Pole piece, preparation method thereof and secondary battery
By designing micro-holes and holes on the active material layer and substrate of the lithium-ion battery electrode sheet, the problem of reducing the electrolyte transmission capacity after the battery energy density is increased, and the battery cycle life is extended and the electrical performance is improved.
Patent Information
- Application Number
- CN202411892662.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-20
- Publication Date
- 2025-05-06
AI Technical Summary
With the increase in the energy density of lithium-ion batteries, the compaction density of the positive electrode sheet and the negative electrode sheet increases, the internal gap of the battery shrinks, and the microscopic gap limit of the active material layer leads to a decrease in the transmission and adsorption capacity of the electrolyte and a significant reduction in the battery cycle life.
An electrode sheet is designed, wherein the active material layer has several micro-pores in the thickness direction, with the diameter of the micro-pores ranging from 5 μm to 100 μm, and the total area accounts for 0.2 or less of the area of the active material layer. Micro-holes are formed on the active material layer by laser etching and other techniques, and holes are opened on the substrate to enhance the transmission channel of the electrolyte.
By increasing the transmission channel of the electrolyte, the infiltration speed and infiltration consistency of the electrolyte in the electrode sheet layer are improved, the cycle life of the battery is extended, and the gas exhaust problem in the battery is improved.
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Figure CN119943847A_ABST
Abstract
Description
Technical Field
[0001] The present application belongs to the technical field of lithium batteries, and more specifically, to a pole piece and a preparation method thereof and a secondary battery. Background Art
[0002] In the field of battery manufacturing, electrolyte is an important component of the battery and plays the role of transferring ions between the positive and negative electrodes of the battery. Therefore, the degree of electrolyte infiltration in the electrodes and the amount of liquid retained directly affect battery performance indicators such as battery energy density and cycle performance.
[0003] In the current lithium battery manufacturing, the positive electrode sheet, negative electrode sheet and diaphragm are mainly assembled into a battery by winding or lamination hot pressing. The electrolyte infiltration steps are: 1) The electrolyte is transmitted in the gap between the electrode sheet and the diaphragm; 2) The electrolyte is preferentially infiltrated and transferred in the pores of the diaphragm; 3) It diffuses to the electrode surfaces on both sides through the diaphragm and penetrates into the active material of the active material layer of the electrode sheet. Among them, the infiltration and filling of the electrolyte inside the active material of the active material layer is particularly slow and difficult, and it is necessary to accelerate the infiltration of the electrolyte at the material level by standing at high temperature for a long time, which has a certain impact on the manufacturing and production cost of lithium-ion batteries. At the same time, with the increase of battery energy density, the compaction density of the positive and negative electrode sheets is getting larger and larger, the gap inside the battery is getting smaller and smaller, the microscopic gap of the material itself of the active material layer is becoming more and more extreme, the ability of the coil to transmit and adsorb electrolytes is getting lower and lower, and the cycle life of the battery is greatly reduced. Summary of the invention
[0004] Based on this, one purpose of the present application is to provide a pole piece to solve the technical problems existing in the prior art that as the energy density of the battery increases, the compaction density of the positive and negative pole pieces becomes larger and larger, the gap inside the battery becomes smaller and smaller, the microscopic gaps of the material of the active material layer itself become more and more extreme, the ability of the core to transmit and adsorb electrolyte becomes lower and lower, and the cycle life of the battery is greatly reduced.
[0005] Another object of the present application is to provide a method for preparing a pole piece.
[0006] Another object of the present application is to provide a secondary battery.
[0007] To achieve the above purpose, the technical solution adopted in this application is:
[0008] A pole piece comprises a substrate and an active material layer, wherein the active material layer is attached to at least one of the two sides of the substrate, and the active material layer has a plurality of micro holes in the thickness direction thereof.
[0009] Optionally, the diameter of the micropores is 5 μm-100 μm.
[0010] Optionally, the total area of the plurality of micropores is M, the area of the surface where the plurality of micropores are located in the active material layer is N, and M and N satisfy: 0<M / N≤0.2.
