WO2024078623A1 - 二次电池以及电子设备 - Google Patents

二次电池以及电子设备 Download PDF

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Publication number
WO2024078623A1
WO2024078623A1 PCT/CN2023/124561 CN2023124561W WO2024078623A1 WO 2024078623 A1 WO2024078623 A1 WO 2024078623A1 CN 2023124561 W CN2023124561 W CN 2023124561W WO 2024078623 A1 WO2024078623 A1 WO 2024078623A1
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WO
WIPO (PCT)
Prior art keywords
area
secondary battery
welding
thinned
shell
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/CN2023/124561
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English (en)
French (fr)
Inventor
邱慎照
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Ningde Amperex Technology Ltd
Original Assignee
Ningde Amperex Technology Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Ningde Amperex Technology Ltd filed Critical Ningde Amperex Technology Ltd
Priority to EP23876822.0A priority Critical patent/EP4579894A4/en
Publication of WO2024078623A1 publication Critical patent/WO2024078623A1/zh
Priority to US19/027,896 priority patent/US20250167355A1/en
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/50—Current conducting connections for cells or batteries
    • H01M50/531—Electrode connections inside a battery casing
    • H01M50/533—Electrode connections inside a battery casing characterised by the shape of the leads or tabs
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/058—Construction or manufacture
    • H01M10/0587—Construction or manufacture of accumulators having only wound construction elements, i.e. wound positive electrodes, wound negative electrodes and wound separators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/10—Primary casings; Jackets or wrappings
    • H01M50/102—Primary casings; Jackets or wrappings characterised by their shape or physical structure
    • H01M50/107—Primary casings; Jackets or wrappings characterised by their shape or physical structure having curved cross-section, e.g. round or elliptic
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/10—Primary casings; Jackets or wrappings
    • H01M50/131—Primary casings; Jackets or wrappings characterised by physical properties, e.g. gas permeability, size or heat resistance
    • H01M50/133—Thickness
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/50—Current conducting connections for cells or batteries
    • H01M50/531—Electrode connections inside a battery casing
    • H01M50/536—Electrode connections inside a battery casing characterised by the method of fixing the leads to the electrodes, e.g. by welding
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/50—Current conducting connections for cells or batteries
    • H01M50/531—Electrode connections inside a battery casing
    • H01M50/538—Connection of several leads or tabs of wound or folded electrode stacks
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application relates to the field of battery technology, and in particular to a secondary battery and an electronic device.
  • the current secondary battery structure generally adopts a structure with tabs at both ends.
  • the tabs are welded to the current collector and then connected to the bottom of the shell by resistance welding or laser welding.
  • the traditional steel shell battery is designed to be thicker.
  • the laser passes through the steel shell to weld to the collector plate or to the pole ear, which requires a large welding power.
  • the accuracy fluctuation of the laser also increases, resulting in a small welding window.
  • problems such as deformation, cracks, and perforations of the battery bottom often occur, which leads to a low welding quality rate.
  • the present application provides a secondary battery and an electronic device, which can solve the problems of deformation, cracks, perforation, etc. of the battery bottom caused by the increase of welding power during laser welding, which is beneficial to improving the welding quality of the battery bottom and can also improve the unreliable welding of the battery bottom.
  • the present application provides a secondary battery, the secondary battery comprising a shell, an electrode assembly and a current collecting plate; the current collecting plate and the electrode assembly are electrically connected; the bottom of the shell comprises a main body area and a thinning area connected to the main body area, that is, a thinning area is provided at the bottom of the shell, and the thinning area is electrically connected to the current collecting plate; the area of the thinning area accounts for 2% to 30% of the total area of the bottom of the shell.
  • the area of the thinning area is the projected area on the bottom of the shell in the direction perpendicular to the main body area.
  • the thinning area By providing a certain area of the thinning area at the bottom of the shell, it is beneficial to reduce the welding power when welding the bottom of the shell, thereby widening the welding window.
  • the area of the thinned zone accounts for too small a proportion of the total area of the bottom of the shell, since the thinned zone is suitable for reducing the welding power when welding the bottom of the battery, if the area of the thinned zone is too small, the welding area of the bottom of the shell is insufficient, and laser welding may weld to the unthinned area (that is, the bottom of the shell does not include other areas of the thinned zone), resulting in a significant decrease in the welding quality rate.
  • the area of the thinned area accounts for 4% to 15% of the total area of the bottom of the shell.
  • the welding rate can be further improved, and at the same time, the reliability of welding can be improved.
  • the ratio of the thickness of the thinned area to the thickness of the main area is 30% to 80%.
  • the ratio of the thickness of the thinned area to the thickness of the main area is 40% to 70%.
  • the outer surface of the bottom of the shell is concave in the direction toward the current collecting disk to form the thinning area; in other embodiments, the inner surface of the bottom of the shell is concave in the direction away from the current collecting disk to form the thinning area; in other embodiments, the outer surface of the bottom of the shell is concave in the direction toward the current collecting disk, and at the same time, the inner surface of the bottom of the shell is concave in the direction away from the current collecting disk to form the thinning area.
  • the thinning area described in the present application can be formed by thinning one side of the outer surface of the bottom of the shell, thinning one side of the inner surface, or thinning both the outer surface and the inner surface at the same time.
  • the collecting plate is provided with a boss at one end facing the bottom of the housing, and the boss is arranged in abutment with the thinning area. Further, the end surface of the raised end of the boss is arranged in abutment with a side surface of the thinning area.
  • the fitting arrangement means that there is no gap or substantially no gap after the end surface of the raised end of the boss fits with the surface of one side of the thinned area, which is the fitting arrangement or fitting described in this application.
  • a large gap between the thinned area and the collector plate can be avoided, thereby avoiding the perforation phenomenon when welding the bottom of the shell, which is beneficial to improving the welding quality of the bottom of the battery and can also improve the reliability of welding.
  • the boss is concentrically arranged with the thinning area.
  • the end surface of the end is concentrically fitted with the surface of one side of the thinned area.
  • the concentric fitting is used to avoid welding penetration during welding, further improve the welding rate of the bottom of the battery, and further improve the reliability of welding.
  • a projected area of the protruding end of the boss is smaller than a projected area of the thinned region.
  • the ratio of the projected area of the raised end of the boss to the projected area of the thinned area is 0.6: 1 to 0.98: 1. In this case, the welding rate of the bottom of the battery is further improved.
  • the thickness of the main region is T 1
  • the thickness of the thinned region is T 2
  • the thickness of the boss is T 0 , satisfying: T 0 ⁇ (T 1 ⁇ T 2 ).
  • the thickness of the main region is T 1
  • the thickness of the thinned region is T 2
  • the thickness of the boss is T 0 , satisfying: 1.0 ⁇ T 0 /(T 1 -T 2 ) ⁇ 1.3.
  • the end surface of the raised end of the boss has the same shape as the thinning area and is arranged in close contact with the thinning area. In this case, it is beneficial to better control the gap between the boss and the thinning area, and further improve the welding rate of the bottom of the battery.
  • the setting of the boss is applicable to three situations in which the bottom of the shell is recessed, namely, the outer surface of the bottom of the shell is recessed inwardly in a direction toward the collecting plate to form the thinning area; and/or the inner surface of the bottom of the shell is recessed inwardly in a direction away from the collecting plate to form the thinning area.
  • the secondary battery includes a pole piece; an empty foil area is left at one end of the pole piece along the axial direction of the secondary battery; and a kneaded flat surface formed by flattening the empty foil area is electrically connected to the current collecting plate.
  • the electrode piece may be a positive electrode piece or a negative electrode piece.
  • the electrode piece is a positive electrode piece, and an empty foil area is left at one end of the positive electrode piece along the axial direction of the secondary battery, and the kneaded flat surface formed by the empty foil area after being kneaded is electrically connected to the positive current collector; or, in other embodiments of the present application, the electrode piece is a negative electrode piece, and an empty foil area is left at one end of the negative electrode piece along the axial direction of the secondary battery, and the kneaded flat surface formed by the empty foil area after being kneaded is electrically connected to the positive current collector.
  • the plane is electrically connected to the negative electrode current collecting disk, and the positive electrode current collecting disk or the negative electrode current collecting disk is electrically connected to the thinned area.
  • the secondary battery is a cylindrical secondary battery, and the cylindrical secondary battery further includes a wound bare cell, and the wound bare cell includes the pole piece.
