Pole piece, battery cell and battery

Abstract

The utility model discloses a pole piece, a battery cell and a battery, the pole piece is used for the battery cell, and the pole piece comprises a first current collector and a first active material layer; the first current collector is suitable for being connected with a first tab; the first active material layer is laminated on the first current collector, the first active material layer comprises a first region and a second region, the first region is closer to the first tab than the second region, the porosity of the first region is a first porosity A, the porosity of the second region is a second porosity B, and A is greater than B. The pole piece provided by the utility model can effectively improve the charging and discharging capability of the edge of the pole piece and reduce lithium precipitation of the edge of the pole piece.

Description

Technical Field

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

[0002] The edge area of ​​the lithium-ion battery's electrode will experience lithium deposition due to poor charging and discharging capabilities after multiple fast charging cycles. The continuous accumulation of deposited lithium will cause the diaphragm to be punctured, posing a serious safety hazard to the lithium-ion battery. Utility Model Content

[0003] The purpose of the utility model is to provide a pole piece, a battery cell and a battery, which solve the problem of lithium deposition caused by poor charge and discharge capacity at the edge of the pole piece.

[0004] In order to achieve the purpose of the present invention, the present invention provides the following technical solutions:

[0005] In a first aspect, the present invention provides a pole piece for a battery cell, comprising:

[0006] a first current collector, adapted to be connected to the first tab;

[0007] A first active material layer is stacked on the first current collector, the first active material layer includes a first region and a second region, the first region is closer to the first electrode tab than the second region, the porosity of the first region is A, the porosity of the second region is B, and the following conditions are satisfied: A>B.

[0008] In one embodiment, the following conditions are also satisfied: 2%≤AB≤5%, and 25%≤B≤30%.

[0009] In one embodiment, a portion of the first current collector corresponding to the first region has a first edge, and the first edge is suitable for arranging the first electrode tab.

[0010] In one embodiment, the first region has a second edge, and in a first direction, the first edge and the second edge are arranged opposite each other, wherein the distance between the first edge and the second edge is C, and satisfies: 0mm≤C≤5mm, and the first direction is the arrangement direction of the first region and the second region. In one embodiment, the first region includes a second edge and a third edge that are opposite each other in the first direction, and the third edge is connected to the second region. In the first direction, the distance between the second edge and the third edge is D, and satisfies: 1mm≤D≤5mm, and the first direction is the arrangement direction of the first region and the second region.

[0011] In one embodiment, the first region comprises a first material, the second region comprises a second material, the density of the first material is less than the density of the second material, and / or the specific surface area of ​​the first material is greater than the specific surface area of ​​the second material.

[0012] In one embodiment, the number of micropores in the material of the first region is greater than the number of micropores in the material of the second region, and / or the average pore size of the micropores in the material of the first region is greater than the average pore size of the micropores in the material of the second region.

[0013] In one embodiment, the compacted density of the material in the first region is less than the compacted density of the material in the second region.

[0014] In one embodiment, the areal density of the material in the first region is less than the areal density of the material in the second region.

[0015] In one embodiment, the electrode sheet is a negative electrode sheet, and the battery cell further includes a positive electrode sheet. The negative electrode sheet includes an overlapping area and an overhang area. The overlapping area is suitable for overlapping with the second active material layer of the positive electrode sheet, and the overhang area includes at least a portion of the first area.

[0016] In one embodiment, the first active material layer further includes a third region, and the third region is located on a side of the second region facing away from the first region. The porosity of the third region is E, satisfying: E>B.

[0017] In one embodiment, the following is also satisfied: 2%≤EB≤5%.

[0018] In a second aspect, the present invention further provides a battery cell comprising a diaphragm and a pole piece according to any one of the various embodiments of the first aspect, wherein the pole piece and the diaphragm are stacked.

[0019] In a third aspect, the present invention further provides a battery, comprising a housing and a battery cell as described in any one of the various embodiments of the second aspect, wherein the battery cell is accommodated in the housing.

