Secondary batteries and electronic devices

Abstract

The present application provides a secondary battery and an electronic device, the secondary battery comprising a pole piece and a pole ear connected to the pole piece, along the width direction of the pole piece after it is unfolded, the pole piece is divided into a first area close to the pole ear, a third area away from the pole ear, and a second area located between the first area and the third area, the width W of the pole piece, the width H1 of the first area, the width H2 of the second area, and the width H3 of the third area satisfy: 0.2W≤H1≤0.6W, 0.2W≤H2≤0.6W, 0.2W≤H3≤0.6W; the first area comprises a first active material, the second area comprises a second active material, the third area comprises a third active material, the particle size of the first active material is Dv50‑1, and the particle size of the second active material is Dv50 ‑2 , the particle size of the third active material is Dv50 ‑3 , 0.7≤Dv50‑1 / Dv50 ‑2 ≤0.9, 0.7≤Dv50‑2 / Dv50 ‑3 ≤0.9, wherein 7.5μm≤Dv50‑2≤12μm. Through the above arrangement, the temperature rise distribution in the width direction of the electrode can be improved, and the cycle performance of the secondary battery can be improved.

Description

Technical Field

[0001] The present application relates to the field of electrochemical technology, and in particular to a secondary battery and an electronic device. Background Art

[0002] In order to solve the severe problems of global energy crisis, environmental pollution, climate change, low-carbon economy, etc., the research and development and application of electric vehicles, large-scale power sources and power sources in the field of energy storage have become inevitable. Secondary batteries (such as lithium-ion batteries) have the advantages of high energy storage density, high open circuit voltage, low self-discharge rate, long cycle life, good safety, etc., and are widely used in various fields such as power storage, mobile electronic devices, electric vehicles and aerospace. As mobile electronic devices and electric vehicles enter a stage of rapid development, the market has put forward higher and higher requirements on the energy density and safety performance of secondary batteries.

[0003] Existing secondary batteries (such as lithium-ion batteries) have different temperature rises in the width direction of the electrode during charging and discharging, especially the temperature rise is large in the area close to the electrode ear, and small in the area far from the electrode ear, resulting in inconsistent temperature distribution of the secondary battery during charging and discharging, affecting the cycle performance of the secondary battery. Summary of the invention

[0004] The purpose of the present application is to provide a secondary battery and an electronic device to improve the temperature rise distribution in the width direction of the electrode piece, thereby improving the cycle performance of the secondary battery.

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

[0006] The first aspect of the present application provides a secondary battery, the secondary battery includes a pole piece and a pole ear connected to the pole piece, along the width direction of the pole piece after it is unfolded, the pole piece is divided into a first area close to the pole ear, a third area away from the pole ear, and a second area between the first area and the third area, the width W of the pole piece, the width H1 of the first area, the width H2 of the second area, and the width H3 of the third area satisfy: 0.2W≤H1≤0.6W, 0.2W≤H2≤0.6W, 0.2W≤H3≤0.6W, and the units of W, H1, H2, and H3 are all mm. The first area includes a first active material, the second area includes a second active material, and the third area includes a third active material. The particle size of the first active material is Dv50-1, and the particle size of the second active material is Dv50 -2 , the particle size of the third active material is Dv50 -3 , 0.7≤Dv50-1 / Dv50 -2 ≤0.9, 0.7≤Dv50-2 / Dv50 -3≤0.9, wherein 7.5μm≤Dv50-2≤12μm. The secondary battery provided in the first aspect of the present application is provided by dividing the pole piece into a first region, a second region and a third region along the width direction, wherein the relationship between the width of each of the first region, the second region and the third region and the width of the pole piece meets the requirements of the present application, and regulating the ratio of the particle size of the first active material in the first region and the second active material in the second region Dv50-1 / Dv50 -2 , the ratio of the particle size of the second active material in the second region to the particle size of the third active material in the third region Dv50-2 / Dv50 -3 As well as the particle size of the second active material in the second region being within the scope of the present application, the temperature rise distribution in the width direction of the pole piece can be improved, and the consistency of the temperature distribution in each region during the charge and discharge process of the secondary battery can be improved, thereby improving the cycle performance of the secondary battery.

[0007] In some embodiments of the present application, the charge transfer impedance of the first region is Rct1, the charge transfer impedance of the second region is Rct2, 0.7≤Rct1 / Rct2≤0.9, 43.5 mΩ / mm 2 ≤Rct2≤113mΩ / mm 2 Regulating the ratio Rct1 / Rct2 of the charge transfer impedance of the first region and the second region and the charge transfer impedance Rct2 of the second region within the above range is beneficial to improving the consistency of temperature distribution during the charging and discharging process of the secondary battery, thereby improving the cycle performance of the secondary battery.

[0008] In some embodiments of the present application, the charge transfer impedance of the third region is Rct3, 0.7≤Rct2 / Rct3≤0.9. Adjusting the ratio of the charge transfer impedance of the second region to the third region Rct2 / Rct3 within the above range is conducive to improving the consistency of temperature distribution during the charging and discharging process of the secondary battery, thereby improving the cycle performance of the secondary battery.

[0009] In some embodiments of the present application, 7μm≤Dv50-1≤10μm, and / or, 8.5μm≤Dv50-3≤15μm. Regulating the particle size of the first active material in the first region and / or the particle size of the third active material in the third region within the above range is conducive to improving the temperature rise distribution in the width direction of the pole piece, improving the consistency of the temperature distribution in each region during the charge and discharge process of the secondary battery, and thus improving the cycle performance of the secondary battery.

[0010] In some embodiments of the present application, 40 mΩ / mm 2 ≤Rct1≤86mΩ / mm 2 , and / or, 49.7mΩ / mm 2 ≤Rct3≤151mΩ / mm 2Regulating the charge transfer impedance of the first region and / or the charge transfer impedance of the third region within the above range is beneficial to improving the temperature rise distribution in the width direction of the electrode piece, improving the consistency of the temperature distribution in each region during the charge and discharge process of the secondary battery, and thus improving the cycle performance of the secondary battery.

[0011] In some embodiments of the present application, the secondary battery satisfies at least one of the following characteristics: (1) 0.80≤Dv50-1 / Dv50 -2 ≤0.85; (2)0.80≤Dv50-2 / Dv50 -3 ≤0.85; (3) 0.80≤Rct1 / Rct2≤0.85; (4) 0.80≤Rct2 / Rct3≤0.85. A secondary battery that satisfies at least one of the above characteristics is conducive to further improving the consistency of the overall temperature distribution in the width direction of the electrode, so that the consistency of the temperature distribution in each area during the charge and discharge process of the secondary battery is further improved, thereby further improving the cycle performance of the secondary battery.

[0012] In some embodiments of the present application, the electrode piece is a positive electrode piece, and the electrode tab is a positive electrode tab. When the electrode piece used in the secondary battery is a positive electrode piece, and the electrode tab is a positive electrode tab, the secondary battery has good cycle performance.

[0013] In some embodiments of the present application, the electrode is a positive electrode, 50 mm ≤ W ≤ 370 mm. Controlling the width of the positive electrode within the above range is conducive to making the positive electrode have good temperature rise distribution consistency in the width direction, and the secondary battery has good cycle performance.

[0014] In some embodiments of the present application, the pole piece is a positive pole piece, and the first active material, the second active material, and the third active material each independently include at least one of lithium nickel cobalt manganese oxide, lithium iron phosphate, lithium manganese iron phosphate, or lithium cobalt oxide. When the first active material, the second active material, and the third active material each independently select the above-mentioned types of materials as positive electrode active materials, it is beneficial for the secondary battery to have good performance, such as good cycle performance, high energy density, good rate performance, etc.

[0015] In some embodiments of the present application, the electrode piece is a negative electrode piece, and the electrode tab is a negative electrode tab. When the electrode piece used in the secondary battery is a negative electrode piece, and the electrode tab is a negative electrode tab, the secondary battery has good cycle performance.

[0016] In some embodiments of the present application, the electrode is a negative electrode, 50 mm ≤ W ≤ 370 mm. Controlling the width of the negative electrode within the above range is conducive to making the negative electrode have good temperature rise distribution consistency in the width direction, and the secondary battery has good cycle performance.

[0017] In some embodiments of the present application, the pole piece is a negative pole piece, and the first active material, the second active material, and the third active material each independently include at least one of artificial graphite, natural graphite, hard carbon, soft carbon, pure silicon, silicon-carbon compound, or silicon-oxygen compound. When the first active material, the second active material, and the third active material each independently select the above-mentioned types of materials as negative electrode active materials, it is beneficial for the secondary battery to have good performance, such as good cycle performance, rate performance, and kinetic performance, and higher energy density.

[0018] The second aspect of the present application provides an electronic device, which comprises the secondary battery described in any of the above embodiments. Therefore, the electronic device has good performance.

[0019] Beneficial effects of this application:

[0020] The embodiment of the present application provides a secondary battery and an electronic device. The secondary battery divides the electrode sheet into a first region, a second region and a third region along the width direction. The relationship between the width of each of the first region, the second region and the third region and the electrode sheet width meets the requirements of the present application, and the ratio of the particle size of the first active material in the first region and the second active material in the second region is regulated. -2 , the ratio of the particle size of the second active material in the second region to the particle size of the third active material in the third region Dv50-2 / Dv50 -3 As well as the particle size of the second active material in the second region being within the scope of the present application, the temperature rise distribution in the width direction of the pole piece can be improved, and the consistency of the temperature distribution in each region during the charge and discharge process of the secondary battery can be improved, thereby improving the cycle performance of the secondary battery.

