Solid-state secondary battery positive electrode, preparation method for solid-state secondary battery positive electrode, and solid-state secondary battery

Abstract

The present application relates to the technical field of solid-state secondary batteries, and provides a solid-state secondary battery positive electrode, a preparation method for the solid-state secondary battery positive electrode, and a solid-state secondary battery. The solid-state secondary battery positive electrode comprises a positive electrode current collector; a first layer located on the positive electrode current collector, the first layer comprising positive electrode small particles, solid electrolyte small particles, a conductive agent and a binder; a second layer located on the first layer, the second layer further comprising positive electrode large particles, solid electrolyte small particles, a conductive agent and a binder; a third layer located on the second layer, the third layer comprising positive electrode small particles, solid electrolyte large particles, a conductive agent and a binder; micron-sized holes distributed in the first layer, the second layer and the third layer, the micron-sized holes being filled with the solid electrolyte small particles, the conductive agent and the binder; and millimeter-sized holes penetrating the first layer, the second layer and the third layer, the millimeter-sized holes being filled with the solid electrolyte small particles, the conductive agent and the binder. The present application reduces the flexibility of a lithium-ion transmission path and improves the rate performance.

Description

Solid-state secondary battery cathode, solid-state secondary battery cathode preparation method and solid-state secondary battery

[0001] This application claims priority to Chinese Patent Application No. CN202411540121.5, filed on October 31, 2024, entitled "Solid-state secondary battery cathode, method for preparing solid-state secondary battery cathode and solid-state secondary battery", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of solid-state secondary battery technology, and in particular to a solid-state secondary battery cathode, a method for preparing a solid-state secondary battery cathode, and a solid-state secondary battery. Background Technology

[0003] In recent years, solid-state batteries have received widespread attention from the industry as a highly safe electrochemical energy storage device. However, solid-state batteries still face many challenges, making it difficult for their performance to surpass that of existing liquid electrolyte-based lithium-ion batteries. One major challenge is the design of the cathode structure; the high tortuosity of the ion transport path in solid-state cathodes limits power density. As the requirements for fast charging in electric vehicles become increasingly stringent, these issues in solid-state cathodes need to be overcome to ensure they meet the prerequisites for practical applications. Technical issues

[0004] The main purpose of this application is to provide a solid-state secondary battery cathode, a method for preparing a solid-state secondary battery cathode, and a solid-state secondary battery, which aims to reduce the tortuosity of the lithium-ion transport path and improve rate performance. Technical solutions

[0005] The purpose of this application is to provide a solid-state secondary battery cathode, a method for preparing a solid-state secondary battery cathode, and a solid-state secondary battery, with the aim of reducing the tortuosity of the lithium-ion transport path and improving rate performance.

[0006] In a first aspect, embodiments of this application provide a solid-state secondary battery positive electrode, comprising:

[0007] Positive current collector;

[0008] A first layer located on the positive current collector; the first layer includes positive electrode particles, solid electrolyte particles, a conductive agent, and a binder;

[0009] A second layer is located on top of the first layer; the second layer also includes positive large particles, solid electrolyte small particles, conductive agent and binder;

[0010] A third layer is located on the second layer; the third layer includes positive electrode small particles, solid electrolyte large particles, conductive agent and binder; wherein, the particle size of the positive electrode small particles is smaller than the particle size of the positive electrode large particles, and the particle size of the solid electrolyte small particles is smaller than the particle size of the solid electrolyte large particles.

[0011] Micron-sized pores are distributed in the first layer, the second layer and the third layer; the micron-sized pores are filled with solid electrolyte particles, conductive agent and binder;

[0012] Millimeter-scale pores penetrating the first, second, and third layers are filled with solid electrolyte particles, conductive agents, and binders.

[0013] Secondly, embodiments of this application provide a method for preparing a solid-state secondary battery cathode, the method being used to prepare the aforementioned solid-state secondary battery cathode, the method comprising:

[0014] The positive electrode particles, solid electrolyte particles, conductive agent, binder and dry ice particles are prepared into a low-temperature dry slurry, which is coated on the positive electrode current collector and then hot-pressed to form a film, forming the first layer.

[0015] A low-temperature dry slurry is prepared by combining positive large particles, solid electrolyte small particles, conductive agent, binder and dry ice particles, and coated on the first layer and then hot-pressed to form a film to form the second layer.

[0016] The positive electrode small particles, solid electrolyte large particles, conductive agent, binder and dry ice particles are prepared into a low temperature dry slurry, which is coated on the second layer and hot-pressed to form a film to form the third layer.

[0017] The three-layer electrode sheet is then perforated.

[0018] Solid electrolyte particles, conductive agent, and binder are mixed into a slurry, which is then applied to the perforated area and dried.

[0019] Furthermore, the step of preparing the positive electrode particles, solid electrolyte particles, conductive agent, binder, and dry ice particles into a low-temperature dry slurry includes:

[0020] A low-temperature dry slurry is prepared by mixing positive electrode particles, solid electrolyte particles, conductive agent, and binder in a mass ratio of 60~85:14~30:0.5~5:0.5~5, with dry ice accounting for 0.5%~5% of the total mass of the four substances in the first layer.