[0020] By setting the first active material layer as the first region and the second region, the first region is closer to the edge of the first current collector than the second region, and the porosity A of the first region and the porosity B of the second region satisfy A>B, the electrolyte wettability of the first region is improved by increasing the porosity of the first region, effectively promoting the liquid phase diffusion of the electrolyte, accelerating the transmission of lithium ions, and improving the charge and discharge capacity of the edge of the electrode. The accumulation of lithium ions at the edge of the electrode during high-rate charge and discharge is avoided, and the edge lithium plating effect caused by lithium ion migration and cycle accumulation is alleviated, effectively solving the battery capacity drop and safety problems caused by edge lithium plating. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the implementation methods of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the implementation methods or the description of the prior art. Obviously, the drawings described below are only some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0022] Figure 1 is a top view of a pole piece of an embodiment;

[0023] Figure 2 is a cross-sectional view of a pole piece of an embodiment;

[0024] Figure 3 is a cross-sectional view of a battery cell according to an embodiment.

[0025] Description of reference numerals:

[0026] 10 - pole piece, 11 - first current collector, 111 - first edge, 112 - fourth edge, 113 - fifth edge, 114 - sixth edge, 12 - first active material layer, 121 - first region, 1211 - second edge, 1212 - third edge, 122 - second region, 123 - third region, 1231 - seventh edge, 1232 - eighth edge;

[0027] 20-second pole piece, 21-second current collector, 22-second active material layer, 30-separator;

[0028] C-first spacing, D-second spacing, F-third spacing, G-fourth spacing, X-first direction. DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0030] It should be noted that when a component is referred to as being "fixed to" another component, it may be directly on the other component or there may be an intermediate component. When a component is referred to as being "connected to" another component, it may be directly connected to the other component or there may be an intermediate component.

[0031] Unless otherwise defined, all technical and scientific terms used in this utility model have the same meanings as commonly understood by those skilled in the art to which this utility model belongs. The terms used in this utility model specification are only for the purpose of describing specific embodiments and are not intended to limit this utility model. The term "and / or" used in this utility model includes any and all combinations of one or more of the relevant listed items.

[0032] The following embodiments of the present invention are described in detail with reference to the accompanying drawings. In the absence of conflict, the following embodiments and features in the embodiments may be combined with each other.

[0033] Please refer to Figure 1 and Figure 2 The utility model provides a pole piece 10, which is used for a battery cell. The pole piece 10 includes a first current collector 11 and a first active material layer 12. The first current collector 11 is suitable for connecting to a first pole tab (not shown in the figure). The first active material layer 12 is stacked on the first current collector 11. The first active material layer 12 includes a first region 121 and a second region 122. The first region 121 is closer to the edge of the first current collector 11 than the second region 122. The porosity of the first region 121 is a first porosity A, and the porosity of the second region 122 is a second porosity B, satisfying: A>B.

[0034] Specifically, the size of the electrode 10 of the present invention in the first direction X is larger than the size of the second electrode 20 in the first direction. When the electrode 10 is a negative electrode, the second electrode 20 is correspondingly set as a positive electrode. When the second electrode 20 is a negative electrode, the electrode 10 is correspondingly set as a negative electrode.

[0035] Optionally, when the electrode 10 is a negative electrode, the first active material layer 12 includes an active material, which includes components such as a negative electrode material, a conductive agent, and a binder. The conductive agent includes one or more of graphite, carbon black, acetylene black, graphene, carbon fiber, C60 (carbon 60) and carbon nanotubes, without limitation. The types of binders include one or more of polyvinylidene chloride, soluble polytetrafluoroethylene, styrene-butadiene rubber, hydroxypropyl methylcellulose, methyl cellulose, carboxymethyl cellulose, polyvinyl alcohol, acrylonitrile copolymer, sodium alginate, chitosan and chitosan derivatives, without limitation.

