Cathode composite, cathode electrode sheet and respective production methods, and battery and electric device comprising the cathode electrode sheet

Abstract

This invention relates to the field of secondary battery technology, and particularly to a cathode composite material, a cathode electrode, methods for preparing the respective, and a battery and electrical device comprising the cathode electrode. The cathode composite material includes a cathode material and a solid electrolyte coated on the surface of the cathode material. Coating the cathode material with a solid electrolyte, when the cathode composite material is in the form of a coating, helps to reduce the contact between the cathode material and the electrolyte, reduce side reactions, and improve battery performance.

Description

Technical Field

[0001] This invention relates to the field of secondary battery technology, and in particular to a cathode composite material, a cathode electrode and its preparation method, as well as a battery and electrical device containing the cathode electrode. Background Technology

[0002] With the rapid growth of portable electronic devices, electric vehicles, and other technologies, the demand for power batteries is also constantly increasing. Among these, the electrochemical performance of batteries is receiving increasing attention.

[0003] There are side reactions during the cycling process of secondary batteries. Summary of the Invention

[0004] The main objective of this application is to provide a cathode composite material that improves battery performance.

[0005] To achieve the above objectives, this application proposes a cathode composite material, which includes a cathode material and a solid electrolyte coating the surface of the cathode material.

[0006] Coating the cathode material with a solid electrolyte, especially when the cathode composite material is used in the coating, helps to reduce the contact between the cathode material and the electrolyte, reduce side reactions, and improve battery performance.

[0007] Optionally, the ratio of the volume average particle size Dv50 of the solid electrolyte to the volume average particle size Dv50 of the cathode material is 1:400 to 1:10, preferably 1:300 to 1:50.

[0008] To address the issue that the large particle size of solid electrolytes makes it difficult to coat the cathode material surface, the ratio of the volume average particle size Dv50 of the solid electrolyte to the volume average particle size Dv50 of the cathode material is 1:400 to 1:10, preferably 1:300 to 1:50.

[0009] Optionally, the volume average particle size Dv50 of the solid electrolyte ranges from 1 nm to 1000 nm, preferably from 10 nm to 500 nm.

[0010] And / or, the volume average particle size Dv50 of the cathode material ranges from 100 nm to 20000 nm, preferably from 500 nm to 5000 nm.

[0011] To improve the coating of solid electrolyte on the cathode material surface, the volume average particle size Dv50 of the solid electrolyte ranges from 1 nm to 1000 nm, preferably from 10 nm to 500 nm.

[0012] To improve the coating of the solid electrolyte on the surface of the cathode material and to reduce the risk of contact between the cathode material and the electrolyte, the volume average particle size Dv50 of the cathode material is in the range of 100 nm to 20000 nm, preferably 500 nm to 5000 nm.

[0013] Optionally, the solid electrolyte is spaced on the surface of the cathode material;

[0014] And / or, the thickness range of the solid electrolyte is greater than 0 and less than or equal to 3 μm, preferably greater than 0 and less than or equal to 100 nm.

[0015] This application does not limit the coating method of solid electrolyte on the surface of cathode material. Considering that the transport of lithium ions in cathode material (taking lithium-ion batteries as an example, but other types of secondary batteries can also be used) is mainly achieved by electrolyte, although solid electrolyte can also achieve lithium ion transport, its transport capacity is not as good as that of electrolyte. In order to improve the problem of solid electrolyte layer blocking electrolyte and affecting the transport of lithium ions by electrolyte, solid electrolyte is spaced on the surface of cathode material. In this way, it is convenient to leave gaps on the surface of cathode material, which helps electrolyte to contact cathode material and improve lithium ion transport.

[0016] To mitigate the impedance increase caused by the coating of solid electrolyte on the cathode material surface, the thickness of the solid electrolyte is greater than 0 and less than or equal to 3 μm, preferably greater than 0 and less than or equal to 100 nm.

[0017] Optionally, the mass ratio of the solid electrolyte to the cathode material is 1:200 to 1:50, preferably 1:150 to 1:60.

[0018] To improve the problem of side reactions caused by direct contact between the electrolyte and the cathode material, and to improve the problem of reduced battery energy density due to the addition of solid electrolyte, the mass ratio of solid electrolyte to cathode material is 1:200 to 1:50, preferably 1:150 to 1:60.

[0019] Optionally, the solid electrolyte includes at least one of polymer solid electrolyte, oxide solid electrolyte, and sulfide solid electrolyte.

[0020] This application does not limit the types of solid electrolytes, including but not limited to at least one of polymer solid electrolytes, oxide solid electrolytes, and sulfide solid electrolytes.

[0021] Optionally, the polymer solid electrolyte includes at least one of polyethylene oxide, polymethacrylate, and polyvinylidene fluoride;

[0022] And / or, the oxide solid electrolyte includes Li 3.3 La 0.56 TiO3, LiTi2(PO4)3, Li 14 Zn(GeO4)4, Li7La3Zr2O 12 At least one of LiPON (Li2PO2O);

[0023] And / or, the sulfide solid electrolytes Li2S-P2S5 and Li2S-P2S5-MS x M includes at least one of Si, Sn, Al, Se, and Ge.

[0024] Polymer solid electrolytes include, but are not limited to, at least one of polyethylene oxide, polymethacrylate, and polyvinylidene fluoride.

[0025] Oxide solid electrolytes include, but are not limited to, Li 3.3 La 0.56 TiO3, LiTi2(PO4)3, Li 14 Zn(GeO4)4, Li7La3Zr2O 12 At least one of LiPON (Li2PO2O).

[0026] Sulfide solid electrolytes include, but are not limited to, Li2S-P2S5 and Li2S-P2S5-MS. x M includes at least one of Si, Sn, Al, Se, and Ge.

[0027] This application also provides a cathode electrode, the cathode electrode comprising a current collector and a coating disposed on at least one side of the current collector, the coating comprising the cathode composite material as described above.

[0028] The coating includes a cathode composite material, which comprises a cathode material and a solid electrolyte coated on the surface of the cathode material. The solid electrolyte is used for ion transport, improves the direct contact between the cathode material and the electrolyte, improves the problem of intergranular / intragranular cracks in the cathode material, helps to reduce side reactions, improves battery cycle performance, and reduces the amount of gas generated during battery storage.

