Magnesium battery cell structure

Abstract

The invention relates to the technical field of magnesium secondary batteries, in particular to a magnesium battery cell structure. Comprising a pole piece unit and a pole lug, the pole piece unit comprises two pole piece assemblies, the two pole piece assemblies are located on the two sides of the pole lug respectively, each pole piece assembly comprises at least two pole piece groups, each pole piece group is formed by attaching a plurality of pole pieces, and each 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, buffer parts are arranged between adjacent main body parts, the thickness of the buffer parts is smaller than that of the main body parts, and slopes are arranged between the buffer parts and the main body parts; the welding parts are in one-to-one correspondence with the main body parts and are fixed with the main body parts, 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 pieces. The magnesium battery cell structure provided by the invention solves the problems of large occupied space, high cost and low welding quality of the cell in the existing magnesium secondary battery.

Description

Technical Field

[0001] The present invention relates to the technical field of magnesium secondary batteries, and in particular to a magnesium battery core structure. Background Art

[0002] Battery technology is an important part of modern energy storage technology and is widely used in portable electronic devices, electric vehicles and energy storage. Among them, magnesium secondary batteries have a high theoretical energy density (magnesium ions carry two electrons and a theoretical volumetric capacity of 3383 mAh / cm 3 ), rich resources, and excellent safety performance have become a research hotspot in the field and are considered to be one of the most promising battery systems to replace lithium batteries. Magnesium secondary batteries refer to recyclable batteries with magnesium metal as the negative electrode. Magnesium secondary batteries mainly include magnesium negative electrode, electrolyte and electrolyte that can embed Mg 2+ The electrode sheet and tab are the structures in the positive and negative electrodes of the battery, used to lead the positive and negative electrodes out of the battery cell and ensure that the current can be transmitted from the inside to the external circuit, and are used to realize the charging and discharging behavior of the battery.

[0003] Electrode sheets and tabs are typically secured by welding. To increase the single-cell capacity and energy density of magnesium secondary batteries, current magnesium batteries employ multiple layers of electrode sheets. The increased number of electrode sheets undoubtedly increases the difficulty of welding the electrode sheets and tabs. Patent application number CN202220864912.3 discloses a tab structure and a battery having the same. The tab structure comprises a plurality of current collector tabs stacked sequentially in thickness to form a tab cluster; a pre-weld welded to the tab cluster for leading out the current collector tabs; and adjacent current collector tabs having unequal areas.

[0004] When welding the above-mentioned pole ear structure, different pole pieces are set to different lengths so that each pole piece is partially exposed. At this time, a curved pre-weld piece can be used to make the pre-weld piece fit into each pole piece, thereby ensuring that all pole pieces are welded, while also preventing the length of the battery cell from being too large.

[0005] However, in the above-mentioned electrode group, the lengths and widths of different electrode sheets vary greatly, and the processing requirements for the electrode sheets are more. The existence of pre-welds also increases the cost of magnesium batteries. Pre-welds are three-dimensional rather than sheet-shaped, and the processing cost of pre-welds is also high. Secondly, three-dimensional pre-welds are easily deformed by stress during storage and transportation. Deformed pre-welds cannot be attached to each electrode of the electrode group and cannot be reused. Therefore, the storage and transportation requirements of pre-welds are high, which undoubtedly increases the manufacturing cost of the tabs and reduces the welding efficiency of the tabs. Finally, in order to further improve the fast charging performance, the number of pole sheets is usually large. As the number of pole sheets increases, the length and width of the pole sheets need to gradually increase from top to bottom. Therefore, the pole sheets at the bottom still maintain a larger size. In order to attach to more pole sheets, the size of the pre-welds will also increase accordingly, so they will still occupy a large 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 occupation, high cost and low welding quality in current magnesium secondary batteries.

