A method for synchronous welding of a multi-layer electrode plate of a magnesium secondary battery

Abstract

The present application relates to the field of magnesium secondary battery, and particularly relates to a magnesium secondary battery multilayer pole piece synchronous welding method.The magnesium secondary battery multilayer pole piece synchronous welding method comprises the following steps: step 1: determining a movable part on a tab, determining both sides of the movable part as welding parts, rotating the movable part until the movable part and the two welding parts are arranged in a linear form; step 2: overlapping multiple pole pieces to form a pole piece group until the number of the pole piece group is greater than or equal to two; step 3: welding the pole piece group on the two welding parts respectively; and step 4: reversely rotating the movable part to make the two welding parts close to each other until the movable part and the two welding parts are distributed in a U shape.The magnesium secondary battery multilayer pole piece synchronous welding method can improve the welding efficiency and the welding qualified rate.

Description

Technical Field

[0001] This invention relates to the field of magnesium secondary batteries, and specifically to a method for synchronous welding of multilayer electrodes for magnesium secondary batteries. Background Technology

[0002] Human demand for portable power banks and high-efficiency energy storage devices is becoming increasingly urgent, leading to fiercer competition in the field of rechargeable battery technology. Traditional lead-acid and nickel-cadmium batteries pose environmental pollution risks, while lithium-ion batteries are widely used due to their superior overall performance. However, their tendency to form lithium dendrites severely limits their safety.

[0003] Magnesium secondary batteries typically employ a "negative electrode-less" structure, where magnesium foil / magnesium alloy foil is used directly as the negative electrode of the cell. This effectively improves the energy density of the cell. The tabs of the magnesium foil negative electrode are directly connected to external tabs, enabling the conduction of the electronic pathway. To improve the single-cell capacity and energy density of magnesium secondary batteries, a multi-layer electrode design is typically required. The negative electrode of a magnesium secondary battery is fixed to the tab by welding. Currently, the thickness of the magnesium foil for the negative electrode of a magnesium secondary battery is usually greater than or equal to 50 μm, while the electrode thickness in traditional lithium batteries is only 5-10 μm. Therefore, the thickness of the magnesium foil for the negative electrode of a magnesium secondary battery is 8-10 times that of traditional electrode sheets. High-quality welding of the multi-layer negative electrode becomes a technological challenge: with a large number of electrodes, welding them one by one would undoubtedly lead to low welding efficiency. While welding multiple electrodes to different welding points on the tab can achieve simultaneous welding of multiple electrodes, the residual stress between different welding points during welding can also lead to inconsistent weld quality. Furthermore, the welding process can cause tearing forces at the welding area, damaging the already welded joints and ultimately resulting in a low welding yield. Summary of the Invention

[0004] The present invention aims to provide a method for synchronous welding of multilayer electrodes for magnesium secondary batteries, so as to improve welding efficiency and welding qualification rate.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a method for synchronous welding of multilayer electrodes for magnesium secondary batteries, comprising the following steps:

[0006] Step 1: Identify the movable part on the electrode tab, and designate both sides of the movable part as the welding part. Rotate the movable part until the movable part and the two welding parts are aligned in a straight line.

[0007] Step 2: Overlap multiple electrodes to form an electrode group until the number of electrode groups is greater than or equal to two;

[0008] Step 3: Weld the electrode groups onto the two welding sections respectively;

[0009] Step 4: Rotate the movable part in the opposite direction to bring the two welded parts closer together until the movable part and the two welded parts are distributed in a U-shape.

[0010] The beneficial effects of this plan are:

[0011] 1. This solution sets welding parts on both sides of the movable part. Before welding in step 3, the two welding parts are located on both sides of the movable part and arranged in a straight line with the movable part. At this time, the distance between the two welding parts is relatively far. During welding, the two weld points will not affect each other, resulting in greater strength of the weld position and a higher welding qualification rate.

