Electrode assembly and battery cell

Abstract

The utility model provides an electrode assembly and a battery cell. The electrode assembly comprises a pole piece, an insulating pad, a tab and a protective layer, the pole piece comprises a current collector and an active layer; the tab is electrically connected with the current collector; the tab comprises a first surface and a second surface, and the first surface and the second surface are respectively provided with an insulating pad; the insulating pads and the pole pieces are arranged at intervals, and the interval distance is 0.3 mm-5 mm; and the protective layer covers one side, far away from the current collector, of the tab. The motor assembly is arranged in the battery cell. Therefore, in the electrode assembly and the battery cell provided by the invention, through a mode that the insulation pads and the pole pieces are arranged at intervals, the problem that electric connection becomes poor due to the fact that the right-angle sides of the insulation pads pierce the current collectors in the pole lug grooves and nearby the pole lug grooves when the pole lugs are bent due to vibration transfer in the production process can be avoided.

Description

Technical Field

[0001] The present application relates to the technical field of battery production, and in particular to an electrode assembly and a battery cell. Background Art

[0002] With the development of lithium-ion battery technology, the industry has higher and higher requirements for the performance of lithium-ion batteries, such as high energy density, super fast charging, high safety, etc. At present, there is a method of transferring the tabs of the positive and negative electrodes to the middle of the electrode to form a tab-centered structure, so as to reduce the internal resistance of the battery cell, reduce polarization, optimize the distribution of current density on the electrode during charging and discharging, and improve the fast charging capability of the battery.

[0003] In some products, the part of the tab extending out of the tab slot is sealed and connected to the cell packaging film through an insulating pad (such as tab glue). However, in the further development of the tab center structure, it was found that when the tab is bent, the right-angle edge of the insulating pad can easily pierce the tab slot and the current collector near it due to the inevitable vibration during the production process, resulting in poor electrical connection. Utility Model Content

[0004] In view of this, the present application provides an electrode assembly and a battery cell, which, by setting the insulating pad and the pole piece at a distance, can avoid the problem of the right-angle edge of the insulating pad piercing the current collector in and near the pole ear groove and causing poor electrical connection when the pole ear is bent due to vibration transfer during the production process.

[0005] In order to achieve the above objectives, this application provides the following technical solutions:

[0006] An electrode assembly, comprising: a pole piece, an insulating pad, a pole ear, and a protective layer;

[0007] The pole piece includes a current collector and an active layer;

[0008] The pole lug is electrically connected to the current collector; the pole lug includes a first surface and a second surface, and the first surface and the second surface are respectively provided with the insulating pad; the insulating pad is spaced apart from the pole piece, and the spacing distance is 0.3mm-5mm;

[0009] The protective layer covers a side of the electrode tab away from the current collector.

[0010] Optionally, in the above electrode assembly, the protective layer and the insulating pad are spaced apart, and the spacing distance between the two is 0-2 mm;

[0011] and / or,

[0012] The outer end of the protective layer extends beyond the side edge of the pole piece to cover at least a portion of the insulating pad, and: in the first direction, the protective layer covers the insulating pad to a size of 0.3mm-5mm; and / or, in the second direction, the protective layer extends beyond the insulating pad to a size of 0.5mm-7mm.

[0013] Optionally, in the above electrode assembly, at least one side surface of the pole piece is provided with a pole lug groove, the pole lug portion is located in the pole lug groove, and its welding point area is connected to the current collector in the pole lug groove; wherein:

[0014] The soldering point area includes a plurality of soldering points, and the plurality of soldering points are arranged in a matrix;

[0015] and / or,

[0016] The first side of the welding point area is close to the insulating pad, the second side of the pole piece is close to the insulating pad, and the distance between the first side and the second side is 0.5mm-4mm; the distance between any other side of the welding point area and the radial outer side of the pole ear is 0.3mm-4mm.

[0017] Optionally, in the above electrode assembly, at least one side surface of the electrode sheet is provided with an electrode tab groove, and the electrode tab portion is located in the electrode tab groove; and:

[0018] In the first direction: the inner end of the protective layer is located on the outer surface of the active layer and exceeds the edge of the tab groove by at least 0.5 mm;

[0019] and / or,

[0020] In the second direction: both side edges of the protective layer are located on the outer surface of the active layer, and respectively extend beyond the edge of the tab groove by at least 0.5 mm.

[0021] Optionally, in the above electrode assembly, in the first direction, the length of the protective layer is Q, the length of the electrode tab groove is T, and T and Q satisfy T≤Q≤T+8mm;

[0022] and / or,

[0023] In the second direction, the width of the protective layer is M, the width of the tab groove is N, and M and N satisfy N≤M≤N+8mm.

[0024] Optionally, in the above electrode assembly, the inner end side edge of the protective layer is a first straight side edge or a first toothed side edge;

[0025] And / or, the outer end side edge of the protective layer is a second straight side edge or a second toothed side edge.

[0026] Optionally, in the above electrode assembly, the tooth-shaped protrusion on the first tooth-shaped side is a triangular protrusion, and its top angle is 10°-75°;

[0027] And / or, the tooth-shaped protrusion on the side of the second tooth-shaped side is a triangular protrusion, and the top angle thereof is 10°-75°;

[0028] And / or, adjacent tooth-shaped protrusions form tooth-shaped grooves, and the bottom angle of the tooth-shaped grooves is 10°-75°.

