CN115312977A - Winding battery cell, preparation method thereof, battery module, battery pack and electric equipment - Google Patents

Winding battery cell, preparation method thereof, battery module, battery pack and electric equipment Download PDF

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Publication number
CN115312977A
CN115312977A CN202211004022.6A CN202211004022A CN115312977A CN 115312977 A CN115312977 A CN 115312977A CN 202211004022 A CN202211004022 A CN 202211004022A CN 115312977 A CN115312977 A CN 115312977A
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sub
diaphragm
winding
thickness
winding body
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CN202211004022.6A
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CN115312977B (en
Inventor
谢鹏飞
梁金云
黄汉川
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Xiamen Hithium Energy Storage Technology Co Ltd
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Xiamen Hithium Energy Storage Technology Co Ltd
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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
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/449—Separators, membranes or diaphragms 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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/058—Construction or manufacture
    • H01M10/0587—Construction or manufacture of accumulators having only wound construction elements, i.e. wound positive electrodes, wound negative electrodes and wound separators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • 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
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/411—Organic material
    • H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
    • 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
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/411—Organic material
    • H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
    • H01M50/417—Polyolefins
    • 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
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/411—Organic material
    • H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
    • H01M50/426—Fluorocarbon polymers
    • 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

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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)
  • Cell Separators (AREA)

Abstract

The invention discloses a winding battery cell, a preparation method of the winding battery cell, a battery module, a battery pack and electric equipment. The winding battery cell comprises a winding body, wherein a winding unit of the winding body comprises a positive plate, a negative plate and two layers of diaphragms, the winding body defines a first winding body and a second winding body, and the second winding body is formed by continuously winding on the first winding body; in at least one layer of diaphragm, the part of the first winding body is used as a first sub-diaphragm, the part of the second winding body is used as a second sub-diaphragm, and the side of the first sub-diaphragm, which is in contact with the negative plate, is provided with a first binder layer, wherein: the side, in contact with the negative plate, of the second sub-diaphragm is not provided with a binder layer; or a second binder layer is arranged on one side, which is in contact with the negative plate, of the second sub-diaphragm, and the thickness of the second binder layer is smaller than that of the first binder layer. The winding battery cell can not only remarkably improve the expansion and wrinkle problems of the negative plate, but also reduce the cost of the diaphragm and the battery cell.

Description

Winding battery cell, preparation method thereof, battery module, battery pack and electric equipment
Technical Field
The invention belongs to the field of batteries, and particularly relates to a winding battery cell, a preparation method of the winding battery cell, a battery module, a battery pack and electric equipment.
Background
The production process of the winding type battery has the advantages of high production speed, good continuity, lower requirement on equipment and easier control of battery consistency. However, the wound battery has the following disadvantages: in a large battery core produced by winding, after full charge, the expansion force of the inner layer negative pole piece cannot be released, and the wrinkles are serious, so that the thickness of the battery is obviously increased or the battery is swelled; in addition, the wrinkles of the negative pole piece can increase the risk of lithium precipitation of the battery cell, so that the battery cell fails in advance, and the electrochemical performance, safety performance and service life of the battery are influenced. At present, in order to improve the wrinkle problem of the negative plate, a gluing diaphragm is contacted with the negative plate, but compared with a diaphragm without gluing, the cost of directly adopting a diaphragm with an adhesive coating is higher, and is usually about 2-3 times of that of the diaphragm without gluing. Therefore, it is very important to provide a wound battery which has low cost and good safety and can effectively solve the problem of the wrinkle of the negative electrode sheet.
Disclosure of Invention
The present invention is directed to solving, at least to some extent, one of the technical problems in the related art. Therefore, the invention aims to provide a winding battery core, a preparation method thereof, a battery module, a battery pack and electric equipment. The winding battery cell can not only remarkably improve the expansion and wrinkle problems of the negative plate, but also reduce the cost of the diaphragm and the battery cell.
The present application is primarily based on the following problems and findings: in the conventional winding battery core, in order to improve the wrinkle problem of the negative electrode sheet, the separator with the adhesive coating is adopted, wherein the adhesive coating is coated on the whole contact surface of the separator, which is in contact with the negative electrode sheet (namely, a full-coating separator), and the inventor finds that the wrinkle of the negative electrode sheet is mainly concentrated on the inner ring of the battery core.
In view of the above, in one aspect of the present invention, a wound cell is provided. According to an embodiment of the present invention, the winding cell includes: the winding unit of the winding body comprises a positive plate, a negative plate and two layers of diaphragms, the winding body defines a first winding body and a second winding body, and the second winding body is formed by continuously winding on the first winding body; in at least one layer of the separator, the part of the first winding body is used as a first sub-separator, the part of the second winding body is used as a second sub-separator, and a first binder layer is arranged on the side, in contact with the negative electrode sheet, of the first sub-separator, wherein: the side, in contact with the negative plate, of the second sub-diaphragm is not provided with a binder layer; or a second binder layer is arranged on one side, in contact with the negative plate, of the second sub-diaphragm, and the thickness of the second binder layer is smaller than that of the first binder layer. The inventor finds that the swelling force and the wrinkles of the inner ring negative plate in the wound battery cell are more obvious in the lithium intercalation process, and the wrinkles of the negative plate are mainly concentrated on the inner ring of the battery cell. Compared with the existing winding battery cell, the invention can obviously improve the problems of expansion and folding of the battery cell cathode plate, reduce the risk of lithium precipitation of the battery cell, improve the safety performance of the battery cell, be beneficial to preventing the electrochemical performance of the battery cell from being reduced or losing efficacy in advance, and also reduce the cost of the diaphragm and the battery cell by only forming the binder layer on one section of the winding body diaphragm or enabling the thickness of the binder layer formed on the two sections of the winding body diaphragms to be smaller than that of one section of the winding body.
