Pole piece and battery cell

Abstract

The invention provides a pole piece and a battery cell. The pole piece comprises a current collector and an active substance layer arranged on at least one side of the current collector, the current collector is provided with an insulating layer, the insulating layer is located at the edge of the active material layer, the insulating layer and the active material layer have an overlapping region in the first direction, and the insulating layer is located between the active material layer and the current collector in the overlapping region, so that the risk of short circuit of the positive electrode and the negative electrode is reduced to a certain extent, and the safety performance of the battery is improved; and the capacity of the battery is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a pole piece and a battery cell. Background Art

[0002] Lithium-ion batteries have the advantages of high energy density and long cycle life. They are not only widely used in portable electronic devices such as mobile phones and laptops, but also in electric vehicles, electric bicycles, energy storage facilities, battery swap stations, smart devices, etc.

[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. The positive electrode sheet includes a positive electrode collector and a positive electrode active material layer arranged on the surface of the positive electrode collector. The negative electrode sheet includes a negative electrode collector and a negative electrode active material layer arranged on the surface of the negative electrode collector. The separator is located between the positive electrode sheet and the negative electrode sheet to isolate the positive electrode sheet from contact with the negative electrode sheet. During the manufacturing process of the battery, the electrode sheet needs to be cut, and the electrode sheet is prone to burrs on its cross section after cutting. The burrs are easy to pierce the separator and cause a short circuit between adjacent electrode sheets. Summary of the invention

[0004] In view of this, the embodiments of the present invention are dedicated to providing a pole piece and a battery cell to reduce the risk of short circuit between the positive and negative poles to a certain extent and improve the safety performance of the battery.

[0005] In a first aspect, the present invention provides a pole piece, comprising a current collector and an active material layer disposed on at least one side of the current collector;

[0006] An insulating layer is disposed on the current collector, the insulating layer is located at the edge of the active material layer, and along the first direction, the insulating layer and the active material layer have an overlapping area;

[0007] In the overlapping region, the insulating layer is located between the active material layer and the current collector. Optionally, the active material layer includes a main body region and an edge region located at one end of the main body region close to the insulating layer;

[0008] A projection of the edge region in the first direction at least partially overlaps with a projection of the insulating layer in the first direction;

[0009] In the second direction, the thickness of the edge region is smaller than the thickness of the main region.

[0010] Optionally, the thickness of the edge region gradually decreases in a direction approaching the insulating layer.

[0011] Optionally, in the overlapping region, the joint surface of the insulating layer and the active material layer is formed as an arc-shaped transition surface;

[0012] and / or, in a direction away from the active material layer, a total thickness of the insulating layer and the active material layer in the overlapping region gradually decreases;

[0013] And / or, a ratio of a total thickness of the insulating layer and the active material layer in the overlapping region to a thickness of the active material layer outside the overlapping region is in a range of 0.5 to 1.3.

[0014] Optionally, a ratio of a total thickness of the insulating layer and the active material layer in the overlapping region to a thickness of the active material layer outside the overlapping region is in a range of 0.5 to 1.1.

[0015] Optionally, along the first direction, the total length of the insulating layer ranges from 1 mm to 3 mm;

[0016] And / or, along the first direction, the length of the insulating layer in the overlapping area ranges from 10 μm to 500 μm;

[0017] And / or, along the first direction, a ratio of the length of the insulating layer in the overlapping area to the total length of the insulating layer is in a range of 1 / 300 to 1 / 2.

[0018] Optionally, the insulating layer includes a first insulating portion and a second insulating portion; the first insulating portion is located in the overlapping region, and the second insulating portion is connected to an end of the first insulating portion away from the active material layer;

[0019] The thickness of the first insulating portion gradually increases in a direction from an end of the insulating layer close to the active material layer to an end of the insulating layer away from the active material layer.

[0020] Optionally, a thickness of at least a portion of the second insulating portion is not less than a maximum thickness of the first insulating portion.

[0021] Optionally, the insulating layer includes a first insulating portion, a second insulating portion and a third insulating portion;

[0022] The first insulating portion is located in the overlapping region, the second insulating portion is connected to an end of the first insulating portion away from the active material layer, and the third insulating portion is connected to an end of the second insulating portion away from the first insulating portion;

[0023] The thickness of the third insulating portion is smaller than the thickness of the second insulating portion.

[0024] Optionally, in a direction from the first insulating portion to the third insulating portion, a thickness of the third insulating portion gradually decreases.

[0025] Optionally, the angle between the surface of the insulating layer in contact with the active material layer and the current collector is in the range of 2° to 50°;

[0026] And / or, the angle between the surface of the insulating layer away from the active material layer and the current collector is in the range of 0.1° to 10°.

[0027] Optionally, the active material layer and the insulating layer are disposed on opposite sides of the current collector;

[0028] The active material layers located on both sides of the current collector have a first staggered distance at one end edge close to the corresponding insulating layer in the first direction;

[0029] The first offset distance is no greater than 2 mm;

[0030] And / or, the edges of the insulating layers on both sides of the current collectors at one end away from the corresponding active material layer have a second staggered distance in the first direction;

[0031] The second offset distance is no greater than 1 mm.

[0032] Optionally, a protrusion protruding in a direction away from the current collector is formed on a side of the active material layer facing away from the current collector.

[0033] Optionally, a projection of the protrusion on the current collector at least partially overlaps with a projection of the insulating layer on the current collector.

[0034] Optionally, the difference between the maximum height of the protrusion and the thickness of the active material layer outside the overlapping area is less than 15 μm;

[0035] And / or, the thickness of the active material layer gradually decreases in a direction from the protrusion to the insulating layer.

[0036] Optionally, the material of the insulating layer includes at least one of aluminum oxide, polyacrylic acid, polyimide, polyamic acid, and boehmite.

[0037] Optionally, the active material layer includes a first sub-active layer and a second sub-active layer, the first sub-active layer is located on one side of the current collector, and the second sub-active layer is located on a side of the first sub-active layer away from the current collector;

[0038] Along the first direction, at least the second sub-active layer and the insulating layer have the overlapping region, and at least a portion of the insulating layer in the overlapping region is located between the second sub-active layer and the current collector.

