental Examples 12 to 14, it can be seen that the solid-state battery prepared by coating the positive electrode active material with a sulfide solid electrolyte can reduce the battery impedance, improve the first discharge specific capacity, the first efficiency and the capacity retention rate. This is because the present application uses a sulfide solid electrolyte to coat the positive electrode active material, which can construct an excellent ion conduction network on the surface of the positive electrode active material, increase the effective contact area between the positive electrode active material and the sulfide solid electrolyte, and greatly increase the lithium ion deintercalation rate. Therefore, when preparing the battery positive electrode, there is no need to add too much sulfide electrolyte, ensuring that the solid-state battery can have a higher battery positive electrode material load and prepare a high-load battery positive electrode. By comparing Experimental Examples 12 to 14 and 15 to 16, it can be seen that when the positive electrode active material is not coated with a sulfide solid electrolyte, it is necessary to appropriately reduce the amount of the positive electrode active material and appropriately increase the amount of the sulfide solid electrolyte Li6PS5Cl to reduce the battery impedance and improve the first discharge specific capacity, the first efficiency and the capacity retention rate.

[0119] The technical solution provided by this application can achieve the following beneficial effects: This application provides a method for preparing a battery positive electrode material, a battery positive electrode, and an all-solid-state battery. This preparation method can increase the contact area between the solid electrolyte and the positive electrode active material, effectively solving the problem of reduced interfacial contact area between traditional solid electrolytes and positive electrode active materials. This enhances the ability of ions to quickly embed or extract from the positive electrode active material, facilitating ion transport and enhancing battery capacity.

[0120] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A method for preparing a positive electrode material for a battery, comprising: dissolving a sulfide solid electrolyte in an organic solvent to form a solution; dispersing a positive electrode active material into the solution; The solution is dried to obtain a battery positive electrode material in which a positive electrode active material is coated with a sulfide solid electrolyte.

2. The method for preparing a positive electrode material for a battery according to claim 1, characterized in that: The organic solvent includes at least one of ethanol, acetonitrile, N-methylformamide and tetrahydrofuran.

3. The method for preparing a positive electrode material for a battery according to claim 2, characterized in that: The sulfide solid electrolyte includes Li 7-a PS 6-a X a , Thio-LISICONs and Li 11-x M 2-x P 1+x S 12 At least one of; Wherein, X is selected from at least one of chlorine, bromine and iodine; 0.5≤a≤2; and M is selected from at least one of Ge, Sn and Si.

4. The method for preparing a positive electrode material for a battery according to claim 1, characterized in that: The positive electrode active material includes LiNi x Co y Mn (1-x-y) O2.

5. The method for preparing a positive electrode material for a battery according to claim 1, characterized in that: The positive electrode active material is coated with a lithium compound coating layer on LiNi x Co y Mn (1-x-y) O2 formation; The lithium compound coating layer includes: at least one of lithium niobate, lithium tantalate, lithium zirconate, lithium germanate, lithium phosphate, lithium iron phosphate, lithium aluminum titanium phosphate (LATP), lithium lanthanum zirconium oxide (LLZO), lithium silicate, lithium carbonate, lithium oxide, and lithium aluminum oxide.

6. The method for preparing a positive electrode material for a battery according to claim 1, characterized in that: The usage ratio of the sulfide solid electrolyte, the organic solvent and the positive electrode active material is 0.002-0.03 g: 5-10 mL: 1 g.

7. The method for preparing a positive electrode material for a battery according to claim 6, characterized in that: The usage ratio of the sulfide solid electrolyte, the organic solvent and the positive electrode active material is 0.002-0.01 g: 5-10 mL: 1 g.

8. The method for preparing a positive electrode material for a battery according to claim 6, characterized in that: The thickness of the coating layer formed by the sulfide solid electrolyte coating the positive electrode active material is 1 to 10 nm.

9. The method for preparing a positive electrode material for a battery according to any one of claims 1 to 8, characterized in that: Before dissolving the sulfide solid electrolyte in the organic solvent to form the solution, the method further comprises: A desiccant is added to the organic solvent and the mixture is allowed to stand to obtain an anhydrous organic solvent.

10. The method for preparing a positive electrode material for a battery according to any one of claims 1 to 8, characterized in that: Before dispersing the positive electrode active material into the solution, the method further comprises: The positive electrode active material is vacuum dried; the vacuum drying treatment temperature is 80 to 120° C., and the vacuum drying treatment time is 5 to 10 hours.

11. The method for preparing a positive electrode material for a battery according to claim 10, characterized in that: The vacuum degree of the vacuum drying is -0.085 to -0.1 MPa.

12. The method for preparing a positive electrode material for a battery according to any one of claims 1 to 8, characterized in that: The average particle size of the sulfide solid electrolyte is 100nm≤D50≤30μm; The average particle size of the positive electrode active material is 10 nm≤D50≤20 μm.

13. The method for preparing a positive electrode material for a battery according to claim 12, characterized in that: The average particle size of the sulfide solid electrolyte is 1 μm≤D50≤5 μm; The average particle size of the positive electrode active material is 1 μm≤D50≤8 μm.

14. The method for preparing a positive electrode material for a battery according to claim 9, characterized in that: The desiccant includes a molecular sieve.

15. The method for preparing a positive electrode material for a battery according to claim 9, characterized in that: The water content of the anhydrous organic solvent is less than 50 ppm.

16. The method for preparing a positive electrode material for a battery according to claim 1, characterized in that: The positive electrode active material may be in the form of particles, rods or sheets.

17. A positive electrode of a battery, characterized in that: A battery positive electrode material prepared by the method for preparing a battery positive electrode material according to any one of claims 1 to 16, a sulfide solid electrolyte, a conductive agent, and a binder; The mass proportion of the battery positive electrode material is 90% to 95%, the mass proportion of the sulfide solid electrolyte is 2.5% to 4%, the mass proportion of the conductive agent is 1.5% to 4%, and the mass proportion of the binder is 0.5% to 1%.

18. The positive electrode of the battery according to claim 17, characterized in that: The conductive agent includes at least one of a carbon material, metal particles, and a conductive polymer.

19. The positive electrode of the battery according to claim 17, characterized in that: The binder is selected from polytetrafluoroethylene (PTFE) or polyvinylidene fluoride.

20. An all-solid-state battery, characterized in that: Comprising the battery positive electrode as claimed in claim 17.

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