Directional diversion and liquid injection process for multi-layer tabs of full-tab battery

Abstract

The invention discloses an all-tab battery multi-layer tab directional flow guide liquid injection process which comprises the following steps: step 1, preparing an all-tab battery pole piece with a multi-layer tab structure, forming directional flow guide grooves and conical flow guide holes in the surface of the pole piece through laser etching or mechanical stamping, and enabling the flow guide grooves to be distributed in a net shape along the length direction of the pole piece, the multiple layers of tab groups are connected in a staggered manner; a multi-layer tab structure is designed on the surface of a pole piece of the full-tab battery, directional diversion trenches and diversion holes are combined, an electrolyte infiltration path is optimized, and the spatial distribution of the multi-layer tabs and the synergistic effect of the diversion trenches are utilized, so that efficient and uniform distribution of an electrolyte is realized, the liquid injection time is remarkably shortened, and bubble residues are reduced; and the battery energy density and cycle life are improved. The diversion design of the multi-layer tabs and dynamic vacuum liquid injection parameter control are suitable for manufacturing high-capacity batteries such as power batteries and energy storage batteries.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-ion battery manufacturing, and in particular relates to a directional flow-guiding and liquid-injecting process for multi-layer tabs of a full-tab battery. Background Art

[0002] Full-tab batteries, with their exceptional low internal resistance and high-rate performance, have been widely used in the new energy vehicle industry. However, traditional electrolyte injection processes face challenges such as uneven electrolyte distribution, long soaking times, and residual bubbles, which severely impact the overall performance and stability of the battery.

[0003] The current technology generally uses a single tab structure coupled with conventional vacuum injection. However, when multiple tabs are stacked, the electrolyte often has difficulty effectively penetrating the center of the battery, affecting the electrochemical performance in this area. Furthermore, areas with dense tabs are prone to liquid resistance, further complicating the challenge of achieving 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 directional guide and liquid injection process for multi-layer tabs of full-tab batteries to solve the problems raised in the above background technology.

[0005] To achieve the above-mentioned object, the present invention provides the following technical solution: a directional flow-guiding and liquid-injecting process for multi-layer tabs of a full-tab battery, comprising the following steps: Step 1: Prepare a full-tab battery electrode sheet with a multi-layer tab structure. Directional guide grooves and conical guide holes are formed on the surface of the electrode sheet by laser etching or mechanical stamping. The guide grooves are distributed in a mesh pattern along the length of the electrode sheet and are staggered with the multi-layer tab group. Step 2: Alternately stack the pole pieces and the diaphragms to form a battery cell. Before injecting the liquid, the battery cell is vacuum dried under the following conditions: temperature 70-100°C, vacuum degree -85kPa to -100kPa, and treatment time 8-24 hours. Step 3: Inject the electrolyte into the battery cell along the guide groove through a multi-stage vacuum injection system. The injection process is divided into three stages: initial low-speed injection, main medium-speed injection, and final stage filling. The injection speeds are 0.1-0.3mL / s, 0.5-1.2mL / s, and 0.1-0.2mL / s, respectively. The injection volume in each stage accounts for 10%-20%, 60%-70%, and 10%-20% of the total injection volume. Step 4: During the injection process, periodic vacuum negative pressure is applied synchronously, with a negative pressure value of -80kPa to -95kPa, each negative pressure lasting 5-15 seconds, with an interval of 3-8 seconds, and combined with step-by-step temperature control, the temperature is gradually increased from 25°C to 50°C, with a temperature increase of 5°C to 10°C in each stage, and the maintenance time is 5-15 minutes; Step 5: After the injection is completed, let it stand for 4-12 hours at an ambient temperature of 25-40°C. Then, use a low current of 0.02C-0.2C for multi-stage formation, including pre-charge, aging and capacity separation steps.

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

[0007] Preferably, the guide grooves are distributed radially or spirally on the surface of the pole piece, and the groove spacing is 3-10 mm. The guide holes are tapered through holes, and the aperture gradually decreases from the surface of the pole piece to the inside. The surface aperture is 0.1-0.8 mm, the bottom aperture is 0.05-0.3 mm, the taper angle is 20°-45°, the hole density is 5-20 / 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-stage series vacuum chambers with vacuum degrees of -50kPa, -75kPa and -90kPa respectively. The injection needle adopts a porous spray structure with a pore size of 0.1-0.5mm. The injection path is dynamically adjusted according to the position of the tab group, and the injection angle is 30°-60° with the direction of the guide groove.

