Battery cell preparation method, battery cell and battery

Abstract

The invention provides a battery cell preparation method, a battery cell and a battery. The battery cell preparation method comprises the following steps: respectively mounting a positive plate with tabs, a negative plate with tabs and a diaphragm on corresponding unwinding mechanisms for unwinding; acquiring the setting position of the positive tab on the positive plate; according to the currently obtained setting position of the positive tab, a first to-be-bent position having a first interval with the currently obtained positive tab and a second to-be-bent position having a second interval with the currently obtained positive tab on the positive plate are obtained, and the first to-be-bent position and the second to-be-bent position are coated with a glue solution according to preset parameters, the glue solution is at least coated on the winding side of the positive plate and the diaphragm; and curing the positive plate coated with the glue solution, and winding the cured positive plate, a negative plate and a diaphragm. The problem of lithium precipitation in the battery bending area can be solved, and the energy density and the production cost of the battery are reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of battery production, and particularly relates to a method for preparing an electrode core, an electrode core and a battery. Background Art

[0002] A square battery is composed of an electrode core, a housing, a cover plate, an electrolyte, etc. When preparing the battery, a separator is disposed between the positive electrode sheet and the negative electrode sheet to isolate the positive electrode sheet and the negative electrode sheet. After the positive electrode sheet, the negative electrode sheet and the separator are wound and hot-pressed to be pressed from a cylinder into a flat body, an electrode core is formed. Due to the hot pressing, the structure of the electrode core forms a bending area and a non-bending area. In the bending area, the distance between the positive and negative electrode sheets increases. During the charge and discharge process, the ion migration distance is longer than that in the non-bending area, and lithium deposition occurs in the bending area. As the number of cycles of the lithium battery increases, the lithium deposition becomes more and more serious. The lithium deposition forms dendrites, piercing the separator to form a short circuit, resulting in battery scrapping and even fire and explosion. To solve the above problems, the existing solutions are as follows: Method 1: In the inner winding, the bending diameter is smaller and the risk is relatively large. A method of sticking a tape on the positive electrode sheet in the bending area of the inner circle is adopted, so that the bending area does not participate in the reaction, avoiding the occurrence of lithium deposition at this part.

[0003] Method 2: An adhesive-coated separator is used. During hot pressing after winding, the adhesive layer is melted by heat, so that the electrode sheet and the separator are adhered together, avoiding the increase in the distance between the electrode sheets and solving the problem of lithium deposition at the bending part.

[0004] However, the first method is only used for the inner circle of the winding core. Since the taped part does not participate in the reaction, the material at this part cannot play a role, resulting in material waste and low capacity. Therefore, only the inner circle can be taped, and it is impossible to tape the bending area of each turn of the winding. It can only reduce the risk of lithium deposition to a certain extent; although the second method can effectively solve the problem of lithium deposition in the bending area, the cost of the adhesive-coated separator used is higher than that of the ordinary separator, resulting in an increase in the cost of the lithium battery. At the same time, due to the presence of the adhesive layer on the separator, it occupies the internal space of the battery and reduces the energy density of the battery. Summary of the Invention

[0005] In order to overcome the defects in the prior art, the embodiments of the present invention provide a method for preparing an electrode core, an electrode core and a battery, which can solve the problem of lithium deposition in the bending area of the electrode core, improve the energy density of the battery and reduce the production cost at the same time.

[0006] To achieve the above object, the technical solution adopted by the present invention is: The first aspect of the present invention discloses a method for preparing an electrode core, including: Unwinding a positive electrode sheet, a negative electrode sheet and a separator provided with tabs respectively on corresponding unwinding mechanisms; Obtaining the position of the positive tab on the positive electrode sheet; According to the currently obtained set position of the positive tab, obtain the first bending position on the positive electrode sheet that has a first interval from the currently obtained positive tab and the second bending position that has a second interval from the currently obtained positive tab, and apply adhesive liquid at the first bending position and the second bending position according to preset parameters. The adhesive liquid is at least applied to one side where the positive electrode sheet is wound with the separator. Cure the positive electrode sheet after applying the adhesive liquid, and wind the cured positive electrode sheet with the negative electrode sheet and the separator.

