Pole piece and battery

Abstract

The present application relates to the field of battery, in particular to a pole piece and a battery comprising the pole piece. The pole piece comprises a current collector and a coating layer coated on one side or both sides of the current collector; the coating layer comprises a first coating layer and a second coating layer; the first coating layer is arranged on the middle region of the current collector and is distributed along the length direction; the second coating layer is arranged on both side edges of the current collector along the length direction, and is connected with or partially overlaps with the first coating layer, and the second coating layer is a porous adhesive material. The pole piece of the present application can fully solve the problem of electrolyte dryness at the edge of the pole piece in the later stage of battery cycle, effectively improve the interface, solve the problems of edge lithium precipitation and battery top and bottom bulging, realize the consideration of normal temperature cycle performance and high temperature cycle performance, and thus improve the comprehensive performance of the battery.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of batteries, in particular to a pole piece and a battery comprising the pole piece. BACKGROUND

[0002] With the continuous development of portable mobile office equipment, the requirements for its use environment have become increasingly demanding, which requires the battery of the portable mobile office equipment to have high performance, and the most important of which is to simultaneously consider the normal temperature cycle performance and the high temperature cycle performance, especially the narrow and long battery which often cannot simultaneously consider the normal temperature cycle performance and the high temperature cycle performance. For the narrow and long battery, due to the size, the distance between the two edges in the length direction is long, and the electrolyte distribution uniformity in the length direction is poor, especially the edge part of the winding core has more polarization and side reactions in the charging and discharging process, which requires a large amount of electrolyte consumption, leading to faster drying of the electrolyte at this position. In the long cycle process, the poor adhesion of the edge interface of the pole piece and even cracking will be caused by the expansion of the positive and negative electrodes and the poor liquid state, and in the case of insufficient negative electrode dynamics, the edge lithium precipitation and the top and bottom bulging of the battery will be finally caused.

[0003] Therefore, it is very important to improve the problems of edge lithium precipitation and the top and bottom bulging of the battery, especially the narrow and long lithium ion battery, so as to simultaneously consider the normal temperature cycle performance and the high temperature cycle performance. SUMMARY

[0004] The purpose of the present application is to overcome the problems of edge lithium precipitation and the top and bottom bulging of the battery, especially the narrow and long lithium ion battery, and to provide a pole piece and a battery comprising the pole piece. The pole piece of the present application can fully solve the problem of drying of the electrolyte at the edge of the pole piece in the later stage of the battery cycle, effectively improve the interface, solve the problems of edge lithium precipitation and the top and bottom bulging of the battery, and realize the consideration of the normal temperature cycle performance and the high temperature cycle performance, so as to improve the comprehensive performance of the battery.

[0005] The first aspect of the present application provides a pole piece, which comprises a current collector and a coating layer coated on one side or both sides of the current collector; the coating layer comprises a first coating layer and a second coating layer; the first coating layer is arranged on the middle region of the current collector and is distributed along the length direction; the second coating layer is arranged on the two side edges of the current collector along the width direction, and is connected or partially overlapped with the first coating layer, and the second coating layer is a porous adhesive material.

[0006] The second aspect of the present application provides a battery, which comprises a first pole piece, a separator and a second pole piece arranged in sequence, the first pole piece is the pole piece of the first aspect of the present application, the second coating layer on the first pole piece is connected with the first coating layer on the first pole piece, and the width of the first coating layer on the first pole piece is less than the width of the second pole piece and is equal to the width of the first pole piece.

[0007] The third aspect of the present application provides a battery, which comprises a first pole piece, a diaphragm and a second pole piece stacked in sequence, the second pole piece is the pole piece of the first aspect of the present application, the second coating layer on the second pole piece partially overlaps the first coating layer on the second pole piece; the width l1 of the overlapping part of the second coating layer on the second pole piece and the first coating layer on the second pole piece is equal to the size of the part of the first coating layer on the second pole piece beyond the first pole piece in the width direction; the width of the part of the second coating layer on the second pole piece arranged on the current collector of the second pole piece is l2.

[0008] Compared with the prior art, the present application has at least the following advantages:

[0009] (1) The pole piece of the present application is coated with porous adhesive material with liquid storage function at both side edge positions, which can store electrolyte and solve the problem of electrolyte drying at the edge of the pole piece in the later stage of the battery cycle; and the porous adhesive material has an adhesive function, which can further strengthen the adhesion of the pole piece and the diaphragm, effectively improve the interface, solve the problem of edge lithium precipitation, realize the consideration of normal temperature cycle performance and high temperature cycle performance, and thus improve the comprehensive performance of the battery;

[0010] (2) The second coating layer on the first pole piece or the second coating layer on the second pole piece of the battery of the present application can fill the thickness difference caused by the large width difference between the first pole piece, the diaphragm and the second pole piece, effectively improving the problem of poor adhesion at the edge of the battery.

[0011] The endpoints of the ranges and any values disclosed in this document are not limited to the precise values recited as the exact dimensions are expected to vary. The endpoints of the ranges and the values of individual points are not to be construed as limiting. Ranges can be expressed in a variety of ways. For example, a range of "between A and B" can be expressed as greater than A and less than B; from A to B; greater than A or less than B; greater than A or less than B; greater than A, less than B, or equal to B; less than A, greater than B, or equal to B; and the like. Each individual value included in a range is disclosed in this document as an endpoint. All combinations of values are considered to be disclosed in this document as if each individual value from Ranges is explicitly written herein. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 The cross-sectional view of the pole piece along the width direction in an example of the present application is shown.

