WO2024093494A1 - 隔膜及电芯 - Google Patents

隔膜及电芯 Download PDF

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Publication number
WO2024093494A1
WO2024093494A1 PCT/CN2023/116186 CN2023116186W WO2024093494A1 WO 2024093494 A1 WO2024093494 A1 WO 2024093494A1 CN 2023116186 W CN2023116186 W CN 2023116186W WO 2024093494 A1 WO2024093494 A1 WO 2024093494A1
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WO
WIPO (PCT)
Prior art keywords
diaphragm
section
width
battery cell
separator
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Application number
PCT/CN2023/116186
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English (en)
French (fr)
Inventor
盛东辉
刘培伦
刘春雨
谢继春
Original Assignee
珠海冠宇电池股份有限公司
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Application filed by 珠海冠宇电池股份有限公司 filed Critical 珠海冠宇电池股份有限公司
Publication of WO2024093494A1 publication Critical patent/WO2024093494A1/zh

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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
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • 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
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/463—Separators, membranes or diaphragms characterised by their shape
    • 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 belongs to the field of battery technology, and specifically relates to a diaphragm and a battery cell.
  • Secondary batteries usually include a cell and a shell.
  • the cells are mainly laminated cells and wound cells according to different manufacturing processes.
  • Wound cells are flat cells made by winding with a winding needle clamping the pole piece and the diaphragm. Wound cells made with traditional diaphragms have the problem of poor cell quality.
  • the purpose of this application is to provide a separator and a battery cell that can improve the quality of the battery.
  • An embodiment of the present application provides a diaphragm, which includes: a first section, a second section and a third section arranged in sequence along the length direction of the diaphragm, the width of the first section is smaller than the width of the second section, and/or the width of the third section is smaller than the width of the second section.
  • the present application divides the diaphragm into areas of different widths, so that the width of the area located at the head and/or at the tail of the diaphragm is smaller than the width of the middle position of the diaphragm.
  • the width at the head of the diaphragm becomes narrower, the contact area between the diaphragm and the winding needle can be reduced, thereby reducing the friction between the diaphragm surface and the winding needle, avoiding part of the diaphragm from being pulled out of the battery cell when the winding needle is withdrawn, and improving the problem of diaphragm core pulling.
  • the width at the tail of the diaphragm becomes narrower, that is, reducing the width of the outer ring diaphragm
  • the swing amplitude of the tail of the diaphragm when the diaphragm is wound can be reduced, and the problem of diaphragm folding when the core is wound can be improved.
  • the quality of the battery can be improved by improving the problem of diaphragm core pulling and/or the problem of diaphragm folding when the core is wound.
  • the width of the first section increases gradually in an extension direction from an end of the first section away from the second section to an end of the first section close to the second section.
  • the width of the first section is set to be gradually narrowed, which can not only ensure the isolation between the pole pieces, but also reduce the contact area between the diaphragm and the winding needle, reduce the friction between the diaphragm surface and the winding needle, and improve the problem of diaphragm core pulling.
  • the width of the third section increases gradually in an extension direction from an end of the third section away from the second section to an end of the third section close to the second section.
  • the swing amplitude of the tail of the diaphragm when the diaphragm is wound can be reduced, and the problem of diaphragm folding when the winding core is wound can be improved.
  • An embodiment of the present application also provides a battery cell, comprising two pole pieces with opposite polarities and a diaphragm located between the two pole pieces, wherein the diaphragm and the two pole pieces are stacked and wound to form a battery cell; the diaphragm is the diaphragm described in any of the above embodiments, and the first section of the diaphragm is located at the beginning of the winding of the battery cell.
  • the length w1 of the first section is: 10%*W ⁇ w1 ⁇ 3*W, where W is the width of the battery cell.
  • the length w2 of the third section of the diaphragm is: 10%*W ⁇ w2 ⁇ 3*W.
  • the length w2 of the third section of the diaphragm is: 10%*W ⁇ w2 ⁇ 3*W, where W is the width of the battery cell.
  • a projection of at least one of the two pole pieces on the plane where the diaphragm is located is located inside the diaphragm.
  • a distance between an outer edge of the second section of the diaphragm and an outer edge of at least one of the two pole pieces is H, and H ⁇ 0.2 mm.
