Positive pole piece and battery

Abstract

The utility model relates to the field of battery manufacturing, in particular to a positive pole piece and a battery, which comprise a current collector, an active material layer and a corner protection layer, the active material layer at least covers part of the current collector; the current collector is provided with a first side edge, a second side edge, a third side edge and a fourth side edge which are connected in sequence, and the first side edge and the third side edge are arranged in parallel; the current collector comprises a plurality of vertex angle parts, and each vertex angle part is formed by intersection of the first side edge and the second side edge, intersection of the first side edge and the fourth side edge, intersection of the third side edge and the second side edge, and intersection of the third side edge and the fourth side edge; wherein the corner protection layer is arranged on at least one top corner part. The corner protection layer is arranged at the top corner part of the positive pole piece of the battery, so that burrs cannot threaten a diaphragm of the battery, the speed of a lithium embedding process at the top corner part is slowed down, the use safety of the battery is improved, and the cycle life of the battery is prolonged.

Description

Technical Field

[0001] This utility model relates to the field of battery manufacturing, and in particular to a positive electrode sheet and a battery. Background Technology

[0002] With the development of technology, the demand for energy storage is getting higher and higher, and the requirements are becoming more and more stringent. Among them, lithium batteries, as an energy storage device with high energy storage efficiency, stable energy storage, many charge and discharge cycles, and long service life, are receiving more and more attention in the field.

[0003] However, in the current manufacturing process of electrode sheets, there are still some problems that greatly affect battery performance. On the one hand, the corners of the electrode sheets are difficult to process, and burrs may be left after processing. These burrs at the corners may puncture the adjacent separators in subsequent processes and use, causing short circuits between the positive and negative electrodes, which greatly reduces the safety of the battery. On the other hand, in the charge and discharge tests of the battery, it has been found that lithium plating is very likely to occur at the corners of the negative electrode during repeated charge and discharge.

[0004] Therefore, how to improve the corner burrs of the electrodes and slow down the lithium insertion process at the battery corners to improve the safety and cycle life of the battery is a problem that urgently needs to be solved by those skilled in the art. Utility Model Content

[0005] The purpose of this invention is to provide a positive electrode sheet and a battery to solve the problems in the prior art, such as the inability to eliminate corner burrs on the electrodes, poor battery safety, and excessively rapid lithium intercalation at the battery corners.

[0006] To solve the above-mentioned technical problems, this utility model provides a positive electrode sheet, including a current collector, an active material layer, and a corner protection layer;

[0007] The active material layer at least partially covers the current collector;

[0008] The current collector has a first side, a second side, a third side, and a fourth side connected in sequence, with the first side and the third side arranged in parallel; the current collector includes a plurality of apex portions, which are formed by the intersection of the first side and the second side, the first side and the fourth side, the third side and the second side, and the third side and the fourth side, respectively;

[0009] The corner protection layer is disposed at at least one of the top corners.

[0010] Optionally, in the positive electrode sheet, the corner protective layer is in direct contact with the current collector;

[0011] The corner protective layer has a dimension of L2 in the first direction, and the current collector has a dimension of L3 on its first side in the first direction; along the second direction, the corner protective layer has a dimension of W2, and the current collector has a dimension of W3 on its third side in the second direction, and the second direction is perpendicular to the first direction;

[0012] The condition W2 and W3 satisfy 0.01 ≤ W2 / W3 ≤ 0.4;

[0013] And / or, L2 and L3 satisfy 0.01≤L2 / L3≤0.8;

[0014] And / or, W2 satisfies 2mm≤W2≤16mm;

[0015] And / or, L2 satisfies 1mm≤L2≤8mm;

[0016] And / or, W3 satisfies 40mm≤W3≤120mm;

[0017] And / or, L3 satisfies 10mm≤L3≤100mm.

[0018] Optionally, in the positive electrode sheet, the first side and the second side form a first apex, the third side and the second side form a second apex, the third side and the fourth side form a third apex, and the first side and the fourth side form a fourth apex.

[0019] The first, second, third, and fourth apex corners are all provided with the corner protection layer.

[0020] Optionally, in the positive electrode sheet, the active material layer includes a main body and a thinned extension portion;

[0021] The main body is disposed in the non-corner region of the current collector, and the active material layer of the thinned extension is disposed between the current collector and the corner protection layer;

[0022] The active material layer of the thinned extension has a thickness D1, the corner protective layer has a thickness D2, and the active material layer of the main body has a thickness D3.

[0023] The conditions D1, D2, and D3 are satisfied that D1 + D2 ≤ D3.

