Super-large cylindrical sodium ion battery structure and safety cooperation system

Abstract

The invention discloses an oversized cylindrical sodium-ion battery structure and a safety cooperation system, and relates to the technical field of sodium-ion battery structures and safety control, the oversized cylindrical sodium-ion battery structure comprises a double-gradient self-adaptive collector plate, spokes are wide in center and narrow in edge, the spacing of the spokes is in a cooperative gradient, and a base material is an aluminum-based composite layer coated with a nano titanium coating; the four-function integrated core rod is internally provided with a flow guide channel and gradient through holes, coated with a temperature-sensitive conductive coating, filled with porous ceramic particles and provided with a pressure relief sheet; according to the positive and negative electrode-diaphragm bidirectional adaptive structure, diaphragm pores are distributed in a gradient manner, composite coatings are arranged on the two sides, and hot sealing glue is coated on the edges; the invention discloses a graded pressure relief-fire extinguishing cooperative safety system. According to the electrolyte-material collaborative optimization system, a high-salt-concentration electrolyte and a multi-component additive are adopted, and infiltration is carried out through a multi-step liquid injection process. Through full-chain innovation, the problems that an existing battery is uneven in current collection, slow in electrolyte infiltration, lagged in safety response and the like are solved; and the process improves the production efficiency, adapts to multiple application scenes, and meets the large-scale mass production requirements.

Description

Technical Field

[0001] This invention relates to the field of sodium-ion battery structure and safety control technology, and in particular to an ultra-large cylindrical sodium-ion battery structure and a safety coordination system. Background Technology

[0002] Ultra-large cylindrical sodium-ion batteries, with their advantages of high integration and low PACK cost, have broad application prospects in large-scale energy storage power stations, low-speed power batteries, and truck start-stop power supplies. Their diameters typically range from 65mm to 500mm and their lengths from 100 to 1200mm, and they are primarily compatible with NFPP iron-based composite polyanionic phosphate cathode and hard carbon anode systems. However, existing technologies have shortcomings in the synergistic matching of "materials-structure-process-safety," making it difficult to balance battery performance, lifespan, and safety, becoming a bottleneck restricting their large-scale application. Furthermore, these problems have not been effectively solved by existing published patents.

[0003] The primary problem is the severe disconnect between the current collector system and the characteristics of the positive and negative electrode materials. Existing patents disclose spoke-type current collectors using homogeneous aluminum material and a spoke design of equal width. This fails to consider the difference between the high current density required for the polyanion framework of the NFPP positive electrode and the low current density corresponding to interlayer storage in the hard carbon negative electrode. This results in a significant increase in polarization voltage and noticeable capacity decay of the NFPP positive electrode at rates above 1C. Simultaneously, the single material of the current collector and its high contact resistance further exacerbate the problem of uneven current distribution, affecting the battery's rate performance and cycle stability.

[0004] The limited functionality of the core rod and poor process-material compatibility further restrict battery performance. Existing hollow core rods only serve as core support, failing to address the uneven electrolyte diffusion problem in ultra-large cylindrical batteries. The closed-cell structure of the hard carbon anode leads to excessively long electrolyte wetting time, severely impacting production efficiency. Furthermore, the core rod lacks temperature regulation capabilities, hindering sodium ion migration at low temperatures and resulting in poor low-temperature capacity retention. At the process level, existing coating processes employ fixed nozzles and homogeneous feeding methods, neglecting the tendency of NFPP nanoparticles to agglomerate, leading to poor electrode coating uniformity. Traditional high-temperature welding processes damage the carbon coating layer of the NFPP cathode, reducing electrode conductivity, while the impedance after tab welding lacks effective monitoring and correction mechanisms, affecting current conduction efficiency.

[0005] The most prominent hidden danger of current technology is the delayed response of safety systems. Existing battery sidewall explosion-proof membranes rely solely on pressure for triggering, failing to consider the low gas production characteristics of the positive and negative electrodes and actual thermal runaway test data. In abnormal situations, the excessively long pressure relief response time can easily lead to localized bulging of the casing, and even cause safety accidents. Furthermore, existing safety systems lack a tiered protection design, only capable of pressure relief and unable to address the potential fire risk after pressure relief, resulting in an incomplete safety protection chain. These defects combine to make it difficult for existing ultra-large cylindrical sodium-ion batteries to meet the comprehensive requirements of performance, lifespan, and safety in practical applications, necessitating a comprehensive and innovative integrated solution. Summary of the Invention

[0006] The present invention proposes an ultra-large cylindrical sodium-ion battery structure and a safety collaborative system to solve the problems mentioned in the prior art.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: an ultra-large cylindrical sodium-ion battery structure and a safety collaborative system, comprising the following modules: The dual-gradient adaptive current collector adopts a spoke design with a wide center and narrow edges. The substrate is an aluminum-based composite layer coated with a nano-titanium coating. Micro-notches are opened in the middle of the spokes to achieve a balance between current collection efficiency and structural strength. The four-function integrated mandrel is made of modified PP and has a regular hexagonal hollow channel filled with porous alumina ceramic particles. The inner wall of the channel has a spiral flow guide groove, and the side wall has a gradient micro-through hole. The outer layer is coated with a temperature-sensitive conductive coating, and the middle is equipped with a temperature-sensitive pressure relief plate, which has the functions of flow guiding, temperature control, pressure relief and conductivity. The positive and negative electrodes and the separator have a bidirectional adaptive structure. The separator adopts a composite structure of PP base layer and non-woven functional layer with a gradient porosity. Different functional coatings are applied to the positive and negative electrode sides respectively. The edge of the separator is wider than the electrode and is coated with heat-sealing adhesive. The graded pressure relief and fire extinguishing coordinated safety system is equipped with three levels of protection: pre-pressure relief, main pressure relief and fire extinguishing. Pre-pressure relief is triggered by a temperature-sensitive pressure relief plate, and main pressure relief is achieved through double-ring grooves on the end cap. A temperature sensor is also configured. The fire extinguishing system uses fire extinguishing material in the mandrel channel. An electrolyte and material synergistic optimization system is developed, using a specific ratio of electrolyte and adding functional additives, through vacuum injection and secondary injection processes.

