Lithium ion battery and preparation method thereof

Abstract

The invention relates to the technical field of lithium ion batteries, in particular to a lithium ion battery and a preparation method thereof. The lithium ion battery comprises a positive plate, a negative plate and a diaphragm, the negative plate is provided with a first insulating sheet covering the negative lug of the negative plate; the positive plate is provided with a second insulating sheet directly facing the negative tab; an empty foil area is arranged in an area, opposite to the first insulating sheet, on the positive plate; the second insulating sheet covers the empty foil area and the positive active material layer at the periphery of the empty foil area; or, the area, opposite to the first insulating sheet, of the positive plate is provided with a hollow area, and the second insulating sheet covers the hollow area and the positive active material layer on the periphery of the hollow area; or, a blocking groove is formed in an area, opposite to the first insulating sheet, on the positive plate; the blocking groove separates the positive electrode active material layers on the two sides of the blocking groove, and the second insulating sheet covers the blocking groove and the positive electrode active material layers on the periphery of the blocking groove.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion batteries, in particular to a lithium ion battery and a preparation method thereof. Background Art

[0002] Lithium-ion battery is a rechargeable battery that relies on the movement of lithium ions between the positive electrode and the negative electrode to achieve charging and discharging purposes. It is mainly composed of four parts: positive electrode, negative electrode, electrolyte and separator.

[0003] During the design and production process of soft-pack lithium batteries with central tabs, adhesive tape needs to be affixed to the positive / negative tabs and the negative / positive electrode sheets corresponding to the positive / negative tabs. On the one hand, it prevents the burrs from laser cleaning and welding from piercing the diaphragm and causing an internal short circuit in the battery. On the other hand, it prevents the active material on the positive electrode sheet corresponding to the negative tab from being de-lithiated and unable to be embedded in the negative electrode, causing risks such as lithium plating.

[0004] However, in the actual process, some lithium ions in the positive electrode material covered by the tape on the positive electrode sheet can still bypass the tape and be transferred to the surface of the negative electrode, causing lithium deposition. Summary of the invention

[0005] The embodiment of the present invention provides a lithium ion battery and a preparation method thereof, so as to solve the problem in the prior art that some lithium ions in the positive electrode material covered by the adhesive tape on the positive electrode sheet can still pass through the positive electrode material to bypass the adhesive tape and transfer to the negative electrode surface, causing lithium deposition.

[0006] The invention discloses a lithium ion battery, comprising a positive electrode sheet, a negative electrode sheet and a separator; the negative electrode sheet is provided with a first insulating sheet covering the negative electrode ear thereof; the positive electrode sheet is provided with a second insulating sheet facing the negative electrode ear;

[0007] An empty foil area is provided in the area of ​​the positive electrode sheet opposite to the first insulating sheet, and the second insulating sheet covers the empty foil area and the positive electrode active material layer around the empty foil area; or,

[0008] A hollow area is provided on the positive electrode sheet in an area opposite to the first insulating sheet, and the second insulating sheet covers the hollow area and the positive electrode active material layer around the hollow area; or,

[0009] A blocking groove is provided in the area of ​​the positive electrode sheet opposite to the first insulating sheet; the blocking groove separates the positive electrode active material layers on both sides thereof, and the second insulating sheet covers the blocking groove and the positive electrode active material layers around the blocking groove.

[0010] Optionally, the blocking groove is arranged around a region of the positive electrode active material layer facing the negative electrode ear, or around a region of the positive electrode active material layer facing the first insulating sheet;

[0011] Both ends of the blocking groove extend to the edge of the positive electrode sheet.

[0012] Optionally, the thickness of the positive electrode active material layer on one side of the positive electrode sheet is T0, the depth of the blocking groove is T1, and the width of the blocking groove is W; wherein 0.7T0≤T1≤0.9T0,0mm <W<10mm。

[0013] Optionally, the distance from the outer peripheral edge of the blocking groove to the outer peripheral edge of the second insulating sheet is L, wherein 0.5 mm≤L≤5 mm.

