A secondary battery and an electric device

Abstract

The application provides a secondary battery and a power utilization device. The secondary battery comprises an electrode assembly, the electrode assembly comprises a positive electrode sheet, a negative electrode sheet and a separator film, the positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer, the positive electrode active material layer comprises a positive electrode active material, the negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer, and the negative electrode active material layer comprises a negative electrode active material; the positive electrode current collector integrally extends to form a plurality of positive electrode tabs, and the negative electrode current collector integrally extends to form a plurality of negative electrode tabs; the coating weight of the positive electrode active material layer is W z , the coating weight of the negative electrode active material layer is W f , W z and W f satisfy the following conditions: 1.6W f ≤W z ≤2.2W f , 3.25 mg / cm 2 ≤W f ≤5.84 mg / cm 2 ; the Dv99 of the positive electrode active material is 27 μm to 33 μm, and the Dv99 of the negative electrode active material is 23 μm to 28 μm. Through the above setting, the processing reliability of the secondary battery can be considered on the basis of improving the cycle dynamics performance of the secondary battery.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrochemistry, in particular to a secondary battery and a power utilization device. BACKGROUND

[0002] Secondary batteries (such as lithium ion batteries) have the characteristics of high specific energy, high working voltage, low self-discharge rate, small volume, light weight, etc., and are widely used in various fields such as electric energy storage, portable electronic devices and electric vehicles. With the continuous iterative development of consumer lithium ion batteries in recent years, the market has increasingly high requirements for the charging speed of lithium ion batteries, and the charging rate of lithium ion batteries is continuously improved. The demand of consumers gradually increases from 1C to more than 5C, but the improvement of the charging rate of lithium ion batteries is often accompanied by poor processing reliability. Therefore, how to improve the cycle dynamics performance of super-fast-charging lithium ion batteries while considering the processing reliability of lithium ion batteries has become a technical problem to be solved by those skilled in the art. SUMMARY

[0003] The purpose of the present application is to provide a secondary battery to improve the cycle dynamics performance of super-fast-charging secondary batteries while considering the processing reliability of the secondary battery, and a power utilization device using the secondary battery is also provided.

[0004] It should be noted that the lithium ion battery is taken as an example to explain the present application in the summary of the present application, but the secondary battery of the present application is not limited to the lithium ion battery, and can also be used in sodium ion batteries and other secondary batteries. The specific technical solutions are as follows:

[0005] The first aspect of the present application provides a secondary battery, wherein the secondary battery comprises an electrode assembly, the electrode assembly comprises a positive electrode sheet, a negative electrode sheet and a separator, the positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer, the positive electrode active material layer comprises a positive electrode active material, the negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer, the negative electrode active material layer comprises a negative electrode active material; the positive electrode current collector integrally extends to form a plurality of positive electrode tabs, and the negative electrode current collector integrally extends to form a plurality of negative electrode tabs; the coating weight of the positive electrode active material layer is W z , the coating weight of the negative electrode active material layer is W f , W z and W f satisfy: 1.6W f ≤W z ≤2.2W f , 3.25mg / cm 2 ≤W f ≤5.84mg / cm 2; the Dv99 of the positive active material is 27-33 pm, and the Dv99 of the negative active material is 23-28 pm. The present application combines the coating weight of the positive active material layer and the negative active material layer, the Dv99 of the positive active material and the negative active material, and the multi-tab structure, so that the coating weight of the positive active material layer and the negative active material layer, the Dv99 of the positive active material and the negative active material, and the multi-tab structure have a good synergistic effect, which can improve the cycle dynamics performance of the secondary battery under the condition of super-fast charging, and also consider the processing reliability of the secondary battery.

[0006] In an embodiment of the present application, N1 layers of positive electrode tabs are arranged between the two adjacent positive electrode tabs, and N2 layers of negative electrode tabs are arranged between the two adjacent negative electrode tabs, and N1 and N2 are each independently selected from 0, 1, 2 or 3. By adjusting N1 and N2 within the above range, there are sufficient number of positive electrode tabs and negative electrode tabs on the positive electrode tab and the negative electrode tab in the secondary battery, so that there are multiple current channels on the positive electrode tab and the negative electrode tab, which can reduce the internal resistance of the secondary battery, reduce the charging temperature rise of the secondary battery, and shorten the charging time, so that the secondary battery has good cycle dynamics performance while considering the processing reliability. It can be understood that adjusting N1 and N2 to 0 can make the positive electrode tab and the negative electrode tab have more current channels, which can further reduce the internal resistance of the secondary battery, further reduce the charging temperature rise of the secondary battery, and further shorten the charging time, so that the secondary battery has good cycle performance and mechanical reliability while further improving its dynamics performance, but this will reduce the energy density of the secondary battery to some extent; adjusting N1 and N2 to 1 or 2 or 3 will reduce the number of tabs and increase the internal resistance to some extent, but can improve the energy density of the secondary battery.

[0007] In an embodiment of the present application, 6.49 mg / cm 2 ≤W z ≤11.69 mg / cm 2 The present application adjusts the coating weight of the positive active material layer within the range of the present application, so that the secondary battery has good cycle dynamics performance while considering the processing reliability.

[0008] In an embodiment of the present application, 4.00 mg / cm 2 ≤W f ≤5.19 mg / cm 2 , and / or 8.00 mg / cm 2 ≤W z ≤10.38 mg / cm 2 W z and / or W fThe coating weight of the positive active material layer and / or the negative active material layer is regulated within the above range, and the coating weight of the positive active material layer and / or the negative active material layer is more preferably within the range, which is beneficial to further improve the cycle kinetics performance of the secondary battery while ensuring the processing reliability.

[0009] In an embodiment of the present application, the Dv99 of the positive active material is 28 μm to 31 μm, and / or the Dv99 of the negative active material is 24 μm to 26 μm. The Dv99 of the positive active material and / or the Dv99 of the negative active material is regulated within the above range, and the Dv99 of the positive active material and / or the Dv99 of the negative active material is more preferably within the range, which is beneficial to further improve the cycle kinetics performance and the processing reliability of the secondary battery.

[0010] In an embodiment of the present application, the negative active material comprises at least one of a carbon-based material, a silicon-based material or a tin-based material, the carbon-based material comprises at least one of natural graphite, artificial graphite, soft carbon, hard carbon or mesocarbon microbeads, the silicon-based material comprises at least one of elemental silicon, silicon-carbon material or silicon-oxygen material, and the tin-based material comprises at least one of elemental tin, tin alloy or oxide of tin. The above-mentioned negative active material has high surface activity, and the secondary battery has good cycle kinetics performance while ensuring the processing reliability.

[0011] In an embodiment of the present application, the carbon-based material has a peak intensity ratio I d / I g of d peak to g peak by Raman test of 0.1 to 1.0. The carbon-based material satisfying the above I d / I g value is applied to the secondary battery, which is beneficial to further improve the cycle kinetics performance of the secondary battery while ensuring the good processing reliability. d / I g

[0012] In an embodiment of the present application, the positive active material comprises at least one of lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium-rich manganese-based material, lithium cobalt oxide, lithium manganese oxide, lithium manganese iron phosphate or lithium titanate. The above-mentioned positive active material has high surface activity, and the secondary battery has good cycle kinetics performance while ensuring the good processing reliability.

[0013] In an embodiment of the present application, the positive active material further comprises a non-metallic element, and the non-metallic element comprises at least one of fluorine, phosphorus, boron, chlorine, silicon or sulfur. The positive active material comprises the above-mentioned non-metallic element, which is beneficial to further improve the stability of the positive active material.

[0014] ​The second aspect of the present application provides a power device comprising the secondary battery according to any one of the foregoing embodiments. Therefore, the power device has good use performance.

[0015] Advantages of the present application:

[0016] The present application provides a secondary battery and a power device, wherein the secondary battery has a multi-tab structure by integrally extending the positive current collector to form a plurality of positive tabs and integrally extending the negative current collector to form a plurality of negative tabs, and the Dv99 of the positive active material and the Dv99 of the negative active material are controlled within the range of the present application, and the coating weight and the relationship between the positive active material layer and the negative active material layer are controlled within the range of the present application, so that the multi-tab structure of the secondary battery, the Dv99 of the positive active material and the negative active material, the coating weight of the positive active material layer, and the relationship between the coating weight of the positive active material layer and the negative active material layer play a good synergistic effect, so that the lithium ion has a shorter transmission path inside the positive / negative active material and a smaller transmission tortuosity and a shorter transmission distance inside the positive / negative electrode sheet during transmission, thereby reducing the concentration polarization of the secondary battery and reducing the probability of breakage of the positive electrode sheet and the negative electrode sheet, so that the secondary battery can improve the cycle kinetics performance of the secondary battery under the condition of super-fast charging while taking into account the processing reliability of the secondary battery. The power device of the present application has good use performance. BRIEF DESCRIPTION OF DRAWINGS

[0017] The accompanying drawings, which are included to provide a further understanding of the present application, form a part of the present application and illustrate the illustrative embodiments of the present application and its description are used to explain the present application and do not constitute an improper limitation on the present application.