[0021] Of course, implementing any product or method of the present application does not necessarily require achieving all of the advantages described above at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other embodiments can also be obtained based on these drawings.

[0023] Figure 1 This is a schematic diagram of the cross-sectional structure of the pole piece of some implementation schemes of the present application along its own length and width directions after being unfolded.

[0024] Reference numerals: 10 - pole piece, 11 - first region, 12 - second region, 13 - third region, 20 - pole ear. DETAILED DESCRIPTION

[0025] The following will be combined with the embodiments of the present application and the accompanying drawings to clearly and completely describe the technical solutions in the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those skilled in the art based on the present application belong to the scope of protection of the present application.

[0026] It should be noted that in the specific implementation manner of the present application, the present application is explained by taking a lithium-ion battery as an example of a secondary battery, but the secondary battery of the present application is not limited to a lithium-ion battery.

[0027] The first aspect of the present application provides a secondary battery, which includes a pole piece and a pole ear connected to the pole piece. Along the width direction of the pole piece after it is unfolded, the pole piece is divided into a first area close to the pole ear, a third area away from the pole ear, and a second area between the first area and the third area. The width W of the pole piece, the width H1 of the first area, the width H2 of the second area, and the width H3 of the third area satisfy: 0.2W≤H1≤0.6W, 0.2W≤H2≤0.6W, 0.2W≤H3≤0.6W. The first area includes a first active material, the second area includes a second active material, and the third area includes a third active material. The particle size of the first active material is Dv50-1, and the particle size of the second active material is Dv50 -2 , the particle size of the third active material is Dv50 -3 , 0.7≤Dv50-1 / Dv50 -2 ≤0.9, 0.7≤Dv50-2 / Dv50 -3 ≤0.9, among which, 7.5μm≤Dv50-2≤12μm.

[0028] For ease of understanding, in this application, the length direction of the pole piece itself is defined as X, and the width direction is defined as Y. It should be understood that the above definition of direction is for the purpose of convenient description of this application, and the direction defined in this application can be understood based on the relative positions of the attached drawings and actual product elements. Figure 1 As shown, the pole piece 10 is connected to the pole lug 20. Along the width direction Y after the pole piece 10 is unfolded, the pole piece 10 is divided into a first area 11 close to the pole lug 20, a third area 13 away from the pole lug 20, and a second area 12 located between the first area 11 and the third area 13. It can be understood that the "close to" and "away from" in the above text are only expressions distinguished relative to the position of the pole lug 20. The width of the pole piece 10 is shown as W, the width of the first area 11 is shown as H1, the width of the second area 12 is shown as H2, and the width of the third area 13 is shown as H3. It can be understood that the sum of the widths of the first area 11, the second area 12, and the third area 13 is the width W of the pole piece 10.

[0029] For example, H1 is 0.2W, 0.3W, 0.4W, 0.5W, 0.6W or any value between any two of the above numerical ranges. H2 is 0.2W, 0.3W, 0.4W, 0.5W, 0.6W or any value between any two of the above numerical ranges. H3 is 0.2W, 0.3W, 0.4W, 0.5W, 0.6W or any value between any two of the above numerical ranges. The width H1 of the first region, the width H2 of the second region or the width H3 of the third region is less than 0.2W, and the width of the first region, the second region or the third region is too small, and the improvement of the temperature rise distribution effect is not obvious; if any of the width H1 of the first region, the width H2 of the second region or the width H3 of the third region is greater than 0.6W, the widths of the other two regions will be reduced to less than 0.2W, which will also affect the temperature rise distribution of the pole piece along the width direction.

[0030] For example, Dv50-1 / Dv50 -2 The value is 0.7, 0.71, 0.73, 0.75, 0.77, 0.78, 0.80, 0.81, 0.83, 0.85, 0.86, 0.87, 0.89, 0.9 or any value between any two of the above ranges. Dv50-1 / Dv50 -2 The value is less than 0.7, the particle size of the first active material is too small relative to the second active material, the ratio of the charge transfer impedance between the first region and the second region is too small, the temperature rise of the first region is too large compared with the temperature rise of the second region, affecting the consistency of the temperature distribution between the first region and the second region in the width direction of the pole piece; Dv50-1 / Dv50 -2 The value is greater than 0.9, the particle sizes of the first active material and the second active material are close, the temperature rise in the first area close to the pole ear will be greater than the temperature rise in the second area, and the possibility of the first area and the second area in the width direction of the pole piece reaching the same temperature distribution is low.

[0031] For example, Dv50-2 / Dv50 -3 The value is 0.7, 0.72, 0.73, 0.75, 0.76, 0.78, 0.79, 0.81, 0.82, 0.84, 0.86, 0.87, 0.89, 0.9 or any value between any two of the above ranges. Dv50-2 / Dv50 -3 The value is less than 0.7, the particle size of the second active material is too small relative to the third active material, the ratio of the charge transfer impedance of the second region and the third region is too small, the temperature rise of the second region is too large compared with the temperature rise of the second region, which affects the consistency of the temperature distribution of the second region and the third region in the width direction of the pole piece; Dv50-1 / Dv50 -2The value is greater than 0.9, the particle size of the second active material is close to that of the third active material. Since the second region is closer to the pole ear than the third region, the temperature rise of the second region will be greater than the temperature rise of the third region. The possibility of the second region and the third region achieving consistent temperature distribution in the width direction of the pole piece is low.

[0032] For example, Dv50-2 is 7.5μm, 7.7μm, 8.2μm, 8.5μm, 9μm, 9.2μm, 9.5μm, 9.8μm, 10.0μm, 10.5μm, 11.0μm, 11.2μm, 11.5μm, 11.7μm, 11.8μm, 12μm or any value between any two of the above numerical ranges. The particle size of the second active material in the second region is less than 7.5μm, the particle size of the second active material is too small, the second active material is easy to agglomerate during the preparation of the active slurry, and the second active material will be unevenly distributed in the second active material layer, affecting the performance of the secondary battery, such as cycle performance, energy density, rate performance, etc.; the particle size of the second active material in the second region is greater than 12μm, the particle size of the second active material is too large, which will affect the contact between the active material particles, affect the conductivity of the second active material layer, and also increase the thickness of the second active material layer, so that the energy density of the secondary battery is lost.

[0033] In general, the secondary battery provided in the first aspect of the present application is characterized in that the relationship between the width of each of the first region, the second region and the third region and the width of the electrode sheet meets the requirements of the present application, and the ratio of the particle size of the first active material in the first region and the second active material in the second region is regulated Dv50-1 / Dv50. -2 , the ratio of the particle size of the second active material in the second region to the particle size of the third active material in the third region Dv50-2 / Dv50 -3 As well as the particle size of the second active material in the second region being within the scope of the present application, the temperature rise distribution in the width direction of the pole piece can be improved, and the consistency of the temperature distribution in each region during the charge and discharge process of the secondary battery can be improved, thereby improving the cycle performance of the secondary battery.

[0034] In some embodiments of the present application, 0.80≤Dv50-1 / Dv50 -2 ≤0.85. For example, Dv50-1 / Dv50 -2 The value is 0.80, 0.81, 0.82, 0.83, 0.84, 0.85 or any value between any two of the above numerical ranges. The ratio of the particle size of the first active material in the first region to the particle size of the second active material in the second region is Dv50-1 / Dv50 -2Controlling within the above range is conducive to further improving the consistency of temperature distribution in the first region and the second region in the width direction of the electrode, thereby further improving the overall consistency of temperature distribution in the width direction of the electrode, and further improving the consistency of temperature distribution in each region during the charge and discharge process of the secondary battery, thereby further improving the cycle performance of the secondary battery.

[0035] In some embodiments of the present application, 0.80≤Dv50-2 / Dv50 -3 ≤0.85. For example, Dv50-2 / Dv50 -3 The value of is 0.80, 0.81, 0.82, 0.83, 0.84, 0.85 or any value between any two of the above numerical ranges. The ratio of the particle size of the second active material in the second region to the particle size of the third active material in the third region is Dv50-2 / Dv50 -3 Controlling within the above range is conducive to further improving the consistency of temperature distribution in the second and third regions in the width direction of the electrode, thereby further improving the overall consistency of temperature distribution in the width direction of the electrode, and further improving the consistency of temperature distribution in each region during the charging and discharging process of the secondary battery, thereby further improving the cycle performance of the secondary battery.

[0036] The present application has no particular limitation on the method for regulating the particle sizes of the first active material, the second active material and the third active material, as long as the purpose of the present application can be achieved. For example, it can be achieved by crushing or screening.

[0037] In the present application, the “particle size of the first active material” refers to the particle size at which the volume accumulation of the first active material particles is 50% from the small particle size side in the volume-based particle size distribution. The “particle size of the second active material” refers to the particle size at which the volume accumulation of the second active material particles is 50% from the small particle size side in the volume-based particle size distribution. The “particle size of the third active material” refers to the particle size at which the volume accumulation of the third active material particles is 50% from the small particle size side in the volume-based particle size distribution.