[0014] Optionally, the blocking groove includes a first sub-groove, a second sub-groove and a third sub-groove that are connected in sequence;

[0015] The first sub-groove and the third sub-groove are arranged in parallel and extend along the width direction of the positive electrode sheet; one end of the first sub-groove and one end of the third sub-groove penetrate the edge of the positive electrode active material layer in the width direction of the positive electrode sheet, and the other end of the first sub-groove and the other end of the third sub-groove are connected to the two ends of the second sub-groove respectively;

[0016] The second sub-groove extends along the length direction of the positive electrode sheet.

[0017] Optionally, the hollow area passes through an edge of the positive electrode active material layer in the width direction of the positive electrode sheet.

[0018] Optionally, the hollow area is a rectangular hollow area, and the shape of the second insulating sheet is a rectangle; the length of the hollow area is a, and the width is b; the length of the second insulating sheet is c, and the width is d; wherein 0mm <c-a<5mm,0mm<d-b<5mm,1mm<a<50mm,1mm<b<50mm。

[0019] Optionally, the empty foil area is formed by removing a portion of the positive electrode active material layer corresponding to the second insulating sheet through laser cleaning; or,

[0020] The hollow area is formed by laser die cutting to remove part of the positive electrode sheet corresponding to the second insulating sheet; or,

[0021] The blocking grooves are formed by laser etching the positive electrode active material layer.

[0022] Optionally, the second insulating sheet is in a rectangular shape; the length of the second insulating sheet is c, and the width is d;

[0023] The shape of the first insulating sheet is rectangular; the length of the first insulating sheet is e, and the width is f; wherein, 0mm <c-e<5mm,0mm<d-f<5mm。

[0024] The present invention also discloses a method for preparing a lithium ion battery, which is applied to the preparation of the above-mentioned lithium ion battery and is characterized in that it comprises the steps of:

[0025] On the positive electrode sheet of the lithium-ion battery, the positive electrode active material layer at the position corresponding to the negative electrode ear of the negative electrode sheet is removed by laser processing equipment to form a hollow foil area; or the positive electrode sheet portion at the position corresponding to the negative electrode ear of the negative electrode sheet is cut off to form a hollow area; or the positive electrode active material layer at the position corresponding to the negative electrode ear of the negative electrode sheet is etched to form a blocking groove;

[0026] A second insulating sheet is attached to the positive electrode active material layer of the positive electrode sheet at a position corresponding to the negative electrode ear of the negative electrode sheet, and the second insulating sheet covers the hollow foil area, the hollow area or the blocking groove; the second insulating sheet covers the hollow foil area and the positive electrode active material layer around the hollow foil area, or the second insulating sheet covers the hollow area and the positive electrode active material layer around the hollow area, or the second insulating sheet of the blocking groove separates the positive electrode active material layers on both sides thereof, and the second insulating sheet covers the blocking groove and the positive electrode active material layer around the blocking groove;

[0027] A first insulating sheet is attached to the negative electrode ear of the negative electrode sheet;

[0028] The positive electrode sheet, the negative electrode sheet and the separator are wound, put into a shell, and the electrolyte is injected to obtain a lithium-ion battery.

[0029] Compared with the prior art, the lithium-ion battery provided by the embodiment of the present invention has the beneficial effect that: the lithium-ion battery of the present invention is provided with a third insulating sheet at the positive ear of the positive electrode sheet, and a second insulating sheet is provided at the position corresponding to the negative ear of the negative electrode sheet, wherein the positive electrode sheet area corresponding to the second insulating sheet is an empty foil area, or the positive electrode sheet area corresponding to the second insulating sheet is hollowed out to form a hollow area, or the positive electrode active material layer area corresponding to the second insulating sheet is provided with a blocking groove, and the blocking groove surrounds the positive electrode active material layer area corresponding to the second insulating sheet, so that the positive electrode active material layer area corresponding to the second insulating sheet is separated from other areas of the positive electrode active material layer. In this way, the existence of the empty foil area, the hollow area or the blocking groove can ensure that there is no positive electrode active material in the positive electrode sheet area corresponding to the second insulating sheet or can reduce the delithiation of the positive electrode active material, and avoid the lithium ions in the positive electrode active material from escaping and migrating to the negative electrode (the negative electrode here is the negative electrode ear position, which is also affixed with adhesive tape, and lithium ions cannot be embedded), causing the risk of lithium precipitation and thickness exceeding the limit. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments, in which:

