A lithium ion battery and a preparation method thereof

Abstract

The present application relates to the technical field of lithium ion batteries, and particularly relates to a lithium ion battery and a preparation method thereof. The lithium ion battery comprises a positive electrode sheet, a negative electrode sheet and a separator; the negative electrode sheet is provided with a first insulating sheet covering a negative electrode tab thereof; the positive electrode sheet is provided with a second insulating sheet opposite to the negative electrode tab; a region of the positive electrode sheet opposite to the first insulating sheet is provided with an empty foil area, the second insulating sheet covers a positive electrode active material layer in the empty foil area and a positive electrode active material layer around the empty foil area; or, a region of the positive electrode sheet opposite to the first insulating sheet is provided with a hollowed-out area, the second insulating sheet covers a positive electrode active material layer in the hollowed-out area and a positive electrode active material layer around the hollowed-out area; or, a region of the positive electrode sheet opposite to the first insulating sheet is provided with a blocking groove; the blocking groove separates the positive electrode active material layers on both sides of the blocking groove, and the second insulating sheet covers the positive electrode active material layers in the blocking groove and around the blocking groove.

Description

TECHNICAL FIELD

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

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

[0003] In the process of designing and producing the soft-pack lithium battery with the middle tab, the positive / negative tab position and the negative / positive sheet corresponding to the positive / negative tab position need to be attached with adhesive paper. On the one hand, it prevents the burrs caused by laser cleaning and welding from piercing the separator, causing internal short circuit of the battery. On the other hand, it prevents the active material on the positive sheet corresponding to the negative tab from being delithiated and embedded in the negative electrode, causing lithium precipitation and other risks.

[0004] However, in the actual process, part of the lithium ions in the positive material covered by the adhesive paper on the positive sheet can still bypass the adhesive paper and transfer to the negative electrode surface, causing lithium precipitation. SUMMARY

[0005] The embodiments of the present application provide a lithium ion battery and a preparation method thereof to solve the problem that part of the lithium ions in the positive material covered by the adhesive paper on the positive sheet can still bypass the positive material and transfer to the negative electrode surface, causing lithium precipitation.

[0006] The present application discloses a lithium ion battery, comprising a positive sheet, a negative sheet and a separator; the negative sheet is provided with a first insulating sheet covering the negative tab thereof; the positive sheet is provided with a second insulating sheet opposite to the negative tab;

[0007] The region of the positive sheet opposite to the first insulating sheet is provided with an empty foil area, and the second insulating sheet covers the positive active material layer in the empty foil area and the periphery of the empty foil area; or,

[0008] The region of the positive sheet opposite to the first insulating sheet is provided with a hollow area, and the second insulating sheet covers the positive active material layer in the hollow area and the periphery of the hollow area; or,

[0009] The region of the positive sheet opposite to the first insulating sheet is provided with a blocking groove; the blocking groove separates the positive active material layers on both sides thereof, and the second insulating sheet covers the positive active material layers in the blocking groove and the periphery of the blocking groove.

[0010] Optionally, the blocking groove is arranged around the region of the positive active material layer opposite to the negative tab, or around the region of the positive active material layer opposite to the first insulating sheet.

[0011] The two ends of the blocking groove extend to the edge of the positive 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, and 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 0.5mm≤L≤5mm.

[0014] Optionally, the blocking groove comprises a first sub-groove, a second sub-groove and a third sub-groove 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 respectively communicate with two ends of the second sub-groove.

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

[0017] Optionally, the hollow area penetrates the 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 rectangular; 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, and 1mm<b<50mm.

[0019] Optionally, the hollow area is formed by laser cleaning to remove the part of the positive electrode active material layer corresponding to the second insulating sheet; or,

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

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

[0022] Optionally, the shape of the second insulating sheet is rectangular; 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 application also discloses a lithium ion battery preparation method applied to the preparation of the lithium ion battery.