[0036] Optionally, at least a portion of the first region 121 is closer to the edge of the first current collector 11 connected to the first tab than at least a portion of the second region 122. For example, if both the first region 121 and the second region 122 are rectangular, and the length of the first region 121 in the direction perpendicular to the first direction X is the same as the length of the second region 122 in the direction perpendicular to the first direction X, then the first region 121 is closer as a whole to the edge of the first current collector 11 connected to the first tab than the second region 122. Alternatively, if the minimum distance from a portion of the edge of the second region 122 to the edge of the first current collector 11 connected to the first tab is the same as the minimum distance from the first region 121 to the edge of the first current collector 11 connected to the first tab, then the first region 121 is positioned directly opposite the first tab in the first direction X, and the second region 122 is concave in shape, surrounding the outer periphery of the first region 121.

[0037] The second region 122 and the first region 121 may be spaced apart, that is, a transition region is provided between the second region 122 and the first region 121 , and the porosity of the transition region is smaller than the first porosity of the first region 121 .

[0038] In a possible embodiment, when the electrode sheet 10 is a negative electrode sheet, the first current collector 11 includes but is not limited to any one of copper foil and aluminum foil. Preferably, the first current collector 11 is copper foil.

[0039] The first electrode tab may partially overlap with the first current collector 11 or may only be connected to the edge of the first current collector 11 , without limitation.

[0040] The first tab can be a full tab, a multi-tab, or a single tab. The tabs can be arranged in the same face, different faces, symmetrical, or asymmetrical forms.

[0041] The first tab can be a flattened tab or a die-cut tab, without limitation. The tab of the pole piece 10 can be made of nickel or copper-nickel. The first tab of the pole piece 10 is primarily used to connect the positive and negative electrodes of the battery, enabling current transfer and directing current from the positive electrode to the negative electrode to facilitate charging and discharging. It also serves to stabilize the internal structure of the lithium battery.

[0042] The first electrode tab may further include a protective adhesive, which may be used to strengthen the fixation between the first electrode tab and the first current collector 11 .

[0043] By setting the first region 121 and the second region 122 with different porosities, and the first porosity A is greater than the second porosity B, the porosity of the first region 121 is increased to improve the electrolyte wettability of the first region 121, the liquid phase diffusion effect of the electrolyte is better, the lithium ion transmission is accelerated, and the accumulation of lithium ions at the edge of the electrode 10 is reduced during high-rate charge and discharge, thereby improving the charge and discharge capacity at the edge of the electrode 10 and reducing the risk of lithium plating.

[0044] In one embodiment, the following conditions are also satisfied: 2%≤AB≤5%, and 25%≤B≤30%.

[0045] Optionally, AB may be 2.5%≤AB≤4.5%, 3%≤AB≤4%. Specifically, AB may be 2%, 2.5%, 3%, 4%, 4.5%, or 5%, without limitation.

[0046] Specifically, B can be 25%, 26%, 127%, 28%, 29%, or 30%, without limitation.

[0047] If AB is less than 2%, it means that the difference between the first porosity A of the first region 121 and the second porosity B of the second region 122 is not obvious, the improvement of the charge and discharge capacity of the edge of the electrode 10 is not obvious, and the effect of mitigating the edge lithium plating effect is weak; if AB is greater than 5%, it means that the difference between the first porosity A of the first region 121 and the second porosity B of the second region 122 is too large, the electrolyte infiltration effect in the first region 121 is poor, and it has a negative effect on the capacity of the battery.

[0048] For reference Figure 1 In one embodiment, the portion of the first current collector 11 corresponding to the first region 121 has a first edge 111, including the first edge 111, and the first edge 111 is suitable for setting a first electrode tab (not shown in the figure).

[0049] For reference Figure 1 In one embodiment, the first region 121 includes a second edge 1211 and a third edge 1212 that are opposite to each other in the first direction X. The first edge 111 is located on a side of the second edge 1211 that is opposite to the third edge 1212 in the first direction X. The third edge 1212 is connected to the second region 122. The first direction X is the arrangement direction of the first region 121 and the second region 122. The second direction is the extension direction of the first edge 111, and the second direction intersects with the first direction X.

