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 electrode plate, the positive electrode plate comprises a positive electrode current collector and a positive electrode film layer located on at least one side of the positive electrode current collector, the positive electrode film layer comprises a positive electrode material, and the positive electrode material comprises: a core comprising a positive electrode active material, the positive electrode active material comprises lithium-containing phosphate; the carbon coating material covers at least part of the surface of the inner core, a Raman spectrum of the carbon coating material has a G peak and a D peak, and ID / IG is smaller than or equal to 0.9. According to the embodiment of the invention, the catalytic oxidation of the positive electrode material on the electrolyte can be reduced, and the high-temperature storage performance of the battery monomer is improved.

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 lifespan of battery cells is one of the most pressing issues to be addressed. 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, the 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: a core including a positive electrode active material, the positive electrode active material including a lithium phosphate; and a carbon coating material covering at least a portion of the surface of the core, the Raman spectrum of the carbon coating material having a G peak and a D peak, and I D / I G Less than or equal to 0.9.

[0006] In this application, by defining the carbon coating material I D / I G The value is within the above range; the smaller the value, the higher the SP content in the carbon-coated material. 2 A higher proportion of hybrid carbon results in a higher degree of graphitization, leading to a more stable structure, higher conductivity, and lower activity. This reduces the catalytic oxidation of the electrolyte by the carbon-coated material, thereby decreasing electrolyte storage consumption. Simultaneously, high SP... 2 Carbon coating materials with hybrid carbon content can form a denser coating layer structure, which can reduce the contact between the positive electrode active material and the electrolyte. While ensuring the lithium-ion pathway, it can reduce the catalytic oxidation of the electrolyte by the high-voltage system, further improve the storage stability of the battery electrolyte, and thus improve the storage life of the battery cell.

[0007] In some embodiments, the discharge voltage plateau of the positive electrode material is greater than 3.65V.

[0008] In some embodiments, the Raman spectrum of the carbon-coated material has G and D peaks, and 0.4 ≤ I D / I G≤0.78.

[0009] In some embodiments, the carbon coating material forms a uniform coating layer on at least a portion of the surface of the core.

[0010] In some embodiments, the uniformity of the coating layer is characterized by the coefficient of variation of the thickness value, wherein the coefficient of variation of the thickness value of the coating layer is less than or equal to 8%.

[0011] In some embodiments, the coefficient of variation for the thickness of the coating layer is 4% to 8%.

[0012] In some embodiments, the thickness of the coating layer is 2 nm to 3 nm.

[0013] In some embodiments, the molar percentage of unsaturated carbon atoms relative to the total number of carbon atoms in the carbon coating material is greater than or equal to 60%.

[0014] In some embodiments, the molar percentage of unsaturated carbon atoms relative to the total number of carbon atoms in the carbon coating material is 60% to 80%.

[0015] In some embodiments, the carbon-coated material includes one or more of styrene-butadiene rubber, phenolic resin, polycyclic aromatic hydrocarbons and their derivatives, benzoic acid and its derivatives, naphthalene sulfonic acid and its derivatives, graphene, graphyne, and tannic acid.

[0016] In some embodiments, the chemical formula of the positive electrode active material is: LiMn x Fe (1-x) PO4, 0.5≤x≤0.8.

[0017] In some embodiments, the volume distribution particle size Dv50 of the cathode material is 1.1 μm to 1.5 μm.

[0018] In some embodiments, the specific surface area of ​​the positive electrode material is 12 m². 2 / g to 16m 2 / g.

[0019] Secondly, embodiments of this application provide a battery device, including a single battery cell from the first aspect of this application.

[0020] Thirdly, embodiments of this application provide an electrical device including a battery device from the second aspect of this application.

[0021] Fourthly, embodiments of this application provide a cathode material comprising: a core, including a cathode active material, the cathode active material comprising lithium phosphate, 0.5 ≤ x ≤ 0.8; and a carbon coating material covering at least a portion of the surface of the core, the Raman spectrum of the carbon coating material having a G peak and a D peak, and ID / I G Less than or equal to 0.9.

[0022] In some embodiments, the discharge voltage plateau of the positive electrode material is greater than 3.65V.

[0023] In some embodiments, the Raman spectrum of the carbon-coated material has G and D peaks, and 0.4 ≤ I D / I G ≤0.78.

[0024] In some embodiments, the carbon coating material forms a uniform coating layer on at least a portion of the surface of the core.

[0025] In some embodiments, the uniformity of the coating layer is characterized by the coefficient of variation of the thickness value, wherein the coefficient of variation of the thickness value of the coating layer is less than or equal to 8%.

[0026] In some embodiments, the coefficient of variation for the thickness of the coating layer is 4% to 8%.

[0027] In some embodiments, the thickness of the coating layer is 2 nm to 3 nm.

[0028] In some embodiments, the molar percentage of unsaturated carbon atoms relative to the total number of carbon atoms in the carbon coating material is greater than or equal to 60%.