In addition, the winding battery cell according to the above embodiment of the present invention may further have the following additional technical features:
in some embodiments of the invention, the ratio of the number of winding turns of the first segment of winding to the number of winding turns of the second segment of winding is 0.2-2.
In some embodiments of the invention, the ratio of the number of windings of the first segment of winding to the number of windings of the second segment of winding is 0.5-1.
In some embodiments of the invention, the first adhesive layer and the second adhesive layer each independently comprise a polymeric adhesive.
In some embodiments of the invention, the polymeric binder comprises at least one selected from the group consisting of polyvinylidene fluoride, polyvinyl alcohol, and carboxymethyl cellulose.
In some embodiments of the invention, the first binder layer further has inorganic particles dispersed therein.
In some embodiments of the invention, the second binder layer further has inorganic particles dispersed therein.
In some embodiments of the invention, the inorganic particles in the first binder layer and the inorganic particles in the second binder layer each independently comprise a material selected from boehmite, alumina, zrO 2 And LLZTO.
In some embodiments of the present invention, in the first binder layer and the second binder layer, the mass ratio of the inorganic particles to the polymer binder is (0.1 to 9.9): (9.9-0.1).
In some embodiments of the invention, the separator is a PE film or a PP film.
In some embodiments of the present invention, in the same layer of the diaphragm, the first sub-diaphragm and the second sub-diaphragm are continuous and uninterrupted structures.
In some embodiments of the present invention, the first sub-diaphragm and the second sub-diaphragm are bonded to each other in the same layer of the diaphragm.
In some embodiments of the present invention, the first sub-diaphragm is thermally fused to the second sub-diaphragm; and/or the first sub-diaphragm and the second sub-diaphragm are overlapped, bonded and connected, and the width of the overlapped area is 2-5 mm.
In some embodiments of the present invention, the hot-melt bonding is performed by performing a hot-pressing process on the joint of the first sub-diaphragm and the second sub-diaphragm, wherein the hot-pressing process is performed at a temperature of 250 to 300 ℃, a pressure of 3000 to 5000kgf, and a time of 5 to 10s.
In some embodiments of the present invention, a thickness of the overlapping region is not greater than 10 μm different from a thickness of the first sub-diaphragm and a thickness of the second sub-diaphragm.
In some embodiments of the present invention, in the overlapping region, the edge of the first sub-diaphragm and the edge of the second sub-diaphragm are independently linear, zigzag, or wavy, respectively, in a width direction of the diaphragm.
In some embodiments of the invention, the jelly roll comprises a planar zone and a fold zone, the overlapping region being located within the fold zone.
In some embodiments of the present invention, at least one of the positive electrode tab and the negative electrode tab is provided with a reduced thickness region corresponding to the overlapping region on a side facing the separator.
In some embodiments of the present invention, the total reduced thickness of the reduced thickness region is 1 to 1.2 times the thickness of the overlap region, and the width of the reduced thickness region is not less than the width of the overlap region; and/or, all be equipped with on the positive plate with on the negative plate the thickness reduces the district, is located the reduction thickness in the thickness reduction district on the positive plate is overlap area thickness (0.7 +/-0.1) times, is located the reduction thickness in the thickness reduction district on the negative plate is overlap area thickness (0.3 +/-0.1) times.
In some embodiments of the present invention, a thickness of the first sub-diaphragm is equal to a thickness of the second sub-diaphragm.
In some embodiments of the present invention, a side of the second sub-separator contacting the negative electrode sheet is not provided with a binder layer, and a total thickness of the first sub-separator and the first binder layer is equal to a thickness of the second sub-separator.
In some embodiments of the present invention, a total thickness of the first sub-diaphragm and the first adhesive layer is equal to a total thickness of the second sub-diaphragm and the second adhesive layer.
According to yet another aspect of the invention, a method of making a wound cell is provided. According to an embodiment of the invention, the method comprises: winding by using a winding unit to obtain a winding body, wherein: the winding unit comprises a positive plate, a negative plate and two layers of diaphragms, the winding body comprises a first winding body and a second winding body, and the second winding body is formed by continuously winding on the first winding body; in at least one layer of the separator, the part of the first winding body is used as a first sub-separator, the part of the second winding body is used as a second sub-separator, and a first binder layer is arranged on the side, in contact with the negative electrode sheet, of the first sub-separator, wherein: the side, in contact with the negative plate, of the second sub-diaphragm is not provided with a binder layer; or a second binder layer is arranged on one side, in contact with the negative electrode plate, of the second sub-diaphragm, and the thickness of the second binder layer is smaller than that of the first binder layer. Compared with the prior art, the method has the advantages that the binder layer is formed on only one section of the winding body diaphragm, or the thickness of the binder layer formed on the two sections of the winding body diaphragms is smaller than that of the one section of the winding body, so that the problems of expansion and folding of the battery cell negative plate can be obviously improved, the lithium precipitation risk of the battery cell is reduced, the safety performance of the battery cell is improved, the reduction or early failure of the electrochemical performance of the battery cell is favorably prevented, and the cost of the diaphragm and the battery cell can be reduced.
