Battery cell assembly and lithium-ion battery

Abstract

The present application belongs to the technical field of chemical batteries. Disclosed are a battery cell assembly and a lithium-ion battery. The battery cell assembly comprises a separator, a negative electrode sheet and a positive electrode sheet, wherein the negative electrode sheet is separated from the positive electrode sheet by means of the separator; the separator comprises a separator body and an edge portion, the projection of the positive electrode sheet on the separator coincides with the separator body, and the edge portion is located on a side portion of the separator body and exposed out of the negative electrode sheet and the positive electrode sheet; and the ion transmittance of the edge portion is less than the ion transmittance of the separator body. Even if the value of overhang between the negative electrode sheet and the positive electrode sheet is decreased due to a winding operation or a lamination operation on the battery cell assembly, the characteristic of the edge portion of the separator hindering the passage of ions can effectively prevent the ions from passing therethrough, thereby effectively reducing the risks of short circuits and lithium deposition caused by a decrease in the value of overhang between positive and negative electrodes.

Description

Battery components and lithium-ion batteries

[0001] This application claims priority to Chinese patent application number 202311455999.4, filed on November 3, 2023, entitled “Battery Cell Assembly and Lithium-ion Battery,” the entire contents of which are incorporated herein by reference. Technical Field

[0002] The present disclosure relates to the technical field of chemical batteries, and in particular to battery cell components and lithium-ion batteries. Background Art

[0003] In a lithium-ion battery cell, the positive and negative electrodes are separated by a separator. The negative electrode, as well as the separator, are designed to have an overhang relative to the positive electrode, to isolate the end regions of the positive and negative electrodes, thus preventing problems such as lithium deposition and lithium dendrites. Currently, lithium-ion battery cell manufacturing methods include winding or stacking. The winding method, in particular, makes it difficult to control the end positions of the electrodes, thereby reducing the overhang between the negative and positive electrodes, resulting in poor overhang.

[0004] In the related art, after the winding operation or the stacking operation, the obtained battery cell products are usually subjected to X-Ray testing to separate the battery cell products with unqualified overhang. However, this method not only affects the product yield, but also leads to higher costs.

[0005] Public content

[0006] In order to solve the technical problem that the overhang value between the negative electrode sheet and the positive electrode sheet of the battery cell assembly provided by the related technology is reduced after the winding operation or stacking operation, resulting in poor overhang, the embodiments of the present disclosure provide a battery cell assembly and a lithium-ion battery to solve this technical problem.

[0007] In one aspect, a battery cell assembly is provided, comprising: a separator, a negative electrode sheet, and a positive electrode sheet, wherein the negative electrode sheet and the positive electrode sheet are separated by the separator;

[0008] The diaphragm includes a diaphragm body and an edge portion, the projection of the positive electrode sheet on the diaphragm coincides with the diaphragm body, and the edge portion is located on the side of the diaphragm body and exposed outside the negative electrode sheet and the positive electrode sheet;

[0009] The ion permeability of the edge portion is lower than the ion permeability of the diaphragm body.

[0010] The battery cell assembly provided by the embodiments of the present disclosure comprises a diaphragm body and an edge portion, wherein the edge portion serves as the overhang region of the diaphragm 1 relative to the negative and positive electrode sheets. Since the ion permeability of the edge portion is lower than that of the diaphragm body, the passage of ions in the electrolyte, such as lithium ions, is blocked. Even if the overhang value between the negative and positive electrode sheets is reduced due to winding or lamination operations, the ion-blocking property of the edge portion of the diaphragm 1 can effectively prevent the passage of ions, thereby effectively reducing the risk of short circuits and lithium deposition caused by the reduction in the overhang value of the positive and negative electrodes.

[0011] In some possible implementations, the porosity of the edge portion is smaller than the porosity of the diaphragm body, so that the ion permeability of the edge portion is smaller than the ion permeability of the diaphragm body.

[0012] In some possible implementations, the porosity of the edge portion is 0% to 90% of the porosity of the diaphragm body. Further, the porosity of the edge portion is 0% to 50% of the porosity of the diaphragm body, which further includes 0% to 40%, 0% to 30%, 0% to 20%, 0% to 10%, 0% to 5%, etc.

[0013] In some possible implementations, the air permeability of the edge portion is lower than the air permeability of the diaphragm body, so that the ion permeability of the edge portion is lower than the ion permeability of the diaphragm body.

[0014] In some possible implementations, the air permeability of the edge portion is 0% to 90% of the air permeability of the diaphragm body. Further, the air permeability of the edge portion is 0% to 50% of the air permeability of the diaphragm body, which further includes 0% to 40%, 0% to 30%, 0% to 20%, 0% to 10%, 0% to 5%, etc.

[0015] In some possible implementations, the edge portion is a closed-pore structure, that is, the air permeability of the edge portion is 0, or the porosity of the edge portion is 0, thereby completely ensuring that lithium ions cannot pass through the edge portion.

[0016] In some possible implementations, the edge portion includes: an edge portion body and an ion barrier coating located on a surface of the edge portion body, and the ion permeability of the ion barrier coating is lower than the ion permeability of the diaphragm body.