[0050] Optionally, the second edge 1211 and the third edge 1212 may be straight lines, curves, etc., without limitation. The second edge 1211 and / or the third edge 1212 may be flush with the edge of the first current collector 11 in the second direction, or may be spaced apart from the edge of the first current collector 11 in the second direction, without limitation.

[0051] Optionally, the first current collector 11 , the first region 121 , and the second region 122 are all rectangular.

[0052] Optionally, the first current collector 11 further includes a fourth edge 112 and a fifth edge 113 opposite to each other, and the fourth edge 112 and the fifth edge 113 are respectively located on both sides of the first edge 111 .

[0053] Optionally, the fourth edge 112 and the fifth edge 113 may be straight lines or curves without limitation; the edges corresponding to the first area 121 and the second area 122 may also be straight lines or curves without limitation.

[0054] Optionally, the first edge 111, the second edge 1211, and the third edge 1212 are parallel, so that the first region 121 has a consistent effect on improving the charge and discharge capabilities of the edge of the electrode 10 along the direction of the first edge 111, which is beneficial to the charging and discharging of the battery. Due to process tolerances, the angle between any two sides of the first edge 111, the second edge 1221, and the third edge 1222 can be 1°-3°, without limitation.

[0055] Optionally, in the first direction X, a distance from any position of the first edge 111 to a corresponding position of the second edge 1211 is a first spacing C, which satisfies: 0 mm ≤ C ≤ 5 mm.

[0056] Optionally, the first spacing C can be 0 mm, 1 mm, 2 mm, 3 mm, 4 mm, or 5 mm, without limitation.

[0057] If C > 5 mm, the area of ​​the first active material layer 12 is too small, wasting space and reducing battery capacity. The first spacing C is set so that the orthographic projection of the first region 121 is located within the first current collector 11. The first region 121 is spaced from the edge of the first current collector 11, facilitating coating of the first region 121 and the second region 122 during production.

[0058] In one embodiment, in the first direction X, the distance from any position of the second edge 1211 to the corresponding position of the third edge 1212 is a second distance D, which satisfies: 1 mm ≤ D ≤ 5 mm.

[0059] Optionally, the second distance D can be 1 mm, 2 mm, 3 mm, 4 mm, or 5 mm, without limitation.

[0060] The second spacing D limits the size of the first region 121, so that the first region 121 corresponds to the edge region of the electrode 10. If D is less than 1 mm, the first region 121 has no obvious effect on improving the charge and discharge capacity at the edge of the electrode 10; if D is greater than 5 mm, the ratio of the first region 121 to the first active material layer 12 is too large, the first porosity A of the first region 121 is large, and the energy provided by the first region 121 is small, resulting in a decrease in battery capacity.

[0061] In one embodiment, the first region 121 includes a first material, the second region 122 includes a second material, the density of the first material is less than the density of the second material, and / or the specific surface area of ​​the first material is greater than the specific surface area of ​​the second material.

[0062] Optionally, compared with the second material, the first material may also include any one of spherical graphite, 3D lithium metal, silicon material, etc., without limitation.

[0063] By setting a first material with low density and / or large specific surface area, the first porosity A of the first region 121 is made greater than the second porosity B of the second region 122, so that the electrolyte wettability of the first region 121 is improved, the liquid phase diffusion effect of the electrolyte is better, the lithium ion transmission is accelerated, and the accumulation of lithium ions at the edge of the electrode 10 is reduced during high-rate charge and discharge, thereby improving the charge and discharge capacity at the edge of the electrode 10 and reducing the risk of lithium plating.

[0064] In one embodiment, the number of micropores in the material of the first region 121 is greater than the number of micropores in the material of the second region 122 , and / or the average pore size of the micropores in the material of the first region 121 is greater than the average pore size of the micropores in the material of the second region 122 .