[0029] In some embodiments, the molar percentage of unsaturated carbon atoms relative to the total number of carbon atoms in the carbon coating material is 60% to 80%.

[0030] In some embodiments, the carbon-coated material includes one or more of styrene-butadiene rubber, phenolic resin, polycyclic aromatic hydrocarbons and their derivatives, benzoic acid and its derivatives, naphthalene sulfonic acid and its derivatives, graphene, graphyne, and tannic acid.

[0031] In some embodiments, the chemical formula of the positive electrode active material is: LiMn x Fe (1-x) PO4, 0.5≤x≤0.8.

[0032] In some embodiments, the volume distribution particle size Dv50 of the cathode material is 1.1 μm to 1.5 μm.

[0033] In some embodiments, the specific surface area of ​​the positive electrode material is 12 m². 2 / g to 16m 2 / g.

[0034] Fifthly, embodiments of this application provide a method for preparing a cathode material, comprising the following steps:

[0035] The system provides a core and a carbon source, respectively, wherein the core comprises a positive electrode active material with the chemical formula LiMn. x Fe (1-x) PO4, 0.5≤x≤0.8; the proportion of unsaturated carbon atoms in the carbon source relative to the total number of carbon atoms is greater than or equal to 60%;

[0036] The carbon source is attached to at least a portion of the surface of the core to form a pre-coating layer, thereby obtaining a pre-coating material;

[0037] The pre-coated material is subjected to a first sintering treatment at a first temperature to obtain a first sintered material;

[0038] The first sintering material is subjected to a second sintering treatment at a second temperature to obtain the positive electrode material; wherein,

[0039] The first temperature is lower than the second temperature.

[0040] In some embodiments, the first temperature is 200°C to 300°C.

[0041] In some embodiments, the second temperature is 600°C to 800°C.

[0042] In some embodiments, the first sintering process takes 2 to 3 hours.

[0043] In some embodiments, the heating rate of the first sintering treatment is from 3°C / min to 10°C / min.

[0044] In some embodiments, the second sintering process takes 6 to 10 hours.

[0045] In some embodiments, the heating rate of the second sintering process is from 3°C / min to 10°C / min.

[0046] In some embodiments, the carbon source includes one or more of styrene-butadiene rubber, phenolic resin, polycyclic aromatic hydrocarbons and their derivatives, benzoic acid and its derivatives, naphthalene sulfonic acid and its derivatives, graphene, graphyne, and tannic acid.

[0047] According to the embodiments of this application, the preparation method provided in the fifth aspect of this application can be used to prepare the cathode material of the fourth aspect of this application. Attached Figure Description

[0048] 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.

[0049] Figure 1 The diagram shows the structural features of a vehicle provided in some embodiments of this application.

[0050] Figure 2 This is an exploded schematic diagram of a battery provided for some embodiments of this application.

[0051] Figure 3 for Figure 2 The diagram shows an exploded view of the battery module.

[0052] Figure 4 This is a schematic diagram showing the selection of measurement points for the thickness of the cathode material coating layer in the embodiments of this application.

[0053] Figure 5 This is a transmission electron microscope (TEM) image of the cathode material in Example 1 of this application.

[0054] Figure 6 This is a transmission electron microscope (TEM) image of the cathode material in Comparative Example 1 of this application.

[0055] The accompanying drawings are not necessarily drawn to scale.

[0056] 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

[0057] 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 to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] In this application, the terms "multiple" or "various" refer to two or more kinds.

[0064] 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.

[0065] Unless otherwise stated, the terms used in this application have the common meanings as commonly understood by those skilled in the art.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] In some embodiments, the battery device may be an energy storage device. Energy storage devices include energy storage containers, energy storage cabinets, etc.

[0073] The technical solutions described in the embodiments of this application are applicable to battery devices and electrical devices that use battery devices.

[0074] 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.

[0075] Electrical devices can choose the type of battery device according to their usage needs, such as individual battery cells, battery modules, or battery packs.

[0076] For ease of explanation, the following embodiments will use a vehicle as an example of an electrical device.

[0077] Figure 1 The diagram shows the structural features of a vehicle provided in some embodiments of this application.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] 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.

[0085] 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.

[0086] Figure 3 for Figure 2 The diagram shows an exploded view of the battery module.

[0087] 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.

[0088] 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.

[0089] The battery cells mentioned in the embodiments of this application may include lithium-ion battery cells or sodium-ion battery cells.

[0090] 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.

[0091] Electrode assemblies generally include a positive electrode, a negative electrode, and a separator.