[0021] Furthermore, the step of preparing the positive electrode particles, solid electrolyte particles, conductive agent, binder, and dry ice particles into a low-temperature dry slurry includes:

[0022] A low-temperature dry slurry is prepared by mixing positive large particles, solid electrolyte small particles, conductive agent, and binder in a mass ratio of 70~97:2~20:0.5~5:0.5~5, and by adding dry ice at 0.5%~5% of the total mass of the four substances in the second layer.

[0023] Furthermore, the step of preparing the positive electrode small particles, solid electrolyte large particles, conductive agent, binder, and dry ice particles into a low-temperature dry slurry includes:

[0024] A low-temperature dry slurry is prepared by mixing small positive electrode particles, large solid electrolyte particles, conductive agent, and binder in a mass ratio of 45~79:20~45:0.5~5:0.5~5, with dry ice accounting for 0.5%~5% of the total mass of the four substances in the third layer.

[0025] Furthermore, the step of preparing the solid electrolyte particles, conductive agent, and binder into a slurry includes:

[0026] Solid electrolyte particles, conductive agent, and binder are mixed in a mass ratio of 90~99:0.5~5:0.5~5 to form a slurry.

[0027] Furthermore, the diameter of the hole formed by the drilling is 1 mm to 10 mm.

[0028] Furthermore, the diameter of the pores formed by the hot-press vaporization of the dry ice particles is 0.1 micrometers to 10 micrometers.

[0029] Thirdly, embodiments of this application provide a solid-state secondary battery, which includes the solid-state secondary battery positive electrode described above. Beneficial effects

[0030] In this application, the first layer comprises small positive electrode particles, small solid electrolyte particles, a conductive agent, and a binder. This first layer provides rapid lithium-ion and electron transport, reducing ohmic impedance and lithium-ion transfer impedance. The second layer comprises large positive electrode particles, small solid electrolyte particles, a conductive agent, and a binder. This second layer provides rapid lithium-ion transport and high load capacity and pressure, increasing electrode areal density and energy density. The third layer comprises small positive electrode particles, large solid electrolyte particles, a conductive agent, and a binder. This third layer provides rapid lithium-ion transport and electronic insulation, preventing interfacial side reactions, improving interfacial stability, and enhancing cycle life. Micron-sized pores distributed in the first, second, and third layers increase porosity and reduce tortuosity. The solid electrolyte fills these micron-sized and millimeter-sized pores, constructing channels for rapid lithium-ion transport, reducing lithium-ion transfer impedance, and improving rate performance. Attached Figure Description

[0031] Figure 1 is a schematic flowchart of the solid-state secondary battery cathode preparation method provided in the embodiments of this application;

[0032] Figure 2 is a schematic diagram of three layers of slurry coated on the positive current collector according to an embodiment of this application;

[0033] Figure 3 is a schematic diagram of the positive current collector after three layers of slurry are coated and holes are drilled, according to an embodiment of this application.

[0034] Figure 4 is a schematic diagram of the positive current collector after three layers of slurry are coated on it and holes are made, and then slurry is coated on the holes, according to an embodiment of this application.

[0035] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. The best embodiment of the present invention

[0036] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0037] Those skilled in the art will understand that, unless explicitly stated otherwise, the singular forms “a,” “an,” “the,” and “the” used herein may also include the plural forms. It should be further understood that the term “comprising” as used in the specification of this application means the presence of features, integers, steps, operations, elements, modules, and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, modules, components, and / or groups thereof. It should be understood that when we say an element is “connected” or “coupled” to another element, it can be directly connected or coupled to the other element, or there may be intermediate elements. Furthermore, “connected” or “coupled” as used herein can include wireless connections or wireless coupling. The term “and / or” as used herein includes all or any modules and all combinations of one or more associated listed items.

[0038] Those skilled in the art will understand that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the same meaning as in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless specifically defined as herein.

[0039] This application embodiment provides a solid-state secondary battery positive electrode. As shown in Figure 4, the larger gray particles are large solid electrolyte particles, the smaller gray particles are small solid electrolyte particles, the larger black particles are large positive electrode particles, and the smaller black particles are small positive electrode particles. The solid-state secondary battery positive electrode includes:

[0040] Positive current collector 1;

[0041] A first layer 2 is located on the positive electrode current collector 1; the first layer 2 includes positive electrode particles, solid electrolyte particles, conductive agent and binder;

[0042] The second layer 3 is located on the first layer 2; the second layer 3 also includes positive large particles, solid electrolyte small particles, conductive agent and binder;

[0043] The third layer 4 is located on the second layer 3; the third layer 4 includes positive electrode small particles, solid electrolyte large particles, conductive agent and binder;

[0044] Micron-sized pores are distributed in the first layer 2, the second layer 3 and the third layer 4; the micron-sized pores are filled with solid electrolyte particles, conductive agent and binder;

[0045] Millimeter-sized holes 5 penetrate the first layer 2, the second layer 3 and the third layer 4, and the millimeter-sized holes 5 are filled with solid electrolyte particles, conductive agent and binder.