[0029] A battery cell comprises a positive electrode assembly, a separator and a negative electrode assembly which are stacked, wherein the positive electrode assembly and / or the negative electrode assembly is the electrode assembly described above.

[0030] Optionally, in the above-mentioned battery cell, in the first direction, the width of the separator is A, the width of the negative electrode sheet in the negative electrode assembly is B, and the width of the positive electrode sheet in the positive electrode assembly is C; wherein,

[0031] A and B satisfy B≤A≤B+5mm;

[0032] And / or, B and C satisfy C≤B≤C+5mm.

[0033] Optionally, in the above battery cell, in the first direction:

[0034] Both side edges of the separator extend beyond the edge of the negative electrode sheet in the negative electrode assembly by at least 0.5 mm;

[0035] And / or, both side edges of the negative electrode sheet in the negative electrode assembly extend beyond the edge of the positive electrode sheet in the positive electrode assembly by at least 0.2 mm.

[0036] Optionally, in the above-mentioned battery cell, a positive insulating pad is provided on the positive electrode tab in the positive electrode assembly, and the spacing distance between the positive electrode sheet in the positive electrode assembly and the positive insulating pad is b;

[0037] A negative insulating pad is arranged on the negative electrode ear in the negative electrode assembly, and the spacing distance between the negative electrode sheet in the negative electrode assembly and the negative insulating pad is d;

[0038] b and d satisfy b>d.

[0039] Optionally, in the above-mentioned battery cell, the portion of the positive electrode tab in the positive electrode assembly located in the positive electrode tab groove is the positive electrode tab connecting portion;

[0040] The portion of the negative electrode lug in the negative electrode assembly located in the negative electrode lug groove is the negative electrode lug connecting portion;

[0041] In the first direction, the length of the positive electrode tab connecting portion is greater than the length of the negative electrode tab connecting portion, and the difference between the two is e, 0.5mm≤e≤10mm.

[0042] Optionally, in the above-mentioned battery cell, the electrode sheet and the protective layer in the negative electrode assembly are respectively a negative electrode sheet and a negative electrode protective layer;

[0043] An additional protective layer is also provided on the surface of the electrode sheet of the positive electrode assembly. The additional protective layer and the negative electrode protective layer are respectively located on both sides of the negative electrode sheet; and, in the third direction, the projection of the negative electrode protective layer is located within the projection of the additional protective layer.

[0044] Optionally, in the above battery cell, in the first direction:

[0045] The length of the additional protective layer is greater than the length of the negative electrode protective layer, and the difference between the two is f, 0.5mm≤f≤5mm;

[0046] And / or, the outer edge of the additional protective layer exceeds the edge of the negative electrode sheet by 0-3 mm;

[0047] And / or, the inner edge of the additional protective layer exceeds the inner edge of the negative electrode protective layer by 0.2 mm to 3 mm;

[0048] And / or, the inner edge of the additional protective layer is flush with the inner edge of the positive electrode protective layer in the positive electrode assembly, or the inner edge of the additional protective layer exceeds the inner edge of the positive electrode protective layer by 0.2 mm-5 mm.

[0049] Optionally, in the above battery cell, in the second direction:

[0050] The width of the additional protective layer is 1 mm to 10 mm greater than the width of the negative electrode protective layer;

[0051] And / or, both opposite edges of the additional protective layer extend beyond the edge of the negative electrode protective layer by at least 0.3 mm.

[0052] In the electrode assembly and battery cell provided in the present application, the functions of the protective layer include: ① preventing the protruding welding points generated by the welding of the pole ear from piercing the diaphragm, causing the positive and negative electrodes to short-circuit and cause the risk of fire and explosion; ② preventing the active material particles protruding from the edge of the pole ear groove from piercing the diaphragm when the pole ear groove for welding the pole ear is provided on the side of the pole piece, causing the positive and negative electrodes to short-circuit and cause the risk of fire and explosion; ③ The pole ear and the pole piece are bonded together with the protective layer, so as to further fix the pole ear and avoid the problem of falling off caused by some uncontrollable factors in the production process; at the same time, the protective layer can make the contact between the pole ear and the current collector closer, reducing the contact impedance; ④ Avoiding the friction between the unwelded part of the pole ear and the current collector, and avoiding the problem of tearing due to shaking friction at the junction of the pole ear and the current collector.

[0053] In addition, in the electrode assembly and battery cell provided by the present application, since the insulating pad and the pole piece are spaced apart, that is, the projections of the insulating pad and the pole piece in the thickness direction of the pole piece do not overlap each other, a gap greater than zero is left at the edges of the two, thereby avoiding the problem that when the vibration transfer during the production process causes the pole ear to bend, the right-angle edge of the insulating pad pierces the collector in and near the pole ear groove, resulting in poor electrical connection. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0055] Figure 1 A schematic diagram of the structure of the pole piece provided in the embodiment of the present application;

[0056] Figure 2 A schematic diagram of a structure in which pole lug grooves are arranged on both sides of a pole piece provided in an embodiment of the present application;

[0057] Figure 3 A schematic diagram of a structure in which a pole piece provided with a pole ear groove on one side in an embodiment of the present application;

[0058] Figure 4 A schematic diagram of the cross-sectional structure of a battery cell provided in an embodiment of the present application;

[0059] Figure 5 A schematic diagram of a battery cell structure provided in an embodiment of the present application, wherein the inner and outer edges of the protective layer are serrated;

[0060] Figure 6 A schematic diagram of a battery cell structure provided in an embodiment of the present application, wherein the inner and outer end edges of the protective layer are straight lines.

