Battery cell and battery

Abstract

The utility model provides a battery cell and a battery. The battery cell comprises a first pole piece, a second pole piece and a diaphragm, the first pole piece, the diaphragm and the second pole piece are laminated and wound to form a winding core; the first pole piece comprises a first current collector and a first active material layer; the first active material layer comprises a first active layer and a second active layer along the first direction, and the first active layer is arranged on at least one side of the first current collector; the number of the second active layers is at least two, the at least two second active layers are arranged on the side, away from the first current collector, of the first active layer in the second direction, and a gap is formed between every two adjacent second active layers; the first pole piece is provided with the first straight area and the first arc bending areas located on the two sides of the first straight area, and at least part of the gap is located in the first arc bending areas, so that the lithium precipitation risk of the battery is reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of batteries, in particular to a battery core and a battery. Background Art

[0002] Currently, lithium-ion batteries are widely used not only in portable electronic devices such as mobile phones and laptops, but also in electric equipment such as electric vehicles and electric bicycles.

[0003] The battery cell is the core component of the lithium-ion battery. The battery cell includes a positive electrode sheet, a negative electrode sheet, and a separator disposed between the positive electrode sheet and the negative electrode sheet. The battery cell is immersed in an electrolyte, and lithium ions move between the positive and negative electrodes through the electrolyte, thereby realizing the charging and discharging of the battery. However, the battery of the related technology has a high risk of lithium plating. Utility Model Content

[0004] In view of this, the embodiments of the present utility model are dedicated to providing a battery cell and a battery to reduce the risk of lithium plating to a certain extent.

[0005] In a first aspect, the utility model provides a battery core, comprising a first pole piece, a second pole piece, and a diaphragm located between the first pole piece and the second pole piece; the first pole piece, the diaphragm, and the second pole piece are stacked and wound to form a winding core;

[0006] The first pole piece includes a first current collector and a first active material layer, the first active material layer includes a first active layer and a second active layer along a first direction, the first active layer is arranged on at least one side of the first current collector; there are at least two second active layers, at least two second active layers are arranged along a second direction on a side of the first active layer away from the first current collector, and there is a gap between two adjacent second active layers;

[0007] The first pole piece has a first straight region and first arc bending regions located on both sides of the first straight region, and at least part of the gap is located in the first arc bending region.

[0008] Optionally, along the second direction, the length of the gap is not less than 3 mm.

[0009] Optionally, in a direction from a winding head to a winding tail of the first pole piece, the lengths of all the gaps are the same;

[0010] Alternatively, in a direction from a winding head portion to a winding tail portion of the first pole piece, the lengths of all the gaps increase sequentially.

[0011] Optionally, the compaction density of the region of the first active material layer having the second active layer is greater than the compaction density of the region of the first active material layer having the gap;

[0012] And / or, the ratio range of the compaction density of the region of the first active material layer having the second active layer to the total thickness of the region of the first active material layer having the second active layer is 0.05 to 0.23.

[0013] Optionally, the areal density of the first active layer is not less than the areal density of the second active layer;

[0014] And / or, the areal density of the first active layer is not less than 60 g / m 2 ;

[0015] And / or, the range of the areal density ρ of the region of the first active material layer having the second active layer satisfies: 90 g / m 2 ≤ ρ ≤ 250 g / m 2 。

[0016] Optionally, along the first direction, the ratio range of the thickness of the first active layer to the total thickness of the region of the first active material layer having the second active layer is 0.56 to 0.96;

[0017] And / or, along the first direction, the thickness range of the second active layer is 7.5 μm to 35 μm.

[0018] Optionally, along the second direction, at a preset distance from the edge of the first active material layer, the total thickness of the first active material layer is greater than the thickness of the first active layer;

[0019] Preferably, the preset distance is not less than 3 mm.

[0020] Optionally, all of the second active layers are located in the first flat region, and at least part of the gap is located in the first arc bending region;

[0021] Or, among all of the second active layers, part of the second active layers are located in the first flat region, part of the second active layers are located in the first arc bending region, and at least part of the gap is located in the first arc bending region.

[0022] Optionally, at the innermost winding circle of the first pole piece, the gap located on the first arc bending region extends to the first flat region.

[0023] Optionally, the second pole piece has a second flat region and second arc bending regions located on both sides of the second flat region, and a second tab is provided on the second flat region;

[0024] The projection of the gap extending to the first flat region in the second direction does not overlap with the projection of the second tab in the second direction.

[0025] Optionally, at the outermost winding of the first pole piece, the second active layer located on the first flat region extends to the first arc bending region.

[0026] Optionally, in the second direction, the second active layer includes a first region and a second region located at at least one end of the first region, and the thickness of the second region in the first direction is less than the thickness of the first region in the first direction.

[0027] Optionally, in the direction away from the first region, the thickness of the second region in the first direction gradually decreases;

[0028] And / or, the surface of the second region facing away from the first active layer is an arc surface;

[0029] And / or, the included angle range between the surface of the second region facing away from the first active layer and the surface of the first active material layer facing away from the first current collector is 1° to 10°;

[0030] And / or, in the second direction, the length range of the second region is 50 μm to 500 μm;

[0031] And / or, in the second direction, the ratio range of the length of the second region to the total length of the second active layer is 1 / 1000 to 1 / 60.

[0032] In a second aspect, the present utility model provides a battery, including the battery cell as described above.

