Battery cell assembly and lithium ion battery

Abstract

The invention discloses a battery cell assembly and a lithium ion battery, and belongs to the technical field of chemical batteries. The battery cell assembly comprises a diaphragm, a negative pole piece and a positive pole piece, wherein the negative pole piece and the positive pole piece are isolated by the diaphragm; the diaphragm comprises a diaphragm body and an edge part, the projection of the positive pole piece on the diaphragm coincides with the diaphragm body, and the edge part is located at the side part of the diaphragm body and is exposed out of the negative pole piece and the positive pole piece; the ion transmittance of the edge portion is smaller than the ion transmittance of the diaphragm body. When the overhang value between the negative pole piece and the positive pole piece of the battery cell assembly is reduced due to winding operation or lamination operation, the ions can be effectively prevented from passing through the battery cell assembly due to the characteristic that the edge part of the diaphragm hinders the ions from passing through, so that the risks of short circuit and lithium separation caused by reduction of the overhang value of the positive pole piece and the negative pole piece are effectively reduced.

Description

Technical Field

[0001] The present disclosure relates to the technical field of chemical batteries, and in particular to battery core components and lithium-ion batteries. Background Art

[0002] In the battery cell of lithium-ion battery, the positive electrode sheet and the negative electrode sheet are separated by a diaphragm, wherein the negative electrode sheet is designed to have an overhang (excessive size) relative to the positive electrode sheet, and the diaphragm is designed to have an overhang (excessive size) relative to the positive electrode sheet, so that the end areas of the positive electrode sheet and the negative electrode sheet are isolated to avoid the problems of lithium precipitation and lithium dendrites. At present, the battery cell manufacturing methods of lithium-ion battery include winding or stacking, especially the winding manufacturing method, which makes it difficult to control the end position of the electrode sheet, thereby reducing the overhang value between the negative electrode sheet and the positive electrode sheet, resulting in poor overhang.

[0003] In the related art, usually after the winding operation or the stacking operation, the obtained battery cell products are 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.

[0004] Public Content

[0005] In order to solve the technical problem that the overhang value between the negative electrode plate and the positive electrode plate of the battery cell assembly provided by the related technology is reduced after the winding operation or the 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.

[0006] In one aspect, a battery cell assembly is provided, the battery cell assembly comprising: a separator, a negative electrode sheet and a positive electrode sheet, the negative electrode sheet and the positive electrode sheet being separated by the separator;

[0007] 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;

[0008] The ion permeability of the edge portion is lower than the ion permeability of the diaphragm body.

[0009] The battery cell assembly provided by the embodiment of the present disclosure has a diaphragm including a diaphragm body and an edge portion, and the edge portion is used as the overhang area of ​​the diaphragm 1 relative to the negative electrode sheet and the positive electrode sheet. Since the ion permeability of the edge portion is lower than the ion permeability 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 electrode sheet and the positive electrode sheet of the battery cell assembly is reduced due to the winding operation or the lamination operation, the ion blocking property of the edge portion of the diaphragm 1 can effectively prevent the ions from passing therethrough, thereby effectively reducing the risk of short circuit and lithium deposition caused by the reduction of the overhang value of the positive and negative electrodes.

[0010] 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.

[0011] 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.

[0012] 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.

[0013] 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.

[0014] In some possible implementations, the edge portion is a closed-cell 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.

[0015] 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 an ion permeability of the ion barrier coating is lower than an ion permeability of the diaphragm body.

[0016] In some possible implementations, the porosity of the ion barrier coating is 0% to 90% of the porosity of the diaphragm body;

[0017] and / or,

[0018] The air permeability of the ion barrier coating is 0% to 90% of the air permeability of the diaphragm body.

[0019] In some possible implementations, the edge portion is located at least one of the first side and the second side of the diaphragm body;

[0020] 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.

[0021] In some possible implementations, the width of the edge portion is 1 mm to 10 mm, wherein the width of the edge portion is the distance between the outer edge of the edge portion and the outer edge of the positive electrode plate. By limiting the width of the edge portion to the above range, it is ensured that the diaphragm effectively blocks ions in the overhang area of ​​the positive and negative electrodes, thereby preventing ions from flowing.

[0022] 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, glue coating treatment, multi-layer diaphragm composite treatment, and strip composite treatment.

[0023] 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;

[0024] 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.

[0025] In some possible implementations, the battery core assembly is a wound structure or a stacked structure.