[0029] Optionally, the mass percentage of the cathode composite material in the total mass of the coating ranges from 80% to 98%, preferably from 85% to 95%.

[0030] To improve battery performance, the mass percentage of the cathode composite material in the total mass of the coating ranges from 80% to 98%, preferably from 85% to 95%.

[0031] It is understood that the coating is a single-layer structure, which may include a cathode composite material. The coating may also be a multi-layer structure, in which at least one layer includes a cathode composite material and at least another layer may not include a cathode composite material. For example, the coating includes a two-layer structure, with the first layer disposed close to the current collector and the second layer disposed on the surface of the first layer. In this case, the first layer may include a cathode composite material and the second layer may include a cathode material.

[0032] Optionally, the mass percentage of the solid electrolyte in the cathode composite material to the total mass of the coating ranges from 0.4% to 2%.

[0033] To improve battery performance, the mass percentage of the solid electrolyte in the cathode composite material ranges from 0.4% to 2% of the total coating mass. Understandably, as the concentration of the solid electrolyte in the cathode composite material increases, the probability of side reactions between the cathode material and the electrolyte decreases. However, as the concentration of the solid electrolyte in the cathode composite material continues to increase, the electrode impedance increases, and the specific capacity decreases.

[0034] Optionally, the coating includes at least two active layers, which are stacked on the same side of the current collector, with at least one active layer disposed on the current collector and at least another active layer disposed on the side of the at least one active layer away from the current collector.

[0035] The mass percentage of solid electrolyte in at least one of the active layers is defined as W1, and the mass percentage of solid electrolyte in at least another active layer is defined as W2, such that W1 > W2.

[0036] One active layer is disposed on the current collector, and another active layer is disposed on the side of the first active layer away from the current collector. Thus, based on their distance from the current collector, one active layer is positioned closer to the current collector, and the other is positioned further away. The mass percentage W1 of the solid electrolyte in the active layer closer to the current collector is greater than the mass percentage W2 of the solid electrolyte in the active layer further away from the current collector. This reduces the contact between the electrolyte and the cathode material in the active layer closer to the current collector, improves the wetting of the active layer further away from the current collector by the electrolyte, enhances ion transport performance, and improves battery performance.

[0037] Understandably, theoretically, ion transport mainly relies on the electrolyte. Although solid electrolytes also play a role in ion transport, their effect is not as good as that of electrolytes. In order to balance the contact between the electrolyte and the cathode material, solid electrolytes of different concentrations are distributed in different active layers. Specifically, the concentration of solid electrolytes distributed from the direction closer to the current collector to the direction farther away from the current collector tends to decrease. This improves the side reactions of the cathode material in the active layer closer to the current collector, while also maintaining the wetting of the electrolyte in the active layer farther away from the current collector. This reduces the side reactions that occur when the electrolyte contacts the cathode material, and also improves the ion transport performance.

[0038] Optionally, 0.4% ≤ W1 ≤ 4%, preferably, 0.4% ≤ W1 ≤ 3%;

[0039] And / or, 0 ≤ W2 ≤ 3.5%, preferably 0 ≤ W2 ≤ 2.5%.

[0040] To improve the contact between the electrolyte and the cathode material, and to improve the ion transport performance, the mass percentage W1 of the solid electrolyte in the active layer near the current collector satisfies 0.4% ≤ W1 ≤ 4%, preferably 0.4% ≤ W1 ≤ 3%; the mass percentage W2 of the solid electrolyte in the active layer away from the current collector satisfies 0 ≤ W2 ≤ 3.5%, preferably 0 ≤ W2 ≤ 2.5%.

[0041] Optionally, the compaction density of the coating is in the range of 2.0 g / cm³. 3 Up to 5.0 g / cm 3 Preferably, 2.3 g / cm³ 3 Up to 4.5 g / cm 3 .

[0042] To improve electrolyte wetting of the coating and enhance ion transport, the compaction density of the coating is set to a range of 2.0 g / cm³. 3 Up to 5.0 g / cm 3 Preferably, 2.3 g / cm³ 3 Up to 4.5 g / cm 3 .

[0043] Optionally, the coating includes at least two active layers, which are stacked on the same side of the current collector, with at least one active layer disposed on the current collector and at least another active layer disposed on the side of the at least one active layer away from the current collector.

[0044] The compaction density of at least one of the active layers is defined as ρ1, and the compaction density of at least another active layer is defined as ρ2, such that ρ1 > ρ2.

[0045] The compaction density of the coating increases with the increase of solid electrolyte. As the compaction density increases, the porosity in the coating decreases. In order to balance the side reactions caused by the contact between the cathode material and the electrolyte and to improve ion transport, the coating includes at least two active layers. The concentration of solid electrolyte in the active layer closer to the current collector is higher than that in the active layer farther from the current collector. Thus, the compaction density ρ1 of the active layer closer to the current collector is greater than the compaction density ρ2 of the active layer farther from the current collector. This reduces the side reactions between the cathode material and the electrolyte in the active layer closer to the current collector, improves the wetting of the active layer farther from the current collector with the electrolyte, and improves ion transport.

[0046] This application also provides a method for preparing a cathode composite material, comprising:

[0047] Prepare cathode material and solid electrolyte, and mix the cathode material and solid electrolyte to obtain cathode composite material.

[0048] A cathode composite material is obtained by simply mixing a solid electrolyte onto the surface of the cathode material. This preparation method is simple, low-cost, and convenient for large-scale production.

[0049] Optionally, the step of mixing the cathode material and the solid electrolyte includes:

[0050] The cathode material and the solid electrolyte are stirred and mixed at a stirring rate of 800 rpm to 2000 rpm for 2 h to 8 h to obtain a cathode composite material.

[0051] To ensure effective mixing, the cathode material and solid electrolyte are stirred at a stirring rate of 800 rpm to 2000 rpm for 2 to 8 hours to obtain a cathode composite material.

[0052] This application also provides a method for preparing a cathode electrode, comprising:

[0053] The cathode material is mixed with a solid electrolyte to obtain a cathode composite material;

[0054] The cathode composite material, binder, conductive agent, and solvent are mixed to obtain a slurry;

[0055] The slurry is coated onto the current collector, dried, and cold-pressed to obtain the cathode electrode.

