Positive plate, lithium ion battery and electric equipment

Abstract

The invention belongs to the technical field of secondary batteries, and particularly relates to a positive plate, a lithium ion battery and electric equipment. A positive active material layer on the positive plate provided by the invention comprises a fast ion conductor material with the mass percentage of 0.1-5%, the fast ion conductor material comprises an inner core and a coating layer located on at least part of the surface of the inner core, the composition of the inner core is Li6PS5Cl, and the composition of the coating layer comprises Li3PO4. According to the invention, the fast ion conductor material with specific composition is added into the positive active material layer according to a certain proportion, so that when the battery is subjected to high-rate charge-discharge cycle, an ion transmission network can be formed through the fast ion conductor, lithium ion transmission is carried out in time, interface impedance is reduced, and the cycle performance of the battery is improved.

Description

Technical Field

[0001] The present application belongs to the technical field of secondary batteries, and specifically relates to a positive electrode sheet, a lithium-ion battery, and an electrical device. Background Art

[0002] Lithium-ion batteries are widely used in devices such as smartphones, laptops, smart wearables, energy storage batteries, and electric vehicles due to their lightweight, high energy density, lack of memory effect, long cycle life, and environmental friendliness. Especially in the electric vehicle sector, new energy vehicles powered by lithium-ion batteries offer advantages over traditional fuel vehicles, such as environmental friendliness, pollution-free operation, and low charging costs. However, long charging times have become a major concern for potential users, directly impacting the market acceptance of electric vehicles. With technological advancements and increasing market application requirements, the demand for charging rates for lithium-ion batteries has gradually increased. High-rate charging and discharging, which shortens charging times, has become a key competitive advantage. Therefore, improving high-rate charging performance of batteries is conducive to enhancing market competitiveness. Improving the fast charging capability of lithium-ion batteries has become a common development goal for battery manufacturers and automakers.

[0003] In the prior art, the separators and electrodes used in lithium-ion batteries suffer from slow lithium ion diffusion and high interfacial impedance under high-rate charging. High impedance can easily lead to performance degradation of the battery during the charge and discharge process, seriously affecting the battery cycle performance. Summary of the Invention

[0004] Therefore, the technical problem to be solved by this application is to overcome the defects of lithium-ion batteries in the prior art such as slow lithium ion diffusion and large interface impedance under high-rate charging, which affect the battery cycle performance, thereby providing a positive electrode sheet, a lithium-ion battery and an electrical device.

[0005] To this end, this application provides the following technical solutions:

[0006] According to one aspect of the present application, a positive electrode sheet is provided, comprising:

[0007] The positive electrode current collector has two opposite surfaces in its thickness direction;

[0008] a positive electrode active material layer, disposed on at least one surface of the positive electrode current collector;

[0009] Wherein, the positive electrode active material layer comprises a fast ion conductor material, and the mass percentage of the fast ion conductor material is 0.1%-5% based on the total mass of the positive electrode active material layer;

[0010] The fast ion conductor material includes a core and a coating layer located on at least a portion of the surface of the core, the core is composed of Li6PS5Cl, and the coating layer is composed of Li3PO4.

[0011] As an example, the mass percentage of the fast ion conductor material in the positive electrode active material layer can be 0.1%, 0.5%, 0.8%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or any range thereof. Within the above-defined range, the greater the amount of fast ion conductor added, the greater the improvement. However, the appropriate amount of addition must be controlled. Excessive addition will reduce the energy density of the battery; too low an addition will not effectively improve the rate performance and cycle performance.

[0012] In this application, by adding a certain proportion of a fast ion conductor material of a specific composition to the positive electrode active material layer, when the battery undergoes a high-rate charge and discharge cycle, an ion transmission network can be formed through the fast ion conductor, which can timely transmit lithium ions, reduce interfacial impedance, and improve battery cycle performance. Specifically, Li6PS5Cl has strong ion conductivity and better stability. The coated Li3PO4 can protect Li6PS5Cl from being oxidized and reducing ion conductivity. At the same time, Li3PO4 has no effect on the performance of the battery cell. Using Li6PS5Cl coated with Li3PO4 as a fast ion conductor material can improve the fast charging performance while improving the battery cycle performance.

