An electric cell

Abstract

The utility model belongs to battery technical field, specifically disclose a kind of electric core, wherein, first pole piece, diaphragm, second pole piece, first pole piece, diaphragm, second pole piece are sequentially laminated and are wound to form electric core, and electric core includes straight area and bending area;First pole piece includes first current collector and first active material layer, and first active material layer is arranged in the two sides of first current collector along its thickness direction;In the winding direction of first pole piece, first pole piece has winding start section located in the inside of electric core and winding end section located in the outside of electric core, and first pole piece located in winding start section has empty foil area, and empty foil area is located in straight area, and empty foil area is provided with liquid absorption layer.Electrolyte can be adsorbed by liquid absorption layer, so that enough electrolyte is soaked in the head of electric core, the supply of electrolyte in the head of electric core is guaranteed, the situation that the head of electric core is easily lithium precipitation in electric core is effectively improved, the deformation of electric core when using is reduced, avoid exceeding design thickness, guarantee the safe use of electric core.

Description

Technical Field

[0001] This utility model relates to the field of battery technology, and in particular to a battery cell. Background Technology

[0002] In existing battery cell structures, after the battery cell is wound, the head of the positive electrode is completely bonded to the separator and the negative electrode. However, because ultra-thin battery cells have fewer electrode layers, the positive electrode head is even more tightly bonded to the separator and the negative electrode during formation. As a result, the electrolyte is difficult to penetrate, which can easily cause lithium plating at the battery head during use, leading to battery cell deformation and exceeding the designed thickness. Utility Model Content

[0003] The purpose of this utility model is to provide a battery cell that solves the technical problem in the prior art where lithium plating easily occurs at the head of the battery cell, leading to cell deformation and exceeding the designed thickness.

[0004] To achieve the above objectives, this utility model provides a battery cell comprising: a first electrode, a separator, and a second electrode, wherein the first electrode, the separator, and the second electrode are sequentially stacked and wound to form the battery cell, and the battery cell includes a flat region and bent regions located at opposite ends of the flat region;

[0005] The first electrode includes a first current collector and a first active material layer, the first active material layer being disposed on both sides of the first current collector along its thickness direction; in the winding direction of the first electrode, the first electrode has a winding start section located inside the battery cell and a winding end section located outside the battery cell, the first electrode located in the winding start section having an empty foil area, the empty foil area being located in the flat area, and the empty foil area being provided with a liquid-absorbing layer.

[0006] Preferably, the liquid-absorbing layer is disposed on both sides of the first current collector along its thickness direction.

[0007] Preferably, the liquid-absorbing layer is provided with a first groove, the opening of the first groove is located on the side of the liquid-absorbing layer away from the first current collector, the depth of the first groove is C, the thickness of the liquid-absorbing layer is D, and C and D satisfy 0.3≤C / D≤0.5.

[0008] Preferably, there are multiple first grooves, and the multiple first grooves are arranged sequentially along the winding direction of the first electrode sheet. The distance between two adjacent first grooves is H, and H satisfies 1mm≤H≤2mm.

[0009] Preferably, the width of the first groove is G, and G satisfies 30μm≤G≤80μm.

[0010] Preferably, in the winding direction of the first electrode, there is a reserved gap between the coating start end of the first active material layer and the coating end end of the liquid absorption layer, the width of the reserved gap being T, and T satisfying 1mm≤T≤1.5mm.

[0011] Preferably, the first active material layer located at the winding start section is provided with a second groove, and the opening of the second groove is located on the side of the first active material layer away from the first current collector. The depth of the second groove is E, and the thickness of the first active material layer is F. E and F satisfy 0.2≤E / F≤0.4.

[0012] Preferably, there are multiple second grooves, and the multiple second grooves are arranged sequentially along the winding direction of the first electrode sheet. The distance between two adjacent second grooves is K, and K satisfies 1mm≤K≤2mm.

[0013] Preferably, the width of the second groove is J, where J satisfies 30μm≤J≤80μm.

[0014] Preferably, in the width direction of the battery cell, the width of the liquid-absorbing layer is A, and the width of the battery cell is B, wherein A and B satisfy 0.1≤A / B≤0.3.

[0015] The battery cell provided by this utility model has an absorbent layer in the empty foil area of ​​the first electrode winding start section. The absorbent layer can adsorb electrolyte, so that there is enough electrolyte to wet the head of the battery cell, ensuring the supply of electrolyte to the head of the battery cell. This allows the battery cell to have enough electrolyte for ion exchange during charge and discharge cycles, effectively improving the situation where lithium plating easily occurs at the head of the battery cell during use, reducing the deformation of the battery cell during use, avoiding exceeding the design thickness, and ensuring the safety of the battery cell during use.

