Water-based sodium-ion battery electrode cutting method and system based on local cryogenic embrittlement

Abstract

The invention discloses an aqueous sodium-ion battery electrode cutting method based on local cryogenic embrittlement, and belongs to the technical field of sodium-ion battery manufacturing, and the aqueous sodium-ion battery electrode cutting method comprises the following steps: S1, forming a cryogenic region with the width of less than or equal to 100 microns by adopting micro-scale liquid nitrogen injection along a preset cutting path of an electrode piece, carrying out local cryogenic embrittlement, and sucking volatile liquid nitrogen gas in real time at the same time; and S2, when the copious cooling area is in a copious cooling state, applying directional mechanical stress to the copious cooling area to enable the electrode plate to generate brittle fracture along the cutting path so as to realize cutting. The invention further discloses a corresponding cutting system. The electrode is locally cryogenically embrittled through micro-scale liquid nitrogen injection, controllable fracture can be realized by applying directional mechanical stress, condensed water pollution is prevented by combining negative pressure adsorption, and the cutting device is suitable for cutting the water-based sodium-ion battery electrode. The edge of the pole piece is neat and free of damage, dust and burrs, side reactions can be reduced, the cycle life is prolonged, and meanwhile safety is improved.

Description

Technical Field

[0001] This invention belongs to the field of sodium-ion battery manufacturing technology, specifically relating to a method and system for achieving non-destructive cutting of electrode sheets through ultra-low temperature local embrittlement, which is particularly suitable for aqueous sodium-ion battery electrodes with a water content >2000ppm. Background Technology

[0002] Traditional electrode slicing processes include mechanical die-cutting, laser cutting, and waterjet cutting. Mechanical die-cutting includes die-cutting and slitting. Die-cutting uses a flat die cutter driven by a servo to vertically press and cut a single electrode sheet with tabs in one pass. Slitting uses upper and lower circular rollers rotating relative to each other to longitudinally and continuously cut a wide electrode into multiple narrow strips. Laser cutting uses a high-energy-density laser beam (usually an infrared picosecond / nanosecond laser) to irradiate the material, causing it to melt, vaporize, or ablate instantaneously, thus achieving non-contact cutting. Waterjet cutting uses a high-energy jet of ultra-high-pressure water (or a mixture of abrasives) for cutting.

[0003] However, traditional electrode slicing processes are not suitable for aqueous sodium-ion battery electrodes. First, mechanical die-cutting generates burrs (>5μm), posing a risk of separator puncture, and dust contamination can cause short circuits. Second, while laser cutting can fundamentally solve the safety hazards of mechanical burrs, its heat-affected zone (HAZ) reaches 20~50μm, which can damage the binder network of aqueous electrodes. In addition, secondary water wetting caused by water jet cutting can lead to the dissolution of active materials (e.g., the solubility of Prussian blue materials is >3%). Summary of the Invention

[0004] To address one or more of the aforementioned deficiencies or improvement needs in existing technologies, this invention provides a method and system for cutting aqueous sodium-ion battery electrodes based on localized cryogenic embrittlement. First, microscale liquid nitrogen injection induces localized cryogenic embrittlement of the electrode; then, directional mechanical stress is applied to achieve controllable fracture. Simultaneously, negative pressure adsorption prevents condensate contamination. This method is suitable for cutting aqueous sodium-ion battery electrodes. The electrode edges are clean, undamaged, dust-free, and burr-free, reducing side reactions, extending cycle life, and improving safety.

[0005] To achieve the above objectives, according to one aspect of the present invention, a method for cutting aqueous sodium-ion battery electrodes based on localized cryogenic embrittlement is provided, comprising the following steps: S1 uses microscale liquid nitrogen injection along the preset cutting path of the electrode sheet to form a cryogenic zone with a width of ≤100μm for local cryogenic embrittlement, while simultaneously drawing in the volatilized liquid nitrogen gas in real time. S2 applies directional mechanical stress to the cryogenic zone when the cryogenic zone is in a cryogenic state, causing the electrode sheet to fracture brittlely along the cutting path to achieve cutting.

