Lithium ion battery cell, preparation method of lithium ion battery cell, lithium ion battery comprising lithium ion battery cell and power utilization device

Abstract

The invention provides a lithium ion battery cell, a preparation method of the lithium ion battery cell, a lithium ion battery comprising the lithium ion battery cell and a power utilization device, and relates to the technical field of lithium ion batteries. The lithium ion battery cell is formed by a positive plate, a negative plate and a diaphragm arranged between the positive plate and the negative plate, and the widths of the positive plate, the negative plate and the diaphragm in the cell are the same; an insulating region coating structure is arranged in the end surface region of the battery cell, and the width of the insulating region coating structure is 0.5-2mm. According to the lithium ion battery cell, the insulation area coating structure is arranged in the edge end face area of the cell, so that the widths of the positive plate, the negative plate and the diaphragm in the cell are the same, the problem of poor alignment of the positive plate, the negative plate and the diaphragm in the prior art is solved through the arrangement of the insulation area, and the edge effect caused by inconsistent sizes of the pole plates is also eliminated; the lithium separation phenomenon caused by the fringe effect is avoided, so that the lithium ion battery prepared from the lithium ion battery cell has better cell cycling stability and safety.

Description

Technical Field

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

[0002] During the charging process of a lithium-ion battery, internal carriers (lithium ions) escape from the positive electrode, flow through the electrolyte, and reach the surface of the negative electrode active material. They then combine with electrons that have reached the negative electrode surface to undergo a reduction reaction, and eventually diffuse into the interior of the negative electrode active particles. If the active materials of the positive and negative electrodes of the battery cell are not aligned, that is, there is no negative electrode active material on the corresponding negative electrode in the area of ​​the positive electrode active material, during the charging process, the carriers will precipitate on the negative electrode current collector, forming lithium dendrites. The continued growth of lithium dendrites can easily pierce the diaphragm, causing the positive and negative electrodes to short-circuit, thereby causing an internal short circuit in the lithium-ion battery, resulting in battery failure. In severe cases, fire and other safety accidents may occur.

[0003] Therefore, during the design and production of existing lithium-ion batteries, the relative sizes of the positive and negative electrode sheets and the separator are typically designed (overhang design), with separator width > negative electrode width > positive electrode width. By increasing the size of the negative electrode and improving the precision of the winding process, the safety risks caused by poor alignment of the positive and negative electrode sheets have been effectively addressed.

[0004] However, the existing Overhang design, due to the inconsistent dimensions (mainly length and width) of the positive and negative electrodes and the diaphragm, results in an uneven electric field between the positive and negative electrodes during charging, causing a local large current to form in the negative electrode area corresponding to the edge of the positive electrode. The local high current location is more prone to lithium deposition, a phenomenon known as the edge effect.

[0005] The edge effect will have two consequences: first, the lithium plating reaction at the edge of the negative electrode during the cycle will consume the active lithium of the battery cell, thereby causing the battery cell capacity to decay; the other is that with the increase in cycles, the continuous growth of lithium dendrites will increase the safety risk of short circuit in the battery cell.

[0006] Therefore, it is necessary and urgent to research and develop a lithium-ion battery cell without edge effect and a preparation method thereof to solve the problem of poor alignment and edge lithium plating caused by overhang design that are prone to occur during the production process of existing lithium-ion battery cells.

[0007] In view of this, the present invention is proposed. Summary of the Invention

[0008] The first object of the present invention is to provide a lithium-ion battery cell, which not only eliminates the problem of poor alignment, but also eliminates the edge effect caused by inconsistent electrode sizes, thereby having better battery cell cycle stability and safety.

[0009] The second object of the present invention is to provide a method for preparing a lithium-ion battery cell.

[0010] The third object of the present invention is to provide a lithium-ion battery prepared from the above-mentioned lithium-ion battery cell.

[0011] A fourth object of the present invention is to provide an electrical device.

