Positive electrode material and preparation method thereof, battery monomer, battery device and power utilization device

Abstract

The invention discloses a positive electrode material and a preparation method thereof, a battery monomer, a battery device and a power utilization device. The battery monomer comprises a positive pole piece, the positive pole piece comprises a positive pole current collector and a positive pole film layer located on at least one side of the positive pole current collector, the positive pole film layer comprises a positive pole material, the positive pole material comprises an inner core and a positive pole active material with the chemical formula of LiFe1-x-yMnxMyPO4, x is more than 0 and less than 1, y is more than or equal to 0 and less than 1, and 1-x-y is more than 0 and less than 1; m is selected from one or more of IIA group elements, IIIA group elements, IVA group elements and transition metal elements; the coating material covers at least part of the surface of the inner core, and the coating material comprises a solid electrolyte; wherein the coating material forms a coating layer on the surface of the inner core, the coating uniformity of the coating layer is represented by a thickness value variation coefficient, and the thickness value variation coefficient of the coating layer is less than or equal to 50%. The battery monomer provided by the embodiment of the invention has improved cycle performance and high-temperature storage performance.

Description

Technical Field

[0001] This application relates to the field of battery technology, specifically to a cathode material and its preparation method, a 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] In the development of battery cells, improving the cycle performance of battery cells is one of the urgent problems to be solved. Summary of the Invention

[0004] To address the aforementioned technical problems, this application provides a cathode material and its preparation method, a battery cell, a battery device, and an electrical device.

[0005] In a first aspect, embodiments of this application provide a 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 material, the positive electrode material including:

[0006] The core, including the chemical formula LiFe 1-x-y Mn x M y The positive electrode active material of PO4, wherein 0 < x < 1, 0 ≤ y < 1, 0 < 1 - xy < 1, and M is selected from one or more elements of Group IIA, Group IIIA, Group IVA, and transition metal elements;

[0007] A coating material covering at least a portion of the surface of the core, the coating material comprising a solid electrolyte;

[0008] The coating material forms a coating layer on the surface of the core, and the coating uniformity of the coating layer is characterized by the coefficient of variation of the thickness value, which is less than or equal to 50%.

[0009] In this embodiment of the application, by adjusting the coefficient of variation of the coating thickness within the above-mentioned range, a more uniform and dense coating structure can be formed. This can further reduce the erosion of the core by the electrolyte under high temperature and high voltage conditions, while further stabilizing the structure of the cathode material, reducing the breakage and manganese dissolution of the lithium manganese iron phosphate material structure, maintaining high structural stability of the cathode material, and further improving the cycle performance and high temperature storage performance of the battery cell.

[0010] In some embodiments, the coefficient of variation of the thickness value of the coating layer is less than or equal to 35%.

[0011] In some embodiments, the coating material covers 85% or more of the core surface.

[0012] In some embodiments, the thickness of the coating layer is 1 nm to 100 nm.

[0013] In some embodiments, the solid electrolyte includes a NASICON-type solid electrolyte.

[0014] In some embodiments, the solid electrolyte includes Li 1.3 Al 0.3 Ti 1.7 (PO4)3, LiTi2(PO4)3, Li3Zr2Si2PO 12 One or more of them.

[0015] In some embodiments, the coating material further includes carbon.

[0016] In some embodiments, the carbon content of the coating layer is from 0.05% to 30%.

[0017] In some embodiments, the lithium-ion diffusion coefficient of the cathode material at 25°C is greater than or equal to 1 × 10⁻⁶. -12 cm 2 / s.

[0018] In some embodiments, the resistivity of the positive electrode material is less than or equal to 300 Ω·cm.

[0019] In some embodiments, the specific surface area of ​​the positive electrode material is 9m². 2 / g to 30m 2 / g.

[0020] In some embodiments, the volume distribution particle size Dv50 of the cathode material is from 0.2 μm to 15 μm.

[0021] Secondly, embodiments of this application provide a battery device, including a single battery cell from the first aspect of this application.

[0022] Thirdly, embodiments of this application provide an electrical device, including a battery cell from the first aspect of this application or a battery device from the second aspect of this application.

[0023] Fourthly, embodiments of this application provide a cathode material, comprising:

[0024] The core, including the chemical formula LiFe 1-x-y Mn x M yThe positive electrode active material of PO4, wherein 0 < x < 1, 0 ≤ y < 1, 0 < 1 - xy < 1, and M is selected from one or more elements of Group IIA, Group IIIA, Group IVA, and transition metal elements;

[0025] A coating material covering at least a portion of the surface of the core, the coating material comprising a solid electrolyte;

[0026] The coating material forms a coating layer on the surface of the core, and the coating uniformity of the coating layer is characterized by the coefficient of variation of the thickness value, which is less than or equal to 50%.

[0027] In some embodiments, the solid electrolyte includes a NASICON-type solid electrolyte.

[0028] Fifthly, embodiments of this application provide a method for preparing a cathode material, comprising the following steps:

[0029] The core precursor material and the coating material raw materials are provided respectively; the chemical formula of the core precursor material is LiFe. 1-x-y Mn x M y PO4, wherein 0 < x < 1, 0 ≤ y < 1, 0 < 1 - xy < 1, and M is selected from one or more elements of Group IIA, Group IIIA, Group IVA, and transition metals; the coating material raw material includes a solid electrolyte;

[0030] The core precursor material is subjected to a sintering process to obtain the precursor sintered material.

