Lithium ion battery cathode with good wettability and preparation method thereof

Abstract

The application discloses a lithium ion battery positive electrode with good wetting performance and a preparation method thereof, and comprises the following steps: S1, mixing positive electrode active material, conductive agent and binder to prepare positive electrode slurry, coating the positive electrode slurry on the surface of a positive electrode current collector, and obtaining a base material positive electrode sheet after drying and rolling; S2, interval coating and solidification are carried out on the surface of the positive electrode active material layer of the base material positive electrode sheet to form a soluble functional coating penetrating through the width direction of the positive electrode sheet, and the lithium ion battery positive electrode sheet is obtained; wherein the soluble functional coating is used for dissolving when preparing a lithium ion battery injection electrolyte in the subsequent step, so that a plurality of penetrating flow guide channels are formed on the surface of the positive electrode sheet. According to the application, the soluble functional coating which meets a specific parameter relationship and is in gradient distribution is constructed on the surface of the positive electrode, and a penetrating capillary liquid guide channel is formed after injection, so that the damage of the positive electrode sheet caused by mechanical kneading is avoided, and the effective balance between the permeation kinetics and the structural stability of the roll core is realized.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery cathode preparation technology, and particularly relates to a lithium-ion battery cathode with good wetting performance and its preparation method. Background Technology

[0002] Cylindrical battery cells are typically manufactured using high-tension winding to ensure energy density and mechanical strength. However, excessively tight winding can reduce internal porosity, hindering electrolyte penetration and wetting. Existing technologies, such as mechanical kneading (e.g., roller kneading), can reduce winding tightness, which, while improving wetting rate, inevitably causes mechanical compression damage to the core electrodes, and may even lead to internal short circuits.

[0003] Furthermore, existing technologies employ coating a layer of ethylene carbonate at the corners of the positive electrode sheet wound into a core. After electrolyte injection, the ethylene carbonate dissolves, leaving a gap at the corner to absorb the expansion stress of the negative electrode and prevent cell deformation. However, this technology only addresses stress relief at specific corner locations and does not systematically solve the problem of difficult electrolyte wetting throughout the entire core, especially in the central region. Simultaneously, the size of the resulting gap is uncontrollable. Under the high winding tension of the entire cell, the simple dissolution and gaps are easily squeezed and closed by adjacent electrode sheets in the initial stage of electrolyte injection, failing to form a long-term effective electrolyte channel.

[0004] Therefore, there is an urgent need for a novel electrode preparation method that can establish an electrolyte wetting network in a comprehensive, efficient and stable manner without damaging the electrode. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing a lithium-ion battery cathode with good wetting performance, addressing the shortcomings of existing technologies. By constructing a soluble functional coating on the cathode surface that conforms to a specific parameter relationship and is distributed in a gradient, a continuous capillary liquid channel is formed after liquid injection. This not only avoids damage to the electrode sheet caused by mechanical rubbing, but also achieves an effective balance between the internal permeation dynamics and structural stability of the core.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing a lithium-ion battery cathode with good wetting properties includes the following steps: S1. Mix the positive electrode active material, conductive agent and binder to form a positive electrode slurry, coat it on the surface of the positive electrode current collector, and obtain the substrate positive electrode sheet after drying and rolling. S2. On the surface of the positive active material layer of the substrate positive electrode sheet, a soluble functional coating is applied at intervals and cured to form a coating that runs through the width direction of the positive electrode sheet, thereby obtaining the lithium-ion battery positive electrode sheet; the width direction is parallel to the axis direction of the positive electrode sheet after it is subsequently wound into a core. The soluble functional coating is used to dissolve during the subsequent preparation of the lithium-ion battery by injecting electrolyte, so as to form several through-flow channels on the surface of the positive electrode sheet. The parameters of the soluble functional coating satisfy the following relationship:

[0007]

[0008] Where: W is the width of a single functional coating, in μm; H is the thickness of a single functional coating, in μm; D is the spacing between two adjacent functional coatings, in μm; d 50 θ represents the median particle size of the positive electrode active material, in μm; θ represents the porosity of the positive electrode active material layer after rolling, 0 < θ < 1.