In some embodiments of the present invention, before the winding, further comprising: and carrying out hot-pressing treatment on the joint of the first sub-diaphragm and the second sub-diaphragm so as to realize the hot-melt connection of the first sub-diaphragm and the second sub-diaphragm.
In some embodiments of the present invention, the winding further comprises, after completion of the winding: and carrying out hot-press molding on the wound body, wherein the hot-press molding temperature is 85-110 ℃, the pressure is 8000-11000 kgf, and the time is not less than 60s.
According to still another aspect of the present invention, a battery module is provided. According to an embodiment of the invention, the battery module comprises the winding battery cell or the winding battery cell prepared by the method for preparing the winding battery cell. All the features and effects described for the aforementioned winding cell and the aforementioned method for preparing a winding cell are also applicable to the battery module, and are not described herein again. Generally speaking, the battery module has the advantages of good volume stability and electrochemical stability, high safety, long service life and low cost.
According to yet another aspect of the present invention, a battery pack is provided. According to an embodiment of the present invention, the battery module includes the foregoing battery module. All the features and effects described for the battery module described above are also applicable to the battery pack, and are not described herein again.
According to another aspect of the invention, the invention provides an electric device. According to an embodiment of the invention, the electric equipment comprises the battery pack, the battery module, the winding battery core prepared by the method for preparing the winding battery core, or the winding battery core. All the features and effects described for the battery pack, the battery module, the method for preparing the winding battery core, and the winding battery core described above are also applicable to the electric device, and are not described herein again. Generally speaking, the electric equipment has better stability and lower safety risk in the using process.
Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
Drawings
The above and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:
fig. 1 is a schematic view of an overall structure of a jelly roll around which a cell is wound according to an embodiment of the present invention.
Fig. 2 is a schematic diagram of a winding structure of a wound battery cell according to an embodiment of the present invention.
Fig. 3 is a schematic structural diagram of a winding unit in a winding cell according to an embodiment of the present invention.
FIG. 4 is a schematic illustration of a comparative construction of adhesive layers for a first wrap and a second wrap in accordance with one embodiment of the present invention.
Fig. 5 is a schematic diagram showing a comparative structure of adhesive layers of a primary winding body and a secondary winding body according to still another embodiment of the present invention.
Fig. 6 is a schematic structural view of an overlapping region of a first sub-diaphragm and a second sub-diaphragm according to an embodiment of the present invention.
Fig. 7 is a schematic view of a winding structure of a wound cell according to still another embodiment of the present invention.
Fig. 8 is a schematic structural view of the positive electrode tab and the negative electrode tab provided with the thickness-reduced region according to one embodiment of the present invention.
Fig. 9 is a schematic structural view of the overall thickness distribution of the same layer of the membrane according to one embodiment of the invention.
Fig. 10 is a schematic structural view of the overall thickness distribution of the same layer of the membrane according to still another embodiment of the present invention.
Description of the drawings:
100-a winding; 10-a length of wound body; 20-two-stage winding; 30-a planar area; 40-a bending zone; a-a negative plate; b-positive plate; c-a separator; c 1-a first sub-membrane; c 2-a second sub-membrane; d 1-first binder layer; d 2-a second binder layer; w-width of the overlap region; s-a reduced thickness region.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention.
In the description of the present invention, the terms "first" and "second" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implying any number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," "secured," and the like are to be construed broadly and can, for example, be fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; they may be directly connected or indirectly connected through intervening media, or they may be connected internally or in any other suitable relationship, unless expressly stated otherwise. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations. In the present invention, unless otherwise expressly stated or limited, the first feature "on" or "under" the second feature may be directly contacting the first and second features or indirectly contacting the first and second features through an intermediate.
In one aspect, the present disclosure is directed to a wound cell. According to an embodiment of the present invention, as understood in conjunction with fig. 1-5, the wound cell includes: the winding body 100, wherein a winding unit (shown in fig. 3) of the winding body 100 comprises a negative electrode sheet a, a positive electrode sheet b and two layers of diaphragms c, the winding body 100 defines a first winding body 10 and a second winding body 20, and the second winding body 20 is formed by continuously winding on the first winding body 10; as will be understood with reference to fig. 4 to 5, of the at least one separator c, a first sub-separator c1 is a portion located in the first wound body 10, and a second sub-separator c2 is a portion located in the second wound body 20, and a first binder layer d1 is provided on a side of the first sub-separator c1 contacting the negative electrode sheet a, where: the side of the second sub-separator c2 in contact with the negative electrode sheet a is not provided with an adhesive layer (as shown in fig. 4); alternatively, the side of the second sub-separator c2 in contact with the negative electrode sheet a is provided with a second adhesive layer d2, and the thickness of the second adhesive layer d2 is smaller than that of the first adhesive layer d1 (as shown in fig. 5). The inventor finds that the swelling force and the wrinkles of the inner ring negative plate in the wound battery cell are more obvious in the lithium intercalation process, and the wrinkles of the negative plate are mainly concentrated on the inner ring of the battery cell. Compared with the existing winding battery cell, the invention can obviously improve the problems of expansion and folding of the battery cell cathode plate, reduce the risk of lithium precipitation of the battery cell, improve the safety performance of the battery cell, be beneficial to preventing the electrochemical performance of the battery cell from being reduced or losing efficacy in advance, and also reduce the cost of the diaphragm and the battery cell by only forming the binder layer on one section of the winding body diaphragm or enabling the thickness of the binder layer formed on the two sections of the winding body diaphragms to be smaller than that of one section of the winding body.