[0046] In this embodiment, the first layer 2 includes small positive electrode particles, small solid electrolyte particles, a conductive agent, and a binder. The first layer 2 provides rapid lithium-ion and electron transport, reducing ohmic impedance and lithium-ion transfer impedance. The second layer 3 includes large positive electrode particles, small solid electrolyte particles, a conductive agent, and a binder. The second layer 3 provides rapid lithium-ion transport and high load capacity and pressure, increasing electrode areal density and energy density. The third layer 4 includes small positive electrode particles, large solid electrolyte particles, a conductive agent, and a binder. The third layer 4 provides rapid lithium-ion transport and electronic insulation, preventing interfacial side reactions, improving interfacial stability, and enhancing cycle life. The micron-sized pores distributed in the first, second, and third layers 2 and 3 can increase porosity and reduce tortuosity. The solid electrolyte fills the micron-sized and millimeter-sized pores 5, constructing channels for rapid lithium-ion transport, reducing lithium-ion transfer impedance, and improving rate performance.

[0047] It should be noted that, as mentioned above, the positive electrode current collector 1 can be aluminum foil, carbon-coated aluminum foil, or stainless steel foil. Both the small positive electrode particles and the large positive electrode particles are positive electrode active materials. Here, "small" refers to the size of the small positive electrode particles relative to the size of the large positive electrode particles; that is, the particle size of the small positive electrode particles is smaller than that of the large positive electrode particles. Similarly, the particle size of the small solid electrolyte particles is smaller than that of the large solid electrolyte particles. The particle size range of the small positive electrode particles is 0.01µm to 10µm, and the particle size range of the large positive electrode particles is 10µm to 100µm; the particle size range of the small solid electrolyte particles is 0.01µm to 15µm, and the particle size range of the large solid electrolyte particles is 15µm to 500µm, where µm is a micrometer. The positive electrode material can be a ternary NCM, lithium iron phosphate (LFP), lithium-rich manganese-based LMR, lithium cobalt oxide (LCO), or lithium manganese iron phosphate (LMFP), etc. The solid electrolyte can be: sulfide electrolytes: lithium phosphorus-sulfur (LPS), lithium phosphorus-sulfur-chlorine (LPSCl), lithium germanium phosphorus-sulfur (LGPS), etc.; oxide solid electrolytes: lithium titanium aluminum phosphate (LATP), lithium lanthanum zirconium oxide (LLZO), lithium lanthanum titanium oxide (LLTO), etc.; polymer solid electrolytes: polyethylene oxide (PEO), polyvinyl carbonate (PVC), polydioxane (PDOL), polysiloxane (PS), polyethylene glycol (PEG), etc. The conductive agents mentioned above can be carbon black (SP), Ketjen black (ECP), carbon nanotubes (CNT), graphene, or vapor-grown carbon fiber reinforcement (VGCF). The binders mentioned above can be polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), p-type polyaniline (PAN), polymethyl methacrylate (PMMA), or hydrogenated nitrile butadiene rubber (HNBR), etc.

[0048] As shown in Figures 1-4, this application also provides a method for preparing a solid-state secondary battery cathode. The method is used to prepare the above-mentioned solid-state secondary battery cathode, and the method includes:

[0049] S1. The positive electrode particles, solid electrolyte particles, conductive agent, binder and dry ice particles are prepared into a low temperature dry slurry, which is coated on the positive electrode current collector 1 and hot-pressed to form a film, forming the first layer 2.

[0050] S2. The positive electrode particles, solid electrolyte particles, conductive agent, binder and dry ice particles are prepared into a low-temperature dry slurry, which is coated on the first layer 2 and hot-pressed to form a film, thus forming the second layer 3.

[0051] S3. The positive electrode small particles, solid electrolyte large particles, conductive agent, binder and dry ice particles are prepared into a low temperature dry slurry, which is coated on the second layer 3 and hot-pressed to form a film, forming the third layer 4.

[0052] S4. Drill holes in the formed three-layer electrode sheet;

[0053] S5. Prepare a slurry by mixing solid electrolyte particles, conductive agent and binder, apply it to the punched area and dry it.

[0054] In step S1, positive electrode particles, solid electrolyte particles, conductive agent, binder, and dry ice particles are mixed in a certain proportion to form a low-temperature dry slurry. This slurry is coated onto any surface of the positive electrode current collector 1 and then hot-pressed to form a film, forming the first layer 2. The first layer 2 provides rapid lithium-ion and electron transport, reducing ohmic impedance and lithium-ion transfer impedance. During the hot-pressing process, the dry ice vaporizes and leaves the electrode, leaving pores in their original positions, thereby increasing porosity and reducing tortuosity. The positive electrode current collector 1 can be aluminum foil, carbon-coated aluminum foil, or stainless steel foil.

[0055] In step S2, positive electrode particles, solid electrolyte particles, conductive agent, binder and dry ice particles are prepared into a low-temperature dry slurry in a certain proportion, coated on the first layer 2 and hot-pressed to form a film, forming the second layer 3; the second layer 3 provides rapid lithium-ion transport and high load and high pressure, improving the electrode surface density and energy density; during the hot-pressing process, the dry ice vaporizes and leaves the electrode, leaving pores in the original position, thereby increasing porosity and reducing tortuosity.

[0056] In step S3, small positive electrode particles, large solid electrolyte particles, conductive agent, binder, and dry ice particles are prepared into a low-temperature dry slurry in a certain proportion, which is then coated onto the second layer 3 and hot-pressed to form a film, forming the third layer 4. The third layer 4 provides rapid lithium-ion transport and electronic insulation, avoids the occurrence of interfacial side reactions, improves interfacial stability, and enhances cycle life. During the hot-pressing process, the dry ice vaporizes and leaves the electrode, leaving pores in their original positions, thereby increasing porosity and reducing tortuosity.

