Secondary battery and electronic device

Abstract

This application provides a secondary battery and an electronic device. The secondary battery includes an electrode, which includes a current collector and a material layer disposed on at least one surface of the current collector. The material layer includes a first material layer and a second material layer. Along the thickness direction of the electrode, the first material layer is located between the second material layer and the current collector. The current collector has a porous structure, with the pore size of a single pore being D μm, where 0.1 ≤ D ≤ 10. Along the length direction of the unfolded electrode, the spacing between two adjacent pores is L1 μm, where 10D ≤ L1 ≤ 1000D. Along the width direction of the unfolded electrode, the spacing between two adjacent pores is L2 μm, where 10D ≤ L2 ≤ 100D. The tensile strength of the current collector is σ MPa, where 180 ≤ σ ≤ 650. Through the above configuration, while considering processing performance, the adhesion of the electrode is improved, and the wetting of the secondary battery by the electrolyte is enhanced, resulting in good kinetic performance of the secondary battery.

Description

Technical Field

[0001] This application relates to the field of electrochemical technology, and in particular to a secondary battery and electronic device. Background Technology

[0002] Secondary batteries, especially lithium-ion batteries (LIBs), possess high energy density (ED) and long lifespan, and are widely used in portable devices (mobile phones, drones, power tools, etc.), electric vehicles (EVs / HEVs / PHEVs, etc.), and energy storage. With the widespread application of lithium-ion batteries in various fields, the market is placing higher demands on their energy density and kinetic performance to meet the needs of increasingly diverse application scenarios.

[0003] Currently, products on the market typically use a complete current collector, increasing the energy density of lithium-ion batteries by increasing the size of individual cells. However, increasing the size of lithium-ion batteries makes it more difficult for the electrolyte to wet the electrodes after injection, leading to problems at the lithium-ion battery interface and the risk of decreased kinetic performance. Furthermore, current cylindrical lithium-ion batteries use a full-tab structure, with the electrolyte injected from the center, allowing only unidirectional upward wetting from the bottom. As the size of lithium-ion batteries increases, electrolyte wetting of the electrodes becomes increasingly difficult, affecting the kinetic performance of the lithium-ion battery. Summary of the Invention

[0004] The purpose of this application is to provide a secondary battery and an electronic device that, while taking into account the processing performance of the secondary battery, improves the adhesion of the electrode sheets and improves the wetting of the secondary battery by the electrolyte, thereby improving the dynamic performance of the secondary battery.

[0005] It should be noted that while this application uses lithium-ion batteries as an example of secondary batteries to explain the invention, the secondary batteries in this application are not limited to lithium-ion batteries. The specific technical solution is as follows:

[0006] The first aspect of this application provides a secondary battery, comprising an electrode, a current collector, and a material layer disposed on at least one surface of the current collector. The material layer comprises a first material layer and a second material layer, wherein the first material layer is located between the second material layer and the current collector along the thickness direction of the electrode. The current collector has a porous structure, with a pore diameter of D μm, 0.1≤D≤10, optionally 0.5≤D≤5. Along the length direction of the unfolded electrode, the spacing between two adjacent pores is L1 μm, 10D≤L1≤1000D; along the width direction of the unfolded electrode, the spacing between two adjacent pores is L2 μm, 10D≤L2≤100D; the tensile strength of the current collector is σMPa, 180≤σ≤650. By setting pores within the scope of this application on the current collector and simultaneously applying a double-layer coating on the current collector, the wetting path of the electrolyte in the electrode is increased, improving the electrolyte's wetting of the electrode. Especially in cylindrical secondary batteries, this improves the wetting of the electrode assembly in both the radial and vertical directions, providing more channels for ion transport within the secondary battery, which is beneficial for lithium-ion transport. This reduces the temperature rise of the secondary battery, improves its high-rate discharge performance, and enhances its kinetic performance. Furthermore, by controlling the tensile strength of the current collector within the scope of this application, the current collector possesses a certain mechanical strength. During subsequent electrode coating, rolling, and other processing, the risk of current collector breakage is reduced, ensuring the integrity of the electrode. This improves processing efficiency and product quality, ultimately enhancing the processing performance of the secondary battery.

[0007] In one or more embodiments of this application, the first material layer includes a first active material with a Dv50 of D1 μm and 0.1 ≤ D1 ≤ 10; and / or, the second material layer includes a second active material with a Dv50 of D2 μm and 1 ≤ D2 ≤ 20. By adjusting the values ​​of D1 and / or D2 within the above ranges, the particle size of the first active material is smaller and the particle size of the second active material is larger, which is beneficial for optimizing the wetting path of the electrolyte in the material layer, thereby improving the wetting of the electrode by the electrolyte, reducing the temperature rise of the secondary battery, improving the high-rate discharge performance of the secondary battery, and improving the kinetic performance of the secondary battery.

[0008] In one or more embodiments of this application, 1.5 ≤ D2 / D1 ≤ 200. By adjusting the value of D2 / D1 within the above range, the large particles of the second active material in the upper layer, combined with the small particles of the first active material in the lower layer, increase the porosity of the electrode surface. This increases the wetting path of the electrolyte in the electrode, which is beneficial for electrolyte wetting and ion diffusion from the electrode surface to the inner layer and through the current collector pores. This reduces ion resistance, further improves electrolyte wetting of the electrode, reduces the risk of poor electrode interface wetting, thereby reducing the temperature rise of the secondary battery, improving the high-rate discharge performance of the secondary battery, and further improving the kinetic performance of the secondary battery.

[0009] In one or more embodiments of this application, the thickness of the first material layer is H1 μm, the thickness of the second material layer is H2 μm, 0.2 ≤ H1 / H2 ≤ 5, and 20 ≤ H2 ≤ 100. By adjusting the values ​​of H1 / H2 and H2 within the above range, the thickness of the material layers is moderate, resulting in a high energy density for the secondary battery. Furthermore, the moderate thickness ratio of the first to second material layers is beneficial for improving the bonding force between the material layers, thereby enhancing the overall adhesion of the electrode. In addition, it facilitates the uniform distribution of the electrolyte in the electrode pores, reducing ion resistance and improving electrolyte wetting of the electrode, thus reducing the risk of poor electrode interface wetting. This, in turn, reduces the temperature rise of the secondary battery, improves its high-rate discharge performance, and enhances its kinetic performance.

[0010] In one or more embodiments of this application, along the width direction after the electrode is unfolded, the current collector has a first edge and a second edge, and the shortest distance between a single hole and the first edge or the second edge is L3 μm, where 300 ≤ L3 ≤ 5000. By adjusting the value of L3 within the above range, the edge of the current collector has high mechanical strength, reducing the risk of current collector breakage and / or tearing during processing, thus maintaining good integrity of the current collector. This is beneficial for improving processing efficiency and product quality, and also reduces the risk of electrolyte accumulation at the edge of the current collector, which is beneficial for the uniformity of electrolyte wetting of the electrode. Therefore, while taking into account processing performance, it also improves the dynamic performance of the secondary battery.

[0011] In one or more embodiments of this application, along the length direction of the unfolded electrode, the current collector has opposing third and fourth edges, and the shortest distance between a single hole and the third or fourth edge is L4 μm, where 10 ≤ L4 ≤ 1000. By adjusting the value of L4 within the above range, the edge of the current collector has higher mechanical strength, reducing the risk of current collector breakage and / or tearing during processing, thus maintaining better integrity of the current collector. This is beneficial for improving processing efficiency and product quality, and also reduces the risk of electrolyte accumulation at the edge of the current collector, which is beneficial for the uniformity of electrolyte wetting of the electrode. Therefore, while taking into account processing performance, it also improves the dynamic performance of the secondary battery.

[0012] In one or more embodiments of this application, the elongation of the current collector is ε, where 2.5% ≤ ε ≤ 8%. By adjusting the value of ε within the above range, the current collector has a certain mechanical strength, which reduces the risk of current collector breakage during subsequent electrode coating, rolling, and other processing. It also helps to alleviate stress concentration in the secondary battery during charging and discharging, ensuring the integrity of the electrode, improving processing efficiency and product quality, and enhancing the processing performance of the secondary battery.

[0013] In one or more embodiments of this application, the dyne value of the current collector is S dyne / cm, where 30 ≤ S ≤ 55. By adjusting the value of S within the above range, the electrolyte has better wettability to the current collector, which is beneficial for the electrolyte to spread on the surface of the current collector, thereby improving the electrolyte's wettability to the electrode, reducing the temperature rise during high-rate discharge of the secondary battery, improving the high-rate discharge performance of the secondary battery, and thus improving the kinetic performance of the secondary battery.

[0014] In one or more embodiments of this application, the thickness of the current collector is H0 μm, where 3 ≤ H0 ≤ 20. By adjusting the value of H0 within the above range, the thickness of the current collector is moderate, giving it certain mechanical strength and good flexibility. This reduces the risk of current collector breakage during subsequent electrode coating, rolling, and other processing, and helps alleviate stress concentration during the charging and discharging process of the secondary battery, ensuring the integrity of the electrode. This improves processing efficiency and product quality, and enhances the processing performance of the secondary battery.

[0015] In one or more embodiments of this application, the holes include through holes, and the proportion of through holes is A, based on the total number of holes on the current collector, where 65% ≤ A ≤ 100%. By adjusting the value of A within the above range, the current collector has a certain mechanical strength while increasing the wetting path of the electrolyte in the electrode, improving the wetting of the electrode by the electrolyte, and providing a direct transport channel for ions, shortening the diffusion distance of ions in the electrode, thereby improving the kinetic performance of the secondary battery.

[0016] In one or more embodiments of this application, the hole further includes a blind hole, with a depth of T μm along the thickness direction of the electrode, and 0.1 ≤ T / H0 ≤ 0.9. By adjusting the value of T / H0 within the above range, the current collector has a certain mechanical strength while making the adhesion between the first material layer and the current collector tighter, thereby reducing the risk of the material layer falling off the current collector, improving the adhesion of the electrode, and thus improving the safety performance of the secondary battery.

[0017] In one or more embodiments of this application, the first material layer includes a first binder, and the mass percentage of the first binder is W1 based on the mass of the first material layer. The second material layer includes a second binder, and the mass percentage of the second binder is W2 based on the mass of the second material layer, where 1 ≤ W2 / W1 ≤ 4 and 0.5% ≤ W1 ≤ 1%. By adjusting the values ​​of W2 / W1 and W1 within the above ranges, the content of the first binder in the first material layer is relatively small. Combined with the second binder in the second material layer, the material layers on both sides of the current collector can be connected through the porous structure of the current collector. This improves electrolyte wetting while increasing the adhesion of the electrode, reducing the amount of binder used in the material layers, increasing the proportion of active material in the material layers, and thus further improving the energy density and kinetic performance of the secondary battery.

