A lithium ion battery thick electrode based on component-structure space collaborative matching and a preparation method thereof

Abstract

The application provides a lithium ion battery thick electrode based on component-structure space collaborative matching and a preparation method thereof. The method comprises the following steps: S1) configuring at least three electrode slurries with different component proportions; S2) coating the different slurries configured in the step S1 on a current collector layer by layer according to a preset component gradient distribution, to obtain an electrode, wherein the preset component gradient distribution is that the content of an active substance increases and the content of a conductive agent decreases along the thickness direction of the electrode; S3) performing roll pressing treatment on the electrode obtained in the step S2; and S4) performing patterning treatment on the surface of the electrode subjected to the roll pressing treatment in the step S3 by using a laser technology, to obtain a conical gradient pore array, thereby obtaining the lithium ion battery thick electrode, wherein the component gradient and the conical pore array form an asymmetric space collaborative matching. The method can solve the problems of slow ion transmission, large polarization, poor rate / cycle and the like of a traditional thick electrode.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, specifically relating to a thick lithium-ion battery electrode based on composition-structure spatial synergistic matching and its preparation method. Background Technology

[0002] Lithium-ion batteries, with their high energy density, long cycle life, and environmental friendliness, have become the core energy source for portable electronic products. As applications expand to high-energy-demand fields such as electric vehicles, aerospace, and large-scale energy storage, improving the energy density of lithium-ion batteries has become an urgent need for industry development. In existing research, increasing electrode thickness is one of the most direct and effective ways to improve battery energy density. This strategy is compatible with various electrode materials and has the advantages of low cost and simple operation. However, increasing electrode thickness also brings serious challenges: the ion / electron transport path is significantly lengthened, leading to a surge in internal resistance and intensified concentration polarization, ultimately affecting the rate performance and cycle stability of the electrode.

[0003] To overcome the aforementioned bottlenecks, researchers have explored various approaches, including new materials, structural design, and advanced fabrication processes. Among these, gradient electrode design—constructing electrodes with different microstructures or compositions along the electrode thickness direction (away from the current collector)—is considered an effective means of improving the performance of thick electrodes. For example, Chinese patent CN102694150B discloses an electrode with a porosity gradient, designed to improve rate performance and suppress lithium plating; while Chinese patent CN111370649B discloses a composition gradient electrode with decreasing active material content and increasing conductive and binder content, achieving a balance between high energy density and good electrochemical performance.

[0004] Despite the positive results achieved by the aforementioned solutions, fundamental limitations remain. First, a long-standing "technical bias" persists in existing technologies: since the areal capacity of the electrode surface is primarily contributed by the active material, it is generally believed in the art that creating large-pore, high-density physical pores (such as laser ablation) in surface regions highly enriched with active material will irreversibly disrupt the continuity of the active material, leading to a severe loss of effective areal capacity. Based on this bias, existing technologies often struggle to achieve true spatial synergy when attempting to combine compositional and structural gradients, and may even exhibit mutual constraints. Furthermore, single-dimensional structural or compositional gradient designs are insufficient to synergistically resolve the contradiction between the mutual constraints between the electron conduction network and ion transport channels within thick electrodes, resulting in limited performance improvements.

[0005] Therefore, how to break through existing technological biases and design and fabricate a multi-gradient thick electrode that can achieve precise spatial matching of compositional and structural gradients and synergistic functional enhancement is a technical problem that urgently needs to be solved. Summary of the Invention

