A magnesium battery cell structure

Abstract

The application relates to the technical field of magnesium secondary batteries, in particular to a magnesium battery cell structure; the magnesium battery cell structure comprises a pole piece unit and a tab, the pole piece unit comprises two pole piece assemblies, the two pole piece assemblies are located on the two sides of the tab, the two pole piece assemblies each comprise at least two pole piece groups, each pole piece group is formed by a plurality of pole pieces being attached to each other, the pole piece group comprises an overlapping part and a welding part; the tab comprises a plurality of main body parts which are sequentially distributed along the length direction, a buffer part is arranged between adjacent main body parts, the thickness of the buffer part is smaller than the thickness of the main body part, and a slope is arranged between the buffer part and the main body part; the welding part corresponds to the main body part one by one and is fixed with the main body part, and the welding parts of the plurality of pole piece groups of the same pole piece assembly are sequentially distributed along the length direction of the pole piece. The magnesium battery cell structure solves the problems of large space occupation, high cost and low welding quality of the cell in the current magnesium secondary battery.

Description

Technical Field

[0001] This invention relates to the field of magnesium secondary battery technology, and specifically to a magnesium battery cell structure. Background Technology

[0002] Battery technology, as a crucial component of modern energy storage technology, is widely used in portable electronic devices, electric vehicles, and energy storage. Among these, magnesium secondary batteries are particularly valuable due to their high theoretical energy density (magnesium ions carry two electrons, with a theoretical volumetric capacity of 3383 mAh / cm³). 3 Magnesium, with its abundant resources and excellent safety performance, has become a research hotspot in the field and is considered one of the most promising battery systems to replace lithium batteries. Magnesium secondary batteries are recyclable batteries that use metallic magnesium as the negative electrode. A magnesium secondary battery mainly includes a magnesium negative electrode, an electrolyte, and a magnesium intercalating element. 2+ The positive electrode material. The electrode sheet and tab are the positive and negative electrodes in the battery, used to lead the positive and negative electrodes out from the inside of the cell and ensure that the current can be transferred from the inside to the external circuit, so as to realize the charging and discharging behavior of the battery.

[0003] Electrodes and tabs are typically fixed by welding. To improve the single-cell capacity and energy density of magnesium secondary batteries, current magnesium batteries use multi-layered electrodes. The increased number of electrodes undoubtedly increases the difficulty of welding them to the tabs. Patent application CN202220864912.3 discloses a tab structure and a battery having this structure. The tab structure includes multiple current collector tabs stacked sequentially in the thickness direction to form a tab group; a pre-welded component welded to the tab group for leading out the current collector tabs; and adjacent current collector tabs having unequal areas.

[0004] During the welding process of the aforementioned electrode structure, by setting different electrode pieces to different lengths, each electrode piece is partially exposed. At this time, a bent pre-welded part can be used to make the pre-welded part fit with each electrode piece, thereby ensuring that all electrode pieces are welded, while also preventing the cell length from becoming too large.

[0005] However, the lengths and widths of the different electrodes in the aforementioned electrode group vary significantly, leading to more complex processing requirements. Furthermore, the presence of pre-welded components increases the cost of magnesium batteries, and these three-dimensional components, rather than sheet-like shapes, also have higher processing costs. Secondly, the three-dimensional pre-welded components are prone to deformation during storage and transportation. Deformed pre-welded components cannot be properly bonded to each electrode in the electrode group and become unusable. Therefore, the storage and transportation requirements for pre-welded components are high, undoubtedly increasing the manufacturing cost of the tabs and reducing their welding efficiency. Finally, to further improve fast-charging performance, the number of electrodes is usually large. With an increased number of electrodes, the length and width of the electrodes need to gradually increase from top to bottom. Therefore, the lower electrodes still maintain a relatively large size, and the size of the pre-welded components also increases to accommodate more electrodes, thus still occupying a considerable amount of space. Summary of the Invention

