Method for improving top bulging of flexible package laminated battery

Abstract

The invention relates to the technical field of laminated batteries, in particular to a method for improving top bulging of a flexible package laminated battery, which at least comprises the following steps of: (1) arranging an inclined silica gel pad on each of an upper table top and a lower table top of a laminated hot-pressing table, and then performing hot-pressing to obtain a silicon rubber pad; the slope areas of the slope silica gel pads of the upper table top and the lower table top completely cover the thinned area of the pole group; (2) after redundant diaphragms are cut off from the stacked pole groups, adhesive tapes are pasted on the pole groups, and the outer edges of the adhesive tapes and the diaphragms are pasted together; and (3) carrying out single battery formation, and restraining the single battery by using a slope silica gel pad in the formation process. According to the invention, enough pressure can be applied to the thin top area of the pole group in the lamination hot-pressing process and the formation hot-pressing process of the battery, so that the positive and negative pole pieces and the diaphragm at the position can be effectively contacted and bonded together, thereby improving the long-term cycle performance of the product and the cycle capacity under extreme use conditions; and the consistency of products is further improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of laminated battery, and particularly relates to a method for improving the top bulging of soft package laminated battery. BACKGROUND

[0002] In the process of preparing the pole piece, the slurry is coated on the substrate to form a wet coating film area with uniform thickness, and then dried in the drying oven, so that the positive and negative electrode materials in the coating film area are firmly adhered to the substrate. However, when the slurry coated on the substrate is baked, the thickness of the edge of the coating film area is thinner, and the drying speed is faster, which causes the solid content of the edge to rise faster than the middle part, so that the surface tension of the slurry at the edge of the coating film area is greater than that in the middle part, thereby causing the slurry to flow to the edge, and finally leading to the edge bulging phenomenon of the baked pole piece after the oven.

[0003] In order to solve this edge bulging problem, whether it is an extrusion coater or a transfer coater, the edge of the coating film area needs to be thinned during coating, so that the edge area of the coating film area presents an approximate slope shape-the edge is the thinnest area, and gradually transitions to the normal thickness, and the thinning range is usually about 10 mm.

[0004] In the pole piece die-cutting link, the light foil without coating is needed to be reserved as the current collector tab, so the thinner area at the top of the pole group cannot be cut off. The laminated battery is formed by stacking a layer of positive pole piece, negative pole piece and separator, and as the number of stacked layers increases, the thickness of the edge at the top of the pole group will gradually be lower than that of other areas, forming a gradient difference at the top. This gradient difference will cause the thinner area and the normal area to expand unevenly during the use of the core package: the edge of the core package has a smaller thickness, and the force it bears during expansion is smaller, which increases the transmission channel distance between the positive and negative pole pieces and the separator, thereby reducing the transmission efficiency of lithium ions, causing lithium precipitation at the edge of the core package, shortening the service life of the core package and reducing its safety performance.

[0005] CN 220021219 U discloses a laminated core package assembly for square aluminum shell lithium ion power battery, which directly compensates the thickness of the core package body by pasting a rubber strip on the outer surface of the core package body, and the thickness compensation is completed before the aluminum shell is assembled. However, there are obvious differences in the preparation process of aluminum shell batteries and soft package batteries, and the above technical solution cannot solve the problem that the thinner area cannot be subjected to sufficient pressure during the hot pressing process of the soft package battery, resulting in that the positive and negative pole pieces and the separator at this position cannot be effectively contacted and bonded together. SUMMARY

[0006] In view of the technical problem that the soft package battery pole piece cannot be subjected to sufficient pressure in the hot pressing process due to uneven thickness, resulting in a gap between the positive and negative pole pieces and the separator, and the product is prone to failure, the present application provides a method for improving the top bulging of a soft package stacked battery, which can subject the top area of the pole group to sufficient pressure during the stacked battery hot pressing process and the formation hot pressing process, so that the positive and negative pole pieces and the separator at the position can be effectively contacted and bonded together, thereby improving the long-term cycle performance and cycle ability of the product under extreme use conditions, and further improving the consistency of the product.