[0061] exist Figure 1-Figure 6middle:

[0062] 01. Positive electrode; 02. Negative electrode;

[0063] 1. Current collector; 2. Tooth-shaped protrusion; 3. Pole ear; 4. Pole ear groove; 5. Protective layer; 6. Insulation pad; 7. Solder point area;

[0064] 013, positive electrode ear; 014, positive electrode ear groove; 015, positive electrode protective layer; 016, positive electrode insulating pad; 018, additional protective layer;

[0065] 023. Negative electrode ear; 024. Negative electrode ear groove; 025. Negative electrode protective layer; 026. Negative electrode insulating pad. DETAILED DESCRIPTION

[0066] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0067] See also Figures 1 to 6 , the embodiment of the present application provides an electrode assembly, including a pole piece, an insulating pad 6, a pole ear 3, and a protective layer 5. The pole piece includes a current collector 1 and an active layer; the pole ear 3 is electrically connected to the current collector 1; the portion of the pole ear 3 extending outside the pole piece includes a first surface and a second surface, and the first surface and the second surface are respectively provided with an insulating pad 6; the insulating pad 6 is spaced from the pole piece, and the spacing distance is 0.3mm-5mm (for example, 0.5mm or 1.5mm, or any other value within the range); the protective layer 5 covers the side of the pole ear 3 away from the current collector 1, that is, one side of the pole ear 3 is connected to the current collector 1, and the other side opposite to the side position is covered by the protective layer 5.

[0068] Among them, the functions of the protective layer 5 include: ① preventing the protruding welding points generated by the welding of the pole ear from piercing the diaphragm, causing the positive and negative electrodes to short-circuit and cause the risk of fire and explosion; ② preventing the active material particles protruding from the edge of the pole ear groove from piercing the diaphragm when the pole ear groove 4 for welding the pole ear 3 is set on the side of the pole piece, causing the positive and negative electrodes to short-circuit and cause the risk of fire and explosion; ③ The pole ear 3 and the pole piece are bonded together with the protective layer 5, so that the pole ear can be further fixed to avoid the problem of falling off caused by some uncontrollable factors in the production process; at the same time, the protective layer 5 can make the contact between the pole ear 3 and the current collector closer, reducing the contact impedance; ④ Avoiding the friction between the unwelded part of the pole ear and the current collector, avoiding the intersection of the pole ear and the current collector (such as Figure 1 The problem of tearing due to shaking friction) is shown in the circular area in the middle.

[0069] In addition, the insulating pad 6 can be specifically a pole ear glue, which is spaced apart from the pole piece, that is, the projections of the insulating pad 6 and the pole piece in the thickness direction of the pole piece do not overlap each other, and a gap greater than zero is left at the edges of the two. Figure 6 b and d, 0.5mm≤b≤1.2mm, 0.5mm≤d≤1.2mm. Since the insulating pad 6 is spaced apart from the pole piece, it is possible to avoid the problem that the right angle edge of the insulating pad 6 pierces the current collector in and near the pole tab slot when the pole tab is bent due to vibration transfer during the production process, resulting in poor electrical connection.

[0070] In some embodiments, the outer end of the protective layer 5 (i.e. Figure 1 The upper edge of the protective layer 5) can extend beyond the side of the pole piece, but be spaced apart from the insulating pad 6, that is, the projections of the protective layer 5 and the insulating pad 6 in the thickness direction of the pole piece do not overlap each other, and the edges of the two just touch or leave a gap greater than zero. In other words, the outer end of the protective layer 5 can extend beyond the edge of the pole piece but does not cover the insulating pad 6. In a specific implementation, the spacing distance between the protective layer 5 and the insulating pad 6 can be set to 0-2mm (for example, 0.5mmm or any other value within this range). When the spacing distance between the protective layer 5 and the insulating pad 6 is zero, it specifically means that the protective layer 5 does not cover the insulating pad 6, the edges of the two just touch, and the gap is zero.

[0071] In some embodiments, the outer end of the protective layer 5 (i.e. Figure 1 The upper edge of the electrode sheet (in the upper edge of the electrode sheet) can extend beyond the side edge of the electrode sheet and cover at least part of the insulating pad 6, that is, the projection of the protective layer 5 and the insulating pad 6 in the thickness direction of the electrode sheet at least partially overlaps. For example, in the first direction (i.e., the width direction of the electrode sheet, see the details for details). Figure 1 ), the size of the protective layer 5 covering the insulating pad 6 is 0.3mm-5mm (for example, 0.5mm, 1.5mm, 2mm or any other value within the range); and / or, in the second direction (i.e., the length direction of the pole piece, see Figure 1 ), the protective layer 5 exceeds the insulating pad 6 by 0.5 mm to 7 mm (e.g., 1 mm, 4 mm, or any other value within the range) on both sides. When the protective layer 5 covers the insulating pad 6, it can protect and fix the right angles on the left and right sides of the lower edge of the insulating pad 6 near the edge of the pole piece, thereby preventing the shaking during the production process from piercing the top diaphragm and causing fire failure.

[0072] In specific implementation, a pole ear groove 4 for welding the pole ear 3 can be provided on a single side of the pole piece (for details, see Figure 3 ), and a pole lug groove 4 for welding the pole lug 3 may also be provided on both sides of the pole piece (for details, see Figure 2 ). Correspondingly, the pole lug 3 located in the pole lug slot 4 and the protective layer 5 covering the outside of the pole lug slot 4 are also arranged on one side or both sides of the pole piece.

