Laminated square lithium ion power battery

Abstract

The invention belongs to the technical field of batteries, and discloses a laminated square lithium ion battery, the laminated square lithium ion battery comprises a shell and an electrode assembly, each corner of the shell is provided with an R corner, the electrode assembly is wrapped in the shell, and the electrode assembly comprises a positive plate, a diaphragm and a negative plate which are mutually laminated. According to the laminated square lithium ion battery disclosed by the invention, the problems of lithium separation, deformation and the like caused by expansion stress of the edge of the laminated battery cell in a battery circulation process are avoided, and the circulation and safety performance of the battery cell is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of batteries, and in particular relates to a laminated square lithium-ion power battery. Background Art

[0002] Lithium-ion batteries are generally wound and laminated. Laminated square lithium-ion batteries can better utilize the space of the square battery R corner, meeting the requirements of high energy density of current energy storage systems and electric vehicles. For example, Patent 2024103842537 discloses a laminated lithium-ion battery and a preparation method thereof, wherein a first additional diaphragm, a second additional diaphragm and a lithium-plated electrode are sequentially stacked on the surface of the core package after lithium plating, and a reference electrode is inserted between the first additional diaphragm and the second additional diaphragm, and then the reference electrode is plated with lithium to obtain a laminated lithium-ion battery. Patent 202310312687.1 discloses a laminated battery pole piece, a laminated battery cell, a preparation method thereof and a lithium-ion battery, wherein the laminated battery pole piece comprises: a current collector; an active material layer, disposed on the surface of the current collector; the active material layer comprises two or more active units, each of which is arranged at intervals along the length direction of the current collector; the gap between adjacent active units on the current collector forms a predetermined bending section of the laminate.

[0003] However, during the battery cell cycle, due to the change in the thickness of the battery cell, the battery cell is constrained by the large surface of the aluminum shell, while the R corner is difficult to deform due to the constraint of the small surface of the aluminum shell, resulting in stress on the edge of the battery cell, further leading to problems such as purple spots on the edge, lithium deposition, deformation, etc., which greatly affects the cycle and safety performance of the battery cell.

[0004] In order to overcome the adverse characteristics of the above-mentioned stacked square lithium-ion power battery in terms of edge stress during cycling, a thick bottom support sheet or frame is generally used to fill the edge of the battery cell, which increases the cost and complexity of battery cell manufacturing and also reduces the energy density of the battery. Summary of the invention

[0005] The purpose of the present invention is to provide a laminated square lithium-ion power battery, which eliminates the thick bottom support sheet or frame at the edge of the battery cell and replaces it with an R-angle arc design of the pole piece to overcome the above-mentioned deficiencies in existing products.

[0006] The purpose of the present invention is to be achieved through the following technical solutions:

[0007] A laminated square lithium-ion power battery, characterized in that the laminated square lithium-ion power battery comprises a shell and an electrode assembly, each corner of the shell is provided with an R angle, the electrode assembly is wrapped inside the shell, and the electrode assembly comprises a positive electrode sheet, a diaphragm and a negative electrode sheet superimposed on each other. By adopting an arc design at the R angle of the square power battery, space is reserved for the expansion of the battery core edge; the influence of the R angle edge force of the laminated power battery on the power battery cycle and safety is eliminated.

[0008] Furthermore, the calculation formula of the negative electrode sheet width is as follows:

[0009]

[0010] L = t max, A + t max, C +2t separator

[0011] Where: A is the width of the negative electrode sheet, H is the maximum width that the negative electrode sheet can reach, R is the inner diameter of the R corner of the aluminum shell, and L is the cumulative thickness of the positive electrode sheet, negative electrode sheet and diaphragm at the R corner; t max, A is the thickness of the negative electrode sheet rebounding when fully charged, t max, C is the thickness of the positive electrode sheet rebounding when fully charged, t separator It is the thickness of the diaphragm after hot pressing.

[0012] By adopting the above calculation method of the width of the negative electrode sheet, it is possible to avoid stress on the edge of the battery cell; at the same time, it also eliminates the influence of stress on the edge of the R corner of the stacked power battery on the cycle and safety of the power battery.

[0013] Furthermore, the calculation formula of the positive electrode sheet width is as follows:

[0014] C = A - 2δ

[0015] Where C is the width of the positive electrode sheet, A is the width of the negative electrode sheet, and δ is the coating amount of the positive and negative electrode sheets along the height direction of the battery cell.

[0016] By adopting the above calculation method of the width of the negative electrode sheet, it is possible to avoid stress on the edge of the battery cell; at the same time, it also eliminates the influence of stress on the edge of the R corner of the stacked power battery on the cycle and safety of the power battery.

[0017] Furthermore, in the electrode assembly, the stacking order is diaphragm, positive electrode sheet, diaphragm, negative electrode sheet. The width of the negative electrode sheet is greater than that of the positive electrode sheet. The above stacking order can make the diaphragm have a better coating effect on the positive electrode sheet and the negative electrode sheet.