[0018] Figure 1 Structure diagram of the electrode assembly according to an embodiment of the present application;

[0019] Figure 2 Structure diagram of the electrode assembly according to another embodiment of the present application;

[0020] Figure 3 Structure diagram of the positive electrode sheet according to an embodiment of the present application;

[0021] Figure 4 Structure diagram of the negative electrode sheet according to an embodiment of the present application;

[0022] Figure 5 Raman spectrum of the negative electrode of Example 2-3. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solutions, and advantages of the present application clearer, the present application is further described in detail below with reference to the drawings and examples. Obviously, the described examples are only some of the examples of the present application, rather than all the examples. All other examples obtained by those skilled in the art based on the present application are within the scope of protection of the present application.

[0024] It should be noted that in the specific embodiments of the present application, the present application is explained by taking lithium-ion batteries as examples of secondary batteries, but the secondary batteries of the present application are not limited to lithium-ion batteries, and can also be used in secondary batteries such as sodium-ion batteries.

[0025] The first aspect of the present application provides a secondary battery, wherein the secondary battery comprises an electrode assembly, the electrode assembly comprises a positive electrode sheet, a negative electrode sheet, and a separator, the positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer, the positive electrode active material layer comprises a positive electrode active material, the negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer, the negative electrode active material layer comprises a negative electrode active material; the positive electrode current collector integrally extends to form a plurality of positive electrode tabs, and the negative electrode current collector integrally extends to form a plurality of negative electrode tabs; the coating weight of the positive electrode active material layer is W z , the coating weight of the negative electrode active material layer is W f , W z , and W f satisfy: 1.6W f ≤W z ≤2.2W f , 3.25 mg / cm 2 ≤W f ≤5.84 mg / cm 2 ; the Dv99 of the positive electrode active material is 27 μm to 33 μm, and the Dv99 of the negative electrode active material is 23 μm to 28 μm.

[0026] In the present application, for the convenience of understanding, it is defined that in the unfolded state, the length direction of the separator is X, the width direction of the separator is Y, and the thickness direction of the separator is Z. It can be understood that the length direction, the width direction, and the thickness direction of the positive electrode sheet and the negative electrode sheet in the unfolded state are the same as those of the separator. After the positive electrode sheet, the separator, and the negative electrode sheet are wound to form an electrode assembly in a wound structure, the winding direction of the electrode assembly is W. As shown in Figure 1 and Figure 2 , the electrode assembly 001 comprises a positive electrode sheet 10, a negative electrode sheet 20, and a separator 30, and the separator 30 is arranged between the positive electrode sheet 10 and the negative electrode sheet 20. The positive electrode sheet 10 comprises a positive electrode current collector 11, as shown in Figure 3As shown, the positive current collector 11 integrally extends to form a plurality of positive tabs 12, wherein the positive current collector 11 comprises a positive tab region 111 and a positive body region 112. It can be understood that the positive tab region 111 refers to a region provided with the positive tabs 12, and the positive body region 112 refers to a region of the positive current collector 11 other than the positive tab region 111. The negative tab sheet 20 comprises a negative current collector 21, as shown. Figure 4 As shown, the negative current collector 21 integrally extends to form a plurality of negative tabs 22, wherein the negative current collector 21 comprises a negative tab region 211 and a negative body region 212. It can be understood that the negative tab region 211 refers to a region provided with the negative tabs 22, and the negative body region 212 refers to a region of the negative current collector 21 other than the negative tab region 211. In the present application, the above-mentioned “integrally extending” refers to integrally forming the current collector and the tab, for example, cutting a plurality of tabs on the edge of the current collector by laser or die cutting, rather than connecting the tab to the current collector by non-integrally forming means such as welding. It should be noted that, Figures 1 to 4 The number, shape and size of the positive and negative tabs are only exemplary and the present application is not limited thereto. In the present application, the above-mentioned “plurality” refers to two or more. In an embodiment of the present application, the plurality refers to at least 2, and the upper limit of the number of tabs can not be particularly required and can be adjusted according to the capacity, size and other factors of the secondary battery. Exemplarily, the plurality can be 2, 3, 4, 5, 6, 7, 20 or 50.

[0027] For example, W z is 1.6 W f , 1.7 W f , 1.8 W f , 1.9 W f , 2.0 W f , 2.1 W f , 2.2 W f or any value within any two of the above-mentioned numerical ranges. For example, W f is 3.25 mg / cm 2 , 3.5 mg / cm 2 , 3.75 mg / cm 2 , 4 mg / cm 2 , 4.25 mg / cm 2 , 4.5 mg / cm 2 , 4.75 mg / cm 2 , 5 mg / cm 2 , 5.25 mg / cm 2 , 5.5 mg / cm 2 , 5.84 mg / cm 2 or any value within any two of the above-mentioned numerical ranges. The coating weight W of the positive active material layerz less than 1.6 W f If the coating weight of the positive active material layer is too large relative to the coating weight of the negative active material layer, the lithium ions are excessively removed, and the negative electrode cannot fully accept the lithium ions removed from the positive electrode. The lithium ions cannot be normally inserted into the negative electrode sheet, which will cause lithium precipitation in the negative electrode sheet, affecting the cycle kinetic performance of the secondary battery. The coating weight of the negative active material layer is less than 3.25 mg / cm z greater than 2.2 W f If the coating weight of the positive active material layer is too large relative to the coating weight of the negative active material layer, the lithium ions are excessively removed, and the negative electrode cannot fully accept the lithium ions removed from the positive electrode. The lithium ions cannot be normally inserted into the negative electrode sheet, which will cause lithium precipitation in the negative electrode sheet, affecting the cycle kinetic performance of the secondary battery. The coating weight of the negative active material layer is less than 3.25 mg / cm 2 The energy density of the secondary battery is reduced, making it difficult to meet the process requirements of the secondary battery; and the coating weight of the negative active material layer is greater than 5.84 mg / cm 2 The transmission distance of lithium ions inside the positive electrode sheet and / or the negative electrode sheet is increased, and the impedance of the secondary battery is increased.

[0028] For example, the Dv99 of the positive active material is 27 μm, 28 μm, 29 μm, 30 μm, 31 μm, 32 μm, 33 μm, or any value within the range between any two of the above values. If the Dv99 of the positive active material is less than 27 μm, the Dv99 of the positive active material is too small, indicating that the volume particle size of the positive active material particles is too small. During the preparation of the positive electrode slurry, the positive active material particles are prone to agglomeration, so that the probability of uniform dispersion of the positive active material in the positive electrode slurry is extremely small, and the distribution of the positive active material particles in the positive active material layer formed is uneven, which will affect the processing stability of the positive electrode sheet and cause uneven coating during the coating of the positive electrode slurry. In addition, the specific surface area of the positive active material particles will be too large, resulting in an increase in the interface between the positive active material particles and the electrolyte, and the side reaction will be intensified, especially under the high kinetic electrolyte system of super-fast charging, the side reaction will be very intense, accelerating the consumption of the electrolyte and the generation of side reaction products, and deteriorating the cycle kinetic performance and processing reliability of the secondary battery. If the Dv99 of the positive active material is greater than 33 μm, the Dv99 of the positive active material is too large, the transmission path of lithium ions inside the positive active material particles is too long, and the tortuosity of the transmission inside the positive electrode sheet is too large, which will cause the concentration polarization inside the secondary battery to be too large, thereby increasing the internal resistance of the secondary battery and reducing the cycle kinetic performance of the secondary battery.

[0029] For example, the Dv99 of the negative active material is 23 μm, 24 μm, 25 μm, 26 μm, 27 μm, 28 μm, or any value within any two of the above ranges. If the Dv99 of the negative active material is less than 23 μm, the Dv99 of the negative active material is too small, indicating that the volume particle size of the negative active material particles is too small, and the negative active material particles are prone to agglomeration during the preparation of the negative electrode slurry. Thus, the probability of uniform dispersion of the negative active material in the negative electrode slurry is extremely small, and the distribution of the negative active material particles in the negative active material layer formed is uneven, which will affect the processing stability of the negative electrode sheet and cause uneven coating during the coating of the negative electrode slurry. In addition, the specific surface area of the negative active material particles will be too large, resulting in an increase in the interface between the negative active material particles and the electrolyte, and the side reaction will intensify, especially under the high kinetic electrolyte system of super-fast charging, the side reaction will be very intense, accelerating the consumption of the electrolyte and the generation of side reaction products, and deteriorating the cycle kinetic performance and processing reliability of the secondary battery. If the Dv99 of the negative active material is greater than 28 μm, the Dv99 of the negative active material is too large, the transmission path of lithium ions inside the negative active material particles is too long, and the tortuosity of the transmission inside the negative electrode sheet is too large, which will cause the concentration polarization inside the secondary battery to be too large, thereby increasing the internal resistance of the secondary battery and reducing the cycle kinetic performance of the secondary battery.

