WO2025199795A1 - 二次电池以及电子装置 - Google Patents

二次电池以及电子装置

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Publication number
WO2025199795A1
WO2025199795A1 PCT/CN2024/084046 CN2024084046W WO2025199795A1 WO 2025199795 A1 WO2025199795 A1 WO 2025199795A1 CN 2024084046 W CN2024084046 W CN 2024084046W WO 2025199795 A1 WO2025199795 A1 WO 2025199795A1
Authority
WO
WIPO (PCT)
Prior art keywords
welding
electrode
electrode assembly
weld
secondary battery
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.)
Pending
Application number
PCT/CN2024/084046
Other languages
English (en)
French (fr)
Inventor
华传山
陶涛
王涛
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 CN202480016878.6A priority Critical patent/CN120981951A/zh
Priority to PCT/CN2024/084046 priority patent/WO2025199795A1/zh
Publication of WO2025199795A1 publication Critical patent/WO2025199795A1/zh
Pending legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Classifications

    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • 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
    • H01M50/502—Interconnectors for connecting terminals of adjacent batteries; Interconnectors for connecting cells outside a battery casing
    • H01M50/514—Methods for interconnecting adjacent batteries or cells
    • H01M50/516—Methods for interconnecting adjacent batteries or cells by welding, soldering or brazing
    • 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
    • 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
    • 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
    • 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
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • the present application relates to the field of energy storage technology, and in particular to a secondary battery and an electronic device.
  • the tabs of a secondary battery are welded to the current collector of the electrode assembly, serving as the positive and negative leads.
  • the thickness of the electrode assembly's pole pieces repeatedly expands, causing the wound electrode assembly to repeatedly contract and expand.
  • the weld marks formed by the tabs and current collectors are subjected to stress, which can easily damage or break the current collector.
  • the present application provides a secondary battery and an electronic device, which are beneficial to improving the tensile strength of the welding part between the tab and the pole piece, and are beneficial to reducing the risk of damage to the pole piece.
  • a secondary battery in a first aspect of the present application, includes an electrode assembly and a first electrode tab.
  • the electrode assembly includes a first electrode sheet, a second electrode sheet, and a separator disposed between the first electrode sheet and the second electrode sheet.
  • the first electrode sheet, the second electrode sheet, and the separator are stacked and wound to form a wound structure.
  • the first electrode sheet includes a first current collector and a first active material layer disposed on the first current collector.
  • the first current collector is provided with a first connection region, and the first connection region is not provided with the first active material layer.
  • the first electrode tab is welded to the first connection region.
  • the first connection region includes a plurality of welding regions, and the plurality of welding regions are arranged along the winding direction of the electrode assembly.
  • the welding region is provided with at least one weld mark formed by welding the first electrode tab to the first connection region. Along the winding direction of the electrode assembly, the weld mark in the welding region closest to the winding center of the electrode assembly has
  • the welding strength of the weld mark in the welding area closest to the winding center of the electrode assembly along the winding direction of the electrode assembly is the smallest, which reduces the damage of the welding to the first current collector in the welding area closest to the winding center of the electrode assembly, thereby helping to improve the tensile strength of the weld mark in the welding area closest to the winding center of the electrode assembly, and helping to resist the pulling force on the welding part of the first electrode ear and the first current collector from the outside to the inside along the winding structure when the electrode assembly expands, and helping to reduce the risk of damage to the electrode sheet.
  • the welding strength of the weld marks in different welding areas gradually decreases.
  • the weld strength decreases as the weld mark approaches the center of the electrode assembly in the winding direction, and the degree of damage to the structural strength of the first current collector caused by the weld is also reduced. This improves the tensile strength of the weld mark on the first electrode sheet, helps resist the pulling force on the weld between the first tab and the first current collector from the outside to the inside of the winding structure when the electrode assembly expands, and helps reduce the risk of damage to the first electrode sheet.
  • the welding tension between the first electrode tab and the first current collector at each weld mark is F, which satisfies 1N ⁇ F ⁇ 80N.
  • the number of welding zones is N.
  • the i-th welding zone is closer to the winding center of the electrode assembly than the i+1-th welding zone.
  • the welding tension of the weld mark of the i-th welding zone is F i
  • the welding tension of the weld mark of the i+1-th welding zone is F i+1 , satisfying 1N ⁇ F i+1 - F i ⁇ 5 N.
  • N is a positive integer greater than or equal to 2
  • i is a positive integer greater than or equal to 1 and less than N.
  • the difference in welding strength between the weld marks in two adjacent welding areas is between 1N and 5N, so that the difference in structural strength between the two adjacent welding areas will not be too large, which is beneficial to reducing the risk of poor welding due to insufficient welding tension, and also helps to reduce the risk of damage to the first current collector due to excessive welding tension.
  • the number of weld marks is S
  • the average value of the welding tension of the S weld marks is K, which satisfies 5N ⁇ K ⁇ 9N.
  • S is a positive integer greater than or equal to 2.
  • the heights of the weld marks in different welding areas in the thickness direction of the first electrode sheet gradually decrease.
  • the height of the weld marks in different weld zones gradually decreases along the winding direction of the electrode assembly from the outside to the inside. This results in welds closer to the winding center of the electrode assembly causing less damage to the structural strength of the first current collector. This improves the tensile strength of the weld marks on the first electrode sheet, helps resist the pulling force on the weld between the first tab and the first current collector from the outside to the inside of the winding structure when the electrode assembly expands, and reduces the risk of damage to the first electrode sheet.
  • the height of the weld mark in the thickness direction of the first pole piece is H, which satisfies 1 um ⁇ H ⁇ 100 um.
  • the number of welding zones is N, and the number of welding zones along the winding direction of the electrode assembly is N.
  • the i-th welding zone is closer to the winding center of the electrode assembly than the i+1-th welding zone.
  • the height of the weld mark of the i-th welding zone in the thickness direction of the first electrode sheet is Hi
  • the height of the weld mark of the i+1-th welding zone in the thickness direction of the first electrode sheet is Hi +1 , satisfying 1 ⁇ m ⁇ Hi+1 - Hi ⁇ 10 ⁇ m.
  • N is a positive integer greater than or equal to 2
  • i is a positive integer greater than or equal to 1 and less than N.
  • the distance between the weld mark closest to the first edge among the multiple weld marks and the first edge is between 0.1 mm and 1 mm, so that the weld mark will not be too close to the first edge, which is beneficial to the welding operation, and the weld mark will not be too far from the first edge, which is beneficial to increase the area of the welding area and improve the utilization rate of the first connection area.
  • an electronic device comprising a secondary battery as described in any of the above embodiments.
  • the weld mark in the welding region closest to the winding center of the electrode assembly among the plurality of welding regions has the smallest welding strength, which is beneficial to reducing damage to the first current collector caused by welding, thereby improving the tensile strength of the weld mark in the welding region closest to the winding center of the electrode assembly, and is beneficial to resisting the pulling force on the weld portion between the first tab and the first current collector from the outside to the inside along the winding structure when the electrode assembly expands, thereby reducing the risk of damage to the first electrode sheet.
  • FIG2 is an exploded schematic diagram of a secondary battery provided in one embodiment of the present application.
  • FIG3 is a side view of an electrode assembly provided in one embodiment of the present application.
  • FIG4 is a partial top view of a first pole piece and a first pole tab provided in one embodiment of the present application.
  • FIG6 is a partial top view of a first pole piece and a first pole tab provided in another embodiment of the present application.
  • FIG7 is a partial top view of a first pole piece and a first pole tab provided in yet another embodiment of the present application.
  • FIG8 is a schematic diagram of an electronic device according to an embodiment of the present application.
  • the thickness of the electrode sheets of the electrode assembly repeatedly expands, causing the wound electrode assembly to repeatedly shrink and expand.
  • the weld edges formed by the welding of the tabs and the current collector are subjected to stress, which can easily cause damage and breakage of the current collector.
  • the present application discloses a secondary battery, comprising an electrode assembly and a tab.
  • the electrode assembly comprises a first pole piece, a second pole piece, and a separator disposed between the first pole piece and the second pole piece.
  • the first pole piece, the second pole piece, and the separator are stacked and wound to form a wound structure.
  • the first pole piece comprises a first current collector and a first active material layer disposed on the first current collector.
  • the first current collector is provided with a first connection region, and the first connection region is not provided with the first active material layer.
  • the tab is welded to the first connection region.
  • the first connection region comprises a plurality of welding regions, the plurality of welding regions being arranged along the winding direction of the electrode assembly.
  • the welding region is provided with at least one weld mark formed by welding the tab to the first connection region.
  • the weld mark in the welding region closest to the winding center of the electrode assembly among the plurality of welding regions has the smallest welding strength.
  • the welding strength of the weld mark in the welding area closest to the winding center of the electrode assembly along the winding direction of the electrode assembly is the smallest.