[0018] Furthermore, the positive electrode sheet and the negative electrode sheet are both provided with foil, wherein the positive electrode sheet foil is aluminum foil and the negative electrode sheet foil is copper foil. Providing foil in the positive electrode sheet and the negative electrode sheet can increase the flexibility and stability of the positive electrode sheet and the negative electrode sheet.

[0019] Furthermore, the number of stacked layers of the separator, positive electrode sheet, separator, and negative electrode sheet is determined according to the cumulative maximum thickness of the separator, positive electrode sheet, separator, and negative electrode sheet. Determining the number of stacked layers according to the cumulative maximum thickness of the separator, positive electrode sheet, separator, and negative electrode sheet can avoid stress on the edge of the battery cell caused by too many stacked layers.

[0020] Furthermore, the shell is made of aluminum. The selection of the shell material can reduce the cost and improve the stability of the shell.

[0021] Furthermore, the separator includes a rubber coating layer. Providing the rubber coating layer on the separator can enhance the stability of the electrode assembly.

[0022] Furthermore, the material of the diaphragm is polypropylene or polyethylene. The selection of the diaphragm material can enhance the flexibility and coating strength of the diaphragm.

[0023] Furthermore, the material of the coating layer is polyvinylidene fluoride or polymethyl methacrylate. The selection of the material of the coating layer can enhance the adhesion of the diaphragm.

[0024] Beneficial Effects

[0025] By adopting an arc design at the R corner of the square power battery, space is reserved for the expansion of the edge of the battery cell; the influence of the force on the edge of the R corner of the stacked power battery on the cycle and safety of the power battery is eliminated; the stacked power battery avoids the need to thicken the bottom support plate of the battery cell or add a frame, which greatly improves the energy density and production efficiency of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of the R corner design of the laminated square lithium-ion power battery according to an embodiment of the present invention;

[0027] Figure 2 A cross-sectional view of a laminated square lithium-ion power battery according to an embodiment of the present invention;

[0028] Figure 3 It is a schematic diagram of the stacking of the stacked square lithium-ion power battery described in an embodiment of the present invention. DETAILED DESCRIPTION

[0029] Example 1

[0030] like Figure 1-3As shown, this embodiment provides a laminated square lithium-ion power battery, the laminated square lithium-ion power battery includes a shell and an electrode assembly, the electrode assembly is wrapped inside the shell, each corner of the shell is provided with an R angle, the electrode assembly is formed by stacking a positive electrode sheet, a diaphragm and a negative electrode sheet, and the stacking order is diaphragm, positive electrode sheet, diaphragm, negative electrode sheet, wherein the width of the negative electrode sheet is greater than the width of the positive electrode sheet; the positive electrode sheet and the negative electrode sheet are both provided with foil materials, wherein the positive electrode sheet foil is aluminum foil or composite aluminum foil, and the negative electrode sheet foil is copper foil or composite copper foil; the principle is that the diaphragm covers the negative electrode, and the negative electrode covers the positive electrode, and the number of stacked layers depends on the maximum cumulative thickness of the diaphragm, the positive electrode sheet, the diaphragm, and the negative electrode sheet. This thickness needs to take into account the expansion of the electrode sheet when it is fully charged, and at the same time, it needs to ensure that there is no interference from the shell at the R angle when the electrode sheet is fully charged, and the material of the shell is aluminum.

[0031] The calculation formula of the negative electrode sheet width is as follows:

[0032] When L = 0, A = H;

[0033] when When A = ;

[0034] L = t max, A + t max, C +2t separator

[0035] The calculation formula of the positive electrode sheet width is as follows:

[0036] C = A - 2δ

[0037] Where: A is the width of the negative electrode sheet, H is the maximum width that the negative electrode sheet can reach, and its value is obtained by deducting the thickness of the mylar film and the bottom support sheet from the internal width of the aluminum shell, and considering factors such as diaphragm compression; R is the inner diameter of the R angle of the aluminum shell, ranging from 0 to 3mm, L is the cumulative thickness of the positive electrode sheet, the negative electrode sheet and the diaphragm at the R angle, if it is not within the R angle range, L is 0; the thickness of the positive electrode sheet and the negative electrode sheet includes the thickness of the foil, wherein the positive electrode sheet adopts aluminum foil or composite aluminum foil, and the negative electrode sheet adopts copper foil or composite copper foil; C is the width of the positive electrode sheet, δ is the overhang of the positive electrode sheet and the negative electrode sheet along the height direction of the battery cell, ranging from 0.5 to 5 mm, t max, A is the thickness of the negative electrode sheet rebounding when fully charged, t max, C is the thickness of the positive electrode sheet rebounding when fully charged, t separator It is the thickness of the diaphragm after hot pressing. The thickness depends on the compression amount of the rubber coating layer and can be tested under actual process conditions.

[0038] The present invention adopts an arc-shaped design at the R corner of the square power battery to reserve space for the expansion of the edge of the battery cell, thereby avoiding the stress on the edge of the battery cell; at the same time, it also eliminates the influence of the edge stress of the R corner of the laminated power battery on the cycle and safety of the power battery; and some laminated power batteries thicken the bottom support sheet of the battery cell or add a frame to avoid the edge stress caused by the excessive width of the pole piece, but it increases the cost of the battery cell, and the additional frame also increases the complexity of the process flow. The present invention avoids these disadvantages and greatly improves the energy density and production efficiency of the battery.

