Lithium battery monomer, phosphate positive electrode active material, preparation method of phosphate positive electrode active material, battery device and power utilization device

Abstract

The invention discloses a lithium battery monomer, a phosphate positive electrode active material, a preparation method of the phosphate positive electrode active material, a battery device and a power utilization device, the lithium battery monomer comprises a positive electrode plate, the positive electrode plate comprises the phosphate positive electrode active material, the phosphate positive electrode active material comprises an inner core, and the inner core comprises lithium-containing transition metal phosphate particles; the coating material at least partially coats the surface of the inner core; and the coating material comprises one or more of a Si-C-N bond and a C-N-Si bond. The lithium battery cell of the present application obtains improved dynamic performance and cycle capacity retention rate. The invention also provides a phosphate positive electrode active material with good powder resistivity and high gram volume and a preparation method thereof. The battery device and the power utilization device provided by the invention at least have the corresponding advantages of the lithium battery monomer.

Description

Technical Field

[0001] This application belongs to the field of battery technology, specifically relating to a lithium battery cell, a phosphate positive electrode active material and its preparation method, a battery device and an electrical device. Background Technology

[0002] Lithium-ion battery cells, as a representative example, utilize the insertion and extraction of lithium ions between the positive and negative electrodes to achieve charging and discharging. The positive electrode active material is a key factor affecting the performance of a lithium-ion battery cell.

[0003] In related technologies, glucose-based organic carbon coating is often used to improve the conductivity of cathode active materials. However, the carbon coating effect is poor, affecting the electrochemical performance of the cathode active material in the battery. Therefore, effective technical means are needed to improve it. Summary of the Invention

[0004] The purpose of this application is to provide a lithium battery cell with improved cycle performance and kinetic performance; this application also provides a phosphate positive electrode active material with good powder resistance, structural stability and high specific capacity and a method for preparing the same; this application also provides a battery device and an electrical device that have at least the advantages of a lithium battery cell.

[0005] In a first aspect, this application provides a lithium battery cell, including a positive electrode sheet, the positive electrode sheet comprising a phosphate positive electrode active material, the phosphate positive electrode active material comprising:

[0006] The core, which includes lithium transition metal phosphate particles;

[0007] The coating material at least partially coats the surface of the core; wherein the coating material includes one or more of Si-CN bonds and CN-Si bonds.

[0008] In the embodiments of this application, the coating material contains one or more of Si-CN bonds and CN-Si bonds, which can improve the internal bonding force of the coating material. The more tightly bonded coating material reduces the powder resistivity of the phosphate cathode active material and improves the cycle capacity retention of the lithium battery cell. The presence of Si-CN bonds and CN-Si bonds can reduce the content of impurity groups on the surface of the phosphate cathode active material. Reducing the content of impurity groups can reduce the side reactions of the phosphate cathode active material and improve the cycle capacity retention of the lithium battery cell.

[0009] The coating material includes one or more of Si-CN bonds and CN-Si bonds. The combined effect of multiple factors improves the powder compaction density, specific capacity and conductivity of the phosphate cathode active material.

[0010] In some optional embodiments, the coating material includes a first coating material and a second coating material; the second coating material is located on the surface of the first coating material, the first coating material includes carbon, and the second coating material includes silicon and nitrogen.

[0011] In this embodiment, the silicon element in the second coating material can optimize the surface structure of the coating material, improve surface activity, and enhance the electrochemical activity of the surface, thereby improving the lithium-ion insertion and extraction process and enhancing the kinetic performance of the lithium battery cell. Silicon can also alter the chemical environment of the coating material, making the SEI layer formed in the lithium battery cell more uniform and stable, thus improving the cycle capacity retention rate of the lithium battery cell.

[0012] In the embodiments of this application, the nitrogen element in the second coating material can form an electron donor or acceptor, improving the conductivity of the phosphate cathode active material; the nitrogen element on the surface of the phosphate cathode active material can improve the chemical stability of the material, reduce possible side reactions in the lithium battery cell, and improve the cycle capacity retention rate of the lithium battery cell.

[0013] In this embodiment, the second coating material includes silicon and nitrogen, indicating that the silicon and nitrogen elements are located on the surface of the phosphate cathode active material, which can reduce the content of impurity groups on the surface. Reducing the content of impurity groups can reduce the side reactions of the phosphate cathode active material and further improve the cycle capacity retention rate of the lithium battery cell.

[0014] In some optional embodiments, the phosphate cathode active material includes 0.5% to 2% carbon by mass, based on the total mass of the phosphate cathode active material. This improves the conductivity of the phosphate cathode active material. Furthermore, the uniform distribution of this carbon in the first coating material further reduces lithium-ion migration resistance and improves conductivity, thereby enhancing the kinetic performance of the lithium-ion battery cell.

[0015] In some optional embodiments, the phosphate cathode active material includes silicon at a mass content of 0.1% to 1%, based on the total mass of the phosphate cathode active material. This silicon content within the aforementioned range improves the mechanical strength of the coating material, further enhancing the cycle capacity retention of the lithium-ion battery cell.

[0016] In some optional embodiments, based on the total mass of the phosphate cathode active material, the phosphate cathode active material includes nitrogen element with a mass content of 0.05% to 0.5%. Therefore, the conductivity of the phosphate cathode active material is further improved; the nitrogen element on the surface of the phosphate cathode active material further enhances the chemical stability of the material, reduces potential side reactions in lithium battery cells, and improves the cycle capacity retention rate of lithium battery cells.

[0017] In some optional embodiments, the mass ratio of nitrogen to silicon is 1:(0.2 to 20). This facilitates the formation of Si-CN and CN-Si bonds, further improving the structural stability and conductivity of the phosphate cathode active material, and further enhancing the kinetic performance and cycle capacity retention of the lithium metal battery.

[0018] In some optional embodiments, the mass ratio of carbon, nitrogen, and silicon is 1:(0.025 to 1):(0.05 to 2). Therefore, the structural stability and conductivity of the phosphate cathode active material are further improved, thereby further enhancing the kinetic performance and cycle capacity retention of the lithium metal battery.

[0019] In some optional embodiments, the coating material includes one or more of Si=C bonds, Si-C bonds, C=N bonds, and CN bonds. The presence of these bonds can reduce the content of impurity groups on the surface of the phosphate cathode active material, further improving the cycle capacity retention of the lithium battery cell.

[0020] In some optional embodiments, at least 80% of the core surface area is covered with a coating material. This further reduces side reactions in the phosphate cathode active material and further improves the cycle capacity retention of the lithium-ion battery cell.

[0021] In some optional embodiments, the average thickness of the coating material on the core surface is 1 nm to 10 nm. Therefore, the specific capacity and ionic conductivity of the phosphate cathode active material are further improved, thereby enhancing the kinetic performance and energy density of the lithium-ion battery cell.

[0022] In some optional embodiments, the phosphate cathode active material includes a coating material with a mass content of 0.25% to 3.5%, based on the total mass of the phosphate cathode active material. This facilitates lithium-ion insertion / extraction and improves the kinetic performance of the lithium-ion battery cell.

[0023] In some optional embodiments, the powder resistivity of the phosphate cathode active material is from 10 Ω·m to 2000 Ω·m. Therefore, the internal resistance of the phosphate cathode active material is further reduced, the conductivity of the material is improved, and the kinetic performance of the lithium-ion battery cell is enhanced.

[0024] Secondly, embodiments of this application provide a phosphate positive electrode active material, comprising:

[0025] The core, which includes lithium transition metal phosphate particles;

[0026] The coating material at least partially coats the surface of the core; wherein the coating material includes one or more of Si-CN bonds and CN-Si bonds.

[0027] In the embodiments of this application, the coating material of the phosphate cathode active material includes one or more of Si-CN bonds and CN-Si bonds. The combined effect of multiple factors improves the powder compaction density, specific capacity and conductivity of the phosphate cathode active material, thereby enabling the lithium battery cell to obtain improved kinetic performance and cycle capacity retention.

[0028] The presence of Si-CN and CN-Si bonds can reduce the content of impurity groups on the surface of phosphate cathode active materials, such as the content of CO functional groups. Reducing the content of impurity groups can increase the migration rate of lithium ions in the coating material. Reducing the content of impurity groups can also reduce the side reactions of phosphate cathode active materials and improve the cycle capacity retention of lithium battery cells.

[0029] In the embodiments of this application, the second coating material contains nitrogen and silicon elements, which improves the hydrophobicity and low moisture adsorption performance of the phosphate cathode active material surface, and is beneficial to the storage and transportation of the phosphate cathode active material.

[0030] In some optional embodiments, the powder resistivity of the phosphate cathode active material is from 10 Ω·m to 2000 Ω·m. Therefore, the internal resistance of the phosphate cathode active material is further reduced, the conductivity of the material is improved, and the kinetic performance of the lithium-ion battery cell is enhanced.

