Electrochemical apparatus and electronic apparatus using same

Abstract

An electrochemical apparatus, comprising a positive electrode, a negative electrode, and an electrolyte. The positive electrode comprises a positive electrode current collector and a positive electrode active layer arranged on at least one surface of the positive electrode current collector. The positive electrode active layer comprises a central region and an edge region disposed around the outer periphery of the central region, the edge region comprises a first positive electrode active material, and the central region comprises a second positive electrode active material. A solid-phase diffusion coefficient of the first positive electrode active material is 10-15 cm2 / s to 10-5 cm2 / s, and the ratio of the solid-phase diffusion coefficient of the first positive electrode active material to a solid-phase diffusion coefficient of the second positive electrode active material is 1:3 to 1:1.05. According to the electrochemical apparatus, the difference in dynamics performance between the central region and the edge region is reduced, and further the overall performance of the capacity of the electrochemical apparatus is improved, so as to enhance the overall performance of the electrochemical apparatus. The present application further provides an electronic apparatus using the electrochemical apparatus.

Description

Electrochemical device and electronic device using the same Technical Field

[0001] The present application relates to the field of electrochemical energy supply, and in particular to an electrochemical device and an electronic device using the electrochemical device. Background Art

[0002] Electrochemical devices, especially lithium-ion batteries, offer advantages such as high energy density, high power, and long cycle life, making them widely used in consumer electronics. However, as their application continues to expand, particularly in electric bicycles and electric vehicles, the performance requirements for electrochemical devices are also increasing. Therefore, ensuring or improving the overall performance of electrochemical devices is a current challenge.

[0003] Summary of the Invention

[0004] In view of the above situation, it is necessary to provide an electrochemical device that improves overall performance by reducing the difference in kinetic performance between the central region and the edge region of the positive electrode, and an electronic device using the electrochemical device.

[0005] In a first aspect, the present application provides an electrochemical device comprising a positive electrode, a negative electrode, and an electrolyte. The positive electrode comprises a positive electrode current collector and a positive electrode active layer disposed on at least one surface of the positive electrode current collector. The positive electrode active layer comprises a central region and an edge region disposed around the outer periphery of the central region, the edge region comprising a first positive electrode active material, and the central region comprising a second positive electrode active material. The solid phase diffusion coefficient of the first positive electrode active material is 10 -15 cm 2 / s to 10 -5 cm 2 / s, and the ratio of the solid phase diffusion coefficient of the first positive electrode active material to the solid phase diffusion coefficient of the second positive electrode active material is 1:3 to 1:1.05.

[0006] In an electrochemical device, the electric field strength in the edge region of each electrode is higher than that in the central region. Since there is no difference in design between the edge region and the central region of the electrode in the prior art, the delithiation rate in the edge region is fast and the amount of delithiation is large, while the delithiation rate in the central region is slow and the amount of delithiation is small, resulting in a decrease in the overall capacity of the electrochemical device and poor overall kinetic performance. In the above-mentioned electrochemical device of the present application, the edge region and the central region of the positive electrode are designed with differentiation. By using a second positive electrode active material with a lower solid-phase diffusion coefficient in the edge region and a first positive electrode active material with a higher solid-phase diffusion coefficient in the central region, it is beneficial to improve the solid-phase diffusion rate of lithium ions in the central region compared to the edge region to improve the kinetic performance of the central region compared to the edge region, thereby helping to narrow the difference in kinetic performance between the central region and the edge region, and narrow the difference in the amount of delithiation between the edge region and the central region, thereby helping to improve the overall capacity of the electrochemical device and improve the overall performance of the electrochemical device. In addition, the solid-phase diffusion rate of lithium ions of the first positive electrode active material having a solid-phase diffusion coefficient in the above range is conducive to the insertion and extraction of lithium ions, which is conducive to improving the overall kinetic performance of the electrochemical device. The above-mentioned specific ratio of the solid-phase diffusion coefficients is also conducive to improving the overall kinetic performance of the electrochemical device while narrowing the difference between the two regions and avoiding the reverse difference.

[0007] Based on the first aspect, in some possible embodiments, the ratio of the solid-phase diffusion coefficient of the first positive electrode active material to the solid-phase diffusion coefficient of the second positive electrode active material is 1:2.8 to 1:1.5, which is beneficial to further improve the overall kinetic performance of the electrochemical device while narrowing the difference between the two regions and avoiding reverse differences.

[0008] Based on the first aspect, in some possible embodiments, the compaction density of the edge region is 2.0 g / cc to 4.35 g / cc, and the compaction density of the edge region is greater than the compaction density of the central region, and the difference is 0.03 g / cc to 0.5 g / cc.

[0009] In the above possible embodiments, by designing an edge region with a higher compaction density and a central region with a lower compaction density, it is beneficial to improve the liquid-phase diffusion capacity of lithium ions in the central region compared to the edge region, thereby improving the kinetic performance of the central region compared to the edge region, thereby helping to narrow the difference in kinetic performance between the central region and the edge region, and thus helping to improve the overall capacity of the electrochemical device, thereby improving the overall performance of the electrochemical device. Furthermore, the edge region having a compaction density within the above range, and the central region having a specific difference range in compaction density from the edge region, are beneficial to improving the overall volume energy density of the electrochemical device, thereby helping to further improve the overall performance of the electrochemical device.

[0010] Based on the first aspect, in some possible implementations, the ratio of the porosity of the edge region to the porosity of the central region is 1:2 to 1:1.1, and the porosity of the edge region is 10% to 45%.

[0011] In the above possible embodiments, by designing a central region with higher porosity and an edge region with lower porosity, it is beneficial to improve the liquid phase diffusion capacity of lithium ions in the central region compared to the edge region to improve the kinetic performance of the central region compared to the edge region, thereby helping to narrow the difference in kinetic performance between the central region and the edge region, and thus helping to improve the overall capacity of the electrochemical device to improve the overall performance of the electrochemical device. Among them, if the porosity of the edge region is too large, it is not conducive to ensuring the volume energy density of the electrochemical device, and if the porosity of the edge region is too small, the kinetic performance of the electrochemical device is poor, which is not conducive to ensuring the overall performance of the electrochemical device. In addition, if the porosity ratio is too small, it is not easy to narrow the difference in kinetic performance between the central region and the edge region, and if the porosity ratio is too large, it is easy to make the difference between the central region and the edge region too large, and thus easily cause a reverse difference, which is also not conducive to improving the overall performance of the electrochemical device.

[0012] Based on the first aspect, in some possible implementations, the width of the edge region is 2 mm to 10 mm.