[0006] The purpose of this invention is to overcome the technical defects of existing gradient electrode designs, such as the disconnect between composition and structure and unclear synergistic effects, and to provide a thick lithium-ion battery electrode and its preparation method based on spatial synergistic matching of composition and structure. This invention does not simply superimpose two gradients, but employs an asymmetric gradient matching strategy. Specifically, it constructs large-pore, high-density ion transport channels on the electrode surface layer enriched with active materials, while maintaining a small-pore, low-density dense structure on the electrode bottom layer enriched with conductive agents. This achieves the synergistic construction of a low-impedance electron conduction network and a low-torsion ion transport path within the thick electrode, fundamentally solving the kinetic bottleneck problem of thick electrodes. According to embodiments of the invention, the thick electrode includes a current collector and an electrode active layer disposed on at least one side thereon, wherein the electrode active layer exhibits a multi-gradient distribution along the direction away from the current collector, characterized by increasing active material content, decreasing conductive agent content, and increasing porosity. The preparation method according to an embodiment of the present invention includes: preparing electrode slurries with different ratios, constructing a composition gradient electrode by coating them layer by layer onto a current collector; after drying and rolling, processing a conical pore array on the electrode surface using laser processing technology to form a low-torsional-degree ion channel with varying pore gradient. This invention effectively optimizes the ion / electron transport performance within a thick electrode through the synergistic design of composition gradient (active material / conductive agent) and structural gradient (conical pores / vertical channels), significantly improving the rate performance, cycle stability, and structural stability of the thick electrode, providing a new solution for electrode design in high-performance lithium-ion batteries.

[0007] In one aspect, the present invention provides a method for preparing a thick electrode for a lithium-ion battery. According to an embodiment of the present invention, the preparation method includes the following steps: S1) Prepare at least three electrode slurries with different component ratios; S2) According to the preset component gradient distribution, different slurries prepared in step S1 are coated layer by layer on the current collector to obtain the electrode. The preset component gradient distribution is as follows: along the electrode thickness direction, the content of active material increases while the content of conductive agent decreases. S3) Roll the electrode obtained in step S2; S4) Laser technology is used to pattern the electrode surface after the rolling process in step S3 to obtain a conical gradient pore array, resulting in a thick electrode for lithium-ion batteries, wherein the composition gradient and the conical pore array form an asymmetric spatial cooperative match.

[0008] According to embodiments of the present invention, the above preparation method may further include at least one of the following additional technical features: According to an embodiment of the present invention, the asymmetric spatial cooperative matching is such that in the electrode surface region with the highest content of active material, the pore diameter of the conical gradient pore structure is the largest and the distribution density is the highest; in the electrode bottom region with the highest content of conductive agent, the pore diameter of the conical gradient pore structure is the smallest and the distribution density is the lowest.

[0009] According to an embodiment of the present invention, in step S1, the electrode slurry includes an active material, a conductive agent, a binder, and a dispersing solvent; the at least three slurries include slurry 1, slurry 2, and slurry 3, and their coating order is slurry 1, slurry 2, and slurry 3; by mass percentage, The composition of the slurry 1 is: 70%~78% active material, 15%~20% conductive agent, and 10%~15% binder; The composition of the slurry 2 is: 79%~85% active material, 8%~14% conductive agent, and 5%~10% binder; and The composition of the slurry 3 is: 86%~95% active material, 2%~7% conductive agent, and 2%~5% binder. This specific, non-overlapping ratio sequence is the basis for achieving a precise composition gradient.

[0010] According to an embodiment of the present invention, the composition of the slurry 1 is: 75% active material, 15% conductive agent, and 10% binder; The composition of the slurry 2 is: 80% active material, 10% conductive agent, and 10% binder; and The composition of the slurry 3 is: 90% active material, 5% conductive agent, and 5% binder.

[0011] According to an embodiment of the present invention, in step S2, during the layer-by-layer coating process, the coating sequence is as follows: first apply slurry 1, then apply slurry 2, and finally apply slurry 3; slurry 1 is close to the current collector, and slurry 3 is close to the diaphragm side.

[0012] According to an embodiment of the present invention, the thick electrode of the lithium-ion battery is a positive electrode; the active material is one of lithium cobalt oxide, lithium iron phosphate, lithium manganese oxide, ternary materials, and lithium-rich manganese-based materials; the conductive agent is one of carbon black, carbon nanotubes, graphene, and other novel conductive agents; the binder is one of polyvinylidene fluoride, hydroxymethyl cellulose, styrene-butadiene rubber latex, polyacrylic acid, and other novel multifunctional binders; and the dispersing solvent includes one of organic solvent systems, aqueous solvent systems, and mixed solvent systems.

