A processing technology and electrode sheet for improving the interlayer peel strength of energy storage cell electrodes

Abstract

This invention discloses a processing technology and electrode sheet for improving the interlayer peel strength of energy storage cell electrodes. The processing technology includes the following steps: preparing a coating slurry by multi-stage dispersion treatment of a slurry; performing surface activation treatment on a current collector to form a rough surface; coating the current collector with the coating slurry to form a coating layer, wherein the binder concentration in the coating layer is distributed in a concentration gradient, with the binder concentration on the side closer to the current collector being higher than that on the side farther from the current collector; performing multi-stage drying treatment on the coated electrode sheet; applying an interface reinforcing agent to the surface of the dried electrode sheet and performing pressure heat treatment to allow the interface reinforcing agent to act on the interface region between the coating layer and the current collector; and performing calendering treatment on the electrode sheet after interface reinforcement treatment. This invention significantly improves the electrode sheet peel strength through the synergistic design of each process, improves the mechanical stability and cycle performance of the battery, and effectively solves the technical problem of insufficient interlayer peel strength of the electrode sheet.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion energy storage battery manufacturing technology, and particularly relates to a processing technology and electrode sheet for improving the interlayer peel strength of energy storage cell electrode sheets. Background Technology

[0002] As a core energy storage device, the performance and reliability of lithium-ion batteries are highly dependent on the structural integrity of the electrodes. Among these, the interlayer peel strength—the bonding force between the active material coating and the metal current collector (such as aluminum or copper foil)—is a key indicator for assessing this integrity. Insufficient peel strength can directly lead to serious consequences: during battery manufacturing, the coating is prone to peeling off during rolling, slitting, or winding, generating dust, reducing yield, and introducing short-circuit risks; during long-term battery cycling, especially under conditions of high-rate charging and discharging accompanied by changes in the volume of the active material, the fragile interface is prone to localized peeling, resulting in a surge in internal resistance, accelerated capacity decay, and a significant increase in the safety hazard of thermal runaway.

[0003] To improve peel strength, existing technologies typically employ discrete process optimization strategies, such as: rigorously screening raw materials (active substances, conductive agents, binders) and controlling their physical properties; cleaning or simple surface roughening of the current collector; using high-precision coating equipment to ensure coating uniformity; and optimizing drying and rolling process parameters. However, these conventional methods have inherent limitations: First, they lack systematicity, with each step being optimized independently, making it difficult to achieve synergistic effects and potentially even hindering each other; second, the interface strengthening methods are crude, whether it's physical roughening of the current collector or relying on the natural distribution of the binder in the slurry, it's difficult to actively construct an ideal interface structure with both high bonding strength and good conductivity at the microscale; third, the precision of key process control is insufficient, conventional drying processes cannot accurately control the gradient distribution of the binder in the coating thickness direction (especially the interface region), and the shear stress generated by traditional rolling processes in pursuit of high compaction density may damage the already formed fragile interface bond.

[0004] Therefore, existing technical solutions are mostly "point-like" optimizations targeting a single link, failing to carry out systematic collaborative design and precise control of the entire process from slurry formulation design, current collector interface modification, coating structure, drying kinetics to post-processing enhancement. This results in a bottleneck in improving the electrode peel strength, making it difficult to meet the stringent requirements of next-generation energy storage batteries with high energy density, long cycle life, and high safety.

[0005] In view of this, the present invention provides a processing technology to improve the interlayer peel strength of the electrode sheets in energy storage cells. Summary of the Invention

[0006] The purpose of this invention is to provide a processing technology to improve the interlayer peel strength of the electrode sheets in energy storage cells, addressing the shortcomings of existing technologies. This process systematically optimizes the interface structure between the coating and the current collector from the source through the coordinated design of steps such as multi-stage dispersion slurry preparation, current collector surface activation treatment, gradient coating, multi-stage drying, interface enhancement treatment, and calendering treatment, significantly improving the interlayer peel strength of the electrode sheets and enhancing the mechanical stability and cycle performance of the battery.

[0007] To achieve the above objectives, the present invention provides the following technical solution: A processing method for improving the interlayer peel strength of electrode sheets in energy storage cells includes the following steps: S1. Slurry preparation: The slurry containing active materials, conductive agents, binders and solvents is subjected to multi-stage dispersion treatment to obtain coating slurry; S2. Surface activation treatment: The current collector is subjected to surface activation treatment to form a rough surface with uneven texture. S3. Gradient coating: The coating slurry is coated onto the current collector after surface activation treatment to form a coating, and the binder in the coating forms a concentration gradient distribution, wherein the binder concentration on the side closer to the current collector is higher than that on the side farther away from the current collector; S4. Multi-stage drying: The coated electrode sheet is dried in multiple stages. S5. Interface enhancement treatment: An interface enhancer is applied to the surface of the dried electrode and subjected to pressure heat treatment, so that the interface enhancer acts on the interface region between the coating and the current collector; the interface enhancer includes organic polymer, conductive agent, crosslinking agent, penetrating agent and solvent; S6. Rolling treatment: The electrode sheet after interface strengthening treatment is rolled.

[0008] Preferably, the multi-stage dispersion process in S1 includes a first-stage dispersion stage, a second-stage dispersion stage, and a third-stage dispersion stage performed sequentially. The first-stage dispersion stage operates at a rotation speed of 2000-4000 rpm for 10-20 minutes; the second-stage dispersion stage operates at a rotation speed of 5000-8000 rpm for 8-15 minutes; and the third-stage dispersion stage operates at a rotation speed of 9000-12000 rpm for 3-6 minutes. There is a 3-5 minute settling interval between adjacent dispersion stages.

[0009] Preferably, the surface activation treatment in S2 adopts one or more of the following methods: plasma treatment, chemical etching treatment, micro / nano coating treatment, and ultrasonic-assisted treatment.

[0010] Preferably, the plasma treatment uses oxygen or argon plasma with a power of 100-300W and a treatment time of 10-60 seconds; the chemical etching treatment uses an acidic or alkaline solution with a concentration of 0.5-3wt% and an etching time of 10-60 seconds; the micro / nano coating treatment uses a dispersion of nano-silica, alumina, or carbon nanotubes with a coating thickness of 0.1-1μm; and the ultrasonic-assisted treatment has a frequency of 20-60kHz, a power of 50-200W, and a treatment time of 5-30 seconds.

[0011] Preferably, the gradient coating in S3 is achieved by a double-slit coating head, wherein the binder content in the slurry flowing out of the first slit near the current collector is higher than the binder content in the slurry flowing out of the second slit away from the current collector.

[0012] Preferably, in step S3, the resulting adhesive concentration gradient distribution satisfies the following relationship: C1 / C2 = 1.2~2.5 Wherein, C1 is the mass concentration of the binder in the coating on the side closer to the current collector, and C2 is the mass concentration of the binder in the coating on the side farther from the current collector.

[0013] Preferably, the multi-stage drying in S4 includes a low-temperature slow drying stage, a medium-temperature fast drying stage, and a high-temperature setting stage performed sequentially; wherein, the temperature of the low-temperature slow drying stage is 50~70℃, the time is 1~3 minutes, and the wind speed is 0.5~1.5m / s; the temperature of the medium-temperature fast drying stage is 80~100℃, the time is 1~2 minutes, and the wind speed is 1.5~3m / s; the temperature of the high-temperature setting stage is 110~140℃, the time is 2~5 minutes, and the wind speed is 0.8~2m / s.

[0014] Preferably, the interface enhancer in S5 comprises, by weight, the following components: 20-50 parts organic polymer, 5-15 parts conductive agent, 3-10 parts crosslinking agent, 2-8 parts penetration aid, and 100-200 parts solvent; The organic polymer is an organosilicon-modified acrylate; the conductive agent is selected from one or more of conductive carbon black, graphite, and carbon nanotubes; the crosslinking agent is selected from one or more of isocyanate crosslinking agents, epoxy resin crosslinking agents, and organosilane crosslinking agents; the penetrating aid is selected from one or more of sodium dodecylbenzenesulfonate, sodium lauryl sulfate, sodium stearate, hexadecyltrimethylammonium bromide, lauryl polyether, polyethylene glycol stearate, ethanol, isopropanol, ethylene glycol monomethyl ether, and ethylene glycol dimethyl ether; the solvent is selected from one or more of N-methylpyrrolidone, acetone, tetrahydrofuran, water, isopropanol, and ethanol.

[0015] Preferably, the pressurized heat treatment in S5 is carried out by hot roller pressing, with a pressure of 0.5~3MPa, a temperature of 60~120℃, and a treatment time of 5~30 seconds.

[0016] Preferably, the calendering process in S6 adopts a differential rolling method, with the linear speed ratio of the upper roll to the lower roll being 1.01~1.10:1, the rolling pressure being 50~200MPa, and the rolling temperature being 50~120℃; Preferably, the calendering process in S6 further includes ultrasonic-assisted vibration, with an ultrasonic frequency of 20~60kHz and an amplitude of 10~50μm.

[0017] Preferably, in step S1, the slurry further contains 0.5-3 wt% of an interfacial coupling agent, wherein the interfacial coupling agent is selected from one or more of silane coupling agents, titanate coupling agents, and aluminate coupling agents.

[0018] Preferably, during the coating process of S3, a tension of 10~50N is applied to the current collector, and the direction of travel of the current collector is at an angle of 85°~89° with the coating direction.

[0019] Preferably, between S3 and S4, a further step S3' is included: primary drying and shaping, in which the coated electrode is dried for a short time using infrared radiation, with an infrared radiation power density of... The processing time is 10-30 seconds.

[0020] In addition, the present invention also provides an electrode sheet prepared by the process described above, wherein the electrode sheet has a 180° peel strength of not less than 30 N / m; preferably 35.7~42.3 N / m.