[0030] Overall, the application sets the positive current collector to integrally extend to form multiple positive electrode tabs, and the negative current collector to integrally extend to form multiple negative electrode tabs, so that the secondary battery has a multiple-tab structure, the positive electrode tab and the negative electrode tab have multiple current channels, the internal resistance of the secondary battery is reduced, the voltage polarization of the secondary battery under large rate (such as 5C to 15C) charging conditions is small, the charging temperature rise of the secondary battery is reduced, and the charging time of the secondary battery is shortened, so that the secondary battery has higher kinetic performance. The application regulates the Dv99 of the positive active material and the negative active material within the above range, so that the lithium ion has a shorter transmission path inside the positive / negative active material and a smaller transmission tortuosity inside the positive / negative electrode tab during transmission, to reduce the concentration polarization of the secondary battery, so that the secondary battery has good cycle kinetics. The application regulates the coating weight of the positive active material layer and the negative active material layer within the above range, which can shorten the transmission distance of lithium ions and electrons inside the positive electrode tab and inside the negative electrode tab, thereby reducing the ohmic polarization and concentration polarization of the secondary battery. The application combines the coating weight of the positive active material layer and the negative active material layer, the Dv99 of the positive active material and the negative active material, and the multiple-tab structure, so that the coating weight of the positive active material layer and the negative active material layer, the Dv99 of the positive active material and the negative active material, and the multiple-tab structure have a good synergistic effect. The positive and negative active materials with small Dv99 match the thin coating required for super-fast charging, and ensure that large particles in the positive and negative active materials do not exceed the thickness of the active material coating during cold pressing, so that the current collector is not squeezed, reducing the probability of damage and fracture of the current collector. Especially the multiple-tab structure, the gap coating method causes the air foil area and the coating film area to be subjected to different stresses due to the thickness difference during cold pressing, and is more prone to breakage due to the squeezing of the current collector by active material particles. The positive and negative active materials with small Dv99 match the thin coating required for super-fast charging, which can alleviate the breakage caused by the squeezing of the current collector by active material particles, thereby improving the cycle kinetics of the secondary battery while ensuring the processing reliability of the secondary battery.

[0031] In the application, Dv99 represents the particle size of the particle reaching 99% of the volume accumulation from the small particle size side in the volume-based particle size distribution. The above-mentioned "particle" in the application can be a particle of the positive active material, and can be a particle of the negative active material. The application does not have a particular limitation on the regulation method of the Dv99 of the positive active material and the negative active material, as long as the application purpose can be achieved. For example, the positive active material and the negative active material with Dv99 within the range of the application can be directly purchased, or can be achieved by crushing, grinding or ball milling.

[0032] In an embodiment of the present application, N1 layers of positive electrode tabs are arranged between two adjacent positive electrode tabs, and N2 layers of negative electrode tabs are arranged between two adjacent negative electrode tabs, wherein N1 and N2 are each independently selected from 0, 1, 2 or 3. Figure 1 As shown in the wound electrode assembly, two adjacent positive electrode tabs 12 or two adjacent negative electrode tabs 22 are distributed on different layers. As viewed from top to bottom in the figure, 0 layers of positive electrode tabs 10 are arranged between two adjacent positive electrode tabs 12, and 0 layers of negative electrode tabs 20 are arranged between two adjacent negative electrode tabs 22. Figure 2 As shown in the wound electrode assembly, two adjacent positive electrode tabs 12 or two adjacent negative electrode tabs 22 are distributed on different layers. As viewed from top to bottom in the figure, 1 layer of positive electrode tabs 10, 2 layers of positive electrode tabs 10 are arranged between two adjacent positive electrode tabs 12, respectively, and 0 layers of negative electrode tabs 20, 3 layers of negative electrode tabs 20 are arranged between two adjacent negative electrode tabs 22, respectively. By adjusting N1 and N2 within the above range, a sufficient number of positive electrode tabs and negative electrode tabs on the positive electrode tabs and the negative electrode tabs in the secondary battery can be obtained, so that the positive electrode tabs and the negative electrode tabs have multiple current channels, which can reduce the internal resistance of the secondary battery, reduce the charging temperature rise of the secondary battery, and shorten the charging time, so that the fast-charging secondary battery has good cycle dynamics while ensuring processing reliability. It can be understood that adjusting N1 and N2 to 0 can make the positive electrode tabs and the negative electrode tabs have more current channels, which can further reduce the internal resistance of the secondary battery, further reduce the charging temperature rise of the secondary battery, and further shorten the charging time, so that the secondary battery has further improved dynamics while ensuring cycle performance and mechanical reliability, but this will reduce the energy density of the secondary battery to some extent; adjusting N1 and N2 to 1 or 2 or 3 can reduce the number of tabs and improve the internal resistance to some extent, but can improve the energy density of the secondary battery.

[0033] In an embodiment of the present application, N1 layers of positive electrode tabs are arranged between two adjacent positive electrode tabs, and N2 layers of negative electrode tabs are arranged between two adjacent negative electrode tabs, wherein N1 and N2 are each independently selected from 0. Figure 1As shown, in the wound electrode assembly, two adjacent positive tabs 12 or two adjacent negative tabs 22 are distributed on different layers, and between the two adjacent positive tabs 12, a 0-layer positive tab 10 is arranged from top to bottom in the figure, and between the two adjacent negative tabs 22, a 0-layer negative tab 20 is arranged. By adjusting N1 and N2 to 0, more positive tabs and negative tabs in the secondary battery have positive tabs and negative tabs, so that more current channels are provided on the positive tabs and negative tabs, which can further reduce the internal resistance of the secondary battery, further reduce the charging temperature rise of the secondary battery, and further shorten the charging time, thereby further improving the kinetic performance of the secondary battery on the basis of considering the cycle performance and mechanical reliability of the secondary battery under super-fast charging conditions, but the energy density will be reduced to some extent.

[0034] In an embodiment of the present application, 6.49 mg / cm 2 ≤W z ≤11.69 mg / cm 2 For example, W z is 6.49 mg / cm 2 , 6.7 mg / cm 2 , 7 mg / cm 2 , 7.23 mg / cm 2 , 7.5 mg / cm 2 , 7.79 mg / cm 2 , 8 mg / cm 2 , 8.24 mg / cm 2 , 8.5 mg / cm 2 , 8.8 mg / cm 2 , 9 mg / cm 2 , 9.2 mg / cm 2 , 9.5 mg / cm 2 , 9.7 mg / cm 2 , 10 mg / cm 2 , 10.2 mg / cm 2 , 10.5 mg / cm 2 , 10.7 mg / cm 2 , 11 mg / cm 2 , 11.69 mg / cm 2 , or any value range between any two of the above values. By adjusting the coating weight of the positive active material layer within the range of the present application, the present application can shorten the transmission distance of lithium ions and electrons on the positive tab, which is beneficial to reduce the ohmic polarization and concentration polarization of the secondary battery, thereby reducing the impedance of the secondary battery, and the secondary battery has good cycle kinetics on the basis of considering the processing reliability.

[0035] In an embodiment of the present application, 4.00 mg / cm 2 ≤ W f ≤ 5.19 mg / cm 2 For example, W f is 4.00 mg / cm 2 , 4.25 mg / cm 2 , 4.5 mg / cm 2 , 4.75 mg / cm 2 , 5 mg / cm 2 , 5.19 mg / cm 2 , or any value between any two of the above-mentioned numerical ranges. Controlling W f within the above-mentioned range, the coating weight range of the negative active material layer is more optimal, which is conducive to further improving the cycle kinetic performance of the secondary battery on the basis of taking into account the processing reliability.

[0036] In an embodiment of the present application, 8.00 mg / cm 2 ≤ W z ≤ 10.38 mg / cm 2 For example, W z is 8 mg / cm 2 , 8.6 mg / cm 2 , 9.1 mg / cm 2 , 9.5 mg / cm 2 , 10 mg / cm 2 , 10.38 mg / cm 2 , or any value between any two of the above-mentioned numerical ranges. Controlling W z within the above-mentioned range, the coating weight range of the positive active material layer is more optimal, which is conducive to further improving the cycle kinetic performance of the secondary battery on the basis of taking into account the processing reliability.

[0037] In an embodiment of the present application, 4 mg / cm 2 ≤ W f ≤ 5.19 mg / cm 2 , 8 mg / cm 2 ≤ W z ≤ 10.38 mg / cm 2 For example, W f is 4 mg / cm 2 , 4.25 mg / cm 2 , 4.5 mg / cm 2 , 4.75 mg / cm 2 , 5 mg / cm 2 , 5.19 mg / cm 2 , or any value between any two of the above-mentioned numerical ranges. For example, W z8 mg / cm 2 8.5 mg / cm 2 9 mg / cm 2 9.5 mg / cm 2 10.38 mg / cm 2 or any value between any two of the above-mentioned numerical ranges. The coating weight of the positive active material layer and the negative active material layer are controlled within the above-mentioned ranges, and the coating weight ranges of the positive active material layer and the negative active material layer are more optimal, which is beneficial to further improve the cycle kinetic performance of the secondary battery on the basis of taking into account the processing reliability. z and W f are controlled within the above-mentioned ranges, and the coating weight ranges of the positive active material layer and the negative active material layer are more optimal, which is beneficial to further improve the cycle kinetic performance of the secondary battery on the basis of taking into account the processing reliability.