[0025] The positive active material layer at the position corresponding to the negative tab of the negative sheet is removed by a laser processing device to form an empty foil area on the positive sheet of the lithium ion battery; or the part of the positive sheet at the position corresponding to the negative tab of the negative sheet is cut off to form a hollowed-out area; or the positive active material layer at the position corresponding to the negative tab of the negative sheet is etched to form a blocking groove;

[0026] The second insulating sheet is attached to the positive active material layer of the positive sheet at the position corresponding to the negative tab of the negative sheet, and the second insulating sheet covers the empty foil area, the hollowed-out area or the blocking groove; the second insulating sheet covers the positive active material layer around the empty foil area, or the second insulating sheet covers the positive active material layer around the hollowed-out area, or the second insulating sheet separates the positive active material layers on both sides of the blocking groove, and the second insulating sheet covers the positive active material layer around the blocking groove;

[0027] The first insulating sheet is attached to the negative tab of the negative sheet;

[0028] The positive sheet, the negative sheet and the separator are wound, the shell is assembled, the electrolyte is injected, and the lithium ion battery is obtained.

[0029] Compared with the prior art, the lithium ion battery provided by the embodiment of the present application has the beneficial effects that the third insulating sheet is arranged at the positive tab of the positive sheet of the lithium ion battery, and the second insulating sheet is arranged at the position corresponding to the negative tab of the negative sheet, wherein the positive sheet region corresponding to the second insulating sheet is an empty foil area, or the positive sheet region corresponding to the second insulating sheet is hollowed out to form a hollowed-out area, or the positive active material layer region corresponding to the second insulating sheet is provided with a blocking groove, and the blocking groove surrounds the positive active material layer region corresponding to the second insulating sheet to separate the positive active material layer region corresponding to the second insulating sheet from other regions of the positive active material layer. In this way, the empty foil area, the hollowed-out area or the blocking groove can ensure that there is no positive active material in the positive sheet region corresponding to the second insulating sheet or can reduce the delithiation of the positive active material, thereby avoiding the risk of lithium ion migration from the positive active material to the negative electrode (the negative electrode here is the negative tab position, and the adhesive paper is also attached, and lithium ion cannot be embedded), causing lithium precipitation and thickness exceeding limit. BRIEF DESCRIPTION OF DRAWINGS

[0030] The technical solutions of the present application will be further described in detail below with reference to the drawings and embodiments, and the drawings are as follows:

[0031] Figure 1 is a schematic diagram of the adhesive paper attached to the position corresponding to the negative tab on the positive sheet in the prior art;

[0032] Figure 2 is a schematic diagram of the positive sheet of the embodiment of the present application;

[0033] Figure 3 is a schematic diagram of the negative sheet of the embodiment of the present application;

[0034] Figure 4 is Figure 2 is a schematic view of a second insulating sheet attached to the positive electrode sheet at a position corresponding to the negative tab position of the negative electrode sheet to cover the empty foil area in an embodiment of part A;

[0035] Figure 5 is Figure 2 is a schematic view of the hollowed-out area after hollowing out the positive electrode sheet at a position corresponding to the negative tab position of the negative electrode sheet in another embodiment of part A;

[0036] Figure 6 is Figure 2 is a schematic view of a blocking groove formed in the positive electrode sheet at a position corresponding to the negative tab position of the negative electrode sheet in a third embodiment of part A;

[0037] Figure 7 is Figure 2 is a schematic view of a second insulating sheet attached to the positive electrode sheet at a position corresponding to the negative tab position of the negative electrode sheet to cover the blocking groove in a third embodiment of part A;

[0038] Figure 8 is Figure 5 is a schematic view of a second insulating sheet attached to the positive electrode sheet at a position corresponding to the negative tab position of the negative electrode sheet to cover the blocking groove in a third embodiment of part A;

[0039] The reference signs in the drawings are as follows:

[0040] 1, positive electrode sheet; 11, positive tab; 12, third insulating sheet; 13, second insulating sheet; 14, empty foil area; 15, hollowed-out area; 16, positive active material layer; 161, blocking groove; 2, negative electrode sheet; 21, negative tab; 22, first insulating sheet; 23, fourth insulating sheet; 3, adhesive paper. DETAILED DESCRIPTION

[0041] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The preferred embodiments of the present application will be described in detail with reference to the drawings.