[0092] [Positive electrode plate]

[0093] Carbon coating is a common method for surface treatment of cathode active materials. By forming a coating layer on the surface of the cathode active material, it can improve the conductivity of the active material, reduce surface defects, and improve electrolyte wettability. Currently, the coating material is mostly SP. 3 Carbon materials with high hybrid carbon content, such as glucose, sucrose, and polyethylene glycol, have high SP content. 3 Carbon materials with hybrid carbon content have a low degree of graphitization and a disordered crystal structure, making it difficult to form a dense coating layer that blocks the contact between metal ions and the electrolyte in the positive electrode active material; furthermore, this high SP 3 The carbon materials with hybrid carbon content in this application exhibit high activity, which reduces the catalytic oxidation potential of the electrolyte, leading to oxidative decomposition of the electrolyte and deteriorating the storage life of the conductive battery cells. This is particularly true for high-voltage phosphate systems, where further catalysis at high voltages can easily result in higher SP levels. 3 Carbon materials with hybrid carbon content react with the electrolyte, catalyzing a decrease in the electrolyte's oxidation potential, exacerbating the electrolyte's oxidative decomposition, and further worsening the battery cell's storage life.

[0094] In the battery cell provided in this application embodiment, for the high-voltage phosphate system, by improving the design of the positive electrode active material coating layer, the contact between the high-voltage phosphate active material and the electrolyte can be reduced, while the reactivity of the coating layer and the electrolyte is reduced, the reaction consumption of the electrolyte is reduced, and thus the storage life and electrochemical performance of the battery cell are improved.

[0095] In some embodiments, the positive electrode sheet 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:

[0096] The core includes positive electrode active materials, which include lithium phosphates.

[0097] A carbon-coated material covers at least part of the surface of the core; wherein the Raman spectrum of the carbon-coated material has G peaks and D peaks, and I D / I G It can be less than or equal to 0.9.

[0098] In this application, I D The D peak (SP) in the Raman spectrum 3 Peak intensity of hybrid carbon atoms, IG The G peak (SP) in the Raman spectrum 2 Peak intensity of hybrid carbon atoms, I D / I G That is, the coating layer SP 3 Hybridized carbon and SP 2 The ratio of hybrid carbon atoms can reflect the degree of graphitization of the coating layer. G and I D This can be measured using methods and instruments known in the art, such as Raman spectroscopy. Specifically, the battery cell can be disassembled to obtain the positive electrode sheet, and powder containing the positive electrode material can be obtained by scraping the positive electrode sheet. The powder can be subjected to Raman spectroscopy, and the peaks of the Raman spectrum can be separated to obtain the Io of the carbon coating material on the surface of the positive electrode material. D and I G .

[0099] In this embodiment of the application, by defining the carbon coating material I D / I G The value is within the above range; the smaller the value, the higher the SP content in the carbon-coated material. 2 A higher proportion of hybrid carbon results in a higher degree of graphitization, leading to a more stable structure, higher conductivity, and lower activity. This reduces the catalytic oxidation of the electrolyte by the carbon-coated material, thereby decreasing electrolyte storage consumption. Simultaneously, high SP... 2 Carbon coating materials with hybrid carbon content can form a denser coating layer structure, which can reduce the contact between the positive electrode active material and the electrolyte. While ensuring the lithium-ion pathway, it can reduce the catalytic oxidation of the electrolyte by the high-voltage system, further improve the storage stability of the battery electrolyte, and thus improve the storage life of the battery cell.

[0100] In some embodiments, the discharge voltage plateau of the positive electrode material can be greater than 3.65V, and optionally, the discharge voltage plateau of the positive electrode material can be greater than 4.0V. By employing the above-described carbon-coated material, the positive electrode material with a higher discharge voltage plateau can exhibit better stability.

[0101] In some embodiments, the Raman spectrum of the carbon-coated material has G and D peaks, and 0.4 ≤ I D / I G ≤0.78.

[0102] I of carbon-coated materials D / I G Values ​​within the above range have higher SP. 2The hybrid carbon content allows for a coating layer with high graphitization, resulting in a cathode material with high conductivity and stability, reducing catalytic oxidation of the electrolyte. Simultaneously, the coating layer exhibits good electrolyte wettability, enabling the battery cell to achieve both improved storage life and cycle performance. The carbon-coated material... D / I G The value is within the above range, and the I of the carbon-coated material D / I G Values ​​within the above range are more conducive to the coating treatment of high-voltage phosphate positive electrode active materials.

[0103] In some embodiments, the carbon coating material forms a uniform coating layer on at least a portion of the surface of the core.

[0104] In some embodiments, the coating uniformity of the coating layer may be less than or equal to 8%, and optionally, the coating uniformity of the coating layer may be 5% to 8%.

[0105] In this application, the coating uniformity refers to the uniformity of the coating layer formed by the carbon coating material on the core surface. This can be detected by sampling the thickness of the coating layer at different locations on the surface of the cathode material particles. Specifically, samples can be taken at intervals on the surface of the cathode material particles. The number of sampling points can be 10, 20, 30, or other values. The sampling points can be evenly distributed at intervals on the surface of the cathode material particles, thereby obtaining the thickness values ​​of the coating layer at different points. The average and standard deviation of all thickness values ​​are calculated, and then the coefficient of variation (COV) is calculated to reflect the coating uniformity: COV(%) = (standard deviation / average) * 100%. The smaller the COV value, the smaller the fluctuation between the data, indicating a smaller difference in the thickness value of the coating layer at different sampling points, and better coating uniformity.