[0073] In summary, the outer end of the protective layer 5 extending beyond the side edge of the electrode has at least the following functions:

[0074] ① When the pole piece has a single-sided pole ear groove 4, the protective layer 5 that exceeds the edge of the pole piece can be bonded to the diaphragm to further fix the pole ear and avoid tearing caused by shaking and friction at the junction of the pole ear and the current collector.

[0075] ② When the pole piece is provided with the pole ear groove 4 on one side, the protective layer 5 that exceeds the edge of the pole piece may be covered on the insulating pad 6 or may not be covered on the insulating pad 6. When the protective layer 5 exceeds the edge of the pole piece and covers the insulating pad 6, it can protect and fix the right angles on both sides of the lower edge of the insulating pad 6 close to the edge of the pole piece, thereby avoiding the problem of shaking caused by other factors during the production process, piercing the top diaphragm and causing fire failure; when the protective layer 5 does not cover the insulating pad 6, the distance between the protective layer 5 and the lower edge of the insulating pad 6 is preferably 0 to 0.5 mm, which can fix the diaphragm, the pole ear, and the protective layer 5 together, thereby further fixing the pole ear and avoiding the problem of falling off caused by some uncontrollable factors during the production process; at the same time, the protective layer 5 can make the contact between the pole ear 3 and the current collector closer, thereby reducing the contact impedance; while avoiding the friction between the unwelded part of the pole ear and the current collector, and avoiding the intersection of the pole ear and the current collector (such as Figure 1 The problem of tearing due to shaking friction) is shown in the circular area in the middle.

[0076] ③ If the pole piece is provided with pole ear grooves 4 on both sides, a protective layer 5 needs to be provided on the outside of each pole ear groove 4. That is, the pole piece is provided with protective layers 5 on both sides of the pole ear groove area, and the protective layers 5 are bonded together beyond the edge of the pole piece, so as to further fix the pole ear and avoid the problem of tearing caused by shaking and friction at the junction of the pole ear and the current collector.

[0077] ④ If the pole piece is provided with pole ear grooves 4 on both sides, when the protective layer 5 exceeds the edge of the pole piece and covers the insulating pad 6, the right angles on the left and right sides of the lower edge of the insulating pad 6 close to the edge of the pole piece can be protected and fixed, thereby avoiding the problem of shaking caused by other factors during the production process and piercing the top diaphragm to cause fire failure; when the protective layer 5 exceeds the edge of the pole piece and does not cover the insulating pad 6, the diaphragm, the pole ear, and the protective layer 5 are fixed together, thereby further fixing the pole ear and avoiding the problem of falling off caused by some uncontrollable factors during the production process; at the same time, the protective layer 5 can make the contact between the pole ear 3 and the current collector closer, thereby reducing the contact impedance; while avoiding the friction between the unwelded part of the pole ear and the current collector, avoiding the intersection of the pole ear and the current collector (such as Figure 1 The problem of tearing due to shaking friction) is shown in the circular area in the middle.

[0078] In some embodiments, at least one side surface of the pole piece is provided with a pole lug groove 4, the pole lug 3 is partially located in the pole lug groove 4, and its welding point area 7 is fixedly connected to the current collector 1 in the pole lug groove 4. Wherein: the welding point area 7 includes a plurality of welding points (the plurality mentioned in this article specifically refers to at least two), and the plurality of welding points are arranged in a matrix. In addition, the first side edge (i.e. Figure 1 The upper side of the middle welding point area 7) is close to the insulating pad 6, and the second side of the pole piece (i.e. Figure 1 The upper side of the electrode in the electrode) is close to the insulating pad 6, and the distance c between the first side and the second side is 0.5mm-4mm (for example, 2mm, or any other value within the range), that is, the spacing distance c between the welding point area 7 and the edge of the electrode satisfies 0.5mm≤c≤4mm (for example, 2mm, or any other value within the range, see Figure 1 ). Moreover, the distance between any other side edge of the welding spot area 7 and the side edge of the pole ear on the radial outer side thereof is 0.3 mm-4 mm, for example Figure 1 The g in the middle satisfies 0.3mm≤g≤4mm. It can be seen that the welding spot area 7 is basically located in the center of the tab slot 4. For specific specifications, please refer to Figure 1 , the distance between the left and right edges of the welding spot area 7 and the left and right edges of the pole tab 3 is in the range of 0.3mm-4mm (for example, 0.5mm or 2mm, or any other value within the range), and the distance between the lower edge of the welding spot area 7 and the lower edge of the pole tab 3 is in the range of 0.3mm-4mm (for example, 0.5mm or 2mm, or any other value within the range). The advantage of doing so is that it can increase the welding tension between the pole tab 3 and the current collector, prevent the pole tab welding end from falling off the pole piece, and prevent the welding equipment from directly welding the point beyond the pole tab welding end to the current collector during the production process, thereby avoiding the risk of the current collector being punctured and causing electrical connection failure.