[0013] Based on the first aspect, in some possible implementations, the positive electrode active layer further includes a transition region connecting the inner periphery of the edge region and the outer periphery of the central region, wherein the width of the transition region is 0.02 mm to 0.5 mm.

[0014] Based on the first aspect, in some possible implementations, the thickness of the central region is greater than the thickness of the edge region and the difference is less than 1 micron, and the thickness of the edge region is 50 microns to 1000 microns.

[0015] In the above possible embodiment, a thickness difference of less than 1 micron between the center region and the edge region is beneficial for improving the flatness of the electrode assembly composed of the positive and negative electrodes, thereby improving the overall flatness of the electrochemical device. In addition, the above-mentioned thickness range of the edge region and the difference range between the center region and the edge region are beneficial for preventing purple spots or lithium deposition caused by flatness from affecting the overall performance of the electrochemical device.

[0016] Based on the first aspect, in some possible implementations, the thickness of the edge region is 100 micrometers to 500 micrometers.

[0017] Based on the first aspect, in some possible embodiments, the ratio of the particle size Dv50 of the first positive active material to the particle size Dv50 of the second positive active material is 1.1:1 to 2:1, and the particle size Dv50 of the first positive active material is 1.0 micron to 25 microns.

[0018] In the above possible embodiments, by designing the edge region to use an active material with a larger particle size and the center region to use an active material with a smaller particle size, it is beneficial to reduce the solid-phase transmission distance of lithium ions in the active material in the center region compared to the edge region to improve the kinetic performance of the center region compared to the edge region, thereby helping to narrow the difference in kinetic performance between the center region and the edge region, and thus helping to improve the overall capacity of the electrochemical device, thereby improving the overall performance of the electrochemical device. The first positive electrode active material in the above-mentioned specific particle size range and the second positive electrode active material having a specific ratio range with the first positive electrode active material are conducive to achieving a higher compaction density and a higher kinetic electrode assembly, thereby facilitating the improvement of the overall performance of the electrochemical device.

[0019] Based on the first aspect, in some possible embodiments, the edge region further includes a first binder, and the central region further includes a second binder. The content of the second binder in the edge region is 0.4 wt% to 4.0 wt%, and the ratio of the content of the second binder in the central region to the content of the first binder in the edge region is 1:1.02 to 1:2.

[0020] In the above possible embodiments, by designing the edge region to adopt a higher binder content and the center region to adopt a lower binder content, it is beneficial to reduce the interface transport barrier of the second binder in the center region to lithium ions compared to the first binder in the edge region, so as to improve the kinetic performance of the center region compared to the edge region, thereby helping to narrow the difference in kinetic performance between the center region and the edge region, thereby helping to improve the overall capacity of the electrochemical device, thereby improving the overall performance of the electrochemical device. Furthermore, the second binder content and the first binder content having a specific ratio range to the second binder content are beneficial to ensuring the binding force between the edge region and the center region and the positive electrode current collector, that is, it is beneficial to ensure the binding force between the positive electrode active layer and the positive electrode current collector, while also helping to improve the kinetic performance of the entire positive electrode active layer, thereby helping to improve the stability of the positive electrode structure while also helping to improve the overall kinetic performance of the electrochemical device, thereby facilitating the improvement of the overall performance of the electrochemical device.

[0021] Based on the first aspect, in some possible implementations, the edge region further includes a first conductive agent, and the central region further includes a second conductive agent. The content of the second conductive agent in the central region is 0.2 wt % to 4.0 wt %, and the content of the second conductive agent in the central region is greater than the content of the first conductive agent in the edge region by a difference of 0.1 wt % to 2.0 wt %.

[0022] In the above possible embodiments, by designing the edge region to use a lower conductive agent content and the center region to use a higher conductive agent content, it is beneficial to improve the electron transport capacity of the center region compared to the edge region, thereby improving the kinetic performance of the center region compared to the edge region, thereby helping to narrow the kinetic performance difference between the edge region and the center region, and thus helping to improve the overall capacity of the electrochemical device, thereby improving the overall performance of the electrochemical device. The above-mentioned specific content of the second conductive agent and the first conductive agent having a content within a specific difference range from the content of the second conductive agent are beneficial to ensuring the positive electrode's electron transport capacity and giving the positive electrode higher kinetic performance, thereby facilitating the improvement of the overall performance of the electrochemical device.

[0023] Based on the first aspect, in some possible embodiments, under 100% SOC conditions, the delithiation amount of the first positive electrode active material in the edge region is greater than the delithiation amount of the second positive electrode active material in the center region, and the difference is 0.1% to 2%.

[0024] In the above possible implementation manner, the difference between the electrochemical reaction in the edge region and the electrochemical reaction in the central region is reduced, thereby facilitating improvement in the overall performance of the electrochemical device.

[0025] The second aspect of the present application provides an electronic device, comprising a body and an electrochemical device as described above, wherein the electrochemical device is electrically connected to the body for powering the body. In the above-mentioned electronic device of the present application, the edge area and the central area of ​​the positive electrode are designed differently, and by using a positive electrode active material with a lower solid-phase diffusion coefficient in the edge area and a positive electrode active material with a higher solid-phase diffusion coefficient in the central area, the solid-phase diffusion rate of lithium ions in the central area is increased compared to the edge area to improve the kinetic performance of the central area compared to the edge area, thereby reducing the difference in kinetic performance between the central area and the edge area, reducing the difference in the amount of lithium desorption between the edge area and the central area, and thereby improving the overall capacity of the electrochemical device, so as to improve the overall performance of the electrochemical device and thereby improve the power supply performance of the electronic device. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] FIG1 is a schematic structural diagram of an electrochemical device according to one embodiment of the present application.

[0027] FIG2 is a schematic cross-sectional view of an electrochemical device according to one embodiment of the present application.

[0028] FIG3 is a schematic cross-sectional view of a positive electrode according to an embodiment of the present application, taken along a direction perpendicular to the thickness.

[0029] FIG4 is a schematic structural diagram of an electronic device according to an embodiment of the present application.

[0030] Description of main component symbols

[0031] The following specific implementation methods will further illustrate the present application in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0032] The following specific embodiments illustrate the implementation of the present application. Those skilled in the art can easily understand other advantages and effects of the present application from the contents disclosed in this specification. Although the description of the present application will be introduced in conjunction with the embodiments, this does not mean that the features of this application are limited to this implementation. On the contrary, the purpose of introducing the application in conjunction with the implementation is to cover other options or modifications that may be extended based on the claims of the present application. In order to provide an in-depth understanding of the present application, the following description will contain many specific details. The present application can also be implemented without using these details. In addition, in order to avoid confusion or blurring the focus of the present application, some specific details will be omitted in the description.