[0042] The present application provides a lithium ion battery, as shown in the drawings, the lithium ion battery comprises 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 tab thereof; the positive electrode sheet is provided with a second insulating sheet opposite to the negative tab; Figures 1 to 8 The area of the positive electrode sheet opposite to the first insulating sheet is provided with an empty foil area, and the second insulating sheet covers the positive active material layer around the empty foil area; or,

[0043] The area of the positive electrode sheet opposite to the first insulating sheet is provided with a hollowed-out area, and the second insulating sheet covers the positive active material layer around the hollowed-out area; or,

[0044]

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

[0046] The lithium ion battery of the present application is provided with a first insulating sheet covering the negative tab on the negative electrode sheet, wherein the region of the positive electrode sheet 1 corresponding to the first insulating sheet 22 is a hollow foil region 14, or the region of the positive electrode sheet 1 corresponding to the first insulating sheet 22 is hollowed out to form a hollowed-out region 15, or the region of the positive electrode active material layer 16 corresponding to the first insulating sheet 22 is provided with a blocking groove 161. In this way, the existence of the hollow foil region 14, the hollowed-out region 15 or the blocking groove 161 can ensure that the region of the positive electrode sheet 1 corresponding to the second insulating sheet 13 does not have positive electrode active material or can reduce the delithiation of the positive electrode active material, avoiding the risk of lithium ion migration from the positive electrode active material to the negative electrode (the negative electrode here is the negative tab position, and the adhesive paper 3 is also attached, and lithium ions cannot be embedded), causing lithium precipitation and thickness exceeding limit.

[0047] Specifically, the hollow foil region 14 is a region where only the positive current collector exists, and there is no corresponding positive electrode active material layer 16 on the positive current collector. In this way, there is no lithium ion migration from the positive electrode active material to the negative electrode, and the above-mentioned risk of lithium precipitation and thickness exceeding limit is avoided. The hollowed-out region 15 is directly hollowed out in the region of the positive electrode sheet 1 corresponding to the second insulating sheet 13. After being hollowed out, this region is in the form of a notch, and both the positive current collector and the positive electrode active material layer 16 do not exist, thus avoiding the above-mentioned risk of lithium precipitation and thickness exceeding limit. The blocking groove 161 reduces the thickness of the positive electrode active material layer 16 at the edge of the region by setting the blocking groove 161, reduces the migration of lithium ions in the region, and has a blocking effect, thereby reducing the migration of lithium ions from the positive electrode active material in the region to the negative electrode, and thus avoiding the above-mentioned risk of lithium precipitation and thickness exceeding limit.

[0048] Specifically, the blocking groove is arranged around the region of the positive electrode active material layer opposite to the negative tab, or around the region of the positive electrode active material layer opposite to the first insulating sheet. The two ends of the blocking groove extend to the edge of the positive electrode sheet.

[0049] Specifically, in an 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, and 0mm<W<10mm. By setting the depth of the blocking groove 161 to T1 and the width to 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 area. Controlling the depth of the blocking groove 161 to be between 0.7T0 and 0.9T0, i.e., the depth of the blocking groove 161 is 70%-90% of the thickness of the positive electrode active material layer 16, 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, which may damage the current collector during processing of the blocking groove 161, affecting the positive electrode active material on the opposite side of the blocking groove 161; the etching depth is too shallow, less than 70% of the thickness of the single-sided positive electrode active material layer 16, which cannot achieve good blocking effect, and more lithium ions will migrate to the negative electrode to produce lithium precipitation.

[0050] As shown in Figure 7 , the blocking groove 161 has three edges marked as ①, ②, and ③, which enclose a rectangular area on the edge of the positive electrode sheet 1, and the second insulating sheet 13 is attached to the area, as shown in Figure 7 . The distance between the blocking groove and the second insulating sheet is L, wherein 0.5mm≤L≤5mm, which can ensure that the second insulating sheet is firmly attached and will not affect lithium ion migration and battery capacity performance due to the excessive area of the second insulating sheet.

