Roll core and battery

Abstract

The invention discloses a roll core and a battery, the roll core comprises an anode sheet, a diaphragm and a cathode sheet which are stacked in sequence, the anode sheet comprises an anode sheet main body and an anode active layer, the cathode sheet comprises a cathode sheet main body and a cathode active layer, the anode active layer covers the cathode active layer, and the diaphragm covers the cathode active layer. The roll core is divided into two free sections and a middle section in the length direction, the width value of at least part of the anode active layer in the middle section is A, the width value of at least part of the anode active layer in the free sections is B, the width value of at least part of the cathode active layer in the middle section is C, and the width value of at least part of the cathode active layer in the middle section is A; the width value of at least part of the cathode active layer at the free section is D, d0 is set to be equal to A-C, d is set to be equal to B-D, both d0 and d are larger than 0, and d is larger than d0; the invention mainly solves the technical problem of how to manufacture the roll core which can still ensure that the anode active layer can completely cover the cathode active layer even if the head and tail swinging phenomenon occurs to a certain extent.

Description

Technical Field

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

[0002] The cells inside the current battery are divided into a stacked structure or a wound structure, i.e., a wound core, wherein the stacked cell is stacked in the order of anode, separator, cathode, separator, anode, etc., wherein the wound cell is stacked by anode, separator and cathode, and then wound, wherein the anode is also called a negative electrode in this field, and the cathode is also called a positive electrode in this field, wherein the separator plays the role of separating the anode and cathode to avoid contact between the anode and cathode and causing a short circuit inside the battery, and the outer dimensions of the separator are usually designed to be larger than the outer dimensions of the anode and the cathode to ensure that the anode and cathode do not contact each other. Specifically, during the charge and discharge process of the cell, ions will pass through the separator under the action of the electrolyte and move between the anode and cathode, that is, the ions will be embedded or de-embedded back and forth on the two electrodes.

[0003] The anode active layer in the anode sheet usually adopts OH (overhang) design. Specifically, the so-called OH design is as follows: Figure 1 As shown, after the anode sheet and the cathode sheet are stacked together through the separator, the anode active layer ( Figure 1 The cathode active layer (shown in dark grey) needs to completely cover the cathode sheet. Figure 1 In other words, when the anode sheet and the cathode sheet are stacked, the anode active layer on the anode sheet will protrude relative to the cathode active layer on the cathode sheet in the width direction, that is, the area of ​​the anode active layer on the anode sheet is larger than the area of ​​the cathode active layer on the cathode sheet, so that the anode active layer on the anode sheet completely covers the cathode active layer on the cathode sheet, thereby ensuring that the ions precipitated from the cathode sheet can be embedded in the anode after passing through the diaphragm, and ensuring that the ions precipitated from the cathode sheet will not be scattered to the area outside the anode sheet, so as to ensure the safety of the battery cell.

[0004] See also Figure 2 When the battery cell adopts a winding structure, there will be two free sections after the battery cell is wound, one of which is wound at the innermost head end, and the other is wound at the outermost end. Since the two free sections have a certain degree of freedom, the anode sheet and / or cathode sheet at the two free sections are prone to offset and misalignment during the winding process (also known as the tail swing problem in this field), especially the terminal free section. During the actual winding process of the battery cell, the terminal free section is more likely to have the problem of relative misalignment of the anode sheet and the cathode sheet under the action of the winding traction tension, resulting in the terminal anode active layer ( Figure 2The cathode active layer at the end (indicated by dark gray) cannot be completely covered Figure 2 The ions precipitated from the cathode sheet will be scattered to the area outside the anode sheet, which will have a great impact on the safety of the battery cell.

[0005] Therefore, it is necessary to improve the existing technology. Summary of the invention

[0006] The present invention provides a winding core and a battery, which mainly solve the technical problem that the anode active layer at the free section of the battery core adopting the winding structure cannot completely cover the cathode active layer.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] A winding core, comprising an anode sheet, a separator and a cathode sheet stacked in sequence, wherein the anode sheet comprises an anode sheet body and an anode active layer arranged on a side of the anode sheet body facing the separator, and the cathode sheet comprises a cathode sheet body and a cathode active layer arranged on a side of the cathode sheet body facing the separator, and the anode active layer covers the cathode active layer;

[0009] The winding core is divided into two free sections and a middle section between the two free sections in the length direction, wherein one of the free sections is a first section for winding inside, and the other free section is a last section for winding outside, the effective width value of at least part of the anode active layer located in the middle section is A, the effective width value of at least part of the anode active layer located in the free section is B, the effective width value of at least part of the cathode active layer located in the middle section is C, and the effective width value of at least part of the cathode active layer located in the free section is D, assuming d 0 =AC, let d=BD, where d 0 and d are both greater than 0, d>d 0 .

[0010] In one of the technical solutions, D is smaller than C.

[0011] In one of the technical solutions, A and B are equal.

[0012] In one of the technical solutions, the effective width value of the cathode active layer of a single free segment is assumed to be the length of the D portion is L, wherein L is 0.1m-0.5m.

[0013] In one of the technical solutions, B is greater than A.

[0014] In one of the technical solutions, D is equal to C.

[0015] In one of the technical solutions, the effective width of the anode active layer of a single free segment is assumed to be the length of portion B is L, wherein L is 0.1m-0.5m.

[0016] In one of the technical solutions, D is smaller than C, and B is larger than A.

[0017] In one of the technical solutions, the d 0 is 1.9-3.5mm, d is 2.2-4.2mm, dd 0 0.3-2.3mm.

[0018] In one of the technical solutions, the d 0 is 1.9-3.5mm, d is 2.5-4.9mm, dd is 0 0.6-3mm.

[0019] In one of the technical solutions, the anode sheet or the cathode sheet is cut from a material strip, and the surface of the material strip is coated with an anode active layer or a cathode active layer before cutting; after the material strip is cut, a plurality of pole ears are cut out of at least one side of the pole sheet in the width direction, and the amount of active layer cut in the width direction of at least one of the first section and the last section of the pole sheet is different from the amount of active layer cut in the width direction of the middle section of the pole sheet.