[0033] For the battery cell and the battery provided by the embodiments of the present utility model, by dividing the first active material layer of the first pole piece into a first active layer and a second active layer in the first direction, setting the first active layer on one side of the first current collector, making at least two second active layers, arranging at least two second active layers on the side of the first active layer facing away from the first current collector in the second direction, and having a gap between adjacent two second active layers, that is to say, making the second active layers among them form an intermittent arrangement, that is, reducing the amount of active material in the entire first active material layer, thereby reducing the amount of lithium ions received by the second pole piece, and further reducing the risk of lithium deposition.

[0034] By making at least part of the gap located in the first arc bending region of the first pole piece, at least reducing the amount of active material in the first arc bending region, reducing the amount of lithium ions received by the second pole piece, especially making the first arc bending region not easy to deposit lithium, reducing the risk of lithium deposition in the first arc bending region, and improving the electrical performance, safety and life of the battery.

[0035] Moreover, the existence of the gap can also play a role in storing the electrolyte, thereby increasing the amount of electrolyte retained by the first electrode sheet, further improving the wetting effect of the electrolyte and the transmission rate of lithium ions, and effectively improving the charge-discharge performance and cycling performance of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 is a schematic structural diagram of the first electrode sheet according to an embodiment of the present invention;

[0037] Figure 2 is Figure 1 the corresponding partial structural diagram;

[0038] Figure 3 is a schematic structural diagram of the second electrode sheet according to an embodiment of the present invention;

[0039] Figure 4 is a schematic structural diagram of the battery cell according to an embodiment of the present invention.

[0040] Wherein, 1, first electrode sheet; 11, first current collector; 12, first active material layer; 121, first active layer; 122, second active layer; 120, first region; 123, second region; 124, arc surface; 101, first flat region; 102, first arc bending region; 13, gap; 14, first tab; 2, second electrode sheet; 21, second current collector; 22, second active material layer; 23, second tab; 201, second flat region; 202, second arc bending region; 3, separator. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0041] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0042] The battery cell of a lithium-ion battery includes a positive electrode sheet, a negative electrode sheet and a separator. Specifically, the positive electrode sheet, the separator and the negative electrode sheet are stacked and wound from the inside out to form a wound core. Among them, the positive electrode sheet includes a positive current collector and a positive active material layer provided on the surface of the positive current collector. The negative electrode sheet includes a negative current collector and a negative active material layer provided on the surface of the negative current collector. The active materials in the positive active material layer and the negative active material layer provide capacity for the battery through an electrochemical reaction. The separator is located between the positive electrode sheet and the negative electrode sheet to isolate the contact between the positive electrode sheet and the negative electrode sheet. The battery cell is immersed in the electrolyte and a wound battery is obtained after encapsulation. After winding, the battery cell includes a flat region and arc bending regions connected to both sides of the flat region.

[0043] The risk of lithium plating in the batteries of related technologies is relatively high, which will directly affect the electrical performance, safety and lifespan of the batteries. For example, lithium plating is particularly likely to occur in the arc bending area. Specifically, the arc bending area may be deformed, the active material layer may be compressed or stretched after winding, etc. As a result, after lithium ions are deintercalated from the positive electrode sheet, they cannot be uniformly embedded in the negative electrode sheet, or the lithium insertion path is abnormal, thus causing lithium plating on the negative electrode sheet.

[0044] Based on this, the embodiments of the present utility model provide a battery cell and a battery. The active material layer of the first electrode sheet is divided into two parts along the thickness direction of the first electrode sheet: a first active layer and a second active layer. The first active layer is disposed on at least one side of the first current collector, and the second active layer is provided with at least two. The at least two second active layers are arranged at intervals on the side of the first active layer away from the first current collector, that is, there is a gap between two adjacent second active layers, and at least part of the gap is located in the first arc bending area, so as to reduce the amount of active material in at least the first arc bending area, thereby reducing the amount of lithium ions received by the second electrode sheet, and thus reducing the risk of lithium plating.

[0045] The following will combine the accompanying drawings and specifically illustrate the battery cell and the battery provided by the present utility model through specific embodiments:

[0046] Refer to Figures 1 to 4 As shown, this embodiment provides a battery cell. The battery cell may specifically be a wound battery cell. The battery cell is applied to a battery, and the battery may be a lithium-ion battery.

[0047] The battery cell of this embodiment specifically includes: a first electrode sheet 1, a second electrode sheet 2, and a separator 3. Among them, the separator 3 is located between the first electrode sheet 1 and the second electrode sheet 2. The first electrode sheet 1, the separator 3, and the second electrode sheet 2 are sequentially stacked and wound to form a core.

[0048] Among them, the first electrode sheet 1 includes a first current collector 11 and a first active material layer 12 disposed on at least one side of the first current collector 11. The second electrode sheet 2 includes a second current collector 21 and a second active material layer 22 disposed on at least one side of the second current collector 21.

[0049] Specifically, the first current collector 11 has opposite sides for coating the first active material layer 12. In specific implementation, refer to Figure 1 and Figure 2 As shown, the first active material layer 12 can be disposed on both sides of the first current collector 11 ( Figure 1 or Figure 2 the upper side and the lower side of the first current collector 11 in

[0050] The second current collector 21 has opposite sides for coating the second active material layer 22. In specific implementation, referring to Figure 3 as shown, the second active material layer 22 can be provided on both sides of the second current collector 21 ( Figure 3 the upper side and the lower side of the second current collector 21 in

[0051] Continuing to refer to Figure 1 and Figure 2 as shown, the first active material layer 12 includes a first active layer 121 and a second active layer 122 along a first direction. The first direction here is, for example, Figure 1 and Figure 2 the up-down direction in

[0052] wherein, the first active layer 121 is provided on at least one side of the first current collector 11. There are at least two second active layers 122, and at least two second active layers 122 are arranged along a second direction on the side of the first active layer 121 away from the first current collector 11, and there is a gap 13 between two adjacent second active layers 122, that is, a pit is formed between two adjacent second active layers 122.