[0038] In some embodiments of the present application, the charge transfer impedance of the first region is Rct1, the charge transfer impedance of the second region is Rct2, 0.7≤Rct1 / Rct2≤0.9, 43.5 mΩ / mm 2 ≤Rct2≤113mΩ / mm 2 For example, the value of Rct1 / Rct2 is 0.7, 0.72, 0.73, 0.75, 0.76, 0.78, 0.79, 0.81, 0.82, 0.84, 0.86, 0.87, 0.89, 0.9 or any value between any two of the above ranges. For example, Rct2 is 43.5 mΩ / mm 2 , 44.5mΩ / mm2 、47mΩ / mm 2 , 49.2mΩ / mm 2 、52mΩ / mm 2 、53mΩ / mm 2 、57mΩ / mm 2 、59.2mΩ / mm 2 、61mΩ / mm 2 、63mΩ / mm 2 、64.2mΩ / mm 2 、67mΩ / mm 2 、68mΩ / mm 2 、70mΩ / mm 2 、80mΩ / mm 2 、87mΩ / mm 2 、92mΩ / mm 2 、96mΩ / mm 2 , 100mΩ / mm 2 , 102mΩ / mm 2 , 105mΩ / mm 2 , 110mΩ / mm 2 , 113mΩ / mm 2 Or any value between any two of the above ranges. Regulating the ratio Rct1 / Rct2 of the charge transfer impedance of the first region and the second region and the charge transfer impedance Rct2 of the second region within the above range is conducive to improving the temperature rise distribution of the first region and the second region in the width direction of the pole piece, thereby improving the overall temperature rise temperature in the width direction of the pole piece, which is conducive to improving the consistency of the temperature distribution during the charging and discharging process of the secondary battery, so that the cycle performance of the secondary battery is improved.

[0039] In some embodiments of the present application, the charge transfer impedance of the third region is Rct3, 0.7≤Rct2 / Rct3≤0.9. For example, the value of Rct2 / Rct3 is 0.7, 0.72, 0.73, 0.75, 0.76, 0.78, 0.79, 0.81, 0.82, 0.84, 0.86, 0.87, 0.89, 0.9 or any value between any two of the above ranges. Regulating the ratio Rct2 / Rct3 of the charge transfer impedance of the second region and the third region within the above range is conducive to improving the temperature rise distribution of the second region and the third region in the width direction of the pole piece, thereby improving the overall temperature rise temperature in the width direction of the pole piece, which is conducive to improving the consistency of the temperature distribution during the charging and discharging process of the secondary battery, so that the cycle performance of the secondary battery is improved.

[0040] The present application has no particular restrictions on the regulation method of the charge transfer impedance of the first region, as long as the purpose of the present application can be achieved. For example, it can be achieved by regulating the particle size of the first active material in the first region. Generally speaking, the larger the particle size of the first active material, the larger the charge transfer impedance of the first region; the smaller the particle size of the first active material, the smaller the charge transfer impedance of the first region. The present application has no particular restrictions on the regulation method of the charge transfer impedance of the second region, as long as the purpose of the present application can be achieved. For example, it can be achieved by regulating the particle size of the second active material in the second region. Generally speaking, the larger the particle size of the second active material, the larger the charge transfer impedance of the second region; the smaller the particle size of the second active material, the smaller the charge transfer impedance of the second region. The present application has no particular restrictions on the regulation method of the charge transfer impedance of the third region, as long as the purpose of the present application can be achieved. For example, it can be achieved by regulating the particle size of the third active material in the third region. Generally speaking, the larger the particle size of the third active material, the larger the charge transfer impedance of the third region; the smaller the particle size of the third active material, the smaller the charge transfer impedance of the third region.

[0041] In some embodiments of the present application, 7μm≤Dv50-1≤10μm. For example, the particle size Dv50-1 of the first active material is 7μm, 7.3μm, 7.6μm, 8.0μm, 8.3μm, 8.5μm, 8.8μm, 9.0μm, 9.2μm, 9.5μm, 9.7μm, 10μm or any value between any two of the above numerical ranges. Regulating the particle size of the first active material in the first region within the above range is conducive to uniformly distributing the first active material particles in the first region, so that the charge transfer impedance of the first region is regulated within the scope of the present application. In this way, it is conducive to improving the temperature rise distribution in the width direction of the pole piece, improving the consistency of the temperature distribution in each region during the charging and discharging process of the secondary battery, and thus improving the cycle performance of the secondary battery.

[0042] In some embodiments of the present application, 8.5 μm ≤ Dv50-3 ≤ 15 μm. For example, the particle size Dv50 of the third active material is -28.5μm, 8.8μm, 9.0μm, 9.2μm, 9.5μm, 9.7μm, 10μm, 10.7μm, 11μm, 11.2μm, 11.6μm, 12μm, 12.6μm, 13.1μm, 13.7μm, 14.3μm, 14.6μm, 15μm or any value between any two of the above numerical ranges. Regulating the particle size of the third active material in the third region within the above range is conducive to uniformly distributing the third active material particles in the third region, so that the charge transfer impedance of the third region is regulated within the scope of this application. In this way, it is conducive to improving the temperature rise distribution in the width direction of the pole piece, improving the consistency of the temperature distribution in each region during the charging and discharging process of the secondary battery, and thus improving the cycle performance of the secondary battery.

[0043] In some embodiments of the present application, 7 μm ≤ Dv50-1 ≤ 10 μm, 8.5 μm ≤ Dv50-3 ≤ 15 μm. For example, the particle size Dv50-1 of the first active material is 7 μm, 7.3 μm, 7.6 μm, 8.0 μm, 8.3 μm, 8.5 μm, 8.8 μm, 9.0 μm, 9.2 μm, 9.5 μm, 9.7 μm, 10 μm, or any value between any two of the above numerical ranges. The particle size Dv50 of the third active material is -3 8.5μm, 8.8μm, 9.0μm, 9.2μm, 9.5μm, 9.7μm, 10μm, 10.7μm, 11μm, 11.2μm, 11.6μm, 12μm, 12.6μm, 13.1μm, 13.7μm, 14.3μm, 14.6μm, 15μm or any value between any two of the above ranges. Regulating the particle size of the first active material in the first region and / or the particle size of the third active material in the third region within the above range is beneficial to improving the temperature rise distribution in the width direction of the pole piece, improving the consistency of the temperature distribution in each region during the charge and discharge process of the secondary battery, thereby improving the cycle performance of the secondary battery.

[0044] In some embodiments of the present application, 40 mΩ / mm 2 ≤Rct1≤86mΩ / mm 2 For example, the charge transfer resistance Rct1 of the first region is 40 mΩ / mm 2 , 44.5mΩ / mm 2 、47mΩ / mm 2 , 49.2mΩ / mm 2 、52mΩ / mm 2 、53mΩ / mm 2 、57mΩ / mm 2 、59.2mΩ / mm 2 、60mΩ / mm 2 、64mΩ / mm2 、70mΩ / mm 2 、73mΩ / mm 2 、80mΩ / mm 2 、86mΩ / mm 2 Or any value between any two of the above value ranges. Adjusting the charge transfer impedance Rct1 of the first region within the above range is beneficial to improving the temperature rise distribution in the width direction of the electrode, improving the consistency of temperature distribution in each region during the charge and discharge process of the secondary battery, and thus improving the cycle performance of the secondary battery.

[0045] In some embodiments of the present application, 49.7 mΩ / mm 2 ≤Rct3≤151mΩ / mm 2 For example, the charge transfer impedance Rct3 of the third region is 49.7 mΩ / mm 2 、52mΩ / mm 2 、53mΩ / mm 2 、57mΩ / mm 2 、59.2mΩ / mm 2 、60mΩ / mm 2 、61mΩ / mm 2 、63mΩ / mm 2 、64.2mΩ / mm 2 、67mΩ / mm 2 、68mΩ / mm 2 、70mΩ / mm 2 、72.2mΩ / mm 2 、74.3mΩ / mm 2 , 75mΩ / mm 2 、77mΩ / mm 2 、80.5mΩ / mm 2 、85mΩ / mm 2 , 90mΩ / mm 2 、96mΩ / mm 2 , 101mΩ / mm 2 , 103mΩ / mm 2 , 113mΩ / mm 2 , 120mΩ / mm 2 , 131mΩ / mm 2 , 147mΩ / mm 2 , 151mΩ / mm 2 Adjusting the charge transfer impedance Rct3 of the third region within the above range is beneficial to improving the temperature rise distribution in the width direction of the electrode, improving the consistency of the temperature distribution in each region during the charge and discharge process of the secondary battery, and thus improving the cycle performance of the secondary battery.