[0009] Preferably, the spacing D between adjacent functional coatings gradually decreases from the end of the positive electrode to the beginning of the coating. And / or, from the tail end to the head end of the positive electrode sheet, the thickness H of the functional coating gradually increases; The tail end is the outermost end of the core formed from the positive electrode sheet, and the head end is the innermost end of the core formed from the positive electrode sheet.

[0010] Preferably, the spacing D between adjacent functional coatings satisfies the following decreasing formula:

[0011]

[0012] Where D0 is the spacing of the outermost coating of the positive electrode; L n L is the length from the current coating position to the roll end; total is the total length of the positive electrode; k is the gradient coefficient, with a value range of 0.2≤k≤0.5.

[0013] Preferably, the soluble functional coating comprises the following components in weight percentages: 60%~80% rapid dissolving agent, selected from at least one of ethylene carbonate and fluoroethylene carbonate; 10%~30% polymer slow-release backbone, selected from at least one of polymethyl methacrylate and polyethylene oxide; 5%~10% inorganic nanopropagator, selected from at least one of nano Al2O3 and nano SiO2, with a particle size of 20~50nm.

[0014] Preferably, the coating thickness H is 3~10μm and the coating width W is 0.5~2mm.

[0015] Preferably, in step S2, the soluble functional coating is applied using one of the following methods: inkjet printing, gravure coating, or screen printing.

[0016] Preferably, the soluble functional coating appears as continuous straight lines, wavy lines, or a grid on the surface of the substrate positive electrode.

[0017] In addition, the present invention also provides a lithium-ion battery cathode with good wetting properties, which is prepared by the method described above for preparing a lithium-ion battery cathode with good wetting properties.

[0018] In addition, the present invention also provides a lithium-ion battery comprising a lithium-ion battery positive electrode, a separator, a negative electrode sheet and an electrolyte with good wettability as described above. The positive electrode, separator, and negative electrode are sequentially stacked and wound to form a core; The soluble functional coating on the surface of the positive electrode dissolves in the electrolyte, forming several through-flow channels between the surface of the positive electrode and the separator.

[0019] Compared with the prior art, the present invention has at least the following beneficial effects: 1) This invention utilizes coating dissolution to replace mechanical kneading, generating in-situ flow channels between electrode layers, fundamentally eliminating the risk of physical damage such as electrode breakage and active material detachment caused by the kneading process, and improving the yield and safety of the battery cell.

[0020] 2) The capillary wetting index formula designed in this invention combines the macroscopic coating cross-sectional area (W×H) with the microscopic electrode particle characteristics (d). 50 The ratio of liquid injection efficiency to porosity (θ) is precisely matched. When the ratio is between 5.0 and 15.0, it can provide the best capillary suction power to prevent the channel from being squeezed and closed by the expansion of the electrode, and avoid losing too much interfacial contact area due to excessive coating area (avoiding increased polarization and local lithium plating). It perfectly balances the contradiction between liquid injection efficiency and battery energy density and cycle life.

[0021] 3) This invention addresses the physical characteristics of increasing internal pressure and deepening liquid penetration path in cylindrical cells by employing a gradient design with decreasing spacing (or increasing thickness). This design creates denser liquid channels in the most difficult-to-wet central area of ​​the core, effectively solving the industry problem of "wetting dead zones" and making the overall wetting of the cell more uniform.

[0022] 4) Compared to the instantaneous dissolution of pure EC coatings, which causes the channels to close instantly under tension, this invention uses a composite coating material consisting of a fast solvent, a swelling polymer, and a nano-support. In the initial stage of liquid injection, the fast solvent quickly dissolves and opens the flow channels; at the same time, the swelling polymer absorbs the liquid and forms a gel skeleton to open the gaps; the nano-inorganic particles act as rigid "bridge piers," maintaining micron-level physical gaps even if the polymer completely dissolves during circulation, achieving long-lasting wetting throughout the entire life cycle. Detailed Implementation