[0013] According to an embodiment of the present invention, the thick electrode of the lithium-ion battery is the negative electrode; the active material is one of graphite, silicon-based materials, lithium titanate, and metal oxides; the conductive agent is one of carbon black, carbon nanotubes, graphene, and other novel conductive agents; the binder is one of hydroxymethyl cellulose, styrene-butadiene rubber latex, polyacrylic acid, and other high-viscosity polymers; and the dispersing solvent includes one of aqueous solvents, organic solvent systems, and mixed solvent systems.

[0014] According to an embodiment of the present invention, in step S2, during the layer-by-layer coating process, an independent intermediate drying treatment is performed after each layer is coated to form a cured interface. The intermediate drying treatment is carried out at a temperature of 40-60°C for 10-30 minutes. According to an embodiment of the present invention, the cured interface ensures a clear interlayer interface and avoids gradient blurring.

[0015] According to an embodiment of the present invention, during the layer-by-layer coating process, the wet coating thickness of each electrode layer is 50~500μm.

[0016] According to an embodiment of the present invention, in the layer-by-layer coating process, the wet coating thickness of each electrode layer is 200~500μm.

[0017] According to an embodiment of the present invention, in step S3, the rolling gap of the rolling process is 40% to 80% of the total thickness of the composition gradient electrode after drying.

[0018] According to an embodiment of the present invention, in step S3, the rolling gap of the rolling process is 40% to 60% of the total thickness of the composition gradient electrode after drying. This proportion ensures better density and stability of the internal structure of the electrode.

[0019] According to an embodiment of the present invention, in step S4, the laser technology employs a nanosecond pulsed laser system, with the following processing parameters: pulse width 80 ns, frequency 30 kHz, defocusing amount 0~3 mm, laser power 1.5~4.5 W, processing speed 50~200 mm / s, and processing times 10~50 times. This combination of parameters ensures the fabrication of the specific conical hole structure while avoiding excessive ablation damage to the electrode material.

[0020] According to an embodiment of the present invention, in step S4, the processing parameters are: laser power 3W, defocusing amount 0 mm, scanning path is an array of holes with a spacing of 100μm-300μm, scanning speed 50 mm / s, and the number of processing times for each hole is 15 times.

[0021] According to an embodiment of the present invention, in step S4, the conical gradient pore structure is a series of conical gradient pore structures that are perpendicular to the electrode surface, with the pore openings facing the diaphragm and the pore bottoms extending into the electrode interior.

[0022] According to an embodiment of the present invention, in step S4, the diameter of the pores in the surface region of the conical gradient pore structure is 50~80 μm, the diameter of the pores in the bottom region is 0~20 μm, and the pore density is 1000~10000 pores / cm².

[0023] According to an embodiment of the present invention, the active layer thickness of the lithium-ion battery thick electrode is 100~300 μm.

[0024] According to an embodiment of the present invention, the pore depth of the tapered gradient pore structure is 70% to 100% of the final thickness of the thick electrode of the lithium-ion battery.

[0025] According to an embodiment of the present invention, the laser processing step must be performed after rolling to ensure the stability of the macroscopic structure of the electrode before constructing the microscopic gradient pores to ensure the integrity of the final electrode structure.

[0026] In another aspect, the present invention also proposes a thick electrode for lithium-ion batteries. According to an embodiment of the present invention, the active layer thickness of the thick electrode is 100~300 μm; the thick electrode has at least three distinct compositional gradient structures, wherein the content of active material increases from the current collector to the surface layer at a rate of 5~15 percentage points, while the content of conductive agent decreases; the large-aperture, high-density conical pores on the electrode surface layer and the dense, low-conductivity agent region on the bottom layer form an asymmetric spatially coordinated matching structure.

[0027] In another aspect, the present invention also proposes a lithium-ion battery. According to an embodiment of the present invention, the lithium-ion battery comprises a lithium-ion battery thick electrode prepared according to the methods described above, or the lithium-ion battery thick electrode described above.

[0028] According to an embodiment of the present invention, the composition gradient and the tapered aperture array form an asymmetric spatial cooperative match as follows: Composition gradient: Along the electrode thickness direction, the mass fraction of active material increases by 5 to 15 percentage points from the current collector to the surface layer, while the mass fraction of conductive agent decreases accordingly.