[0012] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are adopted:

[0013] The present invention provides a lithium-ion battery cell, which is formed by a positive electrode sheet, a negative electrode sheet and a separator arranged therebetween, wherein the positive electrode sheet, the negative electrode sheet and the separator in the cell have the same width;

[0014] An insulating region covering structure is provided in the end face area of ​​the battery core, and the width of the insulating region covering structure is 0.5 to 2 mm.

[0015] Furthermore, when the battery core is a wound component, the positive electrode sheet, the negative electrode sheet and the separator are of the same size in the height direction, and the end surface of the wound component in the height direction is provided with an insulating area covering structure.

[0016] Furthermore, when the battery core is a laminate, the positive electrode sheet and the negative electrode sheet have the same length, and an insulating region covering structure is provided on the end surface of the laminate in the length direction.

[0017] Furthermore, the insulating material in the insulating region coating structure includes one or more of polyvinylidene fluoride, polyimide, polyamide-imide and styrene-butadiene rubber.

[0018] The present invention provides a method for preparing the above-mentioned lithium-ion battery cell, which comprises the following steps:

[0019] (A) evenly coating the active material slurry on the current collector and drying it to form the positive and negative electrode sheets;

[0020] (B) Control the width of the separator, negative electrode sheet, and positive electrode sheet to be consistent, and then wind or stack the basic unit consisting of negative electrode-separator-positive electrode to form a battery cell;

[0021] (C) dissolving the insulating material in a solvent to form an insulating glue; immersing the end face area of ​​the battery cell in step (B) in the insulating glue, and then drying to obtain a battery cell with an insulating region coating structure;

[0022] (D) The battery cell containing the insulating area coating structure is sequentially hot-pressed, shelled, liquid-injected, and sealed to obtain a lithium-ion battery cell.

[0023] Furthermore, the insulating material in step (C) includes one or more of polyvinylidene fluoride, polyimide, polyamide-imide and styrene-butadiene rubber.

[0024] Furthermore, in the step (C), the time for the edge area of ​​the end face of the battery cell to be immersed in the insulating glue is 10 seconds to 5 minutes.

[0025] Furthermore, in the step (C), the depth of the edge area of ​​the end face of the battery cell immersed in the insulating glue is 0.5 mm to 2 mm.

[0026] The present invention provides a lithium ion battery, which includes the above-mentioned lithium ion battery cell.

[0027] The present invention provides an electrical device, which includes the lithium-ion battery mentioned above.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] The lithium-ion battery cell provided by the present invention is formed by a positive electrode sheet, a negative electrode sheet, and a separator disposed therebetween. The positive electrode sheet, negative electrode sheet, and separator in the cell have the same width. The end face region of the cell is provided with an insulating region coating structure, and the width of the insulating region coating structure is 0.5 to 2 mm. The above-mentioned lithium-ion battery cell of the present invention eliminates the design of the electrode overhang by providing an insulating region with a coating structure in the end face region of the cell edge, making the width of the positive electrode sheet, negative electrode sheet, and separator in the cell the same. This solution not only eliminates the problem of poor alignment, but also eliminates the edge effect caused by inconsistent electrode sheet sizes. Due to the absence of lithium plating caused by the edge effect, the lithium-ion battery prepared from the lithium-ion battery cell of the present invention has better cell cycle stability and safety.

[0030] The present invention provides a method for preparing a lithium-ion battery cell. This method utilizes an insulating adhesive to immerse the entire edge of the cell, creating uniformly sized active material regions. This effectively eliminates edge effects caused by poor alignment and inconsistent electrode sizes. Therefore, the method offers the technical advantages of simple processing and ease of operation.

[0031] The lithium-ion battery cell provided by the present invention can be widely used in the preparation of lithium-ion batteries and electrical devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0033] Figure 1 This is a flow chart for preparing the lithium-ion battery cell of this application;

[0034] Figure 2 This is a schematic structural diagram of a battery cell without overhang provided in Example 1 of the present invention;

[0035] Figure 3 This is a schematic structural diagram of a battery cell with an insulating area provided in Example 1 of the present invention;

[0036] Figure 4 The cycle test capacity retention rate of Example 1 and Comparative Example 1 at 25°C provided in Experimental Example 1 of the present invention. DETAILED DESCRIPTION

[0037] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all 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.

