Roll core structure and battery

Abstract

The invention relates to the technical field of batteries, and discloses a roll core structure and a battery, the roll core structure is formed by laminating and winding a positive plate, a diaphragm and a negative plate, and the negative plate is located at the outermost circle of the winding; the positive plate at least comprises a positive current collector and positive active coatings coated on two sides of the positive current collector; the negative plate is provided with a negative electrode double-sided coating area of which the two sides are coated with negative electrode active coatings, and a negative electrode single-sided coating area of which the single side is coated with a negative electrode active coating; and the insulating coating is coated on one side, facing the outer side of the roll core, of the negative current collector in the negative single-side coating area. According to the roll core structure provided by the invention, the negative plate is arranged on the outermost ring of the cell structure, and the cell structure wrapped by the positive aluminum foil in the traditional cell is changed, so that the negative plate is positioned on the outermost side of the roll core, the problem of belt breakage after circulation caused by damage of the pole plate due to local overvoltage of the positive electrode is avoided, and the capacity of the cell is improved; expansion stress borne by the battery cell after cyclic expansion is reduced, and the probability of positive pole piece breakage is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a winding core structure and a battery. Background Art

[0002] In the related art, the outer ring of the cell structure of lithium-ion batteries is often the single-sided coating area of ​​the positive electrode sheet and part of the empty aluminum foil area. As the base aluminum foil becomes thinner and the compaction density becomes larger, and because the particles of the positive electrode material are hard, it is easy for part of the positive electrode material to be embedded in the aluminum foil during the rolling process, causing certain damage to the base aluminum foil, especially near the junction of the double-sided coating area and the single-sided coating area of ​​the positive electrode sheet, and the junction of the single-sided area of ​​the positive electrode and the empty foil area. Due to the change in thickness, it is a sudden change point of pressure during the rolling process, and the damage to the base aluminum foil is particularly serious. The above-mentioned serious damage position is usually located in the outer few turns of the winding core in the aluminum foil-wrapped cell, so that when the expansion occurs during the subsequent cell cycle, the expansion force is superimposed on the outer ring of the cell, causing the outer ring of the cell to be prone to broken belt problems, resulting in a reduction in the actual battery capacity and affecting the user experience. Summary of the invention

[0003] In view of this, the present invention provides a winding core structure and a battery to improve the problem that the outer ring of the battery core is prone to breaking, resulting in a reduction in battery capacity.

[0004] In a first aspect, the present invention provides a winding core structure, the winding core structure comprises a negative electrode sheet, a separator and a positive electrode sheet, and the negative electrode sheet, the separator and the positive electrode sheet are stacked in sequence; wherein, along the thickness direction of the winding core structure, the negative electrode sheet is located at the outermost circle of the winding core structure; the positive electrode sheet comprises a positive electrode current collector and a positive electrode active coating at least partially coated on both sides of the positive electrode current collector along the thickness direction of the positive electrode sheet;

[0005] The negative electrode sheet comprises a negative electrode current collector, a negative electrode double-sided coating area coated on both sides of the negative electrode current collector along the thickness direction of the negative electrode sheet, and a negative electrode single-sided coating area coated on one side of the negative electrode current collector;

[0006] At least part of the negative electrode single-sided coating area is located at the outermost circle of the core structure, wherein the negative electrode current collector of the negative electrode single-sided coating area located at the outermost circle of the core structure faces away from the winding center of the core structure, and the negative electrode active coating of the negative electrode single-sided coating area faces the winding center of the core structure;

[0007] The negative electrode sheet also includes: an insulating coating, at least part of which is coated on the surface of the negative electrode current collector in the negative electrode single-sided coating area of ​​the outermost circle of the winding core structure away from the winding center of the winding core structure.

[0008] Beneficial effect: The winding core structure provided by the embodiment of the present invention sets the negative electrode sheet at the outermost circle of the battery cell structure, which changes the battery cell structure in which the positive electrode aluminum foil is outwrapped in the traditional battery cell, so that the negative electrode sheet is located at the outermost side of the winding core, and then both sides of the positive electrode sheet can be coated with the positive electrode active coating, that is, the positive electrode single-sided area and the positive electrode empty foil area are eliminated, avoiding the problem of the electrode sheet being damaged due to local overvoltage of the positive electrode and causing the belt to break after the cycle, and at the same time improving the capacity of the battery cell. Common negative electrode materials include graphite, silicon-based materials, disordered carbon, etc., and the negative electrode current collector is usually made of copper. Foil, because the particle size of the negative electrode material particles is small and soft, and the compaction is small, it will not cause damage or destruction to the copper foil current collector of the negative electrode after rolling. Therefore, even if the negative electrode single-sided area is located at the outermost circle of the winding core, the problem of negative electrode sheet breakage after cycling will not occur; on the other hand, the negative electrode sheet is set at the outermost circle of the battery cell structure. Even if the positive electrode sheet still has a single-sided area, the positive electrode single-sided area is also located on the inner side of the winding core. After the battery cell cyclic expansion, the expansion stress on the positive electrode sheet is reduced, which can further reduce the probability of positive electrode breakage and reduce the probability of belt breakage in subsequent cycles.

[0009] The negative electrode sheet is arranged at the outermost circle of the winding, and the negative electrode sheet forms a negative electrode single-sided coating area coated with a negative electrode active coating on one side, the negative electrode single-sided coating area is located at the outermost circle of the core structure, the negative electrode current collector of the negative electrode single-sided coating area faces the outside of the core, and the negative electrode active coating of the negative electrode single-sided coating area faces the inside of the core; thereby avoiding material waste caused by the lack of corresponding positive electrode active coating on the outermost circle of the core structure, avoiding increasing the thickness of the core structure, and further improving the energy density of the battery.

[0010] An insulating coating is coated on the side of the negative electrode collector in the negative electrode single-sided coating area facing the outside of the winding core. The insulating coating is made of an insulating material. The insulating coating completely covers the exposed area of ​​the negative electrode collector on the shorter side of the negative electrode sheet coating, and is located at the outermost side of the winding core after winding is completed to prevent the negative electrode collector from being exposed and avoid the risk of corrosion due to contact between the negative electrode collector and the battery casing (such as aluminum-plastic film) that packages the battery cell due to different potentials.