[0006] As a further improvement of the present invention, in S1, the conditions for the microscale liquid nitrogen injection are: the particle size of the injected liquid nitrogen atomized particles is 10~30μm, the injection pressure is 0.2~0.8MPa, and the action time is 20~50ms; and / or, In S1, the temperature of the cryogenic zone is between -150°C and -196°C.

[0007] As a further improvement of the present invention, in S1, the volatilized liquid nitrogen gas is drawn in real time by a negative pressure adsorption mechanism, and the vacuum degree of the negative pressure adsorption mechanism is -10kPa to -50kPa.

[0008] As a further improvement of the present invention, in S2, the directional mechanical stress is applied by: outputting a point stress of 0.5~5N perpendicular to the cutting line through a piezoelectric ceramic actuator, or outputting a distributed stress of 0.1~1N / needle perpendicular to the cutting line through a pneumatic microneedle array.

[0009] As a further improvement of the present invention, it also includes S3, applying hot air treatment to the cut surface after cutting; the temperature of the hot air treatment is 40~60℃ and the time is <100ms.

[0010] As a further improvement of the present invention, it also includes S4, coating the cut surface with a repair adhesive; for the positive electrode sheet, the repair adhesive is an oil-based or oxidation-resistant system; for the negative electrode sheet, the repair adhesive is a water-based or reduction-resistant system.

[0011] According to another aspect of the present invention, a cutting system for aqueous sodium-ion battery electrodes based on localized cryogenic embrittlement is provided for the cutting method described above. The cutting system includes a liquid nitrogen micro-jetting mechanism, a stress application mechanism, and an online quality monitoring mechanism arranged sequentially on the electrode sheet conveying path of the aqueous sodium-ion battery; a negative pressure adsorption mechanism is also provided at the liquid nitrogen micro-jetting mechanism. The liquid nitrogen micro-jet mechanism is used to locally cryogenically embrittle the electrode sheet; the negative pressure adsorption mechanism is used to extract the volatilized liquid nitrogen gas in real time during local cryogenic embrittlement; the stress application mechanism is used to apply directional mechanical stress to the cryogenic zone to cause the electrode sheet to fracture brittlely along the cutting path to achieve cutting; the online quality monitoring mechanism is used to detect interface burrs and interface impedance on the cut surface.

[0012] As a further improvement of the present invention, the liquid nitrogen micro-jet system includes a micro-nozzle array, a liquid nitrogen supply and atomization unit connected to the micro-nozzle array; and / or, The negative pressure adsorption mechanism includes an annular negative pressure adsorption tank arranged around the cryogenic zone. The annular negative pressure adsorption tank is an annular tank with an annular hollow cavity. Several pores are opened on the inner side of the annular tank as gas inlets. The annular tank is connected to a vacuum pump group through a pipe.

[0013] As a further improvement of the present invention, the stress application mechanism includes a piezoelectric ceramic actuator or a pneumatic microneedle array; and / or, The online quality monitoring mechanism includes a laser scanning unit and an EIT detection unit, wherein the laser scanning unit is used to detect interface burrs on the cut surface by laser scanning, and the EIT detection unit is used to detect the interface impedance of the cut surface by impedance tomography.

[0014] As a further improvement of the present invention, the cutting system further includes a hot air drying mechanism and a micro-adhesive coating mechanism located downstream of the stress application mechanism; the hot air drying mechanism is used to perform hot air treatment on the fractured cut surface to eliminate residual stress, and the micro-adhesive coating mechanism is used to apply repair adhesive to the cut surface.

[0015] In summary, the technical solutions conceived by this invention have the following beneficial effects compared with the prior art: (1) The cutting method of the present invention establishes an ultra-low temperature micro-region (-150℃ to -196℃) with a width ≤100μm on the electrode cutting path, causing the material to undergo a brittle transition in a sub-second time. Subsequently, directional mechanical stress is applied to achieve controllable fracture. By combining negative pressure adsorption and liquid nitrogen micro-jetting, not only is ultra-local embrittlement achieved, but more importantly, the refrigerant gas can be removed in time, eliminating the possibility of water vapor condensation on the surface of the sensitive electrode. It is suitable for cutting aqueous sodium-ion battery electrodes, achieving burr-free cutting of aqueous sodium-ion battery electrode sheets and obtaining electrode sheets with better electrochemical performance.

