A dual-domain pore-gradient separator and secondary battery

Abstract

The utility model provides a kind of double-domain pore gradient diaphragm and secondary battery, double-domain pore gradient diaphragm includes base film and coating area, coating area includes first coating part and second coating part, first coating part is set around second coating part, the porosity of first coating part is φ1 Greater than the porosity of second coating part φ2;Secondary battery further includes first pole piece and second pole piece, base film is arranged between first pole piece and second pole piece, to isolate the first pole piece and the second pole piece;The ion conductivity of first coating part is higher, when being applied in lithium ion battery, the transmission speed of lithium ion battery in first coating part is faster, can effectively reduce lithium ion accumulation at pole piece edge, so as to reduce the phenomenon of lithium dendrite precipitation, reduce the risk of analysis.

Description

Technical Field

[0001] This utility model relates to the field of battery technology, specifically to a dual-domain pore gradient separator and a secondary battery. Background Technology

[0002] During the cyclic charging and discharging process, lithium-ion batteries will experience lithium deposition at the edges of the electrodes. The deposited lithium dendrites accumulate at the edges, which can puncture the separator and cause the positive and negative electrodes to conduct, posing a great threat to the safe use of lithium batteries. Utility Model Content

[0003] The embodiments of this utility model provide a dual-domain pore gradient separator and a secondary battery, which can improve the technical problem that the continuous accumulation of precipitated lithium dendrites will cause the separator to be punctured.

[0004] In a first aspect, embodiments of the present invention provide a dual-domain pore gradient membrane, comprising: Base film; The coating region is coated on the base film. The coating region includes a first coating portion and a second coating portion. The first coating portion is arranged around the second coating portion. The porosity of the first coating portion is φ1, and the porosity of the second coating portion is φ2, where φ1 > φ2.

[0005] In one embodiment, the coating area has two layers, and the two coating areas are respectively coated on both sides of the base film.

[0006] When this separator is used in lithium batteries, the two-layer coating area can simultaneously optimize the ion transport path of the electrodes on both sides, thereby reducing the formation of lithium dendrites.

[0007] In one embodiment, φ2 ranges from 35% to 50%.

[0008] In this embodiment, the second coating area is the main transport area of ​​lithium ions in the electrode, and the range of porosity φ2 determines the transport characteristics of lithium ions in the second coating area. When the porosity is between 35% and 50%, it can ensure the efficiency of ion transport, and avoid the coating strength from decreasing due to excessive porosity or the ion transport from being blocked due to excessively low porosity. If the porosity φ2 is less than 35%, the second coating may be too dense, resulting in reduced ion transport efficiency; if the porosity φ2 is greater than 50%, the second coating may become too porous, leading to decreased mechanical strength. Therefore, when used in lithium-ion batteries, lithium ions can move stably in the second coating without generating significant transport resistance due to excessively low porosity, or making the coating too porous due to excessively high porosity, thereby improving the overall performance of the battery.

[0009] In one embodiment, 3%≤φ 1- φ2≤8%.

[0010] Increased porosity leads to increased liquid absorption, increased charge carriers, and increased conductivity. The limitation of the porosity difference φ1-φ2 ​​ensures a reasonable porosity gradient between the first and second coating sections, which effectively reduces the accumulation of lithium ions at the electrode edge. The high porosity of the first coating section can quickly guide ions through, while the low porosity of the second coating section can stabilize ion transport and prevent ions from accumulating at the electrode edge.

[0011] In one embodiment, 5% ≤ φ1 - φ2 ≤ 7%.

[0012] Limiting the porosity difference φ1-φ2 ​​to this range not only creates a significant difference in conductivity, but also improves and mitigates the lithium plating effect. However, when the porosity difference is too large (e.g., the difference is 10% or more), it is highly likely that the electrolyte distribution will be uneven, with local dry areas accounting for more than 30%, thereby causing concentration polarization and a decrease in conductivity.

