Electrode assembly and preparation method of battery

Abstract

The invention belongs to the field of lithium battery manufacturing, and particularly relates to a preparation method of an electrode assembly and a battery. Carrying out cold pressing and slitting on the positive / negative electrode large sheet to obtain a narrow positive / negative electrode sheet; sequentially carrying out tab spot welding on the narrow positive plate on a sheet making machine, pasting two pieces of positive tab protection gummed paper, two pieces of empty foil position aluminum foil protection gummed paper and one piece of B-surface aluminum foil empty foil position tail gummed paper at the tab welding position, and cutting the plate; carrying out tab spot welding on the narrow negative pole piece on a piece making machine, pasting two negative pole tab protection gummed paper at the tab welding position, additionally pasting one copper foil protection gummed paper on the large foil surface of the negative pole piece, and cutting the pole piece; winding the complete positive plate, negative plate and diaphragm to obtain a winding core; and carrying out aluminum plastic film packaging molding, baking, liquid injection, standing activation, formation, secondary packaging molding and PACK on the roll core to obtain the battery. The thermal runaway risk caused by short circuit due to too small contact resistance can be avoided, and the safety of the battery cell is improved.

Description

Technical Field

[0001] The present invention belongs to the field of lithium battery manufacturing, and particularly relates to a method for preparing an electrode assembly and a battery. Background Art

[0002] As one of the most popular forms of energy at present, lithium-ion batteries play an important role both in the power field and in the 3C digital field. Lithium-ion batteries exist in many forms, including soft-pack cylindrical, square, aluminum shell, steel shell, button type, etc. Among them, soft-pack cylindrical cells are a major form. Soft-pack cylindrical cells are mainly formed by winding. Therefore, the gluing method of the positive and negative electrodes plays a vital role in the winding process. If the gluing method is unscientific, it will directly affect the comprehensive performance of the cell, such as extrusion, cycle, and rate.

[0003] Currently, consumer soft-pack cylindrical cells utilize a winding method with a center-exit tab. This method significantly reduces internal resistance and improves the cell's rate capability, making it a common winding method for cylindrical cells. For cylindrical cells with a center-exit tab, the positive and negative electrodes each have a small foil surface (often called the A-side) and a large foil surface (often called the B-side).

[0004] Refer to the attached Figure 1-5 The existing electrode gluing process is to apply 4 layers of glue to the positive electrode, namely: 2 layers of positive electrode ear protection glue at the positive electrode ear position, 2 layers of aluminum foil protection tape at the aluminum foil A side and B side empty foil position, and 3 layers of glue tape to the negative electrode, namely: 2 layers of negative electrode ear protection glue at the negative electrode ear position, and 1 layer of copper foil protection glue at the B side empty foil position. However, under such a gluing process, when winding, the tail area of ​​the empty aluminum foil position on the B side of the positive electrode is directly facing the negative electrode material area and the negative electrode empty foil position, and there is only a layer of separator between them, resulting in a small contact resistance between the aluminum foil and the negative electrode material area, and between the empty aluminum foil position and the empty copper foil position of the negative electrode, which is very prone to the risk of thermal runaway, resulting in reduced safety performance of the battery cell.

[0005] Therefore, how to provide a method for preparing an electrode assembly and a battery to improve battery safety performance has become an issue that those skilled in the art need to consider. Summary of the Invention

[0006] In response to the problems existing in the above-mentioned prior art, the present invention adds a layer of aluminum foil protective tape at the tail of the empty aluminum foil position on the B side to avoid the phenomenon that the empty aluminum foil position faces the negative electrode material area, and the empty aluminum foil position faces the empty negative electrode copper foil position, thereby preventing the risk of thermal runaway when an internal short circuit occurs in this area and improving the safety performance of the battery cell.