[0038] According to one aspect of the present invention, a lithium-ion battery cell is formed by a positive electrode sheet, a negative electrode sheet, and a separator disposed therebetween, wherein the positive electrode sheet, the negative electrode sheet, and the separator in the cell have the same width;

[0039] An insulating region covering structure is provided in the end face area of ​​the battery core, and the width of the insulating region covering structure is 0.5 to 2 mm.

[0040] The lithium-ion battery cell provided by the present invention is formed by a positive electrode sheet, a negative electrode sheet, and a separator disposed therebetween. The positive electrode sheet, negative electrode sheet, and separator in the cell have the same width. The end face region of the cell is provided with an insulating region coating structure, and the width of the insulating region coating structure is 0.5 to 2 mm. The above-mentioned lithium-ion battery cell of the present invention eliminates the design of the electrode overhang by providing an insulating region with a coating structure in the end face region of the cell edge, making the width of the positive electrode sheet, negative electrode sheet, and separator in the cell the same. This solution not only eliminates the problem of poor alignment, but also eliminates the edge effect caused by inconsistent electrode sheet sizes. Due to the absence of lithium plating caused by the edge effect, the lithium-ion battery prepared from the lithium-ion battery cell of the present invention has better cell cycle stability and safety.

[0041] In a preferred embodiment of the present invention, when the battery cell is a wound body, the positive electrode sheet, negative electrode sheet and separator are of the same size in the height direction, and an insulating area covering structure is provided on the end surface of the wound body in the height direction.

[0042] In a preferred embodiment of the present invention, when the battery core is a laminate, the positive and negative electrode sheets have the same length, and an insulating region covering structure is provided on the end faces of the laminate in the length direction.

[0043] In a preferred embodiment of the present invention, the insulating material in the insulating region coating structure includes one or more of polyvinylidene fluoride, polyimide, polyamide-imide and styrene-butadiene rubber.

[0044] According to one aspect of the present invention, a method for preparing the above-mentioned lithium-ion battery cell comprises the following steps:

[0045] (A) evenly coating the active material slurry on the current collector and drying it to form the positive and negative electrode sheets;

[0046] (B) Control the width of the separator, negative electrode sheet, and positive electrode sheet to be consistent, and then wind or stack the basic unit consisting of negative electrode-separator-positive electrode to form a battery cell;

[0047] (C) dissolving the insulating material in a solvent to form an insulating glue; immersing the end face area of ​​the battery cell in step (B) in the insulating glue, and then drying to obtain a battery cell with an insulating region coating structure;

[0048] (D) The battery cell containing the insulating area coating structure is sequentially hot-pressed, shelled, liquid-injected, and sealed to obtain a lithium-ion battery cell.

[0049] The present invention provides a method for preparing a lithium-ion battery cell. This method utilizes an insulating adhesive to immerse the entire edge of the cell, creating uniformly sized active material regions. This effectively eliminates edge effects caused by poor alignment and inconsistent electrode sizes. Therefore, the method offers the technical advantages of simple processing and ease of operation.

[0050] Figure 1 This is a flow chart of the preparation of lithium-ion battery cells for this application.

[0051] Combine Figure 1 , a lithium-ion battery cell of the present application comprises the following steps:

[0052] S01. Evenly apply the slurry composed of active materials on the current collector and dry it to form positive and negative electrode sheets.

[0053] S02. Control the width of the separator, negative electrode sheet, and positive electrode sheet to be consistent, and then wind or stack the basic unit consisting of negative electrode-separator-positive electrode to form a battery cell (JR) without overhang (extension).

[0054] S03. Dissolve an insulating material such as an adhesive in a suitable solvent to form an insulating glue.