[0011] In an optional embodiment, the negative electrode sheet is further formed with a negative electrode blank current collector area on both sides of which the negative electrode active coating is not coated, and the negative electrode blank current collector area is continuously arranged at the tail end of the negative electrode single-sided coating area;

[0012] The insulating coating is also coated on a surface of the negative electrode current collector in the negative electrode blank current collector area on one side away from the winding center of the winding core structure.

[0013] Beneficial effect: A negative electrode blank current collector area is formed by further extending the tail end of the negative electrode single-sided coating area. Neither side of the negative electrode blank current collector area is coated with a negative electrode active coating, but an insulating layer is coated on the negative electrode blank current collector area, so that the blank negative electrode current collector can continue to be wound on the outermost circle of the core structure, which can ensure that the single-sided coating area of ​​the negative electrode is not wrinkled during the winding process, thereby ensuring the winding yield of the battery cell, and the insulating coating is also coated on the side of the negative electrode current collector in the negative electrode blank current collector area facing the outside of the core, so that the insulating coating completely covers the exposed area of ​​the negative electrode current collector of the negative electrode sheet, and is located on the outermost side of the core after winding is completed, preventing the negative electrode current collector from being exposed and avoiding the risk of subsequent corrosion.

[0014] In an optional embodiment, along the winding direction, the negative electrode sheet exceeds the tail end of the separator; and the separator exceeds the tail end of the positive electrode sheet.

[0015] Beneficial effect: Ensure that the negative electrode sheet is on the outermost side of the core structure so that hot melt adhesive can be subsequently pasted to improve the safety performance of the battery.

[0016] In an optional embodiment, the thickness of the insulating coating is H, and the thickness of the negative electrode current collector is H1, satisfying: H=(0.2-4.0)H1.

[0017] Beneficial effect: By limiting the lower limit of the ratio of the thickness of the insulating coating to the thickness of the negative electrode current collector, it can be ensured that the negative electrode current collector will not be exposed; by limiting the upper limit of the ratio of the thickness of the insulating coating to the thickness of the negative electrode current collector, it is possible to avoid the insulating coating being too thick, thereby avoiding causing the battery cell to be too thick and affecting the energy density of the battery.

[0018] In an optional embodiment, the insulating coating contains inorganic materials and / or polymer binders; wherein the inorganic materials contain one or more of aluminum oxide, silicon oxide, zirconium oxide, calcium oxide, boehmite, magnesium oxide, and magnesium hydroxide; and the polymer binder includes one or more of polyvinylidene fluoride, styrene-butadiene rubber, and polyacrylate.

[0019] In an optional embodiment, at least part of the insulating coating is located between the negative electrode active coating and the negative electrode current collector, and along the winding direction, the size of the overlapping area of ​​the insulating coating and the negative electrode active coating is P, satisfying: P≥0.5mm.

[0020] Beneficial effect: The size of the overlapping area between the insulating coating and the negative electrode active coating satisfies P ≥ 0.5 mm, so that the insulating coating and the negative electrode active coating at least partially overlap and both cover the outside of the negative electrode current collector, thereby ensuring that the insulating coating can completely cover the negative electrode current collector, and there is no exposed area of ​​the negative electrode current collector, avoiding safety risks.

[0021] In an optional embodiment, along the width direction of the winding core structure, the winding starting end of the positive electrode sheet and the winding starting end of the negative electrode sheet extend in opposite directions respectively.

[0022] Beneficial effect: By making the winding starting end of the positive electrode sheet and the winding starting end of the negative electrode sheet extend in opposite directions respectively, the positive electrode sheet of this arrangement can be a continuous double-sided coating structure, thereby improving the efficiency of positive electrode coating and facilitating improving the energy density of the battery cell.

[0023] In an optional embodiment, the winding start ends of the positive electrode sheet and the negative electrode sheet are located on the same side in the width direction of the winding core structure.

[0024] In an optional embodiment, along the width direction of the winding core structure, the distance between the tail end of the negative electrode sheet located at the outermost circle of the winding core structure and the winding starting end of the electrode sheet closest thereto is W, satisfying: W≥1.0mm.

[0025] Beneficial effect: By limiting the lower limit of W, it is ensured that the negative electrode sheet of the outermost circle can be closed to the flat area of ​​the core structure, avoiding closing in the arc area, preventing the tape from overlapping and affecting the battery energy density.

[0026] In an optional embodiment, along the winding direction, the length of the insulating coating applied to the blank current collector area of ​​the negative electrode is L2, which satisfies: 5 mm ≤ L2 ≤ 500 mm.

[0027] Beneficial effect: Due to the existence of L2, the wrinkling effect of the negative electrode single-sided coating area can be improved. If L2 is too small, the wrinkling cannot be effectively improved. If L2 is too large, the ineffective thickness of the battery cell will be increased, resulting in a decrease in energy density.

[0028] In an optional embodiment, the area of ​​the surface of the negative electrode collector in the negative electrode single-sided coating area of ​​the outermost circle of the core structure that is coated with the insulating coating and is away from the winding center of the core structure is S1, and the area of ​​the negative electrode collector facing the outside of the core that is not coated with the negative electrode active coating is S2, satisfying: S1 / S2≥0.9.

[0029] Beneficial effect: By limiting S1 / S2≥0.9, it can be ensured that the insulating coating coated on the tail end of the negative electrode sheet can insulate the negative electrode collector from the battery cell membrane shell, thereby improving safety performance.

[0030] In an optional embodiment, the negative electrode sheet also includes a negative electrode head single-sided coating area located at the starting section of the negative electrode winding, wherein the negative electrode current collector in the negative electrode head single-sided coating area is arranged toward the winding center of the core structure, and the negative electrode active coating in the negative electrode head single-sided coating area is arranged away from the winding center of the core structure.

[0031] In an optional embodiment, the negative electrode winding starting section of the negative electrode sheet also includes an empty foil area at the winding starting end that is not coated with negative electrode active coating on both sides. Along the winding direction, the empty foil area at the winding starting end is connected in sequence with the single-sided coating area of ​​the negative electrode head.

