Positive electrode active material, method for producing same, solid-state battery cell, battery device, power-using device

Abstract

The application discloses a positive electrode active material and a preparation method thereof, a solid-state battery cell, a battery device and a power utilization device. The battery cell comprises a positive electrode sheet, the positive electrode sheet comprises a positive electrode current collector and a positive electrode film layer located on at least one side of the positive electrode current collector, and the positive electrode film layer comprises a positive electrode active material. The positive electrode active material comprises: a core; and a coating material covering at least part of the surface of the core, wherein the coating material comprises a gel polymer electrolyte. The core comprises secondary particles formed by primary particles, and gaps exist between the primary particles. The gel polymer electrolyte is filled in at least part of the gaps. The battery cell provided by the embodiments of the application has improved cycle performance.

Description

Technical Field

[0001] This application relates to the field of battery technology, specifically to a positive electrode active material and its preparation method, a solid-state battery cell, a battery device, and an electrical device. Background Technology

[0002] Batteries are widely used in electronic devices such as mobile phones, laptops, electric vehicles, electric cars, electric airplanes, electric ships, electric car toys, electric toy ships, electric toy airplanes, and power tools.

[0003] Compared to liquid batteries, solid-state batteries use solid electrolytes, which are less prone to combustion and explosion, thus offering higher reliability. Improving the cycle performance of individual solid-state battery cells is one of the most pressing issues to be addressed in the development of solid-state batteries. Summary of the Invention

[0004] To address the aforementioned technical problems, this application provides a positive electrode active material and its preparation method, a solid-state battery cell, a battery device, and an electrical device.

[0005] In a first aspect, embodiments of this application provide a solid-state battery cell, including a positive electrode sheet, the positive electrode sheet including a positive current collector and a positive electrode film layer located on at least one side of the positive current collector, the positive electrode film layer including a positive electrode active material, the positive electrode active material including: a core; a coating material covering at least a portion of the surface of the core, the coating material including a gel polymer electrolyte; the core including secondary particles formed from primary particles, the primary particles having gaps between them, at least a portion of the gaps being filled with the gel polymer electrolyte.

[0006] According to embodiments of this application, by coating the core surface with a gel polymer electrolyte, the gel polymer electrolyte, possessing good conductivity and polymer toughness, can reduce the contact between the core and the solid electrolyte membrane, thereby reducing the occurrence of interfacial side reactions. Furthermore, filling the internal gaps of the secondary particles with gel polymer electrolyte, which has high flexibility and good interfacial contact, can alleviate the internal stress of the core, reduce the breakage of secondary particles during charge-discharge cycles, and improve the structural stability of the secondary particles. Moreover, the gel polymer electrolyte filling the gaps can construct stable ion transport channels, improve ion transport stability, and thus improve the cycle performance of the battery cell.

[0007] In some embodiments, the radius of the secondary particle is H1, from the surface of the secondary particle to its center, and the filling depth of the gel polymer electrolyte is H2, wherein H1 and H2 satisfy: 20% ≤ H2 / H1 ≤ 100%.

[0008] In some embodiments, 50% ≤ H 2 / H1≤100%.

[0009] In some embodiments, the coating material forms a coating layer on the surface of the core, and the thickness of the coating layer is 2nm-50nm.

[0010] In some embodiments, the mass content of the gel polymer electrolyte is 0.3%-5% based on the total mass of the core and the coating material.

[0011] In some embodiments, the ionic conductivity of the gel polymer electrolyte is 0.2 S / cm to 5 S / cm.

[0012] In some embodiments, the elastic modulus of the gel polymer electrolyte is 10 MPa-50 MPa.

[0013] In some embodiments, the electrochemical window of the gel polymer electrolyte is 1V-5V.

[0014] In some embodiments, the gel polymer electrolyte includes one or more of polyethylene oxide, polyacrylonitrile, polymethyl methacrylate, and lithium polyvinylidene fluoride-hexafluoropropylene / succinic anionyl nitrile / bis(trifluoromethanesulfonyl)imide.

[0015] In some embodiments, the volume distribution particle size Dv50 of the secondary particles is 3μm-12μm.

[0016] In some embodiments, the core comprises a layered lithium-containing transition metal oxide.

[0017] Secondly, embodiments of this application provide a battery device, including a solid-state battery cell according to the first aspect of this application.

[0018] Thirdly, embodiments of this application provide an electrical device, including a solid-state battery cell according to the first aspect of this application or a battery device according to the second aspect of this application.

[0019] Fourthly, embodiments of this application provide a positive electrode active material, comprising: a core; a coating material covering at least a portion of the surface of the core, the coating material comprising a gel polymer electrolyte; the core comprising secondary particles formed by the stacking of primary particles, the primary particles having gaps between them, and at least a portion of the gaps being filled with the gel polymer electrolyte.

[0020] Fifthly, embodiments of this application provide a method for preparing a positive electrode active material, comprising the following steps:

[0021] A kernel is provided, the kernel comprising secondary particles formed by the stacking of primary particles, the primary particles having gaps between them;

[0022] The core is subjected to vacuum treatment to remove at least a portion of the air in the gap;

[0023] The vacuum-treated core is dispersed in a dispersion containing a gel polymer electrolyte, such that the gel polymer electrolyte coats the surface of the lithium transition metal oxide and fills at least a portion of the gaps.

[0024] In some embodiments, the mass content of the gel polymer electrolyte in the dispersion is 2%-10%.

[0025] In some embodiments, the polymer electrolyte accounts for 0.2%-5% of the total mass of the core and the polymer electrolyte.

[0026] According to the embodiments of this application, the preparation method of the fifth aspect of this application can be used to prepare the positive electrode active material of the fourth aspect of this application. Attached Figure Description

[0027] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly described 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 drawings without creative effort.

[0028] Figure 1 The diagram shows the structural features of a vehicle provided in some embodiments of this application.

[0029] Figure 2 This is an exploded schematic diagram of a battery provided for some embodiments of this application.

[0030] Figure 3 for Figure 2 The diagram shows an exploded view of the battery module.

[0031] The accompanying drawings are not necessarily drawn to scale.