[0065] Optionally, the first material of the first region 121 includes a pore former, and the mass percentage of the pore former in the first material does not exceed 2%.

[0066] Optionally, the pore-forming agent may be any one of lithium oxalate, lithium carbonate, polystyrene, polyvinyl alcohol or polyethylene glycol, etc., without limitation.

[0067] By adding a pore-forming agent, the number of micropores of the material of the first region 121 is made greater than the number of micropores of the material of the second region 122, and / or the average pore size of the micropores of the material of the first region 121 is made greater than the average pore size of the micropores of the material of the second region 122, thereby achieving a first porosity A of the first region 121 greater than a second porosity B of the second region 122, thereby improving the electrolyte wettability of the first region 121, improving the liquid phase diffusion effect of the electrolyte, accelerating the transmission of lithium ions, reducing the accumulation of lithium ions at the edge of the electrode 10 during high-rate charge and discharge, improving the charge and discharge capacity at the edge of the electrode 10, reducing the risk of lithium plating, and effectively solving the battery capacity drop and safety problems caused by edge lithium plating.

[0068] In one embodiment, the compacted density of the material in the first region 121 is less than the compacted density of the material in the second region 122 .

[0069] Optionally, a multi-layer coating technology is used to achieve that the compaction density of the material in the first region 121 is smaller than the compaction density of the material in the second region 122 .

[0070] Optionally, when coating is performed multiple times only on the second region 122 , the first region 121 is coated during the last coating, and then the pole piece is rolled.

[0071] Optionally, the first region 121 may be coated once or multiple times, without any specific limitation.

[0072] Optionally, the coating times of the second region 122 is one or more times greater than the coating times of the first region 121 , without any specific limitation.

[0073] By changing the number of coating times, the compaction density of the material in the first region 121 is less than the compaction density of the material in the second region 122, and the first porosity A of the first region 121 is greater than the second porosity B of the second region 122. Therefore, the electrolyte wettability of the first region 121 is improved, which effectively promotes the liquid phase diffusion of the electrolyte, accelerates the transmission of lithium ions, avoids the accumulation of lithium ions at the edge of the negative electrode during high-rate charge and discharge, and reduces the risk of lithium plating.

[0074] In one embodiment, the areal density of the material in the first region 121 is less than the areal density of the material in the second region 122 .

[0075] The higher surface density of the material in the first region 121 can increase the capacity of the electrode 10, so that the battery can accommodate more charges during the charging and discharging process, thereby extending the cycle life of the battery. In addition, the first region 121 with a higher surface density can accommodate more lithium ions during the charging and discharging process, avoiding the accumulation and precipitation of lithium ions at the edge of the negative electrode during high-rate charging and discharging, alleviating the edge lithium plating effect caused by lithium ion migration and cycle accumulation, and effectively solving the battery capacity drop and safety problems caused by edge lithium plating.

[0076] In one embodiment, the electrode 10 is a negative electrode, and the battery cell further includes a second electrode 20, which is a positive electrode. The electrode 10 includes an overlap region and an overhang region. The overlap region overlaps with the second active material layer 22 of the second electrode 20, and the overhang region includes at least a portion of the first region 121. The overhang region may extend beyond the overlap region in a first direction X, or may extend beyond the overlap region in a second direction. The second direction forms an angle with the first direction X, i.e., the overhang region may surround the overlap region. The second direction is the extension direction of the first edge 111.

[0077] In the first direction X, the area of ​​the first region 121 that exceeds the second active material layer 22 of the second electrode 20 in the first direction X is the overhang area, and the corresponding size in the first direction X is 1mm-3mm. Optionally, the size of the overhang area is 1mm, 2mm, 3mm, etc., without limitation. The overhang area can prevent lithium deposition on the electrode 10 and improve the safety of the battery cell. In one embodiment, the first active material layer 12 also includes a third region 123, and the third region 123 is located on the side of the second region 122 facing away from the first region 121. The porosity of the third region 123 is a third porosity E, satisfying: E>B, wherein the third region 123 is suitable for corresponding to the edge of the second active material layer 22 of the second electrode 20 away from the first electrode tab.