[0016] Additional aspects and advantages of this invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of the first electrode sheet in an embodiment of this utility model;

[0018] Figure 2 This is a schematic diagram of the structure of the liquid-absorbing layer and the first current collector in an embodiment of the present invention;

[0019] Figure 3 This is a schematic diagram of the structure of the first active material layer having a second groove in an embodiment of the present invention;

[0020] Figure 4 This is a schematic diagram of the structure of the first active material layer and the first current collector in an embodiment of this utility model.

[0021] In the figure, 100 is the first electrode; 110 is the first current collector; 120 is the first active material layer; 121 is the second groove; 130 is the winding start section; 140 is the winding end section; 150 is the empty foil area; 160 is the liquid absorption layer; and 161 is the first groove. Detailed Implementation

[0022] The embodiments of this utility model are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this utility model, and should not be construed as limiting this utility model.

[0023] In the description of this utility model, it should be understood that the directional descriptions, such as up, down, front, back, left, right, etc., indicate the directional or positional relationship based on the directional or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0024] In the description of this utility model, "multiple" means two or more; "greater than," "less than," and "exceeding" are understood to exclude the stated number; "above," "below," and "within" are understood to include the stated number. The use of "first" and "second" in the description is merely for distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the quantity or sequence of the indicated technical features.

[0025] In the description of this utility model, unless otherwise explicitly defined, terms such as "setting," "installation," and "connection" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this utility model in conjunction with the specific content of the technical solution.

[0026] Please refer to the following: Figures 1 to 4 The battery electrode provided in the embodiments of this utility model will now be described. The winding direction of the first electrode is the X direction in the figure, and the thickness direction of the first current collector is the Y direction in the figure.

[0027] like Figures 1 to 2As shown, the battery cell of this embodiment includes: a first electrode 100, a separator (not shown), and a second electrode (not shown). The first electrode 100, the separator, and the second electrode are sequentially stacked and wound to form the battery cell. The battery cell includes a flat region (not shown) and bent regions (not shown) located at opposite ends of the flat region; that is, the battery cell is a wound battery cell, the extension direction of the flat region is parallel to the width direction of the battery cell, and the bent regions are located at both ends of the flat region along the width direction of the battery cell. In this embodiment, the first electrode 100 is a positive electrode, and the second electrode is a negative electrode; that is, the positive electrode and the negative electrode, together with the separator, form the battery cell of this embodiment.

[0028] The first electrode 100 includes a first current collector 110 and a first active material layer 120, the first active material layer 120 being disposed on both sides of the first current collector 110 along its thickness direction. In the winding direction of the first electrode 100, the first electrode 100 has a winding start section 130 located inside the battery cell and a winding end section 140 located outside the battery cell. The first electrode 100 located in the winding start section 130 has an empty foil area 150, the empty foil area 150 being located in the flat area, and the empty foil area 150 being provided with a liquid-absorbing layer 160. That is, the winding start section 130 is the head of the first electrode 100, and the winding end section 140 is the tail of the first electrode 100.

[0029] The first current collector 110 is made of aluminum foil, and then the first active material layer 120 is coated on the first current collector 110 to form the first electrode 100; however, an empty foil area 150 is left at the winding start section 130. The empty foil area 150 is the area on the first current collector 110 where the first active material layer 120 is not coated, so that the liquid absorption layer 160 can be coated on the first electrode 100. The first active material layer 120 is responsible for storing and releasing electrical energy and can be made of active materials such as lithium iron phosphate or ternary materials (such as lithium nickel cobalt manganese oxide) to ensure conductivity.

[0030] The absorbent layer 160 can be made of sponge, ceramic powder, or a material that does not react with the electrolyte (such as polypropylene or polyethylene). The thickness of the absorbent layer 160 is the same as the thickness of the first active material layer 120. The porosity of the absorbent layer 160 is controlled to 35%-45%, the rebound ratio is 1%-2%, and the final rebound thickness is 0.5-1.0 μm compared to the first active material layer 120, so as to increase the electrolyte wetting channels.

[0031] The empty foil area 150 is located at the head of the first electrode 100, and the liquid absorbent layer 160 is close to the edge of the empty foil area 150 so that the liquid absorbent layer 160 can better contact the external electrolyte, so that the electrolyte can better wet the winding start section 130 of the first electrode 100, ensuring the supply of electrolyte at the head of the cell, so that there is enough electrolyte for ion exchange during the charge and discharge cycle of the cell, effectively improving the situation where lithium plating easily occurs at the head of the cell during use, reducing the deformation of the cell during use, avoiding exceeding the design thickness, and ensuring the safety of the cell during use.

