Positive plate, battery and electric equipment

Abstract

The invention relates to the field of batteries, in particular to a positive plate, a battery and electric equipment, the positive plate comprises a current collector and a positive film layer arranged on at least one side surface of the current collector, the positive film layer contains a lithium supplement material composition, the lithium supplement material composition comprises n lithium supplement materials with different particle sizes, n is an integer greater than or equal to 2, and n is an integer greater than or equal to 2. The n lithium supplementing materials are a first lithium supplementing material, a second lithium supplementing material,..., an (n-1) th lithium supplementing material and an nth lithium supplementing material from small to large according to the Dv50 particle size; wherein the difference value between the Dv50 particle size of the (i + 1) th lithium supplement material and the Dv50 particle size of the ith lithium supplement material is greater than or equal to 1 [mu] m, and i is an integer from 1 to n-1. The battery adopting the positive plate has relatively good comprehensive performance.

Description

Technical Field

[0001] This application relates to the field of battery technology, specifically to positive electrode sheets, batteries, and electrical devices. Background Technology

[0002] During the initial charge and discharge cycle of a lithium-ion battery, a solid electrolyte interphase (SEI) film forms on the negative electrode surface, and a series of side reactions occur. This process inevitably consumes some active lithium ions, reducing the amount of usable active lithium ions in the battery and consequently decreasing the total reversible lithium content. This results in a lower initial discharge capacity (70-90%) for lithium-ion batteries. Using pre-lithiation technology to replenish active lithium ions can improve the coulombic efficiency of the initial charge and discharge cycle, thereby reducing the loss of active lithium during this process.

[0003] Currently, the main pre-lithiation methods are divided into positive electrode pre-lithiation and negative electrode pre-lithiation. Negative electrode pre-lithiation mainly employs electrochemical lithium replenishment and lithium powder lithium replenishment methods. Positive electrode pre-lithiation is achieved by adding positive electrode additives during the preparation of the positive electrode material. By charging to the positive electrode's lithium-ion delithiation potential, lithium ions are released and migrate to the negative electrode, thus achieving pre-lithiation. Negative electrode lithium replenishment is not widely used due to process limitations. Positive electrode pre-lithiation also suffers from problems such as affecting the compaction density of the positive electrode sheet, severe gas generation, and low specific capacity of the positive electrode lithium replenishment material.

[0004] Therefore, current pre-lithiation technologies still need improvement. Summary of the Invention

[0005] The present invention aims to at least partially solve one of the technical problems in the related art.

[0006] A first aspect of this application provides a positive electrode sheet. According to an embodiment of this application, the positive electrode sheet includes a current collector and a positive electrode film layer disposed on at least one surface of the current collector. The positive electrode film layer contains a lithium replenishing material composition, which includes n lithium replenishing materials with different particle sizes, where n is an integer greater than or equal to 2. The n lithium replenishing materials are, in ascending order of their Dv50 particle size, a first lithium replenishing material, a second lithium replenishing material, ..., the (n-1)th lithium replenishing material, and the nth lithium replenishing material; wherein the difference between the Dv50 particle size of the (i+1)th lithium replenishing material and the Dv50 particle size of the ith lithium replenishing material is greater than or equal to 1 μm, and i is an integer from 1 to n-1. In this positive electrode, by using two or more lithium replenishment materials with different particle sizes, the advantages of different particle sizes can be fully utilized through the synergistic effect between the lithium replenishment materials. This not only reduces the specific surface area and enhances the stability of the contact between the lithium replenishment materials and the electrolyte, but also effectively reduces the amount of gas produced. At the same time, it can effectively utilize the capacity of the lithium replenishment materials and improve the decomposition efficiency of the lithium replenishment materials, thereby significantly improving the overall performance of the battery using this positive electrode.

[0007] According to embodiments of this application, the difference between the Dv50 particle size of the (i+1)th lithium replenishment material and the Dv50 particle size of the i-th lithium replenishment material is greater than or equal to 1 μm and less than or equal to 27 μm. In some specific embodiments, the difference between the Dv50 particle size of the (i+1)th lithium replenishment material and the Dv50 particle size of the i-th lithium replenishment material is greater than or equal to 1 μm and less than or equal to 5 μm.

[0008] According to an embodiment of this application, in the lithium replenishment material composition, the content of the i-th lithium replenishment material is greater than the content of the (i+1)-th lithium replenishment material. Therefore, the decomposition rate of the lithium replenishment material is higher, the capacity of the lithium replenishment material can be effectively utilized, and the battery using this positive electrode sheet has a higher initial efficiency.

[0009] According to an embodiment of this application, the difference between the mass of the i-th lithium replenishing material and the mass of the (i+1)-th lithium replenishing material accounts for 10% to 50% of the total mass of the lithium replenishing material composition. This allows for better utilization of the advantages of lithium replenishing materials with different particle sizes.