[0011] Optionally, the morphology of the plurality of micro holes is at least one of a through hole, a blind hole and a concave groove.
[0012] Optionally, the plurality of micropores are evenly and regularly distributed in the thickness direction of the active material layer.
[0013] Optionally, the substrate is provided with a plurality of holes in the thickness direction thereof, and at least some of the holes are filled with active substances.
[0014] Optionally, the diameter of the holes is ≤15 μm.
[0015] Optionally, the total area of the plurality of holes is X, the area of the surface of the substrate where the holes are located is Y, and X and Y satisfy: 0<X / Y≤0.15.
[0016] Optionally, a plurality of holes are evenly and regularly distributed on the substrate.
[0017] Optionally, the substrate is copper foil or aluminum foil.
[0018] Optionally, the active material layer is a positive electrode slurry layer or a negative electrode slurry layer.
[0019] And, the method for preparing the above-mentioned pole piece comprises the following steps:
[0020] Applying active material slurry to at least one side of the substrate, drying, forming an active material layer, and obtaining an initial electrode;
[0021] The initial pole piece is rolled and compacted, and laser etching is performed on the compacted active material layer to form a number of micro holes in the thickness direction, and then die-cutting is performed to obtain the pole piece.
[0022] Optionally, before the step of coating the active material slurry on at least one side of the substrate, the following steps are further included:
[0023] Performing a pore forming process on the initial substrate to form a plurality of holes in the thickness direction to obtain a substrate;
[0024] When the active material slurry is coated on at least one side of the substrate, part of the active material slurry is filled in the pores.
[0025] Optionally, the pore forming treatment method in the initial substrate includes at least one of plasma etching, acid electrolysis and electrochemical corrosion.
[0026] Optionally, the method for performing micropore forming processing on the compacted active material layer is laser etching.
[0027] And, a secondary battery comprising the above-mentioned electrode sheet.
[0028] The beneficial effects of this application are:
[0029] The electrode provided by the present application has micropores in the thickness direction of the active material layer, which can increase the internal space when the active material layer is in close contact with the diaphragm. The formed micropore capillaries have the ability to quickly siphon the electrolyte on the diaphragm, so that the electrolyte on the surface of the active material layer can quickly penetrate into the interior of the active material layer, thereby achieving the ability to quickly infiltrate the active material layer; on the other hand, the micropores on the surface of the active material layer can provide an exhaust channel for the gas generated by the internal formation of the battery, thereby improving the battery interface problem caused by the difference in battery formation and exhaust;
[0030] Compared with the prior art, the electrode provided by the present application increases the transmission channel of the electrolyte. Even if the compaction density of the positive electrode and the negative electrode is large and the gap inside the battery is small, the electrolyte can be transmitted through the micropores of the active material layer, thereby improving the ability of the winding core to transmit and absorb the electrolyte, thereby improving the degree of electrolyte infiltration in the electrode and increasing the cycle life of the battery.
[0031] The method for preparing the pole piece provided in the present application complies with the structural characteristics of the pole piece, and produces a pole piece with excellent performance, simple operation and high production efficiency;
[0032] The secondary battery provided in the present application is made of the electrode sheet provided in the present application, which effectively increases the cycle life of the battery and improves the electrical performance of the battery. BRIEF DESCRIPTION OF THE DRAWINGS
[0033] The present invention will be further described below in conjunction with the accompanying drawings and embodiments, in which:
[0034] Figure 1 A schematic cross-sectional view of a pole piece according to an embodiment of the present application;
[0035] Figure 2 It is a schematic diagram of the structure of the substrate in the pole piece of an embodiment of the present application.
[0036] Description of reference numerals:
[0037] 1. Pole piece; 10. Matrix; 11. Holes; 20. Active material layer; 21. Micropores; 30. Active material. DETAILED DESCRIPTION
[0038] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.