[0031] Figure 1 It is a schematic diagram of attaching adhesive tape to the position of the positive electrode sheet corresponding to the negative electrode ear in the prior art;

[0032] Figure 2 Schematic diagram of a positive electrode sheet according to an embodiment of the present invention;

[0033] Figure 3 is a schematic diagram of a negative electrode sheet according to an embodiment of the present invention;

[0034] Figure 4 yes Figure 2 Part A of the embodiment of the present invention is a schematic diagram of attaching a second insulating sheet to cover the empty foil area at the position corresponding to the negative electrode ear on the positive electrode sheet;

[0035] Figure 5 yes Figure 2 Part A of the middle part is a schematic diagram of the hollowed-out area on the positive electrode sheet corresponding to the negative electrode ear position in the second embodiment;

[0036] Figure 6 yes Figure 2 Part A of the middle part is a schematic diagram of a blocking groove opened at the position corresponding to the negative electrode ear on the positive electrode sheet of the third embodiment;

[0037] Figure 7 yes Figure 2 Part A of the third embodiment of the present invention is a schematic diagram of attaching a second insulating sheet to cover the blocking groove at the position corresponding to the negative electrode ear on the positive electrode sheet;

[0038] Figure 8 yes Figure 5 Schematic diagram of attaching a second insulating sheet to the hollow area.

[0039] The reference numerals in the figures are:

[0040] 1. Positive electrode sheet; 11. Positive electrode ear; 12. Third insulating sheet; 13. Second insulating sheet; 14. Hollow foil area; 15. Hollow area; 16. Positive electrode active material layer; 161. Blocking groove; 2. Negative electrode sheet; 21. Negative electrode ear; 22. First insulating sheet; 23. Fourth insulating sheet; 3. Adhesive tape. DETAILED DESCRIPTION

[0041] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. Now, in conjunction with the accompanying drawings, the preferred embodiments of the present invention are described in detail.

[0042] The present invention provides a lithium ion battery. Figures 1 to 8 As shown, a lithium-ion battery comprises a positive electrode sheet, a negative electrode sheet and a separator; a first insulating sheet covering the negative electrode ear is provided on the negative electrode sheet; a second insulating sheet facing the negative electrode ear is provided on the positive electrode sheet;

[0043] An empty foil area is provided in the area of ​​the positive electrode sheet opposite to the first insulating sheet, and the second insulating sheet covers the empty foil area and the positive electrode active material layer around the empty foil area; or,

[0044] A hollow area is provided on the positive electrode sheet in an area opposite to the first insulating sheet, and the second insulating sheet covers the hollow area and the positive electrode active material layer around the hollow area; or,

[0045] A blocking groove is provided in the area of ​​the positive electrode sheet opposite to the first insulating sheet; the blocking groove separates the positive electrode active material layers on both sides thereof, and the second insulating sheet covers the blocking groove and the positive electrode active material layers around the blocking groove.

[0046] The lithium-ion battery of the present invention is provided with a first insulating sheet covering the negative electrode ear on the negative electrode sheet, wherein the positive electrode sheet 1 area corresponding to the first insulating sheet 13 is a hollow foil area 14, or the positive electrode sheet 1 area corresponding to the first insulating sheet 13 is hollowed out to form a hollow area 15, or the positive electrode active material layer 16 area corresponding to the first insulating sheet 13 is provided with a blocking groove 161. In this way, the presence of the hollow foil area 14, the hollow area 15 or the blocking groove 161 can ensure that there is no positive electrode active material in the positive electrode sheet 1 area corresponding to the second insulating sheet 13 or can reduce the de-lithiation of the positive electrode active material, and avoid the lithium ions in the positive electrode active material from escaping and migrating to the negative electrode (the negative electrode here is the negative electrode ear position, and the adhesive tape 3 is also affixed, and the lithium ions cannot be embedded), causing the risk of lithium precipitation and thickness exceeding the limit.