[0039] Optionally, along the second direction, a ratio of a thickness of the second sub-active layer to a thickness of the first sub-active layer is in a range of 1:9 to 9:1;

[0040] And / or, the material of the first sub-active layer includes at least one of lithium cobalt oxide, ternary, lithium iron phosphate, and lithium carbonate;

[0041] And / or, the material of the second sub-active layer includes at least one of lithium cobalt oxide, ternary lithium, lithium iron phosphate, and lithium carbonate.

[0042] In a second aspect, the present invention provides a battery cell, comprising a first pole piece, a second pole piece, and a diaphragm disposed between the first pole piece and the second pole piece, wherein the first pole piece and the second pole piece have opposite polarities;

[0043] At least one of the first pole piece and the second pole piece is the pole piece as described above.

[0044] The pole piece and battery cell provided by the embodiment of the present invention are provided with an insulating layer on the current collector, and the insulating layer is located at the edge of the active material layer. The existence of the insulating layer can protect the current collector to a certain extent, thereby reducing the generation of burrs when the pole piece is cut to a certain extent, thereby reducing the risk of the burrs piercing the diaphragm and causing the adjacent pole pieces to contact and cause a short circuit to a certain extent, thereby improving the safety performance of the battery; at the same time, the insulating layer and the active material layer have an overlapping area in the first direction, which can improve the connection strength between the insulating layer and the active material layer, thereby improving the structural stability of the pole piece, and by making the insulating layer between the active material layer and the current collector in the overlapping area, that is, in the overlapping area, the active material layer covers the insulating layer, so that the active material layer located on the insulating layer can normally deintercalate lithium ions, thereby improving the capacity of the battery; compared with the solution of covering the insulating layer on the active material layer, the embodiment of the present invention reduces the risk of short circuit between adjacent pole pieces while improving the capacity of the battery to a certain extent, avoiding the situation where the insulating layer covers the active material layer, causing the covered active material layer to be unable to function normally and causing the loss of battery capacity. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 A cross-sectional structural diagram of a pole piece according to an embodiment of the present invention;

[0046] Figure 2 for Figure 1 A magnified view of the structure at center A;

[0047] Figure 3 for Figure 1 A magnified view of the structure at position I in the middle;

[0048] Figure 4A cross-sectional structural diagram of a pole piece according to an embodiment of the present invention;

[0049] Figure 5 for Figure 4 A magnified view of the structure at position I in the middle;

[0050] Figure 6 for Figure 4 A magnified view of the structure at center A;

[0051] Figure 7 A cross-sectional structural diagram of a pole piece according to an embodiment of the present invention;

[0052] Figure 8 for Figure 7 Enlarged view of the structure at I in the middle.

[0053] Among them, 1. current collector; 10. overlapping area; 2. active material layer; 21. first sub-active layer; 22. second sub-active layer; 20. protrusion; 23. main area; 24. edge area; 3. insulating layer; 31. first insulating part; 32. second insulating part; 33. third insulating part; 30. joint surface. DETAILED DESCRIPTION

[0054] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0055] 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. The positive electrode sheet includes a positive electrode collector and a positive electrode active material layer arranged on the surface of the positive electrode collector. The negative electrode sheet includes a negative electrode collector and a negative electrode active material layer arranged on the surface of the negative electrode collector. The separator is located between the positive electrode sheet and the negative electrode sheet to isolate the positive electrode sheet from contact with the negative electrode sheet. Among them, the positive electrode sheet is provided with a positive electrode ear, and the negative electrode sheet is provided with a negative electrode ear. The ear is connected to the external circuit to charge or discharge the battery.

[0056] During the manufacturing process of batteries, the pole pieces need to be cut, such as cutting the edge of the current collector to form a pole ear through die cutting and other processes. However, after cutting, the pole pieces are prone to burrs on their cross-sections, which can easily pierce the diaphragm and cause short circuits between adjacent pole pieces.

[0057] Based on this, the present invention provides a pole piece and a battery cell, by arranging an insulating layer on the current collector, so that the insulating layer is located at the edge of the active material layer, so that the insulating layer and the active material layer have an overlapping area, and in the overlapping area, the active material layer covers the insulating layer, so that the current collector is protected to a certain extent by the insulating layer, and the generation of burrs during cutting is reduced, thereby reducing the risk of burrs piercing the diaphragm and causing a short circuit between adjacent pole pieces. In addition, since the active material layer covers the insulating layer in the overlapping area, the capacity of the battery is improved.

[0058] The following is a detailed description of the electrode sheet and the battery cell provided by the present invention through specific embodiments in conjunction with the accompanying drawings:

[0059] Reference Figures 1 to 8 As shown, this embodiment provides a pole piece, which is applied to a battery cell, which may be a wound battery cell, for example. The battery cell is applied to a battery, which may be a lithium-ion battery, for example.

[0060] The pole piece of this embodiment includes: a current collector 1 and an active material layer 2 arranged on at least one side of the current collector 1 .

[0061] Specifically, the current collector 1 has two opposite sides, and the two opposite sides are used to coat the active material layer 2. In specific implementation, refer to Figure 1 and Figure 2 As shown, it is possible to form a plurality of electrodes on both sides of the current collector 1 ( Figure 1 or Figure 2 The active material layer 2 is disposed on both the upper and lower sides of the current collector 1. The active material layer 2 may also be disposed on only one side of the current collector 1 (eg, the upper or lower side of the current collector 1).

[0062] The current collector 1 is provided with an insulating layer 3, the insulating layer 3 is located at the edge of the active material layer 2, and along the first direction, the insulating layer 3 and the active material layer 2 have an overlapping region 10. In the overlapping region 10, the insulating layer 3 is located between the active material layer 2 and the current collector 1. That is, in the overlapping region 10, the active material layer 2 covers the insulating layer 3.