[0046] In some embodiments of the present application, 40 mΩ / mm 2 ≤Rct1≤86mΩ / mm 2 , 49.7mΩ / mm 2 ≤Rct3≤151mΩ / mm 2 For example, the charge transfer resistance Rct1 of the first region is 40 mΩ / mm 2 , 44.5mΩ / mm 2 、47mΩ / mm 2 , 49.2mΩ / mm 2 、52mΩ / mm 2 、53mΩ / mm 2 、57mΩ / mm 2 、59.2mΩ / mm 2 、60mΩ / mm 2 、64mΩ / mm 2 、70mΩ / mm 2 、73mΩ / mm 2 、80mΩ / mm 2 、86mΩ / mm 2 Or any value between any two of the above value ranges. The charge transfer impedance Rct3 of the third region is 49.7 mΩ / mm 2 、52mΩ / mm 2 、53mΩ / mm 2 、57mΩ / mm 2 、59.2mΩ / mm 2 、60mΩ / mm 2 、61mΩ / mm 2 、63mΩ / mm 2 、64.2mΩ / mm 2 、67mΩ / mm 2 、68mΩ / mm 2 、70mΩ / mm 2 、72.2mΩ / mm 2 、74.3mΩ / mm 2 , 75mΩ / mm 2 、77mΩ / mm 2 、80.5mΩ / mm 2 、85mΩ / mm 2 , 90mΩ / mm 2 、96mΩ / mm 2 , 101mΩ / mm 2 , 103mΩ / mm 2 , 120mΩ / mm 2 , 131mΩ / mm 2 , 147mΩ / mm2 , 151mΩ / mm 2 Or any value between any two of the above ranges. Adjusting the charge transfer impedance Rct1 of the first region and the charge transfer impedance Rct3 of the third region within the above range is beneficial to improving the temperature rise distribution in the width direction of the electrode piece, improving the consistency of the temperature distribution in each region during the charge and discharge process of the secondary battery, and thus improving the cycle performance of the secondary battery.

[0047] In some embodiments of the present application, 0.80≤Rct1 / Rct2≤0.85. For example, the value of Rct1 / Rct2 is 0.80, 0.81, 0.82, 0.83, 0.84, 0.85 or any value between any two of the above ranges. Regulating the ratio Rct1 / Rct2 of the charge transfer impedance of the first region and the charge transfer impedance of the second region within the above range is conducive to further improving the consistency of the temperature distribution of the first region and the second region in the width direction of the pole piece, thereby further improving the consistency of the overall temperature distribution in the width direction of the pole piece, and further improving the consistency of the temperature distribution of each region during the charge and discharge process of the secondary battery, thereby further improving the cycle performance of the secondary battery.

[0048] In some embodiments of the present application, 0.80≤Rct2 / Rct3≤0.85. For example, the value of Rct2 / Rct3 is 0.80, 0.81, 0.82, 0.83, 0.84, 0.85 or any value between any two of the above ranges. Regulating the ratio Rct2 / Rct3 of the charge transfer impedance of the second region and the charge transfer impedance of the third region within the above range is conducive to further improving the consistency of the temperature distribution of the second region and the third region in the width direction of the pole piece, thereby further improving the consistency of the overall temperature distribution in the width direction of the pole piece, and further improving the consistency of the temperature distribution of each region during the charge and discharge process of the secondary battery, thereby further improving the cycle performance of the secondary battery.

[0049] In some embodiments of the present application, the pole piece is a positive pole piece, and the pole lug is a positive pole lug. When the pole piece used in the secondary battery is a positive pole piece, and the pole lug is a positive pole lug, the overall temperature rise distribution in the width direction of the positive pole piece is consistent, and the consistency of the temperature distribution in each region of the secondary battery during the charge and discharge process is improved, so that the secondary battery has good cycle performance.

[0050] In some embodiments of the present application, the pole piece is a positive pole piece, and 50mm≤W≤370mm. For example, the width W of the positive pole piece is 50mm, 75mm, 90mm, 120mm, 150mm, 160mm, 172mm, 190mm, 210mm, 220mm, 240mm, 270mm, 300mm, 320mm, 340mm, 352mm, 360mm, 370mm or any value between any two of the above numerical ranges. Regulating the width of the positive pole piece within the above range is conducive to making the positive pole piece have good temperature rise distribution consistency in the width direction, the temperature distribution of each region of the secondary battery during the charge and discharge process has good consistency, and the secondary battery has good cycle performance.

[0051] In some embodiments of the present application, the pole piece is a positive pole piece, and the first active material, the second active material, and the third active material each independently include at least one of lithium nickel cobalt manganese oxide, lithium iron phosphate, lithium manganese iron phosphate, or lithium cobalt oxide. When the first active material, the second active material, and the third active material each independently select the above-mentioned types of materials as positive electrode active materials, it is beneficial for the secondary battery to have good performance, such as good cycle performance, high energy density, good rate performance, etc.

[0052] In some embodiments of the present application, the pole piece is a negative pole piece, and the pole lug is a negative pole lug. When the pole piece used in the secondary battery is a negative pole piece, and the pole lug is a negative pole lug, the overall temperature rise distribution in the width direction of the negative pole piece is consistent, and the consistency of the temperature distribution in each region of the secondary battery during the charge and discharge process is improved, so that the secondary battery has good cycle performance.

[0053] In some embodiments of the present application, the pole piece is a negative pole piece, and 50mm≤W≤370mm. For example, the width W of the negative pole piece is 50mm, 77mm, 92mm, 122mm, 152mm, 162mm, 175mm, 192mm, 212mm, 224mm, 242mm, 272mm, 302mm, 322mm, 342mm, 355mm, 362mm, 370mm or any value between any two of the above numerical ranges. Regulating the width of the negative pole piece within the above range is conducive to making the negative pole piece have good temperature rise distribution consistency in the width direction, the temperature distribution of each region of the secondary battery during the charge and discharge process has good consistency, and the secondary battery has good cycle performance.

[0054] In some embodiments of the present application, the pole piece is a negative pole piece, and the first active material, the second active material, and the third active material each independently include at least one of artificial graphite, natural graphite, hard carbon, soft carbon, pure silicon, silicon-carbon compound, or silicon-oxygen compound. When the first active material, the second active material, and the third active material each independently select the above-mentioned types of materials as negative electrode active materials, it is beneficial for the secondary battery to have good performance, such as good cycle performance, rate performance, and kinetic performance, and higher energy density.

[0055] The present application has no particular restrictions on the method of connecting the pole tab and the pole piece, as long as the purpose of the present application can be achieved. For example, at least one of laser welding, ultrasonic welding or resistance welding can be used.

[0056] The present application has no particular restrictions on the material of the positive electrode tab, as long as the purpose of the present application can be achieved. For example, the material of the positive electrode tab includes at least one of aluminum (Al) or an aluminum alloy. The present application has no particular restrictions on the material of the negative electrode tab, as long as the purpose of the present application can be achieved. For example, the material of the negative electrode tab includes at least one of nickel (Ni), copper (Cu) or copper-plated nickel (Ni-Cu).

[0057] The present application has no particular restrictions on the positive electrode sheet, as long as the purpose of the present application can be achieved. For example, in some embodiments, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer, and the positive electrode active material layer is arranged on one surface or two surfaces of the positive electrode current collector. The above-mentioned "surface" can be a partial surface of the positive electrode current collector or the entire surface of the positive electrode current collector. The positive electrode active material layer includes a first positive electrode active material layer, a second positive electrode active material layer and a third positive electrode active material layer, the first positive electrode active material layer is arranged in the first region of the positive electrode sheet, the second positive electrode active material layer is arranged in the second region of the positive electrode sheet, and the third positive electrode active material layer is arranged in the third region of the positive electrode sheet. The first positive electrode active material layer includes a first active material, the second positive electrode active material layer includes a second active material, and the third positive electrode active material layer includes a third active material. The positive electrode active material layer of the present application includes a first active material, a second active material and a third active material. The present application has no particular restrictions on the positive electrode current collector, as long as the purpose of the present application can be achieved. For example, the positive electrode current collector may include aluminum foil or aluminum alloy foil, etc. In the present application, there is no particular restriction on the thickness of the positive current collector and the positive active material layer, as long as the purpose of the present application can be achieved. For example, the thickness of the positive current collector is 5μm to 20μm. The thickness of the single-layer positive active material layer is 30μm to 120μm. Optionally, the first positive active material layer, the second positive active material layer and the third positive active material layer may also independently include at least one of a positive electrode conductor, a dispersant or a positive electrode binder. The present application does not particularly restrict the types of positive electrode conductors, dispersants and positive electrode binders, as long as the purpose of the present application can be achieved. The present application does not particularly restrict the mass ratio of the first active material, the positive electrode conductor, the dispersant and the positive electrode binder in the first positive electrode active material layer, as long as the purpose of the present application can be achieved. The present application does not particularly restrict the mass ratio of the second active material, the positive electrode conductor, the dispersant and the positive electrode binder in the second positive electrode active material layer, as long as the purpose of the present application can be achieved. The present application has no particular limitation on the mass ratio of the third active material, the positive electrode conductor, the dispersant and the positive electrode binder in the third positive electrode active material layer, as long as the purpose of the present application can be achieved.

[0058] The present application has no particular restrictions on the preparation method of the positive electrode sheet, as long as the purpose of the present application can be achieved. For example, in some embodiments, the preparation method of the positive electrode sheet includes but is not limited to the following steps: (1) preparing the first region positive electrode slurry, the second region positive electrode slurry and the third region positive electrode slurry; (2) using a coating machine to simultaneously apply the first region positive electrode slurry, the second region positive electrode slurry and the third region positive electrode slurry on one surface of the positive electrode collector, and drying to obtain a semi-finished positive electrode sheet coated with the first positive electrode active material layer, the second positive electrode active material layer and the third positive electrode active material layer; (3) repeating step (2) on the other surface of the positive electrode collector to obtain a semi-finished positive electrode sheet coated with the first positive electrode active material layer, the second positive electrode active material layer and the third positive electrode active material layer on both sides; (4) cold pressing and cutting to obtain a positive electrode sheet. The present application has no particular restrictions on the solid content of the first region positive electrode slurry, the second region positive electrode slurry and the third region positive electrode slurry, as long as the purpose of the present application can be achieved. The present application has no particular restrictions on the process parameters of the above-mentioned drying, cold pressing and slitting, as long as the purpose of the present application can be achieved.