[0032] Therefore, in this embodiment, the battery cell has an absorbent layer 160 provided in the empty foil area 150 of the winding start section 130 of the first electrode 100. The absorbent layer 160 can absorb electrolyte, thereby ensuring that there is enough electrolyte to wet the head of the battery cell, ensuring the supply of electrolyte to the head of the battery cell. This allows the battery cell to have enough electrolyte for ion exchange during charge and discharge cycles, effectively improving the situation where lithium plating easily occurs at the head of the battery cell during use, reducing the deformation of the battery cell during use, avoiding exceeding the design thickness, and ensuring the safety of the battery cell during use.

[0033] In some embodiments of this utility model, reference is made to Figures 1 to 2 To ensure sufficient electrolyte on both sides of the empty foil area 150 of the first electrode 100, the absorbent layer 160 is disposed on both sides of the first current collector 110 along its thickness direction. The electrolyte adsorbed and retained by the absorbent layer 160 can fully wet both sides of the winding start section 130 of the first electrode 100, so as to better supply electrolyte to the winding start section 130 of the first electrode 100, thereby better ensuring the supply of electrolyte at the head of the cell. This allows the cell to have sufficient electrolyte for ion exchange during charge and discharge cycles, effectively improving the situation where lithium plating easily occurs at the head of the cell during use, reducing the deformation of the cell during use, avoiding exceeding the design thickness, and ensuring the safety of the cell during use.

[0034] In some embodiments of this utility model, reference is made to Figures 1 to 2To ensure sufficient electrolyte wetting of the cell head, the absorbent layer 160 is provided with a first groove 161. The opening of the first groove 161 is located on the side of the absorbent layer 160 opposite to the first current collector 110. The depth of the first groove 161 is C, and the thickness of the absorbent layer 160 is D, where C and D satisfy 0.3 ≤ C / D ≤ 0.5. The first groove 161 forms a electrolyte storage space, allowing the cell to maintain sufficient electrolyte even in the later stages of cycling, avoiding lithium plating due to electrolyte depletion. Furthermore, the first groove 161 allows the thickness of the first electrode 100 in the empty foil area 150 to be reduced, thereby decreasing electrolyte penetration resistance and improving the wetting uniformity of the head of the first electrode 100. Furthermore, the condition that C and D satisfy 0.3≤C / D≤0.5 ensures that the absorbent layer 160 has sufficient capacity to adsorb electrolyte while allowing the electrolyte to better penetrate the entire cell head. This ensures better electrolyte wetting of the cell head, thereby guaranteeing the supply of electrolyte to the cell head, effectively improving the situation where lithium plating easily occurs at the cell head during use, reducing cell deformation during use, avoiding exceeding the design thickness, and ensuring cell safety during use.

[0035] In some embodiments of this utility model, reference is made to Figures 1 to 2 To allow the electrolyte to better wet the head of the cell, there are multiple first grooves 161, and these multiple first grooves 161 are arranged sequentially along the winding direction of the first electrode 100. This creates more liquid storage space and reduces the electrolyte penetration resistance, thereby improving the uniformity of wetting at the head of the first electrode 100. Furthermore, the distance between two adjacent first grooves 161 is H, and H satisfies 1mm≤H≤2mm. This ensures the strength of the absorbent layer 160 and provides it with sufficient thickness to better absorb and retain the electrolyte, thereby better wetting the head of the cell and ensuring the supply of electrolyte at the head of the cell.

[0036] In some embodiments of this utility model, reference is made to Figures 1 to 2 To ensure better electrolyte wetting of the cell head, the width of the first groove 161 is G, where G satisfies 1μm ≤ G ≤ 1.5μm. When the width of the first groove 161 is less than 1μm, the electrolyte has difficulty entering the first groove 161, and the volume of stored electrolyte is small, making it difficult to ensure sufficient electrolyte wetting of the cell head and affecting the uniformity of wetting of the cell head. When the width of the first groove 161 is greater than 1.5μm, it is difficult to retain the electrolyte in the first groove 161, thus affecting the electrolyte storage function of the first groove 161 and reducing the overall ability of the absorbent layer 160 to adsorb and retain electrolyte.