[0007] The technical scheme of the present application is as follows: A method for improving the top bulging of a soft package stacked battery, at least comprising the following steps: (1) A beveled silica gel pad is arranged on each of the upper and lower tables of the stacked battery hot pressing table, and then hot pressing is performed, and the beveled area of the beveled silica gel pad on the upper and lower tables completely covers the thinned area of the pole group; (2) After the stacked pole group is cut to remove the excess separator, a tape is attached to the pole group, and the outer edge of the tape is attached to the separator to avoid delamination of the single-sided pole piece and the separator; (3) The pole group is packaged after the tape is attached, and then the protection film is attached, baked, injected with liquid, and pre-sealed in sequence, and the single battery is obtained by standing, and then the single battery is formed, and the beveled silica gel pad is used to restrain the single battery during the formation process.

[0008] Further, the stacked battery is a square stacked battery or a special-shaped stacked battery.

[0009] Further, in step (1), the beveled silica gel pad is a single-sided beveled silica gel pad, that is, one side of the beveled silica gel pad is a flat surface, and the other side is completely or partially beveled.

[0010] Further, in step (1), the angle of the beveled silica gel pad is adapted to the slope angle of the thinned area of the pole group.

[0011] Further, in step (1), the width of the beveled silica gel pad is not less than the slope width of the thinned area of the pole group, and preferably, the width of the beveled silica gel pad is greater than the slope width of the thinned area of the pole group.

[0012] Further, in step (2), the tape covers the top 7-10 mm of the pole group, and the top of the pole group refers to the end of the pole group where the tab is provided.

[0013] Further, in step (2), the tape is attached to one side or both sides of the pole group, and preferably, the tape is attached to at least one side of the positive pole piece of the pole group.

[0014] Further, the tape in step (2) refers to a conventional lithium battery tape, such as a PI tea color high temperature tape, a PET terminal tape, etc.

[0015] Further, in step (2), the adhesive tape thickness is 16-80 μm, and the adhesive tape thickness is determined according to the thickness of the pole group, and generally the thicker the pole group, the thicker the adhesive tape selected.

[0016] Further, step (3) uses a beveled silica gel pad to constrain the single cell during the formation process.

[0017] The beneficial effects of the present application are: 1. The beveled silica gel pad is added in the lamination process, which can ensure that the top thinning area of the pole group is fully pressed during hot pressing, avoid the phenomenon of traditional hot pressing that the thinning area is not pressed, and further cause the excessive entry of electrolyte, which still cannot be completely and tightly pressed during formation, thereby forming a gap and causing subsequent cycle top bulging failure. The beveled silica gel pad has elasticity and can be compressed and rebounded. The slope set can also compensate for the thickness difference of the pole group itself. The transition of each area of the pole group is gentle and will not introduce new thickness difference, which can ensure the consistency of the pole group state.

[0018] 2. The adhesive tape on the top thinning area of the pole group can further improve the thickness gradient of the position, reduce the thickness difference with the normal area, make it easier to press the top during formation, and avoid the entry of a large amount of electrolyte into the gap between the outermost single-sided pole piece and the corresponding separator and double-sided pole piece, and avoid the electrolyte from being squeezed out to form local poor contact during formation.

[0019] 3. The beveled silica gel used during formation can fully press the originally thin area of the battery during formation, ensure that the positive and negative pole pieces and the separator are fully bonded together, prevent the occurrence of a gap when the electrolyte is less during long-term cycling or extreme use conditions, and further avoid the position from causing the top to bulge due to lithium precipitation.

[0020] 4. The operation method of the present application is simple and easy to operate, and has strong universality, which can greatly improve the cycle consistency of the product. BRIEF DESCRIPTION OF DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, for those skilled in the art, other drawings can also be obtained without creative labor based on these drawings.

[0022] Figure 1 is the front view of the pole group of example 1.

[0023] Figure 2 is the right view of the pole group of example 1.

[0024] Figure 3 is the side view of the upper beveled silica gel pad used in step (1) of example 1.

[0025] Figure 4 is a schematic diagram of the cooperation between the laminated electrode group and the upper inclined silicone rubber pad in step (1) of Example 1.

[0026] Figure 5 is a schematic diagram of the cooperation between the laminated electrode group and the adhesive tape in step (2) of Example 1.