[0053] That is to say, the first active material layer 12 is divided into two parts along the first direction: the first active layer 121 and the second active layer 122, and at the same time, the second active layer 122 is arranged discontinuously, thereby reducing the amount of active material in the first active material layer 12, thereby reducing the amount of lithium ions received by the second electrode sheet 2, and thus reducing the risk of lithium deposition in the battery.

[0054] The existence of the gap 13 can also play a role in storing the electrolyte, thereby improving the electrolyte retention ability of the electrode sheet, improving the wetting effect of the electrolyte and the transmission rate of lithium ions, and thus effectively improving the charge-discharge performance and cycle performance of the battery.

[0055] Referring to Figure 4 as shown, the first electrode sheet 1 has a first flat area 101 and first arc bending areas 102 located on both sides of the first flat area 101. Exemplarily, the first arc bending area is prone to deformation after winding, etc. In this way, after lithium ions are deintercalated from the first electrode sheet, they cannot be evenly embedded in the second electrode sheet, or the lithium intercalation path is abnormal, resulting in lithium deposition on the second electrode sheet. Based on this, at least part of the gap 13 is located in the first arc bending area 102, and by reducing the amount of active material in the first arc bending area 102, the amount of lithium ions received by the second electrode sheet 2 is reduced, thereby reducing the risk of lithium deposition in the first arc bending area 102.

[0056] Exemplarily, in a feasible implementation manner, at least part of the above-mentioned gap 13 is located in the first arc bending region 102. For example, it can be that all the second active layers 122 are located in the first straight region 101, and at least part of the gap 13 is located in the first arc bending region 102.

[0057] In this implementation manner, for example, it can be that the second active layer 122 is normally coated at the position corresponding to the first straight region 101 of the first pole piece 1, and the second active layer 122 is not coated at the position corresponding to the first arc bending region 102. After winding, the gap 13 formed between two adjacent second active layers 122 is exactly located in the first arc bending region 102. Here, it can be understood that all the gaps 13 are located in the first arc bending region 102, or the ends of the gaps 13 located in the first arc bending region 102 extend to the first straight region 101.

[0058] In addition, the above-mentioned normal coating of the second active layer 122 at the position corresponding to the first straight region 101 can specifically be that the second active layer 122 is normally coated in the first straight region 101 and there is no gap 13 in the first straight region 101; or it can be that the second active layer 122 is coated intermittently in the first straight region 101, so that a gap 13 is formed between two adjacent second active layers 122 located in the first straight region 101.

[0059] Exemplarily, in another feasible implementation manner, at least part of the above-mentioned gap 13 is located in the first arc bending region 102. For example, it can also be that among all the second active layers 122, part of the second active layers 122 are located in the first straight region 101, part of the second active layers 122 are located in the first arc bending region 102, and at least part of the gap 13 is located in the first arc bending region 102.

[0060] In this implementation manner, for example, it can be that there are at least two second active layers 122 located in the first arc bending region 102, and at least two second active layers 122 are coated intermittently in the first arc bending region 102, and a gap 13 is formed between two adjacent second active layers 122. For example, it can also be that there is one second active layer 122 coated in the first arc bending region 102, and the coating length of this second active layer 122 (which can be understood as the length in the above-mentioned first direction) is less than the length of the first arc bending region 102. At this time, a gap 13 is exactly formed between the end of this second active layer 122 and the end of the second active layer 122 located in the first straight region 101, and at least part of this gap 13 is located in the first arc bending region 102.

[0061] In addition, part of the above-mentioned second active layer 122 is located in the first flat area 101. It can be understood that the second active layer 122 located on the first flat area 101 is normally coated, and there is no gap 13 in the first flat area 101; or, the second active layer 122 located on the first flat area 101 is coated in an intermittent manner, so that a gap 13 is formed between two adjacent second active layers 122 located on the first flat area 101.

[0062] In specific implementation, exemplarily, the first active material layer 12 can be coated on the first current collector 11 by means of a double-layer coating die. For example, during the coating process, the first active layer 121 is normally coated. According to the designed number of folds of the battery cell, the second active layer 122 is normally coated at the position of the first flat area 101 corresponding to the first electrode sheet 1, and the second active layer 122 is not coated at the position of the first arc bending area 102 corresponding to the first electrode sheet 1. For another example, the second active layer 122 is normally coated at the position of the first flat area 101 corresponding to the first electrode sheet 1, and the second active layer 122 is coated with intermittent gaps at the position corresponding to the first arc bending area 102. Then, subsequent processes such as rolling and winding are carried out. Thus, after the first electrode sheet 1 is wound, at least part of the gap 13 is located in the first arc bending area 102.

[0063] The above-mentioned first electrode sheet 1 can be, for example, a positive electrode sheet, the first current collector 11 can be, for example, an aluminum foil, and the material of the first active material layer 12 can be, for example, a positive electrode active material such as lithium cobaltate, ternary material, lithium iron phosphate, lithium carbonate, lithium manganate, etc. Correspondingly, the second electrode sheet 2 can be a negative electrode sheet, the second current collector 21 can be, for example, a copper foil, and the material of the second active material layer 22 can be, for example, a negative electrode active material such as graphite or silicon-based material.

