WO2021003781A1 - 二次电池 - Google Patents

二次电池 Download PDF

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Publication number
WO2021003781A1
WO2021003781A1 PCT/CN2019/098383 CN2019098383W WO2021003781A1 WO 2021003781 A1 WO2021003781 A1 WO 2021003781A1 CN 2019098383 W CN2019098383 W CN 2019098383W WO 2021003781 A1 WO2021003781 A1 WO 2021003781A1
Authority
WO
WIPO (PCT)
Prior art keywords
packaging film
area
electrode assembly
sealing area
secondary battery
Prior art date
Application number
PCT/CN2019/098383
Other languages
English (en)
French (fr)
Inventor
陈晓
张新羽
陈威
牛少军
Original Assignee
江苏时代新能源科技有限公司
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 江苏时代新能源科技有限公司 filed Critical 江苏时代新能源科技有限公司
Priority to JP2022501194A priority Critical patent/JP7314389B2/ja
Priority to KR1020227000457A priority patent/KR20220018569A/ko
Priority to EP19769979.6A priority patent/EP3783683A4/en
Priority to US16/586,616 priority patent/US20210013538A1/en
Publication of WO2021003781A1 publication Critical patent/WO2021003781A1/zh

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    • 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
    • H01M50/105—Pouches or flexible bags
    • 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
    • H01M50/116—Primary casings; Jackets or wrappings characterised by the material
    • H01M50/124—Primary casings; Jackets or wrappings characterised by the material having a layered structure
    • H01M50/126—Primary casings; Jackets or wrappings characterised by the material having a layered structure comprising three or more layers
    • 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
    • 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
    • H01M50/116—Primary casings; Jackets or wrappings characterised by the material
    • H01M50/124—Primary casings; Jackets or wrappings characterised by the material having a layered structure
    • 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
    • H01M50/116—Primary casings; Jackets or wrappings characterised by the material
    • H01M50/124—Primary casings; Jackets or wrappings characterised by the material having a layered structure
    • H01M50/126—Primary casings; Jackets or wrappings characterised by the material having a layered structure comprising three or more layers
    • H01M50/129—Primary casings; Jackets or wrappings characterised by the material having a layered structure comprising three or more layers with two or more layers of only organic material
    • 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
    • H01M50/172—Arrangements of electric connectors penetrating the casing
    • H01M50/174—Arrangements of electric connectors penetrating the casing adapted for the shape of the cells
    • H01M50/178—Arrangements of electric connectors penetrating the casing adapted for the shape of the cells for pouch or flexible bag cells
    • 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 invention relates to the field of batteries, in particular to a secondary battery.
  • packaging bags made of packaging films can be used instead of metal casings to reduce the weight of the battery and increase the energy density.
  • the known technology usually punches out pits on the packaging film and then bends them into a double-layer structure. Except for the edges where the two layers of packaging film are directly connected, the known technology will heat press at the other edges of the two layers of packaging film to form a sealed part, so that the two layers of packaging film are connected to form a packaging bag.
  • the sealing part occupies a large space and affects the energy density of the secondary battery. Therefore, the known technology usually bends the sealing part to reduce the space occupied by the sealing part.
  • the directly connected edges of the two layers of packaging films will have stress concentration in the area close to the sealing part, which will cause the risk of damage to the packaging film.
  • the object of the present invention is to provide a secondary battery that can increase the energy density and improve the sealing performance.
  • the present invention provides a secondary battery including an electrode assembly and a packaging bag.
  • the packaging bag includes a first packaging film and a second packaging film.
  • the second packaging film and the first packaging film are integrated, and the second packaging film extends from the longitudinal edge of the first packaging film and is folded back to the first packaging film.
  • the electrode assembly is arranged between the first packaging film and the second packaging film.
  • the first packaging film and the second packaging film are connected on the outside of the electrode assembly to form a sealing part, and the sealing part includes a side sealing area and a bottom sealing area.
  • the side sealing area is arranged on the outer side of the electrode assembly along the transverse direction, and the side sealing area is bent in a direction close to the electrode assembly.
  • the bottom sealing area is arranged on the side of the electrode assembly close to the folded back of the second packaging film, and the bottom sealing area is connected to the side sealing area.
  • the edge of the bottom seal area away from the electrode assembly is flush with the edge of the packaging bag.
  • the bottom seal area extends from the side seal area, and along the direction away from the side seal area, the size of the bottom seal area in the longitudinal direction gradually decreases.
  • the width of the bottom seal area is smaller than the width of the side seal area.
  • the side sealing area has a first crease line extending in the longitudinal direction, and the side sealing area is bent toward the electrode assembly along the first crease line. In the transverse direction, the distance between the first crease line and the bottom seal area is 0.1mm-2mm.