  • a distance h1 between an outer edge of the first segment and an outer edge of the pole piece is: 3%*H ⁇ h1 ⁇ 97%*H.
  • the minimum width h2 of the first section and the width h3 of the pole piece satisfy the following relationship: 50%*h3 ⁇ h2 ⁇ h3+h1.
  • a distance h4 between an outer edge of the third section of the diaphragm and an outer edge of the pole piece is: 3%*H ⁇ h4 ⁇ 97%*H.
  • the minimum width h5 of the third section and the width h3 of the pole piece satisfy the following relationship: 50%*h3 ⁇ h5 ⁇ h3+h4.
  • At least one of the two pole pieces includes a hollow foil area and a pole ear arranged in the hollow foil area; the projection of the portion of the pole ear located on the pole piece on the plane where the diaphragm is located is located within the first section.
  • the two pole pieces include a first pole piece and a second pole piece;
  • the diaphragm includes a first diaphragm and a second diaphragm located on two opposite sides of the first pole piece; the first diaphragm and the second diaphragm cover the first pole piece; the first diaphragm, the first pole piece and the second diaphragm are bonded.
  • the first diaphragm and the second diaphragm have the same length.
  • FIG. 1 is a schematic diagram of the structure of a wound battery cell provided in one embodiment of the present application.
  • FIG. 2 is a schematic diagram of core extraction of a wound battery cell provided in an embodiment of the present application.
  • FIG. 3 is a schematic diagram of the structure of a diaphragm provided in one embodiment of the present application.
  • FIG. 4 is a schematic diagram of stacking a diaphragm and a pole piece provided in an embodiment of the present application.
  • FIG5 is a schematic diagram of stacking pole pieces and diaphragms provided in another embodiment of the present application.
  • connection should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two components; it can be a wireless connection or a wired connection.
  • connection should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two components; it can be a wireless connection or a wired connection.
  • FIG1 and FIG2 are schematic diagrams of the structure of a battery cell made by a winding process.
  • a wound battery cell 100 is wound by a positive electrode sheet 101, a negative electrode sheet 102 and a separator 103, wherein the separator 103 is arranged between the positive electrode sheet 101 and the negative electrode sheet 102 to separate the positive electrode sheet 101 and the negative electrode sheet 102.
  • a positive electrode ear (unnumbered) and a negative electrode ear (unnumbered) are respectively arranged on the positive electrode sheet 101 and the negative electrode sheet 102.
  • the head 103a of the separator 103 is bent and overlapped and is located in the innermost layer of the battery cell 100.
  • the battery cell 100 has a head 100a and a tail 100b.
  • the winding needle is pulled out from the side where the head 100a of the battery cell 100 is located.
  • the separator 103 is located in the innermost layer of the battery cell.
  • the winding needle clamps the separator and drives the electrode sheet to be wound together through the separator. Since the diaphragm 103 has a portion in direct contact with the winding needle, there is friction between the surface coating of this portion of the diaphragm and the winding needle. The inner diaphragm is pulled out together, so that part of the diaphragm is pulled out of the battery cell, causing the core pulling phenomenon.
  • the diaphragm is partially pulled out of the head of the battery cell (such as the part in the dotted box in Figure 2).
  • the diaphragm being pulled out will affect the mutual isolation between the positive and negative electrodes, and may cause the positive and negative electrodes to contact each other and short-circuit. In severe cases, it may even cause the core to be scrapped, reducing the product yield.
  • the tail 103b of the diaphragm is easily folded during the termination, resulting in an increase in the thickness of the core, thereby affecting the energy density of the battery.
  • a wound cell is a cell made using a winding process.
  • the wound cell includes two pole pieces with opposite polarities, and the diaphragm is located between the two pole pieces.
  • the winding needle clamps the stacked diaphragm and pole pieces and winds them together to form a cell.
  • the end of the diaphragm located at the innermost layer of the cell is defined as the head of the diaphragm, and the other end of the diaphragm opposite to the head is the tail of the diaphragm.
  • the diaphragm will be used to end the cell, that is, the tail of the diaphragm will be wrapped around the outermost layer of the cell.
  • the innermost layer of the cell is also the winding head of the cell.