[0021] Compared with the prior art, the present invention has at least the following beneficial effects: 1) This invention achieves uniform dispersion and stable distribution of slurry components through a multi-stage dispersion process in step S1. Compared to traditional single dispersion processes, multi-stage dispersion employs a sequence of shear forces from low to high, which can gradually break down large particle agglomerates without damaging the material structure, while ensuring the uniform distribution of small particles (especially binder particles). This refined dispersion process ensures the uniform distribution of the binder in the slurry, laying a material foundation for improving the subsequent interfacial bonding strength.

[0022] 2) This invention innovatively employs a surface activation treatment technology for the current collector through step S2, altering the morphology and chemical properties of the current collector surface at the microscale. The surface activation treatment creates a rough, uneven surface and active functional groups on the current collector surface, significantly increasing the interfacial contact area and chemical bonding points, providing ideal conditions for the mechanical interlocking and chemical bonding between the coating and the current collector. This microscale interface design, compared to traditional simple cleaning treatments, fundamentally improves the interfacial bonding strength.

[0023] 3) The gradient coating technology designed in step S3 of this invention achieves a gradient distribution of binder concentration along the thickness direction in the coating, resulting in a higher binder concentration near the current collector than on the side farther away. This reverse gradient design is the opposite of the binder floating phenomenon caused by drying in traditional coating processes, effectively increasing the binder content in the interface area, thereby strengthening the adhesion between the coating and the current collector.

[0024] 4) The present invention employs a multi-stage drying process in step S4, which precisely controls the temperature and wind speed in three stages: low-temperature slow drying, medium-temperature fast drying, and high-temperature setting. This achieves precise control over the migration behavior of the binder, effectively preventing the phenomenon of a large amount of binder floating to the coating surface in traditional constant-temperature drying, maintaining the ideal concentration gradient distribution established in step S3, and significantly improving the interfacial bonding strength.

[0025] 5) This invention innovatively introduces an interface enhancement process through step S5. An interface enhancer containing an organic polymer, a conductive agent, a crosslinking agent, a penetrating agent, and a solvent is applied to the electrode surface, combined with pressure heat treatment. This allows the enhancer to penetrate into the interface region between the coating and the current collector, forming a chemically bonded reinforced interface layer. The organic polymer provides excellent adhesion and flexibility; the conductive agent ensures that the electronic conduction pathway is not affected; the crosslinking agent promotes interfacial chemical bonding; and the penetrating agent ensures that the enhancer can effectively penetrate into the interface region. This interface-specific enhancement treatment is not available in traditional processes and can achieve a breakthrough improvement in peel strength.

[0026] 6) Through the calendering process in step S6, this invention improves the density of the coating and, by applying pressure to the coating, makes the coating material and the current collector more closely contact each other. Combined with the synergistic effect of the aforementioned steps, the interfacial bonding between the coating and the current collector is further strengthened and enhanced.

[0027] By combining the synergistic effects of the above innovative processes, this invention achieves a significant improvement in electrode peel strength. Compared with electrodes prepared by traditional processes, the peel strength can be increased by more than 50%, providing a new technical path for improving the performance and safety of lithium-ion batteries. Detailed Implementation

[0028] 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.

[0029] According to a first aspect of this application, this application provides a processing method for improving the interlayer peel strength of electrode sheets in energy storage cells, comprising the following steps: S1. Slurry preparation: The slurry containing active materials, conductive agents, binders and solvents is subjected to multi-stage dispersion treatment to obtain coating slurry; S2. Surface activation treatment: The current collector is subjected to surface activation treatment to form a rough surface with uneven texture. S3. Gradient coating: The coating slurry is applied to the current collector after surface activation treatment to form a coating layer, and the binder in the coating layer forms a concentration gradient distribution, wherein the binder concentration on the side closer to the current collector is higher than that on the side farther away from the current collector. S4. Multi-stage drying: The coated electrode sheet is dried in multiple stages. S5. Interface enhancement treatment: An interface enhancer is applied to the surface of the dried electrode and subjected to pressure heat treatment so that the interface enhancer acts on the interface area between the coating and the current collector; the interface enhancer includes organic polymers, conductive agents, crosslinking agents, penetrating agents and solvents; S6. Rolling treatment: The electrode sheet after interface strengthening treatment is rolled.

[0030] In one embodiment of this application, the multi-stage dispersion process in S1 includes a first-stage dispersion stage, a second-stage dispersion stage, and a third-stage dispersion stage performed sequentially. The rotation speed of the first-stage dispersion stage is 2000~4000 rpm, and the time is 10~20 minutes; the rotation speed of the second-stage dispersion stage is 5000~8000 rpm, and the time is 8~15 minutes; the rotation speed of the third-stage dispersion stage is 9000~12000 rpm, and the time is 3~6 minutes; there is a settling interval of 3~5 minutes between adjacent dispersion stages.

[0031] Multi-stage dispersion is a crucial process step in this invention. Through extensive experimental research, the inventors discovered the following shortcomings of traditional single-speed dispersion: While high-speed dispersion can quickly break up large agglomerates, it also generates excessive shear force, potentially damaging the molecular chain structure of the binder and reducing its adhesive properties. Furthermore, the heat generated by high-speed shearing accelerates solvent evaporation, leading to unstable slurry viscosity. Conversely, low-speed dispersion alone fails to completely disperse large agglomerates, affecting the uniformity of the slurry.

[0032] The multi-level distributed strategy employed in this invention has the following working principle and advantages: Primary dispersion stage (2000~4000 rpm, 10~20 minutes): This stage uses a lower rotation speed and a longer time. The main purpose is to allow the components to initially mix and wet, and to break up loose agglomerates with larger particle sizes. Low-speed dispersion generates less shear force, which will not damage the microstructure of the material, while providing sufficient contact and wetting time for each component. Planetary mixers or double planetary mixers can be used for dispersion. The ratio of the impeller diameter to the mixing tank diameter is 0.4~0.6, which is beneficial for the full flow and mixing of the slurry.

[0033] Secondary dispersion stage (5000~8000 rpm, 8~15 minutes): In this stage, the rotation speed is increased, and the shear force is increased to further disperse medium-sized agglomerates, significantly reducing the dispersed particle size of each component in the slurry. A high-speed disperser with a dispersion disc diameter of 40~60mm and a serrated design can be used for this stage to generate strong turbulence and shear force, effectively dispersing medium-sized agglomerates.

[0034] The third-stage dispersion stage (9000~12000 rpm, 3~6 minutes): This stage uses the highest rotation speed but the shortest time. Its main purpose is to achieve final fine dispersion of the slurry, eliminating residual micro-agglomerates and achieving a uniform, nanoscale dispersion. The strong shear force generated by the high rotation speed effectively breaks down micro-agglomerates, but due to the short duration, it does not cause significant damage to the molecular chain structure of the binder. An ultrasonic disperser can be used as an auxiliary method in this stage, with an ultrasonic frequency of 20~40kHz and a power of 100~300W, to further improve the dispersion effect.

[0035] The settling interval (3-5 minutes) between each dispersion stage is also crucial. During settling, the stress accumulated inside the slurry is released, preventing the material from re-agglomerating due to stress. At the same time, maintaining low-speed stirring (100-300 rpm) during settling prevents particle sedimentation and allows air bubbles generated during the dispersion process to rise and escape, improving the uniformity and stability of the slurry.

[0036] The dispersion equipment is a high-speed disperser, which consists of a high-speed spindle, a dispersion disc, a mixing container, a variable frequency speed control system, and a temperature control system. The spindle is driven by a variable frequency motor, with a speed that can be steplessly adjusted within the range of 500~15000 rpm. The dispersion disc is made of hard alloy material, offering good wear resistance, and its surface has a serrated structure to generate strong shearing force. The mixing container is made of stainless steel with a jacketed outer wall, and its temperature is controlled by circulating cooling water to prevent the slurry temperature from becoming too high during dispersion. The temperature control system includes a temperature sensor, a circulating water pump, and a heat exchanger, which can control the slurry temperature within the range of 25±5℃.

[0037] Through comparative experiments, the inventors discovered that the binder dispersion uniformity (D90 / D50 value measured by a laser particle size analyzer) of the slurry treated with multi-stage dispersion was reduced by 30% to 50% compared to the slurry treated with single dispersion, indicating that the binder particles had a more uniform and concentrated particle size distribution. The uniformly dispersed binder can better form a uniform bonding interface with the current collector surface during subsequent coating, avoiding uneven interfacial bonding caused by localized enrichment or absence of binder, thereby improving the overall peel strength of the electrode.

[0038] In one embodiment of this application, in S1, different active materials, conductive agents, binders and solvents are selected according to the need to prepare a positive or negative electrode.

[0039] For the cathode slurry, the active material can be one or more of NCM811 (lithium nickel cobalt manganese oxide), LFP (lithium iron phosphate), and NCA (lithium nickel cobalt aluminum oxide); the conductive agent can be one or more of conductive carbon black (such as Super P, Ketjen black, etc.), graphite (such as KS-6, etc.), and carbon nanotubes; the binder can be PVDF (polyvinylidene fluoride); and the solvent can be NMP (N-methylpyrrolidone). The typical proportions of the components in the cathode slurry are: active material 92~97wt%, conductive agent 1~4wt%, and binder 1~4wt% (based on solid content).

[0040] For the negative electrode slurry, the active material can be one or more of artificial graphite, natural graphite, and silicon-carbon composite materials; the conductive agent can be conductive carbon black (such as Super P); the binder can be a mixture of SBR (styrene-butadiene rubber) and CMC (sodium carboxymethyl cellulose); and the solvent can be deionized water. A typical ratio of components in the negative electrode slurry is: active material 93~97wt%, conductive agent 0.5~3wt%, SBR 1~3wt%, and CMC 0.5~2wt% (based on solid content).

[0041] In one embodiment of this application, in S1, 0.5 to 3 wt% of an interfacial coupling agent is added to the slurry. The interfacial coupling agent is selected from one or more of silane coupling agents, titanate coupling agents, and aluminate coupling agents.