[0057] In the above, the dry ice particles are uniformly distributed during the low-temperature dry pulping process, so the micron-sized pores 6 formed by the dry ice particles are uniformly dispersed in the electrode.

[0058] In step S4, the formed three-layer electrode sheet is further perforated until the positive current collector is reached; that is, the positive current collector is not perforated here. The perforation can be achieved by stamping, drilling, photolithography, or laser methods.

[0059] In step S5, solid electrolyte particles, conductive agent, and binder are mixed into a slurry in a certain proportion, applied to the perforated area, and dried. The solid electrolyte fills the micron-sized pores 6 left by the vaporization of dry ice particles and the millimeter-sized pores 5 left by the perforation, constructing a channel for rapid lithium-ion transport, reducing lithium-ion transfer impedance, and improving rate performance.

[0060] It should be noted that, as mentioned above, both the small positive electrode particles and the large positive electrode particles refer to positive electrode active materials. Here, "small" refers to the size of the small positive electrode particles relative to the size of the large positive electrode particles; that is, the size of the small positive electrode particles is smaller than the size of the large positive electrode particles. Similarly, the size of the small solid electrolyte particles is smaller than the size of the large solid electrolyte particles. The particle size range of the small positive electrode particles is 0.01µm to 10µm, and the particle size range of the large positive electrode particles is 10µm to 100µm; the particle size range of the small solid electrolyte particles is 0.01µm to 15µm, and the particle size range of the large solid electrolyte particles is 15µm to 500µm, where µm stands for micrometer. The positive electrode material can be a ternary NCM, lithium iron phosphate (LFP), lithium-rich manganese-based LMR, lithium cobalt oxide (LCO), or lithium manganese iron phosphate (LMFP), etc. The solid electrolyte can be: sulfide electrolytes: lithium phosphorus-sulfur (LPS), lithium phosphorus-sulfur-chlorine (LPSCl), lithium germanium phosphorus-sulfur (LGPS), etc.; oxide solid electrolytes: lithium titanium aluminum phosphate (LATP), lithium lanthanum zirconium oxide (LLZO), lithium lanthanum titanium oxide (LLTO), etc.; polymer solid electrolytes: polyethylene oxide (PEO), polyvinyl carbonate (PVC), polydioxane (PDOL), polysiloxane (PS), polyethylene glycol (PEG), etc. The conductive agents mentioned above can be carbon black (SP), Ketjen black (ECP), carbon nanotubes (CNT), graphene, or vapor-grown carbon fiber reinforcement (VGCF). The binders mentioned above can be polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), p-type polyaniline (PAN), polymethyl methacrylate (PMMA), or hydrogenated nitrile butadiene rubber (HNBR), etc.

[0061] In one embodiment, the step of preparing the positive electrode particles, solid electrolyte particles, conductive agent, binder, and dry ice particles into a low-temperature dry slurry includes:

[0062] A low-temperature dry slurry is prepared by mixing positive electrode particles, solid electrolyte particles, conductive agent, and binder in a mass ratio of 60~85:14~30:0.5~5:0.5~5, with dry ice accounting for 0.5%~5% of the total mass of the four substances in the first layer.

[0063] In this embodiment, the mass ratio of the positive electrode particles, solid electrolyte particles, conductive agent, and binder is 60~85:14~30:0.5~5:0.5~5; dry ice accounts for 0.5%~5% of the total mass of the four substances (positive electrode particles, solid electrolyte particles, conductive agent, and binder) in the first layer. This embodiment ensures that the first layer provides rapid lithium-ion and electron transport by keeping the components in the first layer slurry within a reasonable range, thereby reducing ohmic impedance and lithium-ion transfer impedance. Simultaneously, the vaporization of dry ice increases porosity and reduces tortuosity.

[0064] In one embodiment, the step of preparing a low-temperature dry slurry from positive electrode particles, solid electrolyte particles, conductive agent, binder, and dry ice particles includes:

[0065] A low-temperature dry slurry is prepared by mixing positive large particles, solid electrolyte small particles, conductive agent, and binder in a mass ratio of 70~97:2~20:0.5~5:0.5~5, and by adding dry ice at 0.5%~5% of the total mass of the four substances in the second layer.

[0066] In this embodiment, the mass ratio of the positive electrode particles, solid electrolyte particles, conductive agent, and binder is 70~97:2~20:0.5~5:0.5~5; dry ice accounts for 0.5%~5% of the total mass of the four substances (positive electrode particles, solid electrolyte particles, conductive agent, and binder) in the second layer. This embodiment ensures that the second layer 3 can provide rapid lithium-ion transport and high load capacity and pressure by keeping the components in the second layer slurry within a reasonable range, thereby improving the electrode surface density and energy density. Simultaneously, dry ice vaporization increases porosity and reduces tortuosity.

[0067] In one embodiment, the step of preparing a low-temperature dry slurry from small positive electrode particles, large solid electrolyte particles, conductive agent, binder, and dry ice particles includes:

[0068] A low-temperature dry slurry is prepared by mixing small positive electrode particles, large solid electrolyte particles, conductive agent, and binder in a mass ratio of 45~79:20~45:0.5~5:0.5~5, with dry ice accounting for 0.5%~5% of the total mass of the four substances in the third layer.