[0023] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0025] According to a first aspect of this application, this application provides a method for preparing a lithium-ion battery positive electrode with good wetting properties, comprising the following steps: S1. Mix the positive electrode active material, conductive agent and binder to form a positive electrode slurry, coat it on the surface of the positive electrode current collector, and obtain the substrate positive electrode sheet after drying and rolling. S2. On the surface of the positive active material layer of the substrate positive electrode sheet, a soluble functional coating is applied and cured at intervals to form a coating that runs through the width direction of the positive electrode sheet, thereby obtaining a lithium-ion battery positive electrode sheet; the width direction is parallel to the axis direction of the positive electrode sheet after it is subsequently wound into a core. Among them, the soluble functional coating is used to dissolve during the subsequent preparation of lithium-ion batteries by injecting electrolyte, so as to form several through-channel micro-flow channels on the surface of the positive electrode sheet. The parameters of the soluble functional coating satisfy the following relationship:

[0026]

[0027] Where: W is the width of a single functional coating, in μm; H is the thickness of a single functional coating, in μm; D is the spacing between two adjacent functional coatings, in μm; d 50 θ represents the median particle size of the positive electrode active material, in μm; θ represents the porosity of the positive electrode active material layer after rolling, 0 < θ < 1.

[0028] The capillary wetting index formula designed in this invention combines the macroscopic coating cross-sectional area (W×H) with the microscopic electrode particle characteristics (d). 50 The ratio (θ) and porosity (θ) are precisely matched. By controlling this ratio within the critical range of 5.0 to 15.0, on the one hand, it can provide a sufficiently strong capillary suction force to ensure that the channels formed after dissolution will not close under the expansion and compression of the electrode; on the other hand, it strictly limits the coating area ratio to avoid losing the effective physical contact area between the electrode and the separator due to excessive coating, thereby preventing increased interfacial polarization and local lithium deposition, effectively balancing the contradiction between liquid injection efficiency and battery energy density and cycle life.

[0029] The coating and curing mechanism of the functional coating is as follows: Because the main component of the soluble functional coating of this invention, ethylene carbonate (EC), has a low melting point, conventional high-temperature baking (such as above 100°C) will cause it to melt and flow, damaging the microstructure and array structure of the coating. To ensure the accuracy of the coating dimensional parameters (width W, thickness H, spacing D) in this invention, and to ensure that the electrodes do not stick together during winding, the following mechanism is adopted in this embodiment to ensure that the coating exhibits a stable solid state at room temperature: Firstly, in addition to serving as a slow-release framework after solvent injection, polymethyl methacrylate (PMMA) or polyethylene oxide (PEO) in the coating formulation acts as a crucial "polymer film-forming agent" during the coating stage. The polymer chains entangle with each other to form a three-dimensional network during solvent evaporation, encapsulating the small EC molecules within the network and separating the microphase. Simultaneously, nano-Al₂O₃ or SiO₂ acts as a "thickening and anti-blocking agent." The synergistic effect of these three components results in a dry, non-sticky solid film at room temperature.

[0030] Secondly, this application can be cured using one of the following two precision coating processes that do not require high-temperature baking: Method 1 (Low-boiling-point solvent low-temperature drying method): When preparing the coating slurry, use low-boiling-point solvents such as acetone, ethyl acetate, or dichloromethane instead of conventional NMP. After coating, the solvent can be rapidly evaporated at room temperature (20~25℃) or a lower temperature (such as a vacuum negative pressure environment at 30℃), and EC will crystallize and form a film with PMMA to cure. The entire process is below the melting point of EC.

[0031] Method 2 (Hot-Melt Spraying and Condensation Method): Without using any solvent, a mixture of EC, PMMA, and nanoparticles is heated to 60-80°C to a plastic fluid state. This mixture is then sprayed onto the surface of the substrate positive electrode at room temperature (25°C) using a piezoelectric hot-melt spray nozzle, following a pattern. Upon contact with the room-temperature electrode, the microdroplets undergo physical cooling, causing the EC to instantly crystallize and solidify, forming clearly defined solid stripes.