  • the side sealing area includes a first area and a second area, the first area is bent along the first crease line, and the second area extends from the end of the first area and is folded back to the side of the first area close to the electrode assembly.
  • the secondary battery further includes an electrode lead connected to the electrode assembly and passing through the sealing part. There are two electrode leads and they are located on the side of the electrode assembly away from the bottom seal area.
  • Both the first packaging film and the second packaging film include a protective layer, a metal layer and a connecting layer.
  • the connecting layer is arranged on the surface of the metal layer facing the electrode assembly, and the protective layer is arranged on the surface of the metal layer away from the electrode assembly.
  • the connecting layer of the first packaging film is welded to the connecting layer of the second packaging film to form a sealing portion.
  • the side sealing area is bent in a direction close to the electrode assembly, so as to reduce the size of the side sealing area in the lateral direction and increase the energy density of the secondary battery.
  • the connection strength between the first packaging film and the second packaging film can be increased, the risk of rupture of the packaging bag can be reduced, and the sealing performance of the packaging bag can be improved.
  • Fig. 1 is a schematic diagram of an embodiment of a secondary battery according to the present invention.
  • Fig. 2 is a cross-sectional view of the secondary battery of Fig. 1 taken along line A-A.
  • Fig. 3 is a cross-sectional view of the secondary battery of Fig. 1 taken along line B-B.
  • Fig. 4 is a schematic diagram of the packaging bag of Fig. 1 before being formed.
  • Figure 5 is a cross-sectional view of the packaging film of the packaging bag of Figure 4.
  • FIG. 6 is a schematic diagram of the secondary battery of FIG. 1 during the molding process.
  • Fig. 7 is an enlarged view of the secondary battery of Fig. 6 in a circular frame.
  • Fig. 8 is a cross-sectional view of the secondary battery of Fig. 7 taken along line C-C.
  • Fig. 9 is a schematic diagram of another embodiment of a secondary battery according to the present invention.
  • the secondary battery of the present application includes an electrode assembly 1, a packaging bag 2, an electrode lead 3, and an insulating member 4.
  • the electrode assembly 1 is the core component of the secondary battery to realize the charge and discharge function.
  • the electrode assembly 1 includes a positive pole piece, a negative pole piece and a separator, and the separator separates the positive pole piece and the negative pole piece.
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer coated on the surface of the positive electrode current collector.
  • the positive electrode current collector may be aluminum foil, and the positive electrode active material layer includes a ternary material, lithium manganate or lithium iron phosphate.
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer coated on the surface of the negative electrode current collector.
  • the negative electrode current collector may be copper foil, and the negative electrode active material layer includes graphite or silicon.
  • the electrode assembly 1 may have a wound structure. Specifically, both the positive pole piece and the negative pole piece are one, and the positive pole piece and the negative pole piece have a strip structure. The positive pole piece, the separator, and the negative pole piece are sequentially stacked and wound two or more turns to form the electrode assembly 1.
  • the electrode assembly 1 can be wound into a hollow cylindrical structure first, and then flattened into a flat shape after the winding.
  • the electrode assembly 1 may also have a laminated structure. Specifically, there are multiple positive pole pieces, and multiple negative pole pieces. The multiple positive pole pieces and negative pole pieces are alternately stacked along the thickness direction Z, and the positive pole pieces and the negative pole pieces are separated by a separator.
  • the packaging bag 2 includes a first packaging film 21 and a second packaging film 22, and the second packaging film 22 and the first packaging film 21 are integrated.
  • the second packaging film 22 extends from the edge of the first packaging film 21 in the longitudinal direction X and is folded back to the first packaging film 21.
  • the second packaging film 22 and the first packaging film 21 may be arranged up and down in the thickness direction Z.
  • the first packaging film 21 and the second packaging film 22 can be formed by bending a piece of packaging film (such as aluminum plastic film, steel plastic film, etc.). Specifically, referring to Figure 4, two cavities can be formed on the piece of packaging film by stamping, and then the piece of packaging film can be bent into two layers along the third crease line L3 to form the present application The first packaging film 21 and the second packaging film 22. Two cavities are formed in the first packaging film 21 and the second packaging film 22, respectively.
  • the electrode assembly 1 is disposed between the first packaging film 21 and the second packaging film 22, and the two cavities enclose an inner cavity for accommodating the electrode assembly 1.
  • the first packaging film 21 and the second packaging film 22 each include a protective layer 24, a metal layer 25, and a connecting layer 26.
  • the protective layer 24 and the connecting layer 26 are respectively disposed on both sides of the metal layer 25.
  • the connecting layer 26 may be provided on the surface of the metal layer 25 facing the electrode assembly 1 through an adhesive
  • the protective layer 24 may be provided on the surface of the metal layer 25 away from the electrode assembly 1 through an adhesive.
  • the material of the protective layer 24 can be nylon or polyethylene terephthalate, the material of the metal layer 25 can be aluminum foil or steel foil, and the material of the connecting layer 26 can be polypropylene.