[0032] In an optional embodiment, the surface of the empty foil area at the starting end of winding away from the winding center is at least partially coated with an insulating coating; the area of ​​the insulating coating coated on the empty foil area at the starting end of winding is S3, and the area of ​​the empty foil area at the starting end of winding is S4, satisfying: S3 / S4≤0.3.

[0033] Beneficial effect: By limiting S3 / S4≤0.3, it can ensure that the area of ​​the insulating coating at the starting end of the winding is not too large, avoiding affecting the thickness of the battery cell. It ensures that the exposed current collector at the tail of the negative electrode is completely coated with the insulating layer, avoiding the occurrence of corrosion caused by leaving part of the negative electrode current collector at the tail during cutting.

[0034] In a second aspect, the present invention further provides a battery, comprising:

[0035] case;

[0036] and a winding core structure as described above disposed in the housing;

[0037] The insulating coating at least partially coated on the negative electrode single-sided coating area of ​​the outermost circle of the winding core structure is located between the shell and the negative electrode current collector.

[0038] Beneficial effect: After the core structure is packaged, the insulating coating 2002 is located between the negative electrode current collector 200 and the battery cell membrane shell, and is set away from the center of the core, thereby preventing the formation of a primary cell between the negative electrode current collector 200 and the battery cell membrane shell, avoiding corrosion, and improving the safety performance of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0040] Figure 1 This is a schematic diagram of the winding core structure before improvement;

[0041] Figure 2 This is a schematic diagram of the positive electrode structure before improvement;

[0042] Figure 3 This is a schematic diagram of a winding core structure of the present invention;

[0043] Figure 4This is another schematic diagram of the winding core structure of the present invention;

[0044] Figure 5 This is a schematic diagram of the structure of a positive electrode sheet of the present invention;

[0045] Figure 6 Schematic diagram of the negative electrode structure of the present invention Figure 1 ;

[0046] Figure 7 Schematic diagram of the negative electrode structure of the present invention Figure 2 ;

[0047] Figure 8 Schematic diagram of the negative electrode structure of the present invention Figure 3 ;

[0048] Fig. 9 Schematic diagram of the negative electrode structure of the present invention Figure 4 ;

[0049] Fig.10 The negative electrode sheet structure of the present invention includes two end portions. Figure 5 ;

[0050] Fig.11 The negative electrode sheet structure of the present invention includes two end portions. Figure 6 ;

[0051] Fig.12 The negative electrode sheet structure of the present invention includes two end portions. Figure 7 ;

[0052] Fig.13 It is a relationship diagram between the capacity ratio of the experimental group and the blank group of the present invention and the number of cycles.

[0053] Description of reference numerals:

[0054] 10. positive electrode sheet; 100. positive electrode current collector; 101. positive electrode active coating;

[0055] 20, negative electrode sheet; 200, negative electrode current collector; 201, negative electrode active coating; 2001, first side negative electrode active coating; 2003, second side negative electrode active coating; 2002, insulating coating;

[0056] 30. diaphragm; 40. tab;

[0057] 50. Negative electrode double-sided coating area; 51. Negative electrode single-sided coating area; 52. Negative electrode blank current collector area; 53. Empty foil area at the start of winding;

[0058] 61. positive electrode single-sided area; 62. positive electrode empty foil area;

[0059] L1 is the width of the pole ear; L2 is the length of the blank current collector;

[0060] P is the dimension of the insulating coating extending into the active coating;

[0061] W is the dimension from the end of the inner ring negative electrode sheet to the end of the outer ring negative electrode sheet;

[0062] H is the thickness of the insulating coating, and H1 is the thickness of the negative electrode current collector. DETAILED DESCRIPTION

[0063] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0064] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0065] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0066] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0067] In the related art, the positive electrode sheet often includes a current collector and an active material coating coated on at least one side of the current collector. Common positive electrode active material coatings include: lithium cobalt oxide (LiCoO2), lithium manganese oxide (LiMn2O4), lithium iron phosphate (LiFePO4), lithium nickel cobalt manganese oxide (Li(NiCoMn)O2), etc. The current collector of the positive electrode sheet is usually made of aluminum foil.

[0068] Combination Figure 1 As shown, in the wound battery, the positive electrode sheet and the negative electrode sheet are overlapped inside, and at the end position, in order to improve the energy density of the battery, especially the outermost circle of the core structure, usually only one side of the positive electrode sheet is coated to correspond to the negative electrode sheet, that is, the positive electrode collector 100 is coated with a positive electrode active coating 101 on the side facing the inside of the wound battery, and the positive electrode collector 100 is no longer coated with a positive electrode active coating 101 on the side facing the outside of the wound battery; and after exceeding the end position of the negative electrode sheet, the positive electrode collector 100 of the positive electrode sheet 10 is no longer coated with a positive electrode active coating 101 on both sides, and only the positive electrode collector 100 continues to be wound. And further combined Figure 2 As shown, at the end of the roll core structure of the lithium-ion battery, there is a positive electrode single-sided area 61 coated with a single-sided positive electrode active coating 101, and a positive electrode empty foil area 62 with a blank positive electrode current collector 100. There is a thickness difference at the transition position of these two areas.

[0069] As the base aluminum foil becomes thinner and the pressure density increases, due to the greater hardness of the positive electrode material particles, part of the positive electrode material is easily embedded in the aluminum foil during the rolling process, causing certain damage to the base aluminum foil, especially at the junction of the single-sided and double-sided coatings on the outermost circle, and at the junction of the coating and the base aluminum foil. Due to the change in thickness, the pressure suddenly changes during the rolling process, and the damage to the base aluminum foil is particularly serious, so that the belt is prone to breakage in the subsequent cycle process, which can easily lead to a reduction in the actual usage capacity and affect the user experience.