[0037] In some embodiments of this utility model, reference is made to Figures 1 to 2To better retain the electrolyte on the first electrode 100, a reserved gap is provided between the coating start end of the first active material layer 120 and the coating end end of the absorbent layer 160 in the winding direction of the first electrode 100. The width of the reserved gap is T, and T satisfies 1mm ≤ T ≤ 1.5mm. The reserved gap forms a liquid storage space between the first active material layer 120 and the absorbent layer 160, allowing the electrolyte to remain in the material area of ​​the first electrode 100. This ensures that the electrolyte fully wets the winding start section 130 of the first electrode 100 and the cell head, thereby improving lithium plating at the cell head, reducing cell deformation during use, preventing the design thickness from being exceeded, and ensuring cell safety during use.

[0038] In some embodiments of this utility model, reference is made to Figure 3 and Figure 4 To better allow the electrolyte to wet the cell head, a second groove 121 is provided on the first active material layer 120 located in the winding start section 130. The opening of the second groove 121 is located on the side of the first active material layer 120 away from the first current collector 110. The depth of the second groove 121 is E, and the thickness of the first active material layer is F, where E and F satisfy 0.2≤E / F≤0.4. The second groove 121 can form a liquid storage space for the first active material layer 120, allowing the cell to maintain sufficient electrolyte in the later stages of cycling, avoiding lithium plating caused by electrolyte depletion. Moreover, the second groove 121 can reduce the thickness of the first active material layer 120, thereby reducing the electrolyte penetration resistance and improving the wetting uniformity of the winding start section 130. The second groove 121 can buffer volume expansion, reserving deformation space for volume changes during the charging and discharging process of the active material, reducing the risk of electrode wrinkling and coating peeling. Furthermore, it can disperse charging and discharging stress during the process, avoiding electrode cracking or pulverization caused by stress concentration, and extending cycle life. Moreover, the condition that E and F satisfy 0.2≤E / F≤0.4 allows the electrolyte to remain better on the first active material layer 120, better wetting the cell head, thus ensuring electrolyte supply to the cell head. This effectively improves the situation where lithium plating easily occurs at the cell head during use, reduces cell deformation during use, avoids exceeding the design thickness, and ensures cell safety.

[0039] In some embodiments of this utility model, reference is made to Figure 3 and Figure 4To improve the electrical performance of the first active material layer 120, multiple second grooves 121 are provided, arranged sequentially along the winding direction of the first electrode 100. The distance between two adjacent second grooves 121 is K, where K satisfies 1mm ≤ K ≤ 2mm. By providing multiple second grooves 121, the effective reactive surface area of ​​the first active material layer 120 is increased, the interface resistance is reduced, and the charge transfer efficiency is improved. Furthermore, the groove structure guides the current to a uniform distribution, reducing local overcharging or over-discharging of the electrode and improving high-rate charge / discharge performance. The condition K satisfies 1mm ≤ K ≤ 2mm, ensuring the strength of the first active material layer 120 and providing sufficient thickness to prevent deformation or detachment during charging and discharging. It should be noted that electrode overcharging refers to the voltage exceeding the rated voltage of the battery during charging, which can easily lead to electrolyte decomposition and electrode material structure damage, thereby shortening battery life or causing safety problems; electrode over-discharging refers to the voltage dropping below the safe threshold during the discharge process of a lithium-ion battery, which can easily cause unnecessary damage to the electrodes and lead to safety problems.

[0040] In some embodiments of this utility model, reference is made to Figure 3 and Figure 4 The width of the second groove 121 is J, where J satisfies 1μm ≤ J ≤ 1.5μm. When the width of the second groove 121 is less than 1μm, the electrolyte is difficult to enter the second groove 121, and the volume of stored electrolyte is small, making it difficult to ensure that the electrolyte fully wets the cell head, affecting the uniformity of wettation at the cell head. When the width of the second groove 121 is greater than 1.5μm, it is difficult to retain the electrolyte in the second groove 121, thus affecting the electrolyte storage function of the second groove 121.

[0041] In some embodiments of this utility model, reference is made to Figure 1 and Figure 2 To ensure better electrolyte wetting of the cell head, the width of the absorbent layer 160 is A, and the width of the cell is B, satisfying 0.1 ≤ A / B ≤ 0.3. This ensures that the absorbent layer 160 is positioned wide enough at the cell head to adsorb electrolyte, allowing for better electrolyte wetting and supply. This ensures sufficient electrolyte for ion exchange during charge-discharge cycles, effectively mitigating lithium plating at the cell head during use, reducing cell deformation, preventing exceedance of design thickness, and ensuring cell safety.