[0029] Structural gradient: The geometric parameters of the conical pore array are spatially correlated with the composition gradient. Specifically, in the surface region where active substances are enriched, the pore diameter of the conical pores is the largest (50~80 μm), which significantly reduces the ion transport impedance; while in the bottom layer region where conductive agents are enriched, the pore diameter of the conical pores is the smallest (0~20 μm), so as to construct the most efficient electron conduction network.

[0030] Compared with the prior art, the method of the present invention has at least one of the following significant effects: (1) Overcoming the technical biases in this field, this invention proposes a reverse design concept of "sacrificing local space for global dynamics". Existing technologies usually avoid large-scale pore formation in the surface layer where active materials are most concentrated, believing that it will result in a loss of areal capacity. However, this invention breaks this bias and creatively introduces a conical pore array with the largest pore diameter and the highest distribution density in the surface region where the mass fraction of active materials is highest. Experiments have shown that although it physically occupies local space, it is actually beneficial to improve the overall utilization rate of active materials and areal capacity by completely opening up the ion transport bottleneck and activating the active materials in the bottom layer that were originally ineffective due to polarization.

[0031] (2) A nonlinear synergistic enhancement effect (1+1>2) was generated, ruling out the possibility of simple superposition. The performance improvement of this invention is not a linear summation of the component gradient optimization and the structural pore-forming effect. Experiments show that the improvement of high-ratio performance by introducing component gradient alone or structural gradient alone has a clear ceiling; however, under specific spatial synergistic matching, the performance improvement of this invention far exceeds the expected value of the superposition of the improvement of the above single means. This proves that the component gradient and structural gradient have an unexpected coupling synergistic effect under the specific space defined by this invention.

[0032] (3) The multilayer coating and laser processing technologies used in this invention are both existing mature industrial technologies, with good process compatibility and scalability, easy to realize large-scale continuous production, and have significant economic value and market application scenarios. Attached Figure Description

[0033] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 A schematic diagram of the structure of a thick electrode for a high-performance lithium-ion battery with synergistic gradient enhancement; Figure 2 SEM images of the planar and cross-sectional areas of the thick electrodes obtained in Examples 1-3; Figure 3 SEM images of the planar and cross-sectional areas of the thick electrodes obtained in Comparative Examples 1-4; Figure 4 The Nyquist curves of the thick electrodes obtained in Examples 1-3 and Comparative Examples 1-4 are shown. Figure 5 The rate performance diagrams are for the thick electrodes obtained in Examples 1-3 and Comparative Examples 1-4. Figure 6 The graphs show the cycling performance of the thick electrodes obtained in Examples 1-3 and Comparative Examples 1-4. Detailed Implementation

[0034] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. 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.

[0035] Furthermore, 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 technical features indicated. 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.

[0036] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0037] Example 1 This embodiment provides a method for preparing a high-performance thick electrode for lithium-ion batteries with synergistic gradient enhancement. The specific steps are as follows: S1. Preparation of electrode slurry: Three lithium iron phosphate (LFP) electrode slurries with different mass ratios were prepared. In this embodiment, the mass ratios of the active material, conductive agent, and binder in the three slurries are as follows: Slurry 1: Lithium iron phosphate: Carbon black: PVDF = 75:15:10; Slurry 2: Lithium iron phosphate: Carbon black: PVDF = 80:10:10; Slurry 3: Lithium iron phosphate: Carbon black: PVDF = 90:5:5; Add appropriate amounts of N-methylpyrrolidone (NMP) solvent to the above slurry and stir continuously using a planetary mixer until a uniform, stable, bubble-free electrode slurry with suitable viscosity is formed.

[0038] S2. Layer-by-layer coating to construct a compositional gradient: Slurry 1, slurry 2, and slurry 3 are sequentially coated onto a 12μm thick aluminum foil current collector. After each slurry layer is coated, the electrode is dried to solidify the coating surface and prevent miscibility during subsequent slurry applications. This also avoids the problem of severe electrode cracking due to excessive thickness caused by simultaneous drying of all three slurry layers. The coating thickness of each wet film is 200μm, the coating speed is 50cm / s, and the coating ambient temperature is 30℃, ultimately forming a three-layer continuous compositional gradient.