[0031] The precursor sintering material is mixed with the coating material raw material and subjected to a secondary sintering process to obtain the cathode material.

[0032] In some embodiments, the temperature of the primary sintering process is 200°C to 900°C.

[0033] In some embodiments, the duration of the first sintering process is 1 hour to 30 hours.

[0034] In some embodiments, the temperature of the secondary sintering process is 400°C to 900°C.

[0035] In some embodiments, the duration of the secondary sintering process is 5 to 50 hours.

[0036] According to the embodiments of this application, the preparation method of the fifth aspect of this application can be used to prepare the cathode material of the fourth aspect of this application. Attached Figure Description

[0037] 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.

[0038] Figure 1 The diagram shows the structural features of a vehicle provided in some embodiments of this application.

[0039] Figure 2 This is an exploded schematic diagram of a battery provided for some embodiments of this application.

[0040] Figure 3 for Figure 2 The diagram shows an exploded view of the battery module.

[0041] Figure 4 This is a schematic diagram of the sampling points for measuring the thickness of the coating layer in the application embodiment.

[0042] The accompanying drawings are not necessarily drawn to scale.

[0043] 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

[0044] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the cathode material, its preparation method, 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] In this application, the terms "multiple" or "various" refer to two or more kinds.

[0051] 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.

[0052] Unless otherwise stated, the terms used in this application have the common meanings as commonly understood by those skilled in the art.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] In some embodiments, the battery device may be an energy storage device. Energy storage devices include energy storage containers, energy storage cabinets, etc.

[0060] The technical solutions described in the embodiments of this application are applicable to battery devices and electrical devices that use battery devices.

[0061] 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.

[0062] Electrical devices can choose the type of battery device according to their usage needs, such as individual battery cells, battery modules, or battery packs.

[0063] For ease of explanation, the following embodiments will use a vehicle as an example of an electrical device.

[0064] Figure 1 The diagram shows the structural features of a vehicle provided in some embodiments of this application.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] Figure 3 for Figure 2 The diagram shows an exploded view of the battery module.

[0074] 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.

[0075] 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.

[0076] The battery cells mentioned in the embodiments of this application may include lithium-ion battery cells or sodium-ion battery cells.

[0077] The battery cell includes an electrode assembly. The electrode assembly can be a wound structure or a stacked structure, and the embodiments of this application are not limited to this.

[0078] Electrode assemblies generally include a positive electrode, a negative electrode, and a separator.

[0079] [Positive electrode plate]

[0080] In some embodiments, 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 including a positive electrode material.

[0081] In some embodiments, the positive electrode material includes:

[0082] The core, including the chemical formula LiFe 1-x-y Mn x M y The positive electrode active material of PO4, wherein 0 < x < 1, 0 ≤ y < 1, 0 < 1 - xy < 1, and M is selected from one or more elements of Group IIA, Group IIIA, Group IVA, and transition metal elements;

[0083] A coating material covers at least a portion of the surface of the core; the coating material includes a solid electrolyte.

[0084] The coating material forms a coating layer on the surface of the core. The coating uniformity is characterized by the coefficient of variation of the thickness value, which is less than or equal to 50%.

[0085] Lithium manganese iron phosphate material (LiFe) 1-x-y Mn x M y PO4 has a higher discharge voltage platform, giving it higher energy density, higher safety performance, and better low-temperature performance. However, lithium manganese iron phosphate has poorer conductivity than lithium iron phosphate. Its structure contains an insulator with a 0.2 eV spin-exchange bandgap and a semiconductor with a 0.3 eV crystal field bandgap. In addition, the manganese dissolution problem caused by the Jamie-Taylor effect further leads to problems such as high resistance, poor high-temperature storage, and poor cycle life.

[0086] In view of the above-mentioned problems of lithium manganese iron phosphate materials, in this embodiment of the application, a coating material including a solid electrolyte material is used to coat lithium manganese iron phosphate. This can form a solid electrolyte fast ion conductor material coating layer on the outside of the lithium manganese iron phosphate particles. Solid electrolyte materials have high stability, and using them as a coating layer can improve the structural stress of lithium manganese iron phosphate, enhance the structural stability of the cathode material, thereby reducing the cracking and dissolution of lithium manganese iron phosphate materials under high temperature and high voltage conditions, blocking the erosion of the core by the electrolyte, improving the structural stability of the cathode material, and thus improving the cycle performance of the battery cell.

[0087] In this application, the coefficient of variation of the coating thickness reflects the uniformity of the coating. The smaller the value, the better the uniformity of the coating thickness, resulting in a more uniform and dense structure. In the embodiments of this application, by further controlling the coefficient of variation of the coating thickness within the above-mentioned range, a more uniform and dense coating structure can be formed. This can further reduce the erosion of the core by the electrolyte under high temperature and high voltage conditions, while further stabilizing the structure of the cathode material, reducing the breakage and manganese dissolution of the lithium manganese iron phosphate material structure, maintaining high structural stability of the cathode material, and further improving the cycle performance and high-temperature storage performance of the battery cell.

[0088] In some embodiments, the coefficient of variation of the coating thickness can be less than or equal to 35%. With the coefficient of variation of the coating thickness limited to the above range, the coating has a denser and more uniform structure, which can further improve the structural stability of the cathode material and improve the cycle performance of the battery cell.