[0106] In this embodiment, the coating layer has high coating uniformity, indicating that the carbon coating material forms a uniform and dense coating structure on the core surface, which can further reduce the contact between the core and the electrolyte, reduce the catalytic oxidation of the electrolyte, and improve the cycle performance of the battery cell.

[0107] In some embodiments, the thickness of the coating layer can be from 2.0 nm to 3.0 nm. For example, the thickness of the coating layer can be 2.0 nm, 2.1 nm, 2.2 nm, 2.3 nm, 2.4 nm, 2.5 nm, 2.6 nm, 2.7 nm, 2.8 nm, 2.9 nm, 3.0 nm, or any range of the above values.

[0108] A coating thickness within the aforementioned range is beneficial for forming a more stable and dense coating structure, which can improve the structural stability and electrochemical performance of the cathode material, thereby further improving the cycle performance and storage life of the battery cell. In this application, the coating thickness is the average thickness.

[0109] In some embodiments, the molar percentage of unsaturated carbon atoms relative to the total number of carbon atoms in the carbon-coated material can be greater than or equal to 60%, and can be selected as 60% to 80%.

[0110] In this application, an unsaturated carbon atom refers to a carbon atom that is bonded to another atom by a double or triple bond. This other atom can be a carbon atom, oxygen atom, nitrogen atom, or any other atom capable of forming a double or triple bond with the carbon atom. The proportion of unsaturated carbon atoms relative to the total number of carbon atoms can be calculated based on the degree of unsaturation of the carbon-coated material. The degree of unsaturation, also known as the hydrogen deficiency index or cycloaddition double bond index, is a quantitative indicator of the degree of unsaturation in organic compound molecules. Specifically, compared to open-chain alkanes with the same number of carbon atoms, for every two hydrogen atoms removed, the degree of unsaturation of the organic compound increases by 1. For example, for a carbon-coated material with the chemical formula C... x H y Or C x H y O z For organic compounds, if y < 2x + 2, then the organic compound has a certain degree of unsaturation, where the degree of unsaturation Ω = x + 1 - y / 2, and the percentage of unsaturated carbon atoms relative to the total number of carbon atoms η = Ω / x * 100%. For example, glucose (C6H4O3) 12 The degree of unsaturation of O6 is 1, and the proportion of unsaturated carbon atoms to the total number of carbon atoms is 16.7%; the degree of unsaturation of benzene (C6H6) is 4, and the proportion of unsaturated carbon atoms to the total number of carbon atoms is 66.7%.

[0111] In this application, carbon coating materials with a high proportion of unsaturated carbon atoms are used. These carbon coating materials contain more SP. 2 Hybridized carbon, SP 2 Hybrid carbon itself has low catalytic activity, and a highly graphitized coating layer can be obtained at a relatively low sintering temperature. This effectively reduces the content of amorphous carbon in the coating layer, thereby reducing the catalytic oxidation effect of the coating layer on the electrolyte. This reduces interfacial reactions and electrolyte oxidative decomposition, thus improving the storage life of the battery cell. Furthermore, by using a coating layer with a higher unsaturated carbon content, a denser and more uniform coating layer can be obtained, improving the conductivity of the cathode material and reducing the internal resistance of the battery cell.

[0112] In some embodiments, the carbon-coated material includes one or more of styrene-butadiene rubber, phenolic resin, polycyclic aromatic hydrocarbons and their derivatives, benzoic acid and its derivatives, naphthalene sulfonic acid and its derivatives, graphene, graphyne, and tannic acid.

[0113] The aforementioned carbon-coated materials all contain abundant unsaturated bonds and have a high content of unsaturated carbon atoms. When used as raw materials for the coating layer, they can be sintered at a lower temperature to form a coating layer with a high degree of graphitization. The coating layer has a low content of amorphous carbon, which helps to reduce the catalytic oxidation of the electrolyte by carbon in the coating layer, thereby improving the cycle stability of the battery cell.

[0114] In some embodiments, the chemical formula of the positive electrode active material can be: LiMn x Fe (1-x) PO4, 0.5≤x≤0.8. Positive electrode active materials with the above chemical formula exhibit a higher discharge voltage plateau.

[0115] In some embodiments, the volumetric particle size Dv50 of the cathode material can be from 1.1 μm to 1.5 μm. Exemplarily, the volumetric particle size Dv50 of the cathode material can be 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, or any range of the above values.

[0116] The volume distribution particle size Dv50 has a well-known meaning in the art and can be determined by methods and instruments well-known in the art. For example, it can be determined by a laser diffractometer in accordance with GB / T 19077-2016 "Particle size analysis by laser diffraction".

[0117] 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.