[0059] The present application has no particular restrictions on the negative electrode sheet, as long as the purpose of the present application can be achieved. For example, in some embodiments, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer, and the negative electrode active material layer is arranged on one surface or two surfaces of the negative electrode current collector. The above-mentioned "surface" can be a partial surface of the negative electrode current collector or the entire surface of the negative electrode current collector. The negative electrode active material layer includes a first negative electrode active material layer, a second negative electrode active material layer and a third negative electrode active material layer, the first negative electrode active material layer is arranged in the first region of the negative electrode sheet, the second negative electrode active material layer is arranged in the second region of the negative electrode sheet, and the third negative electrode active material layer is arranged in the third region of the negative electrode sheet. The first negative electrode active material layer includes a first active material, the second negative electrode active material layer includes a second active material, and the third negative electrode active material layer includes a third active material. The present application has no particular restrictions on the negative electrode current collector, as long as the purpose 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, foamed nickel or foamed copper, etc. In the present application, there is no particular restriction on the thickness of the negative electrode current collector and the negative electrode active material layer, as long as the purpose of the present application can be achieved. For example, the thickness of the negative electrode current collector is 6μm to 10μm, and the thickness of the negative electrode active material layer is 30μm to 130μm. Optionally, the first negative electrode active material layer, the second negative electrode active material layer and the third negative electrode active material layer can also independently include at least one of a negative electrode conductive agent, a dispersant or a negative electrode binder. The present application does not particularly restrict the types of negative electrode conductive agents, dispersants and negative electrode binders, as long as the purpose of the present application can be achieved. The present application does not particularly restrict the mass ratio of the first active material, the negative electrode conductive agent, the dispersant and the negative electrode binder in the first negative electrode active material layer, as long as the purpose of the present application can be achieved. The present application does not particularly restrict the mass ratio of the second active material, the negative electrode conductive agent, the dispersant and the negative electrode binder in the second negative electrode active material layer, as long as the purpose of the present application can be achieved. The present application has no particular limitation on the mass ratio of the third active material, the negative electrode conductor, the dispersant and the negative electrode binder in the third negative electrode active material layer, as long as the purpose of the present application can be achieved.

[0060] The present application has no particular restrictions on the method for preparing the negative electrode sheet, as long as the purpose of the present application can be achieved. For example, in some embodiments, the method for preparing the negative electrode sheet includes but is not limited to the following steps: (1) preparing the first region negative electrode slurry, the second region negative electrode slurry and the third region negative electrode slurry; (2) using a coating machine to simultaneously apply the first region negative electrode slurry, the second region negative electrode slurry and the third region negative electrode slurry on one surface of the negative electrode current collector, and drying to obtain a semi-finished negative electrode sheet coated with the first negative electrode active material layer, the second negative electrode active material layer and the third negative electrode active material layer; (3) repeating step (2) on the other surface of the negative electrode current collector to obtain a semi-finished negative electrode sheet coated with the first negative electrode active material layer, the second negative electrode active material layer and the third negative electrode active material layer on both sides; (4) cold pressing and cutting to obtain the negative electrode sheet. The present application has no particular restrictions on the solid content of the first region negative electrode slurry, the second region negative electrode slurry and the third region negative electrode slurry, as long as the purpose of the present application can be achieved. The present application has no particular restrictions on the process parameters of the above-mentioned drying, cold pressing and slitting, as long as the purpose of the present application can be achieved.

[0061] In some embodiments of the present application, the secondary battery further includes a diaphragm, which is disposed between the positive electrode sheet and the negative electrode sheet. The present application has no particular restrictions on the diaphragm, as long as the purpose of the present application can be achieved. For example, the material of the diaphragm may include, but is not limited to, polyethylene (PE), polypropylene (PP)-based polyolefins (PO), polyesters (e.g., polyethylene terephthalate (PET) films), cellulose, polyimide (PI), polyamide (PA), spandex or at least one of aramid. The type of diaphragm may include at least one of a woven membrane, a non-woven membrane, a microporous membrane, a composite membrane, a rolled membrane or a spun membrane. The present application has no particular restrictions on the thickness of the diaphragm, as long as the purpose of the present application can be achieved.

[0062] In some embodiments of the present application, the secondary battery further comprises an electrolyte. The present application has no particular limitation on the electrolyte, as long as the purpose of the present application can be achieved.

[0063] In some embodiments of the present application, the secondary battery further includes an outer packaging, and the positive electrode sheet, the separator, the negative electrode sheet and the electrolyte are contained in the outer packaging. The present application has no particular restrictions on the outer packaging, as long as the purpose of the present application can be achieved. For example, the outer packaging may include but is not limited to any one of an aluminum-plastic film or a steel shell.

[0064] The secondary battery of the present application is not particularly limited, and may include any device that undergoes an electrochemical reaction. For example, the secondary battery may include, but is not limited to: a lithium metal secondary battery, a lithium ion secondary battery (lithium ion battery), a lithium polymer secondary battery, or a lithium ion polymer secondary battery.

[0065] The present application does not particularly limit the preparation method of the secondary battery, and the preparation method known in the art can be selected as long as the purpose of the present application can be achieved. For example, the preparation method of the secondary battery includes but is not limited to the following steps: stacking the diaphragm, the positive electrode sheet, the diaphragm and the negative electrode sheet in order, and winding, folding and other operations as needed to obtain an electrode assembly of a winding structure, placing the electrode assembly in a packaging bag, injecting the electrolyte into the packaging bag and sealing it to obtain a secondary battery; or stacking the diaphragm, the positive electrode sheet, the diaphragm and the negative electrode sheet in order, and then fixing the four corners of the entire stacked structure to obtain an electrode assembly of a stacked structure, placing the electrode assembly in a packaging bag, injecting the electrolyte into the packaging bag and sealing it to obtain a secondary battery.

[0066] The second aspect of the present application provides an electronic device, which comprises the secondary battery described in any of the above embodiments. Therefore, the electronic device has good performance.

[0067] The electronic device of the present application is not particularly limited, and it can be any electronic device known in the prior art. For example, the electronic device can include, but is not limited to: a laptop computer, a pen-input computer, a mobile computer, an electronic book player, a portable phone, a portable fax machine, a portable copier, a portable printer, a head-mounted stereo headset, a video recorder, an LCD television, a portable cleaner, a portable CD player, a mini-disc, a transceiver, an electronic notepad, a calculator, a memory card, a portable recorder, a radio, a backup power supply, a motor, a car, a motorcycle, a power-assisted bicycle, a bicycle, a lighting fixture, a toy, a game console, a clock, an electric tool, a flashlight, a camera, a large household battery, and a lithium-ion capacitor.

[0068] Example

[0069] Hereinafter, the embodiments of the present application will be described in more detail with reference to Examples and Comparative Examples. Various tests and evaluations were performed according to the following methods.

[0070] Test methods and equipment:

[0071] Particle size test:

[0072] The particle size distribution was tested using a laser particle size analyzer MasterSizer 2000 to obtain the particle sizes of the first active material, the second active material and the third active material.

[0073] Charge transfer impedance test:

[0074] The lithium-ion battery with 50% SOC (state of charge) was disassembled to obtain the negative electrode sheet for sealed storage. The negative electrode sheet was taken out in the glove box, and two rectangular samples with a size of 30mm×15mm were cut in the same area. The two samples were used to assemble a symmetrical battery in the form of negative electrode sheet-diaphragm-negative electrode sheet and a packaging bag, and 0.2g of electrolyte was dropped and packaged. After standing for 6 hours, the charge transfer impedance was obtained by AC impedance spectroscopy (BIS) test, the test temperature was 20±5℃, the frequency range was 30mHz to 500KHz, and the disturbance voltage was 5mV.

[0075] The electrolyte is: in a dry argon atmosphere glove box, ethylene carbonate, propylene carbonate, and diethyl carbonate are mixed in a mass ratio of 3:3:4 to obtain an organic solvent, and then lithium salt LiPF6 is added to the organic solvent to dissolve and mix evenly to obtain an electrolyte. Based on the mass of the electrolyte, the mass percentage of LiPF6 is 12.5%, and the balance is the organic solvent.

[0076] The charge transfer impedance Rct1 of the first area per unit area is obtained by cutting two rectangular samples of 30mm×15mm in size from the first area of ​​the negative electrode sheet and normalizing them according to the sample area. The charge transfer impedance Rct2 of the second area per unit area is obtained by cutting two rectangular samples of 30mm×15mm in size from the second area of ​​the negative electrode sheet and normalizing them according to the sample area. The charge transfer impedance Rct3 of the third area per unit area is obtained by cutting two rectangular samples of 30mm×15mm in size from the third area of ​​the negative electrode sheet and normalizing them according to the sample area.

[0077] Capacity retention test:

[0078] At 25℃, charge the lithium-ion battery to 4.3V at 1C constant current, then charge to 0.05C at 4.3V constant voltage, and let it rest for 10min; then discharge to 2.0V at 4C constant current, and let it rest for 15min. The above is one cycle. Repeat the above cycle to 1000 times, record the discharge capacity of the first cycle as the initial capacity Q0, and the discharge capacity of the 1000th cycle as Q2, and calculate the capacity retention rate of the lithium-ion battery.