[0055] S04. Immerse the non-overhang battery cell in insulating glue to a certain depth and for a certain period of time.

[0056] S05. The dried battery cells are subjected to processes such as hot pressing, shelling, liquid injection, and sealing.

[0057] S06. Finally, a lithium-ion battery cell without edge effect is obtained by assembly.

[0058] In a preferred embodiment of the present invention, the current collector in step (A) comprises a metal current collector or a composite current collector, wherein:

[0059] The metal current collector includes one or more of copper foil and aluminum foil;

[0060] The composite current collector includes one or more of PET, PP insulating plastic copper-plated or aluminum-plated foil materials.

[0061] In a preferred embodiment of the present invention, the active materials in step (A) include ternary materials (NCM), lithium iron phosphate (LFP), lithium iron manganese phosphate (LFMP), lithium manganese oxide (LMO), lithium-rich manganese-based positive electrode materials and graphite, silicon-carbon negative electrode (SiC), silicon oxygen negative electrode (SiO), lithium titanate (LTO), tin-based negative electrode and other negative electrode materials.

[0062] In a preferred embodiment of the present invention, the insulating material in step (C) comprises one or more of polyvinylidene fluoride, polyimide, polyamide-imide and styrene-butadiene rubber.

[0063] In a preferred embodiment of the present invention, in step (C), the time for immersing the edge area of ​​the end face of the battery cell in the insulating adhesive is 10 seconds to 5 minutes, preferably 1-3 minutes.

[0064] In a preferred embodiment of the present invention, in step (C), the depth of the edge area of ​​the end face of the battery cell immersed in the insulating glue is 0.5 mm to 2 mm.

[0065] The present invention provides a lithium ion battery, which includes the above-mentioned lithium ion battery cell.

[0066] The present invention provides an electrical device, which includes the lithium-ion battery mentioned above.

[0067] The technical solution of the present invention will be further described below with reference to embodiments.

[0068] Example 1

[0069] A method for preparing a lithium-ion battery cell, the method comprising the following steps:

[0070] (1) Preparation of positive electrode sheet: In this embodiment, 12 μm thick aluminum foil is used as the positive electrode current collector, and 8 series ternary material is used as the positive electrode active material. The ternary material, conductive agent and PVDF dissolved in NMP are made into positive electrode slurry, wherein the mass ratio of each component is ternary material: conductive agent: PVDF = 100:1.3:1.8.

[0071] The prepared slurry is evenly coated on the aluminum foil, and then dried, slit, and cut into pieces to make positive electrode sheets with a width of 60 mm.

[0072] (2) Preparation of negative electrode sheet: Use 6um thick copper foil as negative electrode current collector and graphite as negative electrode active material. Mix graphite, conductive agent and glue made of SBR, sodium carboxymethyl cellulose (CMC) and water to form negative electrode slurry, wherein the mass ratio of each component is graphite: conductive agent: SBR: CMC = 100:1:1.4:1.8.

[0073] The negative electrode slurry is evenly coated on the copper foil, and then dried, cut and cut into pieces to make negative electrode sheets with a width of 60 mm.

[0074] (3) Prepare a battery cell: Wind the positive and negative electrode sheets and the separator according to the basic unit consisting of negative electrode-separator-positive electrode to form a wound battery cell; the width of the separator is 60 mm;

[0075] The widths of the positive electrode sheet, the negative electrode sheet and the separator in the battery cell are the same;

[0076] Figure 2 Schematic diagram of the structure of the battery cell without overhang in this embodiment.

[0077] (4) Preparation of insulating glue: PVDF is dissolved in NMP to prepare insulating glue, and the mass ratio of PVDF to NMP in the insulating glue is 1:9.

[0078] Figure 3 Schematic diagram of the structure of the battery cell including the insulating area in this embodiment.

[0079] (5) Immerse the end face area of ​​the battery cell in the insulating glue prepared in step (4) for 1 minute, with an immersion depth of 0.5 mm. Then, the battery cell is sequentially subjected to drying, hot pressing, shelling, liquid injection, and sealing steps to assemble into a lithium-ion battery cell.