[0013] Secondly, embodiments of this utility model provide a secondary battery using a dual-domain pore gradient separator, which further includes a first electrode and a second electrode, wherein the base film is disposed between the first electrode and the second electrode to isolate the first electrode and the second electrode.

[0014] In one embodiment, the orthographic projection of the edge of the first electrode toward the coating area and the orthographic projection of the edge of the second electrode toward the coating area are both located in the first coating portion.

[0015] Therefore, the coating area can cover the edges of the first and second electrodes, thus completely enveloping the first and second electrodes, preventing direct contact between the first and second electrodes and causing a short circuit, and ensuring the normal use of the battery.

[0016] In one embodiment, the width of the first electrode is greater than the width of the second electrode, and the first coating portion includes a plurality of sequentially connected side regions, wherein the distance between the boundary line of the side region away from the second coating portion and the boundary line of the first electrode is 0.5mm to 3mm.

[0017] In this embodiment, the boundary of the first coating extends beyond the first electrode by 0.5mm to 3mm. Therefore, by providing additional protection at the edges of the first and second electrodes, the formation of lithium dendrites can be significantly reduced, thereby improving battery safety and lifespan. Furthermore, by setting the above parameters, it is also possible to avoid the boundary of the first coating extending too far beyond the first electrode, thus preventing it from occupying too much internal battery space and causing unnecessary waste.

[0018] In one embodiment, the width of the first electrode is greater than the width of the second electrode, and the first coating portion includes a plurality of sequentially connected side regions, wherein the distance between the boundary line of the side region near the second coating portion and the boundary line of the first electrode is 0.5mm to 4mm.

[0019] Therefore, by setting the above parameters, it is possible to ensure that the overlap area between the first coating and the first electrode is sufficient, thereby improving and mitigating the lithium plating effect at the edge of the first electrode. At the same time, it is also possible to prevent the overlap area between the first coating and the first electrode from being too large, thereby preventing a significant impact on the lithium-ion transport of the first electrode and ensuring the normal use of the battery.

[0020] In one embodiment, the first electrode includes a first part and a second part connected in sequence, the second part being connected to the coating region, and the first part being spaced apart from the coating region to form a first gap between the first part, the second part, and the coating region, for reducing the local current density of the first electrode; and / or, the second electrode includes a third part and a fourth part connected in sequence, the fourth part being connected to the coating region, and the third part being spaced apart from the coating region to form a second gap between the third part, the fourth part, and the coating region, for reducing the local current density of the second electrode.

[0021] By forming a first notch on the first electrode and a second notch on the second electrode, a thinning region is formed on both the first and second electrodes. This allows lithium ions extracted from the first electrode to be successfully inserted into the corresponding active material layer on the second electrode, and vice versa. Furthermore, the difference in porosity between the first and second coating layers effectively reduces lithium dendrite aggregation, thereby effectively suppressing lithium plating during the charging and discharging process of the secondary battery cell.

[0022] In one embodiment, the first part is provided in a plurality of ways, and the plurality of first parts are arranged around the second part; and / or, the third part is provided in a plurality of ways, and the plurality of third parts are arranged around the fourth part.

[0023] By taking advantage of the difference in porosity between the first and second coating layers, the phenomenon of lithium dendrite aggregation can be better reduced, thereby reducing lithium deposition in the secondary battery cells during charging and discharging.

[0024] In one embodiment, the first notch has the same size along the direction away from the second part of the first part; and / or, the second notch has the same size along the direction away from the fourth part of the third part.

[0025] In this embodiment, the notch shape is regular, thereby forming a regular region of reduced thickness to accelerate ionic conductivity and improve lithium ion transport efficiency. Combined with the porosity difference between the first coating and the second coating, it more effectively reduces the accumulation of lithium ions at the electrode edge, which has an excellent promoting effect on the reduction of lithium dendrites and reduces the risk of lithium plating.

[0026] In one embodiment, the size of the first notch gradually increases along the direction away from the second part of the first part; and / or, the size of the second notch gradually increases along the direction away from the fourth part of the third part.