[0064] In the battery cell provided in this embodiment, the first active material layer 12 is arranged in two parts along the first direction: the first active layer 121 and the second active layer 122. The first active layer 121 is arranged on one side of the first current collector 11, so that there are at least two second active layers 122. At least two second active layers 122 are arranged along the second direction on the side of the first active layer 121 away from the first current collector 11, and there is a gap 13 between two adjacent second active layers 122. That is to say, the second active layer 122 is formed into an intermittent arrangement, that is, the amount of active material in the entire first active material layer 12 is reduced, the amount of lithium ions received by the second electrode sheet 2 is reduced, and thus the risk of lithium deposition is reduced.

[0065] By making part of the gap 13 located in the first arc bending area 102, especially the amount of active material in the first arc bending area 102 is reduced, the amount of lithium ions received by the second electrode sheet 2 is reduced. In particular, it makes the first arc bending area 102 not easy to deposit lithium, reduces the risk of lithium deposition in the first arc bending area 102, and improves the electrical performance, safety and life of the battery.

[0066] Moreover, the existence of the gap 13 can also play a role in storing the electrolyte, thereby improving the liquid retention ability of the first electrode sheet 1 for the electrolyte, enhancing the wetting effect of the electrolyte and the transmission rate of lithium ions, and effectively improving the charge-discharge performance and cycle performance of the battery.

[0067] Specifically, the material of the first active layer 121 can be selected from at least one of lithium cobaltate, ternary, lithium iron phosphate, lithium carbonate, and lithium manganate. The material of the second active layer 122 can be selected from at least one of lithium cobaltate, ternary, lithium iron phosphate, lithium carbonate, and lithium manganate.

[0068] Among them, the materials of the first active layer 121 and the second active layer 122 can be the same. Exemplarily, for example, both the first active layer 121 and the second active layer 122 are selected from lithium cobaltate, or both are selected from lithium iron phosphate, etc.

[0069] Of course, the materials of the first active layer 121 and the second active layer 122 can also be different. Exemplarily, for example, the first active layer 121 is selected from lithium iron phosphate, and the second active layer 122 is selected from lithium cobaltate or other materials.

[0070] In some embodiments, in the second direction, the length of the gap 13 is not less than 3 mm. Here, the length of the gap 13 is the length L of the gap 13 in the left-right direction. Exemplarily, the length L can be, for example, 3 mm, 3.3 mm, 3.5 mm, 3.8 mm, 4 mm, 4.5 mm, 5 mm, 5.5 mm, 6 mm, 6.5 mm, 7 mm. Figure 1 Such a setting not only ensures that the coating device can stably coat the second active layer 122 on the first active layer 121, but also further ensures the storage amount of the electrolyte in the gap 13, and further improves the capacity retention rate of the battery during long cycles.

[0071] In some embodiments, as shown in the reference

[0072] In the direction from the winding head to the winding tail of the first electrode sheet 1, the lengths L of all the gaps 13 are the same. For example, each gap L is 3 mm, or 4 mm, or 5 mm, etc. Figure 1 It should be noted that the winding head can be understood as the region where the first electrode sheet 1 starts to wind during the winding process of the battery cell, that is, the head region, which is located inside the battery cell. Correspondingly, the winding tail can be understood as the region where the first electrode sheet 1 finishes winding.

[0073] By making the lengths of all the gaps 13 the same, the process control becomes more convenient, and the error during the coating process is reduced, ensuring the uniformity of the capacities of the batteries in the same batch.

[0074] ​

[0075] Referring to Figure 4 As shown, for example, the length of the first arc bending region 102 located on the outer circle of the core is longer than that of the first arc bending region 102 located on the inner circle of the core. In order to enable the length of the above-mentioned gap 13 in the first active material layer 12 to be better matched with the length of the first arc bending region 102, in some embodiments, referring to Figure 4 As shown, in the direction from the winding head to the winding tail of the first pole piece 1, the lengths of all the gaps 13 increase in sequence. For example, from the winding head to the winding tail, the lengths of the gaps 13 are 3mm, 4mm, 4.5mm, 5mm, 6mm, and 7mm in sequence.

[0076] Such a setting enables the first arc bending region 102 and the gap 13 located on the first arc bending region 102 to achieve a better match, while controlling the number of active lithium ions in the first arc bending region 102, and improving the overall capacity of the battery as much as possible.

[0077] In addition, in other implementation manners, in the direction from the winding head to the winding tail of the first pole piece 1, the lengths of all the gaps 13 show an overall increasing trend, and the lengths of some adjacent gaps 13 are equal. For example, from the winding head to the winding tail, the lengths of the gaps 13 are 3mm, 3mm, 3mm, 4mm, 4mm, 5mm, 6mm, 7mm, 7mm, and 8mm in sequence.

[0078] In some embodiments, the compaction density of the region of the first active material layer 12 having the second active layer 122 is greater than the compaction density of the region of the first active material layer 12 having the gap 13.

[0079] The compaction density of the active material layer refers to the compaction density of the active material coated on the current collector. The compaction density of the active material layer is equal to the ratio of the areal density per unit area to the thickness of the active material. Among them, the thickness of the active material refers to the thickness of the active material after pressing, and the areal density refers to the mass per unit area of the active material with a specified thickness.