[0020] In one of the technical solutions, after the cathode sheet is cut and processed, the D value is smaller than the C value.

[0021] In one of the technical solutions, after the anode sheet is cut and processed, the B value is greater than the A value.

[0022] In one of the technical solutions, an insulating layer is provided on one side of the cathode active layer of the cathode sheet in the width direction.

[0023] In one of the technical solutions, the cathode active layer located in the free section is at least partially covered by the insulating layer in the width direction, so that C is greater than D.

[0024] In one of the technical solutions, let the free length of the free section be L, let △d=dd 0 = (BD) - (AC), △d ≥ 0.5L 2 +0.5L+0.2, where L is 0.1m-0.5m and △d is 0.3mm—0.7mm.

[0025] In one of the technical solutions, when A and B are equal, the △d is the difference of (CD), and the (CD) ≥ 0.5L 2+0.5L+0.2, (CD) is 0.3-0.7mm.

[0026] 16. The winding core according to claim 14, characterized in that when C and D are equal, the Δd is the difference of (BA), and the (BA) ≥ 0.5L 2 +0.5L+0.2, (BA) is 0.3-0.7mm.

[0027] The present application also provides a battery, comprising a shell and the winding core described above, wherein the winding core is accommodated inside the shell.

[0028] Compared with the prior art, the manufacturing method of the winding core provided by the present invention has at least the following beneficial effects:

[0029] In the process of manufacturing the winding core, the middle section of the winding core can be made according to the existing d 0 The width difference is used to coat the corresponding active layer on the anode sheet and the cathode sheet. For example, in the middle section, the coating width A of the anode active layer is originally designed to be 1.2 times the coating width C of the cathode active layer; but for the free section, the winding core of this scheme is designed to be larger than d 0 ; Thereby ensuring that even if the anode sheet or cathode sheet at the free section has a certain degree of tail swinging problem, it can also ensure that the anode active layer at the free section can still completely cover the cathode active layer, thereby improving the stability and safety of the core during the charging and discharging process and helping to extend the service life of the core, so as to meet the design requirements of high safety and long service life for battery applications in the automotive field. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0031] Figure 1 A schematic diagram of the structure of a positive electrode sheet (cathode sheet) and a negative electrode sheet (anode sheet) in a winding core provided by the prior art of the present application when they are stacked on each other in an ideal state;

[0032] Figure 2 A schematic diagram of the structure of a positive electrode sheet (cathode sheet) and a negative electrode sheet (anode sheet) in a winding core provided by the prior art of the present application when they are superimposed on each other in actual situations and a tail swing problem occurs;

[0033] Figure 3 A schematic diagram of the structures of three cathode sheets and two anode sheets provided in Example 1 of the present application;

[0034] Figure 4 A schematic diagram of the structure of a battery cell provided in Example 1 of the present application;

[0035] Figure 5 A schematic diagram of the structure of a battery provided in Example 1 of the present application;

[0036] Figure 6 A schematic diagram of the structure of a small section of a material strip for making a cathode sheet provided in Example 2 of the present application, with multiple cathode ears cut out on both sides in the width direction;

[0037] Figure 7 A schematic diagram of the structure of a small section of a material strip for making an anode sheet provided in Example 2 of the present application, with multiple anode ears cut out on both sides in the width direction;

[0038] Figure 8 A schematic diagram of the structure of a small section of a material strip for making a cathode sheet provided in Example 2 of the present application, both sides of which in the width direction are coated with an insulating layer and a plurality of cathode ears are cut out;

[0039] Fig. 9 A flow chart of a method for manufacturing a first pole piece provided in Embodiment 2 of the present application;

[0040] Fig.10 A flow chart of a method for manufacturing a second pole piece provided in Example 2 of the present application.

[0041] Reference numerals:

[0042] 11. Anode sheet body; 12. Anode active layer; 13. Anode ear; 21. Cathode sheet body; 22. Cathode active layer; 23. Cathode ear; 3. Insulating layer; 4. Outer film; 5. Positive electrode ear; 6. Negative electrode ear; 7. Outer shell; 71. Shell; 72. Top cover; 721. Pole; 8. Cell; 10. Middle section; 20. Free section. DETAILED DESCRIPTION

[0043] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0044] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

[0045] It should be understood that the orientations or positional relationships indicated by terms such as "upper", "lower", "top", "bottom", "inside", and "outside" are based on the orientations or positional relationships shown in the accompanying drawings and are only for the convenience of describing the present application and simplifying the description. They do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0046] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0047] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0048] Embodiment 1

[0049] See also Figure 3 The embodiment of the present invention provides a winding core, which includes an anode sheet, a separator and a cathode sheet. The anode sheet, the separator and the cathode sheet are stacked and wound in sequence to form the winding core. The separator is used to separate the anode sheet and the cathode sheet to prevent the anode sheet and the cathode sheet from directly contacting each other and causing an internal short circuit in the winding core. The anode sheet includes an anode sheet body 11 and an anode active layer 12 coated on the anode sheet body 11. The anode sheet body 11 is used to carry the anode active layer 12. When the anode sheet and the separator are stacked on each other, the side of the anode sheet coated with the anode active layer 12 needs to face the separator. Figure 3 The light grey part in the “first anode sheet” and the “second anode sheet” represents the anode sheet main body 11, wherein the anode sheet main body 11 can be selected as copper foil, or in order to increase the conductivity of the anode sheet, the anode sheet main body 11 can also be selected as copper foil coated with a conductive carbon layer, or in order to increase the bonding force, the anode sheet main body 11 can also be selected as copper foil coated with an adhesive layer. Figure 3 The black part in the "first anode sheet" and "second anode sheet" represents the anode active layer 12. The cathode sheet includes a cathode sheet body 21 and a cathode active layer 22 coated on the cathode sheet body 21. The cathode sheet body 21 is used to carry the cathode active layer 22. The cathode sheet body 21 can be selected as aluminum foil, or in order to increase the conductivity of the cathode sheet, the cathode sheet body 21 can also be selected as aluminum foil coated with a conductive layer, or in order to increase the bonding force, the cathode sheet body 21 can also be selected as aluminum foil coated with an adhesive layer. When the cathode sheet is stacked with the diaphragm, the side of the cathode sheet coated with the cathode active layer 22 needs to face the diaphragm. Figure 3 The light grey portion in the “first cathode sheet”, “second cathode sheet” and “third cathode sheet” represents the cathode sheet main body 21. Figure 3 The black part in the "first cathode sheet", "second cathode sheet" and "third cathode sheet" represents the cathode active layer 22. The design requirement of the winding core is that the anode active layer 12 needs to be larger than the cathode active layer 22 in both the length direction (ie, X direction) and the width direction (ie, Y direction) so that the anode active layer 12 can completely cover the cathode active layer 22.