[0039] See also Figure 1 and Figure 2 The embodiment of the present application provides a pole piece 1, comprising a substrate 10 and an active material layer 20, wherein the active material layer 20 is attached to at least one of the two sides of the substrate 10, and the active material layer 20 has a plurality of micropores 21 in the thickness direction thereof.
[0040] The electrode 1 provided in the embodiment of the present application has a plurality of micropores 21 in the thickness direction of the active material layer 20 in addition to the micropores of the material itself. The micropores 21 on the surface of the active material layer 20 can increase the internal space when the active material layer 20 is in close contact with the diaphragm, and the formed micropore capillaries have the ability to quickly siphon the electrolyte on the diaphragm, so that the electrolyte on the surface of the active material layer 20 can quickly penetrate into the interior of the active material layer 20, thereby achieving the ability to quickly infiltrate the active material layer 20; on the other hand, the micropores 21 on the surface of the active material layer 20 can provide an exhaust channel for the gas generated by the internal formation of the battery, thereby improving the battery interface problem caused by the difference in battery formation and exhaust.
[0041] In some preferred embodiments of the present application, the structure is as follows Figure 1 As shown, the active material layer 20 is attached to both sides of the substrate 10 through the thickness.
[0042] In some embodiments of the present application, the diameter of the several micropores 21 of the active material layer 20 is 5μm-100μm, and the diameter of the several micropores 21 on the active material layer 20 is within 100μm. If the pore size is too large, for example, greater than 100μm, the loss of active material is large, which will exceed the capacity setting threshold of the battery, causing problems such as low capacity. If the pore size of the micropore 21 is too small, for example, less than 5μm, the capillary force of the micropore deteriorates, the transfer speed of the electrolyte does not increase significantly, and the infiltration gain effect is not significant. In some preferred embodiments, the diameter of the micropore 21 is preferably 10μm-30μm.
[0043] In some embodiments of the present application, the total area of the plurality of micropores 21 is M, the area of the surface of the active material layer 20 where the plurality of micropores 21 are located is N, and M and N satisfy: 0<M / N≤0.2, that is, the total area of the micropores 21 is less than or equal to 1 / 5 of the area of the surface where the active material layer 20 is located, so as to ensure that the loss of active material in the active material layer 20 does not exceed the capacity design of the battery.
[0044] In some embodiments of the present application, the morphology of several micro holes 21 is at least one of a through hole, a blind hole and a concave groove, that is, the micro hole can be a through hole, a blind hole or a concave groove, or it can contain two or three morphologies at the same time, such as a combination of through holes and blind holes, a combination of through holes and concave grooves, a combination of blind holes and concave grooves, a combination of through holes, blind holes and concave grooves, etc.
[0045] In the embodiments of the present application, a through hole refers to a micro hole that penetrates the active material layer, and no active material adheres to the substrate at the location of the micro hole; a blind hole refers to a micro hole that does not penetrate the active material layer, and a certain amount of active material adheres to the substrate at the location of the micro hole; a concave groove is a linear groove formed by closely arranged through holes or blind holes.
[0046] In some embodiments of the present application, a plurality of micropores 21 are evenly and regularly distributed on the active material layer 20. Preferably, the area where these evenly and regularly distributed micropores 21 are located forms a through hole, a blind hole and / or a concave groove-shaped hole groove area, which can tend to uniformly and quickly transport electrolyte to a certain area, thereby facilitating the design and adjustment of the electrolyte transmission speed in a certain area.
[0047] In some embodiments of the present application, Figure 1 As shown, the substrate 10 is provided with a plurality of holes 11 in the thickness direction thereof, and at least part of the holes 11 are filled with active material 30 .
[0048] The holes 11 on the substrate 10 increase the surface roughness of the substrate 10, increase the surface tension of the substrate 10, and improve the adhesion of the active material layer 20 on the surface of the substrate 10. At the same time, the holes 11 on the surface of the substrate 10 can form capillaries, thereby siphoning the electrolyte in the micropores 21 of the active material layer 20 and the gaps between the materials, thereby increasing the electrolyte storage capacity and improving the ability of the electrode to quickly infiltrate the electrolyte.
