Electrode sheet, battery cell, and battery

Abstract

An electrode sheet, a battery cell, and a battery. The electrode sheet is used for the battery cell, and the electrode sheet comprises a first current collector and a first active material layer. The first current collector is suitable for being connected to a first tab. The first active material layer is stacked on the first current collector. The first active material layer comprises a first region and a second region, the first region being closer to the first tab than the second region. The porosity of the first region is a first porosity A, and the porosity of the second region is a second porosity B, satisfying A>B.

Description

Electrode sheets, cells and batteries

[0001] Cross-references to related applications

[0002] This application claims priority to Chinese Patent Application No. 202420873085.3, filed on April 24, 2024, entitled "Electrode, Cell and Battery", the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application relates to the field of battery technology, specifically to an electrode, a cell, and a battery. Background Technology

[0004] After multiple fast-charging cycles, lithium plating can occur at the edges of the electrodes in lithium-ion batteries due to poor charge and discharge capabilities. The continuous accumulation of deposited lithium can puncture the separator, posing a serious safety hazard to lithium-ion batteries. Summary of the Invention

[0005] The purpose of this application is to provide an electrode, a cell, and a battery to solve the problem of lithium plating caused by poor charge and discharge capabilities at the edge of the electrode.

[0006] To achieve the objectives of this application, the following technical solution is provided:

[0007] In a first aspect, this application provides an electrode sheet for use in a battery cell, comprising:

[0008] The first current collector is adapted to be connected to the first electrode tab;

[0009] 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 tab than the second region. The porosity of the first region is A, and the porosity of the second region is B, satisfying that A > B.

[0010] In one implementation, the following conditions are also met: 2% ≤ AB ≤ 5%, and 25% ≤ B ≤ 30%.

[0011] In one embodiment, the portion of the first current collector corresponding to the first region has a first edge, and the first edge is adapted to be provided with the first tab.

[0012] In one embodiment, the first region has a second edge, and the first edge and the second edge are arranged opposite to each other in a first direction. The distance between the first edge and the second edge is C, satisfying: 0mm ≤ C ≤ 5mm. The first direction is the arrangement direction of the first region and the second region. In another embodiment, the first region includes a second edge and a third edge opposite to each other in a first direction. 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, satisfying: 1mm ≤ D ≤ 5mm. The first direction is the arrangement direction of the first region and the second region.

[0013] In one embodiment, the first region includes a first material, the second region 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.

[0014] 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 diameter of the micropores in the material of the first region is greater than the average pore diameter of the micropores in the material of the second region.

[0015] In one embodiment, the compaction density of the material in the first region is less than the compaction density of the material in the second region.

[0016] 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.

[0017] In one embodiment, the electrode is a negative electrode, and the battery cell further includes a positive electrode. The negative electrode includes an overlapping region and an overhang region. The overlapping region is adapted to overlap with a second active material layer of the positive electrode, and the overhang region includes at least a portion of the first region.

[0018] In one embodiment, the first active material layer further includes a third region located on the side of the second region opposite to the first region, and the porosity of the third region is E, satisfying: E ​​> B.

[0019] In one implementation, the following condition is also met: 2% ≤ EB ≤ 5%.

[0020] Secondly, this application also provides a battery cell, including a separator and an electrode sheet as described in any one of the various embodiments of the first aspect, wherein the electrode sheet and the separator are stacked.

[0021] Thirdly, this application also provides a battery, including a casing and a cell as described in any one of the various embodiments of the second aspect, wherein the cell is housed within the casing.

[0022] By setting the first active material layer into a first region and a 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. By increasing the porosity of the first region, the electrolyte wettability of the first region is improved, which effectively promotes the liquid phase diffusion of the electrolyte, accelerates lithium ion transport, improves the charge and discharge capability of the electrode edge, avoids the accumulation of lithium ions at the electrode edge during high-rate charge and discharge, alleviates the edge lithium plating effect caused by lithium ion migration and cycle accumulation, and effectively solves the battery capacity drop and safety problems caused by edge lithium plating. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0024] Figure 1 is a top view of an embodiment of the electrode sheet;

[0025] Figure 2 is a cross-sectional view of an electrode sheet according to an embodiment;

[0026] Figure 3 is a cross-sectional view of a battery cell according to one embodiment.