[0056] The cathode material is mixed with a solid electrolyte to obtain a cathode composite material. The cathode composite material, binder, conductive agent, and solvent are then mixed to obtain a slurry. The slurry is coated onto a current collector, dried, and cold-pressed to obtain a cathode electrode. This process is simple and convenient for large-scale production.

[0057] Optionally, the step of coating the slurry onto the current collector, drying, and cold pressing to obtain the cathode electrode includes:

[0058] Prepare a slurry with at least two active layers, coat one of the active layers of the slurry onto the current collector, and dry it.

[0059] A slurry of another active layer is coated onto one of the active layers, dried, and cold-pressed to obtain a cathode electrode sheet;

[0060] The mass percentage of solid electrolyte in the slurry of one active layer is greater than the mass percentage of solid electrolyte in the slurry of the other active layer.

[0061] To prepare a multilayer coating, the steps of coating a slurry onto a current collector, drying, and cold pressing to obtain a cathode electrode include: preparing a slurry with at least two active layers; coating one active layer slurry onto the current collector and drying; coating the other active layer slurry onto one active layer, drying, and cold pressing to obtain the cathode electrode; wherein the mass percentage of solid electrolyte in the slurry of one active layer is greater than the mass percentage of solid electrolyte in the slurry of the other active layer. This improves the side reactions between the cathode material and the electrolyte in one active layer, improves ion transport in the other active layer, and enhances battery performance.

[0062] This application provides a battery comprising: an anode electrode, a cathode electrode, a separator, and an electrolyte, wherein the cathode electrode is a cathode electrode as described above or a cathode electrode obtained by the method described above for preparing a cathode electrode.

[0063] This application provides an electrical device, which includes the battery described above.

[0064] The cathode composite material of this application includes a cathode material and a solid electrolyte coated on the surface of the cathode material. Coating the cathode material with a solid electrolyte, when the cathode composite material is used as a coating, helps to reduce the contact between the cathode material and the electrolyte, decrease side reactions, and improve battery performance. Attached Figure Description

[0065] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0066] Figure 1 This is a schematic flowchart of the method for preparing the cathode electrode of this application;

[0067] Figure 2This is a schematic diagram of the structure of an embodiment of the cathode electrode of this application;

[0068] Figure 3 This is a schematic diagram of the structure of an embodiment of the cathode electrode of this application;

[0069] Figure 4 This is a schematic diagram of a secondary battery according to one embodiment of this application;

[0070] Figure 5 yes Figure 4 An exploded view of a secondary battery according to an embodiment of this application is shown.

[0071] Figure 6 This is a schematic diagram of a battery module according to one embodiment of this application;

[0072] Figure 7 This is a schematic diagram of a battery pack according to one embodiment of this application;

[0073] Figure 8 yes Figure 7 An exploded view of a battery pack according to one embodiment of this application is shown;

[0074] Figure 9 This is a schematic diagram of an electrical device that uses a secondary battery as a power source according to one embodiment of this application.

[0075] Explanation of icon numbers:

[0076] label name label name 100 Cathode plate 3 Lower box 10 current collector 4 Battery Module 20 One active layer 5 Secondary batteries 30 Another active layer 51 case 1 Battery pack 52 Electrode assembly 2 Upper box 53 Top cover assembly

[0077] 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. Detailed Implementation

[0078] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0079] The following detailed description, with appropriate reference to the accompanying drawings, specifically discloses the cathode composite material, cathode electrode, and respective preparation methods, as well as embodiments of batteries and electrical devices comprising the cathode electrode. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0080] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0081] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0082] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0083] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0084] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0085] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0086] The cathode material undergoes side reactions during secondary battery cycling.

[0087] For example, side reactions can occur when the cathode material comes into contact with the electrolyte.

[0088] To address the aforementioned issues, this application provides a cathode composite material comprising a cathode material and a solid electrolyte coated on the surface of the cathode material.

[0089] Solid electrolytes are solid substances that exhibit ionic conductivity.

[0090] Coating refers to the process where solid electrolyte particles are placed on the surface of cathode particles to form a coating state.

[0091] The solid electrolyte coating the surface of the cathode particles enables the cathode composite material to form a core-shell structure. In the core-shell structure, the cathode particles are the core layer, the solid electrolyte is located on the outer surface of the core layer, and the structure coating the surface of the core layer structure is the shell structure.

[0092] The core-shell structure can be observed using a transmission electron microscope (TEM). Specifically, due to the different materials of the core and shell structures, there will be a difference in brightness (mass-thickness contrast) between the core and shell structures in the TEM image. This mass-thickness contrast is the difference in contrast caused by the difference in thickness and mass of different regions of the sample surface. Since different parts of the sample have different electron scattering capabilities, the number of electrons transmitted through the objective lens will also be different, resulting in differences in electron beam intensity. Regions with strong scattering and fewer transmitted electrons will appear dark, while those with strong scattering and fewer transmitted electrons will appear bright.

[0093] Coating the cathode material with a solid electrolyte, especially when the cathode composite material is used in the coating, helps to reduce the direct contact between the cathode material and the electrolyte, thereby reducing side reactions and improving battery performance.

[0094] In one embodiment, the mass ratio of the solid electrolyte to the cathode material is 1:200 to 1:50, preferably 1:150 to 1:60.

[0095] To improve the problem of side reactions caused by direct contact between the electrolyte and the cathode material, and to improve the problem of reduced battery energy density due to the addition of solid electrolyte, the mass ratio of solid electrolyte to cathode material is 1:200 to 1:50, preferably 1:150 to 1:60.

[0096] The values ​​in the range of 1:200 to 1:50 include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the embodiments, and 1:200, 1:190, 1:150, 1:120, 1:100, 1:80, 1:70, 1:50, etc., as well as the range values ​​between any two of the above point values.

[0097] The values ​​in the range of 1:150 to 1:60 include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the embodiments, as well as 1:150, 1:130, 1:110, 1:100, 1:90, 1:60, etc., and the range values ​​between any two point values ​​mentioned above.

[0098] In one embodiment, the ratio of the volume average particle size Dv50 of the solid electrolyte to the volume average particle size Dv50 of the cathode material is 1:400 to 1:10, preferably 1:300 to 1:50.