[0032] In one embodiment according to this application, the soluble functional coating is gradient-distributed along the length of the positive electrode: From the end of the positive electrode to the beginning of the roll, the spacing D between adjacent functional coatings gradually decreases; And / or, from the tail end to the head end of the positive electrode sheet, the thickness H of the functional coating gradually increases; The tail end corresponds to the outermost ring of the core formed from the positive electrode sheet, while the head end corresponds to the innermost ring of the core formed from the positive electrode sheet.

[0033] In cylindrical cells, the pressure distribution and penetration depth are uneven. The closer to the center (inner ring), the greater the winding pressure and the longer the electrolyte penetration path, creating a "wetting dead zone." This application employs a centripetal increasing gradient design, enabling the most difficult-to-wet electrode tip to obtain a denser network of liquid guiding channels. This precisely matches the hydrodynamic resistance gradient inside the cell, achieving uniform and rapid wetting of the entire cell from the outside in.

[0034] In one embodiment according to this application, the spacing D between adjacent functional coatings satisfies the following decreasing formula:

[0035]

[0036] Where D0 is the spacing of the outermost coating of the positive electrode; L n L is the length from the current coating position to the end of the roll; total is the total length of the positive electrode; k is the gradient coefficient, with a value range of 0.2≤k≤0.5.

[0037] This formula provides an optimal shrinkage gradient curve. The gradient coefficient k is limited to 0.2~0.5, ensuring that the increase in channel density is gradual and continuous. If this specific decreasing pattern is not adopted or the k value is too large, it will cause a sudden surge in the coating ratio of the inner electrode, leading to a significant decrease in the utilization rate of the inner active material, and even causing electrode wrinkling due to uneven local tension. This formula ensures a quantitative balance between fluid conductivity and mechanical stability.

[0038] In one embodiment according to this application, the soluble functional coating comprises the following components by weight percentage: Rapid solvent: 60%~80%, selected from at least one of ethylene carbonate and fluoroethylene carbonate; Polymer sustained-release backbone: 10%~30%, selected from at least one of polymethyl methacrylate and polyethylene oxide; Inorganic nanopropeller: 5%~10%, selected from at least one of nano Al2O3 and nano SiO2, with a particle size of 20~50nm.

[0039] The composite formulation exhibits two prominent synergistic effects: First, it prevents channel collapse. Compared to the pure EC coating, which dissolves instantly and causes the channels to close under strong winding tension, the EC in this component quickly dissolves and opens the channels. PMMA then swells upon contact with the liquid to form a gel skeleton that initially opens the gaps. Meanwhile, the highly rigid nano-Al2O3 acts as a "microscopic bridge pier," maintaining micron-level physical gaps even when the polymer is completely dissolved, thus achieving long-term wetting throughout the entire life cycle. Second, it features room-temperature curing. The added polymer (PMMA) and nanoparticles enable the low-melting-point EC to separate into microphases and lose its fluidity within its three-dimensional network. This ensures that the coating formulation can be cured into a dry, non-sticky solid at room temperature, guaranteeing the accuracy of the coating's micro-sizes and the smoothness of subsequent winding.

[0040] In one embodiment of this application, the coating thickness H is 3~10μm and the coating width W is 0.5~2mm. The thickness H, controlled at 3~10μm, provides sufficient fluid-conducting gaps to resist internal cell pressure without significantly increasing the overall electrode thickness and core volume. The width W, at 0.5~2mm, not only meets the macroscopic capillary flow rate requirements of the electrolyte but also ensures the coating's own forming stiffness.

[0041] In one embodiment of this application, in step S2, the soluble functional coating is applied using one of inkjet printing, microgravure coating, or screen printing.

[0042] In one embodiment of this application, the soluble functional coating on the surface of the substrate positive electrode sheet is presented as continuous straight strips, wavy lines, or a grid pattern. Among these, the straight strip pattern is the simplest to prepare and has the lowest longitudinal (axial) flow resistance; while the wavy line or grid pattern can increase the transverse branching penetration path on the basis of the main axis flow guidance, which is conducive to the rapid diffusion of electrolyte in the two-dimensional plane of the positive and negative electrode sheets, further shortening the wetting time and reducing the wetting blind zone.