[0038] In an embodiment of the present application, the Dv99 of the positive active material is 28 μm to 31 μm. For example, the Dv99 of the positive active material is 28 μm, 29 μm, 30 μm, 31 μm, or any value between any two of the above-mentioned numerical ranges. The Dv99 of the positive active material is controlled within the above-mentioned range, and the Dv99 range of the positive active material is more optimal, which is beneficial to further improve the cycle kinetic performance and processing reliability of the secondary battery.

[0039] In an embodiment of the present application, the Dv99 of the negative active material is 24 μm to 26 μm. For example, the Dv99 of the negative active material is 24 μm, 25 μm, 26 μm, or any value between any two of the above-mentioned numerical ranges. The Dv99 of the negative active material is controlled within the above-mentioned range, and the Dv99 range of the negative active material is more optimal, which is beneficial to further improve the cycle kinetic performance and processing reliability of the secondary battery.

[0040] In an embodiment of the present application, the Dv99 of the positive active material is 28 μm to 31 μm, and the Dv99 of the negative active material is 24 μm to 26 μm. For example, the Dv99 of the positive active material is 28 μm, 29 μm, 30 μm, 31 μm, or any value between any two of the above-mentioned numerical ranges. The Dv99 of the negative active material is 24 μm, 25 μm, 26 μm, or any value between any two of the above-mentioned numerical ranges. The Dv99 of the positive active material and the negative active material is controlled within the above-mentioned ranges, and the Dv99 ranges of the positive active material and the negative active material are more optimal, which is beneficial to further improve the cycle kinetic performance and processing reliability of the secondary battery.

[0041] In one embodiment of this application, the negative electrode active material includes at least one of carbon-based, silicon-based, or tin-based materials. The carbon-based material includes at least one of natural graphite, artificial graphite, soft carbon, hard carbon, or mesophase carbon microspheres. The silicon-based material includes at least one of elemental silicon, silicon-carbon materials, or silicon-oxygen materials. The tin-based material includes at least one of elemental tin, tin alloys, or tin oxides. These types of negative electrode active materials possess high surface activity. When applied in secondary batteries, they can increase the active sites for lithium ion insertion / extraction, reduce the electrochemical polarization of the secondary battery, thereby reducing the battery impedance and enabling the secondary battery to exhibit good cycle dynamics performance while maintaining processing reliability.

[0042] In one embodiment of this application, the peak intensity ratio I of the d-peak to the g-peak in Raman spectroscopy of the carbon-based material is... d / I g Satisfy: 0.1≤I d / I g ≤1.0. For example, I d / I g The value is 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, or any value within any two of the above ranges. This indicates that the carbon-based material contains amorphous carbon on its surface. The presence of amorphous carbon on the surface of the carbon-based material can enhance its electrochemical activity, facilitate lithium-ion insertion during secondary battery cycling, reduce electrochemical polarization, thereby lowering the internal impedance of the secondary battery and improving its cycle kinetics performance. The value will satisfy the above I... d / I g The application of valuable carbon-based materials in secondary batteries can help improve their cycle dynamics performance while maintaining good processing reliability.

[0043] In this application, the d peak represents the Raman spectrum of carbon-based material particles with a shift range of 1300 cm⁻¹. -1 Up to 1400cm -1 The peak g is the shifted peak in the Raman spectrum of carbon-based material particles, with a shift range of 1530 cm⁻¹. -1 Up to 1630cm -1 The peak.

[0044] This application relates to I d / I g There are no particular restrictions on the method of adjusting the value, as long as it achieves the purpose of this application. For example, commercially available carbon-based materials with different contents of amorphous carbon on their surface can be selected, and the I value of the carbon-based material can be determined by combining it with the "Raman test" test method in this application. d / I g Select the desired I d / Ig Carbon-based materials.

[0045] This application does not impose any particular limitation on the preparation method of carbon-based materials, as long as it can achieve the purpose of this application. For example, the preparation method of carbon-based materials may include, but is not limited to: mixing carbon-based materials and amorphous carbon evenly, heating to 500°C to 1500°C and holding at that temperature for 10 to 20 hours to obtain carbon-based materials with amorphous carbon coated on the surface.

[0046] In one embodiment of this application, the positive electrode active material includes at least one of lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium-rich manganese-based materials, lithium cobalt oxide, lithium manganese oxide, lithium manganese iron phosphate, or lithium titanate. The chemical formula of the aforementioned "lithium-rich manganese-based material" is LiMnO·LiMO, where M may include Ni, Co, or Mn. These types of positive electrode active materials possess high surface activity. When applied in secondary batteries, they can increase the active sites for lithium ion insertion / extraction, reduce the electrochemical polarization of the secondary battery, thereby reducing the impedance of the secondary battery and enabling it to exhibit good cycle kinetic performance while maintaining processing reliability.

[0047] In one embodiment of this application, the positive electrode active material further includes non-metallic elements, including at least one selected from fluorine, phosphorus, boron, chlorine, silicon, or sulfur. This application does not impose any particular limitation on the content of non-metallic elements in the positive electrode active material, as long as the purpose of this application is achieved. In one embodiment, based on the mass of the positive electrode active material, the mass percentage content of the non-metallic elements is 0.1% to 10%. For example, the mass percentage content of the non-metallic elements is 0.1%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or any value between any two of the above ranges. Including the above-mentioned types of non-metallic elements in the positive electrode active material can further improve the stability of the positive electrode active material.

[0048] In an embodiment of the present application, the positive electrode tab includes a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector. In some embodiments, the positive active material layer is disposed on one surface of the positive current collector, and in other embodiments, the positive active material layer is disposed on both surfaces of the positive current collector. The "surface" described above can be a partial surface or a full surface of the positive current collector. The type of positive current collector is not particularly limited in the present application as long as the purpose of the present application can be achieved. For example, the positive current collector can include, but is not limited to, an aluminum foil or an aluminum alloy foil. The positive active material layer of the present application includes the positive active material described in the aforementioned embodiments. In the present application, the thickness of the positive current collector and the positive active material layer is not particularly limited as long as the purpose of the present application can be achieved. For example, the thickness of the positive current collector is 5 μm to 20 μm, and further, the thickness of the positive current collector can be 6 μm to 18 μm. The thickness of the positive active material layer is 30 μm to 120 μm.

[0049] Optionally, the positive active material layer can further include a positive conductive agent and a positive binder. The type of positive conductive agent and positive binder in the positive active material layer is not particularly limited in the present application as long as the purpose of the present application can be achieved. The mass ratio of the positive active material, the positive conductive agent, and the positive binder in the positive active material layer is not particularly limited in the present application, and a person skilled in the art can select it according to the actual need as long as the purpose of the present application can be achieved. For example, the mass ratio of the positive active material, the positive conductive agent, and the positive binder in the positive active material layer is (95-98):(0.5-2.5):(1.5-3.4).

[0050] In an embodiment of the present application, the negative electrode tab includes a negative current collector and a negative active material layer disposed on at least one surface of the negative current collector. In some embodiments, the negative active material layer is disposed on one surface of the negative current collector, and in other embodiments, the negative active material layer is disposed on both surfaces of the negative current collector. The "surface" described above can be a partial surface or a full surface of the negative current collector. The type of negative current collector is not particularly limited in the present application as long as the purpose of the present application can be achieved. For example, the negative current collector includes, but is not limited to, a copper foil, a copper alloy foil, a nickel foil, a titanium foil, a nickel foam, or a copper foam. The negative active material layer of the present application includes the negative active material described in the aforementioned embodiments. In the present application, the thickness of the negative current collector and the negative active material layer is not particularly limited as long as the purpose of the present application can be achieved. For example, the thickness of the negative current collector is 6 μm to 10 μm, and the thickness of the negative active material layer is 30 μm to 130 μm.

[0051] Optionally, the negative active material layer can further include at least one of a negative conductive agent, a stabilizer, or a negative binder. The present application does not particularly limit the kind of the negative conductive agent, the stabilizer, and the negative binder in the negative active material layer, as long as the present application purpose can be achieved. The present application does not particularly limit the mass ratio of the negative active material, the negative conductive agent, the stabilizer, and the negative binder in the negative active material layer, as long as the present application purpose can be achieved. For example, the mass ratio of the negative active material, the negative conductive agent, the stabilizer, and the negative binder in the negative active material layer is (96-98):(0.5-2):(0-1.5):(1.0-1.9).