[0010] According to embodiments of this application, the Dv50 particle size of any one of the n lithium replenishment materials is 1 μm to 30 μm. In some specific embodiments, the Dv50 particle size of any one of the n lithium replenishment materials is 3 μm to 15 μm. Within this particle size range, lithium replenishment materials with different particle sizes exhibit better synergistic effects and can better exert their lithium replenishment function.

[0011] According to embodiments of this application, n is an integer greater than 2 and less than or equal to 30. In some specific examples, n is an integer greater than 2 and less than or equal to 5. Multiple lithium-supplementing materials with different particle sizes can be used in combination, allowing for a gradual transition between different particle sizes and enabling finer adjustment of the synergistic effects between the various lithium-supplementing materials.

[0012] According to embodiments of this application, the lithium replenishment material includes at least one selected from Li6COO4, LiMnO3, Li2NiO2, Li5FeO4, Li2S, Li2O, Li2O2, and Li3N. According to embodiments of this application, the lithium replenishment material includes Li5FeO4. Therefore, it has a better lithium replenishment effect, and the battery using this cathode sheet has better overall performance.

[0013] According to embodiments of this application, based on the total mass of the positive electrode film, the mass percentage content of the lithium replenishing material composition is 0.1% to 10%. Within this content range, the lithium replenishing material function can be effectively utilized without significantly affecting the energy density of the battery using the positive electrode. According to embodiments of this application, based on the total mass of the positive electrode film, the mass percentage content of the lithium replenishing material composition is 0.1% to 5%. Within the above content range, the lithium replenishing material function can be effectively utilized without significantly affecting the energy density of the battery using the positive electrode.

[0014] According to an embodiment of this application, the positive electrode film layer includes a positive electrode active material, which includes at least one of lithium iron phosphate, lithium manganese iron phosphate, nickel cobalt manganese ternary positive electrode material, nickel cobalt aluminum ternary positive electrode material, lithium-rich manganese-based positive electrode material, lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, and lithium nickel manganese oxide.

[0015] According to embodiments of this application, the positive electrode active material includes at least one of lithium iron phosphate and lithium manganese iron phosphate.

[0016] According to an embodiment of this application, the Dv50 particle size of the positive electrode active material is 1 μm to 5 μm.

[0017] A second aspect of this application provides a battery. According to an embodiment of this application, the battery includes the positive electrode plate described above. This battery possesses all the features and advantages of the positive electrode plate described above, which will not be repeated here.

[0018] A third aspect of this application provides an electrical device. According to an embodiment of this application, the electrical device includes the battery described above. This battery possesses all the features and advantages of the battery described above, which will not be repeated here. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of a positive electrode sheet according to an embodiment of this application.

[0020] Figure 2 This is a schematic diagram of the structure of a positive electrode sheet according to an embodiment of this application.

[0021] Figure 3 This is an SEM image of the positive electrode sheet in Embodiment 5 of this application.

[0022] Figure label:

[0023] 10: Positive electrode current collector; 20: Positive electrode active material; 31: First lithium supplement material; 32: Second lithium supplement material; 33: Third lithium supplement material. Detailed Implementation

[0024] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0025] This application is based on the inventor's discoveries and understanding of the following facts and problems:

[0026] Currently, while cathode pre-lithiation additives can improve battery initial efficiency to some extent, various problems still exist in practical use. These include: affecting the compaction density of the cathode sheet, leading to ineffective energy density improvement through cathode lithiation; increasing battery impedance and degrading battery performance; increasing the thixotropy of the cathode slurry, increasing coating difficulty and reducing coating speed, thus affecting coating capacity; and generating large amounts of gases, such as N2, O2, and S, which may react with the electrolyte, further increasing battery impedance and reducing overall battery performance. Research has found that one reason for these problems is the significant difference in particle size between the cathode lithiation material and the cathode active material. This results in an undesirable particle size distribution, affecting the compaction density of the cathode sheet. Furthermore, this particle size difference increases the diffusion resistance of the cathode liquid phase and reduces the lithium-ion transport rate, thereby increasing battery impedance and reducing battery performance.

[0027] In view of this, the present invention proposes a positive electrode, a battery, and an electrical device that can improve the overall performance of a battery.

[0028] A first aspect of this application provides a positive electrode sheet. According to an embodiment of this application, the positive electrode sheet includes a current collector and a positive electrode film layer disposed on at least one surface of the current collector. The positive electrode film layer contains a lithium replenishing material composition, which includes n lithium replenishing materials with different particle sizes, where n is an integer greater than or equal to 2. The n lithium replenishing materials are, in ascending order of their Dv50 particle size, a first lithium replenishing material, a second lithium replenishing material, ..., the (n-1)th lithium replenishing material, and the nth lithium replenishing material; wherein the difference between the Dv50 particle size of the (i+1)th lithium replenishing material and the Dv50 particle size of the ith lithium replenishing material is greater than or equal to 1 μm, and i is an integer from 1 to n-1.