[0027] In this embodiment, the notch shape is irregular and the notch surface gradually tilts, thereby gradually increasing the thickness of the thinning area. Combined with the porosity difference between the first coating part and the second coating part, it effectively reduces the accumulation of lithium ions at the edge of the electrode, which has an excellent promoting effect on the reduction of lithium dendrites and reduces the risk of lithium plating.

[0028] The beneficial effects of embodiments of the dual-domain pore gradient diaphragm of this invention are as follows: Because a coating region is provided on the base film, wherein the coating region includes a first coating part and a second coating part, the first coating part is arranged around the second coating part, and the porosity φ1 of the first coating part is greater than the porosity φ2 of the second coating part, the ionic conductivity of the first coating part is higher. When used in lithium-ion batteries, the lithium-ion battery has a faster transmission speed in the first coating part, which can effectively reduce the accumulation of lithium ions at the edge of the electrode, thereby reducing the phenomenon of lithium dendrite precipitation and reducing the risk of precipitation. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of this utility model, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a schematic diagram of the structure of the dual-domain pore gradient diaphragm provided in an embodiment of this utility model; Figure 2 This is a cross-sectional view of the dual-domain pore gradient membrane provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of the structure of the secondary battery provided in Embodiment 1 of this utility model; Figure 4 This is a schematic diagram of the structure of the secondary battery provided in Embodiment 2 of this utility model; Figure 5 This is a schematic diagram of the structure of the secondary battery provided in Embodiment 3 of this utility model.

[0031] Marked in the image: 1. Dual-domain pore gradient diaphragm; 110. Base film; 120. Coating area; 121. First coating section; 1211. Side area; 122. Second coating section; 2. Secondary battery; 210. First electrode plate; 211. First part; 212. Second part; 213. First notch; 220. Second pole piece; 221. Third part; 222. Fourth part; 223. Second notch. Detailed Implementation

[0032] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present utility model. In addition, it should be understood that the specific embodiments described herein are only for illustration and explanation of the present utility model and are not intended to limit the present utility model. In the present utility model, unless otherwise stated, directional terms such as "upper" and "lower" generally refer to the upper and lower positions of the device in actual use or operation, specifically the drawing directions in the accompanying drawings; while "inner" and "outer" refer to the outline of the device.

[0033] During the cyclic charging and discharging process, lithium-ion batteries will exhibit lithium deposition at the edges of the electrodes. The continuous accumulation of deposited lithium dendrites will cause the separator to be punctured, thereby making the positive and negative electrodes conductive, posing a great threat to the safe use of lithium batteries.

[0034] Currently, improvements to address lithium plating at the battery cell level include improvements in three areas: materials, structure, and process. In terms of materials, the lithium-ion storage capacity can be improved by using silicon-based composite electrode sheets, which combine nano-silicon and carbon materials (generally about 10 times higher than graphite anodes). This improves storage capacity and reduces the accumulation of lithium dendrites. In terms of structure, thinner electrode sheets are provided to reduce the local current density on the electrode sheet. In terms of process, laser engraving technology is used to add etched microgrooves at the edge of the electrode sheet to increase the electrolyte wetting area and ion intercalation area.

[0035] While the above methods can effectively reduce the growth of lithium dendrites, in order to further improve the effect, this embodiment improves the structure of the separator to further reduce the occurrence of lithium plating.

[0036] Reference Figure 1 As shown, this embodiment of the present invention provides a dual-domain pore gradient membrane 1, which includes a base membrane 110 and a coating region 120. The coating region 120 is coated on the base membrane 110. The coating region 120 includes two regions: a first coating portion 121 and a second coating portion 122. The first coating portion 121 is arranged to surround the second coating portion 122 to form a dual-domain structure. The porosity of the first coating portion 121 is φ1, and the porosity of the second coating portion 122 is φ2, where φ1 > φ2.

