CN116581396A - Battery core and electric equipment - Google Patents

Battery core and electric equipment Download PDF

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Publication number
CN116581396A
CN116581396A CN202310835182.3A CN202310835182A CN116581396A CN 116581396 A CN116581396 A CN 116581396A CN 202310835182 A CN202310835182 A CN 202310835182A CN 116581396 A CN116581396 A CN 116581396A
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positive electrode
active material
negative electrode
section
electrode active
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CN202310835182.3A
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CN116581396B (en
Inventor
柳宁
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Ningde Amperex Technology Ltd
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Ningde Amperex Technology Ltd
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Priority to CN202410309022.XA priority Critical patent/CN118173903A/en
Priority to CN202310835182.3A priority patent/CN116581396B/en
Publication of CN116581396A publication Critical patent/CN116581396A/en
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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
    • 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
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • 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)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Secondary Cells (AREA)
  • Battery Electrode And Active Subsutance (AREA)

Abstract

The application provides a battery cell and electric equipment. The battery cell comprises an electrode assembly and a protective layer; the electrode assembly is of a winding type structure and is provided with a first bending area and a flat area, the electrode assembly comprises a negative electrode plate and a positive electrode plate, the negative electrode plate is provided with a negative electrode winding starting end, the positive electrode plate is provided with a positive electrode current collector and a first positive electrode active material layer arranged on one side of the positive electrode current collector facing a winding axis, the first positive electrode active material layer comprises a plurality of positive electrode bending parts which are positioned in the first bending area and are sequentially arranged from inside to outside, the innermost positive electrode bending part of the first bending area is a first positive electrode active material part, the first positive electrode active material part is arranged facing the negative electrode winding starting end, and the first positive electrode active material layer is provided with a containing groove for containing at least part of the protective layer; and/or the negative electrode sheet is provided with a recess for accommodating at least part of the protective layer; the safety of the battery cell can be improved, and the problem that the volume energy density of the battery cell is reduced due to the arrangement of the protective layer can be solved.

Description

Battery core and electric equipment
Technical Field
The application relates to the technical field of batteries, in particular to a battery cell and electric equipment.
Background
The battery is widely applied to the fields of portable electronic equipment, electric vehicles, electric tools, unmanned aerial vehicles, energy storage equipment and the like. As application environments and conditions become more complex, higher demands are placed on the energy density of the cells.
Disclosure of Invention
The embodiment of the application provides a battery cell and electric equipment, which are used for solving the problem of low energy density of the battery cell.
In a first aspect, an embodiment of the present application provides a battery cell including an electrode assembly and a protective layer; the electrode assembly is of a winding type structure, the electrode assembly is provided with a first bending area and a flat area, the first bending area is connected to one end of the flat area along a first direction, the electrode assembly comprises a negative electrode plate and a positive electrode plate, the negative electrode plate is provided with a negative electrode winding starting end, the positive electrode plate is provided with a positive electrode current collector and a first positive electrode active material layer, the first positive electrode active material layer is arranged on one side of the positive electrode current collector facing to a winding axis of the electrode assembly, and the first positive electrode active material layer comprises a plurality of positive electrode bending parts which are positioned in the first bending area and are sequentially arranged from inside to outside, and the positive electrode bending part positioned at the innermost side of the first bending area is arranged facing to the negative electrode winding starting end; wherein the anode bending part positioned at the innermost side is provided with an accommodating groove; and/or the winding start end is provided with a concave part, at least part of the protective layer is positioned in the accommodating groove and/or the concave part, and the first direction is perpendicular to the extending direction of the winding axis.
In the above technical scheme, the positive electrode bending part located at the innermost side of the first bending region is arranged facing the negative electrode winding starting end, and the protective layer is arranged between the first positive electrode active material part and the negative electrode winding starting end, so that the protective layer can limit the movement of ions of the first positive electrode active material part to the negative electrode winding starting end, the risk of lithium precipitation of the wound electrode assembly at the corresponding positions of the first positive electrode active material part and the negative electrode winding starting end is reduced, and the safety of the battery cell is improved. The positive electrode bending part at the innermost side of the first bending area is provided with a containing groove, and/or the negative electrode winding starting end of the negative electrode plate is provided with a concave part for containing the protective layer, so that the problem that the size of the battery cell is excessively increased due to the arrangement of the protective layer is solved, and the problem that the volume energy density of the battery cell is reduced due to the arrangement of the protective layer is solved.
In some embodiments of the first aspect of the present application, the protective layer includes a first segment located at the first bending region, the first segment being located between the first positive electrode active material portion and the negative electrode winding start end.
In the above technical scheme, the first section of the protective layer is located in the first bending region, and the first section can effectively limit the movement of ions of the first positive electrode active material part to the starting end of the negative electrode winding, so that the risk of lithium precipitation of the electrode assembly at the starting end of the negative electrode winding is effectively reduced, and the safety performance of the battery cell is improved.
In some embodiments of the first aspect of the present application, the protective layer further includes a second section, the second section being located in the flat region, the second section being connected to one end of the first section.
In the above technical scheme, the protective layer further comprises a second section, so that the area that the protective layer can cover is larger, ions of the positive plate can be better limited to move towards the starting end of the negative electrode winding, the risk of lithium precipitation of the electrode assembly at the starting end of the negative electrode winding is further reduced, and the safety performance of the battery cell is improved. The arrangement of the second section can also increase the connection area of the protective layer, and is favorable for the stable connection of the protective layer and other structures.
In some embodiments of the first aspect of the present application, the protective layer further includes a third section, where the third section is located in the flat area, and the third section is connected to the other end of the first section, and is disposed opposite to the third section along a second direction, where the extending direction of the winding axis, the first direction, and the second direction are perpendicular to each other.
Among the above-mentioned technical scheme, the protective layer still includes the third section, can further increase the coverage area of protective layer, and the ion of restriction positive plate that can be better removes to negative pole winding initiating terminal, further reduces electrode assembly and separates the risk of lithium at negative pole winding initiating terminal, improves the security performance of electric core. The arrangement of the third section can further increase the connection area of the protective layer, and is favorable for stable connection of the protective layer and other structures.
In some embodiments of the first aspect of the present application, the protective layer is disposed on the first positive electrode active material layer.
Among the above-mentioned technical scheme, the protective layer sets up in first positive pole active material layer, makes things convenient for the protective layer fixed, also makes the protective layer can better restrict the ion of positive plate to the removal of negative pole winding initiating terminal to reduce the risk that electrode assembly was lithium at negative pole winding initiating terminal.
In some embodiments of the first aspect of the present application, a surface of the first positive electrode active material layer facing the winding axis is provided with the accommodating groove, and the protective layer is at least partially accommodated in the accommodating groove.
According to the technical scheme, the protective layer is at least partially contained in the containing groove of the first positive electrode active material layer, so that the problem that the size of the battery cell is excessively increased due to the arrangement of the protective layer is solved, and the problem that the volume energy density of the battery cell is reduced due to the arrangement of the protective layer is solved.
In some embodiments of the first aspect of the present application, the protective layer is completely contained within the containing groove.
Among the above-mentioned technical scheme, the protective layer holds in the holding tank completely, and the setting of protective layer can not increase the size of electric core in arbitrary direction, then electrode assembly can not lead to the size increase because of being provided with the protective layer to avoid leading to the problem that the volume energy density of electric core reduces because of setting up the protective layer.
In some embodiments of the first aspect of the present application, the first positive electrode active material layer further includes a second positive electrode active material portion, the second positive electrode active material portion being located in the flat region; the negative electrode sheet comprises a negative electrode winding initial section positioned in a flat area, one end of the negative electrode winding initial section, which is close to the first positive electrode active material part, is the negative electrode winding initial end, the second positive electrode active material part is positioned on one side of the negative electrode winding initial section along a second direction, and the extending direction of the winding axis, the first direction and the second direction are perpendicular to each other; the protective layer includes a first section located between the first positive electrode active material portion and the negative electrode winding start end, and a second section located in the flat region and connected to one end of the first section, at least part of the second section being located between the negative electrode winding start end and the second positive electrode active material portion.
In the above technical scheme, the first section of the protective layer is located between the first positive electrode active material part and the negative electrode winding starting end, the second section is located between the negative electrode winding starting end and the second positive electrode active material part, and the coverage area of the protective layer can be increased, so that ions of the positive electrode plate can be better limited to move to the negative electrode winding starting end, the risk of lithium precipitation of the electrode assembly in the negative electrode winding starting end is reduced, and the safety performance of the battery cell is improved.
In some embodiments of the first aspect of the present application, the negative electrode sheet is provided with the recess including a first recess provided on a side of the negative electrode winding start section facing the second positive electrode active material portion, a projection of the second section being located at least partially within the first recess as viewed in the second direction, the first recess extending to the negative electrode winding start end in the first direction.
In the above technical solution, the side of the cathode winding start section facing the second anode active material portion is provided with the first recess extending to the cathode winding start end, and the projection of the second section is at least partially located in the first recess, so that the second section can be at least partially accommodated in the first recess, which is favorable for alleviating the problem that the size of the battery cell excessively increases in the second direction due to the arrangement of the protection layer, thereby alleviating the problem that the volumetric energy density of the battery cell decreases due to the arrangement of the protection layer. The problem that the second section extends to the flat area to cause the electrode assembly thickness difference to be large can be relieved, and the flatness of the battery cell is effectively improved.
In some embodiments of the first aspect of the present application, a surface of the first positive electrode active material layer facing the winding axis is provided with the accommodating groove, and the second segment is located in the accommodating groove; in the second direction, the thickness of the second section is T 1 The depth of the part of the accommodating groove for accommodating the second section is T 2 The depth of the first concave part is T 3 ，5μm≤T 1 ≤T 2 +T 3 。
In the technical scheme, if T 1 The thickness of the second section is smaller than 5 μm, and the movement of ions to the winding start end of the anode cannot be effectively restricted, if T 1 ＞T 2 +T 3 The second segment cannot be completely accommodated in the space defined by the first recess and the accommodating groove, which leads to an increase in the size of the cell in the second direction, and thus 5 μm. Ltoreq.T 1 ≤T 2 +T 3 The lithium ion battery cell structure has the advantages that the protective layer can effectively limit ions to move towards the winding starting end of the negative electrode, the lithium ion precipitation problem is relieved, the safety performance of the battery cell is improved, the second section can be completely contained in a space defined by the containing groove and the first concave part together, the size of the battery cell along the second direction is not increased, the problem that the size of the battery cell along the second direction is increased due to the arrangement of the protective layer is relieved, and therefore the problem that the volume energy density of the battery cell is reduced due to the arrangement of the protective layer is relieved.
In some embodiments of the first aspect of the present application, a surface of the first positive electrode active material layer facing the winding axis is provided with the accommodating groove, and the second segment is located in the accommodating groove; the electrode assembly further includes a first separator, the battery cell further includes a fixing member, the first separator is disposed on a side of the negative electrode winding start section facing the second positive electrode active material portion in the second direction, and the fixing member is configured to fix the first separator to the negative electrode winding start section; the fixing piece comprises a first connecting part positioned in the first concave part, the first isolating film comprises a first separating part positioned in the first concave part and overlapped with the first connecting part along the second direction, and the thickness of the second section is T along the second direction 1 The depth of the part of the accommodating groove for accommodating the second section is T 2 The depth of the first concave part is T 3 The thickness of the first partition part is T 4 The thickness of the first connecting part is T 5 ，T 2 +T 3 ≥T 1 +T 4 +T 5 。
Among the above-mentioned technical scheme, through fixed with first barrier film be fixed in negative pole winding initial section, be favorable to alleviating first barrier film and remove between positive plate and negative plate, produce the risk of fold, reduce the risk of electric core short circuit to improve the security performance of electric core. If it is T 2 +T 3 ＜T 1 +T 4 +T 5 That is, the sum of the depth of the accommodating groove and the depth of the first recess is smaller than the sum of the thickness of the second section, the thickness of the first partition portion and the thickness of the first connection portion, so that the second section, the first partition portion and the first connection portion cannot be completely accommodated in the space defined by the accommodating groove and the first recess in the second direction, and the size of the battery cell in the second direction is increased due to the arrangement of the protective layer, so that the volume energy density of the battery cell is reduced. Thus T 2 +T 3 ≥T 1 +T 4 +T 5 So that the second segment, the first partition portion, and the first connection portion are completely accommodated in the space defined by the accommodating groove and the first recess portion together in the second direction without increasing the size of the electrode assembly in the second direction.
In some embodiments of the first aspect of the present application, at least a portion of the second section overlaps the anode winding start section as viewed in the second direction, and a distance between an end of the second section facing away from the first section and the anode winding start end in the first direction is W 1 The first concave part has a size W 2 ，0≤W 2 -W 1 ≤0.5mm。
In the above technical scheme, if W 2 -W 1 The size of the first concave part is far larger than the size of the overlapped area of the second section and the cathode winding initial section, thereby increasing the processing difficulty and reducing the cathode active material quality of the cathode winding initial section. W is more than or equal to 0 2 -W 1 And the size of the overlapping area of the second section and the cathode winding initial section along the first direction is close to the size of the first concave part, so that the risk of lithium precipitation can be reduced.
In some embodiments of the first aspect of the present application, a distance between an end of the second section facing away from the first section and the winding start end of the negative electrode is W in the first direction 1 ，0.3mm≤W 1 ≤25mm。
In the above technical scheme, if W 1 < 0.3mm, viewed in the second directionThe second section and the cathode winding start section overlap in a smaller size, and the movement of ions of the positive electrode sheet to the cathode winding start end cannot be well restricted, if W 1 The overlapping dimension of the second section and the negative electrode winding initiation section is too large, as seen in the second direction, to make the positive electrode winding initiation section too much positive electrode active material not exert its effect, thus reducing the energy density of the cell. Thus, 0.3 mm.ltoreq.W 1 The second section can effectively limit the movement of ions of the positive plate to the starting end of the negative winding, and reduce the risk of lithium precipitation, so that the safety performance of the battery cell is improved, and the positive active material of the positive winding starting section can play a role to a greater extent, so that the battery cell has higher energy density and capacity.