[0012] 2. In step 2 of this solution, multiple electrode sheets are first overlapped into an electrode sheet group. During welding in step 3, welding one electrode sheet group allows for the simultaneous welding of multiple electrode sheets within that group, effectively improving welding efficiency. Furthermore, the linear arrangement of the movable part and the two welding parts during welding creates a symmetrical structure for the electrode tabs. Whether the electrode sheet is placed on the welding part or the welding part is placed on the electrode sheet, there is no need to position the electrode tabs themselves, thus eliminating the welding step and further improving welding efficiency.

[0013] 3. In this solution, the two welding parts are located on both sides of the movable part. After welding is completed, while positioning the movable part or the main body connected to the middle of the movable part, applying downward pressure to the two welding parts at the same time can quickly bend the movable part. Step 4 is simple and quick, making the whole welding process simple and efficient.

[0014] Further, after determining the moving part and the welding part in step 1, measure the thickness of the moving part and record it as I; measure the thickness of the welding part and record it as d, so that 2 / 5*d≤I≤4 / 5*d.

[0015] The beneficial effects of this solution are as follows: the movable part in this solution can maintain high strength and is less prone to excessive deformation and damage, while the thickness of the welded part is greater than that of the movable part. Therefore, during step 4, even if the force is not applied to the movable part, the movable part can still deform preferentially. At the same time, the greater thickness of the welded part allows it to remain flat during the welding process, thus maintaining a better welding effect.

[0016] Furthermore, the thicknesses of the two welded sections are equal.

[0017] The beneficial effects of this solution are as follows: when the movable part and the two welding parts are arranged in a straight line, the bottom of the two welding parts in this solution are on the same plane, and the top is also on the same plane, so that the electrode tab can be placed vertically without tipping over, ensuring that the electrode tab does not need to be clamped during welding.

[0018] Furthermore, in step 1, the main body is determined and its thickness is measured and denoted as D, such that 1 / 2*D≤d≤D.

[0019] The beneficial effects of this solution are: the main body of the battery cell maintains greater strength to avoid adverse consequences such as welding breakdown, while also avoiding excessive thickness of the main body which would result in a low overall energy density of the battery cell and affect the packaging effect.

[0020] Furthermore, step 3 involves simultaneously welding the electrode groups on both welding sections.

[0021] The beneficial effect of this solution is that simultaneous welding of the electrode plates on both welding parts can further improve welding efficiency.

[0022] Furthermore, in step 4, when rotating the movable part, the two welded parts rotate, and after rotation, the two welded parts are symmetrical along the main body.

[0023] The advantages of this design are: the welded part is larger in size, the force is located on the welded part, making it easier to operate, and the two welded parts are subjected to force at the same time, so that the two welded parts can rotate synchronously with the bending part of the movable part, thus maintaining the symmetrical structure of the tabs after rotation, which is convenient for installation into the magnesium secondary battery.

[0024] Furthermore, in step 3, before welding, the weld points are determined. When determining the weld points, one weld point is determined on each side of each welding part, and the two weld points on the same welding part are staggered.

[0025] The beneficial effects of this solution are: the design of this solution can avoid interference between two weld points on the same welded part, thus affecting the welding qualification rate.

[0026] Furthermore, during step 3 of the welding process, the four electrode groups are simultaneously positioned opposite the four welding points and welded at the same time.

[0027] The beneficial effects of this scheme are as follows: Each welding part in this scheme has two welding points, so four welding points can be determined on one tab, thereby enabling the welding of four electrode groups. When the number of electrodes in each electrode group is equal, the number of electrodes that can be welded is doubled. Since the number of electrodes is proportional to the single-cell capacity and energy density of the magnesium secondary battery, the welding method of this scheme can improve the single-cell capacity and energy density of the magnesium secondary battery.

[0028] The staggered distribution of two weld points on the same weld section can also increase the distance between the two weld points, avoiding mutual interference when welding simultaneously, thus helping to ensure better welding quality.

[0029] Furthermore, after rotating the movable part in step 4, the welded electrode groups are brought into contact.