[0027] Figure 6 is a schematic diagram of the cooperation between the single cell and the inclined silicone rubber pad for formation in step (3) of Example 1.

[0028] In the figure, 1-thinning area, 2-upper inclined silicone rubber pad, 3-inclined area, 4-laminated electrode group, 5-adhesive tape, 6-single cell, 7-inclined silicone rubber pad for formation. DETAILED DESCRIPTION

[0029] In order to make the person skilled in the art better understand the technical solutions in the present application, the technical solutions in the embodiments of the present application will be described clearly and completely below in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by the person skilled in the art without creative labor should belong to the protection scope of the present application.

[0030] The uniformity of pressure in the stages of laminated hot pressing, pre-treatment for formation and single cell formation is a core control element throughout the whole process of battery preparation. In order to solve the local defects of the electrode group caused by the thinned top, and ensure that the electrode sheet and the separator can be tightly combined in each stage, the present application provides a method for improving the top bulging of soft package laminated battery, which at least includes the following steps: (1) An inclined silicone rubber pad is arranged on each of the upper and lower tables of the laminated hot pressing table, and then hot pressing is performed. The inclined area of the inclined silicone rubber pad on the upper and lower tables completely covers the thinned area of the electrode group, so that each layer of electrode sheet and the separator can be fully contacted and tightly bonded, and the micro gap between the electrode sheet and the separator caused by insufficient local pressure can be avoided; (2) After the laminated electrode group is cut to remove the excess separator, the adhesive tape is pasted on the electrode group, and the outer edge of the adhesive tape is pasted together with the separator, so as to avoid the separation of the single-sided electrode sheet and the separator, prevent the deformation of the electrode group during the handling and transfer process, ensure that the electrode group still maintains the optimal structure after hot pressing when entering the formation process, and avoid the influence of the shape deviation on the formation effect; (3) The pasted pole group is put into the shell for packaging, sequentially pasted with a protective film, baked, injected with liquid, and pre-sealed, and then placed to obtain a single battery, and then the single battery is subjected to formation. In the formation process, the beveled silica gel pad restrains the single battery, and the pole piece and the separator always maintain close contact during the charging and discharging process, ensuring that the electrolyte is uniformly infiltrated on the surface of the pole piece, promoting the uniform growth of the SEI film on the surface of the pole piece, ensuring that the SEI film quality, internal resistance, capacity and other key parameters of the same batch of batteries are highly consistent, and reducing the matching problems of the module caused by individual differences.

[0031] As a specific embodiment of the present application, the laminated battery can be a square laminated battery or an L-shaped laminated battery, and the types of L-shaped laminated batteries include right-angle L-shaped laminated batteries, gun-shaped batteries, V-shaped batteries, and the like.

[0032] As a specific embodiment of the present application, the structure design of the beveled silica gel pad used in step (1) is adapted to the structural features of the pole group. The top of the pole group has a specific thinning area due to the thinning of the edges of the pole pieces, and the area presents a slope, while the remaining area of the pole group is in a flat state with normal thickness. The beveled silica gel pad is preferably a single-edge beveled silica gel pad, that is, one side of the silica gel pad is a plane, which is convenient for contacting and fixing with the hot pressing table, and the other side is all or partially beveled. The bevel angle of the beveled area of the beveled silica gel pad is adapted to the slope angle of the thinning area of the pole group. In the hot pressing process, the beveled area of the beveled silica gel pad can coincide with the thinning area of the pole group, thereby achieving thickness compensation of the thinning area of the pole group, and ensuring that the pressure on each part of the pole group is uniform during hot pressing.

[0033] More preferably, the side of the beveled silica gel pad used in step (1) in contact with the pole group is partially provided with a bevel. The advantage of this design is that it can not only apply concentrated and adapted pressure to the thinning area of the pole group through the beveled part to ensure that the area is fully pressed during hot pressing, but also smoothly contact the normal area of the pole group through the flat part to avoid unnecessary pressure load on the normal area of the pole group, thereby ensuring the hot pressing effect while maintaining the stability of the overall structure of the pole group, which meets the precision requirements of the pole group for pressure distribution during hot pressing.

