Cylindrical lithium ion battery

Abstract

The invention provides a cylindrical lithium ion battery which comprises a shell, a negative current collecting disc, a roll core, a positive current collecting disc and a cap, the shell comprises an inner cavity with an opening, the negative current collecting disc, the roll core and the positive current collecting disc are arranged in the inner cavity, the cap covers the opening to seal the inner cavity, and the cap is arranged in the inner cavity. The roll core is formed by winding and rubbing a positive electrode plate, a diaphragm and a negative electrode plate which are arranged in sequence, and the length and area parameters of a positive tab region or a negative tab region in the positive electrode plate and the negative electrode plate are controlled within reasonable intervals; the problems of tab exposure, tab folding, diaphragm scalding, welding burst points and the like of the roll core in the rubbing and welding process are solved.

Description

Technical Field

[0001] The present application relates to the technical field of secondary batteries, and in particular to a cylindrical lithium-ion battery. Background Art

[0002] In the relevant technology, lithium-ion batteries can be divided into three forms according to the packaging form: square, cylindrical and soft pack. Among them, cylindrical lithium-ion batteries have gradually become a hot spot in lithium-ion battery research due to their good consistency, high production efficiency, and strong heat dissipation capacity at the system level. Cylindrical batteries are usually packaged in cylindrical steel shells. Bare cells are made by winding process to form cylindrical cores. When winding, the electrode sheets, diaphragms, and electrode sheets are arranged in sequence and then wound. The two electrode sheets have ear areas at the opposite ends. After winding, the ears at the opposite ends along the height direction of the core are formed. Then, the ears at the opposite ends are flattened to obtain a flattened layer. The collector plate and the flattened layer are welded to lead out the electrodes of the core. In the process of welding the collector plate and the flattened layer of the core, problems such as welding burns the diaphragm, welding explosion points, exposed ears, and folded ears sometimes occur. Summary of the invention

[0003] The embodiment of the present application provides a cylindrical lithium-ion battery to at least solve the technical problems of welding burns to the diaphragm, welding explosion points, exposed tabs, and folded tabs caused by flattening the core of the existing cylindrical lithium-ion battery.

[0004] The first aspect of the present application provides a cylindrical lithium-ion battery, comprising: a shell, a negative electrode current collecting disc, a winding core, a positive electrode current collecting disc and a cap, wherein the shell comprises an open inner cavity, the negative electrode current collecting disc, the winding core and the positive electrode current collecting disc are arranged in the inner cavity, and the cap is arranged on the opening to close the inner cavity;

[0005] The winding core is formed by winding and flattening a positive electrode sheet, a separator and a negative electrode sheet arranged in sequence, the positive electrode sheet comprises a positive current collector, a positive electrode material and a ceramic material, the positive current collector comprises a positive electrode material area and a positive electrode non-material area extending from the positive electrode material area, the positive electrode material area is coated with the positive electrode material, the positive electrode non-material area comprises a ceramic area and a bendable positive electrode tab area, the ceramic area is coated with the ceramic material, and the positive electrode tab area is not coated with the positive electrode material and the ceramic material, The positive electrode tab area is used to form a positive electrode flattened layer after flattening. The ceramic area is located between the positive electrode material area and the positive electrode tab area. Along the width direction of the positive electrode sheet, the width of the positive electrode sheet is L1, the width of the positive electrode tab area is L2, and the width of the ceramic area is L3. 3%≤L2 / L1≤13%, 1%≤L3 / L1≤10%. The area of ​​the positive electrode material area is S1, and the area of ​​the positive electrode non-material area is S2. 1%≤S2 / (S1+S 2)≤15%, the negative electrode sheet comprises a negative electrode current collector and a negative electrode material, the negative electrode current collector comprises a negative electrode material region and a bendable negative electrode tab region extending from the negative electrode material region, the negative electrode material region is coated with the negative electrode material, the negative electrode tab region is not coated with the negative electrode material, the negative electrode tab region is used to form a negative electrode flattening layer after flattening, along the width direction of the negative electrode sheet, the width of the negative electrode sheet is L4, the width of the negative electrode tab region is L5, 2%≤L5 / L 4≤15%, the area of ​​the negative electrode material area is S3, the area of ​​the negative electrode tab area is S4, 1%≤S4 / (S3+S4)≤15%, the winding core comprises a positive terminal and a negative terminal relative to each other in the height direction of the cylindrical lithium-ion battery, the positive electrode tab area is located at the positive terminal, the negative electrode tab area is located at the negative terminal, the cap is connected to the positive terminal of the winding core through the positive current collecting disk, and the outer shell is connected to the negative terminal of the winding core through the negative current collecting disk.

[0006] The cylindrical lithium-ion battery according to the embodiment of the present application has at least the following beneficial effects:

[0007] The cylindrical lithium-ion battery of the embodiment of the present application controls the thickness of the flattened layer in the winding core by limiting the relevant parameters between the material area and the non-material area in the electrode sheet, thereby reducing problems such as diaphragm burns, welding explosion points, exposed tabs, and folded tabs.

[0008] In a possible implementation, along the direction from the negative terminal to the positive terminal, the length of the diaphragm exceeding the positive electrode material region is L6, the length of the negative electrode material region exceeding the positive electrode material region is L7, (L2+L3)>L6, (L2+L3)>L7.