[0027] Explanation of reference numerals in the attached figures: 10-Electrode, 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; 20-Second electrode, 21-Second current collector, 22-Second active material layer, 30-Separator; C-First spacing, D-Second spacing, F-Third spacing, G-Fourth spacing, X-First direction. Detailed Implementation

[0028] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0029] It should be noted that when a component is said to be "fixed" to another component, it can be directly on the other component or it can be in a middle component. When a component is said to be "connected" to another component, it can be directly connected to the other component or it may be in a middle component.

[0030] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. The terminology used in the specification of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used in this application includes any and all combinations of one or more of the associated listed items.

[0031] The following detailed description of some embodiments of this application is provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0032] Referring to Figures 1 and 2, this application provides an electrode 10 for use in a battery cell. The electrode 10 includes a first current collector 11 and a first active material layer 12. The first current collector 11 is adapted to be connected to a first tab (not shown in the figures). 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.

[0033] Specifically, the size of the electrode 10 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 set as a positive electrode, and when the second electrode 20 is a negative electrode, the electrode 10 is set as a negative electrode.

[0034] 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 binder includes 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, without limitation.

[0035] Optionally, the first region 121 is at least partially closer to the edge of the first current collector 11 connected to the first electrode tab than 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 perpendicular direction X is the same as the length of the second region 122 in the perpendicular direction X, then the first region 121 is generally closer to the edge of the first current collector 11 connected to the first electrode tab than the second region 122; or, when 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 electrode 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 electrode tab, the first region 121 is positioned directly opposite the first electrode tab in the first direction X, and the second region 122 is U-shaped, surrounding the outer periphery of the first region 121.

[0036] The second region 122 and the first region 121 can be set at intervals, that is, a transition region is set between the second region 122 and the first region 121, and the porosity of the transition region is less than the first porosity of the first region 121.

[0037] In one possible implementation, when the electrode 10 is a negative electrode, 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.

[0038] The first electrode tab and the first current collector 11 may partially overlap, or they may only be connected to the edge of the first current collector 11, without any restriction.

[0039] The first electrode tab can be in the form of a full electrode tab, a multi-electrode tab, or a single electrode tab. The electrode exiting tab can be in the form of same-plane electrode exiting tab, opposite-plane electrode exiting tab, symmetrical electrode exiting tab, or asymmetrical electrode exiting tab.

[0040] The first tab can be a flattened tab or a die-cut tab; there are no restrictions. The tab of the electrode 10 can be made of nickel or copper-nickel material. The first tab of the electrode 10 is mainly used to connect the positive and negative terminals of the battery, realizing the transfer of current and guiding the current from the positive terminal to the negative terminal to realize the charging and discharging process of the battery. At the same time, the first tab of the electrode 10 also plays a role in fixing the internal structure of the lithium battery.

[0041] The first electrode tab may also include a protective adhesive, which can be used to strengthen the fixation between the first electrode tab and the first current collector 11.

[0042] By setting a first region 121 and a second region 122 with different porosities, and the first porosity A being 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, resulting in better liquid phase diffusion of the electrolyte, faster lithium ion transport, and reduced accumulation of lithium ions at the edge of the electrode 10 during high-rate charge and discharge, thereby improving the charge and discharge capability at the edge of the electrode 10 and reducing the risk of lithium plating.

[0043] In one implementation, the following conditions are also met: 2% ≤ AB ≤ 5%, and 25% ≤ B ≤ 30%.

[0044] Optionally, AB can be 2.5% ≤ AB ≤ 4.5%, or 3% ≤ AB ≤ 4%. Specifically, AB can be 2%, 2.5%, 3%, 4%, 4.5%, or 5%, without restriction.

[0045] Specifically, B can be 25%, 26%, 127%, 28%, 29%, or 30%, without restriction.

[0046] If AB < 2%, it indicates 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 significant, resulting in little improvement in the charge and discharge capability of the electrode 10 edge and a weak effect on mitigating the edge lithium plating effect. If AB > 5%, it indicates 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, resulting in poor wetting effect of the electrolyte in the first region 121 and a negative impact on the battery capacity.