[0031] In some optional embodiments, the powder compaction density of the phosphate cathode active material is 2.0 g / cm³. 3 Up to 2.5g / cm 3 Therefore, it increases the energy density of lithium battery cells; it can reduce the voids between particles, improve the conductivity of materials, and enhance the kinetic performance of lithium battery cells.

[0032] In some optional embodiments, the specific surface area of ​​the phosphate cathode active material is 5 m². 2 / g to 30m 2 / g. This increases the effective reaction interface of the material, providing more channels and interfaces, which facilitates the diffusion of lithium ions within the material, improving the capacity and charge / discharge efficiency of lithium battery cells. Phosphate cathode active materials with a specific surface area within the above range generally have a more stable structure, improving the cycle capacity retention of lithium battery cells.

[0033] In some optional embodiments, the specific capacity of the phosphate cathode active material is 140 to 160 mAh / g. A specific capacity within this range can improve the energy density and overall capacity of the lithium-ion battery cell.

[0034] Thirdly, embodiments of this application provide a method for preparing a phosphate positive electrode active material, including:

[0035] In an inert atmosphere, a gaseous carbon source is deposited on the surface of the core using chemical vapor deposition to obtain a first coating material that coats the core. The core includes lithium transition metal phosphate particles.

[0036] A phosphate cathode active material comprising a second coating material is prepared by using chemical vapor deposition to deposit nitrogen-containing organic matter and gaseous silicon source on the surface of a first coating material using a carrier gas. The second coating material is located on the surface of the first coating material.

[0037] In this embodiment, homogeneous carbon elements were obtained by chemical vapor deposition on the core surface, improving the conductivity of the phosphate cathode active material. A second deposition was performed on the surface of the first coating material, resulting in one or more Si-CN and CN-Si bonds in the coating material, which reduced the powder resistivity of the phosphate cathode active material. The presence of Si-CN and CN-Si bonds can reduce the content of impurity groups on the surface of the phosphate cathode active material, such as the content of CO functional groups. Reducing the content of impurity groups can increase the migration rate of lithium ions in the coating material. Furthermore, reducing the content of impurity groups can decrease side reactions in the phosphate cathode active material and improve the cycle capacity retention rate of the lithium battery cell.

[0038] In some optional embodiments, the nitrogen-containing organic compound includes one or more of polyacrylonitrile, acetonitrile, and malononitrile. The nitrogen element in these nitrogen-containing organic compounds can be bonded to carbon elements, improving the internal stability of the coating material, reducing the content of impurity groups on the surface of the phosphate cathode active material, and further improving the cycle capacity retention rate of the lithium battery cell.

[0039] Fourthly, embodiments of this application provide a battery device including a lithium battery cell as described in the first aspect. The power-consuming device of this application embodiment at least possesses the beneficial effects of a lithium battery cell.

[0040] Fifthly, embodiments of this application provide an electrical device including a single lithium battery cell, as described in the fourth aspect. The electrical device of this application embodiment at least has the beneficial effects of a battery device. Attached Figure Description

[0041] 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.

[0042] Figure 1 A schematic diagram of one embodiment of the lithium battery cell of this application is shown.

[0043] Figure 2 It shows Figure 1 An exploded view of one embodiment of a lithium battery cell is shown.

[0044] Figure 3 A schematic diagram of the battery pack according to one embodiment of this application is shown.

[0045] Figure 4 An exploded view of a battery pack according to one embodiment of this application is shown.

[0046] Figure 5 A schematic diagram of one embodiment of an electrical device incorporating the lithium battery cell of this application as a power source is shown.

[0047] The accompanying drawings are not necessarily drawn to scale.

[0048] The following are the labels in the attached diagram: 1. Battery pack, 2. Upper housing, 3. Lower housing, 4. Battery module, 5. Lithium battery cell. Detailed Implementation

[0049] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the lithium battery cell, phosphate cathode active material, preparation method thereof, 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.

[0050] 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 the 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 specific parameters, it is understood that ranges of 60–110 and 80–120 are also expected. 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 "a–b" represents a shortened representation of any combination of real numbers between a and b, characterized in that a and b are both 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.

[0051] 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.

[0052] 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.

[0053] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, preferably sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it means 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.

[0054] Unless otherwise specified, in this application, the term "active ion" refers to ions that can be inserted and extracted back and forth between the positive and negative electrodes of a lithium battery cell, including but not limited to lithium ions.

[0055] In this application, "multiple" or "more than" refers to two or more items (including two). In this application, "several items" or "multiple items" refers to two or more items (including two).

[0056] The battery device mentioned in the embodiments of this application may include one or more lithium battery cells as a single physical module to provide higher voltage and capacity. For example, the battery device mentioned in this application may include lithium battery cells, battery modules, or battery packs.

[0057] In some alternative embodiments, the battery device can be an energy storage device. Energy storage devices include energy storage containers, energy storage cabinets, etc. The battery device mentioned in the embodiments of this application may include one or more lithium battery cell assemblies for providing voltage and capacity. A lithium battery cell assembly may include multiple lithium battery cells, which are connected in series, parallel, or mixed connections via busbars.

[0058] In some alternative embodiments, a lithium battery cell assembly is typically formed by arranging multiple lithium battery cells; as an example, a lithium battery cell assembly can be a battery module, which is formed by arranging and fixing multiple lithium battery cells into a single module. As an example, a battery module can be formed by bundling multiple lithium battery cells together with cable ties.

[0059] In some alternative embodiments, the battery device may be a battery pack, which may include a housing and one or more lithium battery cell assemblies housed within the housing. In some alternative 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.

[0060] As an example, a lithium battery cell assembly can be a battery module, and the lithium battery cell assembly can be housed in a housing by fixing the battery module in the housing.

[0061] As an example, lithium battery cell assemblies can also be housed in a housing by directly fixing multiple lithium battery cells to the housing.

[0062] A lithium battery cell is the smallest unit that makes up a battery device, and it can independently perform the functions of charging and discharging. A lithium battery cell can be cylindrical, cuboid, or other shapes, and the embodiments of this application are not limited to this. Figure 1 This is an example of a rectangular lithium battery cell 5.

[0063] When there are multiple lithium battery cells, they are connected in series, parallel, or mixed via a busbar. In some optional embodiments, the battery can be a battery module; when there are multiple lithium battery cells, they are arranged and fixed to form a battery module.

[0064] In some alternative embodiments, lithium battery cells can be assembled into battery modules, and the number of lithium battery cells contained in a battery module can be multiple, the specific number of which can be adjusted according to the application and capacity of the battery module. Figure 2 This is a schematic diagram of battery module 4 as an example. Figure 2 As shown, in battery module 4, multiple lithium battery cells 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple lithium battery cells 5 can be fixed in place using fasteners.

[0065] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple lithium battery cells 5 are housed.

[0066] In some alternative embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0067] Figure 3 and Figure 4 This is a schematic diagram of battery pack 1 as an example. Figure 3 and Figure 4 As shown, the battery pack 1 may include a housing and multiple battery modules 4 disposed within the housing. The housing includes an upper housing 2 and a lower housing 3. The upper housing 2 covers the lower housing 3, forming a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the housing.

[0068] The lithium battery cells provided in the embodiments of this application can be rechargeable batteries, primary batteries, etc. A rechargeable battery refers to a lithium battery cell that can be recharged after discharge to activate the active materials and continue to be used.

[0069] The lithium battery cell provided in this application includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode and a negative electrode. The negative electrode can be a lithium metal negative electrode. The electrode assembly can be a wound structure or a stacked structure; this application does not limit this.

[0070] In some embodiments, the electrode assembly further includes a separator disposed between the positive and negative electrode plates. In some embodiments, the separator is a separator membrane. This application does not impose any particular limitation on the type of separator membrane; any known porous separator membrane with good chemical and mechanical stability can be selected.

[0071] A lithium battery cell may also include an outer packaging, which can be used to encapsulate electrode components and electrolyte. The outer packaging can be a rigid shell, such as a hard plastic shell, aluminum shell, or steel shell. The outer packaging can also be a flexible package, such as a pouch-type flexible package. The material of the flexible package can be plastic, such as one or more of aluminum-plastic film, polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0072] A lithium battery cell can be a rechargeable battery or a storage battery, meaning a battery that can be recharged after being discharged to activate its active materials and continue to be used. Typically, a lithium battery cell includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode, a negative electrode, and a separator.