[0050] The winding core can be divided into the first section, the middle section and the last section in the length direction (that is, the direction of conveying the pole piece during the winding process). The first section is located at the starting end of the winding core, and the last section is located at the end of the winding core. The first section and the last section are collectively referred to as the free section. Figure 3 , a single pole piece can be divided into a first section, a middle section 10 and a last section which are connected in sequence in the length direction, wherein, after the anode sheet, the diaphragm and the cathode sheet are wound and cut, the first section is wound at the innermost part and the last section is wound at the outermost part. The first section and the last section are prone to head and tail swinging due to a certain degree of freedom after winding and cutting, so the first section and the last section of the pole piece can be called free sections 20, and the two free sections 20 are equivalent to being arranged at the two ends of the middle section 10 in the length direction. The various figures of this embodiment take a free section 20 on the left as the first section and a free section 20 on the right as the last section as an example. After the winding core is wound, the two free sections 20 have a certain degree of freedom, so the anode sheet or the cathode sheet is more likely to have head and tail swinging problems, resulting in the anode active layer 12 not completely covering the cathode active layer 22 in the end area of ​​the free section 20, especially the free section 20 at the last section is more prone to tail swinging due to the larger radius after winding and the larger degree of freedom. In this regard, this embodiment adopts the following technical means to solve this technical problem:

[0051] like Figure 3 As shown, let the effective width of the anode active layer 12 in the middle section 10 be A, let the effective width of the anode active layer 12 in the free section 20 be B, let the effective width of the cathode active layer 22 in the middle section 10 be C, let the effective width of the cathode active layer 22 in the free section 20 be D, let d 0 =AC, let d=BD, where d 0 and d are both greater than 0, and d of at least part of the free section 20 is greater than d 0 Specifically, when designing the winding core, the middle section 10 of the winding core can be designed according to d 0 For example, conventionally A is designed to be 1.2 times of C, but for the free section 20 of the winding core, the present solution designs the d value to be greater than d 0, thereby ensuring that even if the anode sheet or cathode sheet at the free section 20 has a certain degree of tail swing problem, it can also ensure that the anode active layer 12 at the free section 20 can still completely cover the cathode active layer 22, thereby improving the stability and safety of the core during the charging and discharging process and helping to extend the service life of the core, so as to meet the design requirements of high safety and high service life of batteries in the automotive field. Optionally, the effective width value of part of the middle section 10 can be A, or the effective width value of all the middle sections 10 can be A; similarly, the above settings also apply to B, C, and D, which can be the effective width value of part of the section or the effective width value of the entire section. The effective width value here refers to the length of the active layer of the portion of the electrode sheet that is not covered by its own other inactive substances in the width direction of the electrode sheet, expressed as Figure 3 Taking the third type of electrode as an example, the effective width D of the first section on the far left is the width of the black active layer that is not covered by gray or the like.

[0052] In this embodiment, the two free sections 20 of the winding core are preferably designed to have d greater than d 0 In other embodiments, one of the first free section 20 or the last free section 20 of the winding core is designed to have d greater than d 0 Yes.

[0053] Please refer again Figure 3 , in order to achieve d greater than d 0 , this embodiment provides the following three technical solutions:

[0054] The first technical solution: A and B can be equal, and D is designed to be smaller than C, so that d is greater than d 0 , that is, the core of this solution is equivalent to using Figure 3 The "second anode sheet" and "second cathode sheet" in the embodiment of the present invention are equivalent to the winding core of the present invention. Figure 3 The "second anode sheet" and "third cathode sheet" in ;

[0055] The second technical solution: B is designed to be greater than A, and C is designed to be equal to D, so that d is greater than d 0 , that is, the core of this solution is equivalent to using Figure 3 The "first anode sheet" and "first cathode sheet" in the invention;

[0056] The third technical solution: B is designed to be greater than A, and D is designed to be less than C, so that d is greater than d 0 , that is, the core of this solution is equivalent to using Figure 3 The "first anode sheet" and "second cathode sheet" in the embodiment of the present invention are equivalent to the winding core of the present invention. Figure 3 The “first type of anode sheet” and the “third type of cathode sheet”.

[0057] Optionally, both sides of the pole piece are coated with an active layer, and further, the active layers on both sides of the pole piece body are completely identical.

[0058] Optionally, the effective width value of at least part of the anode active layer of the outermost anode sheet of the winding core is B, and the effective width value of at least part of the cathode active layer of the outermost cathode sheet of the winding core is D. In other words, the d corresponding to at least part of the outermost circle of the winding core is greater than d 0 , here can be the entire outermost circle or part of the outermost circle.

[0059] In the above-mentioned first technical solution and the second technical solution, optionally d 0 is 1.9-3.5mm, d is 2.2-4.2mm, dd 0 In the third technical solution, d 0 is 1.9-3.5mm, d is 2.5-4.9mm, dd is 0 0.6-3mm.