[0026] On the other hand, a lithium-ion battery is provided, comprising a shell and a battery cell assembly located inside the shell, wherein the battery cell assembly is as described above.

[0027] 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, based on the use of the battery cell assembly, the product yield of the lithium-ion battery can be effectively improved and the cost can be reduced.

[0028] 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.

[0029] Illustratively, the lithium-ion battery may be a wound battery or a stacked battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the arrangement structure of the battery cell assembly in the overhang non-displacement state in the related art;

[0031] Figure 2 It is a schematic diagram of the arrangement structure of the battery cell assembly in the overhang misalignment state in the related art;

[0032] Figure 3 A schematic diagram of the arrangement structure of the battery cell assembly provided in an embodiment of the present disclosure in an overhang non-misaligned state;

[0033] Figure 4 A schematic diagram of the arrangement structure of the battery cell assembly provided in an embodiment of the present disclosure in an overhang misaligned state;

[0034] Figure 5 A schematic diagram of the structure of an exemplary diaphragm in a flattened state provided in an embodiment of the present disclosure;

[0035] Figure 6 A front cross-sectional view of an exemplary battery cell assembly provided in an embodiment of the present disclosure;

[0036] Figure 7 A cross-sectional view of an edge portion of another exemplary diaphragm provided in accordance with an embodiment of the present disclosure.

[0037] in, Figure 1-Figure 4 In the figures, 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.

[0038] The reference numerals represent:

[0039] 1. Diaphragm;

[0040] 11. Diaphragm body;

[0041] 12. edge portion; 121. edge portion body; 122. ion barrier coating;

[0042] 2. Negative electrode;

[0043] 3. Positive electrode. DETAILED DESCRIPTION

[0044] For lithium-ion battery cells, the positive electrode sheet and the negative electrode sheet are separated by a separator. The negative electrode sheet is designed to have overhang relative to the positive electrode sheet, and the separator is designed to have overhang relative to the positive electrode sheet and the negative electrode sheet, so that the end areas of the positive electrode sheet and the negative electrode sheet are isolated to avoid problems such as lithium deposition and lithium dendrites.

[0045] See also Figure 1 , the overhang of the diaphragm 1 relative to the positive electrode sheet 3 refers to the portion of the diaphragm 1 that is more than the positive electrode sheet 3, and the overhang of the diaphragm 1 relative to the negative electrode sheet 2 refers to the portion of the diaphragm 1 that is more than the negative electrode sheet 2. Figure 1 As shown, it illustrates the overhang of the separator 1 relative to the positive electrode plate 3, which is defined as A1, the overhang of the separator 1 relative to the negative electrode plate 2, which is defined as A2, and the overhang of the negative electrode plate 2 relative to the positive electrode plate 3, which is defined as A3.

[0046] At present, the production methods of lithium-ion battery cells include winding or lamination. In particular, the winding production method makes it difficult to control the end position of the pole piece, which causes abnormal misalignment of the overhang area, reduces the overhang value, and causes poor overhang. For example, see Figure 2 , which illustrates that after winding or lamination, the overhang A3 of the negative electrode sheet 2 relative to the positive electrode sheet 3 is reduced, and the overhang of the separator 1 relative to both the positive electrode sheet 3 and the negative electrode sheet 2 is reduced, so that the negative electrode has a greater risk of lithium plating.

[0047] In response to the above technical problems, the related technology usually performs X-Ray testing on the obtained battery cell products after the winding operation or the 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.

[0048] In view of the technical problems existing in the related art, on the one hand, the embodiments of the present disclosure provide a battery cell assembly, such as the attached Figure 3 As shown, 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.

[0049] Further integration Figure 5 As shown, the diaphragm 1 includes 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, and 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 less than the ion permeability of the diaphragm body 11.

[0050] 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.

[0051] 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 , which is different from the traditional battery diaphragm 1 , and the edge portion 12 blocks the passage of ions in the electrolyte.

[0052] 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.

[0053] See also Figure 6 In the present application, the overhang of the diaphragm 1 relative to the positive electrode plate 3 is defined as A1, the overhang of the diaphragm 1 relative to the negative electrode plate 2 is defined as A2, and the overhang of the negative electrode plate 2 relative to the positive electrode plate 3 is defined as A3.