[0008] Furthermore, it also includes a current distribution uniformity optimization module for the current collector, which quantifies the current distribution difference through the coordinated design of spoke width and spacing. The calculation formula is as follows: The coefficient for uniformity of current distribution. The width of the center spoke, The distance between the edge spokes, The width of the edge spokes, The center spoke spacing, This is a material correction factor; the calculation achieves uniform current collection by matching the different current density requirements of the positive and negative electrodes through the coordinated ratio of spoke size parameters.

[0009] Furthermore, it also includes a multi-parameter collaborative gradient coating process adaptation module. The positive electrode coating uses three sets of high-precision nozzles arranged along the width direction, with the material supply distributed in a gradient. Combined with ultrasonic vibration, the coating speed and wet film thickness are set to adapt. A laser thickness gauge is installed at the exit to provide real-time feedback and adjust the nozzle height. The negative electrode coating station is equipped with a vacuum hood and uses low-frequency ultrasonic assistance to set the corresponding wet film thickness. The positive electrode compaction adopts a gradient pressure mode, while the negative electrode compaction adopts a constant low pressure, ultimately achieving the adapted positive and negative electrode compaction densities respectively.

[0010] Furthermore, it also includes low-temperature composite welding and impedance closed-loop modules. The welding process adopts a combination of spot welding for fixation, roll welding for conductivity, and inert protection. Laser spot welding uses fiber lasers to control the welding temperature and form uniform weld spots. Ultrasonic roll welding sets the appropriate ultrasonic frequency and roll welding pressure to control the welding temperature rise. High-purity argon gas is introduced into the welding station for inert protection. After welding, a four-probe impedance tester is used to test each point. If the impedance does not meet the standard, the ultrasonic roll welding power is automatically increased for secondary welding. Finally, stress is eliminated by cold pressing.

[0011] Furthermore, it also includes an electrolyte wetting efficiency improvement module, which combines the mandrel flow guiding structure and the diaphragm pore gradient design, and the calculation formula is as follows: For electrolyte wetting efficiency. This represents the total pore area of ​​the diaphragm. Electrolyte conduction velocity, The pressure inside the mandrel channel, For soaking time, The thickness is the membrane thickness; this calculation accelerates the diffusion of electrolyte in the positive and negative electrodes through the synergy of structural and process parameters.

[0012] Furthermore, it also includes a vacuum, pressure, and moisture co-sealing module, employing a three-stage sealing structure; the first stage seal is located between the pole sleeve and the end cap, where nano-addition is used. The modified fluororubber sealing ring; the secondary seal is made by wrapping the outer side of the sealing ring with aluminum foil and polytetrafluoroethylene composite film, and completing the metal seal by laser welding; the tertiary seal adopts a vacuum pressure holding and pressure holding process after liquid injection. The liquid injection station is equipped with an online Karl Fischer moisture meter for real-time monitoring. When the moisture content is not up to standard, the vacuum pressure holding time is automatically extended. The sealing nail and the liquid injection hole of the pole are matched to complete the air permeability and flow guidance.

[0013] Furthermore, it also includes a conical contact current collector optimization module. The current collector is provided with a conical contact area and an annular conductive area. The conical contact area increases the contact area, and the annular conductive area is silver-plated. The edge of the current collector is provided with a silicon steel elastic buckle that engages and fixes with the edge of the electrode. An annular guide groove is opened on the current collector to work together with the core rod guide channel to accelerate the diffusion of electrolyte to the electrode area.

[0014] Furthermore, it also includes a closed-loop control module for process, materials, structure, and performance. The parameters for pulping and coating are linked, and the coating speed is adjusted accordingly to the viscosity of the cathode slurry. The parameters for baking and formation are linked, and the initial formation current is set according to the residual moisture. Multiple online monitoring links are set up to detect the agglomeration rate and dispersion uniformity of the material after pulping, the flatness of the tab after winding, the residual moisture after baking, and the thickness deviation of the SEI film after formation. If any link fails to meet the standard, the subsequent parameters are automatically adjusted.

[0015] Furthermore, it also includes a temperature-sensitive conductive coating adaptive adjustment module. The outer temperature-sensitive conductive coating of the core rod is composed of carbon nanotubes and polyvinylidene fluoride. When the temperature rises, the conductivity of the coating increases, which can quickly dissipate local heat from the positive electrode. In low-temperature environments, the carbon nanotube conductive network assists in the migration of sodium ions, and the electrolyte additives work together to improve the high and low temperature performance of the battery.

[0016] Furthermore, it also includes a module for relieving welding stress and preventing oxidation of the electrode tabs. The electrode tabs are made of aluminum and undergo surface pretreatment to remove the oxide layer before welding. Inert gas covers the entire welding process, and welding stress is eliminated by cold pressing after welding. The connection impedance between the electrode tabs and the collector is strictly controlled.

[0017] Compared with existing technologies, the beneficial effects of this invention are: The ultra-large cylindrical sodium-ion battery structure and safety synergy system provided by this invention comprehensively solves the core pain points of existing technologies through innovative design across the entire chain, bringing significant benefits in many aspects and achieving synergistic improvement in battery performance, process adaptability and safety.

[0018] At the structural design level, the dual-gradient adaptive current collector precisely matches the different current density requirements of the positive and negative electrodes through a coordinated gradient design of spoke width and spacing, effectively optimizing current distribution uniformity, reducing polarization voltage, and improving battery rate performance and cycle stability. The four-function integrated core rod integrates electrolyte conduction, temperature-responsive conductivity regulation, electrolyte adsorption-slow release, and pre-pressure relief functions, not only shortening electrolyte immersion time and improving high and low temperature performance, but also replenishing electrolyte lost during cycling and extending battery life. The bidirectional adaptive structure of the positive and negative electrodes and separator, through pore gradient design and dual-function coating synergy, reduces interfacial impedance, inhibits transition metal dissolution, and regulates SEI film composition. Simultaneously, the edge-sealing design reduces electrolyte leakage, further enhancing battery stability and reliability.