In some embodiments of the first aspect of the present application, the positive electrode sheet has a positive electrode winding start end, and an end of the second positive electrode active material portion facing away from the first positive electrode active material portion extends to the positive electrode winding start end in the first direction.
In the above technical scheme, one end of the second positive electrode active material part deviating from the first positive electrode active material part extends to the positive electrode winding starting end, so that the positive electrode active material of the positive electrode winding starting section has larger quality, and the energy density of the battery core is improved.
In some embodiments of the first aspect of the present application, the first positive electrode active material layer further comprises a third positive electrode active material portion, the third positive electrode active material portion being located in the flat region; the third positive electrode active material part is positioned on the other side of the negative electrode winding starting section along the second direction; the protective layer further includes a third segment located in the flat region and connected to the other end of the first segment, at least a portion of the third segment being located between the winding start segment and the third positive electrode active material portion.
In the above technical scheme, the protective layer further comprises a third section at least partially positioned between the winding initial section and the third positive electrode active material part, and the coverage area of the protective layer can be further increased, so that ions of the positive electrode sheet are better limited to move towards the negative electrode winding initial section, the risk of lithium precipitation of the electrode assembly in the negative electrode winding initial section is reduced, and the safety performance of the battery cell is improved.
In some embodiments of the first aspect of the present application, the negative electrode sheet is provided with the recess, the recess further includes a second recess provided on a side of the negative electrode winding start section facing the third positive electrode active material portion, a projection of the third section being located at least partially within the second recess as viewed in the second direction, the second recess extending to the negative electrode winding start end in the first direction.
In the above technical solution, the side of the cathode winding start section facing the third cathode active material portion is provided with the second recess extending to the cathode winding start end, and the projection of the third section is at least partially located in the second recess, so that the third section can be at least partially contained in the second recess, which is favorable for alleviating the problem that the size of the battery cell excessively increases in the second direction due to the arrangement of the protection layer, thereby alleviating the problem that the volumetric energy density of the battery cell decreases due to the arrangement of the protection layer.
In some embodiments of the first aspect of the present application, a surface of the first positive electrode active material layer facing the winding axis is provided with the accommodating groove, and the third section is located in the accommodating groove; the thickness of the third section is T along the second direction 6 The depth of the part of the accommodating groove for accommodating the third section is T 7 The depth of the second concave part is T 8 ，5μm≤T 6 ≤T 7 +T 8 。
In the technical scheme, if T 6 The thickness of the third section is smaller than 5 μm, and the movement of ions to the winding start end of the anode cannot be effectively restricted, if T 6 ＞T 7 +T 8 The third segment cannot be completely accommodated in the space defined by the second recess and the accommodating groove, which may result in an increase in the size of the electrode assembly in the second direction, and thus 5 μm T 6 ≤T 7 +T 8 The protective layer can effectively limit ions to move to the winding starting end of the negative electrode, the problem of lithium precipitation is relieved, the safety performance of the battery cell is improved, and the third section can be completely accommodated in the space defined by the accommodating groove and the second concave partThe size of the electrode assembly along the second direction is not increased in the cell, and the problem that the size of the battery cell along the second direction is increased due to the arrangement of the protective layer is relieved, so that the problem that the volume energy density of the battery cell is reduced due to the arrangement of the protective layer is relieved.
In some embodiments of the first aspect of the present application, a surface of the first positive electrode active material layer facing the winding axis is provided with the accommodating groove, and the third section is located in the accommodating groove; the electrode assembly further includes a second separator, the battery cell further includes a fixing member, the second separator is disposed on a side of the negative electrode winding start section facing the third positive electrode active material portion in the second direction, and the fixing member is configured to fix the second separator to the negative electrode winding start section; the fixing piece comprises a second connecting part positioned in the second concave part, the second isolating film comprises a second isolating part positioned in the second concave part and overlapped with the second connecting part along the second direction, and the thickness of the third section is T along the second direction 6 The depth of the part of the accommodating groove for accommodating the third section is T 7 The depth of the second concave part is T 8 The thickness of the second partition part is T 9 The thickness of the second connecting part is T 10 ，T 7 +T 8 ≥T 6 +T 9 +T 10 。
Among the above-mentioned technical scheme, through fixed with the second barrier film be fixed in negative pole winding initial section, be favorable to alleviating the second barrier film and remove between positive plate and negative plate, produce the risk of fold, reduce the risk of electric core short circuit to improve the security performance of electric core. If it is T 7 +T 8 ＜T 6 +T 9 +T 10 That is, the sum of the depth of the accommodating groove and the depth of the second recess is smaller than the sum of the thickness of the third section, the thickness of the second partition portion and the thickness of the second connection portion, so that the third section, the second partition portion and the second connection portion cannot be completely accommodated in the space defined by the accommodating groove and the second recess in the second direction, and the size of the battery cell in the second direction is increased due to the arrangement of the protective layer, so that the volume energy density of the battery cell is reduced.Thus T 7 +T 8 ≥T 6 +T 9 +T 10 So that the third section, the second separator and the second connecting part are completely accommodated in the space defined by the accommodating groove and the first recess in the second direction without increasing the size of the electrode assembly in the second direction.
In some embodiments of the first aspect of the present application, at least a portion of the third section overlaps the anode winding start section as viewed in the second direction, and a distance between an end of the third section facing away from the first section and the anode winding start end in the first direction is W 3 The second concave part has a size W 4 ，0≤W 4 -W 3 ≤0.5mm。
In the technical proposal, W 4 -W 3 The size of the second recess is much larger than the size of the overlap region of the third section and the anode winding start section > 0.5, increasing the difficulty of processing and reducing the amount of anode active material in the anode winding start section. W is more than or equal to 0 4 -W 3 And the size of the overlapping area of the third section and the cathode winding initial section along the first direction is close to the size of the second concave part, so that the risk of lithium precipitation can be reduced.
In some embodiments of the first aspect of the present application, a distance between an end of the third section facing away from the first section and the winding start end of the negative electrode is W in the first direction 3 ，0.3mm≤W 3 ≤25mm。
In the above technical scheme, if W 3 If the size of the third section and the cathode winding start section is smaller than 0.3mm and is observed along the second direction, the movement of ions of the positive electrode sheet to the cathode winding start end cannot be well limited, if W 3 The overlapping dimension of the third section and the negative electrode winding initiation section is too large as seen in the second direction, so that too much positive electrode active material in the positive electrode winding initiation section cannot exert its effect, and the profile reduces the energy density of the battery cell. Thus, 0.3 mm.ltoreq.W 3 Not more than 25mm, not only can the third section effectively limit the separation of the positive plateThe electrons move to the starting end of the winding of the negative electrode, the risk of lithium precipitation is reduced, the safety performance of the battery cell is improved, and the positive electrode active material in the starting section of the winding of the positive electrode can play a role to a greater extent, so that the battery cell has higher energy density and capacity.
In some embodiments of the first aspect of the present application, the first positive electrode active material layer further includes a second positive electrode active material portion, the second positive electrode active material portion being located in the flat region; the negative electrode sheet comprises a negative electrode winding initial section positioned in a flat area, one end of the negative electrode winding initial section, which is close to the first positive electrode active material part, is the negative electrode winding initial end, the second positive electrode active material part is positioned on one side of the negative electrode winding initial section along a second direction, and the extending direction of the winding axis, the first direction and the second direction are perpendicular to each other; the electrode assembly further includes a first separator, the battery cell further includes a fixing member, the first separator is disposed on a side of the negative electrode winding start section facing the second positive electrode active material portion along the second direction, and the fixing member is configured to fix the first separator to the negative electrode winding start section.
According to the technical scheme, the first isolating film is fixed on the negative electrode winding initial section through the fixing piece, the risk that the first isolating film moves between the positive electrode plate and the negative electrode plate and wrinkles are generated is reduced, the risk of short circuit of the battery cell is reduced, and the safety performance of the battery cell is improved.
In some embodiments of the first aspect of the present application, the negative electrode sheet is provided with the recess including a first recess provided at a surface of the negative electrode winding start section facing the second positive electrode active material portion, the first recess extending to the negative electrode winding start end, and the fixing member for fixing a portion of the first separator within the first recess.
In the above technical scheme, the fixing member fixes a part of the first separator in the first concave portion of the surface of the negative electrode winding initiation section facing the second positive electrode active material portion, which is favorable for improving the stability of the fixing of the first separator and the negative electrode winding initiation section.
In some embodiments of the first aspect of the present application, the first positive electrode active material layer further includes a third positive electrode active material portion located in the flat region, the third positive electrode active material portion being connected to the other end of the first positive electrode active material portion, the third positive electrode active material portion being located on the other side of the negative electrode winding start section in the second direction; the electrode assembly further includes a second separator disposed on a side of the negative electrode winding start section facing the third positive electrode active material portion in the second direction, and the fixing member is for fixing the second separator to the negative electrode winding start section.
In the technical scheme, the second isolation film is fixed on the negative electrode winding initial section through the fixing piece, so that the risk that the second isolation film moves between the positive electrode plate and the negative electrode plate and wrinkles are generated is reduced, the risk of short circuit of the battery cell is reduced, and the safety performance of the battery cell is improved.
In some embodiments of the first aspect of the present application, the negative electrode sheet is provided with the recess including a second recess provided at a surface of the negative electrode winding start section facing the third positive electrode active material portion, and the fixing member is for fixing a portion of the second separator within the second recess.
In the above technical scheme, a part of the second separator is fixed in the second concave part of the surface of the negative electrode winding initial section facing the third positive electrode active material part by the fixing piece, which is beneficial to improving the stability of the fixation of the second separator and the negative electrode winding initial section.
In some embodiments of the first aspect of the present application, the fixing member includes a first connection portion, a bent portion, and a second connection portion, the bent portion connecting the first connection portion and the second connection portion, and a portion of the first separator, a portion of the second separator, and a portion of the negative electrode winding start section are fixed between the first connection portion and the second connection portion.
In the above technical scheme, the first isolation part, the second isolation film part and a part of the negative electrode winding initial section are fixed between the first connecting part and the second connecting part, and the bending part is connected with the first connecting part and the second connecting part, so that the first connecting part, the bending part and the second connecting part are used for jointly fixing the first isolation film on the negative electrode winding initial section and the second isolation film on the negative electrode winding initial section, and the fixing is more convenient and the stability is better.
In some embodiments of the first aspect of the present application, the negative electrode sheet is provided with the concave portion including a first concave portion provided at a surface of the negative electrode winding start section facing the second positive electrode active material portion and a second concave portion provided at a surface of the negative electrode winding start section facing the third positive electrode active material portion, both the first concave portion and the second concave portion extending to the negative electrode winding start end in the first direction; at least part of the first connecting portion is accommodated in the first concave portion, and at least part of the second connecting portion is accommodated in the second concave portion.
According to the technical scheme, the first isolating film part, the second isolating film part and the negative electrode winding initial section are fixed between the first connecting part and the second connecting part, at least part of the first connecting part is accommodated in the first concave part, and at least part of the second connecting part is accommodated in the second concave part, so that the first isolating film and the second isolating film can be conveniently fixed on the negative electrode winding initial section, the problem that the size of the battery core is increased in the second direction due to the fixing piece can be relieved, and the problem that the volume energy density of the battery core is reduced due to the fixing piece can be relieved.
In a second aspect, an embodiment of the present application provides an electrical apparatus, including a battery cell provided in any embodiment of the first aspect.
In the above technical scheme, the risk of lithium precipitation of the battery cell provided by any embodiment of the first aspect is lower, the safety is higher, and the electricity utilization safety of the electric equipment powered by the battery cell can be improved.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the embodiments will be briefly described below, it being understood that the following drawings only illustrate some embodiments of the present application and therefore should not be considered as limiting the scope, and other related drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
Fig. 1 is a schematic view illustrating a partial structure of a battery cell according to some embodiments of the present application;
FIG. 2 is a schematic diagram illustrating a partial structure of a battery cell according to other embodiments of the present application;
fig. 3 is a schematic structural part of a battery cell according to still other embodiments of the present application;
fig. 4 is a schematic structural part of a battery cell according to still other embodiments of the present application;
fig. 5 is a schematic structural part of a battery cell according to another embodiment of the present application;
Fig. 6 is a schematic structural view of an electrode assembly provided with a receiving groove in a first positive electrode active material layer according to some embodiments of the present application;
FIG. 7 is a schematic view of a portion of the protective layer received in the receiving groove of FIG. 6;
fig. 8 is a schematic view showing the structure of an electrode assembly in which a first positive electrode active material layer is provided with a receiving groove according to other embodiments of the present application;
FIG. 9 is a schematic view of the protective layer fully received in the receiving groove of FIG. 8;
FIG. 10 is a schematic view of the protective layer being received in the receiving groove with the positive plate in an expanded state;
fig. 11 is a schematic structural part of a battery cell according to still other embodiments of the present application;
FIG. 12 is a schematic diagram showing the structural dimensions of the structure of the provided cell of FIG. 10;
FIG. 13 is a schematic view of a negative electrode sheet provided with recesses in an expanded state;
fig. 14 is a schematic structural diagram of a battery cell according to still other embodiments of the present application;
FIG. 15 is a schematic diagram showing the structural dimensions of the structure of the provided cell of FIG. 14;
fig. 16 is a schematic view illustrating a portion of a structure of a battery cell according to another embodiment of the present application;
FIG. 17 is a schematic diagram showing the structural dimensions of the structure of the provided cell of FIG. 16;
Fig. 18 is a schematic view illustrating a portion of a structure of a battery cell according to still other embodiments of the present application;
fig. 19 is a schematic diagram showing the structural dimensions of the structure of the provided cell in fig. 18.