[0006] The present invention aims to provide a magnesium battery cell structure to solve the problems of large cell space, high cost and low welding quality in current magnesium secondary batteries.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: a magnesium battery cell structure, including an electrode unit and an electrode tab, the electrode unit including two electrode assemblies, the two electrode assemblies being located on both sides of the electrode tab, each electrode assembly including at least two electrode groups, each electrode group being formed by multiple electrodes attached together, the electrode group including a fixedly connected overlapping portion and a welded portion;

[0008] The electrode includes multiple main body parts distributed sequentially along the length direction. The number of main body parts is greater than or equal to the sum of the number of electrode groups in two electrode assemblies. A buffer part is provided between adjacent main body parts. The thickness of the buffer part is less than the thickness of the main body part, and a slope is provided between the buffer part and the main body part.

[0009] The welded parts correspond one-to-one with the main body and are fixed to the main body. The welded parts of multiple electrode groups in the same electrode assembly are distributed sequentially along the length of the electrode.

[0010] The beneficial effects of this plan are:

[0011] 1. When there are many electrodes in a magnesium secondary battery, the electrode unit in this solution includes multiple electrode groups. Welding of all electrodes is completed by welding each electrode group separately. Since the number of electrodes in any electrode group is relatively small, compared with the prior art of stacking all the electrodes together, the electrode group in this solution has a smaller thickness. It is not necessary to increase or decrease the length of the electrodes from bottom to top. The electrodes can still be fixed to the tabs during welding. Therefore, the electrodes in this solution do not need to use pre-welded parts to weld and fix to the tabs, resulting in low welding cost and high efficiency.

[0012] Secondly, the tab in this solution includes multiple main body parts, each of which is welded to a group of electrode plates. The buffer part between adjacent main body parts acts as a separator between the two adjacent main body parts, so that there is a large distance between the two adjacent main body parts. Therefore, the adjacent weld points will not be pulled and damaged, and the welding strength is also greater. Thus, more welding can be performed, reducing the welding difficulty.

[0013] 2. Compared to the requirement that the length of each electrode sheet gradually increases or decreases, this solution divides all electrodes into several electrode sheet groups. Within the same electrode sheet group, since each electrode sheet does not need to have a part that is in contact with the tab or pre-welded part, the ends of the electrodes in each electrode sheet group do not need to protrude. That is, the lengths of the electrodes in the same electrode sheet group can be the same or nearly the same, and only the lengths of the electrodes in different electrode sheet groups need to differ. Furthermore, since all electrodes are divided into multiple electrode sheet groups, the number of electrode sheet groups is much less than the number of electrodes. Therefore, even if it is necessary to increase the length of the electrodes in some electrode sheet groups, the length of the electrodes in the outermost electrode sheet group is also smaller than that of the electrodes in the prior art because the number of electrode sheet groups is small.

[0014] 3. The thickness of the buffer section is smaller than that of the main body, making the buffer section more flexible and less prone to breakage of the tabs during welding. Although multi-layered electrodes also exist in current conventional lithium battery systems, the electrodes in lithium batteries are composed of multiple copper foils with a thickness of 5-10 μm, and the tabs are nickel / copper plated nickel tabs. The thickness of the copper foil is small, and even if multiple copper foils are used to form multi-layered electrodes, the thickness of these electrodes is still relatively small.

[0015] However, the tabs in this invention are used in magnesium secondary batteries. Magnesium-ion battery systems use multiple magnesium foils or magnesium alloy foils with a thickness ≥50µm to form multilayer electrodes. The thickness of these electrodes is much greater than that of lithium battery systems. This excessive thickness makes the tabs in magnesium secondary batteries prone to tearing during repeated welding. Conventional designs reduce the number of welding layers to prevent the tabs from breaking under stress and ensure welding quality, but this limits the cell's capacity and energy density.