[0042] The addition of interfacial coupling agents is a preferred method to further improve peel strength. Interfacial coupling agents are a class of organic compounds with two or more different reactive groups. One end of their molecules can chemically react or physically adsorb with inorganic materials (such as active material particles or current collector metal surfaces), while the other end can chemically react or compatibly mix with organic materials (such as adhesive polymer chains), thereby building a "molecular bridge" between the inorganic-organic interface and significantly enhancing the bonding force between the two phases.

[0043] Specifically, the alkoxy end of silane coupling agents (such as γ-aminopropyltriethoxysilane KH-550, γ-methacryloyloxypropyltrimethoxysilane KH-570, etc.) can react with the hydroxyl groups on the surface of metal oxides after hydrolysis to form Si-OM covalent bonds (M is Al or Cu), while the amino or acryloyl groups at their organic ends can form chemical bonds or strong interactions with binders such as PVDF or SBR; titanate coupling agents (such as isopropyltris(dioctylpyrophosphoryloxy)titanate, etc.) and aluminate coupling agents also have similar bifunctional properties, and they are bonded to inorganic surfaces through titanium oxide bonds and aluminum oxide bonds, respectively.

[0044] The interfacial coupling agent is preferably added to the slurry during the settling interval after the secondary dispersion stage. After appropriate stirring (500-1000 rpm, 3-5 minutes) to ensure uniform distribution, it then proceeds to the tertiary dispersion stage. This timing of addition takes into account the following factors: if added during the primary dispersion stage, the coupling agent may be deactivated or degraded due to subsequent high-speed shearing; if added after the tertiary dispersion stage, the slurry viscosity is already high, making it difficult to uniformly disperse the coupling agent. Adding it after the secondary dispersion stage ensures both uniform distribution of the coupling agent and avoids damage to its functional groups due to excessive shearing.

[0045] Through experiments, the inventors discovered that the electrode prepared by adding 1.5 wt% silane coupling agent KH-570 to the positive electrode slurry had a peel strength that was 15% to 25% higher than that of the electrode without the coupling agent. This indicates that the "molecular bridge" effect formed by the interfacial coupling agent between the active material / conductive agent and the binder, as well as between the binder and the current collector, has a significant contribution to improving the interfacial bonding strength.

[0046] In one embodiment of this application, the surface activation treatment in S2 is performed using one or more of the following methods: plasma treatment, chemical etching treatment, micro / nano coating treatment, and ultrasonic-assisted treatment.

[0047] Surface activation treatment of the current collector is one of the key innovations of this invention. Its purpose is to alter the morphology and chemical properties of the current collector surface at the microscale, increasing the interfacial contact area and chemical bonding points, thus creating conditions for a strong bond between the current collector and the subsequent coating. The inventors discovered that traditional current collectors, after simple cleaning and direct coating, have relatively smooth and chemically inert surfaces. Their bonding with the coating mainly relies on physical adsorption, resulting in limited bonding strength that easily decays during long-term cycling. However, surface activation treatment achieves the following effects: (a) increasing surface micro-roughness, creating an "anchor effect," allowing the coating slurry to penetrate into micro-pits and pores, forming a mechanically interlocking structure after drying, significantly improving bonding strength; (b) introducing active functional groups (such as -OH, -COOH, ...) onto the surface. (etc.), providing reaction sites for chemical reactions with binders or interface reinforcing agents, forming chemical bonds, and further enhancing interfacial bonding.

[0048] The various surface activation treatment methods are explained in detail below: Plasma treatment uses oxygen or argon plasma, with a processing power of 100-300W and a processing time of 10-60 seconds. The plasma treatment equipment consists of a plasma generator, a gas supply system, a treatment chamber, and a control system. Plasma treatment can introduce active functional groups such as hydroxyl and carboxyl groups onto the surface of the current collector, while simultaneously removing surface organic contaminants, increasing surface energy, and improving adhesion to coatings. For aluminum foil current collectors, oxygen plasma treatment is more effective; for copper foil current collectors, argon plasma treatment is more suitable.

[0049] Chemical etching uses an acidic or alkaline solution with a concentration of 0.5–3 wt% for an etching time of 10–60 seconds. For aluminum foil, a dilute NaOH solution can be used for alkaline etching; for copper foil, a dilute NaOH solution can be used for alkaline etching. Acidic etching is performed using a solution. Chemical etching can create microscopic pits and rough structures on the surface of the current collector, increasing the contact area for mechanical bonding. After etching, thorough cleaning and drying are required to remove residual reagents.

[0050] The micro / nano coating treatment uses dispersions of nano-silica, alumina, or carbon nanotubes, with a coating thickness of 0.1–1 μm. The micro / nano coating is applied to the current collector surface via dip-coating or spraying, forming an intermediate layer with a high specific surface area, significantly increasing the interfacial contact area. Nano-silica and alumina possess good chemical stability and mechanical strength, making them suitable for various types of current collectors; carbon nanotubes, on the other hand, exhibit excellent electrical conductivity, making them particularly suitable for high-power batteries.

[0051] Ultrasonic-assisted treatment operates at frequencies of 20–60 kHz, power of 50–200 W, and processing times of 5–30 seconds. Ultrasonic treatment generates microscopic vibrations and cavitation effects on the surface of the current collector, removing loose surface materials and simultaneously creating microscopic deformations that increase surface roughness. Ultrasonic treatment is often combined with chemical cleaning or etching processes to significantly improve processing efficiency and uniformity.

[0052] The aforementioned surface activation treatments can be used individually or in combination. For example, chemical etching followed by plasma treatment, and finally micro / nano coating treatment, can alter the surface properties of the current collector at different scales, achieving optimal interfacial bonding.

[0053] In one embodiment of this application, after surface activation treatment, the surface roughness Ra of the current collector in S2 is 0.2~1.0 μm. Surface roughness Ra is an important parameter for measuring the microstructure of a surface, defined as the arithmetic mean of the deviation of the surface profile from the centerline within a sampling length. The inventors have found that when the surface roughness Ra of the current collector is below 0.2 μm, the surface is too smooth, the mechanical interlocking effect is not obvious, and the improvement in interfacial bonding force is limited; when Ra is above 1.0 μm, the surface is too rough, and the coating slurry may not be able to completely fill the deep pits, resulting in void defects at the interface, which in turn reduces the bonding force. When Ra is in the range of 0.2~1.0 μm, the current collector surface forms an appropriate micro-rough structure, providing sufficient mechanical interlocking area for the coating, while not producing obvious interfacial defects, which is the optimal surface state. The surface roughness is measured using atomic force microscopy (AFM) or a contact profilometer.

[0054] In one embodiment of this application, the gradient coating in S3 is achieved by a double-slit coating head, wherein the binder content in the slurry flowing out of the first slit near the current collector is higher than the binder content in the slurry flowing out of the second slit away from the current collector.

[0055] Gradient coating is another important innovation of this invention. Traditional coating processes use a single-component slurry for coating. During the drying process, as the solvent evaporates from the coating surface, a solvent concentration gradient is formed, causing the binder to migrate to the surface with the solvent (i.e., the "binder floating phenomenon"). Ultimately, the binder content on the side closer to the current collector is lower than that on the side farther away from the current collector, which is one of the important reasons for insufficient interfacial peel strength.

[0056] This invention achieves the active construction of a binder concentration gradient through a double-slit coating head. The double-slit coating head is a coating device with two independent feed chambers and two discharge slits, its structure including an upper module, a middle partition, and a lower module. A second slit (away from the current collector side) is formed between the upper module and the middle partition, and a first slit (closer to the current collector side) is formed between the middle partition and the lower module. The two slits are fed by independent feeding systems, allowing the use of slurries with different binder contents.

[0057] The slurry flowing from the first slot (high binder concentration slurry) is first applied to the surface of the current collector, forming a binder-rich underlayer; the slurry flowing from the second slot (low binder concentration slurry) is then applied on top of the underlayer, forming a lower binder content upper layer. Due to the interdiffusion between the two slurry layers in a wet state, the final coating exhibits a continuous binder concentration gradient that gradually decreases from the current collector side to the surface side, rather than obvious interfacial delamination.

[0058] Key parameters of the double-slit coating head include: slit width (0.1~0.5mm), slit spacing (distance between two slits in the coating direction, 5~20mm), coating speed (1~10m / min), and coating gap (distance between the coating head and the current collector, 100~500μm). The optimized combination of these parameters determines the shape and magnitude of the binder concentration gradient in the coating. The feeding system uses a precision metering pump with a flow accuracy of ±0.5%, ensuring a stable and consistent coating amount for both layers of slurry.

[0059] In one embodiment according to this application, in S3, the resulting adhesive concentration gradient distribution satisfies the following relationship: C1 / C2 = 1.2~2.5 Wherein, C1 is the mass concentration of the binder in the coating on the side closer to the current collector, and C2 is the mass concentration of the binder in the coating on the side farther from the current collector.

[0060] The inventors determined the optimal range of C1 / C2 through extensive experimental research. When C1 / C2 is below 1.2, the concentration gradient is too small, the binder enrichment effect near the current collector side is not obvious, and the improvement in peel strength is limited compared with traditional uniform coating. When C1 / C2 is above 2.5, the concentration gradient is too large, and the high content of the bottom binder leads to the following problems: (a) the content of active materials and conductive agents in the bottom layer is relatively reduced, affecting the electronic conduction and ion transport performance of the coating bottom; (b) the high content of the bottom binder may cause excessive elastic deformation in this area during rolling, affecting the compaction uniformity of the coating; (c) the low content of the top binder may lead to insufficient mechanical strength of the top coating, making it prone to cracking and powdering during rolling and slitting.

[0061] When the C1 / C2 ratio is in the range of 1.2 to 2.5, the coating can ensure that there is enough binder in the interface area to provide strong adhesion, and can also ensure the overall electrochemical and mechanical properties of the coating, which is the optimal concentration gradient range.