[0080] Referring to Figures 1 to 4 As shown, for example, the region of the first active material layer 12 coated with the second active layer 122 is defined as the double-layer region, and the region of the first active material layer 12 not coated with the second active layer 122 (i.e., the region corresponding to the gap 13) is defined as the single-layer region. The compaction density of the double-layer region is the compaction density of the entire layer of the first active layer 121 and the second active layer 122, and the compaction density of the single-layer region is the compaction density of the first active layer 121. Among them, the compaction density of the double-layer region is greater than the compaction density of the single-layer region.

[0081] Such a setting can improve the overall structural strength of the first electrode sheet 1, thereby ensuring that no powder shedding occurs in the double-layer region with a relatively large compaction density during the injection liquefaction cycle process. Moreover, the relatively large compaction density in the double-layer region can reduce the overall thickness of the first electrode sheet 1, thereby reducing the thickness of the battery cell, and thus improving the energy density per unit volume of the battery cell. Moreover, the relatively small compaction density in the single-layer region can further improve the wettability of the electrolyte, reduce the resistance to lithium ion insertion and extraction, further improve the lithium plating phenomenon, and improve the charge-discharge performance, cycle performance, and safety of the battery. That is, by making the compaction density of the double-layer region greater than that of the single-layer region, while achieving resistance to powder shedding, the wettability of the electrode sheet, the improvement of the lithium ion insertion and extraction ability, and the improvement of the energy density per unit volume of the battery cell are taken into account.

[0082] In some embodiments, the ratio range of the compaction density of the region of the first active material layer 12 having the second active layer 122 to the total thickness of the region of the first active material layer 12 having the second active layer 122 is 0.05 to 0.23. Exemplarily, the ratio can be, for example, 0.05, 0.08, 0.1, 0.12, 0.14, 0.15, 0.19, 0.2, 0.225, 0.23.

[0083] Referring to Figure 1 as shown, the total thickness of the region of the first active material layer 12 having the second active layer 122 is Figure 1 the thickness h in the up-down direction of the double-layer region of the first active material layer 12 in

[0084] Exemplarily, the total thickness h of the double-layer region of the first active material layer 12 is, for example, between 20 μm and 70 μm, specifically, for example, 20 μm, 30 μm, 40 μm, 45 μm, 50 μm, 60 μm, 70 μm. The compaction density of the double-layer region of the first active material layer 12 is, for example, between 3.8 g / cm 3 ~4.5 g / cm 3 specifically, for example, 3.8 g / cm 3 , 3.9 g / cm 3 , 4 g / cm 3 , 4.1 g / cm 3 , 4.2 g / cm 3 , 4.3 g / cm 3 , 4.4 g / cm 3 , 4.5 g / cm 3 .

[0085] By setting the ratio of the compaction density of the double-layer region of the first active material layer 12 to the total thickness h of the double-layer region within the above range, the powder shedding phenomenon in the double-layer region is further prevented, and thus the structural strength of the electrode sheet is further ensured.

[0086] In some embodiments, the areal density of the region of the first active material layer 12 having the second active layer 122 is defined as ρ, that is, the areal density of the double-layer region of the first active material layer 12 is ρ. The areal density of the first active layer 121 is defined as ρ1, that is, the areal density of the single-layer region of the first active material layer 12 is ρ1. The areal density of the second active layer 122 is defined as ρ2.

[0087] In specific implementation, the specific test method for the areal density is as follows:

[0088] Take the region of the first electrode tab 1 corresponding to the gap 13 (i.e., the single-layer region) as a sample for testing. The areal density ρ1 of this region = (the weight of the sample electrode tab / the area of the sample electrode tab - the areal density of the first current collector 11) / 2, so as to obtain the areal density ρ1 of this region, that is, to obtain the areal density ρ1 of the first active layer 121.

[0089] Take the region of the first electrode tab 1 corresponding to the second active layer 122 (i.e., the double-layer region) as a sample for testing. The areal density ρ of this region = (the weight of the sample electrode tab / the area of the sample electrode tab - the areal density of the first current collector 11) / 2, so as to obtain the areal density ρ of this region, that is, to obtain the areal density ρ of the double-layer region of the first active material layer 12.

[0090] Among them, the areal density ρ2 of the second active layer 122 = ρ - ρ1.

[0091] In some embodiments, the areal density ρ1 of the first active layer 121 can be made not less than the areal density ρ2 of the second active layer 122.

[0092] In some embodiments, the areal density ρ1 of the first active layer 121 can be made not less than 60 g / m 2 . The areal density ρ of the region of the first active material layer 12 having the second active layer 122 satisfies: 90 g / m 2 ≤ρ≤250 g / m 2 .

[0093] By setting like this, by controlling the areal densities of the first active layer 121 and the second active layer 122, the situation of mixing of the first active layer 121 and the second active layer 122 during coating can be better prevented.

[0094] In some embodiments, along the first direction, the ratio range of the thickness of the first active layer 121 to the total thickness h of the region of the first active material layer 12 having the second active layer 122 is 0.56 - 0.96. Exemplarily, the ratio can be, for example, 0.56, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.96.

[0095] Refer to Figure 1As shown, the thickness of the first active layer 121 is specifically the thickness h1 of the first active layer 121 in the up and down direction. The thickness of the second active layer 122 is specifically the thickness h2 of the second active layer 122 in the up and down direction.

[0096] By setting the ratio of the thickness of the first active layer 121 to the total thickness h of the region of the first active material layer 12 having the second active layer 122 within the above range, that is, making the thickness h1 of the first active layer 121 relatively thicker than the thickness h2 of the second active layer 122, the capacity of the battery can be ensured.