[0063] Reference Figure 1 As shown, the first direction here is specifically Figure 1 The first direction may be, for example, the width direction of the pole piece. Exemplarily, both ends of the active material layer 2 along the first direction may be provided with an insulating layer 3, or the insulating layer 3 may be located at one end of the active material layer 2 along the first direction. Of course, the first direction may also be the length direction of the pole piece.

[0064] Exemplarily, in a specific implementation, the coating die head for coating the active material layer 2 and the insulating layer 3 includes an upper die head and a lower die head. The upper die head has an insulating material accommodating cavity and an active material accommodating cavity, and the lower die head has an active material accommodating cavity. The lower die head is located below the upper die head. During coating, the upper die head and the lower die head discharge the material together. Based on the different specific sizes of the upper die head and the lower die head, the active material layer coated by the lower die head is smaller than the active material layer coated by the upper die head. When the lower die head is removed, part of the insulating material will flow into the corresponding position, and part of the active material will cover part of the insulating material, thereby coating the active material layer 2 and the insulating layer 3 on the current collector 1, and the active material layer 2 and the insulating layer 3 have an overlapping area 10, and in the overlapping area 10, the active material layer 2 covers the insulating layer 3.

[0065] The pole piece provided in this embodiment is provided with an insulating layer 3 on the current collector 1, and the insulating layer 3 is located at the edge of the active material layer 2. The existence of the insulating layer 3 can protect the current collector 1 to a certain extent, thereby reducing the generation of burrs when the pole piece is cut to a certain extent, and further reducing the risk of the burrs piercing the diaphragm and causing the adjacent pole pieces to contact and cause a short circuit to a certain extent, thereby improving the safety performance of the battery; at the same time, the insulating layer 3 and the active material layer 2 have an overlapping area 10 in the first direction, so that the connection strength between the insulating layer 3 and the active material layer 2 can be improved, thereby improving the structural stability of the pole piece, and by making In the overlapping area 10, the insulating layer 3 is located between the active material layer 2 and the current collector 1, that is, in the overlapping area 10, the active material layer 2 covers the insulating layer 3. This configuration allows the active material layer 2 located on the insulating layer 3 to normally deintercalate lithium ions, thereby increasing the capacity of the battery. Compared with the solution in which the insulating layer 3 covers the active material layer 2, the embodiment of the present invention reduces the risk of short circuit between adjacent pole pieces while increasing the capacity of the battery to a certain extent, thereby avoiding the situation in which the insulating layer covers the active material layer, causing the covered active material layer to be unable to function normally and resulting in loss of battery capacity.

[0066] In a specific implementation, the material of the insulating layer 3 may include at least one of aluminum oxide, polyacrylic acid, polyimide, polyamic acid, and boehmite.

[0067] In some embodiments, the above-mentioned electrode sheet can specifically be a positive electrode sheet. In this case, the current collector 1 can be, for example, aluminum foil, and the material of the active material layer 2 can include, for example, lithium cobalt oxide, ternary materials, lithium iron phosphate, lithium carbonate and other positive electrode active materials.

[0068] Of course, the above-mentioned electrode sheet may also be a negative electrode sheet. In this case, the current collector 1 may be, for example, copper foil, and the material of the active material layer 2 may be, for example, graphite, silicon-based or other negative electrode active materials.

[0069] Continue to refer to Figure 1 and Figure 2 As shown, in some embodiments, the active material layer 2 may specifically include: a main body region 23 and an edge region 24 located at one end of the main body region 23 close to the insulating layer 3 .

[0070] The projection of the edge region 24 in the first direction at least partially overlaps with the projection of the insulating layer 3 in the first direction. The first direction here is specifically Figure 1 The left and right directions in the figure, the first direction can be, for example, the width direction of the pole piece.

[0071] Along the second direction, the thickness of the edge region 24 is less than the thickness of the main region 23. The second direction here is specifically Figure 1 The up and down direction in the figure may be, for example, the thickness direction of the electrode.

[0072] Such a setting helps to better release the active energy of the active material layer 2 in the edge area 24, and because the thickness of the edge area 24 is smaller than the thickness of the main area 23, when the electrode is a positive electrode, the risk of lithium deposition in the corresponding area of ​​the negative electrode can be reduced by controlling the amount of active material in the edge area 24.

[0073] Moreover, by making the thickness of the edge area 24 smaller than that of the main area 23, while achieving effective coverage of the insulating layer 3 by the active material layer 2 to increase the battery capacity, it can also avoid, to a certain extent, the situation in which the energy density per unit volume of the battery cell is reduced due to the excessive thickness of the electrode.

[0074] In some embodiments, the thickness of the edge region 24 gradually decreases along the direction close to the insulating layer 3. Figure 1 or Figure 2 In the direction from right to left in the drawing, the thickness of the edge region 24 in the up-down direction gradually decreases.

[0075] Such a setting helps to further release the active energy of the active material layer 2 in the edge area 24, and further reduces the risk of lithium deposition in the corresponding area of ​​the negative electrode. At the same time, such a setting can achieve the active material layer 2 covering the insulating layer 3 to increase the battery capacity, and can also further avoid the situation where the thickness of the pole piece is too thick and the energy density per unit volume of the battery cell is reduced to a certain extent. In addition, since the thickness of the edge area 24 tends to gradually decrease, it can avoid the surface stress of the edge area 24 being too large to cause bulging, cracking, etc. to a certain extent, thereby improving the structural stability of the entire active material layer 2.

[0076] Reference Figure 2 and Figure 5As shown, in some embodiments, in the overlapping region 10, the joint surface 30 of the insulating layer 3 and the active material layer 2 is formed as an arc-shaped transition surface. That is, in the overlapping region 10, the insulating layer 3 and the active material layer 2 are spliced ​​to form a better arc-shaped transition, thereby ensuring that the insulating layer 3 and the active material layer 2 can be better bonded after rolling, avoiding the situation where the insulating layer 3 and the active material layer 2 are peeled off due to frequent rolling in subsequent processing steps, thereby improving the bonding strength and stability of the electrode sheet.