[0069] In this embodiment, the mass ratio of the positive electrode small particles, solid electrolyte large particles, conductive agent, and binder is 45~79:20~45:0.5~5:0.5~5; dry ice accounts for 0.5%~5% of the total mass of the four substances in the third layer. This embodiment ensures that the components in the third layer slurry are within a reasonable range, thereby ensuring that the third layer 4 provides rapid lithium-ion transport and electronic insulation, avoiding interfacial side reactions, improving interfacial stability, and enhancing cycle life. Simultaneously, the vaporization of dry ice increases porosity and reduces tortuosity.

[0070] In one embodiment, the step of preparing the solid electrolyte particles, conductive agent, and binder into a slurry includes:

[0071] Solid electrolyte particles, conductive agent, and binder are mixed in a mass ratio of 90~99:0.5~5:0.5~5 to form a slurry.

[0072] In this embodiment, the mass ratio of the solid electrolyte particles, conductive agent, and binder in the slurry applied to the perforated area is 90~99:0.5~5:0.5~5. This embodiment of the invention, by ensuring that the components of the slurry applied to the perforated area are within a reasonable range, further ensures the construction of a channel for rapid lithium-ion transport, reduces lithium-ion transfer impedance, and improves rate performance.

[0073] In one embodiment, the diameter of the hole formed by the punching is 1 mm to 10 mm.

[0074] In the embodiments of this application, if the hole formed at the drilling point is too small, the solid electrolyte slurry will not be easily wetted; if the hole is too large, the proportion of inactive components, such as solid electrolyte, will be too high, affecting the proportion of active materials. By designing the diameter range of the hole to be between 1 mm and 10 mm, a channel for rapid lithium-ion transport can be better constructed, reducing lithium-ion transfer resistance and improving rate performance.

[0075] In one embodiment, the diameter of the pores formed by the hot-press vaporization of the dry ice particles is 0.1 micrometers to 10 micrometers.

[0076] In the embodiments of this application, the pores formed by the hot-press vaporization of dry ice particles are micron-sized pores, that is, the diameter of the pores is micron-sized. The solid electrolyte filling the millimeter-sized and micron-sized pores formed by drilling can better construct the highway for ion transport and reduce the lithium-ion transport impedance.

[0077] This application also provides a method for preparing a solid-state secondary battery, the method comprising:

[0078] Solid-state secondary battery positive electrode sheets were prepared using the solid-state secondary battery positive electrode preparation method described in any of the above embodiments.

[0079] Prepare a solid-state secondary battery negative electrode sheet; specifically, make a negative electrode sheet from silicon carbon, conductive agent, binder, and solid electrolyte; more specifically, make the negative electrode sheet according to the mass ratio of silicon carbon: conductive agent: binder: solid electrolyte = 50~95:0.5~10:0.5~5:4~35.

[0080] Prepare solid electrolyte sheets; specifically, prepare solid electrolyte sheets by combining sulfide electrolyte and binder; more specifically, prepare solid electrolyte sheets by mass ratio of sulfide electrolyte: binder = 90-99.5: 0.5-10.

[0081] A solid-state battery is composed of a solid-state secondary battery positive electrode, a solid-state secondary battery negative electrode, and a solid-state electrolyte sheet.

[0082] After the solid-state battery is assembled, it can be cycle-tested to verify its performance.

[0083] Comparative Example

[0084] (1) The positive electrode NCM, solid electrolyte LPSCl, conductive agent SP and binder PTFE are prepared into a dry slurry in a mass ratio of 75:22:1:2, coated on aluminum foil and hot-pressed to form a film to form a positive electrode sheet.

[0085] (2) A negative electrode sheet is prepared by mixing silicon carbide, conductive agent SP, binder PTFE, and solid electrolyte LPSCl in a mass ratio of 83:5:2:10;

[0086] (3) Solid electrolyte LPSCl and binder PTFE are prepared into solid electrolyte sheets at a mass ratio of 99:1;

[0087] (4) Assemble the above positive electrode, solid electrolyte sheet and negative electrode into a battery and perform cycle testing.

[0088] Example 1

[0089] (1) The positive electrode NCM small particles, solid electrolyte LPSCl small particles, conductive agent SP, and binder PTFE are prepared into a low-temperature dry slurry in a mass ratio of 75:22:1:2, and 1% of dry ice is added. The slurry is coated on aluminum foil and hot-pressed to form a film, thus forming the first layer. The 1% of dry ice mentioned in this paragraph refers to the dry ice accounting for 1% of the total mass of the four substances in the first layer: positive electrode NCM small particles, solid electrolyte LPSCl small particles, conductive agent SP, and binder PTFE.

[0090] (2) The positive electrode NCM large particles, solid electrolyte LPSCl small particles, conductive agent SP, and binder PTFE are prepared into a low-temperature dry slurry in a mass ratio of 92:5:1:2, and 1% of dry ice is added. The slurry is coated on aluminum foil and hot-pressed to form a film to form the second layer. The 1% dry ice mentioned in this paragraph refers to the dry ice accounting for 1% of the total mass of the four substances in the second layer: positive electrode NCM large particles, solid electrolyte LPSCl small particles, conductive agent SP, and binder PTFE.