[0099] Dv50 is the particle size at which the cumulative particle size distribution percentage of a sample reaches 50%. Physically, it means that 50% of the particles are larger than Dv50, and 50% are smaller. Dv50 is also called the median diameter or median particle size. Dv50 is often used to represent the average particle size of powders.

[0100] The volumetric particle size distribution Dv50 can be tested using methods known in the art. As an example, it can be characterized using a Malvern laser particle size analyzer, such as the Malvern Mastersizer-3000, in accordance with GB / T 19077-2016.

[0101] To address the issue that the large particle size of solid electrolytes makes it difficult to coat the cathode material surface, the ratio of the volume average particle size Dv50 of the solid electrolyte to the volume average particle size Dv50 of the cathode material is 1:400 to 1:10, preferably 1:300 to 1:50.

[0102] The values ​​in the range of 1:400 to 1:10 include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the embodiments, and 1:400, 1:380, 1:350, 1:320, 1:300, 1:280, 1:250, 1:220, 1:200, 1:180, 1:150, 1:120, 1:100, 1:90, 1:80, 1:70, 1:60, 1:50, 1:40, 1:30, 1:20, 1:10, etc., as well as the range values ​​between any two of the above point values.

[0103] In one embodiment, the volume average particle size Dv50 of the solid electrolyte ranges from 1 nm to 1000 nm, preferably from 10 nm to 500 nm; and / or, the volume average particle size Dv50 of the cathode material ranges from 100 nm to 20000 nm, preferably from 500 nm to 5000 nm.

[0104] To improve the coating of the solid electrolyte on the cathode material surface, the volume average particle size Dv50 of the solid electrolyte ranges from 1 nm to 1000 nm, preferably from 10 nm to 500 nm. To further improve the coating of the solid electrolyte on the cathode material surface and reduce the risk of contact between the cathode material and the electrolyte, the volume average particle size Dv50 of the cathode material ranges from 100 nm to 20000 nm, preferably from 500 nm to 5000 nm.

[0105] The values ​​in the range of 1nm to 1000nm include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the embodiments, and 1nm, 10nm, 50nm, 80nm, 100nm, 150nm, 200nm, 250nm, 300nm, 350nm, 400nm, 450nm, 500nm, 550nm, 600nm, 650nm, 700nm, 750nm, 800nm, 850nm, 900nm, 950nm, 1000nm, etc., as well as the range values ​​between any two of the above point values.

[0106] The values ​​within the range of 100nm to 20000nm include the minimum and maximum values ​​of this range, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the embodiments, and values ​​of 100nm, 150nm, 200nm, 250nm, 300nm, 350nm, 400nm, 450nm, 500nm, 550nm, 600nm, 650nm, 700nm, 750nm, 800nm, 850nm, 900nm, 950nm, and 1. 000nm, 1100nm, 1300nm, 1500nm, 1800nm, 2000nm, 2500nm, 3000nm, 3500nm, 4000nm, 4500nm, 5000nm, 5500nm, 6000nm, 6500nm, 7000nm, 7500nm, 8000nm, 8500nm, 9000nm, 10000nm, 15000nm, 20000nm, etc., as well as the range between any two of the above point values.

[0107] In one embodiment, the solid electrolyte spacer is disposed on the surface of the cathode material;

[0108] And / or, the thickness range of the solid electrolyte is greater than 0 and less than or equal to 3 μm, preferably greater than 0 and less than or equal to 100 nm.

[0109] This application does not limit the coating method of solid electrolyte on the surface of cathode material. Considering that the transport of lithium ions in cathode material (taking lithium-ion batteries as an example, but other types of secondary batteries can also be used) is mainly achieved by electrolyte, although solid electrolyte can also achieve lithium ion transport, its transport capacity is not as good as that of electrolyte. In order to improve the problem of solid electrolyte layer blocking electrolyte and affecting the transport of lithium ions by electrolyte, solid electrolyte is spaced on the surface of cathode material. In this way, it is convenient to leave gaps on the surface of cathode material, which helps electrolyte to contact cathode material and improve lithium ion transport.

[0110] To mitigate the impedance increase caused by the coating of solid electrolyte on the cathode material surface, the thickness of the solid electrolyte is greater than 0 and less than or equal to 3 μm, preferably greater than 0 and less than or equal to 100 nm.

[0111] The values ​​greater than 0 and less than or equal to 3 μm include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the embodiments, and 0.1nm, 1nm, 10nm, 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm, 100nm, 150nm, 200nm, 300nm, 400nm, 500nm, 600nm, 700nm, 800nm, 900nm, 1000nm, 1100nm, 1500nm, 1800nm, 2000nm, 2100nm, 2500nm, 2990nm, 3000nm, etc., as well as the range values ​​between any two of the above point values.

[0112] In one embodiment, the solid electrolyte includes at least one of polymer solid electrolyte, oxide solid electrolyte, and sulfide solid electrolyte.

[0113] Polymer solid electrolytes are typically composed of polymers and metal salts.

[0114] Oxide solid electrolytes, including lithium lanthanum zirconium oxide (Li7La3Zr2O) 12 ), lithium lanthanum titanium oxide, etc., from a structural point of view, oxide solid electrolytes include oxygen.

[0115] Sulfide solid electrolytes, including Li2S-P2S5, structurally contain sulfur.

[0116] This application does not limit the types of solid electrolytes, including but not limited to at least one of polymer solid electrolytes, oxide solid electrolytes, and sulfide solid electrolytes.

[0117] In one embodiment, the polymer solid electrolyte includes at least one of polyethylene oxide, polymethacrylate, and polyvinylidene fluoride; and / or, the oxide solid electrolyte includes Li 3.3 La 0.56 TiO3, LiTi2(PO4)3, Li 14 Zn(GeO4)4, Li7La3Zr2O 12 At least one of LiPON (Li2PO2O); and / or, sulfide solid electrolytes Li2S-P2S5 and Li2S-P2S5-MS. x M includes at least one of Si, Sn, Al, Se, and Ge.