[0080] Example 2

[0081] This embodiment is the same as the embodiment 1 except that the immersion depth of the end face area of ​​the battery cell in the insulating glue in step (5) is 2 mm.

[0082] Example 3

[0083] This embodiment is the same as the embodiment 1 except that the immersion depth of the end face area of ​​the battery cell in the insulating glue in step (5) is 1 mm.

[0084] Example 4

[0085] This embodiment is the same as the embodiment 1 except that the immersion depth of the end face area of ​​the battery cell in the insulating glue in step (5) is 1.5 mm.

[0086] Example 5

[0087] In this embodiment, the insulating material in step (4) is styrene-butadiene rubber, and the insulating glue is prepared by dissolving styrene-butadiene rubber in an aqueous solution of CMC. The mass ratio of styrene-butadiene rubber, CMC and water is 15:13:47, and the rest is the same as in Example 1.

[0088] Example 6

[0089] In this embodiment, in step (5), the end face area of ​​the battery cell is immersed in the insulating glue of step (4) for 3 minutes, and the rest is the same as in embodiment 1.

[0090] Example 7

[0091] In this embodiment, in step (5), the end face area of ​​the battery cell is immersed in the insulating glue of step (4) for 5 minutes, and the rest is the same as in embodiment 1.

[0092] Example 8

[0093] In this embodiment, in step (5), the end face area of ​​the battery cell is immersed in the insulating glue of step (4) for 10 seconds, and the rest is the same as in embodiment 1.

[0094] Comparative Example 1

[0095] A method for preparing a lithium-ion battery cell, the method comprising the following steps:

[0096] (1) Preparation of positive electrode sheet: same as in Example 1.

[0097] (2) Preparation of negative electrode sheet: The negative electrode sheet of this comparative example is the same as that of Example 1 except that the width is 61.5 mm;

[0098] (3) Prepare a battery cell: Wind the positive and negative electrode sheets and the separator into a basic unit consisting of a negative electrode-separator-positive electrode to form a battery cell; the width of the separator is 63.5 mm;

[0099] (4) The battery cell prepared in step (3) is sequentially subjected to drying, hot pressing, shelling, liquid injection, and sealing steps to assemble a comparative lithium-ion battery cell.

[0100] Comparative Example 2

[0101] In Comparative Example 2, the edge area of ​​the end face of the battery cell is immersed in the insulating glue to a depth of 2.5 mm, and the rest is the same as in Example 1.

[0102] Experimental Example 1

[0103] In order to demonstrate that the lithium-ion battery cells of the present application have no edge effect, the cells prepared in Examples 1 to 4 and Comparative Example 1 were subjected to cycle testing and verification according to the following steps:

[0104] The battery was charged at a constant current of 3.5C to 4.2V, then charged at a constant voltage of 4.2V until the current was less than 0.1C, and discharged at 7.5C to 2.5V. Capacity recovery was performed every 100 cycles at a charge and discharge rate of 0.1C. The test temperature was 25°C. After 500 cycles, the specific results are shown in Table 1.

[0105] Table 1:

[0106] Group Initial capacity Remaining capacity (Ah) Capacity retention rate (%) Example 1 3.972 3.107 78.22 Example 2 3.871 3.02 78.01 Example 3 3.984 3.124 78.41 Example 4 3.903 3.062 78.45 Example 5 3.978 3.103 78.01 Example 6 3.978 3.112 78.23 Example 7 3.978 3.110 78.18 Example 8 3.977 3.103 78.02 Comparative Example 1 3.999 2.542 63.57 Comparative Example 2 3.797 2.986 78.64

[0107] Figure 4 It is the cycle test capacity retention rate of Example 1 and Comparative Example 1 at 25°C.