[0007] Specifically, the present invention discloses the following technical solutions:

[0008] A method for preparing an electrode assembly and a battery comprises the following steps:

[0009] S01. Mixing, stirring, coating and baking;

[0010] S02. Cold-press and cut the positive and negative electrode sheets to obtain narrow positive / negative electrode sheets;

[0011] S03. The narrow positive electrode sheet is spot-welded on the sheet making machine, and two positive electrode ear protection tapes, two empty foil positions, and one B-side aluminum foil empty foil position tail protective tape are affixed to the positive electrode sheet. The positive electrode sheet is cut to meet the specifications.

[0012] S04. The narrow negative electrode sheet is spot welded on the tabs of the film maker, and two tabs are attached to the negative tabs for protection. A large copper foil surface of the negative electrode sheet is attached with a protective tape 7. The negative electrode sheet is cut to obtain a complete negative electrode sheet that meets specifications.

[0013] S05. The complete positive electrode sheet, the complete negative electrode sheet, and the separator are wound to obtain a core;

[0014] S06. The roll core is encapsulated with aluminum-plastic film, baked, injected with liquid, left to activate, formed, double-sealed, and packaged to obtain a battery.

[0015] Furthermore, the width of the narrow positive electrode sheet in step S02 is 15 mm to 55 mm.

[0016] Furthermore, the width of the narrow negative electrode sheet in step S02 is 15 mm to 55 mm.

[0017] Furthermore, in step S03, the two empty foil positions of the aluminum foil protective tape are pasted on top of the two positive electrode tab protective tapes.

[0018] Furthermore, in step S03, a tail protective tape is pasted on the empty foil surface of the aluminum foil.

[0019] Furthermore, in step S04, a layer of copper foil protective tape is pasted on the empty copper foil surface of the large foil surface of the negative electrode sheet.

[0020] Furthermore, the positive electrode tab protection tape and the negative electrode tab protection tape have a width of 6 to 10 mm and a thickness of 0.030 to 0.040 mm.

[0021] Furthermore, the positive electrode tab protective tape and the negative electrode tab protective tape extend 0.2 to 0.8 mm beyond the bottom edge of the tab tape.

[0022] Furthermore, the aluminum foil protective tape for the empty foil position has a thickness of 0.015 to 0.025 mm and a width of 20 to 30 mm.

[0023] Furthermore, the protective adhesive tape at the tail of the blank foil position of the B-side aluminum foil is 0.015-0.025 mm thick and 20-30 mm wide.

[0024] The beneficial effects of the present invention are:

[0025] On the basis of the existing glue sticking method, the present invention upgrades the original 4 layers of glue for the positive electrode and 3 layers of glue for the negative electrode to 5 layers of glue for the positive electrode and 3 layers of glue for the negative electrode. A protective tape is added at the tail of the empty aluminum foil position on the B side of the positive electrode. The tape is 0.022mm thick and 22mm wide. The height of the tape is consistent with the width of the positive aluminum foil. This avoids the phenomenon that the empty aluminum foil position faces the negative electrode material area and the empty aluminum foil position faces the empty negative copper foil position during winding. In addition, the negative electrode tab also happens to fall at this position during winding. Metal burrs are easily generated during the cutting and spot welding of the tab, especially when the battery cell is subjected to external extrusion. Because the diaphragm is damaged and an internal short circuit occurs, a new layer of protective tape is added to the area to avoid the risk of thermal runaway due to the small contact resistance in this area. Since this area avoids the phenomenon of empty foil against empty foil, and empty aluminum foil against the negative electrode material area, even if an internal short circuit occurs, the risk of thermal runaway due to too low contact resistance will be reduced, thereby improving the safety performance of the battery cell; a layer of protective tape is added to the empty aluminum foil position. The protective tape has both insulating effect and a certain degree of flexibility. When the battery cell is subjected to external compression, it also plays a certain buffering role for the diaphragm corresponding to this area, thereby improving the safety of the battery cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is the side view of the original positive electrode sheet with glue attached;

[0027] Figure 2 This is a top view of the original positive electrode sheet glue;

[0028] Figure 3 This is the side view of the original negative electrode sheet glue;

[0029] Figure 4 This is the top view of the original negative electrode sheet glue;

[0030] Figure 5 This is a schematic diagram of the original glue process winding;

[0031] Figure 6 This is a side view of the positive electrode sheet of the present invention;

[0032] Figure 7 This is a top view of the positive electrode sheet of the present invention;

[0033] Figure 8 This is a side view of the negative electrode sheet of the present invention;

[0034] Figure 9 This is a top view of the negative electrode sheet of the present invention;

[0035] Figure 10 It is a schematic diagram of the winding process of the glue laminating process of the present invention.