[0043] According to a second aspect of this application, this application also provides a lithium-ion battery positive electrode with good wetting properties, which is prepared by the method described above for preparing a lithium-ion battery positive electrode with good wetting properties. This positive electrode, due to its built-in micro-current-conducting network, directly endows the electrode with excellent self-wetting characteristics, eliminating the need for mechanical kneading processes at the cell manufacturing stage and effectively solving the risks of microcracks, powder shedding, and internal short circuits caused by physical external forces.

[0044] According to a third aspect of this application, this application also provides a lithium-ion battery comprising a lithium-ion battery positive electrode, a separator, a negative electrode sheet, and an electrolyte with good wetting properties as described above. The positive electrode, separator, and negative electrode are sequentially stacked and wound together to form a core; The soluble functional coating on the surface of the positive electrode dissolves in the electrolyte, forming several interconnected microchannels between the surface of the positive electrode and the separator.

[0045] Among them, the battery assembled with this positive electrode sheet has a leapfrog improvement in electrolyte injection efficiency (especially for high-pressure, high-nickel systems that are difficult to wet). At the same time, due to the extremely uniform distribution of electrolyte, the polarization difference inside the battery is effectively eliminated, thereby greatly improving the battery's first charge and discharge efficiency and long-term cycle life.

[0046] The advantages of the present invention will be further explained in detail below with reference to specific embodiments and comparative examples.

[0047] Example 1

[0048] S1. Preparation of the substrate positive electrode: NCM811 (median particle size d) 50 The positive electrode active material layer is 60 μm thick and has a porosity θ of 0.25 after being mixed with carbon nanotubes and PVDF in a mass ratio of 96:2:2, coated on the surface of aluminum foil, dried and rolled.

[0049] S2. Prepare the functional coating slurry: Dissolve and disperse EC, PMMA, and nano Al2O3 in a low-boiling-point solvent (acetone) at a mass ratio of 70:20:10 to prepare a coating liquid with a suitable viscosity.

[0050] S3. Coating and Curing: The above coating liquid is sprayed intermittently onto the surface of the positive electrode active material using inkjet printing. After the coating is completed, the electrode is placed in a 25°C vacuum drying oven and the air is removed to allow the acetone to evaporate rapidly. The coating crystallizes in situ on the electrode surface and forms a dry, solid strip-shaped coating.

[0051] Parameter settings: After curing, the coating width W=1500μm, the thickness H=5μm, and the spacing D=100μm (equidistant).

[0052] Substitute the relational expression to verify: , satisfying the relational range.

[0053] Cylindrical cell A1 is manufactured using this positive electrode sheet through subsequent conventional winding and liquid injection processes.

[0054] Example 2

[0055] The positive electrode preparation and coating materials are the same as in Example 1. The difference lies in the gradient design of the coating arrangement: width W = 1500 μm and thickness H = 5 μm.

[0056] From the outermost edge (tail end) to the innermost edge (head end), the spacing D gradually decreases. Let the outermost spacing D0 = 150 μm, and the gradient coefficient k = 0.6. In the innermost region (L... n L total The spacing D decreases to approximately 60 μm.

[0057] Calculations show that the overall average parameter is approximately 10.5, which meets the relational range. Cylindrical cell A2 was then manufactured.

[0058] Example 3

[0059] The coating parameters were adjusted to: W=1900μm, H=6μm, D=95μm. Substituting these values ​​into the equation yielded a result of 15.0, which satisfies the equation's range. Cylindrical cell A3 was then fabricated.

[0060] Example 4

[0061] The coating parameters were adjusted to: W=1000μm, H=4μm, D=100μm. Substituting these parameters into the formula yielded a result of 5.0, which satisfies the formula's range. Cylindrical cell A4 was then fabricated.

[0062] Comparative Example 1

[0063] The coating parameters were adjusted to: W=500μm, H=4μm, D=120μm. Substituting these parameters into the formula, the result was 2.08 < 5.0, which is below the lower limit of the formula. Cell B1 was then fabricated.