[0029] It's understandable that the internal reaction of a lithium battery essentially involves active lithium ions shuttling back and forth between the positive and negative electrodes. During this process, lithium ions continuously insert and extract between the electrodes; this is the electrochemical reaction between the material particles and the electrolyte. Therefore, the lithium insertion / extraction behavior of a lithium battery is influenced by the characteristics of the battery material particles. Clearly, controlling the characteristics of the material particles in the battery is key to achieving breakthroughs in lithium battery performance.

[0030] During the initial charging process of a lithium-ion battery, the formation of a solid electrolyte interphase (SEI) film on the negative electrode surface irreversibly consumes the active lithium ions released from the positive electrode, reducing the specific capacity and energy density of the lithium-ion battery. Adding lithium to the lithium-ion battery can compensate for the irreversible consumption of active lithium ions by the formation of the SEI film, thereby improving the energy density and cycle life of the lithium-ion battery. A positive electrode lithium replenishment material is added to the positive electrode, and during the lithium-ion battery formation process, this material decomposes at a certain potential to release active lithium ions to replenish the battery's lithium supply.

[0031] The morphology and size of cathode lithium-ion replenishment materials affect the lithium-ion replenishment performance of the battery, and consequently its electrochemical performance, by influencing the lithium-ion diffusion path, diffusion resistance, and contact area with the electrolyte. Larger-diameter cathode lithium-ion replenishment materials, due to their relatively smaller contact area with the electrolyte, can reduce side reactions occurring during contact, thus reducing gas production during the formation and decomposition stages of the lithium-ion battery. Simultaneously, the higher conductivity of large-diameter powders, which may require fewer particle interfaces to move through, can significantly reduce the impedance of the lithium-ion battery and improve its rate performance. For small-diameter powders, the shorter electron path from the interior to the surface and the larger specific surface area reduce current density and charge overpotential. Therefore, small-particle cathode lithium-ion replenishment materials are easier to decompose completely, thus improving the decomposition efficiency and specific capacity of the cathode lithium-ion replenishment material.

[0032] In the positive electrode of this application, by employing two or more lithium-replenishing materials with different particle sizes, the synergistic effect between the lithium-replenishing materials with different particle sizes can be fully utilized to give full play to the advantages of lithium-replenishing materials with different particle sizes. This can reduce the specific surface area, enhance the contact stability between the lithium-replenishing materials and the electrolyte, reduce gas production, and reduce battery impedance. At the same time, it can effectively maximize the specific capacity of the positive electrode lithium-replenishing materials. Moreover, the combination of multiple lithium-replenishing materials with different particle sizes can better match with the positive electrode active material, making up for the disadvantages of using a single particle size lithium-replenishing material. As a result, a battery with less gas production and higher capacity can be obtained, significantly improving the overall performance of the battery using this positive electrode.

[0033] It is understandable that lithium-supplementing materials with different particle sizes can be obtained by using at least one of the following in the preparation steps: different ball milling times, ball milling power, ball milling speed, and ball-to-material ratio. As an example, taking Li5FeO4 as the lithium-supplementing material, its preparation process may include: mixing lithium hydroxide and nano-iron oxide at a molar ratio of 5.2:1, obtaining a precursor by spray drying, then placing the precursor in a high-speed mixer for mixing, and finally sintering it under an inert gas atmosphere. During the preparation process, the precursor can be ball-milled for different times to obtain lithium-supplementing materials with different particle sizes.

[0034] The particle size Dv50 of lithium replenishment materials refers to the median particle size, also known as the volume average particle size, which represents the particle size corresponding to 50% of the material's cumulative volume distribution. The particle size Dv50 of lithium replenishment materials can be measured using a laser particle size analyzer. For example, the particle size of large-particle lithium replenishment materials and small-particle lithium replenishment materials can be measured separately.

[0035] The particle size Dv50 of the lithium replenishment material can also be obtained through SEM observation. For example, a cross-section of the positive electrode sheet of a certain volume is obtained by using a Cross Section Polisher (CP) to thin or polish the cross-section of the electrode sheet. An SEM image of the positive electrode sheet cross-section is taken at a magnification of 5000x. A region with dimensions of 0.5cm x 0.5cm is selected from the SEM image, and the particle sizes of large and small lithium replenishment materials within this region are statistically analyzed and averaged separately. When the lithium replenishment material particles are irregularly shaped, the maximum diameter of the particles is used as the particle size of the lithium replenishment material. The inventors verified that the data values ​​obtained by the two methods are not significantly different.