[0079] The calculation formula of capacity retention rate is: capacity retention rate (%) = Q2 / Q0×100%.

[0080] Example 1-1

[0081] <Preparation of negative electrode sheet>

[0082] Preparation of the first region negative electrode slurry: The first active material artificial graphite, the negative electrode conductive agent conductive carbon black (Super P), and the negative electrode binder polyvinylidene fluoride (PVDF, weight average molecular weight 9000) are mixed in a mass ratio of 97:0.5:2.5, deionized water is added as a solvent, and stirred in a vacuum mixer until the solid content is 70wt% and the system is uniform. The particle size of the first active material Dv50 -1 =7μm.

[0083] Preparation of the negative electrode slurry in the second region: The second active material artificial graphite, the negative electrode conductive agent Super P, and the negative electrode binder PVDF (weight average molecular weight 9000) were mixed in a mass ratio of 97:0.5:2.5, deionized water was added as a solvent, and stirred under the action of a vacuum mixer until the solid content of the second region negative electrode slurry was 70wt% and the system was uniform. Among them, the particle size of the second active material Dv50 -2 =10μm.

[0084] Preparation of the third region negative electrode slurry: The third active material artificial graphite, negative electrode conductive agent Super P, and negative electrode binder PVDF (weight average molecular weight 9000) are mixed in a mass ratio of 97:0.5:2.5, deionized water is added as a solvent, and stirred in a vacuum mixer until the solid content is 70wt% and the system is uniform. The particle size of the third active material Dv50 -3 =14.3μm.

[0085] The negative electrode slurry of the first region, the negative electrode slurry of the second region and the negative electrode slurry of the third region are coated on one surface of the negative electrode current collector copper foil with a thickness of 8μm by using a coating machine, and dried at 110°C to obtain a semi-finished negative electrode sheet coated with the first negative electrode active material layer, the second negative electrode active material layer and the third negative electrode active material layer. After that, the above steps are repeated on the other surface of the negative electrode current collector to obtain a negative electrode sheet coated with the first negative electrode active material layer, the second negative electrode active material layer and the third negative electrode active material layer on both sides. Cold press, then cut and weld the negative electrode tabs (copper tabs) to obtain a negative electrode sheet with a specification of 76mm×856mm for standby use. Among them, the width of the first region H1=0.3W, the width of the second region H2=0.3W, and the width of the third region H3=0.4W.

[0086] <Preparation of positive electrode sheet>

[0087] The positive electrode active material is lithium nickel cobalt manganese oxide LiNi 0.91 Co 0.06 Mn 0.03O2, positive electrode conductive agent multi-walled carbon nanotubes (CNT), positive electrode conductive agent conductive carbon black (Super P), positive electrode binder polyvinylidene fluoride (PVDF, weight average molecular weight 5×10 5 ) are mixed in a mass ratio of 97:0.6:1:1.4, N-methylpyrrolidone (NMP) is added as a solvent, and stirred under the action of a vacuum mixer until the solid content is 75wt% and the system is uniform. The positive electrode slurry is evenly coated on one surface of a positive electrode current collector aluminum foil with a thickness of 13μm, and dried at 100°C to obtain a positive electrode sheet with a single-sided positive electrode active material layer. Thereafter, the above steps are repeated on the other surface of the aluminum foil to obtain a positive electrode sheet with a double-sided positive electrode active material layer. Cold pressing, cutting and welding of positive electrode ears (aluminum ears) to obtain a positive electrode sheet with a specification of 74mm×851mm for standby use. Among them, the coating weight of the positive electrode active material layer is 13mg / cm 2 The compaction density of the positive electrode active material layer is 3.45 g / cm 3 .

[0088] <Preparation of Separator>

[0089] A polypropylene (PP) film with a thickness of 16 μm is used.

[0090] <Preparation of Electrolyte>

[0091] In a dry argon atmosphere, ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC) and ethyl methyl carbonate (EMC) are mixed in a mass ratio of 20:30:40:10 to obtain an organic solvent, and then lithium salt LiPF6 is added to the organic solvent to dissolve and mix evenly to obtain an electrolyte with a lithium salt concentration of 1 mol / L.

[0092] <Preparation of lithium-ion batteries>

[0093] The prepared separator, negative electrode sheet, separator and positive electrode sheet are stacked and wound in order to obtain an electrode assembly of a wound structure. The electrode assembly is placed in an aluminum-plastic film packaging bag, and after drying, an electrolyte (the amount of liquid injection is 6g) is injected, and a lithium-ion battery is obtained through vacuum packaging, standing, formation, degassing, trimming and other processes. Formation steps: charge to 3.3V at a constant current of 0.02C, and then charge to 3.6V at a constant current of 0.1C.

[0094] Example 1-2 to Example 1-13

[0095] Except for adjusting the particle size of at least one of the first active material, the second active material or the third active material in the negative electrode sheet according to Table 1, the rest is the same as Example 1-1.

[0096] Example 2-1

[0097] Except for adjusting the types of the first active material, the second active material and the third active material in the negative electrode sheet according to Table 2, the rest is the same as Example 1-1.

[0098] Example 3-1 to Example 3-3

[0099] Except for adjusting at least one of the width H1 of the first region, the width H2 of the second region, or the width H3 of the third region in the negative electrode sheet according to Table 2, the rest is the same as Example 1-1.

[0100] Embodiment 3-4

[0101] Except that the specifications of the negative electrode sheet are adjusted to 150mm×2000mm and the specifications of the positive electrode sheet are adjusted to 150mm×2000mm, the rest are the same as Example 1-1.

[0102] Embodiment 3-5

[0103] Except that the specifications of the negative electrode sheet are adjusted to 370mm×3000mm and the specifications of the positive electrode sheet are adjusted to 370mm×3000mm, the rest are the same as Example 1-1.

[0104] Embodiment 3-6

[0105] Except that the specifications of the negative electrode sheet are adjusted to 40 mm×825 mm and the specifications of the positive electrode sheet are adjusted to 38 mm×820 mm, the rest are the same as Example 1-1.

[0106] Embodiment 3-7

[0107] Except that the specifications of the negative electrode sheet are adjusted to 380mm×2930mm and the specifications of the positive electrode sheet are adjusted to 375mm×2920mm, the rest are the same as Example 1-1.

[0108] Example 4-1

[0109] <Preparation of positive electrode sheet>

[0110] Preparation of positive electrode slurry in the first region: The first active material lithium nickel cobalt manganese oxide LiNi 0.91 Co 0.06 Mn 0.03 O2, positive electrode conductive agent multi-walled carbon nanotubes (CNT), positive electrode conductive agent conductive carbon black (Super P), positive electrode binder polyvinylidene fluoride (PVDF, weight average molecular weight 5×10 5) are mixed in a mass ratio of 97:0.6:1:1.4, N-methylpyrrolidone (NMP) is added as a solvent, and stirred in a vacuum mixer until the solid content is 75wt% and the system is uniform to form a first region positive electrode slurry. Among them, the particle size of the first active material is Dv50 -1 =7μm.

[0111] Preparation of the positive electrode slurry in the second region: The second active material lithium nickel cobalt manganese oxide LiNi 0.91 Co 0.06 Mn 0.03 O2, positive electrode conductive agent CNT, positive electrode conductive agent Super P, positive electrode binder PVDF (weight average molecular weight 5×10 5 ) are mixed in a mass ratio of 97:0.6:1:1.4, NMP is added as a solvent, and stirred under a vacuum mixer until the solid content is 75wt% and the system is uniform to obtain a second region positive electrode slurry. Among them, the particle size of the second active material is Dv50 -2 =10μm.

[0112] Preparation of the positive electrode slurry in the third region: The third active material lithium nickel cobalt manganese oxide LiNi 0.91 Co 0.06 Mn 0.03 O2, positive electrode conductive agent CNT, positive electrode conductive agent Super P, positive electrode binder PVDF (weight average molecular weight 5×10 5 ) are mixed in a mass ratio of 97:0.6:1:1.4, NMP is added as a solvent, and stirred under a vacuum mixer until a third region positive electrode slurry with a solid content of 75wt% and a uniform system is obtained. Among them, the particle size of the third active material is Dv50 -3 =14.3μm.

[0113] The positive electrode slurry of the first region, the positive electrode slurry of the second region and the positive electrode slurry of the third region are coated on one surface of the positive electrode current collector aluminum foil with a thickness of 13μm by using a coating machine, and dried at 110°C to obtain a semi-finished positive electrode sheet coated with the first positive electrode active material layer, the second positive electrode active material layer and the third positive electrode active material layer. After that, the above steps are repeated on the other surface of the positive electrode current collector to obtain a semi-finished positive electrode sheet coated with the first positive electrode active material layer, the second positive electrode active material layer and the third positive electrode active material layer on both sides. Cold press, then cut and weld the positive electrode aluminum ear to obtain a positive electrode sheet with a specification of 74mm×851mm for standby use. Among them, the width of the first region H1=0.3W, the width of the second region H2=0.3W, and the width of the third region H3=0.4W.