[0089] In this application, the coefficient of variation (COV) of the coating thickness can be measured using instruments and methods known in the art. For example, it can be detected by the following method: based on the obtained transmission electron microscope (TEM) image of the cathode material, the coating thickness of the cathode material particles at different locations is measured. Specifically, samples can be taken at intervals on the surface of the cathode material. The number of sampling points can be selected according to the actual situation, and the sampling points can be distributed at intervals on the surface of the cathode material particles. This yields the coating thickness values ​​at different locations of the cathode material particles. The average and standard deviation of all thickness data are calculated, and then the coefficient of variation (COV) is calculated using the following formula: COV(%) = (standard deviation / average) × 100%. The smaller the COV value, the smaller the fluctuation of the coating thickness value at each location, the smaller the thickness difference of the coating at different locations, and the better the coating uniformity.

[0090] In some embodiments, the coverage rate of the coating layer may be greater than or equal to 85%, and optionally greater than or equal to 90%.

[0091] In this application, the coating ratio refers to the completeness of the coating layer formed by the coating material on the core surface, which can be characterized by the ratio of the area of ​​the coating layer to the total area of ​​the cathode material particles. The higher the coating ratio, the more area the coating layer covers on the core surface, and the less exposed area of ​​the core. The coating ratio can be detected using instruments and methods known in the art. For example, a combination of TEM and EDS can be used to measure the total area of ​​the cathode material particles and the area of ​​the coating layer, respectively, and then the coating ratio can be calculated by the ratio of their areas.

[0092] In this embodiment of the application, by adjusting the coating rate of the coating layer within the above-mentioned range, the erosion of the core by the electrolyte can be further reduced, the structural stability of the cathode material can be improved, and the cycle performance of the battery cell can be improved.

[0093] In some embodiments, the thickness of the coating layer can be from 1 nm to 100 nm. Exemplarily, the thickness of the coating layer can be 1 nm, 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm, 100 nm, or any range of the above values. Optionally, the thickness of the coating layer can be from 5 nm to 50 nm.

[0094] The thickness of the coating layer can be measured using methods and instruments known in the art. For example, a TEM-EDS coupled instrument can be used to perform a surface scan of the cathode material particles (with a particle size of Dv50 ± 0.1 μm) to determine the boundary between the core and the shell. The distance from the core to the boundary line and the distance from the core to the outermost edge of the shell are measured in the transmission electron microscope image. The measurement is performed 50 times with random orientation. Then, the above test is repeated on 50 cathode material particles. The average value of the difference between the distance from the core to the outermost edge of the shell and the distance from the core to the boundary line is the average thickness of the coating layer.

[0095] In some embodiments, the solid electrolyte may include a NASICON-type solid electrolyte. Optionally, the solid electrolyte may include Li 1.3 Al 0.3 Ti 1.7 (PO4)3, LiTi2(PO4)3, Li3Zr2Si2PO 12 One or more of them.

[0096] The solid electrolyte with the above composition exhibits high stability, which can improve the structural stability of the cathode material under high temperature and high voltage environments, thereby enhancing the cycle performance and high-temperature storage performance of the battery cell. Furthermore, the solid electrolyte possesses high ion conductivity, which can increase the ion migration rate of the cathode material and reduce the internal resistance of the battery cell.

[0097] In some embodiments, the coating material may also include carbon.

[0098] In some embodiments, the carbon content in the coating layer can be from 0.05% to 30%. Exemplarily, the carbon content in the coating layer can be 0.05%, 0.1%, 0.5%, 1%, 5%, 10%, 25%, 20%, 25%, 30%, or any range of the above values. Optionally, the carbon content in the coating layer can be from 5% to 25%.

[0099] Adding a certain amount of carbon material to the coating layer can improve the conductivity of the coating layer, further reduce the internal resistance of the battery cell, and improve the cycle performance of the battery cell.

[0100] In some embodiments, the lithium-ion diffusion coefficient of the cathode material at 25°C can be greater than or equal to 1×10⁻⁶. -12 cm 2 / s.

[0101] The lithium-ion diffusion coefficient can be tested using instruments and methods known in the art. For example, it can be measured using the gas-galvanic intermittent titration (GITT) method: the cathode material is ground into a powder microelectrode; the powder microelectrode is connected to an electrochemical workstation for coulometric titration. The titration time is 1 hour with a pulse current of 20 μA, followed by a 4-hour interval, and the test temperature is 25°C (Note: To compare the effects of pulse current and time, parallel experiments of 10 μA for 10 minutes can be performed). After obtaining the GITT curve, the lithium-ion diffusion coefficient is calculated using the following formula:

[0102]

[0103] Where D is the lithium-ion diffusion coefficient; I0 ​​is the pulse current used (20 μA); V m denoted as , where is the molar volume of the cathode material; F is the Faraday constant; A is the electrode surface area; n is the charge number of lithium ions, where n is 1; dE / dx is the slope of the coulometric titration curve, which is the slope of the open-circuit potential versus the Li concentration curve at a certain concentration; (dE) / (dt1 / 2) is the slope of the polarization voltage versus the t1 / 2 curve.

[0104] When the lithium-ion diffusion rate of the cathode material is within the above range, it is beneficial to improve the lithium-ion conduction rate of the cathode electrode, thereby improving the fast-charging performance and cycle performance of the battery cell.