[0047] Specifically, the empty foil area 14 is an area where there is only a positive electrode current collector, and there is no corresponding positive electrode active material layer 16 on the positive electrode current collector. In this way, there is no lithium ion escape and migration to the negative electrode in this area, and the above-mentioned lithium precipitation and thickness exceeding the limit risk are avoided. The hollow area 15 is directly hollowed out in the area of ​​the positive electrode sheet 1 corresponding to the second insulating sheet 13. After hollowing, this area is in the shape of a gap. Neither the positive electrode current collector nor the positive electrode active material layer 16 exists, and the above-mentioned lithium precipitation and thickness exceeding the limit risk are avoided. The blocking groove 161 reduces the thickness of the positive electrode active material layer 16 at the edge of the area by setting the blocking groove 161, reduces the migration of lithium ions in the area, and plays a barrier effect, thereby reducing the lithium ions in the positive electrode active material in the area from escaping and migrating to the negative electrode, and the above-mentioned lithium precipitation and thickness exceeding the limit risk are avoided.

[0048] Specifically, the blocking groove is arranged around the area of ​​the positive electrode active material layer facing the negative electrode ear, or around the area of ​​the positive electrode active material layer facing the first insulating sheet. Both ends of the blocking groove extend to the edge of the positive electrode sheet.

[0049] Specifically, in one embodiment, the thickness of the positive electrode active material layer 16 on one side of the positive electrode sheet 1 is T0, the depth of the blocking groove 161 is T1, and the width of the blocking groove 161 is W; wherein, 0.7T0 ≤ T1 ≤ 0.9T0, 0 mm < W < 10 mm. By providing the blocking groove 161 with a depth of T1 and a width of W, the local thickness of the positive electrode active material layer 16 can be reduced, and the blocking distance can be ensured, thereby reducing the migration speed and quantity of lithium ions in this region. By controlling the depth of the blocking groove 161 to be between 0.7T0 and 0.9T0, that is, the depth of the blocking groove 161 is 70%-90% of the thickness of the positive electrode active material layer 16, if the etching depth of the blocking groove 161 is too deep, greater than 95% of the thickness of the single-sided positive electrode coating layer, it may damage the current collector during the processing of the blocking groove 161, affecting the positive electrode active material on the reverse side of the blocking groove 161; if the etching depth is too shallow, less than 70% of the thickness of the single-sided positive electrode active material layer 16, it cannot achieve a good blocking effect, and there will still be较多的锂离子会迁移到负极产生析锂。

[0050] As Figure 7 shown, the blocking groove 161 has three sides labeled ①②③, and these three sides enclose a rectangular area at the edge of the positive electrode sheet 1, and the second insulating sheet 13 is attached to this area, specifically as Figure 7 shown. The distance from the blocking groove to the second insulating sheet is L, wherein, 0.5 mm ≤ L ≤ 5 mm, which can ensure the firm attachment of the second insulating sheet and will not affect the lithium ion migration and the battery capacity performance due to the too large area of the second insulating sheet.

[0051] The blocking groove includes a first sub-groove, a second sub-groove, and a third sub-groove that are connected in sequence; the first sub-groove and the third sub-groove are arranged in parallel and extend along the width direction of the positive electrode sheet; one end of the first sub-groove and one end of the third sub-groove penetrate the edge of the positive electrode active material layer in the width direction of the positive electrode sheet, and the other end of the first sub-groove and the other end of the third sub-groove are respectively connected to both ends of the second sub-groove; the second sub-groove extends along the length direction of the positive electrode sheet. The hollow area penetrates the edge of the positive electrode active material layer in the width direction of the positive electrode sheet.