[0077] Continue to refer to Figure 1 and Figure 2 As shown, in some embodiments, in a direction away from the active material layer 2 , the total thickness h of the insulating layer 3 and the active material layer 2 in the overlapping region 10 gradually decreases.

[0078] Specifically, the direction away from the active material layer 2 may be Figure 1 and Figure 2 In the direction from right to left in the figure, for example, in the width direction of the electrode sheet. The total thickness h of the insulating layer 3 and the active material layer 2 in the overlapping area 10 is specifically the thickness of the insulating layer 3 and the active material layer 2 in the overlapping area 10 along the Figure 1 The total thickness in the top-bottom direction.

[0079] Such a setting can, to a certain extent, effectively prevent the occurrence of bulging during the winding or liquid injection process, which causes the uneven interface of the battery cell. That is, it improves the flatness of the battery cell interface to a certain extent, thereby improving the consistency of the battery cell thickness, and further improving the uniformity of the pressure on the battery cell during the formation process, thereby ensuring that the battery has good electrical properties such as charge and discharge performance and cycle performance, and also ensures the appearance quality of the battery cell.

[0080] If the total thickness of the insulating layer 3 and the active material layer 2 in the overlapping area 10 is too thick or too small, the flatness of the cell interface will be affected. Moreover, if the total thickness is too small, the capacity of the cell will be affected, and if it is too thick, powder will fall off during rolling. Based on this, in some embodiments, combined with Figure 1 and Figure 2 As shown, the ratio of the total thickness h of the insulating layer 3 and the active material layer 2 in the overlapping area 10 to the thickness H of the active material layer 2 outside the overlapping area 10 can be set between 0.5 and 1.3. For example, it can be 0.5, 0.6, 0.65, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3.

[0081] Among them, refer to Figure 1 As shown, the thickness of the active material layer 2 outside the overlapping region 10 is, for example, Figure 1 The thickness H of the active material layer 2 on the right side of the overlapping region 10 is ie the thickness of the main region 23 of the active material layer 2 .

[0082] This arrangement ensures that the total thickness of the insulating layer 3 and the active material layer 2 in the overlapping area 10 does not exceed the thickness of the active material layer 2 outside the overlapping area 10 by too much while ensuring the battery capacity, thereby avoiding the situation where powder is rolled off due to excessive excess. It also improves the flatness of the battery cell interface to a certain extent, further improves the uniformity of the pressure on the battery cell during the formation process, thereby ensuring that the battery has good electrical properties such as charge and discharge performance and cycle performance, and also ensures the appearance quality of the battery cell.

[0083] Furthermore, the ratio of the total thickness h of the insulating layer 3 and the active material layer 2 in the overlapping region 10 to the thickness H of the active material layer 2 outside the overlapping region 10 may be set between 0.5 and 1.1.

[0084] This arrangement further ensures the battery capacity while further avoiding the occurrence of powder loss due to roller pressing, and further improves the flatness of the battery cell interface.

[0085] Reference Figure 1 As shown, in some embodiments, along the first direction, the total length L of the insulating layer 3 can be set between 1 mm and 3 mm.

[0086] The first direction is Figure 1 The left and right directions in the diagram may be, for example, the width direction of the pole piece. Of course, in other embodiments, the first direction may also be the length direction of the pole piece.

[0087] Exemplarily, the total length L can be, for example, 1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 2 mm, 2.2 mm, 2.3 mm, 2.5 mm, 2.6 mm, 2.8 mm, 2.9 mm, or 3 mm.

[0088] By setting the total thickness of the insulating layer 3 within the above range, the current collector 1 can be better protected, thereby further reducing the generation of burrs during cutting, and further preventing the burrs from piercing the separator and causing short circuits between the positive and negative electrodes.

[0089] Reference Figure 1 As shown, in some embodiments, along the first direction, the length D of the insulating layer 3 in the overlapping region 10 may be set to be between 10 μm and 500 μm.

[0090] The length D can be the length of the insulating layer 3 along the overlapped area 10. Figure 1Dimensions in the left-right direction. Exemplarily, the length D may be, for example, 10 μm, 30 μm, 50 μm, 80 μm, 100 μm, 120 μm, 150 μm, 200 μm, 250 μm, 255 μm, 270 μm, 280 μm, 300 μm, 340 μm, 370 μm, 400 μm, 420 μm, 450 μm, 480 μm, 500 μm.

[0091] By setting the length D of the insulating layer 3 in the overlapping area 10 within the above range, effective protection of the current collector 1 is achieved while ensuring the contact area between the insulating layer 3 and the active material layer 2, thereby ensuring good adhesion between the insulating layer 3 and the active material layer 2.

[0092] In specific implementation, if the length D of the insulating layer 3 in the overlapping area 10 is too short, it will affect the effective adhesion between the insulating layer 3 and the active material layer 2, which may easily cause powder loss; but if the length D of the insulating layer 3 in the overlapping area 10 is too long, it will cause battery capacity loss. Based on this, in some embodiments, along the first direction (for example Figure 1 In the left-right direction in the drawing, the length D of the insulating layer 3 in the overlapping area 10 and the total length L of the insulating layer 3 can be set between 1 / 300 and 1 / 2.

[0093] Exemplarily, D / L may be, for example, 1 / 300, 1 / 200, 1 / 100, 1 / 50, 1 / 30, 1 / 10, 1 / 5, 1 / 3, or 1 / 2.

[0094] By setting the ratio of the length D of the insulating layer 3 in the overlapping area 10 to the total length L of the insulating layer 3 within the above-mentioned range, not only the effective bonding between the insulating layer 3 and the active material layer 2 is ensured, but also the capacity of the battery is ensured. Moreover, by controlling the ratio within the above-mentioned range, it can also be ensured that the active material layer 2 will not be cut during die cutting (for example, when die cutting to form the pole ear), thereby avoiding capacity loss.