[0018] In one or more embodiments of this application, 1% ≤ W2 ≤ 2%. By adjusting the value of W2 within the above range, the content of the second binder in the second material layer is moderate, and the material layers on both sides of the current collector can be connected through the porous structure of the current collector. This improves the adhesion of the electrode while improving electrolyte wetting, reduces the amount of binder in the material layer, and increases the proportion of active material in the material layer, thereby further improving the energy density and kinetic performance of the secondary battery.

[0019] In one or more embodiments of this application, the electrode is a positive electrode; and / or a negative electrode. When the electrode is a positive electrode and / or a negative electrode, while taking into account the processing performance, it is beneficial to improve the adhesion of the electrode, improve the wetting of the electrolyte in the secondary battery, and the secondary battery has good kinetic performance.

[0020] A second aspect of this application provides an electronic device that includes the secondary battery found in any of the above embodiments. Therefore, the electronic device provided by this application has good performance.

[0021] The beneficial effects of the embodiments of this application are as follows:

[0022] This application provides a secondary battery and an electronic device. By providing holes in the current collector that meet the conditions of this application and ensuring that the tensile strength of the current collector is within the aforementioned range, and by providing a double-layer coating on the current collector, the wetting performance of the electrolyte on the electrode sheets can be improved, and the adhesion between the electrode sheets can be increased. This improves the dynamic performance of the secondary battery while taking into account the processing performance of the secondary battery.

[0023] Of course, implementing any product or method of this application does not necessarily require achieving all of the advantages described above at the same time. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other embodiments can be obtained based on these accompanying drawings.

[0025] Figure 1 This is a partial cross-sectional schematic diagram of the electrode along its length and thickness in one embodiment of this application;

[0026] Figure 2 This is a schematic diagram showing the current collector spreading along its own length in one embodiment of this application;

[0027] Reference numerals: Electrode 001; Current collector 10; Material layer 20; First material layer 21; Second material layer 22; Hole 11; Through hole 111; Blind hole 112; First edge 101; Second edge 102; Third edge 103; Fourth edge 104. Detailed Implementation

[0028] The technical solutions of this application will be clearly and completely described below with reference to the embodiments and accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. All other embodiments obtained by those skilled in the art based on this application are within the scope of protection of this application.

[0029] As the size of secondary batteries increases, the length and width of the electrodes also increase, making it more difficult for the electrolyte to wet the electrodes after injection. This is especially true in cylindrical batteries, where electrolyte injection from the center makes radial wetting difficult, leading to a decrease in the kinetic performance of the secondary battery. Therefore, this application provides a secondary battery and electronic device that, while maintaining processability, improves electrode adhesion and electrolyte wetting, thereby enhancing the kinetic performance of the secondary battery.

[0030] It should be noted that, in the specific embodiments of this application, a lithium-ion battery is used as an example of a secondary battery to explain this application; however, the secondary battery in this application is not limited to lithium-ion batteries. The specific technical solution is as follows:

[0031] The first aspect of this application provides a secondary battery, which includes an electrode, a current collector, and a material layer disposed on at least one surface of the current collector. The material layer includes a first material layer and a second material layer, with the first material layer located between the second material layer and the current collector along the thickness direction of the electrode. The current collector has a porous structure, with the pore size of a single pore being D μm, 0.1≤D≤10, optionally 0.5≤D≤5. For example, the value of D can be 0.1, 0.3, 0.5, 0.8, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, or a range consisting of any two of these values; the value range of D can be 0.1 to 10, 0.2 to 8, 0.3 to 6, 0.5 to 5, 1 to 5, 2 to 4, 2.5 to 3.5, and all such ranges, as well as sub-ranges. Along the length of the unfolded electrode, the spacing between two adjacent holes is L1 μm, where 10D ≤ L1 ≤ 1000D. For example, the value of L1 can be 10D, 50D, 100D, 150D, 200D, 250D, 300D, 350D, 400D, 450D, 500D, 550D, 600D, 650D, 700D, 750D, 800D, 850D, 900D, 950D, 1000D. 0D can be any two of these values; L1 can be 10D to 1000D, 50D to 950D, 100D to 900D, 150D to 850D, 200D to 800D, 250D to 750D, 300D to 700D, 350D to 650D, 400D to 600D, 450D to 550D, 500D to 550D, and all of these ranges and subranges. Along the width direction after the electrode is unfolded, the spacing between two adjacent holes is L2μm, where 10D≤L2≤100D. For example, the value of L2 can be 10D, 15D, 20D, 25D, 30D, 35D, 40D, 45D, 50D, 55D, 60D, 65D, 70D, 75D, 80D, 85D, 90D, 95D, 100D, or any range of two values ​​therein. The range of L2 can be 10D to 100D, 15D to 95D, 20D to 90D, 25D to 85D, 30D to 80D, 35D to 75D, 40D to 70D, 45D to 65D, 50D to 60D, 55D to 65D, and all ranges therein, as well as sub-ranges. The tensile strength of the current collector is σMPa, where 180≤σ≤650.For example, the value of σ can be 180, 185, 190, 195, 200, 205, 210, 215, 220, 225, 230, 235, 240, 245, 250, 255, 260, 265, 270, 275, 280, 290, 300, 320, 350, 380, 400, 420, 450, 480, 500, 520, 550, 580, 600, 620, 650, or any of these values. The range of values ​​for σ is defined by two numerical values. The range of values ​​for σ can be 180 to 650, 180 to 600, 180 to 500, 180 to 400, 180 to 300, 180 to 280, 185 to 275, 190 to 270, 195 to 265, 200 to 260, 205 to 255, 210 to 250, 215 to 245, 220 to 240, 225 to 235, 230 to 235, and all of these ranges, as well as subranges.

[0032] In this application, the electrode can be a positive electrode and / or a negative electrode. The electrode is defined in its unfolded state as having its length direction as the X direction, its width direction as the Y direction, and its thickness direction as the Z direction. It is understood that the material layer and the current collector, in their unfolded state, have the same length, width, and thickness directions as the electrode. For example, as shown... Figure 1 and Figure 2 As shown, the electrode 001 includes a current collector 10 and a material layer 20 disposed on two surfaces of the current collector 10. The material layer 20 includes a first material layer 21 and a second material layer 22. Along the thickness direction Z of the electrode 001, the first material layer 21 is located between the second material layer 22 and the current collector 10. The current collector 10 has a porous structure with multiple holes 11. The diameter of a single hole 11 is D μm. Along the length direction X of the unfolded electrode 001, the distance between two adjacent holes 11 is L1 μm. Along the width direction Y of the unfolded electrode 001, the distance between two adjacent holes 11 is L2 μm.

[0033] The inventors discovered that the porous structure of the current collector increases its contact area with the material layer, enhancing the adhesion between the current collector and the material layer. When the material layer is disposed on the two surfaces of the current collector, the material layers can be connected through the porous structure of the current collector, further improving the interfacial adhesion of the electrode. Stronger interfacial adhesion helps reduce the amount of binder in the material layer and the electron and ion transport impedance of the material layer. Furthermore, by controlling the pore size of a single pore and the spacing between two adjacent pores in the length and width directions within the scope of this application, the pores of the current collector are distributed within a suitable range, increasing the wetting path of the electrolyte in the electrode and improving the wetting of the electrode by the electrolyte. Especially in cylindrical secondary batteries, this is beneficial for improving the wetting of the electrode assembly by the electrolyte in the radial and height directions, providing more channels for ion transport inside the secondary battery, which is conducive to the transport of lithium ions. This reduces the temperature rise of the secondary battery during high-rate discharge, improves the high-rate discharge performance of the secondary battery, and thus improves the kinetic performance of the secondary battery. Furthermore, by controlling the tensile strength of the current collector within the scope of this application, the current collector possesses a certain mechanical strength. This reduces the risk of current collector breakage during subsequent electrode coating, rolling, and other processing, ensuring the integrity of the electrode and improving processing efficiency and product quality, thus enhancing the processing performance of the secondary battery. When the value of D is too small, i.e., less than the lower limit of this application, the small aperture makes it difficult for the electrolyte to pass through, resulting in insignificant improvement in electrode wetting. Furthermore, current equipment struggles to create holes with excessively small D values ​​in the current collector. When the value of D is too large, i.e., greater than the upper limit of this application, the slurry easily flows out from the pores during single-sided coating. In subsequent processes, coating or cold pressing cannot be connected and rewound, leading to frequent tape breakage and making electrode processing difficult. When the value of L1 is too small, i.e., less than the lower limit of this application, the small hole spacing affects the strength and elongation of the current collector, making subsequent processes (such as rolling, slitting, and winding) prone to tape breakage, which is detrimental to processing. When the value of L1 is too large, i.e., greater than the upper limit of this application, the small hole spacing affects the strength and elongation of the current collector, making subsequent processes (such as rolling, slitting, and winding) prone to tape breakage, hindering processing. When the upper limit of the application is too small, the number of holes on the electrode is too small, which does not significantly improve the adhesion and wetting of the electrode, nor does it significantly improve the kinetics of the secondary battery. When the value of L2 is too small, i.e., less than the lower limit of this application, the electrode is prone to breakage during subsequent processing, which is not conducive to processing. When the value of L2 is too large, i.e., greater than the upper limit of this application, the number of holes on the electrode is too small, which does not significantly improve the adhesion and wetting of the electrode, nor does it significantly improve the kinetics of the secondary battery. When the value of σ is too small, i.e., less than the lower limit of this application, the electrode breaks frequently during subsequent processing, making processing difficult. When the value of σ is too large, i.e., greater than the upper limit of this application, the current collector has insufficient elongation, and the electrode breaks frequently during rolling. Therefore, the secondary battery of this application improves the adhesion of the electrode and the wetting of the electrolyte in the secondary battery while taking into account processing performance, and the secondary battery has good kinetic performance.

[0034] The aforementioned "material layer disposed on at least one surface of the current collector" means that the material layer can be located on one surface of the current collector along its own thickness direction, or on two surfaces of the current collector along its own thickness direction. It should be noted that the "surface" here can be the entire area of ​​the current collector surface, or a part of the current collector surface. This application has no particular limitation, as long as the purpose of this application can be achieved.