  • the first packaging film 21 and the second packaging film 22 are connected to the outside of the electrode assembly 1 and form a sealing portion 23. Specifically, by hot pressing, the connecting layer 26 of the first packaging film 21 is welded to the connecting layer 26 of the second packaging film 22 to form the sealing portion 23.
  • the sealing portion 23 seals the inner cavity of the electrode assembly 1 to avoid leakage of electrolyte.
  • the connecting layer 26 located in the sealing part 23 is melted and compressed. Therefore, after hot pressing, the thickness of the sealing part 23 is smaller than the thickness of the first packaging film 21 and the second packaging film 22 before the hot pressing. Sum.
  • the electrode lead 3 is connected to the electrode assembly 1, passes through the sealing part 23 and extends to the outside of the packaging bag 2.
  • there may be two electrode leads 3 one electrode lead 3 is connected to the positive current collector of the positive pole piece, and the other electrode lead 3 is connected to the negative current collector of the negative pole piece.
  • the two electrode leads 3 connect the electrode assembly 1 with other components outside the packaging bag 2 to realize the charge and discharge of the electrode assembly 1.
  • the material of the electrode lead 3 can be aluminum, nickel or copper with nickel plating.
  • the electrode lead 3 passes between the first packaging film 21 and the second packaging film 22, and since the connection layer 26 is thin, the electrode lead 3 is easily in contact with the metal layer 25, causing safety risks. Therefore, the secondary battery of the present application is preferably provided with an insulating member 4.
  • the two insulators 4 separate the two electrode leads 3 from the sealing portion 23, respectively.
  • Each insulating member 4 surrounds the outer side of a corresponding electrode lead 3. A part of the insulating member 4 is clamped between the first packaging film 21 and the second packaging film 22 to separate the electrode lead 3 from the packaging bag 2 and reduce the risk of the electrode lead 3 contacting the metal layer 25.
  • the material of the insulating member 4 may be polypropylene.
  • the connecting layer 26 of the first packaging film 21 and the second packaging film 22 will be welded to the insulating member 4 during hot pressing. .
  • the sealing portion 23 includes a side sealing area 231 and a top sealing area 233.
  • the side sealing area 231 is disposed on the outer side of the electrode assembly 1 along the transverse direction Y, and the top sealing area 233 is disposed on the electrode assembly 1 away from the second package.
  • the two side sealing areas 231 and they are respectively arranged on the outer side of the electrode assembly 1 along the transverse direction Y, and the top sealing area 233 is arranged on one side of the electrode assembly 1 along the longitudinal direction X and connected to the two side sealing areas 231.
  • the two side sealing areas 231 and the top sealing area 233 form a U-shaped structure.
  • the end of the first packaging film 21 and the second packaging film 22 away from the top sealing area 233 in the longitudinal direction X is directly connected, therefore, the side sealing area 231 and the top sealing area 233 can realize the sealing of the packaging bag 2.
  • the side sealing area 231 has a certain width, which causes the size of the secondary battery in the transverse direction Y to be too large, which affects the energy density of the secondary battery. Therefore, preferably, the side sealing area 231 is bent in a direction close to the electrode assembly 1 to reduce the size of the side sealing area 231 in the lateral direction Y and increase the energy density of the secondary battery. After bending and forming, a first crease line L1 extending along the longitudinal direction X is formed on the side sealing area 231; that is, the side sealing area 231 is bent along the first crease line L1 toward the electrode assembly 1.
  • the first packaging film 21 and the second packaging film 22 are relatively bent; when the side sealing area 231 is bent, stress concentration at the edge E1 near the first crease line L1 will be caused.
  • the area of the edge E1 close to the first crease line L1 is a stress concentration area.
  • the first packaging film 21 and the second packaging film 22 are directly connected, so on the side of the electrode assembly 1 away from the top sealing area 233, the first packaging film 21 and the second packaging film 22 will not pass heat ⁇ Pressure connection.
  • the connecting layer 26 of the first packaging film 21 and the connecting layer 26 of the second packaging film 22 are not welded, and the connection strength between the two is low.
  • the portion between the first packaging film 21 and the second packaging film 22 that is not welded and close to the stress concentration area is likely to be broken, thereby causing electrolyte leakage and causing safety risks.
  • the sealing portion 23 of the present application further includes a bottom sealing area 232, the bottom sealing area 232 is disposed on the side of the electrode assembly 1 close to the folded back of the second packaging film 22, and the bottom sealing area 232 is connected to the side sealing area 231. 8, in the bottom sealing area 232, the connecting layer 26 of the first packaging film 21 and the connecting layer 26 of the second packaging film 22 are welded together.