[0091] (3) The positive electrode NCM small particles, solid electrolyte LPSCl large particles, conductive agent SP, and binder PTFE are prepared into a low-temperature dry slurry in a mass ratio of 60:37:1:2, and 1% of dry ice is added. The slurry is coated on aluminum foil and hot-pressed to form a film, thus forming the third layer. The 1% dry ice mentioned in this paragraph refers to the dry ice accounting for 1% of the total mass of the four substances in the third layer: positive electrode NCM small particles, solid electrolyte LPSCl large particles, conductive agent SP, and binder PTFE.

[0092] (4) Use a laser to clean and drill holes in the positive electrode until the foil is formed, with holes of 1 mm in diameter, arranged in a horizontal pattern;

[0093] (5) Solid electrolyte LPSCl small particles, conductive agent SP, and binder PTFE are coated on the laser-cleaned and drilled area in a mass ratio of 97:1:2 and then dried to form a positive electrode sheet; wherein, the solid electrolyte fills the micron-sized pores left by dry ice vaporization and the millimeter-sized pores left by laser drilling.

[0094] (6) A negative electrode sheet is prepared by mixing silicon carbide, conductive agent SP, binder PTFE, and solid electrolyte LPSCl in a mass ratio of 83:5:2:10;

[0095] (7) Solid electrolyte LPSCl and binder PTFE are prepared into solid electrolyte sheets at a mass ratio of 99:1;

[0096] (8) Assemble the positive electrode, solid electrolyte sheet and negative electrode into a battery and perform cycle testing.

[0097] Example 2

[0098] (1) The positive electrode NCM small particles, solid electrolyte LPSCl small particles, conductive agent SP, and binder PTFE are prepared into a low-temperature dry slurry in a mass ratio of 75:22:1:2, and 1% of dry ice is added. The slurry is coated on aluminum foil and hot-pressed to form a film, thus forming the first layer. The 1% of dry ice mentioned in this paragraph refers to the dry ice accounting for 1% of the total mass of the four substances in the first layer: positive electrode NCM small particles, solid electrolyte LPSCl small particles, conductive agent SP, and binder PTFE.

[0099] (2) The positive electrode NCM large particles, solid electrolyte LPSCl small particles, conductive agent SP, and binder PTFE are prepared into a low-temperature dry slurry in a mass ratio of 92:5:1:2, and 1% of dry ice is added. The slurry is coated on aluminum foil and hot-pressed to form a film to form the second layer. The 1% dry ice mentioned in this paragraph refers to the dry ice accounting for 1% of the total mass of the four substances in the second layer: positive electrode NCM large particles, solid electrolyte LPSCl small particles, conductive agent SP, and binder PTFE.

[0100] (3) The positive electrode NCM small particles, solid electrolyte LPSCl large particles, conductive agent SP, and binder PTFE are prepared into a low-temperature dry slurry in a mass ratio of 60:37:1:2, and 1% of dry ice is added. The slurry is coated on aluminum foil and hot-pressed to form a film, thus forming the third layer. The 1% dry ice mentioned in this paragraph refers to the dry ice accounting for 1% of the total mass of the four substances in the third layer: positive electrode NCM small particles, solid electrolyte LPSCl large particles, conductive agent SP, and binder PTFE.

[0101] (4) Use a laser to clean the positive electrode sheet until the foil is cleaned, forming holes with a diameter of 5 mm, arranged in a transverse pattern;

[0102] (5) Solid electrolyte LPSCl small particles, conductive agent SP, and binder PTFE are applied to the perforated area in a mass ratio of 97:1:2 and dried. The solid electrolyte fills the micron-sized pores left by dry ice vaporization and the millimeter-sized pores left by laser drilling.

[0103] (6) A negative electrode sheet is prepared by mixing silicon carbide, conductive agent SP, binder PTFE, and solid electrolyte LPSCl in a mass ratio of 83:5:2:10;

[0104] (7) Solid electrolyte LPSCl and binder PTFE are prepared into solid electrolyte sheets at a mass ratio of 99:1;

[0105] (8) Assemble the positive electrode, solid electrolyte sheet and negative electrode into a battery and perform cycle testing.

[0106] Example 3

[0107] (1) The positive electrode NCM small particles, solid electrolyte LPSCl small particles, conductive agent SP, and binder PTFE are prepared into a low-temperature dry slurry in a mass ratio of 75:22:1:2, and 1% of dry ice is added. The slurry is coated on aluminum foil and hot-pressed to form a film, thus forming the first layer. The 1% of dry ice mentioned in this paragraph refers to the dry ice accounting for 1% of the total mass of the four substances in the first layer: positive electrode NCM small particles, solid electrolyte LPSCl small particles, conductive agent SP, and binder PTFE.

[0108] (2) The positive electrode NCM large particles, solid electrolyte LPSCl small particles, conductive agent, and binder are prepared in a mass ratio of 92:5:1:2, and 1% of dry ice is added to form a low-temperature dry slurry. This slurry is coated on aluminum foil and then hot-pressed to form a film, thus forming the second layer. The 1% dry ice mentioned in this paragraph refers to the dry ice accounting for 1% of the total mass of the four substances in the second layer: positive electrode NCM large particles, solid electrolyte LPSCl small particles, conductive agent SP, and binder PTFE.