[0036] According to embodiments of this application, the difference between the Dv50 particle size of the (i+1)th lithium replenishment material and the Dv50 particle size of the i-th lithium replenishment material is greater than or equal to 1 μm and less than or equal to 27 μm. In some specific embodiments, the difference between the Dv50 particle size of the (i+1)th lithium replenishment material and the Dv50 particle size of the i-th lithium replenishment material is greater than or equal to 1 μm and less than or equal to 5 μm. As an example, the difference between the Dv50 particle size of the (i+1)th lithium replenishment material and the Dv50 particle size of the i-th lithium replenishment material can be 1 μm, 2 μm, 3 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 27 μm, etc. Within the above-mentioned difference range, the particle size distribution of the lithium replenishment material composition is more reasonable, and it can achieve a better synergistic effect.

[0037] According to an embodiment of this application, in the lithium replenishment material composition, the content of the i-th lithium replenishment material is greater than the content of the (i+1)-th lithium replenishment material. Therefore, the decomposition rate of the lithium replenishment material is higher, the capacity of the lithium replenishment material can be effectively utilized, and the battery using this positive electrode sheet has a higher initial efficiency. This is particularly suitable for situations where the positive electrode active material in the positive electrode sheet is a phosphate positive electrode material (such as lithium iron phosphate, lithium manganese iron phosphate, etc.).

[0038] According to embodiments of this application, the difference between the mass of the i-th lithium replenishing material and the mass of the (i+1)-th lithium replenishing material accounts for 10% to 50% of the total mass of the lithium replenishing material composition, specifically 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, etc. This allows for better utilization of the advantages of lithium replenishing materials with different particle sizes.

[0039] According to embodiments of this application, the Dv50 particle size of any one of the n lithium replenishment materials is 1μm to 30μm (specifically, 1μm, 3μm, 5μm, 10μm, 15μm, 20μm, 25μm, 30μm, etc.). In some specific embodiments, the Dv50 particle size of any one of the n lithium replenishment materials is 3μm to 15μm. Within this particle size range, lithium replenishment materials with different particle sizes exhibit better synergistic effects and can better exert their lithium replenishment function.

[0040] According to embodiments of this application, n is an integer greater than 2 and less than or equal to 30. In some specific examples, n is an integer greater than 2 and less than or equal to 5. As examples, n can be 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, etc. The combined use of multiple lithium-ion materials with different particle sizes allows for a gradual transition between different particle sizes and more precise adjustment of the synergistic effects between the various lithium-ion materials. This, in turn, enables more precise control over the overall performance of the lithium-ion battery, thereby meeting the application requirements of different scenarios.

[0041] According to embodiments of this application, the lithium replenishment material includes at least one selected from Li6COO4, LiMnO3, Li2NiO2, Li5FeO4, Li2S, Li2O, Li2O2, and Li3N. As an example, the lithium replenishment material can be Li5FeO4. Therefore, it has a better lithium replenishment effect, and the battery using this cathode has better overall performance.

[0042] It is understood that the specific types of lithium-replenishing materials with different particle sizes in the lithium-replenishing material composition according to the embodiments of this application may be the same or different. Taking the example of a lithium-replenishing material composition including three lithium-replenishing materials with different particle sizes, in some embodiments, the lithium-replenishing material composition may include three types of Li5FeO4 with different particle sizes; in other embodiments, the three lithium-replenishing materials with different particle sizes in the lithium-replenishing material composition are Li5FeO4, Li6COO4, and Li2S.

[0043] According to embodiments of this application, based on the total mass of the positive electrode film, the mass percentage content of the lithium replenishing material composition is 0.1% to 10%, specifically 0.1% to 5%. As an example, based on the total mass of the positive electrode film, the mass percentage content of the lithium replenishing material composition can be 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, etc. Within the above content range, the lithium replenishing material can be effectively utilized without significantly affecting the energy density of the battery using this positive electrode.

[0044] According to embodiments of this application, the positive electrode film layer includes a positive electrode active material, which includes lithium iron phosphate (LiFePO4) and lithium manganese iron phosphate (LiFePO4). x Mn 1-x PO4), nickel-cobalt-manganese ternary cathode material (LiNi) y Co z Mn 1-y-z O2), nickel-cobalt-aluminum ternary cathode material (LiNi) m Co n Al 1-m-n O2), lithium-rich manganese-based cathode materials (rLi2MnO3·(1-r)LiMO2), lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium manganese oxide (LiMn2O4), lithium nickel manganese oxide (LiNi q Mn 2-q At least one of O4). According to some specific embodiments of this application, the positive electrode active material includes at least one of lithium iron phosphate and lithium manganese iron phosphate. Therefore, it can be better matched with the lithium replenishment material composition, thereby improving the overall performance of the battery using this positive electrode.