[0034] As a specific embodiment of the present application, the width of the bevel of the beveled silica gel pad used in step (1) should not be less than the slope width of the thinning area of the pole group, and is preferably slightly greater than the slope width of the thinning area of the pole group. If the width of the thinning area of the pole group is 10 mm, the width of the bevel of the silica gel pad is preferably greater than 10 mm, for example, it can be set to 15 mm or the like. This design can avoid the risk of pressure leakage in the thinning area due to slight deviation of the pole group, and at the same time utilize the elastic deformation of the silica gel to concentrate the pressure to the center of the thinning area, ensuring that the entire thinning area from the edge to the center can be fully pressed, further reducing the risk of unpressed edge.

[0035] The 7-10 mm of the top of the pole group (the end where the pole lug is arranged) is the core area of the thinning area, and is also the part where stress is concentrated and delamination is easy to occur near the pole lug. Therefore, as a specific embodiment of the present application, step (2) covers the 7-10 mm position of the top of the pole group with adhesive tape on the pole group side (i.e. the top) of the pole group. The coverage of the adhesive tape in this range can accurately fill the thickness difference, while strengthening the structural stability around the pole lug, preventing excessive intrusion of electrolyte along the gap of the pole lug into the top of the pole piece, reducing the delamination of the single-sided pole piece and the separator caused by electrolyte immersion, and specifically solving the swelling risk of the pole lug area.

[0036] As a specific embodiment of the present application, the adhesive tape in step (2) can be a PI tea color high temperature adhesive tape or a PET terminal adhesive tape. Such adhesive tapes have the characteristics of high temperature resistance (adapt to the high temperature environment of the subsequent formation process) and electrolyte corrosion resistance, can ensure that they do not degrade and fall off during long-term use of the battery, can avoid the delamination of the pole piece and the separator caused by the failure of the adhesive tape, and can ensure the long-term effectiveness of the method.

[0037] As a specific embodiment of the present application, in step (2), the thickness of the adhesive tape is 16-80 μm. Since the greater the thickness of the pole group, the more obvious the gradient difference of the top thinning area, and the greater the required thickness compensation, the thickness of the adhesive tape needs to be determined according to the thickness of the pole group (generally 3-6 mm, such as 3.4 mm, 4.2 mm, 4.9 mm, 5.4 mm, etc.). For example, 80 μm adhesive tape is selected for thick pole groups, which can balance the thickness difference through a larger physical filling amount; 16 μm adhesive tape is selected for thin pole groups, which can avoid excessive filling that increases the overall thickness of the pole group, does not affect the overall volume of the battery, and balances performance and space efficiency.

[0038] Formation is a key stage of battery activation, and the adhesion strength of the pole piece and the separator has not yet stabilized. As a specific embodiment of the present application, step (3) uses an inclined silicone pad to constrain the single cell on one side or both sides during the formation process, which can continue the pressure compensation effect of the hot pressing stage, ensure that the top thinning area is continuously pressed during the formation process, and promote the close combination of the positive and negative pole pieces and the separator. For pole groups with uneven thickness, two-sided restraint can also balance the pressure and avoid battery deformation caused by one-sided swelling, further reducing the risk of swelling in long-term cycling.

[0039] As a specific embodiment of the present application, the structure design of the inclined silicone pad used in step (3) is adapted to the structural characteristics of the single cell. The inclined silicone pad is preferably a single-sided inclined silicone pad, i.e. one side of the silicone pad is a plane and the other side is all or partially inclined. The inclined angle of the inclined area of the inclined silicone pad is adapted to the slope angle of the thinning area of the pole group in the single cell. During the formation process, the inclined area of the inclined silicone pad can coincide with the thinning area of the pole group in the single cell, thereby achieving thickness compensation of the thinning area of the pole group in the single cell and making the pressure on each part of the pole group uniform and consistent during hot pressing.

