Multi-layer tab directional flow injection process for full-tab battery

Abstract

The application discloses a kind of full tab battery multilayer tab directional flow injection process, comprising the following steps: step one, the full tab battery pole piece with multilayer tab structure is prepared, and the surface of pole piece is formed directional flow groove and conical flow hole by laser etching or mechanical stamping, and flow groove is distributed along the length direction of pole piece and is connected with the staggered connection of multilayer tab group;By designing multilayer tab structure on the surface of the pole piece of full tab battery, combined with directional flow groove and flow hole, the electrolyte infiltration path is optimized, the synergistic effect of the spatial distribution of multilayer tab and flow groove is utilized, the efficient and uniform distribution of electrolyte is realized, the injection time is significantly shortened, the bubble residue is reduced, and the battery energy density and cycle life are improved.The flow design of multilayer tab and dynamic vacuum injection parameter control are suitable for high-capacity battery manufacturing, such as power battery and energy storage battery.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery manufacturing technology, specifically relating to a multi-layer tab directional flow liquid injection process for a full-tab battery. Background Technology

[0002] All-tab batteries have been widely used in the new energy vehicle industry due to their excellent low internal resistance and high rate performance. However, traditional electrolyte injection processes face problems such as uneven electrolyte distribution, long immersion time, and residual air bubbles, which seriously affect the overall performance and stability of the battery.

[0003] In existing technologies, a single tab structure combined with conventional vacuum electrolyte injection is commonly used. However, when multiple electrode layers are stacked, the electrolyte often has difficulty effectively penetrating to the central region of the battery, affecting the electrochemical performance of the central region. Simultaneously, densely packed tab areas are prone to liquid resistance, further increasing the difficulty of uniform electrolyte distribution. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the existing defects and provide a multi-layer tab directional liquid injection process for all-tab batteries to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a multi-layer tab directional liquid injection process for a full-tab battery, comprising the following steps: Step 1: Prepare a full-tab battery electrode sheet with a multi-layer tab structure. The surface of the electrode sheet is formed with directional flow channels and conical flow holes by laser etching or mechanical stamping. The flow channels are distributed in a mesh pattern along the length of the electrode sheet and are interwoven with the multi-layer tab assembly. Step 2: Alternately stack the electrode sheets and separator to assemble the battery cell. Before liquid injection, perform vacuum drying on the battery cell. The drying conditions are: temperature 70-100℃, vacuum degree -85kPa to -100kPa, and treatment time 8-24 hours. Step 3: Electrolyte is injected into the battery cell along the direction of the guide channel using a multi-stage vacuum injection system. The injection process is divided into three stages: initial low-speed injection, main medium-speed injection, and final replenishment. The injection speeds are 0.1-0.3 mL / s, 0.5-1.2 mL / s, and 0.1-0.2 mL / s, respectively, and the injection volume in each stage accounts for 10%-20%, 60%-70%, and 10%-20% of the total injection volume, respectively. Step 4: During the injection process, apply periodic vacuum negative pressure simultaneously. The negative pressure value is -80kPa to -95kPa. Each negative pressure lasts for 5-15 seconds, with an interval of 3-8 seconds. Combine this with stepwise temperature control, gradually increasing the temperature from 25℃ to 50℃. Each stage of temperature increase is 5℃-10℃, and the duration is 5-15 minutes. Step 5: After the liquid injection is completed, let it stand for 4-12 hours at an ambient temperature of 25-40℃. Then, use a small current of 0.02C-0.2C to carry out multi-stage formation, including pre-charging, aging and capacity testing.

[0006] Preferably, the multi-layer tab structure includes at least three tab groups, located at the upper, middle and lower parts of the electrode sheet respectively. The spacing between the tab groups is 8-15mm. Each tab group consists of 3-8 parallel tab units. The tab unit width is 2-5mm. Adjacent tab groups are connected by a guide groove. The guide groove width is 0.5-2.5mm, the depth is 15%-60% of the electrode sheet thickness, and the bottom of the groove has a V-shaped or U-shaped structure with a surface roughness Ra≤0.8μm.