[0009] Preferably, the step-by-step temperature increase control in step 4 is divided into four stages:

[0010] Stage 1: Maintain at 25°C for 5-10 minutes, vacuum pressure -80kPa;

[0011] Stage 2: Maintain at 35°C for 8-12 minutes, vacuum pressure -85kPa;

[0012] Stage 3: Maintain at 45°C for 10-15 minutes, vacuum pressure -90kPa;

[0013] Stage 4: Maintain at 50°C for 5-8 minutes, vacuum pressure -95kPa.

[0014] Preferably, the electrolyte injection amount is 105%-120% of the pore volume of the battery cell, and the electrolyte composition is a carbonate solvent containing 1-2MLiPF6, with 0.5%-5% fluoroethylene carbonate and 1%-3% vinyl sulfate added as additives.

[0015] Preferably, the chemical formation process in step 5 includes:

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

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

[0018] Capacity classification stage: Charge and discharge at a current of 0.1C-0.2C for 3-5 times 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), the coating thickness is 80-150μm; the negative electrode active material is a silicon-carbon composite material, the coating thickness is 90-160μm, and the electrode porosity is 25%-40%.

[0020] Preferably, during the liquid injection process in step 3, the electrolyte infiltration state is monitored in real time by an infrared sensor, and the liquid injection speed and vacuum negative pressure parameters are dynamically adjusted according to the feedback data, with a control accuracy of ±0.05 mL / s and ±2 kPa.

[0021] Preferably, the surfaces of the guide grooves and guide holes are covered with an electrophilic electrolyte coating, the coating material is polyvinylidene fluoride or polyethylene oxide, the thickness is 0.1-1 μm, the contact angle is ≤30°, and the coating is formed by spraying or chemical vapor deposition process.

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

[0023] The present invention processes a multi-layer tab group on the electrode and provides flow guide grooves and flow guide holes to form an electrolyte transmission network. Combining a low-speed, medium-speed, and low-speed injection strategy, the capillary action of the flow guide grooves matches the vacuum adsorption force. Periodic vacuum negative pressure and gradient temperature increase are used to promote deep penetration of the electrolyte into the electrode. This shortens the electrolyte infiltration time by 30%-50% and reduces the bubble residue rate to below 1%. The electrolyte distribution uniformity between the electrode pieces is improved to over 95%, resulting in a 20% increase in battery cycle life and a 5%-8% increase in energy density. By designing a multi-layer tab structure on the electrode surface of a full-tab battery, combined with directional flow guide grooves and flow guide holes, the electrolyte infiltration path is optimized. The spatial distribution of the multi-layer tabs and the synergistic effect of the flow guide grooves achieve efficient and uniform electrolyte distribution, significantly shortening the injection time, reducing bubble residue, and improving battery energy density and cycle life. The multi-layer tab flow guide design and dynamic vacuum injection parameter control are suitable for the manufacture of high-capacity batteries such as power batteries and energy storage batteries. DETAILED DESCRIPTION

[0024] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0025] The present invention provides a technical solution: a directional flow-guiding and liquid-injecting process for multi-layer tabs of a full-tab battery, comprising the following steps:

[0026] Step 1: Prepare a full-tab battery electrode sheet with a multi-layer tab structure. Directional guide grooves and conical guide holes are formed on the surface of the electrode sheet by laser etching or mechanical stamping. The guide grooves are distributed in a mesh pattern along the length of the electrode sheet and are staggered with the multi-layer tab group.

[0027] Step 2: Alternately stack the pole pieces and the diaphragms to form a battery cell. Before injecting the liquid, the battery cell is vacuum dried under the following conditions: temperature 70-100°C, vacuum degree -85kPa to -100kPa, and treatment time 8-24 hours.