[0032] The reference numerals in the attached drawings are explained as follows: 1. Vehicle; 2. Battery unit; 3. Controller; 4. Motor; 5. Housing; 5a. First housing section; 5b. Second housing section; 5c. Reception space; 6. Battery module; 7. Battery cell. Detailed Implementation

[0033] The following detailed description, with appropriate reference to the accompanying drawings, specifically discloses embodiments of the battery cell, battery device, and power-consuming device of this application. 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.

[0034] 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.

[0035] Unless otherwise specified, all embodiments and optional embodiments of this application may be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of this application.

[0036] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions, and such technical solutions shall be deemed to be included in the disclosure of this application.

[0037] 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.

[0038] Unless otherwise specified, in this application, the terms "first," "second," etc., are used to distinguish different objects, rather than to describe a specific order or primary / secondary relationship.

[0039] In this application, the terms "multiple" or "various" refer to two or more kinds.

[0040] In the description of the embodiments of this application, unless otherwise specified, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0041] Unless otherwise stated, the terms used in this application have the common meanings as commonly understood by those skilled in the art.

[0042] Unless otherwise stated, the values ​​of the parameters mentioned in this application can be determined using various testing methods commonly used in the art, for example, according to the testing methods given in the embodiments of this application. Unless otherwise stated, the test temperature for each parameter is 25°C.

[0043] The battery device mentioned in the embodiments of this application can be a single physical module comprising one or more battery cells to provide higher voltage and capacity. For example, the battery mentioned in this application can include battery cells, battery modules, or battery packs.

[0044] A single battery cell is the smallest unit that makes up a battery, and it can independently perform the functions of charging and discharging. When there are multiple battery cells, they are connected in series, parallel, or mixed connections through a busbar.

[0045] In some embodiments, the battery device may be a battery module; when there are multiple battery cells, the multiple battery cells are arranged and fixed to form a battery module.

[0046] In some embodiments, the battery device may be a battery pack, which includes a housing and individual battery cells, with the individual battery cells or battery modules housed within the housing.

[0047] In some embodiments, the housing may be part of the vehicle's chassis structure. For example, a portion of the housing may be at least a part of the vehicle's floor, or a portion of the housing may be at least a part of the vehicle's crossbeams and longitudinal beams.

[0048] In some embodiments, the battery device may be an energy storage device. Energy storage devices include energy storage containers, energy storage cabinets, etc.

[0049] The technical solutions described in the embodiments of this application are applicable to battery devices and electrical devices that use battery devices.

[0050] Battery devices can be used as the power source for electrical devices or as energy storage units for electrical devices. Electrical devices can be, but are not limited to, mobile devices (such as mobile phones, tablets, laptops, etc.), vehicles (such as 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.

[0051] Electrical devices can choose the type of battery device according to their usage needs, such as individual battery cells, battery modules, or battery packs.

[0052] For ease of explanation, the following embodiments will use a vehicle as an example of an electrical device.

[0053] Figure 1 The diagram shows the structural features of a vehicle provided in some embodiments of this application.

[0054] like Figure 1 As shown, a battery device 2 is installed inside the vehicle 1. The battery device 2 can be located at the bottom, front, or rear of the vehicle 1. The battery device 2 can be used to power the vehicle 1; for example, the battery device 2 can serve as the operating power source for the vehicle 1.

[0055] The vehicle 1 may also include a controller 3 and a motor 4. The controller 3 is used to control the battery device 2 to supply power to the motor 4, for example, for the power needs of the vehicle 1 during starting, navigation and driving.

[0056] In some embodiments, the battery device 2 can not only serve as the operating power source for the vehicle 1, but also as the driving power source for the vehicle 1, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1.

[0057] Figure 2 This is a schematic diagram of a battery explosion provided for some embodiments of this application. For example... Figure 2 As shown, the battery device 2 includes a housing 5 and battery cells (not shown), with the battery cells housed within the housing 5.

[0058] The housing 5 is used to house individual battery cells, and the housing 5 can have various structures. In some embodiments, the housing 5 may include a first housing portion 5a and a second housing portion 5b, which overlap each other, and together define a housing space 5c for housing the individual battery cells. The second housing portion 5b may be a hollow structure with one end open, and the first housing portion 5a may be a plate-like structure, with the first housing portion 5a covering the open side of the second housing portion 5b to form a housing 5 with the housing space 5c; alternatively, both the first housing portion 5a and the second housing portion 5b may be hollow structures with one side open, with the open side of the first housing portion 5a covering the open side of the second housing portion 5b to form a housing 5 with the housing space 5c. Of course, the first housing portion 5a and the second housing portion 5b can have various shapes, such as cylinders, cuboids, etc.

[0059] To improve the sealing performance after the first housing part 5a and the second housing part 5b are connected, a sealing element, such as sealant or sealing ring, can also be provided between the first housing part 5a and the second housing part 5b.

[0060] Assuming that the first box section 5a covers the top of the second box section 5b, the first box section 5a can also be called the upper box cover, and the second box section 5b can also be called the lower box.

[0061] In battery device 2, there can be one or more battery cells. If there are multiple battery cells, they can be connected in series, in parallel, or in a mixed configuration. A mixed configuration means that multiple battery cells are connected in both series and parallel configurations. Multiple battery cells can be directly connected in series, in parallel, or in a mixed configuration, and then the whole assembly of multiple battery cells is housed in housing 5. Alternatively, multiple battery cells can first be connected in series, in parallel, or in a mixed configuration to form battery module 6, and then multiple battery modules 6 can be connected in series, in parallel, or in a mixed configuration to form a whole assembly, which is then housed in housing 5.

[0062] Figure 3 for Figure 2 The diagram shows an exploded view of the battery module.

[0063] like Figure 3 As shown, in some embodiments, there are multiple battery cells 7, which are first connected in series, parallel, or mixed to form a battery module 6. The multiple battery modules 6 are then connected in series, parallel, or mixed to form a whole and housed in a casing.

[0064] Multiple battery cells 7 in battery module 6 can be electrically connected through a busbar component to achieve parallel, series, or mixed connection of multiple battery cells 7 in battery module 6.

[0065] The battery cell mentioned in the embodiments of this application can be a solid-state battery cell, such as a solid-state lithium-ion battery cell or a solid-state sodium-ion battery cell.