The winding cells according to the above-described embodiments of the present invention are described in detail below with reference to fig. 1 to 10.
According to an embodiment of the present invention, the ratio of the number of winding turns of the first wound body 10 to the number of winding turns of the second wound body 20 may be 0.2 to 2, and for example, may be 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, etc. The number of windings of the two-stage wound body 20 is the number of windings continued to be wound on the one-stage wound body 10. The inventor finds that based on the constraint of the winding structure of the battery cell and the battery cell shell, the swelling force borne by the inner ring negative plate is larger, the wrinkle is more serious, particularly the inner ring winding body with the winding number within 1/3 (particularly within 1/5) of the total winding number, and the swelling force borne by the outer ring negative plate and the wrinkle problem are gradually reduced along with the increase of the winding number. Preferably, the ratio of the number of winding turns of the first winding body 10 to the number of winding turns of the second winding body 20 may be 0.5 to 1, even if the number of winding turns of the first winding body is 1/3 to 1/2 of the total number of winding turns, thereby not only further improving the problems of swelling and wrinkling of the negative electrode sheet of the wound battery cell, but also better considering the costs of the separator and the battery cell.
According to the embodiment of the present invention, the first adhesive layer d1 and the second adhesive layer d2 may respectively and independently include a polymer adhesive, and it is understood that the first adhesive layer d1 and the second adhesive layer d2 may respectively and independently be pure adhesive layers, that is, may be formed by only a polymer adhesive, or may respectively and independently incorporate some other components, such as an inorganic (ceramic) material, etc., that is, the adhesive layers may be a composite layer formed by a polymer adhesive and an inorganic material. The kind of the polymer binder is not particularly limited, and those skilled in the art can flexibly select the polymer binder according to actual needs, for example, the polymer binders used for the first binder layer d1 and the second binder layer d2 may respectively and independently include at least one selected from polyvinylidene fluoride (PVDF), polyvinyl alcohol (PVA), and carboxymethyl cellulose (CMC). According to some specific examples of the present invention, the first binder layer d1 may further have inorganic particles dispersed therein; in addition, according to some specific examples of the present invention, inorganic particles may also be dispersed in the second adhesive layer d2, wherein the thermal stability, mechanical strength, and wettability of the separator may be more advantageously improved by adding the inorganic particles to the adhesive layer.
It should be noted that the types of the inorganic particles in the first binder layer d1 and the inorganic particles in the second binder layer d2 are not particularly limited, and may be flexibly selected by those skilled in the art according to actual needs, for example, the inorganic particles in the first binder layer d1 and the inorganic particles in the second binder layer d2 may respectively and independently include one or more selected from boehmite, alumina, and ZrO 2 And LLZTO (tantalum-doped lithium lanthanum zirconium oxide), wherein the selection of the above-mentioned kind of inorganic particles is more advantageous for improving the thermal stability, mechanical strength, and wettability of the separator, particularly when boehmite is included in the inorganic particles; when the inorganic particles comprise the LLZTO, the ionic conductivity of the separator can be further improved, and meanwhile, the adhesive layer can resist higher voltage and reduce electrochemical corrosion of the separator. In the present invention, the particle size of the inorganic particles may preferably be in the order of nanometers, and for example, may be not more than 200nm or 100nm, thereby being more advantageous in improving the flatness of the binder layer.
According to some embodiments of the present invention, the mass ratio of the inorganic particles to the polymer binder in the first binder layer d1 and the second binder layer d2 may be (0.1 to 9.9): (9.9 to 0.1), for example, each independently may be 0.1/9.9, 0.5/9.5, 1/9, 1.5/8.5, 2/8, 2.5/7.5, 3/7, 3.5/6.5, 4/6, 4.5/5.5, 5/5, 5.5/4.5, 6/4/6.5/3.5, 7/3, 8/2, 9/1, or 9.9/0.1, etc., wherein increasing the amount of the polymer binder in the binder layer is more advantageous for solving the problems of swelling and wrinkling of the negative electrode sheet, increasing the amount of the inorganic particles is more advantageous for improving the thermal stability, mechanical strength, and wettability of the separator, and considering that an excessive amount of the inorganic particles may affect the bonding strength of the separator and the negative electrode sheet, it may be preferable that the mass ratio of the inorganic particles to the polymer binder is not more than 8/2, for example, the mass ratio of the inorganic particles to the polymer binder may be (0.1 to 5): (5 to 9.9) and the like. According to a specific example of the present invention, when inorganic particles are dispersed in the first binder layer d1 or the second binder layer d2, the polymer binder layer used in the binder layer may preferably be PVDF, so that the binding ability of the binder layer may be further ensured, and the effect of the separator on improving the swelling and wrinkling of the negative electrode sheet may be ensured.
According to the embodiment of the present invention, the material of the diaphragm c is not particularly limited, and those skilled in the art can flexibly select the material according to actual needs, for example, the diaphragm c may be a PE film or a PP film, so that the diaphragm has both good corrosion resistance and good mechanical properties.