[0079] See also Figure 1 In some embodiments, the protective layer 5 can be a protective adhesive tape. In addition, in the first direction (i.e., the width direction of the electrode, see Figure 1 ), the length of the protective layer 5 is Q, the length of the pole ear slot 4 is T, T and Q satisfy T≤Q≤T+8mm, and further, T and Q can also satisfy T+2mm≤Q≤T+6mm; and / or, in the second direction (i.e., the pole piece length direction, see Figure 1 ), the width of the protective layer 5 is M, the width of the pole ear slot 4 is N, M and N satisfy N≤M≤N+8mm, and further, M and N can satisfy N+1mm≤M≤N+4mm. In addition, the outer end of the protective layer 5 (i.e., the end of the protective layer 5 located outside the gap between adjacent pole pieces after the pole pieces are wound or stacked, i.e. Figure 1 In addition, in the first direction (i.e., the width direction of the pole piece, see Figure 1 ), the inner end of the protective layer 5 (i.e., the end of the protective layer 5 extending into and sandwiched between adjacent pole pieces after the pole pieces are wound or stacked) is located on the outer surface of the active layer and exceeds the edge of the pole lug groove 4 by at least 0.5 mm (e.g., 1 mm or 2 mm, or any other value not less than 0.5 mm), that is, Figure 1 The dimension h of the lower edge of the middle protective layer 5 extending beyond the pole lug groove 4 and covering the outer surface of the pole piece active layer satisfies h≥0.5mm, for example, h=1mm or 2mm or any other value not less than 0.5mm. And / or, in the second direction (i.e., the pole piece length direction, see Figure 1 ), both side edges of the protective layer 5 are located on the outer surface of the active layer, and extend beyond the edge of the pole ear groove 4 by at least 0.5 mm (e.g., 1 mm or 2 mm, or any other value not less than 0.5 mm), that is, Figure 1 The left and right sides of the middle protective layer 5 in its width direction respectively exceed the dimension j of the pole tab slot 4 to satisfy j≥0.5mm, for example, j=1mm or 2mm or any other value not less than 0.5mm. Thus, the protective layer 5 covers the entire pole tab slot 4, and the side edges of the protective layer 5 are on the pole piece body instead of in the pole tab slot.

[0080] In a specific implementation, the inner side edge of the protective layer 5 attached to the side of the pole piece can be a straight side edge or a toothed side edge. Moreover, the outer side edge of the protective layer 5 extending out of the edge of the pole piece can be a straight side edge or a toothed side edge. That is, the inner side edge of the protective layer 5 attached to the side of the pole piece is a first straight side edge or a first toothed side edge; and / or, the outer side edge of the protective layer 5 extending out of the edge of the pole piece is a second straight side edge or a second toothed side edge.

[0081] Considering that lithium deposition is prone to occur around the welding position of the pole ear during manufacturing and production, there are safety hazards. Therefore, in a preferred embodiment, the inner side edge of the protective layer 5 attached to the side of the pole piece is designed as a first toothed side edge. Therefore, the inner end of the protective layer located on the side of the pole piece not only has angles at the corners on both sides, but also has multiple angles on the side between the corners on both sides (i.e., the top angle structure of multiple toothed protrusions 2), so that the stress at the two corners can be dispersed and the lithium deposition problem caused by the top angle effect can be reduced. In other words, the number of inner end angles of the protective layer 5 is increased from two to multiple ones dispersedly arranged along the second direction, which is equivalent to dispersing the top angle effect of the inner end area of ​​the protective layer, that is, dispersing the ions gathered at the two corners in the electrolyte to multiple toothed protrusions 2, which is conducive to reducing the lithium deposition problem in the inner end area of ​​the protective layer.

[0082] In specific implementation, the tooth-shaped protrusion 2 on the first tooth-shaped side is preferably a triangular protrusion, the top angle of the triangular protrusion is 10°-75°, and the bottom angle of the tooth-shaped groove formed between adjacent tooth-shaped protrusions 2 is 10°-75°. After testing and verification, when the angle is within the above range, the dispersion effect of corner stress is better. It is preferred that the concave angle and the convex angle are consistent to ensure that the protective layer 5 obtained each time is cut is the same.

[0083] In addition, when the outer end side of the protective layer 5 extending out of the edge of the pole piece is the second tooth-shaped side, the tooth-shaped protrusion 2 can also be a triangular protrusion, the top angle of the triangular protrusion is 10°-75°, and the bottom angle of the tooth-shaped groove formed between adjacent tooth-shaped protrusions 2 is 10°-75°. At this time, because the protective layer 5 is covered on the insulating pad 6 through the second tooth-shaped side, it can not only ensure its coverage size in the first direction, but also reduce the coverage area, and not cover the insulating pad 6 too much, which is conducive to avoiding the problem of liquid leakage caused by virtual sealing during packaging.

[0084] In general, the outer edge and the inner edge of the protective layer 5 are either straight sides or serrated sides, which is caused by continuous production. In a preferred embodiment, in the first direction of the pole piece, the outer end and the inner end of the protective layer 5 are arranged opposite to each other, and the outer end extends outward beyond the pole piece, and the inner end covers the active layer, and the outer end and the inner end are both continuous serrated, and the other two side edges are straight. In this way, the protective layer 5 is generally obtained by cutting a roll of adhesive tape, so that the inner edge of the previous protective layer 5 can be complementary to the outer edge of the next protective layer 5. In continuous production, it is beneficial for each protective layer 5 to be cut once during the cutting process to obtain the designed shape.