[0039] S3. Drying and Rolling Treatment: The multi-layer coated electrodes are placed in a 60℃ forced-air drying oven for 12 hours to thoroughly remove residual solvent. This low-temperature, long-duration drying strategy helps the solvent evaporate slowly, effectively preventing problems such as coating cracking and binder migration caused by rapid drying, and ensuring the integrity of the electrode structure. After drying, the electrodes are rolled to improve their mechanical strength and control their porosity. The rolling gap is adjusted to 50% of the electrode thickness.

[0040] S4. Laser processing to construct structural gradient: The thick electrode after roll forming is fixed on the worktable of the nanosecond pulse laser processing equipment. The laser processing parameters are set as follows: laser power 3W, defocusing amount 0 mm, scanning path is an array of holes with a spacing of 100μm, scanning speed 50 mm / s, and processing times for each hole are 15 times.

[0041] Example 2 The preparation method of the high-performance lithium-ion battery thick electrode with synergistic gradient enhancement in this embodiment is basically the same as that in Example 1, except that in step S4, the array holes with a scanning path spacing of 200 μm are scanned.

[0042] Example 3 The preparation method of the high-performance lithium-ion battery thick electrode with synergistic gradient enhancement in this embodiment is basically the same as that in Example 1, except that in step S4, an array of holes with a scanning path spacing of 300 μm is used.

[0043] Comparative Example 1 (Traditional homogeneous without gradient) This comparative example provides a method for fabricating a gradient-free lithium-ion battery thick electrode (traditional homogeneous thick electrode), comprising the following steps: S1. Preparation of slurry 4: Lithium iron phosphate, carbon black and PVDF are dissolved in an appropriate amount of NMP solvent at a mass ratio of 81.67:10:8.33 and stirred thoroughly to obtain slurry 4; S2. Layer-by-layer coating: The operation is basically the same as in step S2 of Example 1, except that the slurry used for each coating layer is slurry 4; S3. Drying and rolling treatment: The operation is the same as step S3 in Example 1.

[0044] Comparative Example 2 (positive composition gradient + unstructured gradient) This comparative example provides a method for preparing a thick electrode for lithium-ion batteries with only a compositional gradient. The steps are basically the same as in Example 2, except that step S4 is not performed after the electrode rolling process.

[0045] Comparative Example 3 (No composition gradient + positive structure gradient) This comparative example provides a method for fabricating a thick electrode for a lithium-ion battery with only structural gradient. The steps are the same as in Comparative Example 2, but with the same laser parameters used to fabricate a large-aperture tapered hole array on the surface.

[0046] Comparative Example 4 (Reverse Component Gradient + Forward Structure Gradient) This comparative example provides a thick lithium-ion battery electrode with decreasing active material content and increasing conductive agent content along the electrode thickness direction, and a low-torsion conical pore array on the surface. Its preparation method is basically the same as in Example 2, except that in step S2, the electrode slurry is coated in the following order: slurry 3, slurry 2, and slurry 1 (i.e., conductive agent is enriched near the separator side, and active material content is high near the current collector side).

[0047] Figure 2 The images show SEM images of the thick electrode plane and cross-section obtained by the preparation methods of Examples 1-3 of the present invention. The SEM images show that a highly ordered array of micropore structures was successfully constructed on the surface and inside of the thick electrode of Examples 1-3 of the present invention. The pore diameter on the electrode surface is about 60 μm and the pore diameter at the bottom is about 23 μm. Figure 3 The images show the planar and cross-sectional SEM images of the thick electrodes obtained in Comparative Examples 1-4.

[0048] Application examples The thick electrodes prepared in Examples 1-3 and Comparative Examples 1-4 were used as positive electrodes, and lithium metal sheets were used as counter electrodes. CR2032 coin-type lithium-ion batteries were assembled in an inert gas protective glove box using 1.2 M LiPF6 (EC:DMC=3:7) electrolyte and Celgard 2325 separator for subsequent electrochemical performance testing.

