Method for assembling combined lower cover of lithium primary battery

Abstract

The invention relates to the technical field of electrochemical batteries, in particular to an assembling method of a combined lower cover of a lithium primary battery. The method sequentially comprises the steps of assembling an explosion-proof membrane in a bottom cover, assembling a stainless iron sheet in the bottom cover, sealing for the first time and sealing for the second time, and further comprises a step A and a step B. A, after the explosion-proof membrane is arranged in the bottom cover, the explosion-proof membrane needs to be preheated, and then the stainless iron sheet is assembled; and B, carrying out heat sealing on the explosion-proof membrane between the primary sealing step and the secondary sealing step. The preheating means that an integrated preheating module is adopted to heat the explosion-proof membrane, the heating temperature is 90-120 DEG C, and the heating time is 1.5-3 seconds. The heat sealing temperature of the explosion-proof membrane is 250 + / -5 DEG C, and the heat sealing time is 1.5 + / -0.1 s. By optimizing the procedure sequence, adding preheating treatment and improving the fixing mode, the problems of missing adding and falling of stainless iron sheets in the traditional process are thoroughly solved, and meanwhile the product assembling quality, consistency and production efficiency are improved.

Description

Technical Field

[0001] This invention relates to the field of electrochemical battery technology, and more particularly to a method for assembling a lower cover for a lithium primary battery assembly. Background Technology

[0002] As a commonly used type of lithium battery, the bottom cover of a primary lithium battery is a core component, mainly assembled from a bottom cover, an explosion-proof film, and stainless steel sheets. The assembly quality of the bottom cover directly affects the battery's safety performance and reliability. The traditional assembly process for the bottom cover of a primary lithium battery is as follows: explosion-proof film stamping (with the bottom cover added simultaneously) → adding stainless steel sheets → heat sealing the bottom cover → heat seal strength sampling test → primary sealing → secondary sealing → explosion-proof pressure sampling test. However, this traditional process has several technical defects, specifically: Insufficient reliability of stainless steel sheet fixation: In the traditional process, after the stainless steel sheet is added, it is only fixed by the adhesive overflowing during the subsequent heat sealing of the explosion-proof film. During material transfer and transportation, if the amount of overflowing adhesive is insufficient, the adhesive's adhesion is poor, or it is affected by external forces such as transportation vibration, the stainless steel sheet is very likely to fall off. Furthermore, manual or semi-automatic addition methods cannot effectively prevent the omission of stainless steel sheets during assembly, seriously affecting product quality stability. Poor assembly consistency: Traditional processes lack specific pretreatment steps for the explosion-proof film, which can easily lead to gaps or wrinkles between the explosion-proof film and the bottom cover, resulting in weak subsequent heat sealing. Furthermore, the unreasonable sequence of the primary sealing, secondary sealing, and heat sealing processes further reduces the consistency and overall stability of product assembly, resulting in a high failure rate. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention provides a solution to the issue of poor first-pass yield in the assembly of the lower cover of a primary lithium battery pack, and offers an assembly method for the lower cover of a primary lithium battery pack that boasts high production efficiency and a high product qualification rate.

[0004] To solve the above-mentioned technical problems, the technical solution provided by the present invention is: an assembly method for a bottom cover of a lithium primary battery assembly, which includes the steps of assembling an explosion-proof film in the bottom cover, assembling a stainless steel sheet in the bottom cover, primary sealing, and secondary sealing. It also includes steps A and B, wherein in step A, after the explosion-proof film is installed in the bottom cover, the explosion-proof film needs to be preheated before assembling the stainless steel sheet; and in step B, the explosion-proof film needs to be heat-sealed between the primary sealing and secondary sealing steps.

[0005] Further: In the above assembly method for the lower cover of the primary lithium battery pack, the preheating in step A refers to heating the explosion-proof film using a preheating module integrated in the automatic cap assembly equipment, with a heating temperature of 90-120℃ and a heating time of 1.5-3s. The heat sealing of the explosion-proof film in step B refers to heating the explosion-proof film using a heat sealing module integrated in the automatic cap assembly equipment, with a heat sealing temperature of 250±5℃ and a heat sealing time of 1.5±0.1s.