  • the welding strength is relatively small, it is beneficial to reduce the damage to the first current collector caused by welding, thereby helping to improve the tensile strength of the weld mark in the welding area closest to the winding center of the electrode assembly, and helping to resist the pulling force on the welding part of the first electrode ear and the first current collector from the outside to the inside along the winding structure when the electrode assembly expands, and helping to reduce the risk of damage to the first electrode sheet.
  • the first electrode 21 includes a first current collector 211 and a first active material layer 212 disposed on the first current collector 211 .
  • the first active material layer 212 and the first current collector 211 are stacked.
  • the second electrode 22 includes a second current collector 221 and a second active material layer 222 disposed on the second current collector 221 .
  • the second active material layer 222 and the second current collector 221 are stacked.
  • the first electrode 21 is an anode electrode
  • the second electrode 22 is a cathode electrode.
  • the first electrode 21 is a cathode electrode
  • the second electrode 22 is an anode electrode.
  • the cathode electrode sheet includes a cathode current collector and a cathode active material layer that are stacked together
  • the anode electrode sheet includes an anode current collector and an anode active material layer that are stacked together.
  • the cathode current collector may be a metal layer including at least one of aluminum, nickel, tantalum, and titanium, such as aluminum foil.
  • the anode current collector may be a metal layer including at least one of copper, nickel, tantalum, and titanium, such as copper foil.
  • the cathode active material layer includes a cathode active material, which may include at least one of lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium manganese iron phosphate, or lithium manganese oxide.
  • the anode active material layer includes an anode active material, which may include At least one of graphite, hard carbon, soft carbon, silicon, silicon-oxygen material, and silicon-carbon material.
  • the isolation film 23 is made of insulating film materials such as polyethylene film, polypropylene film, polyester film, or polyimide film.
  • the first current collector 211 is provided with a first connection region 2111 , and the first active material layer 212 is not provided in the first connection region 2111 .
  • the first connection region 2111 is formed at the winding end of the first current collector 211 without coating the first active material layer 212 to form an empty foil segment 2113 , and the area on the empty foil segment 2113 used for welding to the first electrode sheet 21 is the first connection region 2111 .
  • the first connection region 2111 is formed after a portion of the first active material layer 212 is washed away from the first current collector 211 having the first active material layer 212 , and the current collector of the first connection region 2111 is exposed.
  • the first electrode tab 30 is connected to the first electrode piece 21 .
  • the material of the first electrode tab 30 may be the same as that of the first current collector 211 .
  • the polarity of the first electrode tab 30 is the same as that of the first electrode piece 21 .
  • the second electrode tab 40 is connected to the second electrode piece 22 .
  • the material of the second electrode tab 40 can be the same as that of the second current collector 221 .
  • the polarity of the second electrode tab 40 is the same as that of the second electrode piece 22 .
  • the secondary battery 100 further includes a shell 10, which accommodates an electrode assembly 20.
  • the electrode assembly 20 is connected to a first electrode tab 30 and a second electrode tab 40. Portions of the first electrode tab 30 and the second electrode tab 40 extend out of the shell 10 to lead the polarity of the electrode assembly 20 out of the shell 10.
  • the secondary battery 100 is a soft-pack battery, and the housing 10 is an aluminum-plastic film. In other embodiments, the secondary battery 100 is a hard-shell battery, and the material of the housing 10 includes any one or more of plastic, steel, or aluminum.
  • an electrolyte (not shown) is further disposed within the housing 10.
  • the electrolyte contains a lithium salt and a solvent.
  • the lithium salt may include at least one of LiPF, LiBF, LiClO, LiB(CH), LiCHSO, LiCFSOLiN(SOCF), LiC(SOCF), or LiBOB.
  • the solvent may be a carbonate compound, a carboxylate compound, an ether compound, other organic solvents, or a combination thereof.
  • the first electrode tab 30 is welded to the first connection region 2111.
  • the first connection region 2111 includes a plurality of welding regions 211a.
  • the plurality of welding regions 211a are arranged along the winding direction X of the electrode assembly 20 (when the first electrode sheet 21 is unfolded as shown in FIG. 4 , the plurality of welding regions 211a are arranged along the length direction X′′ of the first electrode sheet 21).
  • At least one weld mark 203 formed by welding the first electrode tab 30 to the first connection region 2111 is provided in the welding region 211a.
  • the weld mark 203 in the welding region 211a closest to the winding center of the electrode assembly 20 has the smallest welding strength.
  • the weld mark 203 within the welding area 211a closest to the winding center of the electrode assembly 20 along the winding direction X of the electrode assembly 20 is first subjected to the pulling force.
  • the weld mark 203 within the welding area 211a closest to the winding center of the electrode assembly 20 along the winding direction X of the electrode assembly 20 has the lowest welding strength. This helps reduce welding damage to the first current collector 211 in the welding area 211a closest to the winding center of the electrode assembly 20.
  • the welding strength can be characterized by the welding tension and the height of the weld mark 203. The higher the welding strength, the greater the welding tension and the higher the weld mark 203.
  • the welding strengths of the weld marks 203 within the same welding area 211 a are substantially the same.
  • a plurality of welding marks 203 are disposed in each welding region 211 a , and the plurality of welding marks 203 in each welding region 211 a are arranged along the width Y direction of the first electrode 21 .
  • the number of weld marks 203 in different welding areas 211 a may be the same or different, and no specific limitation is given herein.
  • the multiple weld marks 203 of the first connection area 2111 are discretely arranged, which is beneficial to improving the uniformity of welding in the first connection area 2111, improving the uniformity of force in the welding area 211a between the first pole ear 30 and the first pole piece 21, reducing the risk of the first pole ear 30 falling off, and reducing the risk of damage to the first pole piece 21.
  • the welding method is ultrasonic welding, and the ultrasonic welding device includes multiple welding heads.
  • weld marks 203 with different weld strengths can be produced.
  • weld marks 203 with different weld strengths can be produced.
  • the welding method is laser welding, and weld marks 203 with different welding strengths are produced by adjusting different powers.
  • the weld strength of the weld marks 203 in different weld regions 211a gradually decreases, such that, along the winding direction X′ of the electrode assembly 20, the weld strength of the weld marks 203 decreases as they are closer to the winding center of the electrode assembly 20, and the degree of damage to the structural strength of the first current collector 211 caused by welding is also reduced.
  • the welding tension at the welding marks 203 in different welding areas 211a is along the electrode assembly 20
  • the winding direction X' decreases gradually from the outside to the inside.
  • the welding tension at the weld mark 203 in different welding areas 211a gradually decreases along the winding direction X' of the electrode assembly 20 from the outside to the inside. This results in a weld closer to the winding center of the electrode assembly 20 in the winding direction X of the electrode assembly 20 causing less damage to the structural strength of the first current collector 211.
  • Welding tensile testing method After fully discharging the finished secondary battery 100, disassemble it to obtain the first electrode sheet 21 to be measured. Cut the welding pieces of the first electrode sheet 30 and the first connection area 2111 of the first electrode sheet 21 along the width direction Y of the first electrode sheet 21 to obtain the welding pieces of the first electrode sheet 30 and the first current collector 211 corresponding to different welding areas 211a. Each welding piece of the first electrode sheet 30 and the first current collector 211 in each welding area 211a is placed on a high-speed rail tensile testing machine and subjected to a tensile test at a speed of 1 mm/s along the width direction Y of the first electrode sheet 21. The maximum tensile force is recorded as the welding tensile force at the weld mark 203 corresponding to the welding area 211a.
  • the welding tension between the first electrode tab 30 and the first current collector 211 at each weld mark 203 is F, satisfying 1N ⁇ F ⁇ 80N. This is beneficial to reducing the risk of a cold weld due to the welding tension at the weld mark 203 with the smallest welding tension, and is also beneficial to reducing the risk of the first current collector 211 being easily broken due to the welding tension at the weld mark 203 with the largest welding tension being too large.
  • the number of welding zones 211a is N, with the Nth welding zone 211a being farthest from the winding center of the electrode assembly 20 along the winding direction X of the electrode assembly 20, and the first welding zone 211a being closest to the winding center of the electrode assembly 20 along the winding direction X of the electrode assembly 20.
  • the welding tension at the weld mark 203 in different welding zones 211a gradually decreases along the winding direction X' from the outside to the inside of the electrode assembly 20, so that the welding tension at the weld mark 203 in the i-th welding zone 211a is F i , and F i ⁇ F i+1 , where N is a positive integer greater than or equal to 2, and i is a positive integer greater than or equal to 1 and less than N. Then, the following conditions are satisfied: F N ⁇ 80 N, and F 1 ⁇ 1 N.