  • the connection strength between the first packaging film 21 and the second packaging film 22 near the stress concentration area can be increased, the risk of rupture of the packaging bag 2 can be reduced, and the sealing performance of the packaging bag 2 can be improved.
  • the stress concentration area is located on the edge E1 of the packaging bag 2, that is, the edge E1 of the packaging bag 2 has the highest risk of cracking. Therefore, preferably, in the longitudinal direction X, the edge E2 of the bottom seal area 232 away from the electrode assembly 1 is flush with the edge E1 of the packaging bag 2, so as to reduce the risk of breakage as much as possible. At the same time, even if the packaging bag 2 is broken at the edge E1, the bottom sealing area 232 can still function as a seal to avoid electrolyte leakage.
  • the bottom sealing area 232 will occupy the inner space of the packaging bag 2 and affect the secondary battery. Capacity.
  • the bottom seal area 232 extends from the side seal area 231, and along the direction away from the side seal area 231, the size of the bottom seal area 232 in the longitudinal direction X gradually decreases.
  • the size of the bottom seal area 232 in the longitudinal direction X is reduced, the inner space of the packaging bag 2 can be increased, and the capacity of the secondary battery can be increased.
  • the electrode assembly 1 will also release a small amount of gas; at the end of the secondary battery cycle, there will be a certain amount of gas inside the packaging bag 2, so when designing the secondary battery, A certain space is reserved to accommodate the gas produced by the electrode assembly 1.
  • the first packaging film 21 and the second packaging film 22 are not welded, and the gas can expand the first packaging film 21 and the second packaging film 22 and store them in the first packaging film. 21 and the second packaging film 22.
  • the present application can further increase the internal space of the packaging bag 2 and increase the capacity of the secondary battery.
  • the width of the bottom seal area 232 is smaller than the width of the side seal area 231.
  • the width of the side seal area 231 refers to the width of the side seal area 231 between folds, or the width of the side seal area 231 in the unfolded state.
  • the width of the bottom seal area 232 refers to the size of the bottom seal area 232 in the longitudinal direction X
  • the width of the side seal area 231 refers to the size of the side seal area 231 in the transverse direction Y.
  • the width value determines the sealing strength of the bottom seal area 232 and the side seal area 231. Near the bottom sealing area 232, the first packaging film 21 and the second packaging film 22 are directly connected, even without the bottom sealing area 232, they still have a certain sealing strength. Therefore, the bottom sealing area 232 may have a relatively small width. In addition, reducing the width of the bottom sealing area 232 can increase the internal space of the packaging bag 2 and increase the capacity of the secondary battery.
  • the distance between the first crease line L1 and the bottom seal area 232 is D.
  • the side sealing area 231 includes a first area 231a and a second area 231b.
  • the first area 231a is bent along the first crease line L1
  • the second area 231b extends from the end of the first area 231a and is folded back to the first area.
  • a side of a region 231a close to the electrode assembly 1.
  • the side sealing area 231 may be bent along the second crease line L2.
  • the two sides of the second crease line L2 are the first area 231a and the second area 231b, respectively. , And then bend the first area 231a along the first crease line L1.
  • the first packaging film 21 and the second packaging film 22 need to undergo a cutting process during the forming process, and the metal layer 25 is exposed at the cut section.
  • the exposed metal layer 25 is easily corroded and may cause a short circuit risk.
  • the partially exposed metal layer 25 can be clamped between the first region 231a and the cavity wall of the cavity, thereby reducing the exposure of the metal layer 25 and reducing the risk of short circuit.
  • the surface of the second region 231b close to the electrode assembly 1 is bonded to the cavity wall of the cavity, and the surface of the second region 231b away from the electrode assembly 1 is bonded to the first region 231a.
  • the two electrode leads 3 are located on the side of the electrode assembly 1 away from the bottom seal area 232. That is, the two electrode leads 3 extend in the longitudinal direction X and pass through the top seal area 233.
  • the second embodiment there are two side sealing areas 231 which are located on both sides of the electrode assembly 1 along the lateral direction Y, and the two ends of the bottom sealing area 232 along the lateral direction Y are respectively connected to the two side sealing areas 231 .
  • the second embodiment can simplify the hot pressing process and reduce the requirements on the hot pressing equipment.