[0024] Optionally, in the positive electrode sheet, the positive electrode sheet includes a tab, which extends from the first side;

[0025] The projection of the electrode tab on the first side overlaps with the projection of the corner protective layer on the first side.

[0026] Alternatively, the projection of the tab on the first side does not overlap with the projection of the corner protective layer on the first side.

[0027] Optionally, the positive electrode sheet further includes an edge insulating layer;

[0028] The edge insulation layer is disposed on the side close to the first side, and the edge insulation layer is connected to the corner protection layers at both ends of the first side.

[0029] Optionally, in the positive electrode sheet, an electrode insulating layer is further provided on the electrode tab, and the electrode insulating layer is connected to the edge insulating layer;

[0030] Along the extending direction of the tab, the tab insulating layer has a width W1, and the corner protection layer has a width W2;

[0031] The condition 0.15 ≤ W1 / W2 ≤ 1.1 is satisfied between W1 and W2.

[0032] Optionally, in the positive electrode sheet, there is a boundary line between the projection of the corner protective layer on the current collector and the projection of the active material layer on the current collector;

[0033] The boundary line is a straight line segment, and the boundary line forms an angle with the side of the current collector. 1, 1. Satisfies 15°≤ 1≤75°;

[0034] Alternatively, the boundary line is an arc segment; the arc segment bends towards the apex angle of the current collector and has an angle value R0, where R0 satisfies 0.6 ≤ R0 ≤ 1.5; the tangent at the contact point between the arc segment and the side of the current collector forms an angle with the side of the current collector. 2, 2 satisfies 15°≤ 2≤75°.

[0035] Optionally, in the positive electrode, the corner protection layer has a resistance value R1, where R1 satisfies 200mΩ≤R1≤700mΩ;

[0036] The active material layer has a resistance value R2, which satisfies 50mΩ≤R2≤500mΩ;

[0037] And R1 > R2;

[0038] And / or, the corner protective layer has a porosity P1;

[0039] P1 satisfies 10%≤P1≤30%;

[0040] The active material layer has a porosity of P2;

[0041] P2 satisfies 20% ≤ P2 ≤ 40%.

[0042] A battery comprising a negative electrode, a separator, and a positive electrode as described above;

[0043] The positive electrode and the negative electrode are stacked alternately, and a separator is provided between adjacent positive electrode and negative electrode.

[0044] The positive electrode sheet provided by this utility model includes a current collector, an active material layer, and a corner protection layer; the active material layer at least partially covers the current collector; the current collector has a first side, a second side, a third side, and a fourth side connected in sequence, the first side and the third side being arranged in parallel; the current collector includes a plurality of apex portions, the apex portions being formed by the intersection of the first side and the second side, the first side and the fourth side, the third side and the second side, and the third side and the fourth side, respectively; wherein, the corner protection layer is disposed at at least one of the apex portions. In this invention, a corner protection layer is provided at the apex of the positive electrode sheet of the battery. This corner protection layer can cover burrs generated during the current collector processing, preventing them from threatening the battery separator. Furthermore, the presence of the corner protection layer at the corner of the positive electrode sheet artificially reduces the lithium content at the corner, thereby reducing the number of lithium ions acquired by the negative electrode sheet at the apex. This improves the uniformity of lithium ion acquisition across the entire negative electrode sheet, preventing thinning of the negative electrode edge and insufficient vacancies for lithium ions during charging and discharging, which leads to lithium plating. It also slows down the lithium intercalation process at the apex, solving the problem of severe lithium plating at the apex of the negative electrode sheet and significantly improving battery safety and cycle life. This invention also provides a battery with the above-mentioned beneficial effects. Attached Figure Description

[0045] To more clearly illustrate the technical solutions of the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0046] Figure 1-1 A cross-sectional schematic diagram of a specific embodiment of the positive electrode sheet provided by this utility model;

[0047] Figure 1-2 A cross-sectional schematic diagram of another specific embodiment of the positive electrode sheet provided by this utility model;

[0048] Figure 2 A top view schematic diagram of a specific embodiment of the positive electrode sheet provided by this utility model;

[0049] Figure 3 A top view schematic diagram of a specific embodiment of the positive electrode sheet provided by this utility model;

[0050] Figure 4 A top view schematic diagram of another specific embodiment of the positive electrode sheet provided by this utility model;

[0051] Figure 5 A top view schematic diagram of another specific embodiment of the positive electrode sheet provided by this utility model;

[0052] Figure 6 A top view schematic diagram of another specific embodiment of the positive electrode sheet provided by this utility model;

[0053] Figure 7 A cross-sectional schematic diagram of one specific embodiment of the battery provided by this utility model;

[0054] Figure 8-1 , Figure 8-2 , Figure 8-3 , Figure 8-4 , Figure 8-5 , Figure 8-6 A process flow diagram of the battery stacking production method provided by this utility model.