[0097] If the thickness h2 of the second active layer 122 is small, the capacity of the battery will be reduced. However, if the thickness h2 of the second active layer 122 is large, the flatness of the battery cell will be affected. Based on this, in some embodiments, in the first direction, the thickness h2 of the second active layer 122 ranges from 7.5 μm to 35 μm. Exemplarily, for example, the thickness h2 can be 7.5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm.

[0098] By setting the thickness of the second active layer 122 within the above range, while ensuring the battery capacity, it is possible to avoid a decrease in the energy density per unit volume of the battery cell due to excessive thickness, and at the same time, the flatness of the battery cell can be improved to a certain extent, thereby improving the uniformity of the pressure on the battery cell during the formation process, and thus ensuring that the battery has good electrical properties such as charge rate performance and cycle performance.

[0099] Continue to refer to Figure 2 As shown, in some embodiments, in the second direction, at a preset distance d from the edge of the first active material layer 12, the total thickness h3 of the first active material layer 12 is greater than the thickness h1 of the first active layer 121.

[0100] The edge here can be the edge of the first active material layer 12 close to the winding head of the first pole piece 1, that is, the starting coating end of the first active material layer 12, or the edge of the first active material layer 12 close to the winding tail of the first pole piece 1, that is, the coating ending end of the first active material layer 12.

[0101] Refer to Figure 2 As shown, the position at a preset distance d from the edge of the first active material layer 12 can specifically refer to the position reached by presetting a distance d to the right from the leftmost edge of the first active material layer 12 in Figure 2 the first active material layer 12.

[0102] Such a setting is used to ensure that at the preset distance position after the starting coating end or before the coating ending end, the total thickness of the first active material layer 12 is greater than the thickness of the first active layer 121, so as to ensure the main body region of the first active material layer 12 (specifically, it can refer to Figure 2The overall thickness of the region (the region to the right of the preset spacing d) can meet the requirements, thereby ensuring the number of lithium ions in the main region of the first active material layer 12, and further ensuring the capacity of the battery.

[0103] Exemplarily, the above preset spacing d is not less than 3 mm. For example, it can be 3 mm, 3.1 mm, 3.15 mm, 3.2 mm, 3.25 mm, 3.3 mm, 3.4 mm, 3.5 mm.

[0104] In specific implementation, at the end of the first active material layer 12, such as Figure 2 at the left end of the first active material layer 12 in, there is a certain dislocation between the first active layer 121 and the second active layer 122. Of course, in other implementation manners, the left ends of the first active layer 121 and the second active layer 122 can also be aligned.

[0105] In some embodiments, referring to Figure 4 the C region shown, at the innermost winding of the first pole piece 1, the gap 13 located on the first arc bending region 102 extends to the first straight region 101.

[0106] Exemplarily, for example, the second active layer 122 is not coated on the first active layer 121 corresponding to the first arc bending region 102 at the innermost winding, that is, the gap 13 is exactly located on the first arc bending region 102, and the end of the gap 13 extends to the first straight region 101 connected to the first arc bending region 102.

[0107] Such a setting can reduce the stress at the joint of the first straight region 101 and the first arc bending region 102 at the inner winding of the first pole piece 1, relieve the stress concentration at the inner winding of the first pole piece 1, prevent situations such as the fracture of the first pole piece 1, and improve the structural stability of the first pole piece 1.

[0108] Continuing to refer to Figure 4 shown, in specific implementation, the first pole piece 1 further includes a first pole tab 14, and the second pole piece 2 further includes a second pole tab 23.

[0109] In some embodiments, as Figure 4 shown, the second pole piece 2 has a second straight region 201 and second arc bending regions 202 located on both sides of the second straight region 201, and the second pole tab 23 is specifically arranged on the second straight region 201.

[0110] Wherein, the projection of the gap 13 extending to the first straight region 101 in the second direction does not overlap with the projection of the second pole tab 23 in the second direction. The second direction here is, for example, Figure 4 the left - right direction in, specifically, it can be the length direction of the first pole piece 1 after being unfolded.

[0111] By making the projection of the gap 13 in the second direction not overlap with the projection of the second tab 23 in the second direction, the amount of active material in the second active layer 122 within the first flat region 101 is ensured, and the situation of large energy density loss caused by the gap 13 extending too long into the first flat region 101 is avoided.

[0112] Combined Figure 1 with Figure 4 As shown, in some embodiments, at the outermost winding of the first electrode tab 1, the second active layer 122 located on the first flat region 101 extends to the first arc bending region 102.

[0113] Exemplarily, for example, the second active layer 122 is normally coated in the first flat region 101, the gap 13 is exactly located in the first arc bending region 102, and the end of the second active layer 122 on the first flat region 101 at the outermost winding extends to the first arc bending region 102 connected to the first flat region 101.

[0114] Such a setting can reduce the stress at the joint between the first flat region 101 and the first arc bending region 102 on the outermost winding of the first electrode tab 1, relieve the stress concentration in the outermost winding and prevent situations such as the fracture of the first electrode tab 1, thereby improving the structural stability of the first electrode tab 1. Moreover, referring to Figure 4 As shown, since the length of the first arc bending region 102 at the outer circle of the winding core is longer than the length of the first arc bending region 102 at the inner circle of the winding core, by making the second active layer 122 at the outermost winding extend from the first flat region 101 to the first arc bending region 102, the amount of activity in each arc bending region of the winding core is generally ensured, the consistency of the activity amount in each arc bending region is improved, so that the effective lithium ions that can be released in each arc bending region are relatively uniform, thereby improving the uniformity of lithium intercalation and further reducing the risk of lithium precipitation.