[0070] Common negative electrode materials include graphite, silicon-based materials, disordered carbon, etc. The negative electrode current collector usually uses copper foil. Due to its small and soft particle size and low compaction, it will not be embedded in the copper foil after rolling, and thus will not cause damage to the current collector during the rolling process. The winding core structure provided by the embodiment of the present invention adopts continuous coating for the positive electrode and intermittent coating for the negative electrode, and after the winding is completed, the single-sided coating area and the empty foil area of ​​the negative electrode sheet are located at the outermost circle of the winding core. Through the design of continuous coating of the positive electrode sheet, damage to the substrate aluminum foil caused by sudden pressure changes at the starting and ending positions of the coating during the rolling process is avoided, and the problem of broken belts that are prone to occur at the damaged position of the positive electrode sheet after the battery cell cyclic expansion is improved.

[0071] Combine the following Figures 3 to 13 , describing an embodiment of the present invention.

[0072] According to an embodiment of the present invention, on the one hand, a winding core structure is provided, the winding core structure comprises a negative electrode sheet 20, a separator 30 and a positive electrode sheet 10, wherein the negative electrode sheet 20, the separator 30 and the positive electrode sheet 10 are sequentially stacked; wherein, along the thickness direction of the winding core structure, the negative electrode sheet 20 is located at the outermost circle of the winding core structure; the positive electrode sheet 10 comprises a positive electrode current collector 100 and a positive electrode active coating 101 at least partially coated on both sides of the positive electrode current collector 100 along the thickness direction of the positive electrode sheet;

[0073] The negative electrode sheet 20 includes a negative electrode current collector 200, a negative electrode double-sided coating area 50 coated on both sides of the negative electrode current collector 200 along the thickness direction of the negative electrode sheet, and a negative electrode single-sided coating area 51 coated on one side of the negative electrode current collector 200;

[0074] At least part of the negative electrode single-sided coating area 51 is located at the outermost circle of the core structure, wherein the negative electrode current collector 200 of the negative electrode single-sided coating area 51 located at the outermost circle of the core structure is away from the winding center of the core structure, and the negative electrode active coating 201 of the negative electrode single-sided coating area 51 is toward the winding center of the core structure;

[0075] The negative electrode sheet further includes: an insulating coating 2002, at least part of which is coated on the surface of the negative electrode current collector 200 in the negative electrode single-sided coating area 51 of the outermost circle of the winding core structure, which is away from the winding center of the winding core structure.

[0076] The outermost circle of the core structure refers to the layer located at the farthest distance from the winding center along the thickness direction after the core structure is wound. The negative electrode active coating 201 is applied to at least one side of the negative electrode collector 200. Since the negative electrode sheet 20 is in sheet shape, it specifically refers to both sides of the thickness direction of the negative electrode sheet 20 in this embodiment. Similarly, the positive electrode active coating 101 is applied to both sides of the positive electrode collector 100. Since the positive electrode sheet 10 is in sheet shape, it specifically refers to both sides of the thickness direction of the positive electrode sheet 10 in this embodiment.

[0077] The winding core structure provided by the embodiment of the present invention sets the negative electrode sheet 20 at the outermost circle of the battery cell structure, which changes the battery cell structure in which the positive electrode aluminum foil is outwrapped in the traditional battery cell, so that the negative electrode sheet 20 is located at the outermost side of the winding core, and then both sides of the positive electrode sheet 10 can be coated with the positive electrode active coating 101, that is, the positive electrode single-sided area 61 and the positive electrode empty foil area 62 are eliminated, avoiding the problem of the electrode sheet being damaged due to local overvoltage of the positive electrode and causing the belt to break after the cycle, and at the same time improving the capacity of the battery cell. Common negative electrode materials include graphite, silicon-based materials, disordered carbon, etc. The negative electrode current collector 200 is usually made of copper foil. The particle size of the negative electrode material particles is small and soft, and the compaction is small, which will not cause damage or destruction to the copper foil current collector of the negative electrode after rolling. Therefore, even if the negative electrode single-sided coating area 51 is located at the outermost circle of the winding core, the problem of the negative electrode sheet 20 breaking after cycling will not occur; on the other hand, the negative electrode sheet 20 is set at the outermost circle of the battery cell structure. Even if the positive electrode sheet 10 still has the positive electrode single-sided area 61, the positive electrode single-sided area 61 is also located on the inner side of the winding core. After the battery cell cyclic expansion, the expansion stress on the positive electrode sheet 10 is reduced, which can further reduce the probability of positive electrode breakage and reduce the probability of belt breakage in subsequent cycles.

[0078] It should be noted that the positive electrode sheet 10 at least includes a positive electrode current collector 100 and a positive electrode active coating 101 coated on both sides of the positive electrode current collector 100. In addition, the positive electrode sheet 10 may also include a positive electrode single-sided area 61 where the positive electrode active coating 101 is coated only on one side of the positive electrode current collector 100.

[0079] In this embodiment, for the portion where the positive electrode active coating 101 is coated on both sides of the positive electrode current collector 100, the length of the positive electrode active coating 101 on both sides is equal to the length of the positive electrode current collector 100. Thus, the thickness of the positive electrode sheet 10 is more uniform at all locations, and there is no sudden change point of pressure.

[0080] The negative electrode active coating 201 specifically includes: a first side negative electrode active coating 2001, at least partially coated on the side of the negative electrode collector 200 away from the center of the core structure; a second side negative electrode active coating 2003, at least partially coated on the side of the negative electrode collector 200 toward the center of the core structure.

[0081] In order to improve the energy density of the battery, the negative electrode sheet 20 is arranged at the outermost circle of the winding, and the negative electrode sheet 20 forms a negative electrode single-sided coating area 51 coated with a negative electrode active coating 201 on one side, the negative electrode single-sided coating area 51 is located at the outermost circle of the core structure, the negative electrode current collector 200 of the negative electrode single-sided coating area 51 faces the outside of the core, and the negative electrode active coating 201 of the negative electrode single-sided coating area 51 faces the inside of the core; thereby avoiding material waste due to the lack of corresponding positive electrode active coating 101 in the outermost circle of the core structure, avoiding increasing the thickness of the core structure, and further improving the energy density of the battery.