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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)
  • Sealing Battery Cases Or Jackets (AREA)
  • Connection Of Batteries Or Terminals (AREA)

Abstract

本发明提供了一种二次电池，其包括电极组件和包装袋。包装袋包括第一包装膜和第二包装膜，第二包装膜和第一包装膜为一体设置，第二包装膜从第一包装膜沿纵向的边缘延伸且回折到第一包装膜。电极组件设置于第一包装膜和第二包装膜之间。第一包装膜和第二包装膜在电极组件的外侧连接并形成密封部，密封部包括侧封区和底封区。侧封区设置于电极组件沿横向的外侧，且侧封区朝靠近电极组件的方向弯折。底封区设置于电极组件的靠近第二包装膜的回折处的一侧，且底封区连接于侧封区。

Description

二次电池 技术领域
本发明涉及电池领域，尤其涉及一种二次电池。
背景技术
随着便携式电子设备的快速发展，对电池能量密度的要求也越来越高。在二次电池中，可采用由包装膜(例如铝塑膜或钢塑膜)制成的包装袋来代替金属壳体，以降低电池的重量，提高能量密度。
已知技术通常是在包装膜上冲压出凹坑，然后弯折成双层结构。除两层包装膜直接相连的边缘外，已知技术会在两层包装膜的其它的边缘处进行热压并形成密封部，从而使两层包装膜连接并形成包装袋。密封部占用较大的空间，影响二次电池的能量密度，因此，已知技术通常会弯折密封部，以减小密封部占用的空间。然而，在弯折密封部时，两层包装膜直接相连的边缘在靠近密封部的区域会产生应力集中，引发包装膜破损的风险。
发明内容
鉴于背景技术中存在的问题，本发明的目的在于提供一种二次电池，其能提高能量密度，改善密封性能。
为了实现上述目的，本发明提供了一种二次电池，其包括电极组件和包装袋。包装袋包括第一包装膜和第二包装膜，第二包装膜和第一包装膜为一体设置，第二包装膜从第一包装膜沿纵向的边缘延伸且回折到第一包装膜。电极组件设置于第一包装膜和第二包装膜之间。第一包装膜和第二包装膜在电极组件的外侧连接并形成密封部，密封部包括侧封区和底封区。侧封区设置于电极组件沿横向的外侧，且侧封区朝靠近电极组件的方向弯折。底封区设置于电极组件的靠近第二包装膜的回折处的一侧，且底封区连接于侧封区。
在纵向上，底封区远离电极组件的边缘与包装袋的边缘齐平。
底封区从侧封区延伸，且沿远离侧封区的方向，底封区在纵向上的尺寸逐渐减小。
侧封区为两个且分别位于电极组件沿横向的两侧，底封区为两个且分别连接于对应地一个侧封区。在横向上，两个底封区彼此隔开。
底封区的宽度小于侧封区的宽度。
侧封区具有沿纵向延伸的第一折痕线，且侧封区沿第一折痕线朝向电极组件弯折。在横向上，第一折痕线与底封区的距离为0.1mm-2mm。
侧封区包括第一区域和第二区域，第一区域沿第一折痕线弯折，第二区域从第一区域的端部延伸且回折到第一区域的靠近电极组件的一侧。
二次电池还包括电极引线，电极引线连接于电极组件并穿过密封部。电极引线为两个且位于电极组件的远离底封区的一侧。
侧封区为两个且分别位于电极组件沿横向的两侧，底封区沿横向的两端分别连接于两个侧封区。
第一包装膜和第二包装膜均包括保护层、金属层和连接层，连接层设置于金属层的朝向电极组件的表面，保护层设置于金属层的远离电极组件的表面。第一包装膜的连接层熔接于第二包装膜的连接层并形成密封部。
本发明的有益效果如下：侧封区朝靠近电极组件的方向弯折，以减小侧封区在横向上的尺寸，提高二次电池的能量密度。通过设置底封区，可以增大第一包装膜和第二包装膜的连接强度，降低包装袋破裂的风险，改善包装袋的密封性能。
附图说明
图1为根据本发明的二次电池的一实施例的示意图。
图2为图1的二次电池沿线A-A作出的断面图。
图3为图1的二次电池沿线B-B作出的断面图。
图4为图1的包装袋在成型前的示意图。
图5为图4的包装袋的包装膜的断面图。
图6为图1的二次电池在成型过程中的示意图。
图7为图6的二次电池在圆框处的放大图。
图8为图7的二次电池沿线C-C作出的断面图。
图9为根据本发明的二次电池的另一实施例的示意图。
其中，附图标记说明如下：
1 电极组件
2 包装袋
21 第一包装膜
22 第二包装膜
23 密封部
231 侧封区
231a 第一区域
231b 第二区域
232 底封区
24 保护层
25 金属层
26 连接层
3 电极引线
4 绝缘件
L1 第一折痕线
L2 第二折痕线
L3 第三折痕线
X 纵向
Y 横向
Z 厚度方向