[0052] The present application does not particularly limit the separator film, as long as the present application purpose can be achieved. For example, the separator film includes at least one of polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polyimide (PI), or aramid. For example, the polyethylene includes at least one selected from high-density polyethylene, low-density polyethylene, and ultra-high molecular weight polyethylene. The separator film of the present application can have a porous structure, and the present application does not particularly limit the size of the pore diameter of the porous structure of the separator film, as long as the present application purpose can be achieved. For example, the size of the pore diameter can be 0.01 pm to 1 pm. The present application does not particularly limit the thickness of the separator film, as long as the present application purpose can be achieved, for example, the thickness of the separator film can be 5 pm to 500 pm.

[0053] In an embodiment of the present application, the secondary battery further includes a case in which the electrode assembly and the electrolyte are accommodated, and the present application does not particularly limit the case, which can be a case well known in the art, as long as the present application purpose can be achieved. For example, the case includes, but is not limited to, an aluminum laminate film, a steel case.

[0054] The present application does not particularly limit the kind of the secondary battery, which can include any device in which an electrochemical reaction occurs. For example, the secondary battery can include, but is not limited to, a lithium metal secondary battery, a lithium ion secondary battery (lithium ion battery), a sodium ion secondary battery (sodium ion battery), a lithium polymer secondary battery, a lithium ion polymer secondary battery.

[0055] The secondary battery of the present application can be used under super-fast charging conditions, specifically, can be used under conditions in which the charge rate is 5 C to 15 C, for example, the charge rate of the secondary battery can be 5 C, 6 C, 7 C, 8 C, 9 C, 10 C, 11 C, 12 C, 13 C, 14 C, 15 C, or any rate between any two of the above rate ranges.

[0056] The preparation method of the positive electrode tab is not particularly limited in the present application, as long as the purpose of the present application can be achieved. For example, the preparation method of the positive electrode tab includes but is not limited to the following steps: (1) preparing a positive electrode slurry; (2) coating the positive electrode slurry on one surface of the positive electrode main area of the positive electrode current collector, and after drying, forming a positive electrode active material layer on one surface of the positive electrode main area of the positive electrode current collector; (3) coating the positive electrode slurry on the other surface of the positive electrode main area of the positive electrode current collector, and after drying, forming a positive electrode active material layer on each of the two surfaces of the positive electrode main area of the positive electrode current collector; (4) after cold pressing, the positive electrode tab area of the positive electrode current collector is die-cut to make the positive electrode current collector integrally extend to form a plurality of positive electrode tabs, and the strips are separated, i.e. the positive electrode tab is obtained. The content and type of each component in the positive electrode slurry in the above step (1) are not particularly limited in the present application, and those skilled in the art can select according to the actual situation, as long as the purpose of the present application can be achieved. The solid content of the positive electrode slurry in the above step (1) is not particularly limited in the present application, as long as the purpose of the present application can be achieved. The time and temperature of drying in the above steps (2) and (3) are not particularly limited in the present application, as long as the purpose of the present application can be achieved. The process parameters of cold pressing in the above step (4) are not particularly limited in the present application, as long as the purpose of the present application can be achieved.

[0057] The preparation method of the negative electrode tab is not particularly limited in the present application, as long as the purpose of the present application can be achieved. For example, the preparation method of the negative electrode tab includes but is not limited to the following steps: (1) preparing a negative electrode slurry; (2) coating the negative electrode slurry on one surface of the negative electrode main area of the negative electrode current collector, and after drying, forming a negative electrode active material layer on one surface of the negative electrode main area of the negative electrode current collector; (3) coating the negative electrode slurry on the other surface of the negative electrode main area of the negative electrode current collector, and after drying, forming a negative electrode active material layer on each of the two surfaces of the negative electrode main area of the negative electrode current collector; (4) after cold pressing, the negative electrode tab area of the negative electrode current collector is die-cut to make the negative electrode current collector integrally extend to form a plurality of negative electrode tabs, and the strips are separated, i.e. the negative electrode tab is obtained. The content and type of each component in the negative electrode slurry in the above step (1) are not particularly limited in the present application, and those skilled in the art can select according to the actual situation, as long as the purpose of the present application can be achieved. The solid content of the negative electrode slurry in the above step (1) is not particularly limited in the present application, as long as the purpose of the present application can be achieved. The time and temperature of drying in the above steps (2) and (3) are not particularly limited in the present application, as long as the purpose of the present application can be achieved. The process parameters of cold pressing in the above step (4) are not particularly limited in the present application, as long as the purpose of the present application can be achieved.

[0058] The preparation method of the secondary battery is not particularly limited in the present application, and a 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 separator, the positive electrode sheet, the separator and the negative electrode sheet in order, and performing winding, folding and other operations as needed to obtain an electrode assembly with a winding structure, placing the electrode assembly into a shell, injecting an electrolyte into the shell and sealing to obtain a secondary battery. Alternatively, the separator, the positive electrode sheet, the separator and the negative electrode sheet are stacked in order, the four corners of the entire stack structure are fixed to obtain an electrode assembly with a stack structure, the electrode assembly is placed into a shell, an electrolyte is injected into the shell and sealed to obtain a secondary battery.

[0059] The second aspect of the present application provides a power consuming device comprising the secondary battery according to any one of the preceding embodiments. Therefore, the power consuming device has good use performance.

[0060] The power consuming device of the present application is not particularly limited, and can be any power consuming device known in the prior art. For example, the power consuming device can include but is not limited to: a notebook computer, a pen input computer, a mobile computer, an electronic book player, a portable telephone, a portable facsimile machine, a portable copying machine, a portable printer, a head-mounted stereo headphone, a video recorder, a liquid crystal television, a portable cleaner, a portable CD player, a mini disc, a transceiver, an electronic organizer, a calculator, a memory card, a portable recorder, a radio, a backup power supply, an electric motor, an automobile, a motorcycle, a power-assisted bicycle, a bicycle, a lighting appliance, a toy, a game machine, a clock, an electric tool, a flashlight, a camera, a household large storage battery and a lithium ion capacitor.

[0061] Embodiment

[0062] Hereinafter, embodiments and comparative examples are given to more specifically explain the embodiments of the present application. Various tests and evaluations were performed according to the following methods.

[0063] Test method and apparatus:

[0064] Test of Dv99:

[0065] The Dv99 of the positive electrode active material and the negative electrode active material was measured respectively using a laser particle size analyzer.

[0066] Test of coating weight:

[0067] (1) Coating weight W of the positive electrode active material layer z Test:

[0068] The lithium ion battery was disassembled after being discharged at 0.5C to 3.0V, and a positive electrode sheet was obtained. The positive electrode sheet was soaked in a dimethyl carbonate (DMC) solution for 4h, then dried and cut to an area of Amm2 The positive electrode sample was weighed on a balance and recorded as p1. Then the positive active material layer on the positive electrode was washed, and the positive current collector was weighed on a balance and recorded as p2.

[0069] If it is a positive electrode sheet with a positive electrode active material layer coated on only one side, W z = (p1-p2) / A.

[0070] If it is a positive electrode sheet with a double-sided coating of positive active material layers, W z = (p1-p2) / 2A.

[0071] (2) Coating weight W of the negative electrode active material layer f test:

[0072] The lithium-ion battery was discharged to 3.0V at 0.5C and then disassembled to obtain the negative electrode sheet. The negative electrode sheet was immersed in DMC solution for 4 hours, then dried, and a piece with an area of ​​B mm was cut off. 2 The negative electrode sample was weighed on a balance and recorded as q1. Then the negative electrode active material layer on the negative electrode was washed, and the negative electrode current collector was weighed on a balance and recorded as q2.

[0073] If it is a negative electrode sheet with a negative electrode active material layer coated on only one side, W f = (q1-q2) / B.

[0074] If it is a negative electrode sheet with a double-sided coating of negative electrode active material layers, W f = (q1-q2) / 2B.

[0075] Raman test:

[0076] The lithium-ion battery was discharged to 3.0V at 0.5C and then disassembled to obtain the negative electrode sheet. The negative electrode sheet was immersed in DMC solution for 4 hours and then dried. An area of ​​100μm × 100μm was selected on the negative electrode active material layer, and the negative electrode active material particles within this area were scanned using a laser confocal Raman spectrometer (Raman, HR Evolution, HORIBA Scientific Instruments Division). The d-peaks and g-peaks of all negative electrode active material particles within this area were obtained. The data was processed using LabSpec software to obtain the peak intensities of the d-peak and g-peak for each negative electrode active material particle, which are respectively I... d and I g The laser wavelength of the Raman spectrometer is in the range of 532 nm to 785 nm. d / I g The value of I is the I value of all negative electrode active material particles measured within this range. d and I gThe average of the ratios.