[0017] In some possible implementations, the porosity of the ion barrier coating is 0% to 90% of the porosity of the diaphragm body;

[0018] and / or,

[0019] The air permeability of the ion barrier coating is 0% to 90% of the air permeability of the diaphragm body.

[0020] In some possible implementations, the edge portion is located on at least one of the first side and the second side of the diaphragm body;

[0021] The first side is the side of the diaphragm body in the width direction, and the second side is the side of the diaphragm body in the length direction.

[0022] In some possible implementations, the width of the edge portion is 1 mm to 10 mm, where the edge portion width is the distance between the outer edge of the edge portion and the outer edge of the positive electrode tab. By limiting the edge portion width to this range, the separator is ensured to effectively block ions in the overhang region between the positive and negative electrodes, preventing ions from flowing.

[0023] In some possible implementations, the edge portion is obtained by performing at least one of the following treatments on the edge region of the diaphragm: heating treatment, extrusion treatment, gluing treatment, multi-layer diaphragm composite treatment, and strip composite treatment.

[0024] In some possible implementations, the diaphragm is selected from at least one of a single-layer or multi-layer polypropylene diaphragm, a polyethylene diaphragm, and a polypropylene-polyethylene composite diaphragm;

[0025] Alternatively, the diaphragm includes a diaphragm substrate and an insulating coating located on the surface of the diaphragm substrate, and the diaphragm substrate is selected from at least one of a single-layer or multi-layer polypropylene diaphragm, a polyethylene diaphragm, and a polypropylene-polyethylene composite diaphragm.

[0026] In some possible implementations, the battery cell assembly is a wound structure or a laminated structure.

[0027] On the other hand, a lithium-ion battery is provided, comprising a shell and a cell assembly located inside the shell, wherein the cell assembly is as described above.

[0028] The lithium-ion battery provided by the embodiment of the present disclosure has all the advantages of the battery cell assembly provided by the embodiment of the present disclosure. In addition, the use of the battery cell assembly can effectively improve the product yield of the lithium-ion battery and reduce costs.

[0029] Illustratively, lithium-ion batteries include, but are not limited to, lithium iron phosphate system batteries, lithium cobalt oxide system batteries, lithium manganese oxide system batteries, ternary system lithium-ion batteries, and the like.

[0030] Illustratively, the lithium-ion battery may be a wound battery or a stacked battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] FIG1 is a schematic diagram of the arrangement structure of a battery cell assembly in an overhang non-displacement state in the related art;

[0032] FIG2 is a schematic diagram of the arrangement structure of the battery cell assembly in an overhang misalignment state in the related art;

[0033] FIG3 is a schematic diagram of the arrangement structure of the battery cell assembly provided by an embodiment of the present disclosure in an overhang non-misaligned state;

[0034] FIG4 is a schematic diagram of the arrangement structure of the battery cell assembly in an overhang misalignment state provided by an embodiment of the present disclosure;

[0035] FIG5 is a schematic structural diagram of an exemplary diaphragm provided by an embodiment of the present disclosure in a flattened state;

[0036] FIG6 is a front cross-sectional view of an exemplary battery cell assembly provided by an embodiment of the present disclosure;

[0037] FIG. 7 is a cross-sectional view of an edge portion of another exemplary diaphragm provided by an embodiment of the present disclosure.

[0038] 1 to 4 , the diaphragm is partially cut and does not completely cover the negative electrode sheet, so as to show the arrangement relationship between the diaphragm, the negative electrode sheet and the positive electrode sheet.

[0039] The reference numerals represent: 1. diaphragm; 11. diaphragm body; 12. edge portion; 121. edge portion body; 122. ion barrier coating; 2. negative electrode plate; 3. positive electrode plate. DETAILED DESCRIPTION

[0040] For lithium-ion battery cells, the positive electrode and the negative electrode are separated by a separator. The negative electrode is designed to have an overhang relative to the positive electrode, and the separator is designed to have an overhang relative to the positive and negative electrode sheets, so that the end areas of the positive and negative electrode sheets are isolated to avoid problems such as lithium plating and lithium dendrites.

[0041] Referring to Figure 1 , the overhang of the separator 1 relative to the positive electrode sheet 3 refers to the portion of the separator 1 that extends beyond the positive electrode sheet 3, and the overhang of the separator 1 relative to the negative electrode sheet 2 refers to the portion of the separator 1 that extends beyond the negative electrode sheet 2. As shown in Figure 1 , the overhang of the separator 1 relative to the positive electrode sheet 3 is defined as A1, the overhang of the separator 1 relative to the negative electrode sheet 2 is defined as A2, and the overhang of the negative electrode sheet 2 relative to the positive electrode sheet 3 is defined as A3.

[0042] Currently, lithium-ion battery cell manufacturing methods include winding or lamination. The winding method, in particular, makes it difficult to control the end position of the electrode, resulting in abnormal misalignment of the overhang area, reducing the overhang value and causing poor overhang. For example, referring to Figure 2, it illustrates that after winding or lamination, the overhang A3 of the negative electrode electrode 2 relative to the positive electrode electrode 3 is reduced, and the overhang of the separator 1 relative to both the positive electrode electrode 3 and the negative electrode electrode 2 is reduced, resulting in a greater risk of lithium plating at the negative electrode.