  • F can specifically be 80N, 78N, 75N, 72N, 70N, 68N, 65N, 62N, 60N, 58N, 55N, 52N, 50N, 48N, 45N, 42N, 40N, 38N, 35N, 32N, 30N, 28N, 25N, 22N, 20N, 18N, 15N, 12N, 10N, 8N, 5N, 4N, 3N, 2N or 1N.
  • F i+1 -F i may be any one of 5N, 4N, 3N, 2N or 1N.
  • the number of weld marks 203 is S
  • the average welding tension of the S weld marks 203 is The value is K, satisfying 5N ⁇ K ⁇ 9N, and S is a positive integer greater than or equal to 2.
  • K satisfies the range of 5N ⁇ K ⁇ 9N
  • K can be any one of 9N, 8N, 7N, 6N, 5N, 4N, 3N, 2N or 1N.
  • the height of the weld marks 203 in different welding areas 211 a in the thickness direction Z of the first electrode sheet 21 gradually decreases.
  • the height of the weld marks 203 in different welding areas 211a gradually decreases along the winding direction X' of the electrode assembly 20 from the outside to the inside. This reduces the damage to the structural strength of the first current collector 211 as the welds are closer to the winding center of the electrode assembly 20 in the winding direction X. This helps improve the tensile strength of the weld marks 203 of the first electrode sheet 21, helps resist the pulling force on the weld between the first electrode tab 30 and the first current collector 211 from the outside to the inside along the winding structure when the electrode assembly 20 expands, and helps reduce the risk of damage to the first electrode sheet 21.
  • the height of the weld mark 203 in the thickness direction Z of the first pole piece 21 is H, satisfying 1um ⁇ H ⁇ 100um. This is beneficial to reducing the risk of a cold weld due to too small a welding tension at the weld mark 203 where the welding tension is the smallest, and is also beneficial to reducing the risk of damage to the first current collector 211 due to too large a welding tension at the weld mark 203 where the welding tension is the largest.
  • the number of welding zones 211a is N, with the Nth welding zone 211a being farthest from the winding center of the electrode assembly 20 along the winding direction X of the electrode assembly 20, and the first welding zone 211a being closest to the winding center of the electrode assembly 20 along the winding direction X of the electrode assembly 20.
  • the welding tension at the weld marks 203 in different welding zones 211a gradually decreases along the winding direction X' from the outside to the inside of the electrode assembly 20, so that the height of the weld mark 203 of the i-th welding zone 211a in the thickness direction Z of the first electrode sheet 21 is Hi , and Hi ⁇ Hi +1 , where N is a positive integer greater than or equal to 2, and i is a positive integer greater than or equal to 1 and less than N. Then, the following conditions are satisfied: HN ⁇ 100 ⁇ m, -H1 ⁇ 1 ⁇ m .
  • H can specifically be 100um, 98um, 95um, 92um, 90um, 88um, 85um, 82um, 80um, 78um, 75um, 72um, 70um, 68um, 65um, 62um, 60um, 58um, 55um, 52um, 50um, 48um, 45um, 42um, 40um, 38um, 35um, 32um, 30um, 28um, 25um, 22um, 20um, 18um, 15um, 12um, 10um, 8um, 5um, 4um, 3um, 2um or 1um.
  • the number of welding areas 211a is N.
  • the i-th welding area 211a is closer to the winding center of the electrode assembly 20 than the i+1-th welding area 211a.
  • the height of the weld mark 203 of the i-th welding area 211a in the thickness direction Z of the first electrode sheet 21 is Hi
  • the height of the weld mark 203 of the i+1-th welding area 211a in the thickness direction Z of the first electrode sheet 21 is Hi +1 .
  • Hi +1 - Hi can be any one of 10N, 9N, 8N, 7N, 6N, 5N, 4N, 3N, 2N or 1N.
  • the number of weld marks 203 is S
  • the average height of the S weld marks 203 is L, satisfying 5 ⁇ m ⁇ L ⁇ 15 ⁇ m, where S is a positive integer greater than or equal to 2.
  • L satisfies the range of 5 ⁇ m ⁇ L ⁇ 15 ⁇ m, this helps reduce the risk of the first electrode tab 30 falling off due to excessively low overall welding tension between the first electrode tab 30 and the first electrode sheet 21.
  • This allows for reduced welding strength of some weld marks 203 to improve the structural strength of the first electrode sheet 21.
  • This helps achieve a gradual decrease in welding tension at the weld marks 203 in different weld areas 211 a along the winding direction X' from the outside to the inside of the electrode assembly 20, thereby reducing the risk of electrode sheet damage.
  • L can be any one of 15um, 14um, 13um, 12um, 11um, 10um, 9um, 8um, 7um, 6um or 5um.
  • the finished secondary battery 100 After fully discharging the finished secondary battery 100, disassemble it to obtain the first electrode sheet 21 to be measured. Cut along the width direction Y of the first electrode sheet 21 at the first connection area 2111 between the first electrode tab 30 and the first electrode sheet 21 to obtain welding pieces corresponding to different welding areas 211a of the first electrode tab 30 and the first current collector 211.
  • the welding pieces of the first electrode tab 30 and the first current collector 211 in different welding areas 211a are each placed on a high-speed rail tensile tester and subjected to a tensile test at a speed of 1 mm/s along the width direction Y of the first electrode sheet 21. After the test, observe whether there is any residue of the first current collector 211 at the weld mark 203 of the first electrode tab 30. If no residue is observed, the weld mark 203 is a cold joint; otherwise, there is no cold joint.
  • a secondary battery 100 is assembled as follows:
  • anode electrode The anode active materials, artificial graphite, conductive carbon black (Super P), and styrene-butadiene rubber (SBR), were mixed in a weight ratio of 96:1.5:2.5, and deionized water was added as a solvent to prepare a slurry with a weight percentage of 70 wt%. The mixture was stirred evenly. The slurry was evenly coated on one surface of a 10 ⁇ m thick anode current collector copper foil, leaving an empty foil area at the edge of the copper foil. The anode electrode was dried at 110°C to obtain an anode electrode with a coating thickness of 150 ⁇ m and coated on one side with an anode active material layer.
  • the uncoated foil segment 2113 has a first connection region 2111.
  • a copper foil is welded to the first connection region 2111 to serve as the anode tab.
  • the first connection region 2111 includes multiple welding regions 211a, which are arranged along the winding direction X of the electrode assembly 20. Within each welding region 211a are multiple weld marks 203 formed by welding the anode tab to the first connection region 2111. The weld marks 203 within each welding region 211a are arranged along the width direction Y of the anode plate. Along the winding direction X' of the electrode assembly 20 from the outside to the inside, the weld strength of the weld marks 203 in different welding regions 211a gradually decreases.