[0105] In some embodiments, the resistivity of the positive electrode material powder can be less than or equal to 300 Ω·cm.

[0106] Powder resistivity can be measured using instruments and methods known in the art. For example, it can be measured by the following method: weigh a certain amount of sample and place it in a mold, then place the mold in a four-probe resistivity tester, adjust the pressure, and wait until the height of the mold and the pressure are stable. Test the forward resistivity and reverse resistivity of the sample respectively, and take the average of the two as the powder resistivity of the sample.

[0107] In some embodiments, the specific surface area of ​​the cathode material can be 9m². 2 / g to 30m 2 / g. For example, the specific surface area of ​​the cathode material can be 9m². 2 / g, 10m 2 / g、11m 2 / g、12m 2 / g、13m 2 / g、14m 2 / g, 15m 2 / g, 16m 2 / g、17m 2 / g、18m 2 / g、19m 2 / g、20m 2 / g、21m 2 / g、22m 2 / g、23m 2 / g、24m 2 / g、25m 2 / g、26m 2 / g、27m 2 / g、28m 2 / g、29m 2 / g、30m 2 / g, or any range of the above values.

[0108] The specific surface area of ​​the cathode material is a well-known concept in the art and can be measured using instruments and methods known in the art. For example, it can be measured using the nitrogen adsorption specific surface area analysis method according to GB / T 19587-2017, and calculated using the BET (Brunauer Emmett Teller) method. The nitrogen adsorption specific surface area analysis can be performed using a TRISTAR II 3020 specific surface area and porosity analyzer from Micromeritics, Inc., USA.

[0109] When the specific surface area of ​​the cathode material is within the above range, it has better electrolyte wettability, which can further improve the electrochemical performance of the battery cell.

[0110] In some embodiments, the volumetric particle size distribution Dv50 of the cathode material can be from 0.2 μm to 15 μm. Exemplarily, the volumetric particle size distribution Dv50 of the cathode material can be 0.2 μm, 0.5 μm, 0.8 μm, 1.0 μm, 1.5 μm, 2.0 μm, 3.0 μm, 4.0 μm, 5.0 μm, 6.0 μm, 7.0 μm, 8.0 μm, 9.0 μm, 10.0 μm, 11.0 μm, 12.0 μm, 13.0 μm, 14.0 μm, 15.0 μm, or any range of the above values.

[0111] Dv50 can be determined using instruments and methods known in the art, for example, it can be determined using a laser diffractometer in accordance with GB / T 19077-2016 "Particle size analysis by laser diffraction".

[0112] The volume distribution particle size Dv50 of the cathode material is within the above range, which has a suitable ion diffusion distance and can further improve the electrochemical performance of the battery cell.

[0113] In some embodiments, the cathode material can be prepared by the following methods:

[0114] S10 provides raw materials for both the core precursor material and the coating material. The chemical formula of the core precursor material is LiFe. 1-x-y Mn x M y PO4, 0 < x < 1, 0 < y < 1, 0 ≤ 1 - xy < 1, M is selected from one or more elements of Group IIA, Group IIIA, Group IVA, and transition metals; the coating material raw material includes solid electrolyte;

[0115] S20, the core precursor material is sintered once to obtain the precursor sintered material;

[0116] S30 involves mixing the precursor sintering material with the coating material raw material and performing a secondary sintering process to obtain the cathode material.

[0117] In this embodiment, the cathode material is prepared by a two-stage sintering method. The core precursor material is sintered once and then mixed with the coating material raw material for a second sintering. During the first sintering process, the core precursor material forms a crystal structure, which can reduce the doping of metal elements in the solid electrolyte material into the crystal structure of the core during the second sintering process, thereby reducing the damage to the core structure during sintering, improving the stability of the cathode material structure, and thus improving the cycle performance of the battery cell.

[0118] In some embodiments, the temperature of a single sintering process can be from 200°C to 900°C. Exemplarily, the temperature of a single sintering process can be 200°C, 250°C, 300°C, 350°C, 400°C, 450°C, 500°C, 550°C, 600°C, 650°C, 700°C, 750°C, 800°C, 850°C, 900°C, or any range of the above values.

[0119] In some embodiments, the sintering time for one sintering process can be from 1 hour to 30 hours. For example, the sintering time for one sintering process can be 1 hour, 5 hours, 8 hours, 10 hours, 12 hours, 15 hours, 18 hours, 20 hours, 22 hours, 25 hours, 28 hours, 30 hours, or any range of the above values.

[0120] In some embodiments, the temperature of the secondary sintering process can be from 400°C to 900°C. Exemplarily, the temperature of the primary sintering process can be 400°C, 450°C, 500°C, 550°C, 600°C, 650°C, 700°C, 750°C, 800°C, 850°C, 900°C, or any range of the above values.

[0121] In some embodiments, the time for the secondary sintering process can be from 5 hours to 50 hours. For example, the time for the primary sintering process can be 5 hours, 10 hours, 15 hours, 20 hours, 25 hours, 30 hours, 35 hours, 40 hours, 45 hours, 50 hours, or any range of the above values.

[0122] The coating effect of the prepared cathode material can be adjusted by changing the parameters of the two sintering processes and the material ratio. By optimizing the preparation parameters and raw material ratio, the cathode material can have higher coating uniformity and coating rate.