[0062] The method for verifying the binder concentration gradient is as follows: After the coating and drying, the electrode is cut along the thickness direction using a focused ion beam (FIB). Then, elemental analysis is performed at different depths of the coating cross-section by energy dispersive spectroscopy (EDS) or X-ray photoelectron spectroscopy (XPS). The existence and distribution of the concentration gradient are confirmed by detecting the changes in the content of characteristic elements in the binder (such as F in PVDF).

[0063] In one embodiment of this application, during the coating process of S3, a tension of 10 to 50 N is applied to the current collector, and the direction of travel of the current collector is at an angle of 85° to 89° with the coating direction.

[0064] Appropriate tension and angle settings ensure a smooth current collector surface, reducing wavy deformation, and also facilitate uniform distribution and adhesion of the slurry on the surface. Tension control employs a precision tension control roller, with a tension sensor (accuracy ±0.1N) monitoring the tension value in real time. A PID controller automatically adjusts the torque output of the tension roller motor to maintain constant tension.

[0065] The included angle setting refers to the angle between the travel direction of the current collector and the discharge direction of the coating head when it passes through the coating head. When the included angle is 90°, the current collector is completely perpendicular to the coating direction, and the slurry is directly "pressed" onto the current collector from the coating head. When the included angle is slightly less than 90° (85°~89°), the current collector faces the slurry flow at a small angle. This setting has the following advantages: (a) it generates a small drag force, which helps the slurry spread better on the surface of the current collector and reduces air bubble entrainment; (b) it slightly increases the contact time between the slurry and the surface of the current collector, which is beneficial for the slurry to penetrate into the micro-pits formed after surface activation treatment and enhances mechanical interlocking. The included angle is controlled by an adjustable guide roller, which is mounted on a precision angle adjustment mechanism and can adjust the angle with an accuracy of 0.1°.

[0066] When the tension is below 10N, the current collector is prone to relaxation and wavy deformation during its travel, resulting in uneven coating thickness. When the tension is above 50N, the current collector may undergo plastic tensile deformation (especially thinner copper foil), causing the electrode to curl after the tension is released. When the included angle is less than 85°, an excessively large angle may cause the slurry to form an uneven flow pattern on the surface of the current collector. When the included angle is greater than 89°, close to 90°, the dragging effect is not obvious, and it is not much different from traditional coating.

[0067] In one embodiment according to this application, between S3 and S4, a step S3' is further included: primary drying and shaping, in which the coated electrode is dried for a short time using infrared radiation, with an infrared radiation power density of... The processing time is 10-30 seconds.

[0068] The purpose of primary drying and setting is to quickly "pre-cure" the coating immediately after coating, remove 5% to 15% of the surface solvent, and allow the coating to form a preliminary gel network structure to prevent coating deformation and adhesive migration caused by vibration, airflow or gravity during subsequent transfer to multi-stage drying equipment.

[0069] The working principle of infrared radiation drying is as follows: the mid-wave infrared radiation (wavelength 2~4μm) emitted by the infrared lamp is selectively absorbed by solvent molecules (NMP or water) in the coating, converting them into molecular vibrational energy and thermal energy, allowing the solvent molecules to gain sufficient kinetic energy to escape from the coating surface. Since infrared radiation is a non-contact heating method and the energy is concentrated on the coating surface, it does not significantly affect the internal temperature of the coating. Therefore, it can quickly remove surface solvents without disturbing the distribution of the internal binder.

[0070] The infrared drying equipment consists of a mid-wave infrared lamp array. The lamps are made of quartz and filled with halogen gas. The rated power density can reach [missing information]. Adjustable within a certain range. The lamp installation height is 150~200mm from the electrode surface, arranged along the coating direction, with a coverage length of 300~800mm (determined according to processing time and conveyor speed). The control system monitors the electrode surface temperature in real time through thermocouples and infrared temperature sensors, and adjusts the lamp power accordingly to ensure that the surface temperature does not exceed 80℃ (to prevent the coating surface from drying excessively and forming a hard shell, which would hinder the subsequent escape of internal solvents).

[0071] When the infrared radiation power density is lower than When the drying efficiency is too low, the coating remains in a fluid state during transport, making it prone to deformation; when the power density is higher than... If the surface dries too quickly, a dense "shell" may form, hindering the evaporation of the internal solvent during subsequent multi-stage drying, leading to internal bubbles or pore defects. A processing time of 10-30 seconds is the optimal range determined based on the conveyor belt speed and the length of the drying section.

[0072] In one embodiment of this application, the multi-stage drying in S4 includes a low-temperature slow drying stage, a medium-temperature fast drying stage, and a high-temperature setting stage performed sequentially; wherein, the temperature of the low-temperature slow drying stage is 50~70℃, the time is 1~3 minutes, and the wind speed is 0.5~1.5m / s; the temperature of the medium-temperature fast drying stage is 80~100℃, the time is 1~2 minutes, and the wind speed is 1.5~3m / s; the temperature of the high-temperature setting stage is 110~140℃, the time is 2~5 minutes, and the wind speed is 0.8~2m / s.

[0073] Multi-stage drying is another important innovation of this invention. In traditional isothermal drying processes, the coating dries rapidly at high temperatures (typically 100~140℃), and the solvent evaporates quickly from the coating surface, forming a solvent concentration gradient from the surface to the interior, driving the solvent to flow from the interior of the coating to the surface. Since the binder is dissolved or dispersed in the solvent, the binder molecules / particles migrate to the coating surface along with the solvent flow; this is the phenomenon of "binder flotation." The result of binder flotation is that the binder content near the current collector is significantly reduced, and the interfacial bonding force is significantly decreased.

[0074] The multi-stage drying strategy of this invention effectively inhibits binder flotation through the following mechanism: Low-temperature slow drying stage (50~70℃, 1~3 minutes, wind speed 0.5~1.5m / s): In this stage, the temperature is low, the solvent evaporation rate is slow, and a sharp solvent concentration gradient does not form within the coating, thus the driving force for binder migration is very small. During this stage, the solvent on the coating surface gradually evaporates, the surface viscosity increases, and a preliminary "skin" structure begins to form. Once this skin structure is formed, it inhibits the rapid evaporation of solvent and the upward migration of binder in subsequent stages. The low wind speed setting is to avoid deformation of the coating caused by airflow blowing on the wet coating surface. By the end of this stage, approximately 20%~30% of the solvent in the coating has been removed. The drying zone uses indirect heating (heat radiation plates are located above and below the coating) to avoid direct hot air impact on the wet coating.

[0075] Medium-temperature rapid drying stage (80~100℃, 1~2 minutes, wind speed 1.5~3m / s): This stage increases temperature and wind speed to accelerate the evaporation of solvent inside the coating. Since a preliminary gel network structure has already formed on the coating surface during the low-temperature slow drying stage, this structure physically blocks the upward migration of the binder. Therefore, even at higher temperatures, binder migration is effectively suppressed. The main function of the medium-temperature rapid drying stage is to quickly remove most of the solvent inside the coating, rapidly increasing the solid content of the coating to 80%~90%, essentially "freezing" the binder distribution within the gradient state established in step S3. This stage uses convective hot air drying, with hot air blowing in simultaneously from above and below the coating to ensure uniform heating on both sides. The wind speed is controlled within the range of 1.5~3m / s, and the wind direction is at a 45°~90° angle to the electrode travel direction to avoid dragging the coating by airflow along the electrode direction. By the end of this stage, approximately 70%~85% of the solvent in the coating has been removed.

[0076] High-temperature setting stage (110~140℃, 2~5 minutes, wind speed 0.8~2m / s): This stage uses the highest temperature but reduces the wind speed. The main purpose is to completely remove residual solvent (reducing the residual solvent content to below 0.1%) and promote the cross-linking and curing of the binder to form a stable coating structure. High temperature promotes the movement and rearrangement of the binder molecular chains, resulting in a tighter bond between the binder and the active material particles and conductive agent particles. The reason for reducing the wind speed in this stage is that the coating is basically dry, and excessively high wind speed may cause "cracking" on the coating surface (similar to cracking of soil), reducing the integrity and mechanical strength of the coating. This stage uses a combined heating method of hot air and infrared radiation. Infrared radiation provides body heating, while hot air assists in removing evaporated solvent vapors and prevents solvent vapors from condensing and flowing back onto the coating surface.

[0077] The drying equipment is a tunnel-type continuous drying oven, consisting of three independently temperature-controlled drying zones. Insulated curtains and exhaust channels separate each zone to prevent heat exchange between adjacent zones. Each drying zone is equipped with an independent heating system, temperature control system, and air circulation system. The heating system uses electric heating elements or hot air, evenly distributed at the top and bottom of the drying zone, with a heating power density that can reach [amount missing]. The temperature control system employs a multi-point platinum resistance temperature sensor (PT100) and a PID controller, achieving a temperature control accuracy of ±1℃ and temperature uniformity better than ±2℃. The air circulation system consists of a variable frequency fan, air duct, and guide vanes, with a fan power of 0.5~3kW, ensuring uniform distribution of hot air. The air speed can be precisely adjusted within the range of 0.5~3m / s. The conveying system uses a mesh belt conveyor or roller conveyor, with a belt speed adjustable within the range of 0.5~5m / min. The length of the drying zone and the belt speed are set according to the required drying time for each stage.

[0078] Through comparative experiments, the inventors discovered that the binder content in the interfacial region (0-5 μm range near the current collector) of the electrode sheet dried in a multi-stage drying process is 30%-60% higher than that of the electrode sheet dried in a conventional isothermal drying process (confirmed by FIB-SEM cross-sectional EDS analysis). Correspondingly, the peel strength is improved by 25%-40%. This fully demonstrates the significant effect of multi-stage drying in suppressing binder flotation and maintaining the interfacial binder concentration.

[0079] In one embodiment of this application, the interface enhancer in S5 comprises, by weight, the following components: 20-50 parts of organic polymer, 5-15 parts of conductive agent, 3-10 parts of crosslinking agent, 2-8 parts of penetration aid, and 100-200 parts of solvent.