  • the diaphragm is generally in a rectangular structure, and the size of the long side of the rectangle is defined as the length of the diaphragm, and the size of the short side of the rectangle is defined as the width of the diaphragm.
  • an embodiment of the present application provides a diaphragm 1, and the diaphragm 1 includes a first section 1-1, a second section 1-2, and a third section 1-3 connected in sequence along the length direction of the diaphragm 1.
  • the first section 1-1 is located on one side of the head of the diaphragm, that is, when winding, the first section 1-1 is located at the winding head end of the battery cell, that is, located in the inner layer of the battery cell.
  • the third section 1-3 is located on one side of the tail of the diaphragm, that is, when winding, the third section 1-3 is located in the outer layer of the battery cell.
  • the width of the first section 1-1 is smaller than the width of the second section 1-2, and/or the width of the third section 1-3 is smaller than the width of the second section 1-2, so that the diaphragm is narrower at the end than in the middle.
  • the width of the first segment 1-1 and the third segment 1-3 are both smaller than the width of the second segment 1-2, and the width of the first segment 1-1 increases gradually from the end of the first segment 1-1 away from the second segment 1-2 to the end close to the second segment 1-2, that is, the first segment 1-1 becomes narrower and narrower in the direction away from the second segment 1-2; and/or, the width of the third segment 1-3 also increases gradually from the end of the third segment 1-3 away from the second segment 1-2 to the end close to the second segment 1-2, that is, the third segment 1-3 becomes narrower and narrower in the direction away from the second segment 1-2.
  • the width of the narrowest position of the diaphragm 1, that is, the minimum width of the diaphragm 1, is greater than the width of the electrode sheet (positive and/or negative electrode sheet), that is, when the electrode sheet and the diaphragm are flattened and stacked together, the projection of the electrode sheet on the plane where the diaphragm is located is located inside the diaphragm (as shown in Figure 4). This ensures that when the diaphragm and the electrode sheet are stacked or wound, the diaphragm can completely cover the electrode sheet, avoiding contact between electrode sheets of opposite polarity separated by the diaphragm.
  • the present application divides the diaphragm into regions of different widths, so that the width of the region located at the head of the diaphragm (the first section) and/or the region located at the tail of the diaphragm (the third section) is smaller than the width of the middle of the diaphragm.
  • the narrowing of the width at the head of the diaphragm can reduce the contact area between the diaphragm and the winding needle, thereby reducing the friction between the diaphragm surface and the winding needle, avoiding part of the diaphragm being pulled out of the battery cell when the winding needle is withdrawn, and improving the problem of diaphragm core withdrawal.
  • the width of the area at the tail of the diaphragm is also smaller than the width of other positions of the diaphragm, thereby reducing the swing amplitude of the tail of the diaphragm when the diaphragm is wound to the end, thereby improving the problem of diaphragm folding when the winding core is finished.
  • the present application also provides a battery cell, comprising two pole pieces with opposite polarities and a diaphragm located between the two pole pieces, wherein the diaphragm and the two pole pieces are stacked and wound to form a battery cell.
  • the diaphragm may be the diaphragm described in any of the above embodiments, and the first section of the diaphragm is located at the winding head end of the battery cell.
  • the battery cell includes a first pole piece and a second pole piece with opposite polarities
  • the diaphragm includes a first diaphragm and a second diaphragm located on two opposite sides of the first pole piece, and the first diaphragm and the second diaphragm cover the first pole piece.
  • the first pole piece and the first and second diaphragms located on the surfaces of both sides thereof can be compositely bonded together, and then the first pole piece and the second pole piece composited with the diaphragms are stacked and wound.
  • the first diaphragm and the second diaphragm located on two opposite sides of the first pole piece are of equal length, and the use of two diaphragms of equal length can avoid misalignment during winding.
  • the diaphragm 1 is longer and wider than the pole piece Q, and the diaphragm 1 exceeds the pole piece Q in both the length direction and the width direction.
  • the distance between the outer edge of the second section 1-2 of the diaphragm 1 and the outer edge of the pole piece Q on the same side is H, H ⁇ 0.2 mm, that is, in the width direction, the two sides of the diaphragm 1 at the second section 1-2 respectively exceed the pole piece Q by a dimension of H, that is, the two sides of the diaphragm 1 at the second section 1-2 respectively exceed the pole piece by at least 0.2 mm.