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

[0029] Step 4: During the injection process, periodic vacuum negative pressure is applied synchronously, with a negative pressure value of -80kPa to -95kPa, each negative pressure lasting 5-15 seconds, with an interval of 3-8 seconds, and combined with step-by-step temperature control, the temperature is gradually increased from 25°C to 50°C, with a temperature increase of 5°C to 10°C in each stage, and the maintenance time is 5-15 minutes;

[0030] Step 5: After the injection is completed, let it stand for 4-12 hours at an ambient temperature of 25-40°C. Then, use a low current of 0.02C-0.2C for multi-stage formation, including pre-charge, aging and capacity separation steps.

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

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

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

[0034] In the present invention, preferably, the step-by-step temperature increase control in step 4 is divided into four stages:

[0035] Stage 1: Maintain at 25°C for 5-10 minutes, vacuum pressure -80kPa;

[0036] Stage 2: Maintain at 35°C for 8-12 minutes, vacuum pressure -85kPa;

[0037] Stage 3: Maintain at 45°C for 10-15 minutes, vacuum pressure -90kPa;

[0038] Stage 4: Maintain at 50°C for 5-8 minutes, vacuum pressure -95kPa.

[0039] In the present invention, preferably, the electrolyte injection amount is 105%-120% of the pore volume of the battery cell, the electrolyte composition is a carbonate solvent containing 1-2MLiPF6, and 0.5%-5% of fluoroethylene carbonate and 1%-3% of vinyl sulfate are added as additives.

[0040] In the present invention, preferably, the chemical formation process in step 5 includes:

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

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

[0043] Capacity classification stage: Charge and discharge at a current of 0.1C-0.2C for 3-5 times to screen cells with a capacity consistency of ≥98%.

[0044] In the present 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), the coating thickness is 80-150μm; the negative electrode active material is a silicon-carbon composite material, the coating thickness is 90-160μm, and the electrode porosity is 25%-40%.

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

[0046] In the present invention, preferably, the surfaces of the guide grooves and guide holes are covered with an electrophilic electrolyte coating, the coating material is polyvinylidene fluoride or polyethylene oxide, the thickness is 0.1-1 μm, the contact angle is ≤30°, and the coating is formed by spraying or chemical vapor deposition process.

[0047] The content of the present invention is further described below with specific parameters:

[0048] Example 1

[0049] A high-nickel ternary power battery, including a pole piece design:

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

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

[0052] Tab group: 3 layers, 10mm spacing, 4 tab units per group (3mm width);

[0053] Guide groove: V-shaped groove, width 1.0mm, depth 30% of the pole piece thickness;

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

[0055] The injection process of high nickel ternary power battery is described, which includes the following steps:

[0056] Step 1: vacuum drying: 90°C, -95kPa, 12 hours;

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

[0058] Step 3: Dynamic infiltration: vacuum negative pressure -90kPa, step-by-step temperature increase to 45°C, total time 40 minutes;

[0059] Step 4: Standing time: 6 hours, formation 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 a pole piece design:

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

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

[0065] Tab group: 2 layers, 15mm spacing, 6 tab units per group (4mm width);

[0066] Guide groove: U-shaped groove, width 2.0mm, depth 40% of the thickness of the pole piece;

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

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

[0069] Step 1: vacuum drying: 80°C, -90kPa, 18 hours;

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

[0071] Step 3: Dynamic infiltration: vacuum negative pressure -85kPa, step-by-step temperature increase to 50°C, total time 50 minutes;

[0072] Step 4: Standing time: 8 hours, formation 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 a pole piece design:

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

[0077] Negative electrode: hard carbon, coating thickness 130μm, porosity 32%;

[0078] Tab group: 4 layers, 8mm spacing, 5 tab units per group (2.5mm width);

[0079] Guide groove: spiral groove, width 0.8mm, depth 20% of the pole piece thickness;

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

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

[0082] Step 1: vacuum drying: 85°C, -92 kPa, 10 hours;

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

[0084] Step 3: Dynamic infiltration: vacuum negative pressure -88kPa, step-by-step temperature increase to 40°C, total time 35 minutes;

[0085] Step 4: Standing time: 5 hours, formation current 0.04C.

[0086] Experimental results: Immersion time: 4.5 hours; Bubble residual rate: 0.5%; Capacity retention rate after 500 cycles: 95%; Energy density: 280Wh / kg.