[0049] The holes 11 on the substrate 10 provide a channel for the transmission of battery electrolyte, and the double capillaries and double electrolyte storage channels formed by the micropores 21 on the active material layer 20 accelerate the transfer speed of electrolyte between the layers of the electrode 1 and the holes of the active material layer 20, and improve the electrolyte infiltration speed and consistency of the electrode 1. At the same time, the space where several holes 11 converge can store a large amount of electrolyte. The battery will consume a large amount of electrolyte during the cycle. When the battery's liquid retention is improved, the battery's cycle life will also be improved; on the other hand, the holes 11 of the electrode 1 can provide an exhaust channel for the gas generated by the internal formation of the battery, thereby improving the battery interface problem caused by the difference in battery formation and exhaust.
[0050] In some embodiments of the present application, the diameter of the hole 11 is ≤15μm, and the aperture of the hole 11 on the substrate 10 is within 15μm. If the aperture is too large, for example, larger than 15μm, the risk of irregular sawtooth around the hole 11 will increase, the tensile strength of the substrate 10 will deteriorate, and the substrate 10 is prone to abnormal process problems such as broken tape and wrinkling during the coating process. In some preferred embodiments, the diameter of the hole 11 is preferably 3μm-10μm. If the aperture of the hole 11 is too small, for example, less than 3μm, the capillary effect of the hole 11 will deteriorate, the transfer speed of the electrolyte will not increase significantly, and the wetting gain effect will not be significant.
[0051] In some embodiments of the present application, the total area of the plurality of holes 11 is X, the area of the surface of the substrate 10 where the holes 11 are located is Y, and X and Y satisfy: 0<X / Y≤0.15, that is, the total area of the holes 11 is less than or equal to 3 / 20 of the area of the surface where the substrate 10 is located, so as to ensure the overall tensile strength of the substrate 10.
[0052] In some embodiments of the present application, a plurality of holes 11 are evenly and regularly distributed on the substrate 10. Preferably, the area where the evenly and regularly distributed holes 11 are located forms a hole zone, which can tend to uniformly and quickly transport electrolyte to a certain area, thereby facilitating the design and adjustment of the electrolyte transport speed in a certain area.
[0053] In some embodiments of the present application, the substrate 10 is a copper foil or an aluminum foil.
[0054] In some embodiments of the present application, the active material layer 30 is a positive electrode slurry layer or a negative electrode slurry layer. When the active material layer 30 is a positive electrode slurry layer, the pole piece 1 is a positive electrode pole piece; when the active material layer 30 is a negative electrode slurry layer, the pole piece 1 is a negative electrode pole piece.
[0055] Compared with the prior art, the electrode 1 provided in the embodiment of the present application increases the transmission channel of the electrolyte. Even if the compaction density of the positive electrode and the negative electrode is large and the gaps and voids inside the battery material are small, the electrolyte can be transmitted through the holes and micro-pores in the active material layer, thereby improving the ability of the winding core to transmit and adsorb the electrolyte, thereby increasing the degree of electrolyte infiltration in the electrode 1 and increasing the cycle life of the battery.
[0056] The present application also provides a method for preparing the pole piece 1, comprising the following steps:
[0057] S1: coating the active material slurry on at least one side of the substrate 10, drying it, forming an active material layer 21, and obtaining an initial electrode sheet.
[0058] The active material slurry is coated on the substrate 10 , and the active material slurry infiltrates the surface of the substrate 10 . After drying, the active material slurry coated on the surface of the substrate 10 forms an active material layer 20 .
[0059] S2: Roll-compacting the initial pole piece, performing micropore forming treatment on the compacted active material layer 21 to form a plurality of micropores 21 in the thickness direction, and then die-cutting to obtain the pole piece 1.
[0060] In some embodiments of the present application, the method for performing micropore forming processing on the compacted active material layer 20 is laser etching, which can accurately control the morphology and distribution pattern of the micropores 21.