[0118] Polymer solid electrolytes include, but are not limited to, at least one of polyethylene oxide, polymethacrylate, and polyvinylidene fluoride. Oxide solid electrolytes include, but are not limited to, Li. 3.3 La 0.56 TiO3, LiTi2(PO4)3, Li 14 Zn(GeO4)4, Li7La3Zr2O 12 At least one of LiPON (Li2PO2O). Sulfide solid electrolytes include, but are not limited to, Li2S-P2S5 and Li2S-P2S5-MS. x M includes at least one of Si, Sn, Al, Se, and Ge.

[0119] This application also provides a cathode electrode, which includes a current collector and a coating disposed on at least one side of the current collector, the coating including a cathode composite material such as the one described above.

[0120] like Figure 2 and Figure 3 As shown, the cathode electrode 100 includes a current collector 10 and a coating disposed on one side of the current collector 10, such as... Figure 2 As shown, the coating can be a single layer structure, such as Figure 3 As shown, the coating can be a two-layer structure, and of course, the coating can also be placed on the other side of the current collector.

[0121] The coating includes a cathode composite material, which comprises a cathode material and a solid electrolyte coated on the surface of the cathode material. The solid electrolyte is used for ion transport, improves the direct contact between the cathode material and the electrolyte, improves the problem of intergranular / intragranular cracks in the cathode material, helps to reduce side reactions, improves battery cycle performance, and reduces the amount of gas generated during battery storage.

[0122] In one embodiment, the mass percentage of the cathode composite material in the total mass of the coating ranges from 80% to 98%, preferably from 85% to 95%.

[0123] The mass percentage of the cathode composite material in the total mass of the coating. For example, if the total mass of the coating is M0 and the mass of the cathode composite material in the coating is m0, then the calculation formula is (m0 / M0)×100%.

[0124] To improve battery performance, the mass percentage of the cathode composite material in the total mass of the coating ranges from 80% to 98%, preferably from 85% to 95%.

[0125] It is understood that the coating is a single-layer structure, which may include a cathode composite material. The coating may also be a multi-layer structure, in which at least one layer includes a cathode composite material and at least another layer may not include a cathode composite material. For example, the coating includes a two-layer structure, with the first layer disposed close to the current collector and the second layer disposed on the surface of the first layer. In this case, the first layer may include a cathode composite material and the second layer may include a cathode material.

[0126] The values ​​in the range of 80% to 98% include the minimum and maximum values ​​of this range, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the embodiments, and 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, etc., as well as the range values ​​between any two of the above point values.

[0127] In one embodiment, the mass percentage of the solid electrolyte in the cathode composite material to the total mass of the coating ranges from 0.4% to 2%.

[0128] To improve battery performance, the mass percentage of the solid electrolyte in the cathode composite material ranges from 0.4% to 2% of the total coating mass. Understandably, as the concentration of the solid electrolyte in the cathode composite material increases, the probability of side reactions between the cathode material and the electrolyte decreases. However, as the concentration of the solid electrolyte in the cathode composite material continues to increase, the electrode impedance increases, and the specific capacity decreases.

[0129] The values ​​in the range of 0.4% to 2% include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the embodiments, and 0.4%, 0.5%, 0.7%, 0.9%, 1.0%, 1.3%, 1.5%, 1.7%, 1.9%, 2%, etc., as well as the range values ​​between any two of the above point values.

[0130] In one embodiment, the coating includes at least two active layers, which are stacked on the same side of the current collector. At least one active layer is disposed on the current collector, and at least another active layer is disposed on the side of the at least one active layer away from the current collector. The mass percentage of solid electrolyte in the at least one active layer is defined as W1, and the mass percentage of solid electrolyte in the at least another active layer is defined as W2, satisfying W1 > W2.

[0131] The coating includes at least two active layers, meaning that the coating can be a two-layer structure, or a three-layer, four-layer, or other structure.

[0132] At least two active layers are stacked on the same side of the current collector, for example, such as Figure 3 As shown, the two active layers are located on the same side of the current collector and are stacked on one side of the current collector.

[0133] The mass percentage of solid electrolyte in an active layer, for example, if the mass of an active layer is M1 and the mass of solid electrolyte in that layer is m1, then the formula for calculating the mass percentage of solid electrolyte in an active layer is (m1 / M1)×100%.

[0134] One active layer is disposed on the current collector, and another active layer is disposed on the side of at least one active layer away from the current collector. Thus, according to their distance from the current collector, one active layer is positioned closer to the current collector, and the other is positioned further away. The mass percentage W1 of the solid electrolyte in the active layer closer to the current collector is greater than the mass percentage W2 of the solid electrolyte in the active layer further away from the current collector. This reduces the contact between the electrolyte and the cathode material in the active layer closer to the current collector, improves the wetting of the active layer further away from the current collector by the electrolyte, enhances ion transport performance, and improves battery performance.

[0135] Understandably, theoretically, ion transport mainly relies on the electrolyte. Although solid electrolytes also play a role in ion transport, their effect is not as good as that of electrolytes. In order to balance the contact between the electrolyte and the cathode material, solid electrolytes of different concentrations are distributed in different active layers. Specifically, the concentration of solid electrolytes distributed from the direction closer to the current collector to the direction farther away from the current collector tends to decrease. This improves the side reactions of the cathode material in the active layer closer to the current collector, while also maintaining the wetting of the electrolyte in the active layer farther away from the current collector. This reduces the side reactions that occur when the electrolyte contacts the cathode material, and also improves the ion transport performance.

[0136] In one embodiment, 0.4% ≤ W1 ≤ 4%, preferably 0.4% ≤ W1 ≤ 3%; and / or, 0 ≤ W2 ≤ 3.5%, preferably 0 ≤ W2 ≤ 2.5%.

[0137] To improve the contact between the electrolyte and the cathode material, and to improve the ion transport performance, the mass percentage W1 of the solid electrolyte in the active layer near the current collector satisfies 0.4% ≤ W1 ≤ 4%, preferably 0.4% ≤ W1 ≤ 3%; the mass percentage W2 of the solid electrolyte in the active layer away from the current collector satisfies 0 ≤ W2 ≤ 3.5%, preferably 0 ≤ W2 ≤ 2.5%.

[0138] In the above 0.4%≤W1≤4%, the values ​​include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the embodiments, and 0.4%, 0.5%, 0.7%, 0.9%, 1.0%, 1.3%, 1.5%, 1.7%, 1.9%, 2%, 2.5%, 2.7%, 3%, 3.5%, 4%, etc., as well as the range values ​​between any two of the above point values.