[0037] It should be further explained that, in this embodiment, the coating region 120 is provided with two different coating regions, a first coating portion 121 and a second coating portion 122, thereby forming a dual-domain structure on the coating region 120. Furthermore, the first coating portion 121 and the second coating portion 122 are configured with different porosities, thereby forming a porosity gradient difference on the first coating portion 121 and the second coating portion 122, which can effectively reduce the accumulation of lithium ions at the edge of the electrode, thereby reducing the phenomenon of lithium dendrite precipitation and reducing the risk of precipitation.

[0038] Because a coating region 120 is provided on the base film 110, wherein the coating region 120 includes a first coating portion 121 and a second coating portion 122, the first coating portion 121 is arranged around the second coating portion 122, and the porosity φ1 of the first coating portion 121 is greater than the porosity φ2 of the second coating portion 122, the ionic conductivity of the first coating portion 121 is higher. When this structure with different pore gradients is used in lithium-ion batteries, the lithium-ion battery has a faster transmission speed in the first coating portion 121, which can effectively reduce the accumulation of lithium ions at the edge of the electrode, thereby reducing the phenomenon of lithium dendrite precipitation and reducing the risk of precipitation.

[0039] It should also be noted that there are multiple ways to achieve a gradient porosity between the first coating portion 121 and the second coating portion 122. In this embodiment, four different implementation methods are listed: The first implementation method is achieved through regional coating, that is, by adjusting the nozzle pressure or speed of the coating machine to make the first coating part 121 in the edge area thinner or looser. This makes the particle density of the material in the first coating part 121 in the edge area less than the particle density of the material in the second coating part 122, thereby making the porosity φ1 of the first coating part 121 greater than the porosity φ2 of the second coating part 122, so as to form a membrane with a dual-domain structure and a porosity gradient. The second implementation involves segmented drying control, where a lower temperature is used when drying the edge region to reduce thermal shrinkage. This results in the average pore size of the first coating portion 121 located in the edge region being larger than the average pore size of the second coating portion 122, forming a membrane with a dual-domain structure and a porosity gradient. Pore size refers to the diameter of the pores in the membrane; the larger the pore size, the faster the ions migrate within the membrane. The third implementation is as follows: In the membrane structure with uniform pores, a coating containing hollow ceramic particles is superimposed again within the range of the first coating part 121 located in the edge region. The hollow ceramic particles can be Al2O3 hollow spheres, so that the first coating part 121 has a superimposed layer with internal pores, thereby increasing the porosity of the first coating part 121 and forming a membrane with a dual-domain structure and a porosity gradient. The fourth implementation: In a membrane structure with uniform pores, a portion of the coating material is removed from the area of ​​the first coating portion 121 located at the edge region to increase the porosity of the first coating portion 121, thereby forming a membrane with a dual-domain structure and a porosity gradient.

[0040] Of course, in other embodiments, the porosity φ1 of the first coating portion 121 can be made greater than the porosity φ2 of the second coating portion 122 by other means.

[0041] In some embodiments, refer to Figure 2 As shown, the coating region 120 has two layers, which are respectively coated on both sides of the base film 110. When this separator is used in a lithium battery, the two coating regions 120 can simultaneously optimize the ion transport path of the electrodes on both sides, thereby reducing the formation of lithium dendrites.

[0042] Therefore, in this embodiment, the coating region 120 is provided with two layers, and each of the two coating regions 120 is provided with two different coating areas, a first coating portion 121 and a second coating portion 122. Thus, a dual-domain structure is formed on both surfaces of the coating region 120. Furthermore, the first coating portion 121 and the second coating portion 122 are configured with different porosities, thereby forming a porosity gradient difference on the first coating portion 121 and the second coating portion 122. This effectively reduces the accumulation of lithium ions at the edge of the electrode, thereby reducing the phenomenon of lithium dendrite precipitation and lowering the risk of precipitation.