[0013] In some optional embodiments, the average particle size of the core is 70-100 nm; as an example, the average particle size of the core can be 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm, 100 nm, or within a range consisting of any of the above values.

[0014] And / or, the coating layer has a thickness of 5-10 nm. As an example, the coating layer has a thickness of 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, or any range thereof.

[0015] In the present application, the average particle size of the core and the thickness of the coating layer can be measured using methods and equipment known in the art, for example, using a transmission electron microscope (TEM).

[0016] In this application, limiting the core size to the nanometer scale shortens the lithium ion diffusion path and further improves ionic conductivity. By limiting the thickness of the coating layer, the core material is protected from decomposition without affecting its ionic conductivity. This is because the coating material's ionic conductivity is not as good as the core material. Too thick a coating layer would reduce the core's overall ionic conductivity, while too thin a coating layer would compromise its protective effect on the core.

[0017] It should be noted that the fast ion conductor in this application can be obtained through commercial channels or prepared by known methods in the prior art. As an example, the fast ion conductor can be prepared by the following method:

[0018] (1) Li2S, P2S5, and LiCl are mixed in a stoichiometric ratio (e.g., 5:1:1) and placed in an argon-protected ball mill for high-energy ball milling (e.g., 400 rpm, 24 hours) to obtain amorphous Li6PS5Cl. After ball milling, the sample is heat treated at 300-400°C for 2-5 hours to form crystalline Li6PS5Cl nanoparticles.

[0019] (2) The crystalline Li6PS5Cl nanoparticles were dispersed in deionized water, and LiNO3 and NH4H2PO4 were added as lithium and phosphorus sources (molar ratio Li:P ≈ 3:1). The thickness of the coating layer can be controlled by adjusting the amount of lithium and phosphorus sources added.

[0020] (3) Stirring at 60-80°C to form a sol, and then drying to obtain a precursor powder.

[0021] (4) The precursor powder is subjected to high temperature heat treatment (e.g., 400-600°C, 2-4 hours) in an argon / nitrogen atmosphere to allow Li3PO4 to crystallize in situ on the surface of Li6PS5Cl to form a core-shell structure.

[0022] (5) After heat treatment, the sample was washed with ethanol and deionized water to remove by-products (such as NH4NO3), and finally the Li6PS5Cl@Li3PO4 composite material was obtained.

[0023] In some optional embodiments, the positive electrode active material layer further comprises a positive electrode active material, a conductive agent, and a first binder in a mass ratio of 95.5-97.5:0.4-2.2:1.5-2.3.

[0024] In some optional embodiments, the positive electrode active material includes but is not limited to at least one of lithium iron phosphate material, lithium nickel cobalt manganate material, lithium nickel cobalt aluminum oxide material, lithium manganate material, etc.;

[0025] and / or, the conductive agent includes but is not limited to at least one of conductive carbon black, carbon nanotubes, graphene, and carbon fibers;

[0026] And / or, the first binder includes but is not limited to at least one of polyvinylidene fluoride, polytetrafluoroethylene, and polyacrylic acid.

[0027] In this application, the ratios and specific material selections of the positive electrode active material, conductive agent, and first binder in the positive electrode active material layer are conventional in the field. As an example, the mass ratio of the positive electrode active material, conductive agent, and first binder can be 95.5:2.2:2.3, 96:2:2, 97:1.5:1.5, 97.5:0.8:1.7, or any range thereof.

[0028] According to another aspect of the present application, a lithium-ion battery is provided, comprising the above-mentioned positive electrode sheet.