[0009] In a possible implementation manner, along the direction from the positive terminal to the negative terminal, the length of the separator beyond the negative electrode material region is L8, and L5>L8.

[0010] In a possible implementation, along the direction from the negative terminal to the positive terminal, the length of the positive electrode tab region extending beyond the separator is L9, 1mm≤L9≤6mm, and along the direction from the positive terminal to the negative terminal, the length of the negative electrode tab region extending beyond the separator is L10, 1mm≤L10≤6mm. By controlling the lengths of L9 and L10, it helps to balance the safety of the battery and the cost of manufacturing materials.

[0011] In a possible implementation, 3.5 mm ≤ L9 ≤ 4.5 mm, 3.5 mm ≤ L10 ≤ 4.5 mm, the height of the positive electrode flattening layer is H1, the height of the positive electrode flattening layer is the length from the outermost extension of the positive terminal to the ceramic area along the width direction of the positive electrode sheet, the height of the negative electrode flattening layer is H2, the height of the negative electrode flattening layer is the length from the outermost extension of the negative terminal to the negative electrode material area along the width direction of the negative electrode sheet, H1 = 472.2-293×L9+92.96×L9 2 +M1, H2=472.2-293×L10+92.96×L10 2 +M1, -0.15mm≤M1≤0.15mm. This helps to guide technicians in the field to quickly obtain the parameters of L9 and L10 in the electrode sheet according to the thickness requirements of the flattened layer when engaging in research and development work, thereby improving research and development efficiency.

[0012] In a possible implementation, the thickness of the positive electrode collector is D1, the thickness of the negative electrode collector is D2, 0.004 mm ≤ D1 ≤ 0.013 mm, 0.004 mm ≤ D2 ≤ 0.013 mm, the height of the positive electrode flattening layer is H1, the height of the positive electrode flattening layer is the length from the outermost extension of the positive terminal to the ceramic area along the width direction of the positive electrode sheet, the height of the negative electrode flattening layer is H2, the height of the negative electrode flattening layer is the length from the outermost extension of the negative terminal to the negative electrode material area along the width direction of the positive electrode sheet, -0.15mm≤M2≤0.15mm. This helps to guide those skilled in the art to quickly obtain the thickness parameters of the positive electrode current collector or the negative electrode current collector according to the thickness requirements of the flattened layer when engaging in research and development work, thereby improving research and development efficiency.

[0013] In a possible implementation, the positive electrode tab region extends along the length direction of the positive electrode sheet, and the negative electrode tab region extends along the length direction of the negative electrode sheet. Designing both as full tabs helps to achieve a flattened layer with low internal resistance after flattening, improve current flow capacity, reduce heat generation, improve battery energy utilization efficiency, and improve battery safety.

[0014] In a possible embodiment, the winding core includes a starting end for starting winding and an end opposite to the starting end. At the starting end, along the length direction of the positive electrode sheet, the length of the positive electrode material area beyond the positive electrode tab area is N1, and the length of the negative electrode material area beyond the negative electrode tab area is N2, 60mm≤N1≤140mm, 40mm≤N2≤100mm; at the end, along the length direction of the positive electrode sheet, the length of the positive electrode material area beyond the positive electrode tab area is N3, and the length of the negative electrode material area beyond the negative electrode tab area is N4, 40mm≤N3≤100mm, 30mm≤N4≤90mm. By designing the cutting length, it is helpful to balance the battery's overcurrent capacity and reduce the tab flanging.

[0015] In a possible implementation, the height of the winding core is H3, the height of the cylindrical lithium-ion battery is H4, 90%≤H3 / H4≤98%, 65mm≤H3≤160mm. Setting the range of H3 / H4 to 90% to 98% helps to balance the welding effect of the flattening layer and the current collecting plate and the unit volume energy density of the cylindrical lithium-ion battery.

[0016] In a possible implementation, the thickness of the positive electrode collector disk is D3, the thickness of the negative electrode collector disk is D4, 0.1mm≤D3≤1mm, 0.1mm≤D4≤1mm, the height of the positive electrode flattening layer is H1, the height of the positive electrode flattening layer is the length from the outermost extension of the positive terminal to the ceramic area along the width direction of the positive electrode sheet, the height of the negative electrode flattening layer is H2, the height of the negative electrode flattening layer is the length from the outermost extension of the negative terminal to the negative electrode material area along the width direction of the positive electrode sheet, H1=-0.1175+3.55×D3-5×D2 2 +M3, H2=-0.1175+3.55×D4-5×D2 2 +M3, -0.15mm≤M3≤0.15mm. This helps to guide those skilled in the art to quickly obtain the thickness parameters of the positive electrode collector disc or the negative electrode collector disc according to the thickness requirements of the flattened layer when engaging in research and development work, thereby improving research and development efficiency.