[0055] Figure label:

[0056] 10-Corner portion; 20-Non-corner portion region; 001-First side; 002-Second side; 003-Third side; 004-Fourth side; 10a-First corner portion; 10b-Second corner portion; 10c-Third corner portion; 10d-Fourth corner; 01-Current collector; 02-Active material layer; 02a-Main body portion; 02b-Thinning extension portion; 03-Corner protection layer; 04-Taper; 05a-Edge insulation layer; 05b-Taper insulation layer; 100-Negative electrode; 200-Positive electrode; 300-Separator. Detailed Implementation

[0057] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0058] The core of this utility model is to provide a positive electrode sheet, the structural schematic diagram of one specific embodiment of which is shown below. Figures 1-1 to 6 As shown, it is referred to as Specific Implementation Method 1, including current collector 01, active material layer 02 and corner protection layer 03;

[0059] The active material layer 02 at least partially covers the current collector 01;

[0060] The current collector 01 has a first side 001, a second side 002, a third side 003, and a fourth side 004 connected in sequence, with the first side 001 and the third side 003 arranged in parallel; the current collector 01 includes a plurality of apex portions 10, each apex portion 10 being formed by the intersection of the first side 001 with the second side 002, the first side 001 with the fourth side 004, the third side 003 with the second side 002, and the third side 003 with the fourth side 004;

[0061] The corner protection layer 03 is disposed at at least one of the top corner portions 10.

[0062] Preferably, the first side 001 and the second side 002 form a first apex 10a, the third side 003 and the second side 002 form a second apex 10b, the third side 003 and the fourth side 004 form a third apex 10c, and the first side 001 and the fourth side 004 form a fourth apex 10d.

[0063] The first apex 10a, the second apex 10b, the third apex 10c, and the fourth apex 10d are all provided with the corner protection layer 03. The positive electrode sheet is typically a rectangular sheet formed by four sides (though other shapes are possible, which is not limited here). The corner protection layer 03 preferably protects all the apex 10s of the positive electrode sheet (i.e., the first apex 10a, the second apex 10b, the third apex 10c, and the fourth apex 10d), achieving comprehensive protection for the positive electrode sheet 04. However, selective protection of the apex 10s of the positive electrode sheet 04 can be achieved depending on the actual situation, i.e., the four corner protection layers 03 may not be provided; this is not limited here. To ensure clarity in the subsequent drawings, this utility model... Figure 2 The first side 001, the second side 002, the third side 003, the fourth side 004, the first apex 10a, the second apex 10b, the third apex 10c, and the fourth apex 10d are uniformly marked (each apex 10 is circled with a dashed line in the figure; of course, the actual size of the apex 10 can be adjusted as needed). Figure 2(The above figures are for illustrative purposes only.) The various sides and top corners 10 will not be individually labeled in subsequent figures.

[0064] Graphite anodes of different shapes were charged at a rate of 0.5C for 2 hours. At the end of charging, although the total amount of lithium ions reacted was equal to the theoretical saturation capacity of the graphite anode, the color of the graphite electrode after charging did not indicate that the overall saturation state had been achieved. Instead, the electrode edge region showed a LiC6 saturated golden yellow color, and even more lithium dendrite clusters were found to be deposited, while the interior region of the electrode still showed the original black color of graphite. The entire electrode exhibited a highly non-uniform lithiation state. These phenomena indicate that, due to the influence of the electrode shape, some lithium ions were consumed by side reactions during the lithiation process, and an effective lithium intercalation reaction was not achieved.

[0065] Further simulations and experiments revealed that the lithium-ion concentration in the electrolyte exhibits a highly spatially non-uniform distribution after a certain lithiation time. Specifically, the lithium-ion flux is mainly concentrated at the edges of the graphite anode, with particularly significant flux at the sharp corners. Therefore, the edges of the graphite anode readily absorb more lithium-ions, achieving rapid saturation. Conversely, the lithium-ion flux in the electrolyte within the anode's interior is almost zero, making it difficult for the interior to acquire lithium-ions and maintain a lower lithiation state. The reason for this is the extremely high electric field strength at the electrode edges, which affects the transport of lithium-ions from the positive electrode to the graphite anode. This results in a higher lithium-ion concentration at the anode edges and a very low concentration within the interior, leading to non-uniform lithiation. Furthermore, the significantly greater electric field strength along the diagonal of the rectangular electrode compared to the radial direction of the circular electrode indicates that the sharp corners with greater curvature result in a larger electric field, further exacerbating the non-uniformity of lithiation. In this invention, a corner protection layer 03 is applied to the four corners of the positive electrode sheet, which can greatly avoid the influence of the aforementioned sharp corner effect and improve the lithium plating situation.