[0043] In response to the above technical problems, the relevant technology usually performs X-Ray testing on the obtained battery cell products after the winding operation or stacking operation to separate the battery cell products with unqualified overhang. However, this method not only affects the product yield, but also leads to higher costs.

[0044] In response to the technical problems existing in the related technologies, on the one hand, an embodiment of the present disclosure provides a battery cell assembly, as shown in Figure 3, the battery cell assembly includes: a diaphragm 1, a negative electrode plate 2 and a positive electrode plate 3, and the negative electrode plate 2 and the positive electrode plate 3 are separated by the diaphragm 1.

[0045] As further shown in FIG5 , the diaphragm 1 includes a diaphragm body 11 and an edge portion 12. The projection of the positive electrode tab 3 on the diaphragm 1 coincides with the diaphragm body 11. The edge portion 12 is located on the side of the diaphragm body 11 and is exposed to the outside of the negative electrode tab 2 and the positive electrode tab 3. The ion permeability of the edge portion 12 is lower than that of the ion permeability of the diaphragm body 11.

[0046] It should be noted that the "diaphragm body 11" involved in the embodiment of the present disclosure refers to the battery separator 1 in the traditional sense, whose function is to isolate the positive electrode plate 3 and the negative electrode plate 2 so that electrons cannot pass through freely, prevent the two from short-circuiting due to contact, and allow ions in the electrolyte to pass freely.

[0047] The “edge portion 12 ” involved in the embodiment of the present disclosure refers to the overhang area of ​​the diaphragm 1 located at the edge of the diaphragm body 11 . Different from the traditional battery diaphragm 1 , the edge portion 12 blocks the passage of ions in the electrolyte.

[0048] The “projection of the positive electrode sheet 3 on the diaphragm 1 coincides with the diaphragm body 11 ” involved in the embodiments of the present disclosure means that the projection of the positive electrode sheet 3 on the diaphragm 1 is the same as the shape and size of the diaphragm body 11 , and the edges of the two are flush, so that the edge portion 12 is simultaneously located on the side of the projection of the positive electrode sheet 3 on the diaphragm 1 , that is, the edge portion 12 serves as the overhang area of ​​the diaphragm 1 relative to the negative electrode sheet 2 and the positive electrode sheet 3 .

[0049] 6 , in this application, the overhang of the diaphragm 1 relative to the positive electrode sheet 3 is defined as A1 , the overhang of the diaphragm 1 relative to the negative electrode sheet 2 is defined as A2 , and the overhang of the negative electrode sheet 2 relative to the positive electrode sheet 3 is defined as A3 .

[0050] The battery cell assembly provided by the embodiment of the present disclosure comprises a diaphragm 1 including a diaphragm body 11 and an edge portion 12, wherein the edge portion 12 serves as the overhang area of ​​the diaphragm 1 relative to the negative electrode plate 2 and the positive electrode plate 3. Since the ion permeability of the edge portion 12 is lower than the ion permeability of the diaphragm body 11, the ions in the electrolyte, such as lithium ions, are blocked from passing through. Even if the overhang value between the negative electrode plate 2 and the positive electrode plate 3 is reduced due to a winding operation or a lamination operation of the battery cell assembly (see FIG4 ), the characteristic of the edge portion 12 of the diaphragm 1 that blocks the passage of ions can effectively prevent the ions from passing through, thereby effectively reducing the risk of short circuit and lithium deposition caused by the reduction in the overhang value of the positive and negative electrodes.

[0051] As described above, the ion permeability of the edge portion 12 of the diaphragm 1 is lower than the ion permeability of the diaphragm body 11 . For example, when the battery cell assembly is a battery cell assembly of a lithium-ion battery, the lithium ion permeability of the edge portion 12 is lower than the lithium ion permeability of the diaphragm body 11 .

[0052] In some implementations, the ion permeability of the edge portion 12 is 0% to 70% of the ion permeability of the diaphragm body 11, and can further be 0% to 50%, 0% to 40%, 0% to 30%, 0% to 20%, 0% to 10%, etc.

[0053] Ways to adjust the ion permeability of the edge portion 12 include, but are not limited to, at least one of adjusting the pore characteristics of the edge portion 12 and adjusting the material of the edge portion 12 .

[0054] For example, adjusting the pore characteristics of the edge portion 12 can be achieved by reducing the porosity, pore size, pore penetration, air permeability, etc. For example, adjusting the material of the edge portion 12 can be achieved by selecting a dense material to prepare the edge portion 12.

[0055] In some implementations (1), the porosity of the edge portion 12 is made smaller than the porosity of the diaphragm body 11 , thereby making the ion permeability of the edge portion 12 smaller than the ion permeability of the diaphragm body 11 .

[0056] The “porosity” referred to in the embodiments of the present disclosure refers to the percentage of the pore volume in the material to the total volume of the material in its natural state.