  • the length w1 of the first section 1-1 of the diaphragm 1 is: 10%*W ⁇ w1 ⁇ 3*W, where W is the width of the battery cell.
  • W is the width of the battery cell.
  • the distance between the outer edge of the first section 1-1 and the outer edge of the pole piece Q on the same side is h1, 3%*H ⁇ h1 ⁇ 97%*H, that is, on one side in the width direction, the first section 1-1 of the diaphragm 1 at least exceeds the pole piece h1.
  • h1 is a numerical range, not a constant value.
  • h1 is a constant value.
  • the minimum width value h2 of the first section 1-1 and the width h3 of the pole piece Q also satisfy: 50%*h3 ⁇ h2 ⁇ h3+h1, where h3 is the width of the pole piece.
  • the length w2 of the third section 1-3 of the diaphragm 1 is: 10%*W ⁇ w2 ⁇ 3*W.
  • the distance between the outer edge of the third section 1-3 and the outer edge of the pole piece Q on the same side is h4, 3%*H ⁇ h4 ⁇ 97%*H, that is, in the width direction, the two sides of the diaphragm 1 at the third section 1-3 respectively exceed the size of the pole piece Q by at least h4.
  • h4 is a numerical range, not a constant value.
  • h4 is a constant value.
  • the minimum width value h5 of the third section 1-3 and the width h3 of the pole piece Q also satisfy: 50%*h3 ⁇ h5 ⁇ h3+h4.
  • the pole piece Q has an empty foil area N which is not coated with active material, and the empty foil area N is used for welding the pole tab M.
  • the pole tab M is arranged in the empty foil area N of the pole piece Q and extends beyond the pole piece Q along the width direction of the diaphragm 1.
  • the portion of the pole tab M located on the pole piece Q (the portion of the pole tab not extended) is The projection of the empty foil area N of the pole piece Q on the plane where the diaphragm 1 is located is located in the first section 1-1 of the diaphragm 1, that is, the projection of the empty foil area N of the pole piece Q on the plane where the diaphragm 1 is located is located in the first section 1-1 of the diaphragm 1.