[0006] Before assembly, the explosion-proof film needs to be punched. The punching gap is controlled within 0.01-0.03mm. During the punching process, the punching speed is controlled at 50-100 times / minute by a servo drive system. The punching pressure is automatically adjusted according to the thickness of the explosion-proof film (0.05-0.15mm) to avoid stretching deformation or damage. The punching is carried out using an automated explosion-proof film punching equipment that integrates roll unwinding, tension control, and punching functions. The equipment punches the explosion-proof film, which is in roll form and has a width that meets the requirements for subsequent assembly, to obtain a circular explosion-proof film with an outer diameter and edge contour that meet the preset size requirements. The punched explosion-proof film has no burrs, tears, or wrinkles on the edges. The punching equipment is equipped with a precision punching die made of carbide, and the die cutting edge is precision ground.

[0007] Assembling the explosion-proof film in the bottom cover refers to the continuous conveying of the roll-shaped explosion-proof film to the cavity of the punching die by the conveyor mechanism. After the bottom cover is fed in an orderly manner by the vibrating plate, it is accurately conveyed to the punching die and positioned below the explosion-proof film. The punching die drives the punching blade to move downward. In the same process of punching and forming the explosion-proof film, the punched explosion-proof film is simultaneously pressed into the bottom cover below. The combined action of punching and inserting the explosion-proof film into the bottom cover is completed in one go, so that the explosion-proof film initially adheres to the inner wall of the bottom cover.

[0008] Assembling the stainless steel sheet in the bottom cover refers to using a feeding mechanism to place the stainless steel sheet in the center above the preheated explosion-proof membrane.

[0009] The aforementioned first sealing refers to the automatic combination capping equipment that first reverses the outer edge of the bottom cover, with the bent part adhering to the edge of the explosion-proof film and the stainless steel sheet layer.

[0010] The secondary sealing refers to using an automatic capping device to roll and fasten the first bent edge of the bottom cover to the edge of the explosion-proof film and the stainless steel sheet layer.

[0011] The assembly method for the lower cover of the aforementioned primary lithium battery pack also includes a heat-sealing strength testing process and an explosion-proof pressure testing process. Heat-sealing strength testing process: Randomly selected finished products after heat sealing are subjected to a pressure of 3±1 kg using a pressure testing device, and the pressure is maintained for 60±5 seconds. If the explosion-proof membrane shows no damage or leakage, the heat-sealing strength of the finished product is deemed to meet the standard, and the sealing performance is deemed qualified. Explosion-proof pressure testing process: Sampling tests are conducted on the finished products after secondary sealing. A pressure of 10±1 kg is applied to the finished products using a pressure testing device, and the pressure is maintained for 60 seconds. If the explosion-proof membrane explodes during the pressure holding test period, the explosion-proof performance of the finished product is deemed to meet the preset design requirements.

[0012] In the assembly method of the lower cover of the lithium primary battery assembly of the present invention, the lithium primary battery is a CR123A battery.

[0013] Compared with existing technologies, the assembly method of the lower cover of the aforementioned lithium primary battery pack includes the following steps: assembling an explosion-proof film in the bottom cover, assembling a stainless steel sheet in the bottom cover, primary sealing, and secondary sealing. It also includes steps A and B. Step A involves preheating the explosion-proof film after it is installed in the bottom cover before assembling the stainless steel sheet. Step B involves heat-sealing the explosion-proof film between the primary and secondary sealing steps. Step A refers to using an automated temperature-controlled heating device equipped with a precise temperature sensor and feedback adjustment system, enabling real-time monitoring and dynamic correction of the heating temperature. The heating method is contact heating, where a built-in heating plate adheres to the bottom of the bottom cover, evenly transferring heat to the explosion-proof film. This softens the film and ensures a tight fit against the bottom of the bottom cover, completely eliminating gaps and wrinkles, ensuring a smooth and even fit, and preventing deformation or performance degradation due to excessive temperature. This provides a reliable support surface for the subsequent precise placement and stable fixation of the stainless steel sheet. Step B refers to the use of an integrated heat-sealing module in an automated cap-combining equipment. This module incorporates a high-frequency heating element and a pressure control unit, employing high-frequency hot-pressing for heating. During the heat-sealing process, the heating element rapidly heats up to the set temperature while applying stable pressure to ensure tight contact and thermal fusion between the explosion-proof membrane and the bottom cover. This results in a secure connection between the explosion-proof membrane and the bottom cover, guaranteeing the product's sealing performance and preventing damage to the explosion-proof membrane or weak connections due to improper heat-sealing parameters. This invention, by optimizing the process sequence, adding preheating treatment, and improving the fixing method, completely solves the problems of missing or falling stainless steel sheets in traditional processes, while simultaneously improving product assembly quality, consistency, and production efficiency. The technical effects of this invention are as follows; 1. Completely solves the problem of missing or falling stainless steel sheets: This method innovatively optimizes the process sequence by performing a sealing operation immediately after adding the stainless steel sheet, directly fixing the relative position of the stainless steel sheet to the bottom cover and explosion-proof film. This eliminates the traditional method of relying on heat sealing of the explosion-proof film to fix the sheet, thus preventing the stainless steel sheet from falling off due to insufficient adhesive, reduced adhesive strength, or transportation vibration. At the same time, the coordinated operation of automated feeding and sealing processes significantly reduces the risk of missing stainless steel sheets and significantly improves the product qualification rate.