[0043] In some embodiments, φ2 ranges from 35% to 50%. In this embodiment, the second coating region 120 is the main lithium ion transport region in the electrode, and the range of porosity φ2 determines the transport characteristics of lithium ions in the second coating region 122. When the porosity is between 35% and 50%, the efficiency of ion transport can be guaranteed, while avoiding the decrease in coating strength due to excessive porosity or the obstruction of ion transport due to excessively low porosity. If the porosity φ2 is less than 35%, the second coating portion 122 may be too dense, resulting in a decrease in ion transport efficiency; if the porosity φ2 is greater than 50%, the second coating portion 122 may become too porous, resulting in a decrease in mechanical strength. Therefore, when used in lithium-ion batteries, lithium ions can move stably in the second coating portion 122 without generating large transport resistance due to excessively low porosity, or with excessively high porosity causing the coating to become too porous, thereby improving the overall performance of the battery.

[0044] In some embodiments, 3%≤φ 1- φ2≤8%. Increased porosity leads to increased liquid absorption, increased charge carriers, and increased conductivity. The limitation of the porosity difference φ1-φ2 ​​ensures a reasonable porosity gradient between the first coating section 121 and the second coating section 122, thereby effectively reducing the accumulation of lithium ions at the edge of the electrode. The high porosity of the first coating section 121 can quickly guide ions through, while the low porosity of the second coating section 122 can stabilize ion transport and prevent ions from accumulating at the electrode edge.

[0045] Accordingly, a porosity gradient difference can be formed on the first coating portion 121 and the second coating portion 122 to effectively reduce the accumulation of lithium ions at the edge of the electrode, thereby reducing the phenomenon of lithium dendrite precipitation and lowering the risk of precipitation.

[0046] In some embodiments, 5% ≤ φ1-φ2 ​​≤ 7%. Limiting the porosity difference φ1-φ2 ​​to this range not only creates a significant difference in conductivity, but also improves and mitigates the lithium plating effect. However, when the porosity difference is too large (e.g., the difference is 10% or more), it is highly likely to result in uneven electrolyte distribution, with localized dry areas accounting for more than 30%, thereby causing concentration polarization and a decrease in conductivity.

[0047] Secondly, referring to Figure 3 As shown, this utility model embodiment provides a secondary battery 2 using a dual-domain pore gradient separator, which further includes a first electrode 210 and a second electrode 220. A base film 110 is disposed between the first electrode 210 and the second electrode 220 to isolate the first electrode 210 and the second electrode 220.

[0048] Since the base film 110 is disposed between the first electrode 210 and the second electrode 220, and a coating region 120 is disposed on the base film 110, wherein the coating region 120 includes a first coating portion 121 and a second coating portion 122, the first coating portion 121 is disposed around the second coating portion 122, and the porosity φ1 of the first coating portion 121 is greater than the porosity φ2 of the second coating portion 122, the ionic conductivity of the first coating portion 121 is higher. When used in a lithium-ion battery, the lithium-ion battery has a faster transmission speed in the first coating portion 121, which can effectively reduce the accumulation of lithium ions at the edges of the first electrode 210 and the second electrode 220, thereby reducing the phenomenon of lithium dendrite precipitation and reducing the risk of precipitation.

[0049] In some embodiments, the orthographic projection of the edge of the first electrode 210 toward the coating region 120 and the orthographic projection of the edge of the second electrode 220 toward the coating region 120 are both located in the first coating portion 121. Therefore, the coating region 120 can cover the edges of the first electrode 210 and the second electrode 220, thereby completely enclosing the first electrode 210 and the second electrode 220, preventing direct contact between the first electrode 210 and the second electrode 220 and thus avoiding a short circuit, ensuring the normal use of the battery.

[0050] In some embodiments, the width of the first electrode 210 is greater than the width of the second electrode 220. The first coating portion 121 includes a plurality of sequentially connected side regions 1211. The distance between the boundary line of the side region 1211 away from the second coating portion 122 and the boundary line of the first electrode 210 is 0.5mm to 3mm. That is, in this embodiment, the boundary of the first coating portion 121 extends beyond the first electrode 210 by 0.5mm to 3mm. Therefore, by providing additional protection at the edges of the first electrode 210 and the second electrode 220, the formation of lithium dendrites can be significantly reduced, thereby improving the safety and lifespan of the battery. In addition, by setting the above parameters, it is also possible to avoid the boundary of the first coating portion 121 extending too far beyond the first electrode 210, thereby avoiding occupying too much internal space of the battery and causing unnecessary waste.