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Abstract

一种隔膜及电芯，所述隔膜用于和极片一起卷绕制成电芯，该隔膜包括：沿隔膜的长度方向依次设置的第一区段、第二区段及第三区段，所述第一区段的宽度小于所述第二区段的宽度，和/或，所述第三区段的宽度小于所述第二区段的宽度。将隔膜分为宽度不同的区域，使位于隔膜头部和/或尾部的区域的宽度小于隔膜中间位置的宽度。隔膜头部处的宽度变窄，可以减小隔膜和卷针接触的面积，从而降低隔膜表面和卷针之间的摩擦力，改善隔膜抽芯的问题；隔膜尾部处的宽度变窄，可以降低隔膜卷绕收尾时隔膜尾部的甩动幅度，改善卷芯收尾时隔膜打折的问题。通过改善隔膜抽芯问题和/或卷芯收尾时隔膜打折的问题可以提高电池的品质。

Description

隔膜及电芯 技术领域
本申请属于电池技术领域，具体涉及一种隔膜及电芯。
发明背景
二次电池通常包括电芯和外壳，电芯根据制备工艺的不同，主要有叠片式电芯和卷绕式电芯。卷绕式电芯是采用卷绕工艺，用卷针夹着极片和隔膜进行卷绕而制成的扁平状电芯。基于传统的隔膜制作卷绕式电芯存在电芯品质差的问题。
发明内容
本申请的目的在于提供一种可以提高电池品质的隔膜及电芯。
本申请实施例提供了一种隔膜，所述隔膜包括：沿所述隔膜的长度方向依次设置的第一区段、第二区段及第三区段，所述第一区段的宽度小于所述第二区段的宽度，和/或，所述第三区段的宽度小于所述第二区段的宽度。
由以上技术方案可知，本申请将隔膜分为宽度不同的区域，使位于隔膜头部和/或位于尾部的区域的宽度小于隔膜中间位置的宽度。当隔膜头部处的宽度变窄后，可以减小隔膜和卷针接触的面积，从而降低隔膜表面和卷针之间的摩擦力，避免卷针抽针时将部分隔膜扯出电芯，改善隔膜抽芯的问题。当隔膜尾部处的宽度变窄，即减小外圈隔膜的宽度，可以降低隔膜卷绕收尾时隔膜尾部的甩动幅度，改善卷芯收尾时隔膜打折的问题。通过改善隔膜抽芯问题和/或卷芯收尾时隔膜打折的问题可以提高电池的品质。
在一些可选的实施例中，所述第一区段的宽度自所述第一区段的远离所述第二区段的一端向靠近所述第二区段的一端的延伸方向递增。
在第一区段远离第二区段的方向上，将第一区段的宽度设置为逐渐变窄，既可以保证极片之间相互隔离，又可以减小隔膜和卷针接触的面积，降低隔膜表面和卷针之间的摩擦力，改善隔膜抽芯的问题。
在一些可选的实施例中，所述第三区段的宽度自所述第三区段的远离所述第二区段的一端向靠近所述第二区段的一端的延伸方向递增。
通过使隔膜尾部处的宽度变窄，即减小外圈隔膜的宽度，可以降低隔膜卷绕收尾时隔膜尾部的甩动幅度，改善卷芯收尾时隔膜打折的问题。
本申请实施例还提供了一种电芯，包括极性相反的两片极片和位于两片极片之间的隔膜，所述隔膜和所述两片极片叠放卷绕形成电芯；所述隔膜为上述任一实施例所述的隔膜，所述隔膜的第一区段位于所述电芯的卷绕首端。
在一些可选的实施例中，所述第一区段的长度w1为：10％*W≤w1≤3*W，W为所述电芯的宽度。
在一些可选的实施例中，所述隔膜的第三区段的长度w2为：10％*W≤w2≤3*W。
在一些可选的实施例中，所述隔膜的第三区段的长度w2为：10％*W≤w2≤3*W，W为所述电芯的宽度。
在一些可选的实施例中，所述两片极片中的至少一片极片在所述隔膜所在平面上的投影位于所述隔膜内。
在一些可选的实施例中，在所述隔膜的宽度方向上的一侧，所述隔膜的第二区段的外边缘和所述两片极片中至少一片极片的外边缘之间的距离为H，H≥0.2mm。
在一些可选的实施例中，在所述隔膜的宽度方向上的一侧，所述第一区段的外边缘和所述极片的外边缘之间的距离h1为：3％*H≤h1≤97％*H。
在一些可选的实施例中，所述第一区段的最小宽度h2和所述极片的宽度h3之间满足：50％*h3≤h2≤h3+h1。