[0029] In some optional embodiments, the lithium-ion battery further comprises a separator, the separator comprising a base film and a glue layer, the glue layer being located on at least one side surface of the base film, and a fast ion conductor coating being provided between the base film and the glue layer;

[0030] The fast ion conductor coating comprises a fast ion conductor material, and the mass percentage of the fast ion conductor material is 70%-90% based on the total mass of the fast ion conductor coating.

[0031] As an example, the mass percentage of the fast ion conductor material in the fast ion conductor coating can be 70%, 73%, 75%, 78%, 80%, 82%, 85%, 87%, 90%, or any range thereof.

[0032] In this application, by providing a fast ion conductor coating in the diaphragm, the ionic conductivity can be further improved, thereby improving the fast charging performance and cycle stability. The fast ion conductor coating is on the inner side of the adhesive layer and does not affect the adhesion between the diaphragm and the electrode after hot pressing.

[0033] In some optional embodiments, the fast ion conductor coating has a thickness of 1-5 μm. As an example, the fast ion conductor coating may have a thickness of 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, or any range thereof.

[0034] In this application, by limiting the thickness of the fast ion conductor coating, the ion conductivity can be improved while avoiding affecting the energy density of the battery. If the coating thickness is too thin, it will not be conducive to further improving the ion conductivity. If it is too thick, it will reduce the energy density of the battery.

[0035] In some optional embodiments, the composition of the fast ion conductor material in the fast ion conductor coating is the same as the composition of the fast ion conductor material in the positive electrode active material layer. In this application, the fast ion conductor material of a specific composition can further improve the cycling performance of the battery while improving the fast charging performance compared to other fast ion conductor materials.

[0036] In some optional embodiments, the fast ion conductor coating further includes a second binder with a mass percentage of 10%-30%; as an example, the mass percentage of the second binder in the fast ion conductor coating can be 10%, 15%, 20%, 25%, 30%, or within a range consisting of any of the above values.

[0037] In some optional embodiments, a diaphragm is further included, and the diaphragm further includes a ceramic layer, which is disposed between the base membrane and the fast ion conductor coating.

[0038] In the present application, the provision of the ceramic layer can reduce the thermal shrinkage of the diaphragm, improve the thermal stability of the diaphragm, and enhance the safety performance.

[0039] In some optional embodiments, the second binder includes but is not limited to at least one of polyvinylidene fluoride, polytetrafluoroethylene, and polyacrylic acid;

[0040] And / or, the thickness of the ceramic layer is 2-4 μm;

[0041] and / or, the thickness of the adhesive layer is 1-3 μm;

[0042] And / or, the base film has a thickness of 5-10 μm.

[0043] According to another aspect of the present application, there is also provided an electrical device comprising the above-mentioned lithium-ion battery.

[0044] Those skilled in the art will appreciate that the lithium-ion battery provided herein also includes structural components such as an electrolyte and a housing. During the battery's charge and discharge process, lithium ions are intercalated and released back and forth between the positive and negative electrodes. The electrolyte acts as an ion conductor between the positive and negative electrodes. The separator, disposed between the positive and negative electrodes, primarily prevents short circuits between the positive and negative electrodes while allowing lithium ions to pass through.

[0045] As an example, the material, composition, and manufacturing method of the positive electrode sheet used in the lithium-ion battery of the present application may include any technology disclosed in the prior art.

[0046] As an example, a negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer. The negative electrode current collector has two surfaces facing each other in its thickness direction, and the negative electrode active material layer is disposed on either or both of the two facing surfaces of the negative electrode current collector. The materials, composition, and manufacturing method of the negative electrode sheet used in the lithium-ion battery of the present application may include any technology disclosed in the prior art.

[0047] Other materials and shapes of the separator used in the lithium-ion battery of the present application are not particularly limited, and may include any technology disclosed in the prior art.

[0048] The composition and preparation of the electrolyte used in the lithium-ion battery of the present application are not particularly limited and may include any technology disclosed in the prior art.