[0007] To achieve the above-mentioned object, the present invention adopts the following technical solution: a magnesium battery cell structure, comprising a pole piece unit and a pole tab, wherein the pole piece unit comprises two pole piece assemblies, the two pole piece assemblies are respectively located on both sides of the pole tab, and 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 affixed to each other, and the pole piece group comprises a fixedly connected overlapping portion and a welding portion;

[0008] The tab includes a plurality of main bodies distributed in sequence along the length direction, the number of the main bodies being greater than or equal to the sum of the number of pole piece groups in the two pole piece assemblies, a buffer portion being provided between adjacent main bodies, the thickness of the buffer portion being less than that of the main body portion, and a slope being provided between the buffer portion and the main body portion;

[0009] The welding parts correspond to the main body one by one and are fixed to the main body. The welding parts of multiple pole piece groups of the same pole piece assembly are distributed in sequence along the length direction of the pole piece.

[0010] The beneficial effects of this program are:

[0011] 1. When the number of electrode sheets in the magnesium secondary battery is large, the electrode sheet unit in this solution includes multiple electrode sheet groups. The welding of all electrode sheets is completed by welding each electrode sheet group separately. The number of electrode sheets in any electrode sheet group is relatively small. Therefore, compared with the prior art in which all electrode sheets are stacked together, the thickness of the electrode sheet group in this solution is smaller, and there is no need to increase or decrease the length of the electrode sheet from bottom to top. The electrode sheet can still be fixed to the electrode tab during welding. Therefore, the electrode sheet in this solution does not need to use pre-weld parts to be welded to the electrode tab, and the welding cost is low and the efficiency is high.

[0012] Secondly, the tab in this solution includes multiple main parts, each main part is welded to a pole piece group, and the buffer part between adjacent main parts serves to separate the two adjacent main parts, so that there is a larger distance between the two adjacent main parts, so that adjacent welding points will not be pulled and damaged, and the welding strength is also greater, so more welding can be performed, reducing the difficulty of welding.

[0013] 2. Compared with the requirement to gradually increase or decrease the length of each pole piece, in this solution, all pole pieces are divided into several pole piece groups. In the same pole piece group, since each pole piece does not need to be provided with a portion in contact with the pole ear or pre-weld, the end of the pole piece of each pole piece group does not need to protrude, that is, the length of the pole pieces of the same pole piece group can be the same or nearly the same, and only the length of the pole pieces of different pole piece groups is different. Moreover, since all pole pieces are divided into multiple pole piece groups, the number of pole piece groups is far less than the number of pole pieces. Therefore, even if it is necessary to increase the length of the pole pieces in some pole piece groups, because the number of pole piece groups is small, the length of the pole pieces in the outermost pole piece group is also smaller than that of the prior art.

[0014] 3. The thickness of the buffer portion is thinner than that of the main body, making it more flexible and less likely to break during welding. Although multi-layer pole pieces are also present in current conventional lithium battery systems, the pole pieces in lithium batteries are composed of multiple copper foils with a thickness of 5 to 10 μm, and the pole pieces are nickel / copper plated with nickel. The copper foil is thin, so even if multiple layers of copper foil are used to form multi-layer pole pieces, the thickness of these pole pieces is still relatively small.

[0015] However, the tabs used in magnesium secondary batteries utilize multiple layers of magnesium foil or magnesium alloy foil with a thickness of 50 μm or greater. These tabs are much thicker than those used in lithium batteries. This excessive thickness can cause the tabs in magnesium secondary batteries to tear during multiple welds. Conventional designs minimize the number of weld layers to prevent the tabs from breaking under stress and maintain weld quality, but this can limit the capacity and energy density of the battery cell itself.

[0016] However, the buffer portion of the present invention, by reducing its thickness, creates a vulnerable zone that is easily deformed, providing sufficient space for deformation. During multiple welds, the stress between different weld points could cause the electrode tabs to tear. In this case, the buffer portion deforms first, eliminating the interaction between the weld points and reducing the risk of weld failure. Finally, the welded portion of the outer electrode group bends toward the tab. As a result, the electrode in this solution occupies less space in the battery cell, and the energy density of the magnesium secondary battery is higher.

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

[0018] The beneficial effects of this solution are: the pole piece groups are distributed on both sides of the pole ear, making the weight on both sides of the pole ear more uniform, and also making the distance between the outer pole piece group and the pole ear smaller. When welding, the length of the welding part is set to be smaller, that is, it can be attached to the pole ear, thereby reducing the size and material of the pole piece, reducing the cost of the pole piece, and further making the pole piece occupy less space in the battery cell, which is conducive to improving the energy density of the battery.