[0095] Continue to refer to Figures 1 to 3 As shown, in some embodiments, the insulating layer 3 may specifically include: a first insulating portion 31 and a second insulating portion 32. The first insulating portion 31 is located in the overlapping region 10, and the second insulating portion 32 is connected to an end of the first insulating portion 31 away from the active material layer 2. In other words, Figures 1 to 3 As shown, the first insulating portion 31 and the second insulating portion 32 are arranged from right to left, and the second insulating portion 32 is located on the left side of the first insulating portion 31 .

[0096] In some embodiments, in a direction from one end of the insulating layer 3 close to the active material layer 2 to one end away from the active material layer 2 (for example, Figures 1 to 3The thickness of the first insulating portion 31 gradually increases (in the direction from right to left in the figure).

[0097] Specifically, the thickness of the first insulating portion 31 is Figures 1 to 3 The size in the upper and lower directions.

[0098] Through the above arrangement, the thickness of the first insulating part 31 is gradually increased, which can ensure the protection effect of the first insulating part 31 on the current collector 1 to a certain extent.

[0099] Further, continue to refer to Figures 1 to 3 As shown, in some embodiments, a thickness d1 of at least a portion of the second insulating portion 32 is not less than a maximum thickness e of the first insulating portion 31 .

[0100] The thickness d1 of the second insulating portion 32 is Figure 2 The maximum thickness e of the first insulating portion 31 is the thickness at the leftmost end of the first insulating portion 31 .

[0101] Generally speaking, the die-cutting position is specifically at the edge of the current collector 1, that is, the area of ​​the current collector 1 that is not coated with the active material layer 2, that is, the die-cutting position is at the second insulating part 32, such as the middle position of the second insulating part 32 in the left-right direction. By gradually increasing the thickness of the first insulating part 31, so that the thickness d1 of at least part of the second insulating part 32 is not less than the maximum thickness e of the first insulating part 31, the thickness of the second insulating part 32, that is, the thickness of the die-cut part of the insulating layer 3, can be guaranteed to a certain extent, that is, the thickness of the die-cut part of the insulating layer 3 is guaranteed, and further ensure that the insulating layer 3 can play a better protective role on the current collector 1, thereby further reducing the generation of burrs.

[0102] Continue to combine Figure 1 and Figure 3 As shown, in some embodiments, the insulating layer 3 further includes a third insulating portion 33, and the third insulating portion 33 is connected to an end of the second insulating portion 32 away from the first insulating portion 31. Figure 1 As shown, the third insulating portion 33 is located at the left end of the second insulating portion 32 .

[0103] The thickness d2 of the third insulating portion 33 is smaller than the thickness d1 of the second insulating portion 32 .

[0104] This arrangement not only reduces the material usage of the insulating layer 3 and saves production costs, but also ensures a better transition of the current collector 1 at the pole ear produced by die cutting, prevents stress concentration at the pole ear and causes the pole ear to break, and ensures the stability of the overall structure of the current collector 1 and the pole ear.

[0105] In some embodiments, in a direction from the first insulating portion 31 to the third insulating portion 33 , a thickness d2 of the third insulating portion 33 gradually decreases.

[0106] That is, the thickness d of the insulating layer 3 at the end away from the active material layer 2 gradually decreases along the direction from the end of the insulating layer 3 close to the active material layer 2 to the end away from the active material layer 2. Figure 3 In the direction from right to left in FIG. 1 , the thickness d2 of the left end portion of the insulating layer 3 gradually decreases.

[0107] This arrangement, while further ensuring effective protection for the current collector 1, not only further reduces the material usage of the insulating layer 3 and saves production costs, but also ensures a smoother transition of the current collector 1 at the pole ear produced by die cutting, further preventing stress concentration at the pole ear and causing the pole ear to break, thereby ensuring the stability of the overall structure of the current collector 1 and the pole ear.

[0108] Reference Figure 1 and Figure 2 As shown, in some embodiments, the angle a between the side of the insulating layer 3 in contact with the active material layer 2 and the current collector 1 can be set between 2° and 50°. That is, the angle a is the angle between the insulating layer 3 and the current collector 1 located in the overlapping area 10. Exemplarily, for example, it can be 2°, 3°, 4°, 5°, 6°, 7°, 8°, 9°, 10°, 20°, 25°, 26°, 30°, 35°, 40°, 45°, 50°.

[0109] Exemplarily, in some embodiments, the side of the insulating layer 3 in contact with the active material layer 2 is formed as an arc-shaped transition surface. In this case, the angle a is specifically the angle between the tangent of the side of the insulating layer 3 in contact with the active material layer 2 and the surface of the current collector 1 (such as the top surface of the current collector 1).

[0110] By setting the angle a between the side of the insulating layer 3 in contact with the active material layer 2 and the current collector 1 within the above range, a natural transition of the material of the overlapping area 10 is ensured, and the overlapping area 10 will not be easily peeled off due to the difference between the two materials of the insulating layer 3 and the active material layer 2, thereby further improving the bonding strength between the insulating layer 3 and the active material layer 2, and further improving the stability of the electrode and the battery cell.

[0111] Of course, in other embodiments, the surface of the insulating layer 3 in contact with the active material layer 2 may be an inclined plane, and in this case, the angle a refers to the angle between the inclined plane and the surface where the current collector 1 is located.

[0112] Reference Figure 1 and Figure 3As shown, in some embodiments, the angle b between the surface of the insulating layer 3 away from the active material layer 2 and the current collector 1 can be set between 0.1° and 10°. For example, it can be 0.1°, 0.5°, 0.8°, 1°, 2°, 3°, 4°, 5°, 5.5°, 6°, 7°, 8°, 9°, 10°.

[0113] The surface of the insulating layer 3 away from the active material layer 2 may be a surface of the left end of the insulating layer 3 away from the current collector 1 , for example, a surface of the third insulating portion 33 away from the current collector 1 .