[0085] It should be noted that the shape of the tooth-shaped protrusion 2 mentioned herein is not limited to a triangle, but can also be a semicircle, a trapezoid, etc., and the top corner and the bottom groove corner can be a sawtooth shape with sharp tooth tips or a wave shape with smooth tooth tips. In addition, in a specific implementation, the protective layer 5 can be a tape or a viscous diaphragm, and the material of the tape can be any one of rubber tape, polypropylene tape, polyacrylic acid tape, PI tape, SIS tape or others.

[0086] An embodiment of the present application further provides a battery cell, which includes a positive electrode assembly, a separator, and a negative electrode assembly arranged in a stacked manner, wherein the positive electrode assembly and / or the negative electrode assembly is the electrode assembly described above.

[0087] In some embodiments, in the first direction, the width of the separator is A, the width of the negative electrode sheet 02 in the negative electrode assembly is B, and the width of the positive electrode sheet 01 in the positive electrode assembly is C, wherein: A and B satisfy B≤A≤B+5mm, and further A and B can also satisfy B+1mm≤A≤B+3mm; and / or, B and C satisfy C≤B≤C+5mm, and further B and C can also satisfy C+1mm≤B≤C+3mm. Moreover, in the first direction: both side edges of the separator exceed the edge of the negative electrode sheet 02 in the negative electrode assembly by at least 0.5mm; and / or, both side edges of the negative electrode sheet 02 in the negative electrode assembly exceed the edge of the positive electrode sheet 01 in the positive electrode assembly by at least 0.2mm, such as 0.5mm or any other value not less than 0.2mm. Therefore, the diaphragm plays the role of electronic insulation between the positive and negative electrode sheets; the part of the diaphragm extending beyond the negative electrode sheet prevents the paste on the negative electrode sheet from contacting the aluminum-plastic film outside the winding core, thereby avoiding the risk of external short circuit and corrosion under certain specific conditions; the part of the negative electrode sheet extending beyond the positive electrode sheet ensures that the negative electrode's effective active material coating covers the positive electrode's effective active material coating, thereby avoiding the risk of lithium precipitation during the charging process.

[0088] In some embodiments, a positive insulating pad 016 is provided on the positive electrode ear 013 in the positive electrode assembly, and the spacing distance between the positive electrode sheet 01 in the positive electrode assembly and the positive insulating pad 016 is b, b> zero; a negative insulating pad 026 is provided on the negative electrode ear 023 in the negative electrode assembly, and the spacing distance between the negative electrode sheet and the negative insulating pad 026 in the negative electrode assembly is d, d> zero. This can avoid the problem that the right-angle edge of the ear glue pierces the current collector on the ear slot when the ear is bent, which is caused by the vibration transfer that cannot be avoided during the production process, resulting in poor electrical connection. At the same time, the length of the distance b on the positive side is greater than the length of the distance d on the negative side, that is, b>d>zero, because the negative electrode sheet needs to exceed the positive electrode sheet, and the inner edges of the positive and negative insulating pads need to be on the same horizontal line, and the outer edges of the positive and negative insulating pads need to be on the same horizontal line, so as to ensure that the positive insulating pad on the positive ear and the negative insulating pad on the negative ear can be bonded to the aluminum-plastic film outside the winding core during packaging to avoid the risk of leakage. At the same time, it is necessary to ensure that the area from the part of the positive ear that extends beyond the pole piece to the positive insulating pad must be protected by a protective layer to avoid the risk of short circuit caused by short circuit between the protruding part and the edge of the negative pole piece.

[0089] During the production process, it was found that the length of the welding section of the pole ear 3 (i.e., the connection portion where the pole ear is located in the pole ear slot and welded with the current collector) has a great influence on the charging speed and safety performance of the battery cell. Inappropriate welding length often reduces the charging speed of the lithium-ion battery, and even causes short circuit, fire, and explosion problems. Based on the above problems, in some embodiments, the portion of the positive pole ear 013 in the positive electrode assembly located in the positive pole ear slot 014 is the positive pole ear connection portion, and the portion of the negative pole ear 023 in the negative electrode assembly located in the negative pole ear slot 024 is the negative pole ear connection portion. In the first direction, the length of the positive pole ear connection portion is greater than the length of the negative pole ear connection portion, and the difference between the two is e, and e satisfies 0.5mm≤e≤10mm, for example, e=1mm or 8mm or any other value within the range. Therefore, the positive electrode impedance in the lithium-ion battery is greater than the negative electrode impedance. In order to reduce the positive electrode impedance, in addition to using some chemical techniques, studies have found that increasing the length of the tab embedded in the pole piece and increasing the contact area between the tab and the current collector can disperse foreign electrons more evenly and effectively reduce the impedance on the positive electrode side. Further research has found that when the positive tab welding end is longer than the negative tab welding end, that is, the distance e in the figure, the above effect can be achieved.

[0090] Correspondingly, since the positive and negative electrode tab welding sections are of different lengths, that is, the length of the positive electrode tab connection portion is greater than the length of the negative electrode tab connection portion, the difference between the two is e. Therefore, the lengths of the tab slots where the positive and negative electrode tabs are located are also different, specifically, the length of the negative electrode tab slot 024 in the first direction is shorter than the length of the positive electrode tab slot 014 in the first direction, but it needs to comply with the above description of the tab slot and the tab, which will not be repeated here.

[0091] See also Figure 4 In some embodiments, the electrode sheet and the protective layer 5 in the negative electrode assembly are respectively the negative electrode sheet 02 and the negative electrode protective layer 025, and the electrode sheet surface of the positive electrode assembly is further provided with an additional protective layer 018, and the additional protective layer 018 and the negative electrode protective layer 025 are respectively located on both sides of the negative electrode sheet 02. In addition, in the third direction (i.e., the thickness direction of the battery cell, see Figure 4 ), the projection of the negative electrode protection layer 025 is located within the projection of the additional protection layer 018.