According to the embodiment of the present invention, it can be understood that the positive electrode sheet b and the negative electrode sheet a in the first wound body 10 and the second wound body 20 are continuous and integrally molded structures without being cut. In addition, it can be understood that the thickness of the first adhesive layer d1 and the thickness of the second adhesive layer d2 may be fixed values independently (as understood by referring to fig. 4 and 5), or may be gradually reduced with the increase of the number of winding layers, for example, according to a specific example of the present invention, the thickness of the first adhesive layer d1 may be fixed values, and the thickness of the second adhesive layer d2 may be gradually reduced with the increase of the number of winding layers, but considering that the gradual change state of the adhesive layer thickness may cause difficulty in inserting the winding body into the casing or cause a large residual space in the casing after the winding body is installed in the casing, which affects the processability and electrochemical performance of the battery cell, the thickness of the first adhesive layer d1 and the thickness of the second adhesive layer d2 may be fixed values independently in the present invention. In addition, the first sub-diaphragm c1 and the second sub-diaphragm c2 may preferably be made of the same material, so that the uniformity of the entire diaphragm may be further ensured.
According to some embodiments of the present invention, in the same layer of the diaphragm c, the first sub-diaphragm c1 and the second sub-diaphragm c2 may be of a continuous uninterrupted structure, i.e., without cutting. According to the invention, the first section of winding body and the second section of winding body are formed simultaneously by selecting the diaphragms which are not cut, so that not only can the continuity and stability of the whole winding body be ensured, but also the probability that the liquid shortage and/or the lengthening of an ion transmission path possibly occur at the junction of the first sub-diaphragm c1 and the second sub-diaphragm c2 and the risk of influencing the electrochemical performance of the battery are remarkably reduced.
According to still other embodiments of the present invention, referring to fig. 4, it can be understood that, in the same layer of the diaphragm c, the first sub-diaphragm c1 and the second sub-diaphragm c2 may also be bonded, that is, the same layer of the diaphragm c may be formed by splicing two sub-diaphragms. Compared with the method that the binder layer is arranged in a partial area of the same diaphragm or the two binder layers with different thicknesses are arranged on the same diaphragm at the same time, the method and the device are more beneficial to actual operation and reduction of difficulty of the preparation process by separately carrying out (gluing) operation on the two sub-diaphragms and then splicing, and are also more beneficial to better controlling the thicknesses of the binder layers and the diaphragm thicknesses in different areas, thereby being more beneficial to pertinently solving the problems of expansion and wrinkling of the cathode piece of the winding battery cell.
According to an embodiment of the present invention, the connection manner of the first sub-diaphragm c1 and the second sub-diaphragm c2 in the present invention is not particularly limited, and those skilled in the art can flexibly select according to actual needs, for example, the two may be connected by an adhesive layer or by hot melting. The first sub-diaphragm c1 and the second sub-diaphragm c2 are preferably in hot-melt connection, and the inventor finds that the connection area of the first sub-diaphragm and the second sub-diaphragm is larger in thickness relative to other areas, so that the problems of liquid shortage, lithium precipitation and the like caused by the fact that the ion transmission path is lengthened or lithium ions cannot be uniformly inserted into a pole piece due to the increase of the thickness of the diaphragms are easily caused.
According to the embodiment of the present invention, as understood by referring to fig. 2 and 6, the first sub-diaphragm c1 and the second sub-diaphragm c2 may be overlapped and bonded, and the width w of the overlapped region may be 2 to 5mm, for example, 2.5mm, 3mm, 3.5mm, 4mm, or 4.5mm, and the inventors found that if the width of the overlapped region is too small, it is difficult to ensure the bonding strength between the two, and if the width of the overlapped region is too large, the risk of the problems of the battery cell liquid shortage, the influence of the ion transmission path lengthening on the charge-discharge efficiency, the lithium deposition, and the like, and the negative influence generated thereby are significantly increased. Wherein the winding direction shown in fig. 2 is clockwise.
According to some embodiments of the present invention, the hot-melt connection between the first sub-diaphragm c1 and the second sub-diaphragm c2 can be performed by performing a hot-pressing process on the joint of the first sub-diaphragm c1 and the second sub-diaphragm c2, which is not only beneficial to achieving the welding between the two, achieving the integrated bonding effect, ensuring the bonding strength between the two, but also improving the flatness of the bonding (overlapping) area between the two. Further, the temperature of the hot pressing treatment can be 250-300 ℃, for example, 260 ℃, 270 ℃, 280 ℃ or 290 ℃ and the like; the pressure of the hot pressing may be 3000 to 5000kgf, and for example, 3200kgf, 3400kgf, 3600kgf, 3800kgf, 4000kgf, 4200kgf, 4400kgf, 4600kgf or 4800 kgf; the time can be 5-10 s, for example, 6s or 8s, and the like, the melting point of the diaphragm selected in the battery field is usually not more than 200 ℃, for example, the melting point of PE is about 112 ℃, and the melting point of PP is about 165 ℃.
According to the embodiment of the present invention, it can be understood that the wound cell in the present invention can be used as a cylindrical battery or a square battery, and it can be understood with reference to fig. 1 that when the wound cell is used as a square battery, the wound body 100 may include a flat region 30 and a bending region 40 (i.e., a corner region), and in order to further reduce the adverse effect that the thickness and the flatness of the overlapping connection region of the first sub-separator and the second sub-separator may have on the cell, the overlapping region where the first sub-separator c1 and the second sub-separator c2 are connected may be preferably disposed at the bending region.