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

[0020] The beneficial effect of this solution is that the main body in this solution ensures a good welding effect while also preventing the battery cell from being too long and causing adverse effects on the energy density of the battery cell.

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

[0022] The beneficial effects of this solution are: n represents the number of main body parts, L1, L2, L n They are the length of the first main body, the length of the second main body, and the length of the nth main body, respectively. "L1+L2+...+L n " represents the sum of the lengths of all main bodies. In this solution, the length between adjacent main bodies is limited, thereby limiting the length of the buffer portion. This ensures a good buffering effect while also preventing the adverse effects of excessive cell length on energy density.

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

[0024] The beneficial effect of this solution is that there is an obvious length difference in the welding parts of the pole piece groups in the same pole piece assembly, so that the welding parts of the outer pole piece group are bent and the parts that are in contact with the pole ears maintain a certain distance from the inner pole piece group, and the welding points of the inner pole piece group will not be damaged during welding.

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

[0026] The beneficial effect of this solution is that the thickness difference between the buffer part and the main body in this solution is relatively large, which makes the angle between the buffer part and the main body larger, and can avoid the stress concentration caused by the angle being too sharp, resulting in a reduction in the strength of the tab itself.

[0027] Furthermore, the included angle between the slope and the buffer portion is a, 120°≤a≤150°.

[0028] The beneficial effect of this solution is that the slope in this solution disperses stress when subjected to force, so that the contact position between the slope and the buffer portion will not be damaged due to stress concentration.

[0029] Furthermore, a reinforcing rib is fixed on the buffer portion.

[0030] Furthermore, the reinforcing rib is annular.

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

[0032] The beneficial effects of this solution are: the reinforcement ribs can increase the strength of the buffer part, while maintaining the good flexibility of the buffer part, further preventing the buffer part from being easily broken due to thinning, while ensuring that the tab has sufficient mechanical strength, it can also greatly reduce the risk of welding failure and improve the welding qualification rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a front view of embodiment 1 of the present invention;

[0034] Figure 2 for Figure 1 Left view of;

[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 Schematic diagram of welding the electrode tab and the electrode sheet in Example 1 of the present invention;

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

[0039] Figure 7 Schematic diagram of the reinforcing ribs in Example 2 of the present invention. DETAILED DESCRIPTION

[0040] The following is further described in detail through specific implementation methods:

[0041] The reference numerals in the drawings of the specification include: tab glue 1 , main body 2 , buffer portion 3 , slope 4 , electrode group 5 , overlapping portion 51 , welding portion 52 , and reinforcing rib 6 .

[0042] Example 1

[0043] Example 1 is basically as Figure 1-6As shown, a magnesium battery cell structure includes a pole piece unit and a tab. Tab glue 1 is provided in the middle of the tab. Specifically, the arrangement of tab glue 1 is the same as in the prior art and will not be described in detail in this embodiment. Below the tab glue 1 are four main bodies 2. The length of any main body 2 is L. In this embodiment, 8 mm ≤ L ≤ 15 mm.

[0044] A buffer portion 3 is provided between two adjacent main bodies 2. The lengths of all buffer portions 3 are equal, and the thicknesses of all buffer portions 3 are smaller than the thickness of the main body 2. The center line of the buffer portion 3 coincides with the center line of the main body 2. The difference in thickness between the buffer portion 3 and the main body 2 is D n The distance between the bottom of any main body 2 and the top of the adjacent main body 2 below is L0, and the lengths of the four main bodies 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 to the buffer portion 3. The reinforcing ribs 6 include annular shapes. Specifically, the reinforcing ribs 6 in this embodiment are circular. The reinforcing ribs 6 enable the buffer portion 3 to maintain a smaller thickness, thereby improving flexibility and providing greater strength. In actual implementation, the reinforcing ribs 6 may also adopt a quadrilateral, triangle, or other end-to-end shape.