[0060] Please refer again Figure 3 Preferably, the cathode sheet body 21 is cut so that the cathode sheet body 21 has a width direction (i.e. Figure 3 The Y direction in the middle) is connected to one side with multiple Figure 3 The cathode ears 23 are arranged at intervals in the X direction in the anode sheet body 11, and the anode sheet body 11 is cut so that one side of the anode sheet body 11 in the width direction is connected with a plurality of cathode ears 23 arranged in the length direction (i.e. Figure 3 When the anode sheets, separators and cathode sheets are stacked and wound into a wound structure, all cathode ears 23 need to be assembled and welded together to form the positive electrode ears 5, and all anode ears 13 also need to be assembled and welded together to form the negative electrode ears 6. By providing a plurality of cathode ears 23 and a plurality of anode ears 13, the active material inside the roll core can be charged or discharged at various positions at the same time, so that the charging or discharging performance of the roll core is fully exerted.

[0061] In another embodiment, the cathode sheet body 21 is cut so that the cathode sheet body 21 has a width direction (i.e. Figure 3 Both sides of the Y direction are connected with multiple Figure 3 The cathode ears 23 are arranged at intervals in the X direction; the anode sheet body 11 is cut so that the anode sheet body 11 is in the width direction (ie Figure 3 Both sides of the Y direction are connected with multiple Figure 3 Anode ears 13 are arranged at intervals (in the X direction).

[0062] Further optionally, the present solution further coats the root of the cathode ear 23 of the cathode sheet with an insulating layer 3, and the insulating layer 3 and the cathode active layer 22 are arranged on the same surface of the cathode sheet body 21. Figure 3 The dark gray part in the "first cathode sheet", "second cathode sheet" and "third cathode sheet" represents the insulating layer 3. The insulating layer 3 plays a role in strengthening the root of the cathode ear 23 to prevent the cathode ear 23 of the cathode sheet from being too soft and easy to wrinkle. The insulating layer 3 also plays a role in preventing the burrs on the anode sheet from piercing the cathode sheet, reducing the risk of internal short circuit in the winding core and improving the safety of the winding core. The insulating layer 3 is preferably TF8 (a type of thermal conductive silicone grease). The thermal conductivity of TF8 is 12.5W / mK. TF8 has good heat dissipation performance and can more effectively transfer the heat generated by the winding core to the outside. In addition, TF8 has good stability and can maintain stable heat dissipation performance in high temperature environments.

[0063] In other embodiments, there may be no ear portions on the anode sheet main body 11 and the cathode sheet main body 21, that is, the anode sheet main body 11 and the cathode sheet main body 21 may be square rectangular structures, and the external positive ear may be connected to the cathode sheet main body 21 at multiple positions in the length direction through multiple connecting sheets, and the external negative ear may also be connected to the anode sheet main body 11 at multiple positions in the length direction through multiple connecting sheets. In this case, the purpose of simultaneously charging or discharging the active materials in the core roll at various positions to give full play to the charging or discharging performance of the core roll can also be achieved.

[0064] Depend on Figure 3 It can be seen that both the “second cathode sheet” and the “third cathode sheet” are designed with D less than C. In order to achieve D less than C, this embodiment provides the following two manufacturing methods:

[0065] Manufacturing method one: The anode sheet or cathode sheet is cut from a material strip, and the surface of the material strip is coated with an anode active layer or a cathode active layer before cutting. After the material strip is cut, multiple pole ears are cut out on at least one side of the electrode sheet in the width direction (i.e., the Y direction), and the amount of active layer cut in the width direction of at least one of the first and last sections of the electrode sheet is different from the amount of active layer cut in the width direction of the middle section of the electrode sheet. It can be specifically understood that for the cathode sheet, at the first or last section, by cutting the cathode sheet body 21 along the Y direction, part of the cathode active layer 22 is also cut, so that the remaining effective coating width value of the cathode active layer 22 at the first or last section is reduced from the original C value to the D value, thereby forming Figure 3The structure of the "second cathode sheet" shown; for the anode sheet, at the middle section 10, by cutting the anode sheet body 11 along the Y direction and also cutting part of the anode active layer 12, the remaining effective coating width value of the anode active layer 12 at the middle section 10 is reduced from the original B value to the A value.

[0066] Manufacturing method one of the above section is further explained. In one of the schemes, the active layer cutting amount in the width direction of the first and last sections of the electrode sheet may be different from the active layer cutting amount in the width direction of the middle section of the electrode sheet, that is, for the anode sheet, the anode active layer cutting amount in the width direction of the first and last sections of the anode sheet may be smaller than the anode active layer cutting amount in the width direction of the middle section of the anode sheet; for the cathode sheet, the cathode active layer cutting amount in the width direction of the first and last sections of the cathode sheet may be larger than the cathode active layer cutting amount in the width direction of the middle section of the cathode sheet.

[0067] Manufacturing method 2: By increasing the coating width of the insulating layer 3 at the free section 20, the insulating layer 3 covers a small portion of the surface of the cathode active layer 22, so that the remaining effective coating width of the cathode active layer 22 is reduced from the original C value to the D value, thereby forming Figure 3 The structure of the "third cathode sheet" is shown.

[0068] The second manufacturing method of the above section is further described. It can be seen from the above that in this embodiment, a plurality of cathode ears 23 arranged at intervals are preferably connected to at least one side of the cathode sheet main body 21 in the width direction, and the above-mentioned insulating layer 3 is provided at the root of the cathode ear 23. The width of the insulating layer 3 covering the cathode active layer 22 in the middle section 10 is set to E (E is greater than or equal to 0), and the width of the insulating layer 3 covering the cathode active layer 22 in the free section 20 is set to F. At least in one free section 20, F is greater than E, thereby achieving the purpose of D being less than C. If this cathode sheet and Figure 3 If the "second type of anode sheet" is used in combination, then F = E + (CD). Since the two free sections 20 of the winding core of this embodiment are preferably designed with D less than C, the two free sections 20 of the winding core of this embodiment are designed with F greater than E.