[0040] More preferably, the inclined silicon rubber pad used in step (3) is partially provided with an inclined surface on the side in contact with the pole group in the single battery. The advantage of this design is that it can not only exert concentrated and adaptive pressure on the thinned area of the pole group in the single battery through the inclined surface part to ensure that this area is fully pressed during hot pressing, but also smoothly contact the normal area of the pole group through the flat surface part to avoid unnecessary pressure load on the normal area of the pole group, thereby ensuring the hot pressing effect while maintaining the stability of the overall structure of the pole group, meeting the precision requirement of the pressure distribution during the hot pressing process of the laminated battery pole group.

[0041] As a specific embodiment of the present application, the width of the inclined surface of the inclined silicon rubber pad used in step (3) should not be less than the width of the inclined surface of the thinned area of the pole group in the single battery, and is preferably slightly larger than the width of the inclined surface of the thinned area of the pole group in the single battery. If the width of the thinned area of the pole group in the single battery is 10 mm, the width of the inclined surface of the silicon rubber pad is preferably greater than 10 mm, for example, it can be set to 15 mm, etc. This design can avoid the risk of pressure leakage in the thinned area due to slight deviation of the pole group, and at the same time utilize the elastic deformation of the silicon rubber to concentrate the pressure to the center of the thinned area, ensuring that the entire thinned area from the edge to the center can be fully pressed, further reducing the risk of edge unpressing.

[0042] Example 1 A method for improving the top bulging of soft-pack laminated batteries, the width of the thinned area 1 of the pole group is 10 mm, and the thickness of the pole group is 4.2 mm, which specifically comprises the following steps: (1) Set single-sided inclined silicon rubber pads on the upper and lower surfaces of the laminated hot pressing table, respectively, and name them as upper inclined silicon rubber pad 2 and lower inclined silicon rubber pad. The flat side of the upper inclined silicon rubber pad 2 is provided with an adhesive, which can be fixed with the upper surface of the hot pressing table, and the other side of the upper inclined silicon rubber pad 2 comprises two planes with different heights, which are connected by an inclined surface, and the two ends of the inclined surface are connected with the edges of the two planes, respectively, and the width of the inclined surface area 3 is 15 mm; the flat side of the lower inclined silicon rubber pad is provided with an adhesive, which can be fixed with the lower surface of the hot pressing table, and the other side of the lower inclined silicon rubber pad comprises two planes with different heights, which are connected by an inclined surface, and the two ends of the inclined surface are connected with the edges of the two planes, respectively, and the width of the inclined surface area 3 is 15 mm; After being fixed, the inclined surface area 3 of the upper inclined silicon rubber pad 2 and the lower inclined silicon rubber pad corresponds to the position of the thinned area 1 of the pole group during hot pressing and the inclined angle is adapted, and then the upper pressing table is lowered to hot press the positive and negative plates and the separator together.

[0043] (2) After the excess separator is cut off from the stacked electrode group, the top area of the stacked electrode group 4 is taped with adhesive tape 5, which is used to tape the top 8 mm or so of the positive electrode sheet 8 mm or so. The adhesive tape 5 is a 50 μm thick PI tea-colored high-temperature adhesive tape. To avoid excessive electrolyte from entering the top of the outermost single-sided electrode sheet of the electrode group in the subsequent process and forming immersion, the outer edge of the adhesive tape 5 needs to be taped with the separator, so as to avoid the separation of the single-sided electrode sheet and the separator. After the electrode group is taped, it is put into the shell for packaging, and then sequentially undergoes the processes of protective film taping, baking, liquid injection, and pre-sealing, and is left to obtain a single battery.

[0044] (3) The formation cabinet is replaced with a suitable size of a formation inclined silicone pad 7, and an inclined area is arranged on each side of the width direction of the formation inclined silicone pad 7, so as to realize two-side formation. The width of the single-side inclined area of the formation inclined silicone pad 7 is 15 mm, which can completely cover the thinned area of the single battery 6. This setting can make the originally thin area of the single battery 6 also be fully pressed during formation, so as to ensure that the positive and negative electrode sheets and the separator are fully bonded together, prevent the occurrence of gaps when the electrolyte is less in long-term cycling or extreme use conditions, and further avoid the lithium precipitation at this position to cause top swelling.

[0045] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that only the thinned area of the single battery electrode group is compensated in thickness by using the formation inclined silicone pad 7 in the formation process, and the inclined area of the formation inclined silicone pad 7 can completely cover the thinned area of the single battery 6.