[0057] Factors affecting porosity include membrane thickness, membrane pore size, membrane pore size distribution, pore shape and tortuosity, etc. Therefore, by adjusting at least one of the above factors, the porosity can be adjusted accordingly.

[0058] In this implementation, the edge portion 12 and the diaphragm body 11 can be made of the same material, and the porosity of the edge portion 12 can be smaller than that of the diaphragm body 11. This implementation is conducive to simplifying the preparation process of the diaphragm 1 and reducing costs.

[0059] In some examples, the porosity of the edge portion 12 is 0% to 90% of the porosity of the diaphragm body 11. Further, the porosity of the edge portion 12 is 0% to 50% of the porosity of the diaphragm body 11, which further includes 0% to 40%, 0% to 30%, 0% to 20%, 0% to 10%, 0% to 5%, etc.

[0060] In some examples, the porosity of the edge portion 12 is 0%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, etc., of the porosity of the diaphragm body 11.

[0061] By ensuring the porosity of the edge portion 12 is within the above range, the edge portion 12 has excellent lithium-ion barrier properties, thereby mitigating or curbing the risks of short circuits and lithium deposition caused by reduced positive and negative electrode overhang. Testing has shown that when the porosity of the edge portion 12 is 50% of the porosity of the separator body 11, risks such as short circuits, lithium deposition, and lithium dendrites can be effectively avoided.

[0062] In some implementations (2), the air permeability of the edge portion 12 is made smaller than that of the diaphragm body 11 , thereby making the ion permeability of the edge portion 12 smaller than that of the diaphragm body 11 .

[0063] The "air permeability" involved in the embodiments of the present disclosure refers to the time required for a certain amount of gas to pass through a unit area under a unit pressure difference, which can also be called the Gurley index.

[0064] Factors affecting air permeability include membrane thickness, membrane porosity, membrane pore size, membrane pore size distribution, pore shape and tortuosity, etc. Therefore, by adjusting at least one of the above factors, the air permeability can be adjusted accordingly.

[0065] In this implementation, the edge portion 12 and the diaphragm body 11 can be made of the same material, and the air permeability of the edge portion 12 can be lower than that of the diaphragm body 11. This implementation is conducive to simplifying the preparation process of the diaphragm 1 and reducing costs.

[0066] In some examples, the air permeability of the edge portion 12 is 0% to 90% of the air permeability of the diaphragm body 11. Further, the air permeability of the edge portion 12 is 0% to 50% of the air permeability of the diaphragm body 11, which further includes 0% to 40%, 0% to 30%, 0% to 20%, 0% to 10%, 0% to 5%, etc.

[0067] In some examples, the permeability of the edge portion 12 is 0%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, etc. of the permeability of the diaphragm body 11.

[0068] By ensuring the air permeability of the edge portion 12 is within the above range, the edge portion 12 has excellent lithium ion barrier properties, thereby mitigating or curbing the risks of short circuits and lithium deposition caused by reduced positive and negative electrode overhang. Testing has shown that when the air permeability of the edge portion 12 is 50% of that of the separator body 11, risks such as short circuits, lithium deposition, and lithium dendrites can be effectively avoided.

[0069] For the above-mentioned implementation methods (1) and (2), the smaller the porosity or permeability of the edge portion 12, the more advantageous it is in preventing the passage of ions. In some examples, for the above-mentioned implementation methods (1) and (2), the edge portion 12 can be made into a closed-pore structure, that is, the permeability of the edge portion 12 is 0, or the porosity of the edge portion 12 is 0, thereby completely ensuring that lithium ions will not pass through the edge portion 12.

[0070] In some implementations (3), as shown in FIG7 , the edge portion 12 includes an edge portion body 121 and an ion barrier coating 122 located on the surface of the edge portion body 121 , and the ion permeability of the ion barrier coating 122 is lower than the ion permeability of the diaphragm body 11 .

[0071] In this implementation, an ion barrier coating 122 with low ion permeability is provided on the surface of the edge portion body 121 , and based on the low ion permeability of the ion barrier coating 122 , the ion permeability of the edge portion 12 is lower than that of the diaphragm body 11 .

[0072] Illustratively, the porosity of the ion barrier coating 122 is 0% to 90% of the porosity of the diaphragm body 11, further including 0% to 50%, 0% to 40%, 0% to 30%, 0% to 20%, 0% to 10%, 0% to 5%, etc.

[0073] And / or, the air permeability of the ion barrier coating 122 is 0% to 90% of the air permeability of the diaphragm body 11, further including 0% to 50%, 0% to 40%, 0% to 30%, 0% to 20%, 0% to 10%, 0% to 5%, etc.

[0074] Among them, by ensuring that the porosity and / or permeability of the ion barrier coating 122 is within the above range, the edge portion 12 can have good lithium ion barrier properties, thereby alleviating or curbing the risks of short circuit and lithium deposition caused by the reduction of the positive and negative electrode overhang values.

[0075] Illustratively, the ion barrier coating 122 may be a dense polymer coating, such as acrylic resin, polyurethane resin, polyester resin, etc.