[0054] The battery cell assembly provided by the embodiment of the present disclosure comprises a separator 1 including a separator body 11 and an edge portion 12, wherein the edge portion 12 is an overhang area of ​​the separator 1 relative to the negative electrode sheet 2 and the positive electrode sheet 3. Since the ion permeability of the edge portion 12 is lower than the ion permeability of the separator body 11, the ions in the electrolyte, such as lithium ions, are blocked from passing through. When the battery cell assembly has a reduced overhang value between the negative electrode sheet 2 and the positive electrode sheet 3 due to winding or lamination operation (see Figure 4 ), due to the characteristic of the edge portion 12 of the diaphragm 1 that blocks the passage of ions, the passage of ions can be effectively avoided, thereby effectively reducing the risk of short circuit and lithium deposition caused by the reduction of the positive and negative electrode overhang values.

[0055] 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 .

[0056] 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.

[0057] Ways to adjust the ion permeability of the edge portion 12 include, but are not limited to: adjusting at least one of the hole characteristics of the edge portion 12 and adjusting the material of the edge portion 12 .

[0058] 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. of the edge portion 12. For example, adjusting the material of the edge portion 12 can be achieved by selecting a dense material to prepare the edge portion 12.

[0059] 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 .

[0060] 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.

[0061] The 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-mentioned influencing factors, the porosity can be adjusted accordingly.

[0062] For 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 the porosity of the diaphragm body 11. This implementation is conducive to simplifying the preparation process of the diaphragm 1 and reducing costs.

[0063] 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.

[0064] 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.

[0065] By making the porosity of the edge portion 12 within the above range, the edge portion 12 has 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. According to tests, when the porosity of the edge portion 12 is 50% of the porosity of the diaphragm body 11, the risks of short circuit, lithium deposition, lithium dendrites, etc. can be effectively avoided.

[0066] 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 .

[0067] 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.

[0068] 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-mentioned factors, the air permeability can be adjusted accordingly.

[0069] For 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 made smaller than that of the diaphragm body 11. This implementation is conducive to simplifying the preparation process of the diaphragm 1 and reducing costs.

[0070] 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.

[0071] In some examples, the air 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 air permeability of the diaphragm body 11.

[0072] By making the air permeability of the edge portion 12 within the above range, the edge portion 12 has 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. According to tests, when the air permeability of the edge portion 12 is 50% of the air permeability of the diaphragm body 11, the risks of short circuit, lithium deposition, lithium dendrites, etc. can be effectively avoided.

[0073] For the above-mentioned implementations (1) and (2), the smaller the porosity or air permeability of the edge portion 12 is, the more advantageous it is for preventing the passage of ions. In some examples, for the above-mentioned implementations (1) and (2), the edge portion 12 can be made into a closed-cell structure, that is, the air 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.

[0074] In some implementations (3), as shown in the attached Figure 7 As shown, 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 . The ion permeability of the ion barrier coating 122 is lower than the ion permeability of the diaphragm body 11 .

[0075] In this implementation, an ion barrier coating 122 with low ion permeability is provided on the surface of the edge body 121 , and based on the low ion permeability of the ion barrier coating 122 , the ion permeability of the edge 12 is lower than that of the diaphragm body 11 .

[0076] Exemplarily, the porosity of the ion barrier coating 122 is 0% to 90% of the porosity of the diaphragm body 11, and further includes 0% to 50%, 0% to 40%, 0% to 30%, 0% to 20%, 0% to 10%, 0% to 5%, etc.

[0077] 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.

[0078] By making the porosity and / or air permeability of the ion barrier coating 122 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.

[0079] Exemplarily, the ion barrier coating 122 may be a dense polymer coating, such as acrylic resin, polyurethane resin, polyester resin, etc.

[0080] 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.

[0081] 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 .

[0082] When the ion permeability of the edge portion body 121 is less than 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, so that it has a longer service life.

[0083] When the ion permeability of the edge body 121 is equal to that of the diaphragm body 11, the structure and material of the edge body 121 can be the same as those of the diaphragm body 11. For example, the edge body 121 and the diaphragm body 11 are prepared by an integrated molding process. This solution is more advantageous for simplifying the preparation process of the diaphragm 1.

[0084] In some implementations, such as the attached Figure 5 As shown, the edge portion 12 of the diaphragm 1 is located 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 .

[0085] Typically, the separator 1 , the negative electrode sheet 2 , and the positive electrode sheet 3 are all in the shape of rectangular strips, and 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.

[0086] See for example Figure 5 , which illustrates 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.