[0051] In some embodiments, the width of the first electrode 210 is greater than the width of the second electrode 220. The first coating portion 121 includes a plurality of sequentially connected side regions 1211. The distance between the boundary line of the side region 1211 near the second coating portion 122 and the boundary line of the first electrode 210 is 0.5mm to 4mm. Therefore, by setting the above parameters, it is possible to ensure that the overlap area between the first coating portion 121 and the first electrode 210 is sufficient, thereby improving and mitigating the lithium plating effect at the edge region of the first electrode 210. Simultaneously, it is also possible to prevent the overlap area between the first coating portion 121 and the first electrode 210 from being too large, thereby preventing significant impact on the lithium-ion transport of the first electrode 210 and ensuring normal battery operation.

[0052] It should also be noted that in this embodiment, the first electrode 210 is configured as a negative electrode and the second electrode 220 is configured as a positive electrode. In most battery configurations, the area of ​​the first electrode 210 is larger than the area of ​​the second electrode 220, and the edge of the first electrode 210 extends beyond the edge of the second electrode 220 by 1mm to 3mm. This area is called the Overhang area. When the edge of the first electrode 210 extends beyond the edge of the second electrode 220 by 1mm, the overlapping area between the first coating portion 121 and the first electrode 210 should be greater than 1mm. When the edge of the first electrode 210 extends beyond the edge of the second electrode 220 by 3mm, the overlapping area between the first coating portion 121 and the first electrode 210 should be greater than 3mm. This ensures that the overlapping area between the first coating portion 121 and the first electrode 210 exceeds the boundary of the Overhang area, guaranteeing that the edges of the first electrode 210 and the second electrode 220 both fall within the coverage area of ​​the first coating portion 121.

[0053] In other special batteries, when the area of ​​the first electrode 210 is smaller than the area of ​​the second electrode 220, similarly, the overlapping area of ​​the first coating portion 121 and the second electrode 220 should be made to extend beyond the boundary of the overhang region, ensuring that the edges of the first electrode 210 and the edges of the second electrode 220 both fall within the coverage area of ​​the first coating portion 121.

[0054] In some embodiments, refer to Figure 4 and Figure 5 As shown, the first electrode 210 includes a first part 211 and a second part 212 connected in sequence. The second part 212 is connected to the coating region 120. The first part 211 and the coating region 120 are spaced apart to form a first gap 213 between the first part 211, the second part 212 and the coating region 120, so as to reduce the local current density of the first electrode 210. By forming the first gap 213 on the first electrode 210, a thinning region of the first electrode 210 is formed on the first electrode 210. Therefore, the lithium ions extracted from the first electrode 210 can be smoothly inserted into the active material layer on the corresponding second electrode 220. In addition, in combination with the difference in porosity between the first coating part 121 and the second coating part 122, the phenomenon of lithium dendrite aggregation is effectively reduced, thereby effectively suppressing the lithium plating phenomenon of the secondary battery 2 cell during the charging and discharging process.

[0055] In some embodiments, refer to Figure 4 and Figure 5 As shown, the second electrode 220 includes a third part 221 and a fourth part 222 connected in sequence. The fourth part 222 is connected to the coating region 120, and the third part 221 is spaced apart from the coating region 120, so that a second gap is formed between the third part 221, the fourth part 222 and the coating region 120 to reduce the local current density of the second electrode 220. By forming a second gap on the second electrode 220, a thinning region of the second electrode 220 is formed, so that lithium ions extracted from the second electrode 220 can be smoothly inserted into the active material layer on the corresponding first electrode 210. Furthermore, in conjunction with the difference in porosity between the first coating part 121 and the second coating part 122, the phenomenon of lithium dendrite aggregation is effectively reduced, thereby effectively suppressing the lithium plating phenomenon of the secondary battery 2 cell during charging and discharging.