[0019] In terms of process adaptation, the multi-parameter synergistic gradient coating process effectively breaks up NFPP nanoparticle agglomerations through multi-nozzle angle adjustment, material feeding gradient control, and vacuum-ultrasonic synergistic assistance, improving electrode coating uniformity and yield, and is suitable for industrial mass production speed. The low-temperature composite welding-impedance closed-loop process avoids high-temperature damage to electrode materials, reduces tab oxidation and welding stress concentration, and ensures welding quality and smooth current conduction through real-time impedance monitoring and secondary correction. The vacuum-pressure-moisture synergistic sealing process effectively blocks moisture penetration and removes residual gas through a three-stage sealing structure and moisture closed-loop control, reducing the internal moisture content of the battery and avoiding the adverse effects of moisture on battery performance.

[0020] In terms of safety protection, the graded pressure relief-fire extinguishing synergistic safety system constructs a full-chain protection system of "pre-pressure relief - main pressure relief - synchronous fire extinguishing". Through a dual trigger mechanism of temperature and pressure, it significantly shortens the pressure relief response time and avoids risks such as casing bulging. At the same time, fire extinguishing materials are released simultaneously during the pressure relief process, effectively preventing fire accidents and significantly improving the battery's safety performance. The electrolyte-material synergistic optimization system, through the synergistic effect of high-salt-concentration electrolyte and multi-component functional additives, improves the sodium ion migration rate, stabilizes the electrode structure and SEI film, and further optimizes the battery's high and low temperature performance and cycle life.

[0021] Furthermore, the process of this invention is compatible with existing production lines, requiring only minor modifications to achieve large-scale mass production, thus reducing industrialization costs. The ultra-large size structural design reduces the number of connectors in the battery packing process, lowering system integration costs. Simultaneously, the battery's high cycle life, excellent high and low temperature performance, and high safety expand its application in new scenarios such as truck parking power supplies, providing strong support for the large-scale and high-end application of ultra-large cylindrical sodium-ion batteries and driving the development of sodium-ion battery technology towards greater efficiency, safety, and economy. Attached Figure Description

[0022] Figure 1 This is a schematic block diagram of the ultra-large cylindrical sodium-ion battery structure and safety coordination system proposed in this invention. Figure 2 Line graph comparing positive polarization voltages under different collector designs; Figure 3 A bar chart comparing electrolyte wetting times for different mandrel structures; Figure 4 Line graph comparing electrode coating thickness deviations under different coating processes; Figure 5 A bar chart comparing the pressure relief response time of the safety system with the amount of casing bulging. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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.

[0024] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0025] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of the stated features. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified. Furthermore, the terms "installed," "connected," and "linked" should be interpreted broadly; for example, they may refer to a fixed connection, a detachable connection, or an integral connection; they may refer to a mechanical connection or an electrical connection; they may refer to a direct connection or an indirect connection through an intermediate medium; and they may refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. The invention will now be described in further detail with reference to the accompanying drawings.

[0026] Reference Figures 1 to 5 A structure for an ultra-large cylindrical sodium-ion battery and a safety coordination system, comprising the following modules: The dual-gradient adaptive collector has a diameter of 64–497 mm and a thickness of 0.8–1.2 mm. The spokes adopt a center-wide and edge-narrow design, with a center spoke width of 8–12 mm and an edge width of 3–5 mm. The spoke spacing is 5–8 mm at the center and 10–15 mm at the edge. The substrate is an aluminum-based composite layer with a 50–100 nm nano-titanium coating in the middle. A 0.2–0.3 mm wide micro-notch with a depth of one-third of the spoke thickness is opened in the middle of the spoke. The four-function integrated mandrel has an outer diameter of 9–40 mm and a length of 96–1196 mm. It is made of modified PP (including temperature-resistant modification or reinforcing fillers). Internally, it features a regular hexagonal hollow channel with a side length of 3–5 mm. The inner wall of the channel has spiral guide grooves with a pitch of 5–10 mm and a groove depth of 0.5 mm. The sidewalls have gradient micro-holes with an inner diameter of 0.5 mm, an outer diameter of 1.0 mm, and a hole spacing of 10 mm. The outer layer is coated with a 10–20 μm temperature-sensitive conductive coating. The hollow channel is filled with porous material with a particle size of 5–10 μm and a porosity of 50%. The ceramic particles have a 5-8 mm diameter Bi-Sn-Pb low-melting-point alloy and a temperature-sensitive pressure relief plate made of methyl vinyl silicone rubber in the middle. The positive and negative electrode-diaphragm bidirectional adaptive structure uses a 16μm thick PP base layer and a 40-48μm thick non-woven functional layer. The porosity gradually increases from 40% on the inner side of the core to 55% on the outer side. The positive electrode side is coated with a 5-8μm thick... The composite coating has a mass ratio of 3:1, and the negative electrode side is coated with a 3-5 μm thick graphene oxide-carbon nanotube composite coating with a mass ratio of 2:1. The separator width is 2-3 mm wider than the positive and negative electrode sheets, and the edge is coated with a 10-15 μm thick polyimide heat-sealing adhesive. The graded pressure relief and fire extinguishing coordinated safety system consists of three stages: the first stage pre-pressure relief is triggered by a pressure relief plate with a melting point of 150℃ on the mandrel; the second stage main pressure relief end cap explosion-proof area is equipped with double-ring grooves with an inner ring diameter of 15-20mm and an outer ring diameter of 25-30mm, and the groove depth is 65% of the end cap thickness; the explosion-proof pressure is 1.5-2.0MPa and is equipped with a temperature sensor; and the third stage fire extinguishing is achieved by filling the hollow channel of the mandrel with 5-10g of phosphate ester fire extinguishing material with a particle size of 2-5μm. Electrolyte-material synergistic optimization system, using 1.7 mol / L Electrolyte with a volume ratio of 1:1, containing 2% FEC + 1% SES + 0.5% Functional additives are wetted with electrolyte through a process of vacuum injection + standing + secondary injection.

[0027] This invention also includes a current distribution uniformity optimization module for the current collector, which quantifies the current distribution difference through the coordinated design of spoke width and spacing. The calculation formula is as follows: The current distribution uniformity coefficient is set to a value ranging from 0.9 to 1.0. The width of the center spoke, The distance between the edge spokes, The width of the edge spokes, The center spoke spacing, The material correction factor ranges from 0.95 to 1.05. This calculation achieves uniform current collection by matching the different current density requirements of the positive and negative electrodes through the coordinated ratio of spoke size parameters, reducing the increase in polarization voltage caused by local current concentration, and keeping the maximum polarization voltage of the NFPP positive electrode below 0.15V.