[0066] Solid-state battery cells are batteries that use solid electrolytes as the electrolyte material. A solid-state battery cell typically includes a casing and an electrode assembly located within the casing. The electrode assembly generally includes a positive electrode, a negative electrode, and a solid electrolyte membrane. The solid electrolyte membrane is located between the positive and negative electrodes and serves to isolate the positive and negative electrodes and to transport active ions.

[0067] The electrode assembly can be a wound structure or a stacked structure, and the embodiments of this application are not limited in this regard. The electrode assembly generally includes a positive electrode, a negative electrode, and a separator.

[0068] [Positive electrode plate]

[0069] In some embodiments, the positive electrode may include a positive current collector and a positive electrode film layer located on at least one side of the surface of the positive current collector, the positive electrode film layer including a positive active material.

[0070] 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.

[0071] In some embodiments, the positive electrode active material includes a core and a coating material, the coating material covering at least a portion of the surface of the core, the coating material including a gel polymer electrolyte; wherein, the layered lithium-containing transition metal oxide includes secondary particles formed by the stacking of primary particles, with gaps between the primary particles, at least a portion of the gaps being filled with the gel polymer electrolyte.

[0072] In some embodiments, the core may include layered lithium-containing transition metal oxides.

[0073] Layered lithium-containing transition metal oxides have the advantages of high voltage and high reversible capacity. However, they also have high reactivity, and side reactions are prone to occur at the interface between the positive electrode and the solid electrolyte membrane. Furthermore, during charge-discharge cycles, the layered lithium-containing transition metal oxide particles are prone to breakage, which can cause interfacial structural changes and hinder the transport of active ions, thereby affecting the cycle performance of the battery cell.

[0074] In this embodiment, by coating the core surface with a gel polymer electrolyte, which possesses good conductivity and polymer toughness, the contact between the core and the solid electrolyte membrane can be reduced, thereby reducing the occurrence of interfacial side reactions. Furthermore, filling the internal gaps of the secondary particles with gel polymer electrolyte, which has high flexibility and good interfacial contact, can alleviate the internal stress of the core, reduce the breakage of secondary particles during charge-discharge cycles, and improve the structural stability of the secondary particles. Moreover, the gel polymer electrolyte filling the gaps can construct stable ion transport channels, improve ion transport stability, and thus improve the cycle performance of the battery cell.

[0075] In this application, primary particles and secondary particles have meanings known in the art. Primary particles refer to particles that have not formed aggregates, while secondary particles refer to aggregated particles formed by the aggregation of two or more primary particles. Primary particles and secondary particles can be distinguished by taking SEM images using a scanning electron microscope (SEM).

[0076] In some embodiments, the radius of the secondary particle is H1, extending from the surface of the secondary particle to its center, and the filling depth of the gel polymer electrolyte is H2. H1 and H2 can satisfy: 20% ≤ H2 / H1 ≤ 100%, for example, H2 / H1 can be 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100%, or any range of the above values; optionally, 50% ≤ H2 / H1 ≤ 100%.

[0077] In this application, the secondary particles can be spherical or near-spherical. The radius of the secondary particle refers to the actual radius of the spherical particle or the equivalent radius of the near-spherical particle. The radius of the near-spherical particle can be measured using methods and instruments known in the art. For example, the shortest diameter passing through the center point of the projection of the secondary particle can be used as the diameter of the secondary particle, thereby obtaining the radius of the near-spherical secondary particle. When the secondary particle is spherical, the particle center refers to the center of the sphere; when the secondary particle is near-spherical, the particle center refers to the center of mass of the secondary particle.

[0078] According to embodiments of this application, the gel polymer electrolyte filling the gaps between secondary particles can alleviate the internal stress of the layered lithium-containing transition metal oxide secondary particles during charge-discharge cycles, improve their structural stability, and construct stable ion transport channels, thereby enhancing the conductivity of the positive electrode active material. By limiting the filling depth of the gel polymer electrolyte in the gaps between secondary particles to the above-mentioned range, the layered lithium-containing transition metal oxide can possess higher structural stability and stable ion transport channels, which is beneficial for improving the cycle performance of the battery cell.

[0079] According to embodiments of this application, the filling depth of the gel polymer electrolyte in the gaps within the secondary particles can be adjusted by changing the viscosity and molecular weight of the gel polymer, as well as the mixing time between the gel polymer electrolyte and the core. For example, when the viscosity of the gel polymer electrolyte is lower, its permeability is better, making it easier to fill the gaps between the secondary particles; when the mixing time between the gel polymer electrolyte and the core is longer, it can fill to a deeper position in the gaps between the secondary particles.

[0080] In this application, the filling depth of the gel polymer electrolyte can be determined using instruments and methods known in the art, such as focused ion beam electron microscopy (FIB-SEM).

[0081] In some embodiments, the gel polymer electrolyte forms a coating layer on at least a portion of the surface of the core, and the thickness of the coating layer can be 2nm-50nm, for example, it can be 2nm, 5nm, 8nm, 10nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm, 45nm, 50nm, or any range of the above values; optionally, the thickness of the coating layer can be 8nm-40nm.

[0082] In this application, the thickness of the coating layer can be measured using methods and instruments known in the art. For example, it can be measured using a transmission electron microscope (TEM). As an example, the sample to be tested can be placed under a transmission electron microscope to measure the thickness of the coating layer on the particle surface, and the thickness at different locations (e.g., 5 locations) can be measured. The average value can then be taken as the thickness of the carbon coating layer.

[0083] Limiting the thickness of the coating layer within the aforementioned range can further reduce the contact between the layered lithium-containing transition metal oxide and the solid electrolyte membrane, thereby reducing interfacial side reactions. When the coating layer is too thin, its coating effect on the core layered lithium-containing transition metal oxide is limited, resulting in more contact points between the core and the solid electrolyte membrane and severe interfacial side reactions. When the coating layer is too thick, the proportion of active material in the positive electrode active material decreases, leading to a reduction in the capacity of the battery cell.

[0084] In some embodiments, the mass percentage of the gel polymer electrolyte is 0.3%-5% based on the total mass of the core and coating materials, for example, it can be 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.2%, 1.5%, 1.8%, 2.0%, 2.5%, 2.8%, 3.0%, or any range of the above values, optionally 0.5%-2.8%.