[0016] (2) The cutting method of the present invention achieves precise and non-contact separation in the brittle zone by inducing fracture through piezoelectric or pneumatic micro-stress, avoiding burrs and material peeling, and avoiding metal contamination caused by mechanical die-cutting tool wear and active material detachment caused by pressure.

[0017] (3) The cutting method of the present invention combines hot air treatment and repair adhesive coating to optimize the performance of the cutting interface. The mild heating of 40~60°C helps to relax the polymer chain segments, release stress, and prevent microcracks from expanding or coating from peeling off due to stress release during long-term storage or charging and discharging. The repair adhesive can physically isolate the cutting surface from direct contact with the electrolyte, suppress side reactions, and thus improve the cycle life and safety of the aqueous battery.

[0018] (4) The cutting method of the present invention can avoid the HAZ area of ​​traditional laser cutting and the heat-affected zone disappears; the amount of dust generated by brittle fracture is <0.1mg / m² (only 1 / 50 of that of die cutting), and there is no dust pollution; the burr height is <1μm, the perpendicularity deviation is <1°, and the edge quality is improved; it can be stably cut in an environment with a moisture content >5000ppm and is compatible with high water content electrodes; it is suitable for roll-to-roll production of Prussian blue positive electrodes and hard carbon / phosphate negative electrodes, and the cutting speed can reach 8~15m / min. The equipment cost is only less than 40% of that of the laser cutting system.

[0019] (5) The cutting system of the present invention includes a liquid nitrogen micro-jet mechanism (with a negative pressure adsorption mechanism), a stress application mechanism, and an online quality monitoring mechanism arranged sequentially on the electrode conveying path of an aqueous sodium-ion battery; the electrode sheet is conveyed by the conveying mechanism to the corresponding station for embrittlement (with negative pressure anti-condensation adsorption), cutting, and online quality monitoring. This cutting system achieves high-precision, low-damage, and pollution-free cutting of aqueous sodium-ion battery electrodes, and ensures the stability and consistency of the process through online monitoring. Attached Figure Description

[0020] Figure 1 This is a flowchart of an embodiment of the present invention for cutting electrodes of an aqueous sodium-ion battery based on local cryogenic embrittlement; Figure 2 This is a schematic diagram of an aqueous sodium-ion battery electrode cutting system based on localized cryogenic embrittlement, according to an embodiment of the present invention. Figure 3 The images show SEM comparisons of the cutting edges in Embodiment 1 of the present invention (the left image is Embodiment 1 of the present invention, and the right image is traditional hardware die cutting). Figure 4 This is a comparison chart of electrochemical impedance spectroscopy (EIS) of Example 2 of the present invention (where the solid line is Example 2 of the present invention, and the dashed line is traditional hardware die cutting).

[0021] In all the accompanying drawings, the same reference numerals denote the same technical features, specifically: 1. Micro-nozzle array; 2. Annular negative pressure adsorption tank; 3. Piezoelectric ceramic actuator; 4. Hot air drying mechanism; 5. Micro-coating mechanism; 6. Laser scanning unit; 7. EIT detection unit. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0023] The present invention provides an embodiment of a method for cutting aqueous sodium-ion battery electrodes based on localized cryogenic embrittlement, such as... Figure 1 As shown, it includes the following steps: S1 uses microscale liquid nitrogen injection along the preset cutting path of the electrode sheet to form a cryogenic zone with a width of ≤100μm for local cryogenic embrittlement, while simultaneously drawing in the volatilized liquid nitrogen gas in real time.

[0024] Specifically, a liquid nitrogen micro-jet mechanism is used to spray liquid nitrogen atomized particles along a preset cutting path. The liquid nitrogen micro-jet mechanism has a micro-nozzle array, which uses a high-speed, low-temperature, micro-scale jet array to precisely localize ultra-low temperature impacts on the electrode surface, achieving millisecond-level extreme cooling. The electrode coating in this area becomes instantaneously embrittled due to adhesive glass transition and thermal mismatch stress (as well as possible moisture freezing).

[0025] Preferably, the injection pressure is 0.2~0.8MPa, the action time is 20~50ms, the particle size of the injected liquid nitrogen atomized particles is 10~30μm, and the cooling rate is >1000℃ / s.