[0139] In one embodiment, the compaction density of the coating ranges from 2.0 g / cm³. 3 Up to 5.0 g / cm 3 Preferably, 2.3 g / cm³ 3 Up to 4.5 g / cm 3 .

[0140] Compacted density, compacted density = areal density / (thickness of electrode after compaction - thickness of current collector), unit: g / cm³ 3 Surface density is the mass per unit area of ​​a material with a specified thickness.

[0141] To improve electrolyte wetting of the coating and enhance ion transport, the compaction density of the coating is set to a range of 2.0 g / cm³. 3 Up to 5.0 g / cm 3 Preferably, 2.3 g / cm³ 3 Up to 4.5 g / cm 3 .

[0142] The above 2.0 g / cm 3 Up to 5.0 g / cm 3 In this context, the values ​​include the minimum and maximum values ​​within the range, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the embodiments and 2.0 g / cm³. 3 2.3g / cm 3 2.5g / cm 3 2.7g / cm3 3.0g / cm 3 3.5g / cm 3 4.0g / cm 3 4.5g / cm 3 5.0g / cm 3 And so on, as well as the range of values ​​between any two of the above point values.

[0143] In one embodiment, the coating includes at least two active layers, which are stacked on the same side of the current collector. At least one active layer is disposed on the current collector, and at least another active layer is disposed on the side of the at least one active layer away from the current collector. The compaction density of the at least one active layer is defined as ρ1, and the compaction density of the at least another active layer is defined as ρ2, satisfying ρ1 > ρ2.

[0144] The compaction density of the coating increases with the increase of solid electrolyte. As the compaction density increases, the porosity in the coating decreases. To balance the side reactions caused by the contact between the cathode material and the electrolyte, and to improve ion transport, the coating includes at least two active layers. At least one active layer is disposed in the current collector, and at least another active layer is disposed on the side of the at least one active layer away from the current collector. One active layer is disposed close to the current collector, and the other active layer is disposed away from the current collector compared to the first active layer. The concentration of solid electrolyte in the active layer close to the current collector is higher than that in the active layer away from the current collector. Thus, the compaction density ρ1 of the active layer close to the current collector is greater than the compaction density ρ2 of the active layer away from the current collector. This reduces the side reactions between the cathode material and the electrolyte in the active layer close to the current collector, improves the wetting of the active layer away from the current collector with the electrolyte, and improves ion transport.

[0145] This application also provides a method for preparing a cathode composite material, comprising: preparing a cathode material and a solid electrolyte, and mixing the cathode material and the solid electrolyte to obtain a cathode composite material.

[0146] A cathode composite material is obtained by simply mixing a solid electrolyte onto the surface of the cathode material. This preparation method is simple, low-cost, and convenient for large-scale production.

[0147] In one embodiment, the step of mixing the cathode material and the solid electrolyte includes: stirring and mixing the cathode material and the solid electrolyte at a stirring rate of 800 rpm to 2000 rpm for a stirring time of 2 h to 8 h to obtain a cathode composite material.

[0148] To ensure effective mixing, the cathode material and solid electrolyte are stirred at a stirring rate of 800 rpm to 2000 rpm for 2 to 8 hours to obtain a cathode composite material.

[0149] like Figure 1 As shown, this application also provides a method for preparing a cathode electrode, comprising: mixing a cathode material with a solid electrolyte to obtain a cathode composite material; mixing the cathode composite material, a binder, a conductive agent and a solvent to obtain a slurry; coating the slurry on a current collector, drying and cold pressing to obtain a cathode electrode.

[0150] The cathode material is mixed with a solid electrolyte to obtain a cathode composite material. The cathode composite material, binder, conductive agent, and solvent are then mixed to obtain a slurry. The slurry is coated onto a current collector, dried, and cold-pressed to obtain a cathode electrode. This process is simple and convenient for large-scale production.

[0151] In one embodiment, the step of coating the slurry onto the current collector, drying, and cold pressing to obtain the cathode electrode includes: preparing a slurry with at least two active layers; coating the slurry of one active layer onto the current collector and drying; coating the slurry of the other active layer onto one active layer, drying, and cold pressing to obtain the cathode electrode; wherein the mass percentage of solid electrolyte in the slurry of one active layer is greater than the mass percentage of solid electrolyte in the slurry of the other active layer.

[0152] To prepare a multilayer coating, the steps of coating a slurry onto a current collector, drying, and cold pressing to obtain a cathode electrode include: preparing a slurry with at least two active layers; coating one active layer slurry onto the current collector and drying; coating the other active layer slurry onto one active layer, drying, and cold pressing to obtain the cathode electrode; wherein the mass percentage of solid electrolyte in the slurry of one active layer is greater than the mass percentage of solid electrolyte in the slurry of the other active layer. This improves the side reactions between the cathode material and the electrolyte in one active layer, improves ion transport in the other active layer, and enhances battery performance.

[0153] This application provides a battery, comprising: an anode electrode, a cathode electrode, a separator, and an electrolyte, wherein the cathode electrode is a cathode electrode as described above or a cathode electrode obtained by the method described above. Since the cathode electrode employs all the technical solutions of all the above embodiments, it possesses at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be elaborated further here.

[0154] This application also provides an electrical device, which includes the battery described above. Since the battery employs all the technical solutions of all the above embodiments, it possesses at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be elaborated upon here.

[0155] In addition, the secondary battery, battery module, battery pack and power device of this application will be described below with appropriate reference to the accompanying drawings.

[0156] In one embodiment of this application, a secondary battery is provided.

[0157] Typically, a secondary battery includes a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and releasing. The electrolyte acts as a conductor of ions between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits between the electrodes while allowing ions to pass through. The separator described above is the improved separator of this application.

[0158] The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector.

[0159] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0160] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0161] In some embodiments, when the secondary battery is a lithium-ion battery, the positive electrode active material may be a positive electrode active material known in the art for lithium-ion batteries. As an example, the positive electrode active material may include at least one of the following materials: lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as battery positive electrode active materials may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNi). 1 / 3 Co 1 / 3Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 ), lithium nickel cobalt aluminum oxide (such as LiNi) 0.85 Co 0.15 Al 0.05 At least one of O2 and its modified compounds. Examples of lithium phosphates with an olivine structure include, but are not limited to, lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0162] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0163] In some embodiments, the positive electrode film may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0164] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0165] The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector, the negative electrode film layer including a negative electrode active material.