[0035] In one or more embodiments of this application, the first material layer includes a first active material, wherein the Dv50 of the first active material is D1 μm, and 0.1 ≤ D1 ≤ 10. For example, the value of D1 can be 0.1, 0.3, 0.5, 0.8, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, or a range consisting of any two of these values; the value range of D1 can be 0.1 to 10, 0.2 to 8, 0.3 to 6, 0.5 to 5, 1 to 5, 2 to 4, 2.5 to 3.5, and all such ranges and sub-ranges. By adjusting the value of D1 within the aforementioned range, the particle size of the first active material is smaller, which is beneficial for optimizing the transport path of the electrolyte in the first material layer. This improves the electrolyte's wetting of the electrode, thereby reducing the temperature rise during high-rate discharge of the secondary battery, improving its high-rate discharge performance, and ultimately enhancing its kinetic performance. Therefore, the secondary battery of this application, while considering processing performance, improves the adhesion of the electrode, enhances the electrolyte's wetting of the secondary battery, and exhibits good kinetic performance.

[0036] In one or more embodiments of this application, the second material layer includes a second active material, wherein the Dv50 of the second active material is D2μm, and 1≤D2≤20. For example, the value of D2 can be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, or a range consisting of any two of these values; the range of D2 can be 1 to 20, 2 to 19, 3 to 18, 4 to 17, 5 to 16, 6 to 15, 7 to 14, 8 to 13, 9 to 12, 10 to 11, and all such ranges and sub-ranges. By adjusting the value of D2 within the above range, the particle size of the second active material is larger, which facilitates better penetration of the electrolyte from the electrode surface into the interior, thereby improving the electrolyte wetting of the electrode, reducing the temperature rise during high-rate discharge of the secondary battery, improving the high-rate discharge performance of the secondary battery, and thus improving the kinetic performance of the secondary battery. Therefore, the secondary battery of this application improves the adhesion of the electrode and the wetting of the secondary battery by the electrolyte while taking into account the processing performance, and the secondary battery has good kinetic performance.

[0037] In one or more embodiments of this application, the first material layer includes a first active material, wherein the Dv50 of the first active material is D1μm, and 0.1≤D1≤10. For example, the value of D1 can be 0.1, 0.3, 0.5, 0.8, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, or a range of any two values ​​therein; the value range of D1 can be 0.1 to 10, 0.2 to 8, 0.3 to 6, 0.5 to 5, 1 to 5, 2 to 4, 2.5 to 3.5, and... All ranges and sub-ranges thereof; and / or, the second material layer includes a second active material, the second active material having a Dv50 of D2μm, 1≤D2≤20, for example, the value of D2 can be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or any two of these values; the range of D2 can be 1 to 20, 2 to 19, 3 to 18, 4 to 17, 5 to 16, 6 to 15, 7 to 14, 8 to 13, 9 to 12, 10 to 11 and all ranges thereof, as well as sub-ranges thereof. By adjusting the values ​​of D1 and / or D2 within the aforementioned range, the particle size of the first active material is smaller, while the particle size of the second active material is larger. This optimizes the wetting path of the electrolyte in the material layer, thereby improving the electrolyte's wetting of the electrode, reducing the temperature rise during high-rate discharge of the secondary battery, improving its high-rate discharge performance, and ultimately enhancing its kinetic performance. Therefore, the secondary battery of this application, while considering processing performance, improves the adhesion of the electrode, enhances the electrolyte's wetting of the secondary battery, and exhibits good kinetic performance.

[0038] In one or more embodiments of this application, 1.5 ≤ D2 / D1 ≤ 200. For example, the value of D2 / D1 can be 1.5, 2, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200 or a range consisting of any two of these values; the value range of D2 can be 1.5 to 200, 2 to 190, 10 to 180, 20 to 170, 30 to 160, 40 to 150, 50 to 140, 60 to 130, 70 to 120, 80 to 110, 90 to 100 and all of these ranges, as well as sub-ranges. By adjusting the D2 / D1 value within the aforementioned range, the larger particles of the second active material in the upper layer, combined with the smaller particles of the first active material in the lower layer, increase the porosity of the electrode surface. This increases the wetting path of the electrolyte within the electrode, facilitating electrolyte wetting and ion diffusion from the electrode surface to the inner layer and through the current collector pores. This reduces ion resistance, further improves electrolyte wetting of the electrode, lowers the risk of poor electrode interface wetting, and consequently reduces the high-rate discharge temperature rise of the secondary battery, improving its high-rate discharge performance and further enhancing its kinetic performance. Therefore, the secondary battery of this application, while considering processing performance, improves electrode adhesion, enhances electrolyte wetting, and exhibits excellent kinetic performance.

[0039] In this application, Dv50 represents the particle size that, measured from the smallest particle size, reaches 50% of the total volumetric particle size in the particle size distribution based on volume. This application does not impose any particular restrictions on the method of controlling the Dv50 of the first active material and the Dv50 of the second active material, as long as the purpose of this application can be achieved. For example, the desired particle size of the active material can be obtained through mechanical crushing, grinding, or other methods. Alternatively, commercially available active materials with the desired particle size can be purchased.

[0040] In one or more embodiments of this application, the thickness of the first material layer is H1 μm, the thickness of the second material layer is H2 μm, 0.2 ≤ H1 / H2 ≤ 5, and 20 ≤ H2 ≤ 100. For example, the value of H1 / H2 can be 0.2, 0.5, 0.8, 1, 1.2, 1.5, 1.8, 2, 2.2, 2.5, 2.8, 3, 3.2, 3.5, 3.8, 4, 4.2, 4.5, 4.8, 5, or a range of any two of these values. The range of H1 / H2 can be 0.2 to 5, 0.5 to 4.8, 0.8 to 4.5, 1 to 4.2, 1.2 to 4, 1.5 to 3.8, 1.8 to 3.5, 2 to 3.2, 2.2 to 3, 2... The range of H2 can be 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, or any two of these values. The value range of H2 can be 20 to 100, 25 to 95, 30 to 90, 35 to 85, 40 to 80, 45 to 75, 50 to 70, 55 to 65, 60 to 60, and all of these ranges, as well as subranges. For example, as... Figure 1 As shown, the thickness of the first material layer 21 is H1 μm, and the thickness of the second material layer 22 is H2 μm. By adjusting the values ​​of H1 / H2 and H2 within the above range, the thickness of the material layers is moderate, resulting in a high energy density for the secondary battery. Furthermore, the moderate thickness ratio of the first to second material layers is beneficial for improving the bonding force between the material layers, thereby enhancing the overall adhesion of the electrode. In addition, it facilitates the uniform distribution of the electrolyte in the electrode pores, reducing ionic impedance and improving electrolyte wetting of the electrode, thus reducing the risk of poor electrode interface wetting. This, in turn, reduces the high-rate discharge temperature rise of the secondary battery, improves its high-rate discharge performance, and ultimately enhances its kinetic performance. Therefore, the secondary battery of this application, while considering processing performance, improves electrode adhesion, enhances electrolyte wetting, and exhibits good kinetic performance.

[0041] In one or more embodiments of this application, 4 ≤ H1 ≤ 500; optionally, 20 ≤ H1 ≤ 200. For example, the value of H1 can be 4, 5, 10, 20, 30, 50, 80, 100, 120, 150, 180, 200, 220, 250, 280, 300, 320, 350, 380, 400, 420, 450, 480, 500 or a range consisting of any two of these values. The value range of H1 can be 4 to 500, 10 to 400, 10 to 300, 20 to 200, 50 to 200, 80 to 150 and all of these ranges, as well as sub-ranges. By adjusting the value of H1 within the aforementioned range, the secondary battery exhibits a high energy density and facilitates the uniform distribution of electrolyte within the electrode pores. This improves electrolyte wetting of the electrodes, reduces the risk of poor interfacial wetting, and consequently lowers the temperature rise during high-rate discharge, enhancing the high-rate discharge performance and ultimately improving the battery's kinetic performance. Therefore, the secondary battery of this application, while maintaining good processing performance, improves electrode adhesion, enhances electrolyte wetting, and exhibits excellent kinetic performance.

[0042] In this application, the thickness of the first material layer and the thickness of the second material layer can be controlled by means known to those skilled in the art. For example, when the first slurry is coated on the surface of the negative electrode current collector, the thickness of the first material layer can be increased by increasing the coating weight, given that the solid content of the first slurry is constant. When the second slurry is coated on the surface of the first material layer away from the negative electrode current collector, the thickness of the second material layer can be increased by increasing the coating weight, and vice versa, given that the solid content of the second slurry is constant. Alternatively, when the electrode is cold-pressed, the thickness of the first material layer and the second material layer can be decreased by increasing the cold-pressing pressure, and vice versa.

[0043] In one or more embodiments of this application, along the width direction after the electrode is unfolded, the current collector has a first edge and a second edge, and the shortest distance between a single hole and the first edge or the second edge is L3μm, 300≤L3≤5000. For example, the value of L3 can be 300, 500, 800, 1000, 1200, 1500, 1800, 2000, 2200, 2500, 2800, 3000, 3200, 3500, 3800, 4000, 4200, 4500, 4800, 5000, and any two of these values. The value range of L3 can be 300 to 5000, 500 to 4800, 800 to 4500, 1000 to 4200, 1200 to 4000, 1500 to 3800, 1800 to 3500, 2000 to 3200, 2200 to 3000, 2500 to 2800, 2500 to 2600, and all of these ranges, as well as subranges. For example, as... Figure 2 As shown, along the width direction Y of the current collector 10 after it is unfolded, the current collector 10 has a first edge 101 and a second edge 102, and the shortest distance between a single hole 11 and the first edge 101 is L3 μm. By adjusting the value of L3 within the above range, the edge of the current collector has high mechanical strength, reducing the risk of breakage and / or tearing of the current collector during processing, thus maintaining good integrity of the current collector. This is beneficial to improving processing efficiency and product quality, and also reduces the risk of electrolyte accumulation at the edge of the current collector, which is beneficial to the consistency of electrolyte wetting of the electrode. Therefore, while taking into account processing performance, it also improves the kinetic performance of the secondary battery. Thus, the secondary battery of this application, while taking into account processing performance, improves the adhesion of the electrode and the wetting of the secondary battery by the electrolyte, resulting in good kinetic performance.