Icon: 100-cell; 10-an electrode assembly; 11-a negative plate; 111-winding a starting end of the negative electrode; 1111-a first recess; 1112-a second recess; 112-negative current collector; 113-a first anode active material layer; 1131-a first anode active material portion; 114-a second anode active material layer; 1141-a second anode active material portion; 115-a negative electrode winding initiation section; 12-positive plate; 121-positive electrode current collector; 122-a first positive electrode active material layer; 1221-positive electrode bending portion; 1222-a first positive electrode active material portion; 1223-receiving slots; 1224-a second positive electrode active material portion; 1225-a third positive electrode active material portion; 123-a second positive electrode active material layer; 124-winding the starting end of the positive electrode; 13-a first separator; 131-a first partition; 14-a second barrier film; 141-a second partition; 20-a protective layer; 21-a first part; 22-a second part; 23-a third part; 24-a first section; 25-a second section; 26-third section; 30-fixing piece; 31-a first connection; 32-a bending part; 33-a second connection; a1-a first bending region; a2-a second bending region; b-a flat region; x-a first direction; y-a second direction; the direction of extension of the Z-winding axis.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present application more apparent, the technical solutions of the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application, and it is apparent that the described embodiments are some embodiments of the present application, but not all embodiments of the present application. The components of the embodiments of the present application generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations.
Thus, the following detailed description of the embodiments of the application, as presented in the figures, is not intended to limit the scope of the application, as claimed, but is merely representative of selected embodiments of the application. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.
It should be noted that, without conflict, the embodiments of the present application and features of the embodiments may be combined with each other.
It should be noted that: like reference numerals and letters denote like items in the following figures, and thus once an item is defined in one figure, no further definition or explanation thereof is necessary in the following figures.
In the description of the embodiments of the present application, it should be noted that, the indicated orientation or positional relationship is based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship conventionally put in place when the product of this application is used, or the orientation or positional relationship conventionally understood by those skilled in the art, is merely for convenience of describing the present application and simplifying the description, and is not indicative or implying that the apparatus or element referred to must have a specific orientation, be configured and operated in a specific orientation, and therefore should not be construed as limiting the present application. Furthermore, the terms "first," "second," "third," and the like are used merely to distinguish between descriptions and should not be construed as indicating or implying relative importance.
Currently, from the development of market situation, the application of the battery cell is wider. The battery cell is widely applied to electric vehicles such as electric bicycles, electric motorcycles, electric automobiles and the like, and a plurality of fields such as electric vehicles, unmanned aerial vehicles, energy storage equipment and the like. With the continuous expansion of the application field of the battery cell, the market demand of the battery cell is also continuously expanding.
The battery cell comprises an electrode assembly, the electrode assembly comprises an isolating film, a positive plate and a negative plate, and the electrode assembly works by moving between the positive plate and the negative plate through metal ions. The circulation process of the battery cell is a process that metal ions move from the positive electrode plate to the negative electrode plate and then move from the negative electrode plate to the positive electrode plate. In the process that ions move from the positive plate to the negative plate, if the negative plate cannot provide enough space for common ion intercalation, ions separated from the positive plate cannot be intercalated into the negative plate, so that the ions can only be deposited on the surface of the negative plate, crystal branches are formed on the surface of the negative plate, namely lithium is separated, and when the lithium separation is serious, the internal short circuit of a battery cell can be caused, so that the safety problem of the battery cell is caused.
For a coiled electrode assembly, the electrode assembly is provided with a first bending region and a flat region, the negative electrode plate is provided with a negative electrode coiling starting end, the positive electrode plate is provided with a positive electrode current collector and a first positive electrode active material layer, the first positive electrode active material layer is arranged on one side of the positive electrode current collector, which faces the coiling axis of the electrode assembly, the first positive electrode active material layer comprises a plurality of positive electrode bending parts which are arranged in the first bending region from inside to outside in sequence, the positive electrode bending part which is positioned at the innermost side of the first bending region is the first positive electrode active material part, the first positive electrode active material part is arranged facing the negative electrode coiling starting end, the positive electrode active material mass of the first positive electrode active material part is larger than the negative electrode active material mass of the negative electrode coiling starting end, and the negative electrode coiling starting end cannot provide enough embedding space for ions separated from the first positive electrode active material part, so that lithium is easy to separate out at the negative electrode coiling starting end, thereby reducing the safety performance of the battery core. In the related art, the protection layer is arranged between the first positive electrode active material part and the negative electrode winding starting end, and ions of the first positive electrode active material part are limited to move to the negative electrode winding starting end through the protection layer, so that the risk of lithium precipitation at the negative electrode winding starting end is reduced, the risk of short circuit caused by contact between the negative electrode winding starting end and the first positive electrode active material part can be reduced, and the safety performance of the battery cell is improved. However, the arrangement of the protective layer occupies a certain space, increases the size of the battery cell and reduces the volume energy density of the battery cell.
Based on the above-mentioned considerations, in order to improve the problem of low energy density of the volume of the battery cell, the embodiment of the application provides a coiled electrode assembly, the electrode assembly further comprises a protective layer, and the anode bending part at the innermost side of the first bending region is provided with a containing groove; and/or the starting end of the negative electrode winding is provided with a concave part, and at least part of the protective layer is positioned in the accommodating groove and/or the concave part.
The first positive electrode active material portion is arranged facing the negative electrode winding starting end, and the protective layer is arranged between the first positive electrode active material portion and the negative electrode winding starting end, so that ions of the first positive electrode active material portion can be limited to move to the negative electrode winding starting end by the protective layer, the risk of lithium precipitation of a winding type electrode assembly at the corresponding positions of the first positive electrode active material portion and the negative electrode winding starting end is reduced, the risk of short circuit caused by contact between the negative electrode winding starting end and the first positive electrode active material portion is reduced, and the safety of the battery cell is improved.
The first positive electrode active material layer is provided with a containing groove for containing at least part of the protective layer, and/or the negative electrode sheet is provided with a concave portion for containing the protective layer, which is favorable for alleviating the problem of excessive increase in cell size caused by the arrangement of the protective layer, thereby alleviating the problem of reduction in volumetric energy density of the cell caused by the arrangement of the protective layer.
The battery cell disclosed by the embodiment of the application can be used for electric equipment such as an electric two-wheeled vehicle, an electric tool, an unmanned aerial vehicle, energy storage equipment and the like, but is not limited to. The battery core with the working condition of the application can also be used as a power supply system of the electric equipment, thus being beneficial to improving the safety performance of the battery core and the electricity utilization safety of the electric equipment.
The embodiment of the application provides electric equipment using a battery cell as a power supply, wherein the electric equipment can be but is not limited to electronic equipment, electric tools, electric vehicles, unmanned aerial vehicles and energy storage equipment. The electronic equipment can comprise a mobile phone, a tablet, a notebook computer and the like, the electric tool can comprise an electric drill, an electric saw and the like, and the electric vehicle can comprise an electric automobile, an electric motorcycle, an electric bicycle and the like.
As shown in fig. 1, the battery cell 100 includes an electrode assembly 10 and a protective layer 20; the electrode assembly 10 is of a winding structure, the electrode assembly 10 is provided with a first bending region A1 and a flat region B, the first bending region A1 is connected to one end of the flat region B along a first direction X, the electrode assembly 10 comprises a negative electrode plate 11 and a positive electrode plate 12, the negative electrode plate 11 is provided with a negative electrode winding starting end 111, the positive electrode plate 12 is provided with a positive electrode current collector 121 and a first positive electrode active material layer 122, the first positive electrode active material layer 122 is arranged on one side of the positive electrode current collector 121 facing a winding axis of the electrode assembly 10, the first positive electrode active material layer 122 comprises a plurality of positive electrode bending parts 1221 which are arranged in sequence from inside to outside and positioned at the innermost side of the first bending region A1, and the positive electrode bending part 1221 positioned at the innermost side of the first bending region A1 faces the negative electrode winding starting end 111; wherein, the positive electrode bending part 1221 positioned at the innermost side is provided with a containing groove 1223; and/or the anode winding start end 111 is provided with a recess portion accommodating the protective layer 20; at least part of the protective layer 20 is located in the receiving groove 1223 and/or the recess, the first direction X being perpendicular to the direction of extension of the winding axis.
The electrode assembly 10 further includes a second inflection region A2, and the first inflection region A1 and the second inflection region A2 are connected to both ends of the flat region B along the first direction X, respectively.
The negative electrode winding start end 111 of the negative electrode sheet 11 is a winding start end of the negative electrode sheet 11 in the winding direction. The negative electrode sheet 11 includes a negative electrode current collector 112, a first negative electrode active material layer 113 and a second negative electrode active material layer 114, the first negative electrode active material layer 113 and the second negative electrode active material layer 114 being disposed on two surfaces of the negative electrode current collector 112 in a thickness direction thereof, respectively, it being understood that the first negative electrode active material layer 113 and the second negative electrode active material layer 114 are disposed on a surface of the negative electrode current collector 112 facing a winding axis and a surface facing away from the winding axis, respectively, and in this embodiment, the first negative electrode active material layer 113 is disposed on a surface of the negative electrode current collector 112 facing the winding axis, and the second negative electrode active material layer 114 is disposed on a surface of the negative electrode current collector 112 facing away from the winding axis. Taking the battery cell 100 as a lithium ion battery as an example, the material of the negative electrode current collector 112 may be copper, and the materials of the first negative electrode active material layer 113 and the second negative electrode active material layer 114 may be carbon or silicon, etc.
As shown in fig. 1, in some embodiments, the winding start end of the negative electrode current collector 112, the winding start end of the first negative electrode active material layer 113, and the winding start end of the second negative electrode active material layer 114 are flush, together forming a negative electrode winding start end 111, which facilitates manufacturing and shaping of the negative electrode sheet 11, and also facilitates improving the production efficiency of the negative electrode sheet 11.
In other embodiments, the start end of the first anode active material layer 113 and the winding start end of the second anode active material layer 114 may not be flush. In an embodiment in which the start of the first anode active material layer 113 and the winding start of the second anode active material layer 114 are not flush, the anode winding start 111 may be a position where one of the start of the first anode active material layer 113 and the winding start of the second anode active material layer 114, which is closest to the first cathode active material portion 1222 in the first direction X, is located.
The anode winding start 111 may be located in the first bending region A1 or in the flat region B, and the anode winding start 111 may be located at a connection position of the first bending region A1 and the flat region B, as viewed in the second direction Y. The extending direction Z, the first direction X, and the second direction Y of the winding axis of the electrode assembly 10 are perpendicular to each other.
The electrode assembly 10 further includes a negative electrode tab (not shown) that protrudes beyond one end of the negative electrode current collector 112 in the extending direction Z of the winding axis of the electrode assembly 10. The negative electrode tab and the negative electrode current collector 112 may be integrally formed. The negative electrode tab and the negative electrode current collector 112 may be separately provided and integrally connected by welding, conductive adhesive, riveting, or the like.
The electrode assembly 10 further includes a positive tab (not shown) that protrudes beyond one end of the positive current collector in the extending direction Z of the winding axis of the electrode assembly 10. The positive electrode tab and the positive electrode current collector may be integrally formed. The positive electrode lug and the positive electrode current collector can be arranged in a split mode and connected into a whole through welding, conductive adhesive, riveting and the like.
The positive electrode sheet 12 further includes a second positive electrode active material layer 123, and the second positive electrode active material layer 123 is disposed on a surface of the positive electrode current collector 121 facing away from the winding axis. Taking the battery cell 100 as a lithium ion battery as an example, the material of the positive electrode current collector 121 may be aluminum, and the first positive electrode active material layer 122 and the second positive electrode active material layer 123 may be lithium cobaltate, lithium iron phosphate, ternary lithium, lithium manganate, or the like.
After the positive electrode sheet 12 is wound, the first positive electrode active material layer 122 of the positive electrode sheet 12 forms a plurality of positive electrode bent portions sequentially arranged from inside to outside in the first bending region A1 and the second bending region A2, respectively.
In the first bending region A1, the cathode bending portion 1221 located at the innermost side is a first cathode active material portion 1222, and the first cathode active material portion 1222 is provided facing the anode winding start end 111 in the first direction X. The plurality of positive electrode bending parts 1221 located in the first bending region A1 are sequentially arranged from inside to outside, which may be understood as that the plurality of positive electrode bending parts 1221 located in the first bending region A1 are arranged along one side in a direction away from the winding axis.
The protective layer 20 may be an insulating adhesive paper, and the protective layer 20 may prevent ions detached from the first positive electrode active material portion 1222 from passing therethrough, so that the protective layer 20 may limit the ions detached from the first positive electrode active material portion 1222 from reaching the negative electrode winding start end 111, thereby reducing the risk of lithium precipitation from the negative electrode winding start end 111 and improving the safety performance of the battery cell 100.
The protective layer 20 may be entirely located between the first positive electrode active material portion 1222 and the negative electrode winding start end 111, so that ions detached from the first positive electrode active material portion 1222 are restricted from reaching the negative electrode winding start end 111 with less protective layer 20 material, enabling cost saving.
The protection layer 20 may also have a portion located between the first positive electrode active material portion 1222 and the negative electrode winding start end 111, and another portion extending beyond the first positive electrode active material portion 1222 and the negative electrode winding start end 111, so that the protection layer 20 has a larger coverage area, which not only enables the protection layer 20 to better limit the ions detached from the first positive electrode active material portion 1222 from reaching the negative electrode winding start end 111, but also enables the protection layer 20 to have a larger connection area with other structures, thereby facilitating fixation and improving connection stability.
The receiving groove 1223 may be provided only in the first positive electrode active material layer 122. Only the negative electrode winding start end 111 may be provided with a concave portion. The storage groove 1223 may be provided in the first positive electrode active material layer 122, or a recess may be provided in the negative electrode winding start end 111. The concave portion extends from the anode winding start end 111 in a direction away from the first cathode active material portion 1222, and extends to a surface of the anode sheet 11 in the second direction Y.
In an embodiment in which the receiving groove 1223 is provided in only the positive electrode bending portion 1221 located at the innermost side of the first bending region and the negative electrode winding start end 111 is not provided with a recess, the protective layer 20 may be partially received in the receiving groove 1223, and the other portion extends out of the receiving groove 1223, and the protective layer 20 may be completely received in the receiving groove 1223.