[0047] Referring to 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, which is adapted to be provided with a first tab (not shown in the figure).

[0048] Referring to Figure 1, in one embodiment, the first region 121 includes a second edge 1211 and a third edge 1212 opposite to each other in the first direction X. The first edge 111 is located on the side of the second edge 1211 facing away from the third edge 1212 in the first direction X, and 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, and the second direction is the extension direction of the first edge 111, which intersects with the first direction X.

[0049] Optionally, the second edge 1211 and the third edge 1212 can be straight lines, curves, etc., without limitation. The second edge 1211 and / or the third edge 1212 can be flush with the edge of the first current collector 11 in the second direction, or they can be spaced apart from the edge of the first current collector 11 in the second direction, without limitation.

[0050] Optionally, the first current collector 11, the first region 121, and the second region 122 are all rectangular.

[0051] Optionally, the first current collector 11 also includes a fourth edge 112 and a fifth edge 113 opposite to each other, with the fourth edge 112 and the fifth edge 113 located on both sides of the first edge 111 respectively.

[0052] Optionally, the fourth edge 112 and the fifth edge 113 can be straight lines or curves, without restriction; the edges corresponding to the first region 121 and the second region 122 can also be straight lines or curves, without restriction.

[0053] 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 charging and discharging capability of the electrode 10 edge in the direction along the first edge 111, which is beneficial to the charging and discharging of the battery. Due to the existence of process errors, 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.

[0054] Optionally, in the first direction X, the distance from any position of the first edge 111 to the corresponding position of the second edge 1211 is the first spacing C, which satisfies: 0mm≤C≤5mm.

[0055] Optionally, the first spacing C can be 0mm, 1mm, 2mm, 3mm, 4mm, or 5mm, without restriction.

[0056] If C > 5mm, the area of ​​the first active material layer 12 will be too small, wasting space and reducing the 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, and the edges of the first region 121 and the first current collector 11 are spaced apart, which facilitates the coating of the first region 121 and the second region 122 during the production process.

[0057] 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 the second spacing D, which satisfies: 1mm≤D≤5mm.

[0058] Optionally, the second spacing D can be 1mm, 2mm, 3mm, 4mm, or 5mm, without restriction.

[0059] The second spacing D restricts the size of the first region 121, so that the first region 121 corresponds to the edge region of the electrode 10. If D < 1 mm, the first region 121 has no significant effect on improving the charging and discharging capacity at the edge of the electrode 10. If D > 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, the first region 121 provides less energy, resulting in a reduction in battery capacity.

[0060] 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.

[0061] 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.

[0062] By setting a first material with low density and / or high specific surface area, the first porosity A of the first region 121 is greater than the second porosity B of the second region 122, thereby improving the electrolyte wettability of the first region 121, resulting in better liquid phase diffusion of the electrolyte, faster lithium-ion transport, and reduced accumulation of lithium ions at the edge of the electrode 10 during high-rate charge and discharge, thus improving the charge and discharge capability at the edge of the electrode 10 and reducing the risk of lithium plating.

[0063] 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 diameter of the micropores in the material of the first region 121 is greater than the average pore diameter of the micropores in the material of the second region 122.

[0064] Optionally, the first material of the first region 121 includes a pore-forming agent, wherein the pore-forming agent accounts for no more than 2% by mass of the first material.

[0065] Optionally, the pore-forming agent may be any one of lithium oxalate, lithium carbonate, polystyrene, polyvinyl alcohol, or polyethylene glycol, without restriction.

[0066] By adding a pore-forming agent, 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 diameter of the micropores in the material of the first region 121 is greater than the average pore diameter of the micropores in the material of the second region 122. This results in the first porosity A of the first region 121 being greater than the second porosity B of the second region 122. This improves the electrolyte wettability of the first region 121, enhances the liquid phase diffusion effect of the electrolyte, accelerates lithium ion transport, reduces the accumulation of lithium ions at the edge of the electrode 10 during high-rate charging and discharging, improves the charging and discharging capability at the edge of the electrode 10, reduces the risk of lithium plating, and effectively solves the battery capacity drop and safety problems caused by edge lithium plating.