[0069] Manufacturing method three: When coating the active material, the width of the active material coating is controlled so that the width of the active layer in the first section or the last section of the electrode is different from that in the middle section.

[0070] Let △d = dd 0= (BD) - (AC), the free length L of the free section 20 and the data of the tail swing of the anode or cathode sheet are deduced and calculated, and it is found that in order to ensure that the anode active layer 12 at the free section 20 can completely cover the cathode active layer 22, △d and L conform to the quadratic function △d=0.5L 2 +0.5L+0.2, then when △d≥0.5L 2 +0.5L+0.2, it can be ensured that the anode active layer 12 at the free section 20 can completely cover the cathode active layer 22. In other words, as long as the free length L of the free section 20 is confirmed, the minimum value of △d can be determined, thereby confirming the size of the anode active layer 12 widening in the free section 20 or the cathode active layer 22 narrowing in the free section 20, wherein the free length L of the free section 20 can be specifically understood as the area where the cathode active layer 22 on the cathode sheet is narrowed, or, it can be understood as the area where the anode active layer 12 on the anode sheet is widened, and the following table shows three experimental data.

[0071]

[0072] Please refer again Figure 3 , since the first free section 20 on the left is wound at the innermost part, its free length L is shorter, so this embodiment preferably changes the active layer corresponding to a small section L of the first two pole ears (widens the anode active layer 12 and narrows the cathode active layer 22); since the last free section 20 on the right is wound at the outermost part, its free length L is longer, so this embodiment preferably changes the active layer corresponding to a small section L of the last three pole ears (widens the anode active layer 12 and narrows the cathode active layer 22). Usually, the free length L of the free section 20 will fall within the range of 0.1m to 0.5m. According to the relationship of △d=0.5L2+0.5L+0.2, the width dimension △d of the corresponding active layer in the free section 20 falls within the range of 0.3-0.7mm, preferably d 0 is 1.9-3.5mm, and d is 2.2-4.2mm.

[0073] like Figure 3 As shown, when A and B are equal, △d is actually the difference of (CD), then (CD) ≥ 0.5L 2 +0.5L+0.2, (CD) specifically 0.3-0.7mm.

[0074] like Figure 3 As shown, when C and D are equal, △d is actually the difference of (BA), then (BA) ≥ 0.5L 2 +0.5L+0.2, (BA) specifically is 0.3-0.7mm.

[0075] See also Figure 4 The present embodiment further provides a battery cell monomer, which includes an outer film 4 (mostly aluminum-plastic film at present), a positive electrode tab 5, a negative electrode tab 6 and the above-mentioned winding core. A plurality of cathode tabs 23 are assembled and welded to form a positive electrode tab 5 and connected to the cathode sheet body 21. A plurality of anode tabs 13 are assembled and welded to form a negative electrode tab 6 and connected to the anode sheet body 11. The outer film 4 wraps the winding core and is sealed and connected to the positive electrode tab 5 and the negative electrode tab 6 respectively through hot melt adhesive. The positive electrode tab 5 and the negative electrode tab 6 are both exposed relative to the outer film. When the positive electrode tab 5 and the negative electrode tab 6 are respectively connected to the outside, the purpose of charging or discharging the winding core can be achieved.

[0076] See also Figure 5 The present embodiment further provides a battery, which includes a shell 7 and the above-mentioned battery cell 8. The shell 7 generally includes a shell 71 and a top cover 72. At least one battery cell 8 is accommodated in the shell 71. Two poles 721 are generally provided on the top cover 72. One pole 721 is used to connect to the positive electrode tab 5, and the other pole 721 is used to connect to the negative electrode tab 6, so that the positive and negative electrodes inside the winding core are led outward through the pole 721.

[0077] Embodiment 2

[0078] This embodiment provides a method for preparing a pole piece, which mainly includes the following steps:

[0079] S1: Provide a substrate, which can be understood as a current collector made of a metal foil. The substrate can also be understood as a current collector on which other functional layers have been pre-coated on the metal foil. The functional layer may be fully coated on the metal foil or partially coated on the metal foil. The functional layer may be a conductive carbon layer coated to increase conductivity, or an adhesive layer coated to increase the bonding strength between the active layer and the substrate, etc.

[0080] S2: coating the active layer on the substrate using a coating mechanism to form a material strip, Figure 6 to Figure 7 The following are all small sections of the strip, such as Figures 6 to 8 As shown, the material strip includes at least one pole piece active material coating area in the length direction (i.e., X direction) and the width direction (i.e., Y direction), and an active layer is coated on the pole piece active material coating area by a coating mechanism. The pole piece has a first section, a middle section, and a last section connected in sequence in the length direction (i.e., X direction), and the pole piece active material coating area has a corresponding active material coating area first section, an active material coating area middle section, and an active material coating area last section;

[0081] S3: The cutting mechanism cuts the material strip to form the pole piece, and makes the effective width of the active layer of at least part of the first section and / or the last section of the final pole piece different from the effective width of the active layer of at least part of the middle section of the pole piece. In this step, after cutting the material strip, in addition to changing the effective width of the active layer of the first section, the last section or the middle section of the pole piece, it is preferred that at least one side of the pole piece in the width direction can be cut as follows: Figures 6 to 8 A plurality of pole ear portions are shown which are arranged at intervals along the X direction.

[0082] The effective width here refers to the length of the active material on the electrode substrate that is not covered by other inactive materials after coating and cutting in the width direction of the electrode (ie, the Y direction).