[0052] It should be noted that there is an unclear expression "较多的锂离子会迁移到负极产生析锂" in the original text, which may need to be further clarified for more accurate translation.Specifically, in one embodiment, the hollowed-out area 15 is a rectangular hollow, and the hollowed-out area 15 opens at one side edge of the positive electrode sheet 1 close to the second insulating sheet 13. The shape of the second insulating sheet 13 is rectangular, the length of the hollowed-out area is a, and the width is b; the length of the second insulating sheet is c, and the width is d; wherein, 0 < c - a < 5, 0 < d - b < 5, 1 mm < a < 50 mm, 1 mm < b < 50 mm. In this way, both the length and width of the second insulating sheet 13 are greater than those of the hollowed-out area 15, so that the second insulating sheet completely covers the hollowed-out area. Moreover, the design of 0 < c - a < 5, 0 < d - b < 5 can ensure that the second insulating sheet 13 can be firmly attached and completely cover the hollowed-out area 15, providing reliable insulation protection and preventing accidental contact between the positive and negative electrode tabs. Using the rectangular hollowed-out area 15 and the second insulating sheet 13 can simplify the manufacturing process of the battery because the rectangular shape is easy to be precisely cut and positioned by automated equipment, which helps to improve production efficiency and reduce costs. Specifically, the shape of the first insulating sheet is rectangular; the length of the first insulating sheet is e, and the width is f; wherein, 0 mm < c - e < 5 mm, 0 mm < d - f < 5 mm.

[0053] Specifically, in one embodiment, the empty foil area 14 is formed by laser cleaning to remove the positive electrode active material layer 16 corresponding to the second insulating sheet 13. The laser cleaning technology can remove the positive electrode active material layer 16 without damaging the surface of the current collector. Laser cleaning can precisely control the cleaning area by adjusting parameters such as the power, frequency, and scanning speed of the laser, ensuring that there is no residue of electrode powder, no breakage or wrinkling, and no oxidation damage in the cleaning area. Moreover, in this solution, after the positive electrode active material layer 16 is coated on the positive electrode sheet 1, laser cleaning is carried out to remove the positive electrode active material layer 16 corresponding to the second insulating sheet 13, thereby forming the empty foil area 14. This is because the area of the empty foil area 14 is small. If the coating is directly not applied in this area during the process of coating the positive electrode active material layer 16, the coating difficulty is large and the coating precision is difficult to control.

[0054] In one embodiment, the hollowed-out area 15 is formed by laser die-cutting to remove a part of the positive electrode sheet 1 corresponding to the second insulating sheet 13. The laser die-cutting technology has higher cutting precision, less physical wear, and flexible cutting shapes. Moreover, in this solution, after the positive electrode active material layer 16 is coated on the positive electrode sheet 1, laser die-cutting is carried out to remove a part of the positive electrode sheet 1 corresponding to the second insulating sheet 13. This is because if the hollowed-out area 15 is cut out on the current collector in advance, the current collector is likely to crack or break at the hollowed-out area 15 during the subsequent process of coating and rolling the positive electrode active material layer 16.

[0055] In one embodiment, the blocking groove 161 is formed by laser etching the positive electrode active material layer 16. The laser etching technology can precisely control the etching depth and shape of the blocking groove 161.

[0056] Furthermore, a third insulating sheet 12 is provided at the positive electrode ear of the positive electrode sheet, and a fourth insulating sheet 23 is provided at a position corresponding to the positive electrode ear 11 of the positive electrode sheet 1 on the negative electrode active material layer of the negative electrode sheet 2. The third insulating sheet 12 and the fourth insulating sheet 23 can effectively isolate the contact between the positive electrode ear 11 and the negative electrode sheet 2, and effectively isolate the contact between the negative electrode ear 21 and the positive electrode sheet 1, thereby reducing the risk of short circuit and improving the safety of the battery.

[0057] Specifically, the third insulating sheet 12 and the fourth insulating sheet 23 are insulating tapes, and the first insulating sheet 22 and the second insulating sheet 13 are also insulating tapes. Insulating tapes have good electrical insulation properties, can effectively prevent short circuits inside the battery, are easy to cut and paste, and can be cut into different shapes and sizes as needed, which is convenient for application in the battery manufacturing process. Insulating tapes are usually low in cost, which helps to reduce the production cost of the battery. Insulating tapes have good chemical stability and are not easy to react with the chemical substances inside the battery. Insulating tapes also have good high temperature resistance and can remain stable in the high temperature environment generated when the battery is working.