[0044] In one or more embodiments of this application, along the length direction after the electrode is unfolded, the current collector has a third edge and a fourth edge, and the shortest distance between a single hole and the third edge or the fourth edge is L4μm, 10≤L4≤1000. For example, the value of L4 can be 10, 30, 50, 80, 100, 150, 200, 250, 300, 350, 400, 450, 500, 550, 600, 650, 700, 750, 800, 850, 900, 950, 1000, or a range of any two of these values. The value range of L4 can be 10 to 1000, 50 to 950, 100 to 900, 150 to 850, 200 to 800, 250 to 750, 300 to 700, 350 to 650, 400 to 600, 450 to 550, 500 to 550, and all of these ranges, as well as subranges. For example, as... Figure 2As shown, along the X-direction of the unfolded current collector 10, the current collector 10 has opposing third edges 103 and fourth edges 104, and the shortest distance between a single hole 11 and the fourth edge 104 is L4 μm. By adjusting the value of L4 within the above range, the edge of the current collector has high mechanical strength, reducing the risk of breakage and / or tearing during processing, ensuring good integrity of the current collector, improving processing efficiency and product quality, and reducing the risk of electrolyte accumulation at the edge of the current collector, which is beneficial to the consistency of electrolyte wetting of the electrode. Thus, while considering processing performance, it also improves the kinetic performance of the secondary battery. Therefore, the secondary battery of this application, while considering processing performance, improves the adhesion of the electrode and improves the wetting of the secondary battery by the electrolyte, resulting in good kinetic performance.

[0045] In one or more embodiments of this application, the elongation of the current collector is ε, where 2.5% ≤ ε ≤ 8%. For example, the value of ε can be 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, or a range consisting of any two of these values. The value range of ε can be 2.5% to 8%, 5% to 7.5%, 5.5% to 7%, 6% to 6.5%, and all of these ranges, as well as sub-ranges. By controlling the value of ε within the above range, the current collector has a certain mechanical strength, reducing the risk of current collector breakage during subsequent electrode coating, rolling, and other processing. It also helps alleviate stress concentration during the charging and discharging process of the secondary battery, ensuring the integrity of the electrode, improving processing efficiency and product quality, and taking into account the processing performance of the secondary battery. Therefore, the secondary battery of this application, while taking into account processing performance, improves the adhesion of the electrode, improves the wetting of the secondary battery by the electrolyte, and the secondary battery has good kinetic performance.

[0046] In one or more embodiments of this application, the dyne value of the current collector is S dyne / cm, where 30 ≤ S ≤ 55. For example, the value of S can be 30, 32, 35, 38, 40, 42, 45, 48, 50, 52, 55, or a range consisting of any two of these values. The range of S can be 30 to 55, 32 to 52, 35 to 50, 38 to 48, 40 to 45, 42 to 45, and all such ranges and sub-ranges. By adjusting the value of S within the above range, the electrolyte has better wettability on the current collector, which is beneficial for the electrolyte to spread on the surface of the current collector, thereby improving the electrolyte's wetting of the electrode, reducing the temperature rise during high-rate discharge of the secondary battery, improving the high-rate discharge performance of the secondary battery, and thus improving the kinetic performance of the secondary battery. Therefore, the secondary battery of this application, while taking into account processing performance, improves the adhesion of the electrode and the wetting of the secondary battery by the electrolyte, resulting in good kinetic performance.

[0047] In one or more embodiments of this application, the thickness of the current collector is H0 μm, where 3 ≤ H0 ≤ 20. For example, the value of H0 can be 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, or a range consisting of any two of these values. The value range of H0 can be 3 to 20, 5 to 18, 8 to 15, 10 to 12, and all such ranges, as well as sub-ranges. For example, as... Figure 1 As shown, the thickness of the current collector 10 is H0 μm. By adjusting the value of H0 within the above range, the thickness of the current collector is moderate, and the current collector has certain mechanical strength and good flexibility. In subsequent electrode coating, rolling and other processing, the risk of current collector breakage is reduced, and it is also beneficial to alleviate stress concentration in the secondary battery during charging and discharging, ensuring the integrity of the electrode, improving processing efficiency and product quality, and enhancing the processing performance of the secondary battery.

[0048] In one or more embodiments of this application, the hole includes a through hole, exemplarily, such as... Figure 1As shown, hole 11 includes through hole 111. Based on the total number of holes on the current collector, the proportion of through holes is A, 65% ≤ A ≤ 100%. For example, the value of A can be 65%, 68%, 70%, 72%, 75%, 78%, 80%, 82%, 85%, 88%, 90%, 92%, 95%, 98%, 100%, or a range of any two of these values. The range of A can be 65% to 100%, 68% to 98%, 70% to 95%, 72% to 92%, 75% to 90%, 78% to 88%, 80% to 85%, 82% to 85%, and all of these ranges, as well as sub-ranges. By adjusting the value of A within the aforementioned range, the current collector achieves a certain mechanical strength while increasing the wetting path of the electrolyte in the electrode, improving electrolyte wetting of the electrode, and providing a direct transport channel for ions, thus shortening the diffusion distance of ions in the electrode and enhancing the kinetic performance of the secondary battery. Therefore, the secondary battery of this application, while considering processing performance, improves electrode adhesion and electrolyte wetting of the secondary battery, resulting in excellent kinetic performance.

[0049] In one or more embodiments of this application, the aperture further includes blind apertures, with a depth of T μm along the thickness direction of the electrode, where 0.1 ≤ T / H0 ≤ 0.9. For example, the value of T / H0 can be 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, or a range consisting of any two of these values. The range of T / H0 can be 0.1 to 0.9, 0.15 to 0.85, 0.2 to 0.8, 0.25 to 0.75, 0.3 to 0.7, 0.35 to 0.65, 0.4 to 0.6, 0.45 to 0.55, 0.5 to 0.55, and all such ranges, as well as sub-ranges. For example, as... Figure 1 As shown, hole 11 also includes blind hole 112, with a depth of T μm along the thickness direction Z of electrode 001. By adjusting the value of T / H0 within the above range, the current collector has a certain mechanical strength while making the adhesion between the first material layer and the current collector tighter, thereby reducing the risk of the material layer falling off the current collector, improving the adhesion of the electrode, and thus improving the safety performance of the secondary battery.

[0050] In one or more embodiments of this application, the first material layer includes a first adhesive, and the mass percentage of the first adhesive is W1 based on the mass of the first material layer. The second material layer includes a second adhesive, and the mass percentage of the second adhesive is W2 based on the mass of the second material layer, where 1 ≤ W2 / W1 ≤ 4, and 0.5% ≤ W1 ≤ 1%. For example, the value of W2 / W1 can be 1, 1.2, 1.5, 1.8, 2, 2.2, 2.5, 2.8, 3, 3.2, 3.5, 3.8, 4, or a range consisting of any two of these values. The range of W2 / W1 can be 1 to 4, 1.2 to 3.8, 1.5 to 3.5, 1.8 to 3.2, 2 to 3, 2.2 to 2.8, 2.5 to 2.8, and all such ranges and sub-ranges; the value of W1 can be 0.5. The values ​​of W1 can be 0.5% to 1%, 0.55% to 0.95%, 0.6% to 0.65%, 0.7% to 0.75%, 0.8% to 0.85%, 0.9% to 0.95%, and 0.75% to 0.8%, as well as all and sub-ranges thereof. By adjusting the values ​​of W2 / W1 and W1 within the above ranges, the content of the first binder in the first material layer is relatively small. Combined with the second binder in the second material layer, the material layers on both sides of the current collector can be connected through the porous structure of the current collector. This improves the adhesion of the electrode while improving electrolyte wetting. It can reduce the amount of binder in the material layer and increase the proportion of active material in the material layer, thereby further improving the energy density and kinetic performance of the secondary battery.

[0051] In one or more embodiments of this application, 1% ≤ W2 ≤ 2%. For example, the value of W2 can be 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, or a range consisting of any two of these values. The range of W2 can be 1% to 2%, 1.1% to 1.9%, 1.2% to 1.8%, 1.3% to 1.7%, 1.4% to 1.6%, 1.4% to 1.5%, and all of these ranges, as well as sub-ranges. By adjusting the value of W2 within the above range, the content of the second binder in the second material layer is moderate. The material layers on both sides of the current collector can be connected through the porous structure of the current collector. This improves the adhesion of the electrode while improving electrolyte wetting. It can reduce the amount of binder in the material layer and increase the proportion of active material in the material layer, thereby further improving the energy density and kinetic performance of the secondary battery.

[0052] In one or more embodiments of this application, the electrode is a positive electrode; and / or a negative electrode. When the electrode is a positive electrode and / or a negative electrode, while taking into account the processing performance, it is beneficial to improve the adhesion of the electrode, improve the wetting of the electrolyte in the secondary battery, and the secondary battery has good kinetic performance.

[0053] In this application, the shape of the outer contour of a single hole on the surface of the collector includes, but is not limited to, a circle, an ellipse, or a polygon. There are no particular limitations on the shape of the polygon in this application, as long as it achieves the purpose of this application. For example, each polygon can be independently selected from a triangle, rectangle, trapezoid, square, pentagon, or hexagon. When the shape of the outer contour of a single hole on the surface of the collector is other than a circle, it is understood that the diameter of the single hole is the diameter of the largest circumcircle of the outer contour of the single hole on the surface of the collector; the distance between two adjacent holes is the distance between the centers of the largest circumcircle of the outer contours of the two adjacent holes on the surface of the collector; the shortest distance between a single hole and the first or second edge is the shortest distance between the center of the largest circumcircle of the outer contour of the single hole on the surface of the collector and the first or second edge; the shortest distance between a single hole and the third or fourth edge is the shortest distance between the center of the largest circumcircle of the outer contour of the single hole on the surface of the collector and the third or fourth edge.