[0083] See also Figure 3 As can be seen from the above embodiment 1, the first and last sections of the pole piece are equivalent to two free sections 20. When the pole piece is wound to form a winding core, the free section 20 of the first section of the pole piece will be wound at the head position inside the winding core, and the free section 20 of the last section of the pole piece will be wound at the tail position of the winding core. Figures 6 to 8 , Figures 6 to 8 The figures show that a small section of the pole ear (i.e., cathode ear or anode ear) has been cut out of multiple pole pieces after step S3. The active material coating area of ​​each complete pole piece (the area between two dotted line rings along the X direction is a complete pole piece) is understood as Figures 6 to 8 The area coated with the active layer between the "starting end" (the location of the lower dotted line ring) and the "ending end" (the location of the upper dotted line ring) mentioned in Figures 6 to 8 The small section of the material strip shown is equivalent to being understood as including a complete active material coating area coated on the substrate and a portion of the active material coating area in front of the complete active material coating area in the X direction and in the rear of the X direction. Figures 6 to 8 As shown, the material strip of this embodiment is preferably provided with two electrode active material coating areas in the Y direction, that is, the material strip includes two electrode sheets in the Y direction. Correspondingly, the cutting mechanism needs to cut out the pole ear portions on one side of the two electrode sheets respectively in the Y direction. Figure 6 , Figure 7 or Figure 8 The M line segment in the figure can cut the material strip into two pole pieces in the Y direction, thereby improving the manufacturing efficiency of the pole pieces and further improving the manufacturing efficiency of the core.

[0084] Please continue reading Figures 6 to 8In this embodiment, after the pole piece is cut in step S3, a pole ear portion is formed on one side of the first section, the middle section and the last section of the pole piece. Assume that each pole piece is formed with (n-1) pole ear portions in the width direction after cutting in step S3. The (n-1) pole ear portions make the pole piece have n pole ear center distances on one side in the width direction. In this embodiment, preferably, Figure 6 , Figure 7 or Figure 8 The area coated with the active layer between the starting end and the second pole ear shown in is understood as the first section of the active material coating area. In this embodiment, the area coated with the active layer between the second pole ear and the (Dn-3)th pole ear is preferably understood as the middle section of the active material coating area. In this embodiment, the area coated with the active layer between the (Dn-3)th pole ear and the Dnth pole ear is preferably understood as the last section of the active material coating area. In other embodiments, the pole ear may not be provided on one side of the first section and the last section of the pole piece in the width direction, and multiple pole ears are only provided on one side of the middle section of the pole piece.

[0085] In order to achieve that the effective width of the active layer remaining in the first section or / and the last section of the pole piece is different from the effective width of the active layer remaining in the middle section of the pole piece, this embodiment provides a first implementation method (by cutting):

[0086] In the above-mentioned step S3, the cutting mechanism has a first cutting path and a second cutting path for cutting the material strip in different widths in the Y direction, wherein the cutting mechanism cuts according to the first cutting path to obtain the first section and / or the last section of the pole piece; the cutting mechanism cuts according to the second cutting path to obtain the middle section of the pole piece, and the middle section of the pole piece at least partially has a plurality of spaced-apart pole ear portions in the width direction, and the pole ear portion at least includes a portion of the uncoated area of ​​the active material.

[0087] When the active layer coated in step S2 is a cathode active layer, the cutting width of the second cutting path is smaller than the cutting width of the first cutting path, and the cutting mechanism must cut the cathode active layer area when cutting according to the first cutting path, so that the effective width of the cathode active layer remaining in the first section and / or the last section of the electrode piece is smaller than the effective width of the cathode active layer in the middle section of the electrode piece, that is, at this time, it can be formed Figure 3 The second cathode sheet in which D is smaller than C is preferably a "second cathode sheet". Preferably, the width of the cathode active layer cut by the first cutting path in the Y direction is 0.3 mm-0.7 mm. When the cutting mechanism cuts according to the second cutting path, the cathode active layer may or may not be cut. If the cutting mechanism cuts according to the second cutting path, the width of the cathode active layer cut by the second cutting path is preferably 0.1-0.2 mm. Preferably, Figure 6As shown, in step S2, in addition to the cathode active layer, if an insulating layer is also coated, wherein the insulating layer and the cathode active layer are arranged on the same surface of the substrate, and the insulating layer is arranged on one side or both sides of the material strip where multiple cathode ears are to be cut, then the cutting mechanism cuts the cathode active layer area according to the first cutting path to narrow the effective width of the remaining cathode active layer at the first section and / or the last section of the electrode piece, and the cutting mechanism also removes all insulating layers in the non-cathode ear area of ​​the first section of the active material coating area and / or the last section of the active material coating area along the Y direction.

[0088] When the active layer coated in step S2 is an anode active layer, the cutting width of the second cutting path is greater than the cutting width of the first cutting path, and the cutting mechanism must cut the anode active layer region when cutting according to the second cutting path, so that the effective width of the remaining anode active layer of the first section and / or the last section of the electrode piece is greater than the effective width of the anode active layer of the middle section of the electrode piece, that is, at this time, it can be formed Figure 3 In the “first type of anode sheet” where B is greater than A, preferably, the width of the anode active layer cut by the second cutting path in the Y direction is 0.3mm-0.7mm. When the cutting mechanism cuts according to the first cutting path, the anode active layer may not be cut, or the anode active layer may be cut. If the cutting mechanism cuts the anode active layer according to the first cutting path, the width of the anode active layer cut by the first cutting path is preferably 0.1-0.2mm. Here, the width of the active layer cut refers to the length of the active layer portion cut by the cutting mechanism in the width direction of the electrode sheet.

[0089] In order to achieve that the effective width of the active layer remaining in the first section or / and the last section of the pole piece is different from the effective width of the active layer remaining in the middle section of the pole piece, this embodiment provides a second implementation method (by directly coating active layers of different widths on the corresponding areas of the substrate):

[0090] When the active layer coated in step S2 is a cathode active layer, preferably an insulating layer is also coated on the substrate, and the insulating layer and the cathode active layer are arranged on the same surface of the substrate, the width of at least part of the cathode active layer coated on the middle section of the active material coating area of ​​the pole piece is greater than the width of at least part of the cathode active layer coated on the first section and / or the last section of the active material coating area of ​​the pole piece, and after cutting in step S3, the width of at least part of the cathode active layer at the first section and / or the last section of the pole piece is less than the width of at least part of the cathode active layer in the middle section of the pole piece, that is, at this time, it can be formed Figure 3The "second cathode sheet" in which D is less than C. In step S3, preferably, after the electrode sheet is cut by the cutting mechanism, a cathode ear is formed on one side in the width direction. Then, in step S2, the insulating layer needs to be provided on the side where the cathode ear is to be cut. Preferably, in step S2, after the insulating layer and the cathode active layer are coated, the width of at least part of the cathode active layer in the middle section of the electrode sheet active material coating area is 0.3-2 mm larger than the width of at least part of the cathode active layer in the first section and / or the tail section of the electrode sheet active material coating area.