[0092] Specifically, in the first direction: the length n of the additional protective layer 018 is greater than the length m of the negative electrode protective layer 025, and the difference between the two is f, where f satisfies 0.5mm≤f≤5mm, for example, f=1mm or 3mm or any other value within the range; and / or, the outer edge of the additional protective layer 018 (that is, the end edge of the additional protective layer 018 extending outside the side of the electrode sheet, that is, the upper side in Figure 5) exceeds the edge of the negative electrode sheet 02 by 0-3mm (for example, 0.5mm or 1mm or any other value within the range); and / or, the inner edge of the additional protective layer 018 (i.e., the additional protective layer 018 is located inside the battery cell and at the end edge of the electrode surface, i.e., the lower side in Figure 5) exceeds the inner edge of the negative electrode protective layer 025 by 0.2mm-3mm (e.g., 0.5mm or 2mm or any other value within the range); and / or, the inner edge of the additional protective layer 018 is flush with the inner edge of the positive electrode protective layer 015 in the positive electrode assembly, or, the inner edge of the additional protective layer 018 exceeds the inner edge of the positive electrode protective layer 015 by 0.2mm-5mm (e.g., 0.5mm or 2mm or any other value within the range). In addition, in the second direction: the width of the additional protective layer 018 is greater than the width of the negative electrode protective layer 025 by 1mm-10mm (e.g., 2mm or 6mm or any other value within the range); and / or, the two opposite side edges of the additional protective layer 018 both exceed the edge of the negative electrode protective layer 025 by at least 0.3mm (e.g., 0.5mm or any other value not less than 0.3mm).

[0093] In short, a protective layer, namely, an additional protective layer 018, also needs to be affixed to the positive electrode sheet corresponding to the negative electrode protective layer 025. This is to prevent the active material in the area on the negative electrode sheet covered by the negative electrode protective layer 025 from not functioning when there is only the negative electrode protective layer 025, but the active material of the positive electrode opposite to it will function. At this time, the lithium ions of the positive electrode will be released during the charging process and precipitated on the negative electrode protective layer 025 of the negative electrode. Therefore, in order to avoid the above-mentioned problems, it is necessary to affix an additional protective layer 018 to the corresponding positive electrode side; the width of the additional protective layer 018 in the second direction is generally required to be the same as the width of the positive electrode protective layer 015 on the positive electrode sheet in the second direction to reduce the manufacturing difficulty, and it can also be different, but it is necessary to ensure that the width of the additional protective layer 018 in the second direction is greater than the width of the negative electrode protective layer 025 in the second direction by 1mm-10mm, and exceeds the side of the negative electrode protective layer 025 by at least 0.3mm. In the first direction, the outer end of the additional protective layer 018 (i.e. Figure 5 and Figure 6 The upper side of the additional protective layer 018 is 0-3mm (e.g., 0.5mm or 1mm or any other value within the range) beyond the edge of the pole piece to ensure effective coverage. Figure 5 and Figure 6The lower side of the additional protective layer 018 in the first direction may exceed the lower side of the negative electrode protective layer 025 by 0.2 mm-5 mm (e.g., 0.5 mm or 2 mm or any other value within the range) to ensure effective protection. The maximum size of the additional protective layer 018 in the first direction may be flush with the lower edge of the positive electrode protective layer 015 or exceed it by 0.2 mm-5 mm (e.g., 0.5 mm or 2 mm or any other value within the range). The advantage of doing so is to avoid excessive coverage of the positive electrode active material to avoid capacity loss, resulting in reduced energy density.

[0094] Finally, it should be noted that, in this article, relational terms such as first and second, etc. 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 "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device that includes a series of elements includes not only those elements, but also other elements not explicitly listed.

[0095] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0096] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An electrode assembly, characterized in that: include: Pole piece, insulating pad (6), pole ear (3), protective layer (5); The pole piece comprises a current collector (1) and an active layer; The pole lug (3) is electrically connected to the current collector (1); the pole lug (3) comprises a first surface and a second surface, the first surface and the second surface are respectively provided with the insulating pad (6); the insulating pad (6) is spaced apart from the pole piece, and the spacing distance is 0.3 mm to 5 mm; The protective layer (5) covers the side of the electrode tab (3) away from the current collector (1).

2. The electrode assembly according to claim 1, characterized in that: The protective layer (5) and the insulating pad (6) are spaced apart, and the spacing between the two is 0-2 mm; and / or, The outer end of the protective layer (5) extends beyond the side edge of the pole piece to cover at least a portion of the insulating pad (6), and: in a first direction, the protective layer (5) covers the insulating pad (6) by a size of 0.3 mm to 5 mm; and / or, in a second direction, the protective layer (5) extends beyond the insulating pad (6) by a size of 0.5 mm to 7 mm.

3. The electrode assembly according to claim 1, characterized in that: A pole lug groove (4) is provided on at least one side surface of the pole piece, the pole lug (3) is partially located in the pole lug groove (4), and its welding point area (7) is connected to the current collector (1) in the pole lug groove (4); wherein: The welding point area (7) includes a plurality of welding points, and the plurality of welding points are arranged in a matrix; and / or, The first side of the welding spot area (7) is close to the insulating pad (6), the second side of the pole piece is close to the insulating pad (6), and the distance between the first side and the second side is 0.5 mm-4 mm; the distance between any other side of the welding spot area (7) and the side of the pole ear on its radial outer side is 0.3 mm-4 mm.