In the embodiment in which the positive electrode bending portion 1221 located at the innermost side of the first bending region is not provided with the receiving groove 1223 and only the negative electrode winding start end 111 is provided with the recess, a part of the protective layer 20 may be received in the recess, another part may extend out of the recess, and the protective layer 20 may be completely received in the recess.
In the embodiment in which the positive electrode bending portion 1221 located at the innermost side of the first bending region is not provided with the accommodation groove 1223 and the negative electrode winding start end 111 is provided with the concave portion, the protective layer 20 may be partially accommodated in the accommodation groove 1223 and the other portion is located in the concave portion, and the protective layer 20 may be completely accommodated in the concave portion or completely accommodated in the accommodation groove 1223.
The first positive electrode active material portion 1222 is disposed facing the negative electrode winding start end 111, and by disposing the protective layer 20 between the first positive electrode active material portion 1222 and the negative electrode winding start end 111, the protective layer 20 can restrict movement of ions of the first positive electrode active material portion 1222 to the negative electrode winding start end 111, and reduce the risk of lithium precipitation of the wound electrode assembly 10 at positions corresponding to the first positive electrode active material portion 1222 and the negative electrode winding start end 111, thereby contributing to improvement of safety of the battery cell 100.
As shown in fig. 1, in some embodiments, the protective layer 20 is disposed on the first positive electrode active material layer 122.
The protective layer 20 may be a gummed paper with a gum layer, and the protective layer 20 is adhered to the surface of the first positive electrode active material layer 122 facing the winding axis, so that the protective layer 20 is more convenient to be disposed on the first positive electrode active material layer 122. The protective layer 20 may be formed by curing a gel applied to the surface of the first positive electrode active material layer 122 facing the winding axis.
The protective layer 20 is disposed on the first positive electrode active material layer 122, so that the protective layer 20 is convenient to fix, and the protective layer 20 can better limit the movement of ions of the positive electrode sheet 12 to the negative electrode winding start end 111, thereby reducing the risk of lithium precipitation of the electrode assembly 10 at the negative electrode winding start end 111.
In other embodiments, as shown in fig. 2, the protective layer 20 may be disposed on the negative electrode sheet 11, for example, the protective layer 20 is adhered to the negative electrode winding start section 115 of the negative electrode sheet 11 and covers the negative electrode winding start end 111. As shown in fig. 2, the protector includes a first portion 21, a second portion 22, and a third portion 23, the first portion 21 and the second portion 22 being provided to both surfaces of the negative electrode winding start section 115 of the negative electrode sheet 11 in the second direction Y, respectively, the first portion 21 covering a part of one surface of the negative electrode winding start section 115 in the second direction Y, and the second portion 22 covering a part of the other surface of the negative electrode winding start section 115 in the second direction Y. The third portion 23 is located between the anode winding start end 111 and the first cathode active material portion 1222, the third portion 23 connects the first portion 21 and the second portion 22, and the third portion 23 covers the anode winding start end 111.
As shown in fig. 1, in some embodiments, the protective layer 20 includes a first segment 24, the first segment 24 being located at the first bending region A1, the first segment 24 being located between the first positive electrode active material portion 1222 and the negative electrode winding start end 111.
The first segment 24 is located in the first inflection region A1, and it is understood that the projection of the first segment 24 is located in the first inflection region A1 as viewed in the second direction Y. In the embodiment in which the protective layer 20 is provided on the first active material layer, the first segment 24 is bonded to the first positive electrode active material portion 1222, and the first segment 24 completely covers the surface of the first positive electrode active material portion 1222 facing the winding axis.
The first section 24 of the protection layer 20 is located in the first bending region A1, and the first section 24 can effectively limit the movement of ions of the first positive electrode active material portion 1222 toward the negative electrode winding start end 111, so that the risk of lithium precipitation of the electrode assembly 10 at the negative electrode winding start end 111 is effectively reduced, and the safety performance of the battery cell 100 is improved.
As shown in fig. 1, in some embodiments, the protection layer 20 includes only the first segment 24, that is, the first segment 24 is the protection layer 20, and the first segment 24 is located in the first bending region A1, so that the protection layer 20 is completely located between the first positive electrode active material portion 1222 and the negative electrode winding start end 111, and the protection layer 20 is completely located in the first bending region A1.
In other embodiments, as shown in fig. 3 and 4, the protective layer 20 further includes a second section 25, where the second section 25 is located in the flat region B, and the second section 25 is connected to one end of the first section 24.
The second section 25 may be connected to either one of the ends of the first section 24 in the winding direction, and the case where the second section 25 is connected to both ends of the first section 24 in the winding direction is shown in fig. 3 and 4, respectively.
The connection position of the second section 25 and the first section 24 may overlap with the connection position of the first bending region A1 and the flat region B, as viewed in the second direction Y. The second segment 25 and the negative electrode winding start segment 115 of the negative electrode sheet 11 may or may not overlap as viewed in the second direction Y, depending on the position of the negative electrode winding start end 111 in the first direction X and the size of the second segment 25 in the first direction X. In the embodiment in which the second segment 25 overlaps the negative electrode winding start segment 115 of the negative electrode sheet 11 as viewed in the second direction Y, the connection position of the first segment 24 and the second segment 25 may overlap the negative electrode winding start 111 as viewed in the second direction Y, and of course, the connection position of the first segment 24 and the second segment 25 may not overlap the negative electrode winding start 111 as viewed in the second direction Y. Fig. 3 and 4 each show a case where the connection position of the first segment 24 and the second segment 25, the connection position of the flat region B and the first bending region A1, and the anode winding start end 111 overlap as viewed in the second direction Y.
The second segment 25 may be adhered to a portion of the first positive electrode active material layer 122 located at the flat region B.
The protection layer 20 further includes the second section 25, so that the area that the protection layer 20 can cover is larger, and ions of the positive electrode sheet 12 can be better limited to move towards the negative electrode winding starting end 111, so that the risk of lithium precipitation of the electrode assembly 10 at the negative electrode winding starting end 111 is further reduced, and the safety performance of the battery cell 100 is improved. The arrangement of the second section 25 also increases the connection area of the protective layer 20, which is advantageous for a stable connection of the protective layer 20 with other structures.
In other embodiments, as shown in fig. 5, the protective layer 20 further includes a third segment 26, where the third segment 26 is located in the flat area B, and the third segment 26 is connected to the other end of the first segment 24, and the second segment 25 and the third segment 26 are disposed opposite to each other along the second direction Y, and the extending direction Z of the winding axis, the first direction X, and the second direction Y are perpendicular to each other.
The connection location of the third section 26 and the first section 24 may overlap the connection location of the first inflection region A1 and the flat region B, as viewed in the second direction Y. Depending on the position of the anode winding start end 111 in the first direction X and the size of the third segment 26 in the first direction X, the third segment 26 and the anode winding start segment 115 of the anode tab 11 may or may not overlap in the second direction Y. In the embodiment in which the third segment 26 overlaps the anode winding start section 115 of the anode sheet 11 as viewed in the second direction Y, the connection position of the first segment 24 and the third segment 26 may overlap the anode winding start end 111 as viewed in the second direction Y, and of course, the connection position of the first segment 24 and the third segment 26 may not overlap the anode winding start end 111 as viewed in the second direction Y. Fig. 4 shows a case where the connection position of the first segment 24 and the third segment 26, the connection position of the flat region B and the first bending region A1, and the anode winding start end 111 overlap as viewed in the second direction Y.
The third segment 26 may be bonded to a portion of the first positive electrode active material layer 122 located in the flat region B.
The protective layer 20 further includes the third segment 26, which can further increase the coverage area of the protective layer 20, and can better limit the movement of ions of the positive electrode sheet 12 to the negative electrode winding start end 111, further reduce the risk of lithium precipitation of the electrode assembly 10 at the negative electrode winding start end 111, and improve the safety performance of the battery cell 100. The third section 26 can further increase the connection area of the protective layer 20, which is beneficial for the stable connection of the protective layer 20 with other structures.
In other embodiments, the protective layer 20 may also be located entirely in the flat region B, as viewed in the second direction Y.
As shown in fig. 6-12, in some embodiments, the surface of the first positive electrode active material layer 122 facing the winding axis is provided with a receiving groove 1223, and the protective layer 20 is at least partially received within the receiving groove 1223.
The receiving groove 1223 is recessed from the surface of the first positive electrode active material layer 122 facing the winding axis in a direction away from the winding axis. The depth of the receiving groove 1223 is less than or equal to the thickness of the first positive electrode active material layer 122. The drawing shows the case where the depth of the receiving groove 1223 is smaller than the thickness of the first positive electrode active material layer 122.
The protective layer 20 may be entirely accommodated in the accommodating groove 1223, and the protective layer 20 is accommodated in the accommodating groove 1223 in any direction. The protective layer 20 may be partially accommodated in the accommodation groove 1223.
In an embodiment in which the protective layer 20 may be partially accommodated in the accommodating groove 1223, the protective layer 20 may be completely accommodated in the accommodating groove 1223 in the winding direction, and the protective layer 20 may extend out of the accommodating groove 1223 in other directions; the protective layer 20 may be completely accommodated in the accommodating groove 1223 in the depth direction of the accommodating groove 1223, and a part of the protective layer 20 may be accommodated in the accommodating groove 1223 in the winding direction; it is also possible that the protective layer 20 is only partially accommodated in the accommodating groove 1223 in any direction, for example, the protective layer 20 is only partially accommodated in the accommodating groove 1223 in both the winding direction and the depth direction of the accommodating groove 1223.
Illustratively, in the embodiment in which the protection layer 20 includes the first, second and third sections 24, 25 and 26, the accommodation groove 1223 is provided in the first positive electrode active material portion 1222, the first section 24 of the protection layer 20 is accommodated in the accommodation groove 1223, and the second and third sections 25 and 26 are located outside the accommodation groove 1223, so that the problem of the increase in size of the battery cell 100 in the first direction X due to the provision of the protection layer 20 can be alleviated. For another example, as shown in fig. 6 and 7, a part of the accommodating groove 1223 is provided at a position corresponding to the first section 24 of the protection layer 20, another part of the accommodating groove 1223 is provided at a position corresponding to the second section 25 of the protection layer 20, and the second section 25 and the third section 26 of the protection layer 20 are positioned in the accommodating groove 1223, so that the problem of the size increase of the battery cell 100 in the second direction Y due to the provision of the protection layer 20 can be alleviated. As another example, as shown in fig. 8 and 9, the first, second and third sections 24, 25 and 26 are each accommodated in the accommodation groove 1223, so that the problem of increasing the size of the battery cell 100 in any direction due to the provision of the protection layer 20 can be alleviated.
The protective layer 20 is at least partially accommodated in the accommodating groove 1223 on the surface of the first positive electrode active material layer 122, which is advantageous in alleviating the problem of excessive increase in the size of the battery cell 100 due to the provision of the protective layer 20, and thus alleviating the problem of reduction in the volumetric energy density of the battery cell 100 due to the provision of the protective layer 20.
As shown in fig. 8, 9, in some embodiments, the protective layer 20 is fully received within the receiving groove 1223.
In the embodiment in which the protective layer 20 includes the first, second and third sections 24, 25 and 26, a portion of the receiving groove 1223 is located in the first bending region A1 and another portion of the receiving groove 1223 is located in the flat region B in the winding direction. The first section 24 is received in the portion of the receiving groove 1223 located in the first inflection region A1, and the second and third sections 25 and 26 are received in the portion of the receiving groove 1223 located in the flat region B. The protective layer 20 is completely accommodated in the accommodating groove 1223 in any direction.
The protective layer 20 is completely accommodated in the accommodating groove 1223, and the size of the battery cell 100 in any direction is not increased by the arrangement of the protective layer 20, so that the electrode assembly 10 is not increased in size due to the arrangement of the protective layer 20, thereby avoiding the problem of reduction in the volumetric energy density of the battery cell 100 due to the arrangement of the protective layer 20.
As shown in fig. 5, 7, 9, 10, and 11-14, in some embodiments, the first positive electrode active material layer 122 further includes a second positive electrode active material portion 1224, the second positive electrode active material portion 1224 being located in the flat region B; the negative electrode sheet 11 includes a negative electrode winding start section 115 located in the flat region B, one end of the negative electrode winding start section 115, which is close to the first positive electrode active material portion 1222, is a negative electrode winding start end 111, and along the second direction Y, the second positive electrode active material portion 1224 is located on one side of the negative electrode winding start section 115, and the extending direction Z, the first direction X, and the second direction Y of the winding axis are perpendicular to each other; the protective layer 20 includes a first segment 24 and a second segment 25, the first segment 24 is located between the first positive electrode active material portion 1222 and the negative electrode winding start end 111, the second segment 25 is located in the flat region B and connected to one end of the first segment 24, and at least part of the second segment 25 is located between the negative electrode winding start segment 115 and the second positive electrode active material portion 1224.
The anode winding start section 115 is a section where the anode sheet 11 is wound at the beginning. The negative electrode active material layers are arranged on both sides of the negative electrode winding initial section 115, so that the utilization rate of the negative electrode current collector at the winding center is effectively improved.
The second positive electrode active material portion 1224 and the negative electrode winding start section 115 overlap as viewed in the second direction Y. The second segment 25 extends from a connection position with the first segment 24 in the first direction X to between the anode winding start segment 115 and the second cathode active material portion 1224. The second positive electrode active material portion 1224, the negative electrode winding start section 115, and the second section 25 overlap as viewed in the second direction Y.
The first segment 24 is bonded to the first positive electrode active material portion 1222, and the second segment 25 is bonded to the second positive electrode active material portion 1224.
The first section 24 of the protection layer 20 is located between the first positive electrode active material portion 1222 and the negative electrode winding start end 111, and the second section 25 is located between the negative electrode winding start section 115 and the second positive electrode active material portion 1224, so that the coverage area of the protection layer 20 can be increased, the movement of ions of the positive electrode sheet 12 to the negative electrode winding start section 115 can be better limited, the risk of lithium precipitation of the electrode assembly 10 in the negative electrode winding start section 115 is reduced, and the safety performance of the battery cell 100 is improved.