[0073] Currently, the mainstream phosphate cathode active materials for lithium-ion battery cells are generally lithium iron phosphate (LFP) and ternary phosphate (NFP) cathode active materials. Ternary phosphate cathode active materials typically have a voltage platform of 3.7V, significantly higher than LFP's 3.4V, and dominate in power batteries. However, ternary materials contain metals such as cobalt and nickel, resulting in high costs and relatively low reliability. Lithium manganese iron phosphate (LFP), with voltage platforms of 4.1V and 3.4V, possesses a higher voltage platform. Furthermore, LFP and similar phosphate cathode active materials exhibit higher theoretical energy density and compaction density, making them promising candidates for next-generation lithium-ion battery cell phosphate cathode active materials.

[0074] However, phosphate cathode active materials have poor conductivity. To improve these problems, carbon coating is generally used, which affects the cycle performance of lithium battery cells.

[0075] Therefore, this application provides a lithium battery cell that has good kinetic performance as well as good cycle capacity retention.

[0076] According to some optional embodiments provided in this application, a lithium battery cell is provided, including a positive electrode sheet, wherein the positive electrode sheet includes a phosphate positive electrode active material.

[0077] In some optional embodiments, the phosphate positive electrode active material includes:

[0078] The core, which includes lithium transition metal phosphate particles;

[0079] The coating material at least partially coats the surface of the core; wherein the coating material includes one or more of Si-CN bonds and CN-Si bonds.

[0080] In the embodiments of this application, the coating material contains one or more of Si-CN bonds and CN-Si bonds, which can improve the internal bonding force of the coating material. The more tightly bonded coating material reduces the powder resistivity of the phosphate cathode active material and improves the cycle capacity retention of the lithium battery cell. The presence of Si-CN bonds and CN-Si bonds can reduce the content of impurity groups on the surface of the phosphate cathode active material. Reducing the content of impurity groups can reduce the side reactions of the phosphate cathode active material and improve the cycle capacity retention of the lithium battery cell.

[0081] In summary, the coating material includes one or more of Si-CN bonds and CN-Si bonds. The combined effect of multiple factors improves the powder compaction density, specific capacity, and conductivity of the phosphate cathode active material.

[0082] In some optional embodiments, the coating material includes a first coating material and a second coating material; the second coating material is located on the surface of the first coating material, the first coating material includes carbon, and the second coating material includes silicon and nitrogen.

[0083] In this embodiment, silicon, as a relatively flexible material, possesses high elastic modulus and elastic deformation capacity. Silicon can optimize the surface structure of the coating material, improve surface activity, and enhance the electrochemical activity of the surface, thereby improving the lithium-ion insertion and extraction process and enhancing the kinetic performance of the lithium battery cell. Silicon can also alter the chemical environment of the coating material, making the SEI layer formed in the lithium battery cell more uniform and stable, thus improving the cycle capacity retention rate of the lithium battery cell.

[0084] In the embodiments of this application, the nitrogen element in the second coating material can form an electron donor or acceptor, improving the conductivity of the phosphate cathode active material; the nitrogen element on the surface of the phosphate cathode active material can improve the chemical stability of the material, reduce possible side reactions in the lithium battery cell, and improve the cycle capacity retention rate of the lithium battery cell.

[0085] In this embodiment, the second coating material includes silicon and nitrogen, indicating that the silicon and nitrogen elements are located on the surface of the phosphate cathode active material, which can reduce the content of impurity groups on the surface. Reducing the content of impurity groups can reduce the side reactions of the phosphate cathode active material and further improve the cycle capacity retention rate of the lithium battery cell.

[0086] In the embodiments of this application, the first coating material and the second coating material may not have a clear boundary. The second coating material may be dispersed on the surface of the first coating material in a discrete manner or in an island-like pattern.

[0087] Carbon, silicon, and nitrogen can be analyzed using XPS (X-ray photoelectron spectroscopy).

[0088] The functional groups or chemical bonds of phosphate-based positive electrode active materials in the positive electrode sheet can be detected using methods such as infrared spectroscopy, Raman spectroscopy, and nuclear magnetic resonance. For example, infrared spectroscopy can determine the functional groups or chemical bonds contained in the phosphate-based positive electrode active material film layer; for instance, the vibrations of Si-C bonds typically occur between 1000 and 1200 cm⁻¹. -1 In addition to the range, there may be other characteristic peaks, such as 800 cm⁻¹. -1 The triple vibration peak at 960cm -1 The double vibration peak at 1070 cm⁻¹ and 1070 cm⁻¹ -1 The singlet vibration peak is observed at 2200-2260 cm⁻¹. CN bond vibrations typically occur between 2200-2260 cm⁻¹. -1 Within the specified range, N-Si bonds can be identified using the same method. The above methods are combined to detect Si-CN and CN-Si bonds present in the coating material.

[0089] In some optional embodiments, the phosphate cathode active material includes 0.5% to 2% carbon by mass, based on the total mass of the phosphate cathode active material.

[0090] Optionally, the phosphate cathode active material includes carbon elements with a mass content of any value or range thereof, which can be 0.5%, 0.55%, 0.6%, 0.65%, 0.7%, 0.75%, 0.8%, 0.85%, 0.9%, 0.95%, 1%, 1.05%, 1.1%, 1.15%, 1.2%, 1.25%, 1.3%, 1.35%, 1.4%, 1.45%, 1.5%, 1.55%, 1.6%, 1.65%, 1.7%, 1.75%, 1.8%, 1.85%, 1.9%, 1.95%, or 2%. The inclusion of carbon elements with the aforementioned mass content in the phosphate cathode active material can improve the conductivity of the phosphate cathode active material. The uniform distribution of this carbon element in the first coating material further reduces the migration resistance of lithium ions and improves the kinetic performance of the lithium battery cell.

[0091] In some optional embodiments, the phosphate cathode active material includes silicon with a mass content of 0.1% to 1%, based on the total mass of the phosphate cathode active material.

[0092] Optionally, the phosphate cathode active material includes silicon in a mass content of any value or range thereof, such as 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, or 1%. The inclusion of silicon in the phosphate cathode active material at the aforementioned mass content further alleviates the mechanical stress caused by volume changes; it further improves the lubrication performance of the phosphate cathode active material, increases the powder compaction density and specific capacity of the phosphate cathode active material, and further improves the energy density of the lithium battery cell. The silicon mass content within the aforementioned range provides improved mechanical strength to the coating material, further enhancing the cycle capacity retention rate of the lithium battery cell.

[0093] In some optional embodiments, the phosphate cathode active material includes nitrogen element with a mass content of 0.05% to 0.5%, based on the total mass of the phosphate cathode active material.

[0094] Optionally, the phosphate cathode active material includes nitrogen element with a mass content of any value or range thereof from 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, and 0.5%. When the mass content of nitrogen element in the phosphate cathode active material is within the above range, it further improves the conductivity of the phosphate cathode active material; when nitrogen element is on the surface of the phosphate cathode active material, it further enhances the chemical stability of the material, reduces possible side reactions in lithium battery cells, and improves the cycle capacity retention rate of lithium battery cells.

[0095] The mass content of carbon, silicon, and nitrogen in phosphate cathode active materials can be detected using methods commonly used in the art, such as X-ray fluorescence spectroscopy (XRF), inductively coupled plasma optical emission spectroscopy (ICP-OES), and atomic absorption spectroscopy (AAS). For example, phosphate cathode active material samples can be analyzed using XRF by utilizing the characteristic X-rays emitted after the sample is excited by X-rays, enabling the detection of the types and amounts of elements in the sample. Sample pretreatment is not required. Elemental mass content can be detected through sampling, and the results are averaged.

[0096] In some optional embodiments, the mass ratio of nitrogen to silicon is 1:(0.2 to 20).

[0097] Optionally, the mass ratio of nitrogen to silicon can be 1:0.2, 1:0.4, 1:0.6, 1:0.8, 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, 1:5.5, 1:6, 1:6.5, 1:7, 1:7.5, 1:8, 1:8.5, 1:9, 1:9.5, or 1:1. Any ratio or range of composition of nitrogen to silicon within the ranges of 0, 1:10.5, 1:11, 1:11.5, 1:12, 1:12.5, 1:13, 1:13.5, 1:14, 1:14.5, 1:15, 1:15.5, 1:16, 1:16.5, 1:17, 1:17.5, 1:18, 1:18.5, 1:19, 1:19.5, and 1:20. Controlling the mass ratio of nitrogen to silicon within these ranges is beneficial for the formation of Si-CN and CN-Si bonds, further improving the structural stability and conductivity of the phosphate cathode active material, and further improving the kinetic performance and cycle capacity retention of lithium metal batteries.

[0098] In some optional embodiments, the mass ratio of carbon, nitrogen and silicon is 1:(0.025 to 1):(0.05 to 2).