[0054] In this application, when the electrode is a positive electrode, the current collector is a positive current collector. This application does not impose any particular limitation on the positive current collector, as long as it achieves the purpose of this application. For example, the positive current collector may contain aluminum foil, aluminum alloy foil, or a composite current collector (e.g., an aluminum-carbon composite current collector). At this time, both the first material layer and the second material layer are positive electrode material layers, and both the first active material and the second active material are positive electrode active materials. This application does not impose any particular limitation on the types of the first active material and the second active material, as long as they achieve the purpose of this application. For example, the first active material and the second active material may each independently contain lithium nickel cobalt manganese oxide (LiNi). 0.90 Co 0.05 Mn 0.05At least one of the following: O2 (NCM955), NCM811, NCM622, NCM523, NCM111, lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium-rich manganese-based materials, lithium cobalt oxide (LiCoO2), lithium manganese oxide, or lithium manganese iron phosphate. In this application, the first active material and the second active material may also independently contain non-metallic elements, such as at least one of fluorine, phosphorus, boron, chlorine, silicon, or sulfur. In this case, both the first binder and the second binder are positive electrode binders. This application does not have any particular limitation on the types of the first binder and the second binder, as long as they can achieve the purpose of this application. For example, the first binder and the second binder may independently include, but are not limited to, at least one of polyvinylidene fluoride (PVDF), a copolymer of polyvinylidene fluoride and hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyethylene ether, polymethyl methacrylate, polytetrafluoroethylene, or polyhexafluoropropylene. In this application, the first material layer may further include a first conductive agent, and the second material layer may further include a second conductive agent. This application does not impose any particular limitation on the types of the first and second conductive agents, as long as they can achieve the purpose of this application. For example, the first and second conductive agents may each independently include, but are not limited to, at least one of conductive carbon black (Super P), carbon nanotubes (CNTs), carbon fibers, flake graphite, Ketjen black, graphene, metallic materials, or conductive polymers. The aforementioned carbon nanotubes may include, but are not limited to, single-walled carbon nanotubes and / or multi-walled carbon nanotubes. The aforementioned carbon fibers may include, but are not limited to, vapor-grown carbon fibers (VGCF) and / or carbon nanofibers. The aforementioned metallic materials may include, but are not limited to, metal powders and / or metal fibers; specifically, the metal may include, but is not limited to, at least one of copper, nickel, aluminum, or silver. The aforementioned conductive polymers may include, but are not limited to, at least one of polyphenylene derivatives, polyaniline, polythiophene, polyacetylene, or polypyrrole. This application does not impose any particular restrictions on the mass ratio of the first active material, the first conductive agent, and the first binder in the first material layer, nor does it impose any particular restrictions on the mass ratio of the second active material, the second conductive agent, and the second binder in the second material layer. Those skilled in the art can choose according to actual needs, as long as the purpose of this application can be achieved.

[0055] In the present application, when the electrode sheet is a negative electrode sheet, the current collector is a negative electrode current collector. The present application places no particular limitation on the negative electrode current collector, as long as the object of the present application can be achieved. For example, the negative electrode current collector may include copper foil, copper alloy foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, or a composite current collector (such as a lithium-copper composite current collector, a carbon-copper composite current collector, a nickel-copper composite current collector, a titanium-copper composite current collector, etc.). At this time, both the first material layer and the second material layer are negative electrode material layers, and both the first active material and the second active material are negative electrode active materials. The present application places no particular limitation on the types of the first active material and the second active material, as long as the object of the present application can be achieved. For example, the first active material and the second active material may each independently include natural graphite, artificial graphite, mesocarbon microbeads (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composite, SiO x (0 < x < 2), Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO2, spinel-structured lithium titanate Li4Ti5O 12The first and second binders are at least one of Li-Al alloy or metallic lithium. Both the first and second binders are negative electrode binders. This application does not particularly limit the types of the first and second binders, as long as they can achieve the purpose of this application. For example, the first and second binders can each independently include, but are not limited to, at least one of polyvinylidene fluoride, a copolymer of polyvinylidene fluoride and hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, or polyhexafluoropropylene. In this application, the first material layer may also include a first conductive agent, and the second material layer may also include a second conductive agent. This application does not particularly limit the types of the first and second conductive agents, as long as they can achieve the purpose of this application. For example, the first and second conductive agents can each independently include, but are not limited to, at least one of conductive carbon black (Super P), carbon nanotubes (CNTs), carbon fibers, flake graphite, Ketjen black, graphene, metallic materials, or conductive polymers. The aforementioned carbon nanotubes may include, but are not limited to, single-walled carbon nanotubes and / or multi-walled carbon nanotubes. The aforementioned carbon fibers may include, but are not limited to, vapor-grown carbon fibers (VGCF) and / or carbon nanofibers. The aforementioned metallic materials may include, but are not limited to, metal powders and / or metal fibers; specifically, the metal may include, but is not limited to, at least one of copper, nickel, aluminum, or silver. The aforementioned conductive polymer may include, but is not limited to, at least one of polyphenylene derivatives, polyaniline, polythiophene, polyacetylene, or polypyrrole. In one or more embodiments of this application, the first material layer may further include a first thickener, and the second material layer may further include a second thickener. This application does not impose any particular limitation on the types of the first and second thickeners, as long as the purpose of this application can be achieved. For example, the first and second thickeners may each independently include, but are not limited to, at least one of sodium carboxymethyl cellulose or lithium carboxymethyl cellulose. This application does not impose any particular limitation on the mass ratio of the first active material, the first conductive agent, the first binder, and the first thickener in the first material layer, nor on the mass ratio of the second active material, the second conductive agent, the second binder, and the second thickener in the second material layer. Those skilled in the art can choose according to actual needs, as long as the purpose of this application can be achieved.

[0056] This application does not impose any particular restrictions on the preparation method of the electrode sheet, as long as it can achieve the purpose of this application. For example, the preparation method of the electrode sheet includes, but is not limited to, the following steps: (1) preparing a porous current collector; (2) preparing a first material layer slurry and a second material layer slurry; (3) simultaneously and uniformly coating the first material layer slurry and the second material layer slurry prepared above onto one surface of the current collector using a double-layer coating machine, and drying to obtain a negative electrode sheet with a first material layer and a second material layer on one side, wherein, after drying, along the thickness direction of the electrode sheet, the first material layer is located between the second material layer and the current collector; (4) repeating the above steps on the other surface of the current collector, and drying to obtain an electrode sheet with a first material layer and a second material layer on both sides; (5) cold pressing and slitting to obtain the desired electrode sheet.

[0057] It is understandable that when coating the first material layer slurry and the second material layer slurry, the two layers can be directly coated by referring to the preparation method described above, or the first material layer slurry can be uniformly coated on the current collector and dried first, and then the second material layer slurry can be coated on it and dried; or the first material layer slurry can be uniformly coated on the current collector, dried and then cold-pressed, and then the second material layer slurry can be coated on it and dried.

[0058] This application does not impose any particular limitation on the solid content of the slurry, as long as the purpose of this application can be achieved. This application does not impose any particular limitation on the drying temperature and time, as long as the purpose of this application can be achieved. This application does not impose any particular limitation on the process parameters for cold pressing and slitting, as long as the purpose of this application can be achieved.

[0059] In this application, the mass percentage content of the first binder in the first material layer can be controlled by adjusting the mass ratio of each substance added in the first material layer slurry; the mass percentage content of the second binder in the second material layer can be controlled by adjusting the mass ratio of each substance added in the second material layer slurry.

[0060] In this application, the original current collector with the required thickness H0 can be obtained by purchasing commercially available current collectors, i.e., the current collector before the porous structure is set. This application does not impose any particular restrictions on the method of setting the porous structure on the current collector, as long as it achieves the purpose of this application. For example, laser drilling can be used to set the structure, wherein the aperture D of the hole can be adjusted by adjusting the laser power, pulse width, spot size, pulse energy, and focusing position; the distance L1 between two adjacent holes along the length direction after the electrode is unfolded can be adjusted by adjusting the scanning speed, pulse frequency, and motion control system; the distance L2 between two adjacent holes along the width direction after the electrode is unfolded can be adjusted by adjusting the scanning speed, pulse frequency, and motion control system; the shortest distance L3 between a single hole and the first or second edge can be adjusted by adjusting the motion control system; the shortest distance L4 between a single hole and the third or fourth edge can be adjusted by adjusting the motion control system; the proportion A of through holes based on the total number of holes on the current collector can be adjusted by adjusting the laser power, pulse energy, and focusing position; and the depth T of a single blind hole can be adjusted by adjusting the laser power, pulse energy, and focusing position.

[0061] In this application, the tensile strength σ of the current collector can be controlled by adjusting the pore size and pore spacing. For example, when other conditions remain constant, a smaller pore size and / or a larger pore spacing results in a higher tensile strength of the current collector, and vice versa. The elongation ε of the current collector can also be controlled by adjusting the pore size and pore spacing. For example, when other conditions remain constant, a smaller pore size and / or a larger pore spacing results in a higher elongation of the current collector, and vice versa. The current collector with the desired dyne value can be obtained by purchasing commercially available current collectors.

[0062] In this application, the secondary battery also includes an electrolyte, which comprises lithium salts and non-aqueous solvents. This application does not impose any particular limitation on the lithium salt, as long as it achieves the purpose of this application. For example, the lithium salt may include, but is not limited to, at least one of LiPF6, LiBF4, LiAsF6, LiClO4, LiB(C6H5)4, LiCH3SO3, LiCF3SO3, LiN(SO2CF3)2, LiC(SO2CF3)3, Li2SiF6, lithium bis(oxalato)borate (LiBOB), or lithium difluoroborate. This application does not impose any particular limitation on the content of lithium salts in the electrolyte, as long as it achieves the purpose of this application. This application does not impose any particular limitation on the non-aqueous solvent, as long as it achieves the purpose of this application. For example, the non-aqueous solvent may include, but is not limited to, at least one of carbonate compounds, carboxylic acid ester compounds, ether compounds, or other organic solvents. The aforementioned carbonate compounds may include, but are not limited to, at least one of chain carbonate compounds, cyclic carbonate compounds, or fluorocarbonate compounds. The aforementioned chain carbonate compounds may include, but are not limited to, at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), or methyl ethyl carbonate (MEC). The aforementioned cyclic carbonates may include, but are not limited to, at least one of ethylene carbonate (EC), propylene carbonate (PC), butyl carbonate (BC), or vinyl ethylene carbonate (VEC). Fluorinated carbonate compounds may include, but are not limited to, at least one of fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, or trifluoromethylethylene carbonate. The aforementioned carboxylic acid ester compounds may include, but are not limited to, at least one of methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, decanolactone, valproic acid lactone, or caprolactone. The aforementioned ether compounds may include, but are not limited to, at least one of dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, 1-ethoxy-1-methoxyethane, 2-methyltetrahydrofuran, or tetrahydrofuran. The aforementioned other organic solvents may include, but are not limited to, at least one of dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolium ketone, N-methyl-2-pyrrolidone, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, or trioctyl phosphate. This application does not impose any particular limitation on the content of non-aqueous solvents in the electrolyte, as long as the purpose of this application is achieved.