In the embodiment in which the second segment 25 and the anode winding start segment 115 overlap as viewed in the second direction Y, and the anode sheet 11 is provided with the concave portion, as shown in fig. 11, 12, the concave portion includes a first concave portion 1111 provided on a side of the anode winding start segment 115 facing the second cathode active material portion 1224, and the projection of the second segment 25 is at least partially located in the first concave portion 1111 as viewed in the second direction Y, and the first concave portion 1111 extends to the anode winding start end 111 in the first direction X.
A part of the first anode active material layer 113 of the anode sheet 11 is located at the anode winding start section 115, and a part of the second anode active material layer 114 of the anode sheet 11 is located at the anode winding start section 115. The portion of the first anode active material layer 113 located in the anode winding start section 115 is a first anode active material portion 1131, and the portion of the second anode active material layer 114 located in the anode winding start section 115 is a second anode active material portion 1141. The first negative electrode active material portion 1131 is disposed facing the second positive electrode active material portion 1224, the first recess 1111 is disposed in the first negative electrode active material portion 1131, the first recess 1111 extends to the negative electrode winding start end 111 in the first direction X, and then the first recess 1111 is formed with notches in both the surface of the first negative electrode active material portion 1131 facing the second positive electrode active material portion 1224 and the surface of the first negative electrode active material portion 1131 located at the negative electrode winding start end 111 so that the second section 25 snaps into the first recess 1111 in the second direction Y when the electrode assembly 10 is subjected to the pressure in the second direction Y. The first recess 1111 is for accommodating a portion of the second segment 25 overlapping the anode winding start end 111.
The depth of the first concave portion 1111 may be the same as the thickness of the first anode active material portion 1131. The depth of the first concave portion 1111 may also be smaller than the thickness of the first anode active material portion 1131. Fig. 11 shows a case where the depth of the first concave portion 1111 may be smaller than the thickness of the first anode active material portion 1131.
The side of the negative electrode winding start section 115 facing the second positive electrode active material portion 1224 is provided with a first recess 1111 extending to the negative electrode winding start end 111, and the projection of the second section 25 is at least partially located in the first recess 1111, so that the second section 25 can be at least partially accommodated in the first recess 1111, which is advantageous for alleviating the problem of excessively increasing the size of the battery cell 100 in the second direction Y due to the provision of the protective layer 20, thereby alleviating the problem of decreasing the volumetric energy density of the battery cell 100 due to the provision of the protective layer 20.
As shown in fig. 11, 12, in some embodiments, the surface of the first positive electrode active material layer 122 facing the winding axis is provided with a receiving groove 1223, and the second segment 25 is located within the receiving groove 1223; in the second direction Y, the second section 25 has a thickness T 1 The depth of the portion of the accommodation groove 1223 for the second section 25 is T 2 The depth of the first recess 1111 is T 3 ，5μm≤T 1 ≤T 2 +T 3 。
T 1 May be 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, etc. T (T) 2 Refers to the depth of the receiving groove 1223 located on the second positive electrode active material portion 1224 and for receiving the portion of the second segment 25.
The protective layer 20 may have a uniform thickness or a non-uniform thickness. In embodiments where the protective layer 20 is non-uniform in thickness, T 1 Is the maximum thickness of the portion of the second section 25 overlapping the anode winding start section 115.
At least a portion of the receiving groove 1223 overlaps the first recess 1111 as viewed in the second direction Y, the receiving groove 1223 and the first recess 1111 overlap to collectively define a first receiving space for receiving the second segment 25, wherein the second segment 25 may be partially received in the receiving groove 1223 and another portion may be received in the first recess 1111 in the second direction Y, such that the space for receiving the second segment 25 is allocated to the second positive electrode active material portion 1224 and the first negative electrode active material portion 1131, such that the depths of the recesses provided on the second positive electrode active material portion 1224 and the first negative electrode active material portion 1131 are smaller, such that the recess arrangement is more convenient.
If it is T 1 If the thickness of the second segment 25 is smaller than 5. Mu.m, the movement of ions to the anode winding start 111 cannot be effectively restricted, and if T 1 ＞T 2 +T 3 The second section 25 cannot be completely accommodated in the space defined by the first recess 1111 and the accommodation groove 1223, which leads to an increase in the size of the battery cell 100 in the second direction Y, and thus 5 μm T 1 ≤T 2 +T 3 The protective layer 20 can effectively limit the movement of ions to the cathode winding starting end 111, so that the problem of lithium precipitation is relieved, the safety performance of the battery cell 100 is improved, the second section 25 can be completely contained in the space defined by the containing groove 1223 and the first concave portion 1111 together without increasing the size of the battery cell 100 along the second direction Y, and the problem that the size of the battery cell 100 is increased along the second direction Y due to the arrangement of the protective layer 20 is relieved, so that the problem that the volume energy density of the battery cell 100 is reduced due to the arrangement of the protective layer 20 is relieved.
In some embodiments, the first positive electrode active material layer 122 further includes a second positive electrode active material portion 1224, the second positive electrode active material portion 1224 being located in the flat region B; the negative electrode sheet 11 includes a negative electrode winding start section 115 located in the flat region B, one end of the negative electrode winding start section 115, which is close to the first positive electrode active material portion 1222, is a negative electrode winding start end 111, and along the second direction Y, the second positive electrode active material portion 1224 is located on one side of the negative electrode winding start section 115, and the extending direction Z, the first direction X, and the second direction Y of the winding axis are perpendicular to each other; the electrode assembly 10 further includes a first separator 13, and the battery cell 100 further includes a fixing member 30 (shown in fig. 14 and 15), the first separator 13 being disposed on a side of the negative electrode winding start section 115 facing the second positive electrode active material portion 1224 in the second direction Y, the fixing member 30 being used to fix the first separator 13 to the negative electrode winding start section 115.
The first separator 13 serves to separate the positive electrode sheet 12 and the negative electrode sheet 11. The material of the first separator 13 may be PP (polypropylene) or PE (polyethylene), etc.
The first isolating film 13 is fixed on the negative electrode winding initial section 115 through the fixing piece 30, so that the risk of the first isolating film 13 moving between the positive electrode plate 12 and the negative electrode plate 11 and generating wrinkles is reduced, the risk of short circuit of the battery cell 100 is reduced, and the safety performance of the battery cell 100 is improved.
There are various ways of fixing the first separator 13 to the negative electrode winding start section 115 by the fixing member 30, and as illustrated in fig. 11 to 15, for example, in some embodiments, the surface of the first positive electrode active material layer 122 facing the winding axis is provided with a receiving groove 1223, and the second section 25 is located within the receiving groove 1223; the electrode assembly 10 further includes a first separator 13, the battery cell 100 further includes a fixing member 30 disposed on a side of the negative electrode winding start section 115 facing the second positive electrode active material portion 1224 along the second direction Y, the fixing member 30 being for fixing the first separator 13 to the negative electrode winding start section 115; the fixing member 30 includes a first connection portion 31 located in the first recess 1111, the first isolation film 13 includes a first partition portion 131 located in the first recess 1111 and stacked with the first connection portion 31 along a second direction Y, and the thickness of the second section 25 along the second direction Y is T 1 The depth T of the portion of the receiving groove 1223 for receiving the second segment 25 2 The depth of the first recess 1111 is T 3 The first partition 131 has a thickness T 4 The first connecting portion 31 has a thickness T 5 ，T 2 +T 3 ≥T 1 +T 4 +T 5 。
The fixing piece 30 can be made of insulating adhesive paper, and the insulating adhesive paper is provided with adhesive, so that the first isolation film 13 and the negative electrode winding initial section 115 can be fixed, the risk of short circuit of the battery cell 100 can be reduced, and the safety performance of the battery cell 100 can be improved. In some embodiments, the fixture 30 may also limit the ions that are detached from the positive electrode tab 12 from reaching the negative electrode winding initiation section 115, thereby reducing the risk of lithium evolution and thus improving the safety performance of the cell 100.
The first connecting portion 31, the first dividing portion 131, and the second segment 25 overlap as viewed in the second direction Y. In the second direction Y, the first connection portion 31 may be located between the first partition portion 131 and the groove bottom surface of the first recess 1111, and the first partition portion 131 is fixed to the groove bottom surface of the first recess 1111 by the first connection portion 31.
In the second direction Y, the first connection portion 31 may be connected to a surface of the first partition portion 131 facing away from the groove bottom surface of the first recess 1111, and the first connection portion 31 presses the first partition portion 131 against the groove bottom surface of the first recess 1111.
By fixing the first separator 13 to the negative electrode winding start section 115, the risk of the first separator 13 moving between the positive electrode sheet 12 and the negative electrode sheet 11 and generating wrinkles is reduced, the risk of short circuit of the battery cell 100 is reduced, and the safety performance of the battery cell 100 is improved. If it is T 2 +T 3 ＜T 1 +T 4 +T 5 That is, the sum of the depth of the receiving groove 1223 and the depth of the first recess 1111 is smaller than the sum of the thickness of the second section 25, the thickness of the first partition 131 and the thickness of the first connection 31, the second section 25, the first partition 131 and the first connection 31 cannot be completely received in the space defined by the receiving groove 1223 and the first recess 1111 in the second direction Y, and the size of the battery cell 100 in the second direction Y increases due to the provision of the protection layer 20, thereby reducing the volumetric energy density of the battery cell 100. Thus T 2 +T 3 ≥T 1 +T 4 +T 5 So that the second segment 25, the first partition 131 and the first connection part 31 are completely accommodated in the space defined by the accommodating groove 1223 and the first recess 1111 in the second direction Y without increasing the size of the electrode assembly 10 in the second direction Y.
In some embodiments, the fixing member 30 may not be provided in the battery cell 100, and the first receiving space defined by the first recess 1111 and the receiving groove 1223 in the second direction Y may collectively receive the second section 25, and the thickness T of the second section 25 1 Depth T of receiving groove 1223 2 Depth T of first recess 1111 3 Satisfy T 1 ≥T 2 +T 3 So that the second section 25 can be completely accommodated in the first accommodating space defined by the first recess 1111 and the accommodating groove 1223 in the second direction Y, the problem of the size increase of the battery cell 100 in the second direction Y due to the arrangement of the protective layer 20 is alleviated, and the problem of the reduction of the volumetric energy density of the battery cell 100 due to the arrangement of the protective layer 20 is alleviated.
As shown in fig. 11-14, in some embodiments, at least a portion of the second section 25 overlaps the negative electrode winding start section 115 as viewed in the second direction Y, and the distance W between the end of the second section 25 facing away from the first section 24 and the negative electrode winding start end 111 is in the first direction X 1 The first recess 1111 has a size W 2 ，0≤W 2 -W 1 ≤0.5mm。
The second section 25 has a distance W between the end facing away from the first section 24 and the cathode winding start 111 1 The dimensions of the region where the second section 25 and the anode winding start section 115 overlap are also viewed in the second direction Y along the first direction X.
W 2 -W 1 May be 0mm, 0.1mm, 0.15mm, 0.2mm, 0.25mm, 0.3mm, 0.35mm, 0.4mm, 0.45mm, 0.5mm, etc.
W 2 -W 1 The size of the first recess 1111 is much larger than the size of the overlapping area of the second section 25 and the anode winding start section 115 > 0.5mm, increasing the difficulty of processing and reducing the amount of anode active material of the anode winding start section 115. W is more than or equal to 0 2 -W 1 The first recess 1111 completely accommodates the overlapping region of the second section 25 and the anode winding start section 115 in the first direction X after the electrode assembly 10 is compressed, and the size of the overlapping region of the second section 25 and the anode winding start section 115 in the first direction X is close to the size of the first recess 1111, so that the risk of lithium precipitation can be reduced. Wherein 0 < W 2 -W 1 And less than or equal to 0.5mm, so that the first concave part 1111 also reserves a certain assembly error space and a certain deformation space for the second section 25 in the first direction X, and is convenient for the second section 25 to enter the first concave part 1111 and also has a certain deformation space after the second section 25 is extruded and deformed.
As shown in FIGS. 11-15, inIn some embodiments, the distance between the end of the second section 25 facing away from the first section 24 and the anode winding start 111 in the first direction X is W 1 ，0.3mm≤W 1 ≤25mm。
Illustratively, W1 may be 0.3mm, 0.5mm, 1m, 2.8mm, 3mm, 5m, 10mm, 12mm, 15mm, 20mm, 25mm, etc.
If W is 1 Less than 0.3mm, the overlapping dimension of the second section 25 and the anode winding start section 115 is small, as viewed in the second direction Y, and the movement of ions of the positive electrode sheet 12 toward the anode winding start end 111 cannot be well restricted, if W 1 The overlapping dimension of the second section 25 and the negative electrode winding initiation section 115, as viewed in the second direction Y, is too large for too much positive electrode active material of the positive electrode winding initiation section to exert its effect, thus reducing the energy density of the cell 100. Thus, 0.3 mm.ltoreq.W 1 And less than or equal to 25mm, the second section 25 can effectively limit the movement of ions of the positive electrode sheet 12 to the negative electrode winding starting end 111, and reduce the risk of lithium precipitation, so that the safety performance of the battery cell 100 is improved, and the positive electrode active material of the positive electrode winding starting section can play a role to a greater extent, so that the battery cell 100 has higher energy density and capacity.
The second positive electrode active material portion 1224 may be any one of both ends connected to the first positive electrode active material portion 1222 in the winding direction. As shown in fig. 11-15, in some embodiments, the positive electrode sheet 12 has a positive electrode winding start end 124, and an end of the second positive electrode active material portion 1224 facing away from the first positive electrode active material portion 1222 extends to the positive electrode winding start end 124 in the first direction X.
The positive electrode sheet 12 includes a positive electrode winding start section, one end of which forms a positive electrode winding start end 124. In the first direction X, the second positive electrode active material portion 1224 extends from one end of the first positive electrode active material portion 1222 to the positive electrode winding start end 124, and the second positive electrode active material portion 1224 is located at the positive electrode winding start section.
The end of the second positive electrode active material portion 1224 facing away from the first positive electrode active material portion 1222 extends to the positive electrode winding start end 124, so that the positive electrode active material amount of the positive electrode winding start section is larger, which is beneficial to improving the energy density of the battery cell 100.