[0064] Comparative Example 2

[0065] The coating parameters were adjusted to: W=2500μm, H=8μm, D=80μm. Substituting these values ​​into the formula, the result was 31.25>15.0, exceeding the upper limit of the formula. Cell B2 was then manufactured.

[0066] Comparative Example 3

[0067] The functional coating uses only pure ethylene carbonate (EC), without the addition of PMMA and nano-Al2O3. The dimensional parameters are completely consistent with Example 1. Cell B3 was fabricated.

[0068] Comparative Example 4

[0069] A pure EC layer is coated only at the corresponding winding corner of the positive electrode sheet, without dense array arrangement or parameter control. This produces cell B4.

[0070] Comparative Example 5

[0071] The positive electrode sheet has no coating. After conventional winding, the core is continuously rubbed with a mechanical roller for 5 seconds to produce cell B5.

[0072] The electrochemical and physical properties of the cylindrical cells prepared in the examples and comparative examples were tested respectively: 1. Electrolyte wetting rate and time required to reach wetting standard test: Place the core in the injection chamber and inject electrolyte under vacuum. Record the actual mass of electrolyte absorbed after standing for different times. Wetting rate = (actual absorbed mass / theoretical maximum absorption) × 100%. The time required for the wetting rate to reach 95% is defined as "time required to reach wetting standard".

[0073] 2. Microcrack rate test of disassembled electrode sheet: The impregnated core was disassembled, and 100 fields of view were randomly selected in the positive electrode sheet using a scanning electron microscope (SEM) to count the percentage of fields of view with microcracks or detachment of active material layer.

[0074] 3. Initial charge and discharge efficiency test: The first charge and discharge is performed at a rate of 0.1C. The initial efficiency is calculated as (initial discharge capacity / initial charge capacity) × 100%.

[0075] 4. Capacity retention test after 100 cycles: 100 charge-discharge cycles were performed at 1C rate. The capacity retention rate = (100th discharge capacity / 1st discharge capacity) × 100%.

[0076] The test results are shown in Table 1.

[0077] Table 1

[0078]

[0079] The analysis of the above test results is as follows: 1. Comparative analysis of Example 1 and Comparative Examples 1 and 2 shows that: Comparative Example 1 (below the lower limit of the equation) suffers from excessively small and widely spaced channels that easily close under winding tension, resulting in a wetting time of up to 22 hours and poor cycle retention. Comparative Example 2 (above the upper limit of the equation) exhibits extremely fast wetting (4 hours), but the excessively large coating area severely sacrifices the effective contact area between the electrode and the separator, leading to a surge in interfacial polarization resistance, a drop in initial efficiency to 82.1%, and a sharp decline in cycle retention to 81.2%. In contrast, the parameters of Examples 1, 3, and 4 fall within the [5.0, 15.0] range of the equation of this invention, effectively balancing high wettability with the electrochemical performance of the battery.

[0080] 2. Comparative analysis of Example 1 and Example 2 shows that: Example 2 introduces a gradient distribution design, with a denser channel network in the innermost ring of the core, which is the most difficult to wet. Compared with Example 1, Example 2 significantly shortens the wettability time (from 8 hours to 5 hours), while achieving more uniform wettability and preventing localized lithium plating. This results in a capacity retention rate of 96.5% after 100 cycles, demonstrating the advanced synergistic effect of the preferred technical solution.

[0081] 3. Comparative analysis of Example 1 and Comparative Example 3 shows that: Comparative Example 3 used a pure EC coating, which dissolved instantly after injection and caused the channel to collapse and close prematurely under strong winding tension. In contrast, Example 1 added PMMA and nano Al2O3 to construct a dual framework of "gel + rigid support", which significantly shortened the immersion time from 15h to 8h, demonstrating the key role of the composite material in maintaining the effectiveness of the microchannel.