[0028] This invention also includes a multi-parameter collaborative gradient coating process adaptation module. The positive electrode uses three sets of high-precision nozzles arranged 50mm apart along the width direction, with nozzle angles adjustable from 30° to 60°. The material feed rate increases by 5% to 8% from the center to the edge, coupled with 20-30kHz ultrasonic vibration with an amplitude of 5-10μm, a coating speed of 30-50m / min, and a wet film thickness of 150-200μm. A laser thickness gauge is installed at the outlet to provide real-time feedback and adjust the nozzle height. The negative electrode coating station is equipped with a vacuum hood with a vacuum degree of less than 10Pa, using 25kHz low-frequency ultrasonic vibration with an amplitude of 8-12μm, and a wet film thickness of 120-160μm. The positive electrode compaction uses a gradient pressure of 10MPa initially and 25MPa finally, while the negative electrode compaction uses a constant low pressure of 15MPa. The final positive electrode compaction density... negative electrode .

[0029] This invention also includes a low-temperature composite welding-impedance closed-loop module. The welding process adopts a combination of spot welding for fixation, roll welding for conductivity, and inert protection. Laser spot welding uses a 1064nm fiber laser with a power of 50-80W, a spot diameter of 0.5mm, a weld spacing of 5-8mm, a weld depth of 0.1-0.2mm, and a temperature below 180℃. Ultrasonic roll welding uses a 20kHz ultrasonic frequency, a roll welding pressure of 0.2-0.3MPa, and a roll welding width of 2-3mm. The temperature rise during the welding process is below 50℃. 99.999% high-purity argon gas is introduced into the welding station at a flow rate of 5L / min. After welding, a four-probe impedance tester is used to test each point. When the impedance is greater than 5mΩ, a secondary ultrasonic roll welding is automatically triggered, increasing the power by 10%. After welding, 0.5MPa cold pressing is used for 10s to eliminate stress.

[0030] This invention also includes an electrolyte wetting efficiency improvement module, which, combined with the mandrel flow guiding structure and diaphragm pore gradient design, quantifies the wetting effect. The calculation formula is as follows: The electrolyte wetting efficiency is set within the range of 0.95 to 1.0. This represents the total pore area of ​​the diaphragm. Electrolyte conduction velocity, The pressure inside the mandrel channel, For soaking time, The thickness is the membrane thickness. This calculation, through the synergy of structural and process parameters, accelerates the diffusion of the electrolyte in the positive and negative electrodes, shortening the hard carbon negative electrode wetting time to less than 48 hours and achieving a wettability greater than 98%.

[0031] This invention also includes a vacuum-pressure-moisture synergistic sealing module, employing a three-stage sealing structure. The first stage seal involves adding 5%–8% nano-sized components between the pole sleeve and the end cap. The modified fluororubber sealing ring has a hardness of 65 Shore A and a pre-compression of 25%. The secondary seal is made by wrapping the outer side of the sealing ring with a 50μm thick aluminum foil-PTFE composite film, and the metal seal is achieved by welding with a 150W laser with a spot diameter of 1mm. After the tertiary seal is injected, it is vacuum pressure maintained for 30 minutes with a vacuum degree of less than 1Pa and pressure maintained for 60 minutes with a pressure of 0.4MPa. The injection station is equipped with an online Karl Fischer moisture analyzer for real-time monitoring. When the moisture content is greater than 150ppm, the vacuum pressure maintenance time is automatically extended. The sealing nail has a 0.1-0.2mm vent hole inside, which is matched with the spiral guide groove of the injection hole of the pole.

[0032] This invention also includes a conical contact current collector optimization module. The current collector has a conical contact area and an annular conductive area. The conical contact area has a cone angle of 30° to 45° and the contact area is 30% larger than that of a planar current collector. The annular conductive area is 5 to 8 mm wide and is silver-plated. The edge of the current collector is provided with a silicon steel elastic buckle, which has a clamping force of 100 to 150 g with the edge of the electrode. An annular guide groove with a width of 1 to 2 mm and a depth of 0.5 mm is opened on the current collector, which works in conjunction with the core rod guide channel to accelerate the diffusion of electrolyte to the electrode area.

[0033] This invention also includes a closed-loop control module for process, materials, structure, and performance. The pulping and coating parameters are linked; the coating speed is adjusted by 5 m / min for every 500 mPa·s change in the positive electrode slurry viscosity. The baking and formation parameters are also linked; the initial formation current is 0.05 C when the residual moisture is less than or equal to 150 ppm, and 0.03 C when the moisture content is between 150 and 200 ppm. Multiple online monitoring stages are set up: after pulping, a laser particle size analyzer detects that the NFPP agglomeration rate is less than or equal to 5% and the hard carbon dispersion uniformity is greater than or equal to 90%; after winding, a laser flatness meter detects that the tab flatness is less than or equal to 0.2 mm; after baking, a Karl Fischer meter detects that the moisture content is less than or equal to 150 ppm; and after formation, an AFM analyzer detects that the SEI film thickness deviation is less than or equal to 10 nm. If any stage fails to meet the standards, subsequent parameters are automatically adjusted.

[0034] This invention also includes a temperature-sensitive conductive coating adaptive adjustment module. The outer temperature-sensitive conductive coating of the core rod is composed of 5%–8% carbon nanotubes and 92%–95% polyvinylidene fluoride. When the temperature is above 60°C, the conductivity increases from... Upgraded to •cm, quickly dissipates local heat from the NFPP positive electrode, and at -40℃, sodium ions migrate through a carbon nanotube conductive network. Combined with electrolyte additives, it synergistically improves the high and low temperature performance of the battery, resulting in a capacity retention rate of ≥92% at -40℃ and a capacity retention rate of ≥85% after 500 cycles at 60℃.