[0123] In some embodiments, the mass ratio of the core precursor material to the coating material raw material can be 1:(0.001-0.5), or optionally 1:(0.01-0.4).

[0124] By controlling the mass ratio of the core precursor material to the coating material raw material within the above range, it is beneficial to form a coating layer with a stable structure and uniform coating.

[0125] In some embodiments, the coating material may also include a carbon source.

[0126] Optionally, the carbon source may include one or more of organic and inorganic carbon sources. For example, the carbon source may include one or more of citric acid, glucose, sucrose, polyvinyl alcohol, polypyrrole, polyethylene glycol, pitch, anthracene, and aniline.

[0127] In some embodiments, the mass content of the carbon source in the coating material can be from 0.05% to 80%, and optionally from 0.1% to 50%.

[0128] In some embodiments, the positive electrode active material may further include one or more of the following: lithium-containing phosphates, layered lithium-containing transition metal oxides, Prussian blue compounds, polyanionic compounds, and sodium transition metal oxides, which are different from the positive electrode active materials described above.

[0129] 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.

[0130] Lithium-containing phosphates may include one or more of lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, and their respective modified compounds.

[0131] 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.

[0132] 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.

[0133] The higher the Ni content in layered lithium-containing transition metal oxides, the higher the energy density of the battery cell.

[0134] 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; 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.

[0135] 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 0.02One or more of O2.

[0136] 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 material addition. After charge-discharge cycles, the molar Li content may change when the positive electrode active material is applied to the battery cell.

[0137] In some embodiments, as an example, sodium transition metal oxides may include, but are not limited to:

[0138] Na 1-x Cu h Fe k Mn l 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;

[0139] 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;

[0140] 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,

[0141] 0.67 <d+e<0.8,b+c+d+e=1。

[0142] In some embodiments, as an example, the polyanionic compound may include, but is not limited to:

[0143] A 1 f M 3 g (PO4) i O j X1 3-j , where A is one or more of H, Li, Na, K, and NH4, M 3 is one or more of Ti, Cr, Mn, Fe, Co, Ni, V, Cu, and Zn, X 1 is one or more of F, Cl, and Br, 0 < f ≤ 4, 0 < g ≤ 2, 1 ≤ i ≤ 3, 0 ≤ j ≤ 2;

[0144] Na n M 4 PO4X 2 , where M 4 is one or more of Mn, Fe, Co, Ni, Cu, and Zn, X 2 is one or more of F, Cl, and Br, 0 < n ≤ 2;

[0145] 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;

[0146] 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.

[0147] In some embodiments, by way of example, Prussian blue compounds may include, but are not limited to:

[0148] 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+ , Mg 2+Ca 2+ 、Sr 2+ Ba 2+ and Ra 2+ One or more of them, M 6 and M 7 Each is an independently selected cation of one or more transition metal elements chosen from Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sn, and W. Optionally, A is Li. + Na + and K + One or more of them, M 6 It is a cation of one or more transition metal elements selected from Mn, Fe, Co, Ni, and Cu, M 7 It is a cation of one or more transition metal elements selected from Mn, Fe, Co, Ni and Cu.

[0149] 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.

[0150] 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.

[0151] 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.

[0152] 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.

[0153] 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.

[0154] 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.

[0155] 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.

[0156] 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.

[0157] [Negative electrode plate]

[0158] In some embodiments, the negative electrode sheet includes 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.

[0159] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode material 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 optional.

[0160] 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.

[0161] 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.

[0162] 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.

[0163] 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).

[0164] 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), PTC thermistor materials, etc.

[0165] 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).

[0166] 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.

[0167] 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.

[0168] [Electrolytes]

[0169] A single battery cell includes an electrolyte.

[0170] In some embodiments, the electrolyte is an electrolyte solution, which includes an electrolyte salt and an organic solvent.

[0171] In some embodiments, the electrolyte includes anion, which may include bis(fluorosulfonyl)imide anion (FSI). -), bis(trifluoromethanesulfonyl)imide anion (TFSI) - ), dioxaborate anion (BOB) - ), difluorooxalate borate anion (DFOB) - ), difluorodioxanol phosphate anion (DFOP) - ), tetrafluorooxalate phosphate anion (TFOP) - ), difluorophosphate anion (PO2F2) - ), hexafluorophosphate anion (PF6) - ), tetrafluoroborate anion (BF4) - ), hexafluoroarsenate anion (AsF6) - ), trifluoromethanesulfonate anion (CF3SO3) - One or more of the following.

[0172] In some embodiments, the electrolyte includes cations, which may include one or more of lithium ions and sodium ions.

[0173] In some embodiments, the concentration of the electrolyte salt may be 0.3 mol / L or higher, optionally 0.7 mol / L or higher, and further optionally 4 mol / L or lower, optionally 2.5 mol / L or lower, or 1.7 mol / L or lower. When the concentration of the electrolyte salt is within the above range, the electrolyte can have a suitable ionic conductivity.

[0174] Organic solvents may include, but are not limited to, one or more of esters, ethers, sulfones, and nitriles. Esters may include, but are not limited to, one or more of carbonates, phosphate esters, carboxylic esters, sulfate esters, and sulfonates. Carbonates may include cyclic carbonates and / or chain carbonates; optionally, carbonates may include both cyclic and chain carbonates. Chain carbonates may include low-viscosity polar chain carbonates, aliphatic branched carbonates, etc.