  • an embodiment of the present application further provides an electronic device 1000, which includes the secondary battery 100 of any of the aforementioned embodiments. Because the electronic device 1000 employs the technical solution of the secondary battery 100 of any of the aforementioned embodiments, it at least has the beneficial effects brought about by the technical solution of the secondary battery 100 of any of the aforementioned embodiments, which will not be further elaborated here.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
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Abstract

一种二次电池（100）以及电子装置（1000），二次电池（100）包括电极组件（20）和第一极耳（30）。电极组件（20）包括第一极片（21）、第二极片（22）以及设于第一极片（21）和第二极片（22）之间的隔离膜（23），第一极片（21）、第二极片（22）以及隔离膜（23）形成卷绕结构。第一极片（21）包括层叠的第一集流体（211）和第一活性物质层（212），第一集流体（211）设有第一连接区（2111），第一连接区（2111）未设置第一活性物质层（212）。第一极耳（30）焊接于第一连接区（2111），第一连接区（2111）包括多个焊接区（211a），多个焊接区（211a）沿电极组件（20）的卷绕方向布置，焊接区（211a）内设有由第一极耳（30）与第一连接区（2111）焊接形成的至少一个焊印（203）。沿电极组件（20）的卷绕方向，多个焊接区（211a）中最靠近电极组件（20）卷绕中心的焊接区（211a）内的焊印（203）的焊接强度最小，有利于提高第一连接区（2111）的抗拉能力，有利于降低第一极片（21）受损的风险。

Description

二次电池以及电子装置 技术领域
本申请涉及储能技术领域，尤其涉及一种二次电池以及电子装置。
背景技术
二次电池的极耳焊接在电极组件的集流体上，以作为二次电池的正负极引出。相关技术中，二次电池在循环过程中，电极组件的极片的厚度反复膨胀，导致卷绕结构的电极组件反复收缩和膨胀，在此过程中极耳与集流体焊接形成的焊印边缘受力，容易导致集流体受损、断裂。
发明内容
有鉴于此，本申请提供一种二次电池以及电子装置，有利于提升极耳和极片焊接部分的抗拉能力，有利于降低极片受损的风险。
本申请第一方面，提供一种二次电池，二次电池包括电极组件和第一极耳，电极组件包括第一极片、第二极片以及设于第一极片和第二极片之间的隔离膜，第一极片、第二极片以及隔离膜层叠并卷绕形成卷绕结构。第一极片包括第一集流体和设于第一集流体上的第一活性物质层，第一集流体设有第一连接区，第一连接区未设置第一活性物质层。第一极耳焊接于第一连接区，第一连接区包括多个焊接区，多个焊接区沿电极组件的卷绕方向布置，焊接区内设有由第一极耳与第一连接区焊接形成的至少一个焊印，沿电极组件的卷绕方向，多个焊接区中最靠近电极组件卷绕中心的焊接区内的焊印的焊接强度最小。
上述实施例中，多个焊接区中，沿电极组件的卷绕方向最靠近电极组件卷绕中心的焊接区内的焊印的焊接强度最小，降低了焊接对最靠近电极组件卷绕中心的焊接区的第一集流体的破坏，从而有利于提高最靠近电极组件卷绕中心的焊接区内的焊印处的抗拉能力，有利于抵抗电极组件膨胀时沿卷绕结构由外向内的方向对第一极耳与第一集流体焊接部分的拉扯力，有利于降低极片受损的风险。
在以上一个或多个实施例中，沿电极组件由外向内的卷绕方向，不同焊接区中的焊印的焊接强度逐渐减小。
上述实施例中，在电极组件的卷绕方向上，越靠近电极组件卷绕中心的焊印的焊接强度越小，焊接对第一集流体结构强度的破坏的程度也越低。有利于提高第一极片的焊印处的抗拉能力，有利于抵抗电极组件膨胀时沿卷绕结构由外向内的方向对第一极耳与第一集流体焊接部分的拉扯力，有利于降低第一极片受损的风险。
在以上一个或多个实施例中，每个焊印处的第一极耳与第一集流体之间存在焊接拉力，不同焊接区中焊印处的焊接拉力沿电极组件由外向内的卷绕 方向逐渐减小。
上述实施例中，在电极组件的卷绕方向上，越靠近电极组件卷绕中心的焊接对第一集流体结构强度的破坏的程度也越低。有利于提高第一极片的焊印处的抗拉能力，有利于抵抗电极组件膨胀时沿卷绕结构由外向内的方向对第一极耳与第一集流体焊接部分的拉扯力，有利于降低第一极片受损的风险。
在以上一个或多个实施例中，每个焊印处的第一极耳与第一集流体的焊接拉力为F，满足1N≤F≤80N。
上述实施例中，在满足1N≤F≤80N时，有利于降低焊接拉力最小的焊印处的焊接拉力过小而虚焊的风险，还有利于降低焊接拉力最大的焊印处的焊接拉力过大而导致第一集流体受损的风险。
在以上一个或多个实施例中，焊接区的数量为N，沿电极组件的卷绕方向，第i个焊接区相较于第i+1个焊接区更靠近电极组件的卷绕中心，第i个焊接区的焊印的焊接拉力为Fi，第i+1个焊接区的焊印的焊接拉力为Fi+1，满足1N≤Fi+1-Fi≤5N。N为大于等于2的正整数，i为大于等于1且小于N的正整数。
上述实施例中，相邻两个焊接区中的焊印的焊接强度的差值处于1N-5N之间，让相邻的两个焊接区的结构强度差距不会过大，有利于降低焊接拉力过小而虚焊的风险，还有利于降低焊接拉力过大而导致第一集流体受损的风险。
在以上一个或多个实施例中，焊印的数量为S，S个焊印的焊接拉力的均值为K满足5N≤K≤9N。S为大于等于2的正整数。
上述实施例中，K满足5N≤K≤9N这一范围时，有利于降低第一极耳与第一极片的整体焊接拉力过小而导致第一极耳脱落的风险，容许部分焊印的焊接强度降低以提高第一极片的结构强度，有利于实现在不同焊接区中焊印处的焊接拉力沿电极组件由外向内的卷绕方向逐渐减小，从而有利于降低极片受损的风险。
在以上一个或多个实施例中，沿电极组件由外向内的卷绕方向，不同焊接区中的焊印在第一极片的厚度方向上的高度逐渐降低。
上述实施例中，不同焊接区中的焊印高度沿电极组件由外向内的卷绕方向逐渐减小，使在电极组件的卷绕方向上，越靠近电极组件卷绕中心的焊接对第一集流体结构强度的破坏的程度也越低。有利于提高第一极片的焊印处的抗拉能力，有利于抵抗电极组件膨胀时沿卷绕结构由外向内的方向对第一极耳与第一集流体焊接部分的拉扯力，有利于降低第一极片受损的风险。
在以上一个或多个实施例中，焊印在第一极片的厚度方向上的高度为H，满足1um≤H≤100um。
上述实施例中，在满足1um≤H≤100um时，有利于降低焊接拉力最小的焊印处的焊接拉力过小而虚焊的风险，还有利于降低焊接拉力最大的焊印处的焊接拉力过大而导致第一集流体受损的风险。
在以上一个或多个实施例中，焊接区的数量为N，沿电极组件的卷绕方 向，第i个焊接区相较于第i+1个焊接区更靠近电极组件的卷绕中心，第i个焊接区的焊印在第一极片的厚度方向上的高度为Hi，第i+1个所述焊接区的所述焊印在所述第一极片的厚度方向上的高度为Hi+1，满足1um≤Hi+1-Hi≤10um。N为大于等于2的正整数，i为大于等于1且小于N的正整数。
上述实施例中，相邻两个焊接区中的焊印的高度的差值处于1um-10um之间，让相邻的两个焊接区的结构强度差距不会过大，有利于降低焊接拉力过小而虚焊的风险，还有利于降低焊接拉力过大而导致第一集流体受损的风险。
在以上一个或多个实施例中，焊印的数量为S，S个焊印的高度均值为L，满足5um≤L≤15um。S为大于等于2的正整数。
上述实施例中，L满足5um≤L≤15um这一范围时，有利于降低第一极耳与第一极片的整体焊接拉力过小而导致第一极耳脱落的风险，容许部分焊印的焊接强度降低以提高第一极片的结构强度，有利于实现在不同焊接区中焊印处的焊接拉力沿电极组件由外向内的卷绕方向逐渐减小，从而有利于降低极片受损的风险。
在以上一个或多个实施例中，定义第一极耳在电极组件由外向内的卷绕方向上靠近电极组件卷绕中心一侧的边缘为第一边缘，多个焊接区中的焊印距第一边缘的最小距离为A，多个焊印的总宽度为W，多个焊印距第一边缘的最大距离为B＝A+W。
在以上一个或多个实施例中，满足0.1mm≤A≤1mm。