[0007] The above technical solution obtains the position of the positive tab on the positive electrode sheet before winding the electrode sheet, thereby obtaining two bending regions of the positive electrode sheet in each winding circle. Apply adhesive liquid to the positive electrode sheet in each winding circle's bending region. After applying the adhesive liquid, the positive electrode sheet is wound with the negative electrode sheet and the separator, hot-pressed, and subsequent processes. On the one hand, because the adhesive liquid is applied to the bending region of the positive electrode sheet, it avoids the increase in the distance between the electrode sheets at the bending position, thereby avoiding the longer ion migration distance in the bending region compared to the non-bending region, avoiding lithium deposition at the bending position, and improving the safety and service life of the battery. On the other hand, because the adhesive liquid is applied to the positive electrode sheet, there is no need to use a coated separator, which can reduce the cost increased by using a coated separator. Moreover, the method of applying the adhesive liquid only at the bending position according to preset parameters improves the space utilization rate in the thickness direction of the battery cell, and can increase the internal space of the battery compared to the method of using a coated separator, improving the energy density of the battery.

[0008] Further, the first interval is: 0.5C + B, and the second interval is: A - 0.5C - B, where A is the width of the battery cell, B is the distance from the edge of the positive tab to the first end of the battery cell, and C is the width of the tab.

[0009] The distance from the edge of the positive tab to the first end of the battery cell, the width of the tab, and the width of the battery cell are all known. For each obtained position of the positive tab, the first bending position and the second bending position relative to the current positive tab can be obtained according to the current position of the positive tab.

[0010] Further, the preset parameters include the coating thickness, coating gap, and coating width of the adhesive liquid. Applying the adhesive liquid according to the preset parameters can make the adhesive liquid only be applied to the bending position of the positive electrode sheet, avoiding occupying the internal space of the battery.

[0011] Further, the coating width gradually increases as the number of obtained positive tabs increases. The first bending position and the second bending position are the central positions of the bending regions of the positive electrode sheet. For each obtained position of the positive tab, the number of winding circles increases by one. During the winding process of the battery cell, as the number of winding circles increases, the winding diameter of each circle gradually increases, resulting in the gradual increase of the bending regions from the inner layer to the outer layer. The coating width needs to gradually increase as the number of winding circles of the battery cell increases to cover the bending regions of each circle of the battery cell.

[0012] Further, the coating thickness is 1 - 5 μm, and the coating width is 5 - 50 mm. When the coating thickness is too small, the adhesive force is insufficient due to the too thin adhesive liquid. When the coating thickness is too large, the resistance of the battery increases, and occupying a certain space will lead to a decrease in the energy density of the battery. When the coating width is too small, the entire bending area of the positive electrode sheet and the separator cannot be bonded, resulting in an increase in the distance between the positive and negative electrode sheets. When the coating width is too large, it affects the resistance and occupies the internal space of the battery, reducing the energy density of the battery.

[0013] Further, the positive electrode sheet has a plurality of positive electrode tabs, and each positive electrode tab is correspondingly provided with a first bending position to be bent and a second bending position to be bent. After hot pressing, the first bending position to be bent is located at one end of the battery cell close to the positive electrode tab, and the second bending position to be bent is located at the other end of the battery cell far from the positive electrode tab. As the positive electrode sheet is wound, after obtaining the position of one positive electrode tab, continue to obtain the position of the next positive electrode tab until the bending areas of each winding turn are coated with the adhesive liquid.

[0014] Further, the adhesive liquid is a mixture of polyvinylidene fluoride and N-methylpyrrolidone, and the viscosity of the mixed adhesive liquid is 2000 - 10000 mPa·s. The viscosity of the adhesive liquid should be convenient for coating and does not produce obvious flow phenomenon when coated on the electrode sheet. The viscosity is inversely proportional to the solvent amount. When the viscosity is low, the solvent proportion is high, which is not conducive to the formation of solidification after the adhesive liquid is coated. When the viscosity is too high, the fluidity of the adhesive liquid is poor, which is not conducive to the transfer and coating of the adhesive liquid.