[0016] However, the buffer section in this invention, by reducing its thickness, actually creates a weak area that is easily deformable, providing a certain deformation space. During multiple welding processes, the stress between different weld points may cause the electrode tabs to tear. In this case, the buffer section deforms preferentially to eliminate the interaction force between the weld points, reducing the risk of weld point failure. Finally, the welded parts of the outer electrode group bend towards the side closer to the tabs, so the electrodes in this design occupy less cell space, resulting in a higher energy density for the magnesium secondary battery.

[0017] Furthermore, the welding portions of the two electrode assemblies and the fixing portions between them are alternately distributed along the length of the electrode tabs.

[0018] The beneficial effects of this solution are as follows: the distribution of the electrode clusters on both sides of the tab makes the weight distribution on both sides of the tab more uniform, and also allows for a smaller distance between the outer electrode clusters and the tab. During welding, the length of the weld portion can be shortened to ensure close contact with the tab, thereby reducing the size and material usage of the electrode, lowering electrode costs, and further reducing the space occupied by the electrode in the cell, which is beneficial to improving the energy density of the battery.

[0019] Furthermore, the length of any one of the main body parts is L, where 8mm ≤ L ≤ 15mm.

[0020] The beneficial effects of this solution are: while ensuring good welding results, the main body of this solution also avoids the adverse effects of excessive cell length on cell energy density.

[0021] Furthermore, the distance between adjacent main body parts is L0, where 5mm ≤ L0 ≤ (1 / n)*(L1 + L2 + ... + L n ).

[0022] The beneficial effects of this scheme are: where n represents the number of main body parts, L1, L2, L... n These are the lengths of the first main body, the second main body, and the nth main body, respectively, "L1+L2+……+L n "" represents the sum of the lengths of all main body sections. In this scheme, the length between adjacent main body sections is limited, thereby limiting the length of the buffer section. This ensures that the buffer section provides a good buffering effect while also preventing the excessive length of the battery cell from adversely affecting the energy density.

[0023] Furthermore, the difference between the length of the welded portion of any electrode group in the same electrode assembly and the length of the welded portion of the adjacent inner electrode group is denoted as A, where 8mm≤A≤16mm.

[0024] The beneficial effects of this solution are: there is a significant length difference in the welded parts of the electrode group in the same electrode assembly, so that the part of the welded part of the outer electrode group that is bent and in contact with the electrode tab maintains a certain distance from the inner electrode group, and the welding will not damage the weld points of the inner electrode group.

[0025] Furthermore, the thickness difference between the buffer section and the main body is D. n D / 10≤D n ≤D / 4.

[0026] The beneficial effects of this solution are as follows: The thickness difference between the buffer part and the main body part in this solution is relatively large, which makes the angle between the replacement part and the main body part larger, thus avoiding stress concentration caused by an excessively sharp angle, which would reduce the strength of the tab itself.

[0027] Furthermore, the angle between the slope and the buffer section is α, where 120°≤α≤150°.

[0028] The beneficial effect of this solution is that the slope is stress-dispersed when subjected to force, so that the contact point between the slope and the buffer section will not be damaged due to stress concentration.

[0029] Furthermore, reinforcing ribs are fixed on the buffer section.

[0030] Furthermore, the reinforcing ribs are ring-shaped.

[0031] Furthermore, the reinforcing ribs are strip-shaped.

[0032] The beneficial effects of this solution are as follows: the reinforcing ribs can increase the strength of the buffer section, and while maintaining the good flexibility of the buffer section, further prevent the buffer section from easily breaking due to the thinning of the thickness. While ensuring that the electrode lug has sufficient mechanical strength, it can also greatly reduce the risk of welding failure and improve the welding qualification rate. Attached Figure Description

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

[0034] Figure 2 for Figure 1 The left view;

[0035] Figure 3 for Figure 2 Enlarged view of point A in the middle;

[0036] Figure 4 for Figure 1 Enlarged view of point B in the middle;

[0037] Figure 5 This is a schematic diagram of the welding of the electrode tab and the electrode sheet in Embodiment 1 of the present invention;

[0038] Figure 6 for Figure 5 Enlarged view of point C in the middle;

[0039] Figure 7 This is a schematic diagram of the reinforcing rib in Embodiment 2 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: tab adhesive 1, main body 2, buffer 3, ramp 4, electrode group 5, overlapping part 51, welding part 52, and reinforcing rib 6.