[0082] In this embodiment, by placing the negative electrode sheet 20 at the outermost circle of the winding, that is, adopting the form of negative electrode outsourcing, the positive electrode sheet 10 can be located on the inner side of the negative electrode sheet 20, and then the positive electrode sheet 10 can be set as a continuous double-sided area, so that the thickness of the positive electrode sheet 10 is more uniform everywhere, there is no sudden change point of pressure, and the rolling will not damage it, so the battery cell will not break after cycling. Even if the positive electrode sheet 10 is not a continuous double-sided coating area, that is, there is a single-sided area of ​​the positive electrode sheet, but the single-sided area of ​​the positive electrode sheet 10 is also located on the inner side of the winding core. Even if the rolling is still damaged, the damaged part is also located in the area of ​​several folds inside the winding core, which is subject to less expansion stress, thereby reducing the probability of breaking.

[0083] On this basis, an insulating coating 2002 is coated on the side of the negative electrode current collector 200 facing the outside of the winding core in the negative electrode single-sided coating area 51. The insulating coating 2002 is made of an insulating material. The insulating coating 2002 completely covers the exposed area of ​​the negative electrode current collector 200 on the shorter side of the negative electrode sheet 20 coating, and is located at the outermost side of the winding core after winding is completed, preventing the negative electrode current collector 200 from being exposed and avoiding the risk of corrosion caused by the contact between the negative electrode current collector 200 and the battery casing (such as an aluminum-plastic film) that packages the battery cell due to different potentials.

[0084] In addition, the negative electrode current collector 200 in the negative electrode single-sided coating area 51 is coated with an insulating coating 2002 on one side facing the outer side of the winding core, which can also solve the problem of wrinkling of the negative electrode single-sided area during the winding process to a certain extent.

[0085] The main purpose of providing the insulating coating 2002 on the outermost negative electrode current collector 200 of the core structure is to play an insulating role, so as to prevent the core structure from forming a primary cell between the core structure and the aluminum-plastic film of the battery cell shell after liquid injection, thereby preventing corrosion and causing safety risks.

[0086] In some embodiments, in combination Figure 6 As shown, the negative electrode sheet 20 is also formed with a negative electrode blank current collector area 52 on both sides of which are not coated with the negative electrode active coating 201, and the negative electrode blank current collector area 52 is continuously arranged at the tail end of the negative electrode single-sided coating area 51;

[0087] The insulating coating 2002 is also coated on the surface of the negative electrode current collector 200 in the negative electrode blank current collector region 52 , which is away from the winding center of the winding core structure.

[0088] A negative electrode blank current collector area 52 is formed by further extending the tail end of the negative electrode single-sided coating area 51, and the negative electrode blank current collector area 52 is not coated with the negative electrode active coating 201 on both sides, so that the blank negative electrode current collector 200 can continue to be wound on the outermost circle of the winding core structure, which can ensure that the single-sided coating area of ​​the negative electrode is not wrinkled during the winding process, thereby ensuring the winding yield of the battery cell, and the insulating coating 2002 is also coated on the side of the negative electrode current collector 200 of the negative electrode blank current collector area 52 facing the outside of the winding core, so that the insulating coating 2002 completely covers the exposed area of ​​the negative electrode current collector 200 of the negative electrode sheet 20, and is located at the outermost side of the winding core after the winding is completed, preventing the negative electrode current collector 200 from being exposed and avoiding the risk of subsequent corrosion.

[0089] In some embodiments, in combination Figure 3 , Figure 4 As shown, along the winding direction, the negative electrode sheet 20 exceeds the tail end of the separator 30 ; and the separator 30 exceeds the tail end of the positive electrode sheet 10 .

[0090] The negative electrode sheet 20 is beyond the tail end of the separator 30, and the separator 30 is beyond the tail end of the positive electrode sheet 10, that is, the negative electrode sheet 20 is terminated at the outermost side of the winding core structure, the negative electrode sheet 20 is arranged beyond the tail end of the separator 30, and the separator 30 is arranged beyond the tail end of the positive electrode sheet 10. The negative electrode sheet 20 is ensured to be at the outermost side of the winding core structure so that the hot melt adhesive can be subsequently pasted to improve the safety performance of the battery.

[0091] In some embodiments, in combination Fig. 9 As shown, the thickness of the insulating coating 2002 is H, and the thickness of the negative electrode current collector 200 is H1, satisfying: H = (0.2 ~ 4.0) H1.

[0092] By limiting the lower limit of the ratio of the thickness of the insulating coating 2002 to the thickness of the negative electrode current collector 200, it can be ensured that the negative electrode current collector 200 will not be exposed; by limiting the upper limit of the ratio of the thickness of the insulating coating 2002 to the thickness of the negative electrode current collector 200, it can be avoided that the thickness of the insulating coating 2002 is too large, which will cause the battery cell to be too thick and affect the energy density of the battery.

[0093] In some embodiments, the insulating coating 2002 comprises inorganic materials and / or polymer binders; wherein the inorganic materials comprise one or more of aluminum oxide, silicon oxide, zirconium oxide, calcium oxide, boehmite, magnesium oxide, and magnesium hydroxide; and the polymer binders comprise one or more of polyvinylidene fluoride, styrene-butadiene rubber, and polyacrylate.

[0094] In some embodiments, in combination Figure 8As shown, at least part of the insulating coating 2002 is located between the negative electrode active coating 201 and the negative electrode current collector 200 . Along the winding direction, the size of the overlapping area between the insulating coating 2002 and the negative electrode active coating 201 is P, satisfying: P≥0.5 mm.

[0095] The insulating coating 2002 at least partially extends to between the negative electrode active coating 201 and the negative electrode current collector 200 facing the outside of the winding core, that is, part of the negative electrode active coating 201 is coated on the surface of the insulating coating 2002; that is, Figure 8 The position shown in dimension P.

[0096] The size of the overlapping area between the insulating coating 2002 and the negative electrode active coating 201 satisfies P ≥ 0.5 mm, so that the insulating coating 2002 and the negative electrode active coating 201 at least partially overlap and both cover the outside of the negative electrode collector 200, thereby ensuring that the insulating coating 2002 can completely cover the negative electrode collector 200, and there is no exposed area of ​​the negative electrode collector 200, avoiding safety risks.