[0108] As can be seen from the above, the experimental cells of Examples 1 to 4 and Example 5 of the present application using styrene-butadiene rubber as the insulating material have a significant advantage in capacity retention after 500 cycles compared to the conventional lithium-ion battery cell with an overhang design in Comparative Example 1. However, the conventional lithium-ion battery cell with an overhang design in Comparative Example 1 cannot achieve the same performance as the present application in terms of both residual capacity and capacity retention.

[0109] Examples 6 to 8 are examples of the present application that investigate the time for which the end face of the battery cell is immersed in the insulating adhesive. According to the results in Table 1, it can be seen that the embodiments with an immersion time of 10 seconds to 5 minutes all have a good battery cell capacity retention rate.

[0110] Furthermore, the depth of immersion of the edge regions of the cell end faces in the insulating adhesive significantly impacted the capacity of the resulting lithium-ion battery cell. For example, in Comparative Example 2, when the immersion depth was greater than 2 mm (2.5 mm), while the cell had a relatively good capacity retention rate, both the initial capacity and the residual capacity of the lithium-ion battery cell showed a significant decrease.

[0111] In summary, the embodiments of the present invention can effectively avoid the edge effect caused by the overhang size and greatly improve the safety of the battery cell. At the same time, since there is no edge lithium deposition to consume active lithium, the cycle stability of the battery cell can be effectively improved.

[0112] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A lithium-ion battery cell, characterized in that: The lithium-ion battery cell is formed by a positive electrode sheet, a negative electrode sheet and a separator arranged between the two, and the positive electrode sheet, the negative electrode sheet and the separator in the cell have the same width; An insulating region covering structure is provided on the end surface area of ​​the battery core, and the width of the insulating region covering structure is 0.5 to 2 mm.

2. The lithium-ion battery cell according to claim 1, characterized in that When the battery core is a wound part, the positive electrode sheet, the negative electrode sheet and the separator are of the same size in the height direction, and the end surface of the wound part in the height direction is provided with an insulating area covering structure.

3. The lithium-ion battery cell according to claim 1, characterized in that When the battery core is a laminate, the positive electrode sheet and the negative electrode sheet have the same length, and an insulating region covering structure is provided on the end surface of the laminate in the length direction.

4. The lithium-ion battery cell according to any one of claims 1 to 3, characterized in that: The insulating material in the insulating region coating structure includes one or more of polyvinylidene fluoride, polyimide, polyamide-imide and styrene-butadiene rubber.

5. A method for preparing a lithium-ion battery cell according to any one of claims 1 to 4, characterized in that: The preparation method comprises the following steps: (A) evenly coating the active material slurry on the current collector and drying it to form the positive and negative electrode sheets; (B) Control the width of the separator, negative electrode sheet, and positive electrode sheet to be consistent, and then wind or stack the basic unit consisting of negative electrode-separator-positive electrode to form a battery cell; (C) dissolving the insulating material in a solvent to form an insulating glue; immersing the end face area of ​​the battery cell in step (B) in the insulating glue, and then drying to obtain a battery cell with an insulating region coating structure; (D) The battery cell containing the insulating area coating structure is sequentially hot-pressed, shelled, liquid-injected, and sealed to obtain a lithium-ion battery cell.

6. The method for preparing a lithium-ion battery cell according to claim 5, wherein: The insulating material in step (C) includes one or more of polyvinylidene fluoride, polyimide, polyamide-imide and styrene-butadiene rubber.

7. The method for preparing a lithium-ion battery cell according to claim 5, wherein: In the step (C), the time for the edge area of ​​the end face of the battery cell to be immersed in the insulating glue is 10 seconds to 5 minutes.

8. The method for preparing a lithium-ion battery cell according to claim 5, wherein: In the step (C), the edge area of ​​the end face of the battery cell is immersed in the insulating glue to a depth of 0.5 mm to 2 mm.

9. A lithium-ion battery, characterized in that: It comprises the lithium-ion battery cell according to any one of claims 1 to 4.

10. An electrical device, characterized in that: The electric device includes the lithium-ion battery according to claim 9.

Images