According to the embodiment of the present invention, as understood by referring to fig. 2 and 6, the thickness difference between the overlapping region and the first sub-separator c1 and the thickness difference between the overlapping region and the second sub-separator c2 may not be greater than 10 μm, and considering that the thickness of the separator is usually 10 to 13 μm, and the thickness of the adhesive layer disposed on the separator facing the negative electrode sheet in the conventional wound cell is usually 1 to 3 μm (after rolling), by controlling the thickness difference between the overlapping region and the first sub-separator and the thickness difference between the overlapping region and the second sub-separator to not be greater than 10 μm, the risk of the problems of cell starvation, influence on charge-discharge efficiency and lithium deposition due to the lengthening of the ion transport path, and the negative effects caused thereby, the negative effects that the adhesive region may have on the electrochemical performance of the battery can be further reduced on the basis of having better adhesive strength between the two sub-separators.
According to an embodiment of the present invention, as understood in conjunction with fig. 2 and 7, in the overlapping region, the edge shape of the first sub-diaphragm c1 and the edge shape of the second sub-diaphragm c2 are not particularly limited, and those skilled in the art may flexibly select according to actual needs, for example, the edge of the first sub-diaphragm c1 and the edge of the second sub-diaphragm c2 may be independently linear, zigzag, or wavy, respectively, in the width direction of the diaphragm.
According to the embodiment of the present invention, as can be understood with reference to fig. 8, in consideration of the problems that the overlapping region of the first sub-separator c1 and the second sub-separator c2 is liable to suffer from a shortage of liquid due to an increase in thickness, the ion transport path is lengthened due to an increase in the thickness of the separators, or lithium ions are not uniformly inserted into the pole pieces to cause lithium deposition, etc., at least one of the positive pole piece b and the negative pole piece a may be provided with a reduced thickness region S corresponding to the overlapping region on the side facing the separator c, wherein the problems of shortage of liquid and lengthening of the ion transport path may be effectively avoided by providing the reduced thickness region. Further, the total thickness of the reduced thickness region S may be 1 to 1.2 times of the thickness of the overlapping region, for example, may be 1.05 times, 1.1 times or 1.15 times of the thickness of the overlapping region, and the width of the reduced thickness region S may be not less than the width w of the overlapping region, and preferably 1 to 1.2 times of the width of the overlapping region. More preferably, the positive plate b and the negative plate a may be both provided with a thickness reduction region, the thickness reduction region on the positive plate b may be (0.7 ± 0.1) times the thickness of the overlapping region, and the thickness reduction region on the negative plate a may be (0.3 ± 0.1) times the thickness of the overlapping region, in the existing electric core, the thickness of the positive plate is usually about 1.5 times the thickness of the negative plate.
According to the embodiment of the present invention, the thickness of the first sub-diaphragm c1 and the thickness of the second sub-diaphragm c2 may be equal or may not be equal. When the thicknesses of the two are equal, only one specification of the diaphragm needs to be provided.
According to the embodiment of the invention, referring to fig. 9, it is understood that when the side of the second sub-diaphragm c2, which is in contact with the negative electrode sheet a, is not provided with the adhesive layer, the total thickness of the first sub-diaphragm c1 and the first adhesive layer d1 may be equal to the thickness of the second sub-diaphragm c2, and at this time, the thickness of the same layer of diaphragm on the whole may be ensured to be unchanged, so that the problem that the winding body is difficult to enter the case or the residual space in the battery cell case is large due to the thickness change of the diaphragm can be effectively avoided.
According to the embodiment of the invention, as can be understood by referring to fig. 10, the total thickness of the first sub-diaphragm c1 and the first adhesive layer d1 may be equal to the total thickness of the second sub-diaphragm c2 and the second adhesive layer d2, and at this time, the thickness of the same layer of diaphragm may be ensured to be unchanged, so that the problem that the winding body is difficult to enter the case or the residual space in the battery cell case is large due to the thickness change of the diaphragm can be effectively avoided.
According to the embodiment of the present invention, it can be understood that the wound battery cell may further include a cell casing for accommodating the wound body 100, wherein the specific type of the cell casing is not particularly limited, and a person skilled in the art may flexibly select the cell casing according to actual needs, for example, the cell casing may be a square cell casing. In addition, it is understood that the side of the separator facing the positive electrode sheet may also be provided with an adhesive layer, preferably in a segment of the winding body, so that the positive electrode sheet and the negative electrode sheet can be tightly adhered together through the separator after hot pressing, and the problems of expansion and wrinkling of the inner ring negative electrode sheet can be further improved.
Based on the same inventive concept, according to yet another aspect of the present invention, a method of manufacturing a wound cell is proposed. According to an embodiment of the invention, as understood in connection with fig. 1-5, the method comprises: the wound body 100 is obtained by winding with a winding unit, in which: the winding unit comprises a positive plate b, a negative plate a and two layers of diaphragms c, the winding body 100 comprises a first winding body 10 and a second winding body 20, and the second winding body 20 is formed by continuously winding on the first winding body 10; in at least one layer of the separator c, a part of the first sub-separator c1 located in the first winding body 10 is a first sub-separator c1, a part of the second winding body 20 is a second sub-separator c2, and a first adhesive layer d1 is arranged on the side, in contact with the negative electrode sheet a, of the first sub-separator c1, wherein: the side of the second sub-diaphragm c2, which is in contact with the negative electrode sheet a, is not provided with a binder layer; or a second adhesive layer d2 is arranged on one side of the second sub-membrane c2, which is in contact with the negative electrode sheet a, and the thickness of the second adhesive layer d2 is smaller than that of the first adhesive layer d 1. Compared with the prior art, the method has the advantages that the binder layer is formed on only one section of the winding body diaphragm, or the thickness of the binder layer formed on the two sections of the winding body diaphragms is smaller than that of the one section of the winding body, so that the problems of expansion and folding of the battery cell negative plate can be obviously improved, the lithium precipitation risk of the battery cell is reduced, the safety performance of the battery cell is improved, the reduction or early failure of the electrochemical performance of the battery cell is favorably prevented, and the cost of the diaphragm and the battery cell can be reduced. In addition, it should be further noted that the method for preparing the winding battery core and the winding battery core described above are proposed based on the same inventive concept, and all the features and effects described for the winding battery core described above are also applicable to the method for preparing the winding battery core, and are not repeated herein.