[0013] Figure 2 The top view of the pole piece in an example of the present application is shown.

[0014] Figure 3 The positional relationship between the first coating layer and the second coating layer of the pole piece in an example of the present application is shown (cross-sectional view along the width direction of the pole piece).

[0015] Figure 4A schematic view of the thickness of the first coating layer and the thickness of the second coating layer on the pole piece in one example of the present application (cross-sectional view along the width direction of the pole piece) is shown.

[0016] Figure 5 A cross-sectional schematic view of the battery along the width direction of the pole piece in one example of the present application is shown.

[0017] Figure 6 A schematic view of the stacking position of the first pole piece, the second pole piece and the separator in a battery of the prior art is shown.

[0018] Figure 7 A cross-sectional schematic view of the battery along the width direction of the pole piece in one example of the present application is shown.

[0019] Figure 8 A cross-sectional schematic view of the battery along the width direction of the pole piece in one example of the present application is shown.

[0020] Figure 9 A cross-sectional schematic view of the battery along the width direction of the pole piece in one example of the present application is shown.

[0021] BRIEF DESCRIPTION OF DRAWINGS

[0022] 1 - current collector;

[0023] 2 - coating layer; 21 - first coating layer; 22 - second coating layer;

[0024] 3 - first pole piece; 3-1 first pole current collector; 3-2 - first pole piece coating layer; 3-21 - first pole piece first coating layer; 3-22 - first pole piece second coating layer;

[0025] 4 - separator;

[0026] 5 - second pole piece; 5-1 second pole current collector; 5-2 - second pole piece coating layer; 5-21 - second pole piece first coating layer; 5-22 - second pole piece second coating layer. DETAILED DESCRIPTION

[0027] The specific embodiments of the present application are described in detail below. It should be understood that the specific embodiments described herein are merely illustrative and explanatory and are not intended to limit the present application.

[0028] The first aspect of the present application provides a pole piece, which can include a current collector and a coating layer coated on one or both sides of the current collector; the coating layer can include a first coating layer and a second coating layer; the first coating layer can be arranged on the middle region of the current collector and distributed along the length direction; the second coating layer can be arranged on both side edges of the current collector along the length direction, and connected or partially overlapped with the first coating layer, and the second coating layer can be a porous adhesive material.

[0029] In the present application, the "first coating layer" can include a coating layer conventionally provided on the outside of the current collector in the art, for example: the first coating layer includes an active material layer.

[0030] In the present application, the "length direction" refers to the direction along the long side of the current collector.

[0031] As shown in Figure 1 , it is a schematic view of the cross section of the pole piece along the width direction in an example of the present application, wherein Figure 1 (a) and Figure 1 (b) respectively show the case where the coating layer is coated on one side and both sides of the current collector. In Figure 1 (a), the pole piece includes a current collector 1 and a coating layer 2 coated on one side surface of the current collector 1, and the coating layer 2 includes a first coating layer 21 and a second coating layer 22; in Figure 1 (b), the pole piece includes a current collector 1 and a coating layer 2 coated on both side surfaces of the current collector 1, and the coating layer 2 includes a first coating layer 21 and a second coating layer 22.

[0032] As shown in Figure 2 , it is a schematic view of the pole piece in an example of the present application. In Figure 2 , the first coating layer 21 is provided on the middle region of the current collector and distributed along the length direction, and the second coating layer 22 is provided on both side edges along the width direction of the current collector. Along the first direction, the size of the first coating layer on the first pole piece is smaller than the size of the second pole piece, and the size of the second pole piece is less than or equal to the size of the first pole piece.

[0033] As shown in Figure 3 , it is a schematic view of the position relationship of the first coating layer and the second coating layer of the pole piece in an example of the present application (cross section along the width direction of the pole piece), wherein Figure 3 (a) and Figure 3 (b) respectively show the case where the second coating layer is connected with the first coating layer and partially overlaps. In Figure 3 (a), the second coating layer 22 is connected with the first coating layer 21; in Figure 3 (b), the second coating layer 22 partially overlaps the first coating layer 21.

[0034] In the present application, the thickness of the second coating layer is not less than the thickness of the first coating layer. That is, the thickness of the second coating layer can be greater than the thickness of the first coating layer, and the thickness of the second coating layer can also be equal to the thickness of the first coating layer.

[0035] As shown in Figure 4Fig. 1 shows a schematic view of the thickness of the first coating layer and the thickness of the second coating layer on the pole piece in an example of the present application (cross-sectional view along the width direction of the pole piece), Figure 4 (a) shows a case where the thickness of the first coating layer is equal to the thickness of the second coating layer, Figure 4 (b) shows a case where the thickness of the first coating layer is less than the thickness of the second coating layer, and Figure 4 (c) shows a case where the thickness of the first coating layer is less than the thickness of the second coating layer. Figure 4 In (a), the thickness of the first coating layer 21 is equal to the thickness of the second coating layer 22; in Figure 4 In (b), the thickness of the first coating layer 21 is less than the thickness of the second coating layer 22; in Figure 4 In (c), the thickness of the first coating layer 21 is less than the thickness of the second coating layer 22.

[0036] In an example, the thickness of the second coating layer is greater than the thickness of the first coating layer.

[0037] In an example, the thickness of the second coating layer is equal to the thickness of the first coating layer.