[0067] In one embodiment, 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.

[0068] Optionally, a multilayer coating technique can be used to achieve a compaction density of the material in the first region 121 that is lower than that in the second region 122.

[0069] Optionally, when only the second region 122 is coated multiple times, the first region 121 is coated during the last coating, and then the electrode is rolled.

[0070] Optionally, the number of coatings applied to the first region 121 can be one or multiple times, without specific restrictions.

[0071] Optionally, the second region 122 may be coated one or more times more than the first region 121, without any specific limitation.

[0072] By changing the number of coatings, the compaction density of the material in the first region 121 is less than that of the material in the second region 122, making the first porosity A of the first region 121 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 lithium ion transport, avoids the accumulation of lithium ions at the edge of the negative electrode during high-rate charging and discharging, and reduces the risk of lithium plating.

[0073] 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.

[0074] The higher areal density of the material in the first region 121 can increase the capacity of the electrode 10, enabling the battery to hold more charge during charging and discharging, thereby extending the cycle life of the battery. Furthermore, the higher areal density of the first region 121 during charging and discharging can hold more lithium ions, avoiding the accumulation and deposition of lithium ions at the edge of the negative electrode during high-rate charging and discharging. This alleviates the edge lithium plating effect caused by lithium ion migration and cycle accumulation, effectively solving the battery capacity drop and safety issues caused by edge lithium plating.

[0075] In one embodiment, electrode 10 is a negative electrode, and the cell further includes a second electrode 20, which is a positive electrode. Electrode 10 includes an overlapping region and an overhang region. The overlapping region overlaps with the second active material layer 22 of the second electrode 20. The overhang region includes at least a portion of the first region 121. The overhang region may extend beyond the overlapping region in a first direction X, or it may extend beyond the overlapping region in a second direction. The second direction forms an angle with the first direction X, meaning the overhang region may surround the overlapping region. The second direction is the extension direction of the first edge 111.

[0076] In the first direction X, the region of the first region 121 that extends beyond the second active material layer 22 of the second electrode 20 is called the overhang region, and its size in the first direction X is 1mm-3mm. Optionally, the size of the overhang region is 1mm, 2mm, 3mm, etc., without limitation. The overhang region can prevent lithium plating on the electrode 10 and improve the safety of the battery cell. In one embodiment, the first active material layer 12 further includes a third region 123, which is located on the side of the second region 122 away from the first region 121. The porosity of the third region 123 is a third porosity E, which satisfies: E>B. The third region 123 is adapted to correspond to the edge of the second active material layer 22 of the second electrode 20 away from the first tab.

[0077] Optionally, electrode 10 is a negative electrode, second electrode 20 is a positive electrode, and the overhang region also includes at least part of the third region 123.

[0078] The portion of the third region 123 that extends beyond the second active material layer 22 of the second electrode 20 in the first direction X is also an overhang region, with a corresponding dimension of 1mm-3mm in the first direction X. The overhang region can also extend beyond the overlap region in the second direction, that is, the overhang region can be arranged around the overlap region.

[0079] The overhang area of ​​the third region 123, which is set in accordance with the overhang area of ​​the first region 121, can also prevent lithium deposition on the electrode 10 and improve the safety of the cell.

[0080] Optionally, the electrode 10 is provided with a first electrode tab and a second electrode tab. At least a portion of 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. Similarly, at least a portion of 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 both the third region 123 and the second region 122 are 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 generally closer 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 positioned directly opposite the second electrode tab in the first direction X, and the second region 122 is U-shaped, surrounding the outer periphery of the third region 123.

[0081] In one implementation, the following condition is also met: 2% ≤ EB ≤ 5%.

[0082] Optionally, EB can be 2.5% ≤ EB ≤ 4.5%, 3% ≤ EB ≤ 4%, and specifically, EB can be 2%, 2.5%, 3%, 4%, 4.5%, or 5%, without restriction.