[0076] In some examples, the ion barrier coating 122 can be prepared by a solution method, a sol-gel method, a plasma polymerization method, or the like.

[0077] For this implementation (3), the ion permeability of the edge portion body 121 may be less than the ion permeability of the diaphragm body 11 , or may be equal to the ion permeability of the diaphragm body 11 .

[0078] When the ion permeability of the edge portion body 121 is lower than that of the ion permeability of the diaphragm body 11, the edge portion body 121 may have the porosity or air permeability characteristics of the edge portion 12 as described in the above implementation (1) or implementation (2). This solution is more advantageous for enhancing the ion barrier properties of the edge portion 12 and making the ion barrier properties of the edge portion 12 more stable, thereby extending its service life.

[0079] When the ion permeability of the edge portion body 121 is equal to that of the diaphragm body 11, the structure and material of the edge portion body 121 can be the same as those of the diaphragm body 11. For example, the edge portion body 121 and the diaphragm body 11 can be manufactured using an integrated molding process. This solution is more advantageous for simplifying the manufacturing process of the diaphragm 1.

[0080] In some implementations, as shown in FIG5 , the edge portion 12 of the diaphragm 1 is located on at least one of the first side D1 and the second side D2 of the diaphragm body 11 , wherein the first side D1 is the side in the width direction of the diaphragm body 11 and the second side D2 is the side in the length direction of the diaphragm body 11 .

[0081] Typically, the separator 1 , the negative electrode sheet 2 , and the positive electrode sheet 3 are all in the shape of rectangular strips. The extending direction of the short sides of the three is called the width direction, and the extending direction of the long sides of the three is called the length direction.

[0082] For example, referring to FIG. 5 , it is illustrated that the side of the diaphragm body 11 in the width direction is the first side D1 , and the side of the diaphragm body 11 in the length direction is the second side D2 .

[0083] In one example, the edge portion 12 of the diaphragm 1 may be located on the first side D1 of the diaphragm body 11 . Further, the edge portion 12 of the diaphragm 1 may be located on one or both of two oppositely arranged first sides D1 of the diaphragm body 11 .

[0084] In another example, the edge portion 12 of the diaphragm 1 may be located on the second side D2 of the diaphragm body 11 . Further, the edge portion 12 of the diaphragm 1 may be located on one or both of two oppositely arranged second sides D2 of the diaphragm body 11 .

[0085] Another example is that the edge portion 12 of the diaphragm 1 can be located on the first side D1 and the second side D2 of the diaphragm body 11 at the same time. Further, the edge portion 12 of the diaphragm 1 can be located on one or both of the two oppositely arranged first sides D1 of the diaphragm body 11, and also on one or both of the two oppositely arranged second sides D2 of the diaphragm body 11.

[0086] In some embodiments, the edge portion 12 of the diaphragm 1 may be located on both first sides D1 and both second sides D2 of the diaphragm body 11 . That is, the edge portion 12 is arranged around the outside of the diaphragm body 11 .

[0087] In some examples, the tab side of the positive electrode plate 3 and the negative electrode plate 2 is consistent with one of the first sides D1 of the diaphragm body 11, that is, the first side D1 of the diaphragm body 11 is consistent with the direction of the tab side of the electrode plate and the non-tab side opposite thereto.

[0088] For the edge portion 12, the pore structure characteristics thereon can be consistent or variable, and the variation can be linear or random, as long as any area on the edge portion 12 can achieve effective barrier to lithium ions.

[0089] In some implementations, as shown in FIG5 , the width L of the edge portion 12 is 1 mm to 10 mm. The width L of the edge portion 12 is the distance between the outer edge of the edge portion 12 and the outer edge of the positive electrode tab 3 , and is also the dimension of the short side of the edge portion 12 . Also, referring to FIG5 , the width of the edge portion 12 can also be considered the overhang of the separator 1 relative to the positive electrode tab 3 .

[0090] In addition, the width L of the edge portion 12 mentioned here includes not only the width of the edge portion 12 located on the first side D1 of the diaphragm body 11 , but also the width of the edge portion 12 located on the second side D2 of the diaphragm body 11 .

[0091] Exemplarily, the width dimensions of the edge portion 12 include, but are not limited to, 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm, 5 mm, 5.5 mm, 6 mm, 6.5 mm, 7 mm, 7.5 mm, 8 mm, 8.5 mm, 9 mm, 9.5 mm, 10 mm, etc.

[0092] By limiting the width of the edge portion 12 to the above range, the separator 1 is ensured to effectively block ions in the overhang region between the positive and negative electrodes, thereby preventing ions from flowing.

[0093] The edge portion 12 includes a first part and a second part, the first part of the edge portion 12 is opposite to the overhang area of ​​the negative electrode plate 2 relative to the positive electrode plate 3 (that is, the projection of the overhang area of ​​the negative electrode plate 2 relative to the positive electrode plate 3 on the edge portion 12 coincides with the first part of the edge portion 12), and the second part of the edge portion 12 is located outside the negative electrode plate 2.