[0045] According to embodiments of this application, the Dv50 particle size of the positive electrode active material is 1μm to 5μm, specifically 1μm, 2μm, 3μm, 4μm, 5μm, etc. With the aforementioned particle size, the positive electrode active material particles can be distributed around the lithium replenishment material particles in the positive electrode sheet, ensuring sufficient contact between the two and thus facilitating the effective utilization of the lithium replenishment capacity.

[0046] It is understood that, in addition to the lithium-supplementing material composition and positive electrode active material mentioned above, the positive electrode film layer may also include a binder and a conductive agent. In some embodiments, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins. In some embodiments, the conductive agent may include at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0047] In some embodiments, the positive electrode film layer of the positive electrode sheet in this application contains lithium-supplementing materials of different particle sizes uniformly dispersed within the positive electrode active material. This structure fully leverages the advantages of lithium-supplementing materials of different particle sizes, not only reducing the specific surface area but also enhancing environmental stability and effectively reducing gas production. As an example, Figure 1 and Figure 2 Schematic diagrams are shown for lithium replenishment materials containing two different particle sizes and lithium replenishment materials containing three different particle sizes, respectively.

[0048] In some embodiments, the positive electrode sheet can be prepared by the following steps: dispersing the lithium supplementation materials of different particle sizes uniformly, then uniformly mixing them with positive electrode active materials, conductive agents, binders, optional dispersants, solvents, etc., and then uniformly coating the obtained positive electrode slurry onto the positive electrode current collector, and obtaining the positive electrode sheet through drying, rolling, etc.

[0049] A second aspect of this application provides a battery. According to an embodiment of this application, the battery includes the aforementioned positive electrode. This battery exhibits lower gas production, lower impedance, higher lithium replenishment material decomposition rate, higher initial efficiency, and better overall performance.

[0050] It is understood that the battery is a lithium battery, including but not limited to lithium-ion batteries and lithium metal batteries. The specific shape of the battery can be square, cylindrical, or other regular or irregular shapes; the outer packaging of the battery can be a hard shell (such as a steel shell, hard plastic shell, etc.) or a soft shell (such as aluminum-plastic film, pouch soft shell, etc.). The battery can be a single battery cell, a secondary battery assembled from multiple battery cells, or a battery module, battery pack, etc., which can be further assembled.

[0051] It is understood that, in addition to the aforementioned positive electrode, the battery may also include a negative electrode, a separator, an electrolyte (including electrolyte solution, semi-solid electrolyte, solid electrolyte, etc.), and outer packaging. Taking the electrolyte solution as an example, in this battery, the positive electrode, separator, and negative electrode are stacked sequentially and formed into an electrode assembly through a winding or stacking process. The electrode assembly and electrolyte solution can be housed in the outer packaging.

[0052] A third aspect of this application provides an electrical device. According to an embodiment of this application, the electrical device includes the battery described above. This electrical device possesses all the features and advantages of the battery described above, which will not be repeated here.

[0053] According to embodiments of this application, the electrical equipment may include mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but is not limited thereto. The battery may be used as a power source for the electrical equipment or as an energy storage unit for the electrical equipment.

[0054] It is understandable that, in addition to the battery mentioned above, the electrical equipment may also include the necessary structures and components of conventional electrical equipment. Taking electric vehicles as an example, it may include the body, windows, chassis, engine, seats, tires, and other necessary structures and components, which will not be elaborated here.

[0055] The embodiments of this application are described in detail below.

[0056] Example 1

[0057] Li5FeO4 particles with a diameter of 3 μm and 30 μm were mixed at a mass ratio of 5.5:4.5.

[0058] The fully dispersed Li5FeO4 was uniformly mixed with CNT, PVDF, PVP, lithium iron phosphate, and NMP in a mass ratio of 2.5:1:2.5:0.5:100:60. After being uniformly dispersed into a positive electrode slurry, it was uniformly coated onto an aluminum foil current collector. The surface density of the positive electrode sheet on one side was 200 g / m². 2 The positive electrode sheet is obtained by rolling, die-cutting, and baking. The particle size of lithium iron phosphate is 1.8 μm.

[0059] Graphite, conductive carbon black, sodium carboxymethyl cellulose dispersant, water, and NMP solvent were mixed in a mass ratio of 100:2:1:120:5 to form a slurry. After homogenization, the material was coated onto copper foil, and the single-sided surface density of the negative electrode sheet was 200 g / m². 2After the negative electrode sheet is evenly coated and baked, it is rolled and die-cut to obtain the negative electrode sheet.