[0030] The beneficial effect of this scheme is that the bonding can reduce the space occupied by the two electrode groups, thereby reducing the internal space occupied by the magnesium secondary battery.

[0031] Furthermore, after determining the active part in step 1, multiple recesses are machined on the upper surface of the active part near the main body, and the recesses are distributed sequentially between the two welding parts.

[0032] The beneficial effects of this solution are: the recess can provide deformation space to release stress; when the movable part is rotated so that the movable part and the two welded parts are arranged in a straight line, the presence of the recess can avoid stress concentration points inside the movable part, thus reducing the overall strength. Attached Figure Description

[0033] Figure 1 This is a front view of the electrode tab in Embodiment 1 of the present invention;

[0034] Figure 2 for Figure 1 Enlarged view of point A in the middle;

[0035] Figure 3 This is a schematic diagram of the state during electrode group welding in Embodiment 1 of the present invention;

[0036] Figure 4 This is a schematic diagram of the state of the movable part after it has been rotated in the opposite direction in Embodiment 1 of the present invention;

[0037] Figure 5 This is a schematic diagram of the cell structure obtained after welding the electrode group above the welding section.

[0038] Figure 6 This is a schematic diagram of the state during electrode group welding in Embodiment 4 of the present invention;

[0039] Figure 7 This is a front view of the outer electrode used in Comparative Examples 1 to 3 of the present invention. Detailed Implementation

[0040] The following detailed description illustrates the specific implementation method:

[0041] The reference numerals in the accompanying drawings include: movable part 1, recess 11, main body part 2, welding part 3, and electrode group 4.

[0042] This invention discloses Examples 1-3, which disclose a method for synchronous welding of multilayer electrodes for magnesium secondary batteries, including the following steps:

[0043] Step 1: Combining Figure 1 and Figure 2The movable part 1 and the main body part 2 on the electrode tab are determined. Both sides of the movable part 1 are determined as welding parts 3. Multiple pits 11 are machined on the upper surface of the movable part 1 near the main body part 2, and the pits 11 are distributed between the two welding parts 3 in sequence.

[0044] Measure the thickness of the movable part 1 and record it as I; measure the thickness of the welded part 3 and record it as d, so that the thicknesses of the two welded parts 3 are equal, 2 / 5*d≤I≤4 / 5*d; measure the thickness of the main body 2 and record it as D, so that 1 / 2*D≤d≤D; then rotate the movable part 1 until the movable part 1 and the two welded parts 3 are arranged in a straight line.

[0045] Step 2: Overlap multiple electrodes to form an electrode group 4 until the number of electrode groups 4 is greater than or equal to two;

[0046] Step 3: Combining Figure 3 Two welding parts 3 are respectively positioned opposite two electrode groups 4, and the two electrode groups 4 are welded simultaneously. In actual implementation, the welding parts 3 can be placed above the electrode groups 4, or the electrode groups 4 can be placed above the welding parts 3.

[0047] Step 4: Rotate the movable part 1 in the opposite direction to make the two welding parts 3 rotate synchronously and move closer to each other, thus joining them. Figure 4 and Figure 5 Until the active part 1 and the two welding parts 3 are distributed in a U-shape and the welded electrode group 4 are in contact.

[0048] In Examples 1-3, each electrode group includes 4, 5, and 6 electrodes, respectively. Apart from this, the other steps in Examples 1-3 are the same.

[0049] The present invention also discloses embodiment 4.

[0050] Example 4 discloses a method for synchronous welding of multilayer electrodes for magnesium secondary batteries. Based on Example 1, steps 2 and 3 in this example differ from those in Example 1:

[0051] Step 2: Overlap multiple electrodes to form an electrode group 4 until the number of electrode groups 4 is greater than or equal to four;

[0052] Step 3: Combining Figure 6 Before welding, the welding points are determined. When determining the welding points, one welding point is determined on both sides of each welding part 3, and the two welding points on the same welding part 3 are staggered. During welding, the four electrode groups 4 are respectively aligned with the four welding points, and the four electrode groups 4 are welded at the same time.