  • the present application adopts a cell structure of a bare cell with a full-pole lug structure to improve the temperature rise problem under high-rate discharge; the bare cell with a full-pole lug structure is further a bare cell with a full-pole lug winding type; specifically, a positive electrode slurry is applied on the surface of a positive electrode collector (such as an aluminum foil) to form a positive electrode sheet, and an empty aluminum foil area is left at one end of the positive electrode sheet; a negative electrode slurry is applied on the surface of a negative electrode collector (such as a copper foil) to form a negative electrode sheet, and an empty copper foil area is left at one end of the negative electrode sheet; an isolation film is also provided between the positive electrode sheet and the negative electrode sheet to separate the positive electrode sheet and the negative electrode sheet.
  • a positive electrode collector such as an aluminum foil
  • a negative electrode slurry is applied on the surface of a negative electrode collector (such as a copper foil) to form a negative electrode sheet, and an empty copper foil area is
  • the positive electrode sheet, the isolation film and the negative electrode sheet are stacked and wound to form the full-tab wound bare battery cell, and the empty aluminum foil area and the empty copper foil area are respectively arranged at the two ends of the full-tab wound bare battery cell; the empty aluminum foil area and the empty copper foil area are respectively kneaded by a kneading device to form a kneaded flat surface, the kneaded flat surface formed by the empty aluminum foil area after being kneaded is electrically connected to the positive current collector disk, and the kneaded flat surface formed by the empty copper foil area after being kneaded is electrically connected to the negative current collector disk; the positive current collector disk or the negative current collector disk is then electrically connected to the thinning area.
  • the present application provides an electronic device, wherein the electronic device comprises the secondary battery described above.
  • the present application provides the thinning area at the bottom of the shell, and the thinning area is used for welding the bottom of the shell.
  • the area of the thinning area accounts for 2% to 30% of the total area of the bottom of the shell, which is conducive to reducing the welding power during welding, widening the welding window, and improving the welding quality rate of the bottom of the battery;
  • a boss is provided at the end of the current collecting disk facing one end of the thinning area, and the end surface of the raised end of the boss is in contact with the thinning area to avoid a large gap between the current collecting disk and the thinning area, which is conducive to improving the welding quality rate; at the same time, the projection area of the raised end of the boss in the axial direction of the battery and the thickness range of the boss are regulated, which is conducive to further improving the welding quality rate of the bottom of the battery;
  • the present application adopts a full-tab wound bare cell.
  • the hollow foil area at the end of the full-tab wound bare cell is flattened to form a flat surface that is electrically connected to the current collector, which is beneficial to improving safety hazards such as overheating inside the battery.
  • FIG1 is a cross-sectional view of a secondary battery according to an embodiment of the present application.
  • FIG2 is a partial enlarged view of the bottom of a secondary battery according to an embodiment of the present application.
  • FIG3 is a partial cross-sectional view of the bottom of a secondary battery according to an embodiment of the present application.
  • FIG4 is a partial cross-sectional view of the bottom of a secondary battery according to another embodiment of the present application.
  • FIG5 is a bottom schematic diagram of a secondary battery according to an embodiment of the present application.
  • FIG6 is a bottom schematic diagram of a secondary battery according to another embodiment of the present application.
  • FIG7 is a bottom schematic diagram of a secondary battery according to another embodiment of the present application.
  • FIG8 is a schematic diagram of bottom welding of a secondary battery according to an embodiment of the present application.
  • FIG. 9 is a schematic diagram of bottom welding of a secondary battery according to another embodiment of the present application.
  • the first embodiment of the secondary battery of the present application includes a shell 11, wherein a bare cell 12 is accommodated inside the shell 11, wherein the bare cell 12 is a wound bare cell, which is formed by winding a positive electrode sheet, a negative electrode sheet and a separator, wherein a first empty foil area is provided on the positive electrode sheet, and a second empty foil area is provided on the negative electrode sheet, wherein the first empty foil area and the second empty foil area are respectively provided at two ends of the bare cell 12, and a first kneaded plane and a second kneaded plane are formed after the first empty foil area and the second empty foil area are kneaded and flattened, and are respectively electrically connected to a positive current collector 13 and a negative current collector 14;
  • the positive electrode current collecting plate 13 is located at the upper end of the housing 11.
  • the negative electrode current collecting plate 14 is located at the lower end of the shell 11, and the lower end of the shell 11 is the shell bottom 110.
  • the shell bottom 110 includes a thinning area 1101 and a main body area 1102.
  • the thinning area 1101 is arranged at the middle position of the shell bottom 110, and the other area of the shell bottom 110 that does not include the thinning area 1101 is the main body area 1102.
  • the main body area 1102 is arranged around the outer periphery of the thinning area 1101 and is connected to the thinning area.
  • the thinning area 1101 is integrally formed on the shell bottom 110, and the thinning area 1101 is electrically connected to the negative electrode current collecting plate 14 by laser welding (such as penetration welding).
  • the positive electrode current collecting disk 13 is located at the lower end of the shell 11, and a thinning area 1101 is provided at the middle position of the shell bottom 110, and the thinning area 1101 is electrically connected to the positive electrode current collecting disk 13 by laser welding (such as penetration welding).
  • the thinning area 1101 can also be provided on the shell bottom 110 in a non-integrated manner. As long as it can reduce the welding power and widen the welding window, the present application has no limitation on this.
  • the thinning area 1101 and the main area 1102 connected to the thinning area 1101 are arranged on the shell bottom 110, and the thickness of the thinning area 1101 is controlled to be smaller than the thickness of the main area 1102.
  • laser welding is performed at the position of the thinning area 1101, so that the shell bottom 110 and the positive electrode collector plate 13 or the negative electrode collector plate 14 are electrically connected in a fixed position.
  • the arrangement of the thinning area 1101 can effectively reduce the welding power when welding the shell bottom 110, widen the welding window, and help improve the welding quality rate.
  • the thinning zone 1101 is formed by thinning the initial thickness of the shell bottom 110, the thinned area is the thinning zone 1101, and the unthinned area is the main body zone 1102, therefore, the thickness of the thinning zone 1101 is undoubtedly smaller than the initial thickness of the shell bottom 110, and the thickness direction of the thinning zone 1101 is perpendicular to the bottom surface of the shell 11, and the thickness direction of the main body zone 1102 is parallel to the thickness direction of the thinning zone 1101.
  • the area of the thinned area 1101 accounts for 2% to 30% of the total area of the shell bottom 110; the total area of the shell bottom 110 includes the sum of the area of the main body area 1102 and the area of the thinned area 1101 (hereinafter sometimes referred to as the shell bottom area).
  • the ratio of the area of the thinned area to the area of the shell bottom within a suitable range, it is helpful to improve the welding rate when welding the battery bottom. For example, if the area of the thinned area accounts for 2% to 30% of the total area of the shell bottom The proportion of the bottom area of the shell is too small (for example, less than 2% of the bottom area of the shell).
  • the thinning area is suitable for reducing the welding power when welding the bottom of the battery, if the area of the thinning area is too small, the welding area of the bottom of the shell is insufficient, and laser welding may weld to the unthinned area (that is, the bottom of the shell does not include other areas of the thinning area), which may easily cause the laser to fail to penetrate the bottom of the shell, resulting in poor welding, and thus significantly reducing the welding quality and the reliability of welding.
  • the area of the thinning area is too large, the strength of the bottom of the shell will weaken, and the gas generation of the battery after electrical connection will cause the bottom of the shell to bulge and deform, thereby affecting the welding quality.
  • the area of the thinned zone 1101 accounts for a range consisting of any two values of 2%, 5%, 8%, 10%, 15%, 20%, 25%, and 30% of the total area of the shell bottom 110 .
  • the area of the thinned region 1101 accounts for 4% to 15% of the total area of the shell bottom 110 .
  • the area of the thinned area 1101 accounts for any two values of 4%, 6%, 8%, 10%, 12%, 14%, and 15% of the total area of the shell bottom 110. At this time, by further controlling the area of the thinned area to account for 4% to 15% of the total area of the shell bottom, it is beneficial to improve the welding quality rate and the welding reliability.
  • a ratio of a thickness of the thinned region 1101 to a thickness of the main region 1102 is 30% to 80%.