[0087] 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 .

[0088] 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 .

[0089] 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.

[0090] 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 .

[0091] In some examples, the tab side of the positive pole piece 3 and the negative pole piece 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 on the pole piece and the non-tab side opposite thereto.

[0092] 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.

[0093] In some implementations, such as the attached Figure 5 As shown, the width dimension L of the edge portion 12 is 1 mm to 10 mm, wherein the width dimension 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 sheet 3, and is also the dimension of the short side of the edge portion 12. Figure 5 The width dimension of the edge portion 12 can also be considered as the overhang dimension of the separator 1 relative to the positive electrode sheet 3 .

[0094] In addition, the width dimension L of the edge portion 12 mentioned here includes not only the width dimension of the edge portion 12 located on the first side D1 of the diaphragm body 11 , but also the width dimension of the edge portion 12 located on the second side D2 of the diaphragm body 11 .

[0095] 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.

[0096] By limiting the width of the edge portion 12 to the above range, it is ensured that the separator 1 effectively blocks ions in the overhang region of the positive and negative electrodes, thereby preventing ions from flowing.

[0097] 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.

[0098] The distance between the outer edge of the edge portion 12 and the outer edge of the negative electrode plate 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 plate 2 .

[0099] 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.

[0100] In the disclosed embodiment, the edge portion 12 is obtained by performing at least one of the following treatments on the edge region of the diaphragm 1: heating treatment, extrusion treatment, glue coating treatment, multi-layer diaphragm 1 composite treatment, and strip composite treatment.

[0101] The heating treatment is suitable for treating the diaphragm 1 made of polymer material. The polymer material is heated to melt it so as to shrink the pores or even close the pores, thereby obtaining the edge portion 12 with low ion passing rate.

[0102] 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. And, after the heating process, the thickness of the edge portion 12 is less than the thickness of the diaphragm body 11.

[0103] Exemplarily, 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.

[0104] After testing, for the edge portion 12 of polypropylene material, after hot pressing for 5 seconds, the edge portion 12 can achieve closed cells and obtain a closed cell structure, and appear transparent in appearance. And for the edge portion 12 of polyethylene material, after hot pressing for 3 seconds, the edge portion 12 can achieve closed cells and obtain a closed cell structure, and appear white or off-white in appearance.

[0105] 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.

[0106] The extrusion treatment is suitable for treating the diaphragm 1 made of 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 passing rate.

[0107] 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. Also, after the extrusion process, the thickness of the edge portion 12 is less than the thickness of the diaphragm body 11 .

[0108] 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.

[0109] The composite treatment of the multilayer membrane 1 is not only suitable for the membrane 1 made of polymer material, but also for the membrane 1 made of ceramic material. It can be a composite of two layers of membrane 1 for the edge portion 12, or a composite treatment of three or more layers of membrane 1 for the edge portion 12. Through the composite treatment of the multilayer membrane 1, the holes in each layer of the membrane 1 are staggered, that is, not connected, so as to obtain the edge portion 12 with low ion pass rate.

[0110] The tape composite treatment is not only suitable for polymer diaphragms 1, but also for ceramic diaphragms 1. It can use densely structured tapes and other tapes to wrap the surface of the edge 12 of the diaphragm 1, thereby obtaining an edge 12 with a low ion pass rate.

[0111] One preparation scheme of the diaphragm 1 is to prepare a diaphragm 1 intermediate using the diaphragm 1 material, wherein the diaphragm 1 intermediate includes a diaphragm body 11 and an edge intermediate located on the side of the diaphragm body 11. The edge 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 12, thereby obtaining the diaphragm 1.

[0112] 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 .

[0113] In the disclosed embodiment, the diaphragm 1 can be prepared by using common diaphragm 1 materials, and the diaphragm 1 itself can be a single-layer film structure or a multi-layer film structure.

[0114] 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 .

[0115] 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.

[0116] 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.

[0117] In the disclosed embodiments, 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 pole piece fluctuations, increased width errors during pole piece cutting, and abnormal pole piece alignment, thereby causing the overhang value of the negative pole piece 2 relative to the positive pole piece 3 to decrease, the edge portion 12 will hinder the flow of ions between the two poles, thereby avoiding the risks of short circuits, lithium precipitation, lithium dendrites, etc.