[0042] Example 1

[0043] Example 1 is basically as follows Figure 1-6As shown, a magnesium battery cell structure includes an electrode unit and a tab. A tab adhesive 1 is provided in the middle of the tab. Specifically, the arrangement of the tab adhesive 1 is the same as in the prior art, and will not be described again in this embodiment. Below the tab adhesive 1 are four main body parts 2, the length of any one of the main body parts 2 being L. In this embodiment, 8mm ≤ L ≤ 15mm.

[0044] A buffer section 3 is provided between each two adjacent main body sections 2. All buffer sections 3 have the same length, and their thickness is less than the thickness of the main body section 2. The centerline of the buffer section 3 coincides with the centerline of the main body section 2. The difference in thickness between the buffer section 3 and the main body section 2 is D. n The distance between the bottom of any main body 2 and the top of the adjacent main body 2 below it is L0. The lengths of the four main body 2 are L1, L2, L3 and L4, respectively. In this embodiment, D / 10 ≤ D n ≤D / 4, 5mm≤L0≤(1 / 4)*(L1+L2+L3+L4). Several reinforcing ribs 6 are fixed on the buffer section 3. The reinforcing ribs 6 include rings; specifically, in this embodiment, the reinforcing ribs 6 are circular. The reinforcing ribs 6 allow the buffer section 3 to maintain a smaller thickness, thus improving flexibility while having greater strength. In actual implementation, the reinforcing ribs 6 can also adopt shapes such as quadrilaterals or triangles with their ends connected.

[0045] Two ramps 4 are provided at both ends of the buffer part 3, and the two ramps 4 are located on both sides of the buffer part 3 respectively. All ramps 4 are connected to the buffer part 3 at one end and to the adjacent main body part 2 at the other end. The included angle between the ramp 4 and the surface of the buffer part 3 is α. In this embodiment, 120°≤α≤150°.

[0046] The electrode unit includes two electrode assemblies, which are located on the upper and lower sides of the electrode tab, respectively. Each electrode assembly includes multiple electrode groups 5. Specifically, in this embodiment, each electrode assembly includes two electrode groups 5. Each electrode group 5 includes multiple electrodes. The thickness of the electrode group 5 gradually decreases from the side closer to the electrode tab to the side farther away from the electrode tab. In this embodiment, this is achieved by reducing the number of electrodes in the electrode group 5. Specifically, in the same electrode assembly, the electrode group 5 on the side closer to the electrode tab includes five electrodes, and the electrode group 5 on the side farther away from the electrode tab includes four electrodes. In actual implementation, when the number of electrode groups 5 in the same electrode assembly is greater than two, the number of electrodes in the electrode group 5 gradually decreases from the side closer to the electrode tab to the side farther away from the electrode tab.

[0047] All electrodes within the same electrode group 5 are in contact with each other. Each electrode group 5 includes an overlapping portion 51 and a welded portion 52. Specifically, the overlapping portions 51 of the innermost electrode groups 5 closest to the tab of two electrode assemblies are in contact with each other, and the right side of the welded portion 52 is in contact with the main body portion 2 on the tab, causing the welded portion 52 near the overlapping portion 51 to bend and deform. Taking the upper electrode assembly as an example, the overlapping portion 51 of the upper electrode group 5 of the same electrode assembly is in contact with the lower electrode group 5. The length of the welded portion 52 of the upper electrode group 5 is greater than the length of the welded portion 52 of the lower electrode group 5. Specifically, the difference in length between the two welded portions 52 is denoted as A, where 8mm ≤ A ≤ 16mm. The overlapping portion 51 of the upper electrode group 5 covers the welding portion 52 of the lower electrode group 5. The welding portion 52 of the upper electrode group 5 is bent downwards to the position where it is in contact with the electrode tab, so that the right end of the welding portion 52 of the upper electrode group 5 is opposite to the right end of the welding portion 52 of the lower electrode group 5. The distance between the two welding portions 52 and the positions where they are in contact with the electrode tab is greater than or equal to 6 mm.