Of course, the second positive electrode active material portion 1224 may be located in the flat region B, and both ends of the second positive electrode active material portion 1224 in the first direction X may be connected to the first positive electrode active material portion 1222 and the positive electrode bent portion of the first positive electrode active material layer 122 located at the innermost side of the second bent region A2, respectively.
As shown in fig. 9-15, in some embodiments, the first positive electrode active material layer 122 further includes a third positive electrode active material portion 1225, the third positive electrode active material portion 1225 being located in the flat region B; a third positive electrode active material portion 1225 is located on the other side of the negative electrode winding start section 115 in the second direction Y; the protective layer 20 further includes a third segment 26, the third segment 26 being located at the flat region B and connected to the other end of the first segment 24, at least a portion of the third segment 26 being located between the winding start section and the third positive electrode active material portion 1225.
The third positive electrode active material portion 1225 and the negative electrode winding start section 115 overlap as viewed in the second direction Y. The third segment 26 extends from the connection position with the first segment 24 in the first direction X to between the anode winding start segment 115 and the third positive electrode active material portion 1225. The third positive electrode active material portion 1225, the negative electrode winding start section 115, and the third section 26 overlap as viewed in the second direction Y.
The third segment 26 may be bonded to the third positive electrode active material portion 1225.
The protective layer 20 further includes a third segment 26 at least partially disposed between the winding initiation segment and the third positive active material portion 1225, which can further cover the area of the protective layer, so as to better limit the movement of ions of the positive electrode sheet 12 toward the negative winding initiation segment 115, reduce the risk of lithium precipitation of the electrode assembly 10 at the negative winding initiation segment 115, and improve the safety performance of the battery cell 100.
As shown in fig. 11 to 15, in the embodiment in which the negative electrode sheet 11 is provided with the concave portion, the concave portion further includes a second concave portion 1112 provided on the side of the negative electrode winding start section 115 facing the third positive electrode active material portion 1225, and the projection of the third section 26 is located at least partially within the second concave portion 1112 as viewed in the second direction Y, and the second concave portion 1112 extends to the negative electrode winding start end 111 in the first direction X.
The second negative electrode active material portion 1141 of the negative electrode winding start section 115 is disposed facing the third positive electrode active material portion 1225, the second recess 1112 is disposed in the second negative electrode active material portion 1141, the second recess 1112 extends in the first direction X to the negative electrode winding start end 111, and then the second recess 1112 is formed with notches in both the surface of the second negative electrode active material portion 1141 facing the third positive electrode active material portion 1225 and the surface of the second negative electrode active material portion 1141 at the negative electrode winding start end 111 so that the third section 26 snaps into the second recess 1112 in the second direction Y when the electrode assembly 10 is subjected to the pressure in the second direction Y. The second recess 1112 is for accommodating a portion of the second segment 25 overlapping the anode winding start end 111.
The depth of the second recess 1112 may be the same as the thickness of the second anode active material portion 1141. The depth of the second recess 1112 may be smaller than the thickness of the second anode active material portion 1141. Fig. 11 to 15 show a case where the depth of the second concave portion 1112 may be smaller than the thickness of the second anode active material portion 1141. The depth of the second recess 1112 may be the same as or different from the depth of the first recess 1111.
The side of the negative electrode winding start section 115 facing the third positive electrode active material portion 1225 is provided with the second recess 1112 extending to the negative electrode winding start end 111, and the projection of the third section 26 is at least partially located in the second recess 1112, so that the third section 26 can be at least partially accommodated in the second recess 1112, which is advantageous in alleviating the problem of excessive increase in size of the battery cell 100 in the second direction Y due to the provision of the protective layer 20, and thus alleviating the problem of reduction in volumetric energy density of the battery cell 100 due to the provision of the protective layer 20.
As shown in fig. 11-15, in some embodiments, the surface of the first positive electrode active material layer 122 facing the winding axis is provided with a receiving groove 1223, and the third segment 26 is located within the receiving groove 1223; in the second direction Y, the third section 26 has a thickness T 6 The depth of the portion of the receiving groove 1223 for the third section 26 is T 7 The depth of the second concave portion 1112 is T8,5 μm.ltoreq.T 6 ≤T 7 +T 8 。
T 6 May be 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, etc. T (T) 7 Refers to the depth of the portion of the receiving groove 1223 located in the third positive electrode active material portion 1225. In some embodiments, T 2 Can sum to T 7 Equal. Of course T 2 And T 7 Or may be unequal.
The protective layer 20 may have a uniform thickness or a non-uniform thickness. In embodiments where the protective layer 20 is non-uniform in thickness, T 6 Is the maximum thickness of the portion of the third section 26 overlapping the anode winding start section 115.
At least a portion of the accommodation groove 1223 overlaps the second recess 1112 as viewed in the second direction Y, the accommodation groove 1223 and the second recess 1112 overlap to collectively define a second accommodation space for accommodating the third segment 26, wherein, in the second direction Y, the third segment 26 may be partially accommodated in the accommodation groove 1223 and the other portion is accommodated in the second recess 1112, so that the space accommodating the third segment 26 is allocated to the third positive electrode active material portion 1225 and the second negative electrode active material portion 1141, so that the depths of the recesses provided on the third positive electrode active material portion 1225 and the second negative electrode active material portion 1141 are smaller, so that the recess setting is more convenient.
If it is T 6 If the thickness of the third segment 26 is smaller than 5. Mu.m, the movement of ions to the anode winding start 111 cannot be effectively restricted, and if T 6 ＞T 7 +T 8 The third section 26 cannot be completely accommodated in the space defined by the second recess 1112 and the accommodation groove 1223, which results in an increase in the size of the electrode assembly 10 in the second direction Y, and thus 5 μm T 6 ≤T 7 +T 8 The protective layer 20 can effectively limit the movement of ions to the cathode winding starting end 111, so that the problem of lithium precipitation is relieved, the safety performance of the battery cell 100 is improved, the third section 26 can be completely contained in the space defined by the containing groove 1223 and the second concave portion 1112 together without increasing the size of the electrode assembly 10 along the second direction Y, and the problem that the size of the battery cell 100 is increased along the second direction Y due to the arrangement of the protective layer 20 is relieved, so that the problem that the volume energy density of the battery cell 100 is reduced due to the arrangement of the protective layer 20 is relieved.
In some embodiments, the first positive electrode active material layer 122 further includes a third positive electrode active material portion 1225 located in the flat region B, the third positive electrode active material portion 1225 being connected to the other end of the first positive electrode active material portion 1222, the third positive electrode active material portion 1225 being located on the other side of the negative electrode winding initiation section 115 in the second direction Y; the electrode assembly 10 further includes a second separator 14, the second separator 14 being disposed at a side of the negative electrode winding start section 115 facing the third positive electrode active material portion 1225 in the second direction Y, and the fixing member 30 for fixing the second separator 14 to the negative electrode winding start section 115.
The second separator 14 serves to separate the positive electrode sheet 12 and the negative electrode sheet 11. The second separator 14 may be PP, PE, or the like. The materials of the first separator 13 and the second separator 14 may be the same or different.
The second separator 14 is fixed to the negative electrode winding start section 115 by the fixing member 30, so that the risk of the second separator 14 moving between the positive electrode sheet 12 and the negative electrode sheet 11 and generating wrinkles is reduced, the risk of short circuit of the battery cell 100 is reduced, and the safety performance of the battery cell 100 is improved.
There are various ways of fixing the first separator 13 to the negative electrode winding start section 115 by the fixing member 30, and as illustrated in fig. 11 to 15, for example, in some embodiments, the surface of the first positive electrode active material layer 122 facing the winding axis is provided with a receiving groove 1223, and the third section 26 is located in the receiving groove 1223; the electrode assembly 10 further includes a second separator 14, the battery cell 100 further includes a fixing member 30 disposed on a side of the negative electrode winding start section 115 facing the third positive electrode active material portion 1225 in the second direction Y, the fixing member 30 being for fixing the second separator 14 to the negative electrode winding start section 115; the fixing element 30 comprises a second connecting portion 33 located in a second recess 1112, the second isolation film 14 comprises a second partition 141 located in the second recess 1112 and stacked with the second connecting portion 33 along the second direction Y, and the thickness of the third section 26 along the second direction Y is T 6 The depth of the portion of the receiving groove 1223 for receiving the third section 26 is T 7 The depth of the second recess 1112 is T 8 The second partition 141 has a thickness T 9 The thickness of the second connection portion 33 is T 10 ，T 7 +T 8 ≥T 6 +T 9 +T 10 。
T 7 Refers to the depth of the portion of the receiving groove 1223 that receives the third section 26.
The fixing piece 30 can be made of insulating adhesive paper, and the insulating adhesive paper is provided with adhesive, so that the second isolation film 14 and the negative electrode winding initial section 115 can be fixed, the risk of short circuit of the battery cell 100 can be reduced, and the safety performance of the battery cell 100 can be improved. In some embodiments, the fixture 30 may also limit the ions that are detached from the positive electrode tab 12 from reaching the negative electrode winding initiation section 115, thereby reducing the risk of lithium evolution and thus improving the safety performance of the cell 100.
The second connecting portion 33, the second dividing portion 141, and the third segment 26 overlap as viewed in the second direction Y. In the second direction Y, the second connection portion 33 may be located between the first person's dividing portion and the bottom surface of the second recess 1112, and the second dividing portion 141 is fixed to the bottom surface of the second recess 1112 through the second connection portion 33. The second connection part 33 may be double-sided adhesive tape with adhesive, and the second connection part 33 may be formed by curing a gel coated on the bottom surfaces of the second partition 141 and the second recess 1112.
By fixing the second separator 14 to the negative electrode winding start section 115, the risk of the second separator 14 moving between the positive electrode sheet 12 and the negative electrode sheet 11 and generating wrinkles is reduced, the risk of short circuit of the battery cell 100 is reduced, and the safety performance of the battery cell 100 is improved. If it is T 7 +T 8 ＜T 6 +T 9 +T 10 That is, the sum of the depth of the receiving groove 1223 and the depth of the second recess 1112 is smaller than the sum of the thickness of the third section 26, the thickness of the second partition 141 and the thickness of the second connection part 33, the third section 26, the second partition 141 and the second connection part 33 cannot be completely received in the space defined by the receiving groove 1223 and the second recess 1112 in the second direction Y, and the size of the battery cell 100 in the second direction Y increases due to the provision of the protection layer 20, thereby reducing the volumetric energy density of the battery cell 100. Thus T 7 +T 8 ≥T 6 +T 9 +T 10 So that the third section 26, the second partition 141 and the second connection portion 33 are completely accommodated in the space defined by the accommodation groove 1223 and the second recess 1112 in the second direction YWithout increasing the size of the electrode assembly 10 in the second direction Y.
In some embodiments, the fixing member 30 may not be provided in the battery cell 100, and the second receiving space defined by the second recess 1112 and the receiving groove 1223 in the second direction Y may collectively receive the third section 26, and the thickness T of the third section 26 6 Depth T of the portion of the accommodation groove 1223 for accommodating the third segment 7 Depth T of second recess 1112 8 Satisfy T 6 ≥T 7 +T 6 So that the third section 26 can be completely accommodated in the second accommodating space defined by the second concave portion 1112 and the accommodating groove 1223 in the second direction Y, the problem that the size of the battery cell 100 in the second direction Y is increased due to the arrangement of the protective layer 20 is alleviated, and the problem that the volume energy density of the battery cell 100 is reduced due to the arrangement of the protective layer 20 is alleviated.
As shown in fig. 11-15, in some embodiments, at least a portion of the third section 26 overlaps the negative electrode winding start section 115 as viewed in the second direction Y, and the distance W between the end of the third section 26 facing away from the first section 24 and the negative electrode winding start end 111 is in the first direction X 3 The second recess 1112 has a dimension W 4 ，0≤W 4 -W 3 ≤0.5mm。
The third section 26 is spaced apart from the first section 24 by a distance W between the end thereof and the beginning 111 of the negative electrode winding 3 The dimensions of the region where the third section 26 and the anode winding start section 115 overlap are also viewed in the second direction Y along the first direction X.
W 4 -W 3 May be 0mm, 0.1mm, 0.15mm, 0.2mm, 0.25mm, 0.3mm, 0.35mm, 0.4mm, 0.45mm, 0.5mm, etc.
W 4 -W 3 The size of the second recess 1112 is much larger than the overlap area size of the third section 26 and the anode winding start section 115, increasing the difficulty of processing and reducing the amount of anode active material of the anode winding start section 115. W is more than or equal to 0 4 -W 3 Less than or equal to 0.5mm, i.e., after compression of the electrode assembly 10, the second recess 1112 completely accommodates the overlapping region of the third section 26 and the negative electrode winding start section 115 in the first direction X, and the overlapping region of the third section 26 and the negative electrode winding start section 115 follows the first direction XThe dimension in the direction X is close to the dimension of the second concave portion 1112, and the risk of lithium precipitation can be reduced.
As shown in fig. 11-15, in some embodiments, the distance between the end of the third segment 26 facing away from the first segment 24 and the beginning of the negative electrode winding 111 is W in the first direction X 3 ，0.3mm≤W 3 ≤25mm。
W3 and W4 may be the same or different. Illustratively, W3 may be 0.3mm, 0.5mm, 1m, 2.8mm, 3mm, 5m, 10mm, 12mm, 15mm, 20mm, 25mm, etc.
If W is 3 Less than 0.3mm, the third section 26 and the negative electrode winding start section 115 overlap in a small size, as viewed in the second direction Y, and do not restrict movement of ions of the positive electrode sheet 12 toward the negative electrode winding start end 111 well, if W 3 The overlapping dimension of the third section 26 and the negative electrode winding initiation section 115, viewed in the second direction Y, is too large for too much positive electrode active material of the positive electrode winding initiation section to perform its function, thus reducing the energy density of the cell 100. Thus, 0.3 mm.ltoreq.W 3 And less than or equal to 25mm, the third section 26 can effectively limit the movement of ions of the positive electrode sheet 12 to the negative electrode winding starting end 111, and reduce the risk of lithium precipitation, so that the safety performance of the battery cell 100 is improved, and the positive electrode active material of the positive electrode winding starting section can play a role to a greater extent, so that the battery cell 100 has higher energy density and capacity.