[0118] The battery cell assembly provided in the embodiment of the present disclosure is shown in Figure 6 , which may include one battery cell unit or multiple battery cell units, and adjacent battery cell units are separated by a diaphragm 1. Each battery cell unit includes a negative electrode sheet 2 and a positive electrode sheet 3, and the negative electrode sheet 2 and the positive electrode sheet 3 are separated by a diaphragm 1.

[0119] In summary, the battery cell assembly provided by the embodiment of the present disclosure reduces the ion permeability of the edge portion 12 of the diaphragm 1, that is, the overhang area, for example, by reducing its porosity and / or permeability, thereby reducing the probability of lithium ions passing therethrough. When the edge portion 12 is a closed-cell structure, lithium ions cannot pass through the edge portion 12, thereby effectively reducing the risk of lithium plating caused by the reduction of the overhang between the positive and negative electrodes of the lithium-ion battery.

[0120] In addition, both the negative electrode plate 2 and the positive electrode plate 3 can adopt a traditional electrode plate 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 plate structure and improving the electrode plate commonality.

[0121] 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.

[0122] 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, based on the use of the battery cell assembly, the product yield of the lithium-ion battery can be effectively improved and the cost can be reduced.

[0123] 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.

[0124] 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.

[0125] The lithium-ion battery involved in the embodiments of the present disclosure may be a wound battery or a stacked battery.

[0126] The exemplary embodiments of the present disclosure will be described in more detail below. Although the 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. If no specific technology or conditions are specified in the embodiments, the technology or conditions described in the literature in the art or the product specifications are used.

[0127] The following embodiments provide a wound cell assembly, as shown in the attached Figure 3 As shown, it includes a diaphragm 1, a negative electrode sheet 2 and a positive electrode sheet 3, and the negative electrode sheet 2 and the positive electrode sheet 3 are separated by the diaphragm 1. The diaphragm 1 includes a diaphragm body 11 and an edge portion 12 (i.e., an overhang area), and the edge portion 12 is arranged around the diaphragm body 11 and exposed outside the negative electrode sheet 2 and the positive electrode sheet 3. Figure 5 As shown, the edge portion 12 is located at both the first side D1 and the second side D2 of the diaphragm body 11 .

[0128] The diaphragm 1 is a polyethylene diaphragm, that is, the materials of the diaphragm body 11 and the edge portion 12 are both polyethylene, and the thickness of the diaphragm body 11 is 9 microns. The overhang width of the diaphragm 1 relative to the positive electrode plate 3 (that is, the width of the edge portion 12) is 5 mm, and the overhang width of the diaphragm 1 relative to the negative electrode plate 2 (that is, the width of the second part of the edge portion 12) is 3 mm.

[0129] In the battery cell assembly provided in the above embodiments, the preparation method of the edge portion 12, and the porosity and air permeability parameters of the edge portion 12 are respectively shown in Table 1.

[0130] In addition, a comparative wound cell assembly is also provided as a comparative example, which differs from the cell assemblies of the above-mentioned embodiments in that its edge portion 12 (ie, the overhang area) is the same as the diaphragm body 11, so that the air permeability and porosity of the two are consistent.

[0131] After the battery cell assemblies provided in the above embodiments and comparative examples are wound and assembled, an X-ray test is performed to test whether lithium is deposited at the edge of the negative electrode plate 2 after the battery cell assembly has poor alignment. Please refer to Table 1 for the test results.

[0132] Table 1

[0133]

[0134] 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.

[0135] It can be seen from Table 1 that, 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.

[0136] 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.

[0137] In the present embodiment, the term "and / or" is merely a term used to describe 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.

[0138] The above description is only for the purpose of facilitating those skilled in the art to understand the technical solution of the present disclosure and is not intended to limit the present disclosure. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present disclosure shall be included in the protection scope of the present disclosure.

Claims

1. A battery cell assembly, characterized in that: 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, characterized in that: 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, characterized in that: The porosity of the edge portion (12) is 0% to 90% of the porosity of the diaphragm body (11).

4. The battery core assembly according to claim 1, characterized in that: 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, characterized in that: 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, characterized in that: The edge portion (12) is a closed-cell structure.

7. The battery cell assembly according to claim 1, characterized in that: 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, characterized in that: 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, characterized in that: 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 core assembly according to claim 9, characterized in that: 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, characterized in that: 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 core assembly according to claim 9, characterized in that: 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, characterized in that: The battery core assembly is a winding structure or a stacked structure.

14. A lithium ion battery, characterized in that: 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.

Images