[0036] Among them, A: large foil surface of positive electrode sheet (side B); B: aluminum foil; C: small foil surface of positive electrode sheet (side A); D: positive electrode sheet area; E: aluminum foil protective tape, F: positive electrode tab; G: positive electrode tab protective tape; H: empty foil surface of aluminum foil; I: protective tape at the tail of the empty foil position of aluminum foil;

[0037] 1- small foil surface of negative electrode sheet (side A); 2- copper foil; 3- large foil surface of negative electrode sheet (side B); 4- negative electrode sheet area; 5- negative electrode tab; 6- negative electrode tab protective tape; 7- copper foil protective tape; 8- empty foil surface of copper foil. DETAILED DESCRIPTION

[0038] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0039] Example 1

[0040] like Figure 6-10 As shown, this embodiment discloses a method for preparing an electrode assembly and a battery, comprising the following steps:

[0041] S01. Mixing, stirring, coating and baking;

[0042] S02. Cold-press and cut the positive and negative electrode sheets to obtain narrow positive / negative electrode sheets;

[0043] S03. The rolled narrow positive electrode sheet (mainly composed of aluminum foil B and positive electrode sheet area D) is subjected to the following operations on the sheet making machine: the positive electrode tab F is welded to the corresponding position on the small foil surface (A) C of the positive electrode sheet, two layers of positive electrode tab protective tape G are affixed to the tab welding positions corresponding to the large foil surface (B) A and the small foil surface (A) C of the positive electrode sheet, two layers of aluminum foil protective tape E are affixed on the two layers of positive electrode tab protective tape G, and one layer of aluminum foil protective tape I is affixed to the tail of the empty foil position H of the aluminum foil. The electrode sheet is cut to obtain a complete positive electrode sheet that meets the specifications;

[0044] S04. The rolled narrow negative electrode sheet (primarily composed of copper foil 2 and negative electrode sheet material area 4) is subjected to the following operations on a sheet making machine: the negative electrode tabs 5 are welded to the corresponding positions on the small foil surface (A) 1 of the negative electrode sheet, two layers of negative electrode tab protection tape 6 are affixed to the tab welding positions corresponding to the small foil surface (A) 1 and the large foil surface (B) 3 of the negative electrode sheet, and one layer of copper foil protection tape 7 is affixed to the blank copper foil surface 8 of the large foil surface (B) 3 of the negative electrode sheet. The electrode sheet is then cut to obtain a complete negative electrode sheet that meets the specifications;

[0045] S05. The complete positive electrode sheet, the complete negative electrode sheet, and the separator are wound to obtain a core;

[0046] S06. The roll core is encapsulated with aluminum-plastic film, baked, injected with liquid, left to activate, formed, double-sealed, and packaged to obtain a battery.

[0047] As a preferred embodiment of the present invention, the width of the narrow positive electrode sheet and the narrow negative electrode sheet are both 15 mm.

[0048] As a preferred embodiment of the present invention, the positive electrode tab protective tape has a width of 6 mm and a thickness of 0.035 mm.

[0049] As a preferred embodiment of the present invention, the positive / negative electrode tab protective tape extends 0.2 mm beyond the bottom edge of the tab tape.

[0050] As a preferred embodiment of the present invention, the blank foil position aluminum foil protective adhesive tape is 0.022 mm thick and 22 mm wide.

[0051] As a preferred embodiment of the present invention, the adhesive tape at the tail of the empty aluminum foil is 0.022 mm thick and 22 mm wide.