[0166] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0167] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0168] In some embodiments, the negative electrode active material may be a negative electrode active material known in the art for use in batteries. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. Silicon-based materials may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0169] In some embodiments, the negative electrode film layer may optionally include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0170] In some embodiments, the negative electrode film may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0171] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0172] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0173] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not specify any particular type of electrolyte; it can be selected according to requirements.

[0174] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0175] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0176] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0177] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0178] In some embodiments, the secondary battery also includes a separator. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0179] In some embodiments, the diaphragm material can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The diaphragm can be a single-layer film or a multi-layer composite film, without particular limitation. When the diaphragm is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0180] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0181] In some embodiments, the secondary battery may include an outer packaging. This outer packaging may be used to encapsulate the electrode assembly and electrolyte described above.

[0182] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the secondary battery can also be a soft pack, such as a pouch. The material of the soft pack can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0183] This application does not impose any particular limitation on the shape of the secondary battery; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 4 This is an example of a square-structured secondary battery 5.

[0184] In some implementations, refer to Figure 5 The outer packaging may include a housing 51 and a cover 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover 53 can be placed over the opening to close the receiving cavity. The positive electrode, negative electrode, and separator may be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The secondary battery 5 may contain one or more electrode assemblies 52, which can be selected by those skilled in the art according to specific practical needs.

[0185] In some implementations, the secondary batteries can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery module.

[0186] Figure 6 This is battery module 4, used as an example. (See reference...) Figure 6 In battery module 4, multiple secondary batteries 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple secondary batteries 5 can be fixed in place using fasteners.

[0187] Optionally, the battery module 4 may also include a housing with a receiving space in which a plurality of secondary batteries 5 are received.

[0188] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0189] Figure 7 and Figure 8 This is battery pack 1 as an example. (See reference...) Figure 7 and Figure 8 The battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3, with the upper body 2 covering the lower body 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0190] In addition, this application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided in this application. The secondary battery, battery module, or battery pack can be used as the power source of the electrical device or as the energy storage unit of the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0191] As an electrical device, a secondary battery, battery module, or battery pack can be selected according to its usage requirements.

[0192] Figure 9 This is an example of an electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the secondary battery for this device, a battery pack or battery module can be used.

[0193] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a rechargeable battery as their power source.

[0194] Example

[0195] Anode preparation

[0196] Artificial graphite, conductive agent acetylene black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC-Na) were added to deionized water at a mass ratio of 96.2:1.0:1.6:1.2. The mixture was thoroughly stirred and mixed to prepare a negative electrode slurry (solid content 63%). This negative electrode slurry was then subjected to a concentration of 98 g / m³. 2 The loading amount is coated on the copper foil of the negative electrode current collector, and then dried, cold-pressed and slit to obtain the negative electrode sheet.

[0197] electrolyte

[0198] At 25°C, ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1 to obtain a mixed solvent. LiPF6 is then dissolved in the above mixed solvent to obtain an electrolyte, wherein the concentration of LiPF6 is 1 mol / L.

[0199] diaphragm

[0200] A commercially available PE microporous film with a thickness of 7μm and an average pore size of 80nm (from Zhuogao Electronic Technology Co., Ltd.) was used.

[0201] Battery assembly

[0202] The cathode electrode, separator, and anode electrode are stacked, wound, and cold-pressed in sequence to obtain a battery cell (during which the separator and electrode are bonded together). The battery cell is placed in an outer package, and the electrolyte prepared above is added. After processes such as encapsulation, standing, formation, and aging, a secondary battery is obtained.

[0203] Performance testing

[0204] Battery gas generation test

[0205] The battery cells were adjusted to 95% SOC, and the voltage was monitored and replenished daily. They were stored at 60°C for 60 days, and the gas production was measured by the water displacement method.

[0206] Impedance test

[0207] A symmetrical cell (positive electrode to positive electrode) was prepared using cathode electrodes. After adding electrolyte, the electrochemical impedance spectroscopy was tested at the cell's open-circuit voltage. The AC amplitude was 5 mV, and the scanning frequency range was 100 kHz to 25 mHz. The measured impedance spectrum was fitted and analyzed using the SIM software built into the IM6 electrochemical analyzer.

[0208] Example 1

[0209] solid electrolyte (Li) 3.3 La 0.56 TiO3) and cathode materials (NCM811, LiNi) 0.8 Co 0.1 Mn 0.1 O2) is mixed at a mass ratio of 1:97 to obtain a cathode composite material.

[0210] The cathode composite material, binder (polyvinylidene fluoride (PVDF)), conductive agent (carbon black), and solvent (N-methylpyrrolidone (NMP)) were mixed in a mass ratio of 98:1:1:60 to obtain the slurry.

[0211] The slurry is coated onto the current collector aluminum foil, and then dried, cold-pressed, and slit to obtain the cathode electrode.

[0212] Example 2 and Example 3

[0213] Based on Example 1, the mass ratio of solid electrolyte to cathode material was adjusted to 1:200 and 1:50 to obtain Example 2 and Example 3.

[0214] Example 4

[0215] Based on Example 3, the type of solid electrolyte was changed to obtain Example 4.

[0216] Example 5

[0217] Based on Example 3, the coating is set to two layers, with the mass ratio of solid electrolyte to cathode material in the first layer being greater than that in the second layer.

[0218] Examples 6 to 12

[0219] Based on Example 1, the volume average particle size Dv50 of the solid electrolyte and cathode material was adjusted to obtain Examples 6 to 12.

[0220] Comparative Example 1 was obtained by not adding a solid electrolyte, based on Example 1.

[0221] Table 1 List of experimental parameters

[0222]

[0223]

[0224] Table 2 List of Experimental Parameters

[0225]

[0226]

[0227] Table 3 Performance Parameter List

[0228]

[0229] As can be seen from the table above, coating the cathode material with a solid electrolyte can improve the gas production of the battery and enhance the gas production and maintenance of the cell. Furthermore, as can be seen from Examples 3 and 5, in the two coating layers, the mass ratio of solid electrolyte to cathode material in the first layer is greater than that in the second layer, resulting in better performance.