[0085] In this application, the mass content of the gel polymer electrolyte can be determined using methods known in the art in a single step. For example, it can be detected using thermogravimetric analysis (TGA) according to JYT014-1996. Specifically, based on the mass loss during the heating process, a mass-temperature curve (TG curve) can be plotted. The total mass of the gel polymer electrolyte is obtained by reading the corresponding mass loss at the decomposition temperature of the gel polymer electrolyte, and the mass content of the gel polymer electrolyte can be calculated from this. During the test, a nitrogen atmosphere can be used with a purge gas flow rate of 60 mL / min and a protective gas flow rate of 20 mL / min; the temperature program is 10 °C / min, 35 °C-600 °C.

[0086] In this application, the gel polymer electrolyte includes a gel polymer electrolyte coating the core surface and a gel polymer electrolyte filling the internal gaps of the secondary particles. By limiting the mass percentage of the gel polymer electrolyte within the aforementioned range, it is beneficial to form a stable and uniform coating layer on the surface of the layered lithium transition metal oxide, and it can better fill the internal gaps of the layered lithium transition metal oxide secondary particles, stabilizing the structure of the secondary particles. When the gel polymer electrolyte content is low, the coating layer is thinner, and the amount of gel polymer electrolyte filling the internal gaps of the secondary particles is limited, resulting in poor structural stability of the positive electrode active material; when the gel polymer electrolyte content is high, the proportion of active material in the positive electrode active material is lower, resulting in lower capacity of the battery cell.

[0087] In some embodiments, the ionic conductivity of the gel polymer electrolyte can be 0.2 S / cm to 5 S / cm, for example, 0.2 S / cm, 0.3 S / cm, 0.4 S / cm, 0.5 S / cm, 0.6 S / cm, 0.7 S / cm, 0.8 S / cm, 0.9 S / cm, 1.0 S / cm, 1.5 S / cm, 2.0 S / cm, 2.5 S / cm, 3.0 S / cm, 3.5 S / cm, 4.0 S / cm, 4.5 S / cm, 5.0 S / cm, or any combination of the above values, and can be selected as 0.5 S / cm to 4.5 S / cm.

[0088] In this application, the ionic conductivity of the gel polymer electrolyte has a well-known meaning in the art and can be detected using methods and instruments known in the art. For example, the gel polymer electrolyte can be made into a disc with a diameter of 16 mm, immersed in electrolyte for 1 hour, removed, and the residual electrolyte on the surface wiped off. The ionic conductivity of the gel polymer electrolyte can be calculated using the formula σ = d / (R×A). d is the sample thickness, which can be measured with a micrometer; A is the sample area; R is the sample impedance, which can be obtained by assembling the sample into a symmetrical cell (the electrode can be a stainless steel electrode) and testing it using an electrochemical workstation. The testing frequency can be 10. -6 -10 -1 The voltage amplitude can be 5mV, and the intersection of the graph and the horizontal axis is taken as the sample impedance R. The electrolyte can be prepared as follows: using dimethyl ethylene glycol (DME) as the solvent, LiFSI is added in batches to the solvent, and the mixture is heated and stirred to dissolve the LiFSI, resulting in an electrolyte with a concentration of 1 mol / L. The electrochemical workstation can be a Shanghai Chenhua CHI660C electrochemical workstation.

[0089] According to the embodiments of this application, limiting the ionic conductivity of the gel polymer electrolyte to the above range is beneficial for constructing stable ion transport channels in the internal gaps of the layered lithium-containing transition metal oxide secondary particles, thereby improving the conductivity of the positive electrode active material and improving the cycle performance of the battery cell.

[0090] In some implementations, the elastic modulus of the gel polymer electrolyte can be 10 MPa-50 MPa, for example, 10 MPa, 15 MPa, 20 MPa, 25 MPa, 30 MPa, 35 MPa, 40 MPa, 45 MPa, 50 MPa, or any range of the above values.

[0091] In this application, the elastic modulus of the gel polymer electrolyte has a meaning known in the art and can be tested using instruments and methods known in the art. The test temperature can be 25°C. For example, the gel polymer electrolyte can be made into a strip with a length of 150 mm and a width of 20 mm, and then subjected to a tensile test using a universal testing machine. The tensile distance can be 100 mm, and the tensile speed can be 50 mm / min. The elastic modulus is calculated based on the maximum tensile force of the gel polymer electrolyte. The testing instrument can be an Instron 33652 tensile testing machine.

[0092] According to the embodiments of this application, the elastic modulus of the gel polymer electrolyte is limited to the above range. It fills the internal gaps of the layered lithium transition metal oxide secondary particles. During the charge-discharge cycle, it can better relieve the internal stress of the secondary particles, reduce the damage of the secondary particles during the charge-discharge cycle, improve its structural stability, and thus improve the cycle performance of the battery cell.

[0093] In some embodiments, the electrochemical window of the gel polymer electrolyte can be 1V-5V, for example, 1V, 2V, 3V, 4V, 5V, or any combination of the above values.

[0094] In this application, the electrochemical window of the gel polymer electrolyte has a well-known meaning in the art and can be tested using instruments and methods known in the art. For example, it can be tested using a linear voltammetry module of an electrochemical workstation. The gel polymer electrolyte and the binder PVDF are mixed at a mass ratio of 95:5 and drop-coated onto the surface of a glassy carbon electrode to form a working electrode. A voltammetric curve is tested using 1 mol / L LiPF6 as the electrolyte and a lithium sheet as the counter electrode. The voltage range is 2.5V-5V, the scan rate is 0.5mV / s, and the recorded oxidation potential is the electrochemical window.

[0095] In some embodiments, the gel polymer electrolyte may include one or more of polyethylene oxide (PEO), polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), and lithium polyvinylidene fluoride-hexafluoropropylene / succinic anionyl nitrile / bis(trifluoromethanesulfonyl)imide (PSL).

[0096] In some embodiments, the volume distribution particle size Dv50 of the secondary particles can be 3μm-12μm, such as 3μm, 4μm, 5μm, 6μm, 7μm, 9μm, 10μm, 11μm, 12μm, or any range of the above values.

[0097] In this application, the volume distribution particle size of secondary particles has a well-known meaning in the art and can be determined using methods and instruments known in the art, such as laser diffraction particle size analysis, referring to standard GB / T 19077-2016, using a laser particle size analyzer (e.g., Malvern Master Size 3000).