[0066] In addition, the corner protection layer 03 has a resistance value R1, which satisfies 200mΩ≤R1≤700mΩ;

[0067] The active material layer O2 has a resistance value R2, which satisfies 50mΩ≤R2≤500mΩ;

[0068] And R1>R2.

[0069] This specific embodiment not only specifies the range of the resistance R1 of the corner protection layer 03 (such as any one of 200.0mΩ, 512.4mΩ or 700.0mΩ) and the range of the resistance R2 of the active material layer 02 (such as any one of 50.0mΩ, 222.4mΩ or 500.0mΩ), but also indicates that the resistance R1 of the corner protection layer 03 is higher than the resistance R2 of the active material layer 02. In a long cycle, once an extreme situation occurs, thermal runaway caused by heat generation from the contact between the positive and negative electrodes can be avoided, further ensuring battery safety.

[0070] Preferably, the corner protective layer 03 has a porosity P1;

[0071] P1 satisfies 10%≤P1≤30%, such as any one of 10.0%, 22.4%, or 30.0%;

[0072] The active material layer O2 has a porosity P2;

[0073] P2 satisfies 20%≤P2≤40%, such as any one of 20.0%, 31.4%, or 40.0%.

[0074] Among the above preferred parameters, compared with other existing technologies, the porosity of the corner protective layer 03 is increased, which can better block the deintercalation process of lithium ions at the top corner 10.

[0075] The corner protective layer 03 comprises inorganic oxides, nano-spherical hot-melt polymer materials, conductive agents, binders, and dispersants. The inorganic oxides comprise 90-95% by mass, the nano-spherical hot-melt polymer materials comprise 0.2-0.8% by mass, the conductive agents comprise 0.5-1.2% by mass, and the binders comprise 1-2% by mass.

[0076] Furthermore, the inorganic oxide is composed of various materials, including but not limited to metal oxides, phosphates, and sulfides, with main components such as Al2O3, MgO, CeO2, ZrO2, and Co3O4, which possess high chemical stability. The functional coating can oxidize during charging, forming an SEI film rich in inorganic substances such as LiF and LiCO3, which typically exhibit good electrochemical stability.

[0077] The nanosphere-shaped hot-melt polymer material includes polyacrylonitrile, polyvinyl alcohol, polyamide, polyimide, polyacrylates and vinyl acetate, polyethylene, polypropylene and polypropylene / polyethylene copolymers, etc.

[0078] In one specific implementation, the corner protective layer 03 is in direct contact with the current collector 01;

[0079] The corner protective layer 03 has a dimension of L2 in the first direction, and the current collector 01 has a dimension of L3 on its first side 001 in the first direction; along the second direction, the corner protective layer 03 has a dimension of W2, and the current collector 01 has a dimension of W3 on its third side 003 in the second direction, the second direction being perpendicular to the first direction (see reference). Figure 5 , Figure 6 (The first direction and the second direction are marked in the two figures above).

[0080] The relationship between W2 and W3 satisfies 0.01≤W2 / W3≤0.4, such as any one of 0.010, 0.121 or 0.400;

[0081] And / or, L2 and L3 satisfy 0.01≤L2 / L3≤0.8, such as any one of 0.01, 0.111 or 0.800;

[0082] And / or, W2 satisfies 2mm≤W2≤16mm, such as any one of 2.0mm, 8.1mm or 16.0mm;

[0083] And / or, L2 satisfies 1mm≤L2≤8mm, such as any one of 1.0mm, 5.1mm or 8.0mm;

[0084] And / or, W3 satisfies 40mm≤W3≤120mm, such as any one of 40.0mm, 61.7mm or 120.0mm;

[0085] And / or, L3 satisfies 10mm≤L3≤100mm, such as any one of 10.0mm, 63.1mm or 100.0mm.

[0086] The above parameter range ensures the effectiveness of the encapsulation and the safety of the battery cell while guaranteeing the safety coating covers the lithium plating area. Of course, adjustments can be made according to actual conditions, and this utility model does not limit this. In addition, the above-mentioned limitation on the size of the corner protective layer 03 refers to the maximum size of the corner protective layer 03 in the corresponding direction.