[0077] Cyclic dynamic performance testing:

[0078] The lithium-ion batteries of each embodiment and comparative example were subjected to cycle kinetic performance tests at a charging rate of 10C. The specific steps are as follows:

[0079] (1) Adjust the test temperature to a constant 25℃, place the temperature sensing wire of the multi-channel temperature measuring instrument at the center of the lithium-ion battery surface, and perform the following steps: 1) 10C constant current charging to 4.1V; 2) 7C constant current charging to 4.3V; 3) 6C constant current charging to 4.4V; 4) 4.4V constant voltage charging to 0.05C; 5) Let stand for 30min; 6) 1C constant current discharging to 3.0V; 7) Let stand for 30min; End;

[0080] Charging speed: that is, the time from step 1) to step 4) in step (1);

[0081] Charging temperature rise: The difference between the maximum temperature of the process from step 1) to step 4) in step (1) of the lithium-ion battery surface temperature sensing line and the room temperature.

[0082] (2) Adjust the test temperature to a constant 25℃ and start the test: 1) Charge at a constant current of 10C to 4.2V; 2) Charge at a constant current of 8C to 4.3V; 3) Charge at a constant current of 6C to 4.45V; 4) Charge at a constant voltage of 4.45V to 0.05C; 5) Let stand for 5 minutes; 6) Discharge at a constant current of 1C to 3.0V; 7) Let stand for 5 minutes; 8) Cycle steps 1) to 7) 1000 times (cls); End;

[0083] Capacity retention (%) = Discharge capacity after 1000 cls / Discharge capacity of the first cycle × 100%.

[0084] Cyclic kinetic performance is characterized by charging speed, charging temperature rise, and capacity retention. Shorter charging time and smaller charging temperature rise indicate better initial kinetic performance of lithium-ion batteries, while higher capacity retention indicates better cycle performance.

[0085] Testing of manufacturing reliability:

[0086] (1) Negative electrode segment band frequency P f The test:

[0087] Record the number of times the negative electrode sheet of any 1000m length breaks when cold-pressed for 10000m every 10000m under a cold pressing pressure of 60t for each embodiment and comparative example.

[0088] (2) Positive electrode segment frequency P z The test:

[0089] Record the number of times the positive electrode sheet of any 1000m length breaks when cold-pressed for 10000m every 10000m under a cold pressing pressure of 60t for each embodiment and comparative example.

[0090] Example 1-1

[0091] <Preparation of Negative Electrode Sheets>

[0092] The negative electrode active material, the negative electrode conductive agent superconducting carbon (Super P), and the stabilizer sodium carboxymethyl cellulose (CMC-Na, Mw = 7 × 10⁻⁶) are combined. 5 ), negative electrode binder styrene-butadiene rubber (SBR, Mw = 7 × 10), 6 The materials were mixed at a mass ratio of 96.5:1.0:1.0:1.5, and then deionized water was added as a solvent. The mixture was stirred under vacuum until a homogeneous negative electrode slurry with a solid content of 58 wt% was obtained. The negative electrode slurry was uniformly coated onto the negative electrode body area of ​​one surface of a 10 μm thick copper foil current collector, and dried at 85°C to obtain a negative electrode sheet with a single-sided coating of negative electrode active material. The above steps were then repeated on the negative electrode body area of ​​the other surface of the copper foil to obtain a negative electrode sheet with a double-sided coating of negative electrode active material. The negative electrode tabs were then formed by cold pressing, die-cutting in the negative electrode tab area of ​​the negative electrode current collector, and slitting. After slitting, the sheets were dried at 110°C under vacuum for 4 hours to obtain negative electrode sheets with a size of 55 mm × 1300 mm for later use. The single-layer thickness of the negative electrode active material layer was 58.5 μm, and the thickness of the negative electrode sheet was 127 μm. The negative electrode tab region of the negative electrode current collector extends integrally (see structure). Figure 4 But not with Figure 4 (To a limited extent) 32 negative electrode tabs are formed. The compacted density of the negative electrode sheet is 1.5 g / cm³. 3 The Dv99 of the negative electrode active material is 25 μm. The coating weight W of the negative electrode active material layer is... f It is 5.19 mg / cm³ 2 The types of negative electrode active materials are shown in Table 2.

[0093] <Preparation of the positive electrode>

[0094] The positive electrode active material is lithium cobalt oxide, the positive electrode conductive agent is Super P, and the positive electrode binder is polyvinylidene fluoride (PVDF, Mw = 7 × 10⁻⁶). 6) mixed in a mass ratio of 96:2:2, N-methyl pyrrolidone (NMP) was added as a solvent, and stirring was performed under the action of a vacuum stirrer until the solid content was 75 wt% and the system was uniform. The positive electrode slurry was uniformly coated on the positive electrode main area of one surface of a positive electrode current collector aluminum foil with a thickness of 13 μm, dried at 95°C, to obtain a positive electrode sheet with a single-sided coated positive electrode active material layer. Then, the above steps were repeated on the positive electrode main area of the other surface of the aluminum foil, to obtain a positive electrode sheet with a double-sided coated positive electrode active material layer. After cold pressing, die cutting to form positive electrode tabs on the positive electrode tab area of the positive electrode current collector, and slitting, the positive electrode sheet was dried at 85°C under vacuum for 4 h, to obtain a positive electrode sheet with a specification of 51 mm x 1200 mm. The single-layer thickness of the positive electrode active material layer was 38.5 μm, and the thickness of the positive electrode sheet was 90 μm. The positive electrode tab area of the positive electrode current collector extended integrally (see the structure in Figure 3 , but not limited to Figure 3 ) to form 32 positive electrode tabs. The tap density of the positive electrode sheet was 4.0 g / cm 3 . The Dv99 of the lithium cobaltate was 30 μm. The coating weight W z of the positive electrode active material layer was 10.38 mg / cm 2 .

[0095] <Preparation of electrolyte>

[0096] In an environment with a water content of less than 10 ppm, propyl propionate, ethylene carbonate, and diethyl carbonate were mixed in a mass ratio of 34:33:33 as a solvent, and lithium salt lithium hexafluorophosphate (LiPF6), the solvent, and the additive glutaronitrile were prepared in a mass ratio of 15:83:2 to obtain an electrolyte.

[0097] <Preparation of separator>

[0098] A porous polyethylene film with a thickness of 15 μm was selected as a separator.

[0099] <Preparation of lithium ion battery>

[0100] The separator, the positive electrode sheet, the separator, and the negative electrode sheet were sequentially stacked in order, with the separator between the positive electrode sheet and the negative electrode sheet to play a separating role, and the electrode assembly was obtained by winding. The positive electrode tabs were introduced by spot welding with aluminum tabs, and the negative electrode tabs were introduced by spot welding with nickel tabs. Among them, N1 = 0 layers of positive electrode sheets were arranged between the two adjacent positive electrode tabs in the electrode assembly after winding, N2 = 0 layers of negative electrode sheets were arranged between the two adjacent negative electrode tabs, there was one positive electrode tab on each layer of positive electrode sheet arranged with a positive electrode tab, and there was one negative electrode tab on each layer of negative electrode sheet arranged with a negative electrode tab (see the arrangement of the positive and negative electrode tabs in Figure 1 , but not limited to Figure 1 ).

[0101] The electrode assembly is placed in an aluminum-plastic film shell, and after drying, an electrolyte is injected. After vacuum packaging, standing, formation, capacity, degassing, and edge cutting processes, a lithium ion battery is obtained.

[0102] Example 1-2

[0103] <Preparation of the positive electrode sheet>

[0104] Except that the positive tab area of the positive current collector is integrally extended to form 16 positive tabs, the rest is the same as Example 1-1.

[0105] <Preparation of the negative electrode sheet>

[0106] Except that the negative tab area of the negative current collector is integrally extended to form 16 negative tabs, the rest is the same as Example 1-1.

[0107] <Preparation of the lithium ion battery>

[0108] Except that N1 = 1 layer of positive electrode sheets is arranged between the two adjacent positive tabs, and N2 = 1 layer of negative electrode sheets is arranged between the two adjacent negative tabs, the rest is the same as Example 1-1.

[0109] <Preparation of the separator> and <Preparation of the electrolyte> are the same as Example 1-1.

[0110] Example 1-3

[0111] <Preparation of the positive electrode sheet>

[0112] Except that the positive tab area of the positive current collector is integrally extended to form 10 positive tabs, the rest is the same as Example 1-1.

[0113] <Preparation of the negative electrode sheet>

[0114] Except that the negative tab area of the negative current collector is integrally extended to form 10 negative tabs, the rest is the same as Example 1-1.

[0115] <Preparation of the lithium ion battery>

[0116] Except that N1 = 2 layers of positive electrode sheets are arranged between the two adjacent positive tabs, and N2 = 2 layers of negative electrode sheets are arranged between the two adjacent negative tabs, the rest is the same as Example 1-1.

[0117] <Preparation of the separator> and <Preparation of the electrolyte> are the same as Example 1-1.

[0118] Examples 1-4 to 1-19

[0119] Except for adjusting the relevant preparation parameters according to Table 1, the rest is the same as Example 1-1.

[0120] Example 2-1

[0121] The rest was the same as Example 1-1 except that the relevant preparation parameters were adjusted according to Table 2.