上述实施例中，多个焊印中与第一边缘最近的一个焊印与第一边缘的距离在0.1mm-1mm之间，使焊印不会距第一边缘过近，从而有利于焊接操作，也不会让焊印距离第一边缘过远，从而有利于增加焊接区的面积，有利于提升第一连接区的利用率。
在以上一个或多个实施例中，满足1mm≤W≤3mm。
上述实施例中，在满足1mm≤W≤3mm时，多个焊印占据的区域不至于过小，从而有利于提升多个焊接区的总面积，有利于提升第一极耳与第一极片的连接强度，容许部分焊印的焊接强度降低以提高第一极片的结构强度，有利于实现在不同焊接区中焊印处的焊接拉力沿电极组件由外向内的卷绕方向逐渐减小，从而有利于降低极片受损的风险。
在以上一个或多个实施例中，满足1.1mm≤B≤4mm。
在以上一个或多个实施例中，沿电极组件由外向内的卷绕方向，第一集流体包括依次设置的空箔段涂覆段和，涂覆段设有第一活性物质层，空箔段未设置第一活性物质层，空箔段的至少部分位于第一极片的最外圈，第一连接区位于空箔段并位于第一极片的最外圈。
上述实施例中，多个焊接区中，沿电极组件的卷绕方向最靠近电极组件卷绕中心的焊接区内的焊印的焊接强度最小，降低了焊接对最靠近电极组件卷绕中心的焊接区的第一集流体的破坏，从而有利于提高最靠近电极组件卷绕中心的焊接区内的焊印处的抗拉能力，有利于降低极片受损的风险。
在以上一个或多个实施例中，焊印的形状包括菱形、方形、圆形中的至 少一种。
本申请第二方面，还提供一种电子装置，电子装置包括如上述任一实施例中的二次电池。
上述实施例中，二次电池的极片受损概率降低，有利于提升电子装置使用的可靠性。
本申请中的二次电池包括电极组件和极耳，电极组件包括层叠并卷绕的第一极片、第二极片以及设于第一极片和第二极片之间的隔离膜。第一极片包括层叠的第一集流体和第一活性物质层，第一集流体设有未设置第一活性物质层的第一连接区。极耳焊接于第一连接区，第一连接区包括沿电极组件的卷绕方向布置的多个焊接区，焊接区内设有至少一个焊印。沿电极组件的卷绕方向，多个焊接区中最靠近电极组件卷绕中心的焊接区内的焊印的焊接强度最小，有利于降低焊接对第一集流体的破坏，从而有利于提高最靠近电极组件卷绕中心的焊接区内的焊印处的抗拉能力，有利于抵抗电极组件膨胀时沿卷绕结构由外向内的方向对第一极耳与第一集流体焊接部分的拉扯力，有利于降低第一极片受损的风险。
附图说明
图1为本申请一实施例提供的二次电池的结构示意图。
图2为本申请一实施例提供的二次电池的分解示意图。
图3为本申请一实施例提供的电极组件的侧视图。
图4为本申请一实施例提供的第一极片和第一极耳的局部俯视图。
图5为本申请一实施例提供的第一极片和第一极耳的局部侧视图。
图6为本申请另一实施例提供的第一极片和第一极耳的局部俯视图。
图7为本申请又一实施例提供的第一极片和第一极耳的局部俯视图。
图8为本申请一实施例提供电子装置的示意图。
主要元件符号说明
二次电池                        100
壳体                            10
电极组件                        20
第一极片                        21
第一集流体                      211
第一连接区                      2111
焊接区                          211a
涂覆段                          2112
空箔段                          2113
第一活性物质层                  212
第二极片                        22
第二集流体                       221
第二活性物质层                   222
隔离膜                           23
第一极耳                         30
焊印                             203
第二极耳                         40
电极组件的卷绕方向               X
电极组件由外到内的卷绕方向       X’
第一极片的长度方向               X”
第一极片的宽度方向               Y
第一极片的厚度方向               Z
装置主体                         200
电子装置                         1000
具体实施方式
下面将结合本申请实施例中的附图，对本申请实施例中的技术方案进行描述，显然，所描述的实施例仅仅是本申请一部分实施例，而不是全部的实施例。
需要说明的是，本申请中，极片的中心是指层状结构的极片的重心，可以理解地，层状结构的重心可通过悬挂法确定，将层状结构用细线吊起，以细线起点在竖直方向上做一直线，再次将层状结构以不同于第一次的端点吊起，并按之前方法另作一直线，两条直线的交点即为平面形状的重心。
需要说明的是，除非另有明确的规定和限定，术语“安装”、“相连”、“连接”、“固定”等术语应做广义理解，例如，可以是固定连接，也可以是可拆卸连接，或一体地连接；可以是机械连接，也可以是电连接。当一个组件被认为是“连接”另一个组件，它可以是直接连接到另一个组件或者可能同时存在居中组件。当一个组件被认为是“设于”另一个组件，它可以是直接设置在另一个组件上或者可能同时存在居中组件。
除非特别说明，本文所使用的术语“多个”指两个或者两个以上。
术语“第一”、“第二”等仅用于区别不同对象，不能理解为指示或暗示相对重要性或者隐含所指示的技术特征的数量、特定顺序或主次关系。
需要说明的是，当某参数大于、等于或小于某一端点值时，应该理解为端点值允许存在±5％的公差。
需要认识的是，附图所示的层、区域、柱或凸部等的尺寸是为了更好的理解和更方便的描述而给出，本申请不限于附图所示的尺寸。为了使本发明清晰，与描述无关的元件从本说明书的细节中省略。
除非另有定义，本文所使用的所有的技术和科学术语与属于本申请的技术领域的技术人员通常理解的含义相同。本文中在本申请的说明书中所使用的术语只是为了描述具体的实施例的目的，不是旨在于限制本申请。
相关技术中，二次电池在循环过程中，电极组件的极片的厚度反复膨胀，导致卷绕结构的电极组件反复收缩和膨胀，在此过程中极耳与集流体焊接形成的焊印边缘受力，容易导致集流体受损、断裂。
本申请公开一种二次电池，二次电池包括电极组件和极耳，电极组件包括第一极片、第二极片以及设于第一极片和第二极片之间的隔离膜，第一极片、第二极片以及隔离膜层叠并卷绕形成卷绕结构。第一极片包括第一集流体和设于第一集流体上的第一活性物质层，第一集流体设有第一连接区，第一连接区未设置第一活性物质层。极耳焊接于第一连接区，第一连接区包括多个焊接区，多个焊接区沿电极组件的卷绕方向布置，焊接区内设有由极耳与第一连接区焊接形成的至少一个焊印，沿电极组件的卷绕方向，多个焊接区中最靠近电极组件卷绕中心的焊接区内的焊印的焊接强度最小。
上述多个焊接区中沿电极组件的卷绕方向最靠近电极组件卷绕中心的焊接区内的焊印的焊接强度最小，焊接强度较小时，有利于降低焊接对第一集流体的破坏，从而有利于提高最靠近电极组件卷绕中心的焊接区内的焊印处的抗拉能力，有利于抵抗电极组件膨胀时沿卷绕结构由外向内的方向对第一极耳与第一集流体焊接部分的拉扯力，有利于降低第一极片受损的风险。
下面将结合附图，对本申请的一些实施例做出说明。在不冲突的情况下，下述的实施例及实施例中的特征可以相互结合。
请参阅图1至图3，本申请实施例提供一种二次电池100，二次电池100包括电极组件20，电极组件20包括第一极片21、第二极片22以及设于第一极片21和第二极片22之间的隔离膜23，第一极片21和第二极片22的极性相反，隔离膜23用于隔离第一极片21和第二极片22，第一极片21、第二极片22以及隔离膜23层叠并卷绕形成卷绕结构。
在一些实施例中，请参阅图3，第一极片21包括第一集流体211和设于第一集流体211上的第一活性物质层212，第一活性物质层212和第一集流体211层叠设置。
在一些实施例中，请参阅图3，第二极片22包括第二集流体221和设于第二集流体221上的第二活性物质层222，第二活性物质层222和第二集流体221层叠设置。
在一些实施例中，第一极片21为阳极极片，第二极片22为阴极极片。在另外一些实施例中，第一极片21为阴极极片，第二极片22为阳极极片。
在一些实施例中，阴极极片包括层叠设置的阴极集流体和阴极活性物质层，阳极极片包括层叠设置的阳极集流体和阳极活性物质层。
在一些实施例中，阴极集流体可以是包括铝、镍、钽、钛中至少一种的金属层，例如铝箔。阳极集流体可以是包括铜、镍、钽、钛中至少一种的金属层，例如铜箔。