[0007] Preferably, the guide grooves are distributed radially or spirally on the electrode surface, with a groove spacing of 3-10 mm. The guide holes are tapered through holes with the hole diameter gradually decreasing from the electrode surface to the interior. The surface hole diameter is 0.1-0.8 mm, the bottom hole diameter is 0.05-0.3 mm, the taper angle is 20°-45°, the hole density is 5-20 holes / cm², and the position of the guide holes is aligned with the intersection of the guide grooves.

[0008] Preferably, the multi-stage vacuum injection system in step three includes three series vacuum chambers with vacuum levels of -50kPa, -75kPa and -90kPa, respectively. The injection needle adopts a multi-hole spray structure with a hole diameter of 0.1-0.5mm. The injection path is dynamically adjusted according to the position of the tab assembly, and the injection angle is at an angle of 30°-60° with the direction of the guide groove.

[0009] Preferably, the stepped temperature control in step four is divided into four stages:

[0010] First stage: Maintain 25℃ for 5-10 minutes, vacuum negative pressure -80kPa;

[0011] Second stage: Maintain 35℃ for 8-12 minutes, vacuum negative pressure -85kPa;

[0012] Third stage: Maintain 45℃ for 10-15 minutes, vacuum negative pressure -90kPa;

[0013] Fourth stage: Maintain 50℃ for 5-8 minutes, vacuum negative pressure -95kPa.

[0014] Preferably, the electrolyte injection amount is 105%-120% of the cell pore volume, the electrolyte composition is a carbonate solvent containing 1-2M LiPF6, and 0.5%-5% fluoroethylene carbonate and 1%-3% ethylene sulfate are added as additives.

[0015] Preferably, the formation process in step five includes:

[0016] Pre-charge stage: Charge at 0.02C-0.05C current to 3.0-3.5V, and let stand for 2-4 hours;

[0017] Aging stage: Store at 40-60℃ for 24-72 hours;

[0018] Capacity assessment stage: Cycle the cells 3-5 times with a charge-discharge current of 0.1C-0.2C to screen cells with a capacity consistency of ≥98%.

[0019] Preferably, the electrode is a double-sided coated electrode, and the positive electrode active material is a high-nickel ternary material (LiNi). x Co y Mn z O2 (x≥0.8), with a coating thickness of 80-150μm; the negative electrode active material is a silicon-carbon composite material with a coating thickness of 90-160μm and an electrode porosity of 25%-40%.

[0020] Preferably, during the electrolyte injection process in step three, the electrolyte wetting status is monitored in real time by an infrared sensor, and the injection speed and vacuum negative pressure parameters are dynamically adjusted based on the feedback data, with a control accuracy of ±0.05mL / s and ±2kPa.

[0021] Preferably, the surfaces of the flow channel and the flow hole are covered with an electrophilic coating. The coating material is polyvinylidene fluoride or polyethylene oxide, with a thickness of 0.1-1 μm and a contact angle ≤30°. The coating is formed by spraying or chemical vapor deposition.

[0022] Compared with the prior art, the present invention provides a multi-layer tab directional liquid injection process for all-tab batteries, which has the following beneficial effects:

[0023] This invention processes multi-layer tabs on the electrode sheet and incorporates flow channels and orifices to form an electrolyte transport network. Combining a low-speed-medium-speed-low-speed electrolyte injection strategy, and matching the capillary action and vacuum adsorption force of the flow channels, periodic vacuum negative pressure and gradient heating promote electrolyte penetration into the deeper layers of the electrode sheet. This reduces electrolyte wetting time by 30%-50% and reduces bubble residue to below 1%. Electrolyte distribution uniformity between electrodes is improved to over 95%. Battery cycle life is increased by 20%, and energy density increases by 5%-8%. By designing a multi-layer tab structure on the electrode surface of a full-tab battery, combined with directional flow channels and orifices, the electrolyte wetting path is optimized. The spatial distribution of the multi-layer tabs and the synergistic effect of the flow channels achieve efficient and uniform electrolyte distribution, significantly shortening injection time, reducing bubble residue, and improving battery energy density and cycle life. The multi-layer tab flow design and dynamic vacuum injection parameter control are suitable for manufacturing high-capacity batteries such as power batteries and energy storage batteries. Detailed Implementation

[0024] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] This invention provides a technical solution: a multi-layer tab directional liquid injection process for a full-tab battery, comprising the following steps:

[0026] Step 1: Prepare a full-tab battery electrode sheet with a multi-layer tab structure. The surface of the electrode sheet is formed with directional flow channels and conical flow holes by laser etching or mechanical stamping. The flow channels are distributed in a mesh pattern along the length of the electrode sheet and are interwoven with the multi-layer tab assembly.