  • the ratio of the thickness of the thinning zone 1101 to the thickness of the main zone 1102 is too small (for example, the thickness ratio is less than 30%), that is, the thickness of the thinning zone 1101 is too thin compared with the thickness of the main zone 1102, the overall strength of the bottom of the shell will be weakened, and the gas production of the battery after electrical connection will cause the bottom of the shell to bulge or even deform; if the thickness of the thinning zone 1101 to the thickness of the main zone 1102 is too large (for example, the thickness ratio is greater than 80%), that is, the thinning effect of the bottom of the shell is not obvious, and the welding power during bottom welding will also increase. A large welding power will cause cracks to form at the bottom of the shell.
  • the ratio of the thickness of the thinned area 1101 to the thickness of the shell bottom 110 is a range consisting of any two values of 30%, 40%, 50%, 60%, 70%, and 80%.
  • the ratio of the thickness of the thinned area 1101 to the thickness of the main area 1102 is 40% to 70%.
  • the ratio of the thickness of the thinned area 1101 to the thickness of the main area 1102 is in a range consisting of any two values of 40%, 45%, 50%, 55%, 60%, 65%, and 70%.
  • the outer surface of the shell bottom 110 is concave in the direction toward the negative electrode current collecting disk 14 to form the thinning area 1101.
  • the spacing shown in b in FIG. 3 is the thickness of the thinning area 1101
  • the spacing shown in a is the thickness of the main area 1102.
  • the outer surface of the shell bottom 110 is thinned on the outside to make its outer surface concave to form the thinning area 1101, and the thinning area 1101 is integrally formed with the shell bottom 110.
  • the thinning area 1101 can also be formed on the bottom 110 of the shell body in a non-integrated manner.
  • the material of the thinning area 1101 can be the same as the material of the shell body, or it can be different from the material of the shell body. As long as it can reduce the bottom welding power, improve the bottom welding rate and improve the welding reliability, this application has no restrictions on this.
  • the negative electrode current collector 14 is provided with a boss 140 at one end facing the bottom 110 of the shell body 11, and the boss 140 is arranged in affixed with the thinning area 1101; further, the end surface of the raised end of the boss 140 is arranged in affixed with a side surface of the thinning area 1101.
  • the boss 140 By arranging the boss 140 at one end of the negative electrode current collector 14, the raised end of the boss 140 extends toward the thinning area 1101 and the end face of the raised end is in contact with the outer surface of the thinning area 1101, so as to avoid a large gap between the thinning area 1101 and the negative electrode current collector 14, thereby avoiding perforation during welding of the bottom of the shell, which is beneficial to improving the welding quality rate of the bottom of the battery and improving the reliability of welding.
  • the positive electrode current collecting disk and the thinning area can also be electrically connected by laser welding.
  • a boss 140 is provided at one end of the positive electrode current collecting disk facing the bottom 110 of the shell 11, and the end face of the raised end of the boss 140 is fitted with a side surface of the thinning area 1101.
  • the end surface of the protruding end of the boss 140 is concentrically fitted with the side surface of the thinning area 1101; by controlling the end surface of the protruding end of the boss 140 to be concentrically fitted with the outer surface of the thinning area 1101, because the welding is welded at the center of the bottom 110 of the shell 11, by The 140° concentric setting is used to avoid welding penetration, thereby improving the welding quality rate at the bottom of the battery and enhancing the reliability of welding.
  • the projected area of the raised end of the boss 140 is smaller than the projected area of the thinned area 1101 , and the ratio of the projected area of the raised end of the boss 140 to the projected area of the thinned area 1101 is 0.6:1 to 0.98:1.
  • the projection area of the raised end of the boss 140 is too small (for example, the ratio of the projection area of the boss 140 to the projection area of the thinned area 1101 is less than 0.6:1), it is easy to cause welding penetration. This is because after the laser passes through the thinning area 1101 at the middle position of the bottom 110 of the shell 11, if the corresponding position does not have the fitting arrangement of the boss 140, perforation will occur due to welding penetration, which is not conducive to improving the welding quality rate; and if the area of the end face of the raised end of the boss 140 is too large, the collector plate will be deformed due to external force, and the deformation of the collector plate will cause non-fitting welding. The non-fitting arrangement between the end face of the boss 140 and the thinning area 1101 will produce a large gap. The large gap will cause laser welding penetration, resulting in perforation of the shell after electrical connection, which is not conducive to improving the welding quality rate.
  • the ratio of the projected area of the raised end of the boss 140 to the projected area of the thinned area 1101 is in a range consisting of any two values of 0.6:1, 0.7:1, 0.8:1, 0.9:1, and 0.98:1.
  • the welding rate of the bottom of the battery is further improved.
  • the thickness of the main body region 1102 is T 1 (i.e., the spacing shown in a of FIG. 3 ). It should be noted that the thickness of the main body region 1102 described in the present application refers to the thickness of the unthinned area on the bottom 110 of the shell (i.e., the initial thickness of the bottom of the shell); the thickness of the thinned area 1101 is T 2 (i.e., the spacing shown in b of FIG. 3 ), and the thickness of the boss 140 is T 0 , and satisfies: T 0 ⁇ (T 1 -T 2 ). The thickness of the boss 140 refers to the spacing between the bottom of the boss 140 and the top thereof in the axial direction of the secondary battery.
  • the thickness of the boss 140 By controlling the thickness of the boss 140 to be greater than the difference between the thickness of the main body region 1102 and the thickness of the thinned area 1101, it is beneficial to improve the welding rate of the bottom of the battery and improve the reliability of the welding of the bottom of the battery.
  • the thickness of the main region 1102 is T 1
  • the thickness of the thinned region 1101 is T 2
  • the thickness of the boss 140 is T 0 , satisfying: 1.0 ⁇ T 0 /(T 1 -T 2 ) ⁇ 1.3.
  • the thickness T0 of the boss 140 is equal to the thickness T1 of the main area 1102 and the thickness T2 of the thinned area 1101.
  • the ratio of the difference in thickness T2 is a range consisting of any two values of 1.0, 1.1, 1.2, and 1.3.
  • the end face of the raised end of the boss 140 has the same shape as the thinning area 1101, and the end face of the raised end of the boss 140 is arranged in contact with the surface of one side of the thinning area 1101; in this case, it is beneficial to better control the gap between the boss and the thinning area, and further improve the welding quality of the bottom of the battery.
  • the end face of the raised end of the boss 140 is circular, square or annular.
  • the raised end face of the boss 140 can also be a triangle, polygon or other planar shape. As long as the above-mentioned restrictions can be met to improve the bottom welding quality and reliability, the present application has no restrictions on this.
  • FIG. 4 it is a schematic diagram of the structure of the second embodiment of the secondary battery described in the present application.
  • the structure of the secondary battery is substantially the same as that of the first embodiment, except that the inner surface of the bottom 110 of the housing is concave in a direction away from the negative electrode current collecting disc 14 or the positive electrode current collecting disc 13 to form the thinning area 1101.
  • the end of the negative electrode current collecting disc 14 or the positive electrode current collecting disc 13 close to the thinning area 1101 is provided with the boss 140, and the arrangement of the boss 140 is the same as that of the first embodiment.
  • the secondary battery described in the present application also has a third embodiment (not shown), which is substantially the same in structure as the first embodiment, except that: the inner surface of the bottom 110 of the housing is concave in a direction away from the negative current collecting disc 14 or the positive current collecting disc 13, and the outer surface of the bottom 110 of the housing is concave in a direction toward the negative current collecting disc 14 or the positive current collecting disc 13, that is, the inner and outer surfaces of the bottom 110 of the housing are concave at the same time to form the thinning area 1101.
  • the end of the negative current collecting disc 14 or the positive current collecting disc 13 close to the thinning area 1101 is provided with the boss 140, and the arrangement of the boss 140 is the same as that of the first embodiment.
  • the center point of the thinning area 1101 is located on the central axis of the bottom surface of the shell 11, and the shape of the thinning area 1101 is selected from any one of a circle, a square, and a ring; referring to Figures 8 and 9, the thinning area 1101 is welded to the negative electrode current collecting disk 14 or the positive electrode current collecting disk 13 by penetration welding, and the welding morphology is selected from any one of spot welding, line welding or spiral welding; in other embodiments of the present application, the center point of the thinning area 1101 can be located at other positions on the bottom surface of the shell 11, and the shape of the thinning area 1101 can also be selected from any one of a triangle and a polygon, as long as it can achieve the improvement of the bottom welding superiority and the improvement of the welding reliability, the present invention is not limited to this.