[0060] LiPF6 was dissolved in a solvent with a mass ratio of DMC / EMC / DEC of 1:1:1 to obtain an electrolyte with a LiPF6 concentration of 1 mol / L.

[0061] The diaphragm is made of polypropylene membrane with a thickness of 16μm.

[0062] The positive electrode, separator, and negative electrode are stacked to form an electrode assembly. The electrode assembly is then placed in an aluminum-plastic film outer packaging, filled with electrolyte, and sealed to form a battery. The battery undergoes formation, aging, and capacity testing to evaluate its performance.

[0063] Example 2

[0064] Li5FeO4 particles with a diameter of 3 μm and 30 μm were mixed at a mass ratio of 8:2.

[0065] The fully dispersed Li5FeO4 was uniformly mixed with CNT, PVDF, PVP, lithium iron phosphate, and NMP in a mass ratio of 2.5:1:2.5:0.5:100:60. After being uniformly dispersed into a positive electrode slurry, it was uniformly coated onto an aluminum foil current collector. The surface density of the positive electrode sheet on one side was 200 g / m². 2 The positive electrode sheet is obtained by rolling, die-cutting, and baking.

[0066] Everything else is the same as in Example 1.

[0067] Example 3

[0068] Li5FeO4 particles with a diameter of 3 μm and 30 μm were mixed at a mass ratio of 7:3.

[0069] The fully dispersed Li5FeO4 was uniformly mixed with CNT, PVDF, PVP, lithium iron phosphate, and NMP in a mass ratio of 2.5:1:2.5:0.5:100:60. After being uniformly dispersed into a positive electrode slurry, it was uniformly coated onto an aluminum foil current collector. The surface density of the positive electrode sheet on one side was 200 g / m². 2 The positive electrode sheet is obtained by rolling, die-cutting, and baking.

[0070] Everything else is the same as in Example 1.

[0071] Example 4

[0072] Li5FeO4 particles with a diameter of 3 μm and 30 μm were mixed at a mass ratio of 6:4.

[0073] The fully dispersed Li5FeO4 was uniformly mixed with CNT, PVDF, PVP, lithium iron phosphate, and NMP in a mass ratio of 2.5:1:2.5:0.5:100:60. After being uniformly dispersed into a positive electrode slurry, it was uniformly coated onto an aluminum foil current collector. The surface density of the positive electrode sheet on one side was 200 g / m². 2 The positive electrode sheet is obtained by rolling, die-cutting, and baking.

[0074] Everything else is the same as in Example 1.

[0075] Example 5

[0076] Li5FeO4 particles with a diameter of 3 μm and 6 μm were mixed at a mass ratio of 6:4.

[0077] The fully dispersed Li5FeO4 was uniformly mixed with CNT, PVDF, PVP, lithium iron phosphate, and NMP in a mass ratio of 2.5:1:2.5:0.5:100:60. After being uniformly dispersed into a positive electrode slurry, it was uniformly coated onto an aluminum foil current collector. The surface density of the positive electrode sheet on one side was 200 g / m². 2 Rolling, die-cutting, and baking are used to obtain the positive electrode sheet, and its scanning electron microscope image is shown below. Figure 3 ,from Figure 3 The image clearly shows the distribution of lithium-filling materials of different particle sizes (as indicated by the red circle) in the positive electrode sheet.

[0078] Everything else is the same as in Example 1.

[0079] Example 6

[0080] Li5FeO4 particles with a diameter of 5 μm and 10 μm were mixed at a mass ratio of 6:4.

[0081] The fully dispersed Li5FeO4 was uniformly mixed with CNT, PVDF, PVP, lithium iron phosphate, and NMP in a mass ratio of 2.5:1:2.5:0.5:100:60. After being uniformly dispersed into a positive electrode slurry, it was uniformly coated onto an aluminum foil current collector. The surface density of the positive electrode sheet on one side was 200 g / m². 2 The positive electrode sheet is obtained by rolling, die-cutting, and baking.

[0082] Everything else is the same as in Example 1.

[0083] Example 7

[0084] Li5FeO4 particles with a diameter of 7 μm and 15 μm were mixed at a mass ratio of 6:4.

[0085] The fully dispersed Li5FeO4 was uniformly mixed with CNT, PVDF, PVP, lithium iron phosphate, and NMP in a mass ratio of 2.5:1:2.5:0.5:100:60. After being uniformly dispersed into a positive electrode slurry, it was uniformly coated onto an aluminum foil current collector. The surface density of the positive electrode sheet on one side was 200 g / m². 2 The positive electrode sheet is obtained by rolling, die-cutting, and baking.

[0086] Everything else is the same as in Example 1.

[0087] Example 8

[0088] Li5FeO4 particles with a particle size of 3 μm, 10 μm, and 15 μm were mixed in a mass ratio of 1:3:5.