[0099] Optionally, the mass ratio of carbon, nitrogen, and silicon can be 1:0.025:0.05, 1:0.025:0.5, 1:0.025:1, 1:0.025:1.5, 1:0.025:2, 1:0.05:0.05, 1:0.05:0.2, 1:0.05:0.5, 1:0.05:1, 1:0.05:2, 1:0.075:0.05, 1:0.075:0.2, 1:0.075:0.5, 1:0.075:1, 1:0.075:1.5, 1:0.075:2.0, 1:0.1:0.05, 1:0.1:0.5, 1:0.1:1, or 1:0.1. The range of any ratios or combinations thereof from 1:1.5, 1:0.1:2, 1:0.125:0.05, 1:0.125:0.4, 1:0.125:0.5, 1:0.125:1, 1:0.125:1.5, 1:0.125:2, 1:0.15:0.05, 1:0.15:1.5, 1:0.15:2, 1:0.2:0.05, 1:0.2:1.5, 1:0.2:2, 1:0.25:0.1, 1:0.25:1.5, 1:0.3:2, 1:0.35:0.2, 1:0.5:2, 1:0.8:0.2, 1:0.8:2, 1:1:1, 1:1:2. With the mass ratio of carbon, nitrogen, and silicon within the above range, the structural stability and conductivity of the phosphate cathode active material are further improved, which in turn improves the kinetic performance and cycle capacity retention of the lithium metal battery.

[0100] In some optional embodiments, the coating material includes one or more of Si=C bonds, Si-C bonds, C=N bonds, and CN bonds. Therefore, these bonds improve the bonding strength between the first and second coating materials, i.e., improve the internal bonding strength of the coating materials, further enhancing the stability of the phosphate cathode active material and further reducing the powder resistivity of the phosphate cathode active material. The presence of these bonds can reduce the content of impurity groups on the surface of the phosphate cathode active material, such as the content of CO functional groups, further improving the cycle capacity retention of the lithium battery cell.

[0101] In some optional embodiments, at least 80% of the core surface area is covered with a coating material. This further reduces side reactions in the phosphate cathode active material and further improves the cycle capacity retention of the lithium-ion battery cell.

[0102] In some optional embodiments, the average thickness of the coating material on the core surface is between 1 nm and 10 nm. Optionally, the average thickness of the coating material can be any ratio or combination of 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, and 10 nm. Therefore, the specific capacity and ionic conductivity of the phosphate cathode active material are further improved, thereby enhancing the kinetic performance and energy density of the lithium-ion battery cell.

[0103] In some optional embodiments, based on the total mass of the phosphate cathode active material, the phosphate cathode active material includes a coating material with a mass content of 0.25% to 3.5%. Optionally, the phosphate cathode active material includes any value or range of its composition from 0.25%, 0.75%, 1.0%, 1.25%, 1.75%, 2.0%, 2.25%, 2.75%, 3.0%, 3.25%, and 3.5%. Therefore, it is beneficial for lithium-ion intercalation and deintercalation, improving the kinetic performance of the lithium battery cell.

[0104] In some alternative embodiments, the powder resistivity of the phosphate cathode active material is from 10 Ω·m to 2000 Ω·m.

[0105] The resistivity of the phosphate positive electrode active material powder can be any value or a range of combinations thereof from 10 Ω·m, 20 Ω·m, 30 Ω·m, 40 Ω·m, 50 Ω·m, 60 Ω·m, 70 Ω·m, 80 Ω·m, 90 Ω·m, 100 Ω·m, 110 Ω·m, 210 Ω·m, 310 Ω·m, 410 Ω·m, 510 Ω·m, 610 Ω·m, 710 Ω·m, 810 Ω·m, 910 Ω·m, 1010 Ω·m, 1110 Ω·m, 1210 Ω·m, 1310 Ω·m, 1410 Ω·m, 1510 Ω·m, 1610 Ω·m, 1710 Ω·m, 1810 Ω·m, 1910 Ω·m, and 2000 Ω·m. Therefore, the internal resistance of the phosphate cathode active material was further reduced, the conductivity of the material was improved, and the dynamic performance of the lithium battery cell was enhanced.

[0106] In some optional embodiments, the specific capacity of the phosphate cathode active material is 140 to 160 mAh / g.

[0107] Optionally, the specific capacity of the phosphate cathode active material is any value or a range thereof from 140 mAh / g, 145 mAh / g, 150 mAh / g, 155 mAh / g, and 160 mAh / g. A specific capacity within the above range for the phosphate cathode active material can improve the energy density and overall capacity of the lithium-ion battery cell.

[0108] In some alternative embodiments, the chemical formula of the lithium transition metal phosphate particles is: Li a Fe m Mn j M n P b O (4-c) , 0.8≤a≤1.2, 0.95≤b≤1, 0≤c≤0.5, m>0, j≥0, n≥0, m+j+n≤1, M includes one or more of Ti, Mg, V, Cr, Zr, Nb and W. In some optional embodiments, m+j+n=1. In some optional embodiments, m+2j+n=1.

[0109] For example, the chemical formula of the phosphate particles can be LiFePO4, LiMn x Fe 1-x PO4, where 0 < x < 1. Depending on the value of x, lithium manganese iron phosphate includes LiMn. 0.8 Fe 0.2 PO4 (LMFP82), LiMn 0.6 Fe 0.4 PO4 (LMFP64), LiMn 0.4 Fe 0.6 PO4 (LMFP46) and LiMn 0.2 Fe 0.8 PO4 (LMFP28), etc.

[0110] According to the embodiments of this application, the phosphate particles can be lithium iron phosphate material, lithium manganese iron phosphate material, or lithium iron phosphate material or lithium manganese iron phosphate material modified by other metal elements.

[0111] The chemical formula of phosphate cathode active materials can be determined by measuring the mass fractions of lithium, manganese, iron, phosphorus, and doping elements in the test solution using an inductively coupled plasma optical emission spectrometer (ICP-OES, instrument brand: Agilent 5800). Furthermore, the molar percentages of each element in the phosphate cathode active material can be calculated based on the mass fractions of each element in the precursor's test solution, thereby determining the chemical formula and element molar ratio of the phosphate cathode active material.

[0112] As an example, weigh 0.2g of phosphate positive electrode active material into a 100mL beaker, add 10mL of 10% w / w nitric acid solution, heat and digest at 120℃ for 0.5 hours, and then dilute to volume with a 100mL volumetric flask; then use a pipette to transfer 1mL to a 100mL volumetric flask and dilute to volume to obtain the test solution, which can then be detected and calculated using an inductively coupled plasma optical emission spectrometer.

[0113] In some optional embodiments, the powder compaction density of the phosphate cathode active material is 2.0 g / cm³.3 Up to 2.5g / cm 3 Optionally, the powder compaction density of the phosphate positive electrode active material can be 2.0 g / cm³. 3 2.1g / cm 3 2.2g / cm 3 2.3g / cm 3 2.4g / cm 3 2.5g / cm 3 Any value or range of its composition in the above range. A powder compaction density of phosphate cathode active material within the above range means that the phosphate cathode active material has a higher bulk density, which increases the energy density of the lithium battery cell; it can also reduce the voids between particles, improve the material's conductivity, and enhance the kinetic performance of the lithium battery cell.

[0114] In some optional embodiments, the specific surface area of ​​the phosphate cathode active material is 5 m². 2 / g to 30m 2 / g.

[0115] Optionally, the specific surface area of ​​the phosphate cathode active material can be 5 m². 2 / g、6m 2 / g、7m 2 / g、8m 2 / g、9m 2 / g, 10m 2 / g, 15m 2 / g、20m 2 / g、25m 2 / g、30m 2 Any value in / g or a range thereof.

[0116] Phosphate cathode active materials with a specific surface area within the aforementioned range increase the effective reaction interface of the material, providing more channels and interfaces, which facilitates the diffusion of lithium ions within the material and improves the capacity and charge / discharge efficiency of lithium battery cells. Phosphate cathode active materials with a specific surface area within the aforementioned range generally have a more stable structure, improving the cycle capacity retention rate of lithium battery cells.

[0117] In some optional embodiments, the volume average particle size D of the phosphate cathode active material V 50 is 0.1 μm to 2 μm. Optionally, the volume average particle size D of the phosphate cathode active material is... V 50 can be any value or a range of combinations thereof from 0.1μm, 0.2μm, 0.4μm, 0.5μm, 0.6μm, 0.8μm, 1μm, 1.2μm, 1.4μm, 1.5μm, 1.6μm, 1.8μm, and 2μm.

[0118] The volume average particle size D of phosphate positive electrode active material V A particle size of 50 within the above range indicates a suitable specific surface area, increasing the effective reaction interface of the material, providing more channels and interfaces, facilitating the diffusion of lithium ions in the material, and improving the capacity and charge / discharge efficiency of lithium battery cells. Phosphate cathode active materials with a volume average particle size within the above range generally have a more stable structure, improving the cycle capacity retention rate of lithium battery cells.

[0119] This application provides a method for preparing a phosphate positive electrode active material, including:

[0120] In an inert atmosphere, a gaseous carbon source is deposited on the surface of the core using chemical vapor deposition to obtain a first coating material that coats the core. The core includes lithium transition metal phosphate particles.