[0080] The organic polymer is an organosilicon-modified acrylate; the conductive agent is selected from one or more of conductive carbon black, graphite, and carbon nanotubes; the crosslinking agent is selected from one or more of isocyanate crosslinking agents, epoxy resin crosslinking agents, and organosilane crosslinking agents; the penetrating aid is selected from one or more of sodium dodecylbenzenesulfonate, sodium lauryl sulfate, sodium stearate, hexadecyltrimethylammonium bromide, lauryl polyether, polyethylene glycol stearate, ethanol, isopropanol, ethylene glycol monomethyl ether, and ethylene glycol dimethyl ether; the solvent is selected from one or more of N-methylpyrrolidone, acetone, tetrahydrofuran, water, isopropanol, and ethanol.

[0081] Among them, the interface enhancement treatment is another innovation of the present invention. By spraying a specially formulated interface enhancer onto the surface of the electrode and combining it with pressure heat treatment, the enhancer penetrates into the interface area between the coating and the current collector, forming a reinforced interface layer and significantly improving the peel strength.

[0082] Organosilicon-modified acrylate polymers are the main component of the interface reinforcing agent, possessing both excellent adhesion and flexibility, and capable of forming a well-compatible interface with the binder in the electrode coating. The organosilicon groups provide good affinity with the current collector metal surface, while the acrylate portion forms good compatibility and entanglement with the binder in the coating.

[0083] Conductive agents ensure that the interface reinforcement layer has good electronic conductivity without increasing the battery's internal resistance. Different conductive agents have different advantages: conductive carbon black has good dispersibility and is suitable for conventional systems; graphite has high conductivity and is suitable for high energy density systems; carbon nanotubes have high conductivity and a network structure, making them particularly suitable for high-power applications.

[0084] Crosslinking agents are responsible for promoting the crosslinking and curing of interface reinforcing agents, forming a stable network structure, and simultaneously forming chemical bonds with the current collector surface. Different crosslinking agents are suitable for different systems: isocyanates are suitable for reacting with systems containing hydroxyl groups; epoxy resins have excellent bonding strength and chemical stability; organosilanes are particularly suitable for forming chemical bonds with metal surfaces.

[0085] Penetration aids are selected from one or more of surfactants, alcohols, and ethers to reduce the surface tension of interfacial reinforcing agents and promote their penetration into the interface region between the coating and the current collector. Surfactants can significantly reduce the surface tension of liquids, such as sodium dodecylbenzenesulfonate, sodium lauryl sulfate, sodium stearate, hexadecyltrimethylammonium bromide, lauryl polyether, and polyethylene glycol stearate; alcohols such as ethanol and isopropanol have good wetting and volatility; ethers such as ethylene glycol monomethyl ether and ethylene glycol dimethyl ether have both good solubility and penetration.

[0086] Solvent selection needs to consider compatibility with the electrode coating. For PVDF systems, NMP and acetone can be selected; for aqueous systems, water / alcohol mixed solvents can be selected. The solvent evaporation rate is also an important consideration, ensuring that the interface enhancer has sufficient time to penetrate to the interface without forming a thick coating on the surface.

[0087] The preparation process of the interface enhancer includes the following steps: (i) dissolving the silicone-modified acrylate polymer in a suitable solvent and stirring at 500-1000 rpm for 30-60 minutes until completely dissolved to form a homogeneous polymer solution; (ii) adding a penetrating agent and continuing to stir at 500 rpm for 5-10 minutes to ensure uniform distribution; (iii) adding a conductive agent and dispersing it using a high-speed disperser at 3000-5000 rpm for 15-30 minutes to ensure uniform dispersion of the conductive agent in the solution; (iv) finally adding a crosslinking agent and gently stirring at 300-500 rpm for 3-5 minutes to mix evenly (avoiding premature crosslinking reaction). It is recommended to use the prepared interface enhancer within 24 hours to ensure optimal results and avoid premature reaction of the crosslinking agent during storage, which could lead to thickening or gelation.

[0088] The interface enhancer application equipment can employ a precision spraying system, including an ultrasonic atomizing nozzle (atomized particle size 10~50μm), a precision flow meter (accuracy ±1%), an XY moving platform (stroke covering electrode width and length), and a control system. The spraying volume is controlled within... Ensure the coating is thin and uniform. During spraying, fix the electrode on the vacuum adsorption platform and keep it flat. After spraying, let it stand for 30-60 seconds to allow the interface enhancer to fully penetrate into the coating pores.

[0089] Alternatively, the interfacial reinforcing agent can be applied by impregnation, that is, the dried electrode can be impregnated in an interfacial reinforcing agent solution and then dried.

[0090] In one embodiment of this application, the pressure heat treatment in S5 is carried out by hot roller pressing, with a pressure of 0.5~3MPa, a temperature of 60~120℃, and a treatment time of 5~30 seconds.

[0091] The pressurized heat treatment equipment consists of a pair of heated rollers, with a diameter of 200-400 mm. The roller surfaces are made of chrome-plated steel or ceramic coating, with a surface roughness Ra < 0.1 μm to ensure no damage to the electrode surface. The rollers have built-in heating elements (electric heating rods or circulating heat transfer oil), maintaining temperature uniformity within ±2℃. The pressure control system precisely controls the pressure between the rollers via pneumatic or hydraulic cylinders, achieving pressure uniformity better than ±5%. The electrode passes through the roller gap between the two rollers; the gap distance is adjustable, and the processing time is determined by the belt conveyor speed and the roller contact arc length.

[0092] The mechanisms of pressurized heat treatment include: (a) Heat effect: Heating accelerates the evaporation of solvent in the interface reinforcing agent; at the same time, the increase in temperature causes the binder in the coating (PVDF has a glass transition temperature of about -35°C and a melting point of about 170°C; SBR has a glass transition temperature of about -50°C) to be in a highly elastic or viscous flow state, and the molecular chain movement intensifies, promoting the mutual diffusion and entanglement between the organic polymer molecular chains in the interface reinforcing agent and the coating binder molecular chains, forming a molecular-level "welding".

[0093] (b) Pressure effect: The pressure generated by roller pressing promotes close contact between the interface reinforcing agent and the coating, "pressing" the interface reinforcing agent into the pores of the coating and accelerating the penetration process. At the same time, the pressure further densifies the coating material, reduces the porosity inside the coating, and helps to improve the overall adhesion of the coating.

[0094] (c) Crosslinking: Under the combined action of temperature and pressure, the crosslinking agent is activated and begins to react chemically with the organic polymer, the functional groups on the surface of the current collector, and the functional groups of the binder in the coating to form a three-dimensional network structure with covalent bonds, thereby realizing the chemical bonding between the coating, the interface reinforcement layer and the current collector.

[0095] When the pressure is below 0.5 MPa, the interface reinforcing agent does not contact the coating tightly enough, resulting in poor penetration. When the pressure is above 3 MPa, it may cause excessive compression of the coating structure, damaging the active material particles or causing deformation of the current collector. When the temperature is below 60℃, the crosslinking reaction rate is too slow, and the activity of the binder molecular chains is insufficient. When the temperature is above 120℃, it may cause excessive softening of the coating binder, destroying the formed coating structure. The optimal processing time is 5–30 seconds, determined based on the belt speed and the roller contact arc length.

[0096] In one embodiment of this application, the calendering process in S6 adopts a differential rolling method, the linear speed ratio of the upper roll to the lower roll is 1.01~1.10:1, the rolling pressure is 50~200MPa, and the rolling temperature is 50~120℃.

[0097] Calendering is the final and crucial step in electrode preparation. Its purpose is to compact the coating to the target density, thereby improving the contact tightness between active material particles and between the active material and the current collector. This invention innovatively uses differential speed rolling instead of traditional constant speed rolling. Its working principle and advantages are as follows: The differential rolling mill consists of two calendering rolls (roll diameter 300~600mm, roll surface material high-chromium alloy steel, surface roughness Ra<0.05μm), an independent variable frequency motor drive system, a precision gear transmission mechanism, a hydraulic pressure regulating system, and a temperature control device. The upper and lower rolls are each driven by an independent variable frequency motor, with the motor speed precisely controlled by a frequency converter to achieve different linear velocities between the rolls. The pressure between the upper and lower rolls is controlled by a hydraulic system, with hydraulic cylinders symmetrically installed at both ends of the rolls to ensure uniform pressure distribution and pressure fluctuations controlled within ±2%. Temperature control utilizes built-in heating elements (electromagnetic induction heating or heat transfer oil circulation heating) and temperature sensors to ensure uniform temperature distribution on the roll surface within a set range, with temperature uniformity better than ±2℃.

[0098] The key to differential rolling is the difference in linear velocity between the upper and lower rollers. When the linear velocity of the upper roller is slightly higher than that of the lower roller (speed ratio 1.01~1.10:1), as the electrode passes through the roller gap, the upper and lower surfaces of the coating are subjected to frictional forces from the roller surfaces at different speeds, generating shear stress in the coating thickness direction. The effects of this shear stress include: (a) Promotes particle rearrangement: Shear force causes small relative slippage of active material particles during calendering, allowing the particles to rearrange more effectively to the densest packing position, reducing the gaps between particles, increasing the compaction density while reducing the required normal pressure, thereby reducing damage to the coating and current collector.

[0099] (b) Releasing internal stress: In traditional constant speed rolling, the normal pressure accumulates a large amount of elastic strain energy inside the coating. When the electrode passes through the roll gap, the release of this strain energy will cause "elastic rebound", which will cause the coating to expand and the interface to crack. The shear stress generated by differential speed rolling can cause the coating material to undergo plastic rheology during the calendering process, effectively releasing elastic strain energy and reducing elastic rebound.

[0100] (c) Enhanced interfacial bonding: Shear force causes the materials in the interfacial region (including the binder and interfacial reinforcement layer in the coating) to flow and rearrange at the interface, increasing the contact area and tightness between the coating and the current collector, and further strengthening the interfacial bonding.