[0118] In some embodiments, the specific surface area of ​​the cathode material is 12 m². 2 / g to 16m 2 / g. For example, the specific surface area of ​​the cathode material can be 12m². 2 / g、13m 2 / g、14m 2 / g, 15m 2 / g, 16m 2 / g or any range of the above values.

[0119] The specific surface area of ​​a material is a term known in the art and can be determined 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 the TRISTAR II 3020 specific surface area and porosity analyzer from Micromeritics, Inc., USA.

[0120] 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.

[0121] In some embodiments, the cathode material can be prepared by the following methods:

[0122] S10 provides both the core and the carbon source; the core includes LiMn... x Fe (1-x) PO4, a positive electrode active material with a carbon source of 0.5 ≤ x ≤ 0.8, wherein the proportion of unsaturated carbon atoms to the total number of carbon atoms is greater than or equal to 60%;

[0123] S20, the carbon source is attached to at least a portion of the surface of the core to form a pre-coating layer, thus obtaining a pre-coated material;

[0124] S30, the pre-coated material is subjected to a first sintering treatment at a first temperature to obtain a first sintered material;

[0125] S40, the first sintering material undergoes a second sintering treatment at a second temperature to obtain the cathode material; wherein,

[0126] The first temperature is lower than the second temperature.

[0127] In this embodiment, carbon materials with an unsaturated carbon atom molar ratio of 60% or higher are used as carbon sources. These carbon sources contain a high content of SP2 heterocyclic carbon, and a coating layer with a high degree of graphitization can be obtained by sintering at a relatively low temperature. This effectively coats the positive electrode active material while reducing the structural damage to the positive electrode active material caused by high-temperature sintering. The high-graphitization coating layer formed by sintering has a low content of amorphous carbon, thus reducing the catalytic oxidation between the coating layer and the electrolyte, thereby reducing electrolyte storage consumption and improving the storage life of the battery cell. In addition, the structure of the high-graphitization coating layer is more compact, which can reduce the contact between the electrolyte and the phosphate positive electrode active material in the high-voltage system, further reducing the catalytic oxidation of the electrolyte by the high-voltage system, thereby further improving the storage life of the battery cell.

[0128] In some embodiments, the first temperature can be from 200°C to 300°C. For example, the first temperature can be 200°C, 210°C, 220°C, 230°C, 240°C, 250°C, 260°C, 270°C, 280°C, 290°C, 300°C, or any range of the above values.

[0129] In some embodiments, the second sintering temperature can be from 600°C to 800°C. Exemplarily, the second sintering temperature can be 600°C, 610°C, 620°C, 630°C, 640°C, 650°C, 660°C, 670°C, 680°C, 690°C, 700°C, 710°C, 720°C, 730°C, 740°C, 750°C, 760°C, 770°C, 780°C, 790°C, 800°C, or any range of the above values.

[0130] After coating at least a portion of the surface of the cathode material with a carbon source to form a pre-coating, a first sintering treatment is performed at a lower temperature. At this lower sintering temperature, the carbon source is pre-graphitized on the surface of the cathode active material to form a pre-coating layer, reducing the damage to the cathode active material structure caused by excessively high initial sintering temperatures. Following the first sintering treatment, a second sintering treatment is performed on the cathode material at a higher sintering temperature. During the first sintering treatment, the pre-coating layer is fully graphitized to form a coating layer. By performing two sintering treatments at different sintering temperatures, with the highest sintering temperature controlled below 800℃, a graphitized coating layer with a certain degree of graphitization can be formed on the surface of the cathode active material, while simultaneously reducing the structural damage to the cathode active material caused by high temperatures. This allows the cathode material to exhibit both lower activity and higher cycle stability, thereby enabling the battery cell to achieve improved storage and cycle performance.

[0131] In some embodiments, the time for the first sintering treatment can be from 2.0h to 3.0h. For example, the time for the first sintering treatment can be 2.1h, 2.2h, 2.3h, 2.4h, 2.5h, 2.6h, 2.7h, 2.8h, 2.9h, 3.0h, or any range of the above values.

[0132] In some embodiments, the heating rate of the first sintering process can be from 3°C / min to 10°C / min. Exemplarily, the heating rate of the first sintering process can be 3°C / min, 4°C / min, 5°C / min, 6°C / min, 7°C / min, 8°C / min, 9°C / min, 10°C / min, or any range of the above values.

[0133] In some embodiments, the second sintering process can be performed for 6 to 10 hours. For example, the second sintering process can be performed for 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, or any range of the above values.

[0134] In some embodiments, the heating rate of the second sintering process can be from 3°C / min to 10°C / min. Exemplarily, the heating rate of the second sintering process can be 3°C / min, 4°C / min, 5°C / min, 6°C / min, 7°C / min, 8°C / min, 9°C / min, 10°C / min, or any range of the above values.