[0094] The distance between the outer edge of the edge portion 12 and the outer edge of the negative electrode sheet 2 is the width dimension of the second part of the edge portion 12 . The width dimension of the second part of the edge portion 12 can also be considered as the overhang dimension of the separator 1 relative to the negative electrode sheet 2 .

[0095] In some examples, the width of the second portion of the edge portion 12 is 1 mm to 5 mm, including but not limited to: 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm, 5 mm, etc.

[0096] In the embodiment of the present disclosure, the edge portion 12 is obtained by performing at least one of the following treatments on the edge area of ​​the diaphragm 1: heating treatment, extrusion treatment, glue coating treatment, multi-layer diaphragm 1 composite treatment, and strip composite treatment.

[0097] The heat treatment is suitable for treating the polymer material diaphragm 1. The polymer material is heated to melt to achieve the purpose of shrinking the pores or even closing the pores, thereby obtaining the edge portion 12 with a low ion pass rate.

[0098] In some examples, the heating process is a hot pressing process, that is, heating and pressing, so as to achieve low porosity and / or low air permeability characteristics of the edge portion 12. Moreover, after the heating process, the thickness of the edge portion 12 is less than the thickness of the diaphragm body 11.

[0099] For example, the hot pressing time is controlled according to the material of the edge portion 12 or the required porosity or air permeability. For example, the hot pressing time may be 2s to 10s.

[0100] Testing has shown that, for polypropylene edge portions 12, after 5 seconds of heat pressing, the cells in the edge portion 12 are closed, resulting in a closed-cell structure and a transparent appearance. Furthermore, for polyethylene edge portions 12, after 3 seconds of heat pressing, the cells in the edge portion 12 are closed, resulting in a closed-cell structure and a white or off-white appearance.

[0101] The hot pressing treatment can be carried out using equipment such as a hot press and a winder. Of course, when using a winder, the following gluing treatment can also be carried out at the same time.

[0102] The extrusion treatment is suitable for treating the diaphragm 1 made of a polymer material. By extruding the polymer material, the micropores therein are shrunk or even closed, thereby obtaining an edge portion 12 with a low ion pass rate.

[0103] In some examples, the extrusion process may be a single-layer extrusion process or a multi-layer extrusion process, and the extrusion methods include but are not limited to: plate extrusion, roller extrusion, etc. Moreover, after the extrusion process, the thickness of the edge portion 12 is less than the thickness of the diaphragm body 11 .

[0104] The glue coating process is not only suitable for the diaphragm 1 made of polymer material, but also suitable for the diaphragm 1 made of ceramic material, and has strong adaptability. Some applicable glue materials include but are not limited to: acrylic resin, polyurethane resin, polyester resin, etc.

[0105] The composite treatment of the multilayer diaphragm 1 is not only suitable for diaphragms 1 made of polymer materials, but also for diaphragms 1 made of ceramic materials. It can be a composite of two layers of diaphragms 1 for the edge portion 12, or a composite treatment of three or more layers of diaphragms 1 for the edge portion 12. Through the composite treatment of the multilayer diaphragm 1, the holes in each layer of the diaphragm 1 are staggered, that is, not connected, thereby obtaining an edge portion 12 with a low ion pass rate.

[0106] The strip composite treatment is not only suitable for polymer diaphragms 1, but also for ceramic diaphragms 1. It can use densely structured tapes or other strips to wrap the surface of the edge portion 12 of the diaphragm 1, thereby obtaining an edge portion 12 with a low ion pass rate.

[0107] One method for preparing the diaphragm 1 is to use the diaphragm 1 material to prepare a diaphragm 1 intermediate, wherein the diaphragm 1 intermediate includes the diaphragm body 11 and an edge portion intermediate located on the side of the diaphragm body 11. The edge portion intermediate is subjected to at least one of the following treatments: heating treatment, extrusion treatment, glue coating treatment, multi-layer diaphragm 1 composite treatment, and strip composite treatment to obtain the edge portion 12, thereby obtaining the diaphragm 1.

[0108] Furthermore, the edge portion intermediate is subjected to at least one of a heating treatment and an extrusion treatment, for example, a hot pressing treatment, to obtain the edge portion 12 .

[0109] In the embodiment of the present disclosure, the diaphragm 1 can be prepared using common diaphragm 1 materials, and the diaphragm 1 itself can be a single-layer membrane structure or a multi-layer membrane structure.

[0110] In some examples, the separator 1 is selected from at least one of a single-layer or multi-layer polypropylene separator 1 , a polyethylene separator 1 , and a polypropylene-polyethylene composite separator 1 .

[0111] In other examples, the diaphragm 1 includes a diaphragm substrate and an insulating coating located on the surface of the diaphragm substrate, and the diaphragm substrate is selected from at least one of a single-layer or multi-layer polypropylene diaphragm, a polyethylene diaphragm, and a polypropylene-polyethylene composite diaphragm 1.

[0112] The insulating coating also has the property of blocking electrons and allowing ions to pass through. For example, the insulating coating can be a ceramic coating or a polymer coating.