[0015] Further, when the positive electrode sheet coated with the adhesive liquid is subjected to a curing treatment, the positive electrode sheet moves horizontally. The uncured adhesive liquid has a certain fluidity. After the uncured adhesive liquid is coated on the positive electrode sheet, if the positive electrode sheet is in an inclined state during curing, the adhesive liquid will flow and cannot be uniformly cured on the positive electrode sheet, reducing the bonding effect of the adhesive liquid.

[0016] In a second aspect of the present invention, a battery cell is disclosed. The battery cell is manufactured by using the battery cell manufacturing method according to any one of the first aspect. The battery cell includes a positive electrode sheet, a negative electrode sheet, and a separator. The positive electrode sheet is provided with a plurality of positive electrode tabs. The positive electrode sheet is correspondingly provided with a first bending position to be bent and a second bending position to be bent for each positive electrode tab. The first bending position to be bent has a first interval from the positive electrode tab, and the second bending position to be bent has a second interval from the positive electrode tab. Glue layers are provided on both the first bending position to be bent and the second bending position to be bent. The glue layer is formed by curing the adhesive liquid coated at least on one side where the positive electrode sheet and the separator are wound.

[0017] In a third aspect of the present invention, a battery is disclosed, including a battery body. The battery includes the battery cell according to the second aspect.

[0018] Due to the application of the above technical solutions, the present invention has the following advantages compared with the prior art: 1. Before winding the electrode sheet, the present application obtains the position of the positive electrode tab on the positive electrode sheet, thereby obtaining the area to be bent for each turn of the positive electrode sheet. A glue solution is coated on the positive electrode sheet in the area to be bent for each turn. After the glue solution is coated, the positive electrode sheet is wound together with the negative electrode sheet and the separator. During hot pressing and subsequent processes, the glue layer melts when heated, causing the electrode sheets to adhere to the separator, avoiding an increase in the distance between the electrode sheets at the bent position, thereby preventing lithium deposition at the bent position and improving the safety and service life of the battery.

[0019] 2. By coating a glue solution on the positive electrode sheet, the present application does not require the use of a coated separator, which can reduce the cost increased by using a coated separator. Moreover, the method of coating the glue solution only at the bent position with preset parameters improves the space utilization rate in the thickness direction of the battery cell. Compared with the method of using a coated separator, it can increase the internal space of the battery and improve the energy density of the battery.

[0020] To make the above and other objects, features, and advantages of the present invention more obvious and understandable, the following specific preferred embodiments are given, in conjunction with the accompanying drawings, and are described in detail as follows. Description of the Drawings

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0022] Figure 1 It is a flowchart of a method for preparing a battery cell provided by an embodiment of the present application; Figure 2 It is a device diagram for preparing a battery cell provided by an embodiment of the present application; Figure 3 It is a diagram of a die-cut electrode sheet provided by an embodiment of the present application; Figure 4 It is a schematic diagram of winding a battery cell provided by an embodiment of the present application; Figure 5 It is a cross-sectional view of a battery cell provided by an embodiment of the present application.

[0023] Reference numerals of the above drawings: 1. Positive electrode sheet; 2. Negative electrode sheet; 3. Separator; 4. First unwinding mechanism; 5. Second unwinding mechanism; 6. Third unwinding mechanism; 7. Winding mechanism; 8. Glue storage tank; 9. Screw pump; 10. Glue coating die head; 11. Curing device; 12. First position to be bent; 13. Second position to be bent; 14. Positive electrode tab; 15. Negative electrode tab; 16. Glue coating area. Detailed Embodiments

[0024] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Additionally, the accompanying drawings of the present invention are only for simple schematic illustration and are not drawn according to actual dimensions. This is stated in advance.