[0098] In this application, the various parameter tests for the positive electrode active material can be performed directly on the positive electrode active material or by sampling from a single battery cell.

[0099] When the test sample is obtained from a single battery cell, as an example, the sampling can be performed according to the following steps: Discharge the battery cell (generally to a fully discharged state), remove the positive electrode after disassembling the battery cell, and soak the positive electrode in dimethyl carbonate (DMC) for a certain period of time (e.g., 2-10 hours); then remove the positive electrode and dry it at a certain temperature and time (e.g., 60°C, 4h), and remove the positive electrode after drying; bake the dried positive electrode at a certain temperature and time (e.g., 400°C, 2h), select a region from the baked positive and negative electrode cells, and sample the positive active material (sampling can be done by scraping powder with a blade); sieve the collected positive active material (e.g., sieve through a 200-mesh sieve), and finally obtain a positive active material sample that can be used to test the material parameters mentioned above in this application.

[0100] In this embodiment, by coating secondary particles with a gel polymer electrolyte and filling the gaps between the secondary particles, the lithium-ion diffusion coefficient can be improved, thereby enhancing the cycle performance of the battery cell. In this application, the lithium-ion diffusion coefficient has a well-known meaning in the art and can be measured using methods and instruments known in the art, such as cyclic voltammetry (CV), electrochemical impedance spectroscopy (ES), and galvanostatic titration (GITT).

[0101] In some embodiments, the positive electrode active material may further include one or more of lithium phosphate, Prussian blue compounds, polyanionic compounds, and sodium transition metal oxides.

[0102] If the positive electrode active material is one or more of lithium phosphate and layered lithium transition metal oxide, then the positive electrode active material can be used in lithium-ion battery cells; if the positive electrode active material is one or more of Prussian blue compounds, polyanionic compounds, and sodium transition metal oxide, then the positive electrode material can be used in sodium-ion battery cells.

[0103] Examples of layered lithium-containing transition metal oxides may include one or more of lithium cobalt oxides, lithium nickel oxides, lithium manganese oxides, lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, lithium nickel cobalt manganese oxides, lithium nickel cobalt aluminum oxides, and their respective modified compounds.

[0104] In some embodiments, the layered lithium-containing transition metal oxide may include Ni. The molar amount of Ni may account for more than 70% of the total molar amount of transition metal elements in the layered lithium-containing transition metal oxide; optionally, the molar amount of Ni may account for more than 80% of the total molar amount of transition metal elements in the layered lithium-containing transition metal oxide; more preferably, the molar amount of Ni may account for more than 90% of the total molar amount of transition metal elements in the layered lithium-containing transition metal oxide.

[0105] The higher the Ni content in layered lithium-containing transition metal oxides, the higher the energy density of the battery cell.

[0106] In some embodiments, layered lithium-containing transition metal oxides may include Li a Ni b Co c M d O e A f Wherein, 0 < a ≤ 1.2; 0.8 ≤ b < 1; 0 < c < 1; 0 < d < 1; b + c + d = 1; 1 ≤ e ≤ 2; 0 ≤ f ≤ 1; M includes, but is not limited to, one or more of Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, and B; A includes, but is not limited to, one or more of N, F, S, and Cl. This can further improve the energy density of individual battery cells.

[0107] In some embodiments, as an example, layered lithium-containing transition metal oxides may include, but are not limited to, LiNi. 0.8 Co 0.1 Mn 0.1 O2, LiNi 0.8 Co 0.15 Al 0.05 O2, LiNi 0.9 Co 0.06 Mn 0.04 O2, LiNi 0.92 Co 0.06 Mn 0.02 O2, LiNi 0.96 Co 0.02 Mn 0.02 O2, LiNi 0.96 Co 0.02 Mn 0.02 O2N 0.02 One or more of them.

[0108] During the charging and discharging process of a battery cell, Li undergoes insertion / extraction and consumption, resulting in varying molar Li content at different discharge states. In the examples of positive electrode active materials in this application, the molar Li content refers to the initial state of the material, i.e., the state before feeding. After charge-discharge cycles, the molar Li content may change when the positive electrode active material is applied to the battery cell.

[0109] In some embodiments, as an example, sodium transition metal oxides may include, but are not limited to:

[0110] Na 1-x Cu h Fe k Mnl M 1 m O 2-y M 1 It is one or more of Li, Be, B, Mg, Al, K, Ca, Ti, Co, Ni, Zn, Ga, Sr, Y, Nb, Mo, In, Sn, and Ba, 0 <x≤0.33,0<h≤0.24,0≤k≤0.32,0<l≤0.68,0≤m<0.1,h+k+l+m=1,0≤y<0.2;

[0111] Na 0.67 Mn 0.7 Ni z M 2 0.3-z O2, where M 2 It is one or more of Li, Mg, Al, Ca, Ti, Fe, Cu, Zn and Ba, 0 <z≤0.1;

[0112] Na a Li b Ni c Mn d Fe e O2, of which 0.67 <a≤1,0<b<0.2,0<c<0.3,

[0113] 0.67 <d+e<0.8,b+c+d+e=1。

[0114] In some embodiments, as an example, the polyanionic compound may include, but is not limited to:

[0115] A 1 f M 3 g (PO4) i O j X 1 3-j Where A is one or more of H, Li, Na, K, and NH4, and M 3 It is one or more of Ti, Cr, Mn, Fe, Co, Ni, V, Cu and Zn, X 1 It is one or more of F, Cl and Br, 0 <f≤4,0<g≤2,1≤i≤3,0≤j≤2;

[0116] Na n M 4 PO4X 2 M 4 It is one or more of Mn, Fe, Co, Ni, Cu and Zn, X 2is one or more of F, Cl, and Br, 0 < n ≤ 2;

[0117] Na p M 5 q (SO4)3, where M 5 is one or more of Mn, Fe, Co, Ni, Cu, and Zn, 0 < p ≤ 2, 0 < q ≤ 2;

[0118] Na s Mn t Fe 3-t (PO4)2(P2O7), where 0 < s ≤ 4, 0 ≤ t ≤ 3, for example, t is 0, 1, 1.5, 2, or 3.