[0114] <Preparation of negative electrode sheet>

[0115] The negative electrode active material artificial graphite, negative electrode conductive agent Super P, and negative electrode binder PVDF (weight average molecular weight 9000) are mixed in a mass ratio of 97:0.5:2.5, deionized water is added as a solvent, and stirred under the action of a vacuum mixer until the solid content is 70wt% and the system is uniform. The negative electrode slurry is coated on one surface of the negative electrode current collector copper foil with a thickness of 8μm, and dried at 110°C to obtain a semi-finished negative electrode sheet coated with a negative electrode active material layer. After that, the above steps are repeated on the other surface of the negative electrode current collector to obtain a negative electrode sheet coated with a negative electrode active material layer on both sides. Cold pressing, cutting and welding of negative electrode copper tabs to obtain a negative electrode sheet with a specification of 76mm×856mm for standby use.

[0116] <Preparation of separator>, <Preparation of electrolyte>, and <Preparation of lithium ion battery> were the same as those in Example 1-1.

[0117] Example 4-2 to Example 4-13

[0118] Except for adjusting the particle size of at least one of the first active material, the second active material or the third active material in the positive electrode sheet according to Table 4, the rest is the same as Example 1-1.

[0119] Example 5-1

[0120] Except for adjusting the types of the first active material, the second active material and the third active material in the positive electrode sheet according to Table 5, the rest is the same as Example 4-1.

[0121] Example 6-1 to Example 6-3

[0122] Except for adjusting at least one of the width H1 of the first region, the width H2 of the second region, or the width H3 of the third region in the positive electrode sheet according to Table 2, the rest is the same as Example 1-1.

[0123] Example 6-4

[0124] Except that the specifications of the positive electrode sheet are adjusted to 150mm×2000mm and the specifications of the negative electrode sheet are adjusted to 150mm×2000mm, the rest are the same as Example 1-1.

[0125] Example 6-5

[0126] Except that the specifications of the positive electrode sheet are adjusted to 370mm×3000mm and the specifications of the negative electrode sheet are adjusted to 370mm×3000mm, the rest are the same as Example 1-1.

[0127] Example 6-6

[0128] Except that the specifications of the positive electrode sheet are adjusted to 38mm×820mm and the specifications of the negative electrode sheet are adjusted to 40mm×825mm, the rest are the same as Example 1-1.

[0129] Embodiment 6-7

[0130] Except that the specifications of the positive electrode sheet are adjusted to 375mm×2920mm and the specifications of the negative electrode sheet are adjusted to 380mm×2930mm, the rest are the same as Example 1-1.

[0131] Comparative Example 1-1

[0132] <Preparation of negative electrode sheet>

[0133] The negative electrode slurry of the second region in Example 1-1 is selected as the negative electrode slurry of the first region, the negative electrode slurry of the second region and the negative electrode slurry of the third region at the same time.

[0134] The rest is the same as Example 1-1.

[0135] <Preparation of positive electrode sheet>, <Preparation of separator>, <Preparation of electrolyte>, and <Preparation of lithium-ion battery> are the same as those in Example 1-1.

[0136] Comparative Example 1-2 to Comparative Example 1-4

[0137] Except for adjusting the particle size of at least one of the first active material, the second active material or the third active material in the negative electrode sheet according to Table 1, the rest is the same as Example 1-1.

[0138] Comparative Example 3-1 to Comparative Example 3-3

[0139] Except for adjusting at least one of the width H1 of the first region, the width H2 of the second region, or the width H3 of the third region in the negative electrode sheet according to Table 3, the rest is the same as Example 1-1.

[0140] Comparative Example 4-1

[0141] <Preparation of positive electrode sheet>

[0142] The second region positive electrode slurry in Example 4-1 is selected as the first region negative electrode slurry, the second region negative electrode slurry and the third region negative electrode slurry at the same time.

[0143] The rest is the same as Example 4-1.

[0144] <Preparation of negative electrode sheet>, <Preparation of separator>, <Preparation of electrolyte>, and <Preparation of lithium-ion battery> are the same as those in Example 4-1.

[0145] Comparative Example 4-2 to Comparative Example 4-4

[0146] Except for adjusting the particle size of at least one of the first active material, the second active material or the third active material in the positive electrode sheet according to Table 4, the rest is the same as Example 4-1.

[0147] Comparative Example 6-1 to Comparative Example 6-3

[0148] Except for adjusting at least one of the width H1 of the first region, the width H2 of the second region, or the width H3 of the third region in the positive electrode sheet according to Table 6, the rest is the same as Example 4-1.

[0149] The preparation parameters and performance parameters of each embodiment and comparative example are shown in Tables 1 to 6.

[0150] Table 1

[0151]

[0152]

[0153] Note: For Comparative Examples 1-1 to 1-3, since the same negative electrode slurry is used for the first region, the second region and the third region, it can also be understood that the negative electrode sheets in Comparative Examples 1-1 to 1-3 do not distinguish between the first region, the second region and the third region in the width direction.

[0154] It can be seen from Examples 1-1 to 1-13 and Comparative Examples 1-1 to 1-4 that the secondary battery of the embodiment of the present application is divided into a first region, a second region and a third region along the width direction by dividing the negative electrode sheet, the width W of the negative electrode sheet, the width H1 of the first region, the width H2 of the second region and the width H3 of the third region satisfy: 0.2W≤H1≤0.6W, 0.2W≤H2≤0.6W, 0.2W≤H3≤0.6W, and the particle size Dv50 of the first active material in the first region is regulated. -1 , the particle size Dv50 of the second active material in the second region -2 and a particle size Dv50 of the third active material in the third region -3 Satisfy: 0.7≤Dv50-1 / Dv50 -2 ≤0.9、0.7≤Dv50-2 / Dv50 -3 ≤0.9, 7.5μm≤Dv50-2≤12μm, which enables the secondary battery to have a higher capacity retention rate after 1000 cycles, indicating that the secondary battery of the present application embodiment has a higher cycle performance. In the secondary battery of the comparative example, the negative electrode sheet does not distinguish between the first region, the second region and the third region, or the ratio of the particle size of the first active material in the first region to the second active material in the second region Dv50-1 / Dv50 -2, the ratio of the particle size of the second active material in the second region to the particle size of the third active material in the third region Dv50-2 / Dv50 -3 And at least one of the particle sizes of the second active material in the second region is not within the scope of the present application. The secondary battery of the comparative example has a lower capacity retention rate after 1000 cycles, indicating that the secondary battery of the comparative example of the present application has a lower cycle performance.

[0155] The ratio of the particle size of the first active material in the first region of the negative electrode sheet to the particle size of the second active material in the second region is Dv50-1 / Dv50 -2 , the ratio of the particle size of the second active material in the second region to the particle size of the third active material in the third region Dv50-2 / Dv50 -3 The particle size of the second active material in the second region usually affects the cycle performance of the secondary battery. From Examples 1-1 to 1-6 and Comparative Examples 1-1 to 1-4, it can be seen that the ratio of the particle size of the first active material in the first region of the negative electrode sheet to the particle size of the second active material in the second region Dv50-1 / Dv50 -2 , the ratio of the particle size of the second active material in the second region to the particle size of the third active material in the third region Dv50-2 / Dv50 -3 And the secondary battery in which the particle size of the second active material in the second region is within the scope of the present application has a higher capacity retention rate after 1000 cycles, indicating that the secondary battery has good cycle performance.

[0156] The particle size Dv50-1 of the first active material in the first region of the negative electrode sheet and the particle size Dv50-1 of the third active material in the third region -3 It usually affects the cycle performance of the secondary battery. From Examples 1-1 to 1-6, and Examples 1-10 to 1-13, it can be seen that the particle size Dv50-1 of the first active material in the first region and the particle size Dv50-2 of the third active material in the third region are selected. -3 The secondary battery within the scope of the present application has a high capacity retention rate after 1000 cycles, indicating that the secondary battery has good cycle performance.

[0157] The charge transfer impedance of the first region of the negative electrode sheet is Rct1, the charge transfer impedance of the second region is Rct2, the charge transfer impedance of the third region is Rct3, the values ​​of Rct1 / Rct2 and Rct2 / Rct3 usually affect the cycle performance of the secondary battery. From Examples 1-1 to 1-9, it can be seen that the secondary battery in which the charge transfer impedance of the first region is Rct1, the charge transfer impedance of the second region is Rct2, and the charge transfer impedance of the third region is Rct3, Rct1 / Rct2 and Rct2 / Rct3 values ​​are within the scope of the present application has a high capacity retention rate after 1000 cycles, indicating that the secondary battery has good cycle performance.

[0158] Table 2

[0159]

[0160] The types of the first active material, the second active material and the third active material of the negative electrode sheet usually affect the cycle performance of the secondary battery. It can be seen from Example 1-1 and Example 2-1 that the secondary battery in which the types of the first active material, the second active material and the third active material are within the scope of the present application has a high capacity retention rate after 1000 cycles, indicating that the secondary battery has good cycle performance.

[0161] Table 3

[0162]

[0163]

[0164] The width H1 of the first region, the width H2 of the second region, and the width H3 of the third region in the negative electrode sheet usually affect the cycle performance of the secondary battery. It can be seen from Example 1-1, Example 3-1 to Example 3-3, and Comparative Examples 3-1 to Comparative Examples 3-3 that the secondary battery selected with the width H1 of the first region, the width H2 of the second region, and the width H3 of the third region within the scope of the present application has a higher capacity retention rate after 1000 cycles, indicating that the secondary battery has good cycle performance. However, for the secondary batteries of Comparative Examples 3-1 to Comparative Examples 3-3, the widths of the first region, the second region, and the third region of the negative electrode sheet are not within the scope of the present application, and the secondary batteries of Comparative Examples 3-1 to Comparative Examples 3-3 have a lower capacity retention rate after 1000 cycles, indicating that the secondary batteries of the comparative examples of the present application have lower cycle performance.