[0025] In the present invention, it should be noted that the orientation or positional relationships indicated by the terms "upper", "lower", "inner", "outer", "frontward", "backward", "between", "close to", "far from", etc. are based on the orientation or positional relationships shown in the accompanying drawings. These are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the devices or elements referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present invention. It should also be noted that unless otherwise clearly defined and limited, the terms "installation" and "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected or indirectly connected. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0026] It should be understandable that although terms such as "first", "second", "third", etc. may be used in this article to describe various components or signals, these components or signals should not be limited by these terms. These terms are mainly used to distinguish one component from another, or one signal from another. Additionally, the term "or" used in this article should, depending on the actual situation, possibly include any one or a combination of more of the associated listed items.

[0027] Refer to Figure 1 As shown, an embodiment of the present application provides a method for preparing an electrode core, including: Step 101, respectively install the positive electrode sheet 1, negative electrode sheet 2, and separator 3 provided with electrode tabs on corresponding unwinding mechanisms for unwinding; Step 102, obtain the setting position of the positive electrode tab 14 on the positive electrode sheet 1; Step 103, according to the currently obtained setting position of the positive electrode tab 14, obtain a first bending position 12 on the positive electrode sheet 1 that has a first interval from the currently obtained positive electrode tab 14 and a second bending position 13 that has a second interval from the currently obtained positive electrode tab 14, and apply glue at the first bending position 12 and the second bending position 13 according to preset parameters. The glue is applied at least on the side where the positive electrode sheet 1 and the separator 3 are wound; Step 104, perform a curing treatment on the positive electrode sheet 1 coated with glue, and wind the cured positive electrode sheet 1 with the negative electrode sheet 2 and the separator 3.

[0028] Through the above method, during the process of hot pressing the wound positive electrode sheet 1, negative electrode sheet 2, and separator 3 to form a battery cell and subsequent curing, the adhesive layer after curing is heated and melted, causing the electrode sheets to adhere to the separator, avoiding an increase in the distance between the electrode sheets at the bending position, thereby preventing lithium deposition at the bending position, improving the safety and service life of the battery. At the same time, in the embodiments of the present application, the step of coating the adhesive liquid on the positive electrode sheet is set between the unwinding and winding of the positive electrode sheet, negative electrode sheet, and separator, which can improve the processing efficiency of the battery cell and thus enhance the production efficiency of the battery.

[0029] It should be noted that the process of obtaining the installation position of the positive electrode tab 14 and coating the adhesive liquid in steps 102 to 103 includes, but is not limited to, manual operation and automatic processing.

[0030] In the embodiments of the present application, there are two or more positive electrode tabs on the positive electrode sheet, each positive electrode tab is located within one layer of winding, and each positive electrode tab is correspondingly provided with a first bending position to be bent and a second bending position to be bent. For each obtained position of a positive electrode tab, step 103 is executed.

[0031] To improve the coating efficiency of the adhesive liquid and the processing efficiency of the battery cell, referring to Figure 2 as shown, the embodiments of the present application provide a battery cell preparation device, including: An unwinding mechanism, the unwinding mechanism includes a first unwinding mechanism 4 for unwinding the positive electrode sheet 1, a second unwinding mechanism 5 for unwinding the negative electrode sheet 2, and a third unwinding mechanism 6 for unwinding the separator 3; A winding mechanism 7, the winding mechanism 7 is used for winding the positive electrode sheet 1, negative electrode sheet 2, and separator 3; A coating mechanism, the coating mechanism is arranged on the unwinding path of the positive electrode sheet 1, the coating mechanism includes a glue storage tank 8, a screw pump 9 connected to the glue storage tank 8, a coating die head 10 connected to the screw pump 9, an ear induction device, a curing device 11, and a control device. The ear induction device is arranged between the first unwinding mechanism 4 and the coating die head 10 for sensing the position of the positive electrode tab 14. The curing device 11 is arranged between the coating die head 10 and the winding mechanism 7 for curing the positive electrode sheet 1 after coating the adhesive liquid. The control device is connected to the winding mechanism 7 and the coating mechanism for controlling the operation of the screw pump 9, coating die head 10, ear induction device, and curing device 11.