[0121] A phosphate cathode active material comprising a second coating material is prepared by using chemical vapor deposition to deposit nitrogen-containing organic matter and gaseous silicon source on the surface of a first coating material using a carrier gas. The second coating material is located on the surface of the first coating material.

[0122] In the embodiments of this application, chemical vapor deposition coating technology can be used to obtain coating materials with uniform thickness, thereby improving the electrochemical performance of the materials. Modifying the material surface with silicon and nitrogen can introduce hydrophobic silicon groups, optimize surface defects, improve material processing performance, and also give the material low moisture adsorption capacity, which is beneficial to improving the cycle performance of phosphate cathode active materials.

[0123] In the embodiments of this application, Si-CN and CN-Si bonds improve the bonding force between the first and second coating materials, that is, they improve the bonding force within the coating materials, thereby enhancing the stability of the phosphate cathode active material and reducing the powder resistivity of the phosphate cathode active material. The presence of Si-CN and CN-Si bonds can reduce the content of impurity groups on the surface of the phosphate cathode active material, such as the content of CO functional groups. Reducing the content of impurity groups can increase the migration rate of lithium ions in the coating material; reducing the content of impurity groups can also reduce side reactions of the phosphate cathode active material and improve the cycle capacity retention rate of the lithium battery cell.

[0124] In some optional embodiments, the preparation of a first coating material covering the core by chemical vapor deposition of a gaseous carbon source on the core surface in an inert atmosphere includes: introducing a first mixed gas into a closed environment and depositing the carbon source gas on the core surface by chemical vapor deposition to prepare the first coating material covering the core, wherein the first mixed gas includes a protective gas, a gaseous carbon source, and a reducing gas; based on the total volume of the first mixed gas, the volume fraction of the gaseous carbon source is 3% to 50%, and the volume fraction of the reducing gas is 5% to 60%.

[0125] Optionally, the volume fraction of the gaseous carbon source can be any value or a range thereof from 3%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, and 50%. Optionally, the volume fraction of the reducing gas can be any value or a range thereof from 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, and 65%.

[0126] In this embodiment, under the action of protective gas and reducing gas, gaseous carbon source is deposited to obtain a first coating material including carbon elements. This further reduces the content of impurity groups, such as CO groups, in the first coating material, increases the proportion of carbon elements in the first coating material, reduces the internal resistance of the phosphate positive electrode active material, and improves conductivity.

[0127] In some optional embodiments, the reducing gas can be H2, CH4, CO, etc. In some optional embodiments, the protective gas can be helium, argon, krypton, xenon, etc.

[0128] In some optional embodiments, the temperature of the first deposition is 600°C to 1000°C, and the duration of the first deposition is 2 to 20 hours.

[0129] Optionally, the temperature of the first deposition can be any value or a range of combinations thereof from 600℃, 650℃, 700℃, 750℃, 800℃, 850℃, 900℃, 950℃, and 1000℃. Optionally, the duration of the first deposition can be any value or a range of combinations thereof from 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, and 20h.

[0130] In this embodiment, by controlling the temperature and time of the first deposition, the thickness of the first coating material can be controlled, which is beneficial to the graphitization degree of carbon elements in the first coating material, further improving the conductivity of the first coating material in the phosphate cathode active material; it is also beneficial to the tight bonding between the first coating material and the core, further improving the structural stability of the material.

[0131] The duration of the first deposition can be understood as the holding time. Within a certain range, as the holding time increases, the carbon content in the phosphate cathode active material increases, correspondingly improving the material's conductivity and specific capacity. However, carbon, as an inactive substance, cannot contribute to capacity. Beyond a certain value, the specific capacity decreases with longer holding times. A suitable duration for the first deposition can form an effective coating material, allowing the lithium transition metal phosphate particles in the core to fully exert their capacity. Therefore, the duration of the first deposition can be 9 to 11 hours, with 10 hours being a suitable option.

[0132] In some alternative embodiments, the heating rate in the first deposition can be 1°C to 50°C / min.

[0133] In some alternative embodiments, the gaseous carbon source includes one or more combinations of methane, ethylene, acetylene, propane, methanol, ethanol, propylene, butane, and butene.

[0134] In some optional embodiments, a second deposition of nitrogen-containing organic matter and gaseous silicon source on the surface of a first coating material is performed using chemical vapor deposition (CVD) with a carrier gas. This includes: introducing a second mixed gas into a sealed environment and performing a second deposition of the gaseous silicon source on the first coating material using CVD to obtain a phosphate positive electrode active material comprising the second coating material. The second mixed gas comprises a protective gas and a gaseous silicon source, and the volume fraction of the gaseous silicon source is 1% to 25% based on the total volume of the second mixed gas.

[0135] Optionally, the volume fraction of the gaseous silicon source can be any value or a range of combinations thereof, such as 1%, 5%, 10%, 15%, 20%, 25%.

[0136] In some optional embodiments, the temperature of the second deposition is 200°C to 500°C, and the duration of the second deposition is 1 to 10 hours.

[0137] Optionally, the temperature of the second deposition can be any value or a range of combinations thereof from 200℃, 250℃, 300℃, 350℃, 400℃, 450℃, and 500℃. Optionally, the duration of the second deposition can be any value or a range of combinations thereof from 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, and 10h.

[0138] In some alternative embodiments, the gaseous silicon source includes one or more combinations of silicon tetrafluoride, silane, and chlorosilane.

[0139] In some alternative embodiments, after a second mixed gas is introduced into a closed environment and a gaseous silicon source is second-deposited on the first coating material using chemical vapor deposition, the method includes: depositing nitrogen-containing organic matter on the surface of the first coating material using a bubbling method.

[0140] In some optional embodiments, the carrier gas in the bubbling method is a mixture of an inert gas and a reducing gas. In some optional embodiments, the carrier gas passes through an organic solution in the bubbling method to deposit nitrogen from the nitrogen-containing organic material onto the surface of the first coating material; the organic solution includes one or more of polyacrylonitrile solution, acetonitrile solution, and malononitrile solution.

[0141] In this embodiment, when the carrier gas enters the polyacrylonitrile solution, bubbles are generated. The gas carries nitrogen-containing organic compounds, such as polyacrylonitrile. The dehydrogenation reaction of these nitrogen-containing organic compounds is inhibited in a hydrogen environment, and the residual -NH bonds on the carbon chain form CN-SI bonds with the subsequently deposited silicon, increasing the bonding strength. During the deposition process, oxygen-containing functional groups, such as hydroxyl and carboxyl groups, are inevitably introduced onto the silicon surface, increasing the surface energy and causing the material to become hygroscopic. Therefore, hydrogen is added to the mixed gas to reduce the surface energy and improve hydrophobicity.

[0142] In some alternative embodiments, the solvent of the organic solution includes one or more of dimethylformamide, dimethyl sulfoxide, and sulfolane.

[0143] In some optional embodiments, the nitrogen-containing organic compound includes one or more of polyacrylonitrile, acetonitrile, and malononitrile. The nitrogen element in these nitrogen-containing organic compounds can be bonded to carbon elements, improving the internal stability of the coating material, reducing the content of impurity groups on the surface of the phosphate cathode active material, and further improving the cycle capacity retention rate of the lithium battery cell.

[0144] In some alternative embodiments, the nitrogen-containing organic compound may be a cyanide-containing organic compound.

[0145] In some optional embodiments, the mass ratio of nitrogen to silicon in the gaseous silicon source and the nitrogen-containing organic compound is 1:(0.2 to 20).

[0146] Optionally, the mass ratio of nitrogen to silicon can be 1:0.2, 1:0.4, 1:0.6, 1:0.8, 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, 1:5.5, 1:6, 1:6.5, 1:7, 1:7.5, 1:8, 1:8.5, 1:9, 1:9.5, or 1:1. Any ratio or range thereof from 0, 1:10.5, 1:11, 1:11.5, 1:12, 1:12.5, 1:13, 1:13.5, 1:14, 1:14.5, 1:15, 1:15.5, 1:16, 1:16.5, 1:17, 1:17.5, 1:18, 1:18.5, 1:19, 1:19.5, 1:20.

[0147] In this embodiment, the mass ratio of nitrogen to silicon is within the above range, which is conducive to the formation of Si-CN bonds and CN-Si bonds, further improving the structural stability and conductivity of the phosphate cathode active material, and further improving the kinetic performance and cycle capacity retention of the lithium metal battery.

[0148] In some alternative embodiments, the positive electrode active material film layer comprises 85% to 99% phosphate positive electrode active material.

[0149] In some alternative embodiments, the positive electrode active material film layer includes a binder and a conductive agent. In some embodiments, the positive electrode active material film layer includes 0.1% to 5% binder and 0.1% to 5% conductive agent.