[0061] In some embodiments of the present application, the following steps are also included before step S1:
[0062] S1-1: performing a pore forming process on the initial substrate to form a plurality of holes 11 in the thickness direction to obtain a substrate 10;
[0063] When the active material slurry is coated on at least one surface of the substrate 10 , a portion of the active material slurry is filled in the pores 11 .
[0064] When the active material slurry is coated on the substrate 10 , part of the active material slurry penetrates into the pores 11 . After drying, the active material slurry filled in the pores 11 forms active material solids.
[0065] The hole forming method can adopt a variety of hole forming processing methods. In some embodiments of the present application, the hole forming method includes at least one of plasma etching, pickling electrolysis and electrochemical corrosion. Through plasma etching, pickling electrolysis or electrochemical corrosion, or a combination of two of them, holes with smaller apertures can be formed, with good forming effect and fast processing speed.
[0066] It should be noted that the initial substrate in the embodiment of the present application is the substrate 1 that has not been subjected to pore forming treatment.
[0067] The method for preparing the pole piece 1 provided in the embodiment of the present application complies with the structural characteristics of the pole piece 1, and produces a pole piece 1 with excellent performance, which is simple to operate and has high production efficiency.
[0068] The embodiment of the present application also provides a secondary battery including the above-mentioned pole piece 1, which is manufactured using the pole piece 1 provided in the embodiment of the present application, effectively increasing the cycle life of the battery and improving the electrical performance of the battery.
[0069] The following uses a number of embodiments to illustrate aspects such as the electrode and its preparation method and the performance of the secondary battery.
[0070] Example 1
[0071] The positive electrode sheet of this embodiment includes a positive electrode substrate and an active material layer. The positive electrode substrate is aluminum foil, and the active material layer is a positive electrode slurry layer. The positive electrode substrate has a plurality of holes in its thickness direction, and at least some of the holes are filled with positive electrode slurry solids; the positive electrode slurry layer is attached to both sides of the thickness of the positive electrode substrate. The diameter of the hole is 7μm, and the total area of the plurality of holes accounts for 0.03 of the area of the surface of the substrate where the holes are located.
[0072] The negative electrode sheet of this embodiment includes a negative electrode substrate and an active material layer. The negative electrode substrate is a copper foil, and the active material layer is a negative electrode slurry layer. The negative electrode substrate has a plurality of holes in its thickness direction, and at least some of the holes are filled with negative electrode slurry solids; the negative electrode slurry layer is attached to both sides of the thickness of the negative electrode substrate. The diameter of the hole is 10μm, and the total area of the plurality of holes accounts for 0.05 of the area of the surface of the substrate where the holes are located.
[0073] The method for preparing the positive electrode sheet of this embodiment comprises the following steps:
[0074] S1: A plasma etching method is used to perform pore forming treatment on the initial positive electrode substrate, forming a plurality of holes with a diameter of 7 μm in the thickness direction to obtain a positive electrode substrate.
[0075] S2: coating the positive electrode slurry on both sides of the positive electrode substrate, partially filling the pores with the positive electrode slurry, and drying the positive electrode slurry coated on the surface of the positive electrode substrate to form a positive electrode slurry layer to obtain an initial positive electrode sheet.
[0076] S3: Roll-compact the initial positive electrode sheet, perform laser etching on the compacted positive electrode slurry layer to form a number of micro holes in the thickness direction, the micro holes are concave grooves, the width of the concave grooves is 10 μm, and then die-cut to obtain the positive electrode sheet.
[0077] The method for preparing the negative electrode sheet of this embodiment comprises the following steps:
[0078] S1: A plasma etching method is used to perform pore forming treatment on the initial substrate of the negative electrode, and a plurality of holes with a diameter of 10 μm are formed in the thickness direction to obtain a substrate.
[0079] S2: coating the negative electrode slurry on both sides of the substrate, partially filling the pores with the negative electrode slurry, and drying the negative electrode slurry coated on the surface of the negative electrode substrate to form a negative electrode slurry layer to obtain an initial negative electrode sheet.