[0038] In the present application, the porosity of the porous adhesive material can be 30-80%, for example, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, or 80%.

[0039] In an example, the porosity of the porous adhesive material is 50-70%.

[0040] The porous adhesive material can include a bulk particle, a thickening agent, and a binder.

[0041] The bulk particle can be selected from at least one of an organic particle and an inorganic particle.

[0042] The inorganic particle can include alumina, magnesia, silica, titania, zirconia, zinc oxide, barium sulfate, boron nitride, aluminum nitride, magnesium nitride, tin dioxide, magnesium hydroxide, boehmite, and calcium carbonate.

[0043] The organic particle can include polyvinyl chloride resin, vinyl chloride-vinylidene chloride copolymer resin, vinyl chloride-vinyl acetate copolymer resin, polyvinylidene fluoride, and polymethyl methacrylate.

[0044] The thickening agent can be selected from at least one of sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, and polyvinylidene fluoride.

[0045] The binder can be selected from at least one of styrene butadiene rubber, styrene-acrylic emulsion, acrylic emulsion, polyethyl acrylate, polymethyl methacrylate, polybutyl methacrylate, ethylene-vinyl acetate copolymer, polyvinyl acetate, and polyurethane.

[0046] The content of the stacked particles can be 40-80 wt% (for example 40 wt%, 45 wt%, 50 wt%, 55 wt%, 60 wt%, 65 wt%, 70 wt%, 75 wt% or 80 wt%) based on the total weight of the porous adhesive material, the content of the thickening agent can be 15-45 wt% (for example 45 wt%, 40 wt%, 35 wt%, 30 wt%, 25 wt%, 20 wt% or 15 wt%) based on the total weight of the porous adhesive material, and the content of the binder can be 1-15 wt% (for example 15 wt%, 14 wt%, 13 wt%, 12 wt%, 11 wt%, 10 wt%, 9 wt%, 8 wt%, 7 wt%, 6 wt%, 5 wt%, 4 wt%, 3 wt%, 2 wt% or 1 wt%) based on the total weight of the porous adhesive material.

[0047] The inventors of the present application have found that the porous adhesive material has a specific ratio, so that the porous adhesive material has a more excellent liquid absorption function, and thus can more effectively solve the problem of dryness of electrolyte at the edge of the electrode sheet in the later stage of battery cycle.

[0048] In an example, the content of the stacked particles is 50-70 wt% based on the total weight of the porous adhesive material, the content of the thickening agent is 20-40 wt% based on the total weight of the porous adhesive material, and the content of the binder is 3-10 wt% based on the total weight of the porous adhesive material.

[0049] The inorganic particles can have a porous structure, or can be non-porous inorganic particles.

[0050] In an example, the inorganic particles have a porous structure.

[0051] It can be understood that both the porous inorganic particles and the non-porous inorganic particles can form the porous adhesive material. When the stacked particles are porous inorganic particles, the "pores" of the porous adhesive material are composed of the pores of the porous inorganic particles themselves and the pores formed by the stacking of the porous inorganic particles; when the stacked particles are non-porous inorganic particles, the "pores" of the porous adhesive material are formed by the stacking of the non-porous inorganic particles.

[0052] In an example, the porosity of the inorganic particles is 5%-30%. In the present application, the porosity of the inorganic particles refers to the porosity of the inorganic particles themselves, and does not include the porosity of the pores formed by the stacking of the inorganic particles.

[0053] The median particle size D 50 satisfies: 1 μm≤D 50 ≤12 μm, for example, D 50 is equal to 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm or 12 μm.

[0054] In an example, the inorganic particles have a median particle size D 50 satisfying: 2 μm≤D 50 ≤8 μm.

[0055] The inventors of the present application have found that the inorganic particles have a specific shape and / or a specific aspect ratio, which can further improve the liquid absorption function of the porous adhesive material.

[0056] The inorganic particles can have a shape of a spheroid, such as a sphere, an ellipsoid, etc.

[0057] The inorganic particles can have an aspect ratio of 1:(1-2.1), such as 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9, 1:2 or 1:2.1.

[0058] In an example, the inorganic particles have an aspect ratio of 1:(1.1-1.5).

[0059] The electrode tab of the present application is coated with a porous adhesive material having a liquid storage function at both side edges in the length direction, which can store electrolyte, solve the problem of electrolyte dryness at the edge of the electrode tab in the later stage of the cycle, and the porous adhesive material has an adhesive function, which can further strengthen the adhesion of the edge of the electrode tab and the separator, effectively improve the interface, solve the problem of lithium precipitation at the edge, realize the balance of normal temperature cycle performance and high temperature cycle performance, and thus improve the comprehensive performance of the battery.

[0060] The second aspect of the present application provides a battery, which can include a first electrode tab, a separator and a second electrode tab stacked in sequence.

[0061] In the present application, the battery can be a stacked battery or a wound battery.

[0062] In the present application, the "stacked in sequence" does not limit the battery of the present application to a stacked battery. It can be understood that, before winding, the first electrode tab, the second electrode tab and the separator need to be stacked in sequence, and then wound.

[0063] The first electrode tab can be the electrode tab of the first aspect of the present application.

[0064] The second coating layer on the first electrode tab can be connected to the first coating layer on the first electrode tab.

[0065] In an example, the second coating layer on the first electrode tab is connected to the first coating layer on the first electrode tab.