[0113] In the embodiment of the present disclosure, the battery cell assembly is a winding structure or a stacked structure. Based on the design of the edge portion 12 of the diaphragm 1, when the battery cell assembly is assembled using a winding operation or a stacking operation, even if there are problems such as electrode fluctuation, increased width error during electrode cutting, and abnormal electrode alignment, thereby causing the overhang value of the negative electrode 2 relative to the positive electrode 3 to decrease, the edge portion 12 will hinder the flow of ions between the two poles, thereby avoiding the risks of short circuit, lithium precipitation, lithium dendrites, etc.

[0114] The battery cell assembly provided in the embodiment of the present disclosure, as shown in FIG6 , may include one battery cell unit or multiple battery cell units, and adjacent battery cell units are separated by a separator 1. Each battery cell unit includes a negative electrode plate 2 and a positive electrode plate 3, and the negative electrode plate 2 and the positive electrode plate 3 are separated by the separator 1.

[0115] In summary, the battery cell assembly provided by the embodiments of the present disclosure reduces the ion permeability of the edge portion 12 of the separator 1, i.e., the overhang region, by, for example, reducing its porosity and / or permeability, thereby reducing the probability of lithium ions passing therethrough. When the edge portion 12 has a closed-pore structure, lithium ions cannot pass through the edge portion 12, thereby effectively reducing the risk of lithium plating in lithium-ion batteries due to the reduced overhang between the positive and negative electrodes.

[0116] In addition, both the negative electrode plate 2 and the positive electrode plate 3 can adopt a traditional electrode structure. For example, the overhang area of ​​the negative electrode plate 2 does not need to be designed to be inconsistent with its normal area (i.e., the non-overhang area), and the end of the positive electrode plate 3 does not need to be provided with a coating such as a ceramic coating or an at9 coating, thereby simplifying the electrode structure and improving the electrode universality.

[0117] On the other hand, an embodiment of the present disclosure further provides a lithium-ion battery, which includes a shell and a battery cell assembly located inside the shell, and the battery cell assembly is as described above.

[0118] The lithium-ion battery provided by the embodiment of the present disclosure has all the advantages of the battery cell assembly provided by the embodiment of the present disclosure. In addition, the use of the battery cell assembly can effectively improve the product yield of the lithium-ion battery and reduce costs.

[0119] The lithium-ion battery provided in the embodiment of the present disclosure also includes an electrolyte as a medium for ion migration. The lithium-ion battery provided in the embodiment of the present disclosure, its battery cell assembly may include one battery cell unit, or may include multiple battery cell units, and adjacent battery cell units are separated by a diaphragm 1. Each battery cell unit includes a negative electrode plate 2 and a positive electrode plate 3, and the negative electrode plate 2 and the positive electrode plate 3 are separated by a diaphragm 1.

[0120] The lithium-ion batteries involved in the embodiments of the present disclosure include, but are not limited to, lithium iron phosphate system batteries, lithium cobalt oxide system batteries, lithium manganese oxide system batteries, ternary system lithium-ion batteries, etc.

[0121] The lithium-ion battery involved in the embodiments of the present disclosure can be a wound battery or a stacked battery.

[0122] The following describes exemplary embodiments of the present disclosure in more detail. Although exemplary embodiments of the present disclosure are described below, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments described herein. Where specific techniques or conditions are not specified in the examples, the techniques or conditions described in the literature in the art or in the product specifications shall be followed.

[0123] The following embodiments each provide a wound battery cell assembly, as shown in FIG3 , comprising a separator 1, a negative electrode sheet 2, and a positive electrode sheet 3, wherein the negative electrode sheet 2 and the positive electrode sheet 3 are separated by the separator 1. The separator 1 comprises a separator body 11 and an edge portion 12 (i.e., an overhang region), which is disposed around the separator body 11 and exposed to the negative electrode sheet 2 and the positive electrode sheet 3. As shown in FIG5 , the edge portion 12 is located on both the first side D1 and the second side D2 of the separator body 11.

[0124] The separator 1 is a polyethylene separator, i.e., both the separator body 11 and the edge portion 12 are made of polyethylene. The thickness of the separator body 11 is 9 microns. The overhang width of the separator 1 relative to the positive electrode plate 3 (i.e., the width of the edge portion 12) is 5 mm, and the overhang width of the separator 1 relative to the negative electrode plate 2 (i.e., the width of the second portion of the edge portion 12) is 3 mm.

[0125] In the battery cell assemblies provided in the above embodiments, the preparation method of the edge portion 12, as well as the porosity and permeability parameters of the edge portion 12 are respectively shown in Table 1.

[0126] In addition, a comparative wound cell assembly is also provided as a comparative example. The difference between it and the cell assembly of the above embodiments is that its edge portion 12 (i.e., the overhang area) is the same as the diaphragm body 11, so that the permeability and porosity of the two are consistent.

[0127] After the battery cell assemblies provided in the above embodiments and comparative examples were wound and assembled, an X-ray test was performed to test whether lithium was deposited at the edge of the negative electrode 2 after the battery cell assembly had poor alignment. The test results are shown in Table 1.