[0017] In a possible implementation, along the radial direction of the winding core, the hypotenuse of the positive electrode tab region located at the outermost epitaxial portion forming the positive electrode flattening layer forms an angle θ with the radius of the winding core, 20°≤θ≤90°. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the description of the embodiments of the present application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0019] Figure 1 is a cross-sectional schematic diagram of a cylindrical lithium-ion battery provided in an embodiment of the present application;

[0020] Figure 2 It is a structural schematic diagram of a cylindrical lithium-ion battery roll core provided in an embodiment of the present application;

[0021] Figure 3 is a side view of a cylindrical lithium-ion battery core provided in an embodiment of the present application when stacked before winding;

[0022] Figure 4 This is a schematic diagram of a positive electrode sheet of a cylindrical lithium-ion battery provided in an embodiment of the present application before winding;

[0023] Figure 5 This is a schematic diagram of a negative electrode sheet of a cylindrical lithium-ion battery provided in an embodiment of the present application before winding;

[0024] Figure 6 yes Figure 5 The local schematic diagram of the A in the middle;

[0025] Figure 7 is a cross-sectional schematic diagram of a cylindrical lithium-ion battery core provided in an embodiment of the present application;

[0026] Figure 8 is a cross-sectional schematic diagram of a positive electrode current collecting disk of a cylindrical lithium-ion battery provided in an embodiment of the present application;

[0027] Fig. 9 It is a cross-sectional schematic diagram of a negative electrode current collecting disk of a cylindrical lithium-ion battery provided in an embodiment of the present application.

[0028] Reference numerals:

[0029] 100-housing;

[0030] 200-negative electrode current collecting plate;

[0031] 300-winding core, 310-positive electrode sheet, 311-positive current collector, 3111-positive material area, 3112-positive non-material area, 3112a-ceramic area, 3112b-positive pole ear area, 3113-positive electrode flattening layer, 3114-starting end, 3115-end, 312-positive electrode material, 313-ceramic material, 320-diaphragm, 330-negative electrode sheet, 331-negative current collector, 3311-negative electrode material area, 3312-negative pole ear area, 3313-negative electrode flattening layer, 332-negative electrode material, 340-positive terminal, 350-negative terminal, 360-center hole;

[0032] 400-positive electrode current collecting plate;

[0033] 500-blocked shots. DETAILED DESCRIPTION

[0034] Embodiments of the present embodiment are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present embodiment, and should not be construed as limiting the present embodiment.

[0035] In the description of this embodiment, it should be understood that descriptions involving orientation, such as up, down, front, back, left, right, etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing this embodiment and simplifying the description, and 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 this embodiment.

[0036] In the description of this embodiment, "several" means one or more, "more" means more than two, "greater than", "less than", "exceed", etc. are understood to exclude the number itself, and "above", "below", "within", etc. are understood to include the number itself. If there is a description of "first" or "second", it is only used for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0037] In the description of this embodiment, unless otherwise clearly defined, terms such as setting, installing, connecting, etc. should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in this embodiment based on the specific content of the technical solution.

[0038] In the related art, a cylindrical lithium-ion battery includes a shell, a negative current collector, a winding core, a positive current collector and a cap. The shell includes an open inner cavity, the negative current collector, the winding core and the positive current collector are arranged in the inner cavity, and the cap is arranged on the opening to close the inner cavity. The production of the winding core includes winding and flattening processes. The materials used to make the winding core include positive electrode sheets, diaphragms and negative electrode sheets. Both the positive electrode sheets and the negative electrode sheets are roughly rectangular. Along the width direction of the electrode sheets, they include a material area and a non-material area extending from the material area. Both the material area and the non-material area extend along the length direction of the electrode sheets. The material area is coated with electrode material, the positive electrode sheet is coated with positive electrode material, the negative electrode sheet is coated with negative electrode material, and the non-material area is not coated with electrode material. Arrange the positive electrode sheet, the separator and the negative electrode sheet in sequence, and arrange the long sides of the positive electrode sheet and the negative electrode sheet in correspondence, wherein the non-material area of ​​the positive electrode sheet is arranged opposite to the non-material area of ​​the negative electrode sheet, that is, along the width direction of the electrode sheet, the non-material area of ​​the positive electrode sheet is located at one end, and the non-material area of ​​the negative electrode sheet is located at the other end, and the non-material areas of the two electrode sheets are arranged oppositely. After the arrangement is completed, use one wide side of the electrode sheet as the starting end to wind the two arranged electrode sheets and the separator along the length direction of the electrode sheet to form a cylinder, and the opposite ends of the cylinder along its height direction correspond to the non-material area of ​​the positive electrode sheet and the non-material area of ​​the negative electrode sheet, respectively, and the non-material area can also be called a pole ear. After the winding is completed, a flattening process is carried out to flatten the non-material areas at both ends of the cylinder to form a flattened layer. After the current collecting plate and the flattened layer are welded, the positive and negative electrodes of the winding core are led out. The current collecting plate and the flattened layer bear the role of current overcurrent during the subsequent use of the battery, so the welding effect of the current collecting plate and the flattened layer will affect the subsequent use of the battery.

[0039] During the flattening process of the core production, the tabs may sometimes be exposed or folded. The tabs extend in the height direction of the core before being flattened. During the flattening process, the tabs are flattened toward the axis of the core. Under normal circumstances, the tabs will not exceed the outer edge of the cylinder in the radial direction of the core. If they exceed the outer edge, it is called exposed tabs. Since the size specifications of cylindrical lithium-ion batteries have been relatively established in the industry, the diameter of the battery shell is fixed. At the same time, in order to improve the energy density of the battery, the diameter of the core will be increased as much as possible. Therefore, once the tabs are exposed from the outer edge of the core or the tabs are folded, the flattened core will not be able to enter the battery shell normally due to the obstruction of the exposed tabs. In the process of welding the collector plate to the flattened layer, problems such as diaphragm burns and welding explosion points may sometimes occur.