[0033] It should be noted that, unless there is any conflict, the embodiments and features in the embodiments of this application can be combined with each other.

[0034] Hereinafter, if used, the terms "first," "second," etc., are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature qualified as "first," "second," etc. may explicitly or implicitly include one or more of such features. In the description of this application, unless otherwise specified, "plurality" means two or more.

[0035] Further, when describing embodiments of the present application, the use of “may” refers to “one or more embodiments of the present application.”

[0036] The technical terms used herein are for the purpose of describing specific embodiments and are not intended to limit this application. As used herein, the singular is intended to include the plural, unless the context clearly indicates otherwise. It should be further understood that the term "comprising", when used in this specification, refers to the presence of the described features, values, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, values, steps, operations, elements, components and / or combinations thereof.

[0037] The following describes the embodiments of the present application in conjunction with the accompanying drawings. The data ranges recorded in this application are inclusive unless otherwise specified. The electrochemical device of this application uses a lithium-ion battery as an example to illustrate its effects.

[0038] The energy density of lithium-ion batteries is usually improved by increasing the capacity and voltage of the active materials in the electrodes and increasing the content of the active materials in the electrodes. Among them, increasing the compaction density of the active materials and preparing thicker electrode active layers can both increase the content of the active materials.

[0039] In lithium-ion batteries, there are differences in electric field strength, potential and polarization between the edge and center areas of the electrode, resulting in uneven electrochemical reactions between the edge and main areas of the electrode. This uneven electrochemical reaction phenomenon becomes more obvious with the increase of active layer thickness and active layer compaction density, thereby deteriorating the overall performance of the battery (including but not limited to affecting cycle life, causing thermal safety issues, etc.) and restricting a substantial increase in active layer thickness and compaction density.

[0040] In view of this, embodiments of the present application provide an electrochemical device and an electronic device using the electrochemical device.

[0041] Please refer to Figure 1 for an electrochemical device 100 according to an embodiment of the present application. Please refer to Figure 2 , which shows the electrochemical device 100 including a positive electrode 10, a negative electrode 30, and a separator 50. The separator 50 is disposed between the positive electrode 10 and the negative electrode 30. As shown in Figure 2 , the positive electrode 10, separator 50, and negative electrode 30 can be alternately stacked in a thickness direction X to form a laminated electrode assembly A, or the positive electrode 10, separator 50, and negative electrode 30 can be stacked in sequence and then wound around a central axis to form a wound electrode assembly (not shown). The following description will use the laminated electrode assembly A as an example.

[0042] The electrochemical device 100 also includes a housing 20 and an electrolyte 60. The electrolyte 60 and the electrode assembly A are contained within the housing 20. The housing 20 can be a packaging bag formed using a packaging film, such as, but not limited to, an aluminum-plastic film. That is, the electrochemical device can be a soft-pack battery. The housing 20 can also be, but is not limited to, those disclosed in the prior art, such as steel-cased batteries and aluminum-cased batteries.

[0043] The positive electrode 10 includes a positive electrode current collector 11 and a positive electrode active layer 13 disposed on at least one surface of the positive electrode current collector 11. In this embodiment, as shown in FIG2 , the positive electrode active layer 13 may be disposed on only one side of the positive electrode current collector 11, or may be disposed on two opposite surfaces of the positive electrode current collector 11.

[0044] The positive electrode current collector 11 may be made of aluminum foil or nickel foil, or any composite current collector disclosed in the prior art, such as but not limited to a current collector formed by combining the aforementioned conductive foil and a polymer substrate.

[0045] Referring to FIG3 , the positive electrode active layer 13 includes a central region 131 and an edge region 133 disposed around the outer periphery of the central region 131. When the positive electrode 10 forms a laminated electrode assembly A, as shown in FIG3 , the edge region 133 is annular (a rectangular ring as shown in FIG3 ) surrounding the central region 131 when viewed along the thickness direction X. When the positive electrode 10 forms a wound electrode assembly, when the positive electrode 10 is flattened, i.e., unwound, the edge region 133 is annular (a rectangular ring as shown in FIG3 ) surrounding the central region 131 when viewed along the thickness direction of the positive electrode 10. When the positive electrode 10 is wound to form a wound electrode assembly, the edge region 133 includes the starting and ending ends of the positive electrode active layer 13, as well as two ends of the positive electrode active layer 13 that are oppositely disposed along the central axis of the winding.

[0046] The edge region 133 includes the first positive electrode active material, and the center region 131 includes the second positive electrode active material. The ratio of the solid phase diffusion coefficient of the first positive electrode active material (which can be recorded as Ds1) to the solid phase diffusion coefficient of the second positive electrode active material (which can be recorded as Ds2) is 1:3 to 1:1.05, and the solid phase diffusion coefficient of the first positive electrode active material is 10 -15 cm 2 / s to 10 -5 cm 2 / s. By using a first positive electrode active material with a lower solid-phase diffusion coefficient in the edge region 133 and a second positive electrode active material with a higher solid-phase diffusion coefficient in the center region 131 to form a differentiated design of the edge region 133 and the center region 131 of the positive electrode 10, the solid-phase diffusion rate of lithium ions in the center region 131 is improved compared with the edge region 133, and the kinetic performance of the center region 131 is improved compared with the edge region 133, thereby reducing the difference in kinetic performance between the center region 131 and the edge region 133, reducing the difference in the amount of lithium desorption between the edge region 133 and the center region 131, and thus improving the overall capacity of the electrochemical device to improve the overall performance of the electrochemical device. In some embodiments, the solid-phase diffusion coefficient Ds1 of the first positive electrode active material may be 10 -15 cm 2 / s, 10 -14 cm 2 / s, 10 -12 cm 2 / s, 10 -10 cm 2 / s, 10 -9 cm 2 / s, 10 -7 cm2 / s, 10 -5 cm 2 / s or any specific value between any two adjacent values ​​mentioned above. Ds1:Ds2 may be 1:3, 1:2.75, 1:2.5, 1:2, 1:7.5, 1:1.5, 1:1.05 or any specific ratio between any two adjacent ratios mentioned above. The solid-phase diffusion rate of lithium ions of the first positive electrode active material having a solid-phase diffusion coefficient in the above-mentioned range is conducive to the insertion and extraction of lithium ions, and is conducive to improving the overall kinetic performance of the electrochemical device 100, and the above-mentioned specific ratio of solid-phase diffusion coefficients is also conducive to reducing the difference between the two regions and avoiding early reverse differences while improving the overall kinetic performance of the electrochemical device 100. In some embodiments, Ds1:Ds2 may be 1:2.8 to 1:1.5. Under 100% SOC conditions, the amount of lithium desorbed from the first positive electrode active material in the edge region 133 is greater than the amount of lithium desorbed from the second positive electrode active material in the central region 131, and the difference is 0.1% to 2%, for example, it can be 0.1%, 0.3%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.7%, 2% or any specific value between any two adjacent values ​​mentioned above, thereby reducing the difference between the electrochemical reaction in the edge region and the electrochemical reaction in the central region, which is beneficial to improving the overall performance of the electrochemical device.