[0128] Table 1

[0129] Among them, the “ / ” involved in Table 1 means that the operation does not exist. The glue applied in Example 10 and Example 11 is acrylic resin. The “no lithium deposition” involved in Table 1 means that the lithium deposition area is 0; “very slight lithium deposition” means that the lithium deposition area is less than 10% of the total area of ​​the sample; “slight lithium deposition” means that the lithium deposition area is 10% to 20% of the total area of ​​the sample; “lithium deposition” means that the lithium deposition area is greater than 20% of the total area of ​​the sample.

[0130] As can be seen from Table 1, compared with the diaphragm without any treatment in the related art, Examples 1 to 11 are based on the use of the diaphragm provided by the embodiments of the present disclosure, so that the lithium deposition at the edge of the negative electrode of the battery cell assembly after the winding operation is significantly improved.

[0131] In the embodiments of the present disclosure, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance. The term "plurality" refers to two or more, unless otherwise clearly defined.

[0132] In the present embodiment, the term "and / or" is merely a description of the association relationship between associated objects, indicating that three relationships may exist. For example, A and / or B may represent three situations: A exists alone, A and B exist at the same time, and B exists alone.

[0133] The above description is only for the purpose of facilitating those skilled in the art to understand the technical solutions of the present disclosure and is not intended to limit the present disclosure. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present disclosure shall be included in the scope of protection of the present disclosure.

Claims

1. A battery cell assembly, wherein: The battery cell assembly comprises: a diaphragm (1), a negative electrode sheet (2) and a positive electrode sheet (3), wherein the negative electrode sheet (2) and the positive electrode sheet (3) are separated from each other by the diaphragm (1); The diaphragm (1) comprises a diaphragm body (11) and an edge portion (12); the projection of the positive electrode sheet (3) on the diaphragm (1) coincides with the diaphragm body (11); the edge portion (12) is located on the side of the diaphragm body (11) and is exposed outside the negative electrode sheet (2) and the positive electrode sheet (3); The ion permeability of the edge portion (12) is lower than the ion permeability of the diaphragm body (11).

2. The battery cell assembly according to claim 1, wherein: The porosity of the edge portion (12) is smaller than the porosity of the diaphragm body (11), so that the ion permeability of the edge portion (12) is smaller than the ion permeability of the diaphragm body (11).

3. The battery cell assembly according to claim 2, wherein: The porosity of the edge portion (12) is 0% to 90% of the porosity of the diaphragm body (11).

4. The battery cell assembly according to claim 1, wherein: The air permeability of the edge portion (12) is lower than the air permeability of the diaphragm body (11), so that the ion permeability of the edge portion (12) is lower than the ion permeability of the diaphragm body (11).

5. The battery cell assembly according to claim 4, wherein: The air permeability of the edge portion (12) is 0% to 90% of the air permeability of the diaphragm body (11).

6. The battery core assembly according to any one of claims 1 to 5, wherein: The edge portion (12) is a closed-cell structure.

7. The battery cell assembly according to claim 1, wherein: The edge portion (12) comprises: an edge portion body (121) and an ion barrier coating (122) located on the surface of the edge portion body (121); the ion permeability of the ion barrier coating (122) is lower than the ion permeability of the diaphragm body (11).

8. The battery cell assembly according to claim 7, wherein: The porosity of the ion barrier coating (122) is 0% to 90% of the porosity of the diaphragm body (11); and / or, The air permeability of the ion barrier coating (122) is 0% to 90% of the air permeability of the diaphragm body (11).

9. The battery core assembly according to any one of claims 1 to 8, wherein: The edge portion (12) is located at least one of the first side and the second side of the diaphragm body (11); The first side is the side of the diaphragm body (11) in the width direction, and the second side is the side of the diaphragm body (11) in the length direction.

10. The battery cell assembly according to claim 9, wherein: The width of the edge portion (12) is 1 mm to 10 mm, wherein the width of the edge portion (12) is the distance between the outer edge of the edge portion (12) and the outer edge of the positive electrode sheet (3).

11. The battery core assembly according to any one of claims 1 to 10, wherein: The edge portion (12) is obtained by subjecting the edge region of the diaphragm (1) to at least one of the following treatments: heating treatment, extrusion treatment, glue coating treatment, multi-layer diaphragm (1) composite treatment, and strip composite treatment.

12. The battery cell assembly according to claim 9, wherein: The diaphragm (1) is selected from at least one of a single-layer or multi-layer polypropylene diaphragm, a polyethylene diaphragm, and a polypropylene-polyethylene composite diaphragm; Alternatively, the diaphragm (1) comprises a diaphragm substrate and an insulating coating located on the surface of the diaphragm substrate, and the diaphragm substrate is selected from at least one of a single-layer or multi-layer polypropylene diaphragm, a polyethylene diaphragm, and a polypropylene-polyethylene composite diaphragm.

13. The battery core assembly according to any one of claims 1 to 12, wherein: The battery core assembly is a winding structure or a stacked structure.

14. A lithium ion battery, wherein: The lithium-ion battery comprises a shell and a battery cell assembly located inside the shell, and the battery cell assembly is as described in any one of claims 1-13.

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