[0097] In some embodiments, in combination Figure 3 As shown, along the width direction of the winding core structure, the winding starting end of the positive electrode sheet 10 and the winding starting end of the negative electrode sheet 20 extend in opposite directions respectively.

[0098] By extending the winding starting end of the positive electrode sheet 10 and the winding starting end of the negative electrode sheet 20 in opposite directions, the positive electrode sheet 10 in this arrangement can be a continuous double-sided coating structure, which improves the efficiency of positive electrode coating and is beneficial to improving the energy density of the battery cell.

[0099] Further preferably, in combination Figure 4 As shown, the winding start ends of the positive electrode sheet 10 and the negative electrode sheet 20 are located on the same side along the width direction of the winding core structure.

[0100] In some embodiments, in combination Figure 3 As shown, along the width direction of the winding core structure, the distance between the tail end of the negative electrode sheet 20 located at the outermost circle of the winding core structure and the winding start end of the electrode sheet closest thereto is W;

[0101] Satisfies: W ≥ 1.0mm.

[0102] W is the distance from the end of the negative electrode current collector of the outermost circle of the core structure to the end of the positive electrode sheet 10 or the negative electrode sheet 20 of the innermost circle of the core structure. In one embodiment, Figure 3 As shown, when the number of folds of the battery cell is an odd number ( Figure 3In another embodiment, when the number of turns of the arc area of ​​the electrode sheet on one side of the width of the battery cell is 5), W is the distance from the end of the negative electrode collector of the outermost circle of the roll core structure to the starting end of the negative electrode sheet 20 of the innermost circle of the roll core structure; in another embodiment, when the number of turns of the battery cell is an even number (for example, when the number of turns of the arc area on one side of the battery cell is 6), W is the distance from the end of the negative electrode collector of the outermost circle of the roll core structure to the starting end of the positive electrode sheet 10 of the innermost circle of the roll core structure. After the winding of the roll core structure is completed, by limiting the lower limit of W, it is ensured that the negative electrode sheet 20 of the outermost circle can be wound to the plane area of ​​the roll core structure, avoiding winding in the arc area, preventing the tape from overlapping and affecting the battery energy density. Among them, the arc area refers to the area in an arc state on both ends of the roll core structure, and the plane area refers to the straight section of the roll core structure. The plane area is located in the middle area of ​​the arc area on both sides.

[0103] In some embodiments, in combination Figure 8 As shown, the winding core structure further includes a pole ear 40 , the width of the pole ear 40 is L1 , and the length of the negative electrode blank current collector area 52 is L2 , satisfying: L2 = (1 to 10) L1 .

[0104] The winding core structure further includes a tab 40, which is connected to the positive electrode sheet 10 and / or the negative electrode sheet 20. In this embodiment, taking the negative electrode sheet 20 as an example, the negative electrode current collector 200 of the negative electrode sheet 20 partially eliminates the negative electrode active coating 201, so that the tab 40 is directly connected to the negative electrode current collector 200, and the connection can be specifically made by welding.

[0105] By limiting the length of the negative electrode blank current collector area 52 to at least 1 times the width of the electrode tab 40 , the negative electrode blank current collector area 52 is ensured to have a certain length, thereby preventing the negative electrode single-sided coating area 51 from wrinkling.

[0106] Since the negative electrode single-sided coating area 51 is coated on one side, the uncoated side is prone to curling during the coating process. In this embodiment, a negative electrode blank current collector area 52 is formed by further extending the tail end of the negative electrode single-sided coating area 51, and the length of the negative electrode blank current collector area 52 is ensured. By stretching the negative electrode blank current collector area 52, the occurrence of wrinkling in the negative electrode single-sided coating area 51 can be delayed, thereby meeting the coating requirements of the negative electrode single-sided coating area 51 and preventing the negative electrode single-sided coating area 51 from wrinkling.

[0107] In this embodiment, the width L1 of the electrode tab 40 is not less than 10 mm, that is, the length L2 of the negative electrode blank current collector area 52 is not less than 10 mm.

[0108] In some embodiments, along the winding direction, the length of the insulating coating 2002 coated on the negative electrode blank current collector region 52 is L2, satisfying: 5 mm≤L2≤500 mm.

[0109] Due to the existence of L2, the wrinkling effect of the negative electrode single-sided coating area can be improved. If L2 is too small, the wrinkling cannot be effectively improved. If L2 is too large, the ineffective thickness of the battery cell will increase, resulting in a decrease in energy density.

[0110] By limiting the upper limit of the length L2 of the negative electrode blank current collector area 52 , it is avoided that the length of the negative electrode blank current collector area 52 is too long to cause material waste.

[0111] In some embodiments, in combination Fig.11 , Fig.12 As shown, the area of ​​the surface of the negative electrode collector 200 on the side facing away from the winding center of the core structure where the insulating coating 2002 is coated in the negative electrode single-sided coating area 51 of the outermost circle of the core structure is S1, and the area of ​​the negative electrode collector 200 facing the outside of the core that is not coated with the negative electrode active coating 201 is S2, satisfying: S1 / S2≥0.9.

[0112] By limiting S1 / S2≥0.9, it can be ensured that the insulating coating 2002 coated on the tail end of the negative electrode sheet 20 can insulate the negative electrode current collector 200 from the battery cell membrane shell, thereby improving safety performance.

[0113] In some embodiments, the negative electrode sheet 20 also includes a negative electrode head single-sided coating area located at the starting section of the negative electrode winding, wherein the negative electrode current collector 200 in the negative electrode head single-sided coating area is arranged toward the winding center of the core structure, and the negative electrode active coating 201 in the negative electrode head single-sided coating area is arranged away from the winding center of the core structure.

[0114] In some embodiments, the negative electrode winding start section of the negative electrode sheet 20 also includes a winding start end empty foil area 53 which is not coated with the negative electrode active coating 201 on both sides. Along the winding direction, the winding start end empty foil area 53 is sequentially connected with the negative electrode head single-sided coating area.

[0115] In some embodiments, in combination Fig.11 , Fig.12 As shown, the surface of the empty foil area 53 at the starting end of winding away from the winding center is at least partially coated with an insulating coating 2002; the area of ​​the insulating coating 2002 coated on the empty foil area 53 at the starting end of winding is S3, and the area of ​​the empty foil area 53 at the starting end of winding is S4, satisfying: S3 / S4≤0.3.