[0026] Preferably, the temperature in the cryogenic zone is between -150°C and -196°C. This temperature needs to be maintained below the embrittlement critical point of the electrode binder material. For example, the embrittlement point of PVDF is -150°C, and that of CMC-Na is -130°C.

[0027] This invention cools the electrode sheet of an aqueous sodium-ion battery (which typically contains active materials, conductive agents, and binders) below its glass transition temperature, making the polymer binder (such as CMC, SBR) and the entire composite material system brittle, reducing its ductility and toughness, which facilitates subsequent brittle fracture and avoids crack formation.

[0028] However, when a jet of liquid nitrogen at -196°C impacts the surface of an electrode at room temperature, it not only vaporizes itself but also drastically cools the air above and around it. Water vapor in the air instantly becomes supersaturated and condenses into liquid droplets or solid ice crystals, centered on the electrode surface and suspended particles. Without protection, these condensates fall directly onto the freshly processed electrode surface, which is still extremely cold. The liquid water, upon contact with the electrode, is absorbed by hydrophilic materials (Prussian blue analogues and binders such as CMC and sodium alginate), directly disrupting the chemical integrity of the area. Furthermore, if the condensate first freezes and covers the surface, when the electrode returns to room temperature, the ice melts and water still seeps into the coating, causing further damage. In addition, residual moisture can also affect subsequent adhesive repairs.

[0029] Therefore, in the preferred embodiment, during local cryogenic embrittlement, the volatilized liquid nitrogen gas is drawn off in real time to prevent water vapor in the air from condensing, frosting, or even freezing on the surface of the ultra-low temperature electrode.

[0030] More preferably, a negative pressure adsorption mechanism arranged around the cutting zone (cryogenic zone) is used to continuously extract the volatilized liquid nitrogen gas, preventing condensate contamination. Around the area where the liquid nitrogen microjets impact the electrode plates, the low-temperature nitrogen gas generated by vaporization, as well as any trace amounts of water vapor, ice crystals, and coating particles that may be entrained, are captured and discharged instantly and efficiently. More specifically, the vacuum level of the negative pressure adsorption mechanism is -10 kPa to -50 kPa.

[0031] S2 applies directional mechanical stress to the cryogenic zone when the cryogenic zone is in a cryogenic state, causing the electrode sheet to fracture brittlely along the cutting path to achieve cutting.

[0032] Preferably, a stress perpendicular to the cutting line is applied to the cryogenic zone in step S1 to achieve directional stress fracture. A highly localized, directional mechanical stress (such as peeling force, shear force, or three-point bending force) is applied at a predetermined location in the embrittled region (the starting point of the cutting line or along the line). This induces low-energy brittle fracture of the material along the predetermined cutting path. Ideally, the crack can propagate along the coating / foil interface or the embrittled adhesive network, thereby causing the coating to neatly separate from the foil or break off on its own. The applied stress value is preferably 0.5~3N, which can be adjusted according to the electrode thickness.

[0033] More preferably, the directional mechanical stress is applied by outputting a point stress of 0.5~5N perpendicular to the cutting line through a piezoelectric ceramic actuator, or by outputting a distributed stress of 0.1~1N / needle perpendicular to the cutting line through a pneumatic microneedle array. The fracture propagation rate is preferably controlled at 0.5~2m / s to avoid irregular cracks. The specific adjustment can be made according to the thickness of the electrode sheet.

[0034] Among them, piezoelectric ceramic actuators can achieve nanometer-level precision displacement control, controllable stress application, and minimal edge damage, making them suitable for high-precision, complex-shaped electrode cutting. Pneumatic microneedle arrays are suitable for large-area, high-efficiency batch cutting; through array design, multiple pieces or complex patterns can be cut in one operation. Compared with traditional mechanical cutting (die-cutting, laser cutting), the use of piezoelectric ceramic actuators and pneumatic microneedle arrays avoids problems such as burrs, heat-affected zones (especially important for water systems, as there is no thermal decomposition), and dust, improving the neatness and consistency of the cut surface.

[0035] S3 applies hot air treatment to the cut surface after cutting to eliminate residual stress.