[0014] 2. Significantly improve product assembly stability and consistency: The addition of a preheating process for the explosion-proof film effectively solves the technical pain points of poor adhesion between the explosion-proof film and the bottom cover, resulting in wrinkles and gaps; each core process uses automated equipment to precisely control key parameters, ensuring the consistency of product assembly quality, significantly reducing the defect rate, and improving product batch stability.

[0015] 3. Ensure product safety performance: By scientifically setting the technical parameters of each process and combining them with strict sampling and testing procedures, the heat sealing performance and explosion-proof performance of the product are doubly guaranteed to meet the design requirements, providing a reliable guarantee for the safe use of the battery and reducing safety hazards during battery use.

[0016] 4. Improve production efficiency and adapt to large-scale production: Fully automated operation reduces human intervention, and the smooth and efficient connection between each process significantly improves overall production efficiency; at the same time, the stability and reliability of the process enable it to adapt to the needs of large-scale batch production, reduce production costs, and enhance the market competitiveness of products. Attached Figure Description

[0017] Figure 1 This is a simplified structural diagram of the longitudinal section of the combined lower cover of the present invention; The components include: 1. bottom cover; 2. explosion-proof film; 3. stainless steel sheet. Detailed Implementation

[0018] The main purpose of this invention is to completely solve the problems of missing or falling stainless steel sheets in traditional processes by optimizing the process sequence, adding preheating treatment and improving the fixing method, while improving the product assembly quality, consistency and production efficiency.

[0019] Example: Figure 1A method for assembling a CR123A battery pack bottom cover includes the following steps: assembling an explosion-proof film 2 into the bottom cover 1; assembling a stainless steel sheet 3 into the bottom cover 1; primary sealing; and secondary sealing. The method further includes steps A and B. Step A involves preheating the explosion-proof film 2 after it is installed into the bottom cover before assembling the stainless steel sheet 3. Step B involves heat-sealing the explosion-proof film between the primary and secondary sealing steps. The preheating in step A refers to using a preheating module integrated into an automatic cap assembly device, with a heating temperature of 90-120℃ and a heating time of 1.5-3 seconds. Step B involves heat-sealing the explosion-proof film using a heat-sealing module integrated into the automatic cap assembly device, with a heat-sealing temperature of 250±5℃ and a heat-sealing time of 1.5±0.1 seconds. Before assembly, the explosion-proof film needs to be punched, with the punching gap controlled at 0.01-0.03mm. During the punching process, the punching speed is controlled at 50-100 times / minute by a servo drive system, and the punching pressure is automatically adjusted according to the thickness of the explosion-proof film (0.05-0.15mm). Assembling the explosion-proof film 2 in the bottom cover 1 means that while the explosion-proof film is being punched and formed by the punching die, the explosion-proof film 2 is pressed into the bottom cover 1, so that the explosion-proof film adheres to the inner wall of the bottom cover. Assembling the stainless steel sheet 3 in the bottom cover 1 means that the stainless steel sheet is placed centered on top of the preheated explosion-proof film using a feeding mechanism. The first sealing refers to the automatic cap assembly equipment bending the outer edge of the bottom cover in the reverse direction for the first time, with the bent part adhering to the edge where the explosion-proof film and stainless steel sheet are stacked. The second sealing refers to the automatic cap assembly equipment rolling and fastening the first bent edge of the bottom cover to the edge where the explosion-proof film and stainless steel sheet are stacked. It also includes a heat-sealing strength test process and an explosion-proof pressure test process.