[0066] As Figure 5Fig. 1 shows a schematic view of a cross section of a battery along the width direction of the electrode tab in an example of the present application, Figure 5 In an example, the battery comprises a first electrode tab 3, a separator 4 and a second electrode tab 5 stacked in sequence; the second coating layer 3-22 on the first electrode tab 3 is connected to the first coating layer 3-21; the width of the first electrode tab 3 = the total width of the second coating layer 3-22 on the first electrode tab 3 + the width of the first coating layer 3-21 on the first electrode tab 3, wherein the total width of the second coating layer 3-22 = 2 x the width of the second coating layer 3-22; the width of the first coating layer 3-21 on the first electrode tab 3 < the width of the second electrode tab 5 ≤ the width of the first electrode tab 3; the size d1 of the part of the separator 4 beyond the first electrode tab 3 in the width direction of the electrode tab ≤ 1 mm (e.g. 1 mm, 0.9 mm, 0.8 mm, 0.7 mm, 0.6 mm, 0.5 mm, 0.4 mm, 0.3 mm, 0.2 mm, 0.1 mm or 0).

[0067] It should be noted that in the present application, the width of the second coating layer refers to the width of the second coating layer on one side; the part of the separator beyond the first electrode tab refers to the part of the separator on one side beyond the first electrode tab on one side; the "one side" refers to the left side or the right side in the width direction of the electrode tab.

[0068] In an example, the size d1 of the part of the separator beyond the first electrode tab in the width direction is ≤ 0.5 mm.

[0069] In a specific embodiment, the width of the separator - the width of the first electrode tab = 0, i.e. the width of the separator is equal to the width of the first electrode tab.

[0070] The width of the second coating layer on the first electrode tab can be 0.5-10 mm, e.g. 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm, 5 mm, 5.5 mm, 6 mm, 6.5 mm, 7 mm, 7.5 mm, 8 mm, 8.5 mm, 9 mm, 9.5 mm or 10 mm.

[0071] In an example, the width of the second coating layer on the first electrode tab is 1-6 mm.

[0072] In an example, the width of the second coating layer on the first electrode tab is 2-3 mm.

[0073] In an example, the size of the part of the second electrode tab beyond the first coating layer on the first electrode tab in the width direction is 0.5-1.5 mm.

[0074] The thickness of the second coating layer on the first tab can be greater than the thickness of the first coating layer on the first tab, or equal to the thickness of the first coating layer on the first tab.

[0075] When the thickness of the second coating layer on the first tab is greater than the thickness of the first coating layer on the first tab, the ratio of the thickness of the first coating layer on the first tab to the thickness of the second coating layer on the first tab is 1:(1.03-1.08), for example 1:1.03, 1:1.04, 1:1.05, 1:1.06, 1:1.07 or 1:1.08.

[0076] In an example, the thickness of the second coating layer on the first tab is equal to the thickness of the first coating layer on the first tab.

[0077] The following description is made in conjunction with the accompanying drawings that illustrate the preferred embodiments of the application. Figure 6 and 7 The differences and beneficial effects of the battery according to the second aspect of the application over the prior art are described.

[0078] As Figure 6 The following shows the stacking position of the first tab, the second tab and the separator in the prior art battery, wherein Figure 6 (a) is a top view, Figure 6 (b) is a cross-sectional view along the width direction. In order to enable the second tab 5 to completely accommodate the lithium ions stripped from the corresponding first tab 3, the size of the second tab 5 in the length direction and the width direction is greater than that of the corresponding first tab 3, and in order to enable the battery to have more excellent safety performance, the separator 4 arranged between the first tab 3 and the second tab 5 has a size in the length direction and the width direction that is greater than that of the first tab 3 and the second tab 5 separated by it, thus, there is a difference in the thickness of the edge portion of the jelly-roll or the wound core of the battery, which leads to more polarization and side reactions during the charging and discharging process of the battery, aggravates the consumption of electrolyte around the edge of the jelly-roll or the wound core, further causes poor adhesion of the edge of the jelly-roll or the wound core and even cracking, and finally causes lithium precipitation at the edge and bulging at the top and bottom of the battery.

[0079] In the battery, the width of the first tab is the smallest, followed by the second tab, and the width of the separator is the largest, thus, the difference in the width between the first tab and the separator is the main reason for the difference in the edge portion of the battery, the inventors of the present application found that filling the difference in the width between the conventional first tab and the separator with the porous adhesive material not only fills the thickness difference of this part and improves the problem of poor adhesion of the edge of the battery, but also does not affect the energy density of the battery, and the porous adhesive material has the function of absorbing liquid and can store electrolyte, fully solving the problem of lithium precipitation caused by the dryness of electrolyte at the edge of the first tab in the later stage of the cycle.

[0080] AsFigure 7 As shown in the cross-sectional view of the battery along the width direction of the pole piece in an example of the present application, the battery comprises a first pole piece 3, a diaphragm 4 and a second pole piece 5 stacked in sequence; the width of the first pole piece 3 is equal to the width of the diaphragm 4. The area of the first pole piece on which the second coating layer is coated is the area of the diaphragm exceeding the first pole piece in the conventional battery. The second coating layer arranged on this area not only fills the difference in the thickness direction caused by the width difference between the first pole piece and the diaphragm in the conventional battery, but also does not adversely affect the energy density of the battery; and the second coating layer is a porous adhesive material, which has a liquid absorption function and an adhesive function, can store electrolyte to solve the lithium precipitation problem caused by the dryness of electrolyte at the edge of the first pole piece in the later stage of the cycle, and can strengthen the adhesion between the edge of the first pole piece and the diaphragm, effectively improve the interface, and fully solve the edge lithium precipitation problem.