[0087] You can refer to this. Figure 1-1In this specific embodiment, the top corner portion 10 only has the corner protection layer 03 and no active material layer 02. The corner protection layer 03 is directly coated on the current collector 01. Preferably, the thickness of the corner protection layer 03 is 5-20 μm, the thickness of the active material layer 02 is 20-200 μm, and the volume ratio of the corner protection layer 03 to the active material layer 02 is η1, where η1 satisfies 0.02 ≤ η1 ≤ 0.07. This configuration is suitable for cases with severe lithium plating, effectively preventing lithium intercalation at the corner of the electrode 04 and avoiding lithium plating on the battery electrode 04.

[0088] In another specific embodiment, the active material layer 02 includes a main body portion 02a and a thinned extension portion 02b;

[0089] The main body 02a is disposed in the non-corner region 20 of the current collector 01, and the active material layer 02 of the thinned extension 02b is disposed between the current collector 01 and the corner protection layer 03.

[0090] The active material layer 02 of the thinned extension 02b has a thickness D1, the corner protective layer 03 has a thickness D2, and the active material layer 02 of the main body 02a has a thickness D3.

[0091] The conditions D1, D2, and D3 are satisfied that D1 + D2 ≤ D3.

[0092] In other words, in this specific embodiment, the active material layer 02 is disposed not only in the non-corner region 20 but also in the corner region 10. Simultaneously, the corner protection layer 03 covers the active material layer 02 in the corner region 10 (i.e., in the direction away from the current collector 01). The corner protection layer 03 and the current collector 01 are separated by an active material layer 02 of a certain thickness (i.e., the thinned extension 02b). (Refer to...) Figure 1-2 In this specific embodiment, the volume ratio of the corner protective layer 03 to the active material layer 02 is η2, and η2 satisfies 0.03≤η2≤1. Higher energy density can be obtained on the positive electrode 04 in this specific embodiment, increasing the capacity of the corresponding battery.

[0093] Furthermore, in this preferred embodiment, even with two stacked layers—the active material layer 02 and the corner protection layer 03—in the top corner portion 10, the total thickness of the top corner portion 10 does not exceed the thickness of the active material layer 02 of the main body portion 02a. Preferably, the thickness of the corner protection layer 03 ranges from 5 to 20 μm, the thickness of the active material layer 02 in the thinned extension portion 02b ranges from 20 to 150 μm, and the thickness of the active material layer 02 in the main body portion 02a ranges from 20 to 200 μm. This arrangement can better improve the surface flatness of the electrode 04.

[0094] In one specific embodiment, the corner protective layer 03 and the current collector 01 have a peeling force N1, where N1 satisfies 10N / m≤N1≤25N / m, such as any one of 10.0N / m, 14.2N / m or 25.0N / m;

[0095] The active material layer 02 and the current collector 01 have a peeling force N2, where N2 satisfies 5N / m≤N2≤20N / m, such as any one of 5.0N / m, 14.2N / m or 20.0N / m;

[0096] And N1 > N2.

[0097] In this specific embodiment, the peel force between the corner protective layer 03 and the current collector 01 is limited to be greater than the peel force between the active material layer 02 and the current collector 01, so as to avoid the shedding of the active material layer 02 during the long cycle of the battery and improve the cycle life of the battery.

[0098] In another preferred embodiment, the positive electrode includes a tab 04, which extends from the first side 001;

[0099] The projection of the tab 04 on the first side 001 overlaps with the projection of the corner protective layer 03 on the first side 001.

[0100] Alternatively, the projection of the tab 04 on the first side 001 does not overlap with the projection of the corner protection layer 03 on the first side 001.

[0101] Please refer to Figure 3For a thinner current collector 01, when the projection of the tab 04 on the first side 001 overlaps with the projection of the corner protection layer 03 on the first side 001, it can effectively prevent the tab 04 from accidentally connecting to the active material layer 02 or the current collector 01 after being folded by external force, thereby improving the process efficiency and yield of the battery cell. Of course, the projection of the tab 04 on the first side 001 may not overlap with the projection of the corner protection layer 03 on the first side 001; the corresponding structural diagram can be found in the provided diagram. Figure 4 At this time, the area ratio of the corner protective layer 03 on the current collector 01 is reduced, and more area on the current collector 01 is used to coat the active material layer 02, which can greatly improve the battery capacity.

[0102] Preferably, when the projection of the tab 04 onto the first side 001 does not overlap with the projection of the corner protective layer 03 onto the first side 001, the distance D1 between the corner protective layer 03 and the tab 04 ranges from 5mm to 30mm; when the projection of the tab 04 onto the first side 001 overlaps with the projection of the corner protective layer 03 onto the first side 001, the distance D2 by which the corner protective layer 03 covers the tab 04 ranges from 30mm to 60mm.

[0103] In addition, the positive electrode sheet also includes an edge insulating layer 05a;

[0104] The edge insulation layer 05a is disposed on the side close to the first side 001, and the edge insulation layer 05a is connected to the corner protection layer 03 at both ends of the first side 001.