According to an embodiment of the present invention, before the winding, the method may further include: and performing hot-pressing treatment on the joint of the first sub-diaphragm c1 and the second sub-diaphragm c2, so as to realize hot-melt connection of the first sub-diaphragm and the second sub-diaphragm, wherein the temperature, the pressure and the time of the hot-pressing treatment and the beneficial effect of controlling the corresponding hot-pressing treatment conditions are described in detail in the foregoing part, and are not repeated here. In addition, if the width of the overlapping area of the hot-melt connection of the diaphragm after the hot-pressing treatment is increased, the width of the diaphragm in the overlapping area can be kept consistent with that in other areas by further comprising a cutting treatment.
According to an embodiment of the present invention, after the winding is completed, the method may further include: the winding body is subjected to hot press molding, so that on one hand, the full contact between the negative plate and the bonding layer can be facilitated, the binding effect of the diaphragm on the negative plate is improved, and the problems of expansion and wrinkling of the negative plate are solved; on the other hand, the wound body may be pressed into a desired shape according to actual needs, for example, a shape as shown in fig. 1. Further, the temperature of the hot press molding may be 85 to 110 ℃, for example, 90 ℃, 95 ℃, 100 ℃, 105 ℃ or the like; the pressure may be 8000 to 11000kgf, for example, 8500kgf, 9000kgf, 9500kgf, 10000kgf or 10500 kgf; the time can be not less than 60s, for example, 1.5min, 2min or 5min, etc., and by controlling the temperature, pressure and time of the hot press molding to be within the ranges, the binding effect of the adhesive layer on the expansion and wrinkle of the negative electrode sheet can be further ensured on the basis of not affecting the stability of the diaphragm, and the winding body structure with the expected shape can be obtained more favorably, so that the assembly of the shell is more favorably realized.
It should be noted that the method for preparing the winding electric core and the winding electric core described above are proposed based on the same inventive concept, and all the features and effects described for the winding electric core described above are also applicable to the method for preparing the winding electric core, and are not described in detail herein.
According to still another aspect of the present invention, a battery module is provided. According to an embodiment of the invention, the battery module comprises the winding battery cell or the winding battery cell prepared by the method for preparing the winding battery cell. It should be noted that all the features and effects described for the aforementioned winding cell and the aforementioned method for preparing the winding cell are also applicable to the battery module, and are not described herein again. Generally speaking, the battery module not only has better volume stability and electrochemical stability, but also has high safety, longer service life and lower cost.
According to yet another aspect of the present invention, a battery pack is provided. According to an embodiment of the present invention, the battery module includes the foregoing battery module. It should be noted that all the features and effects described for the aforementioned battery module are also applicable to the battery pack, and are not described herein again.
According to yet another aspect of the present invention, an electrical device is provided. According to an embodiment of the invention, the electric equipment comprises the battery pack, the battery module, the winding battery core prepared by the method for preparing the winding battery core, or the winding battery core. It should be noted that all the features and effects described for the foregoing battery pack, battery module, method for preparing winding battery cell, and winding battery cell are also applicable to the electric device, and are not described herein again. Generally speaking, the electric equipment has better stability and lower safety risk in the using process. In addition, it should be noted that the specific type of the electric device is not particularly limited, and those skilled in the art can flexibly select the electric device according to actual needs, for example, the electric device may be a vehicle, an electronic device, or a domestic electric appliance.
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.
Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.

Claims (17)

1. A wound cell, comprising: the winding unit of the winding body comprises a positive plate, a negative plate and two layers of diaphragms, the winding body defines a first winding body and a second winding body, and the second winding body is formed by continuously winding on the first winding body; in at least one layer of the separator, the part of the first winding body is used as a first sub-separator, the part of the second winding body is used as a second sub-separator, and a first binder layer is arranged on the side, in contact with the negative electrode sheet, of the first sub-separator, wherein:
the side, in contact with the negative plate, of the second sub-diaphragm is not provided with a binder layer; alternatively, the first and second electrodes may be,
and a second binder layer is arranged on one side of the second sub-diaphragm, which is in contact with the negative plate, and the thickness of the second binder layer is smaller than that of the first binder layer.
2. The winding battery cell of claim 1, wherein the ratio of the number of windings of the first winding body to the number of windings of the second winding body is 0.2-2.
3. The winding battery cell of claim 2, wherein the ratio of the number of winding turns of the first segment of winding body to the number of winding turns of the second segment of winding body is 0.5-1.
4. The wound cell of any of claims 1-3, wherein the first adhesive layer and the second adhesive layer each independently comprise a polymeric adhesive.