[0135] In some embodiments, step S20 may include:

[0136] S21, Disperse the carbon source in water to obtain a carbon source dispersion;

[0137] S22, the kernel is added to the dispersion so that the carbon source covers at least a portion of the surface of the kernel;

[0138] S23, the pre-coated material is dried and then sintered. After sintering, it is crushed and sieved to obtain the cathode material.

[0139] In some embodiments, the drying method may include one or more of spray drying, vacuum drying, and thermal drying.

[0140] In some other embodiments, the carbon source may include one or more of styrene-butadiene rubber, phenolic resin, polycyclic aromatic hydrocarbons and their derivatives, benzoic acid and its derivatives, naphthalene sulfonic acid and its derivatives, graphene, graphyne, and tannic acid.

[0141] 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 phosphate positive electrode active materials described above.

[0142] 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.

[0143] Lithium-containing phosphates may include one or more of lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, and their respective modified compounds.

[0144] 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.

[0145] 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.

[0146] The higher the Ni content in layered lithium-containing transition metal oxides, the higher the energy density of the battery cell.

[0147] 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.

[0148] 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 One or more of O2.

[0149] 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.

[0150] In some embodiments, as an example, sodium transition metal oxides may include, but are not limited to:

[0151] 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;

[0152] 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;

[0153] 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,

[0154] 0.67 <d+e<0.8,b+c+d+e=1。

[0155] In some embodiments, as an example, the polyanionic compound may include, but is not limited to:

[0156] 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;

[0157] Na nM 4 PO4X 2 , where M 4 is one or more of Mn, Fe, Co, Ni, Cu, and Zn, and X 2 is one or more of F, Cl, and Br; 0 < n ≤ 2;

[0158] 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;

[0159] 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.

[0160] In some embodiments, by way of example, Prussian blue compounds may include, but are not limited to:

[0161] A u M 6 v [M 7 (CN)6] w ·xH2O, where A is H + , NH4 + , an alkali metal cation, or an alkaline earth metal cation, and 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+ , and M 6 and M 7 are each independently cations of one or more transition metal elements selected 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.

[0162] 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.

[0163] 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.

[0164] 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.

[0165] 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.

[0166] 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.

[0167] 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.

[0168] 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.

[0169] 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.

[0170] [Negative electrode plate]

[0171] 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.

[0172] 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.

[0173] 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.

[0174] 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.

[0175] 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.

[0176] 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).

[0177] 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.

[0178] 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).

[0179] 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.

[0180] 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.

[0181] [Electrolytes]

[0182] A single battery cell includes an electrolyte.

[0183] In some embodiments, the electrolyte is an electrolyte solution, which includes an electrolyte salt and an organic solvent.

[0184] 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.

[0185] In some embodiments, the electrolyte includes cations, which may include one or more of lithium ions and sodium ions.

[0186] 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.

[0187] 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.

[0188] 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.

[0189] 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.

[0190] [Isolation Component]

[0191] In some embodiments, the electrode assembly further includes an isolator disposed between the positive and negative electrodes.

[0192] 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.

[0193] 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.

[0194] 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.

[0195] Example

[0196] 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.

[0197] Example 1

[0198] Positive electrode sheet

[0199] S10, disperse the carbon source β-naphthalenesulfonic acid in an appropriate amount of water and stir thoroughly at 8000 r / min for 2 h to obtain a carbon source dispersion;

[0200] S20, with lithium manganese iron phosphate (LiMn) as the positive electrode active material 0.6 Fe 0.4 PO4) was added to the carbon source dispersion, with the mass ratio of positive electrode active material to carbon source being 10:1, and the mixture was stirred and mixed for 2 hours.

[0201] S30, the mixture in step S20 is spray-dried under stirring, and the pre-coated material is obtained after drying;

[0202] S40, the pre-coated material is placed in an atmosphere furnace for the first sintering treatment. The sintering atmosphere is argon, the sintering temperature is 250℃, the heating rate is 5℃ / min, and the sintering time is 2.5h. After sintering, the first sintered material is obtained.

[0203] S50, the first sintered material is further subjected to a second sintering treatment at 750℃, with a heating rate of 5℃ / min and a sintering time of 8h. After sintering, the positive electrode material is obtained.

[0204] S50, the above-prepared positive electrode material, conductive carbon black, and binder polyvinylidene fluoride (PVDF) are mixed in a mass ratio of 90:5:5 and then added to the solvent N-methylpyrrolidone (NMP) to uniformly disperse and 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.

[0205] Negative electrode sheet

[0206] A negative electrode slurry is prepared by uniformly mixing graphite (a negative electrode active material), Super P (a conductive agent), carboxymethyl cellulose (CMC) (a thickener), and styrene-butadiene rubber (SBR) (a binder) in deionized water at a mass ratio of 80:15:3:2. The negative electrode slurry is then uniformly coated onto copper foil (a current collector) and dried at 85°C. After cold pressing and slitting, the negative electrode sheet is obtained.