[0101] When the ratio of the linear speeds of the upper and lower rollers is less than 1.01:1, the speed difference is too small, the shearing effect is not obvious, and there is little difference from constant speed rolling. When the speed ratio is greater than 1.10:1, the shearing force is too large, which may cause the coating to slip off at the interface or generate transverse cracks on the coating surface, thus reducing the quality of the electrode.

[0102] The rolling pressure range of 50~200MPa is determined according to the different requirements of the positive and negative electrodes: positive electrode coating (such as NCM811, target compaction density) High rolling pressure (100~200MPa) is typically required for the negative electrode coating (e.g., graphite, target compaction density). The required roller pressure is relatively low (50~120MPa).

[0103] The rolling temperature is set at 50~120℃ to keep the binder in the coating in a softened state (highly elastic state), which is beneficial for particle rearrangement and interfacial bonding. If the temperature is too low, the binder will be too hard, making particle rearrangement difficult and requiring greater pressure; if the temperature is too high, the binder will be over-softened, which may cause the coating to stick to the roller or the structure to collapse.

[0104] In one embodiment of this application, the calendering process in S6 further includes ultrasonic-assisted vibration, with an ultrasonic frequency of 20~60kHz and an amplitude of 10~50μm.

[0105] The ultrasonic auxiliary device consists of an ultrasonic generator (power 500~2000W), a piezoelectric ceramic transducer, an amplitude transformer, and a waveguide system. The ultrasonic generator produces a high-frequency electrical signal of 20~60kHz; the piezoelectric ceramic transducer converts the electrical signal into mechanical vibration; the amplitude transformer amplifies the vibration to achieve a set amplitude range (10~50μm); the waveguide system transfers the vibration energy to the lower roller (or through an ultrasonic vibration roller), so that the electrode sheet is simultaneously subjected to ultrasonic vibration during the calendering process. The control system monitors and adjusts the ultrasonic parameters in real time using a frequency tracking algorithm to ensure the stability and uniformity of vibration under varying load conditions (fluctuations in electrode sheet thickness and hardness).

[0106] According to a second aspect of this application, this application also provides an electrode sheet prepared by the above-mentioned process for improving the interlayer peel strength of the electrode sheet of the energy storage cell, wherein the 180° peel strength of the electrode sheet is not less than 30 N / m, preferably 35.7~42.3 N / m.

[0107] The electrode structure, from bottom to top, includes a current collector, an active material coating, and an interface reinforcement layer. The binder in the active material coating exhibits a concentration gradient distribution that gradually decreases from the current collector side to the surface side, with a high binder concentration region closer to the current collector and a low binder concentration region further away. The surface of the current collector, after activation treatment, has a micro-rough structure (Ra = 0.2~1.0 μm), and the active material coating is tightly bonded to the current collector through mechanical interlocking and chemical bonding. The interface reinforcement layer is distributed in the interface region between the active material coating and the current collector, as well as in the pores of the active material coating, chemically "welding" the active material coating and the current collector together.

[0108] According to a third aspect of this application, this application also provides a lithium-ion battery, including a cell formed of a positive electrode, a negative electrode and a separator, an electrolyte, and an aluminum-plastic film or a square aluminum shell wrapping the cell, wherein the positive electrode and / or the negative electrode are prepared by the above-described processing technology.

[0109] The method for preparing the lithium-ion battery of the present invention is well known to those skilled in the art. Generally, the method includes winding or stacking a positive electrode sheet, a separator, and a negative electrode sheet to form a battery cell, placing the battery cell in packaging material, adding an electrolyte, and then encapsulating it. The battery is obtained through processes such as formation and capacity testing. The encapsulation method, the composition of the battery cell and the electrolyte, and the amounts used are well known to those skilled in the art.

[0110] The present application will be further described below with reference to specific embodiments. Example 1

[0111] This embodiment provides a processing technology to improve the interlayer peel strength of the positive electrode sheet, including the following steps: S1. Slurry Preparation: NCM811 positive electrode active material (94.5 wt%), conductive carbon black Super P (2.5 wt%), and PVDF binder (3 wt%) were added to NMP solvent (based on solid content) and subjected to multi-stage dispersion treatment. Primary dispersion stage: 3000 rpm for 15 minutes; settling interval 4 minutes (maintaining low-speed stirring at 200 rpm); Secondary dispersion stage: 6000 rpm for 10 minutes; settling interval 4 minutes; Tertiary dispersion stage: 10000 rpm for 5 minutes. The resulting coating slurry had a solid content of 65%.

[0112] S2. Surface activation treatment: The aluminum foil current collector (16μm thick) was treated with oxygen plasma. The treatment parameters were: power 200W, oxygen flow rate 120sccm, and treatment time 30 seconds. After treatment, the surface roughness Ra of the aluminum foil was 0.5μm, and the surface exhibited a micro-rough structure with uneven texture.

[0113] S3. Gradient Coating: Gradient coating is performed using a double-slit coating head. The PVDF content in the slurry in the first slit (closer to the current collector) is 4.5 wt% (based on solids content), and the PVDF content in the slurry in the second slit (away from the current collector) is 2.5 wt%. The coating speed is 5 m / min, and the coating gap is 300 μm. The total areal density of the coating is... The binder concentration gradient in the coating after application is C1 / C2 = 1.8.

[0114] S4. Multi-stage drying: Low temperature slow drying stage: temperature 60℃, time 2 minutes, wind speed 1.0m / s; Medium temperature fast drying stage: temperature 90℃, time 1.5 minutes, wind speed 2.0m / s; High temperature setting stage: temperature 120℃, time 3 minutes, wind speed 1.2m / s.

[0115] S5. Interface Reinforcement Treatment: Prepare an interface reinforcing agent, by weight: 35 parts silicone-modified acrylate, 8 parts conductive carbon black Super P, 2 parts carbon nanotubes, 5 parts isocyanate crosslinking agent (HDI trimer), 2 parts organosilane crosslinking agent (MTMS), 3 parts lauryl alcohol polyether, 3 parts isopropanol, 100 parts NMP, and 50 parts acetone. Spray the interface reinforcing agent onto the electrode surface, with a spraying amount of... Then, a pressure heat treatment is performed: using hot roller pressing, with a pressure of 1.5 MPa, a temperature of 80℃, and a treatment time of 15 seconds.

[0116] S6. Calendering process: Differential rolling is adopted, with the linear speed ratio of the upper roll to the lower roll being 1.05:1, the rolling pressure being 150MPa, and the rolling temperature being 80℃.

[0117] Lithium-ion battery manufacturing: The above-mentioned positive electrode sheet, negative electrode sheet (artificial graphite negative electrode, prepared using conventional processes), and separator (PP / PE / PP three-layer composite separator, 16μm thick) are wound into a battery cell; the battery cell is then placed in an aluminum-plastic film package and injected with electrolyte ( The solvent is EC:DEC:DMC=3:4:3 (volume ratio). After encapsulation, the lithium-ion battery is produced through formation and capacity testing. Example 2

[0118] This embodiment provides a processing technology to improve the interlayer peel strength of the negative electrode sheet, which differs from Embodiment 1 in that: S1. Slurry Preparation: Artificial graphite anode active material (95.5 wt%), conductive carbon black Super P (1 wt%), SBR binder (2 wt%), and CMC thickener (1.5 wt%) were added to a deionized water solvent (based on solid content) and subjected to multi-stage dispersion treatment. Primary dispersion stage: 2500 rpm, 15 minutes; settling interval 4 minutes; Secondary dispersion stage: 5500 rpm, 12 minutes; settling interval 4 minutes; Tertiary dispersion stage: 9500 rpm, 5 minutes. The resulting coating slurry had a solid content of 50%.

[0119] S2. Surface activation treatment: The copper foil current collector (8μm thick) was treated with argon plasma. The treatment parameters were: power 250W, argon flow rate 100sccm, and treatment time 40 seconds. After treatment, the surface roughness Ra of the copper foil was 0.4μm.

[0120] S3. Gradient Coating: Gradient coating is performed using a double-slit coating head. The SBR content in the first slit slurry is 3 wt% (based on solids content), and the SBR content in the second slit slurry is 1.5 wt%. The coating speed is 4 m / min, and the coating gap is 250 μm. The total areal density of the coating is... The binder concentration gradient in the coating after application is C1 / C2 = 2.0.

[0121] S4. Multi-stage drying: Low temperature slow drying stage: temperature 55℃, time 2.5 minutes, wind speed 0.8m / s; Medium temperature fast drying stage: temperature 85℃, time 1.5 minutes, wind speed 2.0m / s; High temperature setting stage: temperature 115℃, time 3 minutes, wind speed 1.0m / s.

[0122] S5. Interface Reinforcement Treatment: Prepare an interface reinforcement agent, by weight: 30 parts silicone-modified acrylate, 10 parts conductive carbon black Super P, 6 parts epoxy resin crosslinking agent (E-51), 2 parts lauryl alcohol polyether, 4 parts ethanol, 120 parts water, and 60 parts ethanol. Spray the interface reinforcement agent onto the electrode surface, with a spraying amount of... Then, pressure heat treatment is performed: pressure 1.0 MPa, temperature 70℃, treatment time 20 seconds.

[0123] S6. Calendering process: Differential rolling is used, with the linear speed ratio of the upper roll to the lower roll being 1.03:1, the rolling pressure being 80MPa, and the rolling temperature being 60℃. Ultrasonic auxiliary vibration is applied simultaneously, with an ultrasonic frequency of 35kHz and an amplitude of 25μm.