[0036] Preferably, the hot air treatment temperature is 40~60℃, and the time is <100ms. Excessive temperature will cause the binder to soften and the electrode to deform; too low a temperature will result in poor performance. For most aqueous sodium electrode materials (including Prussian blue analogues), 40~60℃ is far below the critical temperature (usually above 80~100℃) that may cause a large and rapid release of crystal water, which is compatible with the material's thermal stability and greatly reduces the risk of thermal damage to the electrode material.

[0037] On the one hand, by locally heating to a certain temperature (far below the material's melting point, but above its recrystallization temperature or glass transition temperature), sufficient energy is provided to the metal atoms and crystal defects, enabling them to move and rearrange, thereby releasing elastic strain capacity. On the other hand, it can restore some chain segment mobility to the glassy binder (PVDF's Tg is approximately -35℃, and SBR's Tg is approximately -60℃), promoting the interdiffusion of polymer chains on the brittle fracture surface, achieving "self-healing," and repairing microcracks. Furthermore, gentle heating helps to dissipate trace amounts of water molecules that may be adsorbed on the cut surface, ensuring interface dryness, and can also soften the tips of microcracks at the cut edge, resulting in a more uniform stress distribution.

[0038] S4 is coated with nano-level conductive repair adhesive on the cut surface; The post-processing steps also include coating the cut surface with a nanoscale repair adhesive. First, the adhesive seals microscopic cracks invisible to the naked eye that occur during the brittle fracture process, restoring the mechanical integrity of the cut area. Second, it repairs conductive pathways (such as carbon black) damaged by fracture, ensuring that the electronic conductivity of the cut edge area matches the bulk, reducing local impedance. Additionally, it provides a protective layer to the cut surface, mitigating potential side reactions of the electrolyte on the fresh fracture surface.

[0039] The repair adhesive must be compatible with aqueous systems (alkali-resistant, does not introduce harmful impurities), have appropriate viscosity and bonding strength, good conductivity after curing, and not affect ion transport within the battery. Preferably, for the positive electrode, the repair adhesive is an oil-based or oxidation-resistant system; for the negative electrode, the repair adhesive is an aqueous or reduction-resistant system. More preferably, the thickness of the repair adhesive is preferably 200-500 nm.

[0040] The electrode cutting method for aqueous sodium-ion batteries of the present invention can be used for cutting both positive and negative electrode sheets of aqueous sodium-ion batteries. The specific parameters in the above steps can be adjusted for different sodium-ion electrode materials (positive / negative electrodes).

[0041] Taking positive electrode sheets (Prussian blue type) and negative electrode sheets (hard carbon / phosphate type) as examples, in step S1, the liquid nitrogen micro-jet spraying pressure for the positive electrode sheet is higher and the time is longer, while the pressure for the negative electrode sheet is lower and the time is shorter. Preferably, during embrittlement, the liquid nitrogen micro-jet spraying pressure for the positive electrode sheet is 0.4~0.8MPa, and the action time is 30~50ms; the liquid nitrogen micro-jet spraying pressure for the negative electrode sheet is 0.2~0.5MPa, and the action time is 20~40ms. In step S2, the parameters for cutting the positive and negative electrode sheets using piezoelectric ceramic actuators or pneumatic microneedle arrays are basically the same; in step S3, the hot air post-treatment parameters for the positive and negative electrode sheets are basically the same. In step S4, the post-treatment step for applying the repair adhesive includes a PVDF (polyvinylidene fluoride) binder, a carbon nanotube (CNT) conductive agent, and an NMP (N-methylpyrrolidone) solvent, wherein the solid content is preferably 3% to 8%. The repair adhesive for the negative electrode includes an SBR (styrene-butadiene rubber) binder, conductive carbon black (Super P), and a deionized water solvent, wherein the solid content is preferably 5% to 10%.

[0042] The electrode cutting method for aqueous sodium-ion batteries employing the localized cryogenic embrittlement method of this invention produces clean, undamaged electrode edges, reducing side reactions, lowering polarization, and extending cycle life. The absence of dust and burrs also reduces the risk of internal short circuits, improving safety. It is particularly suitable for processing electrodes made from high-capacity active materials with poor mechanical properties (such as certain Prussian blue analogues and organic electrode materials).