[0230] The above are merely preferred embodiments of this application and do not limit the scope of the patent application. Any equivalent structural transformations made based on the inventive concept of this application and the contents of the specification and drawings of this application, or direct / indirect applications in other related technical fields, are included within the scope of patent protection of this application.

Claims

1. A cathode electrode, characterized in that, The cathode electrode includes a current collector (10) and a coating disposed on at least one side of the current collector (10). The coating includes a cathode composite material, which includes a cathode material and a solid electrolyte coating the surface of the cathode material. The coating includes at least two active layers, which are stacked on the same side of the current collector, with at least one active layer disposed on the current collector and at least another active layer disposed on the side of the at least one active layer away from the current collector. The mass percentage of solid electrolyte in at least one of the active layers is defined as W1, and the mass percentage of solid electrolyte in at least another active layer is defined as W2, such that W1 > W2.

2. The cathode electrode as described in claim 1, characterized in that, The ratio of the volume average particle size Dv50 of the solid electrolyte to the volume average particle size Dv50 of the cathode material is 1:400 to 1:

10.

3. The cathode electrode as described in claim 2, characterized in that, The ratio of the volume average particle size Dv50 of the solid electrolyte to the volume average particle size Dv50 of the cathode material is 1:300 to 1:

50.

4. The cathode electrode sheet according to any one of claims 1 to 3, characterized in that, The volume average particle size Dv50 of the solid electrolyte ranges from 1 nm to 1000 nm. And / or, the volume average particle size Dv50 of the cathode material ranges from 100 nm to 20000 nm.

5. The cathode electrode as described in claim 4, characterized in that, The volume average particle size Dv50 of the solid electrolyte ranges from 10 nm to 500 nm. And / or, the volume average particle size Dv50 of the cathode material ranges from 500 nm to 5000 nm.

6. The cathode electrode sheet according to any one of claims 1 to 5, characterized in that, The solid electrolyte is spaced on the surface of the cathode material; And / or, the thickness range of the solid electrolyte is greater than 0 and less than or equal to 3 μm.

7. The cathode electrode as described in claim 6, characterized in that, The thickness of the solid electrolyte is greater than 0 and less than or equal to 100 nm.

8. The cathode electrode sheet according to any one of claims 1 to 7, characterized in that, The mass ratio of the solid electrolyte to the cathode material is 1:200 to 1:

50.

9. The cathode electrode as described in claim 8, characterized in that, The mass ratio of the solid electrolyte to the cathode material is 1:150 to 1:

60.

10. The cathode electrode sheet according to any one of claims 1 to 9, characterized in that, The solid electrolyte includes at least one of polymer solid electrolyte, oxide solid electrolyte, and sulfide solid electrolyte.

11. The cathode electrode as described in claim 10, characterized in that, The polymer solid electrolyte includes at least one of polyethylene oxide, polymethacrylate, and polyvinylidene fluoride. And / or, the oxide solid electrolyte includes Li 3.3 La 0.56 TiO3, LiTi2(PO4)3, Li 14 Zn(GeO4)4, Li7La3Zr2O 12 At least one of LiPON; And / or, the sulfide solid electrolyte includes Li2S-P2S5, Li2S-P2S5-MS x M includes at least one of Si, Sn, Al, Se, and Ge.

12. The cathode electrode as described in any one of claims 1 to 11, characterized in that, The mass percentage of the cathode composite material in the total mass of the coating ranges from 80% to 98%.

13. The cathode electrode as described in claim 12, characterized in that, The mass percentage of the cathode composite material in the total mass of the coating ranges from 85% to 95%.

14. The cathode electrode as described in any one of claims 1 to 13, characterized in that, The mass percentage of the solid electrolyte in the cathode composite material to the total mass of the coating ranges from 0.4% to 2%.

15. The cathode electrode as described in any one of claims 1 to 14, characterized in that, 0.4％≤W1≤4％； And / or, 0 ≤ W2 ≤ 3.5%.

16. The cathode electrode as described in claim 15, characterized in that, 0.4％≤W1≤3％； And / or, 0 ≤ W2 ≤ 2.5%.

17. The cathode electrode sheet according to any one of claims 1 to 16, characterized in that, The compaction density of the coating ranges from 2.0 g / cm³. 3 Up to 5.0 g / cm 3 .

18. The cathode electrode as described in claim 17, characterized in that, The compaction density of the coating ranges from 2.3 g / cm³. 3 Up to 4.5 g / cm 3 .

19. The cathode electrode as described in claim 17 or 18, characterized in that, The compaction density of at least one of the active layers is defined as ρ1, and the compaction density of at least another active layer is defined as ρ2, such that ρ1 > ρ2.

20. A method for preparing a cathode electrode sheet as described in any one of claims 1 to 19, characterized in that, include: The cathode material is mixed with a solid electrolyte to obtain a cathode composite material; The cathode composite material, binder, conductive agent, and solvent are mixed to obtain a slurry; The slurry is coated onto the current collector, dried, and cold-pressed to obtain the cathode electrode sheet; The step of coating the slurry onto the current collector, drying, and cold pressing to obtain the cathode electrode includes: Prepare a slurry with at least two active layers, coat one of the active layers of the slurry onto the current collector, and dry it. A slurry of another active layer is coated onto one of the active layers, dried, and cold-pressed to obtain a cathode electrode sheet; The mass percentage of solid electrolyte in the slurry of one active layer is greater than the mass percentage of solid electrolyte in the slurry of the other active layer.

21. The method for preparing the cathode electrode as described in claim 20, characterized in that, The step of mixing the cathode material and the solid electrolyte includes: The cathode material and the solid electrolyte are stirred and mixed at a stirring rate of 800 rpm to 2000 rpm for 2 h to 8 h to obtain a cathode composite material.

22. A battery, characterized in that, include: An anode, a cathode, a separator, and an electrolyte, wherein the cathode is a cathode obtained by any one of claims 1 to 19 or by the method of preparing a cathode as described in claim 20 or 21.

23. An electrical appliance, characterized in that, The electrical device includes the battery as described in claim 22.

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