[0080] S3: Roll-compact the initial negative electrode sheet, perform laser etching on the compacted negative electrode slurry layer to form a number of micro holes in the thickness direction, the micro holes are concave grooves, the width of the concave grooves is 10 μm, and then die-cut to obtain the negative electrode sheet.
[0081] S3: The obtained positive electrode sheet and negative electrode sheet are wound or stacked together with the separator to form a battery core, and the core is shelled, injected, packaged, formed and tested to obtain a finished battery cell.
[0082] Example 2
[0083] The positive electrode sheet of this embodiment includes a positive electrode substrate and a positive electrode slurry layer, the positive electrode substrate is not processed by the pore generation process, and the conventional positive electrode slurry layer is attached to the two sides of the thickness of the positive electrode substrate. The positive electrode substrate is aluminum foil.
[0084] The negative electrode sheet of this embodiment includes a negative electrode substrate and a negative electrode slurry layer, the negative electrode substrate is not processed by the hole generation process; the conventional negative electrode slurry layer is attached to both sides of the negative electrode substrate. The negative electrode substrate is copper foil.
[0085] The method for preparing the positive electrode sheet of this embodiment comprises the following steps:
[0086] S1: The positive electrode slurry is coated on both sides of the aluminum foil respectively, and after drying, a positive electrode slurry layer is formed on the surface of the aluminum foil to obtain an initial positive electrode sheet.
[0087] S2: Roll-compact the initial positive electrode sheet, perform laser etching on the compacted positive electrode slurry layer, form a number of micro holes in the thickness direction, the micro holes are concave grooves, the width of the concave grooves is 15 μm, and die-cut to obtain the positive electrode sheet.
[0088] S3: coating the negative electrode slurry on both sides of the copper foil respectively, and drying to form a negative electrode slurry layer on the surface of the copper foil to obtain an initial negative electrode sheet.
[0089] S4: Roll-compact the initial negative electrode sheet, perform laser etching on the compacted negative electrode slurry layer, form a number of micro holes in the thickness direction, the micro holes are concave grooves, the width of the concave grooves is 15 μm, and die-cut to obtain the negative electrode sheet.
[0090] S5: The obtained positive electrode sheet, negative electrode sheet and separator are wound or stacked together to form a battery core, and the core is shelled, injected, packaged, formed and tested to obtain a finished battery cell.
[0091] Example 3
[0092] The positive electrode sheet of this embodiment includes a positive electrode substrate and a positive electrode slurry layer. The positive electrode substrate has a plurality of holes in its thickness direction, and at least some of the holes are filled with positive electrode slurry solids; the positive electrode slurry layer is attached to both sides of the thickness of the positive electrode substrate. The diameter of the hole is 5μm, and the total area of the plurality of holes accounts for 0.04 of the area of the surface of the substrate where the holes are located. The positive electrode substrate is aluminum foil.
[0093] The negative electrode sheet of this embodiment includes a negative electrode substrate and a negative electrode slurry layer. The negative electrode substrate has a plurality of holes in its thickness direction, and at least some of the holes are filled with negative electrode slurry solids; the negative electrode slurry layer is attached to both sides of the thickness of the negative electrode substrate. The diameter of the hole is 6μm, and the total area of the plurality of holes accounts for 0.05 of the area of the surface of the substrate where the holes are located. The negative electrode substrate is copper foil.
[0094] The method for preparing the positive electrode sheet of this embodiment comprises the following steps:
[0095] S1: A plasma etching method is used to perform pore forming treatment on the initial positive electrode substrate, forming a plurality of holes with a diameter of 5 μm in the thickness direction to obtain a positive electrode substrate, and the total area of the plurality of holes accounts for 0.04 of the area of the surface of the substrate where the holes are located.