[0165] The width W of the negative electrode sheet usually affects the cycle performance of the secondary battery. It can be seen from Examples 1-1, 3-4 to 3-7 that the secondary battery with the width W of the negative electrode sheet within the range of the present application has a high capacity retention rate after 1000 cycles, indicating that the secondary battery has good cycle performance.

[0166] Table 4

[0167]

[0168]

[0169] Note: In Comparative Examples 4-1 to 4-3, since the same positive electrode slurry is used for the first region, the second region and the third region, it can also be understood that the positive electrode sheets in Comparative Examples 4-1 to 4-3 do not distinguish between the first region, the second region and the third region in the width direction.

[0170] It can be seen from Examples 4-1 to 4-13 and Comparative Examples 4-1 to 4-4 that the secondary battery of the embodiment of the present application is divided into a first region, a second region and a third region along the width direction by dividing the positive electrode sheet, the width W of the positive electrode sheet, the width H1 of the first region, the width H2 of the second region and the width H3 of the third region satisfy: 0.2W≤H1≤0.6W, 0.2W≤H2≤0.6W, 0.2W≤H3≤0.6W, and the particle size Dv50 of the first active material in the first region is regulated. -1 , the particle size Dv50 of the second active material in the second region -2 and a particle size Dv50 of the third active material in the third region -3 Satisfy: 0.7≤Dv50-1 / Dv50 -2 ≤0.9、0.7≤Dv50-2 / Dv50 -3 ≤0.9, 7.5μm≤Dv50-2≤12μm, which enables the secondary battery to have a higher capacity retention rate after 1000 cycles, indicating that the secondary battery of the present application embodiment has a higher cycle performance. In the secondary battery of the comparative example, the positive electrode sheet does not distinguish between the first region, the second region and the third region, or the ratio of the particle size of the first active material in the first region to the second active material in the second region Dv50-1 / Dv50 -2 , the ratio of the particle size of the second active material in the second region to the particle size of the third active material in the third region Dv50-2 / Dv50 -3 And at least one of the particle sizes of the second active material in the second region is not within the scope of the present application. The secondary battery of the comparative example has a lower capacity retention rate after 1000 cycles, indicating that the secondary battery of the comparative example of the present application has a lower cycle performance.

[0171] The ratio of the particle size of the first active material in the first region of the positive electrode sheet to the particle size of the second active material in the second region is Dv50-1 / Dv50 -2 , the ratio of the particle size of the second active material in the second region to the particle size of the third active material in the third region Dv50-2 / Dv50 -3 The particle size of the second active material in the second region usually affects the cycle performance of the secondary battery. From Examples 4-1 to 4-5 and Comparative Examples 4-1 to 4-4, it can be seen that the ratio of the particle size of the first active material in the first region to the particle size of the second active material in the second region Dv50-1 / Dv50 -2 , the ratio of the particle size of the second active material in the second region to the particle size of the third active material in the third region Dv50-2 / Dv50 -3 And the secondary battery in which the particle size of the second active material in the second region is within the scope of the present application has a higher capacity retention rate after 1000 cycles, indicating that the secondary battery has good cycle performance.

[0172] The particle size Dv50-1 of the first active material in the first region of the positive electrode sheet and the particle size Dv50-1 of the third active material in the third region -3 It usually affects the cycle performance of the secondary battery. From Examples 4-1 to 4-5, and Examples 4-10 to 3-13, it can be seen that the particle size Dv50-1 of the first active material in the first region and the particle size Dv50-2 of the third active material in the third region are selected. -3 The secondary battery within the scope of the present application has a high capacity retention rate after 1000 cycles, indicating that the secondary battery has good cycle performance.

[0173] The charge transfer impedance of the first region of the positive electrode sheet is Rct1, the charge transfer impedance of the second region is Rct2, the charge transfer impedance of the third region is Rct3, the values ​​of Rct1 / Rct2 and Rct2 / Rct3 usually affect the cycle performance of the secondary battery. From Examples 4-1 to 4-9, it can be seen that the secondary battery with the charge transfer impedance of the first region being Rct1, the charge transfer impedance of the second region being Rct2, the charge transfer impedance of the third region being Rct3, Rct1 / Rct2 and Rct2 / Rct3 being within the scope of the present application has a high capacity retention rate after 1000 cycles, indicating that the secondary battery has good cycle performance.

[0174] Table 5

[0175]

[0176] The types of the first active material, the second active material and the third active material in the positive electrode sheet usually affect the cycle performance of the secondary battery. It can be seen from Example 4-1 and Example 5-1 that the secondary battery in which the types of the first active material, the second active material and the third active material are within the scope of the present application has a high capacity retention rate after 1000 cycles, indicating that the secondary battery has good cycle performance.

[0177] Table 6

[0178]

[0179]

[0180] The width H1 of the first region, the width H2 of the second region, and the width H3 of the third region in the positive electrode sheet usually affect the cycle performance of the secondary battery. It can be seen from Example 4-1, Example 6-1 to Example 6-3, and Comparative Examples 6-1 to Comparative Examples 6-3 that the secondary battery selected with the width H1 of the first region, the width H2 of the second region, and the width H3 of the third region within the scope of the present application has a higher capacity retention rate after 1000 cycles, indicating that the secondary battery has good cycle performance. However, for the secondary batteries of Comparative Examples 6-1 to Comparative Examples 6-3, the widths of the first region, the second region, and the third region of the positive electrode sheet are not within the scope of the present application, and the secondary batteries of Comparative Examples 6-1 to Comparative Examples 6-3 have a lower capacity retention rate after 1000 cycles, indicating that the secondary batteries of the comparative examples of the present application have lower cycle performance.

[0181] The width W of the positive electrode sheet usually affects the cycle performance of the secondary battery. It can be seen from Examples 4-1, 6-4 and 6-7 that the secondary battery with the width W of the positive electrode sheet within the range of the present application has a high capacity retention rate after 1000 cycles, indicating that the secondary battery has good cycle performance.

[0182] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0183] Each embodiment in this specification is described in a related manner, and the same or similar parts between the embodiments can be referenced to each other, and each embodiment focuses on the differences from other embodiments.

[0184] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A secondary battery, comprising a pole piece and a pole ear connected to the pole piece, wherein along the width direction of the pole piece after being unfolded, the pole piece is divided into a first area close to the pole ear, a third area away from the pole ear, and a second area between the first area and the third area, and the width W of the pole piece, the width H1 of the first area, the width H2 of the second area, and the width H3 of the third area satisfy the following conditions: 0.2W≤H1≤0.6W, 0.2W≤H2≤0.6W, 0.2W≤H3≤0.6W; The first region includes a first active material, the second region includes a second active material, and the third region includes a third active material. The particle size of the first active material is Dv50-1, and the particle size of the second active material is Dv50 -2 , the particle size of the third active material is Dv50 -3 , 0.7≤Dv50-1 / Dv50 -2 ≤0.9, 0.7≤Dv50-2 / Dv50 -3 ≤0.9, where 7.5μm≤Dv50-2≤12μm.

2. The secondary battery according to claim 1, wherein 7μm≤Dv50-1≤10μm, and / or, 8.5μm≤Dv50-3≤15μm.

3. The secondary battery according to claim 1 or 2, wherein: The charge transfer impedance of the first region is Rct1, the charge transfer impedance of the second region is Rct2, 0.7≤Rct1 / Rct2≤0.9, 43.5 mΩ / mm 2 ≤Rct2≤113mΩ / mm 2 .

4. The secondary battery according to claim 3, wherein The charge transfer impedance of the third region is Rct3, 0.7≤Rct2 / Rct3≤0.

9.

5. The secondary battery according to claim 3 or 4, wherein: 40mΩ / mm 2 ≤Rct1≤86mΩ / mm 2 , and / or, 49.7mΩ / mm 2 ≤Rct3≤151mΩ / mm 2 .

6. The secondary battery according to any one of claims 3 to 5, wherein The secondary battery satisfies at least one of the following characteristics: (1)0.80≤Dv50-1 / Dv50 -2 ≤0.85; (2)0.80≤Dv50-2 / Dv50 -3 ≤0.85; (3) 0.80≤Rct1 / Rct2≤0.85; (4)0.80≤Rct2 / Rct3≤0.

85.

7. The secondary battery according to any one of claims 1 to 6, wherein The pole piece is a positive pole piece, and the pole lug is a positive pole lug.

8. The secondary battery according to claim 7, wherein The first active material, the second active material and the third active material each independently include at least one of lithium nickel cobalt manganese oxide, lithium iron phosphate, lithium manganese iron phosphate or lithium cobalt oxide.

9. The secondary battery according to any one of claims 1 to 6, wherein The pole piece is a negative pole piece, and the pole lug is a negative pole lug.

10. The secondary battery according to claim 9, wherein The first active material, the second active material and the third active material each independently include at least one of artificial graphite, natural graphite, hard carbon, soft carbon, pure silicon, a silicon-carbon compound or a silicon-oxygen compound.

11. The secondary battery according to any one of claims 7 to 10, wherein 50mm≤W≤370mm.

12. An electronic device, wherein: The electronic device includes the secondary battery according to any one of claims 1 to 11.

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