[0087] Example 4

[0088] A solid electrolyte pre-impregnation battery, including a pole piece design:

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

[0090] Negative electrode: metal lithium foil, thickness 50μm;

[0091] Guide groove: U-shaped groove, width 1.5mm, depth 50% of the thickness of the pole piece;

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

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

[0094] A solid electrolyte pre-impregnation battery injection process comprises the following steps:

[0095] Step 1: vacuum drying: 95°C, -98kPa, 15 hours;

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

[0097] Step 3: Dynamic infiltration: vacuum negative pressure -93kPa, step-by-step temperature increase to 55°C, total time 45 minutes;

[0098] Step 4: Standing time: 10 hours, formation current 0.02C.

[0099] Experimental results: Solid electrolyte infiltration time: 8 hours (traditional process requires 24 hours); interface impedance: 18Ω·cm² (traditional process: 50Ω·cm²); capacity retention rate after 300 cycles: 90%.

[0100] Example 5

[0101] A high-power lithium titanate battery, including a pole piece design:

[0102] Positive electrode: Li4Ti5O 12 , coating thickness 90μm, porosity 38%;

[0103] Negative electrode: graphene composite negative electrode, coating thickness 100μm, porosity 40%;

[0104] Guide groove: radial groove, width 0.5mm, depth 15% of the thickness of the pole piece;

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

[0106] A high-power lithium titanate battery injection process comprises the following steps:

[0107] Step 1: vacuum drying: 75°C, -88kPa, 8 hours;

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

[0109] Step 3: Dynamic infiltration: vacuum negative pressure -80kPa, step-by-step temperature increase to 30°C, total time 25 minutes;

[0110] Step 4: Standing time: 4 hours, formation current 0.1C.

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

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

[0113] Tab structure: single-layer tab, located at one end of the electrode; no guide groove or guide hole; injection method: constant injection rate of 0.5mL / s, injection volume is 150% of the pore volume; vacuum drying: 80℃, -90kPa, 24 hours; standing time: 24 hours.

[0114] Experimental results: Immersion time: 18 hours; electrode coverage: 78%; bubble residue rate: 8%; capacity retention rate after 1,000 cycles: 75%.

[0115] Comparative Example 2: Design without diversion groove

[0116] Tab group: 3 layers (same as in Example 1); no guide grooves and guide holes; liquid injection is divided into three stages (same as in Example 1).

[0117] Experimental results: Immersion time: 10 hours; electrode coverage: 85%; bubble residue rate: 3%; capacity retention rate after 1,000 cycles: 82%.

[0118] Comparative Example 3: Constant Rate Liquid Injection Process

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

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

[0121] Comparative Example 4: No lyophilic coating

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

[0123] Experimental results: Solid electrolyte infiltration time: 16 hours; interface impedance: 35Ω·cm²; capacity retention rate after 300 cycles: 80%.

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

[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] index Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Immersion time (h) 5.5 18 10 8 16 5 Pole coverage (%) 98 78 85 90 82 95 Residual bubble rate (%) 0.5 8 3 2.5 4 1.2 Cycle capacity retention rate (%) 93 75 82 85 80 88 Injection volume utilization rate (percentage of pore volume) (%) 105 150 105 130 105 150

[0128] Comparison of the examples with the comparative examples demonstrates that the present invention, through innovations such as a multi-layered tab flow-guiding structure, a phased liquid injection strategy, and a lyophilic coating, significantly shortens the wetting time, improves electrolyte distribution uniformity, and reduces residual bubbles. In contrast, conventional processes (e.g., no flow-guiding grooves and constant-rate liquid injection) in the comparative examples exhibit significant disadvantages, further demonstrating the technical necessity and practical application value of the present invention.