[0175] As an example, organic solvents may include, but are not limited to, ethylene carbonate (EC), propylene carbonate (PC), butene carbonate, ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), diethyl sulfone (ESE), dimethyl ether tetraethylene glycol (TEGDME), ethylene glycol dimethyl ether (DME), 1,3-dioxolane (DOL), trimethyl phosphate, 3-methoxypropionitrile, H(CF2)2OCH3, C4F9O CH3, H(CF2)2OCH2CH3, H(CF2)2OCH2CF3, H(CF2)2CH2O(CF2)2H, CF3CHFCF2OCH3, CF3CHFCF2OCH2CH3, 2-trifluoromethylhexafluoropropyl methyl ether, 2-trifluoromethylhexafluoropropyl ethyl ether, 2-trifluoromethylhexafluoropropyl propyl ether, 3-trifluoromethyloctafluorobutyl methyl ether, 3-trifluoromethyloctafluorobutyl ethyl ether, 3-trifluoromethyloctafluorobutyl propyl ether, 4-trifluoromethyl One or more of the following: decafluoropentyl methyl ether, 4-trifluoromethyl decafluoropentyl ethyl ether, 4-trifluoromethyl decafluoropentyl propyl ether, 5-trifluoromethyl dodecylfluorohexyl methyl ether, 5-trifluoromethyl dodecylfluorohexyl ethyl ether, 5-trifluoromethyl dodecylfluorohexyl propyl ether, 6-trifluoromethyl tetradecafluoroheptyl methyl ether, 6-trifluoromethyl tetradecafluoroheptyl ethyl ether, 6-trifluoromethyl tetradecafluoroheptyl propyl ether, 7-trifluoromethyl hexadecylfluorooctyl methyl ether, 7-trifluoromethyl hexadecylfluorooctyl ethyl ether, and 7-trifluoromethyl hexadecylfluorooctyl propyl ether.

[0176] In some embodiments, the electrolyte may optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature performance, additives that improve battery low-temperature power performance, etc.

[0177] [Isolation Component]

[0178] In some embodiments, the electrode assembly further includes an isolator disposed between the positive and negative electrodes.

[0179] In some embodiments, the isolation chamber includes an isolation membrane. This application does not impose any particular limitation on the type of isolation membrane; any known porous membrane with good chemical and mechanical stability can be selected.

[0180] In some embodiments, the material of the separator may include at least one selected from glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer may be the same or different, without particular limitation. The separator may be a single component located between the positive and negative electrodes, or it may be attached to the surfaces of the positive and negative electrodes. An inorganic particle coating, an organic particle coating, or an organic / inorganic composite coating may also be applied to the surface of the separator.

[0181] In some embodiments, the separator is a solid electrolyte. The solid electrolyte is disposed between the positive and negative electrodes, serving both to transport ions and to isolate the positive and negative electrodes.

[0182] Example

[0183] 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.

[0184] Example 1

[0185] cathode materials

[0186] S10: 766g LiOH, 3325g NH4H2PO4, 2899g MnSO4, and 1945g FeSO4 were dispersed in 14kg deionized water. The mixture was stirred thoroughly to form a precipitate. The precipitate was then washed with deionized water, filtered, ball-milled, dried, and crushed to obtain a dry powder. The dry powder was sintered in a nitrogen atmosphere sintering furnace at a constant temperature of 500℃ for 3 hours to obtain the precursor sintering material LiFe. 0.4 Mn 0.6 PO4;

[0187] S20, the precursor sintering material prepared above, 1 kg glucose, 30.7 g Li2CO3, 15.0 g Al(OH)3, 86.9 g TiO2, and 199.6 g NH4H2PO4 are dispersed in ethanol. After grinding in a sand mill for 2 hours, the mixture is filtered through a 400-mesh sieve. Citric acid is added to the mixed slurry for complexation precipitation. The precipitate is filtered, dried, and then sintered in a nitrogen atmosphere furnace at 800℃ for 6 hours. After sintering, the precipitate is crushed until it completely passes through an 800-mesh sieve to obtain the cathode material. The cathode material is externally composed of Li... 1.3 Al 0.3 Ti 1.7 A carbon-containing coating layer composed of (PO4)3.

[0188] Positive electrode sheet

[0189] The positive electrode material, binder polyvinylidene fluoride (PVDF), and conductive agent conductive carbon black prepared above are dispersed in solvent N-methylpyrrolidone (NMP) at a mass ratio of 95:2.5:2.5. The mixture is stirred and mixed thoroughly to form a positive electrode slurry. The positive electrode slurry is then uniformly coated onto the positive electrode current collector aluminum foil. After drying, cold pressing, and slitting, the positive electrode sheet is obtained.

[0190] Negative electrode sheet

[0191] Artificial graphite (anode active material), acetylene black (conductive agent), styrene-butadiene rubber (SBR) (binder), and sodium carboxymethyl cellulose (CMC-Na) (thickener) were dissolved in deionized water at a weight ratio of 95.5:1.5:1.8:1.2. The mixture was stirred and mixed thoroughly to prepare a cathode slurry. The cathode slurry was coated onto copper foil (anode current collector), and then dried, cold-pressed, and slit to obtain the cathode sheet.

[0192] Separating membrane

[0193] Polypropylene film is used.