As shown in fig. 14 and 15, in an embodiment in which the anode winding start section 115 is provided with the first concave portion 1111 and the second concave portion 1112 on both sides in the second direction Y, the fixing member 30 may include the first connection portion 31, the bent portion 32, and the second connection portion 33, the bent portion 32 connecting the first connection portion 31 and the second connection portion 33, and a portion of the first separator 13, a portion of the second separator 14, and a portion of the anode winding start section 115 are fixed between the first connection portion 31 and the second connection portion 33. Specifically, in the second direction Y, the first connection portion 31 of the mount 30 is laminated on a side of the first partition portion 131 of the first separator 13 facing away from the groove bottom surface of the first recess 1111, and the second connection portion 33 of the mount 30 is laminated on a side of the second partition portion 141 of the second separator 14 facing away from the groove bottom surface of the second recess 1112. The bent portion 32 connects the first connection portion 31 and the second connection portion such that the first connection portion 31 and the second connection portion 33 collectively fix the first partition portion 131 of the first separator 13 in the first recess 1111 and fix the second partition portion 141 of the second separator 14 in the second recess 1112.
As shown in fig. 16 and 17, in the embodiment in which the receiving groove 1223 is not provided in the first positive electrode active material layer 122, the fixing member 30 may fix the first separator 13 and the second separator 14 to the negative electrode winding start section 115 in the same manner as the fixing member 30 fixes the first separator 13 and the second separator 14 to the negative electrode winding start section 115 in the embodiment in which the receiving groove 1223 is provided in the first positive electrode active material layer 122. For example, the concave portion on the negative electrode sheet 11 includes a first concave portion 1111 provided on the surface of the negative electrode winding start section 115 facing the second positive electrode active material portion 1224, the first concave portion 1111 extending to the negative electrode winding start end 111, and the fixing member 30 is used to fix a part (first partition portion 131) of the first separator 13 in the first concave portion 1111. Specifically, in the second direction Y, the first connection portion 31 of the mount 30 is laminated on the side of the first partition portion 131 of the first separator 13 facing away from the groove bottom surface of the first recess 1111. In such an embodiment, the depth T of the first recess 1111 3 Thickness T of second section 25 1 The first partition portion 131 of the first isolation film 13 has a thickness T 4 Thickness T of first connecting portion 31 of fixing member 30 5 Can satisfy T 3 ≥T 1 +T 4 +T 5 So that the portion of the protective layer 20, the first separator 13, and the fixture 30 stacked in the second direction Y as a whole can be completely accommodated in the first recess 1111, the fixture 30 and the protector are prevented from being disposed in a size that increases the size of the battery cell 100 in the second direction Y, thereby reducing the volumetric energy density of the battery cell 100. Further, the fixing member 30 fixes a part of the first separator 13 in the first concave portion 1111 of the surface of the anode winding start section 115 facing the second cathode active material portion 1224, which is advantageous in improving the stability of fixing the first separator 13 and the anode winding start section 115.
With continued reference to fig. 16 and 17, in an embodiment in which the first positive electrode active material layer 122 is not provided with the receiving groove 1223, the negative electrode sheet 11 further includes a second recess 1112 provided at a surface of the anode winding start section 115 facing the third cathode active material portion 1225, the second recess 1112 extending to the anode winding start end 111, and the fixing member 30 is for fixing a portion (second partition 141) of the second separator 14 in the second recess 1112. Specifically, the second connection portion 33 of the mount 30 is laminated on a side of the second partition portion 141 of the second separator 14 facing away from the bottom surface of the second recess 1112 in the second direction Y. In such an embodiment, the depth T of the second recess 1112 8 Thickness T of third section 26 6 The thickness of the second partition 141 of the second isolation film 14 is T 9 Thickness T of second connecting portion 33 of fixture 30 10 Can satisfy T 8 ≥T 6 +T 9 +T 10 So that the portion of the protective layer 20, the second separator 14, and the fixing member 30 stacked in the second direction Y as a whole can be completely accommodated in the second recess 1112, the fixing member 30 and the protective member are prevented from being disposed in a size that increases the size of the battery cell 100 in the second direction Y, thereby reducing the volumetric energy density of the battery cell 100. Further, fixing a part of the second separator 14 in the second concave portion 1112 of the surface of the anode winding start section 115 facing the third cathode active material portion 1225 by the fixing member 30 is advantageous in improving the stability of the fixation of the second separator 14 and the anode winding start section 115.
Specifically, the fixing member 30 includes a first connection portion 31, a bent portion 32, and a second connection portion 33, the bent portion 32 connecting the first connection portion 31 and the second connection portion 33, and a portion of the first separator 13, a portion of the second separator 14, and a portion of the anode winding start section 115 are fixed between the first connection portion 31 and the second connection portion 33. The bent portion 32 connects the first connection portion 31 and the second connection portion such that the first connection portion 31 and the second connection portion 33 collectively fix the first partition portion 131 of the first separator 13 in the first recess 1111 and fix the second partition portion 141 of the second separator 14 in the second recess 1112.
The first isolated portion, the second isolated portion of the second isolation film 14 and a portion of the negative electrode winding initiation section 115 are fixed between the first connection portion 31 and the second connection portion 33, and the bending portion 32 connects the first connection portion 31 and the second connection portion 33, so that the first connection portion 31, the bending portion 32 and the second connection portion 33 together fix the first isolation film 13 to the negative electrode winding initiation section 115 and fix the second isolation film 14 to the negative electrode winding initiation section 115, and the fixing is more convenient and the stability is better.
The portion of the first separator 13, the portion of the second separator 14, and the portion of the negative electrode winding start section 115 are fixed between the first connection portion 31 and the second connection portion 33, at least part of the first connection portion 31 is accommodated in the first recess 1111, and at least part of the second connection portion 33 is accommodated in the second recess, not only facilitating the fixation of the first separator 13 and the second separator 14 to the negative electrode winding start section 115, but also alleviating the problem of the increase in size of the battery cell 100 in the second direction Y due to the provision of the fixture 30, thereby facilitating the alleviation of the problem of the decrease in volumetric energy density of the battery cell 100 due to the provision of the fixture 30.
In the embodiment in which the first separator 13 and the second separator 14 are fixed to the anode winding start section 115 by the fixing member 30, the anode winding start section 115 may not be provided with the first concave portion 1111 and the second concave portion 1112, as shown in fig. 18 and 19, the fixing member 30 includes the first connecting portion 31, the bent portion 32, and the second connecting portion 33, the first connecting portion 31 is connected to the surface of the first separator 131 of the first separator 13 facing away from the anode winding start section 115, the second connecting portion 33 is connected to the surface of the second separator 141 of the second separator 14 facing away from the anode winding start section 115, and the bent portion 32 connects the first connecting portion 31 and the second connecting portion 33 and covers the anode winding start end 111. This can avoid the problem of lithium precipitation due to the decrease in the amount of the negative electrode active material in the negative electrode winding start section 115 caused by the provision of the first concave portion 1111 and the second concave portion 1112 in the negative electrode winding start section 115.
In the embodiment shown in fig. 15, if the first positive electrode active material layer 122 is provided with the accommodation groove 1223, and the first connection portion 31 and the second connection portion 33 are both located in the accommodation groove 1223 as viewed in the second direction Y, if the protection layer 20 includes the second segment 25, the second segment 25 is accommodated in a portion of the accommodation groove 1223 located on the second positive electrode active material portion 1224, and the accommodation groove 1223 is located in a portion of the second positive electrode active material portion 1224Depth T 2 Thickness T of the second section 25 1 Thickness T of first connecting portion 31 5 Satisfy T 2 ≥T 1 +T 5 The method comprises the steps of carrying out a first treatment on the surface of the If the protective layer 20 includes the third segment 26, the third segment 26 is accommodated in a portion of the accommodating groove 1223 located on the third positive electrode active material portion 1225, and the accommodating groove 1223 is located at a depth T of the portion of the third positive electrode active material portion 1225 7 The thickness T6 of the third section 26, the thickness T10 of the second connecting portion 33, satisfy T 7 ≥T 6 +T 10 The size of the battery cell 100 in the second direction Y is not increased by adding the protection layer 20 and the fixing member 30, thereby reducing the volumetric energy density of the battery cell 100.
In other embodiments, if the protective layer 20 includes only the first segment 24, the receiving groove 1223 is located at the depth T of the portion of the second positive electrode active material portion 1224 2 Thickness T of first connecting portion 31 5 Satisfy T 2 ≥T 5 The receiving groove 1223 is located at the depth T of the portion of the third positive electrode active material portion 1225 7 Thickness T of the second connection portion 33 10 Satisfy T 2 ≥T 10 The size of the battery cell 100 in the second direction Y is not increased by adding the protection layer 20 and the fixing member 30, thereby reducing the volumetric energy density of the battery cell 100.
In some embodiments, the positive electrode collector of the positive electrode sheet 12 is coated with a positive electrode active material layer on both sides, the positive electrode collector of the positive electrode sheet has no single-side coating area and no empty foil area with both sides uncoated, both sides of the negative electrode winding start section 115 are provided with a negative electrode active material layer, both sides of the negative electrode sheet 11 are respectively provided with a first separator 13 and a second separator 14, and the positive electrode sheet is rolled after the negative electrode sheet 11, the first separator 13 and the second separator 14 are wound for half a turn. In order to fully improve the energy density, the tail-collecting section of the negative plate is coated on one side.
In the winding core, only the first positive electrode active material layer 122 is provided with the accommodating groove 1223, and the protective layer 20 is stuck in the accommodating groove 1223, so that not only the ion precipitation of the first positive electrode active material portion 1222 but also the contact short circuit between the positive electrode sheet 12 and the negative electrode sheet 11 due to the burr penetration can be prevented.
The second and third sections 25 and 26 of the protective layer 20 are each accommodated in the accommodation groove 1223, and the depth T of the recess of the portion of the accommodation groove 1223 for accommodating the second section 25 is set to be equal to or greater than the depth T of the recess of the portion of the accommodation groove 1223 for accommodating the second section 25 2 Depth T of recess of portion of accommodation groove 1223 for accommodating third segment 26 =40 μm 7 =40 μm, the thickness t1=30 μm of the second section 25 of the protective layer 20, and the thickness t6=30 μm of the third section 26 of the protective layer 20. After the electrode assembly is integrally flattened in the second direction Y, the protective layer does not protrude beyond the receiving groove 1223 in the second direction (also the thickness direction of the battery cell).
In the first direction (the width direction of the battery cell), the second section 25 exceeds the length w1=3 mm of the anode winding start 111 (i.e., the distance between the end of the second section 25 facing away from the first section 24 and the anode winding start 111), and the third section 26 exceeds the length W of the anode winding start 111 (i.e., the distance between the end of the third section 26 facing away from the first section 24 and the anode winding start 111) 3 =3mm, ensure good adhesive strength. In addition, the positive plate and the negative plate are also provided with tabs (not shown in the figure) for leading out electrodes, and the positive tab, the negative tab and the gummed paper thereof are not overlapped with the lithium separation protection gummed paper and the diaphragm fixing gummed paper in the thickness direction of the battery cell.
In other embodiments, the positive current collector of the positive electrode sheet 12 is coated with a positive active material layer on both sides, the positive current collector of the positive electrode sheet has no single-sided coating area and no empty foil area with both sides uncoated, both sides of the negative electrode winding start section 115 are provided with a negative active material layer, both sides of the negative electrode sheet 11 are respectively provided with a first separator 13 and a second separator 14, and the positive electrode sheet is wound in a roll after the negative electrode sheet 11, the first separator 13 and the second separator 14 are all wound for half a turn. In order to improve the coating efficiency of the negative plate and reduce the production cost, both sides of the ending section of the negative plate are coated with a negative active material layer.
At the winding core, only the negative electrode winding start section 115 is provided with a first concave portion 1111 and a second concave portion 1112 on both sides in the second direction, respectively. Depth T of first recess 1111 3 =35 μm, the dimension W of the first recess 1111 in the first direction 2 Depth T of second recess 1112 =3.2 mm 8 Dimension W of the second recess 1112 in the first direction =35 μm 4 =3.2mm。
The protective layer 20 has a second section 25 and a third section 26 extending to a flat region and overlapping the anode winding start section 115 in the second direction, the thickness t1=25μm of the second section 25, and the dimension of the second section 25 in the first direction (the distance between the end of the second section 25 facing away from the first section 24 and the anode winding start end 111 is) W 1 =2.8mm. Thickness t6=25 μm of the third segment 26, and the dimension of the third segment 26 in the first direction (the distance between the end of the third segment 26 facing away from the first segment 24 and the anode winding start end 111 is) W 3 =2.8mm。
After the electrode assembly is flattened in the second direction Y as a whole, the second section 25 does not protrude beyond the first recess 1111 in the second direction (also the thickness direction of the battery cell), and the third section 26 does not protrude beyond the second recess 1112. Not only can the function of preventing ion precipitation of the first positive electrode active material portion 1222 but also the function of preventing the contact short circuit between the positive electrode sheet 12 and the negative electrode sheet 11 due to burr penetration.
In addition, the positive plate and the negative plate are also provided with tabs (not shown in the figure) for leading out electrodes, and the positive tab, the negative tab and the gummed paper thereof are not overlapped with the lithium separation protection gummed paper and the diaphragm fixing gummed paper in the thickness direction of the battery cell.
In still other embodiments, the positive electrode collector of the positive electrode sheet 12 is coated with the positive electrode active material layer on both sides, the positive electrode collector of the positive electrode sheet has no single-sided coating region and no hollow foil region with both sides uncoated, both sides of the negative electrode winding start section 115 are provided with the negative electrode active material layer, both sides of the negative electrode sheet 11 are respectively provided with the first separator 13 and the second separator 14, and the positive electrode sheet 11, the first separator 13 and the second separator 14 are wound for half a turn and then the positive electrode sheet is rolled. In order to fully improve the energy density, a negative electrode active material layer is coated on one side of the ending section of the negative electrode plate.