[0105] Please refer to Figure 3 and Figure 4 The edge insulating layer 05a is set along the entire length of the first side 001, and the two ends of the edge insulating layer 05a respectively contact the two corner protective layers 03 at both ends of the first side 001, so that the first edge where the tab 04 is set is completely insulated, which further avoids accidental short circuits, improves the working stability of the battery, and simplifies the production process and improves production efficiency.

[0106] Furthermore, an electrode insulating layer 05b is also provided on the electrode tab 04, and the electrode insulating layer 05b is connected to the edge insulating layer 05a;

[0107] Along the extending direction of the tab 04, the tab insulating layer 05b has a width W1, and the corner protection layer 03 has a width W2;

[0108] The relationship between W1 and W2 satisfies 0.15 ≤ W1 / W2 ≤ 1.1, such as any one of 0.150, 0.985 or 1.100.

[0109] In this specific embodiment, the junction insulating layer is added, which strengthens the thickness of the root of the tab 04. While improving insulation, it makes the tab 04 less prone to bending. It limits the ratio range between the width W1 of the tab insulating layer 05b and the width W2 of the corner protection layer 03. When W1 / W2 < 0.15, the tab 04 is very easy to bend, which affects the overall process yield. When W1 / W2 > 1.1, the battery ED (energy density) loss is small.

[0110] In a preferred embodiment, there is a boundary line between the projection of the corner protective layer 03 onto the current collector 01 and the projection of the active material layer 02 onto the current collector 01;

[0111] The boundary line is a straight line segment, and the boundary line forms an angle with the side of the current collector 01. 1, 1. Satisfies 15°≤ 1≤75°;

[0112] Alternatively, the boundary line is an arc segment; the arc segment bends towards the apex of the current collector 01 and has an angle R0, where R0 satisfies 0.6 ≤ R0 ≤ 1.5; the tangent at the contact point between the arc segment and the side of the current collector 01 forms an angle with the side of the current collector 01. 2, 2 satisfies 15°≤ 2≤75°.

[0113] For the case where the boundary line is a straight segment, please refer to [the relevant documentation]. Figure 5 When the boundary line is a straight segment, a single corner protective layer 03 can be considered as a triangle, which is easier to process and reduces production costs; for the case where the boundary line is an arc segment, please refer to [the relevant documentation]. Figure 6 When the boundary line is an arc segment, the corner protection layer 03 occupies a smaller area, the active material layer 02 has a larger area, and the resulting energy density is higher.

[0114] Furthermore, when the boundary line is a straight line segment, the straight line segment itself forms an angle with the side of the current collector 01. 1. When the boundary line is an arc segment, the tangent at the endpoint of the boundary line forms an angle with the side. 2, regardless of 1 or 2. Both satisfy 15°≤ 1. 2 ≤ 75°, such as any one of 15.0°, 60.0° or 75.0°.

[0115] When the included angle 1 or When the angle is 15° or 75°, tape breakage can be effectively improved, while increasing process yield. Furthermore, when... 1 or When 2 is 45°, the area of ​​the corner protection layer 03 is the largest, which can effectively reduce the lithium insertion / extraction reaction at the corner, that is, the top corner 10, and greatly improve the battery safety.

[0116] Furthermore, the arc segment has an angle R value R0, where R0 satisfies 0.6 ≤ R0 ≤ 1.5, such as any one of 0.60, 0.99, or 1.50. When the angle R value R0 < 0.6, the area of ​​the corner protection layer 03 is too small and cannot effectively mitigate the lithium desorption problem. When the angle R value R0 > 1.5, the area of ​​the positive electrode active material layer 02 is small, resulting in severe battery ED loss.

[0117] The positive electrode sheet provided by this utility model includes a current collector 01, an active material layer 02, and a corner protection layer 03; the active material layer 02 at least partially covers the current collector 01; the current collector 01 has a first side 001, a second side 002, a third side 003, and a fourth side 004 connected in sequence, the first side 001 and the third side 003 being arranged in parallel; the current collector 01 includes a plurality of apex corner portions 10, the apex corner portions 10 being formed by the intersection of the first side 001 and the second side 002, the first side 001 and the fourth side 004, the third side 003 and the second side 002, and the third side 003 and the fourth side 004; wherein, the corner protection layer 03 is disposed on at least one of the apex corner portions 10. In this invention, a corner protection layer 03 is provided at the top corner 10 of the positive electrode sheet of the battery. The corner protection layer 03 can cover the burrs generated during the processing of the current collector 01, so that the burrs cannot threaten the battery separator. In addition, since there is a corner protection layer 03 at the corner of the positive electrode sheet, the lithium content at the corner of the positive electrode sheet is artificially reduced, thereby reducing the number of lithium ions acquired by the negative electrode sheet at the top corner 10, improving the uniformity of lithium ion acquisition across the entire surface of the negative electrode sheet, avoiding the thinning of the negative electrode edge, and preventing insufficient vacancies for receiving lithium ions during charging and discharging, which would lead to lithium plating. This slows down the lithium intercalation process at the top corner 10, solves the problem of severe lithium plating at the top corner 10 of the negative electrode sheet of the battery, and greatly improves the safety and cycle life of the battery.