[0032] During the winding process of the electrode sheet and the separator, preset parameters for coating the adhesive liquid are pre-stored in the control device. The preset parameters include coating thickness, coating gap, and coating width. The control device adjusts the coating thickness by adjusting the pump speed of the screw pump 9, and at the same time adjusts the distance between the nozzle of the coating die head 10 and the positive electrode sheet 1 to adjust the coating gap, thereby further adjusting the coating thickness.

[0033] During the unwinding process of the positive electrode sheet 1, after the ear sensing device senses the positive electrode ear 14, it sends the position of the positive electrode ear 14 to the control device, and the control device controls the screw pump 9 and the coating die head 10 to coat the positive electrode sheet 1 with glue according to preset parameters.

[0034] As Figures 3 to 5 shown, according to the structure setting of the battery cell, the battery cell has multiple winding turns, and each winding turn is provided with two positions to be bent. The position to be bent is the central position of the area to be bent. The positions to be bent include a first position to be bent 12 and a second position to be bent 13. After hot pressing, the first position to be bent 12 is close to the positive electrode ear 14, and the second position to be bent 13 is close to the negative electrode ear 15. Moreover, as the number of winding turns increases, the area of the area to be bent where the first position to be bent 12 and the second position to be bent 13 are located gradually increases. Due to bending, the distance between the positive and negative electrode sheets in the area to be bent is larger than that in the non-bent area, and lithium deposition is likely to occur. Coating glue in the area to be bent to form a coated area 16 can reduce the distance between the positive and negative electrode sheets in the area to be bent, thereby avoiding lithium deposition in the bent area and improving the safety and service life of the battery.

[0035] In the embodiment of the present application, the calculation starting points of the first interval and the second interval are the central axis of the currently obtained positive electrode ear 14. The direction of the central axis is the same as the extending direction of the positive electrode ear extending out of the battery cell. The central axis is as Figure 5 shown by the dotted line in the figure. Among them, the first interval of the first position to be bent 12 relative to the currently obtained positive electrode ear 14 is: 0.5C + B, and the second interval of the second position to be bent 13 relative to the currently obtained positive electrode ear 14 is: A - 0.5C - B, where A is the width of the battery cell, B is the distance from the side edge of the positive electrode ear close to the first end of the battery cell to the first end of the battery cell, and C is the width of the ear at the connection with the battery cell. The first end of the battery cell is the end of the two ends of the battery cell with a shorter distance from the positive electrode ear 14. The specific position direction and relationship are as Figure 5 shown.

[0036] After obtaining the position of a positive electrode ear, any position of the currently obtained positive electrode ear can be used as the starting point for calculating the first position to be bent and the second position to be bent, and the positions to be bent relative to the starting point are calculated, so as to adjust the formulas for calculating the first interval and the second interval. For example, in other possible embodiments, taking the side edge of the positive electrode ear close to the first end of the battery cell as the calculation starting point, the first interval is B, and the second interval is A - B. The present application does not limit this here.

[0037] Optionally, the coating thickness is 1 - 5um, the coating width is 5 - 50mm, and the coating width gradually increases as the number of winding turns of the battery cell increases to ensure that the coated glue can completely cover the area to be bent of each turn.

[0038] Optionally, the adhesive solution is a mixture of polyvinylidene fluoride and N-methylpyrrolidone, and the viscosity of the prepared adhesive solution is 2000-10000 mPa·s, so as to facilitate coating and there is no obvious flow phenomenon when coated on the electrode sheet. The prepared adhesive solution is stored in the glue storage tank 8 and is coated on the positive electrode sheet 1 by a screw pump 9 and a coating die head 10 during use.