[0124] Lithium-ion battery manufacturing: The above-mentioned negative electrode, positive electrode (NCM811 positive electrode, prepared by conventional process), separator, and electrolyte were used to prepare a lithium-ion battery according to the same specifications and procedures as in Example 1. Example 3

[0125] Unlike Example 1, this example further adds 1.5 wt% of silane coupling agent KH-570 as an interfacial coupling agent to the slurry in step S1. The silane coupling agent is added to the slurry during the settling interval after the secondary dispersion stage, and after stirring at 800 rpm for 4 minutes to ensure uniform distribution, the tertiary dispersion stage begins. Other steps and parameters are the same as in Example 1, and will not be repeated here. Example 4

[0126] Unlike Example 1, this example adds a primary drying and setting step S3' between steps S3 and S4: a mid-wave infrared lamp array (wavelength 2~4μm) is used, with an infrared radiation power density of... The lamp tube was installed 180mm above the electrode surface, and the processing time was 20 seconds. After processing, a preliminary gel structure was formed on the coating surface, removing approximately 10% of the surface solvent. Other steps and parameters were the same as in Example 1, and will not be repeated here. Example 5

[0127] Unlike Example 1, in this example, during the coating process in step S3, a tension of 30N is applied to the current collector, and the current collector's travel direction forms an angle of 87° with the coating direction. Tension control employs a precision tension control roller, which is monitored in real-time and automatically adjusted by a tension sensor; angle control is achieved through an adjustable guide roller with an adjustment accuracy of 0.1°. Other steps and parameters are the same as in Example 1 and will not be repeated here.

[0128] Comparative Example 1 Unlike Example 1, step S1 in this comparative example did not involve multi-stage dispersion of the slurry; only a single-stage dispersion process was used: a rotation speed of 6000 rpm for 30 minutes with no settling interval. Other steps and parameters were the same as in Example 1 and will not be repeated here.

[0129] Comparative Example 2 Unlike Example 1, in this comparative example, step S2 did not involve surface activation treatment of the current collector. The aluminum foil was used directly after routine cleaning and drying, and the surface roughness Ra of the aluminum foil was approximately 0.05 μm. Other steps and parameters were the same as in Example 1, and will not be repeated here.

[0130] Comparative Example 3 Unlike Example 1, step S3 in this comparative example only uses conventional single-slit coating with a single-component slurry (3wt% PVDF content), thus avoiding a concentration gradient distribution of the binder in the coating. After coating, the binder distribution in the coating is uniform, with C1 / C2 ≈ 1.0. Other steps and parameters are the same as in Example 1 and will not be repeated here.

[0131] Comparative Example 4 Unlike Example 1, step S4 in this comparative example did not employ multi-stage drying; instead, it used conventional constant-temperature drying: temperature 120°C, time 6 minutes, and air velocity 2.0 m / s. Other steps and parameters were the same as in Example 1 and will not be repeated here.

[0132] Comparative Example 5 Unlike Example 1, in this comparative example, step S5 did not involve applying an interface reinforcing agent to the electrode, thus omitting the interface reinforcement treatment step. The dried electrode directly proceeded to the S6 calendering process. The other steps and parameters were the same as in Example 1, and will not be repeated here.

[0133] Comparative Example 6 Unlike Example 1, the calendering in step S6 of this comparative example does not use differential speed rolling, but rather conventional constant speed rolling (the linear speeds of the upper and lower rollers are equal, with a speed ratio of 1:1). The rolling pressure is 150 MPa, and the rolling temperature is 80°C. Other steps and parameters are the same as in Example 1, and will not be repeated here.

[0134] Comparative Example 7 Unlike Example 1, in step S3 of this comparative example, the PVDF content in the slurry of the first slit (near the current collector) of the double-slit coating head is 1.5 wt%, and the PVDF content in the slurry of the second slit (away from the current collector) is 2.5 wt%. That is, the binder concentration on the side near the current collector is lower than that on the side away from the current collector, C1 / C2=0.6. Other steps and parameters are the same as in Example 1, and will not be repeated here.

[0135] The electrodes and lithium-ion batteries prepared in Examples 1-5 and Comparative Examples 1-7 were subjected to the following performance tests, and the test results are shown in Table 1.

[0136] (a) Peel strength test The peel strength of the electrode was tested using the 180° peel test method. The specific operating steps are as follows: (1) Sampling: Cut the prepared electrode into strips with a width of 25 mm and a length of 150 mm, and take 5 parallel samples for each group.

[0137] (2) Applying adhesive: Apply 3M double-sided tape (model VHB 4910) to the coated surface of the electrode, ensuring that the tape is completely adhered to the coated surface without air bubbles. Then fix the electrode with tape on it to the stainless steel base plate and roll it back and forth 3 times with a 2kg roller to ensure that it is firmly bonded.

[0138] (3) Peel test: Fix the stainless steel base plate on the lower clamp of the universal tensile testing machine (Instron 5944 model), and clamp the free end of the current collector (aluminum foil or copper foil) on the upper clamp. Set the tensile speed to 100 mm / min, and the tensile direction is at a 180° angle to the electrode plane (that is, fold and peel the current collector backward along the coating surface).

[0139] (4) Data recording: The tensile testing machine automatically records the force-displacement curve during the peeling process. The average force value of the stable peeling section (usually the middle 80mm interval) is taken as the peeling force F (N). The peeling strength P (N / m) = F / specimen width (0.025m).

[0140] (5) The average value of 5 parallel samples is taken as the final test result.

[0141] (II) Battery High-Temperature Cycling Performance Test The battery's cycle performance was evaluated using a 60℃ high-temperature cycle test. The specific operating steps are as follows: (1) Battery preparation: The lithium-ion batteries (soft pack batteries with a capacity of about 2Ah) prepared in each example and comparative example were activated by three charge-discharge cycles at 25°C (0.1C charge / 0.1C discharge, voltage range 2.8~4.2V), and then fully charged to 4.2V at 0.5C.

[0142] (2) High temperature cycling: The battery was placed in a 60℃ constant temperature chamber for charge-discharge cycle testing. Charging regime: 0.5C constant current charging to 4.2V, then constant voltage charging until the current drops to 0.05C; Discharging regime: 0.5C constant current discharging to 2.8V.

[0143] (3) Data recording: Record the discharge capacity for each week, and calculate the capacity retention rate after 500 cycles. Capacity retention rate (%) = discharge capacity in week 500 / discharge capacity in week 1 × 100%.

[0144] Table 1

[0145] The test results in Table 1 above are analyzed as follows: 1) The peel strength of Example 1 was 34.6% higher than that of Comparative Example 1. Comparative Example 1 used only a single rotation speed (6000 rpm) for 30 minutes. Although the total dispersion time was comparable to that of Example 1, the uniformity of binder dispersion in the slurry was not as good as that of Example 1 due to the lack of a combination of low-speed pre-dispersion and high-speed fine dispersion, as well as the static buffer between each stage. Unevenly dispersed binder is prone to local enrichment and local loss after coating, resulting in uneven interfacial bonding and reduced overall peel strength. This indicates that multi-stage dispersion treatment plays an important role in ensuring uniform distribution of binder and improving interfacial bonding.

[0146] In terms of high-temperature cycling performance, Example 1 (91.2%) was also superior to Comparative Example 1 (87.3%). This is because the uniformly dispersed binder can maintain the integrity of the coating structure during long-term cycling, reducing the deactivation of active materials and the increase in internal resistance caused by local debonding.

[0147] 2) The peel strength of Example 1 was 52.8% higher than that of Comparative Example 2. The current collector in Comparative Example 2 underwent only routine cleaning without surface activation treatment, resulting in an aluminum foil surface roughness Ra of only about 0.05 μm, far lower than the 0.5 μm of Example 1. The smooth surface of the current collector lacks the mechanical interlocking points provided by the microscopic rough structure, and also lacks the chemical bonding points provided by the active functional groups introduced by plasma treatment. The bonding between the coating and the current collector mainly relies on physical adsorption force, resulting in limited adhesion. This fully demonstrates the crucial role of current collector surface activation treatment in increasing the interfacial contact area and chemical bonding points, fundamentally improving the interfacial bonding strength.

[0148] In terms of high-temperature cycling performance, Comparative Example 2 (85.6%) was significantly lower than Example 1 (91.2%), indicating that the electrode without surface activation treatment is more prone to coating peeling during high-temperature cycling, which leads to the interruption of the electronic conduction path between the active material and the current collector, accelerating capacity decay.

[0149] 3) The peel strength of Example 1 was 38.5% higher than that of Comparative Example 3. Comparative Example 3 used conventional single-slit coating, resulting in a uniform binder distribution in the coating (C1 / C2≈1.0). During the subsequent drying process (although multi-stage drying was also used), due to the uniform initial concentration, even though binder flotation was suppressed, the binder concentration in the interface region remained at only the average level. In contrast, Example 1 actively enriched the interface region with more binder through gradient coating (C1 / C2=1.8), allowing more binder molecules to participate in interfacial bonding and significantly improving the peel strength. This demonstrates the unique advantages of gradient coating technology in actively constructing an interfacial binder-enriched layer and strengthening interfacial bonding.

[0150] 4) The peel strength of Example 1 was 45.3% higher than that of Comparative Example 4. Comparative Example 4 used conventional isothermal drying, where the solvent on the coating surface evaporated rapidly at high temperatures, forming a strong solvent concentration gradient that drove a large amount of adhesive to migrate to the surface. Even if a good concentration gradient (C1 / C2=1.8) was established in step S3, isothermal drying would severely disrupt this gradient, resulting in a significant decrease in the adhesive concentration in the final interface region and a significant drop in peel strength. This fully demonstrates the irreplaceable role of multi-stage drying in maintaining the adhesive gradient distribution and preventing adhesive from floating.

[0151] In terms of high-temperature cycling performance, Comparative Example 4 (86.2%) was significantly lower than Example 1 (91.2%), indicating that the interfacial weakening caused by the binder floating was further aggravated during high-temperature cycling, and the coating was more likely to fall off under the combined effect of the volume change of the active material and thermal stress.

[0152] 5) The peel strength of Example 1 is 58.4% higher than that of Comparative Example 5. Comparative Example 5 omitted the interface reinforcement treatment step and has the lowest peel strength among all comparative examples (except Comparative Example 7). This strongly demonstrates that the interface reinforcement treatment is the innovative point that contributes significantly to the improvement of peel strength in this invention. The interface reinforcement agent penetrates into the interface region between the coating and the current collector to form a chemically bonded reinforced interface layer, "welding" the coating and the current collector together. This interface-specific reinforcement treatment is not available in traditional processes.