[0043] like Figure 2 As shown, this embodiment of the invention also provides a cutting system corresponding to the method for cutting aqueous sodium-ion battery electrodes with localized cryogenic embrittlement. The system includes a liquid nitrogen micro-jet mechanism 1, a stress application mechanism 3, and an online quality monitoring mechanism sequentially arranged along the electrode conveying path. A negative pressure adsorption mechanism 2 is also provided at the liquid nitrogen micro-jet mechanism. The electrode is conveyed by the conveying mechanism to the corresponding workstation for embrittlement (simultaneously subjected to negative pressure anti-condensation adsorption), cutting, and online quality monitoring.

[0044] The liquid nitrogen micro-jet mechanism is used to locally cryogenically embrittle the electrode plates. The liquid nitrogen micro-jet system includes a micro-nozzle array 1 and a liquid nitrogen supply and atomization unit connected to the micro-nozzle array. Preferably, the liquid nitrogen supply and atomization unit includes a multi-stage pressure-reducing and flow-stabilizing chamber.

[0045] Preferably, the micro-nozzle array consists of tens to hundreds of nozzles with apertures in the micrometer range. The array can be designed as a one-dimensional linear array (for scanning cutting) or a two-dimensional planar array (for area processing). More preferably, the aperture of the micro-nozzle array is 50~200μm, the particle size of the sprayed liquid nitrogen atomized particles is 10~30μm, the spray pressure is 0.2~0.8MPa, the action time is 20~50ms, and the cooling rate is >1000℃ / s.

[0046] The negative pressure adsorption mechanism is used to extract volatile liquid nitrogen gas in real time during localized cryogenic embrittlement, preventing condensate contamination. Preferably, the negative pressure adsorption mechanism includes an annular negative pressure adsorption tank 2 arranged around the cutting zone (cryogenic zone). The annular negative pressure adsorption tank 2 is an annular groove with an annular hollow cavity. Several pores are opened on the inner side of the annular groove (near the injection center) as gas inlets. The annular groove is connected to a vacuum pump group through a pipe, thereby forming a stable negative pressure (vacuum degree) within the groove. More specifically, the vacuum degree of the negative pressure adsorption mechanism is -10kPa to -50kPa.

[0047] The stress application mechanism is used to apply stress perpendicular to the cutting line to the cryogenic zone to achieve directional stress fracture. The stress application mechanism includes a piezoelectric ceramic actuator 3 or a pneumatic microneedle array. Preferably, a position synchronization triggering system (PSD) from the prior art is used to synchronously control the piezoelectric ceramic actuator or the pneumatic microneedle array. When the embrittled area of ​​the electrode on the conveyor belt reaches below the stress application head, the actuator or microneedle quickly moves downward a set distance, only contacting the electrode surface to apply pressure without piercing the current collector, and quickly retracts after applying stress. In addition, the arrangement of the pneumatic microneedle array is not specifically limited here, as long as it is consistent with the shape of the preset cutting path (straight line or curve).

[0048] The online quality monitoring system includes a laser scanning unit 6 and an EIT detection unit 7. The laser scanning unit 6 is used to detect interface burrs on the cut surface by laser scanning, and the EIT detection unit 7 is used to detect the interface impedance of the cut surface by impedance tomography.

[0049] In a preferred embodiment, the cutting system further includes a hot air drying mechanism 4 and a micro-adhesive coating mechanism 5 located downstream of the stress application mechanism; wherein the hot air drying mechanism is used to treat the fractured cut surface with hot air to eliminate residual stress, and the micro-adhesive coating mechanism is used to coat the cut surface with repair adhesive.

[0050] In a preferred embodiment, the liquid nitrogen micro-jet mechanism and the piezoelectric stress application mechanism are also equipped with corresponding motion and positioning platforms, which are used to drive the micro-nozzle array of the liquid nitrogen micro-jet mechanism and the end of the stress application mechanism to align with the electrode plate and travel along a preset path to achieve local cryogenic embrittlement and brittle fracture under cryogenic conditions. The liquid nitrogen micro-jet mechanism and the piezoelectric stress application mechanism can share the same motion and positioning platform or have separate independent motion and positioning platforms.

[0051] For example, the motion and positioning platform of the piezoelectric stress application mechanism includes a high-frequency Z-axis lifting module and a gantry spanning the conveyor belt. The piezoelectric ceramic actuator or pneumatic microneedle array is mounted on the high-frequency Z-axis lifting module, which is fixed on the gantry spanning the conveyor belt (capable of moving along the X and Y axes). The actuator or microneedle is driven by the Z-axis module to quickly apply stress and then retract rapidly.