  • the cylindrical secondary battery includes a shell and a wound bare cell, the bottom of the shell is provided with a thinning area, and the wound bare cell includes a pole piece, which can be a positive pole piece or a negative pole piece; in some embodiments of the present application, the pole piece is a positive pole piece, and an empty foil area is left at one end of the positive pole piece along the axial direction of the secondary battery, and a kneaded flat surface formed by flattening the empty foil area is electrically connected to the positive current collector disk; or, in other embodiments of the present application, the pole piece is a negative pole piece, and an empty foil area is left at one end of the negative pole piece along the axial direction of the secondary battery, and a kneaded flat surface formed by flattening the empty foil area is electrically connected to the negative current collector disk, and the positive current collector disk or the negative current collector disk is electrically connected to the thinning area.
  • the pole piece is a positive pole piece, and an empty foil area is left at one end of
  • the axial direction of the secondary battery refers to the length direction of the secondary battery. As shown in FIG. 1 , the length direction of the secondary battery refers to the direction from the bottom to the top of the secondary battery housing, or from the top to the bottom.
  • the electronic device includes any one of the above secondary batteries.
  • the electronic device of the present application can be used for, but not limited to, laptop computers, pen-input computers, mobile computers, e-book players, portable phones, portable fax machines, portable copiers, portable printers, head-mounted stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini-discs, transceivers, electronic notepads, calculators, memory cards, portable recorders, radios, backup power supplies, motors, cars, motorcycles, power-assisted bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries and lithium-ion capacitors, etc.
  • the positive electrode sheet, the negative electrode sheet and the separator are wound to form the bare cell 12, the positive electrode sheet is provided with a first empty foil area, the negative electrode sheet is provided with a second empty foil area, the first empty foil area and the second empty foil area are respectively provided at two ends of the bare cell 12, and the first empty foil area and the second empty foil area are respectively flattened by a flattening device to form a first A kneading plane and a second kneading plane, the first kneading plane is electrically connected to the positive electrode collector disc 13, the second kneading plane is electrically connected to the negative electrode collector disc 14, and a boss 140 is arranged on the side of the negative electrode collector disc 14 away from the second kneading plane.
  • the various parameters of the boss 140 are shown in Table 1.
  • the steel shell of the common battery on the market is used as the shell of the initial thickness of the present application.
  • the parameters of the shell diameter, shell bottom thickness and shell bottom area of the initial shell are shown in Table 1.
  • the middle area of the bottom of the shell of the initial thickness is thinned to form a shell 11 having a thinning area 1101.
  • the various parameters of the thinning area 1101 are shown in Table 1.
  • the prepared battery cell assembly is placed in the prepared shell 11, the end face of the protruding end of the boss 140 is concentrically fitted with the surface of one side of the thinning area 1101, the thinning area 1101 is welded to the boss 140 by penetration welding, the thinning area 1101 is welded to the negative electrode collector 14, and the electrolyte is injected after drying, the positive electrode collector 13 at the other end of the bare battery 12 is welded to the cap, the cap is positively charged, and finally the cover plate and the shell are laser sealed or jaw sealed to form the secondary battery.
  • Table 2 The test results are shown in Table 2.
  • Example 2 Different from Example 1, in the process of preparing the battery cell assembly and the battery housing, various parameters of the initial housing, various parameters of the boss 140 and various parameters of the thinning area 1101 are adjusted respectively, as shown in Table 1. The test results are shown in Table 2.
  • Example 2 Different from Example 1, in the process of preparing the battery cell assembly and the battery housing, various parameters of the boss 140 and various parameters of the thinning area 1101 are adjusted respectively, as shown in Table 1. The test results are shown in Table 2.
  • Battery bottom welding quality rate number of good batteries/total number of batteries
  • the number of good batteries refers to the number of batteries that, after the bare battery cell is installed in the shell, the negative electrode collector is electrically connected to the shell through bottom penetration welding in the thinned area at the bottom of the shell, and after the electrical connection, there is no abnormality such as poor welding, deformation, cracks, and perforations in the shell.
  • Table 1 Note: The “/” in Table 1 is a comparison between the two, for example: thinning area area/total shell bottom area, that is, the percentage of the thinning area area compared to the total shell bottom area. Other similarities will not be repeated.
  • Example 1 Compared with Example 1, in Example 1, the ratio of the area of the thinning zone to the total area of the bottom of the shell in Example 1 is only 1% (lower than the range of 2% to 30% described in the present application), and the welding failure rate of Example 1 during the battery bottom welding test is as high as 0.50%, resulting in its welding excellent rate of only 99.49%, which is lower than the welding excellent rate of 99.81% in Example 1, which is about 0.32% lower; in Example 2, the ratio of the area of the thinning zone to the total area of the bottom of the shell is as high as 32% (higher than the range of 2% to 30% described in the present application), and the deformation rate of Example 2 during the battery bottom welding test is as high as 0.28%, and its welding excellent rate is 99.71%, which is lower than the welding excellent rate of Example 1, which is about 0.1% lower.
  • the ratio of the area of the thinning zone to the bottom area of the shell is in a suitable range, which is conducive to improving the welding excellent rate.
  • Comparative Example 3 does not have the thinning area at the bottom of the shell.
  • the crack rate of Comparative Example 3 during the battery bottom welding test is as high as 0.45%, and its welding quality rate is only 99.55%, which is much lower than the welding quality rate of Example 1, which is about 0.26% lower. It can be seen that setting the thinning area at the bottom of the shell is conducive to improving the welding quality rate of the battery bottom.
  • Example 18 Compared with Example 1, in Example 17 and Example 18, the ratio of the thickness of the thinned area to the thickness of the main area in Example 17 is only 25% (lower than the range of 30% to 80% described in this application), and the deformation rate of Example 17 during the battery bottom welding test is 0.15%, and the perforation rate is 0.05%, resulting in its welding excellent rate of only 99.79%, which is lower than the welding excellent rate of Example 1; in Example 18, the ratio of the thickness of the thinned area to the thickness of the main area is as high as 85% (higher than the range of 30% to 80% described in this application), and the crack rate of Example 18 during the battery bottom welding test is as high as 0.4%, and its welding excellent rate is only 99.60%, which is lower than the welding excellent rate of Example 1, which is about 0.21% lower. It can be seen that the ratio of the thickness of the thinned area to the thickness of the main area at the bottom of the shell is in a suitable range, which is conducive to improving the welding excellent rate.
  • Example 19 Compared with Example 1, in Example 19, the ratio of the projection area of the raised end of the boss to the projection area of the thinned area is only 0.5:1 (lower than the range of 0.6:1 to 0.98:1 described in the present application), and the perforation rate during the bottom welding test is 0.25%, resulting in a welding quality rate of only 99.75%. It can be seen that the ratio of the projection area of the raised end of the boss to the projection area of the thinned area is within a suitable range, which is conducive to improving the welding quality rate of the bottom of the battery.
  • Example 20 Compared with Example 1, in Example 20, the ratio of the boss thickness to the difference between the main area thickness and the thinned area thickness is only 0.8 (lower than the range of 1.0 to 1.3 described in the present application), and the perforation rate during the bottom welding test is 0.25%, and the welding quality rate is only 99.74%. It can be seen that the ratio of the boss thickness to the difference between the main area thickness and the thinned area thickness is in a suitable range, which is conducive to improving the welding quality rate of the bottom of the battery.
  • Examples 2 to 16 are parallel examples of Example 1.
  • the welding excellence rates of Examples 1 to 16 are all above 99.81%, and the highest welding excellence rate can reach 99.99%. It can be seen that the welding excellence rate of the battery bottom can be further improved by optimizing the area of the thinning area, the thickness of the thinning area, and setting a suitable boss size.