[0039] The positive electrode sheet 1 coated with the adhesive solution first passes through a curing device 11 for pre-curing to avoid the uncured adhesive solution sticking to the over-roller when passing through the over-roller. Optionally, to ensure the curing effect of the adhesive solution, the curing distance is set to 500-1000 mm, and when the positive electrode sheet 1 coated with the adhesive solution is cured, the positive electrode sheet 1 moves horizontally.

[0040] The embodiment of the present application also provides an electric core, which is made by using the electric core preparation method described in the above embodiment. The electric core includes a positive electrode sheet, a negative electrode sheet and a separator. A plurality of positive electrode tabs are provided on the positive electrode sheet. A first bending position to be bent and a second bending position to be bent are provided on the positive electrode sheet corresponding to each positive electrode tab. The first bending position to be bent has a first interval from the positive electrode tab, and the second bending position to be bent has a second interval from the positive electrode tab. Glue layers are provided on both the first bending position to be bent and the second bending position to be bent, and the glue layer is formed by curing an adhesive solution coated at least on one side where the positive electrode sheet and the separator are wound.

[0041] The embodiment of the present application also provides a battery, which includes a battery body and also includes the electric core described in the above embodiment.

[0042] In the present invention, specific embodiments are used to elaborate on the principle and implementation manner of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. A method for preparing a battery cell, characterized in that: include: The positive electrode sheet, the negative electrode sheet and the separator provided with the tabs are respectively mounted on the corresponding unwinding mechanisms for unwinding; Obtaining the setting position of the positive electrode ear on the positive electrode sheet; According to the setting position of the currently acquired positive electrode ear, a first position to be bent having a first interval with the currently acquired positive electrode ear and a second position to be bent having a second interval with the currently acquired positive electrode ear are acquired on the positive electrode sheet, and a glue solution is applied on the first position to be bent and the second position to be bent according to preset parameters, and the glue solution is applied on at least one side of the positive electrode sheet and the separator winding; The positive electrode sheet coated with the glue is cured, and the cured positive electrode sheet is wound with the negative electrode sheet and the separator.

2. A method for preparing a battery cell according to claim 1, characterized in that: The first interval is: 0.5C+B, and the second interval is: A-0.5CB, wherein A is the width of the battery cell, B is the distance from the edge of the positive electrode ear to the first end of the battery cell, and C is the width of the electrode ear.

3. A method for preparing a battery cell according to claim 1, characterized in that: The preset parameters include the coating thickness, coating gap and coating width of the glue.

4. A method for preparing a battery cell according to claim 3, characterized in that: The coating width gradually increases as the number of positive electrode ears obtained increases.

5. A method for preparing a battery cell according to claim 3, characterized in that: The coating thickness is 1-5 um, and the coating width is 5-50 mm.

6. A method for preparing a battery cell according to claim 1, characterized in that: The positive electrode sheet is provided with a plurality of positive electrode ears, and each positive electrode ear is correspondingly provided with a first position to be bent and a second position to be bent.

7. A method for preparing a battery cell according to claim 1, characterized in that: The glue is a mixture of polyvinylidene fluoride and N-methyl pyrrolidone, and the viscosity of the mixed glue is 2000-10000 mPa.s.

8. A method for preparing a battery cell according to claim 1, characterized in that: When the positive electrode sheet coated with the glue is cured, the positive electrode sheet moves horizontally.

9. A battery cell, characterized in that: The battery cell is made by the battery cell preparation method according to any one of claims 1 to 8, the battery cell comprises a positive electrode sheet, a negative electrode sheet and a separator, the positive electrode sheet is provided with a plurality of positive electrode ears, the positive electrode sheet is provided with a first bending position and a second bending position corresponding to each positive electrode ear, the first bending position and the positive electrode ear have a first interval, the second bending position and the positive electrode ear have a second interval, the first bending position and the second bending position are both provided with a glue layer, the glue layer is formed by curing a glue liquid coated on at least one side of the positive electrode sheet and the separator being wound.

10. A battery, comprising a battery body, characterized in that: The battery adopts the battery cell as claimed in claim 9.

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