[0040] Since the above-mentioned problems involve the flattening process, welding process and the winding core itself, the applicant found after careful study that the design of the winding core itself will have a greater direct relationship with the above-mentioned problems. Among them, through experimental research, it was found that the thickness of the flattening layer has a direct relationship with the occurrence of the above-mentioned problems. When the thickness of the flattening layer is too thick, the internal extrusion deformation of the pole ear is serious during flattening, and the pole ear is easily squeezed out in the radial direction of the winding core under the action of the flattening force, resulting in the exposure of the pole ear or the folding of the pole ear. When the flattening layer is too thin, during the welding process, the collector plate is welded to the outer surface of the flattening layer, and the welding heat is transferred from the outer surface to the direction away from the outer surface. At this time, the flattening layer is very thin, and the heat is quickly transferred to the material area next to the flattening layer, wherein the material area contains a thin film. At this time, the heat will burn the thin film, causing the battery to be scrapped. If the welding time is reduced, there may be a problem of insufficient welding between the collector plate and the flattening layer. If the flattening layer is too thin, there will be the problem of welding explosion points. Welding explosion points refer to that some parts are not welded in place. When the pole ear is wound, the pole ear corresponding to the starting end is pressed by the subsequent pole ear, showing a step-like shape. The place where multiple layers of pole ears are stacked is thicker. If the number of stacked layers is not enough, the thinner area will sometimes be welded through during welding, which is the explosion point. After welding through, the contact between the collector plate and the flattening layer is insufficient, which will lead to poor current flow effect and cause obvious temperature rise at the connection between the collector plate and the flattening layer.

[0041] In view of the above situation, the present application aims to control the thickness of the flattened layer after flattening in order to reduce the probability of the above problem. During the research process, the applicant found that controlling the length of the non-material area (ear area) to be flattened in the width direction of the electrode sheet can effectively control the thickness of the flattened layer.

[0042] This application provides a cylindrical lithium-ion battery, please refer to Figures 1 to 9, including a shell 100, a negative electrode current collecting disc 200, a winding core 300, a positive electrode current collecting disc 400 and a cap 500, wherein the shell 100 includes an open inner cavity, the negative electrode current collecting disc 200, the winding core 300 and the positive electrode current collecting disc 400 are arranged in the inner cavity, and the cap 500 is covered on the opening to close the inner cavity. The winding core 300 is formed by winding and flattening a positive electrode sheet 310, a separator 320 and a negative electrode sheet 330 arranged in sequence, wherein the positive electrode sheet 310 comprises a positive current collector 311, a positive electrode material 312 and a ceramic material 313, wherein the positive current collector 311 comprises a positive electrode material area 3111 and a positive electrode non-material area 3112 extending from the positive electrode material area 3111, wherein the positive electrode material area 3111 is coated with the positive electrode material 312, wherein the positive electrode non-material area 3112 comprises a ceramic area 3112a and a bendable positive electrode ear area 3112b, wherein the ceramic area 3112a is coated with the ceramic material 313, the positive electrode tab area 3112b is not coated with the positive electrode material 312 and the ceramic material 313, the positive electrode tab area 3112b is used to form a positive electrode flattened layer 3113 after flattening, the ceramic area 3112a is located between the positive electrode material area 3111 and the positive electrode tab area 3112b, along the width direction of the positive electrode sheet 310, the width of the positive electrode sheet 310 is L1, the width of the positive electrode tab area 3112b is L2, and the width of the ceramic area 3112a is L3, 3%≤L2 / L1≤13%, 1%≤L3 / L1≤10%. L2 / L1 affects the length L2 of the positive electrode tab area 3112b. If L2 / L1 is too small, the positive electrode tab area 3112b is too short, and the thickness of the positive electrode flattening layer 3113 is too thin after flattening, which is not conducive to welding the positive electrode flattening layer 3113 with the positive electrode collector 400; if L2 / L1 is too large, the positive electrode tab area 3112b is too long, and the thickness of the positive electrode flattening layer 3113 is too thick after flattening, which will cause material waste when the current can be satisfied, and the positive electrode flattening layer 3113 is too thick, which will slow down the electrolyte injection and infiltration speed. It can be understood that since the winding core 300 has undergone a flattening process, the widths of L1, L2, etc. refer to the width after the flattening layer of the winding core 300 is unfolded, or the length of the electrode sheet before it is wound, and the subsequent parameters related to the length are the same.

[0043] As an implementation method, the area of ​​the positive electrode material area 3111 is S1, and the area of ​​the positive electrode non-material area 3112 is S2, 1%≤S2 / (S1+S2)≤15%. If S2 / (S1+S2) is too small, it means that the positive electrode non-material area 3112 is too small, which is not conducive to the process and the flattening of the pole ear. If S2 / (S1+S2) is too large, it means that the positive electrode non-material area 3112 is too large, which wastes materials and increases the risk of rolling breakage.