[0207] Separating membrane

[0208] A polyethylene (PE) film with a thickness of 13μm was selected.

[0209] electrolyte

[0210] The electrolyte solvent is a mixture of ethylene carbonate, diethyl carbonate, and dimethyl carbonate in a volume ratio of 1:1:1. The electrolyte salt is LiPF6, and the concentration of the electrolyte salt is 1 mol / L.

[0211] battery cell

[0212] The positive electrode, negative electrode, and separator are stacked in sequence and then injected with electrolyte to obtain a coin cell.

[0213] Examples 2 to 9

[0214] The difference from Example 1 is that the composition parameters of the cathode material are different, as detailed in Table 1.

[0215] Example 10

[0216] The difference from Example 1 is that the cathode material is prepared by the following method:

[0217] S10, disperse the carbon source β-naphthalenesulfonic acid in an appropriate amount of water and stir thoroughly at 8000 r / min for 2 h to obtain a carbon source dispersion;

[0218] S20, with lithium manganese iron phosphate (LiMn) as the positive electrode active material 0.6Fe 0.4 PO4) was added to the carbon source dispersion, with the mass ratio of positive electrode active material to carbon source being 10:1, and the mixture was stirred and mixed for 2 hours.

[0219] S30, the mixture in step S20 is spray-dried under stirring, and the pre-coated material is obtained after drying;

[0220] S40, the pre-coated material is placed in an atmosphere furnace for sintering. The sintering atmosphere is argon, the sintering temperature is 750℃, the heating rate is 5℃ / min, and the sintering time is 10h. After sintering, the cathode material is obtained.

[0221] Comparative Examples 1 to 2

[0222] The difference from Example 1 is that the composition parameters of the cathode material are different, as detailed in Table 1.

[0223] Test section

[0224] 1. Coating uniformity

[0225] TEM images of the cathode material are obtained through TEM testing. The thickness of the coating layer at different locations is then measured within the TEM images. Specific sampling points can be found in [reference needed]. 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%.

[0226] 2. Battery cell initial efficiency and specific capacity testing

[0227] After constant current charging and discharging at 0.1C to the upper limit of cutoff voltage 4.3V, constant voltage charging is performed to 0.05C, followed by constant current discharging at 0.1C to the lower limit of cutoff voltage 2.0V. The ratio of the first discharge capacity to the first charge capacity of a battery cell is used as the first efficiency of the battery cell, and the ratio of the first discharge capacity to the mass of the active material is used as the specific capacity of the battery cell.

[0228] 3. Battery cell life test

[0229] The battery cells were charged at a constant current of 0.1C to the upper limit cutoff voltage of 4.3V, and then stored in a 60℃ oven. Every once in a while, the cells were taken out to test the reversible capacity and the ratio of the reversible capacity to the initial capacity after 60 days of storage was recorded.

[0230] 4. Diaphragm resistance test

[0231] Eight circular samples were punched from the electrode sheet. The resistance of each circular sample was tested using a film resistance tester. The average film resistance of each small circular sample was taken as the film resistance of the electrode sheet.

[0232] The test results are detailed in Table 1.

[0233]

[0234] Figure 5 and Figure 6 This document shows TEM images of the cathode materials in Example 1 and Comparative Example 1. It can be seen that using high SP... 2 Tannins with hybrid carbon content, when used as coating materials, produce more uniform and dense coating layers. Combining the data in Table 1, by using high SP... 2 Coating high-voltage lithium manganese iron phosphate cells with carbon materials containing hybrid carbon content can effectively improve the high-temperature storage performance of individual cells.

[0235] 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 by, 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 includes a positive electrode active material, wherein the positive electrode active material includes a lithium phosphate; A carbon coating material covers at least a portion of the surface of the core. The Raman spectrum of the carbon-coated material has a G peak and a D peak, and I D / I G is less than or equal to 0.

9.

2. The battery cell of claim 1, wherein, The Raman spectrum of the carbon-coated material has a G peak and a D peak, and 0.4≤I D / I G ≤0.

78.

3. The battery cell according to claim 1 or 2, characterized in that, The discharge voltage plateau of the positive electrode material is greater than 3.65V.

4. The battery cell according to any one of claims 1 to 3, characterized in that, The carbon coating material forms a uniform coating layer on at least a portion of the surface of the core.

5. The battery cell of claim 4, wherein, The uniformity of the coating layer is characterized by the coefficient of variation of the thickness value, which is less than or equal to 8%.

6. The battery cell of claim 5, wherein, The coefficient of variation for the thickness of the coating layer is 4% to 8%.

7. The battery cell according to any one of claims 4 to 6, characterized in that, The thickness of the coating layer is 2 nm to 3 nm.

8. The battery cell of any one of claims 1 to 7, wherein, The molar percentage of unsaturated carbon atoms relative to the total carbon atoms in the carbon-coated material is greater than or equal to 60%.