[0115] Continuing to refer to Figure 1 and Figure 2 As shown, in some embodiments, in the second direction, the second active layer 122 includes a first region 120 and a second region 123 located at at least one end of the first region 120. Among them, the thickness of the second region 123 in the first direction is less than the thickness of the first region 120 in the first direction.

[0116] Among them, the second direction can be, for example, Figure 1 and Figure 2 the left - right direction in, specifically, for example, the length direction of the first electrode tab 1. Of course, it can also be the width direction of the first electrode tab 1. Among them, the first direction is, for example, Figure 1 and Figure 2 the up - down direction in.

[0117] The above - mentioned at least one end can be, for example,Figure 1 and Figure 2 Second regions 123 are formed at both the left end and the right end of the first region 120 in Figure 2 , or a second region 123 may be formed at the left end of the first region 120, or a second region 123 may be formed at the right end of the first region 120.

[0118] That is to say, by reducing the thickness of the end of the second active layer 122, while reducing the risk of lithium plating, a better transition can be achieved at the joint of the first active layer 121 and the second active layer 122, preventing stress concentration at the joint from causing the first pole piece 1 to rupture or the active layer to fall off due to powdering; moreover, such a setting enables the second region 123 to play a certain buffering role when the first pole piece 1 is roll-pressed, avoiding the phenomenon of bright stripes on the pole piece caused by sudden change in force during roll-pressing of the first pole piece 1, and ensuring the appearance quality of the first pole piece 1.

[0119] Referring to Figure 1 and Figure 2 As shown in Figure 2 , in some embodiments, in the direction away from the first region 120, the thickness of the second region 123 gradually decreases in the first direction.

[0120] For example, referring to Figure 1 , for the second region 123 located at the right end of the first region 120, in the direction from left to right in Figure 1 , the thickness of the second region 123 gradually decreases; for another example, for the second region 123 located at the left end of the first region 120, in the direction from right to left in Figure 1 , the thickness of the second region 123 gradually decreases. Figure 1 Figure 1 Figure 1

[0121] This enables a better transition at the joint of the end of the second active layer 122 and the first active layer 121, further avoiding stress concentration from causing fracture or bulging at the joint, etc., and at the same time enabling the second region 123 to play a better buffering effect, further avoiding the situation of bright stripes on the pole piece caused by sudden change in force during roll-pressing; moreover, such a setting helps the active energy of this part of the second active layer 122 to be released better. In addition, by reducing the amount of active material at the end of the second region 123, the risk of lithium plating in the corresponding region of the second pole piece 2 is further reduced.

[0122] In some embodiments, the surface of the second region 123 facing away from the first active layer 121 is an arc surface 124. This enables a smooth transition at the joint of the end of the second active layer 122 and the first active layer 121, further avoiding stress concentration, improving the structural strength and stability of the first pole piece 1. And it enables the second region 123 to play a better buffering effect, further avoiding the situation of bright stripes on the pole piece caused by sudden change in force during roll-pressing of the pole piece.

[0123] In some embodiments, continue to refer toFigure 2 As shown, the included angle α between the surface of the second region 123 facing away from the first active layer 121 and the surface of the first active material layer 12 facing away from the first current collector 11 ranges from 1° to 10°. For example, the included angle α can be 1°, 2°, 3°, 4°, 5°, 5.5°, 6°, 7°, 8°, 9°, 10°.

[0124] Among them, the surface of the second region 123 facing away from the first active layer 121 here can specifically be Figure 2 the tangent of the arc surface 124 in

[0125] By setting the included angle α within the above range, the smooth transition between the second active layer 122 and the first active layer 121 is further ensured. While improving the structural strength and stability of the first electrode sheet 1, the phenomenon of bright stripes generated when the electrode sheet is pressed is further avoided.

[0126] Of course, in other implementation manners, in the direction away from the first region 120, the thickness of the second region 123 can also decrease in a stepped trend, for example.

[0127] In some embodiments, referring to Figure 1 as shown, in the second direction, the length X1 of the second region 123 ranges from 50 μm to 500 μm. For example, it can specifically be 50 μm, 100 μm, 200 μm, 250 μm, 275 μm, 300 μm, 400 μm, 500 μm.

[0128] In the second direction, the ratio of the length X1 of the second region 123 to the total length X2 of the second active layer 122 ranges from 1 / 1000 to 1 / 60. For example, the ratio can specifically be 1 / 1000, 1 / 500, 1 / 300, 1 / 100, 1 / 80, 1 / 60.

[0129] The above-mentioned second direction is, for example, Figure 1 the left - right direction in

[0130] This setting makes the length of the second region 123 account for a small proportion of the length of the second active layer 122, thus avoiding the problem that the excessive length of the second region 123 affects the overall capacity of the battery. That is, while avoiding the appearance problem of bright stripes on the electrode sheet caused by sudden change in force during electrode rolling, the overall capacity of the battery is also taken into account.

[0131] This embodiment also provides a battery, which can be, for example, a lithium - ion battery. The battery can be used as the power supply or energy storage unit of an electronic device. The electronic device can be, but is not limited to, mobile devices (such as mobile phones, laptops, tablets, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, electric bicycles, etc.).

[0132] The battery specifically includes a battery cell. The structure and implementation principle of this battery cell are the same as those of the battery cell provided in the above embodiment, and can bring the same or similar technical effects, which will not be elaborated one by one here. For details, reference can be made to the description of the above embodiment.