[0096] S2: coating the positive electrode slurry on both sides of the positive electrode substrate, partially filling the pores with the positive electrode slurry, and drying the positive electrode slurry coated on the surface of the positive electrode substrate to form a positive electrode slurry layer to obtain an initial positive electrode sheet.
[0097] S3: The initial positive electrode sheet is rolled and compacted, and laser etching is performed on the compacted positive electrode slurry layer to form a number of micro holes in the thickness direction. The micro holes are concave grooves with a width of 12 μm, and then die-cutting is performed to obtain the positive electrode sheet.
[0098] S4: A plasma etching method is used to perform pore forming treatment on the negative electrode initial substrate, forming a plurality of holes with a diameter of 6 μm in the thickness direction to obtain a negative electrode substrate, and the total area of the plurality of holes accounts for 0.05 of the area of the surface of the substrate where the holes are located.
[0099] S5: coating the negative electrode slurry on both sides of the negative electrode substrate, partially filling the pores with the negative electrode slurry, and drying the negative electrode slurry coated on the surface of the negative electrode substrate to form a negative electrode slurry layer to obtain an initial negative electrode sheet.
[0100] S6: Roll-compact the initial negative electrode sheet, perform laser etching on the compacted negative electrode slurry layer to form a number of micro holes in the thickness direction, the micro holes are concave grooves, the width of the concave grooves is 8 μm, and then die-cut to obtain the negative electrode sheet.
[0101] S7: The obtained positive electrode sheet, negative electrode sheet and separator are wound or stacked together to form a battery core, and the core is shelled, injected, packaged, formed and tested to obtain a finished battery cell.
[0102] Comparative Example 1
[0103] The positive electrode sheet of this comparative example includes a positive electrode substrate and a positive electrode slurry layer, the positive electrode substrate is not processed by a pore generation process, and a conventional positive electrode slurry layer is attached to both sides of the thickness of the positive electrode substrate. The positive electrode substrate is aluminum foil.
[0104] The negative electrode sheet of this comparative example includes a negative electrode substrate and a negative electrode slurry layer, the negative electrode substrate is not processed by a hole generation process, and a conventional negative electrode slurry layer is attached to both sides of the negative electrode substrate. The negative electrode substrate is a copper foil.
[0105] The preparation method of the positive electrode sheet of this comparative example comprises the following steps:
[0106] S1: The positive electrode slurry is coated on both sides of the aluminum foil, and the negative electrode slurry is coated on both sides of the copper foil, and the positive electrode sheet and the negative electrode sheet are obtained through drying, rolling and die-cutting.
[0107] S2: The obtained positive electrode sheet, negative electrode sheet and separator are wound together to form a battery core, and the core is shelled, injected, packaged, formed and tested to obtain a finished battery cell.
[0108] The batteries prepared in Examples 1-3 and Comparative Example 1 are all 314Ah batteries, and the electrolyte wettability test is performed on these batteries. The test method is as follows.
[0109] Electrolyte wettability standard method 1:
[0110] The battery cells of the embodiment and the comparative example were injected with the same amount of electrolyte, about 1136g, and left at high temperature for 10 hours. The battery after high temperature was disassembled, and the flowing electrolyte in the battery was poured into a beaker, and the amount of flowing electrolyte in the beaker was weighed to characterize the electrolyte infiltration effect of the battery. The test results are shown in Table 1.
[0111] Table 1
[0112] Amount of electrolyte injected / g Mobile electrolyte / g Adsorption electrolyte / g Implementation Case 1 1136 75.5 1060.5 Implementation Case 2 1136 81 1055 Implementation Case 3 1136 125.3 1010.7 Comparative Case 1 1136 137.4 998.6
[0113] From the test results, it can be seen that the batteries of Examples 1-3 have better electrolyte adsorption capabilities. Part of the electrolyte injected into the battery is adsorbed by the micropores of the positive electrode sheet, the negative electrode sheet and the diaphragm, and the other part exists in the gap between the electrode core and the shell in the form of flowing electrolyte.