[0049] The present application does not specifically limit the preparation method of the lithium-ion battery, and the lithium-ion battery can be prepared using conventional preparation methods in the art. For example, the positive electrode sheet, the separator, and the negative electrode sheet are stacked in sequence, with the separator positioned between the positive and negative electrode sheets, and a battery cell is obtained through a stacking or winding process. The battery cell is then baked, injected, formed, and packaged to obtain the lithium-ion battery of the present application.

[0050] The shape of the lithium-ion battery in this application is not specifically limited and may be blade-shaped, cylindrical, square or other shapes.

[0051] It is understood that in the electrical equipment provided herein, the lithium-ion battery can be used as a power source for the electrical equipment or as an energy storage unit for the electrical equipment. The electrical equipment 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, satellites, energy storage systems, etc.

[0052] The technical solution of this application has the following advantages:

[0053] The positive electrode sheet provided in the present application includes a positive electrode current collector having two opposite surfaces in the thickness direction thereof; a positive electrode active material layer provided on at least one surface of the positive electrode current collector; wherein the positive electrode active material layer includes a fast ion conductor material, and the mass percentage of the fast ion conductor material is 0.1%-5% based on the total mass of the positive electrode active material layer; the fast ion conductor material includes a core and a coating layer located on at least a portion of the surface of the core, the core is composed of Li6PS5Cl, and the coating layer is composed of Li3PO4. By adding a certain proportion of a fast ion conductor material of a specific composition to the positive electrode active material layer, the present application can form an ion transport network through the fast ion conductor when the battery undergoes a high-rate charge and discharge cycle, thereby enabling timely lithium ion transport, reducing interfacial impedance, and improving battery cycle performance.

[0054] The lithium-ion battery and electrical equipment provided in this application have the same advantages as the above-mentioned positive electrode sheets due to the use of the positive electrode sheets provided in this application, and will not be described in detail here.

[0055] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become obvious from the description below, or will be learned through practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] In order to more clearly illustrate the specific implementation methods of the present application or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the specific implementation methods or the description of the prior art. Obviously, the drawings described below are some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0057] Figure 1 This is a schematic structural diagram of the positive electrode sheet in an embodiment of the present application;

[0058] Reference numerals:

[0059] 1. Positive electrode current collector; 2. Positive electrode active material layer; 3. Fast ion conductor material. DETAILED DESCRIPTION

[0060] The following examples are provided to further better understand the present application, but are not limited to the best implementation mode described herein, and do not limit the content and protection scope of the present application. Any product identical or similar to the present application obtained by anyone under the inspiration of the present application or by combining the features of the present application with other prior arts shall fall within the scope of protection of the present application.

[0061] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein are for the purpose of describing specific embodiments only and are not intended to limit this application; the terms "including" and "having" and any variations thereof in this application text are intended to cover non-exclusive inclusions.

[0062] In the description of the embodiments of the present application, technical terms such as "first" and "second" are only used to distinguish different objects and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features.

[0063] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0064] The "range" disclosed in this application is defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range. The range defined in this way can be inclusive or exclusive of the end values ​​and can be arbitrarily combined, i.e., any lower limit can be combined with any upper limit to form a range. In this application, unless otherwise specified, the numerical range "ab" represents an abbreviation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" have been listed herein, and "0-5" is just an abbreviation of these numerical combinations. In addition, when stating that a certain parameter is an integer ≥2, it is equivalent to disclosing that the parameter can be, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0065] In the description of the embodiments of the present application, the term "and / or" is merely a description of an association relationship between associated objects, indicating that three relationships may exist. For example, A and / or B can represent three situations: A exists alone, A and B exist simultaneously, and B exists alone. In the description of the embodiments of the present application, the term "at least one" refers to one or more than two (including two).

[0066] Unless otherwise specified, all steps of the present 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 may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0067] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in this field can be used. If the manufacturer of the reagents or instruments is not specified, they are all commercially available conventional reagents.

[0068] The present application is described below with reference to specific embodiments. It should be noted that these embodiments are merely illustrative and do not limit the present application in any way.