4. The electrode assembly according to claim 1, characterized in that: A pole lug groove (4) is provided on at least one side surface of the pole piece, and the pole lug (3) is partially located in the pole lug groove (4); and: In the first direction: the inner end of the protective layer (5) is located on the outer surface of the active layer and exceeds the edge of the tab groove (4) by at least 0.5 mm; and / or, In the second direction: both side edges of the protective layer (5) are located on the outer surface of the active layer, and respectively extend beyond the edge of the tab groove (4) by at least 0.5 mm.

5. The electrode assembly according to claim 4, characterized in that: In the first direction, the length of the protective layer (5) is Q, the length of the tab groove (4) is T, and T and Q satisfy T≤Q≤T+8mm; and / or, In the second direction, the width of the protective layer (5) is M, the width of the tab groove (4) is N, and M and N satisfy N≤M≤N+8mm.

6. The electrode assembly according to claim 4, characterized in that: The inner end side edge of the protective layer (5) is a first straight side edge or a first toothed side edge; And / or, the outer end side edge of the protective layer (5) is a second straight side edge or a second toothed side edge.

7. The electrode assembly according to claim 6, characterized in that: The tooth-shaped protrusion (2) on the first tooth-shaped side is a triangular protrusion, and the top angle thereof is 10°-75°; And / or, the tooth-shaped protrusion (2) on the second tooth-shaped side is a triangular protrusion, and its top angle is 10°-75°; And / or, adjacent tooth-shaped protrusions (2) form tooth-shaped grooves, and the bottom angle of the tooth-shaped grooves is 10°-75°.

8. A battery cell, characterized in that: The invention comprises a positive electrode assembly, a separator and a negative electrode assembly which are stacked, wherein the positive electrode assembly and / or the negative electrode assembly is the electrode assembly according to any one of claims 1 to 7.

9. The battery cell according to claim 8, characterized in that: In the first direction, the width of the separator is A, the width of the negative electrode sheet (02) in the negative electrode assembly is B, and the width of the positive electrode sheet (01) in the positive electrode assembly is C; wherein, A and B satisfy B≤A≤B+5mm; And / or, B and C satisfy C≤B≤C+5mm.

10. The battery cell according to claim 8, characterized in that: In the first direction: The edges of both sides of the separator extend beyond the edge of the negative electrode sheet (02) in the negative electrode assembly by at least 0.5 mm; And / or, both side edges of the negative electrode sheet (02) in the negative electrode assembly extend beyond the edge of the positive electrode sheet (01) in the positive electrode assembly by at least 0.2 mm.

11. The battery cell according to claim 8, characterized in that: A positive insulating pad (016) is arranged on the positive electrode ear (013) in the positive electrode assembly, and the spacing distance between the positive electrode sheet (01) in the positive electrode assembly and the positive insulating pad (016) is b; A negative insulating pad (026) is arranged on the negative electrode ear (023) in the negative electrode assembly, and the spacing distance between the negative electrode sheet in the negative electrode assembly and the negative insulating pad (026) is d; b and d satisfy b>d.

12. The battery cell according to claim 8, characterized in that: The portion of the positive electrode lug (013) in the positive electrode assembly located in the positive electrode lug groove (014) is the positive electrode lug connection portion; The portion of the negative electrode lug (023) in the negative electrode assembly located in the negative electrode lug groove (024) is the negative electrode lug connection portion; In the first direction, the length of the positive electrode tab connecting portion is greater than the length of the negative electrode tab connecting portion, and the difference between the two is e, 0.5mm≤e≤10mm.

13. The battery cell according to claim 8, characterized in that: The electrode sheet and the protective layer (5) in the negative electrode assembly are respectively a negative electrode sheet (02) and a negative electrode protective layer (025); An additional protective layer (018) is also provided on the surface of the electrode sheet of the positive electrode assembly, and the additional protective layer (018) and the negative electrode protective layer (025) are respectively located on both sides of the negative electrode sheet (02); and, in the third direction, the projection of the negative electrode protective layer (025) is located within the projection of the additional protective layer (018).

14. The battery cell according to claim 13, characterized in that: In the first direction: The length of the additional protective layer (018) is greater than the length of the negative electrode protective layer (025), and the difference between the two is f, 0.5 mm ≤ f ≤ 5 mm; and / or, the outer edge of the additional protective layer (018) exceeds the edge of the negative electrode sheet (02) by 0-3 mm; And / or, the inner edge of the additional protective layer (018) exceeds the inner edge of the negative electrode protective layer (025) by 0.2 mm to 3 mm; And / or, the inner edge of the additional protective layer (018) is flush with the inner edge of the positive electrode protective layer (015) in the positive electrode assembly, or the inner edge of the additional protective layer (018) exceeds the inner edge of the positive electrode protective layer (015) by 0.2 mm-5 mm.

15. The battery cell according to claim 13, characterized in that: In the second direction: The width of the additional protective layer (018) is 1 mm to 10 mm greater than the width of the negative electrode protective layer (025); And / or, the two opposite edges of the additional protective layer (018) both extend beyond the edge of the negative electrode protective layer (025) by at least 0.3 mm.

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