[0114] Among them, the amount of flowing electrolyte in Examples 1-3 is 75.5g, 81g, and 125.3g, respectively, which is much smaller than 137.7g in Comparative Example 1, proving that the battery of the embodiment has good electrolyte infiltration ability, can significantly increase the electrolyte injection amount of the battery, and is beneficial to increasing the service life of the battery.
[0115] Electrolyte Wettability Standard Method 2:
[0116] The batteries of Examples 1-3 and Comparative Example 1 were formed and divided into different capacities. The capacity of the formed capacity and the divided capacity charged to 3.65V was the first charge capacity. The capacity of the battery discharged from 3.65V to 2.5V was the first discharge capacity. The first charge and discharge efficiency was: first discharge capacity / first charge capacity*100%. The test results are shown in Table 2.
[0117] Table 2
[0118]
[0119] By comparing the first discharge capacity and the first charge and discharge efficiency, it was found that the first charge and discharge efficiency and discharge capacity of Examples 1-3 were better than those of Comparative Example 1. After the surface of the electrode was fully infiltrated with the electrolyte, the lithium ion deintercalation of the positive electrode lithium iron phosphate and the lithium ion embedding of the negative electrode graphite would be more efficient, and the corresponding battery capacity and first charge and discharge efficiency would be further improved.
[0120] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application should be included in the protection scope of the present application.
Claims
1. A pole piece, characterized in that: The invention comprises a substrate (10) and an active material layer (20), wherein the active material layer (20) is attached to at least one of two sides of the substrate (10) in thickness, and the active material layer (20) has a plurality of micro holes (21) in the thickness direction thereof.
2. The pole piece according to claim 1, characterized in that: The diameter of the micropores (21) is 5 μm-100 μm; and / or, The total area of the plurality of micropores (21) is M, the area of the surface of the active material layer (20) where the plurality of micropores (21) are located is N, and M and N satisfy: 0<M / N≤0.
2.
3. The pole piece according to claim 1, characterized in that: The micro hole (21) has a shape of at least one of a through hole, a blind hole and a concave groove; and / or, The plurality of micropores (21) are evenly and regularly distributed in the thickness direction of the active material layer (20).
4. The pole piece according to claim 1, characterized in that: The substrate (10) is provided with a plurality of holes (11) in the thickness direction thereof, and at least some of the holes (11) are filled with active substances (30).
5. The pole piece according to claim 4, characterized in that: The diameter of the hole (11) is ≤15 μm; and / or, The total area of the plurality of holes (11) is X, the area of the surface of the substrate (10) where the holes (11) are located is Y, and X and Y satisfy: 0<X / Y≤0.15; and / or, The plurality of holes (11) are evenly and regularly distributed on the substrate (10).
6. The pole piece according to claim 1, characterized in that: The substrate (10) is copper foil or aluminum foil; and / or, The active material layer (20) is a positive electrode slurry layer or a negative electrode slurry layer.
7. A method for preparing a pole piece according to any one of claims 1 to 6, characterized in that: The following steps are involved: Applying active material slurry to at least one side of the substrate (10), drying, forming an active material layer (20), and obtaining an initial electrode; The initial pole piece is rolled and compacted, a micropore forming process is performed on the compacted active material layer (20) to form a plurality of micropores (21) in the thickness direction, and then die-cutting is performed to obtain a pole piece.
8. The method for preparing a pole piece according to claim 7, characterized in that: Before the step of coating the active material slurry on at least one side of the substrate (10), the following steps are also included: Performing a pore forming process on the initial substrate to form a plurality of holes (11) in the thickness direction to obtain the substrate (10); When the active material slurry is coated on at least one side of the substrate (10), part of the active material slurry fills the holes (11).
9. The method for preparing a pole piece according to claim 8, characterized in that: The pore forming treatment method of the initial substrate comprises at least one of plasma etching, pickling electrolysis and electrochemical corrosion; and / or, The method for performing micropore forming processing on the compacted active material layer (20) is laser etching.
10. A secondary battery, characterized in that: A pole piece comprising any one of claims 1 to 6.