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Abstract

一种二次电池以及电子设备，所述二次电池包括壳体、电极组件和集流盘；所述集流盘和所述电极组件电连接；所述壳体的底部包括主体区和连接所述主体区的减薄区，所述减薄区与所述集流盘电连接；所述减薄区的面积占所述壳体底部的总面积的2％至30％。通过在壳体底部的中间区域设置减薄区，所述减薄区与集流盘通过激光焊接连接，所述减薄区可明显降低底部焊接时的焊接功率，拓宽焊接窗口，有效提升电池底部的焊接优率；同时，涉及的技术方案具有较广的适用性，可适用于多种尺寸以及多种厚度的电池壳体，且均可以获得较好的焊接优率。

Description

二次电池以及电子设备 技术领域
本申请涉及电池技术领域，尤其涉及一种二次电池以及电子设备。
背景技术
目前的二次电池结构，一般采用两端引出极耳的结构，极耳与集流体焊接后引出，极耳再与壳体底部通过电阻焊或激光焊接连接。
传统的钢壳电池为了保证电池的耐冲击性，从而电池壳体设计较厚，但是，这导致在底部激光焊接过程中，激光穿过钢壳与集流盘焊接或者其与极耳焊接，需要较大的焊接功率，随着焊接功率的增大，激光的精度波动也随之增大，导致焊接窗口小；在电池结构生产过程中，经常出现电池底部形变、裂纹、穿孔等问题，进而导致焊接优率低。
发明内容
本申请提供一种二次电池以及电子设备，能够解决在激光焊接过程中由于焊接功率的增大导致电池底部形变、裂纹、穿孔等问题，利于提高电池底部的焊接优率，还能够改善电池底部的焊接不可靠。
第一方面，本申请提供了一种二次电池，所述二次电池包括壳体、电极组件和集流盘；所述集流盘和所述电极组件电连接；所述壳体的底部包括主体区和连接所述主体区的减薄区，即壳体底部设置有减薄区，所述减薄区与所述集流盘电连接；所述减薄区的面积占所述壳体底部的总面积的2％至30％。减薄区的面积为在垂直主体区方向上在壳体底部的投影面积。通过在所述壳体底部设置一定面积的所述减薄区，利于降低壳体底部焊接时的焊接功率，进而扩宽焊接窗口。一方面，若所述减薄区的面积占所述壳体底部总面积的比例过小，由于所述减薄区适用于降低电池底部焊接时的焊接功率，所述减薄区的面积过小则壳体底部的焊接面积不够，激光焊接时可能会焊接到未打薄区域(即所述壳体的底部不包括减薄区的其他区域)，导致焊接优率明显下降，这是因为未打薄区域需要更大的焊接功率，而更大的焊接功率会导致焊接的精度降低；另一方面，若所述减薄区的面积过大，则壳体底部的强度会变 弱，电连接后电池的产气现象会使壳体底部出现鼓包并且发生变形，进而影响焊接优率。
在一些实施方式中，所述减薄区的面积占所述壳体底部的总面积的4％至15％。通过进一步控制所述减薄区的面积占所述壳体底部总面积的4％至15％，利于进一步提高焊接优率，同时，可以提高焊接的可靠性。
在一些实施方式中，所述减薄区的厚度与所述主体区的厚度之比为30％至80％。通过控制所述减薄区的厚度与所述主体区的厚度之比在合适的范围，利于提高焊接优率，若所述减薄区的厚度与所述主体区的厚度之比过小，则会导致壳体底部的整体强度会变弱，电连接后电池产气会导致壳体底部鼓包甚至变形；若所述减薄区的厚度与所述主体区的厚度之比过大，则会导致底部焊接时的焊接功率变大，焊接功率大会导致壳体底部产生裂纹。
在一些实施方式中，所述减薄区的厚度与所述主体区的厚度之比为40％至70％。通过进一步控制所述减薄区的厚度与所述主体区的厚度之比在40％至70％的范围内，利于进一步提高焊接优率，避免壳体底部产生裂纹。
在一些实施方式中，所述壳体底部的外表面以朝向所述集流盘的方向内凹以形成所述减薄区；在另一些实施方式中，所述壳体底部的内表面以背离所述集流盘的方向内凹以形成所述减薄区；在其他实施方式中，所述壳体底部的外表面以朝向所述集流盘的方向内凹，同时，所述壳体底部的内表面以背离所述集流盘的方向内凹，以形成所述减薄区。可见，所述壳体底部外表面的一侧打薄、内表面的一侧打薄或者外表面和内表面两侧的同时打薄均可以形成本申请所述的减薄区。
在一些实施方式中，所述集流盘朝向所述壳体底部的一端设有凸台，所述凸台与所述减薄区贴合设置。进一步地，所述凸台的凸起端的端面与所述减薄区的一侧表面贴合设置。
贴合设置是指所述凸台的凸起端的端面与所述减薄区的一侧表面贴合后无间隙或者基本无间隙，即为本申请所述的贴合设置或者贴合。此时，可以避免所述减薄区和所述集流盘之间存在较大的缝隙，进而避免壳体底部焊接时的穿孔现象，利于提高电池底部焊接优率，还可以提高焊接的可靠性。
在一些实施方式中，所述凸台与所述减薄区同心贴合设置。进一步地，所述凸台的凸起 端的端面与所述减薄区的一侧表面同心贴合设置。所述的同心贴合设置用以避免焊接时的焊穿，进一步提高电池底部的焊接优率，以及进一步提升焊接时的可靠性。
在一些实施方式中，在所述二次电池的轴向方向，所述凸台的凸起端的投影面积小于所述减薄区的投影面积。
在一些实施方式中，所述凸台的凸起端的投影面积与所述减薄区的投影面积之比为0.6:1至0.98:1。此时，利于进一步提高电池底部的焊接优率。
在一些实施方式中，所述主体区的厚度为T1，所述减薄区的厚度为T2，所述凸台的厚度为T0，满足：T0≥(T1-T2)。
在一些实施方式中，所述主体区的厚度为T1，所述减薄区的厚度为T2，所述凸台的厚度为T0，满足：1.0≤T0/(T1-T2)≤1.3。通过控制所述凸台的厚度大于所述主体区的厚度与所述减薄区的厚度之差，并将所述凸台的厚度T0与所述主体区的厚度T1和所述减薄区的厚度T2之差的比值调控在一定范围内，利于优化电池底部焊接优率，进一步提升电池底部的焊接可靠性。
在一些实施方式中，所述凸台的凸起端的端面具有与所述减薄区相同的形状且与所述减薄区贴合设置。此时，利于更好地控制所述凸台与所述减薄区之间的间隙，进一步提高电池底部的焊接优率。
需要说明的是，所述凸台的设置适用于所述壳体底部凹陷的三种情况，即所述壳体底部的外表面以朝向所述集流盘的方向内凹形成所述减薄区；和/或，所述壳体底部的内表面以背离所述集流盘的方向内凹形成所述减薄区。
在一些实施方式中，所述二次电池包括极片；所述极片沿所述二次电池轴向的一端部留有空箔区；所述空箔区经揉平后形成的揉平面与所述集流盘电连接。
所述的极片可以是正极极片，也可以是负极极片。在本申请的一些实施例中，所述极片是正极极片，所述正极极片沿所述二次电池轴向的一端部留有空箔区，所述空箔区经揉平后形成的揉平面与正极集流盘电连接；或者，在本申请的另一些实施例中，所述极片是负极极片，所述负极极片沿所述二次电池轴向的一端部留有空箔区，所述空箔区经揉平后形成的揉 平面与负极集流盘电连接，所述正极集流盘或所述负极集流盘与所述减薄区电连接。
在一些实施方式中，上述二次电池为圆柱形二次电池，所述圆柱形二次电池还包括绕卷式裸电芯，所述绕卷式裸电芯包括上述的极片。
本申请采用全极耳结构裸电芯的电芯结构，用以改善高倍率放电下的升温问题；所述的全极耳结构裸电芯进一步为全极耳卷绕式裸电芯；具体地，在正极集流体(例如铝箔)表面涂布正极浆料形成正极极片，所述正极极片的一端留有空铝箔区；在负极集流体(例如铜箔)表面涂布负极浆料形成负极极片，所述负极极片的一端留有空铜箔区；所述正极极片和所述负极极片之间还设置有隔离膜，将所述正极极片、所述隔离膜以及所述负极极片层叠卷绕形成所述全极耳卷绕式裸电芯，所述空铝箔区和所述空铜箔区分别设置在所述全极耳卷绕式裸电芯的两端；将所述空铝箔区和所述空铜箔区通过揉平设备分别揉平形成揉平面，所述空铝箔区经揉平后形成的揉平面与正极集流盘电连接，所述空铜箔区经揉平后形成的揉平面与负极集流盘电连接；所述正极集流盘或所述负极集流盘再与所述减薄区电连接。
第二方面，本申请提供了一种电子设备，所述电子设备包括上述的二次电池。