[0044] As an embodiment, the negative electrode sheet 330 includes a negative electrode current collector 331 and a negative electrode material 332, the negative electrode current collector 331 includes a negative electrode material area 3311 and a bendable negative electrode tab area 3312 extending from the negative electrode material area 3311, the negative electrode material area 3311 is coated with the negative electrode material 332, the negative electrode tab area 3312 is not coated with the negative electrode material 332, the negative electrode tab area 3312 is used to form a negative electrode flattening layer 3313 after flattening, along the width direction of the negative electrode sheet 330, the width of the negative electrode sheet 330 is L4, and the width of the negative electrode tab area 3312 is L5, 2%≤L5 / L4≤15%, L5 / L4 affects the width L4 of the negative pole ear area 3312 (the part used for flattening) of the negative electrode sheet 330. If L5 / L4 is too small, the negative pole ear area 3312 is too short, and the thickness of the negative electrode flattening layer 3313 is too thin after flattening, which is not conducive to welding the negative electrode flattening layer 3313 with the negative current collector 200; if L5 / L4 is too large, the negative pole ear area 3312 is too long, and the thickness of the negative electrode flattening layer 3313 is too thick after flattening, which will cause material waste when the current can be satisfied, and the excessive thickness of the negative electrode flattening layer 3313 will slow down the electrolyte infiltration speed. As an embodiment, the length of the positive electrode sheet 310 and the negative electrode sheet 330 is 1300mm to 1600mm.

[0045] As an implementation method, the area of ​​the negative electrode material area 3311 is S3, and the area of ​​the negative electrode lug area 3312 is S4, 1%≤S4 / (S3+S4)≤15%. If S4 / (S3+S4) is too small, it means that the negative electrode lug area 3312 is too small, which is not conducive to the process and lug flattening and forming. If S4 / (S3+S4) is too large, it means that the negative electrode lug area 3312 is too large, which wastes materials and increases the risk of rolling breakage.

[0046] As an embodiment, the core 300 includes a positive terminal 340 and a negative terminal 350 relative to each other along the height direction of the cylindrical lithium-ion battery, the positive electrode tab area 3112b is located at the positive terminal 340, the negative electrode tab area 3312 is located at the negative terminal 350, the cap 500 is connected to the positive terminal 340 of the core 300 through the positive electrode collecting disk 400, and the outer shell 100 is connected to the negative terminal 350 of the core 300 through the negative electrode collecting disk 200.

[0047] As an embodiment, the positive terminal 340 of the winding core 300 is connected to the cap 500 through the positive electrode collector disk 400, and the cap 500 leads the positive electrode of the winding core 300, and the cap 500 is the positive electrode of the battery. The outer shell 100 of the battery is a steel outer shell 100, and the negative terminal 350 of the winding core 300 is connected to the outer shell 100 through the negative electrode collector disk 200, that is, the steel outer shell 100 serves as the negative electrode of the battery. It is understandable that the outer shell 100 can also be made of other conductive materials that do not react with the battery electrolyte.

[0048] As an embodiment, the positive electrode material area 3111, the ceramic area 3112a and the positive electrode tab area 3112b of the positive electrode current collector 311 all extend along the length direction of the positive electrode sheet 310. As an embodiment, the ceramic area is coated with a ceramic material 313, and the ceramic material 313 is composed of one or more inorganic material particles of silicon dioxide, titanium dioxide, zirconium dioxide, zinc oxide, iron trioxide, aluminum trioxide, manganese dioxide, magnesium oxide, boehmite, gypsum, talc, and calcite. The ceramic material 313 made of the above-mentioned inorganic material particles has good thermal stability and can still play the role of electrical insulation in a high temperature environment; at the same time, it can provide mechanical support for the positive active material coating and enhance structural stability.

[0049] As an embodiment, along the direction from the negative terminal 350 to the positive terminal 340, the length of the diaphragm 320 exceeding the positive electrode material area 3111 is L6, and the length of the negative electrode material area 3311 exceeding the positive electrode material area 3111 is L7, (L2+L3)>L6, (L2+L3)>L7, so that the diaphragm 320 insulates the positive electrode collector 311 and the negative electrode collector 331, and at the same time can prevent the burrs of the positive electrode collector 311 and the negative electrode collector 331 from piercing the diaphragm 320.

[0050] As an embodiment, along the direction from the positive terminal 340 to the negative terminal 350, the length of the diaphragm 320 exceeding the negative electrode material area 3311 is L8, L5>L8, when the pole lug area (including the positive pole lug area 3112b and the negative pole lug area 3312) is flattened into a flattened layer, avoid kneading the diaphragm 320 into the flattened layer to avoid damaging the diaphragm 320.

[0051] As an embodiment, along the direction from the negative terminal 350 to the positive terminal 340, the length of the positive pole ear area 3112b beyond the diaphragm 320 is L9, 1mm≤L9≤6mm, and along the direction from the positive terminal 340 to the negative terminal 350, the length of the negative pole ear area 3312 beyond the diaphragm 320 is L10, 1mm≤L10≤6mm. If L9 and L10 are too short, it is difficult to flatten and form during the flattening process, and the thickness of the flattening layer (including the positive pole flattening layer 3113 and the negative pole flattening layer 3313) is relatively thin, and there is a risk of welding through and scalding the diaphragm 320 when welding with the current collecting plate, and there is almost no process window. At the same time, the positive pole ear area 3112b or the negative pole ear area 3312 after flattening is not in a straightened state, and displacement will occur during the use of the battery, which has a shunting effect on the current, increases the heat generation, and produces an electrostatic effect, thereby affecting the stability and safety of the battery charge and discharge cycle. If L9 and L10 are too long, the flattened layer will be thicker, the material cost of the electrode sheet will increase, and the effect of electrolyte injection and infiltration will be reduced. By controlling the length of L9 and L10, it helps to balance the safety of the battery and the cost of manufacturing materials.