[0056] In some embodiments, a plurality of first portions 211 are provided, and the plurality of first portions 211 are arranged around the second portion 212; that is, in this embodiment, the first electrode 210 includes four first portions 211 disposed at its edge, which, in conjunction with the difference in porosity on the first coating portion 121 and the second coating portion 122, can better reduce the phenomenon of lithium dendrite aggregation, thereby reducing the lithium plating phenomenon of the secondary battery 2 cell during the charging and discharging process.

[0057] In some embodiments, multiple third portions 221 are provided, and the multiple third portions 221 are arranged around the fourth portion 222. That is, in this embodiment, the second electrode 220 includes four third portions 221 disposed at its edges. In conjunction with the difference in porosity on the first coating portion 121 and the second coating portion 122, the phenomenon of lithium dendrite aggregation can be better reduced, thereby reducing the lithium deposition phenomenon of the secondary battery 2 cell during the charging and discharging process.

[0058] In some embodiments, refer to Figure 4 As shown, along the direction away from the second part 212 in the first part 211, the size of the first notch 213 is the same; that is, in this embodiment, the notch shape of the first notch 213 is regular, thereby forming a regular region of reduced thickness on the first electrode 210, so as to accelerate the ionic conductivity on the first part 211 and improve the transport efficiency of lithium ions on the first part 211. Combined with the porosity difference between the first coating part 121 and the second coating part 122, it can more effectively reduce the accumulation of lithium ions at the edge of the electrode, which has an excellent promoting effect on the reduction of lithium dendrites and reduces the risk of lithium plating.

[0059] In some embodiments, refer to Figure 4 As shown, the second notch has the same size along the direction from the fourth part 222 away from the third part 221. That is, in this embodiment, the notch shape of the second notch is regular, thereby forming a regular region of reduced thickness on the first electrode 210 to accelerate the ionic conductivity on the third part 221 and improve the transport efficiency of lithium ions on the third part 221. Combined with the porosity difference between the first coating part 121 and the second coating part 122, it more effectively reduces the accumulation of lithium ions at the edge of the electrode, which has an excellent promoting effect on the reduction of lithium dendrites and reduces the risk of lithium plating.

[0060] In some embodiments, refer to Figure 5 As shown, along the direction of the first part 211 away from the second part 212, the size of the first notch 213 gradually increases; that is, in this embodiment, the notch shape of the first notch 213 is irregular, and along the direction of the first part 211 away from the second part 212, the notch surface of the first notch 213 gradually tilts, thereby making the thickness of the thinning area formed on the first electrode 210 gradually increase. Combined with the porosity difference between the first coating part 121 and the second coating part 122, it effectively reduces the accumulation of lithium ions at the edge of the electrode, has an excellent promoting effect on the reduction of lithium dendrites, and reduces the risk of lithium plating. In some embodiments, refer to Figure 5As shown, the size of the second notch gradually increases along the direction from the fourth part 222 away from the third part 221. That is, in this embodiment, the shape of the second notch is irregular, and the surface of the second notch gradually slopes along the direction from the fourth part 222 away from the third part 221, thereby gradually increasing the thickness of the thinning region formed on the second electrode 220. Combined with the porosity difference between the first coating part 121 and the second coating part 122, this effectively reduces the accumulation of lithium ions at the edge of the electrode, has an excellent promoting effect on the reduction of lithium dendrites, and reduces the risk of lithium plating.

[0061] In summary, in this embodiment, since a coating region 120 is provided on the base film 110, the coating region 120 includes a first coating portion 121 and a second coating portion 122 forming a dual-domain structure. Furthermore, the first coating portion 121 and the second coating portion 122 are configured with different porosities. The first coating portion 121 with a larger porosity is located at the edge of the coating region 120, resulting in a high ion permeability. The second coating portion 122 with a smaller porosity is located in the middle of the coating region 120, preventing the coating region from being too loose and ensuring the overall performance of the battery. Accordingly, a porosity gradient difference is formed on the first coating portion 121 and the second coating portion 122 to effectively reduce the accumulation of ions at the edge of the electrode, thereby reducing the phenomenon of lithium dendrite precipitation and lowering the risk of precipitation.