[0150] When the positive electrode active material film layer contains conductive agents or binders, it gives the positive electrode active material film layer a certain cohesive strength, which can improve the flexibility of the positive electrode active material film layer, reduce the probability of breakage or cracking caused by the positive electrode active material film layer when it is wound or folded, and at the same time improve the conductivity of the positive electrode sheet and reduce the internal resistance of the positive electrode sheet.

[0151] In some optional embodiments, based on the total mass of the positive electrode active material film, the positive electrode active material film includes: 0.4% to 10% conductive agent, optionally 0.7% to 5%.

[0152] The content of conductive agent in the positive electrode active material film layer within the above range is beneficial to reducing the internal resistance of the positive electrode sheet, reducing the internal resistance of the cell, facilitating electron transfer, and improving the charging and discharging efficiency of the battery.

[0153] In some embodiments, the compaction density of the positive electrode active material film layer is 1.5–4 g / cm³. 3 .

[0154] According to the embodiments of this application, controlling the compaction density of the positive electrode active material film can effectively enhance the mixing uniformity and contact between the high dielectric material and the positive electrode active material, which is beneficial to the electrochemical performance of the positive electrode sheet in the battery.

[0155] This application does not impose any particular limitation on the type of positive electrode conductive agent. As an example, the positive electrode conductive agent includes one or more of the following: superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0156] In some embodiments, the positive electrode active material film layer may optionally include a positive electrode binder. This application does not impose any particular limitation on the type of positive electrode binder. As an example, the positive electrode 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.

[0157] In some alternative embodiments, the positive electrode may include a positive current collector and a positive active material disposed on at least one surface of the positive current collector.

[0158] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive active material is disposed on either or both of the two opposite surfaces of the positive current collector.

[0159] As an example, the positive current collector can be a metal foil, a conductive polymer material, a carbon material, or a composite current collector. For example, as a metal foil, pure metals, alloys, or surface-treated metals can be used, including but not limited to stainless steel, copper, aluminum, nickel, titanium, or silver. The composite current collector may include a polymer material base layer and a metal layer. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0160] The positive electrode active material film layer is typically formed by coating a positive electrode slurry onto a positive electrode current collector, followed by drying and cold pressing. The positive electrode slurry is usually formed by dispersing positive electrode active material particles, optional conductive agents, optional binders, and any other components in a solvent and stirring until homogeneous. The solvent can be N-methylpyrrolidone (NMP), but is not limited to it.

[0161] As an example, based on the total mass of the positive electrode active material, conductive agent, and binder, the total amount of binder added is preferably 1wt% to 2.5wt%, for example, 1wt%, 1.5wt%, 2wt%, and 2.5wt%. If the amount of polymer or binder added is too low, insufficient binder will not be able to support the strength of the positive electrode active material film layer, thus failing to meet the requirements of rolling and thinning. If the amount of binder added is too high, it will cause the positive electrode active material film layer to have high viscosity, making it easy for the film to stick to the rollers during the rolling process, making it impossible to perform thinning and current collector bonding.

[0162] [Negative electrode plate]

[0163] The specific composition and structure of the negative electrode sheet can be selected according to the type of lithium battery cell, and the embodiments of this application are not limited in this regard.

[0164] The negative electrode sheet includes a negative current collector and a negative active material film layer disposed on at least one surface of the negative current collector and comprising a negative active material. For example, the negative current collector has two surfaces opposite each other in its thickness direction, and the negative active material film layer is disposed on either or both of the two opposite surfaces of the negative current collector.

[0165] The negative electrode active material is a material capable of extracting and inserting active ions, and can be any material known in the art. As examples, negative electrode active materials include, but are not limited to, one or more of natural graphite, artificial graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. Silicon-based materials may include one or more of elemental silicon, silicon oxide, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may include one or more of elemental tin, tin oxide, and tin alloys. This application is not limited to these materials, and other conventionally known materials that can be used as negative electrode active materials may also be used.

[0166] In some embodiments, the negative electrode active material film layer may optionally include a negative electrode conductive agent. This application does not impose any particular limitation on the type of negative electrode conductive agent. As an example, the negative electrode conductive agent may include one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0167] In some embodiments, the negative electrode active material film layer may optionally include a negative electrode binder. This application does not impose any particular limitation on the type of negative electrode binder. As an example, the negative electrode binder may include one or more of the following: 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).

[0168] In some embodiments, the negative electrode active material film layer may optionally include other additives. As an example, other additives may include thickeners, such as sodium carboxymethyl cellulose (CMC-Na), PTC thermistor materials, etc.

[0169] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. As an example of a metal foil, copper foil may be used. The composite current collector may include a polymeric material substrate and a metal material layer formed on at least one surface of the polymeric material substrate. As an example, the metal material may include one or more of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. As an example, the polymeric material substrate may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0170] The negative electrode active material film layer is typically formed by coating a negative electrode slurry onto a negative electrode current collector, followed by drying and cold pressing. The negative electrode slurry is usually formed by dispersing the negative electrode active material, optional conductive agent, optional binder, and other optional additives in a solvent and stirring until homogeneous. The solvent can be N-methylpyrrolidone (NMP) or deionized water, but is not limited to these.

[0171] The negative electrode sheet does not exclude other additional functional layers besides the negative electrode active material film layer. For example, in some embodiments, the negative electrode sheet of this application may also include a conductive undercoat layer (e.g., composed of a conductive agent and a binder) sandwiched between the negative electrode current collector and the negative electrode active material film layer and disposed on the surface of the negative electrode current collector; in some embodiments, the negative electrode sheet of this application may also include a protective layer covering the surface of the negative electrode active material film layer.

[0172] The negative electrode sheet in a lithium battery cell may not include a negative electrode active material capable of extracting and embedding active ions. For example, in some embodiments, the negative electrode sheet may include a lithium sheet or a lithium alloy sheet; in other embodiments, the negative electrode sheet includes a mesh or foam-like three-dimensional framework layer, such as foamed copper or copper alloy, foamed nickel or nickel alloy, foamed aluminum or aluminum alloy, copper or copper alloy mesh, nickel or nickel alloy mesh, aluminum or aluminum alloy mesh, etc.

[0173] [Isolation Component]

[0174] In some embodiments, the electrode assembly further includes a spacer disposed between the positive electrode and the negative electrode.

[0175] In some embodiments, the separator is a separator membrane. This application does not impose any particular limitation on the type of separator membrane; any known porous separator membrane with good chemical and mechanical stability can be selected.

[0176] As an example, the main material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, polyvinylidene fluoride, and ceramic. The separator can 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 can be the same or different, without particular limitation. The separator can be a single component located between the positive and negative electrodes, or it can 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 can also be applied to the surface of the separator.

[0177] 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.

[0178] [Electrolytes]

[0179] In some embodiments, the lithium battery cell includes an electrolyte. The electrolyte acts as a conductor of active ions between the positive and negative electrode plates. This application does not impose specific limitations on the type of electrolyte and it can be selected according to requirements. For example, in some embodiments, the lithium battery cell further includes an electrolyte, which acts as a conductor of ions between the positive and negative electrode plates. This application does not impose specific limitations on the type of electrolyte and it can be selected according to requirements. The electrolyte can be liquid, gel, or solid.

[0180] Liquid electrolytes include electrolyte salts and solvents.

[0181] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0182] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone. The solvent may also be an ether solvent. Ether solvents may include one or more of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane, tetrahydrofuran, methyl tetrahydrofuran, diphenyl ether, and crown ethers.

[0183] In some optional embodiments, the electrolyte may also include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain properties of lithium battery cells, such as additives that improve the overcharge / fast charge performance of lithium battery cells, additives that improve the high-temperature performance of lithium battery cells, and additives that improve the low-temperature performance of lithium battery cells.

[0184] [Preparation methods for lithium battery cells]

[0185] The method for preparing the lithium battery cell of this application is well known. In some optional embodiments, a positive electrode, a separator, a negative electrode, and an electrolyte can be assembled to form a lithium battery cell. As an example, the positive electrode, separator, and negative electrode can be formed into an electrode assembly through a winding process and / or a stacking process. The electrode assembly is placed in an outer packaging, dried, and then injected with electrolyte. After encapsulation, settling, formation, and shaping processes, a lithium battery cell is obtained.

[0186] In some alternative embodiments, the method for preparing a lithium battery cell includes: preparing a positive electrode sheet.

[0187] In some alternative embodiments, the preparation of the positive electrode sheet includes:

[0188] A positive electrode slurry is coated onto a positive electrode current collector and dried to obtain a positive electrode sheet. The positive electrode slurry includes a phosphate positive electrode active material.

[0189] Electrical appliances

[0190] This application provides an electrical device, including the battery device described above.