[0153] In terms of high-temperature cycling performance, Comparative Example 5 had the lowest capacity retention rate (except for Comparative Example 7), indicating that the electrode without an interface reinforcement layer suffered the most severe interface degradation during long-term high-temperature cycling. The separation of the active material from the current collector led to a continuous increase in the battery's internal resistance, accelerating capacity decay.

[0154] 6) The peel strength of Example 1 was 19.9% ​​higher than that of Comparative Example 6. Comparative Example 6 used conventional constant-speed rolling instead of differential-speed rolling. The peel strength of Comparative Example 6 was relatively high among all comparative examples, indicating that the preceding steps S1 to S5 had laid a good foundation for interfacial bonding. However, differential rolling further improved the peel strength by about 20%, which is attributed to the shear force generated by differential rolling promoting the flow and rearrangement of interfacial materials and further strengthening the interfacial bonding.

[0155] 7) The peel strength of Example 1 was 105.9% higher than that of Comparative Example 7. Comparative Example 7 was a reverse gradient design (C1 / C2=0.6), meaning that the binder concentration near the current collector was lower than that away from the current collector, which is similar to the effect of binder floating in conventional coating. The reverse gradient design resulted in a severe lack of binder in the interface area, and the peel strength was even lower than that of Comparative Example 3 (uniform coating). This is because the reverse gradient design actively reduced the interfacial binder, which is more unfavorable than natural distribution (slight floating caused by drying after uniform coating).

[0156] The high-temperature cycling capacity retention rate of Comparative Example 7 was also the lowest, further illustrating that insufficient interfacial binder concentration is the direct cause of electrode performance degradation.

[0157] This set of comparisons (Example 1 vs Comparative Example 7 vs Comparative Example 3) strongly demonstrates the decisive influence of the adhesive concentration gradient direction on peel strength: positive gradient (C1 / C2>1) >> uniform distribution (C1 / C2≈1) >> negative gradient (C1 / C2<1).

[0158] 8) The comparative analysis between the various embodiments is as follows: The peel strength range of Examples 1-5 is much higher than that of the comparative examples, indicating that the synergistic effect of each step of the present invention can stably achieve a significant improvement in the peel strength of the electrode.

[0159] The peel strength of Example 2 is slightly lower than that of Example 1. This is mainly because the negative electrode uses an aqueous binder system (SBR / CMC), whose bonding strength is inherently slightly lower than that of the PVDF system, and the chemical activity of the copper foil current collector is lower than that of the aluminum foil. However, even so, the peel strength of Example 2 is still much higher than that of the negative electrode sheet prepared by conventional processes (typically 10~15 N / m), indicating that the processing technology of the present invention has a significant improvement effect on both the positive and negative electrode sheets.

[0160] Example 3 exhibited the highest peel strength among all examples, exceeding that of Example 1 by 9.9%. This demonstrates that the addition of the silane coupling agent KH-570 to the slurry further strengthens the interfacial bonding by establishing "molecular bridges" between the active material / conductive agent and the binder, as well as between the binder and the current collector. Example 3 also showed the best high-temperature cycling performance (92.8%), indicating that the chemical bonds formed by the coupling agent maintained good stability during long-term high-temperature cycling.

[0161] The peel strength of Example 4 was 4.2% higher than that of Example 1. The initial drying and setting step rapidly formed a preliminary gel structure on the coating surface through infrared radiation, which further suppressed the migration of the binder during the subsequent multi-stage drying process and better maintained the binder concentration gradient established by the gradient coating, thus improving the peel strength.

[0162] The peel strength of Example 5 was 3.4% higher than that of Example 1. Appropriate tension and angle settings kept the current collector flat and the slurry distribution more uniform. At the same time, the slight drag force helped the slurry penetrate into the micro-pits on the surface of the current collector, enhancing the mechanical interlocking effect.

[0163] In summary, the processing technology provided by this invention achieves a breakthrough improvement in the interlayer peel strength of the electrode (35.7~42.3 N / m) through the systematic and synergistic design of six steps: S1 multi-level dispersion, S2 surface activation, S3 gradient coating, S4 multi-stage drying, S5 interface enhancement treatment, and S6 calendering treatment. This far exceeds the level of traditional processes. At the same time, the high-temperature cycle performance of the battery is also significantly improved (capacity retention ≥90.5% after 500 cycles at 60℃), which can effectively meet the requirements of high-performance and high-reliability lithium-ion energy storage batteries.

[0164] 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.

Claims

1. A processing method for improving the interlayer peel strength of electrode sheets in energy storage cells, characterized in that, Includes the following steps: S1. Slurry preparation: The slurry containing active materials, conductive agents, binders and solvents is subjected to multi-stage dispersion treatment to obtain coating slurry; S2. Surface activation treatment: The current collector is subjected to surface activation treatment to form a rough surface with uneven texture. S3. Gradient coating: The coating slurry is coated onto the current collector after surface activation treatment to form a coating, and the binder in the coating forms a concentration gradient distribution, wherein the binder concentration on the side closer to the current collector is higher than that on the side farther away from the current collector; S4. Multi-stage drying: The coated electrode sheet is dried in multiple stages. S5. Interface enhancement treatment: An interface enhancer is applied to the surface of the dried electrode and subjected to pressure heat treatment, so that the interface enhancer acts on the interface region between the coating and the current collector; the interface enhancer includes organic polymer, conductive agent, crosslinking agent, penetrating agent and solvent; S6. Rolling treatment: The electrode sheet after interface strengthening treatment is rolled.

2. The processing method for improving the interlayer peel strength of energy storage cell electrodes according to claim 1, characterized in that: The multi-stage dispersion process in S1 includes a first-stage dispersion stage, a second-stage dispersion stage, and a third-stage dispersion stage performed sequentially. The rotation speed of the first-stage dispersion stage is 2000~4000 rpm, and the time is 10~20 minutes; the rotation speed of the second-stage dispersion stage is 5000~8000 rpm, and the time is 8~15 minutes; the rotation speed of the third-stage dispersion stage is 9000~12000 rpm, and the time is 3~6 minutes; there is a settling interval of 3~5 minutes between adjacent dispersion stages.

3. The processing method for improving the interlayer peel strength of energy storage cell electrodes according to claim 1, characterized in that: The gradient coating in S3 is achieved through a double-slit coating head, wherein the binder content in the slurry flowing out of the first slit near the current collector is higher than the binder content in the slurry flowing out of the second slit far from the current collector.

4. The processing method for improving the interlayer peel strength of energy storage cell electrodes according to claim 1, characterized in that: In step S3, the resulting adhesive concentration gradient distribution satisfies the following relationship: C1 / C2 = 1.2~2.5 Wherein, C1 is the mass concentration of the binder in the coating on the side closer to the current collector, and C2 is the mass concentration of the binder in the coating on the side farther from the current collector.

5. The processing method for improving the interlayer peel strength of energy storage cell electrodes according to claim 1, characterized in that: The multi-stage drying process in S4 includes a low-temperature slow drying stage, a medium-temperature fast drying stage, and a high-temperature setting stage performed sequentially. Specifically, the low-temperature slow drying stage has a temperature of 50-70°C, a time of 1-3 minutes, and an air velocity of 0.5-1.5 m / s; the medium-temperature fast drying stage has a temperature of 80-100°C, a time of 1-2 minutes, and an air velocity of 1.5-3 m / s; and the high-temperature setting stage has a temperature of 110-140°C, a time of 2-5 minutes, and an air velocity of 0.8-2 m / s.

6. The processing method for improving the interlayer peel strength of energy storage cell electrodes according to claim 1, characterized in that: The interface enhancer in S5 comprises, by weight, the following components: 20-50 parts organic polymer, 5-15 parts conductive agent, 3-10 parts crosslinking agent, 2-8 parts penetration aid, and 100-200 parts solvent. The organic polymer is an organosilicon-modified acrylate; the conductive agent is selected from one or more of conductive carbon black, graphite, and carbon nanotubes; the crosslinking agent is selected from one or more of isocyanate crosslinking agents, epoxy resin crosslinking agents, and organosilane crosslinking agents; the penetrating aid is selected from one or more of sodium dodecylbenzenesulfonate, sodium lauryl sulfate, sodium stearate, hexadecyltrimethylammonium bromide, lauryl polyether, polyethylene glycol stearate, ethanol, isopropanol, ethylene glycol monomethyl ether, and ethylene glycol dimethyl ether; the solvent is selected from one or more of N-methylpyrrolidone, acetone, tetrahydrofuran, water, isopropanol, and ethanol.

7. The processing method for improving the interlayer peel strength of energy storage cell electrode sheets according to claim 1, characterized in that: The pressurized heat treatment in S5 is carried out by hot roller pressing, with a pressure of 0.5~3MPa, a temperature of 60~120℃, and a treatment time of 5~30 seconds.

8. The processing method for improving the interlayer peel strength of energy storage cell electrode sheets according to claim 1, characterized in that: The calendering process in S6 adopts a differential rolling method, with the linear speed ratio of the upper roll to the lower roll being 1.01~1.10:1, the rolling pressure being 50~200MPa, and the rolling temperature being 50~120℃. And / or, the calendering process in S6 further includes ultrasonic-assisted vibration, with an ultrasonic frequency of 20~60kHz and an amplitude of 10~50μm.

9. The processing method for improving the interlayer peel strength of energy storage cell electrodes according to claim 1, characterized in that: In step S1, the slurry further contains 0.5-3 wt% of an interfacial coupling agent, which is selected from one or more of silane coupling agents, titanate coupling agents, and aluminate coupling agents.

10. An electrode sheet, characterized in that, The electrode is prepared by the processing technology described in any one of claims 1-9, and the 180° peel strength of the electrode is not less than 30 N / m.

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