[0027] Step 2: Alternately stack the electrode sheets and separator to assemble the battery cell. Before liquid injection, perform vacuum drying on the battery cell. The drying conditions are: temperature 70-100℃, vacuum degree -85kPa to -100kPa, and treatment time 8-24 hours.

[0028] Step 3: Electrolyte is injected into the battery cell along the direction of the guide channel using a multi-stage vacuum injection system. The injection process is divided into three stages: initial low-speed injection, main medium-speed injection, and final replenishment. The injection speeds are 0.1-0.3 mL / s, 0.5-1.2 mL / s, and 0.1-0.2 mL / s, respectively, and the injection volume in each stage accounts for 10%-20%, 60%-70%, and 10%-20% of the total injection volume, respectively.

[0029] Step 4: During the injection process, apply periodic vacuum negative pressure simultaneously. The negative pressure value is -80kPa to -95kPa. Each negative pressure lasts for 5-15 seconds, with an interval of 3-8 seconds. Combine this with stepwise temperature control, gradually increasing the temperature from 25℃ to 50℃. Each stage of temperature increase is 5℃-10℃, and the duration is 5-15 minutes.

[0030] Step 5: After the liquid injection is completed, let it stand for 4-12 hours at an ambient temperature of 25-40℃. Then, use a small current of 0.02C-0.2C to carry out multi-stage formation, including pre-charging, aging and capacity testing.

[0031] In this invention, preferably, the multi-layer tab structure includes at least three tab groups, located at the upper, middle and lower parts of the electrode sheet respectively. The spacing between the tab groups is 8-15mm. Each tab group consists of 3-8 parallel tab units. The tab unit width is 2-5mm. Adjacent tab groups are connected by a guide groove. The guide groove width is 0.5-2.5mm, the depth is 15%-60% of the electrode sheet thickness, and the bottom of the groove has a V-shaped or U-shaped structure with a surface roughness Ra≤0.8μm.

[0032] In this invention, preferably, the guide grooves are distributed radially or spirally on the electrode surface, with a groove spacing of 3-10 mm. The guide holes are tapered through holes with the hole diameter gradually decreasing from the electrode surface to the interior. The surface hole diameter is 0.1-0.8 mm, the bottom hole diameter is 0.05-0.3 mm, the taper angle is 20°-45°, the hole density is 5-20 holes / cm², and the position of the guide hole is aligned with the intersection of the guide grooves.

[0033] In this invention, preferably, the multi-stage vacuum injection system in step three includes three series vacuum chambers with vacuum levels of -50kPa, -75kPa and -90kPa, respectively. The injection needle adopts a multi-hole spray structure with a hole diameter of 0.1-0.5mm. The injection path is dynamically adjusted according to the position of the tab assembly, and the injection angle is at an angle of 30°-60° with the direction of the guide groove.

[0034] In this invention, preferably, the stepped temperature control in step four is divided into four stages:

[0035] First stage: Maintain 25℃ for 5-10 minutes, vacuum negative pressure -80kPa;

[0036] Second stage: Maintain 35℃ for 8-12 minutes, vacuum negative pressure -85kPa;

[0037] Third stage: Maintain 45℃ for 10-15 minutes, vacuum negative pressure -90kPa;

[0038] Fourth stage: Maintain 50℃ for 5-8 minutes, vacuum negative pressure -95kPa.

[0039] In this invention, preferably, the electrolyte injection amount is 105%-120% of the cell pore volume, the electrolyte composition is a carbonate solvent containing 1-2M LiPF6, and 0.5%-5% fluoroethylene carbonate and 1%-3% ethylene sulfate are added as additives.

[0040] In this invention, preferably, the formation process in step five includes:

[0041] Pre-charge stage: Charge at 0.02C-0.05C current to 3.0-3.5V, and let stand for 2-4 hours;

[0042] Aging stage: Store at 40-60℃ for 24-72 hours;

[0043] Capacity assessment stage: Cycle the cells 3-5 times with a charge-discharge current of 0.1C-0.2C to screen cells with a capacity consistency of ≥98%.