[0119] In some embodiments, by way of example, Prussian blue compounds may include, but are not limited to:

[0120] A u M 6 v [M 7 (CN)6] w ·xH2O, where A is H + 、NH4 + 、an alkali metal cation, and an alkaline earth metal cation, M 6 and M 7 are each independently one or more of transition metal cations, 0 < u ≤ 2, 0 < v ≤ 1, 0 < w ≤ 1, 0 < x < 6. For example, A is H + 、Li + 、Na + 、K + 、NH4 + 、Rb + 、Cs + 、Fr + 、Be 2+ [[ID=6^0]]、Mg 2+ 、Ca 2+ 、Sr 2+ 、Ba 2+ and Ra 2+ among others, M 6 and M 7 are each independently cations of one or more transition metal elements of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sn, and W. Optionally, A is Li + 、Na + and K + among others, M 6 is one or more cations of transition metal elements of Mn, Fe, Co, Ni, and Cu, M 7It is a cation of one or more transition metal elements selected from Mn, Fe, Co, Ni and Cu.

[0121] In the examples of positive electrode active materials in this application, the molar content of O is only a theoretical value. Oxygen release from the crystal lattice will cause the molar content of O to change, and the actual molar content of O will fluctuate.

[0122] The modified compounds for the above-mentioned positive electrode active materials can be obtained by doping and / or surface coating of the positive electrode active materials.

[0123] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins.

[0124] In some implementations, the weight percentage of the binder in the positive electrode film layer is greater than or equal to 0.5%, which is beneficial for obtaining good adhesion performance.

[0125] In some embodiments, the positive electrode film layer further includes a conductive agent. As an example, the conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0126] 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 made by forming a metal material, such as aluminum, aluminum alloy, copper, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, on the polymer substrate. The polymer substrate may include polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), and other substrates.

[0127] In some embodiments, the thickness of the positive current collector is from 4 μm to 20 μm. It is optionally from 6 μm to 18 μm, and more preferably from 8 μm to 16 μm.

[0128] 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.

[0129] Another embodiment of this application provides a method for preparing a positive electrode active material, comprising the following steps:

[0130] S10 provides a layered lithium-containing transition metal oxide, which includes secondary particles formed by the stacking of primary particles, with gaps between the primary particles.

[0131] S20, Vacuum treatment is performed on the layered lithium-containing transition metal oxide to remove at least part of the air in the gaps;

[0132] S30, a layered lithium transition metal oxide that has undergone vacuum treatment is dispersed in a dispersion containing a gel polymer electrolyte, such that the gel polymer electrolyte coats the surface of the lithium transition metal oxide and fills at least part of the gaps.

[0133] According to the embodiments of this application, by performing vacuum treatment on the layered lithium-containing transition metal oxide secondary particles to remove the air in the gaps, the gel polymer electrolyte can be better filled into the internal gaps of the secondary particles, thereby increasing the filling amount and filling depth.

[0134] In some embodiments, the mass content of the gel polymer electrolyte in the dispersion can be 2%-10%, for example, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or any range of the above values.

[0135] In some embodiments, based on the total amount of layered lithium-containing transition metal oxide and polymer electrolyte, the mass percentage of polymer electrolyte is 0.2%-5%, for example, it can be 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.2%, 1.5%, 1.8%, 2.0%, 2.5%, 2.8%, 3.0%, or any range of the above values, and can be selected as 0.5%-2.8%.

[0136] In some embodiments, the solvent of the dispersion may be one or both of dimethylamide (DMF) and dimethyl sulfoxide (DMSO).

[0137] [Negative electrode plate]

[0138] In some embodiments, the negative electrode sheet can be a metal sheet, such as a lithium sheet or a lithium alloy sheet, or it can be prepared by a dry method, such as by pressing the negative electrode active material, or by a wet method.

[0139] The negative electrode may or may not include a negative electrode current collector.

[0140] In some embodiments, the negative electrode sheet may include a negative current collector and a negative electrode film layer located on at least one side of the negative current collector, the negative electrode film layer including a negative electrode active material.

[0141] 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. The negative electrode current collector can be made of materials such as metal foil, carbon-coated metal foil, or porous metal plate, and copper foil is an option.

[0142] As an example, the negative electrode active material may include one or more of the following: artificial graphite, natural graphite, mesophase micro carbon spheres, hard carbon, soft carbon, silicon, and silicon-carbon composites.

[0143] Silicon-based composite materials can be prepared by methods known in the art. For example, they can be prepared by vapor deposition using graphite and silicon materials as raw materials.

[0144] In some embodiments, the negative electrode film layer may further include a negative electrode conductive agent. As an example, the negative electrode conductive agent may include, but is not limited to, one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0145] In some embodiments, the negative electrode film layer may further include a negative electrode binder. As an example, the negative electrode binder may include, but is not limited to, one or more of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, waterborne acrylic resins (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0146] In some embodiments, the negative electrode film layer may also include other additives. As an example, other additives may include thickeners, such as sodium carboxymethyl cellulose (CMC-Na), PTC thermistor materials, etc.

[0147] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. Examples of metal foils include copper foil, copper alloy foil, aluminum foil, and aluminum alloy foil. The composite current collector may include a polymeric material substrate and a metal material layer formed on at least one side of the polymeric material substrate. Examples of metal materials include, but are not limited to, one or more of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. Examples of polymeric material substrates include, but are not limited to, one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0148] The negative electrode sheet does not exclude other additional functional layers besides the negative electrode film layer. For example, in some embodiments, the negative electrode sheet may also include a conductive undercoat layer sandwiched between the negative electrode current collector and the negative electrode film layer and located on the surface of the negative electrode current collector, which may be composed of a conductive agent and a binder; in some embodiments, the negative electrode sheet may also include a protective layer covering the surface of the negative electrode film layer.

[0149] The negative electrode sheet can be prepared as follows: The negative electrode active material, negative electrode binder, negative electrode conductive agent, and optional other additives are dispersed in a solvent and stirred evenly to form a negative electrode slurry; the negative electrode slurry is coated onto a negative electrode current collector, and after drying, rolling, and other processes, a negative electrode sheet is formed. The solvent can be N-methylpyrrolidone (NMP) or deionized water, but is not limited to these.