[0069] Example 1

[0070] This embodiment provides a positive electrode sheet, the structural diagram of which is shown in FIG. Figure 1As shown, the positive electrode sheet includes a positive electrode current collector 1 and a positive electrode active material layer 2 located on both sides of the positive electrode current collector. The positive electrode active material layer 2 includes a fast ion conductor material 3. The specific preparation method of the positive electrode sheet includes the following steps:

[0071] Lithium iron phosphate, conductive carbon black, carbon nanotubes, and polyvinylidene fluoride were added in a mass ratio of 96.5:1.0:0.5:2.0, and N-methylpyrrolidone was used as a solvent to obtain a positive electrode slurry. A certain amount of Li6PS5Cl@Li3PO4 fast ion conductor particles (specific amounts are shown in Table 1) was added to the positive electrode slurry to obtain a mixed slurry;

[0072] In this embodiment, Li6PS5Cl@Li3PO4 fast ion conductor particles were prepared in the laboratory by the following steps:

[0073] (1) Li2S, P2S5, and LiCl were mixed in a stoichiometric ratio of 5:1:1 and placed in an argon-protected ball mill for high-energy ball milling (400 rpm, 24 h) to obtain amorphous Li6PS5Cl. After ball milling, the sample was heat treated at 350°C for 4 h to form crystalline Li6PS5Cl nanoparticles.

[0074] (2) The crystalline Li6PS5Cl nanoparticles were dispersed in deionized water, and LiNO3 and NH4H2PO4 were added as lithium and phosphorus sources (molar ratio Li:P ≈ 3:1). The thickness of the coating layer was controlled by the amount of lithium and phosphorus sources added;

[0075] (3) stirring at 70°C to form a sol, and then drying to obtain a precursor powder;

[0076] (4) The precursor powder was subjected to high temperature heat treatment (500°C, 3 hours) in an argon / nitrogen atmosphere to allow Li3PO4 to crystallize in situ on the surface of Li6PS5Cl to form a core-shell structure;

[0077] (5) After heat treatment, the sample was washed with ethanol and deionized water to remove by-products, and finally the Li6PS5Cl@Li3PO4 composite material was obtained;

[0078] The prepared mixed slurry was evenly coated on both sides of the aluminum foil. After drying, a positive electrode sheet with uniform distribution of Li6PS5Cl@Li3PO4 was obtained with a surface density of 360g / m 2 , where the mass percentage of the fast ion conductor, the size of the Li6PS5Cl core, and the thickness of the Li3PO4 coating layer are shown in Table 1, calculated based on the mass of the positive electrode active material layer.

[0079] Example 2-Example 9

[0080] This embodiment provides a positive electrode sheet. Compared with embodiment 1, the difference lies in that the content and / or composition of the fast ion conductor material is different, as shown in Table 1.

[0081] Table 1

[0082]

[0083] Example 10

[0084] This embodiment provides a lithium-ion battery, including the positive electrode sheet, separator, negative electrode sheet and electrolyte provided in Example 1. The composition and preparation method of the lithium-ion battery are as follows:

[0085] Composition and preparation of diaphragm:

[0086] A polyethylene (PE) base film with a thickness of 7 μm is coated with a 2 μm ceramic layer on each side, and then coated with a 2 μm fast ion conductor coating on each side. The total mass of the fast ion conductor coating includes 90% Li6PS5Cl@Li3PO4 (its composition and preparation method are the same as those of the fast ion conductor in the above-mentioned positive electrode sheet) and 10% PVDF. Then, a 1.5 μm polyvinylidene fluoride (PVDF) coating is coated on the outer layer to obtain a separator.