[0114] Exemplarily, in some embodiments, the thickness of the left end of the insulating layer 3 gradually decreases from right to left, that is, the thickness of the third insulating portion 33 gradually decreases from right to left. In this case, the surface of the insulating layer 3 away from the active material layer 2 is formed as an arc surface. The angle b between the surface of the insulating layer 3 away from the active material layer 2 and the current collector 1 can be understood as the angle between the tangent of the arc surface and the surface of the current collector 1 (such as the top surface of the current collector 1).

[0115] By setting the angle b between the surface of the insulating layer 3 away from the active material layer 2 and the current collector 1 within the above range, a natural transition between the end of the insulating layer 3 away from the active material layer 2 and the current collector 1 is ensured, avoiding stress concentration in the transition area and fracture.

[0116] Of course, in other embodiments, the surface of the insulating layer 3 away from the active material layer 2 may also be formed as an inclined plane, in which case the angle b refers to the angle between the inclined plane and the surface where the current collector 1 is located.

[0117] Reference Figures 4 to 7 As shown, active material layers 2 and insulating layers 3 are disposed on opposite sides of the current collector 1 .

[0118] In specific implementation, in some embodiments, the edges of the active material layer 2 located on both sides of the current collector 1 and close to the corresponding insulating layer 3 have a first offset distance X1 in the first direction. Figure 5 As shown in the figure, the left edge of the active material layer 2 located on the upper side of the current collector 1 and the left edge of the active material layer 2 located on the lower side of the current collector 1 are offset from each other in the left-right direction to form the first offset distance X1.

[0119] In some embodiments, the first offset spacing X1 can be no greater than 2 mm, for example, X1 is 0.5 mm, 0.7 mm, 1 mm, 1.3 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, or 2 mm.

[0120] By setting the first misalignment distance X1 within the above range, the active material layers 2 on both sides of the current collector 1 will not be misaligned too much, thereby avoiding the situation where the capacity on both sides of the corresponding negative electrode (when the above-mentioned electrode is a positive electrode, it is a negative electrode here) is greatly different due to excessive misalignment, so as to ensure the electrical performance of the battery.

[0121] When implementing it, continue to refer to Figure 5 As shown, when the left end of the active material layer 2 on the upper side of the current collector 1 and the left end of the active material layer 2 on the lower side of the current collector 1 are misaligned, the right end of the insulating layer 3 on the upper side of the current collector 1 and the right end of the insulating layer 3 on the lower side of the current collector 1 are also misaligned accordingly.

[0122] Continue to refer to Figure 4 , Figure 6 and Figure 7 As shown, in some embodiments, the edges of the insulating layer 3 located on both sides of the current collector 1 at one end away from the corresponding active material layer 2 have a second offset distance X2 in the first direction.

[0123] Specifically, Figure 6 As shown in the figure, the left edge of the insulating layer 3 located on the upper side of the current collector 1 and the left edge of the insulating layer 3 located on the lower side of the current collector 1 are offset from each other in the left-right direction to form the second offset distance X2.

[0124] In some embodiments, the second offset spacing X2 may be no greater than 1 mm, for example, X2 is 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, or 1 mm.

[0125] By making the first offset distance X1 no greater than 2 mm and the second offset distance X2 no greater than 1 mm, it is ensured to a certain extent that the distribution position of the insulating layer 3 on the opposite sides of the current collector 1 is basically consistent, thereby ensuring the accuracy of subsequent die-cutting positioning.

[0126] Reference Figure 7 and Figure 8 As shown, in some embodiments, a protrusion 20 protruding in a direction away from the current collector 1 is formed on a surface of the active material layer 2 facing away from the current collector 1 .

[0127] By providing the protrusions 20 , the number of active lithium ions in the active material layer 2 can be increased to a certain extent, thereby increasing the capacity of the battery and ensuring the charge and discharge performance, cycle performance, etc. of the battery.

[0128] In some embodiments, a projection of the protrusion 20 on the current collector 1 at least partially overlaps with a projection of the insulating layer 3 on the current collector 1 .

[0129] That is, at least part of the protrusion 20 is located in the overlapping region 10. This arrangement can further ensure the number of active lithium ions in the region, thereby further ensuring the capacity of the battery and the charge and discharge performance, cycle performance, etc. of the battery.

[0130] Reference Figure 8 As shown, illustratively, the left end region of the active material layer 2 located on the upper side of the current collector 1 can form an upward protrusion 20, and the left end region of the active material layer 2 located on the lower side of the current collector 1 can form a downward protrusion 20, thereby ensuring the number of active lithium ions on both sides of the current collector 1, thereby further improving the capacity, charge and discharge performance, cycle performance, etc. of the battery.

[0131] If the height of the protrusion 20 is too large, it will affect the flatness of the battery cell. Based on this, in some embodiments, the difference p between the maximum height h1 of the protrusion 20 and the thickness H of the active material layer 2 outside the overlapping area 10 can be set to be less than 15 μm.

[0132] like Figure 8 As shown, the protrusion 20 on the active material layer 2 located on the upper side of the current collector 1 is taken as an example for explanation: the maximum height h1 of the protrusion 20 specifically refers to the distance between the highest point of the protrusion 20 and the upper surface of the current collector 1 in the up and down direction; the thickness H of the active material layer 2 refers to the dimension between the top surface of the main area of ​​the active material layer 2 located outside the overlapping area 10 and the upper surface of the current collector 1 in the up and down direction.

[0133] By setting the difference p within the above range, the number of active lithium ions in the area is guaranteed, the battery capacity is increased, and the consistency of the electrode thickness is improved, thereby improving the flatness of the battery cell interface and further improving the uniformity of the pressure on the battery cell during the formation process, thereby ensuring that the battery has good electrical properties such as charge and discharge performance and cycle performance, and also ensuring the appearance quality of the battery cell.

[0134] For example, the maximum height h1 of the protrusion 20 is 67.01 μm, the total thickness of the insulating layer 3 and the active material layer 2 at the leftmost end of the overlapping area 10 (the thickness of the current collector 1 on one side) is 38.76 μm, and the thickness H of the active material layer 2 outside the overlapping area 10 (the thickness of the active material layer 2 on one side) is 57.7 μm.