[0133] In this article, it should be noted that unless otherwise clearly specified and limited, the terms "installation", "connection", and "coupling" should be understood in a broad sense. For example, it can be a fixed connection, or indirectly connected through an intermediate medium, and can be the internal communication between two components or the interaction relationship between two components. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances. In addition, the orientation or positional relationship indicated by the terms "upper", "lower", "left", "right", "front", "rear", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing this application and simplifying the description, rather than indicating or implying that the device or component referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of this application.

[0134] In this article, relative terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprising", "including" or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or further includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "including one..." does not exclude the existence of additional identical elements in the process, method, article or device including the said element.

[0135] The above are only the preferred embodiments of the present utility model and are not intended to limit the present utility model. Any modifications, equivalent replacements, etc. made within the spirit and principle of the present utility model shall be included within the protection scope of the present utility model.

Claims

1. A battery cell, characterized in that, The invention comprises a first pole piece (1), a second pole piece (2) and a diaphragm (3) located between the first pole piece (1) and the second pole piece (2); the first pole piece (1), the diaphragm (3) and the second pole piece (2) are stacked and wound to form a winding core; The first pole piece (1) comprises a first current collector (11) and a first active material layer (12); the first active material layer (12) comprises a first active layer (121) and a second active layer (122) along a first direction; the first active layer (121) is arranged on at least one side of the first current collector (11); there are at least two second active layers (122); at least two second active layers (122) are arranged on a side of the first active layer (121) away from the first current collector (11) along a second direction, and a gap (13) is provided between two adjacent second active layers (122); The first pole piece (1) has a first straight region (101) and first arc bending regions (102) located on both sides of the first straight region (101), and at least part of the gap (13) is located in the first arc bending region (102).

2. The battery cell according to claim 1, wherein, In the second direction, the length of the gap (13) is not less than 3 mm.

3. The battery cell according to claim 1, characterized in that In the direction from the winding head to the winding tail of the first pole piece (1), the lengths of all the gaps (13) are the same; Alternatively, in the direction from the winding head to the winding tail of the first pole piece (1), the lengths of all the gaps (13) increase sequentially.

4. The battery cell according to claim 1, wherein The compaction density of the region of the first active material layer (12) having the second active layer (122) is greater than the compaction density of the region of the first active material layer (12) having the gap (13); And / or, the ratio of the compaction density of the region of the first active material layer (12) having the second active layer (122) to the total thickness of the region of the first active material layer (12) having the second active layer (122) is in the range of 0.05 to 0.

23.

5. The battery cell according to claim 1, characterized in that, The surface density of the first active layer (121) is not less than the surface density of the second active layer (122); and / or, the areal density of the first active layer (121) is not less than 60 g / m 2 ; And / or, the areal density ρ of the region of the first active material layer (12) having the second active layer (122) satisfies: 90 g / m 2 ≤ ρ ≤ 250 g / m 2 .

6. The battery cell according to claim 1, characterized in that, Along the first direction, the ratio of the thickness of the first active layer (121) to the total thickness of the region of the first active material layer (12) having the second active layer (122) is in the range of 0.56 to 0.96; And / or, along the first direction, the thickness of the second active layer (122) ranges from 7.5 μm to 35 μm.

7. The cell according to claim 1, characterized in that, Along the second direction, at a preset distance from the edge of the first active material layer (12), the total thickness of the first active material layer (12) is greater than the thickness of the first active layer (121).

8. The battery cell according to any one of claims 1 to 7, characterized in that All of the second active layers (122) are located in the first straight area (101), and at least part of the gaps (13) are located in the first arc bending area (102); Alternatively, in all of the second active layers (122), a part of the second active layer (122) is located in the first flat region (101), a part of the second active layer (122) is located in the first arc bending region (102), and at least a part of the gap (13) is located in the first arc bending region (102).

9. The battery cell according to any one of claims 1 to 7, characterized in that, At the innermost winding layer of the first pole piece (1), the gap (13) located in the first arc bending region (102) extends to the first flat region (101).

10. The battery cell according to claim 9, wherein, The second pole piece (2) has a second flat region (201) and second arc bending regions (202) located on both sides of the second flat region (201), and a second tab (23) is provided on the second flat region (201); The projection of the gap (13) extending to the first flat region (101) in the second direction does not overlap with the projection of the second tab (23) in the second direction.

11. The battery cell according to any one of claims 1 to 7, characterized in that, At the outermost winding layer of the first pole piece (1), the second active layer (122) located in the first flat region (101) extends to the first arc bending region (102).

12. The battery cell according to any one of claims 1 to 7, characterized in that, In the second direction, the second active layer (122) includes a first region (120) and a second region (123) located at at least one end of the first region (120), and the thickness of the second region (123) in the first direction is smaller than the thickness of the first region (120) in the first direction.

13. The battery cell according to claim 12, characterized in that, In the direction away from the first region (120), the thickness of the second region (123) in the first direction gradually decreases; and / or, the surface of the second region (123) facing away from the first active layer (121) is an arc surface (124); and / or, the included angle range between the surface of the second region (123) facing away from the first active layer (121) and the surface of the first active material layer (12) facing away from the first current collector (11) is 1° to 10°; and / or, in the second direction, the length range of the second region (123) is 50 μm to 500 μm; and / or, in the second direction, the ratio range of the length of the second region (123) to the total length of the second active layer (122) is 1 / 1000 to 1 / 60.

14. The battery cell according to claim 7, wherein, The preset spacing is not less than 3 mm.

15. A battery, characterized in that, Comprising the battery cell according to any one of claims 1 to 14.

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