[0191] The battery device can be a power source for the electrical device or an energy storage unit for the electrical device. The technical solutions described in the embodiments of this application are applicable to various electrical devices that use lithium battery cells, such as mobile phones, portable devices, laptops, electric vehicles, electric toys, power tools, vehicles, ships, and spacecraft, etc. For example, spacecraft include airplanes, rockets, space shuttles, and spacecraft.

[0192] Figure 5 This is a schematic diagram of an example electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the device's requirements for high power and high energy density, a battery pack or battery module can be used.

[0193] Example

[0194] 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.

[0195] Example 1

[0196] Preparation of phosphate positive electrode active materials:

[0197] Step 1.1, lithium manganese iron phosphate (LiMn) 0.8 Fe 0.2 PO4) was placed in a coated rotary kiln and nitrogen was introduced for gas washing. After two hours of gas washing, the rotary kiln was heated at a rate of 10°C / min and nitrogen was continuously introduced. Throughout the process, the gas pressure inside the kiln was kept at a slightly positive pressure, and the gas pressure was between 100 and 10000 Pa.

[0198] Step 1.2: When the rotary kiln for coating reaches 700°C, stop the nitrogen supply and start the supply of a first gas. The first gas consists of 20% acetylene, 20% hydrogen, and 60% nitrogen. Maintain a slightly positive pressure inside the furnace. Perform the first vapor deposition (CVD) coating of lithium manganese iron phosphate under a continuously flowing acetylene atmosphere for 10 hours. After the first CVD coating is completed, turn off the heating power and stop the gas supply.

[0199] Step 1.3: When the furnace temperature drops to 400℃, the furnace insulation process is initiated. Nitrogen gas is stopped, and a second gas (comprising 10% SIF4, 80% nitrogen, and 10% hydrogen by volume) is continuously introduced. This gas carries polyacrylonitrile from the organic solution into the furnace via a bubbling method. In the bubbling method, the solute in the organic solution is polyacrylonitrile, the solvent is dimethylformamide, and the second gas is introduced for 1 hour. Simultaneously, the furnace pressure is maintained at a slightly positive pressure, and a second vapor deposition of lithium manganese iron phosphate is performed at 400℃ to modify its surface. This process lasts for 5 hours, resulting in a lithium manganese iron phosphate cathode active material with a coating material content of 1.8%.

[0200] Preparation of lithium battery cells:

[0201] Preparation of the positive electrode: The above-prepared lithium manganese iron phosphate positive electrode active material, conductive agent acetylene black, and binder polyvinylidene fluoride were thoroughly mixed in an N-methylpyrrolidone solvent system at a mass ratio of 95:3:2. The positive electrode slurry was then prepared at a concentration of 13.6 mg / cm³. 2 The coating density was uniformly applied to an aluminum foil with a thickness of 13 μm; then dried, cold-pressed, and slit to obtain the positive electrode sheet of Example 1.

[0202] Preparation of the negative electrode sheet: Hard carbon negative electrode material, conductive agent acetylene black, binder styrene-butadiene rubber (SBR), and dispersant sodium carboxymethyl cellulose (CMC-Na) are dispersed in deionized water at a weight ratio of 97:1:1:1, and stirred until homogeneous to prepare a negative electrode slurry. The negative electrode slurry is then prepared at a concentration of 7 mg / cm³. 2 The coating density is uniformly coated on the negative electrode current collector aluminum foil, and after drying, cold pressing and slitting, the negative electrode sheet of Example 1 is obtained.

[0203] Electrolyte: LiPF6 is dispersed in a solvent, which is a mixture of ethylene carbonate (EC), dimethyl carbonate (DMC), and ethylene dimethyl carbonate in a volume ratio of 1:1:1, and the concentration of LiPF6 is 1 mol / L.

[0204] Separating membrane: A 7μm thick polypropylene microporous membrane is used as the separating membrane.

[0205] Assembly: The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. The electrodes are then wound to obtain a bare cell. The bare cell is placed in an outer package, injected with the electrolyte described above, and sealed to obtain an assembled lithium battery cell.

[0206] Examples 2 to 6

[0207] The difference between Examples 2 to 6 and Example 1 is that the mass content of carbon, silicon and nitrogen in the coating material of the phosphate positive electrode active material is different, as shown in Table 1.

[0208] Examples 7 to 8

[0209] The difference between Examples 7 and 8 and Example 1 is that the types of nitrogen-containing organic compounds are different, as shown in Table 1.

[0210] Examples 9 to 10

[0211] The difference between Examples 9 and 10 and Example 1 is that the temperatures at which the second vapor deposition (CVD) surface modification of lithium manganese iron phosphate is performed in step 1.3 are different, namely 300℃ and 500℃ respectively, and the results are shown in Table 2.

[0212] Comparative Example 1

[0213] The difference between Comparative Example 1 and Example 1 lies in the preparation method of the coating material. Steps 1.2 and 1.3 are omitted; instead, glucose-based organic carbon coating is used. Specifically, lithium manganese iron phosphate and glucose are sequentially added to a reactor containing 4L of deionized water and stirred thoroughly. The stirring rate is controlled at 200 rpm for 2 hours to obtain a slurry. The slurry is then fed into a sand mill for grinding using 0.6mm zirconium beads for 5 hours. The ground slurry is then spray-dried using a spray dryer with an inlet temperature of 200°C and an outlet temperature of 110°C to obtain powder. This powder is placed in a crucible and then into a box furnace, heated to 700°C at a heating rate of 5°C / min, held at that temperature for 12 hours, and then cooled to obtain carbon-coated lithium manganese iron phosphate cathode material. The carbon content in the material is 1.7% by mass.

[0214] Comparative Example 2

[0215] The difference between Comparative Example 1 and Example 1 lies in the differences in steps 1.2 and 1.3. In step 1.2, the duration is different, being 12 hours, and the carbon content in the material is 1.2% by mass. In step 1.3, when the furnace temperature drops to 400°C, the furnace insulation process is initiated, nitrogen is stopped, and a third gas (comprising 10% SIF4, 80% nitrogen, and 10% hydrogen by volume fraction) is continuously introduced. This gas does not pass through the organic solution. Simultaneously, the furnace pressure is maintained at a slightly positive pressure, and a second CVD surface modification deposition of lithium manganese iron phosphate is performed at 400°C for 5 hours, yielding a lithium manganese iron phosphate positive electrode active material with a coating material.

[0216] Comparative Example 3

[0217] The difference between Comparative Example 3 and Example 1 lies in the following steps: Steps 1.2 and 1.3 are different. In Step 1.2, the duration is different, being 15 hours, and the carbon content in the material is 1.5% by mass. In Step 1.3, when the furnace temperature drops to 400°C, the furnace insulation process is initiated, nitrogen gas is stopped, and a third gas (comprising 90% nitrogen and 10% hydrogen by volume) is continuously introduced. This gas carries the liquid polyacrylonitrile from the organic solution into the furnace via a bubbling method. In the bubbling method, the solute in the organic solution is polyacrylonitrile, and the solvent is dimethylformamide. The second gas is continuously introduced for 1 hour. Simultaneously, the furnace pressure is maintained at a slightly positive pressure, and a second CVD surface modification deposition of lithium manganese iron phosphate is performed at 400°C for 5 hours, resulting in a lithium manganese iron phosphate positive electrode active material with a coating material.

[0218] Comparative Example 4

[0219] The difference between Comparative Example 4 and Example 1 is that in step 1.3, the polyacrylonitrile in the organic solution is replaced with dodecyltrimethylammonium bromide.

[0220] Test section

[0221] The lithium battery cells prepared in the examples and comparative examples were subjected to electrochemical performance tests. The test voltage range for lithium iron phosphate was 2.0–3.7 V, and the test voltage range for lithium manganese iron phosphate was 2.0–4.6 V, at a temperature of 25 °C. The specific test methods are as follows.

[0222] 1) Test of the chemical formula of lithium manganese iron phosphate positive electrode active material: Weigh 0.2g of phosphate positive electrode active material into a 100mL beaker, add 10mL of 10% w / w nitric acid solution, heat and digest at 120℃ for 0.5 hours, and then make up to volume with a 100mL volumetric flask; then use a pipette to transfer 1mL to a 100mL volumetric flask and make up to volume to obtain the test solution.

[0223] The mass fractions of lithium, manganese, iron, phosphorus, and dopant elements in the test solution were determined using an inductively coupled plasma optical emission spectrometer (ICP-OES, Agilent 5800). Based on the mass fractions of each element in the test solution of the precursor, the molar ratio of each element in the phosphate cathode active material was calculated, thereby determining the chemical formula and element molar ratio of the phosphate cathode active material.

[0224] 3) Test of 0.1C charge / discharge capacity: The lithium battery cells prepared above were cycle-charged and discharged at a charge / discharge rate of 0.1C using the Shenzhen Xinwei Battery Testing System. The test temperature was 25.0℃ and the charge / discharge voltage was 2.0V-4.3V to obtain the charge / discharge capacity of the first cycle.