[0052] As an implementation manner, L9 and L10 are further preferably 3.5 mm≤L9≤4.5 mm, 3.5 mm≤L10≤4.5 mm.

[0053] As an embodiment, the height of the positive electrode flattening layer 3113 is H1, which is the length from the outermost extension of the positive terminal 340 to the ceramic area 3112a along the width direction of the positive electrode sheet 310, and the height of the negative electrode flattening layer 3313 is H2, which is the length from the outermost extension of the negative terminal 350 to the negative electrode material area 3311 along the width direction of the negative electrode sheet 330, H1=472.2-293×L9+92.96×L9 2 +M1, H2=472.2-293×L10+92.96×L10 2 +M1, -0.15mm≤M1≤0.15mm. The above has explained the important role of controlling the thickness of the flattening layer in the flattening process and the welding process, and the control of the thickness of the flattening layer is achieved by changing the parameters of the electrode sheet. This embodiment proposes a mathematical relationship between the thickness of the flattening layer and the relevant parameters of the electrode sheet, which can guide technical personnel in this field to quickly obtain the parameters of L9 and L10 in the electrode sheet according to the requirements of the thickness of the flattening layer when engaged in research and development work, thereby improving research and development efficiency. In the formula, the length units of H1, H2, L9 and L10 are all mm.

[0054] As an embodiment, the thickness of the positive electrode current collector 311 is D1, the thickness of the negative electrode current collector 331 is D2, 0.004 mm ≤ D1 ≤ 0.013 mm, 0.004 mm ≤ D2 ≤ 0.013 mm, the height of the positive electrode flattening layer 3113 is H1, and the height of the positive electrode flattening layer 3113 is the length from the outermost extension of the positive terminal 340 to the ceramic area 3112a along the width direction of the positive electrode sheet 310, and the height of the negative electrode flattening layer 3313 is H2, and the height of the negative electrode flattening layer 3313 is the length from the outermost extension of the negative terminal 350 to the negative electrode material area 3311 along the width direction of the positive electrode sheet 310, -0.15mm≤M2≤0.15mm. In the formula, the length units of H1, H2, D1 and D2 are all mm. This embodiment proposes a mathematical relationship between the thickness of the positive current collector 311 and the negative current collector 331 and the thickness of the flattened layer, which can guide those skilled in the art to quickly obtain the thickness parameters of the positive current collector 311 or the negative current collector 331 according to the thickness requirements of the flattened layer when engaged in research and development work, thereby improving research and development efficiency.

[0055] As an implementation method, the positive electrode tab region 3112b extends along the length direction of the positive electrode sheet 310, and the negative electrode tab region 3312 extends along the length direction of the negative electrode sheet 330. Both the positive electrode tab region 3112b and the negative electrode tab region 3312 are tabs, and designing both as full tabs helps to achieve a flattened layer with low internal resistance after flattening, improve current flow capacity, reduce heat generation, improve battery energy utilization efficiency, and improve battery safety.

[0056] As an embodiment, the winding core 300 includes a starting end 3114 for starting winding and an end 3115 opposite to the starting end 3114. At the starting end 3114, along the length direction of the positive electrode sheet 310, the length of the positive electrode material area 3111 exceeding the positive electrode lug area 3112b is N1, and the length of the negative electrode material area 3311 exceeding the negative electrode lug area 3312 is N2, 60mm≤N1≤140mm, 40mm≤N2≤100mm; at the end 3115, along the length direction of the positive electrode sheet 310, the length of the positive electrode material area 3111 exceeding the positive electrode lug area 3112b is N3, and the length of the negative electrode material area 3311 exceeding the negative electrode lug area 3312 is N4, 40mm≤N3≤100mm, and 30mm≤N4≤90mm. After the positive electrode sheet 310 and the negative electrode sheet 330 are coated with electrode materials, the shapes of the two are roughly rectangular, and a portion of the positive electrode tab area 3112b of the positive electrode sheet 310 and the negative electrode tab area 3312 of the negative electrode sheet 330 are cut. After cutting, winding begins, and the winding is carried out with the wide side (compared to the long side) of the electrode sheet as the axis, and the wide side is the starting end 3114. After winding into a winding core 300, a central hole 360 ​​along the axial direction of the winding core 300 is formed in the central part of the winding core 300, and the starting end 3114 is located at the central hole 360 ​​of the winding core 300, and the end 3115 is located on the outer surface of the winding core 300. The purpose of cutting is to control the number of stacked layers of the flattened layer and the appearance of the flattened layer, and to control the internal resistance at the same time. When cutting, if the cutting length of the end 3115 is too long, the thickness of the outer circle of the flattening layer will be too low, the internal resistance of the battery will increase, and the battery performance will be affected; if the cutting length of the end 3115 is too short, the thickness of the outer circle of the flattening layer will be too high, causing the pole ear to turn outward or fold. If the cutting length of the starting end 3114 is too long, the thickness of the inner circle of the flattening layer will be too low, the internal resistance of the battery will increase, and the battery performance will be affected; if the cutting length of the starting end 3114 is too short, the center hole 360 ​​will be blocked, the thickness of the inner circle of the flattening layer will be large, and the injection efficiency will be slowed down. By designing the cutting length, it is helpful to balance the battery's current capacity and reduce the edge.