[0051] The blocking groove includes a first sub-groove, a second sub-groove, and a third sub-groove connected in sequence; the first sub-groove and the third sub-groove are arranged in parallel and extend in 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 respectively communicate with both ends of the second sub-groove; the second sub-groove extends in 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] Specifically, in an embodiment, the hollowed-out area 15 is a rectangular hollowed-out area, and the hollowed-out area 15 is open along one side of the positive electrode sheet 1 close to the second insulating sheet 13. The second insulating sheet 13 has a rectangular shape, and 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, and 1 mm < b < 50 mm. In this way, the length and width of the second insulating sheet 13 are both greater than the length and width 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 and 0 < d-b < 5 can ensure that the second insulating sheet 13 can firmly adhere to and completely cover the hollowed-out area 15, providing reliable insulation protection to prevent accidental contact between the positive and negative electrode tabs. Using a rectangular hollowed-out area 15 and a second insulating sheet 13 can simplify the manufacturing process of the battery, because the rectangular shape is easy to accurately cut and position by automated equipment, which helps to improve production efficiency and reduce costs. Specifically, the first insulating sheet has a rectangular shape; the length of the first insulating sheet is e, and the width is f; wherein 0 mm < c-e < 5 mm, and 0 mm < d-f < 5 mm.

[0053] Specifically, in an embodiment, the hollow foil area 14 is formed by laser cleaning to remove the positive active material layer 16 corresponding to the second insulating sheet 13. Laser cleaning technology can remove the positive active material layer 16 without damaging the surface of the current collector. Laser cleaning can accurately control the cleaning area by adjusting parameters such as laser power, frequency, and scanning speed, ensuring that the cleaning area has no residual powder, no damage and no oxidation damage. Moreover, the present scheme is to perform laser cleaning to remove the positive active material layer 16 corresponding to the second insulating sheet 13 after forming the positive active material layer 16 on the positive electrode sheet 1, thereby forming the hollow foil area 14. This is because the hollow foil area 14 has a small area, and it is difficult to control the coating precision if the area is not coated directly during the process of coating the positive active material layer 16.

[0054] In an embodiment, the hollowed-out area 15 is formed by laser die cutting to cut off part of the positive electrode sheet 1 corresponding to the second insulating sheet 13. Laser die cutting technology has higher cutting precision, and has small physical wear and tear and flexible cutting shape. Moreover, the present scheme is to perform laser die cutting to cut off part of the positive electrode sheet 1 corresponding to the second insulating sheet 13 after forming the positive active material layer 16 on the positive electrode sheet 1, because if the hollowed-out area 15 is pre-cut on the current collector, the current collector is easy to crack or break at the hollowed-out area 15 during the subsequent coating and rolling of the positive active material layer 16.

[0055] In an embodiment, the blocking groove 161 is formed by laser etching to etch the positive active material layer 16. Laser etching technology can accurately control the etching depth and shape of the blocking groove 161.

[0056] Further, the third insulating sheet 12 is arranged on the positive pole tab of the positive pole sheet, and the fourth insulating sheet 23 is arranged on the negative pole active material layer of the negative pole sheet 2, corresponding to the position of the positive pole tab 11 of the positive pole sheet 1. Through the third insulating sheet 12 and the fourth insulating sheet 23, the contact between the positive pole tab 11 and the negative pole sheet 2 can be effectively isolated, and the contact between the negative pole tab 21 and the positive pole sheet 1 can be effectively isolated, 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 adhesive paper, and the first insulating sheet 22 and the second insulating sheet 13 are also insulating adhesive paper. The insulating adhesive paper has good electrical insulation performance, can effectively prevent short circuit in the battery, is easy to cut and paste, can be cut into different shapes and sizes as needed, is convenient to apply in the battery manufacturing process, and generally has low cost, which helps to reduce the production cost of the battery. The insulating adhesive paper has good chemical stability and is not easy to react with the chemicals in the battery. The insulating adhesive paper also has good high temperature resistance and can remain stable in the high temperature environment generated during the operation of the battery.

[0058] The application also discloses a preparation method of the lithium ion battery.