[0052] The following are specific examples: Example 1 (Prussian Blue Positive Electrode Cutting) In this embodiment, the electrode parameters of the Prussian blue cathode are: thickness 180 μm, water content 2500 ppm, and CMC binder dosage 6%.

[0053] In this embodiment, the method for cutting locally cryogenically embrittled aqueous sodium-ion battery electrodes includes the following steps: 1) A cryogenic zone with a width of 80 μm is formed along the preset cutting path of the electrode sheet by a liquid nitrogen micro-jet mechanism to perform local cryogenic embrittlement; the liquid nitrogen jet pressure is 0.5 MPa, the time is 30 ms, and the temperature is -170℃. At the same time, the volatilized liquid nitrogen gas is drawn in real time by a negative pressure adsorption mechanism, and the vacuum degree of the negative pressure adsorption is -30 kPa.

[0054] 2) When the cryogenic zone is in a cryogenic state, a piezoelectric ceramic actuator is used to apply point stress perpendicular to the cutting line in the cryogenic zone of step 1), so that the electrode sheet undergoes brittle fracture along the cutting path to achieve cutting; the piezoelectric stress of the piezoelectric ceramic actuator is 1.8N (pulse width 10ms, response time <1ms).

[0055] 3) After cutting, treat the cut surface with 55℃ hot air for 80ms to repair the edges.

[0056] The SEM comparison image of the electrode cutting edge in this embodiment is as follows: Figure 3 As shown, the cut surface of Example 1 exhibits a flat, smooth surface and neat, burr-free edges (cutting edge burrs < 0.5 μm), with no active material shedding, indicating minimal mechanical damage to the material during the cutting process. In contrast, the cut surface produced by traditional metal die-cutting methods is rough and uneven, with serrated edges and a large amount of burrs and debris, indicating significant mechanical stress generated during the cutting process, causing obvious damage to the material.

[0057] Example 2 (Cut-off Hard Carbon Anode) In this embodiment, the electrode parameters of the hard carbon anode are: thickness 120μm, water content 3000ppm, and SBR binder dosage 8%.

[0058] In this embodiment, the method for cutting locally cryogenically embrittled aqueous sodium-ion battery electrodes includes the following steps: 1) A 60μm wide cryogenic zone is formed along the preset cutting path of the electrode sheet using a liquid nitrogen micro-jet mechanism to perform local cryogenic embrittlement; the liquid nitrogen jet pressure is 0.3MPa, the time is 40ms, and the temperature is -160℃. At the same time, the volatilized liquid nitrogen gas is drawn in real time by a negative pressure adsorption mechanism, and the vacuum degree of the negative pressure adsorption is -30kPa.

[0059] 2) When the cryogenic zone is in a cryogenic state, a pneumatic microneedle array is used to apply distributed stress perpendicular to the cutting line to the cryogenic zone in step 1), so that the electrode sheet undergoes brittle fracture along the cutting path to achieve cutting; the array spacing of the pneumatic microneedle array is 200μm, the diameter of a single needle is 100μm, and the force of a single needle is 0.7N.

[0060] 3) After cutting, treat the cut surface with 55℃ hot air for 80ms to repair the edges.

[0061] The electrochemical impedance spectroscopy (EIS) comparison diagram of this embodiment is as follows: Figure 4 As shown, the impedance of the electrode after cutting in this embodiment is much smaller than that of the electrode sheet cut by traditional metal die cutting, indicating that the cutting method in this embodiment causes less damage to the electrode sheet and is a better cutting method.

[0062] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for cutting electrodes in aqueous sodium-ion batteries based on localized cryogenic embrittlement, characterized in that, Includes the following steps: S1 uses microscale liquid nitrogen injection along the preset cutting path of the electrode sheet to form a cryogenic zone with a width of ≤100μm for local cryogenic embrittlement, while simultaneously drawing in the volatilized liquid nitrogen gas in real time. S2 applies directional mechanical stress to the cryogenic zone when the cryogenic zone is in a cryogenic state, causing the electrode sheet to fracture brittlely along the cutting path to achieve cutting.