9. The battery cell of claim 8, wherein, The molar percentage of unsaturated carbon atoms relative to the total carbon atoms in the carbon-coated material is 60% to 80%.

10. The battery cell of any one of claims 1 to 9, wherein, The carbon-coated material includes one or more of the following: styrene-butadiene rubber, phenolic resin, polycyclic aromatic hydrocarbons and their derivatives, benzoic acid and its derivatives, naphthalene sulfonic acid and its derivatives, graphene, graphyne, and tannic acid.

11. The battery cell of any one of claims 1 to 10, wherein, The positive active material has a chemical formula of LiMn x Fe (1-x) PO4, 0.5≤x≤0.

8.

12. The battery cell of any one of claims 1 to 11, wherein, The volumetric particle size distribution (Dv50) of the cathode material is 1.1 μm to 1.5 μm; and / or The specific surface area of the positive electrode material is 12 m 2 / g to 16 m 2 / g.

13. A battery device characterized by comprising: Includes the battery cell according to any one of claims 1 to 12.

14. An electrical device, comprising: Includes the battery device as described in claim 13.

15. A positive electrode material, characterized in that, include: The core includes a positive electrode active material, wherein the positive electrode active material includes a lithium phosphate; A carbon coating material covers at least a portion of the surface of the core. The Raman spectrum of the carbon-coated material has a G peak and a D peak, and I D / I G ≤ 0.

9.

16. The cathode material of claim 15, wherein, The Raman spectrum of the carbon-coated material has a G peak and a D peak, and 0.4≤I D / I G ≤0.

78.

17. The cathode material of claim 15 or 16, wherein, The discharge voltage plateau of the positive electrode material is greater than 3.65V.

18. The cathode material of any one of claims 15-17, wherein, The carbon coating material forms a uniform coating layer on at least a portion of the surface of the core.

19. The cathode material of claim 18, wherein, The uniformity of the coating layer is characterized by the coefficient of variation of the thickness value, which is less than or equal to 8%.

20. The cathode material of claim 19, wherein, The coefficient of variation for the thickness of the coating layer is 4% to 8%.

21. The cathode material of any one of claims 18-20, wherein, The thickness of the coating layer is 2 nm to 3 nm.

22. The cathode material of any one of claims 15 to 21, wherein, The molar percentage of unsaturated carbon atoms relative to the total carbon atoms in the carbon-coated material is greater than or equal to 60%.

23. The cathode material of claim 22, wherein, The molar percentage of unsaturated carbon atoms relative to the total carbon atoms in the carbon-coated material is 60% to 80%.

24. The cathode material of any one of claims 15-23, wherein, The carbon-coated material includes one or more of the following: styrene-butadiene rubber, phenolic resin, polycyclic aromatic hydrocarbons and their derivatives, benzoic acid and its derivatives, naphthalene sulfonic acid and its derivatives, graphene, graphyne, and tannic acid.

25. The cathode material of any one of claims 15-24, wherein, The positive active material has a chemical formula of LiMn x Fe (1-x) PO4, 0.5≤x≤0.

8.

26. The cathode material of any one of claims 15-25, wherein, The volumetric particle size distribution (Dv50) of the cathode material is 1.1 μm to 1.5 μm; and / or The specific surface area of the positive electrode material is 12 m 2 / g to 16 m 2 / g.

27. A method of producing a positive electrode material, characterized by, Includes the following steps: The system provides a core and a carbon source, wherein the core includes a positive electrode active material, the positive electrode active material includes a lithium phosphate; and the carbon source contains at least 60% unsaturated carbon atoms relative to the total number of carbon atoms. The carbon source is attached to at least a portion of the surface of the core to form a pre-coating layer, thereby obtaining a pre-coating material; The pre-coated material is subjected to a first sintering treatment at a first temperature to obtain a first sintered material; The first sintering material is subjected to a second sintering treatment at a second temperature to obtain the positive electrode material; wherein, The first temperature is lower than the second temperature.

28. The preparation method according to claim 27, characterized in that, the first temperature is 200℃ to 300℃; and / or the second temperature is 600℃ to 800℃.

29. The method of manufacturing according to claim 27 or 28, wherein, the time of the first sintering treatment is 2h to 3h; and / or the temperature increasing rate of the first sintering treatment is 3℃ / min to 10℃ / min; and / or the time of the second sintering treatment is 6h to 10h; and / or the temperature increasing rate of the second sintering treatment is 3℃ / min to 10℃ / min.

30. The method of any one of claims 27-29, wherein, the carbon source comprises one or more of styrene butadiene rubber, phenol formaldehyde resin, condensed polycyclic aromatic hydrocarbon and derivatives thereof, benzoic acid and derivatives thereof, naphthalene sulfonic acid and derivatives thereof, graphene, graphyne, tannic acid.

31. The method of manufacturing according to any one of claims 27 to 30, wherein, The positive electrode material has a chemical formula of LiMn x Fe (1-x) PO4, 0.5≤x≤0.8.

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