在一些实施例中，阴极活性物质层包括阴极活性材料，阴极活性材料可以包括钴酸锂、镍钴锰酸锂、镍钴铝酸锂、磷酸铁锂、磷酸锰铁锂或锰酸锂中的至少一种。阳极活性物质层包括阳极活性材料，阳极活性材料可以包括 石墨、硬碳、软碳、硅、硅氧材料、硅碳材料中的至少一种。
在一些实施例中，隔离膜23为聚乙烯膜、聚丙烯膜、聚酯膜或者聚酰亚胺膜等能够绝缘的膜料。
在一些实施例中，请参阅图3，第一集流体211设有第一连接区2111，第一连接区2111未设置第一活性物质层212。
在一些实施例中，第一连接区2111是在第一集流体211的卷绕末端未涂覆第一活性物质层212而形成空箔段2113，空箔段2113上用于和第一极片21焊接的区域为第一连接区2111。
在另外一些实施例中，第一连接区2111是在设有第一活性物质层212的第一集流体211上清洗掉部分第一活性物质层212后形成的区域，第一连接区2111的集流体显露。
在一些实施例中，请参阅图3和图4，二次电池100还包括第一极耳30，第一极耳30与电极组件20连接。
在一些实施例中，第一极耳30与第一极片21连接，第一极耳30的材料可以和第一集流体211采用的材料相同，第一极耳30的极性与第一极片21相同。
在一些实施例中，请参阅图3，二次电池100还包括第二极耳40，第二极耳40与电极组件20连接。
在一些实施例中，第二极耳40与第二极片22连接，第二极耳40的材料可以和第二集流体221采用的材料相同，第二极耳40的极性与第二极片22相同。
在一些实施例中，请参阅图1和图2，二次电池100还包括壳体10，壳体10收容电极组件20，电极组件20与第一极耳30和第二极耳40连接，第一极耳30和第二极耳40的部分伸出壳体10，以将电极组件20的极性引出壳体10外。
在一些实施例中，二次电池100为软包电池，壳体10为铝塑膜。在另外一些实施例中，二次电池100为硬壳电池，壳体10的材料包括塑料、钢或者铝中任意一者或者多者。
在一些实施例中，壳体10内还设有电解液(图未示)，电解液含有锂盐和溶剂，锂盐可以包括LiPF、LiBF、LiClO、LiB(CH)、LiCHSO、LiCFSOLiN(SOCF)、LiC(SOCF)或LiBOB的至少一种。溶剂可为碳酸酯化合物、羧酸酯化合物、醚化合物、其它有机溶剂或它们的组合。
在一些实施例中，请参阅图4，第一极耳30焊接于第一连接区2111，第一连接区2111包括多个焊接区211a，多个焊接区211a沿电极组件20的卷绕方向X布置(在如图4所示的第一极片21展开状态下，多个焊接区211a沿第一极片21的长度方向X”排布)，焊接区211a内设有由第一极耳30与第一连接区2111焊接形成的至少一个焊印203。沿电极组件20的卷绕方向X，多个焊接区211a中最靠近电极组件20卷绕中心的焊接区211a内的焊印203的焊接强度最小。
电极组件20膨胀时，第一极耳30与第一连接区2111焊接的区域受到沿电极组件20由外向内的拉扯力。多个焊接区211a中，沿电极组件20的卷绕方向X最靠近电极组件20卷绕中心的焊接区211a内的焊印203最先受到拉扯力。本申请设置多个焊接区211a中，沿电极组件20的卷绕方向X最靠近电极组件20卷绕中心的焊接区211a内的焊印203的焊接强度最小，有利于降低焊接对最靠近电极组件20卷绕中心的焊接区211a的第一集流体211的破坏，从而有利于提高最靠近电极组件20卷绕中心的焊接区211a内的焊印203处的抗拉能力，有利于抵抗电极组件20膨胀时沿卷绕结构由外向内的方向对第一极耳30与第一集流体211焊接部分的拉扯力，有利于降低极片受损的风险。
需要说明地，焊接强度越高时，第一极耳30与第一连接区2111的焊合力越大，并且焊接对第一集流体211结构强度的破坏的程度也越高。焊接强度可以由焊接拉力和焊印203高度进行表征，焊接强度越高，焊接拉力越大，焊印203越高。
在一些实施例中，同一个焊接区211a内的焊印203的焊接强度基本相同。
在一些实施例中，请参阅图4，每个焊接区211a内均设有多个焊印203，每个焊接区211a内的多个焊印203沿第一极片21的宽度Y方向排布。
在一些实施例中，不同焊接区211a内的焊印203的数量可以相同，也可以不同，在此不做具体的限定。
在一些实施例中，第一连接区2111的多个焊印203离散排布，有利于提高第一连接区2111焊接的均匀性，有利于提升第一极耳30与第一极片21的焊接区211a域受力的均匀性，有利于降低第一极耳30脱落的风险以及有利于降低第一极片21受损的风险。
在一些实施例中，焊接方式为超声波焊接，超声波焊接装置包括多个焊头。可以通过让不同焊头上设置不同的刻纹的深度，从而焊接出不同焊接强度的焊印203。也可以通过控制不同焊头的能量不同，从而焊接出不同焊接强度的焊印203。
在另外一些实施例中，焊接方式为激光焊接，通过调整不同的功率而焊接出不同焊接强度的焊印203。
在一些实施例中，请参阅图4，沿电极组件20由外向内的卷绕方向X’，不同焊接区211a中的焊印203的焊接强度逐渐减小，使在电极组件20的卷绕方向X上，越靠近电极组件20卷绕中心的焊印203的焊接强度越小，焊接对第一集流体211结构强度的破坏的程度也越低。有利于提高第一极片21的焊印203处的抗拉能力，有利于抵抗电极组件20膨胀时沿卷绕结构由外向内的方向对第一极耳30与第一集流体211焊接部分的拉扯力，有利于降低第一极片21受损的风险。
在一些实施例中，每个焊印203处的第一极耳30与第一集流体211之间存在焊接拉力，不同焊接区211a中焊印203处的焊接拉力沿电极组件20 由外向内的卷绕方向X’逐渐减小。
不同焊接区211a中焊印203处的焊接拉力沿电极组件20由外向内的卷绕方向X’逐渐减小，使在电极组件20的卷绕方向X上，越靠近电极组件20卷绕中心的焊接对第一集流体211结构强度的破坏的程度也越低。有利于提高第一极片21的焊印203处的抗拉能力，有利于抵抗电极组件20膨胀时沿卷绕结构由外向内的方向对第一极耳30与第一集流体211焊接部分的拉扯力，有利于降低第一极片21受损的风险。
焊接拉力测试方法：将成品二次电池100满放后拆解得到需要测量的第一极片21。沿第一极片21的宽度方向Y，在第一极耳30与第一极片21的第一连接区2111裁切得到对应不同焊接区211a的第一极耳30和第一集流体211的焊接片。将不同焊接区211a的第一极耳30和第一集流体211的焊接片分别拿到高铁拉力机上沿第一极片21宽度方向Y以1mm/s的速度进行拉力测试，记录最大拉力值即为此对应焊接区211a的焊印203处的焊接拉力。
在不同焊接区211a中焊印203处的焊接拉力沿电极组件20由外向内的卷绕方向X’逐渐减小的实施例中，每个焊印203处的第一极耳30与第一集流体211的焊接拉力为F，满足1N≤F≤80N，有利于降低焊接拉力最小的焊印203处的焊接拉力过小而虚焊的风险，还有利于降低焊接拉力最大的焊印203处的焊接拉力过大而导致第一集流体211容易断裂的风险。
作为示例性举例，焊接区211a的数量为N，第N个焊接区211a沿电极组件20卷绕方向X最远离电极组件20卷绕中心，第1个焊接区211a沿电极组件20卷绕方向X最靠近电极组件20卷绕中心。不同焊接区211a中焊印203处的焊接拉力沿电极组件20由外向内的卷绕方向X’逐渐减小，使第i个焊接区211a中的焊印203处的焊接拉力为Fi，且Fi＜Fi+1，其中N为大于等于2的正整数，i为大于等于1且小于N的正整数。则满足：FN≤80N，F1≥1N。
例如，F具体可以是80N、78N、75N、72N、70N、68N、65N、62N、60N、58N、55N、52N、50N、48N、45N、42N、40N、38N、35N、32N、30N、28N、25N、22N、20N、18N、15N、12N、10N、8N、5N、4N、3N、2N或1N。
在一些实施例中，焊接区211a的数量为N，沿电极组件20的卷绕方向X，第i个焊接区211a相较于第i+1个焊接区211a更靠近所述电极组件20的卷绕中心，第i个焊接区211a的焊印203的焊接拉力为Fi，第i+1个焊接区211a的焊印203的焊接拉力为Fi+1，满足1N≤Fi+1-Fi≤5N，使相邻两个焊接区211a中的焊印203的焊接强度的差值处于1N-5N之间，使相邻的两个焊接区211a的结构强度差距不会过大，有利于降低虚焊的风险，还有利于降低焊接拉力过大导致第一极片21受损的风险。
作为示例性举例，Fi+1-Fi具体可以是5N、4N、3N、2N或1N中的任意一者。
在一些实施例中，焊印203的数量为S，S个焊印203的焊接拉力的均 值为K，满足5N≤K≤9N，S为大于等于2的正整数。K满足5N≤K≤9N这一范围时，有利于降低第一极耳30与第一极片21的整体焊接拉力过小而导致第一极耳30脱落的风险，容许部分焊印203的焊接强度降低以提高第一极片21的结构强度，有利于实现在不同焊接区211a中焊印203处的焊接拉力沿电极组件20由外向内的卷绕方向X’逐渐减小，从而有利于降低极片受损的风险。