[0078] Optionally, the electrode 10 is a negative electrode, the second electrode 20 is a positive electrode, and the overhang area further includes at least a portion of the third region 123 .

[0079] The portion of the third region 123 that extends beyond the second active material layer 22 of the second electrode sheet 20 in the first direction X is also an overhang region, and its corresponding size in the first direction X is 1 mm to 3 mm. The overhang region may also extend beyond the overlap region in the second direction, i.e., the overhang region may be disposed around the overlap region.

[0080] The overhang area of ​​the third region 123 corresponding to the overhang area of ​​the first region 121 can also prevent lithium deposition on the electrode 10 , thereby improving the safety of the battery cell.

[0081] Optionally, the electrode sheet 10 is provided with a first electrode tab and a second electrode tab. The first region 121 is closer to the edge of the first current collector 11 connected to the first electrode tab than at least a portion of the second region 122, and the third region 123 is closer to the edge of the first current collector 11 connected to the second electrode tab than at least a portion of the second region 122. For example, if the third region 123 and the second region 122 are both rectangular, and the length of the third region 123 in the second direction is the same as the length of the second region 122 in the second direction, then the third region 123 is closer as a whole to the edge of the first current collector 11 connected to the second electrode tab than the second region 122. Alternatively, if the minimum distance from a portion of the edge of the second region 122 to the edge of the first current collector 11 connected to the second electrode tab is the same as the minimum distance from the third region 123 to the edge of the first current collector 11 connected to the second electrode tab, then the third region 123 is disposed directly opposite the second electrode tab in the first direction X, the second region 122 is in a concave shape, and the second region 122 surrounds the outer periphery of the third region 123.

[0082] In one embodiment, the following is also satisfied: 2%≤EB≤5%.

[0083] Optionally, EB may be 2.5%≤EB≤4.5%, 3%≤EB≤4%. Specifically, EB may be 2%, 2.5%, 3%, 4%, 4.5%, or 5%, without limitation.

[0084] Optionally, the first current collector 11 further includes a sixth edge 114, which is disposed opposite the first edge 111. The third region 123 includes a seventh edge 1231 and an eighth edge 1232, which are opposite to each other. The sixth edge 114 is located on the side of the seventh edge 1231 facing away from the eighth edge 1232, and the eighth edge 1232 is connected to the second region 122.

[0085] Optionally, the sixth edge 114, the seventh edge 1231, and the eighth edge 1232 are parallel. Due to process errors, the angle between any two edges of the sixth edge 114, the seventh edge 1231, and the eighth edge 1232 may be 1°-3° without limitation.

[0086] Optionally, the shape and size of the third area 123 and the first area 121 may be consistent or inconsistent, without limitation.

[0087] Optionally, the third porosity E and the first porosity A may be equal or unequal, without limitation.

[0088] Optionally, referring to the first spacing C, the distance from any position on the sixth edge 114 to the corresponding position on the seventh edge 1231 in the first direction X is a third spacing F, satisfying the following: 0 mm ≤ F ≤ 5 mm. Optionally, the third spacing F can be 0 mm, 1 mm, 2 mm, 3 mm, 4 mm, or 5 mm, without limitation.

[0089] Optionally, referring to the second spacing D, the distance from any position on the seventh edge 1231 to the corresponding position on the eighth edge 1232 in the first direction X is a fourth spacing G, satisfying the following: 1 mm ≤ G ≤ 5 mm. Optionally, the fourth spacing G can be 1 mm, 2 mm, 3 mm, 4 mm, or 5 mm, without limitation.