[0083] Optionally, the first current collector 11 further includes a sixth edge 114, which is disposed opposite to the first edge 111. The third region 123 includes a seventh edge 1231 and an eighth edge 1232, with the sixth edge 114 located on the side of the seventh edge 1231 facing away from the eighth edge 1232, and the eighth edge 1232 connected to the second region 122.

[0084] Optionally, the sixth edge 114, the seventh edge 1231, and the eighth edge 1232 are parallel. Due to manufacturing errors, the angle between any two of the sixth edge 114, the seventh edge 1231, and the eighth edge 1232 can be 1°-3°, without restriction.

[0085] Optionally, the shape and size of the third region 123 and the first region 121 may or may not be the same, and there is no restriction.

[0086] Optionally, the third porosity E may or may not be equal to the first porosity A; there is no restriction.

[0087] Optionally, referring to the first spacing C, the distance from any position of the sixth edge 114 to the corresponding position of the seventh edge 1231 in the first direction X is the third spacing F, satisfying: 0mm≤F≤5mm. Optionally, the third spacing F can be 0mm, 1mm, 2mm, 3mm, 4mm, or 5mm, without restriction.

[0088] Optionally, referring to the second spacing D, the fourth spacing G is the distance from any position of the seventh edge 1231 to the corresponding position of the eighth edge 1232 in the first direction X, satisfying: 1mm≤G≤5mm. Optionally, the fourth spacing G can be 1mm, 2mm, 3mm, 4mm, or 5mm, without restriction.

[0089] A third region 123 is provided, and the third porosity E of the third region 123 is greater than the second porosity B of the second region 122. This improves the electrolyte wettability of the first region 121 and the third region 123 on both sides of the second region 122, enhances the liquid phase diffusion effect of the electrolyte, accelerates lithium ion transport, and reduces the accumulation of lithium ions at the edge of the electrode 10 during high-rate charging and discharging. Compared with providing the first region 121 only on one side of the second region 122, the improvement of the charging and discharging capability at the edge of the electrode 10 is more significant, effectively solving the battery capacity drop and safety issues caused by edge lithium plating.

[0090] Please refer to Figure 3. This application also provides a battery cell, which includes an electrode 10, a second electrode 20, and a separator 30. The electrode 10, the separator 30, and the second electrode 20 are stacked. The electrode 10 is the electrode described in any of the foregoing embodiments. In the orthographic projection of the second electrode 20 onto the electrode 10, the edge of the second active material layer 22 of the second electrode 20 near the first tab falls in the first region 121.

[0091] Optionally, the edge of the second active material layer 22 of the second electrode 20, away from the first electrode tab, falls in the third region 123.

[0092] Optionally, the second electrode 20 includes a second current collector 21, on which a second active material layer 22 is formed. Specifically, when the second electrode 20 is a positive electrode, the second active material layer 22 includes components such as a positive electrode material, a conductive agent, and a binder. This application does not specifically limit these materials, and suitable materials can be selected according to actual application requirements. The second current collector 21 includes, but is not limited to, any one of copper foil and 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 oxide phosphate, lithium fluorinated vanadium phosphate, 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 content of the conductive agent in the positive electrode active layer is 3wt%-5wt%. The types of binders include one or more of polyvinylidene chloride, soluble polytetrafluoroethylene, styrene-butadiene rubber, hydroxypropyl methylcellulose, methylcellulose, carboxymethylcellulose, 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%.

[0093] Optionally, the second current collector 21 may have the same size as the second active material layer 22 or may be larger than the size of the second active material layer 22, without limitation.

[0094] Optionally, the diaphragm 30 can be any of the following: woven membrane, nonwoven membrane (non-woven fabric), microporous membrane, composite membrane, diaphragm 30 paper, rolled membrane, etc., without limitation.

[0095] In the orthographic projection of the second electrode 20 onto the electrode 10, the edge of the second electrode 20 falls on the first region 121, realizing the structure of the electrode 10 wrapping the second electrode 20. Moreover, the edge charging and discharging capability of the electrode 10 provided by this application is 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, extends the cell life, and improves safety.

[0096] This application also provides a battery, including a casing and a cell according to any of the foregoing embodiments, wherein the cell is housed within the casing.