[0225] 4) Battery capacity retention test at 25℃: The Shenzhen Xinwei Battery Testing System was used to cycle the prepared lithium battery cells at a 1C charge-discharge rate for 2000 cycles. The test temperature was 25.0℃ and the charge-discharge voltage was 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.

[0226] 5) Lithium-ion battery cell kinetic performance (rate capability) testing: At 25℃, the cell was inserted into copper wire to prepare a three-electrode cell. First, lithium plating was performed using the positive electrode-copper wire at 20uA for 2h and the negative electrode-copper wire at 20uA for 2h as reference electrodes to test the negative electrode potential. Then, the cell was fully charged at 1 / 3C, allowed to stand for 60min, and then discharged at 1 / 3C to 10% SOC. The cell was then charged at 3C, 2C, 1C, 0.5C, 0.2C, 0.1C, and 0.05C respectively. When the negative electrode potential reached 0V, the cell was disassembled and the negative electrode interface was observed. The maximum fast charging rate was determined by combining the negative electrode potential and the interface condition. After fully charging the battery cell, discharge it to 90% SOC at 1 / 3C. Then charge the battery cell at 3C, 2C, 1C, 0.5C, 0.2C, 0.1C, and 0.05C respectively. When the negative electrode potential reaches 0V, disassemble the battery cell and observe the negative electrode interface. Determine the maximum fast charging rate by combining the negative electrode potential and the interface condition.

[0227] 6) Testing the resistivity of phosphate cathode active materials:

[0228] Powder resistivity of phosphate positive electrode active material before ultrasound: Weigh 1g of sample and place it in the mold, then place the mold in a four-probe resistivity tester, adjust the pressure to 8.0MPa, and wait for the mold height and pressure to stabilize. 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.

[0229] Test of powder resistivity of phosphate positive electrode active material after ultrasonication: Weigh 5g of sample and place it in 100g of deionized water, ultrasonically treat it at 20000Hz for 30 minutes, and then dry it to obtain the ultrasonicated sample. Weigh 1g of the above sample and place it in a mold to perform the above powder resistivity test.

[0230] 7) Powder compaction density test of phosphate positive electrode active material: Refer to Appendix L of national standard GB / T 24533-2009, "Test method for powder compaction density". The density is determined using a compaction density meter. The test method is as follows: Weigh 1g of the above phosphate positive electrode active material and add a 1.298cm³ cross-sectional area... 2 In a metal cylindrical sleeve, pressure is applied to 300 kg (equivalent to 3 kN), held for 30 seconds, and then the pressure is released. The change in the height of the top column exposed outside the sleeve before and after compaction is recorded. Then, the compaction density of the phosphate positive electrode active material powder under 3 kN pressure is recorded and calculated.

[0231] 8) Water adsorption performance test of phosphate positive electrode active material: After exposing the phosphate positive electrode active material to a 45% humidity environment at room temperature for 60 minutes, the water content was measured using a Karl Fischer moisture analyzer.

[0232] The test results of the examples and comparative examples are shown in Table 1.

[0233]

[0234]

[0235] As can be seen from Table 1, through Examples 1 to 7 and the Comparative Example, the Examples introduced nitrogen and silicon elements into the phosphate cathode active material, forming Si-CN bonds and CN-Si bonds. Compared with the Comparative Example, which did not form Si-CN bonds and CN-Si bonds, the phosphate cathode active material containing the above bonds, as shown in Examples 1 and Comparative Example 1, has a better resistivity than Comparative Example 1, and also improves the 0.1C specific capacity, cycle capacity retention rate and rate capability of the lithium battery cell.

[0236] Examples 1 to 3 show that as the carbon content increases, the powder compaction density decreases, and the powder resistivity decreases. Examples 1, 4, and 5 show that the silicon source significantly modifies the carbon layer surface, improving lubricity and increasing the powder compaction density of the phosphate cathode active material. It also introduces hydrophobic silicon-based groups onto the surface of the particles in the material, reducing the moisture adsorption performance of the lithium manganese iron phosphate material, which is beneficial for the preservation of the phosphate cathode active material and improves the cycle stability of the lithium battery cell. Examples 1 and 6 show that adding different amounts of nitrogen, and introducing different amounts of nitrogen into the carbon layer, can affect the resistivity to a certain extent.

[0237] As can be seen from Table 2, compared with Example 1, Example 9 and Example 10, the difference in the temperature of the second vapor deposition, as shown by the difference in the powder resistivity before and after ultrasonication, indicates that the bonding force between the first coating material and the second coating material is different. The greater the bonding force, the better the capacity retention rate at 25°C after 2000 cycles. The different silicon content introduced by the different temperatures of the second vapor deposition results in different water adsorption performance of the lithium manganese iron phosphate material during storage.

[0238] 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 lithium battery cell comprising a positive electrode sheet comprising a phosphate positive electrode active material, characterized in that, The phosphate positive electrode active material comprises: an inner core comprising lithium-containing transition metal phosphate particles; a coating material at least partially coated on the surface of the inner core; wherein the coating material comprises one or more of Si-C-N bonds, C-N-Si bonds.

2. The lithium battery cell of claim 1, wherein, The phosphate positive electrode active material comprises, based on the total mass of the phosphate positive electrode active material, a mass content of 0.5% to 2% of carbon elements.

3. The lithium battery cell according to claim 1 or 2, characterized in that, The phosphate positive electrode active material comprises, based on the total mass of the phosphate positive electrode active material, a mass content of 0.1% to 1% of silicon elements.

4. The lithium battery cell according to any one of claims 1 to 3, characterized in that The phosphate positive electrode active material comprises, based on the total mass of the phosphate positive electrode active material, a mass content of 0.05% to 0.5% of nitrogen elements.

5. The lithium battery cell according to any one of claims 1 to 4, characterized in that The coating material comprises one or more of Si=C bonds, Si-C bonds, C=N bonds and C-N bonds.

6. The lithium battery cell according to any one of claims 1 to 5, characterized in that The mass ratio of the nitrogen elements to the silicon elements is 1:(0.2 to 20), and / or the mass ratio of the carbon elements, the nitrogen elements and the silicon elements is 1:(0.025 to 1):(0.05 to 2).

7. The lithium battery cell according to any one of claims 1 to 6, characterized in that The coating material comprises a first coating material and a second coating material; the second coating material is located on the surface of the first coating material, the first coating material comprises carbon elements, and the second coating material comprises silicon elements and nitrogen elements.

8. The lithium battery cell according to any one of claims 1 to 7, characterized in that The coating material satisfies one or more of the following conditions: 1) The surface of the inner core is coated with the coating material by at least 80% or more in area; 2) The average thickness of the coating material on the surface of the inner core is 1 nm to 10 nm.

9. The lithium battery cell according to any one of claims 1 to 8, characterized in that The phosphate positive electrode active material comprises, based on the total mass of the phosphate positive electrode active material, a mass content of 0.25% to 3.5% of the coating material.

10. A phosphate positive electrode active material comprising: an inner core comprising lithium-containing transition metal phosphate particles; a coating material at least partially coated on the surface of the inner core; wherein the coating material comprises one or more of Si-C-N bonds, C-N-Si bonds.

11. The phosphate salt cathode active material according to claim 10, characterized in that, The phosphate positive electrode active material satisfies one or more of the following conditions: 1) the specific surface area of the phosphate positive electrode active material is 5 m 2 / g to 30 m 2 / g; 2) the powder tap density of the phosphate positive electrode active material is 2.0 g / cm 3 to 2.5 g / cm 3 ; 3) The powder resistivity of the phosphate positive electrode active material is 10 Ω·m to 2000 Ω·m; 4) The specific capacity of the phosphate positive electrode active material is 140 to 160 mAh / g.

12. A method for producing a phosphate positive electrode active material, characterized by, comprises: a first deposition of a gaseous carbon source on the surface of the inner core in an inert atmosphere by chemical vapor deposition to obtain a first coating material coating the inner core, wherein the inner core comprises lithium-containing transition metal phosphate particles; a second deposition of a nitrogen-containing organic matter and a gaseous silicon source on the surface of the first coating material by chemical vapor deposition through a carrier gas to obtain a phosphate positive electrode active material comprising a second coating material, wherein the second coating material is located on the surface of the first coating material.

13. The method of claim 12, wherein, The nitrogen-containing organic matter comprises one or more of polyacrylonitrile, acetonitrile, and malonitrile.

14. A battery device characterized by comprising: A lithium battery cell comprising the lithium battery cell of any one of claims 1 to 9 or a phosphate cathode active material prepared by the method of claim 10 or 11 or claim 12 or 13.

15. An electrical device, comprising: A battery device comprising the battery device of claim 14.

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