[0044] In this invention, preferably, the electrode is a double-sided coated electrode, and the positive electrode active material is a high-nickel ternary material (LiNi). xCo y Mn z O2 (x≥0.8), with a coating thickness of 80-150μm; the negative electrode active material is a silicon-carbon composite material with a coating thickness of 90-160μm and an electrode porosity of 25%-40%.

[0045] In this invention, preferably, during the electrolyte injection process in step three, the electrolyte wetting status is monitored in real time by an infrared sensor, and the injection speed and vacuum negative pressure parameters are dynamically adjusted based on the feedback data, with a control accuracy of ±0.05mL / s and ±2kPa.

[0046] In this invention, preferably, the surfaces of the flow channel and the flow hole are covered with an electrophilic coating. The coating material is polyvinylidene fluoride or polyethylene oxide, with a thickness of 0.1-1 μm and a contact angle ≤30°. The coating is formed by spraying or chemical vapor deposition.

[0047] The following describes the contents of this invention in further detail with specific parameters:

[0048] Example 1

[0049] A high-nickel ternary lithium battery, including electrode design:

[0050] Cathode: LiNi 0.8 Co 0.1 Mn 0.1 O2, coating thickness 120μm, porosity 30%;

[0051] Anode: Silicon-carbon composite material (Si-C), coating thickness 140μm, porosity 35%;

[0052] Electrode assembly: 3 layers, 10mm spacing, 4 electrode units per group (3mm width).

[0053] Guide groove: V-shaped groove, 1.0mm wide, with a depth of 30% of the electrode thickness;

[0054] Drainage holes: taper angle 30°, surface hole diameter 0.3mm, density 10 holes / cm².

[0055] The electrolyte injection process for high-nickel ternary lithium-ion batteries is explained, including the following steps:

[0056] Step 1: Vacuum drying: 90℃, -95kPa, 12 hours;

[0057] Step 2: Injection is divided into three stages: 0.2 mL / s (10% of the injection volume), 0.8 mL / s (70% of the injection volume), and 0.15 mL / s (20% of the injection volume).

[0058] Step 3, Dynamic impregnation: Vacuum negative pressure -90kPa, stepwise temperature increase to 45℃, total time 40 minutes;

[0059] Step 4, resting time: 6 hours, conversion current 0.03C.

[0060] Experimental results: Immersion time: 5.5 hours; Electrode coverage: 98%; Capacity retention after 1000 cycles: 93%; 3C discharge efficiency: 95%.

[0061] Example 2

[0062] A lithium iron phosphate energy storage battery, including an electrode design:

[0063] Positive electrode: LiFePO4, coating thickness 150μm, porosity 25%;

[0064] Negative electrode: Graphite, coating thickness 160μm, porosity 30%;

[0065] Electrode assembly: 2 layers, 15mm spacing, 6 electrode units per group (4mm width);

[0066] Flow guide channel: U-shaped channel, 2.0mm wide, with a depth of 40% of the electrode thickness;

[0067] Drainage holes: taper angle 40°, surface hole diameter 0.5mm, density 8 holes / cm².

[0068] A process for injecting electrolyte into a lithium iron phosphate energy storage battery includes the following steps:

[0069] Step 1: Vacuum drying: 80℃, -90kPa, 18 hours;

[0070] Step 2: Injection is divided into three stages: 0.1 mL / s (15% of the injection volume), 1.0 mL / s (65% of the injection volume), and 0.1 mL / s (20% of the injection volume).

[0071] Step 3, Dynamic impregnation: Vacuum negative pressure -85kPa, stepwise temperature increase to 50℃, total time 50 minutes;

[0072] Step 4, resting time: 8 hours, conversion current 0.05C.

[0073] Experimental results: Immersion time: 7 hours; Electrode coverage: 96%; Capacity retention after 2000 cycles: 88%; 1C discharge efficiency: 98%.