[0049] Figure 4-6 The Nyquist curve test results of lithium-ion batteries assembled from thick electrodes prepared in Examples 1-3 and Comparative Examples 1-4 are shown, comparing rate performance and cycle performance. Analysis of the results in the figures shows that: (1) The electrode of Comparative Example 1 (traditional homogeneous no gradient) exhibited the largest charge transfer resistance and the worst rate performance and cycling stability. This was mainly due to the obstruction of the ion / electron transport path inside the thick electrode, which led to increased concentration polarization and a significant increase in internal resistance.

[0050] (2) The electrodes of Comparative Example 2 (composition gradient only) and Comparative Example 3 (structural gradient only) showed improvement over Comparative Example 1, but the improvement was limited and there was a clear performance bottleneck. This indicates that relying solely on compositional control and structural pore creation in a single dimension is insufficient to achieve synergistic optimization of the ion / electron transport network inside the electrode.

[0051] (3) The performance of the electrode in Comparative Example 4 (reverse composition + structural gradient) was investigated when the direction of the composition gradient did not match the spatial distribution of the structural gradient. In Comparative Example 4, the conductive agent was enriched and a large pore size was introduced near the membrane side, while the active material was enriched and the pore size was smaller near the current collector side. The data showed that the electrochemical performance of Comparative Example 4 was not only much lower than that of the embodiments of the present invention, but also worse than that of Comparative Example 2 or Comparative Example 3, which only had a single gradient. This indicates that non-specific gradient combinations not only fail to improve performance, but also further degrade the overall kinetic performance by introducing large pores in the core region of the conductive network, which disrupts the electron conduction path, and by insufficient ion channels in the reaction core region.

[0052] (4) The performance of Examples 1-3 of the present invention is significantly higher than that of Comparative Examples 2 and 3, and the performance improvement exhibits a significant nonlinear synergistic enhancement effect. In particular, Example 2 achieved a capacity retention of 77.56% at a 2C rate (far exceeding that of Comparative Examples 2 and 3), with a decay rate of only 1.1% after 100 cycles. This indicates that the present invention effectively promotes electrolyte wetting and shortens the ion diffusion path by constructing a specific spatial synergistic matching structure of "large-pore, high-density ion donor on the surface and small-pore, low-density electron retainer on the bottom layer," while maintaining a highly efficient electron conduction network. This specific matching mechanism breaks through the physical limits of single-gradient design and achieves a significant improvement in the comprehensive electrochemical performance of thick electrodes.

[0053] 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.

[0054] 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 method for preparing a thick electrode for a lithium-ion battery, characterized by, Includes the following steps: S1) Prepare at least three electrode slurries with different component ratios; S2) According to the preset component gradient distribution, different slurries prepared in step S1 are coated layer by layer on the current collector to obtain the electrode. The preset component gradient distribution is as follows: along the electrode thickness direction, the content of active material increases while the content of conductive agent decreases. S3) Roll the electrode obtained in step S2; S4) Laser technology is used to pattern the electrode surface after the rolling process in step S3 to obtain a conical gradient pore array, resulting in a thick electrode for lithium-ion batteries, wherein the composition gradient and the conical pore array form an asymmetric spatial cooperative match.

2. The thick electrode for lithium-ion batteries according to claim 1, wherein The asymmetric spatial cooperative matching means that in the electrode surface region with the highest active material content, the pore diameter of the conical gradient pore structure is the largest and the distribution density is the highest; in the electrode bottom region with the highest conductive agent content, the pore diameter of the conical gradient pore structure is the smallest and the distribution density is the lowest.

3. The thick electrode for lithium-ion batteries according to claim 1, wherein In step S1, the electrode slurry includes an active material, a conductive agent, a binder, and a dispersing solvent; the at least three slurries include slurry 1, slurry 2, and slurry 3, and their coating order is slurry 1, slurry 2, and slurry 3; by mass percentage, The composition of the slurry 1 is: 70%~78% active material, 15%~20% conductive agent, and 10%~15% binder; The composition of the slurry 2 is: 79%~85% active material, 8%~14% conductive agent, and 5%~10% binder; and The composition of the slurry 3 is: 86%~95% active material, 2%~7% conductive agent, and 2%~5% binder; Preferably, the composition of the slurry 1 is: 75% active material, 15% conductive agent, and 10% binder; The composition of the slurry 2 is: 80% active material, 10% conductive agent, and 10% binder; and The composition of the slurry 3 is: 90% active material, 5% conductive agent, and 5% binder; Optionally, in step S2, during the layer-by-layer coating process, the coating sequence is as follows: first apply slurry 1, then apply slurry 2, and finally apply slurry 3; slurry 1 is close to the current collector, and slurry 3 is close to the diaphragm side.