[0063] In this application, the secondary battery also includes a separator. This application does not impose any particular limitation on the separator, as long as it achieves the purpose of this application. For example, the separator material may include, but is not limited to, at least one of polyethylene (PE), polyolefins (PO) primarily composed of polypropylene (PP), polyester (e.g., polyethylene terephthalate (PET) film), cellulose, polyimide (PI), polyamide (PA), spandex, or aramid. The separator type may include at least one of woven membrane, nonwoven membrane, microporous membrane, composite membrane, rolled membrane, or spun membrane. In some embodiments of this application, the separator may include a substrate layer and a surface treatment layer. The substrate layer may be a nonwoven membrane or composite membrane with a porous structure, and the material of the substrate layer may include at least one of polyethylene, polypropylene, polyethylene terephthalate, or polyimide. Optionally, a polypropylene porous membrane, a polyethylene porous membrane, a polypropylene nonwoven fabric, a polyethylene nonwoven fabric, or a polypropylene-polyethylene-polypropylene porous composite membrane may be used. Optionally, a surface treatment layer is disposed on at least one surface of the substrate layer. The surface treatment layer may be a polymer layer or an inorganic layer, or a layer formed by a mixture of polymer and inorganic materials. In some embodiments of this application, the inorganic layer includes inorganic particles and a binder. This application does not particularly limit the inorganic particles; for example, the inorganic particles may include at least one of alumina, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, or barium sulfate. This application does not particularly limit the binder; for example, the binder may be at least one of the binders described above. In some embodiments of this application, the polymer layer includes a polymer, and the polymer material includes at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, or polyvinylidene fluoride or poly(vinylidene fluoride-hexafluoropropylene). In this application, there is no particular limitation on the thickness of the diaphragm, as long as it can achieve the purpose of this application. For example, the thickness of the diaphragm can be from 3 μm to 20 μm.

[0064] The secondary battery also includes a casing for housing the positive electrode, separator, negative electrode, and electrolyte, as well as other components known in the field of secondary batteries. This application does not limit the scope of these other components. This application does not impose any particular limitation on the casing; it can be a casing known in the art, as long as it achieves the purpose of this application. For example, the casing can be a rigid casing or a flexible casing. The material of the rigid casing can be metal or rigid plastic. This application does not limit the type of metal; metal casings known in the art can be used, as long as they achieve the purpose of this application. The flexible casing can be a metal-plastic film, such as aluminum-plastic film, steel-plastic film, etc.

[0065] The fabrication process of the secondary battery described in this application is well known to those skilled in the art, and this application does not impose any particular limitations. For example, the fabrication process of the secondary battery may include, but is not limited to, the following steps: stacking the positive electrode, separator, and negative electrode in sequence, and performing operations such as winding and folding as needed to obtain a wound electrode assembly; placing the electrode assembly into a housing; injecting electrolyte into the housing and sealing it to obtain the secondary battery. Alternatively, stacking the positive electrode, separator, and negative electrode in sequence, and then fixing the four corners of the entire stacked structure with tape to obtain a stacked electrode assembly; placing the electrode assembly into a housing; injecting electrolyte into the housing and sealing it to obtain the secondary battery. In addition, overcurrent protection elements, conductive plates, etc., may be placed in the housing as needed to prevent pressure rise and overcharging / discharging inside the secondary battery.

[0066] A second aspect of this application provides an electronic device that includes the secondary battery found in any of the above embodiments. Therefore, the electronic device provided by this application has good performance.

[0067] This application does not specifically limit the type of electronic device; it can be any electronic device known in the prior art. In some embodiments of this application, the electronic device may include, but is not limited to, laptops, pen input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini CDs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries, and lithium-ion capacitors, etc.

[0068] Example

[0069] The embodiments and comparative examples provided below illustrate the implementation of this application in more detail. Various tests and evaluations were conducted according to the methods described below. Furthermore, unless otherwise specified, "parts" and "%" are quality standards.

[0070] Test methods and equipment:

[0071] Tests for D, L1, L2, L3, L4, H1, H2, H0, T, and A:

[0072] At an ambient temperature of 25℃, the lithium-ion battery was discharged to 2.5V at 0.5C and then disassembled to obtain the electrode assembly. The electrode sheets were removed from the electrode assembly, immersed and cleaned five times with dimethyl carbonate (DMC), and then placed in an oven and dried at 80℃ for 12 hours to obtain test samples of the electrode sheets.

[0073] The electrode is unfolded to prepare a cross-section along its own thickness direction. The cross-section is then ion-polished and observed using a scanning electron microscope (SEM) to determine the boundary lines between the first and second material layers, as well as the boundary line between the first material layer and the current collector. Fifteen points are randomly selected on the surface of the electrode, and the thicknesses of the first, second, and current collectors at the corresponding locations are measured. The average values ​​of these values ​​are then taken to obtain the thicknesses H1, H2, and H0 of the first, second, and current collectors.

[0074] The material layer is scraped off the electrode to obtain the current collector. The electrode is unfolded along its length, and its surface is observed using SEM. The number of through holes is counted, and the proportion A of through holes is calculated based on the total number of holes in the current collector. If there are blind holes in the current collector, one blind hole is randomly selected, and the distances from the surface of the current collector to the bottom of the single blind hole are measured at five locations. The average value is taken to obtain the depth T of the single blind hole.

[0075] The aperture D of a single hole is measured using SEM. The distance L1 between the centers of two adjacent holes is measured along the length direction of the unfolded electrode sheet, and the distance L2 between the centers of two adjacent holes is measured along the width direction of the unfolded electrode sheet.

[0076] Along the width direction of the unfolded electrode, determine the first and second edges of the current collector, and use SEM to measure the shortest distance L3 between the center of a single hole and the first or second edge. Along the length direction of the unfolded electrode, determine the third and fourth edges of the current collector, and use SEM to measure the shortest distance L4 between the center of a single hole and the third or fourth edge.

[0077] Tests for σ and ε:

[0078] The current collector was obtained by referring to the test of "D, L1, L2, L3, L4, H1, H2, H0, T, A". A sampler was used to cut a sample along the edge of the unfolded current collector. The sample length was 100 mm and the width was 80 mm. The sample was tested using a universal tensile testing machine at a tensile speed of 5 mm / min until the sample broke. The tensile strength and elongation were calculated based on the obtained data. Five samples were tested in parallel and the average value was taken to obtain the tensile strength σ and elongation ε of the current collector.

[0079] Tests D1 and D2:

[0080] At an ambient temperature of 25℃, the lithium-ion battery was discharged to 2.5V at 0.5C and then disassembled to obtain the electrode assembly. The electrode sheets were removed from the assembly and rinsed five times with dimethyl carbonate (DMC). The electrodes were then placed in an oven and dried at 80℃ for 12 hours to obtain test samples. The thickness direction of the electrodes was observed using a scanning electron microscope (SEM) to determine the boundaries between the first and second material layers, as well as the boundary between the first material layer and the current collector. The second and first material layers were scraped off the electrodes to obtain powders of the second and first material layers, respectively.

[0081] The powder of the first material layer was mixed with N-methylpyrrolidone at a weight ratio of 1:3, and dispersed with a single rod dispersant for 3 hours until completely dissolved and uniformly dispersed to obtain the first dispersion. The above sample dispersion was tested using a laser particle size analyzer (model MasterSizer2000) to obtain the Dv50 of the first active material, i.e., D1.

[0082] The powder of the second material layer was mixed with N-methylpyrrolidone at a weight ratio of 1:3, and dispersed with a single rod dispersant for 3 hours until completely dissolved and uniformly dispersed to obtain a second dispersion. The above sample dispersion was tested using a laser particle size analyzer (model MasterSizer2000) to obtain the Dv50 of the second active material, i.e., D2.

[0083] Dv50 refers to the particle size that reaches 50% of the volumetric cumulative size in the particle size distribution based on volume.

[0084] S's test:

[0085] The current collector is obtained according to the "D, L1, L2, L3, L4, H1, H2, H0, T, A test". Different sizes of dyne pens (such as 30 Dyne / cm, 32 Dyne / cm, 34 Dyne / cm, 36 Dyne / cm, 38 Dyne / cm, 40 Dyne / cm, 42 Dyne / cm, 44 Dyne / cm, 46 Dyne / cm, 48 Dyne / cm, 50 Dyne / cm, 52 Dyne / cm, 54 Dyne / cm, 56 Dyne / cm) are used to scribble lines on the surface of the current collector. The scribbles must remain unchanged for 3 seconds to meet the dyne value requirement. The dyne value of the current collector to be tested should be determined. Otherwise, it fails and is retested using a different size of dyne pen.

[0086] Tests W1 and W2:

[0087] The powders of the second material layer and the first material layer were obtained according to the "D1 and D2 tests". The powder of the first material layer was weighed to obtain mass m1, and then thermogravimetric analysis was performed at a temperature range of 25℃ to 500℃. The residual material after heating was weighed to obtain mass m2. The mass percentage W1 of the first binder in the first material layer was obtained by (m1-m2) / m1.

[0088] The powder of the second material layer was weighed to obtain mass m3, and then thermogravimetric analysis was performed at a temperature range of 25℃ to 500℃. The residual material after heating was weighed to obtain mass m4. The mass percentage W2 of the second binder in the second material layer was obtained by (m3-m4) / m3.

[0089] 25℃ 10C discharge capacity retention rate and 25℃ 10C discharge temperature rise test:

[0090] 1) The test temperature is 25℃;

[0091] 2) Let stand for 10 minutes (sampling method is 10 seconds);

[0092] 3) Charge at a constant current of 2C to 4.2V, then charge at a constant voltage of 4.2V to 0.025C (sampling method is 10s);

[0093] 4) Let stand for 30 minutes;

[0094] 5) Discharge at a constant current of 0.2C to 2.5V (set the cutoff capacity for this step to variable parameter C1; sampling mode is 10s);

[0095] 6) Let stand for 15 minutes (sampling method is 10 seconds);

[0096] 7) Charge at 2C constant current to 4.2V, then charge at 4.2V constant voltage to 0.05C (sampling method is 10s);

[0097] 8) Let stand for 60 minutes (sampling method is 10 seconds);

[0098] 9) Discharge at 10C constant current to 2.5V (set the cutoff capacity for this step to variable parameter C2; sampling mode is 1s);

[0099] 10) Let stand for 60 minutes (sampling method is 10 seconds);

[0100] 11) 25℃ 10C discharge capacity retention rate = C2 / C1×100%, and the temperature of the lithium-ion battery surface in step 9) is measured using a multi-channel temperature measuring instrument (model LR8401-21, HIOKI), and the highest temperature is recorded as the 25℃ 10C discharge temperature rise.