[0135] Continue to refer to Figure 8 As shown, in some embodiments, the thickness of the active material layer 2 in the direction from the protrusion 20 to the insulating layer 3 gradually decreases. That is, the active material layer 2 in the direction from the protrusion 20 to the left edge of the active material layer 2 ( Figure 8 The thickness of the substrate decreases gradually from right to left.

[0136] This arrangement can control the number of active lithium ions in the area, avoiding lithium precipitation caused by excessive active lithium ions. In addition, it can also ensure a better transition between the left end of the active material layer 2 and the insulating layer 3, avoiding the peeling phenomenon between the two, and improving the stability of the overall structure of the electrode.

[0137] In some embodiments, in combination Figure 1 and Figure 2 As shown, the active material layer 2 may specifically include a first sub-active layer 21 and a second sub-active layer 22. The first sub-active layer 21 is located on one side of the current collector 1, and the second sub-active layer 22 is located on the side of the first sub-active layer 21 away from the current collector 1. Taking the case where both sides of the current collector 1 are provided with active material layers 2 as an example, the active material layer 2 located on the upper side of the current collector 1 is formed into a double-layer structure including the first sub-active layer 21 and the second sub-active layer 22, and the active material layer 2 located on the lower side of the current collector 1 is formed into a double-layer structure including the first sub-active layer 21 and the second sub-active layer 22.

[0138] Specifically, along the first direction, at least the second sub-active layer 22 and the insulating layer 3 have an overlapping region 10 , and at least a portion of the insulating layer 3 located in the overlapping region 10 is located between the second sub-active layer 22 and the current collector 1 .

[0139] That is, the second sub-active layer 22 and the first sub-active layer 21 may have overlapping areas with the insulating layer 3, for example, Figure 2 As shown, the overlapping region 10 includes part of the insulating layer 3 , part of the second sub-active layer 22 and part of the first sub-active layer 21 , or only the second sub-active layer 22 and the insulating layer 3 may have an overlapping region.

[0140] Exemplarily, when coating the active material layer 2 and the insulating layer 3 on the current collector 1, for example, the coating die includes an upper die and a lower die, wherein the upper die has an insulating material accommodating cavity and a second sub-active material accommodating cavity, and the lower die has a first sub-active material accommodating cavity, and the lower die is located below the upper die. During coating, the upper die and the lower die discharge material together. Based on the different specific sizes of the upper die and the lower die, the active material layer coated by the lower die is smaller than the active material layer coated by the upper die. When the lower die is removed, part of the insulating material will flow into the corresponding position, and part of the second sub-active material will cover part of the insulating material, so that the formed insulating layer 3 and the active material layer 2 have an overlapping area 10, that is, at least the second sub-active layer 22 has an overlapping area 10 with the insulating layer 3.

[0141] Continue to refer to Figure 1 and Figure 2 As shown, in some embodiments, along the second direction, the ratio of the thickness of the second sub-active layer 22 to the thickness of the first sub-active layer 21 is in the range of 1:9 to 9:1. The second direction may be Figure 1 and Figure 2 Up and down directions shown.

[0142] For example, the ratio of the two layers can be 1:9, 1:5, 1:3, 1:2, 1:1, 2:1, 5:1, 6:1, 7:1, 8:1, 9:1.

[0143] The material of the first sub-active layer 21 includes at least one of lithium cobalt oxide, ternary metal, lithium iron phosphate, and lithium carbonate. The material of the second sub-active layer 22 includes at least one of lithium cobalt oxide, ternary metal, lithium iron phosphate, and lithium carbonate.

[0144] In specific implementation, for example, the second sub-active layer 22 uses lithium iron phosphate, and the first sub-active layer 21 uses lithium cobalt oxide or ternary materials, which can improve the safety performance of the battery. For another example: the first sub-active layer 21 and the second sub-active layer 22 both use ternary materials, but the second sub-active layer 22 uses low-gram capacity ternary materials, and the first sub-active layer 21 uses high-gram capacity ternary materials. This setting can further improve the release of the gram capacity of the pole piece and increase the battery capacity. For another example, the first sub-active layer 21 and the second sub-active layer 22 both use lithium cobalt oxide, but the second sub-active layer 22 uses low-gram capacity lithium cobalt oxide, and the first sub-active layer 21 uses high-gram capacity lithium cobalt oxide, thereby reducing the problem of easy cracking of the surface of the active material layer 2 in long cycles, thereby further improving the long cycle performance and furnace temperature performance of the battery.

[0145] An embodiment of the present invention further provides a battery cell, comprising a first pole piece, a second pole piece, and a diaphragm disposed between the first pole piece and the second pole piece.

[0146] The polarities of the first electrode and the second electrode are opposite, for example, the first electrode is a positive electrode and the second electrode is a negative electrode. Alternatively, the first electrode is a negative electrode and the second electrode is a positive electrode.

[0147] Among them, at least one of the positive electrode sheet and the negative electrode sheet has the same structure and implementation principle as the electrode sheet provided in the above embodiment, and can bring the same or similar technical effects, which will not be described one by one here, and the details can be referred to the description of the above embodiment.

[0148] In this article, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, or it can be indirectly connected through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to the specific circumstances. In addition, the orientation or position relationship indicated by the terms "upper", "lower", "left", "right", "front", "back", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc. are based on the orientation or position relationship shown in the accompanying drawings, which is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application.

[0149] In this article, relational terms such as "first" and "second" are used only 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 "comprises", "comprising" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the statement "comprising a ..." does not exclude the presence of other identical elements in the process, method, article or device including the element.

[0150] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A pole piece, characterized in that: It comprises a current collector (1) and an active material layer (2) arranged on at least one side of the current collector (1); An insulating layer (3) is provided on the current collector (1), the insulating layer (3) is located at the edge of the active material layer (2), and along a first direction, the insulating layer (3) and the active material layer (2) have an overlapping area (10); In the overlapping region (10), the insulating layer (3) is located between the active material layer (2) and the current collector (1).