[0091] When the active layer coated in step S2 is an anode active layer, the width of at least part of the anode active layer coated on the middle section of the active material coating area of ​​the pole piece is smaller than the width of at least part of the anode active layer coated on the first section and / or the last section of the active material coating area of ​​the pole piece. After cutting in step S3, the width of at least part of the anode active layer at the first section and / or the last section of the pole piece is finally greater than the width of at least part of the anode active layer in the middle section of the pole piece, that is, at this time, it can be formed. Figure 3 The “first type of anode sheet” in which B is smaller than A. Preferably, in step S2, after coating the anode active layer, the width of at least part of the anode active layer coating in the middle section of the active material coating area of ​​the electrode sheet is 0.3-2 mm greater than the width of at least part of the anode active layer coating in the first section and / or the tail section of the active material coating area of ​​the electrode sheet.

[0092] In order to achieve that the effective width of the active layer remaining in the first section or / and the last section of the pole piece is different from the effective width of the active layer remaining in the middle section of the pole piece, this embodiment provides a third implementation method (by covering a part of the active layer with an insulating layer):

[0093] In step S2, the coating mechanism has a first covering width and a second covering width with different covering widths for the active layer. The coating mechanism coats the insulating layer of the first covering width on at least one side in the width direction of the middle section of the active material coating area. The coating mechanism coats the insulating layer of the second covering width on at least one side in the width direction of the first section and / or the last section of the active material coating area.

[0094] In step S2, if the active layer is a cathode active layer, the second covering width is greater than 0, the first covering width is greater than or equal to 0, and the second covering width is greater than the first covering width.

[0095] In step S3, the electrode sheet can be cut according to the conventional cutting width, so that at least part of the cathode active layer of the first section or the last section of the final electrode sheet is covered by the insulating layer, thereby forming Figure 3The third cathode sheet in which D is less than C. More specifically, when the third implementation is used, the electrode sheet is cut in arrangement S3 only to cut the cathode sheet body part or the cathode sheet body and part of the insulating layer area, so that the cathode sheet is cut out of the cathode ear part, and this process does not require cutting the effective cathode active layer area.

[0096] In step S2, if the active layer is an anode active layer, the second covering width is greater than or equal to 0, the first covering width is greater than 0, and the second covering width is less than the first covering width. In step S3, the pole piece can be cut according to the conventional cutting width, so that at least part of the anode active layer in the middle section of the final pole piece is covered by the insulating layer. More specifically, when the third implementation is used, the pole piece is cut in arrangement S3 only to cut the anode sheet body or the anode sheet body and part of the insulating layer area, so that the anode ear is cut out of the anode sheet, and this process does not require cutting the effective anode active layer area.

[0097] See also Fig. 9 , Fig. 9 The step S3 in the method for preparing the pole piece of this embodiment is shown as the specific method adopted by the first implementation method described above:

[0098] First, the cutting mechanism uses the second cutting path to cut the middle section of the pole piece (the middle section of the pole piece in this embodiment is preferably Figure 6 and Figure 7 A plurality of spaced-apart pole lugs are cut out on at least one side in the width direction (i.e., a middle area between the second pole lug of the first section and the third pole lug of the last section) Figure 6 and Figure 7 The cutting mechanism uses the first cutting path to cut the first section of one of the pole pieces (preferably the first section of one of the pole pieces) corresponding to the regions D3 to Dn-3 shown in FIG. Figure 6 and Figure 7 The area between the starting end and the second pole ear shown in the figure) and the end section of another adjacent pole piece (preferably Figure 6 and Figure 7 A plurality of pole lugs (i.e., the area between the third last pole lug and the end end shown in FIG. 1 ) are cut out on at least one side in the width direction (i.e., the Y direction) to form a plurality of pole lugs (i.e., the area between the third last pole lug and the end end shown in FIG. Figure 6 and Figure 7 The regions corresponding to Dn-3 to D2 shown in FIG. Figure 3 The "second cathode sheet" or "first anode sheet" described in the present invention.

[0099] Next, the cutting mechanism and the material strip move relative to each other along the length direction of the material strip (it can be understood that the material strip can be stationary and then the cutting mechanism moves, or it can be understood that the material strip is continuously released and the cutting mechanism does not move along the length direction of the material strip), and the cutting mechanism repeats the above cutting process for the remaining pole pieces along the length direction of the material strip.

[0100] Among them, along Figure 6 or Figure 7 The step of cutting the pole sheet into two pole sheets along the M line segment can be completed after executing the above step S3 and before executing the above step S2, or the material strip can be wound up after all the pole sheets in the material strip have executed steps S2 and S3 (that is, after all the pole sheets in the material strip have their pole ears cut out), and then the material strip can be released again at other positions and cut along the M line segment.

[0101] This paragraph supplements the explanation that the widths of the active layers of the two free segments of the anode sheet or cathode sheet produced by the first implementation method mentioned above are changed, and the changed width value is actually (BA) or (CD). In other embodiments, if the width of the active layer of only one of the free segments of the anode sheet or cathode sheet needs to be changed, the first cutting path may be applied to one of the first or last segments of the electrode sheet, and the second cutting path may be applied to the other segment.