[0047] The particle size Dv50 of the first positive electrode active material can be larger than the particle size Dv50 of the second positive electrode active material. By designing the edge region 133 to use an active material with a larger particle size and the center region 131 to use an active material with a smaller particle size, the solid-phase transmission distance of lithium ions in the active material in the center region 131 is reduced compared to that in the edge region 133, thereby improving the kinetic performance of the center region 131 compared to the edge region 133, thereby narrowing the kinetic performance difference between the center region 131 and the edge region 133, thereby improving the overall capacity of the electrochemical device and improving the overall performance of the electrochemical device. Specifically, the ratio of the particle size Dv50 of the first positive electrode active material to the particle size Dv50 of the second positive electrode active material can be 1.1:1 to 2:1, for example, 1.1:1, 1.3:1, 1.5:1, 1.7:1, 1.9:1, 2:1, or any specific ratio between any two adjacent ratios mentioned above. In some embodiments, the particle size Dv50 of the first positive electrode active material may be 1.0 μm to 25 μm, for example, 1.0 μm, 5.0 μm, 7.0 μm, 10.0 μm, 14.0 μm, 15.0 μm, 17.0 μm, 25 μm, or any specific value between any two adjacent values ​​thereof. The first positive electrode active material having the above-mentioned specific particle size range and the second positive electrode active material having a specific ratio range to the first positive electrode active material are conducive to achieving a higher compaction density and a higher kinetic electrode assembly, thereby facilitating the improvement of the overall performance of the electrochemical device 100.

[0048] The first positive electrode active material and the second positive electrode active material each include a compound that can reversibly intercalate and deintercalate lithium ions (i.e., a lithiated intercalation compound). In some embodiments, the first positive electrode active material and the second positive electrode active material each include a lithium transition metal composite oxide. The lithium transition metal composite oxide contains lithium and at least one element selected from cobalt, manganese and nickel. In some embodiments, the first positive electrode active material may include but is not limited to lithium cobalt oxide (LiCoO2), lithium nickel manganese cobalt ternary material (NCM), lithium manganese oxide (LiMn2O4), lithium nickel manganese oxide (LiNi 0.5 Mn 1.5 O4) or lithium iron phosphate (LiFePO4). The second positive electrode active material may include but is not limited to lithium cobalt oxide (LiCoO2), lithium nickel manganese cobalt ternary material (NCM), lithium manganese oxide (LiMn2O4), lithium nickel manganese oxide (LiNi 0.5 Mn 1.5 O4) or lithium iron phosphate (LiFePO4) and the like.

[0049] In some embodiments, the width of the edge region 133 may be 2 mm to 10 mm, for example, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, or any specific value between any two adjacent values ​​mentioned above. The width refers to the distance from any position of the outer periphery of the edge region 133 away from the central region 131, that is, any position of the outer periphery of the entire positive electrode active layer 13, to the closest point where the adjacent edge region 133 connects to the inner periphery of the central region 131.

[0050] Because the positive electrode active layer 13 undergoes a lamination process during its formation, the outer edge of the central region 131 and the inner edge of the edge region 133, which are adjacent or connected to each other before lamination, merge with each other after lamination to form a transition region 135. That is, the positive electrode active layer 13 also includes a transition region 135, which connects the inner periphery of the edge region 133 and the outer periphery of the central region 131. In some embodiments, the width of the transition region 135 can be 0.02 mm to 0.5 mm, for example, 0.02 mm, 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, or any specific value between any two adjacent values ​​mentioned above.

[0051] In addition, since the positive electrode active layer 13 undergoes a lamination process during its formation, the thickness of each region varies before and after lamination. The edge region 133 may extend away from the center region 131. However, since the center region 131 is surrounded by the edge region 133, the movable space of the center region 131 during lamination is limited by the edge region 133. Therefore, the thickness of the center region 131 is generally greater than the thickness of the edge region 133. In some embodiments, the difference between the thickness of the center region 131 and the thickness of the edge region 133 may be less than 1 micron, which helps improve the flatness of the electrode assembly composed of the positive electrode 10 and the negative electrode 30, thereby improving the overall flatness of the electrochemical device. In some embodiments, the thickness of the edge region may be between 50 microns and 1000 microns. The above-mentioned thickness range of the edge region 133 and the difference range between the center region 131 and the edge region 133 help avoid the impact of purple spots or lithium precipitation caused by flatness on the overall performance of the electrochemical device. Furthermore, the thickness of the edge region may be 100 μm to 500 μm, for example, 100 μm, 200 μm, 300 μm, 400 μm, 500 μm or any specific value between any two adjacent values ​​mentioned above.

[0052] In some embodiments, the compaction density of the edge region 133 may be greater than the compaction density of the central region 131. By designing the edge region 133 with a higher compaction density and the central region 131 with a lower compaction density, the liquid-phase diffusion capacity of lithium ions in the central region 131 is improved compared to the edge region 133, thereby improving the kinetic performance of the central region 131 compared to the edge region 133. This reduces the difference in kinetic performance between the central region 131 and the edge region 133, thereby increasing the overall capacity of the electrochemical device and improving the overall performance of the electrochemical device. Specifically, the difference between the compaction density of the edge region 133 and the compaction density of the central region 131 may be between 0.03 g / cc and 0.5 g / cc, for example, 0.03 g / cc, 0.06 g / cc, 0.1 g / cc, 0.2 g / cc, 0.3 g / cc, 0.4 g / cc, 0.5 g / cc, or any specific value between any two adjacent values ​​thereof. In some embodiments, the edge region 133 may have a compacted density of 2.0 g / cc to 4.35 g / cc, for example, 2.0 g / cc, 2.3 g / cc, 2.6 g / cc, 3.0 g / cc, 3.35 g / cc, 3.5 g / cc, 4.0 g / cc, 4.35 g / cc, or any specific value between any two adjacent values ​​thereof. The edge region 133 having a compacted density within the above range, and the central region 131 having a specific difference in compacted density from the edge region 133, are beneficial for improving the overall volumetric energy density of the electrochemical device 100, thereby further improving the overall performance of the electrochemical device 100.