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

Claims

1. A method for directional flow guidance and liquid injection of multi-layer tabs of a full-tab battery, characterized in that: The following steps are involved: Step 1: forming directional guide grooves and conical guide holes on the surface of a full-tab battery electrode sheet with a multi-layer tab structure by laser etching or mechanical stamping. The guide grooves are distributed in a mesh pattern along the length of the electrode sheet and are staggered with the multi-layer tab group; Step 2: Alternately stack the pole pieces and the diaphragms to form a battery cell. Before injecting the liquid, the battery cell is vacuum dried under the following conditions: temperature 70-100°C, vacuum degree -85kPa to -100kPa, and treatment time 8-24 hours. Step 3: Inject the electrolyte into the battery cell along the guide groove through a multi-stage vacuum injection system. The injection process is divided into three stages: initial low-speed injection, main medium-speed injection, and final stage filling. The injection speeds are 0.1-0.3mL / s, 0.5-1.2mL / s, and 0.1-0.2mL / s, respectively. The injection volume in each stage accounts for 10%-20%, 60%-70%, and 10%-20% of the total injection volume. Step 4: During the injection process, periodic vacuum negative pressure is applied synchronously, with a negative pressure value of -80kPa to -95kPa, each negative pressure lasting 5-15 seconds, with an interval of 3-8 seconds, and combined with step-by-step temperature control, the temperature is gradually increased from 25°C to 50°C, with a temperature increase of 5°C to 10°C in each stage, and the maintenance time is 5-15 minutes; Step 5: After the injection is completed, let it stand for 4-12 hours at an ambient temperature of 25-40°C. Then, use a low current of 0.02C-0.2C for multi-stage formation, including pre-charge, aging and capacity separation steps.

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

3. The process for directional flow guidance and liquid injection of multi-layer tabs of a full-tab battery according to claim 2, characterized in that: The guide grooves are distributed radially or spirally on the surface of the pole piece, with a groove spacing of 3-10 mm. The guide holes are tapered through holes, and the aperture gradually decreases from the surface of the pole piece to the inside. The surface aperture is 0.1-0.8 mm, the bottom aperture is 0.05-0.3 mm, the taper angle is 20°-45°, the hole density is 5-20 / cm², and the position of the guide holes is aligned with the intersection of the guide grooves.

4. The process for directional flow guidance and liquid injection of multi-layer tabs for full-tab batteries according to claim 1, characterized in that: The multi-stage vacuum injection system in step three includes three-stage series vacuum chambers with vacuum degrees of -50kPa, -75kPa and -90kPa respectively. The injection needle adopts a porous spray structure with a pore size of 0.1-0.5mm. The injection path is dynamically adjusted according to the position of the tab group, and the injection angle is at an angle of 30°-60° with the direction of the guide groove.

5. The process for directional flow guidance and liquid injection of multi-layer tabs of a full-tab battery according to claim 1, characterized in that: The step-by-step temperature control in step 4 is divided into four stages: Stage 1: Maintain at 25°C for 5-10 minutes, vacuum pressure -80kPa; Stage 2: Maintain at 35°C for 8-12 minutes, vacuum pressure -85kPa; Stage 3: Maintain at 45°C for 10-15 minutes, vacuum pressure -90kPa; Stage 4: Maintain at 50°C for 5-8 minutes, vacuum pressure -95kPa.

6. The process for directional flow guidance and liquid injection of multi-layer tabs for full-tab batteries according to claim 1, characterized in that: The electrolyte injection amount is 105%-120% of the pore volume of the battery cell. The electrolyte composition is a carbonate solvent containing 1-2M LiPF6, and 0.5%-5% fluoroethylene carbonate and 1%-3% vinyl sulfate are added as additives.

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

8. The process for directional flow guidance and liquid injection of multi-layer tabs for full-tab batteries 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), the coating thickness is 80-150μm; the negative electrode active material is a silicon-carbon composite material, the coating thickness is 90-160μm, and the electrode porosity is 25%-40%.

9. The process for directional flow guidance and liquid injection of multi-layer tabs for full-tab batteries according to claim 1, characterized in that: During the injection process in step 3, the electrolyte infiltration state is monitored in real time by an infrared sensor, and the injection speed and vacuum negative pressure parameters are dynamically adjusted according to the feedback data, with a control accuracy of ±0.05 mL / s and ±2 kPa.

10. The process for directional flow guidance and liquid injection of multi-layer tabs for full-tab batteries according to claim 1, characterized in that: The surfaces of the guide grooves and guide holes are covered with an electrophilic electrolyte 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.