[0118] This utility model also provides a battery, the structural schematic diagram of one specific embodiment of which is shown below. Figure 7As shown, the battery includes a negative electrode 100, a separator 300, and a positive electrode 200 as described above.

[0119] The positive electrode 200 and the negative electrode 100 are alternately stacked, and the separator 300 is disposed between adjacent positive electrode 200 and negative electrode 100.

[0120] The positive electrode 200 provided by this utility model includes a current collector 01, an active material layer 02, and a corner protection layer 03; the active material layer 02 at least partially covers the current collector 01; the current collector 01 has a first side 001, a second side 002, a third side 003, and a fourth side 004 connected in sequence, the first side 001 and the third side 003 being arranged in parallel; the current collector 01 includes a plurality of apex corner portions 10, the apex corner portions 10 being formed by the intersection of the first side 001 and the second side 002, the first side 001 and the fourth side 004, the third side 003 and the second side 002, and the third side 003 and the fourth side 004; wherein, the corner protection layer 03 is disposed on at least one of the apex corner portions 10. In this invention, a corner protection layer 03 is provided at the top corner 10 of the positive electrode 200 of the battery. The corner protection layer 03 can cover the burrs generated during the processing of the current collector 01, so that the burrs cannot threaten the separator 300 of the battery. In addition, since there is a corner protection layer 03 at the corner of the positive electrode 200, the lithium content at the corner of the positive electrode 200 is artificially reduced, thereby reducing the number of lithium ions acquired by the negative electrode 100 at the top corner 10, improving the uniformity of lithium ion acquisition across the entire surface of the negative electrode 100, avoiding the thinning of the negative electrode edge, and preventing insufficient vacancies for receiving lithium ions during charging and discharging, which would lead to lithium plating. This slows down the lithium intercalation process at the top corner 10, solves the problem of severe lithium plating at the top corner 10 of the negative electrode 100 of the battery, and greatly improves the safety and cycle life of the battery.

[0121] This utility model also provides a method for producing stacked battery cells, including:

[0122] S1: Electrode 04 Coating—Pre-slitting: The coating paste (i.e., the active material layer 02) and the insulating layer at the edge of the coating paste are applied to the current collector 01 by extrusion coating. The coated electrode 04 is pressed to the process thickness and compaction density by a pressure roller. After roller pressing, pre-slitting is performed. Edge insulating layer 05a and empty foil are distributed from the inside to the outside on both sides of the coating paste. Please refer to [reference needed]. Figure 8-1 .

[0123] S2: Electrode 04 Die-cutting: After pre-splitting, electrode 04 is die-cut to produce electrode tabs 04 according to the height and width requirements of electrode tabs 04. Please refer to [reference needed]. Figure 8-2 .

[0124] S3: Electrode 04 Cleaning: The positive electrode 04 with tabs 04 is further cleaned using laser cleaning to remove the area where the functional coating will be applied. The cleaning location and dimensions must meet the process requirements. Please refer to [reference needed]. Figure 8-3 .

[0125] S4: Functional Layer Spot Coating: Apply functional coating to the cleaned area in spots. The applied functional coating needs to be dried. Please refer to [reference needed]. Figure 8-4 .

[0126] S5: Cutting and preparing the sheet: According to the attached... Figure 8-5 Cut at the position of the dashed line to obtain a positive electrode sheet 04 with functional coating (i.e., the corner protective layer 03) at the four corners.

[0127] S6: Stacking: Stack the wafers according to the Z or E stacking method to form a stacked core. Please see [link to relevant documentation]. Figure 8-6 , Figure 8-6 The diagram shows a Z-shaped stacking pattern. The black electrode 04 in the diagram is the positive electrode 04, and the electrode filled with diagonal lines is the negative electrode 04.

[0128] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to in the method section.