[0053] In some embodiments, the porosity of the edge region 133 may be lower than the porosity of the central region 131. By designing the central region 131 with a higher porosity and the edge region 133 with a lower porosity, the liquid-phase diffusion capacity of lithium ions in the central region 131 is improved compared to the edge region 133, thereby improving the kinetic performance of the central region 131 compared to the edge region 133, thereby narrowing the difference in kinetic performance between the central region 131 and the edge region 133, thereby improving the overall capacity of the electrochemical device and improving the overall performance of the electrochemical device. Specifically, the ratio of the porosity of the edge region 133 to the porosity of the central region 131 may be 1:2 to 1:1.1, for example, 1:2, 1:1.85, 1:1.75, 1:1.5, 1:1.3, 1:1.2, 1:1.1, or any specific value between any two adjacent values ​​thereof. In some embodiments, the porosity of the edge region 133 may be between 10% and 45%, for example, 10%, 14%, 15%, 18%, 20%, 23%, 25%, 29%, 30%, 35%, 38%, 41%, 45%, or any specific value between any two adjacent values ​​thereof. The porosity and porosity ratio within the above ranges are beneficial for reducing the difference between the central region 131 and the edge region 133 while ensuring the kinetic performance of the electrochemical device.

[0054] The edge region 133 further includes a first binder for bonding the first positive electrode active material particles to facilitate film formation and improve the bonding strength between the edge region 133 and the positive electrode current collector 11. The central region 131 further includes a second binder for bonding the second positive electrode active material particles to facilitate film formation and improve the bonding strength between the central region 131 and the positive electrode current collector 11.

[0055] The content of the second binder in the central region 131 can be less than the content of the first binder in the edge region 133. By designing a higher binder content in the edge region 133 and a lower binder content in the central region 131, the interfacial transport barrier of lithium ions by the second binder in the central region 131 is reduced compared to the first binder in the edge region 133, thereby improving the kinetic performance of the central region 131 compared to the edge region 133. This, in turn, narrows the kinetic performance difference between the central region 131 and the edge region 133, thereby increasing the overall capacity of the electrochemical device and improving the overall performance of the electrochemical device. Specifically, the ratio of the second binder content in the central region 131 to the first binder content in the edge region 133 can be between 1:1.02 and 1:2, for example, 1:1.02, 1:1.25, 1:1.5, 1:1.75, 1:2, or any specific ratio between any two adjacent ratios described above. In some embodiments, the content of the second binder in the edge region 133 may be 0.4 wt % to 4.0 wt %, for example, 0.4 wt %, 1.0 wt %, 1.5 wt %, 2.0 wt %, 2.5 wt %, 3.0 wt %, 3.5 wt %, 4.0 wt %, or any specific value between any two adjacent values. The above-mentioned content of the second binder and the first binder having a specific ratio range to the content of the second binder are beneficial for ensuring the bonding strength between the edge region 133 and the central region 131 and the positive electrode current collector 11, that is, for ensuring the bonding strength between the positive electrode active layer 13 and the positive electrode current collector 11, while also improving the dynamic performance of the entire positive electrode active layer 13, thereby promoting the stability of the positive electrode 10 structure while also improving the overall dynamic performance of the electrochemical device 100, thereby facilitating the improvement of the overall performance of the electrochemical device 100.

[0056] The first binder and the second binder may each include, but are not limited to, at least one of polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polyvinylidene fluoride (PVDF), a polymer containing ethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, or nylon. The first binder and the second binder may be the same or different.

[0057] The edge region 133 may further include a first conductive agent, and the central region 131 may further include a second conductive agent. The content of the second conductive agent in the central region 131 may be greater than the content of the first conductive agent in the edge region 133. By designing the edge region 133 to have a lower conductive agent content and the central region 131 to have a higher conductive agent content, the electron transport capability of the central region 131 is improved compared to the edge region 133, thereby improving the kinetic performance of the central region 131 compared to the edge region 133, thereby narrowing the kinetic performance difference between the edge region 133 and the central region 131, thereby improving the overall capacity of the electrochemical device and improving the overall performance of the electrochemical device. Specifically, the difference between the content of the second conductive agent in the central region 131 and the content of the first conductive agent in the edge region 133 may be 0.1 wt% to 2.0 wt%, for example, 0.1 wt%, 0.5 wt%, 1.0 wt%, 1.5 wt%, 2.0 wt%, or any specific value between any two adjacent values ​​mentioned above. In some embodiments, the content of the second conductive agent in the central region 131 may be 0.2 wt % to 4.0 wt %, for example, 0.2 wt %, 0.5 wt %, 1.0 wt %, 1.5 wt %, 2.0 wt %, 2.5 wt %, 3.0 wt %, 3.5 wt %, 4.0 wt %, or any specific value between any two adjacent values ​​thereof. The above-mentioned specific content of the second conductive agent and the first conductive agent having a content within a specific difference range from the content of the second conductive agent are beneficial for ensuring the electron transport capability of the positive electrode 10 and making the positive electrode 10 have higher kinetic performance, thereby facilitating the improvement of the overall performance of the electrochemical device 100.

[0058] The first conductive agent and the second conductive agent may include, but are not limited to, carbon-based materials, metal-based materials, conductive polymers, or any combination thereof. In some embodiments, carbon-based materials may include, but are not limited to, natural graphite, artificial graphite, carbon black (SP), carbon nanotubes (CNTs), acetylene black, Ketjen black, carbon fibers, or any combination thereof. In some embodiments, metal-based materials may include, but are not limited to, metal powders or metal fibers, such as copper, nickel, aluminum, or silver. In some embodiments, the conductive polymer may be a polyphenylene derivative. The first conductive agent and the second conductive agent may be the same or different.

[0059] The negative electrode 30 includes a negative electrode current collector 31 and a negative electrode active layer 33 disposed on at least one surface of the negative electrode current collector 31. In this embodiment, as shown in FIG3 , the negative electrode active layer 33 may be disposed on two opposite surfaces of the negative electrode current collector 31, respectively.

[0060] The negative electrode current collector 31 can be made of at least one of copper foil, nickel foil, stainless steel foil, titanium foil or a carbon-based current collector, or any composite current collector disclosed in the prior art, such as but not limited to a current collector formed by combining the aforementioned conductive foil and a polymer substrate.