[0020] 1000 pieces of semi-finished explosion-proof film assembly bottom covers were randomly selected from both the above-mentioned bottom cover assembly method and the traditional assembly method after heat sealing, and the differences in heat sealing strength were compared: Table 1

[0021] 100 pieces of the finished product lower cover assembly after secondary sealing were randomly selected from both the lower cover assembly method described above and the traditional assembly method, and the difference in explosion-proof pressure was compared: Table 2

[0022] Table 1 shows that with traditional processes, 2% of the explosion-proof film products become loose during heat-sealing strength testing, resulting in gaps between the film and the bottom cover. These gaps lead to electrolyte leakage in the finished product. However, the combined bottom cover produced using the method of this invention achieves 100% compliance in heat-sealing strength testing of the explosion-proof film. Table 2 shows that with traditional processes, 1% of the products fail to meet explosion-proof requirements in standard explosion-proof film testing. However, the combined bottom cover produced using the method of this invention achieves 100% compliance in explosion-proof requirements. This invention optimizes the assembly process of the lithium primary battery combined bottom cover, adding preheating treatment and improving the fixing method, completely solving the problems of missing or falling stainless steel sheets in traditional processes. The heat-sealing and explosion-proof pass rate of the explosion-proof film reaches 100%, while simultaneously improving product assembly quality, consistency, and production efficiency.

[0023] The embodiments described above are merely preferred implementations of the present invention and are not intended to limit the scope of the present invention. Any obvious modifications and substitutions made without departing from the concept of the present invention are within the protection scope of the present invention.

Claims

1. A method for assembling a bottom cover of a lithium primary battery assembly, comprising the steps of assembling an explosion-proof film (2) in the bottom cover (1), assembling a stainless steel sheet (3) in the bottom cover (1), a primary sealing, and a secondary sealing, characterized in that: It also includes steps A and B. In step A, after the explosion-proof film (2) is installed into the bottom cover, the explosion-proof film (2) needs to be preheated before the stainless steel sheet (3) is assembled. In step B, the explosion-proof film needs to be heat-sealed between the first sealing and the second sealing steps.

2. The assembly method of the lower cover of the lithium primary battery assembly according to claim 1, characterized in that: The preheating in step A refers to heating the explosion-proof film using a preheating module integrated in an automatic combination capping device. The heating temperature is 90-120℃ and the heating time is 1.5-3 seconds.

3. The assembly method of the lower cover of the lithium primary battery assembly according to claim 2, characterized in that: Step B, heat sealing of the explosion-proof film, refers to heating the explosion-proof film using a heat sealing module integrated by an automatic combination capping device. The heat sealing temperature is 250±5℃, and the heat sealing time is 1.5±0.1s.

4. The assembly method of the lower cover of the lithium primary battery assembly according to claim 3, characterized in that: Before assembly, the explosion-proof film needs to be punched. The punching gap is controlled at 0.01-0.03mm. During the punching process, the punching speed is controlled by a servo drive system at 50-100 times / minute. The punching pressure is automatically adjusted according to the thickness of the explosion-proof film of 0.05-0.15mm.

5. The assembly method of the lower cover of the lithium primary battery assembly according to claim 4, characterized in that: Assembling the explosion-proof film (2) in the bottom cover (1) means that while the explosion-proof film is being punched and formed by the punching die, the explosion-proof film (2) is pressed into the bottom cover (1) so that the explosion-proof film adheres to the inner wall of the bottom cover.

6. The assembly method of the lower cover of the lithium primary battery assembly according to claim 5, characterized in that: Assembling the stainless steel sheet (3) in the bottom cover (1) means using the feeding mechanism to place the stainless steel sheet in the center above the preheated explosion-proof film.

7. The assembly method of the lower cover of the lithium primary battery assembly according to claim 6, characterized in that: The aforementioned first sealing refers to the automatic combination capping equipment that first reverses the outer edge of the bottom cover, with the bent part adhering to the edge of the explosion-proof film and the stainless steel sheet layer.

8. The assembly method of the lower cover of the lithium primary battery assembly according to claim 7, characterized in that: The secondary sealing refers to using an automatic capping device to roll and fasten the first bent edge of the bottom cover to the edge of the explosion-proof film and the stainless steel sheet layer.

9. The assembly method of the lower cover of the lithium primary battery assembly according to claim 8, characterized in that: It also includes heat sealing strength testing and explosion-proof pressure testing processes.

10. The method for assembling the lower cover of the lithium primary battery assembly according to any one of claims 1-9, characterized in that: The lithium primary battery mentioned is a CR123A battery.

Images