2. The pole piece according to claim 1, characterized in that: The active material layer (2) comprises a main body region (23) and an edge region (24) located at one end of the main body region (23) close to the insulating layer (3); The projection of the edge area (24) in the first direction at least partially overlaps with the projection of the insulating layer (3) in the first direction; In the second direction, the thickness of the edge region (24) is smaller than the thickness of the main region (23).

3. The pole piece according to claim 2, characterized in that: The thickness of the edge region (24) gradually decreases in a direction approaching the insulating layer (3).

4. The pole piece according to claim 1, characterized in that: In the overlapping region (10), the joint surface (30) of the insulating layer (3) and the active material layer (2) is formed as an arc-shaped transition surface; and / or, in a direction away from the active material layer (2), the total thickness of the insulating layer (3) and the active material layer (2) in the overlapping area (10) gradually decreases; and / or the ratio of the total thickness of the insulating layer (3) and the active material layer (2) in the overlapping region (10) to the thickness of the active material layer (2) outside the overlapping region (10) is in the range of 0.5 to 1.3; Preferably, the ratio of the total thickness of the insulating layer (3) and the active material layer (2) in the overlapping region (10) to the thickness of the active material layer (2) outside the overlapping region (10) is in the range of 0.5 to 1.

1.

5. The pole piece according to claim 1, characterized in that: In the first direction, the total length of the insulating layer (3) ranges from 1 mm to 3 mm; And / or, along the first direction, the length of the insulating layer (3) in the overlapping area (10) ranges from 10 μm to 500 μm; And / or, along the first direction, the ratio of the length of the insulating layer (3) in the overlapping area (10) to the total length of the insulating layer (3) is in the range of 1 / 300 to 1 / 2.

6. The pole piece according to claim 1, characterized in that: The insulating layer (3) comprises a first insulating portion (31) and a second insulating portion (32); the first insulating portion (31) is located in the overlapping region (10), and the second insulating portion (32) is connected to an end of the first insulating portion (31) away from the active material layer (2); The thickness of the first insulating portion (31) gradually increases in a direction from an end of the insulating layer (3) close to the active material layer (2) to an end away from the active material layer (2).

7. The pole piece according to claim 6, characterized in that: The thickness of at least a portion of the second insulating portion (32) is not less than the maximum thickness of the first insulating portion (31).

8. The pole piece according to claim 1, characterized in that: The insulating layer (3) comprises a first insulating portion (31), a second insulating portion (32) and a third insulating portion (33); The first insulating portion (31) is located in the overlapping region (10), the second insulating portion (32) is connected to an end of the first insulating portion (31) away from the active material layer (2), and the third insulating portion (33) is connected to an end of the second insulating portion (32) away from the first insulating portion (31); The thickness of the third insulating portion (33) is smaller than the thickness of the second insulating portion (32).

9. The pole piece according to claim 8, characterized in that: In the direction from the first insulating portion (31) to the third insulating portion (33), the thickness of the third insulating portion (33) gradually decreases.

10. The pole piece according to claim 1, characterized in that: The angle between the side of the insulating layer (3) in contact with the active material layer (2) and the current collector (1) is in the range of 2° to 50°; And / or, the angle between the surface of the insulating layer (3) away from the active material layer (2) and the current collector (1) is in the range of 0.1° to 10°.

11. The pole piece according to claim 1, characterized in that: The active material layer (2) and the insulating layer (3) are arranged on opposite sides of the current collector (1); The active material layer (2) located on both sides of the current collector (1) has a first offset distance in the first direction at one end edge close to the corresponding insulating layer (3); The first offset distance is no greater than 2 mm; and / or, the edges of the insulating layers (3) located on both sides of the current collector (1) at one end away from the corresponding active material layer (2) have a second offset distance in the first direction; The second offset distance is no greater than 1 mm.

12. The pole piece according to claim 1, characterized in that: A protrusion (20) protruding in a direction away from the current collector (1) is formed on the side of the active material layer (2) facing away from the current collector (1).

13. The pole piece according to claim 12, characterized in that: The projection of the protrusion (20) on the current collector (1) at least partially overlaps with the projection of the insulating layer (3) on the current collector (1); and / or the difference between the maximum height of the protrusion (20) and the thickness of the active material layer (2) outside the overlapping area (10) is less than 15 μm; And / or, the thickness of the active material layer (2) gradually decreases in the direction from the protrusion (20) to the insulating layer (3).

14. The pole piece according to any one of claims 1 to 13, characterized in that: The material of the insulating layer (3) includes at least one of aluminum oxide, polyacrylic acid, polyimide, polyamic acid, and boehmite.

15. The pole piece according to any one of claims 1 to 13, characterized in that: The active material layer (2) comprises a first sub-active layer (21) and a second sub-active layer (22), wherein the first sub-active layer (21) is located on one side of the current collector (1), and the second sub-active layer (22) is located on a side of the first sub-active layer (21) that is away from the current collector (1); Along the first direction, at least the second sub-active layer (22) and the insulating layer (3) have the overlapping region (10), and at least a portion of the insulating layer (3) within the overlapping region (10) is located between the second sub-active layer (22) and the current collector (1).

16. The pole piece according to claim 15, characterized in that: Along the second direction, the ratio of the thickness of the second sub-active layer (22) to the thickness of the first sub-active layer (21) is in the range of 1:9 to 9:1; And / or, the material of the first sub-active layer (21) includes at least one of lithium cobalt oxide, ternary lithium, lithium iron phosphate, and lithium carbonate; And / or, the material of the second sub-active layer (22) includes at least one of lithium cobalt oxide, ternary lithium, lithium iron phosphate, and lithium carbonate.

17. A battery cell, characterized in that: It comprises a first pole piece, a second pole piece and a diaphragm arranged between the first pole piece and the second pole piece, wherein the first pole piece and the second pole piece have opposite polarities; At least one of the first pole piece and the second pole piece is the pole piece according to any one of claims 1 to 16.

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