[0122] Examples 2-2 to 2-4

[0123] The rest was the same as Example 1-1 except that the artificial graphite coated with amorphous carbon on the surface was selected as the negative active material in the preparation of the negative electrode tab. Among them, the mass ratio of artificial graphite and amorphous carbon was adjusted according to Table 3.

[0124] Examples 2-5 and 2-6

[0125] The rest was the same as Example 1-1 except that the relevant preparation parameters were adjusted according to Table 2.

[0126] Comparative Example 1

[0127] Preparation of the negative electrode tab

[0128] The negative active material, negative conductive agent Super P, stabilizer carboxymethyl cellulose sodium (CMC-Na, Mw = 7 x 10 5 ), and negative binder styrene-butadiene rubber (SBR, Mw = 7 x 10 6 ) were mixed in a mass ratio of 96.5:1.0:1.0:1.5, and then deionized water was added as a solvent. The negative electrode slurry was stirred in a vacuum stirrer until the solid content was 58wt% and the system was uniform. The negative electrode slurry was uniformly coated on one surface of a negative current collector copper foil with a thickness of 10μm, and dried at 85℃ to obtain a negative electrode tab with a single coated negative active material layer. Then, the above steps were repeated on the other surface of the copper foil to obtain a negative electrode tab with a double coated negative active material layer. After cold pressing, cutting, and striping, the striping was dried at 110℃ under vacuum conditions for 4h, and a negative tab nickel tab was welded on the surface of the negative current collector to obtain a negative electrode tab with a specification of 55mm x 1300mm. Among them, the single layer thickness of the negative active material layer was 58.5μm, and the thickness of the negative electrode tab was 127μm. The tap density of the negative electrode tab was 1.5g / cm 3 . The Dv99 of the negative active material was 25μm. The coating weight W f of the negative active material layer was 5.19mg / cm 2 . The type of negative active material was the same as Example 1-1.

[0129] Preparation of the positive electrode tab

[0130] The positive active material lithium cobaltate, the positive conductive agent super carbon (Super P), and the positive binder polyvinylidene fluoride (PVDF, Mw = 70 x 10 5 ) were mixed in a mass ratio of 96:2:2, N-methyl pyrrolidone (NMP) was added as a solvent, and the positive slurry was stirred in a vacuum stirrer until the solid content was 75 wt% and the system was uniform. The positive slurry was uniformly coated on one surface of a positive current collector aluminum foil with a thickness of 13 μm, dried at 95°C, and a positive electrode tab with a single coated positive active material layer was obtained. Then, the above steps were repeated on the other surface of the aluminum foil, and a positive electrode tab with a double coated positive active material layer was obtained. After cold pressing, cutting, and striping, the strip was dried at 85°C for 4 h under vacuum, and a positive electrode tab with a size of 51 mm x 1200 mm was obtained by welding a positive tab aluminum tab on the surface of the positive current collector. The single layer thickness of the positive active material layer was 38.5 μm, and the thickness of the positive electrode tab was 90 μm. The tap density of the positive electrode tab was 4.0 g / cm 3 . The Dv99 of lithium cobaltate was 30 μm. The coating weight W z of the positive active material layer was 10.38 mg / cm 2 .

[0131] <Preparation of lithium ion battery>

[0132] The positive electrode tab, the separator, and the negative electrode tab were sequentially stacked in order, with the separator between the positive electrode tab and the negative electrode tab to act as a separator, and the electrode assembly was obtained by winding. The electrode assembly was placed in an aluminum plastic film shell, dried, and then injected with electrolyte. After vacuum packaging, standing, formation, capacity, degassing, and edge cutting processes, a lithium ion battery was obtained.

[0133] <Preparation of separator>, <Preparation of electrolyte>, and Example 1-1 were the same.

[0134] Comparative Examples 2 to 9

[0135] Except for adjusting the relevant preparation parameters according to Table 1, the rest was the same as Example 1-1.

[0136] Comparative Examples 10 to 15

[0137] In <Preparation of positive electrode tab> and <Preparation of negative electrode tab>, except for adjusting the relevant preparation parameters according to Table 1, the rest was the same as Comparative Example 1.

[0138] <Preparation of separator>, <Preparation of electrolyte>, and <Preparation of lithium ion battery> were the same as Comparative Example 1.

[0139] Comparative Examples 16 and 17

[0140] The rest is the same as Example 1-1 except that the relevant preparation parameters are adjusted according to Table 1.

[0141] The preparation parameters and performance parameters of each example and comparative example are shown in Table 1 and Table 2.

[0142] Table 1

[0143]

[0144]

[0145] Note: “ / ” in Table 1 means no corresponding parameter.

[0146] As can be seen from Example 1-1 to Example 1-19 and Comparative Example 1 to Comparative Example 17, the secondary battery of the embodiments of the present application has the ratio of the coating weight W z of the positive electrode active material layer to the coating weight W f of the negative electrode active material layer W z / W f and the value of W f within the range of the present application, and the Dv99 of the positive electrode active material and the Dv99 of the negative electrode active material are within the range of the present application, and the positive electrode current collector integrally extends to form a plurality of positive electrode tabs, and the negative electrode current collector integrally extends to form a plurality of negative electrode tabs to have a multi-tab structure, so that the secondary battery has a shorter charging time (i.e., a higher charging speed), a lower charging temperature rise, and a higher capacity retention rate at a charging rate of 10C, indicating that the secondary battery has better cycle dynamics under super-fast charging conditions. The positive electrode tab and the negative electrode tab have a lower strip frequency, indicating that the secondary battery has good processing reliability. Thus, the secondary battery of the embodiments of the present application can have good cycle dynamics under super-fast charging conditions while taking into account the processing reliability. The secondary battery of Comparative Example 1 has an embedded single-tab structure rather than the multi-tab structure of the present application; the secondary batteries of Comparative Example 2 and Comparative Example 3 have a coating weight W f of the negative electrode active material layer not within the range of the present application; the secondary batteries of Comparative Example 4 and Comparative Example 5 have a ratio of the coating weight W z of the positive electrode active material layer to the coating weight W f of the negative electrode active material layer W z / W fnot within the scope of the present application; the secondary batteries of Comparative Example 6 and Comparative Example 7, whose Dv99 of the negative electrode active material is not within the scope of the present application; the secondary batteries of Comparative Example 8 and Comparative Example 9, whose Dv99 of the positive electrode active material is not within the scope of the present application; the secondary batteries of Comparative Example 10 and Comparative Example 11, which have an embedded single tab structure instead of the multi-tab structure of the present application, and whose Dv99 of the negative electrode active material, Dv99 of the positive electrode active material are not within the scope of the present application; the secondary batteries of Comparative Example 12 and Comparative Example 13, which have an embedded single tab structure instead of the multi-tab structure of the present application, and whose Dv99 of the positive electrode active material, Dv99 of the negative electrode active material, W f not within the scope of the present application; the secondary batteries of Comparative Example 14 and Comparative Example 15, which have an embedded single tab structure instead of the multi-tab structure of the present application, and whose Dv99 of the positive electrode active material, Dv99 of the negative electrode active material, W z not within the scope of the present application; the secondary batteries of Comparative Example 14 and Comparative Example 15, which have an embedded single tab structure instead of the multi-tab structure of the present application, and whose Dv99 of the positive electrode active material, Dv99 of the negative electrode active material, W f not within the scope of the present application; the secondary batteries of Comparative Example 14 and Comparative Example 15, which have an embedded single tab structure instead of the multi-tab structure of the present application, and whose Dv99 of the positive electrode active material, Dv99 of the negative electrode active material, W z not within the scope of the present application; the secondary batteries of Comparative Example 14 and Comparative Example 15, which have an embedded single tab structure instead of the multi-tab structure of the present application, and whose Dv99 of the positive electrode active material, Dv99 of the negative electrode active material, W f not within the scope of the present application; the secondary batteries of Comparative Example 14 and Comparative Example 15, which have an embedded single tab structure instead of the multi-tab structure of the present application, and whose Dv99 of the positive electrode active material, Dv99 of the negative electrode active material, W f not within the scope of the present application; the secondary batteries of Comparative Example 14 and Comparative Example 15, which have an embedded single tab structure instead of the multi-tab structure of the present application, and whose Dv99 of the positive electrode active material, Dv99 of the negative electrode active material, W f of Comparative Examples 1 to 17 have longer charging time (i.e. lower charging speed) and / or higher charging temperature rise and / or lower capacity retention at a charge rate of 10C, or the positive electrode tab and / or the negative electrode tab has a higher strip frequency, indicating that the secondary batteries cannot balance the charging speed, charging temperature rise, cycle performance and processing performance under the condition of super-fast charging.