本申请一些实施例提供的技术方案带来的有益效果至少包括：
(1)本申请通过在壳体的底部设置所述减薄区，所述减薄区用以壳体底部的焊接，所述减薄区的面积占所述壳体底部的总面积的2％至30％，其利于降低焊接时的焊接功率，拓宽焊接窗口，且能够提升电池底部的焊接优率；
(2)本申请中集流盘朝向所述减薄区一端的端部设置有凸台，所述凸台的凸起端的端面与所述减薄区贴合，用以避免所述集流盘与所述减薄区之间存在较大的缝隙，利于提高焊接优率；同时，调控所述凸台的凸起端在电池轴向的投影面积以及所述凸台的厚度范围，利于进一步提升电池底部焊接优率；
(3)本申请采用全极耳卷绕式裸电芯，所述全极耳卷绕式裸电芯端部的空箔区经揉平后形成的揉平面与集流盘电连接，利于改善电池内部过热等安全隐患。
附图说明
为了更清楚地说明本申请实施例或现有技术中的技术方案，下面将对实施例或现有技术 描述中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图仅仅是本申请的一些实施例，对于本领域技术人员来讲，在不付出创造性劳动的前提下，还可以根据这些附图获得其他的附图。
图1为本申请一实施例的二次电池的剖视图；
图2为本申请一实施例的二次电池的底部局部放大图；
图3为本申请一实施例的二次电池的底部局部剖视图；
图4为本申请另一实施例的二次电池的底部局部剖视图；
图5为本申请一实施例的二次电池的底部示意图；
图6为本申请另一实施例的二次电池的底部示意图；
图7为本申请再一实施例的二次电池的底部示意图；
图8为本申请一实施例的二次电池的底部焊接示意图；
图9为本申请另一实施例的二次电池的底部焊接示意图。
图中：11、壳体；12、裸电芯；13、正极集流盘；14、负极集流盘；110、壳体底部；1101、减薄区；1102、主体区；140、凸台。
具体实施方式
为了使本申请的目的、技术方案及优点更加清楚明白，以下结合附图及实施例，对本申请进行进一步详细说明。应当理解，此处所描述的具体实施例仅仅用以解释本申请，并不用于限定本申请。
请参阅图1和图2所示，本申请所述二次电池的第一实施方式包括壳体11，所述壳体11的内部容置有裸电芯12，所述裸电芯12为卷绕式裸电芯，由正极极片、负极极片和隔离膜卷绕后形成，所述正极极片上设置有第一空箔区，所述负极极片上设置有第二空箔区，所述第一空箔区和所述第二空箔区分别设置在所述裸电芯12的两端，所述第一空箔区和所述第二空箔区经揉平后形成的第一揉平面和第二揉平面，其分别与正极集流盘13和负极集流盘14电连接；
在本申请第一实施方式的一些实施例中，所述正极集流盘13位于所述壳体11的上端， 所述负极集流盘14位于所述壳体11的下端，所述壳体11的下端端部为壳体底部110，所述壳体底部110包括减薄区1101和主体区1102，所述减薄区1101设置在所述壳体底部110的中间位置处，所述壳体底部110不包括减薄区1101的其他区域即为主体区1102，所述主体区1102环绕所述减薄区1101的外周设置并与所述减薄区连接，所述减薄区1101一体成型于所述壳体底部110上，所述减薄区1101通过激光焊(例如穿透焊)与所述负极集流盘14电连接。
在本申请第一实施方式的另一些实施例中，所述正极集流盘13位于所述壳体11的下端，所述壳体底部110的中间位置处设置有减薄区1101，所述减薄区1101通过激光焊(例如穿透焊)与所述正极集流盘13电连接。
在本申请的其他实施例中，所述减薄区1101还可以非一体成型设于所述壳体底部110，只要能够实现降低焊接功率，拓宽焊接窗口，本申请对此并无限制。
本申请通过在所述壳体底部110设置所述减薄区1101以及与所述减薄区1101连接的所述主体区1102，同时控制所述减薄区1101的厚度小于所述主体区1102的厚度，在壳体底部的焊接过程中，通过在所述减薄区1101位置处进行激光焊接，使得所述壳体底部110与所述正极集流盘13或负极集流盘14实现位置固定的电连接，所述减薄区1101的设置可以有效降低所述壳体底部110焊接时的焊接功率，扩宽焊接窗口，利于提高焊接优率。
需要说明的是，在本申请中，所述减薄区1101是通过在所述壳体底部110的初始厚度上进行打薄形成的，打薄区域即为减薄区1101，未打薄区域即为主体区1102，因此，所述减薄区1101的厚度毫无质疑的小于所述壳体底部110的初始厚度，而且，所述减薄区1101的厚度方向与所述壳体11的底面垂直，所述主体区1102的厚度方向与所述减薄区1101的厚度方向平行。
在一些示例性的实施例中，所述减薄区1101的面积占所述壳体底部110总面积的2％至30％；所述壳体底部110的总面积包括所述主体区1102的面积与减薄区1101的面积之和(下文中有时也称壳体底部面积)。通过控制所述减薄区的面积与所述壳体底部面积的比例在合适的范围，利于提高电池底部焊接时的焊接优率，例如，若所述减薄区的面积占所述壳 体底部面积的比例过小(例如小于壳体底部面积的2％)，由于所述减薄区适用于降低电池底部焊接时的焊接功率，所述减薄区的面积过小则壳体底部的焊接面积不够，激光焊接时可能会焊接到未打薄区域(即所述壳体底部不包括所述减薄区的其他区域)，易造成激光未穿透壳体底部，导致焊接不良，进而使得焊接优率明显下降，焊接的可靠性也降低；另一方面，若所述减薄区的面积过大，则壳体底部的强度会变弱，电连接后电池的产气现象会使壳体底部出现鼓包并且发生变形，进而影响焊接优率。
示例性地，所述减薄区1101面积占所述壳体底部110总面积的2％、5％、8％、10％、15％、20％、25％、30％中的任意两个值组成的范围。
在一些示例性的实施例中，所述减薄区1101面积占所述壳体底部110总面积的4％至15％。
示例性地，所述减薄区1101面积占所述壳体底部110总面积的4％、6％、8％、10％、12％、14％、15％中的任意两个值组成的范围。此时，通过进一步控制所述减薄区的面积占所述壳体底部总面积的4％至15％，利于提高焊接优率，还可以提高焊接的可靠性。
在一些示例性的实施例中，所述减薄区1101的厚度与所述主体区1102的厚度之比为30％至80％。通过控制所述减薄区1101的厚度与所述主体区1102的厚度之比在合适的范围，利于进一步提高焊接优率，具体地，若所述减薄区1101的厚度与所述主体区1102的厚度比过小(例如厚度比小于30％)，即所述减薄区1101的厚度相比于所述主体区1102的厚度过薄，则壳体底部的整体强度会变弱，电连接后电池产气会导致壳体的底部鼓包甚至变形；若所述减薄区1101的厚度与所述主体区1102的厚度比过大(例如厚度比大于80％)，即壳体底部的打薄效果不明显，底部焊接时的焊接功率也会变大，焊接功率大则会导致壳体的底部产生裂纹，这是由于集流盘和壳体底部的材质不同、熔点不同，功率越大，则集流盘所含材料偏析到熔池的比例越大，导致冷却后两元素不相溶，裂纹越大。可见，所述减薄区的厚度与所述壳体底部的厚度之比过大或者过小均不利于提高焊接优率。示例性地，所述减薄区1101厚度与所述壳体底部110厚度之比为30％、40％、50％、60％、70％、80％中的任意两个值组成的范围。
在一些示例性的实施例中，所述减薄区1101的厚度与所述主体区的1102厚度之比为40％至70％。通过进一步控制所述减薄区1101的厚度与所述壳主体区的1102的厚度之比在40％至70％的范围内，利于进一步提高焊接优率，避免壳体底部产生裂纹。
示例性地，所述减薄区1101的厚度与所述主体区1102的厚度之比为40％、45％、50％、55％、60％、65％、70％中的任意两个值组成的范围。