[0074] Example 3

[0075] A high-voltage lithium cobalt oxide battery, including an electrode design:

[0076] Positive electrode: LiCoO2, coating thickness 100μm, porosity 28%;

[0077] Anode: Hard carbon, coating thickness 130μm, porosity 32%;

[0078] Electrode assembly: 4 layers, 8mm spacing, 5 electrode units per group (2.5mm width);

[0079] Guide groove: spiral groove, 0.8mm wide, with a depth of 20% of the electrode thickness;

[0080] Drainage holes: taper angle 25°, surface hole diameter 0.2mm, density 15 holes / cm².

[0081] A liquid injection process for a high-voltage lithium cobalt oxide battery includes the following steps:

[0082] Step 1: Vacuum drying: 85℃, -92kPa, 10 hours;

[0083] Step 2: Injection is divided into three stages: 0.3 mL / s (20% of the injection volume), 0.7 mL / s (60% of the injection volume), and 0.2 mL / s (20% of the injection volume).

[0084] Step 3, Dynamic impregnation: Vacuum negative pressure -88kPa, stepwise temperature increase to 40℃, total time 35 minutes;

[0085] Step 4, resting time: 5 hours, conversion current 0.04C.

[0086] Experimental results: wetting time: 4.5 hours; bubble residue rate: 0.5%; capacity retention rate after 500 cycles: 95%; energy density: 280 Wh / kg.

[0087] Example 4

[0088] A solid electrolyte pre-wetted battery, including an electrode design:

[0089] Cathode: LiNi 0.6 Co 0.2 Mn 0.2 O2, coating thickness 110μm, porosity 22%;

[0090] Negative electrode: Lithium metal foil, 50μm thick;

[0091] Guide channel: U-shaped channel, 1.5mm wide, with a depth of 50% of the electrode thickness;

[0092] Drainage holes: taper angle 35°, surface hole diameter 0.4mm, density 12 holes / cm²;

[0093] Hydrophilic coating: PVDF, thickness 0.5μm, contact angle 15°.

[0094] A liquid injection process for a solid electrolyte pre-wetting battery includes the following steps:

[0095] Step 1: Vacuum drying: 95℃, -98kPa, 15 hours;

[0096] Step 2: Injection is divided into three stages: 0.25 mL / s (15% of the injection volume), 0.9 mL / s (65% of the injection volume), and 0.1 mL / s (20% of the injection volume).

[0097] Step 3, Dynamic impregnation: Vacuum negative pressure -93kPa, stepwise temperature increase to 55℃, total time 45 minutes;

[0098] Step 4, resting time: 10 hours, conversion current 0.02C.

[0099] Experimental results: Solid electrolyte wetting time: 8 hours (24 hours for traditional process); Interfacial impedance: 18 Ω·cm² (50 Ω·cm² for traditional process); Capacity retention after 300 cycles: 90%.

[0100] Example 5

[0101] A high-power lithium titanate battery, including an electrode design:

[0102] Positive electrode: Li4Ti5O 12 The coating thickness is 90 μm and the porosity is 38%.

[0103] Negative electrode: Graphene composite negative electrode, with a coating thickness of 100μm and a porosity of 40%;

[0104] Guide groove: radial groove, 0.5mm wide, and 15% of the electrode thickness in depth;

[0105] Drainage holes: taper angle 20°, surface hole diameter 0.1mm, density 20 holes / cm².

[0106] A liquid injection process for a high-power lithium titanate battery includes the following steps:

[0107] Step 1: Vacuum drying: 75℃, -88kPa, 8 hours;

[0108] Step 2: Injection is divided into three stages: 0.15 mL / s (10% of the injection volume), 1.2 mL / s (70% of the injection volume), and 0.1 mL / s (20% of the injection volume).

[0109] Step 3, Dynamic impregnation: Vacuum negative pressure -80kPa, stepwise temperature increase to 30℃, total time 25 minutes;

[0110] Step 4, resting time: 4 hours, conversion current 0.1C.

[0111] Experimental results: Immersion time: 3 hours; 10C rate discharge efficiency: 99%; Capacity retention after 5000 cycles: 85%.

[0112] Comparative Example 1: Traditional Monopolar Ear Injection Process

[0113] Electrode structure: Single-layer electrode, located at one end of the electrode sheet; no guide groove or guide hole; Liquid injection method: constant injection rate of 0.5 mL / s, the injection volume is 150% of the pore volume; Vacuum drying: 80℃, -90 kPa, 24 hours; Standing time: 24 hours.