[0042] In some preferred embodiments, the width B of the bare cell is 51 mm, the width A of the liquid-absorbing layer 160 on the first electrode 100 at the cell head is 8 mm, the width T of the reserved gap between the liquid-absorbing layer 160 and the first active material layer 120 is 1 mm, the depth C of the first groove 161 of the liquid-absorbing layer 160 and the thickness D of the liquid-absorbing layer 160 satisfy C / D = 0.4; the width G of the first groove 161 is 1 μm, and the spacing between two adjacent first grooves 161 is 1 mm.

[0043] In some other preferred embodiments, the width B of the bare cell is 71 mm, the width A of the liquid-absorbing layer 160 on the first electrode 100 at the cell head is 10 mm, the width T of the reserved gap between the liquid-absorbing layer 160 and the first active material layer 120 is 1.2 mm, the depth C of the first groove 161 of the liquid-absorbing layer 160 and the thickness D of the liquid-absorbing layer 160 satisfy C / D = 0.35; the width G of the first groove 161 is 1.2 μm, and the spacing between two adjacent first grooves 161 is 1 mm.

[0044] In summary, the battery cell of this embodiment has an absorbent layer 160 provided in the empty foil area 150 of the winding start section 130 of the first electrode 100. The absorbent layer 160 can adsorb electrolyte, thereby ensuring that there is enough electrolyte to wet the head of the battery cell, ensuring the supply of electrolyte to the head of the battery cell. This allows the battery cell to have enough electrolyte for ion exchange during charge and discharge cycles, effectively improving the situation where lithium plating easily occurs at the head of the battery cell during use, reducing the deformation of the battery cell during use, avoiding exceeding the design thickness, and ensuring the safety of the battery cell during use.

[0045] The above are merely preferred embodiments of this utility model. It should be noted that, for those skilled in the art, several improvements and substitutions can be made without departing from the technical principles of this utility model, and these improvements and substitutions should also be considered within the protection scope of this utility model.

Claims

1. A battery cell, characterized in that, include: The battery cell is formed by stacking and winding the first electrode, the separator, and the second electrode in sequence. The battery cell includes a flat region and bent regions located at opposite ends of the flat region. The first electrode includes a first current collector and a first active material layer, the first active material layer being disposed on both sides of the first current collector along its thickness direction; in the winding direction of the first electrode, the first electrode has a winding start section located inside the battery cell and a winding end section located outside the battery cell, the first electrode located in the winding start section having an empty foil area, the empty foil area being located in the flat area, and the empty foil area being provided with a liquid-absorbing layer.

2. The battery cell according to claim 1, characterized in that, The liquid-absorbing layer is disposed on both sides of the first current collector along its thickness direction.

3. The battery cell according to claim 2, characterized in that, The liquid-absorbing layer is provided with a first groove, the opening of the first groove is located on the side of the liquid-absorbing layer away from the first current collector, the depth of the first groove is C, the thickness of the liquid-absorbing layer is D, and C and D satisfy 0.3≤C / D≤0.

5.

4. The battery cell according to claim 3, characterized in that, The number of the first grooves is multiple, and the multiple first grooves are arranged sequentially along the winding direction of the first electrode sheet. The distance between two adjacent first grooves is H, and H satisfies 1mm≤H≤2mm.

5. The battery cell according to claim 3, characterized in that, The width of the first groove is G, and G satisfies 30μm≤G≤80μm.

6. The battery cell according to claim 1, characterized in that, In the winding direction of the first electrode, there is a reserved gap between the coating start end of the first active material layer and the coating end end of the liquid absorption layer, the width of the reserved gap is T, and T satisfies 1mm≤T≤1.5mm.

7. The battery cell according to claim 1, characterized in that, The first active material layer located at the starting section of the winding is provided with a second groove, and the opening of the second groove is located on the side of the first active material layer away from the first current collector. The depth of the second groove is E, and the thickness of the first active material layer is F. E and F satisfy 0.2≤E / F≤0.

4.

8. The battery cell according to claim 7, characterized in that, The number of the second grooves is multiple, and the multiple second grooves are arranged sequentially along the winding direction of the first electrode. The distance between two adjacent second grooves is K, and K satisfies 1mm≤K≤2mm.

9. The battery cell according to claim 8, characterized in that, The width of the second groove is J, and J satisfies 30μm≤J≤80μm.

10. The battery cell according to any one of claims 1-9, characterized in that, In the width direction of the battery cell, the width of the liquid-absorbing layer is A, and the width of the battery cell is B, where A and B satisfy 0.1≤A / B≤0.3.

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