[0039] The isolation membrane is a rubber-coated membrane; the membrane material includes but is not limited to polypropylene (PP) and polyethylene (PE), and the rubber coating layer includes but is not limited to polyvinylidene fluoride (PVDF), polymethyl methacrylate (PMMA) and the like.

[0040] Example 2

[0041] A laminated square lithium-ion power battery is prepared by thermal composite lamination. The thermal composite lamination adopts a thermal composite lamination machine to heat the glue-coated diaphragm, the negative electrode sheet, and the positive electrode sheet respectively, and the negative electrode is bonded to the inner side of the two layers of diaphragms through the composite roller, and the heated positive electrode is bonded to the outer side of the two layers of diaphragms. Finally, each small unit is laminated in a "Z" shape to form a stacked core.

[0042] By adopting the lamination process of the present invention, since the R corner of the edge of the stacked core adopts an arc-shaped design, in the subsequent battery cell charge and discharge cycle, the edge is not subject to the risk of overvoltage caused by the constraint of the aluminum shell, and there is no adverse phenomenon such as lithium deposition caused by overvoltage of the electrode piece at the edge of the electrode piece, thereby effectively improving the cycle and safety performance of the battery cell.

[0043] Example 3

[0044] A stacked square lithium-ion power battery adopts a Z-stack stacking process. The Z-stack adopts a traditional stacking machine and stacks in the order of a diaphragm, a negative electrode, a diaphragm, and a positive electrode. The diaphragm needs to cover the negative electrode, and the negative electrode needs to cover the positive electrode.

[0045] By adopting the lamination process of the present invention, since the R corner of the edge of the stacked core adopts an arc-shaped design, there is no risk of overvoltage caused by the edge being constrained by the aluminum shell in the subsequent charge and discharge cycle of the battery cell, and there is no adverse phenomenon such as lithium deposition caused by overvoltage of the electrode piece at the edge of the electrode piece, which effectively improves the cycle and safety performance of the battery cell. However, if a lamination scheme other than that described in the present invention is adopted, rapid cycle attenuation will occur during the cycle process.

[0046] Although the present invention has been specifically shown and described in conjunction with the embodiments, those skilled in the art should understand that various changes may be made to the present invention in form and details without departing from the spirit and scope of the present invention as defined in the appended claims, all of which are within the scope of protection of the present invention.

Claims

1. A laminated square lithium-ion power battery, characterized in that: The stacked square lithium-ion power battery comprises a shell and an electrode assembly, each corner of the shell is provided with an R angle, the electrode assembly is wrapped inside the shell, and the electrode assembly comprises a positive electrode sheet, a separator and a negative electrode sheet stacked on each other.

2. The laminated square lithium-ion power battery according to claim 1, characterized in that: The calculation formula of the negative electrode sheet width is as follows: L= t max, A + t max, C +2t separator Where: A is the width of the negative electrode sheet, H is the maximum width that the negative electrode sheet can reach, R is the inner diameter of the R corner of the aluminum shell, and L is the cumulative thickness of the positive electrode sheet, negative electrode sheet and diaphragm at the R corner; t max, A is the thickness of the negative electrode sheet rebounding when fully charged, t max, C is the thickness of the positive electrode sheet rebounding when fully charged, t separator It is the thickness of the diaphragm after hot pressing.

3. The laminated square lithium-ion power battery according to claim 2, characterized in that: The calculation formula of the positive electrode width is as follows: C = A-2δ; Where C is the width of the positive electrode sheet, A is the width of the negative electrode sheet, and δ is the coating amount of the positive and negative electrode sheets along the height direction of the battery cell.

4. The laminated square lithium-ion power battery according to claim 1, characterized in that: In the electrode assembly, the stacking order is diaphragm, positive electrode sheet, diaphragm, negative electrode sheet; the width of the negative electrode sheet is greater than that of the positive electrode sheet.

5. The laminated square lithium-ion power battery according to claim 1, characterized in that: The positive electrode sheet and the negative electrode sheet are both provided with foil materials, wherein the positive electrode sheet foil is aluminum foil, and the negative electrode sheet foil is copper foil.

6. The laminated square lithium-ion power battery according to claim 4, characterized in that: The number of stacked layers of the separator, positive electrode sheet, separator, and negative electrode sheet is determined according to the cumulative maximum thickness of the separator, positive electrode sheet, separator, and negative electrode sheet.

7. The laminated square lithium-ion power battery according to claim 1, characterized in that: The shell is made of aluminum.

8. The laminated square lithium-ion power battery according to claim 1, characterized in that: The diaphragm includes a rubber coating layer.

9. The laminated square lithium-ion power battery according to claim 1, characterized in that: The material of the diaphragm is polypropylene or polyethylene.

10. The laminated square lithium-ion power battery according to claim 8, characterized in that: The material of the adhesive layer is polyvinylidene fluoride or polymethyl methacrylate.

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