[0090] A third region 123 is provided, and at the same time, a third porosity E of the third region 123 is greater than a second porosity B of the second region 122, so that the electrolyte wettability of the first region 121 and the third region 123 on both sides of the second region 122 is improved, the liquid phase diffusion effect of the electrolyte is improved, the transmission of lithium ions is accelerated, and the accumulation of lithium ions at the edge of the electrode 10 during high-rate charge and discharge is reduced. Compared with providing the first region 121 only on one side of the second region 122, the improvement of the charge and discharge capacity of the edge of the electrode 10 is more obvious, and the battery capacity drop and safety problems caused by edge lithium plating are effectively solved.

[0091] Please refer to Figure 3The present invention also provides a battery cell, which includes a pole piece 10, a second pole piece 20, and a diaphragm 30. The pole piece 10, the diaphragm 30, and the second pole piece 20 are stacked. The pole piece 10 is the pole piece described in any of the various embodiments described above. In the orthographic projection of the second pole piece 20 on the pole piece 10, the edge of the second active material layer 22 of the second pole piece 20 close to the first pole ear falls in the first area 121.

[0092] Optionally, the edge of the second active material layer 22 of the second electrode sheet 20 away from the first electrode tab falls in the third region 123 .

[0093] Optionally, the second electrode sheet 20 includes a second current collector 21, which has a second active material layer 22 thereon. Specifically, when the second electrode sheet 20 is a positive electrode sheet, the second active material layer 22 includes components such as a positive electrode material, a conductive agent, and a binder. These materials are not specifically limited in this invention, and appropriate materials can be selected based on actual application requirements. The second current collector 21 includes, but is not limited to, copper foil or aluminum foil. Preferably, the second current collector 21 is aluminum foil. The positive electrode active material can be a phosphate positive electrode active material or a ternary positive electrode active material. In specific embodiments, it includes one or more of lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, lithium manganese iron phosphate, lithium vanadium phosphate, lithium vanadium oxyphosphate, lithium vanadium phosphate fluorophosphate, lithium titanate, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide. The conductive agent includes one or more of graphite, carbon black, acetylene black, graphene, carbon fiber, C60, and carbon nanotubes, and the conductive agent content in the positive electrode active layer is 3 wt% to 5 wt%. The types of binders include one or more of polyvinylidene chloride, soluble polytetrafluoroethylene, styrene-butadiene rubber, hydroxypropyl methylcellulose, methylcellulose, carboxymethyl cellulose, polyvinyl alcohol, acrylonitrile copolymer, sodium alginate, chitosan and chitosan derivatives, and the content of the binder in the positive electrode active layer is 2wt%-4wt%.

[0094] Optionally, the second current collector 21 may have the same size as the second active material layer 22 or may be larger than the second active material layer 22 , without limitation.

[0095] Optionally, the separator 30 may be any one of a woven membrane, a non-woven membrane (non-woven fabric), a microporous membrane, a composite membrane, separator 30 paper, a laminated membrane, etc., without limitation.

[0096] In the orthographic projection of the second pole piece 20 on the pole piece 10, the edge of the second pole piece 20 falls on the first area 121, realizing the structure of the pole piece 10 wrapping the second pole piece 20, and the edge charging and discharging capabilities of the pole piece 10 provided by the utility model are improved, which alleviates the edge lithium plating effect caused by lithium ion migration and cycle accumulation, effectively solves the battery capacity drop and safety problems caused by edge lithium plating, and the battery cell life can be extended, and the safety is good.

[0097] The utility model also provides a battery, comprising a shell and a battery core according to any one of the aforementioned various embodiments, wherein the battery core is accommodated in the shell.

[0098] Optionally, the battery may be a square shell battery, a cylindrical battery, or other types such as a prismatic battery, without limitation.

[0099] Optionally, the shell is made of a material with high structural strength, specifically metal materials, high-strength plastics, ceramics, etc. Metal materials include aluminum, aluminum alloys, magnesium alloys, iron and iron alloys, etc. The shell includes a bottom plate and side panels. The shell can be an integrated structure, that is, the bottom plate and the side panels are an integrated structure made by an integrated molding process. The integrated molding process can be specifically stamping, casting, etc., without limitation. The shell can also be a split structure, and the side panels and the bottom panel can be connected and fixed by welding, bonding, clamping, screwing, etc. The wall thickness of the shell can be roughly uniform everywhere, that is, the thickness of the side panels can be roughly uniform, and the thickness of the bottom panel and the side panels can also be roughly the same.