[0097] Optionally, the battery can be a prismatic battery, a cylindrical battery, or other types such as a prismatic battery, without limitation.

[0098] Optionally, the outer shell can be made of a material with high structural strength, such as metal, high-strength plastic, or ceramic. Metal materials include aluminum, aluminum alloys, magnesium alloys, iron, and iron alloys. The outer shell includes a base plate and side plates. The shell can be a one-piece structure, meaning the base plate and side plates are manufactured using a single molding process, such as stamping or casting, without limitation. Alternatively, the shell can be a separate structure, with the side plates and base plate connected and fixed by welding, bonding, snap-fitting, or screwing. The wall thickness of the outer shell can be approximately uniform throughout; that is, the side plates can have a roughly uniform thickness, and the base plate and side plates can also have roughly the same thickness.

[0099] The battery provided in this application uses the electrode 10 in the embodiments of this application, 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 battery life, and improve safety.

[0100] In the description of the embodiments of this application, it should be noted that the orientation or positional relationship of the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" and other indicators are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0101] The above-disclosed embodiments are merely preferred embodiments of this application and should not be construed as limiting the scope of this application. Those skilled in the art will understand that all or part of the processes for implementing the above embodiments and equivalent variations made in accordance with the claims of this application are still within the scope of this application.

Claims

1. An electrode sheet for use in a battery cell, comprising: The first current collector (11) is adapted to be connected to the first electrode tab; A 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 first tab than the second region (122). The porosity of the first region (121) is A, and the porosity of the second region (122) is B, satisfying: A > B.

2. The electrode according to claim 1 further satisfies: 2% ≤ AB ≤ 5%, and 25% ≤ B ≤ 30%.

3. The electrode according to claim 1 or 2, comprising: the portion of the first current collector (11) corresponding to the first region (121) having a first edge (111), the first edge (111) being adapted to provide the first electrode tab.

4. The electrode according to claim 3, comprising: the first region (121) having a second edge (1211), wherein, in a first direction, the first edge (111) and the second edge (1211) are arranged opposite to each other, wherein, The distance between the first edge (111) and the second edge (1211) is C, which satisfies: 0mm≤C≤5mm, and the first direction is the arrangement direction of the first region (121) and the second region (122).

5. The electrode according to any one of claims 1 to 4, comprising: the first region (121) including a second edge (1211) and a third edge (1212) opposite to each other in a first direction, the third edge (1212) being connected to the second region (122); in the first direction, the distance between the second edge (1211) and the third edge (1212) is D, satisfying: 1mm≤D≤5mm; the first direction is the arrangement direction of the first region (121) and the second region (122).

6. The electrode according to any one of claims 1 to 5, comprising: the first region (121) comprising a first material; the second region (122) comprising a second material; the density of the first material being less than the density of the second material; and / or the specific surface area of ​​the first material being greater than the specific surface area of ​​the second material.

7. The electrode according to any one of claims 1 to 6, comprising: 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 diameter of the micropores in the material of the first region (121) is greater than the average pore diameter of the micropores in the material of the second region (122).

8. The electrode according to any one of claims 1 to 7, wherein 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).

9. The electrode according to any one of claims 1 to 8, wherein 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).

10. The electrode according to any one of claims 1 to 9, wherein the electrode (10) is a negative electrode, the cell further includes a positive electrode, the negative electrode includes an overlap region and an overhang region, the overlap region being adapted to overlap with a second active material layer (22) of the positive electrode, the overhang region including at least a portion of the first region (121).

11. The electrode according to any one of claims 1 to 10, comprising, wherein the first active material layer (12) further comprises a third region (123), the third region (123) being located on the side of the second region (122) facing away from the first region (121), and the porosity of the third region (123) being E, satisfying: E ​​> B.

12. The electrode according to claim 11 further satisfies: 2% ≤ EB ≤ 5%.

13. A battery cell comprising a separator (30) and an electrode as claimed in any one of claims 1 to 12, wherein the electrode (10) and the separator (30) are stacked.

14. A battery comprising a casing and a cell as claimed in claim 13, the cell being housed within the casing.

Images