[0081] The third aspect of the present application provides a battery, which can comprise a first pole piece, a diaphragm and a second pole piece stacked in sequence, and the second pole piece can be the pole piece of the first aspect of the present application.

[0082] The second coating layer on the second pole piece can partially overlap the first coating layer on the second pole piece.

[0083] In an example, the second coating layer on the second pole piece partially overlaps the first coating layer on the second pole piece.

[0084] The overlapping part of the second coating layer on the second pole piece and the first coating layer on the second pole piece has a width of l1, and the part of the second coating layer on the second pole piece arranged on the current collector of the second pole piece has a width of l2.

[0085] As Figure 8 As shown in the cross-sectional view of the battery along the width direction of the pole piece in an example of the present application, Figure 8 The second coating layer 5-22 on the second pole piece 5 partially overlaps the first coating layer 5-21; the overlapping part of the second coating layer 5-22 on the second pole piece 5 and the first coating layer 5-21 on the second pole piece 5 has a width of l1, which is equal to the size of the part of the first coating layer on the second pole piece exceeding the first pole piece in the width direction, the part of the second coating layer 5-22 on the second pole piece 5 arranged on the current collector of the second pole piece 5 has a width of l2, and the width of the second pole piece 5 = the width of the first coating layer 5-21 on the second pole piece 5 + 2xl2.

[0086] l1+l2 can be 0.4-10mm, for example 0.4mm, 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1mm, 1.5mm, 2mm, 2.5mm, 3mm, 3.5mm, 4mm, 4.5mm, 5mm, 5.5mm, 6mm, 6.5mm, 7mm, 7.5mm, 8mm, 8.5mm, 9mm, 9.5mm or 10mm.

[0087] In one example, l1+l2 is 1-6mm.

[0088] In one example, l1+l2 is 2-3 mm.

[0089] The portion of the diaphragm extending beyond the second electrode has a width dimension ≤1mm, for example 1mm, 0.9mm, 0.8mm, 0.7mm, 0.6mm, 0.5mm, 0.4mm, 0.3mm, 0.2mm, 0.1mm or 0.

[0090] In one example, the portion of the diaphragm extending beyond the second electrode has a width dimension of ≤0.5 mm.

[0091] It should be noted that, in this invention, the width of the second coating layer refers to the width of the second coating layer on one side; the portion of the diaphragm that extends beyond the second electrode refers to the portion of the diaphragm on one side that extends beyond the second electrode on one side; the portion of the first coating layer on the second electrode that extends beyond the first electrode refers to the portion of the first coating layer on the second electrode on one side that extends beyond the first electrode; and "one side" refers to the left or right side along the width direction of the electrode.

[0092] like Figure 8 As shown, the height of the overlapping portion of the second coating layer 5-22 on the second electrode 5 and the first coating layer 5-21 on the second electrode 5 is D, where D ≤ 1 / 2 of the thickness of the first electrode.

[0093] In one specific embodiment, D = 1 / 2 of the thickness of the first electrode.

[0094] The following is in conjunction with the appendix Figure 9 This invention explains the differences and beneficial effects of the battery described in the third aspect compared to the prior art.

[0095] As described above, generally, the size of the separator of the battery in the length direction and the width direction is greater than the first electrode plate and the second electrode plate separated by the separator, that is, there is a thickness difference between the first electrode plate and the separator at the edge position, and there is also a thickness difference between the second electrode plate and the separator at the edge position, the inventors of the present application find that the difference between the width of the conventional second electrode plate and the width of the separator is filled with the porous adhesive material, which can fill the thickness difference of this part, improve the poor adhesion of the battery edge, and solve the problem of dry electrolyte at the edge of the second electrode plate in the later stage of the cycle; and the inventors of the present application also find that since the separator is deformable, the porous adhesive material provided on the second electrode plate can be further expanded, so that it can fill the thickness difference between the first electrode plate and the separator at the edge position, effectively improve the interface, solve the problem of lithium precipitation at the edge, and realize the compromise of normal temperature cycle performance and high temperature cycle performance.

[0096] As Figure 9 The battery along the width direction of the electrode plate is shown in the example of the present application, in order to clearly show the height of the overlapping part of the second coating layer on the second electrode plate and the first coating layer on the second electrode plate and the relationship with the first electrode plate, the separator is omitted in Figure 9 Figure 9 In the second coating layer 5-22 on the second electrode plate 5, the height is composed of two parts, one part is equal to the height of the first coating layer 5-21 on the second electrode plate 5, and the other part is the height of the overlapping part of the first coating layer 5-21 (such as Figure 8 In the second coating layer 5-22 on the second electrode plate 5, the height is composed of two parts, one part is equal to the height of the first coating layer 5-21 on the second electrode plate 5, and the other part is the height of the overlapping part of the first coating layer 5-21 (such as

[0097] The battery can also include electrolyte, which can be selected conventionally in the art.

[0098] The assembly method of the battery can be performed in a conventional manner in the art.

[0099] The battery of the present application can solve the problem of lithium precipitation caused by dry electrolyte at the edge of the electrode plate in the later stage of the cycle without affecting the energy density; improve the problem of poor adhesion of the battery edge caused by the thickness difference of the electrode plate edge; realize the compromise of normal temperature cycle performance and high temperature cycle performance.