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

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

[0047] All the pole pieces in the same pole piece group 5 are in contact with each other, and all the pole piece groups 5 include overlapping portions 51 and welding portions 52. Specifically, the overlapping portions 51 of the inner pole piece groups 5 closest to the pole tabs of the two pole piece assemblies are in contact with each other, and the right portion of the welding portion 52 is in contact with the main body 2 on the pole tab, so that the portion of the welding portion 52 close to the overlapping portion 51 is bent and deformed. Taking the pole piece assembly on the upper side as an example, the overlapping portion 51 of the upper pole piece group 5 of the same pole piece assembly is in contact with the lower pole piece group 5, and the length of the welding portion 52 of the upper pole piece group 5 is greater than the length of the welding portion 52 of the lower pole piece group 5. Specifically, the difference in length of the two welding portions 52 is recorded as A, 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 downward to abut against 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 electrode tab is greater than or equal to 6 mm.

[0048] The specific implementation process is as follows:

[0049] When welding the pole piece group 5, the welding positions of the pole piece group 5 and the pole tab are arranged in sequence from left to right, and the pole piece groups 5 of the two pole piece assemblies are distributed alternately. The welding portion 52 of the pole piece is attached to the middle of the main body 2, and then laser welding is performed. After welding, the first pole piece group 5 of the lower pole piece assembly is abutted against the top middle of the main body 2 on the right and welded, and the welding is performed alternately. During the welding process, the flexibility of the buffer portion 3 enables the buffer portion 3 to bend and deform without breaking the pole tab, effectively improving the welding pass rate. In actual welding tests, while ensuring the welding strength, the number of pole piece layers that can be welded on the pole tab in the present invention is greater than or equal to 10 layers, proving that the welding difficulty is lower and the welding pass rate is high.

[0050] Example 2

[0051] On the basis of Example 1, Figure 7 As shown, the reinforcing ribs 6 in this embodiment are strip-shaped. Specifically, the reinforcing ribs 6 are wavy and extend along the width direction of the buffer portion 3. In actual implementation, the reinforcing ribs 6 of both Embodiments 1 and 2 may be used simultaneously. In this case, the annular reinforcing ribs 6 may be independent of the strip-shaped reinforcing ribs 6, or the annular reinforcing ribs 6 may be fixed to 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 repeated in this embodiment.

[0052] The above is only an embodiment of the present invention, and the common knowledge such as the specific technical solutions and / or characteristics in the solution are not described in detail here. It should be pointed out that for those skilled in the art, without departing from the technical solution of the present invention, several variations and improvements can be made, which should also be regarded as the scope of protection of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the description can be used to interpret the content of the claims.

Claims

1. A magnesium battery cell structure, comprising a pole piece unit and a pole tab, characterized in that: The pole piece unit includes two pole piece assemblies, which are respectively located on both sides of the pole ear. The two pole piece assemblies each include at least two pole piece groups. Each pole piece group is formed by a plurality of pole pieces attached to each other. The pole piece group includes an overlapping portion and a welding portion that are fixedly connected. The tab includes a plurality of main bodies distributed in sequence along the length direction, the number of the main bodies being greater than or equal to the sum of the number of pole piece groups in the two pole piece assemblies, a buffer portion being provided between adjacent main bodies, the thickness of the buffer portion being less than that of the main body portion, and a slope being provided between the buffer portion and the main body portion; The welding parts correspond to the main body one by one and are fixed to the main body. The welding parts of multiple pole piece groups of the same pole piece assembly are distributed in sequence along the length direction of the pole piece.

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

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

4. A magnesium battery cell structure according to claim 3, characterized in that: The distance between adjacent main bodies is L0, 5mm≤L0≤(1 / n)*(L1+L2+……+L n ).

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

6. The magnesium battery cell structure according to claim 1, characterized in that: The difference in thickness between the buffer part and the main body is D n , D / 10≤D n ≤D / 4.

7. The magnesium battery cell structure according to claim 1, characterized in that: The included angle between the slope and the buffer portion is a, 120°≤a≤150°.

8. The magnesium battery cell structure according to claim 1, characterized in that: A reinforcing rib is fixed on the buffer portion.

9. The magnesium battery cell structure according to claim 8, characterized in that: The reinforcement ribs are annular.

10. The magnesium battery cell structure according to claim 8, characterized in that: The reinforcement ribs are strip-shaped.

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