[0035] This invention also includes a module for relieving welding stress and preventing oxidation of the electrode tabs. The electrode tabs are made of aluminum. Before welding, the surface is pretreated to remove the oxide layer, and the thickness is controlled to be less than 10nm. During the welding process, inert gas is used to cover the entire process to reduce secondary oxidation. After welding, cold pressing is performed to eliminate welding stress and reduce the probability of the electrode tabs cracking due to stress concentration during cycling. The connection impedance between the electrode tabs and the current collector is controlled to be less than 2mΩ to ensure smooth current conduction, improve battery cycle stability, and make the capacity retention rate greater than or equal to 75% after 1C cycle life of 12,000 cycles.

[0036] The following two examples further illustrate the specific implementation of this system: Example 1: 200mm diameter ultra-large cylindrical sodium-ion battery for large-scale energy storage power stations This embodiment is applied to a large-scale energy storage power station. The battery has a diameter of 200mm and a length of 800mm, and is compatible with NFPP cathode and hard carbon anode systems. The core requirements are high cycle life, high safety, and low degradation rate, making it suitable for long-term charge-discharge cycles and stringent safety standards of energy storage power stations. Through the structural design and process optimization of this invention, problems such as uneven current collection, slow electrolyte wetting, and delayed safety response in existing batteries are solved, achieving a synergistic improvement in performance and safety.

[0037] I. Core Implementation Details Dual-gradient adaptive current collector assembly: The current collector has a diameter of 197mm and a thickness of 1.0mm. The spokes feature a gradient design with a center width of 10mm and an edge width of 4mm. The spoke spacing is 6mm at the center and 12mm at the edge, precisely matching the high current density requirements of the NFPP positive electrode and the low current density requirements of the hard carbon negative electrode. The current collector substrate is an aluminum-based composite layer with an 80nm thick nano-titanium coating deposited in the middle using magnetron sputtering. The coating adhesion reaches 55MPa. The aluminum layers on both sides ensure compatibility with the positive and negative current collectors, and the contact impedance is controlled at 2.8mΩ. A 0.25mm wide micro-notch is opened in the middle of the spoke, with a depth of one-third of the spoke thickness. It generates a 0.15mm elastic deformation when the current fluctuates, adaptively adjusting the current distribution.

[0038] Four-function integrated mandrel assembly: The mandrel has an outer diameter of 25mm and a length of 796mm, made of modified PP. It features an internal hexagonal hollow channel with a side length of 4mm. The inner wall of the channel has a spiral guide groove with a pitch of 8mm and a depth of 0.5mm. The sidewall has gradient micro-holes with an inner diameter of 0.5mm, an outer diameter of 1.0mm, and a hole spacing of 10mm. The outer layer of the mandrel is coated with a 15μm thick temperature-sensitive conductive coating composed of 6% carbon nanotubes and 94% polyvinylidene fluoride, enabling temperature-responsive conductivity regulation. The hollow channel is filled with porous material with an 8μm particle size and a porosity of 50%. The ceramic particles adsorb 30% of their own weight in electrolyte. A pressure relief sheet made of Bi-Sn-Pb low-melting-point alloy with a diameter of 6mm and methyl vinyl silicone rubber is installed in the middle, with a melting point set at 150℃.

[0039] Fabrication of the bidirectional adaptive structure between positive and negative electrodes and the separator: The separator consists of a 16μm thick PP base layer and a 45μm thick nonwoven functional layer, with the porosity gradually increasing from 40% on the inner side of the core to 55% on the outer side. A 6μm thick layer of nonwoven fabric is coated on the positive electrode side using the sol-gel method. Composite coating, mass ratio 3:1 The content is controlled at 4% of the total coating mass; a 4μm thick graphene oxide-carbon nanotube composite coating is applied to the negative electrode side at a mass ratio of 2:1 to construct a conductive network and regulate the SEI film composition. The separator width is 2.5mm wider than the positive and negative electrode sheets, and the edges are coated with a 12μm thick polyimide heat-sealing adhesive. After the core is wound, it is hot-pressed at 120℃ under a pressure of 0.3MPa to achieve edge sealing.

[0040] Key process execution: For the positive electrode coating, three sets of high-precision nozzles are used, spaced 50mm apart along the width direction. The nozzle angle is adjusted to 45°, and the feed rate increases by 6% from the center to the edge. This is combined with 25kHz ultrasonic vibration at an amplitude of 8μm to break up NFPP nanoparticle agglomerations. The coating speed is 40m / min, and the wet film thickness is 180μm. A laser thickness gauge at the exit provides real-time feedback to adjust the nozzle height. For the negative electrode coating, a vacuum hood is installed, with the vacuum level controlled at 8Pa. 25kHz low-frequency ultrasound with an amplitude of 10μm is used, resulting in a wet film thickness of 140μm. Positive electrode compaction uses a gradient pressure of 10MPa initially and 25MPa finally, while negative electrode compaction uses a constant low pressure of 15MPa. The final positive electrode compaction density... ,negative electrode .

[0041] Low-temperature composite welding and sealing: Laser spot welding uses a 1064nm fiber laser with a power of 60W, a spot diameter of 0.5mm, a weld spacing of 6mm, a weld depth of 0.15mm, and a temperature control of 170℃; ultrasonic roll welding uses a frequency of 20kHz, a welding pressure of 0.25MPa, a width of 2.5mm, and a welding temperature rise of 45℃. 99.999% high-purity argon gas is introduced into the welding station at a flow rate of 5L / min. After welding, a four-probe impedance tester is used to check each point. When the impedance exceeds 5mΩ, a secondary ultrasonic roll welding is automatically triggered, increasing the power by 10%. After welding, stress is relieved by cold pressing at 0.5MPa for 10s. The sealing adopts a three-stage structure, with the first stage using a modified fluororubber sealing ring with 6% nano-polymer added. The process involves laser welding of a secondary aluminum foil-PTFE composite film, followed by 30 minutes of vacuum pressure holding and 60 minutes of pressure holding after 3-stage liquid injection, with real-time monitoring using an online Karl Fischer moisture analyzer to ensure that the moisture content is controlled below 140 ppm.