[0100] The battery provided by the present invention uses the electrode 10 in the embodiment of the present invention, which can alleviate the edge lithium plating effect caused by lithium ion migration and cycle accumulation, effectively solve the battery capacity drop and safety problems caused by edge lithium plating, extend the battery life, and improve safety.

[0101] In the description of the embodiments of the present invention, it should be noted that the orientation or positional relationship of terms such as "center", "up", "down", "left", "right", "vertical", "horizontal", "inside" and "outside" is based on the orientation or positional relationship described in the accompanying drawings, which is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0102] The above disclosure is only a preferred embodiment of the present invention, and certainly cannot be used to limit the scope of rights of the present invention. Ordinary technicians in this field can understand that all or part of the processes of the above embodiment and equivalent changes made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. A pole piece for a battery cell, characterized in that: include: A first current collector, suitable for connecting to the first electrode tab; A first active material layer is stacked on the first current collector, the first active material layer includes a first region and a second region, the first region is closer to the first electrode tab than the second region, the porosity of the first region is A, the porosity of the second region is B, and the following is satisfied: A>B.

2. The pole piece according to claim 1, characterized in that: It also satisfies: 2%≤AB≤5%, and 25%≤B≤30%.

3. The pole piece according to claim 1, characterized in that: A portion of the first current collector corresponding to the first region has a first edge, and the first edge is suitable for arranging the first electrode tab.

4. The pole piece according to claim 3, characterized in that: The first area has a second edge, and in a first direction, the first edge and the second edge are arranged relative to each other, wherein the distance between the first edge and the second edge is C, satisfying: 0mm≤C≤5mm, and the first direction is the arrangement direction of the first area and the second area.

5. The pole piece according to claim 1, characterized in that: The first area includes a second edge and a third edge opposite to each other in a first direction, the third edge is connected to the second area, and in the first direction, the distance between the second edge and the third edge is D, satisfying: 1mm≤D≤5mm, and the first direction is the arrangement direction of the first area and the second area.

6. The pole piece according to claim 1, characterized in that: The first region includes a first material, the second region includes a second material, the density of the first material is lower than the density of the second material, and / or the specific surface area of ​​the first material is higher than the specific surface area of ​​the second material.

7. The pole piece according to claim 1, characterized in that: The number of micropores in the material of the first region is greater than the number of micropores in the material of the second region, and / or the average pore size of the micropores in the material of the first region is greater than the average pore size of the micropores in the material of the second region.

8. The pole piece according to claim 1, characterized in that: The compacted density of the material of the first region is less than the compacted density of the material of the second region.

9. The pole piece according to claim 1, characterized in that: The area density of the material of the first region is less than the area density of the material of the second region.

10. The pole piece according to claim 1, characterized in that: The electrode sheet is a negative electrode sheet, and the battery cell further includes a positive electrode sheet. The negative electrode sheet includes an overlapping area and an overhang area, the overlapping area is suitable for overlapping with the second active material layer of the positive electrode sheet, and the overhang area includes at least a portion of the first region.

11. The pole piece according to any one of claims 1 to 10, characterized in that: The first active material layer further includes a third region, which is located on a side of the second region facing away from the first region. The porosity of the third region is E, satisfying: E>B.

12. The pole piece according to claim 11, characterized in that: Also meets the following requirements: 2%≤EB≤5%.

13. A battery cell, characterized in that: It comprises a diaphragm and a pole piece as claimed in any one of claims 1 to 12, wherein the pole piece and the diaphragm are stacked.

14. A battery, characterized in that: It comprises a shell and the battery core as claimed in claim 13, wherein the battery core is accommodated in the shell.

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