[0100] ​The application will be described in detail below by way of examples. The examples described in the application are only a part of the examples of the application, but not all the examples. Based on the examples in the application, all the other examples obtained by those skilled in the art without creative labor fall within the scope of protection of the application.

[0101] In the following examples, the materials used are commercially available analytical pure unless otherwise specified.

[0102] The following Group I examples are used to illustrate the first electrode plate of the application.

[0103] Example I1

[0104] The first electrode plate is prepared according to the following steps:

[0105] (1) Preparation of the porous adhesive slurry:

[0106] Alumina (D50 of 5 μm, porosity of 15%, shape of ellipsoid, aspect ratio of 1:1.3), sodium carboxymethyl cellulose and butadiene-styrene rubber are mixed uniformly at a mass ratio of 65:30:5, N-methyl pyrrolidone is added, the solid content is 40%, and it is stirred uniformly and passed through a 200-mesh sieve;

[0107] (2) Preparation of the active material slurry:

[0108] Lithium cobaltate, conductive carbon black and polyvinylidene fluoride are added to a stirring tank at a mass ratio of 97.2:1.5:1.3, semiconductor zirconium dioxide is added, the amount of zirconium dioxide added is 12% of the mass of the conductive carbon black, N-methyl pyrrolidone is added, it is stirred uniformly and thoroughly, and it is passed through a 200-mesh sieve, the solid content being 70%;

[0109] (3) Preparation of the first electrode plate:

[0110] The active material slurry obtained in step (2) is coated on both sides of the surface of an aluminum foil (the thickness of the aluminum foil is 9 μm) using a coating machine, and dried at 120°C to form a first coating layer; the porous adhesive slurry obtained in step (1) is coated on both sides of the edges of the first coating layer, and dried at 120°C to form a second coating layer;

[0111] The porosity of the porous adhesive material is 60%, the width of the first coating layer is 120 mm, the thickness of the first coating layer on one side is 60 μm, the width of the second coating layer is 3 mm, and the thickness of the second coating layer on one side is 60 μm.

[0112] Example I2

[0113] The examples in this group are carried out according to the steps of Example I1, except that the porous adhesive material is changed, specifically:

[0114] In Example I2a, the preparation of the porous adhesive material slurry: boehmite (D50 of 2 μm, porosity of 5%, shape of spheroid, aspect ratio of 1:1.1), lithium carboxymethyl cellulose and styrene-butadiene rubber were mixed uniformly according to the mass ratio of 50:40:10, N-methyl pyrrolidone was added, the solid content was 45%, stirred uniformly, and then sieved through a 200-mesh screen. The porosity of the obtained porous adhesive material was 50%;

[0115] In Example I2b, the preparation of the porous adhesive material slurry: silicon oxide (D50 of 8 μm, porosity of 30%, shape of ellipsoid, aspect ratio of 1:1.5), polyvinylidene fluoride and styrene-butadiene rubber were mixed uniformly according to the mass ratio of 70:20:10, N-methyl pyrrolidone was added, the solid content was 42%, stirred uniformly, and then sieved through a 200-mesh screen. The porosity of the obtained porous adhesive material was 70%;

[0116] In Example I2c, the preparation of the porous adhesive material slurry: polyvinylidene fluoride resin, sodium carboxymethyl cellulose and styrene-butadiene rubber were mixed uniformly according to the mass ratio of 65:30:5, N-methyl pyrrolidone was added, the solid content was 41%, stirred uniformly, and then sieved through a 200-mesh screen. The porosity of the obtained porous adhesive material was 66%;

[0117] In Example I2d, the preparation of the porous adhesive material slurry: aluminum oxide (D50 of 5 μm, no pores, shape of ellipsoid, aspect ratio of 1:1.3), sodium carboxymethyl cellulose and styrene-butadiene rubber were mixed uniformly according to the mass ratio of 70:22:8, N-methyl pyrrolidone was added, the solid content was 40%, stirred uniformly, and then sieved through a 200-mesh screen. The porosity of the obtained porous adhesive material was 54%;

[0118] In Example I2e, the preparation of the porous adhesive material slurry: aluminum oxide (D50 of 5 μm, porosity of 40%, shape of ellipsoid, aspect ratio of 1:1.3), sodium carboxymethyl cellulose and styrene-butadiene rubber were mixed uniformly according to the mass ratio of 65:30:5, N-methyl pyrrolidone was added, the solid content was 40%, stirred uniformly, and then sieved through a 200-mesh screen. The porosity of the obtained porous adhesive material was 38%;

[0119] In Example I2f, the preparation of the porous adhesive material slurry: aluminum oxide (D50 of 5 μm, porosity of 15%, shape of irregular polyhedron), sodium carboxymethyl cellulose and styrene-butadiene rubber were mixed uniformly according to the mass ratio of 65:30:5, N-methyl pyrrolidone was added, the solid content was 40%, stirred uniformly, and then sieved through a 200-mesh screen. The porosity of the obtained porous adhesive material was 43%;

[0120] In Example I2g, the porous adhesive material slurry was prepared as follows: alumina (D50 of 5 μm, porosity of 15%, shape of ellipsoid, aspect ratio of 1:2), sodium carboxymethyl cellulose and styrene-butadiene rubber were mixed uniformly at a mass ratio of 65:30:5, N-methyl pyrrolidone was added, the solid content was 40%, stirred uniformly, and sieved through a 200-mesh screen. The porosity of the obtained porous adhesive material was 32%.