[0101] The sampling method is 10s, meaning the test system records a set of relevant parameters of the tested lithium-ion battery every 10 seconds, and 1s, meaning the test system records a set of relevant parameters of the tested lithium-ion battery every 1 second.

[0102] Determining whether an electrode can be processed:

[0103] When the tensile strength of the current collector is less than 180 MPa and the elongation is less than 2.5%, the coating and / or cold pressing cannot be connected and wound up in subsequent processes, which easily leads to frequent tape breakage. In this case, the electrode sheet is difficult to process during production, and the judgment is "no".

[0104] Example 1

[0105] <Preparation of the positive electrode>

[0106] The electrode is a positive electrode, with the first active material being a single-crystal LiNi. 0.9 Co 0.05 Mn 0.05 O2, CNT (the first conductive agent), and PVDF (the first binder) are mixed in a weight ratio of 98:1.2:0.8. N-methylpyrrolidone (NMP) is added as a solvent, and the mixture is stirred evenly to form a first material layer slurry with a solid content of 70wt%.

[0107] The second active material is polycrystalline LiNi 0.9 Co 0.05 Mn 0.05 O2, CNT (a second conductive agent), and PVDF (a second binder) are mixed in a weight ratio of 96:2:2, and N-methylpyrrolidone (NMP) is added as a solvent to prepare a second material layer slurry with a solid content of 65wt%.

[0108] Aluminum foil with a thickness H0 of 12 μm was selected as the original positive electrode current collector, i.e., the current collector before drilling. A porous structure was set on the aluminum foil by laser drilling. The proportion A of the total number of holes on the current collector based on the through holes was 100%, and the diameter D of a single hole was 3 μm. Along the length direction of the current collector after it was unfolded, the distance L1 between two adjacent holes was 1500 μm. Along the width direction of the current collector after it was unfolded, the distance L2 between two adjacent holes was 150 μm. The shortest distance between a single hole and the first edge and the shortest distance between a single hole and the second edge were both 1000 μm. The shortest distance between a single hole and the third edge and the shortest distance between a single hole and the fourth edge were both 500 μm.

[0109] The first and second material layer slurries prepared above were simultaneously and uniformly coated onto one surface of a current collector with a thickness H0 of 12 μm using a double-layer coating machine. The coated surfaces were then dried at 90°C to obtain a positive electrode sheet with a single-sided coating of the first and second material layers. The above steps were then repeated on the other surface of the current collector to obtain a positive electrode sheet with a double-sided coating of the first and second material layers. After cold pressing and slitting, positive electrode sheets with a size of 60 mm × 1680 mm were obtained for later use. The first active material's Dv50 (D1) was 2 μm, and the second active material's Dv50 (D2) was 10 μm; the coating weight of the first material layer was 0.355 mg / mm². 2 The coating weight of the second material layer is 0.163 mg / mm². 2 The thickness of the first material layer is H1, which is 100 μm, and the thickness of the second material layer is H2, which is 50 μm. Based on the mass of the first material layer, the mass percentage of the first adhesive, W1, is 0.8%, and based on the mass of the second material layer, the mass percentage of the second adhesive, W2, is 2%.

[0110] <Preparation of Negative Electrode Sheets>

[0111] Artificial graphite (negative electrode active material), styrene-butadiene rubber (SBR) (binder), sodium carboxymethyl cellulose (CMC) (dispersant), and conductive carbon black (conductive agent) (conductive agent) were mixed in a mass ratio of 96:2:1:1. Deionized water was added as a solvent to prepare a slurry with a solid content of 50 wt%. The slurry was stirred evenly in a vacuum mixer to obtain the negative electrode slurry. The negative electrode slurry was uniformly coated onto one surface of a 6 μm thick copper foil current collector and dried at 90 °C to obtain a negative electrode sheet with a single-sided coating of negative electrode material layer. The coating weight of the negative electrode material layer was 0.121 mg / mm². 2 The above steps are then repeated on the other surface of the copper foil to obtain a negative electrode sheet with a double-sided coating of negative electrode material. After drying at 90°C, the sheet is cold-pressed and cut into strips to obtain negative electrode sheets with a size of 64mm × 1730mm for later use. The thickness of the single-sided negative electrode material layer is 76μm.

[0112] <Preparation of Electrolyte>

[0113] In an environment with a water content of less than 10 ppm, ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), and methyl ethyl carbonate (EMC) were mixed in a mass ratio of 20:30:40:10 to obtain an organic solvent. Lithium hexafluorophosphate (LiPF6) was then added to the organic solvent and mixed thoroughly to obtain the electrolyte. The concentration of the lithium salt was 1 mol / L, and the remainder was the organic solvent.

[0114] <Septum>

[0115] A porous polyethylene film with a thickness of 7μm was used as the diaphragm.

[0116] <Preparation of Lithium-ion Batteries>

[0117] The prepared separator, negative electrode, and positive electrode are stacked in sequence, with the separator positioned between the positive and negative electrode to act as a separator. The electrode assembly is then wound to obtain the final product. After processes including flattening, current collector welding, casing, inkjet printing, vacuum drying, electrolyte injection, sealing, high-temperature settling, and capacity testing, a lithium-ion battery is obtained. The upper limit of the formation voltage is 4.25V, the formation temperature is 45℃, and the formation settling time is 12 hours.

[0118] Examples 2 to 25

[0119] Except for adjusting the relevant preparation parameters according to Table 1, the rest is the same as in Example 1. Specifically, when the Dv50 of the first active material and / or the Dv50 of the second active material changes, the grinding time is adjusted so that the values ​​of D1 and / or D2 are as shown in Table 1; in Example 18, the number of blind holes accounts for 35% of the total number of holes on the current collector, and based on the thickness direction of the electrode, the depth T of a single blind hole is 6 μm, i.e., the value of T / H0 is 0.5; in Example 19, the number of blind holes accounts for 20% of the total number of holes on the current collector, and based on the thickness direction of the electrode, the depth T of a single blind hole is 6 μm, i.e., the value of T / H0 is 0.5; when the value of W1 changes, the mass percentage of the first conductive agent remains unchanged, while the mass percentage of the first active material changes accordingly; when the value of W2 changes, the mass percentage of the second conductive agent remains unchanged, while the mass percentage of the second active material changes accordingly; when the thickness of the first material layer and / or the thickness of the second material layer changes, the coating weight of the first material layer and / or the coating weight of the second material layer is adjusted so that the values ​​of H1 and / or H2 are as shown in Table 1.

[0120] Example 26

[0121] Except for the preparation of the positive and negative electrode sheets according to the following steps, the rest is the same as in Example 1.

[0122] <Preparation of Negative Electrode Sheets>

[0123] The electrode is a negative electrode. The first active material artificial graphite, the first conductive agent conductive carbon black, the first binder SBR, and the first dispersant CMC are mixed in a weight ratio of 97:1:1:1. Deionized water is added as a solvent, and the mixture is stirred evenly to form a first material layer slurry with a solid content of 55wt%.

[0124] The second active material, artificial graphite, the second conductive agent, conductive carbon black, the second binder, SBR, and the second dispersant, CMC, are mixed in a weight ratio of 96:1:2:1. Deionized water is added as a solvent to prepare a second material layer slurry with a solid content of 50wt%.

[0125] A copper foil with a thickness H0 of 6 μm was selected as the original negative electrode current collector, i.e., the current collector before drilling. A porous structure was set on the copper foil by laser drilling. The proportion A of the total number of holes on the current collector based on the through holes was 100%, and the diameter D of a single hole was 3 μm. Along the length direction after the current collector was unfolded, the distance L1 between two adjacent holes was 1500 μm. Along the width direction after the current collector was unfolded, the distance L2 between two adjacent holes was 150 μm. The shortest distance between a single hole and the first edge and the shortest distance between a single hole and the second edge were both 1000 μm. The shortest distance between a single hole and the third edge and the shortest distance between a single hole and the fourth edge were both 500 μm.

[0126] The first and second material layer slurries prepared above were simultaneously and uniformly coated onto one surface of a current collector with a thickness H0 of 6 μm using a double-layer coating machine. The coated surfaces were then dried at 90°C to obtain a negative electrode sheet with a single-sided coating of the first and second material layers. The above steps were then repeated on the other surface of the current collector to obtain a negative electrode sheet with a double-sided coating of the first and second material layers. After cold pressing and slitting, negative electrode sheets with a size of 64 mm × 1730 mm were obtained for later use. The Dv50 (D1) of the first active material was 2 μm, and the Dv50 (D2) of the second active material was 10 μm; the coating weight of the first material layer was 0.086 mg / mm². 2 The coating weight of the second material layer is 0.036 mg / mm². 2 The thickness of the first material layer is H1, which is 53 μm, and the thickness of the second material layer is H2, which is 23 μm. Based on the mass of the first material layer, the mass percentage of the first adhesive, W1, is 1%, and based on the mass of the second material layer, the mass percentage of the second adhesive, W2, is 2%.

[0127] <Preparation of the positive electrode>

[0128] Single-crystal LiNi, the positive electrode active material 0.9 Co 0.05 Mn 0.05O2, PVDF binder, and CNT conductive agent were mixed in a mass ratio of 97:2:1. N-methylpyrrolidone (NMP) was added as a solvent to prepare a slurry with a solid content of 65 wt%. The mixture was then stirred evenly in a vacuum mixer to obtain the positive electrode slurry. This positive electrode slurry was uniformly coated onto one surface of a 12 μm thick aluminum foil used as a positive electrode current collector. The foil was then dried at 90°C to obtain a positive electrode sheet with a single-sided coating of the positive electrode material layer. The coating weight of the positive electrode material layer was 0.260 mg / mm². 2 Then, repeat the above steps on the other surface of the aluminum foil to obtain a positive electrode sheet with a double-sided coating of positive electrode material. After drying at 90°C, it is cold-pressed and cut into strips to obtain positive electrode sheets with a size of 60mm × 1680mm for later use. The thickness of the single-sided positive electrode material layer is 74μm.

[0129] Example 27

[0130] Except for adjusting the relevant preparation parameters according to Table 1, the rest is the same as in Example 26.

[0131] Example 28

[0132] Except for the preparation of the positive electrode sheet, which is the same as in Example 1, and the preparation of the negative electrode sheet, which is the same as in Example 27, and the relevant preparation parameters are adjusted according to Table 1, the rest is the same as in Example 1.