[0053] This invention discloses comparative examples 1 to 3, combined with Figure 7As shown, the outer tabs of Comparative Examples 1 to 3 include a main body, tab adhesive, and a welding part. The length, width, and thickness of the electrode are the same as those of the electrode in Example 1. The number of electrode layers welded in Comparative Examples 1 to 3 are 4, 5, and 6, respectively.

[0054] When welding the electrode to the outer tab, the electrode and the outer tab are welded in the same manner as in Example 1 to achieve electrical connection. The weld quality of the fabricated cell structure is tested, and the ratio between the number of qualified welds and the number of tested cell structures is recorded as the weld quality rate. The weld quality rate results are shown in the table below:

[0055]

[0056] The comparison shows that using the technology shown in this patent for electrode welding can achieve welding of more layers of cell electrode sheets while maintaining a high welding yield, which is beneficial to improving the capacity and energy density of a single cell.

[0057] Secondly, the test results of Comparative Examples 1-3 show that when using existing external tabs, if the number of electrodes to be welded is greater than 4, each additional electrode leads to a sharp decrease in the welding yield. Comparing the test results of Examples 1-3, the increase in the number of electrodes in this solution has almost no impact on the welding yield. Therefore, the welding method of this invention ensures that welding of multi-layered electrodes can be achieved.

[0058] The above descriptions are merely embodiments of the present invention, and common knowledge such as specific technical solutions and / or characteristics are not described in detail here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical solutions of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A method for synchronous welding of multilayer electrodes for magnesium secondary batteries, characterized in that: Includes the following steps: Step 1: Determine the movable part, main body, and welded part on the electrode tab. The welded part is fixed on both sides of the movable part, and the main body is connected to the middle of the movable part. Measure the thickness of the main body and record it as D. Measure the thickness of the welded part and record it as d. Make 1 / 2 D≤d≤D; Multiple pits are machined on the upper surface of the movable part near the main body, and the pits are distributed between the two welded parts in sequence. Rotate the movable part until the movable part and the two welded parts are arranged in a straight line. Step 2: Overlap multiple electrodes to form an electrode group until the number of electrode groups is greater than or equal to two; Step 3: Weld the electrode groups onto the two welding sections respectively; Step 4: Rotate the movable part in the opposite direction to bring the two welded parts closer together until the movable part and the two welded parts are distributed in a U-shape.

2. The method for synchronous welding of multilayer electrodes for magnesium secondary batteries according to claim 1, characterized in that: After determining the moving part and the welding part in step 1, measure the thickness of the moving part and record it as I; make 2 / 5 d≤I≤4 / 5 d.

3. The method for synchronous welding of multilayer electrodes for magnesium secondary batteries according to claim 2, characterized in that: The two welded parts have the same thickness.

4. The method for synchronous welding of multilayer electrodes for magnesium secondary batteries according to claim 1, characterized in that: Step 3 involves simultaneously welding the electrode groups on both welding sections.

5. The method for synchronous welding of multilayer electrodes for magnesium secondary batteries according to claim 4, characterized in that: Step 4: When rotating the movable part, the two welded parts will rotate, and after rotation, the two welded parts will be symmetrical along the main body.

6. The method for synchronous welding of multilayer electrodes for magnesium secondary batteries according to claim 1, characterized in that: Step 3: Before welding, determine the weld points. When determining the weld points, determine one weld point on each side of each welding part, and the two weld points on the same welding part are staggered.

7. The method for synchronous welding of multilayer electrodes for magnesium secondary batteries according to claim 6, characterized in that: In step 3, during welding, the four electrode groups are simultaneously aligned with the four welding points and welded at the same time.

8. The method for synchronous welding of multilayer electrodes for magnesium secondary batteries according to claim 1, characterized in that: After rotating the movable part in step 4, the welded electrode groups are brought into contact.

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