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。
在本申请的描述中，除非另有明确的规定和限定，术语“第一”、“第二”、“第三”仅用于描述的目的，而不能理解为指示或暗示相对重要性；术语“多个”是指两个以上(包括两个)；除非另有规定或说明，术语“连 接”应做广义理解，例如，“连接”可以是固定连接，也可以是可拆卸连接，或一体地连接，或电连接，或信号连接；“连接”可以是直接相连，也可以通过中间媒介间接相连。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在本申请中的具体含义。
本说明书的描述中，需要理解的是，本申请实施例所描述的“上”、“下”等方位词是以附图所示的角度来进行描述的，不应理解为对本申请实施例的限定。下面通过具体的实施例并结合附图对本申请做进一步的详细描述。
参照图1至图3，在第一实施例中，本申请的二次电池包括电极组件1、包装袋2、电极引线3和绝缘件4。
电极组件1是二次电池实现充放电功能的核心构件。电极组件1包括正极极片、负极极片和隔膜，隔膜将正极极片和负极极片隔开。正极极片包括正极集流体和涂覆于正极集流体表面的正极活性物质层，正极集流体可为铝箔，正极活性物质层包括三元材料、锰酸锂或磷酸铁锂。负极极片包括负极集流体和涂覆于负极集流体表面的负极活性物质层，负极集流体可为铜箔，负极活性物质层包括石墨或硅。
电极组件1可为卷绕式结构。具体地，正极极片和负极极片均为一个，且正极极片和负极极片为带状结构。将正极极片、隔膜和负极极片依次层叠并卷绕两圈以上以形成电极组件1。在制备电极组件1时，电极组件1可先卷绕成中空的柱形结构，卷绕后再压平为扁平状。
可替代地，电极组件1也可为叠片式结构。具体地，正极极片设置为多个，负极极片设置为多个，所述多个正极极片和负极极片沿厚度方向Z交替层叠，隔膜将正极极片和负极极片隔开。
包装袋2包括第一包装膜21和第二包装膜22，第二包装膜22和第一包装膜21为一体设置。第二包装膜22从第一包装膜21沿纵向X的边缘延伸且回折到第一包装膜21。第二包装膜22和第一包装膜21可沿厚度方向Z上下布置。
第一包装膜21和第二包装膜22可由一张包装膜(例如铝塑膜、钢塑膜等)弯折而成。具体地，参照图4，可通过冲压在所述一张包装膜上形成两个凹腔，然后将所述一张包装膜沿着第三折痕线L3弯折成两层，即形成本申请的第一包装膜21和第二包装膜22。两个凹腔分别形成于第一包装膜21 和第二包装膜22。电极组件1设置于第一包装膜21和第二包装膜22之间，两个凹腔围成收容电极组件1的内腔。
参照图5，第一包装膜21和第二包装膜22均包括保护层24、金属层25和连接层26，保护层24和连接层26分别设置于金属层25的两侧。具体地，连接层26可通过粘接剂设置于金属层25的朝向电极组件1的表面，保护层24可通过粘接剂设置于金属层25的远离电极组件1的表面。
保护层24的材质可为尼龙或聚对苯二甲酸乙二醇酯，金属层25的材质可为铝箔或钢箔，连接层26的材质可为聚丙烯。
第一包装膜21和第二包装膜22在电极组件1的外侧连接并形成密封部23。具体地，通过热压，第一包装膜21的连接层26熔接于第二包装膜22的连接层26并形成密封部23。密封部23将收容电极组件1的内腔密封，避免电解液泄露。
在热压的过程中，位于密封部23的连接层26熔化且被压缩，因此，热压成型后，密封部23的厚度小于第一包装膜21和第二包装膜22在热压前的厚度之和。
参照图3，电极引线3连接于电极组件1、穿过密封部23并延伸到包装袋2外部。具体地，电极引线3可为两个，一个电极引线3连接于正极极片的正极集流体，另一个电极引线3连接于负极极片的负极集流体。两个电极引线3将电极组件1与包装袋2外部的其它构件连接，进而实现电极组件1的充放电。电极引线3的材质可为铝、镍或铜镀镍。
电极引线3从第一包装膜21和第二包装膜22之间穿过，而由于连接层26较薄，所以电极引线3容易与金属层25接触，引发安全风险。因此，本申请的二次电池优选设置绝缘件4。
绝缘件4可为两个。两个绝缘件4分别将两个电极引线3与密封部23隔开。各绝缘件4环绕在对应一个电极引线3的外侧。绝缘件4的一部分夹持在第一包装膜21和第二包装膜22之间，从而将电极引线3与包装袋2隔开，降低电极引线3与金属层25接触的风险。绝缘件4的材质可为聚丙烯。
由于绝缘件4的一部分夹持在第一包装膜21和第二包装膜22之间，因此，热压时，第一包装膜21和第二包装膜22的连接层26会熔接于绝缘件4。
参照图1和图6，密封部23包括侧封区231和顶封区233，侧封区231 设置于电极组件1沿横向Y的外侧，顶封区233设置于电极组件1的远离第二包装膜22的回折处的一侧。