[0114] Experimental results: wetting time: 18 hours; electrode coverage: 78%; bubble residue rate: 8%; capacity retention rate after 1000 cycles: 75%.

[0115] Comparative Example 2: Design without Guide Channels

[0116] Tab assembly: 3 layers (same as in Example 1); no guide groove or guide hole; liquid injection in three stages (same as in Example 1).

[0117] Experimental results: wetting time: 10 hours; electrode coverage: 85%; bubble residue rate: 3%; capacity retention rate after 1000 cycles: 82%.

[0118] Comparative Example 3: Constant Rate Injection Process

[0119] The electrode and guide groove design are the same as in Example 1; the liquid injection method is a constant rate of 0.5 mL / s, and the liquid injection volume is 130% of the pore volume; there is no dynamic vacuum negative pressure and step temperature control.

[0120] Experimental results: wetting time: 8 hours; electrode coverage: 90%; bubble residue rate: 2.5%; capacity retention rate after 1000 cycles: 85%.

[0121] Comparative Example 4: No hydrophilic coating

[0122] The electrode and guide groove design are the same as in Example 4; the surface of the guide groove is not coated with PVDF / PEO; other processes are the same as in Example 4.

[0123] Experimental results: Solid electrolyte wetting time: 16 hours; Interfacial impedance: 35 Ω·cm²; Capacity retention after 300 cycles: 80%.

[0124] Comparative Example 5: Excessive fluid injection (150% of pore volume)

[0125] The process is the same as in Example 1; the injection volume is 150% of the pore volume.

[0126] Experimental results: Immersion time: 5 hours; Electrolyte leakage rate: 5%; Capacity retention rate after 1000 cycles: 88%.

[0127] Immersion time (h) 5.5 18 10 8 16 5 Electrode coverage (%) 98 78 85 90 82 95 Bubble Residue Rate (%) 0.5 8 3 2.5 4 1.2 Cyclic capacity retention (%) 93 75 82 85 80 88 Liquid injection utilization rate (percentage of pore volume) (%) 105 150 105 130 105 150

[0128] A comparison of the embodiments and comparative examples shows that the present invention, through innovations such as a multi-layer tab flow guiding structure, a staged liquid injection strategy, and a hydrophilic coating, significantly shortens the immersion time, improves the uniformity of electrolyte distribution, and reduces the bubble residue rate. In contrast, traditional processes in the comparative examples (such as those without flow guides and constant-rate liquid injection) exhibit significant disadvantages, further verifying the technical necessity and practical application value of the present invention.

[0129] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for directional liquid injection into a multi-layer tab battery with multiple tabs, characterized in that, Includes the following steps: Step 1: Directional flow channels and conical flow holes are formed on the surface of the multi-tab battery electrode sheet with a multi-tab structure by laser etching or mechanical stamping. The flow channels are distributed in a mesh pattern along the length of the electrode sheet and are interwoven with the multi-tab group. Step 2: Alternately stack the electrode sheets and separator to assemble the battery cell. Before liquid injection, perform vacuum drying on the battery cell. The drying conditions are: temperature 70-100℃, vacuum degree -85kPa to -100kPa, and treatment time 8-24 hours. Step 3: Electrolyte is injected into the battery cell along the direction of the guide channel using a multi-stage vacuum injection system. The injection process is divided into three stages: initial low-speed injection, main medium-speed injection, and final replenishment. The injection speeds are 0.1-0.3 mL / s, 0.5-1.2 mL / s, and 0.1-0.2 mL / s, respectively, and the injection volume in each stage accounts for 10%-20%, 60%-70%, and 10%-20% of the total injection volume, respectively. Step 4: During the injection process, apply periodic vacuum negative pressure simultaneously. The negative pressure value is -80kPa to -95kPa. Each negative pressure lasts for 5-15 seconds, with an interval of 3-8 seconds. Combine this with stepwise temperature control, gradually increasing the temperature from 25℃ to 50℃. Each stage of temperature increase is 5℃-10℃, and the duration is 5-15 minutes. Step 5: After the liquid injection is completed, let it stand for 4-12 hours at an ambient temperature of 25-40℃. Then, use a small current of 0.02C-0.2C to carry out multi-stage formation, including pre-charging, aging and capacity testing.