[0089] The fully dispersed Li5FeO4 was uniformly mixed with CNT, PVDF, PVP, lithium iron phosphate, and NMP in a mass ratio of 2.5:1:2.5:0.5:100:60. After being uniformly dispersed into a positive electrode slurry, it was uniformly coated onto an aluminum foil current collector. The surface density of the positive electrode sheet on one side was 200 g / m². 2 The positive electrode sheet is obtained by rolling, die-cutting, and baking.

[0090] Everything else is the same as in Example 1.

[0091] Example 9

[0092] Li5FeO4 particles with a diameter of 3 μm, 8 μm, and 13 μm were mixed in a mass ratio of 1:3:5.

[0093] The fully dispersed Li5FeO4 was uniformly mixed with CNT, PVDF, PVP, lithium iron phosphate, and NMP in a mass ratio of 2.5:1:2.5:0.5:100:60. After being uniformly dispersed into a positive electrode slurry, it was uniformly coated onto an aluminum foil current collector. The surface density of the positive electrode sheet on one side was 200 g / m². 2 The positive electrode sheet is obtained by rolling, die-cutting, and baking.

[0094] Everything else is the same as in Example 1.

[0095] Example 10

[0096] L with particle sizes of 3μm and 6μm and 9μm i5 FeO4 was mixed in a mass ratio of 1:3:5.

[0097] The fully dispersed Li5FeO4 was uniformly mixed with CNT, PVDF, PVP, lithium iron phosphate, and NMP in a mass ratio of 2.5:1:2.5:0.5:100:60. After being uniformly dispersed into a positive electrode slurry, it was uniformly coated onto an aluminum foil current collector. The surface density of the positive electrode sheet on one side was 200 g / m². 2 The positive electrode sheet is obtained by rolling, die-cutting, and baking.

[0098] Everything else is the same as in Example 1.

[0099] Example 11

[0100] Li5FeO4 particles with particle sizes of 3μm, 6μm, 10μm, and 15μm were mixed in a mass ratio of 1:2:3:4.

[0101] The fully dispersed Li5FeO4 was uniformly mixed with CNT, PVDF, PVP, lithium iron phosphate, and NMP in a mass ratio of 2.5:1:2.5:0.5:100:60. After being uniformly dispersed into a positive electrode slurry, it was uniformly coated onto an aluminum foil current collector. The surface density of the positive electrode sheet on one side was 200 g / m². 2 The positive electrode sheet is obtained by rolling, die-cutting, and baking.

[0102] Everything else is the same as in Example 1.

[0103] Comparative Example 1

[0104] Li5FeO4 with a particle size of 3μm was uniformly mixed with CNT, PVDF, PVP, lithium iron phosphate, and NMP in a mass ratio of 2.5:1:2.5:0.5:100:60. After being uniformly dispersed into a positive electrode slurry, it was uniformly coated onto an aluminum foil current collector. The surface density of the positive electrode sheet on one side was 200 g / m². 2 The positive electrode sheet is obtained by rolling, die-cutting, and baking.

[0105] Everything else is the same as in Example 1.

[0106] Comparative Example 2

[0107] Li5FeO4 with a particle size of 30μm was uniformly mixed with CNT, PVDF, PVP, lithium iron phosphate, and NMP in a mass ratio of 2.5:1:2.5:0.5:100:60. After being uniformly dispersed into a positive electrode slurry, it was uniformly coated onto an aluminum foil current collector. The surface density of the positive electrode sheet on one side was 200 g / m². 2 The positive electrode sheet is obtained by rolling, die-cutting, and baking.

[0108] Everything else is the same as in Example 1.

[0109] The lithium-ion batteries prepared in the above embodiments and comparative examples were subjected to performance tests, and the test results are shown in Table 1.

[0110] 1. Specific capacity test of positive electrode lithium replenishment material: The lithium replenishment composition, carbon nanotubes, PDVF and NMP were mixed in a mass ratio of 100:1:10:400 as positive electrode slurry. The positive electrode sheet was prepared according to the method in Example 1, and then the lithium-ion battery was prepared according to the method in Example 1.

[0111] The lithium-ion battery was charged at 0.02C for 10 hours, rested for 30 minutes, then charged at 0.5C constant current and constant voltage to 3.9V (cutoff current is 0.01C), rested for 30 minutes, and then charged at 0.2C constant current and constant voltage to 4.3V (cutoff current is 0.01C) to obtain the decomposition capacity.

[0112] The mass of the lithium replenishment composition in a lithium-ion battery can be calculated from the ratio of the areal density to the lithium replenishment composition described above. The specific capacity of the lithium replenishment composition is obtained by dividing the decomposition capacity obtained above by the previously calculated mass of the lithium replenishment composition.