[0147] The values of N1 and N2 generally affect the cycle kinetics and processing reliability of the secondary battery. As can be seen from Example 1-1 to Example 1-3, the secondary batteries selected with the values of N1 and N2 within the scope of the present application have shorter charging time (i.e. higher charging speed), lower charging temperature rise and higher capacity retention on the whole at a charge rate of 10C, and the positive electrode tab and the negative electrode tab have a lower strip frequency, indicating that the secondary batteries can balance the processing reliability on the basis of good cycle kinetics performance under the condition of super-fast charging.

[0148] The coating weight W f of the negative electrode active material layer generally affects the cycle kinetics and processing reliability of the secondary battery. As can be seen from Example 1-1, Example 1-4 to Example 1-9, Comparative Example 2 and Comparative Example 3, the secondary batteries selected with the coating weight W fThe secondary battery within the scope of the present application has a shorter charging time, a lower charging temperature rise, and a higher capacity retention rate as a whole at a charging rate of 10C, and the positive electrode sheet and the negative electrode sheet have a lower strip frequency, indicating that the secondary battery can have good cycle dynamics under the condition of super-fast charging while taking into account the processing reliability.

[0149] The ratio W of the coating weight W of the positive electrode active material layer to the coating weight W of the negative electrode active material layer z The ratio W of the coating weight W of the positive electrode active material layer to the coating weight W of the negative electrode active material layer f The ratio W of the coating weight W of the positive electrode active material layer to the coating weight W of the negative electrode active material layer z The ratio W of the coating weight W of the positive electrode active material layer to the coating weight W of the negative electrode active material layer f Generally affects the cycle dynamics and processing reliability of the secondary battery. As can be seen from Example 1-1, Example 1-10, Example 1-11, Comparative Example 4, and Comparative Example 5, the secondary battery selected with the ratio W of the coating weight W of the positive electrode active material layer to the coating weight W of the negative electrode active material layer within the scope of the present application has a shorter charging time, a lower charging temperature rise, and a higher capacity retention rate as a whole at a charging rate of 10C, and the positive electrode sheet and the negative electrode sheet have a lower strip frequency, indicating that the secondary battery can have good cycle dynamics under the condition of super-fast charging while taking into account the processing reliability. z The ratio W of the coating weight W of the positive electrode active material layer to the coating weight W of the negative electrode active material layer f The ratio W of the coating weight W of the positive electrode active material layer to the coating weight W of the negative electrode active material layer z The ratio W of the coating weight W of the positive electrode active material layer to the coating weight W of the negative electrode active material layer f The secondary battery within the scope of the present application has a shorter charging time, a lower charging temperature rise, and a higher capacity retention rate as a whole at a charging rate of 10C, and the positive electrode sheet and the negative electrode sheet have a lower strip frequency, indicating that the secondary battery can have good cycle dynamics under the condition of super-fast charging while taking into account the processing reliability.

[0150] The Dv99 of the negative electrode active material generally affects the cycle dynamics and processing reliability of the secondary battery. As can be seen from Example 1-1, Example 1-12 to Example 1-15, Comparative Example 6, and Comparative Example 7, the secondary battery selected with the Dv99 of the negative electrode active material within the scope of the present application has a shorter charging time, a lower charging temperature rise, and a higher capacity retention rate as a whole at a charging rate of 10C, and the positive electrode sheet and the negative electrode sheet have a lower strip frequency, indicating that the secondary battery can have good cycle dynamics under the condition of super-fast charging while taking into account the processing reliability.

[0151] The Dv99 of the positive electrode active material generally affects the cycle dynamics and processing reliability of the secondary battery. As can be seen from Example 1-1, Example 1-16 to Example 1-19, Comparative Example 8, and Comparative Example 9, the secondary battery selected with the Dv99 of the positive electrode active material within the scope of the present application has a shorter charging time, a lower charging temperature rise, and a higher capacity retention rate as a whole at a charging rate of 10C, and the positive electrode sheet and the negative electrode sheet have a lower strip frequency, indicating that the secondary battery can have good cycle dynamics under the condition of super-fast charging while taking into account the processing reliability.

[0152] Table 2

[0153]

[0154] Note: “ / ” in Table 2 means no corresponding parameter; “Mr” in Table 2 means the mass ratio of artificial graphite and amorphous carbon.

[0155] The type of negative active material, the I d / I g value will generally affect the cycle kinetic performance and processing reliability of the secondary battery. As can be seen from Example 1-1, Example 2-1 to Example 2-4, the secondary battery selected from the type of negative active material, the I d / I g value within the scope of the present application has a shorter charging time, a lower charging temperature rise and a higher capacity retention rate as a whole at a charging rate of 10C, and the positive electrode sheet and the negative electrode sheet have a lower strip frequency, indicating that the secondary battery can have good cycle kinetic performance under the condition of super-fast charging, and also takes into account the processing reliability. Among them, Figure 5 the Raman spectrum of Example 2-3 is shown, and from Figure 5 it can be seen that the I d / I g value of the high kinetic negative active material is higher, indicating that it has good surface activity.

[0156] The type of positive active material will generally affect the cycle kinetic performance and processing reliability of the secondary battery. As can be seen from Example 1-1, Example 2-5 and Example 2-6, the secondary battery selected from the type of positive active material, the I d / I g value within the scope of the present application has a shorter charging time, a lower charging temperature rise and a higher capacity retention rate as a whole at a charging rate of 10C, and the positive electrode sheet and the negative electrode sheet have a lower strip frequency, indicating that the secondary battery can have good cycle kinetic performance under the condition of super-fast charging, and also takes into account the processing reliability.

[0157] It should be noted that the relational terms herein such as first and second and the like are used only to differentiate one entity or action from another, and do not necessarily require or imply that any such actual relationship or order exists between or among the entities or actions. Also, the terms “comprises”, “comprising”, or any other variations thereof are intended to cover non-exclusive inclusions, so that a process, method, article, or apparatus that comprises a list of elements does not only include those elements, but also includes other elements not expressly listed or inherent to such process, method, article, or apparatus.

[0158] The various embodiments in the specification are described in a related manner, and the same or similar parts between the various embodiments can be referred to each other, and each embodiment focuses on the difference from other embodiments.

[0159] The above only describes the preferred embodiments of the present application, and is not used to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A secondary battery, wherein, The electrode assembly comprises a positive electrode tab, a negative electrode tab and a separator film, the positive electrode tab comprises a positive electrode current collector and a positive electrode active material layer, the positive electrode active material layer comprises a positive electrode active material, the negative electrode tab comprises a negative electrode current collector and a negative electrode active material layer, and the negative electrode active material layer comprises a negative electrode active material. The positive electrode current collector integrally extends to form a plurality of positive electrode tabs, and the negative electrode current collector integrally extends to form a plurality of negative electrode tabs; the coating weight of the positive electrode active material layer is W z , the coating weight of the negative electrode active material layer is W f , W z , and W f satisfy: 1.6W f ≤W z ≤2.2W f , 3.25 mg / cm 2 ≤W f ≤5.84 mg / cm 2 ; The Dv99 of the positive electrode active material is 27 μm to 33 μm, and the Dv99 of the negative electrode active material is 23 μm to 28 μm.

2. The secondary battery according to claim 1, wherein N1 layers of positive electrode tabs are arranged between two adjacent positive electrode tabs, N2 layers of negative electrode tabs are arranged between two adjacent negative electrode tabs, and the N1 and N2 are each independently selected from 0, 1, 2 or 3.

3. The secondary battery according to claim 1, wherein 6.49 mg / cm 2 ≤ 11.69 mg / cm z ≤ 11.69 mg / cm 2 .

4. The secondary battery according to claim 1, wherein 4.00 mg / cm 2 ≤ W f ≤ 5.19 mg / cm 2 , and / or, 8.00 mg / cm 2 ≤ W z ≤ 10.38 mg / cm 2 .

5. The secondary battery according to claim 1, wherein The Dv99 of the positive electrode active material is 28 μm to 31 μm, and / or the Dv99 of the negative electrode active material is 24 μm to 26 μm.

6. The secondary battery according to claim 1, wherein The negative electrode active material comprises at least one of a carbon-based material, a silicon-based material or a tin-based material, the carbon-based material comprises at least one of natural graphite, artificial graphite, soft carbon, hard carbon or mesocarbon microbeads, the silicon-based material comprises at least one of elemental silicon, silicon-carbon material or silicon-oxygen material, and the tin-based material comprises at least one of elemental tin, tin alloy or oxide of tin.

7. The secondary battery according to claim 6, wherein The peak intensity ratio I d / I g of the d peak and the g peak of the carbon-based material through Raman test satisfies: 0.1≤I d / I g ≤1.

0.

8. The secondary battery according to claim 1, wherein The positive electrode active material comprises at least one of lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium-rich manganese-based material, lithium cobalt oxide, lithium manganese oxide, lithium manganese iron phosphate or lithium titanate.

9. The secondary battery according to claim 8, wherein The positive electrode active material further comprises a non-metallic element, and the non-metallic element comprises at least one of fluorine, phosphorus, boron, chlorine, silicon or sulfur.

10. An electrical device comprising the secondary battery of any one of claims 1 to 9.

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