The first positive electrode active material layer 122 is provided with a receiving groove 1223, and the protective layer 20 is attached to the receiving groove 1223, so that not only the ion precipitation of the first positive electrode active material portion 1222 but also the contact short circuit between the positive electrode sheet 12 and the negative electrode sheet 11 due to the penetration of burrs can be prevented.
The second section 25 and the third section 26 of the protective layer 20 are each received in a receiving slot 1223 1223 depth T of recess for accommodating part of the second section 25 2 =30μm, depth T of recess of the portion of accommodation groove 1223 for accommodating third segment 26 7 Thickness T of second section 25 of protective layer 20 =30 μm 1 Thickness T of third section 26 of protective layer 20 =20 μm 6 =20μm。
The second section 25 extends beyond the length (i.e., the distance between the end of the second section 25 facing away from the first section 24 and the anode winding start 111) W of the anode winding start 111 in the first direction (the width direction of the cell) 1 The third section 26 exceeds the length W of the anode winding start 111 (i.e., the distance between the end of the third section 26 facing away from the first section 24 and the anode winding start 111) =12 mm 3 =12 mm, ensuring good adhesive strength.
The negative electrode winding start section 115 is provided with a first concave portion 1111 and a second concave portion 1112 on both sides in the second direction, respectively. The first connection portion 31 of the mount 30 and the first partition portion 131 of the first separation film 13 are accommodated in the first recess 1111, and the second connection portion 33 of the mount 30 and the second partition portion 141 of the second separation film 14 are accommodated in the second recess 1112. The fixing member 30 can also function to restrict the movement of ions on the first positive electrode active material layer 122 to the negative electrode winding start section 115, reduce the risk of lithium precipitation and reduce the risk of contact shorting of the positive electrode sheet 12 and the negative electrode sheet 11.
Thickness T of first connecting portion 31 5 Thickness T of first partition 131 =25 μm 4 =8μm. Thickness T of the second connection portion 33 10 Thickness T of second partition 141 =25 μm 9 =8μm. The fixing member 30 fixes a portion of the first separator 13 and a portion of the second separator 14 to the first recess 1111 and the second recess 1112, respectively, preventing the risk of the first separator and the second separator wrinkling to cause a short circuit.
Depth T of first recess 1111 3 =40 μm, the dimension W of the first recess 1111 in the first direction 2 Depth T of second recess 1112 =10 mm 8 =40 μm, the dimension W of the second recess 1112 in the first direction 4 =10mm。
After the pressing in the thickness direction (second direction Y) of the winding core, the first connecting portion 31 does not protrude beyond the first concave portion 1111 in the cell width direction (first direction X), and the second connecting portion 33 does not protrude beyond the second concave portion 1112 in the cell width direction (first direction X). In the second direction, the protective layer 20 can completely cover the first recess 1111 and the second recess 1112.
And the negative plate and the positive plate are also provided with tabs (not shown in the figure) for leading out electrodes, and the positive tab, the negative tab and the gummed paper thereof are not overlapped with the lithium separation protection gummed paper and the diaphragm fixing gummed paper in the thickness direction of the battery cell.
The battery cell 100 further includes a housing (not shown) formed with a receiving cavity in which the electrode assembly 10 and the protective layer 20 are received, the housing providing a safe and reliable circulation space for the electrode assembly 10 and the protective layer 20. An electrolyte, such as an electrolyte solution, may also be contained within the containment chamber.
The embodiment of the application also provides electric equipment, which comprises the battery cell 100 provided by any embodiment.
The risk of lithium precipitation of the battery cell 100 provided by any embodiment is low, the safety is high, and the electricity utilization safety of electric equipment powered by the battery cell 100 can be improved.
The above is only a preferred embodiment of the present application, and is not intended to limit the present application, but various modifications and variations can be made to the present application by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims (27)

1. A cell, comprising:
the electrode assembly is of a winding type structure, the electrode assembly is provided with a first bending area and a straight area, the first bending area is connected to one end of the straight area along a first direction, the electrode assembly comprises a negative electrode plate and a positive electrode plate, the negative electrode plate is provided with a negative electrode winding starting end, the positive electrode plate is provided with a positive electrode current collector and a first positive electrode active material layer, the first positive electrode active material layer is arranged on one side of the positive electrode current collector facing the winding axis of the electrode assembly, the first positive electrode active material layer comprises a plurality of positive electrode bending parts which are positioned in the first bending area and sequentially arranged from inside to outside, and the positive electrode bending part positioned at the innermost side is arranged facing the negative electrode winding starting end;
A protective layer;
wherein the anode bending part positioned at the innermost side is provided with an accommodating groove; and/or the cathode winding start end is provided with a concave part; at least part of the protective layer is located in the accommodating groove and/or the recess;
the first direction is perpendicular to the direction of extension of the winding axis.
2. The cell of claim 1, wherein the positive electrode bend located innermost in the first bend region is a first positive electrode active material portion;
the protective layer includes a first segment located at the first bending region, the first segment being located between the first positive electrode active material portion and the negative electrode winding start end.
3. The cell of claim 2, wherein the protective layer further comprises a second section, the second section being located in the flat region, the second section being connected to one end of the first section.
4. The cell of claim 3, wherein the protective layer further comprises a third segment, the third segment being located in the flat region, the third segment being connected to the other end of the first segment, the second segment and the third segment being disposed opposite each other in a second direction, the extension direction of the winding axis, the first direction, and the second direction being perpendicular to each other.
5. The cell of claim 1, wherein the protective layer is disposed on the first positive active material layer.
6. The cell according to claim 5, wherein a surface of the first positive electrode active material layer facing the winding axis is provided with the accommodating groove, and the protective layer is at least partially accommodated in the accommodating groove.
7. The cell of claim 6, wherein the protective layer is fully received within the receiving groove.
8. The cell of claim 1, wherein the first positive electrode active material layer further comprises a second positive electrode active material portion, the second positive electrode active material portion being located in the flat region;
the positive electrode bending part at the innermost side of the first bending region is a first positive electrode active material part, the negative electrode sheet comprises a negative electrode winding starting section at a flat region, one end of the negative electrode winding starting section, which is close to the first positive electrode active material part, is the negative electrode winding starting end, along a second direction, the second positive electrode active material part is positioned at one side of the negative electrode winding starting section, and the extending direction of the winding axis, the first direction and the second direction are perpendicular to each other;
The protective layer includes a first section located between the first positive electrode active material portion and the negative electrode winding start end, and a second section located in the flat region and connected to one end of the first section, at least part of the second section being located between the negative electrode winding start end and the second positive electrode active material portion.
9. The battery cell according to claim 8, wherein the negative electrode sheet is provided with the recess including a first recess provided on a side of the negative electrode winding start section facing the second positive electrode active material portion, a projection of the second section being located at least partially within the first recess as viewed in the second direction, the first recess extending to the negative electrode winding start end in the first direction.
10. The cell according to claim 9, wherein a surface of the first positive electrode active material layer facing the winding axis is provided with the accommodating groove, and the second segment is located in the accommodating groove;
in the second direction, the thickness of the second section is T 1 The depth of the part of the accommodating groove for accommodating the second section is T 2 The depth of the first concave part is T 3 ，5μm≤T 1 ≤T 2 +T 3 。
11. The cell according to claim 9, wherein a surface of the first positive electrode active material layer facing the winding axis is provided with the accommodating groove, and the second segment is located in the accommodating groove;
the electrode assembly further includes a first separator, the battery cell further includes a fixing member, the first separator is disposed on a side of the negative electrode winding start section facing the second positive electrode active material portion in the second direction, and the fixing member is configured to fix the first separator to the negative electrode winding start section;
the fixing piece comprises a first connecting part positioned in the first concave part, the first isolating film comprises a first separating part positioned in the first concave part and overlapped with the first connecting part along the second direction, and the thickness of the second section is T along the second direction 1 The depth of the part of the accommodating groove for accommodating the second section is T 2 The depth of the first concave part is T 3 The thickness of the first partition part is T 4 The thickness of the first connecting part is T 5 ，T 2 +T 3 ≥T 1 +T 4 +T 5 。
12. The cell of claim 9, wherein at least a portion of the second segment overlaps the negative electrode winding initiation segment as viewed in the second direction, and wherein a distance between an end of the second segment facing away from the first segment and the negative electrode winding initiation end in the first direction is W 1 The size of the first concave partIs W 2 ，0≤W 2 -W 1 ≤0.5mm。
13. The cell of claim 9, wherein in the first direction, a distance between an end of the second segment facing away from the first segment and the beginning of the negative electrode winding is W 1 ，0.3mm≤W 1 ≤25mm。
14. The cell defined in claim 8, wherein the positive electrode tab has a positive electrode winding start end, and wherein an end of the second positive electrode active material portion facing away from the first positive electrode active material portion extends to the positive electrode winding start end in the first direction.
15. The cell of claim 8, wherein the first positive electrode active material layer further comprises a third positive electrode active material portion, the third positive electrode active material portion being located in the flat region;
the third positive electrode active material part is positioned on the other side of the negative electrode winding starting section along the second direction;
the protective layer further includes a third segment located in the flat region and connected to the other end of the first segment, at least a portion of the third segment being located between the winding start segment and the third positive electrode active material portion.
16. The cell according to claim 15, wherein the negative electrode sheet is provided with the recess, the recess further comprising a second recess provided at a side of the negative electrode winding start section facing the third positive electrode active material portion, a projection of the third section being located at least partially within the second recess as viewed in the second direction, the second recess extending to the negative electrode winding start end in the first direction.
17. The cell according to claim 16, wherein a surface of the first positive electrode active material layer facing the winding axis is provided with the accommodating groove, and the third segment is located in the accommodating groove;
the thickness of the third section is T along the second direction 6 The depth of the part of the accommodating groove for accommodating the third section is T 7 The depth of the second concave part is T 8 ，5μm≤T 6 ≤T 7 +T 8 。
18. The cell according to claim 16, wherein a surface of the first positive electrode active material layer facing the winding axis is provided with the accommodating groove, and the third segment is located in the accommodating groove;
the electrode assembly further includes a second separator, the battery cell further includes a fixing member, the second separator is disposed on a side of the negative electrode winding start section facing the third positive electrode active material portion in the second direction, and the fixing member is configured to fix the second separator to the negative electrode winding start section;
the fixing piece comprises a second connecting part positioned in the second concave part, the second isolating film comprises a second isolating part positioned in the second concave part and overlapped with the second connecting part along the second direction, and the thickness of the third section is T along the second direction 6 The depth of the part of the accommodating groove for accommodating the third section is T 7 The depth of the second concave part is T 8 The thickness of the second partition part is T 9 The thickness of the second connecting part is T 10 ，T 7 +T 8 ≥T 6 +T 9 +T 10 。
19. The cell of claim 17, wherein at least a portion of the third segment overlaps the negative electrode winding initiation segment as viewed in the second direction, and wherein a distance between an end of the third segment facing away from the first segment and the negative electrode winding initiation end in the first direction is W 3 The second concave part has a size W 4 ，0≤W 4 -W 3 ≤0.5mm。
20. The cell of claim 15, wherein in the first direction, the distance between the end of the third segment facing away from the first segment and the beginning of the negative electrode winding is W 3 ，0.3mm≤W 3 ≤25mm。
21. The cell of claim 1, wherein the first positive electrode active material layer further comprises a second positive electrode active material portion, the second positive electrode active material portion being located in the flat region;
the positive electrode bending part at the innermost side of the first bending region is a first positive electrode active material part, the negative electrode sheet comprises a negative electrode winding starting section at a flat region, one end of the negative electrode winding starting section, which is close to the first positive electrode active material part, is the negative electrode winding starting end, along a second direction, the second positive electrode active material part is positioned at one side of the negative electrode winding starting section, and the extending direction of the winding axis, the first direction and the second direction are perpendicular to each other;
The electrode assembly further includes a first separator, the battery cell further includes a fixing member, the first separator is disposed on a side of the negative electrode winding start section facing the second positive electrode active material portion along the second direction, and the fixing member is configured to fix the first separator to the negative electrode winding start section.
22. The cell according to claim 21, wherein the negative electrode sheet is provided with the recess including a first recess provided in a surface of the negative electrode winding start section facing the second positive electrode active material portion, the first recess extending to the negative electrode winding start end, the fixing member for fixing a portion of the first separator within the first recess.
23. The cell of claim 21, wherein the first positive electrode active material layer further comprises a third positive electrode active material portion located in the flat region, the third positive electrode active material portion being connected to the other end of the first positive electrode active material portion, the third positive electrode active material portion being located on the other side of the negative electrode winding initiation section in the second direction;
the electrode assembly further includes a second separator disposed on a side of the negative electrode winding start section facing the third positive electrode active material portion in the second direction, and the fixing member is for fixing the second separator to the negative electrode winding start section.
24. The cell according to claim 23, wherein the negative electrode sheet is provided with the recess including a second recess provided on a surface of the negative electrode winding start section facing the third positive electrode active material portion, and the fixing member is for fixing a portion of the second separator in the second recess.
25. The cell of claim 23, wherein the fixture comprises a first connection portion, a bent portion, and a second connection portion, the bent portion connecting the first connection portion and the second connection portion, a portion of the first separator, a portion of the second separator, and a portion of the negative electrode winding initiation section being fixed between the first connection portion and the second connection portion.
26. The battery cell according to claim 25, wherein the negative electrode sheet is provided with the concave portion including a first concave portion provided at a surface of the negative electrode winding start section facing the second positive electrode active material portion and a second concave portion provided at a surface of the negative electrode winding start section facing the third positive electrode active material portion, the first concave portion and the second concave portion each extending to the negative electrode winding start end in the first direction;
At least part of the first connecting portion is accommodated in the first concave portion, and at least part of the second connecting portion is accommodated in the second concave portion.
27. A powered device comprising a cell according to any one of claims 1-26.
CN202310835182.3A 2023-07-10 2023-07-10 Battery core and electric equipment Active CN116581396B (en)

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