参阅图3所示，为本申请的一种实施方式，所述壳体底部110的外表面以朝向所述负极集流盘14的方向内凹以形成所述减薄区1101，图3中b所示的间距即为所述减薄区1101的厚度，a所示的间距即为所述主体区1102的厚度；通过在所述壳体底部110的外表面做外侧打薄，用以使其外表面内凹形成所述减薄区1101，所述减薄区1101与所述壳体底部110一体成型。
所述减薄区1101还可以非一体成型设于所述壳体底部110上，所述减薄区1101的材质可以与所述壳体的材质相同，也可以与所述壳体的材质不相同，只要能够实现降低底部焊接功率、提高底部焊接优率以及提高焊接可靠性即可，本申请对此并无限制。结合图2所示，所述负极集流盘14朝向所述壳体11的底部110的一端端部设有凸台140，所述凸台140与所述减薄区1101贴合设置；进一步地，所述凸台140的凸起端的端面与所述减薄区1101的一侧表面贴合设置。通过在所述负极集流体14的一端端部设置所述凸台140，所述凸台140的凸起端朝向所述减薄区1101延伸且所述凸起端的端面与所述减薄区1101外表面贴合，用以避免所述减薄区1101和所述负极集流盘14之间存在较大缝隙，进而避免壳体底部焊接时的穿孔现象，利于提高电池底部焊接优率，且利于提升焊接的可靠性。
需要说明的是，在本申请的其他实施例中，还可以是正极集流盘与减薄区通过激光焊实现电连接，此时，所述正极集流盘朝向所述壳体11的底部110的一端端部设有凸台140，所述凸台140的凸起端的端面与所述减薄区1101的一侧表面贴合设置。
在一些示例性的实施例中，所述凸台140凸起端的端面与所述减薄区1101的一侧表面同心贴合设置；通过控制所述凸台140凸起端的端面与所述减薄区1101的外表面同心贴合设置，因为焊接是焊在所述壳体11的底部110的中心，通过将所述减薄区1101与所述凸台 140同心设置用以避免焊穿，进而提高电池底部焊接优率，以及提升焊接的可靠性。
在一些示例性的实施例中，在所述二次电池的轴向方向，所述凸台140的凸起端的投影面积小于所述减薄区1101的投影面积，而且，所述凸台140的凸起端的投影面积与所述减薄区1101的投影面积之比为0.6:1至0.98:1。
所述凸台140凸起端的投影面积过小(例如其与所述打薄区1101的投影面积之比小于0.6:1)则容易导致焊穿，这因为激光经过所述壳体11底部110中间位置处的减薄区1101后，对应位置处若是没有所述凸台140的贴合设置就会因焊穿导致穿孔，不利于提高焊接优率；而若所述凸台140凸起端端面的面积过大，则会因外力导致集流盘变形，集流盘变形会造成不贴合焊接，所述凸台140的端面与所述减薄区1101的不贴合设置会产生较大的间隙，较大的间隙会导致激光的焊穿，造成电连接后壳体的穿孔，不利于提高焊接优率。
示例性地，所述凸台140的凸起端的投影面积与所述减薄区1101的投影面积之比为0.6:1、0.7:1、0.8:1、0.9:1、0.98:1中的任意两个值组成的范围。此时，利于进一步提高电池底部的焊接优率。
在一些示例性的实施例中，所述主体区1102的厚度为T1(即图3中a所示的间距)，需要说明的是，本申请中所述的主体区1102的厚度指的是壳体底部110上未打薄区域的厚度(即壳体底部的初始厚度)；所述减薄区1101的厚度为T2(即图3中b所示的间距)，所述凸台140的厚度为T0，且满足：T0≥(T1-T2)。所述凸台140的厚度是指在所述二次电池的轴向方向，所述凸台140的底部与其顶部之间的间距。通过控制所述凸台140的厚度大于所述主体区1102的厚度与所述减薄区1101的厚度之差，利于提高电池底部的焊接优率，提升电池底部焊接的可靠性。
在一些示例性的实施例中，所述主体区1102的厚度为T1，所述减薄区1101的厚度为T2，所述凸台140的厚度为T0，满足：1.0≤T0/(T1-T2)≤1.3。通过将所述凸台140的厚度T0与所述主体区1102的厚度T1和所述减薄区的厚度T2之差的比值调控在一定范围内，利于进一步优化电池底部焊接优率，以及进一步提升电池底部焊接的可靠性。
示例性地，所述凸台140的厚度T0与所述主体区1102的厚度T1和所述减薄区1101的 厚度T2之差的比值为1.0、1.1、1.2、1.3中的任意两个值组成的范围。
在一些示例性的实施例中，所述凸台140凸起端的端面具有与所述减薄区1101相同的形状，且所述凸台140凸起端的端面与所述减薄区1101的一侧表面贴合设置；此时，利于更好地控制所述凸台与所述减薄区之间的间隙，进一步提高电池底部的焊接优率。例如，在本申请实施例中，所述凸台140凸起端的端面为圆形、方形或者环形，在本申请的其他实施例中，所述凸台140凸起端面还可以为三角形、多边形等其他平面形状，只要能够满足上述限制条件，实现提升底部焊接优率以及可靠性，本申请对此并无限制。
参阅图4，为本申请所述的二次电池的第二实施方式的结构示意图，第二实施方式中，所述二次电池的结构与第一实施方式的结构大体相同，不同之处在于：所述壳体底部110的内表面以背离所述负极集流盘14或正极集流盘13的方向内凹以形成所述减薄区1101。所述负极集流盘14或正极集流盘13靠近所述减薄区1101的端部设置有所述凸台140，所述凸台140的设置与第一实施方式相同。
本申请所述的二次电池还有第三种实施方式(图未示)，其与第一实施方式的结构大体相同，不同之处在于：所述壳体底部110的内表面以背离所述负极集流盘14或正极集流盘13的方向内凹，同时所述壳体底部110的外表面以朝向所述负极集流盘14或正极集流盘13的方向内凹，即所述壳体底部110的内表面和外表面同时凹陷，以形成所述减薄区1101。所述负极集流盘14或正极集流盘13靠近所述减薄区1101的端部设置有所述凸台140，所述凸台140的设置与第一实施方式相同。
参阅图5至图7，在本申请实施例中，所述减薄区1101的中心点位于所述壳体11底面的中轴线上，所述减薄区1101的形状选自圆形、方形、环形中的任一种；参阅图8和图9，所述减薄区1101与所述负极集流盘14或正极集流盘13通过穿透焊焊接，焊接的形貌选自点焊、线焊或螺旋焊接中的任一种；在本申请的其他实施例中，所述减薄区1101的中心点可以位于所述壳体11底面上的其他位置，所述减薄区1101的形状还可以选自三角形、多边形中的任一种，只要能够实现提升底部焊接优率，提高焊接的可靠性，本发明对此并无限制。
一种圆柱形二次电池
所述圆柱形二次电池包括壳体和卷绕式裸电芯，所述壳体的底部设有减薄区，所述卷绕式裸电芯包括极片，所述的极片可以是正极极片，也可以是负极极片；在本申请的一些实施例中，所述极片是正极极片，所述正极极片沿所述二次电池轴向的一端部留有空箔区，所述空箔区经揉平后形成的揉平面与正极集流盘电连接；或者，在本申请的另一些实施例中，所述极片是负极极片，所述负极极片沿所述二次电池轴向的一端部留有空箔区，所述空箔区经揉平后形成的揉平面与负极集流盘电连接，所述正极集流盘或所述负极集流盘与所述减薄区电连接。
所述二次电池的轴向方向是指沿所述二次电池的长度方向，结合图1所示，所述二次电池的长度方向是指所述二次电池壳体的底端到顶端的方向，或者其顶端到底端的方向。
一种电子设备
所述电子设备包括如上的任意一种二次电池。本申请的电子设备置可用于，但不限于，笔记本电脑、笔输入型计算机、移动电脑、电子书播放器、便携式电话、便携式传真机、便携式复印机、便携式打印机、头戴式立体声耳机、录像机、液晶电视、手提式清洁器、便携CD机、迷你光盘、收发机、电子记事本、计算器、存储卡、便携式录音机、收音机、备用电源、电机、汽车、摩托车、助力自行车、自行车、照明器具、玩具、游戏机、钟表、电动工具、闪光灯、照相机、家庭用大型蓄电池和锂离子电容器等。
以下将结合具体实施例对本申请作进一步详细的说明。
实施例1
电芯组件制备