侧封区231为两个且分别设置于电极组件1沿横向Y的外侧，顶封区233设置于电极组件1沿纵向X的一侧且连接于两个侧封区231。两个侧封区231和顶封区233形成U形结构。第一包装膜21和第二包装膜22沿纵向X远离顶封区233的一端直接相连，因此，侧封区231和顶封区233即可实现包装袋2的密封。
参照图6，热压成型后，侧封区231具有一定的宽度，导致二次电池在横向Y上的尺寸偏大，影响二次电池的能量密度。因此，优选地，侧封区231朝靠近电极组件1的方向弯折，以减小侧封区231在横向Y上的尺寸，提高二次电池的能量密度。弯折成型后，侧封区231上形成沿纵向X延伸的第一折痕线L1；也就是说，侧封区231沿着第一折痕线L1朝靠近电极组件1的方向弯折。
在包装袋2的边缘E1处，第一包装膜21和第二包装膜22相对弯折；在弯折侧封区231时，会导致边缘E1在靠近第一折痕线L1的区域应力集中，也就是说，边缘E1的靠近第一折痕线L1的区域为应力集中区域。
在已知技术中，第一包装膜21和第二包装膜22直接相连，所以在电极组件1的远离顶封区233的一侧，第一包装膜21和第二包装膜22不会通过热压连接。也就是说，在两个侧封区231之间，第一包装膜21的连接层26和第二包装膜22的连接层26并未熔接，两者之间的连接强度较低。
当二次电池受到冲击时，第一包装膜21和第二包装膜22之间的未熔接且靠近应力集中区域的部分容易破裂，从而导致电解液泄露，引发安全风险。
因此，本申请的密封部23还包括底封区232，底封区232设置于电极组件1的靠近第二包装膜22的回折处的一侧，且底封区232连接于侧封区231。参照图8，在底封区232，第一包装膜21的连接层26和第二包装膜22的连接层26熔接在一起。
通过设置底封区232，可以增大第一包装膜21和第二包装膜22在应力集中区域附近的连接强度，降低包装袋2破裂的风险，改善包装袋2的密封性能。
在弯折侧封区231时，应力集中区域位于包装袋2的边缘E1上，也就 是说，包装袋2的边缘E1处破裂的风险最高。因此，优选地，在纵向X上，底封区232远离电极组件1的边缘E2与包装袋2的边缘E1齐平，这样可以尽可能的降低破裂的风险。同时，即使包装袋2在边缘E1处破裂，底封区232仍然可以起到密封的作用，避免电解液泄露。另外，在底封区232宽度一致的前提下，如果底封区232的边缘E2不与包装袋2的边缘E1齐平，那么底封区232会占用包装袋2的内部空间，影响二次电池的容量。
参照图1、图6和图7，底封区232从侧封区231延伸，且沿远离侧封区231的方向，底封区232在纵向X上的尺寸逐渐减小。距离侧封区231越远，包装袋2受到的应力越小，破损的风险越低。因此，沿远离侧封区231的方向，即使底封区232在纵向X上的尺寸逐渐减小，也能够保证密封性能。另外，当底封区232在纵向X上的尺寸减小时，可以增大包装袋2的内部空间，提高二次电池的容量。
优选地，底封区232为两个且分别连接于对应地一个侧封区231；在横向Y上，两个底封区232彼此隔开。在二次电池正常的工作过程中，电极组件1也会释放出少量的气体；在二次电池循环的末期，包装袋2的内部会存在一定量的气体，所以在设计二次电池时，会预留一定的空间来容纳电极组件1的产气。而在两个底封区232之间，第一包装膜21和第二包装膜22并未熔接，产气可以撑开第一包装膜21和第二包装膜22，并储存在第一包装膜21和第二包装膜22之间。也就是说，本申请可以进一步增大包装袋2的内部空间，提高二次电池的容量。
参照图6，底封区232的宽度小于侧封区231的宽度。在此补充的时，侧封区231的宽度指的是侧封区231在弯折之间的宽度，或者说侧封区231在展开状态下的宽度。其中，底封区232的宽度指的是底封区232在纵向X上的尺寸，侧封区231的宽度指的是侧封区231在横向Y上的尺寸。
宽度值决定底封区232和侧封区231的密封强度。在底封区232附近，第一包装膜21和第二包装膜22直接相连，即使没有底封区232也具有一定的密封强度，因此，底封区232可以具有相对较小的宽度。另外，减小底封区232的宽度，可以增大包装袋2的内部空间，提高二次电池的容量。
参照图7，在横向Y上，第一折痕线L1与底封区232的距离为D。D的值越小，弯折侧封区231时底封区232受到力也就越大；D的值大，侧封 区231弯折后，其在横向Y上占用的空间也就越大。因此，优选地，D的值为0.1mm-2mm。
参照图2，侧封区231包括第一区域231a和第二区域231b，第一区域231a沿第一折痕线L1弯折，第二区域231b从第一区域231a的端部延伸且回折到第一区域231a的靠近电极组件1的一侧。参照图6，在二次电池的成型过程中，可以先沿着第二折痕线L2弯折侧封区231，第二折痕线L2的两侧分别为第一区域231a和第二区域231b，然后再沿着第一折痕线L1弯折第一区域231a。