[0042] The graded pressure relief-extinguishing system and electrolyte system: The mandrel pressure relief plate melts when the temperature exceeds 150℃, achieving pre-pressure relief and releasing 18% of the generated gas; the explosion-proof area of ​​the end cap has double-ring grooves, with an inner diameter of 18mm and an outer diameter of 28mm, and the groove depth is 65% of the end cap thickness. The explosion-proof pressure is 1.8MPa. A temperature sensor detects a temperature exceeding 250℃ or a pressure exceeding 1.5MPa, triggering dual pressure relief with a response time of 0.4s. The hollow channel of the mandrel is filled with 8g of phosphate ester extinguishing material with a particle size of 3μm, which is released simultaneously during pressure relief. The electrolyte is 1.7mol / L. The formula has a 1:1 volume ratio and contains 2% FEC, 1% SES, and 0.5% [unclear - possibly a specific ingredient or ingredient]. The electrolyte wettability is ensured to reach 98.5% through a process of vacuum injection, 24-hour standing, and secondary injection.

[0043] Table 1 clearly demonstrates the significant advantages of this invention in large-scale energy storage power station applications. Existing technologies suffer from high positive electrode polarization voltage due to uneven current collection, slow electrolyte wetting affecting production efficiency, and delayed safety response reducing the pass rate of needle penetration tests. This invention optimizes current distribution through a dual-gradient adaptive current collector, significantly reducing polarization voltage; the gradient current guiding design of the four-functional core rod shortens wetting time; and the graded pressure relief-fire extinguishing system improves safety response speed, with no fire or explosion observed during needle penetration testing. These advantages stem from the deep coupling of structural design and material properties, and the precise matching of process and performance, fully meeting the core requirements of large-scale energy storage power stations for long lifespan, high safety, and high efficiency, providing reliable support for the stable operation of energy storage systems.

[0044] Example 2: 100mm diameter extra-large cylindrical sodium-ion battery for truck start-stop power supply This embodiment is applied to a truck start-stop power supply. The battery has a diameter of 100mm and a length of 500mm, and is compatible with NFPP positive and hard carbon negative electrodes. The core requirements are excellent high and low temperature performance, vibration resistance, and rapid start-stop adaptability, solving the problems of battery performance degradation and safety hazards caused by frequent truck start-stop, large ambient temperature fluctuations, and severe vibration. Through the multifunctional integrated design and process optimization of this invention, stable operation of the battery under complex operating conditions is achieved.

[0045] I. Core Implementation Details Dual-gradient adaptive current collector and conical contact optimization: The current collector has a diameter of 97mm and a thickness of 0.9mm. The spoke center width is 9mm, the edge width is 3.5mm, and the spacing is 5.5mm at the center and 11mm at the edge, adapting to the difference in current density between the positive and negative electrodes. The current collector substrate is an aluminum-based composite layer with a 60nm nano-titanium coating deposited in the middle, achieving a contact impedance of 3.0mΩ. A 0.22mm wide micro-notch in the center of the spokes enables adaptive adjustment of current fluctuations. The current collector features a conical contact area and an annular conductive area. The conical contact area has a cone angle of 35°, increasing the contact area by 30% compared to a planar current collector. The annular conductive area is 6mm wide and silver-plated. The edge is secured with a silicon steel elastic clip that engages with the electrode tab with a locking force of 120g to prevent loosening due to vibration. The connection impedance between the electrode tab and the current collector is controlled at 1.8mΩ.

[0046] The four-functional integrated core rod and annular flow guide work synergistically: The core rod has an outer diameter of 15mm and a length of 496mm, made of modified PP. It features an internal hexagonal hollow channel with a side length of 3.5mm, a spiral flow guide groove with a pitch of 7mm and a depth of 0.5mm, and gradient micro-perforations on the sidewalls working in conjunction with the annular flow guide groove of the collector plate to accelerate electrolyte diffusion to the tab region, achieving an electrolyte retention rate of 96% in the tab region. The core rod is coated with a 12μm temperature-sensitive conductive coating with 7% carbon nanotube content, significantly improving conductivity above 60℃ for rapid heat dissipation; at -40℃, it assists in sodium ion migration, improving low-temperature performance. The hollow channel is filled with 6μm diameter porous particles. Ceramic particles adsorb electrolyte to replenish circulation losses, and a 5.5mm diameter pressure relief plate in the middle ensures pre-pressure relief triggering at 150℃, buying time for main pressure relief.

[0047] Bidirectional Adaptation and Vibration-Resistant Design for Positive and Negative Electrodes and Separator: The separator utilizes a 16μm PP base layer and a 42μm non-woven functional layer, with a porosity gradient adapted to the migration rates of ions on both the positive and negative electrodes. The positive electrode side is 5μm thick... The composite coating stabilizes the polyanionic framework and inhibits the dissolution of transition metals; the 3.5μm thick graphene oxide-carbon nanotube coating on the negative electrode side regulates the SEI film and improves the first coulombic efficiency. After the separator edge is sealed by heat-sealing with polyimide heat-sealing adhesive, combined with the shock-absorbing structure of the battery casing, the vibration resistance is enhanced to meet the vibration environment requirements of truck driving.

[0048] Process adaptation and closed-loop control: For the positive electrode coating, the angle of the three nozzles is adjusted to 40°, the feed rate is increased by 5%, and 22kHz ultrasonic vibration is used to break up NFPP agglomerates. The coating speed is 35m / min, and the wet film thickness is 160μm. For the negative electrode coating, the vacuum hood has a vacuum degree of 9Pa, and 25kHz low-frequency ultrasound is used to avoid damage to the hard carbon structure. The wet film thickness is 130μm. The initial compaction pressure of the positive electrode is 10MPa, and the final compaction pressure is 24MPa. The compaction pressure of the negative electrode is 15MPa to ensure the stability of the electrode structure. Low-temperature composite welding uses laser spot welding with a power of 55W and a weld spot spacing of 5.5mm. The ultrasonic rolling welding pressure is 0.23MPa, the welding temperature rise is 42℃, argon gas protection is used to prevent electrode tab oxidation, and cold pressing is used after welding to relieve stress. The electrode tab cracking rate is controlled at 0.8%. Vacuum-pressure-moisture synergistic sealing ensures that the moisture content is ≤145ppm and the residual gas volume is ≤0.4mL.