在一些可选的实施例中，在所述隔膜的宽度方向上的一侧，所述隔膜的第三区段的外边缘和所述极片的外边缘之间的距离h4为：3％*H≤h4≤97％*H。
在一些可选的实施例中，所述第三区段的最小宽度h5和所述极片的宽度h3之间满足：50％*h3≤h5≤h3+h4。
在一些可选的实施例中，所述两片极片中至少一片极片包括空箔区和设置于所述空箔区的极耳；所述极耳的位于所述极片上的部分在所述隔膜所在平面上的投影位于所述第一区段内。
在一些可选的实施例中，所述两片极片包括第一极片和第二极片；所述隔膜包括位于所述第一极片的两相对侧的第一隔膜和第二隔膜；所述第一隔膜和所述第二隔膜覆盖所述第一极片；所述第一隔膜、第一极片和所述第二隔膜粘结。
在一些可选的实施例中，所述第一隔膜和所述第二隔膜的长度相同。
附图简要说明
为了更清楚地说明本申请实施例，下面将对实施例或现有技术描述中所需要使用的附图做简单介绍，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，对于本领域普通技术人员来讲，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为本申请一实施例提供的卷绕式电芯的结构示意图。
图2为本申请一实施例提供的卷绕式电芯的抽芯示意图。
图3为本申请一实施例提供的隔膜的结构示意图。
图4为本申请一实施例提供的隔膜和极片的叠放示意图。
图5为本申请另一实施例提供的极片和隔膜的叠放示意图。
以下结合附图对本申请的具体实施方式作进一步详细地说明。
实施本发明的方式
下面结合附图对本申请进行详细描述，在详述本申请实施例时，为便于说明，表示器件结构的附图会不依一般比例做局部放大，而且所述示意图只是示例，其在此不应限制本申请保护的范围。需要说明的是，附图采用简化的形式且均使用非精准的比例，仅用以方便、清晰地辅助说明本申请实施例的目的。同时，在本申请的描述中，术语“第一”、“第二”等仅用于区分描述，而不能理解为指示或暗示相对重要性或者隐含指明所指示的技术特征的数量；术语“正”、“反”、“底”、“上”、“下”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，因此不能理解为对本申请的限制。
在本申请的描述中，需要说明的是，除非另有明确的规定和限定，术语“相连”、“连接”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；可以是直接相连，也可以通过中间媒介间接相连，还可以是两个元件内部的连通；可以是无线连接，也可以是有线连接。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。
图1和图2为采用卷绕工艺制成的电芯的结构示意图，如图1和图2所示，卷绕式电芯100由正极片101、负极片102及隔膜103卷绕而成，其中，隔膜103设置于正极片101和负极片102之间，以将正极片101和负极片102隔开。在正极片101和负极片102上分别设置有正极耳(未标号)和负极耳(未标号)。卷绕时，隔膜103的头部103a弯折重叠，位于电芯100的最内层。电芯100具有头部100a和尾部100b，卷绕完成后卷针从电芯100的头部100a所在的一侧抽出。卷绕式电芯中隔膜103位于电芯的最内层，卷绕时卷针夹着隔膜并通过隔膜带动极片一起卷绕。由于隔膜103具有和卷针直接接触的部分，因此这部分隔膜的表面涂层和卷针之间存在摩擦。当卷绕完成后，在卷针拔针过程中，卷针容易带着 内层的隔膜一起拔出，使得部分隔膜被抽出于电芯外，造成抽芯的现象。例如，隔膜被部分抽出电芯的头部外(如图2中虚线框内的部分)。隔膜被抽出会影响正极片和负极片之间的相互隔离，可能会导致正负极片互相接触而发生短路，严重时甚至会导致卷芯报废，使得产品良率降低。此外，对于一些用隔膜收尾的卷绕式电芯来说，由于隔膜的宽度较宽，而且质地较软，收尾时隔膜的尾部103b容易打折，导致卷芯的厚度增加，从而影响电池的能量密度。
卷绕式电芯是采用卷绕工艺制成的电芯，卷绕式电芯包括极性相反的两片极片，隔膜位于两片极片之间。卷绕时卷针夹着叠放的隔膜和极片一起卷绕，形成电芯。为了便于说明，将隔膜的位于电芯最内层的一端定义为隔膜的头部，隔膜的和头部相对的另一端则为隔膜的尾部，在一些卷绕工艺中会用隔膜收尾，即隔膜的尾部会外包在电芯的最外层。电芯的最内层亦为电芯的卷绕首端。