[0116] Since the negative electrode sheet 20 of this embodiment is formed with a negative electrode double-sided coating area 50 with negative electrode active coating 201 on both sides, and a negative electrode single-sided coating area 51 with negative electrode active coating 201 on one side, a negative electrode blank current collector area 52 is also formed without negative electrode active coating 201 on both sides.

[0117] Before being cut into the length required by a single winding core structure, the negative electrode sheet 20 is often arranged in a roll, usually with multiple negative electrode sheets 20 arranged continuously. The tail end of one electrode sheet is connected to the winding start end of another electrode sheet. During normal cutting, in order to ensure that the entire area of ​​the tail end is covered with the insulating coating 2002, it is usually necessary to keep a little insulating coating 2002 at the winding start end of the other electrode sheet, so as to avoid the negative electrode blank collector area 52 at the tail end, prevent the negative electrode collector 200 from being exposed at the tail end, and thus avoid short circuit.

[0118] By limiting S3 / S4≤0.3, it is possible to ensure that the area of ​​the insulating coating 2002 at the start of the winding is not too large, thereby avoiding affecting the thickness of the battery cell. It is ensured that the exposed current collector at the tail of the negative electrode is completely coated with the insulating layer, thereby avoiding the occurrence of corrosion caused by leaving part of the negative electrode current collector at the tail during cutting.

[0119] The performance of the core structure provided by the embodiment of the present invention is verified by comparing a blank group with a test group.

[0120] The positive electrode current collector 100 of the blank group and the experimental group was aluminum foil, the negative electrode current collector 200 was copper foil, and the width of the tab 40 was 6 mm.

[0121] Blank group:

[0122] The positive electrode sheet 10 and the negative electrode sheet 20 are both coated in a gap manner. After coating, the positive electrode sheet 10 is composed of a double-sided coating area, a single-sided coating area and a blank current collector area. Figure 2 As shown; the positive electrode sheet 10 is located at the outermost circle of the winding, and the negative electrode sheet 20 is located at the innermost layer of the winding. After the winding is completed, the Figure 1 As shown, the outermost side of the roll core structure is a single-sided positive electrode active coating 101 and a blank current collector, and the positive electrode active coating 101 faces the inner side of the roll core; the innermost side of the roll core is the negative electrode single-sided coating area 51 of the negative electrode sheet 20.

[0123] Experimental Group:

[0124] The positive electrode sheet 10 is coated continuously, that is, the positive electrode sheet has only a double-sided coating area, no single-sided coating area, and no blank current collector area (refer to Figure 5 As shown); the negative electrode sheet 20 is coated in a gap coating manner. After coating, the negative electrode sheet 20 is composed of a negative electrode double-sided coating area 50, a negative electrode single-sided coating area 51 and a negative electrode blank current collector area 52 (reference Figure 6), the length L2 of the negative electrode blank current collector area 52 is about 20mm. At the same time, an insulating coating 2002 is coated on the side of the negative electrode current collector 200 of the negative electrode sheet 20 facing the outer side of the winding core. The insulating coating 2002 is mainly composed of a binder and ceramic (aluminum oxide). The thickness of the insulating coating 2002 after rolling is about 6um to 8um. In order to ensure that there is no exposure of the negative electrode current collector 200 on the side of the second side negative electrode active coating 2003, the insulating coating 2002 extends between the second side negative electrode active coating 2003 and the negative electrode current collector 200, and its size P is about 2mm. After winding is completed, the outermost side of the core structure is the negative single-sided coating area 51 of the negative electrode sheet 20 and the negative blank current collector area 52, wherein the insulating coating 2002 on the negative current collector 200 is located on the side of the negative electrode sheet away from the center of the core, and the first side negative active coating 2001 faces the center of the core; the double-sided coating of the positive electrode sheet 10 on the innermost side of the core and the negative double-sided coating area 50 of the negative electrode sheet 20 are arranged opposite to each other, and the winding starting end of the positive electrode sheet 10 and the winding starting end of the negative electrode sheet 20 are respectively located on both sides of the width direction of the core structure.

[0125] After the winding of the blank group and the experimental group is completed, they flow down the production line simultaneously. After the packaging, liquid injection, formation, capacity division and other processes, the batteries are taken for inspection. The relevant parameters in the production process are kept consistent.

[0126] Combination Fig.13 As shown, during the cycle, it was found that the blank group experienced a cliff drop in capacity retention rate at about 150 cycles, while the experimental group did not experience this phenomenon. Disassembly revealed that the main reason for this phenomenon in the blank group was that the positive electrode sheet 10 had broken pieces at the junction of the double-sided coating area and the single-sided coating area on the outside of the winding core, resulting in its capacity not being able to function normally, leading to a cliff-like drop in capacity retention rate. The reason why the experimental group was able to improve the problem of broken pieces of the positive electrode sheet 10 is mainly because the positive electrode sheet 10 in the experimental group adopts a continuous coating method, and compared with the blank group, the design of the single-sided coating area is cancelled. During the rolling process, the positive electrode collector 100 will not be damaged due to the sudden change of pressure at the junction of the double-sided coating area and the single-sided coating area, thereby avoiding a reduction in its tensile strength, thereby improving the problem of cycle broken pieces.

[0127] According to an embodiment of the present invention, on the other hand, a battery is provided, comprising:

[0128] case;

[0129] and a winding core structure as described above disposed in the housing;

[0130] The insulating coating 2002 at least partially coated on the negative electrode single-sided coating area of ​​the outermost circle of the core structure is located between the shell and the negative electrode collector 200 of the outermost circle of the negative electrode sheet 20.

[0131] The shell includes a cell membrane shell. After the core structure is packaged, the insulating coating 2002 is located between the negative electrode current collector 200 and the cell membrane shell, and is arranged away from the center of the core, thereby preventing the formation of a galvanic cell between the negative electrode current collector 200 and the cell membrane shell, avoiding corrosion, and improving the safety performance of the battery.