[0082] 4. Comparative analysis of Example 1 and Comparative Examples 4 and 5 shows that: Compared with the existing partial coating technology (Comparative Example 4), the present invention (Example 1) constructs an array of through channels, which has an order-of-magnitude advantage in wetting efficiency. Compared with the mechanical rubbing method (Comparative Example 5), the present invention achieves better wetting performance while reducing the microcrack rate from 8.5% to 0%, effectively solving the core problem of mechanical damage to the electrode sheet and significantly improving the reliability of the battery cell.

[0083] It should be noted that the contents not described in detail in this specification are existing technologies known to those skilled in the art, and will not be elaborated here.

[0084] Based on the disclosure and teachings of the foregoing specification, those skilled in the art can make changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments described above, and any obvious improvements, substitutions, or modifications made by those skilled in the art based on the present invention are within the scope of protection of the present invention. Furthermore, although some specific terms are used in this specification, these terms are only for convenience of explanation and do not constitute any limitation on the present invention.

Claims

1. A method for preparing a lithium-ion battery positive electrode with good wetting properties, characterized in that, Includes the following steps: S1. Mix the positive electrode active material, conductive agent and binder to form a positive electrode slurry, coat it on the surface of the positive electrode current collector, and obtain the substrate positive electrode sheet after drying and rolling. S2. On the surface of the positive active material layer of the substrate positive electrode sheet, a soluble functional coating is applied at intervals and cured to form a coating that runs through the width direction of the positive electrode sheet, thereby obtaining the lithium-ion battery positive electrode sheet; the width direction is parallel to the axis direction of the positive electrode sheet after it is subsequently wound into a core. The soluble functional coating is used to dissolve during the subsequent preparation of the lithium-ion battery by injecting electrolyte, so as to form several through-flow channels on the surface of the positive electrode sheet. The parameters of the soluble functional coating satisfy the following relationship: Where: W is the width of a single functional coating, in μm; H is the thickness of a single functional coating, in μm; D is the spacing between two adjacent functional coatings, in μm; d 50 θ represents the median particle size of the positive electrode active material, in μm; θ represents the porosity of the positive electrode active material layer after rolling, 0 < θ < 1.

2. The method for preparing a lithium-ion battery cathode with good wetting properties according to claim 1, characterized in that, From the end of the positive electrode to the beginning of the roll, the spacing D between adjacent functional coatings gradually decreases; And / or, from the tail end to the head end of the positive electrode sheet, the thickness H of the functional coating gradually increases; The tail end is the outermost end of the core formed from the positive electrode sheet, and the head end is the innermost end of the core formed from the positive electrode sheet.

3. The method for preparing a lithium-ion battery cathode with good wetting properties according to claim 2, characterized in that, The spacing D between adjacent functional coatings satisfies the following decreasing formula: Where D0 is the spacing of the outermost coating of the positive electrode; L n L is the length from the current coating position to the roll end; total is the total length of the positive electrode; k is the gradient coefficient, with a value range of 0.2≤k≤0.

5.

4. The method for preparing a lithium-ion battery cathode with good wetting properties according to claim 1, characterized in that, The soluble functional coating comprises the following components by weight percentage: 60%~80% rapid dissolving agent, selected from at least one of ethylene carbonate and fluoroethylene carbonate; 10%~30% polymer slow-release backbone, selected from at least one of polymethyl methacrylate and polyethylene oxide; 5%~10% inorganic nanopropagator, selected from at least one of nano Al2O3 and nano SiO2, with a particle size of 20~50nm.

5. The method for preparing a lithium-ion battery cathode with good wetting properties according to claim 1, characterized in that, The coating thickness H is 3~10μm, and the coating width W is 0.5~2mm.

6. The method for preparing a lithium-ion battery cathode with good wetting properties according to claim 1, characterized in that, In step S2, the soluble functional coating is applied using one of the following methods: inkjet printing, gravure coating, or screen printing.

7. The method for preparing a lithium-ion battery cathode with good wetting properties according to claim 1, characterized in that, The soluble functional coating appears as continuous straight lines, wavy lines, or grids on the surface of the substrate positive electrode.

8. A lithium-ion battery positive electrode with good wetting properties, characterized in that: It is prepared by the method for preparing a lithium-ion battery cathode with good wetting performance as described in any one of claims 1 to 7.

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