[0057] As an embodiment, the short sides of the positive electrode tab area 3112b and the negative electrode tab area 3312 remaining after cutting form an acute angle α with the length direction of the electrode sheet, so that the electrode sheet is not easy to wrinkle when winding, and the flattened layer is more uniform after flattening.

[0058] As an implementation method, the height of the winding core 300 is H3, and the height of the cylindrical lithium-ion battery is H4, 90% ≤ H3 / H4 ≤ 98%, 65mm ≤ H3 ≤ 160mm. In order to ensure the capacity of the cylindrical lithium-ion battery, the material area height of the electrode sheet is generally determined. If the thickness of the flattening layer is increased, the total height of the winding will be increased, so that the total height of the cylindrical lithium-ion battery will be increased after the winding core 300 is loaded into the outer shell 100 of the cylindrical lithium-ion battery. After the cylindrical lithium-ion battery is assembled into a battery pack, the unit volume energy density of the battery pack will be reduced. Designing H3 / H4 to 90% to 98% helps to balance the welding effect of the flattening layer and the collector plate and the unit volume energy density of the cylindrical lithium-ion battery.

[0059] As an embodiment, the thickness of the positive electrode collector plate 400 is D3, the thickness of the negative electrode collector plate 200 is D4, 0.1 mm ≤ D3 ≤ 1 mm, 0.1 mm ≤ D4 ≤ 1 mm, the height of the positive electrode flattening layer 3113 is H1, the height of the positive electrode flattening layer 3113 is the length from the outermost extension of the positive terminal 340 to the ceramic area 3112a along the width direction of the positive electrode sheet 310, the height of the negative electrode flattening layer 3313 is H2, the height of the negative electrode flattening layer 3313 is the length from the outermost extension of the negative terminal 350 to the negative electrode material area 3311 along the width direction of the positive electrode sheet 310, H1 = -0.1175 + 3.55 × D3 - 5 × D3 2 +M3, H2=-0.1175+3.55×D4-5×D4 2 +M3, -0.15mm≤M3≤0.15mm. If the thickness of the current collecting disk is too small, firstly, the current collecting disk itself is too difficult to manufacture, and secondly, the current collecting disk is easily deformed during the welding process with the flattening layer, and the connection with the winding core 300 is not firm after welding. If the thickness of the current collecting disk is too large, the internal space is reduced and the manufacturing cost is increased. Specifically, the thickness of the current collecting disk refers to the thickness of the part that is in welding contact with the winding core 300. This embodiment proposes a mathematical relationship between the thickness of the positive current collecting disk 400 and the negative current collecting disk 200 and the thickness of the flattening layer, which can guide technical personnel in the field to quickly obtain the thickness parameters of the positive current collecting disk 400 or the negative current collecting disk 200 according to the thickness requirements of the flattening layer when engaged in research and development work, thereby improving research and development efficiency.

[0060] As an embodiment, in the positive electrode flattening layer 3113, along the radial direction of the winding core 300, the hypotenuse of the positive electrode tab region 3112b of the positive electrode flattening layer 3113 located at the outermost epitaxial portion forms an angle θ with the radius of the winding core 300, 20°≤θ≤90°, to ensure that the positive electrode flattening layer 3113 has sufficient thickness to improve the current flow capacity of the positive electrode flattening layer. Similarly, the negative electrode flattening layer 3313 also has the angle θ.

[0061] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present implementation. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0062] Although examples of the present embodiment have been shown and described, those skilled in the art will appreciate that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present embodiment, and the scope of the present embodiment is defined by the claims and their equivalents.

Claims

1. A cylindrical lithium-ion battery, characterized in that: include: A shell, a negative electrode current collecting disc, a winding core, a positive electrode current collecting disc and a cap, wherein the shell comprises an open inner cavity, the negative electrode current collecting disc, the winding core and the positive electrode current collecting disc are arranged in the inner cavity, and the cap is arranged on the opening to close the inner cavity; The winding core is formed by winding and flattening a positive electrode sheet, a separator and a negative electrode sheet arranged in sequence, the positive electrode sheet comprises a positive current collector, a positive electrode material and a ceramic material, the positive current collector comprises a positive electrode material area and a positive electrode non-material area extending from the positive electrode material area, the positive electrode material area is coated with the positive electrode material, the positive electrode non-material area comprises a ceramic area and a bendable positive electrode tab area, the ceramic area is coated with the ceramic material, and the positive electrode tab area is not coated with the positive electrode material and the ceramic material, The positive electrode tab area is used to form a positive electrode flattened layer after flattening. The ceramic area is located between the positive electrode material area and the positive electrode tab area. Along the width direction of the positive electrode sheet, the width of the positive electrode sheet is L1, the width of the positive electrode tab area is L2, and the width of the ceramic area is L3. 3%≤L2 / L1≤13%, 1%≤L3 / L1≤10%. The area of ​​the positive electrode material area is S1, and the area of ​​the positive electrode non-material area is S2. 1%≤S2 / (S1+S 2)≤15%, the negative electrode sheet comprises a negative electrode current collector and a negative electrode material, the negative electrode current collector comprises a negative electrode material region and a bendable negative electrode tab region extending from the negative electrode material region, the negative electrode material region is coated with the negative electrode material, the negative electrode tab region is not coated with the negative electrode material, the negative electrode tab region is used to form a negative electrode flattening layer after flattening, along the width direction of the negative electrode sheet, the width of the negative electrode sheet is L4, the width of the negative electrode tab region is L5, 2%≤L5 / L 4≤15%, the area of ​​the negative electrode material area is S3, the area of ​​the negative electrode tab area is S4, 1%≤S4 / (S3+S4)≤15%, the winding core comprises a positive terminal and a negative terminal relative to each other in the height direction of the cylindrical lithium-ion battery, the positive electrode tab area is located at the positive terminal, the negative electrode tab area is located at the negative terminal, the cap is connected to the positive terminal of the winding core through the positive current collecting disk, and the outer shell is connected to the negative terminal of the winding core through the negative current collecting disk.