4. The thick electrode for lithium-ion batteries according to claim 3, wherein The thick electrode of the lithium-ion battery is the positive electrode; the active material is one of lithium cobalt oxide, lithium iron phosphate, lithium manganese oxide, ternary materials, and lithium-rich manganese-based materials; the conductive agent is one of carbon black, carbon nanotubes, graphene, and other novel conductive agents; the binder is one of polyvinylidene fluoride, hydroxymethyl cellulose, styrene-butadiene rubber latex, polyacrylic acid, and other novel multifunctional binders; the dispersion solvent includes one of organic solvent systems, aqueous solvent systems, and mixed solvent systems. Optionally, the thick electrode of the lithium-ion battery is the negative electrode; the active material is one of graphite, silicon-based materials, lithium titanate, and metal oxides; the conductive agent is one of carbon black, carbon nanotubes, graphene, and other novel conductive agents; the binder is one of hydroxymethyl cellulose, styrene-butadiene rubber latex, polyacrylic acid, and other high-viscosity polymers; and the dispersing solvent includes one of aqueous solvents, organic solvent systems, and mixed solvent systems.

5. The thick electrode for lithium-ion batteries according to claim 1, wherein In step S2, during the layer-by-layer coating process, after each layer is coated, an independent intermediate drying treatment is performed to form a cured interface. The intermediate drying treatment is carried out at a temperature of 40~60℃ for 10~30 minutes. Optionally, during the layer-by-layer coating process, the wet coating thickness of each electrode layer is 50~500μm, preferably 200~500μm.

6. The thick electrode for lithium-ion batteries according to claim 1, wherein In step S3, the roller gap of the roller pressing process is 40% to 80% of the total thickness of the composition gradient electrode after drying, preferably 40% to 60%.

7. The thick electrode for a lithium-ion battery according to claim 1, characterized in that, In step S4, the laser technology uses a nanosecond pulsed laser system with the following processing parameters: pulse width 80 ns, frequency 30 kHz, defocusing amount 0~3 mm, laser power 1.5~4.5 W, processing speed 50~200 mm / s, and processing times 10~50 times. Preferably, the processing parameters are: laser power 3W, defocusing amount 0 mm, scanning path is an array of holes with a spacing of 100μm-300μm, scanning speed 50 mm / s, and processing times for each hole are 15 times.

8. The thick electrode for a lithium-ion battery according to claim 1, characterized in that, In step S4, the conical gradient pore structure is a series of conical gradient pore structures that are perpendicular to the electrode surface, with the pore openings facing the diaphragm and the pore bottoms extending into the electrode interior. Optionally, in step S4, the diameter of the pores in the surface region of the tapered gradient pore structure is 50~80 μm, the diameter of the pores in the bottom region is 0~20 μm, and the pore density is 1000~10000 pores / cm². Optionally, the active layer thickness of the lithium-ion battery thick electrode is 100~300 μm; Optionally, the pore depth of the tapered gradient pore structure is 70% to 100% of the final thickness of the thick electrode of the lithium-ion battery.

9. A thick electrode for a lithium-ion battery, characterized in that, The active layer thickness of the lithium-ion battery thick electrode is 100~300 μm; the lithium-ion battery thick electrode has at least three distinct compositional gradient structures, wherein the content of active material increases from the current collector to the surface layer by 5~15 percentage points, while the content of conductive agent decreases; the large-aperture high-density conical pores on the electrode surface layer and the dense low-conductivity agent region at the bottom layer form an asymmetric spatial synergistic matching structure.

10. A lithium-ion battery, characterized in that, The lithium-ion battery thick electrode prepared by the method according to any one of claims 1-8 or the lithium-ion battery thick electrode according to claim 9.

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