[0087] The composition of the negative electrode:

[0088] The negative electrode sheet includes a negative electrode current collector copper foil, and a negative electrode active material layer is provided on both sides of the copper foil. The composition of the negative electrode active material layer is graphite: conductive carbon black: carboxymethyl cellulose sodium: styrene butadiene rubber in a mass ratio of 96:0.5:1.5:2.0. The surface density of the negative electrode sheet is 162g / m 2 , compaction 1.58g / cm 3 The specific preparation method is conventional in the field and is not specifically limited;

[0089] The composition of the electrolyte:

[0090] The solvent composition is as follows: the mass ratio of solvent: ethylene carbonate: diethyl carbonate: ethyl methyl carbonate is 30:20:35; lithium salt: lithium hexafluorophosphate, the addition amount is 12.5wt%; functional additive: vinylene carbonate (VC): 2.5wt%;

[0091] Preparation of lithium-ion batteries:

[0092] The above-prepared positive electrode sheet (Example 1), diaphragm, and negative electrode sheet are stacked to form a pole core, and the positive and negative pole ears of the pole core are welded to the positive and negative pole covers, and the pole core is placed in the shell, and the electrolyte is injected. The formation and capacity separation processes are carried out to produce a lithium-ion battery (a 150Ah blade battery cell in this embodiment).

[0093] Example 11-Example 18

[0094] This embodiment provides a lithium-ion battery. Compared with embodiment 10, the difference lies in that the positive electrode sheets of the above embodiments 2 to 9 are used in sequence.

[0095] Example 19

[0096] This embodiment provides a lithium ion battery. Compared with Example 16, the difference is that the thickness of the fast ion conductor coating is 1 μm.

[0097] Example 20

[0098] This embodiment provides a lithium ion battery. Compared with Example 16, the difference is that the thickness of the fast ion conductor coating is 5 μm.

[0099] Example 21

[0100] This embodiment provides a lithium ion battery. Compared with Example 16, the difference is that the fast ion conductor coating includes 80% Li6PS5Cl@Li3PO4 and 20% PVDF.

[0101] Example 22

[0102] This embodiment provides a lithium ion battery. Compared with Example 16, the difference is that the fast ion conductor coating includes 70% Li6PS5Cl@Li3PO4 and 30% PVDF.

[0103] Example 23

[0104] This embodiment provides a lithium ion battery. Compared with Example 16, the difference is that the separator does not include a fast ion conductor coating.

[0105] Comparative Example 1

[0106] This comparative example provides a lithium ion battery, which is different from Example 10 in that the active material layer of the positive electrode sheet does not include a fast ion conductor.

[0107] Comparative Example 2

[0108] This comparative example provides a lithium ion battery. Compared with Example 10, the difference is that the fast ion conductor in the active material layer of the positive electrode sheet is composed of lithium lanthanum zirconium oxide LLZO.

[0109] Comparative Example 3

[0110] This comparative example provides a lithium ion battery, which is different from Example 10 in that the composition of the fast ion conductor in the active material layer of the positive electrode sheet is Li6PS5Cl.

[0111] Comparative Example 4

[0112] This comparative example provides a lithium ion battery, which is different from Example 10 in that the fast ion conductor in the active material layer of the positive electrode sheet is composed of Li3PO4.

[0113] Comparative Example 5

[0114] This comparative example provides a lithium ion battery. Compared with comparative example 1, the difference is that the diaphragm includes a fast ion conductor coating, and the diaphragm composition is the same as that of Example 16.

[0115] Comparative Example 6

[0116] This comparative example provides a lithium ion battery, which is different from Example 10 in that the composition of the fast ion conductor in the active material layer of the positive electrode sheet is Li6PS5Cl@C.

[0117] Comparative Example 7

[0118] This comparative example provides a lithium ion battery, which is different from Example 10 in that the fast ion conductor in the active material layer of the positive electrode sheet is composed of LLZO@Li3PO4.

[0119] Test Case

[0120] The lithium ion batteries provided in each embodiment and comparative example were subjected to performance tests, and the specific test methods are as follows:

[0121] (1) Battery rate test

[0122] The lithium-ion battery was subjected to rate charge and discharge tests at 25°C (charge and discharge rates of 0.5C, 1C, and 3C, and a voltage range of 2.0-3.75V). The capacity retention rate at different discharge rates was calculated, with the 0.5C capacity as the benchmark.