[0109] (3) The positive electrode NCM small particles, solid electrolyte LPSCl large particles, conductive agent SP, and binder PTFE are prepared in a mass ratio of 60:37:1:2, and 1% of dry ice is added to form a low-temperature dry slurry. This slurry is coated onto aluminum foil and then hot-pressed to form a film, thus forming the third layer. The 1% dry ice mentioned in this paragraph refers to the dry ice accounting for 1% of the total mass of the four substances in the third layer: positive electrode NCM small particles, solid electrolyte LPSCl large particles, conductive agent SP, and binder PTFE.

[0110] (4) Use a laser to clean and drill holes in the positive electrode sheet until the foil material is formed, with holes of 10 mm in diameter, arranged in a horizontal pattern;

[0111] (5) Solid electrolyte particles LPSCl, conductive agent SP, and binder PTFE are coated on the perforated area in a mass ratio of 97:1:2 and then dried to form a positive electrode sheet; wherein, the solid electrolyte fills the micron-sized pores left by dry ice vaporization and the millimeter-sized pores left by laser drilling.

[0112] (6) A negative electrode sheet is prepared by mixing silicon carbide, conductive agent SP, binder PTFE, and solid electrolyte LPSCl in a mass ratio of 83:5:2:10;

[0113] (7) Solid electrolyte LPSCl and binder PTFE were prepared into solid electrolyte sheets at a mass ratio of 99:1;

[0114] (8) Assemble the positive electrode, solid electrolyte sheet and negative electrode into a battery and perform cycle testing.

[0115] Table 1 Cyclic Performance

[0116] DCR (mΩ) 200-cycle performance: Capacity retention at 1C / 0.33C and at 2C / 0.33C. Comparative examples: Example 1: 45% 71%, 85% 70%; Example 2: 35% 93%, 98% 92%; Example 3: 30% 93.5%, 98.2% 94%.

[0117] In the above Examples 1-3, the proportion of positive NCM in the second layer is higher than that in the comparative example. Therefore, the energy density of the second layer in the above Examples 1-3 is higher than that in the comparative example, and the energy density of all solid-state secondary batteries in the above Examples 1-3 is higher than that in the comparative example.

[0118] The comparative examples in Table 2 below are the same as those described above. Examples 4 and 5 are identical to Example 2 except for the different proportions of the components injected in the first layer, second layer, third layer and the perforation.

[0119] [Revised according to Rule 26, 03.07.2025] Table 2 Cyclic Performance

[0120]

[0120] [Corrected according to Rule 26 03.07.2025]

[0121] As can be seen from Table 1-2, this application can reduce DCR (DC internal resistance), improve rate performance and cycle performance compared to the comparative example.

[0122] The comparative examples in Table 3 below are the same as those described above. Examples 6 and 7 are identical to Example 2 except for the different proportions of the first layer.

[0123] Table 3

[0124] The composition and ratio of the first layer: DCR (mΩ) Comparative Example 7: 5:22:1:245 Example 2: 75:22:1:232 Example 6: 60:30:5:530 Example 7: 85:14:0.5:0.538

[0125] As shown in Table 3, the first layer of the solid-state secondary battery cathode in this application provides fast lithium-ion and electron transport, reducing ohmic impedance and lithium-ion transfer impedance.

[0126] The comparative examples in Table 4 below are the same as those described above. Examples 8 and 9 are identical to Example 2 except for the different proportions of the second layer.

[0127] Table 4

[0128] The composition and ratio of the second layer: 1C / 0.33C capacity retention ratio (Comparative Example / 85%): Example 2: 92:5:1:2 (97.8%); Example 8: 70:20:5:5 (97.5%); Example 9: 97:2:0.5:0.5 (95.5%).

[0129] As shown in Table 4, the second layer of the solid-state secondary battery cathode in this application provides fast lithium-ion transport and high load and high pressure, thereby improving the electrode surface density and energy density.

[0130] The comparative examples in Table 5 below are the same as those described above. Examples 10 and 11 are identical to Example 2 except for the different proportion of the third layer.

[0131] Table 5

[0132] The composition ratio of the third layer, after 200 cycles, shows the following performance comparisons: Example 2: 60:37:1:294%; Example 10: 45:45:5:596%; Example 11: 79:20:0.5:0.592%.

[0133] Table 5

[0134] As shown in Table 5, the third layer of the solid-state secondary battery cathode in this application provides fast lithium-ion transport and electronic insulation, avoids the occurrence of interfacial side reactions, improves interfacial stability, and enhances cycle life.

[0135] The comparative examples in Table 6 below are the same as those described above. Examples 12 and 13 are identical to Example 2 except for the proportion of the component injected at the perforation.

[0136] Table 6

[0137] Composition and ratio injected at the drilling site: 2C / 0.33C; Capacity retention rate: Comparative example / 70%; Example 2: 97:1:293%; Example 12: 90:5:594.5%; Example 13: 99:0.5:0.590%.

[0138] As can be seen from Table 6, the slurry applied to the perforated area helps to construct a channel for rapid lithium-ion transport, reduces lithium-ion transfer resistance, and improves rate performance.