2. The method for cutting aqueous sodium-ion battery electrodes based on localized cryogenic embrittlement according to claim 1, characterized in that, In S1, the conditions for the microscale liquid nitrogen injection are: the particle size of the injected liquid nitrogen atomized particles is 10~30μm, the injection pressure is 0.2~0.8MPa, and the action time is 20~50ms; and / or, In S1, the temperature of the cryogenic zone is between -150°C and -196°C.

3. The method for cutting aqueous sodium-ion battery electrodes based on localized cryogenic embrittlement according to claim 1, characterized in that, In S1, the volatilized liquid nitrogen gas is drawn in real time by a negative pressure adsorption mechanism, and the vacuum degree of the negative pressure adsorption mechanism is -10kPa to -50kPa.

4. The method for cutting aqueous sodium-ion battery electrodes based on localized cryogenic embrittlement according to claim 1, characterized in that, In S2, the directional mechanical stress is applied by: outputting a point stress of 0.5~5N perpendicular to the cutting line through a piezoelectric ceramic actuator, or outputting a distributed stress of 0.1~1N / needle perpendicular to the cutting line through a pneumatic microneedle array.

5. The method for cutting aqueous sodium-ion battery electrodes based on localized cryogenic embrittlement according to any one of claims 1-4, characterized in that, It also includes S3, which applies hot air treatment to the cut surface after cutting; the temperature of the hot air treatment is 40~60℃ and the time is <100ms.

6. The method for cutting aqueous sodium-ion battery electrodes based on localized cryogenic embrittlement according to claim 5, characterized in that, It also includes S4, coating the cut surface with a repair adhesive; for the positive electrode sheet, the repair adhesive is an oil-based or oxidation-resistant system; for the negative electrode sheet, the repair adhesive is a water-based or reduction-resistant system.

7. A water-based sodium-ion battery electrode cutting system based on localized cryogenic embrittlement, characterized in that, The cutting method according to any one of claims 1-6 is characterized in that the cutting system includes a liquid nitrogen micro-jet mechanism, a stress application mechanism, and an online quality monitoring mechanism arranged sequentially on the electrode sheet conveying path of an aqueous sodium-ion battery; a negative pressure adsorption mechanism is also provided at the liquid nitrogen micro-jet mechanism; The liquid nitrogen micro-jet mechanism is used to locally cryogenically embrittle the electrode sheet; the negative pressure adsorption mechanism is used to extract the volatilized liquid nitrogen gas in real time during local cryogenic embrittlement; the stress application mechanism is used to apply directional mechanical stress to the cryogenic zone to cause the electrode sheet to fracture brittlely along the cutting path to achieve cutting; the online quality monitoring mechanism is used to detect interface burrs and interface impedance on the cut surface.

8. The aqueous sodium-ion battery electrode cutting system based on localized cryogenic embrittlement according to claim 7, characterized in that, The liquid nitrogen micro-jet system includes a micro-nozzle array, a liquid nitrogen supply and atomization unit connected to the micro-nozzle array; and / or The negative pressure adsorption mechanism includes an annular negative pressure adsorption tank arranged around the cryogenic zone. The annular negative pressure adsorption tank is an annular tank with an annular hollow cavity. Several pores are opened on the inner side of the annular tank as gas inlets. The annular tank is connected to a vacuum pump group through a pipe.

9. The aqueous sodium-ion battery electrode cutting system based on localized cryogenic embrittlement according to claim 8, characterized in that, The stress application mechanism includes a piezoelectric ceramic actuator or a pneumatic microneedle array; and / or, The online quality monitoring mechanism includes a laser scanning unit and an EIT detection unit, wherein the laser scanning unit is used to detect interface burrs on the cut surface by laser scanning, and the EIT detection unit is used to detect the interface impedance of the cut surface by impedance tomography.

10. The aqueous sodium-ion battery electrode cutting system based on localized cryogenic embrittlement according to any one of claims 7-9, characterized in that, The cutting system also includes a hot air drying mechanism and a micro-adhesive coating mechanism located downstream of the stress application mechanism; the hot air drying mechanism is used to treat the fractured cut surface with hot air to eliminate residual stress, and the micro-adhesive coating mechanism is used to apply repair adhesive to the cut surface.

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