[0150] [Solid electrolyte membrane]

[0151] Solid electrolyte membranes may include solid electrolyte materials. Solid electrolyte materials may include one or more of the following: sulfide solid electrolytes, oxide solid electrolytes, and organic solid electrolytes.

[0152] Sulfide solid electrolytes have high 10 -2 S / cm to 10 -3 A lithium-ion conductivity of S / cm facilitates the formation of contact interfaces between electrodes and exhibits high mechanical strength and flexibility. In this application embodiment, there are no particular limitations on the type of sulfide-based solid electrolyte, and all known sulfide materials used in the battery field are acceptable. In this application embodiment, the sulfide-based solid electrolyte may include Li6PS5Cl (LPSCl), Thio-LISICON (Li 3.25 Ge 0.25 P 0.75 S4), Li2S-P2S5-LiCl, Li2S-SiS2, LiI-Li2S-SiS2, LiI-Li2S-P2S5, LiI-Li2S-P2O5, LiI-Li3PO4-P2S5, Li2S-P2S5, Li3PS4, Li7P3S 11 , LiI-Li2S-B2S3, Li3PO4-Li2S-Si2S, Li3PO4-Li2S-SiS2, LiPO4-Li2S-SiS, Li 10 GeP2S 12 Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 and Li7P3S 11 One or more of them.

[0153] Oxide-based solid electrolytes exhibit high safety in air and have a 10 -3 S / cm to 10 -4 The lithium-ion conductivity (S / cm) is lower than that of sulfide-based solid electrolytes, but relatively higher. Furthermore, oxide-based solid electrolytes exhibit high electrochemical safety and mechanical strength. However, oxide-based solid electrolytes have high oxidation voltage. Additionally, solid electrolytes have high grain boundary resistance, making it difficult to form a contact interface between the electrode and electrolyte, requiring high-temperature heat treatment processes of 1000°C or higher, and these processes are difficult to scale up. In the embodiments of this application, the oxide-based solid electrolyte can be any known oxide material used in the field of lithium batteries. In the embodiments of this application, the oxide-based solid electrolyte includes perovskite solid electrolyte, sodium superionic conductor solid electrolyte (NASICON), lithium superionic conductor solid electrolyte (LISICON), and lithium lanthanum zirconium oxide solid electrolyte (LLZO).

[0154] Organic solid electrolytes (OSEs) are a type of solid electrolyte. OSEs can readily form electrode interfaces and minimize dendrite growth, thus ensuring stable reactions between OSEs and lithium metal. The disadvantages of OSEs are their relatively low lithium-ion conductivity and the fact that they typically require high-temperature operation. In this embodiment, the OSE comprises polyethylene oxide (PEO).

[0155] The thickness of the solid electrolyte membrane can be selected differently depending on the properties of the desired all-solid-state battery. Specifically, in some embodiments, the thickness of the solid electrolyte membrane can be from 0.1 μm to 1000 μm; in other embodiments, the thickness of the solid electrolyte membrane can be from 1 μm to 500 μm; in still other embodiments, the thickness of the solid electrolyte membrane can be from 20 μm to 30 μm; this application does not limit it in this regard.

[0156] For ease of subsequent description and understanding, the preparation method of the battery cell and the battery cell in the embodiments of this application can use sulfide-based solid electrolytes.

[0157] Battery cells can be prepared using methods known in the art, such as battery cell assembly methods including but not limited to coin cells, molded cells, prismatic cells, and pouch cells.

[0158] In some embodiments, the method for preparing a battery cell includes the following steps: grinding a positive electrode active material and a positive electrode conductive agent to obtain a positive electrode powder; adding a solid electrolyte for forming an electrolyte layer into a model battery and performing a first cold pressing treatment; adding the positive electrode powder to one side of the model battery and performing a second cold pressing treatment; adding a negative electrode to the other side of the model battery and performing a third cold pressing treatment, thereby obtaining a battery cell.

[0159] Example

[0160] The following embodiments describe the disclosure of this application in more detail. These embodiments are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of the disclosure of this application. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on mass, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the embodiments are commercially available.

[0161] Example 1

[0162] Positive electrode active material

[0163] Layered lithium-containing transition metal oxide LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811) secondary particles were placed in a vacuum mixer for vacuum heating treatment at a vacuum degree of -100 kPa, a heating temperature of 80℃, and a treatment time of 12 h to obtain vacuum-treated secondary particles.

[0164] Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), succinate (SN), and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) were mixed in a mass ratio of 70:10:20 and dispersed in dimethylformamide (DMF) and stirred until completely dissolved. The solid content was controlled at 5% to obtain a gel polymer electrolyte (PSL).

[0165] Maintaining a vacuum environment, the vacuum-treated secondary particles are mixed with PSL at a mass ratio of 97:3. The mixture is stirred thoroughly to allow the gel electrolyte to fill the gaps between the secondary particles and coat the surface of the secondary particles, thus obtaining the positive electrode active material.

[0166] Positive electrode sheet

[0167] The positive electrode active material, conductive carbon black, and polyvinylidene fluoride (PVDF) prepared above are mixed and dispersed evenly in a mass ratio of 8:1:1 to obtain a positive electrode slurry. The positive electrode slurry is coated onto the surface of the positive electrode current collector aluminum foil, and then dried, cold-pressed, and slit to obtain the positive electrode sheet.

[0168] Solid-state battery cells

[0169] In an argon atmosphere, the solid electrolyte Li7La3Zr2O 12(LLZO) and binder nitrile rubber (NBR) are mixed at a mass ratio of 99:1 and dispersed in p-xylene. The solid content is controlled at 50%. The mixture is stirred evenly and coated onto a PET film. After drying, a solid electrolyte film is obtained.

[0170] A lithium metal sheet is used as the negative electrode and bonded to a solid electrolyte membrane. After removing the PET film, it is bonded to the positive electrode prepared above to assemble a solid-state battery cell.

[0171] Examples 2-4

[0172] The preparation method of the battery cell is similar to that in Example 1, except that the content of gel polymer electrolyte in the positive electrode active material is different, as detailed in Table 1.

[0173] Comparative Example 1

[0174] The preparation method of the battery cell is similar to that in Example 1, except that the content of gel polymer electrolyte in the positive electrode active material is different, as detailed in Table 1.