[0139] In summary, this application prepares a low-temperature dry slurry by mixing small positive electrode particles, small solid electrolyte particles, conductive agent, binder, and dry ice particles in a certain proportion. This slurry is then coated onto any surface of the positive electrode current collector 1 and hot-pressed to form a film, forming the first layer. The first layer provides rapid lithium-ion and electron transport, reducing ohmic impedance and lithium-ion transfer impedance. The second layer is prepared by mixing large positive electrode particles, small solid electrolyte particles, conductive agent, binder, and dry ice particles in a certain proportion. This slurry is then coated onto the first layer and hot-pressed to form a film, forming the second layer. The second layer provides rapid lithium-ion transport and high load capacity and pressure, increasing the electrode surface density and energy density. The third layer is prepared by mixing small positive electrode particles, large solid electrolyte particles, conductive agent, binder, and dry ice particles in a certain proportion. This slurry is then coated onto the second layer and hot-pressed to form a film, forming the third layer. The third layer provides rapid lithium-ion transport and electronic insulation, preventing interfacial side reactions, improving interfacial stability, and enhancing cycle life. In addition, during the hot pressing process to form the film, dry ice vaporizes and leaves the electrode, leaving pores in the original position, thereby increasing porosity and reducing tortuosity; perforating the electrode sheet creates a highway for ion transport, reduces lithium-ion transport impedance, and improves rate performance and cycle performance.

[0140] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, apparatus, article, or method that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, apparatus, article, or method. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, apparatus, article, or method that includes that element.

[0141] The above description is only a preferred embodiment of this application and does not limit the patent scope of this application. Any equivalent structural or procedural changes made based on the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

Claims

1. A solid-state secondary battery positive electrode, wherein, include: Positive current collector; A first layer located on the positive current collector; the first layer includes positive electrode particles, solid electrolyte particles, a conductive agent, and a binder; A second layer is located on top of the first layer; the second layer also includes positive large particles, solid electrolyte small particles, conductive agent and binder; A third layer is located on the second layer; the third layer includes positive electrode small particles, solid electrolyte large particles, conductive agent and binder; wherein, the particle size of the positive electrode small particles is smaller than the particle size of the positive electrode large particles, and the particle size of the solid electrolyte small particles is smaller than the particle size of the solid electrolyte large particles. Micron-sized pores are distributed in the first layer, the second layer and the third layer; the micron-sized pores are filled with solid electrolyte particles, conductive agent and binder; Millimeter-scale pores penetrating the first, second, and third layers are filled with solid electrolyte particles, conductive agents, and binders.

2. A method for preparing a solid-state secondary battery cathode, wherein, The method is used to prepare the solid-state secondary battery cathode according to claim 1, and the method includes: The positive electrode particles, solid electrolyte particles, conductive agent, binder and dry ice particles are prepared into a low-temperature dry slurry, which is coated on the positive electrode current collector and then hot-pressed to form a film, forming the first layer. A low-temperature dry slurry is prepared by combining positive large particles, solid electrolyte small particles, conductive agent, binder and dry ice particles, and coated on the first layer and then hot-pressed to form a film to form the second layer. The positive electrode small particles, solid electrolyte large particles, conductive agent, binder and dry ice particles are prepared into a low temperature dry slurry, which is coated on the second layer and hot-pressed to form a film to form the third layer. The three-layer electrode sheet is then perforated. Solid electrolyte particles, conductive agent, and binder are mixed into a slurry, which is then applied to the perforated area and dried.

3. The method for preparing a solid-state secondary battery cathode according to claim 2, wherein, The step of preparing a low-temperature dry slurry from positive electrode particles, solid electrolyte particles, conductive agent, binder, and dry ice particles includes: A low-temperature dry slurry is prepared by mixing positive electrode particles, solid electrolyte particles, conductive agent, and binder in a mass ratio of 60~85:14~30:0.5~5:0.5~5, with dry ice accounting for 0.5%~5% of the total mass of the four substances in the first layer.

4. The method for preparing a solid-state secondary battery cathode according to claim 2, wherein, The step of preparing a low-temperature dry slurry from positive electrode particles, solid electrolyte particles, conductive agent, binder, and dry ice particles includes: A low-temperature dry slurry is prepared by mixing positive large particles, solid electrolyte small particles, conductive agent, and binder in a mass ratio of 70~97:2~20:0.5~5:0.5~5, and by adding dry ice at 0.5%~5% of the total mass of the four substances in the second layer.

5. The method for preparing a solid-state secondary battery cathode according to claim 2, wherein, The step of preparing a low-temperature dry slurry from small positive electrode particles, large solid electrolyte particles, conductive agent, binder, and dry ice particles includes: A low-temperature dry slurry is prepared by mixing small positive electrode particles, large solid electrolyte particles, conductive agent, and binder in a mass ratio of 45~79:20~45:0.5~5:0.5~5, with dry ice accounting for 0.5%~5% of the total mass of the four substances in the third layer.

6. The method for preparing a solid-state secondary battery cathode according to claim 2, wherein, The step of preparing a slurry from solid electrolyte particles, conductive agent, and binder includes: Solid electrolyte particles, conductive agent, and binder are mixed in a mass ratio of 90~99:0.5~5:0.5~5 to form a slurry.

7. The method for preparing a solid-state secondary battery cathode according to claim 2, wherein, The diameter of the hole formed by the drilling is 1 mm to 10 mm.

8. The method for preparing a solid-state secondary battery cathode according to claim 2, wherein, The diameter of the pores formed by the hot-press vaporization of the dry ice particles is 0.1 micrometers to 10 micrometers.

9. A solid-state secondary battery, wherein, The solid-state secondary battery includes the positive electrode of the solid-state secondary battery as described in claim 1.

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