[0046] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that only the top area of the electrode group is taped after the lamination and hot pressing.

[0047] 50 single batteries obtained by the methods of Example 1, Comparative Example 1, and Comparative Example 2 are selected for charge-discharge cycling test, wherein the single battery preparation processes not specified in the examples and comparative examples are carried out in the conventional manner according to the prior art, and are consistent.

[0048] The specific steps of the charge-discharge cycling test are as follows: The single batteries are placed in a constant temperature oven, and the temperature is set to 20℃±5℃. The charging device is used to charge the battery at a current of 1C, and the discharging test device is used to discharge at a current of 1C. At 50 times, 100 times, 300 times, 600 times, and 1000 times of cycling, 10 single batteries are selected, the top thickness of the battery is checked, and when the top thickness increases by more than 8%, it is considered to be swollen. If all the 10 selected single batteries are swollen in a certain check, the charge-discharge will not be continued.

[0049] The results show that the single batteries of Example 1 do not show top swelling after 1000 cycles; The single cells of Comparative Example 1 showed top swelling in one cell after 300 cycles, and in all cells after 600 cycles; The single cells of Comparative Example 2 showed top swelling in one cell after 50 cycles, in three cells after 100 cycles, and in all cells after 300 cycles.

[0050] Although the present application has been described in detail with reference to the preferred embodiments, the application is not limited to the preferred embodiments. Various equivalent modifications or substitutions can be made to the embodiments of the present application by those skilled in the art without departing from the spirit and scope of the present application. Any modifications or substitutions made by those skilled in the art within the technical scope disclosed in the present application should be encompassed within the scope of the present application.

Claims

1. A method for improving the top bulging of a soft-packaged laminated battery, characterized in that: At least the following steps are included: (1) A beveled silicone pad is placed on the upper and lower surfaces of the lamination hot pressing table, and then hot pressing is performed. The beveled areas of the beveled silicone pads on the upper and lower surfaces completely cover the thinned area of ​​the electrode group; (2) After cutting off the excess diaphragm from the stacked electrode group, apply tape to the electrode group, with the outer edge of the tape attached to the diaphragm to prevent delamination of the single-sided electrode and the diaphragm; (3) After the electrode group is glued, it is placed in a shell for packaging. After the protective film is applied, baking, liquid injection and pre-sealing processes are carried out in sequence, the single battery is obtained by being placed aside. The single battery is then formed. During the formation process, a beveled silicone pad is used to restrain the single battery.

2. A method for improving top bulging of a soft-packaged laminated battery according to claim 1, characterized in that: The laminated battery is a square laminated battery or a special-shaped laminated battery.

3. The method for improving the top bulging of a soft-packaged laminated battery according to claim 1, characterized in that: In step (1), one side of the inclined silicone pad is a plane, and the other side is entirely or partially inclined.

4. A method for improving top bulging of a soft-packaged laminated battery according to claim 1 or 3, characterized in that: In step (1), the slope angle of the beveled silicone pad is adapted to the slope angle of the electrode group thinning area.

5. A method for improving top bulging of a soft-packaged laminated battery according to claim 1 or 3, characterized in that: In step (1), the slope width of the sloped silicone pad is not less than the slope width of the electrode group thinning area.

6. The method for improving top bulging of a flexible packaged laminated battery according to claim 1, wherein: In step (2), the tape covers the top 7 to 10 mm of the electrode group.

7. A method for improving top bulging of a soft-packaged laminated battery according to claim 1 or 6, characterized in that: In step (2), tape is applied to one or both sides of the electrode group.

8. A method for improving top bulging of a soft-packaged laminated battery according to claim 1 or 6, characterized in that: The tape in step (2) is PI brown high temperature tape or PET termination tape.

9. The method for improving top bulging of a flexible packaged laminated battery according to claim 1 or 6, characterized in that: In step (2), the tape thickness is 16-80 μm.

10. The method for improving the top bulge of a soft-packaged laminated battery according to claim 1, characterized in that: In step (3), during the formation process, a beveled silicone pad is used on the tab side of the single cell to restrain the single cell.

Images