[0058] The present invention also discloses a method for preparing a lithium ion battery, which is applied to the preparation of the above lithium ion battery and comprises the steps of:

[0059] On the positive electrode sheet of the lithium-ion battery, the positive electrode active material layer at the position corresponding to the negative electrode ear of the negative electrode sheet is removed by laser processing equipment to form a hollow foil area; or the positive electrode sheet portion at the position corresponding to the negative electrode ear of the negative electrode sheet is cut off to form a hollow area; or the positive electrode active material layer at the position corresponding to the negative electrode ear of the negative electrode sheet is etched to form a blocking groove;

[0060] A second insulating sheet is attached to the positive electrode active material layer of the positive electrode sheet at a position corresponding to the negative electrode ear of the negative electrode sheet, and the second insulating sheet covers the hollow foil area, the hollow area or the blocking groove; the second insulating sheet covers the hollow foil area and the positive electrode active material layer around the hollow foil area, or the second insulating sheet covers the hollow area and the positive electrode active material layer around the hollow area, or the second insulating sheet of the blocking groove separates the positive electrode active material layers on both sides thereof, and the second insulating sheet covers the blocking groove and the positive electrode active material layer around the blocking groove;

[0061] A first insulating sheet is attached to the negative electrode ear of the negative electrode sheet;

[0062] The positive electrode sheet, the negative electrode sheet and the separator are wound, put into a shell, and the electrolyte is injected to obtain a lithium-ion battery.

[0063] Specifically, in the above steps, the positive electrode sheet 1 is precisely processed using laser processing equipment, including removing the positive electrode active material layer 16 at the position corresponding to the negative electrode ear 21 to form an empty foil area 14; or cutting off the positive electrode sheet 1 at the position corresponding to the negative electrode ear 21 to form a hollow area 15; or etching the positive electrode active material layer 16 at the position corresponding to the negative electrode ear 21 to form a blocking groove 161. A second insulating sheet 13 is attached to the positive electrode active material layer 16 of the positive electrode sheet 1 at a position corresponding to the negative electrode ear 21 of the negative electrode sheet 2, covering the empty foil area 14, the hollow area 15 or the blocking groove 161. At the same time, a third insulating sheet 12 is attached to the positive electrode ear 11 of the positive electrode sheet 1 to ensure the safety and reliability of the battery.

[0064] The preparation method of the lithium-ion battery generally includes the preparation of the positive electrode sheet 1 and the negative electrode sheet 2, the winding of the positive electrode sheet 1, the negative electrode sheet 2 and the separator, and the welding, formation, and capacity separation of the battery shell, which will not be repeated here.

[0065] It should be understood that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. For those skilled in the art, the technical solutions described in the above embodiments can be modified, or some of the technical features therein can be replaced by equivalents; and all these modifications and replacements should fall within the scope of protection of the claims attached to the present invention.

Claims

1. A lithium ion battery, characterized in that: It comprises a positive electrode sheet, a negative electrode sheet and a separator; the negative electrode sheet is provided with a first insulating sheet covering its negative electrode ear; the positive electrode sheet is provided with a second insulating sheet facing the negative electrode ear; A hollow foil area is provided in the area of ​​the positive electrode sheet opposite to the first insulating sheet, and the second insulating sheet covers the hollow foil area and the positive electrode active material layer around the hollow foil area; or, A hollow area is provided on the positive electrode sheet in an area opposite to the first insulating sheet, and the second insulating sheet covers the hollow area and the positive electrode active material layer around the hollow area; or, A blocking groove is provided in the area of ​​the positive electrode sheet opposite to the first insulating sheet; the blocking groove separates the positive electrode active material layers on both sides thereof, and the second insulating sheet covers the blocking groove and the positive electrode active material layers around the blocking groove.