[0175] Table 1

[0176] project Mass content of gel polymer electrolyte in positive electrode active material Example 1 3％ Example 2 5％ Example 3 0.3％ Example 4 7％ Comparative Example 1 0

[0177] Examples 5-7

[0178] The preparation method of the battery cell is similar to that in Example 1, except that the filling depth of the gel polymer electrolyte in the internal gaps of the layered lithium-containing transition metal oxide secondary particles is different, as detailed in Table 2.

[0179] Table 2

[0180] project <![CDATA[H2 / H1]]> Example 1 100％ Example 5 52％ Example 6 21％ Example 7 12％

[0181] Examples 8-10

[0182] The preparation method of the battery cell is similar to that in Example 1, except that the type of gel polymer electrolyte is different, as detailed in Table 3.

[0183] Table 3

[0184]

[0185] Comparative Example 2

[0186] The preparation method of the battery cell is similar to that in Example 1, except that the preparation method of the positive electrode active material is different, specifically:

[0187] Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), succinate (SN), and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) were mixed in a mass ratio of 70:10:20 and dispersed in dimethylformamide (DMF) and stirred until completely dissolved. The solid content was controlled at 5% to obtain a gel polymer electrolyte (PSL).

[0188] NCM811 secondary particles and PSL were mixed at a mass ratio of 97:3 and stirred thoroughly to obtain the positive electrode active material.

[0189] Test section

[0190] 1. Cycle performance of individual battery cells at 60℃

[0191] At 60℃, the battery cell was charged to 3.65V at a constant current of 0.5C, allowed to stand for 30 minutes, and then discharged to 2.5V at a constant current of 0.5C. The discharge capacity C0 was recorded. The battery cell was allowed to stand for 30 minutes, and the above charge and discharge process was repeated. The discharge capacity C0 of each charge and discharge cycle was recorded. 500 The discharge capacity C after 1000 charge-discharge cycles 1000 Calculate the capacity retention rate P after 500 and 1000 cycles respectively. 500 and P 1000 P 500 =C 500 / C0*100%, P 1000 =C 1000 / C0*100%.

[0192] The test results are detailed in Table 4.

[0193] Table 4

[0194]

[0195] As shown in Table 4, the embodiments of this application, by coating the layered lithium-containing transition metal oxide secondary particles with a condensed polymer electrolyte and filling the internal gaps of the secondary particles, can alleviate the internal stress of the secondary particles, improve their structural stability, reduce breakage during charge-discharge cycles, and thus improve the cycle performance of the battery cell. By adjusting parameters such as the filling depth of the gel polymer electrolyte in the internal gaps of the secondary particles, the structural stability and conductivity of the positive electrode active material can be further improved, thereby enhancing the cycle performance of the battery cell.

[0196] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A solid-state battery cell, characterized in that, The positive electrode includes a positive current collector and a positive electrode film layer located on at least one side of the positive current collector. The positive electrode film layer includes a positive electrode active material, which includes: kernel; A coating material is applied to at least a portion of the surface of the core, the coating material comprising a gel polymer electrolyte; The core comprises secondary particles formed from primary particles, with gaps between the primary particles, at least a portion of which are filled with the gel polymer electrolyte.

2. The solid-state battery cell according to claim 1, characterized in that, The radius of the secondary particle is H1, and the distance from the surface of the secondary particle to its center is H2. The filling depth of the gel polymer electrolyte is H2, and H1 and H2 satisfy: 20% ≤ H2 / H1 ≤ 100%.

3. The solid-state battery cell according to claim 2, characterized in that, 50%≤H 2 / H1≤100%。 4. The solid-state battery cell according to any one of claims 1-3, characterized in that, The coating material forms a coating layer on the surface of the core, and the thickness of the coating layer is 2nm-50nm.

5. The solid-state battery cell according to any one of claims 1-4, characterized in that, Based on the total mass of the core and the coating material, the mass content of the gel polymer electrolyte is 0.3%-5%.

6. The solid-state battery cell according to any one of claims 1-5, characterized in that, The gel polymer electrolyte satisfies at least one of the following conditions (1) to (3): (1) The ionic conductivity of the gel polymer electrolyte is 0.2 S / cm-5 S / cm; (2) The elastic modulus of the gel polymer electrolyte is 10MPa-50MPa; (3) The electrochemical window of the gel polymer electrolyte is 1V-5V.

7. The solid-state battery cell according to any one of claims 1-6, characterized in that, The gel polymer electrolyte includes one or more of polyethylene oxide, polyacrylonitrile, polymethyl methacrylate, and lithium polyvinylidene fluoride-hexafluoropropylene / succinic anhydride / bis(trifluoromethanesulfonyl)imide.

8. The solid-state battery cell according to any one of claims 1-7, characterized in that, The volume distribution particle size Dv50 of the secondary particles is 3μm-12μm.

9. The solid-state battery cell according to any one of claims 1-8, characterized in that, The core comprises layered lithium-containing transition metal oxides.

10. A battery device, characterized in that, Includes the solid-state battery cell according to any one of claims 1 to 9.

11. An electrical appliance, characterized in that, Includes the solid-state battery cell according to any one of claims 1 to 9 or the battery device according to claim 10.

12. A positive electrode active material, characterized in that, include: kernel; A coating material is applied to at least a portion of the surface of the core, the coating material comprising a gel polymer electrolyte; The core comprises secondary particles formed by the stacking of primary particles, with gaps between the primary particles, at least a portion of which are filled with the gel polymer electrolyte.

13. A method for preparing a positive electrode active material, characterized in that, Includes the following steps: A kernel is provided, the kernel comprising secondary particles formed by the stacking of primary particles, the primary particles having gaps between them; The core is subjected to vacuum treatment to remove at least a portion of the air in the gap; The vacuum-treated core is dispersed in a dispersion containing a gel polymer electrolyte, such that the gel polymer electrolyte coats at least a portion of the surface of the core and fills at least a portion of the gaps.

14. The preparation method according to claim 13, characterized in that, The mass content of the gel polymer electrolyte in the dispersion is 2%-10%.

15. The preparation method according to claim 13 or 14, characterized in that, Based on the total amount of the core and the polymer electrolyte, the polymer electrolyte accounts for 0.2%-5% of the total mass.

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