第一包装膜21和第二包装膜22在成型过程中需要经过裁切工艺，在裁切的断面处，金属层25露出。露出的金属层25容易被腐蚀，且可能会引发短路风险。而本申请通过两次弯折侧封区231，可以将部分露出的金属层25夹持在第一区域231a和凹腔的腔壁之间，从而减少金属层25外露，降低短路风险。在横向Y上，第二区域231b的靠近电极组件1的表面粘接于凹腔的腔壁，第二区域231b的远离电极组件1的表面粘接于第一区域231a。
在本申请中，两个电极引线3位于电极组件1的远离底封区232的一侧。也就是说，两个电极引线3沿纵向X延伸并穿过顶封区233。
下面对本申请的二次电池的第二实施例进行说明。为了简化描述，以下仅主要介绍第二实施例与第一实施例的不同之处，未描述的部分可以参照第一实施例进行理解。
参照图9，在第二实施例中，侧封区231为两个且分别位于电极组件1沿横向Y的两侧，底封区232沿横向Y的两端分别连接于两个侧封区231。与第一实施例相比，第二实施例可以简化热压工艺，降低对热压设备的要求。

Claims (10)

  1. 一种二次电池，其特征在于，包括电极组件(1)和包装袋(2)；
    包装袋(2)包括第一包装膜(21)和第二包装膜(22)，第二包装膜(22)和第一包装膜(21)为一体设置，第二包装膜(22)从第一包装膜(21)沿纵向(X)的边缘延伸且回折到第一包装膜(21)；
    电极组件(1)设置于第一包装膜(21)和第二包装膜(22)之间；
    第一包装膜(21)和第二包装膜(22)在电极组件(1)的外侧连接并形成密封部(23)，密封部(23)包括侧封区(231)和底封区(232)；
    侧封区(231)设置于电极组件(1)沿横向(Y)的外侧，且侧封区(231)朝靠近电极组件(1)的方向弯折；
    底封区(232)设置于电极组件(1)的靠近第二包装膜(22)的回折处的一侧，且底封区(232)连接于侧封区(231)。
  2. 根据权利要求1所述的二次电池，其特征在于，在纵向(X)上，底封区(232)远离电极组件(1)的边缘与包装袋(2)的边缘齐平。
  3. 根据权利要求1或2所述的二次电池，其特征在于，底封区(232)从侧封区(231)延伸，且沿远离侧封区(231)的方向，底封区(232)在纵向(X)上的尺寸逐渐减小。
  4. 根据权利要求3所述的二次电池，其特征在于，
    侧封区(231)为两个且分别位于电极组件(1)沿横向(Y)的两侧，底封区(232)为两个且分别连接于对应地一个侧封区(231)；
    在横向(Y)上，两个底封区(232)彼此隔开。
  5. 根据权利要求1所述的二次电池，其特征在于，底封区(232)的宽度小于侧封区(231)的宽度。
  6. 根据权利要求1所述的二次电池，其特征在于，
    侧封区(231)具有沿纵向(X)延伸的第一折痕线(L1)，且侧封区(231)沿第一折痕线(L1)朝向电极组件(1)弯折；
    在横向(Y)上，第一折痕线(L1)与底封区(232)的距离为0.1mm-2mm。
  7. 根据权利要求6所述的二次电池，其特征在于，
    侧封区(231)包括第一区域(231a)和第二区域(231b)，第一区域(231a)沿第一折痕线(L1)弯折，第二区域(231b)从第一区域(231a)的端部延伸且回折到第一区域(231a)的靠近电极组件(1)的一侧。
  8. 根据权利要求1所述的二次电池，其特征在于，
    二次电池还包括电极引线(3)，电极引线(3)连接于电极组件(1)并穿过密封部(23)；
    电极引线(3)为两个且位于电极组件(1)的远离底封区(232)的一侧。
  9. 根据权利要求1所述的二次电池，其特征在于，侧封区(231)为两个且分别位于电极组件(1)沿横向(Y)的两侧，底封区(232)沿横向(Y)的两端分别连接于两个侧封区(231)。
  10. 根据权利要求1所述的二次电池，其特征在于，
    第一包装膜(21)和第二包装膜(22)均包括保护层(24)、金属层(25)和连接层(26)，连接层(26)设置于金属层(25)的朝向电极组件(1)的表面，保护层(24)设置于金属层(25)的远离电极组件(1)的表面；
    第一包装膜(21)的连接层(26)熔接于第二包装膜(22)的连接层(26)并形成密封部(23)。
PCT/CN2019/098383 2019-07-08 2019-07-30 二次电池 WO2021003781A1 (zh)

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