[0048] The specific implementation process is as follows:

[0049] When welding electrode group 5, the welding positions of electrode group 5 and electrode tab are arranged sequentially from left to right, and the electrode groups 5 of the two electrode assemblies are alternately distributed. The welding part 52 of the electrode is attached to the middle of the main body 2, and then laser welding is performed. After welding, the first electrode group 5 of the lower electrode assembly is abutted against the top middle of the main body 2 on the right and welded, and so on, alternating welding. During the welding process, the flexibility of the buffer part 3 allows the buffer part 3 to bend and deform, preventing the electrode tab from breaking, effectively improving the welding qualification rate. In actual welding tests, while ensuring welding strength, the number of electrode layers that can be welded on the electrode tab of the present invention is greater than or equal to 10 layers, proving that the welding difficulty is lower and the welding qualification rate is higher.

[0050] Example 2

[0051] Based on Example 1, such as Figure 7 As shown, the reinforcing rib 6 in this embodiment is strip-shaped. Specifically, the reinforcing rib 6 is wavy and extends along the width direction of the buffer portion 3. In actual implementation, the reinforcing ribs 6 of both Embodiment 1 and Embodiment 2 can be used simultaneously. In this case, the annular reinforcing rib 6 can be independent of the strip-shaped reinforcing rib 6, or the annular reinforcing rib 6 can be fixed with one or more strip-shaped reinforcing ribs 6 to form a Q-shaped reinforcing rib 6. Apart from this, the welding method in this embodiment is the same as that in Embodiment 1, and will not be described again in this embodiment.

[0052] 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 magnesium battery cell structure, comprising an electrode unit and electrode tabs, characterized in that: The electrode unit includes two electrode assemblies, which are located on both sides of the electrode tab. Each electrode assembly includes at least two electrode groups, and each electrode group is formed by multiple electrodes attached together. The electrode group includes an overlapping part and a welded part that are fixedly connected. The electrode includes multiple main body parts distributed sequentially along the length direction. The number of main body parts is greater than or equal to the sum of the number of electrode groups in two electrode assemblies. A buffer part is provided between adjacent main body parts. The thickness of the buffer part is less than the thickness of the main body part, and a slope is provided between the buffer part and the main body part. The welded parts correspond one-to-one with the main body and are fixed to the main body. The welded parts of multiple electrode groups in the same electrode assembly are distributed sequentially along the length of the electrode.

2. The magnesium battery cell structure according to claim 1, characterized in that: The welding parts of the two electrode assemblies and the fixing parts between the electrode tabs are alternately distributed along the length of the electrode tabs.

3. The magnesium battery cell structure according to claim 1, characterized in that: The length of any one of the main parts is L, where 8mm ≤ L ≤ 15mm.

4. The magnesium battery cell structure according to claim 3, characterized in that: The distance between adjacent main body parts is L0, where 5mm ≤ L0 ≤ (1 / n). (L1+L2+……+L) n L1, L2, L n These are the lengths of the first main body, the second main body, and the nth main body, respectively.

5. A magnesium battery cell structure according to claim 3 or 4, characterized in that: The difference between the length of the welded portion of any electrode group in the same electrode assembly and the length of the welded portion of the adjacent inner electrode group is denoted as A, where 8 mm ≤ A ≤ 16 mm.

6. The magnesium battery cell structure according to claim 1, characterized in that: The angle between the slope and the buffer section is α, where 120°≤a≤150°.

7. A magnesium battery cell structure according to claim 1, characterized in that: The buffer section is fixed with reinforcing ribs.

8. A magnesium battery cell structure according to claim 7, characterized in that: The reinforcing ribs are ring-shaped.

9. A magnesium battery cell structure according to claim 7, characterized in that: The reinforcing ribs are strip-shaped.

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