5. The wound cell of claim 4, wherein at least one of the following conditions is met:
the polymer binder includes at least one selected from the group consisting of polyvinylidene fluoride, polyvinyl alcohol, and carboxymethyl cellulose;
inorganic particles are also dispersed in the first adhesive layer;
inorganic particles are also dispersed in the second binder layer.
6. The winding cell of claim 5, located inThe inorganic particles in the first binder layer and the inorganic particles in the second binder layer each independently comprise a material selected from boehmite, alumina, zrO 2 And LLZTO; and/or the presence of a gas in the gas,
in the first binder layer and the second binder layer, the mass ratio of the inorganic particles to the polymer binder is (0.1 to 9.9): (9.9-0.1).
7. The wound cell of claim 1 or 6, wherein at least one of the following conditions is met:
the diaphragm is a PE film or a PP film;
in the same layer of the diaphragm, the first sub-diaphragm and the second sub-diaphragm are of a continuous uninterrupted structure;
in the same layer of diaphragm, the first sub-diaphragm is bonded and connected with the second sub-diaphragm.
8. The wound cell of claim 7, wherein the first sub-separator is thermally fused to the second sub-separator; and/or the presence of a gas in the gas,
the first sub-diaphragm and the second sub-diaphragm are overlapped, bonded and connected, and the width of an overlapping area is 2-5 mm.
9. The wound cell of claim 8, wherein at least one of the following conditions is met:
the hot-melt connection is completed by carrying out hot-pressing treatment on the joint of the first sub-diaphragm and the second sub-diaphragm, wherein the temperature of the hot-pressing treatment is 250-300 ℃, the pressure is 3000-5000 kgf, and the time is 5-10 s;
the thickness difference between the thickness of the overlapped area and the thickness of the first sub-diaphragm and the thickness difference between the thickness of the overlapped area and the thickness of the second sub-diaphragm are not more than 10 μm;
in the overlapping region, the edge of the first sub-diaphragm and the edge of the second sub-diaphragm are respectively and independently linear, zigzag or wavy along the width direction of the diaphragm;
the winding body comprises a plane area and a bending area, and the overlapping area is positioned in the bending area;
at least one of the positive electrode tab and the negative electrode tab is provided with a thickness-reduced region corresponding to the overlapping region on a side facing the separator.
10. The wound cell of claim 9, wherein the total reduced thickness of the reduced thickness region is 1 to 1.2 times the thickness of the overlap region, and the width of the reduced thickness region is not less than the width of the overlap region; and/or the presence of a gas in the gas,
the positive pole piece with all be equipped with on the negative pole piece thickness reduction district, be located the reduction thickness in thickness reduction district on the positive pole piece does overlap region thickness (0.7 +/-0.1) times, is located the reduction thickness in thickness reduction district on the negative pole piece does overlap region thickness (0.3 +/-0.1) times.
11. The winding cell of claim 1 or 10, wherein one of the following conditions is met:
the thickness of the first sub-diaphragm is equal to that of the second sub-diaphragm;
the side, in contact with the negative electrode piece, of the second sub-diaphragm is not provided with a binder layer, and the total thickness of the first sub-diaphragm and the first binder layer is equal to the thickness of the second sub-diaphragm;
the total thickness of the first sub-diaphragm and the first adhesive layer is equal to the total thickness of the second sub-diaphragm and the second adhesive layer.
12. A method of making a wound cell, comprising: winding by using a winding unit to obtain a winding body, wherein:
the winding unit comprises a positive plate, a negative plate and two layers of diaphragms, the winding body comprises a first winding body and a second winding body, and the second winding body is formed by continuously winding on the first winding body; in at least one layer of the separator, the part of the first winding body is used as a first sub-separator, the part of the second winding body is used as a second sub-separator, and a first binder layer is arranged on the side, in contact with the negative electrode sheet, of the first sub-separator, wherein:
the side, in contact with the negative plate, of the second sub-diaphragm is not provided with a binder layer; alternatively, the first and second electrodes may be,
and a second binder layer is arranged on one side of the second sub-diaphragm, which is in contact with the negative plate, and the thickness of the second binder layer is smaller than that of the first binder layer.
13. The method of claim 12, further comprising, prior to said winding:
and carrying out hot-pressing treatment on the joint of the first sub-diaphragm and the second sub-diaphragm so as to realize the hot-melt connection of the first sub-diaphragm and the second sub-diaphragm.
14. The method of claim 12 or 13, further comprising, after completion of the winding: and carrying out hot-press molding on the winding body, wherein the temperature of the hot-press molding is 85-110 ℃, the pressure is 8000-11000 kgf, and the time is not less than 60s.
15. A battery module comprising the wound cell of any one of claims 1 to 11 or the wound cell produced by the method of any one of claims 12 to 14.
16. A battery pack comprising the battery module according to claim 15.
17. An electric device, comprising the battery pack of claim 16, or the battery module of claim 15, or a wound cell prepared by the method of any one of claims 12 to 14, or a wound cell of any one of claims 1 to 11.
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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2007071122A1 (en) * 2005-12-23 2007-06-28 Shenzhen Bak Battery Co., Ltd A wind type lithium ion battery with a soft package case and a method of manufacture the same
CN201345383Y (en) * 2008-08-26 2009-11-11 比亚迪股份有限公司 Lithium ion secondary battery
JP2013045636A (en) * 2011-08-24 2013-03-04 Hitachi Vehicle Energy Ltd Square battery and manufacturing method therefor
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