[0123] (2) Battery cycle test

[0124] The lithium-ion battery was fast-charged and cycled at 25°C with an average charge rate of 4C and a discharge rate of 1C. The cycle test voltage range was 2.0-3.75V. The capacity retention rate after 800 cycles was calculated.

[0125] The specific test results are shown in the table below:

[0126] Table 2

[0127]

[0128] From the test results in the above table, it can be seen that adding fast ion conductors to the active material layer of the positive electrode sheet can significantly improve the battery rate discharge performance and fast charge cycle performance. As the amount of fast ion conductor added increases, the improvement effect becomes more obvious. At the same time, adding fast ion conductors to the positive electrode sheet and the diaphragm coating respectively has a better improvement effect than adding them to the positive electrode sheet alone.

[0129] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A positive electrode sheet, characterized in that: include: The positive electrode current collector has two opposite surfaces in its thickness direction; a positive electrode active material layer, disposed on at least one surface of the positive electrode current collector; Wherein, the positive electrode active material layer comprises a fast ion conductor material, and the mass percentage of the fast ion conductor material is 0.1%-5% based on the total mass of the positive electrode active material layer; The fast ion conductor material includes a core and a coating layer located on at least a portion of the surface of the core, the core is composed of Li6PS5Cl, and the coating layer is composed of Li3PO4.

2. The positive electrode sheet according to claim 1, characterized in that The average particle size of the core is 70-100 nm; And / or, the coating layer has a thickness of 5-10 nm.

3. The positive electrode sheet according to claim 1 or 2, characterized in that: The positive electrode active material layer further includes a positive electrode active material, a conductive agent and a first binder in a mass ratio of 95.5-97.5:0.4-2.2:1.5-2.

3.

4. The positive electrode sheet according to claim 3, characterized in that The positive electrode active material includes at least one of lithium iron phosphate material, lithium nickel cobalt manganate material, lithium nickel cobalt aluminum oxide material, and lithium manganate material; And / or, the conductive agent includes at least one of conductive carbon black, carbon nanotubes, graphene, and carbon fiber; And / or, the first binder includes at least one of polyvinylidene fluoride, polytetrafluoroethylene, and polyacrylic acid.

5. A lithium-ion battery, characterized in that: The positive electrode sheet comprises the positive electrode sheet according to any one of claims 1 to 4.

6. The lithium-ion battery according to claim 5, characterized in that The device further comprises a diaphragm, wherein the diaphragm comprises a base film and a glue layer, wherein the glue layer is located on at least one side surface of the base film, and a fast ion conductor coating is provided between the base film and the glue layer; The fast ion conductor coating comprises a fast ion conductor material, and the mass percentage of the fast ion conductor material is 70%-90% based on the total mass of the fast ion conductor coating.

7. The lithium-ion battery according to claim 6, characterized in that The thickness of the fast ion conductor coating is 1-5 μm; And / or, the composition of the fast ion conductor material is the same as the composition of the fast ion conductor material in the positive electrode sheet according to claim 1 or 2.

8. The lithium-ion battery according to any one of claims 6 to 7, characterized in that: The fast ion conductor coating further includes a second binder having a mass percentage of 10% to 30%; And / or, the diaphragm further includes a ceramic layer disposed between the base membrane and the fast ion conductor coating.

9. The lithium-ion battery according to claim 8, characterized in that The second binder includes at least one of polyvinylidene fluoride, polytetrafluoroethylene, and polyacrylic acid; And / or, the thickness of the ceramic layer is 2-4 μm; and / or, the thickness of the adhesive layer is 1-3 μm; And / or, the base film has a thickness of 5-10 μm.

10. An electrical device, characterized in that: A lithium-ion battery comprising the lithium-ion battery according to any one of claims 5 to 9.

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