[0061] The negative electrode active layer 33 includes a negative electrode active material, which can be any known negative electrode active material capable of reversible deintercalation of active ions, and is not limited in this application. For example, it can include, but is not limited to, at least one of graphite, soft carbon, hard carbon, carbon fiber, mesocarbon microbeads, silicon-based materials, tin-based materials, lithium titanate, or other metals capable of forming alloys with lithium. The graphite can be selected from at least one of artificial graphite, natural graphite, and modified graphite; the silicon-based material can be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, and silicon alloys; and the tin-based material can be selected from at least one of elemental tin, tin oxide compounds, and tin alloys.

[0062] The negative electrode active layer 33 also includes a binder to bind the negative electrode active material particles to facilitate film formation and improve the bonding between the negative electrode active layer and the negative electrode current collector. In some embodiments, the binder in the negative electrode active layer 33 may include, but is not limited to, polyvinyl alcohol, carboxymethyl cellulose (CMC), hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber (SBR), acrylated styrene-butadiene rubber, epoxy resin, or nylon.

[0063] The isolation membrane 50 comprises a porous film layer, and its material may include at least one of polyethylene, polypropylene, polyvinylidene fluoride, polyethylene terephthalate, polyimide, or aramid. For example, the polyethylene may include at least one of high-density polyethylene, low-density polyethylene, or ultra-high molecular weight polyethylene. Polyethylene and polypropylene are particularly effective in improving short circuits and can enhance the stability of the electrochemical device 100 through a shutdown effect.

[0064] The electrolyte 60 may be in one or more of a gel state, a solid state, and a liquid state. The liquid electrolyte includes a lithium salt and a non-aqueous solvent. The lithium salt is selected from one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium hexafluoroarsenate (LiAsF6), lithium perchlorate (LiClO4), lithium tetraphenylborate (LiB(C6H5)4), lithium methanesulfonate (LiCH3SO3), lithium bis(trifluoromethanesulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiCF3SO3), lithium bis(trifluoromethylsulfonyl)imide (LiN(SO2CF3)2, tris(trifluoromethylsulfonyl)methyl lithium (LiC(SO2CF3)3), lithium bis(oxalatoborate) (LiBOB) and lithium difluorophosphate (LiPO2F2). For example, the lithium salt is selected from LiPF6 because it can provide high ionic conductivity and improve cycle characteristics. The non-aqueous solvent can be a carbonate compound, a carboxylate compound, an ether compound, Compounds, nitrile compounds, other organic solvents or combinations thereof. Examples of carbonate compounds are diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), ethyl methyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinyl ethylene carbonate (VEC), fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, trifluoromethylethylene carbonate and combinations thereof.

[0065] 4 , the electrochemical device 100 can be applied to an electronic device 200. The electronic device 200 further includes a body 201, and the electrochemical device 100 is electrically connected to the body 201 for powering the body 201. The electronic device 200 may include, but is not limited to, a laptop computer, a pen-type computer, a mobile computer, an e-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, an automobile, a motorcycle, a power-assisted bicycle, a bicycle, lighting fixtures, toys, a game console, a clock, an electric tool, a flashlight, a camera, a large household battery, and a lithium-ion capacitor.

[0066] The present application is described in detail below through comparative examples and examples. It is understood that the parameters in the present application are not limited to those described in the comparative examples and examples, and can be selected according to actual needs.

[0067] Example 1

[0068] Preparation of positive electrode:

[0069] The positive electrode active material lithium cobalt oxide (solid phase diffusion coefficient Ds2 is 2*10 -5 cm 2 / s,D V 50 is 16.7 microns, which is D V 50 中 ), binder PVDF, conductive agent SP and conductive agent CNT are added to N-methylpyrrolidone (NMP) in a ratio of 97.5:1.0:1.0:0.5, mixed and dispersed to prepare a first slurry (solid content of 75%), and the first slurry is extruded onto an aluminum foil current collector with a thickness of 9 microns and dried to form a first electrode sheet. The first slurry is correspondingly cured to form a first active layer (corresponding to the central area).

[0070] The positive electrode active material lithium cobalt oxide (solid phase diffusion coefficient Ds1 is 1*10 -5 cm 2 / s,D V 50 is 25 microns, which is D V 50 边 ), adhesive PVDF, conductive agent SP and conductive agent CNT are added to the mixed dispersed NMP in a ratio of 97.75:1.25:0.5:0.5 to prepare a second slurry (solid content of 75%), and the second slurry is coated with a width of 2 mm on the outer periphery of the first active layer of the first electrode sheet through a gravure, and a second electrode sheet is formed after drying. The second slurry is correspondingly cured to form a second active layer (corresponding to the edge area).

[0071] The cold pressed positive electrode was formed by cold pressing at a pressure of 80t and a speed of 20m / min (the compaction density of the edge area was 4.35g / cc and the porosity was 10%, and the compaction density of the center area was 4.25g / cc and the porosity was 15%), and then die-cut to form the positive electrode. The width W of the transition area in the positive electrode is 过渡 The width of the edge area is 0.2mm. 边 The thickness of the center area is 0.5 microns greater than that of the edge area, that is, △Tk is 0.5 microns, and the thickness of the edge area Tk 边 The size of the positive electrode is approximately 70mm*80mm.

[0072] Preparation of negative electrode:

[0073] Anode active material graphite, binder SBR, and binder CMC were mixed and dispersed in deionized water at a ratio of 97:1.6:1.4 to prepare anode slurry (48% solid content). The slurry was then extrusion-coated onto a 6-micron copper current collector and dried to form the anode. The slurry also formed the anode active layer, which was 120 microns thick. The dimensions of the anode were approximately 72mm by 82mm.

[0074] Preparation of lithium-ion batteries:

[0075] The positive electrode, separator (a PE film with a thickness of 5 microns and a porosity of about 35%) and the negative electrode are alternately stacked in sequence to form a laminated electrode assembly. After the tabs are welded, they are placed in a battery shell and injected with electrolyte (1M LiPF6in EC:DEC:EMC=1:1:1). After that, they are packaged and formed to form a lithium-ion battery, i.e., an electrochemical device.

[0076] At 100% SOC, the difference in the amount of lithium depletion between the edge area and the center area is 1%.