[0121] In Example I2h, the porous adhesive material slurry was prepared as follows: alumina (D50 of 5 μm, porosity of 15%, shape of spheroid, aspect ratio of 1:1.3), sodium carboxymethyl cellulose and styrene-butadiene rubber were mixed uniformly at a mass ratio of 45:40:15, N-methyl pyrrolidone was added, the solid content was 40%, stirred uniformly, and sieved through a 200-mesh screen. The porosity of the obtained porous adhesive material was 47%.

[0122] Example I3

[0123] The examples in this group were prepared according to the procedure of Example II, except that the coating width of the porous adhesive slurry was changed, specifically: the coating width of the porous adhesive slurry was 2.5 mm.

[0124] Example I4

[0125] The examples in this group were prepared according to the procedure of Example II, except that the coating thickness of the porous adhesive slurry was changed, specifically: the thickness of the second coating layer was 80 μm.

[0126] Comparative Example 1

[0127] The examples in this group were prepared according to the procedure of Example II, except that the porous adhesive slurry was not coated.

[0128] The following Group II examples are used to illustrate the second pole piece of the application.

[0129] Example II1

[0130] The second pole piece was prepared according to the following procedure:

[0131] (1) Preparation of the porous adhesive slurry:

[0132] Alumina (D50 of 5 μm, porosity of 15%, shape of ellipsoid, aspect ratio of 1:1.3), sodium carboxymethyl cellulose and styrene-butadiene rubber were mixed uniformly at a mass ratio of 65:30:5, N-methyl pyrrolidone was added, the solid content was 40%, stirred uniformly, and sieved through a 200-mesh screen;

[0133] (2) Preparation of the active material slurry:

[0134] Synthetic graphite, conductive carbon black, butadiene styrene rubber and sodium carboxymethyl cellulose were added into a stirring tank according to a mass ratio of 95.9:1.5:1.3:1.3, deionized water was added, and the mixture was fully stirred and uniformly mixed, and then passed through a 150-mesh screen, wherein the solid content was 40%;

[0135] (3) Preparation of the second pole piece:

[0136] The active material slurry obtained in step (2) was coated on both sides of the copper foil (thickness of the copper foil was 6 μm) using a coating machine, and dried at 120°C to form a first coating layer; porous adhesive slurry was coated on both sides of the edges of the first coating layer and partially covered the first coating layer, and dried at 120°C to form a second coating layer;

[0137] wherein the porosity of the porous adhesive material was 60%, the width of the first coating layer was 123 mm, the thickness of the first coating layer on one side was 90 μm, l1=1.5 mm, l2=1.5 mm, and D=64.5 μm.

[0138] Example II2

[0139] The examples in this group were prepared according to the steps of Example II1, except that the value of l2 was changed, specifically: l2=1 mm.

[0140] Example II3

[0141] The examples in this group were prepared according to the steps of Example II1, except that the thickness of the second coating layer was changed, specifically: D=50 μm.

[0142] Comparative Example 2

[0143] The examples in this group were prepared according to the steps of Example II1, except that no porous adhesive slurry was coated.

[0144] The following Group III examples are used to illustrate the battery of the present application.

[0145] Example III

[0146] The battery was prepared according to the following steps:

[0147] (1) Separator: the base was a polyethylene film, and a PVDF adhesive layer and a ceramic layer were coated on both sides of the base from inside to outside, and the width of the separator was 126 mm;

[0148] (2) EC:DEC=50:50, 1 mol / L LiPF6 electrolyte was used;

[0149] (3) The first pole piece, the separator and the second pole piece were sequentially stacked and wound to obtain a battery cell, which was packaged with an aluminum plastic film, baked to remove moisture, injected with electrolyte, and subjected to a hot pressing formation process to obtain a battery.

[0150] wherein the first and second pole pieces are specifically selected as shown in Table 1 below.

[0151] Table 1

[0152]

[0153]

[0154] Test Example

[0155] (1) High-temperature cycle test

[0156] The batteries obtained in the examples and the comparative examples of Group III were subjected to 2C charging / 0.7C discharging at 45°C, and cycled for 700T, and the 700T capacity retention rate and the 700T expansion rate were recorded in Table 2, wherein,

[0157] 700T capacity retention rate = capacity at 700T ÷ capacity at 1T

[0158] 700T expansion rate = full charge thickness at 700T ÷ half charge thickness at 1T - 1.

[0159] (2) Normal-temperature cycle test

[0160] The batteries obtained in the examples and the comparative examples of Group III were subjected to 2C charging / 0.7C discharging at 25°C, and cycled for 100T, 600T and 1000T, respectively, and the 1000T capacity retention rate and the 1000T expansion rate were recorded in Table 2, and the batteries after 100T and 600T cycles were disassembled, and the lithium precipitation at the edge of the second pole was observed, and the results were recorded in Table 2.

[0161] Table 2

[0162]

[0163]

[0164] As can be seen from Table 2, the batteries obtained from the pole pieces of the present application have a significantly improved 700T capacity retention rate and a significantly reduced 700T expansion rate in the high-temperature cycle test, and no lithium precipitation occurs at 100T, and no lithium precipitation occurs or only slight lithium precipitation occurs at 600T in the normal-temperature cycle test, i.e. the lithium precipitation of the batteries of the present application is effectively improved, and the 1000T capacity retention rate is significantly improved and the 1000T expansion rate is significantly reduced.