[0129] It should be noted that, in this specification, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0130] The positive electrode plate 04 and the battery provided by this utility model have been described in detail above. Specific examples have been used to illustrate the principle and implementation of this utility model. The descriptions of the embodiments above are only for the purpose of helping to understand the method and core idea of ​​this utility model. It should be noted that for those skilled in the art, several improvements and modifications can be made to this utility model without departing from the principle of this utility model, and these improvements and modifications also fall within the protection scope of the claims of this utility model.

Claims

1. A positive electrode sheet, characterized by, The positive electrode plate comprises a current collector, an active material layer, and an angle position protection layer. The active material layer covers at least part of the current collector. The current collector has a first side edge, a second side edge, a third side edge, and a fourth side edge connected in sequence, and the first side edge and the third side edge are arranged in parallel. The current collector comprises a plurality of top corner portions formed by the intersection of the first side edge and the second side edge, the first side edge and the fourth side edge, the third side edge and the second side edge, and the third side edge and the fourth side edge.

2. The cathode sheet of claim 1, wherein, The angle position protection layer is arranged at at least one of the top corner portions. The angle position protection layer is in direct contact with the current collector. The angle position protection layer has a size L2 in a first direction, and the first side edge of the current collector has a size L3 in the first direction. In a second direction perpendicular to the first direction, the size of the angle position protection layer is W2, and the size of the third side edge of the current collector in the second direction is W3. 0.01≤W2 / W3≤0.4 is satisfied between W2 and W3. 0.01≤L2 / L3≤0.8 is satisfied between L2 and L3. 2mm≤W2≤16mm is satisfied for W2. 1mm≤L2≤8mm is satisfied for L2. 40mm≤W3≤120mm is satisfied for W3.

3. The cathode sheet of claim 1, wherein 10mm≤L3≤100mm is satisfied for L3. The first side edge and the second side edge form a first top corner portion, the third side edge and the second side edge form a second top corner portion, the third side edge and the fourth side edge form a third top corner portion, and the first side edge and the fourth side edge form a fourth top corner portion.

4. The cathode sheet of claim 1, wherein The first top corner portion, the second top corner portion, the third top corner portion, and the fourth top corner portion are all provided with the angle position protection layer. The active material layer comprises a main body portion and a thinned extension portion. The main body portion is arranged in a non-top corner portion region of the current collector, and the active material layer of the thinned extension portion is arranged between the current collector and the angle position protection layer. The active material layer of the thinned extension portion has a thickness D1, the angle position protection layer has a thickness D2, and the active material layer of the main body portion has a thickness D3.

5. The cathode sheet of claim 1, wherein D1+D2≤D3 is satisfied between D1, D2, and D3. The positive electrode plate comprises a tab, and the tab extends from the first side edge. The projection of the tab on the first side edge overlaps the projection of the angle position protection layer on the first side edge.

6. The cathode sheet of claim 5, wherein, Or, the projection of the tab on the first side edge does not overlap the projection of the angle position protection layer on the first side edge. An edge insulation layer is further included.

7. The cathode sheet of claim 6, wherein, The edge insulation layer is arranged on one side close to the first side edge, and the edge insulation layer connects the angle position protection layers at both ends of the first side edge. A tab insulation layer is further arranged on the tab, and the tab insulation layer is connected with the edge insulation layer. In the extension direction of the tab, the tab insulation layer has a width W1, and the angle position protection layer has a width W2. 0.15≤W1 / W2≤1.1 is satisfied between W1 and W2.

8. The cathode sheet of claim 1, wherein, An intersection line exists between a projection of the corner position protection layer on the current collector and a projection of the active material layer on the current collector; The intersection line is a straight line segment, and the intersection line forms an included angle with the side of the current collector 1, 1 meets 15°≤ 1≤75°; Or, the junction line is an arc segment; the arc segment is curved to a top corner of the current collector and has an R corner value R0, R0 satisfies 0.6≤R0≤1.5; a tangent line at a contact point of the arc segment and a side of the current collector forms an included angle with the side of the current collector 2, 2 satisfies 15°≤ 2≤75°.

9. The cathode sheet of claim 1, wherein, The corner position protection layer has a resistance R1, and R1 satisfies 200 mΩ≤R1≤700 mΩ; The active material layer has a resistance R2, and R2 satisfies 50 mΩ≤R2≤500 mΩ; And R1>R2; And / or, the corner position protection layer has a porosity P1; P1 satisfies 10%≤P1≤30%; The active material layer has a porosity P2; P2 satisfies 20%≤P2≤40%.

10. A battery, characterized by The battery comprises a negative electrode sheet, a separator, and the positive electrode sheet according to any one of claims 1 to 9; The positive electrode sheet and the negative electrode sheet are alternately stacked, and the separator is arranged between adjacent positive electrode sheet and negative electrode sheet.

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