[0077] XRD characterization of lithium removal: ① Apply the first slurry to a 35µm copper foil using a 200µm scraper and dry at 110°C to form a coated electrode. This is then cold-pressed at 80t pressure and 20m / min to form a cold-pressed positive electrode. The positive electrode is then assembled into a button-shaped half-cell (using a specific button-shaped half-cell mold with a window on the top to allow X-ray transmission and ensure sealing). ② The button-shaped cell assembled in step 1 is charged at a constant current rate of 0.1C to a cutoff voltage of 4.47V. This is then charged at a constant voltage of 4.47V to a cutoff current of 50µA. After 5 minutes of rest, the cell is discharged at a constant current rate of 0.1C to 3.0V. This cycle is repeated three times. Simultaneously test XRD during the charge and discharge process; ③ Model the XRD 003 crystal plane interlayer spacing d tested in step ② and the amount of lithium cobalt oxide delithiation x during the charge and discharge process (the ratio of the charge or discharge capacity at different voltage states to the rated capacity) to form a linear equation d = -0.7372x + 5.2329; ④ Fully charge the battery cell, disassemble it to obtain the edge area and the middle area, and test XRD separately; ⑤ Substitute the d obtained in step ④ into the corresponding relationship in step ③ to obtain the delithiation amount of the edge area and the middle area, and the difference between the two is the difference in delithiation amount.

[0078] Comparative Example 1

[0079] The difference between Comparative Example 1 and Example 1 lies in the preparation of the positive electrode: the positive electrode active material lithium cobalt oxide (solid phase diffusion coefficient Ds1 is 1*10 -5 cm 2 / s,D V50 (25 microns), binder PVDF, conductive agent SP, and conductive agent CNT were added to a mixed and dispersed NMP at a ratio of 97.75:1.25:0.5:0.5 to prepare a positive electrode slurry (solid content 75%). The positive electrode slurry was extrusion-coated onto a 9-micron thick aluminum foil current collector and dried to form a positive electrode active layer. The positive electrode was then cold-pressed at a pressure of 80 tons and a speed of 20 m / min to form a cold-pressed positive electrode (the compaction density of each area of ​​the positive electrode active layer was 4.35 g / cc and the porosity was 10%). The positive electrode was then die-cut to form the positive electrode. The thickness of the positive electrode active layer was 100 microns.

[0080] Laminated lithium-ion batteries corresponding to Examples 2-33 were prepared according to the above steps and the following tables, and laminated lithium-ion batteries corresponding to Comparative Examples 2-3 were prepared according to the above steps and Table 9. The lithium-ion batteries corresponding to Examples 1-33 and Comparative Examples 1-3 had the same parameters except for those in the tables.

[0081] The following performance tests were conducted on each of the above examples and comparative examples: DC-rate @ 1°C, CC / (CC+CV) capacity @ 1°C, and -20°C DC-rate @ 0.2°C. The test results are summarized in Tables 1-8 and 10. The specific methods for each performance test are described below.

[0082] DC-rate@1C: At 25°C, charge the battery at a constant current rate of 0.2C to the cutoff voltage. Then charge the battery at the cutoff voltage to a current ≤0.05C to fully charge it. After 5 minutes of rest, discharge the battery at a constant current of 0.2C to the cutoff voltage. The discharge capacity is D0. After 5 minutes of rest, charge the battery at a constant current rate of 0.2C to the cutoff voltage. After 5 minutes of rest, discharge the battery at a constant current of 1C to the cutoff voltage. The discharge capacity is D1. The ratio of D1 to D0 is the capacity retention rate for DC-rate@1C.

[0083] CC / (CC+CV)capacity@1C: At 25°C, charge at a constant current rate of 1C to the cut-off voltage, and charge at the cut-off voltage to a current ≤ 0.05C to fully charge the cell. The capacity in the constant current stage is C CC ; The capacity in the constant voltage stage is C CV , where C CC and (C CC +C CV ) is CC / (CC+CV)capacity@1C.

[0084] -20℃ DC-rate@0.2C: At 25℃, charge at a constant current rate of 0.2C to the cut-off voltage. Charge at the cut-off voltage with a constant voltage until the current is ≤0.05C, so that the battery reaches a full charge state. After standing for 5 minutes, discharge at a constant current of 0.2C to the cut-off voltage. The discharge capacity is D0. After standing for 5 minutes, adjust the temperature to -20℃. After standing for 5 minutes, charge at a constant current rate of 0.2C to the cut-off voltage at a constant voltage after 0.2C. Charge at the cut-off voltage with a constant voltage until the current is ≤0.05C, so that the battery reaches a full charge state again. After standing for 5 minutes, discharge at a constant current of 0.2C to the cut-off voltage. The discharge capacity is D1. The ratio of D1 to D0 is the capacity retention rate of -20℃ DC-rate@0.2C.