将正极极片、负极极片和隔膜卷绕后形成所述裸电芯12，所述正极极片上设置有第一空箔区，所述负极极片上设置有第二空箔区，所述第一空箔区和所述第二空箔区分别设置在所述裸电芯12的两端，所述第一空箔区和所述第二空箔区分别经揉平设备揉平后形成第一 揉平面和第二揉平面，所述第一揉平面和正极集流盘13电连接，所述第二揉平面和负极集流盘14，所述负极集流盘14背离所述第二揉平面的一侧设置凸台140，所述凸台140的各项参数参见表1所示。
电池壳体制备
将市面上常见的电池的钢壳作为本申请初始厚度的壳体，初始壳体的壳体直径、壳体底部厚度以及壳体底部面积的参数见表1，将初始厚度的壳体的底部的中间区域进行打薄处理，形成具有减薄区1101的壳体11，所述减薄区1101的各项参数参见表1。
二次电池制备
将上述制备得到的电芯组件置于上述制备得到的壳体11中，所述凸台140的凸起端的端面与所述减薄区1101的一侧表面同心贴合设置，所述减薄区1101通过穿透焊焊接在所述凸台140上，所述减薄区1101与所述负极集流盘14焊接导通，干燥后注入电解液，将所述裸电芯12另一端的正极集流盘13与盖帽焊接，盖帽带正电，最后盖板与壳体进行端盖激光密封焊接或钳口密封，形成所述二次电池。测试效果见表2。
实施例2至实施例20
与实施例1不同的是，在电芯组件和电池壳体的制备过程中，分别调控初始壳体的各项参数、凸台140的各项参数以及减薄区1101的各项参数，具体参见表1。测试效果见表2。
对比例1至对比例3
与实施例1不同的是，在电芯组件和电池壳体的制备过程中，分别调控凸台140的各项参数以及减薄区1101的各项参数，具体参见表1。测试效果见表2。
电池底部焊接优率测试
电池底部焊接优率＝电池良品数/电池总数；
其中，电池良品数是指裸电芯装入壳体后通过底部穿透焊在壳体底部的减薄区将负极集流盘与壳体电连接，电连接后壳体未发生焊接不良、形变、裂纹、穿孔的异常的电池数量。
表1

备注：表1中的“/”为两者相比，例如：减薄区面积/壳体底部总面积，即，减薄区面积与
壳体底部总面积相比的百分占比，其他类似，不再赘述。
表2
对比例1至对比例2和实施例1相比，对比例1中减薄区面积与壳体底部总面积之比仅为1％(低于本申请所述的2％至30％的范围)，对比例1在电池底部焊接测试过程中的焊接不良率高达0.50％，导致其焊接优率仅为99.49％，低于实施例1的焊接优率99.81％，低约0.32％；对比例2中减薄区面积与壳体底部总面积之比高达32％(高于本申请所述的2％至30％的范围)，对比例2在电池底部焊接测试过程中的变形率高达0.28％，其焊接优率为99.71％，低于实施例1的焊接优率，低约0.1％。可见，减薄区面积与壳体底部面积之比在合适的范围，利于提高焊接优率。对比例3和实施例1相比，对比例3的壳体底部没有设置所述减薄区，对比例3在电池底部焊接测试过程中的裂纹率高达0.45％，其焊接优率仅为99.55％，远低于实施例1的焊接优率，低约0.26％。可见，在壳体底部设置所述减薄区利于提高电池底部的焊接优率。
实施例17至实施例18和实施例1相比，实施例17中减薄区厚度与主体区厚度之比仅为25％(低于本申请所述的30％至80％的范围)，实施例17在电池底部焊接测试过程中的变形率为0.15％，穿孔率为0.05％，导致其焊接优率仅为99.79％，低于实施例1的焊接优率；实施例18中减薄区厚度与主体区厚度之比高达85％(高于本申请所述的30％至80％的范围)，实施例18在电池底部焊接测试过程中的裂纹率高达0.4％，其焊接优率仅为99.60％，低于实施例1的焊接优率，低约0.21％。可见，壳体底部的减薄区厚度与主体区厚度之比在合适的范围，利于提高焊接优率。
实施例19和实施例1相比，实施例19中凸台凸起端投影面积与减薄区投影面积之比仅为0.5:1(低于本申请所述的0.6:1至0.98:1的范围)，其在底部焊接测试过程中的穿孔率为0.25％，导致焊接优率仅为99.75％。可见，凸台凸起端投影面积与减薄区投影面积之比在合适的范围，利于提高电池底部的焊接优率。
实施例20和实施例1相比，实施例20中凸台厚度与主体区厚度和减薄区厚度之差的比值仅为0.8(低于本申请所述的1.0至1.3的范围)，其在底部焊接测试过程中的穿孔率为0.25％，焊接优率仅为99.74％。可见，凸台厚度与主体区厚度和减薄区厚度之差的比值在合适的范围，利于提高电池底部的焊接优率。
实施例2至实施例16均为实施例1的平行实施例，实施例1至实施例16的焊接优率均在99.81％以上，且焊接优率最高可达99.99％。可见，通过优化减薄区的面积、减薄区的厚度以及设置合适的凸台尺寸可以进一步提高电池底部的焊接优率。
本实施例的附图中相同或相似的标号对应相同或相似的部件；在本申请的描述中，需要理解的是，若有术语“上”、“下”、“左”、“右”等指示的方位或位置关系为基于附图所示的方位或位置关系，仅是为了便于描述本申请和简化描述，而不是指示或暗示所指的装置或元件必须具有特定的方位、以特定的方位构造和操作，因此附图中描述位置关系的用语仅用于示例性说明，不能理解为对本专利的限制，对于本领域的普通技术人员而言，可以根据具体情况理解上述术语的具体含义。
以上所述仅为本申请的较佳实施例而已，并不用以限制本申请，凡在本申请的精神和 原则之内所作的任何修改、等同替换和改进等，均应包含在本申请的保护范围之内。

Claims (15)

  1. 一种二次电池，其特征在于，包括壳体、电极组件和集流盘；
    所述集流盘和所述电极组件电连接；
    所述壳体的底部包括主体区和连接所述主体区的减薄区，所述减薄区与所述集流盘电连接；
    沿垂直所述主体区的方向，所述减薄区的投影面积占所述壳体底部的总面积的2％至30％。
  2. 根据权利要求1所述的二次电池，其中，所述减薄区的投影面积占所述壳体底部的总面积的4％至15％。
  3. 根据权利要求1所述的二次电池，其中，所述减薄区的厚度与所述主体区的厚度之比为30％至80％。
  4. 根据权利要求3所述的二次电池，其中，所述减薄区的厚度与所述主体区的厚度之比为40％至70％。
  5. 根据权利要求1所述的二次电池，其中，所述壳体底部的外表面以朝向所述集流盘的方向内凹形成所述减薄区；和/或，
    所述壳体底部的内表面以背离所述集流盘的方向内凹形成所述减薄区。
  6. 根据权利要求5所述的二次电池，其中，所述集流盘朝向所述壳体底部的一端设有凸台，所述凸台与所述减薄区贴合设置。
  7. 根据权利要求6所述的二次电池，其中，所述凸台与所述减薄区同心贴合设置。
  8. 根据权利要求6所述的二次电池，其中，在所述二次电池的轴向方向，所述凸台的凸起端的投影面积小于所述减薄区的投影面积。
  9. 根据权利要求8所述的二次电池，其中，所述凸台的凸起端的投影面积与所述减薄区的投影面积之比为0.6:1至0.98:1。
  10. 根据权利要求6所述的二次电池，其中，所述主体区的厚度为T1，所述减薄区的厚度为T2，所述凸台的厚度为T0，满足：T0≥(T1-T2)。
  11. 根据权利要求10所述的二次电池，其中，满足：1.0≤T0/(T1-T2)≤1.3。
  12. 根据权利要求8-11任一项所述的二次电池，其中，所述凸台的凸起端的端面具有与所述减薄区相同的形状且与所述减薄区贴合设置。
  13. 根据权利要求1所述的二次电池，其中，所述电极组件包括极片；
    所述极片沿所述二次电池轴向的一端部留有空箔区；
    所述空箔区经揉平后形成的揉平面与所述集流盘电连接。
  14. 根据权利要求1所述的二次电池，其中，所述二次电池为圆柱形二次电池。
  15. 一种电子设备，其中，所述电子设备包括权利要求1至14任一项所述的二次电池。
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