2. The cylindrical lithium-ion battery according to claim 1, characterized in that: Along the direction from the negative terminal to the positive terminal, the length of the diaphragm exceeding the positive electrode material area is L6, and the length of the negative electrode material area exceeding the positive electrode material area is L7, (L2+L3)>L6, (L2+L3)>L7.

3. The cylindrical lithium-ion battery according to claim 1, characterized in that: Along the direction from the positive terminal to the negative terminal, the length of the separator beyond the negative electrode material region is L8, and L5>L8.

4. The cylindrical lithium-ion battery according to claim 1, characterized in that: Along the direction from the negative terminal to the positive terminal, the width of the positive electrode tab area beyond the diaphragm is L9, 1mm≤L9≤6mm, and along the direction from the positive terminal to the negative terminal, the width of the negative electrode tab area beyond the diaphragm is L10, 1mm≤L10≤6mm.

5. The cylindrical lithium-ion battery according to claim 4, characterized in that: 3.5mm≤L9≤4.5mm, 3.5mm≤L10≤4.5mm, the height of the positive electrode flattening layer is H1, the height of the positive electrode flattening layer is the length from the outermost extension of the positive terminal to the ceramic area along the width direction of the positive electrode sheet, the height of the negative electrode flattening layer is H2, the height of the negative electrode flattening layer is the length from the outermost extension of the negative terminal to the negative electrode material area along the width direction of the negative electrode sheet, H1=472.2-293×L9+92.96×L9 2 +M1, H2=472.2-293×L10+92.96×l10 2 +M1,-0.15mm≤M1≤0.15mm.

6. The cylindrical lithium-ion battery according to claim 1, characterized in that: The thickness of the positive electrode current collector is D1, the thickness of the negative electrode current collector is D2, 0.004mm≤D1≤0.013mm, 0.004mm≤D2≤0.013mm, the height of the positive electrode flattening layer is H1, the height of the positive electrode flattening layer is the length from the outermost extension of the positive terminal to the ceramic area along the width direction of the positive electrode sheet, the height of the negative electrode flattening layer is H2, the height of the negative electrode flattening layer is the length from the outermost extension of the negative terminal to the negative electrode material area along the width direction of the negative electrode sheet, 7. The cylindrical lithium-ion battery according to claim 1, characterized in that: The positive electrode tab region extends along the length direction of the positive electrode sheet, and the negative electrode tab region extends along the length direction of the negative electrode sheet.

8. The cylindrical lithium-ion battery according to claim 1, characterized in that: The winding core includes a starting end for starting winding and an end opposite to the starting end, wherein at the starting end, along the length direction of the positive electrode sheet, the length of the positive electrode material area beyond the positive electrode tab area is N1, and the length of the negative electrode material area beyond the negative electrode tab area is N2, 60mm≤N1≤140mm, 40mm≤N2≤100mm; at the end, along the length direction of the positive electrode sheet, the length of the positive electrode material area beyond the positive electrode tab area is N3, and the length of the negative electrode material area beyond the negative electrode tab area is N4, 40mm≤N3≤100mm, 30mm≤N4≤90mm.

9. The cylindrical lithium-ion battery according to claim 1, characterized in that: The height of the winding core is H3, the height of the cylindrical lithium-ion battery is H4, 90%≤H3 / H4≤98%, 65mm≤H3≤160mm.

10. The cylindrical lithium-ion battery according to claim 1, characterized in that: The thickness of the positive electrode collector disk is D3, the thickness of the negative electrode collector disk is D4, 0.1mm≤D3≤1mm, 0.1mm≤D4≤1mm, the height of the positive electrode flattening layer is H1, the height of the positive electrode flattening layer is the length from the outermost extension of the positive terminal to the ceramic area along the width direction of the positive electrode sheet, the height of the negative electrode flattening layer is H2, the height of the negative electrode flattening layer is the length from the outermost extension of the negative terminal to the negative electrode material area along the width direction of the positive electrode sheet, H1=-0.1175+3.55×D3-5×D3 2 +M3, H2=-0.1175+3.55×D4-5×D4 2 +M3, -0.15mm≤M3≤0.15mm.

11. The cylindrical lithium-ion battery according to claim 1, wherein in the positive electrode flattening layer, along the radial direction of the winding core, the hypotenuse of the positive electrode tab region located at the outermost extension of the positive electrode flattening layer forms an angle θ with the radius of the winding core, 20°≤θ≤90°.

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