[0194] electrolyte

[0195] Ethyl carbonate (EC), methyl ethyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1. LiPF6 was then uniformly dissolved in this solution to obtain the electrolyte. The concentration of LiPF6 in the electrolyte was 1 mol / L.

[0196] battery cell

[0197] The positive electrode, separator, and negative electrode are stacked and wound in sequence to obtain an electrode assembly. The electrode assembly is placed in an outer packaging, and the electrolyte prepared above is added. After processes such as encapsulation, standing, formation, and aging, a coin cell is obtained.

[0198] Examples 2 to 9

[0199] Examples 2 to 9 are prepared using methods similar to those used in Example 1 for the preparation of the battery cells. The different product parameters are detailed in Table 1.

[0200] Comparative Examples 1-2

[0201] Examples 1 and 2 are prepared using methods similar to those used in Example 1 for the preparation of the battery cells. The different product parameters are detailed in Table 1.

[0202] Table 1

[0203]

[0204]

[0205] Comparative Example 4

[0206] The preparation method of the cathode material differs from that in Example 1, as follows:

[0207] S10: 766g LiOH, 3325g NH4H2PO4, 2899g MnSO4, and 1945g FeSO4 are dispersed in 14kg of deionized water, and the mixture is stirred and mixed to form a precipitate. The precipitate is then washed with deionized water, filtered, ball-milled, dried, and crushed to obtain a dry powder.

[0208] S20: The dried powder obtained above, 1 kg of glucose, 30.7 g of Li2CO3, 15.0 g of Al(OH)3, 86.9 g of TiO2, and 199.6 g of NH4H2PO4 are dispersed in ethanol. After grinding in a sand mill for 2 hours, the mixture is filtered through a 400-mesh sieve. Citric acid is added to the mixed slurry to perform complexation precipitation. The precipitate is filtered, dried, and then sintered in a nitrogen atmosphere furnace at 800°C for 6 hours. After sintering, the precipitate is crushed until it completely passes through an 800-mesh sieve to obtain the positive electrode material.

[0209] Test section

[0210] 1. Thickness of the coating layer

[0211] The cathode material particles (with a particle size of Dv50 ± 0.1 μm) were surface-scanned using TEM-EDS to determine the boundary between the core and the shell. The distance from the core to the boundary and the distance from the core to the outermost edge of the shell were measured in the TEM image. The measurement was performed 50 times with random orientation. Then, 50 cathode material particles were selected and the above test was repeated. Twice the average distance from the core to the boundary is the average diameter of the core. The average difference between the distance from the core to the outermost edge of the shell and the distance from the core to the boundary is the average thickness of the coating layer.

[0212] 2. Dv50 particle size of the cathode material

[0213] Take an appropriate amount of sample, add 20 mL of deionized water, and sonicate for 5 minutes (53 kHz, 120 W) to completely disperse the sample. Use a laser particle size analyzer (MasterSizer 2000) to determine the Dv50 particle size of the material.

[0214] 3. Uniformity of cathode material coating

[0215] The thickness of the coating layer at different locations was measured in the TEM image of the cathode material. Specific sampling points are referenced. Figure 4 The number of sampling points is 20. The sampling points are evenly distributed on the surface of the positive electrode material particles. The thickness value of the coating layer at different points is obtained. The average and standard deviation of all thickness values ​​are calculated respectively. Then, the coating uniformity is reflected by calculating the coefficient of variation (COV) of the thickness value. COV (%) = (standard deviation / average) × 100%.

[0216] 4. Coverage ratio of cathode material

[0217] The coating rate is the percentage of the surface area of ​​the coating layer formed by the coating material to the surface area of ​​the cathode material particles. In the SEM image of the cathode material, a single particle is selected and its surface area is measured. The number of sampling points is 50. The total surface area is calculated. Then, for these 50 sampling points, the surface area ratio of the coating layer is measured and calculated using EDS to obtain the total coated surface area. Finally, the coating rate is calculated as: total coated surface area / total surface area.

[0218] 5. Powder resistivity of positive electrode material

[0219] Weigh 1g of sample and place it in the mold. Then place the mold in a four-probe resistivity tester and adjust the pressure to 7.85MPa. After the mold height and pressure are stable, test the forward resistivity and reverse resistivity of the sample respectively, and take the average of the two as the powder resistivity of the sample.

[0220] 6. Lithium-ion diffusion coefficient of cathode material

[0221] The positive electrode material was ground into a powder microelectrode; the powder microelectrode was then connected to an electrochemical workstation for coulometric titration. A pulsed current of 20 μA was used, with a titration time of 1 h followed by a 4 h interval, and a test temperature of 25°C (Note: To compare the effects of pulsed current and time, parallel experiments of 10 μA for 10 min can be performed). After obtaining the GITT curve, the lithium-ion diffusion coefficient was calculated using the following formula:

[0222]

[0223] Where D is the lithium-ion diffusion coefficient; I0 ​​is the pulse current used (20 μA); V m denoted as , where is the molar volume of the cathode material; F is the Faraday constant; A is the electrode surface area; n is the charge number of lithium ions, where n is 1; dE / dx is the slope of the coulometric titration curve, which is the slope of the open-circuit potential versus the Li concentration curve at a certain concentration; (dE) / (dt1 / 2) is the slope of the polarization voltage versus the t1 / 2 curve.