隔膜一般呈长方形结构，将长方形的长边的尺寸定义为隔膜的长度，将长方形的短边的尺寸定义为隔膜的宽度。如图3和图4所示，本申请实施例提供一种隔膜1，隔膜1包括沿隔膜1的长度方向依次连接的第一区段1-1、第二区段1-2及第三区段1-3。第一区段1-1位于隔膜头部的一侧，即卷绕时，第一区段1-1位于电芯的卷绕首端，即位于电芯内层。第三区段1-3位于隔膜尾部的一侧，即卷绕时，第三区段1-3位于电芯外层。第一区段1-1的宽度小于第二区段1-2的宽度，和/或，第三区段1-3的宽度小于第二区段1-2的宽度，使隔膜呈端部比中间窄的形状。
在一些实施例中，第一区段1-1和第三区段1-3的宽度均小于第二区段1-2的宽度，且第一区段1-1的宽度自第一区段1-1的远离第二区段1-2的一端向靠近第二区段1-2的一端的延伸方向递增，即第一区段1-1沿远离第二区段1-2的方向越来越窄；和/或，第三区段1-3的宽度也自第三区段1-3的远离第二区段1-2的一端向靠近第二区段1-2的一端的延伸方向递增，即第三区段1-3沿远离第二区段1-2的方向越来越窄。为了保证将正、负极片隔开，隔膜1的最窄位置处的宽度，也就是隔膜1的最小宽度大于极片(正和/或负极片)的宽度，即极片和隔膜展平叠放在一起时，极片在隔膜所在平面上的投影位于隔膜内(如图4)，这样可以保证隔膜和极片叠放或卷绕时，隔膜都能将极片完全覆盖，避免被隔膜隔开的极性相反的极片相互接触。
本申请通过将隔膜分为宽度不同的区域，使位于隔膜头部的区域(第一区段)和/或位于隔膜尾部的区域(第三区段)的宽度小于隔膜中间位置的宽度。隔膜头部处的宽度变窄，可以减小隔膜和卷针接触的面积，从而降低隔膜表面和卷针之间的摩擦力，避免卷针抽针时将部分隔膜扯出电芯，改善隔膜抽芯的问题。在 一些实施例中，隔膜尾部的区域的宽度也小于隔膜其他位置的宽度，从而可以降低隔膜卷绕收尾时隔膜尾部的甩动幅度，以改善卷芯收尾时隔膜打折的问题。
本申请实施例还提供一种电芯，包括极性相反的两片极片和位于两片极片之间的隔膜，隔膜和两片极片叠放卷绕形成电芯。该隔膜可以为上述任一实施例所述的隔膜，隔膜的第一区段位于电芯的卷绕首端。
在一些实施例中，电芯包括极性相反的第一极片和第二极片，隔膜包括位于第一极片的两相对侧的第一隔膜和第二隔膜，第一隔膜和第二隔膜覆盖第一极片。如图5所示，作为本申请一种可选的实施方式，可以在第一极片、第二极片和第一、第二隔膜进行卷绕前，将第一极片和位于其两侧表面的第一、第二隔膜复合粘结在一起，然后再将复合了隔膜的第一极片和第二极片叠放进行卷绕。在一些可选的实施例中，分别位于第一极片两相对侧的第一隔膜和第二隔膜等长，采用等长的两片隔膜可以避免卷绕时发生错位。
如图4所示，隔膜1比极片Q长，也比极片Q宽，隔膜1在长度方向和宽度方向上均超出极片Q。在一些实施例中，在隔膜的宽度方向上，隔膜1的第二区段1-2的外边缘和极片Q位于同侧的外边缘之间的距离为H，H≥0.2mm，也就是在宽度方向上，在第二区段1-2处隔膜1的两侧分别超出于极片Q的尺寸为H，即在第二区段1-2处隔膜1的两侧分别至少超出极片0.2mm。
隔膜1的第一区段1-1的长度w1为：10％*W≤w1≤3*W，W为电芯的宽度。在隔膜的宽度方向上，第一区段1-1的外边缘和极片Q的位于同侧的外边缘之间的距离为h1，3％*H≤h1≤97％*H，也就是在宽度方向上的某一侧，隔膜1的第一区段1-1至少超出极片h1。当第一区段1-1的宽度沿远离第二区段1-2的方向递减时，h1为一个数值范围，而不是一个定值，当第一区段1-1是一个宽度不变的方形区域时，h1为一个定值。第一区段1-1的最小宽度值h2和极片Q的宽度h3之间还满足：50％*h3≤h2≤h3+h1，式中的h3为极片的宽度。
隔膜1的第三区段1-3的长度w2为：10％*W≤w2≤3*W。在宽度方向上，第三区段1-3的外边缘和极片Q的位于同侧的外边缘之间的距离为h4，3％*H≤h4≤97％*H，也就是在宽度方向上，在第三区段1-3处隔膜1的两侧分别至少超出极片Q的尺寸为h4。同样的，当第三区段1-3的宽度沿远离第二区段1-2的方向递减时，h4为一个数值范围，而不是一个定值，当第三区段1-3是一个宽度不变的方形区域时，h4为一个定值。第三区段1-3的最小宽度值h5和极片Q的宽度h3之间还满足：50％*h3≤h5≤h3+h4。