[0049] Staged pressure relief and fire suppression synergy with electrolyte optimization: The first-stage pre-pressure relief is triggered by a 150°C pressure relief plate on the mandrel, releasing 16% of the generated gas; the second-stage main pressure relief end cap features double-ring grooves (inner ring 16mm, outer ring 26mm), an explosion-proof pressure of 1.6MPa, and dual triggering by temperature and pressure sensors with a response time of 0.35s; the third-stage fire suppression utilizes 7g of phosphate ester-based extinguishing material within the mandrel, simultaneously covering the core during pressure relief, achieving a fire suppression efficiency of 96%. The electrolyte used is 1.7mol / L. The formula contains 2% FEC + 1% SES + 0.5% The vacuum injection + standing + secondary injection process ensures a 98% wettability and improves high and low temperature cycle stability. A closed-loop control system encompassing process, materials, structure, and performance is implemented, with real-time monitoring of parameters at each stage of slurry preparation, winding, baking, and formation. Automatic adjustments are made in case of abnormalities to ensure battery consistency.

[0050] Table 2 highlights the advantages of this invention in truck start-stop power supply scenarios. Existing technologies suffer from poor low-temperature performance, and vibration leads to loosening of the electrode connections and rapid capacity decay, making it difficult to meet the demands of frequent truck starts and stops and complex operating conditions. This invention improves high and low temperature performance through a synergistic effect of a temperature-sensitive conductive coating and electrolyte additives; a conical contact current collector and elastic snap-fit ​​design enhance vibration resistance, significantly improving electrode connection stability; a four-function core rod and annular guide groove work together to ensure uniform electrolyte distribution and reduce cycle decay; and a graded pressure relief-fire suppression system ensures safety. These advantages fully meet the stringent requirements of truck start-stop power supplies, enabling stable operation under complex conditions, extending battery life, and reducing maintenance costs.

[0051] Reference Figure 2This figure clearly illustrates the impact of the current collector design on the positive electrode polarization voltage and the significant advantages of this invention. Traditional homogeneous current collectors, due to their uniform spoke dimensions, cannot adapt to the different current density requirements of the positive and negative electrodes. As the discharge rate increases, the polarization voltage rises sharply, reaching 0.68V at 2.5C, leading to a significant capacity decay. This invention's dual-gradient adaptive current collector, through a synergistic gradient design of spoke width and spacing, combined with aluminum-based composite material and micro-notch adaptive functionality, effectively optimizes current distribution and reduces contact resistance. The polarization voltage is only 0.09V at 0.5C and remains controlled at 0.35V at 2.5C. This difference stems from the current collector's precise matching of the high current density of the NFPP positive electrode and the low current density of the hard carbon negative electrode, avoiding localized current concentration and fully demonstrating the deep coupling between structural design and material properties.

[0052] Reference Figure 3 This figure visually demonstrates the role of integrated mandrel functions in improving electrolyte wetting efficiency. Traditional hollow mandrels only serve a supporting function, and the closed-cell structure of the hard carbon negative electrode results in a wetting time as long as 72 hours, severely impacting production efficiency. Single-function to three-function mandrels have gradually shortened the wetting time by adding flow guiding, temperature regulation, and electrolyte slow-release functions, but still have not achieved optimal results. The four-function integrated mandrel of this invention utilizes the synergistic design of a regular hexagonal hollow channel, a spiral flow guiding groove, and gradient micro-perforations, combined with a porous structure... The adsorption-slow release effect of ceramic particles accelerates electrolyte diffusion, shortening the immersion time to 48 hours. This breakthrough stems from the multi-functional integrated design of the core rod, which integrates "current conduction, temperature regulation, slow release, and pre-pressure relief." This design not only solves the problem of uneven electrolyte wetting but also replenishes electrolyte during battery cycling, extending battery life and fully demonstrating the innovative value of integrated structure and function.

[0053] Reference Figure 4 This figure highlights the core advantage of the coating process of this invention in terms of coating uniformity. Traditional fixed-nozzle coating does not consider the tendency of NFPP nanoparticles to agglomerate. As the coating length increases, particle agglomeration intensifies, and the coating thickness deviation rises from 3.8% to 6.8%, severely affecting the consistency of electrode performance. The multi-parameter synergistic gradient coating of this invention effectively breaks up particle agglomerates through the synergy of three sets of high-precision nozzles with adjustable angles, material gradient control, and 20-30kHz ultrasonic vibration. At the same time, vacuum-ultrasonic composite assistance reduces hard carbon oxidation, and the coating thickness deviation is consistently controlled within 1.2% to 1.6%. This advantage stems from the precise matching of process parameters and material properties. The industrial coating speed of 30-50 m / min is suitable for mass production requirements, and the real-time feedback from the laser thickness gauge further ensures coating uniformity, laying a technological foundation for high-performance and high-consistency batteries.

[0054] Reference Figure 5This figure fully demonstrates the advantages of the safety collaborative system of this invention. Traditional single pressure triggering systems have a response time as long as 1.2s and a bulge size of 5.8mm, which easily leads to safety hazards. Although pressure-temperature dual triggering and simplified graded pressure relief have improved these aspects, they still do not solve the risk of fire and bulging problems after pressure relief. The graded pressure relief-fire extinguishing collaborative system of this invention shortens the response time to 0.4s and controls the bulge size to 1.5mm through three levels of protection: pre-pressure relief at 150℃ on the core rod, main pressure relief triggered by pressure-temperature dual triggering on the end cap, and release of fire extinguishing material from the core rod. This breakthrough stems from the precise adaptation of battery thermal runaway data. The pre-pressure relief of the low-melting-point pressure relief plate buys time for the main pressure relief, the double-ring grooves ensure smooth pressure relief, and the simultaneous release of fire extinguishing material blocks the fire chain, constructing a full-chain protection of "early warning-pressure relief-fire extinguishing," which significantly improves the safety and reliability of ultra-large cylindrical batteries.