[0224] 7. The charging capacity and discharging capacity of a single battery cell

[0225] The coin cell battery was subjected to cyclic charging and discharging at a charge / discharge rate of 0.1C, with a test temperature of 25.0℃ and a charge / discharge voltage of 2.0V-4.3V. The charge capacity was obtained by dividing the charge capacity of the first cycle by the mass of the positive electrode material, and the discharge capacity was obtained by dividing the discharge capacity of the first cycle by the mass of the positive electrode material.

[0226] 8. Battery cell capacity retention test at 25℃:

[0227] The coin cell battery was subjected to 2000 charge-discharge cycles at a 1C charge-discharge rate, at a test temperature of 25.0℃, and at a charge-discharge voltage of 2.0V-4.3V. The capacity retention rate was obtained by dividing the discharge capacity of the last cycle by the discharge capacity of the first cycle.

[0228] 9. Testing of battery cell storage performance at 60℃:

[0229] The Shenzhen Xinwei Battery Testing System was used to perform the first charge-discharge test on the coin cells at a 1C charge-discharge rate, with a charge-discharge voltage ranging from 2.0V to 4.3V. After charging, the cells were placed in a 60℃ constant temperature furnace. Every 7 days, the cells were removed and subjected to a 1C charge-discharge test, then charged again and placed back into the 60℃ constant temperature furnace, repeating this cycle for 60 days. The capacity retention rate was obtained by dividing the final measured discharge capacity by the discharge capacity of the first cycle.

[0230] The test results are detailed in Table 2.

[0231] Table 2

[0232]

[0233] Based on the data in Table 2, the use of solid electrolyte for coating and adjustment of coating parameters in this embodiment can further improve the cycle performance and high-temperature storage performance of the battery cells.

[0234] 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 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 material, which includes: The core, including the chemical formula LiFe 1-x-y Mn x M y The positive electrode active material of PO4, wherein 0 < x < 1, 0 ≤ y < 1, 0 < 1 - xy < 1, and M is selected from one or more elements of Group IIA, Group IIIA, Group IVA, and transition metal elements; A coating material covering at least a portion of the surface of the core, the coating material comprising a solid electrolyte; The coating material forms a coating layer on the surface of the core, and the coating uniformity of the coating layer is characterized by the coefficient of variation of the thickness value, which is less than or equal to 50%.

2. The battery cell according to claim 1, characterized in that, The coefficient of variation of the thickness of the coating layer is less than or equal to 35%.

3. The battery cell according to claim 1 or 2, characterized in that, The coating material covers 85% or more of the core surface.

4. The battery cell according to any one of claims 1 to 3, characterized in that, The thickness of the coating layer is from 1 nm to 100 nm.

5. The battery cell according to any one of claims 1 to 4, characterized in that, The solid electrolyte includes a NASICON-type solid electrolyte.

6. The battery cell according to claim 5, characterized in that, The solid electrolyte includes Li 1.3 Al 0.3 Ti 1.7 (PO4)3, LiTi2(PO4)3, Li3Zr2Si2PO 12 One or more of them.

7. The battery cell according to any one of claims 1 to 6, characterized in that, The coating material also includes carbon.

8. The battery cell according to claim 7, characterized in that, The carbon content of the coating layer is between 0.05% and 30%.

9. The battery cell according to any one of claims 1 to 8, characterized in that, The cathode material satisfies at least one of the following conditions: (1) The lithium-ion diffusion coefficient of the cathode material at 25℃ is greater than or equal to 1×10⁻⁶. -12 cm 2 / s; (2) The resistivity of the positive electrode material is less than or equal to 300 Ω·cm; (3) The specific surface area of ​​the positive electrode material is 9m². 2 / g to 30m 2 / g; (4) The volume distribution particle size Dv50 of the positive electrode material is 0.2 μm to 15 μm.

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

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

12. A positive electrode material, characterized in that, include: The core, including the chemical formula LiFe 1-x-y Mn x M y The positive electrode active material of PO4, wherein 0 < x < 1, 0 ≤ y < 1, 0 < 1 - xy < 1, and M is selected from one or more elements of Group IIA, Group IIIA, Group IVA, and transition metal elements; A coating material covering at least a portion of the surface of the core, the coating material comprising a solid electrolyte; The coating material forms a coating layer on the surface of the core, and the coating uniformity of the coating layer is characterized by the coefficient of variation of the thickness value, which is less than or equal to 50%.

13. The cathode material according to claim 12, characterized in that, The solid electrolyte includes a NASICON-type solid electrolyte.

14. A method for preparing a positive electrode material, characterized in that, Includes the following steps: The core precursor material and the coating material raw materials are provided respectively; the chemical formula of the core precursor material is LiFe. 1-x- y Mn x M y PO4, wherein 0 < x < 1, 0 ≤ y < 1, 0 < 1 - xy < 1, and M is selected from one or more elements of Group IIA, Group IIIA, Group IVA, and transition metals; the coating material raw material includes a solid electrolyte; The core precursor material is subjected to a sintering process to obtain the precursor sintered material. The precursor sintering material is mixed with the coating material raw material and subjected to a secondary sintering process to obtain the cathode material.

15. The preparation method according to claim 14, characterized in that, The temperature of the primary sintering process is between 200°C and 900°C, and / or The duration of the first sintering process is 1 hour to 30 hours; and / or The secondary sintering treatment is performed at a temperature of 400°C to 900°C; and / or The duration of the secondary sintering process is 5 to 50 hours.

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