[0062] The embodiments of this utility model have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this utility model. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of this utility model. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this utility model. Therefore, the content of this specification should not be construed as a limitation of this utility model.

Claims

1. A dual-domain pore gradient membrane, characterized in that, include: Base film (110); A coating region (120) is coated on the base film (110). The coating region (120) includes a first coating portion (121) and a second coating portion (122). The first coating portion (121) is arranged around the second coating portion (122). The porosity of the first coating portion (121) is φ1, and the porosity of the second coating portion (122) is φ2, where φ1 > φ2.

2. The dual-domain pore gradient membrane according to claim 1, characterized in that, The coating area (120) has two layers, and the two coating areas (120) are respectively coated on both sides of the base film (110).

3. The dual-domain pore gradient membrane according to claim 1, characterized in that, The range of φ2 is 35%~50%.

4. The dual-domain pore gradient membrane according to any one of claims 1-3, characterized in that, 3%≤φ1-φ2≤8%.

5. The dual-domain pore gradient membrane according to claim 4, characterized in that, 5%≤φ1-φ2≤7%.

6. A secondary battery, characterized in that, Using the dual-domain pore gradient separator according to any one of claims 1-5, the secondary battery (2) further includes a first electrode (210) and a second electrode (220), and the base film (110) is disposed between the first electrode (210) and the second electrode (220) to isolate the first electrode (210) and the second electrode (220).

7. The secondary battery according to claim 6, characterized in that, The orthographic projection of the edge of the first electrode (210) toward the coating area (120) and the orthographic projection of the edge of the second electrode (220) toward the coating area (120) are both located in the first coating portion (121).

8. The secondary battery according to claim 6, characterized in that, The width of the first electrode (210) is greater than the width of the second electrode (220). The first coating portion (121) includes a plurality of side regions (1211) connected in sequence. The distance between the boundary line of the side region (1211) away from the second coating portion (122) and the boundary line of the first electrode (210) is 0.5mm to 3mm.

9. The secondary battery according to claim 6, characterized in that, The width of the first electrode (210) is greater than the width of the second electrode (220). The first coating portion (121) includes a plurality of side regions (1211) connected in sequence. The distance between the boundary line of the side region (1211) near the second coating portion (122) and the boundary line of the first electrode (210) is 0.5mm to 4mm.

10. The secondary battery according to claim 6, characterized in that, The first electrode (210) includes a first part (211) and a second part (212) connected in sequence. The second part (212) is connected to the coating area (120). The first part (211) and the coating area (120) are spaced apart to form a first gap (213) between the first part (211), the second part (212) and the coating area (120) to reduce the local current density of the first electrode (210). And / or, the second electrode (220) includes a third part (221) and a fourth part (222) connected in sequence. The fourth part (222) is connected to the coating area (120). The third part (221) and the coating area (120) are spaced apart to form a second gap (223) between the third part (221), the fourth part (222) and the coating area (120) to reduce the local current density of the second electrode (220).

11. The secondary battery according to claim 10, characterized in that, The first part (211) is provided in multiple ways, and the multiple first parts (211) are arranged around the second part (212); and / or, the third part (221) is provided in multiple ways, and the multiple third parts (221) are arranged around the fourth part (222).

12. The secondary battery according to claim 11, characterized in that, Along the direction of the first part (211) away from the second part (212), the first notch (213) has the same size; and / or, along the direction of the third part (221) away from the fourth part (222), the second notch (223) has the same size.

13. The secondary battery according to claim 11, characterized in that, Along the direction of the first part (211) away from the second part (212), the size of the first notch (213) gradually increases; and / or, along the direction of the third part (221) away from the fourth part (222), the size of the second notch (223) gradually increases.

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