[0059] The positive pole active material layer at the position corresponding to the negative pole tab of the negative pole sheet is removed on the positive pole sheet of the lithium ion battery by a laser processing device to form an empty foil area; or the part of the positive pole sheet at the position corresponding to the negative pole tab of the negative pole sheet is cut off to form a hollow area; or the positive pole active material layer at the position corresponding to the negative pole tab of the negative pole sheet is etched to form a blocking groove;

[0060] The second insulating sheet is attached to the positive pole active material layer of the positive pole sheet at the position corresponding to the negative pole tab of the negative pole sheet, and the second insulating sheet covers the empty foil area, the hollow area or the blocking groove; the second insulating sheet covers the positive pole active material layer in the empty foil area and around the empty foil area, or the second insulating sheet covers the positive pole active material layer in the hollow area and around the hollow area, or the second insulating sheet separates the positive pole active material layers on the two sides of the blocking groove, and the second insulating sheet covers the positive pole active material layer in the blocking groove and around the blocking groove;

[0061] The first insulating sheet is attached to the negative pole tab of the negative pole sheet.

[0062] The positive pole sheet, the negative pole sheet and the diaphragm are wound, the shell is assembled, the electrolyte is injected, and the lithium ion battery is obtained.

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

[0064] The preparation method of the lithium ion battery generally further includes preparation of the positive plate 1 and the negative plate 2, winding of the positive plate 1, the negative plate 2 and the separator, and welding of the battery shell, formation, capacity distribution, etc., which are not described here.

[0065] It should be understood that the above embodiments are only used to illustrate the technical solutions of the present application, but not to limit them. For those skilled in the art, the technical solutions described in the above embodiments can be modified, or some technical features can be replaced by equivalents; all these modifications and replacements shall belong to the protection scope of the appended claims of the present application.

Claims

1. A lithium-ion battery, characterized by, The lithium ion battery comprises a positive electrode sheet, a negative electrode sheet and a separator; the negative electrode sheet is provided with a first insulating sheet covering a negative electrode tab thereof; the positive electrode sheet is provided with a second insulating sheet opposite to the negative electrode tab; The positive electrode sheet is provided with a blocking groove at a region opposite to the first insulating sheet; the blocking groove separates the positive electrode active material layers on both sides of the blocking groove; the second insulating sheet covers the blocking groove and the positive electrode active material layers around the blocking groove; The blocking groove surrounds the region of the positive electrode active material layer opposite to the negative electrode tab or surrounds the region of the positive electrode active material layer opposite to the first insulating sheet; the two ends of the blocking groove extend to the edge of the positive electrode sheet; 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; The distance from the outer periphery edge of the blocking groove to the outer periphery edge of the second insulating sheet is L, wherein 0.5mm≤L≤5mm; the second insulating sheet is rectangular in shape; the length of the second insulating sheet is c, and the width is d; the first insulating sheet is rectangular in shape; the length of the first insulating sheet is e, and the width is f; wherein 0mm <c-e<5mm, 0mm <d-f<5mm.

2. The lithium-ion battery of claim 1, wherein, The blocking groove comprises a first sub-groove, a second sub-groove and a third sub-groove connected in sequence; The first sub-groove and the third sub-groove are arranged in parallel and extend in 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 respectively communicate with the two ends of the second sub-groove; The second sub-groove extends in the length direction of the positive electrode sheet.

3. The lithium-ion battery of claim 1, wherein, The blocking groove is formed by laser etching the positive electrode active material layer.

4. A method for manufacturing a lithium ion battery, applied to the manufacture of a lithium ion battery according to any one of claims 1 to 3, characterized in that, The method comprises the following steps: A blocking groove is formed on the positive electrode sheet of the lithium ion battery by laser processing equipment to etch the positive electrode active material layer at a position corresponding to the negative electrode tab of the negative electrode sheet; 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 tab of the negative electrode sheet, and the second insulating sheet covers the blocking groove; the blocking groove separates the positive electrode active material layers on both sides of the blocking groove, and the second insulating sheet covers the blocking groove and the positive electrode active material layers around the blocking groove; A first insulating sheet is attached to the negative electrode tab of the negative electrode sheet; The positive electrode sheet, the negative electrode sheet and the separator are wound, the shell is assembled, the electrolyte is injected, and the lithium ion battery is obtained.

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