[0165] The preferred embodiments of the present application are described in detail above, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including that each technical feature is combined in any other suitable manner. These simple modifications and combinations should also be considered as disclosed by the present application and fall within the protection scope of the present application.

Claims

1. A battery comprising a first electrode sheet, a separator, and a second electrode sheet which are sequentially stacked, characterized by The first pole piece comprises a current collector and a coating layer coated on one side or both sides of the current collector; the coating layer comprises a first coating layer and a second coating layer; the first coating layer is arranged on the middle region of the current collector and is distributed along the length direction; the second coating layer is arranged on both side edges of the current collector along the width direction and is connected with the first coating layer; the thickness of the second coating layer is not less than the thickness of the first coating layer; along the first direction, the width of the first coating layer on the first pole piece is less than the width of the second pole piece, and the width of the second pole piece is less than or equal to the width of the first pole piece; the second coating layer is a porous adhesive material.

2. The battery of claim 1, wherein, The size of the part of the separator exceeding the first pole piece in the width direction is ≤1 mm, and the width of the second coating layer on the first pole piece is 0.5-10 mm.

3. The battery according to claim 1 or 2, wherein The porosity of the porous adhesive material is 30%-80%.

4. The battery according to claim 1 or 2, wherein The porous adhesive material comprises stacked particles, a thickening agent and a binder, the content of the stacked particles is 40-80% by weight based on the total weight of the porous adhesive material, the content of the thickening agent is 15-45% by weight, and the content of the binder is 1-15% by weight; the stacked particles comprise organic particles and / or inorganic particles.

5. The battery of claim 4, wherein, The inorganic particles are selected from at least one of alumina, magnesia, silica, titania, zirconia, zinc oxide, barium sulfate, boron nitride, aluminum nitride, magnesium nitride, tin dioxide, magnesium hydroxide, boehmite and calcium carbonate; and / or, The organic particles are selected from at least one of polyvinyl chloride resin, chloroethylene-vinylidene dichloride copolymer resin, chloroethylene-vinyl acetate copolymer resin, polyvinylidene fluoride and polymethyl methacrylate.

6. The battery of claim 4, wherein, The inorganic particles have a porous structure, and the porosity of the inorganic particles is 5%-30%; and / or, The inorganic particles have a median particle diameter D 50 satisfy: 1 μm ≤ D 50 ≤ 12 μm; and / or, The aspect ratio of the inorganic particles is 1: (1-2.1).

7. The battery of claim 1, wherein, The size of the part of the second pole piece exceeding the first coating layer on the first pole piece in the width direction is 0.5-1.5 mm.

8. A battery comprising a first electrode sheet, a separator, and a second electrode sheet which are sequentially stacked, characterized by The second pole piece comprises a current collector and a coating layer coated on one side or both sides of the current collector; the coating layer comprises a first coating layer and a second coating layer; the first coating layer is arranged on the middle region of the current collector and is distributed along the length direction; the second coating layer is arranged on both side edges of the current collector along the width direction and partially overlaps with the first coating layer; the thickness of the second coating layer is not less than the thickness of the first coating layer; the second coating layer is a porous adhesive material; The width l1 of the overlapping part of the second coating layer on the second pole piece with the first coating layer on the second pole piece is equal to the size of the part of the first coating layer on the second pole piece exceeding the first pole piece in the width direction; the width of the part of the second coating layer on the second pole piece arranged on the current collector of the second pole piece is l2.

9. The battery of claim 8, wherein, l1+l2 is 0.4-10 mm, and the size of the part of the separator exceeding the second pole piece in the width direction is ≤1 mm.

10. The battery of claim 9, wherein, l1+l2 is 2-3 mm, and the dimension of the part of the diaphragm beyond the second pole piece in the width direction is ≤0.5 mm; and / or, The height of the overlapping part of the second-coated layer on the second pole piece and the first-coated layer on the second pole piece is D, and D≤1 / 2 of the thickness of the first pole piece.

11. The battery of claim 8, wherein, The porosity of the porous adhesive material is 30%-80%.

12. The battery of claim 8, wherein, The porous adhesive material comprises bulk particles, a thickening agent, and a binder, the content of the bulk particles is 40-80% by weight, the content of the thickening agent is 15-45% by weight, and the content of the binder is 1-15% by weight, based on the total weight of the porous adhesive material; the bulk particles comprise organic particles and / or inorganic particles.

13. The battery of claim 12, wherein, The inorganic particles are selected from at least one of alumina, magnesia, silica, titania, zirconia, zinc oxide, barium sulfate, boron nitride, aluminum nitride, magnesium nitride, tin dioxide, magnesium hydroxide, boehmite, and calcium carbonate; and / or, The organic particles are selected from at least one of polyvinyl chloride resin, vinyl chloride-vinylidene chloride copolymer resin, vinyl chloride-vinyl acetate copolymer resin, polyvinylidene fluoride, and polymethyl methacrylate.

14. The battery of claim 12, wherein, The inorganic particles have a porous structure, and the porosity of the inorganic particles is 5%-30%; and / or, The inorganic particles have a median particle diameter D 50 satisfies: 1 μm ≤ D 50 ≤ 12 μm; and / or, The aspect ratio of the inorganic particles is 1: (1-2.1).

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