作为示例性举例，K具体可以是9N、8N、7N、6N、5N、4N、3N、2N或1N中的任意一者。
在一些实施例中，请参阅图5，沿电极组件20由外向内的卷绕方向X’，不同焊接区211a中的焊印203在第一极片21的厚度方向Z上的高度逐渐降低。
不同焊接区211a中的焊印203高度沿电极组件20由外向内的卷绕方向X’逐渐减小，使在电极组件20的卷绕方向X上，越靠近电极组件20卷绕中心的焊接对第一集流体211结构强度的破坏的程度也越低。有利于提高第一极片21的焊印203处的抗拉能力，有利于抵抗电极组件20膨胀时沿卷绕结构由外向内的方向对第一极耳30与第一集流体211焊接部分的拉扯力，有利于降低第一极片21受损的风险。
在一些实施例中，请参阅图5，焊印203在第一极片21的厚度方向Z上的高度为H，满足1um≤H≤100um，有利于降低焊接拉力最小的焊印203处的焊接拉力过小而虚焊的风险，还有利于降低焊接拉力最大的焊印203处的焊接拉力过大而导致第一集流体211受损的风险。
作为示例性举例，焊接区211a的数量为N，第N个焊接区211a沿电极组件20卷绕方向X最远离电极组件20卷绕中心，第1个焊接区211a沿电极组件20卷绕方向X最靠近电极组件20卷绕中心。不同焊接区211a中焊印203处的焊接拉力沿电极组件20由外向内的卷绕方向X’逐渐减小，使第i个焊接区211a的焊印203在第一极片21的厚度方向Z上的高度为Hi，且Hi＜Hi+1，其中N为大于等于2的正整数，i为大于等于1且小于N的正整数。则满足：HN≤100um，-H1≥1um。
例如，H具体可以是100um、98um、95um、92um、90um、88um、85um、82um、80um、78um、75um、72um、70um、68um、65um、62um、60um、58um、55um、52um、50um、48um、45um、42um、40um、38um、35um、32um、30um、28um、25um、22um、20um、18um、15um、12um、10um、8um、5um、4um、3um、2um或1um。
在一些实施例中，焊接区211a的数量为N，沿电极组件20的卷绕方向X，第i个焊接区211a相较于第i+1个焊接区211a更靠近所述电极组件20的卷绕中心，第i个焊接区211a的焊印203在第一极片21的厚度方向Z上的高度为Hi，第i+1个焊接区211a的焊印203在第一极片21的厚度方向Z上的高度为Hi+1，满足1um≤Hi+1-Hi≤10um，使相邻两个焊接区211a中的焊印203的高度的差值处于1um-10um之间，让相邻的两个焊接区211a的结构 强度差距不会过大，有利于降低虚焊的风险，还有利于降低焊接拉力过大导致第一极片21受损的风险。作为示例性举例，Hi+1-Hi具体可以是10N、9N、8N、7N、6N、5N、4N、3N、2N或1N中的任意一者。
在一些实施例中，焊印203的数量为S，S个焊印203的高度均值为L，满足5um≤L≤15um，S为大于等于2的正整数。L满足5um≤L≤15um这一范围时，有利于降低第一极耳30与第一极片21的整体焊接拉力过小而导致第一极耳30脱落的风险，容许部分焊印203的焊接强度降低以提高第一极片21的结构强度，有利于实现在不同焊接区211a中焊印203处的焊接拉力沿电极组件20由外向内的卷绕方向X’逐渐减小，从而有利于降低极片受损的风险。
作为示例性举例，L具体可以是15um、14um、13um、12um、11um、10um、9um、8um、7um、6um或5um中的任意一者。
为了验证焊印203处的焊接拉力与焊印203高度对虚焊和极片受损的影响，做了以下试验：
虚焊测试：
将成品二次电池100满放后拆解得到需要测量的第一极片21。沿第一极片21的宽度方向Y，在第一极耳30与第一极片21的第一连接区2111裁切得到对应不同焊接区211a的第一极耳30和第一集流体211的焊接片。将不同焊接区211a的第一极耳30和第一集流体211的焊接片分别拿到高铁拉力机上沿第一极片21宽度方向Y以1mm/s的速度进行拉力测试，测试完之后观察第一极耳30的焊印203处是否有第一集流体211残留，如果观察不到残留，则此焊印203为虚焊，反之则无虚焊。
极片受损测试：
对二次电池100进行电池循环试验：将二次电池100置于25℃环境中静置30分钟，然后以下述步骤进行充放电。以2.5C恒流充电至4.2V，再恒压充电至0.5C；然后以0.5C恒流充电至4.45V，再恒压充电至0.02C；静置5分钟，以1C恒流放电至3V，静置5分钟，此为一个循环。按照上述循环步骤循环500圈，拆解二次电池100观察第一极片21是否受损。
上述试验中，每个实施例或对比例取20个电池进行试验，若第一极片21上未存在虚焊且第一极片21未受损则通过测试，反之则未通过。通过率＝(通过数/20)×100％。
以下对实施例与对比例中的二次电池100的具体实施方式进行说明。
实施例：
一种二次电池100，组装过程如下：
(1)阳极极片的制备：将阳极活性材料人造石墨、导电炭黑(Super P)、丁苯橡胶(SBR)按照重量比96:1.5:2.5进行混合，加入去离子水作为溶剂，调配成重量百分比为70wt％的浆料，并搅拌均匀。将浆料均匀涂覆在厚度为10μm的阳极集流体铜箔的一个表面上，在铜箔边缘预留空箔区，110℃条件下烘干，得到涂层厚度为150μm的单面涂覆有阳极活性材料层的阳极极片。 在该阳极极片的另一个表面上重复以上步骤，得到双面涂覆有阳极活性材料层的阳极极片。然后，阳极极片的卷绕末端未涂覆阳极活性材料层，未涂覆阳极活性材料层的空箔段2113具有第一连接区2111，将一铜箔焊接于第一连接区2111以作为阳极极耳。第一连接区2111包括多个焊接区211a，多个焊接区211a沿电极组件20的卷绕方向X布置，焊接区211a内设有由阳极极耳与第一连接区2111焊接形成的多个焊印203，每个焊接区211a内的多个焊印203均沿阳极极片的宽度方向Y排布。沿电极组件20由外向内的卷绕方向X’，不同焊接区211a中的焊印203的焊接强度逐渐减小。
(2)阴极极片的制备：将阴极活性材料钴酸锂(LiCoO2)、导电炭黑(Super P)、聚偏二氟乙烯(PVDF)按照重量比97.5:1.0:1.5进行混合，加入N-甲基吡咯烷酮(NMP)作为溶剂，调配成固含量为75wt％的浆料，并搅拌均匀。将浆料均匀涂覆在厚度为12μm的阴极集流体铝箔的一个表面上，在铝箔边缘预留空箔区，然后90℃条件下烘干，得到阴极活性材料层厚度为100μm的阴极极片。当制备双面涂覆的其它第一极片21时，在铝箔的另一个表面上重复以上涂覆步骤。然后，阴极极片的一部分未设置阴极活性材料层并露出集流体，集流体焊接一铝箔以作为阴极极耳。
(3)电解液的制备：在干燥氩气气氛中，首先将碳酸乙烯酯(EC)、碳酸甲乙酯(EMC)和碳酸二乙酯(DEC)以质量比EC:EMC:DEC＝30:50:20混合形成基础有机溶剂，然后向基础有机溶剂中加入锂盐六氟磷酸锂(LiPF6)溶解并混合均匀，得到锂盐的浓度为1.15mol/L的电解液。
(4)隔离膜23的制备：采用三层结构的隔离膜23，其包括层叠设置的第一粘接层、第一基材层和第一粘接层。第一基材层材质为聚乙烯(PE)，第一粘接层中包含第一粘接剂，第一粘接层还包含无机陶瓷颗粒Al2O3。
(5)电极组件20制备：将阴极极片、隔离膜23以及阳极极片层叠设置，将层叠后得到的结构在温度为80℃、压力为1.5Mpa的条件下通过平板热压10秒以组成电极组件20以备用。
(6)电极组件20组装：将冲坑成型的铝塑膜置于组装夹具内，坑面朝上，将电极组件20置于坑内，施加外力压紧。然后将另一个冲坑成型的铝塑膜坑面朝下覆盖于电极组件20上，采用热压的方式热封两个铝塑膜的四周，得到组装电极组件20。
(7)注液封装：给组装电极组件20注入电解液，经过真空封装、静置、热压化成、整形等工序，即制得二次电池100。
对比例：
与实施例的区别在于，对比例1的阳极极片与阳极极耳焊接形成的各个焊印203的焊接强度基本一致，对比例2的阳极极片的阳极极耳焊接形成的多个焊印203的焊接强度，沿电极组件20由外向内的卷绕方向X’，不同焊接区211a中的焊印203的焊接强度逐渐增大。
各实施例和对比例的主要参数控制以及测试结果如表1所示：
表1
根据上述表1可知，相对于对比例1和2，实施例1-12满足：沿电极组件20的卷绕方向X，多个焊接区211a中最靠近电极组件20卷绕中心的焊接区211a内的焊印203的焊接强度最小，有利于降低焊接对最靠近电极组件20卷绕中心的焊接区211a的第一集流体211的破坏，从而有利于提高最靠近电极组件20卷绕中心的焊接区211a内的焊印203处的抗拉能力，有利于降低极片受损的风险。