[0055] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A structure for an ultra-large cylindrical sodium-ion battery and a safety collaborative system, characterized in that, Includes the following modules: The dual-gradient adaptive current collector adopts a spoke design with a wide center and narrow edges. The substrate is an aluminum-based composite layer coated with a nano-titanium coating. Micro-notches are opened in the middle of the spokes to achieve a balance between current collection efficiency and structural strength. The four-function integrated mandrel is made of modified PP and has a regular hexagonal hollow channel filled with porous alumina ceramic particles. The inner wall of the channel has a spiral flow guide groove, and the side wall has a gradient micro-through hole. The outer layer is coated with a temperature-sensitive conductive coating, and the middle is equipped with a temperature-sensitive pressure relief plate, which has the functions of flow guiding, temperature control, pressure relief and conductivity. The positive and negative electrodes and the separator have a bidirectional adaptive structure. The separator adopts a composite structure of PP base layer and non-woven functional layer with a gradient porosity. Different functional coatings are applied to the positive and negative electrode sides respectively. The edge of the separator is wider than the electrode and is coated with heat-sealing adhesive. The graded pressure relief and fire extinguishing coordinated safety system is equipped with three levels of protection: pre-pressure relief, main pressure relief and fire extinguishing. Pre-pressure relief is triggered by a temperature-sensitive pressure relief plate, and main pressure relief is achieved through double-ring grooves on the end cap. A temperature sensor is also configured. The fire extinguishing system uses fire extinguishing material in the mandrel channel. An electrolyte and material synergistic optimization system is developed, using a specific ratio of electrolyte and adding functional additives, through vacuum injection and secondary injection processes.

2. The ultra-large cylindrical sodium-ion battery structure and safety collaborative system according to claim 1, characterized in that, It also includes a current distribution uniformity optimization module for the current collector, which quantifies the difference in current distribution through the coordinated design of spoke width and spacing. This calculation achieves current collection uniformity by matching the different current density requirements of the positive and negative poles through the coordinated ratio of spoke size parameters.

3. The ultra-large cylindrical sodium-ion battery structure and safety collaborative system according to claim 1, characterized in that, It also includes a multi-parameter collaborative gradient coating process adaptation module. The positive electrode coating uses three sets of high-precision nozzles arranged along the width direction, with the material supply distributed in a gradient. Combined with ultrasonic vibration, the coating speed and wet film thickness are set to adapt. A laser thickness gauge is installed at the outlet to provide real-time feedback and adjust the nozzle height. The negative electrode coating station is equipped with a vacuum hood and uses low-frequency ultrasonic assistance to set the corresponding wet film thickness. The positive electrode compaction adopts a gradient pressure mode, while the negative electrode compaction adopts a constant low pressure, ultimately achieving the adapted positive and negative electrode compaction densities respectively.

4. The ultra-large cylindrical sodium-ion battery structure and safety collaborative system according to claim 1, characterized in that, It also includes low-temperature composite welding and impedance closed-loop modules. The welding process adopts a combination of spot welding for fixation, roll welding for conductivity, and inert protection. Laser spot welding uses fiber laser to control the welding temperature and form uniform weld spots. Ultrasonic roll welding sets the appropriate ultrasonic frequency and roll welding pressure to control the welding temperature rise. High-purity argon gas is introduced into the welding station for inert protection. After welding, a four-probe impedance tester is used to test each point. If the impedance does not meet the standard, the ultrasonic roll welding power is automatically increased for secondary welding. Finally, stress is eliminated by cold pressing.

5. The ultra-large cylindrical sodium-ion battery structure and safety collaborative system according to claim 1, characterized in that, It also includes an electrolyte wetting efficiency improvement module, which combines the core rod flow guiding structure and the membrane pore gradient design. This calculation accelerates the diffusion of electrolyte in the positive and negative electrodes through the synergy of structural parameters and process parameters.

6. The ultra-large cylindrical sodium-ion battery structure and safety collaborative system according to claim 1, characterized in that, It also includes a vacuum, pressure, and moisture co-sealing module, employing a three-stage sealing structure; the first stage seal is located between the pole sleeve and the end cap, where nano-addition is used. The modified fluororubber sealing ring; the secondary seal is made by wrapping the outer side of the sealing ring with aluminum foil and polytetrafluoroethylene composite film, and completing the metal seal by laser welding; the tertiary seal adopts a vacuum pressure holding and pressure holding process after liquid injection. The liquid injection station is equipped with an online Karl Fischer moisture meter for real-time monitoring. When the moisture content is not up to standard, the vacuum pressure holding time is automatically extended. The sealing nail and the liquid injection hole of the pole are matched to complete the air permeability and flow guidance.

7. The ultra-large cylindrical sodium-ion battery structure and safety collaborative system according to claim 1, characterized in that, It also includes a conical contact current collector optimization module. The current collector is equipped with a conical contact area and an annular conductive area. The conical contact area increases the contact area, and the annular conductive area is silver-plated. The edge of the current collector is equipped with a silicon steel elastic buckle that engages and fixes with the edge of the electrode. An annular flow guide groove is opened on the current collector to work with the core rod flow guide channel to accelerate the diffusion of electrolyte to the electrode area.

8. The ultra-large cylindrical sodium-ion battery structure and safety collaborative system according to claim 1, characterized in that, It also includes a closed-loop control module for process, materials, structure, and performance. The parameters for pulping and coating are linked, and the coating speed is adjusted accordingly to the viscosity of the cathode slurry. The parameters for baking and formation are linked, and the initial formation current is set according to the residual moisture. Multiple online monitoring links are set up to detect the agglomeration rate and dispersion uniformity of the material after pulping, the flatness of the tab after winding, the residual moisture after baking, and the thickness deviation of the SEI film after formation. If any link fails to meet the standard, the subsequent parameters are automatically adjusted.

9. The ultra-large cylindrical sodium-ion battery structure and safety collaborative system according to claim 1, characterized in that, It also includes a temperature-sensitive conductive coating adaptive adjustment module. The outer temperature-sensitive conductive coating of the core rod is composed of carbon nanotubes and polyvinylidene fluoride. When the temperature rises, the conductivity of the coating increases, which can quickly dissipate local heat from the positive electrode. In low-temperature environments, the carbon nanotube conductive network assists in the migration of sodium ions, and the electrolyte additives work together to improve the high and low temperature performance of the battery.

10. The ultra-large cylindrical sodium-ion battery structure and safety collaborative system according to claim 1, characterized in that, It also includes a module for stress relief and anti-oxidation of electrode tabs. The electrode tabs are made of aluminum and undergo surface pretreatment to remove the oxide layer before welding. Inert gas covers the entire welding process, and cold pressing is used to eliminate welding stress after welding. The connection impedance between the electrode tabs and the collector is strictly controlled.

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