如图4所示，极片Q上具有未涂覆活性材料的空箔区N，空箔区N用于焊接极耳M。极耳M设置于极片Q的空箔区N，并沿隔膜1的宽度方向延伸超出极片Q。极耳M设置于极片Q上后，极耳M的位于极片Q上的部分(极耳的未延 伸超出极片的部分)在隔膜1所在平面上的投影位于隔膜1的第一区段1-1内，亦即，极片Q的空箔区N在隔膜1所在平面上的投影位于隔膜1的第一区段1-1内。
对所公开的实施例的上述说明，使本领域专业技术人员能够实现或使用本申请。对这些实施例的多种修改对本领域的专业技术人员来说将是显而易见的，本文中所定义的一般原理可以在不脱离本申请的精神或范围的情况下，在其它实施例中实现。因此，本申请将不会被限制于本文所示的实施例，而是要符合与本文所公开的原理和新颖特点相一致的最宽范围。

Claims (16)

  1. 一种隔膜，其特征在于，所述隔膜包括：沿所述隔膜的长度方向依次设置的第一区段、第二区段及第三区段，所述第一区段的宽度小于所述第二区段的宽度，和/或，所述第三区段的宽度小于所述第二区段的宽度。
  2. 如权利要求1所述的隔膜，其特征在于，所述第一区段的宽度自所述第一区段的远离所述第二区段的一端向靠近所述第二区段的一端的延伸方向递增。
  3. 如权利要求1或2所述的隔膜，其特征在于，所述第三区段的宽度自所述第三区段的远离所述第二区段的一端向靠近所述第二区段的一端的延伸方向递增。
  4. 一种电芯，包括极性相反的两片极片和位于所述两片极片之间的隔膜，所述隔膜和所述两片极片叠放卷绕形成所述电芯；其特征在于，所述隔膜为权利要求1至3任一项所述的隔膜，所述隔膜的第一区段位于所述电芯的卷绕首端。
  5. 如权利要求4所述的电芯，其特征在于，所述第一区段的长度w1为：10％*W≤w1≤3*W，W为所述电芯的宽度。
  6. 如权利要求5所述的电芯，其特征在于，所述隔膜的第三区段的长度w2为：10％*W≤w2≤3*W。
  7. 如权利要求4所述的电芯，其特征在于，所述隔膜的第三区段的长度w2为：10％*W≤w2≤3*W，W为所述电芯的宽度。
  8. 如权利要求4至7中任一项所述的电芯，其特征在于，所述两片极片中的至少一片极片在所述隔膜所在平面上的投影位于所述隔膜内。
  9. 如权利要求4至8中任一项所述的电芯，其特征在于，在所述隔膜的宽度方向上的一侧，所述隔膜的第二区段的外边缘和所述两片极片中至少一片极片的外边缘之间的距离为H，H≥0.2mm。
  10. 如权利要求9所述的电芯，其特征在于，
    在所述隔膜的宽度方向上的一侧，所述第一区段的外边缘和所述极片的外边缘之间的距离h1为：3％*H≤h1≤97％*H。
  11. 如权利要求10所述的电芯，其特征在于，所述第一区段的最小宽度h2和所述极片的宽度h3之间满足：50％*h3≤h2≤h3+h1。
  12. 如权利要求9至11中任一项所述的电芯，其特征在于，
    在所述隔膜的宽度方向上的一侧，所述隔膜的第三区段的外边缘和所述极片的外边缘之间的距离h4为：3％*H≤h4≤97％*H。
  13. 如权利要求12所述的电芯，其特征在于，所述第三区段的最小宽度h5和所述极片的宽度h3之间满足：50％*h3≤h5≤h3+h4。
  14. 如权利要求4至13中任一项所述的电芯，其特征在于，
    所述两片极片中至少一片极片包括空箔区和设置于所述空箔区的极耳；
    所述极耳的位于所述极片上的部分在所述隔膜所在平面上的投影位于所述第一区段内。
  15. 如权利要求4至14中任一项所述的电芯，其特征在于，
    所述两片极片包括第一极片和第二极片；
    所述隔膜包括位于所述第一极片的两相对侧的第一隔膜和第二隔膜；
    所述第一隔膜和所述第二隔膜覆盖所述第一极片；
    所述第一隔膜、所述第一极片和所述第二隔膜粘结。
  16. 如权利要求15所述的电芯，其特征在于，所述第一隔膜和所述第二隔膜的长度相同。
PCT/CN2023/116186 2022-10-31 2023-08-31 隔膜及电芯 WO2024093494A1 (zh)

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