根据上述表1可知，相对于实施例1和12，实施例2-11满足：1N≤Fi+1-Fi≤5N，使相邻的两个焊接区211a的结构强度差距不会过大，有利于降低虚焊的风险，还有利于降低焊接拉力过大导致第一极片21受损的风险。
根据上述表1可知，相对于实施例1和12，实施例2-11满足：1um≤Hi+1-Hi≤10um，使相邻的两个焊接区211a的结构强度差距不会过大，有利于降低虚焊的风险，还有利于降低焊接拉力过大导致第一极片21受损的风险。
根据上述表1可知，相对于实施例13和18，实施例6，实施例14-17满足：5N≤K≤9N，有利于降低第一极耳30与第一极片21的整体焊接拉力过小而导致第一极耳30脱落的风险，有利于减少虚焊的可能，还容许部分焊印203的焊接强度降低以提高第一极片21的结构强度，有利于实现在不同焊接区211a中焊印203处的焊接拉力沿电极组件20由外向内的卷绕方向X’逐渐减小，从而有利于降低极片受损的风险。
在一些实施例中，请参阅图4，定义第一极耳30在电极组件20由外向内的卷绕方向X’上靠近电极组件20卷绕中心一侧的边缘为第一边缘。多个焊接区211a中的焊印203距第一边缘的最小距离为A，满足0.1mm≤A≤1mm，使得多个焊印203中与第一边缘最近的一个焊印203与第一边缘的距离在0.1mm-1mm之间，使焊印203不会距第一边缘过近，从而有利于焊接操作， 也不会让焊印203距离第一边缘过远，从而有利于增加焊接区211a的面积，有利于提升第一连接区2111的利用率。
作为示例性举例，A具体可以是0.1mm、0.2mm、0.3mm、0.4mm、0.5mm、0.6mm、0.7mm、0.8mm、0.9mm或者1mm中的任意一者。
在一些实施例中，请参阅图4，沿电极组件20的卷绕方向X(第一极片21展开状态下，第一极片21的长度方向Y)，多个焊印203的总宽度为W，满足1mm≤W≤3mm，使得多个焊印203占据的区域不至于过小，从而有利于提升多个焊接区211a的总面积，有利于提升第一极耳30与第一极片21的连接强度，容许部分焊印203的焊接强度降低以提高第一极片21的结构强度，有利于实现在不同焊接区211a中焊印203处的焊接拉力沿电极组件20由外向内的卷绕方向X’逐渐减小，从而有利于降低极片受损的风险。
在一些实施例中，请参阅图4，多个焊印203距第一边缘的最大距离为B＝A+W。
在以上一个或多个实施例中，请参阅图3和图4，沿电极组件20由外向内的卷绕方向X’，第一集流体211包括依次设置的空箔段2113和涂覆段2112，涂覆段2112设有第一活性物质层212，空箔段2113未设置第一活性物质层212，空箔段2113的至少部分位于第一极片21的最外圈，第一连接区2111位于空箔段2113并位于第一极片21的最外圈。
经发明人研究发现，卷绕结构的电极组件20在循环过程中，第一极片21的脱嵌锂导致第一极片21厚度的反复膨胀，从而导致电极组件20的反复收缩和膨胀,最外圈的第一极片21受到的拉扯力最大。本实施例中通过设置多个焊接区211a中，沿电极组件20的卷绕方向X最靠近电极组件20卷绕中心的焊接区211a内的焊印203的焊接强度最小，降低了焊接对最靠近电极组件20卷绕中心的焊接区211a的第一集流体211的破坏，从而有利于提高最靠近电极组件20卷绕中心的焊接区211a内的焊印203处的抗拉能力，有利于降低极片受损的风险。
在一些实施例中，请参阅图4、图6和图7，焊印203的形状包括菱形、方形、圆形中的至少一种。
在一些实施例中，第二极耳40与第二极片22的连接方式采用与第一极耳30和第一极片21基本相同的连接方式，第二极耳40与第二极片22连接的具体实施方式可以参照关于第一极耳30与第一极片21连接的实施例，在此不再赘述。
请参阅图8,本申请中的实施例还提供一种电子装置1000，该电子装置1000包括上述任一实施例中的二次电池100。由于本电子装置1000采用了上述任一实施例中的二次电池100的技术方案，因此至少具有上述任一实施例的二次电池100的技术方案所带来的有益效果，在此不再一一赘述。
在一些实施例中，请参阅图8，电子装置1000还包括装置主体200，二次电池100安装于装置主体200。
在一些实施例中，电子装置1000可以是手机、平板电脑、电子阅读器、 AR眼镜或VR眼镜等等，在此不再一一列举。
另外，本技术领域的普通技术人员应当认识到，以上的实施例仅是用来说明本申请，而并非用作为对本申请的限定，只要在本申请的实质范围之内，对以上实施例所作的适当改变和变化都落在本申请公开的范围之内。

Claims (14)

  1. 一种二次电池，其特征在于，包括：
    电极组件，所述电极组件包括第一极片、第二极片以及设于所述第一极片和所述第二极片之间的隔离膜，所述第一极片、所述第二极片以及所述隔离膜层叠并卷绕形成卷绕结构；所述第一极片包括第一集流体和设于所述第一集流体上的第一活性物质层，所述第一集流体设有第一连接区，所述第一连接区未设置所述第一活性物质层；
    第一极耳，所述第一极耳焊接于所述第一连接区，所述第一连接区包括多个焊接区，所述多个焊接区沿所述电极组件的卷绕方向布置，所述焊接区内设有由所述第一极耳与所述第一连接区焊接形成的至少一个焊印，沿所述电极组件的卷绕方向，所述多个焊接区中最靠近所述电极组件卷绕中心的所述焊接区内的所述焊印的焊接强度最小。
  2. 根据权利要求1所述的二次电池，其特征在于，沿所述电极组件由外向内的卷绕方向，不同所述焊接区中的所述焊印的焊接强度逐渐减小。
  3. 根据权利要求2所述的二次电池，其特征在于，每个所述焊印处的所述第一极耳与所述第一集流体之间存在焊接拉力，不同所述焊接区中所述焊印处的焊接拉力沿所述电极组件由外向内的卷绕方向逐渐减小。
  4. 根据权利要求3所述的二次电池，其特征在于，每个所述焊印处的所述第一极耳与所述第一集流体的焊接拉力为F，满足1N≤F≤80N。
  5. 根据权利要求4所述的二次电池，其特征在于，所述焊接区的数量为N，沿所述电极组件的卷绕方向，第i个所述焊接区相较于第i+1个所述焊接区更靠近所述电极组件的卷绕中心，第i个所述焊接区的所述焊印的焊接拉力为Fi，第i+1个所述焊接区的所述焊印的焊接拉力为Fi+1，满足1N≤Fi+1-Fi≤5N；
    N为大于等于2的正整数，i为大于等于1且小于N的正整数。
  6. 根据权利要求4所述的二次电池，其特征在于，所述焊印的数量为S，S个所述焊印的焊接拉力的均值为K满足5N≤K≤9N；
    S为大于等于2的正整数。
  7. 根据权利要求2所述的二次电池，其特征在于，沿所述电极组件由外向内的卷绕方向，不同所述焊接区中的所述焊印在所述第一极片的厚度方向上的高度逐渐降低。
  8. 根据权利要求7所述的二次电池，其特征在于，所述焊印在所述第一极片的厚度方向上的高度为H，满足1um≤H≤100um。
  9. 根据权利要求8所述的二次电池，其特征在于，所述焊接区的数量为N，沿所述电极组件的卷绕方向，第i个所述焊接区相较于第i+1个所述焊接区更靠近所述电极组件的卷绕中心，第i个所述焊接区的所述焊印在所述第一极片的厚度方向上的高度为Hi，第i+1个所述焊接区的所述焊印在所述第一极片的厚度方向上的高度为Hi+1，满足1um≤Hi+1-Hi≤10um；
    N为大于等于2的正整数，i为大于等于1且小于N的正整数。
  10. 根据权利要求8所述的二次电池，其特征在于，所述焊印的数量为S，S个所述焊印的高度均值为L，满足5um≤L≤15um；
    S为大于等于2的正整数。
  11. 根据权利要求1至10中任意一项所述的二次电池，其特征在于，定义所述第一极耳在所述电极组件由外向内的卷绕方向上靠近所述电极组件卷绕中心一侧的边缘为第一边缘，所述多个焊接区中的所述焊印距所述第一边缘的最小距离为A，所述多个焊印的总宽度为W，所述多个焊印距所述第一边缘的最大距离为B＝A+W，所述二次电池满足以下条件(1)至(3)中的至少一者：
    (1)0.1mm≤A≤1mm；
    (2)1mm≤W≤3mm；
    (3)1.1mm≤B≤4mm。
  12. 根据权利要求1至10中任意一项所述的二次电池，其特征在于，沿所述电极组件由外向内的卷绕方向，所述第一集流体包括依次设置的空箔段和涂覆段，所述涂覆段设有所述第一活性物质层，所述空箔段未设置所述第一活性物质层，所述空箔段的至少部分位于所述第一极片的最外圈，所述第一连接区位于所述空箔段并位于所述第一极片的最外圈。
  13. 根据权利要求1至10中任意一项所述的二次电池，其特征在于，所述焊印的形状包括菱形、方形、圆形中的至少一种。
  14. 一种电子装置，其特征在于，包括如权利要求1至13中任意一项所述的二次电池。
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