2. The lithium-ion battery according to claim 1, characterized in that The blocking groove is arranged around the area where the positive electrode active material layer faces the negative electrode ear, or around the area where the positive electrode active material layer faces the first insulating sheet; Both ends of the blocking groove extend to the edge of the positive electrode sheet.

3. The lithium ion battery according to claim 1, characterized in that The thickness of the positive electrode active material layer on one side of the positive electrode sheet is T0, the depth of the blocking groove is T1, and the width of the blocking groove is W; wherein, 0.7T0≤T1≤0.9T0,0mm <W<10mm。 4. The lithium ion battery according to claim 1, characterized in that The distance from the outer peripheral edge of the blocking groove to the outer peripheral edge of the second insulating sheet is L, wherein 0.5 mm≤L≤5 mm.

5. The lithium ion battery according to claim 1, characterized in that The blocking groove comprises a first sub-groove, a second sub-groove and a third sub-groove which are connected in sequence; The first sub-groove and the third sub-groove are arranged in parallel and extend along the width direction of the positive electrode sheet; one end of the first sub-groove and one end of the third sub-groove penetrate the edge of the positive electrode active material layer in the width direction of the positive electrode sheet, and the other end of the first sub-groove and the other end of the third sub-groove are connected to the two ends of the second sub-groove respectively; The second sub-groove extends along the length direction of the positive electrode sheet.

6. The lithium ion battery according to claim 1, characterized in that The hollow area passes through the edge of the positive electrode active material layer in the width direction of the positive electrode sheet.

7. The lithium ion battery according to claim 1, characterized in that The hollow area is a rectangular hollow area, and the shape of the second insulating sheet is a rectangle; the length of the hollow area is a, and the width is b; the length of the second insulating sheet is c, and the width is d; wherein, 0mm <c-a<5mm,0mm<d-b<5mm,1mm<a<50mm,1mm<b<50mm。 8. The lithium ion battery according to claim 1, characterized in that The empty foil area is formed by removing the portion of the positive electrode active material layer corresponding to the second insulating sheet through laser cleaning; or, The hollow area is formed by laser die cutting to remove the portion of the positive electrode sheet corresponding to the second insulating sheet; or, The blocking groove is formed by laser etching the positive electrode active material layer.

9. The lithium ion battery according to any one of claims 1 to 8, characterized in that: The second insulating sheet is in a rectangular shape; the length of the second insulating sheet is c and the width is d; The shape of the first insulating sheet is rectangular; the length of the first insulating sheet is e, and the width is f; wherein, 0mm <c-e<5mm,0mm<d-f<5mm。 10. A method for preparing a lithium ion battery, applied to the preparation of a lithium ion battery according to any one of claims 1 to 9, characterized in that: Includes steps: On the positive electrode sheet of the lithium-ion battery, the positive electrode active material layer at the position corresponding to the negative electrode ear of the negative electrode sheet is removed by laser processing equipment to form a hollow foil area; or the positive electrode sheet portion at the position corresponding to the negative electrode ear of the negative electrode sheet is cut off to form a hollow area; or the positive electrode active material layer at the position corresponding to the negative electrode ear of the negative electrode sheet is etched to form a blocking groove; A second insulating sheet is attached to the positive electrode active material layer of the positive electrode sheet at a position corresponding to the negative electrode ear of the negative electrode sheet, and the second insulating sheet covers the hollow foil area, the hollow area or the blocking groove; the second insulating sheet covers the hollow foil area and the positive electrode active material layer around the hollow foil area, or the second insulating sheet covers the hollow area and the positive electrode active material layer around the hollow area, or the second insulating sheet of the blocking groove separates the positive electrode active material layers on both sides thereof, and the second insulating sheet covers the blocking groove and the positive electrode active material layer around the blocking groove; A first insulating sheet is attached to the negative electrode ear of the negative electrode sheet; The positive electrode sheet, the negative electrode sheet and the separator are wound, put into a shell, and the electrolyte is injected to obtain a lithium-ion battery.

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