[0113] 2. Decomposition Gas Generation Test: The lithium-ion battery was charged at 0.02C for 10 hours, rested for 30 minutes, then charged at 0.5C constant current and constant voltage to 3.9V (cutoff current 0.01C), rested for 30 minutes, and then charged at 0.2C constant current and constant voltage to 4.3V (cutoff current 0.01C). The decomposition gas generation of the above lithium-ion battery replenishment composition was then tested according to Archimedes' water displacement method.

[0114] 3. Storage gas production test: After the battery produced gas under the decomposition gas production test conditions was vented, it was placed in a 60℃ oven for high-temperature storage for 15 days. The gas production volume was measured again according to Archimedes' water displacement method to obtain the storage gas production.

[0115] 4. Battery DC Internal Resistance (DCIR) Test: At room temperature (25±3℃), each lithium-ion battery after formation was charged at a constant current of 1 / 3C to the upper limit voltage of 4.2V, and then discharged at 1 / 3C to the lower limit voltage of 2.0V. After 3 cycles, the battery was charged at a constant current of 1 / 3C to 50% SOC at room temperature, and the battery voltage after resting for 1 hour was recorded as V1; then it was discharged at 1.5C for 30s, and the battery voltage after the discharge was recorded as V2, where DCIR = (V1-V2) / 1.5C.

[0116] Table 1: Battery Performance Test Results

[0117]

[0118] The test results above show that using lithium replenishment materials with different particle sizes in combination can make the battery have both high capacity and low gas production, resulting in better overall battery performance. However, using lithium replenishment materials with a single particle size significantly worsens the overall battery performance.

[0119] In the description of this invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0120] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0121] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A positive electrode sheet characterized by comprising: The positive electrode film layer comprises a lithium supplement material composition, the lithium supplement material composition comprises n kinds of lithium supplement materials with different particle sizes, n is an integer greater than or equal to 2, and the n kinds of lithium supplement materials are sequentially the first lithium supplement material, the second lithium supplement material, the (n-1)th lithium supplement material, and the nth lithium supplement material from small to large in terms of Dv50 particle size; wherein the difference between the Dv50 particle size of the (i+1)th lithium supplement material and the Dv50 particle size of the ith lithium supplement material is greater than or equal to 1 μm, i is an integer from 1 to n-1.

2. The positive electrode sheet according to claim 1, characterized by the difference between the Dv50 particle size of the i+1th lithium supplementing material and the Dv50 particle size of the ith lithium supplementing material is greater than or equal to 1 μm and less than or equal to 27 μm ， Preferably, it is greater than or equal to 1 μm and less than or equal to 5 μm.

3. The positive electrode sheet according to claim 1, characterized by In the lithium supplement material composition, the content of the ith lithium supplement material is greater than the content of the (i+1)th lithium supplement material.

4. The positive electrode sheet according to claim 3, characterized by The difference between the mass of the ith lithium supplement material and the mass of the (i+1)th lithium supplement material accounts for 10% to 50% of the total mass of the lithium supplement material composition.

5. The positive electrode sheet according to claim 1, characterized by The Dv50 particle size of any one of the n kinds of lithium supplement materials is 1 μm to 30 μm, preferably 3 μm to 15 μm.

6. The positive electrode sheet according to claim 1, characterized by n is an integer greater than 2 and less than or equal to 30, preferably n is an integer greater than 2 and less than or equal to 5.

7. The positive electrode sheet according to claim 1, characterized by The lithium supplement material comprises at least one of Li6COO4, LiMnO3, Li2NiO2, Li5FeO4, Li2S, LI2O, Li2O2, and Li3N, preferably the lithium supplement material comprises Li5FeO4.

8. The positive electrode sheet according to claim 1, characterized by The mass percentage content of the lithium supplement material composition is 0.1% to 10%, preferably 0.1% to 5%, based on the total mass of the positive electrode film layer.

9. The positive electrode sheet according to any one of claims 1 to 8, characterized by, The positive electrode film layer comprises a positive electrode active material, the positive electrode active material comprises at least one of lithium iron phosphate, lithium manganese iron phosphate, nickel-cobalt-manganese ternary positive electrode material, nickel-cobalt-aluminum ternary positive electrode material, lithium-rich manganese-based positive electrode material, lithium cobaltate, lithium nickelate, lithium manganate, and lithium nickel manganate, preferably the positive electrode active material comprises at least one of lithium iron phosphate and lithium manganese iron phosphate.

10. The positive electrode sheet according to claim 9, characterized by The Dv50 particle size of the positive electrode active material is 1 μm to 5 μm.

11. A battery, characterized by The positive electrode sheet comprises the positive electrode film layer according to any one of claims 1 to 10.

12. An electrical device, characterized by The battery comprises the positive electrode sheet according to claim 11.

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