[0102] Preferably, please refer again to Figure 6 , Figure 7 and Fig. 9 , when the surface of the electrode piece is pre-coated with an insulating layer before executing the step S3, when the cutting mechanism cuts the first section of one electrode piece and the last section of another adjacent electrode piece along the width direction of the electrode piece during the execution of the step S3, the cutting mechanism will remove part of the cathode active layer while also removing part of the cathode ear area (i.e. Figure 6 and Figure 7 All the insulating layers are removed from the respective areas Dn-3 to D2 shown in the figure.

[0103] See also Fig.10 , Fig.10 The following is a specific method used in step S2 and step S3 of the method for preparing the pole piece of this embodiment when applying the third implementation method described above:

[0104] First, in step S2, the middle section of the electrode piece (the middle section in this embodiment is preferably Figure 8 The first section of one of the pole pieces (preferably the middle area between the second pole ear of the first section and the third pole ear of the last section) is coated with an insulating layer of a first covering width on at least one side in the width direction. Figure 8The area between the starting end and the second pole ear shown in the figure) and the end section of another adjacent pole piece (preferably Figure 8 The electrode piece is coated with an insulating layer of a second covering width on at least one side in the width direction (the area between the third last pole ear portion and the end end shown in FIG); then, in step S3, a cutting mechanism is used to cut the side of the pole piece coated with the insulating layer in the width direction, so that the pole ear portion is cut out of the first section, the middle section and the last section of the pole piece, so that Figure 3 The "third cathode sheet" described in.

[0105] Then, the coating mechanism repeats the coating process described in the previous paragraph on the remaining pole pieces along the length direction of the material strip, and the cutting mechanism repeats the cutting process described in the previous paragraph on the remaining pole pieces along the length direction of the material strip.

[0106] This paragraph supplements the explanation that the width of the active layer of the two free segments of the anode sheet or cathode sheet produced by the second implementation method mentioned above can also be changed, and the changed width value is actually (BA) or (CD). In other embodiments, if the width of the active layer of only one of the free segments of the anode sheet or cathode sheet needs to be changed, then one of the first or last segments of the electrode sheet shall apply the first covering width, and the other segment may apply the second covering width.

[0107] The above are only preferred embodiments of the present invention, and only specifically describe the technical principles of the present invention. These descriptions are only for explaining the principles of the present invention and cannot be interpreted as limiting the scope of protection of the present invention in any way. Based on the explanations here, any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention, and other specific implementations of the present invention that can be associated with by technicians in this field without creative labor, should be included in the scope of protection of the present invention.

Claims

1. A winding core, comprising an anode sheet, a separator and a cathode sheet stacked in sequence, The anode sheet comprises an anode sheet main body and an anode active layer disposed on the anode sheet main body, the cathode sheet comprises a cathode sheet main body and a cathode active layer disposed on the cathode sheet main body, the anode active layer covers the cathode active layer, and is characterized in that: The winding core is divided into two free sections and a middle section between the two free sections in the length direction, one of the free sections is a first section for winding inside, and the other free section is a last section for winding on the outermost side, the effective width value of at least part of the anode active layer located in the middle section is A, the effective width value of at least part of the anode active layer located in the free section is B, the effective width value of at least part of the cathode active layer located in the middle section is C, and the effective width value of at least part of the cathode active layer located in the free section is D, let d0=AC, let d=BD, wherein d0 and d are both greater than 0, and d>d0.

2. The winding core according to claim 1, characterized in that: The D is smaller than the C.

3. The winding core according to claim 2, characterized in that: A and B are equal.

4. The winding core according to any one of claims 2 or 3, characterized in that: Assume that the length of a single free segment is L, where L is 0.1m-0.5m.

5. The winding core according to claim 1, characterized in that: The B is greater than the A.

6. The winding core according to claim 5, characterized in that: The D is equal to the C.

7. The winding core according to any one of claims 5 or 6, characterized in that: Assume that the length of a single free segment is L, where L is 0.1m-0.5m.

8. The winding core according to claim 1, characterized in that: The D is smaller than the C, and the B is larger than the A.

9. The winding core according to claim 1, characterized in that: The d0 is 1.9-3.5 mm, d is 2.2-4.2 mm, and d-d0 is 0.3-2.3 mm.

10. The winding core according to claim 1, characterized in that: The d0 is 1.9-3.5 mm, d is 2.5-4.9 mm, and d-d0 is 0.6-3 mm.

11. The winding core according to any one of claims 1-3, 5, 6, 8-10, characterized in that: The anode active layer is disposed on both sides of the anode sheet main body, and the cathode active layer is disposed on both sides of the cathode sheet main body.

12. The winding core according to claim 11, characterized in that The anode active layers disposed on both sides of the anode sheet main body are completely identical, or the cathode active layers disposed on both sides of the cathode sheet main body are completely identical.

13. The winding core according to claim 11, characterized in that: The effective width value of at least part of the anode active layer of the outermost anode sheet of the winding core is B, and the effective width value of at least part of the cathode active layer of the outermost cathode sheet of the winding core is D.

14. The winding core according to any one of claims 1-3, 5, 6, 8-10, characterized in that: The cathode active layer of the cathode sheet is provided with an insulating layer on one side in a width direction.

15. The winding core according to claim 14, characterized in that The cathode active layer located in the free section is at least partially covered by the insulating layer in the width direction, so that C is greater than D.

16. The winding core according to claim 1, characterized in that: Assume that the free length of the free segment is L, and △d=d-d0=(BD)-(AC), and △d≥0.5L 2 +0.5L+0.2, where L is 0.1m-0.5m and △d is 0.3mm—0.7mm.

17. The winding core according to claim 16, characterized in that When A and B are equal, the △d is the difference of (CD), and the (CD) ≥ 0.5L 2 +0.5L+0.2, (CD) is 0.3-0.7mm.

18. The winding core according to claim 16, characterized in that C and D are equal, the △d is the difference of (BA), the (BA) ≥ 0.5L 2 +0.5L+0.2, (BA) is 0.3-0.7mm.

19. A battery, characterized in that: It comprises an outer shell and a winding core as claimed in any one of claims 1 to 18, wherein the winding core is accommodated inside the outer shell.

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