[0052] The solution in this embodiment is simple and effective. Compared with the existing process in the background technology, only a layer of protective tape is added to the tail of the empty aluminum foil position, and the equipment can support it without increasing costs due to equipment changes. Currently, this solution has been used in mass production. Compared with the previous gluing process, it can avoid the risk of thermal runaway caused by internal short circuit of the battery cell, and improve the safety performance and cycle life of the battery cell.

[0053] Example 2

[0054] In order to adapt to different electrode assemblies, the width of the positive / negative tab protective tape in this embodiment is 7mm and the thickness is 0.032mm. The positive / negative tab protective tape extends 0.4mm beyond the bottom edge of the tab.

[0055] As a preferred embodiment of the present invention, the blank foil position aluminum foil protective adhesive tape is 0.021 mm thick and 25 mm wide.

[0056] As a preferred embodiment of the present invention, the protective adhesive tape at the tail of the empty aluminum foil is 0.021 mm thick and 25 mm wide.

[0057] Compared with the existing process in the background art, this embodiment can avoid the risk of thermal runaway of the battery cell due to internal short circuit, and improve the safety performance and cycle life of the battery cell.

[0058] The above description is merely a preferred embodiment of the present invention and does not limit the technical scope of the present invention. Therefore, any minor modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for preparing an electrode assembly and a battery, characterized in that: The following steps are involved: S01. Mixing, stirring, coating and baking; S02. Cold-press and cut the positive and negative electrode sheets to obtain narrow positive / negative electrode sheets; S03. The narrow positive electrode sheet is spot-welded on the sheet making machine, and two positive electrode ear protection tapes, two empty foil positions, and one B-side aluminum foil empty foil position tail protective tape are affixed to the positive electrode sheet. The positive electrode sheet is cut to meet the specifications. S04. The narrow negative electrode sheet is spot welded on the tabs of the sheet making machine. Two negative tabs are attached to the tab welding position. A copper foil protective tape is attached to the large foil surface of the negative electrode sheet. The electrode sheet is cut to obtain a complete negative electrode sheet that meets the specifications. S05. The complete positive electrode sheet, the complete negative electrode sheet, and the separator are wound to obtain a core; S06. The roll core is encapsulated with aluminum-plastic film, baked, injected with liquid, left to activate, formed, double-sealed, and packaged to obtain a battery.

2. The method for preparing an electrode assembly and a battery according to claim 1, wherein: The width of the narrow positive electrode sheet in step S02 is 15 mm to 55 mm.

3. The method for preparing an electrode assembly and a battery according to claim 1, wherein: The width of the narrow negative electrode sheet in step S02 is 15 mm to 55 mm.

4. The method for preparing an electrode assembly and a battery according to claim 1, wherein: In step S03, the two empty foil positions of the aluminum foil protective tape are pasted on top of the two positive electrode tab protective tapes.

5. The method for preparing an electrode assembly and a battery according to claim 1, wherein: In step S03, a tail protective tape is pasted on the empty foil surface of the aluminum foil.

6. The method for preparing an electrode assembly and a battery according to claim 1, wherein: In step S04, a layer of copper foil protective tape is pasted on the empty copper foil surface of the large foil surface of the negative electrode sheet.

7. The method for preparing an electrode assembly and a battery according to claim 1, wherein: The positive electrode tab protection tape and the negative electrode tab protection tape have a width of 6 to 10 mm and a thickness of 0.030 to 0.040 mm.

8. The method for preparing an electrode assembly and a battery according to claim 2, wherein: The positive electrode tab protection tape and the negative electrode tab protection tape extend 0.2 to 0.8 mm beyond the bottom edge of the tab tape.

9. The method for preparing an electrode assembly and a battery according to claim 1, wherein: The aluminum foil protective tape for the empty foil position has a thickness of 0.015 to 0.025 mm and a width of 20 to 30 mm.

10. The method for preparing an electrode assembly and a battery according to claim 1, wherein: The protective adhesive tape at the tail of the empty foil portion of the B-side aluminum foil has a thickness of 0.015 to 0.025 mm and a width of 20 to 30 mm.

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