[0085] Table 1

[0086] Table 2

[0087] Table 3

[0088] Table 4

[0089] Table 5

[0090] Table 6

[0091] Table 7

[0092] Table 8

[0093] Table 9

[0094] Table 10

[0095] As shown in Tables 1-10, based on the data from Examples 1-33 and Comparative Examples 1-3, the differentiated design of the edge region 133 and the central region 131 of the positive electrode 10 reduces the amount of lithium removed from the lithium-ion battery and improves rate performance, thereby improving the overall kinetic performance of the lithium-ion battery. Simultaneously, the capacity of the lithium-ion battery is also increased, thereby improving the overall performance of the lithium-ion battery. Furthermore, as shown in Table 1, based on the data from Examples 1-5, the wider the edge region 133 of the positive electrode 10, the smaller the difference in the amount of lithium removed between the central region 131 and the edge region 133, the smaller the difference in kinetic performance, the higher the overall kinetic performance of the lithium-ion battery, and the better the charge-discharge performance. As can be seen from the data of Example 1 and Examples 6-9 in Table 1, when the ratio of the solid-phase diffusion coefficient between the edge region 133 and the central region 131 of the positive electrode 10 is between 1:1.5 and 1:2.8, the smaller the difference in the amount of lithium removed between the central region 131 and the edge region 133, the smaller the difference in kinetic performance can be maintained within a smaller range, and the overall kinetic performance of the lithium-ion battery is better and the charge-discharge performance is higher. As can be seen from the data of Example 1 and Examples 10-13 in Table 2, the smaller the difference in the amount of lithium removed between the central region 131 and the edge region 133 of the positive electrode 10, the smaller the difference in kinetic performance, and the smaller the difference in kinetic performance, the overall kinetic performance of the lithium-ion battery is higher and the charge-discharge performance is better. As can be seen from the data of Example 1 and Examples 14-17 in Table 3, the smaller the ratio of the porosity between the central region 131 and the edge region 133 of the positive electrode 10, the smaller the difference in the amount of lithium removed between the central region 131 and the edge region 133, the smaller the difference in kinetic performance, and the smaller the difference in kinetic performance, the overall kinetic performance of the lithium-ion battery is higher and the charge-discharge performance is better. From the data of Example 1 and Examples 18-19 in Table 4, it can be seen that the narrower the width of the transition region of the positive electrode 10, the smaller the difference in the amount of lithium removed between the central region 131 and the edge region 133, the smaller the difference in kinetic performance, the higher the overall kinetic performance of the lithium-ion battery, and the better the charge-discharge performance. From the data of Example 1 and Examples 20-21 in Table 5, it can be seen that the smaller the difference in thickness between the central region 131 and the edge region 133, the smaller the difference in the amount of lithium removed between the central region 131 and the edge region 133, the smaller the difference in kinetic performance, and the better the overall kinetic performance of the lithium-ion battery, and the better the charge-discharge performance. From the data of Example 1 and Examples 22-23 in Table 5, it can be seen that the smaller the thickness of the positive electrode active layer 13, the smaller the difference in the amount of lithium removed between the central region 131 and the edge region 133, the smaller the difference in kinetic performance, and the better the overall kinetic performance of the lithium-ion battery, and the better the charge-discharge performance. From the data of Example 1 and Examples 24-25 in Table 6, it can be seen that the larger the particle size ratio of the positive electrode active material between the edge area 133 and the central area 131, the smaller the difference in lithium desorption between the central area 131 and the edge area 133, and the smaller the difference in kinetic performance, the higher the overall kinetic performance of the lithium-ion battery and the better the charge and discharge performance.From the data of Example 1 and Examples 26-27 in Table 7, it can be seen that the greater the ratio of the binder content between the edge region 133 and the central region 131, the smaller the difference in the amount of lithium removed between the central region 131 and the edge region 133, the smaller the difference in kinetic performance, the higher the overall kinetic performance of the lithium-ion battery, and the better the charge-discharge performance. From the data of Example 1 and Examples 28-29 in Table 8, it can be seen that the greater the difference in the content of the conductive agent between the central region 131 and the edge region 133, the smaller the difference in the amount of lithium removed between the central region 131 and the edge region 133, the smaller the difference in kinetic performance, the higher the overall kinetic performance of the lithium-ion battery, and the better the charge-discharge performance. From the data between Example 1 and Comparative Example 1, between Example 30 and Comparative Example 2, and between Example 32 and Comparative Example 3 in Table 9, it can be seen that even for positive electrode active materials of different materials, the differentiated design of the edge region 133 and the central region 131 of the positive electrode 10 can also improve the overall kinetic performance and capacity of the lithium-ion battery. As shown in the data of Example 1 and Examples 30-33 in Table 9, the lithium-ion batteries with positive electrode active materials of different materials have relatively good dynamic performance and capacity after the differentiated design of the positive electrode 10 in the edge area 133 and the central area 131.

[0096] In addition, those skilled in the art can make various other corresponding changes and modifications based on the technical concept of this application, and all these changes and modifications should fall within the scope of protection of this application.

Claims

1. An electrochemical device comprising a positive electrode, a negative electrode and an electrolyte, wherein the positive electrode comprises a positive electrode current collector and a positive electrode active layer disposed on at least one surface of the positive electrode current collector, wherein: The positive electrode active layer includes a central region and an edge region arranged around the outer periphery of the central region, the edge region includes a first positive electrode active material, the central region includes a second positive electrode active material, and the solid phase diffusion coefficient of the first positive electrode active material is 10 -15 cm 2 / s to 10 -5 cm 2 / s, and the ratio of the solid phase diffusion coefficient of the first positive electrode active material to the solid phase diffusion coefficient of the second positive electrode active material is 1:3 to 1:1.

05.

2. The electrochemical device according to claim 1, wherein The ratio of the solid phase diffusion coefficient of the first positive electrode active material to the solid phase diffusion coefficient of the second positive electrode active material is 1:2.8 to 1:1.

5.

3. The electrochemical device according to claim 1, wherein The compacted density of the edge region is 2.0 g / cc to 4.35 g / cc, and the compacted density of the edge region is greater than the compacted density of the central region, and the difference is 0.03 g / cc to 0.5 g / cc.

4. The electrochemical device according to claim 1, wherein The ratio of the porosity of the edge region to the porosity of the central region is 1:2 to 1:1.1, and the porosity of the edge region is 10% to 45%.

5. The electrochemical device according to claim 1, wherein The width of the edge region is 2 mm to 10 mm.

6. The electrochemical device according to claim 1, wherein The positive electrode active layer further includes a transition region, wherein the transition region connects the inner periphery of the edge region and the outer periphery of the central region, and a width of the transition region is 0.02 mm to 0.5 mm.

7. The electrochemical device according to claim 1, wherein: The thickness of the central area is greater than the thickness of the edge area and the difference is less than 1 micron, and the thickness of the edge area is 50 microns to 1000 microns.

8. The electrochemical device according to claim 7, wherein: The thickness of the edge region is 100 micrometers to 500 micrometers.

9. The electrochemical device according to claim 1, wherein: The ratio of the particle size Dv50 of the first positive electrode active material to the particle size Dv50 of the second positive electrode active material is 1.1:1 to 2:1, and the particle size Dv50 of the first positive electrode active material is 1.0 micrometer to 25 micrometers.

10. The electrochemical device according to claim 1, wherein The edge region also includes a first binder, and the center region also includes a second binder, the content of the second binder in the edge region is 0.4wt% to 4.0wt%, and the ratio of the content of the second binder in the center region to the content of the first binder in the edge region is 1:1.02 to 1:

2.

11. The electrochemical device according to claim 1, wherein: The edge region further includes a first conductive agent, and the central region further includes a second conductive agent, wherein the content of the second conductive agent in the central region is 0.2wt% to 4.0wt%, and the content of the second conductive agent in the central region is greater than the content of the first conductive agent in the edge region and the difference is 0.1wt% to 2.0wt%.

12. The electrochemical device according to claim 1, wherein Under the condition of 100% SOC, the amount of lithium removed from the first positive electrode active material in the edge region is greater than the amount of lithium removed from the second positive electrode active material in the central region, and the difference is 0.1% to 2%.

13. An electronic device, comprising a body, wherein the electronic device further comprises an electrochemical device as claimed in any one of claims 1 to 12, and the electrochemical device is electrically connected to the body for supplying power to the body.

Images