[0133] Comparative Example 1

[0134] Except for the absence of a porous structure on the current collector in the <Preparation of the Positive Electrode> section, and the adjustment of the relevant preparation parameters according to Table 1, the rest is the same as in Example 1. Specifically, when the value of W1 changes, the mass percentage of the first conductive agent remains unchanged, while the mass percentage of the first active material changes accordingly; when the value of W2 changes, the mass percentage of the second conductive agent remains unchanged, while the mass percentage of the second active material changes accordingly.

[0135] Comparative Examples 2 to 4

[0136] Except for adjusting the relevant preparation parameters according to Table 1, everything else is the same as in Example 1.

[0137] The preparation and performance parameters of each embodiment and comparative example are shown in Table 1.

[0138]

[0139]

[0140] Note: " / " in Table 1 indicates that there are no relevant preparation parameters.

[0141] As can be seen from Examples 1 to 28 and Comparative Examples 1 to 4, by setting holes on the current collector that meet the requirements of this application, ensuring that the tensile strength of the current collector is within the aforementioned range, and simultaneously applying a double-layer coating on the current collector, the lithium-ion battery exhibits a lower temperature rise at 25°C during 10C discharge and a higher capacity retention rate at 25°C during 10C discharge, indicating that the lithium-ion battery of this application has good kinetic performance. Comparative Example 1 uses a conventional current collector; the spacing between two adjacent holes in Comparative Example 3 is not within the range of this application; the lithium-ion batteries of Comparative Examples 1 and 3 exhibit higher temperature rise at 25°C during 10C discharge and lower capacity retention rates at 25°C during 10C discharge, indicating that the lithium-ion batteries of Comparative Examples 1 and 3 have poorer kinetic performance. In Comparative Example 2, the diameter of a single hole is larger than the upper limit of this application. This excessively large diameter results in low tensile strength and elongation of the current collector. During electrode processing, coating or cold pressing cannot be properly connected and wound, leading to frequent tape breakage. The electrode is difficult to process in actual production. In Comparative Example 4, the diameter of a single hole is smaller than the lower limit of this application, and the spacing between adjacent holes along the unfolded length and width directions is too small. Current lasers or other technologies do not have the capability to prepare the porous current collector of Comparative Example 4, making the electrode impossible to process in actual production. In contrast, the lithium-ion batteries in Examples 1 to 28 exhibit low temperature rise at 25°C and high capacity retention at 25°C, indicating that the lithium-ion battery of this application has excellent kinetic performance.

[0142] The value of D typically affects the kinetic performance of lithium-ion batteries. As can be seen from Examples 1 to 7, when the value of D is within the range of this application, the lithium-ion battery exhibits a lower temperature rise at 25°C during 10C discharge and a higher capacity retention rate at 25°C during 10C discharge, indicating that the lithium-ion battery of this application has good kinetic performance.

[0143] The values ​​of D1 and D2 typically affect the kinetic performance of lithium-ion batteries. As can be seen from Examples 1, 8 to 12, when the values ​​of D1 and D2 are within the range of this application, the lithium-ion battery exhibits a low temperature rise at 25°C during 10C discharge and a high capacity retention rate at 25°C during 10C discharge, indicating that the lithium-ion battery of this application has good kinetic performance.

[0144] The value of D2 / D1 typically affects the kinetic performance of lithium-ion batteries. As can be seen from Examples 1, 8 to 12, when the value of D2 / D1 is within the range of this application, the lithium-ion battery exhibits a lower temperature rise at 25°C during 10C discharge and a higher capacity retention rate at 25°C during 10C discharge, indicating that the lithium-ion battery of this application possesses excellent kinetic performance.

[0145] The values ​​of H1 / H2 and H2 typically affect the kinetic performance of lithium-ion batteries. As can be seen from Examples 1, 13, and 14, when the values ​​of H1 / H2 and H2 are within the range of this application, the lithium-ion battery exhibits a low temperature rise during 10C discharge at 25°C and a high capacity retention rate during 10C discharge at 25°C, indicating that the lithium-ion battery of this application possesses excellent kinetic performance.

[0146] The value of L3 typically affects the kinetic performance of lithium-ion batteries. As can be seen from Examples 1, 15 to 17, when the value of L3 is within the range of this application, the lithium-ion battery exhibits a lower temperature rise at 25°C during 10C discharge and a higher capacity retention rate at 25°C during 10C discharge, indicating that the lithium-ion battery of this application has good kinetic performance.

[0147] The value of L4 typically affects the kinetic performance of lithium-ion batteries. As can be seen from Examples 1, 15 to 17, when the value of L4 is within the range of this application, the lithium-ion battery exhibits a lower temperature rise at 25°C during 10C discharge and a higher capacity retention rate at 25°C during 10C discharge, indicating that the lithium-ion battery of this application has good kinetic performance.

[0148] The value of A typically affects the kinetic performance of lithium-ion batteries. As can be seen from Examples 1, 18 to 19, when the value of A is within the range of this application, the lithium-ion battery exhibits a lower temperature rise at 25°C during 10C discharge and a higher capacity retention rate at 25°C during 10C discharge, indicating that the lithium-ion battery of this application has good kinetic performance.

[0149] The values ​​of W2 / W1 and W1 typically affect the kinetic performance of lithium-ion batteries. As can be seen from Examples 1, 20 to 24, when the values ​​of W2 / W1 and W1 are within the range of this application, the lithium-ion battery exhibits a low temperature rise at 25°C during 10C discharge and a high capacity retention rate at 25°C during 10C discharge, indicating that the lithium-ion battery of this application has good kinetic performance.

[0150] The value of W2 typically affects the kinetic performance of lithium-ion batteries. As can be seen from Examples 1, 20 to 24, when the value of W2 is within the range of this application, the lithium-ion battery exhibits a lower temperature rise at 25°C during 10C discharge and a higher capacity retention rate at 25°C during 10C discharge, indicating that the lithium-ion battery of this application has good kinetic performance.

[0151] The value of H0 typically affects the kinetic performance of lithium-ion batteries. As can be seen from Examples 1, 25 to 27, when the value of H0 is within the range of this application, the lithium-ion battery exhibits a low temperature rise at 25°C during 10C discharge and a high capacity retention rate at 25°C during 10C discharge, indicating that the lithium-ion battery of this application has good kinetic performance.

[0152] The processing of positive and / or negative electrodes typically affects the kinetic performance of lithium-ion batteries. As can be seen from Examples 1, 25 to 28, when the processed electrodes are positive and / or negative, the lithium-ion battery exhibits a lower temperature rise at 25°C during 10C discharge and a higher capacity retention rate at 25°C during 10C discharge, indicating that the lithium-ion battery of this application possesses excellent kinetic performance.

[0153] The value of ε typically affects the kinetic performance of lithium-ion batteries. As can be seen from Examples 1 to 7 and Examples 25 to 26, when the value of ε is within the range of this application, the lithium-ion battery exhibits a low temperature rise at 25°C during 10C discharge and a high capacity retention rate at 25°C during 10C discharge, indicating that the lithium-ion battery of this application has good kinetic performance.

[0154] The value of S typically affects the kinetic performance of lithium-ion batteries. As can be seen from Examples 1 to 7 and Examples 25 to 26, when the value of S is within the range of this application, the lithium-ion battery exhibits a lower temperature rise at 25°C during 10C discharge and a higher capacity retention rate at 25°C during 10C discharge, indicating that the lithium-ion battery of this application has good kinetic performance.

[0155] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, or article that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, or article.

[0156] The various embodiments in this specification are described in a related manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

[0157] The above description is only a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A secondary battery, comprising an electrode, the electrode comprising a current collector and a material layer disposed on at least one surface of the current collector, the material layer comprising a first material layer and a second material layer, wherein the first material layer is located between the second material layer and the current collector along the thickness direction of the electrode; The current collector has a porous structure, with a pore diameter of D μm, where 0.1 ≤ D ≤ 10. Along the length of the unfolded electrode, the distance between two adjacent pores is L1 μm, where 10D ≤ L1 ≤ 1000D. Along the width of the unfolded electrode, the distance between two adjacent pores is L2 μm, where 10D ≤ L2 ≤ 100D. The tensile strength of the current collector is σMPa, 180≤σ≤650.

2. The secondary battery according to claim 1, wherein, 0.5≤D≤5。 3. The secondary battery according to claim 1, wherein, The first material layer includes a first active material, wherein the Dv50 of the first active material is D1μm and 0.1≤D1≤10; and / or, the second material layer includes a second active material, wherein the Dv50 of the second active material is D2μm and 1≤D2≤20.

4. The secondary battery according to claim 3, wherein, 1.5≤D2 / D1≤200.

5. The secondary battery according to claim 1, wherein, The thickness of the first material layer is H1μm, the thickness of the second material layer is H2μm, 0.2≤H1 / H2≤5, and 20≤H2≤100.

6. The secondary battery according to claim 1, wherein, Along the width direction after the electrode is unfolded, the current collector has a first edge and a second edge, and the shortest distance between a single hole and the first edge or the second edge is L3μm, 300≤L3≤5000.

7. The secondary battery according to claim 1, wherein, Along the length direction after the electrode is unfolded, the current collector has a third edge and a fourth edge, and the shortest distance between a single hole and the third edge or the fourth edge is L4μm, 10≤L4≤1000.

8. The secondary battery according to claim 1, wherein, The elongation of the current collector is ε, where 2.5% ≤ ε ≤ 8%.

9. The secondary battery according to claim 1, wherein, The dyne value of the current collector is S dyne / cm, where 30≤S≤55.

10. The secondary battery according to claim 1, wherein, The thickness of the current collector is H0 μm, and 3 ≤ H0 ≤ 20.

11. The secondary battery according to claim 10, wherein, The holes include through holes, and the percentage of through holes on the current collector is A, where 65% ≤ A ≤ 100%.

12. The secondary battery according to claim 11, wherein, The aperture also includes blind apertures, and the depth of a single blind aperture is T μm along the thickness direction of the electrode, where 0.1 ≤ T / H0 ≤ 0.

9.

13. The secondary battery according to claim 1, wherein, The first material layer includes a first adhesive, and the mass percentage of the first adhesive is W1 based on the mass of the first material layer. The second material layer includes a second adhesive, and the mass percentage of the second adhesive is W2 based on the mass of the second material layer. 1 ≤ W2 / W1 ≤ 4, and 0.5% ≤ W1 ≤ 1%.

14. The secondary battery according to claim 13, wherein, 1％≤W2≤2％。 15. The secondary battery according to any one of claims 1 to 14, wherein, The electrode is a positive electrode; and / or a negative electrode.

16. An electronic device comprising a secondary battery as claimed in any one of claims 1 to 15.

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