[0132] Obviously, the above embodiments are only examples for clear explanation and are not intended to limit the implementation methods. Although the embodiments of the present invention are described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations all fall within the scope defined by the present invention.

Claims

1. A winding core structure, characterized in that: The winding core structure comprises a negative electrode sheet (20), a separator (30) and a positive electrode sheet (10), wherein the negative electrode sheet (20), the separator (30) and the positive electrode sheet (10) are stacked in sequence, wherein along the thickness direction of the winding core structure, the negative electrode sheet (20) is located at the outermost circle of the winding core structure, and the outermost circle is the layer farthest from the winding center along the thickness direction of the winding core; the positive electrode sheet (10) comprises a positive electrode current collector (100) and a positive electrode active coating (101) at least partially coated on the surfaces of both sides of the positive electrode current collector (100); The negative electrode sheet (20) comprises a negative electrode current collector (200), a negative electrode double-sided coating area (50) coated on both sides of the negative electrode current collector (200) along the thickness direction of the negative electrode sheet, and a negative electrode single-sided coating area (51) coated on one side of the negative electrode current collector (200); At least part of the negative electrode single-sided coating area (51) is located at the outermost circle of the winding core structure, wherein the negative electrode current collector (200) of the negative electrode single-sided coating area (51) located at the outermost circle of the winding core structure faces away from the winding center of the winding core structure, and the negative electrode active coating (201) of the negative electrode single-sided coating area (51) faces the winding center of the winding core structure; The negative electrode sheet also includes: an insulating coating (2002), at least a portion of which is coated on a surface of the negative electrode current collector (200) in the negative electrode single-sided coating area (51) of the outermost circle of the winding core structure, which is away from the winding center of the winding core structure.

2. The winding core structure according to claim 1, characterized in that: The negative electrode sheet (20) is also formed with a negative electrode blank current collector area (52) on both sides of which the negative electrode active coating (201) is not coated, and the negative electrode blank current collector area (52) is continuously arranged at the tail end of the negative electrode single-sided coating area (51); The insulating coating (2002) is also coated on a surface of the negative electrode current collector (200) in the negative electrode blank current collector region (52) that is away from the winding center of the winding core structure.

3. The winding core structure according to claim 2, characterized in that: Along the winding direction, the negative electrode sheet (20) exceeds the tail end of the separator (30); and the separator (30) exceeds the tail end of the positive electrode sheet (10).

4. The winding core structure according to claim 1, characterized in that: The thickness of the insulating coating (2002) is H, and the thickness of the negative electrode current collector (200) is H1, satisfying: H=(0.2-4.0)H1.

5. The winding core structure according to claim 1, characterized in that: The insulating coating (2002) comprises inorganic materials and / or polymer binders; wherein the inorganic materials comprise one or more of aluminum oxide, silicon oxide, zirconium oxide, calcium oxide, boehmite, magnesium oxide, and magnesium hydroxide; and the polymer binder comprises one or more of polyvinylidene fluoride, styrene-butadiene rubber, and polyacrylate.

6. The winding core structure according to claim 1, characterized in that: At least part of the insulating coating (2002) is located between the negative electrode active coating (201) and the negative electrode current collector (200), and along the winding direction, the size of the overlapping area of ​​the insulating coating (2002) and the negative electrode active coating (201) is P, satisfying: P≥0.5mm.

7. The winding core structure according to any one of claims 1 to 6, characterized in that: Along the width direction of the winding core structure, the winding start end of the positive electrode sheet (10) and the winding start end of the negative electrode sheet (20) extend in opposite directions respectively.

8. The winding core structure according to claim 1, characterized in that: The winding start ends of the positive electrode sheet (10) and the negative electrode sheet (20) are located on the same side in the width direction of the winding core structure.

9. The winding core structure according to claim 7, characterized in that: Along the width direction of the winding core structure, the distance between the tail end of the negative electrode sheet (20) located at the outermost circle of the winding core structure and the winding start end of the electrode sheet closest thereto is W; Satisfies: W ≥ 1.0 mm.

10. The winding core structure according to claim 2, characterized in that: Along the winding direction, the length of the insulating coating (2002) coated on the negative electrode blank current collector region (52) is L2, satisfying: 5mm≤L2≤500mm.

11. The winding core structure according to claim 1 or 2, characterized in that: The area of ​​the surface of the negative electrode current collector (200) on the side facing away from the winding center of the core structure where the insulating coating (2002) is coated in the negative electrode single-sided coating area (51) of the outermost circle of the core structure is S1, and the area of ​​the negative electrode current collector (200) on the side facing the outer side of the core that is not coated with the negative electrode active coating (201) is S2, satisfying: S1 / S2≥0.

9.

12. The winding core structure according to any one of claims 1 to 6 or 8, characterized in that: The negative electrode sheet (20) further comprises a negative electrode head single-sided coating area located at the starting section of the negative electrode winding, wherein the negative electrode current collector (200) in the negative electrode head single-sided coating area is arranged toward the winding center of the winding core structure, and the negative electrode active coating (201) in the negative electrode head single-sided coating area is arranged away from the winding center of the winding core structure.

13. The winding core structure according to claim 12, characterized in that: The negative electrode winding start section of the negative electrode sheet (20) further comprises a winding start end empty foil area (53) which is not coated with the negative electrode active coating (201) on both sides, and along the winding direction, the winding start end empty foil area (53) is sequentially connected with the negative electrode head single-sided coating area.

14. The winding core structure according to claim 13, characterized in that: The surface of the empty foil area (53) at the starting end of winding away from the winding center is at least partially coated with the insulating coating (2002); the area of ​​the insulating coating (2002) coated on the empty foil area (53) at the starting end of winding is S3, and the area of ​​the empty foil area (53) at the starting end of winding is S4, satisfying: S3 / S4≤0.

3.

15. A battery, characterized in that: include: case; and a winding core structure as claimed in any one of claims 1 to 14 disposed in the housing; The insulating coating (2002) at least partially coated on the negative electrode single-sided coating area of ​​the outermost circle of the winding core structure is located between the shell and the negative electrode collector (200) of the outermost circle of the negative electrode sheet (20).

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