2. The method for directional liquid injection into a multi-layer tab battery according to claim 1, characterized in that: The multi-layer tab structure includes at least three tab groups, located at the upper, middle and lower parts of the electrode sheet respectively. The spacing between the tab groups is 8-15mm. Each tab group consists of 3-8 parallel tab units. The tab unit width is 2-5mm. Adjacent tab groups are connected by a guide groove. The guide groove width is 0.5-2.5mm, the depth is 15%-60% of the electrode sheet thickness, and the bottom of the groove has a V-shaped or U-shaped structure with a surface roughness Ra≤0.8μm.

3. The method for directional liquid injection into a multi-layer tab battery according to claim 2, characterized in that: The flow channels are radially or spirally distributed on the electrode surface, with a channel spacing of 3-10 mm. The flow holes are tapered through holes, with the hole diameter gradually decreasing from the electrode surface to the interior. The surface hole diameter is 0.1-0.8 mm, the bottom hole diameter is 0.05-0.3 mm, the taper angle is 20°-45°, and the hole density is 5-20 holes / cm². 2 The position of the guide hole is aligned with the intersection of the guide groove.

4. The method for directional liquid injection into a multi-layer tab battery according to claim 1, characterized in that: The multi-stage vacuum injection system in step three includes three series vacuum chambers with vacuum levels of -50kPa, -75kPa and -90kPa, respectively. The injection needle adopts a multi-hole spray structure with a hole diameter of 0.1-0.5mm. The injection path is dynamically adjusted according to the position of the tab assembly, and the injection angle is at an angle of 30°-60° with the direction of the guide groove.

5. The method for directional liquid injection into a multi-layer tab battery according to claim 1, characterized in that: The stepped temperature control in step four is divided into four stages: First stage: Maintain 25℃ for 5-10 minutes, vacuum negative pressure -80kPa; Second stage: Maintain 35℃ for 8-12 minutes, vacuum negative pressure -85kPa; Third stage: Maintain 45℃ for 10-15 minutes, vacuum negative pressure -90kPa; Fourth stage: Maintain 50℃ for 5-8 minutes, vacuum negative pressure -95kPa.

6. The method for directional liquid injection into a multi-layer tab battery according to claim 1, characterized in that: The electrolyte injection amount is 105%-120% of the cell pore volume. The electrolyte composition is 1-2M LiPF6 and carbonate solvent, with 0.5%-5% fluoroethylene carbonate and 1%-3% ethylene sulfate added as additives.

7. The method for directional liquid injection into a multi-layer tab battery according to claim 1, characterized in that: The formation process in step five includes: Pre-charge stage: Charge at 0.02C-0.05C current to 3.0-3.5V, and let stand for 2-4 hours; Aging stage: Store at 40-60℃ for 24-72 hours; Capacity assessment stage: Cycle the cells 3-5 times with a charge-discharge current of 0.1C-0.2C to screen cells with a capacity consistency of ≥98%.

8. The method for directional liquid injection into a multi-layer tab battery according to claim 1, characterized in that: The electrode is a double-sided coated electrode, and the positive electrode active material is a high-nickel ternary material (LiNi). x Co y Mn z O2 (x≥0.8), with a coating thickness of 80-150μm; the negative electrode active material is a silicon-carbon composite material with a coating thickness of 90-160μm and an electrode porosity of 25%-40%.

9. The method for directional liquid injection into a multi-layer tab battery according to claim 1, characterized in that: During the electrolyte injection process in step three, the electrolyte wetting status is monitored in real time by an infrared sensor, and the injection speed and vacuum negative pressure parameters are dynamically adjusted based on the feedback data, with a control accuracy of ±0.05mL / s and ±2kPa.

10. The method for directional liquid injection into a multi-layer tab battery according to claim 1, characterized in that: The surfaces of the flow channels and flow holes are covered with an electrophilic coating. The coating material is polyvinylidene fluoride or polyethylene oxide, with a thickness of 0.1-1 μm and a contact angle of ≤30°. The coating is formed by spraying or chemical vapor deposition.